MgO-templated carbon as a negative electrode material for Na-ion capacitors

NASA Astrophysics Data System (ADS)

Kado, Yuya; Soneda, Yasushi

2016-12-01

In this study, MgO-templated carbon with different pore structures was investigated as a negative electrode material for Na-ion capacitors. With increasing the Brunauer-Emmett-Teller surface area, the irreversible capacity increased, and the coulombic efficiency of the 1st cycle decreased because of the formation of solid electrolyte interface layers. MgO-templated carbon annealed at 1000 °C exhibited the highest capacity and best rate performance, suggesting that an appropriate balance between surface area and crystallinity is imperative for fast Na-ion storage, attributed to the storage mechanism: combination of non-faradaic electric double-layer capacitance and faradaic Na intercalation in the carbon layers. Finally, a Na-ion capacitor cell using MgO-templated carbon and activated carbon as the negative and positive electrodes, respectively, exhibited an energy density at high power density significantly greater than that exhibited by the cell using a commercial hard carbon negative electrode.

Dielectric surface discharges: Effects of combined low-energy and high-energy incident electrons

NASA Technical Reports Server (NTRS)

Balmain, K. G.; Hirt, W.

1981-01-01

Dielectric surface discharges affected by the addition of high energy electrons at 5 pA/sq cm to a primary 20 keV, 10 nA/sq cm electron beam with the high energy broad spectrum particles coming from the beta decay of Strontium 90 are studied. Kapton exhibits significantly increased discharge strength, increased waiting time between discharges, and a decreased number of discharges per specimen before discharge cessation. Mylar exhibits similar but less pronounced effects, while Teflon is relatively unaffected. With Kapton and Mylar, the high energy electrons act in some way to delay the instant of discharge ignition so that more charge can be accumulated and hence released during discharge.

Influence of Surface Features for Increased Heat Dissipation on Tool Wear

PubMed Central

Beno, Tomas; Hoier, Philipp; Wretland, Anders

2018-01-01

The critical problems faced during the machining process of heat resistant superalloys, (HRSA), is the concentration of heat in the cutting zone and the difficulty in dissipating it. The concentrated heat in the cutting zone has a negative influence on the tool life and surface quality of the machined surface, which in turn, contributes to higher manufacturing costs. This paper investigates improved heat dissipation from the cutting zone on the tool wear through surface features on the cutting tools. Firstly, the objective was to increase the available surface area in high temperature regions of the cutting tool. Secondly, multiple surface features were fabricated for the purpose of acting as channels in the rake face to create better access for the coolant to the proximity of the cutting edge. The purpose was thereby to improve the cooling of the cutting edge itself, which exhibits the highest temperature during machining. These modified inserts were experimentally investigated in face turning of Alloy 718 with high-pressure coolant. Overall results exhibited that surface featured inserts decreased flank wear, abrasion of the flank face, cutting edge deterioration and crater wear probably due to better heat dissipation from the cutting zone. PMID:29693579

Multicolor fluorescence enhancement from a photonics crystal surface

NASA Astrophysics Data System (ADS)

Pokhriyal, A.; Lu, M.; Huang, C. S.; Schulz, S.; Cunningham, B. T.

2010-09-01

A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ˜3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ =632.8 nm laser (cyanine-5) and a dye excited by a λ =532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays.

Multicolor fluorescence enhancement from a photonics crystal surface

PubMed Central

Pokhriyal, A.; Lu, M.; Huang, C. S.; Schulz, S.; Cunningham, B. T.

2010-01-01

A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ∼3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ=632.8 nm laser (cyanine-5) and a dye excited by a λ=532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays. PMID:20957067

Friction and hardness of gold films deposited by ion plating and evaporation

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1983-01-01

Sliding friction experiments were conducted with ion-plated and vapor-deposited gold films on various substrates in contact with a 0.025-mm-radius spherical silicon carbide rider in mineral oil. Hardness measurements were also made to examine the hardness depth profile of the coated gold on the substrate. The results indicate that the hardness is influenced by the depth of the gold coating from the surface. The hardness increases with an increase in the depth. The hardness is also related to the composition gradient in the graded interface between the gold coating and the substrate. The graded interface exhibited the highest hardness resulting from an alloy hardening effect. The coefficient of friction is inversely related to the hardness, namely, the load carrying capacity of the surface. The greater the hardness that the metal surface possesses, the lower is the coefficient of friction. The graded interface exhibited the lowest coefficient of friction.

BET surface area distributions in polar stream sediments: Implications for silicate weathering in a cold-arid environment

USGS Publications Warehouse

Marra, Kristen R.; Elwood Madden, Megan E; Soreghan, Gerilyn S.; Hall, Brenda L

2014-01-01

BET surface area values are critical for quantifying the amount of potentially reactive sediments available for chemical weathering and ultimately, prediction of silicate weathering fluxes. BET surface area values of fine-grained (<62.5 μm) sediment from the hyporheic zone of polar glacial streams in the McMurdo Dry Valleys, Antarctica (Wright and Taylor Valleys) exhibit a wide range (2.5–70.6 m2/g) of surface area values. Samples from one (Delta Stream, Taylor Valley) of the four sampled stream transects exhibit high values (up to 70.6 m2/g), which greatly exceed surface area values from three temperate proglacial streams (0.3–12.1 m2/g). Only Clark stream in Wright Valley exhibits a robust trend with distance, wherein surface area systematically decreases (and particle size increases) in the mud fraction downstream, interpreted to reflect rapid dissolution processes in the weathering environment. The remaining transects exhibit a range in variability in surface area distributions along the length of the channel, likely related to variations in eolian input to exposed channel beds, adjacent snow drifts, and to glacier surfaces, where dust is trapped and subsequently liberated during summer melting. Additionally, variations in stream discharge rate, which mobilizes sediment in pulses and influences water:rock ratios, the origin and nature of the underlying drift material, and the contribution of organic acids may play significant roles in the production and mobilization of high-surface area sediment. This study highlights the presence of sediments with high surface area in cold-based glacier systems, which influences models of chemical denudation rates and the impact of glacial systems on the global carbon cycle.

Dielectric surface discharges - Effects of combined low-energy and high-energy incident electrons

NASA Technical Reports Server (NTRS)

Balmain, K. G.; Hirt, W.

1983-01-01

Dielectric surface discharges affected by the addition of high energy electrons at 5 pA/sq cm to a primary 20 keV, 10 nA/sq cm electron beam with the high energy broad spectrum particles coming from the beta decay of Strontium 90 are studied. Kapton exhibits significantly increased discharge strength, increased waiting time between discharges, and a decreased number of discharges per specimen before discharge cessation. Mylar exhibits similar but less pronounced effects, while Teflon is relatively unaffected. With Kapton and Mylar, the high energy electrons act in some way to delay the instant of discharge ignition so that more charge can be accumulated and hence released during discharge. Previously announced in STAR as N82-14222

Optimization of a cryoprotective medium to increase the viability of freeze-dried Streptococcus thermophilus by response surface methodology

USDA-ARS?s Scientific Manuscript database

Streptococcus thermophilus normally exhibits different survival rates in different bacteria medium during freeze-drying. In this study, response surface methodology (RSM) was applied on the design of experiments for optimizing the cryoprotective medium. Results showed that the most significant facto...

Role of subsurface physics in the assimilation of surface soil moisture observations

USDA-ARS?s Scientific Manuscript database

Soil moisture controls the exchange of water and energy between the land surface and the atmosphere and exhibits memory that may be useful for climate prediction at monthly time scales. Though spatially distributed observations of soil moisture are increasingly becoming available from remotely sense...

Hypoxia-inducible factor regulates alphavbeta3 integrin cell surface expression.

PubMed

Cowden Dahl, Karen D; Robertson, Sarah E; Weaver, Valerie M; Simon, M Celeste

2005-04-01

Hypoxia-inducible factor (HIF)-deficient placentas exhibit a number of defects, including changes in cell fate adoption, lack of fetal angiogenesis, hypocellularity, and poor invasion into maternal tissue. HIF is a heterodimeric transcription factor consisting of alpha and beta aryl hydrocarbon receptor nuclear translocator or ARNT) subunits. We used undifferentiated trophoblast stem (TS) cells to characterize HIF-dependent adhesion, migration, and invasion. Arnt(-/-) and Hifalpha(-/-) TS cells exhibit reduced adhesion and migration toward vitronectin compared with wild-type cells. Furthermore, this defect is associated with decreased cell surface expression of integrin alphavbeta3 and significantly decreased expression of this integrin in focal adhesions. Because of the importance of adhesion and migration in tumor progression (in addition to placental development), we examined the affect of culturing B16F0 melanoma cells in 1.5% oxygen (O(2)). Culturing B16F0 melanoma cells at 1.5% O(2) resulted in increased alphavbeta3 integrin surface expression and increased adhesion to and migration toward vitronectin. Together, these data suggest that HIF and O(2) tension influence placental invasion and tumor migration by increasing cell surface expression of alphavbeta3 integrin.

Hypoxia-inducible Factor Regulates αvβ3 Integrin Cell Surface Expression

PubMed Central

Cowden Dahl, Karen D.; Robertson, Sarah E.; Weaver, Valerie M.; Simon, M. Celeste

2005-01-01

Hypoxia-inducible factor (HIF)-deficient placentas exhibit a number of defects, including changes in cell fate adoption, lack of fetal angiogenesis, hypocellularity, and poor invasion into maternal tissue. HIF is a heterodimeric transcription factor consisting of α and β aryl hydrocarbon receptor nuclear translocator or ARNT) subunits. We used undifferentiated trophoblast stem (TS) cells to characterize HIF-dependent adhesion, migration, and invasion. Arnt-/- and Hifα-/- TS cells exhibit reduced adhesion and migration toward vitronectin compared with wild-type cells. Furthermore, this defect is associated with decreased cell surface expression of integrin αvβ3 and significantly decreased expression of this integrin in focal adhesions. Because of the importance of adhesion and migration in tumor progression (in addition to placental development), we examined the affect of culturing B16F0 melanoma cells in 1.5% oxygen (O2). Culturing B16F0 melanoma cells at 1.5% O2 resulted in increased αvβ3 integrin surface expression and increased adhesion to and migration toward vitronectin. Together, these data suggest that HIF and O2 tension influence placental invasion and tumor migration by increasing cell surface expression of αvβ3 integrin. PMID:15689487

Molecular Insight into the Slipperiness of Ice.

PubMed

Weber, Bart; Nagata, Yuki; Ketzetzi, Stefania; Tang, Fujie; Smit, Wilbert J; Bakker, Huib J; Backus, Ellen H G; Bonn, Mischa; Bonn, Daniel

2018-05-16

Measurements of the friction coefficient of steel-on-ice over a large temperature range reveal very high friction at low temperatures (-100 °C) and a steep decrease in the friction coefficient with increasing temperature. Very low friction is only found over the limited temperature range typical for ice skating. The strong decrease in the friction coefficient with increasing temperature exhibits Arrhenius behavior with an activation energy of E a ≈ 11.5 kJ mol -1 . Remarkably, molecular dynamics simulations of the ice-air interface reveal a very similar activation energy for the mobility of surface molecules. Weakly hydrogen-bonded surface molecules diffuse over the surface in a rolling motion, their number and mobility increasing with increasing temperature. This correlation between macroscopic friction and microscopic molecular mobility indicates that slippery ice arises from the high mobility of its surface molecules, making the ice surface smooth and the shearing of the weakly bonded surface molecules easy.

Molecular simulation insights on the in vacuo adsorption of amino acids on graphene oxide surfaces with varying surface oxygen densities

NASA Astrophysics Data System (ADS)

Rahmani, Farzin; Nouranian, Sasan; Mahdavi, Mina; Al-Ostaz, Ahmed

2016-11-01

In this fundamental study, a series of molecular dynamics simulations were performed in vacuo to investigate the energetics and select geometries of 20 standard amino acids (AAs) on pristine graphene (PG) and graphene oxide (GO) surfaces as a function of graphene surface oxygen density. These interactions are of key interest to graphene/biomolecular systems. Our results indicate that aromatic AAs exhibit the strongest total interactions with the PG surfaces due to π-π stacking. Tryptophan (Trp) has the highest aromaticity due to its indole side chain and, hence, has the strongest interaction among all AAs (-16.66 kcal/mol). Aliphatic, polar, and charged AAs show various levels of affinity to the PG sheets depending on the strength of their side chain hydrophobic interactions. For example, arginine (Arg) with its guanidinium side chain exhibits the strongest interaction with the PG sheets (-13.81 kcal/mol) following aromatic AAs. Also, glycine (Gly; a polar AA) has the weakest interaction with the PG sheets (-7.29 kcal/mol). When oxygen-containing functional groups are added to the graphene sheets, the π-π stacking in aromatic AAs becomes disrupted and perfect parallelism of the aromatic rings is lost. Moreover, hydrogen bonding and/or electrostatic interactions become more pronounced. Charged AAs exhibit the strongest interactions with the GO surfaces. In general, the AA-GO interactions increase with increasing surface oxygen density, and the effect is more pronounced at higher O/C ratios. This study provides a quantitative measure of AA-graphene interactions for the design and tuning of biomolecular systems suitable for biosensing, drug delivery, and gene delivery applications.

Spatial and thickness dependence of coupling interaction of surface states and influence on transport and optical properties of few-layer Bi2Se3

NASA Astrophysics Data System (ADS)

Li, Zhongjun; Chen, Shi; Sun, Jiuyu; Li, Xingxing; Qiu, Huaili; Yang, Jinlong

2018-02-01

Coupling interaction between the bottom and top surface electronic states and the influence on transport and optical properties of Bi2Se3 thin films with 1-8 quintuple layers (QLs) have been investigated by first principles calculations. Obvious spatial and thickness dependences of coupling interaction are found by analyzing hybridization of two surface states. In the thin film with a certain thickness, from the outer to inner atomic layers, the coupling interaction exhibits an increasing trend. On the other hand, as thickness increases, the coupling interaction shows a disproportionate decrease trend. Moreover, the system with 3 QLs exhibits stronger interaction than that with 2 QLs. The presence of coupling interaction would suppress destructive interference of surface states and enhance resistance in various degrees. In view of the inversely proportional relation to transport channel width, the resistance of thin films should show disproportionate thickness dependence. This prediction is qualitatively consistent with the transport measurements at low temperature. Furthermore, the optical properties also exhibit obvious thickness dependence. Especially as the thickness increases, the coupling interaction results in red and blue shifts of the multiple-peak structures in low and high energy regions of imaginary dielectric function, respectively. The red shift trend is in agreement with the recent experimental observation and the blue shift is firstly predicted by the present calculation. The present results give a concrete understanding of transport and optical properties in devices based on Bi2Se3 thin films with few QLs.

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces fabricated by double rolling

NASA Astrophysics Data System (ADS)

Wang, Xi-yong; Liu, Xue-feng; Zou, Wen-jiang; Xie, Jian-xin

2013-12-01

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, and the surface roughness values are 61 and 1095 nm, respectively. The roughness value of matt surface can meet the requirement for bonding the resin matrix with copper foils used for flexible printed circuit boards, thus may omit traditional roughening treatment; the microstructure of double-rolled copper foils demonstrates an obviously asymmetric gradient feature. From bright surface to matt surface in thickness direction, the average grain size first increases from 2.3 to 7.4 μm and then decreases to 3.6 μm; compared with conventional rolled copper foils, the double-rolled copper foils exhibit a remarkably increased bending fatigue life, and the increased range is about 16.2%.

Instability and sound emission from a flow over a curved surface

NASA Technical Reports Server (NTRS)

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

1988-01-01

The growth and decay of a wavepacket convecting in a boundary layer over a concave-convex surface is studied numerically using direct computations of the Navier-Stokes equations. The resulting sound radiation is computed using the 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 wavepacket 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 exhibits a decay characteristic of acoustic waves in two dimensions. The far-field acoustic pressure exhibits a peak at a frequency corresponding to the inflow instability frequency.

Diurnal Variations of the Flux Imbalance Over Homogeneous and Heterogeneous Landscapes

NASA Astrophysics Data System (ADS)

Zhou, Yanzhao; Li, Dan; Liu, Heping; Li, Xin

2018-05-01

It is well known that the sum of the turbulent sensible and latent heat fluxes as measured by the eddy-covariance method is systematically lower than the available energy (i.e., the net radiation minus the ground heat flux). We examine the separate and joint effects of diurnal and spatial variations of surface temperature on this flux imbalance in a dry convective boundary layer using the Weather Research and Forecasting model. Results show that, over homogeneous surfaces, the flux due to turbulent-organized structures is responsible for the imbalance, whereas over heterogeneous surfaces, the flux due to mesoscale or secondary circulations is the main contributor to the imbalance. Over homogeneous surfaces, the flux imbalance in free convective conditions exhibits a clear diurnal cycle, showing that the flux-imbalance magnitude slowly decreases during the morning period and rapidly increases during the afternoon period. However, in shear convective conditions, the flux-imbalance magnitude is much smaller, but slightly increases with time. The flux imbalance over heterogeneous surfaces exhibits a diurnal cycle under both free and shear convective conditions, which is similar to that over homogeneous surfaces in free convective conditions, and is also consistent with the general trend in the global observations. The rapid increase in the flux-imbalance magnitude during the afternoon period is mainly caused by the afternoon decay of the turbulent kinetic energy (TKE). Interestingly, over heterogeneous surfaces, the flux imbalance is linearly related to the TKE and the difference between the potential temperature and surface temperature, ΔT; the larger the TKE and ΔT values, the smaller the flux-imbalance magnitude.

Effect of hydrodynamics and surface roughness on the electrochemical behaviour of carbon steel in CSG produced water

NASA Astrophysics Data System (ADS)

Eyu, Gaius Debi; Will, Geoffrey; Dekkers, Willem; MacLeod, Jennifer

2015-12-01

The influence of fluid flow, surface roughness and immersion time on the electrochemical behaviour of carbon steel in coal seam gas produced water under static and hydrodynamic conditions has been studied. The disc electrode surface morphology before and after the corrosion test was characterized using scanning electron microscopy (SEM). The corrosion product was examined using X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD).The results show that the anodic current density increased with increasing surface roughness and consequently a decrease in corrosion surface resistance. Under dynamic flow conditions, the corrosion rate increased with increasing rotating speed due to the high mass transfer coefficient and formation of non-protective akaganeite β-FeO(OH) and goethite α-FeO(OH) corrosion scale at the electrode surface. The corrosion rate was lowest at 0 rpm. The corrosion rate decreased in both static and dynamic conditions with increasing immersion time. The decrease in corrosion rate is attributed to the deposition of corrosion products on the electrode surface. SEM results revealed that the rougher surface exhibited a great tendency toward pitting corrosion.

Effects of intraoral aging on surface properties of coated nickel-titanium archwires.

PubMed

Rongo, Roberto; Ametrano, Gianluca; Gloria, Antonio; Spagnuolo, Gianrico; Galeotti, Angela; Paduano, Sergio; Valletta, Rosa; D'Antò, Vincenzo

2014-07-01

To evaluate the effects of intraoral aging on surface properties of esthetic and conventional nickel-titanium (NiTi) archwires. Five NiTi wires were considered for this study (Sentalloy, Sentalloy High Aesthetic, Superelastic Titanium Memory Wire, Esthetic Superelastic Titanium Memory Wire, and EverWhite). For each type of wire, four samples were analyzed as received and after 1 month of clinical use by an atomic force microscope (AFM) and a scanning electronic microscope (SEM). To evaluate sliding resistance, two stainless steel plates with three metallic or three monocrystalline brackets, bonded in passive configuration, were manufactured; four as-received and retrieved samples for every wire were pulled five times at 5 mm/min for 1 minute by means of an Instron 5566, recording the greatest friction value (N). Data were analyzed by one-way analysis of variance and by Student's t-test. After clinical use, surface roughness increased considerably. The SEM images showed homogeneity for the as-received control wires; however, after clinical use esthetic wires exhibited a heterogeneous surface with craters and bumps. The lowest levels of friction were observed with the as-received Superelastic Titanium Memory Wire on metallic brackets. When tested on ceramic brackets, all the wires exhibited an increase in friction (t-test; P < .05). Furthermore, all the wires, except Sentalloy, showed a statistically significant increase in friction between the as-received and retrieved groups (t-test; P < .05). Clinical use of the orthodontic wires increases their surface roughness and the level of friction.

Analysis of Hydrodynamics and Heat Transfer in a Thin Liquid Film Flowing over a Rotating Disk by Integral Method

NASA Technical Reports Server (NTRS)

Basu, S.; Cetegen, B. M.

2005-01-01

An integral analysis of hydrodynamics and heat transfer in a thin liquid film flowing over a rotating disk surface is presented for both constant temperature and constant heat flux boundary conditions. The model is found to capture the correct trends of the liquid film thickness variation over the disk surface and compare reasonably well with experimental results over the range of Reynolds and Rossby numbers covering both inertia and rotation dominated regimes. Nusselt number variation over the disk surface shows two types of behavior. At low rotation rates, the Nusselt number exhibits a radial decay with Nusselt number magnitudes increasing with higher inlet Reynolds number for both constant wall temperature and heat flux cases. At high rotation rates, the Nusselt number profiles exhibit a peak whose location advances radially outward with increasing film Reynolds number or inertia. The results also compare favorably with the full numerical simulation results from an earlier study as well as with the reported experimental results.

Effect of membranes with various hydrophobic/hydrophilic properties on lipase immobilized activity and stability.

PubMed

Chen, Guan-Jie; Kuo, Chia-Hung; Chen, Chih-I; Yu, Chung-Cheng; Shieh, Chwen-Jen; Liu, Yung-Chuan

2012-02-01

In this study, three membranes: regenerated cellulose (RC), glass fiber (GF) and polyvinylidene fluoride (PVDF), were grafted with 1,4-diaminobutane (DA) and activated with glutaraldehyde (GA) for lipase covalent immobilization. The efficiencies of lipases immobilized on these membranes with different hydrophobic/hydrophilic properties were compared. The lipase immobilized on hydrophobic PVDF-DA-GA membrane exhibited more than an 11-fold increase in activity compared to its immobilization on a hydrophilic RC-DA-GA membrane. The relationship between surface hydrophobicity and immobilized efficiencies was investigated using hydrophobic/hydrophilic GF membranes which were prepared by grafting a different ratio of n-butylamine/1,4-diaminobutane (BA/DA). The immobilized lipase activity on the GF membrane increased with the increased BA/DA ratio. This means that lipase activity was exhibited more on the hydrophobic surface. Moreover, the modified PVDF-DA membrane was grafted with GA, epichlorohydrin (EPI) and cyanuric chloride (CC), respectively. The lipase immobilized on the PVDF-DA-EPI membrane displayed the highest specific activity compared to other membranes. This immobilized lipase exhibited more significant stability on pH, thermal, reuse, and storage than did the free enzyme. The results exhibited that the EPI modified PVDF is a promising support for lipase immobilization. Copyright © 2011 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Fireworks induced particle pollution: A spatio-temporal analysis

NASA Astrophysics Data System (ADS)

Kumar, M.; Singh, R. K.; Murari, V.; Singh, A. K.; Singh, R. S.; Banerjee, T.

2016-11-01

Diwali-specific firework induced particle pollution was measured in terms of aerosol mass loading, type, optical properties and vertical distribution. Entire nation exhibited an increase in particulate concentrations specifically in Indo-Gangetic Plain (IGP). Aerosol surface mass loading at middle IGP revealed an increase of 56-121% during festival days in comparison to their background concentrations. Space-borne measurements (Aqua and Terra-MODIS) typically identified IGP with moderate to high AOD (0.3-0.8) during pre-festive days which transmutes to very high AOD (0.4-1.8) during Diwali-day with accumulation of aerosol fine mode fractions (0.3-1.0). Most of the aerosol surface monitoring stations exhibited increase in PM2.5 especially on Diwali-day while PM10 exhibited increase on subsequent days. Elemental compositions strongly support K, Ba, Sr, Cd, S and P to be considered as firework tracers. The upper and middle IGP revealed dominance of absorbing aerosols (OMI-AI: 0.80-1.40) while CALIPSO altitude-orbit-cross-section profiles established the presence of polluted dust which eventually modified with association of smoke and polluted continental during extreme fireworks. Diwali-specific these observations have implications on associating fireworks induced particle pollution and human health while inclusion of these observations should improve regional air quality model.

Carbon nanotube epoxy nanocomposites: the effects of interfacial modifications on the dynamic mechanical properties of the nanocomposites.

PubMed

Yoonessi, Mitra; Lebrón-Colón, Marisabel; Scheiman, Daniel; Meador, Michael A

2014-10-08

Surface functionalization of pretreated carbon nanotubes (CNT) using aromatic, aliphatic, and aliphatic ether diamines was performed. The pretreatment of the CNT consisted of either acid- or photo-oxidation. The acid treated CNT had a higher initial oxygen content compared to the photo-oxidized CNT and this resulted in a higher density of functionalization. X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) were used to verify the presence of the oxygenated and amine moieties on the CNT surfaces. Epoxy/0.1 wt % CNT nanocomposites were prepared using the functionalized CNT and the bulk properties of the nanocomposites were examined. Macroscale correlations between the interfacial modification and bulk dynamic mechanical and thermal properties were observed. The amine modified epoxy/CNT nanocomposites exhibited up to a 1.9-fold improvement in storage modulus (G') below the glass transition (Tg) and up to an almost 4-fold increase above the Tg. They also exhibited a 3-10 °C increase in the glass transition temperature. The aromatic diamine surface modified epoxy/CNT nanocomposites resulted in the largest increase in shear moduli below and above the Tg and the largest increase in the Tg. Surface examination of the nanocomposites with scanning electron microscopy (SEM) revealed indications of a greater adhesion of the epoxy resin matrix to the CNT, most likely due to the covalent bonding.

The influence of surface integrin binding patterns on specific biomaterial-cell interactions

NASA Astrophysics Data System (ADS)

Beranek, Maggi Marie

As the future of biomaterials progresses toward bioactivity, the biomaterial surface must control non-specific protein adsorption and encourage selective protein and cell adsorption. Integrins alphavbeta3, alpha 1beta1, alpha5beta1 and alpha Mbeta2 are expressed on cells involved in endothelialization, inflammation, and intimal hyperplasia. These cellular events play a vital role in biomaterial biocompatibility, especially in the vascular environment. The overall hypothesis of these studies is that biomaterial surfaces exhibit selective integrin binding, which then specifies differential cell binding. To test this hypothesis, four specific aims were developed. The first aim was designed to determine whether metal and polymeric biomaterials exhibit selective integrin binding. The tested materials included 316L stainless steel, nitinol, gold, Elgiloy RTM, poly(D, L-lactide-co-glycolide), polycarbonate urethane and expanded polytetrafluoroethylene. Discrete integrin binding patterns were detected microscopically using integrin specific fluorescent antibodies. Stainless steel exhibited high level integrin alpha1beta 1 and low level integrin alphaMbeta2 binding pattern. This suggests that this metal surface should selectively encourage endothelial cell to inflammatory cell binding. In contrast, gold bound ten times the amount of integrin alphaMbeta2 compared to integrin alpha1beta1, which should encourage inflammatory cell adhesion. The 65/35 poly(D, L-lactide-co-glycolide) was the only polymeric biomaterial tested that had integrin binding levels comparable to metal biomaterials. Based on these observations, a combinational biomaterial with a surface pattern of 65/35 poly(D, L-lactide-co-glycolide) dots on a 316L stainless steel background was created. A pattern of high level integrin alpha1beta1 binding and low level integrin alpha Mbeta2 binding on this combinational surface indicates that this surface should selectively favor endothelial cell binding. In the second aim, the response of surface-bound integrins to flow-related shear stress was examined. Based on fluorescent analysis, total alphavbeta 3, alpha1beta1, and alpha5beta 1 appeared to increase on stainless steel after 90-minute low shear stress exposure, whereas only alpha5beta1 appeared to increase when exposed to high shear. 65/35 poly(D, L-lactide-co-glycolide) exhibited increased total binding of alpha5beta1 and alphaMbeta2, when exposed to either shear stress level. Exposure to either shear stress regimen appeared to increase binding of all integrins on the combinational surface. These responses to shear stress suggest differential integrin binding affinity compared to stainless steel. Using antibodies specific to the integrin subunits, the apparent increase in surface-bound integrins was found to be related to a surface disassociation of alpha and beta subunits. The third aim evaluated human aortic endothelial cells and acute monocytic leukemia cells (THP-1) cell binding to the tested biomaterial surfaces under both static and flow conditions. Both stainless steel and the combinational surface had increased endothelial cell binding compared to monocyte attachment. Pre-incubation of the surface with the specific integrins significantly inhibited human aortic endothelial cell binding. Aim four was designed to investigate the influence of surface bound integrins on human aortic endothelial cell migration under shear stress. If biomaterial surface integrin binding patterns are specific, then pre-bound surface integrins should competitively inhibit binding of cellular integrins to the surface. Cell migration distance on to alphavbeta3, alpha 1beta1, and alpha5beta1 pre-incubated stainless steel was decreased ten-fold, and decreased by three-fold on both 65/35 poly(D, L-lactide-coglycolide) and combinational surfaces compared to the respective bare surfaces. In contrast, migration distance on to alphaMbeta2 pre-coated stainless steel and combinational surface was decreased by only sixty percent and only fifty percent on alphaMbeta2 precoated 65/35 poly(D, L -lactide-co-glycolide). These results suggested that surface binding sites are selective and critical in governing endothelial cell migration. In conclusion, these results support the hypothesis that a surface that encourages specific integrin binding would promote differential cell binding. The novel integrin binding model used in this investigation may be a methodology that can be employed to evaluate potential vascular biomaterials.

Use of radiation in biomaterials science

NASA Astrophysics Data System (ADS)

Benson, Roberto S.

2002-05-01

Radiation is widely used in the biomaterials science for surface modification, sterilization and to improve bulk properties. Radiation is also used to design of biochips, and in situ photopolymerizable of bioadhesives. The energy sources most commonly used in the irradiation of biomaterials are high-energy electrons, gamma radiation, ultraviolet (UV) and visible light. Surface modification involves placement of selective chemical moieties on the surface of a material by chemical reactions to improve biointeraction for cell adhesion and proliferation, hemocompatibility and water absorption. The exposure of a polymer to radiation, especially ionizing radiation, can lead to chain scission or crosslinking with changes in bulk and surface properties. Sterilization by irradiation is designed to inactivate most pathogens from the surface of biomedical devices. An overview of the use of gamma and UV radiation to improve surface tissue compatibility, bulk properties and surface properties for wear resistance, formation of hydrogels and curing dental sealants and bone adhesives is presented. Gamma and vacuum ultraviolet (VUV) irradiated ultrahigh molecular weight polyethylene (UHMWPE) exhibit improvement in surface modulus and hardness. The surface modulus and hardness of UHMWPE showed a dependence on type of radiation, dosage and processing. VUV surface modified e-PTFE vascular grafts exhibit increases in hydrophilicity and improvement towards adhesion of fibrin glue.

Pyrrole-regulated precipitation of titania nanorods on polymer fabrics for photocatalytic degradation of trace toluene in air

NASA Astrophysics Data System (ADS)

Gu, Yi-Jie; Wen, Wei; Xu, Yang; Wu, Jin-Ming

2018-03-01

When compared with nanoparticulate counterparts, TiO2 thin films with vertically aligned one-dimensional (1D) nanostructures exhibit enhanced photocatalytic activity because of the highly accessible surface area. The perpendicular of the 1D nanostructure reduces the charge migration path and hence the carrier recombination rate, which also contributes to the photocatalytic activity. Furthermore, TiO2 thin films on flexible substrates are more suitable to degrade pollutants in either water or air because of its easy recovery and free-bending shape. In this study, flexible polyethylene fabrics were firstly coated with a sol-gel nanoparticulate TiO2 seed layer. Quasi-aligned TiO2 nanorods were then precipitated homogeneously under an atmospheric pressure and a low temperature not exceeding 80 °C, using a peroxy-titanium complex precursor with the additive of pyrrole. It is found that the density of TiO2 nanorods increased with the increasing amount of pyrrole monomers. The resultant TiO2 film on polyethylene fabrics exhibited a much reduced band gap of ca. 2.86 eV, which can be attributed to the surface oxygen deficiencies. When utilized to assist photocatalytic degradation of trace toluene in air under the UV light illumination, the TiO2 film exhibited a gradually increased photocatalytic activity upon the increasing cycles for up to six, because of the gradual removal of trace organics on the TiO2 surface. The highest photocatalytic efficiency is recorded to be 5 times that of TiO2 nanotube arrays, which are regarded as an excellent photocatalyst for air cleaning.

The effects of ultrasonic nanocrystal surface modification temperature on the mechanical properties and fretting wear resistance of Inconel 690 alloy

NASA Astrophysics Data System (ADS)

Amanov, A.; Umarov, R.

2018-05-01

In this study, a combination of local heat treatment (LHT) with (w/) and without (w/o) ultrasonic nanocrystal surface modification (UNSM) technique was applied to Inconel 690 alloy at room and high temperatures (RT and HT). The main purpose of this study is to investigate the influence of LHT w/ and w/o UNSM processing on the mechanical and fretting wear mitigation of Inconel 690 alloy. The surface roughness of the specimens was increased with increasing the LHT temperature w/ and w/o UNSM from RT to HT at 700 °C, while the surface hardness of the RT and HT at 300 °C specimens was increased and softening occurred at HT at 700 °C. The mechanical properties of the specimens were investigated using a tensile stress test. It was found that the stress-strain curve of the UNSM-treated at RT exhibited better mechanical characteristics in comparison with the as-received one. Moreover, the specimens treated at HT at 300 and 700 °C exhibited better results in terms of strain, but there was no significant difference in stress. The UNSM treated specimens at HT of 300 °C had better results in comparison with other specimens. In addition, the fretting wear resistance of those specimens was assessed using a ball-on-disk fretting wear tester at temperatures of 25 and 80 °C. The fretting wear resistance of Inconel 690 alloy was also increased by the combination of LHT + UNSM processing, which may be attributed to the increase in mechanical properties, increase in surface roughness, induced compressive residual stress and the presence of a nanostructured surface layer. Hence, Inconel 690 alloy with the increased mechanical properties and fretting wear resistance by the combination of LHT + UNSM processing could be beneficial for nuclear applications.

Effects and mechanism on Kapton film under ozone exposure in a ground near space simulator

NASA Astrophysics Data System (ADS)

Wei, Qiang; Yang, Guimin; Liu, Gang; Jiang, Haifu; Zhang, Tingting

2018-05-01

The effect on aircraft materials in the near space environment is a key part of air-and-space integration research. Ozone and aerodynamic fluids are important organizational factors in the near space environment and both have significant influences on the performance of aircraft materials. In the present paper a simulated ozone environment was used to test polyimide material that was rotated at the approximate velocity of 150-250 m/s to form an aerodynamic fluid field. The goal was to evaluate the performance evolution of materials under a comprehensive environment of ozone molecular corrosion and aerodynamic fluids. The research results show that corrosion and sputtering by ozone molecules results in Kapton films exhibiting a rugged "carpet-like" morphology exhibits an increase in surface roughness. The morphology after ozone exposure led to higher surface roughness and an increase in surface optical diffuse reflection, which is expressed by the lower optical transmittance and the gradual transition from light orange to brown. The mass loss test, XPS, and FTIR analysis show that the molecular chains on the surface of the Kapton film are destroyed resulting in Csbnd C bond breaking to form small volatile molecules such as CO2 or CO, which are responsible for a linear increase in mass loss per unit area. The Csbnd N and Csbnd O structures exhibit weakening tendency under ozone exposure. The present paper explores the evaluation method for Kapton's adaptability under the ozone exposure test in the near space environment, and elucidates the corrosion mechanism and damage mode of the polyimide material under the combined action of ozone corrosion and the aerodynamic fluid. This work provides a methodology for studying materials in the near-space environment.

Effect of Interfacial Microstructures on the Bonding Strength of Sn-3.0Ag-0.5Cu Pb-Free Solder Bump

NASA Astrophysics Data System (ADS)

Kim, Jae-Myeong; Jeong, Myeong-Hyeok; Yoo, Sehoon; Park, Young-Bae

2012-05-01

The effect of interfacial microstructures on the bonding strength of Sn-3.0Ag-0.5Cu Pb-free solder bumps with respect to the loading speed, annealing time, and surface finish was investigated. The shear strength increased and the ductility decreased with increasing shear speed, primarily because of the time-independent plastic hardening and time-dependent strain-rate sensitivity of the solder alloy. The shear strength and toughness decreased for all surface finishes under the high-speed shear test of 500 mm/s as a result of increasing intermetallic compound (IMC) growth and pad interface weakness associated with increased annealing time. The immersion Sn and organic solderability preservative (OSP) finishes showed lower shear strength compared to the electroless nickel immersion gold (ENIG) finish. With increasing annealing time, the ENIG finish exhibited the pad open fracture mode, whereas the immersion Sn and OSP finishes exhibited the brittle fracture mode. In addition, the shear strength of the solder joints was correlated with each fracture mode.

Adsorption of organic molecules on a porous polymer surface modified with the supramolecular structure of melamine-cyanuric acid

NASA Astrophysics Data System (ADS)

Gainullina, Yu. Yu.; Guskov, V. Yu.

2017-10-01

The adsorption of organic molecules on the surface of a porous polymeric sorbent modified with a mixed cyanuric acid-melamine supramolecular structure is studied. The parameters of thermodynamic adsorption are considered and the contributions from intermolecular interactions to the Helmholtz energy of adsorption are assessed. Analysis of the molar changes in internal energy and adsorption entropy shows that the supramolecular structure formed on the surface could not exhibit dimension effects, indicating there were no cavities. The contributions from nonspecific interactions to the Helmholtz energy of adsorption generally fall, while those of specific interactions increase, indicating an increase in the polarity of the sorbent surface.

Effect of Hot Isostatic Pressing and Powder Feedstock on Porosity, Microstructure, and Mechanical Properties of Selective Laser Melted AlSi10Mg

DOE PAGES

Finfrock, Christopher B.; Exil, Andrea; Carroll, Jay D.; ...

2018-06-06

AlSi10Mg tensile bars were additively manufactured using the powder-bed selective laser melting process. Samples were subjected to stress relief annealing and hot isostatic pressing. Tensile samples built using fresh, stored, and reused powder feedstock were characterized for microstructure, porosity, and mechanical properties. Fresh powder exhibited the best mechanical properties and lowest porosity while stored and reused powder exhibited inferior mechanical properties and higher porosity. The microstructure of stress relieved samples was fine and exhibited (001) texture in the z-build direction. Microstructure for hot isostatic pressed samples was coarsened with fainter (001) texture. To investigate surface and interior defects, scanning electronmore » microscopy, optical fractography, and laser scanning microscopy techniques were employed. Hot isostatic pressing eliminated internal pores and reduced the size of surface porosity associated with the selective laser melting process. Hot isostatic pressing tended to increase ductility at the expense of decreasing strength. Furthermore, scatter in ductility of hot isostatic pressed parts suggests that the presence of unclosed surface porosity facilitated fracture with crack propagation inward from the surface of the part.« less

Effect of Hot Isostatic Pressing and Powder Feedstock on Porosity, Microstructure, and Mechanical Properties of Selective Laser Melted AlSi10Mg

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

Finfrock, Christopher B.; Exil, Andrea; Carroll, Jay D.

AlSi10Mg tensile bars were additively manufactured using the powder-bed selective laser melting process. Samples were subjected to stress relief annealing and hot isostatic pressing. Tensile samples built using fresh, stored, and reused powder feedstock were characterized for microstructure, porosity, and mechanical properties. Fresh powder exhibited the best mechanical properties and lowest porosity while stored and reused powder exhibited inferior mechanical properties and higher porosity. The microstructure of stress relieved samples was fine and exhibited (001) texture in the z-build direction. Microstructure for hot isostatic pressed samples was coarsened with fainter (001) texture. To investigate surface and interior defects, scanning electronmore » microscopy, optical fractography, and laser scanning microscopy techniques were employed. Hot isostatic pressing eliminated internal pores and reduced the size of surface porosity associated with the selective laser melting process. Hot isostatic pressing tended to increase ductility at the expense of decreasing strength. Furthermore, scatter in ductility of hot isostatic pressed parts suggests that the presence of unclosed surface porosity facilitated fracture with crack propagation inward from the surface of the part.« less

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.

Nonlinear Wavelength Selection in Surface Faceting under Electromigration

NASA Astrophysics Data System (ADS)

Barakat, Fatima; Martens, Kirsten; Pierre-Louis, Olivier

2012-08-01

We report on the control of the faceting of crystal surfaces by means of surface electromigration. When electromigration reinforces the faceting instability, we find perpetual coarsening with a wavelength increasing as t1/2. For strongly stabilizing electromigration, the surface is stable. For weakly stabilizing electromigration, a cellular pattern is obtained, with a nonlinearly selected wavelength. The selection mechanism is not caused by an instability of steady states, as suggested by previous works in the literature. Instead, the dynamics is found to exhibit coarsening before reaching a continuous family of stable nonequilibrium steady states.

Surface critical behavior of thin Ising films at the ‘special point’

NASA Astrophysics Data System (ADS)

Moussa, Najem; Bekhechi, Smaine

2003-03-01

The critical surface phenomena of a magnetic thin Ising film is studied using numerical Monte-Carlo method based on Wolff cluster algorithm. With varying the surface coupling, js= Js/ J, the phase diagram exhibits a special surface coupling jsp at which all the films have a unique critical temperature Tc for an arbitrary thickness n. In spite of this, the critical exponent of the surface magnetization at the special point is found to increase with n. Moreover, non-universal features as well as dimensionality crossover from two- to three-dimensional behavior are found at this point.

Reverse Non-Equilibrium Molecular Dynamics Demonstrate That Surface Passivation Controls Thermal Transport at Semiconductor-Solvent Interfaces.

PubMed

Hannah, Daniel C; Gezelter, J Daniel; Schaller, Richard D; Schatz, George C

2015-06-23

We examine the role played by surface structure and passivation in thermal transport at semiconductor/organic interfaces. Such interfaces dominate thermal transport in semiconductor nanomaterials owing to material dimensions much smaller than the bulk phonon mean free path. Utilizing reverse nonequilibrium molecular dynamics simulations, we calculate the interfacial thermal conductance (G) between a hexane solvent and chemically passivated wurtzite CdSe surfaces. In particular, we examine the dependence of G on the CdSe slab thickness, the particular exposed crystal facet, and the extent of surface passivation. Our results indicate a nonmonotonic dependence of G on ligand-grafting density, with interfaces generally exhibiting higher thermal conductance for increasing surface coverage up to ∼0.08 ligands/Å(2) (75-100% of a monolayer, depending on the particular exposed facet) and decreasing for still higher coverages. By analyzing orientational ordering and solvent penetration into the ligand layer, we show that a balance of competing effects is responsible for this nonmonotonic dependence. Although the various unpassivated CdSe surfaces exhibit similar G values, the crystal structure of an exposed facet nevertheless plays an important role in determining the interfacial thermal conductance of passivated surfaces, as the density of binding sites on a surface determines the ligand-grafting densities that may ultimately be achieved. We demonstrate that surface passivation can increase G relative to a bare surface by roughly 1 order of magnitude and that, for a given extent of passivation, thermal conductance can vary by up to a factor of ∼2 between different surfaces, suggesting that appropriately tailored nanostructures may direct heat flow in an anisotropic fashion for interface-limited thermal transport.

Photonic crystal surface-emitting lasers

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

Chua, Song Liang; Lu, Ling; Soljacic, Marin

2015-06-23

A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-planemore » feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.« less

The effects of surface wettability on the fog and dew moisture harvesting performance on tubular surfaces

PubMed Central

Seo, Donghyun; Lee, Junghun; Lee, Choongyeop; Nam, Youngsuk

2016-01-01

The efficient water harvesting from air-laden moisture has been a subject of great interest to address world-wide water shortage issues. Recently, it has been shown that tailoring surface wettability can enhance the moisture harvesting performance. However, depending on the harvesting condition, a different conclusion has often been reported and it remains unclear what type of surface wettability would be desirable for the efficient water harvesting under the given condition. Here we compare the water harvesting performance of the surfaces with various wettability under two different harvesting conditions–dewing and fogging, and show that the different harvesting efficiency of each surface under these two conditions can be understood by considering the relative importance of the water capturing and removal efficiency of the surface. At fogging, the moisture harvesting performance is determined by the water removal efficiency of the surface with the oil-infused surfaces exhibiting the best performance. Meanwhile, at dewing, both the water capturing and removal efficiency are crucial to the harvesting performance. And well-wetting surfaces with a lower barrier to nucleation of condensates exhibit a better harvesting performance due to the increasing importance of the water capture efficiency over the water removal efficiency at dewing. PMID:27063149

Controlled preparation of Ag–Cu{sub 2}O nanocorncobs and their enhanced photocatalytic activity under visible light

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

Yang, Siyuan; Zhang, Shengsen; College of Science, South China Agricultural University, Guangzhou 510642

Graphical abstract: The corncob-like Ag–Cu{sub 2}O nanostructure with suitably exposed Ag surface exhibited much higher photocatalytic activity than Ag@Cu{sub 2}O nanocables and Cu{sub 2}O nanowires. - Highlights: • Ag–Cu{sub 2}O nanocorncobs have been controllably prepared by a simple synthesis. • The possible formation mechanism of Ag–Cu{sub 2}O has been studied. • Ag–Cu{sub 2}O exhibits noticeable improved photocurrent compared with the pure Cu{sub 2}O NWs. • Ag–Cu{sub 2}O with suitably exposed Ag surface shows much higher photocatalytic activity. - Abstract: Novel corncob-like nano-heterostructured Ag–Cu{sub 2}O photocatalyst has been controllably prepared by adjusting the synthetic parameters, and the possible formation mechanism hasmore » been also studied. The photoelectrochemical and photocatalytic performances demonstrated that the as-prepared Ag–Cu{sub 2}O nanocorncobs exhibited higher photocatalytic activity than both pure Cu{sub 2}O nanowires and cable-like Ag@Cu{sub 2}O nano-composites. It was concluded that Ag–Cu{sub 2}O nanocorncobs with suitably exposed Ag surface not only effectively inhibit the recombination of electron–hole pairs but also suitably increase the active sites of electronic conduction, and thus increasing the photocatalytic activity under visible light irradiation.« less

Near-infrared-emitting colloidal Ag2S quantum dots exhibiting upconversion luminescence

NASA Astrophysics Data System (ADS)

Zhang, Yanyan; Jiang, Danyu; Yang, Wei; Wang, Dandan; Zheng, Huiping; Du, Yuansheng; Li, Xi; Li, Qiang

2017-02-01

Ag2S quantum dots (QDs) coated with thioglycolic acid (Ag2S QDs-TGA) have been synthesized in an organic solvent via a stepwise addition of reagents. When excited by a 980 nm laser, the near-infrared-emitting colloidal Ag2S QDs-TGA exhibit upconversion luminescence (UCL). The observed photoluminescence (PL) was attributed to the presence of ligand-modified Ag2S on the QD surfaces. Hence, upon dilution of the solution, the PL intensity initially increased before subsequently decreasing, accompanied by a blue shift in the PL spectra. The PL phenomena can be attributed to the increase in the amount of ligand-modified Ag2S on the QD surfaces upon dilution, which in turn affected the fluorescence resonance energy transfer (FRET) and re-emission of the surface energy level. The relations between the emission intensity of Ag2S QDs-TGA and the excitation power are investigated, and the results confirm that the UCL in Ag2S QDs-TGA can be ascribed to a two-photon-assisted absorption process via a real energy state.

Surface tension and density of Si-Ge melts

NASA Astrophysics Data System (ADS)

Ricci, Enrica; Amore, Stefano; Giuranno, Donatella; Novakovic, Rada; Tuissi, Ausonio; Sobczak, Natalia; Nowak, Rafal; Korpala, Bartłomiej; Bruzda, Grzegorz

2014-06-01

In this work, the surface tension and density of Si-Ge liquid alloys were determined by the pendant drop method. Over the range of measurements, both properties show a linear temperature dependence and a nonlinear concentration dependence. Indeed, the density decreases with increasing silicon content exhibiting positive deviation from ideality, while the surface tension increases and deviates negatively with respect to the ideal solution model. Taking into account the Si-Ge phase diagram, a simple lens type, the surface tension behavior of the Si-Ge liquid alloys was analyzed in the framework of the Quasi-Chemical Approximation for the Regular Solutions model. The new experimental results were compared with a few data available in the literature, obtained by the containerless method.

Estrogen and androgen receptor activities of hydraulic fracturing chemicals and surface and ground water in a drilling-dense region

USGS Publications Warehouse

Kassotis, Christopher D.; Tillitt, Donald E.; Davis, J. Wade; Hormann, Anette M.; Nagel, Susan C.

2014-01-01

The rapid rise in natural gas extraction using hydraulic fracturing increases the potential for contamination of surface and ground water from chemicals used throughout the process. Hundreds of products containing more than 750 chemicals and components are potentially used throughout the extraction process, including more than 100 known or suspected endocrine-disrupting chemicals. We hypothesized thataselected subset of chemicalsusedin natural gas drilling operationsandalso surface and ground water samples collected in a drilling-dense region of Garfield County, Colorado, would exhibit estrogen and androgen receptor activities. Water samples were collected, solid-phase extracted, and measured for estrogen and androgen receptor activities using reporter gene assays in human cell lines. Of the 39 unique water samples, 89%, 41%, 12%, and 46% exhibited estrogenic, antiestrogenic, androgenic, and antiandrogenic activities, respectively. Testing of a subset of natural gas drilling chemicals revealed novel antiestrogenic, novel antiandrogenic, and limited estrogenic activities. The Colorado River, the drainage basin for this region, exhibited moderate levels of estrogenic, antiestrogenic, and antiandrogenic activities, suggesting that higher localized activity at sites with known natural gas–related spills surrounding the river might be contributing to the multiple receptor activities observed in this water source. The majority of water samples collected from sites in a drilling-dense region of Colorado exhibited more estrogenic, antiestrogenic, or antiandrogenic activities than reference sites with limited nearby drilling operations. Our data suggest that natural gas drilling operationsmayresult in elevated endocrine-disrupting chemical activity in surface and ground water.

Diffusion of GPI-anchored proteins is influenced by the activity of dynamic cortical actin

PubMed Central

Saha, Suvrajit; Lee, Il-Hyung; Polley, Anirban; Groves, Jay T.; Rao, Madan; Mayor, Satyajit

2015-01-01

Molecular diffusion at the surface of living cells is believed to be predominantly driven by thermal kicks. However, there is growing evidence that certain cell surface molecules are driven by the fluctuating dynamics of cortical cytoskeleton. Using fluorescence correlation spectroscopy, we measure the diffusion coefficient of a variety of cell surface molecules over a temperature range of 24–37°C. Exogenously incorporated fluorescent lipids with short acyl chains exhibit the expected increase of diffusion coefficient over this temperature range. In contrast, we find that GPI-anchored proteins exhibit temperature-independent diffusion over this range and revert to temperature-dependent diffusion on cell membrane blebs, in cells depleted of cholesterol, and upon acute perturbation of actin dynamics and myosin activity. A model transmembrane protein with a cytosolic actin-binding domain also exhibits the temperature-independent behavior, directly implicating the role of cortical actin. We show that diffusion of GPI-anchored proteins also becomes temperature dependent when the filamentous dynamic actin nucleator formin is inhibited. However, changes in cortical actin mesh size or perturbation of branched actin nucleator Arp2/3 do not affect this behavior. Thus cell surface diffusion of GPI-anchored proteins and transmembrane proteins that associate with actin is driven by active fluctuations of dynamic cortical actin filaments in addition to thermal fluctuations, consistent with expectations from an “active actin-membrane composite” cell surface. PMID:26378258

Rapid and Clean Covalent Attachment of Methylsiloxane Polymers and Oligomers to Silica Using B(C6F5)3 Catalysis.

PubMed

Flagg, Daniel H; McCarthy, Thomas J

2017-08-22

The rapid, room-temperature covalent attachment of alkylhydridosilanes (R 3 Si-H) to silicon oxide surfaces to form monolayers using tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 , BCF) catalysis has recently been described. This method, unlike alternative routes to monolayers, produces only unreactive H 2 gas as a byproduct and reaches completion within minutes. We report the use of this selective reaction between surface silanols and hydridosilanes to prepare surface-grafted poly(dimethylsiloxane)s (PDMSs) with various graft architectures that are controlled by the placement of hydridosilane functionality at one end, both ends, or along the chain of PDMS samples of controlled molecular weight. We also report studies of model methylsiloxane monolayers prepared from pentamethyldisiloxane, heptamethyltrisiloxane (two isomers), heptamethylcyclotetrasiloxane, and tris(trimethylsiloxy)silane. These modified silica surfaces with structurally defined methylsiloxane groups are not accessible by conventional silane surface chemistry and proved to be useful in exploring the steric limitations of the reaction. Linear monohydride- and dihydride-terminated PDMS-grafted surfaces exhibit increasing thickness and decreasing contact angle hysteresis with increasing molecular weight up to a particular molecular weight value. Above this value, the hysteresis increases with increasing molecular weight of end-grafted polymers. Poly(hydridomethyl-co-dimethylsiloxane)s with varied hydride content (3-100 mol %) exhibit decreasing thickness, decreasing contact angle, and increasing contact angle hysteresis with increasing hydride content. These observations illustrate the importance of molecular mobility in three-phase contact line dynamics on low-hysteresis surfaces. To calibrate our preparative procedure against both monolayers prepared by conventional approaches as well as the recent reports, a series of trialkylsilane (mostly, n-alkyldimethylsilane) monolayers was prepared to determine the reaction time required to achieve the maximum bonding density using dynamic contact angle analysis. Monolayers prepared from hydridosilanes with BCF catalysis have lower bonding densities than those derived from chlorosilanes, and the reactions are more sensitive to alkyl group sterics. This lower bonding density renders greater flexibility to the n-alkyl groups in monolayers and can decrease the contact angle hysteresis.

Synthesis of antireflective silica coatings through the synergy of polypeptide layer-by-layer assemblies and biomineralization

NASA Astrophysics Data System (ADS)

Lee, Yung-Lun; Lin, Ting-Xuan; Hsu, Feng-Ming; Jan, Jeng-Shiung

2016-01-01

We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting more than 6% increase in transmittance in the near UV/visible spectral range can be obtained at an optimized refractive index, thickness, and surface roughness. The abrasion test showed that the silica coatings exhibited sufficient structural durability due to continuous silica nanostructures and low surface roughness. This study demonstrated that nanostructured thin films can be synthesized for AR coatings using the synergy between the LbL assembly technique and biomineralization.We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting more than 6% increase in transmittance in the near UV/visible spectral range can be obtained at an optimized refractive index, thickness, and surface roughness. The abrasion test showed that the silica coatings exhibited sufficient structural durability due to continuous silica nanostructures and low surface roughness. This study demonstrated that nanostructured thin films can be synthesized for AR coatings using the synergy between the LbL assembly technique and biomineralization. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06948c

Use of Several Thermal Analysis Techniques to Study the Cracking of an Nitrile Butadiene Rubber (NBR) Insulator on the Booster Separation Motor (BSM) of the Space Shuttle

NASA Technical Reports Server (NTRS)

Wingard, Charles D.; Whitaker, Ann F. (Technical Monitor)

2000-01-01

Two different vendor rubber formulations have been used to produce the silica-filled NBR insulators for the BSM used on both of the Solid Rocket Boosters (SRBs) of the Space Shuttle. A number of lots of the BSM insulator in 1998-99 exhibited surface cracks and/or crazing. Each insulator is bonded to the BSM aluminum aft closure with an epoxy adhesive. Induced insulator stresses from adhesive cure are likely greatest where the insulator/adhesive contour is the greatest, thus showing increased insulator surface cracking in this area. Thermal analysis testing by Dynamic Mechanical Analyzer (DMA) and Thermomechanical Analysis (TMA) was performed on one each of the two vendor BSM insulators previously bonded that exhibited the surface cracking. The TMA data from the film/fiber technique yielded the most meaningful results, with thin insulator surface samples containing cracks having roughly the same modulus (stiffness) as thin insulator bulk samples just underneath.

Shear strength of metal-sapphire contacts

NASA Technical Reports Server (NTRS)

Pepper, S. V.

1976-01-01

The shear strength of polycrystalline Ag, Cu, Ni, and Fe contacts on clean (0001) sapphire has been studied in ultrahigh vacuum. Both clean metal surfaces and surfaces exposed to O2, Cl2, and C2H4 were used. The results indicate that there are two sources of strength of Al2O3-metal contacts: an intrinsic one that depends on the particular clean metal in contact with Al2O3 and an additional one due to intermediate films. The shear strength of the clean metal contacts correlated directly with the free energy of oxide formation for the lowest metal oxide, in accord with the hypothesis that a chemical bond is formed between metal cations and oxygen anions in the sapphire surface. Contacts formed by metals exposed to chlorine exhibited uniformly low shear strength indicative of van der Waals bonding between chlorinated metal surfaces and sapphire. Contacts formed by metals exposed to oxygen exhibited enhanced shear strength, in accord with the hypothesis that an intermediate oxide layer increases interfacial strength.

Round-patterned ZnO nanostructure coated with siloxane-based polymer for nerve agent detection

NASA Astrophysics Data System (ADS)

Choi, Hyun Ji; Lee, Ji Won; Jeong, Dong-Cheol; Ha, Seonggyun; Song, Changsik; Boo, Jin-Hyo

2018-01-01

The alignment of zinc oxide (ZnO) nanostructures is expected to improve device sensitivities due to large surface areas which can be utilized to capture significant quantities of gas particles. In this study, we investigated patterned ZnO nanorods modified with polystyrene monolayers synthesized directly onto a quartz crystal microbalance (QCM) cell to increase the coating surface area of the sensing material. Also, we designed and synthesized a siloxane-based polymer (S1 polymer) as a sensing material. The patterned ZnO nanorods coated with S1 polymers were fabricated and used for the detection of dimethyl methylphosphonate (DMMP). The resonance frequency of QCM was shifted due to the adsorption and desorption of a compound at the surface of the modified electrodes. We have synthesized an S1 polymer that exhibited high sensitivity to DMMP. The patterned ZnO nanorods coated with the polymer also exhibited improved sensitivity due to an enhanced surface area capable of adsorbing more DMMP vapor.

Engineering Surface Energy and Nanostructure of Microporous Films for Expanded Membrane Distillation Applications.

PubMed

Boo, Chanhee; Lee, Jongho; Elimelech, Menachem

2016-08-02

We investigated the factors that determine surface omniphobicity of microporous membranes and evaluated the potential application of these membranes in desalination of low surface tension wastewaters by membrane distillation (MD). Specifically, the effects of surface morphology and surface energy on membrane surface omniphobicity were systematically investigated by evaluating wetting resistance to low surface tension liquids. Single and multilevel re-entrant structures were achieved by using cylindrical glass fibers as a membrane substrate and grafting silica nanoparticles (SiNPs) on the fibers. Surface energy of the membrane was tuned by functionalizing the fiber substrate with fluoroalkylsilane (FAS) having two different lengths of fluoroalkyl chains. Results show that surface omniphobicity of the modified fibrous membrane increased with higher level of re-entrant structure and with lower surface energy. The secondary re-entrant structure achieved by SiNP coating on the cylindrical fibers was found to play a critical role in enhancing the surface omniphobicity. Membranes coated with SiNPs and chemically modified by the FAS with a longer fluoroalkyl chain (or lower surface energy) exhibited excellent surface omniphobicity and showed wetting resistance to low surface tension liquids such as ethanol (22.1 mN m(-1)). We further evaluated performance of the membranes in desalination of saline feed solutions with varying surface tensions by membrane distillation (MD). The engineered membranes exhibited stable MD performance with low surface tension feed waters, demonstrating the potential application omniphobic membranes in desalinating complex, high salinity industrial wastewaters.

Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

NASA Astrophysics Data System (ADS)

Wang, Jingjing; Wei, Jun

2016-09-01

Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

Outstanding catalytic activity of ultra-pure platinum nanoparticles.

PubMed

Januszewska, Aneta; Dercz, Grzegorz; Piwowar, Justyna; Jurczakowski, Rafal; Lewera, Adam

2013-12-09

Small (4 nm) nanoparticles with a narrow size distribution, exceptional surface purity, and increased surface order, which exhibits itself as an increased presence of basal crystallographic planes, can be obtained without the use of any surfactant. These nanoparticles can be used in many applications in an as-received state and are threefold more active towards a model catalytic reaction (oxidation of ethylene glycol). Furthermore, the superior properties of this material are interesting not only due to the increase in their intrinsic catalytic activity, but also due to the exceptional surface purity itself. The nanoparticles can be used directly (i.e., as-received, without any cleaning steps) in biomedical applications (i.e., as more efficient drug carriers due to an increased number of adsorption sites) and in energy-harvesting/data-storage devices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carefully designed oxygen-containing functional groups and defects of porous carbon spheres with UV-O3 treatment and their enhanced catalytic performance

NASA Astrophysics Data System (ADS)

Han, Weiliang; Huang, Xiaosheng; Lu, Gongxuan; Tang, Zhicheng

2018-04-01

In this paper, the support surface properties (surface oxygen-containing functional groups and structure defects) of porous carbon spheres (PCSs) were carefully designed by as UV assisted O3 technology. CO catalytic oxidation reactions performed over the supported Pd-Ce catalysts on modified porous carbon spheres. Results illustrated that the Pd-Ce/PCSs catalysts exhibited high CO catalytic activity, which were increased at first, and then decreased with UV assistant-O3 treatment time. The Pd-Ce/PCSs-30 catalyst exhibited superior activity and T100 was only 15 °C. Moreover, the Pd-Ce/PCSs-30 catalyst obtained an excellent stability, and 100% CO conversion could be maintained as the time on stream evolutes up to 16h in the presence of H2O in the feed. Based on characterization results, there were two main factors: (a) the surface area and pore volume were decreased with UV-O3 treatment, leading to the enhancement of Pd-Ce particle size, and the decrease of Pd-Ce nanoparticle dispersion and mass transfer efficiency, as well as the decrease of catalytic activity of Pd-Ce/PCSs, (b) the surface oxygen content and defect sites of PCSs were raised by UV-O3 treatment, which could improve surface loading of Pd, Ce and enhance Pdsbnd Osbnd Ce bonding interactions, thereby increasing the activity of Pd-Ce/PCSs.

Nanocolloids in Natural Water: Isolation, Characterization, and Toxicity.

PubMed

Ouyang, Shaohu; Hu, Xiangang; Zhou, Qixing; Li, Xiaokang; Miao, Xinyu; Zhou, Ruiren

2018-04-17

Nanocolloids are widespread in natural water systems, but their characterization and ecological risks are largely unknown. Herein, tangential flow ultrafiltration (TFU) was used to separate and concentrate nanocolloids from surface waters. Unexpectedly, nanocolloids were present in high concentrations ranging from 3.7 to 7.2 mg/L in the surface waters of the Harihe River in Tianjin City, China. Most of the nanocolloids were 10-40 nm in size, contained various trace metals and polycyclic aromatic hydrocarbons, and exhibited fluorescence properties. Envelopment effects and aggregation of Chlorella vulgaris in the presence of nanocolloids were observed. Nanocolloids entered cells and nanocolloid-exposed cells exhibited stronger plasmolysis, chloroplast damage and more starch grains than the control cells. Moreover, nanocolloids inhibited the cell growth, promoted reactive oxygen species (ROS), reduce the chlorophyll a content and increased the cell permeability. The genotoxicity of nanocolloids was also observed. The metabolomics analysis revealed a significant ( p < 0.05) downregulation of amino acids and upregulation of fatty acids contributing to ROS increase, chlorophyll a decrease and plasmolysis. The present work reveals that nanocolloids, which are different from specific, engineered nanoparticles (e.g., Ag nanoparticles), are present at high concentrations, exhibit an obvious toxicity in environments, and deserve more attention in the future.

Laser irradiation of Mg-Al-Zn alloy: Reduced electrochemical kinetics and enhanced performance in simulated body fluid.

PubMed

Florian, David C; Melia, Michael A; Steuer, Fritz W; Briglia, Bruce F; Purzycki, Michael K; Scully, John R; Fitz-Gerald, James M

2017-05-11

As a lightweight metal with mechanical properties similar to natural bone, Mg and its alloys are great prospects for biodegradable, load bearing implants. However, rapid degradation and H 2 gas production in physiological media has prevented widespread use of Mg alloys. Surface heterogeneities in the form of intermetallic particles dominate the corrosion response. This research shows that surface homogenization significantly improved the biological corrosion response observed during immersion in simulated body fluid (SBF). The laser processed Mg alloy exhibited a 50% reduction in mass loss and H 2 evolution after 24 h of immersion in SBF when compared to the wrought, cast alloy. The laser processed samples exhibited increased wettability as evident from wetting angle studies, further suggesting improved biocompatibility. Electrochemical analysis by potentiodynamic polarization measurements showed that the anodic and cathodic kinetics were reduced following laser processing and are attributed to the surface chemical homogeneity.

Surface wind, pressure and temperature fields near tornadic and non-tornadic narrow cold-frontal rainbands

NASA Astrophysics Data System (ADS)

Clark, Matthew; Parker, Douglas

2014-05-01

Narrow cold frontal rainbands (NCFRs) occur frequently in the UK and other parts of northwest Europe. At the surface, the passage of an NCFR is often marked by a sharp wind veer, abrupt pressure increase and a rapid temperature decrease. Tornadoes and other instances of localised wind damage sometimes occur in association with meso-gamma-scale vortices (sometimes called misocyclones) that form along the zone of abrupt horizontal wind veer (and associated vertical vorticity) at the leading edge of the NCFR. Using one-minute-resolution data from a mesoscale network of automatic weather stations, surface pressure, wind and temperature fields in the vicinity of 12 NCFRs (five of which were tornadic) have been investigated. High-resolution surface analyses were obtained by mapping temporal variations in the observed parameters to equivalent spatial variations, using a system velocity determined by analysis of the radar-observed movement of NCFR precipitation segments. Substantial differences were found in the structure of surface wind and pressure fields close to tornadic and non-tornadic NCFRs. Tornadic NCFRs exhibited a large wind veer (near 90°) and strong pre- and post-frontal winds. These attributes were associated with large vertical vorticity and horizontal convergence across the front. Tornadoes typically occurred where vertical vorticity and horizontal convergence were increasing. Here, we present surface analyses from selected cases, and draw comparisons between the tornadic and non-tornadic NCFRs. Some Doppler radar observations will be presented, illustrating the development of misocyclones along parts of the NCFR that exhibit strong, and increasing, vertical vorticity stretching. The influence of the stability of the pre-frontal air on the likelihood of tornadoes will also be discussed.

Investigation of the effect of Mg doping for improvements of optical and electrical properties

NASA Astrophysics Data System (ADS)

Caglar, Mujdat; Caglar, Yasemin; Ilican, Saliha

2016-03-01

Sol-gel spin coating method was used for the deposition of nanostructured undoped and Mg doped ZnO films. The effects of magnesium incorporation on the crystalline structure were investigated by XRD measurements and the structural deterioration was observed in the crystalline quality of the films with respect to increasing in Mg doping. All the samples exhibited a wurtzite structure. From the scanning electron microscopy (SEM) images obtained to investigate the surface morphology it was detected that an increase in Mg doping caused an improvement on the surface roughness and a reduction in the number of voids on the surface. To evaluate the absorption edges of the produced samples depending on the Mg, different methods were used and according to the obtained results, a shifting towards to high energies for the optical band gap was observed in each method. By using the single oscillator model, developed by DiDomenico and Wemple, the refractive index dispersion of the films was analyzed. Eo and Ed values of the 5% Mg doped film were found to be 5.76 eV and 11.80 eV, respectively. Within the scope of electrical properties, from Hall effect measurements, it was determined that all the films exhibited n-type behavior and the carrier concentration increased from 1.49×1016 to 1.20×1017 cm-3 with increasing Mg doping.

Multifactor analysis and simulation of the surface runoff and soil infiltration at different slope gradients

NASA Astrophysics Data System (ADS)

Huang, J.; Kang, Q.; Yang, J. X.; Jin, P. W.

2017-08-01

The surface runoff and soil infiltration exert significant influence on soil erosion. The effects of slope gradient/length (SG/SL), individual rainfall amount/intensity (IRA/IRI), vegetation cover (VC) and antecedent soil moisture (ASM) on the runoff depth (RD) and soil infiltration (INF) were evaluated in a series of natural rainfall experiments in the South of China. RD is found to correlate positively with IRA, IRI, and ASM factors and negatively with SG and VC. RD decreased followed by its increase with SG and ASM, it increased with a further decrease with SL, exhibited a linear growth with IRA and IRI, and exponential drop with VC. Meanwhile, INF exhibits a positive correlation with SL, IRA and IRI and VC, and a negative one with SG and ASM. INF was going up and then down with SG, linearly rising with SL, IRA and IRI, increasing by a logit function with VC, and linearly falling with ASM. The VC level above 60% can effectively lower the surface runoff and significantly enhance soil infiltration. Two RD and INF prediction models, accounting for the above six factors, were constructed using the multiple nonlinear regression method. The verification of those models disclosed a high Nash-Sutcliffe coefficient and low root-mean-square error, demonstrating good predictability of both models.

SEM/XPS analysis of fractured adhesively bonded graphite fibre-reinforced polyimide composites

NASA Technical Reports Server (NTRS)

Devilbiss, T. A.; Messick, D. L.; Wightman, J. P.; Progar, D. J.

1985-01-01

The surfaces of the graphite fiber-reinforced polyimide composites presently pretreated prior to bonding with polyimide adhesive contained variable amounts of a fluoropolymer, as determined by X-ray photoelectron spectroscopy. Lap shear strengths were determined for unaged samples and for those aged over 500- and 1000-hour periods at 177 and 232 C. Unaged sample lap strengths, which were the highest obtained, exhibited no variation with surface pretreatment, but a significant decrease is noted with increasing aging temperature. These thermally aged samples, however, had increased surface fluorine concentration, while a minimal concentration was found in unaged samples. SEM demonstrated a progressive shift from cohesive to adhesive failure for elevated temperature-aged composites.

Leaf Area Influence on Surface Layer in a Deciduous Forest. Part 2; Detecting Leaf Area and Surface Resistance During Transition Seasons

NASA Technical Reports Server (NTRS)

Sakai, Ricardo K.; Fitzjarrald, David R.; Moore, Kathleen E.; Sicker, John W.; Munger, Willian J.; Goulden, Michael L.; Wofsy, Steven C.

1996-01-01

Temperate deciduous forest exhibit dramatic seasonal changes in surface exchange properties following on the seasonal changes in leaf area index. The canopy resistance to water vapor transport r(sub c) decreased abruptly at leaf emergence in each year but then also continued to decrease slowly during the remaining growing season due to slowly increasing LAI. Canopy resistance and PAR-albedo (albedo from photosynthetically active radiation) began to increase about one month before leaf fall with the diminishment of CO2 gradient above the canopy as well. At this time evaporation begun to be controlled as if the canopy were leafless.

Deposition of Cubic AlN Films on MgO (100) Substrates by Laser Molecular Beam Epitaxy

NASA Astrophysics Data System (ADS)

Mo, Z. K.; Yang, W. J.; Weng, Y.; Fu, Y. C.; He, H.; Shen, X. M.

2017-12-01

Cubic AlN (c-AlN) films were deposited on MgO (100) substrates by laser molecular beam epitaxy (LMBE) technique. The crystal structure and surface morphology of deposited films with various laser pulse energy and substrate temperature were investigated. The results indicate that c-AlN films exhibit the (200) preferred orientation, showing a good epitaxial relationship with the substrate. The surface roughness of c-AlN films increases when the laser pulse energy and substrate temperature increase. The film grown at laser pulse energy of 150 mJ and substrate temperature of 700 °C shows the best crystalline quality and relatively smooth surface.

Hydrogen generation from water/methanol under visible light using aerogel prepared strontium titanate (SrTiO3) nanomaterials doped with ruthenium and rhodium metals

NASA Astrophysics Data System (ADS)

Kuo, Yenting; Klabunde, Kenneth J.

2012-07-01

Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO3 structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh3 + ; however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H2 production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.

Surface design and engineering of hierarchical hybrid nanostructures for asymmetric supercapacitors with improved electrochemical performance.

PubMed

Achilleos, Demetra S; Hatton, T Alan

2015-06-01

With the current rising world demand for energy sufficiency, there is an increased necessity for the development of efficient energy storage devices. To address these needs, the scientific community has focused on the improvement of the electrochemical properties of the most well known energy storage devices; the Li-ion batteries and electrochemical capacitors, also called supercapacitors. Despite the fact that supercapacitors exhibit high power densities, good reversibility and long cycle life, they still exhibit lower energy densities than batteries, which limit their practical application. Various strategies have been employed to circumvent this problem, specifically targetting an increase in the specific capacitance and the broadening of the potential window of operation of these systems. In recent years, sophisticated surface design and engineering of hierarchical hybrid nanostructures has facilitated significant improvements in the specific and volumetric storage capabilities of supercapacitors. These nanostructured electrodes exhibit higher surface areas for ion adsorption and reduced ion diffusion lengths for the electrolyte ions. Significant advances have also been achieved in broadening the electrochemical window of operation of these systems, as realized via the development of asymmetric two-electrode cells consisting of nanocomposite positive and negative electrodes with complementary electrochemical windows, which operate in environmentally benign aqueous media. We provide an overview of the diverse approaches, in terms of chemistry and nanoscale architecture, employed recently for the development of asymmetric supercapacitors of improved electrochemical performance. Copyright © 2014 Elsevier Inc. All rights reserved.

Preparation and characterization of bio-nanocomposite films of agar and silver nanoparticles: laser ablation method.

PubMed

Rhim, Jong-Whan; Wang, Long-Feng; Lee, Yonghoon; Hong, Seok-In

2014-03-15

Silver nanoparticles (AgNPs) were prepared by a laser ablation method and composite films with the AgNPs and agar were prepared by solvent casting method. UV-vis absorbance test and transmission electron microscopy (TEM) analysis results revealed that non-agglomerated spherical AgNPs were formed by the laser ablation method. The surface color of the resulting agar/AgNPs films exhibited the characteristic plasmonic effect of the AgNPs with the maximum absorption peaks of 400-407 nm. X-ray diffraction (XRD) test results also exhibited characteristic AgNPs crystals with diffraction peaks observed at 2θ values of 38.39°, 44.49°, and 64.45°, which were corresponding to (111), (200), and (220) crystallographic planes of face-centered cubic (fcc) silver crystals, respectively. Thermogravimetric analysis (TGA) results showed that thermal stability of the agar/AgNPs composite films was increased by the inclusion of metallic silver. Water vapor barrier properties and surface hydrophobicity of the agar/AgNPs films increased slightly with the increase in AgNPs content but they were not statistically significant (p>0.05), while mechanical strength and stiffness of the composite films decreased slightly (p<0.05). The agar/AgNPs films exhibited distinctive antimicrobial activity against both Gram-positive (Listeria monocytogenes) and Gram-negative (Escherichia coli O157:H7) bacterial pathogens. Copyright © 2014 Elsevier Ltd. All rights reserved.

Novel hydrophobic PDVB/R-SiO2 for adsorption of volatile organic compounds from highly humid gas stream.

PubMed

Lu, Han-feng; Cao, Jie-jing; Zhou, Ying; Zhan, De-li; Chen, Yin-fei

2013-11-15

A novel organic-inorganic hydrophobic polydivinylbenzene-silica adsorbent (PDVB/R-SiO2) was successfully prepared by introducing a specific amount of divinylbenzene and solvent (i.e., tetrahydrofuran) to SiO2pores and initiating polymerization under solvothermal conditions. New smaller structures and surface areas were formed in the SiO2 pores. The PDVB/R-SiO2-0.5 samples exhibited a bimodal pore size distribution with both SiO2 micropores/mesopores (0.5-2.0 nm) and mesopores (2.0-5.0 nm). The surface areas increased from 116 m(2)/g (SiO2) to 246 m(2)/g. The breakthrough curves of toluene adsorption indicated that the amount adsorbed on PDVB/R-SiO2-0.5 was 12 times higher than that on SiO2. The highly humid environment exhibited no effect on adsorption because the surface of PDVB was functionalized. The adsorbed toluene was easily desorbed in hot N2 stream at 100 °C. After 10 adsorption-desorption cycles, PDVB/R-SiO2-0.5 continued exhibiting excellent adsorption, indicating superior structural and regeneration abilities. Copyright © 2013 Elsevier B.V. All rights reserved.

Structural Origin of Enhanced Dynamics at the Surface of a Glassy Alloy

NASA Astrophysics Data System (ADS)

Sun, Gang; Saw, Shibu; Douglass, Ian; Harrowell, Peter

2017-12-01

The enhancement of mobility at the surface of an amorphous alloy is studied using a combination of molecular dynamic simulations and normal mode analysis of the nonuniform distribution of Debye-Waller factors. The increased mobility at the surface is found to be associated with the appearance of Arrhenius temperature dependence. We show that the transverse Debye-Waller factor exhibits a peak at the surface. Over the accessible temperature range, we find that the bulk and surface diffusion coefficients obey the same empirical relationship with the respective Debye-Waller factors. Extrapolating this relationship to lower T , we argue that the observed decrease in the constraint at the surface is sufficient to account for the experimentally observed surface enhancement of mobility.

Fabrication and properties of polyvinyl alcohol/starch blend films: Effect of composition and humidity.

PubMed

Tian, Huafeng; Yan, Jiaan; Rajulu, A Varada; Xiang, Aimin; Luo, Xiaogang

2017-03-01

In this work, starch/polyvinyl alcohol (PVA) blend films with different compositions were prepared by melt processing. The effect of the composition and relative humidity (RH) on the structure and properties of the resulting blends were investigated. OH groups on starch and PVA formed hydrogen bonding interactions, which could improve the compatibility of the two components. With the increase of starch, the degree of crystallinity of PVA component decreased. The fracture surface of the blend films exhibited rough surface, suggesting the tough fracture. With the increase of starch, the water uptake at equilibrium decreased. With the increase of RH, the water uptake at equilibrium of the resulting blends increased. The tensile strength, elongation at break and Young's modulus decreased with increasing content of starch. However, at 50% starch content, the flexibility of the blend films was still high, with the elongation at break more than 1000% and tensile strength of 9MPa, which was superior to the commonly LDPE package films. The tensile strength and Young's modulus decreased with the increase of RH, while the elongation at break was enhanced dramatically, indicating the improved flexibility. Therefore, these kinds of blend films exhibited wide application potentials as packaging materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Calcium influences sensitivity to growth inhibition induced by a cell surface sialoglycopeptide

NASA Technical Reports Server (NTRS)

Betz, N. A.; Fattaey, H. K.; Johnson, T. C.; Spooner, B. S. (Principal Investigator)

1994-01-01

While studies concerning mitogenic factors have been an important area of research for many years, much less is understood about the mechanisms of action of cell surface growth inhibitors. We have purified an 18 kDa cell surface sialoglycopeptide growth inhibitor (CeReS-18) which can reversibly inhibit the proliferation of diverse cell types. The studies discussed in this article show that three mouse keratinocyte cell lines exhibit sixty-fold greater sensitivity than other fibroblasts and epithelial-like cells to CeReS-18-induced growth inhibition. Growth inhibition induced by CeReS-18 treatment is a reversible process, and the three mouse keratinocyte cell lines exhibited either single or multiple cell cycle arrest points, although a predominantly G0/G1 cell cycle arrest point was exhibited in Swiss 3T3 fibroblasts. The sensitivity of the mouse keratinocyte cell lines to CeReS-18-induced growth inhibition was not affected by the degree of tumorigenic progression in the cell lines and was not due to differences in CeReS-18 binding affinity or number of cell surface receptors per cell. However, the sensitivity of both murine fibroblasts and keratinocytes could be altered by changing the extracellular calcium concentration, such that increased extracellular calcium concentrations resulted in decreased sensitivity to CeReS-18-induced proliferation inhibition. Thus the increased sensitivity of the murine keratinocyte cell lines to CeReS-18 could be ascribed to the low calcium concentration used in their propagation. Studies are currently under way investigating the role of calcium in CeReS-18-induced growth arrest. The CeReS-18 may serve as a very useful tool to study negative growth control and the signal transduction events associated with cell cycling.

Energy transfer networks: Quasicontinuum photoluminescence linked to high densities of defects

DOE PAGES

Laurence, Ted A.; Ly, Sonny; Bude, Jeff D.; ...

2017-11-06

In a series of studies related to laser-induced damage of optical materials and deposition of plastics, we discovered a broadly emitting photoluminescence with fast lifetimes that we termed quasicontinuum photoluminescence (QC-PL). Here in this paper, we suggest that a high density of optically active defects leads to QC-PL, where interactions between defects affect the temporal and spectral characteristics of both excitation and emission. We develop a model that predicts the temporal characteristics of QC-PL, based on energy transfer interactions between high densities of defects. Our model does not explain all spectral broadening and redshifts found in QC-PL, since we domore » not model spectral changes in defects due to proximity to other defects. However, we do provide an example of a well-defined system that exhibits the QC-PL characteristics of a distribution in shortened lifetimes and broadened, redshifted energy levels: an organic chromophore (fluorescein) that has been dried rapidly on a fused silica surface. Recently, we showed that regions of fused silica exposed to up to 1 billion high-fluence laser shots at 351 rm nm at subdamage fluences exhibit significant transmission losses at the surface. Here, we find that these laser-exposed regions also exhibit QC-PL. Increases in the density of induced defects on these laser-exposed surfaces, as measured by the local transmission loss, lead to decreases in the observed lifetime and redshifts in the spectrum of the QC-PL, consistent with our explanation for QC-PL. In conclusion, we have found QC-PL in an increasing variety of situations and materials, and we believe it is a phenomenon commonly found on surfaces and nanostructured materials.« less

Energy transfer networks: Quasicontinuum photoluminescence linked to high densities of defects

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

Laurence, Ted A.; Ly, Sonny; Bude, Jeff D.

In a series of studies related to laser-induced damage of optical materials and deposition of plastics, we discovered a broadly emitting photoluminescence with fast lifetimes that we termed quasicontinuum photoluminescence (QC-PL). Here in this paper, we suggest that a high density of optically active defects leads to QC-PL, where interactions between defects affect the temporal and spectral characteristics of both excitation and emission. We develop a model that predicts the temporal characteristics of QC-PL, based on energy transfer interactions between high densities of defects. Our model does not explain all spectral broadening and redshifts found in QC-PL, since we domore » not model spectral changes in defects due to proximity to other defects. However, we do provide an example of a well-defined system that exhibits the QC-PL characteristics of a distribution in shortened lifetimes and broadened, redshifted energy levels: an organic chromophore (fluorescein) that has been dried rapidly on a fused silica surface. Recently, we showed that regions of fused silica exposed to up to 1 billion high-fluence laser shots at 351 rm nm at subdamage fluences exhibit significant transmission losses at the surface. Here, we find that these laser-exposed regions also exhibit QC-PL. Increases in the density of induced defects on these laser-exposed surfaces, as measured by the local transmission loss, lead to decreases in the observed lifetime and redshifts in the spectrum of the QC-PL, consistent with our explanation for QC-PL. In conclusion, we have found QC-PL in an increasing variety of situations and materials, and we believe it is a phenomenon commonly found on surfaces and nanostructured materials.« less

Energy transfer networks: Quasicontinuum photoluminescence linked to high densities of defects

NASA Astrophysics Data System (ADS)

Laurence, Ted A.; Ly, Sonny; Bude, Jeff D.; Baxamusa, Salmaan H.; Lepró, Xavier; Ehrmann, Paul

2017-11-01

In a series of studies related to laser-induced damage of optical materials and deposition of plastics, we discovered a broadly emitting photoluminescence with fast lifetimes that we termed quasicontinuum photoluminescence (QC-PL). Here, we suggest that a high density of optically active defects leads to QC-PL, where interactions between defects affect the temporal and spectral characteristics of both excitation and emission. We develop a model that predicts the temporal characteristics of QC-PL, based on energy transfer interactions between high densities of defects. Our model does not explain all spectral broadening and redshifts found in QC-PL, since we do not model spectral changes in defects due to proximity to other defects. However, we do provide an example of a well-defined system that exhibits the QC-PL characteristics of a distribution in shortened lifetimes and broadened, redshifted energy levels: an organic chromophore (fluorescein) that has been dried rapidly on a fused silica surface. Recently, we showed that regions of fused silica exposed to up to 1 billion high-fluence laser shots at 351 rm nm at subdamage fluences exhibit significant transmission losses at the surface. Here, we find that these laser-exposed regions also exhibit QC-PL. Increases in the density of induced defects on these laser-exposed surfaces, as measured by the local transmission loss, lead to decreases in the observed lifetime and redshifts in the spectrum of the QC-PL, consistent with our explanation for QC-PL. We have found QC-PL in an increasing variety of situations and materials, and we believe it is a phenomenon commonly found on surfaces and nanostructured materials.

TAZ-8A Alloy Increases The Thermal Endurance Of Steel

NASA Technical Reports Server (NTRS)

Waters, William J.

1990-01-01

TAZ-8A exhibits high strength at temperatures as high as 1,400 degrees F (760 degrees C) and resistance to oxidation; also exhibits excellent cyclic shock resistance between 600 and 2,000 degrees F (316 and 1,093 degrees C) and superplasticity at 1,800 degrees F (982 degrees C). Converts into fine powder and then flame-, plasma-, arc-, or wire-sprayed onto inexpensive steel substrate. Surface treatment with this alloy prolongs service life and reduces costs.

Monitoring very-long-period seismicity at Kilauea Volcano, Hawaii

USGS Publications Warehouse

Dawson, Phillip B.; Benítez, M. C.; Chouet, Bernard A.; Wilson, David; Okubo, Paul G.

2010-01-01

On 19 March, 2008 eruptive activity returned to the summit of Kilauea Volcano, Hawaii with the formation of a new vent within the Halemaumau pit crater. The new vent has been gradually increasing in size, and exhibiting sustained degassing and the episodic bursting of gas slugs at the surface of a lava pond ∼200 m below the floor of Halemaumau. The spectral characteristics, source location obtained by radial semblance, and Hidden Markov Model pattern recognition of the degassing burst signals are consistent with an increase in gas content in the magma transport system beginning in October, 2007. This increase plateaus between March – September 2008, and exhibits a fluctuating pattern until 31 January, 2010, suggesting that the release of gas is slowly diminishing over time.

Mechanism and Characteristics of Humidity Sensing with Polyvinyl Alcohol-Coated Fiber Surface Plasmon Resonance Sensor.

PubMed

Shao, Yu; Wang, Ying; Cao, Shaoqing; Huang, Yijian; Zhang, Longfei; Zhang, Feng; Liao, Changrui; Wang, Yiping

2018-06-25

A surface plasmon resonance (SPR) sensor based on a side-polished single mode fiber coated with polyvinyl alcohol (PVA) is demonstrated for relative humidity (RH) sensing. The SPR sensor exhibits a resonant dip in the transmission spectrum in ambient air after PVA film coating, and the resonant wavelength shifts to longer wavelengths as the thickness of the PVA film increases. When RH changes, the resonant dip of the sensor with different film-thicknesses exhibits interesting characteristics for optical spectrum evolution. For sensors with initial wavelengths between 550 nm and 750 nm, the resonant dip shifts to longer wavelengths with increasing RH. The averaged sensitivity increases firstly and then drops, and shows a maximal sensitivity of 1.01 nm/RH%. Once the initial wavelength of the SPR sensor exceeds 850 nm, an inflection point of the resonant wavelength shift can be observed with RH increasing, and the resonant dip shifts to shorter wavelengths for RH values exceeding this point, and sensitivity as high as −4.97 nm/RH% can be obtained in the experiment. The sensor is expected to have potential applications in highly sensitive and cost effective humidity sensing.

Evidence of Space Weathering Processes Across the Surface of Vesta

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Blewett, David T.; Gaffey, Michael; Mittlefehldt, David W.; CristinaDeSanctis, Maria; Reddy, Vishnu; Coradini, Angioletta; Nathues, Andreas; Denevi, Brett W.; Li, Jian-Yang;

Ferroelectric triggering of carbon monoxide adsorption on lead zirco-titanate (001) surfaces

PubMed Central

Tănase, Liviu Cristian; Apostol, Nicoleta Georgiana; Abramiuc, Laura Elena; Tache, Cristian Alexandru; Hrib, Luminița; Trupină, Lucian; Pintilie, Lucian; Teodorescu, Cristian Mihail

2016-01-01

Atomically clean lead zirco-titanate PbZr0.2Ti0.8O3 (001) layers exhibit a polarization oriented inwards P(−), visible by a band bending of all core levels towards lower binding energies, whereas as introduced layers exhibit P(+) polarization under air or in ultrahigh vacuum. The magnitude of the inwards polarization decreases when the temperature is increased at 700 K. CO adsorption on P(−) polarized surfaces saturates at about one quarter of a monolayer of carbon, and occurs in both molecular (oxidized) and dissociated (reduced) states of carbon, with a large majority of reduced state. The sticking of CO on the surface in ultrahigh vacuum is found to be directly related to the P(−) polarization state of the surface. A simple electrostatic mechanism is proposed to explain these dissociation processes and the sticking of carbon on P(−) polarized areas. Carbon desorbs also when the surface is irradiated with soft X-rays. Carbon desorption when the polarization is lost proceeds most probably in form of CO2. Upon carbon desorption cycles, the ferroelectric surface is depleted in oxygen and at some point reverses its polarization, owing to electrons provided by oxygen vacancies which are able to screen the depolarization field produced by positive fixed charges at the surface. PMID:27739461

Mirror-finished superhydrophobic aluminum surfaces modified by anodic alumina nanofibers and self-assembled monolayers

NASA Astrophysics Data System (ADS)

Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Suzuki, Ryosuke O.

2018-05-01

We demonstrate mirror-finished superhydrophobic aluminum surfaces fabricated via the formation of anodic alumina nanofibers and subsequent modification with self-assembled monolayers (SAMs). High-density anodic alumina nanofibers were formed on the aluminum surface via anodizing in a pyrophosphoric acid solution. The alumina nanofibers became tangled and bundled by further anodizing at low temperature because of their own weight, and the aluminum surface was completely covered by the long falling nanofibers. The nanofiber-covered aluminum surface exhibited superhydrophilic behavior, with a contact angle measuring less than 10°. As the nanofiber-covered aluminum surface was modified with n-alkylphosphonic acid SAMs, the water contact angle drastically shifted to superhydrophobicity, measuring more than 150°. The contact angle increased with the applied voltage during pyrophosphoric acid anodizing, the anodizing time, and the number of carbon atoms contained in the SAM molecules modified on the alumina nanofibers. By optimizing the anodizing and SAM-modification conditions, superhydrophobic behavior could be achieved with only a brief pyrophosphoric acid anodizing period of 3 min and subsequent simple immersion in SAM solutions. The superhydrophobic aluminum surface exhibited a high reflectance, measuring approximately 99% across most of the visible spectrum, similar to that of an electropolished aluminum surface. Therefore, our mirror-finished superhydrophobic aluminum surface based on anodic alumina nanofibers and SAMs can be used as a reflective mirror in various optical applications such as concentrated solar power systems.

Theoretical study of surface plasmon resonance sensors based on 2D bimetallic alloy grating

NASA Astrophysics Data System (ADS)

Dhibi, Abdelhak; Khemiri, Mehdi; Oumezzine, Mohamed

2016-11-01

A surface plasmon resonance (SPR) sensor based on 2D alloy grating with a high performance is proposed. The grating consists of homogeneous alloys of formula MxAg1-x, where M is gold, copper, platinum and palladium. Compared to the SPR sensors based a pure metal, the sensor based on angular interrogation with silver exhibits a sharper (i.e. larger depth-to-width ratio) reflectivity dip, which provides a big detection accuracy, whereas the sensor based on gold exhibits the broadest dips and the highest sensitivity. The detection accuracy of SPR sensor based a metal alloy is enhanced by the increase of silver composition. In addition, the composition of silver which is around 0.8 improves the sensitivity and the quality of SPR sensor of pure metal. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensor based on a metal alloy not only has a high sensitivity and a high detection accuracy, but also exhibits a good linearity and a good quality.

Temporal Arctic longwave surface emissivity feedbacks in the Community Earth System Model

NASA Astrophysics Data System (ADS)

Kuo, C.; Feldman, D.; Huang, X.; Flanner, M.; Yang, P.; Chen, X.

2017-12-01

We have investigated how the inclusion of realistic and consistent surface emissivity in both land-surface and atmospheric components of the CESM coupled-climate model affects a wide range of climate variables. We did this by replacing the unit emissivity values in RRTMG_LW for water, fine-grained snow, and desert scenes with spectral emissivity values, and by replacing broadband emissivity values in surface components with the Planck-curve weighted counterparts. We find that this harmonized treatment of surface emissivity within CESM can be important for reducing high-latitude temperature biases. We also find that short-term effects of atmospheric dynamics and spectral information need to be considered to understand radiative effects in higher detail, and are possible with radiative kernels computed for every grid and time point for the entire model integration period. We find that conventional climatological feedback calculations indicate that sea-ice emissivity feedback is positive in sign, but that the radiative effects of the difference in emissivity between frozen and unfrozen surfaces exhibit seasonal dependence. Furthermore, this seasonality itself exhibits meridional asymmetry due to differences in sea-ice response to climate forcing between the Arctic and the Antarctic. In the Arctic, this seasonal, temporally higher order analysis exhibits increasing outgoing surface emissivity radiative response in a warming climate. While the sea-ice emissivity feedback and seasonal sea-ice emissivity radiative response amplitudes are a few percent of surface albedo feedbacks, the feedback analysis methods outlined in this work demonstrate that spatially and temporally localized feedback analysis can give insight into the mechanisms at work on those scales which differ in amplitude and sign from conventional climatological analyses. We note that the inclusion of this realistic physics leads to improved agreement between CESM model results and Arctic surface temperatures and sea-ice trends. This reduction of persistent high-latitude model biases suggests that the current unrealistic representation of surface emissivity in model component radiation routines may be an important contributing factor to cold-pole biases.

Enhanced Osteoblast Response to Porosity and Resolution of Additively Manufactured Ti-6Al-4V Constructs with Trabeculae-Inspired Porosity

PubMed Central

Cheng, Alice; Humayun, Aiza; Schwartz, Zvi

2016-01-01

Abstract The addition of porosity to the traditionally used solid titanium metal implants has been suggested to more closely mimic the natural mechanical properties of bone and increase osseointegration in dental and orthopedic implants. The objective of this study was to evaluate cellular response to three-dimensional (3D) porous Ti-6Al-4V constructs fabricated by additive manufacturing using laser sintering with low porosity (LP), medium porosity (MP), and high porosity (HP) with low resolution (LR) and high resolution (HR) based on a computed tomography scan of human trabecular bone. After surface processing, construct porosity ranged from 41.0% to 76.1%, but all possessed micro-/nanoscale surface roughness and similar surface chemistry containing mostly Ti, O, and C. Biological responses (osteoblast differentiation, maturation, and local factor production) by MG63 osteoblast-like cells and normal human osteoblasts favored 3D than two-dimensional (2D) solid constructs. First, MG63 cells were used to assess differences in cell response to 2D compared to LR and HR porous 3D constructs. MG63 cells were sensitive to porosity resolution and exhibited increased osteocalcin (OCN), vascular endothelial growth factor (VEGF), osteoprotegerin (OPG), and bone morphogenetic protein 2 (BMP2) on HR 3D constructs than on 2D and LR 3D constructs. MG63 cells also exhibited porosity-dependent responses on HR constructs, with up to a 6.9-fold increase in factor production on LP-HR and MP-HR constructs than on HP-HR constructs. NHOsts were then used to validate biological response on HR constructs. NHOsts exhibited decreased DNA content and alkaline phosphatase activity and up to a 2.9-fold increase in OCN, OPG, VEGF, BMP2, and BMP4 on 3D HR constructs than on 2D controls. These results indicate that osteoblasts prefer a 3D architecture than a 2D surface and that osteoblasts are sensitive to the resolution of trabecular detail and porosity parameters of laser-sintered 3D Ti-6Al-4V constructs. PMID:28804735

Enhanced Osteoblast Response to Porosity and Resolution of Additively Manufactured Ti-6Al-4V Constructs with Trabeculae-Inspired Porosity.

PubMed

Cheng, Alice; Humayun, Aiza; Boyan, Barbara D; Schwartz, Zvi

2016-03-01

The addition of porosity to the traditionally used solid titanium metal implants has been suggested to more closely mimic the natural mechanical properties of bone and increase osseointegration in dental and orthopedic implants. The objective of this study was to evaluate cellular response to three-dimensional (3D) porous Ti-6Al-4V constructs fabricated by additive manufacturing using laser sintering with low porosity (LP), medium porosity (MP), and high porosity (HP) with low resolution (LR) and high resolution (HR) based on a computed tomography scan of human trabecular bone. After surface processing, construct porosity ranged from 41.0% to 76.1%, but all possessed micro-/nanoscale surface roughness and similar surface chemistry containing mostly Ti, O, and C. Biological responses (osteoblast differentiation, maturation, and local factor production) by MG63 osteoblast-like cells and normal human osteoblasts favored 3D than two-dimensional (2D) solid constructs. First, MG63 cells were used to assess differences in cell response to 2D compared to LR and HR porous 3D constructs. MG63 cells were sensitive to porosity resolution and exhibited increased osteocalcin (OCN), vascular endothelial growth factor (VEGF), osteoprotegerin (OPG), and bone morphogenetic protein 2 (BMP2) on HR 3D constructs than on 2D and LR 3D constructs. MG63 cells also exhibited porosity-dependent responses on HR constructs, with up to a 6.9-fold increase in factor production on LP-HR and MP-HR constructs than on HP-HR constructs. NHOsts were then used to validate biological response on HR constructs. NHOsts exhibited decreased DNA content and alkaline phosphatase activity and up to a 2.9-fold increase in OCN, OPG, VEGF, BMP2, and BMP4 on 3D HR constructs than on 2D controls. These results indicate that osteoblasts prefer a 3D architecture than a 2D surface and that osteoblasts are sensitive to the resolution of trabecular detail and porosity parameters of laser-sintered 3D Ti-6Al-4V constructs.

Photonic crystal surface-emitting lasers enabled by an accidental Dirac point

DOEpatents

Chua, Song Liang; Lu, Ling; Soljacic, Marin

2014-12-02

A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

NASA Astrophysics Data System (ADS)

Yan, Xinzhu; Li, Jian; Li, Licheng; Huang, Zhengyong; Wang, Feipeng; Wei, Yuan

2016-10-01

In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

Trends in surface ozone over Europe, 1978-1990

NASA Technical Reports Server (NTRS)

Low, Pak Sum; Kelly, P. Michael; Davies, Trevor D.

1994-01-01

It has been suggested that surface ozone concentrations in rural areas of Europe have been increasing at a rate of 1 to 3 percent per year over the past two to three decades, presumably due to human influences (Feister and Warmbt, 1987; Bojkov, 1988; Penkett, 1989). Recently, we have analyzed surface ozone data from 20 European stations of differing character (remote, rural, suburban and urban) for a common period of 1978-1988 (Low et al., 1992). It was found that there were pronounced annual and seasonal variations in the linear trends in different areas, and there was no dominant region-wide trend. In spring and, most notably, summer, stations on the maritime fringe of the network generally exhibited negative trends whilst those located further into the continental interior exhibited positive trends. In winter, most of the stations in the network exhibited positive trends. Relatively few of these trends were statistically significant. This paper updates our earlier analysis by extending the data sets of the network up to the year 1990. The spatial variations in surface ozone trends over the extended period 1978-1990 are examined and discussed in comparison to the 1978-1988 patterns. The update confirms the overall conclusions of the earlier analysis, specifically that caution should be exercised in interpreting the results of trend analyses based on station data representative of a limited period of time and/or geographical area.

Surface phenomena of hydroxyapatite film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants.

PubMed

Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol

2013-03-01

In this study, surface phenomena of hydroxyapatite (HA) film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants have been investigated by electron beam physical vapor deposition (EB-PVD), field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), potentiostat and contact angle. The microstructure of Ti-29Nb-xZr alloys exhibited equiaxed structure and alpha" phase decreased, whereas beta phase increased as Zr content increased. The increment of Zr contents in HA coated nanotubular Ti-29Nb-xZr alloys showed good corrosion potential in 0.9% NaCI solution. The wettability of HA coated nanotubular surface was higher than that of non-coated samples.

The influence of zeolites fly ash bead/TiO2 composite material surface morphologies on their adsorption and photocatalytic performance

NASA Astrophysics Data System (ADS)

Yang, Lu; Wang, Fazhou; Hakki, Amer; Macphee, Donald E.; Liu, Peng; Hu, Shuguang

2017-01-01

A low cost zeolite fly ash bead/TiO2 (ZFABT) composite materials with various surface structure features were prepared for describing those structures importance on TiO2 coating, adsorbability and photocatalytic performances. The results indicated that fly ash bead (FAB) surface was significantly altered by the precipitation/growth of secondary zeolite phases after alkali activation, which generates abundant open pores and stacked petal-liked spherical beads (∼2 μm, Sodalite zeolites). More importantly, this porosity increases as activation time was increased from 2 h to 12 h, through the precipitation of sodalite and then Na-P1 (lamellar crystals) and Na-X (octahedral crystals) zeolite structures. Compared to those of unsupported TiO2 or inactivated support/TiO2 samples, all of ZFABT samples exhibited a higher adsorption capacity and photocatalytic efficiency for RhB removal. However, adsorption is not only one factor to influence TiO2 surface reaction, the intraparticle diffusion rate of rhodamine B (RhB) molecules, and light penetration are also important parameters. Alkali activated 4 h ZFABT sample exhibited the highest photocatalytic activity, indicating its pore structure provided a better balance for those parameters to achieve a synergistic adsorption/photocatalytic process. The kinetics model suggested its high intraparticle diffusion rate allowed for more RhB molecules to easily reach the reaction surface, which is more important for high efficiency photocatalysis.

F + H2 collisions on two electronic potential energy surfaces - Quantum-mechanical study of the collinear reaction

NASA Technical Reports Server (NTRS)

Zimmerman, I. H.; Baer, M.; George, T. F.

1979-01-01

Collinear quantum calculations are carried out for reactive F + H2 collisions on two electronic potential energy surfaces. The resulting transmission and reflection probabilities exhibit much greater variation with energy than single-surface studies would lead us to anticipate. Transmission to low-lying product channels is increased by orders of magnitude by the presence of the second surface; however, branching ratios among product states are found to be independent of the initial electronic state of the reactants. These apparently contradictory aspects of the calculation are discussed and a tentative explanation put forward to resolve them.

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

Schaeffer, Daniel A.; Polizos, Georgios; Smith, D. Barton

Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a self-cleaning effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 16≥0° to 175°. This result is remarkable because such behavior cannotmore » be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, surfaces exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the contact angle and optical transmission between 190 to 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents isopropyl alcohol and 4-chlorobenzotrifluoride (PCBTF) and a proprietary ceramic binder (Cerakote ). Finally, this solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 minutes, these coatings exhibited superhydrophobic behavior with a static CA ≥160°.« less

Topographic design and application of hierarchical polymer surfaces replicated by microinjection compression molding

NASA Astrophysics Data System (ADS)

Guan, Wei-Sheng; Huang, Han-Xiong; Wang, Bin

2013-10-01

In recent years, the fast growing demand for biomimetic surfaces featuring unique wettability and functionality in various fields highlights the necessity of developing a reliable technique for mass production. In this work, hierarchical topography designs of templates were applied to prepare superhydrophobic surfaces via microinjection compression molding, comprehensively considering the feasibility of mechanical demolding and the superhydrophobicity and mechanical robustness of the molded polypropylene parts. Mimicking the wettability of a lotus leaf or rose petal, superhydrophobic surfaces were replicated. An unstable wetting state formed on the surface exhibiting the petal effect. On such a surface, the increased water pressure could cause water penetration into the micro gaps between the hierarchical asperities featuring low-roughness sidewalls and bottom surface; the resultant water membrane led to drastically increased water adhesion of the surface. Moreover, the low-adhesion superhydrophobicity of the molded surface was changed into superhydrophilicity, by means of introducing carbonyl groups via ultraviolet/ozone treatment and the subsequent water membrane preserved in microstructures via the pre-wetting process. Patterning the superhydrophilic micro channel on the superhydrophobic surface developed the surface microfluidic devices for micro-liter fluid pumping and mixing processes driven by surface tension.

Brain development during adolescence: A mixed-longitudinal investigation of cortical thickness, surface area, and volume.

PubMed

Vijayakumar, Nandita; Allen, Nicholas B; Youssef, George; Dennison, Meg; Yücel, Murat; Simmons, Julian G; Whittle, Sarah

2016-06-01

What we know about cortical development during adolescence largely stems from analyses of cross-sectional or cohort-sequential samples, with few studies investigating brain development using a longitudinal design. Further, cortical volume is a product of two evolutionarily and genetically distinct features of the cortex - thickness and surface area, and few studies have investigated development of these three characteristics within the same sample. The current study examined maturation of cortical thickness, surface area and volume during adolescence, as well as sex differences in development, using a mixed longitudinal design. 192 MRI scans were obtained from 90 healthy (i.e., free from lifetime psychopathology) adolescents (11-20 years) at three time points (with different MRI scanners used at time 1 compared to 2 and 3). Developmental trajectories were estimated using linear mixed models. Non-linear increases were present across most of the cortex for surface area. In comparison, thickness and volume were both characterised by a combination of non-linear decreasing and increasing trajectories. While sex differences in volume and surface area were observed across time, no differences in thickness were identified. Furthermore, few regions exhibited sex differences in the cortical development. Our findings clearly illustrate that volume is a product of surface area and thickness, with each exhibiting differential patterns of development during adolescence, particularly in regions known to contribute to the development of social-cognition and behavioral regulation. These findings suggest that thickness and surface area may be driven by different underlying mechanisms, with each measure potentially providing independent information about brain development. Hum Brain Mapp 37:2027-2038, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Comparison of posture and balance in cancer survivors and age-matched controls.

PubMed

Schmitt, Abigail C; Repka, Chris P; Heise, Gary D; Challis, John H; Smith, Jeremy D

2017-12-01

The combination of peripheral neuropathy and other treatment-associated side effects is likely related to an increased incidence of falls in cancer survivors. The purpose of this study was to quantify differences in postural stability between healthy age-matched controls and cancer survivors. Quiet standing under four conditions (eyes open/closed, rigid/compliant surface) was assessed in 34 cancer survivors (2 males, 32 females; age: 54(13) yrs., height: 1.62(0.07) m; mass: 78.5(19.5) kg) and 34 age-matched controls (5 males, 29 females; age: 54(15) yrs.; height: 1.62(0.08) m; mass: 72.8(21.1) kg). Center of pressure data were collected for 30s and the trajectories were analyzed (100Hz). Three-factor (group*surface*vision) mixed model MANOVAs with repeated measures were used to determine the effect of vision and surface on postural steadiness between groups. Cancer survivors exhibited larger mediolateral root-mean square distance and velocity of the center of pressure, as well as increased 95% confidence ellipse area (P<0.01) when compared with their age-matched counterparts. For example, when removing visual input, cancer survivors had an average increase in 95% confidence ellipse area of 91.8mm 2 while standing on a rigid surface compared to a 68.6mm 2 increase for the control group. No frequency-based center of pressure measures differed between groups. Cancer survivors exhibit decreased postural steadiness when compared with age-matched controls. For cancer survivors undergoing rehabilitation focused on existing balance deficits, a small subset of the center of pressure measures presented here can be used to track progress throughout the intervention and potentially mitigate fall risk. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of isotropic and anisotropic slip on droplet impingement on a superhydrophobic surface

NASA Astrophysics Data System (ADS)

Clavijo, Cristian E.; Crockett, Julie; Maynes, Daniel

2015-12-01

The dynamics of single droplet impingement on micro-textured superhydrophobic surfaces with isotropic and anisotropic slip are investigated. While several analytical models exist to predict droplet impact on superhydrophobic surfaces, no previous model has rigorously considered the effect of the shear-free region above the gas cavities resulting in an apparent slip that is inherent for many of these surfaces. This paper presents a model that accounts for slip during spreading and recoiling. A broad range of Weber numbers and slip length values were investigated at low Ohnesorge numbers. The results show that surface slip exerts negligible influence throughout the impingement process for low Weber numbers but can exert significant influence for high Weber numbers (on the order of 102). When anisotropic slip prevails, the droplet exhibits an elliptical shape at the point of maximum spread, with greater eccentricity for increasing slip and increasing Weber number. Experiments were performed on isotropic and anisotropic micro-structured superhydrophobic surfaces and the agreement between the experimental results and the model is very good.

Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors.

PubMed

He, Tao; Wu, Yanfei; D'Avino, Gabriele; Schmidt, Elliot; Stolte, Matthias; Cornil, Jérôme; Beljonne, David; Ruden, P Paul; Würthner, Frank; Frisbie, C Daniel

2018-05-30

Understanding relationships between microstructure and electrical transport is an important goal for the materials science of organic semiconductors. Combining high-resolution surface potential mapping by scanning Kelvin probe microscopy (SKPM) with systematic field effect transport measurements, we show that step edges can trap electrons on the surfaces of single crystal organic semiconductors. n-type organic semiconductor crystals exhibiting positive step edge surface potentials display threshold voltages that increase and carrier mobilities that decrease with increasing step density, characteristic of trapping, whereas crystals that do not have positive step edge surface potentials do not have strongly step density dependent transport. A device model and microelectrostatics calculations suggest that trapping can be intrinsic to step edges for crystals of molecules with polar substituents. The results provide a unique example of a specific microstructure-charge trapping relationship and highlight the utility of surface potential imaging in combination with transport measurements as a productive strategy for uncovering microscopic structure-property relationships in organic semiconductors.

Creating gradient wetting surfaces via electroless displacement of zinc-coated carbon steel by nickel ions

NASA Astrophysics Data System (ADS)

Xu, Chang; Liu, Huicong; Liang, Weitao; Zhu, Liqun; Li, Weiping; Chen, Haining

2018-03-01

Gradient wetting surfaces are getting increasing attention due to their wide application in multiple fields such as droplet movement and biosorption. However, the fabrication processes of full gradient wetting surfaces are still complex and costly. In present work, a facile and low-cost chemical immersion method was used to create a full gradient wetting surface. By controlling the displacement time in Ni2+ solution, the prepared surfaces perform hydrophilic to superhydrophilic. After being modified by stearic acid, the gradient hydrophilic surfaces convert into hydrophobic. The surface morphology, composition, and wetting behaviors of the as-prepared surfaces were systematically studied and discussed. The gradient wetting property could be attributed to the change in microroughness and surface energy. In addition, these surfaces also exhibited excellent self-cleaning and wax prevention properties. Furthermore, high stability and corrosion resistance were also found for these surfaces, which further highlight their promising practical applications in many fields.

Nanometer polymer surface features: the influence on surface energy, protein adsorption and endothelial cell adhesion

NASA Astrophysics Data System (ADS)

Carpenter, Joseph; Khang, Dongwoo; Webster, Thomas J.

2008-12-01

Current small diameter (<5 mm) synthetic vascular graft materials exhibit poor long-term patency due to thrombosis and intimal hyperplasia. Tissue engineered solutions have yielded functional vascular tissue, but some require an eight-week in vitro culture period prior to implantation—too long for immediate clinical bedside applications. Previous in vitro studies have shown that nanostructured poly(lactic-co-glycolic acid) (PLGA) surfaces elevated endothelial cell adhesion, proliferation, and extracellular matrix synthesis when compared to nanosmooth surfaces. Nonetheless, these studies failed to address the importance of lateral and vertical surface feature dimensionality coupled with surface free energy; nor did such studies elicit an optimum specific surface feature size for promoting endothelial cell adhesion. In this study, a series of highly ordered nanometer to submicron structured PLGA surfaces of identical chemistry were created using a technique employing polystyrene nanobeads and poly(dimethylsiloxane) (PDMS) molds. Results demonstrated increased endothelial cell adhesion on PLGA surfaces with vertical surface features of size less than 18.87 nm but greater than 0 nm due to increased surface energy and subsequently protein (fibronectin and collagen type IV) adsorption. Furthermore, this study provided evidence that the vertical dimension of nanometer surface features, rather than the lateral dimension, is largely responsible for these increases. In this manner, this study provides key design parameters that may promote vascular graft efficacy.

Acetazolamide on the ventral medulla of the cat increases phrenic output and delays the ventilatory response to CO2.

PubMed Central

Coates, E L; Li, A H; Nattie, E E

1991-01-01

1. Acetazolamide (0.1 mM) applied to the surface of the rostral ventrolateral medulla or microinjected beneath the medullary surface in chloralose-urethane-anaesthetized, vagotomized, carotid-denervated, paralysed, servo-ventilated cats produced a long-lasting increase in integrated phrenic nerve activity. 2. Extracellular pH measured beneath the rostral ventrolateral medulla exhibited a long-lasting decrease after surface acetazolamide but was not a good predictor, in each individual animal, of changes in phrenic activity. 3. Medullary carbonic anhydrase inhibition reduced the slope and the half-time of the phrenic response to rapid step CO2 increases. Conversely, acetazolamide did not affect the phrenic response to steady-state CO2 increases. 4. These data indicate that localized inhibition of medullary carbonic anhydrase causes a centrally mediated increase in ventilation that we attribute to medullary tissue hypercapnia and acidosis. In addition, these data indicate that medullary carbonic anhydrase may play a role in central CO2 chemotransduction. Images Fig. 8 PMID:1816381

Long-range interaction between heterogeneously charged membranes.

PubMed

Jho, Y S; Brewster, R; Safran, S A; Pincus, P A

2011-04-19

Despite their neutrality, surfaces or membranes with equal amounts of positive and negative charge can exhibit long-range electrostatic interactions if the surface charge is heterogeneous; this can happen when the surface charges form finite-size domain structures. These domains can be formed in lipid membranes where the balance of the different ranges of strong but short-ranged hydrophobic interactions and longer-ranged electrostatic repulsion result in a finite, stable domain size. If the domain size is large enough, oppositely charged domains in two opposing surfaces or membranes can be strongly correlated by the electrostatic interactions; these correlations give rise to an attractive interaction of the two membranes or surfaces over separations on the order of the domain size. We use numerical simulations to demonstrate the existence of strong attractions at separations of tens of nanometers. Large line tensions result in larger domains but also increase the charge density within the domain. This promotes correlations and, as a result, increases the intermembrane attraction. On the other hand, increasing the salt concentration increases both the domain size and degree of domain anticorrelation, but the interactions are ultimately reduced due to increased screening. The result is a decrease in the net attraction as salt concentration is increased. © 2011 American Chemical Society

Effects of surface morphology of ZnO seed layers on growth of ZnO nanostructures prepared by hydrothermal method and annealing.

PubMed

Yim, Kwang Gug; Kim, Min Su; Leem, Jae-Young

2013-05-01

ZnO nanostructures were grown on Si (111) substrates by a hydrothermal method. Prior to growing the ZnO nanostructures, ZnO seed layers with different post-heat temperatures were prepared by a spin-coating process. Then, the ZnO nanostructures were annealed at 500 degrees C for 20 min under an Ar atmosphere. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out at room temperature (RT) to investigate the structural and optical properties of the as-grown and annealed ZnO nanostructures. The surface morphologies of the seed layers changed from a smooth surface to a mountain chain-like structure as the post-heating temperatures increased. The as-grown and annealed ZnO nanostructures exhibited a strong (002) diffraction peak. Compared to the as-grown ZnO nanostructures, the annealed ZnO nanostructures exhibited significantly strong enhancement in the PL intensity ratio by almost a factor of 2.

Elucidation of the Oxygen Reduction Volcano in Alkaline Media using a Copper-Platinum(111) Alloy.

PubMed

Jensen, Kim D; Tymoczko, Jakub; Rossmeisl, Jan; Bandarenka, Aliaksandr S; Chorkendorff, Ib; Escudero-Escribano, María; Stephens, Ifan E L

2018-03-05

The relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media was experimentally explored. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, the surface reactivity was tuned. In both 0.1 m NaOH and 0.1 m KOH, the optimal catalyst should exhibit OH binding circa 0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports. In 0.1 m KOH, the alloy catalyst at the peak of the volcano exhibits a maximum activity of 101±8 mA cm -2 at 0.9 V vs. a reversible hydrogen electrode (RHE). This activity constitutes a circa 60-fold increase over Pt(111) in 0.1 m HClO 4 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thin metal bilayer for surface plasmon resonance sensors in a multimode plastic optical fiber: the case of palladium and gold metal films

NASA Astrophysics Data System (ADS)

Cennamo, Nunzio; Zuppella, Paola; Bacco, Davide; Corso, Alain J.; Pelizzo, Maria G.; Pesavento, Maria; Zeni, Luigi

2016-05-01

A novel sensing platform based on thin metal bilayer for surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) has been designed, implemented and tested. The experimental results are congruent with the numerical studies. This platform has been properly optimized to work in the 1.38 -1.42 refractive index range and it exhibits excellent sensitivity. This refractive index range is very interesting for bio-chemical applications, where the polymer layer are used as receptors (e.g. molecularly imprinted polymer) or to immobilize the bio-receptor on the metal surface. The proposed metallic bilayer is based on palladium and gold films and replaces the traditional gold by exhibiting higher performances. Furthermore, the deposition of the thin bilayer is a single process and no further manufacturing step is required. In fact, in this case the photoresist buffer layer between the POF core and the metal layer, usually required to increase the refractive index range, is no longer necessary.

Spatial Periodicity of Escherichia coli K-12 Biofilm Microstructure Initiates during a Reversible, Polar Attachment Phase of Development and Requires the Polysaccharide Adhesin PGA

PubMed Central

Agladze, Konstantin; Wang, Xin; Romeo, Tony

2005-01-01

Using fast Fourier transform (FFT) analysis, we previously observed that cells within Escherichia coli biofilm are organized in nonrandom or periodic spatial patterns (K. Agladze et al., J. Bacteriol. 185:5632-5638, 2003). Here, we developed a gravity displacement assay for examining cell adherence and used it to quantitatively monitor the formation of two distinct forms of cell attachment, temporary and permanent, during early biofilm development. Temporarily attached cells were mainly surface associated by a cell pole; permanent attachments were via the lateral cell surface. While temporary attachment precedes permanent attachment, both forms can coexist in a population. Exposure of attached cells to gravity liberated an unattached population capable of rapidly reassembling a new monolayer, composed of temporarily attached cells, and possessing periodicity. A csrA mutant, which forms biofilm more vigorously than its wild-type parent, exhibited an increased proportion of permanently attached cells and a form of attachment that was not apparent in the parent strain, permanent polar attachment. Nevertheless, it formed periodic attachment patterns. In contrast, biofilm mutants with altered lipopolysaccharide synthesis (waaG) exhibited increased cell-cell interactions, bypassed the polar attachment step, and produced FFT spectra characteristic of aperiodic cell distribution. Mutants lacking the polysaccharide adhesin β-1,6-N-acetyl-d-glucosamine (ΔpgaC) also exhibited aperiodic cell distribution, but without apparent cell-cell interactions, and were defective in forming permanent attachments. Thus, spatial periodicity of biofilm microstructure is genetically determined and evident during the formation of temporary cell surface attachments. PMID:16321928

Gradual Crossover from Subdiffusion to Normal Diffusion: A Many-Body Effect in Protein Surface Water

NASA Astrophysics Data System (ADS)

Tan, Pan; Liang, Yihao; Xu, Qin; Mamontov, Eugene; Li, Jinglai; Xing, Xiangjun; Hong, Liang

2018-06-01

Dynamics of hydration water is essential for the function of biomacromolecules. Previous studies have demonstrated that water molecules exhibit subdiffusion on the surface of biomacromolecules; yet the microscopic mechanism remains vague. Here, by performing neutron scattering, molecular dynamics simulations, and analytic modeling on hydrated perdeuterated protein powders, we found water molecules jump randomly between trapping sites on protein surfaces, whose waiting times obey a broad distribution, resulting in subdiffusion. Moreover, the subdiffusive exponent gradually increases with observation time towards normal diffusion due to a many-body volume-exclusion effect.

Analysis of Life Cycle within Various Strains of Cyanobacteria with a Focus on Internal Regulators & Toxin Production

EPA Science Inventory

Cyanobacteria are photosynthetic bacteria that exhibit some similarities to algae and can be found naturally in lakes, streams, ponds, and other surface waters. However, toxin producing cyanobacteria have become an increasing concern as growth rates have been escalating. Neverthe...

Localized stress fluctuations drive shear thickening in dense suspensions

NASA Astrophysics Data System (ADS)

Rathee, Vikram; Blair, Daniel L.; Urbach, Jeffrey S.

2017-08-01

Dense particulate suspensions exhibit a dramatic increase in average viscosity above a critical, material-dependent shear stress. This thickening changes from continuous to discontinuous as the concentration is increased. Using direct measurements of spatially resolved surface stresses in the continuous thickening regime, we report the existence of clearly defined dynamic localized regions of substantially increased stress that appear intermittently at stresses above the critical stress. With increasing applied stress, these regions occupy an increasing fraction of the system, and the increase accounts quantitatively for the observed shear thickening. The regions represent high-viscosity fluid phases, with a size determined by the distance between the shearing surfaces and a viscosity that is nearly independent of shear rate but that increases rapidly with concentration. Thus, we find that continuous shear thickening arises from increasingly frequent localized discontinuous transitions between distinct fluid phases with widely differing viscosities.

Low damage electrical modification of 4H-SiC via ultrafast laser irradiation

NASA Astrophysics Data System (ADS)

Ahn, Minhyung; Cahyadi, Rico; Wendorf, Joseph; Bowen, Willie; Torralva, Ben; Yalisove, Steven; Phillips, Jamie

2018-04-01

The electrical properties of 4H-SiC under ultrafast laser irradiation in the low fluence regime (<0.50 J/cm2) are presented. The appearance of high spatial frequency laser induced periodic surface structures is observed at a fluence near 0.25 J/cm2 and above, with variability in environments like in air, nitrogen, and a vacuum. In addition to the formation of periodic surface structures, ultrafast laser irradiation results in possible surface oxidation and amorphization of the material. Lateral conductance exhibits orders of magnitude increase, which is attributed to either surface conduction or modification of electrical contact properties, depending on the initial material conductivity. Schottky barrier formation on ultrafast laser irradiated 4H-SiC shows an increase in the barrier height, an increase in the ideality factor, and sub-bandgap photovoltaic responses, suggesting the formation of photo-active point defects. The results suggest that the ultrafast laser irradiation technique provides a means of engineering spatially localized structural and electronic modification of wide bandgap materials such as 4H-SiC with relatively low surface damage via low temperature processing.

Martian impact craters - Correlations of ejecta and interior morphologies with diameter, latitude, and terrain

NASA Technical Reports Server (NTRS)

Barlow, Nadine G.; Bradley, Tracy L.

1990-01-01

An effort is made to establish the ability of a correlation between crater morphology and latitude, diameter, and terrain, to discriminate among the effects of impact energy, atmosphere, and subsurface volatiles in 3819 larger-than-8 km diameter craters distributed over the Martian surface. It is noted that changes in ejecta and interior morphology correlate with increases in crater diameter, and that while many of the interior structures exhibit distributions interpretable as terrain-dependent, central peak and peak ring interior morphologies exhibit minimal relationships with planetary properties.

Evolution of residual stress, free volume, and hardness in the laser shock peened Ti-based metallic glass

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

Wang, Liang; Wang, Lu; Nie, Zhihua

Laser shock peening (LSP) with different cycles was performed on the Ti-based bulk metallic glasses (BMGs). The sub-surface residual stress of the LSPed specimens was measured by high-energy X-ray diffraction (HEXRD) and the near-surface residual stress was measured by scanning electron microscope/focused ion beam (SEM/FIB) instrument. The sub-surface residual stress in the LSP impact direction (about-170MPa) is much lower than that perpendicular to the impact direction (about -350 MPa), exhibiting anisotropy. The depth of the compressive stress zone increases from 400 mu m to 500 mu m with increasing LSP cycles. The highest near-surface residual stress is about -750 MPa.more » LSP caused the free volume to increase and the maximum increase appeared after the first LSP process. Compared with the hardness (567 +/- 7 HV) of the as-cast BMG, the hardness (590 +/- 9 HV) on the shocked surface shows a hardening effect due to the hardening mechanism of compressive residual stress; and the hardness (420 +/- 9 HV) on the longitudinal section shows a softening effect due to the softening mechanism of free volume.« less

O2 Plasma Etching and Antistatic Gun Surface Modifications for CNT Yarn Microelectrode Improve Sensitivity and Antifouling Properties.

PubMed

Yang, Cheng; Wang, Ying; Jacobs, Christopher B; Ivanov, Ilia N; Venton, B Jill

2017-05-16

Carbon nanotube (CNT) based microelectrodes exhibit rapid and selective detection of neurotransmitters. While different fabrication strategies and geometries of CNT microelectrodes have been characterized, relatively little research has investigated ways to selectively enhance their electrochemical properties. In this work, we introduce two simple, reproducible, low-cost, and efficient surface modification methods for carbon nanotube yarn microelectrodes (CNTYMEs): O 2 plasma etching and antistatic gun treatment. O 2 plasma etching was performed by a microwave plasma system with oxygen gas flow and the optimized time for treatment was 1 min. The antistatic gun treatment flows ions by the electrode surface; two triggers of the antistatic gun was the optimized number on the CNTYME surface. Current for dopamine at CNTYMEs increased 3-fold after O 2 plasma etching and 4-fold after antistatic gun treatment. When the two treatments were combined, the current increased 12-fold, showing the two effects are due to independent mechanisms that tune the surface properties. O 2 plasma etching increased the sensitivity due to increased surface oxygen content but did not affect surface roughness while the antistatic gun treatment increased surface roughness but not oxygen content. The effect of tissue fouling on CNT yarns was studied for the first time, and the relatively hydrophilic surface after O 2 plasma etching provided better resistance to fouling than unmodified or antistatic gun treated CNTYMEs. Overall, O 2 plasma etching and antistatic gun treatment improve the sensitivity of CNTYMEs by different mechanisms, providing the possibility to tune the CNTYME surface and enhance sensitivity.

Recovery of Active and Efficient Photocatalytic H 2 Production for CdSe Quantum Dots

DOE PAGES

Burke, Rebeckah; Cogan, Nicole M. Briglio; Oi, Aidan; ...

2018-05-07

Recently, colloidal semiconductor quantum dots (QDs) have shown great promise as photocatalysts for the production of chemical fuels by sunlight. Here, the efficiency of photocatalytic hydrogen (H 2) production for integrated systems of large diameter (4.4 nm) CdSe QDs as light harvesting nanoparticles with varying concentrations of nickel-dihydrolipoic acid (Ni-DHLA) small molecule catalysts was measured. While exhibiting excellent robustness and longevity, the efficiency of H 2 production for equimolar catalyst and QDs was relatively poor. However, the efficiency was found to increase substantially with increasing Ni-DHLA:QD molar ratios Surprisingly, this high activity was only observed with the use of 3-mercaptopropionicmore » acid (MPA) ligands, while CdSe QDs capped with dihydrolipoic acid (DHLA) exhibited poor performance in comparison, indicating that the QD capping ligand has a substantial impact on the catalytic performance. Finally, ultrafast transient absorption spectroscopic measurements of the electron transfer (ET) dynamics show fast ET to the catalyst. Importantly, an increase in ET efficiency is observed as the catalyst concentration is increased. Together, these results suggest that for these large QDs, tailoring the QD surface environment for facile ET and increasing catalyst concentrations increases the probability of ET from QDs to Ni-DHLA, overcoming the relatively small driving force for ET and decreased surface electron density for large diameter QDs.« less

Recovery of Active and Efficient Photocatalytic H 2 Production for CdSe Quantum Dots

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

Burke, Rebeckah; Cogan, Nicole M. Briglio; Oi, Aidan

Recently, colloidal semiconductor quantum dots (QDs) have shown great promise as photocatalysts for the production of chemical fuels by sunlight. Here, the efficiency of photocatalytic hydrogen (H 2) production for integrated systems of large diameter (4.4 nm) CdSe QDs as light harvesting nanoparticles with varying concentrations of nickel-dihydrolipoic acid (Ni-DHLA) small molecule catalysts was measured. While exhibiting excellent robustness and longevity, the efficiency of H 2 production for equimolar catalyst and QDs was relatively poor. However, the efficiency was found to increase substantially with increasing Ni-DHLA:QD molar ratios Surprisingly, this high activity was only observed with the use of 3-mercaptopropionicmore » acid (MPA) ligands, while CdSe QDs capped with dihydrolipoic acid (DHLA) exhibited poor performance in comparison, indicating that the QD capping ligand has a substantial impact on the catalytic performance. Finally, ultrafast transient absorption spectroscopic measurements of the electron transfer (ET) dynamics show fast ET to the catalyst. Importantly, an increase in ET efficiency is observed as the catalyst concentration is increased. Together, these results suggest that for these large QDs, tailoring the QD surface environment for facile ET and increasing catalyst concentrations increases the probability of ET from QDs to Ni-DHLA, overcoming the relatively small driving force for ET and decreased surface electron density for large diameter QDs.« less

Comparing the diurnal and seasonal variabilities of atmospheric and surface urban heat islandsbased on the Beijing urban meteorological network

NASA Astrophysics Data System (ADS)

Jiang, S.; Wang, K.; Wang, J.; Zhou, C.; Wang, X.; Lee, X.

2017-12-01

This study compared the diurnal and seasonal cycles of atmospheric and surface urban heat islands (UHIs) based on hourly air temperatures (Ta) collected at 65 out of 262 stations in Beijing and land surface temperature (Ts) derived from Moderate Resolution Imaging Spectroradiometer in the years 2013-2014. We found that the nighttime atmospheric and surface UHIs referenced to rural cropland stations exhibited significant seasonal cycles, with the highest in winter. However, the seasonal variations in the nighttime UHIs referenced to mountainous forest stations were negligible, because mountainous forests have a higher nighttime Ts in winter and a lower nighttime T a in summer than rural croplands. Daytime surface UHIs showed strong seasonal cycles, with the highest in summer. The daytime atmospheric UHIs exhibited a similar but less seasonal cycle under clear-sky conditions, which was not apparent under cloudy-sky conditions. Atmospheric UHIs in urban parks were higher in daytime. Nighttime atmospheric UHIs are influenced by energy stored in urban materials during daytime and released during nighttime. The stronger anthropogenic heat release in winter causes atmospheric UHIs to increase with time during winter nights, but decrease with time during summer nights. The percentage of impervious surfaces is responsible for 49%-54% of the nighttime atmospheric UHI variability and 31%-38% of the daytime surface UHI variability. However, the nighttime surface UHI was nearly uncorrelated with the percentage of impervious surfaces around the urban stations.

Wear behavior of austenite containing plate steels

NASA Astrophysics Data System (ADS)

Hensley, Christina E.

As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing and DSRW samples were observed. Different microstructures exhibited different scratching behaviors. Martensitic microstructures exhibited chipping and cracking, whereas Q&P microstructures exhibited limited or no chipping. The Q&P samples exhibited more deformation at greater loads and hardness levels than the martensitic microstructures. Austenitic microstructures exhibited significant deformation adjacent to the scratches.

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

Maiti, Debtanu; Daza, Yolanda A.; Yung, Matthew M.

Density functional theory (DFT) based investigation of two parameters of prime interest -- oxygen vacancy and surface terminations along (100) and (110) planes -- has been conducted for La (1-x)Sr xFe(1-y)Co yO (3-more » $$\\delta$$) perovskite oxides in view of their application towards thermochemical carbon dioxide conversion reactions. The bulk oxygen vacancy formation energies for these mixed perovskite oxides are found to increase with increasing lanthanum and iron contents in the 'A' site and 'B' site, respectively. Surface terminations along (100) and (110) crystal planes are studied to probe their stability and their capabilities to accommodate surface oxygen vacancies. Amongst the various terminations, the oxygen-rich (110) surface and strontium-rich (100) surface are the most stable, while transition metal-rich terminations along (100) revealed preference towards the production of oxygen vacancies. The carbon dioxide adsorption strength, a key descriptor for CO 2 conversion reactions, is found to increase on oxygen vacant surfaces thus establishing the importance of oxygen vacancies in CO 2 conversion reactions. Amongst all the surface terminations, the lanthanum-oxygen terminated surface exhibited the strongest CO 2 adsorption strength. Finally, the theoretical prediction of the oxygen vacancy trends and the stability of the samples were corroborated by the temperature-programmed reduction and oxidation reactions and in situ XRD crystallography.« less

Satellite monitoring of sea surface pollution

NASA Technical Reports Server (NTRS)

Fielder, G.; Telfer, D. J. (Principal Investigator)

1979-01-01

The author has identified the following significant results. Image processing techniques developed are well adapted to the exploration and isolation of local areas which exhibit small temperature differences between themselves and their surroundings. In the worst case of imagery of small areal extent of sea surface having no coastal boundary in the area, there is yet no method of distinguishing unambiguously an oil spill from fog, cloud, the effect produced by shallow sediments, or the effects of naturally occuring thermal fronts. In the case of uniform slicks of liquid North Sea oil in still air, laboratory simulation experiments show that, for oil thicknesses in excess of 1 or 2 mm, there is, under equilibrium conditions, little dependence of oil surface temperature on the thickness of the oil layer. The surface temperature of oil is consistently higher than that of water, the difference being about 1 K at low values of relative humidity, but tending to increase as the relative humidity increases.

Traffic jams reduce hydrolytic efficiency of cellulase on cellulose surface.

PubMed

Igarashi, Kiyohiko; Uchihashi, Takayuki; Koivula, Anu; Wada, Masahisa; Kimura, Satoshi; Okamoto, Tetsuaki; Penttilä, Merja; Ando, Toshio; Samejima, Masahiro

2011-09-02

A deeper mechanistic understanding of the saccharification of cellulosic biomass could enhance the efficiency of biofuels development. We report here the real-time visualization of crystalline cellulose degradation by individual cellulase enzymes through use of an advanced version of high-speed atomic force microscopy. Trichoderma reesei cellobiohydrolase I (TrCel7A) molecules were observed to slide unidirectionally along the crystalline cellulose surface but at one point exhibited collective halting analogous to a traffic jam. Changing the crystalline polymorphic form of cellulose by means of an ammonia treatment increased the apparent number of accessible lanes on the crystalline surface and consequently the number of moving cellulase molecules. Treatment of this bulky crystalline cellulose simultaneously or separately with T. reesei cellobiohydrolase II (TrCel6A) resulted in a remarkable increase in the proportion of mobile enzyme molecules on the surface. Cellulose was completely degraded by the synergistic action between the two enzymes.

Microstructural and mechanical characteristics of Ni–Cr thin films

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

Petley, Vijay; Sathishkumar, S.; Thulasi Raman, K.H.

2015-06-15

Highlights: • Ni–Cr thin films of varied composition deposited by DC magnetron co-sputtering. • Thin film with Ni–Cr: 80–20 at% composition exhibits most distinct behavior. • The films were tensile tested and exhibited no cracking till the substrate yielding. - Abstract: Ni–Cr alloy thin films have been deposited using magnetron co-sputtering technique at room temperature. Crystal structure was evaluated using GIXRD. Ni–Cr solid solution upto 40 at% of Cr exhibited fcc solid solution of Cr in Ni and beyond that it exhibited bcc solid solution of Ni in Cr. X-ray diffraction analysis shows formation of (1 1 1) fiber texturemore » in fcc and (2 2 0) fiber texture in bcc Ni–Cr thin films. Electron microscopy in both in-plane and transverse direction of the film surface revealed the presence of columnar microstructure for films having Cr upto 40 at%. Mechanical properties of the films are evaluated using nanoindentation. The modulus values increased with increase of Cr at% till the film is fcc. With further increase in Cr at% the modulus values decreased. Ni–Cr film with 20 at% Ni exhibits reduction in modulus and is correlated to the poor crystallization of the film as reflected in XRD analysis. The Ni–Cr thin film with 80 at% Ni and 20 at% Cr exhibited the most distinct columnar structure with highest electrical resistivity, indentation hardness and elastic modulus.« less

Modification and properties characterization of heterogeneous anion-exchange membranes by electrodeposition of graphene oxide (GO)

NASA Astrophysics Data System (ADS)

Li, Yujiao; Shi, Shaoyuan; Cao, Hongbin; Zhao, Zhijuan; Wen, Hao

2018-06-01

The heterogeneous anion exchange membranes (AEMs) were modified by electrodeposition of graphene oxide (GO) under different conditions. The physicochemical properties of GO-modified membranes were characterized systemically to obtain the optimized conditions for the electrodeposition of GO on the surface of AEMs. The results indicated that the contact angle and zeta potential of the modified AEMs decreased when increasing the concentration of GO from 0.05 g/L to 0.1 g/L. The higher concentration of NaCl, as the supporting electrolyte, could hinder the electrodeposition of GO on the AEMs for the competitive migration between the GO and Cl- ions. The increase of current density had a positive effect on properties of GO-modified membranes in the range of 1-5 mA/cm2. Compared with the pristine AEM, all the GO-modified AEMs exhibited smoother surface, higher hydrophilicity and negative zeta potential. It was also found that the GO modifying layer did not increase electrical resistance and had only a negligible effect on the desalination performance of AEMs. In the fouling experiments with sodium dodecyl benzene sulfonate (SDBS) as the model foulant, the GO-modified AEMs exhibited improved fouling resistance to SDBS.

Evaluation of Giga-cycle Fatigue Properties of Austenitic Stainless Steels Using Ultrasonic Fatigue Test

NASA Astrophysics Data System (ADS)

Takahashi, Kyouhei; Ogawa, Takeshi

Ultrasonic fatigue tests have been performed in austenitic stainless steel, SUS316NG, in order to investigate giga-cycle fatigue strength of pre-strained materials, i.e. 5, 10 and 20% tensile pre-strains and -20% compressive pre-strain. The pre-strains were applied before specimen machining. The austenitic stainless steels are known to exhibit remarkable self-heating during the fatigue experiment. Therefore, heat radiation method was established by setting fatigue specimens in a low temperature chamber at about -100°C. The self-heating was controlled by intermittent loading condition, which enabled us to maintain the test section of the specimens at about room temperature. The results revealed that the fatigue strength increased with increasing pre-strain levels. Fish-eye fracture was observed for -20% pre-strained specimen fractured at 4.11×107 cycles, while the other specimens exhibited ordinary fatigue fracture surface originated from stage I facet on the specimen surface. The increase in fatigue limit was predicted by Vickers hardness, HV, which depended on the size of indented region. The prediction was successful using HV values obtained by the size of the indented region similar to those of the stage I facets.

Determination of refractive indices of opaque rough surfaces

NASA Astrophysics Data System (ADS)

Destouches, Nathalie; Deumié, Carole; Giovannini, Hugues; Amra, Claude

2004-02-01

The refractive indices of optical materials are usually determined from spectrophotometric andellipsometric measurements of specular beams. When the roughness of the interfaces increases, the energy in the specularly reflected and transmitted beams decreases and scattering becomes predominant. For strong roughness (compared to the incident wavelength) a surface does not exhibit specular reflection or transmission, making difficult the determination of the refractive index. We describe two techniques, based on scattering measurements, that one can use to determine the refractive indices of opaque inhomogeneous media.

Draft Genome Sequences of Acinetobacter and Bacillus Strains Isolated from Spacecraft-Associated Surfaces

PubMed Central

Seuylemezian, Arman; Vaishampayan, Parag; Cooper, Kerry

2018-01-01

ABSTRACT We report here the draft genome sequences of four strains isolated from spacecraft-associated surfaces exhibiting increased resistance to stressors such as UV radiation and exposure to H2O2. The draft genomes of strains 1P01SCT, FO-92T, 50v1, and 2P01AA had sizes of 5,500,894 bp, 4,699,376 bp, 3,174,402 bp, and 4,328,804 bp, respectively. PMID:29439046

A study of laser surface treatment in bonded repair of composite aircraft structures.

PubMed

Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-03-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

A study of laser surface treatment in bonded repair of composite aircraft structures

NASA Astrophysics Data System (ADS)

Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-03-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

A study of laser surface treatment in bonded repair of composite aircraft structures

PubMed Central

Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-01-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen. PMID:29657748

Tin doped indium oxide anodes with artificially controlled nano-scale roughness using segregated Ag nanoparticles for organic solar cells

NASA Astrophysics Data System (ADS)

Kim, Hyo-Joong; Ko, Eun-Hye; Noh, Yong-Jin; Na, Seok-In; Kim, Han-Ki

2016-09-01

Nano-scale surface roughness in transparent ITO films was artificially formed by sputtering a mixed Ag and ITO layer and wet etching of segregated Ag nanoparticles from the surface of the ITO film. Effective removal of self-segregated Ag particles from the grain boundaries and surface of the crystalline ITO film led to a change in only the nano-scale surface morphology of ITO film without changes in the sheet resistance and optical transmittance. A nano-scale rough surface of the ITO film led to an increase in contact area between the hole transport layer and the ITO anode, and eventually increased the hole extraction efficiency in the organic solar cells (OSCs). The heterojunction OSCs fabricated on the ITO anode with a nano-scale surface roughness exhibited a higher power conversion efficiency of 3.320%, than that (2.938%) of OSCs made with the reference ITO/glass. The results here introduce a new method to improve the performance of OSCs by simply modifying the surface morphology of the ITO anodes.

Universality of (2+1)-dimensional restricted solid-on-solid models

NASA Astrophysics Data System (ADS)

Kelling, Jeffrey; Ódor, Géza; Gemming, Sibylle

2016-08-01

Extensive dynamical simulations of restricted solid-on-solid models in D =2 +1 dimensions have been done using parallel multisurface algorithms implemented on graphics cards. Numerical evidence is presented that these models exhibit Kardar-Parisi-Zhang surface growth scaling, irrespective of the step heights N . We show that by increasing N the corrections to scaling increase, thus smaller step-sized models describe better the asymptotic, long-wave-scaling behavior.

Quantitative biological surface science: challenges and recent advances.

PubMed

Höök, Fredrik; Kasemo, Bengt; Grunze, Michael; Zauscher, Stefan

2008-12-23

Biological surface science is a broad, interdisciplinary subfield of surface science, where properties and processes at biological and synthetic surfaces and interfaces are investigated, and where biofunctional surfaces are fabricated. The need to study and to understand biological surfaces and interfaces in liquid environments provides sizable challenges as well as fascinating opportunities. Here, we report on recent progress in biological surface science that was described within the program assembled by the Biomaterial Interface Division of the Science and Technology of Materials, Interfaces and Processes (www.avs.org) during their 55th International Symposium and Exhibition held in Boston, October 19-24, 2008. The selected examples show that the rapid progress in nanoscience and nanotechnology, hand-in-hand with theory and simulation, provides increasingly sophisticated methods and tools to unravel the mechanisms and details of complex processes at biological surfaces and in-depth understanding of biomolecular surface interactions.

Tribological properties of fish scale inspired underwater superoleophobic hierarchical structure in aqueous environment

NASA Astrophysics Data System (ADS)

Lian, Zhongxu; Xu, Jinkai; Wan, Yanling; Li, Yiquan; Yu, Zhanjiang; Liu, Qimeng; Yu, Huadong

2017-10-01

Underwater superoleophobic surfaces are becoming increasingly important in regard to self-cleaning, anti-fouling, oil droplet transportation and water/oil separation. Although a great number of underwater superoleophobic surfaces have been demonstrated, their tribological properties remain impractical for the purposes of real-life applications. Herein, a two-step method of high speed wire electrical discharge machining and boiling water treatment was adopted to fabricate fish scale inspired underwater oil repellent hierarchical structure on an aluminum (Al) alloy 5083 surface. The hierarchical roughness and hydroxyl groups were obtained on the surface, and the surface exhibited the ability to prevent contact with organic fluids when submerged in water. Moreover, the tribological properties of underwater superoleophobic Al surfaces in aqueous environments were analyzed. The average friction coefficient of underwater superoleophobic surfaces was decreased compared with the polished Al surface. We believe that this research will contribute to the engineering application of underwater superoleophobic surfaces in the future.

Surface-plasmon resonance-enhanced multiphoton emission of high-brightness electron beams from a nanostructured copper cathode.

PubMed

Li, R K; To, H; Andonian, G; Feng, J; Polyakov, A; Scoby, C M; Thompson, K; Wan, W; Padmore, H A; Musumeci, P

2013-02-15

We experimentally investigate surface-plasmon assisted photoemission to enhance the efficiency of metallic photocathodes for high-brightness electron sources. A nanohole array-based copper surface was designed to exhibit a plasmonic response at 800 nm, fabricated using the focused ion beam milling technique, optically characterized and tested as a photocathode in a high power radio frequency photoinjector. Because of the larger absorption and localization of the optical field intensity, the charge yield observed under ultrashort laser pulse illumination is increased by more than 100 times compared to a flat surface. We also present the first beam characterization results (intrinsic emittance and bunch length) from a nanostructured photocathode.

An experimental model of COD abatement in MBBR based on biofilm growth dynamic and on substrates' removal kinetics.

PubMed

Siciliano, Alessio; De Rosa, Salvatore

2016-08-01

In this study, the performance of a lab-scale Moving Bed Biofilm Reactor (MBBR) under different operating conditions was analysed. Moreover, the dependence of the reaction rates both from the concentration and biodegradability of substrates and from the biofilm surface density, by means of several batch kinetic tests, was investigated. The reactor controls exhibited an increasing COD (Chemical Oxygen Demand) removal, reaching maximum yields (close to 90%) for influent loadings of up to12.5 gCOD/m(2)d. From this value, the pilot plant performance decreased to yields of only about 55% for influent loadings greater than 16 gCOD/m(2)d. In response to the influent loading increase, the biofilm surface density exhibited a logistic growing trend until reaching a maximum amount of total attached solids of about 9.5 g/m(2). The kinetic test results indicated that the COD removal rates for rapidly biodegradable, rapidly hydrolysable and slowly biodegradable substrates were not affected by the organic matter concentrations. Instead, first-order kinetics were detected with respect to biofilm surface density. The experimental results permitted the formulation of a mathematical model to predict the MBBR organic matter removal efficiency. The validity of the model was successfully tested in the lab-scale plant.

Extrinsic pseudocapacitve Li-ion storage of SnS anode via lithiation-induced structural optimization on cycling

NASA Astrophysics Data System (ADS)

Lian, Qingwang; Zhou, Gang; Liu, Jiatu; Wu, Chen; Wei, Weifeng; Chen, Libao; Li, Chengchao

2017-10-01

Here, we report a new enhanced extrinsic pseudocapacitve Li-ion storage mechanism via lithiation-induced structural optimization strategy. The flower-like C@SnS and bulk SnS exhibit initial capacity decay and subsequent increase of capacity on cycling. After a long-term lithiation/delithiation process, flower-like C@SnS and bulk SnS exhibit improved rate performance and reversible capacity in comparison with those of initial state. Moreover, a high capacity of 530 mAh g-1 is still remained even after 1550 cycles at a high current density of 5.0 A g-1 for flower-like C@SnS after pre-lithiation of 350 cycles. According to the comprehensive analysis of structural evolution and electrochemical performance, it demonstrates that SnS electrodes experience crystal size reduction and further amorphization on cycling, which enhances the reversibility of conversion reaction for SnS, leading to increasing capacity. On the other hand, surface-dominated extrinsic pseudocapacitive contribution results in enhanced rate performance because electrodes expose a large fraction of Li+ sites on surface or near-surface region with structural optimization on cycling. This study reveals that extrinsic pseudocapacitance of SnS can be stimulated via lithiation-induced structural optimization, which gives rise to high-rate and long-lived performances.

Channel layer thickness dependence of In-Ti-Zn-O thin-film transistors fabricated using pulsed laser deposition

NASA Astrophysics Data System (ADS)

Zhang, Q.; Shan, F. K.; Liu, G. X.; Liu, A.; Lee, W. J.; Shin, B. C.

2014-05-01

Amorphous indium-titanium-zinc-oxide (ITZO) thin-film transistors (TFTs) with various channel thicknesses were fabricated at room temperature by using pulsed laser deposition. The channel layer thickness (CLT) dependence of the TFTs was investigated. All the ITZO thin films were amorphous, and the surface roughnesses decreased slightly first and then increased with increasing CLT. With increasing CLT from 35 to 140 nm, the on/off current ratio and the field-effect mobility increased, and the subthreshold swing decreased. The TFT with a CLT of 210 nm exhibited the worst performance, while the ITZO TFT with a CLT of 140 nm exhibited the best performance with a subthreshold voltage of 2.86 V, a mobility of 53.9 cm2V-1s-1, a subthreshold swing of 0.29 V/decade and an on/off current ratio of 109.

The oxidation of copper catalysts during ethylene epoxidation.

PubMed

Greiner, M T; Jones, T E; Johnson, B E; Rocha, T C R; Wang, Z J; Armbrüster, M; Willinger, M; Knop-Gericke, A; Schlögl, R

2015-10-14

The oxidation of copper catalysts during ethylene epoxidation was characterized using in situ photoemission spectroscopy and electron microscopy. Gas chromatography, proton-transfer reaction mass spectrometry and electron-ionization mass spectrometry were used to characterize the catalytic properties of the oxidized copper. We find that copper corrodes during epoxidation in a 1 : 1 mixture of oxygen and ethylene. The catalyst corrosion passes through several stages, beginning with the formation of an O-terminated surface, followed by the formation of Cu2O scale and eventually a CuO scale. The oxidized catalyst exhibits measurable activity for ethylene epoxidation, but with a low selectivity of <3%. Tests on pure Cu2O and CuO powders confirm that the oxides intrinsically exhibit partial-oxidation activity. Cu2O was found to form acetaldehyde and ethylene epoxide in roughly equal amounts (1.0% and 1.2% respectively), while CuO was found to form much less ethyl aldehyde than ethylene epoxide (0.1% and 1.0%, respectively). Metallic copper catalysts were examined in extreme dilute-O2 epoxidation conditions to try and keep the catalyst from oxidizing during the reaction. It was found that in feed of 1 part O2 to 2500 parts C2H4 (PO2 = 1.2 × 10(-4) mbar) the copper surface becomes O-terminated. The O-terminated surface was found to exhibit partial-oxidation selectivity similar to that of Cu2O. With increasing O2 concentration (>8/2500) Cu2O forms and eventually covers the surface.

Anodized aluminum on LDEF

NASA Technical Reports Server (NTRS)

Golden, Johnny L.

1993-01-01

A compilation of reported analyses and results obtained for anodized aluminum flown on the Long Duration Exposure Facility (LDEF) was prepared. Chromic acid, sulfuric acid, and dyed sulfuric acid anodized surfaces were exposed to the space environment. The vast majority of the anodized surface on LDEF was chromic acid anodize because of its selection as a thermal control coating for use on the spacecraft primary structure, trays, tray clamps, and space end thermal covers. Reports indicate that the chromic acid anodize was stable in solar absorptance and thermal emittance, but that contamination effects caused increases in absorptance on surfaces exposed to low atomic oxygen fluences. There were some discrepancies, however, in that some chromic acid anodized specimens exhibited significant increases in absorptance. Sulfuric acid anodized surfaces also appeared stable, although very little surface area was available for evaluation. One type of dyed sulfuric acid anodize was assessed as an optical baffle coating and was observed to have improved infrared absorptance characteristics with exposure on LDEF.

Bio-functionalisation of polyether ether ketone using plasma immersion ion implantation

NASA Astrophysics Data System (ADS)

Wakelin, Edgar; Yeo, Giselle; Kondyurin, Alexey; Davies, Michael; McKenzie, David; Weiss, Anthony; Bilek, Marcela

2015-12-01

Plasma immersion ion implantation (PIII) is used here to improve the surface bioactivity of polyether ether ketone (PEEK) by modifying the chemical and mechanical properties and by introducing radicals. Modifications to the chemical and mechanical properties are characterised as a function of ion fluence (proportional to treatment time) to determine the suitability of the treated surfaces for biological applications. Radical generation increases with treatment time, where treatments greater than 400 seconds result in a high concentration of long-lived radicals. Radical reactions are responsible for oxidation of the surface, resulting in a permanent increase in the polar surface energy. The nano-scale reduced modulus was found to increase with treatment time at the surface from 4.4 to 5.2 GPa. The macromolecular Young's modulus was also found to increase, but by an amount corresponding to the volume fraction of the ion implanted region. The treated surface layer exhibited cracking under cyclical loads, associated with an increased modulus due to dehydrogenation and crosslinking, however it did not show any sign of delamination, indicating that the modified layer is well integrated with the substrate - a critical factor for bioactive surface coatings to be used in-vivo. Protein immobilisation on the PIII treated surfaces was found to saturate after 240 seconds of treatment, indicating that there is room to tune surface mechanical properties for specific applications without affecting the protein coverage. Our findings indicate that the modification of the chemical and mechanical properties by PIII treatments as well as the introduction of radicals render PEEK well suited for use in orthopaedic implantable devices.

Optically transparent and environmentally durable superhydrophobic coating based on functionalized SiO 2 nanoparticles

DOE PAGES

Schaeffer, Daniel A.; Polizos, Georgios; Smith, D. Barton; ...

2015-01-09

Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a self-cleaning effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 16≥0° to 175°. This result is remarkable because such behavior cannotmore » be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, surfaces exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the contact angle and optical transmission between 190 to 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents isopropyl alcohol and 4-chlorobenzotrifluoride (PCBTF) and a proprietary ceramic binder (Cerakote ). Finally, this solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 minutes, these coatings exhibited superhydrophobic behavior with a static CA ≥160°.« less

Why Low Bounce Balls Exhibit High Rolling Resistance

ERIC Educational Resources Information Center

Cross, Rod

2015-01-01

A simple experiment is described to measure the coefficient of rolling friction for a low bounce ball rolling on a horizontal surface. As observed previously by others, the coefficient increased with rolling speed. The energy loss due to rolling friction can be explained in terms of the measured coefficient of restitution for the ball, meaning…

Organic photosensitive devices

DOEpatents

Rand, Barry P; Forrest, Stephen R

2013-11-26

The present invention generally relates to organic photosensitive optoelectronic devices. More specifically, it is directed to organic photosensitive optoelectronic devices having a photoactive organic region containing encapsulated nanoparticles that exhibit plasmon resonances. An enhancement of the incident optical field is achieved via surface plasmon polariton resonances. This enhancement increases the absorption of incident light, leading to a more efficient device.

A simple way to achieve bioinspired hybrid wettability surface with micro/nanopatterns for efficient fog collection.

PubMed

Yin, Kai; Du, Haifeng; Dong, Xinran; Wang, Cong; Duan, Ji-An; He, Jun

2017-10-05

Fog collection is receiving increasing attention for providing water in semi-arid deserts and inland areas. Inspired by the fog harvesting ability of the hydrophobic-hydrophilic surface of Namib desert beetles, we present a simple, low-cost method to prepare a hybrid superhydrophobic-hydrophilic surface. The surface contains micro/nanopatterns, and is prepared by incorporating femtosecond-laser fabricated polytetrafluoroethylene nanoparticles deposited on superhydrophobic copper mesh with a pristine hydrophilic copper sheet. The as-prepared surface exhibits enhanced fog collection efficiency compared with uniform (super)hydrophobic or (super)hydrophilic surfaces. This enhancement can be tuned by controlling the mesh number, inclination angle, and fabrication structure. Moreover, the surface shows excellent anti-corrosion ability after immersing in 1 M HCl, 1 M NaOH, and 10 wt% NaCl solutions for 2 hours. This work may provide insight into fabricating hybrid superhydrophobic-hydrophilic surfaces for efficient atmospheric water collection.

Enhanced catalyst activity by decorating of Au on Ag@Cu2O nanoshell

NASA Astrophysics Data System (ADS)

Chen, Lei; Liu, Maomao; Zhao, Yue; Kou, Qiangwei; Wang, Yaxin; Liu, Yang; Zhang, Yongjun; Yang, Jinghai; Jung, Young Mee

2018-03-01

We successfully synthesized Au-decorated Ag@Cu2O heterostructures via a simple galvanic replacement method. As the Au precursor concentration increased, the density of the Au nanoparticles (NPs) on the Ag@Cu2O surface increased, which changed the catalytic activity of the Ag@Cu2O-Au structure. The combination of Au, Ag, and Cu2O exhibited excellent catalytic properties, which can further effect on the catalyst activity of the Ag@Cu2O-Au structure. In addition, the proposed Ag@Cu2O-Au nanocomposite was used to transform the organic, toxic pollutant, 4-nitrophenol (4-NP), into its nontoxic and medicinally important amino derivative via a catalytic reduction to optimize the material performance. The proposed Au-decorated Ag@Cu2O exhibited excellent catalytic activity, and the catalytic reduction time greatly decreased (5 min). Thus, three novel properties of Ag@Cu2O-Au, i.e., charge redistribution and transfer, adsorption, and catalytic reduction of organic pollutants, were ascertained for water remediation. The proposed catalytic properties have potential applications for photocatalysis and localized surface plasmon resonance (LSPR)- and peroxidase-like catalysis.

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst.

PubMed

Wu, Chien-Chen; Chen, Dong-Hwang

2012-06-19

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe3O4 nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe3O4 nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles.

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst

PubMed Central

2012-01-01

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe3O4 nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe3O4 nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles. PMID:22713480

Surface modification of malachite with ethanediamine and its effect on sulfidization flotation

NASA Astrophysics Data System (ADS)

Feng, Qicheng; Zhao, Wenjuan; Wen, Shuming

2018-04-01

Ethanediamine was used to modify the mineral surface of malachite to improve its sulfidization and flotation behavior. The activation mechanism was investigated by adsorption experiments, X-ray photoelectron spectroscopy (XPS) analysis, and zeta potential measurements. Microflotation experiments showed that the flotation recovery of malachite was enhanced after the pretreatment of the mineral particles with ethanediamine prior to the addition of Na2S. Adsorption tests revealed that numerous sulfide ion species in the pulp solution were transferred onto the mineral surface through the formation of more copper sulfide species. This finding was confirmed by the results of the XPS measurements. Ethanediamine modification not only increased the contents of copper sulfide species on the malachite surface but also enhanced the reactivity of the sulfidization products. During sulfidization, Cu(II) species on the mineral surface were reduced into Cu(I) species, and the percentages of S22- and Sn2- relative to the total S increased after modification, resulting in increased surface hydrophobicity. The results of zeta potential measurements showed that the ethanediamine-modified mineral surface adsorbed with more sulfide ion species was advantageous to the attachment of xanthate species, thereby improving malachite floatability. The proposed ethanediamine modification followed by sulfidization xanthate flotation exhibits potential for industrial application.

Evaluation of the surface roughness effect on suspended particle deposition near unpaved roads

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

Zhu, Dongzi; Gillies, J. A.; Etyemezian, V.

2015-11-11

The downwind transport and deposition of suspended dust raised by a vehicle driving on unpaved roads was studied for four differently vegetated surfaces in the USA states of Kansas and Washington, and one barren surface in Nevada. A 10 m high tower adjacent to the source (z10 m downwind) and an array of multi-channel optical particle counters at three positions downwind of the source measured the flux of particles and the particle size distribution in the advecting dust plumes in the horizontal and vertical directions. Aerodynamic parameters such as friction velocity (u*) and surface roughness length (z0) were calculated frommore » wind speed measurements made on the tower. Particle number concentration, PM10 mass exhibited an exponential decay along the direction of transport. Coarse particles accounted for z95% of the PM10 mass, at least to a downwind distance of 200 m from the source. PM10 removed by deposition was found to increase with increasing particle size and increasing surface roughness under similar moderate wind speed conditions. The surface of dense, long grass (1.2 m high and complete surface cover) had the greatest reduction of PM10 among the five surfaces tested due to deposition induced by turbulence effects created by the rougher surface and by enhanced particle impaction/ interception effects to the grass blades.« less

Cellulose nanocrystals with tunable surface charge for nanomedicine

NASA Astrophysics Data System (ADS)

Hosseinidoust, Zeinab; Alam, Md Nur; Sim, Goeun; Tufenkji, Nathalie; van de Ven, Theo G. M.

2015-10-01

Crystalline nanoparticles of cellulose exhibit attractive properties as nanoscale carriers for bioactive molecules in nanobiotechnology and nanomedicine. For applications in imaging and drug delivery, surface charge is one of the most important factors affecting the performance of nanocarriers. However, current methods of preparation offer little flexibility for controlling the surface charge of cellulose nanocrystals, leading to compromised colloidal stability under physiological conditions. We report a synthesis method that results in nanocrystals with remarkably high carboxyl content (6.6 mmol g-1) and offers continuous control over surface charge without any adjustment to the reaction conditions. Six fractions of nanocrystals with various surface carboxyl contents were synthesized from a single sample of softwood pulp with carboxyl contents varying from 6.6 to 1.7 mmol g-1 and were fully characterized. The proposed method resulted in highly stable colloidal nanocrystals that did not aggregate when exposed to high salt concentrations or serum-containing media. Interactions of these fractions with four different tissue cell lines were investigated over a wide range of concentrations (50-300 μg mL-1). Darkfield hyperspectral imaging and confocal microscopy confirmed the uptake of nanocrystals by selected cell lines without any evidence of membrane damage or change in cell density; however a charge-dependent decrease in mitochondrial activity was observed for charge contents higher than 3.9 mmol g-1. A high surface carboxyl content allowed for facile conjugation of fluorophores to the nanocrystals without compromising colloidal stability. The cellular uptake of fluoresceinamine-conjugated nanocrystals exhibited a time-dose dependent relationship and increased significantly with doubling of the surface charge.Crystalline nanoparticles of cellulose exhibit attractive properties as nanoscale carriers for bioactive molecules in nanobiotechnology and nanomedicine. For applications in imaging and drug delivery, surface charge is one of the most important factors affecting the performance of nanocarriers. However, current methods of preparation offer little flexibility for controlling the surface charge of cellulose nanocrystals, leading to compromised colloidal stability under physiological conditions. We report a synthesis method that results in nanocrystals with remarkably high carboxyl content (6.6 mmol g-1) and offers continuous control over surface charge without any adjustment to the reaction conditions. Six fractions of nanocrystals with various surface carboxyl contents were synthesized from a single sample of softwood pulp with carboxyl contents varying from 6.6 to 1.7 mmol g-1 and were fully characterized. The proposed method resulted in highly stable colloidal nanocrystals that did not aggregate when exposed to high salt concentrations or serum-containing media. Interactions of these fractions with four different tissue cell lines were investigated over a wide range of concentrations (50-300 μg mL-1). Darkfield hyperspectral imaging and confocal microscopy confirmed the uptake of nanocrystals by selected cell lines without any evidence of membrane damage or change in cell density; however a charge-dependent decrease in mitochondrial activity was observed for charge contents higher than 3.9 mmol g-1. A high surface carboxyl content allowed for facile conjugation of fluorophores to the nanocrystals without compromising colloidal stability. The cellular uptake of fluoresceinamine-conjugated nanocrystals exhibited a time-dose dependent relationship and increased significantly with doubling of the surface charge. Electronic supplementary information (ESI) available: Additional results are presented in the ESI in Fig. S1 through S4. See DOI: 10.1039/c5nr02506k

High-Temperature Growth of GaN and Al x Ga1- x N via Ammonia-Based Metalorganic Molecular-Beam Epitaxy

NASA Astrophysics Data System (ADS)

Billingsley, Daniel; Henderson, Walter; Doolittle, W. Alan

2010-05-01

The effect of high-temperature growth on the crystalline quality and surface morphology of GaN and Al x Ga1- x N grown by ammonia-based metalorganic molecular-beam epitaxy (NH3-MOMBE) has been investigated as a means of producing atomically smooth films suitable for device structures. The effects of V/III ratio on the growth rate and surface morphology are described herein. The crystalline quality of both GaN and AlGaN was found to mimic that of the GaN templates, with (002) x-ray diffraction (XRD) full-widths at half- maximum (FWHMs) of ~350 arcsec. Nitrogen-rich growth conditions have been found to provide optimal surface morphologies with a root-mean-square (RMS) roughness of ~0.8 nm, yet excessive N-rich environments have been found to reduce the growth rate and result in the formation of faceted surface pitting. AlGaN exhibits a decreased growth rate, as compared with GaN, due to increased N recombination as a result of the increased pyrolysis of NH3 in the presence of Al. AlGaN films grown directly on GaN templates exhibited Pendellösung x-ray fringes, indicating an abrupt interface and a planar AlGaN film. AlGaN films grown for this study resulted in an optimal RMS roughness of ~0.85 nm with visible atomic steps.

Idealized modeling of convective organization with changing sea surface temperatures using multiple equilibria in weak temperature gradient simulations

NASA Astrophysics Data System (ADS)

Sentić, Stipo; Sessions, Sharon L.

2017-06-01

The weak temperature gradient (WTG) approximation is a method of parameterizing the influences of the large scale on local convection in limited domain simulations. WTG simulations exhibit multiple equilibria in precipitation; depending on the initial moisture content, simulations can precipitate or remain dry for otherwise identical boundary conditions. We use a hypothesized analogy between multiple equilibria in precipitation in WTG simulations, and dry and moist regions of organized convection to study tropical convective organization. We find that the range of wind speeds that support multiple equilibria depends on sea surface temperature (SST). Compared to the present SST, low SSTs support a narrower range of multiple equilibria at higher wind speeds. In contrast, high SSTs exhibit a narrower range of multiple equilibria at low wind speeds. This suggests that at high SSTs, organized convection might occur with lower surface forcing. To characterize convection at different SSTs, we analyze the change in relationships between precipitation rate, atmospheric stability, moisture content, and the large-scale transport of moist entropy and moisture with increasing SSTs. We find an increase in large-scale export of moisture and moist entropy from dry simulations with increasing SST, which is consistent with a strengthening of the up-gradient transport of moisture from dry regions to moist regions in organized convection. Furthermore, the changes in diagnostic relationships with SST are consistent with more intense convection in precipitating regions of organized convection for higher SSTs.

Proof Test Diagrams for a Lithia-Alumina-Silica Glass-Ceramic

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.

2003-01-01

The glass-ceramic (Zerodur, Schott Glaswerke, Mainz, Germany) contains 70% to 78% by weight crystalline phase of high-quartz structure with a mean crystal size of 50-55 nm. The vitreous phase has a positive thermal expansion coefficient which is practically balanced by the negative coefficient of the crystalline phase. This results in a material which can maintain longitudinal stability during thermal cycling. This was one of the reasons for its choice as the material for the grazing incidence mirrors for the Chandra X-Ray Facility. Brittle materials such as glass and glass-ceramics which exhibit slow crack growth and subsequent fast fracture to failure exhibit a time dependence in strength. The decrease in strength for a constant applied load is known as static fatigue. In many cases, environment plays a major role in the material lifetime. It has been shown for silicate glasses that crack velocity will increase as the amount of water vapor in the environment surface finish and rate of loading. A rough surface finish leads to a lower tensile strength than for an optically polished surface. The strength of glass is observed in general to increase with increasing load rate. This phenomena is known as dynamic fatigue. This was observed for Zerodur by Tucker and Gent and Tucker in previous dynamic fatigue studies, in which lifetimes were obtained. All of the above named factors need to be considered when glass is to be used in load bearing applications.

L1 stimulation of human glioma cell motility correlates with FAK activation

PubMed Central

Yang, Muhua; Li, Yupei; Chilukuri, Kalyani; Brady, Owen A.; Boulos, Magdy I.; Kappes, John C.

2011-01-01

The neural adhesion/recognition protein L1 (L1CAM; CD171) has been shown or implicated to function in stimulation of cell motility in several cancer types, including high-grade gliomas. Our previous work demonstrated the expression and function of L1 protein in stimulation of cell motility in rat glioma cells. However, the mechanism of this stimulation is still unclear. This study further investigated the function of L1 and L1 proteolysis in human glioblastoma multiforme (GBM) cell migration and invasion, as well as the mechanism of this stimulation. L1 mRNA was found to be present in human T98G GBM cell line but not in U-118 MG grade III human glioma cell line. L1 protein expression, proteolysis, and release were found in T98G cells and human surgical GBM cells by Western blotting. Exosome-like vesicles released by T98G cells were purified and contained full-length L1. In a scratch assay, T98G cells that migrated into the denuded scratch area exhibited upregulation of ADAM10 protease expression coincident with loss of surface L1. GBM surgical specimen cells exhibited a similar loss of cell surface L1 when xenografted into the chick embryo brain. When lentivirally introduced shRNA was used to attenuate L1 expression, such T98G/shL1 cells exhibited significantly decreased cell motility by time lapse microscopy in our quantitative Super Scratch assay. These cells also showed a decrease in FAK activity and exhibited increased focal complexes. L1 binding integrins which activate FAK were found in T98G and U-118 MG cells. Addition of L1 ectodomain-containing media (1) rescued the decreased cell motility of T98G/shL1 cells and (2) increased cell motility of U-118 MG cells but (3) did not further increase T98G cell motility. Injection of L1-attenuated T98G/shL1 cells into embryonic chick brains resulted in the absence of detectable invasion compared to control cells which invaded brain tissue. These studies support a mechanism where glioma cells at the edge of a cell mass upregulate ADAM10 to proteolyze surface L1 and the resultant ectodomain increases human glioma cell migration and invasion by binding to integrin receptors, activating FAK, and increasing turnover of focal complexes. PMID:21373966

L1 stimulation of human glioma cell motility correlates with FAK activation.

PubMed

Yang, Muhua; Li, Yupei; Chilukuri, Kalyani; Brady, Owen A; Boulos, Magdy I; Kappes, John C; Galileo, Deni S

2011-10-01

The neural adhesion/recognition protein L1 (L1CAM; CD171) has been shown or implicated to function in stimulation of cell motility in several cancer types, including high-grade gliomas. Our previous work demonstrated the expression and function of L1 protein in stimulation of cell motility in rat glioma cells. However, the mechanism of this stimulation is still unclear. This study further investigated the function of L1 and L1 proteolysis in human glioblastoma multiforme (GBM) cell migration and invasion, as well as the mechanism of this stimulation. L1 mRNA was found to be present in human T98G GBM cell line but not in U-118 MG grade III human glioma cell line. L1 protein expression, proteolysis, and release were found in T98G cells and human surgical GBM cells by Western blotting. Exosome-like vesicles released by T98G cells were purified and contained full-length L1. In a scratch assay, T98G cells that migrated into the denuded scratch area exhibited upregulation of ADAM10 protease expression coincident with loss of surface L1. GBM surgical specimen cells exhibited a similar loss of cell surface L1 when xenografted into the chick embryo brain. When lentivirally introduced shRNA was used to attenuate L1 expression, such T98G/shL1 cells exhibited significantly decreased cell motility by time lapse microscopy in our quantitative Super Scratch assay. These cells also showed a decrease in FAK activity and exhibited increased focal complexes. L1 binding integrins which activate FAK were found in T98G and U-118 MG cells. Addition of L1 ectodomain-containing media (1) rescued the decreased cell motility of T98G/shL1 cells and (2) increased cell motility of U-118 MG cells but (3) did not further increase T98G cell motility. Injection of L1-attenuated T98G/shL1 cells into embryonic chick brains resulted in the absence of detectable invasion compared to control cells which invaded brain tissue. These studies support a mechanism where glioma cells at the edge of a cell mass upregulate ADAM10 to proteolyze surface L1 and the resultant ectodomain increases human glioma cell migration and invasion by binding to integrin receptors, activating FAK, and increasing turnover of focal complexes.

Additively manufactured 3D porous Ti-6Al-4V constructs mimic trabecular bone structure and regulate osteoblast proliferation, differentiation and local factor production in a porosity and surface roughness dependent manner.

PubMed

Cheng, Alice; Humayun, Aiza; Cohen, David J; Boyan, Barbara D; Schwartz, Zvi

2014-10-07

Additive manufacturing by laser sintering is able to produce high resolution metal constructs for orthopedic and dental implants. In this study, we used a human trabecular bone template to design and manufacture Ti-6Al-4V constructs with varying porosity via laser sintering. Characterization of constructs revealed interconnected porosities ranging from 15-70% with compressive moduli of 2579-3693 MPa. These constructs with macro porosity were further surface-treated to create a desirable multi-scale micro-/nano-roughness, which has been shown to enhance the osseointegration process. Osteoblasts (MG63 cells) exhibited high viability when grown on the constructs. Proliferation (DNA) and alkaline phosphatase specific activity, an early differentiation marker, decreased as porosity increased, while osteocalcin, a late differentiation marker, as well as osteoprotegerin, vascular endothelial growth factor and bone morphogenetic proteins 2 and 4 increased with increasing porosity. Three-dimensional (3D) constructs with the highest porosity and surface modification supported the greatest osteoblast differentiation and local factor production. These results indicate that additively manufactured 3D porous constructs mimicking human trabecular bone and produced with additional surface treatment can be customized for increased osteoblast response. Increased factors for osteoblast maturation and differentiation on high porosity constructs suggest the enhanced performance of these surfaces for increasing osseointegration in vivo.

Multigenerational memory and adaptive adhesion in early bacterial biofilm communities.

PubMed

Lee, Calvin K; de Anda, Jaime; Baker, Amy E; Bennett, Rachel R; Luo, Yun; Lee, Ernest Y; Keefe, Joshua A; Helali, Joshua S; Ma, Jie; Zhao, Kun; Golestanian, Ramin; O'Toole, George A; Wong, Gerard C L

2018-04-24

Using multigenerational, single-cell tracking we explore the earliest events of biofilm formation by Pseudomonas aeruginosa During initial stages of surface engagement (≤20 h), the surface cell population of this microbe comprises overwhelmingly cells that attach poorly (∼95% stay <30 s, well below the ∼1-h division time) with little increase in surface population. If we harvest cells previously exposed to a surface and direct them to a virgin surface, we find that these surface-exposed cells and their descendants attach strongly and then rapidly increase the surface cell population. This "adaptive," time-delayed adhesion requires determinants we showed previously are critical for surface sensing: type IV pili (TFP) and cAMP signaling via the Pil-Chp-TFP system. We show that these surface-adapted cells exhibit damped, coupled out-of-phase oscillations of intracellular cAMP levels and associated TFP activity that persist for multiple generations, whereas surface-naïve cells show uncorrelated cAMP and TFP activity. These correlated cAMP-TFP oscillations, which effectively impart intergenerational memory to cells in a lineage, can be understood in terms of a Turing stochastic model based on the Pil-Chp-TFP framework. Importantly, these cAMP-TFP oscillations create a state characterized by a suppression of TFP motility coordinated across entire lineages and lead to a drastic increase in the number of surface-associated cells with near-zero translational motion. The appearance of this surface-adapted state, which can serve to define the historical classification of "irreversibly attached" cells, correlates with family tree architectures that facilitate exponential increases in surface cell populations necessary for biofilm formation.

Ion-beam-induced nanodots formation from Au/Si thin films on quartz surface

NASA Astrophysics Data System (ADS)

Datta, D. P.; Siva, V.; Singh, A.; Joshi, S. R.; Kanjilal, D.; Sahoo, P. K.

2016-07-01

We report the synthesis of Si nanodots on quartz surface using ion irradiation. When a bi-layer of ultrathin Au and Si on quartz surface is irradiated by 500 keV Xe-ion beam, the bi-layer spontaneously transforms into nanodots at a fluence of 5 × 1014 ions cm-2. The spatial density and diameter of the nanodots are reduced with increase in applied ion fluence. The nanostructures exhibit photoluminescence in the visible range at room temperature where the intensity and wavelength depends upon ion fluence. The observed evolution seems to be correlated to ion beam mixing induced silicide formation at Au-Si interface.

Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan.

PubMed

Gu, X N; Zheng, Y F; Lan, Q X; Cheng, Y; Zhang, Z X; Xi, T F; Zhang, D Y

2009-08-01

The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10(5) for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

Mucoadhesive microparticles with a nanostructured surface for enhanced bioavailability of glaucoma drug.

PubMed

Park, Chun Gwon; Kim, Young Kook; Kim, Mi Jeung; Park, Min; Kim, Myung Hun; Lee, Seung Ho; Choi, Sung Yoon; Lee, Won Seok; Chung, You Jung; Jung, Young Eun; Park, Ki Ho; Choy, Young Bin

2015-12-28

Topical drug administration to the eye is limited by low drug bioavailability due to its rapid clearance from the preocular surface. Thus, multiple daily administrations are often needed, but patient compliance is low, hence a high chance of unsatisfactory treatment of ocular diseases. To resolve this, we propose mucoadhesive microparticles with a nanostructured surface as potential carriers for delivery of brimonidine, an ocular drug for glaucoma treatment. For sustained drug delivery, the microparticles were composed mainly of a diffusion-wall material, poly(lactic-co-glycolic acid) and a mucoadhesive polymer, polyethylene glycol, was used as an additive. Due to their nanostructured surface, the microparticles with a mucoadhesive material exhibited a 13-fold increase in specific surface area and could thus adhere better to the mucous layer on the eye, as compared with the conventional spherical microparticles. When loaded with brimonidine, the mucoadhesive microparticles with a nanostructured surface increased both drug bioavailability and its activity period by a factor of more than 2 over Alphagan P, a marketed eye drop of brimonidine. Copyright © 2015 Elsevier B.V. All rights reserved.

Transmittance enhancement of sapphires with antireflective subwavelength grating patterned UV polymer surface structures by soft lithography.

PubMed

Lee, Soo Hyun; Leem, Jung Woo; Yu, Jae Su

2013-12-02

We report the total and diffuse transmission enhancement of sapphires with the ultraviolet curable SU8 polymer surface structures consisting of conical subwavelength gratings (SWGs) at one- and both-side surfaces for different periods. The SWGs patterns on the silicon templates were transferred into the SU8 polymer film surface on sapphires by a simple and cost-effective soft lithography technique. For the fabricated samples, the surface morphologies, wetting behaviors, and optical characteristics were investigated. For theoretical optical analysis, a rigorous coupled-wave analysis method was used. At a period of 350 nm, the sample with SWGs on SU8 film/sapphire exhibited a hydrophobic surface and higher total transmittance compared to the bare sapphire over a wide wavelength of 450-1000 nm. As the period of SWGs was increased, the low total transmittance region of < 85% was shifted towards the longer wavelengths and became broader while the diffuse transmittance was increased (i.e., larger haze ratio). For the samples with SWGs at both-side surfaces, the total and diffuse transmittance spectra were further enhanced compared to the samples with SWGs at one-side surface. The theoretical optical calculation results showed a similar trend to the experimentally measured data.

Traitement de surface par explosif du cuivre polycristallin : caractérisation microstructurale et comportement en fatigue plastique

NASA Astrophysics Data System (ADS)

Gerland, M.; Dufour, J. P.; Presles, H. N.; Violan, P.; Mendez, J.

1991-10-01

A new surface treatment technique with a primary explosive deposited in thin layer was applied to a polycrystalline pure copper. After treatment, surface roughness remains of high quality especially when compared to shot peened surfaces. The treated zone extends over several hundreds microns in depth and the microhardness profile exhibits a significant increasing of hardness with a maximum reaching 100% at the surface. The transmission electron microscopy shows a microstructure which changes with depth : below the surface, there is a thin recrystallized layer with very small grains followed by a region with numerous mechanical twins the density of which decreases when depth increases. Tested in fatigue with a constant plastic strain amplitude, the treated copper specimens exhibit a strong hardening from the first cycles compared to the untreated specimen ; however this initial hardening erases after 2% of the fatigue life. The fatigue resistance is not modified by the treatment. Une nouvelle technique de traitement de surface à l'aide d'un explosif primaire déposé en couche mince a été utilisée sur du cuivre pur polycristallin. L'état de surface après traitement reste de très bonne qualité, surtout comparé aux surfaces grenaillées. La zone traitée s'étend sur une profondeur de quelques centaines de microns et le profil de microdureté montre une importante augmentation de dureté avec un maximum en surface pouvant atteindre 100%. La micrcrostructure, observée par microscopie électronique en transmission, est caractérisée par une fine recristallisation en surface, puis par un abondant maclage dont la densité décroît lorsque la profondeur augmente. Testé en fatigue à déformation plastique imposée, le cuivre traité présente un fort écrouissage initial dès les premiers cycles, mais qui s'efface progressivement au cours du cyclage après 2% de la durée de vie, cette dernière n'étant pas modifiée par le traitement.

Polydopamine-mediated surface-functionalization of graphene oxide for heavy metal ions removal

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

Dong, Zhihui; University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049; Zhang, Feng

2015-04-15

By utilizing polydopamine (PD) nano-thick interlayer as mediator, polyethylenimine (PEI) brushes with abundant amine groups were grafted onto the surface of PD coated graphene oxide (GO) uniformly via a Michael-Addition reaction and produced a PEI–PD/GO composite nanosheets. The PEI–PD/GO composite exhibited an improved performance for adsorption of heavy metal ions as compared to PEI-coated GO and pure GO. The adsorption capacities for Cu{sup 2+}, Cd{sup 2+}, Pb{sup 2+}, Hg{sup 2+} are up to 87, 106, 197, and 110 mg/g, respectively. To further make the GO based composite operable, PEI–PD/RGO aerogel was prepared through hydrothermal and achieved a high surface areamore » up to 373 m{sup 2}/g. Although the adsorption capacity of PEI–PD/RGO aerogel for heavy metal ions decreases a little as compared to PEI–PD/GO composite dispersion (38, 32, 95, 113 mg/g corresponding to Cu{sup 2+}, Cd{sup 2+}, Pb{sup 2+}, and Hg{sup 2+}, respectively), it could be recycled several times in a simple way by releasing adsorbed metal ions, indicating its potential application for cleaning wastewater. - Graphical abstract: Polyethylenimine (PEI) brushes were grafted onto the surface of graphene oxide (GO) uniformly via a Michael-Addition reaction between the PEI and polydopamine interlayer coated on GO surface. The PEI–PD/GO composite exhibited an improved performance for adsorption of heavy metal ions compared to PEI-coated GO and pure GO. - Highlights: • We prepared polyethylenimine grafted polydopamine-mediated graphene oxide composites. • Introduction of PD layer increases metal ions adsorption capacity. • PEI–PD/RGO aerogel exhibited a superior adsorption performance. • PEI–PD/RGO aerogel can be recycled several times in a simple way.« less

Diffusion of GPI-anchored proteins is influenced by the activity of dynamic cortical actin.

PubMed

Saha, Suvrajit; Lee, Il-Hyung; Polley, Anirban; Groves, Jay T; Rao, Madan; Mayor, Satyajit

2015-11-05

Molecular diffusion at the surface of living cells is believed to be predominantly driven by thermal kicks. However, there is growing evidence that certain cell surface molecules are driven by the fluctuating dynamics of cortical cytoskeleton. Using fluorescence correlation spectroscopy, we measure the diffusion coefficient of a variety of cell surface molecules over a temperature range of 24-37 °C. Exogenously incorporated fluorescent lipids with short acyl chains exhibit the expected increase of diffusion coefficient over this temperature range. In contrast, we find that GPI-anchored proteins exhibit temperature-independent diffusion over this range and revert to temperature-dependent diffusion on cell membrane blebs, in cells depleted of cholesterol, and upon acute perturbation of actin dynamics and myosin activity. A model transmembrane protein with a cytosolic actin-binding domain also exhibits the temperature-independent behavior, directly implicating the role of cortical actin. We show that diffusion of GPI-anchored proteins also becomes temperature dependent when the filamentous dynamic actin nucleator formin is inhibited. However, changes in cortical actin mesh size or perturbation of branched actin nucleator Arp2/3 do not affect this behavior. Thus cell surface diffusion of GPI-anchored proteins and transmembrane proteins that associate with actin is driven by active fluctuations of dynamic cortical actin filaments in addition to thermal fluctuations, consistent with expectations from an "active actin-membrane composite" cell surface. © 2015 Saha et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Nitrogen-Doped Carbon Nanotube-Supported Pd Catalyst for Improved Electrocatalytic Performance toward Ethanol Electrooxidation

NASA Astrophysics Data System (ADS)

Wei, Ying; Zhang, Xinyuan; Luo, Zhiyong; Tang, Dian; Chen, Changxin; Zhang, Teng; Xie, Zailai

2017-07-01

In this study, hydrothermal carbonization (HTC) was applied for surface functionalization of carbon nanotubes (CNTs) in the presence of glucose and urea. The HTC process allowed the deposition of thin nitrogen-doped carbon layers on the surface of the CNTs. By controlling the ratio of glucose to urea, nitrogen contents of up to 1.7 wt% were achieved. The nitrogen-doped carbon nanotube-supported Pd catalysts exhibited superior electrochemical activity for ethanol oxidation relative to the pristine CNTs. Importantly, a 1.5-fold increase in the specific activity was observed for the Pd/HTC-N1.67%CNTs relative to the catalyst without nitrogen doping (Pd/HTC-CNTs). Further experiments indicated that the introduction of nitrogen species on the surface of the CNTs improved the Pd(0) loading and increased the binding energy.

Corrosion resistance of the microarc oxidation coatings prepared on magnesium alloy

NASA Astrophysics Data System (ADS)

Lv, Ying; Li, Jun Gang; Wu, Ming Zhong; Ma, Zhen; Zhang, Jing Qiang; Wang, Le Le

2018-06-01

Ceramic coatings were prepared on the surface of AZ91D magnesium alloy by microarc oxidation technology. The effects of different voltages on morphology, phase composition and thickness of the coatings were characterized by SEM and XRD. The corrosion resistance of the coatings was measured by electrochemical workstation. Results indicated that the microarc oxidation coatings prepared in sodium silicate electrolyte exhibited porous surface and mainly comprised MgO, Mg2SiO4 and a small amount of MgAl2O4. The thickness of the oxide coatings increased rapidly with the increase of voltage. The coating prepared at 400V voltage had good electrochemical corrosion resistance in 3.5wt% NaCl solution.

Wetting behavior and drainage of water droplets on microgrooved brass surfaces.

PubMed

Rahman, M Ashiqur; Jacobi, Anthony M

2012-09-18

In the present study, contact angle hysteresis and sliding behavior of water droplets on parallel, periodic microgrooved brass surfaces are investigated experimentally for enhancement of water drainage and compared to that on flat baseline surfaces. The surfaces (a total of 17 microgrooved samples, with a range of groove depth of 22 to 109 μm, pillar width of 26 to 190 μm, and groove width of 103 and 127 μm) are fabricated using a mechanical micromachining process. The wetting state and shape/elongation of deposited water droplets, anisotropy of the contact angle hysteresis, and the drainage behavior of water droplets on the microgrooved surfaces are found to be strongly dependent on the topography of the groove geometry, which is analyzed in detail. The wetting state is found to be Wenzel for microgrooved surfaces with very low aspect ratio (<0.2) and narrow pillars (pillar width to groove width ratio of ≈0.2), and also for the two deepest grooved surfaces of two different sample series, all of which exhibit high contact angle hysteresis. Mechanisms of the advancing and receding motions are identified. The critical sliding angle (the angle from horizontal at incipient motion of the advancing confluence) for the microgrooved surfaces is found to be significantly smaller than for flat surfaces. The sliding angle exhibits significant groove geometry dependence and is found to increase with pillar width and decrease with groove depth. The findings of this study may be useful in a broad range of applications where water retention plays an important role.

Cyclic fluctuations of water level as a basis for determining aquifer transmissibility

USGS Publications Warehouse

Ferris, John G.

1952-01-01

In coastal areas, wells near bodies of tidal water frequently exhibit sinusoidal fluctuations of water level, in response to periodic changes of tidewater stage.  Inland, the regulation of a surface reservoir often produces correlative changes of ground-water stage in wells adjacent either to the reservoir or to its attendant stream.  As the stage of the surface water rises, the head upon the subaqueous outcrop of the aquifer increases and thereby either increases the rate of inflow to the aquifer or reduces the rate of outflow therefrom.  The increase in recharge or reduction in discharge results in a general recovery of water level in the aquifer. On the subsequent falling stage this pattern is reversed.  When the stage of the surface body fluctuates as a simple harmonic motion a train of sinusoidal waves is propagated shoreward through the sub-outcrop of the aquifer.  With increasing distance from the sub-outcrop, the amplitude of the transmitted wave decreases and the time lag of a given maximum or minimum increases.

Divergent surface and total soil moisture projections under global warming

USGS Publications Warehouse

Berg, Alexis; Sheffield, Justin; Milly, Paul C.D.

2017-01-01

Land aridity has been projected to increase with global warming. Such projections are mostly based on off-line aridity and drought metrics applied to climate model outputs but also are supported by climate-model projections of decreased surface soil moisture. Here we comprehensively analyze soil moisture projections from the Coupled Model Intercomparison Project phase 5, including surface, total, and layer-by-layer soil moisture. We identify a robust vertical gradient of projected mean soil moisture changes, with more negative changes near the surface. Some regions of the northern middle to high latitudes exhibit negative annual surface changes but positive total changes. We interpret this behavior in the context of seasonal changes in the surface water budget. This vertical pattern implies that the extensive drying predicted by off-line drought metrics, while consistent with the projected decline in surface soil moisture, will tend to overestimate (negatively) changes in total soil water availability.

Effect of electrode sub-micron surface feature size on current generation of Shewanella oneidensis in microbial fuel cells

NASA Astrophysics Data System (ADS)

Ye, Zhou; Ellis, Michael W.; Nain, Amrinder S.; Behkam, Bahareh

2017-04-01

Microbial fuel cells (MFCs) are envisioned to serve as compact and sustainable sources of energy; however, low current and power density have hindered their widespread use. Introduction of 3D micro/nanostructures on the MFC anode is known to improve its performance by increasing the surface area available for bacteria attachment; however, the role of the feature size remains poorly understood. To delineate the role of feature size from the ensuing surface area increase, nanostructures with feature heights of 115 nm and 300 nm, both at a height to width aspect ratio of 0.3, are fabricated in a grid pattern on glassy carbon electrodes (GCEs). Areal current densities and bacteria attachment densities of the patterned and unpatterned GCEs are compared using Shewanella oneidensis Δbfe in a three-electrode bioreactor. The 115 nm features elicit a remarkable 40% increase in current density and a 78% increase in bacterial attachment density, whereas the GCE with 300 nm pattern does not exhibit significant change in current density or bacterial attachment density. The current density dependency on feature size is maintained over the entire 160 h experiment. Thus, optimally sized surface features have a substantial effect on current production that is independent of their effect on surface area.

Chromospheric Heating in Late-Type Stars: Evidence for Magnetic and Nonmagnetic Surface Structure

NASA Technical Reports Server (NTRS)

Cuntz, Manfred

1996-01-01

The aim of this paper is to evaluate recent observational and theoretical results concerning the physics of chromospheric heating as inferred from IUE, HST-GHRS and ROSAT data. These results are discussed in conjunction with theoretical model calculations based on acoustic and magnetic heating to infer some conclusions about the magnetic and non-magnetic surface structure of cool luminous stars. I find that most types of stars may exhibit both magnetic and nonmagnetic structures. Candidates for pure nonmagnetic surface structure include M-type giants and super-giants. M-type supergiants are also ideal candidates for identifying direct links between the appearance of hot spots on the stellar surface (perhaps caused by large convective bubbles) and temporarily increased chromospheric heating and emission.

Deuterium retention and surface modification of tungsten macrobrush samples exposed in FTU Tokamak

NASA Astrophysics Data System (ADS)

Maddaluno, G.; Giacomi, G.; Rufoloni, A.; Verdini, L.

2007-06-01

The effect of discrete structures such as macrobrush or castellated surfaces on power handling and deuterium retention of plasma facing components is to be assessed since such geometrical configurations are needed for increasing the lifetime of the armour to heat-sink joint. Four small macrobrush W and W + 1%La2O3 samples have been exposed in the Frascati Tokamak Upgrade (FTU) scrape-off layer up to the last closed flux surface by means of the Sample Introduction System. FTU is an all metal machine with no carbon source inside vacuum vessel; it exhibits ITER relevant energy and particle fluxes on the plasma facing components. Here, results on morphological surface changes (SEM), chemical composition (EDX) and deuterium retention (TDS) are reported.

A Tad pilus promotes the establishment and resistance of Vibrio vulnificus biofilms to mechanical clearance.

PubMed

Pu, Meng; Rowe-Magnus, Dean Allistair

2018-01-01

Vibrio vulnificus is autochthonous to estuaries and warm coastal waters. Infection occurs via open wounds or ingestion, where its asymptomatic colonization of seafood, most infamously oysters, provides a gateway into the human food chain. Colonization begins with initial surface contact, which is often mediated by bacterial surface appendages called pili. Type IV Tad pili are widely distributed in the Vibrionaceae, but evidence for a physiological role for these structures is scant. The V. vulnificus genome codes for three distinct tad loci. Recently, a positive correlation was demonstrated between the expression of tad-3 and the phenotypes of a V. vulnificus descendent (NT) that exhibited increased biofilm formation, auto-aggregation, and oyster colonization relative to its parent. However, the mechanism by which tad pilus expression promoted these phenotypes was not determined. Here, we show that deletion of the tad pilin gene ( flp ) altered the near-surface motility profile of NT cells from high curvature, orbital retracing patterns characteristic of cells actively probing the surface to low curvature traces indicative of wandering and diminished bacteria-surface interactions. The NT flp pilin mutant also exhibited decreased initial surface attachment, attenuated auto-aggregation and formed fragile biofilms that disintegrated under hydrodynamic flow. Thus, the tad-3 locus, designated iam , promoted i nitial surface attachment, a uto-aggregation and resistance to m echanical clearance of V. vulnificus biofilms. The prevalence of tad loci in the Vibrionaceae suggests that they may play equally important roles in other family members.

Effect of softening precipitate composition and surface characteristics on natural organic matter adsorption.

PubMed

Russell, Caroline G; Lawler, Desmond F; Speitel, Gerald E; Katz, Lynn E

2009-10-15

Natural organic matter (NOM) removal during water softening is thought to occur through adsorption onto or coprecipitation with calcium and magnesium solids. However, details of precipitate composition and surface chemistry and subsequent interactions with NOM are relatively unknown. In this study, zeta potentiometry analyses of precipitates formed from inorganic solutions under varying conditions (e.g., Ca-only, Mg-only, Ca + Mg, increasing lime or NaOH dose) indicated that both CaCO3 and Mg(OH)2 were positively charged at higher lime (Ca(OH)2) and NaOH doses (associated with pH values above 11.5), potentially yielding a greater affinity for adsorbing negatively charged organic molecules. Environmental scanning electron microscopy (ESEM) images of CaCO3 solids illustrated the rhombohedral shape characteristic of calcite. In the presence of increasing concentrations of magnesium, the CaCO3 rhombs shifted to more elongated crystals. The CaCO3 solids also exhibited increasingly positive surface charge from Mg incorporation into the crystal lattice, potentially creating more favorable conditions for adsorption of organic matter. NOM adsorption experiments using humic substances extracted from Lake Austin and Missouri River water elucidated the role of surface charge and surface area on adsorption.

Quasi-ballistic Electronic Thermal Conduction in Metal Inverse Opals.

PubMed

Barako, Michael T; Sood, Aditya; Zhang, Chi; Wang, Junjie; Kodama, Takashi; Asheghi, Mehdi; Zheng, Xiaolin; Braun, Paul V; Goodson, Kenneth E

2016-04-13

Porous metals are used in interfacial transport applications that leverage the combination of electrical and/or thermal conductivity and the large available surface area. As nanomaterials push toward smaller pore sizes to increase the total surface area and reduce diffusion length scales, electron conduction within the metal scaffold becomes suppressed due to increased surface scattering. Here we observe the transition from diffusive to quasi-ballistic thermal conduction using metal inverse opals (IOs), which are metal films that contain a periodic arrangement of interconnected spherical pores. As the material dimensions are reduced from ∼230 nm to ∼23 nm, the thermal conductivity of copper IOs is reduced by more than 57% due to the increase in surface scattering. In contrast, nickel IOs exhibit diffusive-like conduction and have a constant thermal conductivity over this size regime. The quasi-ballistic nature of electron transport at these length scales is modeled considering the inverse opal geometry, surface scattering, and grain boundaries. Understanding the characteristics of electron conduction at the nanoscale is essential to minimizing the total resistance of porous metals for interfacial transport applications, such as the total electrical resistance of battery electrodes and the total thermal resistance of microscale heat exchangers.

An Investigation of the Effects of Self-Assembled Monolayers on Protein Crystallisation

PubMed Central

Zhang, Chen-Yan; Shen, He-Fang; Wang, Qian-Jin; Guo, Yun-Zhu; He, Jin; Cao, Hui-Ling; Liu, Yong-Ming; Shang, Peng; Yin, Da-Chuan

2013-01-01

Most protein crystallisation begins from heterogeneous nucleation; in practice, crystallisation typically occurs in the presence of a solid surface in the solution. The solid surface provides a nucleation site such that the energy barrier for nucleation is lower on the surface than in the bulk solution. Different types of solid surfaces exhibit different surface energies, and the nucleation barriers depend on the characteristics of the solid surfaces. Therefore, treatment of the solid surface may alter the surface properties to increase the chance to obtain protein crystals. In this paper, we propose a method to modify the glass cover slip using a self-assembled monolayer (SAM) of functional groups (methyl, sulfydryl and amino), and we investigated the effect of each SAM on protein crystallisation. The results indicated that both crystallisation success rate in a reproducibility study, and crystallisation hits in a crystallisation screening study, were increased using the SAMs, among which, the methyl-modified SAM demonstrated the most significant improvement. These results illustrated that directly modifying the crystallisation plates or glass cover slips to create surfaces that favour heterogeneous nucleation can be potentially useful in practical protein crystallisation, and the utilisation of a SAM containing a functional group can be considered a promising technique for the treatment of the surfaces that will directly contact the crystallisation solution. PMID:23749116

Liquid Phase Plasma Synthesis of Iron Oxide Nanoparticles on Nitrogen-Doped Activated Carbon Resulting in Nanocomposite for Supercapacitor Applications.

PubMed

Lee, Heon; Lee, Won-June; Park, Young-Kwon; Ki, Seo Jin; Kim, Byung-Joo; Jung, Sang-Chul

2018-03-25

Iron oxide nanoparticles supported on nitrogen-doped activated carbon powder were synthesized using an innovative plasma-in-liquid method, called the liquid phase plasma (LPP) method. Nitrogen-doped carbon (NC) was prepared by a primary LPP reaction using an ammonium chloride reactant solution, and an iron oxide/NC composite (IONCC) was prepared by a secondary LPP reaction using an iron chloride reactant solution. The nitrogen component at 3.77 at. % formed uniformly over the activated carbon (AC) surface after a 1 h LPP reaction. Iron oxide nanoparticles, 40~100 nm in size, were impregnated homogeneously over the NC surface after the LPP reaction, and were identified as Fe₃O₄ by X-ray photoelectron spectroscopy and X-ray diffraction. NC and IONCCs exhibited pseudo-capacitive characteristics, and their specific capacitance and cycling stability were superior to those of bare AC. The nitrogen content on the NC surface increased the compatibility and charge transfer rate, and the composites containing iron oxide exhibited a lower equivalent series resistance.

Preparation of nanobiochar as magnetic solid acid catalyst by pyrolysis-carbonization from oil palm empty fruit bunches

NASA Astrophysics Data System (ADS)

Jenie, S. N. Aisyiyah; Kristiani, Anis; Kustomo, Simanungkalit, Sabar; Mansur, Dieni

2017-11-01

Nanomaterials based on carbon exhibits unique properties, both physical and chemical, that can be utilized in various application, including catalyst. These nanomaterials were prepared through pyrolysis-carbonization process of biomass, oil palm empty fruit bunches. The effect of carbonization temperature in range of 500°C-600°C were also studied. The magnetic nanobiochar samples, MBC, were sulfonated by using sulfuric acid to increase their properties as solid acid catalyst. Their chemical and physical properties were characterized by Surface Area Analyzer and Porositymeter, X-Ray Diffraction, Scanning Electron Microscopy, Fourier Transform Infra-Red. The magnetic biochar samples obtained from carbonization at 873 K, MBC02-SO3H, was proven to have higher surface area, crystallinity properties and surface chemical composition after sulfonation process, which were confirmed by the BET, XRD and FT-IR analysis. Moreover, sample MBC02-SO3H exhibit promising catalytic acitivity in a catalysed esterification reaction, producing an ester yield of 64%. The result from this work opens new opportunities for the development of magnetic heterogenous acid catalyst from biomass waste.

PEG-template for surface modification of zeolite: A convenient material to the design of polypropylene based composite for packaging films

NASA Astrophysics Data System (ADS)

Toommee, S.; Pratumpong, P.

2018-06-01

Zeolite was successfully modified by conventional synthetic route. Polyethylene glycol was employed for surface modification of zeolite. The surface of zeolite exhibited therefore hydrophobic properties. Less than 5 wt% of modified zeolites with uniform size and shape were integrated into polypropylene matrix. Mechanical properties of composite exhibited the similar trend compare to neat polypropylene. Oxygen transmission rate and water vapor transmission rate were evaluated and it exhibited the strong potential to be a good candidate material in active packaging.

Chitosan: A macromolecule as green corrosion inhibitor for mild steel in sulfamic acid useful for sugar industry.

PubMed

Gupta, Neeraj Kumar; Joshi, P G; Srivastava, Vandana; Quraishi, M A

2018-01-01

The present investigation aims at investigation of low cost nontoxic carbohydrate biopolymer chitosan as corrosion inhibitor alone and in combination with KI for mild steel in 1M sulfamic acid medium using gravimetric, electrochemical and surface analysis techniques. It is found that chitosan alone exhibits inhibition efficiency of 73.8% at 200ppm concentration. However, in combination with KI (5ppm), it gave more than 90% inhibition efficiency. The significant increase in the inhibition performance of chitosan has been explained by the synergistic mechanism. The results of Potentiodynamic polarization study shows that chitosan and its blend with KI decreases both anodic and cathodic reactions occurring at mild steel surface in 1M sulfamic acid medium by blocking active sites of the metal and acts as mixed type inhibitor. EIS study reveals that the polarization resistance increases with increase in the concentration of inhibitors which increases charge transfer resistance across the metal/solution interface. The adsorption of chitosan followed the Langmuir adsorption isotherm. The formation of inhibitor film on metal surface was supported by scanning electron microscopy (SEM) and atomic force microscopy (AFM) surface studies. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of sucrose ester concentration on the interfacial characteristics and physical properties of sodium caseinate-stabilized oil-in-water emulsions.

PubMed

Zhao, Qiangzhong; Liu, Daolin; Long, Zhao; Yang, Bao; Fang, Min; Kuang, Wanmei; Zhao, Mouming

2014-05-15

The effect of sucrose ester (SE) concentration on interfacial tension and surface dilatational modulus of SE and sodium caseinate (NaCas)-SE solutions were investigated. The critical micelle concentration (CMC) of SE was presumed to be 0.05% by measuring interfacial tension of SE solution. The interfacial tension of NaCas-SE solution decreased with increased SE concentration. A sharp increase in surface dilatational modulus of NaCas solution was observed when 0.01% SE was added and a decline was occurred at higher SE level. The influence of SE concentration on droplet size and confocal micrograph, surface protein concentration, ζ-potential and rheological properties of oil-in-water (O/W) emulsions prepared with 1% NaCas was also examined. The results showed that addition of SE reduced droplet size and surface protein concentration of the O/W emulsions. The ζ-potential of the O/W emulsions increased initially and decreased afterward with increased SE concentration. All the O/W emulsions exhibited a shear-thinning behaviour and the data were well-fitted into the Herschel-Bulkley model. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mechanochemical activation and patterning of an adhesive surface toward nanoparticle deposition.

PubMed

Baytekin, H Tarik; Baytekin, Bilge; Huda, Sabil; Yavuz, Zelal; Grzybowski, Bartosz A

2015-02-11

Mechanical pulling of adhesive tape creates radicals on the tape's surface. These radicals are capable of reducing metal salts to the corresponding metal nanoparticles. In this way, the mechanically activated tape can be decorated with various types of nanoparticles, including Au, Ag, Pd, or Cu. While retaining their mechanical properties and remaining "sticky," the tapes can exhibit new properties derived from the presence of metal nanoparticles (e.g., bacteriostaticity, increased electrical conductivity). They can also be patterned with nanoparticles only at selective locations of mechanical activation.

First-Principles Study of MoO3/Graphene Composite as Cathode Material for High-Performance Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Cui, Yanhua; Zhao, Yu; Chen, Hong; Wei, Kaiyuan; Ni, Shuang; Cui, Yixiu; Shi, Siqi

2018-03-01

Using first-principles calculations, we have systematically investigated the adsorption and diffusion behavior of Li in MoO3 bulk, on MoO3 (010) surface and in MoO3/graphene composite. Our results indicate that, in case of MoO3 bulk, Li diffusion barriers in the interlayer and intralayer spaces are 0.55 eV and 0.58 eV respectively, which are too high to warrant fast Lithium-ion charge/discharge processes. While on MoO3 (010) surface, Li exhibits a diffusion barrier as low as 0.07 eV which guarantees an extremely fast Li diffusion rate during charge/discharge cycling. However, in MoO3/graphene monolayer, Li diffusion barrier is at the same level as that on MoO3 (010) surface, which also ensures a very rapid Li charge/discharge rate. The rapid Li charge/discharge rate in this system originates from the removal of the upper dangling O1 atoms which hinder the Li diffusion on the lower MoO3 layer. Besides this, due to the interaction between Li and graphene, the Li average binding energy increases to 0.14 eV compared to its value on MoO3 (010) surface which contributes to a higher voltage. Additionally, the increased ratio of surface area provides more space for Li storage and the capacity of MoO3/graphene composite increases up to 279.2 mAhg-1. The last but not the least, due to the high conductivity of graphene, the conductivity of MoO3/graphene composite enhances greatly which is beneficial for electrode materials. In the light of present results, MoO3/graphene composite exhibits higher voltage, good conductivity, large Li capacity and very rapid Li charge/discharge rate, which prove it as a promising cathode material for high-performance lithium-ion batteries (LIBs).

Long-term hypoxia increases calcium affinity of BK channels in ovine fetal and adult cerebral artery smooth muscle

PubMed Central

Tao, Xiaoxiao; Lin, Mike T.; Thorington, Glyne U.; Wilson, Sean M.; Longo, Lawrence D.

2015-01-01

Acclimatization to high-altitude, long-term hypoxia (LTH) reportedly alters cerebral artery contraction-relaxation responses associated with changes in K+ channel activity. We hypothesized that to maintain oxygenation during LTH, basilar arteries (BA) in the ovine adult and near-term fetus would show increased large-conductance Ca2+ activated potassium (BK) channel activity. We measured BK channel activity, expression, and cell surface distribution by use of patch-clamp electrophysiology, flow cytometry, and confocal microscopy, respectively, in myocytes from normoxic control and LTH adult and near-term fetus BA. Electrophysiological data showed that BK channels in LTH myocytes exhibited 1) lowered Ca2+ set points, 2) left-shifted activation voltages, and 3) longer dwell times. BK channels in LTH myocytes also appeared to be more dephosphorylated. These differences collectively make LTH BK channels more sensitive to activation. Studies using flow cytometry showed that the LTH fetus exhibited increased BK β1 subunit surface expression. In addition, in both fetal groups confocal microscopy revealed increased BK channel clustering and colocalization to myocyte lipid rafts. We conclude that increased BK channel activity in LTH BA occurred in association with increased channel affinity for Ca2+ and left-shifted voltage activation. Increased cerebrovascular BK channel activity may be a mechanism by which LTH adult and near-term fetal sheep can acclimatize to long-term high altitude hypoxia. Our findings suggest that increasing BK channel activity in cerebral myocytes may be a therapeutic target to ameliorate the adverse effects of high altitude in adults or of intrauterine hypoxia in the fetus. PMID:25599571

Regression analysis of traction characteristics of traction fluids

NASA Technical Reports Server (NTRS)

Loewenthal, S. H.; Rohn, D. A.

1983-01-01

Traction data for Santotrac 50 and TDF-88 over a wide range of operating conditions were analyzed. An eight term correlation equation to predict the maximum traction coefficient and a six term correlation equation to predict the initial slope of the traction curve were developed. The slope correlation was corrected for size effect considering the compliance of the disks. The effects of different operating conditions on the traction performance of each traction fluid were studied. Both fluids exhibited a loss in traction with increases in spin, but the losses with the TDF-88 fluid were not as severe as those with Santotrac 50. Overall, both fluids exhibited similar performance, showing an increase in traction with contact pressure up to about 2.0 GPa, and a reduction in traction with higher surface speeds up to about 100 m/sec. The apparent stiffness of the traction contact, that is, film disk combination, increases with contact pressure and decreases with speed.

Biodegradation and surfactant-mediated biodegradation of diesel fuel by 218 microbial consortia are not correlated to cell surface hydrophobicity.

PubMed

Owsianiak, Mikołaj; Szulc, Alicja; Chrzanowski, Łukasz; Cyplik, Paweł; Bogacki, Mariusz; Olejnik-Schmidt, Agnieszka K; Heipieper, Hermann J

2009-09-01

In this study, we elucidated the role of cell surface hydrophobicity (microbial adhesion to hydrocarbons method, MATH) and the effect of anionic rhamnolipids and nonionic Triton X-100 surfactants on biodegradation of diesel fuel employing 218 microbial consortia isolated from petroleum-contaminated soils. Applied enrichment procedure with floating diesel fuel as a sole carbon source in liquid cultures resulted in consortia of varying biodegradation potential and diametrically different cell surface properties, suggesting that cell surface hydrophobicity is a conserved parameter. Surprisingly, no correlations between cell surface hydrophobicity and biodegradation of diesel fuel were found. Nevertheless, both surfactants altered cell surface hydrophobicity of the consortia in similar manner: increased for the hydrophilic and decreased for the hydrophobic cultures. In addition to this, the surfactants exhibited similar influence on diesel fuel biodegradation: Increase was observed for initially slow-degrading cultures and the opposite for fast degraders. This indicates that in the surfactant-mediated biodegradation, effectiveness of surfactants depends on the specification of microorganisms and not on the type of surfactant. In contrary to what was previously reported for pure strains, cell surface hydrophobicity, as determined by MATH, is not a good descriptor of biodegrading potential for mixed cultures.

Hydrogen-Bonding Surfaces for Ice Mitigation

NASA Technical Reports Server (NTRS)

Smith, Joseph G., Jr.; Wohl, Christopher J.; Kreeger, Richard E.; Hadley, Kevin R.; McDougall, Nicholas

2014-01-01

Ice formation on aircraft, either on the ground or in-flight, is a major safety issue. While ground icing events occur predominantly during the winter months, in-flight icing can happen anytime during the year. The latter is more problematic since it could result in increased drag and loss of lift. Under a Phase I ARMD NARI Seedling Activity, coated aluminum surfaces possessing hydrogen-bonding groups were under investigation for mitigating ice formation. Hydroxyl and methyl terminated dimethylethoxysilanes were prepared via known chemistries and characterized by spectroscopic methods. These materials were subsequently used to coat aluminum surfaces. Surface compositions were based on pure hydroxyl and methyl terminated species as well as mixtures of the two. Coated surfaces were characterized by contact angle goniometry. Receding water contact angle data suggested several potential surfaces that may exhibit reduced ice adhesion. Qualitative icing experiments performed under representative environmental temperatures using supercooled distilled water delivered via spray coating were inconclusive. Molecular modeling studies suggested that chain mobility affected the interface between ice and the surface more than terminal group chemical composition. Chain mobility resulted from the creation of "pockets" of increased free volume for longer chains to occupy.

Detection of nerve gases using surface-enhanced Raman scattering substrates with high droplet adhesion

NASA Astrophysics Data System (ADS)

Hakonen, Aron; Rindzevicius, Tomas; Schmidt, Michael Stenbæk; Andersson, Per Ola; Juhlin, Lars; Svedendahl, Mikael; Boisen, Anja; Käll, Mikael

2016-01-01

Threats from chemical warfare agents, commonly known as nerve gases, constitute a serious security issue of increasing global concern because of surging terrorist activity worldwide. However, nerve gases are difficult to detect using current analytical tools and outside dedicated laboratories. Here we demonstrate that surface-enhanced Raman scattering (SERS) can be used for sensitive detection of femtomol quantities of two nerve gases, VX and Tabun, using a handheld Raman device and SERS substrates consisting of flexible gold-covered Si nanopillars. The substrate surface exhibits high droplet adhesion and nanopillar clustering due to elasto-capillary forces, resulting in enrichment of target molecules in plasmonic hot-spots with high Raman enhancement. The results may pave the way for strategic life-saving SERS detection of chemical warfare agents in the field.Threats from chemical warfare agents, commonly known as nerve gases, constitute a serious security issue of increasing global concern because of surging terrorist activity worldwide. However, nerve gases are difficult to detect using current analytical tools and outside dedicated laboratories. Here we demonstrate that surface-enhanced Raman scattering (SERS) can be used for sensitive detection of femtomol quantities of two nerve gases, VX and Tabun, using a handheld Raman device and SERS substrates consisting of flexible gold-covered Si nanopillars. The substrate surface exhibits high droplet adhesion and nanopillar clustering due to elasto-capillary forces, resulting in enrichment of target molecules in plasmonic hot-spots with high Raman enhancement. The results may pave the way for strategic life-saving SERS detection of chemical warfare agents in the field. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06524k

Ecological relationships of fauna and flora on a pre-law coal surface-mined area in Perry County, Illinois

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

Smith, J.R.

1986-01-01

Pre-law coal surface-mined lands in Pyramid State Park, Perry County, Illinois, were examined 1976-1980 to determine changes in fauna and flora from that on the area in 1954-1960. Vegetative development on naturally revegetated spoils reflected diverse habitat conditions with interspersion of cover types; some of oldest spoils displayed inhibited succession while others exhibited early flood plain forest development. Ground and overstory species richness and overstory density increased since mid 1950's and ground cover domination by therophytes in 1954-1956 shifted to phanerophytes and hemicryptophytes in 1976-1978. Thirty vegetative compositional and structural parameters indicated that ground cover was limited by subcanopy rathermore » than large scattered trees. Aquatic vegetation communities developed but hydrosphere was not well represented; emergent vegetation was limited by morphology of basins. Although isolated sites exhibited deleterious conditions, vegetation was not generally inhibited by physico-chemical factors. The 29 mammals reflected an increase in species richness. Abundance of early successional forms decreased while occupants of shrub/forest increased. Past habitat enhancement influenced wildlife distribution; and plantations attracted woodland fauna. Leveled spoil crests, valleys and clearings with fescue retarded succession and provided open areas and edges for others.« less

Powder Metallurgy Fabrication of Porous 51(at.%)Ni-Ti Shape Memory Alloys for Biomedical Applications

NASA Astrophysics Data System (ADS)

Ibrahim, Mustafa K.; Hamzah, E.; Saud, Safaa N.; Nazim, E. M.

2018-05-01

The effect of time and temperature on the microwave sintering of 51(at.%)Ni-Ti shape memory alloys (SMAs) was investigated in the current research. Furthermore, the microstructure, mechanical properties, and bio-corrosion properties were analyzed based on the sintering conditions. The results revealed that the sintering condition of 700 °C for 15 min produced a part with coherent surface survey that does not exhibit gross defects. Increasing the sintering time and temperature created defects on the outer surface, while reducing the temperature to 550 °C severely affected the mechanical properties. The microstructure of these samples showed two regions of Ni-rich region and Ti-rich region between them Ti2Ni, NiTi, and Ni3Ti phases. The differential scanning calorimeter (DSC) curves of Ni-Ti samples exhibited a multi-step phase transformation B19'-R-B2 during heating and cooling. An increase in the sintering temperature from 550 to 700 °C was found to increase the fracture strength significantly and decreased the fracture strain slightly. Reducing the sintering temperature from 700 to 550 °C severely affected the corrosion behaviors of 51%Ni-Ti SMAs. This research aims to select the optimum parameters to produce Ni-Ti alloys with desired microstructure, mechanical properties, and corrosion behaviors for biomedical applications.

Design and synthesis of inorganic/organic hybrid electrochemical materials

NASA Astrophysics Data System (ADS)

Harreld, John H.

An ambient pressure method for drying sol-gel materials is developed to synthesize high porosity (80--90%), high surface area vanadium oxide and silica aerogel materials (150--300 and 1000 m2/g for vanadium pentoxide and silica, respectively). The synthesis approach uses liquid exchange to replace the pore fluid with a low surface tension, nonpolar solvent which reduces the capillary pressures developed during drying. The Good-Girifalco interaction parameter is used to calculate pore stresses resulting from drying silica gels from various liquids. Vanadium oxide/polypyrrole hybrid aerogels are prepared using three strategies. These approaches focus on either sequential or consecutive polymerization of the inorganic and organic networks. Microcomposite aerogels are synthesized by encapsulating a dispersion of preformed polypyrrole in a vanadium pentoxide gel. In the second approach, pyrrole is polymerized and doped within the pore volume of preformed vanadium pentoxide gel. When the inorganic and organic precursors are polymerized simultaneously, the resulting gels exhibited a nanometer scaled microstructure with homogeneous distributions of either phases. Through this route, a suitable microstructure and composition for a lithium secondary battery cathode is obtained. Lithiated aerogels of hydrated nickel, cobalt, and mixed nickel-cobalt oxides are synthesized from lithium hydroxide and transition metal acetate precursors. The XRD analyses indicate that the nickel containing gels exhibit a lithium deficiency (less than 1 Li/transition metal. By increasing the concentration of the lithium precursor the lithium content in nickel oxides is increased, and additional base solution is no longer required to catalyze gelation. A non-hydrolytic sol-gel approach is utilized to create tin oxide and tin-aluminum binary oxide aerogels with high porosity (90%) and high surface area (300 m2/g). XRD data from single phase tin oxide aerogel indicates the growth of SnO2 crystallites between 150--400°C in air, accompanied by a reduction in surface area (30 m2/g). Heated tin oxide aerogel exhibits comparable reversible specific capacity (390 mAh/g) as that of commercial SnO2 (420 mAh/g). Amorphous tin oxide aerogel is stabilized to higher temperatures when aluminum oxide is incorporated into the structure. The tin oxide phase remains electrochemically active towards lithium insertion and exhibits excellent reversibility during cycling.

The use of fractography to supplement analysis of bone mechanical properties in different strains of mice.

PubMed

Wise, L M; Wang, Z; Grynpas, M D

2007-10-01

Fractography has not been fully developed as a useful technique in assessing failure mechanisms of bone. While fracture surfaces of osteonal bone have been explored, this may not apply to conventional mechanical testing of mouse bone. Thus, the focus of this work was to develop and evaluate the efficacy of a fractography protocol for use in supplementing the interpretation of failure mechanisms in mouse bone. Micro-computed tomography and three-point bending were performed on femora of two groups of 6-month-old mice (C57BL/6 and a mixed strain background of 129SV/C57BL6). SEM images of fracture surfaces were collected, and areas of "tension", "compression" and "transition" were identified. Percent areas of roughness were identified and estimated within areas of "tension" and "compression" and subsequently compared to surface roughness measurements generated from an optical profiler. Porosity parameters were determined on the tensile side. Linear regression analysis was performed to evaluate correlations between certain parameters. Results show that 129 mice exhibit significantly increased bone mineral density (BMD), number of "large" pores, failure strength, elastic modulus and energy to failure compared to B6 mice (p<0.001). Both 129 and B6 mice exhibit significantly (p<0.01) more percent areas of tension (49+/-1%, 42+/-2%; respectively) compared to compression (26+/-2%, 31+/-1%; respectively). In terms of "roughness", B6 mice exhibit significantly less "rough" areas (30+/-4%) compared to "smooth" areas (70+/-4%) on the tensile side only (p<0.001). Qualitatively, 129 mice demonstrate more evidence of bone toughening through fiber bridging and loosely connected fiber bundles. The number of large pores is positively correlated with failure strength (p=0.004), elastic modulus (p=0.002) and energy to failure (p=0.041). Percent area of tensile surfaces is positively correlated with failure strength (p<0.001), elastic modulus (p=0.016) and BMD (p=0.037). Percent area of rough compressive surfaces is positively correlated with energy to failure (p=0.039). Evaluation of fracture surfaces has helped to explain why 129 mice have increased mechanical properties compared to B6 mice, namely via toughening mechanisms on the compressive side of failure. Several correlations exist between fractography parameters and mechanical behavior, supporting the utility of fractography with skeletal mouse models.

Boosting surface charge-transfer doping efficiency and robustness of diamond with WO3 and ReO3

NASA Astrophysics Data System (ADS)

Tordjman, Moshe; Weinfeld, Kamira; Kalish, Rafi

2017-09-01

An advanced charge-transfer yield is demonstrated by employing single monolayers of transition-metal oxides—tungsten trioxide (WO3) and rhenium trioxide (ReO3)—deposited on the hydrogenated diamond surface, resulting in improved p-type sheet conductivity and thermal stability. Surface conductivities, as determined by Hall effect measurements as a function of temperature for WO3, yield a record sheet hole carrier concentration value of up to 2.52 × 1014 cm-2 at room temperature for only a few monolayers of coverage. Transfer doping with ReO3 exhibits a consistent narrow sheet carrier concentration value of around 3 × 1013 cm-2, exhibiting a thermal stability of up to 450 °C. This enhanced conductivity and temperature robustness exceed those reported for previously exposed surface electron acceptor materials used so far on a diamond surface. X-ray photoelectron spectroscopy measurements of the C1s core level shift as a function of WO3 and ReO3 layer thicknesses are used to determine the respective increase in surface band bending of the accumulation layers, leading to a different sub-surface two-dimensional hole gas formation efficiency in both cases. This substantial difference in charge-exchange efficiency is unexpected since both surface acceptors have very close work functions. Consequently, these results lead us to consider additional factors influencing the transfer doping mechanism. Transfer doping with WO3 reveals the highest yet reported transfer doping efficiency per minimal surface acceptor coverage. This improved surface conductivity performance and thermal stability will promote the realization of 2D diamond-based electronic devices facing process fabrication challenges.

Spectroscopic Studies on the Effect of Some Ferrocene Derivatives in the Formation of Silver Nanoparticles.

PubMed

Sanyal, Manik Kumar; Biswas, Bipul; Chowdhury, Avijit; Mallik, Biswanath

2016-06-01

Silver nanoparticles were prepared by microwave assisted method using silver nitrate as precursor in the presence of some ferrocene derivatives. The formation of the silver nanoparticles was monitored using UV-Vis spectroscopy. The UV-Vis spectroscopy revealed the formation of silver nanoparticles by exhibiting typical surface plasmon absorption band. The position of plasmon band (406-429 nm) was observed to depend on the nature of a particular ferrocene derivative used. TEM images indicated that the nanoparticles were spherical in shape and well-dispersed. Quantum dots (3.2 nm) were prepared by using ferrocenecarboxylic acid. The surface plasmon absorption band has shown red shift with increasing concentration of ferrocene derivative. For different duration of microwave heating time, intensity of absorption spectra in general was found to increase except in presence of ferrocene carbaldehyde where it decreased. Time-dependent spectra have indicated almost stable position of the surface plasmon band with increasing time of observation confirming that the as prepared silver nanoparticles did not aggregate with lapse of time.

Synthesis and characterization of high-surface-area millimeter-sized silica beads with hierarchical multi-modal pore structure by the addition of agar

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

Han, Yosep; Choi, Junhyun; Tong, Meiping, E-mail: tongmeiping@iee.pku.edu.cn

2014-04-01

Millimeter-sized spherical silica foams (SSFs) with hierarchical multi-modal pore structure featuring high specific surface area and ordered mesoporous frameworks were successfully prepared using aqueous agar addition, foaming and drop-in-oil processes. The pore-related properties of the prepared spherical silica (SSs) and SSFs were systematically characterized by field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), small-angle X-ray diffraction (SAXRD), Hg intrusion porosimetry, and N{sub 2} adsorption–desorption isotherm measurements. Improvements in the BET surface area and total pore volume were observed at 504 m{sup 2} g{sup −1} and 5.45 cm{sup 3} g{sup −1}, respectively, after an agar addition and foaming process. Despitemore » the increase in the BET surface area, the mesopore wall thickness and the pore size of the mesopores generated from the block copolymer with agar addition were unchanged based on the SAXRD, TEM, and BJH methods. The SSFs prepared in the present study were confirmed to have improved BET surface area and micropore volume through the agar loading, and to exhibit interconnected 3-dimensional network macropore structure leading to the enhancement of total porosity and BET surface area via the foaming process. - Highlights: • Millimeter-sized spherical silica foams (SSFs) are successfully prepared. • SSFs exhibit high BET surface area and ordered hierarchical pore structure. • Agar addition improves BET surface area and micropore volume of SSFs. • Foaming process generates interconnected 3-D network macropore structure of SSFs.« less

One stone, two birds: silica nanospheres significantly increase photocatalytic activity and colloidal stability of photocatalysts

NASA Astrophysics Data System (ADS)

Rasamani, Kowsalya D.; Foley, Jonathan J., IV; Sun, Yugang

2018-03-01

Silver-doped silver chloride [AgCl(Ag)] nanoparticles represent a unique class of visible-light-driven photocatalysts, in which the silver dopants introduce electron-abundant mid-gap energy levels to lower the bandgap of AgCl. However, free-standing AgCl(Ag) nanoparticles, particularly those with small sizes and large surface areas, exhibit low colloidal stability and low compositional stability upon exposure to light irradiation, leading to easy aggregation and conversion to metallic silver and thus a loss of photocatalytic activity. These problems could be eliminated by attaching the small AgCl(Ag) nanoparticles to the surfaces of spherical dielectric silica particles with submicrometer sizes. The high optical transparency in the visible spectral region (400-800 nm), colloidal stability, and chemical/electronic inertness displayed by the silica spheres make them ideal for supporting photocatalysts and significantly improving their stability. The spherical morphology of the dielectric silica particles can support light scattering resonances to generate significantly enhanced electric fields near the silica particle surfaces, on which the optical absorption cross-section of the AgCl(Ag) nanoparticles is dramatically increased to promote their photocatalytic activity. The hybrid silica/AgCl(Ag) structures exhibit superior photocatalytic activity and stability, suitable for supporting photocatalysis sustainably; for instance, their efficiency in the photocatalytic decomposition of methylene blue decreases by only ˜9% even after ten cycles of operation.

Influence of storage methods on the surface roughness of tissue conditioners.

PubMed

Hong, Guan; Li, YingAi; Maeda, Takeshi; Mizumachi, Wataru; Sadamori, Shinsuke; Hamada, Taizo; Murata, Hiroshi

2008-03-01

The purpose of this study was to compare the influence of three kinds of storage methods on surface roughness of tissue conditioners. Four commercial tissue conditioners (GC Soft Liner, Softone, Fictioner, and Hydro-Cast) were used in this study. Five samples of each material were stored in distilled water, air, and a denture cleanser (Polident). Mean surface roughness (R(a)) values of dental stone casts made from the tissue conditioners were measured after 0, 1, 3, 7, and 14 days of immersion using a profilometer. Significant differences in the R(a) values of the specimens were found among the three storage methods. The values of R(a) significantly increased with increase in immersion time for each storage method, except for the materials stored in air. It was found that the materials stored in air showed the most stable and lowest values of R(a). Results obtained suggested that a tissue conditioner exhibited smooth and minimal change in surface roughness with time when stored in air than in distilled water and denture cleanser.

Enhancing Enantiomeric Separation with Strain: The Case of Serine on Cu(531)

DOE PAGES

Wang, Yonghui; Yang, Sha; Fuentes-Cabrera, Miguel; ...

2017-05-26

Serine has two enantiomers, d and l, which exhibit identical physical and chemical properties but have dramatically different physiological effects. For the pharmaceutical industry, it is very important to be able to separate both enantiomers. Here we study the enantioselectivity of the (531) surfaces of Cu, Ag, Au, and Pd using density functional theory with an accurate treatment of the van der Waals interactions. Among these surfaces, it is found that Cu(531) is the most efficient for energetically separating serine enantiomers. This greater efficiency is ultimately related to a conformational strain imposed in serine and most of all in themore » supporting substrate. Motivated by this, we decorated the step sites of Cu(531) with Ni atoms and showed that serine enantioselectivity increases by 36% as compared to that of pristine Cu(531). Furthermore, these results suggest that efficient enantiomeric separation of small chiral molecules could be achieved with bimetallic stepped surfaces for which strain, both in the surface and the molecule, increases significantly upon deposition.« less

Cellulose microfibrils grafted with PBA via surface-initiated atom transfer radical polymerization for biocomposite reinforcement.

PubMed

Li, Shuzhao; Xiao, Miaomiao; Zheng, Anna; Xiao, Huining

2011-09-12

Immobilizing poly(butyl acrylate) (PBA) on cellulose microfibrils (CMFs) by atom transfer radical polymerization (ATRP) of butyl acrylate (BA) on the surface of 2-bromoisobutyryl-functionalized CMF generated highly hydrophobic microfibrils (CMF-PBA) with a hard core and a soft-shell structure. TGA and static water contact angle results suggested that the surfaces of the modified CMF samples were not completely covered by PBA chains until the molecular weight of grafts became sufficiently long. The GPC results indicated that the grafts with low molecular weight showed controlled/"living" characteristics of the surface-initiated ATRP; however, there existed more side reactions with the increase in molecular weights. Biocomposites consisting of polypropylene (PP) and CMF-PBA samples exhibited significantly improved compatibility, interface adhesion, and mechanical properties with the increase in PBA graft length. The findings confirmed that the longer grafts facilitated the better entanglement of PBA grafts with PP macromolecules and thus further improved the mechanical properties.

Bioinspired assembly of surface-roughened nanoplatelets.

PubMed

Lin, Tzung-Hua; Huang, Wei-Han; Jun, In-Kook; Jiang, Peng

2010-04-15

Here we report a novel electrophoretic deposition technology for assembling surface-roughened inorganic nanoplatelets into ordered multilayers that mimic the brick-and-mortar nanostructure found in the nacreous layer of mollusk shells. A thin layer of sol-gel silica is coated on smooth gibbsite nanoplatelets in order to increase the surface roughness to mimic the asperity of aragonite platelets found in nacres. To avoid the severe cracking caused by the shrinkage of sol-gel silica during drying, polyelectrolyte polyethyleneimine is used to reverse the surface charge of silica-coated-gibbsite nanoplatelets and increase the adherence and strength of the electrodeposited films. Polymer nanocomposites can then be made by infiltrating the interstitials of the aligned nanoplatelet multilayers with photocurable monomer followed by photopolymerization. The resulting self-standing films are highly transparent and exhibit nearly three times higher tensile strength and one-order-of-magnitude higher toughness than those of pure polymer. The measured tensile strength agrees with that predicted by a simple shear lag model. Published by Elsevier Inc.

Tailoring properties of reduced graphene oxide by oxygen plasma treatment

NASA Astrophysics Data System (ADS)

Kondratowicz, Izabela; Nadolska, Małgorzata; Şahin, Samet; Łapiński, Marcin; Prześniak-Welenc, Marta; Sawczak, Mirosław; Yu, Eileen H.; Sadowski, Wojciech; Żelechowska, Kamila

2018-05-01

We report an easily controllable, eco-friendly method for tailoring the properties of reduced graphene oxide (rGO) by means of oxygen plasma. The effect of oxygen plasma treatment time (1, 5 and 10 min) on the surface properties of rGO was evaluated. Physicochemical characterization using microscopic, spectroscopic and thermal techniques was performed. The results revealed that different oxygen-containing groups (e.g. carboxyl, hydroxyl) were introduced on the rGO surface enhancing its wettability. Furthermore, upon longer treatment time, other functionalities were created (e.g. quinones, lactones). Moreover, external surface of rGO was partially etched resulting in an increase of the material surface area and porosity. Finally, the oxygen plasma-treated rGO electrodes with bilirubin oxidase were tested for oxygen reduction reaction. The study showed that rGO treated for 10 min exhibited twofold higher current density than untreated rGO. The oxygen plasma treatment may improve the enzyme adsorption on rGO electrodes by introduction of oxygen moieties and increasing the porosity.

Drug-Induced Trafficking of P-Glycoprotein in Human Brain Capillary Endothelial Cells as Demonstrated by Exposure to Mitomycin C

PubMed Central

Noack, Andreas; Noack, Sandra; Hoffmann, Andrea; Maalouf, Katia; Buettner, Manuela; Couraud, Pierre-Olivier; Romero, Ignacio A.; Weksler, Babette; Alms, Dana; Römermann, Kerstin; Naim, Hassan Y.; Löscher, Wolfgang

2014-01-01

P-glycoprotein (Pgp; ABCB1/MDR1) is a major efflux transporter at the blood-brain barrier (BBB), restricting the penetration of various compounds. In other tissues, trafficking of Pgp from subcellular stores to the cell surface has been demonstrated and may constitute a rapid way of the cell to respond to toxic compounds by functional membrane insertion of the transporter. It is not known whether drug-induced Pgp trafficking also occurs in brain capillary endothelial cells that form the BBB. In this study, trafficking of Pgp was investigated in human brain capillary endothelial cells (hCMEC/D3) that were stably transfected with a doxycycline-inducible MDR1-EGFP fusion plasmid. In the presence of doxycycline, these cells exhibited a 15-fold increase in Pgp-EGFP fusion protein expression, which was associated with an increased efflux of the Pgp substrate rhodamine 123 (Rho123). The chemotherapeutic agent mitomycin C (MMC) was used to study drug-induced trafficking of Pgp. Confocal fluorescence microscopy of single hCMEC/D3-MDR1-EGFP cells revealed that Pgp redistribution from intracellular pools to the cell surface occurred within 2 h of MMC exposure. Pgp-EGFP exhibited a punctuate pattern at the cell surface compatible with concentrated regions of the fusion protein in membrane microdomains, i.e., lipid rafts, which was confirmed by Western blot analysis of biotinylated cell surface proteins in Lubrol-resistant membranes. MMC exposure also increased the functionality of Pgp as assessed in three functional assays with Pgp substrates (Rho123, eFluxx-ID Gold, calcein-AM). However, this increase occurred with some delay after the increased Pgp expression and coincided with the release of Pgp from the Lubrol-resistant membrane complexes. Disrupting rafts by depleting the membrane of cholesterol increased the functionality of Pgp. Our data present the first direct evidence of drug-induced Pgp trafficking at the human BBB and indicate that Pgp has to be released from lipid rafts to gain its full functionality. PMID:24505408

Drug-induced trafficking of p-glycoprotein in human brain capillary endothelial cells as demonstrated by exposure to mitomycin C.

PubMed

Noack, Andreas; Noack, Sandra; Hoffmann, Andrea; Maalouf, Katia; Buettner, Manuela; Couraud, Pierre-Olivier; Romero, Ignacio A; Weksler, Babette; Alms, Dana; Römermann, Kerstin; Naim, Hassan Y; Löscher, Wolfgang

2014-01-01

P-glycoprotein (Pgp; ABCB1/MDR1) is a major efflux transporter at the blood-brain barrier (BBB), restricting the penetration of various compounds. In other tissues, trafficking of Pgp from subcellular stores to the cell surface has been demonstrated and may constitute a rapid way of the cell to respond to toxic compounds by functional membrane insertion of the transporter. It is not known whether drug-induced Pgp trafficking also occurs in brain capillary endothelial cells that form the BBB. In this study, trafficking of Pgp was investigated in human brain capillary endothelial cells (hCMEC/D3) that were stably transfected with a doxycycline-inducible MDR1-EGFP fusion plasmid. In the presence of doxycycline, these cells exhibited a 15-fold increase in Pgp-EGFP fusion protein expression, which was associated with an increased efflux of the Pgp substrate rhodamine 123 (Rho123). The chemotherapeutic agent mitomycin C (MMC) was used to study drug-induced trafficking of Pgp. Confocal fluorescence microscopy of single hCMEC/D3-MDR1-EGFP cells revealed that Pgp redistribution from intracellular pools to the cell surface occurred within 2 h of MMC exposure. Pgp-EGFP exhibited a punctuate pattern at the cell surface compatible with concentrated regions of the fusion protein in membrane microdomains, i.e., lipid rafts, which was confirmed by Western blot analysis of biotinylated cell surface proteins in Lubrol-resistant membranes. MMC exposure also increased the functionality of Pgp as assessed in three functional assays with Pgp substrates (Rho123, eFluxx-ID Gold, calcein-AM). However, this increase occurred with some delay after the increased Pgp expression and coincided with the release of Pgp from the Lubrol-resistant membrane complexes. Disrupting rafts by depleting the membrane of cholesterol increased the functionality of Pgp. Our data present the first direct evidence of drug-induced Pgp trafficking at the human BBB and indicate that Pgp has to be released from lipid rafts to gain its full functionality.

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.

The Effects of Impurities on Protein Crystal Growth and Nucleation: A Preliminary Study

NASA Technical Reports Server (NTRS)

Schall, Constance A.

1998-01-01

Kubota and Mullin (1995) devised a simple model to account for the effects of impurities on crystal growth of small inorganic and organic molecules in aqueous solutions. Experimentally, the relative step velocity and crystal growth of these molecules asymptotically approach zero or non-zero values with increasing concentrations of impurities. Alternatively, the step velocity and crystal growth can linearly approach zero as the impurity concentration increases. The Kubota-Mullin model assumes that the impurity exhibits Langmuirian adsorption onto the crystal surface. Decreases in step velocities and subsequent growth rates are related to the fractional coverage (theta) of the crystal surface by adsorbed impurities; theta = Kx / (I +Kx), x = mole fraction of impurity in solution. In the presence of impurities, the relative step velocity, V/Vo, and the relative growth rate of a crystal face, G/Go, are proposed to conform to the following equations: V/Vo approx. = G/Go = 1 - (alpha)(theta). The adsorption of impurity is assumed to be rapid and in quasi-equilibrium with the crystal surface sites available. When the value of alpha, an effectiveness factor, is one the growth will asymptotically approach zero with increasing concentrations of impurity. At values less than one, growth approaches a non-zero value asymptotically. When alpha is much greater than one, there will be a linear relationship between impurity concentration and growth rates. Kubota and Mullin expect alpha to decrease with increasing supersaturation and shrinking size of a two dimensional nucleus. It is expected that impurity effects on protein crystal growth will exhibit behavior similar to that of impurities in small molecule growth. A number of proteins were added to purified chicken egg white lysozyme, the effect on crystal nucleation and growth assessed.

Oxygen vacancy formation characteristics in the bulk and across different surface terminations of La (1₋x)Sr xFe (1₋y)Co yO (3₋δ) perovskite oxides for CO 2 conversion

DOE PAGES

Maiti, Debtanu; Daza, Yolanda A.; Yung, Matthew M.; ...

2016-03-07

Density functional theory (DFT) based investigation of two parameters of prime interest -- oxygen vacancy and surface terminations along (100) and (110) planes -- has been conducted for La (1-x)Sr xFe(1-y)Co yO (3-more » $$\\delta$$) perovskite oxides in view of their application towards thermochemical carbon dioxide conversion reactions. The bulk oxygen vacancy formation energies for these mixed perovskite oxides are found to increase with increasing lanthanum and iron contents in the 'A' site and 'B' site, respectively. Surface terminations along (100) and (110) crystal planes are studied to probe their stability and their capabilities to accommodate surface oxygen vacancies. Amongst the various terminations, the oxygen-rich (110) surface and strontium-rich (100) surface are the most stable, while transition metal-rich terminations along (100) revealed preference towards the production of oxygen vacancies. The carbon dioxide adsorption strength, a key descriptor for CO 2 conversion reactions, is found to increase on oxygen vacant surfaces thus establishing the importance of oxygen vacancies in CO 2 conversion reactions. Amongst all the surface terminations, the lanthanum-oxygen terminated surface exhibited the strongest CO 2 adsorption strength. Finally, the theoretical prediction of the oxygen vacancy trends and the stability of the samples were corroborated by the temperature-programmed reduction and oxidation reactions and in situ XRD crystallography.« less

Anomalous photoconductive behavior of a single InAs nanowire photodetector

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

Li, Junshuai; Yan, Xin; Sun, Fukuan

2015-12-28

We report on a bare InAs nanowire photodetector which exhibits an anomalous photoconductive behavior. Under low-power illumination, the current is smaller than the dark current, and monotonously decreases as the excitation power increases. When the excitation power is high enough, the current starts to increase normally. The phenomenon is attributed to different electron mobilities in the “core” and “shell” of a relatively thick nanowire originating from the surface effect, which result in a quickly dropped “core current” and slowly increased “shell current” under illumination.

A general strategy for the ultrafast surface modification of metals.

PubMed

Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

2016-12-07

Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments.

Enhanced MC3T3-E1 preosteoblast response and bone formation on the addition of nano-needle and nano-porous features to microtopographical titanium surfaces.

PubMed

Zhuang, X-M; Zhou, B; Ouyang, J-L; Sun, H-P; Wu, Y-L; Liu, Q; Deng, F-L

2014-08-01

Micro/nanotopographical modifications on titanium surfaces constitute a new process to increase osteoblast response to enhance bone formation. In this study, we utilized alkali heat treatment at high (SB-AH1) and low temperatures (SB-AH2) to nano-modify sandblasted titanium with microtopographical surfaces. Then, we evaluated the surface properties, biocompatibility and osteogenic capability of SB-AH1 and SB-AH2 in vitro and in vivo, and compared these with conventional sandblast-acid etching (SLA) and Ti control surfaces. SB-AH1 and SB-AH2 surfaces exhibited micro/nanotopographical modifications of nano-needle structures and nano-porous network layers, respectively, compared with the sole microtopographical surface of macro and micro pits on the SLA surface and the relatively smooth surface on the Ti control. SB-AH1 and SB-AH2 showed different roughness and elemental components, but similar wettability. MC3T3-E1 preosteoblasts anchored closely on the nanostructures of SB-AH1 and SB-AH2 surfaces, and these two surfaces more significantly enhanced cell proliferation and alkaline phosphatase (ALP) activity than others, while the SB-AH2 surface exhibited better cell proliferation and higher ALP activity than SB-AH1. All four groups of titanium domes with self-tapping screws were implanted in rabbit calvarial bone models, and these indicated that SB-AH1 and SB-AH2 surfaces achieved better peri-implant bone formation and implant stability, while the SB-AH2 surface achieved the best percentage of bone-implant contact (BIC%). Our study demonstrated that the micro/nanotopographical surface generated by sandblasting and alkali heat treatment significantly enhanced preosteoblast proliferation, ALP activity and bone formation in vitro and in vivo, and nano-porous network topography may further induce better preosteoblast proliferation, ALP activity and BIC%.

Nanopolishing by colloidal nanodiamond in elastohydrodynamic lubrication

NASA Astrophysics Data System (ADS)

Shirvani, Khosro A.; Mosleh, Mohsen; Smith, Sonya T.

2016-08-01

In this paper, the feasibility of using explosion synthesized diamond nanoparticles with an average particle size (APS) of 3-5 nm with a concentration of 1 % by weight for improving lubrication and friction in elastohydrodynamic lubrication (EHL) was investigated. Owing to the orders of magnitude increase in the viscosity of the lubricant in the EHL contact zone, diamond nanoparticles in the lubricant polish the surfaces at the nanoscale which decreases the composite roughness of contacting surfaces. The reduced composite roughness results in an increased film thickness ratio which yields lower friction. In the numerical analysis, governing equations of lubricant flow in the full elastohydrodynamic lubrication were solved, and the shear stress distribution over the fluid film was calculated. Using an abrasion model and the shear stress distribution profile, the material removal by the nanofluid containing nanoparticles and the resultant surface roughness were determined. The numerical analysis showed that in full EHL regime, the nanolubricant can reduce the composite roughness of moving surfaces. Experimental results from prior studies which exhibited surface polishing by such nanolubricants in boundary, mixed, and full elastohydrodynamic lubrication were used for comparison to the numerical model.

Spontaneous jumping, bouncing and trampolining of hydrogel drops on a heated plate.

PubMed

Pham, Jonathan T; Paven, Maxime; Wooh, Sanghyuk; Kajiya, Tadashi; Butt, Hans-Jürgen; Vollmer, Doris

2017-10-13

The contact between liquid drops and hot solid surfaces is of practical importance for industrial processes, such as thermal spraying and spray cooling. The contact and bouncing of solid spheres is also an important event encountered in ball milling, powder processing, and everyday activities, such as ball sports. Using high speed video microscopy, we demonstrate that hydrogel drops, initially at rest on a surface, spontaneously jump upon rapid heating and continue to bounce with increasing amplitudes. Jumping is governed by the surface wettability, surface temperature, hydrogel elasticity, and adhesion. A combination of low-adhesion impact behavior and fast water vapor formation supports continuous bouncing and trampolining. Our results illustrate how the interplay between solid and liquid characteristics of hydrogels results in intriguing dynamics, as reflected by spontaneous jumping, bouncing, trampolining, and extremely short contact times.Drops of liquid on a hot surface can exhibit fascinating behaviour such as the Leidenfrost effect in which drops hover on a vapour layer. Here Pham et al. show that when hydrogel drops are placed on a rapidly heated plate they bounce to increasing heights even if they were initially at rest.

Experimental and Computational Evidence of Highly Active Fe Impurity Sites on the Surface of Oxidized Au for the Electrocatalytic Oxidation of Water in Basic Media

DOE PAGES

Klaus, Shannon; Trotochaud, Lena; Cheng, Mu-Jeng; ...

2015-10-22

Addition of Fe to Ni- and Co-based (oxy)hydroxides has been shown to enhance the activity of these materials for electrochemical oxygen evolution. Here we show that Fe cations bound to the surface of oxidized Au exhibit enhanced oxygen evolution reaction (OER) activity. We find that the OER activity increases with increasing surface concentration of Fe. Density functional theory analysis of the OER energetics reveals that oxygen evolution over Fe cations bound to a hydroxyl-terminated oxidized Au (Fe-Au 2O 3) occurs at an overpotential ~0.3V lower than over hydroxylated Au 2O 3 (0.82V). This finding agrees well with experimental observations andmore » is a consequence of the more optimal binding energetics of OER reaction intermediates at Fe cations bound to the surface of Au 2O 3. These findings suggest that the enhanced OER activity reported recently upon low-potential cycling of Au may be due to surface Fe impurities rather than to "superactive" Au(III) surfaquo species.« less

Characteristics of ozone vertical profile observed in the boundary layer around Beijing in autumn.

PubMed

Ma, Zhiqiang; Zhang, Xiaoling; Xu, Jing; Zhao, Xiujuan; Meng, Wei

2011-01-01

In the autumn of 2008, the vertical profiles of ozone and meteorological parameters in the low troposphere (0-1000 m) were observed at two sites around Beijing, specifically urban Nanjiao and rural Shangdianzi. At night and early morning, the lower troposphere divided into two stratified layers due to temperature inversion. Ozone in the lower layer showed a large gradient due to the titration of NO. Air flow from the southwest brought ozone-rich air to Beijing, and the ozone profiles were marked by a continuous increase in the residual layer at night. The accumulated ozone in the upper layer played an important role in the next day's surface peak ozone concentration, and caused a rapid increase in surface ozone in the morning. Wind direction shear and wind speed shear exhibited different influences on ozone profiles and resulted in different surface ozone concentrations in Beijing.

Improved mechanical performance of PBO fiber-reinforced bismaleimide composite using mixed O2/Ar plasma

NASA Astrophysics Data System (ADS)

Liu, Dong; Chen, Ping; Yu, Qi; Ma, Keming; Ding, Zhenfeng

2014-06-01

The mixed O2/Ar plasma was employed to enhance mechanical properties of the PBO/bismaleimide composite. The interlaminar shear strength was improved to 61.6 MPa or by 38.1%, but the composite brittleness increased. The plasma gas compositions exhibited notable effects on the interfacial adhesion strength. XPS results suggested that the mixed plasma presented higher activation effects on the surface chemical compositions than pure gas plasmas and a larger number of oxygen atoms and hydrophilic groups were introduced on the fiber surface due to the synergy effect, but the synergy effect was considerably performed only within the O2 percentage range of 40-60%. The fibers surface was increasingly etched with growing the O2 contents in the plasma, deteriorating the fibers tensile strength. SEM micrographs demonstrated that the composite shear fracture changed from debonding to cohesive failure in the matrices, and the improving mechanisms were discussed.

Effect of nitric acid treatment on activated carbon derived from oil palm shell

NASA Astrophysics Data System (ADS)

Allwar, Allwar; Hartati, Retno; Fatimah, Is

2017-03-01

The primary object of this work is to study the effect of nitric acid on the porous and morphology structure of activated carbon. Production of activated carbon from oil palm shell was prepared with pyrolysis process at temperature 900°C and by introduction of 10 M nitric acid. Determination of surface area, pore volume and pore size distribution of activated carbon was conducted by the N2 adsorption-desorption isotherm at 77 K. Morphology structure and elemental micro-analysis of activated carbon were estimated by Scanning Electron Microscopy (SEM) and energy dispersive X-ray (EDX), respectively. The result shows that activated carbon after treating with nitric acid proved an increasing porous characteristics involving surface area, pore volume and pore size distribution. It also could remove the contaminants including metals and exhibit an increasing of pores and crevices all over the surface.

Improvement of GaN light-emitting diodes with surface-treated Al-doped ZnO transparent Ohmic contacts by holographic photonic crystal

NASA Astrophysics Data System (ADS)

Yang, W. F.; Liu, Z. G.; Xie, Y. N.; Cai, J. F.; Liu, S.; Gong, H.; Wu, Z. Y.

2012-06-01

This letter presents a holographic photonic crystal (H-PhC) Al-doped ZnO (AZO) transparent Ohmic contact layer on p-GaN to increase the light output of GaN-based LEDs without destroying the p-GaN. The operating voltage of the PhC LEDs at 20 mA was almost the same as that of the typical planar AZO LEDs. While the resultant PhC LED devices exhibited significant improvements in light extraction, up to 1.22 times that of planar AZO LEDs without PhC integration. Temperature dependence of the integrated photoluminescence intensity indicates that this improvement can be attributed to the increased extraction efficiency due to the surface modification. These results demonstrate that the surface-treated AZO layer by H-PhCs is suitable for fabricating high-brightness GaN-based LEDs.

The Role of Ru Redox in pH-Dependent Oxygen Evolution on Rutile Ruthenium Dioxide Surfaces

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

Stoerzinger, Kelsey A.; Rao, Reshma R.; Wang, Xiao Renshaw

Rutile RuO 2 is known to exhibit high catalytic activity for the oxygen evolution reaction (OER) and large pseudocapacitance associated with redox of surface Ru, however the mechanistic link between these properties and the role of pH is yet to be understood. Here we report that the OER activities of the (101), (001) and (111) RuO 2 surfaces were found to increase while the potential of a pseudocapacitive feature just prior to OER shifted to lower potentials (“super-Nernstian” shift) with increasing pH on the reversible hydrogen electrode (RHE) scale. This behavior is in contrast to the (100) and (110) surfacesmore » that have pH-independent Ru redox and OER activity. The link in catalytic and pseudocapacitive behavior illustrates the importance of this redox feature in generating active sites, building new mechanistic understanding of the OER.« less

Antiangiogenic cancer drug sunitinib exhibits unexpected proangiogenic effects on endothelial cells

PubMed Central

Norton, Kerri-Ann; Han, Zheyi; Popel, Aleksander S; Pandey, Niranjan B

2014-01-01

Angiogenesis, the formation of new blood vessels, is an essential step for cancer progression, but antiangiogenic therapies have shown limited success. Therefore, a better understanding of the effects of antiangiogenic treatments on endothelial cells is necessary. In this study, we evaluate the changes in cell surface vascular endothelial growth factor receptor (VEGFR) expression on endothelial cells in culture treated with the antiangiogenic tyrosine kinase inhibitor drug sunitinib, using quantitative flow cytometry. We find that proangiogenic VEGFR2 cell surface receptor numbers are increased with sunitinib treatment. This proangiogenic effect might account for the limited effects of sunitinib as a cancer therapy. We also find that this increase is inhibited by brefeldin A, an inhibitor of protein transport from the endoplasmic reticulum to the Golgi apparatus. The complex dynamics of cell surface VEGFRs may be important for successful treatment of cancer with antiangiogenic therapeutics. PMID:25228815

Additively Manufactured 3D Porous Ti-6Al-4V Constructs Mimic Trabecular Bone Structure and Regulate Osteoblast Proliferation, Differentiation and Local Factor Production in a Porosity and Surface Roughness Dependent Manner

PubMed Central

Cheng, Alice; Humayun, Aiza; Cohen, David J.; Boyan, Barbara D.; Schwartz, Zvi

2014-01-01

Additive manufacturing by laser sintering is able to produce high resolution metal constructs for orthopaedic and dental implants. In this study, we used a human trabecular bone template to design and manufacture Ti-6Al-4V constructs with varying porosity via laser sintering. Characterization of constructs revealed interconnected porosities ranging from 15–70% with compressive moduli of 2063–2954 MPa. These constructs with macro porosity were further surface-treated to create a desirable multi-scale micro-/nano-roughness, which has been shown to enhance the osseointegration process. Osteoblasts (MG63 cells) exhibited high viability when grown on the constructs. Proliferation (DNA) and alkaline phosphatase specific activity (ALP), an early differentiation marker, decreased as porosity increased, while osteocalcin (OCN), a late differentiation marker, as well as osteoprotegerin (OPG), vascular endothelial growth factor (VEGF) and bone morphogenetic proteins 2 and 4 (BMP2, BMP4) increased with increasing porosity. 3D constructs with the highest porosity and surface modification supported the greatest osteoblast differentiation and local factor production. These results indicate that additively manufactured 3D porous constructs mimicking human trabecular bone and produced with additional surface treatment can be customized for increased osteoblast response. Increased factors for osteoblast maturation and differentiation on high porosity constructs suggest the enhanced performance of these surfaces for increasing osseointegration in vivo. PMID:25287305

Optimization of additive compositions for anode in Ni-MH secondary battery using the response surface method

NASA Astrophysics Data System (ADS)

Yang, Dong-Cheol; Jang, In-Su; Jang, Min-Ho; Park, Choong-Nyeon; Park, Chan-Jin; Choi, Jeon

2009-06-01

We optimized the composition of additives for the anode in a Ni-MH battery using the response surface method (RSM) to improve the electrode discharge capacities. When the amount of additives was small, the discharge characteristics of the electrode were degraded by charge-discharge cycling due to the low binding strength among the alloy powders and the resultant separation of the powder from the electrode surface. In contrast, the addition of a large amount of the additives increased the electrical impedance of the electrode. Through a response optimization process, we found an optimum composition range of additives to exhibit the greatest discharge capacity of the electrode.

Entropy and caloric curve for mononuclei considering both surface diffuseness and self-similar expansion degrees of freedom

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

Sobotka, L.G.; Department of Physics, Washington University, St. Louis, Missouri 63130; Charity, R.J.

2006-01-15

The caloric curve for mononuclear configurations is studied with a model that allows for both increased surface diffusness and self-similar expansion. The evolution of the effective mass with density and excitation is included in a schematic fashion. The entropies, extracted in a local-density approximation, confirm that nuclei posess a soft mode that is predominately a surface expansion. We also find that the mononuclear caloric curve (temperature versus excitation energy) exhibits a plateau. Thus a plateau should be the expectation with or without a multifragmentationlike phase transition. This conclusion is relevant only for reactions that populate the mononuclear region of phasemore » space.« less

Nonlinear Acoustic Experiments Involving Landmine Detection: Connections with Mesoscopic Elasticity and Slow Dynamics in Geomaterials

NASA Astrophysics Data System (ADS)

Korman, Murray S.; Sabatier, James M.

2006-05-01

The vibration interaction between the top-plate of a buried VS 2.2 plastic, anti-tank landmine and the soil above it appears to exhibit similar characteristics to the nonlinear mesoscopic/nanoscale effects that are observed in geomaterials like rocks or granular materials. [J. Acoust. Soc. Am. 116, 3354-3369 (2004)]. When airborne sound at two primary frequencies f1 and f2 (closely spaced near resonance) undergo acoustic-to-seismic coupling, (A/S), interactions with the mine and soil generate combination frequencies | n f1 ± m f2 | which affect the surface vibration velocity. Profiles at f1, f2, f1 -(f2 - f1) and f2 +(f2 - f1) exhibit single peaks whereas other combination frequencies may involve higher order modes. A family of increasing amplitude tuning curves, involving the surface vibration over the landmine, exhibits a linear relationship between the peak particle velocity and corresponding resonant frequency. Subsequent decreasing amplitude tuning curves exhibit hysteresis effects. New experiments for a buried VS 1.6 anti-tank landmine and a "plastic drum head" mine simulant behave similarly. Slow dynamics explains the amplitude difference in tuning curves for first sweeping upward and then downward through resonance, provided the soil modulus drops after periods of high strain. [Support by U.S. Army RDECOM CERDEC, NVESD, Fort Belvoir, VA.

Thermoregulation of Capsule Production by Streptococcus pyogenes

PubMed Central

Kang, Song Ok; Wright, Jordan O.; Tesorero, Rafael A.; Lee, Hyunwoo; Beall, Bernard; Cho, Kyu Hong

2012-01-01

The capsule of Streptococcus pyogenes serves as an adhesin as well as an anti-phagocytic factor by binding to CD44 on keratinocytes of the pharyngeal mucosa and the skin, the main entry sites of the pathogen. We discovered that S. pyogenes HSC5 and MGAS315 strains are further thermoregulated for capsule production at a post-transcriptional level in addition to the transcriptional regulation by the CovRS two-component regulatory system. When the transcription of the hasABC capsular biosynthetic locus was de-repressed through mutation of the covRS system, the two strains, which have been used for pathogenesis studies in the laboratory, exhibited markedly increased capsule production at sub-body temperature. Employing transposon mutagenesis, we found that CvfA, a previously identified membrane-associated endoribonuclease, is required for the thermoregulation of capsule synthesis. The mutation of the cvfA gene conferred increased capsule production regardless of temperature. However, the amount of the capsule transcript was not changed by the mutation, indicating that a post-transcriptional regulator mediates between CvfA and thermoregulated capsule production. When we tested naturally occurring invasive mucoid strains, a high percentage (11/53, 21%) of the strains exhibited thermoregulated capsule production. As expected, the mucoid phenotype of these strains at sub-body temperature was due to mutations within the chromosomal covRS genes. Capsule thermoregulation that exhibits high capsule production at lower temperatures that occur on the skin or mucosal surface potentially confers better capability of adhesion and invasion when S. pyogenes penetrates the epithelial surface. PMID:22615992

Influence of Direct Current Electric Field on Corrosion Behavior of Tin Under a Thin Electrolyte Layer

NASA Astrophysics Data System (ADS)

Huang, H. L.; Bu, F. R.; Tian, J.; Liu, D.

2017-12-01

The influence of a direct current electric field (DCEF) on corrosion behavior of tin under a thin electrolyte layer was investigated based on an array electrode technology by polarization, electrochemical impedance spectroscopy and surface analysis. The experimental results indicate that the corrosion rate of tin near the positive plate of DCEF increases with increased electric field intensity, which could be attributed to the acceleration of the migration of ions, the removal of corrosion products under DCEF and the damage of tin surface oxide film. Furthermore, tin at different positions in a DCEF exhibits different corrosion behavior, which could be ascribed to the difference of the local corrosion environment caused by the DCEF.

Structural, transport and microwave properties of 123/sapphire films: Thickness effect

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

Predtechensky, MR.; Smal, A.N.; Varlamov, Y.D.

1994-12-31

The effect of thickness and growth conditions on the structure and microwave properties has been investigated for the 123/sapphire films. It has been shown that in the conditions of epitaxial growth and Al atoms do not diffuse from substrate into the film and the films with thickness up to 100nm exhibit the excellent DC properties. The increase of thickness of GdBaCuO films causes the formation of extended line-mesh defects and the increase of the surface resistance (R{sub S}). The low value of surface resistance R{sub S}(75GHz,77K)=20 mOhm has been obtained for the two layer YBaCuO/CdBaCuO/sapphire films.

Formation of tungsten oxide nanowires by ion irradiation and vacuum annealing

NASA Astrophysics Data System (ADS)

Zheng, Xu-Dong; Ren, Feng; Wu, Heng-Yi; Qin, Wen-Jing; Jiang, Chang-Zhong

2018-04-01

Here we reported the fabrication of tungsten oxide (WO3-x ) nanowires by Ar+ ion irradiation of WO3 thin films followed by annealing in vacuum. The nanowire length increases with increasing irradiation fluence and with decreasing ion energy. We propose that the stress-driven diffusion of the irradiation-induced W interstitial atoms is responsible for the formation of the nanowires. Comparing to the pristine film, the fabricated nanowire film shows a 106-fold enhancement in electrical conductivity, resulting from the high-density irradiation-induced vacancies on the oxygen sublattice. The nanostructure exhibits largely enhanced surface-enhanced Raman scattering effect due to the oxygen vacancy. Thus, ion irradiation provides a powerful approach for fabricating and tailoring the surface nanostructures of semiconductors.

Impacts of Climate Change on Surface Ozone and Intercontinental Ozone Pollution: A Multi-Model Study

NASA Technical Reports Server (NTRS)

Doherty, R. M.; Wild, O.; Shindell, D. T.; Zeng, G.; MacKenzie, I. A.; Collins, W. J.; Fiore, A. M.; Stevenson, D. S.; Dentener, F. J.; Schultz, M. G.;

Mechanical properties, microstructure, and specific adhesion of phospholipid monolayer-coated microbubbles

NASA Astrophysics Data System (ADS)

Kim, Dennis Heejong

1999-10-01

The objective of this study was to characterize properties of phospholipid monolayer shells formed on gas microbubbles, specifically (1)yield shear and shear viscosity as a function of the shell composition, (2)yield shear, shear viscosity, and microstructural domain density as a function of the quenching rate of the microbubbles following production, and (3)the adhesion of a lipid-coated microbubble to a colloidal substrate via receptor-ligand mediated specific interaction, either enhanced or inhibited by the presence of surface-grafted polymeric structures. The primary experimental technique employed was the micromanipulation method, wherein tapered fluid-filled pipets with bores on the order of 4-10 microns were used to (1)capture and maneuver individual micron scale bubbles in aqueous medium, and (2)apply suction pressures over the range of 1 dyn cm-2 to 10 5 dyn cm-2 (10-6 to 10 -1 atm) and track the corresponding deformation of the microbubble under applied pressure. The yield shear and shear viscosity increase with increasing acyl chain length of the lipid; an equivalent statement is that the yield shear and shear viscosity increase with reduced temperature of the shell material. Crystalline lipid domain sizes are dictated by the rate at which the system is (temperature) quenched in a manner predicted by classic materials science and metallurgy: rapidly cooled samples form the smallest grains and exhibit the lowest levels of yield shear and shear viscosity. Slowly cooled samples produce large grains and exhibit high levels of yield and viscosity. The success and strength of adhesion of a microbubble to a substrate is dictated by the identity of the adhesive molecules participating in the adhesion, as well as the surface architecture of the interfaces participating in adhesion. The term surface architecture is used to describe the physical arrangement of the full complement of steric stabilizers, spacers, and binding molecules present at the surface of a typical coated microbubble shell. Adhesion is successful for systems where the binding ligand is not impeded by the presence of surface-grafted poly(ethylene glycol) (PEG) moieties. Like the shell composition itself, the surface construct can be engineered to produce optimal performance in adhesion.

Effect of artificial aging on the surface roughness and microhardness of resin-based materials.

PubMed

Santos, M Jacinta M C; Rêgo, Heleine Maria Chagas; Mukhopadhyay, Anuradha; El Najjar, Mai; Santos, Gildo C

2016-01-01

This study sought to verify the effects of aging on the surface roughness (Ra) and microhardness (Knoop hardness number [KHN]) of resin-based restorative materials protected with a surface sealer. Disc specimens of 2 resin-modified glass ionomers (RMGIs) and 1 composite resin (CR) were fabricated in a metal mold. Specimens of each material were divided into 1 group that was covered with surface sealer and 1 group that was not. Both groups of each material were then subdivided according to whether they were stored (aged) in cola or distilled water. Surface roughness and KHN values were obtained from each specimen before and after storage. After aging of the specimens, significantly higher Ra values were observed in the 2 RMGIs when they were not covered with a surface sealer, while the CR was not affected. The KHN values varied by materials and storage conditions (with and without a surface sealer). All the groups with a surface sealer exhibited increased Ra values after aging.

Fabrication of hydrophobic compressed oil palm trunk surface by sol-gel process

NASA Astrophysics Data System (ADS)

Muzakir, Syafiqah; Salim, Nurjannah; Huda Abu Bakar, Nurul; Roslan, Rasidi; Sin, Lim Wan; Hashim, Rokiah

2018-04-01

Improvement of the robustness of hydrophobic surfaces is crucial to achieving commercial applications of these surfaces in such various areas as self-cleaning, water repellency and corrosion resistance. Compressed oil palm trunk (OPT) panel is one of potential product which can be used as panelling and indoor furniture application. By adding hydrophobic properties to compressed oil palm trunk panel might increase the application of compressed oil palm trunk especially for outdoor application. In this study, fabrication is using the sol-gel technique. Sol-gel was prepared by adding ethanol with Hexadecyl Trimethyl Ammonium Bromide (CTAB) solution with Tetraethyl Orthosilicate (TEOS) with surface modification of chlorotrimethylsilane (CTMS). The surface with hydrophobic coating was undergone surface analysis with contact angle machine with the aid of software SCA 20 and the determined of the morphology of surface with scanning electron microscope (SEM). The produced compressed oil palm trunk surfaces exhibited promising hydrophobic properties with a contact angle of 104° and the relatively better mechanical robustness.

Specific surface area of a crushed welded tuff before and after aqueous dissolution

USGS Publications Warehouse

Reddy, M.M.; Claassen, H.C.

1994-01-01

Specific surface areas were measured for several reference minerals (anorthoclase, labradorite and augite), welded tuff and stream sediments from Snowshoe Mountain, near Creede, Colorado. Crushed and sieved tuff had an unexpectedly small variation in specific surface area over a range of size fractions. Replicate surface area measurements of the largest and smallest tuff particle size fractions examined (1-0.3 mm and <0.212 mm) were 2.3 ?? 0.2 m2/g for each size fraction. Reference minerals prepared in the same way as the tuff had smaller specific surface areas than that of the tuff of the same size fraction. Higher than expected tuff specific surface areas appear to be due to porous matrix. Tuff, reacted in solutions with pH values from 2 to 6, had little change in specific surface area in comparison with unreacted tuff. Tuff, reacted with solutions having high acid concentrations (0.1 M hydrochloric acid or sulfuric-hydrofluoric acid), exhibited a marked increase in specific surface area compared to unreacted tuff. ?? 1994.

In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.

PubMed

Das, Mitun; Bhattacharya, Kaushik; Dittrick, Stanley A; Mandal, Chitra; Balla, Vamsi Krishna; Sampath Kumar, T S; Bandyopadhyay, Amit; Manna, Indranil

2014-01-01

Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants. © 2013 Elsevier Ltd. All rights reserved.

Study on the electrochemical properties of cubic ordered mesoporous carbon for supercapacitors

NASA Astrophysics Data System (ADS)

Lang, Jun-Wei; Yan, Xing-Bin; Yuan, Xiao-Yan; Yang, Jie; Xue, Qun-Ji

Highly ordered, three-dimensional (3D) cubic mesoporous carbon CMK-8 is prepared by a facile nanocasting approach using cubic mesoporous silica KIT-6 as starting template. Afterwards, in order to increase the active sites of surface electrochemical reactions and promote the wettability in aqueous electrolyte, a chemical surface modification is carried out on the CMK-8 by nitric acid treatment. Two electrodes are prepared from the CMK-8 and the acid-modified CMK-8 (H-CMK-8) and used as the active materials for supercapacitors. The unique 3D mesoporous network combined with high specific surface area makes the nano-channel surfaces of the CMK-8 carbon favorable for charging the electric double-layer, resulting in that the CMK-8 and the H-CMK-8 electrodes both show well supercapacitive properties. Furthermore, the specific capacitance of the CMK-8 can be further improved by acid treatment, so that the H-CMK-8 exhibits the largest specific capacitance of 246 F g -1 at a current density of 0.625 A g -1 in 2 M KOH electrolyte. Also, the two carbon electrodes both exhibit good cycling stability and lifetime. Therefore, based on the above investigations, such CMK-8 carbon, especially H-CMK-8 carbon can be a potential candidate for supercapacitors.

Transition Regimes of Jet Impingement on Rib and Cavity Superhydrophobic Surfaces

NASA Astrophysics Data System (ADS)

Johnson, Michael; Maynes, Daniel; Webb, Brent

2010-11-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 2000.The superhydrophobic surfaces are fabricated with both silicon and PDMS surfaces and exhibit micro-ribs and cavities coated with a hydrophobic coating. In general, the hydraulic jump exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. When the water depth downstream of the jump was imposed at a predetermined value, the major and minor axis of the jump increased with decreasing water depth, following classical hydraulic jump behavior. When no water depth was imposed, a regime change was observed within the Weber number range explained. For We < 1200, the flow forms a filament at the edge of the ellipse, where the flow moves along the rim of the ellipse toward the major axis. The filaments then join and continue to move parallel to the ribs. For 1200 < We < 1800, the filaments beyond the ellipse break into multiple streams and droplets and begin to take on a component perpendicular to the ribs. For We > 1800 a small amount of water flows purely in the transverse direction.

Influence of packing density and surface roughness of vertically-aligned carbon nanotubes on adhesive properties of gecko-inspired mimetics.

PubMed

Chen, Bingan; Zhong, Guofang; Oppenheimer, Pola Goldberg; Zhang, Can; Tornatzky, Hans; Esconjauregui, Santiago; Hofmann, Stephan; Robertson, John

2015-02-18

We have systematically studied the macroscopic adhesive properties of vertically aligned nanotube arrays with various packing density and roughness. Using a tensile setup in shear and normal adhesion, we find that there exists a maximum packing density for nanotube arrays to have adhesive properties. Too highly packed tubes do not offer intertube space for tube bending and side-wall contact to surfaces, thus exhibiting no adhesive properties. Likewise, we also show that the surface roughness of the arrays strongly influences the adhesion properties and the reusability of the tubes. Increasing the surface roughness of the array strengthens the adhesion in the normal direction, but weakens it in the shear direction. Altogether, these results allow progress toward mimicking the gecko's vertical mobility.

Homologous stress adaptation, antibiotic resistance, and biofilm forming ability of Salmonella enterica serovar Heidelberg (ATCC8326) on different food-contact surfaces following exposure to sub-lethal chlorine concentrations

USDA-ARS?s Scientific Manuscript database

Salmonella enterica serovar Heidelberg (American Type Culture Collection; ATCC 8326) was examined for the ability to adapt to the homologous stress of chlorine through exposure to increasing chlorine concentrations (25 ppm daily increments) in tryptic soy broth (TSB). The tested strain exhibited an ...

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

Ravikumar, Patta; Kisan, Bhagaban; Perumal, A., E-mail: perumal@iitg.ernet.in

We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO) band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinementmore » effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μ{sub B}/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (T{sub C}) around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR) studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high T{sub C} and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.« less

New Insights into Mechanism of Surface Reactions of ZnO Nanorods During Electrons Beam Irradiation.

PubMed

Cho, Youngseung; Ji, Hyunjin; Kim, Hyoungsub; Yoon, Jinsuop; Choi, Byoungdeog

2018-09-01

This study provides new insight into mechanisms of ionic reactions on the surface of ZnO nanorod networks, which could result in enhanced performance in optical or molecular sensors. The current- voltage characteristics of ZnO nanorod network devices exhibit typical nonlinear behavior in air, which implies the formation of a Schottky barrier when metals are used as contacts. The conductance of the device increased significantly in vacuum, which can be explained by the desorption of hydroxyl groups at very low pressure. While physisorbed water or oxygen-related ions can detach from the ZnO surface during evacuation, exposure to high energy in the electron beam is believed to detach the chemisorbed anions of O- and O-2 from the surface of ZnO nanorods, which releases more electrons into the channel. The increase in available electrons enhances the conductance of the ZnO nanorods. Slow initialization of the conductance under ambient conditions indicates that the ionic re-adsorption is inactive under these conditions. Thus, the electron irradiation process can be used to reset the surface ionic molecules on metal oxide nano-structures by tuning the surface potential prior to the passivation process.

Preliminary evaluation of cavitation resistance of type 316LN stainless steel in mercury using a vibratory horn

NASA Astrophysics Data System (ADS)

Pawel, S. J.; Manneschmidt, E. T.

2003-05-01

Type 316LN stainless steel in a variety of conditions (annealed, cold-worked, surface-modified) was exposed to cavitation conditions in stagnant mercury using a vibratory horn. The test conditions included peak-to-peak displacement of the specimen surface of 25 μm at a frequency of 20 kHz and a mercury temperature in the range -5 to 80 °C. Following a brief incubation period in which little or no damage was observed, specimens of annealed 316LN exhibited increasing weight loss and surface roughening with increasing exposure times. Examination of test surfaces with the scanning electron microscope revealed primarily general/uniform wastage in all cases but, for long exposure times, a few randomly oriented 'pits' were also observed. Type 316LN that was 50% cold-worked was considerably more resistant to cavitation erosion damage than annealed material, but the surface modifications (CrN coating, metallic glass coating, laser treatment to form a diamond-like surface) provided little or no protection for the substrate. In addition, the cavitation erosion resistance of other materials - Inconel 718, Nitronic 60, and Stellite 3 - was also compared with that of 316LN for identical screening test conditions.

Angle-dependent lubricated tribological properties of stainless steel by femtosecond laser surface texturing

NASA Astrophysics Data System (ADS)

Wang, Zhuo; Li, Yang-Bo; Bai, Feng; Wang, Cheng-Wei; Zhao, Quan-Zhong

2016-07-01

Lubricated tribological properties of stainless steel were investigated by femtosecond laser surface texturing. Regular-arranged micro-grooved textures with different spacing and micro-groove inclination angles (between micro-groove path and sliding direction) were produced on AISI 304L steel surfaces by an 800 nm femtosecond laser. The spacing of micro-groove was varied from 25 to 300 μm, and the inclination angles of micro-groove were measured as 90° and 45°. The tribological properties of the smooth and textured surfaces with micro-grooves were investigated by reciprocating ball-on-flat tests against Al2O3 ceramic balls under starved oil lubricated conditions. Results showed that the spacing of micro-grooves significantly affected the tribological property. With the increase of micro-groove spacing, the average friction coefficients and wear rates of textured surfaces initially decreased then increased. The tribological performance also depended on the inclination angles of micro-grooves. Among the investigated patterns, the micro-grooves perpendicular to the sliding direction exhibited the lowest average friction coefficient and wear rate to a certain extent. Femtosecond laser-induced surface texturing may remarkably improve friction and wear properties if the micro-grooves were properly distributed.

Loss of FliL alters Proteus mirabilis surface sensing and temperature-dependent swarming.

PubMed

Lee, Yi-Ying; Belas, Robert

2015-01-01

Proteus mirabilis is a dimorphic motile bacterium well known for its flagellum-dependent swarming motility over surfaces. In liquid, P. mirabilis cells are 1.5- to 2.0-μm swimmer cells with 4 to 6 flagella. When P. mirabilis encounters a solid surface, where flagellar rotation is limited, swimmer cells differentiate into elongated (10- to 80-μm), highly flagellated swarmer cells. In order for P. mirabilis to swarm, it first needs to detect a surface. The ubiquitous but functionally enigmatic flagellar basal body protein FliL is involved in P. mirabilis surface sensing. Previous studies have suggested that FliL is essential for swarming through its involvement in viscosity-dependent monitoring of flagellar rotation. In this study, we constructed and characterized ΔfliL mutants of P. mirabilis and Escherichia coli. Unexpectedly and unlike other fliL mutants, both P. mirabilis and E. coli ΔfliL cells swarm (Swr(+)). Further analysis revealed that P. mirabilis ΔfliL cells also exhibit an alteration in their ability to sense a surface: e.g., ΔfliL P. mirabilis cells swarm precociously over surfaces with low viscosity that normally impede wild-type swarming. Precocious swarming is due to an increase in the number of elongated swarmer cells in the population. Loss of fliL also results in an inhibition of swarming at <30°C. E. coli ΔfliL cells also exhibit temperature-sensitive swarming. These results suggest an involvement of FliL in the energetics and function of the flagellar motor. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Surface modification effects of fluorine-doped tin dioxide by oxygen plasma ion implantation

NASA Astrophysics Data System (ADS)

Tang, Peng; Liu, Cai; Zhang, Jingquan; Wu, Lili; Li, Wei; Feng, Lianghuan; Zeng, Guanggen; Wang, Wenwu

2018-04-01

SnO2:F (FTO), as a kind of transparent conductive oxide (TCO), exhibits excellent transmittance and conductivity and is widely used as transparency electrodes in solar cells. It's very important to modifying the surface of FTO for it plays a critical role in CdTe solar cells. In this study, modifying effects of oxygen plasma on FTO was investigated systematically. Oxygen plasma treatment on FTO surface with ion accelerating voltage ranged from 0.4 kV to 1.6 kV has been processed. The O proportion of surface was increased after ion implantation. The Fermi level of surface measurement by XPS valance band spectra was lowered as the ion accelerating voltage increased to 1.2 kV and then raised as accelerating voltage was elevated to 1.6 kV. The work function measured by Kelvin probe force microscopy increased after ion implanting, and it was consistent with the variation of Fermi level. The change of energy band structure of FTO surface mainly originated from the surface composition variation. As FTO conduction was primarily due to oxyanion hole, the carrier was electron and its concentration was reduced while O proportion was elevated at the surface of FTO, as a result, the Fermi level lowered and the work function was enlarged. It was proved that oxygen plasma treatment is an effective method to modulate the energy band structure of the surface as well as other properties of FTO, which provides much more space for interface and surface modification and then photoelectric device performance promotion.

Creating micro-scale surface topology to achieve anisotropic wettability on an aluminum surface

NASA Astrophysics Data System (ADS)

Sommers, Andrew D.; Jacobi, Anthony M.

2006-08-01

A technique for fabricating micropatterned aluminum surfaces with parallel grooves 30 µm wide and tens of microns in depth is described. Standard photolithographic techniques are used to obtain this precise surface-feature patterning. Positive photoresists, S1813 and AZ4620, are selected to mask the surface, and a mixture of BCl3 and Cl2 gases is used to perform the etching. Experimental data show that a droplet placed on the micro-grooved aluminum surface using a micro-syringe exhibits an increased apparent contact angle, and for droplets condensed on these etched surfaces, more than a 50% reduction in the volume needed for the onset of droplet sliding is manifest. No chemical surface treatment is necessary to achieve this water repellency; it is accomplished solely by an anisotropic surface morphology that manipulates droplet geometry and creates and exploits discontinuities in the three-phase contact line. These micro-structured surfaces are proposed for use in a broad range of air-cooling applications, where the management of condensate and defrost liquid on the heat transfer surface is essential to the energy-efficient operation of the machine.

Vertical Stratification of Peat Pore Water Dissolved Organic Matter Composition in a Peat Bog in Northern Minnesota

NASA Astrophysics Data System (ADS)

Tfaily, Malak M.; Wilson, Rachel M.; Cooper, William T.; Kostka, Joel E.; Hanson, Paul; Chanton, Jeffrey P.

2018-02-01

We characterized dissolved organic matter (DOM) composition throughout the peat column at the Marcell S1 forested bog in northern Minnesota and tested the hypothesis that redox oscillations associated with cycles of wetting and drying at the surface of the fluctuating water table correlate with increased carbon, sulfur, and nitrogen turn over. We found significant vertical stratification of DOM molecular composition and excitation-emission matrix parallel factor analysis components within the peat column. In particular, the intermediate depth zone ( 50 cm) was identified as a zone where maximum decomposition and turnover is taking place. Surface DOM was dominated by inputs from surface vegetation. The intermediate depth zone was an area of high organic matter reactivity and increased microbial activity with diagenetic formation of many unique compounds, among them polycyclic aromatic compounds that contain both nitrogen and sulfur heteroatoms. These compounds have been previously observed in coal-derived compounds and were assumed to be responsible for coal's biological activity. Biological processes triggered by redox oscillations taking place at the intermediate depth zone of the peat profile at the S1 bog are assumed to be responsible for the formation of these heteroatomic PACs in this system. Alternatively, these compounds could stem from black carbon and nitrogen derived from fires that have occurred at the site in the past. Surface and deep DOM exhibited more similar characteristics, compared to the intermediate depth zone, with the deep layer exhibiting greater input of microbially degraded organic matter than the surface suggesting that the entire peat profile consists of similar parent material at different degrees of decomposition and that lateral and vertical advection of pore water from the surface to the deeper horizons is responsible for such similarities. Our findings suggest that molecular composition of DOM in peatland pore water is dynamic and is a function of ecosystem activity, water table, redox oscillation, and pore water advection.

Vertical Stratification of Peat Pore Water Dissolved Organic Matter Composition in a Peat Bog in Northern Minnesota: Pore Water DOM composition in a peat bog

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

Tfaily, Malak M.; Wilson, Rachel M.; Cooper, William T.

We characterized dissolved organic matter (DOM) composition throughout the peat column at the Marcell S1 forested bog in northern Minnesota and tested the hypothesis that redox oscillations associated with cycles of wetting and drying at the surface of the fluctuating water table correlate with increased carbon, sulfur and nitrogen turn over. We found significant vertical stratification of DOM molecular composition and EEM-PARAFAC components within the peat column. In particular the intermediate depth zone (~ 50 cm) was identified as a zone where maximum decomposition and turnover is taking place. Surface DOM was dominated by inputs from surface vegetation. The intermediate-depthmore » zone was an area of high organic matter reactivity and increased microbial activity with diagenetic formation of many unique compounds, among them polycyclic aromatic compounds (PAC) that contain both nitrogen and sulfur heteroatoms. These compounds have been previously observed in coal-derived compounds and were assumed to be responsible for coal's biological activity. Biological processes triggered by redox oscillations taking place at the intermediate depth zone of the peat profile at the S1 bog are assumed to be responsible for the formation of these heteroatomic PACs in this system. Alternatively these compounds could stem from black carbon and nitrogen derived from fires that have occurred at the site in the past. Surface and deep DOM exhibited more similar characteristics, compared to the intermediate-depth zone, with the deep layer exhibiting greater input of microbially degraded organic matter than the surface suggesting that the entire peat profile consists of similar parent material at different degrees of decomposition and that lateral and vertical advection of pore water from the surface to the deeper horizons is responsible for such similarities. Our findings suggest that molecular composition of DOM in peatland pore water is dynamic and is a function of ecosystem activity, water table and redox oscillation and porewater advection.« less

Rapid temperature increase near the anode and cathode in the afterglow of a pulsed positive streamer discharge

NASA Astrophysics Data System (ADS)

Ono, Ryo

2018-06-01

The spatiotemporal evolution of the temperature in the afterglow of point-to-plane, pulsed positive streamer discharge was measured near the anode tip and cathode surface using laser-induced predissociation fluorescence of OH radicals. The temperature exhibited a rapid increase and displayed a steep spatial gradient after a discharge pulse. The rate of temperature rise reached 84 K μs‑1 at mm, where z represents the distance from the anode tip. The temperature rise was much faster than in the middle of the gap; it was only 2.8 K μs‑1 at mm. The temperature reached 1700 K near the anode tip at s and 1500 K near the cathode surface at s, where t represents the postdischarge time. The spatial gradient reached 1280 K mm‑1 near the anode tip at s. The mechanism responsible for the rapid temperature increase was discussed, including rapid heating of the gas in the early postdischarge phase (s), and vibration-to-translation energy transfer in the later postdischarge phase (s). The high temperatures near the anode tip and cathode surface are particularly important for the ignition of combustible mixtures and for surface treatments, including solid-surface treatments, water treatments, and plasma medicine using pulsed streamer discharges.

Oxygen Plasma Treatment on 3D-Printed Chitosan/Gelatin/Hydroxyapatite Scaffolds for Bone Tissue Engineering.

PubMed

Lee, Chang-Min; Yang, Seong-Won; Jung, Sang-Chul; Kim, Byung-Hoon

2017-04-01

The 3D hydroxyapatite/gelatin/chitosan composite scaffolds were fabricated by 3D printing technique. The scaffolds were treated by oxygen plasma to improve the bioactivity and its surface characterization and in vitro cell culture were investigated. The scaffolds exhibited the good porosity and interconnectivity of pores. After oxygen plasma etching, roughness and wettability on the scaffolds surface are increased. Plasma treated scaffolds showed higher proliferation than that of untreated scaffolds. Oxygen plasma treatment could be used as potential tool to enhance the biocompatibility on the 3D composite scaffolds.

Sequence stratigraphy of the Monterey Formation, Santa Barbara County: Integration of physical, chemical, and biofacies data from outcrop and subsurface

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

Bohacs, K.M.

1991-02-01

Deep basinal rocks of the Monterey Formation can be allocated to different depositional environments based on an integration of bedding, stacking patterns of facies, lithology, biofacies, and inorganic and organic chemistry. These rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level changes and basin evolution. Even deep-basinal environments are affected by changing sea level through changes in circulation patterns and intensities, nutrient budgets and dispersal patterns, and location and intensity of the oceanic oxygen minimum. The sequence-stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed bymore » typing the outcrop sections to an integrated will-log/seismic grid through outcrop gamma-ray spectral profiles. Interpretation of a sequence boundary was based on increased proportions of hemipelagic facies and evidence of increased bottom-energy levels above the boundary, and local erosion and relief on the surface. The proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary. Downlap surfaces exhibited increased proportions of pelagic facies around the surface, a secular change in the dominant lithology across the surface, evidence of decreased bottom-energy levels and terrigenous sedimentation rates, and little or not significant erosion on the surface. The proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface; there was no evidence of reworked individuals. The detailed sequence-stratigraphic framework makes it possible to tie rock properties to genetic processes for construction of predictive models.« less

Physicochemical properties of crystalline silica dusts and their possible implication in various biological responses.

PubMed

Fubini, B; Bolis, V; Cavenago, A; Volante, M

1995-01-01

The effect of grinding, heating, and etching was investigated on polymorphs of silicon dioxide exhibiting different biological responses. Diatomaceous earths were converted into cristobalite at 1000 degrees C. Dusts obtained by grinding crystalline minerals exhibited different micromorphology and a propensity to originate surface radicals which decrease in the sequence cristobalite --> quartz --> coesite --> stishovite. The production of surface radicals was suppressed by grinding in the presence of water. Thermal treatments selectively quenched the radicals and decreased surface hydrophilicity. Quartz treated with aluminum lactate exhibited higher surface acidity when compared with pure quartz, with a reduction in fibrogenicity. Etching by hydrofluoric acid smoothed the particles with loss of specific surface. Adsorption of water on three cristobalite dusts of different origin (ground mineral, ex-diatomite, heated quartz) indicated a loss in heated quartz (1300 degrees C) that was relatable to the corresponding reduction in fibrogenicity.

Nitrate Accumulation and Leaching in Surface and Ground Water Based on Simulated Rainfall Experiments

PubMed Central

Wang, Hong; Gao, Jian-en; Li, Xing-hua; Zhang, Shao-long; Wang, Hong-jie

2015-01-01

To evaluate the process of nitrate accumulation and leaching in surface and ground water, we conducted simulated rainfall experiments. The experiments were performed in areas of 5.3 m2 with bare slopes of 3° that were treated with two nitrogen fertilizer inputs, high (22.5 g/m2 NH4NO3) and control (no fertilizer), and subjected to 2 hours of rainfall, with. From the 1st to the 7th experiments, the same content of fertilizer mixed with soil was uniformly applied to the soil surface at 10 minutes before rainfall, and no fertilizer was applied for the 8th through 12th experiments. Initially, the time-series nitrate concentration in the surface flow quickly increased, and then it rapidly decreased and gradually stabilized at a low level during the fertilizer experiments. The nitrogen loss in the surface flow primarily occurred during the first 18.6 minutes of rainfall. For the continuous fertilizer experiments, the mean nitrate concentrations in the groundwater flow remained at less than 10 mg/L before the 5th experiment, and after the 7th experiment, these nitrate concentrations were greater than 10 mg/L throughout the process. The time-series process of the changing concentration in the groundwater flow exhibited the same parabolic trend for each fertilizer experiment. However, the time at which the nitrate concentration began to change lagged behind the start time of groundwater flow by approximately 0.94 hours on average. The experiments were also performed with no fertilizer. In these experiments, the mean nitrate concentration of groundwater initially increased continuously, and then, the process exhibited the same parabolic trend as the results of the fertilization experiments. The nitrate concentration decreased in the subsequent experiments. Eight days after the 12 rainfall experiments, 50.53% of the total nitrate applied remained in the experimental soil. Nitrate residues mainly existed at the surface and in the bottom soil layers, which represents a potentially more dangerous pollution scenario for surface and ground water. The surface and subsurface flow would enter into and contaminate water bodies, thus threatening the water environment. PMID:26291616

Nitrate Accumulation and Leaching in Surface and Ground Water Based on Simulated Rainfall Experiments.

PubMed

Wang, Hong; Gao, Jian-en; Li, Xing-hua; Zhang, Shao-long; Wang, Hong-jie

2015-01-01

To evaluate the process of nitrate accumulation and leaching in surface and ground water, we conducted simulated rainfall experiments. The experiments were performed in areas of 5.3 m2 with bare slopes of 3° that were treated with two nitrogen fertilizer inputs, high (22.5 g/m2 NH4NO3) and control (no fertilizer), and subjected to 2 hours of rainfall, with. From the 1st to the 7th experiments, the same content of fertilizer mixed with soil was uniformly applied to the soil surface at 10 minutes before rainfall, and no fertilizer was applied for the 8th through 12th experiments. Initially, the time-series nitrate concentration in the surface flow quickly increased, and then it rapidly decreased and gradually stabilized at a low level during the fertilizer experiments. The nitrogen loss in the surface flow primarily occurred during the first 18.6 minutes of rainfall. For the continuous fertilizer experiments, the mean nitrate concentrations in the groundwater flow remained at less than 10 mg/L before the 5th experiment, and after the 7th experiment, these nitrate concentrations were greater than 10 mg/L throughout the process. The time-series process of the changing concentration in the groundwater flow exhibited the same parabolic trend for each fertilizer experiment. However, the time at which the nitrate concentration began to change lagged behind the start time of groundwater flow by approximately 0.94 hours on average. The experiments were also performed with no fertilizer. In these experiments, the mean nitrate concentration of groundwater initially increased continuously, and then, the process exhibited the same parabolic trend as the results of the fertilization experiments. The nitrate concentration decreased in the subsequent experiments. Eight days after the 12 rainfall experiments, 50.53% of the total nitrate applied remained in the experimental soil. Nitrate residues mainly existed at the surface and in the bottom soil layers, which represents a potentially more dangerous pollution scenario for surface and ground water. The surface and subsurface flow would enter into and contaminate water bodies, thus threatening the water environment.

Sequence stratigraphy of the Monterey Formation, Santa Barbara County: Integration of physical, chemical, and biofacies data from outcrop and subsurface

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

Bohacs, K.M.

1990-05-01

Deep basinal rocks of the Monterey Formation can be allocated to different depositional environments based on an integration of bedding, facies stacking patterns, lithology, biofacies, and inorganic and organic chemistry. These rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level change and basin evolution. Even deep-basinal environments are affected by changing sea level through changes in circulation patterns and intensities nutrient budgets and dispersal patterns, and location and intensity of the oceanic oxygen minimum. The sequence-stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed by typingmore » the outcrop sections to an integrated well-log/seismic grid through outcrop gamma-ray-spectral profiles. Interpretation of a sequence boundary was based on increased proportions of hemipelagic facies, evidence of increased bottom-energy levels above the boundary, and local erosion and relief on the surface. The proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary, Downlap surfaces exhibited increased proportions of pelagic facies around the surface, evidence of decreased bottom-energy levels and terrigenous sedimentation rates, and little or no significant erosion on the surface. The proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface; there was no evidence of reworked individuals. The detailed sequence-stratigraphic framework makes it possible to the rock properties to genetic processes for construction of predictive models.« less

Biochar characteristics produced from rice husks and their sorption properties for the acetanilide herbicide metolachlor.

PubMed

Wei, Lan; Huang, Yufen; Li, Yanliang; Huang, Lianxi; Mar, Nyo Nyo; Huang, Qing; Liu, Zhongzhen

2017-02-01

Rice husk biochar (RHBC) was prepared for use as adsorbents for the herbicide metolachlor. The characteristics and sorption properties of metolachlor adsorbed by the RHBC prepared at different pyrolysis temperatures were determined by analysis of physico-chemical characteristics, Fourier transform infrared spectroscopy (FTIR), Boehm titration, scanning electron microscopy (SEM), and thermodynamics and kinetics adsorption. With increasing pyrolysis temperature, the RHBC surface area greatly increased (from 2.57 to 53.08 m 2  g -1 ). RHBC produced at the highest temperature (750 °C) had the greatest surface area; SEM also showed the formation of a porous surface on RH-750 biochar. The sorption capacity of RHBC also increased significantly with increasing pyrolysis temperature and was characterized by the Freundlich constant K f for the adsorption capacity increasing from 125.17-269.46 (pyrolysis at 300 °C) to 339.94-765.24 (pyrolysis at 750 °C). The results indicated that the surface area and pore diameter of RHBC produced with high pyrolysis temperature (i.e., 750 °C) had the greatest impact on the adsorption of metolachlor. The FTIR, Boehm titration, and SEM analysis showed that the greatest number of surface groups were on RHBC produced at the lowest temperature (300 °C). The biochars produced at different pyrolysis temperatures had different mechanisms of adsorbing metolachlor, which exhibited a transition from hydrogen bonds dominant at low pyrolytic temperature to pore-filling dominant at higher pyrolytic temperature.

Microstructure and Sliding Wear Behaviour of In-Situ TiC-Reinforced Composite Surface Layers Fabricated on Ductile Cast Iron by Laser Alloying.

PubMed

Janicki, Damian

2018-01-05

TiC-reinforced composite surface layers (TRLs) on a ductile cast iron EN-GJS-700-2 grade (DCI) substrate were synthesized using a diode laser surface alloying with a direct injection of titanium powder into the molten pool. The experimental results were compared with thermodynamic calculations. The TRLs having a uniform distribution of the TiC particles and their fraction up to 15.4 vol % were achieved. With increasing titanium concentration in the molten pool, fractions of TiC and retained austenite increase and the shape of TiC particles changes from cubic to dendritic form. At the same time, the cementite fraction decreases, lowering the overall hardness of the TRL. A good agreement between experimental and calculated results was achieved. Comparative dry sliding wear tests between the as-received DCI, the TRLs and also laser surface melted layers (SMLs) have been performed following the ASTM G 99 standard test method under contact pressures of 2.12 and 4.25 MPa. For both the as-received DCI and the SMLs, the wear rates increased with increasing contact pressure. The TRLs exhibited a significantly higher wear resistance than the others, which was found to be load independent.

Microstructure and Sliding Wear Behaviour of In-Situ TiC-Reinforced Composite Surface Layers Fabricated on Ductile Cast Iron by Laser Alloying

PubMed Central

Janicki, Damian

2018-01-01

TiC-reinforced composite surface layers (TRLs) on a ductile cast iron EN-GJS-700-2 grade (DCI) substrate were synthesized using a diode laser surface alloying with a direct injection of titanium powder into the molten pool. The experimental results were compared with thermodynamic calculations. The TRLs having a uniform distribution of the TiC particles and their fraction up to 15.4 vol % were achieved. With increasing titanium concentration in the molten pool, fractions of TiC and retained austenite increase and the shape of TiC particles changes from cubic to dendritic form. At the same time, the cementite fraction decreases, lowering the overall hardness of the TRL. A good agreement between experimental and calculated results was achieved. Comparative dry sliding wear tests between the as-received DCI, the TRLs and also laser surface melted layers (SMLs) have been performed following the ASTM G 99 standard test method under contact pressures of 2.12 and 4.25 MPa. For both the as-received DCI and the SMLs, the wear rates increased with increasing contact pressure. The TRLs exhibited a significantly higher wear resistance than the others, which was found to be load independent. PMID:29304001

Citrobacter amalonaticus Phytase on the Cell Surface of Pichia pastoris Exhibits High pH Stability as a Promising Potential Feed Supplement

PubMed Central

Li, Cheng; Lin, Ying; Huang, Yuanyuan; Liu, Xiaoxiao; Liang, Shuli

2014-01-01

Phytase expressed and anchored on the cell surface of Pichia pastoris avoids the expensive and time-consuming steps of protein purification and separation. Furthermore, yeast cells with anchored phytase can be used as a whole-cell biocatalyst. In this study, the phytase gene of Citrobacter amalonaticus was fused with the Pichia pastoris glycosylphosphatidylinositol (GPI)-anchored glycoprotein homologue GCW61. Phytase exposed on the cell surface exhibits a high activity of 6413.5 U/g, with an optimal temperature of 60°C. In contrast to secreted phytase, which has an optimal pH of 5.0, phytase presented on the cell surface is characterized by an optimal pH of 3.0. Moreover, our data demonstrate that phytase anchored on the cell surface exhibits higher pH stability than its secreted counterpart. Interestingly, our in vitro digestion experiments demonstrate that phytase attached to the cell surface is a more efficient enzyme than secreted phytase. PMID:25490768

Citrobacter amalonaticus phytase on the cell surface of Pichia pastoris exhibits high pH stability as a promising potential feed supplement.

PubMed

Li, Cheng; Lin, Ying; Huang, Yuanyuan; Liu, Xiaoxiao; Liang, Shuli

2014-01-01

Phytase expressed and anchored on the cell surface of Pichia pastoris avoids the expensive and time-consuming steps of protein purification and separation. Furthermore, yeast cells with anchored phytase can be used as a whole-cell biocatalyst. In this study, the phytase gene of Citrobacter amalonaticus was fused with the Pichia pastoris glycosylphosphatidylinositol (GPI)-anchored glycoprotein homologue GCW61. Phytase exposed on the cell surface exhibits a high activity of 6413.5 U/g, with an optimal temperature of 60°C. In contrast to secreted phytase, which has an optimal pH of 5.0, phytase presented on the cell surface is characterized by an optimal pH of 3.0. Moreover, our data demonstrate that phytase anchored on the cell surface exhibits higher pH stability than its secreted counterpart. Interestingly, our in vitro digestion experiments demonstrate that phytase attached to the cell surface is a more efficient enzyme than secreted phytase.

Friction and wear on laser textured Ti6Al4V surface subjected to laser shock peening with contacting foil

NASA Astrophysics Data System (ADS)

Dai, F. Z.; Geng, J.; Tan, W. S.; Ren, X. D.; Lu, J. Z.; Huang, Shu

2018-07-01

The Ti6Al4V micro-dimple surfaces fabricated by a masked laser surface texturing (MLST) technique within water were subjected to soft contact laser shock peening (SCLSP) and hard contact laser shock peening (HCLSP). The effects of these two LSP methods on topography, micro-hardness and residual stress distribution were studied. The friction and wear performance under dry friction and oil lubrication were also studied. The enclosure of micro cracks in the micro-dimple bottom was observed when treated by SCLSP and HCLSP. The dry friction and wear test showed that the MLST+HCLSP surfaces had the best wear resistance performance. In the oil lubricated friction test, the occurrence of the hydrodynamic lubrication effect occurred on the micro-dimple surfaces. The MLST+HCLSP exhibited the best friction and wear resistance performance. These were due to the micro-hardness increase, the producing of compressive residual stress and the surface roughness reduction of as treated surfaces.

Sharp improvement of flashover strength from composite micro-textured surfaces

NASA Astrophysics Data System (ADS)

Huo, Yankun; Liu, Wenyuan; Ke, Changfeng; Chang, Chao; Chen, Changhua

2017-09-01

A composite micro-textured surface structure is proposed and demonstrated to enhance the surface flashover strength of polymer insulators used in vacuum. The structure is fabricated in two stages, with periodic triangular grooves of approximately 210 μm in width formed in the first stage and micro-holes of approximately 2 μm coated on the inner surface of grooves in the second. The aim is to exploit the synergistic effects between the grooves and micro-holes to suppress the secondary electron yield to obtain a better flashover performance. To acquire insulators with the composite micro-textured surface, the CO2 laser processing technique is applied to treat the surface of the PMMA insulators. The test results show that the flashover voltages of the insulators with the two-stage fabricated structure increase by 150% compared with the untreated samples in the best state. Compared with the traditional macro-groove structures on insulators, the proposed composite micro-textured insulators exhibit a better surface flashover performance.

Photo-responsive surface topology in chiral nematic media

NASA Astrophysics Data System (ADS)

Liu, Danqing; Bastiaansen, Cees W. M.; Toonder, Jaap. M. J.; Broer, Dirk J.

2012-03-01

We report on the design and fabrication of 'smart surfaces' that exhibit dynamic changes in their surface topology in response to exposure to light. The principle is based on anisotropic geometric changes of a liquid crystal network upon a change of the molecular order parameter. The photomechanical property of the coating is induced by incorporating an azobenzene moiety into the liquid crystal network. The responsive surface topology consists of regions with two different types of molecular order: planar chiral-nematic areas and homeotropic. Under flood exposure with 365 nm light the surfaces deform from flat to one with a surface relief. The height of the relief structures is of the order of 1 um corresponding to strain difference of around 20%. Furthermore, we demonstrate surface reliefs can form either convex or concave structures upon exposure to UV light corresponding to the decrease or increase molecular order parameter, respectively, related to the isomeric state of the azobenzene crosslinker. The reversible deformation to the initial flat state occurs rapidly after removing the light source.

Surface modification of epoxy resin using He/CF4 atmospheric pressure plasma jet for flashover withstanding characteristics improvement in vacuum

NASA Astrophysics Data System (ADS)

Chen, Sile; Wang, Shuai; Wang, Yibo; Guo, Baohong; Li, Guoqiang; Chang, Zhengshi; Zhang, Guan-Jun

2017-08-01

For enhancing the surface electric withstanding strength of insulating materials, epoxy resin (EP) samples are treated by atmospheric pressure plasma jet (APPJ) with different time interval from 0 to 300s. Helium (He) and tetrafluoromethane (CF4) mixtures are used as working gases with the concentration of CF4 ranging 0%-5%, and when CF4 is ∼3%, the APPJ exhibits an optimal steady state. The flashover withstanding characteristics of modified EP in vacuum are greatly improved under appropriate APPJ treatment conditions. The surface properties of EP samples are evaluated by surface roughness, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. It is considered that both physical and chemical effects lead to the enhancement of flashover strength. The physical effect is reflected in the increase of surface roughness, while the chemical effect is reflected in the graft of fluorine groups.

A general strategy for the ultrafast surface modification of metals

PubMed Central

Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

2016-01-01

Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments. PMID:27924909

Applications of Fractal Analytical Techniques in the Estimation of Operational Scale

NASA Technical Reports Server (NTRS)

Emerson, Charles W.; Quattrochi, Dale A.

2000-01-01

The observational scale and the resolution of remotely sensed imagery are essential considerations in the interpretation process. Many atmospheric, hydrologic, and other natural and human-influenced spatial phenomena are inherently scale dependent and are governed by different physical processes at different spatial domains. This spatial and operational heterogeneity constrains the ability to compare interpretations of phenomena and processes observed in higher spatial resolution imagery to similar interpretations obtained from lower resolution imagery. This is a particularly acute problem, since longterm global change investigations will require high spatial resolution Earth Observing System (EOS), Landsat 7, or commercial satellite data to be combined with lower resolution imagery from older sensors such as Landsat TM and MSS. Fractal analysis is a useful technique for identifying the effects of scale changes on remotely sensed imagery. The fractal dimension of an image is a non-integer value between two and three which indicates the degree of complexity in the texture and shapes depicted in the image. A true fractal surface exhibits self-similarity, a property of curves or surfaces where each part is indistinguishable from the whole, or where the form of the curve or surface is invariant with respect to scale. Theoretically, if the digital numbers of a remotely sensed image resemble an ideal fractal surface, then due to the self-similarity property, the fractal dimension of the image will not vary with scale and resolution, and the slope of the fractal dimension-resolution relationship would be zero. Most geographical phenomena, however, are not self-similar at all scales, but they can be modeled by a stochastic fractal in which the scaling properties of the image exhibit patterns that can be described by statistics such as area-perimeter ratios and autocovariances. Stochastic fractal sets relax the self-similarity assumption and measure many scales and resolutions to represent the varying form of a phenomenon as the pixel size is increased in a convolution process. We have observed that for images of homogeneous land covers, the fractal dimension varies linearly with changes in resolution or pixel size over the range of past, current, and planned space-borne sensors. This relationship differs significantly in images of agricultural, urban, and forest land covers, with urban areas retaining the same level of complexity, forested areas growing smoother, and agricultural areas growing more complex as small pixels are aggregated into larger, mixed pixels. Images of scenes having a mixture of land covers have fractal dimensions that exhibit a non-linear, complex relationship to pixel size. Measuring the fractal dimension of a difference image derived from two images of the same area obtained on different dates showed that the fractal dimension increased steadily, then exhibited a sharp decrease at increasing levels of pixel aggregation. This breakpoint of the fractal dimension/resolution plot is related to the spatial domain or operational scale of the phenomenon exhibiting the predominant visible difference between the two images (in this case, mountain snow cover). The degree to which an image departs from a theoretical ideal fractal surface provides clues as to how much information is altered or lost in the processes of rescaling and rectification. The measured fractal dimension of complex, composite land covers such as urban areas also provides a useful textural index that can assist image classification of complex scenes.

Assessment of Surface Water Storage trends for increasing groundwater areas in India

NASA Astrophysics Data System (ADS)

Banerjee, Chandan; Kumar, D. Nagesh

2018-07-01

Recent studies based on Gravity Recovery and Climate Experiment (GRACE) satellite mission suggested that groundwater has increased in central and southern parts of India. However, surface water, which is an equally important source of water in these semi-arid areas has not been studied yet. In the present study, the study areas were outlined based on trends in GRACE data followed by trend identification in surface water storages and checking the hypothesis of causality. Surface Water Extent (SWE) and Surface Soil Moisture (SSM) derived from Moderate-resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) respectively, are selected as proxies of surface water storage (SWS). Besides SWE and SSM, trend test was performed for GRACE derived terrestrial water storage (TWS) for the study areas named as R1, R2, GOR1 and KOR1. Granger-causality test is used to test the hypothesis that rainfall is a causal factor of the inter-annual variability of SWE, SSM and TWS. Positive trends were observed in TWS for R1, R2 and GOR1 whereas SWE and SSM show increasing trends for all the study regions. Results suggest that rainfall is the granger-causal of all the storage variables for R1 and R2, the regions exhibiting the most significant positive trends in TWS.

Quantification of the effect of surface heating on shock wave modification by a plasma actuator in a low-density supersonic flow over a flat plate

NASA Astrophysics Data System (ADS)

Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

2015-05-01

This paper describes experimental and numerical investigations focused on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. A weakly ionized plasma was created above the plate by generating a glow discharge with a negative dc potential applied to the upstream electrode. The natural flow exhibited a shock wave with a hyperbolic shape. Pitot measurements and ICCD images of the modified flow revealed that when the discharge was ignited, the shock wave angle increased with the discharge current. The spatial distribution of the surface temperature was measured with an IR camera. The surface temperature increased with the current and decreased along the model. The temperature distribution was reproduced experimentally by placing a heating element instead of the active electrode, and numerically by modifying the boundary condition at the model surface. For the same surface temperature, experimental investigations showed that the shock wave angle was lower with the heating element than for the case with the discharge switched on. The results show that surface heating is responsible for roughly 50 % of the shock wave angle increase, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed.

Methylammonium lead iodide grain boundaries exhibit depth-dependent electrical properties

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

MacDonald, Gordon A.; Yang, Mengjin; Berweger, Samuel

In this paper, the nanoscale through-film and lateral photo-response and conductivity of large-grained methylammonium lead iodide (MAPbI 3) thin films are studied. In perovskite solar cells (PSC), these films result in efficiencies >17%. The grain boundaries (GBs) show high resistance at the top surface of the film, and act as an impediment to photocurrent collection. However, lower resistance pathways between grains exist below the top surface of the film, indicating that there exists a depth-dependent resistance of GBs (R GB(z)). Furthermore, lateral conductivity measurements indicate that R GB(z) exhibits GB-to-GB heterogeneity. These results indicate that increased photocurrent collection along GBsmore » is not a prerequisite for high-efficiency PSCs. Rather, better control of depth-dependent GB electrical properties, and an improvement in the homogeneity of the GB-to-GB electrical properties, must be managed to enable further improvements in PSC efficiency. Finally, these results refute the implicit assumption seen in the literature that the electrical properties of GBs, as measured at the top surface of the perovskite film, necessarily reflect the electrical properties of GBs within the thickness of the film.« less

Photocatalytic properties and selective antimicrobial activity of TiO2(Eu)/CuO nanocomposite

NASA Astrophysics Data System (ADS)

Michal, Robert; Dworniczek, Ewa; Caplovicova, Maria; Monfort, Olivier; Lianos, Panagiotis; Caplovic, Lubomir; Plesch, Gustav

2016-05-01

TiO2(Eu)/CuO nanocomposites were prepared by precipitation method. The anatase nanocrystallites with a size of 26 nm exhibited well crystallized and characteristical dipyramidal morphology and {1 0 1} and {0 0 1} faceting. Transmission electron microscopy photographs with atomic resolution showed that the Eu(III) dopants were bounded on surface of titania. In the composites, the CuO nanocrystals exhibiting a monoclinic tenorite structure with a size in the range from 2 to 5 nm were grafted to the surface of titania. The influence of copper(II) oxide led to distinct selectivity in the photocatalytic and antimicrobial properties of the investigated TiO2(Eu)/CuO nanocomposites. While the presence of CuO nanocrystals strongly increased the photocatalytic production of hydrogen by ethanol reforming, it decreased the activity in photoinduced total mineralization of phenol comparing with non-modified TiO2(Eu). In investigated TiO2(Eu)/CuO powders, the photoinduced antimicrobial activity against membranes of Enterococcus species was influenced by the selective binding of CuO to the surface of the microorganism leading to distinct selectivity in their action. The activity against Enterococcus faecalis was higher than against Enterococcus faecium.

Pore-scale water dynamics during drying and the impacts of structure and surface wettability

NASA Astrophysics Data System (ADS)

Cruz, Brian C.; Furrer, Jessica M.; Guo, Yi-Syuan; Dougherty, Daniel; Hinestroza, Hector F.; Hernandez, Jhoan S.; Gage, Daniel J.; Cho, Yong Ku; Shor, Leslie M.

2017-07-01

Plants and microbes secrete mucilage into soil during dry conditions, which can alter soil structure and increase contact angle. Structured soils exhibit a broad pore size distribution with many small and many large pores, and strong capillary forces in narrow pores can retain moisture in soil aggregates. Meanwhile, contact angle determines the water repellency of soils, which can result in suppressed evaporation rates. Although they are often studied independently, both structure and contact angle influence water movement, distribution, and retention in soils. Here drying experiments were conducted using soil micromodels patterned to emulate different aggregation states of a sandy loam soil. Micromodels were treated to exhibit contact angles representative of those in bulk soil (8.4° ± 1.9°) and the rhizosphere (65° ± 9.2°). Drying was simulated using a lattice Boltzmann single-component, multiphase model. In our experiments, micromodels with higher contact angle surfaces took 4 times longer to completely dry versus micromodels with lower contact angle surfaces. Microstructure influenced drying rate as a function of saturation and controlled the spatial distribution of moisture within micromodels. Lattice Boltzmann simulations accurately predicted pore-scale moisture retention patterns within micromodels with different structures and contact angles.

Methylammonium lead iodide grain boundaries exhibit depth-dependent electrical properties

DOE PAGES

MacDonald, Gordon A.; Yang, Mengjin; Berweger, Samuel; ...

2016-09-23

In this paper, the nanoscale through-film and lateral photo-response and conductivity of large-grained methylammonium lead iodide (MAPbI 3) thin films are studied. In perovskite solar cells (PSC), these films result in efficiencies >17%. The grain boundaries (GBs) show high resistance at the top surface of the film, and act as an impediment to photocurrent collection. However, lower resistance pathways between grains exist below the top surface of the film, indicating that there exists a depth-dependent resistance of GBs (R GB(z)). Furthermore, lateral conductivity measurements indicate that R GB(z) exhibits GB-to-GB heterogeneity. These results indicate that increased photocurrent collection along GBsmore » is not a prerequisite for high-efficiency PSCs. Rather, better control of depth-dependent GB electrical properties, and an improvement in the homogeneity of the GB-to-GB electrical properties, must be managed to enable further improvements in PSC efficiency. Finally, these results refute the implicit assumption seen in the literature that the electrical properties of GBs, as measured at the top surface of the perovskite film, necessarily reflect the electrical properties of GBs within the thickness of the film.« less

The effect of laser surface melting on microstructure and corrosion behavior of friction stir welded aluminum alloy 2219

NASA Astrophysics Data System (ADS)

Ma, Shengchong; Zhao, Yong; Zou, Jiasheng; Yan, Keng; Liu, Chuan

2017-11-01

This study aimed to explore the electrochemical properties and microstructure of friction stir welds to understand the correlation between their properties and processing. Friction stir welding is a promising solid-state joining process for high-strength aluminum alloys (AA). Although friction stir welding (FSW) eliminates the problems of fusion welding due to the fact that it is performed below Tm, it causes severe plastic deformation in the material. Some AA welded by FSW exhibit relatively poor corrosion resistance. In this research, the corrosion resistance of such welds was enhanced through laser surface melting. A friction stir weld of AA 2219 was laser melted. The melt depth and microstructure were observed using optical and scanning electron microscopy. The melt zone exhibited epitaxially grown columnar grains. The redistribution of elemental composition was analyzed using energy-dispersive spectroscopy. The anticorrosion properties of both laser-melted and original welds were studied in aqueous 3.5% NaCl solution using cyclic potentiodynamic polarization. The results indicated a noticeable increase in the pitting corrosion resistance after the laser treatment on the surface. The repassivation potential was nobler than the corrosion potential after the laser treatment, confirming that the resistance to pitting growth improved.

Phonons on fcc (100), (110), and (111) surfaces using Lennard-Jones potentials. II. Temperature dependence of surface phonons studied with molecular dynamics

NASA Astrophysics Data System (ADS)

Koleske, D. D.; Sibener, S. J.

In this paper we present temperature dependent studies of the surface phonon dispersion relations for fcc (100), (110), and (111) faces using molecular dynamics (MD) simulations and Lennard-Jones potentials. This study was conducted in order to investigate how anharmonic potential terms influence the dynamical properties of the surface. This was accomplished by examining the temperature dependence of the Q-resolved phonon spectral density function. All phonon frequencies were found to decrease linearly in T as the temperature was increased, while at low temperatures the phonon linewidths increased linearly with T. At higher temperatures, some of the phonon linewidths changed from having a linear to a quadratic dependence on T. The temperature at which this T to T2 change occurs is surface dependent and occurs at the lowest temperature on the (110) surface. The T2 dependence arises from the increasing importance of higher-order phonon-phonon scattering terms. The phonons which exhibit T2 dependence tend to be modes which propagate perpendicularly or nearly perpendicularly to the direction of maximum root-mean-squared displacement (RMSD). This is especially true for the linewidth of the S 1 mode at overlineX on the (110) surface where, at T ≈ 15-23% of the melting temperature, the RMSD perpendicular to the atomic rows become larger than the RMSD normal to the surface. Our results indicate that the dynamics on the (110) surface may be significantly influenced by anharmonic potential terms at temperatures as low as 15% of the melting temperature.

Various fates of neuronal progenitor cells observed on several different chemical functional groups

NASA Astrophysics Data System (ADS)

Liu, Xi; Wang, Ying; He, Jin; Wang, Xiu-Mei; Cui, Fu-Zhai; Xu, Quan-Yuan

2011-12-01

Neuronal progenitor cells cultured on gold-coated glass surfaces modified by different chemical functional groups, including hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), bromo (-Br), mercapto (-SH), - Phenyl and methyl (-CH3), were studied here to investigate the influence of surface chemistry on the cells' adhesion, morphology, proliferation and functional gene expression. Focal adhesion staining indicated in the initial culture stage cells exhibited morphological changes in response to different chemical functional groups. Cells cultured on -NH2 grafted surface displayed focal adhesion plaque and flattened morphology and had the largest contact area. However, their counter parts on -CH3 grafted surface displayed no focal adhesion and rounded morphology and had the smallest contact area. After 6 days culture, the proliferation trend was as follows: -NH2 > -SH> -COOH> - Phenyl > - Br > -OH> -CH3. To determine the neural functional properties of the cells affected by surface chemistry, the expression of glutamate decarboxylase (GAD67), nerve growth factor (NGF) and brainderived neurotrophic factor (BDNF) were characterized. An increase of GAD67 expression was observed on -NH2, -COOH and -SH grafted surfaces, while no increase in NGF and BDNF expression was observed on any chemical surfaces. These results highlight the importance of surface chemistry in the fate determination of neuronal progenitor cells, and suggest that surface chemistry must be considered in the design of biomaterials for neural tissue engineering.

Development of functional biointerfaces by surface modification of polydimethylsiloxane with bioactive chlorogenic acid.

PubMed

Wu, Ming; He, Jia; Ren, Xiao; Cai, Wen-Sheng; Fang, Yong-Chun; Feng, Xi-Zeng

2014-04-01

The effect of physicochemical surface properties and chemical structure on the attachment and viability of bacteria and mammalian cells has been extensively studied for the development of biologically relevant applications. In this study, we report a new approach that uses chlorogenic acid (CA) to modify the surface wettability, anti-bacterial activity and cell adhesion properties of polydimethylsiloxane (PDMS). The chemical structure of the surface was obtained by X-ray photoelectron spectroscopy (XPS), the roughness was measured by atomic force microscopy (AFM), and the water contact angle was evaluated for PDMS substrates both before and after CA modification. Molecular modelling showed that the modification was predominately driven by van der Waals and electrostatic interactions. The exposed quinic-acid moiety improved the hydrophilicity of CA-modified PDMS substrates. The adhesion and viability of E. coli and HeLa cells were investigated using fluorescence and phase contrast microscopy. Few viable bacterial cells were found on CA-coated PDMS surfaces compared with unmodified PDMS surfaces. Moreover, HeLa cells exhibited enhanced adhesion and increased spreading on the modified PDMS surface. Thus, CA-coated PDMS surfaces reduced the ratio of viable bacterial cells and increased the adhesion of HeLa cells. These results contribute to the purposeful design of anti-bacterial surfaces for medical device use. Copyright © 2013 Elsevier B.V. All rights reserved.

Fluid Mechanical Properties of Silkworm Fibroin Solutions

NASA Astrophysics Data System (ADS)

Matsumoto, Akira

2005-11-01

The aqueous solution behavior of silk fibroin is of interest due to the assembly and processing of this protein related to the spinning of protein fibers that exhibit remarkable mechanical properties. To gain insight into the origins of this functional feature, it is desired to determine how the protein behaves under a range of solution conditions. Pure fibroin at different concentrations in water was studied for surface tension, as a measure of surfactancy. In addition, shear induced changes on these solutions in terms of structure and morphology was also determined. Fibroin solutions exhibited shear rate-sensitive viscosity changes and precipitated at a critical shear rate where a dramatic increase of 75-150% of the initial value was observed along with a decrease in viscosity. In surface tension measurements, critical micelle concentrations were in the range of 3-4% w/v. The influence of additional factors, such as sericin protein, divalent and monovalent cations, and pH on the solution behavior in relation to structural and morphological features will also be described.

Elevated gold ellipse nanoantenna dimers as sensitive and tunable surface enhanced Raman spectroscopy substrates

DOE PAGES

Jubb, A. M.; Jiao, Y.; Eres, Gyula; ...

2016-02-15

Here we demonstrate large area arrays of elevated gold ellipse dimers with precisely controlled gaps for use as sensitive and highly controllable surface enhanced Raman scattering (SERS) substrates. The significantly enhanced Raman signal observed with SERS arises from both localized and long range plasmonic effects. By controlling the geometry of a SERS substrate, in this case the size and aspect ratio of individual ellipses, the plasmon resonance can be tuned in a broad wavelength range, providing a method for designing the response of SERS substrates at different excitation wavelengths. Plasmon effects exhibited by the elevated gold ellipse dimer substrates aremore » also demonstrated and confirmed through finite difference time domain (FDTD) simulations. A plasmon resonance red shift with an increase of the ellipse aspect ratio is observed, allowing systematic control of the resulting SERS signal intensity. Optimized elevated ellipse dimer substrates with 10±2 nm gaps exhibit uniform SERS enhancement factors on the order of 10 9 for adsorbed p-mercaptoaniline molecules.« less

Surface modification of 316L stainless steel with magnetron sputtered TiN/VN nanoscale multilayers for bio implant applications.

PubMed

Subramanian, B; Ananthakumar, R; Kobayashi, Akira; Jayachandran, M

2012-02-01

Nanoscale multilayered TiN/VN coatings were developed by reactive dc magnetron sputtering on 316L stainless steel substrates. The coatings showed a polycrystalline cubic structure with (111) preferential growth. XPS analysis indicated the presence of peaks corresponding to Ti2p, V2p, N1s, O1s, and C1s. Raman spectra exhibited the characteristic peaks in the acoustic range of 160-320 cm(-1) and in the optic range between 480 and 695 cm(-1). Columnar structure of the coatings was observed from TEM analysis. The number of adherent platelets on the surface of the TiN/VN multilayer, VN, TiN single layer coating exhibit fewer aggregation and pseudopodium than on substrates. The wear resistance of the multilayer coatings increases obviously as a result of their high hardness. Tafel plots in simulated bodily fluid showed lower corrosion rate for the TiN/VN nanoscale multilayer coatings compared to single layer and bare 316L SS substrate.

Hyaluronan preserves the proliferation and differentiation potentials of long-term cultured murine adipose-derived stromal cells

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

Chen, P.-Y.; Huang, Lynn L.H.; Hsieh, H.-J.

2007-08-17

For long-term culture, murine adipose-derived stromal cells (mADSCs) at latter passages demonstrated a marked decline in proliferative activity, exhibited senescent morphology and reduced differentiation potentials, particularly osteogenesis. To extend the lifespan of mADSCs, two culture conditions containing hyaluronan (HA) was compared in our study, one as a culture medium supplement (SHA), and the other where HA was pre-coated on culture surface (CHA). mADSCs cultivated with SHA exhibited a prolonged lifespan, reduced cellular senescence, and enhanced osteogenic potential compared to regular culture condition (control). Upon CHA treatment, mADSCs tended to form cell aggregates with gradual growth profiles, while their differentiation activitiesmore » remained similar to SHA groups. After transferring mADSCs from CHA to control surface, they were shown to have an extended lifespan and an increase of osteogenic potential. Our results suggested that HA can be useful for preserving the proliferation and differentiation potentials of long-term cultured mADSCs.« less

Role of surface electromagnetic waves in metamaterial absorbers

DOE PAGES

Chen, Wen -Chen; Cardin, Andrew; Koirala, Machhindra; ...

2016-03-18

Metamaterial absorbers have been demonstrated across much of the electromagnetic spectrum and exhibit both broad and narrow-band absorption for normally incident radiation. Absorption diminishes for increasing angles of incidence and transverse electric polarization falls off much more rapidly than transverse magnetic. We unambiguously demonstrate that broad-angle TM behavior cannot be associated with periodicity, but rather is due to coupling with a surface electromagnetic mode that is both supported by, and well described via the effective optical constants of the metamaterial where we achieve a resonant wavelength that is 19.1 times larger than the unit cell. Furthermore, experimental results are supportedmore » by simulations and we highlight the potential to modify the angular response of absorbers by tailoring the surface wave.« less

Experimental study of elliptical jet from sub to supercritical conditions

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

Muthukumaran, C. K.; Vaidyanathan, Aravind, E-mail: aravind7@iist.ac.in

2014-04-15

The jet mixing at supercritical conditions involves fluid dynamics as well as thermodynamic phenomena. All the jet mixing studies at critical conditions to the present date have focused only on axisymmetric jets. When the liquid jet is injected into supercritical environment, the thermodynamic transition could be well understood by considering one of the important fluid properties such as surface tension since it decides the existence of distinct boundary between the liquid and gaseous phase. It is well known that an elliptical liquid jet undergoes axis-switching phenomena under atmospheric conditions due to the presence of surface tension. The experimental investigations weremore » carried out with low speed elliptical jet under supercritical condition. Investigation of the binary component system with fluoroketone jet and N{sub 2} gas as environment shows that the surface tension force dominates for a large downstream distance, indicating delayed thermodynamic transition. The increase in pressure to critical state at supercritical temperature is found to expedite the thermodynamic transition. The ligament like structures has been observed rather than droplets for supercritical pressures. However, for the single component system with fluoroketone jet and fluoroketone environment shows that the jet disintegrates into droplets as it is subjected to the chamber conditions even for the subcritical pressures and no axis switching phenomenon is observed. For a single component system, as the pressure is increased to critical state, the liquid jet exhibits gas-gas like mixing behavior and that too without exhibiting axis-switching behavior.« less

Ultrasonic soldering of Cu alloy using Ni-foam/Sn composite interlayer.

PubMed

Xiao, Yong; Wang, Qiwei; Wang, Ling; Zeng, Xian; Li, Mingyu; Wang, Ziqi; Zhang, Xingyi; Zhu, Xiaomeng

2018-07-01

In this study, Cu alloy joints were fabricated with a Ni-foam reinforced Sn-based composite solder with the assistance of ultrasonic vibration. Effects of ultrasonic soldering time on the microstructure and mechanical properties of Cu/Ni-Sn/Cu joints were investigated. Results showed that exceptional metallurgic bonding could be acquired with the assistance of ultrasonic vibration using a self-developed Ni-foam/Sn composite solder. For joint soldered for 5 s, a (Cu,Ni) 6 Sn 5 intermetallic compound (IMC) layer was formed on the Cu substrate surface, Ni skeletons distributed randomly in the soldering seam and a serrated (Ni,Cu) 3 Sn 4 IMC layer was formed on the Ni skeleton surface. Increasing the soldering time to 20 s, the (Ni,Cu) 3 Sn 4 IMC layer grew significantly and exhibited a loose porous structure on the Ni skeleton surface. Further increase the soldering time to 30 s, Ni skeletons were largely dissolved in the Sn base solder, and micro-sized (Ni,Cu) 3 Sn 4 particles were formed and dispersed homogeneously in the soldering seam. The formation of (Ni,Cu) 3 Sn 4 particles was mainly ascribed to acoustic cavitations induced erosion and grain refining effects. The joint soldered for 30 s exhibited the highest shear strength of 64.9 ± 3.3 MPa, and the shearing failure mainly occurred at the soldering seam/Cu substrate interface. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of Surface Wettability on the Porosity and Wickability of Frost

NASA Astrophysics Data System (ADS)

Witt, Katherine; Ahmadi, Farzad; Boreyko, Jonathan

2017-11-01

The wicking of liquids through porous media has been studied for many materials, but never for frost, despite its implications for arctic oil spills and oil-infused surfaces. Here, we characterize silicone oils wicking up frost sheets. A layer of frost was grown on aluminum plates of varying surface wettability: superhydrophilic, hydrophilic, hydrophobic, and superhydrophobic. Once the desired frost thickness was grown, a humidity chamber was used to maintain the frost at the dew point and the bottom of the plate was dipped in a reservoir of fluorescent silicone oil. For all surfaces, the wicking rate of the oil increased with increasing wettability. For the wetting surfaces, this is manifested in the length vs. time data following the classical Washburn equation, exhibiting a power slope of about 1/2 and resulting in a larger effective pore radius with increasing wettability. However, we observed that on the non-wetting surfaces, the discrete distribution of the frosted dew droplets resulted in a new scaling law with a slope much less than 1/2, especially for the superhydrophobic surface which promoted jumping-droplet condensation. This research shows that the wicking of oil up a layer of frost can give insight into the morphology of frost. Conversely, if the underlying wettability of a frost sheet can be controlled, the spread of oil can be widely tuned. This work was supported by a Virginia Space Grant Consortium Undergraduate Research Scholarship (PMPTX7EP).

Sputtered protective coatings for die casting dies

NASA Technical Reports Server (NTRS)

Mirtich, M. J.; Nieh, C.-Y.; Wallace, J. F.

1981-01-01

Three experimental research designs investigating candidate materials and processes involved in protective die surface coating procedures by sputter deposition, using ion beam technologies, are discussed. Various pre-test results show that none of the coatings remained completely intact for 15,000 test cycles. The longest lifetime was observed for coatings such as tungsten, platinum, and molybdenum which reduced thermal fatigue, but exhibited oxidation and suppressed crack initiation only as long as the coating did not fracture. Final test results confirmed earlier findings and coatings with Pt and W proved to be the candidate materials to be used on a die surface to increase die life. In the W-coated specimens, which remained intact on the surface after thermal fatigue testing, no oxidation was found under the coating, although a few cracks formed on the surface where the coating broke down. Further research is planned.

Bose Condensation at He-4 Interfaces

NASA Technical Reports Server (NTRS)

Draeger, E. W.; Ceperley, D. M.

2003-01-01

Path Integral Monte Carlo was used to calculate the Bose-Einstein condensate fraction at the surface of a helium film at T = 0:77 K, as a function of density. Moving from the center of the slab to the surface, the condensate fraction was found to initially increase with decreasing density to a maximum value of 0.9, before decreasing. Long wavelength density correlations were observed in the static structure factor at the surface of the slab. A surface dispersion relation was calculated from imaginary-time density-density correlations. Similar calculations of the superfluid density throughout He-4 droplets doped with linear impurities (HCN)(sub n) are presented. After deriving a local estimator for the superfluid density distribution, we find a decreased superfluid response in the first solvation layer. This effective normal fluid exhibits temperature dependence similar to that of a two-dimensional helium system.

Solution-Processed Organic and Halide Perovskite Transistors on Hydrophobic Surfaces.

PubMed

Ward, Jeremy W; Smith, Hannah L; Zeidell, Andrew; Diemer, Peter J; Baker, Stephen R; Lee, Hyunsu; Payne, Marcia M; Anthony, John E; Guthold, Martin; Jurchescu, Oana D

2017-05-31

Solution-processable electronic devices are highly desirable due to their low cost and compatibility with flexible substrates. However, they are often challenging to fabricate due to the hydrophobic nature of the surfaces of the constituent layers. Here, we use a protein solution to modify the surface properties and to improve the wettability of the fluoropolymer dielectric Cytop. The engineered hydrophilic surface is successfully incorporated in bottom-gate solution-deposited organic field-effect transistors (OFETs) and hybrid organic-inorganic trihalide perovskite field-effect transistors (HTP-FETs) fabricated on flexible substrates. Our analysis of the density of trapping states at the semiconductor-dielectric interface suggests that the increase in the trap density as a result of the chemical treatment is minimal. As a result, the devices exhibit good charge carrier mobilities, near-zero threshold voltages, and low electrical hysteresis.

Developing a Novel Hydrogen Sponge with Ideal Binding Energy and High Surface Area for Practical Hydrogen Storage

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

Chung, T. C. Mike

This Phase I (5 quarters) research project was to examine the validity of a new class of boron-containing polymer (B-polymer) frameworks, serving as the adsorbents for the practical onboard H2 storage applications. Three B-polymer frameworks were synthesized and investigated, which include B-poly(butyenylstyrene) (B-PBS) framework (A), B-poly(phenyldiacetyene) (B-PPDA) framework (B), and B-poly(phenyltriacetylene) (B-PPTA) framework (C). They are 2-D polymer structures with the repeating cyclic units that spontaneously form open morphology and the B-doped (p-type) π-electrons delocalized surfaces. The ideal B-polymer framework shall exhibit open micropores (pore size in the range of 1-1.5nm) with high surface area (>3000 m 2/g), and themore » B-dopants in the conjugated framework shall provide high surface energy for interacting with H 2 molecules (an ideal H 2 binding energy in the range of 15-25 kJ/mol). The pore size distribution and H2 binding energy were investigated at both Penn State and NREL laboratories. So far, the experimental results show the successful synthesis of B-polymer frameworks with the relatively well-defined planar (2-D) structures. The intrinsically formed porous morphology exhibits a broad pore size distribution (in the range of 0.5-10 nm) with specific surface area (~1000 m 2/g). The miss-alignment between 2-D layers may block some micropore channels and limit gas diffusion throughout the entire matrix. In addition, the 2-D planar conjugated structure may also allow free π-electrons delocalization throughout the framework, which significantly reduces the acidity of B-moieties (electron-deficiency).The resulting 2-D B-polymer frameworks only exhibit a small increase of H 2 binding energy in the range of 8-9 KJ/mole (quite constant over the whole sorption range).« less

Corrosion mitigation of N-(2-hydroxy-3-trimethyl ammonium)propyl chitosan chloride as inhibitor on mild steel.

PubMed

Sangeetha, Y; Meenakshi, S; SairamSundaram, C

2015-01-01

The biopolymer N-(2-hydroxy-3-trimethyl ammonium)propyl chitosan chloride (HTACC) was synthesised and its influence as a novel corrosion inhibitor on mild steel in 1M HCl was studied using gravimetric and electrochemical experiments. The compound obtained was characterised using FTIR and NMR studies. The inhibition efficiency increased with the increase in concentration and reached a maximum of 98.9% at 500 ppm concentration. Polarisation studies revealed that HTACC acts both as anodic and cathodic inhibitor. Electrochemical impedance studies confirmed that the inhibition is through adsorption on the metal surface. The extent of inhibition exhibits a negative trend with increase in temperature. Langmuir isotherm provides the best description on the adsorption nature of the inhibitor. SEM analysis indicated the presence of protective film formed by the inhibitor on the metal surface. Copyright © 2014 Elsevier B.V. All rights reserved.

Annealing induced reorientation of crystallites in Sn doped ZnO films

NASA Astrophysics Data System (ADS)

Ravichandran, K.; Vasanthi, M.; Thirumurugan, K.; Sakthivel, B.; Karthika, K.

2014-11-01

Tin doped ZnO thin films were prepared by employing a simplified spray pyrolysis technique using a perfume atomizer and subsequently annealed under different temperatures from 350 °C to 500 °C in steps of 50 °C. The structural, optical, electrical, photoluminescence and surface morphological properties of the as-deposited films were studied and compared with that of the annealed films. The X-ray diffraction studies showed that as-deposited film exhibits preferential orientation along the (0 0 2) plane and it changes in favour of (1 0 0) plane after annealing. The increase in crystallite size due to annealing is explained on the basis of Ostwald ripening effect. It is found that the optical transmittance and band gap increases with increase in annealing temperature. A slight decrease in resistivity caused by annealing is discussed in correlation with annealing induced defect modifications and surface morphology.

Lifting the Green Veil: A Fresh Look at Synoptic Vegetation Dynamics

NASA Astrophysics Data System (ADS)

Henebry, G. M.; Vina, A.; Gitelson, A. A.

2003-12-01

Observing the dynamics of the vegetated land surface synoptically from spaceborne sensors plays a key role in understanding the global water, carbon, and nitrogen cycles, land cover and land use change, and biodiversity mapping. For the past three decades the study of global and regional vegetation dynamics has relied on satellite observations of the distinctive spectral contrast between red and near infrared reflectance exhibited by photosynthetically active green vegetation. It has long been recognized, however, that the spectral vegetation index with the widest currency-the Normalized Difference Vegetation Index (NDVI)-suffers a rapid decrease of sensitivity even at moderate Leaf Area Index (LAI) values of 2 to 4, as are commonly encountered in croplands and woodlands. This decrease in NDVI sensitivity casts a green veil over the land surface that obscures vegetation dynamics across vast areas during much of the growing season. This veil has important consequences for monitoring vegetation dynamics, developing land surface climatologies, and detecting significant changes. A straightforward modification of the NDVI, developed to increase its sensitivity under higher green biomass conditions, was applied to a standard, widely available AVHRR NDVI dataset for the conterminous US. The new Wide Dynamic Range Vegetation Index (WDRVI) exhibited increases in sensitivity between 30%-50% for Omernik Level III ecoregions dominated by woodlands, croplands, and grasslands. Ecoregions with lower aboveground net primary production, such as aridlands and semi-arid grasslands, showed no increase in sensitivity of the WDRVI over the NDVI. This powerful, new but simple approach creates an opportunity for a fresh look at the satellite data record. Further, it offers the possibility for significant improvements in the retrievals of canopy variables for carbon and nitrogen models, more accurate land surface characterizations for numerical weather prediction models, more sensitive analyses of land cover / land use change, and improvements in habitat mapping for biodiversity management.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

Selective Catalytic Reduction of NO by NH 3 with WO 3-TiO 2 Catalysts: Influence of Catalyst Synthesis Method

DOE PAGES

He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; ...

2016-02-02

A series of supported WO 3/TiO 2 catalysts was prepared by a new synthesis procedure involving co-precipitation of an aqueous TiO(OH) 2 and (NH 4) 10W 12O 41*5H 2O slurry under controlled pH conditions. The morphological properties, molecular structures, surface acidity and surface chemistry of the supported WO 3/TiO 2 catalysts were determined with BET, in situ Raman, in situ IR and temperature-programmed surface reaction (TPSR) spectroscopy, respectively. Isotopic 18O- 16O exchange demonstrated that tungsten oxide was exclusively present as surface WO x species on the TiO 2 support with mono-oxo W=O coordination. In contrast to previous studies employing impregnationmore » synthesis that found only surface one mono-oxo O=WO 4 site on TiO 2, the co-precipitation procedure resulted in the formation of two distinct surface WO x species: mono-oxo O=WO 4 (~1010-1017 cm -1) on low defect density patches of TiO 2 and a second mono-oxo O=WO 4 (~983-986 cm -1) on high defect density patches of TiO 2. The concentration of the second WO x surface species increases as a function of solution pH. Both surface WOx sites, however, exhibited the same NO/NH 3 SCR reactivity. The co-precipitated WO 3-TiO 2 catalysts synthesized in alkaline solutions exhibited enhanced performance for the NO/NH 3 SCR reaction that is ascribed to the greater number of surface defects on the resulting TiO2 support. For the co-precipitated catalyst prepared at pH10, surface NH 4 + species on Br nsted acid sites were found to be more reactive than surface NH 3* species on Lewis acid sites for SCR of NO with NH 3.« less

Water Plasma Functionalized CNTs/MnO2 Composites for Supercapacitors

PubMed Central

Hussain, Shahzad; Jover, Eric; Bertran, Enric

2013-01-01

A water plasma treatment applied to vertically-aligned multiwall carbon nanotubes (CNTs) synthesized by plasma enhanced chemical vapour deposition gives rise to surface functionalization and purification of the CNTs, along with an improvement of their electrochemical properties. Additional increase of their charge storage capability is achieved by anodic deposition of manganese dioxide lining the surface of plasma-treated nanotubes. The morphology (nanoflower, layer, or needle-like structure) and oxidation state of manganese oxide depend on the voltage window applied during charge-discharge measurements and are found to be key points for improved efficiency of capacitor devices. MnO2/CNTs nanocomposites exhibit an increase in their specific capacitance from 678 Fg−1, for untreated CNTs, up to 750 Fg−1, for water plasma-treated CNTs. PMID:24348189

Water plasma functionalized CNTs/MnO2 composites for supercapacitors.

PubMed

Hussain, Shahzad; Amade, Roger; Jover, Eric; Bertran, Enric

2013-01-01

A water plasma treatment applied to vertically-aligned multiwall carbon nanotubes (CNTs) synthesized by plasma enhanced chemical vapour deposition gives rise to surface functionalization and purification of the CNTs, along with an improvement of their electrochemical properties. Additional increase of their charge storage capability is achieved by anodic deposition of manganese dioxide lining the surface of plasma-treated nanotubes. The morphology (nanoflower, layer, or needle-like structure) and oxidation state of manganese oxide depend on the voltage window applied during charge-discharge measurements and are found to be key points for improved efficiency of capacitor devices. MnO2/CNTs nanocomposites exhibit an increase in their specific capacitance from 678 Fg(-1), for untreated CNTs, up to 750 Fg(-1), for water plasma-treated CNTs.

Construction of titanium dioxide nanorod/graphite microfiber hybrid electrodes for a high performance electrochemical glucose biosensor

NASA Astrophysics Data System (ADS)

Zhang, Jian; Yu, Xin; Guo, Weibo; Qiu, Jichuan; Mou, Xiaoning; Li, Aixue; Liu, Hong

2016-04-01

The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring.The demand for a highly sensitive and selective glucose biosensor which can be used for implantable or on-time monitoring is constantly increasing. In this work, TiO2 nanorods were synthesized in situ on the surface of graphite microfibers to yield TiO2 nanorod/graphite microfiber hybrid electrodes. The TiO2 nanorods not only retain the high activity of the immobilized glucose molecule, but also promote the direct electron transfer process on the electrode surface. As a working electrode in an electrochemical glucose biosensor in a flowing system, the microfiber hybrid electrodes exhibit high sensitivity, selectivity and stability. Due to its simplicity, low cost, high stability, and unique morphology, the TiO2 nanorod/graphite microfiber hybrid electrode is expected to be an excellent candidate for an implantable biosensor or for in situ flow monitoring. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01360k

Highlighting the Importance of Surface Grafting in Combination with a Layer-by-Layer Approach for Fabricating Advanced 3D Poly(l-lactide) Microsphere Scaffolds

PubMed Central

2016-01-01

A combined surface treatment (i.e., surface grafting and a layer-by-layer (LbL) approach) is presented to create advanced biomaterials, i.e., 3D poly(l-lactide) (PLLA) microsphere scaffolds, at room temperature. The grafted surface plays a crucial role in assembling polyelectrolyte multilayers (PEMs) onto the surface of the microspheres, thus improving the physicochemical properties of the 3D microsphere scaffolds. The grafted surface of the PLLA microspheres demonstrates much better PEM adsorption, improved surface coverage at low pH, and smoother surfaces at high pH compared with those of nongrafted surfaces of PLLA microspheres during the assembly of PEMs. They induce more swelling than nongrafted surfaces after the assembly of the PEMs and exhibit blue emission after functionalization of the microsphere surface with a fluorescent dye molecule. The 3D scaffolds functionalized with and without nanosheets not only exhibit good mechanical performance similar to the compressive modulus of cancellous bone but also exhibit the porosity required for cancellous bone regeneration. The magnetic nanoparticle-functionalized 3D scaffolds result in an electrical conductivity in the high range of semiconducting materials (i.e., 1–250 S cm–1). Thus, these 3D microsphere scaffolds fabricated by surface grafting and the LbL approach are promising candidates for bone tissue engineering. PMID:29503506

Streptococcus mutans adhesion on nickel titanium (NiTi) and copper-NiTi archwires: A comparative prospective clinical study.

PubMed

Abraham, Kirubaharan S; Jagdish, Nithya; Kailasam, Vignesh; Padmanabhan, Sridevi

2017-05-01

To compare the adhesion of Streptococcus mutans to nickel titanium (NiTi) and copper-NiTi (Cu-NiTi) archwires and to correlate the adhesion to surface characteristics (surface free energy and surface roughness) of these wires. A total of 16 patients undergoing orthodontic treatment with preadjusted edgewise appliances were included in the study. 0.016" and 0.016" × 0.022" NiTi and Cu-NiTi archwires in as-received condition and after 4 weeks of intraoral use were studied for S mutans adhesion using real-time polymerase chain reaction. Surface roughness and surface free energy were studied by three-dimensional surface profilometry and dynamic contact angle analysis, respectively. S mutans adhesion was more in Cu-NiTi archwires. These wires exhibited rougher surface and higher surface free energy when compared to NiTi archwires. S mutans adhesion, surface roughness, and surface free energy were greater in Cu-NiTi than NiTi archwires. Surface roughness and surface free energy increased after 4 weeks of intraoral exposure for all of the archwires studied. A predominantly negative correlation was seen between the cycle threshold value of adherent bacteria and surface characteristics.

Super-Hydrophobic Surface Prepared by Lanthanide Oxide Ceramic Deposition Through PS-PVD Process

NASA Astrophysics Data System (ADS)

Li, Jie; Li, Cheng-Xin; Chen, Qing-Yu; Gao, Jiu-Tao; Wang, Jun; Yang, Guan-Jun; Li, Chang-Jiu

2017-02-01

Super-hydrophobic surface has received widespread attention in recent years. Both the surface morphology and chemical composition have significant impact on hydrophobic performance. A novel super-hydrophobic surface based on plasma spray-vapor deposition was introduced in the present paper. Samaria-doped ceria, which has been proved as an intrinsic hydrophobic material, was used as feedstock material. Additionally, in order to investigate the influence of surface free energy on the hydrophobicity, chemical modification by low surface free energy materials including stearic acid and 1,1,2,2-tetrahydroperfluorodecyltrimethoxysilane (FAS) was used on coating surface. Scanning electron microscopy and Fourier transform infrared spectroscopy were employed to characterize the coating surface. The results show that the obtained surface has a hierarchical structure composed by island-like structures agglomerated with angular-like sub-micrometer-sized particles. Moreover, with the surface free energy decreases, the hydrophobic property of the surface improves gradually. The water contact angle of the as-sprayed coating surface increases from 110° to 148° after modification by stearic acid and up to 154° by FAS. Furthermore, the resultant surface with super-hydrophobicity exhibits an excellent stability.

The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.

PubMed

Mauldin, F William; Owen, Kevin; Tiouririne, Mohamed; Hossack, John A

2012-06-01

The portability, low cost, and non-ionizing radiation associated with medical ultrasound suggest that it has potential as a superior alternative to X-ray for bone imaging. However, when conventional ultrasound imaging systems are used for bone imaging, clinical acceptance is frequently limited by artifacts derived from reflections occurring away from the main axis of the acoustic beam. In this paper, the physical source of off-axis artifacts and the effect of transducer geometry on these artifacts are investigated in simulation and experimental studies. In agreement with diffraction theory, the sampled linear-array geometry possessed increased off-axis energy compared with single-element piston geometry, and therefore, exhibited greater levels of artifact signal. Simulation and experimental results demonstrated that the linear-array geometry exhibited increased artifact signal when the center frequency increased, when energy off-axis to the main acoustic beam (i.e., grating lobes) was perpendicularly incident upon off-axis surfaces, and when off-axis surfaces were specular rather than diffusive. The simulation model used to simulate specular reflections was validated experimentally and a correlation coefficient of 0.97 between experimental and simulated peak reflection contrast was observed. In ex vivo experiments, the piston geometry yielded 4 and 6.2 dB average contrast improvement compared with the linear array when imaging the spinous process and interlaminar space of an animal spine, respectively. This work indicates that off-axis reflections are a major source of ultrasound image artifacts, particularly in environments comprising specular reflecting (i.e., bone or bone-like) objects. Transducer geometries with reduced sensitivity to off-axis surface reflections, such as a piston transducer geometry, yield significant reductions in image artifact.

Electrospun Nanofibers Made of Silver Nanoparticles, Cellulose Nanocrystals, and Polyacrylonitrile as Substrates for Surface-Enhanced Raman Scattering

PubMed Central

Ren, Suxia; Dong, Lili; Zhang, Xiuqiang; Lei, Tingzhou; Ehrenhauser, Franz; Song, Kunlin; Li, Meichun; Sun, Xiuxuan; Wu, Qinglin

2017-01-01

Nanofibers with excellent activities in surface-enhanced Raman scattering (SERS) were developed through electrospinning precursor suspensions consisting of polyacrylonitrile (PAN), silver nanoparticles (AgNPs), silicon nanoparticles (SiNPs), and cellulose nanocrystals (CNCs). Rheology of the precursor suspensions, and morphology, thermal properties, chemical structures, and SERS sensitivity of the nanofibers were investigated. The electrospun nanofibers showed uniform diameters with a smooth surface. Hydrofluoric (HF) acid treatment of the PAN/CNC/Ag composite nanofibers (defined as p-PAN/CNC/Ag) led to rougher fiber surfaces with certain pores and increased mean fiber diameters. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirmed the existence of AgNPs that were formed during heat and HF acid treatment processes. In addition, thermal stability of the electrospun nanofibers increased due to the incorporation of CNCs and AgNPs. The p-PAN/CNC/Ag nanofibers were used as a SERS substrate to detect p-aminothiophenol (p-ATP) probe molecule. The results show that this substrate exhibited high sensitivity for the p-ATP probe detection. PMID:28772428

Analysis of water microdroplet condensation on silicon surfaces

NASA Astrophysics Data System (ADS)

Honda, Takuya; Fujimoto, Kenya; Yoshimoto, Yuta; Mogi, Katsuo; Kinefuchi, Ikuya; Sugii, Yasuhiko; Takagi, Shu; Univ. of Tokyo Team; Tokyo Inst. of Tech. Team

2016-11-01

We observed the condensation process of water microdroplets on flat silicon (100) surfaces by means of the sequential visualization of the droplets using an environmental scanning electron microscope. As previously reported for nanostructured surfaces, the condensation process of water microdroplets on the flat silicon surfaces also exhibits two modes: the constant base (CB) area mode and the constant contact angle (CCA) mode. In the CB mode, the contact angle increases with time while the base diameter is constant. Subsequently, in the CCA mode, the base diameter increases with time while the contact angle remains constant. The dropwise condensation model regulated by subcooling temperature does not reproduce the experimental results. Because the subcooling temperature is not constant in the case of a slow condensation rate, this model is not applicable to the condensation of the long time scale ( several tens of minutes). The contact angle of water microdroplets ( several μm) tended to be smaller than the macro contact angle. Two hypotheses are proposed as the cause of small contact angles: electrowetting and the coalescence of sub- μm water droplets.

Degradation of orthodontic wires under simulated cariogenic and erosive conditions.

PubMed

Jaber, Laura Cavalcante Lima; Rodrigues, José Augusto; Amaral, Flávia Lucisano Botelho; França, Fabiana Mantovani Gomes; Basting, Roberta Tarkany; Turssi, Cecilia Pedroso

2014-01-01

This study examined the effect of cariogenic and erosive challenges (CCs and ECs, respectively) on the degradation of copper-nickel-titanium (CuNiTi) orthodontic wires. Sixty wire segments were divided into four treatment groups and exposed to CCs, ECs, artificial saliva, or dry storage (no-treatment control). CC and EC were simulated using a demineralizing solution (pH 4.3) and a citric acid solution (pH 2.3), respectively. Following treatment, the average surface roughness (Ra) of the wires was assessed, and friction between the wires and a passive self-ligating bracket was measured. CuNiTi wires subjected to ECs exhibited significantly higher Ra values than did those that were stored in artificial saliva. In contrast, surface roughness was not affected by CCs. Finally, friction between the treated wires and brackets was not affected by ECs or CCs. Our results indicate that CuNiTi orthodontic wires may suffer degradation within the oral cavity, as ECs increased the surface roughness of these wires. However, rougher surfaces did not increase friction between the wire and the passive self-ligating bracket.

Effect of adsorbed films on friction of Al2O3-metal systems

NASA Technical Reports Server (NTRS)

Pepper, S. V.

1976-01-01

The kinetic friction of polycrystalline Al2O3 sliding on Cu, Ni, and Fe in ultrahigh vacuum was studied as a function of the surface chemistry of the metal. Clean metal surfaces were exposed to O2, Cl2, C2H4, and C2H3Cl, and the change in friction due to the adsorbed species was observed. Auger electron spectroscopy assessed the elemental composition of the metal surface. It was found that the systems exposed to Cl2 exhibited low friction, interpreted as the van der Waals force between the Al2O3 and metal chloride. The generation of metal oxide by oxygen exposures resulted in an increase in friction, interpreted as due to strong interfacial bonds established by reaction of metal oxide with Al2O3 to form the complex oxide (spinel). The only effect of C2H4 was to increase the friction of the Fe system, but C2H3Cl exposures decreases friction in both Ni and Fe systems, indicating the dominance of the chlorine over the ethylene complex on the surface

Structural and Interfacial Properties of Hyperbranched-Linear Polymer Surfactant.

PubMed

Qiang, Taotao; Bu, Qiaoqiao; Huang, Zhaofeng; Wang, Xuechuan

2014-01-01

With oleic acid grafting modification, a series of hyperbranched-linear polymer surfactants (HLPS) were prepared by hydroxyl-terminated hyperbranched polymer (HBP), which was gained through a step synthesis method using trimethylolpropane and AB 2 monomer. The AB 2 monomers were obtained through the Michael addition reaction of methyl acrylate and diethanol amine. The structures of HLPS were characterised by Fourier transform infrared spectrophotometer and nuclear magnetic resonance (NMR), which indicated that HBP was successfully modified by oleic acid. Furthermore, the properties of surface tension and critical micelle concentration of HLPS solution showed that HLPS can significantly reduce the surface tension of water. The morphology of the HLPS solution was characterised by dynamic light scattering, which revealed that HLPS exhibited a nonmonotonic appearance in particle size at different scattering angles owing to the different replaced linear portions. The relationships of the surface pressure to monolayer area and time were measured using the Langmuir-Blodgett instrument, which showed that the surface tension of monolayer molecules increased with the increasing of hydrophobic groups. In addition, the interface conditions of different replaced HLPS solutions were simulated.

Changes in Land Surface Water Dynamics since the 1990s and Relation to Population Pressure

NASA Technical Reports Server (NTRS)

Prigent, C.; Papa, F.; Aires, F.; Jimenez, C.; Rossow, W. B.; Matthews, E.

2012-01-01

We developed a remote sensing approach based on multi-satellite observations, which provides an unprecedented estimate of monthly distribution and area of land-surface open water over the whole globe. Results for 1993 to 2007 exhibit a large seasonal and inter-annual variability of the inundation extent with an overall decline in global average maximum inundated area of 6% during the fifteen-year period, primarily in tropical and subtropical South America and South Asia. The largest declines of open water are found where large increases in population have occurred over the last two decades, suggesting a global scale effect of human activities on continental surface freshwater: denser population can impact local hydrology by reducing freshwater extent, by draining marshes and wetlands, and by increasing water withdrawals. Citation: Prigent, C., F. Papa, F. Aires, C. Jimenez, W. B. Rossow, and E. Matthews (2012), Changes in land surface water dynamics since the 1990s and relation to population pressure, in section 4, insisting on the potential applications of the wetland dataset.

Nonlinear acoustic experiments involving landmine detection: Connections with mesoscopic elasticity and slow dynamics in geomaterials

NASA Astrophysics Data System (ADS)

Korman, Murray S.; Fenneman, Douglas J.; Sabatier, James M.

2004-10-01

The vibration interaction between the top-plate of a buried VS 1.6 plastic, anti-tank landmine and the soil above it appears to exhibit similar characteristics to the nonlinear mesoscopic/nanoscale effects that are observed in geomaterials like rocks or granular materials. In nonlinear detection schemes, airborne sound at two primary frequencies f1 and f2 (chosen several Hz apart on either side of resonance) undergo acoustic-to-seismic coupling. Interactions with the compliant mine and soil generate combination frequencies that, through scattering, can effect the vibration velocity at the surface. Profiles at f1, f2, f1-(f2-f1) and f2+(f2-f1) exhibit a single peak while profiles at 2f1-(f2-f1), f1+f2 and 2f2+(f2-f1) are attributed to higher order mode shapes. Near resonance (~125 Hz for a mine buried 3.6 cm deep), the bending (softening) of a family of increasing amplitude tuning curves (involving the surface vibration over the landmine) exhibits a linear relationship between the peak particle velocity and corresponding frequency. Subsequent decreasing amplitude tuning curves exhibit hysteresis effects. Slow dynamics explains the amplitude difference in tuning curves for first sweeping upward and then downward through resonance, provided the soil modulus drops after periods of high strain. [Work supported by U.S. Army RDECOM, CERDEC, NVESD, Fort Belvoir, VA.

Effects of Inductively Coupled Plasma Hydrogen on Long-Wavelength Infrared HgCdTe Photodiodes

NASA Astrophysics Data System (ADS)

Boieriu, P.; Buurma, C.; Bommena, R.; Blissett, C.; Grein, C.; Sivananthan, S.

2013-12-01

Bulk passivation of semiconductors with hydrogen continues to be investigated for its potential to improve device performance. In this work, hydrogen-only inductively coupled plasma (ICP) was used to incorporate hydrogen into long-wavelength infrared HgCdTe photodiodes grown by molecular-beam epitaxy. Fully fabricated devices exposed to ICP showed statistically significant increases in zero-bias impedance values, improved uniformity, and decreased dark currents. HgCdTe photodiodes on Si substrates passivated with amorphous ZnS exhibited reductions in shunt currents, whereas devices on CdZnTe substrates passivated with polycrystalline CdTe exhibited reduced surface leakage, suggesting that hydrogen passivates defects in bulk HgCdTe and in CdTe.

Computational simulation of the effects of oxygen on the electronic states of hydrogenated 3C-porous SiC

PubMed Central

2012-01-01

A computational study of the dependence of the electronic band structure and density of states on the chemical surface passivation of cubic porous silicon carbide (pSiC) was performed using ab initio density functional theory and the supercell method. The effects of the porosity and the surface chemistry composition on the energetic stability of pSiC were also investigated. The porous structures were modeled by removing atoms in the [001] direction to produce two different surface chemistries: one fully composed of silicon atoms and one composed of only carbon atoms. The changes in the electronic states of the porous structures as a function of the oxygen (O) content at the surface were studied. Specifically, the oxygen content was increased by replacing pairs of hydrogen (H) atoms on the pore surface with O atoms attached to the surface via either a double bond (X = O) or a bridge bond (X-O-X, X = Si or C). The calculations show that for the fully H-passivated surfaces, the forbidden energy band is larger for the C-rich phase than for the Si-rich phase. For the partially oxygenated Si-rich surfaces, the band gap behavior depends on the O bond type. The energy gap increases as the number of O atoms increases in the supercell if the O atoms are bridge-bonded, whereas the band gap energy does not exhibit a clear trend if O is double-bonded to the surface. In all cases, the gradual oxygenation decreases the band gap of the C-rich surface due to the presence of trap-like states. PMID:22913486

A comparative study of the nanoscale and macroscale tribological attributes of alumina and stainless steel surfaces immersed in aqueous suspensions of positively or negatively charged nanodiamonds

PubMed Central

Curtis, Colin K; Marek, Antonin; Smirnov, Alex I

2017-01-01

This article reports a comparative study of the nanoscale and macroscale tribological attributes of alumina and stainless steel surfaces immersed in aqueous suspensions of positively (hydroxylated) or negatively (carboxylated) charged nanodiamonds (ND). Immersion in −ND suspensions resulted in a decrease in the macroscopic friction coefficients to values in the range 0.05–0.1 for both stainless steel and alumina, while +ND suspensions yielded an increase in friction for stainless steel contacts but little to no increase for alumina contacts. Quartz crystal microbalance (QCM), atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements were employed to assess nanoparticle uptake, surface polishing, and resistance to solid–liquid interfacial shear motion. The QCM studies revealed abrupt changes to the surfaces of both alumina and stainless steel upon injection of –ND into the surrounding water environment that are consistent with strong attachment of NDs and/or chemical changes to the surfaces. AFM images of the surfaces indicated slight increases in the surface roughness upon an exposure to both +ND and −ND suspensions. A suggested mechanism for these observations is that carboxylated −NDs from aqueous suspensions are forming robust lubricious deposits on stainless and alumina surfaces that enable gliding of the surfaces through the −ND suspensions with relatively low resistance to shear. In contrast, +ND suspensions are failing to improve tribological performance for either of the surfaces and may have abraded existing protective boundary layers in the case of stainless steel contacts. This study therefore reveals atomic scale details associated with systems that exhibit starkly different macroscale tribological properties, enabling future efforts to predict and design complex lubricant interfaces. PMID:29046852

Lithography-free glass surface modification by self-masking during dry etching

NASA Astrophysics Data System (ADS)

Hein, Eric; Fox, Dennis; Fouckhardt, Henning

2011-01-01

Glass surface morphologies with defined shapes and roughness are realized by a two-step lithography-free process: deposition of an ~10-nm-thin lithographically unstructured metallic layer onto the surface and reactive ion etching in an Ar/CF4 high-density plasma. Because of nucleation or coalescence, the metallic layer is laterally structured during its deposition. Its morphology exhibits islands with dimensions of several tens of nanometers. These metal spots cause a locally varying etch velocity of the glass substrate, which results in surface structuring. The glass surface gets increasingly rougher with further etching. The mechanism of self-masking results in the formation of surface structures with typical heights and lateral dimensions of several hundred nanometers. Several metals, such as Ag, Al, Au, Cu, In, and Ni, can be employed as the sacrificial layer in this technology. Choice of the process parameters allows for a multitude of different glass roughness morphologies with individual defined and dosed optical scattering.

Effect of intrinsic surface roughness on the efficiency of intermodal phase matching in silica optical nanofibers.

PubMed

Khudus, Muhammad I M Abdul; Lee, Timothy; Horak, Peter; Brambilla, Gilberto

2015-04-01

We investigate the effect of intrinsic surface roughness associated to frozen thermal oscillations from the fiber fabrication process on the efficiency of third-harmonic generation via intermodal phase matching in silica nanofibers. Already a periodic wave with roughness of 0.2 nm reduces the efficiency by roughly 50% in a 1-mm optical nanofiber, with the divergence growing quadratically with distance. The surface wave period does not exhibit a large impact on the efficiency, due to averaging effects. However, both the location of the surface waves with respect to the phase matching radius as well as the surface wave amplitude have substantial effect on the efficiency, with the former presenting the possibility of transferring the power back to the pump wavelength. Simulations with a realistic superposition of random surface waves indicate that the conversion efficiency increases only for a few mm of propagation and reaches a maximum of less than 1%.

Influence of nanoscale topology on bactericidal efficiency of black silicon surfaces

NASA Astrophysics Data System (ADS)

Linklater, Denver P.; Khuong Duy Nguyen, Huu; Bhadra, Chris M.; Juodkazis, Saulius; Ivanova, Elena P.

2017-06-01

The nanostructuring of materials to create bactericidal and antibiofouling surfaces presents an exciting alternative to common methods of preventing bacterial adhesion. The fabrication of synthetic bactericidal surfaces has been inspired by the anti-wetting and anti-biofouling properties of insect wings, and other topologies found in nature. Black silicon is one such synthetic surfaces which has established bactericidal properties. In this study we show that time-dependent plasma etching of silicon wafers using 15, 30, and 45 min etching intervals, is able to produce different surface geometries with linearly increasing heights of approximately 280, 430, and 610 nm, respectively. After incubation on these surfaces with Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacterial cells it was established that smaller, more densely packed pillars exhibited the greatest bactericidal activity with 85% and 89% inactivation of bacterial cells, respectively. The decrease in the pillar heights, pillar cap diameter and inter-pillar spacing corresponded to a subsequent decrease in the number of attached cells for both bacterial species.

Short-Term Retrospective Land Data Assimilation Schemes

NASA Technical Reports Server (NTRS)

Houser, P. R.; Cosgrove, B. A.; Entin, J. K.; Lettenmaier, D.; ODonnell, G.; Mitchell, K.; Marshall, C.; Lohmann, D.; Schaake, J. C.; Duan, Q.;

Enhanced performance of Zn(II)-doped lead-acid batteries with electrochemical active carbon in negative mass

NASA Astrophysics Data System (ADS)

Xiang, Jiayuan; Hu, Chen; Chen, Liying; Zhang, Dong; Ding, Ping; Chen, Dong; Liu, Hao; Chen, Jian; Wu, Xianzhang; Lai, Xiaokang

2016-10-01

The effect and mechanism of Zn(II) on improving the performances of lead-acid cell with electrochemical active carbon (EAC) in negative mass is investigated. The hydrogen evolution of the cell is significantly reduced due to the deposition of Zn on carbon surface and the increased porosity of negative mass. Zn(II) additives can also improve the low-temperature and high-rate capacities of the cell with EAC in negative mass, which ascribes to the formation of Zn on lead and carbon surface that constructs a conductive bridge among the active mass. Under the co-contribution of EAC and Zn(II), the partial-state-of-charge cycle life is greatly prolonged. EAC optimizes the NAM structure and porosity to enhance the charge acceptance and retard the lead sulfate accumulation. Zn(II) additive reduces the hydrogen evolution during charge process and improves the electric conductivity of the negative electrode. The cell with 0.6 wt% EAC and 0.006 wt% ZnO in negative mass exhibits 90% reversible capacity of the initial capacity after 2100 cycles. In contrast, the cell with 0.6 wt% EAC exhibits 84% reversible capacity after 2100 cycles and the control cell with no EAC and Zn(II) exhibits less than 80% reversible capacity after 1350 cycles.

Optimization of implant/bone attachment: The effects of implant surface porosity, bioactive ceramic coatings, and delivery of adsorbed growth factors

NASA Astrophysics Data System (ADS)

Melican, Mora Carolynne

Various surface treatments and coating materials have been tested for use on metal alloy orthopaedic implants. Their purpose has been to enhance the bioactivity of the implant surfaces, and thus to increase the rate and degree of bony attachment in vivo in an attempt to hasten recovery time, increase implant service lifetime, and lessen pain associated with loosened orthopaedic implants. A series of in vivo and in vitro studies were performed to determine the influence of different implant surfaces including porous metal surfaces with varied porosity with depth, resorbable and non-resorbable plasma-sprayed hydroxyapatite (HA) coatings, and finally HA coatings with an adsorbed layer of human recombinant bone morphogenetic protein (rhBMP-2), an osteoinductive protein. Textured as-cast metal surfaces produced by investment casting in three dimensionally printed ceramic molds have exhibited superior bony ingrowth and attachment. Plasma-sprayed HA coatings have been shown to be appropriate substrates for osteoblast proliferation (particularly on highly crystalline HA) and stem cell proliferation (particularly on less crystalline HA). Less crystalline HA coatings have shown promise as delivery systems for different levels of rhBMP-2. The osteoinductive protein has been shown to remain active after delivery to the system, and was most effective when delivered in concentrations ranging from 30 to 50 ng/ml. Combinations of these surface treatments for metal implant surfaces warrant further investigation.

Microwave remote sensing of snowpacks

NASA Technical Reports Server (NTRS)

Stiles, W. H.; Ulaby, F. T.

1980-01-01

The interaction mechanisms responsible for the microwave backscattering and emission behavior of snow were investigated, and models were developed relating the backscattering coefficient (sigma) and apparent temperature (T) to the physical parameters of the snowpack. The microwave responses to snow wetness, snow water equivalent, snow surface roughness, and to diurnal variations were investigated. Snow wetness was shown to have an increasing effect with increasing frequency and angle of incidence for both active and passive cases. Increasing snow wetness was observed to decrease the magnitude sigma and increase T. Snow water equivalent was also observed to exhibit a significant influence sigma and T. Snow surface configuration (roughness) was observed to be significant only for wet snow surface conditions. Diurnal variations were as large as 15 dB for sigma at 35 GHz and 120 K for T at 37 GHz. Simple models for sigma and T of a snowpack scene were developed in terms of the most significant ground-truth parameters. The coefficients for these models were then evaluated; the fits to the sigma and T measurements were generally good. Finally, areas of needed additional observations were outlined and experiments were specified to further the understanding of the microwave-snowpack interaction mechanisms.

The Unprecedented 2016-2017 Arctic Sea Ice Growth Season: The Crucial Role of Atmospheric Rivers and Longwave Fluxes

NASA Astrophysics Data System (ADS)

Hegyi, Bradley M.; Taylor, Patrick C.

2018-05-01

The 2016-2017 Arctic sea ice growth season (October-March) exhibited one of the lowest values for end-of-season sea ice volume and extent of any year since 1979. An analysis of Modern-Era Retrospective Analysis for Research and Applications, Version 2 atmospheric reanalysis data and Clouds and the Earth's Radiant Energy System radiative flux data reveals that a record warm and moist Arctic atmosphere supported the reduced sea ice growth. Numerous regional episodes of increased atmospheric temperature and moisture, transported from lower latitudes, increased the cumulative energy input from downwelling longwave surface fluxes. In those same episodes, the efficiency of the atmosphere cooling radiatively to space was reduced, increasing the amount of energy retained in the Arctic atmosphere and reradiated back toward the surface. Overall, the Arctic radiative cooling efficiency shows a decreasing trend since 2000. The results presented highlight the increasing importance of atmospheric forcing on sea ice variability demonstrating that episodic Arctic atmospheric rivers, regions of elevated poleward water vapor transport, and the subsequent surface energy budget response is a critical mechanism actively contributing to the evolution of Arctic sea ice.

Glycosylation controls cooperative PECAM-VEGFR2-β3 integrin functions at the endothelial surface for tumor angiogenesis.

PubMed

Imamaki, Rie; Ogawa, Kazuko; Kizuka, Yasuhiko; Komi, Yusuke; Kojima, Soichi; Kotani, Norihiro; Honke, Koichi; Honda, Takashi; Taniguchi, Naoyuki; Kitazume, Shinobu

2018-05-02

Most of the angiogenesis inhibitors clinically used in cancer treatment target the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathway. However, the current strategies for treating angiogenesis have limited efficacy. The issue of how to treat angiogenesis and endothelial dysfunction in cancer remains a matter of substantial debate. Here we demonstrate a glycosylation-dependent regulatory mechanism for tumor angiogenesis. St6gal1 -/- mice, lacking the α2,6-sialylation enzyme, were shown to exhibit impaired tumor angiogenesis through enhanced endothelial apoptosis. In a previous study, St6gal1 -/- endothelial cells exhibited a reduction in the cell surface residency of platelet endothelial cell adhesion molecule (PECAM). In this study, we found that cooperative functionality of PECAM-VEGFR2-integrin β3 was disturbed in St6gal1 -/- mice. First, cell surface PECAM-VEGFR2 complexes were lost, and both VEGFR2 internalization and the VEGFR-dependent signaling pathway were enhanced. Second, enhanced anoikis was observed, suggesting that the absence of α2,6-sialic acid leads to dysregulated integrin signaling. Notably, ectopic expression of PECAM increased cell surface integrin-β3, indicating that the reduction of cell surface integrin-β3 involves loss-of-endothelial PECAM. The results suggest that the cell surface stability of these glycoproteins is significantly reduced by the lack of α2,6-sialic acid, leading to abnormal signal transduction. The present findings highlight that α2,6-sialylation is critically involved in endothelial survival by controlling the cell surface stability and signal transduction of angiogenic molecules, and could be a novel target for anti-angiogenesis therapy.

Self-assembly of fatty acids on hydroxylated Al surface and effects of their stability on wettability and nanoscale organization.

PubMed

Liascukiene, Irma; Steffenhagen, Marie; Asadauskas, Svajus J; Lambert, Jean-François; Landoulsi, Jessem

2014-05-27

The self-assembly of fatty acids (FA) on the surfaces of inorganic materials is a relevant way to control their wetting properties. While the mechanism of adsorption on model flat substrate is well described in the literature, interfacial processes remain poorly documented on nanostructured surfaces. In this study, we report the self-assembly of a variety of FA on a hydroxylated Al surface which exhibits a random nanoscale organization. Our results revealed a peculiar fingerprint due to the FA self-assembly which consists in the formation of aligned nanopatterns in a state of hierarchical nanostructuration, regardless of the molecular structure of the FA (chain length, level of unsaturation). After a significant removal of adsorbed FA using UV/O3 treatment, a complete wetting was reached, and a noticeable disturbance of the surface morphology was observed, evidencing the pivotal role of FA molecules to maintain these nanostructures. The origin of wetting properties was investigated prior to and after conditioning of FA-modified samples taking into account key parameters, namely the surface roughness and its composition. For this purpose, the Wenzel roughness, defined as the third moment of power spectral density, was used, as it is sensitive to high spatial frequency and thus to the obtained hierarchical level of nanostructuration. Our results revealed that no correlation can be made between water contact angles (θ(w)) and the Wenzel roughness. By contrast, θ(w) strongly increased with the amount of -CHx- groups exhibited by adsorbed FA. These findings suggest that the main origin of hydrophobization is the presence of self-assembled molecules and that the surface roughness has only a small contribution to the wettability.

Surface oxidation of tin chalcogenide nanocrystals revealed by 119Sn-Mössbauer spectroscopy.

PubMed

de Kergommeaux, Antoine; Faure-Vincent, Jérôme; Pron, Adam; de Bettignies, Rémi; Malaman, Bernard; Reiss, Peter

2012-07-18

Narrow band gap tin(II) chalcogenide (SnS, SnSe, SnTe) nanocrystals are of high interest for optoelectronic applications such as thin film solar cells or photodetectors. However, charge transfer and charge transport processes strongly depend on nanocrystals' surface quality. Using (119)Sn-Mössbauer spectroscopy, which is the most sensitive tool for probing the Sn oxidation state, we show that SnS nanocrystals exhibit a Sn((IV))/Sn((II)) ratio of around 20:80 before and 40:60 after five minutes exposure to air. Regardless of the tin or sulfur precursors used, similar results are obtained using six different synthesis protocols. The Sn((IV)) content before air exposure arises from surface related SnS(2) and Sn(2)S(3) species as well as from surface Sn atoms bound to oleic acid ligands. The increase of the Sn((IV)) content upon air exposure results from surface oxidation. Full oxidation of the SnS nanocrystals without size change is achieved by annealing at 500 °C in air. With the goal to prevent surface oxidation, SnS nanocrystals are capped with a cadmium-phosphonate complex. A broad photoluminescence signal centered at 600 nm indicates successful capping, which however does not reduce the air sensitivity. Finally we demonstrate that SnSe nanocrystals exhibit a very similar behavior with a Sn((IV))/Sn((II)) ratio of 43:57 after air exposure. In the case of SnTe nanocrystals, the ratio of 55:45 is evidence of a more pronounced tendency for oxidation. These results demonstrate that prior to their use in optoelectronics further surface engineering of tin chalcogenide nanocrystals is required, which otherwise have to be stored and processed under inert atmosphere.

The linkage between stratospheric water vapor and surface temperature in an observation-constrained coupled general circulation model

NASA Astrophysics Data System (ADS)

Wang, Yuan; Su, Hui; Jiang, Jonathan H.; Livesey, Nathaniel J.; Santee, Michelle L.; Froidevaux, Lucien; Read, William G.; Anderson, John

2017-04-01

We assess the interactions between stratospheric water vapor (SWV) and surface temperature during the past two decades using satellite observations and the Community Earth System Model (CESM). From 1992 to 2013, to first order, the observed SWV exhibited three distinct piece-wise trends: a steady increase from 1992 to 2000, an abrupt drop from 2000 to 2004, and a gradual recovery after 2004, while the global-mean surface temperature experienced a strong increase until 2000 and a warming hiatus after 2000. The atmosphere-only CESM shows that the seasonal variation of tropical-mean (30°S-30°N) SWV is anticorrelated with that of the tropical-mean sea surface temperature (SST), while the correlation between the tropical SWV and SST anomalies on the interannual time scale is rather weak. By nudging the modeled SWV to prescribed profiles in coupled atmosphere-slab ocean experiments, we investigate the impact of SWV variations on surface temperature change. We find that a uniform 1 ppmv (0.5 ppmv) SWV increase (decrease) leads to an equilibrium global mean surface warming (cooling) of 0.12 ± 0.05 °C (-0.07 ± 0.05 °C). Sensitivity experiments show that the equilibrium response of global mean surface temperature to SWV perturbations over the extratropics is larger than that over the tropics. The observed sudden drop of SWV from 2000 to 2004 produces a global mean surface cooling of about -0.048 ± 0.041 °C, which suggests that a persistent change in SWV would make an imprint on long-term variations of global-mean surface temperature. A constant linear increase in SWV based on the satellite-observed rate of SWV change yields a global mean surface warming of 0.03 ± 0.01 °C/decade over a 50-year period, which accounts for about 19 % of the observed surface temperature increase prior to the warming hiatus. In the same experiment, trend analyses during different periods reveal a multi-year adjustment of surface temperature before the response to SWV forcing becomes strong relative to the internal variability in the model.

Fracture Toughness of Thin Plates by the Double-Torsion Test Method

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Radovic, Miladin; Lara-Curzio, Edgar; Nelson, George

2006-01-01

Double torsion testing can produce fracture toughness values without crack length measurement that are comparable to those measured via standardized techniques such as the chevron-notch, surface-crack-in-flexure and precracked beam if the appropriate geometry is employed, and the material does not exhibit increasing crack growth resistance. Results to date indicate that 8 < W/d < 80 and L/W > 2 are required if crack length is not considered in stress intensity calculations. At L/W = 2, the normalized crack length should be 0.35 < a/L < 0.65; whereas for L/W = 3, 0.2 < a/L < 0.75 is acceptable. In addition, the load-points need to roll to reduce friction. For an alumina exhibiting increasing crack growth resistance, values corresponding to the plateau of the R-curve were measured. For very thin plates (W/d > 80) nonlinear effects were encountered.

Inhibition of bacterial and leukocyte adhesion under shear stress conditions by material surface chemistry.

PubMed

Patel, Jasmine D; Ebert, Michael; Stokes, Ken; Ward, Robert; Anderson, James M

2003-01-01

Biomaterial-centered infections, initiated by bacterial adhesion, persist due to a compromised host immune response. Altering implant materials with surface modifying endgroups (SMEs) may enhance their biocompatibility by reducing bacterial and inflammatory cell adhesion. A rotating disc model, which generates shear stress within physiological ranges, was used to characterize adhesion of leukocytes and Staphylococcus epidermidis on polycarbonate-urethanes and polyetherurethanes modified with SMEs (polyethylene oxide, fluorocarbon and dimethylsiloxane) under dynamic flow conditions. Bacterial adhesion in the absence of serum was found to be mediated by shear stress and surface chemistry, with reduced adhesion exhibited on materials modified with polydimethylsiloxane and polyethylene oxide SMEs. In contrast, bacterial adhesion was enhanced on materials modified with fluorocarbon SMEs. In the presence of serum, bacterial adhesion was primarily neither material nor shear dependent. However, bacterial adhesion in serum was significantly reduced to < or = 10% compared to adhesion in serum-free media. Leukocyte adhesion in serum exhibited a shear dependency with increased adhesion occurring in regions exposed to lower shear-stress levels of < or = 7 dyne/cm2. Additionally, polydimethylsiloxane and polyethylene oxide SMEs reduced leukocyte adhesion on polyether-urethanes. In conclusion, these results suggest that surface chemistry and shear stress can mediate bacterial and cellular adhesion. Furthermore, materials modified with polyethylene oxide SMEs are capable of inhibiting bacterial adhesion, consequently minimizing the probability of biomaterial-centered infections.

A nanometric Rh overlayer on a metal foil surface as a highly efficient three-way catalyst.

PubMed

Misumi, Satoshi; Yoshida, Hiroshi; Hinokuma, Satoshi; Sato, Tetsuya; Machida, Masato

2016-07-08

Pulsed arc-plasma (AP) deposition of an Rh overlayer on an Fe-Cr-Al stainless steel foil produced a composite material that exhibited high activity for automotive three-way catalysis (TWC). The AP pulses deposited metallic Rh nanoparticles 1-3 nm in size, whose density on the surface increased with the number of pulses. This led to coalescence and grain growth on the foil surface and the eventual formation of a uniform two-dimensional Rh overlayer. Full coverage of the 51 μm-thick flat foil by a 3.2 nm-thick Rh overlayer was achieved after 1,000 pulses. A simulated TWC reaction using a miniature honeycomb fabricated using flat and corrugated foils with the Rh overlayers exhibited successful light-off at a practical gaseous hourly space velocity of 1.2 × 10(5) h(-1). The turnover frequency for the NO-CO reaction over the metallic honeycomb catalyst was ca. 80-fold greater than that achieved with a reference Rh/ZrO2-coated cordierite honeycomb prepared using a conventional wet impregnation and slurry coating procedure. Despite the nonporosity and low surface area of the foil-supported Rh overlayer compared with conventional powder catalysts (Rh/ZrO2), it is a promising alternative design for more efficient automotive catalysts that use less Rh loading.

Dynamic stability of passive dynamic walking on an irregular surface.

PubMed

Su, Jimmy Li-Shin; Dingwell, Jonathan B

2007-12-01

Falls that occur during walking are a significant health problem. One of the greatest impediments to solve this problem is that there is no single obviously "correct" way to quantify walking stability. While many people use variability as a proxy for stability, measures of variability do not quantify how the locomotor system responds to perturbations. The purpose of this study was to determine how changes in walking surface variability affect changes in both locomotor variability and stability. We modified an irreducibly simple model of walking to apply random perturbations that simulated walking over an irregular surface. Because the model's global basin of attraction remained fixed, increasing the amplitude of the applied perturbations directly increased the risk of falling in the model. We generated ten simulations of 300 consecutive strides of walking at each of six perturbation amplitudes ranging from zero (i.e., a smooth continuous surface) up to the maximum level the model could tolerate without falling over. Orbital stability defines how a system responds to small (i.e., "local") perturbations from one cycle to the next and was quantified by calculating the maximum Floquet multipliers for the model. Local stability defines how a system responds to similar perturbations in real time and was quantified by calculating short-term and long-term local exponential rates of divergence for the model. As perturbation amplitudes increased, no changes were seen in orbital stability (r(2)=2.43%; p=0.280) or long-term local instability (r(2)=1.0%; p=0.441). These measures essentially reflected the fact that the model never actually "fell" during any of our simulations. Conversely, the variability of the walker's kinematics increased exponentially (r(2)>or=99.6%; p<0.001) and short-term local instability increased linearly (r(2)=88.1%; p<0.001). These measures thus predicted the increased risk of falling exhibited by the model. For all simulated conditions, the walker remained orbitally stable, while exhibiting substantial local instability. This was because very small initial perturbations diverged away from the limit cycle, while larger initial perturbations converged toward the limit cycle. These results provide insight into how these different proposed measures of walking stability are related to each other and to risk of falling.

Atmospheric-pressure DBD plasma-assisted surface modification of polymethyl methacrylate: A study on cell growth/proliferation and antibacterial properties

NASA Astrophysics Data System (ADS)

Rezaei, Fatemeh; Shokri, Babak; Sharifian, M.

2016-01-01

This paper reports polymethyl methacrylate (PMMA) surface modification by atmospheric-pressure oxygen dielectric barrier discharge (DBD) plasma to improve its biocompatibility and antibacterial effects. The role of plasma system parameters, such as electrode gap, treatment time and applied voltage, on the surface characteristics and biological responses was studied. The surface characteristics of PMMA films before and after the plasma treatments were analyzed by water contact angle (WCA) goniometry, atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Also, acid-base approach was used for evaluation of surface free energy (SFE) and its components. Stability of plasma treatment or aging effect was examined by repeating water contact angle measurements in a period of 9 days after treatment. Moreover, the antibacterial properties of samples were investigated by bacterial adhesion assay against Escherichia coli. Additionally, all samples were tested for the biocompatibility by cell viability assay of mouse embryonic fibroblast. WCA measurements indicated that the surface wettability of PMMA films was improved by increasing surface free energy via oxygen DBD plasma treatments. AFM measurement revealed that surface roughness was slightly increased after treatments, and ATR-FTIR analysis showed that more polar groups were introduced on the plasma-treated PMMA film surface. The results also demonstrated an enhancement of antibacterial performance of the modified surfaces. Furthermore, it was observed that plasma-treated samples exhibited significantly better biocompatibility, comparing to the pristine one.

Membrane Lipid Peroxidation in Copper Alloy-Mediated Contact Killing of Escherichia coli

PubMed Central

Hong, Robert; Kang, Tae Y.; Michels, Corinne A.

2012-01-01

Copper alloy surfaces are passive antimicrobial sanitizing agents that kill bacteria, fungi, and some viruses. Studies of the mechanism of contact killing in Escherichia coli implicate the membrane as the target, yet the specific component and underlying biochemistry remain unknown. This study explores the hypothesis that nonenzymatic peroxidation of membrane phospholipids is responsible for copper alloy-mediated surface killing. Lipid peroxidation was monitored with the thiobarbituric acid-reactive substances (TBARS) assay. Survival, TBARS levels, and DNA degradation were followed in cells exposed to copper alloy surfaces containing 60 to 99.90% copper or in medium containing CuSO4. In all cases, TBARS levels increased with copper exposure levels. Cells exposed to the highest copper content alloys, C11000 and C24000, exhibited novel characteristics. TBARS increased immediately at a very rapid rate but peaked at about 30 min. This peak was associated with the period of most rapid killing, loss in membrane integrity, and DNA degradation. DNA degradation is not the primary cause of copper-mediated surface killing. Cells exposed to the 60% copper alloy for 60 min had fully intact genomic DNA but no viable cells. In a fabR mutant strain with increased levels of unsaturated fatty acids, sensitivity to copper alloy surface-mediated killing increased, TBARS levels peaked earlier, and genomic DNA degradation occurred sooner than in the isogenic parental strain. Taken together, these results suggest that copper alloy surface-mediated killing of E. coli is triggered by nonenzymatic oxidative damage of membrane phospholipids that ultimately results in the loss of membrane integrity and cell death. PMID:22247141

Surface modification by electrolytic plasma processing for high Nb-TiAl alloys

NASA Astrophysics Data System (ADS)

Gui, Wanyuan; Hao, Guojian; Liang, Yongfeng; Li, Feng; Liu, Xiao; Lin, Junpin

2016-12-01

Metal surface modification by electrolytic plasma processing (EPP) is an innovative treatment widely commonly applied to material processing and pretreatment process of coating and galvanization. EPP involves complex processes and a great deal of parameters, such as preset voltage, current, solution temperature and processing time. Several characterization methods are presented in this paper for evaluating the micro-structure surfaces of Ti45Al8Nb alloys: SEM, EDS, XRD and 3D topography. The results showed that the oxide scale and other contaminants on the surface of Ti45Al8Nb alloys can be effectively removed via EPP. The typical micro-crater structure of the surface of Ti45Al8Nb alloys were observed by 3D topography after EPP to find that the mean diameter of the surface structure and roughness value can be effectively controlled by altering the processing parameters. The mechanical properties of the surface according to nanomechanical probe testing exhibited slight decrease in microhardness and elastic modulus after EPP, but a dramatic increase in surface roughness, which is beneficial for further processing or coating.

Apparent Activation Energies Associated with Protein Dynamics on Hydrophobic and Hydrophilic Surfaces

PubMed Central

Langdon, Blake B.; Kastantin, Mark; Schwartz, Daniel K.

2012-01-01

With the use of single-molecule total internal reflection fluorescence microscopy (TIRFM), the dynamics of bovine serum albumin (BSA) and human fibrinogen (Fg) at low concentrations were observed at the solid-aqueous interface as a function of temperature on hydrophobic trimethylsilane (TMS) and hydrophilic fused silica (FS) surfaces. Multiple dynamic modes and populations were observed and characterized by their surface residence times and squared-displacement distributions (surface diffusion). Characteristic desorption and diffusion rates for each population/mode were generally found to increase with temperature, and apparent activation energies were determined from Arrhenius analyses. The apparent activation energies of desorption and diffusion were typically higher on FS than on TMS surfaces, suggesting that protein desorption and mobility were hindered on hydrophilic surfaces due to favorable protein-surface and solvent-surface interactions. The diffusion of BSA on TMS appeared to be activationless for several populations, whereas diffusion on FS always exhibited an apparent activation energy. All activation energies were small in absolute terms (generally only a few kBT), suggesting that most adsorbed protein molecules are weakly bound and move and desorb readily under ambient conditions. PMID:22713578

Preparation of protein- and cell-resistant surfaces by hyperthermal hydrogen induced cross-linking of poly(ethylene oxide).

PubMed

Bonduelle, Colin V; Lau, Woon M; Gillies, Elizabeth R

2011-05-01

The functionalization of surfaces with poly(ethylene oxide) (PEO) is an effective means of imparting resistance to the adsorption of proteins and the attachment and growth of cells, properties that are critical for many biomedical applications. In this work, a new hyperthermal hydrogen induced cross-linking (HHIC) method was explored as a simple one-step approach for attaching PEO to surfaces through the selective cleavage of C-H bonds and subsequent cross-linking of the resulting carbon radicals. In order to study the effects of the process on the polymer, PEO-coated silicon wafers were prepared and the effects of different treatment times were investigated. Subsequently, using an optimized treatment time and a modified butyl polymer with increased affinity for PEO, the technique was applied to butyl rubber surfaces. All of the treated surfaces exhibited significantly reduced protein adsorption and cell growth relative to control surfaces and compared favorably with surfaces that were functionalized with PEO using conventional chemical methods. Thus HHIC is a simple and effective means of attaching PEO to non-functional polymer surfaces.

Altering the concentration of silica tunes the functional properties of collagen-silica composite scaffolds to suit various clinical requirements.

PubMed

Perumal, Sathiamurthi; Ramadass, Satiesh Kumar; Gopinath, Arun; Madhan, Balaraman; Shanmugam, Ganesh; Rajadas, Jayakumar; Mandal, Asit Baran

2015-12-01

The success of a tissue engineering scaffold depends on a fine balance being achieved between the physicochemical and biological properties. This study attempts to understand the influence of silica concentration on the functional properties of collagen-silica (CS) composite scaffolds for soft tissue engineering applications. Increasing the ratio of silica to collagen (0.25, 0.5, 0.75, 1.0, 1.25, 1.5 and 2.0 w/w) gave a marked advantage in terms of improving the water uptake and compressive modulus of the CS scaffolds, while also enhancing the biological stability and the turnover time. With increase in silica concentration the water uptake and compressive modulus increased concurrently, whereas it was not so for surface porous architecture and biocompatibility which are crucial for cell adhesion and infiltration. Silica:collagen ratio of ≤1 exhibits favourable surface biocompatibility, and any further increase in silica concentration has a detrimental effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

Angle-Dependent Atomic Force Microscopy Single-Chain Pulling of Adsorbed Macromolecules from Planar Surfaces Unveils the Signature of an Adsorption-Desorption Transition.

PubMed

Grebíková, Lucie; Whittington, Stuart G; Vancso, Julius G

2018-05-23

The adsorption-desorption behavior of polymer chains is at the heart of macromolecular surface science and technology. With the current developments in atomic force microscopy (AFM), it has now become possible to address the desorption problem from the perspective of a single macromolecule. Here, we report on desorption of single polymer chains on planar surfaces by AFM-based single molecule force spectroscopy (SMFS) as a function of the pulling angle with respect to the surface-normal direction. SMFS experiments were performed in water with various substrates using different polymers covalently attached to the AFM probe tip. End-grafting at the AFM tip was achieved by surface-initiated polymerization using initiator functionalized tips. We found that the desorption force increases with a decreasing pulling angle, i.e., an enhanced adhesion of the polymer chain was observed. The magnitude of the desorption force shows a weak angular dependence at pulling angles close to the surface normal. A significant increase of the force is observed at shallower pulling from a certain pulling angle. This behavior carries the signature of an adsorption-desorption transition. The angular dependence of the normalized desorption force exhibits a universal behavior. We compared and interpreted our results using theoretical predictions for single-chain adsorption-desorption transitions.

Angle-Dependent Atomic Force Microscopy Single-Chain Pulling of Adsorbed Macromolecules from Planar Surfaces Unveils the Signature of an Adsorption–Desorption Transition

PubMed Central

2018-01-01

The adsorption–desorption behavior of polymer chains is at the heart of macromolecular surface science and technology. With the current developments in atomic force microscopy (AFM), it has now become possible to address the desorption problem from the perspective of a single macromolecule. Here, we report on desorption of single polymer chains on planar surfaces by AFM-based single molecule force spectroscopy (SMFS) as a function of the pulling angle with respect to the surface-normal direction. SMFS experiments were performed in water with various substrates using different polymers covalently attached to the AFM probe tip. End-grafting at the AFM tip was achieved by surface-initiated polymerization using initiator functionalized tips. We found that the desorption force increases with a decreasing pulling angle, i.e., an enhanced adhesion of the polymer chain was observed. The magnitude of the desorption force shows a weak angular dependence at pulling angles close to the surface normal. A significant increase of the force is observed at shallower pulling from a certain pulling angle. This behavior carries the signature of an adsorption–desorption transition. The angular dependence of the normalized desorption force exhibits a universal behavior. We compared and interpreted our results using theoretical predictions for single-chain adsorption–desorption transitions. PMID:29712430

Long range surface plasmon resonance (LRSPR) based highly sensitive refractive index sensor using Kretschmann prism coupling arrangement

NASA Astrophysics Data System (ADS)

Paliwal, Ayushi; Sharma, Anjali; Tomar, Monika; Gupta, Vinay

2016-04-01

Long range surface plasmon resonance (LRSPR) when exploited for sensing purpose exhibit less losses in comparison to the sensors based on conventional SPR technique leading to the development of highly sensitive refractive index sensor. In order to excite long range surface plasmon (LRSP) mode, a high refractive index prism is used as coupler and a thin metal layer is sandwiched between a dielectric having similar refractive index with that of another semi-infinite dielectric. LRSP mode has been excited in symmetric configuration where metal (Au) layer is sandwiched between the two similar refractive index dielectrics (LiF thin film and a fixed concentration of sugar solution) for realization of a refractive index sensor. When the concentration of sugar solution is slightly increased from 30% to 40%, the LRSPR angle increases from 64.6° to 67.9° and the sensor is found to be highly sensitive with sensitivity of 0.0911 °/(mg/dl).

Structure and photoelectrochemistry of silver-copper-indium-diselenide ((AgCu)InSe2) thin film

NASA Astrophysics Data System (ADS)

Zhang, Lin Rui; Li, Tong; Wang, Hao; Pang, Wei; Chen, Yi Chuan; Song, Xue Mei; Zhang, Yong Zhe; Yan, Hui

2018-02-01

In this work, silver (Ag) precursors with different thicknesses were sputtered on the surfaces of CuIn alloys, and (AgCu)InSe2 (ACIS) films were formed after selenization at 550 °C under nitrogen condition using a rapid thermal process furnace. The structure and electrical properties of the ACIS films were investigated. The result showed that the distribution of Ag+ ion was more uniform with increasing the thickness of Ag precursor, and the surface of the thin-film became more homogeneous and denser. When Ag/Cu ratio ≥0.249, the small grain particles disappeared. The band gap can be rationally controlled by adjusting Ag content. When (Ag + Cu)/In ratio ≥ 1.15, the surface of the ACIS thin-film mainly exhibited n-type semiconductor. Through the photoelectrochemistry measurement, it was observed that the incorporation of Ag+ ions could improve photocurrent by adjusting the band gap. With the Ag precursor thickness increased, the dark current decreased at the more negative potential.

Flow cytometric single cell analysis reveals heterogeneity between adipose depots

PubMed Central

Boumelhem, Badwi B.; Assinder, Stephen J.; Bell-Anderson, Kim S.; Fraser, Stuart T.

2017-01-01

ABSTRACT Understanding adipose tissue heterogeneity is hindered by the paucity of methods to analyze mature adipocytes at the single cell level. Here, we report a system for analyzing live adipocytes from different adipose depots in the adult mouse. Single cell suspensions of buoyant adipocytes were separated from the stromal vascular fraction and analyzed by flow cytometry. Compared to other lipophilic dyes, Nile Red uptake effectively distinguished adipocyte populations. Nile Red fluorescence increased with adipocyte size and granularity and could be combined with MitoTracker® Deep Red or fluorescent antibody labeling to further dissect adipose populations. Epicardial adipocytes exhibited the least mitochondrial membrane depolarization and highest fatty-acid translocase CD36 surface expression. In contrast, brown adipocytes showed low surface CD36 expression. Pregnancy resulted in reduced mitochondrial membrane depolarisation and increased CD36 surface expression in brown and epicardial adipocyte populations respectively. Our protocol revealed unreported heterogeneity between adipose depots and highlights the utility of flow cytometry for screening adipocytes at the single cell level. PMID:28453382

The clear-sky greenhouse effect sensitivity to a sea surface temperature change

NASA Technical Reports Server (NTRS)

Duvel, J. PH.; Breon, F. M.

1991-01-01

The clear-sky greenhouse effect response to a sea surface temperature (SST or Ts) change is studied using outgoing clear-sky longwave radiation measurements from the Earth Radiation Budget Experiment. Considering geographical distributions for July 1987, the relation between the SST, the greenhouse effect (defined as the outgoing infrared flux trapped by atmospheric gases), and the precipitable water vapor content (W), estimated by the Special Sensor Microwave Imager, is analyzed first. A fairly linear relation between W and the normalized greenhouse effect g, is found. On the contrary, the SST dependence of both W and g exhibits nonlinearities with, especially, a large increase for SST above 25 C. This enhanced sensitivity of g and W can be interpreted in part by a corresponding large increase of atmospheric water vapor content related to the transition from subtropical dry regions to equatorial moist regions. Using two years of data (1985 and 1986), the normalized greenhouse effect sensitivity to the sea surface temperature is computed from the interannual variation of monthly mean values.

Super-Anticoagulant Heparin-Mimicking Hydrogel Thin Film Attached Substrate Surfaces to Improve Hemocompatibility.

PubMed

He, Min; Cui, Xiaofei; Jiang, Huiyi; Huang, Xuelian; Zhao, Weifeng; Zhao, Changsheng

2017-02-01

In this study, heparin-mimicking hydrogel thin films are covalently attached onto poly(ether sulfone) membrane surfaces to improve anticoagulant property. The hydrogel films display honeycomb-like porous structure with well controlled thickness and show long-term stability. After immobilizing the hydrogel films, the membranes show excellent anticoagulant property confirmed by the activated partial thromboplastin time values exceeding 600 s. Meanwhile, the thrombin time values increase from 20 to 61 s as the sodium allysulfonate proportions increase from 0 to 80 mol%. In vitro investigations of protein adsorption and blood-related complement activation also confirm that the membranes exhibit super-anticoagulant property. Furthermore, gentamycin sulfate is loaded into the hydrogel films, and the released drug shows significant inhibition toward E. coli bacteria. It is believed that the surface attached heparin-mimicking hydrogel thin films may show high potential for the applications in various biological fields, such as blood contacting materials and drug loading materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancement of the antimicrobial properties of orthorhombic molybdenum trioxide by thermal induced fracturing of the hydrates.

PubMed

Shafaei, Shahram; Van Opdenbosch, Daniel; Fey, Tobias; Koch, Marcus; Kraus, Tobias; Guggenbichler, Josef Peter; Zollfrank, Cordt

2016-01-01

The oxides of the transition metal molybdenum exhibit excellent antimicrobial properties. We present the preparation of molybdenum trioxide dihydrate (MoO3 × 2H2O) by an acidification method and demonstrate the thermal phase development and morphological evolution during and after calcination from 25 °C to 600 °C. The thermal dehydration of the material was found to proceed in two steps. Microbiological roll-on tests using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed and exceptional antimicrobial activities were determined for anhydrous samples with orthorhombic lattice symmetry and a large specific surface area. The increase in the specific surface area is due to crack formation and to the loss of the hydrate water after calcination at 300 °C. The results support the proposed antimicrobial mechanism for transition metal oxides, which based on a local acidity increase as a consequence of the augmented specific surface area. Copyright © 2015 Elsevier B.V. All rights reserved.

Increased Chain Length Promotes Pneumococcal Adherence and Colonization

PubMed Central

Rodriguez, Jesse L.; Dalia, Ankur B.

2012-01-01

Streptococcus pneumoniae is a mucosal pathogen that grows in chains of variable lengths. Short-chain forms are less likely to activate complement, and as a consequence they evade opsonophagocytic clearance more effectively during invasive disease. When grown in human nasal airway surface fluid, pneumococci exhibited both short- and long-chain forms. Here, we determined whether longer chains provide an advantage during colonization when the organism is attached to the epithelial surface. Chain-forming mutants and the parental strain grown under conditions to promote chain formation showed increased adherence to human epithelial cells (A549 cells) in vitro. Additionally, adherence to A549 cells selected for longer chains within the wild-type strain. In vivo in a murine model of colonization, chain-forming mutants outcompeted the parental strain. Together, our results demonstrate that morphological heterogeneity in the pneumococcus may promote colonization of the upper respiratory tract by enhancing the ability of the organism to bind to the epithelial surface. PMID:22825449

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

Nozaki, T., E-mail: nozaki@ecei.tohoku.ac.jp; Oida, M.; Ashida, T.

We investigated the effect of Pt insertion on a Cr{sub 2}O{sub 3}/Co exchange coupling system. The perpendicular exchange bias μ{sub 0}H{sub ex} decreased with increasing Pt insertion layer thickness, and we observed positive μ{sub 0}H{sub ex} for samples with relatively thick Pt insertion layers. We also examined the cooling field μ{sub 0}H{sub fc} dependence of μ{sub 0}H{sub ex} for the samples. At small μ{sub 0}H{sub fc}, all samples exhibited negative μ{sub 0}H{sub ex}. With increasing μ{sub 0}H{sub fc}, a shift of μ{sub 0}H{sub ex} from negative to positive was observed. In the past, similar behaviors were observed for FeF{sub 2}/Femore » systems exhibiting positive μ{sub 0}H{sub ex}. In addition, the μ{sub 0}H{sub fc} dependence of μ{sub 0}H{sub ex} was well fitted by an equation taking into account the Zeeman energy at the surface of an antiferromagnet as well as an antiferromagnetic exchange coupling. The results strongly suggest that (1) Cr{sub 2}O{sub 3} surface spin is affected by the external magnetic field and (2) the coupling at the Cr{sub 2}O{sub 3}/Pt/Co interface is antiferromagnetic.« less

Micro-indentation fracture behavior of human enamel.

PubMed

Padmanabhan, Sanosh Kunjalukkal; Balakrishnan, Avinash; Chu, Min-Cheol; Kim, Taik Nam; Cho, Seong Jai

2010-01-01

The purpose of this study was to determine the crack resistance behavior (K(R)) of human enamel in relation to its microstructure. Human molar teeth were precision cut, polished and tested using Vickers micro-indentation at different loads ranging from 0.98 to 9.8 N. Five indentation load levels were considered, 20 indentation cracks for each load level were introduced on the surface of the test specimen (10 indentations per tooth) and their variability was evaluated using Weibull statistics and an empirical model. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the crack morphology and propagation mechanisms involved. The results showed that enamel exhibited increasing cracking resistance (K(R)) with increasing load. It was found that the crack propagation mainly depended on the location and the microstructure it encountered. SEM showed the formation of crack bridges and crack deflection near the indentation crack tip. The crack mode was of Palmqvist type even at larger loads of 9.8 N. This was mainly attributed to the large process zone created by the interwoven lamellar rod like microstructure exhibited by the enamel surface. This study shows that there are still considerable prospects for improving dental ceramics and for mimicking the enamel structure developed by nature.

The effect of NaOH concentration on the steam-hydrothermally treated bioactive microarc oxidation coatings containing Ca, P, Si and Na on pure Ti surface.

PubMed

Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

2015-04-01

The microarc oxidation (MAO) coating covered pure Ti plates are steam-hydrothermally treated in autoclaves containing NaOH solutions with different concentrations of 0, 0.001, 0.01, 0.1 and 1mol·L(-1). Due to the composition of Ti, O, Ca, P, Si and Na elements in the MAO coating, anatase and hydroxyapatite (HA) crystals are generated from the previously amorphous MAO coating after the steam-hydrothermal treatment. Meanwhile, it is noticed that the amount of HA crystals increases but showing a decline trend in aspect ratio in morphologies with the increasing of NaOH concentration. Interestingly, the steam-hydrothermally treated MAO coatings exhibit better bonding strength with Ti substrate (up to 43.8±1.1MPa) than that of the untreated one (20.1±3.1MPa). In addition, benefiting from the corrosive attack of the dissolved NaOH in water vapor on the MAO coating, Ti-OH is also formed on the steam-hydrothermally treated MAO coating surface, which can trigger apatite nucleation. Thus, the steam-hydrothermally treated MAO coatings exhibit good apatite-inducing ability. Copyright © 2015 Elsevier B.V. All rights reserved.

The Dependence of Galactic Outflows on the Properties and Orientation of zCOSMOS Galaxies at z ~ 1

NASA Astrophysics Data System (ADS)

Bordoloi, R.; Lilly, S. J.; Hardmeier, E.; Contini, T.; Kneib, J.-P.; Le Fevre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Zamorani, G.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Caputi, K.; Carollo, C. M.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Garilli, B.; Iovino, A.; Kampczyk, P.; Kovač, K.; Knobel, C.; Lamareille, F.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Mignoli, M.; Oesch, P.; Pello, R.; Peng, Y.; Perez Montero, E.; Presotto, V.; Silverman, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Cappi, A.; Cimatti, A.; Coppa, G.; Franzetti, P.; Koekemoer, A.; Moresco, M.; Nair, P.; Pozzetti, L.

2014-10-01

We present an analysis of cool outflowing gas around galaxies, traced by Mg II absorption lines in the coadded spectra of a sample of 486 zCOSMOS galaxies at 1 <= z <= 1.5. These galaxies span a range of stellar masses (9.45 <= log10[M */M ⊙] <= 10.7) and star formation rates (0.14 <= log10[SFR/M ⊙ yr-1] <= 2.35). We identify the cool outflowing component in the Mg II absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses, the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong correlation with the star formation surface density (ΣSFR) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from -150 km s-1 ~-200 km s-1 and, on average, the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit mass outflow rates >5-7 M ⊙ yr-1 and a mass loading factor ({ η = \\dot{M}out /SFR}) comparable to the star formation rates of the galaxies. Based on observations undertaken at the European Southern Observatory (ESO) Very Large Telescope (VLT) under Large Program 175.A-0839.

Strong climate and tectonic control on plagioclase weathering in granitic terrain

USGS Publications Warehouse

Rasmussen, C.; Brantley, S.; Richter, D.D.B.; Blum, A.; Dixon, J.; White, A.F.

2011-01-01

Investigations to understand linkages among climate, erosion and weathering are central to quantifying landscape evolution. We approach these linkages through synthesis of regolith data for granitic terrain compiled with respect to climate, geochemistry, and denudation rates for low sloping upland profiles. Focusing on Na as a proxy for plagioclase weathering, we quantified regolith Na depletion, Na mass loss, and the relative partitioning of denudation to physical and chemical contributions. The depth and magnitude of regolith Na depletion increased continuously with increasing water availability, except for locations with mean annual temperature <5??C that exhibited little Na depletion, and locations with physical erosion rates <20gm-2yr-1 that exhibited deep and complete regolith Na depletion. Surface Na depletion also tended to decrease with increasing physical erosion. Depth-integrated Na mass loss and regolith depth were both three orders of magnitude greater in the fully depleted, low erosion rate sites relative to other locations. These locations exhibited strong erosion-limitation of Na chemical weathering rates based on correlation of Na chemical weathering rate to total Na denudation. Sodium weathering rates in cool locations with positive annual water balance were strongly correlated to total Na denudation and precipitation, and exhibited an average apparent activation energy (Ea) of 69kJmol-1 Na. The remaining water-limited locations exhibited kinetic limitation of Na weathering rates with an Ea of 136kJmol-1 Na, roughly equivalent to the sum of laboratory measures of Ea and dissolution reaction enthalpy for albite. Water availability is suggested as the dominant factor limiting rate kinetics in the water-limited systems. Together, these data demonstrate marked transitions and nonlinearity in how climate and tectonics correlate to plagioclase chemical weathering and Na mass loss. ?? 2010 Elsevier B.V.

Near-surface Salinity and Temperature Structure Observed with Dual-Sensor Drifters in the Subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, Shenfu; Goni, Gustavo; Volkov, Denis; Lumpkin, Rick; Foltz, Gregory

2017-04-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 m and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific Ocean with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of the differences. Measurements from these drifters indicate that, on average, water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths often occur when surface winds are weak. In addition to the expected surface freshening and cooling during rainfall events, surface salinification occurs under weak wind conditions when there is strong surface warming that enhances evaporation and upper ocean stratification. Further examination of the drifter measurements demonstrate that (i) the amount of surface freshening and vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 m and 5 m are positively correlated with the corresponding temperature differences, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 4 m/s. Its phase is consistent with diurnal changes in surface temperature-induced evaporation. Below a wind speed of 6 m/s, the amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. Wind speed also affects the phasing of the diurnal cycle of T5m with the time of maximum T5m increasing gradually with decreasing wind speed. Wind speed does not affect the phasing of the diurnal cycle of T0.2m. At 0.2 m and 5 m, the diurnal cycle of temperature also depends on surface solar radiation, with the amplitude and time of diurnal maximum increasing as solar radiation increases.

Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings

NASA Astrophysics Data System (ADS)

Suresh Babu, P.; Rao, D. S.; Rao, G. V. N.; Sundararajan, G.

2007-06-01

The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.

T cells expanded in presence of IL-15 exhibit increased antioxidant capacity and innate effector molecules

PubMed Central

Kaur, Navtej; Naga, Osama S.; Norell, Håkan; Al-Khami, Amir A.; Scheffel, Matthew J.; Chakraborty, Nitya G.; Voelkel-Johnson, Christina; Mukherji, Bijay; Mehrotra, Shikhar

2011-01-01

Persistence of effector cytotoxic T lymphocytes (CTLs) during an immunological response is critical for successfully controlling a viral infection or tumor growth. Various cytokines are known to play an important part in regulating the immune response. The IL-2 family of cytokines that includes IL-2 and IL-15 are known to function as growth and survival factors for antigen-experienced T cells. IL-2 and IL-15 possess similar properties, including the ability to induce T cell proliferation. Whereas long term IL-2 exposure has been shown to promote apoptosis and limit CD8+ memory T cell survival and proliferation, it is widely believed that IL-15 can inhibit apoptosis and helps maintain a memory CD8+ T-cell population. However, mechanisms for superior outcomes for IL-15 as compared to IL-2 are still under investigation. Our data shows that human T cells cultured in the presence of IL-15 exhibit increased expression of anti-oxidant molecules Glutathione reductase (GSR), Thioredoxin reductase 1 (TXNDR1), Peroxiredoxin (PRDX), Superoxide dismutase (SOD). An increased expression of cell-surface thiols, intracellular glutathione, and thioredoxins was also noted in IL-15 cultured T cells. Additionally, IL-15 cultured T cells also showed an increase in cytolytic effector molecules. Apart from increased level of Granzyme A and Granzyme B, IL-15 cultured T cells exhibit increased accumulation of reactive oxygen (ROS) and reactive nitrogen (RNS) species as compared to IL-2 cultured T cells. Overall, this study suggests that T cells cultured in IL-15 show increase persistence not only due to increased anti-apoptotic proteins but also due to increased anti-oxidant levels, which is further complimented by increased cytolytic effector functions. PMID:21602054

Optical response from lenslike semiconductor nipple arrays

NASA Astrophysics Data System (ADS)

Wu, H.-M.; Lai, C.-M.; Peng, L.-H.

2008-11-01

The authors reported the use of recessive size reduction in self-assembled polystyrene sphere mask with anisotropic etching to form lenslike nipple arrays onto the surface of silicon and gallium nitride. These devices are shown to exhibit a filling factor near to an ideal close-packed condition and paraboloidlike etch profile with slope increased proportionally to the device aspect ratio. Specular reflectivity of less than 3% was observed over the visible spectral range for the 0.35-μm-period nipple-lens arrays. Using two-dimensional rigorous coupled-wave analysis, the latter phenomenon can be ascribed to a gradual index matching mechanism accessed by a high surface-coverage semiconductor nipple array structure.

Manipulation of subsurface carbon nanoparticles in Bi 2 Sr 2 CaCu 2 O 8 + δ using a scanning tunneling microscope

DOE PAGES

Stollenwerk, A. J.; Hurley, N.; Beck, B.; ...

2015-03-19

In this study, we present evidence that subsurface carbon nanoparticles in Bi₂Sr₂CaCu₂O 8+δ can be manipulated with nanometer precision using a scanning tunneling microscope. High resolution images indicate that most of the carbon particles remain subsurface after transport observable as a local increase in height as the particle pushes up on the surface. Tunneling spectra in the vicinity of these protrusions exhibit semiconducting characteristics with a band gap of approximately 1.8 eV, indicating that the incorporation of carbon locally alters the electronic properties near the surface.

Sources, behaviors and degradation of dissolved organic matter in the East China Sea

NASA Astrophysics Data System (ADS)

Chen, Yan; Yang, Gui-Peng; Liu, Li; Zhang, Peng-Yan; Leng, Wei-Song

2016-03-01

Concentrations of dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON) and its major compound classes-total hydrolysable amino acids (THAA) were measured at 4 cross-shelf transects of the East China Sea in July 2011. Surface concentrations of DOC, DIN, DON and THAA at the nearshore stations were mostly in excess of those found at the offshore sites, indicating either substantial autochthonous production or allochthonous inputs from the Changjiang River. The vertical distributions of DOC, DON and THAA showed similar trends with higher values in the surface layer, whereas the elevated concentrations of DIN were observed in the bottom layer. Major constituents of THAA presented in the study area were glycine, serine, alanine, glutamic acid, aspartic acid and valine. The mole percentages of neutral amino acids increased from surface water to bottom water, whereas acidic and hydroxy amino acids decreased with the water depth. Concentrations of DOC and THAA were negatively correlated to the ΔDIN values (the difference between the real concentration and theoretical concentration), respectively, indicating the coupling relation between dissolved organic matter (DOM) remineralization and nutrient regeneration in the water column. The C/N ratios in the water column exhibited different characteristics with elevated values appearing in the surface and bottom layers. Box and whisker plots showed that both degradation index (DI) values and THAA yields displayed a decreasing trend from the surface layer to the bottom layer, implying increasing degradation with the water depth. Our data revealed that glycine and alanine increased in relative abundance with decreasing DI, while tyrosine, valine, phenylalanine and isoleucine increased with increasing DI.

Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

DOE PAGES

McKee, George R.; Austin, Max E.; Boedo, Jose A.; ...

2017-07-12

Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75 < ρ < 0.9 are transiently reduced to exceptionally low levels during early times and from 0.8 < ρ < 0.9 at late times in the ramp-up in a manner that is different from behavior observed duringmore » steady-state plasma conditions with similar values of q 95. Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. Here, this indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.« less

Residual stress profiles in veneering ceramic on Y-TZP, alumina and ZTA frameworks: measurement by hole-drilling.

PubMed

Fukushima, K A; Sadoun, M J; Cesar, P F; Mainjot, A K

2014-02-01

The residual stress profile developed within the veneering ceramic during the manufacturing process is an important predicting factor in chipping failures, which constitute a well-known problem with yttria-tetragonal-zirconia polycrystal (Y-TZP) based restorations. The objectives of this study are to measure and to compare the residual stress profile in the veneering ceramic layered on three different polycrystalline ceramic framework materials: Y-TZP, alumina polycrystal (AL) and zirconia toughened alumina (ZTA). The stress profile was measured with the hole-drilling method in bilayered disk samples of 19 mm diameter with a 0.7 mm thick Y-TZP, AL or ZTA framework and a 1.5mm thick layer of the corresponding veneering ceramic. The AL samples exhibited increasing compressive stresses with depth, while compressive stresses switching into interior tensile stresses were measured in Y-TZP samples. ZTA samples exhibited compressive stress at the ceramic surface, decreasing with depth up to 0.6mm from the surface, and then becoming compressive again near the framework. Y-TZP samples exhibited a less favorable stress profile than those of AL and ZTA samples. Results support the hypothesis of the occurrence of structural changes within the Y-TZP surface in contact with the veneering ceramic to explain the presence of tensile stresses. Even if the presence of Y-TZP in the alumina matrix seems to negatively affect the residual stress profiles in ZTA samples in comparison with AL samples, the registered profiles remain positive in terms of veneer fracture resistance. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

NASA Astrophysics Data System (ADS)

McKee, G. R.; Austin, M.; Boedo, J.; Bravenec, R.; Holland, C.; Jackson, G.; Luce, T. C.; Rhodes, T. L.; Rudakov, D.; Wang, G.; Yan, Z.; Zeng, L.; Zhao, Y.

2017-08-01

Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75  <  ρ  <  0.9 are transiently reduced to exceptionally low levels during early times and from 0.8  <  ρ  <  0.9 at late times in the ramp-up in a manner that is different from behavior observed during steady-state plasma conditions with similar values of q 95. Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. This indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.

Livelihoods Poised Between Cold and Dry: Modeling Land Surface Phenologies and Phenometric Lapse Rates in Central Asian Highland Pastures

NASA Astrophysics Data System (ADS)

Henebry, G. M.; Tomaszewska, M. A.; Krehbiel, C. P.; Kelgenbaeva, K.

2016-12-01

To explore the vulnerability of high-elevation communities in the Kyrgyz Republic and in Uzbekistan to changing climatic, sociodemographic, and socioeconomic conditions, we assembled image time series to characterize the condition of pastures near villages at high elevation (>2000 masl) and in remote pastures at higher elevations. Here we describe the application of the convex quadratic (CxQ) model of land surface phenology to highland pasturelands for selected oblasts in the Kyrgyz Republic and in eastern Uzbekistan. We used 16 years (2000-2015) of Landsat normalized difference vegetation index (NDVI) data with MODIS land surface temperature data processed into accumulated growing degree-days. The peak height of the NDVI and the thermal time to peak are two key phenological metrics derived analytically from the fitted parameter coefficients of the CxQ model for each pixel time series. Both exhibited sensitivity to elevation, which we describe in terms of phenometric lapse rates (PLRs). Interannual variation in PLRs was expressed differently for the peak NDVI and the thermal time to peak. Peak NDVI increased with elevation up to a point but also exhibited more spatial variation in dry years than in wetter years. Thermal time to peak exhibited strong, highly significant negative linear relationships to elevation with steeper slopes in drier years. Both types of PLRs were modulated by aspect. These relationships and the associated CxQ models by elevation and aspect can provide expectations against which to detect changes in pasture status as a result of management or weather.

Characterizations of Ca- and Mg-incorporating micro/nano-structured surfaces on titanium fabricated by microarc oxidation and hydrothermal treatments

NASA Astrophysics Data System (ADS)

Ko, Sang-Hoon; Hwang, Moon-Jin; Moon, Won-Jin; Park, Yeong-Joon; Song, Ho-Jun

2015-12-01

The micro/nano-surface characteristics of magnesium- and calcium-incorporating titanium oxide layers fabricated on titanium metal using microarc oxidation (MAO) and hydrothermal (HT) treatments were investigated. Calcium acetate monohydrate (CA), magnesium acetate monohydrate (MA), and β-glycerophosphoric acid disodium salt pentahydrate were used as electrolytes for MAO treatment of titanium disks. CA/MA electrolyte concentrations (all in M) were 0.2/0.0 (CA20-MAO), 0.15/0.05 (CA15MA5-MAO), 0.1/0.1 (CA10MA10-MAO), 0.05/0.15 (CA5MA15-MAO), and 0.0/0.2 (MA20-MAO). MAO-HT groups were prepared by hydrothermal treatment of MAO groups. The porous surface morphology was consistent even after HT treatment. The incorporation of Mg ions in the oxide layer during MAO treatment was more favorable than incorporation of Ca ions. However, Mg ions were released more rapidly than Ca ions after HT treatment. The anatase TiO2 structure was dominant for all the groups and an increase in the rutile TiO2 structure was observed with an increase in MA concentration. Nano-sized crystallites were observed on the porous surface for all MAO-HT groups. Nano-needle-like crystallites were observed on the surface of CA20-MAO-HT. The crystallites exhibited shorter and thicker characteristics with an increase in Mg concentration.

Early osteoblast responses to orthopedic implants: Synergy of surface roughness and chemistry of bioactive ceramic coating.

PubMed

Aniket; Reid, Robert; Hall, Benika; Marriott, Ian; El-Ghannam, Ahmed

2015-06-01

Pro-osteogenic stimulation of bone cells by bioactive ceramic-coated orthopedic implants is influenced by both surface roughness and material chemistry; however, their concomitant impact on osteoblast behavior is not well understood. The aim of this study is to investigate the effects of nano-scale roughness and chemistry of bioactive silica-calcium phosphate nanocomposite (SCPC50) coated Ti-6Al-4V on modulating early bone cell responses. Cell attachment was higher on SCPC50-coated substrates compared to the uncoated controls; however, cells on the uncoated substrate exhibited greater spreading and superior quality of F-actin filaments than cells on the SCPC50-coated substrates. The poor F-actin filament organization on SCPC50-coated substrates is thought to be due to the enhanced calcium uptake by the ceramic surface. Dissolution analyses showed that an increase in surface roughness was accompanied by increased calcium uptake, and increased phosphorous and silicon release, all of which appear to interfere with F-actin assembly and osteoblast morphology. Moreover, cell attachment onto the SCPC50-coated substrates correlated with the known adsorption of fibronectin, and was independent of surface roughness. High-throughput genome sequencing showed enhanced expression of extracellular matrix and cell differentiation related genes. These results demonstrate a synergistic relationship between bioactive ceramic coating roughness and material chemistry resulting in a phenotype that leads to early osteoblast differentiation. © 2014 Wiley Periodicals, Inc.

The Great Lakes' regional climate regimes

NASA Astrophysics Data System (ADS)

Sugiyama, Noriyuki

For the last couple of decades, the Great Lakes have undergone rapid surface warming. In particular, the magnitude of the summer surface-warming trends of the Great Lakes have been much greater than those of surrounding land (Austin and Colman, 2007). Among the Great Lakes, the deepest Lake Superior exhibited the strongest warming trend in its annual, as well as summer surface water temperature. We find that many aspects of this behavior can be explained in terms of the tendency of deep lakes to exhibit multiple regimes characterized, under the same seasonally varying forcing, by the warmer and colder seasonal cycles exhibiting different amounts of wintertime lake-ice cover and corresponding changes in the summertime lake-surface temperatures. In this thesis, we address the problem of the Great Lakes' warming using one-dimensional lake modeling to interpret diverse observations of the recent lake behavior. (Abstract shortened by ProQuest.).

Nanoporous Ni with High Surface Area for Potential Hydrogen Storage Application.

PubMed

Zhou, Xiaocao; Zhao, Haibo; Fu, Zhibing; Qu, Jing; Zhong, Minglong; Yang, Xi; Yi, Yong; Wang, Chaoyang

2018-06-01

Nanoporous metals with considerable specific surface areas and hierarchical pore structures exhibit promising applications in the field of hydrogen storage, electrocatalysis, and fuel cells. In this manuscript, a facile method is demonstrated for fabricating nanoporous Ni with a high surface area by using SiO₂ aerogel as a template, i.e., electroless plating of Ni into an SiO₂ aerogel template followed by removal of the template at moderate conditions. The effects of the prepared conditions, including the electroless plating time, temperature of the structure, and the magnetism of nanoporous Ni are investigated in detail. The resultant optimum nanoporous Ni with a special 3D flower-like structure exhibited a high specific surface area of about 120.5 m²/g. The special nanoporous Ni exhibited a promising prospect in the field of hydrogen storage, with a hydrogen capacity of 0.45 wt % on 4.5 MPa at room temperature.

Influence of mineral oil and additives on microhardness and surface chemistry of magnesium oxide (001) surface

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Shigaki, H.; Buckley, D. H.

1982-01-01

X-ray photoelectron spectroscopy analyses and hardness experiments were conducted with cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved into specimens along the /001/ surface, and indentations were made on the cleaved surface in laboratory air, in nitrogen gas, or in degassed mineral oil with and without an additive while not exposing specimen surface to any other environment. The various additives examined contained sulfur, phosphorus, chlorine, or oleic acid. The sulfur-containing additive exhibited the highest hardness and smallest dislocation patterns evidencing plastic deformation; the chlorine-containing additive exhibited the lowest hardness and largest dislocation patterns evidencing plastic deformation. Hydrocarbon and chloride (MgCl2) films formed on the magnesium oxide surface. A chloride film was responsible for the lowest measured hardness.

Growth of carbon nanotubes in arc plasma treated graphite disc: microstructural characterization and electrical conductivity study

NASA Astrophysics Data System (ADS)

Nayak, B. B.; Sahu, R. K.; Dash, T.; Pradhan, S.

2018-03-01

Circular graphite discs were treated in arc plasma by varying arcing time. Analysis of the plasma treated discs by field emission scanning electron microscope revealed globular grain morphologies on the surfaces, but when the same were observed at higher magnification and higher resolution under transmission electron microscope, growth of multiwall carbon nanotubes of around 2 nm diameter was clearly seen. In situ growth of carbon nanotube bundles/bunches consisting of around 0.7 nm tube diameter was marked in the case of 6 min treated disc surface. Both the untreated and the plasma treated graphite discs were characterized by X-ray diffraction, energy dispersive spectra of X-ray, X-ray photoelectron spectroscopy, transmission electron microscopy, micro Raman spectroscopy and BET surface area measurement. From Raman spectra, BET surface area and microstructure observed in transmission electron microscope, growth of several layers of graphene was identified. Four-point probe measurements for electrical resistivity/conductivity of the graphite discs treated under different plasma conditions showed significant increase in conductivity values over that of untreated graphite conductivity value and the best result, i.e., around eightfold increase in conductivity, was observed in the case of 6 min plasma treated sample exhibiting carbon nanotube bundles/bunches grown on disc surface. By comparing the microstructures of the untreated and plasma treated graphite discs, the electrical conductivity increase in graphite disc is attributed to carbon nanotubes (including bundles/bunches) growth on disc surface by plasma treatment.

From brittle to ductile fracture in disordered materials.

PubMed

Picallo, Clara B; López, Juan M; Zapperi, Stefano; Alava, Mikko J

2010-10-08

We introduce a lattice model able to describe damage and yielding in heterogeneous materials ranging from brittle to ductile ones. Ductile fracture surfaces, obtained when the system breaks once the strain is completely localized, are shown to correspond to minimum energy surfaces. The similarity of the resulting fracture paths to the limits of brittle fracture or minimum energy surfaces is quantified. The model exhibits a smooth transition from brittleness to ductility. The dynamics of yielding exhibits avalanches with a power-law distribution.

Silver vanadate nanoribbons: A label-free bioindicator in the conversion between human serum transferrin and apotransferrin via surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Zhou, Qing; Shao, Mingwang; Que, Ronghui; Cheng, Liang; Zhuo, Shujuan; Tong, Yanhua; Lee, Shuit-Tong

2011-05-01

Silver vanadate nanoribbons were synthesized via a hydrothermal process, which exhibited surface-enhanced Raman scattering effect. This surface-enhanced substrate was stable and reproducible for identifying human serum transferrin and human serum apotransferrin in the concentration of 1×10-5 M, which further exhibited significant sensitivity in monitoring the conversion of these two proteins in turn. This result showed that the silver vanadate nanoribbon might be employed as biomonitor in such systems.

Surface Nb-ALLOYING on 0.4C-13Cr Stainless Steel: Microstructure and Tribological Behavior

NASA Astrophysics Data System (ADS)

Yu, Shengwang; You, Kai; Liu, Xiaozhen; Zhang, Yihui; Wang, Zhenxia; Liu, Xiaoping

2016-02-01

0.4C-13Cr stainless steel was alloyed with niobium using double glow plasma surface alloying and tribological properties of Nb-alloyed steel such as hardness, friction and wear were measured. Effects of the alloying temperature on microstructure and the tribological behavior of the alloyed steel were investigated compared with untreated steel. Formation mechanisms of Nb-alloyed layers and increased wear resistance were also studied. The result shows that after surface Nb-alloying treatment, the 0.4C-13Cr steel exhibits a diffusion adhesion at the alloyed layer/substrate interface and improved tribological property. The friction coefficient of Nb-alloyed steel is decreased by about 0.3-0.45 and the wear rate after Nb-alloying is only 2-5% of untreated steel.

Mixing, diffusion, and percolation in binary supported membranes containing mixtures of lipids and amphiphilic block copolymers.

PubMed

Gettel, Douglas L; Sanborn, Jeremy; Patel, Mira A; de Hoog, Hans-Peter; Liedberg, Bo; Nallani, Madhavan; Parikh, Atul N

2014-07-23

Substrate-mediated fusion of small polymersomes, derived from mixtures of lipids and amphiphilic block copolymers, produces hybrid, supported planar bilayers at hydrophilic surfaces, monolayers at hydrophobic surfaces, and binary monolayer/bilayer patterns at amphiphilic surfaces, directly responding to local measures of (and variations in) surface free energy. Despite the large thickness mismatch in their hydrophobic cores, the hybrid membranes do not exhibit microscopic phase separation, reflecting irreversible adsorption and limited lateral reorganization of the polymer component. With increasing fluid-phase lipid fraction, these hybrid, supported membranes undergo a fluidity transition, producing a fully percolating fluid lipid phase beyond a critical area fraction, which matches the percolation threshold for the immobile point obstacles. This then suggests that polymer-lipid hybrid membranes might be useful models for studying obstructed diffusion, such as occurs in lipid membranes containing proteins.

Graphene-Based Long-Period Fiber Grating Surface Plasmon Resonance Sensor for High-Sensitivity Gas Sensing

PubMed Central

Wei, Wei; Nong, Jinpeng; Zhang, Guiwen; Tang, Linlong; Jiang, Xiao; Chen, Na; Luo, Suqin; Lan, Guilian; Zhu, Yong

2016-01-01

A graphene-based long-period fiber grating (LPFG) surface plasmon resonance (SPR) sensor is proposed. A monolayer of graphene is coated onto the Ag film surface of the LPFG SPR sensor, which increases the intensity of the evanescent field on the surface of the fiber and thereby enhances the interaction between the SPR wave and molecules. Such features significantly improve the sensitivity of the sensor. The experimental results demonstrate that the sensitivity of the graphene-based LPFG SPR sensor can reach 0.344 nm%−1 for methane, which is improved 2.96 and 1.31 times with respect to the traditional LPFG sensor and Ag-coated LPFG SPR sensor, respectively. Meanwhile, the graphene-based LPFG SPR sensor exhibits excellent response characteristics and repeatability. Such a SPR sensing scheme offers a promising platform to achieve high sensitivity for gas-sensing applications. PMID:28025483

Highly cytocompatible and flexible three-dimensional graphene/polydimethylsiloxane composite for culture and electrochemical detection of L929 fibroblast cells.

PubMed

Waiwijit, Uraiwan; Maturos, Thitima; Pakapongpan, Saithip; Phokharatkul, Ditsayut; Wisitsoraat, Anurat; Tuantranont, Adisorn

2016-08-01

Recently, three-dimensional graphene interconnected network has attracted great interest as a scaffold structure for tissue engineering due to its high biocompatibility, high electrical conductivity, high specific surface area and high porosity. However, free-standing three-dimensional graphene exhibits poor flexibility and stability due to ease of disintegration during processing. In this work, three-dimensional graphene is composited with polydimethylsiloxane to improve the structural flexibility and stability by a new simple two-step process comprising dip coating of polydimethylsiloxane on chemical vapor deposited graphene/Ni foam and wet etching of nickel foam. Structural characterizations confirmed an interconnected three-dimensional multi-layer graphene structure with thin polydimethylsiloxane scaffold. The composite was employed as a substrate for culture of L929 fibroblast cells and its cytocompatibility was evaluated by cell viability (Alamar blue assay), reactive oxygen species production and vinculin immunofluorescence imaging. The result revealed that cell viability on three-dimensional graphene/polydimethylsiloxane composite increased with increasing culture time and was slightly different from a polystyrene substrate (control). Moreover, cells cultured on three-dimensional graphene/polydimethylsiloxane composite generated less ROS than the control at culture times of 3-6 h. The results of immunofluorescence staining demonstrated that fibroblast cells expressed adhesion protein (vinculin) and adhered well on three-dimensional graphene/polydimethylsiloxane surface. Good cell adhesion could be attributed to suitable surface properties of three-dimensional graphene/polydimethylsiloxane with moderate contact angle and small negative zeta potential in culture solution. The results of electrochemical study by cyclic voltammetry showed that an oxidation current signal with no apparent peak was induced by fibroblast cells and the oxidation current at an oxidation potential of +0.9 V increased linearly with increasing cell number. Therefore, the three-dimensional graphene/polydimethylsiloxane composite exhibits high cytocompatibility and can potentially be used as a conductive substrate for cell-based electrochemical sensing. © The Author(s) 2016.

Adsorption and photocatalytic degradation of methylene blue using high surface area titanate nanotubes (TNT) synthesized via hydrothermal method

NASA Astrophysics Data System (ADS)

Subramaniam, M. N.; Goh, P. S.; Abdullah, N.; Lau, W. J.; Ng, B. C.; Ismail, A. F.

2017-06-01

Removal of methylene blue (MB) via adsorption and photocatalysis using titanate nanotubes (TNTs) with different surface areas were investigated and compared to commercial titanium dioxide (TiO2) P25 Degussa nanoparticles. The TNTs with surface area ranging from 20 m2/g to 200 m2/g were synthesized via hydrothermal method with different reaction times. TEM imaging confirmed the tubular structure of TNT while XRD spectra indicated all TNTs exhibited anatase crystallinity. Batch adsorption rate showed linearity with surface properties of TNTs, where materials with higher surface area showed higher adsorption rate. The highest MB adsorption (70%) was achieved by TNT24 in 60 min whereas commercial TiO2 exhibited the lowest adsorption of only 10% after 240 min. Adsorption isotherm studies indicated that adsorption using TNT is better fitted into Langmuir adsorption isotherm than Freundlich isotherm model. Furthermore, TNT24 was able to perform up to 90% removal of MB within 120 min, demonstrating performance that is 2-fold better compared to commercial TiO2. The high surface area and surface Bronsted acidity are the main reasons for the improvement in MB removal performance exhibited by TNT24. The improvement in surface acidity enhanced the adsorption properties of all the nanotubes prepared in this study.

Heteroatom-doped nanoporous carbon derived from MOF-5 for CO2 capture

NASA Astrophysics Data System (ADS)

Ma, Xiancheng; Li, Liqing; Chen, Ruofei; Wang, Chunhao; Li, Hailong; Wang, Shaobin

2018-03-01

Four nanoporous carbons (MUCT) were prepared from metal-organic framework (MOF-5) template and additional carbon source (i.e. urea) by carbonization at different temperatures (600-900 °C). The results showed that specific surface area of four samples was obtained in the range from 1030 to 2307 m2 g-1. By changing the carbonization temperature it can finely tune the pore volume of the MUCT, which having a uniform pore size of around 4.0 nm. With an increasing carbonization temperature, the micropore surface area of MUCT samples varied slightly, but mesopore surface area increased obviously, which had little influence on carbon dioxide (CO2) adsorption capacity. The as-obtained sample MUC900 exhibited the superior CO2 capture capacity of 3.7 mmol g-1 at 0 °C (1 atm). First principle calculations were conducted on carbon models with various functional groups to distinguish heterogeneity and understand carbon surface chemistry for CO2 adsorption. The interaction between CO2 and N-containing functional groups is mainly weak Lewis acid-base interaction. On the other hand, the pyrrole and amine groups show exceptional hydrogen-bonding interaction. The hydroxyls promote the interaction between carbon dioxide and functional groups through hydrogen-bonding interactions and electrostatic potentials, thereby increasing CO2 capture of MUCT.

A method for examining temporal changes in cyanobacterial ...

EPA Pesticide Factsheets

Cyanobacterial harmful algal blooms (CyanoHAB) are thought to be increasing globally over the past few decades, but relatively little quantitative information is available about the spatial extent of blooms. Satellite remote sensing provides a potential technology for identifying cyanoHABs in multiple water bodies and across geo-political boundaries. An assessment method was developed using MEdium Resolution Imaging Spectrometer (MERIS) imagery to quantify cyanoHAB surface area extent, transferable to different spatial areas, in Florida, Ohio, and California for the test period of 2008 to 2012. Temporal assessment was used to evaluate changes in satellite resolvable inland waterbodies for each state of interest. To further assess cyanoHAB risk within the states, the World Health Organization’s (WHO) recreational guidance level thresholds were used to categorize surface area of cyanoHABs into three risk categories: low, moderate, and high-risk bloom area. Results showed that in Florida, the area of cyanoHABs increased largely due to observed increases in high-risk bloom area. California exhibited a slight decrease in cyanoHAB extent, primarily attributed to decreases in Northern California. In Ohio (excluding Lake Erie), little change in cyanoHAB surface area was observed. This study uses satellite remote sensing to quantify changes in inland cyanoHAB surface area across numerous water bodies within an entire state. The temporal assessment method developed here

Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces

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

King, Sean W., E-mail: sean.king@intel.com; Davis, Robert F.; Nemanich, Robert J.

2014-09-01

The adsorption and desorption of halogen and other gaseous species from surfaces is a key fundamental process for both wet chemical and dry plasma etch and clean processes utilized in nanoelectronic fabrication processes. Therefore, to increase the fundamental understanding of these processes with regard to aluminum nitride (AlN) surfaces, temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) have been utilized to investigate the desorption kinetics of water (H{sub 2}O), fluorine (F{sub 2}), hydrogen (H{sub 2}), hydrogen fluoride (HF), and other related species from aluminum nitride thin film surfaces treated with an aqueous solution of buffered hydrogen fluoride (BHF) dilutedmore » in methanol (CH{sub 3}OH). Pre-TPD XPS measurements of the CH{sub 3}OH:BHF treated AlN surfaces showed the presence of a variety of Al-F, N-F, Al-O, Al-OH, C-H, and C-O surfaces species in addition to Al-N bonding from the AlN thin film. The primary species observed desorbing from these same surfaces during TPD measurements included H{sub 2}, H{sub 2}O, HF, F{sub 2}, and CH{sub 3}OH with some evidence for nitrogen (N{sub 2}) and ammonia (NH{sub 3}) desorption as well. For H{sub 2}O, two desorption peaks with second order kinetics were observed at 195 and 460 °C with activation energies (E{sub d}) of 51 ± 3 and 87 ± 5 kJ/mol, respectively. Desorption of HF similarly exhibited second order kinetics with a peak temperature of 475 °C and E{sub d} of 110 ± 5 kJ/mol. The TPD spectra for F{sub 2} exhibited two peaks at 485 and 585 °C with second order kinetics and E{sub d} of 62 ± 3 and 270 ± 10 kJ/mol, respectively. These values are in excellent agreement with previous E{sub d} measurements for desorption of H{sub 2}O from SiO{sub 2} and AlF{sub x} from AlN surfaces, respectively. The F{sub 2} desorption is therefore attributed to fragmentation of AlF{sub x} species in the mass spectrometer ionizer. H{sub 2} desorption exhibited an additional high temperature peak at 910 °C with E{sub d} = 370 ± 10 kJ/mol that is consistent with both the dehydrogenation of surface AlOH species and H{sub 2} assisted sublimation of AlN. Similarly, N{sub 2} exhibited a similar higher temperature desorption peak with E{sub d} = 535 ± 40 kJ/mol that is consistent with the activation energy for direct sublimation of AlN.« less

A fractal analysis of protein to DNA binding kinetics using biosensors.

PubMed

Sadana, Ajit

2003-08-01

A fractal analysis of a confirmative nature only is presented for the binding of estrogen receptor (ER) in solution to its corresponding DNA (estrogen response element, ERE) immobilized on a sensor chip surface [J. Biol. Chem. 272 (1997) 11384], and for the cooperative binding of human 1,25-dihydroxyvitamin D(3) receptor (VDR) to DNA with the 9-cis-retinoic acid receptor (RXR) [Biochemistry 35 (1996) 3309]. Ligands were also used to modulate the first reaction. Data taken from the literature may be modeled by using a single- or a dual-fractal analysis. Relationships are presented for the binding rate coefficient as a function of either the analyte concentration in solution or the fractal dimension that exists on the biosensor surface. The binding rate expressions developed exhibit a wide range of dependence on the degree of heterogeneity that exists on the surface, ranging from sensitive (order of dependence equal to 1.202) to very sensitive (order of dependence equal to 12.239). In general, the binding rate coefficient increases as the degree of heterogeneity or the fractal dimension of the surface increases. The predictive relationships presented provide further physical insights into the reactions occurring on the biosensor surface. Even though these reactions are occurring on the biosensor surface, the relationships presented should assist in understanding and in possibly manipulating the reactions occurring on cellular surfaces.

Dependence of nanomechanical modification of polymers on plasma-induced cross-linking

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

Tajima, S.; Komvopoulos, K.

2007-01-01

The nanomechanical properties of low-density polyethylene (LDPE) modified by inductively coupled, radio-frequency Ar plasma were investigated by surface force microscopy. The polymer surface was modified under plasma conditions of different ion energy fluences and radiation intensities obtained by varying the sample distance from the plasma power source. Nanoindentation results of the surface stiffness versus maximum penetration depth did not reveal discernible differences between untreated and plasma-treated LDPE, presumably due to the small thickness of the modified surface layer that resulted in a substrate effect. On the contrary, nanoscratching experiments demonstrated a significant increase in the surface shear resistance of plasma-modifiedmore » LDPE due to chain cross-linking. These experiments revealed an enhancement of cross-linking with increasing ion energy fluence and radiation intensity, and a tip size effect on the friction force and dominant friction mechanisms (adhesion, plowing, and microcutting). In addition, LDPE samples with a LiF crystal shield were exposed to identical plasma conditions to determine the role of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation in the cross-linking process. The cross-linked layer of plasma-treated LDPE exhibited much higher shear strength than that of VUV/UV-treated LDPE. Plasma-induced surface modification of the nanomechanical properties of LDPE is interpreted in the context of molecular models of the untreated and cross-linked polymer surfaces derived from experimental findings.« less

Evaluation of biocidal efficacy of copper alloy coatings in comparison with solid metal surfaces: generation of organic copper phosphate nanoflowers.

PubMed

Gutierrez, H; Portman, T; Pershin, V; Ringuette, M

2013-03-01

To analyse the biocidal efficacy of thermal sprayed copper surfaces. Copper alloy sheet metals containing >60% copper have been shown to exhibit potent biocidal activity. Surface biocidal activity was assessed by epifluorescence microscopy. After 2-h exposure at 20 °C in phosphate-buffered saline (PBS), contact killing of Gram-negative Escherichia coli and Gram-positive Staphylococcus epidermidis by brass sheet metal and phosphor bronze was 3-4-times higher than that by stainless steel. SEM observations revealed that the surface membranes of both bacterial strains were slightly more irregular when exposed to brass sheet metal than stainless steel. However, when exposed to phosphor bronze coating, E. coli were 3-4 times larger with irregular membrane morphology. In addition, the majority of the cells were associated with spherical carbon-copper-phosphate crystalline nanostructures characteristic of nanoflowers. The membranes of many of the S. epidermidis exhibited blebbing, and a small subset was also associated with nanoflowers. Our data indicate that increasing the surface roughness of copper alloys had a pronounced impact on the membrane integrity of Gram-positive and, to a lesser degree, Gram-negative bacteria. In the presence of PBS, carbon-copper-phosphate-containing nanoflowers were formed, likely nucleated by components derived from killed bacteria. The intimate association of the bacteria with the nanoflowers and phosphor bronze coating likely contributed to their nonreversible adhesion. Thermal spraying of copper alloys provides a strategy for the rapid coating of three-dimensional organic and inorganic surfaces with biocidal copper alloys. Our study demonstrates that the macroscale surface roughness generated by the thermal spray process enhances the biocidal activity of copper alloys compared with the nanoscale surface roughness of copper sheet metals. Moreover, the coating surface topography provides conditions for the rapid formation of organic copper phosphate nanocrystals/nanoflowers. © 2012 The Society for Applied Microbiology.

Analysis of concentric and eccentric contractions in biceps brachii muscles using surface electromyography signals and multifractal analysis.

PubMed

Marri, Kiran; Swaminathan, Ramakrishnan

2016-06-23

Muscle contractions can be categorized into isometric, isotonic (concentric and eccentric) and isokinetic contractions. The eccentric contractions are very effective for promoting muscle hypertrophy and produce larger forces when compared to the concentric or isometric contractions. Surface electromyography signals are widely used for analyzing muscle activities. These signals are nonstationary, nonlinear and exhibit self-similar multifractal behavior. The research on surface electromyography signals using multifractal analysis is not well established for concentric and eccentric contractions. In this study, an attempt has been made to analyze the concentric and eccentric contractions associated with biceps brachii muscles using surface electromyography signals and multifractal detrended moving average algorithm. Surface electromyography signals were recorded from 20 healthy individuals while performing a single curl exercise. The preprocessed signals were divided into concentric and eccentric cycles and in turn divided into phases based on range of motion: lower (0°-90°) and upper (>90°). The segments of surface electromyography signal were subjected to multifractal detrended moving average algorithm, and multifractal features such as strength of multifractality, peak exponent value, maximum exponent and exponent index were extracted in addition to conventional linear features such as root mean square and median frequency. The results show that surface electromyography signals exhibit multifractal behavior in both concentric and eccentric cycles. The mean strength of multifractality increased by 15% in eccentric contraction compared to concentric contraction. The lowest and highest exponent index values are observed in the upper concentric and lower eccentric contractions, respectively. The multifractal features are observed to be helpful in differentiating surface electromyography signals along the range of motion as compared to root mean square and median frequency. It appears that these multifractal features extracted from the concentric and eccentric contractions can be useful in the assessment of surface electromyography signals in sports medicine and training and also in rehabilitation programs. © IMechE 2016.

Trapping dynamics of xenon on Pt(111)

NASA Astrophysics Data System (ADS)

Arumainayagam, Christopher R.; Madix, Robert J.; Mcmaster, Mark C.; Suzawa, Valerie M.; Tully, John C.

1990-02-01

The dynamics of Xe trapping on Pt(111) was studied using supersonic atomic beam techniques. Initial trapping probabilities ( S0) were measured directly as a function of incident translational energy ( EinT) and angle of incidence (θ i) at a surface temperature ( Tins) 95 K. The initial trapping probability decreases smoothly with increasing ET cosθ i;, rather than ET cos 2θ i, suggesting participation of parallel momentum in the trapping process. Accordingly, the measured initial trapping probability falls off more slowly with increasing incident translational energy than predicted by one-dimensional theories. This finding is in near agreement with previous mean translational energy measurements for Xe desorbing near the Pt(111) surface normal, assuming detailed balance applies. Three-dimensional stochastic classical trajectory calculations presented herein also exhibit the importance of tangential momentum in trapping and satisfactorily reproduce the experimental initial trapping probabilities.

Distinctive receptor binding properties of the surface glycoprotein of a natural feline leukemia virus isolate with unusual disease spectrum.

PubMed

Bolin, Lisa L; Chandhasin, Chandtip; Lobelle-Rich, Patricia A; Albritton, Lorraine M; Levy, Laura S

2011-05-13

Feline leukemia virus (FeLV)-945, a member of the FeLV-A subgroup, was previously isolated from a cohort of naturally infected cats. An unusual multicentric lymphoma of non-T-cell origin was observed in natural and experimental infection with FeLV-945. Previous studies implicated the FeLV-945 surface glycoprotein (SU) as a determinant of disease outcome by an as yet unknown mechanism. The present studies demonstrate that FeLV-945 SU confers distinctive properties of binding to the cell surface receptor. Virions bearing the FeLV-945 Env protein were observed to bind the cell surface receptor with significantly increased efficiency, as was soluble FeLV-945 SU protein, as compared to the corresponding virions or soluble protein from a prototype FeLV-A isolate. SU proteins cloned from other cohort isolates exhibited increased binding efficiency comparable to or greater than FeLV-945 SU. Mutational analysis implicated a domain containing variable region B (VRB) to be the major determinant of increased receptor binding, and identified a single residue, valine 186, to be responsible for the effect. The FeLV-945 SU protein binds its cell surface receptor, feTHTR1, with significantly greater efficiency than does that of prototype FeLV-A (FeLV-A/61E) when present on the surface of virus particles or in soluble form, demonstrating a 2-fold difference in the relative dissociation constant. The results implicate a single residue, valine 186, as the major determinant of increased binding affinity. Computational modeling suggests a molecular mechanism by which residue 186 interacts with the receptor-binding domain through residue glutamine 110 to effect increased binding affinity. Through its increased receptor binding affinity, FeLV-945 SU might function in pathogenesis by increasing the rate of virus entry and spread in vivo, or by facilitating entry into a novel target cell with a low receptor density.

Humic acid facilitates the transport of ARS-labeled hydroxyapatite nanoparticles in iron oxyhydroxide-coated sand.

PubMed

Wang, Dengjun; Bradford, Scott A; Harvey, Ronald W; Gao, Bin; Cang, Long; Zhou, Dongmei

2012-03-06

Hydroxyapatite nanoparticles (nHAP) have been widely used to remediate soil and wastewater contaminated with metals and radionuclides. However, our understanding of nHAP transport and fate is limited in natural environments that exhibit significant variability in solid and solution chemistry. The transport and retention kinetics of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated packed columns that encompassed a range of humic acid concentrations (HA, 0-10 mg L(-1)), fractional surface coverage of iron oxyhydroxide coatings on sand grains (λ, 0-0.75), and pH (6.0-10.5). HA was found to have a marked effect on the electrokinetic properties of ARS-nHAP, and on the transport and retention of ARS-nHAP in granular media. The transport of ARS-nHAP was found to increase with increasing HA concentration because of enhanced colloidal stability and the reduced aggregate size. When HA = 10 mg L(-1), greater ARS-nHAP attachment occurred with increasing λ because of increased electrostatic attraction between negatively charged nanoparticles and positively charged iron oxyhydroxides, although alkaline conditions (pH 8.0 and 10.5) reversed the surface charge of the iron oxyhydroxides and therefore decreased deposition. The retention profiles of ARS-nHAP exhibited a hyperexponential shape for all test conditions, suggesting some unfavorable attachment conditions. Retarded breakthrough curves occurred in sands with iron oxyhydroxide coatings because of time-dependent occupation of favorable deposition sites. Consideration of the above effects is necessary to improve remediation efficiency of nHAP for metals and actinides in soils and subsurface environments.

Fractography of unidirectional graphite-epoxy as a function of moisture, temperature and specimen quality

NASA Technical Reports Server (NTRS)

Clements, L. L.

1986-01-01

Optical microscopy and SEM have been used to examine the tensile failure surfaces of (0-deg)8 T300/5208 graphite-epoxy specimens, and fractography is employed to determine how moisture content and temperature, together with specimen preparation, affect failure modes. A low energy failure morphology is noted in defective specimens; specimens made from nondefective prepregs appeared to exhibit a decrease in flaw sensitivity and increasing strength with either temperature or moisture, although moisture also seemed to increase interfacial debonding between filament and matrix. The combination of temperature and moisture degraded performance by increasing interfacial debonding, and rendering the epoxy more prone to fracture.

Browning of Adirondack, NY Lakes: Rates and Effects

NASA Astrophysics Data System (ADS)

Driscoll, C. T.; Mota, Y.; Fakhraei, H.; Todorova, S.; Leach, T.; Rose, K. C.; O'Donnell, S.

2017-12-01

Browning, or increases in the concentrations of dissolved organic matter (DOM), is an intriguing recent phenomenon occurring in northern freshwaters. It is hypothesized that browning is a watershed response to decreases in acid deposition, although changing in climate may also contribute. The Adirondack region of NY is experiencing marked increases in lake concentrations of dissolved organic carbon (DOC), with 29 out of 48 lakes in the Adirondack Long-Term Monitoring (ALTM) program showing significant increases and two exhibiting decreases since 1992. Increases in DOC is altering the acid base status of Adirondack lakes largely due increases in DOM with strongly acidic functional groups. DOM mobilization limits increases in acid neutralizing capacity that can be achieved in recovery of surface waters from acid deposition. A subset of ALTM lakes also appear to be experiencing changes in their physical characteristics during the summer stratification period, consistent with increases in DOM and browning. Of 28 lakes monitored for water column profiles since 1994: 8 are showing declines in thermocline depth (5 significant, p<0.05); all are exhibiting increases in epilimnetic temperature (9 significant); 26 are experiencing increases in the difference between epilimnetic and hypolimnetic temperatures (6 significant); and 17 are experiencing decreases in hypolimnetic dissolved oxygen concentrations (6 significant decreases, 1 increase). These changes may be a manifestation of increases in the attenuation of light associated with increases in DOM, increasing the intensity and duration of thermal stratification.

The birth and evolution of surface science: child of the union of science and technology.

PubMed

Duke, C B

2003-04-01

This article is an account of the birth and evolution of surface science as an interdisciplinary research area. Surface science emanated from the confluence of concepts and tools in physics and chemistry with technological innovations that made it possible to determine the structure and properties of surfaces and interfaces and the dynamics of chemical reactions at surfaces. The combination in the 1960s and 1970s of ultra-high-vacuum (i.e., P < 10(-7) Pascal or 10(-9) Torr) technology with the recognition that electrons in the energy range from 50 to 500 eV exhibited inelastic collision mean free paths of the order of a few angstroms fostered an explosion of activity. The results were a reformulation of the theory of electron solid scattering, the nearly universal use of electron spectroscopies for surface characterization, the rise of surface science as an independent interdisciplinary research area, and the emergence of the American Vacuum Society (AVS) as a major international scientific society. The rise of microelectronics in the 1970s and 1980s resulted in huge increases in computational power. These increases enabled more complex experiments and the utilization of density functional theory for the quantitative prediction of surface structure and dynamics. Development of scanning-probe microscopies in the 1990s led to atomic-resolution images of macroscopic surfaces and interfaces as well as videos of atoms moving about on surfaces during growth and diffusion. Scanning probes have since brought solid-liquid interfaces into the realm of atomic-level surface science, expanding its scope to more complex systems, including fragile biological materials and processes.

P-polarized reflectance spectroscopy: A high sensitive real-time monitoring technique to study surface kinetics under steady state epitaxial deposition conditions

NASA Technical Reports Server (NTRS)

Dietz, Nikolaus; Bachmann, Klaus J.

1995-01-01

This paper describes the results of real-time optical monitoring of epitaxial growth processes by p-polarized reflectance spectroscopy (PRS) using a single wavelength application under pulsed chemical beam epitaxy (PCBE) condition. The high surface sensitivity of PRS allows the monitoring of submonolayer precursors coverage on the surface as shown for GaP homoepitaxy and GaP on Si heteroepitaxy as examples. In the case of heteroepitaxy, the growth rate and optical properties are revealed by PRS using interference oscillations as they occur during growth. Super-imposed on these interference oscillations, the PRS signal exhibits a fine structure caused by the periodic alteration of the surface chemistry by the pulsed supply of chemical precursors. This fine structure is modeled under conditions where the surface chemistry cycles between phosphorus supersaturated and phosphorus depleted surfaces. The mathematical model describes the fine structure using a surface layer that increases during the tertiarybutyl phosphine (TBP) supply and decreases during and after the triethylgallium (TEG) pulse, which increases the growing GaP film thickness. The imaginary part of the dielectric function of the surface layer is revealed from the turning points in the fine structure, where the optical response to the first precursor pulse in the cycle sequence changes sign. The amplitude of the fine structure is determined by the surface layer thickness and the complex dielectric functions for the surface layer with the underlying bulk film. Surface kinetic data can be obtained by analyzing the rise and decay transients of the fine structure.

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

Aytug, Tolga

Maintaining clarity and avoiding the accumulation of water and dirt on optically transparent surfaces such as US military vehicle windshields, viewports, periscope optical head windows, and electronic equipment cover glasses are critical to providing a high level of visibility, improved survivability, and much-needed safety for warfighters in the field. Through a combination of physical vapor deposition techniques and the exploitation of metastable phase separation in low-alkali borosilicate, a novel technology was developed for the fabrication of optically transparent, porous nanostructured silica thin film coatings that are strongly bonded to glass platforms. The nanotextured films, initially structurally superhydrophilic, exhibit superior superhydrophobicity,more » hence antisoiling ability, following a simple but robust modification in surface chemistry. The surfaces yield water droplet contact angles as high as 172°. Moreover, the nanostructured nature of these coatings provides increased light scattering in the UV regime and reduced reflectivity (i.e., enhanced transmission) over a broad range of the visible spectrum. In addition to these functionalities, the coatings exhibit superior mechanical resistance to abrasion and are thermally stable to temperatures approaching 500°C. The overall process technology relies on industry standard equipment and inherently scalable manufacturing processes and demands only nontoxic, naturally abundant, and inexpensive base materials. Such coatings, applied to the optical components of current and future combat equipment and military vehicles will provide a significant strategic advantage for warfighters. The inherent self-cleaning properties of such superhydrophobic coatings will also mitigate biofouling of optical windows exposed to high-humidity conditions and can help decrease repair/replacement costs, reduce maintenance, and increase readiness by limiting equipment downtime.« less

Assimilation of GRACE Terrestrial Water Storage into a Land Surface Model: Evaluation 1 and Potential Value for Drought Monitoring in Western and Central Europe

NASA Technical Reports Server (NTRS)

Li, Bailing; Rodell, Matthew; Zaitchik, Benjamin F.; Reichle, Rolf H.; Koster, Randal D.; van Dam, Tonie M.

2012-01-01

A land surface model s ability to simulate states (e.g., soil moisture) and fluxes (e.g., runoff) is limited by uncertainties in meteorological forcing and parameter inputs as well as inadequacies in model physics. In this study, anomalies of terrestrial water storage (TWS) observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission were assimilated into the NASA Catchment land surface model in western and central Europe for a 7-year period, using a previously developed ensemble Kalman smoother. GRACE data assimilation led to improved runoff correlations with gauge data in 17 out of 18 hydrological basins, even in basins smaller than the effective resolution of GRACE. Improvements in root zone soil moisture were less conclusive, partly due to the shortness of the in situ data record. In addition to improving temporal correlations, GRACE data assimilation also reduced increasing trends in simulated monthly TWS and runoff associated with increasing rates of precipitation. GRACE assimilated root zone soil moisture and TWS fields exhibited significant changes in their dryness rankings relative to those without data assimilation, suggesting that GRACE data assimilation could have a substantial impact on drought monitoring. Signals of drought in GRACE TWS correlated well with MODIS Normalized Difference Vegetation Index (NDVI) data in most areas. Although they detected the same droughts during warm seasons, drought signatures in GRACE derived TWS exhibited greater persistence than those in NDVI throughout all seasons, in part due to limitations associated with the seasonality of vegetation.

Special issue on aluminium plasmonics

DOE PAGES

Gerard, Davy; Gray, Stephen K.

2015-04-08

Plasmonics is a rapidly growing field that takes advantage of the intense and confined electromagnetic fields that appear near metallic nanostructures illuminated at frequencies near their surface plasmon resonances. As plasmonics continues to develop, it faces the need to find new materials supporting well-defined surface plasmon resonances in different frequency ranges. In the visible and near-infrared ranges the noble metals, most typically gold and silver, exhibit relatively low losses. This is why they are quite ubiquitous in plasmonics literature. However it is somewhat ironic to see that a non-noble metal, aluminium, the metal upon which surface plasmons where first evidencedmore » in the 1950s, is now reappearing after fifty years of near oblivion as one of the 'hottest' materials for plasmonics. Several reasons explain the return of aluminium to the centre stage. First, aluminium exhibits good plasmonic properties in the ultraviolet and deep ultraviolet—a spectral range where gold and silver no longer behave as metals. Second, aluminium is cheap and widely available (Al is the third most abundant element in the earth's crust), criteria of paramount importance when discussing industry-related applications. It is furthermore compatible with complementary metal–oxide–semiconductor (CMOS) technology. In conclusion, this is why an ever-increasing number of papers report new advances on aluminium plasmonics.« less

Special issue on aluminium plasmonics

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

Gerard, Davy; Gray, Stephen K.

Plasmonics is a rapidly growing field that takes advantage of the intense and confined electromagnetic fields that appear near metallic nanostructures illuminated at frequencies near their surface plasmon resonances. As plasmonics continues to develop, it faces the need to find new materials supporting well-defined surface plasmon resonances in different frequency ranges. In the visible and near-infrared ranges the noble metals, most typically gold and silver, exhibit relatively low losses. This is why they are quite ubiquitous in plasmonics literature. However it is somewhat ironic to see that a non-noble metal, aluminium, the metal upon which surface plasmons where first evidencedmore » in the 1950s, is now reappearing after fifty years of near oblivion as one of the 'hottest' materials for plasmonics. Several reasons explain the return of aluminium to the centre stage. First, aluminium exhibits good plasmonic properties in the ultraviolet and deep ultraviolet—a spectral range where gold and silver no longer behave as metals. Second, aluminium is cheap and widely available (Al is the third most abundant element in the earth's crust), criteria of paramount importance when discussing industry-related applications. It is furthermore compatible with complementary metal–oxide–semiconductor (CMOS) technology. In conclusion, this is why an ever-increasing number of papers report new advances on aluminium plasmonics.« less

Graft polymerization of styryl bisphosphonate monomer onto polypropylene films for inhibition of biofilm formation.

PubMed

Steinmetz, Hanna P; Rudnick-Glick, Safra; Natan, Michal; Banin, Ehud; Margel, Shlomo

2016-11-01

There has been increased concern during the past few decades over the role bacterial biofilms play in causing a variety of health problems, especially since they exhibit a high degree of resistance to antibiotics and are able to survive in hostile environments. Biofilms consist of bacterial aggregates enveloped by a self-produced matrix attached to the surface. Ca(2+) ions promote the formation of biofilms, and enhance their stability, viscosity, and strength. Bisphosphonates exhibit a high affinity for Ca(2+) ions, and may inhibit the formation of biofilms by acting as sequestering agents for Ca(2+) ions. Although the antibacterial activity of bisphosphonates is well known, research into their anti-biofilm behavior is still in its early stages. In this study, we describe the synthesis of a new thin coating composed of poly(styryl bisphosphonate) grafted onto oxidized polypropylene films for anti-biofilm applications. This grafting process was performed by graft polymerization of styryl bisphosphonate vinylic monomer onto O2 plasma-treated polypropylene films. The surface modification of the polypropylene films was confirmed using surface measurements, including X-ray photoelectron spectroscopy, atomic force microscopy, and water contact angle goniometry. Significant inhibition of biofilm formation was achieved for both Gram-negative and Gram-positive bacteria. Copyright © 2016 Elsevier B.V. All rights reserved.

Bioinspired Superhydrophobic Highly Transmissive Films for Optical Applications.

PubMed

Vüllers, Felix; Gomard, Guillaume; Preinfalk, Jan B; Klampaftis, Efthymios; Worgull, Matthias; Richards, Bryce; Hölscher, Hendrik; Kavalenka, Maryna N

2016-11-01

Inspired by the transparent hair layer on water plants Salvinia and Pistia, superhydrophobic flexible thin films, applicable as transparent coatings for optoelectronic devices, are introduced. Thin polymeric nanofur films are fabricated using a highly scalable hot pulling technique, in which heated sandblasted steel plates are used to create a dense layer of nano- and microhairs surrounding microcavities on a polymer surface. The superhydrophobic nanofur surface exhibits water contact angles of 166 ± 6°, sliding angles below 6°, and is self-cleaning against various contaminants. Additionally, subjecting thin nanofur to argon plasma reverses its surface wettability to hydrophilic and underwater superoleophobic. Thin nanofur films are transparent and demonstrate reflection values of less than 4% for wavelengths ranging from 300 to 800 nm when attached to a polymer substrate. Moreover, used as translucent self-standing film, the nanofur exhibits transmission values above 85% and high forward scattering. The potential of thin nanofur films for extracting substrate modes from organic light emitting diodes is tested and a relative increase of the luminous efficacy of above 10% is observed. Finally, thin nanofur is optically coupled to a multicrystalline silicon solar cell, resulting in a relative gain of 5.8% in photogenerated current compared to a bare photovoltaic device. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Seismic Anisotropy from Surface Refraction Measurements

NASA Astrophysics Data System (ADS)

Vilhelm, J.; Hrdá, J.; Klíma, K.; Lokajícek, T.; Pros, Z.

2003-04-01

The contribution deals with the methods of determining P and S wave velocities in the shallow refraction seismics. The comparison of a P-wave anisotropy from samples and field surface measurement is performed. The laboratory measurement of the P-wave velocity is realized as omni directional ultrasound measurement on oriented spherical samples (diameter 5 cm) under a hydrostatic pressure up to 400 MPa. The field measurement is based on the processing of at least one pair of reversed time-distance curves of refracted waves. Different velocity calculation techniques are involved including tomographic approach from the surface. It is shown that field seismic measurement can reflect internal rock fabric (lineation, mineral anisotropy) as well as effects connected with the fracturing and weathering. The elastic constants derived from laboratory measurements exhibit transversal isotropy. For the estimation of anisotropy influence we perform ray-tracing by the software package ANRAY (Consortium Seismic Waves in Complex 3-D Structures). The use of P and S wave anisotropy measurement to determine hard rock hydro-geological collector (water resource) is presented. In a relatively homogeneous lutaceous sedimentary medium we identified a transversally isotropic layer which exhibits increased value of permeability (transmisivity). The seismic measurement is realized by three component geophones with both vertical and shear seismic sources. VLF and resistivity profiling accompany the filed survey.

The role of crystallographic texture in achieving low friction zinc oxide nanolaminate films

NASA Astrophysics Data System (ADS)

Mojekwu, Nneoma

Metal oxide nanolaminate films are potential high temperature solid lubricants due to their ability to exhibit significant plasticity when grain size is reduced to the nanometer scale, and defective growth structure is achieved by condensation of oxygen vacancies to form intrinsic stacking faults. This is in contrast to conventional microcrystalline and single crystal oxides that exhibit brittle fracture during loading in a sliding contact. This study emphasizes the additional effect of growth orientation, in particular crystallographic texture, on determining the sliding friction behavior in nanocolumnar grain zinc oxide films grown by atomic layer deposition. It was determined that zinc oxide low (0002) versus higher (101¯3) surface energy crystallographic planes influenced the sliding friction coefficient. Texturing of the (0002) grains resulted in a decreased adhesive component of friction thereby lowering the sliding friction coefficient to ˜0.25, while the friction coefficient doubled to ˜0.5 with increasing contribution of surface (101¯3) grains. In addition, the variation of the x-ray grazing incident angle from 0.5° to 5° was studied to better understand the surface grain orientation as a function of ZnO layer thickness in one versus four bilayer nanolaminates where the under layer (seed layer) was load-bearing Zn(Ti,Zr)O3.

All-trans retinoic acid results in irregular repair of septa and fails to inhibit proinflammatory macrophages.

PubMed

Seifart, C; Muyal, J P; Plagens, A; Yildirim, A Ö; Kohse, K; Grau, V; Sandu, S; Reinke, C; Tschernig, T; Vogelmeier, C; Fehrenbach, H

2011-08-01

All-trans retinoic acid (ATRA) is controversially discussed in emphysema therapy. We re-evaluated ATRA in the elastase model and hypothesised that beneficial effects should be reflected by increased alveolar surface area, elastin expression and downregulation of inflammatory mediators and matrix metalloproteinases (MMPs). Emphysema was induced by porcine pancreatic elastase versus saline in Sprague-Dawley rats. On days 26-37, rats received daily intraperitoneal injections with ATRA (500 μg · kg(-1) body weight) versus olive oil. Lungs were removed at day 38. Rat alveolar epithelial L2 cells were incubated with/without elastase followed by ATRA- or vehicle-treatment, respectively. ATRA only partially ameliorated structural defects. Alveolar walls exhibited irregular architecture: increased arithmetic mean thickness, reduction in surface coverage by alveolar epithelial cells type II. ATRA only partially restored reduced soluble elastin. It tended to increase the ratio of ED1(+):ED2(+) macrophages. Bronchoalveolar lavage (BAL) cells exhibited a proinflammatory state and high expression of interleukin-1β, cytokine-induced neutrophil chemoattractant-1, tumour necrosis factor-α, nuclear factor-κB, MMP-2, MMP-9, MMP-12, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in emphysema, with ATRA exerting only few effects. MMP-7 was highly induced by ATRA in healthy but not in emphysematous lungs. ATRA reduced both MMP-2 and TIMP-1 activity in BAL fluid of emphysematous lungs. ATRA-therapy may bear the risk of unwanted side-effects on alveolar septal architecture in emphysematous lungs.

The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming.

PubMed

Castillo, Karl D; Ries, Justin B; Bruno, John F; Westfield, Isaac T

2014-12-22

Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1-0.3 pH units and sea surface temperature to increase by 1-4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate-suggesting that ocean warming poses a more immediate threat than acidification for this important coral species.

The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming

PubMed Central

Castillo, Karl D.; Ries, Justin B.; Bruno, John F.; Westfield, Isaac T.

2014-01-01

Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1–0.3 pH units and sea surface temperature to increase by 1–4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate—suggesting that ocean warming poses a more immediate threat than acidification for this important coral species. PMID:25377455

Biofouling behavior and performance of forward osmosis membranes with bioinspired surface modification in osmotic membrane bioreactor.

PubMed

Li, Fang; Cheng, Qianxun; Tian, Qing; Yang, Bo; Chen, Qianyuan

2016-07-01

Forward osmosis (FO) has received considerable interest for water and energy related applications in recent years. Biofouling behavior and performance of cellulose triacetate (CTA) forward osmosis membranes with bioinspired surface modification via polydopamine (PD) coating and poly (ethylene glycol) (PEG) grafting (PD-g-PEG) in a submerged osmotic membrane bioreactor (OMBR) were investigated in this work. The modified membranes exhibited lower flux decline than the pristine one in OMBR, confirming that the bioinspired surface modification improved the antifouling ability of the CTA FO membrane. The result showed that the decline of membrane flux related to the increase of the salinity and MLSS concentration of the mixed liquid. It was concluded that the antifouling ability of modified membranes ascribed to the change of surface morphology in addition to the improvement of membrane hydrophilicity. The bioinspired surface modifications might improve the anti-adhesion for the biopolymers and biocake. Copyright © 2016 Elsevier Ltd. All rights reserved.

Antimicrobial and Antifouling Polymeric Agents for Surface Functionalization of Medical Implants.

PubMed

Zeng, Qiang; Zhu, Yiwen; Yu, Bingran; Sun, Yujie; Ding, Xiaokang; Xu, Chen; Wu, Yu-Wei; Tang, Zhihui; Xu, Fu-Jian

2018-05-09

Combating implant-associated infections is an urgent demand due to the increasing numbers in surgical operations such as joint replacements and dental implantations. Surface functionalization of implantable medical devices with polymeric antimicrobial and antifouling agents is an efficient strategy to prevent bacterial fouling and associated infections. In this work, antimicrobial and antifouling branched polymeric agents (GPEG and GEG) were synthesized via ring-opening reaction involving gentamicin and ethylene glycol species. Due to their rich primary amine groups, they can be readily coated on the polydopamine-modified implant (such as titanium) surfaces. The resultant surface coatings of Ti-GPEG and Ti-GEG produce excellent in vitro antibacterial efficacy toward both Staphylococcus aureus and Escherichia coli, while Ti-GPEG exhibit better antifouling ability. Moreover, the infection model with S. aureus shows that implanted Ti-GPEG possessed excellent antibacterial and antifouling ability in vivo. This study would provide a promising strategy for the surface functionalization of implantable medical devices to prevent implant-associated infections.

Volume and Surface Properties of a Bismuth-Containing Separating Nickel Melt

NASA Astrophysics Data System (ADS)

Filippov, K. S.

2017-11-01

The influence of a bismuth impurity on the properties of solid and liquid alloys in the concentration range that obeys Henry's law is considered. The structural and physicochemical properties, specifically, the density and the surface tension, of real melts are studied on relatively pure metals. The changes in the properties of the melts are estimated from changes in the temperature dependences of the density and the surface tension upon heating and cooling and in the concentration dependences of these parameters at a constant temperature. These dependences exhibit a correlation between the volume and surface properties of the melts: the density and the surface tension increase or decrease simultaneously. The introduction of bismuth in the nickel melt is accompanied by the appearance of a relatively strong compression effect (i.e., a decrease in the melt volume). At a certain bismuth content in the melt, the compression effect weakens because of the appearance of an excess phase or its associates and melt separation.

In Vivo Neural Recording and Electrochemical Performance of Microelectrode Arrays Modified by Rough-Surfaced AuPt Alloy Nanoparticles with Nanoporosity

PubMed Central

Zhao, Zongya; Gong, Ruxue; Zheng, Liang; Wang, Jue

2016-01-01

In order to reduce the impedance and improve in vivo neural recording performance of our developed Michigan type silicon electrodes, rough-surfaced AuPt alloy nanoparticles with nanoporosity were deposited on gold microelectrode sites through electro-co-deposition of Au-Pt-Cu alloy nanoparticles, followed by chemical dealloying Cu. The AuPt alloy nanoparticles modified gold microelectrode sites were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and in vivo neural recording experiment. The SEM images showed that the prepared AuPt alloy nanoparticles exhibited cauliflower-like shapes and possessed very rough surfaces with many different sizes of pores. Average impedance of rough-surfaced AuPt alloy nanoparticles modified sites was 0.23 MΩ at 1 kHz, which was only 4.7% of that of bare gold microelectrode sites (4.9 MΩ), and corresponding in vitro background noise in the range of 1 Hz to 7500 Hz decreased to 7.5 μVrms from 34.1 μVrms at bare gold microelectrode sites. Spontaneous spike signal recording was used to evaluate in vivo neural recording performance of modified microelectrode sites, and results showed that rough-surfaced AuPt alloy nanoparticles modified microelectrode sites exhibited higher average spike signal-to-noise ratio (SNR) of 4.8 in lateral globus pallidus (GPe) due to lower background noise compared to control microelectrodes. Electro-co-deposition of Au-Pt-Cu alloy nanoparticles combined with chemical dealloying Cu was a convenient way for increasing the effective surface area of microelectrode sites, which could reduce electrode impedance and improve the quality of in vivo spike signal recording. PMID:27827893

Anti-biofilm formation of a novel stainless steel against Staphylococcus aureus.

PubMed

Nan, Li; Yang, Ke; Ren, Guogang

2015-06-01

Staphylococcus aureus (S. aureus) is a bacterium frequently found proliferating on metal surfaces such as stainless steels used in healthcare and food processing facilities. Past research has shown that a novel Cu-bearing 304 type stainless steel (304CuSS) exhibits excellent antibacterial ability (i.e. against S. aureus) in a short time period (24h.). This work was dedicated to investigate the 304CuSS's inhibition ability towards the S. aureus biofilm formation for an extended period of 7days after incubation. It was found that the antibacterial rate of the 304CuSS against sessile bacterial cells reached over 99.9% in comparison with the 304SS. The thickness and sizes of the biofilms on the 304SS surfaces increased markedly with period of contact, and thus expected higher risk of bio-contamination, indicated by the changes of surface free energy between biofilm and the steel surfaces. The results demonstrated that the 304CuSS exhibited strong inhibition on the growth and adherence of the biofilms. The surface free energy of the 304CuSS after contact with sessile bacterial cells was much lower than that of the 304SS towards the same culture times. The continuously dissolved Cu(2+) ions well demonstrated the dissolution ability of Cu-rich precipitates after exposure to S. aureus solution, from 3.1ppm (2days) to 4.5ppm (7days). For this to occur, a hypothesis mechanism might be established for 304CuSS in which the Cu(2+) ions were released from Cu-rich phases that bond with extracellular polymeric substances (EPS) of the microorganisms. And these inhibited the activities of cell protein/enzymes and effectively prevented planktonic bacterial cells attaching to the 304CuSS metal surface. Copyright © 2015. Published by Elsevier B.V.

CO Adsorption on Reconstructed Ir(100) Surfaces from UHV to mbar Pressure: A LEED, TPD, and PM-IRAS Study

PubMed Central

2016-01-01

Clean and stable surface modifications of an iridium (100) single crystal, i.e., the (1 × 1) phase, the (5 × 1) reconstruction, and the oxygen-terminated (2 × 1)-O surface, were prepared and characterized by low energy electron diffraction (LEED), temperature-programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS) and polarization modulation IRAS (PM-IRAS). The adsorption of CO in UHV and at elevated (mbar) pressure/temperature was followed both ex situ and in situ on all three surface modifications, with a focus on mbar pressures of CO. The Ir(1 × 1) surface exhibited c(4 × 2)/c(2 × 2) and c(6 × 2) CO structures under low pressure conditions, and remained stable up to 100 mbar and 700 K. For the (2 × 1)-O reconstruction CO adsorption induced a structural change from (2 × 1)-O to (1 × 1), as confirmed by LEED, TPD, and IR. For Ir (2 × 1)-O TPD indicated that CO reacted with surface oxygen forming CO2. The (5 × 1) reconstruction featured a reversible and dynamic behavior upon CO adsorption, with a local lifting of the reconstruction to (1 × 1). After CO desorption, the (5 × 1) structure was restored. All three reconstructions exhibited CO adsorption with on-top geometry, as evidenced by IR. With increasing CO exposure the resonances shifted to higher wavenumber, due to adsorbate–adsorbate and adsorbate–substrate interactions. The largest wavenumber shift (from 2057 to 2100 cm–1) was observed for Ir(5 × 1) upon CO dosing from 1 L to 100 mbar. PMID:27257467

Quantification of Kinetic Rate Law Parameters of Uranium Release from Sodium Autunite as a Function of Aqueous Bicarbonate Concentrations

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

Gudavalli, Ravi; Katsenovich, Yelena; Wellman, Dawn M.

2013-09-05

ABSTRACT: Hydrogen carbonate is one of the most significant components within the uranium geochemical cycle. In aqueous solutions, hydrogen carbonate forms strong complexes with uranium. As such, aqueous bicarbonate may significantly increase the rate of uranium release from uranium minerals. Quantifying the relationship of aqueous hydrogen carbonate solutions to the rate of uranium release during dissolution is critical to understanding the long-term fate of uranium within the environment. Single-pass flow-through (SPTF) experiments were conducted to estimate the rate of uranium release from Na meta-autunite as a function of bicarbonate solutions (0.0005-0.003 M) under the pH range of 6-11 and temperaturesmore » of 5-60oC. Consistent with the results of previous investigation, the rate of uranium release from sodium autunite exhibited minimal dependency on temperature; but were strongly dependent on pH and increasing concentrations of bicarbonate solutions. Most notably at pH 7, the rate of uranium release exhibited 370 fold increases relative to the rate of uranium release in the absence of bicarbonate. However, the effect of increasing concentrations of bicarbonate solutions on the release of uranium was significantly less under higher pH conditions. It is postulated that at high pH values, surface sites are saturated with carbonate, thus the addition of more bicarbonate would have less effect on uranium release. Results indicate the activation energies were unaffected by temperature and bicarbonate concentration variations, but were strongly dependent on pH conditions. As pH increased from 6 to 11, activation energy values were observed to decrease from 29.94 kJ mol-1 to 13.07 kJ mol-1. The calculated activation energies suggest a surface controlled dissolution mechanism.« less

SCN3A deficiency associated with increased seizure susceptibility

PubMed Central

Lamar, Tyra; Vanoye, Carlos G.; Calhoun, Jeffrey; Wong, Jennifer C.; Dutton, Stacey B.B.; Jorge, Benjamin S.; Velinov, Milen; Escayg, Andrew; Kearney, Jennifer A.

2017-01-01

Mutations in voltage-gated sodium channels expressed highly in the brain (SCN1A, SCN2A, SCN3A, and SCN8A) are responsible for an increasing number of epilepsy syndromes. In particular, mutations in the SCN3A gene, encoding the pore-forming Nav1.3 α subunit, have been identified in patients with focal epilepsy. Biophysical characterization of epilepsy-associated SCN3A variants suggests that both gain- and loss-of-function SCN3A mutations may lead to increased seizure susceptibility. In this report, we identified a novel SCN3A variant (L247P) by whole exome sequencing of a child with focal epilepsy, developmental delay, and autonomic nervous system dysfunction. Voltage clamp analysis showed no detectable sodium current in a heterologous expression system expressing the SCN3A-L247P variant. Furthermore, cell surface biotinylation demonstrated a reduction in the amount of SCN3A-L247P at the cell surface, suggesting the SCN3A-L247P variant is a trafficking-deficient mutant. To further explore the possible clinical consequences of reduced SCN3A activity, we investigated the effect of a hypomorphic Scn3a allele (Scn3aHyp) on seizure susceptibility and behavior using a gene trap mouse line. Heterozygous Scn3a mutant mice (Scn3a+/Hyp) did not exhibit spontaneous seizures nor were they susceptible to hyperthermia-induced seizures. However, they displayed increased susceptibility to electroconvulsive (6 Hz) and chemiconvulsive (flurothyl and kainic acid) induced seizures. Scn3a+/Hyp mice also exhibited deficits in locomotor activity and motor learning. Taken together, these results provide evidence that loss-of-function of SCN3A caused by reduced protein expression or deficient trafficking to the plasma membrane may contribute to increased seizure susceptibility. PMID:28235671

In vivo evaluation of needle force and friction stress during insertion at varying insertion speed into the brain.

PubMed

Casanova, Fernando; Carney, Paul R; Sarntinoranont, Malisa

2014-11-30

Convection enhanced delivery (CED) infuses drugs directly into brain tissue. Needle insertion is required and results in tissue damage which can promote flowback along the needle track and improper targeting. The goal of this study was to evaluate friction stress (calculated from needle insertion force) as a measure of tissue contact and damage during needle insertion for varying insertion speeds. Forces and surface dimpling during needle insertion were measured in rat brain in vivo. Needle retraction forces were used to calculate friction stresses. These measures were compared to track damage from a previous study. Differences between brain tissues and soft hydrogels were evaluated for varying insertion speeds: 0.2, 2, and 10mm/s. In brain tissue, average insertion force and surface dimpling increased with increasing insertion speed. Average friction stress along the needle-tissue interface decreased with insertion speed (from 0.58 ± 0.27 to 0.16 ± 0.08 kPa). Friction stress varied between brain regions: cortex (0.227 ± 0.27 kPa), external capsule (0.222 ± 0.19 kPa), and CPu (0.383 ± 0.30 kPa). Hydrogels exhibited opposite trends for dimpling and friction stress with insertion speed. Previously, increasing needle damage with insertion speed has been measured with histological methods. Friction stress appears to decrease with increasing tissue damage and decreasing tissue contact, providing the potential for in vivo and real time evaluation along the needle track. Force derived friction stress decreased with increasing insertion speed and was smaller within white matter regions. Hydrogels exhibited opposite trends to brain tissue. Copyright © 2014 Elsevier B.V. All rights reserved.

Detection of nerve agent stimulants based on photoluminescent porous silicon interferometer

NASA Astrophysics Data System (ADS)

Kim, Seongwoong; Cho, Bomin; Sohn, Honglae

2012-09-01

Porous silicon (PSi) exhibiting dual optical properties, both Fabry-Pérot fringe and photolumincence, was developed and used as chemical sensors. PSi samples were prepared by an electrochemical etch of p-type silicon under the illumination of 300-W tungsten lamp during the etch process. The surface of PSi was characterized by cold field-emission scanning electron microscope. PSi samples exhibited a strong visible orange photoluminescence at 610 nm with an excitation wavelength of 460 nm as well as Fabry-Pérot fringe with a tungsten light source. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organophosphate vapors. An increase of optical thickness and quenching photoluminescences under the exposure of various organophosphate vapors were observed.

Method for reducing pressure drop through filters, and filter exhibiting reduced pressure drop

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

Sappok, Alexander; Wong, Victor

Methods for generating and applying coatings to filters with porous material in order to reduce large pressure drop increases as material accumulates in a filter, as well as the filter exhibiting reduced and/or more uniform pressure drop. The filter can be a diesel particulate trap for removing particulate matter such as soot from the exhaust of a diesel engine. Porous material such as ash is loaded on the surface of the substrate or filter walls, such as by coating, depositing, distributing or layering the porous material along the channel walls of the filter in an amount effective for minimizing ormore » preventing depth filtration during use of the filter. Efficient filtration at acceptable flow rates is achieved.« less

Nanofibers of fullerene C60 through interplay of ball-and-socket supermolecules.

PubMed

Hubble, Lee J; Raston, Colin L

2007-01-01

Mixing solutions of p-tBu-calix[5]arene and C(60) in toluene results in a 1:1 complex (C(60)) intersection(p-tBu-calix[5]arene), which precipitates as nanofibers. The principle structural unit is based on a host-guest ball-and-socket nanostructure of the two components, with an extended structure comprising zigzag/helical arrays of fullerenes (powder X-ray diffraction data coupled with molecular modeling). Under argon at temperatures above 309 degrees C, the fibers undergo selective volatilization of the calixarenes to afford C(60)-core nanostructures encapsulated in a graphitic material sheath, which exhibits a dramatic increase in surface area. Above 650 degrees C the material exhibits an ohmic conductance response, due to the encapsulation process.

Analysis of surface EMG spike shape across different levels of isometric force.

PubMed

Gabriel, David A; Lester, Steven M; Lenhardt, Sean A; Cambridge, Edward D J

2007-01-15

This research evaluated changes in surface electromyographic (SEMG) spike shape across different levels of isometric force. Ninety-six subjects generated three 5-s isometric step contractions of the elbow flexors at 40, 60, 80, and 100% of maximal voluntary contraction (MVC). Force and bipolar SEMG activity were monitored concurrently. The mean spike amplitude (MSA) exhibited a linear increase across the four levels of force. The mean spike frequency (MSF) remained stable from 40 to 80% of MVC; it then decreased from 80 to 100% of MVC. There was a concomitant increase in mean spike slope (MSS) that indicates that the biceps brachii (BB) relied on the recruitment of higher threshold motor units (MUs) from 40 to 80% of MVC. However, there progressive decrease in the mean number of peaks per spike (MNPPS) that suggests that MU synchronization was additionally required to increase force from 80 to 100% of MVC. The spike shape measures, taken together, indicate that the decrease in frequency content of the signal was due to synchronization, not an increased probability of temporal overlap due an increase in rate-coding.

Fabrication and characterization of crushed titanium-beryllium intermetallic compounds

NASA Astrophysics Data System (ADS)

Kim, Jae-Hwan; Nakamichi, Masaru

2018-01-01

To develop a technique for the mass production of beryllide pebbles, a crushing method for the granulation of beryllides was used in this study. Two types of crushed Be12Ti pebbles were prepared using mortar-ground (MG) and planetary-ball-milled (PM) powders. A granulation yield of approximately 50 wt.% with sizes in the range of 0.85-1.18 mm was achieved. Scanning electron microscopy (SEM) images revealed that the MG pebbles exhibited larger porosity because the larger size of the powder resulted in lower density with higher porosity. However, the considerably larger fraction of fine pores in the PM pebbles resulted in an increased Brunauer-Emmett-Teller (BET) specific surface area, as clearly demonstrated by high-magnification SEM images. To evaluate the reactivity with water vapor, the weight gain and H2 generation rate were also investigated. The results suggested that the PM pebbles exhibited notably lower reactivity, weight gain, and H2 generation rate, which may be due to the dramatically decreased BET specific surface. The fine pores were filled with stable oxides followed by a significant decrease of the surface area during oxidation. Optimization was performed to improve the circularity of the crushed pebbles. Grinding tests using planetary milling without balls for different times clearly demonstrated that the circularity improved (with an estimated value of 0.8) by cutting and polishing the sharp edges; however, long-duration milling for 99 h resulted in attachment of the polished powders to the pebble surface, leading to surface color variation of the crushed pebbles.

Radial Surface Density Profiles of Gas and Dust in the Debris Disk Around 49 Ceti

NASA Technical Reports Server (NTRS)

Hughes, A. Meredith; Lieman-Sifry, Jesse; Flaherty, Kevin M.; Daley, Cail M.; Roberge, Aki; Kospal, Agnes; Moor, Attila; Kamp, Inga; Wilner, David J.; Andrews, Sean M.;

Evaluation of an alternative technique to optimize direct bonding of orthodontic brackets to temporary crowns.

PubMed

Dias, Francilena Maria Campos Santos; Pinzan-Vercelino, Célia Regina Maio; Tavares, Rudys Rodolfo de Jesus; Gurgel, Júlio de Araújo; Bramante, Fausto Silva; Fialho, Melissa Nogueira Proença

2015-01-01

To compare shear bond strength of different direct bonding techniques of orthodontic brackets to acrylic resin surfaces. The sample comprised 64 discs of chemically activated acrylic resin (CAAR) randomly divided into four groups: discs in group 1 were bonded by means of light-cured composite resin (conventional adhesive); discs in group 2 had surfaces roughened with a diamond bur followed by conventional direct bonding by means of light-cured composite resin; discs in group 3 were bonded by means of CAAR (alternative adhesive); and discs in group 4 had surfaces roughened with a diamond bur followed by direct bonding by means of CAAR. Shear bond strength values were determined after 24 hours by means of a universal testing machine at a speed of 0.5 mm/min, and compared by analysis of variance followed by post-hoc Tukey test. Adhesive remnant index (ARI) was measured and compared among groups by means of Kruskal-Wallis and Dunn tests. Groups 3 and 4 had significantly greater shear bond strength values in comparison to groups 1 and 2. Groups 3 and 4 yielded similar results. Group 2 showed better results when compared to group 1. In ARI analyses, groups 1 and 2 predominantly exhibited a score equal to 0, whereas groups 3 and 4 predominantly exhibited a score equal to 3. Direct bonding of brackets to acrylic resin surfaces using CAAR yielded better results than light-cured composite resin. Surface preparation with diamond bur only increased shear bond strength in group 2.

Structural and emission characteristics of ion-irradiated Reticulated Vitreous Carbon

NASA Astrophysics Data System (ADS)

Chacon, Judith Rebecca

Cathodes formed from Reticulated Vitreous Carbon (RVC) were treated under varying conditions of Argon-ion beam current, beam voltage and irradiation duration. Surface structures, such as balls, cones, nanowires, and nanowhiskers were formed in the RVC network through a series of ion-impact sputtering and self-diffusion reactions. Raman shifts to the D and E2g' peak suggest C=C bonding within the original RVC structure was converted to the lesser-bound C-C bonding structure. Cathodes demonstrating the most stable electronic configuration exhibited significant vertical growth to graphitic domains as determined by calculations based on XRD measurements. Carbon nanotubes at the surface were observed at the surface through micro-Raman techniques. The surface structures formed by argon-bombardment, are responsible for cathodes exhibiting lower field-emission extraction fields. The electric field required for the onset of electron emission was measured to change from 6.03 V/micron in non-irradiated RVC to 1.62V/micron for RVC irradiated for 15 minutes at a beam voltage of 1200V and beam current of 200mA (ion-beam current density 2.24mA/cm2). Treated surfaces were also responsible for increased stability in emission over time. For untreated RVC, the field required for emission dropped 25% over a 48 hour training period, whilst modestly treated RVC (15min, 1200V, 100mA, or 1.52mA/cm2) rose as little as 3%. Field-emissive RVC, is an inexpensively produced, mechanically robust cathode with potential applications in lighting, displays and microwave sources.

Building 3D Layer-by-Layer Graphene-Gold Nanoparticle Hybrid Architecture with Tunable Interlayer Distance

DTIC Science & Technology

2014-06-26

supercapacitors .11 On the other hand, because of the anisotropic graphene structure, it exhibits strong direction- dependent properties, including...GNPs has the advantage of increased surface area for supercapacitor .11 2. EXPERIMENTAL SECTION 2.1. Materials and Instruments. All chemicals and...rectangular, which means that this material has good potential for applications such as supercapacitors .22 In an ideal situation, it can be envisioned that

Polymeric surfaces exhibiting photocatalytic activity and controlled anisotropic wettability

NASA Astrophysics Data System (ADS)

Anastasiadis, Spiros H.; Frysali, Melani A.; Papoutsakis, Lampros; Kenanakis, George; Stratakis, Emmanuel; Vamvakaki, Maria; Mountrichas, Grigoris; Pispas, Stergios

2015-03-01

In this work we focus on surfaces, which exhibit controlled, switchable wettability in response to one or more external stimuli as well as photocatalytic activity. For this we are inspired from nature to produce surfaces with a dual-scale hierarchical roughness and combine them with the appropriate inorganic and/or polymer coating. The combination of the hierarchical surface with a ZnO coating and a pH- or temperature-responsive polymer results in efficient photo-active properties as well as reversible superhydrophobic / superhydrophilic surfaces. Furthermore, we fabricate surfaces with unidirectional wettability variation. Overall, such complex surfaces require advanced design, combining hierarchically structured surfaces with suitable polymeric materials. Acknowledgment: This research was partially supported by the European Union (European Social Fund, ESF) and Greek national funds through the ``ARISTEIA II'' Action (SMART-SURF) of the Operational Programme ``Education and Lifelong Learning,'' NSRF 2007-2013, via the General Secretariat for Research & Technology, Ministry of Education and Religious Affairs, Greece.

Vertical Stratification of Peat Pore Water Dissolved Organic Matter Composition in a Peat Bog in Northern Minnesota: Pore Water DOM composition in a peat bog

DOE PAGES

Tfaily, Malak M.; Wilson, Rachel M.; Cooper, William T.; ...

2018-01-29

Here, we characterized dissolved organic matter (DOM) composition throughout the peat column at the Marcell S1 forested bog in northern Minnesota and tested the hypothesis that redox oscillations associated with cycles of wetting and drying at the surface of the fluctuating water table correlate with increased carbon, sulfur, and nitrogen turn over. We found significant vertical stratification of DOM molecular composition and excitation-emission matrix parallel factor analysis components within the peat column. In particular, the intermediate depth zone (~ 50 cm) was identified as a zone where maximum decomposition and turnover is taking place. Surface DOM was dominated by inputsmore » from surface vegetation. The intermediate depth zone was an area of high organic matter reactivity and increased microbial activity with diagenetic formation of many unique compounds, among them polycyclic aromatic compounds that contain both nitrogen and sulfur heteroatoms. These compounds have been previously observed in coal-derived compounds and were assumed to be responsible for coal's biological activity. Biological processes triggered by redox oscillations taking place at the intermediate depth zone of the peat profile at the S1 bog are assumed to be responsible for the formation of these heteroatomic PACs in this system. Alternatively, these compounds could stem from black carbon and nitrogen derived from fires that have occurred at the site in the past. Surface and deep DOM exhibited more similar characteristics, compared to the intermediate depth zone, with the deep layer exhibiting greater input of microbially degraded organic matter than the surface suggesting that the entire peat profile consists of similar parent material at different degrees of decomposition and that lateral and vertical advection of pore water from the surface to the deeper horizons is responsible for such similarities. Lastly, our findings suggest that molecular composition of DOM in peatland pore water is dynamic and is a function of ecosystem activity, water table, redox oscillation, and pore water advection.« less

Vertical Stratification of Peat Pore Water Dissolved Organic Matter Composition in a Peat Bog in Northern Minnesota: Pore Water DOM composition in a peat bog

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

Tfaily, Malak M.; Wilson, Rachel M.; Cooper, William T.

Here, we characterized dissolved organic matter (DOM) composition throughout the peat column at the Marcell S1 forested bog in northern Minnesota and tested the hypothesis that redox oscillations associated with cycles of wetting and drying at the surface of the fluctuating water table correlate with increased carbon, sulfur, and nitrogen turn over. We found significant vertical stratification of DOM molecular composition and excitation-emission matrix parallel factor analysis components within the peat column. In particular, the intermediate depth zone (~ 50 cm) was identified as a zone where maximum decomposition and turnover is taking place. Surface DOM was dominated by inputsmore » from surface vegetation. The intermediate depth zone was an area of high organic matter reactivity and increased microbial activity with diagenetic formation of many unique compounds, among them polycyclic aromatic compounds that contain both nitrogen and sulfur heteroatoms. These compounds have been previously observed in coal-derived compounds and were assumed to be responsible for coal's biological activity. Biological processes triggered by redox oscillations taking place at the intermediate depth zone of the peat profile at the S1 bog are assumed to be responsible for the formation of these heteroatomic PACs in this system. Alternatively, these compounds could stem from black carbon and nitrogen derived from fires that have occurred at the site in the past. Surface and deep DOM exhibited more similar characteristics, compared to the intermediate depth zone, with the deep layer exhibiting greater input of microbially degraded organic matter than the surface suggesting that the entire peat profile consists of similar parent material at different degrees of decomposition and that lateral and vertical advection of pore water from the surface to the deeper horizons is responsible for such similarities. Lastly, our findings suggest that molecular composition of DOM in peatland pore water is dynamic and is a function of ecosystem activity, water table, redox oscillation, and pore water advection.« less

The effects of size and surface modification of amorphous silica particles on biodistribution and liver metabolism in mice

NASA Astrophysics Data System (ADS)

Lu, Xiaoyan; Ji, Cai; Jin, Tingting; Fan, Xiaohui

2015-05-01

Engineered nanoparticles, with unconventional properties, are promising platforms for biomedical applications. Since they may interact with a wide variety of biomolecules, it is critical to understand the impact of the physicochemical properties of engineered nanoparticles on biological systems. In this study, the effects of particle size and surface modification alone or in combination of amorphous silica particles (SPs) on biological responses were determined using a suite of general toxicological assessments and metabonomics analysis in mice model. Our results suggested that amino or carboxyl surface modification mitigated the liver toxicity of plain-surface SPs. 30 nm SPs with amino surface modification were found to be the most toxic SPs among all the surface-modified SP treatments at the same dosage. When treatment dose was increased, submicro-sized SPs with amino or carboxyl surface modification also induced liver toxicity. Biodistribution studies suggested that 70 nm SPs were mainly accumulated in liver and spleen regardless of surface modifications. Interestingly, these two organs exhibited different uptake trends. Furthermore, metabonomics studies indicated that surface modification plays a more dominant role to affect the liver metabolism than particle size.

Durable anti-fogging effect and adhesion improvement on polymer surfaces

NASA Astrophysics Data System (ADS)

Moser, E. M.; Gilliéron, D.; Henrion, G.

2010-01-01

The hydrophobic properties of polymeric surfaces may cause fogging in transparent packaging and poor adhesion to printing colours and coatings. Novel plasma processes for durable functionalization of polypropylene and polyethylene terephthalate substrates were developed and analysed using optical emission spectroscopy. A worm-like nano pattern was created on the polypropylene surface prior to the deposition of thin polar plasma polymerised layers. For both substrates, highly polar surfaces exhibiting a surface tension of up to 69 mN/m and a water contact angle of about 10° were produced - providing the anti-fogging effect. The deposition of thin plasma polymerised layers protects the increased surface areas and enables to tailoring the surface energy of the substrate in a wide range. Wetting characteristics were determined by dynamic contact angle measurements. Investigations of the chemical composition of several layers using X-ray photoelectron spectroscopy and FT-infrared spectroscopy were correlated with functional testing. The surface topography was investigated using atomic force microscopy. The weldability and peeling-off characteristics of the plasma treated polymer films could be adjusted by varying the process parameters. Global and specific migration analyses were undertaken in order to ensure the manufacturing of plasma treated polymer surfaces for direct food contact purposes.

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface.

PubMed

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-03-02

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length ( L ), interval ( S ), and height ( H ) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure.

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface

PubMed Central

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-01-01

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length (L), interval (S), and height (H) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure. PMID:28772613

Surface Energy Budget Components Over an Arid Scrubland Site in Idaho

NASA Astrophysics Data System (ADS)

Zurawski, A. M.; Russell, E. S.; Liu, H.; Gao, Z.

2015-12-01

Sagebrush ecosystems comprise a large area of the North American West, and serve as habitat to threatened species such as the sagebrush sparrow. Due to natural and anthropogenic disturbances, these ecosystems are experiencing widespread degradation, causing changes to the ecosystem-atmosphere interactions. Quantifying the surface energy budget components is crucial to understanding the impacts of ecosystem degradation on climate. Eddy covariance data were collected from May through August of 2014 from sensors installed at a height of 16 m over sagebrush-dominated ecosystems near Idaho Falls, Idaho. Our objective is to study how meteorological variables affect the partitioning of surface-based net radiation into latent, sensible, and soil heat fluxes. In this arid region, decrease in soil moisture led to a decrease in latent heat flux, and an increase in sensible heat flux. Air temperature increase had no noticeable effect on latent heat flux, and led to increase in sensible heat flux. Consequently, potential climate warming and drought in this region will likely lead to increased sensible heat flux during the day time. An increase in sensible heat flux will cause an increase in atmospheric heat. This indicates that this ecosystem exhibits a positive feedback to climate warming. Night time data needs to be analyzed to better understand the effect of meteorological variables on heat fluxes during the summer season in this ecosystem.

Unidirectional superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Prakash, Manu; Bush, John

2007-11-01

It has long been known that the hairy, waxy cuticle of water-walking insects renders them water-repellent; they thus exhibit high static contact angles. We have recently demonstrated that by the virtue of the geometry and flexibility of the hair, the integument is also directionally anisotropic and so plays a key propulsive role. We here report our attempts to design and implement an analogous synthetic surface that exhibits unidirectional adhesion. The surface effectively acts like a fluidic-diode; allowing contact lines to advance in only one direction. When vibrated randomly, drops suspended on the surface advance in only one direction. Applications in valve-less pumps and drop transport in microfluidic devices are discussed.

Experimental demonstration of scaling behavior for ionic transport and its fluctuations in individual carbon nanotube

NASA Astrophysics Data System (ADS)

Bocquet, Lyderic; Secchi, Eleonora; Nigues, Antoine; Siria, Alessandro

2015-11-01

We perform an experimental study of ionic transport and current fluctuations inside individual Carbon Nanotubes (CNT) with a size ranging from 40 down to 7 nanometers in radius. The conductance exhibits a power law behavior dependence on the salinity, with an exponent close to 1/3. This is in contrast to Boron-Nitride nanotubes which exhibits a constant surface conductance. This scaling behavior is rationalized in terms of a model accounting for hydroxide adsorption at the (hydrophobic) carbon surface. This predicts a density dependent surface charge with a exponent 1/3 in full agreement with the experimental observations. Then we measure the low frequency noise of the ionic current in single CNTs. The noise exhibits a robust 1/f characteristic, with an amplitude which scales proportionaly to the surface charge measured independently. Data for the various CNT at a given pH do collapse on a master curve. This behavior is rationalized in terms of the fluctuations of the surface charge based on the adsorption behavior. This suggests that the low frequency noise takes its origin in the process occuring at the surface of the carbon nanotube.

A quantitative AFM analysis of nano-scale surface roughness in various orthodontic brackets.

PubMed

Lee, Gi-Ja; Park, Ki-Ho; Park, Young-Guk; Park, Hun-Kuk

2010-10-01

In orthodontics, the surface roughnesses of orthodontic archwire and brackets affect the effectiveness of arch-guided tooth movement, corrosion behavior, and the aesthetics of orthodontic components. Atomic force microscopy (AFM) measurements were used to provide quantitative information on the surface roughness of the orthodontic material. In this study, the changes in surface roughness of various orthodontic bracket slots before and after sliding movement of archwire in vitro and in vivo were observed through the utilization of AFM. Firstly, we characterized the surface of four types of brackets slots as follows: conventional stainless steel (Succes), conventional ceramic (Perfect), self-ligating stainless steel (Damon) and self-ligating ceramic (Clippy-C) brackets. Succes) and Damon brackets showed relatively smooth surfaces, while Perfect had the roughest surface among the four types of brackets used. Secondly, after in vitro sliding test with beta titanium wire in two conventional brackets (Succes and Perfect), there were significant increases in only stainless steel bracket, Succes. Thirdly, after clinical orthodontic treatment for a maximum of 2 years, the self-ligating stainless steel bracket, Damon, showed a significant increase in surface roughness. But self-ligating ceramic brackets, Clippy-C, represented less significant changes in roughness parameters than self-ligating stainless steel ones. Based on the results of the AFM measurements, it is suggested that the self-ligating ceramic bracket has great possibility to exhibit less friction and better biocompatibility than the other tested brackets. This implies that these bracket slots will aid in the effectiveness of arch-guided tooth movement.

Insight into the role of the promoters Pt, Ru and B in inhibiting the deactivation of Co catalysts in Fischer-Tropsch synthesis

NASA Astrophysics Data System (ADS)

Zhang, Riguang; Liu, Hongxia; Li, Qiaohong; Wang, Baojun; Ling, Lixia; Li, Debao

2018-09-01

In order to probe into the roles of the promoters Pt, Ru and B in inhibiting the deactivation of Co catalysts in FTS reactions, the adsorption ability of neighboring surface C and subsurface C atom around the promoters (Pt, Ru and B), and the mechanisms of surface C diffusion, accumulation, hydrogenation and penetration are examined by density functional theory calculations over the promoters Pt, Ru and B-modified Co catalysts, as well as the pure Co catalysts. Our results clearly show that compared to Co catalysts, both PtCo and RuCo bimetallic catalysts promote surface C hydrogenation, and inhibit surface C diffusion, accumulation and penetration, and therefore the ability of resistance toward deactivation and the stability of Co-based catalysts are enhanced; the promoter B cannot effectively improve the ability of resistance toward deactivation. Thus, the sequence for resistance toward deactivation of Co-based catalyst is BCo < Co < PtCo < RuCo. Moreover, the activation free energy of surface C accumulation to C2 species increases with the increasing of surface C adsorption free energy, namely, the adsorption characteristic of surface C species well represent the surface carbon deposition. Our results not only give an explanation for reported experiment that the Pt, Ru and B-modified Co catalysts exhibit ability of resistance toward deactivation in FTS at a molecular level, but also provide a clue for the design of efficient Co-based catalysts in FTS reactions.

Patients with metabolic syndrome exhibit higher platelet activity than those with conventional risk factors for vascular disease.

PubMed

Serebruany, Victor L; Malinin, Alex; Ong, Stephen; Atar, Dan

2008-04-01

The metabolic syndrome is a matter of ongoing debate with regard to its existence, classification, clinical meaningfulness, and associated risks for vessel occlusion. Considering that persistent platelet activation is a cornerstone for the development of acute vascular events, and that patients with type 2 diabetes consistently exhibit high platelet activity, these characteristics may be critical for distinguishing and triageing specific features of metabolic syndrome among established risk factors for vascular disease. We assessed the platelet activity by conventional aggregation, expression of major surface receptors by flow cytometry, and quantitatively by rapid bedside analyzers in 20 aspirin-naïve patients with documented metabolic syndrome, and compared these with 20 untreated subjects with multiple cardiovascular risk factors. Closure time by the PFA-100 analyzer was significantly (P = 0.002) shorter in patients with metabolic syndrome indicating platelet inhibition under high shear conditions. Ultegra analyzer readings revealed increased fibrinogen binding (P = 0.0003) what in combination with the increased expression of PAC-1 (P = 0.32) strongly suggest activation of platelet glycoprotein IIb/IIIa receptor. Surface expression of CD107a (P = 0.014), and SPAN-12 (P = 0.003) were also higher in patients with metabolic syndrome. In contrast, platelet aggregation induced by collagen or ADP, CD31, CD41, CD42b, CD51/61, CD62p, CD63, CD154, CD165, so as formation of platelet-monocyte aggregates, PAR-1 thrombin receptor, and thrombospondin did not differ between groups. Patients with metabolic syndrome exhibited a higher degree of platelet activation than subjects with conventional risk factors for vascular disease. Conceptually, applying adequate antiplatelet strategies may reduce the risk of acute thrombotic events in these patients. Further prospective studies exploring this notion are encouraged.

Tyrosine Phosphorylation of the Human Serotonin Transporter: A Role in the Transporter Stability and Function

PubMed Central

Annamalai, Balasubramaniam; Mannangatti, Padmanabhan; Arapulisamy, Obulakshmi; Shippenberg, Toni S.; Jayanthi, Lankupalle D.

2012-01-01

The serotonin (5-HT) transporter (SERT) regulates serotoninergic neurotransmission by clearing 5-HT released into the synaptic space. Phosphorylation of SERT on serine and threonine mediates SERT regulation. Whether tyrosine phosphorylation regulates SERT is unknown. Here, we tested the hypothesis that tyrosine-phosphorylation of SERT regulates 5-HT transport. In support of this, alkali-resistant 32P-labeled SERT was found in rat platelets, and Src-tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo [3,4,d]pyrimidine (PP2) decreased platelet SERT function and expression. In human placental trophoblast cells expressing SERT, PP2 reduced transporter function, expression, and stability. Although siRNA silencing of Src expression decreased SERT function and expression, coexpression of Src resulted in PP2-sensitive increases in SERT function and expression. PP2 treatment markedly decreased SERT protein stability. Compared with WT-SERT, SERT tyrosine mutants Y47F and Y142F exhibited reduced 5-HT transport despite their higher total and cell surface expression levels. Moreover, Src-coexpression increased total and cell surface expression of Y47F and Y142F SERT mutants without affecting their 5-HT transport capacity. It is noteworthy that Y47F and Y142F mutants exhibited higher protein stability compared with WT-SERT. However, similar to WT-SERT, PP2 treatment decreased the stability of Y47F and Y142F mutants. Furthermore, compared with WT-SERT, Y47F and Y142F mutants exhibited lower basal tyrosine phosphorylation and no further enhancement of tyrosine phosphorylation in response to Src coexpression. These results provide the first evidence that SERT tyrosine phosphorylation supports transporter protein stability and 5HT transport. PMID:21992875

Tollen’s reagent assisted synthesis of hollow polyaniline microsphere/Ag nanocomposite and its applications in sugar sensing and electromagnetic shielding

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

Panigrahi, R.; Srivastava, S.K., E-mail: sunit@chem.iitkgp.ernet.in

Graphical abstract: Probable scheme to demonstrate the mechanism of PnHMAg showing enhanced EMI shielding compared to PnHM. - Highlights: • Hollow polyaniline microsphere (PnHM) exhibits superior properties due to its enhanced surface to volume ratio. • PnHMAg has been used in developing efficient sensor for the detection of sugar. • Presence of Ag nanoparticles enhances the electrical conductivity of PnHMAg resulting in the improvement of electromagnetic interference shielding in both X- and S-band regions. • Such properties could be harnessed effectively for development of devices for commercial as well as national purposes. - Abstract: The present study is focused onmore » synthesis of polyaniline hollow microspheres (PnHM) nanocomposites of silver (Ag) i.e., PnHMAg by emulsion polymerization of aniline and Tollen’s reagent as a source for Ag nanoparticles. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis of PnHMAg indicated presence of silver nanoparticles dispersed on polyaniline surface. The electrical conductivity of PnHMAg is increased by ∼6 times compared to PnHM. Cyclic voltammogram of PnHM in sugar sensing exhibits characteristics redox peaks at ∼0.09 (sugar) and ∼0.53 V (polyaniline). Interestingly, PnHMAg showed a single peak at ∼−0.18 V with increased intensity (∼5 times) indicating its high sugar sensing ability. PnHMAg also exhibits high shielding efficiency of 19.5 dB (11.2 GHz) due to the presence of highly conducting Ag nanoparticles. TEM studies confirmed that Ag nanoparticles are well distributed on PnHM. As a result, a continuous electronic path is developed due to enhanced interconnectivity of PnHM.« less

Pollution status of polycyclic aromatic hydrocarbons in surface sediments from the Yangtze River Estuary and its adjacent coastal zone.

PubMed

Wang, Chenglong; Zou, Xinqing; Gao, Jianhua; Zhao, Yifei; Yu, Wenwen; Li, Yali; Song, Qiaochu

2016-11-01

Polycyclic aromatic hydrocarbons (PAHs) are mainly produced by incomplete combustion and are used as indicators of anthropogenic activities on the environment. This study analyses the PAHs level in the Yangtze River Estuary (YRE), an important component of Yangtze River and a developed and populated region in China. Surface sediments were collected from 77 sites at the YRE and its adjacent coastal zone (IACZ) for a comprehensive study of PAHs. Kriging interpolation technology and Positive matrix factorization (PMF) model were applied to explore the spatial distribution and sources of PAHs. Concentrations of 16 PAHs (ΣPAHs) varied from 27.2 ng g(-1) to 621.6 ng g(-1) dry weight, with an average value of 158.2 ng g(-1). Spatially, ΣPAHs exhibited wide fluctuation and exhibited an increasing tendency from north to south. In addition, ΣPAHs exhibited a decreasing trend with increasing distance between the estuary and IACZ. The deposition flux of PAHs indicated that more than 107.8 t a(-1) PAHs was deposited in the study area annually. The results of the PMF model revealed that anthropogenic activities were the main sources of PAHs in the study area. Vehicle emissions and marine engines were the most important sources and accounted for 40.9% of the pollution. Coal combustion, petrogenic sources, and wood combustion were other sources that contributed 23.9%, 23.6%, and 11.5%, respectively. The distribution patterns of PAHs in the YRE and IACZ were influenced by many complicated factors such as sediment grain size, hydrodynamics and so on. Copyright © 2016 Elsevier Ltd. All rights reserved.

Gene Expression Profiles of Human Dendritic Cells Interacting with Aspergillus fumigatus in a Bilayer Model of the Alveolar Epithelium/Endothelium Interface

PubMed Central

Morton, Charles Oliver; Fliesser, Mirjam; Dittrich, Marcus; Mueller, Tobias; Bauer, Ruth; Kneitz, Susanne; Hope, William; Rogers, Thomas Richard; Einsele, Hermann; Loeffler, Juergen

2014-01-01

The initial stages of the interaction between the host and Aspergillus fumigatus at the alveolar surface of the human lung are critical in the establishment of aspergillosis. Using an in vitro bilayer model of the alveolus, including both the epithelium (human lung adenocarcinoma epithelial cell line, A549) and endothelium (human pulmonary artery epithelial cells, HPAEC) on transwell membranes, it was possible to closely replicate the in vivo conditions. Two distinct sub-groups of dendritic cells (DC), monocyte-derived DC (moDC) and myeloid DC (mDC), were included in the model to examine immune responses to fungal infection at the alveolar surface. RNA in high quantity and quality was extracted from the cell layers on the transwell membrane to allow gene expression analysis using tailored custom-made microarrays, containing probes for 117 immune-relevant genes. This microarray data indicated minimal induction of immune gene expression in A549 alveolar epithelial cells in response to germ tubes of A. fumigatus. In contrast, the addition of DC to the system greatly increased the number of differentially expressed immune genes. moDC exhibited increased expression of genes including CLEC7A, CD209 and CCL18 in the absence of A. fumigatus compared to mDC. In the presence of A. fumigatus, both DC subgroups exhibited up-regulation of genes identified in previous studies as being associated with the exposure of DC to A. fumigatus and exhibiting chemotactic properties for neutrophils, including CXCL2, CXCL5, CCL20, and IL1B. This model closely approximated the human alveolus allowing for an analysis of the host pathogen interface that complements existing animal models of IA. PMID:24870357

Fractography of the high temperature hydrogen attack of a medium carbon steel

NASA Technical Reports Server (NTRS)

Melson, H. G.; Moorhead, R. D.

1975-01-01

Microscopic fracture processes were studied which are associated with hydrogen attack of a medium carbon steel in a well-controlled, high-temperature, high-purity hydrogen environment. Exposure to a hydrogen pressure and temperature of 3.5 MN/m2 and 575 C was found to degrade room temperature tensile properties with increasing exposure time. After 408 hr, yield and ultimate strengths were reduced by more than 40 percent and elongation was reduced to less than 2 percent. Initial fissure formation was found to be associated with manganese rich particles, most probably manganese oxide, aligned in the microstructure during the rolling operation. Fissure growth was found to be associated with a reduction in carbide content of the microstructure and was inhibited by the depletion of carbon. The interior surfaces of sectioned fissures or bubbles exhibit both primary and secondary cracking by intergranular separation. The grain surfaces were rough and rounded, suggesting a diffusion-associated separation process. Specimens that failed at room temperature after exposure to hydrogen were found to exhibit mixed mode fracture having varying amounts of intergranular separation, dimple formation, and cleavage, depending on exposure time.

On sub-T(g) dewetting of nanoconfined liquids and autophobic dewetting of crystallites.

PubMed

Souda, Ryutaro

2012-03-28

The glass transition temperature (T(g)) of thin films is reduced by nanoconfinement, but it is also influenced by the free surface and substrate interface. To gain more insights into their contributions, dewetting behaviors of n-pentane, 3-methylpentane, and toluene films are investigated on various substrates as functions of temperature and film thickness. It is found that monolayers of these molecules exhibit sub-T(g) dewetting on a perfluoro-alkyl modified Ni substrate, which is attributable to the evolution of a 2D liquid. The onset temperature of dewetting increases with film thickness because fluidity evolves via cooperative motion of many molecules; sub-T(g) dewetting is observed for films thinner than 5 monolayers. In contrast, monolayers wet substrates of graphite, silicon, and amorphous solid water until crystallization occurs. The crystallites exhibit autophobic dewetting on the substrate covered with a wetting monolayer. The presence of premelting layers is inferred from the fact that n-pentane crystallites disappear on amorphous solid water via intermixing. Thus, the properties of quasiliquid formed on the crystallite surface differ significantly from those of the 2D liquid formed before crystallization.

Porous WO3/graphene/polyester textile electrode materials with enhanced electrochemical performance for flexible solid-state supercapacitors.

PubMed

Jin, Li-Na; Liu, Ping; Jin, Chun; Zhang, Jia-Nan; Bian, Shao-Wei

2018-01-15

In this work, a flexible and porous WO 3 /grapheme/polyester (WO 3 /G/PT) textile electrode was successfully prepared by in situ growing WO 3 on the fiber surface inside G/PT composite fabrics. The unique electrode structure facilitates to enhance the energy storage performance because the 3D conductive network constructed by the G/PT increase the electron transportation rate, nanotructured WO 3 exposed enhanced electrochemically active surface area and the hierarchically porous structure improved the electrolyte ion diffusion rate. The optimized WO 3 /G/PT textile electrode exhibited good electrochemical performance with a high areal capacitance of 308.2mFcm -2 at a scan rate of 2mVs -1 and excellent cycling stability. A flexible asymmetric supercapacitor (ASC) device was further fabricated by using the WO 3 /G/PT electrode and G/PT electrode, which exhibited a good specific capacitance of 167.6mFcm -3 and high energy density of 60μWhcm -3 at the power density of 2320 μWcm -3 . Copyright © 2017 Elsevier Inc. All rights reserved.

Efficient Carrier Multiplication in Colloidal Silicon Nanorods

DOE PAGES

Stolle, Carl Jackson; Lu, Xiaotang; Yu, Yixuan; ...

2017-08-01

In this study, auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimesmore » increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy E g. Beyond a critical length, the CM quantum yield decreases. Finally, nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2.9E g, which corresponded to a multiexciton yield that was twice as high as observed for the spherical nanocrystals.« less

Effect of grafted oligopeptides on friction.

PubMed

Iarikov, Dmitri D; Ducker, William A

2013-05-14

Frictional and normal forces in aqueous solution at 25 °C were measured between a glass particle and oligopeptide films grafted from a glass plate. Homopeptide molecules consisting of 11 monomers of either glutamine, leucine, glutamic acid, lysine, or phenylalanine and one heteropolymer were each "grafted from" an oxidized silicon wafer using microwave-assisted solid-phase peptide synthesis. The peptide films were characterized using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. Frictional force measurements showed that the oligopeptides increased the magnitude of friction compared to that on a bare hydrophilic silicon wafer but that the friction was a strong function of the nature of the monomer unit. Overall we find that the friction is lower for more hydrophilic films. For example, the most hydrophobic monomer, leucine, exhibited the highest friction whereas the hydrophilic monomer, polyglutamic acid, exhibited the lowest friction at zero load. When the two surfaces had opposite charges, there was a strong attraction, adhesion, and high friction between the surfaces. Friction for all polymers was lower in phosphate-buffered saline than in pure water, which was attributed to lubrication via hydrated salt ions.

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

Stolle, Carl Jackson; Lu, Xiaotang; Yu, Yixuan

In this study, auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimesmore » increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy E g. Beyond a critical length, the CM quantum yield decreases. Finally, nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2.9E g, which corresponded to a multiexciton yield that was twice as high as observed for the spherical nanocrystals.« less

Electrochemical Migration Behavior of Copper-Clad Laminate and Electroless Nickel/Immersion Gold Printed Circuit Boards under Thin Electrolyte Layers

PubMed Central

Yi, Pan; Xiao, Kui; Ding, Kangkang; Dong, Chaofang; Li, Xiaogang

2017-01-01

The electrochemical migration (ECM) behavior of copper-clad laminate (PCB-Cu) and electroless nickel/immersion gold printed circuit boards (PCB-ENIG) under thin electrolyte layers of different thicknesses containing 0.1 M Na2SO4 was studied. Results showed that, under the bias voltage of 12 V, the reverse migration of ions occurred. For PCB-Cu, both copper dendrites and sulfate precipitates were found on the surface of FR-4 (board material) between two plates. Moreover, the Cu dendrite was produced between the two plates and migrated toward cathode. Compared to PCB-Cu, PCB-ENIG exhibited a higher tendency of ECM failure and suffered from seriously short circuit failure under high relative humidity (RH) environment. SKP results demonstrated that surface potentials of the anode plates were greater than those of the cathode plates, and those potentials of the two plates exhibited a descending trend as the RH increased. At the end of the paper, an electrochemical migration corrosion failure model of PCB was proposed. PMID:28772497

Notch Signaling Is Involved in Neurogenic Commitment of Human Periodontal Ligament-Derived Mesenchymal Stem Cells

PubMed Central

Osathanon, Thanaphum; Manokawinchoke, Jeeranan; Nowwarote, Nunthawan; Aguilar, Panuroot; Palaga, Tanapat

2013-01-01

Notch signaling plays critical roles in stem cells by regulating cell fate determination and differentiation. The aim of this study was to evaluate the participation of Notch signaling in neurogenic commitment of human periodontal ligament-derived mesenchymal stem cells (hPDLSCs) and to examine the ability to control differentiation of these cells using modified surfaces containing affinity immobilized Notch ligands. Neurogenic induction of hPDLSCs was performed via neurosphere formation. Cells were aggregated and form spheres as early 1 day in culture. In addition, the induced cells exhibited increased mRNA and protein expression of neuronal markers that is, β3-tubulin and neurofilament. During neuronal differentiation, a significant increase of Hes1 and Hey1 mRNA expression was noted. Using pharmacological inhibition (γ-secretase inhibitor) or genetic manipulation (overexpression of dominant negative mastermind-like transcription co-activators), neurosphere formation was attenuated and a marked decrease in neurogenic mRNA expression was observed. To confirm the role of Notch signaling in neuronal differentiation of hPDLSCs, the Notch ligand, Jagged-1, is bound to the surface using an affinity immobilization technique. The hPDLSC cultured on a Jagged-1-modified surface had increased expression of Notch signaling target genes, Hes-1 and Hey-1, confirming the activity and potency of surface-bound Jagged-1. Further, hPDLSC on surface-bound Jagged-1 under serum-free conditions showed multiple long and thin neurite-like extensions, and an increase in the expression of neurogenic mRNA markers was observed. Pretreatment of the cells with γ-secretase inhibitor, DAPT, before seeding on the Jagged-1-modified surface blocked development of the neurite-like morphology. Together, the results in this study suggest the involvement of Notch signaling in neurogenic commitment of hPDLSCs. PMID:23379739

Chemical weathering rates of a soil chronosequence on granitic alluvium: I. Quantification of mineralogical and surface area changes and calculation of primary silicate reaction rates

USGS Publications Warehouse

White, A.F.; Blum, A.E.; Schulz, M.S.; Bullen, T.D.; Harden, J.W.; Peterson, M.L.

1996-01-01

Mineral weathering rates are determined for a series of soils ranging in age from 0.2-3000 Ky developed on alluvial terraces near Merced in the Central Valley of California. Mineralogical and elemental abundances exhibit time-dependent trends documenting the chemical evolution of granitic sand to residual kaolinite and quartz. Mineral losses with time occur in the order: hornblende > plagioclase > K-feldspar. Maximum volume decreases of >50% occur in the older soils. BET surface areas of the bulk soils increase with age, as do specific surface areas of aluminosilicate mineral fractions such as plagioclase, which increases from 0.4-1.5 m2 g-1 over 600 Ky. Quartz surface areas are lower and change less with time (0.11-0.23 m2 g-1). BET surface areas correspond to increasing external surface roughness (?? = 10-600) and relatively constant internal surface area (??? 1.3 m2 g-1). SEM observations confirm both surface pitting and development of internal porosity. A numerical model describes aluminosilicate dissolution rates as a function of changes in residual mineral abundance, grain size distributions, and mineral surface areas with time. A simple geometric treatment, assuming spherical grains and no surface roughness, predicts average dissolution rates (plagioclase, 10-17.4; K-feldspar, 10-17.8; and hornblende, 10-17.5 mol cm-1 s-1) that are constant with time and comparable to previous estimates of soil weathering. Average rates, based on BET surface area measurements and variable surface roughnesses, are much slower (plagioclase, 10-19.9; K-feldspar, 10-20.5; and hornblende 10-20.1 mol cm-2 s-1). Rates for individual soil horizons decrease by a factor of 101.5 over 3000 Ky indicating that the surface reactivities of minerals decrease as the physical surface areas increase. Rate constants based on BET estimates for the Merced soils are factors of 103-104 slower than reported experimental dissolution rates determined from freshly prepared silicates with low surface roughness (?? <10). This study demonstrates that the utility of experimental rate constants to predict weathering in soils is limited without consideration of variable surface areas and processes that control the evolution of surface reactivity with time.

Measurement of UO2 surface oxidation using grazing-incidence x-ray diffraction: Implications for nuclear forensics

NASA Astrophysics Data System (ADS)

Tracy, Cameron L.; Chen, Chien-Hung; Park, Sulgiye; Davisson, M. Lee; Ewing, Rodney C.

2018-04-01

Nuclear forensics involves determination of the origin and history of interdicted nuclear materials based on the detection of signatures associated with their production and trafficking. The surface oxidation undergone by UO2 when exposed to air is a potential signature of its atmospheric exposure during handling and transport. To assess the sensitivity of this oxidation to atmospheric parameters, surface sensitive grazing-incidence x-ray diffraction (GIXRD) measurements were performed on UO2 samples exposed to air of varying relative humidity (34%, 56%, and 95% RH) and temperature (room temperature, 50 °C, and 100 °C). Near-surface unit cell contraction was observed following exposure, indicating oxidation of the surface and accompanying reduction of the uranium cation ionic radii. The extent of unit cell contraction provides a measure of the extent of oxidation, allowing for comparison of the effects of various exposure conditions. No clear influence of relative humidity on the extent of oxidation was observed, with samples exhibiting similar degrees of unit cell contraction at all relative humidities investigated. In contrast, the thickness of the oxidized layers increased substantially with increasing temperature, such that differences on the order of 10 °C yielded readily observable crystallographic signatures of the exposure conditions.

Suppression of Lateral Diffusion and Surface Leakage Currents in nBn Photodetectors Using an Inverted Design

NASA Astrophysics Data System (ADS)

Du, X.; Savich, G. R.; Marozas, B. T.; Wicks, G. W.

2018-02-01

Surface leakage and lateral diffusion currents in InAs-based nBn photodetectors have been investigated. Devices fabricated using a shallow etch processing scheme that etches through the top contact and stops at the barrier exhibited large lateral diffusion current but undetectably low surface leakage. Such large lateral diffusion current significantly increased the dark current, especially in small devices, and causes pixel-to-pixel crosstalk in detector arrays. To eliminate the lateral diffusion current, two different approaches were examined. The conventional solution utilized a deep etch process, which etches through the top contact, barrier, and absorber. This deep etch processing scheme eliminated lateral diffusion, but introduced high surface current along the device mesa sidewalls, increasing the dark current. High device failure rate was also observed in deep-etched nBn structures. An alternative approach to limit lateral diffusion used an inverted nBn structure that has its absorber grown above the barrier. Like the shallow etch process on conventional nBn structures, the inverted nBn devices were fabricated with a processing scheme that only etches the top layer (the absorber, in this case) but avoids etching through the barrier. The results show that inverted nBn devices have the advantage of eliminating the lateral diffusion current without introducing elevated surface current.

Combined Effect of Textured Patterns and Graphene Flake Additives on Tribological Behavior under Boundary Lubrication

PubMed Central

Cai, Zhen-bing; Zhao, Lei; Zhang, Xu; Yue, Wen; Zhu, Min-hao

2016-01-01

A ball-on-plate wear test was employed to investigate the effectiveness of graphene (GP) nanoparticles dispersed in a synthetic-oil-based lubricant in reducing wear. The effect by area ratio of elliptically shaped dimple textures and elevated temperatures were also explored. Pure PAO4 based oil and a mixture of this oil with 0.01 wt% GP were compared as lubricants. At pit area ratio of 5%, GP-base oil effectively reduced friction and wear, especially at 60 and 100°C. Under pure PAO4 oil lubrication, the untextured surfaces gained low friction coefficients (COFs) and wear rates under 60 and 100°C. With increasing laser—texture area ratio, the COF and wear rate decreased at 25 and 150°C but increased at 60 and 100°C. Under the GP-based oil lubrication, the textured surface with 5% area ratio achieved the lowest COF among those of the area ratios tested at all test temperatures. Meanwhile, the textured surface with 20% area ratio obtained the highest COF among those of the area ratios. With the joint action of GP and texture, the textured surface with 10% area ratio exhibited the best anti-wear performance among all of the textured surfaces at all test temperatures. PMID:27054762

Cockroach protease allergen induces allergic airway inflammation via epithelial cell activation

PubMed Central

Kale, Sagar L.; Agrawal, Komal; Gaur, Shailendra Nath; Arora, Naveen

2017-01-01

Protease allergens are known to enhance allergic inflammation but their exact role in initiation of allergic reactions at mucosal surfaces still remains elusive. This study was aimed at deciphering the role of serine protease activity of Per a 10, a major cockroach allergen in initiation of allergic inflammation at mucosal surfaces. We demonstrate that Per a 10 increases epithelial permeability by disruption of tight junction proteins, ZO-1 and occludin, and enhances the migration of Monocyte derived dendritic cell precursors towards epithelial layer as exhibited by trans-well studies. Per a 10 exposure also leads to secretion of IL-33, TSLP and intracellular Ca2+ dependent increase in ATP levels. Further, in vivo experiments revealed that Per a 10 administration in mice elevated allergic inflammatory parameters along with high levels of IL-33, TSLP, IL-1α and uric acid in the mice lungs. We next demonstrated that Per a 10 cleaves CD23 (low affinity IgE receptor) from the surface of PBMCs and purified B cells and CD25 (IL-2 receptor) from the surface of PBMCs and purified T cells in an activity dependent manner, which might favour Th2 responses. In conclusion, protease activity of Per a 10 plays a significant role in initiation of allergic airway inflammation at the mucosal surfaces. PMID:28198394

Tissue response to surface-treated tantalum implants: preliminary observations in primates.

PubMed

Meenaghan, M A; Natiella, J R; Moresi, J L; Flynn, H E; Wirth, J E; Baier, R E

1979-07-01

Samples of capacitor grade tantalum were surface-treated by a variety of methods. These surface treatments allowed testing of the same basic material which was mill-finished, metallurgically polished, electrochemically oxidized, sintered with a porous surface, and glow-discharged. Surface characterization was accomplished by contact angle measurements, Scanning Electron Microscopy, energy-dispensed x-ray analysis, and internal reflection spectroscopy. Subsequent to characterization, the material was surgically implanted in the subperiosteal region of the mandible, the buccal mucosa, and the subcutaneous paravertebral region of the back of Macaca speciosa (stumptail monkey). The tissue reaction at intervals of up to three weeks was evaluated morphologically and ultrastructurally. Significant differences in tissue response were noted at the interfaces with glow-discharge-treated versus lower surface energy samples. Adjacent to the glow-discharge-treated implants, two distinct tissue zones were identified. Zone No. 1, nearest the implant, exhibited an increased cellularity. This consisted of 4-5 layers of highly active mesenchymal cells or fibroblast-like cells with spindle-shaped nuclei and prominent cytoplasmic features. At various foci along the interface, hyperchromatic nuclear forms were noted to project into the space left by removal of the implant. These observations, coupled with a predominance of intercellular ground-substance material and less collagen at the interface, may indicate some form of bioadhesion. The deeper Zone No. 2 was 2-3 times as thick consisted of typical fibroblastic cells with a lamellar configuration, bordered by an occasional delicate-lined space. Independent of implantation site or surface texture, all other implants showed occasional multinucleated giant cells and a decrease in the cellular character of Zone No. 1. Both zones were reduced in thickness and composed of more mature fibroblasts. Some specimens exhibited intracytoplasmic vacuolization. It may be concluded, therefore, that surface-free energy of the implanted specimens played a significant role in inducing differential tissue response to otherwise similar pure metal samples.

Biofunctionalization of silicone rubber with microgroove-patterned surface and carbon-ion implantation to enhance biocompatibility and reduce capsule formation.

PubMed

Lei, Ze-Yuan; Liu, Ting; Li, Wei-Juan; Shi, Xiao-Hua; Fan, Dong-Li

Silicone rubber implants have been widely used to repair soft tissue defects and deformities. However, poor biocompatibility can elicit capsule formation, usually resulting in prosthesis contracture and displacement in long-term usage. To overcome this problem, this study investigated the properties of silicone rubber materials with or without a microgroove-patterned surface and with or without carbon (C)-ion implantation. Atomic force microscopy, X-ray photoelectron spectroscopy, and a water contact angle test were used to characterize surface morphology and physicochemical properties. Cytocompatibility was investigated by a cell adhesion experiment, immunofluorescence staining, a Cell Counting Kit-8 assay, and scanning electron microscopy in vitro. Histocompatibility was evaluated by studying the inflammatory response and fiber capsule formation that developed after subcutaneous implantation in rats for 7 days, 15 days, and 30 days in vivo. Parallel microgrooves were found on the surfaces of patterned silicone rubber (P-SR) and patterned C-ion-implanted silicone rubber (PC-SR). Irregular larger peaks and deeper valleys were present on the surface of silicone rubber implanted with C ions (C-SR). The silicone rubber surfaces with microgroove patterns had stable physical and chemical properties and exhibited moderate hydrophobicity. PC-SR exhibited moderately increased dermal fibroblast cell adhesion and growth, and its surface microstructure promoted orderly cell growth. Histocompatibility experiments on animals showed that both the anti-inflammatory and antifibrosis properties of PC-SR were slightly better than those of the other materials, and there was also a lower capsular contracture rate and less collagen deposition around implants made from PC-SR. Although the surface chemical properties, dermal fibroblast cell growth, and cell adhesion were not changed by microgroove pattern modification, a more orderly cell arrangement was obtained, leading to enhanced biocompatibility and reduced capsule formation. Thus, this approach to the modification of silicone rubber, in combination with C-ion implantation, should be considered for further investigation and application.

Surface Premelting Coupled with Bulk Phase Transitions in Colloidal Crystals

NASA Astrophysics Data System (ADS)

Li, Bo; Wang, Feng; Zhou, Di; Cao, Xin; Peng, Yi; Ni, Ran; Liao, Maijia; Han, Yilong

2015-03-01

Colloids have been used as outstanding model systems for the studies of various phase transitions in bulk, but not at interface yet. Here we obtained equilibrium crystal-vapor interfaces using tunable attractive colloidal spheres and studied the surface premelting at the single-particle level by video microscopy. We found that monolayer crystals exhibit a bulk isostructural solid-solid transition which triggers the surface premelting. The premelting is incomplete due to the interruption of a mechanical-instability-induced bulk melting. By contrast, two- or multilayer crystals do not have the solid-solid transition and the mechanical instability, hence they exhibit complete premelting with divergent surface-liquid thickness. These novel interplays between bulk and surface phase transitions cast new lights for both types of transitions.

Dimensionality of Carbon Nanomaterials Determines the Binding and Dynamics of Amyloidogenic Peptides: Multiscale Theoretical Simulations

PubMed Central

Hine, Nicholas D. M.; Mostofi, Arash A.; Yarovsky, Irene

2013-01-01

Experimental studies have demonstrated that nanoparticles can affect the rate of protein self-assembly, possibly interfering with the development of protein misfolding diseases such as Alzheimer's, Parkinson's and prion disease caused by aggregation and fibril formation of amyloid-prone proteins. We employ classical molecular dynamics simulations and large-scale density functional theory calculations to investigate the effects of nanomaterials on the structure, dynamics and binding of an amyloidogenic peptide apoC-II(60-70). We show that the binding affinity of this peptide to carbonaceous nanomaterials such as C60, nanotubes and graphene decreases with increasing nanoparticle curvature. Strong binding is facilitated by the large contact area available for π-stacking between the aromatic residues of the peptide and the extended surfaces of graphene and the nanotube. The highly curved fullerene surface exhibits reduced efficiency for π-stacking but promotes increased peptide dynamics. We postulate that the increase in conformational dynamics of the amyloid peptide can be unfavorable for the formation of fibril competent structures. In contrast, extended fibril forming peptide conformations are promoted by the nanotube and graphene surfaces which can provide a template for fibril-growth. PMID:24339760

Transport of ARS-labeled hydroxyapatite nanoparticles in saturated granular media is influenced by surface charge variability even in the presence of humic acid.

PubMed

Wang, Dengjun; Bradford, Scott A; Harvey, Ronald W; Hao, Xiuzhen; Zhou, Dongmei

2012-08-30

Hydroxyapatite nanoparticle (nHAP) is increasingly being used to remediate soils and water polluted by metals and radionuclides. The transport and retention of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated granular media. Experiments were carried out over a range of ionic strength (I(c), 0-50mM NaCl) conditions in the presence of 10 mg L(-1) humic acid. The transport of ARS-nHAP was found to decrease with increasing suspension I(c) in part, because of enhanced aggregation and chemical heterogeneity. The retention profiles (RPs) of ARS-nHAP exhibited hyperexponential shapes (a decreasing rate of retention with increasing transport distance) for all test conditions, suggesting that some of the attachment was occurring under unfavorable conditions. Surface charge heterogeneities on the collector surfaces and especially within the ARS-nHAP population were contributing causes for the hyperexponential RPs. Consideration of the effect(s) of I(c) in the presence of HA is needed to improve the efficacy of nHAP for scavenging metals and actinides in real soils and groundwater environments. Copyright © 2012 Elsevier B.V. All rights reserved.

Transport of ARS-labeled hydroxyapatite nanoparticles in saturated granular media is influenced by surface charge variability even in the presence of humic acid

USGS Publications Warehouse

Wang, Dengjun; Bradford, Scott A.; Harvey, Ronald W.; Hao, Xiuzhen; Zhou, Dongmei

2012-01-01

Hydroxyapatite nanoparticle (nHAP) is increasingly being used to remediate soils and water polluted by metals and radionuclides. The transport and retention of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated granular media. Experiments were carried out over a range of ionic strength (Ic, 0–50 mM NaCl) conditions in the presence of 10 mg L−1 humic acid. The transport of ARS-nHAP was found to decrease with increasing suspension Ic in part, because of enhanced aggregation and chemical heterogeneity. The retention profiles (RPs) of ARS-nHAP exhibited hyperexponential shapes (a decreasing rate of retention with increasing transport distance) for all test conditions, suggesting that some of the attachment was occurring under unfavorable conditions. Surface charge heterogeneities on the collector surfaces and especially within the ARS-nHAP population were contributing causes for the hyperexponential RPs. Consideration of the effect(s) of Ic in the presence of HA is needed to improve the efficacy of nHAP for scavenging metals and actinides in real soils and groundwater environments.

Tribological properties of boron nitride synthesized by ion beam deposition

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Spalvins, T.

1985-01-01

The adhesion and friction behavior of boron nitride films on 440 C bearing stainless steel substrates was examined. The thin films containing the boron nitride were synthesized using an ion beam extracted from a borazine plasma. Sliding friction experiments were conducted with BN in sliding contact with itself and various transition metals. It is indicated that the surfaces of atomically cleaned BN coating film contain a small amount of oxides and carbides, in addition to boron nitride. The coefficients of friction for the BN in contact with metals are related to the relative chemical activity of the metals. The more active the metal, the higher is the coefficient of friction. The adsorption of oxygen on clean metal and BN increases the shear strength of the metal - BN contact and increases the friction. The friction for BN-BN contact is a function of the shear strength of the elastic contacts. Clean BN surfaces exhibit relatively strong interfacial adhesion and high friction. The presence of adsorbates such as adventitious carbon contaminants on the BN surfaces reduces the shear strength of the contact area. In contrast, chemically adsorbed oxygen enhances the shear strength of the BN-BN contact and increases the friction.

Surface damage of thin AlN films with increased oxygen content by nanosecond and femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Salakhutdinov, Ildar; Chen, J. K.; Danylyuk, Yuriy; McCullen, Erik; Auner, Gregory

2009-10-01

AlN films deposited on sapphire substrates were damaged by single UV nanosecond (at 248 nm) and IR femtosecond (at 775 nm) laser pulses in air at normal pressure. The films had high (27-35 atomic %) concentration of oxygen introduced into thin surface layer (5-10 nm thickness). We measured damage threshold and studied morphology of the damage sites with atomic force and Nomarski optical microscopes with the objective to determine a correlation between damage processes and oxygen content. The damage produced by nanosecond pulses was accompanied by significant thermal effects with evident signatures of melting, chemical modification of the film surface, and specific redistribution of micro-defect rings around the damage spots. The nanosecond-damage threshold exhibited pronounced increase with increase of the oxygen content. In contrast to that, the femtosecond pulses produced damage without any signs of thermal, thermo-mechanical or chemical effects. No correlation between femtosecond-damage threshold and oxygen content as well as presence of defects within the laser-damage spot was found. We discuss the influence of the oxygen contamination on film properties and related mechanisms responsible for the specific damage effects and morphology of the damage sites observed in the experiments.

Graphene Coating via Chemical Vapor Deposition for Improving Friction and Wear of Gray Cast Iron at Interfaces.

PubMed

Tripathi, Khagendra; Gyawali, Gobinda; Lee, Soo Wohn

2017-09-20

This study reports the influence of CVD-graphene on the tribological performance of gray cast iron (GCI) from the internal combustion engine (ICE) cylinder liners by performing a ball-on-disk friction tests. The graphene-coated specimen exhibited a significant reduction (∼53%) of friction as compared to that of the uncoated specimen, whereas wear resistance increased by 2- and 5-fold regarding the wear of specimen and ball, respectively. Extremely low shear strength and highly lubricating nature of graphene contribute to the formation of a lubricative film between the sliding surfaces and decreases the interaction between surfaces in the dry environment. Under the applied load, a uniform film of iron oxides such as Fe 2 O 3 , Fe 3 O 4 , and FeOOH is found to be formed between the surfaces. It is proposed that the graphene encapsulation with the metal debris and oxides formed between the specimens increases the lubricity and decreases the shear force. The transformation of graphene/graphite into nanocrystalline graphites across the contact interfaces following the amorphization trajectory further increases the lubricity of the film that ultimately reduces friction and wear of the material.

The Extract of Roots of Sophora flavescens Enhances the Recovery of Motor Function by Axonal Growth in Mice with a Spinal Cord Injury.

PubMed

Tanabe, Norio; Kuboyama, Tomoharu; Kazuma, Kohei; Konno, Katsuhiro; Tohda, Chihiro

2015-01-01

Although axonal extension to reconstruct spinal tracts should be effective for restoring function after spinal cord injury (SCI), chondroitin sulfate proteoglycan (CSPG) levels increase at spinal cord lesion sites, and inhibit axonal regrowth. In this study, we found that the water extract of roots of Sophora flavescens extended the axons of mouse cortical neurons, even on a CSPG-coated surface. Consecutive oral administrations of S. flavescens extract to SCI mice for 31 days increased the density of 5-HT-positive axons at the lesion site and improved the motor function. Further, the active constituents in the S. flavescens extract were identified. The water and alkaloid fractions of the S. flavescens extract each exhibited axonal extension activity in vitro. LC/MS analysis revealed that these fractions mainly contain matrine and/or oxymatrine, which are well-known major compounds in S. flavescens. Matrine and oxymatrine promoted axonal extension on the CSPG-coated surface. This study is the first to demonstrate that S. flavescens extract, matrine, and oxymatrine enhance axonal growth in vitro, even on a CSPG-coated surface, and that S. flavescens extract improves motor function and increases axonal density in SCI mice.

Characteristics of Iron-Palladium alloy thin films deposited by magnetron sputtering

NASA Astrophysics Data System (ADS)

Chiu, Y.-J.; Shen, C.-Y.; Chang, H.-W.; Jian, S.-R.

2018-06-01

The microstructural features, magnetic, nanomechanical properties and wettability behaviors of Iron-Palladium (FePd) alloy thin films are investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), nanoindentation and water contact angle (CA) techniques, respectively. The FePd alloy thin films were deposited on glass substrates using a magnetron sputtering system. The post-annealing processes of FePd alloy thin films were carried out at 400 °C and 750 °C and resulted in a significant increase of both the average grain size and surface roughness. The XRD analysis showed that FePd alloy thin films exhibited a predominant (1 1 1) orientation. The magnetic field dependence of magnetization of all FePd thin films are measured at room temperature showed the ferromagnetic characteristics. The nanoindentation with continuous stiffness measurement (CSM) is used to measure the hardness and Young's modulus of present films. The contact angle (θCA) increased with increasing surface roughness. The maximum θCA of 75° was achieved for the FePd alloy thin film after annealing at 750 °C and a surface roughness of 4.2 nm.

Many-body instabilities and mass generation in slow Dirac materials

NASA Astrophysics Data System (ADS)

Triola, Christopher; Zhu, Jian-Xin; Migliori, Albert; Balatsky, Alexander V.

2015-07-01

Some Kondo insulators are expected to possess topologically protected surface states with linear Dirac spectrum: the topological Kondo insulators. Because the bulk states of these systems typically have heavy effective electron masses, the surface states may exhibit extraordinarily small Fermi velocities that could force the effective fine structure constant of the surface states into the strong coupling regime. Using a tight-binding model, we study the many-body instabilities of these systems and identify regions of parameter space in which the system exhibits spin density wave and charge density wave order.

Thin film growth by 3D multi-particle diffusion limited aggregation model: Anomalous roughening and fractal analysis

NASA Astrophysics Data System (ADS)

Nasehnejad, Maryam; Nabiyouni, G.; Gholipour Shahraki, Mehran

2018-03-01

In this study a 3D multi-particle diffusion limited aggregation method is employed to simulate growth of rough surfaces with fractal behavior in electrodeposition process. A deposition model is used in which the radial motion of the particles with probability P, competes with random motions with probability 1 - P. Thin films growth is simulated for different values of probability P (related to the electric field) and thickness of the layer(related to the number of deposited particles). The influence of these parameters on morphology, kinetic of roughening and the fractal dimension of the simulated surfaces has been investigated. The results show that the surface roughness increases with increasing the deposition time and scaling exponents exhibit a complex behavior which is called as anomalous scaling. It seems that in electrodeposition process, radial motion of the particles toward the growing seeds may be an important mechanism leading to anomalous scaling. The results also indicate that the larger values of probability P, results in smoother topography with more densely packed structure. We have suggested a dynamic scaling ansatz for interface width has a function of deposition time, scan length and probability. Two different methods are employed to evaluate the fractal dimension of the simulated surfaces which are "cube counting" and "roughness" methods. The results of both methods show that by increasing the probability P or decreasing the deposition time, the fractal dimension of the simulated surfaces is increased. All gained values for fractal dimensions are close to 2.5 in the diffusion limited aggregation model.

Impact cratering experiments in Bingham materials and the morphology of craters on Mars and Ganymede

NASA Technical Reports Server (NTRS)

Fink, J. H.; Greeley, R.; Gault, D. E.

1982-01-01

Results from a series of laboratory impacts into clay slurry targets are compared with photographs of impact craters on Mars and Ganymede. The interior and ejecta lobe morphology of rampart-type craters, as well as the progression of crater forms seen with increasing diameter on both Mars and Ganymede, are equalitatively explained by a model for impact into Bingham materials. For increasing impact energies and constant target rheology, laboratory craters exhibit a morphologic progression from bowl-shaped forms that are typical of dry planetary surfaces to craters with ejecta flow lobes and decreasing interior relief, characteristic of more volatile-rich planets. A similar sequence is seen for uniform impact energy in slurries of decreasing yield strength. The planetary progressions are explained by assuming that volatile-rich or icy planetary surfaces behave locally in the same way as Bingham materials and produce ejecta slurries with yield strenghs and viscosities comparable to terrestrial debris flows. Hypothetical impact into Mars and Ganymede are compared, and it is concluded that less ejecta would be produced on Ganymede owing to its lower gravitational acceleration, surface temperature, and density of surface materials.

Particle size reduction of Si3N4 with Si3N4 milling hardware

NASA Technical Reports Server (NTRS)

Herbell, T. P.; Freedman, M. R.; Kiser, J. D.

1986-01-01

The grinding of Si3N4 powder using reaction bonded Si3N4 attrition, vibratory, and ball mills with Si3N4 media was examined. The rate of particle size reduction and the change in the chemical composition of the powder were determined in order to compare the grinding efficiency and the increase in impurity content resulting from mill and media wear for each technique. Attrition and vibratory milling exhibited rates of specific surface area increase that were approximately eight times that observed in ball milling. Vibratory milling introduced the greatest impurity pickup.

Coffee-Ring-Free Quantum Dot Thin Film Using Inkjet Printing from a Mixed-Solvent System on Modified ZnO Transport Layer for Light-Emitting Devices.

PubMed

Jiang, Congbiao; Zhong, Zhiming; Liu, Baiquan; He, Zhiwei; Zou, Jianhua; Wang, Lei; Wang, Jian; Peng, JunBiao; Cao, Yong

2016-10-05

Inkjet printing has been considered an available way to achieve large size full-color RGB quantum dots LED display, and the key point is to obtain printed film with uniform and flat surface profile. In this work, mixed solvent of 20 vol % 1,2-dichlorobenzene (oDCB) with cyclohexylbenzene (CHB) was used to dissolve green quantum dots (QDs) with CdSe@ZnS/ZnS core/shell structure. Then, by inkjet printing, a flat dotlike QDs film without the coffee ring was successfully obtained on polyetherimide (PEI)-modified ZnO layer, and the printed dots array exhibited great stability and repeatability. Here, adding oDCB into CHB solutions was used to reduce surface tension, and employing ZnO nanoparticle layer with PEI-modified was used to increase the surface free energy. As a result, a small contact angle is formed, which leads to the enhancement of evaporation rate, and then the coffee ring effect was suppressed. The printed dots with flat surface profile were eventually realized. Moreover, inverted green QD-LEDs with PEI-modified ZnO film as electron transport layer (ETL) and printed green QDs film as emission layer were successfully fabricated. The QD-LEDs exhibited the maximum luminance of 12 000 cd/m 2 and the peak current efficiency of 4.5 cd/A at luminance of 1500 cd/m 2 .

High growth rate hydride vapor phase epitaxy at low temperature through use of uncracked hydrides

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

Schulte, Kevin L.; Braun, Anna; Simon, John

We demonstrate hydride vapor phase epitaxy (HVPE) of GaAs with unusually high growth rates (RG) at low temperature and atmospheric pressure by employing a hydride-enhanced growth mechanism. Under traditional HVPE growth conditions that involve growth from Asx species, RG exhibits a strong temperature dependence due to slow kinetics at the surface, and growth temperatures >750 degrees C are required to obtain RG > 60 um/h. We demonstrate that when the group V element reaches the surface in a hydride, the kinetic barrier is dramatically reduced and surface kinetics no longer limit RG. In this regime, RG is dependent on massmore » transport of uncracked AsH3 to the surface. By controlling the AsH3 velocity and temperature profile of the reactor, which both affect the degree of AsH3 decomposition, we demonstrate tuning of RG. We achieve RG above 60 um/h at temperatures as low as 560 degrees C and up to 110 um/h at 650 degrees C. We incorporate high-RG GaAs into solar cell devices to verify that the electronic quality does not deteriorate as RG is increased. The open circuit voltage (VOC), which is a strong function of non-radiative recombination in the bulk material, exhibits negligible variance in a series of devices grown at 650 degrees C with RG = 55-110 um/h. The implications of low temperature growth for the formation of complex heterostructure devices by HVPE are discussed.« less

High growth rate hydride vapor phase epitaxy at low temperature through use of uncracked hydrides

DOE PAGES

Schulte, Kevin L.; Braun, Anna; Simon, John; ...

2018-01-22

We demonstrate hydride vapor phase epitaxy (HVPE) of GaAs with unusually high growth rates (RG) at low temperature and atmospheric pressure by employing a hydride-enhanced growth mechanism. Under traditional HVPE growth conditions that involve growth from Asx species, RG exhibits a strong temperature dependence due to slow kinetics at the surface, and growth temperatures >750 degrees C are required to obtain RG > 60 um/h. We demonstrate that when the group V element reaches the surface in a hydride, the kinetic barrier is dramatically reduced and surface kinetics no longer limit RG. In this regime, RG is dependent on massmore » transport of uncracked AsH3 to the surface. By controlling the AsH3 velocity and temperature profile of the reactor, which both affect the degree of AsH3 decomposition, we demonstrate tuning of RG. We achieve RG above 60 um/h at temperatures as low as 560 degrees C and up to 110 um/h at 650 degrees C. We incorporate high-RG GaAs into solar cell devices to verify that the electronic quality does not deteriorate as RG is increased. The open circuit voltage (VOC), which is a strong function of non-radiative recombination in the bulk material, exhibits negligible variance in a series of devices grown at 650 degrees C with RG = 55-110 um/h. The implications of low temperature growth for the formation of complex heterostructure devices by HVPE are discussed.« less

Methods for increasing the rate of anammox attachment in a sidestream deammonification MBBR.

PubMed

Klaus, Stephanie; McLee, Patrick; Schuler, Andrew J; Bott, Charles

2016-01-01

Deammonification (partial nitritation-anammox) is a proven process for the treatment of high-nitrogen waste streams, but long startup time is a known drawback of this technology. In a deammonification moving bed biofilm reactor (MBBR), startup time could potentially be decreased by increasing the attachment rate of anammox bacteria (AMX) on virgin plastic media. Previous studies have shown that bacterial adhesion rates can be increased by surface modification or by the development of a preliminary biofilm. This is the first study on increasing AMX attachment rates in a deammonification MBBR using these methods. Experimental media consisted of three different wet-chemical surface treatments, and also media transferred from a full-scale mainstream fully nitrifying integrated fixed-film activated sludge (IFAS) reactor. Following startup of a full-scale deammonification reactor, the experimental media were placed in the full-scale reactor and removed for activity rate measurements and biomass testing after 1 and 2 months. The media transferred from the IFAS process exhibited a rapid increase in AMX activity rates (1.1 g/m(2)/day NH(4)(+) removal and 1.4 g/m(2)/day NO(2)(-) removal) as compared to the control (0.2 g/m(2)/day NH(4)(+) removal and 0.1 g/m(2)/day NO(2)(-) removal) after 1 month. Two out of three of the surface modifications resulted in significantly higher AMX activity than the control at 1 and 2 months. No nitrite oxidizing bacteria activity was detected in either the surface modified media or IFAS media batch tests. The results indicate that startup time of a deammonification MBBR could potentially be decreased through surface modification of the plastic media or through the transfer of media from a mature IFAS process.

The formation of periodic micro/nano structured on stainless steel by femtosecond laser irradiation

NASA Astrophysics Data System (ADS)

Yao, Caizhen; Gao, Wei; Ye, Yayun; Jiang, Yong; Xu, Shizhen; Yuan, Xiaodong

2017-07-01

Stainless steel surface was irradiated by linear polarized laser (800 nm, 35 fs, 4 Hz and 0.7 J/cm2) with different pulse numbers. Environmental scanning electron microscope (ESEM/EDS) was used for detailed morphology, microstructure and composition studies. The wettability of irradiated steel surface was tested by Interface Tensiometer JC-2000X and compared with untreated stainless steel. Results showed that micro/nanostripes with different periods were formed. The period increased with the increasing pulse numbers from 450 nm for 90 pulses to 500 nm for 180 pulses. The orientation of those stripes was parallel with the laser beam polarization. Nanoparticles were observed on those periodic structures. EDS indicated that the atomic ratio of Cr increased and the atomic ratios of Fe and Ni decreased after laser irradiation, which may enhance the corrosion resistance due to the Cr-rich layer. The prepared structure exhibited hydrophobic property without further treatment. The formation mechanism of micro/nanoperiodic structures was also explored.

Critical impact of vegetation physiology on the continental hydrologic cycle in response to increasing CO2

NASA Astrophysics Data System (ADS)

Lemordant, Léo; Gentine, Pierre; Swann, Abigail S.; Cook, Benjamin I.; Scheff, Jacob

2018-04-01

Predicting how increasing atmospheric CO2 will affect the hydrologic cycle is of utmost importance for a range of applications ranging from ecological services to human life and activities. A typical perspective is that hydrologic change is driven by precipitation and radiation changes due to climate change, and that the land surface will adjust. Using Earth system models with decoupled surface (vegetation physiology) and atmospheric (radiative) CO2 responses, we here show that the CO2 physiological response has a dominant role in evapotranspiration and evaporative fraction changes and has a major effect on long-term runoff compared with radiative or precipitation changes due to increased atmospheric CO2. This major effect is true for most hydrological stress variables over the largest fraction of the globe, except for soil moisture, which exhibits a more nonlinear response. This highlights the key role of vegetation in controlling future terrestrial hydrologic response and emphasizes that the carbon and water cycles are intimately coupled over land.

Effect of V/III ratio on the surface morphology and electrical properties of m-plane (10 1 bar 0) GaN homoepitaxial layers

NASA Astrophysics Data System (ADS)

Barry, Ousmane I.; Tanaka, Atsushi; Nagamatsu, Kentaro; Bae, Si-Young; Lekhal, Kaddour; Matsushita, Junya; Deki, Manato; Nitta, Shugo; Honda, Yoshio; Amano, Hiroshi

2017-06-01

We have investigated the effect of V/III ratio on the surface morphology, impurity concentration and electrical properties of m-plane (10 1 bar 0) Gallium Nitride (GaN) homoepitaxial layers. Four-sided pyramidal hillocks are observed on the nominally on-axis m-plane GaN films. Hillocks sizes relatively increase by increasing the V/III ratio. All facets of pyramidal hillocks exhibit well-defined step-terrace features. Secondary ion mass spectrometry depth profiles reveal that carbon impurities decrease by increasing the V/III ratio while the lowest oxygen content is found at an optimized V/III ratio of 900. Vertical Schottky barrier diodes fabricated on the m-GaN samples were characterized. Low leakage current densities of the order of 10-10 A/cm2 at -5 V are obtained at the optimum V/III ratio. Oxygen impurities and screw-component dislocations around hillocks are found to have more detrimental impact on the leakage current mechanism.

Correlation of film thickness to optical band gap of Sol-gel derived Ba0.9Gd0.1TiO3 thin films for optoelectronic applications

NASA Astrophysics Data System (ADS)

Teh, Yen Chin; Saif, Ala'eddin A.; Azhar Zahid Jamal, Zul; Poopalan, Prabakaran

2017-11-01

Ba0.9Gd0.1TiO3 thin films have been fabricated on SiO2/Si and fused silica by sol-gel method. The films are prepared through a spin coating process and annealed at 900 °C to obtain crystallized films. The effect of film thickness on the microstructure and optical band gap has been investigated using X-ray diffractometer, atomic force microscope and ultraviolet-visible spectroscopy, respectively. XRD patterns confirm that the films crystallized with tetragonal phase perovskite structure. The films surface morphology is analysed through amplitude parameter analysis to find out that the grain size and surface roughness are increased with the increase of films thickness. The transmittance and absorbance spectra reveal that all films exhibit high absorption in UV region. The evaluated optical band gap is obtained in the range of 3.67 - 3.78 eV and is found to be decreased as the thickness increase.

The effects of plasma inhomogeneity on the nanoparticle coating in a low pressure plasma reactor

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

Pourali, N.; Foroutan, G.

2015-10-15

A self-consistent model is used to study the surface coating of a collection of charged nanoparticles trapped in the sheath region of a low pressure plasma reactor. The model consists of multi-fluid plasma sheath module, including nanoparticle dynamics, as well as the surface deposition and particle heating modules. The simulation results show that the mean particle radius increases with time and the nanoparticle size distribution is broadened. The mean radius is a linear function of time, while the variance exhibits a quadratic dependence. The broadening in size distribution is attributed to the spatial inhomogeneity of the deposition rate which inmore » turn depends on the plasma inhomogeneity. The spatial inhomogeneity of the ions has strong impact on the broadening of the size distribution, as the ions contribute both in the nanoparticle charging and in direct film deposition. The distribution width also increases with increasing of the pressure, gas temperature, and the ambient temperature gradient.« less

Highly sensitive determination of iron (III) ion based on phenanthroline probe: Surface-enhanced Raman spectroscopy methods

NASA Astrophysics Data System (ADS)

Chen, Lei; Ma, Ning; Park, Yeonju; Jin, Sila; Hwang, Hoon; Jiang, Dayu; Jung, Young Mee

2018-05-01

In this paper, we introduced Raman spectroscopy techniques that were based on the traditional Fe3 + determination method with phenanthroline as a probe. Interestingly, surface-enhanced Raman spectroscopy (SERS)-based approach exhibited excellent sensitivities to phenanthroline. Different detection mechanisms were observed for the RR and SERS techniques, in which the RR intensity increased with increasing Fe3 + concentration due to the observation of the RR effect of the phenanthroline-Fe2 + complex, whereas the SERS intensity increased with decreasing Fe3 + concentration due to the observation of the SERS effect of the uncomplexed phenanthroline. More importantly, the determination sensitivity was substantially improved in the presence of a SERS-active substrate, giving a detection limit as low as 0.001 μg/mL, which is 20 times lower than the limit of the UV-vis and RR methods. Furthermore, the proposed SERS method was free from other ions interference and can be used quality and sensitivity for the determination of the city tap water.

SnO2/TiO2 bilayer thin films exhibiting superhydrophilic properties

NASA Astrophysics Data System (ADS)

Talinungsang, Nibedita Paul; Purkayastha, Debarun Dhar

2017-05-01

Nanostructured thin films of TiO2, SnO2, and SnO2/TiO2 have been deposited by sol-gel method. The films are characterized by X-ray diffraction, wettability and optical properties. In the present work, we have achieved a way of converting hydrophilic to super-hydrophilic state by incorporating TiO2 buffer layer in between substrate and SnO2 film, which has its utility in anti-fogging surfaces. The decrease in contact angle of water over SnO2/TiO2 bilayer is attributed to the increase in roughness of the film as well as surface energy of the substrate.

A novel snowflake-like SnO2 hierarchical architecture with superior gas sensing properties

NASA Astrophysics Data System (ADS)

Li, Yanqiong

2018-02-01

Snowflake-like SnO2 hierarchical architecture has been synthesized via a facile hydrothermal method and followed by calcination. The SnO2 hierarchical structures are assembled with thin nanoflakes blocks, which look like snowflake shape. A possible mechanism for the formation of the SnO2 hierarchical structures is speculated. Moreover, gas sensing tests show that the sensor based on snowflake-like SnO2 architectures exhibited excellent gas sensing properties. The enhancement may be attributed to its unique structures, in which the porous feature on the snowflake surface could further increase the active surface area of the materials and provide facile pathways for the target gas.

Composites with improved fiber-resin interfacial adhesion

NASA Technical Reports Server (NTRS)

Cizmecioglu, Muzaffer (Inventor)

1989-01-01

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

Preparation of robust braid-reinforced poly(vinyl chloride) ultrafiltration hollow fiber membrane with antifouling surface and application to filtration of activated sludge solution.

PubMed

Zhou, Zhuang; Rajabzadeh, Saeid; Fang, Lifeng; Miyoshi, Taro; Kakihana, Yuriko; Matsuyama, Hideto

2017-08-01

Braid-reinforced hollow fiber membranes with high mechanical properties and considerable antifouling surface were prepared by blending poly(vinyl chloride) (PVC) with poly(vinyl chloride-co-poly(ethylene glycol) methyl ether methacrylate) (poly(VC-co-PEGMA)) copolymer via non-solvent induced phase separation (NIPS). The tensile strength of the braid-reinforced PVC hollow fiber membranes were significantly larger than those of previously reported various types of PVC hollow fiber membranes. The high interfacial bonding strength indicated the good compatibility between the coating materials and the surface of polyethylene terephthalate (PET)-braid. Owing to the surface segregation phenomena, the membrane surface PEGMA coverage increased upon increasing the poly(VC-co-PEGMA)/PVC blending ratio, resulting in higher hydrophilicities and bovine serum albumin (BSA) repulsion. To compare the fouling properties, membranes with similar PWPs were prepared by adjusting the dope solution composition to eliminate the effect of hydrodynamic conditions on the membrane fouling performance. The blend membranes surface exhibited considerable fouling resistance to the molecular adsorption from both BSA solution and activated sludge solution. In both cases, the flux recovered to almost 80% of the initial flux using only water backflush. Considering their great mechanical properties and antifouling resistance to activated sludge solution, these novel membranes show good potential for application in wastewater treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface tension and density of liquid In-Sn-Zn alloys

NASA Astrophysics Data System (ADS)

Pstruś, Janusz

2013-01-01

Using the dilatometric method, measurements of the density of liquid alloys of the ternary system In-Sn-Zn in four sections with a constant ratio Sn:In = 24:1, 3:1, 1:1, 1:3, for various Zn additions (5, 10, 14, 20, 3 5, 50 and 75 at.% Zn) were performed at the temperature ranges of 500-1150 K. Density decreases linearly for all compositions. The molar volume calculated from density data exhibits close to ideal dependence on composition. Measurements of the surface tension of liquid alloys have been conducted using the method of maximum pressure in the gas bubbles. There were observed linear dependences on temperature with a negative gradients dσ/dT. Generally, with two exceptions, there was observed the increase of surface tension with increasing content of zinc. Using the Butler's model, the surface tension isotherms were calculated for temperatures T = 673 and 1073 K. Calculations show that only for high temperatures and for low content of zinc (up to about 35 at.%), the modeling is in very good agreement with experiment. Using the mentioned model, the composition of the surface phase was defined at two temperatures T = 673 and 973 K. Regardless of the temperature and of the defined section, the composition of the bulk is very different in comparison with the composition of the surface.

An investigation of phase transformation and crystallinity in laser surface modified H13 steel

NASA Astrophysics Data System (ADS)

Aqida, S. N.; Brabazon, D.; Naher, S.

2013-03-01

This paper presents a laser surface modification process of AISI H13 tool steel using 0.09, 0.2 and 0.4 mm size of laser spot with an aim to increase hardness properties. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). X-ray diffraction analysis (XRD) was conducted to measure crystallinity of the laser-modified surface. X-ray diffraction patterns of the samples were recorded using a Bruker D8 XRD system with Cu K α ( λ=1.5405 Å) radiation. The diffraction patterns were recorded in the 2 θ range of 20 to 80°. The hardness properties were tested at 981 mN force. The laser-modified surface exhibited reduced crystallinity compared to the un-processed samples. The presence of martensitic phase was detected in the samples processed using 0.4 mm spot size. Though there was reduced crystallinity, a high hardness was measured in the laser-modified surface. Hardness was increased more than 2.5 times compared to the as-received samples. These findings reveal the phase source of the hardening mechanism and grain composition in the laser-modified surface.

Nitrogen termination of single crystal (100) diamond surface by radio frequency N{sub 2} plasma process: An in-situ x-ray photoemission spectroscopy and secondary electron emission studies

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

Chandran, Maneesh, E-mail: maneesh@tx.technion.ac.il, E-mail: choffman@tx.technion.ac.il; Shasha, Michal; Michaelson, Shaul

2015-09-14

In this letter, we report the electronic and chemical properties of nitrogen terminated (N-terminated) single crystal (100) diamond surface, which is a promising candidate for shallow NV{sup −} centers. N-termination is realized by an indirect RF nitrogen plasma process without inducing a large density of surface defects. Thermal stability and electronic property of N-terminated diamond surface are systematically investigated under well-controlled conditions by in-situ x-ray photoelectron spectroscopy and secondary electron emission. An increase in the low energy cut-off of the secondary electron energy distribution curve (EDC), with respect to a bare diamond surface, indicates a positive electron affinity of themore » N-terminated diamond. Exposure to atomic hydrogen results in reorganization of N-terminated diamond to H-terminated diamond, which exhibited a negative electron affinity surface. The change in intensity and spectral features of the secondary electron EDC of the N-terminated diamond is discussed.« less

Effect of the Cold-Sprayed Aluminum Coating-Substrate Interface Morphology on Bond Strength for Aircraft Repair Application

NASA Astrophysics Data System (ADS)

Blochet, Quentin; Delloro, Francesco; N'Guyen, Franck; Jeulin, Dominique; Borit, François; Jeandin, Michel

2017-04-01

This article is dealing with the effects of surface preparation of the substrate on aluminum cold-sprayed coating bond strength. Different sets of AA2024-T3 specimens have been coated with pure Al 1050 feedstock powder, using a conventional cold spray coating technique. The sets were grit-blasted (GB) before coating. The study focuses on substrate surface topography evolution before coating and coating-substrate interface morphology after coating. To study coating adhesion by LASAT® technique for each set, specimens with and without preceding GB treatment were tested in load-controlled conditions. Then, several techniques were used to evaluate the effects of substrate surface treatment on the final coating mechanical properties. Irregularities induced by the GB treatment modify significantly the interface morphology. Results showed that particle anchoring was improved dramatically by the presence of craters. The substrate surface was characterized by numerous anchors. Numerical simulation results exhibited the increasing deformation of particle onto the grit-blasted surface. In addition, results showed a strong relationship between the coating-substrate bond strength on the deposited material and surface preparation.

Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

NASA Astrophysics Data System (ADS)

Ford, B.; Heald, C. L.

2013-04-01

We investigate the seasonality in aerosols over the Southeastern United States using observations from several satellite instruments (MODIS, MISR, CALIOP) and surface network sites (IMPROVE, SEARCH, AERONET). We find that the strong summertime enhancement in satellite-observed aerosol optical depth (factor 2-3 enhancement over wintertime AOD) is not present in surface mass concentrations (25-55% summertime enhancement). Goldstein et al. (2009) previously attributed this seasonality in AOD to biogenic organic aerosol; however, surface observations show that organic aerosol only accounts for ~35% of PM2.5 mass and exhibits similar seasonality to total PM2.5. The GEOS-Chem model generally reproduces these surface aerosol measurements, but under represents the AOD seasonality observed by satellites. We show that seasonal differences in water uptake cannot sufficiently explain the magnitude of AOD increase. As CALIOP profiles indicate the presence of additional aerosol in the lower troposphere (below 700 hPa), which cannot be explained by vertical mixing; we conclude that the discrepancy is due to a missing source of aerosols above the surface in summer.

Working Fluids for Increasing Capacities of Heat Pipes

NASA Technical Reports Server (NTRS)

Chao, David F.; Zhang, Nengli

2004-01-01

A theoretical and experimental investigation has shown that the capacities of heat pipes can be increased through suitable reformulation of their working fluids. The surface tensions of all of the working fluids heretofore used in heat pipes decrease with temperature. As explained in more detail below, the limits on the performance of a heat pipe are associated with the decrease in the surface tension of the working fluid with temperature, and so one can enhance performance by reformulating the working fluid so that its surface tension increases with temperature. This improvement is applicable to almost any kind of heat pipe in almost any environment. The heat-transfer capacity of a heat pipe in its normal operating-temperature range is subject to a capillary limit and a boiling limit. Both of these limits are associated with the temperature dependence of surface tension of the working fluid. In the case of a traditional working fluid, the decrease in surface tension with temperature causes a body of the liquid phase of the working fluid to move toward a region of lower temperature, thus preventing the desired spreading of the liquid in the heated portion of the heat pipe. As a result, the available capillary-pressure pumping head decreases as the temperature of the evaporator end of the heat pipe increases, and operation becomes unstable. Water has widely been used as a working fluid in heat pipes. Because the surface tension of water decreases with increasing temperature, the heat loads and other aspects of performance of heat pipes that contain water are limited. Dilute aqueous solutions of long-chain alcohols have shown promise as substitutes for water that can offer improved performance, because these solutions exhibit unusual surface-tension characteristics: Experiments have shown that in the cases of an aqueous solution of an alcohol, the molecules of which contain chains of more than four carbon atoms, the surface tension increases with temperature when the temperature exceeds a certain value. There are also other liquids that have surface tensions that increase with temperature and could be used as working fluids in heat pipes. For example, as a substitute for ammonia, which is the working fluid in some heat pipes, one could use a solution of ammonia and an ionic surfactant.

Effects of the morphology of CIPs on microwave absorption behaviors

NASA Astrophysics Data System (ADS)

Woo, Soobin; Yoo, Chan-Sei; Kim, Hwijun; Lee, Mijung; Quevedo-Lopez, Manuel; Choi, Hyunjoo

2017-11-01

Electromagnetic (EM) wave absorption properties are affected by the thickness and surface area of absorbing materials. In this study, a facile ball-milling process was introduced to effectively reduce the diameter and increase the aspect ratio of carbonyl iron powder (CIP), which is one of the most commercially available EM-absorbing materials. The size, aspect ratio, and consequent surface area of CIP were manipulated by controlling the milling parameters to investigate their effects on EM absorption properties. The results indicated that ball-milled CIPs exhibited better EM wave absorption ability when compared with that of pristine CIPs. However, significant differences in minimum reflection loss values were not observed between CIPs with different morphologies and similar specific surface areas. Hence, both fine and flaky CIPs were considered as beneficial for EM wave absorption.[Figure not available: see fulltext.

Magneto-Fluorescent Core-Shell Supernanoparticles

PubMed Central

Chen, Ou; Riedemann, Lars; Etoc, Fred; Herrmann, Hendrik; Coppey, Mathieu; Barch, Mariya; Farrar, Christian T.; Zhao, Jing; Bruns, Oliver T.; Wei, He; Guo, Peng; Cui, Jian; Jensen, Russ; Chen, Yue; Harris, Daniel K.; Cordero, Jose M.; Wang, Zhongwu; Jasanoff, Alan; Fukumura, Dai; Reimer, Rudolph; Dahan, Maxime; Jain, Rakesh K.; Bawendi, Moungi G.

2014-01-01

Magneto-fluorescent particles have been recognized as an emerging class of materials that exhibit great potential in advanced applications. However, synthesizing such magneto-fluorescent nanomaterials that simultaneously exhibit uniform and tunable sizes, high magnetic content loading, maximized fluorophore coverage at the surface, and a versatile surface functionality has proven challenging. Here we report a simple approach for co-assembling magnetic nanoparticles with fluorescent quantum dots to form colloidal magneto-fluorescent supernanoparticles. Importantly, these supernanoparticles exhibit a superstructure consisting of a close packed magnetic nanoparticle “core” which is fully surrounded by a “shell” of fluorescent quantum dots. A thin layer of silica-coating provides high colloidal stability and biocompatiblity and a versatile surface functionality. We demonstrate that after surface pegylation, these silica-coated magneto-fluorescent supernanoparticles can be magnetically manipulated inside living cells while being optically tracked. Moreover, our silica-coated magneto-fluorescent supernanoparticles can also serve as an in vivo multi-photon and magnetic resonance dual-modal imaging probe. PMID:25298155

Morphological characterization of as-received and in vivo orthodontic stainless steel archwires.

PubMed

Daems, Julie; Celis, Jean-Pierre; Willems, Guy

2009-06-01

This study was undertaken to evaluate the material degradation of clinical bracket-archwire-contacting surfaces after in vivo orthodontic use. Twenty-four stainless steel multiloop edgewise archwires with two different cross sections (0.016 x 0.016 and 0.016 x 0.022 inches) were used for at least 6 months in the mouths of 14 patients. The surfaces of both as-received (cross-section of 0.016 x 0.016, 0.016 x 0.022, and 0.017 x 0.025 inches) and the in vivo wires were examined using scanning electron microscopy. The as-received wires exhibited an inhomogeneous surface with different surface irregularities resulting from the manufacturing process. For the in vivo archwires, an increase in the variety, type, and number of surface irregularities were observed. Crevice corrosion occurred not only at surface irregularities formed during manufacturing and orthodontic handling but also at the bracket-archwire-contacting surfaces and at the archwire surfaces coated with plaque and food remnants. This corrosion may be linked to the formation of a micro-environment at these locations. In addition, a limited number of signs of degradation induced during in vivo testing due to wear and friction were observed.

Fluorogenic Green-Inside Red-Outside (GIRO) Labeling Approach Reveals Adenylyl Cyclase-Dependent Control of BKα Surface Expression

PubMed Central

2015-01-01

The regulation of surface levels of protein is critical for proper cell function and influences properties including cell adhesion, ion channel contributions to current flux, and the sensitivity of surface receptors to ligands. Here we demonstrate a two-color labeling system in live cells using a single fluorogen activating peptide (FAP) based fusion tag, which enables the rapid and simultaneous quantification of surface and internal proteins. In the nervous system, BK channels can regulate neural excitability and neurotransmitter release, and the surface trafficking of BK channels can be modulated by signaling cascades and assembly with accessory proteins. Using this labeling approach, we examine the dynamics of BK channel surface expression in HEK293 cells. Surface pools of the pore-forming BKα subunit were stable, exhibiting a plasma membrane half-life of >10 h. Long-term activation of adenylyl cyclase by forskolin reduced BKα surface levels by 30%, an effect that could not be attributed to increased bulk endocytosis of plasma membrane proteins. This labeling approach is compatible with microscopic imaging and flow cytometry, providing a solid platform for examining protein trafficking in living cells. PMID:26301573

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.

Quantitative assessment of surface functionality effects on microglial uptake and retention of PAMAM dendrimers

NASA Astrophysics Data System (ADS)

Liaw, Kevin; Gök, Ozgul; DeRidder, Louis B.; Kannan, Sujatha; Kannan, Rangaramanujam M.

2018-04-01

Dendrimers are a promising class of polymeric nanoparticles for delivery of therapeutics and diagnostics. Polyamidoamine (PAMAM) dendrimers have shown significant efficacy in many animal models, with performance dependent on surface functionalities. Understanding the effects of end groups on biological interactions is critical for rational design of dendrimer-mediated therapies. In this study, we quantify the cellular trafficking kinetics (endocytosis and exocytosis) of generation 4 neutral (D4-OH), cationic (D4-NH2), anionic (D3.5-COOH), and generation 6 neutral (D6-OH) PAMAM dendrimers to investigate the nanoscale effects of surface functionality and size on cellular interactions. Resting and LPS-activated microglia were studied due to their central roles in dendrimer therapies for central nervous system disorders. D4-OH exhibits greater cellular uptake and lower retention than the larger D6-OH. D4-OH and D3.5-COOH exhibit similar trafficking kinetics, while D4-NH2 exhibits significant membrane interactions, resulting in faster cell association but lower internalization. Cationic charge may also enhance vesicular escape for greater cellular retention and preferential partitioning to nuclei. LPS activation further improves uptake of dendrimers, with smaller and cationic dendrimers experiencing the greatest increases in uptake compared to resting microglia. These studies have implications for the dependence of trafficking pathway on dendrimer properties and inform the design of dendrimer constructs tailored to specific therapeutic needs. Cationic dendrimers are ideal for delivering genetic materials to nuclei, but toxicity may be a limiting factor. Smaller, neutral dendrimers are best suited for delivering high levels of therapeutics in acute neuroinflammation, while larger or cationic dendrimers provide robust retention for sustained release of therapeutics in longer-term diseases.

Electrophilic surface sites as precondition for the chemisorption of pyrrole on GaAs(001) surfaces

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

Bruhn, Thomas; Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Str.9, 12489 Berlin; Fimland, Bjørn-Ove

We report how the presence of electrophilic surface sites influences the adsorption mechanism of pyrrole on GaAs(001) surfaces. For this purpose, we have investigated the adsorption behavior of pyrrole on different GaAs(001) reconstructions with different stoichiometries and thus different surface chemistries. The interfaces were characterized by x-ray photoelectron spectroscopy, scanning tunneling microscopy, and by reflectance anisotropy spectroscopy in a spectral range between 1.5 and 5 eV. On the As-rich c(4 × 4) reconstruction that exhibits only nucleophilic surface sites, pyrrole was found to physisorb on the surface without any significant modification of the structural and electronic properties of the surface. Onmore » the Ga-rich GaAs(001)-(4 × 2)/(6 × 6) reconstructions which exhibit nucleophilic as well as electrophilic surface sites, pyrrole was found to form stable covalent bonds mainly to the electrophilic (charge deficient) Ga atoms of the surface. These results clearly demonstrate that the existence of electrophilic surface sites is a crucial precondition for the chemisorption of pyrrole on GaAs(001) surfaces.« less

Study of oxide surfaces using time of flight positron annihilation induced Auger electron spectroscopy

NASA Astrophysics Data System (ADS)

Nadesalingam, Manori Prasadika

Transition metal oxides (TMOs) exhibit a rich collection of interesting and intriguing properties which can be used for wide variety of applications. In this dissertation, I will discuss the first PAES measurements on vacuum anneal induced changes in the surface layers of Cu2O/Ta, Cu 2O/TCO and oxidized Cu(100) prepared by spray coated, electrochemically deposition and thermal oxidation techniques respectively. PAES measurements on Cu2O/TCO shows that the a very large increase in the intensity of the Cu (M2,3 VV) Auger peak after annealing at 250°C. Similar but significantly smaller changes were observed in the EAES spectra consistent with the fact that PAES is primarily sensitive to the top-most atomic layer due to the fact that the positrons are trapped just outside the surface prior to annihilation while EAES samples several atomic layers. While PAES measurements on oxidized Cu(100) show a large monotonic increase in the intensity of the annihilation induced Cu (M2,3 VV) Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300°C. The intensity then decreases monotonically as the annealing temperature is increase to ˜500°C. These results provide a clear demonstration of the thermal reduction of the copper oxide surface after annealing at 300°C followed by re-oxidation of the copper surface at the higher annealing temperatures presumably due to the diffusion of subsurface oxygen to the surface.

Roughness transitions of diamond(100) induced by hydrogen-plasma treatment

NASA Astrophysics Data System (ADS)

Koslowski, B.; Strobel, S.; Wenig, M. J.; Ziemann, P.

To investigate the influence of hydrogen-plasma treatment on diamond(100) surfaces, heavily boron (B)-doped HPHT diamond crystals were mechanically and chemo-mechanically polished, and exposed to a microwave-assisted hydrogen plasma on a time scale of several minutes. The resulting surface morphology was analyzed on macroscopic scales by stylus profilometry (PFM) and on microscopic scales by STM and AFM. The polished samples have a roughness of typically 100 pmrms (PFM), with no obvious anisotropic structures at the surface. After exposure of the B-doped diamond(100) to the H-plasma, the roughness increases dramatically, and pronounced anisotropic structures appear, these being closely aligned with the crystallographic axis' and planes. An exposure for 3 minutes to the plasma leads to an increase of the roughness to 2-4 nmrms (STM), and a `brick-wall' pattern appears, formed by weak cusps running along <110>. Very frequently, the cusps are replaced by `negative' pyramids that are bordered by {11X} facets. After an exposure of an additional 5 minutes, the surface roughness of the B-doped samples increases further to 20-40 nmrms (STM), and frequently exhibits a regular pattern with structures at a characteristic length scale of about 100 nm. Those structures are aligned approximately with <110> and they are faceted with faces of approximately {XX1}. These results will be discussed in terms of strain relaxation, similar to the surface roughening observed on SiGe/Si and anisotropic etching.

Responses of Surface Runoff to Climate Change and Human Activities in the Arid Region of Central Asia: A Case Study in the Tarim River Basin, China

NASA Astrophysics Data System (ADS)

Xu, Changchun; Chen, Yaning; Chen, Yapeng; Zhao, Ruifeng; Ding, Hui

2013-04-01

Based on hydrological and climatic data and land use/cover change data covering the period from 1957 to 2009, this paper investigates the hydrological responses to climate change and to human activities in the arid Tarim River basin (TRB). The results show that the surface runoff of three headstreams (Aksu River, Yarkant River and Hotan River) of the Tarim River exhibited a significant increasing trend since 1960s and entered an even higher-runoff stage in 1994. In the contrary, the surface runoff of Tarim mainstream displayed a persistent decreasing trend since 1960s. The increasing trend of surface runoff in the headstreams can be attributed to the combined effects of both temperature and precipitation changes during the past five decades. But, the decreasing trend of surface runoff in the mainstream and the observed alterations of the temporal and spatial distribution patterns were mainly due to the adverse impacts of human activities. Specifically, increasingly intensified water consumption for irrigation and the associated massive constructions of water conservancy projects were responsible for the decreasing trend of runoff in the mainstream. And, the decreasing trend has been severely jeopardizing the ecological security in the lower reaches. It is now unequivocally clear that water-use conflicts among different sectors and water-use competitions between upper and lower reaches are approaching to dangerous levels in TRB that is thus crying for implementing an integrated river basin management scheme.

Responses of surface runoff to climate change and human activities in the arid region of central Asia: a case study in the Tarim River basin, China.

PubMed

Xu, Changchun; Chen, Yaning; Chen, Yapeng; Zhao, Ruifeng; Ding, Hui

2013-04-01

Based on hydrological and climatic data and land use/cover change data covering the period from 1957 to 2009, this paper investigates the hydrological responses to climate change and to human activities in the arid Tarim River basin (TRB). The results show that the surface runoff of three headstreams (Aksu River, Yarkant River and Hotan River) of the Tarim River exhibited a significant increasing trend since 1960s and entered an even higher-runoff stage in 1994. In the contrary, the surface runoff of Tarim mainstream displayed a persistent decreasing trend since 1960s. The increasing trend of surface runoff in the headstreams can be attributed to the combined effects of both temperature and precipitation changes during the past five decades. But, the decreasing trend of surface runoff in the mainstream and the observed alterations of the temporal and spatial distribution patterns were mainly due to the adverse impacts of human activities. Specifically, increasingly intensified water consumption for irrigation and the associated massive constructions of water conservancy projects were responsible for the decreasing trend of runoff in the mainstream. And, the decreasing trend has been severely jeopardizing the ecological security in the lower reaches. It is now unequivocally clear that water-use conflicts among different sectors and water-use competitions between upper and lower reaches are approaching to dangerous levels in TRB that is thus crying for implementing an integrated river basin management scheme.

Variation with thermal cycling in microstructure and area specific resistance of a ferritic stainless steel having rough surfaces

NASA Astrophysics Data System (ADS)

Song, Myoung Youp; Mumm, Daniel R.; Song, Jiunn

2013-03-01

Crofer22 APU specimens were prepared by grinding with grit 120 and 400 SiC grinding papers, and were then thermally cycled. The variation in oxidation behavior with thermal cycling was then investigated. Observation of microstructures, measurement of area-specific resistance (ASR), analysis of the atomic percentages of the elements by EDX, and XRD analysis were performed. XRD patterns showed that the (Cr, Mn)3O4 spinel phase grew on the surface of the Crofer22 APU samples ground using grit 120. For the samples ground with grit 400, ASR increased as the number of thermal cycles ( n) increased. Plots of ln (ASR/T) vs. 1/ T for the samples ground with grit 400 after n = 4, 20, and 40 exhibited good linearity, and the apparent activation energies were between 73.4 kJ/mole and 82.5 kJ/mole.