plasma surface activation: Topics by Science.gov

Sample records for plasma surface activation

Atmospheric-pressure plasma activation and surface characterization on polyethylene membrane separator

NASA Astrophysics Data System (ADS)

Tseng, Yu-Chien; Li, Hsiao-Ling; Huang, Chun

2017-01-01

The surface hydrophilic activation of a polyethylene membrane separator was achieved using an atmospheric-pressure plasma jet. The surface of the atmospheric-pressure-plasma-treated membrane separator was found to be highly hydrophilic realized by adjusting the plasma power input. The variations in membrane separator chemical structure were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Chemical analysis showed newly formed carbonyl-containing groups and high surface concentrations of oxygen-containing species on the atmospheric-pressure-plasma-treated polymeric separator surface. It also showed that surface hydrophilicity primarily increased from the polar component after atmospheric-pressure plasma treatment. The surface and pore structures of the polyethylene membrane separator were examined by scanning electron microscopy, revealing a slight alteration in the pore structure. As a result of the incorporation of polar functionalities by atmospheric-pressure plasma activation, the electrolyte uptake and electrochemical impedance of the atmospheric-pressure-plasma-treated membrane separator improved. The investigational results show that the separator surface can be controlled by atmospheric-pressure plasma surface treatment to tailor the hydrophilicity and enhance the electrochemical performance of lithium ion batteries.
Contact activation of blood-plasma coagulation

NASA Astrophysics Data System (ADS)

Golas, Avantika

Surface engineering of biomaterials with improved hemocompatibility is an imperative, given the widespread global need for cardiovascular devices. Research summarized in this dissertation focuses on contact activation of FXII in buffer and blood plasma frequently referred to as autoactivation. The extant theory of contact activation imparts FXII autoactivation ability to negatively charged, hydrophilic surfaces. According to this theory, contact activation of plasma involves assembly of proteins comprising an "activation complex" on activating surfaces mediated by specific chemical interactions between complex proteins and the surface. This work has made key discoveries that significantly improve our core understanding of contact activation and unravel the existing paradigm of plasma coagulation. It is shown herein that contact activation of blood factor XII (FXII, Hageman factor) in neat-buffer solution exhibits a parabolic profile when scaled as a function of silanized-glass-particle activator surface energy (measured as advancing water adhesion tension t°a=g° Iv costheta in dyne/cm, where g°Iv is water interfacial tension in dyne/cm and theta is the advancing contact angle). Nearly equal activation is observed at the extremes of activator water-wetting properties --36 < t°a < 72 dyne/cm (O° ≤ theta < 120°), falling sharply through a broad minimum within the 20 < t°a < 40 dyne/cm (55° < theta < 75°). Furthermore, contact activation of FXII in buffer solution produces an ensemble of protein fragments exhibiting either procoagulant properties in plasma (proteolysis of blood factor XI or prekallikrein), amidolytic properties (cleavage of s-2302 chromogen), or the ability to suppress autoactivation through currently unknown biochemistry. The relative proportions of these fragments depend on activator surface chemistry/energy. We have also discovered that contact activation is moderated by adsorption of plasma proteins unrelated to coagulation through an "adsorption-dilution" effect that blocks FXII contact with hydrophobic activator surfaces. The adsorption-dilution effect explains the apparent specificity for hydrophilic activators pursued by earlier investigators. Finally a comparison of FXII autoactivation in buffer, serum, protein cocktail, and plasma solutions is shown herein. Activation of blood plasma coagulation in vitro by contact with material surfaces is demonstrably dependent on plasma-volume-to-activator-surface-area ratio. However, activation of factor XII dissolved in buffer, protein cocktail, heat-denatured serum, and FXI deficient plasma does not exhibit activator surface-area dependence. Instead, a highly-variable burst of procoagulant-enzyme yield is measured that exhibits no measurable kinetics, sensitivity to mixing, or solution-temperature dependence. Thus, FXII activation in both buffer and protein-containing solutions does not exhibit characteristics of a biochemical reaction but rather appears to be a "mechanochemical" reaction induced by FXII molecule interactions with hydrophilic activator particles that do not formally adsorb blood proteins from solution. Results strongly suggest that activator surface-area dependence observed in contact activation of plasma coagulation does not solely arise at the FXII activation step of the intrinsic pathway.
Contact Activation of Blood Plasma and Factor XII by Ion-exchange Resins

PubMed Central

Yeh, Chyi-Huey Josh; Dimachkie, Ziad O.; Golas, Avantika; Cheng, Alice; Parhi, Purnendu; Vogler, Erwin A.

2011-01-01

Sepharose ion-exchange particles bearing strong Lewis acid/base functional groups (sulfopropyl, carboxymethyl, quarternary ammonium, dimethyl aminoethyl, and iminodiacetic acid) exhibiting high plasma protein adsorbent capacities are shown to be more efficient activators of blood factor XII in neat-buffer solution than either hydrophilic clean-glass particles or hydrophobic octyl sepharose particles ( FXII→surfaceactivatorFXIIa; a.k.a autoactivation, where FXII is the zymogen and FXIIa is a procoagulant protease). In sharp contrast to the clean-glass standard of comparison, ion-exchange activators are shown to be inefficient activators of blood plasma coagulation. These contrasting activation properties are proposed to be due to the moderating effect of plasma-protein adsorption on plasma coagulation. Efficient adsorption of blood plasma proteins unrelated to the coagulation cascade impedes FXII contacts with ion-exchange particles immersed in plasma, reducing autoactivation, and causing sluggish plasma coagulation. By contrast, plasma proteins do not adsorb to hydrophilic clean glass and efficient autoactivation leads directly to efficient activation of plasma coagulation. It is also shown that competitive-protein adsorption can displace FXIIa adsorbed to the surface of ion-exchange resins. As a consequence of highly-efficient autoactivation and FXIIa displacement by plasma proteins, ion-exchange particles are slightly more efficient activators of plasma coagulation than hydrophobic octyl sepharose particles that do not bear strong Lewis acid/base surface functionalities but to which plasma proteins adsorb efficiently. Plasma proteins thus play a dual role in moderating contact activation of the plasma coagulation cascade. The principal role is impeding FXII contact with activating surfaces but this same effect can displace FXIIa from an activating surface into solution where the protease can potentiate subsequent steps of the plasma coagulation cascade. PMID:21982294
Effect of plasma-induced surface charging on catalytic processes: application to CO2 activation

NASA Astrophysics Data System (ADS)

Bal, Kristof M.; Huygh, Stijn; Bogaerts, Annemie; Neyts, Erik C.

2018-02-01

Understanding the nature and effect of the multitude of plasma-surface interactions in plasma catalysis is a crucial requirement for further process development and improvement. A particularly intriguing and rather unique property of a plasma-catalytic setup is the ability of the plasma to modify the electronic structure, and hence chemical properties, of the catalyst through charging, i.e. the absorption of excess electrons. In this work, we develop a quantum chemical model based on density functional theory to study excess negative surface charges in a heterogeneous catalyst exposed to a plasma. This method is specifically applied to investigate plasma-catalytic CO2 activation on supported M/Al2O3 (M = Ti, Ni, Cu) single atom catalysts. We find that (1) the presence of a negative surface charge dramatically improves the reductive power of the catalyst, strongly promoting the splitting of CO2 to CO and oxygen, and (2) the relative activity of the investigated transition metals is also changed upon charging, suggesting that controlled surface charging is a powerful additional parameter to tune catalyst activity and selectivity. These results strongly point to plasma-induced surface charging of the catalyst as an important factor contributing to the plasma-catalyst synergistic effects frequently reported for plasma catalysis.
Immobilization of Active Bacteriophages on Polyhydroxyalkanoate Surfaces.

PubMed

Wang, Chanchan; Sauvageau, Dominic; Elias, Anastasia

2016-01-20

A rapid, efficient technique for the attachment of bacteriophages (phages) onto polyhydroxyalkanoate (PHA) surfaces has been developed and compared to three reported methods for phage immobilization. Polymer surfaces were modified to facilitate phage attachment using (1) plasma treatment alone, (2) plasma treatment followed by activation by 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (sulfo-NHS), (3) plasma-initiated acrylic acid grafting, or (4) plasma-initiated acrylic acid grafting with activation by EDC and sulfo-NHS. The impact of each method on the surface chemistry of PHA was investigated using contact angle analysis and X-ray photoelectron spectroscopy. Each of the four treatments was shown to result in both increased hydrophilicity and in the modification of the surface functional groups. Modified surfaces were immersed in suspensions of phage T4 for immobilization. The highest level of phage binding was observed for the surfaces modified by plasma treatment alone. The change in chemical bond states observed for surfaces that underwent plasma treatment is suspected to be the cause of the increased binding of active phages. Plasma-treated surfaces were further analyzed through phage-staining and fluorescence microscopy to assess the surface density of immobilized phages and their capacity to capture hosts. The infective capability of attached phages was confirmed by exposing the phage-immobilized surfaces to the host bacteria Escherichia coli in both plaque and infection dynamic assays. Plasma-treated surfaces with immobilized phages displayed higher infectivity than surfaces treated with other methods; in fact, the equivalent initial multiplicity of infection was 2 orders of magnitude greater than with other methods. Control samples - prepared by immersing polymer surfaces in phage suspensions (without prior plasma treatment) - did not show any bacterial growth inhibition, suggesting they did not bind phages from the suspension.
A Comparison of Blood Factor XII Autoactivation in Buffer, Protein Cocktail, Serum, and Plasma Solutions

PubMed Central

Golas, Avantika; Yeh, Chyi-Huey Josh; Pitakjakpipop, Harit; Siedlecki, Christopher A.; Vogler, Erwin A.

2012-01-01

Activation of blood plasma coagulation in vitro by contact with material surfaces is demonstrably dependent on plasma-volume-to-activator-surface-area ratio. The only plausible explanation consistent with current understanding of coagulation-cascade biochemistry is that procoagulant stimulus arising from the activation complex of the intrinsic pathway is dependent on activator surface area. And yet, it is herein shown that activation of the blood zymogen factor XII (Hageman factor, FXII) dissolved in buffer, protein cocktail, heat-denatured serum, and FXI deficient plasma does not exhibit activator surface-area dependence. Instead, a highly-variable burst of procoagulant-enzyme yield is measured that exhibits no measurable kinetics, sensitivity to mixing, or solution-temperature dependence. Thus, FXII activation in both buffer and protein-containing solutions does not exhibit characteristics of a biochemical reaction but rather appears to be a “mechanochemical” reaction induced by FXII molecule interactions with hydrophilic activator particles that do not formally adsorb blood proteins from solution. Results of this study strongly suggest that activator surface-area dependence observed in contact activation of plasma coagulation does not solely arise at the FXII activation step of the intrinsic pathway. PMID:23117212
Fabrication of silicon-on-diamond substrate with an ultrathin SiO2 bonding layer

NASA Astrophysics Data System (ADS)

Nagata, Masahiro; Shirahama, Ryouya; Duangchan, Sethavut; Baba, Akiyoshi

2018-06-01

We proposed and demonstrated a sputter etching method to prepare both a flat surface (root-mean-square surface roughness of approximately 0.2–0.3 nm) and an ultrathin SiO2 bonding layer at an accuracy of approximately 5 nm in thickness to fabricate a silicon-on-diamond substrate (SOD). We also investigated a plasma activation method on a SiO2 surface using various gases. We found that O2 plasma activation is more suitable for the bonding between SiO2 and Si than N2 or Ar plasma activation. We speculate that the concentration of hydroxyl groups on the SiO2 surface was increased by O2 plasma activation. We fabricated the SOD substrate with an ultrathin (15 nm in thickness) SiO2 bonding layer using the sputter etching and O2 plasma activation methods.
Particulate contamination removal from wafers using plasmas and mechanical agitation

DOEpatents

Selwyn, G.S.

1998-12-15

Particulate contamination removal from wafers is disclosed using plasmas and mechanical agitation. The present invention includes the use of plasmas with mechanical agitation for removing particulate matter from the surface of a wafer. The apparatus hereof comprises a mechanical activator, at least one conducting contact pin for transferring the vibration from the activator to the wafer, clamp fingers that maintain the wafer`s position, and means for generating a plasma in the vicinity of the surface of the wafer, all parts of the cleaning apparatus except the mechanical activator and part of the contact pin being contained inside the processing chamber. By exposing a wafer to a plasma and providing motion thereto in a direction perpendicular to its surface, the bonding between the particulate matter and the surface may be overcome. Once free of the wafer surface, the particulates become charged by electrons from the plasma and are drawn into the plasma by attractive forces which keep them from redepositing. The introduction of a flowing gas through the plasma sweeps the particulates away from the wafer and out of the plasma. The entire surface is cleaned during one cleaning step. The use of an rf plasma to accomplish the particulate removal was found to remove more than 90% of the particulates. 4 figs.
Particulate contamination removal from wafers using plasmas and mechanical agitation

DOEpatents

Selwyn, Gary S.

1998-01-01

Particulate contamination removal from wafers using plasmas and mechanical agitation. The present invention includes the use of plasmas with mechanical agitation for removing particulate matter from the surface of a wafer. The apparatus hereof comprises a mechanical activator, at least one conducting contact pin for transferring the vibration from the activator to the wafer, clamp fingers that maintain the wafer's position, and means for generating a plasma in the vicinity of the surface of the wafer, all parts of the cleaning apparatus except the mechanical activator and part of the contact pin being contained inside the processing chamber. By exposing a wafer to a plasma and providing motion thereto in a direction perpendicular to its surface, the bonding between the particulate matter and the surface may be overcome. Once free of the wafer surface, the particulates become charged by electrons from the plasma and are drawn into the plasma by attractive forces which keep them from redepositing. The introduction of a flowing gas through the plasma sweeps the particulates away from the wafer and out of the plasma. The entire surface is cleaned during one cleaning step. The use of an rf plasma to accomplish the particulate removal was found to remove more than 90% of the particulates.
Application of atmospheric pressure plasma in polymer and composite adhesion

NASA Astrophysics Data System (ADS)

Yu, Hang

An atmospheric pressure helium and oxygen plasma was used to investigate surface activation and bonding in polymer composites. This device was operated by passing 1.0-3.0 vol% of oxygen in helium through a pair of parallel plate metal electrodes powered by 13.56 or 27.12 MHz radio frequency power. The gases were partially ionized between the capacitors where plasma was generated. The reactive species in the plasma were carried downstream by the gas flow to treat the substrate surface. The temperature of the plasm gas reaching the surface of the substrate did not exceed 150 °C, which makes it suitable for polymer processing. The reactive species in the plasma downstream includes ~ 1016-1017 cm-3 atomic oxygen, ~ 1015 cm-3 ozone molecule, and ~ 10 16 cm-3 metastable oxygen molecule (O2 1Deltag). The substrates were treated at 2-5 mm distance from the exit of the plasma. Surface properties of the substrates were characterized using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). Subsequently, the plasma treated samples were bonded adhesively or fabricated into composites. The increase in mechanical strength was correlated to changes in the material composition and structure after plasma treatment. The work presented hereafter establishes atmospheric pressure plasma as an effective method to activate and to clean the surfaces of polymers and composites for bonding. This application can be further expanded to the activation of carbon fibers for better fiber-resin interactions during the fabrication of composites. Treating electronic grade FR-4 and polyimide with the He/O2 plasma for a few seconds changed the substrate surface from hydrophobic to hydrophilic, which allowed complete wetting of the surface by epoxy in underfill applications. Characterization of the surface by X-ray photoelectron spectroscopy shows formation of oxygenated functional groups, including hydroxyl, carbonyl, and carboxyl groups, on the polymer surface after plasma treatment. The resulting strength of the bond based on lap-shear and T-peel tests correlates well with the concentration of oxygen on the polymer surface. The failure modes observed for lap-shear and T-peel tests changed from interfacial to cohesive after the plasma activation. Treating carbon-fiber-reinforced epoxy composites with the atmospheric plasma resulted in the removal of fluorinated contaminants in shallow surface layers. For contaminants that diffused deeply into the composite surface, mechanical abrasion was needed in addition to the plasma treatment to remove the impurities. While cleaning the composite, plasma also generated active oxygen groups on the substrate surface. The presence of these groups improved the adhesive bonding strength of the composite even in the presence of residual fluorine contaminants. Thus, it was speculated that plasma treatment can promote better polymer adhesion with or without fluorine contamination. Carbon nanotube sheets were also treated by the helium oxygen plasma, and the CNT surface turn from super hydrophobic to hydrophilic after a few seconds of exposure. The nanotube surface contained 15% of oxygen in the form of hydroxyl groups. Chemical coupling agents were added to the plasma activated CNT surfaces in order to crosslink the CNTs and to create bonding sites for the resin matrix. Stretched, activated and functionalized CNT was cured with dicyclopentadiene (DCPD) to produce a sheet composite with a tensile strength of 636 MPa, a modulus of 28 GPa, and a density of 1.4 g/cm 3. This may be compared to aerospace-grade aluminum with tensile strength of 572 MPa, modulus of 72 GPa, and density of 2.7 g/cm3. This work demonstrates that new high-strength composite can be produced with the use of atmospheric plasma activation and chemical crosslinking of the fiber matrix.
Immobilization of β-galactosidase from Kluyveromyces lactis onto polymeric membrane surfaces: effect of surface characteristics.

PubMed

Güleç, Hacı Ali

2013-04-01

The aim of this study was to investigate the effects of surface characteristics of plain and plasma modified cellulose acetate (CA) membranes on the immobilization yield of β-galactosidases from Kluyveromyces lactis (KLG) and its galacto-oligosaccharide (GOS) yield, respectively. Low pressure plasma treatments involving oxygen plasma activation, plasma polymerization (PlsP) of ethylenediamine (EDA) and PlsP of 2-mercaptoethanol were used to modify plain CA membrane surfaces. KLG enzyme was immobilized onto plain and oxygen plasma treated membrane surfaces by simple adsorption. Oxygen plasma activation increased the hydrophylicity of CA membrane surfaces and it improved the immobilization yield of the enzyme by 42%. KLG enzyme was also immobilized onto CA membrane surfaces through amino groups created by PlsP of EDA via covalent binding. Plasma action at 60W plasma power and 15 min. exposure time improved the amount of membrane bounded enzyme by 3.5-fold. The enrichment of the amount of amino groups via polyethyleneimine (PEI) addition enhanced this increase from 3.5-fold to 4.5-fold. Although high enzyme loading was achived (65-83%), both of the methods dramatically decreased the enzyme activity (11-12%) and GOS yield due to probably negative effects of active amino groups. KLG enzyme was more effectively immobilized onto thiolated CA membrane surface created by PlsP of 2-mercaptoethanol with high immobilization yield (70%) and especially high enzyme activity (46%). Immobilized enzymes on the CA membranes treated by PlsP were successively reutilized for 5-8 cycles at 25°C and enzymatic derivatives retained approximately 75-80% of their initial activites at the end of the reactions. Copyright © 2012 Elsevier B.V. All rights reserved.
Adhesion enhancement of Al coatings on carbon/epoxy composite surfaces by atmospheric plasma

NASA Astrophysics Data System (ADS)

Coulon, J. F.; Tournerie, N.; Maillard, H.

2013-10-01

Adhesion strengths between aluminium thin film coatings and manufactured carbon/epoxy composite surfaces were measured by assessing fracture tensile strengths using pull-off tests. The effect of the substrate roughness (nm to μm) of these composite surfaces on adhesion was studied by examining the surface free energies and adhesion strengths. The adhesion strengths of the coatings varied significantly. To improve the coating adhesion, each composite surface was treated with atmospheric plasma prior to deposition, which resulted in an increase in the surface free energy from approximately 40 mJ/m2 to 70 mJ/m2 because the plasma pretreatment led to the formation of hydrophilic Csbnd O and Cdbnd O bonds on the composite surfaces, as demonstrated by X-ray photoelectron spectroscopy analyses. The adhesion strengths of the coatings were enhanced for all surface roughnesses studied. In our study, the effect of mechanical adhesion due to roughness was separated from the effect of modifying the chemical bonds with plasma activation. The adhesion ability of the pure resin was relatively weak. Increasing the surface roughness largely improved the adhesion of the resin surface. Plasma treatment of the pure resin also increased the surface adhesion. Our study shows that plasma activation effectively enhances the adhesion of manufactured composites, even when the surface roughness is on the order of microns. The ageing of the surface activation was also investigated, and the results demonstrate that atmospheric plasma has potential for use in the pretreatment of composite materials.
Surface-mediated molecular events in material-induced blood-plasma coagulation

NASA Astrophysics Data System (ADS)

Chatterjee, Kaushik

Coagulation and thrombosis persist as major impediments associated with the use of blood-contacting medical devices. We are investigating the molecular mechanism underlying material-induced blood-plasma coagulation focusing on the role of the surface as a step towards prospective development of improved hemocompatible biomaterials. A classic observation in hematology is that blood/blood-plasma in contact with clean glass surface clots faster than when in contact with many plastic surfaces. The traditional biochemical theory explaining the underlying molecular mechanism suggests that hydrophilic surfaces, like that of glass, are specific activators of the coagulation cascade because of the negatively-charged groups on the surface. Hydrophobic surfaces are poor procoagulants or essentially "benign" because they lack anionic groups. Further, these negatively-charged surfaces are believed to not only activate blood factor XII (FXII), the key protein in contact activation, but also play a cofactor role in the amplification and propagation reactions that ultimately lead to clot formation. In sharp contrast to the traditional theory, our investigations indicate a need for a paradigm shift in the proposed sequence of contact activation events to incorporate the role of protein adsorption at the material surfaces. These studies have lead to the central hypothesis for this work proposing that protein adsorption to hydrophobic surfaces attenuates the contact activation reactions so that poorly-adsorbent hydrophilic surfaces appear to be stronger procoagulants relative to hydrophobic surfaces. Our preliminary studies measuring the plasma coagulation response of activated FXII (FXIIa) on different model surfaces suggested that the material did not play a cofactor role in the processing of this enzyme dose through the coagulation pathway. Therefore, we focused our efforts on studying the mechanism of initial production of enzyme at the procoagulant surface. Calculations for the amounts of FXIIa generated at material surfaces in plasma using a mathematical model for measured coagulation responses indicate that the relative contributions of the individual pathways of enzyme generation are similar at both hydrophilic and hydrophobic surfaces, only the amounts of enzyme generated scale with surface energy and area of the activating surface. Further, from direct measurement of enzyme activation at test surfaces we observed that contact activation reactions are not specific to negatively-charged hydrophilic surfaces. Rather, the molecular interactions are attenuated at hydrophobic surfaces due to protein adsorption so that poorly-adsorbent hydrophilic surfaces exhibit an apparent specificity for contact activation reactions. Preliminary studies were preformed to assay the plasma coagulation response to low-fouling surfaces prepared by either grafting poly(ethylene glycol) chains or using zwitterions. Results indicate that poly(ethylene glycol)-modified surfaces are significantly weaker procoagulants than surfaces containing zwitterions underscoring a need to specifically evaluate the coagulation response despite similarities in observed protein adsorption to both surfaces. In summary, our studies demonstrate a need to incorporate protein-adsorption competition at procoagulant surfaces into the mechanism of contact activation to account for the observed moderation of FXII activation by blood proteins unrelated to the plasma coagulation cascade.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowman, Adam J.; Scherrer, Joseph R.; Reiserer, Ronald S., E-mail: ron.reiserer@vanderbilt.edu

We present a simple apparatus for improved surface modification of polydimethylsiloxane (PDMS) microfluidic devices. A single treatment chamber for plasma activation and chemical/physical vapor deposition steps minimizes the time-dependent degradation of surface activation that is inherent in multi-chamber techniques. Contamination and deposition irregularities are also minimized by conducting plasma activation and treatment phases in the same vacuum environment. An inductively coupled plasma driver allows for interchangeable treatment chambers. Atomic force microscopy confirms that silane deposition on PDMS gives much better surface quality than standard deposition methods, which yield a higher local roughness and pronounced irregularities in the surface.
Influence of Chemical Precleaning on the Plasma Treatment Efficiency of Aluminum by RF Plasma Pencil

NASA Astrophysics Data System (ADS)

Vadym, Prysiazhnyi; Pavel, Slavicek; Eliska, Mikmekova; Milos, Klima

2016-04-01

This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces. The results of our study showed that the state of the topmost surface layer (i.e. the surface morphology and chemical groups) of plasma modified aluminum significantly depends on the chemical precleaning. Commonly used chemicals (isopropanol, trichlorethane, solution of NaOH in deionized water) were used as precleaning agents. The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University, which operates in Ar, Ar/O2 gas mixtures. The effectiveness of the plasma treatment was estimated by the wettability measurements, showing high wettability improvement already after 0.3 s treatment. The effects of surface cleaning (hydrocarbon removal), surface oxidation and activation (generation of OH groups) were estimated using infrared spectroscopy. The changes in the surface morphology were measured using scanning electron microscopy. Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.
Surface Modification by Atmospheric Pressure Plasma for Improved Bonding

NASA Astrophysics Data System (ADS)

Williams, Thomas Scott

An atmospheric pressure plasma source operating at temperatures below 150?C and fed with 1.0-3.0 volume% oxygen in helium was used to activate the surfaces of the native oxide on silicon, carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024. Helium and oxygen were passed through the plasma source, whereby ionization occurred and ˜10 16 cm-3 oxygen atoms, ˜1015 cm -3 ozone molecules and ˜1016 cm-3 metastable oxygen molecules (O21Deltag) were generated. The plasma afterglow was directed onto the substrate material located 4 mm downstream. Surface properties of the plasma treated materials have been investigated using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and x-ray photoelectron spectroscopy (XPS). The work presented herein establishes atmospheric-pressure plasma as a surface preparation technique that is well suited for surface activation and enhanced adhesive bond strength in a variety of materials. Atmospheric plasma activation presents an environmentally friendly alternative to wet chemical and abrasive methods of surface preparation. Attenuated total internal reflection infrared spectroscopy was used to study the aging mechanism of the native oxide on silicon. During storage at ambient conditions, the water contact angle of a clean surface increased from <5° to 40° over a period of 12 hours. When stored under a nitrogen purge, the water contact angle of a clean surface increased from <5° to 30° over a period of 40-60 hours. The change in contact angle resulted from the adsorption of nonanal onto the exposed surface hydroxyl groups. The rate of adsorption of nonanal under a nitrogen purged atmosphere ranged from 0.378+/-0.011 hr-1 to 0.182+/-0.008 hr -1 molecules/(cm2•s), decreasing as the fraction of hydrogen-bonded hydroxyl groups increased from 49% to 96% on the SiO 2 surface. The adsorption of the organic contaminant could be suppressed indefinitely by storing the silicon wafers in the presence of activated carbon or in a freezer at -22°C. The enhancement of adhesive bond strength and durability for carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024 was demonstrated with the atmospheric pressure helium-oxygen plasma. All surfaces studied were converted from a hydrophobic state with a water contact angle of 65° to 80° into a hydrophilic state with a water contact angle between 20° and 40° within 5 seconds of plasma exposure. X-ray photoelectron spectroscopy confirmed that the carbon atoms on the carbon-fiber/epoxy composite were oxidized, yielding 17 atom% carboxylic acid groups, 10% ketones or aldehydes and 9% alcohols. Analysis of stainless steel and aluminum by XPS illustrate oxidation of the metal surface and an increase in the concentration of hydroxyl groups in the oxide film. Following plasma activation, the total hydroxyl species concentration on stainless steel increased from 31% to 57%, while aluminum exhibited an increase from 4% to 16% hydroxyl species. Plasma activation of the surface led to an increase in bond strength of the different surfaces by up to 150% when using Cytec FM300 and FM300-2 epoxy adhesives. Wedge crack extension tests following plasma activation revealed cohesive failure percentages of 97% for carbon-fiber/epoxy composite bonded to stainless steel, and 96% for aluminum bonded to itself. The bond strength and durability of the substrates correlated with changes in the specific surface chemistry, not the wetting angle or the morphological properties of the material. This suggests that enhanced chemical bonding at the interface was responsible for the improvement in mechanical properties following plasma activation. The surface preparation of polymers and composites using atmospheric pressure plasmas is a promising technique for replacing traditional methods of surface preparation by sanding, grit blasting or peel ply. After oxygen plasma activation and joining the materials together with epoxy, one observes 100% cohesive failure within the cured film adhesive. Depending on the material, the lap shear strength can be increased several fold over that achieved by either solvent wiping or abrasion. The trends in adhesion with plasma exposure time do not correlate well with surface wetting or roughness; instead they correlate with the fraction of the polymer surface sites that are converted into carboxylic acid groups.
Plasma-deposited tetraglyme surfaces greatly reduce total blood protein adsorption, contact activation, platelet adhesion, platelet procoagulant activity, and in vitro thrombus deposition.

PubMed

Cao, Lan; Chang, Mark; Lee, Chi-Ying; Castner, David G; Sukavaneshvar, Sivaprasad; Ratner, Buddy D; Horbett, Thomas A

2007-06-15

The ability of tetraethylene glycol dimethyl ether (tetraglyme) plasma deposited coatings exhibiting ultralow fibrinogen adsorption to reduce blood activation was studied with six in vitro methods, namely fibrinogen and von Willebrand's factor adsorption, total protein adsorption, clotting time in recalcified plasma, platelet adhesion and procoagulant activity, and whole blood thrombosis in a disturbed flow catheter model. Surface plasmon resonance results showed that tetraglyme surfaces strongly resisted the adsorption of all proteins from human plasma. The clotting time in the presence of tetraglyme surfaces was lengthened compared with controls, indicating a lower activation of the intrinsic coagulation cascade. Platelet adhesion and thrombin generation by adherent platelets were greatly reduced on tetraglyme-coated materials, compared with uncoated and Biospan-coated glass slides. In the in vitro disturbed blood flow model, tetraglyme plasma coated catheters had 50% less thrombus than did the uncoated catheters. Tetraglyme-coated materials thus had greatly reduced blood interactions as measured with all six methods. The improved blood compatibility of plasma-deposited tetraglyme is thus not only due to their reduced platelet adhesion and activation, but also to a generalized reduction in blood interactions. (c) 2007 Wiley Periodicals, Inc.
Synthesis of antibacterial surfaces by plasma grafting of zinc oxide based nanocomposites onto polypropylene.

PubMed

de Rancourt, Yoann; Couturaud, Benoit; Mas, André; Robin, Jean Jacques

2013-07-15

Antibacterial polymer surfaces were designed using ZnO nanoparticles as a bactericide. Mineral encapsulated nanoparticles were grafted onto activated polymer surfaces through their shells. Polypropylene (PP) surfaces were treated using an innovative process coupling core-shell technology and plasma grafting, well-known techniques commonly used to obtain active surfaces for biomedical applications. First, ZnO nanoparticles were encapsulated by (co)polymers: poly(acrylic acid) (PAA) or a poly(methyl methacrylate-co-methacrylic acid) copolymer [P(MMA-MA)]. Second, PP substrates were activated using plasma treatment. Finally, plasma-treated surfaces were immersed in solutions containing the encapsulated nanoparticles dispersed in an organic solvent and allowed to graft onto it. The presence of nanoparticles on the substrates was demonstrated using Fourier-Transform Infrared Spectroscopy (FTIR) analysis, Scanning Electron Microspcopy (SEM)/Energy-Dispersive X-ray (EDX), and Atomic Force Microscopy (AFM) studies. Indeed, the ZnO-functionalized substrates exhibited an antibacterial response in Escherichia coli adhesion tests. Moreover, this study revealed that, surprisingly, native ZnO nanoparticles without any previous functionalization could be directly grafted onto polymeric surfaces through plasma activation. The antibacterial activity of the resulting sample was shown to be comparable to that of the other samples. Copyright © 2013 Elsevier Inc. All rights reserved.
Plasma treatment of polypropylene fabric for improved dyeability with soluble textile dyestuff

NASA Astrophysics Data System (ADS)

Yaman, Necla; Özdoğan, Esen; Seventekin, Necdet; Ayhan, Hakan

2009-05-01

The impact of plasma treatment parameters on the surface morphology, physical-chemical, and dyeing properties of polypropylene (PP) using anionic and cationic dyestuffs were investigated in this study. Argon plasma treatment was used to activate PP fabric surfaces. Activated surfaces were grafted different compounds: 6-aminohexanoic acid (6-AHA), acrylic acid (AA), ethylendiamine (EDA), acryl amide (AAMID) and hexamethyldisiloxane (HMDS). Compounds were applied after the plasma treatment and the acid and basic dyeing result that was then observed, were quite encouraging in certain conditions. The possible formed oxidizing groups were emphasized by FTIR and ATR and the surface morphology of plasma treated PP fibers was also investigated with scanning electron microscopy (SEM). PP fabric could be dyed with acid and basic dyestuffs after only plasma treatment and plasma induced grafting, and fastnesses of the dyed samples were satisfactory.
Electrocatalytically Active Nickel-Based Electrode Coatings Formed by Atmospheric and Suspension Plasma Spraying

NASA Astrophysics Data System (ADS)

Aghasibeig, M.; Mousavi, M.; Ben Ettouill, F.; Moreau, C.; Wuthrich, R.; Dolatabadi, A.

2014-01-01

Ni-based electrode coatings with enhanced surface areas, for hydrogen production, were developed using atmospheric plasma spray (APS) and suspension plasma spray (SPS) processes. The results revealed a larger electrochemical active surface area for the coatings produced by SPS compared to those produced by APS process. SEM micrographs showed that the surface microstructure of the sample with the largest surface area was composed of a large number of small cauliflower-like aggregates with an average diameter of 10 μm.

Application of non-equilibrium plasmas in treatment of wool fibers and seeds

NASA Astrophysics Data System (ADS)

Petrović, Zoran

2003-10-01

While large effort is under way to achieve stable, large area, non-equilibrium plasma reactors operating at atmospheric pressure we should still consider application of low pressure reactors, which provide well defined, easily controlled reactive plasmas. Therefore, the application of low pressure rf plasmas for the treatment of wool and seed was investigated. The studies were aimed at establishing optimal procedure to achieve better wettability, dyeability and printability of wool. Plasma treatment led to a modification of wool fiber topography and formation of new polar functional groups inducing the increase of wool hydrophylicity. Plasma activation of fiber surface was also used to achieve better binding of biopolymer chitosan to wool in order to increase the content of favorable functional groups and thus improving sorption properties of recycled wool fibers for heavy metal ions and acid dyes. In another study, the increase of germination percentage of seeds induced by plasmas was investigated. We have selected dry (unimbibed) Empress tree seeds (Paulownia tomentosa Steud.). Empress tree seed has been studied extensively and its mechanism of germination is well documented. Germination of these seeds is triggered by light in a limited range of wavelengths. Interaction between activated plasma particles and seed, inside the plasma reactor, leads to changes in its surface topography, modifies the surface layer and increases the active surface area. Consequently, some bioactive nitrogeneous compounds could be bound to the activated surface layer causing the increment of germination percentage.
Effects of O 2 plasma and UV-O 3 assisted surface activation on high sensitivity metal oxide functionalized multiwalled carbon nanotube CH 4 sensors

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

Humayun, Md Tanim; Sainato, Michela; Divan, Ralu

We present a comparative analysis of UV-O 3 (UVO) and O 2 plasma-based surface activation processes of multi-walled carbon nanotubes (MWCNTs) enabling highly effective functionalization with metal oxide nanocrystals (MONCs). Experimental results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy show that by forming COOH (carboxyl), C-OH (hydroxyl), and C=O (carbonyl) groups on the MWCNT surface that act as active nucleation sites, O 2 plasma and UVO-based dry pre-treatment techniques greatly enhance the affinity between MWCNT surface and the functionalizing MONCs. MONCs, such as ZnO and SnO 2, deposited by atomic layermore » deposition (ALD) technique, were implemented as the functionalizing material following UVO and O 2 plasma activation of MWCNTs. In conclusion, a comparative study on the relative resistance changes of O 2 plasma and UVO activated MWCNT functionalized with MONC in the presence of 10 ppm methane (CH 4) in air, is presented as well.« less
Effects of O 2 plasma and UV-O 3 assisted surface activation on high sensitivity metal oxide functionalized multiwalled carbon nanotube CH 4 sensors

DOE PAGES

Humayun, Md Tanim; Sainato, Michela; Divan, Ralu; ...

2017-07-28

We present a comparative analysis of UV-O 3 (UVO) and O 2 plasma-based surface activation processes of multi-walled carbon nanotubes (MWCNTs) enabling highly effective functionalization with metal oxide nanocrystals (MONCs). Experimental results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy show that by forming COOH (carboxyl), C-OH (hydroxyl), and C=O (carbonyl) groups on the MWCNT surface that act as active nucleation sites, O 2 plasma and UVO-based dry pre-treatment techniques greatly enhance the affinity between MWCNT surface and the functionalizing MONCs. MONCs, such as ZnO and SnO 2, deposited by atomic layermore » deposition (ALD) technique, were implemented as the functionalizing material following UVO and O 2 plasma activation of MWCNTs. In conclusion, a comparative study on the relative resistance changes of O 2 plasma and UVO activated MWCNT functionalized with MONC in the presence of 10 ppm methane (CH 4) in air, is presented as well.« less
Impact of Plasma Surface Treatment on Bamboo Charcoal/silver Nanocomposite

NASA Astrophysics Data System (ADS)

Vignesh, K.; Vijayalakshmi, K. A.; Karthikeyan, N.

2016-10-01

Bamboo charcoal (BC) accompanied silver (Ag) nanocomposite is synthesized through sol-gel method. The produced BC/Ag nanocomposite was surface modified by air and oxygen plasma treatments. Silver ions (Ag+) will serve to improve the antibacterial activity as well as the surface area of BC. Plasma treatment has improved the surface functional groups, crystalline intensity and antibacterial activity of the prepared nanocomposite. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies show that Ag nanoparticles have good agreement with BC and the particle size has a mean diameter of 20-40nm. We observe the carboxyl functional groups in Fourier transform infrared spectroscopy (FTIR) after the oxygen plasma treatment. Moreover surface area and adsorption were analyzed by using the Brunauer, Emmett and Teller (BET) surface area (SBET) and UV-Vis spectroscopy.
Laboratory demonstration model: Active cleaning technique device. [for removal of contaminants from an optical surface

NASA Technical Reports Server (NTRS)

Shannon, R. L.; Gillette, R. B.

1974-01-01

The technique which utilizes exposure to a plasma to remove contaminants from a surface was incorporated into a laboratory model which demonstrates active cleaning by both plasma cleaning and ion sputtering modes of operation. The development phase is reported and includes discussion of the plasma tube configuration, device design, and performance tests. A general description of the active cleaning device is provided which includes information on the main power/plasma discharge sensors, and the power, gas supply, and ion accelerator systems. Development of the active cleaning species at high vacuum conditions is described and results indicate that plasma cleaning occurs in the region of a visible plume which extends from the end of the plasma tube. Recommendations are made for research to determine the plasma cleaning mechanism and the plasma species responsible for the cleaning, as well limitations on the type of contaminants that can be removed.
Surface oxidation of GaN(0001): Nitrogen plasma-assisted cleaning for ultrahigh vacuum applications

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

Gangopadhyay, Subhashis; Schmidt, Thomas, E-mail: tschmidt@ifp.uni-bremen.de; Kruse, Carsten

The cleaning of metal-organic vapor-phase epitaxial GaN(0001) template layers grown on sapphire has been investigated. Different procedures, performed under ultrahigh vacuum conditions, including degassing and exposure to active nitrogen from a radio frequency nitrogen plasma source have been compared. For this purpose, x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and scanning tunneling microscopy have been employed in order to assess chemical as well as structural and morphological surface properties. Initial degassing at 600 °C under ultrahigh vacuum conditions only partially eliminates the surface contaminants. In contrast to plasma assisted nitrogen cleaning at temperatures as low as 300 °C, active-nitrogen exposure at temperaturesmore » as high as 700 °C removes the majority of oxide species from the surface. However, extended high-temperature active-nitrogen cleaning leads to severe surface roughening. Optimum results regarding both the removal of surface oxides as well as the surface structural and morphological quality have been achieved for a combination of initial low-temperature plasma-assisted cleaning, followed by a rapid nitrogen plasma-assisted cleaning at high temperature.« less
A study on the antimicrobial efficacy of RF oxygen plasma and neem extract treated cotton fabrics

NASA Astrophysics Data System (ADS)

Vaideki, K.; Jayakumar, S.; Thilagavathi, G.; Rajendran, R.

2007-06-01

The paper deals with a thorough investigation on the antimicrobial activity of RF oxygen plasma and Azadirachtin (neem extract) treated cotton fabric. The hydrophilicity of cotton fabric was found to improve when treated with RF oxygen plasma. The process parameters such as electrode gap, time of exposure and oxygen pressure have been varied to study their effect on improving the hydrophilicity of the cotton fabric. The static immersion test has been carried out to assess the hydrophilicity of the oxygen plasma treated samples and the process parameters were optimized based on these test results. The formation of carbonyl group during surface modification in the plasma treated sample was analysed using FTIR studies. The surface morphology has been studied using SEM micrographs. The antimicrobial activity was imparted to the RF oxygen plasma treated samples using methanolic extract of neem leaves containing Azadirachtin. The antimicrobial activity of these samples has been analysed and compared with the activity of the cotton fabric treated with neem extract alone. The investigation reveals that the surface modification due to RF oxygen plasma was found to increase the hydrophilicity and hence the antimicrobial activity of the cotton fabric when treated with Azadirachtin.
Effect of oxygen plasma treatment on the electrochemical performance of the rayon and polyacrylonitrile based carbon felt for the vanadium redox flow battery application

NASA Astrophysics Data System (ADS)

Dixon, D.; Babu, D. J.; Langner, J.; Bruns, M.; Pfaffmann, L.; Bhaskar, A.; Schneider, J. J.; Scheiba, F.; Ehrenberg, H.

2016-11-01

Oxygen plasma treatment was applied on commercially available graphite felt electrodes based on rayon (GFA) and polyacrylonitrile (GFD). The formation of functional groups on the surface of the felt was confirmed by X-ray photoelectron spectroscopy measurements. The BET studies of the plasma treated electrodes showed no significant increase in surface area for both the rayon as well as the PAN based felts. Both plasma treated electrodes showed significantly enhanced V3+/V2+ redox activity compared to the pristine electrodes. Since an increase of the surface area has been ruled out for plasma treated electrode the enhanced activity could be attributed to surface functional groups. Interestingly, plasma treated GFD felts showed less electrochemical activity towards V5+/V4+ compared to the pristine electrode. Nevertheless, an overall increase of the single cell performance was still observed as the negative electrode is known to be the performance limiting electrode. Thus, to a great extent the present work helps to preferentially understand the importance of functional groups on the electrochemical activity of negative and positive redox reaction. The study emphasizes the need of highly active electrodes especially at the negative electrode side as inactive electrodes can still facilitate hydrogen evolution and degrade the electrolyte in VRFBs.
Surface grafting of a thermoplastic polyurethane with methacrylic acid by previous plasma surface activation and by ultraviolet irradiation to reduce cell adhesion.

PubMed

Alves, P; Pinto, S; Kaiser, Jean-Pierre; Bruinink, Arie; de Sousa, Hermínio C; Gil, M H

2011-02-01

The material performance, in a biological environment, is mainly mediated by its surface properties and by the combination of chemical, physical, biological, and mechanical properties required, for a specific application. In this study, the surface of a thermoplastic polyurethane (TPU) material (Elastollan(®)1180A50) was activated either by plasma or by ultra-violet (UV) irradiation. After surface activation, methacrylic acid (MAA) was linked to the surface of TPU in order to improve its reactivity and to reduce cell adhesion. Grafted surfaces were evaluated by X-ray photoelectron spectroscopy (XPS), by atomic force microscopy (AFM) and by contact angle measurements. Blood compatibility studies and cell adhesion tests with human bone marrow cells (HBMC) were also performed. If was found that UV grafting method led to better results than the plasma activation method, since cell adhesion was reduced when methacrylic acid was grafted to the TPU surface by UV. Copyright © 2010 Elsevier B.V. All rights reserved.
Surface modification of polylactic acid films by atmospheric pressure plasma treatment

NASA Astrophysics Data System (ADS)

Kudryavtseva, V. L.; Zhuravlev, M. V.; Tverdokhlebov, S. I.

2017-09-01

A new approach for the modification of polylactic acid (PLA) materials using atmospheric pressure plasma (APP) is described. PLA films plasma exposure time was 20, 60, 120 s. The surface morphology and wettability of the obtained PLA films were investigated by atomic force microscopy (AFM) and the sitting drop method. The atmospheric pressure plasma increased the roughness and surface energy of PLA film. The wettability of PLA has been improved with the application of an atmospheric plasma surface treatment. It was shown that it is possible to obtain PLA films with various surface relief and tunable wettability. Additionally, we demonstrated that the use of cold atmospheric pressure plasma for surface activation allows for the immobilization of bioactive compounds like hyaluronic acid (HA) on the surface of obtained films. It was shown that composite PLA-HA films have an increased long-term hydrophilicity of the films surface.
Conversion of CH4/CO2 to syngas over Ni-Co/Al2O3-ZrO2 nanocatalyst synthesized via plasma assisted co-impregnation method: Surface properties and catalytic performance

NASA Astrophysics Data System (ADS)

Rahemi, Nader; Haghighi, Mohammad; Akbar Babaluo, Ali; Fallah Jafari, Mahdi; Khorram, Sirous

2013-09-01

Ni/Al2O3 catalyst promoted by Co and ZrO2 was prepared by co-impregnation method and treated with glow discharge plasma. The catalytic activity of the synthesized nanocatalysts has been tested toward conversion of CH4/CO2 to syngas. The physicochemical characterizations like XRD, EDX, FESEM, TEM, BET, FTIR, and XPS show that plasma treatment results in smaller particle size, more surface concentration, and uniform morphology. The dispersion of nickel in plasma-treated nanocatalyst was also significantly improved, which was helpful for controlling the ensemble size of active phase atoms on the support surface. Improved physicochemical properties caused 20%-30% enhancement in activity of plasma-treated nanocatalyst that means to achieve the same H2 or CO yield, the plasma-treated nanocatalyst needed about 100 °C lower reaction temperature. The H2/CO ratio got closer to 1 at higher temperatures and finally at 850 °C H2/CO = 1 is attained for plasma-treated nanocatalyst. Plasma-treated nanocatalyst due to smaller Ni particles and strong interaction between active phase and support has lower tendency to keep carbon species on its structure and hence excellent stability can be observed for this catalyst.
Paper-based plasma sanitizers

NASA Astrophysics Data System (ADS)

Xie, Jingjin; Chen, Qiang; Suresh, Poornima; Roy, Subrata; White, James F.; Mazzeo, Aaron D.

2017-05-01

This work describes disposable plasma generators made from metallized paper. The fabricated plasma generators with layered and patterned sheets of paper provide a simple and flexible format for dielectric barrier discharge to create atmospheric plasma without an applied vacuum. The porosity of paper allows gas to permeate its bulk volume and fuel plasma, while plasma-induced forced convection cools the substrate. When electrically driven with oscillating peak-to-peak potentials of ±1 to ±10 kV, the paper-based devices produced both volume and surface plasmas capable of killing microbes. The plasma sanitizers deactivated greater than 99% of Saccharomyces cerevisiae and greater than 99.9% of Escherichia coli cells with 30 s of noncontact treatment. Characterization of plasma generated from the sanitizers revealed a detectable level of UV-C (1.9 nWṡcm-2ṡnm-1), modest surface temperature (60 °C with 60 s of activation), and a high level of ozone (13 ppm with 60 s of activation). These results deliver insights into the mechanisms and suitability of paper-based substrates for active antimicrobial sanitization with scalable, flexible sheets. In addition, this work shows how paper-based generators are conformable to curved surfaces, appropriate for kirigami-like “stretchy” structures, compatible with user interfaces, and suitable for sanitization of microbes aerosolized onto a surface. In general, these disposable plasma generators represent progress toward biodegradable devices based on flexible renewable materials, which may impact the future design of protective garments, skin-like sensors for robots or prosthetics, and user interfaces in contaminated environments.
Paper-based plasma sanitizers.

PubMed

Xie, Jingjin; Chen, Qiang; Suresh, Poornima; Roy, Subrata; White, James F; Mazzeo, Aaron D

2017-05-16

This work describes disposable plasma generators made from metallized paper. The fabricated plasma generators with layered and patterned sheets of paper provide a simple and flexible format for dielectric barrier discharge to create atmospheric plasma without an applied vacuum. The porosity of paper allows gas to permeate its bulk volume and fuel plasma, while plasma-induced forced convection cools the substrate. When electrically driven with oscillating peak-to-peak potentials of ±1 to ±10 kV, the paper-based devices produced both volume and surface plasmas capable of killing microbes. The plasma sanitizers deactivated greater than 99% of Saccharomyces cerevisiae and greater than 99.9% of Escherichia coli cells with 30 s of noncontact treatment. Characterization of plasma generated from the sanitizers revealed a detectable level of UV-C (1.9 nW⋅cm -2 ⋅nm -1 ), modest surface temperature (60 °C with 60 s of activation), and a high level of ozone (13 ppm with 60 s of activation). These results deliver insights into the mechanisms and suitability of paper-based substrates for active antimicrobial sanitization with scalable, flexible sheets. In addition, this work shows how paper-based generators are conformable to curved surfaces, appropriate for kirigami-like "stretchy" structures, compatible with user interfaces, and suitable for sanitization of microbes aerosolized onto a surface. In general, these disposable plasma generators represent progress toward biodegradable devices based on flexible renewable materials, which may impact the future design of protective garments, skin-like sensors for robots or prosthetics, and user interfaces in contaminated environments.
Elaboration of nano-structured grafted polymeric surface.

PubMed

Vrlinic, Tjasa; Debarnot, Dominique; Mozetic, Miran; Vesel, Alenka; Kovac, Janez; Coudreuse, Arnaud; Legeay, Gilbert; Poncin-Epaillard, Fabienne

2011-10-15

The surface grafting of multi-polymeric materials can be achieved by grafting as components such as polymers poly(N-isopropylacrylamide) and/or surfactant molecules (hexatrimethylammonium bromide, polyoxyethylene sorbitan monolaurate). The chosen grafting techniques, i.e. plasma activation followed by coating, allow a large spectrum of functional groups that can be inserted on the surface controlling the surface properties like adhesion, wettability and biocompatibility. The grafted polypropylene surfaces were characterized by contact angle analyses, XPS and AFM analyses. The influence of He plasma activation, of the coating parameters such as concentrations of the various reactive agents are discussed in terms of hydrophilic character, chemical composition and morphologic surface heterogeneity. The plasma pre-activation was shown inevitable for a permanent polymeric grafting. PNIPAM was grafted alone or with a mixture of the surfactant molecules. Depending on the individual proportion of each component, the grafted surfaces are shown homogeneous or composed of small domains of one component leading to a nano-structuration of the grafted surface. Copyright © 2011 Elsevier Inc. All rights reserved.
Bactericidal effects of plasma-modified surface chemistry of silicon nanograss

NASA Astrophysics Data System (ADS)

Ostrikov, Kola; Macgregor-Ramiasa, Melanie; Cavallaro, Alex; (Ken Ostrikov, Kostya; Vasilev, Krasimir

2016-08-01

The surface chemistry and topography of biomaterials regulate the adhesion and growth of microorganisms in ways that are still poorly understood. Silicon nanograss structures prepared via inductively coupled plasma etching were coated with plasma deposited nanometer-thin polymeric films to produce substrates with controlled topography and defined surface chemistry. The influence of surface properties on Staphylococcus aureus proliferation is demonstrated and explained in terms of nanograss substrate wetting behaviour. With the combination of the nanograss topography; hydrophilic plasma polymer coatings enhanced antimicrobial activity while hydrophobic coatings reduced it. This study advances the understanding of the effects of surface wettability on the bactericidal properties of reactive nano-engineered surfaces.
Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhou, Xiaoyan; Zhang, Xiaotao; Bian, Jie; Shi, Shukai; Nguyen, Thiphuong; Chen, Minzhi; Wan, Jinglin

2017-06-01

The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and Sisbnd Osbnd C. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.
Mechanism of virus inactivation by cold atmospheric-pressure plasma and plasma-activated water.

PubMed

Guo, Li; Xu, Ruobing; Gou, Lu; Liu, Zhichao; Zhao, Yiming; Liu, Dingxin; Zhang, Lei; Chen, Hailan; Kong, Michael G

2018-06-18

Viruses are serious pathogenic contamination that severely affect the environment and human health. Cold atmospheric-pressure plasma efficiently inactivates pathogenic bacteria, however, the mechanism of virus inactivation by plasma is not fully understood. In this study, surface plasma in argon mixed with 1% air and plasma-activated water were used to treat water containing bacteriophages. Both agents efficiently inactivated bacteriophages T4, Φ174, and MS2 in a time-dependent manner. Prolonged storage had marginal effects on the anti-viral activity of plasma-activated water. DNA and protein analysis revealed that the reactive species generated by plasma damaged both nucleic acid and proteins, in consistent with the morphological examination showing that plasma treatment caused the aggregation of bacteriophages. The inactivation of bacteriophages was alleviated by the singlet oxygen scavengers, demonstrating that singlet oxygen played a primary role in this process. Our findings provide a potentially effective disinfecting strategy to combat the environmental viruses using cold atmospheric-pressure plasma and plasma-activated water. Importance Contamination with pathogenic and infectious viruses severely threaten human health and animal husbandry. Current methods for disinfection have different disadvantages, such as inconvenience and contamination of disinfection by-products (e.g. chlorine disinfection). In this study, atmospheric surface plasma in argon mixed with air and plasma-activated water were found to efficiently inactivate bacteriophages, and plasma-activated water still had strong anti-viral activity after prolonged storage. Furthermore, it was shown that bacteriophage inactivation was associated with the damage to nucleic acid and proteins by singlet oxygen. The understanding of the biological effects of plasma-based treatment is useful to inform the development of plasma into a novel disinfecting strategy with convenience and no by-product. Copyright © 2018 Guo et al.
Antibacterial properties of modified biodegradable PHB non-woven fabric.

PubMed

Slepička, P; Malá, Z; Rimpelová, S; Švorčík, V

2016-08-01

The antibacterial properties of poly(hydroxybutyrate) (PHB) non-woven fabric were explored in this study. The PHB was activated by plasma modification and subsequently processed with either immersion into a solution of nanoparticles or direct metallization. The wettability and surface chemistry of the PHB surface was determined. The thickness of the sputtered nanolayer on PHB fabric was characterized. It was found that plasma modification led to a formation of strongly hydrophilic surface, while the subsequent metallization by silver or gold resulted in a significantly increased water contact angle. Further, it was found that antibacterial activity may be controlled by the type of a metal and deposition method used. The immersion of plasma modified fabric into Ag nanoparticle solution led to enhanced antibacterial efficiency of PHB against Escherichia coli (E. coli). Direct silver sputtering on PHB fabric was proved to be a simple method for construction of a surface with strong antibacterial potency against both Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis). We demonstrated the antibacterial activity of PHB fabric modified by plasma activation and consecutive selection of a treatment method for an effective antibacterial surface construction. Copyright © 2016 Elsevier B.V. All rights reserved.
Paper-based plasma sanitizers

PubMed Central

Xie, Jingjin; Chen, Qiang; Suresh, Poornima; Roy, Subrata; White, James F.

2017-01-01

This work describes disposable plasma generators made from metallized paper. The fabricated plasma generators with layered and patterned sheets of paper provide a simple and flexible format for dielectric barrier discharge to create atmospheric plasma without an applied vacuum. The porosity of paper allows gas to permeate its bulk volume and fuel plasma, while plasma-induced forced convection cools the substrate. When electrically driven with oscillating peak-to-peak potentials of ±1 to ±10 kV, the paper-based devices produced both volume and surface plasmas capable of killing microbes. The plasma sanitizers deactivated greater than 99% of Saccharomyces cerevisiae and greater than 99.9% of Escherichia coli cells with 30 s of noncontact treatment. Characterization of plasma generated from the sanitizers revealed a detectable level of UV-C (1.9 nW⋅cm−2⋅nm−1), modest surface temperature (60 °C with 60 s of activation), and a high level of ozone (13 ppm with 60 s of activation). These results deliver insights into the mechanisms and suitability of paper-based substrates for active antimicrobial sanitization with scalable, flexible sheets. In addition, this work shows how paper-based generators are conformable to curved surfaces, appropriate for kirigami-like “stretchy” structures, compatible with user interfaces, and suitable for sanitization of microbes aerosolized onto a surface. In general, these disposable plasma generators represent progress toward biodegradable devices based on flexible renewable materials, which may impact the future design of protective garments, skin-like sensors for robots or prosthetics, and user interfaces in contaminated environments. PMID:28461476
Surface cracking and melting of different tungsten grades under transient heat and particle loads in a magnetized coaxial plasma gun

NASA Astrophysics Data System (ADS)

Kikuchi, Y.; Sakuma, I.; Iwamoto, D.; Kitagawa, Y.; Fukumoto, N.; Nagata, M.; Ueda, Y.

2013-07-01

Surface damage of pure tungsten (W), W alloys with 2 wt.% tantalum (W-Ta) and vacuum plasma spray (VPS) W coating on a reduced activation material of ferritic steel (F82H) due to repetitive ELM-like pulsed (˜0.3 ms) deuterium plasma irradiation has been investigated by using a magnetized coaxial plasma gun. Surface cracks appeared on a pure W sample exposed to 10 plasma pulses of ˜0.3 MJ m-2, while a W-Ta sample did not show surface cracks with similar pulsed plasma irradiation. The energy density threshold for surface cracking was significantly increased by the existence of the alloying element of tantalum. No surface morphology change of a VPS W coated F82H sample was observed under 10 plasma pulses of ˜0.3 MJ m-2, although surface melting and cracks in the resolidification layer occurred at higher energy density of ˜0.9 MJ m-2. There was no indication of exfoliation of the W coating from the substrate of F82H after the pulsed plasma exposures.

Theoretical modeling to study the impact of different oxidizers (etchants) on the plasma-assisted catalytic carbon nanofiber growth

NASA Astrophysics Data System (ADS)

Gupta, Ravi; Sharma, Suresh C.

2017-07-01

An analytical model based on the various surface deposition processes and plasma sheath kinetics of the plasma species (electrons, positively charged ions, radicals, and neutrals) has been developed to investigate the effects of different plasmas (different etchants) on the catalyzed plasma aided growth of carbon nanofibers (CNFs). In particular, the model accounts the poisoning of the catalyst nanoparticle, i.e., the formation of the amorphous carbon layer on the catalyst active surface due to the continuous dissociation of incoming hydrocarbon species from the plasma. It is observed that oxidizers (H2O and O2) in the typical hydrocarbon/hydrogen (C2H2 + H2) plasma act as the dominant etchants and remove the amorphous carbon layer from the catalyst surface and, thus, preserve and enhance the catalyst activity. However, the growth rate of CNFs is much higher when O2 is added as an etchant in the reactive plasma as compared to H2O. This is due to the dual role played by the oxygen, i.e., (i) removal of amorphous carbon from the catalyst active surface, (ii) removal of hydrogen radicals that interact with the carbon species generated on the catalyst surface and suppress their diffusion through the catalyst nanoparticles. The CNF grows much longer in the presence of O2, therefore, etching of CNF tip and deformation of catalyst nanoparticle is the maximum, and hence, the CNF tip diameter is least. Moreover, in the present investigation, we also found that the relative concentrations of H2O or O2 species in the reactive plasma have significant effects on the CNF growth. Our theoretical results are in good agreement with the experimental observations.
Fabrication of photocatalytically active vanadium oxide nanostructures via plasma route

NASA Astrophysics Data System (ADS)

Kajita, Shin; Yoshida, Tomoko; Ohno, Noriyasu; Ichino, Yusuke; Yoshida, Naoaki

2018-05-01

Plasma irradiation was used to create nanostructured vanadium oxide with potential commercial and industrial applications. Morphology changes were induced at the nano- and micro-meter scale, accompanied by the growth of helium nanobubbles. Micrometer-sized pillars, cube-shaped nanostructures, and fuzzy fiberform nanostructures were grown on the surface; the necessary conditions in terms of the incident ion energy and the surface temperature for those morphology changes were revealed. Hydrogen production experiments using a photocatalytic reaction with aqueous methanol solution were conducted on the fabricated samples. Enhanced H2 production was confirmed with the plasma irradiated nanostructured sample that had been oxidized in air atmosphere. Photocatalytically inactive vanadium oxide exhibited a high photocatalytic activity after nanostructurization of the surface by helium plasma irradiation.
Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

PubMed

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

2017-09-13

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

NASA Astrophysics Data System (ADS)

Jamison, K. A.; Niiler, Andrus

1987-04-01

Plasma-driven railguns are now in operation at several locations throughout the world. All share common problems in barrel erosion arising from the fact that the bore surface must contain a high temperature plasma armature which transmits the acceleration force to a projectile. The plasma temperature at the core of the armature is estimated to be 30 000 K or higher. Such conditions are erosive to most materials even when the exposure time is 100 μs or less. We have adapted two accelerator based techniques to aid in the study of this erosion. The first technique involves the collection and analysis of material ablated and left behind by the plasma. This analysis is based on the unfolding of the Rutherford backscattered (RBS) spectra of 1 MeV deuterons incident on residue collected from a railgun bore. The second technique is an erosion measurement involving thin layer activation (TLA) of surfaces. In this process, the copper rail surface is activated by 2.4 MeV protons creating a relatively thin (3 m) layer sparsely seeded with a long lived zinc isotope. Monitoring the decay of the activated sample before and after a firing can detect surface wear of about 0. 1 m. Results from the RBS and TLA experiments on the BRL plasma driven railgun are described.
Non-Equilibrium Plasma Processing for the Preparation of Antibacterial Surfaces

PubMed Central

Sardella, Eloisa; Palumbo, Fabio; Camporeale, Giuseppe; Favia, Pietro

2016-01-01

Non-equilibrium plasmas offer several strategies for developing antibacterial surfaces that are able to repel and/or to kill bacteria. Due to the variety of devices, implants, and materials in general, as well as of bacteria and applications, plasma assisted antibacterial strategies need to be tailored to each specific surface. Nano-composite coatings containing inorganic (metals and metal oxides) or organic (drugs and biomolecules) compounds can be deposited in one step, and used as drug delivery systems. On the other hand, functional coatings can be plasma-deposited and used to bind antibacterial molecules, for synthesizing surfaces with long lasting antibacterial activity. In addition, non-fouling coatings can be produced to inhibit the adhesion of bacteria and reduce the formation of biofilm. This paper reviews plasma-based strategies aimed to reduce bacterial attachment and proliferation on biomedical materials and devices, but also onto materials used in other fields. Most of the activities described have been developed in the lab of the authors. PMID:28773637
Optimization of hydrolysis conditions for bovine plasma protein using response surface methodology.

PubMed

Seo, Hyun-Woo; Jung, Eun-Young; Go, Gwang-Woong; Kim, Gap-Don; Joo, Seon-Tea; Yang, Han-Sul

2015-10-15

The purpose of this study was to establish optimal conditions for the hydrolysis of bovine plasma protein. Response surface methodology was used to model and optimize responses [degree of hydrolysis (DH), 2,2-diphenyl-1-picrydrazyl (DPPH) radical-scavenging activity and Fe(2+)-chelating activity]. Hydrolysis conditions, such as hydrolysis temperature (46.6-63.4 °C), hydrolysis time (98-502 min), and hydrolysis pH (6.32-9.68) were selected as the main processing conditions in the hydrolysis of bovine plasma protein. Optimal conditions for maximum DH (%), DPPH radical-scavenging activity (%) and Fe(2+)-chelating activity (%) of the hydrolyzed bovine plasma protein, were respectively established. We discovered the following three conditions for optimal hydrolysis of bovine plasma: pH of 7.82-8.32, temperature of 54.1 °C, and time of 338.4-398.4 min. We consequently succeeded in hydrolyzing bovine plasma protein under these conditions and confirmed the various desirable properties of optimal hydrolysis. Copyright © 2015 Elsevier Ltd. All rights reserved.
Hydrophilic surface modification of coronary stent using an atmospheric pressure plasma jet for endothelialization.

PubMed

Shim, Jae Won; Bae, In-Ho; Park, Dae Sung; Lee, So-Youn; Jang, Eun-Jae; Lim, Kyung-Seob; Park, Jun-Kyu; Kim, Ju Han; Jeong, Myung Ho

2018-03-01

The first two authors contributed equally to this study. Bioactivity and cell adhesion properties are major factors for fabricating medical devices such as coronary stents. The aim of this study was to evaluate the advantages of atmospheric-pressure plasma jet in enhancing the biocompatibility and endothelial cell-favorites. The experimental objects were divided into before and after atmospheric-pressure plasma jet treatment with the ratio of nitrogen:argon = 3:1, which is similar to air. The treated surfaces were basically characterized by means of a contact angle analyzer for the activation property on their surfaces. The effect of atmospheric-pressure plasma jet on cellular response was examined by endothelial cell adhesion and XTT analysis. It was difficult to detect any changeable morphology after atmospheric-pressure plasma jet treatment on the surface. The roughness was increased after atmospheric-pressure plasma jet treatment compared to nonatmospheric-pressure plasma jet treatment (86.781 and 7.964 nm, respectively). The X-ray photoelectron spectroscopy results showed that the surface concentration of the C-O groups increased slightly from 6% to 8% after plasma activation. The contact angle dramatically decreased in the atmospheric-pressure plasma jet treated group (22.6 ± 15.26°) compared to the nonatmospheric-pressure plasma jet treated group (72.4 ± 15.26°) ( n = 10, p < 0.05). The effect of the increment in hydrophilicity due to the atmospheric-pressure plasma jet on endothelial cell migration and proliferation was 85.2% ± 12.01% and 34.2% ± 2.68%, respectively, at 7 days, compared to the nonatmospheric-pressure plasma jet treated group (58.2% ± 11.44% in migration, n = 10, p < 0.05). Taken together, the stent surface could easily obtain a hydrophilic property by the atmospheric-pressure plasma jet method. Moreover, the atmospheric-pressure plasma jet might affect re-endothelialization after stenting.
Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation

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

Wu, S.; Wang, Z.; Huang, Q.

2013-02-15

Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generatedmore » by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.« less
Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane with highly effective blood compatibility via atmospheric plasma-induced surface copolymerization.

PubMed

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

2011-04-01

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

NASA Astrophysics Data System (ADS)

Tani, Atsushi; Fukui, Satoshi; Ikawa, Satoshi; Kitano, Katsuhisa

2015-10-01

We investigated fatty acid oxidation by atmospheric-pressure nonthermal helium plasma using linoleic acid, an unsaturated fatty acid, together with evaluating active species induced in liquids. If the ambient gas contains oxygen, direct plasma such as plasma jets coming into contact with the liquid surface supplies various active species, such as singlet oxygen, ozone, and superoxide anion radicals, to the liquid. The direct plasma easily oxidizes linoleic acid, indicating that fatty acid oxidation will occur in the direct plasma. In contrast, afterglow flow, where the plasma is terminated in a glass tube and does not touch the surface of the liquid sample, supplies mainly superoxide anion radicals. The fact that there was no clear observation of linoleic acid oxidation using the afterglow reveals that it may not affect lipids, even in an atmosphere containing oxygen. The afterglow flow can potentially be used for the sterilization of aqueous solutions using the reduced pH method, in medical and dental applications, because it provides bactericidal activity in the aqueous solution despite containing a smaller amount of active species.
Effect of plasma superficial treatments on antibacterial functionalization and coloration of cellulosic fabrics

NASA Astrophysics Data System (ADS)

Ibrahim, Nabil A.; Eid, Basma M.; Abdel-Aziz, Mohamed S.

2017-01-01

Remarkable improvement in antibacterial activity and durability of different cellulosic substrates namely cotton, linen, viscose and lyocell was achieved by pre-surface modification using N2-plasma to create new active and binding sites, -NH2 groups, onto the modified fabric surfaces followed by subsequent loading of biosynthesized silver nanoparticles (Ag NPs) alone and in combination with certain antibiotics using exhaustion method. The imparted antibacterial activity against both G+ve (S. aureus) and G-ve (E. coli) pathogens was governed by type of substrate, extent of modification and subsequent loading of antibacterial agent, synergistic effect, and antibacterial activity as well as type of harmful bacteria. A remarkable antibacterial activity still retained even after 15 washings. In addition, incorporation of Ag NPs into pigment printing paste and into acid dyeing bath for combined coloration and functionalization of O2-plasma and N2-plasma pre-modified substrates respectively were successfully achieved. Moreover, both SEM images and EDS spectra of selected substrates revealed the change in surface morphology as well as the presence of the loaded Ag element onto the post-treated substrates.
Investigation on the effect of RF air plasma and neem leaf extract treatment on the surface modification and antimicrobial activity of cotton fabric

NASA Astrophysics Data System (ADS)

Vaideki, K.; Jayakumar, S.; Rajendran, R.; Thilagavathi, G.

2008-02-01

A thorough investigation on the antimicrobial activity of RF air plasma and azadirachtin (neem leaf extract) treated cotton fabric has been dealt with in this paper. The cotton fabric was given a RF air plasma treatment to improve its hydrophilicity. The process parameters such as electrode gap, time of exposure and RF power have been varied to study their effect in improving the hydrophilicity of the cotton fabric and they were optimized based on the static immersion test results. The neem leaf extract (azadirachtin) was applied on fabric samples to impart antimicrobial activity. The antimicrobial efficacy of the samples have been analysed and compared with the efficacy of the cotton fabric treated with the antimicrobial finish alone. The investigation reveals that the RF air plasma has modified the surface of the fabric, which in turn increased the antimicrobial activity of the fabric when treated with azadirachtin. The surface modification due to RF air plasma treatment has been analysed by comparing the FTIR spectra of the untreated and plasma treated samples. The molecular interaction between the fabric, azadirachtin and citric acid which was used as a cross linking agent to increase the durability of the antimicrobial finish has also been analysed using FTIR spectra.
Biocompatibility of modified ultra-high-molecular-weight polyethylene

NASA Astrophysics Data System (ADS)

Novotná, Z.; Lacmanová, V.; Rimpelová, S.; Juřik, P.; Polívková, M.; Å vorčik, V.

2016-09-01

Ultra-high-molecular-weight polyethylene (UHMWPE, PE) is a synthetic polymer used for biomedical applications because of its high impact resistance, ductility and stability in contact with physiological fluids. Therefore this material is being used in human orthopedic implants such as total joint replacements. Surface modification of this material relates to changes of its surface hydrophilicity, energy, microstructure, roughness, and morphology, all influencing its biological response. In our recent work, PE was treated by an Ar+ plasma discharge and then grafted with biologically active polyethylene glycol in order to enhance adhesion and proliferation of mouse fibroblast (L929). The surface properties of pristine PE and its grafted counterparts were studied by goniometry (surface wettability). Furthermore, Atomic Force Microscopy was used to determine the surface morphology and roughness. The biological response of the L929 cell lines seeded on untreated and plasma treated PE matrices was quantified in terms of the cell adhesion, density, and metabolic activity. Plasma treatment leads to the ablation of the polymer surface layers. Plasma treatment and subsequent poly(ethylene glycol) grafting lead to dramatic changes in the polymer surface morphology and roughness. Biological tests, performed in vitro, show increased adhesion and proliferation of cells on modified polymers. Grafting with poly(ethylene glycol) increases cell proliferation compared to plasma treatment.
Measurement of adhesion of human platelets in plasma to protein surfaces in microplates.

PubMed

Eriksson, Andreas C; Whiss, Per A

2005-01-01

Platelet adhesion is an initial, crucial and complex event for inhibiting blood loss upon vascular injury. Activation and adhesion of platelets also play a fundamental role in the development of thrombosis. A combination of exposed extracellular matrix proteins in the vascular wall and release of activating compounds from the participating cells activate the platelets. New potent anti-platelet agents are in progress but there is a shortage of methods that measure the concerted action of adhesive surfaces and soluble compounds upon platelet adhesion in vitro. The aim of this work was to develop a method to measure adhesion of platelets in plasma with standard laboratory equipment. Platelet-rich plasma from healthy humans was used in studies to optimise the conditions of the present assay. Different proteins were coated in microplate wells and various soluble platelet activators and inhibitors were added to establish the ability of the current method to detect increased as well as decreased platelet adhesion. The amount of platelet adhesion was measured by the reaction between p-nitrophenyl phosphate and the intracellular enzyme acid phosphatase. Adhesion of platelets in plasma to microplate wells coated with albumin, collagen, fibrinogen and activated plasma showed significant surface dependency. The known soluble platelet activators adenosine diphosphate, adrenaline and ristocetin enhanced the levels of adhesion. Available anti-platelet agents such as prostacyclin, forskolin, acetylsalicylic acid and RGD containing peptides caused dose-dependent inhibition of platelet adhesion. This report describes a further development of a previously described method and offers the advantage to use platelets in plasma to measure platelet adhesion to protein surfaces. The assay is simple and flexible and is suitable in basic research for screening and characterisation of platelet adhesion responsiveness.
Hemocompatible control of sulfobetaine-grafted polypropylene fibrous membranes in human whole blood via plasma-induced surface zwitterionization.

PubMed

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

2012-12-21

In this work, the hemocompatibility of zwitterionic polypropylene (PP) fibrous membranes with varying grafting coverage of poly(sulfobetaine methacrylate) (PSBMA) via plasma-induced surface polymerization was studied. Charge neutrality of PSBMA-grafted layers on PP membrane surfaces was controlled by the low-pressure and atmospheric plasma treatment in this study. The effects of grafting composition, surface hydrophilicity, and hydration capability on blood compatibility of the membranes were determined. Protein adsorption onto the different PSBMA-grafted PP membranes from human fibrinogen solutions was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Blood platelet adhesion and plasma clotting time measurements from a recalcified platelet-rich plasma solution were used to determine if platelet activation depends on the charge bias of the grafted PSBMA layer. The charge bias of PSBMA layer deviated from the electrical balance of positively and negatively charged moieties can be well-controlled via atmospheric plasma-induced interfacial zwitterionization and was further tested with human whole blood. The optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and keeps its original blood-inert property of antifouling, anticoagulant, and antithrmbogenic activities when it comes into contact with human blood. This work suggests that the hemocompatible nature of grafted PSBMA polymers by controlling grafting quality via atmospheric plasma treatment gives a great potential in the surface zwitterionization of hydrophobic membranes for use in human whole blood.
Alkaline phosphatase, 5'-nucleotidase and magnesium-dependent adenosine triphosphatase activities in the transitional epithelium of the rat urinary bladder.

PubMed

Zhang, S X; Kobayashi, T; Okada, T; García del Saz, E; Seguchi, H

1991-07-01

The cerium-based method was used to demonstrate cytochemically the ultrastructural localization of alkaline phosphatase (ALPase), 5'-nucleotidase (5'-Nase) and magnesium-dependent adenosine triphosphatase (Mg-ATPase) on the transitional epithelium of the rat urinary bladder. The reaction product for ALPase was found on the plasma membrane of all epithelial cells, except the luminal surface of superficial cells. The activity of 5'-Nase appeared on the plasma membrane of all bladder transitional epithelial cells, including the free surface of superficial cells. The Mg-ATPase reaction product was seen on the plasma membrane of superficial, intermediate and basal cells, but never on the luminal surface of superficial cells and it was only occasionally seen on the basal surface. The possible functions of these phosphatases have been discussed, and it was emphasized that the 5'-Nase activity present on the luminal surface of superficial cells may play a special role in the membrane movement of these cells in the transitional epithelium.
Plasma-grafting polymerization on carbon fibers and its effect on their composite properties

NASA Astrophysics Data System (ADS)

Zhang, Huanxia; Li, Wei

2015-11-01

Interfacial adhesion between matrix and fibers plays a crucial role in controlling the performance of composites. Carbon fibers have the major constraint of chemical interness and hence have limited adhesion with the matrix. Surface treatment of fibers is the best solution to this problem. In this work, carbon fibers were activated by plasma and grafting polymerization. The grafting ratio of polymerization was obtained by acid-base titration. The chemical and physical changes induced by the treatments on carbon fiber surface was examined using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique. The interfacial adhesion of CF/EP (carbon fiber/epoxy) composites were analyzed by a single fiber composite (SFC) for filament fragmentation test. Experimental results show that the grafting rate was not only the function of the plasma-treat time but also the concentration of the grafting polymerization. The oxygen-containing groups (such as Csbnd O, Cdbnd O, and Osbnd Cdbnd O) and the interfacial shear strength (IFSS) of the plasma-grafting carbon fiber increased more significantly than the carbon fiber without plasma treatment grafted with MAH. This demonstrates that the surfaces of the carbon fiber samples are more active, hydrophilic, and rough after plasma-grafting treatments using a DBD operating in ambient argon mixture with oxygen. With DBD (dielectric barrier discharges) operating in ambient argon mixture with oxygen, the more active, hydrophilic, and rough surface was obtained by the plasma-grafting treatments.
Plasma Surface Modification of Polyaramid Fibers for Protective Clothing

NASA Astrophysics Data System (ADS)

Widodo, Mohamad

2011-12-01

The purpose of this research was to develop a novel process that would achieve biocidal properties on Kevlar fabric via atmospheric pressure plasma jet (APPJ) induced-graft polymerization of monomers. In the course of the study, experiments were carried out to understand plasma-monomer-substrate interactions, particularly, how each of the main parameters in the plasma processing affects the formation of surface radicals and eventually the degree of graft polymerization of monomers. The study also served to explore the possibility of developing plasma-initiated and plasma-controlled graft polymerization for continuous operation. In this regards, three methods of processing were studied, which included two-step plasma graft-polymerization with immersion, two-step and one-step plasma graft-polymerization with pad-dry. In general, plasma treatment did not cause visible damage to the surface of Kevlar fibers, except for the appearance of tiny globules distributed almost uniformly indicating a minor effect of plasma treatment to the surface morphology of the polymer. From the examination of SEM images, however, it was found that a very localized surface etching seemed to have taken place, especially at high RF power (800 W) and long time of exposure (60 s), even in plasma downstream mode of operation. It was suggested that a small amount of charged particles might have escaped and reached the substrate surface. High density of surface radicals, which is the prerequisite for high graft density and high antimicrobial activity, was achieved by the combination of high RF power and short exposure time or low RF power and long time of exposure. This was a clear indication that the formation of surface radicals is a function of amount of the dissipated energy, which also explained the two-factor interaction between the two process parameters. XPS results showed that hydrolysis of the anilide bond of PPTA chains took place to some extent on the surface of Kevlar, leading to the formation carboxylic and phenyl amine groups, which may provide additional active sites for grafting by way of hydrogen abstraction from the latter. Further analysis of XPS data, however, showed that macroradicals and active sites of grafting were formed at least at one of the carbon atoms in the aromatic ring. A reduction of microbial activity up to 3-log reduction was achieved by plasma treated Kevlar grafted by either diallyl diammonium chloride (DADMAC) or 3- ((trimethoxysilyl)-propyl) dimethylammonium chloride (TMS), with the latter being the one with better performance. It was found that high antimicrobial activity was obtained by the combination of high RF power, short time of exposure, and low concentration of monomer. Of the three processing methods studied, the one with immersion method produced higher graft yield. However, one-step plasma graft-polymerization with pad-dry method has proven itself more interesting due to its potential for an open continuous process. This research has been successful in producing effective antimicrobial properties on Kevlar fabric by plasma-initiated and plasma-controlled graft polymerization, which is unprecedented. The design of experiments showed that better results with higher order of log reduction can be obtained by process optimization, e.g. by using response surface methods. It would also be very beneficial to continue the research for the development of plasma graft-polymerization process with more rigorous design, which involves the use of crosslinker and antimicrobial monomers with different chemistry. A study that involves the development of a robust design for processes that perform consistently as intended under a wide range of user's conditions and yet produce high-level performance with high reliability would also be advantageous. The major implication of the findings from this research for the finishing of Kevlar is that a wide array of different surface functionalities may become more readily available now than ever. Plasma technology has made surface chemistry functionalization of Kevlar more straightforward and easier to perform, which opens new avenues for achieving functional and multifunctional Kevlar fabrics using a fast, more economic and environmentally friendly continuous process for niche market such as military applications and protective clothing for emergency responders.
Active cleaning technique device

NASA Technical Reports Server (NTRS)

Shannon, R. L.; Gillette, R. B.

1973-01-01

The objective of this program was to develop a laboratory demonstration model of an active cleaning technique (ACT) device. The principle of this device is based primarily on the technique for removing contaminants from optical surfaces. This active cleaning technique involves exposing contaminated surfaces to a plasma containing atomic oxygen or combinations of other reactive gases. The ACT device laboratory demonstration model incorporates, in addition to plasma cleaning, the means to operate the device as an ion source for sputtering experiments. The overall ACT device includes a plasma generation tube, an ion accelerator, a gas supply system, a RF power supply and a high voltage dc power supply.
Plasma enhanced modification of TMP fiber and its effect on tensile strength of wood fiber/PP composite

Treesearch

Sangyeob Lee; Todd F. Shupe; Chung Y. Hse

2009-01-01

Plasma-assisted surface treatment on thermomechanical pulp (TMP) fiber and polypropylene (PP) film was investigated to obtain interfacial adhesion at the wood fiber and PP interface. A metal plate between electrodes prevented thermal damage to the TMP fiber handsheets and PP film. Oxygen-plasma treatment provided better surface activation on the TMP fiber and...

Understanding plasma biofilm interactions for controlling infection and virulence

NASA Astrophysics Data System (ADS)

Flynn, Padrig B.; Gilmore, Brendan F.

2018-07-01

Bacterial biofilms are surface adhered communities of bacteria encased within a protective extracellular polymeric matrix. These heterogeneous microbial communities are characterized by elevated tolerance to antimicrobial agents, host immune clearance mechanisms and physical disinfection approaches. Atmospheric pressure non-thermal plasmas have proven to be highly effective in the eradication of bacteria and fungi in both planktonic and biofilm modes of growth at low temperatures, making it a promising approach for surface decontamination of both biotic and abiotic surfaces alike. In addition, non-thermal plasmas as a putative non-antibiotic approach to controlling infectious microorganisms, holds significant promise as an antibiotic alternative infection control strategy, with demonstrated efficacy against antibiotic resistant microorganisms. This topical review introduces the reader to key concepts in biofilm tolerance mechanisms relevant to treatment and control of these surface adhered bacterial communities with cold plasmas. In addition, the ability of plasma-derived active species to interact with both biofilm extracellular matrix components and bacterial cellular targets will be discussed in order to elucidate the mechanisms of antimicrobial and antibiofilm action. By understanding these fundamental interactions, plasma sources may be precisely tailored for antimicrobial applications, specifically for biofilm control where bacterial and fungal physiology (and sensitivity to physical and chemical decontamination) is markedly different from that of their planktonic, or free swimming, counterparts. Recently, novel roles for reactive oxygen and nitrogen species in the activity of conventional antibiotics have been proposed. This extends the possibility that plasmas may enhance the activity of conventional antibiotics and biocides in controlling these highly tolerant microbial populations. Lessons from classical biofilm microbiology can be usefully translated and applied to the design of plasma-based approaches aimed at biofilm control, while potential for tolerance and persistence to plasma in bacterial communities will be reviewed.
Surface modification and deuterium retention in reduced-activation steels exposed to low-energy, high-flux pure and helium-seeded deuterium plasmas

NASA Astrophysics Data System (ADS)

Alimov, V. Kh; Ogorodnikova, O. V.; Hatano, Y.; Gasparyan, YuM.; Efimov, V. S.; Mayer, M.; Zhou, Z.; Oyaizu, M.; Isobe, K.; Nakamura, H.; Hayashi, T.

2018-04-01

Surface topography of and deuterium (D) retention in reduced activation ferritic-martensitic Eurofer'97 and ferritic oxide dispersion strengthening ODS-16Cr steels have been studied after exposure at 600 K to low-energy (70 and 200 eV), high-flux (∼1022 D/m2s) pure D and D-10%He plasmas with D fluence of 2 × 1025 D/m2. The methods used were scanning electron microscopy, energy-scanning D(3He,p)4He nuclear reaction, and thermal desorption spectroscopy. As a result of the plasma exposures, nano-sized structures are formed on the steel surfaces. After exposure to pure D plasmas, a significant fraction of D is accumulated in the bulk, at depths larger than 8 μm. After exposures to D-He plasmas, D is retained mainly in the near-surface layers. In spite of the fact that the He fluence was lower than the D fluence, the He retention in the steels is one order of magnitude higher than the D retention.
Formation of Nanocones on Highly Oriented Pyrolytic Graphite by Oxygen Plasma

PubMed Central

Vesel, Alenka; Eleršič, Kristina; Modic, Martina; Junkar, Ita; Mozetič, Miran

2014-01-01

Improvement in hemocompatibility of highly oriented pyrolytic graphite (HOPG) by formation of nanostructured surface by oxygen plasma treatment is reported. We have showed that by appropriate fine tuning of plasma and discharge parameters we are able to create nanostructured surface which is densely covered with nanocones. The size of the nanocones strongly depended on treatment time. The optimal results in terms of material hemocompatibility were obtained after treatment with oxygen plasma for 15 s, when both the nanotopography and wettability were the most favorable, since marked reduction in adhesion and activation of platelets was observed on this surface. At prolonged treatment times, the rich surface topography was lost and thus also its antithrombogenic properties. Chemical composition of the surface was always more or less the same, regardless of its morphology and height of the nanocones. Namely, on all plasma treated samples, only a few atomic percent of oxygen was found, meaning that plasma caused mostly etching, leading to changes in the surface morphology. This indicates that the main preventing mechanism against platelets adhesion was the right surface morphology. PMID:28788553
Effect of Microwave Non thermal Plasma Irradiation on the Adsorptive Properties of Active Carbon Preliminarily Impregnated with Poly(vinyl alcohol)

NASA Astrophysics Data System (ADS)

Ueshima, Masato; Toda, Eriko; Nakajima, Yuki; Sugiyama, Kazuo

2010-08-01

Microwave non thermal plasma irradiation was conducted on active carbon (AC) preliminarily impregnated with poly(vinyl alcohol) (PVA) in order to modify the adsorption properties of active carbon, particularly to increase hydrophobicity. The plasma was produced by applying microwave power on the PVA-impregnated active carbon (PVA/AC) placed in a low vacuum chamber (<10 Torr). The surface of the plasma-treated PVA/AC was imaged using scanning electron microscopy and atomic force microscopy (SEM and AFM, respectively), and analyzed using X-ray photoelectron spectroscopy (XPS). Hydrophobicity of the plasma-treated PVA/AC was compared to that of untreated PVA/AC and AC by a sinking test in water/methanol mixed solutions. The hydrophobicity drastically increased for PVA/AC treatment with 1-min plasma irradiation. The AFM results indicated that the surface roughness of the PVA/AC was dependent upon the hydrophobicity, rather than reduction of free energy due to reduction of polarized functional groups. NaOH and HCl adsorption onto the plasma-treated PVA/AC was also measured. Adsorption capacity of plasma-treated PVA/AC increased for NaOH, whereas it decreased for HCl. The plasma treatment not only increased the hydrophobicity of PVA/AC, but also changed its acid-base adsorption properties. We have developed a new material based on active carbon, which is light, hydrophobic and electrically conductive by using a combination of PVA sintering and plasma irradiation.
Enhanced adherence of mouse fibroblast and vascular cells to plasma modified polyethylene.

PubMed

Reznickova, Alena; Novotna, Zdenka; Kolska, Zdenka; Kasalkova, Nikola Slepickova; Rimpelova, Silvie; Svorcik, Vaclav

2015-01-01

Since the last decade, tissue engineering has shown a sensational promise in providing more viable alternatives to surgical procedures for harvested tissues, implants and prostheses. Biomedical polymers, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE), were activated by Ar plasma discharge. Degradation of polymer chains was examined by determination of the thickness of ablated layer. The amount of an ablated polymer layer was measured by gravimetry. Contact angle, measured by goniometry, was studied as a function of plasma exposure and post-exposure aging times. Chemical structure of modified polymers was characterized by angle resolved X-ray photoelectron spectroscopy. Surface chemistry and polarity of the samples were investigated by electrokinetic analysis. Changes in surface morphology were followed using atomic force microscopy. Cytocompatibility of plasma activated polyethylene foils was studied using two distinct model cell lines; VSMCs (vascular smooth muscle cells) as a model for vascular graft testing and connective tissue cells L929 (mouse fibroblasts) approved for standardized material cytotoxicity testing. Specifically, the cell number, morphology, and metabolic activity of the adhered and proliferated cells on the polyethylene matrices were studied in vitro. It was found that the plasma treatment caused ablation of the polymers, resulting in dramatic changes in their surface morphology and roughness. ARXPS and electrokinetic measurements revealed oxidation of the polymer surface. It was found that plasma activation has a positive effect on the adhesion and proliferation of VSMCs and L929 cells. Copyright © 2015 Elsevier B.V. All rights reserved.
ISS Local Environment Spectrometers (ISLES)

NASA Technical Reports Server (NTRS)

Krause, Linda Habash; Gilchrist, Brian E.

2014-01-01

In order to study the complex interactions between the space environment surrounding the ISS and the ISS surface materials, we propose to use lowcost, high-TRL plasma sensors on the ISS robotic arm to probe the ISS space environment. During many years of ISS operation, we have been able to condut effective (but not perfect) extravehicular activities (both human and robotic) within the perturbed local ISS space environment. Because of the complexity of the interaction between the ISS and the LEO space environment, there remain important questions, such as differential charging at solar panel junctions (the so-called "triple point" between conductor, dielectric, and space plasma), increased chemical contamination due to ISS surface charging and/or thruster activation, water dumps, etc, and "bootstrap" charging of insulating surfaces. Some compelling questions could synergistically draw upon a common sensor suite, which also leverages previous and current MSFC investments. Specific questions address ISS surface charging, plasma contactor plume expansion in a magnetized drifting plasma, and possible localized contamination effects across the ISS.
Blood antioxidant enzymes as markers of exposure or effect in coal miners.

PubMed Central

Perrin-Nadif, R; Auburtin, G; Dusch, M; Porcher, J M; Mur, J M

1996-01-01

OBJECTIVE--To investigate if blood Cu++/Zn++ superoxide dismutase, glutathione peroxidase, catalase, and total plasma antioxidant activities could be markers of biological activity resulting from exposure to respirable coal mine dust in active miners, and of pneumoconiosis in retired miners. METHODS--Blood samples were randomly obtained from active surface workers (n = 30) and underground miners (n = 34), and from retired miners without (n = 21), and with (n = 33) pneumoconiosis. Antioxidant enzyme activities and total plasma antioxidants were measured in erythrocytes and plasma. Non-parametric tests were completed by analyses of covariance to compare antioxidants between groups, taking into account potential confounding factors (age, smoking history (pack-years)). RESULTS--Erythrocyte Cu++/Zn++ superoxide dismutase activity was significantly higher in the group of underground miners than the group of surface workers. The differences in total plasma antioxidants and plasma glutathione peroxidase activity between both groups were related to age. Glutathione peroxidase activity increased in the plasma of retired miners with pneumoconiosis, compared with retired miners without pneumoconiosis. No differences were found either in erythrocyte antioxidant enzyme activities or in total plasma antioxidants between the groups of retired miners without and with pneumoconiosis. CONCLUSIONS--In this study, erythrocyte Cu++/Zn++ superoxide dismutase activity may be considered as a marker of effect of respirable coal mine dust in exposed workers. This result is in agreement with the hypothesis that reactive oxygen species are involved in cell injury induced by coal mine dust, and may be predictive of the degree of inflammation and pneumoconiosis induced by coal mine dust. The increase in glutathione peroxidase activity in the plasma of retired miners with pneumoconiosis may be the result of a response to the increasing hydrogen peroxide (H2O2) production due to the disease process. PMID:8563856
A comparative study of thermochemical and cold plasma treatment on lignin-based activated carbon for adsorbing Fe(III)

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

PubMed

Nordheim, T A; Jones, G H; Roussos, E; Leisner, J S; Coates, A J; Kurth, W S; Khurana, K K; Krupp, N; Dougherty, M K; Waite, J H

2014-10-28

On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn's small, irregularly shaped moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon's surface. Plasma wave activity detected by the Radio and Plasma Wave instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. We show that this constitutes a remote detection of a strongly negative (∼ -200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator.
Synthetic Aperture Microwave Imaging (SAMI) of the plasma edge on NSTX-U

NASA Astrophysics Data System (ADS)

Vann, Roddy; Taylor, Gary; Brunner, Jakob; Ellis, Bob; Thomas, David

2016-10-01

The Synthetic Aperture Microwave Imaging (SAMI) system is a unique phased-array microwave camera with a +/-40° field of view in both directions. It can image cut-off surfaces corresponding to frequencies in the range 10-34.5GHz; these surfaces are typically in the plasma edge. SAMI operates in two modes: either imaging thermal emission from the plasma (often modified by its interaction with the plasma edge e.g. via BXO mode conversion) or ``active probing'' i.e. injecting a broad beam at the plasma surface and imaging the reflected/back-scattered signal. SAMI was successfully pioneered on the Mega-Amp Spherical Tokamak (MAST) at Culham Centre for Fusion Energy. SAMI has now been installed and commissioned on the National Spherical Torus Experiment Upgrade (NSTX-U) at Princeton Plasma Physics Laboratory. The firmware has been upgraded to include real-time digital filtering, which enables continuous acquisition of the Doppler back-scattered active probing data. In this poster we shall present SAMI's analysis of the plasma edge on NSTX-U including measurements of the edge pitch angle on NSTX-U using SAMI's unique 2-D Doppler-backscattering capability.
Selective protein adsorption modulates platelet adhesion and activation to oligo(ethylene glycol)-terminated self-assembled monolayers with C18 ligands.

PubMed

Gonçalves, Inês C; Martins, M Cristina L; Barbosa, Mário A; Naeemi, Esmaeel; Ratner, Buddy D

2009-06-01

This study focuses on the selective binding of albumin to a nanostructured surfaces to inhibit other blood proteins from adsorbing thereby reducing platelet adhesion and activation. Tetra (ethylene-glycol)-terminated self-assembled monolayers (EG4 SAMs) with different percentages of C18 ligands on the surface were characterized by contact angle measurements, X-ray photoelectron microscopy, infrared reflection-absorption spectroscopy, and ellipsometry. A specific surface (2.5% C18 SAM) was found to be selective for human serum albumin (HSA) in the presence of both albumin and fibrinogen (HFG). The importance of this concentration of C18 ligands was stressed in reversibility studies since that surface exchanged almost all the preadsorbed HSA by HSA in solution, but not by HFG. The effect of protein adsorption in the subsequent adhesion and activation of platelets was studied by pre-immersing the surfaces in albumin and plasma before contact with platelets. Scanning electron microscopy and glutaraldehyde induced fluorescence technique images showed that as surfaces got more hydrophobic due to the immobilization of C18 ligands, the number of adherent platelets increased and their morphology changed from round to fully spread. Pre-immersion in HSA led to an 80% decrease in platelet adhesion and reduction of activation. Pre-immersion in 1% plasma was only relevant in 2.5% C18 SAMs since this was the only surface that demonstrated less adhesion of platelets comparing with buffer pre-immersion. However, they still adsorb more platelets then when HSA was preadsorbed. This was confirmed in competition studies between HSA and plasma that suggested that other plasma proteins were also adsorbing to this surface. 2008 Wiley Periodicals, Inc.
Biochar activated by oxygen plasma for supercapacitors

NASA Astrophysics Data System (ADS)

Gupta, Rakesh Kumar; Dubey, Mukul; Kharel, Parashu; Gu, Zhengrong; Fan, Qi Hua

2015-01-01

Biochar, also known as black carbon, is a byproduct of biomass pyrolysis. As a low-cost, environmental-friendly material, biochar has the potential to replace more expensive synthesized carbon nanomaterials (e.g. carbon nanotubes) for use in future supercapacitors. To achieve high capacitance, biochar requires proper activation. A conventional approach involves mixing biochar with a strong base and baking at a high temperature. However, this process is time consuming and energy inefficient (requiring temperatures >900 °C). This work demonstrates a low-temperature (<150 °C) plasma treatment that efficiently activates a yellow pine biochar. Particularly, the effects of oxygen plasma on the biochar microstructure and supercapacitor characteristics are studied. Significant enhancement of the capacitance is achieved: 171.4 F g-1 for a 5-min oxygen plasma activation, in comparison to 99.5 F g-1 for a conventional chemical activation and 60.4 F g-1 for untreated biochar. This enhancement of the charge storage capacity is attributed to the creation of a broad distribution in pore size and a larger surface area. The plasma activation mechanisms in terms of the evolution of the biochar surface and microstructure are further discussed.
Surface analysis using a new plasma assisted desorption/ionisation source for mass spectrometry in ambient air

NASA Astrophysics Data System (ADS)

Bowfield, A.; Barrett, D. A.; Alexander, M. R.; Ortori, C. A.; Rutten, F. M.; Salter, T. L.; Gilmore, I. S.; Bradley, J. W.

2012-06-01

The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution.
Highly roughened polycaprolactone surfaces using oxygen plasma-etching and in vitro mineralization for bone tissue regeneration: fabrication, characterization, and cellular activities.

PubMed

Kim, YongBok; Kim, GeunHyung

2015-01-01

Herein, poly(ɛ-caprolactone) (PCL) surfaces were treated to form various roughness values (R(a)=290-445 nm) and polar functional groups on the surfaces using a plasma-etching process, followed by immersion into simulated body fluid (SBF) for apatite formation. The surface morphology, chemical composition, and mean roughness of the plasma-etched PCL surfaces were measured, and various physical and morphological properties (water contact angles, protein absorption ability, and crystallite size of the apatite layer) of the in vitro mineralized PCL surfaces were evaluated. The roughened PCL surface P-3, which was treated with a sufficient plasma exposure time (4 h), achieved homogeneously distributed apatite formation after soaking in SBF for 7 days, as compared with other surfaces that were untreated or plasma-treated for 30 min or 2 h. Furthermore, to demonstrate their feasibility as a biomimetic surface, pre-osteoblast cells (MC3T3-E1) were cultured on the mineralized PCL surfaces, and cell viability, DAPI-phalloidin fluorescence assay, and alizarin red-staining of the P-3 surface were highly improved compared to the P-1 surface treated with a 30-min plasma exposure time; compared to untreated mineralized PCL surface (N-P), P-3 showed even greater improvements in cell viability and DAPI-phalloidin fluorescence assay. Based on these results, we found that the mineralized PCL surface supplemented with the appropriate plasma treatment can be implicitly helpful to achieve rapid hard tissue regeneration. Copyright © 2014 Elsevier B.V. All rights reserved.
The surface modification of clay particles by RF plasma technique

NASA Astrophysics Data System (ADS)

Lee, Sang-Keol

In this study, the surface coatings of ball clay, organoclay and exfoliated clay prepared by sol-gel process were done by RF plasma polymerization to improve the surface activity of the clay filler. Characterization of the above plasma-treated clays has been carried out by various techniques. The effects of plasma-treated clays as substitute of carbon black in styrene-butadiene rubber (SBR) and ethylene-propylene-diene monomer (EPDM) on the curing and mechanical properties were investigated. After plasma treatment, the tensile properties of organo and exfoliated clay were not unsatisfactory to that of carbon black filler system. Moreover, only 10 phr filler loading of plasma-treated organoclay in EPDM vulcanizates showed better results than 40 phr filler loading of carbon black in EPDM vulcanizates. The main objective of this study was to verify the applicability of the plasma technique for modifying clay surfaces for their use in the tire manufacturing industry. Another purpose was to reveal the advantage of the plasma technique used to obtain modified-clay and improved properties that those materials can display.
In-situ plasma processing to increase the accelerating gradients of SRF cavities

DOE PAGES

Doleans, Marc; Afanador, Ralph; Barnhart, Debra L.; ...

2015-12-31

A new in-situ plasma processing technique is being developed at the Spallation Neutron Source (SNS) to improve the performance of the cavities in operation. The technique utilizes a low-density reactive oxygen plasma at room temperature to remove top surface hydrocarbons. The plasma processing technique increases the work function of the cavity surface and reduces the overall amount of vacuum and electron activity during cavity operation; in particular it increases the field emission onset, which enables cavity operation at higher accelerating gradients. Experimental evidence also suggests that the SEY of the Nb surface decreases after plasma processing which helps mitigating multipactingmore » issues. This article discusses the main developments and results from the plasma processing R&D are presented and experimental results for in-situ plasma processing of dressed cavities in the SNS horizontal test apparatus.« less
Au-nanoparticles grafted on plasma treated PE

NASA Astrophysics Data System (ADS)

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

2010-03-01

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

PubMed

Stoleru, Elena; Zaharescu, Traian; Hitruc, Elena Gabriela; Vesel, Alenka; Ioanid, Emil G; Coroaba, Adina; Safrany, Agnes; Pricope, Gina; Lungu, Maria; Schick, Christoph; Vasile, Cornelia

2016-11-23

Both cold nitrogen radiofrequency plasma and gamma irradiation have been applied to activate and functionalize the polylactic acid (PLA) surface and the subsequent lactoferrin immobilization. Modified films were comparatively characterized with respect to the procedure of activation and also with unmodified sample by water contact angle measurements, mass loss, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), and chemiluminescence measurements. All modified samples exhibit enhanced surface properties mainly those concerning biocompatibility, antimicrobial, and antioxidant properties, and furthermore, they are biodegradable and environmentally friendly. Lactoferrin deposited layer by covalent coupling using carbodiimide chemistry showed a good stability. It was found that the lactoferrin-modified PLA materials present significantly increased oxidative stability. Gamma-irradiated samples and lactoferrin-functionalized samples show higher antioxidant, antimicrobial, and cell proliferation activity than plasma-activated and lactoferrin-functionalized ones. The multifunctional materials thus obtained could find application as biomaterials or as bioactive packaging films.
Improvement of adhesion properties of low density polyethylene (LDPE) substrate using atmospheric plasma

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

Sanchez-Nacher, L.; Garcia-Sanoguera, D.; Fenollar, O.

2010-06-02

In this work we have used atmospheric plasma technology on polyethylene surface with different treatment conditions. These modify surface pre-treatments on polyethylene, thus having a positive effect on overall surface activity of polymer surface and, consequently, adhesion properties can be remarkably improved. We have evaluated the influence of the nozzle/substrate distance and atmospheric plasma speed on wettability changes and adhesion properties. Wettability changes have been studied by contact angle measurements and subsequent surface energy calculation. Mechanical characterization of adhesion joints has been carried out in two different ways: peel and shear tensile test. The overall results show a remarkable increasemore » in mechanical properties of adhesion joints for low nozzle/substrate distances and low speed. So plasma atmospheric technology is highly useful to increase adhesion properties of polypropylene.« less
Collaborative Research: Fundamental studies of plasma control using surface embedded electronic devices

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

Raja, Laxminarayan L.; PanneerChelvam, PremKumar; Levko, Dimtry

2016-02-26

The proposed study will investigate the effect of active electron injection of from electrode surfaces To the best of our knowledge, no such a study has ever been attempted even though it could lead to the formation of whole new classes of plasma based devices and systems. We are motivated by recent articles and simple theory which gives strong reason to believe that embedded electronic devices can be used to exert control over the SEE coefficient of semiconductor surfaces (and maybe other surface types as well). Furthermore, the research will explore how such sub-surface electronic devices can best be usedmore » to exert control over an associated plasma.« less

Graft Polymerization of Acrylic Acid on a Polytetrafluoroethylene Panel by an Inductively Coupled Plasma

NASA Astrophysics Data System (ADS)

Lan, Yan; You, Qingliang; Cheng, Cheng; Zhang, Suzhen; Ni, Guohua; Nagatsu, M.; Meng, Yuedong

2011-02-01

Surface modification on a polytetrafluoroethylene (PTFE) panel was performed with sequential nitrogen plasma treatments and surface-initiated polymerization. By introducing COO- groups to the surface of the PTFE panel through grafting polymerization of acrylic acid (AA), a transparent poly (acrylic acid) (PAA) membrane was achieved from acrylic acid solution. Grafting polymerization initiating from the active groups was achieved on the PTFE panel surface after the nitrogen plasma treatment. Utilizing the acrylic acid as monomers, with COO- groups as cross link sites to form reticulation structure, a transparent poly (acrylic acid) membrane with arborescent macromolecular structure was formed on the PTFE panel surface. Analysis methods, such as fourier transform infrared spectroscopy (FTIR), microscopy and X-ray photoelectron spectroscopy (XPS), were utilized to characterize the structures of the macromolecule membrane on the PTFE panel surface. A contact angle measurement was performed to characterize the modified PTFE panels. The surface hydrophilicities of modified PTFE panels were significantly enhanced after the plasma treatment. It was shown that the grafting rate is related to the treating time and the power of plasma.
Atomic layer deposition of ruthenium on plasma-treated vertically aligned carbon nanotubes for high-performance ultracapacitors.

PubMed

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

2014-10-31

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

PubMed

Custodio, William; Silva, Wander J; Paes Leme, Adriana F; Cury, Jaime A; Del Bel Cury, Altair A

2015-11-01

The objective of the present study was to determine if blood plasma proteins could change the proteome of the acquired denture pellicle by label-free quantitative proteomics. As pellicle proteome modulates the interaction between substrates and Candida cells, we investigated its effect on the surface free energy (SFE) of the coated resin and on Candida albicans phospholipase and aspartyl proteinase activities. Poly(methylmethacrylate) discs were exposed to saliva (control) or saliva enriched with blood plasma (experimental group). The pellicle proteome was analyzed by mass spectrometry coupled with liquid chromatography. SFE was determined by acid-base technique. After biofilm formation, phospholipase and proteinase activities were determined accordingly to classic plate methods. Data were analyzed by two-way anova and Tukey test (P < 0.05). α-Amylase, cystatins, mucins, and host-immune system proteins were the main proteins identified in the control group. Fibrinogen and albumin were observed only in the experimental group. Coated discs of the experimental group presented an increased SFE (P < 0.05). For both enzymes tested, the experimental group showed higher proteolytic activity (P < 0.001). Blood plasma changes the proteome of the acquired denture pellicle, increasing surface free energy and the activity of Candida albicans phospholipase and aspartyl proteinase. © 2014 Wiley Publishing Asia Pty Ltd.
2D Thermoluminescence imaging of dielectric surface long term charge memory of plasma surface interaction in DBD discharges

NASA Astrophysics Data System (ADS)

Ambrico, Paolo F.; Ambrico, Marianna; Schiavulli, Luigi; De Benedictis, Santolo

2014-07-01

The charge trapping effect due to the exposure of alumina surfaces to plasma has been studied in a volume dielectric barrier discharge (DBD) in Ar and He noble gases. The long lasting charge trapping of alumina dielectric plates, used as barriers in DBDs, is evidenced by an ex situ thermoluminescence (TL) experiment performed with a standard and a custom two-dimensional (2D)-TL apparatus. The spatial density of trapped surface charges is found to be strongly correlated to the plasma morphology, and the surface spatial memory lasted for several minutes to hours after plasma exposure. In the case of Ar, the plasma channel impact signature on the surface shows a higher equivalent radiation dose with respect to the surface plasma wave and the post-discharge species signature. As a consequence, for the development of discharges, inside the dielectric surface the availability of lower energy trapped electrons is larger in the first region of plasma impact. The reported spatial memory increases the likelihood of the occurrence of plasma filaments in the same position in different runs. In He plasmas, the dielectric barrier shows an almost uniform distribution of trapped charges, meaning that there is no preferred region for the development of the discharge. In all cases a slight asymmetry was shown in the direction of the gas flow. This can be interpreted as being due to the long-living species moving in the direction of the gas flow, corresponding with the TL side experiment on the sample exposed to the plasma afterglow. The maximum values and the integral of the 2D-TL images showed a linear relation with the total charge per ac cycle, corresponding with findings for the TL glow curve. In conclusion, 2D-TL images allow the retrieval of information regarding the plasma surface interaction such as the plasma morphology, trap sites and their activation temperature.
Tailored adhesion behavior of polyelectrolyte thin films deposited on plasma-treated poly(dimethylsiloxane) for functionalized membranes

NASA Astrophysics Data System (ADS)

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

2016-04-01

Completely homogenous films formed via the layer-by-layer assembly of poly(diallyldimethylammonium chloride) (PDADMAC) and the poly(styrene sulfonate) were successfully obtained on plasma-treated poly(dimethylsiloxane) (PDMS) substrates. To modify the hydrophobicity of the PDMS surface, a cold plasma treatment was previously applied to the membrane, which led to the creation of hydrophilic groups on the surface of the membrane. PDMS wettability and surface morphology were successfully correlated with the plasma parameters. A combination of contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis was used to demonstrate that homogeneous and hydrophilic surfaces could be achieved on PDMS cold-plasma-treated membranes. The stability of the assembled PEL layer on the PDMS was evaluated using a combination of pull-off testing and X-ray photoelectron spectroscopy (XPS), which confirmed the relevance of a plasma pre-treatment as the adhesion of the polyelectrolyte multilayers was greatly enhanced when the deposition was completed on an activated PDMS surface at 80 W for 5 min.
Dependence of the quality of adhesion between poly(dimethylsiloxane) and glass surfaces on the conditions of treatment with oxygen plasma.

PubMed

Millare, Brent; Thomas, Marlon; Ferreira, Amy; Xu, Hong; Holesinger, Madison; Vullev, Valentine I

2008-11-18

Treatment with oxygen-containing plasma is an essential step for the fabrication of devices containing components of polydimethylsiloxane (PDMS). Such oxidative treatment chemically modifies the surface of PDMS allowing it to permanently adhere to glass, quartz, PDMS and other silica-based substrates. Overexposure of PDMS to oxidative gas plasma, however, compromises its adhesiveness. Therefore, regulation of the duration and the conditions of the plasma treatment is crucial for achieving sufficient surface activation without overoxidation. Using a semiquantitative ternary approach, we evaluated the quality of adhesion ( QA) between flat PDMS and glass substrates pretreated with oxygen plasma under a range of different conditions. The quality of adhesion manifested good correlation trends with the surface properties of the pretreated PDMS. Examination of the QA dependence on the treatment duration and on the pressure and the RF power of the plasma revealed a range of oxidative conditions that allowed for permanent adhesion with quantitative yields.
Effect of plasma pretreatment on adhesion and mechanical properties of UV-curable coatings on plastics

NASA Astrophysics Data System (ADS)

Gururaj, T.; Subasri, R.; Raju, K. R. C. Soma; Padmanabham, G.

2011-02-01

An attempt was made to study the effect of plasma surface activation on the adhesion of UV-curable sol-gel coatings on polycarbonate (PC) and polymethylmethacrylate (PMMA) substrates. The sol was synthesized by the hydrolysis and condensation of a UV-curable silane in combination with Zr-n-propoxide. Coatings deposited by dip coating were cured using UV-radiation followed by thermal curing between 80 °C and 130 °C. The effect of plasma surface treatment on the wettability of the polymer surface prior to coating deposition was followed up by measuring the water contact angle. The water contact angle on the surface of as-cleaned substrates was 80° ± 2° and that after plasma treatment was 43° ± 1° and 50° ± 2° for PC and PMMA respectively. Adhesion as well as mechanical properties like scratch resistance and taber abrasion resistance were evaluated for coatings deposited over plasma treated and untreated surfaces.
Plasma Membrane Factor XIIIA Transglutaminase Activity Regulates Osteoblast Matrix Secretion and Deposition by Affecting Microtubule Dynamics

PubMed Central

Al-Jallad, Hadil F.; Myneni, Vamsee D.; Piercy-Kotb, Sarah A.; Chabot, Nicolas; Mulani, Amina; Keillor, Jeffrey W.; Kaartinen, Mari T.

2011-01-01

Transglutaminase activity, arising potentially from transglutaminase 2 (TG2) and Factor XIIIA (FXIIIA), has been linked to osteoblast differentiation where it is required for type I collagen and fibronectin matrix deposition. In this study we have used an irreversible TG-inhibitor to ‘block –and-track’ enzyme(s) targeted during osteoblast differentiation. We show that the irreversible TG-inhibitor is highly potent in inhibiting osteoblast differentiation and mineralization and reduces secretion of both fibronectin and type I collagen and their release from the cell surface. Tracking of the dansyl probe by Western blotting and immunofluorescence microscopy demonstrated that the inhibitor targets plasma membrane-associated FXIIIA. TG2 appears not to contribute to crosslinking activity on the osteoblast surface. Inhibition of FXIIIA with NC9 resulted in defective secretory vesicle delivery to the plasma membrane which was attributable to a disorganized microtubule network and decreased microtubule association with the plasma membrane. NC9 inhibition of FXIIIA resulted in destabilization of microtubules as assessed by cellular Glu-tubulin levels. Furthermore, NC9 blocked modification of Glu-tubulin into 150 kDa high-molecular weight Glu-tubulin form which was specifically localized to the plasma membrane. FXIIIA enzyme and its crosslinking activity were colocalized with plasma membrane-associated tubulin, and thus, it appears that FXIIIA crosslinking activity is directed towards stabilizing the interaction of microtubules with the plasma membrane. Our work provides the first mechanistic cues as to how transglutaminase activity could affect protein secretion and matrix deposition in osteoblasts and suggests a novel function for plasma membrane FXIIIA in microtubule dynamics. PMID:21283799
Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

PubMed Central

Reis, Rackel; Dumée, Ludovic F.; Tardy, Blaise L.; Dagastine, Raymond; Orbell, John D.; Schutz, Jürg A.; Duke, Mikel C.

2016-01-01

Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties. PMID:27363670
Activation of the novel estrogen receptor G protein-coupled receptor 30 (GPR30) at the plasma membrane.

PubMed

Filardo, E; Quinn, J; Pang, Y; Graeber, C; Shaw, S; Dong, J; Thomas, P

2007-07-01

G protein-coupled receptor 30 (GPR30), a seven-transmembrane receptor (7TMR), is associated with rapid estrogen-dependent, G protein signaling and specific estrogen binding. At present, the subcellular site of GPR30 action is unclear. Previous studies using antibodies and fluorochrome-labeled estradiol (E2) have failed to detect GPR30 on the cell surface, suggesting that GPR30 may function uniquely among 7TMRs as an intracellular receptor. Here, we show that detectable expression of GPR30 on the surface of transfected HEK-293 cells can be selected by fluorescence-activated cell sorting. Expression of GPR30 on the cell surface was confirmed by confocal microscopy using the lectin concanavalin A as a plasma membrane marker. Stimulation of GPR30-expressing HEK-293 cells with 17beta-E2 caused sequestration of GPR30 from the cell surface and resulted in its codistribution with clathrin and mobilization of intracellular calcium stores. Evidence that GPR30 signals from the cell surface was obtained from experiments demonstrating that the cell-impermeable E2-protein conjugates E2-BSA and E2-horseradish peroxidase promote GPR30-dependent elevation of intracellular cAMP concentrations. Subcellular fractionation studies further support the plasma membrane as a site of GPR30 action with specific [3H]17beta-E2 binding and G protein activation associated with plasma membrane but not microsomal, or other fractions, prepared from HEK-293 or SKBR3 breast cancer cells. These results suggest that GPR30, like other 7TMRs, functions as a plasma membrane receptor.
Plasma assisted surface treatments of biomaterials.

PubMed

Minati, L; Migliaresi, C; Lunelli, L; Viero, G; Dalla Serra, M; Speranza, G

2017-10-01

The biocompatibility of an implant depends upon the material it is composed of, in addition to the prosthetic device's morphology, mechanical and surface properties. Properties as porosity and pore size should allow, when required, cells penetration and proliferation. Stiffness and strength, that depend on the bulk characteristics of the material, should match the mechanical requirements of the prosthetic applications. Surface properties should allow integration in the surrounding tissues by activating proper communication pathways with the surrounding cells. Bulk and surface properties are not interconnected, and for instance a bone prosthesis could possess the necessary stiffness and strength for the application omitting out prerequisite surface properties essential for the osteointegration. In this case, surface treatment is mandatory and can be accomplished using various techniques such as applying coatings to the prosthesis, ion beams, chemical grafting or modification, low temperature plasma, or a combination of the aforementioned. Low temperature plasma-based techniques have gained increasing consensus for the surface modification of biomaterials for being effective and competitive compared to other ways to introduce surface functionalities. In this paper we review plasma processing techniques and describe potentialities and applications of plasma to tailor the interface of biomaterials. Copyright © 2017 Elsevier B.V. All rights reserved.
LARGE—A Plasma Torch for Surface Chemistry Applications and CVD Processes—A Status Report

NASA Astrophysics Data System (ADS)

Zimmermann, Stephan; Theophile, Eckart; Landes, Klaus; Schein, Jochen

2008-12-01

The LARGE ( LONG ARG GENERATOR) is a new generation DC-plasma torch featuring an extended arc which is operated with a perpendicular gas flow to create a wide (up to 45 cm) plasma jet well suited for large area plasma processing. Using plasma diagnostic systems like high speed imaging, enthalpy probe, emission spectroscopy, and tomography, the LARGE produced plasma jet characteristics have been measured and sources of instability have been identified. With a simple model/simulation of the system LARGE III-150 and numerous experimental results, a new nozzle configuration and geometry (LARGE IV-150) has been designed, which produces a more homogenous plasma jet. These improvements enable the standard applications of the LARGE plasma torch (CVD coating process and surface activation process) to operate with higher efficiency.
Effect of tetraethoxysilane coating on the improvement of plasma treated polypropylene adhesion

NASA Astrophysics Data System (ADS)

Pantoja, M.; Encinas, N.; Abenojar, J.; Martínez, M. A.

2013-09-01

Polypropylene is one of the most used polymers due to its lightweight and recyclability properties, among others. However, its poor characteristics regarding surface energy and lack of polar functional groups have to be overcome to perform adhesion processes. The main objective of this work is to improve the adhesion behavior of polypropylene by combining atmospheric pressure plasma surface activation and silane adhesion promoter. Tetraethoxysilane hydrolysis and condensation are followed through infrared spectroscopy by attenuated total reflectance in order to set the coating conditions. Contact angle measurements and surface energy calculations as well as infrared and X-ray photoelectron spectroscopy are used to evaluate polymer chemical modifications. Morphological changes are studied through scanning electron and atomic force microscopy. Results show the ability of plasma treatment to create active oxydised functional groups on the polypropylene surface. These groups lead to a proper wetting of the polymer by the silane. Shear strength of single-lap bonding of polypropylene with a polyurethane adhesive suffers a significant improvement when the silane coating is applied on previously plasma activated samples. It has been also demonstrated that the silane curing conditions play a decisive role on the adhesion response. Finally, the stability of the silane solution is tested up to 30 days, yielding diminished but still acceptable adhesion strength values.
Plasma and serum serotonin concentrations and surface-bound platelet serotonin expression in Cavalier King Charles Spaniels with myxomatous mitral valve disease.

PubMed

Cremer, Signe E; Kristensen, Annemarie T; Reimann, Maria J; Eriksen, Nynne B; Petersen, Stine F; Marschner, Clara B; Tarnow, Inge; Oyama, Mark A; Olsen, Lisbeth H

2015-06-01

To investigate serum and plasma serotonin concentrations, percentage of serotonin-positive platelets, level of surface-bound platelet serotonin expression (mean fluorescence intensity [MFI]), and platelet activation (CD62 expression) in platelet-rich plasma from Cavalier King Charles Spaniels with myxomatous mitral valve disease (MMVD). Healthy dogs (n = 15) and dogs with mild MMVD (18), moderate-severe MMVD (19), or severe MMVD with congestive heart failure (CHF; 10). Blood samples were collected from each dog. Serum and plasma serotonin concentrations were measured with an ELISA, and surface-bound platelet serotonin expression and platelet activation were determined by flow cytometry. Dogs with mild MMVD had higher median serum (746 ng/mL) and plasma (33.3 ng/mL) serotonin concentrations, compared with MMVD-affected dogs with CHF (388 ng/mL and 9.9 ng/mL, respectively), but no other group differences were found. Among disease groups, no differences in surface-bound serotonin expression or platelet activation were found. Thrombocytopenic dogs had lower serum serotonin concentration (482 ng/mL) than nonthrombocytopenic dogs (731 ng/mL). In 26 dogs, a flow cytometry scatterplot subpopulation (FSSP) of platelets was identified; dogs with an FSSP had a higher percentage of serotonin-positive platelets (11.0%), higher level of surface-bound serotonin expression (MFI, 32,068), and higher platelet activation (MFI, 2,363) than did dogs without an FSSP (5.7%, 1,230, and 1,165, respectively). An FSSP was present in 93.8% of thrombocytopenic dogs and in 29.5% of nonthrombocytopenic dogs. A substantive influence of circulating serotonin on MMVD stages prior to CHF development in Cavalier King Charles Spaniels was not supported by the study findings. An FSSP of highly activated platelets with pronounced serotonin binding was strongly associated with thrombocytopenia but not MMVD.
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.
Physical and biological mechanisms of nanosecond- and microsecond-pulsed FE-DBD plasma interaction with biological objects

NASA Astrophysics Data System (ADS)

Dobrynin, Danil

2013-09-01

Mechanisms of plasma interaction with living tissues and cells can be quite complex, owing to the complexity of both the plasma and the tissue. Thus, unification of all the mechanisms under one umbrella might not be possible. Here, analysis of interaction of floating electrode dielectric barrier discharge (FE-DBD) with living tissues and cells is presented and biological and physical mechanisms are discussed. In physical mechanisms, charged species are identified as the major contributors to the desired effect and a mechanism of this interaction is proposed. Biological mechanisms are also addressed and a hypothesis of plasma selectivity and its effects is offered. Spatially uniform nanosecond and sub-nanosecond short-pulsed dielectric barrier discharge plasmas are gaining popularity in biological and medical applications due to their increased uniformity, lower plasma temperature, lower surface power density, and higher concentration of the active species produced. In this presentation we will compare microsecond pulsed plasmas with nanosecond driven systems and their applications in biology and medicine with specific focus on wound healing and tissue regeneration. Transition from negative to positive streamer will be discussed with proposed hypothesis of uniformity mechanisms of positive streamer and the reduced dependence on morphology and surface chemistry of the second electrode (human body) being treated. Uniform plasma offers a more uniform delivery of active species to the tissue/surface being treated thus leading to better control over the biological results.
Surface analysis of 316 stainless steel treated with cold atmospheric plasma

NASA Astrophysics Data System (ADS)

Williams, David F.; Kellar, Ewen J. C.; Jesson, David A.; Watts, John F.

2017-05-01

The surface of 316 stainless steel has been modified using cold atmospheric plasma (CAP) to increase the surface free energy (by cleaning the and chemically activating the surface)IN preparation for subsequent processes such as painting, coating or adhesive bonding. The analyses carried out, on CAP treated 316 stainless steel surfaces, includes X-ray photoelectron spectroscopy (XPS), imaging XPS (iXPS), and surface free energy (SFE) analysis using contact angle measurements. The CAP treatment is shown to increase the SFE of as-received 316 stainless steel from ∼39 mJ m-1 to >72 mJ m-1 after a short exposure to the plasma torch. This was found to correlate to a reduction in adventitious carbon, as determined by XPS analysis of the surface. The reduction from ∼90 at% to ∼30% and ∼39 at%, after being plasma treated for 5 min and 15 s respectively, shows that the process is relatively quick at changing the surface. It is suggested that the mechanism that causes the increase in surface free energy is chain scission of the hydrocarbon contamination triggered by free electrons in the plasma plume followed by chemical functionalisation of the metal oxide surface and some of the remaining carbon contamination layer.
Manganese-cerium oxide catalysts prepared by non-thermal plasma for NO oxidation: Effect of O2 in discharge atmosphere

NASA Astrophysics Data System (ADS)

Liu, Lu; Zheng, Chenghang; Wu, Shenghao; Gao, Xiang; Ni, Mingjiang; Cen, Kefa

2017-09-01

Non-thermal plasma with different O2 concentration in discharge atmosphere was applied to synthesize manganese and cerium mixed-oxides catalysts, which were compared in NO oxidation activity. Discharge atmosphere displayed a crucial influence on the performance of the catalysts prepared by plasma. Relatively low O2 concentration in discharge atmosphere allows synthesizing manganese-cerium oxides catalysts in a moderate environment and therefore is favorable for better physicochemical properties which lead to superior catalytic behavior. The best catalyst was obtained by treatment with 10% O2/N2 plasma and presented over 80% NO conversion in the temperature range of 275-325 °C, whereas catalyst prepared in pure O2 discharge atmosphere had the same activity with a catalyst prepared by calcinations. A correlation between the surface properties of the plasma prepared catalysts and its catalytic activity in NO oxidation is proposed. The amount of the surface adsorbed oxygen has an obvious linear correlation with the amount of Ce3+, the H2 consumption at low temperatures and the catalytic performance. The superior catalytic performance is mainly attributed to the stronger interaction between manganese oxides and ceria, and the formation of poorly crystallized Mn-O-Ce phase in the catalyst which resulted from the slow decomposition of nitrates and organics during plasma treatment. Catalysts prepared in relatively low O2 concentration have large specific surface area and is abundant in Ce3+ species and active oxygen species. The study suggests that plasma treatment with proper discharge gas components is a promising method to prepare effective manganese- cerium oxides catalyst for NO oxidation.
Mechanism of solid-state plasma-induced dewetting for formation of copper and gold nanoparticles.

PubMed

Kwon, Soon-Ho; Choe, Han Joo; Lee, Hyo-Chang; Chung, Chin-Wook; Lee, Jung-Joong

2013-09-01

Cu and Au nanoparticles were fabricated by plasma treatment on Cu and Au films at 653 K. The nanoparticles were formed by dewetting the metallic films using plasma. Scanning electron microscopy and transmission electron microscopy investigations showed that the plasma-induced dewetting of the Cu and Au films proceeded through heterogeneous hole nucleation and growth along the grain boundaries to lower the surface energy. The amount of energy transferred to surface atoms by one Ar ion was calculated to be 16.1 eV, which was sufficient for displacing Cu and Au atoms. Compared to thermally activated dewetting, more uniform particles could be obtained by plasma-induced dewetting because a much larger number of holes with smaller sizes was generated. The plasma dewetting process is less sensitive to the oxidation of metallic films compared to the annealing process. As a result, Cu nanoparticles could be fabricated at 653 K, whereas the thermally activated dewetting was not possible.
Effect of plasma treatments to graphite nanofibers supports on electrochemical behaviors of metal catalyst electrodes.

PubMed

Lee, Hochun; Jung, Yongju; Kim, Seok

2012-02-01

In the present work, we had studied the graphite nanofibers as catalyst supports after a plasma treatment for studying the effect of surface modification. By controlling the plasma intensity, a surface functional group concentration was changed. The nanoparticle size, loading efficiency, and catalytic activity were studied, after Pt-Ru deposition by a chemical reduction. Pt-Ru catalysts deposited on the plasma-treated GNFs showed the smaller size, 3.58 nm than the pristine GNFs. The catalyst loading contents were enhanced with plasma power and duration time increase, meaning an enhanced catalyst deposition efficiency. Accordingly, cyclic voltammetry result showed that the specific current density was increased proportionally till 200 W and then the value was decreased. Enhanced activity of 40 (mA mg(-1)-catalyst) was accomplished at 200 W and 180 sec duration time. Consequently, it was found that the improved electroactivity was originated from the change of size or morphology of catalysts by controlling the plasma intensity.

Chlorine-rich plasma polymer coating for the prevention of attachment of pathogenic fungal cells onto materials surfaces

NASA Astrophysics Data System (ADS)

Lamont-Friedrich, Stephanie J.; Michl, Thomas D.; Giles, Carla; Griesser, Hans J.; Coad, Bryan R.

2016-07-01

The attachment of pathogenic fungal cells onto materials surfaces, which is often followed by biofilm formation, causes adverse consequences in a wide range of areas. Here we have investigated the ability of thin film coatings from chlorinated molecules to deter fungal colonization of solid materials by contact killing of fungal cells reaching the surface of the coating. Coatings were deposited onto various substrate materials via plasma polymerization, which is a substrate-independent process widely used for industrial coating applications, using 1,1,2-trichloroethane as the process vapour. XPS surface analysis showed that the coatings were characterized by a highly chlorinated hydrocarbon polymer nature, with only a very small amount of oxygen incorporated. The activity of these coatings against human fungal pathogens was quantified using a recently developed, modified yeast assay and excellent antifungal activity was observed against Candida albicans and Candida glabrata. Plasma polymer surface coatings derived from chlorinated hydrocarbon molecules may therefore offer a promising solution to preventing yeast and mould biofilm formation on materials surfaces, for applications such as air conditioners, biomedical devices, food processing equipment, and others.
Plasma treatments of dressings for wound healing: a review.

PubMed

Eswaramoorthy, Nithya; McKenzie, David R

2017-12-01

This review covers the use of plasma technology relevant to the preparation of dressings for wound healing. The current state of knowledge of plasma treatments that have potential to provide enhanced functional surfaces for rapid and effective healing is summarized. Dressings that are specialized to the needs of individual cases of chronic wounds such as diabetic ulcers are a special focus. A summary of the biology of wound healing and a discussion of the various types of plasmas that are suitable for the customizing of wound dressings are given. Plasma treatment allows the surface energy and air permeability of the dressing to be controlled, to ensure optimum interaction with the wound. Plasmas also provide control over the surface chemistry and in cases where the plasma creates energetic ion bombardment, activation with long-lived radicals that can bind therapeutic molecules covalently to the surface of the dressing. Therapeutic innovations enabled by plasma treatment include the attachment of microRNA or antimicrobial peptides. Bioactive molecules that promote subsequent cell adhesion and proliferation can also be bound, leading to the recruitment of cells to the dressing that may be stem cells or patient-derived cells. The presence of a communicating cell population expressing factors promotes healing.
S180 cell growth on low ion energy plasma treated TiO 2 thin films

NASA Astrophysics Data System (ADS)

Dhayal, Marshal; Cho, Su-In; Moon, Jun Young; Cho, Su-Jin; Zykova, Anna

2008-03-01

X-ray photoelectron spectroscopy (XPS) was used to characterise the effects of low energy (<2 eV) argon ion plasma surface modification of TiO 2 thin films deposited by radio frequency (RF) magnetron sputter system. The low energy argon ion plasma surface modification of TiO 2 in a two-stage hybrid system had increased the proportion of surface states of TiO 2 as Ti 3+. The proportion of carbon atoms as alcohol/ether (C sbnd OX) was decreased with increase the RF power and carbon atoms as carbonyl (C dbnd O) functionality had increased for low RF power treatment. The proportion of C( dbnd O)OX functionality at the surface was decreased at low power and further increase in power has showed an increase in its relive proportion at the surface. The growth of S180 cells was observed and it seems that cells are uniformly spreads on tissue culture polystyrene surface and untreated TiO 2 surfaces whereas small-localised cell free area can be seen on plasma treated TiO 2 surfaces which may be due to decrease in C( dbnd O)OX, increase in C dbnd O and active sites at the surface. A relatively large variation in the surface functionalities with no change in the surface roughness was achieved by different RF plasma treatments of TiO 2 surface whereas no significant change in S180 cell growth with different plasma treatments. This may be because cell growth on TiO 2 was mainly influenced by nano-surface characteristics of oxide films rather than surface chemistry.
Unprecedented covalently attached ATRP initiator onto OH-functionalized mica surfaces.

PubMed

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

2008-01-15

Mica substrates were activated by a plasma method leading to OH-functionalized surfaces to which an atom transfer radical polymerization (ATRP) radical initiator was covalently bound using standard siloxane protocols. The unprecedented covalently immobilized initiator underwent radical polymerization with tert-butyl acrylate, yielding for the first time end-grafted polymer brushes that are covalently linked to mica. The initiator grafting on the mica substrate was confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS), while the change in the water contact angle of the OH-activated mica surface was used to follow the change in surface coverage of the initiator on the surface. The polymer brush and initiator film thicknesses relative to the virgin mica were confirmed by atomic force microscopy (AFM). This was done by comparing the atomic step-height difference between a protected area of freshly cleaved mica and a zone exposed to plasma activation, initiator immobilization, and then ATRP.
Surface pre-treatment for barrier coatings on polyethylene terephthalate

NASA Astrophysics Data System (ADS)

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

2013-02-01

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

NASA Technical Reports Server (NTRS)

Shannon, R. L.; Gillette, R. B.; Cruz, G. A.

1973-01-01

An active cleaning technique for removing contaminants from optical surfaces in space was investigated with emphasis on the feasibility of using plasma exposure as a means of in-situ cleaning. The major work accomplished includes: (1) development of an in-situ reflectometer for use in conjunction with the contaminant film deposition/cleaning facility; (2) completion of Apollo Telescope Mount (ATM) filter treatment experiments to assess the effects of plasma exposure on the UV transmittance; (3) attempts to correlate the atomic oxygen flux with cleaning rate; (4) completion of in-situ butadien contamination/plasma cleaning/UV reflectance measurement experiments; (5) carbon cleaning experiments using various gases; (6) completion of silicone contamination/cleaning experiments; and (7) experiments conducted at low chamber pressures to determine cleaning rate distribution and contamination of surfaces adjacent to those being cleaned.
Expression and nutritional regulation of the (pro)renin receptor in rat visceral adipose tissue.

PubMed

Achard, V; Tassistro, V; Boullu-Ciocca, S; Grino, M

2011-12-01

Early life nutritional environment plays an important role in the development of visceral adipose tissue and interacts with nutritional regulations in adulthood, leading to metabolic dysregulations. We hypothesized that the renin-angiotensin system may play a role in the programming-induced development of visceral adipose tissue. We studied, using a model of programming of overweight and glucose intolerance, obtained by post-natal overfeeding with consecutive highfat diet, the status of plasma renin activity and mesenteric adipose renin-angiotensin system, including the recently identified (pro)renin receptor, in adult rats. Post-natal overfeeding or high-fat feeding lead to overweight with increased visceral fat mass and adipocytes surface. When both paradigms were associated, adipocytes surface showed a disproportionate increase. A strong immunoreactivity for (pro)renin receptor was found in stromal cells. Plasma renin activity increased in programmed animals whereas (pro)renin receptor expressing cells density was stimulated by high-fat diet. There was a positive, linear relationship between plasma renin activity and (pro)renin receptor expressing cells density and adipocytes surface. Our experiments demonstrate that association of post-natal overfeeding and high-fat diet increased plasma renin activity and adipose (pro)renin receptor expression. Such phenomenon could explain, at least in part, the associated disproportionate adipocyte hypertrophy and its accompanying increased glucose intolerance.
Spatially selective modification of PLLA surface: From hydrophobic to hydrophilic or to repellent

NASA Astrophysics Data System (ADS)

Bastekova, Kristina; Guselnikova, Olga; Postnikov, Pavel; Elashnikov, Roman; Kunes, Martin; Kolska, Zdenka; Švorčík, Vaclav; Lyutakov, Oleksiy

2017-03-01

A universal approach to controlled surface modification of polylactic acid (PLLA) films using diazonium chemistry was proposed. The multistep procedure includes surface activation of PLLA by argon plasma treatment and chemical activation of arenediazonium tosylates by NaBH4. The surface of PLLA film was grafted with different functional organic groups (OFGs), changing the PLLA surface properties (wettability, morphology, zeta potential, chemical composition, and mechanical response). Three approaches of OFG grafting were examined: (i) plasma treatment following by PLLA immersion into diazonium salt aqueous solution; (ii) grafting of PLLA surface through the reaction with chemically created aryl radicals; (iii) mutual combination of both methods The best results were achieved in the last case, where the previous plasma treatment was combined with further reaction of PLLA surface with generated aryl radicals. Using this method PLLA surface was successfully grafted with amino, carboxyl, aliphatic and fluorinated OFGs. Further investigation of surface properties from potential biological and medical points of view was performed using zeta potential, biodegradation and biofouling tests. It was shown that proposed technique allows preparation of biorepellent or bioabsorptive surfaces, tuning of PLLA biodegradation rate and nanomechanical properties, as well as the introduction of inverse properties (such as hydrophilic and hydrophobic) on both sides of PLLA films.
Investigation of antibacterial and wettability behaviours of plasma-modified PMMA films for application in ophthalmology

NASA Astrophysics Data System (ADS)

Rezaei, Fatemeh; Abbasi-Firouzjah, Marzieh; Shokri, Babak

2014-02-01

The main objective of this research is the experimental investigation of the surface properties of polymethyl methacrylate (PMMA) such as wettability and the roughness effect on Escherichia coli (gram negative) cell adhesion. Radio frequency (RF; 13.56 MHz) oxygen plasma was used to enhance the antibacterial and wettability properties of this polymer for biomedical applications, especially ophthalmology. The surface was activated by O2 plasma to produce hydrophilic functional groups. Samples were treated with various RF powers from 10 to 80 W and different gas flow rates from 20 to 120 sccm. Optical emission spectroscopy was used to monitor the plasma process. The modified surface hydrophilicity, morphology and transparency characteristics were studied by water contact angle measurements, atomic force microscopy and UV-vis spectroscopy, respectively. Based on the contact angle measurements of three liquids, surface free energy variations were investigated. Moreover, the antibacterial properties were evaluated utilizing the method of plate counting of Escherichia coli. Also, in order to investigate stability of the plasma treatment, an ageing study was carried out by water contact angle measurements repeated in the days after the treatment. For biomedical applications, especially eye lenses, highly efficient antibacterial surfaces with appropriate hydrophilicity and transparency are of great importance. In this study, it is shown that the plasma process is a reliable and convenient method to achieve these purposes. A significant alteration in the hydrophilicity of a pristine PMMA surface was observed after treatment. Also, our results indicated that the plasma-modified PMMAs exhibit appropriate antibacterial performance. Moreover, surface hydrophilicity and surface charge have more influence on bacterial adhesion rate than surface roughness. UV-vis analysis results do not show a considerable difference for transparency of samples after plasma treatment.
Atmospheric-Pressure Plasma Interaction with Soft Materials as Fundamental Processes in Plasma Medicine.

PubMed

Takenaka, Kosuke; Miyazaki, Atsushi; Uchida, Giichiro; Setsuhara, Yuichi

2015-03-01

Molecular-structure variation of organic materials irradiated with atmospheric pressure He plasma jet have been investigated. Optical emission spectrum in the atmospheric-pressure He plasma jet has been measured. The spectrum shows considerable emissions of He lines, and the emission of O and N radicals attributed to air. Variation in molecular structure of Polyethylene terephthalate (PET) film surface irradiated with the atmospheric-pressure He plasma jet has been observed via X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). These results via XPS and FT-IR indicate that the PET surface irradiated with the atmospheric-pressure He plasma jet was oxidized by chemical and/or physical effect due to irradiation of active species.
Effect of Surface Plasma Treatments on the Adhesion of Mars JSC 1 Simulant Dust to RTV 655, RTV 615, and Sylgard 184

PubMed Central

Sabri, Firouzeh; Marchetta, Jeffrey G.; Sinden-Redding, M.; Habenicht, James J.; Chung, Thien Phung; Melton, Charles N.; Hatch, Chris J.; Lirette, Robert L.

2012-01-01

Background Dust accumulation on surfaces of critical instruments has been a major concern during lunar and Mars missions. Operation of instruments such as solar panels, chromatic calibration targets, as well as Extra Vehicular Activity (EVA) suits has been severely compromised in the past as a result of dust accumulation and adhesion. Wind storms with wind speeds of up to 70 mph have not been effective in removing significant amounts of the deposited dust. This is indeed an indication of the strength of the adhesion force(s) involved between the dust particles and the surface(s) that they have adhered to. Complications associated with dust accumulation are more severe for non-conducting surfaces and have been the focus of this work. Methodology Argon plasma treatment was investigated as a mechanism for lowering dust accumulation on non-conducting polymeric surfaces. Polymers chosen for this study include a popular variety of silicones routinely used for space and terrestrial applications namely RTV 655, RTV 615, and Sylgard 184. Surface properties including wettability, surface potential, and surface charge density were compared before and after plasma treatment and under different storage conditions. Effect of ultraviolet radiation on RTV 655 was also investigated and compared with the effect of Ar plasma treatment. Conclusion/Significance Gravimetric measurements proved Ar plasma treatment to be an effective method for eliminating dust adhesion to all three polymers after short periods of exposure. No physical damage was detected on any of the polymer surfaces after Ar plasma treatment. The surface potential of all three polymers remained zero up to three months post plasma exposure. Ultraviolet radiation however was not effective in reducing surface and caused damage and significant discoloration to RTV 655. Therefore, Ar plasma treatment can be an effective and non-destructive method for treating insulating polymeric surfaces in order to eliminate dust adhesion and accumulation. PMID:23077496
Interrogating Surface Functional Group Heterogeneity of Activated Thermoplastics Using Super-Resolution Fluorescence Microscopy.

PubMed

ONeil, Colleen E; Jackson, Joshua M; Shim, Sang-Hee; Soper, Steven A

2016-04-05

We present a novel approach for characterizing surfaces utilizing super-resolution fluorescence microscopy with subdiffraction limit spatial resolution. Thermoplastic surfaces were activated by UV/O3 or O2 plasma treatment under various conditions to generate pendant surface-confined carboxylic acids (-COOH). These surface functional groups were then labeled with a photoswitchable dye and interrogated using single-molecule, localization-based, super-resolution fluorescence microscopy to elucidate the surface heterogeneity of these functional groups across the activated surface. Data indicated nonuniform distributions of these functional groups for both COC and PMMA thermoplastics with the degree of heterogeneity being dose dependent. In addition, COC demonstrated relative higher surface density of functional groups compared to PMMA for both UV/O3 and O2 plasma treatment. The spatial distribution of -COOH groups secured from super-resolution imaging were used to simulate nonuniform patterns of electroosmotic flow in thermoplastic nanochannels. Simulations were compared to single-particle tracking of fluorescent nanoparticles within thermoplastic nanoslits to demonstrate the effects of surface functional group heterogeneity on the electrokinetic transport process.
Deposition of gold nano-particles and nano-layers on polyethylene modified by plasma discharge and chemical treatment

NASA Astrophysics Data System (ADS)

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

2009-08-01

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

NASA Technical Reports Server (NTRS)

1977-01-01

Topics include surface studies (surface theory, basic surface experiments, and activation chamber experiments); plasma studies (converter theory and enhanced mode conversion experiments); and component development (low temperature conversion experiments, high efficiency conversion experiments, and hot shell development).
Surface modification of electrospun PVA/chitosan nanofibers by dielectric barrier discharge plasma at atmospheric pressure and studies of their mechanical properties and biocompatibility.

PubMed

Das, Punamshree; Ojah, Namita; Kandimalla, Raghuram; Mohan, Kiranjyoti; Gogoi, Dolly; Dolui, Swapan Kumar; Choudhury, Arup Jyoti

2018-03-22

In this paper, surface of electrospun PVA/Cs nanofibers is modified using dielectric barrier discharge (DBD) plasma and the relationship between the observed mechanical properties and biocompatibility of the nanofibers and plasma-induced surface properties is discussed. Plasma treatment of electrospun PVA/Cs nanofibers is carried out with both inert (argon, Ar) and reactive (oxygen, O 2 ) gases at atmospheric pressure. Incorporation of oxygen-containing polar functional groups on the surface of Ar-plasma treated (PVA/Cs/Ar) and O 2 -plasma treated (PVA/Cs/O 2 ) nanofibers and increase in surface roughness contribute to the improvement of surface wettability and the decrease of contact angle with water of the nanofibers. Both PVA/Cs/Ar and PVA/Cs/O 2 nanofibers show high tensile strength (11.6-15.6%) and Young's modulus (33.8-37.3%) as compared to the untreated one. Experimental results show that in terms of haemolytic activity the PVA/Cs/Ar and PVA/Cs/O 2 nanofibers do not cause structural changes of blood cells and meet the biocompatibility requirements for blood-contacting polymeric materials. MTT cell viability results further reveals improvement in biocompatibility of PVA/Cs nanofibers after Ar and O 2 plasma treatment. The results suggest that DBD plasma treated electrospun PVA/Cs nanofibers have the potential to be used as wound dressing and scaffolds for tissue engineering. Copyright © 2018 Elsevier B.V. All rights reserved.
Immobilization of biomolecules to plasma polymerized pentafluorophenyl methacrylate.

PubMed

Duque, Luis; Menges, Bernhard; Borros, Salvador; Förch, Renate

2010-10-11

Thin films of plasma polymerized pentafluorophenyl methacrylate (pp-PFM) offer highly reactive ester groups throughout the structure of the film that allow for subsequent reactions with different aminated reagents and biological molecules. The present paper follows on from previous work on the plasma deposition of pentafluorophenyl methacrylate (PFM) for optimum functional group retention (Francesch, L.; Borros, S.; Knoll, W.; Foerch, R. Langmuir 2007, 23, 3927) and reactivity in aqueous solution (Duque, L.; Queralto, N.; Francesch, L.; Bumbu, G. G.; Borros, S.; Berger, R.; Förch, R. Plasma Process. Polym. 2010, accepted for publication) to investigate the binding of a biologically active peptide known to induce cellular adhesion (IKVAV) and of biochemically active proteins such as BSA and fibrinogen. Analyses of the films and of the immobilization of the biomolecules were carried out using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The attachment of the biomolecules on pulsed plasma polymerized pentafluorophenyl methacrylate was monitored using surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the presence of immobilized biomolecules on the plasma polymer and was used to determine the mass coverage of the peptide and proteins adsorbed onto the films. The combined analysis of the surfaces suggests the covalent binding of the peptide and proteins to the surface of the pp-PFM.
Oxygen Plasma Modification of Poss-Coated Kapton(Registered TradeMark) HN Films

NASA Technical Reports Server (NTRS)

Wohl, C. J.; Belcher, M. A.; Ghose, S.; Connell, J. W.

2008-01-01

The surface energy of a material depends on both surface composition and topographic features. In an effort to modify the surface topography of Kapton(Registered TradeMark) HN film, organic solutions of a polyhedral oligomeric silsesquioxane, octakis(dimethylsilyloxy)silsesquioxane (POSS), were spray-coated onto the Kapton(Registered TradeMark) HN surface. Prior to POSS application, the Kapton(Registered TradeMark) HN film was activated by exposure to radio frequency (RF)-generated oxygen plasma. After POSS deposition and solvent evaporation, the films were exposed to various durations of RF-generated oxygen plasma to create a topographically rich surface. The modified films were characterized using optical microscopy, attenuated total reflection infrared (ATR-IR) spectroscopy, and high-resolution scanning electron microscopy (HRSEM). The physical properties of the modified films will be presented.
Surface Functionalization of WO3 Thin Films with (3-Aminopropyl)triethoxysilane and Succinic Anhydride

NASA Astrophysics Data System (ADS)

Ta, Thi Kieu Hanh; Tran, Thi Nhu Hoa; Tran, Quang Minh Nhat; Pham, Duy Phong; Pham, Kim Ngoc; Cao, Thi Thanh; Kim, Yong Soo; Tran, Dai Lam; Ju, Heongkyu; Phan, Bach Thang

2017-06-01

We report effects of oxygen plasma treatment on the surface functionalization of WO3 thin films with (3-aminopropyl)triethoxysilane (APTES) and succinic anhydride (SA). X-ray diffraction and x-ray photoelectron spectroscopy results indicate the existence of the WO3 phase. Fourier transform infrared spectroscopy measurement shows clear bands at 1040 cm-1 (Si-O-Si), 1556 cm-1 (N-H), 1655 cm-1 (C=O), 2937 cm-1 (C-H) and 3298 cm-1 (N-H), confirming the surface functionalization efficiency enhanced by prior treatment of oxygen plasma. It thus follows that the prior oxygen plasma treatment activates hydroxylation with more -OH groups on the WO3 surface, which can pave a highly efficient way to the surface functionalization by APTES and SA.
Plasma combined self-assembled monolayer pretreatment on electroplated-Cu surface for low temperature Cu-Sn bonding in 3D integration

NASA Astrophysics Data System (ADS)

Wang, Junqiang; Wang, Qian; Wu, Zijian; Tan, Lin; Cai, Jian; Wang, Dejun

2017-05-01

A novel pretreatment of plasma combined self-assembled monolayer (PcSAM) was proposed to improve surface properties of electroplated Cu for low temperature Cu-Sn bonding in 3D integration. Measurement results revealed that self-assemble monolayer (SAM) would be easier absorbed on plasma-activated Cu surface and protect the clean surface from re-oxidation when storage. The absorbed SAM layer could be removed by thermal desorption during bonding process. With optimal PcSAM pretreatment, oxygen content of the Cu surface was reduced to as low as 1.39%. The followed Cu-Sn bonding was realized at low temperature of 200 °C. Finally, bonding interface exhibited a defect-free interconnection, and bonding strength has reached as high as 68.7 MPa.
On a non-thermal atmospheric pressure plasma jet used for the deposition of silicon-organic films

NASA Astrophysics Data System (ADS)

Schäfer, Jan; Sigeneger, Florian; Foest, Rüdiger; Loffhagen, Detlef; Weltmann, Klaus-Dieter

2018-05-01

This work represents a concise overview on the results achieved by the authors over the last years on the plasma of a non-thermal reactive plasma jet at atmospheric pressure and of related thin film formation by plasma enhanced chemical vapour deposition (PECVD). The source was developed considering the application of the plasma self-organization for PECVD. The experimental methods comprise spectroscopic measurements of plasma parameters in the active zone, temperature measurements in the active zone and the effluent as well as the analysis of deposited films at the substrate surface. The theoretical investigations are devoted to a single filament in the active zone using a phase-resolved model and to an overall description of the jet including the substrate using a period-averaged model.

Comparison Between Dielectric Barrier Discharge Plasma and Ozone Regenerations of Activated Carbon Exhausted with Pentachlorophenol

NASA Astrophysics Data System (ADS)

Qu, Guangzhou; Liang, Dongli; Qu, Dong; Huang, Yimei; Li, Jie

2014-06-01

In this study, two regeneration methods (dielectric barrier discharge (DBD) plasma and ozone (O3) regeneration) of saturated granular activated carbon (GAC) with pentachlorophenol (PCP) were compared. The results show that the two regeneration methods can eliminate contaminants from GAC and recover its adsorption properties to some extent. Comparing the DBD plasma with O3 regeneration, the adsorption rate and the capacity of the GAC samples after DBD plasma regeneration are greater than those after O3 regeneration. O3 regeneration decreases the specific surface area of GAC and increases the acidic surface oxygen groups on the surface of GAC, which causes a decrease in PCP on GAC uptake. With increasing regeneration cycles, the regeneration efficiencies of the two methods decrease, but the decrease in the regeneration efficiencies of GAC after O3 regeneration is very obvious compared with that after DBD plasma regeneration. Furthermore, the equilibrium data were fitted by the Freundlich and Langmuir models using the non-linear regression technique, and all the adsorption equilibrium isotherms fit the Langmuir model fairly well, which demonstrates that the DBD plasma and ozone regeneration processes do not appear to modify the adsorption process, but to shift the equilibrium towards lower adsorption concentrations. Analyses of the weight loss of GAC show that O3 regeneration has a lower weight loss than DBD plasma regeneration.
Effect of spark plasma sintering on the microstructure and in vitro behavior of plasma sprayed HA coatings.

PubMed

Yu, L-G; Khor, K A; Li, H; Cheang, P

2003-07-01

The crystalline phases and degree of crystallinity in plasma sprayed calcium phosphate coatings on Ti substrates are crucial factors that influence the biological interactions of the materials in vivo. In this study, plasma sprayed hydroxyapatite (HA) coatings underwent post-spray treatment by the spark plasma sintering (SPS) technique at 500 degrees C, 600 degrees C, and 700 degrees C for duration of 5 and 30 min. The activity of the HA coatings before and after SPS are evaluated in vitro in a simulated body fluid. The surface microstructure, crystallinity, and phase composition of each coating is characterized by scanning electron microscopy and X-ray diffractometry before, and after in vitro incubation. Results show that the plasma sprayed coatings treated for 5 min in SPS demonstrated increased proportion of beta-TCP phase with a preferred-orientation in the (214) plane, and the content of beta-TCP phase corresponded to SPS temperature, up to 700 degrees C. SPS treatment at 700 degrees C for 30 min enhanced the HA content in the plasma spray coating as well. The HA coatings treated in SPS for 5 min revealed rapid surface morphological changes during in vitro incubation (up to 12 days), indicating that the surface activity is enhanced by the SPS treatment. The thickest apatite layer was found in the coating treated by SPS at 700 degrees C for 5 min.
Flux of OH and O radicals onto a surface by an atmospheric-pressure helium plasma jet measured by laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Yonemori, Seiya; Ono, Ryo

2014-03-01

The atmospheric-pressure helium plasma jet is of emerging interest as a cutting-edge biomedical device for cancer treatment, wound healing and sterilization. Reactive oxygen species such as OH and O radicals are considered to be major factors in the application of biological plasma. In this study, density distribution, temporal behaviour and flux of OH and O radicals on a surface are measured using laser-induced fluorescence. A helium plasma jet is generated by applying pulsed high voltage of 8 kV with 10 kHz using a quartz tube with an inner diameter of 4 mm. To evaluate the relation between the surface condition and active species production, three surfaces are used: dry, wet and rat skin. When the helium flow rate is 1.5 l min-1, radial distribution of OH density on the rat skin surface shows a maximum density of 1.2 × 1013 cm-3 at the centre of the plasma-mediated area, while O atom density shows a maximum of 1.0 × 1015 cm-3 at 2.0 mm radius from the centre of the plasma-mediated area. Their densities in the effluent of the plasma jet are almost constant during the intervals of the discharge pulses because their lifetimes are longer than the pulse interval. Their density distribution depends on the helium flow rate and the surface humidity. With these results, OH and O production mechanisms in the plasma jet and their flux onto the surface are discussed.
An Overview of NSTX Research Facility and Recent Experimental Results

NASA Astrophysics Data System (ADS)

Ono, Masayuki

2006-10-01

The 2006 NSTX experimental campaign yielded significant new experimental results in many areas. Improved plasma control achieved the highest elongation of 2.9 and plasma shape factor q95Ip/aBT = 42 MA/m.T. Active feedback correction of error fields sustained the plasma rotation and increased the pulse length of high beta discharges. Active feedback stabilization of the resistive wall mode in high-beta, low-rotation plasmas was demonstrated for ˜100 resistive wall times. Operation at higher toroidal field showed favorable plasma confinement and HHFW heating efficiency trends with the field. A broader current profile, measured by the 12-channel MSE diagnostic in high beta discharges revealed an outward anomalous diffusivity of energetic ions due to the n=1 MHD modes. A tangential microwave scattering diagnostic measured localized electron gyro-scale fluctuations in L-mode, H-mode and reversed-shear plasmas. Evaporation of lithium onto plasma facing surfaces yielded lower density, higher temperature and improved confinement. A strong dependence of the divertor heat load and ELM behavior on the plasma triangularity was observed. Coaxial helicity injection produced a start-up current of 160 kA on closed flux surfaces.
Study on surface adhesion of Plasma modified Polytetrafluoroethylene hollow fiber membrane

NASA Astrophysics Data System (ADS)

Chen, Jiangrong; Zhang, Huifeng; Liu, Guochang; Guo, Chungang; Lv, Jinglie; Zhangb, Yushan

2018-01-01

Polytetrafluoroethylene (PTFE) is popular membrane material because of its excellent thermal stability, chemical stability and mechanical stability. However, the low surface energy and non-sticky property of PTFE present challenges for modification. In the present study, plasma treatment was performed to improve the surface adhesion of PTFE hollow fiber membrane. The effect of discharge voltage, treatment time on the adhesion of PTFE hollow fiber membrane was symmetrically evaluated. Results showed that the plasma treatment method contributed to improve the surface activity and roughness of PTFE hollow fiber membrane, and the adhesion strength depend significantly on discharge voltage, which was beneficial to seepage pressure of PTFE hollow fiber membrane module. The adhesion strength of PTFE membrane by plasma treated at 220V for 3min reached as high as 86.2 N, far surpassing the adhesion strength 12.7 N of pristine membrane. Furthermore, improvement of content of free radical and composition analysis changes of the plasma modified PTFE membrane were investigated. The seepage pressure of PTFE membrane by plasma treated at 220V for 3min was 0.375 MPa, which means that the plasma treatment is an effective technique to improve the adhesion strength of membrane.
Controllable Surface Reorganization Engineering on Cobalt Phosphide Nanowire Arrays for Efficient Alkaline Hydrogen Evolution Reaction.

PubMed

Xu, Kun; Cheng, Han; Lv, Haifeng; Wang, Jingyu; Liu, Linqi; Liu, Si; Wu, Xiaojun; Chu, Wangsheng; Wu, Changzheng; Xie, Yi

2018-01-01

Developing highly efficient hydrogen evolution reaction (HER) catalysts in alkaline media is considered significant and valuable for water splitting. Herein, it is demonstrated that surface reorganization engineering by oxygen plasma engraving on electocatalysts successfully realizes a dramatically enhanced alkaline HER activity. Taking CoP nanowire arrays grown on carbon cloth (denoted as CoP NWs/CC) as an example, the oxygen plasma engraving can trigger moderate CoO x species formation on the surface of the CoP NWs/CC, which is visually verified by the X-ray absorption fine structure, high-resolution transmission electron microscopy, and energy-dispersive spectrometer (EDS) mapping. Benefiting from the moderate CoO x species formed on the surface, which can promote the water dissociation in alkaline HER, the surface reorganization of the CoP NWs/CC realizes almost fourfold enhanced alkaline HER activity and a 180 mV decreased overpotential at 100 mA cm -2 , compared with the pristine ones. More interestingly, this surface reorganization strategy by oxygen plasma engraving can also be effective to other electrocatalysts such as free-standing CoP, Co 4 N, O-CoSe 2 , and C-CoSe 2 nanowires, which verifies the universality of the strategy. This work thus opens up new avenues for designing alkaline HER electrocatalysts based on oxygen plasma engraving. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Corona plasma modification of polyamide 66 for the design of textile delivery systems for cosmetic therapy

NASA Astrophysics Data System (ADS)

Labay, C.; Canal, J. M.; Navarro, A.; Canal, C.

2014-10-01

Cosmetic and medical applications of technical textiles are a research expanding field. One of the added values of these new materials would be that they are suitable to contain and release active ingredients in a controlled manner. The influence of the initial state of the surface of polyamide 6.6 (PA66) fibers on the wetting properties of the fibers as well as on the incorporation of caffeine on the fibers and on its release kinetics from the fibers has been investigated. Comparison between industrially-finished PA66 fabrics and laboratory washed fabrics has been done to carry out this study. Furthermore, surface modification of the PA66 fibers by low temperature plasma has been studied regarding the modification of the physical, chemical and topographical properties of the textile fibers. Corona plasma treatment has been investigated to achieve surface modification in the first nanometers of polymer fibers surface in order to modulate the incorporation and the release of caffeine. It has been demonstrated that both initial state of the PA66 surface and prior plasma treatment of the PA66 fibers before the active principle incorporation condition caffeine release kinetics from the textile fibers. The final release percentage increases linearly with the C-O and Cdbnd O functional groups incorporated by plasma on the surface. It has also been established that the release amounts of caffeine achieved after 8 h from the PA66 fabric are in the same order of magnitude than topical doses of commercial gel-based formulations.
The role of energetic ions from plasma in the creation of nanostructured materials and stable polymer surface treatments

NASA Astrophysics Data System (ADS)

Bilek, M. M. M.; Newton-McGee, K.; McKenzie, D. R.; McCulloch, D. G.

2006-01-01

Plasma processes for the synthesis of new materials as thin films have enabled the production of a wide variety of new materials. These include meta-stable phases, which are not readily found in nature, and more recently, materials with structure on the nanoscale. Study of plasma synthesis processes at the fundamental level has revealed that ion energy, depositing flux and growth surface temperature are the critical parameters affecting the microstructure and the properties of the thin film materials formed. In this paper, we focus on the role of ion flux and impact energy in the creation of thin films with nanoscale structure in the form of multilayers. We describe three synthesis strategies, based on the extraction of ions from plasma sources and involving modulation of ion flux and ion energy. The microstructure, intrinsic stress and physical properties of the multilayered samples synthesized are studied and related back to the conditions at the growth surface during deposition. When energetic ions of a non-condensing species are used, it is possible to place active groups on the surfaces of materials such as polymers. These active groups can then be used as bonding sites in subsequent chemical attachment of proteins or other macromolecules. If the energy of the non-condensing ions is increased to a few keV then modified layers buried under the surface can be produced. Here we describe a method by which the aging effect, which is often observed in plasma surface modifications on polymers, can be reduced and even eliminated using high energy ion bombardment.
Cell adhesion and proliferation on poly(tetrafluoroethylene) with plasma-metal and plasma-metal-carbon interfaces

NASA Astrophysics Data System (ADS)

Reznickova, Alena; Kvitek, Ondrej; Kolarova, Katerina; Smejkalova, Zuzana; Svorcik, Vaclav

2017-06-01

The aim of this article is to investigate the effect of the interface between plasma activated, gold and carbon coated poly(tetrafluoroethylene) (PTFE) on in vitro adhesion and spreading of mouse fibroblasts (L929). Surface properties of pristine and modified PTFE were studied by several experimental techniques. The thickness of a deposited gold film is an increasing function of the sputtering time, conversely thickness of carbon layer decreases with increasing distance between carbon source and the substrate. Because all the used surface modification techniques take place in inert Ar plasma, oxidized degradation products are formed on the PTFE surface, which affects wettability of the polymer surface. Cytocompatibility tests indicate that on samples with Au/C interface, the cells accumulate on the part of sample with evaporated carbon. Number of L929 cells proliferated on the studied samples is comparable to tissue culture polystyrene standard.
Corrosion Behavior of Active Screen Plasma Nitrided 38CrMoAl Steel under Marine Environment

NASA Astrophysics Data System (ADS)

Yang, Li; He, Yongyong; Mao, JunYuan; Zhang, Lei

2017-10-01

The 38CrMoAl steels were nitrided at different temperatures for 7 h using active screen plasma discharge. The analysis showed that the thick compound layer composed of ɛ-Fe2-3N and γ‧-Fe4N was formed on the surface. The corrosion behavior was evaluated by measuring the anodic polarization curves in natural sea water (similar 3.5% NaCl solution), and observation of corroded surface were conducted. The electromechanical measurements indicated that the corrosion potential of the nitrided specimens shifted to a nobler value compared to that of untreated specimens. Passive regions were also observed in the polarization curves for all the nitrided specimens. These results indicate that active screen plasma nitriding can enhance the corrosion resistance of the 38CrMoAl steel under marine environment.
Polyimide surface modification by using microwave plasma for adhesion enhancement of Cu electroless plating.

PubMed

Cho, Sang-Jin; Nguyen, Trieu; Boo, Jin-Hyo

2011-06-01

Microwave (MW) plasma was applied to the surface of polyimide (PI) films as a treatment to enhance the adhesion between copper deposition layer and PI surface for electroless plating. The influences of nitrogen MW plasma treatment on chemical composition of the PI surface were investigated by using X-Ray photoelectron spectroscopy (XPS). The wettability was also investigated by water contact angle measurement. The surface morphologies of PI films before and after treatment were characterized with atomic force microscopy (AFM). The contact angle results show that was dramatically decreased to 16.1 degrees at the optimal treatment condition from 72.1 degrees (untreated PI). However, the root mean square (RMS) roughness of treated PI film was almost unchanged. The AFM roughness was stayed from 1.0 to 1.2 with/without plasma treatment. XPS data show a nitrogen increase when PI films exposed to N2 MW plasma. Electroless copper depositions were carried out with the free-formaldehyde method using glyoxylic acid as the reducing reagent and mixture palladium chloride, tin chloride as activation solution. Adhesion property between polyimide surface and copper layer was investigated by tape test.
Active screen cage pulsed dc discharge for implanting copper in polytetrafluoroethylene (PTFE)

NASA Astrophysics Data System (ADS)

Zaka-ul-Islam, Mujahid; Naeem, Muhammad; Shafiq, Muhammad; Sitara; Jabbar Al-Rajab, Abdul; Zakaullah, Muhammad

2017-07-01

Polymers such as polytetrafluoroethylene (PTFE) are widely used in artificial organs where long-term anti-bacterial properties are required to avoid bacterial proliferation. Copper or silver ion implantation on the polymer surface is known as a viable method to generate long-term anti-bacterial properties. Here, we have tested pulsed DC plasma with copper cathodic cage for the PTFE surface treatment. The surface analysis of the treated specimens suggests that the surface, structural properties, crystallinity and chemical structure of the PTFE have been changed, after the plasma treatment. The copper release tests show that copper ions are released from the polymer at a slow rate and quantity of the released copper increases with the plasma treatment time.
Basic Research in Plasma Medicine - A Throughput Approach from Liquids to Cells

PubMed Central

Bekeschus, Sander; Schmidt, Anke; Niessner, Felix; Gerling, Torsten; Weltmann, Klaus-Dieter; Wende, Kristian

2017-01-01

In plasma medicine, ionized gases with temperatures close to that of vertebrate systems are applied to cells and tissues. Cold plasmas generate reactive species known to redox regulate biological processes in health and disease. Pre-clinical and clinical evidence points to beneficial effects of plasma treatment in the healing of chronic ulcer of the skin. Other emerging topics, such as plasma cancer treatment, are receiving increasing attention. Plasma medical research requires interdisciplinary expertise in physics, chemistry, and biomedicine. One goal of plasma research is to characterize plasma-treated cells in a variety of specific applications. This includes, for example, cell count and viability, cellular oxidation, mitochondrial activity, cytotoxicity and mode of cell death, cell cycle analysis, cell surface marker expression, and cytokine release. This study describes the essential equipment and workflows required for such research in plasma biomedicine. It describes the proper operation of an atmospheric pressure argon plasma jet, specifically monitoring its basic emission spectra and feed gas settings to modulate reactive species output. Using a high-precision xyz-table and computer software, the jet is hovered in millisecond-precision over the cavities of 96-well plates in micrometer-precision for maximal reproducibility. Downstream assays for liquid analysis of redox-active molecules are shown, and target cells are plasma-treated. Specifically, melanoma cells are analyzed in an efficient sequence of different consecutive assays but using the same cells: measurement of metabolic activity, total cell area, and surface marker expression of calreticulin, a molecule important for the immunogenic cell death of cancer cells. These assays retrieve content-rich biological information about plasma effects from a single plate. Altogether, this study describes the essential steps and protocols for plasma medical research. PMID:29286412
Basic Research in Plasma Medicine - A Throughput Approach from Liquids to Cells.

PubMed

Bekeschus, Sander; Schmidt, Anke; Niessner, Felix; Gerling, Torsten; Weltmann, Klaus-Dieter; Wende, Kristian

2017-11-17

In plasma medicine, ionized gases with temperatures close to that of vertebrate systems are applied to cells and tissues. Cold plasmas generate reactive species known to redox regulate biological processes in health and disease. Pre-clinical and clinical evidence points to beneficial effects of plasma treatment in the healing of chronic ulcer of the skin. Other emerging topics, such as plasma cancer treatment, are receiving increasing attention. Plasma medical research requires interdisciplinary expertise in physics, chemistry, and biomedicine. One goal of plasma research is to characterize plasma-treated cells in a variety of specific applications. This includes, for example, cell count and viability, cellular oxidation, mitochondrial activity, cytotoxicity and mode of cell death, cell cycle analysis, cell surface marker expression, and cytokine release. This study describes the essential equipment and workflows required for such research in plasma biomedicine. It describes the proper operation of an atmospheric pressure argon plasma jet, specifically monitoring its basic emission spectra and feed gas settings to modulate reactive species output. Using a high-precision xyz-table and computer software, the jet is hovered in millisecond-precision over the cavities of 96-well plates in micrometer-precision for maximal reproducibility. Downstream assays for liquid analysis of redox-active molecules are shown, and target cells are plasma-treated. Specifically, melanoma cells are analyzed in an efficient sequence of different consecutive assays but using the same cells: measurement of metabolic activity, total cell area, and surface marker expression of calreticulin, a molecule important for the immunogenic cell death of cancer cells. These assays retrieve content-rich biological information about plasma effects from a single plate. Altogether, this study describes the essential steps and protocols for plasma medical research.
The diverse applications of plasma

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

Sharma, Mukul, E-mail: mukulsharma@acropolis.edu.in; Darwhekar, Gajanan, E-mail: gdarwhekar@acropolis.edu.in; Dubey, Shivani, E-mail: dubeyshivani08@rediffmail.com

Plasma being the fourth state of matter has always been an attraction for Physicists and Chemists. With the advent of time, plasma energy has been recognized in having widening horizons in the field of Biomedical Sciences. Plasma medicine can be subdivided into three main fields; Non-thermal atmospheric-pressure direct plasma for medical therapy; Plasma-assisted modification of bio-relevant surfaces and Plasma-based bio-decontamination and sterilization. The basis of the research is that as it has free carrier molecules, it has the ability to target specific cells and regulate functions like wound healing. Plasma does not harm healthy human cells but can kill bacteriamore » and possibly even cancer cells to help treat various diseases. Nosocomial infection control, prevention and containment of contagious diseases, disinfection of medical devices, surface treatment (heat and UV sensitive surfaces) are research of interest. Recent success in generating plasma at very low temperature ie. Cold plasma makes the therapy painless. It has the ability to activate cellular responses and important mechanisms in the body. They target specific molecules such as prothrombin for blood coagulation, cytokines for killing bacteria, and angiogenesis for tissue regeneration. Plasma has bactericidal, fungicidal and virucidal properties. Plasma technology has flourishing future in diverse fields like Textiles, Nanofabrication, Automotives, Waste management, Microbiology, Food Hygiene, Medical Science like Skin treatments, sterilisation of wounds, Hand disinfection, Dental treatments etc. Food hygiene using plasma can be achieved in disinfection of food containers, food surface disinfection, hygiene in food handling, preparation and packaging. Therefore Plasma is most promising field for budding Scientist for fluorishing research in Biological Sciences.« less
The diverse applications of plasma

NASA Astrophysics Data System (ADS)

Sharma, Mukul; Dubey, Shivani; Darwhekar, Gajanan; Jain, Sudhir Kumar

2015-07-01

Plasma being the fourth state of matter has always been an attraction for Physicists and Chemists. With the advent of time, plasma energy has been recognized in having widening horizons in the field of Biomedical Sciences. Plasma medicine can be subdivided into three main fields; Non-thermal atmospheric-pressure direct plasma for medical therapy; Plasma-assisted modification of bio-relevant surfaces and Plasma-based bio-decontamination and sterilization. The basis of the research is that as it has free carrier molecules, it has the ability to target specific cells and regulate functions like wound healing. Plasma does not harm healthy human cells but can kill bacteria and possibly even cancer cells to help treat various diseases. Nosocomial infection control, prevention and containment of contagious diseases, disinfection of medical devices, surface treatment (heat and UV sensitive surfaces) are research of interest. Recent success in generating plasma at very low temperature ie. Cold plasma makes the therapy painless. It has the ability to activate cellular responses and important mechanisms in the body. They target specific molecules such as prothrombin for blood coagulation, cytokines for killing bacteria, and angiogenesis for tissue regeneration. Plasma has bactericidal, fungicidal and virucidal properties. Plasma technology has flourishing future in diverse fields like Textiles, Nanofabrication, Automotives, Waste management, Microbiology, Food Hygiene, Medical Science like Skin treatments, sterilisation of wounds, Hand disinfection, Dental treatments etc. Food hygiene using plasma can be achieved in disinfection of food containers, food surface disinfection, hygiene in food handling, preparation and packaging. Therefore Plasma is most promising field for budding Scientist for fluorishing research in Biological Sciences.
Characteristics of Surface Sterilization using ECR Plasma

NASA Astrophysics Data System (ADS)

Yonesu, Akira; Hara, Kazufumi; Nishikawa, Tatsuya; Hayashi, Nobuya

2015-09-01

Plasma sterilization techniques have superior characteristics such as a short treatment times, non-toxicity and low thermal damages on the sterilized materials. In plasma sterilization, microorganisms can be sterilized by active radicals, energetic charged particles, and vacuum UV radiation. The influence of each factor depends on the plasma operating parameters. Microwave discharges under the electron cyclotron resonance (ECR) condition produce higher electron temperature and density plasma as compared with other plasma generation techniques. In the present study, characteristics of surface sterilization using ECR plasma have been investigated.The experiment was performed in the vacuum chamber which contains a magnet holder. A pair of rectangular Sm-Co permanent magnets is aligned parallel to each other within the magnet holder. The region of the magnetic field for ECR exists near the magnet holder surface. When the microwave is introduced into the vacuum chamber, a ECR plasma is produced around surface of the magnet holder. High energy electrons and oxygen radicals were observed at ECR zone by electric probe method and optical spectroscopic method. Biological indicators (B.I.) having spore of 106 was sterilized in 2min for oxygen discharge. The temperature of the B.I. installation position was about 55°. The sterilization was achieved by the effect of oxygen radicals and high energy electrons.
Heating and cooling of the earth's plasma sheet

NASA Technical Reports Server (NTRS)

Goertz, C. K.

1990-01-01

Magnetic-field models based on pressure equilibrium in the quiet magnetotail require nonadiabatic cooling of the plasma as it convects inward or a decrease of the flux tube content. Recent in situ observations of plasma density and temperature indicate that, during quiet convection, the flux tube content may actually increase. Thus the plasma must be cooled during quiet times. The earth plasma sheet is generally significantly hotter after the expansion phase of a substorm than before the plasma sheet thinning begins and cools during the recovery phase. Heating mechanisms such as reconnection, current sheet acceleration, plasma expansion, and resonant absorption of surface waves are discussed. It seems that all mechanisms are active, albeit in different regions of the plasma sheet. Near-earth tail signatures of substorms require local heating as well as a decrease of the flux tube content. It is shown that the resonant absorption of surface waves can provide both.
The feed gas composition determines the degree of physical plasma-induced platelet activation for blood coagulation

NASA Astrophysics Data System (ADS)

Bekeschus, Sander; Brüggemeier, Janik; Hackbarth, Christine; Weltmann, Klaus-Dieter; von Woedtke, Thomas; Partecke, Lars-Ivo; van der Linde, Julia

2018-03-01

Cold atmospheric (physical) plasma has long been suggested to be a useful tool for blood coagulation. However, the clinical applicability of this approach has not been addressed sufficiently. We have previously demonstrated the ability of a clinically accepted atmospheric pressure argon plasma jet (kINPen® MED) to coagulate liver incisions in mice with similar performance compared to the gold standard electrocauterization. We could show that plasma-mediated blood coagulation was dependent on platelet activation. In the present work, we extended on this by investigating kINPen®-mediated platelet activation in anticoagulated human donor blood ex vivo. With focus on establishing high-throughput, multi-parametric platelet activation assays and performing argon feed gas parameter studies we achieved the following results: (i) plasma activated platelets in heparinized but not in EDTA-anticoagulated blood; (ii) plasma decreased total platelet counts but increased numbers of microparticles; (iii) plasma elevated the expression of several surface activation markers on platelets (CD62P, CD63, CD69, and CD41/61); (iv) in platelet activation, wet and dry argon plasma outperformed feed gas admixtures with oxygen and/or nitrogen; (v) plasma-mediated platelet activation was accompanied by platelet aggregation. Platelet aggregation is a necessary requirement for blood clot formation. These findings are important to further elucidate molecular details and clinical feasibility of cold physical plasma-mediated blood coagulation.
Engineering surfaces for bioconjugation: developing strategies and quantifying the extent of the reactions.

PubMed

Gauvreau, Virginie; Chevallier, Pascale; Vallières, Karine; Petitclerc, Eric; Gaudreault, René C; Laroche, Gaétan

2004-01-01

This study presents two-step and multistep reactions for modifying the surface of plasma-functionalized poly(tetrafluoroethylene) (PTFE) surfaces for subsequent conjugation of biologically relevant molecules. First, PTFE films were treated by a radiofrequency glow discharge (RFGD) ammonia plasma to introduce amino groups on the fluoropolymer surface. This plasma treatment is well optimized and allows the incorporation of a relative surface concentration of approximately 2-3.5% of amino groups, as assessed by chemical derivatization followed by X-ray photoelectron spectroscopy (XPS). In a second step, these amino groups were further reacted with various chemical reagents to provide the surface with chemical functionalities such as maleimides, carboxylic acids, acetals, aldehydes, and thiols, that could be used later on to conjugate a wide variety of biologically relevant molecules such as proteins, DNA, drugs, etc. In the present study, glutaric and cis-aconitic anhydrides were evaluated for their capability to provide carboxylic functions to the PTFE plasma-treated surface. Bromoacetaldehyde diethylacetal was reacted with the aminated PTFE surface, providing a diethylacetal function, which is a latent form of aldehyde functionality. Reactions with cross-linkers such as sulfo-succinimidyl derivatives (sulfo-SMCC, sulfo-SMPB) were evaluated to provide a highly reactive maleimide function suitable for further chemical reactions with thiolated molecules. Traut reagent (2-iminothiolane) was also conjugated to introduce a thiol group onto the fluoropolymer surface. PTFE-modified surfaces were analyzed by XPS with a particular attention to quantify the extent of the reactions that occurred on the polymer. Finally, surface immobilization of fibronectin performed using either glutaric anhydride or sulfo-SMPB activators demonstrated the importance of selecting the appropriate conjugation strategy to retain the protein biological activity.

Hydrophobic and superhydrophobic surfaces fabricated using atmospheric pressure cold plasma technology: A review.

PubMed

Dimitrakellis, Panagiotis; Gogolides, Evangelos

2018-04-01

Hydrophobic surfaces are often used to reduce wetting of surfaces by water. In particular, superhydrophobic surfaces are highly desired for several applications due to their exceptional properties such as self-cleaning, anti-icing, anti-friction and others. Such surfaces can be prepared via numerous methods including plasma technology, a dry technique with low environmental impact. Atmospheric pressure plasma (APP) has recently attracted significant attention as lower-cost alternative to low-pressure plasmas, and as a candidate for continuous rather than batch processing. Although there are many reviews on water-repellent surfaces, and a few reviews on APP technology, there are hardly any review works on APP processing for hydrophobic and superhydrohobic surface fabrication, a topic of high importance in nanotechnology and interface science. Herein, we critically review the advances on hydrophobic and superhydrophobic surface fabrication using APP technology, trying also to give some perspectives in the field. After a short introduction to superhydrophobicity of nanostructured surfaces and to APPs we focus this review on three different aspects: (1) The atmospheric plasma reactor technology used for fabrication of (super)hydrophobic surfaces. (2) The APP process for hydrophobic surface preparation. The hydrophobic surface preparation processes are categorized methodologically as: a) activation, b) grafting, c) polymerization, d) roughening and hydrophobization. Each category includes subcategories related to different precursors used. (3) One of the most important sections of this review concerns superhydrophobic surfaces fabricated using APP. These are methodologically characterized as follows: a) single step processes where micro-nano textured topography and low surface energy coating are created at the same time, or b) multiple step processes, where these steps occur sequentially in or out of the plasma. We end the review with some perspectives in the field. We aspire to address scientists, who will get involved in the fields of (super)hydrophobicity and/or in atmospheric pressure plasma processing. Copyright © 2018 Elsevier B.V. All rights reserved.
Electrochemical Characterization of O2 Plasma Functionalized Multi-Walled Carbon Nanotube Electrode for Legionella pneumophila DNA Sensor

NASA Astrophysics Data System (ADS)

Park, Eun Jin; Lee, Jun-Yong; Hyup Kim, Jun; Kug Kim, Sun; Lee, Cheol Jin; Min, Nam Ki

2010-08-01

An electrochemical DNA sensor for Legionella pneumophila detection was constructed using O2 plasma functionalized multi-walled carbon nanotube (MWCNT) film as a working electrode (WE). The cyclic voltammetry (CV) results revealed that the electrocatalytic activity of plasma functionalized MWCNT (pf-MWCNT) significantly changed depending on O2 plasma treatment time due to some oxygen containing functional groups on the pf-MWCNT surface. Scanning electron microscope (SEM) images and X-ray photoelectron spectroscopy (XPS) spectra were also presented the changes of their surface morphologies and oxygen composition before and after plasma treatment. From a comparison study, it was found that the pf-MWCNT WEs had higher electrocatalytic activity and more capability of probe DNA immobilization: therefore, electrochemical signal changes by probe DNA immobilization and hybridization on pf-MWCNT WEs were larger than on Au WEs. The pf-MWCNT based DNA sensor was able to detect a concentration range of 10 pM-100 nM of target DNA to detect L. pneumophila.
Physico-chemical induced modification of seed germination and early development in artichoke (Cynara scolymus L.) using low energy plasma technology

NASA Astrophysics Data System (ADS)

Hosseini, Seyed Iman; Mohsenimehr, Soad; Hadian, Javad; Ghorbanpour, Mansour; Shokri, Babak

2018-01-01

In this study, low pressure non-thermal radiofrequency nitrogen plasma at very low power has been used to treat the artichoke seeds on the powered cathode for the first time. The influence of treatment time on the surface physical properties, germination rate, seedling growth, and enzyme activity of the seeds has been investigated. Results showed that plasma treatment considerably improved the germination rate and seedling growth. The root length grew by 28.5% and 50% and root dry weight increased by 13% and 53%, respectively, for 10 and 15 min of treatment. The same trend has been found for the shoot growth parameters although the greater stimulatory efficacy on root has been obtained. The nitrogen plasma treatment substantially made the seeds' surface hydrophilic which leads to 36.9% improvement in seed's water uptake at 15 min of treatment. Our study showed the activity of peroxidase and catalase enzymes slightly increased after the plasma treatment.
Modifications of aluminum film caused by micro-plasmoids and plasma spots in the effluent of an argon non-equilibrium plasma jet

NASA Astrophysics Data System (ADS)

Engelhardt, Max; Ries, Stefan; Hermanns, Patrick; Bibinov, Nikita; Awakowicz, Peter

2017-09-01

A smooth layer of hard aluminium film is deposited onto a glass substrate with a multi-frequency CCP discharge and then treated in the effluent of a non-equilibrium atmospheric pressure plasma jet (N-APPJ) operated with Ar flow. A thin filament is formed in the argon N-APPJ through contraction of a diffuse feather-like discharge. The aluminium surface treated in the effluents of the N-APPJ is significantly modified. Erosion tracks of different forms and micro-balls composed of aluminium are observed on the treated surface. Based on CCD images of active plasma discharge channels, SEM images of the treated surface and current-voltage characteristics, these surface modifications are interpreted as traces of plasma spots and plasmoids. Plasma spots are focused plasma channels, which are characterized by an intense emission in CCD images at the contact point of a plasma channel with the treated metal surface and by deep short tracks on the aluminium surface, observed in SEM images. Plasmoids are plasma objects without contact to any power supply which can produce long, thin and shallow traces, as can be observed on the treated surface using electron microscopy. Based on observed traces and numerous transformations of plasma spots to plasmoids and vice versa, it is supposed that both types of plasma objects are formed by an extremely high axial magnetic field and differ from each other due to the existence or absence of contact to a power supply and the consequential transport of electric current. The reason for the magnetic field at the axis of these plasma objects is possibly a circular current of electron pairs in vortices, which are formed in plasma by the interaction of ionization waves with the substrate surface. The extremely high magnetic field of plasma spots and plasmoids leads to a local destruction of the metal film and top layer of the glass substrate and to an attraction of paramagnetic materials, namely aluminium and oxygen. The magnetic attraction of aluminium is a reason for the extraction of some pieces of metal and the formation of erosion tracks and holes in the metal film. In the absence of metal atomization, the extracted aluminium forms spherical micro-particles, which are distributed over the surface of the treated metal film by the gas flow. A thin (100 nm) gold (diamagnetic) layer on top of the aluminium film surface reduces the erosion rate of plasma spots and plasmoids drastically (more than three orders of magnitude).
Effects of low temperature plasmas and plasma activated waters on Arabidopsis thaliana germination and growth

PubMed Central

Martinez, Yves; Merbahi, Nofel; Eichwald, Olivier; Dunand, Christophe

2018-01-01

Two plasma devices at atmospheric pressure (air dielectric barrier discharge and helium plasma jet) have been used to study the early germination of Arabidopsis thaliana seeds during the first days. Then, plasma activated waters are used during the later stage of plant development and growth until 42 days. The effects on both testa and endospserm ruptures during the germination stage are significant in the case of air plasma due to its higher energy and efficiency of producing reactive oxygen species than the case of helium plasma. The latter has shown distinct effects only for testa rupture. Analysis of germination stimulations are based on specific stainings for reactive oxygen species production, peroxidase activity and also membrane permeability tests. Furthermore, scanning electron microscopy (SEM) has shown a smoother seed surface for air plasma treated seeds that can explain the plasma induced-germination. During the growth stage, plants were watered using 4 kinds of water (tap and deionized waters activated or not by the low temperature plasma jet). With regards to other water kinds, the characterization of the tap water has shown a larger conductivity, acidity and concentration of reactive nitrogen and oxygen species. Only the tap water activated by the plasma jet has shown a significant effect on the plant growth. This effect could be correlated to reactive nitrogen species such as nitrite/nitrate species present in plasma activated tap water. PMID:29630641
Highly efficient low-temperature plasma-assisted modification of TiO2 nanosheets with exposed {001} facets for enhanced visible-light photocatalytic activity.

PubMed

Li, Beibei; Zhao, Zongbin; Zhou, Quan; Meng, Bo; Meng, Xiangtong; Qiu, Jieshan

2014-11-03

Anatase TiO2 nanosheets with exposed {001} facets have been controllably modified under non-thermal dielectric barrier discharge (DBD) plasma with various working gas, including Ar, H2 , and NH3 . The obtained TiO2 nanosheets possess a unique crystalline core/amorphous shell structure (TiO2 @TiO2-x ), which exhibit the improved visible and near-infrared light absorption. The types of dopants (oxygen vacancy/surface Ti(3+) /substituted N) in oxygen-deficient TiO2 can be tuned by controlling the working gases during plasma discharge. Both surface Ti(3+) and substituted N were doped into the lattice of TiO2 through NH3 plasma discharge, whereas the oxygen vacancy or Ti(3+) (along with the oxygen vacancy) was obtained after Ar or H2 plasma treatment. The TiO2 @TiO2-x from NH3 plasma with a green color shows the highest photocatalytic activity under visible-light irradiation compared with the products from Ar plasma or H2 plasma due to the synergistic effect of reduction and simultaneous nitridation in the NH3 plasma. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Active control for stabilization of neoclassical tearing modesa)

NASA Astrophysics Data System (ADS)

Humphreys, D. A.; Ferron, J. R.; La Haye, R. J.; Luce, T. C.; Petty, C. C.; Prater, R.; Welander, A. S.

2006-05-01

This work describes active control algorithms used by DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] to stabilize and maintain suppression of 3/2 or 2/1 neoclassical tearing modes (NTMs) by application of electron cyclotron current drive (ECCD) at the rational q surface. The DIII-D NTM control system can determine the correct q-surface/ECCD alignment and stabilize existing modes within 100-500ms of activation, or prevent mode growth with preemptive application of ECCD, in both cases enabling stable operation at normalized beta values above 3.5. Because NTMs can limit performance or cause plasma-terminating disruptions in tokamaks, their stabilization is essential to the high performance operation of ITER [R. Aymar et al., ITER Joint Central Team, ITER Home Teams, Nucl. Fusion 41, 1301 (2001)]. The DIII-D NTM control system has demonstrated many elements of an eventual ITER solution, including general algorithms for robust detection of q-surface/ECCD alignment and for real-time maintenance of alignment following the disappearance of the mode. This latter capability, unique to DIII-D, is based on real-time reconstruction of q-surface geometry by a Grad-Shafranov solver using external magnetics and internal motional Stark effect measurements. Alignment is achieved by varying either the plasma major radius (and the rational q surface) or the toroidal field (and the deposition location). The requirement to achieve and maintain q-surface/ECCD alignment with accuracy on the order of 1cm is routinely met by the DIII-D Plasma Control System and these algorithms. We discuss the integrated plasma control design process used for developing these and other general control algorithms, which includes physics-based modeling and testing of the algorithm implementation against simulations of actuator and plasma responses. This systematic design/test method and modeling environment enabled successful mode suppression by the NTM control system upon first-time use in an experimental discharge.
Validity of "sputtering and re-condensation" model in active screen cage plasma nitriding process

NASA Astrophysics Data System (ADS)

Saeed, A.; Khan, A. W.; Jan, F.; Abrar, M.; Khalid, M.; Zakaullah, M.

2013-05-01

The validity of "sputtering and re-condensation" model in active screen plasma nitriding for nitrogen mass transfer mechanism is investigated. The dominant species including NH, Fe-I, N2+, N-I and N2 along with Hα and Hβ lines are observed in the optical emission spectroscopy (OES) analysis. Active screen cage and dc plasma nitriding of AISI 316 stainless steel as function of treatment time is also investigated. The structure and phases composition of the nitrided layer is studied by X-ray diffraction (XRD). Surface morphology is studied by scanning electron microscopy (SEM) and hardness profile is obtained by Vicker's microhardness tester. Increasing trend in microhardness is observed in both cases but the increase in active screen plasma nitriding is about 3 times greater than that achieved by dc plasma nitriding. On the basis of metallurgical and OES observations the use of "sputtering and re-condensation" model in active screen plasma nitriding is tested.
Development of active porous medium filters based on plasma textiles

NASA Astrophysics Data System (ADS)

Kuznetsov, Ivan A.; Saveliev, Alexei V.; Rasipuram, Srinivasan; Kuznetsov, Andrey V.; Brown, Alan; Jasper, Warren

2012-05-01

Inexpensive, flexible, washable, and durable materials that serve as antimicrobial filters and self-decontaminating fabrics are needed to provide active protection to people in areas regularly exposed to various biohazards, such as hospitals and bio research labs working with pathogens. Airlines and cruise lines need such material to combat the spread of infections. In households these materials can be used in HVAC filters to fight indoor pollution, which is especially dangerous to people suffering from asthma. Efficient filtering materials are also required in areas contaminated by other types of hazardous dust particulates, such as nuclear dust. The primary idea that guided the undertaken study is that a microplasma-generating structure can be embedded in a textile fabric to generate a plasma sheath ("plasma shield") that kills bacterial agents coming in contact with the fabric. The research resulted in the development of a plasma textile that can be used for producing new types of self-decontaminating garments, fabrics, and filter materials, capable of activating a plasma sheath that would filter, capture, and destroy any bacteriological agent deposited on its surface. This new material relies on the unique antimicrobial and catalytic properties of cold (room temperature) plasma that is benign to people and does not cause thermal damage to many polymer textiles, such as Nomex and polypropylene. The uniqueness of cold plasma as a disinfecting agent lies in the inability of bacteria to develop resistance to plasma exposure, as they can for antibiotics. Plasma textiles could thus be utilized for microbial destruction in active antimicrobial filters (for continuous decontamination and disinfection of large amounts of air) as well as in self-decontaminating surfaces and antibacterial barriers (for example, for creating local antiseptic or sterile environments around wounds and burns).
Development of active porous medium filters based on plasma textiles

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

Kuznetsov, Ivan A.; Saveliev, Alexei V.; Rasipuram, Srinivasan

2012-05-15

Inexpensive, flexible, washable, and durable materials that serve as antimicrobial filters and self-decontaminating fabrics are needed to provide active protection to people in areas regularly exposed to various biohazards, such as hospitals and bio research labs working with pathogens. Airlines and cruise lines need such material to combat the spread of infections. In households these materials can be used in HVAC filters to fight indoor pollution, which is especially dangerous to people suffering from asthma. Efficient filtering materials are also required in areas contaminated by other types of hazardous dust particulates, such as nuclear dust. The primary idea that guidedmore » the undertaken study is that a microplasma-generating structure can be embedded in a textile fabric to generate a plasma sheath (''plasma shield'') that kills bacterial agents coming in contact with the fabric. The research resulted in the development of a plasma textile that can be used for producing new types of self-decontaminating garments, fabrics, and filter materials, capable of activating a plasma sheath that would filter, capture, and destroy any bacteriological agent deposited on its surface. This new material relies on the unique antimicrobial and catalytic properties of cold (room temperature) plasma that is benign to people and does not cause thermal damage to many polymer textiles, such as Nomex and polypropylene. The uniqueness of cold plasma as a disinfecting agent lies in the inability of bacteria to develop resistance to plasma exposure, as they can for antibiotics. Plasma textiles could thus be utilized for microbial destruction in active antimicrobial filters (for continuous decontamination and disinfection of large amounts of air) as well as in self-decontaminating surfaces and antibacterial barriers (for example, for creating local antiseptic or sterile environments around wounds and burns).« less
Method of processing a substrate

DOEpatents

Babayan, Steven E [Huntington Beach, CA; Hicks, Robert F [Los Angeles, CA

2008-02-12

The invention is embodied in a plasma flow device or reactor having a housing that contains conductive electrodes with openings to allow gas to flow through or around them, where one or more of the electrodes are powered by an RF source and one or more are grounded, and a substrate or work piece is placed in the gas flow downstream of the electrodes, such that said substrate or work piece is substantially uniformly contacted across a large surface area with the reactive gases emanating therefrom. The invention is also embodied in a plasma flow device or reactor having a housing that contains conductive electrodes with openings to allow gas to flow through or around them, where one or more of the electrodes are powered by an RF source and one or more are grounded, and one of the grounded electrodes contains a means of mixing in other chemical precursors to combine with the plasma stream, and a substrate or work piece placed in the gas flow downstream of the electrodes, such that said substrate or work piece is contacted by the reactive gases emanating therefrom. In one embodiment, the plasma flow device removes organic materials from a substrate or work piece, and is a stripping or cleaning device. In another embodiment, the plasma flow device kills biological microorganisms on a substrate or work piece, and is a sterilization device. In another embodiment, the plasma flow device activates the surface of a substrate or work piece, and is a surface activation device. In another embodiment, the plasma flow device etches materials from a substrate or work piece, and is a plasma etcher. In another embodiment, the plasma flow device deposits thin films onto a substrate or work piece, and is a plasma-enhanced chemical vapor deposition device or reactor.
TFEB activation promotes the recruitment of lysosomal glycohydrolases β-hexosaminidase and β-galactosidase to the plasma membrane

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

Magini, Alessandro; Department of Medical and Biological Sciences; Polchi, Alice

2013-10-18

Highlights: •TFEB activation promotes the increase of Hex and Gal activities. •The increase of Hex and Gal activities is related to transcriptional regulation. •TFEB promotes the recruitment of mature Hex and Gal on cell surface. -- Abstract: Lysosomes are membrane-enclosed organelles containing acid hydrolases. They mediate a variety of physiological processes, such as cellular clearance, lipid homeostasis, energy metabolism and pathogen defence. Lysosomes can secrete their content through a process called lysosome exocytosis in which lysosomes fuse with the plasma membrane realising their content into the extracellular milieu. Lysosomal exocytosis is not only responsible for the secretion of lysosomal enzymes,more » but it also has a crucial role in the plasma membrane repair. Recently, it has been demonstrated that lysosome response to the physiologic signals is regulated by the transcription factor EB (TFEB). In particular, lysosomal secretion is transcriptionally regulated by TFEB which induces both the docking and fusion of lysosomes with the plasma membrane. In this work we demonstrated that TFEB nuclear translocation is accompanied by an increase of mature glycohydrolases β-hexosaminidase and β-galactosidase on cell surface. This evidence contributes to elucidate an unknown TFEB biological function leading the lysosomal glycohydrolases on plasma membrane.« less
Adhesion and Growth of Vascular Smooth Muscle Cells on Nanostructured and Biofunctionalized Polyethylene

PubMed Central

Novotna, Katarina; Bacakova, Marketa; Kasalkova, Nikola Slepickova; Slepicka, Petr; Lisa, Vera; Svorcik, Vaclav; Bacakova, Lucie

2013-01-01

Cell colonization of synthetic polymers can be regulated by physical and chemical modifications of the polymer surface. High-density and low-density polyethylene (HDPE and LDPE) were therefore activated with Ar+ plasma and grafted with fibronectin (Fn) or bovine serum albumin (BSA). The water drop contact angle usually decreased on the plasma-treated samples, due to the formation of oxidized groups, and this decrease was inversely related to the plasma exposure time (50–300 s). The presence of nitrogen and sulfur on the polymer surface, revealed by X-ray photoelectron spectroscopy (XPS), and also by immunofluorescence staining, showed that Fn and BSA were bound to this surface, particularly to HDPE. Plasma modification and grafting with Fn and BSA increased the nanoscale surface roughness of the polymer. This was mainly manifested on HDPE. Plasma treatment and grafting with Fn or BSA improved the adhesion and growth of vascular smooth muscle cells in a serum-supplemented medium. The final cell population densities on day 6 after seeding were on an average higher on LDPE than on HDPE. In a serum-free medium, BSA grafted to the polymer surface hampered cell adhesion. Thus, the cell behavior on polyethylene can be modulated by its type, intensity of plasma modification, grafting with biomolecules, and composition of the culture medium. PMID:28809234
Macrophages discriminate glycosylation patterns of apoptotic cell-derived microparticles.

PubMed

Bilyy, Rostyslav O; Shkandina, Tanya; Tomin, Andriy; Muñoz, Luis E; Franz, Sandra; Antonyuk, Volodymyr; Kit, Yuriy Ya; Zirngibl, Matthias; Fürnrohr, Barbara G; Janko, Christina; Lauber, Kirsten; Schiller, Martin; Schett, Georg; Stoika, Rostyslav S; Herrmann, Martin

2012-01-02

Inappropriate clearance of apoptotic remnants is considered to be the primary cause of systemic autoimmune diseases, like systemic lupus erythematosus. Here we demonstrate that apoptotic cells release distinct types of subcellular membranous particles (scMP) derived from the endoplasmic reticulum (ER) or the plasma membrane. Both types of scMP exhibit desialylated glycotopes resulting from surface exposure of immature ER-derived glycoproteins or from surface-borne sialidase activity, respectively. Sialidase activity is activated by caspase-dependent mechanisms during apoptosis. Cleavage of sialidase Neu1 by caspase 3 was shown to be directly involved in apoptosis-related increase of surface sialidase activity. ER-derived blebs possess immature mannosidic glycoepitopes and are prioritized by macrophages during clearance. Plasma membrane-derived blebs contain nuclear chromatin (DNA and histones) but not components of the nuclear envelope. Existence of two immunologically distinct types of apoptotic blebs may provide new insights into clearance-related diseases.
Tuning the adhesion between polyimide substrate and MWCNTs/epoxy nanocomposite by surface treatment

NASA Astrophysics Data System (ADS)

Bouhamed, Ayda; Kia, Alireza Mohammadian; Naifar, Slim; Dzhagan, Volodymyr; Müller, Christian; Zahn, Dietrich R. T.; Choura, Slim; Kanoun, Olfa

2017-11-01

MWCNTs/epoxy nanocomposite thin films are coated on the polyimide (PI) flexible substrate, to be used as a strain sensor. Previous studies showed that the adhesion between polyimide and other materials are very poor. In this work, two approaches, oxygen plasma cleaning and simple solvent cleaning are performed for activation of the polyimide surface. In order to understand the impact of both cleaning techniques, the physicochemical properties of PI are measured and characterized using contact angle measurements (CAMs), X-ray photoelectron spectroscopy(XPS), and atomic force microscopy (AFM). In addition, the adhesion properties of PI/[MWCNTs/epoxy] systems by varying surface treatment time are investigated and evaluated using force-distance measurements by AFM. The results illustrate that the activated surface exhibits higher surface energy for oxygen plasma cleaning in comparison with the solvent cleaning method. The improvement can be related to the increase of oxygen concentration, which is accompanied by the enhancement of the polar component to 53.79 mN/m due to the formation of functional groups on the surface and the change of the substrate surface roughness from 1.72 nm to 15.5 nm. As a result, improved adhesion was observed from force-distance measurement between PI/[MWCNTs/epoxy] systems due to oxygen plasma effects.
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 chitosan-coated polyethylene packaging films by DBD plasma treatment.

PubMed

Theapsak, Siriporn; Watthanaphanit, Anyarat; Rujiravanit, Ratana

2012-05-01

Polyethylene (PE) packaging films were coated with chitosan in order to introduce the antibacterial activity to the films. To augment the interaction between the two polymers, we modified the surfaces of the PE films by dielectric barrier discharge (DBD) plasma before chitosan coating. After that the plasma-treated PE films were immersed in chitosan acetate solutions with different concentrations of chitosan. The optimum plasma treatment time was 10 s as determined from contact angle measurement. Effect of the plasma treatment on the surface roughness of the PE films was investigated by atomic force microscope (AFM) while the occurrence of polar functional groups was observed by X-ray photoelectron spectroscope (XPS) and Fourier transformed infrared spectroscope (FTIR). It was found that the surface roughness as well as the occurrence of oxygen-containing functional groups (i.e., C═O, C-O, and -OH) of the plasma-treated PE films increased from those of the untreated one, indicating that the DBD plasma enhanced hydrophilicity of the PE films. The amounts of chitosan coated on the PE films were determined after washing the coated films in water for several number of washing cycles prior to detection of the chitosan content by the Kjaldahl method. The amounts of chitosan coated on the PE films were constant after washing for three times and the chitosan-coated PE films exhibited appreciable antibacterial activity against Escherichia coli and Staphylococcus aureus. Hence, the obtained chitosan-coated PE films could be a promising candidate for antibacterial food packaging.
The Lunar dusty plasmas -levitation and transport.

NASA Astrophysics Data System (ADS)

Atamaniuk, Barbara; Rothkaehl, Hanna

Lunar dust can exhibit unusual behavior -due to electron photoemission via solar-UV radiation the lunar surface represents a complex plasma -"dusty plasma". The dust grains and lunar surface are electrostatically charged by the Moon's interaction with the local plasma environ-ment and the photoemission of electrons due to solar UV and X-rays. This effect causes the like-charged surface and dust particles to repel each other, and creates a near-surface electric field. Lunar dust must be treated as a dusty plasma. Using analytic (kinetic (Vlasov) and magnetohydrodynamic theory ) and numerical modeling we show physical processes related to levitation and transport dusty plasma on the Moon. These dust grains could affect the lunar environment for radio wave and plasma diagnostics and interfere with exploration activities. References: 1. Wilson T.L. (1992), in Analysis of Interplanetary Dust, M. Zolensky et al. AIP Conf.Proc. 310, 33-44 (AIP, NY), 2.Wilson T.L."LUNAR DUST AND DUSTY PLASMA PHYSICS".40th Lunar and Planetary Science Conference (2009), 3. Grün E., et al.(1993),Nature 363, 144. 4. Morfill G. and Grün E.(1979), Planet. Space Sci.. 27, 1269, 1283, 5. Manka R. and Michel F. (1971), Proc. 2nd Lun. Sci. Conf. 2, 1717 (MIT Press, Cambridge). 6. Manka R. et al.(1973), Lun. Sci.-III, 504. 7. Barbara Atamaniuk "Kinetic Description of Localized Plasma Structure in Dusty Plasmas". Czechoslovak Journal of Physics Vol.54 C 2004
Influence of plasma treatment of carbon blacks on electrochemical activity of Pt/carbon blacks catalysts for DMFCs

NASA Astrophysics Data System (ADS)

Kim, Seok; Cho, Mi-Hwa; Lee, Jae-Rock; Park, Soo-Jin

In this work, in order to improve the dispersion of platinum catalysts deposited on carbon materials, the effects of surface plasma treatment of carbon blacks (CBs) were investigated. The surface characteristics of the CBs were determined by fourier transformed-infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and Boehm's titration method. The electrochemical properties of the plasma-treated CBs-supported Pt (Pt/CBs) catalysts were analyzed by linear sweep voltammetry (LSV) experiments. From the results of FT-IR and acid-base values, N 2-plasma treatment of the CBs at 300 W intensity led to a formation of a free radical on the CBs. The peak intensity increased with increase of the treatment time, due to the formation of new basic functional groups (such as C-N, C dbnd N, -NH 3 +, -NH, and dbnd NH) by the free radical on the CBs. Accordingly, the basic values were enhanced by the basic functional groups. However, after a specific reaction time, N 2-plasma treatment could hardly influence on change of the surface functional groups of CBs, due to the disappearance of free radical. Consequently, it was found that optimal treatment time was 30 s for the best electro activity of Pt/CBs catalysts and the N 2-plasma treated Pt/CBs possessed the better electrochemical properties than the pristine Pt/CBs.
Dusty Plasma Dynamics Near Surfaces in Space

NASA Technical Reports Server (NTRS)

Colwell, Joshua E.; Robertson, S.; Horanyi, M.; Nahra, Henry (Technical Monitor)

1998-01-01

The investigation 'Dusty Plasma Dynamics Near Surfaces in Space' is an experimental and theoretical study of the dynamics of dust particles on airless bodies in the solar system in the presence of a photoelectron sheath generated by solar ultraviolet light impinging on the surface. Solar UV illumination of natural and manmade surfaces in space produces photoelectrons which form a plasma sheath near the surface. Dust particles on the surface acquire a charge and may be transported by electric fields in the photoelectron sheath generated by inhomogeneities in the surface or the illumination (such as shadows). The sheath itself has a finite vertical extent leading to (at least) an electric field normal to the illuminated surface. If dust particles are launched from the surface by some other process, such as meteoroid impact, or spacecraft activity on the surface, these grains become charged and move under the influence of gravity and the electric field. This can give rise to suspension of the particles above the surface, loss from the parent body entirely (if accelerated beyond escape velocity), and a different distribution of dust ejecta from what would be expected with purely gravitational dynamics.

Plasma Surface Modification for Immobilization of Bone Morphogenic Protein-2 on Polycaprolactone Scaffolds

NASA Astrophysics Data System (ADS)

Kim, Byung Hoon; Myung, Sung Woon; Jung, Sang Chul; Ko, Yeong Mu

2013-11-01

The immobilization of recombinant human bone formation protein-2 (rhBMP-2) on polycaprolactone (PCL) scaffolds was performed by plasma polymerization. RhBMP-2, which induces osteoblast differentiation in various cell types, is a growth factor that plays an important role in bone formation and repair. The surface of the PCL scaffold was functionalized with the carboxyl groups of plasma-polymerized acrylic acid (PPAA) thin films. Plasma polymerization was carried out at a discharge power of 60 W at an acrylic acid flow rate of 7 sccm for 5 min. The PPAA thin film exhibited moderate hydrophilic properties and possessed a high density of carboxyl groups. Carboxyl groups and rhBMP-2 on the PCL scaffolds surface were identified by attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, respectively. The alkaline phosphatase activity assay showed that the rhBMP-2 immobilized PCL scaffold increased the level of MG-63 cell differentiation. Plasma surface modification for the preparation of biomaterials, such as biofunctionalized polymer scaffolds, can be used for the binding of bioactive molecules in tissue engineering.
Surface Reflectometry and Ionosphere Sounding from the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON)

NASA Astrophysics Data System (ADS)

Grima, C.; Blankenship, D. D.; Schroeder, D. M.; Moussessian, A.; Soderlund, K. M.; Gim, Y.; Plaut, J. J.; Greenbaum, J. S.; Lopez Garcia, E.; Campbell, B. A.; Putzig, N. E.; Patterson, G.

2015-12-01

The Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) has been selected for the scientific payload of a NASA's multiple flyby mission to explore the icy moon Europa. REASON is an active dual-frequency (9/60 MHz) instrument led by the University of Texas Institute for Geophysics (UTIG). It is designed to achieve multi-disciplinary measurements to investigate subsurface waters and the ice shell structure (Sounding), the surface elevation and tides (Altimetry), the surface physical properties (Reflectometry), and the ionospheric environment (Plasma/Particles). We will present the concepts behind the "Reflectometry" and "Plasma/Particles" measurements, demonstrate their efficiency with planetary analogs, and anticipate their capabilities for the exploration of Europa. We will also highlight the potential synergies with other instruments selected for the Europa mission payload.The "Reflectometry" compares the statistical behavior of the surface echo amplitudes with theoretical stochastic models to separate the reflected and scattered contributions to the signal. Once those two components are deduced they are used in a backscattering model to invert surface properties such as roughness, density, and/or impurity load. "Reflectometry" measurements will contribute to the statistical characterization of the surface over ~ 10-km-long areas with a ~ 10 m skin depth for geological investigation, near-surface brine detection, plume-deposited snow characterization, and landing site reconnaissance. The "Plasma/Particles" measurement relies on the dispersive signal delays induced by the ionospheric content integrated along the radio propagation path. Correction of this delay with existing techniques provides the total electron content below the spacecraft. "Plasma/Particles" measurements will constrain the ionosphere's shape and variability along the acquisition track and might detect transient plume-induced ionosphere when active.
Regulation of Plasminogen Activation on Cell Surfaces and Fibrin.

PubMed

Urano, Tetsumei; Castellino, Francis J; Suzuki, Yuko

2018-05-20

The fibrinolytic system dissolves fibrin and maintains vascular patency. Recent advances in imaging analyses allowed visualization of the spatiotemporal regulatory mechanism of fibrinolysis, as well as its regulation by other plasma haemostasis cofactors. Vascular endothelial cells (VECs) retain tissue-type plasminogen activator (tPA) after secretion and maintain high plasminogen (plg) activation potential on their surfaces. As in plasma, the serpin, plasminogen activator inhibitor type 1 (PAI-1), regulates fibrinolytic potential via inhibition of the VEC surface-bound plg activator, tPA. Once fibrin is formed, plg activation by tPA is initiated and effectively amplified on the surface of fibrin, and fibrin is rapidly degraded. The specific binding of plg and tPA to lytic edges of partly degraded fibrin via newly generated C-terminal lysine residues, which amplifies fibrin digestion, is a central aspect of this pathophysiological mechanism. Thrombomodulin (TM) plays a role in the attenuation of the plg binding on fibrin and the associated fibrinolysis, which is reversed by a carboxypeptidase B inhibitor. This suggests that the plasma procarboxypeptidase B, thrombin activatable fibrinolysis inhibitor (TAFI), which is activated by thrombin bound to TM on VECs, is a critical aspect of the regulation of plg activation on VECs and subsequent fibrinolysis. Platelets also contain PAI-1, TAFI, TM and the fibrin crosslinking enzyme, Factor (F) XIIIa, and either secrete or expose these agents upon activation in order to regulate fibrinolysis. In this review, the native machinery of plg activation and fibrinolysis, as well as their spatiotemporal regulatory mechanisms, as revealed by imaging analyses, are discussed. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Influence of ethanol vapor addition on the surface modification of polyethylene in a dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Van Deynse, Annick; Morent, Rino; Leys, Christophe; De Geyter, Nathalie

2017-10-01

In this paper, ethanol vapor up to 50% is added to an argon, air or nitrogen dielectric barrier discharge at medium pressure to profoundly investigate the effect of ethanol addition on the surface modification of low density polyethylene (LDPE). Water contact angle (WCA) and X-ray photoelectron spectroscopy (XPS) measurements show that the ethanol vapor addition effect on the LDPE surface depends on the used carrier gas. Adding ethanol to an argon plasma has no significant effect on the wettability nor on the chemical composition of LDPE compared to a pure argon plasma treatment. Ethanol addition does however slightly increase the LDPE surface roughness. Addition of small amounts of ethanol vapor to an air plasma makes it possible to incorporate additional nitrogen and oxygen groups on the LDPE surface, resulting in an extra decrease of 11% in WCA value. Moreover, the LDPE surface roughness is slightly increased due to the ethanol vapor addition. The most significant effect of ethanol addition is however observed when nitrogen is used as carrier gas. After an N2/2% ethanol plasma treatment, an 85% reduction in WCA value to 8.5° is found compared to a pure N2 plasma treatment. This very hydrophilic LDPE surface is obtained due to a significantly high incorporation of oxygen and nitrogen groups on the surface with an O/C and N/C ratio reaching 32% and 53% respectively. FTIR measurements also reveal that the observed extremely high wettability of LDPE is not the result of plasma activation but is due to plasma polymerization effects occurring on the surface resulting into the deposition of a plasma polymer containing ketones, amides as well as Cdbnd N groups. In addition, ageing studies have also been conducted and these studies reveal that for all carrier gases, ethanol addition to the discharge gas significantly suppresses the ageing effect. All the above mentioned conclusions therefore indicate that ethanol vapor based plasmas can be an excellent tool to increase the surface energy of polymers.
[Bone cement adhesion on ceramic surfaces - surface activation of retention surfaces of knee prostheses by atmospheric plasma versus thermal surface treatment].

PubMed

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

2015-04-01

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

PubMed

Freitas, Sidónio C; Maia, Sílvia; Figueiredo, Ana C; Gomes, Paula; Pereira, Pedro J B; Barbosa, Mário A; Martins, M Cristina L

2014-03-01

Blood-contacting medical devices have been associated with severe clinical complications, such as thrombus formation, triggered by the activation of the coagulation cascade due to the adsorption of certain plasma proteins on the surface of biomaterials. Hence, the coating of such surfaces with antithrombotic agents has been used to increase biomaterial haemocompatibility. Biomaterial-induced clotting may also be decreased by albumin adsorption from blood plasma in a selective and reversible way, since this protein is not involved in the coagulation cascade. In this context, this paper reports that the immobilization of the thrombin inhibitor D-Phe-Pro-D-Arg-D-Thr-CONH2 (fPrt) onto nanostructured surfaces induces selective and reversible adsorption of albumin, delaying the clotting time when compared to peptide-free surfaces. fPrt, synthesized with two glycine residues attached to the N-terminus (GGfPrt), was covalently immobilized onto self-assembled monolayers (SAMs) having different ratios of carboxylate-hexa(ethylene glycol)- and tri(ethylene glycol)-terminated thiols (EG6-COOH/EG3) that were specifically designed to control GGfPrt orientation, exposure and density at the molecular level. In solution, GGfPrt was able to inactivate the enzymatic activity of thrombin and to delay plasma clotting time in a concentration-dependent way. After surface immobilization, and independently of its concentration, GGfPrt lost its selectivity to thrombin and its capacity to inhibit thrombin enzymatic activity against the chromogenic substrate n-p-tosyl-Gly-Pro-Arg-p-nitroanilide. Nevertheless, surfaces with low concentrations of GGfPrt could delay the capacity of adsorbed thrombin to cleave fibrinogen. In contrast, GGfPrt immobilized in high concentrations was found to induce the procoagulant activity of the adsorbed thrombin. However, all surfaces containing GGfPrt have a plasma clotting time similar to the negative control (empty polystyrene wells), showing resistance to coagulation, which is explained by its capacity to adsorb albumin in a selective and reversible way. This work opens new perspectives to the improvement of the haemocompatibility of blood-contacting medical devices. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Immobilized enzymes in blood plasma exchangers via radiation grafting

NASA Astrophysics Data System (ADS)

Gombotz, Wayne; Hoffman, Allan; Schmer, Gottfried; Uenoyama, Satoshi

The enzyme asparaginase was immobilized onto a porous hollow polypropylene (PP) fiber blood plasma exchange device for the treatment of acute lymphocytic leukemia. The devices were first radiation grafted with polymethacrylic acid (poly(MAAc)). This introduces carboxyl groups onto the surface of the fibers. Several variables were studied in the grafting reaction including the effects of solvent type and monomer concentration. The carboxyl groups were activated with N-hydroxy succinimide (NHS) using carbodiimide chemistry. Asparaginase was then covalently immobilized on the activated surfaces. Quantitative relationships were found relating the percent graft to the amount of immobilized enzyme which was active. The enzyme reactor was tested both in vitro and in vivo using a sheep as an animal model.
Activated complement components and complement activator molecules on the surface of cell‐derived microparticles in patients with rheumatoid arthritis and healthy individuals

PubMed Central

Biró, Éva; Nieuwland, Rienk; Tak, Paul P; Pronk, Loes M; Schaap, Marianne C L; Sturk, Augueste; Hack, C Erik

2007-01-01

Objectives In vitro, microparticles can activate complement via the classical pathway. If demonstrable ex vivo, this mechanism may contribute to the pathogenesis of rheumatoid arthritis (RA). We therefore investigated the presence of activated complement components and complement activator molecules on the surface of cell‐derived microparticles of RA patients and healthy individuals. Methods Microparticles from synovial fluid (n = 8) and plasma (n = 9) of 10 RA patients and plasma of sex‐ and age‐matched healthy individuals (n = 10) were analysed by flow cytometry for bound complement components (C1q, C4, C3) and complement activator molecules (C‐reactive protein (CRP), serum amyloid P component (SAP), immunoglobulin (Ig) M, IgG). Results Microparticles with bound C1q, C4, and/or C3 were abundant in RA synovial fluid, while in RA and control plasma much lower levels were present. Microparticles with bound C1q correlated with those with bound C3 in synovial fluid (r = 0.961, p = 0.0001), and with those with bound C4 in plasma (RA: r = 0.908, p = 0.0007; control: r = 0.632, p = 0.0498), indicating classical pathway activation. In synovial fluid, microparticles with IgM and IgG correlated with those with C1q (r = 0.728, p = 0.0408; r = 0.952, p = 0.0003, respectively), and in plasma, microparticles with CRP correlated with those with C1q (RA: r = 0.903, p = 0.0021; control: r = 0.683, p = 0.0296), implicating IgG and IgM in the classical pathway activation in RA synovial fluid, and CRP in the low level classical pathway activation in plasma. Conclusions This study demonstrates the presence of bound complement components and activator molecules on microparticles ex vivo, and supports their role in low grade complement activation in plasma and increased complement activation in RA synovial fluid. PMID:17261534
Surface Structure and Surface Electronic States Related to Plasma Cleaning of Silicon and Germanium

NASA Astrophysics Data System (ADS)

Cho, Jaewon

This thesis discusses the surface structure and the surface electronic states of Si and Ge(100) surfaces as well as the effects of oxidation process on the silicon oxide/Si(100) interface structure. The H-plasma exposure was performed in situ at low temperatures. The active species, produced in the H-plasma by the rf-excitation of H_2 gas, not only remove microcontaminants such as oxygen and carbon from the surface, but also passivate the surface with atomic hydrogen by satisfying the dangling bonds of the surface atoms. The surfaces were characterized by Angle Resolved UV-Photoemission Spectroscopy (ARUPS) and Low Energy Electron Diffraction (LEED). In the case of Si(100), H-plasma exposure produced ordered H-terminated crystallographic structures with either a 2 x 1 or 1 x 1 LEED pattern. The hydride phases, found on the surfaces of the cleaned Si(100), were shown to depend on the temperature of the surface during H-plasma cleaning. The electronic states for the monohydride and dihydride phases were identified by ARUPS. When the plasma cleaned surface was annealed, the phase transition from the dihydride to monohydride was observed. The monohydride Si-H surface bond was stable up to 460^circC, and the dangling bond surface states were identified after annealing at 500^circC which was accompanied by the spectral shift. The H-terminated surface were characterized to have a flat band structure. For the Ge(100) surface, an ordered 2 x 1 monohydride phase was obtained from the surface cleaned at 180 ^circC. After plasma exposure at <=170^circC a 1 x 1 surface was observed, but the ARUPS indicated that the surface was predominantly composed of disordered monohydride structures. After annealing above the H-dissociation temperatures, the shift in the spectrum was shown to occur with the dangling bond surface states. The H-terminated surfaces were identified to be unpinned. The interface structure of silicon oxide/Si(100) was studied using ARUPS. Spectral shifts were observed, which were dependent on the processes of surface preparation and oxidation. The shift was characterized in association with the band bending. The origins of the spectral shifts were discussed, including defects at interface and H-passivation in Si. The interface structure is considered to be dependent on the surface preparation and oxidation process.
Lunar interactions: Abstracts of papers presented at the Conference on Interactions of the Interplanetary Plasma with the Modern and Ancient Moon

NASA Technical Reports Server (NTRS)

Criswell, D. R. (Editor); Freeman, J. W. (Editor)

1974-01-01

Reviewed are the active mechanisms relating the moon to its environment and the linkage between these mechanisms and their records in the lunar sample and geophysical data. Topics: (1) large scale plasma interactions with the moon and non-magnetic planets; (2) ancient and present day lunar surface magnetic and electric fields; (3) dynamics and evolution of the lunar atmosphere; (4) evolution of the solar plasma; (5) lunar record of solar radiations; (6) non-meteoritic and meteoritic disturbance and transport of lunar surface materials; and (7) future lunar exploration.
Plasma processing of superconducting radio frequency cavities

NASA Astrophysics Data System (ADS)

Upadhyay, Janardan

The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the asymmetry was studied by changing the contour of the inner electrode. The optimized contour of the electrode based on these measurements was chosen for SRF cavity processing.
Transparent, superhydrophobic, and wear-resistant surfaces using deep reactive ion etching on PDMS substrates.

PubMed

Ebert, Daniel; Bhushan, Bharat

2016-11-01

Surfaces that simultaneously exhibit superhydrophobicity, low contact angle hysteresis, and high transmission of visible light are of interest for many applications, such as optical devices, solar panels, and self-cleaning windows. Superhydrophobicity could also find use in medical devices where antifouling characteristics are desirable. These applications also typically require mechanical wear resistance. The fabrication of such surfaces is challenging due to the competing goals of superhydrophobicity and transmittance in terms of the required degree of surface roughness. In this study, deep reactive ion etching (DRIE) was used to create rough surfaces on PDMS substrates using a O2/CF4 plasma. Surfaces then underwent an additional treatment with either octafluorocyclobutane (C4F8) plasma or vapor deposition of perfluorooctyltrichlorosilane (PFOTCS) following surface activation with O2 plasma. The effects of surface roughness and the additional surface modifications were examined with respect to the contact angle, contact angle hysteresis, and optical transmittance. To examine wear resistance, a sliding wear experiment was performed using an atomic force microscope (AFM). Copyright © 2016 Elsevier Inc. All rights reserved.
Time-dependent effects of ultraviolet and nonthermal atmospheric pressure plasma on the biological activity of titanium

NASA Astrophysics Data System (ADS)

Choi, Sung-Hwan; Jeong, Won-Seok; Cha, Jung-Yul; Lee, Jae-Hoon; Yu, Hyung-Seog; Choi, Eun-Ha; Kim, Kwang-Mahn; Hwang, Chung-Ju

2016-09-01

Here, we evaluated time-dependent changes in the effects of ultraviolet (UV) and nonthermal atmospheric pressure plasma (NTAPPJ) on the biological activity of titanium compared with that of untreated titanium. Grade IV machined surface titanium discs (12-mm diameter) were used immediately and stored up to 28 days after 15-min UV or 10-min NTAPPJ treatment. Changes of surface characteristics over time were evaluated using scanning electron microscopy, surface profiling, contact angle analysis, X-ray photoelectron spectroscopy, and surface zeta-potential. Changes in biological activity over time were as determined by analysing bovine serum albumin adsorption, MC3T3-E1 early adhesion and morphometry, and alkaline phosphatase (ALP) activity between groups. We found no differences in the effects of treatment on titanium between UV or NTAPPJ over time; both treatments resulted in changes from negatively charged hydrophobic (bioinert) to positively charged hydrophilic (bioactive) surfaces, allowing enhancement of albumin adsorption, osteoblastic cell attachment, and cytoskeleton development. Although this effect may not be prolonged for promotion of cell adhesion until 4 weeks, the effects were sufficient to maintain ALP activity after 7 days of incubation. This positive effect of UV and NTAPPJ treatment can enhance the biological activity of titanium over time.
NK-1 receptor desensitization and neutral endopeptidase terminate SP-induced pancreatic plasma extravasation.

PubMed

Maa, J; Grady, E F; Kim, E H; Yoshimi, S K; Hutter, M M; Bunnett, N W; Kirkwood, K S

2000-10-01

Substance P (SP) induces plasma extravasation and neutrophil infiltration by activating the neurokinin-1 receptor (NK1-R). We characterized the mechanisms regulating this response in the rat pancreas. Anesthetized rats were continuously infused with SP, and plasma extravasation was quantified using Evans blue (EB) dye. Continuous infusion of SP (8 nmol. kg(-1). h(-1)) resulted in a threshold increase in EB at 15 min, a peak effect at 30 min (150% increase), and a return to baseline by 60 min. The NK1-R antagonist CP-96,345 blocked SP-induced plasma extravasation. After 60 min, the NK1-R was desensitized to agonist challenge. Resensitization was first detected at 20 min and increased until full recovery was seen at 30 min. Inhibition of the cell-surface protease neutral endopeptidase (NEP) by phosphoramidon potentiated the effect of exogenous SP; therefore endogenous NEP attenuates SP-induced plasma extravasation. Thus the continuous infusion of SP stimulates plasma extravasation in the rat pancreas via activation of the NK1-R, and these effects are terminated by both desensitization of the NK1-R and the cell-surface protease NEP.
Platelet Surface-Associated Activation and Secretion-Mediated Inhibition of Coagulation Factor XII

PubMed Central

Zakharova, Natalia V.; Artemenko, Elena O.; Podoplelova, Nadezhda A.; Sveshnikova, Anastasia N.; Demina, Irina A.; Ataullakhanov, Fazly I.; Panteleev, Mikhail A.

2015-01-01

Coagulation factor XII (fXII) is important for arterial thrombosis, but its physiological activation mechanisms are unclear. In this study, we elucidated the role of platelets and platelet-derived material in fXII activation. FXII activation was only observed upon potent platelet stimulation (with thrombin, collagen-related peptide, or calcium ionophore, but not ADP) accompanied by phosphatidylserine exposure and was localised to the platelet surface. Platelets from three patients with grey platelet syndrome did not activate fXII, which suggests that platelet-associated fXII-activating material might be released from α-granules. FXII was preferentially bound by phosphotidylserine-positive platelets and annexin V abrogated platelet-dependent fXII activation; however, artificial phosphotidylserine/phosphatidylcholine microvesicles did not support fXII activation under the conditions herein. Confocal microscopy using DAPI as a poly-phosphate marker did not reveal poly-phosphates associated with an activated platelet surface. Experimental data for fXII activation indicates an auto-inhibition mechanism (k i/k a = 180 molecules/platelet). Unlike surface-associated fXII activation, platelet secretion inhibited activated fXII (fXIIa), particularly due to a released C1-inhibitor. Platelet surface-associated fXIIa formation triggered contact pathway-dependent clotting in recalcified plasma. Computer modelling suggests that fXIIa inactivation was greatly decreased in thrombi under high blood flow due to inhibitor washout. Combined, the surface-associated fXII activation and its inhibition in solution herein may be regarded as a flow-sensitive regulator that can shift the balance between surface-associated clotting and plasma-dependent inhibition, which may explain the role of fXII at high shear and why fXII is important for thrombosis but negligible in haemostasis. PMID:25688860
Interaction of platelets, fibrinogen and endothelial cells with plasma deposited PEO-like films

NASA Astrophysics Data System (ADS)

Yang, Zhilu; Wang, Jin; Li, Xin; Tu, Qiufen; Sun, Hong; Huang, Nan

2012-02-01

For blood-contacting biomedical implants like retrievable vena cava filters, surface-based diagnostic devices or in vivo sensors, limiting thrombosis and cell adhesion is paramount, due to a decrease even failure in performance. Plasma deposited PEO-like films were investigated as surface modifications. In this work, mixed gas composed of tetraethylene glycol dimethyl ether (tetraglyme) vapor and oxygen was used as precursor. It was revealed that plasma polymerization under high ratio of oxygen/tetraglyme led to deposition of the films that had high content of ether groups. This kind of PEO-like films had good stability in phosphate buffer solution. In vitro hemocompatibility and endothelial cell (EC) adhesion revealed low platelet adhesion, platelet activation, fibrinogen adhesion, EC adhesion and proliferation on such plasma deposited PEO-like films. This made it a potential candidate for the applications in anti-fouling surfaces of blood-contacting biomedical devices.
Changing the surface properties on naval steel as result of non-thermal plasma treatment

NASA Astrophysics Data System (ADS)

Hnatiuc, B.; Sabău, A.; Dumitrache, C. L.; Hnatiuc, M.; Crețu, M.; Astanei, D.

2016-08-01

The problem of corrosion, related to Biofouling formation, is an issue with very high importance in the maritime domain. According to new rules, the paints and all the technologies for the conditioning of naval materials must fulfil more restrictive environmental conditions. In order to solve this issue, different new clean technologies have been proposed. Among them, the use of non-thermal plasmas produced at atmospheric pressure plays a very important role. This study concerns the opportunity of plasma treatment for preparation or conditioning of naval steel OL36 type. The plasma reactors chosen for the experiments can operate at atmospheric pressure and are easy to use in industrial conditions. They are based on electrical discharges GlidArc and Spark, which already proved their efficiency for the surface activation or even for coatings of the surface. The non-thermal character of the plasma is ensured by a gas flow blown through the electrical discharges. One power supply has been used for reactors that provide a 5 kV voltage and a maximum current of 100 mA. The modifications of the surface properties and composition have been studied by XPS technique (X-ray Photoelectron Spectroscopy). There were taken into consideration 5 samples: 4 of them undergoing a Mini-torch plasma, a Gliding Spark, a GlidArc with dry air and a GlidArc with CO2, respectively the fifth sample which is the untreated witness. Before the plasma treatment, samples of naval steel were processed in order to obtain mechanical gloss. The time of treatment was chosen to 12 minutes. In the spectroscopic analysis, done on a ULVAC-PHI, Inc. PHI 5000 Versa Probe scanning XPS microprobe, a monocromated Al Kα X-ray source with a spot size of 100 μm2 was used to scan each sample while the photoelectrons were collected at a 45-degree take-off angle. Differences were found between atomic concentrations in each individual case, which proves that the active species produced by each type of plasma affects the surface properties of the treated naval steel.
Activated platelets are the source of elevated levels of soluble CD40 ligand in the circulation of inflammatory bowel disease patients.

PubMed

Danese, S; Katz, J A; Saibeni, S; Papa, A; Gasbarrini, A; Vecchi, M; Fiocchi, C

2003-10-01

The CD40/CD40L system, a key regulator and amplifier of immune reactivity, is activated in inflammatory bowel disease (IBD) mucosa. To determine whether plasma levels of sCD40L are elevated in Crohn's disease (CD) and ulcerative colitis (UC) patients compared with normal controls, to investigate the cellular source of sCD40L, and to explore CD40L induction mechanisms. CD, UC, and normal control subjects were studied. The concentration of sCD40L in plasma and supernatants of freshly isolated platelets and autologous peripheral blood T cells (PBT) was measured by ELISA. Surface CD40L expression level was measured by flow cytometry in resting and thrombin activated platelets, and unstimulated and CD3/CD28 stimulated PBT before and after coculture with human intestinal microvascular endothelial cells (HIMEC). Compared with normal controls, plasma sCD40L levels were significantly higher in both CD and UC patients and proportional to the extent of mucosal inflammation. Platelets from IBD patients displayed a significantly higher surface CD40L expression than those from control subjects, and released greater amounts of sCD40L than autologous PBT. Contact with IL-1beta activated HIMEC induced significant upregulation of CD40L surface expression and release by platelets. Elevated levels of sCD40L in the circulation of IBD patients reflect enhanced surface expression and release of CD40L by platelets. This phenomenon translates to an increased platelet activation state apparently induced by passage through an inflamed mucosal microvascular bed, a conclusion supported by the positive correlation of plasma sCD40L levels with the extent of anatomical involvement by IBD. These results suggest that platelet-endothelial interactions critically contribute to activation of the CD40 pathway in IBD.
Plasma-Etching of Spray-Coated Single-Walled Carbon Nanotube Films for Biointerfaces

NASA Astrophysics Data System (ADS)

Kim, Joon Hyub; Lee, Jun-Yong; Min, Nam Ki

2012-08-01

We present an effective method for the batch fabrication of miniaturized single-walled carbon nanotube (SWCNT) film electrodes using oxygen plasma etching. We adopted the approach of spray-coating for good adhesion of the SWCNT film onto a pre-patterned Pt support and used O2 plasma patterning of the coated films to realize efficient biointerfaces between SWCNT surfaces and biomolecules. By these approaches, the SWCNT film can be easily integrated into miniaturized electrode systems. To demonstrate the effectiveness of plasma-etched SWCNT film electrodes as biointerfaces, Legionella antibody was selected as analysis model owing to its considerable importance to electrochemical biosensors and was detected using plasma-etched SWCNT film electrodes and a 3,3',5,5'-tetramethyl-benzidine dihydrochloride/horseradish peroxidase (TMB/HRP) catalytic system. The response currents increased with increasing concentration of Legionella antibody. This result indicates that antibodies were effectively immobilized on plasma-etched and activated SWCNT surfaces.

Study on plasma pre-functionalized PVC film grafted with TiO2/PVP to improve blood compatible and antibacterial properties

NASA Astrophysics Data System (ADS)

Suganya, Arjunan; Shanmugavelayutham, Gurusamy; Serra Rodríguez, Carmen

2017-04-01

Research into the design of new biopolymers/polymer functionalized with nanoparticles is of tremendous interest to the medical sector, particularly with regard to blood-contacting devices. In this present study, a steady blood compatible and active antibacterial coating was fabricated by the grafting of titanium dioxide (TiO2)/polyvinylpyyrolidone (PVP) onto a polyvinyl chloride (PVC) film surface via the direct-current glow discharge plasma method. To enhance the chemical interaction between TiO2/PVP and PVC, the surfaces of the PVC films were functionalized by different plasmas (air, argon, and oxygen) before coating. In this study, the plasma parameters were varied, such as treatment time of about 5-20 min for a constant power of 100 W, potential 300 V, and a constant gas pressure of 2 Pa for air, argon, and oxygen gas environment. Then, the different plasma treatments on the PVC films, TiO2/PVP were grafted using a simple dip-coating method. In addition, the TiO2/PVP-grafted PVC films were characterized by contact angle, attenuated total reflectance Fourier transform infrared spectroscopy, field-emission scanning electron microscope, and x-ray photo electron spectroscopy. Importantly, TiO2/PVP is grafted onto the PVC surface due to the plasma-based retained functionality and demonstrates adhesive efficiency, which was observed by XPS. The bio-stability of the TiO2/PVP-modified PVC film was evaluated by in vitro platelet activation analysis and protein adsorption analysis. Then, the antibacterial properties were evaluated by the agar diffusion method against Escherichia coli. The result reveals that the grafting of TiO2/PVP was slightly higher for the 15 min oxygen plasma-functionalized PVC, which significantly decreases the platelet adhesion and protein adsorption. Moreover, the antibacterial properties of the 15 min oxygen plasma-functionalized PVC with TiO2/PVP-grafted film is also greatly improved compared with an air- and argon-functionalized surface. Our present study demonstrates that the plasma treatment is a beneficial and eco-friendly method to achieve higher hydrophilicity. Furthermore, our results indicated that the plasma-modified PVC exhibits appropriate anti-fouling performance.
Characterization of activated cyclic olefin copolymer: effects of ethylene/norbornene content on the physiochemical properties.

PubMed

O'Neil, Colleen E; Taylor, Scott; Ratnayake, Kumuditha; Pullagurla, Swathi; Singh, Varshni; Soper, Steven A

2016-11-28

The ethylene/norbornene content within cyclic olefin copolymer (COC) is well known to affect the chemical and physical properties of the copolymer, such as the glass transition temperature (T g ) and transparency. However, no work has been reported evaluating the effects of the ethylene/norbornene content on the surface properties of COC following UV/O 3 or O 2 plasma activation. Activation with either O 2 plasma or UV/O 3 is often used to assist in thermal assembly of fluidic devices, increasing the wettability of the surfaces, or generating functional scaffolds for the attachment of biological elements. Thus, we investigated differences in the physiochemical surface properties of various ethylene/norbornene compositions of COC following activation using analytical techniques such as water contact angle (WCA), ATR-FTIR, XPS, TOF-SIMS, UV-VIS, AFM and a colorimetric assay utilizing Toluidine Blue O (TBO). Results showed that increased norbornene content led to the generation of more oxygen containing functionalities such as alcohols, ketones, aldehydes and carboxyl groups when activated with either UV/O 3 or O 2 plasma. Specifically, COC with ∼60% norbornene content showed a significantly higher -COOH functional group density when compared to COC with a 50% norbornene content and COC with a 35% norbornene content following UV/O 3 or O 2 plasma activation. Furthermore, COC with large norbornene contents showed a smaller average RMS roughness (0.65 nm) when compared to COC containing low norbornene contents (0.95 nm) following activation making this substrate especially suited for nanofluidic applications, which require smooth surfaces to minimize effects arising from dielectrophoretic trapping or non-specific adsorption. Although all COC substrates showed >90% transparency at wavelengths >475 nm, COC possessing high norbornene contents showed significantly less transparency at wavelengths below 475 nm following activation, making optical detection in this region difficult. Our data showed distinct physiochemical differences in activated COC that was dependent upon the ethylene/norbornene content of the thermoplastic and thus, careful selection of the particular COC grade must be considered for micro- and nanofluidics.
Evidence that the platelet plasma membrane does not contain a (Ca2+ + Mg2+)-dependent ATPase.

PubMed

Steiner, B; Lüscher, E F

1985-09-10

The present study was designed to determine the subcellular distribution of the platelet (Ca2+ + Mg2+)-ATPase. Human platelets were surface labeled by the periodate-boro[3H]hydride method. Plasma membrane vesicles were then isolated to a purity of approx. 90% by a procedure utilizing wheat germ agglutinin affinity chromatography. These membranes were found to be 2.6-fold enriched in surface glycoproteins compared to an unfractionated vesicle fraction and almost 7-fold enriched compared to intact platelets. In contrast, the isolated plasma membranes showed a decreased specific activity of the (Ca2+ + Mg2+)-ATPase compared to the unfractionated vesicle fraction. This decrease in specific activity was found to be similar to that of an endoplasmic reticulum marker, glucose-6-phosphatase, and to that of a platelet inner membrane marker, phospholipase A2. We conclude, therefore, that the (Ca2+ + Mg2+)-ATPase is not located in the platelet plasma membrane but is restricted to membranes of intracellular origin.
2D surface temperature measurement of plasma facing components with modulated active pyrometry

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

Amiel, S.; Loarer, T.; Pocheau, C.

2014-10-01

In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ε ~more » 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ε ~ 0.1–0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity.« less
In-situ monitoring of etching of bovine serum albumin using low-temperature atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Kousal, J.; Shelemin, A.; Kylián, O.; Slavínská, D.; Biederman, H.

2017-01-01

Bio-decontamination of surfaces by means of atmospheric pressure plasma is nowadays extensively studied as it represents promising alternative to commonly used sterilization/decontamination techniques. The non-equilibrium atmospheric pressure plasmas were already reported to be highly effective in removal of a wide range of biological residual from surfaces. Nevertheless the kinetics of removal of biological contamination from surfaces is still not well understood as the majority of performed studies were based on ex-situ evaluation of etching rates, which did not allow investigating details of plasma action on biomolecules. This study therefore presents a real-time, in-situ ellipsometric characterization of removal of bovine serum albumin (BSA) from surfaces by low-temperature atmospheric plasma jet operated in argon. Non-linear and at shorter distances between treated samples and nozzle of the plasma jet also non-monotonic dependence of the removal rate on the treatment duration was observed. According to additional measurements focused on the determination of chemical changes of treated BSA as well as temperature measurements, the observed behavior is most likely connected with two opposing effects: the formation of a thin layer on the top of BSA deposit enriched in inorganic compounds, whose presence causes a gradual decrease of removal efficiency, and slight heating of BSA that facilitates its degradation and volatilization induced by chemically active radicals produced by the plasma.
Effect of Atmospheric Pressure Plasma Treatment on Surface Characteristics and Adhesive Bond Quality of Peel Ply Prepared Composites

NASA Astrophysics Data System (ADS)

Tracey, Ashley C.

The purpose of this research was to investigate if atmospheric pressure plasma treatment could modify peel ply prepared composite surfaces to create strong adhesive bonds. Two peel ply surface preparation composite systems previously shown to create weak bonds (low fracture energy and adhesion failure) that were potential candidates for plasma treatment were Toray T800/3900-2 carbon fiber reinforced polymer (CFRP) prepared with Precision Fabrics Group, Inc. (PFG) 52006 nylon peel ply and Hexcel T300/F155 CFRP prepared with PFG 60001 polyester peel ply. It was hypothesized that atmospheric pressure plasma treatment could functionalize and/or remove peel ply remnants left on the CFRP surfaces upon peel ply removal. Surface characterization measurements and double cantilever beam (DCB) testing were used to determine the effects of atmospheric pressure plasma treatment on surface characteristics and bond quality of peel ply prepared CFRP composites. Previous research showed that Toray T800/3900-2 carbon fiber reinforced epoxy composites prepared with PFG 52006 peel ply and bonded with Cytec MetlBond 1515-3M structural film adhesive failed in adhesion at low fracture energies when tested in the DCB configuration. Previous research also showed that DCB samples made of Hexcel T300/F155 carbon fiber reinforced epoxy composites prepared with PFG 60001 peel ply and bonded with Henkel Hysol EA 9696 structural film adhesive failed in adhesion at low fracture energies. Recent research suggested that plasma treatment could be able to activate these "un-bondable" surfaces and result in good adhesive bonds. Nylon peel ply prepared 177 °C cure and polyester peel ply prepared 127 °C cure CFRP laminates were treated with atmospheric pressure plasma after peel ply removal prior to bonding. Atmospheric pressure plasma treatment was capable of significantly increasing fracture energies and changing failure modes. For Toray T800/3900-2 laminates prepared with PFG 52006 and bonded with MetlBond 1515-3M, plasma treatment increased fracture energies from 460 J/m 2. Atmospheric pressure plasma treatment also increased fracture energies of Hexcel T300/F155 laminates prepared with PFG 60001 and bonded with EA 9696 from 1500 J/m2. It was demonstrated that atmospheric pressure plasma treatment was able to transform poor bonding surfaces into acceptable ones by reversing the negative effects of incorrect peel ply usage. To determine if the primary reason for adhesion was functionalization or removal, a number of experiments were performed. Surface characteristics of peel ply only and plasma treated samples were determined using contact angle (CA) measurements, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). CA was used to assess solid surface energy that was useful to determine wetting of the adhesive on the adherend, one requirement of adhesion. FTIR and XPS were used to analyze composite surface chemistry, including the identification of functional groups that were a product of atmospheric pressure plasma treatment, as well as contaminants that can inhibit adhesive bonding. SEM was used to capture surface morphology to identify peel ply remnants and whether these remnants were physically removed or modified due to plasma treatment. This research supported that atmospheric pressure plasma treatment resulted in adhesion primarily due to functionalization of peel ply remnants, though a removal mechanism was not disproven. It was also shown that surface energy exhibited potential for predicting adhesion. Lastly, this research indicated that plasma treatment is a robust surface preparation, as strong bonds were observed up to 30 days after treatment.
Decreased platelet inhibition by nitric oxide in two brothers with a history of arterial thrombosis.

PubMed Central

Freedman, J E; Loscalzo, J; Benoit, S E; Valeri, C R; Barnard, M R; Michelson, A D

1996-01-01

Highly reactive oxygen species rapidly inactivate nitric oxide (NO), and endothelial product which inhibits platelet activation. We studied platelet inhibition by NO in two brothers with a cerebral thrombotic disorder. Both children had hyperreactive platelets, as determined by whole blood platelet aggregometry and flow cytometric analysis of the platelet surface expression of P-selectin. Mixing experiments showed that the patients'platelets behaved normally in control plasma; however, control platelets suspended in patient plasma were not inhibited by NO. As determined by flow cytometry, in the presence of plasma from either patient there was normal inhibition of the thrombin-induced expression of platelet surface P-selectin by prostacyclin, but not NO. Using a scopoletin assay, we measured a 2.7-fold increase in plasma H2O2 generation in one patient and a 3.4-fold increase in the second patient, both compared woth control plasma. Glutathione peroxidase (GSH-Px) activity was decreased in the patients' plasmas compared with control plasma. The addition of exogenous GSH-Px led to restoration of platelet inhibition by NO. These data show that, in these patients' plasmas, impaired metabolism of reactive oxygen species reduces the bioavailability of NO and impairs normal platelet inhibitory mechanisms. These findings suggest that attenuated NO-mediated platelet inhibition produced by increased reactive oxygen species or impaired antioxidant defense may cause a thrombotic disorder in humans. PMID:8613552
Optical properties of relativistic plasma mirrors

PubMed Central

Vincenti, H.; Monchocé, S.; Kahaly, S.; Bonnaud, G.; Martin, Ph.; Quéré, F.

2014-01-01

The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas. The most promising of these are known as plasma mirrors, formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse and can be used as active optical elements to manipulate its temporal and spatial properties. Unfortunately, the considerable pressures exerted by the laser can deform the mirror surface, unfavourably affecting the reflected beam and complicating, or even preventing, the use of plasma mirrors at ultrahigh intensities. Here we derive a simple analytical model of the basic physics involved in laser-induced deformation of a plasma mirror. We validate this model numerically and experimentally, and use it to show how such deformation might be mitigated by appropriate control of the laser phase. PMID:24614748
Heterogeneous processes in CF4/O2 plasmas probed using laser-induced fluorescence of CF2

NASA Astrophysics Data System (ADS)

Hansen, S. G.; Luckman, G.; Nieman, George C.; Colson, Steven D.

1990-09-01

Laser-induced fluorescence of CF2 is used to monitor heterogeneous processes in ≊300 mTorr CF4/O2 plasmas. CF2 is rapidly removed at fluorinated copper and silver surfaces in 13.56-MHz rf discharges as judged by a distinct dip in its spatial distribution. These metals, when employed as etch masks, are known to accelerate plasma etching of silicon, and the present results suggest catalytic dehalogenation of CF2 is involved in this process. In contrast, aluminum and silicon dioxide exhibit negligible reactivity with CF2, which suggests that aluminum masks will not appreciably accelerate silicon etching and that ground state CF2 does not efficiently etch silicon dioxide. Measurement of CF2 decay in a pulsed discharge coupled with direct laser sputtering of metal into the gas phase indicates the interaction between CF2 and the active metals is purely heterogeneous. Aluminum does, however, exhibit homogeneous reactivity with CF2. Redistribution of active metal by plasma sputtering readily occurs; silicon etch rates may also be enhanced by the metal's presence on the silicon surface. Polymers contribute CF2 to the plasma as they etch. The observation of an induction period suggests fluorination of the polymer surface is the first step in its degradation. Polymeric etch masks can therefore depress the silicon etch rate by removal of F atoms, the primary etchants.
Enhanced Carbon Dioxide Electroreduction to Carbon Monoxide over Defect-Rich Plasma-Activated Silver Catalysts

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

Mistry, Hemma; Choi, Yong-Wook; Bagger, Alexander

Efficient, stable catalysts with high selectivity for a single product are essential if electroreduction of CO 2 is to become a viable route to the synthesis of industrial feedstocks and fuels. A plasma oxidation pre-treatment of silver foil enhances the number of low-coordinated catalytically active sites, which dramatically lowers the overpotential and increases the activity of CO 2 electroreduction to CO. At -0.6 V versus RHE more than 90 % Faradaic efficiency towards CO was achieved on a pre-oxidized silver foil. While transmission electron microscopy (TEM) and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulkmore » of the catalyst during the reaction, quasi in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. Finally, DFT calculations reveal that the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields drastically decrease the overpotential of CO 2 electroreduction.« less
Enhanced Carbon Dioxide Electroreduction to Carbon Monoxide over Defect-Rich Plasma-Activated Silver Catalysts

DOE PAGES

Mistry, Hemma; Choi, Yong-Wook; Bagger, Alexander; ...

2017-07-14

Efficient, stable catalysts with high selectivity for a single product are essential if electroreduction of CO 2 is to become a viable route to the synthesis of industrial feedstocks and fuels. A plasma oxidation pre-treatment of silver foil enhances the number of low-coordinated catalytically active sites, which dramatically lowers the overpotential and increases the activity of CO 2 electroreduction to CO. At -0.6 V versus RHE more than 90 % Faradaic efficiency towards CO was achieved on a pre-oxidized silver foil. While transmission electron microscopy (TEM) and operando X-ray absorption spectroscopy showed that oxygen species can survive in the bulkmore » of the catalyst during the reaction, quasi in situ X-ray photoelectron spectroscopy showed that the surface is metallic under reaction conditions. Finally, DFT calculations reveal that the defect-rich surface of the plasma-oxidized silver foils in the presence of local electric fields drastically decrease the overpotential of CO 2 electroreduction.« less
Hemocompatibility of poly(vinylidene fluoride) membrane grafted with network-like and brush-like antifouling layer controlled via plasma-induced surface PEGylation.

PubMed

Chang, Yung; Shih, Yu-Ju; Ko, Chao-Yin; Jhong, Jheng-Fong; Liu, Ying-Ling; Wei, Ta-Chin

2011-05-03

In this work, the hemocompatibility of PEGylated poly(vinylidene fluoride) (PVDF) microporous membranes with varying grafting coverage and structures via plasma-induced surface PEGylation was studied. Network-like and brush-like PEGylated layers on PVDF membrane surfaces were achieved by low-pressure and atmospheric plasma treatment. The chemical composition, physical morphology, grafting structure, surface hydrophilicity, and hydration capability of prepared membranes were determined to illustrate the correlations between grafting qualities and hemocompatibility of PEGylated PVDF membranes in contact with human blood. Plasma protein adsorption onto different PEGylated PVDF membranes from single-protein solutions and the complex medium of 100% human plasma were measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Hemocompatibility of the PEGylated membranes was evaluated by the antifouling property of platelet adhesion observed by scanning electron microscopy (SEM) and the anticoagulant activity of the blood coagulant determined by testing plasma-clotting time. The control of grafting structures of PEGylated layers highly regulates the PVDF membrane to resist the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. It was found that PVDF membranes grafted with brush-like PEGylated layers presented higher hydration capability with binding water molecules than with network-like PEGylated layers to improve the hemocompatible character of plasma protein and blood platelet resistance in human blood. This work suggests that the hemocompatible nature of grafted PEGylated polymers by controlling grafting structures gives them great potential in the molecular design of antithrombogenic membranes for use in human blood.
Shaping thin film growth and microstructure pathways via plasma and deposition energy: a detailed theoretical, computational and experimental analysis.

PubMed

Sahu, Bibhuti Bhusan; Han, Jeon Geon; Kersten, Holger

2017-02-15

Understanding the science and engineering of thin films using plasma assisted deposition methods with controlled growth and microstructure is a key issue in modern nanotechnology, impacting both fundamental research and technological applications. Different plasma parameters like electrons, ions, radical species and neutrals play a critical role in nucleation and growth and the corresponding film microstructure as well as plasma-induced surface chemistry. The film microstructure is also closely associated with deposition energy which is controlled by electrons, ions, radical species and activated neutrals. The integrated studies on the fundamental physical properties that govern the plasmas seek to determine their structure and modification capabilities under specific experimental conditions. There is a requirement for identification, determination, and quantification of the surface activity of the species in the plasma. Here, we report a detailed study of hydrogenated amorphous and crystalline silicon (c-Si:H) processes to investigate the evolution of plasma parameters using a theoretical model. The deposition processes undertaken using a plasma enhanced chemical vapor deposition method are characterized by a reactive mixture of hydrogen and silane. Later, various contributions of energy fluxes on the substrate are considered and modeled to investigate their role in the growth of the microstructure of the deposited film. Numerous plasma diagnostic tools are used to compare the experimental data with the theoretical results. The film growth and microstructure are evaluated in light of deposition energy flux under different operating conditions.
The effect of oxygen plasma pretreatment and incubation in modified simulated body fluids on the formation of bone-like apatite on poly(lactide-co-glycolide) (70/30).

PubMed

Qu, Xue; Cui, Wenjin; Yang, Fei; Min, Changchun; Shen, Hong; Bei, Jianzhong; Wang, Shenguo

2007-01-01

In this study, biodegradable poly(lactide-co-glycolide) (PLGA) (70/30) films and scaffolds were first treated with oxygen plasma and then incubated in a modified simulated body fluid 1.5SBF0 to prepare a bone-like apatite layer. The formation of the apatite and its influence on osteoblast-like cells growth were investigated. It was found that the bone-like apatite formability of PLGA(70/30) was enhanced by plasma pretreatment. The changes of surface chemistry and surface topography induced by oxygen plasma treatment were both effective for apatite formation. The apatite formability increased with increasing plasma-treating time. Under a treating condition of 20 W for 30 min, oxygen plasma treatment could penetrate into the inner scaffold. After 6 days incubation, the apatite formed in plasma-treated scaffold was better distributed than in untreated scaffold, and the weight and mechanical strength of the plasma-treated scaffold were both enhanced. Compared with PLGA(70/30), the apatite layer formed on oxygen plasma-treated PLGA(70/30) surface enhanced adhesion and proliferation of OCT-1 osteoblast-like cell, but had no significant effect on cell's ALP activity at day 7. A prolonged investigation is being in process to further verify the bone-like apatite effects on osteogenic differentiation.
Retention of Antibacterial Activity in Geranium Plasma Polymer Thin Films

PubMed Central

Al-Jumaili, Ahmed; Bazaka, Kateryna

2017-01-01

Bacterial colonisation of biomedical devices demands novel antibacterial coatings. Plasma-enabled treatment is an established technique for selective modification of physicochemical characteristics of the surface and deposition of polymer thin films. We investigated the retention of inherent antibacterial activity in geranium based plasma polymer thin films. Attachment and biofilm formation by Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was significantly reduced on the surfaces of samples fabricated at 10 W radio frequency (RF) power, compared to that of control or films fabricated at higher input power. This was attributed to lower contact angle and retention of original chemical functionality in the polymer films fabricated under low input power conditions. The topography of all surfaces was uniform and smooth, with surface roughness of 0.18 and 0.69 nm for films fabricated at 10 W and 100 W, respectively. Hardness and elastic modules of films increased with input power. Independent of input power, films were optically transparent within the visible wavelength range, with the main absorption at ~290 nm and optical band gap of ~3.6 eV. These results suggest that geranium extract-derived polymers may potentially be used as antibacterial coatings for contact lenses. PMID:28902134
Novel procedure to enhance PLA surface properties by chitosan irreversible immobilization

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

NASA Astrophysics Data System (ADS)

Ke, Zhigang; Ma, Yulong; Zhu, Zhongjie; Zhao, Hongwei; Wang, Qi; Huang, Qing

2018-01-01

Graphene-based materials (GMs) are promising antibacterial agents which provide an alternative route to treat pathogenic bacteria with resistance to conventional antibiotics. To further improve their antibacterial activity, many methods have been developed to functionalize the GMs with chemicals. However, the application of additional chemicals may pose potential risks to the environment and human being. Herein, a radio-frequency-driven inductively coupled non-thermal hydrogen plasma was used to treat and reduce graphene oxide (GO) without using any other chemicals, and we found that the plasma-reduced GO (prGO) is with significantly higher bactericidal activity against Escherichia coli. The mechanism of the increased antibacterial activity of prGO is due to that plasma processing breaks down the GO sheets into smaller layers with more rough surface defects, which can thus induce more destructive membrane damages to the bacteria. This work sets another good example, showing that plasma processing is a green and low-cost alternative for GM modification for biomedical applications.
A model of Martian surface chemistry

NASA Technical Reports Server (NTRS)

Oyama, V. I.; Berdahl, B. J.

1979-01-01

Alkaline earth and alkali metal superoxides and peroxides, gamma-Fe2O3 and carbon suboxide polymer, are proposed to be constituents of the Martian surface material. These reactive substances explain the water modified reactions and thermal behaviors of the Martian samples demonstrated by all of the Viking Biology Experiments. It is also proposed that the syntheses of these substances result mainly from electrical discharges between wind-mobilized particles at Martian pressures; plasmas are initiated and maintained by these discharges. Active species in the plasma either combine to form or react with inorganic surfaces to create the reactive constituents.
Development of an Organosilicon-Based Superhydrophobic/Icephobic Surface Using an Atmospheric Pressure Plasma Jet =

NASA Astrophysics Data System (ADS)

Asadollahi, Siavash

During the past few decades, plasma-based surface treatment methods have gained a lot of interest in various applications such as thin film deposition, surface etching, surface activation and/or cleaning, etc. Generally, in plasma-based surface treatment methods, high-energy plasma-generated species are utilized to modify the surface structure or the chemical composition of a substrate. Unique physical and chemical characteristics of the plasma along with the high controllability of the process makes plasma treatment approaches very attractive in several industries. Plasma-based treatment methods are currently being used or investigated for a number of practical applications, such as adhesion promotion in auto industry, wound management and cancer treatment in biomedical industry, and coating development in aerospace industry. In this study, a two-step procedure is proposed for the development of superhydrophobic/icephobic coatings based on atmospheric-pressure plasma treatment of aluminum substrates using air and nitrogen plasma. The effects of plasma parameters on various surface properties are studied in order to identify the optimum conditions for maximum coating efficiency against icing and wetting. In the first step, the interactions between air or nitrogen plasma and the aluminum surface are studied. It is shown that by reducing jet-to-substrate distance, air plasma treatment, unlike nitrogen plasma treatment, is capable of creating micro-porous micro-roughened structures on the surface, some of which bear a significant resemblance to the features observed in laser ablation of metals with short and ultra-short laser pulses. The formation of such structures in plasma treatment is attributed to a transportation of energy from the jet to the surface over a very short period of time, in the range of picoseconds to microseconds. This energy transfer is shown to occur through a streamer discharge from the rotating arc source in the jet body to a close proximity of the surface, and then through multiple seemingly random electric arcs on the surface. The formation of these discharges is facilitated by the near-infinite conductivity of the air plasma column. The micro-porous micro-roughened structure developed in this step is then used as the substrate for coating deposition. In the next step, first the plasma jet is slightly modified with a quartz tube surrounding the jet-head. This modification allows for ignition and maintenance of a very weak plasma while hindering the diffusion of oxygen into the plasma and thus increasing the amount of organic deposition on the surface. This is confirmed by the chemical characterization of the surfaces developed using the modified jet. Furthermore, it is shown that this modification can significantly affect surface morphology, leading to a finer surface structure with different levels of roughness. Hydrophobic materials are then deposited on the surface in the presence of HMDSO using nitrogen plasma. Several samples are prepared with different precursor flow rates, plasma generation powers and number of deposition passes. All coatings are characterized regarding their surface morphology, chemical composition, wetting behavior and icephobic characteristics. It is shown that at low precursor flow rates, coating deposition is not enough for a full coverage of the surface. On the other hand, at high flow rates coating deposition can completely cover the surface features originated from the air plasma treatment process, thus negating the effects of an important roughness level. At the median flow rate, which was identified to be 5 g/h, the coating can fully cover the surface while maintaining the pre-existing surface features. It is also shown that by increasing the number of plasma deposition passes, surface features become slightly larger while the amount of organic deposition on the surface increases. Finally, it is shown that in high plasma generation powers, the amount of oxide deposition on the surface increases, leading to lower contact angles and higher ice adhesion strengths. In order to estimate coatings' efficiency in practical applications, coating's stability against some environmental factors is studied. At first, the effects of multiple icing/deicing cycles on surface properties is investigated. SEM studies confirm the removal of the coating material from the surface in all cases after multiple icing/deicing cycles. However, it is shown that the sample resulting from the lowest generation power combined with median flow rate and 3 passes of plasma deposition can maintain its hydrophobicity and icephobicity for up to 10 cycles of icing/deicing. This sample is then exposed to an equivalent of up to 4 years of natural ultraviolet exposure and the effects of UV on surface properties were studied. It is suggested that ultraviolet exposure may be capable of reorganizing the organic functions in the coating structure, leading to shorter siloxane chains with denser methyl functionalization, thus affecting the wetting and icing behavior of the surface. Ice adhesion strength was shown to decrease significantly after the equivalent of 3 years of natural UV exposure. The procedure introduced in this thesis is a cheap, quick, and environmentally friendly method for development of superhydrophobic/icephobic coatings on aluminum substrates. Therefore, it can be easily implemented in several industrial applications where outdoor structures are expected to be exposed to severe icing events.
Hydrogen Storage in Diamond Powder Utilizing Plasma NaF Surface Treatment for Fuel Cell Applications

NASA Astrophysics Data System (ADS)

Leal, David A.; Velez, Angel; Prelas, Mark A.; Gosh, Tushar; Leal-Quiros, E.

2006-12-01

Hydrogen Fuel Cells offer the vital solution to the world's socio-political dependence on oil. Due to existing difficulty in safe and efficient hydrogen storage for fuel cells, storing the hydrogen in hydrocarbon compounds such as artificial diamond is a realistic solution. By treating the surface of the diamond powder with a Sodium Fluoride plasma exposure, the surface of the diamond is cleaned of unwanted molecules. Due to fluorine's electro negativity, the diamond powder is activated and ready for hydrogen absorption. These diamond powder pellets are then placed on a graphite platform that is heated by conduction in a high voltage circuit made of tungsten wire. Then, the injection of hydrogen gas into chamber allows the storage of the Hydrogen on the surface of the diamond powder. By neutron bombardment in the nuclear reactor, or Prompt Gamma Neutron Activation Analysis, the samples are examined for parts per million amounts of hydrogen in the sample. Sodium Fluoride surface treatment allows for higher mass percentage of stored hydrogen in a reliable, resistant structure, such as diamond for fuel cells and permanently alters the diamonds terminal bonds for re-use in the effective storage of hydrogen. The highest stored amount utilizing the NaF plasma surface treatment was 22229 parts per million of hydrogen in the diamond powder which amounts to 2.2229% mass increase.

Positive Feedback Loops for Factor V and Factor VII Activation Supply Sensitivity to Local Surface Tissue Factor Density During Blood Coagulation

PubMed Central

Balandina, A.N.; Shibeko, A.M.; Kireev, D.A.; Novikova, A.A.; Shmirev, I.I.; Panteleev, M.A.; Ataullakhanov, F.I.

2011-01-01

Blood coagulation is triggered not only by surface tissue factor (TF) density but also by surface TF distribution. We investigated recognition of surface TF distribution patterns during blood coagulation and identified the underlying molecular mechanisms. For these investigations, we employed 1), an in vitro reaction-diffusion experimental model of coagulation; and 2), numerical simulations using a mathematical model of coagulation in a three-dimensional space. When TF was uniformly immobilized over the activating surface, the clotting initiation time in normal plasma increased from 4 min to >120 min, with a decrease in TF density from 100 to 0.7 pmol/m2. In contrast, surface-immobilized fibroblasts initiated clotting within 3–7 min, independently of fibroblast quantity and despite a change in average surface TF density from 0.5 to 130 pmol/m2. Experiments using factor V-, VII-, and VIII-deficient plasma and computer simulations demonstrated that different responses to these two TF distributions are caused by two positive feedback loops in the blood coagulation network: activation of the TF–VII complex by factor Xa, and activation of factor V by thrombin. This finding suggests a new role for these reactions: to supply sensitivity to local TF density during blood coagulation. PMID:22004734
Preparation of Caco-2 cell sheets using plasma polymerised acrylic acid as a weak boundary layer.

PubMed

Majani, Ruby; Zelzer, Mischa; Gadegaard, Nikolaj; Rose, Felicity R; Alexander, Morgan R

2010-09-01

The use of cell sheets for tissue engineering applications has considerable advantages over single cell seeding techniques. So far, only thermoresponsive surfaces have been used to manufacture cell sheets without chemically disrupting the cell-surface interactions. Here, we present a new and facile technique to prepare sheets of epithelial cells using plasma polymerised acrylic acid films. The cell sheets are harvested by gentle agitation of the media without the need of any additional external stimulus. We demonstrate that the plasma polymer deposition conditions affect the viability and metabolic activity of the cells in the sheet and relate these effects to the different surface properties of the plasma polymerised acrylic acid films. Based on surface analysis data, a first attempt is made to explain the mechanism behind the cell sheet formation. The advantage of the epithelial cell sheets generated here over single cell suspensions to seed a PLGA scaffold is presented. The scaffold itself, prepared using a mould fabricated via photolithography, exhibits a unique architecture that mimics closely the dimensions of the native tissue (mouse intestine). Copyright 2010 Elsevier Ltd. All rights reserved.
Spectroscopic and antimicrobial studies of polystyrene films under air plasma and He-Ne laser treatment

NASA Astrophysics Data System (ADS)

Pawde, S. M.; Parab, Sanmesh S.

2008-05-01

Polystyrene (PS) films are used in packaging and biomedical applications because of their transparency and good environmental properties. The present investigation is centered on the antifungal and antibacterial activities involved in the film surface. Subsequently, microbial formations were immobilized on the modified PS films. Living microorganisms such as bacteria and yeast were used. Untreated PS films show very fast rate of growth of bacteria within few hours. The study involves developments of polymer surfaces with bacterial growth and further studies after giving antibacterial treatment such as plasma treatment. Major emphasis has been given to study the effect of various parameters which can affect the performance of the improved material. Films were prepared by two methods: plasma treatment under vacuum and under ongoing He-Ne laser source. The parameters such as (1) surface area by contact angle measurements, (2) quality of material before and after treatment by SEM and FTIR spectra and (3) material characterization by UV-vis spectra were studied. It was observed that plasma treatment of the PS material for different processing time improved the surface properties of PS films.
Adhesion and proliferation of fibroblasts on RF plasma-deposited nanostructured fluorocarbon coatings: evidence of FAK activation.

PubMed

Rosso, Francesco; Marino, Gerardo; Muscariello, Livio; Cafiero, Gennaro; Favia, Pietro; D'Aloia, Erica; d'Agostino, Riccardo; Barbarisi, Alfonso

2006-06-01

We used combined plasma-deposition process to deposit smooth and nanostructured fluorocarbon coatings on polyethylenethereftalate (PET) substrates, to obtain surfaces with identical chemical composition and different roughness, and investigate the effect of surface nanostructures on adhesion and proliferation of 3T3 Swiss Albino Mouse fibroblasts. Untreated PET and polystyrene (PS) were used as controls for cell culture. We have found that the statistically significant increase of cell proliferation rate and FAK (a nonreceptor tyrosine kinase) activation detected on ROUGH fluorocarbon surfaces is due to the presence of nanostructures. Changes in cytoskeletal organization and phospho FAK (tyr 397) localization were evident after 60 min on cells adhering to ROUGH surfaces. This change was characterized by the formation of actin stress fibers along lamellar membrane protrusion instead of usual focal contacts. Also the morphology of the adhering fibroblasts (60 min) adhering on ROUGH surfaces was found quite different compared to cells adhering on smooth ones. Copyright 2006 Wiley-Liss, Inc.
Evaluation of the potentials of humic acid removal in water by gas phase surface discharge plasma.

PubMed

Wang, Tiecheng; Qu, Guangzhou; Ren, Jingyu; Yan, Qiuhe; Sun, Qiuhong; Liang, Dongli; Hu, Shibin

2016-02-01

Degradation of humic acid (HA), a predominant type of natural organic matter in ground water and surface waters, was conducted using a gas phase surface discharge plasma system. HA standard and two surface waters (Wetland, and Weihe River) were selected as the targets. The experimental results showed that about 90.9% of standard HA was smoothly removed within 40 min's discharge plasma treatment at discharge voltage 23.0 kV, and the removal process fitted the first-order kinetic model. Roles of some active species in HA removal were studied by evaluating the effects of solution pH and OH radical scavenger; and the results presented that O3 and OH radical played significant roles in HA removal. Scanning electron microscope (SEM) and FTIR analysis showed that HA surface topography and molecular structure were changed during discharge plasma process. The mineralization of HA was analyzed by UV-Vis spectrum, dissolved organic carbon (DOC), specific UV absorbance (SUVA), UV absorption ratios, and excitation-emission matrix (EEM) fluorescence. The formation of disinfection by-products during HA sample chlorination was also identified, and CHCl3 was detected as the main disinfection by-product, but discharge plasma treatment could suppress its formation to a certain extent. In addition, approximately 82.3% and 67.9% of UV254 were removed for the Weihe River water and the Wetland water after 40 min of discharge plasma treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.
Low Temperature Plasma Science: Not Only the Fourth State of Matter but All of Them. Report of the Department of Energy Office of Fusion Energy Sciences Workshop on Low Temperature Plasmas, March 25-57, 2008

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

None

2008-09-01

Low temperature plasma science (LTPS) is a field on the verge of an intellectual revolution. Partially ionized plasmas (often referred to as gas discharges) are used for an enormous range of practical applications, from light sources and lasers to surgery and making computer chips, among many others. The commercial and technical value of low temperature plasmas (LTPs) is well established. Modern society would simply be less advanced in the absence of LTPs. Much of this benefit has resulted from empirical development. As the technology becomes more complex and addresses new fields, such as energy and biotechnology, empiricism rapidly becomes inadequatemore » to advance the state of the art. The focus of this report is that which is less well understood about LTPs - namely, that LTPS is a field rich in intellectually exciting scientific challenges and that addressing these challenges will result in even greater societal benefit by placing the development of plasma technologies on a solid science foundation. LTPs are unique environments in many ways. Their nonequilibrium and chemically active behavior deviate strongly from fully ionized plasmas, such as those found in magnetically confined fusion or high energy density plasmas. LTPs are strongly affected by the presence of neutral species-chemistry adds enormous complexity to the plasma environment. A weakly to partially ionized gas is often characterized by strong nonequilibrium in the velocity and energy distributions of its neutral and charged constituents. In nonequilibrium LTP, electrons are generally hot (many to tens of electron volts), whereas ions and neutrals are cool to warm (room temperature to a few tenths of an electron volt). Ions and neutrals in thermal LTP can approach or exceed an electron volt in temperature. At the same time, ions may be accelerated across thin sheath boundary layers to impact surfaces, with impact energies ranging up to thousands of electron volts. These moderately energetic electrons can efficiently create reactive radical fragments and vibrationally and electronically excited species from collisions with neutral molecules. These chemically active species can produce unique structures in the gas phase and on surfaces, structures that cannot be produced in other ways, at least not in an economically meaningful way. Photons generated by electron impact excited species in the plasma can interact more or less strongly with other species in the plasma or with the plasma boundaries, or they can escape from the plasma. The presence of boundaries around the plasma creates strong gradients where plasma properties change dramatically. It is in these boundary regions where externally generated electromagnetic radiation interacts most strongly with the plasma, often producing unique responses. And it is at bounding surfaces where complex plasma-surface interactions occur. The intellectual challenges associated with LTPS center on several themes, and these are discussed in the chapters that follow this overview. These themes are plasma-surface interactions; kinetic, nonlinear properties of LTP; plasmas in multiphase media; scaling laws for LTP; and crosscutting themes: diagnostics, modeling, and fundamental data.« less
Enhanced chromium adsorption capacity via plasma modification of natural zeolites

NASA Astrophysics Data System (ADS)

Cagomoc, Charisse Marie D.; Vasquez, Magdaleno R., Jr.

2017-01-01

Natural zeolites such as mordenite are excellent adsorbents for heavy metals. To enhance the adsorption capacity of zeolite, sodium-exchanged samples were irradiated with 13.56 MHz capacitively coupled radio frequency (RF) argon gas discharge. Hexavalent chromium [Cr(VI)] was used as the test heavy metal. Pristine and plasma-treated zeolite samples were soaked in 50 mg/L Cr solution and the amount of adsorbed Cr(VI) on the zeolites was calculated at predetermined time intervals. Compared with untreated zeolite samples, initial Cr(VI) uptake was 70% higher for plasma-treated zeolite granules (50 W 30 min) after 1 h of soaking. After 24 h, all plasma-treated zeolites showed increased Cr(VI) uptake. For a 2- to 4-month period, Cr(VI) uptake increased about 130% compared with untreated zeolite granules. X-ray diffraction analyses between untreated and treated zeolite samples revealed no major difference in terms of its crystal structure. However, for plasma-treated samples, an increase in the number of surface defects was observed from scanning electron microscopy images. This increase in the number of surface defects induced by plasma exposure played a crucial role in increasing the number of active sorption sites on the zeolite surface.
Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

PubMed

Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

2014-01-01

The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.
Binding of heparin to plasma proteins and endothelial surfaces is inhibited by covalent linkage to antithrombin.

PubMed

Chan, Anthony K C; Paredes, Nethnapha; Thong, Bruce; Chindemi, Paul; Paes, Bosco; Berry, Leslie R; Monagle, Paul

2004-05-01

Unfractionated heparin (UFH) and low molecular weight heparin (LMWH) are used for prophylaxis and treatment of thrombosis. However, UFH has a short plasma half-life and variable anticoagulant response in vivo due to plasma or vessel wall protein binding and LMWH has a decreased ability to inactivate thrombin, the pivotal enzyme in the coagulation cascade. Covalent linkage of antithrombin to heparin gave a complex (ATH) with superior anticoagulant activity compared to UFH and LMWH, and longer intravenous half-life compared to UFH. We found that plasma proteins bound more to UFH than ATH, and least to LMWH. Also, UFH bound significantly more to endothelial cells than ATH, with 100% of UFH and 94% of ATH binding being on the cell surface and the remainder was endocytosed. Competition studies with UFH confirmed that ATH binding was likely through its heparin moiety. These findings suggest that differences in plasma protein and endothelial cell binding may be due to available heparin chain length. Although ATH is polydisperse, the covalently-linked antithrombin may shield a portion of the heparin chain from association with plasma or endothelial cell surface proteins. This model is consistent with ATH's better bioavailability and more predictable dose response.
Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface

NASA Astrophysics Data System (ADS)

Homin, Taras; Korsun, Anatolii

High electric fields and currents are occurred in the spacecrafts plasma environment by onboard electric generators. Thus the high voltage solar array (SA) of the American segment of International Space Station (ISS) generates potential 160 V. Its negative pole is shorted to the frames of all the ISS segments. There is electric current between the SA and the frame through the plasma environment, i.e. electric discharge occurs. As a result a potential drop exists between the frames of all the ISS segments and the environmental plasma [1], which is cathode drop potential varphi _{c} defined. When ISS orbiting, the φc varies greatly in the range 0-100 V. A large area of the ISS frames and SA surface is coated with a thin dielectric film. Because of cathode drop potential the frame surfaces accumulate ion charges and the SA surfaces accumulate electron charges. These surfaces become plasma capacitors, which accumulate much charge and energy. Micrometeorite impacts or buildup of potential drop in excess of breakdown threshold varphi_{b} (varphi _{c} > varphi _{b} = 60 V) may cause breakdowns of these capacitors. Following a breakdown, the charge collected at the surfaces disperses and transforms into a layer of dense plasma [2]. This plasma environment of the spacecraft produces great pulsed electric fields E at the frame surfaces as well as heavy currents between construction elements which in turn induce great magnetic fields H. Therefore the conductive frame and the environmental plasma is plasma inductors. We have calculated that the densities of these pulsing and high-frequency fields E and H generated in the plasma environment of the spacecraft may exceed values hazardous to human. Besides, these fields must induce large electromagnetic impulses in the space-suit and in the power supply and control circuits of onboard systems. During astronaut’s space-suit activity, these fields will penetrate the space-suit and the human body with possible hazardous effects. These effects need to be studied, and appropriate remedies are to be developed. References 1. Mikatarian, R., et al., «Electrical Charging of the International Space Station», AIAA Paper No. 2003-1079, 41th. Aerospace Sciences Meeting and Exhibit, January 2003. 2. A.G. Korsun, «Electric discharge processes intensification mechanisms on International Space Station surface». Astronautics and rocket production, 1, 2011 (in Russian).
Selective cell-surface labeling of the molecular motor protein prestin

PubMed Central

McGuire, Ryan M.; Silberg, Jonathan J.; Pereira, Fred A.; Raphael, Robert M.

2011-01-01

Prestin, a multipass transmembrane protein whose N- an C-termini are localized to the cytoplasm, must be trafficked to the plasma membrane to fulfill its cellular function as a molecular motor. One challenge in studying prestin sequence-function relationships within living cells is separating the effects of amino acid substitutions on prestin trafficking, plasma membrane localization and function. To develop an approach for directly assessing prestin levels at the plasma membrane, we have investigated whether fusion of prestin to a single pass transmembrane protein results in a functional fusion protein with a surface-exposed N-terminal tag that can be detected in living cells. We find that fusion of the biotin-acceptor peptide (BAP) and transmembrane domain of the platelet-derived growth factor receptor (PDGFR) to the N-terminus of prestin-GFP yields a membrane protein that can be metabolically-labeled with biotin, trafficked to the plasma membrane, and selectively detected at the plasma membrane using fluorescently-tagged streptavidin. Furthermore, we show that the addition of a surface detectable tag and a single-pass transmembrane domain to prestin does not disrupt its voltage-sensitive activity. PMID:21651892
Effect of plasma treatment on the performance of two drug-loaded hydrogel formulations for therapeutic contact lenses.

PubMed

Paradiso, Patrizia; Chu, Virginia; Santos, Luís; Serro, Ana Paula; Colaço, Rogério; Saramago, Benilde

2015-07-01

Although the plasma technology has long been applied to treat contact lenses, the effect of this treatment on the performance of drug-loaded contact lenses is still unclear. The objective of this work is to study the effect of nitrogen plasma treatment on two drug-loaded polymeric formulations which previously demonstrated to be suitable for therapeutic contact lenses: a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel loaded with levofloxacin and a silicone-based hydrogel loaded with chlorhexidine. Modifications of the surface and the optical properties, and alterations in the drug release profiles and possible losses of the antimicrobial activities of the drugs induced by the plasma treatment were assessed. The results showed that, depending on the system and on the processing conditions, the plasma treatment may be beneficial for increasing wettability and refractive index, without degrading the lens surface. From the point of view of drug delivery, plasma irradiation at moderate power (200 W) decreased the initial release rate and the amount of released drug, maintaining the drug activity. For lower (100 W) and higher powers (300 W), almost no effect was detected because the treatment was, respectively, too soft and too aggressive for the lens materials. © 2014 Wiley Periodicals, Inc.
Effects induced by high and low intensity laser plasma on SiC Schottky detectors

NASA Astrophysics Data System (ADS)

Sciuto, Antonella; Torrisi, Lorenzo; Cannavò, Antonino; Mazzillo, Massimo; Calcagno, Lucia

2018-01-01

Silicon-Carbide detectors are extensively employed as diagnostic devices in laser-generated plasma, allowing the simultaneous detection of photons, electrons and ions, when used in time-of-flight configuration. The plasma generated by high intensity laser (1016 W/cm2) producing high energy ions was characterized by SiC detector with a continuous front-electrode, and a very thick active depth, while SiC detector with an Interdigit front-electrode was used to measure the low energy ions of plasma generated by low intensity laser (1010 W/cm2). Information about ion energy, number of charge states, plasma temperature can be accurately obtained. However, laser exposure induces the formation of surface and bulk defects whose concentration increases with increasing the time to plasma exposure. The surface defects consist of clusters with a main size of the order of some microns and they modify the diode barrier height and the efficiency of the detector as checked by alpha spectrometry. The bulk defects, due to the energy loss of detected ions, strongly affect the electrical properties of the device, inducing a relevant increase of the leakage (reverse) current and decrease the forward current related to a deactivation of the dopant in the active detector region.
Experimental study of the visible-light photocatalytic activity of oxygen-deficient TiO2 prepared with Ar/H2 plasma surface treatment

NASA Astrophysics Data System (ADS)

Nakano, Takuma; Yazawa, Shota; Araki, Shota; Kogoshi, Sumio; Katayama, Noboru; Kudo, Yusuke; Nakanishi, Tetsuya

2015-01-01

Oxygen-deficient TiO2 (TiO2-x) has been proposed as a visible-light-responsive photocatalyst. TiO2-x thin films were prepared by Ar/H2 plasma surface treatment, applying varying levels of microwave input power and processing times. The highest visible light photocatalytic activity was observed when using an input power of 200 W, a plasma processing time of 10 min, and a 1:1 \\text{Ar}:\\text{H}2 ratio, conditions that generate an electron temperature of 5.7(±1.0) eV and an electron density of 8.5 × 1010 cm-3. The maximum formaldehyde (HCHO) removal rate of the TiO2-x film was 2.6 times higher than that obtained from a TiO2-xNx film under the same test conditions.
Investigations of the surface activation of thermoplastic polymers by atmospheric pressure plasma treatment with a stationary plasma jet

NASA Astrophysics Data System (ADS)

Moritzer, Elmar; Nordmeyer, Timo; Leister, Christian; Schmidt, Martin Andreas; Grishin, Artur; Knospe, Alexander

2016-03-01

The production of high-quality thermoplastic parts often requires an additional process step after the injection molding stage. This may be a coating, bonding process or a 2K-injection moulding process. A commonly used process to improve the bond strength is atmospheric pressure plasma treatment. A variety of applications are realized with the aid of CNC systems. Although they ensure excellent reproducibility, they make it difficult to implement inline applications. This paper therefore examines the possibility of surface treatment using a stationary plasma jet. However, before it is possible to integrate this technology into a production process, preliminary trials need to be carried out to establish which factors influence the process. Experimental tests were performed using a special test set-up, enabling geometric, plasma-specific parameters to be identified. These results can help with the practical integration of this technology into existing production processes.
Improved confinement region without large magnetohydrodynamic activity in TPE-RX reversed-field pinch plasma

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

Yambe, Kiyoyuki; Hirano, Yoichi; Sakakita, Hajime

2014-11-15

We found that spontaneous improved confinement was brought about depending on the operating region in the Toroidal Pinch Experiment-Reversed eXperiment (TPE-RX) reversed-field pinch plasma [Y. Yagi et al., Fusion Eng. Des. 45, 421 (1999)]. Gradual decay of the toroidal magnetic field at plasma surface B{sub tw} reversal makes it possible to realize a prolonged discharge, and the poloidal beta value and energy confinement time increase in the latter half of the discharge, where reversal and pinch parameters become shallow and low, respectively. In the latter half of the discharge, the plasma current and volume-averaged toroidal magnetic field 〈B{sub t}〉 increasemore » again, the electron density slowly decays, the electron temperature and soft X-ray radiation intensity increase, and the magnetic fluctuations are markedly reduced. In this period of improved confinement, the value of (〈B{sub t}〉-B{sub tw})/B{sub pw}, where B{sub pw} is the poloidal magnetic field at the plasma surface, stays almost constant, which indicates that the dynamo action occurs without large magnetohydrodynamic activities.« less
A simple process based on NH2- and CH3-terminated monolayers for low contact resistance and adherent Au electrode in bottom-contact OTFTs

NASA Astrophysics Data System (ADS)

Abdur, Rahim; Lim, Jeongeun; Jeong, Kyunghoon; Rahman, Mohammad Arifur; Kim, Jiyoung; Lee, Jaegab

2016-03-01

An efficient process for the low contact resistance and adherent source/drain Au electrode in bottom-contact organic thin film transistors (OTFTs) was developed. This was achieved by using two different surface-functional groups of self-assembled monolayers, 3-aminopropyltriethoxysilane (APS), and octadecyltrichlorosilane (OTS), combined with atmospheric-pressure (AP) plasma treatment. Prior to the deposition of Au electrode, the aminoterminated monolayer self-assembles on SiO2 dielectrics, enhancing the adhesion of Au electrode as a result of the acid-base interaction of Au with the amino-terminal groups. AP plasma treatment of the patterned Au electrode on the APS-coated surface activates the entire surface to form an OTS monolayer, allowing the formation of a high quality pentacene layer on both the electrode and active region by evaporation. In addition, negligible damage by AP plasma was observed for the device performance. The fabricated OTFTs based on the two monolayers by AP plasma treatment showed the mobility of 0.23 cm2/Vs, contact resistance of 29 kΩ-cm, threshold voltage of -1.63 V, and on/off ratio of 9.8 × 105, demonstrating the application of the simple process for robust and high-performance OTFTs. [Figure not available: see fulltext.
Inhibitory spectrum of alpha 2-plasmin inhibitor.

PubMed Central

Saito, H; Goldsmith, G H; Moroi, M; Aoki, N

1979-01-01

alpha 2-Plasmin inhibitor (alpha 2PI) has been recently characterized as a fast-reacting inhibitor of plasmin in human plasma and appears to play an important role in the regulation of fibrinolysis in vivo. We have studied the effect of purified alpha 2PI upon various proteases participating in human blood coagulation and kinin generation. At physiological concentration (50 microgram/ml), alpha 2PI inhibited the clot-promoting and prekallikrein-activating activity of Hageman factor fragments, the amidolytic, kininogenase, and clot-promoting activities of plasma kallikrein, and the clot-promoting properties of activated plasma thromboplastin antecedent (PTA, Factor XIa) and thrombin. alpha 2PI had minimal inhibitory effect on surface-bound activated PTA and activated Stuart factor (Factor Xa). alpha 2PI did not inhibit the activity of activated Christmas factor (Factor IXa) or urinary kallikrein. Heparin (1.5-2.0 units/ml) did not enhance the inhibitory function of alpha 2PI. These results suggest that, like other plasma protease inhibitors, alpha 2PI possesses a broad in vitro spectrum of inhibitory properties. PMID:156364
Computational study of sheath structure in oxygen containing plasmas at medium pressures

NASA Astrophysics Data System (ADS)

Hrach, Rudolf; Novak, Stanislav; Ibehej, Tomas; Hrachova, Vera

2016-09-01

Plasma mixtures containing active species are used in many plasma-assisted material treatment technologies. The analysis of such systems is rather difficult, as both physical and chemical processes affect plasma properties. A combination of experimental and computational approaches is the best suited, especially at higher pressures and/or in chemically active plasmas. The first part of our study of argon-oxygen mixtures was based on experimental results obtained in the positive column of DC glow discharge. The plasma was analysed by the macroscopic kinetic approach which is based on the set of chemical reactions in the discharge. The result of this model is a time evolution of the number densities of each species. In the second part of contribution the detailed analysis of processes taking place during the interaction of oxygen containing plasma with immersed substrates was performed, the results of the first model being the input parameters. The used method was the particle simulation technique applied to multicomponent plasma. The sheath structure and fluxes of charged particles to substrates were analysed in the dependence on plasma pressure, plasma composition and surface geometry.
Lunar Electric Fields: Observations and Implications

NASA Astrophysics Data System (ADS)

Halekas, J. S.; Delory, G. T.; Stubbs, T. J.; Farrell, W. M.; Vondrak, R. R.

2006-12-01

Alhough the Moon is typically thought of as having a relatively dormant environment, it is in fact very electrically active. The lunar surface, not protected by any substantial atmosphere, is directly exposed to solar UV and X-rays as well as solar wind plasma and energetic particles. This creates a complex electrodynamic environment, with the surface typically charging positive in sunlight and negative in shadow, and surface potentials varying over orders of magnitude in response to changing solar illumination and plasma conditions. Observations from the Apollo era and theoretical considerations strongly suggest that surface charging also drives dust electrification and horizontal and vertical dust transport. We present a survey of the lunar electric field environment, utilizing both newly interpreted Lunar Prospector (LP) orbital observations and older Apollo surface observations, and comparing to theoretical predictions. We focus in particular on time periods when the most significant surface charging was observed by LP - namely plasmasheet crossings (when the Moon is in the Earth's magnetosphere) and space weather events. During these time periods, kV-scale potentials are observed, and enhanced surface electric fields can be expected to drive significant horizontal and vertical dust transport. Both dust and electric fields can have serious effects on habitability and operation of machinery, so understanding the coupled dust-plasma-electric field system around the Moon is critically important for planning exploration efforts, in situ resource utilization, and scientific observations on the lunar surface. Furthermore, from a pure science perspective, this represents an excellent opportunity to study fundamental surface-plasma interactions.

Novel application for the prevention and treatment of Staphylococcus aureus biofilm formation

NASA Astrophysics Data System (ADS)

Traba, Christian

Formation of bacterial biofilms at solid-liquid interfaces creates numerous problems in both industrial and biomedical sciences. In this dissertation, the application of plasma from two very different facets was studied. In part one, the susceptibility of pre-formed Staphylococcus aureus biofilms on biomaterials to different plasmas was investigated. It was found that the distinct chemical/physical properties of plasmas generated from oxygen, nitrogen, and argon all demonstrated very potent but very different anti-biofilm mechanisms of action. An in depth analysis of these results show: 1) different reactive species produced in each plasma demonstrate specific activity, and 2) the commonly associated etching effect could be manipulated and even controlled, depending on experimental conditions and the discharge gas. These studies provide insights into the anti-biofilm mechanisms of plasma as well as the effects of different reactive species on biofilm inactivation. Under experimental parameters, bacterial cells in Staphylococcus aureus biofilms were killed (>99.9%) by plasmas within minutes of exposure and no bacteria nor biofilm re-growth from discharge gas treated biofilms was observed throughout the life-span of the re-growth experiment. The decontamination ability of plasmas for the treatment of biofilm related infections on biomedical materials was confirmed and novel applications involving the use of low power argon and oxygen for the treatment of biofilm contaminated biomaterials and indwelling devices is proposed. The second facet of this dissertation explores the interaction between biofilm forming Staphylococcus aureus bacteria on different antibacterial/anti-biofilm surfaces. The antibiotic-free anti-fouling surfaces constructed in this study were generated from the plasma-assisted graft polymerization technique. These sophisticated surfaces were stable, biocompatible and capable of preventing biofilm formation on biomaterials and medical devices. Under optimal experimental conditions, the antibacterial activities of these sophisticated surfaces had two distinct mechanisms: 1) reducing bacterial attachment and 2) eradicating adherent bacteria. The excellent antibacterial and anti-biofilm properties of these modified surfaces were initially tested in stationary cultures and later confirmed through a microfluidic cultivation system, which mimicked the in-vivo conditions of implanted catheters. Information gathered, suggests the graft polymerization of negatively charged monomers may be utilized to permanently prevent biofouling on inserted biomaterials, as well as implanted medical devices.
Tailoring the surface properties of polypropylene films through cold atmospheric pressure plasma (CAPP) assisted polymerization and immobilization of biomolecules for enhancement of anti-coagulation activity

NASA Astrophysics Data System (ADS)

Navaneetha Pandiyaraj, K.; Ram Kumar, M. C.; Arun Kumar, A.; Padmanabhan, P. V. A.; Deshmukh, R. R.; Bah, M.; Ismat Shah, S.; Su, Pi-Guey; Halleluyah, M.; Halim, A. S.

2016-05-01

Enhancement of anti-thrombogenic properties of polypropylene (PP) to avert the adsorption of plasma proteins (fibrinogen and albumin), adhesion and activation of the platelets are very important for vast biomedical applications. The cold atmospheric pressure plasma (CAPP) assisted polymerization has potential to create the specific functional groups such as Osbnd Cdbnd O, Cdbnd O, Csbnd N and Ssbnd S. on the surface of polymeric films using selective precursor in vapour phase to enhance anti-thrombogenic properties. Such functionalized polymeric surfaces would be suitable for various biomedical applications especially to improve the blood compatibility. The eventual aspiration of the present investigation is to develop the biofunctional coating onto the surface of PP films using acrylic acid (AAc) and polyethylene glycol (PEG) as a precursor in a vapour phase by incorporating specific functional groups for immobilization of biomolecules such as heparin (HEP), chitosan (CHI) and insulin (INS) on the surface of plasma modified PP films. The surface properties such as hydrophilicity, chemical composition, surface topography of the surface modified PP films were analyzed by contact angle (CA), Fourier transform infrared spectroscopy (FTIR), X-ray photo electron spectroscopy (XPS) and atomic force microscopy (AFM). Furthermore the anti-thrombogenic properties of the surface modified PP films were studied by in vitro tests which include platelet adhesion and protein adsorption analysis. It was found that the anti-thrombogenic properties of the PP films are effectively controlled by the CAPP grafting of AAc and PEG followed by immobilization of biomolecules of heparin, chitosan and insulin. The grafting and immobilization was confirmed by FTIR and XPS through the recognition of specific functional groups such as COOH, Csbnd O, Ssbnd S and Csbnd N. on the surface of PP film. Furthermore, the surface morphology and hydrophilic nature of the PP films also tailored significantly by the successful grafting and immobilization which is confirmed by AFM and CA analysis. Owing to the physico-chemical changes on the surface of PP films induced by CAPP assisted polymerization, the anti-thrombogenic properties of PP films were enhanced as confirmed by in vitro analysis.
Generation and remote delivery of plasma activated species

NASA Astrophysics Data System (ADS)

Maguire, Paul; Mahony, Charles; Kelsey, Colin; Rutherford, David; Mariotti, Davide; Macias-Montero, Manuel; Perez-Martin, Fatima; Diver, Declan

2016-09-01

Plasma interactions with microdroplets offer new opportunities to deliver active chemical agents and nanoparticles to remote substrates downstream with many potential applications from cancer theranostics and wound healing in biomedicine, gentle food decontamination and seed germination in plasma agriculture to catalyst production and photonic structures fabrication, among others. We demonstrate plasma-liquid based pristine nanomaterials synthesis in flight and subsequent delivery up to 120mm from the atmospheric pressure plasma source. Monosized and non-aggregating metal nanoparticles are formed in the rf plasma in less than 100us, representing an increase in precursor reduction rate that is many (>4) orders of magnitude faster than that observed with standard colloidal chemistry or via high energy radiolytic techniques. Also the collection and purification limitations of the latter are avoided. Plasma activated liquid including OH radicals and H2O2 are transported over 120mm and have demonstrated high efficacy bacterial decontamination. These results will be compared with charge species and radical transport from the rf plasma without microdroplets. Reaction models based on high solvated surface electron concentrations will be presented. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).
Development and characterisation of chitosan or alginate-coated low density polyethylene films containing Satureja hortensis extract.

PubMed

Rahmani, Bahareh; Hosseini, Hedayat; Khani, Mohammadreza; Farhoodi, Mehdi; Honarvar, Zohreh; Feizollahi, Ehsan; Shokri, Babak; Shojaee-Aliabadi, Saeedeh

2017-12-01

This study aimed to develop novel bilayer films based on alginate, chitosan and low-density polyethylene (LDPE) containing different concentrations of summer savory extract (SSE). The cold atmospheric plasma system was used to increase the surface energy of LDPE. Initially, water contact angle, surface roughness and the functional group of LDPE before and after plasma treatment were investigated. Then physical, mechanical, optical, antioxidant and microstructure properties of plasma-treated and untreated bilayer films and antioxidant films incorporated with SSE were characterized. Results showed that plasma treatment increased oxygen-containing the polar group, surface roughness and decreased water contact angle of LDPE surface (from 90.47° to 48.73°) and in result enhanced adhesion between polysaccharide coating and LDPE. Tensile strength of both alginate and chitosan coated-LDPE increased from 10.096 to 14.372 and 11.513 to 13.459MPa, respectively after plasma pretreatment. However chitosan-based films had lower water solubility. Although, incorporation of SSE into chitosan and alginate coated-LDPE despite slight adverse effects on the physical and mechanical properties of films, it provided antioxidant activity. Chitosan coated-LDPE containing SSE had potential to use as antioxidant food packaging. Copyright © 2017 Elsevier B.V. All rights reserved.
Precursor-Surface Reactions in Plasma Deposition of Silicon Thin Films

NASA Astrophysics Data System (ADS)

Bakos, Tamas

2005-03-01

Device-quality hydrogenated amorphous silicon (a-Si:H) thin films are usually grown by plasma deposition under conditions where the SiH3 radical is the dominant deposition precursor. In this presentation, we report results of first-principles density functional theory calculations on the interactions of the SiH3 radical with the crystalline Si(100)-(2x1):H surface in conjunction with molecular-dynamics simulations of a-Si:H thin film growth by SiH3 radicals, which elucidate the pathways and energetics of surface reactions that govern important film properties. In particular, we show that an SiH3 radical can insert into strained surface Si-Si dimer bonds, abstract surface H through an Eley-Rideal mechanism, and passivate surface dangling bonds; these reactions follow exothermic and barrierless pathways that lead to a temperature-independent growth rate in agreement with experimental measurements. We also identify a thermally activated surface H abstraction process, in which the SiH3 radical diffuses through overcoordinated surface Si atoms until it encounters a favorable site for H abstraction; the diffusion and H-abstraction steps have commensurate activation barriers. This mechanism explains partly the reduction of the film H content at elevated substrate temperatures.
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
Mechanisms and energetics of hydride dissociation reactions on surfaces of plasma-deposited silicon thin films

NASA Astrophysics Data System (ADS)

Singh, Tejinder; Valipa, Mayur S.; Mountziaris, T. J.; Maroudas, Dimitrios

2007-11-01

We report results from a detailed analysis of the fundamental silicon hydride dissociation processes on silicon surfaces and discuss their implications for the surface chemical composition of plasma-deposited hydrogenated amorphous silicon (a-Si:H) thin films. The analysis is based on a synergistic combination of first-principles density functional theory (DFT) calculations of hydride dissociation on the hydrogen-terminated Si(001)-(2×1) surface and molecular-dynamics (MD) simulations of adsorbed SiH3 radical precursor dissociation on surfaces of MD-grown a-Si :H films. Our DFT calculations reveal that, in the presence of fivefold coordinated surface Si atoms, surface trihydride species dissociate sequentially to form surface dihydrides and surface monohydrides via thermally activated pathways with reaction barriers of 0.40-0.55eV. The presence of dangling bonds (DBs) results in lowering the activation barrier for hydride dissociation to 0.15-0.20eV, but such DB-mediated reactions are infrequent. Our MD simulations on a-Si :H film growth surfaces indicate that surface hydride dissociation reactions are predominantly mediated by fivefold coordinated surface Si atoms, with resulting activation barriers of 0.35-0.50eV. The results are consistent with experimental measurements of a-Si :H film surface composition using in situ attenuated total reflection Fourier transform infrared spectroscopy, which indicate that the a-Si :H surface is predominantly covered with the higher hydrides at low temperatures, while the surface monohydride, SiH(s ), becomes increasingly more dominant as the temperature is increased.
Heat shock protein 70 surface-positive tumor exosomes stimulate migratory and cytolytic activity of natural killer cells.

PubMed

Gastpar, Robert; Gehrmann, Mathias; Bausero, Maria A; Asea, Alexzander; Gross, Catharina; Schroeder, Josef A; Multhoff, Gabriele

2005-06-15

Detergent-soluble membrane vesicles are actively released by human pancreas (Colo-/Colo+) and colon (CX-/CX+) carcinoma sublines, differing in their capacity to present heat shock protein 70 (Hsp70)/Bag-4 on their plasma membranes. Floating properties, acetylcholine esterase activity, and protein composition characterized them as exosomes. An enrichment of Rab-4 documented their intracellular transport route from early endosomes to the plasma membrane. After solubilization, comparable amounts of cytosolic proteins, including tubulin, Hsp70, Hsc70, and Bag-4, but not ER-residing Grp94 and calnexin, were detectable in tumor-derived exosomes. However, with respect to the exosomal surface, only Colo+/CX+ but not Colo-/CX- derived exosomes were Hsp70 membrane positive. Therefore, concomitant with an up-regulated cell surface density of activation markers, migration and Hsp70 reactivity of natural killer (NK) cells was stimulated selectively by Hsp70/Bag-4 surface-positive exosomes, but not by their negative counterparts and tumor cell lysates. Moreover, the exosome-mediated lytic activity of NK cells was blockable by Hsp70-specific antibody. As already shown for TKD stimulation, NK cells preincubated with Hsp70 surface-positive exosomes initiated apoptosis in tumors through granzyme B release. In summary, our data provide an explanation how Hsp70 reactivity in NK cells is induced by tumor-derived exosomes.
Heat Shock Protein 70 Surface-Positive Tumor Exosomes Stimulate Migratory and Cytolytic Activity of Natural Killer Cells

PubMed Central

Gastpar, Robert; Gehrmann, Mathias; Bausero, Maria A.; Asea, Alexzander; Gross, Catharina; Schroeder, Josef A.

2006-01-01

Detergent-soluble membrane vesicles are actively released by human pancreas (Colo−/Colo+) and colon (CX−/CX+) carcinoma sublines, differing in their capacity to present heat shock protein 70 (Hsp70)/Bag-4 on their plasma membranes. Floating properties, acetylcholine esterase activity, and protein composition characterized them as exosomes. An enrichment of Rab-4 documented their intracellular transport route from early endosomes to the plasma membrane. After solubilization, comparable amounts of cytosolic proteins, including tubulin, Hsp70, Hsc70, and Bag-4, but not ER-residing Grp94 and calnexin, were detectable in tumor-derived exosomes. However, with respect to the exosomal surface, only Colo+/CX+ but not Colo−/CX exosomes were Hsp70 membrane derived positive. Therefore, concomitant with an up-regulated cell surface density of activation markers, migration and Hsp70 reactivity of natural killer (NK) cells was stimulated selectively by Hsp70/Bag-4 surface-positive exosomes, but not by their negative counterparts and tumor cell lysates. Moreover, the exosome-mediated lytic activity of NK cells was blockable by Hsp70-specific antibody. As already shown for TKD stimulation, NK cells preincubated with Hsp70 surface-positive exosomes initiated apoptosis in tumors through granzyme B release. In summary, our data provide an explanation how Hsp70 reactivity in NK cells is induced by tumor-derived exosomes. PMID:15958569
Development and use of culture systems to modulate specific cell responses

NASA Astrophysics Data System (ADS)

Martin, Yves

Culture surfaces that induce specific localized cell responses are required to achieve tissue-like cell growth in three-dimensional (3D) environments, as well as to develop more efficient cell-based diagnostic techniques, noticeably when working with fragile cells such as stem cells or platelets. As such, Chapter 1 of this thesis work is devoted to the review of 3D cell-material interactions in vitro and the corresponding existing culture systems available to achieve in vivo-like cell responses. More adequate 3D culture systems will need to be developed to mimic several characteristics of in vivo environments, including lowered non-specific cell-material interactions and localized biochemical signaling. The experimental work in this thesis is based on the hypothesis that well-studied and optimized surface treatments will be able to lower non-specific cell-material interactions and allow local chemical modification in order to achieve specific localized cell-material interactions for different applications. As such, in Chapter 2 and Chapter 3 of this thesis, surface treatments were developed using plasma polymerization and covalent immobilization of a low-fouling polymer (i.e., poly(ethylene glycol)) and characterized and optimized using a large number of techniques including atomic force microscopy, quartz crystal microbalance, surface plasmon resonance, x-ray photoelectron spectroscopy and fluorescence-based techniques. The main plasma polymerization parameter important for surface chemical content, specifically nitrogen to carbon content, was identified as being glow discharge power, while reaction time and power determined plasma film thickness. Moreover, plasma films were shown to be stable in aqueous environments. Covalently-bound poly(ethylene glycol) (PEG) layers physicochemical and mechanical properties are dependent on fabrication methods. Polymer concentration in solution is an important indicator of final layer properties, and use of a theta solvent induces complex aggregation phenomena in solution yielding layers with widely different properties. Chemically available primary amine groups are also shown to be present, paving the way for the immobilization of bio-active molecules. An application of low-fouling locally modified surfaces is given in Chapter 4 by the development of a novel diagnostic surface to evaluate platelet activation which is until now very difficult as platelets are readily activated by in vitro manipulations. Significant results from volunteer donors indicate that this diagnostic instrument has the potential to allow the rapid estimation of platelet activation levels in whole blood.
Integrin activation by a cold atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Volotskova, Olga; Stepp, Mary Ann; Keidar, Michael

2012-05-01

Current breakthrough research on cold atmospheric plasma (CAP) demonstrates that CAP has great potential in various areas, including medicine and biology, thus providing a new tool for living tissue treatment. In this paper, we explore potential mechanisms by which CAP alters cell migration and influences cell adhesion. We focus on the study of CAP interaction with fibroblasts and corneal epithelial cells. The data show that fibroblasts and corneal epithelial cells have different thresholds (treatment times) required to achieve maximum inhibition of cell migration. Both cell types reduced their migration rates by ˜30-40% after CAP compared to control cells. Also, the impact of CAP treatment on cell migration and persistence of fibroblasts after integrin activation by MnCl2, serum starvation or replating cells onto surfaces coated with integrin ligands is assessed; the results show that activation by MnCl2 or starvation attenuates cells’ responses to plasma. Studies carried out to assess the impact of CAP treatment on the activation state of β1 integrin and focal adhesion size by using immunofluorescence show that fibroblasts have more active β1 integrin on their surface and large focal adhesions after CAP treatment. Based on these data, a thermodynamic model is presented to explain how CAP leads to integrin activation and focal adhesion assembly.
Nanosecond-Pulsed DBD Plasma-Generated Reactive Oxygen Species Trigger Immunogenic Cell Death in A549 Lung Carcinoma Cells through Intracellular Oxidative Stress

PubMed Central

Lin, Abraham; Truong, Billy; Patel, Sohil; Kaushik, Nagendra; Choi, Eun Ha; Fridman, Gregory; Fridman, Alexander; Miller, Vandana

2017-01-01

A novel application for non-thermal plasma is the induction of immunogenic cancer cell death for cancer immunotherapy. Cells undergoing immunogenic death emit danger signals which facilitate anti-tumor immune responses. Although pathways leading to immunogenic cell death are not fully understood; oxidative stress is considered to be part of the underlying mechanism. Here; we studied the interaction between dielectric barrier discharge plasma and cancer cells for oxidative stress-mediated immunogenic cell death. We assessed changes to the intracellular oxidative environment after plasma treatment and correlated it to emission of two danger signals: surface-exposed calreticulin and secreted adenosine triphosphate. Plasma-generated reactive oxygen and charged species were recognized as the major effectors of immunogenic cell death. Chemical attenuators of intracellular reactive oxygen species successfully abrogated oxidative stress following plasma treatment and modulated the emission of surface-exposed calreticulin. Secreted danger signals from cells undergoing immunogenic death enhanced the anti-tumor activity of macrophages. This study demonstrated that plasma triggers immunogenic cell death through oxidative stress pathways and highlights its potential development for cancer immunotherapy. PMID:28467380
Preferential inhibition of the plasma membrane NADH oxidase (NOX) activity by diphenyleneiodonium chloride with NADPH as donor

NASA Technical Reports Server (NTRS)

Morre, D. James

2002-01-01

The cell-surface NADH oxidase (NOX) protein of plant and animal cells will utilize both NADH and NADPH as reduced electron donors for activity. The two activities are distinguished by a differential inhibition by the redox inhibitor diphenyleneiodonium chloride (DPI). Using both plasma membranes and cells, activity with NADPH as donor was markedly inhibited by DPI at submicromolar concentrations, whereas with NADH as donor, DPI was much less effective or had no effect on the activity. The possibility of the inhibition being the result of two different enzymes was eliminated by the use of a recombinant NOX protein. The findings support the concept that NOX proteins serve as terminal oxidases for plasma membrane electron transport involving cytosolic reduced pyridine nucleotides as the natural electron donors and with molecular oxygen as the electron acceptor.
Damage-free polymer surface modification employing inward-type plasma

NASA Astrophysics Data System (ADS)

Kanou, Ryo; Suga, Hiroshi; Utsumi, Hideyuki; Takahashi, Satoshi; Shirayama, Yuya; Watanabe, Norimichi; Petit, Stèphane; Shimizu, Tetsuo

2017-08-01

Inward-type plasmas, which spread upstream against the gas flow in the capillary tube where the gas is discharged, can react with samples placed near the entrance of such a capillary tube. In this study, surface modification of polymer surfaces is conducted using inward plasma. The modification is also done by conventional microplasma jet, and the modified surfaces with two plasma techniques are characterized by contact angle measurement, X-ray photoemission spectroscopy (XPS), and atomic force microscopy (AFM). Although inward-plasma-treated surfaces are less hydrophilic than conventional plasma-treated ones, they are still sufficiently hydrophilic for surface coatings. In addition, it turns out that the polymer surfaces irradiated with the inward plasma yield much smoother surfaces than those treated with the conventional plasma jet. Thus, the inward plasma treatment is a viable technique when the surface flatness is crucial, such as for the surface coating of plastic lenses.
Plasma Torch for Plasma Ignition and Combustion of Coal

NASA Astrophysics Data System (ADS)

Ustimenko, Alexandr; Messerle, Vladimir

2015-09-01

Plasma-fuel systems (PFS) have been developed to improve coal combustion efficiency. PFS is a pulverized coal burner equipped with arc plasma torch producing high temperature air stream of 4000 - 6000 K. Plasma activation of coal at the PFS increases the coal reactivity and provides more effective ignition and ecologically friendly incineration of low-rank coal. The main and crucial element of PFS is plasma torch. Simplicity and reliability of the industrial arc plasma torches using cylindrical copper cathode and air as plasma forming gas predestined their application at heat and power engineering for plasma aided coal combustion. Life time of these plasma torches electrodes is critical and usually limited to 200 hours. Considered in this report direct current arc plasma torch has the cathode life significantly exceeded 1000 hours. To ensure the electrodes long life the process of hydrocarbon gas dissociation in the electric arc discharge is used. In accordance to this method atoms and ions of carbon from near-electrode plasma deposit on the active surface of the electrodes and form electrode carbon condensate which operates as ``actual'' electrode. Complex physicochemical investigation showed that deposit consists of nanocarbon material.
The isolation and subfractionation of plasma membrane from the cellular slime mould Dictyostelium discoideum

PubMed Central

Green, Anita A.; Newell, Peter C.

1974-01-01

A procedure for the isolation and separation of three different subfractions of plasma membrane from the cellular slime mould Dictyostelium discoideum is described. The cells were disrupted by freeze-thawing in liquid N2 and plasma membranes were purified by equilibrium centrifugation in a sucrose gradient. The cell surface was labelled with radioactive iodide by using the lactoperoxidase iodination method. Alkaline phosphatase was identified as a plasma-membrane marker by its co-distribution with [125I]iodide. 5′-Nucleotidase, which has been widely described as a plasma-membrane marker enzyme in mammalian tissues, was not localized to any marked extent in D. discoideum plasma membrane. The isolated plasma membranes showed a 24-fold enrichment of alkaline phosphatase specific activity relative to the homogenate and a yield of 50% of the total plasma membranes. Determination of succinate dehydrogenase and NADPH–cytochrome c reductase activities indicated that the preparation contained 2% of the total mitochondria and 3% of the endoplasmic reticulum. When the plasma-membrane preparation was further disrupted in a tight-fitting homogenizer, three plasma-membrane subfractions of different densities were obtained by isopycnic centrifugation. The enrichment of alkaline phosphatase was greatest in the subfraction with the lowest density. This fraction was enriched 36-fold relative to the homogenate and contained 19% of the total alkaline phosphatase activity but only 0.08% of the succinate dehydrogenase activity and 0.34% of the NADPH–cytochrome c reductase activity. Electron microscopy of this fraction showed it to consist of smooth membrane vesicles with no recognizable contaminants. ImagesPLATE 1 PMID:4156170
Cell-derived microparticles and complement activation in preeclampsia versus normal pregnancy.

PubMed

Biró, E; Lok, C A R; Hack, C E; van der Post, J A M; Schaap, M C L; Sturk, A; Nieuwland, R

2007-01-01

Inflammation plays a major role in the vascular dysfunction seen in preeclampsia, and several studies suggest involvement of the complement system. To investigate whether complement activation on the surface of microparticles is increased in plasma of preeclamptic patients versus healthy pregnant controls. Microparticles from plasma of preeclamptic (n=10), healthy pregnant (n=10) and healthy nonpregnant (n=10) women were analyzed by flow cytometry for bound complement components (C1q, C4, C3) and complement activator molecules (C-reactive protein [CRP], serum amyloid P component [SAP], immunoglobulin [Ig]M, IgG). Fluid phase complement activation products and activator molecules were also determined. Levels of microparticles with bound complement components showed no increase in complement activation on the microparticle surface in preeclamptic women, in line with levels of fluid phase complement activation products. In healthy nonpregnant and pregnant women, bound CRP was associated with classical pathway activation on the microparticle surface, and in healthy pregnant women IgM and IgG molecules also contributed. In preeclamptic women, microparticles with bound SAP and those with IgG seemed to contribute to C1q binding without a clear association to further classical pathway activation. Furthermore, significantly increased levels of microparticles with bound CRP were present in preeclamptic compared with healthy pregnant women (median 178x10(6)/L versus 47x10(6)/L, P<0.01), but without concomitant increases in complement activation. We found no evidence of increased complement activation on the microparticle surface in preeclamptic women. Microparticles with bound CRP were significantly increased, but in contrast to healthy pregnant and nonpregnant women, this was not associated with increased classical pathway activation on the surface of the microparticles.
Ultra-thin microporous/hybrid materials

DOEpatents

Jiang, Ying-Bing [Albuquerque, NM; Cecchi, Joseph L [Albuquerque, NM; Brinker, C Jeffrey [Albuquerque, NM

2012-05-29

Ultra-thin hybrid and/or microporous materials and methods for their fabrication are provided. In one embodiment, the exemplary hybrid membranes can be formed including successive surface activation and reaction steps on a porous support that is patterned or non-patterned. The surface activation can be performed using remote plasma exposure to locally activate the exterior surfaces of porous support. Organic/inorganic hybrid precursors such as organometallic silane precursors can be condensed on the locally activated exterior surfaces, whereby ALD reactions can then take place between the condensed hybrid precursors and a reactant. Various embodiments can also include an intermittent replacement of ALD precursors during the membrane formation so as to enhance the hybrid molecular network of the membranes.
Lunar plasma measurement by MAP-PACE onboard KAGUYA (SELENE)

NASA Astrophysics Data System (ADS)

Saito, Yoshifumi

Low energy charged particles around the Moon were vigorously observed by Moon orbiting satellites and plasma instrumentation placed on the lunar surface in 1960s and 1970s. Though there were some satellites that explored the Moon afterwards, most of them were dedicated to the global mapping of the lunar surface. KAGUYA(SELENE) is a Japanese lunar orbiter that studies the origin and evolution of the Moon by means of global mapping of element abundances, mineralogical composition, and surface geographical mapping from 100km altitude. KAGUYA was successfully launched on 14 September 2007 by HIIA launch vehicle from Tanegashima Space Center in Japan. KAGUYA was inserted into a circular lunar polar orbit of 100km altitude and started continuous observation in mid-December 2007. One of the fourteen science instruments MAP-PACE (MAgnetic field and Plasma experiment - Plasma energy Angle and Composition Experiment) was developed for the comprehensive three-dimensional plasma measurement around the Moon. MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measure the distribution function of low energy electrons below 15keV. IMA and IEA measure the distribution function of low energy ions below 28keV/q. IMA has an ability to discriminate the ion mass with high mass resolution. PACE sensors have been measuring solar wind, plasmas in the wake region of the Moon and plasmas in the Earth's magnetosphere. ESA sensors have discovered electron heating over magnetic anomalies on the lunar surface. ESA sensors have also observed electrons accelerated from the lunar surface in the wake region. PACE ion sensors have discovered new features of low energy ions around the Moon. IMA has discovered the existence of alkali ions that are originated from the lunar surface or lunar atmosphere and are picked up by the solar wind. IEA and IMA sensors discovered solar wind reflection by the Moon. PACE ion sensors also discovered that ions are rarefied over the magnetic anomaly on the lunar surface while electrons are heated. MAP-PACE has been revealing unexpectedly active plasma environment around the Moon.
Prereduction of Metal Oxides via Carbon Plasma Treatment for Efficient and Stable Electrocatalytic Hydrogen Evolution.

PubMed

Zhang, Yongqi; Ouyang, Bo; Xu, Kun; Xia, Xinhui; Zhang, Zheng; Rawat, Rajdeep Singh; Fan, Hong Jin

2018-04-01

Prereduction of transition metal oxides is a feasible and efficient strategy to enhance their catalytic activity for hydrogen evolution. Unfortunately, the prereduction via the common H 2 annealing method is unstable for nanomaterials during the hydrogen evolution process. Here, using NiMoO 4 nanowire arrays as the example, it is demonstrated that carbon plasma (C-plasma) treatment can greatly enhance both the catalytic activity and the long-term stability of transition metal oxides for hydrogen evolution. The C-plasma treatment has two functions at the same time: it induces partial surface reduction of the NiMoO 4 nanowire to form Ni 4 Mo nanoclusters, and simultaneously deposits a thin graphitic carbon shell. As a result, the C-plasma treated NiMoO 4 can maintain its array morphology, chemical composition, and catalytic activity during long-term intermittent hydrogen evolution process. This work may pave a new way for simultaneous activation and stabilization of transition metal oxide-based electrocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Atmospheric Plasma Treatment to Titanium Surface on Initial Osteoblast-Like Cell Spreading. .

PubMed

Kim, In-Hye; Son, Jun-Sik; Kwon, Tae-Yub; Kim, Kyo-Han

2015-01-01

Plasma treatments are becoming a popular method for modifying the characteristics of a range of substrate surfaces. Atmospheric pressure plasma is cost-efficient, safe and simple compared to high-pressure plasma. This study examined the effects of atmospheric pressure plasma to a titanium (Ti) surface on osteoblast-like cell (osteoblast) spreading and cellular networks. The characteristics of the Ti surface before and after the atmospheric plasma treatment were analyzed by X-ray photoemission spectroscopy (XPS), scanning electron microscopy (SEM), contact angle measurements, and an optical 3D profiling system. The morphology of osteoblasts attached to the Ti surfaces was observed by SEM and confocal laser scanning microscopy. The atmospheric pressure plasma made the Ti surfaces more hydrophilic. The osteoblasts that adhered to the untreated surface were round and spherical, whereas the cells covered a larger surface area on the plasma-treated surface. The plasma-treated Ti surface showed enhanced cell spreading and migration with more developed cellular networks. In conclusion, an atmospheric plasma treatment is a potential surface modifying method that can enhance the initial the cell affinity at the early stages in vitro.
Increasing the Detection Limit of the Parkinson Disorder through a Specific Surface Chemistry Applied onto Inner Surface of the Titration Well.

PubMed

Mille, Caroline; Debarnot, Dominique; Zorzi, Willy; El Moualij, Benaïssa; Coudreuse, Arnaud; Legeay, Gilbert; Quadrio, Isabelle; Perret-Liaudet, Armand; Poncin-Epaillard, Fabienne

2012-04-18

The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic-phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°), negatively charged and smooth inner surface.
Increasing the Detection Limit of the Parkinson Disorder through a Specific Surface Chemistry Applied onto Inner Surface of the Titration Well

PubMed Central

Mille, Caroline; Debarnot, Dominique; Zorzi, Willy; Moualij, Benaïssa El; Coudreuse, Arnaud; Legeay, Gilbert; Quadrio, Isabelle; Perret-Liaudet, Armand; Poncin-Epaillard, Fabienne

2012-01-01

The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic—phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°), negatively charged and smooth inner surface. PMID:24955533
A study of oxidative stress induced by non-thermal plasma-activated water for bacterial damage

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

Zhang, Qian; Ma, Ruonan; Tian, Ying

2013-05-20

Ar/O{sub 2} (2%) cold plasma microjet was used to create plasma-activated water (PAW). The disinfection efficacy of PAW against Staphylococcus aureus showed that PAW can effectively disinfect bacteria. Optical emission spectra and oxidation reduction potential results demonstrated the inactivation is attributed to oxidative stress induced by reactive oxygen species in PAW. Moreover, the results of X-ray photoelectron spectroscopy, atomic absorption spectrometry, and transmission electron microscopy suggested that the chemical state of cell surface, the integrity of cell membrane, as well as the cell internal components and structure were damaged by the oxidative stress.
Advances and directions of ion nitriding/carburizing

NASA Technical Reports Server (NTRS)

Spalvins, Talivaldis

1989-01-01

Ion nitriding and carburizing are plasma activated thermodynamic processes for the production of case hardened surface layers not only for ferrous materials, but also for an increasing number of nonferrous metals. When the treatment variables are properly controlled, the use of nitrogenous or carbonaceous glow discharge medium offers great flexibility in tailoring surface/near-surface properties independently of the bulk properties. The ion nitriding process has reached a high level of maturity and has gained wide industrial acceptance, while the more recently introduced ion carburizing process is rapidly gaining industrial acceptance. The current status of plasma mass transfer mechanisms into the surface regarding the formation of compound and diffusion layers in ion nitriding and carbon build-up ion carburizing is reviewed. In addition, the recent developments in design and construction of advanced equipment for obtaining optimized and controlled case/core properties is summarized. Also, new developments and trends such as duplex plasma treatments and alternatives to dc diode nitriding are highlighted.
Increase in the Hydrophilicity and Lewis Acid-Base Properties of Solid Surfaces Achieved by Electric Gliding Discharge in Humid Air: Effects on Bacterial Adherence

NASA Astrophysics Data System (ADS)

Kamgang, J. O.; Naitali, M.; Herry, J.-M.; Bellon-Fontaine, M.-N.; Brisset, J.-L.; Briandet, R.

2009-04-01

This study addressed the effects of treatment with gliding discharge plasma on the surface properties of solid materials, as well as the consequences concerning adherence of a model bacterium. As evaluated by contact angles with selected liquids, plasma treatment caused an increase in surface hydrophilicity and in the Lewis acid-base components of the surface energy of all materials tested. These modifications were more marked for low density polyethylene and stainless steel than for polytetrafluoroethylene. After treatment, the hydrophilicity of the materials remained relatively stable for at least 20 days. Moreover, analysis of the topography of the materials by atomic force microscopy revealed that the roughness of both polymers was reduced by glidarc plasma treatment. As a result of all these modifications, solid substrates were activated towards micro-organisms and the adherence of S. epidermidis, a negatively charged Lewis-base and mildly hydrophilic strain selected as the model, was increased in almost all the cases tested.
Effect of surface properties of NiFe2O4 nanoparticles synthesized by dc thermal plasma route on antimicrobial activity

NASA Astrophysics Data System (ADS)

Bhosale, S. V.; Ekambe, P. S.; Bhoraskar, S. V.; Mathe, V. L.

2018-05-01

The present work reports the role of surface properties of NiFe2O4 nanoparticles on the antimicrobial activity. The NiFe2O4 nanoparticles were synthesized by gas phase condensation and chemical co-precipitation route. These nanoparticles were extensively investigated using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electro-kinetic property measurements. The HRTEM was used to analyze surface morphology of nickel ferrite nanoparticles obtained by two different routes. Electro-kinetic properties of the nanoparticles under investigation were recorded, analyzed and correlated with the antimicrobial properties. It was observed that nickel ferrite nanoparticles synthesized by thermal plasma route (NFOTP) formed highly stable colloidal solution as compared to chemically synthesized (NFOCP), as the later tends to agglomerate due to low surface charge. The antimicrobial activity of NiFe2O4 nanoparticles were investigated on two Gram positive bacteria Staphylococcus aureus and Streptococcus pyogenes, two Gram negative bacteria Escherichia coli and Salmonella typhimurium and one fungal species Candida albicans. It was noted that the surface properties of NiFe2O4 particles have revealing effect on the antimicrobial activity. The NFOTP nanoparticles showed significant activity for gram negative E. coli bacteria however no activity was observed for other bacteria's and fungi under study. Moreover NFOCP particles did not show any significant activity for both bacteria's and fungi. Further, antimicrobial activity of nickel ferrite nanoparticles were studied even for different concentration to obtain the minimum inhibition concentration (MIC).
Select α-arrestins control cell-surface abundance of the mammalian Kir2.1 potassium channel in a yeast model.

PubMed

Hager, Natalie A; Krasowski, Collin J; Mackie, Timothy D; Kolb, Alexander R; Needham, Patrick G; Augustine, Andrew A; Dempsey, Alison; Szent-Gyorgyi, Christopher; Bruchez, Marcel P; Bain, Daniel J; Kwiatkowski, Adam V; O'Donnell, Allyson F; Brodsky, Jeffrey L

2018-05-21

Protein composition at the plasma membrane is tightly regulated, with rapid protein internalization and selective targeting to the cell surface occurring in response to environmental changes. For example, ion channels are dynamically relocalized to or from the plasma membrane in response to physiological alterations, allowing cells and organisms to maintain osmotic and salt homeostasis. To identify additional factors that regulate the selective trafficking of a specific ion channel, we used a yeast model for a mammalian potassium channel, the K+ inwardly rectifying channel Kir2.1. Kir2.1 maintains potassium homeostasis in heart muscle cells, and Kir2.1 defects lead to human disease. By examining the ability of Kir2.1 to rescue the growth of yeast cells lacking endogenous potassium channels, we discovered that specific α-arrestins regulate Kir2.1 localization. Specifically, we found that the Ldb19/Art1, Aly1/Art6, and Aly2/Art3 α-arrestin adaptor proteins promote Kir2.1 trafficking to the cell surface, increase Kir2.1 activity at the plasma membrane, and raise intracellular potassium levels. To better quantify the intracellular and cell-surface populations of Kir2.1, we created fluorescence-activating protein fusions and for the first time used this technique to measure the cell-surface residency of a plasma membrane protein in yeast. Our experiments revealed that two α-arrestin effectors also control Kir2.1 localization. In particular, both the Rsp5 ubiquitin ligase and the protein phosphatase calcineurin facilitated the α-arrestin-mediated trafficking of Kir2.1. Together, our findings implicate α-arrestins in regulating an additional class of plasma membrane proteins and establish a new tool for dissecting the trafficking itinerary of any membrane protein in yeast. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.
A new flexible DBD device for treating infected wounds: in vitro and ex vivo evaluation and comparison with a RF argon plasma jet

NASA Astrophysics Data System (ADS)

Boekema, B. K. H. L.; Vlig, M.; Guijt, D.; Hijnen, K.; Hofmann, S.; Smits, P.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P.; Middelkoop, E.

2016-02-01

Cold plasma has been shown to provide a promising alternative antimicrobial treatment for wound healing. We developed and tested a flexible surface dielectric barrier discharge (DBD) and compared it to an argon gas based plasma jet operated remotely with a distance between plasma plume and sample of 8 mm. Tests were conducted using different models: on cultured cells, on ex vivo human skin and on bacteria (Pseudomonas aeruginosa) (on agar, in suspension, in collagen/elastin matrix or on ex vivo human skin), allowing us to directly compare bactericidal with safety aspects under identical conditions. Both plasma devices were highly efficient when used on bacteria in non-buffered solutions, but DBD was faster in reaching the maximum bacterial reduction. Treatment of bacteria on intact skin with DBD resulted in up to 6 log reductions in 3 min. The jet was far less efficient on intact skin. Even after 8 min treatment no more than 2 log reductions were obtained with the jet. Treatment of bacteria in burn wound models with DBD for 6 min resulted in a 4.5 log reduction. Even when using DBD for 6 min on infected burn wound models with colonizing or biofilm phase bacteria, the log reductions were 3.8 or 3.2 respectively. DBD plasma treatment for 6 min did not affect fibroblast viability, whereas a treatment for 8 min was detrimental. Similarly, treatment with DBD or plasma jet for 6 min did also not affect the metabolic activity of skin biopsies. After treatment for 8 min with DBD or plasma jet, 78% or 60% of activity in skin biopsies remained, respectively. Multiple treatments of in vitro burn wound models with surface DBD for 6 min or with plasma jet for 8 min did not affect re-epithelialization. With the flexible surface DBD plasma strip we were able to quickly inactivate large numbers of bacteria on and in skin. Under the same conditions, viability of skin cells or re-epithelialization was not affected. The DBD source has potential for treating larger wound areas.
Simulation of MST tokamak discharges with resonant magnetic perturbations

NASA Astrophysics Data System (ADS)

Cornille, B. S.; Sovinec, C. R.; Chapman, B. E.; Dubois, A.; McCollam, K. J.; Munaretto, S.

2016-10-01

Nonlinear MHD modeling of MST tokamak plasmas with an applied resonant magnetic perturbation (RMP) reveals degradation of flux surfaces that may account for the experimentally observed suppression of runaway electrons with the RMP. Runaway electrons are routinely generated in MST tokamak discharges with low plasma density. When an m = 3 RMP is applied these electrons are strongly suppressed, while an m = 1 RMP of comparable amplitude has little effect. The computations are performed using the NIMROD code and use reconstructed equilibrium states of MST tokamak plasmas with q (0) < 1 and q (a) = 2.2 . Linear computations show that the (1 , 1) -kink and (2 , 2) -tearing modes are unstable, and nonlinear simulations produce sawtoothing with a period of approximately 0.5 ms, which is comparable to the period of MHD activity observed experimentally. Adding an m = 3 RMP in the computation degrades flux surfaces in the outer region of the plasma, while no degradation occurs with an m = 1 RMP. The outer flux surface degradation with the m = 3 RMP, combined with the sawtooth-induced distortion of flux surfaces in the core, may account for the observed suppression of runaway electrons. Work supported by DOE Grant DE-FC02-08ER54975.
Design of anticoagulant surfaces based on cellulose nanocrystals.

PubMed

Ehmann, Heike M A; Mohan, Tamilselvan; Koshanskaya, Maria; Scheicher, Sylvia; Breitwieser, Doris; Ribitsch, Volker; Stana-Kleinschek, Karin; Spirk, Stefan

2014-11-07

The anticoagulant activity of surfaces decorated with cellulose nanocrystals (CNCs) prepared via sulfuric acid hydrolysis, is explored. Such surfaces bear a high amount of negatively charged sulfate groups, which mimic the naturally occurring anticoagulant heparin in terms of charge density. It is demonstrated that CNC decorated surfaces significantly enhance the coagulation times of blood plasma and whole blood as proven by QCM-D and simple clotting tests.
Development of a laboratory demonstration model active cleaning device

NASA Technical Reports Server (NTRS)

Shannon, R. L.; Gillette, R. B.

1975-01-01

A laboratory demonstration model of a device for removing contaminant films from optical surfaces in space was developed. The development of a plasma tube, which would produce the desired cleaning effects under high vacuum conditions, represented the major problem in the program. This plasma tube development is discussed, and the resulting laboratory demonstration-model device is described.
Selective cell-surface labeling of the molecular motor protein prestin.

PubMed

McGuire, Ryan M; Silberg, Jonathan J; Pereira, Fred A; Raphael, Robert M

2011-06-24

Prestin, a multipass transmembrane protein whose N- and C-termini are localized to the cytoplasm, must be trafficked to the plasma membrane to fulfill its cellular function as a molecular motor. One challenge in studying prestin sequence-function relationships within living cells is separating the effects of amino acid substitutions on prestin trafficking, plasma membrane localization and function. To develop an approach for directly assessing prestin levels at the plasma membrane, we have investigated whether fusion of prestin to a single pass transmembrane protein results in a functional fusion protein with a surface-exposed N-terminal tag that can be detected in living cells. We find that fusion of the biotin-acceptor peptide (BAP) and transmembrane domain of the platelet-derived growth factor receptor (PDGFR) to the N-terminus of prestin-GFP yields a membrane protein that can be metabolically-labeled with biotin, trafficked to the plasma membrane, and selectively detected at the plasma membrane using fluorescently-tagged streptavidin. Furthermore, we show that the addition of a surface detectable tag and a single-pass transmembrane domain to prestin does not disrupt its voltage-sensitive activity. Copyright © 2011 Elsevier Inc. All rights reserved.
Characterization and Properties of Electroless Nickel Plated Poly (ethylene terephthalate) Nonwoven Fabric Enhanced by Dielectric Barrier Discharge Plasma Pretreatment

NASA Astrophysics Data System (ADS)

Geng, Yamin; Lu, Canhui; Liang, Mei; Zhang, Wei

2010-12-01

In order to develop a more economical pretreatment method for electroless nickel plating, a dielectric barrier discharge (DBD) plasma at atmospheric pressure was used to improve the hydrophilicity and adhesion of poly (ethylene terephthalate) (PET) nonwoven fabric. The properties of the PET nonwoven fabric including its liquid absorptive capacity (WA), aging behavior, surface chemical composition, morphology of the surface, adhesion strength, surface electrical resistivity and electromagnetic interference (EMI)- shielding effectiveness (SE) were studied. The liquid absorptive capacity (WA) increased due to the incorporation of oxygen-containing and nitrogen-containing functional groups on the surface of PET nonwoven fabric after DBD air-plasma treatment. The surface morphology of the nonwoven fibers became rougher after plasma treatment. Therefore, the surface was more prone to absorb tin sensitizer and palladium catalyst to form an active layer for the deposition of electroless nickel. SEM and X-ray diffraction (XRD) measurements indicated that a uniform coating of nickel was formed on the PET nonwoven fabric. The average EMI-SE of Ni-plating of PET nonwoven fabric maintained a relatively stable value (38.2 dB to 37.3 dB) in a frequency range of 50 MHz to 1500 MHz. It is concluded that DBD is feasible for pretreatment of nonwoven fabric for electroless nickel plating to prepare functional material with good EMI-SE properties.
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.
Mini-Magnetospheres at the Moon in the Solar Wind and the Earth's Plasma Sheet

NASA Astrophysics Data System (ADS)

Harada, Y.; Futaana, Y.; Barabash, S. V.; Wieser, M.; Wurz, P.; Bhardwaj, A.; Asamura, K.; Saito, Y.; Yokota, S.; Tsunakawa, H.; Machida, S.

2014-12-01

Lunar mini-magnetospheres are formed as a consequence of solar-wind interaction with remanent crustal magnetization on the Moon. A variety of plasma and field perturbations have been observed in a vicinity of the lunar magnetic anomalies, including electron energization, ion reflection/deflection, magnetic field enhancements, electrostatic and electromagnetic wave activities, and low-altitude ion deceleration and electron acceleration. Recent Chandrayaan-1 observations of the backscattered energetic neutral atoms (ENAs) from the Moon in the solar wind revealed upward ENA flux depletion (and thus depletion of the proton flux impinging on the lunar surface) in association with strongly magnetized regions. These ENA observations demonstrate that the lunar surface is shielded from the solar wind protons by the crustal magnetic fields. On the other hand, when the Moon was located in the Earth's plasma sheet, no significant depletion of the backscattered ENA flux was observed above the large and strong magnetic anomaly. It suggests less effective magnetic shielding of the surface from the plasma sheet protons than from the solar wind protons. We conduct test-particle simulations showing that protons with a broad velocity distribution are more likely to reach a strongly magnetized surface than those with a beam-like velocity distribution. The ENA observations together with the simulation results suggest that the lunar crustal magnetic fields are no longer capable of standing off the ambient plasma when the Moon is immersed in the hot magnetospheric plasma.
Physicochemical processes in the indirect interaction between surface air plasma and deionized water

NASA Astrophysics Data System (ADS)

Liu, Z. C.; Liu, D. X.; Chen, C.; Li, D.; Yang, A. J.; Rong, M. Z.; Chen, H. L.; Kong, M. G.

2015-12-01

One of the most central scientific questions for plasma applications in healthcare and environmental remediation is the chemical identity and the dose profile of plasma-induced reactive oxygen and nitrogen species (ROS/RNS) that can act on an object inside a liquid. A logical focus is on aqueous physicochemical processes near a sample with a direct link to their upstream gaseous processes in the plasma region and a separation gap from the liquid bulk. Here, a system-level modeling framework is developed for indirect interactions of surface air plasma and a deionized water bulk and its predictions are found to be in good agreement with the measurement of gas-phase ozone and aqueous long-living ROS/RNS concentrations. The plasma region is described with a global model, whereas the air gap and the liquid region are simulated with a 1D fluid model. All three regions are treated as one integrated entity and computed simultaneously. With experimental validation, the system-level modeling shows that the dominant aqueous ROS/RNS are long-living species (e.g. H2O2 aq, O3 aq, nitrite/nitrate, H+ aq). While most short-living gaseous species could hardly survive their passage to the liquid, aqueous short-living ROS/RNS are generated in situ through reactions among long-living plasma species and with water molecules. This plasma-mediated remote production of aqueous ROS/RNS is important for the abundance of aqueous HO2 aq, HO3 aq, OHaq and \\text{O}2- aq as well as NO2 aq and NO3 aq. Aqueous plasma chemistry offers a novel and significant pathway to activate a given biological outcome, as exemplified here for bacterial deactivation in plasma-activated water. Additional factors that may synergistically broaden the usefulness of aqueous plasma chemistry include an electric field by aqueous ions and liquid acidification. The system-modeling framework will be useful in assisting designs and analyses of future investigations of plasma-liquid and plasma-cell interactions.
Low-Temperature Silicon Epitaxy by Remote, Plasma - Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Habermehl, Scott Dwight

The dynamics of low temperature Si homoepitaxial and heteroepitaxial growth, by remote plasma enhanced chemical vapor deposition, RPECVD, have been investigated. For the critical step of pre-deposition surface preparation of Si(100) surfaces, the attributes of remote plasma generated atomic H are compared to results obtained with a rapid thermal desorption, RTD, technique and a hybrid H-plasma/RTD technique. Auger electron spectroscopy, AES, and electron diffraction analysis indicate the hybrid technique to be very effective at surface passivation, while the RTD process promotes the formation of SiC precipitates, which induce defective epitaxial growth. For GaP and GaAs substrates, the use of atomic H exposure is investigated as a surface passivation technique. AES shows this technique to be effective at producing atomically clean surfaces. For processing at 400^circrm C, the GaAs(100) surface is observed to reconstruct to a c(8 x 2)Ga symmetry while, at 530^ circrm C the vicinal GaP(100) surface, miscut 10^circ , is observed to reconstruct to a (1 x n) type symmetry; an unreconstructed (1 x 1) symmetry is observed for GaP(111). Differences in the efficiency with which native oxides are removed from the surface are attributed to variations in the local atomic bonding order of group V oxides. The microstructure of homoepitaxial Si films, deposited at temperatures of 25-450^circ rm C and pressures of 50-500 mTorr, is catalogued. Optimized conditions for the deposition of low defect, single crystal films are identified. The existence of two pressure dependent regimes for process activation are observed. In-situ mass spectral analysis indicates that the plasma afterglow is dominated by monosilane ions below 200 mTorr, while above 200 mTorr, low mass rm H_{x} ^+ (x = 1,2,3) and rm HHe^+ ions dominate. Consideration of the growth rate data indicates that downstream dissociative silane ionization, in the lower pressure regime, is responsible for an enhanced surface H abstraction rate. The observed increase in growth rate is concluded to be a manifestation of increased deposition site activation, resulting from the enhanced H abstraction mechanism. Secondary ion mass spectrometry measurements, of H incorporation in the Si films, yield an "effective" activation energy for the abstraction of surface H. A shift in the activation energy between 50 mTorr (0.7 eV) and 500 mTorr (0.3 eV) supports the conclusions for an ion-induced H abstraction mechanism. From this, a chemical sputtering reaction is proposed, whereby impinging ions react with chemisorbed H to form volatile species. Heteroepitaxial Si thin films are deposited upon GaP and GaAs surfaces. AES is used to evaluate the growth mode of Si on GaP(111) and vicinal GaP(100). In both instances, the data indicates a modified layer-plus-island growth mechanism, with possible interfacial alloy mixing. High quality epitaxial growth is observed to proceed on vicinal GaP(100) surfaces beyond the predicted critical thickness for strain relief of 140 A. For GaP(111), defective structures are observed well below the predicted critical thickness. This discrepancy is attributed to low precursor surface diffusion kinetics that are accommodated by the presence of steps on the vicinal surface. For deposition of Si on GaAs(100), disordered structure is observed within the first few monolayers of growth, which is in agreement with the predicted critical thickness for this system of approximately 10 A.
ADAMTS-13 rapidly cleaves newly secreted ultralarge von Willebrand factor multimers on the endothelial surface under flowing conditions.

PubMed

Dong, Jing-fei; Moake, Joel L; Nolasco, Leticia; Bernardo, Aubrey; Arceneaux, Wendy; Shrimpton, Corie N; Schade, Alicia J; McIntire, Larry V; Fujikawa, Kazuo; López, José A

2002-12-01

Thrombotic thrombocytopenic purpura (TTP) is a devastating thrombotic disorder caused by widespread microvascular thrombi composed of platelets and von Willebrand factor (VWF). The disorder is associated with a deficiency of the VWF-cleaving metalloprotease, ADAMTS-13, with consequent accumulation of ultralarge (UL) VWF multimers in the plasma. ULVWF multimers, unlike plasma forms of VWF, attach spontaneously to platelet GP Ibalpha, a component of the GP Ib-IX-V complex. We have found that ULVWF multimers secreted from stimulated endothelial cells (ECs) remained anchored to the endothelial surface where platelets and Chinese hamster ovary cells expressing the GP Ib-IX-V complex attached to form long beads-on-a-string structures in the presence of fluid shear stresses in both the venous (2.5 dyne/cm(2)) and arterial (20 and 50 dyne/cm(2)) ranges. Although measurement of the activity of the ADAMTS-13 VWF-cleaving metalloprotease in vitro requires prolonged incubation of the enzyme with VWF under nonphysiologic conditions, EC-derived ULVWF strings with attached platelets were cleaved within seconds to minutes in the presence of normal plasma (containing approximately 100% ADAMTS-13 activity) or in the presence of partially purified ADAMTS-13. By contrast, the strings persisted for the entire period of perfusion (10 minutes) in the presence of plasma from patients with TTP containing 0% to 10% ADAMTS-13 activity. These results suggest that cleavage of EC-derived ULVWF multimers by ADAMTS-13 is a rapid physiologic process that occurs on endothelial cell surfaces.
Oxygen reduction reaction properties of nitrogen-incorporated nanographenes synthesized using in-liquid plasma from mixture of ethanol and iron phthalocyanine

NASA Astrophysics Data System (ADS)

Amano, Tomoki; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

2018-04-01

Nanographenes were synthesized using in-liquid plasma from a mixture of iron phthalocyanine and ethanol. In a previous study, micrometer-scale flakes with nitrogen incorporation were obtained. A nonprecious metal catalytic activity was observed with 3.13 electrons in an oxygen reduction reaction under an acidic solute condition. Large-surface-area, high-graphene-crystallinity, and iron-carbon-bonding sites were found owing to a high catalytic activity in Fe-N/nanographene.

The type II cGMP dependent protein kinase regulates GluA1 levels at the plasma membrane of developing cerebellar granule cells

PubMed Central

Incontro, Salvatore; Ciruela, Francisco; Ziff, Edward; Hofmann, Franz; Sánchez-Prieto, José; Torres, Magdalena

2014-01-01

Trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is regulated by specific interactions with other proteins and by post-translational mechanisms, such as phosphorylation. We have found that the type II cGMP-dependent protein kinase (cGKII) phosphorylates GluA1 (formerly GluR1) at S845, augmenting the surface expression of AMPARs at both synaptic and extrasynaptic sites. Activation of cGKII by 8-Br-cGMP enhances the surface expression of GluA1, whereas its inhibition or suppression effectively diminished the expression of this protein at the cell surface. In granule cells, NMDA receptor activation (NMDAR) stimulates nitric oxide and cGMP production, which in turn activates cGKII and induces the phosphorylation of GluA1, promoting its accumulation in the plasma membrane. GluA1 is mainly incorporated into calcium permeable AMPARs as exposure to 8-Br-cGMP or NMDA activation enhanced AMPA-elicited calcium responses that are sensitive to NASPM inhibition. We summarize evidence for an increase of calcium permeable AMPA receptors downstream of NMDA receptor activation that might be relevant for granule cell development and plasticity. PMID:23545413
Characterization of the ribonuclease activity on the skin surface

PubMed Central

Probst, Jochen; Brechtel, Sonja; Scheel, Birgit; Hoerr, Ingmar; Jung, Günther; Rammensee, Hans-Georg; Pascolo, Steve

2006-01-01

The rapid degradation of ribonucleic acids (RNA) by ubiquitous ribonucleases limits the efficacy of new therapies based on RNA molecules. Therefore, our aim was to characterize the natural ribonuclease activities on the skin and in blood plasma i.e. at sites where many drugs in development are applied. On the skin surfaces of Homo sapiens and Mus musculus we observed dominant pyrimidine-specific ribonuclease activity. This activity is not prevented by a cap structure at the 5'-end of messenger RNA (mRNA) and is not primarily of a 5'- or 3'-exonuclease type. Moreover, the ribonuclease activity on the skin or in blood plasma is not inhibited by chemical modifications introduced at the 2'OH group of cytidine or uridine residues. It is, however, inhibited by the ribonuclease inhibitor RNasin® although not by the ribonuclease inhibitor SUPERase· In™. The application of our findings in the field of medical science may result in an improved efficiency of RNA-based therapies that are currently in development. PMID:16732888
FAST TRACK COMMUNICATION: Plasma agents in bio-decontamination by dc discharges in atmospheric air

NASA Astrophysics Data System (ADS)

Machala, Zdenko; Chládeková, Lenka; Pelach, Michal

2010-06-01

Bio-decontamination of water and surfaces contaminated by bacteria (Salmonella typhimurium) was investigated in two types of positive dc discharges in atmospheric pressure air, in needle-to-plane geometry: the streamer corona and its transition to a novel regime called transient spark with short high current pulses of limited energy. Both generate a cold non-equilibrium plasma. Electro-spraying of treated water through a needle electrode was applied for the first time and resulted in fast bio-decontamination. Experiments providing separation of various biocidal plasma agents, along with the emission spectra and coupled with oxidation stress measurements in the cell membranes helped to better understand the mechanisms of microbial inactivation. The indirect exposure of contaminated surfaces to neutral active species was almost as efficient as the direct exposure to the plasma, whereas applying only UV radiation from the plasma had no biocidal effects. Radicals and reactive oxygen species were identified as dominant biocidal agents.
Space Technology Plasma Issues in 2001

NASA Technical Reports Server (NTRS)

Garrett, Henry (Editor); Feynman, Joan (Editor); Gabriel, Stephen (Editor)

1986-01-01

The purpose of the workshop was to identify and discuss plasma issues that need to be resolved during the next 10 to 20 years (circa 2001) to facilitate the development of the advanced space technology that will be required 20 or 30 years into the future. The workshop consisted of 2 days of invited papers and 2 sessions of contributed poster papers. During the third day the meeting broke into 5 working groups, each of which held discussions and then reported back to the conference as a whole. The five panels were: Measurements Technology and Active Experiments Working Group; Advanced High-Voltage, High-Power and Energy-Storage Space Systems Working Group; Large Structures and Tethers Working Group; Plasma Interactions and Surface/Materials Effects Working Group; and Beam Plasmas, Electronic Propulsion and Active Experiments Using Beams Working Group.
Hydrophobic Surface Modification of Silk Fabric Using Plasma-Polymerized Hmdso

NASA Astrophysics Data System (ADS)

Rani, K. Vinisha; Chandwani, Nisha; Kikani, Purvi; Nema, S. K.; Sarma, Arun Kumar; Sarma, Bornali

In this work, we study the hydrophobic properties of silk fabrics by deposition of plasma-polymerized (pp) hexamethyldisiloxane (HMDSO) using low-pressure plasma-enhanced chemical vapor deposition. Recently, hydrophobic properties are under active research in textile industry. The effects of coating time and power on the HMDSO-coated silk fabrics are investigated. Water contact angle of pp-HMDSO-coated silk fabric surface is measured as a function of power and coating time. Fabric surface shows an enhancement in hydrophobicity after coating. Attenuated total reflectance-Fourier transform infrared spectroscopy reveals the surface chemistry, and scanning electron microscopy shows the surface morphology of the uncoated and HMDSO-coated fabrics, respectively. In the case of uncoated fabric, water droplet absorbs swiftly, whereas in the case of HMDSO-coated fabric, water droplet remains on the fabric surface with a maximum contact angle of 140∘. The HMDSO-deposited silk surface is found to be durable after detergent washing. Common stains such as ink, tea, milk, turmeric and orange juice are tested on the surface of both fabrics. In HMDSO-coated fabrics, all the stains are bedded like ball droplet. In order to study the self-cleaning property, the fabric is tilted to 45∘ angle; stain droplets easily roll off from the fabric.
Investigation of surface endothelialization on biomedical nitinol (NiTi) alloy: Effects of surface micropatterning combined with plasma nanocoatings.

PubMed

Shen, Yang; Wang, Guixue; Chen, Liang; Li, Hao; Yu, Ping; Bai, Mengjun; Zhang, Qin; Lee, James; Yu, Qingsong

2009-11-01

Plasma nanocoated films with trimethylsilane-oxygen monomers showed outstanding biocompatibility in our previous studies. In this study, endothelialization on biomedical nitinol alloy surfaces was systematically investigated. Our study focuses on elucidating the effects of surface micropatternings with micropores and microgrooves combined with plasma nanocoating. Plasma nanocoatings with controlled thickness between 40 and 50 nm were deposited onto micropatterned nitinol surface in a direct current plasma reactor. Bovine aortic endothelial cells were cultured in vitro on these nitinol samples for 1, 3 and 5 days. It was found that rougher surfaces could enhance cell adhesion compared with the smoother surfaces; the surfaces patterned with micropores showed much more endothelialization than microgrooved surface after a 3 days culture. The cell culture results also showed that plasma nanocoatings significantly further increased cell proliferation and cell adhesion on the micropatterned nitinol surfaces, as compared with non-plasma nanocoated surface of nitinol samples. The surface micropatternings combined with plasma nanocoatings could improve the cell adhesion and accelerate surface endothelialization after implantation of intravascular stents, which is expected to reduce in-stent restenosis.
Research of Adhesion Bonds Between Gas-Thermal Coating and Pre-Modified Base

NASA Astrophysics Data System (ADS)

Kovalevskaya, Z.; Zaitsev, K.; Klimenov, V.

2016-08-01

Nature of adhesive bonds between gas-thermal nickel alloy coating and carbon steel base was examined using laser profilometry, optical metallography, transmission and scanning electron microscopy. The steel surface was plastically pre-deformed by an ultrasonic tool. Proved that ultrasound pre-treatment modifies the steel surface. Increase of dislocation density and formation of sub micro-structure are base elements of surface modification. While using high-speed gas-flame, plasma and detonation modes of coatings, surface activation occurs and durable adhesion is formed. Ultrasonic pre-treatment of base material is effective when sprayed particles and base material interact through physical-chemical bond formation. Before applying high-speed gas flame and plasma sprayed coatings, authors recommend ultrasonic pretreatment, which creates periodic wavy topography with a stroke of 250 microns on the steel surface. Before applying detonation sprayed coatings, authors recommend ultrasound pretreatment that create modified surface with a uniform micro-topography.
Improvement and mechanism of interfacial adhesion in PBO fiber/bismaleimide composite by oxygen plasma treatment

NASA Astrophysics Data System (ADS)

Liu, Dong; Chen, Ping; Mu, Jujie; Yu, Qi; Lu, Chun

2011-05-01

The improved interfacial adhesion of PBO fiber-reinforced bismaleimide composite by oxygen plasma processing was investigated in this paper. After treatment, the maximum value of interlaminar shear strength was 57.5 MPa, with an increase of 28.9%. The oxygen concentration of the fiber surface increased, as did the surface roughness, resulting in improvement of the surface wettability. The cleavage and rearrangement of surface bonds created new functional groups O dbnd C sbnd O, N sbnd C dbnd O and N sbnd O, thereby activating the fiber surface. And long-time treatment increased the reaction degree of surface groups while destroyed the newly-created physical structures. The enhancement of adhesion relied primarily on the strengthening of chemical bonding and mechanical interlocking between the fiber and the matrix. The composite rupture planes indicated that the fracture failure shifted from the interface to the matrix or the fiber.
In situ plasma fabrication of ceramic-like structure on polymeric implant with enhanced surface hardness, cytocompatibility and antibacterial capability.

PubMed

Liu, Jun; Zhang, Wei; Shi, Haigang; Yang, Kun; Wang, Gexia; Wang, Pingli; Ji, Junhui; Chu, Paul K

2016-05-01

Polymeric materials are commonly found in orthopedic implants due to their unique mechanical properties and biocompatibility but the poor surface hardness and bacterial infection hamper many biomedical applications. In this study, a ceramic-like surface structure doped with silver is produced by successive plasma implantation of silicon (Si) and silver (Ag) into the polyamine 66 (PA66) substrate. Not only the surface hardness and elastic modulus are greatly enhanced due to the partial surface carbonization and the ceramic-like structure produced by the reaction between energetic Si and the carbon chain of PA66, but also the antibacterial activity is improved because of the combined effects rendered by Ag and SiC structure. Furthermore, the modified materials which exhibit good cytocompatibility upregulate bone-related genes and proteins expressions of the contacted bone mesenchymal stem cells (BMSCs). For the first time, it explores out that BMSCs osteogenesis on the antibacterial ceramic-like structure is mediated via the iNOS and nNOS signal pathways. The results reveal that in situ plasma fabrication of an antibacterial ceramic-like structure can endow PA66 with excellent surface hardness, cytocompatibility, as well as antibacterial capability. © 2016 Wiley Periodicals, Inc.
Surface Penetrating Radar Simulations for Europa

NASA Technical Reports Server (NTRS)

Markus, T.; Gogineni, S. P.; Green, J. L.; Fung, S. F.; Cooper, J. F.; Taylor, W. W. L.; Garcia, L.; Reinisch, B. W.; Song, P.; Benson, R. F.

2004-01-01

The space environment above the icy surface of Europa is a source of radio noise in this frequency range from natural sources in the Jovian magnetosphere. The ionospheric and magnetospheric plasma environment of Europa affects propagation of transmitted and return signals between the spacecraft and the solid surface in a frequency-dependent manner. The ultimate resolution of the subsurface sounding measurements will be determined, in part, by a capability to mitigate these effects. We discuss an integrated multi-frequency approach to active radio sounding of the Europa ionospheric and local magnetospheric environments, based on operational experience from the Radio Plasma Imaging @PI) experiment on the IMAGE spacecraft in Earth orbit, in support of the subsurface measurement objectives.
One-step microwave plasma enhanced chemical vapor deposition (MW-PECVD) for transparent superhydrophobic surface

NASA Astrophysics Data System (ADS)

Thongrom, Sukrit; Tirawanichakul, Yutthana; Munsit, Nantakan; Deangngam, Chalongrat

2018-02-01

We demonstrate a rapid and environmental friendly fabrication technique to produce optically clear superhydrophobic surfaces using poly (dimethylsiloxane) (PDMS) as a sole coating material. The inert PDMS chain is transformed into a 3-D irregular solid network through microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. Thanks to high electron density in the microwave-activated plasma, coating can be done in just a single step with rapid deposition rate, typically much shorter than 10 s. Deposited layers show excellent superhydrophobic properties with water contact angles of ∼170° and roll-off angles as small as ∼3°. The plasma-deposited films can be ultrathin with thicknesses under 400 nm, greatly diminishing the optical loss. Moreover, with appropriate coating conditions, the coating layer can even enhance the transmission over the entire visible spectrum due to a partial anti-reflection effect.
Synchronous oscillation prior to disruption caused by kink modes in HL-2A tokamak plasmas

NASA Astrophysics Data System (ADS)

Jiang, M.; Hu, D.; Wang, X. G.; Shi, Z. B.; Xu, Y.; Chen, W.; Ding, X. T.; Zhong, W. L.; Dong, Y. B.; Ji, X. Q.; Zhang, Y. P.; Gao, J. M.; Li, J. X.; Yang, Z. C.; Li, Y. G.; Liu, Y.

2015-08-01

A class of evident MHD activities prior to major disruption has been observed during recent radiation induced disruptions of the HL-2A tokamak discharges. It can be named SOD, synchronous oscillations prior to disruption, characterized by synchronous oscillation of electron cyclotron emission (ECE), core soft x-ray, Mirnov coil, and {{D}α} radiation signals at the divertor plate. The SOD activity is mostly observed in a parametric regime where the poloidal beta is low enough before disruption, typically corresponding to those radiation-induced disruptions. It has been found that the m/n = 2/1 mode is dominant during the SODs, and consequently it is the drop of the mode frequency and the final mode locking that lead to thermal quench. The mode frequency before the mode locking corresponds to the toroidal rotation frequency of the edge plasma. It is also found that during SODs, the location of the q = 2 surface is moving outward, and most of the plasma current is enclosed within the surface. This demonstrates that the current channel lies inside the rational surface during SOD, and thus the resistive kink mode is unstable. Further analysis of the electron temperature perturbation structure shows that the plasma is indeed dominated by the resistive kink mode, with kink-like perturbation in the core plasma region. It suggests that it is the nonlinear growth of the m/n = 2/1 resistive kink mode and its higher order harmonics, rather than the spontaneous overlapping of multiple neighboring islands, that ultimately triggered the disruption.
Investigations of nitrogen oxide plasmas: Fundamental chemistry and surface reactivity and monitoring student perceptions in a general chemistry recitation

NASA Astrophysics Data System (ADS)

Blechle, Joshua M.

Part I of this dissertation focuses on investigations of nitrogen oxide plasma systems. With increasing concerns over the environmental presence of NxOy species, there is growing interest in utilizing plasma-assisted conversion techniques. Advances, however, have been limited because of the lack of knowledge regarding the fundamental chemistry of these plasma systems. Understanding the kinetics and thermodynamics of processes in these systems is vital to realizing their potential in a range of applications. Unraveling the complex chemical nature of these systems, however, presents numerous challenges. As such, this work serves as a foundational step in the diagnostics and assessment of these NxOy plasmas. The partitioning of energy within the plasma system is essential to unraveling these complications as it provides insight into both gas and surface reactivity. To obtain this information, techniques such as optical emission spectroscopy (OES), broadband absorption spectroscopy (BAS), and laser induced fluorescence (LIF) were utilized to determine species energetics (vibrational, rotational, translational temperatures). These temperature data provide mechanistic insight and establish the relationships between system parameters and energetic outcomes. Additionally, these data are also correlated to surface reactivity data collected with the Imaging of Radicals Interacting with Surfaces (IRIS) technique. IRIS data demonstrate the relationship between internal temperatures of radicals and their observed surface scatter coefficients (S), the latter of which is directly related to surface reactivity (R) [R = 1-S]. Furthermore, time-resolved (TR) spectroscopic techniques, specifically TR-OES, revealed kinetic trends in NO and N2 formation from a range of precursors (NO, N2O, N2/O2). By examining the rate constants associated with the generation and destruction of various plasma species we can investigate possible mechanistic implications. All told, such data provides unparalleled insight into the chemistry of these plasma systems. Part II of this work is focused on understanding the efficacy of a general chemistry recitation program. Such programs can be an valuable tool for improving students' problem solving skills and understanding using methods that are difficult to implement in large lecture settings. Here, general chemistry students at Colorado State University participated in a variety of recitation activities throughout the first semester of a 2-semester general chemistry sequence, including peer-led exercises, games, and scaffolded worksheets. Through weekly surveys, students were asked to evaluate and assess recitation activities for both interest and effectiveness as part of their course homework. Also included in these survey assignments were content questions relevant to the weekly themes, providing a measure of student learning of recitation topics. Student opinions were correlated with content retention, and these data were compared against student responses to a pre-survey administered before the first recitation session. This analysis allows for monitoring students' expectations of recitation courses and how well those expectations are met through the various types of activities employed. Ultimately, this work has found that students have positive feeling with respect to individual assignments, but that perspectives on chemistry and the course in general decrease dramatically from the beginning to the end of the semester. Thus, this work can serve as a significant starting points for future efforts to monitor and record student perceptions in the general chemistry recitation classroom, leading to further investigation into the source of changing attitudes and the role that week-to-week activities have on global course attitudes.
Activation of cell-surface proteases promotes necroptosis, inflammation and cell migration.

PubMed

Cai, Zhenyu; Zhang, Anling; Choksi, Swati; Li, Weihua; Li, Tao; Zhang, Xue-Min; Liu, Zheng-Gang

2016-08-01

Necroptosis is a programmed, caspase-independent cell death that is morphologically similar to necrosis. TNF-induced necroptosis is mediated by receptor-interacting protein kinases, RIP1 and RIP3, and the mixed lineage kinase domain-like (MLKL). After being phosphorylated by RIP3, MLKL is translocated to the plasma membrane and mediates necroptosis. However, the execution of necroptosis and its role in inflammation and other cellular responses remain largely elusive. In this study, we report that MLKL-mediated activation of cell-surface proteases of the a disintegrin and metalloprotease (ADAM) family promotes necroptosis, inflammation and cell migration. ADAMs are specifically activated at the early stage of necroptosis when MLKL is phosphorylated and translocated to the cell plasma membrane. Activation of ADAMs induces ectodomain shedding of diverse cell-surface proteins including adhesion molecules, receptors, growth factors and cytokines. Importantly, the shedding of cell-surface proteins disrupts cell adhesion and accelerates necroptosis, while the soluble fragments of the cleaved proteins trigger the inflammatory responses. We also demonstrate that the shedding of E-cadherin ectodomain from necroptotic cells promotes cell migration. Thus, our study provides a novel mechanism of necroptosis-induced inflammation and new insights into the physiological and pathological functions of this unique form of cell death.
Activation of cell-surface proteases promotes necroptosis, inflammation and cell migration

PubMed Central

Cai, Zhenyu; Zhang, Anling; Choksi, Swati; Li, Weihua; Li, Tao; Zhang, Xue-Min; Liu, Zheng-Gang

2016-01-01

Necroptosis is a programmed, caspase-independent cell death that is morphologically similar to necrosis. TNF-induced necroptosis is mediated by receptor-interacting protein kinases, RIP1 and RIP3, and the mixed lineage kinase domain-like (MLKL). After being phosphorylated by RIP3, MLKL is translocated to the plasma membrane and mediates necroptosis. However, the execution of necroptosis and its role in inflammation and other cellular responses remain largely elusive. In this study, we report that MLKL-mediated activation of cell-surface proteases of the a disintegrin and metalloprotease (ADAM) family promotes necroptosis, inflammation and cell migration. ADAMs are specifically activated at the early stage of necroptosis when MLKL is phosphorylated and translocated to the cell plasma membrane. Activation of ADAMs induces ectodomain shedding of diverse cell-surface proteins including adhesion molecules, receptors, growth factors and cytokines. Importantly, the shedding of cell-surface proteins disrupts cell adhesion and accelerates necroptosis, while the soluble fragments of the cleaved proteins trigger the inflammatory responses. We also demonstrate that the shedding of E-cadherin ectodomain from necroptotic cells promotes cell migration. Thus, our study provides a novel mechanism of necroptosis-induced inflammation and new insights into the physiological and pathological functions of this unique form of cell death. PMID:27444869
Correlation of membrane binding and hydrophobicity to the chaperone-like activity of PDC-109, the major protein of bovine seminal plasma.

PubMed

Sankhala, Rajeshwer S; Damai, Rajani S; Swamy, Musti J

2011-03-08

The major protein of bovine seminal plasma, PDC-109 binds to choline phospholipids present on the sperm plasma membrane upon ejaculation and plays a crucial role in the subsequent events leading to fertilization. PDC-109 also shares significant similarities with small heat shock proteins and exhibits chaperone-like activity (CLA). Although the polydisperse nature of this protein has been shown to be important for its CLA, knowledge of other factors responsible for such an activity is scarce. Since surface exposure of hydrophobic residues is known to be an important factor which modulates the CLA of chaperone proteins, in the present study we have probed the surface hydrophobicity of PDC-109 using bisANS and ANS. Further, effect of phospholipids on the structure and chaperone-like activity of PDC-109 was studied. Presence of DMPC was found to increase the CLA of PDC-109 significantly, which could be due to the considerable exposure of hydrophobic regions on the lipid-protein recombinants, which can interact productively with the nonnative structures of target proteins, resulting in their protection. However, inclusion of DMPG instead of DMPC did not significantly alter the CLA of PDC-109, which could be due to the lower specificity of PDC-109 for DMPG as compared to DMPC. Cholesterol incorporation into DMPC membranes led to a decrease in the CLA of PDC-109-lipid recombinants, which could be attributed to reduced accessibility of hydrophobic surfaces to the substrate protein(s). These results underscore the relevance of phospholipid binding and hydrophobicity to the chaperone-like activity of PDC-109.
Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

NASA Technical Reports Server (NTRS)

Cooper, John F.; Hill, Matthew E.; Richardson, John D.; Sturner, Steven J.

2010-01-01

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.
Kinetically controlled indium surface coverage effects on PAMBE-growth of InN/GaN(0001) quantum well structures

NASA Astrophysics Data System (ADS)

Li, Chen; Maidaniuk, Yurii; Kuchuk, Andrian V.; Shetty, Satish; Ghosh, Pijush; White, Thomas P.; Morgan, Timothy Al.; Hu, Xian; Wu, Yang; Ware, Morgan E.; Mazur, Yuriy I.; Salamo, Gregory J.

2018-05-01

We report the effects of nitrogen (N) plasma and indium (In) flux on the In adatom adsorption/desorption kinetics on a GaN(0001) surface at the relatively high plasma-assisted molecular beam epitaxy-growth temperature of 680 °C. We experimentally demonstrate that under an active N flux, the (√{3 }×√{3 })R 30 ° surface reconstruction containing In and N quickly appears and the dynamically stable In adlayers sitting on this surface exhibit a continuous change from 0 to 2 MLs as a function of In flux. Compared to the bare GaN 1 ×1 surface which is stable during In exposure without an active N flux, we observed a much faster desorption for the bottom In adlayer and the absence of an In flux window corresponding to an In coverage of 1 ML. Moreover, when the In coverage exceeds 2 MLs, the desorption rates become identical for both surfaces. Finally, the importance of In surface coverage before GaN capping was shown by growing a series of InN/GaN multiple quantum well samples. The photoluminescence data show that a consistent quantum well structure is only formed if the surface is covered by excess In droplets before GaN capping.
Oxidation of limonene using activated carbon modified in dielectric barrier discharge plasma

NASA Astrophysics Data System (ADS)

Glonek, Karolina; Wróblewska, Agnieszka; Makuch, Edyta; Ulejczyk, Bogdan; Krawczyk, Krzysztof; Wróbel, Rafał. J.; Koren, Zvi C.; Michalkiewicz, Beata

2017-10-01

The waste from industrial fruits processing is utilized for the extraction of limonene, a renewable terpene biomass compound obtained from orange peels. This was followed by limonene oxidation, which produces highly useful oxygenated derivatives (carveol, and perillyl alcohol, 1,2-epoxylimonene and its diol). New catalysts were obtained by treating relatively inexpensive commercially available EuroPh and FPV activated carbons with plasma. These catalysts were characterized by the following instrumental methods XRD, sorption of N2 and CO2, SEM, EDS, TEM, XPS, and Raman spectroscopy. The activities of the plasma-treated catalysts were measured in the oxidation of limonene by means of either hydrogen peroxide or t-butyl hydroperoxide as the oxidizing agents. During the oxidation with hydrogen peroxide the new plasma-treated catalysts were more active than their untreated counterparts. This effect was noticeable in the considerable increase in the conversion of limonene. The mechanism explaining this property is proposed, and it takes into account the role of the appropriate functional groups on the surface of the catalysts. This work has shown for the first time that the commercial EuroPh and FPV activated carbons, after having been treated by plasma, are active catalysts for the selective limonene oxidation for the production of value-added industrial products.
Verotoxin and neuraminidase induced platelet aggregating activity in plasma: their possible role in the pathogenesis of the haemolytic uraemic syndrome.

PubMed Central

Rose, P E; Armour, J A; Williams, C E; Hill, F G

1985-01-01

Certain strains of Escherichia coli producing verotoxin have been isolated in the stools of patients with the haemolytic uraemic syndrome. A platelet aggregating activity has been found in normal plasma after incubation with verotoxin at 37 degrees C for 24 h. This activity, unlike neuraminidase, has an effect that is independent of changing factor VIII related antigen, but requires the IIA and IIIB platelet surface glycoprotein (deficient in thrombasthenia) to mediate its effect. Prostacyclin totally inhibited this effect, but other antiplatelet drugs and heparin were without inhibitory effects. PMID:2859303

Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators

NASA Technical Reports Server (NTRS)

Hoskinson, Alan R.

2012-01-01

This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.
Modulation of release kinetics by plasma polymerization of ampicillin-loaded β-TCP ceramics

NASA Astrophysics Data System (ADS)

Labay, C.; Buxadera-Palomero, J.; Avilés, M.; Canal, C.; Ginebra, M. P.

2016-08-01

Beta-tricalcium phosphate (β-TCP) bioceramics are employed in bone repair surgery. Their local implantation in bone defects puts them in the limelight as potential materials for local drug delivery. However, obtaining suitable release patterns fitting the required therapeutics is a challenge. Here, plasma polymerization of ampicillin-loaded β-TCP is studied for the design of a novel antibiotic delivery system. Polyethylene glycol-like (PEG-like) coating of β-TCP by low pressure plasma polymerization was performed using diglyme as precursor, and nanometric PEG-like layers were obtained by simple and double plasma polymerization processes. A significant increase in hydrophobicity, and the presence of plasma polymer was visible on the surface by SEM and quantified by XPS. As a main consequence of the plasma polymerisation, the release kinetics were successfully modified, avoiding burst release, and slowing down the initial rate of release leading to a 4.5 h delay in reaching the same antibiotic release percentage, whilst conservation of the activity of the antibiotic was simultaneously maintained. Thus, plasma polymerisation on the surface of bioceramics may be a good strategy to design controlled drug delivery matrices for local bone therapies.
Preparation of active antibacterial LDPE surface through multistep physicochemical approach II: graft type effect on antibacterial properties.

PubMed

Bílek, František; Sulovská, Kateřina; Lehocký, Marián; Sáha, Petr; Humpolíček, Petr; Mozetič, Miran; Junkar, Ita

2013-02-01

Three monomers (allylamine, N-allylmethylamine and N,N-dimethylallylamine) were used for grafting onto air plasma activated LDPE surface. Antibacterial agent triclosan was anchored on such substrates. Influence of graft type on the antibacterial properties was determined. Increase of antibacterial activity and amount of deposited antibacterial agent for N-allylmethylamine and N,N-dimethylallylamine monomers were examined. Surface characteristics were measured by means of static contact angle measurement with surface energy evaluation, ATR-FTIR spectroscopy, XPS and SEM characterization analysis. Antibacterial properties were tested in vitro by inhibition zone method on agar plates for Staphylococcus aureus and Escherichia coli strains. Copyright © 2012 Elsevier B.V. All rights reserved.
Densification kinetics of nanocrystalline zirconia powder using microwave and spark plasma sintering--a comparative study.

PubMed

Vasylkiv, Oleg; Demirskyi, Dmytro; Sakka, Yoshio; Ragulya, Andrey; Borodianska, Hanna

2012-06-01

Two-stage densification process of nanosized 3 mol% yttria-stabilized zirconia (3Y-SZ) polycrystalline compacts during consolidation via microwave and spark-plasma sintering have been observed. The values of activation energies obtained for microwave and spark-plasma sintering 260-275 kJ x mol(-1) are quite similar to that of conventional sintering of zirconia, suggesting that densification during initial stage is controlled by the grain-boundary diffusion mechanism. The sintering behavior during microwave sintering was significantly affected by preliminary pressing conditions, as the surface diffusion mechanism (230 kJ x mol(-1)) is active in case of cold-isostatic pressing procedure was applied.
Inhibition of the plasma SCUBE1, a novel platelet adhesive protein, protects mice against thrombosis.

PubMed

Wu, Meng-Ying; Lin, Yuh-Charn; Liao, Wei-Ju; Tu, Cheng-Fen; Chen, Ming-Huei; Roffler, Steve R; Yang, Ruey-Bing

2014-07-01

Signal peptide-CUB-EGF domain-containing protein 1 (SCUBE1), a secreted and surface-exposed glycoprotein on activated platelets, promotes platelet-platelet interaction and supports platelet-matrix adhesion. Its plasma level is a biomarker of platelet activation in acute thrombotic diseases. However, the exact roles of plasma SCUBE1 in vivo remain undefined. We generated new mutant (Δ) mice lacking the soluble but retaining the membrane-bound form of SCUBE1. Plasma SCUBE1-depleted Δ/Δ mice showed normal hematologic and coagulant features and expression of major platelet receptors, but Δ/Δ platelet-rich plasma showed impaired platelet aggregation in response to ADP and collagen treatment. The addition of purified recombinant SCUBE1 protein restored the aggregation of platelets in Δ/Δ platelet-rich plasma and further enhanced platelet aggregation in +/+ platelet-rich plasma. Plasma deficiency of SCUBE1 diminished arterial thrombosis in mice and protected against lethal thromboembolism induced by collagen-epinephrine treatment. Last, antibodies directed against the epidermal growth factor-like repeats of SCUBE1, which are involved in trans-homophilic protein-protein interactions, protected mice against fatal thromboembolism without causing bleeding in vivo. We conclude that plasma SCUBE1 participates in platelet aggregation by bridging adjacent activated platelets in thrombosis. Blockade of soluble SCUBE1 might represent a novel antithrombotic strategy. © 2014 American Heart Association, Inc.
Comparison of ONIX simulation results with experimental data from the BATMAN testbed for the study of negative ion extraction

NASA Astrophysics Data System (ADS)

Mochalskyy, Serhiy; Fantz, Ursel; Wünderlich, Dirk; Minea, Tiberiu

2016-10-01

The development of negative ion (NI) sources for the ITER neutral beam injector is strongly accompanied by modelling activities. The ONIX (Orsay Negative Ion eXtraction) code simulates the formation and extraction of negative hydrogen ions and co-extracted electrons produced in caesiated sources. In this paper the 3D geometry of the BATMAN extraction system, and the source characteristics such as the extraction and bias potential, and the 3D magnetic field were integrated in the model. Calculations were performed using plasma parameters experimentally obtained on BATMAN. The comparison of the ONIX calculated extracted NI density with the experimental results suggests that predictive calculations of the extraction of NIs are possible. The results show that for an ideal status of the Cs conditioning the extracted hydrogen NI current density could reach ~30 mA cm-2 at 10 kV and ~20 mA cm-2 at 5 kV extraction potential, with an electron/NI current density ratio of about 1, as measured in the experiments under the same plasma and source conditions. The dependency of the extracted NI current on the NI density in the bulk plasma region from both the modeling and the experiment was investigated. The separate distributions composing the NI beam originating from the plasma bulk region and the PG surface are presented for different NI plasma volume densities and NI emission rates from the plasma grid (PG) wall, respectively. The extracted current from the NIs produced at the Cs covered PG surface, initially moving towards the bulk plasma and then being bent towards the extraction surfaces, is lower compared to the extracted NI current from directly extracted surface produced ions.
Activation of peroxydisulfate by gas-liquid pulsed discharge plasma to enhance the degradation of p-nitrophenol

NASA Astrophysics Data System (ADS)

Shang, Kefeng; Wang, Hao; Li, Jie; Lu, Na; Jiang, Nan; Wu, Yan

2017-06-01

Pulsed discharge in water and over water surfaces generates ultraviolet radiation, local high temperature, shock waves, and chemical reactive species, including hydroxyl radicals, hydrogen peroxide, and ozone. Pulsed discharge plasma (PDP) can oxidize and mineralize pollutants very efficiently, but high energy consumption restricts its application for industrial wastewater treatment. A novel method for improving the energy efficiency of wastewater treatment by PDP was proposed, in which peroxydisulfate (PDS) was added to wastewater and PDS was activated by PDP to produce more strong oxidizing radicals, including sulfate radicals and hydroxyl radicals, leading to a higher oxidation capacity for the PDP system. The experimental results show that the increase in solution conductivity slightly decreased the discharge power of the pulse discharge over the water surface. An increase in the discharge intensity improved the activation of PDS and therefore the degradation efficiency and energy efficiency of p-nitrophenol (PNP). An increase in the addition dosage of PDS greatly facilitated the degradation of PNP at a molar ratio of PDS to PNP of lower than 80:1, but the performance enhancement was no longer obvious at a dosage of more than 80:1. Under an applied voltage of 20 kV and a gas discharge gap of 2 mm, the degradation efficiency and energy efficiency of the PNP reached 90.7% and 45.0 mg kWh-1 for the plasma/PDS system, respectively, which was 34% and 18.0 mg kWh-1 higher than for the discharge plasma treatment alone. Analysis of the physical and chemical effects indicated that ozone and hydrogen peroxide were important for PNP degradation and UV irradiation and heat from the discharge plasma might be the main physical effects for the activation of PDS.
The search for active Europa plumes in Galileo plasma particle detector data: the E12 flyby

NASA Astrophysics Data System (ADS)

Huybrighs, H.; Roussos, E.; Krupp, N.; Fraenz, M.; Futaana, Y.; Barabash, S. V.; Glassmeier, K. H.

2017-12-01

Hubble Space Telescope observations of Europa's auroral emissions and transits in front of Jupiter suggest that recurring water vapour plumes originating from Europa's surface might exist. If conclusively proven, the discovery of these plumes would be significant, because Europa's potentially habitable ocean could be studied remotely by taking in-situ samples of these plumes from a flyby mission. The first opportunity to collect in-situ evidence of the plumes will not arise before the early 2030's when ESA's JUICE mission or NASA's Europa Clipper are set to arrive. However, it may be possible that NASA's Galileo mission has already encountered the plumes when it was active in the Jupiter system from 1995 to 2003. It has been suggested that the high plasma densities and anomalous magnetic fields measured during one of the Galileo flybys of Europa (flyby E12) could be connected to plume activity. In the context of the search for Europa plume signatures in Galileo particle data we present an overview of the in-situ plasma particle data obtained by the Galileo spacecraft during the E12 flyby. Focus is in particular on the data obtained with the plasma particle instruments PLS (low energy ions and electrons) and EPD (high energy ions and electrons). We search for signs of an extended exosphere/ionosphere that could be consistent with ongoing plume activity. The PLS data obtained during the E12 flyby show an extended interaction region between Europa and the plasma from Jupiter's magnetosphere, hinting at the existence of an extended ionosphere and exosphere. Furthermore we show how the EPD data are analyzed and modelled in order to evaluate whether a series of energetic ion depletions can be attributed to losses on the moon's surface or its neutral exosphere.
Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition and Dynamics on Kuiper Belt and Oort Cloud Bodies

NASA Technical Reports Server (NTRS)

Cooper, John F.; Richardson, John D.

2010-01-01

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environment. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Cycles of atmospheric formation and surface freezeout can further account for temporal variation as observed on Pluto. The diversity of causative processes must therefore be understood to account for observationally apparent diversities of the object surfaces.
Surface fluorination of zirconia: adhesive bond strength comparison to commercial primers.

PubMed

Piascik, Jeffrey R; Swift, Edward J; Braswell, Krista; Stoner, Brian R

2012-06-01

This study evaluated contact angle and shear bond strength of three commercial zirconia primers and compared them to a recently developed fluorination pre-treatment. Earlier investigations reported that plasma fluorinated zirconia modifies the chemical bonding structure creating a more reactive surface. Yttria-stabilized zirconia (LAVA, 3M ESPE) plates were highly polished using 3μm diamond paste (R(a) ∼200nm) prior to pretreatments. After primer and fluorination treatment, contact angles were measured to quantify surface hydrophobicity before and after ethanol clean. Additionally, simple shear bond tests were performed to measure the adhesion strength to a composite resin. Plasma fluorination produced the lowest contact angle (7.8°) and the highest shear bond strength (37.3MPa) suggesting this pretreatment facilitates a more "chemically" active surface for adhesive bonding. It is hypothesized that plasma fluorination increase hydroxylation at the surface, making it more reactive, thus allowing for covalent bonding between zirconia surface and resin cement. A strong correlation was observed between contact angle and adhesion strength for all specimens; a relationship which may help understand the frequency and modes of failures, clinically. It is also believed that this surface treatment can increase long-term viability of zirconia restorations over other adhesive techniques. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
A comparative study for the inactivation of multidrug resistance bacteria using dielectric barrier discharge and nano-second pulsed plasma

PubMed Central

Hoon Park, Ji; Kumar, Naresh; Hoon Park, Dae; Yusupov, Maksudbek; Neyts, Erik C.; Verlackt, Christof C. W.; Bogaerts, Annemie; Ho Kang, Min; Sup Uhm, Han; Ha Choi, Eun; Attri, Pankaj

2015-01-01

Bacteria can be inactivated through various physical and chemical means, and these have always been the focus of extensive research. To further improve the methodology for these ends, two types of plasma systems were investigated: nano-second pulsed plasma (NPP) as liquid discharge plasma and an Argon gas-feeding dielectric barrier discharge (Ar-DBD) as a form of surface plasma. To understand the sterilizing action of these two different plasma sources, we performed experiments with Staphylococcus aureus (S. aureus) bacteria (wild type) and multidrug resistant bacteria (Penicillum-resistant, Methicillin-resistant and Gentamicin-resistant). We observed that both plasma sources can inactivate both the wild type and multidrug-resistant bacteria to a good extent. Moreover, we observed a change in the surface morphology, gene expression and β-lactamase activity. Furthermore, we used X-ray photoelectron spectroscopy to investigate the variation in functional groups (C-H/C-C, C-OH and C=O) of the peptidoglycan (PG) resulting from exposure to plasma species. To obtain atomic scale insight in the plasma-cell interactions and support our experimental observations, we have performed molecular dynamics simulations to study the effects of plasma species, such as OH, H2O2, O, O3, as well as O2 and H2O, on the dissociation/formation of above mentioned functional groups in PG. PMID:26351132
Surface analysis under ambient conditions using plasma-assisted desorption/ionization mass spectrometry.

PubMed

Ratcliffe, Lucy V; Rutten, Frank J M; Barrett, David A; Whitmore, Terry; Seymour, David; Greenwood, Claire; Aranda-Gonzalvo, Yolanda; Robinson, Steven; McCoustra, Martin

2007-08-15

A novel plasma-assisted desorption/ionization (PADI) method that can be coupled with atmospheric pressure sampling mass spectrometry to yield mass spectral information under ambient conditions of pressure and humidity from a range of surfaces without the requirement for sample preparation or additives is reported. PADI is carried out by generating a nonthermal plasma which interacts directly with the surface of the analyte. Desorption and ionization then occur at the surface, and ions are sampled by the mass spectrometer. The PADI technique is demonstrated and compared with desorption electrospray ionization (DESI) for the detection of active ingredients in a range of over-the-counter and prescription pharmaceutical formulations, including nonsterodial anti-inflammatory drugs (mefenamic acid, Ibugel, and ibuprofen), analgesics (paracetamol, Anadin Extra), and Beecham's "all in one" cold and flu remedy. PADI has also been successfully applied to the analysis of nicotine in tobacco and thiosulfates in garlic. PADI experiments have been performed using a prototype source interfaced with a Waters Platform LCZ single-quadrupole mass spectrometer with limited modifications and a Hiden Analytical HPR-60 molecular beam mass spectrometer (MBMS). The ability of PADI to rapidly detect active ingredients in pharmaceuticals without the need for prior sample preparation, solvents, or exposed high voltages demonstrates the potential of the technique for high-throughput screening in a pharmaceutical or forensic environment.
Involvement of Rab9 and Rab11 in the intracellular trafficking of TRPC6.

PubMed

Cayouette, Sylvie; Bousquet, Simon M; Francoeur, Nancy; Dupré, Emilie; Monet, Michaël; Gagnon, Hugo; Guedri, Youssef B; Lavoie, Christine; Boulay, Guylain

2010-07-01

TRPC proteins become involved in Ca2+ entry following the activation of Gq-protein coupled receptors. TRPC6 is inserted into the plasma membrane upon stimulation and remains in the plasma membrane as long as the stimulus is present. However, the mechanism that regulates the trafficking of TRPC6 is unclear. In the present study, we highlighted the involvement of two Rab GTPases in the trafficking of TRPC6. Rab9 co-localized in vesicular structures with TRPC6 in HeLa cells and co-immunoprecipitated with TRPC6. When co-expressed with TRPC6, Rab9(S21N), a dominant negative mutant, caused an increase in the level of TRPC6 at the plasma membrane and in TRPC6-mediated Ca2+ entry upon activation by a muscarinic receptor agonist. Similarly, the expression of Rab11 also caused an increase in TRPC6 expression at the cell surface and an increase in TRPC6-mediated Ca2+ entry. The co-expression of TRPC6 with the dominant negative mutant Rab11(S25N) abolished CCh-induced TRPC6 activation and reduced the level of TRPC6 at the plasma membrane. This study demonstrates that the trans-Golgi network and recycling endosomes are involved in the intracellular trafficking of TRPC6 by regulating channel density at the cell surface. 2010 Elsevier B.V. All rights reserved.
Influence of the Ambient Electric Field on Measurements of the Actively Controlled Spacecraft Potential by MMS

NASA Astrophysics Data System (ADS)

Torkar, K.; Nakamura, R.; Andriopoulou, M.; Giles, B. L.; Jeszenszky, H.; Khotyaintsev, Y. V.; Lindqvist, P.-A.; Torbert, R. B.

2017-12-01

Space missions with sophisticated plasma instrumentation such as Magnetospheric Multiscale, which employs four satellites to explore near-Earth space benefit from a low electric potential of the spacecraft, to improve the plasma measurements and therefore carry instruments to actively control the potential by means of ion beams. Without control, the potential varies in anticorrelation with plasma density and temperature to maintain an equilibrium between the plasma current and the one of photoelectrons produced at the surface and overcoming the potential barrier. A drawback of the controlled, almost constant potential is the difficulty to use it as convenient estimator for plasma density. This paper identifies a correlation between the spacecraft potential and the ambient electric field, both measured by double probes mounted at the end of wire booms, as the main responsible for artifacts in the potential data besides the known effect of the variable photoelectron production due to changing illumination of the surface. It is shown that the effect of density variations is too weak to explain the observed correlation with the electric field and that a correction of the artifacts can be achieved to enable the reconstruction of the uncontrolled potential and plasma density in turn. Two possible mechanisms are discussed: the asymmetry of the current-voltage characteristic determining the probe to plasma potential and the fact that a large equipotential structure embedded in an electric field results in asymmetries of both the emission and spatial distribution of photoelectrons, which results in an increase of the spacecraft potential.
Theory of Electromagnetic Surface Waves in Plasma with Smooth Boundaries

NASA Astrophysics Data System (ADS)

Kuzelev, M. V.

2018-05-01

A theory of nonpotential surface waves in plasma with smooth boundaries is developed. The complex frequencies of surface waves for plasma systems of different geometries and different profiles of the plasma density are calculated. Expressions for the rates of collisionless damping of surface waves due to their resonance interaction with local plasma waves of continuous spectrum are obtained. The influence of collisions in plasma is also considered.
Investigation of a Potential Protective Mechanism Against Heparin-Induced Thrombocytopenia in Patients on Chronic Intermittent Hemodialysis

PubMed Central

Tanhehco, Yvette C.; Cuker, Adam; Rudnick, Michael; Sachais, Bruce S.

2015-01-01

BACKGROUND Heparin-induced thrombocytopenia (HIT) develops as a result of platelet (PLT) activation by anti-platelet factor 4 (PF4)/heparin complex antibodies. Despite repeated exposure to heparin, patients undergoing chronic intermittent hemodialysis (HD) rarely develop HIT. We investigated the possibility that HD decreases/removes PF4 from PLT surfaces and/or plasma, thereby disfavoring immune complex formation as a mechanism of protection against HIT. MATERIALS AND METHODS We enrolled 20 patients undergoing chronic HD at the Penn Presbyterian Medical Center. Blood samples were drawn before, during and after treatment in the presence and absence of heparin. PF4, PF4/heparin antibody, heparin, and P-selectin levels were measured. RESULTS No patients demonstrated clinical symptoms of HIT. PLT surface PF4 levels decreased and plasma PF4 levels increased concurrently with increase in plasma heparin concentration. In the absence of heparin, PLT surface and plasma PF4 levels were unchanged. Anti-PF4/heparin antibodies, which were non-functional by the serotonin release assay, were detectable in 8 patients. PLT surface P-selectin levels did not change during treatment. CONCLUSIONS Removal of PLT surface and/or plasma PF4 as a mechanism of protection against HIT in patients undergoing HD is not supported by the results of our study, although the transient decrease in PLT surface PF4 in the presence of large amounts of heparin remains a candidate mechanism. The small sample size, single type of dialyzer membrane, and early sampling time points may have led to the inability to detect changes in PF4 levels. Future studies should explore other potential protective mechanisms. PMID:23305841
Preparation of active antibacterial LDPE surface through multistep physicochemical approach: I. Allylamine grafting, attachment of antibacterial agent and antibacterial activity assessment.

PubMed

Bílek, František; Křížová, Táňa; Lehocký, Marián

2011-11-01

Low-density polyethylene (LDPE) samples were treated in air plasma discharge, coated by polyallyamine brush thought copolymeric grafting surface-from reaction and deposited four common antibacterial agents (benzalkonium chloride, bronopol, chlorhexidine and triclosan) to gain material with active antibacterial properties. Surface characteristics were evaluated by static contact angle measurement with surface energy evaluation ATR-FTIR, X-ray Photoelectron Spectroscopy (XPS) and SEM analysis. Inhibition zone on agar was used as in vitro test of antibacterial properties on two representative gram positive Staphylococcus aureus (S. aureus) and gram negative Escherichia coli (E. coli) strains. It was confirmed, that after grafting of polyallyamine, more antibacterial agent is immobilized on the surface. The highest increase of antibacterial activity was observed by the sample containing triclosan. Samples covered by bronopol did not show significant antibacterial activity. Copyright © 2011 Elsevier B.V. All rights reserved.
Conformational dynamics underlie the activity of the auxin-binding protein, Nt-abp1.

PubMed

David, K; Carnero-Diaz, E; Leblanc, N; Monestiez, M; Grosclaude, J; Perrot-Rechenmann, C

2001-09-14

The auxin-binding protein 1 (ABP1) has been proposed to be involved in the perception of the phytohormone at the plasma membrane. Site-directed mutagenesis was performed on highly conserved residues at the C terminus of ABP1 to investigate their relative importance in protein folding and activation of a functional response at the plasma membrane. Detailed analysis of the dynamic interaction of the wild-type ABP1 and mutated proteins with three distinct monoclonal antibodies recognizing conformation-dependent epitopes was performed by surface plasmon resonance. The influence of auxin on these interactions was also investigated. The Cys(177) as well as Asp(175) and Glu(176) were identified as critical residues for ABP1 folding and action at the plasma membrane. On the contrary, the C-terminal KDEL sequence was demonstrated not to be essential for auxin binding, interaction with the plasma membrane, or activation of the transduction cascade although it does appear to be involved in the stability of ABP1. Taken together, the results confirmed that ABP1 conformational change is the critical step for initiating the signal from the plasma membrane.
Plasma rich in growth factors (PRGF-Endoret) stimulates proliferation and migration of primary keratocytes and conjunctival fibroblasts and inhibits and reverts TGF-beta1-Induced myodifferentiation.

PubMed

Anitua, Eduardo; Sanchez, Mikel; Merayo-Lloves, Jesus; De la Fuente, Maria; Muruzabal, Francisco; Orive, Gorka

2011-08-01

Plasma rich in growth factors (PRGF-Endoret) technology is an autologous platelet-enriched plasma obtained from patient's own blood, which after activation with calcium chloride allows the release of a pool of biologically active proteins that influence and promote a range of biological processes including cell recruitment, and growth and differentiation. Because ocular surface wound healing is mediated by different growth factors, we decided to explore the potential of PRGF-Endoret technology in stimulating the biological processes related with fibroblast-induced tissue repair. Furthermore, the anti-fibrotic properties of this technology were also studied. Blood from healthy donors was collected, centrifuged and, whole plasma column (WP) and the plasma fraction with the highest platelet concentration (F3) were drawn off, avoiding the buffy coat. Primary human cells including keratocytes and conjunctival fibroblasts were used to perform the "in vitro" investigations. The potential of PRGF-Endoret in promoting wound healing was evaluated by means of a proliferation and migration assays. Fibroblast cells were induced to myofibroblast differentiation after the treatment with 2.5 ng/mL of TGF-β1. The capability of WP and F3 to prevent and inhibit TGF-β1-induced differentiation was evaluated. Results show that this autologous approach significantly enhances proliferation and migration of both keratocytes and conjunctival fibroblasts. In addition, plasma rich in growth factors prevents and inhibits TGF-β1-induced myofibroblast differentiation. No differences were found between WP and F3 plasma fractions. These results suggest that PRGF-Endoret could reduce scarring while stimulating wound healing in ocular surface. F3 or whole plasma column show similar biological effects in keratocytes and conjunctival fibroblast cells.
Copper circuit patterning on polymer using selective surface modification and electroless plating

NASA Astrophysics Data System (ADS)

Park, Sang Jin; Ko, Tae-Jun; Yoon, Juil; Moon, Myoung-Woon; Oh, Kyu Hwan; Han, Jun Hyun

2017-02-01

We have examined a potential new and simple method for patterning a copper circuit on PET substrate by copper electroless plating, without the pretreatment steps (i.e., sensitization and activation) for electroless plating as well as the etching processes of conventional circuit patterning. A patterned mask coated with a catalyst material, Ag, for the reduction of Cu ions, is placed on a PET substrate. Subsequent oxygen plasma treatment of the PET substrate covered with the mask promotes the selective generation of anisotropic pillar- or hair-like nanostructures coated with co-deposited nanoparticles of the catalyst material on PET. After oxygen plasma treatment, a Cu circuit is well formed just by dipping the plasma-treated PET into a Cu electroless plating solution. By increasing the oxygen gas pressure in the chamber, the height of the nanostructures increases and the Ag catalyst particles are coated on not only the top but also the side surfaces of the nanostructures. Strong mechanical interlocking between the Cu circuit and PET substrate is produced by the large surface area of the nanostructures, and enhances peel strength. Results indicate this new simple two step (plasma surface modification and pretreatment-free electroless plating) method can be used to produce a flexible Cu circuit with good adhesion.

Atmospheric-pressure-plasma-enhanced fabrication of nonfouling nanocoatings for 316 stainless steel biomaterial interfaces

NASA Astrophysics Data System (ADS)

Huang, Chun; Lin, Jin-He; Li, Chi-Heng; Yu, I.-Chun; Chen, Ting-Lun

2018-03-01

Atmospheric-pressure plasma, which was generated with electrical RF power, was fed to a tetramethyldisiloxane/argon gas mixture to prepare bioinert organosilicon coatings for 316 stainless steel. The surface characteristics of atmospheric-pressure-plasma-deposited nanocoatings were evaluated as a function of RF plasma power, precursor gas flow, and plasma working distance. After surface deposition, the chemical features, elemental compositions, and surface morphologies of the organosilicon nanocoatings were examined. It was found that RF plasma power and plasma working distance are the essential factors that affect the formation of plasma-deposited nanocoatings. Fourier transform infrared spectroscopy spectra indicate that the atmospheric-pressure-plasma-deposited nanocoatings formed showed inorganic features. Atomic force microscopy analysis showed the surface roughness variation of the plasma-deposited nanocoating at different RF plasma powers and plasma working distances during surface treatment. From these surface analyses, it was found that the plasma-deposited organosilicon nanocoatings under specific operational conditions have relatively hydrophobic and inorganic characteristics, which are essential for producing an anti-biofouling interface on 316 stainless steel. The experimental results also show that atmospheric-pressure-plasma-deposited nanocoatings have potential use as a cell-resistant layer on 316 stainless steel.
Measurement of corner separation zone response on a compression ramp to plasma actuation within the hypersonic boundary layer

NASA Astrophysics Data System (ADS)

Hedlund, Brock E.; Houpt, Alec W.; Gordeyev, Stanislav V.; Leonov, Sergey B.

2017-10-01

This study was performed to characterize the dominant frequencies present in the boundary layer uptsream of and in the corner separation zone of a compression surface in Mach 4.5 flow and to determine a control effect of transient plasma actuation on the boundary layer. Schlieren imaging was used to distinguish the corner separation zone for 20°, 25°, and 30° compression ramps mounted on flat plates. Spectra of the natural disturbances present in the boundary layer and separation zone were gathered using a high-speed Shack-Hartmann wavefront sensor and surface mounted PCBTM pressure sensors while varying flow parameters by adjusting total pressure, temperature, and ramp angle. Shallow cavity discharge plasma actuators were used as a high-frequency localized thermal forcing mechanism of the boundary layer. The plasma effect was negligible for forcing frequencies (50 kHz) below the natural dominant frequency (~55-80 kHz). High frequency perturbations that can promote the transition to turbulence were amplified when the plasma forcing frequency (100 kHz) was higher than the natural dominant frequency (~55-80 kHz). This technique can potentially be used for active control of hypersonic boundary layer transition and the supersonic flow structure on the compression surface.
Glucose Sensing with Surface-Enhanced Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Yonzon, Chanda Ranjit; Lyandres, Olga; Shah, Nilam C.; Dieringer, Jon A.; Van Duyne, Richard P.

Since the discovery of SERS nearly thirty years ago, it has progressed from model-system studies of pyridine to state-of-the-art surface-science studies coupled with real-world applications. We have demonstrated a SERS-based glucose sensor as an example of the latter. A SERS-active surface functionalized with a mixed SAM was shown to partition and departition glucose efficiently. The two components of the SAM, DT and MH, provide the appropriate balance of hydrophobic and hydrophilic groups. The DT/MH-functionalized SERS surface partitioned and departitioned glucose in less than 1 min, which indicates that the sensor can be used in real-time, continuous sensing. Furthermore, quantitative glucose measurements, in the physiological concentration range, in a mixture of interfering analytes and in bovine plasma were also demonstrated. Finally, the DT/MH-functionalized SERS surface showed temporal stability for at least 10 days in bovine plasma, making it a potential candidate for implantable sensing.
Lactobacillus plantarum 299v surface-bound GAPDH: a new insight into enzyme cell walls location.

PubMed

Saad, N; Urdaci, M; Vignoles, C; Chaignepain, S; Tallon, R; Schmitter, J M; Bressollier, P

2009-12-01

The aim of this study was to provide new insight into the mechanism whereby the housekeeping enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) locates to cell walls of Lactobacillus plantarum 299v. After purification, cytosolic and cell wall GAPDH (cw-GAPDH) forms were characterized and shown to be identical homotetrameric active enzymes. GAPDH concentration on cell walls was growth-time dependent. Free GAPDH was not observed on the culture supernatant at any time during growth, and provoked cell lysis was not concomitant with any reassociation of GAPDH onto the cell surface. Hence, with the possibility of cw-GAPDH resulting from autolysis being unlikely, entrapment of intracellular GAPDH on the cell wall after a passive efflux through altered plasma membrane was investigated. Flow cytometry was used to assess L. plantarum 299v membrane permeabilization after labeling with propidium iodide (PI). By combining PI uptake and cw-GAPDH activity measurements, we demonstrate here that the increase in cw-GAPDH concentration from the early exponential phase to the late stationary phase is closely related to an increase in plasma membrane permeability during growth. Moreover, we observed that increases in both plasma membrane permeability and cw-GAPDH activity were delayed when glucose was added during L. plantarum 299v growth. Using a double labeling of L. plantarum 299v cells with anti-GAPDH antibodies and propidium iodide, we established unambiguously that cells with impaired membrane manifest five times more cw-GAPDH than unaltered cells. Our results show that plasma membrane permeability appears to be closely related to the efflux of GAPDH on the bacterial cell surface, offering new insight into the understanding of the cell wall location of this enzyme.
In vitro study of 3D PLGA/n-HAp/β-TCP composite scaffolds with etched oxygen plasma surface modification in bone tissue engineering

NASA Astrophysics Data System (ADS)

Roh, Hee-Sang; Jung, Sang-Chul; Kook, Min-Suk; Kim, Byung-Hoon

2016-12-01

Three-dimensional (3D) scaffolds have many advantageous properties for bone tissue engineering application, due to its controllable properties such as pore size, structural shape and interconnectivity. In this study, effects on oxygen plasma surface modification and adding of nano-hydroxyapatite (n-HAp) and β-tricalcium phosphate (β-TCP) on the 3D PLGA/n-HAp/β-TCP scaffolds for improving preosteoblast cell (MC3T3-E1) adhesion, proliferation and differentiation were investigated. The 3D PLGA/n-HAp/β-TCP scaffolds were fabricated by 3D Bio-Extruder equipment. The 3D scaffolds were prepared with 0°/90° architecture and pore size of approximately 300 μm. In addition 3D scaffolds surface were etched by oxygen plasma to enhance the hydrophilic property and surface roughness. After oxygen plasma treatment, the surface chemistry and morphology were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. And also hydrophilic property was measured by contact angle. The MC3T3-E1 cell proliferation and differentiation were investigated by MTT assay and ALP activity. In present work, the 3D PLGA/HAp/beta-TCP composite scaffold with suitable structure for the growth of osteoblast cells was successfully fabricated by 3D rapid prototyping technique. The surface hydrophilicity and roughness of 3D scaffold increased by oxygen plasma treatment had a positive effect on cell adhesion, proliferation, and differentiation. Furthermore, the differentiation of MC3T3-E1 cell was significantly enhanced by adding of n-HAp and β-TCP on 3D PLGA scaffold. As a result, combination of bioceramics and oxygen plasma treatment showed a synergistic effect on biocompatibility of 3D scaffolds. This result confirms that this technique was useful tool for improving the biocompatibility in bone tissue engineering application.
Transmission of Free Radicals through and Damage to Freestanding Single and Multilayer Dielectric Film

NASA Astrophysics Data System (ADS)

Choudhury, Faraz Anwar

A high concentration of free radicals is present in many processing plasmas, which affects the processing conditions and the properties of materials exposed to the plasma. Measuring the types and concentrations of free radicals present in the plasma is critical in order to determine their effects on the materials being processed. Current methods for detecting free radicals in a plasma require multiple expensive and bulky instruments, complex setups and often modifications to the plasma reactor. In this work, we present a simple technique that detects reactive-oxygen radicals incident on a surface from a plasma. The measurements are made using a fluorophore dye that is commonly used in biological and cellular systems for assay labeling in liquids. Using fluorometric analysis, it was found that the fluorophore reacts with oxygen radicals incident from the plasma, which is indicated by degradation of its fluorescence. As plasma power was increased, the quenching of the fluorescence significantly increased. Both immobilized and non-immobilized fluorophore dyes were used and the results indicate that both states function effectively under vacuum conditions. Using radical-sensitive dyes and free-standing films, the transmission of oxygen radicals through silicon nitride and silicon dioxide dielectric films is measured and their absorption lengths are determined. The absorption lengths were found to be 33, 37 and 40 nm for 15, 30 and 45-minute oxygen plasma exposures respectively. FTIR and XRR measurements show that a silicon oxynitride-like layer forms on the surface of the film which has a lower density than silicon nitride. The increase in absorption length with plasma-exposure time is attributed to the formation of the surface layer. In silicon dioxide films, the absorption length of oxygen radicals was found to be 70 nm after 20 minutes of plasma exposure. After 30 minutes of plasma exposure under the same conditions, the absorption length was reduced to 66 nm. XRR and FTIR measurements both reveal that the oxygen plasma exposure leads to surface oxidation of the silicon dioxide film and the formation of a denser surface layer which restricts the transmission of the radicals through the film. It was found that the extent of modification of the film partially depends on the radical dose. The calculated enthalpies of the reactions show that they are all exothermic reactions, however, the radicals need enough energy to overcome the activation energy for the reaction to take place.
An in vitro bacterial adhesion assessment of surface-modified medical-grade PVC.

PubMed

Asadinezhad, Ahmad; Novák, Igor; Lehocký, Marián; Sedlarík, Vladimir; Vesel, Alenka; Junkar, Ita; Sáha, Petr; Chodák, Ivan

2010-06-01

Medical-grade polyvinyl chloride was surface modified by a multistep physicochemical approach to improve bacterial adhesion prevention properties. This was fulfilled via surface activation by diffuse coplanar surface barrier discharge plasma followed by radical graft copolymerization of acrylic acid through surface-initiated pathway to render a structured high density brush. Three known antibacterial agents, bronopol, benzalkonium chloride, and chlorhexidine, were then individually coated onto functionalized surface to induce biological properties. Various modern surface probe techniques were employed to explore the effects of the modification steps. In vitro bacterial adhesion and biofilm formation assay was performed. Escherichia coli strain was found to be more susceptible to modifications rather than Staphylococcus aureus as up to 85% reduction in adherence degree of the former was observed upon treating with above antibacterial agents, while only chlorhexidine could retard the adhesion of the latter by 50%. Also, plasma treated and graft copolymerized samples were remarkably effective to diminish the adherence of E. coli. Copyright 2010 Elsevier B.V. All rights reserved.
Nonequilibrium-Plasma-Synthesized ZnO Nanocrystals with Plasmon Resonance Tunable via Al Doping and Quantum Confinement.

PubMed

Greenberg, Benjamin L; Ganguly, Shreyashi; Held, Jacob T; Kramer, Nicolaas J; Mkhoyan, K Andre; Aydil, Eray S; Kortshagen, Uwe R

2015-12-09

Metal oxide semiconductor nanocrystals (NCs) exhibit localized surface plasmon resonances (LSPRs) tunable within the infrared (IR) region of the electromagnetic spectrum by vacancy or impurity doping. Although a variety of these NCs have been produced using colloidal synthesis methods, incorporation and activation of dopants in the liquid phase has often been challenging. Herein, using Al-doped ZnO (AZO) NCs as an example, we demonstrate the potential of nonthermal plasma synthesis as an alternative strategy for the production of doped metal oxide NCs. Exploiting unique, thoroughly nonequilibrium synthesis conditions, we obtain NCs in which dopants are not segregated to the NC surfaces and local doping levels are high near the NC centers. Thus, we achieve overall doping levels as high as 2 × 10(20) cm(-3) in NCs with diameters ranging from 12.6 to 3.6 nm, and for the first time experimentally demonstrate a clear quantum confinement blue shift of the LSPR energy in vacancy- and impurity-doped semiconductor NCs. We propose that doping of central cores and heavy doping of small NCs are achievable via nonthermal plasma synthesis, because chemical potential differences between dopant and host atoms-which hinder dopant incorporation in colloidal synthesis-are irrelevant when NC nucleation and growth proceed via irreversible interactions among highly reactive gas-phase ions and radicals and ligand-free NC surfaces. We explore how the distinctive nucleation and growth kinetics occurring in the plasma influences dopant distribution and activation, defect structure, and impurity phase formation.
Glow discharge plasma pretreatment enhances osteoclast differentiation and survival on titanium plates.

PubMed

Kawai, Hiroyuki; Shibata, Yo; Miyazaki, Takashi

2004-05-01

Despite the fact that several reports have demonstrated osteoclast activity on various bioactive ceramics, osteoclast functions on surface-modified titanium have not come under focus. This study aimed to examine whether the increasing surface energy of glow discharge plasma (GDP) involved in protein adhesion containing the RGD (Arg-Gly-Asp) sequence affects osteoclast responses on titanium plates. We examined osteoclast differentiation and survival rates on titanium plates with and without GDP. The amounts of osteoclasts on titanium plates were not increased by GDP after 1 week. However, osteoclast differentiation was greatly activated by GDP pretreatment, as tartrate-resistant acid phosphatase synthesis significantly increased on the titanium plates with GDP. Additionally, since the presence of osteoclasts was detected only on the titanium plates with GDP, even after 4h cultivation in a coculture test, the osteoclasts survival rate was increased by GDP pretreatment. As osteoclast responses were affected even on surface modified metallic materials, we concluded that novel approaches are needed not only for osteoclastic resorption on ceramic materials but also for osteoclast responses on surface-modified metallic materials.
Kinetic modeling of microscopic processes during electron cyclotron resonance microwave plasma-assisted molecular beam epitaxial growth of GaN/GaAs-based heterostructures

NASA Astrophysics Data System (ADS)

Bandić, Z. Z.; Hauenstein, R. J.; O'Steen, M. L.; McGill, T. C.

1996-03-01

Microscopic growth processes associated with GaN/GaAs molecular beam epitaxy (MBE) are examined through the introduction of a first-order kinetic model. The model is applied to the electron cyclotron resonance microwave plasma-assisted MBE (ECR-MBE) growth of a set of δ-GaNyAs1-y/GaAs strained-layer superlattices that consist of nitrided GaAs monolayers separated by GaAs spacers, and that exhibit a strong decrease of y with increasing T over the range 540-580 °C. This y(T) dependence is quantitatively explained in terms of microscopic anion exchange, and thermally activated N surface-desorption and surface-segregation processes. N surface segregation is found to be significant during GaAs overgrowth of GaNyAs1-y layers at typical GaN ECR-MBE growth temperatures, with an estimated activation energy Es˜0.9 eV. The observed y(T) dependence is shown to result from a combination of N surface segregation/desorption processes.
Initial biocompatibility of plasma polymerized hexamethyldisiloxane films with different wettability

NASA Astrophysics Data System (ADS)

Krasteva, N. A.; Toromanov, G.; Hristova, K. T.; Radeva, E. I.; Pecheva, E. V.; Dimitrova, R. P.; Altankov, G. P.; Pramatarova, L. D.

2010-11-01

Understanding the relationships between material surface properties, behaviour of adsorbed proteins and cellular responses is essential to design optimal material surfaces for tissue engineering. In this study we modify thin layers of plasma polymerized hexamethyldisiloxane (PPHMDS) by ammonia treatment in order to increase surface wettability and the corresponding biological response. The physico-chemical properties of the polymer films were characterized by contact angle (CA) measurements and Fourier Transform Infrared Spectroscopy (FTIR) analysis.Human umbilical vein endothelial cells (HUVEC) were used as model system for the initial biocompatibility studies following their behavior upon preadsorption of polymer films with three adhesive proteins: fibronectin (FN), fibrinogen (FG) and vitronectin (VN). Adhesive interaction of HUVEC was evaluated after 2 hours by analyzing the overall cell morphology, and the organization of focal adhesion contacts and actin cytoskeleton. We have found similar good cellular response on FN and FG coated polymer films, with better pronounced vinculin expression on FN samples while. Conversely, on VN coated surfaces the wettability influenced significantly initial celular interaction spreading. The results obtained suggested that ammonia plasma treatment can modulate the biological activity of the adsorbed protein s on PPHMDS surfaces and thus to influence the interaction with endothelial cells.
Assessing the electrochemical performance of a supercapacitor electrode made of copper oxide and activated carbon using liquid phase plasma

NASA Astrophysics Data System (ADS)

Ki, Seo Jin; Lee, Heon; Park, Young-Kwon; Kim, Sun-Jae; An, Kay-Hyeok; Jung, Sang-Chul

2018-07-01

Successful modification of surface properties of a nanocomposite electrode is prerequisite to enhancing the overall performance of electrochemical supercapacitors. The present study was designed to describe the microstructural and electrochemical characteristics of a new composite electrode assembled by activated carbon (AC) powder (as a host) and copper precursor (as a guest) using liquid phase plasma. The fabrication processes were conducted by changing plasma discharge time from 30 to 90 min in the presence and absence of (thermal) oxidation. We observed that merging plasma and oxidation treatments raised the content of copper oxide nanoparticles precipitated (evenly) on the AC surface, along with oxygen. A mixed valence state of copper oxides (in the forms of Cuo, Cu2O, and CuO) was found in different composites with and without oxidation, where CuO and Cuo affected a specific capacitance in positive and negative ways, respectively. This led to the difference of electrochemical stability and resistance among the assembled composites. For instance, the best cycling performance was observed in the plasma-treated composite for 90 min with oxidation, whereas that of 60 min without oxidation recorded the lowest resistance. Therefore, a proper balance between the capacitance and resistance appears to be required for effective fabrication of the supercapacitor electrode, specifically in cases involving copper oxides.
Long-term reduction in poly(dimethylsiloxane) surface hydrophobicity via cold-plasma treatments.

PubMed

Larson, B J; Gillmor, S D; Braun, J M; Cruz-Barba, L E; Savage, D E; Denes, F S; Lagally, M G

2013-10-22

Poly(dimethylsiloxane), PDMS, a versatile elastomer, is the polymer of choice for microfluidic systems. It is inexpensive, relatively easy to pattern, and permeable to oxygen. Unmodified PDMS is highly hydrophobic. It is typically exposed to an oxygen plasma to reduce this hydrophobicity. Unfortunately, the PDMS surface soon returns to its original hydrophobic state. We present two alternative plasma treatments that yield long-term modification of the wetting properties of a PDMS surface. An oxygen plasma pretreatment followed by exposure to a SiCl4 plasma and an oxygen-CCl4 mixture plasma both cause a permanent reduction in the hydrophobicity of the PDMS surface. We investigate the properties of the plasma-treated surfaces with X-ray photoelectron spectroscopy (XPS) and contact angle measurements. We propose that the plasma treated PDMS surface is a dynamic mosaic of high- and low-contact-angle functionalities. The SiCl4 and CCl4 plasmas attach polar groups that block coverage of the surface by low-molecular-weight groups that exist in PDMS. We describe an application that benefits from these new plasma treatments, the use of a PDMS stencil to form dense arrays of DNA on a surface.
Size and Aging Effects on Antimicrobial Efficiency of Silver Nanoparticles Coated on Polyamide Fabrics Activated by Atmospheric DBD Plasma.

PubMed

Zille, Andrea; Fernandes, Margarida M; Francesko, Antonio; Tzanov, Tzanko; Fernandes, Marta; Oliveira, Fernando R; Almeida, Luís; Amorim, Teresa; Carneiro, Noémia; Esteves, Maria F; Souto, António P

2015-07-01

This work studies the surface characteristics, antimicrobial activity, and aging effect of plasma-pretreated polyamide 6,6 (PA66) fabrics coated with silver nanoparticles (AgNPs), aiming to identify the optimum size of nanosilver exhibiting antibacterial properties suitable for the manufacture of hospital textiles. The release of bactericidal Ag(+) ions from a 10, 20, 40, 60, and 100 nm AgNPs-coated PA66 surface was a function of the particles' size, number, and aging. Plasma pretreatment promoted both ionic and covalent interactions between AgNPs and the formed oxygen species on the fibers, favoring the deposition of smaller-diameter AgNPs that consequently showed better immediate and durable antimicrobial effects against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. Surprisingly, after 30 days of aging, a comparable bacterial growth inhibition was achieved for all of the fibers treated with AgNPs <100 nm in size. The Ag(+) in the coatings also favored the electrostatic stabilization of the plasma-induced functional groups on the PA66 surface, thereby retarding the aging process. At the same time, the size-related ratio (Ag(+)/Ag(0)) of the AgNPs between 40 and 60 nm allowed for the controlled release of Ag(+) rather than bulk silver. Overall, the results suggest that instead of reducing the size of the AgNPs, which is associated with higher toxicity, similar long-term effects can be achieved with larger NPs (40-60 nm), even in lower concentrations. Because the antimicrobial efficiency of AgNPs larger than 30 nm is mainly ruled by the release of Ag(+) over time and not by the size and number of the AgNPs, this parameter is crucial for the development of efficient antimicrobial coatings on plasma-treated surfaces and contributes to the safety and durability of clothing used in clinical settings.
The influence of surface properties on the plasma dynamics in radio-frequency driven oxygen plasmas: Measurements and simulations

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

Greb, Arthur; Niemi, Kari; O'Connell, Deborah

2013-12-09

Plasma parameters and dynamics in capacitively coupled oxygen plasmas are investigated for different surface conditions. Metastable species concentration, electronegativity, spatial distribution of particle densities as well as the ionization dynamics are significantly influenced by the surface loss probability of metastable singlet delta oxygen (SDO). Simulated surface conditions are compared to experiments in the plasma-surface interface region using phase resolved optical emission spectroscopy. It is demonstrated how in-situ measurements of excitation features can be used to determine SDO surface loss probabilities for different surface materials.
Improving the work function of the niobium surface of SRF cavities by plasma processing

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

Tyagi, P. V.; Doleans, M.; Hannah, B.

2016-01-01

An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature was developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5₋1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.
Effects of heat-treatment on plasma rich in growth factors-derived autologous eye drop.

PubMed

Anitua, E; Muruzabal, F; De la Fuente, M; Merayo-Lloves, J; Orive, G

2014-02-01

We have developed and characterized a new type of plasma rich in growth factors (PRGF) derived eye-drop therapy for patients suffering from autoimmune diseases. To determine the concentration of several growth factors, proteins, immunoglobulins and complement activity of the heat-inactivated eye-drop and to study its biological effects on cell proliferation and migration of different ocular surface cells, blood from healthy donors was collected, centrifuged and PRGF was prepared avoiding the buffy coat. The half volume of the obtained plasma supernatant from each donor was heat-inactivated at 56 °C for 1 h (heat-inactivated PRGF). The concentration of several proteins involved on corneal wound healing, immunoglubolins G, M and E and functional integrity of the complement system assayed by CH50 test were determined. The proliferative and migratory potential of inactivated and non-inactivated PRGF eye drops were assayed on corneal epithelial cells (HCE), keratocytes (HK) and conjunctival fibroblasts (HConF). Heat-inactivated PRGF preserves the content of most of the proteins and morphogens involved in its wound healing effects while reduces drastically the content of IgE and complement activity. Heat-inactivated PRGF eye drops increased proliferation and migration potential of ocular surface cells with regard to PRGF showing significant differences on proliferation and migration rate of HCE and HConF respectively. In summary, heat-inactivation of PRGF eye drops completely reduced complement activity and deceased significantly the presence of IgE, maintaining the biological activity of PRGF on ocular surface cells. Copyright © 2013 Elsevier Ltd. All rights reserved.
Structural and magnetic characterization of copper sulfonated phthalocyanine grafted onto treated polyethylene

NASA Astrophysics Data System (ADS)

Reznickova, A.; Kolska, Z.; Orendac, M.; Cizmar, E.; Sajdl, P.; Svorcik, V.

2016-08-01

This study focuses on high density polyethylene (HDPE) activated by Ar plasma treatment, subsequently grafted with copper sulfonated phthalocyanine (CuPc) especially pointing out to the surface and magnetic properties of those composites. Properties of pristine PE and their plasma treated counterparts were studied by different experimental techniques: X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, zeta potential and by electron spin resonance (ESR). XPS analysis confirmed the successful grafting of phthalocyanine. The highest absorption was found for the sample grafted with bCuPc for 1 h. Electrokinetic analysis also confirmed the plasma treatment and also subsequent CuPc grafting influence significantly the surface chemistry and charge. These results correspond well with XPS determination. ESR studies confirmed the presence of CuPc grafted on HDPE. It was found, that grafting is mediated by magnetically inactive functional groups, rather than radicals. Magnetic properties of CuPc do not seem to change significantly after grafting CuPc on polyethylene surface.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Kajita, Shin; Yoshida, Tomoko; Kitaoka, Daiki

It has been found recently that low-energy helium (He) plasma irradiation to tungsten (W) leads to the growth of W nanostructures on the surface. The process to grow the nanostructure is identified as a self-growth process of He bubbles and has a potential to open up a new plasma processing method. Here, we show that the metallic nanostructure formation process by the exposure to He plasma can occur in various metals such as, titanium, nickel, iron, and so on. When the irradiation conditions alter, the metallic cone arrays including nanobubbles inside are formed on the surface. Different from W cases,more » other processes than growth of fiberform structure, i.e., physical sputtering and the growth of large He bubbles, can be dominant on other metals during irradiation; various surface morphology changes can occur. The nanostructured W, part of which was oxidized, has revealed a significant photocatalytic activity under visible light (wavelength >700 nm) in decolorization of methylene blue without any co-catalyst.« less
Rover wheel charging on the lunar surface

NASA Astrophysics Data System (ADS)

Jackson, Telana L.; Farrell, William M.; Zimmerman, Michael I.

2015-03-01

The environment at the Moon is dynamic, with highly variable solar wind plasma conditions at the lunar dayside, terminator, and night side regions. Moving objects such as rover wheels will charge due to contact electrification with the surface, but the degree of charging is controlled by the local plasma environment. Using a dynamic charging model of a wheel, it is demonstrated herein that moving tires will tribocharge substantially when venturing into plasma-current starved regions such as polar craters or the lunar nightside. The surface regolith distribution and the overall effect on charge accumulation of grains cohesively sticking to the rover tire has been incorporated into the model. It is shown that dust sticking can limit the overall charge accumulated on the system. However charge dissipation times are greatly increased in shadowed regions and can present a potential hazard to astronauts and electrical systems performing extra-vehicular activities. We show that dissipation times change with wheel composition and overall system tribocharging is dependent upon wheel velocity.

Properties and Commercial Application of Manual Plasma Hardening

NASA Astrophysics Data System (ADS)

Korotkov, V. A.

2016-11-01

A new method and a device for plasma hardening of various parts are considered. Installation of the new device does not require too much investment (the active mechanical productions are appropriate for its accommodation) and special choice of personnel (welders train to use it without difficulty). Plasma hardening does not deform and worsen the smoothness of the surface, which makes it possible to employ many hardened parts without finishing mechanical treatment required after bulk or induction hardening. The hardened layer (about 1 mm) produced by plasma hardening exhibits better wear resistance than after bulk hardening with tempering, which prolongs the service life of the parts.
Correlation of Membrane Binding and Hydrophobicity to the Chaperone-Like Activity of PDC-109, the Major Protein of Bovine Seminal Plasma

PubMed Central

Sankhala, Rajeshwer S.; Damai, Rajani S.; Swamy, Musti J.

2011-01-01

The major protein of bovine seminal plasma, PDC-109 binds to choline phospholipids present on the sperm plasma membrane upon ejaculation and plays a crucial role in the subsequent events leading to fertilization. PDC-109 also shares significant similarities with small heat shock proteins and exhibits chaperone-like activity (CLA). Although the polydisperse nature of this protein has been shown to be important for its CLA, knowledge of other factors responsible for such an activity is scarce. Since surface exposure of hydrophobic residues is known to be an important factor which modulates the CLA of chaperone proteins, in the present study we have probed the surface hydrophobicity of PDC-109 using bisANS and ANS. Further, effect of phospholipids on the structure and chaperone-like activity of PDC-109 was studied. Presence of DMPC was found to increase the CLA of PDC-109 significantly, which could be due to the considerable exposure of hydrophobic regions on the lipid-protein recombinants, which can interact productively with the nonnative structures of target proteins, resulting in their protection. However, inclusion of DMPG instead of DMPC did not significantly alter the CLA of PDC-109, which could be due to the lower specificity of PDC-109 for DMPG as compared to DMPC. Cholesterol incorporation into DMPC membranes led to a decrease in the CLA of PDC-109-lipid recombinants, which could be attributed to reduced accessibility of hydrophobic surfaces to the substrate protein(s). These results underscore the relevance of phospholipid binding and hydrophobicity to the chaperone-like activity of PDC-109. PMID:21408153
Development of advanced antimicrobial and sterilized plasma polypropylene grafted muga (Antheraea assama) silk as suture biomaterial.

PubMed

Gogoi, Dolly; Choudhury, Arup Jyoti; Chutia, Joyanti; Pal, Arup Ratan; Khan, Mojibur; Choudhury, Manash; Pathak, Pallabi; Das, Gouranga; Patil, Dinkar S

2014-04-01

Surface modification of silk fibroin (SF) materials using environmentally friendly and non-hazardous process to tailor them for specific application as biomaterials has drawn a great deal of interest in the field of biomedical research. To further explore this area of research, in this report, polypropylene (PP) grafted muga (Antheraea assama) SF (PP-AASF) suture is developed using plasma treatment and plasma graft polymerization process. For this purpose, AASF is first sterilized in argon (Ar) plasma treatment followed by grafting PP onto its surface. AASF is a non-mulberry variety having superior qualities to mulberry SF and is still unexplored in the context of suture biomaterial. AASF, Ar plasma treated AASF (AASFAr) and PP-AASF are subjected to various characterization techniques for better comparison and the results are attempted to correlate with their observed properties. Excellent mechanical strength, hydrophobicity, antibacterial behavior, and remarkable wound healing activity of PP-AASF over AASF and AASFAr make it a promising candidate for application as sterilized suture biomaterial. Copyright © 2013 Wiley Periodicals, Inc.
Saturn Magnetospheric Impact on Surface Molecular Chemistry and Astrobiological Potential of Enceladus

NASA Technical Reports Server (NTRS)

Cooper, Paul D.; Cooper, John F.; Sittler, Edward C.; Burger, Matthew H.; Sturner, Steven J.; Rymer, Abigail M.

2008-01-01

The active south polar surface of Enceladus is exposed to strong chemical processing by direct interaction with charged plasma and energetic particles in the local magnetospheric environment of this icy moon. Chemical oxidation activity is suggested by detection of H202 at the surface in this region and less directly by substantial presence of C02, CO, and N2 in the plume gases. Molecular composition of the uppermost surface, including ejecta from plume activity, is radiolytically transformed mostly by penetrating energetic electrons with lesser effects from more depleted populations of energetic protons. The main sources of molecular plasma ions and E-ring dust grains in the magnetospheric environment are the cryovolcanic plume emissions from Enceladus. These molecular ions and the dust grains are chemically processed by magnetospheric interactions that further impact surface chemistry on return to Enceladus. For example, H20 neutrals dominating the emitted plume gas return to the surface mostly as H30+ ions after magnetospheric processing. Surface oxidant loading is further increased by return of radiolytically processed ice grains from the E-ring. Plume frost deposition and micrometeoroid gardening protect some fraction of newly produced molecular species from destruction by further irradiation. The evident horizontal and vertical mobility of surface ices in the south polar region drive mixing of these processed materials into the moon interior with potential impacts on deep ice molecular chemistry and plume gas production. Similarly as suggested previously for Europa, the externally driven source of radiolytic oxidants could affect evolution of life in any subsurface liquid water environments of Enceladus.
Effects of atmospheric air plasma treatment of graphite and carbon felt electrodes on the anodic current from Shewanella attached cells.

PubMed

Epifanio, Monica; Inguva, Saikumar; Kitching, Michael; Mosnier, Jean-Paul; Marsili, Enrico

2015-12-01

The attachment of electrochemically active microorganisms (EAM) on an electrode is determined by both the chemistry and topography of the electrode surface. Pre-treatment of the electrode surface by atmospheric air plasma introduces hydrophilic functional groups, thereby increasing cell attachment and electroactivity in short-term experiments. In this study, we use graphite and carbon felt electrodes to grow the model EAM Shewanella loihica PV-4 at oxidative potential (0.2 V vs. Ag/AgCl). Cell attachment and electroactivity are measured through electrodynamic methods. Atmospheric air plasma pre-treatment increases cell attachment and current output at graphite electrodes by 25%, while it improves the electroactivity of the carbon felt electrodes by 450%. Air plasma pre-treatment decreased the coulombic efficiency on both carbon felt and graphite electrodes by 60% and 80%, respectively. Microbially produced flavins adsorb preferentially at the graphite electrode, and air plasma pre-treatment results in lower flavin adsorption at both graphite and carbon felt electrodes. Results show that air plasma pre-treatment is a feasible option to increase current output in bioelectrochemical systems. Copyright © 2015 Elsevier B.V. All rights reserved.
The inductive, steady-state sustainment of stable spheromaks

NASA Astrophysics Data System (ADS)

Hossack, A. C.; Jarboe, T. R.; Morgan, K. D.; Sutherland, D. A.; Hansen, C. J.; Everson, C. J.; Penna, J. M.; Nelson, B. A.

2016-10-01

Inductive helicity injection current drive with imposed perturbations has led to the breakthrough of spheromak sustainment while maintaining stability. Sustained spheromaks show coherent, imposed plasma motion and low plasma-generated mode activity, indicating stability. Additionally, record current gain of 3.9 has been achieved with evidence of pressure confinement. The Helicity Injected Torus - Steady Inductive (HIT-SI) experiment studies efficient, steady-state current drive for magnetic confinement plasmas using a novel experimental method which is ideal for low aspect ratio, toroidal geometries and is compatible with closed flux surfaces. Analysis of surface magnetic probes indicates large n = 0 and 1 toroidal Fourier mode amplitudes and little energy in higher modes. Biorthogonal decomposition shows that almost all of the n = 1 energy is imposed by the injectors, rather than plasma-generated. Ion Doppler spectroscopy (IDS) measurements show coherent, imposed plasma motion of +/-2.5 cm in the region inside r 10 cm (a = 23 cm) and the size of the separate spheromak is consistent with that predicted by Imposed-dynamo Current Drive (IDCD). Coherent motion indicates that the spheromak is stable and a lack of plasma-generated n = 1 energy indicates that the maximum q is maintained below 1 for stability during sustainment.
In situ oxygen plasma cleaning of microswitch surfaces—comparison of Ti and graphite electrodes

NASA Astrophysics Data System (ADS)

Oh, Changho; Streller, Frank; Ashurst, W. Robert; Carpick, Robert W.; de Boer, Maarten P.

2016-11-01

Ohmic micro- and nanoswitches are of interest for a wide variety of applications including radio frequency communications and as low power complements to transistors. In these switches, it is of paramount importance to maintain surface cleanliness in order to prevent frequent failure by tribopolymer growth. To prepare surfaces, an oxygen plasma clean is expected to be beneficial compared to a high temperature vacuum bakeout because of shorter cleaning time (<5 min compared to ~24 h) and active removal of organic contaminants. We demonstrate that sputtering of the electrode material during oxygen plasma cleaning is a critical consideration for effective cleaning of switch surfaces. With Ti electrodes, a TiO x layer forms that increases electrical contact resistance. When plasma-cleaned using graphite electrodes, the resistance of Pt-coated microswitches exhibit a long lifetime with consistently low resistance (<0.5 Ω variation over 300 million cycles) if the test chamber is refilled with ultra-high purity nitrogen and if the devices are not exposed to laboratory air. Their current-voltage characteristic is also linear at the millivolt level. This is important for nanoswitches which will be operated in that range.
Low temperature plasma biomedicine: A tutorial review

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

Graves, David B., E-mail: graves@berkeley.edu

2014-08-15

Gas discharge plasmas formed at atmospheric pressure and near room temperature have recently been shown to be potentially useful for surface and wound sterilization, antisepsis, bleeding cessation, wound healing, and cancer treatment, among other biomedical applications. This tutorial review summarizes the field, stressing the likely role of reactive oxygen and nitrogen species created in these plasmas as the biologically and therapeutically active agents. Reactive species, including radicals and non-radical compounds, are generated naturally within the body and are now understood to be essential for normal biological functions. These species are known to be active agents in existing therapies for woundmore » healing, infection control, and cancer treatment. But they are also observed at elevated levels in persons with many diseases and are associated with aging. The physical and chemical complexity of plasma medical devices and their associated biochemical effects makes the development of safe, effective plasma medical devices and procedures a challenge, but encouragingly rapid progress has been reported around the world in the last several years.« less
Low temperature plasma biomedicine: A tutorial reviewa)

NASA Astrophysics Data System (ADS)

Graves, David B.

2014-08-01

Gas discharge plasmas formed at atmospheric pressure and near room temperature have recently been shown to be potentially useful for surface and wound sterilization, antisepsis, bleeding cessation, wound healing, and cancer treatment, among other biomedical applications. This tutorial review summarizes the field, stressing the likely role of reactive oxygen and nitrogen species created in these plasmas as the biologically and therapeutically active agents. Reactive species, including radicals and non-radical compounds, are generated naturally within the body and are now understood to be essential for normal biological functions. These species are known to be active agents in existing therapies for wound healing, infection control, and cancer treatment. But they are also observed at elevated levels in persons with many diseases and are associated with aging. The physical and chemical complexity of plasma medical devices and their associated biochemical effects makes the development of safe, effective plasma medical devices and procedures a challenge, but encouragingly rapid progress has been reported around the world in the last several years.
Ion cyclotron range of frequencies heating of plasma with small impurity production

DOEpatents

Ohkawa, Tihiro

1987-01-01

Plasma including plasma ions is magnetically confined by a magnetic field. The plasma has a defined outer surface and is intersected by resonance surfaces of respective common ion cyclotron frequency of a predetermined species of plasma ions moving in the magnetic field. A radio frequency source provides radio frequency power at a radio frequency corresponding to the ion cyclotron frequency of the predetermined species of plasma ions moving in the field at a respective said resonance surface. RF launchers coupled to the radio frequency source radiate radio frequency energy at the resonance frequency onto the respective resonance surface within the plasma from a plurality of locations located outside the plasma at such respective distances from the intersections of the respective resonance surface and the defined outer surface and at such relative phases that the resulting interference pattern provides substantially null net radio frequency energy over regions near and including substantial portions of the intersections relative to the radio frequency energy provided thereby at other portions of the respective resonance surface within the plasma.
Increase of electrodeposited catalyst stability via plasma grown vertically oriented graphene nanoparticle movement restriction.

PubMed

Vanrenterghem, Bart; Hodnik, Nejc; Bele, Marjan; Šala, Martin; Amelinckx, Giovanni; Neukermans, Sander; Zaplotnik, Rok; Primc, Gregor; Mozetič, Miran; Breugelmans, Tom

2017-08-17

Beside activity, electrocatalyst stability is gaining in importance. The most common degradation mechanism is the loss of the active surface area due to nanoparticle growth via coalescence/agglomeration. We propose a particle confinement strategy via vertically oriented graphene deposition to overcome degradation of the nanoparticles.
Optimization Study of Pulsed DC Nitrogen-Hydrogen Plasma in the Presence of an Active Screen Cage

NASA Astrophysics Data System (ADS)

Saeed, A.; W. Khan, A.; F., Jan; U. Shah, H.; Abrar, M.; Zaka-Ul-Islam, M.; Khalid, M.; Zakaullah, M.

2014-05-01

A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density, filling pressure and hydrogen concentrations using optical emission spectroscopy (OES). The samples of AISI 304 are nitrided for different treatment times under optimum conditions. The treated samples were analyzed by X-ray diffraction (XRD) to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of iron and chromium nitrides arising from incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of treatment time (h). The results showed clear evidence of improved surface hardness and a substantial amount of decrease in the treatment time compared with the previous work.
Comparative study on gamma irradiation and cold plasma pretreatment for a cellulosic substrate modification with phenolic compounds

NASA Astrophysics Data System (ADS)

Irimia, Anamaria; Ioanid, Ghiocel Emil; Zaharescu, Traian; Coroabă, Adina; Doroftei, Florica; Safrany, Agnes; Vasile, Cornelia

2017-01-01

The efficiency of the activation of the cellulose/chitin mix substrate by cold plasma or γ-radiation exposure in order to modify it with bioactive compounds was studied. The eugenol or vegetable oils such as grape seed oil and rosehip seed oil have been grafted onto activated substrate. The examination of modified cellulose/chitin mix substrate by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy confirms that the structural and morphological changes took place in both cases. The grafting degrees of the surface layer estimated from XPS data varied from 31.1% to 58.7% for air cold plasma activation and from 9.7% to 22.8% for γ-irradiation treatment. They depend both on bioactive compound used and procedure of substrate activation. Higher grafting degree are obtain by using vegetable oils than in the case of modification with eugenol and the air cold plasma activation seems to be much efficient than γ-irradiation. By grafting the polymeric substrate with bioactive compounds, antimicrobial and antioxidant properties have been conferred. Such materials can be considered promising for food packaging applications and medical textiles and also the applied procedures are environmental friendly ones.
Effect of dialyzer geometry on granulocyte and complement activation.

PubMed

Schaefer, R M; Heidland, A; Hörl, W H

1987-01-01

During hemodialysis with cuprophan membranes, the complement system as well as leukocytes become activated. In order to clarify the role of dialyzer geometry, the effect of hollow-fiber versus flat-sheet dialyzers and of different surface areas on C3a generation and leukocyte degranulation was investigated. Plasma levels of leukocyte elastase in complex with alpha 1-proteinase inhibitor were significantly increased after 1 h (+55%) and 3 h (+62%) of hemodialysis with flat-sheet dialyzers as compared to hollow-fiber devices. In addition, plasma levels of lactoferrin, released from the specific granules of leukocytes during activation, were significantly higher (+42%) 3 h after the onset of dialysis treatment with flat-sheet than with hollow-fiber dialyzers. With respect to surface area, larger dialyzers tended to cause more release of leukocyte elastase as compared to dialyzers with smaller surface areas, irrespectively of the configuration of the dialyzer used. On the other hand, activation of the complement system, as measured by the generation of C3a-desarg, did not differ with both types of configurations. The same held true for leukopenia, which was almost identical for hollow-fiber and flat-sheet dialyzers. From these findings two lines of evidence emerge: First, not only the type of membrane material used in a dialyzer may influence its biocompatibility, but the geometry of the extracorporeal device also determines the degree of compatibility. Hence, the extent of leukocyte activation correlated with both configuration of the dialyzer and surface area of the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of growth parameters on crystallinity and properties of ZnO films grown by plasma assisted MOCVD

NASA Astrophysics Data System (ADS)

Losurdo, M.; Giangregorio, M. M.; Sacchetti, A.; Capezzuto, P.; Bruno, G.; Malandrino, G.; Fragalà, I. L.

2007-07-01

Thin films of ZnO have been grown by plasma assisted metal-organic chemical vapour deposition (PA-MOCVD) using a 13.56 MHz O 2 plasma and the Zn(TTA)•tmed (HTTA=2-thenoyltrifluoroacetone, TMED=N,N,N',N'-tetramethylethylendiamine) precursor. The effects of growth parameters such as the plasma activation, the substrate, the surface temperature, and the ratio of fluxes of precursors on the structure, morphology, and optical and electrical properties of ZnO thin films have been studied. Under a very low plasma power of 20 W, c-axis oriented hexagonal ZnO thin films are grown on hexagonal sapphire (0001), cubic Si(001) and amorphous quartz substrates. The substrate temperature mainly controls grain size.
Factors regulating the abundance and localization of synaptobrevin in the plasma membrane

PubMed Central

Dittman, Jeremy S.; Kaplan, Joshua M.

2006-01-01

After synaptic vesicle fusion, vesicle proteins must be segregated from plasma membrane proteins and recycled to maintain a functional vesicle pool. We monitored the distribution of synaptobrevin, a vesicle protein required for exocytosis, in Caenorhabditis elegans motor neurons by using a pH-sensitive synaptobrevin GFP fusion protein, synaptopHluorin. We estimated that 30% of synaptobrevin was present in the plasma membrane. By using a panel of endocytosis and exocytosis mutants, we found that the majority of surface synaptobrevin derives from fusion of synaptic vesicles and that, in steady state, synaptobrevin equilibrates throughout the axon. The surface synaptobrevin was enriched near active zones, and its spatial extent was regulated by the clathrin adaptin AP180. These results suggest that there is a plasma membrane reservoir of synaptobrevin that is supplied by the synaptic vesicle cycle and available for retrieval throughout the axon. The size of the reservoir is set by the relative rates of exo- and endocytosis. PMID:16844789
Development of barrier coatings for cellulosic-based materials by cold plasma methods

NASA Astrophysics Data System (ADS)

Denes, Agnes Reka

Cellulose-based materials are ideal candidates for future industries that need to be based on environmentally safe technologies and renewable resources. Wood represents an important raw material and its application as construction material is well established. Cellophane is one of the most important cellulosic material and it is widely used as packaging material in the food industry. Outdoor exposure of wood causes a combination of physical and chemical degradation processes due to the combined effects of sunlight, moisture, fungi, and bacteria. Cold-plasma-induced surface modifications are an attractive way for tailoring the characteristics of lignocellulosic substrates to prevent weathering degradation. Plasma-polymerized hexamethyldisiloxane (PPHMDSO) was deposited onto wood surfaces to create water repellent characteristics. The presence of a crosslinked macromolecular structure was detected. The plasma coated samples exhibited very high water contact angle values indicating the existence of hydrophobic surfaces. Reflective and electromagnetic radiation-absorbent substances were incorporated with a high-molecular-weight polydimethylsiloxane polymer in liquid phase and deposited as thin layers on wood surfaces. The macromolecular films, containing the dispersed materials, were then converted into a three dimensional solid state network by exposure to a oxygen-plasma. It was demonstrated that both UV-absorbent and reflectant components incorporated into the plasma-generated PDMSO matrix protected the wood from weathering degradation. Reduced oxidation and less degradation was observed after simulated weathering. High water contact angle values indicated a strong hydrophobic character of the oxygen plasma-treated PDMSO-coated samples. Plasma-enhanced surface modifications and coatings were employed to create water-vapor barrier layers on cellophane substrate surfaces. HMDSO was selected as a plasma gas and oxygen was used to ablate amorphous regions. Oxygen plasma treated cellophane and oxygen plasma treated and PPHMDSO coated cellophane surfaces were comparatively analyzed and the corresponding surface wettability characteristics were evaluated. The plasma generated surface topographies controlled the morphology of the PPHMDSO layers. Higher temperature HMDSO plasma-state environments lead to insoluble, crosslinked layers. Continuous and pulsed Csb2Fsb6 plasmas were also used for surface modification and excellent surface fluorination was achieved under the pulsed plasma conditions.
Ground Simulations of Near-Surface Plasma Field and Charging at the Lunar Terminator

NASA Astrophysics Data System (ADS)

Polansky, J.; Ding, N.; Wang, J.; Craven, P.; Schneider, T.; Vaughn, J.

2012-12-01

Charging in the lunar terminator region is the most complex and is still not well understood. In this region, the surface potential is sensitively influenced by both solar illumination and plasma flow. The combined effects from localized shadow generated by low sun elevation angles and localized wake generated by plasma flow over the rugged terrain can generate strongly differentially charged surfaces. Few models currently exist that can accurately resolve the combined effects of plasma flow and solar illumination over realistic lunar terminator topographies. This paper presents an experimental investigation of lunar surface charging at the terminator region in simulated plasma environments in a vacuum chamber. The solar wind plasma flow is simulated using an electron bombardment gridded Argon ion source. An electrostatic Langmuir probe, nude Faraday probes, a floating emissive probe, and retarding potential analyzer are used to quantify the plasma flow field. Surface potentials of both conducting and dielectric materials immersed in the plasma flow are measured with a Trek surface potential probe. The conducting material surface potential will simultaneously be measured with a high impedance voltmeter to calibrate the Trek probe. Measurement results will be presented for flat surfaces and objects-on-surface for various angles of attack of the plasma flow. The implications on the generation of localized plasma wake and surface charging at the lunar terminator will be discussed. (This research is supported by the NASA Lunar Advanced Science and Exploration Research program.)
The robust bio-immobilization based on pulsed plasma polymerization of cyclopropylamine and glutaraldehyde coupling chemistry

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

NASA Astrophysics Data System (ADS)

Privat-Maldonado, Angela; O'Connell, Deborah; Welch, Emma; Vann, Roddy; van der Woude, Marjan W.

2016-10-01

Low temperature plasmas (LTPs) generate a cocktail of reactive nitrogen and oxygen species (RNOS) with bactericidal activity. The RNOS however are spatially unevenly distributed in the plasma. Here we test the hypothesis that this distribution will affect the mechanisms underpinning plasma bactericidal activity focussing on the level of DNA damage in situ. For the first time, a quantitative, single cell approach was applied to assess the level of DNA damage in bacteria as a function of the radial distance from the centre of the plasma jet. Salmonella enterica on a solid, dry surface was treated with two types of LTP: an atmospheric-pressure dielectric barrier discharge plasma jet (charged and neutral species) and a radio-frequency atmospheric-pressure plasma jet (neutral species). In both cases, there was an inverse correlation between the degree of DNA damage and the radial distance from the centre of the plasma, with the highest DNA damage occurring directly under the plasma. This trend was also observed with Staphylococcus aureus. LTP-generated UV radiation was eliminated as a contributing factor. Thus valuable mechanistic information can be obtained from assays on biological material, which can inform the development of LTP as a complementary or alternative therapy for (topical) bacterial infections.

Spatial Dependence of DNA Damage in Bacteria due to Low-Temperature Plasma Application as Assessed at the Single Cell Level

PubMed Central

Privat-Maldonado, Angela; O’Connell, Deborah; Welch, Emma; Vann, Roddy; van der Woude, Marjan W.

2016-01-01

Low temperature plasmas (LTPs) generate a cocktail of reactive nitrogen and oxygen species (RNOS) with bactericidal activity. The RNOS however are spatially unevenly distributed in the plasma. Here we test the hypothesis that this distribution will affect the mechanisms underpinning plasma bactericidal activity focussing on the level of DNA damage in situ. For the first time, a quantitative, single cell approach was applied to assess the level of DNA damage in bacteria as a function of the radial distance from the centre of the plasma jet. Salmonella enterica on a solid, dry surface was treated with two types of LTP: an atmospheric-pressure dielectric barrier discharge plasma jet (charged and neutral species) and a radio-frequency atmospheric-pressure plasma jet (neutral species). In both cases, there was an inverse correlation between the degree of DNA damage and the radial distance from the centre of the plasma, with the highest DNA damage occurring directly under the plasma. This trend was also observed with Staphylococcus aureus. LTP-generated UV radiation was eliminated as a contributing factor. Thus valuable mechanistic information can be obtained from assays on biological material, which can inform the development of LTP as a complementary or alternative therapy for (topical) bacterial infections. PMID:27759098
Coherent nonlinear coupling between a long-wavelength mode and small-scale turbulence in the TEXT tokamak

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

Tsui, H.Y.W.; Rypdal, K.; Ritz, C.P.

1993-04-26

Bispectral analysis of Langmuir probe data indicates that coherent nonlinear coupling, in addition to the noncoherent turbulent interactions, exists in the edge plasma of the tokamak TEXT. Not all the modes involved reside within the spectral region of the usual broadband turbulence. At a major resonant surface the small-scale turbulent activity interacts [ital coherently] with a localized long-wavelength mode; a signature of regular or coherent structure. By the observed coupling to the transport related turbulence, the long-wavelength mode can influence plasma confinement indirectly. These observations signify the influence of low-order resonant surfaces on the edge turbulence in tokamaks.
Investigation of hybrid plasma-catalytic removal of acetone over CuO/γ-Al2O3 catalysts using response surface method.

PubMed

Zhu, Xinbo; Tu, Xin; Mei, Danhua; Zheng, Chenghang; Zhou, Jinsong; Gao, Xiang; Luo, Zhongyang; Ni, Mingjiang; Cen, Kefa

2016-07-01

In this work, plasma-catalytic removal of low concentrations of acetone over CuO/γ-Al2O3 catalysts was carried out in a cylindrical dielectric barrier discharge (DBD) reactor. The combination of plasma and the CuO/γ-Al2O3 catalysts significantly enhanced the removal efficiency of acetone compared to the plasma process using the pure γ-Al2O3 support, with the 5.0 wt% CuO/γ-Al2O3 catalyst exhibiting the best acetone removal efficiency of 67.9%. Catalyst characterization was carried out to understand the effect the catalyst properties had on the activity of the CuO/γ-Al2O3 catalysts in the plasma-catalytic reaction. The results indicated that the formation of surface oxygen species on the surface of the catalysts was crucial for the oxidation of acetone in the plasma-catalytic reaction. The effects that various operating parameters (discharge power, flow rate and initial concentration of acetone) and the interactions between these parameters had on the performance of the plasma-catalytic removal of acetone over the 5.0 wt% CuO/γ-Al2O3 catalyst were investigated using central composite design (CCD). The significance of the independent variables and their interactions were evaluated by means of the Analysis of Variance (ANOVA). The results showed that the gas flow rate was the most significant factor affecting the removal efficiency of acetone, whilst the initial concentration of acetone played the most important role in determining the energy efficiency of the plasma-catalytic process. Copyright © 2016 Elsevier Ltd. All rights reserved.
Influence of atmospheric pressure low-temperature plasma treatment on the shear bond strength between zirconia and resin cement.

PubMed

Ito, Yuki; Okawa, Takahisa; Fukumoto, Takahiro; Tsurumi, Akiko; Tatsuta, Mitsuhiro; Fujii, Takamasa; Tanaka, Junko; Tanaka, Masahiro

2016-10-01

Zirconia exhibits excellent strength and high biocompatibility in technological applications and it is has therefore been investigated for clinical applications and research. Before setting prostheses, a crown prosthesis inner surface is sandblasted with alumina to remove contaminants and form small cavities. This alumina sandblasting causes stress-induced phase transition of zirconia. Atmospheric-pressure low-temperature plasma has been applied in the dental industry, particularly for adhesives, as a surface treatment to activate the surface energy and remove contaminants. The purpose of this study was to examine the influence of atmospheric-pressure low-temperature plasma treatment on the shear bond strength between zirconia and adhesive resin cement. The surface treatment method was classified into three groups: untreated (Cont group), alumina sandblast treatment (Sb group), and atmospheric-pressure low-temperature plasma treatment (Ps group). Adhesive resin cement was applied to stainless steel and bonded to zirconia. Shear adhesion tests were performed after complete hardening of the cement. Multiple comparisons were performed using a one-way analysis of variance and the Bonferroni method. X-ray diffractometry was used to examine the change in zirconia crystal structure. Statistically significant differences were noted between the control and Sb groups and between the control and Ps groups. In contrast, no statistically significant differences were noted for the Ps and Sb bond strength. Atmospheric-pressure low-temperature plasma treatment did not affect the zirconia crystal structure. Atmospheric-pressure low-temperature plasma treatment improves the bonding strength of adhesive resin cement as effectively as alumina sandblasting, and does not alter the zirconia crystal structure. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Kinetics and Chemistry of Ionization Wave Discharges Propagating Over Dielectric Surfaces

NASA Astrophysics Data System (ADS)

Petrishchev, Vitaly

Experimental studies of near-surface ionization wave electric discharges generated by high peak voltage (20-30 kV), nanosecond duration pulses (full width at half-maximum 50-100 ns) of positive and negative polarity and propagating over dielectric surfaces have been performed. A novel way to sustain diffuse, reproducible, ns pulse surface plasmas at a liquid-vapor interface is demonstrated at buffer gas pressures ranging from 10 to 200 Torr. Generation of surface ionization waves well reproduced shot-to-shot and sustaining diffuse near-surface plasmas is one of the principal advantages of the use of ns pulse discharge waveforms. This makes possible characterization of these plasmas in repetitively pulsed experiments. Numerous applications of these plasmas include low-temperature plasma assisted combustion, plasma fuel reforming, plasma flow control, plasma materials processing, agriculture, biology, and medicine. The objectives of the present work are (i) to demonstrate that surface ionization wave discharge plasmas sustained at a liquid-vapor interface can be used as an experimental platform for studies of near-surface plasma chemical reaction kinetics, at the conditions when the interface acts as a high-yield source of radical species, and (ii) to obtain quantitative insight into dynamics, kinetics and chemistry of surface ionization wave discharges and provide experimental data for validation of kinetic models, to assess their predictive capability. Generation of the initial radical pool may trigger a number of plasma chemical processes leading to formation of a variety of stable product species, depending on the initial composition of the liquid and the buffer gas flow. One of the products formed and detected during surface plasma / liquid water interaction is hydroxyl radical, which is closely relevant to applications of plasmas for biology and medicine. The present work includes detailed studies of surface ionization wave discharges sustained in different buffer gases over solid and liquid dielectric surfaces, such as quartz, distilled water, saline solution, and alcohols, over a wide range of pressures. Specific experiments include: measurements of ionization wave speed; plasma emission imaging using a ns gate camera; detection of surface discharge plasma chemistry products using Fourier transform infrared absorption spectroscopy; surface charge dynamics on short (ns) and long (hundreds of mus) time scales; time-resolved electron density and electron temperature measurements in a ns pulse surface discharge in helium by Thomson scattering; spatially-resolved absolute OH and H atom concentration measurements in ns pulse discharges over distilled water by single-photon and two-photon Laser Induced Fluorescence; and schlieren imaging of perturbations generated by a ns pulse dielectric barrier discharge in a surface plasma actuator in quiescent atmospheric pressure air.
Downregulation of surface sodium pumps by endocytosis during meiotic maturation of Xenopus laevis oocytes

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

Schmalzing, G.; Eckard, P.; Kroener, S.P.

1990-01-01

During meiotic maturation, plasma membranes of Xenopus laevis oocytes completely lose the capacity to transport Na and K and to bind ouabain. To explore whether the downregulation might be due to an internalization of the sodium pump molecules, the intracellular binding of ouabain was determined. Selective permeabilization of the plasma membrane of mature oocytes (eggs) by digitonin almost failed to disclose ouabain binding sites. However, when the eggs were additionally treated with 0.02% sodium dodecyl sulfate (SDS) to permeabilize inner membranes, all sodium pumps present before maturation were recovered. Phosphorylation by (gamma-32P)ATP combined with SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiographymore » showed that sodium pumps were greatly reduced in isolated plasma membranes of eggs. According to sucrose gradient fractionation, maturation induced a shift of sodium pumps from the plasma membrane fraction to membranes of lower buoyant density with a protein composition different from that of the plasma membrane. Endocytosed sodium pumps identified on the sucrose gradient from (3H)ouabain bound to the cell surface before maturation could be phosphorylated with inorganic (32P)phosphate. The findings suggest that downregulation of sodium pumps during maturation is brought about by translocation of surface sodium pumps to an intracellular compartment, presumably endosomes. This contrasts the mechanism of downregulation of Na-dependent cotransport systems, the activities of which are reduced as a consequence of a maturation-induced depolarization of the membrane without a removal of the corresponding transporter from the plasma membrane.« less
Miniaturized cathodic arc plasma source

DOEpatents

Anders, Andre; MacGill, Robert A.

2003-04-15

A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.
Evaluation of mechanism of cold atmospheric pressure plasma assisted polymerization of acrylic acid on low density polyethylene (LDPE) film surfaces: Influence of various gaseous plasma pretreatment

NASA Astrophysics Data System (ADS)

Ramkumar, M. C.; Pandiyaraj, K. Navaneetha; Arun Kumar, A.; Padmanabhan, P. V. A.; Uday Kumar, S.; Gopinath, P.; Bendavid, A.; Cools, P.; De Geyter, N.; Morent, R.; Deshmukh, R. R.

2018-05-01

Owing to its exceptional physiochemical properties, low density poly ethylene (LDPE) has wide range of tissue engineering applications. Conversely, its inadequate surface properties make LDPE an ineffectual candidate for cell compatible applications. Consequently, plasma-assisted polymerization with a selected precursor is a good choice for enhancing its biocompatibility. The present investigation studies the efficiency of plasma polymerization of acrylic acid (AAC) on various gaseous plasma pretreated LDPE films by cold atmospheric pressure plasma, to enhance its cytocompatibility. The change in chemical composition and surface topography of various gaseous plasma pretreated and acrylic deposited LDPE films has been assessed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The changes in hydrophilic nature of surface modified LDPE films were studied by contact angle (CA) analysis. Cytocompatibility of the AAC/LDPE films was also studied in vitro, using RIN-5F cells. The results acquired by the XPS and AFM analysis clearly proved that cold atmospheric pressure (CAP) plasma assisted polymerization of AAC enhances various surface properties including carboxylic acid functional group density and increased surface roughness on various gaseous plasma treated AAC/LDPE film surfaces. Moreover, contact angle analysis clearly showed that the plasma polymerized samples were hydrophilic in nature. In vitro cytocompatibility analysis undoubtedly validates that the AAC polymerized various plasma pretreated LDPE films surfaces stimulate cell distribution and proliferation compared to pristine LDPE films. Similarly, cytotoxicity analysis indicates that the AAC deposited various gaseous plasma pretreated LDPE film can be considered as non-toxic as well as stimulating cell viability significantly. The cytocompatible properties of AAC polymerized Ar + O2 plasma pretreated LDPE films were found to be more pronounced compared to the other plasma pretreated AAC/LDPE films.
Oxygen plasma surface modification augments poly(L-lactide-co-glycolide) cytocompatibility toward osteoblasts and minimizes immune activation of macrophages.

PubMed

Scislowska-Czarnecka, Anna; Szmigiel, Dariusz; Genet, Michel; Dupont-Gillain, Christine; Pamula, Elzbieta; Kolaczkowska, Elzbieta

2015-12-01

Here, we report on modification of one of the model biomedical polymers, poly L-lactide-co-glycolide (PLGA; 85:15), by reactive ion etching (RIE) oxygen plasma treatment. PLGA's major disadvantage is high hydrophobicity which restrains binding of cell-adhesive proteins and host cells. In the current approach, we aimed to answer two questions: (1) will only short (10 s) and moderate (20-200 mTorr, 45-90 W) RIE oxygen plasma treatment, leading to decrease of water contact angle by only up to 10°, sufficiently improve PLGA adherence to cells, and (2) how will this affect osteoblasts and activation of the immune system? All obtained modified PLGAs had improved hydrophilicity but unaltered roughness (as revealed by water contact angle measurements, X-ray photoelectron spectroscopy, and atomic force microscopy) resulting in significantly improved adhesion of osteoblasts (MG-63) and their low activation. Importantly, macrophages (RAW 264.7), one of the key cells initiating inflammation and bone resorption, responded significantly less vigorously to the modified polymers, expressing/releasing lower amounts of nitric oxide, matrix metalloproteinases (MMP-9), and pro-inflammatory cytokines (TNF-α, IL-6, IL-12p70, IFN-γ, IL-10). We conclude that already slight RIE oxygen plasma modification of PLGA is sufficient to improve its surface properties, and enhance cytocompatibility. Most importantly, this type of modification prevents excessive immune response. © 2015 Wiley Periodicals, Inc.
Surface modification of ethylene-co-tetrafluoroethylene copolymer (ETFE) by plasma

NASA Astrophysics Data System (ADS)

Inagaki, N.

2003-08-01

Surface modification of ETFE surfaces by remote H 2, O 2 and Ar plasmas were investigated from the viewpoint of selective modification of CH 2-CH 2 or CF 2-CF 2 component. The remote H 2 and Ar plasmas modified effectively ETFE surfaces into hydrophilic, but the remote O 2 plasma did not. The remote H 2 plasma interacted with CF 2 component rather than CH 2 component in ETFE. The remote O 2 plasma interacted with CH 2 component as well as CF 2 component in ETFE chains.
A New Kinetic Simulation Model with Self-Consistent Calculation of Regolith Layer Charging for Moon-Plasma Interactions

NASA Astrophysics Data System (ADS)

Han, D.; Wang, J.

2015-12-01

The moon-plasma interactions and the resulting surface charging have been subjects of extensive recent investigations. While many particle-in-cell (PIC) based simulation models have been developed, all existing PIC simulation models treat the surface of the Moon as a boundary condition to the plasma flow. In such models, the surface of the Moon is typically limited to simple geometry configurations, the surface floating potential is calculated from a simplified current balance condition, and the electric field inside the regolith layer cannot be resolved. This paper presents a new full particle PIC model to simulate local scale plasma flow and surface charging. A major feature of this new model is that the surface is treated as an "interface" between two mediums rather than a boundary, and the simulation domain includes not only the plasma but also the regolith layer and the bedrock underneath it. There are no limitations on the surface shape. An immersed-finite-element field solver is applied which calculates the regolith surface floating potential and the electric field inside the regolith layer directly from local charge deposition. The material property of the regolith layer is also explicitly included in simulation. This new model is capable of providing a self-consistent solution to the plasma flow field, lunar surface charging, the electric field inside the regolith layer and the bedrock for realistic surface terrain. This new model is applied to simulate lunar surface-plasma interactions and surface charging under various ambient plasma conditions. The focus is on the lunar terminator region, where the combined effects from the low sun elevation angle and the localized plasma wake generated by plasma flow over a rugged terrain can generate strongly differentially charged surfaces and complex dust dynamics. We discuss the effects of the regolith properties and regolith layer charging on the plasma flow field, dust levitation, and dust transport.
Surface Modification of Nonwoven fabrics by Atmospheric Brush Plasma

NASA Astrophysics Data System (ADS)

Oksuz, Lutfi; Uygun, Emre; Bozduman, Ferhat; Yurdabak Karaca, Gozde; Asan, Orkun Nuri; Uygun Oksuz, Aysegul

2017-10-01

Polypropylene nonwoven fabrics (PPNF) are used in disposable absorbent articles, such as diapers, feminine care products, wipes. PPNF need to be wettable by water or aqueous-based liquid. Plasma surface treatment/modification has turned out to be a well-accepted method since it offers superior surface property enhancement than other chemical methods. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical application. The purpose of this study was to reveal the effectiveness of non-thermal atmospheric plasma brush in surface wettability and modification of two different nonwoven surfaces.
Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber

NASA Astrophysics Data System (ADS)

Basak, Ganesh C.; Bandyopadhyay, Abhijit; Neogi, Sudarsan; Bhowmick, Anil K.

2011-01-01

Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon-oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C-O and -Cdbnd O functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.
Mitochondrial and Plasma Membrane Pools of Stomatin-Like Protein 2 Coalesce at the Immunological Synapse during T Cell Activation

PubMed Central

Christie, Darah A.; Kirchhof, Mark G.; Vardhana, Santosh; Dustin, Michael L.; Madrenas, Joaquín

2012-01-01

Stomatin-like protein 2 (SLP-2) is a member of the stomatin – prohibitin – flotillin – HflC/K (SPFH) superfamily. Recent evidence indicates that SLP-2 is involved in the organization of cardiolipin-enriched microdomains in mitochondrial membranes and the regulation of mitochondrial biogenesis and function. In T cells, this role translates into enhanced T cell activation. Although the major pool of SLP-2 is associated with mitochondria, we show here that there is an additional pool of SLP-2 associated with the plasma membrane of T cells. Both plasma membrane-associated and mitochondria-associated pools of SLP-2 coalesce at the immunological synapse (IS) upon T cell activation. SLP-2 is not required for formation of IS nor for the re-localization of mitochondria to the IS because SLP-2-deficient T cells showed normal re-localization of these organelles in response to T cell activation. Interestingly, upon T cell activation, we found the surface pool of SLP-2 mostly excluded from the central supramolecular activation complex, and enriched in the peripheral area of the IS where signalling TCR microclusters are located. Based on these results, we propose that SLP-2 facilitates the compartmentalization not only of mitochondrial membranes but also of the plasma membrane into functional microdomains. In this latter location, SLP-2 may facilitate the optimal assembly of TCR signalosome components. Our data also suggest that there may be a net exchange of membrane material between mitochondria and plasma membrane, explaining the presence of some mitochondrial proteins in the plasma membrane. PMID:22623988
Nanostructuring of Palladium with Low-Temperature Helium Plasma

PubMed Central

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

2015-01-01

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

PubMed

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

2015-11-25

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

PubMed

Liu, Han-Yuan; Chen, Wei-Liang; Ober, Christopher K; Daniel, Susan

2018-01-23

Reconstituted supported lipid bilayers (SLB) are widely used as in vitro cell-surface models because they are compatible with a variety of surface-based analytical techniques. However, one of the challenges of using SLBs as a model of the cell surface is the limited complexity in membrane composition, including the incorporation of transmembrane proteins and lipid diversity that may impact the activity of those proteins. Additionally, it is challenging to preserve the transmembrane protein native orientation, function, and mobility in SLBs. Here, we leverage the interaction between cell plasma membrane vesicles and polyelectrolyte brushes to create planar bilayers from cell plasma membrane vesicles that have budded from the cell surface. This approach promotes the direct incorporation of membrane proteins and other species into the planar bilayer without using detergent or reconstitution and preserves membrane constituents. Furthermore, the structure of the polyelectrolyte brush serves as a cushion between the planar bilayer and rigid supporting surface, limiting the interaction of the cytosolic domains of membrane proteins with this surface. Single particle tracking was used to analyze the motion of GPI-linked yellow fluorescent proteins (GPI-YFP) and neon-green fused transmembrane P2X2 receptors (P2X2-neon) and shows that this platform retains over 75% mobility of multipass transmembrane proteins in its native membrane environment. An enzyme accessibility assay confirmed that the protein orientation is preserved and results in the extracellular domain facing toward the bulk phase and the cytosolic side facing the support. Because the platform presented here retains the complexity of the cell plasma membrane and preserves protein orientation and mobility, it is a better representative mimic of native cell surfaces, which may find many applications in biological assays aimed at understanding cell membrane phenomena.
In vitro characterization of two different atmospheric plasma jet chemical functionalizations of titanium surfaces

NASA Astrophysics Data System (ADS)

Mussano, F.; Genova, T.; Verga Falzacappa, E.; Scopece, P.; Munaron, L.; Rivolo, P.; Mandracci, P.; Benedetti, A.; Carossa, S.; Patelli, A.

2017-07-01

Plasma surface activation and plasma polymers deposition are promising technologies capable to modulate biologically relevant surface features of biomaterials. The purpose of this study was to evaluate the biological effects of two different surface modifications, i.e. amine (NH2-Ti) and carboxylic/esteric (COOH/R-Ti) functionalities obtained from 3-aminopropyltriethoxysilane (3-APTES) and methylmethacrylate (MMA) precursors, respectively, through an atmospheric plasma jet RF-APPJ portable equipment. The coatings were characterized by Scanning Electron Microscopy, FT-IR spectroscopy, XPS and surface energy calculations. Stability in water and after UV sterilization were also verified. The pre-osteoblastic murine cell line MC3T3-E1 was used to perform the in-vitro tests. The treated samples showed a higher quantity of adsorbed proteins and improved osteoblast cells adhesion on the surfaces compared to the pristine titanium, in particular the COOH/R-Ti led to a nearly two-fold improvement. Cell proliferation on coated samples was initially (at 24 h) lower than on titanium control, while, at 48 h, COOH/R-Ti reached the proliferation rate of pristine titanium. Cells grown on NH2-Ti were more tapered and elongated in shape with lower areas than on COOH/R-Ti enriched surfaces. Finally, NH2-Ti significantly enhanced osteocalcin production, starting from 14 days, while COOH/R-Ti had this effect only from 21 days. Notably, NH2-Ti was more efficient than COOH/R-Ti at 21 days. The amine functionality elicited the most relevant osteogenic effect in terms of osteocalcin expression, thus establishing an interesting correlation between early cell morphology and later differentiation stages. Taken together, these data encourage the use of the functionalization procedures here reported in further studies.
Space environmental interactions with spacecraft surfaces

NASA Technical Reports Server (NTRS)

Stevens, J. N.

1979-01-01

Environmental interactions are defined as the response of spacecraft surfaces to the charged-particle environment. These interactions are divided into two broad categories: spacecraft passive, in which the environment acts on the surfaces and spacecraft active, in which the spacecraft or a system on the spacecraft causes the interaction. The principal spacecraft passive interaction of concern is the spacecraft charging phenomenon. The spacecraft active category introduces the concept of interactions with the thermal plasma environment and Earth's magnetic fields, which are important at all altitudes and must be considered the designs of proposed large space structures and space power systems. The status of the spacecraft charging investigations is reviewed along with the spacecraft active interactions.
Creation of fluorocarbon barriers on surfaces of starch-based products through cold plasma treatment

NASA Astrophysics Data System (ADS)

Han, Yousoo

Two kinds of starch foam trays (starch and aspen-starch foam trays) were produced using a lab model baking machine. Surfaces of the trays were treated with CF4 and SF6 plasma to create fluorine-rich layers on the surfaces, which might show strong water resistance. The plasma parameters, such like RF power, gas pressure and reaction time, were varied to evaluate the effects of each parameter on fluorination of surfaces. The atomic concentrations of fluorine, oxygen and carbon on samples' surfaces were earned from ESCA (electron spectroscopy for chemical analysis) and contact angles of sample surfaces were measured for hydrophobicity. For water resistance of plasma treated surfaces, liquid water uptake and water vapor uptake test were performed. Also, equilibrium moisture contents of unmodified and plasma treated samples were measured to evaluate biodegradability of plasma treated samples. Fluorine-rich barriers were created on sample surfaces treated with CF 4 and SF6 plasma. The fluorine atomic concentrations of treated sample surfaces were ranged from 34.4% to 64.4% (CF4 treatment) and 43.6% to 57.9% (SF6 treatment). It was found at both plasma gases that plasma parameters affected total fluorine concentration and carbon-peak shapes in ESCA surveys, which imply different distributions of mono- or multi-fluoro carbon's contents. In various reaction times, it was found that total fluorine contents were decreased after a critical point as the reaction time was prolonged, which may imply that a dominant mechanism has been changed from deposition or functionalization to etching. Oxygen atomic concentration was decreased at sample surfaces treated by both plasmas. In the case of SF6 plasma, it was proved that the removal of oxygen surely occurred because there was no addition of sulfur species. Plasma treated sample surfaces had high contact angles with distilled water up to 150° and the high values of angles have been kept constant up to for 15 minutes. Fluorine-rich barriers created by plasma showed lower water liquid and vapor permeability than untreated surfaces did. Plasma treated samples had similar moisture contents with untreated samples at all relative humidity tested. AFM and SEM images were taken for sample surfaces' morphology and topography.

Composites in small and simple devices to increase mixing on detector surfaces

NASA Astrophysics Data System (ADS)

Hernandez, L. F.; Lima, R. R.; Leite, A. R.; Fachini, E. R.; Silva, M. L. P.

2013-03-01

This work aims at three different applications for the betterment of plasma generated-composite thin films: pre-mixing, spray formation in miniaturized structures and an increase in the performance of detector surfaces. Miniaturized structures were projected, simulated with FEMLAB® 3.2 software and then constructed. Clustered films made from tetraethoxysilane (TEOS) and nonafluoro(iso)butyl ether (HFE®) precursors were deposited on silicon, acrylic and quartz substrates for different kinds of film characterization/or in the projected structures. Physical and chemical characterization guided the selection of best films previous to/after UVC exposure. The active surfaces (plasma-deposited films) in structures were modified by UVC exposure and then tested. The applications include pre-mixing of liquids and/or spray formation, best results being obtained with surface covered by derivative-HFE films, which acted as passivation layers. Preliminary results show good humidity sensing for TEOS-derivative films.
Surface modification of gutta-percha cones by non-thermal plasma.

PubMed

Prado, Maíra; Menezes, Marilia Santana de Oliveira; Gomes, Brenda Paula Figueiredo de Almeida; Barbosa, Carlos Augusto de Melo; Athias, Leonardo; Simão, Renata Antoun

2016-11-01

This study was designed to evaluate the effects of Oxygen and Argon plasma on gutta-percha surfaces. A total of 185 flat smooth gutta-percha surfaces were used. Samples were divided into groups: control: no plasma treatment; Oxygen: treatment with Oxygen plasma for 1min; Argon: treatment with Argon plasma for 1min. Samples were evaluated topographically by scanning electron microscopy and atomic force microscopy; and chemically by Fourier Transform-infrared Spectroscopy. A goniometer was used to determine the surface free energy and the wettability of the endodontic sealers. Additionally 60 bovine teeth were filled using pellets of gutta-percha (control, oxygen and argon plasma) and the sealers. Teeth were evaluated by push-out and microleakage tests. Data were statistically analyzed using specific tests. Argon plasma did not change the surface topography, while Oxygen plasma led to changes. Both treatments chemically modified the gutta-percha surface. Argon and Oxygen plasma increased the surface free energy and favored the wettability of AH Plus and Pulp Canal Sealer EWT. Regarding bond strength analysis, for AH Plus sealer, both plasma treatments on gutta-percha favored the bond strength to dentin. However, for Pulp Canal Sealer, there is no statistically significant influence. For leakage test, dye penetration occurred between sealer and dentin in all groups. In conclusion, Oxygen plasma led to both topographic and chemical changes in the gutta-percha surface, while Argon plasma caused only chemical changes. Both treatments increased the surface free energy, favoring the wettability of AH Plus and Pulp Canal Sealer EWT sealers and influenced positively in the adhesion and leakage. Copyright © 2016 Elsevier B.V. All rights reserved.
Incorporation of low energy activated nitrogen onto HOPG surface: Chemical states and thermal stability studies by in-situ XPS and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Chandran, Maneesh; Shasha, Michal; Michaelson, Shaul; Hoffman, Alon

2016-09-01

In this paper we report the chemical states analysis of activated nitrogen incorporated highly oriented pyrolytic graphite (HOPG) surface under well-controlled conditions. Nitrogen incorporation is carried out by two different processes: an indirect RF nitrogen plasma and low energy (1 keV) N2+ implantation. Bonding configuration, concentration and thermal stability of the incorporated nitrogen species by aforesaid processes are systematically compared by in-situ X-ray photoelectron spectroscopy (XPS). Relatively large concentration of nitrogen is incorporated onto RF nitride HOPG surface (16.2 at.%), compared to N2+ implanted HOPG surface (7.7 at.%). The evolution of N 1s components (N1, N2, N3) with annealing temperature is comprehensively discussed, which indicates that the formation and reorganization of local chemical bonding states are determined by the process of nitridation and not by the prior chemical conditioning (i.e., amorphization or hydrogenation) of the HOPG surface. A combined XPS and Raman spectroscopy studies revealed that N2+ implantation process resulted in a high level of defects to the HOPG surface, which cannot be annealed-out by heat treatment up to 1000 °C. On the other hand, the RF nitrogen plasma process did not produce a high level of surface defects, while incorporating nearly the same amount of stable nitrogen species.
Stability of Atmospheric-Pressure Plasma Induced Changes on Polycarbonate Surfaces

NASA Technical Reports Server (NTRS)

Sharma, Rajesh; Holcomb, Edward; Trigwell, Steve

2006-01-01

Polycarbonate films are subjected to plasma treatment in a number of applications such as improving adhesion between polycarbonate and silicon alloy in protective and optical coatings. The changes in surface chemistry due to plasma treatment have tendency to revert back. Thus stability of the plasma induced changes on polymer surfaces over desired time period is very important. The objective of this study was to examine the effect of ageing on atmospheric pressure helium-plasma treated polycarbonate (PC) sample as a function of treatment time. The ageing effects were studied over a period of 10 days. The samples were plasma treated for 0.5, 2, 5 and 10 minutes. Contact angle measurements were made to study surface energy changes. Modification of surface chemical structure was examined using, X-ray Photoelectron Spectroscopy (XPS). Contact angle measurements on untreated and plasma treated surfaces were made immediately, 24, 48, 72 and 96 hrs after treatment. Contact angle decreased from 93 deg for untreated sample to 30 deg for sample plasma treated for 10 minutes. After 10 days the contact angles for the 10 minute plasma treated sample increased to 67 deg, but it never reverted back to that of untreated surface. Similarly the O/C ratio increased from 0.136 for untreated sample to 0.321 for 10 minute plasma treated sample indication increase in surface energy.
Numerical Prediction of the Influence of Process Parameters on Large Area Diamond Deposition by DC Arcjet with ARC Roots Rotating and Operating at Gas Recycling Mode

NASA Astrophysics Data System (ADS)

Lu, F. X.; Huang, T. B.; Tang, W. Z.; Song, J. H.; Tong, Y. M.

A computer model have been set up for simulation of the flow and temperature field, and the radial distribution of atomic hydrogen and active carbonaceous species over a large area substrate surface for a new type dc arc plasma torch with rotating arc roots and operating at gas recycling mode A gas recycling radio of 90% was assumed. In numerical calculation of plasma chemistry, the Thermal-Calc program and a powerful thermodynamic database were employed. Numerical calculations to the computer model were performed using boundary conditions close to the experimental setup for large area diamond films deposition. The results showed that the flow and temperature field over substrate surface of Φ60-100mm were smooth and uniform. Calculations were also made with plasma of the same geometry but no arc roots rotation. It was clearly demonstrated that the design of rotating arc roots was advantageous for high quality uniform deposition of large area diamond films. Theoretical predictions on growth rate and film quality as well as their radial uniformity, and the influence of process parameters on large area diamond deposition were discussed in detail based on the spatial distribution of atomic hydrogen and the carbonaceous species in the plasma over the substrate surface obtained from thermodynamic calculations of plasma chemistry, and were compared with experimental observations.
Cold air plasma to decontaminate inanimate surfaces of the hospital environment.

PubMed

Cahill, Orla J; Claro, Tânia; O'Connor, Niall; Cafolla, Anthony A; Stevens, Niall T; Daniels, Stephen; Humphreys, Hilary

2014-03-01

The hospital environment harbors bacteria that may cause health care-associated infections. Microorganisms, such as multiresistant bacteria, can spread around the patient's inanimate environment. Some recently introduced biodecontamination approaches in hospitals have significant limitations due to the toxic nature of the gases and the length of time required for aeration. This study evaluated the in vitro use of cold air plasma as an efficient alternative to traditional methods of biodecontamination of hospital surfaces. Cultures of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli, and Acinetobacter baumannii were applied to different materials similar to those found in the hospital environment. Artificially contaminated sections of marmoleum, mattress, polypropylene, powder-coated mild steel, and stainless steel were then exposed to a cold air pressure plasma single jet for 30 s, 60 s, and 90 s, operating at approximately 25 W and 12 liters/min flow rate. Direct plasma exposure successfully reduced the bacterial load by log 3 for MRSA, log 2.7 for VRE, log 2 for ESBL-producing E. coli, and log 1.7 for A. baumannii. The present report confirms the efficient antibacterial activity of a cold air plasma single-jet plume on nosocomial bacterially contaminated surfaces over a short period of time and highlights its potential for routine biodecontamination in the clinical environment.
Novel Mechanisms in the Regulation of G Protein-coupled Receptor Trafficking to the Plasma Membrane*

PubMed Central

Tholanikunnel, Baby G.; Joseph, Kusumam; Kandasamy, Karthikeyan; Baldys, Aleksander; Raymond, John R.; Luttrell, Louis M.; McDermott, Paul J.; Fernandes, Daniel J.

2010-01-01

β2-Adrenergic receptors (β2-AR) are low abundance, integral membrane proteins that mediate the effects of catecholamines at the cell surface. Whereas the processes governing desensitization of activated β2-ARs and their subsequent removal from the cell surface have been characterized in considerable detail, little is known about the mechanisms controlling trafficking of neo-synthesized receptors to the cell surface. Since the discovery of the signal peptide, the targeting of the integral membrane proteins to plasma membrane has been thought to be determined by structural features of the amino acid sequence alone. Here we report that localization of translationally silenced β2-AR mRNA to the peripheral cytoplasmic regions is critical for receptor localization to the plasma membrane. β2-AR mRNA is recognized by the nucleocytoplasmic shuttling RNA-binding protein HuR, which silences translational initiation while chaperoning the mRNA-protein complex to the cell periphery. When HuR expression is down-regulated, β2-AR mRNA translation is initiated prematurely in perinuclear polyribosomes, leading to overproduction of receptors but defective trafficking to the plasma membrane. Our results underscore the importance of the spatiotemporal relationship between β2-AR mRNA localization, translation, and trafficking to the plasma membrane, and establish a novel mechanism whereby G protein-coupled receptor (GPCR) responsiveness is regulated by RNA-based signals. PMID:20739277
Activation of classical protein kinase C reduces the expression of human cationic amino acid transporter 3 (hCAT-3) in the plasma membrane.

PubMed

Rotmann, Alexander; Vékony, Nicole; Gassner, Davina; Niegisch, Günter; Strand, Dennis; Martiné, Ursula; Closs, Ellen I

2006-04-01

We have previously shown that activation of PKC (protein kinase C) results in internalization of hCAT-1 [human CAT-1 (cationic amino acid transporter 1)] and a decrease in arginine transport [Rotmann, Strand, Martiné and Closs (2004) J. Biol. Chem. 279, 54185-54192]. However, others found increased transport rates for arginine in response to PKC activation, suggesting a differential effect of PKC on different CAT isoforms. Therefore we investigated the effect of PKC on hCAT-3, an isoform expressed in thymus, brain, ovary, uterus and mammary gland. In Xenopus laevis oocytes and human U373MG glioblastoma cells, hCAT-3-mediated L-arginine transport was significantly reduced upon treatment with compounds that activate classical PKC. In contrast, inactive phorbol esters and an activator of novel PKC isoforms had no effect. PKC inhibitors (including the PKCalpha-preferring Ro 31-8280) reduced the inhibitory effect of the PKC-activating compounds. Microscopic analyses revealed a PMA-induced reduction in the cell-surface expression of fusion proteins between hCAT-3 and enhanced green fluorescent protein expressed in X. laevis oocytes and glioblastoma cells. Western-blot analysis of biotinylated surface proteins demonstrated a PMA-induced decrease in hCAT-3 in the plasma membrane, but not in total protein lysates. Pretreatment with a PKC inhibitor also reduced this PMA effect. It is concluded that similar to hCAT-1, hCAT-3 activity is decreased by PKC via reduction of transporter molecules in the plasma membrane. Classical PKC isoforms seem to be responsible for this effect.
Optimizing growth and post treatment of diamond for high capacitance neural interfaces.

PubMed

Tong, Wei; Fox, Kate; Zamani, Akram; Turnley, Ann M; Ganesan, Kumaravelu; Ahnood, Arman; Cicione, Rosemary; Meffin, Hamish; Prawer, Steven; Stacey, Alastair; Garrett, David J

2016-10-01

Electrochemical and biological properties are two crucial criteria in the selection of the materials to be used as electrodes for neural interfaces. For neural stimulation, materials are required to exhibit high capacitance and to form intimate contact with neurons for eliciting effective neural responses at acceptably low voltages. Here we report on a new high capacitance material fabricated using nitrogen included ultrananocrystalline diamond (N-UNCD). After exposure to oxygen plasma for 3 h, the activated N-UNCD exhibited extremely high electrochemical capacitance greater than 1 mF/cm(2), which originates from the special hybrid sp(2)/sp(3) structure of N-UNCD. The in vitro biocompatibility of the activated N-UNCD was then assessed using rat cortical neurons and surface roughness was found to be critical for healthy neuron growth, with best results observed on surfaces with a roughness of approximately 20 nm. Therefore, by using oxygen plasma activated N-UNCD with appropriate surface roughness, and considering the chemical and mechanical stability of diamond, the fabricated neural interfaces are expected to exhibit high efficacy, long-term stability and a healthy neuron/electrode interface. Copyright © 2016 Elsevier Ltd. All rights reserved.
Cracks and nanodroplets produced on tungsten surface samples by dense plasma jets

NASA Astrophysics Data System (ADS)

Ticoş, C. M.; Galaţanu, M.; Galaţanu, A.; Luculescu, C.; Scurtu, A.; Udrea, N.; Ticoş, D.; Dumitru, M.

2018-03-01

Small samples of 12.5 mm in diameter made from pure tungsten were exposed to a dense plasma jet produced by a coaxial plasma gun operated at 2 kJ. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after applying consecutive plasma shots. Cracks and craters were produced in the surface due to surface tensions during plasma heating. Nanodroplets and micron size droplets could be observed on the samples surface. An energy-dispersive spectroscopy (EDS) analysis revealed that the composition of these droplets coincided with that of the gun electrode material. Four types of samples were prepared by spark plasma sintering from powders with the average particle size ranging from 70 nanometers up to 80 μm. The plasma power load to the sample surface was estimated to be ≈4.7 MJ m-2 s-1/2 per shot. The electron temperature and density in the plasma jet had peak values 17 eV and 1.6 × 1022 m-3, respectively.
Plasma properties at 67P/Churyumov-Gerasimenko: a comparision between PP-SESAME/Philae/Rosetta and RPC/MIP/Rosetta

NASA Astrophysics Data System (ADS)

Schmidt, Walter; Henri, Pierre; Lebreton, Jean Pierre; Vallières, Xavier; Grard, Réjean; Hamelin, Michel; Le Gall, Alice; Lethuillier, Anthony; Ciarletti, Valerie; Caujolle-Bert, Sylvain; Seidensticker, Klaus; Fischer, Hans-Herbert

2016-04-01

On November 12, 2014, the Rosetta landing module Philae approached the nucleus of 67P/Churyumov-Gerasimenko and eventually settled on the surface in a location named Abydos, though its exact coordinates are still unknown. The Permittivity Probe (PP) as part of the SESAME (Surface Electric Sounding and Acoustic Monitoring Experiment) instrument package [1] was designed to not only measure the electrical properties of the comet's surface material by actively injecting an alternating current at different frequencies into the material underneath the Lander but also to monitor potential variations between its two receivers and the electrical conductivity of the plasma environment while still in space. By sampling the potential difference at 40 kHz between the soles of two of the feet attached to Philae's landing gear, plasma waves between 20 and 20 000 Hz should be detectable if their amplitudes are large enough. The injection of low frequency currents into the plasma environment during Philae's descent gives indications for changes of the plasma density when approaching the comet. In this paper we present observations from the cross-calibration campaign with the Rosetta plasma package instrument MIP (Mutual Impedance Probe) [2] during the Pre-Delivery Calibration and Science (PDCS) operations on October 17, 2014, during the descent towards the comet surface on November 12, 2014, and from the First Science Sequence at Abydos on November 13. During the PDCS campaign most PP observation slots coincided with plasma waves dominantly in the 100 to 150 kHz range according to MIP measurements. Accordingly PP did not register any signals. Only in the afternoon of the 17th low frequency waves were recorded by MIP. At the same time the measured PP wave power signal was above the background for frequencies below 500 Hz in several subsequent measurements. During the descent [3] the injected current at 758 Hz dropped suddenly by about 5 % possibly indicating a decrease in the plasma density at an altitude of about 18.5 km above the comet surface. During the First Science Sequence PP was monitoring low frequency wave-like activities starting two hours after local sunset. References: [1] K. J. Seidensticker, H-H. Fischer, D. Medlener, S. Schieke, K. Thiel, A. Peter, W. Schmidt and R. Trautner, 2004: The Rosetta lander experiment sesame and the new target comet 67P/Churyumov-Gerasimenko. The New ROSETTA Targets - Observations, Simulations and Instrument Performances, Astrophys. Space Sci. 311, 297-307 [2] J. G. Trotignon et al., RPC-MIP: the Mutual Impedance Probe of the Rosetta Plasma Consortium, Space Science Reviews, February 2007, Volume 128, Issue 1, pp 713-728 [3] H.Krüger et al., Dust Impact Monitor (SESAME-DIM) Measurements at Comet 67P/Churyumov-Gerasimenko, Astronomy&Astrophysics, Volume 583, November 2015, DOI http://dx.doi.org/10.1051/0004-6361/201526400
Dependence of LTX plasma performance on surface conditions as determined by in situ analysis of plasma facing components

NASA Astrophysics Data System (ADS)

Lucia, M.; Kaita, R.; Majeski, R.; Bedoya, F.; Allain, J. P.; Abrams, T.; Bell, R. E.; Boyle, D. P.; Jaworski, M. A.; Schmitt, J. C.

2015-08-01

The Materials Analysis and Particle Probe (MAPP) diagnostic has been implemented on the Lithium Tokamak Experiment (LTX) at PPPL, providing the first in situ X-ray photoelectron spectroscopy (XPS) surface characterization of tokamak plasma facing components (PFCs). MAPP samples were exposed to argon glow discharge conditioning (GDC), lithium evaporations, and hydrogen tokamak discharges inside LTX. Samples were analyzed with XPS, and alterations to surface conditions were correlated against observed LTX plasma performance changes. Argon GDC caused the accumulation of nm-scale metal oxide layers on the PFC surface, which appeared to bury surface carbon and oxygen contamination and thus improve plasma performance. Lithium evaporation led to the rapid formation of a lithium oxide (Li2O) surface; plasma performance was strongly improved for sufficiently thick evaporative coatings. Results indicate that a 5 h argon GDC or a 50 nm evaporative lithium coating will both significantly improve LTX plasma performance.
Protection of ATP-Depleted Cells by Impermeant Strychnine Derivatives

PubMed Central

Dong, Zheng; Venkatachalam, Manjeri A.; Weinberg, Joel M.; Saikumar, Pothana; Patel, Yogendra

2001-01-01

Glycine and structurally related amino acids with activities at chloride channel receptors in the central nervous system also have robust protective effects against cell injury by ATP depletion. The glycine receptor antagonist strychnine shares this protective activity. An essential step toward identification of the molecular targets for these compounds is to determine whether they protect cells through interactions with intracellular targets or with molecules on the outer surface of plasma membranes. Here we report cytoprotection by a cell-impermeant derivative of strychnine. A strychnine-fluorescein conjugate (SF) was synthesized, and impermeability of plasma membranes to this compound was verified by fluorescence confocal microscopy. In an injury model of Madin-Darby canine kidney cells, ATP depletion led to lactate dehydrogenase release. SF prevented lactate dehydrogenase leakage without ameliorating ATP depletion. This was accompanied by preservation of cellular ultrastructure and exclusion of vital dyes. SF protection was also shown for ATP-depleted rat hepatocytes. On the other hand, when a key structural motif in the active site of strychnine was chemically blocked, the SF lost its protective effect, establishing strychnine-related specificity for SF protection. Cytoprotective effects of the cell-impermeant strychnine derivative provide compelling evidence suggesting that molecular targets on the outer surface of plasma membranes may mediate cytoprotection by strychnine and glycine. PMID:11238050
Protection of ATP-depleted cells by impermeant strychnine derivatives: implications for glycine cytoprotection.

PubMed

Dong, Z; Venkatachalam, M A; Weinberg, J M; Saikumar, P; Patel, Y

2001-03-01

Glycine and structurally related amino acids with activities at chloride channel receptors in the central nervous system also have robust protective effects against cell injury by ATP depletion. The glycine receptor antagonist strychnine shares this protective activity. An essential step toward identification of the molecular targets for these compounds is to determine whether they protect cells through interactions with intracellular targets or with molecules on the outer surface of plasma membranes. Here we report cytoprotection by a cell-impermeant derivative of strychnine. A strychnine-fluorescein conjugate (SF) was synthesized, and impermeability of plasma membranes to this compound was verified by fluorescence confocal microscopy. In an injury model of Madin-Darby canine kidney cells, ATP depletion led to lactate dehydrogenase release. SF prevented lactate dehydrogenase leakage without ameliorating ATP depletion. This was accompanied by preservation of cellular ultrastructure and exclusion of vital dyes. SF protection was also shown for ATP-depleted rat hepatocytes. On the other hand, when a key structural motif in the active site of strychnine was chemically blocked, the SF lost its protective effect, establishing strychnine-related specificity for SF protection. Cytoprotective effects of the cell-impermeant strychnine derivative provide compelling evidence suggesting that molecular targets on the outer surface of plasma membranes may mediate cytoprotection by strychnine and glycine.
Hydroxychloroquine protects the annexin A5 anticoagulant shield from disruption by antiphospholipid antibodies: evidence for a novel effect for an old antimalarial drug.

PubMed

Rand, Jacob H; Wu, Xiao-Xuan; Quinn, Anthony S; Ashton, Anthony W; Chen, Pojen P; Hathcock, James J; Andree, Harry A M; Taatjes, Douglas J

2010-03-18

Annexin A5 (AnxA5) is a potent anticoagulant protein that crystallizes over phospholipid bilayers (PLBs), blocking their availability for coagulation reactions. Antiphospholipid antibodies disrupt AnxA5 binding, thereby accelerating coagulation reactions. This disruption may contribute to thrombosis and miscarriages in the antiphospholipid syndrome (APS). We investigated whether the antimalarial drug, hydroxychloroquine (HCQ), might affect this prothrombotic mechanism. Binding of AnxA5 to PLBs was measured with labeled AnxA5 and also imaged with atomic force microscopy. Immunoglobulin G levels, AnxA5, and plasma coagulation times were measured on cultured human umbilical vein endothelial cells and a syncytialized trophoblast cell line. AnxA5 anticoagulant activities of APS patient plasmas were also determined. HCQ reversed the effect of antiphospholipid antibodies on AnxA5 and restored AnxA5 binding to PLBs, an effect corroborated by atomic force microscopy. Similar reversals of antiphospholipid-induced abnormalities were measured on the surfaces of human umbilical vein endothelial cells and syncytialized trophoblast cell lines, wherein HCQ reduced the binding of antiphospholipid antibodies, increased cell-surface AnxA5 concentrations, and prolonged plasma coagulation to control levels. In addition, HCQ increased the AnxA5 anticoagulant activities of APS patient plasmas. In conclusion, HCQ reversed antiphospholipid-mediated disruptions of AnxA5 on PLBs and cultured cells, and in APS patient plasmas. These results support the concept of novel therapeutic approaches that address specific APS disease mechanisms.
Overview of the HIT-SI3 spheromak experiment

NASA Astrophysics Data System (ADS)

Hossack, A. C.; Jarboe, T. R.; Chandra, R. N.; Morgan, K. D.; Sutherland, D. A.; Everson, C. J.; Penna, J. M.; Nelson, B. A.

2017-10-01

The HIT-SI and HIT-SI3 spheromak experiments (a = 23 cm) study efficient, steady-state current drive for magnetic confinement plasmas using a novel method which is ideal for low aspect ratio, toroidal geometries. Sustained spheromaks show coherent, imposed plasma motion and low plasma-generated mode activity, indicating stability. Analysis of surface magnetic fields in HIT-SI indicates large n = 0 and 1 mode amplitudes and little energy in higher modes. Within measurement uncertainties all the n = 1 energy is imposed by the injectors, rather than being plasma-generated. The fluctuating field imposed by the injectors is sufficient to sustain the toroidal current through dynamo action whereas the plasma-generated field is not (Hossack et al., Phys. Plasmas, 2017). Ion Doppler spectroscopy shows coherent, imposed plasma motion inside r 10 cm in HIT-SI and a smaller volume of coherent motion in HIT-SI3. Coherent motion indicates the spheromak is stable and a lack of plasma-generated n = 1 energy indicates the maximum q is maintained below 1 for stability during sustainment. In HIT-SI3, the imposed mode structure is varied to test the plasma response (Hossack et al., Nucl. Fusion, 2017). Imposing n = 2, n = 3, or large, rotating n = 1 perturbations is correlated with transient plasma-generated activity. Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-96ER54361.
Plasma treatment of polymers for improved adhesion

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

Kelber, J.A.

1988-01-01

A variety of plasma treatments of polymer surfaces for improved adhesion are reviewed: noble and reactive gas treatment of fluoropolymers; noble and reactive treatment of polyolefins, and plasma-induced amination of polymer fibers. The plasma induced surface chemical and morphological changes are discussed, as are the mechanisms of adhesion to polymeric adhesives, particularly epoxy. Noble gas plasma etching of flouropolymers produces a partially defluorinated, textured surface. The mechanical interlocking of this textured surface is the primary cause of improved adhesion to epoxy. Reactive gas plasmas also induce defluorination, but oxygen containing gases cause continual ablation of the fluoropolymer surface. Noble andmore » reactive gas (exept for hydrogen) etching of polyolefins results in surface oxidation and improved adhesion via hydrogen bonding of these oxygen containing groups across the interface. The introduction of amine groups to a polymer surface by amonia or amine plasma treatment generally results in improved adhesion to epoxy. However, amine-epoxy ring interactions can be severely effected by steric factors due to chemical groups surrounding the amine. 41 refs.« less
Apparatus for coating a surface with a metal utilizing a plasma source

DOEpatents

Brown, I.G.; MacGill, R.A.; Galvin, J.E.

1991-05-07

An apparatus and method are disclosed for coating or layering a surface with a metal utilizing a metal vapor vacuum arc plasma source. The apparatus includes a trigger mechanism for actuating the metal vacuum vapor arc plasma source in a pulsed mode at a predetermined rate. The surface or substrate to be coated or layered is supported in position with the plasma source in a vacuum chamber. The surface is electrically biased for a selected period of time during the pulsed mode of operation of the plasma source. Both the pulsing of the metal vapor vacuum arc plasma source and the electrical biasing of the surface are synchronized for selected periods of time. 10 figures.
Apparatus for coating a surface with a metal utilizing a plasma source

DOEpatents

Brown, Ian G.; MacGill, Robert A.; Galvin, James E.

1991-01-01

An apparatus and method for coating or layering a surface with a metal utilizing a metal vapor vacuum arc plasma source. The apparatus includes a trigger mechanism for actuating the metal vacuum vapor arc plasma source in a pulsed mode at a predetermined rate. The surface or substrate to be coated or layered is supported in position with the plasma source in a vacuum chamber. The surface is electrically biased for a selected period of time during the pulsed mode of operation of the plasma source. Both the pulsing of the metal vapor vacuum arc plasma source and the electrical biasing of the surface are synchronized for selected periods of time.
Method for atmospheric pressure reactive atom plasma processing for surface modification

DOEpatents

Carr, Jeffrey W [Livermore, CA

2009-09-22

Reactive atom plasma processing can be used to shape, polish, planarize and clean the surfaces of difficult materials with minimal subsurface damage. The apparatus and methods use a plasma torch, such as a conventional ICP torch. The workpiece and plasma torch are moved with respect to each other, whether by translating and/or rotating the workpiece, the plasma, or both. The plasma discharge from the torch can be used to shape, planarize, polish, and/or clean the surface of the workpiece, as well as to thin the workpiece. The processing may cause minimal or no damage to the workpiece underneath the surface, and may involve removing material from the surface of the workpiece.

Non-thermal atmospheric-pressure plasma possible application in wound healing.

PubMed

Haertel, Beate; von Woedtke, Thomas; Weltmann, Klaus-Dieter; Lindequist, Ulrike

2014-11-01

Non-thermal atmospheric-pressure plasma, also named cold plasma, is defined as a partly ionized gas. Therefore, it cannot be equated with plasma from blood; it is not biological in nature. Non-thermal atmospheric-pressure plasma is a new innovative approach in medicine not only for the treatment of wounds, but with a wide-range of other applications, as e.g. topical treatment of other skin diseases with microbial involvement or treatment of cancer diseases. This review emphasizes plasma effects on wound healing. Non-thermal atmospheric-pressure plasma can support wound healing by its antiseptic effects, by stimulation of proliferation and migration of wound relating skin cells, by activation or inhibition of integrin receptors on the cell surface or by its pro-angiogenic effect. We summarize the effects of plasma on eukaryotic cells, especially on keratinocytes in terms of viability, proliferation, DNA, adhesion molecules and angiogenesis together with the role of reactive oxygen species and other components of plasma. The outcome of first clinical trials regarding wound healing is pointed out.
Non-Thermal Atmospheric-Pressure Plasma Possible Application in Wound Healing

PubMed Central

Haertel, Beate; von Woedtke, Thomas; Weltmann, Klaus-Dieter; Lindequist, Ulrike

2014-01-01

Non-thermal atmospheric-pressure plasma, also named cold plasma, is defined as a partly ionized gas. Therefore, it cannot be equated with plasma from blood; it is not biological in nature. Non-thermal atmospheric-pressure plasma is a new innovative approach in medicine not only for the treatment of wounds, but with a wide-range of other applications, as e.g. topical treatment of other skin diseases with microbial involvement or treatment of cancer diseases. This review emphasizes plasma effects on wound healing. Non-thermal atmospheric-pressure plasma can support wound healing by its antiseptic effects, by stimulation of proliferation and migration of wound relating skin cells, by activation or inhibition of integrin receptors on the cell surface or by its pro-angiogenic effect. We summarize the effects of plasma on eukaryotic cells, especially on keratinocytes in terms of viability, proliferation, DNA, adhesion molecules and angiogenesis together with the role of reactive oxygen species and other components of plasma. The outcome of first clinical trials regarding wound healing is pointed out. PMID:25489414
Strategies to improve the adhesion of rubbers to adhesives by means of plasma surface modification

NASA Astrophysics Data System (ADS)

Martín-Martínez, J. M.; Romero-Sánchez, M. D.

2006-05-01

The surface modifications produced by treatment of a synthetic sulfur vulcanized styrene-butadiene rubber with oxidizing (oxygen, air, carbon dioxide) and non oxidizing (nitrogen, argon) RF low pressure plasmas, and by treatment with atmospheric plasma torch have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the low pressure plasma treatment depended on the gas atmosphere used to generate the plasma. A lack of relationship between surface polarity and wettability, and peel strength values was obtained, likely due to the cohesive failure in the rubber obtained in the adhesive joints. In general, acceptable adhesion values of plasma treated rubber were obtained for all plasmas, except for nitrogen plasma treatment during 15 minutes due to the creation of low molecular weight moieties on the outermost rubber layer. A toluene wiping of the N{2 } plasma treated rubber surface for 15 min removed those moieties and increased adhesion was obtained. On the other hand, the treatment of the rubber with atmospheric pressure by means of a plasma torch was proposed. The wettability of the rubber was improved by decreasing the rubber-plasma torch distance and by increasing the duration because a partial removal of paraffin wax from the rubber surface was produced. The rubber surface was oxidized by the plasma torch treatment, and the longer the duration of the plasma torch treatment, the higher the degree of surface oxidation (mainly creation of C O moieties). However, although the rubber surface was effectively modified by the plasma torch treatment, the adhesion was not greatly improved, due to the migration of paraffin wax to the treated rubber-polyurethane adhesive interface once the adhesive joint was produced. On the other hand, the extended treatment with plasma torch facilitated the migration of zinc stearate to the rubber-adhesive interface, also contributing to deteriorate the adhesion in greater extent. Finally, it has been found that cleaning of SBS rubber in an ultrasonic bath prior to plasma torch treatment produced a partial removal of paraffin waxes from the surface, and thus improved adhesion was obtained.
Plasma surface modification of polypropylene track-etched membrane to improve its performance properties

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

NASA Astrophysics Data System (ADS)

Fanara, Carlo; Shore, Paul; Nicholls, John R.; Lyford, Nicholas; Sommer, Phil; Fiske, Peter

2006-06-01

The next generation of 30-100 metre diameter extremely large telescopes (ELTs) requires large numbers of hexagonal primary mirror segments. As part of the Basic Technology programme run jointly by UCL and Cranfield University, a reactive atomic plasma technology (RAP(tm)) emerged from the US Lawrence Livermore National Laboratory (LLNL), is employed for the finishing of these surfaces. Results are presented on this novel etching technology. The Inductively Coupled Plasma (ICP) operated at atmospheric pressure using argon, activates the chemical species injected through its centre and promotes the fluorine-based chemical reactions at the surface. Process assessment trials on Ultra Low Expansion (ULE(tm)) plates, previously ground at high material removal rates, have been conducted. The quality of the surfaces produced on these samples using the RAP process are discussed. Substantial volumetric material removal rates of up to 0.446(21) mm 3/s at the highest process speed (1,200 mm/min) were found to be possible without pre-heating the substrate. The influences of power transfer, process speed and gas concentration on the removal rates have been determined. The suitability of the RAP process for revealing and removing sub-surface damage induced by high removal rate grinding is discussed. The results on SiC samples are reported elsewhere in this conference.
Plasma power recycling at the divertor surface

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

Tang, Xian -Zhu; Guo, Zehua

With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migrationmore » in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. Lastly, it is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.« less
Plasma power recycling at the divertor surface

DOE PAGES

Tang, Xian -Zhu; Guo, Zehua

2016-12-03

With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migrationmore » in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. Lastly, it is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.« less
An experiment on the dynamics of ion implantation and sputtering of surfaces

NASA Astrophysics Data System (ADS)

Wright, G. M.; Barnard, H. A.; Kesler, L. A.; Peterson, E. E.; Stahle, P. W.; Sullivan, R. M.; Whyte, D. G.; Woller, K. B.

2014-02-01

A major impediment towards a better understanding of the complex plasma-surface interaction is the limited diagnostic access to the material surface while it is undergoing plasma exposure. The Dynamics of ION Implantation and Sputtering Of Surfaces (DIONISOS) experiment overcomes this limitation by uniquely combining powerful, non-perturbing ion beam analysis techniques with a steady-state helicon plasma exposure chamber, allowing for real-time, depth-resolved in situ measurements of material compositions during plasma exposure. Design solutions are described that provide compatibility between the ion beam analysis requirements in the presence of a high-intensity helicon plasma. The three primary ion beam analysis techniques, Rutherford backscattering spectroscopy, elastic recoil detection, and nuclear reaction analysis, are successfully implemented on targets during plasma exposure in DIONISOS. These techniques measure parameters of interest for plasma-material interactions such as erosion/deposition rates of materials and the concentration of plasma fuel species in the material surface.
An experiment on the dynamics of ion implantation and sputtering of surfaces.

PubMed

Wright, G M; Barnard, H A; Kesler, L A; Peterson, E E; Stahle, P W; Sullivan, R M; Whyte, D G; Woller, K B

2014-02-01

A major impediment towards a better understanding of the complex plasma-surface interaction is the limited diagnostic access to the material surface while it is undergoing plasma exposure. The Dynamics of ION Implantation and Sputtering Of Surfaces (DIONISOS) experiment overcomes this limitation by uniquely combining powerful, non-perturbing ion beam analysis techniques with a steady-state helicon plasma exposure chamber, allowing for real-time, depth-resolved in situ measurements of material compositions during plasma exposure. Design solutions are described that provide compatibility between the ion beam analysis requirements in the presence of a high-intensity helicon plasma. The three primary ion beam analysis techniques, Rutherford backscattering spectroscopy, elastic recoil detection, and nuclear reaction analysis, are successfully implemented on targets during plasma exposure in DIONISOS. These techniques measure parameters of interest for plasma-material interactions such as erosion/deposition rates of materials and the concentration of plasma fuel species in the material surface.
Modification of Pulsed Electric Field Conditions Results in Distinct Activation Profiles of Platelet-Rich Plasma.

PubMed

Frelinger, Andrew L; Gerrits, Anja J; Garner, Allen L; Torres, Andrew S; Caiafa, Antonio; Morton, Christine A; Berny-Lang, Michelle A; Carmichael, Sabrina L; Neculaes, V Bogdan; Michelson, Alan D

2016-01-01

Activated autologous platelet-rich plasma (PRP) used in therapeutic wound healing applications is poorly characterized and standardized. Using pulsed electric fields (PEF) to activate platelets may reduce variability and eliminate complications associated with the use of bovine thrombin. We previously reported that exposing PRP to sub-microsecond duration, high electric field (SMHEF) pulses generates a greater number of platelet-derived microparticles, increased expression of prothrombotic platelet surfaces, and differential release of growth factors compared to thrombin. Moreover, the platelet releasate produced by SMHEF pulses induced greater cell proliferation than plasma. To determine whether sub-microsecond duration, low electric field (SMLEF) bipolar pulses results in differential activation of PRP compared to SMHEF, with respect to profiles of activation markers, growth factor release, and cell proliferation capacity. PRP activation by SMLEF bipolar pulses was compared to SMHEF pulses and bovine thrombin. PRP was prepared using the Harvest SmartPreP2 System from acid citrate dextrose anticoagulated healthy donor blood. PEF activation by either SMHEF or SMLEF pulses was performed using a standard electroporation cuvette preloaded with CaCl2 and a prototype instrument designed to take into account the electrical properties of PRP. Flow cytometry was used to assess platelet surface P-selectin expression, and annexin V binding. Platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), endothelial growth factor (EGF) and platelet factor 4 (PF4), and were measured by ELISA. The ability of supernatants to stimulate proliferation of human epithelial cells in culture was also evaluated. Controls included vehicle-treated, unactivated PRP and PRP with 10 mM CaCl2 activated with 1 U/mL bovine thrombin. PRP activated with SMLEF bipolar pulses or thrombin had similar light scatter profiles, consistent with the presence of platelet-derived microparticles, platelets, and platelet aggregates whereas SMHEF pulses primarily resulted in platelet-derived microparticles. Microparticles and platelets in PRP activated with SMLEF bipolar pulses had significantly lower annexin V-positivity than those following SMHEF activation. In contrast, the % P-selectin positivity and surface P-selectin expression (MFI) for platelets and microparticles in SMLEF bipolar pulse activated PRP was significantly higher than that in SMHEF-activated PRP, but not significantly different from that produced by thrombin activation. Higher levels of EGF were observed following either SMLEF bipolar pulses or SMHEF pulses of PRP than after bovine thrombin activation while VEGF, PDGF, and PF4 levels were similar with all three activating conditions. Cell proliferation was significantly increased by releasates of both SMLEF bipolar pulse and SMHEF pulse activated PRP compared to plasma alone. PEF activation of PRP at bipolar low vs. monopolar high field strength results in differential platelet-derived microparticle production and activation of platelet surface procoagulant markers while inducing similar release of growth factors and similar capacity to induce cell proliferation. Stimulation of PRP with SMLEF bipolar pulses is gentler than SMHEF pulses, resulting in less platelet microparticle generation but with overall activation levels similar to that obtained with thrombin. These results suggest that PEF provides the means to alter, in a controlled fashion, PRP properties thereby enabling evaluation of their effects on wound healing and clinical outcomes.
Plasma technologies application for building materials surface modification

NASA Astrophysics Data System (ADS)

Volokitin, G. G.; Skripnikova, N. K.; Volokitin, O. G.; Shehovtzov, V. V.; Luchkin, A. G.; Kashapov, N. F.

2016-01-01

Low temperature arc plasma was used to process building surface materials, such as silicate brick, sand lime brick, concrete and wood. It was shown that building surface materials modification with low temperature plasma positively affects frost resistance, water permeability and chemical resistance with high adhesion strength. Short time plasma processing is rather economical than traditional processing thermic methods. Plasma processing makes wood surface uniquely waterproof and gives high operational properties, dimensional and geometrical stability. It also increases compression resistance and decreases inner tensions level in material.
On a theory of surface waves in a smoothly inhomogeneous plasma in an external magnetic field

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

Kuzelev, M. V., E-mail: kuzelev@mail.ru; Orlikovskaya, N. G.

2016-12-15

A theory of surface waves in a magnetoactive plasma with smooth boundaries has been developed. A dispersion equation for surface waves has been derived for a linear law of density change at the plasma boundary. The frequencies of surface waves and their collisionless damping rates have been determined. A generalization to an arbitrary density profile at the plasma boundary is given. The collisions have been taken into account, and the application of the Landau rule in the theory of surface wave damping in a spatially inhomogeneous magnetoactive collisional plasma has been clarified.
Diagnostics of microwave assisted electron cyclotron resonance plasma source for surface modification of nylon 6

NASA Astrophysics Data System (ADS)

More, Supriya E.; Das, Partha Sarathi; Bansode, Avinash; Dhamale, Gayatri; Ghorui, S.; Bhoraskar, S. V.; Sahasrabudhe, S. N.; Mathe, Vikas L.

2018-01-01

Looking at the increasing scope of plasma processing of materials surface, here we present the development and diagnostics of a microwave assisted Electron Cyclotron Resonance (ECR) plasma system suitable for surface modification of polymers. Prior to the surface-treatment, a detailed diagnostic mapping of the plasma parameters throughout the reactor chamber was carried out by using single and double Langmuir probe measurements in Ar plasma. Conventional analysis of I-V curves as well as the elucidation form of the Electron Energy Distribution Function (EEDF) has become the source of calibration of plasma parameters in the reaction chamber. The high energy tail in the EEDF of electron temperature is seen to extend beyond 60 eV, at much larger distances from the ECR zone. This proves the suitability of the rector for plasma processing, since the electron energy is much beyond the threshold energy of bond breaking in most of the polymers. Nylon 6 is used as a representative candidate for surface processing in the presence of Ar, H2 + N2, and O2 plasma, treated at different locations inside the plasma chamber. In a typical case, the work of adhesion is seen to almost get doubled when treated with oxygen plasma. Morphology of the plasma treated surface and its hydrophilicity are discussed in view of the variation in electron density and electron temperature at these locations. Nano-protrusions arising from plasma treatment are set to be responsible for the hydrophobicity. Chemical sputtering and physical sputtering are seen to influence the surface morphology on account of sufficient electron energies and increased plasma potential.
Presenilin-1 affects trafficking and processing of βAPP and is targeted in a complex with nicastrin to the plasma membrane

PubMed Central

Kaether, Christoph; Lammich, Sven; Edbauer, Dieter; Ertl, Michaela; Rietdorf, Jens; Capell, Anja; Steiner, Harald; Haass, Christian

2002-01-01

Amyloid β-peptide (Aβ) is generated by the consecutive cleavages of β- and γ-secretase. The intramembraneous γ-secretase cleavage critically depends on the activity of presenilins (PS1 and PS2). Although there is evidence that PSs are aspartyl proteases with γ-secretase activity, it remains controversial whether their subcellular localization overlaps with the cellular sites of Aβ production. We now demonstrate that biologically active GFP-tagged PS1 as well as endogenous PS1 are targeted to the plasma membrane (PM) of living cells. On the way to the PM, PS1 binds to nicastrin (Nct), an essential component of the γ-secretase complex. This complex is targeted through the secretory pathway where PS1-bound Nct becomes endoglycosidase H resistant. Moreover, surface-biotinylated Nct can be coimmunoprecipitated with PS1 antibodies, demonstrating that this complex is located to cellular sites with γ-secretase activity. Inactivating PS1 or PS2 function by mutagenesis of one of the critical aspartate residues or by γ-secretase inhibitors results in delayed reinternalization of the β-amyloid precursor protein and its accumulation at the cell surface. Our data suggest that PS is targeted as a biologically active complex with Nct through the secretory pathway to the cell surface and suggest a dual function of PS in γ-secretase processing and in trafficking. PMID:12147673
Combining 3D human in vitro methods for a 3Rs evaluation of novel titanium surfaces in orthopaedic applications

PubMed Central

Stevenson, G.; Rehman, S.; Draper, E.; Hernández‐Nava, E.; Hunt, J.

2016-01-01

ABSTRACT In this study, we report on a group of complementary human osteoblast in vitro test methods for the preclinical evaluation of 3D porous titanium surfaces. The surfaces were prepared by additive manufacturing (electron beam melting [EBM]) and plasma spraying, allowing the creation of complex lattice surface geometries. Physical properties of the surfaces were characterized by SEM and profilometry and 3D in vitro cell culture using human osteoblasts. Primary human osteoblast cells were found to elicit greater differences between titanium sample surfaces than an MG63 osteoblast‐like cell line, particularly in terms of cell survival. Surface morphology was associated with higher osteoblast metabolic activity and mineralization on rougher titanium plasma spray coated surfaces than smoother surfaces. Differences in osteoblast survival and metabolic activity on titanium lattice structures were also found, despite analogous surface morphology at the cellular level. 3D confocal microscopy identified osteoblast organization within complex titanium surface geometries, adhesion, spreading, and alignment to the biomaterial strut geometries. Mineralized nodule formation throughout the lattice structures was also observed, and indicative of early markers of bone in‐growth on such materials. Testing methods such as those presented are not traditionally considered by medical device manufacturers, but we suggest have value as an increasingly vital tool in efficiently translating pre‐clinical studies, especially in balance with current regulatory practice, commercial demands, the 3Rs, and the relative merits of in vitro and in vivo studies. Biotechnol. Bioeng. 2016;113: 1586–1599. © 2015 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. PMID:26702609
Characteristic analysis of surface waves in a sensitive plasma absorption probe

NASA Astrophysics Data System (ADS)

You, Wei; Li, Hong; Tan, Mingsheng; Liu, Wandong

2018-01-01

With features that are simple to construct and a symmetric configuration, the sensitive plasma absorption probe (SPAP) is a dependable probe for industry plasma diagnosis. The minimum peak in the characteristic curve of the coefficient of reflection stems from the surface wave resonance in plasma. We use numerical simulation methods to analyse the details of the excitation and propagation of these surface waves. With this method, the electromagnetic field structure and the resonance and propagation characteristics of the surface wave were analyzed simultaneously using the simulation method. For this SPAP structure, there are three different propagation paths for the propagating plasma surface wave. The propagation characteristic of the surface wave along each path is presented. Its dispersion relation is also calculated. The objective is to complete the relevant theory of the SPAP as well as the propagation process of the plasma surface wave.
Reversing gastric mucosal alterations during ethanol-induced chronic gastritis in rats by oral administration of Opuntia ficus-indica mucilage

PubMed Central

Vázquez-Ramírez, Ricardo; Olguín-Martínez, Marisela; Kubli-Garfias, Carlos; Hernández-Muñoz, Rolando

2006-01-01

AIM: To study the effect of mucilage obtained from cladodes of Opuntia ficus-indica (Cactaceae) on the healing of ethanol-induced gastritis in rats. METHODS: Chronic gastric mucosa injury was treated with mucilage (5 mg/kg per day) after it was induced by ethanol. Lipid composition, activity of 5’-nucleotidase (a membrane-associated ectoenzyme) and cytosolic activities of lactate and alcohol dehydrogenases in the plasma membrane of gastric mucosa were determined. Histological studies of gastric samples from the experimental groups were included. RESULTS: Ethanol elicited the histological profile of gastritis characterized by loss of the surface epithelium and infiltration of polymorphonuclear leukocytes. Phosphatidylcholine (PC) decreased and cholesterol content increased in plasma membranes of the gastric mucosa. In addition, cytosolic activity increased while the activity of alcohol dehydrogenases decreased. The administration of mucilage promptly corrected these enzymatic changes. In fact, mucilage readily accelerated restoration of the ethanol-induced histological alterations and the disturbances in plasma membranes of gastric mucosa, showing a univocal anti-inflammatory effect. The activity of 5’-nucleotidase correlated with the changes in lipid composition and the fluidity of gastric mucosal plasma membranes. CONCLUSION: The beneficial action of mucilage seems correlated with stabilization of plasma membranes of damaged gastric mucosa. Molecular interactions between mucilage monosaccharides and membrane phospholipids, mainly PC and phosphatidylethanolamine (PE), may be the relevant features responsible for changing activities of membrane-attached proteins during the healing process after chronic gastric mucosal damage. PMID:16865772
Reversing gastric mucosal alterations during ethanol-induced chronic gastritis in rats by oral administration of Opuntia ficus-indica mucilage.

PubMed

Vázquez-Ramírez, Ricardo; Olguín-Martínez, Marisela; Kubli-Garfias, Carlos; Hernández-Muñoz, Rolando

2006-07-21

To study the effect of mucilage obtained from cladodes of Opuntia ficus-indica (Cactaceae) on the healing of ethanol-induced gastritis in rats. Chronic gastric mucosa injury was treated with mucilage (5 mg/kg per day) after it was induced by ethanol. Lipid composition, activity of 5'-nucleotidase (a membrane-associated ectoenzyme) and cytosolic activities of lactate and alcohol dehydrogenases in the plasma membrane of gastric mucosa were determined. Histological studies of gastric samples from the experimental groups were included. Ethanol elicited the histological profile of gastritis characterized by loss of the surface epithelium and infiltration of polymorphonuclear leukocytes. Phosphatidylcholine (PC) decreased and cholesterol content increased in plasma membranes of the gastric mucosa. In addition, cytosolic activity increased while the activity of alcohol dehydrogenases decreased. The administration of mucilage promptly corrected these enzymatic changes. In fact, mucilage readily accelerated restoration of the ethanol-induced histological alterations and the disturbances in plasma membranes of gastric mucosa, showing a univocal anti-inflammatory effect. The activity of 5'-nucleotidase correlated with the changes in lipid composition and the fluidity of gastric mucosal plasma membranes. The beneficial action of mucilage seems correlated with stabilization of plasma membranes of damaged gastric mucosa. Molecular interactions between mucilage monosaccharides and membrane phospholipids, mainly PC and phosphatidylethanolamine (PE), may be the relevant features responsible for changing activities of membrane-attached proteins during the healing process after chronic gastric mucosal damage.
Switchable hydrophobic/hydrophilic surface of electrospun poly (l-lactide) membranes obtained by CF₄microwave plasma treatment

DOE PAGES

Yue, Mengyao; Zhou, Baoming; Jiao, Kunyan; ...

2014-11-29

A switchable surface that promotes either hydrophobic or hydrophilic wettability of poly (L-lactide) (PLLA) microfibrous membranes is obtained by CF₄ microwave plasma treatment in this paper. The results indicated that both etching and grafting process occurred during the CF₄ plasma treatment and these two factors synergistically affected the final surface wettability of PLLA membranes. When plasma treatment was taken under a relatively low power, the surface wettability of PLLA membranes turned from hydrophobic to hydrophilic. Especially when CF₄ plasma treatment was taken under 100 W for 10 min and 150 W for 5 min, the water contact angle sharply decreasedmore » from 116 ± 3.0° to ~0°. According to Field-emission scanning electron microscopy (FESEM) results, the PLLA fibers were notably etched by CF₄ plasma treatment. Combined with the X-ray photoelectron spectroscopy (XPS) measurements, only a few fluorine-containing groups were grafted onto the surface, so the etching effect directly affected the surface wettability of PLLA membranes in low plasma power condition. However, with the plasma power increasing to 200 W, the PLLA membrane surface turned to hydrophobic again. In contrast, the morphology changes of PLLA fiber surfaces were not obvious while a large number of fluorine-containing groups grafted onto the surface. So the grafting effect gradually became the major factor for the final surface wettability.« less
Surface morphology evolution during plasma etching of silicon: roughening, smoothing and ripple formation

NASA Astrophysics Data System (ADS)

Ono, Kouichi; Nakazaki, Nobuya; Tsuda, Hirotaka; Takao, Yoshinori; Eriguchi, Koji

2017-10-01

Atomic- or nanometer-scale roughness on feature surfaces has become an important issue to be resolved in the fabrication of nanoscale devices in industry. Moreover, in some cases, smoothing of initially rough surfaces is required for planarization of film surfaces, and controlled surface roughening is required for maskless fabrication of organized nanostructures on surfaces. An understanding, under what conditions plasma etching results in surface roughening and/or smoothing and what are the mechanisms concerned, is of great technological as well as fundamental interest. In this article, we review recent developments in the experimental and numerical study of the formation and evolution of surface roughness (or surface morphology evolution such as roughening, smoothing, and ripple formation) during plasma etching of Si, with emphasis being placed on a deeper understanding of the mechanisms or plasma-surface interactions that are responsible for. Starting with an overview of the experimental and theoretical/numerical aspects concerned, selected relevant mechanisms are illustrated and discussed primarily on the basis of systematic/mechanistic studies of Si etching in Cl-based plasmas, including noise (or stochastic roughening), geometrical shadowing, surface reemission of etchants, micromasking by etch inhibitors, and ion scattering/chanelling. A comparison of experiments (etching and plasma diagnostics) and numerical simulations (Monte Carlo and classical molecular dynamics) indicates a crucial role of the ion scattering or reflection from microscopically roughened feature surfaces on incidence in the evolution of surface roughness (and ripples) during plasma etching; in effect, the smoothing/non-roughening condition is characterized by reduced effects of the ion reflection, and the roughening-smoothing transition results from reduced ion reflections caused by a change in the predominant ion flux due to that in plasma conditions. Smoothing of initially rough surfaces as well as non-roughening of initially planar surfaces during etching (normal ion incidence) and formation of surface ripples by plasma etching (off-normal ion incidence) are also presented and discussed in this context.

Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma

NASA Astrophysics Data System (ADS)

Sun, Fang; Hung, Hsiang-Chieh; Sinclair, Andrew; Zhang, Peng; Bai, Tao; Galvan, Daniel David; Jain, Priyesh; Li, Bowen; Jiang, Shaoyi; Yu, Qiuming

2016-11-01

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling. We demonstrate how this modification can enable TDM applications by quantitatively and dynamically measuring the concentrations of several analytes--including an anticancer drug (doxorubicin), several TDM-requiring antidepressant and anti-seizure drugs, fructose and blood pH--in undiluted plasma. This hierarchical surface chemistry is widely applicable to many analytes and provides a generalized platform for SERS-based biosensing in complex real-world media.
Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma

PubMed Central

Sun, Fang; Hung, Hsiang-Chieh; Sinclair, Andrew; Zhang, Peng; Bai, Tao; Galvan, Daniel David; Jain, Priyesh; Li, Bowen; Jiang, Shaoyi; Yu, Qiuming

2016-01-01

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling. We demonstrate how this modification can enable TDM applications by quantitatively and dynamically measuring the concentrations of several analytes—including an anticancer drug (doxorubicin), several TDM-requiring antidepressant and anti-seizure drugs, fructose and blood pH—in undiluted plasma. This hierarchical surface chemistry is widely applicable to many analytes and provides a generalized platform for SERS-based biosensing in complex real-world media. PMID:27834380
Improvement of wheat seed vitality by dielectric barrier discharge plasma treatment.

PubMed

Guo, Qiao; Meng, Yiran; Qu, Guangzhou; Wang, Tiecheng; Yang, Fengning; Liang, Dongli; Hu, Shibin

2018-02-01

Influences of discharge voltage on wheat seed vitality were investigated in a dielectric barrier discharge (DBD) plasma system at atmospheric pressure and temperature. Six different treatments were designed, and their discharge voltages were 0.0, 9.0, 11.0, 13.0, 15.0, and 17.0 kV, respectively. Fifty seeds were exposed to the DBD plasma atmosphere with an air flow rate of 1.5 L min -1 for 4 min in each treatment, and then the DBD plasma-treated seeds were prepared for germination in several Petri dishes. Each treatment was repeated three times. Germination indexes, growth indexes, surface topography, water uptake, permeability, and α-amylase activity were measured. DBD plasma treatment at appropriate energy levels had positive effects on wheat seed germination and seedling growth. The germination potential, germination index, and vigor index significantly increased by 31.4%, 13.9%, and 54.6% after DBD treatment at 11.0 kV, respectively, in comparison to the control. Shoot length, root length, dry weight, and fresh weight also significantly increased after the DBD plasma treatment. The seed coat was softened and cracks were observed, systematization of the protein was strengthened, and amount of free starch grain increased after the DBD plasma treatment. Water uptake, relative electroconductivity, soluble protein, and α-amylase activity of the wheat seed were also significantly improved after the DBD plasma treatment. Roles of active species and ultraviolet radiation generated in the DBD plasma process in wheat seed germination and seedling growth are proposed. Bioelectromagnetics. 39:120-131, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Acrylic acid plasma polymerization for biomedical use

NASA Astrophysics Data System (ADS)

Bitar, Rim; Cools, Pieter; De Geyter, Nathalie; Morent, Rino

2018-08-01

Since a few decades, polymeric materials have played a central role in regenerative medicine and tissue engineering as artificial tissue replacements and organ transplantation devices. Chemical and topographical surface modifications of biomaterials are often required to achieve an overall better biocompatibility. Non-thermal plasma is a non-invasive, solvent-free alternative for modifying polymeric surface properties without affecting the bulk of the material. Plasma polymerization of organic compounds has proven to be an effective tool for thin film production with specific surface chemistries, useful for biomedical applications. These polymer layers have received a growing interest in tissue regeneration and biomolecules immobilization processes. Many different types of chemical functional groups can be introduced, but the focus of this review will be on carboxylic acid groups. Thin films consisting of carboxylic acid functional groups are considered attractive for biomedical applications since these are known for stimulating the adhesion and proliferation of fibroblasts and other kind of cells. Therefore, an overview on the use of acrylic acid (AAc) as a precursor or for the plasma-assisted deposition of carboxylic-group containing-films in bio-interface research activities, will be described in this review. The review will specifically focus on plasma polymerized acrylic acid (PPAA) coatings that are obtained using a variety of plasma deposition techniques. Moreover, the influence of plasma parameters on surface properties such as wettability, surface topography and chemical composition will be discussed in detail. The correlation between different parameters will be studied and a general recipe leading to the successful deposition of COOH-rich stable coatings will be extracted and linked to their ability to improve cell growth, proliferation and differentiation, all leading to the further progress in the biomedical field. A lot of publications claim to have developed suitable coatings for biomedical applications, but neglect the importance of coating stability. For those publications exhibiting sufficient coating stability, a lot of initial in vitro experiments were performed, but the number in-depth studies on the mechanisms behind the cell-material interactions is limited. Although AAc forms an excellent precursor for biomedical coatings, its potential still needs to be explored in more details.
Formation of hydrophobic coating on glass surface using atmospheric pressure non-thermal plasma in ambient air

NASA Astrophysics Data System (ADS)

Fang, Z.; Qiu, Y.; Kuffel, E.

2004-08-01

Non-thermal plasmas under atmospheric pressure are of great interest in material surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of a glass surface for improving hydrophobicity using a non-thermal plasma generated by a dielectric barrier corona discharge (DBCD) with a needle array-to-plane electrode arrangement in atmospheric air is conducted, and the surface properties of the glass before and after the DBCD treatment are studied using contact angle measurement, surface resistance measurement and the wet flashover voltage test. The effects of the plasma dose (the product of average discharge power and treatment time) of DBCD on the surface modification are studied, and the mechanism of interaction between the plasma and glass surface is discussed. It is found that a layer of hydrophobic coating is formed on the glass surface through DBCD treatment, and the improvement of hydrophobicity depends on the plasma dose of the DBCD. It seems that there is an optimum plasma dose for the surface treatment. The test results of thermal ageing and chemical ageing show that the hydrophobic layer has quite stable characteristics.
Essentially All Excess Fibroblast Cholesterol Moves from Plasma Membranes to Intracellular Compartments

PubMed Central

Lange, Yvonne; Ye, Jin; Steck, Theodore L.

2014-01-01

It has been shown that modestly increasing plasma membrane cholesterol beyond its physiological set point greatly increases the endoplasmic reticulum and mitochondrial pools, thereby eliciting manifold feedback responses that return cell cholesterol to its resting state. The question arises whether this homeostatic mechanism reflects the targeting of cell surface cholesterol to specific intracellular sites or its general equilibration among the organelles. We now show that human fibroblast cholesterol can be increased as much as two-fold from 2-hydroxypropyl-β-cyclodextrin without changing the size of the cell surface pool. Rather, essentially all of the added cholesterol disperses rapidly among cytoplasmic membranes, increasing their overall cholesterol content by as much as five-fold. We conclude that the level of plasma membrane cholesterol is normally at capacity and that even small increments above this physiological set point redistribute essentially entirely to intracellular membranes, perhaps down their chemical activity gradients. PMID:25014655
Plasma Vehicle Charging Analysis for Orion Flight Test 1

NASA Technical Reports Server (NTRS)

Lallement, L.; McDonald, T.; Norgard, J.; Scully, B.

2014-01-01

In preparation for the upcoming experimental test flight for the Orion crew module, considerable interest was raised over the possibility of exposure to elevated levels of plasma activity and vehicle charging both externally on surfaces and internally on dielectrics during the flight test orbital operations. Initial analysis using NASCAP-2K indicated very high levels of exposure, and this generated additional interest in refining/defining the plasma and spacecraft models used in the analysis. This refinement was pursued, resulting in the use of specific AE8 and AP8 models, rather than SCATHA models, as well as consideration of flight trajectory, time duration, and other parameters possibly affecting the levels of exposure and the magnitude of charge deposition. Analysis using these refined models strongly indicated that, for flight test operations, no special surface coatings were necessary for the thermal protection system, but would definitely be required for future GEO, trans-lunar, and extra-lunar missions...
High density gold nanoparticles immobilized on surface via plasma deposited APTES film for decomposing organic compounds in microchannels

NASA Astrophysics Data System (ADS)

Rao, Xi; Guyon, Cédric; Ognier, Stephanie; Da Silva, Bradley; Chu, Chenglin; Tatoulian, Michaël; Hassan, Ali Abou

2018-05-01

Immobilization of colloidal particles (e.g. gold nanoparticles (AuNps)) on the inner surface of micro-/nano- channels has received a great interest for catalysis. A novel catalytic ozonation setup using a gold-immobilized microchannel reactor was developed in this work. To anchor AuNps, (3-aminopropyl) triethoxysilane (APTES) with functional amine groups was deposited using plasma enhanced chemical vapor deposition (PECVD) process. The results clearly evidenced that PECVD processing exhibited relatively high efficiency for grafting amine groups and further immobilizing AuNPs. The catalytic activity of gold immobilized microchannel was evaluated by pyruvic acid ozonation. The decomposition rate calculated from High Performance Liquid Chromatography (HPLC) indicated a much better catalytic performance of gold in microchannel than that in batch. The results confirmed immobilizing gold nanoparticles on plasma deposited APTES for preparing catalytic microreactors is promising for the wastewater treatment in the future.
Plasma Vehicle Charging Analysis for Orion Flight Test 1

NASA Technical Reports Server (NTRS)

Scully, B.; Norgard, J.

2015-01-01

In preparation for the upcoming experimental test flight for the Orion crew module, considerable interest was raised over the possibility of exposure to elevated levels of plasma activity and vehicle charging both externally on surfaces and internally on dielectrics during the flight test orbital operations. Initial analysis using NASCAP-2K indicated very high levels of exposure, and this generated additional interest in refining/defining the plasma and spacecraft models used in the analysis. This refinement was pursued, resulting in the use of specific AE8 and AP8 models, rather than SCATHA models, as well as consideration of flight trajectory, time duration, and other parameters possibly affecting the levels of exposure and the magnitude of charge deposition. Analysis using these refined models strongly indicated that, for flight test operations, no special surface coatings were necessary for the Thermal Protection System (TPS), but would definitely be required for future GEO, trans-lunar, and extra-lunar missions.
Optical emission diagnostics of plasmas in chemical vapor deposition of single-crystal diamond

DOE PAGES

Hemawan, Kadek W.; Hemley, Russell J.

2015-08-03

Here, a key aspect of single crystal diamond growth via microwave plasma chemical vapor deposition is in-process control of the local plasma-substrate environment, that is, plasma gas phase concentrations of activated species at the plasma boundary layer near the substrate surface. Emission spectra of the plasma relative to the diamond substrate inside the microwave plasma reactor chamber have been analyzed via optical emission spectroscopy. The spectra of radical species such as CH, C 2, and H (Balmer series) important for diamond growth were found to be more depndent on operating pressure than on microwave power. Plasma gas temperatures were calculatedmore » from measurements of the C 2 Swan band (d 3Π → a 3Π transition) system. The plasma gas temperature ranges from 2800 to 3400 K depending on the spatial location of the plasma ball, microwave power and operating pressure. Addition of Ar into CH 4 + H 2 plasma input gas mixture has little influence on the Hα, Hβ, and Hγ intensities and single-crystal diamond growth rates.« less
Mechanism for Ring-Opening of Aromatic Polymers by Remote Atmospheric Pressure Plasma

NASA Astrophysics Data System (ADS)

Gonzalez, Eleazar; Barankin, Michael; Guschl, Peter; Hicks, Robert

2009-10-01

A low-temperature, atmospheric pressure oxygen and helium plasma was used to treat the surfaces of polyetheretherketone, polyphenylsulfone, polyethersulfone, and polysulfone. These aromatic polymers were exposed to the afterglow of the plasma, which contained oxygen atoms, and to a lesser extent metastable oxygen (^1δg O2) and ozone. After less than 2.5 seconds treatment, the polymers were converted from a hydrophobic state with a water contact angle of 85±5 to a hydrophilic state with a water contact angle of 13±5 . It was found that plasma activation increased the bond strength to adhesives by as much as 4 times. X-ray photoelectron spectroscopy revealed that between 7% and 27% of the aromatic carbon atoms on the polymer surfaces was oxidized and converted into aldehyde and carboxylic acid groups. Analysis of polyethersulfone by internal reflection infrared spectroscopy showed that a fraction of the aromatic carbon atoms were transformed into C=C double bonds, ketones, and carboxylic acids after plasma exposure. It was concluded that the oxygen atoms generated by the atmospheric pressure plasma insert into the double bonds on the aromatic rings, forming a 3-member epoxy ring, which subsequently undergoes ring opening and oxidation to yield an aldehyde and a carboxylic acid group.
X6.9-CLASS FLARE-INDUCED VERTICAL KINK OSCILLATIONS IN A LARGE-SCALE PLASMA CURTAIN AS OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY

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

Srivastava, A. K.; Goossens, M.

2013-11-01

We present rare observational evidence of vertical kink oscillations in a laminar and diffused large-scale plasma curtain as observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The X6.9-class flare in active region 11263 on 2011 August 9 induces a global large-scale disturbance that propagates in a narrow lane above the plasma curtain and creates a low density region that appears as a dimming in the observational image data. This large-scale propagating disturbance acts as a non-periodic driver that interacts asymmetrically and obliquely with the top of the plasma curtain and triggers the observed oscillations. In themore » deeper layers of the curtain, we find evidence of vertical kink oscillations with two periods (795 s and 530 s). On the magnetic surface of the curtain where the density is inhomogeneous due to coronal dimming, non-decaying vertical oscillations are also observed (period ≈ 763-896 s). We infer that the global large-scale disturbance triggers vertical kink oscillations in the deeper layers as well as on the surface of the large-scale plasma curtain. The properties of the excited waves strongly depend on the local plasma and magnetic field conditions.« less
Regulated internalization of caveolae

PubMed Central

1994-01-01

Caveolae are specialized invaginations of the plasma membrane which have been proposed to play a role in diverse cellular processes such as endocytosis and signal transduction. We have developed an assay to determine the fraction of internal versus plasma membrane caveolae. The GPI-anchored protein, alkaline phosphatase, was clustered in caveolae after antibody-induced crosslinking at low temperature and then, after various treatments, the relative amount of alkaline phosphatase on the cell surface was determined. Using this assay we were able to show a time- and temperature-dependent decrease in cell-surface alkaline phosphatase activity which was dependent on antibody-induced clustering. The decrease in cell surface alkaline phosphatase activity was greatly accelerated by the phosphatase inhibitor, okadaic acid, but not by a protein kinase C activator. Internalization of clustered alkaline phosphatase in the presence or absence of okadaic acid was blocked by cytochalasin D and by the kinase inhibitor staurosporine. Electron microscopy confirmed that okadaic acid induced removal of caveolae from the cell surface. In the presence of hypertonic medium this was followed by the redistribution of groups of caveolae to the center of the cell close to the microtubule-organizing center. This process was reversible, blocked by cytochalasin D, and the centralization of the caveolar clusters was shown to be dependent on an intact microtubule network. Although the exact mechanism of internalization remains unknown, the results show that caveolae are dynamic structures which can be internalized into the cell. This process may be regulated by kinase activity and require an intact actin network. PMID:7962085
Duty cycle dependent chemical structure and wettability of RF pulsed plasma copolymers of acrylic acid and octafluorocyclobutane

NASA Astrophysics Data System (ADS)

Muzammil, I.; Li, Y. P.; Li, X. Y.; Lei, M. K.

2018-04-01

Octafluorocyclobutane and acrylic acid (C4F8-co-AA) plasma copolymer coatings are deposited using a pulsed wave (PW) radio frequency (RF) plasma on low density polyethylene (LDPE). The influence of duty cycle in pulsed process with the monomer feed rate on the surface chemistry and wettability of C4F8-co-AA plasma polymer coatings is studied. The concentration of the carboxylic acid (hydrophilic) groups increase, and that of fluorocarbon (hydrophobic) groups decrease by lowering the duty cycle. The combined effect of surface chemistry and surface morphology of the RF pulsed plasma copolymer coatings causes tunable surface wettability and surface adhesion. The gradual emergence of hydrophilic contents leads to surface heterogeneity by lowering duty cycle causing an increased surface adhesion in hydrophobic coatings. The C4F8-co-AA plasma polymer coatings on the nanotextured surfaces are tuned from repulsive superhydrophobicity to adhesive superhydrophobicity, and further to superhydrophilicity by adjusting the duty cycles with the monomer feed rates.
Oleyl group-functionalized insulating gate transistors for measuring extracellular pH of floating cells

NASA Astrophysics Data System (ADS)

Imaizumi, Yuki; Goda, Tatsuro; Toya, Yutaro; Matsumoto, Akira; Miyahara, Yuji

2016-01-01

The extracellular ionic microenvironment has a close relationship to biological activities such as by cellular respiration, cancer development, and immune response. A system composed of ion-sensitive field-effect transistors (ISFET), cells, and program-controlled fluidics has enabled the acquisition of real-time information about the integrity of the cell membrane via pH measurement. Here we aimed to extend this system toward floating cells such as T lymphocytes for investigating complement activation and pharmacokinetics through alternations in the plasma membrane integrity. We functionalized the surface of tantalum oxide gate insulator of ISFET with oleyl-tethered phosphonic acid for interacting with the plasma membranes of floating cells without affecting the cell signaling. The surface modification was characterized by X-ray photoelectron spectroscopy and water contact angle measurements. The Nernst response of -37.8 mV/pH was obtained for the surface-modified ISFET at 37 °C. The oleyl group-functionalized gate insulator successfully captured Jurkat T cells in a fluidic condition without acute cytotoxicity. The system was able to record the time course of pH changes at the cells/ISFET interface during the process of instant addition and withdrawal of ammonium chloride. Further, the plasma membrane injury of floating cells after exposure by detergent Triton™ X-100 was successfully determined using the modified ISFET with enhanced sensitivity as compared with conventional hemolysis assays.
Oleyl group-functionalized insulating gate transistors for measuring extracellular pH of floating cells

PubMed Central

Imaizumi, Yuki; Goda, Tatsuro; Toya, Yutaro; Matsumoto, Akira; Miyahara, Yuji

2016-01-01

Abstract The extracellular ionic microenvironment has a close relationship to biological activities such as by cellular respiration, cancer development, and immune response. A system composed of ion-sensitive field-effect transistors (ISFET), cells, and program-controlled fluidics has enabled the acquisition of real-time information about the integrity of the cell membrane via pH measurement. Here we aimed to extend this system toward floating cells such as T lymphocytes for investigating complement activation and pharmacokinetics through alternations in the plasma membrane integrity. We functionalized the surface of tantalum oxide gate insulator of ISFET with oleyl-tethered phosphonic acid for interacting with the plasma membranes of floating cells without affecting the cell signaling. The surface modification was characterized by X-ray photoelectron spectroscopy and water contact angle measurements. The Nernst response of −37.8 mV/pH was obtained for the surface-modified ISFET at 37 °C. The oleyl group-functionalized gate insulator successfully captured Jurkat T cells in a fluidic condition without acute cytotoxicity. The system was able to record the time course of pH changes at the cells/ISFET interface during the process of instant addition and withdrawal of ammonium chloride. Further, the plasma membrane injury of floating cells after exposure by detergent Triton™ X-100 was successfully determined using the modified ISFET with enhanced sensitivity as compared with conventional hemolysis assays. PMID:27877886
Molecular-dynamics analysis of mobile helium cluster reactions near surfaces of plasma-exposed tungsten

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

Hu, Lin; Maroudas, Dimitrios, E-mail: maroudas@ecs.umass.edu; Hammond, Karl D.

We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (He{sub n}, 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes ofmore » helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He{sub 4} and He{sub 5} clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.« less
Antitumor activity and systemic effects of PVM/MA-shelled selol nanocapsules in lung adenocarcinoma-bearing mice

NASA Astrophysics Data System (ADS)

de Souza, Ludmilla Regina; Alexandre Muehlmann, Luis; Carneiro Matos, Lívia; Simón-Vázquez, Rosana; Guerreiro Marques Lacava, Zulmira; Maurício Batista De-Paula, Alfredo; Mosiniewicz-Szablewska, Ewa; Suchocki, Piotr; César Morais, Paulo; González-Fernández, África; Nair Báo, Sônia; Bentes Azevedo, Ricardo

2015-12-01

Selol is a semi-synthetic compound containing selenite that is effective against cancerous cells and safer for clinical applications in comparison with other inorganic forms of selenite. Recently, we have developed a formulation of poly(methyl vinyl ether-co-maleic anhydride)-shelled selol nanocapsules (SPN), which reduced the proliferative activity of lung adenocarcinoma cells and presented little deleterious effects on normal cells in in vitro studies. In this study, we report on the antitumor activity and systemic effects induced by this formulation in chemically induced lung adenocarcinoma-bearing mice. The in vivo antitumor activity of the SPN was verified by macroscopic quantification, immunohistochemistry and morphological analyses. Toxicity analyses were performed by evaluations of the kidney, liver, and spleen; analyses of hemogram and plasma levels of alanine aminotransferase, aspartate transaminase, urea, and creatinine; and DNA fragmentation and cell cycle activity of the bone marrow cells. Furthermore, we investigated the potential of the SPN formulation to cause hemolysis, activate the complement system, provoke an inflammatory response and change the conformation of the plasma proteins. Our results showed that the SPN reduced the area of the surface tumor nodules but not the total number of tumor nodules. The biochemical and hematological findings were suggestive of the low systemic toxicity of the SPN formulation. The surface properties of the selol nanocapsules point to characteristics that are consistent with the treatment of the tumors in vivo: low hemolytic activity, weak inflammatory reaction with no activation of the complement system, and mild or absent conformational changes of the plasma proteins. In conclusion, this report suggests that the SPN formulation investigated herein exhibits anti-tumoral effects against lung adenocarcinoma in vivo and is associated with low systemic toxicity and high biocompatibility.
CF4 plasma treatment of poly(dimethylsiloxane): effect of fillers and its application to high-aspect-ratio UV embossing.

PubMed

Yan, Y H; Chan-Park, M B; Yue, C Y

2005-09-13

Surface modification of poly(dimethylsiloxane) (PDMS) was carried out via CF4 plasma treatment. The test PDMS used contains significant amounts of quartz and silica fillers, while the control material is the same PDMS with quartz removed by centrifugation. Fluorination accompanied with roughening was produced on both PDMS surfaces. With short plasma times (15 min or less), a macromolecular fluorocarbon layer was formed on the PDMS surfaces because of the dominant fluorination, leading to significant increase in F concentration, decrease of surface energy, and some roughening. With intermediate plasma times (15-30 min), dynamic balance between fluorination and ablation was achieved, leading to a plateau of the surface roughness, fluorine content, and [F-Si]/[F-C] ratio. At our longest investigated plasma time of 45 min, the plasma ablated the fluorinated covering layer on the PDMS surfaces, leading to significant increase in roughness and [F-Si]/[F-C] ratio and decrease of surface F concentration. The effect of additional quartz in the test PDMS on surface F concentration, [F-Si]/[F-C] ratio, and roughness was dramatic only when ablation was significant (i.e., 45 min). The obtained Teflon-like surface displays long-term stability as opposed to hydrophobic recovery of other plasma-treated PDMS surfaces to increase hydrophilicity. On the basis of the optimized plasma treatment time of 15 min, a microstructured PDMS mold was plasma treated and successfully used for multiple high-aspect-ratio (about 8) UV embossing of nonpolar polypropylene glycol diacrylate (PPGDA) resin.
Surface cleaning for enhanced adhesion to packaging surfaces: Effect of oxygen and ammonia plasma

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

Gaddam, Sneha; Dong, Bin; Driver, Marcus

2015-03-15

The effects of direct plasma chemistries on carbon removal from silicon nitride (SiN{sub x}) and oxynitride (SiO{sub x}N{sub y}) surfaces have been studied by in-situ x-ray photoelectron spectroscopy (XPS) and ex-situ contact angle measurements. The data indicate that O{sub 2} and NH{sub 3} capacitively coupled plasmas are effective at removing adventitious carbon from silicon nitride (SiN{sub x}) and Si oxynitride (SiO{sub x}N{sub y}) surfaces. O{sub 2} plasma treatment results in the formation of a silica overlayer. In contrast, the exposure to NH{sub 3} plasma results in negligible additional oxidation of the SiN{sub x} or SiO{sub x}N{sub y} surface. Ex-situ contactmore » angle measurements show that SiN{sub x} and SiO{sub x}N{sub y} surfaces exposed to oxygen plasma are initially more hydrophilic than surfaces exposed to NH{sub 3} plasma, indicating that the O{sub 2} plasma-induced SiO{sub 2} overlayer is highly reactive toward ambient. At longer ambient exposures (≳10 h), however, surfaces treated by either O{sub 2} or NH{sub 3} plasma exhibit similar steady state contact angles, correlated with rapid uptake of adventitious carbon, as determined by XPS. Surface passivation by exposure to molecular hydrogen prior to ambient exposure significantly retards the increase in contact angle upon exposure to ambient. The results suggest a practical route to enhancing the time available for effective bonding to surfaces in microelectronics packaging applications.« less

Plasma-modified graphene nanoplatelets and multiwalled carbon nanotubes as fillers for advanced rubber composites

NASA Astrophysics Data System (ADS)

Sicinski, M.; Gozdek, T.; Bielinski, D. M.; Szymanowski, H.; Kleczewska, J.; Piatkowska, A.

2015-07-01

In modern rubber industry, there still is a room for new fillers, which can improve the mechanical properties of the composites, or introduce a new function to the material. Modern fillers like carbon nanotubes or graphene nanoplatelets (GnP), are increasingly applied in advanced polymer composites technology. However, it might be hard to obtain a well dispersed system for such systems. The polymer matrix often exhibits higher surface free energy (SFE) level with the filler, which can cause problems with polymer-filler interphase adhesion. Filler particles are not wet properly by the polymer, and thus are easier to agglomerate. As a consequence, improvement in the mechanical properties is lower than expected. In this work, multi-walled carbon nanotubes (MWCNT) and GnP surface were modified with low-temperature plasma. Attempts were made to graft some functionalizing species on plasma-activated filler surface. The analysis of virgin and modified fillers’ SFE was carried out. MWCNT and GnP rubber composites were produced, and ultimately, their morphology and mechanical properties were studied.
Surface Interaction Kinetics of GaAs (100) Surfaces Under Electron Cyclotron Resonance Nitrogen Plasma Exposure

NASA Astrophysics Data System (ADS)

O'Steen, M. L.; Hauenstein, R. J.; Bandić, Z. Z.; Feenstra, R. M.; Hwang, S. J.; McGill, T. C.

1996-03-01

GaN is a robust semiconducting material offering a large, direct bandgap appropriate for use in blue-green to UV light emitting diodes and laser diodes. Attainment of device quality GaN has been difficult due to the lack of substrate materials that are suitably matched to the unusually small lattice parameter of GaN. To better control heteroepitaxial growth quality, a fundamental study of the initial stages of GaN growth by Electron Cyclotron Resonance Nitrogen Plasma-Assisted Molecular Beam Epitaxy (ECR-MBE) has been performed. The effect of an ECR Nitrogen plasma on a GaAs (100) surface is examined through time resolved reflection high energy electron diffraction, high resolution x-ray diffraction, and cross-sectional scanning tunneling microscopy. Fully commensurate GaN_yAs_1-y/GaAs heterostructures involving ultrathin GaN_yAs_1-y layers are obtained, and thermally activated microscopic growth processes are identified and quantitatively characterized through the aid of a specially developed kinetic model. The implications for ECR-MBE growth of GaN/GaAs mutilayers is discussed.
Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration

PubMed Central

Ritts, Andy Charles; Li, Hao; Yu, Qingsong; Xu, Changqi; Yao, Xiaomei; Hong, Liang; Wang, Yong

2010-01-01

The objective of this study is to investigate the treatment effects of non-thermal atmospheric gas plasmas on dentin surfaces for composite restoration. Extracted unerupted human third molars were used by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated by using a non-thermal atmospheric argon plasma brush for various durations. The molecular changes of the dentin surfaces were analyzed using FTIR/ATR and an increase in carbonyl groups on dentin surfaces was detected with plasma treated dentin. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro-bars as the specimens for tensile test. Student Newman Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s plasma treatment. However, the bonding strength to plasma treated inner dentin did not show any improvement. It was found that plasma treatment of peripheral dentin surface up to 100 s gave an increase in interfacial bonding strength, while a prolong plasma treatment of dentin surfaces, e.g., 5 min treatments, showed a decrease in interfacial bonding strength. PMID:20831586
Concept for a beryllium divertor with in-situ plasma spray surface regeneration

NASA Astrophysics Data System (ADS)

Smith, M. F.; Watson, R. D.; McGrath, R. T.; Croessmann, C. D.; Whitley, J. B.; Causey, R. A.

1990-04-01

Two serious problems with the use of graphite tiles on the ITER divertor are the limited lifetime due to erosion and the difficulty of replacing broken tiles inside the machine. Beryllium is proposed as an alternative low-Z armor material because the plasma spray process can be used to make in-situ repairs of eroded or damaged surfaces. Recent advances in plasma spray technology have produced beryllium coatings of 98% density with a 95% deposition efficiency and strong adhesion to the substrate. With existing technology, the entire active region of the ITER divertor surface could be coated with 2 mm of beryllium in less than 15 h using four small plasma spray guns. Beryllium also has other potential advantages over graphite, e.g., efficient gettering of oxygen, ten times less tritium inventory, reduced problems of transient fueling from D/T exchange and release, no runaway erosion cascades from self-sputtering, better adhesion of redeposited material, as well as higher strength, ductility, and fracture toughness than graphite. A 2-D finite element stress analysis was performed on a 3 mm thick Be tile brazed to an OFHC soft-copper saddle block, which was brazed to a high-strength copper tube. Peak stresses remained 50% below the ultimate strength for both brazing and in-service thermal stresses.
Effects of atmospheric air plasma treatment on interfacial properties of PBO fiber reinforced composites

NASA Astrophysics Data System (ADS)

Zhang, Chengshuang; Li, Cuiyun; Wang, Baiya; Wang, Bin; Cui, Hong

2013-07-01

Poly(p-phenylene benzobisoxazole) (PBO) fiber was modified by atmospheric air plasma treatment. The effects of plasma treatment power and speed on both surface properties of PBO fibers and interfacial properties of PBO/epoxy composites were investigated. Surface chemical composition of PBO fibers were analyzed by X-ray photoelectron spectroscopy (XPS). Surface morphologies of the fibers and interface structures of the composites were examined using scanning electron microscopy (SEM). Interfacial adhesion property of the composites was evaluated by interlaminar shear strength (ILSS). Mechanical properties of PBO multifilament were measured by universal testing machine. The results indicate that atmospheric air plasma treatment introduced some polar or oxygen-containing groups to PBO fiber surfaces, enhanced surface roughness and changed surface morphologies of PBO fibers by plasma etching and oxidative reactions. The plasma treatment also improved interfacial adhesion of PBO/epoxy composites but has little effect on tensile properties of PBO multifilament. The ILSS of PBO/epoxy composites increased to 40.0 MPa after atmospheric air plasma treatment with plasma treatment power of 300 W and treatment speed of 6 m/min.
Plasma protein adsorption to zwitterionic poly (carboxybetaine methacrylate) modified surfaces: chain chemistry and end-group effects on protein adsorption kinetics, adsorbed amounts and immunoblots.

PubMed

Abraham, Sinoj; Bahniuk, Markian S; Unsworth, Larry D

2012-12-01

Protein-surface interactions are crucial to the overall biocompatability of biomaterials, and are thought to be the impetus towards the adverse host responses such as blood coagulation and complement activation. Only a few studies hint at the ultra-low fouling potential of zwitterionic poly(carboxybetaine methacrylate) (PCBMA) grafted surfaces and, of those, very few systematically investigate their non-fouling behavior. In this work, single protein adsorption studies as well as protein adsorption from complex solutions (i.e. human plasma) were used to evaluate the non-fouling potential of PCBMA grafted silica wafers prepared by nitroxide-mediated free radical polymerization. PCBMAs used for surface grafting varied in charge separating spacer groups that influence the overall surface charges, and chain end-groups that influence the overall hydrophilicity, thereby, allows a better understanding of these effects towards the protein adsorption for these materials. In situ ellipsometry was used to quantify the adsorbed layer thickness and adsorption kinetics for the adsorption of four proteins from single protein buffer solutions, viz, lysozyme, α-lactalbumin, human serum albumin and fibrinogen. Total amount of protein adsorbed on surfaces differed as a function of surface properties and protein characteristics. Finally, immunoblots results showed that human plasma protein adsorption to these surfaces resulted, primarily, in the adsorption of human serum albumin, with total protein adsorbed amounts being the lowest for PCBMA-3 (TEMPO). It was apparent that surface charge and chain hydrophilicity directly influenced protein adsorption behavior of PCBMA systems and are promising materials for biomedical applications.
A Huygens immersed-finite-element particle-in-cell method for modeling plasma-surface interactions with moving interface

NASA Astrophysics Data System (ADS)

Cao, Huijun; Cao, Yong; Chu, Yuchuan; He, Xiaoming; Lin, Tao

2018-06-01

Surface evolution is an unavoidable issue in engineering plasma applications. In this article an iterative method for modeling plasma-surface interactions with moving interface is proposed and validated. In this method, the plasma dynamics is simulated by an immersed finite element particle-in-cell (IFE-PIC) method, and the surface evolution is modeled by the Huygens wavelet method which is coupled with the iteration of the IFE-PIC method. Numerical experiments, including prototypical engineering applications, such as the erosion of Hall thruster channel wall, are presented to demonstrate features of this Huygens IFE-PIC method for simulating the dynamic plasma-surface interactions.
Optimization of the Silver Nanoparticles PEALD Process on the Surface of 1-D Titania Coatings

PubMed Central

Radtke, Aleksandra; Kozak, Wiesław; Sadowska, Beata; Więckowska-Szakiel, Marzena; Talik, Ewa; Mäkelä, Maarit; Leskelä, Markku; Piszczek, Piotr

2017-01-01

Plasma enhanced atomic layer deposition (PEALD) of silver nanoparticles on the surface of 1-D titania coatings, such as nanotubes (TNT) and nanoneedles (TNN), has been carried out. The formation of TNT and TNN layers enriched with dispersed silver particles of strictly defined sizes and the estimation of their bioactivity was the aim of our investigations. The structure and the morphology of produced materials were determined using X-ray photoelectron spectroscopy (XPS) and scanning electron miscroscopy (SEM). Their bioactivity and potential usefulness in the modification of implants surface have been estimated on the basis of the fibroblasts adhesion and proliferation assays, and on the basis of the determination of their antibacterial activity. The cumulative silver release profiles have been checked with the use of inductively coupled plasma-mass spectrometry (ICPMS), in order to exclude potential cytotoxicity of silver decorated systems. Among the studied nanocomposite samples, TNT coatings, prepared at 3, 10, 12 V and enriched with silver nanoparticles produced during 25 cycles of PEALD, revealed suitable biointegration properties and may actively counteract the formation of bacterial biofilm. PMID:28737725
Tritium retention in reduced-activation ferritic/martensitic steels

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

Hatano, Y.; Abe, S.; Matsuyama, M.

Reduced-activation ferritic/martensitic (RAFM) steels are structural material candidates for breeding blankets of future fusion reactors. Therefore, tritium (T) retention in RAFM steels is an important problem in assessing the T inventory of blankets. In this study, specimens of RAFM steels were subjected to irradiation of 20 MeV W ions to 0.54 displacements per atom (dpa), exposure to high flux D plasmas at 400 and 600 K and that to pulsed heat loads. The specimens thus prepared were exposed to DT gas at 473 K. Despite severe modification in the surface morphology, heat loads had negligible effects on T retention. Significantmore » increase in T retention at the surface and/or subsurface was observed after D plasma exposure. However, T trapped at the surface/subsurface layer was easily removed by maintaining the specimens in the air at about 300 K. Displacement damage led to increase in T retention in the bulk due to the trapping effects of defects, and T trapped was stable at 300 K. It was therefore concluded that displacement damages had the largest influence on T retention under the present conditions.« less
Understanding the molecular-level chemistry of water plasmas and the effects of surface modification and deposition on a selection of oxide substrates

NASA Astrophysics Data System (ADS)

Trevino, Kristina J.

2011-12-01

This dissertation first examines electrical discharges used to study wastewater samples for contaminant detection and abatement. Two different water samples contaminated with differing concentrations of either methanol (MeOH) or methyl tert-butyl ether (MTBE) were used to follow breakdown mechanisms. Emission from CO* was used to monitor the contaminant and for molecular breakdown confirmation through actinometric OES as it can only arise from the carbon-based contaminant in either system. Detection was achieved at concentrations as low as 0.01 ppm, and molecular decomposition was seen at a variety of plasma parameters. This dissertation also explores the vibrational (thetaV), rotational (thetaR) and translational (thetaT) temperatures for a range of diatomic species in different plasma systems. For the majority of the plasma species studied, thetaV are much higher than thetaR and thetaT. This suggests that more energy is partitioned into the vibrational degrees of freedom in our plasmas. The thetaR reported are significantly lower in all the plasma systems studied and this is a result of radical equilibration to the plasma gas temperature. thetaT values show two characteristics; (1) they are less than the thetaV and higher than the theta R and (2) show varying trends with plasma parameters. Radical energetics were examined through comparison of thetaR, thetaT, and thetaV, yielding significant insight on the partitioning of internal and kinetic energies in plasmas. Correlations between energy partitioning results and corresponding radical surface scattering coefficients obtained using our imaging of radicals interacting with surfaces (IRIS) technique are also presented. Another aspect of plasma process chemistry, namely surface modification via plasma treatment, was investigated through characterization of metal oxides (SiOxNy, nat-SiO2, and dep-SiO2) following their exposure to a range of plasma discharges. Here, emphasis was placed on the surface wettability, surface charge, and isoelectric point (IEP). The results demonstrate that 100% Ar, H2O, and NH3 plasma treatments cause changes in surface charge, wettability, and IEP values for all treated surfaces. Observed variations in these values depend primarily on the specific mechanism for surface functionalization with each plasma treatment. These results highlight the utility of IEP measurements for characterizing plasma treated surfaces and suggest the possibility that plasmas may provide a valuable means of controlling surface charge and wettability of metal oxides. The incorporation of functional groups on the surface of Zeolite X was also examined as an additional form of plasma surface modification. The intention of these studies was to (1) alter the surface functionality by simple plasmas treatments, as characterized by XPS data; (2) change the hydrophilic nature of the zeolite to be more hydrophobic with fluorocarbon plasmas; (3) gain total surface area functionality with our new rotating drum reactor; and (4) ensure that damage was not occurring to the zeolite structure, as evidenced by SEM images. Results showed the incorporation of different surface functionality was accomplished with all plasma systems studied (CF4, C2 F6, C3F8), the zeolite structure was not damaged by the plasma, and the potential for altering the entire surface area of these porous materials exists. The final portion of this dissertation addresses aspects of work designed to understand the adhesion behavior of amorphous carbon nitride (a-CN x) films deposited from a CH3CN and BrCN plasmas. In particular, films obtained from CH3CH plasmas stayed intact whereas BrCN plasmas produced films that delaminated upon their exposure to atmosphere. These results have been attributed to humidity, film stress, hydrocarbon species, and the Br content in the film. The major contributions to this work made here center on the chemical composition and binding environments of the deposited films as measured by XPS, which are shown to be critical in understanding the mechanical properties of a-CNx films. (Abstract shortened by UMI.)
Attachment of Poly(l-lactide) Nanoparticles to Plasma-Treated Non-Woven Polymer Fabrics Using Inkjet Printing.

PubMed

Ivanova, Tatiana V; Baier, Grit; Landfester, Katharina; Musin, Eduard; Al-Bataineh, Sameer A; Cameron, David C; Homola, Tomáš; Whittle, Jason D; Sillanpää, Mika

2015-09-01

Active dressings that based on fabric materials are an area of interest for the treatment of wounds. Poly(l-lactide) nanoparticles containing the antimicrobial agent octenidine can be controllably lysed by toxins released by pathogenic bacteria thus releasing antimicrobial material in response to the presence of the bacterial toxins and so counteracting the infection. We developed an integrated engineering solution that allows for the stable immobilisation of nanoparticles on non-woven fabrics. The process involves coating nanoparticles on non-woven polymer surfaces by using an inkjet printing process. In order to improve the adhesion and retention of the nanoparticles on the fabric, surface pretreatment of the non-woven fabric using plasma jet treatment can be applied to increase its surface energy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Vapor shielding effects on energy transfer from plasma-gun generated ELM-like transient loads to material surfaces

NASA Astrophysics Data System (ADS)

Kikuchi, Y.; Sakuma, I.; Asai, Y.; Onishi, K.; Isono, W.; Nakazono, T.; Nakane, M.; Fukumoto, N.; Nagata, M.

2016-02-01

Energy transfer processes from ELM-like pulsed helium (He) plasmas with a pulse duration of ˜0.1 ms to aluminum (Al) and tungsten (W) surfaces were experimentally investigated by the use of a magnetized coaxial plasma gun device. The surface absorbed energy density of the He pulsed plasma on the W surface measured with a calorimeter was ˜0.44 MJ m-2, whereas it was ˜0.15 MJ m-2 on the Al surface. A vapor layer in front of the Al surface exposed to the He pulsed plasma was clearly identified by Al neutral emission line (Al i) measured with a high time resolution spectrometer, and fast imaging with a high-speed visible camera filtered around the Al i emission line. On the other hand, no clear evaporation in front of the W surface exposed to the He pulsed plasma was observed in the present condition. Discussions on the reduction in the surface absorbed energy density on the Al surface are provided by considering the latent heat of vaporization and radiation cooling due to the Al vapor cloud.
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.
Compact Plasma Accelerator

NASA Technical Reports Server (NTRS)

Foster, John E.

2004-01-01

A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.
Quantitative Microscopic Analysis of Plasma Membrane Receptor Dynamics in Living Plant Cells.

PubMed

Luo, Yu; Russinova, Eugenia

2017-01-01

Plasma membrane-localized receptors are essential for cellular communication and signal transduction. In Arabidopsis thaliana, BRASSINOSTEROID INSENSITIVE1 (BRI1) is one of the receptors that is activated by binding to its ligand, the brassinosteroid (BR) hormone, at the cell surface to regulate diverse plant developmental processes. The availability of BRI1 in the plasma membrane is related to its signaling output and is known to be controlled by the dynamic endomembrane trafficking. Advances in fluorescence labeling and confocal microscopy techniques enabled us to gain a better understanding of plasma membrane receptor dynamics in living cells. Here we describe different quantitative microscopy methods to monitor the relative steady-state levels of the BRI1 protein in the plasma membrane of root epidermal cells and its relative exocytosis and recycling rates. The methods can be applied also to analyze similar dynamics of other plasma membrane-localized receptors.
Optical Emission Spectroscopy of an Atmospheric Pressure Plasma Jet During Tooth Bleaching Gel Treatment.

PubMed

Šantak, Vedran; Zaplotnik, Rok; Tarle, Zrinka; Milošević, Slobodan

2015-11-01

Optical emission spectroscopy was performed during atmospheric pressure plasma needle helium jet treatment of various tooth-bleaching gels. When the gel sample was inserted under the plasma plume, the intensity of all the spectral features increased approximately two times near the plasma needle tip and up to two orders of magnitude near the sample surface. The color change of the hydroxylapatite pastille treated with bleaching gels in conjunction with the atmospheric pressure plasma jet was found to be in correlation with the intensity of OH emission band (309 nm). Using argon as an additive to helium flow (2 L/min), a linear increase (up to four times) of OH intensity and, consequently, whitening (up to 10%) of the pastilles was achieved. An atmospheric pressure plasma jet activates bleaching gel, accelerates OH production, and accelerates tooth bleaching (up to six times faster).
Evolutionary clade affects resistance of Clostridium difficile spores to Cold Atmospheric Plasma

NASA Astrophysics Data System (ADS)

Connor, Mairéad; Flynn, Padrig B.; Fairley, Derek J.; Marks, Nikki; Manesiotis, Panagiotis; Graham, William G.; Gilmore, Brendan F.; McGrath, John W.

2017-02-01

Clostridium difficile is a spore forming bacterium and the leading cause of colitis and antibiotic associated diarrhoea in the developed world. Spores produced by C. difficile are robust and can remain viable for months, leading to prolonged healthcare-associated outbreaks with high mortality. Exposure of C. difficile spores to a novel, non-thermal atmospheric pressure gas plasma was assessed. Factors affecting sporicidal efficacy, including percentage of oxygen in the helium carrier gas admixture, and the effect on spores from different strains representing the five evolutionary C. difficile clades was investigated. Strains from different clades displayed varying resistance to cold plasma. Strain R20291, representing the globally epidemic ribotype 027 type, was the most resistant. However all tested strains displayed a ~3 log reduction in viable spore counts after plasma treatment for 5 minutes. Inactivation of a ribotype 078 strain, the most prevalent clinical type seen in Northern Ireland, was further assessed with respect to surface decontamination, pH, and hydrogen peroxide concentration. Environmental factors affected plasma activity, with dry spores without the presence of organic matter being most susceptible. This study demonstrates that cold atmospheric plasma can effectively inactivate C. difficile spores, and highlights factors that can affect sporicidal activity.
Design, Analysis and R&D of the EAST In-Vessel Components

NASA Astrophysics Data System (ADS)

Yao, Damao; Bao, Liman; Li, Jiangang; Song, Yuntao; Chen, Wenge; Du, Shijun; Hu, Qingsheng; Wei, Jing; Xie, Han; Liu, Xufeng; Cao, Lei; Zhou, Zibo; Chen, Junling; Mao, Xinqiao; Wang, Shengming; Zhu, Ning; Weng, Peide; Wan, Yuanxi

2008-06-01

In-vessel components are important parts of the EAST superconducting tokamak. They include the plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structural design, analysis and related R&D have been completed. The divertor is designed in an up-down symmetric configuration to accommodate both double null and single null plasma operation. Passive plates are used for plasma movement control. In-vessel coils are used for the active control of plasma vertical movements. Each cryo-pump can provide an approximately 45 m3/s pumping rate at a pressure of 10-1 Pa for particle exhaust. Analysis shows that, when a plasma current of 1 MA disrupts in 3 ms, the EM loads caused by the eddy current and the halo current in a vertical displacement event (VDE) will not generate an unacceptable stress on the divertor structure. The bolted divertor thermal structure with an active cooling system can sustain a load of 2 MW/m2 up to a 60 s operation if the plasma facing surface temperature is limited to 1500 °C. Thermal testing and structural optimization testing were conducted to demonstrate the analysis results.
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.
Absence of cell surface expression of human ACE leads to perinatal death

PubMed Central

Michaud, Annie; Acharya, K. Ravi; Masuyer, Geoffrey; Quenech'du, Nicole; Gribouval, Olivier; Morinière, Vincent; Gubler, Marie-Claire; Corvol, Pierre

2014-01-01

Renal tubular dysgenesis (RTD) is a recessive autosomal disease characterized most often by perinatal death. It is due to the inactivation of any of the major genes of the renin-angiotensin system (RAS), one of which is the angiotensin I-converting enzyme (ACE). ACE is present as a tissue-bound enzyme and circulates in plasma after its solubilization. In this report, we present the effect of different ACE mutations associated with RTD on ACE intracellular trafficking, secretion and enzymatic activity. One truncated mutant, R762X, responsible for neonatal death was found to be an enzymatically active, secreted form, not inserted in the plasma membrane. In contrast, another mutant, R1180P, was compatible with life after transient neonatal renal insufficiency. This mutant was located at the plasma membrane and rapidly secreted. These results highlight the importance of tissue-bound ACE versus circulating ACE and show that the total absence of cell surface expression of ACE is incompatible with life. In addition, two missense mutants (W594R and R828H) and two truncated mutants (Q1136X and G1145AX) were also studied. These mutants were neither inserted in the plasma membrane nor secreted. Finally, the structural implications of these ACE mutations were examined by molecular modelling, which suggested some important structural alterations such as disruption of intra-molecular non-covalent interactions (e.g. salt bridges). PMID:24163131

Low-density lipoprotein receptor-related protein 1: a physiological Aβ homeostatic mechanism with multiple therapeutic opportunities

PubMed Central

Sagare, Abhay P.; Deane, Rashid; Zlokovic, Berislav V.

2012-01-01

Low-density lipoprotein receptor-related protein-1 (LRP1) is the main cell surface receptor involved in brain and systemic clearance of the Alzheimer's disease (AD) toxin amyloid-beta (Aβ). In plasma, a soluble form of LRP1 (sLRP1) is the major transport protein for peripheral Aβ. LRP1 in brain endothelium and mural cells mediates Aβ efflux from brain by providing a transport mechanism for A across the blood-brain barrier (BBB). sLRP1 maintains a plasma ‘sink’ activity for Aβ through binding of peripheral Aβ which in turn inhibits re-entry of free plasma Aβ into the brain. LRP1 in the liver mediates systemic clearance of Aβ. In AD, LRP1 expression at the BBB is reduced and Aβ binding to circulating sLRP1 is compromised by oxidation. Cell surface LRP1 and circulating sLRP1 represent druggable targets which can be therapeutically modified to restore the physiological mechanisms of brain Aβ homeostasis. In this review, we discuss how increasing LRP1 expression at the BBB and liver with lifestyle changes, statins, plant-based active principles and/or gene therapy on one hand, and how replacing dysfunctional plasma sLRP1 on the other regulate Aβ clearance from brain ultimately controlling the onset and/or progression of AD. PMID:22820095
Surface wave and linear operating mode of a plasma antenna

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

Bogachev, N. N., E-mail: bgniknik@yandex.ru; Bogdankevich, I. L.; Gusein-zade, N. G.

The relation between the propagation conditions of a surface electromagnetic wave along a finiteradius plasma cylinder and the linear operating mode of a plasma antenna is investigated. The solution to the dispersion relation for a surface wave propagating along a finite-radius plasma cylinder is analyzed for weakly and strongly collisional plasmas. Computer simulations of an asymmetrical plasma dipole antenna are performed using the KARAT code, wherein the dielectric properties of plasma are described in terms of the Drude model. The plasma parameters corresponding to the linear operating mode of a plasma antenna are determined. It is demonstrated that the characteristicsmore » of the plasma antenna in this mode are close to those of an analogous metal antenna.« less
Use of Atmospheric-Pressure Plasma Jet for Polymer Surface Modification: An Overview

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

Kuettner, Lindsey A.

Atmospheric-pressure plasma jets (APPJs) are playing an increasingly important role in materials processing procedures. Plasma treatment is a useful tool to modify surface properties of materials, especially polymers. Plasma reacts with polymer surfaces in numerous ways thus the type of process gas and plasma conditions must be explored for chosen substrates and materials to maximize desired properties. This report discusses plasma treatments and looks further into atmospheric-pressure plasma jets and the effects of gases and plasma conditions. Following the short literature review, a general overview of the future work and research at Los Alamos National Laboratory (LANL) is discussed.
Antiplatelet Agents Can Promote Two-Peaked Thrombin Generation in Platelet Rich Plasma: Mechanism and Possible Applications

PubMed Central

Tarandovskiy, Ivan D.; Artemenko, Elena O.; Panteleev, Mikhail A.; Sinauridze, Elena I.; Ataullakhanov, Fazoil I.

2013-01-01

Background Thrombin generation assay is a convenient and widely used method for analysis of the blood coagulation system status. Thrombin generation curve (TGC) is usually bell-shaped with a single peak, but there are exceptions. In particular, TGC in platelet-rich plasma (PRP) can sometimes have two peaks. Objective We sought to understand the mechanism underlying the occurrence of two peaks in the PRP thrombin generation curve. Methods Tissue factor-induced thrombin generation in PRP and platelet-poor plasma (PPP) was monitored using continuous measurement of the hydrolysis rate of the thrombin-specific fluorogenic substrate Z-Gly-Gly-Arg-AMC. Expression of phosphatidylserine (PS) and CD62P on the surface of activated platelets was measured by flow cytometry using corresponding fluorescently labeled markers. Results The addition of the P2Y12 receptor antagonist MeS-AMP (160 µM), 83 nM prostaglandin E1 (PGE1), or 1.6% DMSO to PRP caused the appearance of two peaks in the TGC. The PS exposure after thrombin activation on washed platelets in a suspension supplemented with DMSO, PGE1 or MeS-AMP was delayed, which could indicate mechanism of the second peak formation. Supplementation of PRP with 1.6% DMSO plus 830 nM PGE1 mediated the disappearance of the second peak and decreased the amplitude of the first peak. Increasing the platelet concentration in the PRP promoted the consolidation of the two peaks into one. Conclusions Procoagulant tenase and prothrombinase complexes in PRP assemble on phospholipid surfaces containing PS of two types - plasma lipoproteins and the surface of activated platelets. Thrombin generation in the PRP can be two-peaked. The second peak appears in the presence of platelet antagonists as a result of delayed PS expression on platelets, which leads to delayed assembly of the membrane-dependent procoagulant complexes and a second wave of thrombin generation. PMID:23405196
Removal of hydrocarbon contaminant film from spacecraft optical surfaces using a radiofrequency-excited oxygen plasma.

NASA Technical Reports Server (NTRS)

Beverly, W. D.; Gillete, R. B.; Cruz, G. A.

1973-01-01

Results of a study on the feasibility of removing contaminant films from optical surfaces in vacuum, using an oxygen plasma, are discussed. Contaminant films were deposited onto optical surfaces from butadiene and methane gases at a pressure of about 4 torr in the presence of ultraviolet radiation. Optical surfaces evaluated included ultraviolet-reflecting mirrors, gratings, quartz disks, and spacecraft thermal control surfaces. In general, it was found that contaminants could be removed successfully from surfaces using an oxygen plasma. Exceptions were the white-paint thermal control surfaces, which, when contaminated, degraded further during exposure to the oxygen plasma.
Correlation between the plasma characteristics and the surface chemistry of plasma-treated polymers through partial least-squares analysis.

PubMed

Mavadat, Maryam; Ghasemzadeh-Barvarz, Massoud; Turgeon, Stéphane; Duchesne, Carl; Laroche, Gaétan

2013-12-23

We investigated the effect of various plasma parameters (relative density of atomic N and H, plasma temperature, and vibrational temperature) and process conditions (pressure and H2/(N2 + H2) ratio) on the chemical composition of modified poly(tetrafluoroethylene) (PTFE). The plasma parameters were measured by means of near-infrared (NIR) and UV-visible emission spectroscopy with and without actinometry. The process conditions of the N2-H2 microwave discharges were set at various pressures ranging from 100 to 2000 mTorr and H2/(N2+H2) gas mixture ratios between 0 and 0.4. The surface chemical composition of the modified polymers was determined by X-ray photoelectron spectroscopy (XPS). A mathematical model was constructed using the partial least-squares regression algorithm to correlate the plasma information (process condition and plasma parameters as determined by emission spectroscopy) with the modified surface characteristics. To construct the model, a set of data input variables containing process conditions and plasma parameters were generated, as well as a response matrix containing the surface composition of the polymer. This model was used to predict the composition of PTFE surfaces subjected to N2-H2 plasma treatment. Contrary to what is generally accepted in the literature, the present data demonstrate that hydrogen is not directly involved in the defluorination of the surface but rather produces atomic nitrogen and/or NH radicals that are shown to be at the origin of fluorine atom removal from the polymer surface. The results show that process conditions alone do not suffice in predicting the surface chemical composition and that the plasma characteristics, which cannot be easily correlated with these conditions, should be considered. Process optimization and control would benefit from plasma diagnostics, particularly infrared emission spectroscopy.
Surface interaction of polyimide with oxygen ECR plasma

NASA Astrophysics Data System (ADS)

Naddaf, M.; Balasubramanian, C.; Alegaonkar, P. S.; Bhoraskar, V. N.; Mandle, A. B.; Ganeshan, V.; Bhoraskar, S. V.

2004-07-01

Polyimide (Kapton-H), was subjected to atomic oxygen from an electron cyclotron resonance plasma. An optical emission spectrometer was used to characterize the atomic oxygen produced in the reactor chamber. The energy of the ions was measured using a retarding field analyzer, placed near the substrate. The density of atomic oxygen in the plasma was estimated using a nickel catalytic probe. The surface wettability of the polyimide samples monitored by contact angle measurements showed considerable improvement when treated with plasma. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic studies showed that the atomic oxygen in the plasma is the main specie affecting the surface chemistry and adhesion properties of polyimide. The improvement in the surface wettability is attributed to the high degree of cross-linking and large concentration of polar groups generated in the surface region of polyimide, after plasma treatment. The changes in the surface region of polyimide were observed by atomic force microscopic analysis.
Validation of cold plasma treatment for protein inactivation: a surface plasmon resonance-based biosensor study

NASA Astrophysics Data System (ADS)

Bernard, C.; Leduc, A.; Barbeau, J.; Saoudi, B.; Yahia, L'H.; DeCrescenzo, G.

2006-08-01

Gas plasma is being proposed as an interesting and promising tool to achieve sterilization. The efficacy of gas plasma to destroy bacterial spores (the most resistant living microorganisms) has been demonstrated and documented over the last ten years. In addition to causing damage to deoxyribonucleic acid by UV radiation emitted by excited species originating from the plasma, gas plasma has been shown to promote erosion of the microorganism in addition to possible oxidation reactions within the microorganism. In this work, we used lysozyme as a protein model to assess the effect of gas plasma on protein inactivation. Lysozyme samples have been subjected to the flowing afterglow of a gas discharge achieved in a nitrogen-oxygen mixture. The efficiency of this plasma treatment on lysozyme has been tested by two different assays. These are an enzyme-linked immunosorbent assay (ELISA) and a surface plasmon resonance (SPR)-based biosensor assay. The two methods showed that exposure to gas plasma can abrogate lysozyme interactions with lysozyme-specific antibodies, more likely by destroying the epitopes responsible for the interaction. More specifically, two SPR-based assays were developed since our ELISA approach did not allow us to discriminate between background and low, but still intact, quantities of lysozyme epitope after plasma treatment. Our SPR results clearly demonstrated that significant protein destruction or desorption was achieved when amounts of lysozyme less than 12.5 ng had been deposited in polystyrene 96-well ELISA plates. At higher lysozyme amounts, traces of available lysozyme epitopes were detected by SPR through indirect measurements. Finally, we demonstrated that a direct SPR approach in which biosensor-immobilized lysozyme activity is directly measured prior and after plasma treatment is more sensitive, and thus, more appropriate to define plasma treatment efficacy with more certainty.
Direct plasma interaction with living tissue

NASA Astrophysics Data System (ADS)

Fridman, Gregory

For some time, plasma has been used in medicine to cauterize or cut tissue using heat and mechanical energy. In the recent decade, some researchers around the world have started to investigate how gas jets that pass through thermal plasma can be employed in medicine. This thesis presents the first investigation of biomedical uses of non-thermal plasma discharge which comes in direct contact with living tissue. It is demonstrated that the direct application of non-thermal plasma in air can cause rapid deactivation of bacteria on surfaces of tissues without causing any visible tissue damage. Medical need for such a device is discussed. Construction and operation of various types of non-thermal plasma power supplies and many types of treatment electrodes are presented as well. Application of this plasma to living organisms is shown to be safe from both the electrical perspective and from the biological perspective. Biological safety is revealed through a series of differential skin toxicity trials on human cadaver tissue, live hairless mouse skin tissue, live pig skin tissue, and finally in an open wound model on pigs. Direct non-thermal plasma in air is shown to deactivate bacteria about 100 times faster than indirect application using jets. A series of experiments reveal that this effectiveness is due to the ability of direct discharge to bring charges to tissue surfaces. It is demonstrated that neither ultraviolet (UV) radiation nor neutral active species such as hydroxyl radicals or ozone produced in plasma are responsible for the main effect on bacteria. Although much additional work remains on establishing detailed mechanism by which charges from plasma achieve this effect, the work carried out in this thesis clearly demonstrates that direct application of non-thermal plasma in air can be a very useful tool in medicine.
Single and multiple streamer DBD micro-discharges for testing inactivation of biologically contaminated surfaces

NASA Astrophysics Data System (ADS)

Prukner, Vaclav; Dolezalova, Eva; Simek, Milan

2014-10-01

Highly reactive environment produced by atmospheric-pressure, non-equilibrium plasmas generated by surface dielectric barrier discharges (SDBDs) may be used for inactivation of biologically contaminated surfaces. We investigated decontamination efficiency of reactive environment produced by single/multiple surface streamer micro-discharge driven by amplitude-modulated AC power in coplanar electrode geometry on biologically contaminated surface by Escherichia coli. The discharges were fed by synthetic air with water vapor admixtures at atmospheric pressure, time of treatment was set from 10 second to 10 minutes, diameters of used SDBD electrodes (single and multiple streamer) and homogeneously contaminated disc samples were equal (25 mm), the distance between the electrode and contaminated surface was 2 mm. Both a conventional cultivation and fluorescent method LIVE/DEAD Bacterial Viability kit were applied to estimate counts of bacteria after the plasma treatment. Inactivation was effective and bacteria partly lost ability to grow and became injured and viable/active but non-cultivable (VBNC/ABNC). Work was supported by the MEYS under Project LD13010, VES13 COST CZ (COST Action MP 1101).
GPU based 3D feature profile simulation of high-aspect ratio contact hole etch process under fluorocarbon plasmas

NASA Astrophysics Data System (ADS)

Chun, Poo-Reum; Lee, Se-Ah; Yook, Yeong-Geun; Choi, Kwang-Sung; Cho, Deog-Geun; Yu, Dong-Hun; Chang, Won-Seok; Kwon, Deuk-Chul; Im, Yeon-Ho

2013-09-01

Although plasma etch profile simulation has been attracted much interest for developing reliable plasma etching, there still exist big gaps between current research status and predictable modeling due to the inherent complexity of plasma process. As an effort to address this issue, we present 3D feature profile simulation coupled with well-defined plasma-surface kinetic model for silicon dioxide etching process under fluorocarbon plasmas. To capture the realistic plasma surface reaction behaviors, a polymer layer based surface kinetic model was proposed to consider the simultaneous polymer deposition and oxide etching. Finally, the realistic plasma surface model was used for calculation of speed function for 3D topology simulation, which consists of multiple level set based moving algorithm, and ballistic transport module. In addition, the time consumable computations in the ballistic transport calculation were improved drastically by GPU based numerical computation, leading to the real time computation. Finally, we demonstrated that the surface kinetic model could be coupled successfully for 3D etch profile simulations in high-aspect ratio contact hole plasma etching.
An assessment of surface emissivity variation effects on plasma uniformity analysis using IR cameras

NASA Astrophysics Data System (ADS)

Greenhalgh, Abigail; Showers, Melissa; Biewer, Theodore

2017-10-01

The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) is a linear plasma device operating at Oak Ridge National Laboratory (ORNL). Its purpose is to test plasma source and heating concepts for the planned Material Plasma Exposure eXperiment (MPEX), which has the mission to test the plasma-material interactions under fusion reactor conditions. In this device material targets will be exposed to high heat fluxes (>10 MW/m2). To characterize the heat fluxes to the target a IR thermography system is used taking up to 432 frames per second videos. The data is analyzed to determine the surface temperature on the target in specific regions of interest. The IR analysis has indicated a low level of plasma uniformity; the plasma often deposits more heat to the edge of the plate than the center. An essential parameter for IR temperature calculation is the surface emissivity of the plate (stainless steel). A study has been performed to characterize the variation in the surface emissivity of the plate as its temperature changes and its surface finish is modified by plasma exposure.
Edge plasma boundary layer generated by kink modes in tokamaks

NASA Astrophysics Data System (ADS)

Zakharov, Leonid E.

2011-06-01

This paper describes the structure of the electric current generated by external wall touching and free boundary kink modes at the plasma edge using the ideally conducting plasma model. Both kinds of modes generate δ-functional surface current at the plasma edge. Free boundary kink modes also perturb the core plasma current, which in the plasma edge compensates the difference between the δ-functional surface currents of free boundary and wall touching kink modes. In addition, the resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.
Auxin-activated NADH oxidase activity of soybean plasma membranes is distinct from the constitutive plasma membrane NADH oxidase and exhibits prion-like properties

NASA Technical Reports Server (NTRS)

Morre, D. James; Morre, Dorothy M.; Ternes, Philipp

2003-01-01

The hormone-stimulated and growth-related cell surface hydroquinone (NADH) oxidase activity of etiolated hypocotyls of soybeans oscillates with a period of about 24 min or 60 times per 24-h day. Plasma membranes of soybean hypocotyls contain two such NADH oxidase activities that have been resolved by purification on concanavalin A columns. One in the apparent molecular weight range of 14-17 kDa is stimulated by the auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The other is larger and unaffected by 2,4-D. The 2,4-D-stimulated activity absolutely requires 2,4-D for activity and exhibits a period length of about 24 min. Also exhibiting 24-min oscillations is the rate of cell enlargement induced by the addition of 2,4-D or the natural auxin indole-3-acetic acid (IAA). Immediately following 2,4-D or IAA addition, a very complex pattern of oscillations is frequently observed. However, after several hours a dominant 24-min period emerges at the expense of the constitutive activity. A recruitment process analogous to that exhibited by prions is postulated to explain this behavior.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Mengyao; Zhou, Baoming; Jiao, Kunyan

A switchable surface that promotes either hydrophobic or hydrophilic wettability of poly (L-lactide) (PLLA) microfibrous membranes is obtained by CF₄ microwave plasma treatment in this paper. The results indicated that both etching and grafting process occurred during the CF₄ plasma treatment and these two factors synergistically affected the final surface wettability of PLLA membranes. When plasma treatment was taken under a relatively low power, the surface wettability of PLLA membranes turned from hydrophobic to hydrophilic. Especially when CF₄ plasma treatment was taken under 100 W for 10 min and 150 W for 5 min, the water contact angle sharply decreasedmore » from 116 ± 3.0° to ~0°. According to Field-emission scanning electron microscopy (FESEM) results, the PLLA fibers were notably etched by CF₄ plasma treatment. Combined with the X-ray photoelectron spectroscopy (XPS) measurements, only a few fluorine-containing groups were grafted onto the surface, so the etching effect directly affected the surface wettability of PLLA membranes in low plasma power condition. However, with the plasma power increasing to 200 W, the PLLA membrane surface turned to hydrophobic again. In contrast, the morphology changes of PLLA fiber surfaces were not obvious while a large number of fluorine-containing groups grafted onto the surface. So the grafting effect gradually became the major factor for the final surface wettability.« less
Characteristics of a DC-Driven Atmospheric Pressure Air Microplasma Jet

NASA Astrophysics Data System (ADS)

Choi, Jaegu; Matsuo, Keita; Yoshida, Hidekazu; Namihira, Takao; Katsuki, Sunao; Akiyama, Hidenori

2008-08-01

A dc-driven atmospheric pressure air plasma jet has been investigated for some applications, such as local dental treatment, the inner surface treatment of capillaries, stimuli for microorganisms, and the local cleaning of semiconductor devices. The main experimental results are as follows. The discharge in the pulsed mode occurs repetitively despite of the dc input, and the pulsed mode transfers to the continuous mode as the current exceeds a threshold. The measured emission spectrum from the arc column of the air discharge reveals that most energy of activated electrons is used for the excitation of N2 (second positive system bands) and part of the energy for the dissociation of O2. The length of the plasma torch depends on the tube length, inner gap distance, and flow rate. The maximum torch length of about 40 mm is obtained under certain conditions. The spatial distributions of plasma gas temperature are measured and confirmed by the visualization of the gas flow using Schlieren images. Furthermore, surface treatment and decolorization using the generated plasma torch are carried out, focusing on industrial applications.
Air Purification Pavement Surface Coating by Atmospheric Pressure Cold Plasma

NASA Astrophysics Data System (ADS)

Westergreen, Joe; Pedrow, Patrick; Shen, Shihui; Jobson, Bertram

2011-10-01

This study develops an atmospheric pressure cold plasma (APCP) reactor to produce activated radicals from precursor molecules, and to immobilize nano titanium dioxide (TiO2) powder to substrate pavement materials. TiO2 has photocatalytic properties and under UV light can be used to oxidize and remove volatile organic compounds (VOCs) and nitrogen oxides (NOx) from the atmosphere. Although TiO2 treated paving materials have great potential to improve air quality, current techniques to adhere TiO2 to substrate materials are either not durable or reduce direct contact of TiO2 with UV light, reducing the photocatalytic effect. To solve this technical difficulty, this study introduces APCP techniques to transportation engineering to coat TiO2 to pavement. Preliminary results are promising and show that TiO2 can be incorporated successfully into an APCP environment and can be immobilized at the surface of the asphalt substrate. The TiO2 coated material with APCP shows the ability to reduce nitrogen oxides when exposed to UV light in an environmental chamber. The plasma reactor utilizes high voltage streamers as the plasma source.
Hemocompatibility and cytocompatibility of pristine and plasma-treated silver-zeolite-chitosan composites

NASA Astrophysics Data System (ADS)

Taaca, Kathrina Lois M.; Vasquez, Magdaleno R.

2018-02-01

Silver-exchanged zeolite-chitosan (AgZ-Ch) composites with varying AgZ content were prepared by solvent casting and modified under argon (Ar) plasma excited by a 13.56 MHz radio frequency (RF) power source. Silver (Ag) was successfully incorporated in a natural zeolite host without losing its antibacterial activity against Escherichia coli and Staphylococcus aureus. The AgZ particles were incorporated into a chitosan matrix without making significant changes in the matrix structure. The composites also exhibited antibacterial sensitivity due to the inclusion of AgZ. Plasma treatment enhanced the surface wettability of polar and nonpolar test liquids of the composites. The average increase in total surface free energy after treatment was around 49% with the polar component having a significant change. Cytocompatibility tests showed at least 87% cell viability for pristine and plasma-treated composites comparable with supplemented RPMI as positive control. Hemocompatibility tests revealed that pristine composites does not promote hemolysis and the blood clotting ability is less than 10 min. Coupled with antibacterial property, the fabricated composites have promising biomedical applications.
Surface modifications on toughened, fine-grained, recrystallized tungsten with repetitive ELM-like pulsed plasma irradiation

NASA Astrophysics Data System (ADS)

Kikuchi, Y.; Sakuma, I.; Kitagawa, Y.; Asai, Y.; Onishi, K.; Fukumoto, N.; Nagata, M.; Ueda, Y.; Kurishita, H.

2015-08-01

Surface modifications of toughened, fine-grained, recrystallized tungsten (TFGR W) materials with 1.1 wt.% TiC and 3.3 wt.% TaC dispersoids due to repetitive ELM-like pulsed (∼0.15 ms) helium plasma irradiation have been investigated by using a magnetized coaxial plasma gun. No surface cracking at the center part of the TFGR W samples exposed to 20 plasma pulses of ∼0.3 MJ m-2 was observed. The suppression of surface crack formation due to the increase of the grain boundary strength by addition of TiC and TaC dispersoids was confirmed in comparison with a pure W material. On the other hand, surface cracks and small pits appeared at the edge part of the TFGR W sample after the pulsed plasma irradiation. Erosion of the TiC and TaC dispersoids due to the pulsed plasma irradiation could cause the small pits on the surface, resulting in the surface crack formation.
Effect of different methods of preliminary surface treatment and magnetron sputtering on the adhesion of Si coatings

NASA Astrophysics Data System (ADS)

Borisov, D. P.; Slabodchikov, V. A.; Kuznetsov, V. M.

2017-05-01

The paper presents research results on the adhesion of Si coatings deposited by magnetron sputtering on NiTi substrates after preliminary surface treatment (cleaning and activation) with low-energy ion beams and gas discharge plasma. The adhesion properties of the coatings obtained by two methods are analyzed and compared using data of scratch and spherical abrasion tests.

Microstructure evolution and tribological properties of acrylonitrile-butadiene rubber surface modified by atmospheric plasma treatment

NASA Astrophysics Data System (ADS)

Shen, Ming-xue; Zhang, Zhao-xiang; Peng, Xu-dong; Lin, Xiu-zhou

2017-09-01

For the purpose of prolonging the service life for rubber sealing elements, the frictional behavior of acrylonitrile-butadiene rubber (NBR) surface by dielectric barrier discharge plasma treatments was investigated in this paper. Surface microstructure and chemical composition were measured by atomic force microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. Water contact angles of the modified rubber surface were also measured to evaluate the correlation between surface wettability and tribological properties. The results show that plasma treatments can improve the properties of the NBR against friction and wear effectively, the surface microstructure and roughness of plasma-modified NBR surface had an important influence on the surface tribological behavior, and the wear depth first decreased and then increased along with the change of plasma treatment time. It was found that the wettability of the modified surface was gradually improved, which was mainly due to the change of the chemical composition after the treatment. This study suggests that the plasma treatment could effectively improve the tribological properties of the NBR surface, and also provides information for developing wear-resistant NBR for industrial applications.
Real-time and post-plasma studies of influence of low levels of tungsten on carbon erosion and surface evolution behaviour in D2 plasma

NASA Astrophysics Data System (ADS)

Weilnboeck, F.; Fox-Lyon, N.; Oehrlein, G. S.; Doerner, R. P.

2010-02-01

A profound influence of monolayer tungsten coverage of hard carbon films on the evolution of carbon surface erosion behaviour, surface chemistry and morphology in D2 plasma has been established by real-time ellipsometry, x-ray photoelectron spectroscopy and atomic force microscopy measurements. The erosion of tungsten-covered carbon showed two distinct stages of plasma material interactions: rapid tungsten removal during the initial erosion period and steady-state amorphous carbon removal accompanied by large-scale surface roughness development. The initial removal of tungsten takes place at a rate that significantly exceeds typical sputter yields at the ion energies used here and is attributed to elimination of weakly bonded tungsten from the surface. The tungsten remaining on the a-C : H film surface causes surface roughness development of the eroding carbon surface by a masking effect, and simultaneously leads to a seven fold reduction of the steady-state carbon erosion rate for long plasma surface interaction times (~100 s). Results presented are of direct relevance for material transport and re-deposition, and the interaction of those films with plasma in the divertor region and on mirror surfaces of fusion devices.
Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air.

PubMed

Nguyen Dinh, M T; Giraudon, J-M; Vandenbroucke, A M; Morent, R; De Geyter, N; Lamonier, J-F

2016-08-15

The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH=10%) in the presence of CO2 (520ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150°C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x=1-2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process. Copyright © 2016 Elsevier B.V. All rights reserved.
Material Surface Characteristics and Plasma Performance in the Lithium Tokamak Experiment

NASA Astrophysics Data System (ADS)

Lucia, Matthew James

The performance of a tokamak plasma and the characteristics of the surrounding plasma facing component (PFC) material surfaces strongly influence each other. Despite this relationship, tokamak plasma physics has historically been studied more thoroughly than PFC surface physics. The disparity is particularly evident in lithium PFC research: decades of experiments have examined the effect of lithium PFCs on plasma performance, but the understanding of the lithium surface itself is much less complete. This latter information is critical to identifying the mechanisms by which lithium PFCs affect plasma performance. This research focused on such plasma-surface interactions in the Lithium Tokamak Experiment (LTX), a spherical torus designed to accommodate solid or liquid lithium as the primary PFC. Surface analysis was accomplished via the novel Materials Analysis and Particle Probe (MAPP) diagnostic system. In a series of experiments on LTX, the MAPP x-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) capabilities were used for in vacuo interrogation of PFC samples. This represented the first application of XPS and TDS for in situ surface analysis of tokamak PFCs. Surface analysis indicated that the thin (dLi ˜ 100nm) evaporative lithium PFC coatings in LTX were converted to Li2O due to oxidizing agents in both the residual vacuum and the PFC substrate. Conversion was rapid and nearly independent of PFC temperature, forming a majority Li2O surface within minutes and an entirely Li2O surface within hours. However, Li2O PFCs were still capable of retaining hydrogen and sequestering impurities until the Li2 O was further oxidized to LiOH, a process that took weeks. For hydrogen retention, Li2O PFCs retained H+ from LTX plasma discharges, but no LiH formation was observed. Instead, results implied that H+ was only weakly-bound, such that it almost completely outgassed as H 2 within minutes. For impurity sequestration, LTX plasma performance---ascertained from plasma current and density measurements---progressively improved as plasma carbon and oxygen impurity levels fell. This was true for PFC conditioning by vacuum baking and argon glow discharge cleaning, as well as by lithium evaporation. Some evidence suggested that impurity sequestration was more important than hydrogen retention in enhancing LTX plasma performance. In contrast with expectations for lithium PFCs, heating the Li2 O PFCs in LTX caused increased plasma impurity levels that tended to reduce plasma performance.
Activation of classical protein kinase C reduces the expression of human cationic amino acid transporter 3 (hCAT-3) in the plasma membrane

PubMed Central

Rotmann, Alexander; Vékony, Nicole; Gassner, Davina; Niegisch, Günter; Strand, Dennis; Martiné, Ursula; Closs, Ellen I.

2005-01-01

We have previously shown that activation of PKC (protein kinase C) results in internalization of hCAT-1 [human CAT-1 (cationic amino acid transporter 1)] and a decrease in arginine transport [Rotmann, Strand, Martiné and Closs (2004) J. Biol. Chem. 279, 54185–54192]. However, others found increased transport rates for arginine in response to PKC activation, suggesting a differential effect of PKC on different CAT isoforms. Therefore we investigated the effect of PKC on hCAT-3, an isoform expressed in thymus, brain, ovary, uterus and mammary gland. In Xenopus laevis oocytes and human U373MG glioblastoma cells, hCAT-3-mediated L-arginine transport was significantly reduced upon treatment with compounds that activate classical PKC. In contrast, inactive phorbol esters and an activator of novel PKC isoforms had no effect. PKC inhibitors (including the PKCα-preferring Ro 31-8280) reduced the inhibitory effect of the PKC-activating compounds. Microscopic analyses revealed a PMA-induced reduction in the cell-surface expression of fusion proteins between hCAT-3 and enhanced green fluorescent protein expressed in X. laevis oocytes and glioblastoma cells. Western-blot analysis of biotinylated surface proteins demonstrated a PMA-induced decrease in hCAT-3 in the plasma membrane, but not in total protein lysates. Pretreatment with a PKC inhibitor also reduced this PMA effect. It is concluded that similar to hCAT-1, hCAT-3 activity is decreased by PKC via reduction of transporter molecules in the plasma membrane. Classical PKC isoforms seem to be responsible for this effect. PMID:16332251
Anti-adhesive characteristics of CHF{sub 3}/O{sub 2} and C{sub 4}F{sub 8}/O{sub 2} plasma-modified silicon molds for nanoimprint lithography

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

Lee, Jaemin; Lee, Junmyung; Lee, Hyun Woo

The anti-adhesive characteristics of a plasma-modified silicon mold surface for nanoimprint lithography are presented. Both CHF{sub 3}/O{sub 2} and C{sub 4}F{sub 8}/O{sub 2} plasma were used to form an anti-adhesive layer on silicon mold surfaces. The gas mixing ratios of CHF{sub 3}/O{sub 2} and C{sub 4}F{sub 8}/O{sub 2} were experimentally changed between 0% and 80% to optimize the plasma conditions to obtain a low surface energy of the silicon mold. The plasma characteristics were examined by optical emission spectroscopy (OES). In order to investigate the changes in surface energy and surface chemistry of the anti-adhesive layer during repeated demolding cycles,more » contact angle measurements and X-ray photoelectron spectroscopy (XPS) were performed on the plasma-modified silicon mold surface. Simultaneously, the surface morphology of the demolded resists was evaluated by field-emission scanning electron microscope (FE-SEM) in order to examine the effect of the anti-adhesive layers on the duplicated patterns of the resists. It was observed that the anti-adhesive layer formed by CHF{sub 3}/O{sub 2} plasma treatment was worn out more easily during repeated demolding cycles than the film formed by C{sub 4}F{sub 8}/O{sub 2} plasma treatment, because CHF{sub 3}/O{sub 2} gas plasma formed a thinner plasma-polymerized film over the same plasma treatment time.« less
Effect of a Dusty Layer on Surface-Wave Produced Plasmas

NASA Astrophysics Data System (ADS)

Ostrikov, Kostyantyn; Yu, Ming; Xu, Shuyan

2000-10-01

The effect of near-sheath dusts on the RF power loss in a surface-wave sustained gas discharge is studied. The planar plasma is bounded by a dielectric and consists of an inhomogeneous near-wall transition layer (sheath), a dusty plasma layer, and the outer dust-free plasma. The discharge is maintained by high-frequency axially-symmetric surface waves. The surface-wave power loss from the most relevant dissipative mechanisms in typical discharge plasmas is analyzed. Our model allows one to consider the main effects of dust particles on surface-wave produced discharge plasmas. We demonstrate that the dusts released in the discharge can strongly modify the plasma conductivity and lead to a significant redistribution of the total charge. They affect the electron quasi-momenta, but do not absorb the energy transmitted to the plasma through elastic collisions, and therefore they remain cold at the room temperature. It is shown that the improvement of the efficiency of energy transfer from the wave source to the plasma can be achieved by selecting operation regimes when the efficiency of the power loss in the plasma through electron-neutral collisions is higher than that through electron-dust interactions.
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
Innovative potential of plasma technology

NASA Astrophysics Data System (ADS)

Budaev, V. P.

2017-11-01

The review summarizes recent experimental observations of materials exposed to extreme hot plasma loads in fusion devices and plasma facilities with high-temperature plasma. Plasma load on the material in such devices lead to the stochastic clustering and fractal growth of the surface on scales from tens of nanometers to hundreds of micrometers forming statistical self-similarity of the surface roughness with extremely high specific area. Statistical characteristics of hierarchical granularity and scale invariance of such materials surface qualitatively differ from the properties of the roughness of the ordinary Brownian surface which provides a potential of innovative plasma technologies for synthesis of new nanostructured materials with programmed roughness properties, for hypersonic technologies, for biotechnology and biomedical applications.
Atmospheric-Pressure Plasma Jet Surface Treatment for Use in Improving Adhesion

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

Kuettner, Lindsey Ann

Atmospheric-pressure plasma jets (APPJs) are a method of plasma treatment that plays an important role in material processing and modifying surface properties of materials, especially polymers. Gas plasmas react with polymer surfaces in numerous ways such as oxidation, radical formation, degradation, and promotion of cross-linking. Because of this, gas and plasma conditions can be explored for chosen processes to maximize desired properties. The purpose of this study is to investigate plasma parameters in order to modify surface properties for improved adhesion between aluminum and epoxy substrates using two types of adhesives. The background, results to date, and future work willmore » be discussed.« less
Stochastic clustering of material surface under high-heat plasma load

NASA Astrophysics Data System (ADS)

Budaev, Viacheslav P.

2017-11-01

The results of a study of a surface formed by high-temperature plasma loads on various materials such as tungsten, carbon and stainless steel are presented. High-temperature plasma irradiation leads to an inhomogeneous stochastic clustering of the surface with self-similar granularity - fractality on the scale from nanoscale to macroscales. Cauliflower-like structure of tungsten and carbon materials are formed under high heat plasma load in fusion devices. The statistical characteristics of hierarchical granularity and scale invariance are estimated. They differ qualitatively from the roughness of the ordinary Brownian surface, which is possibly due to the universal mechanisms of stochastic clustering of material surface under the influence of high-temperature plasma.
Numerical implementation of a cold-ion, Boltzmann-electron model for nonplanar plasma-surface interactions

NASA Astrophysics Data System (ADS)

Holgate, J. T.; Coppins, M.

2018-04-01

Plasma-surface interactions are ubiquitous in the field of plasma science and technology. Much of the physics of these interactions can be captured with a simple model comprising a cold ion fluid and electrons which satisfy the Boltzmann relation. However, this model permits analytical solutions in a very limited number of cases. This paper presents a versatile and robust numerical implementation of the model for arbitrary surface geometries in cartesian and axisymmetric cylindrical coordinates. Specific examples of surfaces with sinusoidal corrugations, trenches, and hemi-ellipsoidal protrusions verify this numerical implementation. The application of the code to problems involving plasma-liquid interactions, plasma etching, and electron emission from the surface is discussed.
Ebola virus requires a host scramblase for externalization of phosphatidylserine on the surface of viral particles.

PubMed

Nanbo, Asuka; Maruyama, Junki; Imai, Masaki; Ujie, Michiko; Fujioka, Yoichiro; Nishide, Shinya; Takada, Ayato; Ohba, Yusuke; Kawaoka, Yoshihiro

2018-01-01

Cell surface receptors for phosphatidylserine contribute to the entry of Ebola virus (EBOV) particles, indicating that the presence of phosphatidylserine in the envelope of EBOV is important for the internalization of EBOV particles. Phosphatidylserine is typically distributed in the inner layer of the plasma membrane in normal cells. Progeny virions bud from the plasma membrane of infected cells, suggesting that phosphatidylserine is likely flipped to the outer leaflet of the plasma membrane in infected cells for EBOV virions to acquire it. Currently, the intracellular dynamics of phosphatidylserine during EBOV infection are poorly understood. Here, we explored the role of XK-related protein (Xkr) 8, which is a scramblase responsible for exposure of phosphatidylserine in the plasma membrane of apoptotic cells, to understand its significance in phosphatidylserine-dependent entry of EBOV. We found that Xkr8 and transiently expressed EBOV glycoprotein GP often co-localized in intracellular vesicles and the plasma membrane. We also found that co-expression of GP and viral major matrix protein VP40 promoted incorporation of Xkr8 into ebolavirus-like particles (VLPs) and exposure of phosphatidylserine on their surface, although only a limited amount of phosphatidylserine was exposed on the surface of the cells expressing GP and/or VP40. Downregulating Xkr8 or blocking caspase-mediated Xkr8 activation did not affect VLP production, but they reduced the amount of phosphatidylserine on the VLPs and their uptake in recipient cells. Taken together, our findings indicate that Xkr8 is trafficked to budding sites via GP-containing vesicles, is incorporated into VLPs, and then promote the entry of the released EBOV to cells in a phosphatidylserine-dependent manner.
Ebola virus requires a host scramblase for externalization of phosphatidylserine on the surface of viral particles

PubMed Central

Imai, Masaki; Ujie, Michiko; Fujioka, Yoichiro; Nishide, Shinya; Takada, Ayato; Ohba, Yusuke; Kawaoka, Yoshihiro

2018-01-01

Cell surface receptors for phosphatidylserine contribute to the entry of Ebola virus (EBOV) particles, indicating that the presence of phosphatidylserine in the envelope of EBOV is important for the internalization of EBOV particles. Phosphatidylserine is typically distributed in the inner layer of the plasma membrane in normal cells. Progeny virions bud from the plasma membrane of infected cells, suggesting that phosphatidylserine is likely flipped to the outer leaflet of the plasma membrane in infected cells for EBOV virions to acquire it. Currently, the intracellular dynamics of phosphatidylserine during EBOV infection are poorly understood. Here, we explored the role of XK-related protein (Xkr) 8, which is a scramblase responsible for exposure of phosphatidylserine in the plasma membrane of apoptotic cells, to understand its significance in phosphatidylserine-dependent entry of EBOV. We found that Xkr8 and transiently expressed EBOV glycoprotein GP often co-localized in intracellular vesicles and the plasma membrane. We also found that co-expression of GP and viral major matrix protein VP40 promoted incorporation of Xkr8 into ebolavirus-like particles (VLPs) and exposure of phosphatidylserine on their surface, although only a limited amount of phosphatidylserine was exposed on the surface of the cells expressing GP and/or VP40. Downregulating Xkr8 or blocking caspase-mediated Xkr8 activation did not affect VLP production, but they reduced the amount of phosphatidylserine on the VLPs and their uptake in recipient cells. Taken together, our findings indicate that Xkr8 is trafficked to budding sites via GP-containing vesicles, is incorporated into VLPs, and then promote the entry of the released EBOV to cells in a phosphatidylserine-dependent manner. PMID:29338048
Superhydrophobic nanostructured Kapton® surfaces fabricated through Ar + O2 plasma treatment: Effects of different environments on wetting behaviour

NASA Astrophysics Data System (ADS)

Barshilia, Harish C.; Ananth, A.; Gupta, Nitant; Anandan, C.

2013-03-01

Kapton® [poly (4,4'-oxy diphenylene pyromellitimide)] polyimides have widespread usage in semiconductor devices, solar arrays, protective coatings and space applications, due to their excellent chemical and physical properties. In addition to their inherent properties, imparting superhydrophobicity on these surfaces will be an added advantage. Present work describes the usage of Ar + O2 plasma treatment for the preparation of superhydrophobic Kapton® surfaces. Immediately after the plasma treatment, the surfaces showed superhydrophilicity as a result of high energy dangling bonds and polar group concentration. But the samples kept in low vacuum for 48 h exhibited superhydrophobicity with high water contact angles (>150°). It is found that the post plasma treatment process, called ageing, especially in low vacuum plays an important role in delivering superhydrophobic property to Kapton®. Field emission scanning electron microscopy and atomic force microscopy were used to probe the physical changes in the surface of the Kapton®. The surfaces showed formation of nano-feathers and nano-tussock microstructures with variation in surface roughness against plasma treatment time. A thorough chemical investigation was performed using Fourier transform infrared spectroscopy and micro-Raman spectroscopy, which revealed changes in the surface of the Ar + O2 plasma treated Kapton®. Surface chemical species of Kapton® were confirmed again by X-ray photoelectron spectroscopy spectra for untreated surfaces whereas Ar + O2 plasma treated samples showed the de-bonding and re-organization of structural elements. Creation of surface roughness plays a dominant role in the contribution of superhydrophobicity to Kapton® apart from the surface modifications due to Ar + O2 plasma treatment and ageing in low vacuum.
Co-ordinated spatial propagation of blood plasma clotting and fibrinolytic fronts

PubMed Central

Zhalyalov, Ansar S.; Panteleev, Mikhail A.; Gracheva, Marina A.; Ataullakhanov, Fazoil I.

2017-01-01

Fibrinolysis is a cascade of proteolytic reactions occurring in blood and soft tissues, which functions to disintegrate fibrin clots when they are no more needed. In order to elucidate its regulation in space and time, fibrinolysis was investigated using an in vitro reaction-diffusion experimental model of blood clot formation and dissolution. Clotting was activated by a surface with immobilized tissue factor in a thin layer of recalcified blood plasma supplemented with tissue plasminogen activator (TPA), urokinase plasminogen activator or streptokinase. Formation and dissolution of fibrin clot was monitored by videomicroscopy. Computer systems biology model of clot formation and lysis was developed for data analysis and experimental planning. Fibrin clot front propagated in space from tissue factor, followed by a front of clot dissolution propagating from the same source. Velocity of lysis front propagation linearly depended on the velocity clotting front propagation (correlation r2 = 0.91). Computer model revealed that fibrin formation was indeed the rate-limiting step in the fibrinolysis front propagation. The phenomenon of two fronts which switched the state of blood plasma from liquid to solid and then back to liquid did not depend on the fibrinolysis activator. Interestingly, TPA at high concentrations began to increase lysis onset time and to decrease lysis propagation velocity, presumably due to plasminogen depletion. Spatially non-uniform lysis occurred simultaneously with clot formation and detached the clot from the procoagulant surface. These patterns of spatial fibrinolysis provide insights into its regulation and might explain clinical phenomena associated with thrombolytic therapy. PMID:28686711
Carbaryl exposure and recovery modify the interrenal and thyroidal activities and the mitochondria-rich cell function in the climbing perch Anabas testudineus Bloch.

PubMed

Peter, Valsa S; Babitha, G S; Bonga, S E Wendelaar; Peter, M C Subhash

2013-01-15

We examined the effects of carbaryl (1-naphthyl methylcarbamate; sevin), a carbamate pesticide, on interrenal and thyroid activities and mitochondrial rich (MR) cell function in climbing perch to understand the physiological basis of toxicity acclimation in this fish to the chemical stressor. Carbaryl exposure (5-20 mg L(-1)) for 48 h increased cortisol and glucose, but decreased the T(3) level without affecting T(4) concentration in the plasma. These responses of the carbaryl-exposed fish were nullified and a rise in plasma T(4) occurred in these fish when they were kept for 96 h recovery in clean water. A tight plasma mineral control was indicated in the carbaryl-exposed fish as reflected by the unchanged plasma Na, K, Ca and inorganic phosphate levels. The ouabain-sensitive Na(+), K(+)-ATPase activity showed an increase in the gills but the intestinal and renal tissues showed little response to carbaryl treatment. However, substantial increases in the intestinal and renal Na(+), K(+)-ATPase activities occurred in the recovery fish. The MR cells in the branchial epithelia showed a strong Na(+), K(+)-ATPase immunoreactivity to carbaryl treatment indicating an activated MR cell function. The numerical MR cell density remained unchanged, but stretching of secondary gill lamellae as part of gill remodeling occurred during carbaryl exposure. The increased surface of these lamellae with abundant MR cells as a result of its migration into the lamellar surface points to marked structural and functional modifications of these cells in the carbaryl-treated fish which is likely to a target for carbaryl action. The rise in plasma T(4) and the restoration of normal branchial epithelia in the recovery fish indicate a thyroidal involvement in the recovery response and survival. Our data thus provide evidence that carbaryl exposure and its recovery evoke interrenal and thyroid disruption in this fish leading to a modified osmotic response including an altered MR cell function. Copyright © 2012 Elsevier B.V. All rights reserved.
[ACTIVITY OF ANTIMICROBIAL NANOSTRUCTURED BARRIER LAYERS BASED ON POLYETHYLENETEREPHTHALATE IN RELATION TO CLINICAL STRAINES OF MICROORGANISMS FOR SICK PERSONS OF GASTROENTEROLOGICAL PROFILE].

PubMed

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

2015-01-01

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

PubMed

Li, Chun-Yi; Liao, Ying-Chih

2016-05-11

In this study, a plasma surface modification with printing process was developed to fabricate printed flexible conductor patterns or devices directly on polydimethylsiloxane (PDMS) surface. An atmospheric plasma treatment was first used to oxidize the PDMS surface and create a hydrophilic silica surface layer, which was confirmed with photoelectron spectra. The plasma operating parameters, such as gas types and plasma powers, were optimized to obtain surface silica layers with the longest lifetime. Conductive paste with epoxy resin was screen-printed on the plasma-treated PDMS surface to fabricate flexible conductive tracks. As a result of the strong binding forces between epoxy resin and the silica surface layer, the printed patterns showed great adhesion on PDMS and were undamaged after several stringent adhesion tests. The printed conductive tracks showed strong mechanical stability and exhibited great electric conductivity under bending, twisting, and stretching conditions. Finally, a printed pressure sensor with good sensitivity and a fast response time was fabricated to demonstrate the capability of this method for the realization of printed electronic devices.
Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

NASA Astrophysics Data System (ADS)

Hatayama, A.; Nishioka, S.; Nishida, K.; Mattei, S.; Lettry, J.; Miyamoto, K.; Shibata, T.; Onai, M.; Abe, S.; Fujita, S.; Yamada, S.; Fukano, A.

2018-06-01

The present status of kinetic modeling of particle dynamics in hydrogen negative ion (H‑) source plasmas and their comparisons with experiments are reviewed and discussed with some new results. The main focus is placed on the following topics, which are important for the research and development of H‑ sources for intense and high-quality H‑ ion beams: (i) effects of non-equilibrium features of electron energy distribution function on volume and surface H‑ production, (ii) the origin of the spatial non-uniformity in giant multi-cusp arc-discharge H‑ sources, (iii) capacitive to inductive (E to H) mode transition in radio frequency-inductively coupled plasma H‑ sources and (iv) extraction physics of H‑ ions and beam optics, especially the present understanding of the meniscus formation in strongly electronegative plasmas (so-called ion–ion plasmas) and its effect on beam optics. For these topics, mainly Japanese modeling activities, and their domestic and international collaborations with experimental studies, are introduced with some examples showing how models have been improved and to what extent the modeling studies can presently contribute to improving the source performance. Close collaboration between experimental and modeling activities is indispensable for the validation/improvement of the modeling and its contribution to the source design/development.

Dusty Plasmas on the Lunar Surface

NASA Astrophysics Data System (ADS)

Horanyi, M.; Andersson, L.; Colwell, J.; Ergun, R.; Gruen, E.; McClintock, B.; Peterson, W. K.; Robertson, S.; Sternovsky, Z.; Wang, X.

2006-12-01

The electrostatic levitation and transport of lunar dust remains one of the most interesting and controversial science issues from the Apollo era. This issue is also of great engineering importance in designing human habitats and protecting optical and mechanical devices. As function of time and location, the lunar surface is exposed to solar wind plasma, UV radiation, and/or the plasma environment of our magnetosphere. Dust grains on the lunar surface collect an electrostatic charge; alter the large-scale surface charge density distribution, ?and subsequently develop an interface region to the background plasma and radiation. There are several in situ and remote sensing observations that indicate that dusty plasma processes are likely to be responsible for the mobilization and transport of lunar soil. These processes are relevant to: a) understanding the lunar surface environment; b) develop dust mitigation strategies; c) to understand the basic physical processes involved in the birth and collapse of dust loaded plasma sheaths. This talk will focus on the dusty plasma processes on the lunar surface. We will review the existing body of observations, and will also consider future opportunities for the combination of in situ and remote sensing observations. Our goals are to characterize: a) the temporal variation of the spatial and size distributions of the levitated/transported dust; and b) the surface plasma environment
Diagnostics of hydrogen plasma with in situ optical emission and silicon probes

NASA Astrophysics Data System (ADS)

Lee, Szetsen; Chung, Yi-Jie

2005-11-01

In this work, an approach has been adopted to explore plasma properties by combining an in situ optical emission technique with a contact angle measurement. Hydrogen plasma was generated with a radio-frequency power source. The plasma parameters such as number densities and temperatures were derived from the optical emission spectroscopic data. Small silicon chips were placed at various positions inside a discharge tube as probes for the plasma conditions. The hydrogen-plasma-treated silicon chip surfaces were characterized with the contact angle measurement method. The change of wettability on the silicon surface was observed with various plasma treatment times. The spectroscopic information about the plasma is correlated with the results of the surface characterization. It is found that the rate of the increasing hydrophilicity is sensitive to the amount of helium added and the location in the discharge tube. A simple model describing the relation between the surface coverage area of water droplet and the variation of contact angle has been established. We have proposed plasma excitation and reaction mechanisms for the observed correlation between plasma temperatures and the wettability of the silicon surface. It shows that small silicon chips can serve as "litmus tests" for the plasma conditions without introducing too much perturbation.
Microplasma effect on skin scaffold for melanoma cancer treatment

NASA Astrophysics Data System (ADS)

Abdullah, Zulaika; Zaaba, S. K.; Mustaffa, M. T.; Mohamad, C. W. S. R.; Zakaria, A.

2017-03-01

An atmospheric plasma system using Helium gas was developed. The effect of helium plasma treatment on skin scaffold surface was studied by scanning electron microscopy (SEM). The changes of skin scaffold surfaces before and after helium plasma treatment was recorded. The surface of skin scaffold changed with the prolonged of helium plasma treatment time. The depth of helium plasma penetration was studied using methylene blue dye staining method. The methylene blue will detect the presence or absence of an oxygen that was induced from plasma excitation. The presence of the oxygen indicated on the depth of helium plasma penetration. Results showed plasma are able to penetrate 4mm of skin scaffold after 1200 seconds of exposure.
The Plasma Interaction Experiment (PIX) description and test program. [electrometers

NASA Technical Reports Server (NTRS)

Ignaczak, L. R.; Haley, F. A.; Domino, E. J.; Culp, D. H.; Shaker, F. J.

1978-01-01

The plasma interaction experiment (PIX) is a battery powered preprogrammed auxiliary payload on the LANDSAT-C launch. This experiment is part of a larger program to investigate space plasma interactions with spacecraft surfaces and components. The varying plasma densities encountered during available telemetry coverage periods are deemed sufficient to determine first order interactions between the space plasma environment and the biased experimental surfaces. The specific objectives of the PIX flight experiment are to measure the plasma coupling current and the negative voltage breakdown characteristics of a solar array segment and a gold plated steel disk. Measurements will be made over a range of surface voltages up to plus or minus kilovolt. The orbital environment will provide a range of plasma densities. The experimental surfaces will be voltage biased in a preprogrammed step sequence to optimize the data returned for each plasma region and for the available telemetry coverage.
Mechanisms behind surface modification of polypropylene film using an atmospheric-pressure plasma jet

NASA Astrophysics Data System (ADS)

Shaw, David; West, Andrew; Bredin, Jerome; Wagenaars, Erik

2016-12-01

Plasma treatments are common for increasing the surface energy of plastics, such as polypropylene (PP), to create improved adhesive properties. Despite the significant differences in plasma sources and plasma properties used, similar effects on the plastic film can be achieved, suggesting a common dominant plasma constituent and underpinning mechanism. However, many details of this process are still unknown. Here we present a study into the mechanisms underpinning surface energy increase of PP using atmospheric-pressure plasmas. For this we use the effluent of an atmospheric-pressure plasma jet (APPJ) since, unlike most plasma sources used for these treatments, there is no direct contact between the plasma and the PP surface; the APPJ provides a neutral, radical-rich environment without charged particles and electric fields impinging on the PP surface. The APPJ is a RF-driven plasma operating in helium gas with small admixtures of O2 (0-1%), where the effluent propagates through open air towards the PP surface. Despite the lack of charged particles and electric fields on the PP surface, measurements of contact angle show a decrease from 93.9° to 70.1° in 1.4 s and to 35° in 120 s, corresponding to a rapid increase in surface energy from 36.4 mN m-1 to 66.5 mN m-1 in the short time of 1.4 s. These treatment effects are very similar to what is found in other devices, highlighting the importance of neutral radicals produced by the plasma. Furthermore, we find an optimum percentage of oxygen of 0.5% within the helium input gas, and a decrease of the treatment effect with distance between the APPJ and the PP surface. These observed effects are linked to two-photon absorption laser-induced fluorescence spectroscopy (TALIF) measurements of atomic oxygen density within the APPJ effluent which show similar trends, implying the importance of this radical in the surface treatment of PP. Analysis of the surface reveals a two stage mechanism for the production of polar bonds on the surface of the polymer: a fast reaction producing carboxylic acid, or a similar ketone, followed by a slower reaction that includes nitrogen from the atmosphere on the surface, producing amides from the ketones.
Collaborative Research. Fundamental Science of Low Temperature Plasma-Biological Material Interactions

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

Graves, David Barry; Oehrlein, Gottlieb

2014-09-01

Low temperature plasma (LTP) treatment of biological tissue is a promising path toward sterilization of bacteria due to its versatility and ability to operate under well-controlled and relatively mild conditions. The present collaborative research of an interdisciplinary team of investigators at University of Maryland, College Park (UMD), and University of California, Berkeley (UCB) focused on establishing our knowledge based with regard to low temperature plasma-induced chemical modifications in biomolecules that result in inactivation due to various plasma species, including ions, reactive radicals, and UV/VUV photons. The overall goals of the project were to identify and quantify the mechanisms by whichmore » low and atmospheric pressure plasma deactivates endotoxic biomolecules. Additionally, we wanted to understand the mechanism by which atmospheric pressure plasmas (APP) modify surfaces and how these modifications depend on the interaction of APP with the environment. Various low pressure plasma sources, a vacuum beam system and several atmospheric pressure plasma sources were used to accomplish this. In our work we elucidated for the first time the role of ions, VUV photons and radicals in biological deactivation of representative biomolecules, both in a UHV beam system and an inductively coupled, low pressure plasma system, and established the associated atomistic biomolecule changes. While we showed that both ions and VUV photons can be very efficient in deactivation of biomolecules, significant etching and/or deep modification (~200 nm) accompanied these biological effects. One of the most important findings in this work is the significant radical-induced deactivation and surface modification can occur with minimal etching. However, if radical fluxes and corresponding etch rates are relatively high, for example at atmospheric pressure, endotoxic biomolecule film inactivation may require near-complete removal of the film. These findings motivated further work at atmospheric pressure using several types of low temperature plasma sources, for which radical induced interactions generally dominate due to short mean free paths of ions and VUV photons. For these conditions we demonstrated the importance of environmental interactions when atmospheric pressure plasma sources are used to modify biomolecules. This is evident from both gas phase characterization data and in-situ surface characterization of treated biomolecules. Environmental interactions can produce unexpected outcomes due to the complexity of reactions of reactive species with the atmosphere which determines the composition of reactive fluxes and atomistic changes of biomolecules. Overall, this work clarified a richer spectrum of scientific opportunities and challenges for the field of low temperature plasma-biomolecule surface interactions than initially anticipated, in particular for plasma sources operating at atmospheric pressure. The insights produced in this work, e.g. demonstration of the importance of environmental interactions, are generally important for applications of APP to materials modifications. Thus one major contributions of this research has been the establishment of methodologies to more systematically study the interaction of plasma with bio-molecules. In particular, our studies of atmospheric pressure plasma sources using very well-defined experimental conditions enabled to combine atomistic surface modifications of biomolecules with changes in their biological function. The clarification of the role of ions, VUV photons and radicals in deactivation of biomolecules during low pressure and atmospheric pressure plasma-biomolecule interaction has broad implications, e.g. for the emerging field of plasma medicine. The development of methods to detect the effects of plasma treatment on immune-active biomolecules will be helpful in many future studies.« less
The dynamics of a surface plasma generated by an independent source in the field of laser emission

NASA Astrophysics Data System (ADS)

Kovalev, A. S.; Popov, A. M.; Seleznev, B. V.; Feoktistov, V. A.

1986-09-01

A study is made of the evolution of a plasma formation generated by a high-power short pulse of an Nd laser on a metal surface, with the relatively weak emission of a CO2 laser focused on the surface. The thresholds of a sustained breakdown plasma are measured as a function of the plasma-generating pulse energy. The dynamics of plasma front propagation along the target surface and in the direction opposite to the laser beam direction is investigated. It is shown that the use of an additional laser with an energy less than that of the CO2 laser by 2-3 orders of magnitude makes it possible to generate a surface plasma capable of absorbing and transferring to the target a significantly greater fraction of the CO2 laser energy.
Combining 3D human in vitro methods for a 3Rs evaluation of novel titanium surfaces in orthopaedic applications.

PubMed

Stevenson, G; Rehman, S; Draper, E; Hernández-Nava, E; Hunt, J; Haycock, J W

2016-07-01

In this study, we report on a group of complementary human osteoblast in vitro test methods for the preclinical evaluation of 3D porous titanium surfaces. The surfaces were prepared by additive manufacturing (electron beam melting [EBM]) and plasma spraying, allowing the creation of complex lattice surface geometries. Physical properties of the surfaces were characterized by SEM and profilometry and 3D in vitro cell culture using human osteoblasts. Primary human osteoblast cells were found to elicit greater differences between titanium sample surfaces than an MG63 osteoblast-like cell line, particularly in terms of cell survival. Surface morphology was associated with higher osteoblast metabolic activity and mineralization on rougher titanium plasma spray coated surfaces than smoother surfaces. Differences in osteoblast survival and metabolic activity on titanium lattice structures were also found, despite analogous surface morphology at the cellular level. 3D confocal microscopy identified osteoblast organization within complex titanium surface geometries, adhesion, spreading, and alignment to the biomaterial strut geometries. Mineralized nodule formation throughout the lattice structures was also observed, and indicative of early markers of bone in-growth on such materials. Testing methods such as those presented are not traditionally considered by medical device manufacturers, but we suggest have value as an increasingly vital tool in efficiently translating pre-clinical studies, especially in balance with current regulatory practice, commercial demands, the 3Rs, and the relative merits of in vitro and in vivo studies. Biotechnol. Bioeng. 2016;113: 1586-1599. © 2015 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. © 2015 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.
Synergistic effects of plasma-catalyst interactions for CH4 activation.

PubMed

Kim, Jongsik; Go, David B; Hicks, Jason C

2017-05-24

The elucidation of catalyst surface-plasma interactions is a challenging endeavor and therefore requires thorough and rigorous assessment of the reaction dynamics on the catalyst in the plasma environment. The first step in quantifying and defining catalyst-plasma interactions is a detailed kinetic study that can be used to verify appropriate reaction conditions for comparison and to discover any unexpected behavior of plasma-assisted reactions that might prevent direct comparison. In this paper, we provide a kinetic evaluation of CH 4 activation in a dielectric barrier discharge plasma in order to quantify plasma-catalyst interactions via kinetic parameters. The dry reforming of CH 4 with CO 2 was studied as a model reaction using Ni supported on γ-Al 2 O 3 at temperatures of 790-890 K under atmospheric pressure, where the partial pressures of CH 4 (or CO 2 ) were varied over a range of ≤25.3 kPa. Reaction performance was monitored by varying gas hourly space velocity, plasma power, bulk gas temperature, and reactant concentration. After correcting for gas-phase plasma reactions, a linear relationship was observed in the log of the measured rate constant with respect to reciprocal power (1/power). Although thermal catalysis displays typical Arrhenius behavior for this reaction, plasma-assisted catalysis occurs from a complex mixture of sources and shows non-Arrhenius behavior. However, an energy barrier was obtained from the relationship between the reaction rate constant and input power to exhibit ≤∼20 kJ mol -1 (compared to ∼70 kJ mol -1 for thermal catalysis). Of additional importance, the energy barriers measured during plasma-assisted catalysis were relatively consistent with respect to variations in total flow rates, types of diluent, or bulk reaction temperature. These experimental results suggest that plasma-generated vibrationally-excited CH 4 favorably interacts with Ni sites at elevated temperatures, which helps reduce the energy barrier required to activate CH 4 and enhance CH 4 reforming rates.
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.
Modification of titanium surfaces by adding antibiotic-loaded PHB spheres and PEG for biomedical applications.

PubMed

Rodríguez-Contreras, Alejandra; Marqués-Calvo, María Soledad; Gil, Francisco Javier; Manero, José María

2016-08-01

Novel researches are focused on the prevention and management of post-operative infections. To avoid this common complication of implant surgery, it is preferable to use new biomaterials with antibacterial properties. Therefore, the aim of this work is to develop a method of combining the antibacterial properties of antibiotic-loaded poly(3-hydroxybutyrate) (PHB) nano- and micro-spheres and poly(ethylene glycol) (PEG) as an antifouling agent, with titanium (Ti), as the base material for implants, in order to obtain surfaces with antibacterial activity. The Ti surfaces were linked to both PHB particles and PEG by a covalent bond. This attachment was carried out by firstly activating the surfaces with either Oxygen plasma or Sodium hydroxide. Further functionalization of the activated surfaces with different alkoxysilanes allows the reaction with PHB particles and PEG. The study confirms that the Ti surfaces achieved the antibacterial properties by combining the antibiotic-loaded PHB spheres, and PEG as an antifouling agent.
A Self Consistent RF Discharge, Plasma Chemistry and Surface Model for Plasma Enhanced Chemical Vapor Deposition

DTIC Science & Technology

1988-06-30

consists of three submodels for the electron kinetics, plasma chemistry , and surface deposition kinetics for a-Si:H deposited from radio frequency...properties. Plasma enhanced, Chemical vapor deposition, amorphous silicon, Modeling, Electron kinetics, Plasma chemistry , Deposition kinetics, Rf discharge, Silane, Film properties, Silicon.
Consequences of plasma oxidation and vacuum annealing on the chemical properties and electron accumulation of In2O3 surfaces

NASA Astrophysics Data System (ADS)

Berthold, Theresa; Rombach, Julius; Stauden, Thomas; Polyakov, Vladimir; Cimalla, Volker; Krischok, Stefan; Bierwagen, Oliver; Himmerlich, Marcel

2016-12-01

The influence of oxygen plasma treatments on the surface chemistry and electronic properties of unintentionally doped and Mg-doped In2O3(111) films grown by plasma-assisted molecular beam epitaxy or metal-organic chemical vapor deposition is studied by photoelectron spectroscopy. We evaluate the impact of semiconductor processing technology relevant treatments by an inductively coupled oxygen plasma on the electronic surface properties. In order to determine the underlying reaction processes and chemical changes during film surface-oxygen plasma interaction and to identify reasons for the induced electron depletion, in situ characterization was performed implementing a dielectric barrier discharge oxygen plasma as well as vacuum annealing. The strong depletion of the initial surface electron accumulation layer is identified to be caused by adsorption of reactive oxygen species, which induce an electron transfer from the semiconductor to localized adsorbate states. The chemical modification is found to be restricted to the topmost surface and adsorbate layers. The change in band bending mainly depends on the amount of attached oxygen adatoms and the film bulk electron concentration as confirmed by calculations of the influence of surface state density on the electron concentration and band edge profile using coupled Schrödinger-Poisson calculations. During plasma oxidation, hydrocarbon surface impurities are effectively removed and surface defect states, attributed to oxygen vacancies, vanish. The recurring surface electron accumulation after subsequent vacuum annealing can be consequently explained by surface oxygen vacancies.
Low-temperature direct bonding of glass nanofluidic chips using a two-step plasma surface activation process.

PubMed

Xu, Yan; Wang, Chenxi; Dong, Yiyang; Li, Lixiao; Jang, Kihoon; Mawatari, Kazuma; Suga, Tadatomo; Kitamori, Takehiko

2012-01-01

Owing to the well-established nanochannel fabrication technology in 2D nanoscales with high resolution, reproducibility, and flexibility, glass is the leading, ideal, and unsubstitutable material for the fabrication of nanofluidic chips. However, high temperature (~1,000 °C) and a vacuum condition are usually required in the conventional fusion bonding process, unfortunately impeding the nanofluidic applications and even the development of the whole field of nanofluidics. We present a direct bonding of fused silica glass nanofluidic chips at low temperature, around 200 °C in ambient air, through a two-step plasma surface activation process which consists of an O(2) reactive ion etching plasma treatment followed by a nitrogen microwave radical activation. The low-temperature bonded glass nanofluidic chips not only had high bonding strength but also could work continuously without leakage during liquid introduction driven by air pressure even at 450 kPa, a very high pressure which can meet the requirements of most nanofluidic operations. Owing to the mild conditions required in the bonding process, the method has the potential to allow the integration of a range of functional elements into nanofluidic chips during manufacture, which is nearly impossible in the conventional high-temperature fusion bonding process. Therefore, we believe that the developed low-temperature bonding would be very useful and contribute to the field of nanofluidics.
RF atmospheric plasma jet surface treatment of paper

NASA Astrophysics Data System (ADS)

Pawlat, Joanna; Terebun, Piotr; Kwiatkowski, Michał; Diatczyk, Jaroslaw

2016-09-01

A radio frequency RF atmospheric pressure plasma jet was used to enhance the wettability of cellulose-based paper of 90 g m-2 and 160 g m-2 grammage as a perspective platform for antibiotic sensitivity tests. Helium and argon were the carrier gases for oxygen and nitrogen; pure water and rapeseed oil were used for goniometric tests. The influence of the flow rate and gas type, the power of the discharge, and distance from the nozzle was examined. The surface structure was observed using an optical microscope. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra were investigated in order to determine whether cellulose degradation processes occurred. The RF plasma jet allowed us to decrease the surface contact angle without drastic changes in other features of the tested material. Experiments confirmed the significant influence of the distance between the treated sample and reactor nozzle, especially for treatment times longer than 15 s due to the greater concentration of reactive species at the surface of the sample, which decreases with distance—and their accumulation effect with time. The increase of discharge power plays an important role in decreasing the surface contact angle for times longer than 10 s. Higher power had a positive effect on the amount of generated active particles and facilitated the ignition of discharge. However, a too high value can cause a rise in temperature of the material and heat-caused damage.
Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene substrates

NASA Astrophysics Data System (ADS)

Zanini, S.; Orlandi, M.; Colombo, C.; Grimoldi, E.; Riccardi, C.

2009-08-01

A detailed study of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) substrates (membranes and films) is presented. The process consists of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. Influence of the solution and plasma parameters on the process efficiency evaluated in terms of amount of grafted polymer, coverage uniformity and substrates wettability, are investigated. The plasma-induced graft-polymerization of PEGA is then followed by sample weighting, water droplet adsorption time and contact angle measurements, attenuated total reflection infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in phosphate buffer saline (PBS) at 37 °C. Results clearly indicates that plasma-induced graft-polymerization of PEGA is a practical methodology for anti-fouling surface modification of materials.
Efficiency of surface cleaning by a glow discharge for plasma spraying coating

NASA Astrophysics Data System (ADS)

Kadyrmetov, A. M.; Kashapov, N. F.; Sharifullin, S. N.; Saifutdinov, A. I.; Fadeev, S. A.

2016-06-01

The article presents the results of experimental studies of the quality of cleaning steel surfaces by a glow discharge for plasma spraying. Shows the results of measurements of the angle of surface wetting and bond strength of the plasma coating to the surface treated. The dependence of the influence of the glow discharge power, chamber pressure, distance between the electrodes and the processing time of the surface on cleaning efficiency. Optimal fields of factors is found. It is shown increase joint strength coating and base by 30-80% as a result of cleaning the substrate surface by a glow discharge plasma spraying.
Hydrophilic property of 316L stainless steel after treatment by atmospheric pressure corona streamer plasma using surface-sensitive analyses

NASA Astrophysics Data System (ADS)

Al-Hamarneh, Ibrahim; Pedrow, Patrick; Eskhan, Asma; Abu-Lail, Nehal

2012-10-01

Surgical-grade 316L stainless steel (SS 316L) had its surface hydrophilic property enhanced by processing in a corona streamer plasma reactor using O2 gas mixed with Ar at atmospheric pressure. Reactor excitation was 60 Hz ac high-voltage (0-10 kVRMS) applied to a multi-needle-to-grounded screen electrode configuration. The treated surface was characterized with a contact angle tester. Surface free energy (SFE) for the treated stainless steel increased measurably compared to the untreated surface. The Ar-O2 plasma was more effective in enhancing the SFE than Ar-only plasma. Optimum conditions for the plasma treatment system used in this study were obtained. X-ray photoelectron spectroscopy (XPS) characterization of the chemical composition of the treated surfaces confirms the existence of new oxygen-containing functional groups contributing to the change in the hydrophilic nature of the surface. These new functional groups were generated by surface reactions caused by reactive oxidation of substrate species. Atomic force microscopy (AFM) images were generated to investigate morphological and roughness changes on the plasma treated surfaces. The aging effect in air after treatment was also studied.
Fibrinogen adsorption, platelet adhesion and activation on mixed hydroxyl-/methyl-terminated self-assembled monolayers.

PubMed

Rodrigues, Sofia N; Gonçalves, Inês C; Martins, M C L; Barbosa, Mário A; Ratner, Buddy D

2006-11-01

The effect of surface wettability on fibrinogen adsorption, platelet adhesion and platelet activation was investigated using self-assembled monolayers (SAMs) containing different ratios of longer chain methyl- and shorter chain hydroxyl-terminated alkanethiols (C15CH3 vs. C11OH) on gold. Protein adsorption studies were performed using radiolabeled human fibrinogen (HFG). Platelet adhesion and activation studies with and without pre-adsorbed fibrinogen, albumin and plasma were assessed using scanning electron microscopy (SEM) and a glutaraldehyde-induced fluorescence technique (GIFT). Results demonstrated a linear decrease of HFG adsorption with the increase of OH groups on the monolayer (increase of the hydrophilicity). Platelet adhesion and activation also decrease with increase of hydrophilicity of surface. Concerning SAMs pre-immersed in proteins, fibrinogen adsorption was related with high platelet adhesion and activation. The passivant effect of albumin on platelet adhesion and activation was only demonstrated on SAMs contained C11OH. When all the blood proteins are present (plasma) platelet adhesion was almost absent on SAMs with 65% and 100% C11OH. This could be explained by the higher albumin affinity of the SAMs with 65% C11OH and the lower total protein adsorption associated with SAMs with 100% C11OH.
Surface chemical structure of poly(ethylene naphthalate) films during degradation in low-pressure high-frequency plasma treatments

NASA Astrophysics Data System (ADS)

Kamata, Noritsugu; Yuji, Toshifumi; Thungsuk, Nuttee; Arunrungrusmi, Somchai; Chansri, Pakpoom; Kinoshita, Hiroyuki; Mungkung, Narong

2018-06-01

The surface chemical structure of poly(ethylene naphthalate) (PEN) films treated with a low-pressure, high-frequency plasma was investigated by storing in a box at room temperature to protect the PEN film surface from dust. The functional groups on the PEN film surface changed over time. The functional groups of –C=O, –COH, and –COOH were abundant in the Ar + O2 mixture gas plasma-treated PEN samples as compared with those in untreated PEN samples. The changes occurred rapidly after 2 d following the plasma treatment, reaching steady states 8 d after the treatment. Hydrophobicity had an inverse relationship with the concentration of these functional groups on the surface. Thus, the effect of the low-pressure high-frequency plasma treatment on PEN varies as a function of storage time. This means that radical oxygen and oxygen molecules are clearly generated in the plasma, and this is one index to confirm that radical reaction has definitely occurred between the gas and the PEN film surface with a low-pressure high-frequency plasma.

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