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Sample records for enhanced mechanical polishing

  1. Electro-Chemically Enhanced Mechanical Polishing of Nickel Mandrels

    NASA Technical Reports Server (NTRS)

    Gubarev, Mikhail; Ramsey, Brian; Engelhaupt, Darell

    2006-01-01

    Grinding and mechanical polishing techniques used for x-ray optics mandrel figuring lead to mid-frequency surface ripple. These small figure variations have to be addressed in order to improve the performance of the resulting x-ray mirrors. If the electrochemical etching is combined with mechanical polishing, the figuring and the surface finishing cm be done simultaneously and be used to correct the mid-frequency surface ripple. It is shown that the electrochemical mechanical polishing method allows selective removal of nickel alloy without mandrel surface microroughness degradation.

  2. Chemical-mechanical polishing: Enhancing the manufacturability of MEMS

    SciTech Connect

    Sniegowski, J.J.

    1996-10-01

    The planarization technology of Chemical-Mechanical-Polishing (CMP), used for the manufacturing of multi-level metal interconnects for high-density Integrated Circuits (IC), is also readily adaptable as an enabling technology in Micro Electro Mechanical Systems (MEMS) fabrication, particularly polysilicon surface micromachining. CMP not only eases the design and manufacturability of MEMS devices by eliminating several photolithographic and film issues generated by severe topography, but also enables far greater flexibility with process complexity and associated designs. Thus, the CMP planarization technique alleviates processing problems associated with fabrication of multi-level polysilicon structures, eliminates design constraints linked with non-planar topography, and provides an avenue for integrating different process technologies. Examples of these enhancements include: an simpler extension of surface micromachining fabrication to multiple mechanical layers, a novel method of monolithic integration of electronics and MEMS, and a novel combination of bulk and surface micromachining.

  3. Electrochemical aspects of chemical mechanical polishing of tungsten and aluminum

    NASA Astrophysics Data System (ADS)

    Kneer, Emil Anton

    1998-12-01

    Chemical mechanical polishing (CMP) of metals has emerged as a critical process step for the fabrication of advanced integrated circuit devices in the semiconductor industry. In a typical metal CMP process, the metal film is blanket deposited to fill recessed features on a patterned dielectric on silicon. Following metal deposition and gap fill, the metal overabundance is polished away by CMP, leaving an inlayed metal pattern or damascene structure on the substrate. Removal of the metal overabundance also planarizes the wafer surface for subsequent processing steps. The material removal process occurring during CMP is thought to involve the combined action of chemical oxidation and dissolution, and mechanical removal of material by abrasives. However, the relative contribution of mechanical and chemical effects during metal CMP is not well understood. The objective of this research was to characterize the fundamental electrochemical behavior of tungsten and aluminum thin films in polishing chemistries of interest to CMP. It was also of interest to determine the extent to which electrochemical oxidation and dissolution, or mechanical removal by abrasive action assists in material removal during CMP. A simultaneous electrochemical tester and polishing tool was developed to characterize the electrochemical behavior of tungsten and aluminum during and after abrasion. Small-scale polishing experiments were also carried out to measure polishing (removal) rates of the metals during CMP. Electrochemical dissolution rates and polishing rates were compared. It was found that the electrochemical dissolution rate of tungsten or aluminum during or after abrasion was very small compared to actual polishing rates. However, the presence of an oxidant enhanced polishing rates dramatically. The findings indicate that the mechanism for removal during CMP is primarily corrosion assisted metal removal, and not electrochemical dissolution and/or removal of the oxidation product of the

  4. Use of chemical mechanical polishing in micromachining

    DOEpatents

    Nasby, R.D.; Hetherington, D.L.; Sniegowski, J.J.; McWhorter, P.J.; Apblett, C.A.

    1998-09-08

    A process for removing topography effects during fabrication of micromachines. A sacrificial oxide layer is deposited over a level containing functional elements with etched valleys between the elements such that the sacrificial layer has sufficient thickness to fill the valleys and extend in thickness upwards to the extent that the lowest point on the upper surface of the oxide layer is at least as high as the top surface of the functional elements in the covered level. The sacrificial oxide layer is then polished down and planarized by chemical-mechanical polishing. Another layer of functional elements is then formed upon this new planarized surface. 4 figs.

  5. Use of chemical mechanical polishing in micromachining

    DOEpatents

    Nasby, Robert D.; Hetherington, Dale L.; Sniegowski, Jeffry J.; McWhorter, Paul J.; Apblett, Christopher A.

    1998-01-01

    A process for removing topography effects during fabrication of micromachines. A sacrificial oxide layer is deposited over a level containing functional elements with etched valleys between the elements such that the sacrificial layer has sufficient thickness to fill the valleys and extend in thickness upwards to the extent that the lowest point on the upper surface of the oxide layer is at least as high as the top surface of the functional elements in the covered level. The sacrificial oxide layer is then polished down and planarized by chemical-mechanical polishing. Another layer of functional elements is then formed upon this new planarized surface.

  6. Chemical Mechanical Polishing of Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony; Pirouz

    1999-01-01

    The High Temperature Integrated Electronics and Sensors (HTIES) team at the NASA Lewis Research Center is developing silicon carbide (SiC) as an enabling electronic technology for many aerospace applications. The Lewis team is focusing on the chemical vapor deposition of the thin, single-crystal SiC films from which devices are fabricated. These films, which are deposited (i.e., epitaxially "grown") on commercial wafers, must consist of a single crystal with very few structural defects so that the derived devices perform satisfactorily and reliably. Working in collaboration (NASA grant) with Professor Pirouz of Case Western Reserve University, we developed a chemical-mechanical polishing (CMP) technique for removing the subsurface polishing damage prior to epitaxial growth of the single-crystal SiC films.

  7. Chemical mechanical polishing of boron-doped polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    Pirayesh, Hamidreza; Cadien, Kenneth

    2014-03-01

    Chemical mechanical polishing (CMP) is a technique which helps to print a smaller depth of focus and smoother surface in micro fabrication industry. In this project, boron doped polysilicon is used as a fill material for Through Silicon Vias (TSV) creating a 3D package. It is shown that the presence of boron as dopant suppresses the polysilicon polish rate. To increase the polish rate, understanding the mechanism of polish rate retardation is essential. We believe that the electrical effects play the major role in this phenomenon and by reducing this effect we are able to increase the polish rate.

  8. Chemical mechanical polishing (CMP) of sapphire

    NASA Astrophysics Data System (ADS)

    Zhu, Honglin

    The concept of chemical mechanical polishing (CMP) was examined for finishing sapphire. In this study sapphire was used as a model system for oxide ceramics. The removal rates were determined by weight loss. Surface quality and structure were characterized with surface probe microscopy (SPM). Polishing experiments were designed to test the chemically modified surface layer. A series of abrasives with various hardnesses including mono-crystalline and polycrystalline diamond, alpha and gamma alumina, zirconia, ceria and silica were used. Diaspore was also evaluated. The results indicated that, with similar particle size and shape, harder abrasives do not necessarily cause faster material removal and better surface finish, and abrasives with hardness equal to or less than sapphire such as alpha alumina and gamma alumina achieved the best surface finish and efficient material removal. A hypothesis was proposed that the sapphire surface was modified by water to form a thin hydration laver with structure and hardness close to diaspore. Abrasives with a hardness between diaspore and sapphire polished the c-plane of sapphire with good surface finish and efficient removal. SPM indicated the hydration layer on the c-plane surface was about 1 nm thick. Removal rate and surface finish as a function of pH were also examined on c-plane sapphire with nano-alumina abrasives. The removal rate as a function of pH was compared to the solubility behavior of alumina. The results showed the deviation of pH from the lowest solubility pH for alumina (pH = 5) was a driving force for the surface reaction to form a hydration layer. The anisotropy of sapphire strongly affects removal rate and surface quality in CMP. The relationships among orientation. pH and abrasive were studied for sapphire with c (0001), a (11-20), and m (10-10) planes. Based on the results, the CMP process for sapphire includes chemical reaction of the surface to form a thin reaction layer that is softer than sapphire

  9. Defect centers in chemical-mechanical polished MOS oxides

    SciTech Connect

    Shaneyfelt, M.R.; Warren, W.L.; Hetherington, D.L.; Timon, R.P.; Resnick, P.J.; Winokur, P.S.

    1994-12-31

    Defect centers generated in vacuum-ultraviolet irradiated chemical-mechanical polished oxides have been characterized using electron paramagnetic resonance and C-V analysis. Both oxide trap E{sub {gamma}} and interface trap P{sub b0} centers were detected in unpolished and polished oxides. In addition, another interface defect center known as the P{sub b1} center was only identified in the polished oxides, suggesting that the polishing process altered the SiO{sub 2}/Si interface.

  10. Mechanical interactions at the interface of chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Shan, Lei

    This thesis addresses the mechanical aspects of sliding hard surface over a soft polymer pad in the presence of a fluid. This process is termed Chemical Mechanical Polishing (CMP) in semiconductor manufacturing. With the increasing integration density, especially the emergence of new materials and technologies, CMP has become an indispensable process for microelectronics fabrication. The manufacturability of current CMP processes however is limited by the poor understanding of the mechanisms, and fundamental studies are included in this thesis to improve CMP performance. The major contributions of this thesis to the existing CMP theories are to correlate the material removal and planarization mechanisms with mechanical interactions at a polishing interface. For the first time, a "nano-film" is suggested to exist between the load-supporting asperities and a target surface, and the material removal is associated with the thickness of the nano-film as well as the abrasive particle size. Accordingly, the material removal rate is related to the "contact" area and thus to the applied load for a given abrasive density. The polishing uniformity or planarization across a wafer is associated with the contact stress distribution. Since the contact stress is a result of both applied load and the interfacial fluid pressure, the latter was studied extensively. It was found that a subambient fluid pressure exists at the polishing interfaces [1], and the magnitude and distribution of this fluid pressure varies with process variables. Both an exact analysis and numerical models were developed to understand and predict the fluid pressure, and a finite element analysis is used to determine the resulting contact stress. Experiments were designed to justify the theories and models. The friction measurements show agreement with the existence of the nanofilm, and the results from polishing experiments are consistent with an estimation of the nano-film thickness. The polishing profile

  11. Chemical Mechanical Polishing of Ruthenium, Cobalt, and Black Diamond Films

    NASA Astrophysics Data System (ADS)

    Peethala, Brown Cornelius

    V from about 550 mV in the absence of additives. A removal mechanism with KIO4 as the oxidizing agent is proposed based on the formation of several ruthenium oxides, some of which formed residues on the polishing pad below a pH of ˜7. Next, a colloidal silica-based slurry with hydrogen peroxide (H 2O2) as the oxidizer (1 wt%), and arginine (0.5 wt%) as the complexing agent was developed to polish Co at pH 10. The Eoc between Cu and Co at the above conditions was reduced to ˜20 mV compared to ˜250 mV in the absence of additives, suggestive of reduced galvanic corrosion during the Co polishing. The slurry also has the advantages of good post-polish surface quality at pH 10, and no dissolution rate. BTA at a concentration of 5mM in this slurry inhibited Cu dissolution rates and yielded a Cu/Co RR ratio of ˜0.8:1 while the open potential difference between Cu and Co was further reduced to ˜10 mV. The role of H2O2, complexing agent (arginine), silica abrasives, and Co removal mechanism during polishing is discussed. Also, during the barrier CMP, a part of the underlying low-k (SiCOH) material has to be polished to remove any modified surface film. Black Diamond (BD) is a SiCOH type material with a dielectric constant of ˜2.9 and here, polishing of BD was investigated in order to understand the polishing behavior of SiCOH-based materials using the barrier slurries. The slurries that were developed for polishing Co and Ru in this work and Ta/TaN (earlier) were investigated for polishing the Black Diamond (BD) films. Here, it was found that ionic salts play a major role in enhancing the BD RRs to ˜65 nm/min compared to no removal rates in the absence of additives. A removal mechanism in the presence of ionic salts is proposed.

  12. Laser polishing

    NASA Astrophysics Data System (ADS)

    Temmler, A.; Willenborg, E.; Wissenbach, K.

    2012-03-01

    A new approach to polish metallic freeform surfaces is polishing by means of laser radiation. In this technology a thin surface layer is molten and the surface tension leads to a material flow from the peaks to the valleys. No material is removed but reallocated while molten. As the typical processing time is 1 min/cm2 laser polishing is up to 30 times faster than manual polishing. Reducing the roughness by laser polishing is achieved for several different materials such as hot work steels for the die and molding industries or titanium alloys for medical engineering. Enhancing the appearance of design surfaces is achieved by creating a dual-gloss effect by selective laser polishing (SLP). In comparison to conventional polishing processes laser polishing opens up the possibility of selective processing of small areas (< 0.1 mm2). A dual-gloss effect is based on a space-resolved change in surface roughness. In comparison to the initial surface the roughness of the laser polished surface is reduced significantly up to spatial wavelengths of 80 microns and therefore the gloss is raised considerably. The surface roughness is investigated by a spectral analysis which is achieved by a discrete convolution of the surface profile with a Gaussian loaded function. The surfaces roughness is split into discrete wavelength intervals and can be evaluated and optimized. Laser polishing is carried out by using a special tailored five-axis mechanical handling system, combined with a three axis laser scanning system and a fibre laser.

  13. Mechanistic, kinetic, and processing aspects of tungsten chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Stein, David

    This dissertation presents an investigation into tungsten chemical mechanical polishing (CMP). CMP is the industrially predominant unit operation that removes excess tungsten after non-selective chemical vapor deposition (CVD) during sub-micron integrated circuit (IC) manufacture. This work explores the CMP process from process engineering and fundamental mechanistic perspectives. The process engineering study optimized an existing CMP process to address issues of polish pad and wafer carrier life. Polish rates, post-CMP metrology of patterned wafers, electrical test data, and synergy with a thermal endpoint technique were used to determine the optimal process. The oxidation rate of tungsten during CMP is significantly lower than the removal rate under identical conditions. Tungsten polished without inhibition during cathodic potentiostatic control. Hertzian indenter model calculations preclude colloids of the size used in tungsten CMP slurries from indenting the tungsten surface. AFM surface topography maps and TEM images of post-CMP tungsten do not show evidence of plow marks or intergranular fracture. Polish rate is dependent on potassium iodate concentration; process temperature is not. The colloid species significantly affects the polish rate and process temperature. Process temperature is not a predictor of polish rate. A process energy balance indicates that the process temperature is predominantly due to shaft work, and that any heat of reaction evolved during the CMP process is negligible. Friction and adhesion between alumina and tungsten were studied using modified AFM techniques. Friction was constant with potassium iodate concentration, but varied with applied pressure. This corroborates the results from the energy balance. Adhesion between the alumina and the tungsten was proportional to the potassium iodate concentration. A heuristic mechanism, which captures the relationship between polish rate, pressure, velocity, and slurry chemistry, is presented

  14. Chemical-mechanical polishing of recessed microelectromechanical devices

    DOEpatents

    Barron, C.C.; Hetherington, D.L.; Montague, S.

    1999-07-06

    A method is disclosed for micromachining recessed layers (e.g. sacrificial layers) of a microelectromechanical system (MEMS) device formed in a cavity etched into a semiconductor substrate. The method uses chemical-mechanical polishing (CMP) with a resilient polishing pad to locally planarize one or more of the recessed layers within the substrate cavity. Such local planarization using the method of the present invention is advantageous for improving the patterning of subsequently deposited layers, for eliminating mechanical interferences between functional elements (e.g. linkages) of the MEMS device, and for eliminating the formation of stringers. After the local planarization of one or more of the recessed layers, another CMP step can be provided for globally planarizing the semiconductor substrate to form a recessed MEMS device which can be integrated with electronic circuitry (e.g., CMOS, BiCMOS or bipolar circuitry) formed on the surface of the substrate. 23 figs.

  15. Chemical-mechanical polishing of recessed microelectromechanical devices

    DOEpatents

    Barron, Carole C.; Hetherington, Dale L.; Montague, Stephen

    1999-01-01

    A method is disclosed for micromachining recessed layers (e.g. sacrificial layers) of a microelectromechanical system (MEMS) device formed in a cavity etched into a semiconductor substrate. The method uses chemical-mechanical polishing (CMP) with a resilient polishing pad to locally planarize one or more of the recessed layers within the substrate cavity. Such local planarization using the method of the present invention is advantageous for improving the patterning of subsequently deposited layers, for eliminating mechanical interferences between functional elements (e.g. linkages) of the MEMS device, and for eliminating the formation of stringers. After the local planarization of one or more of the recessed layers, another CMP step can be provided for globally planarizing the semiconductor substrate to form a recessed MEMS device which can be integrated with electronic circuitry (e.g. CMOS, BiCMOS or bipolar circuitry) formed on the surface of the substrate.

  16. Adsorption behavior of anionic polyelectrolyte for chemical mechanical polishing (CMP).

    PubMed

    Kim, Sarah; So, Jae-Hyun; Lee, Dong-Jun; Yang, Seung-Man

    2008-03-01

    In this work, we investigated the adsorption characteristics of anionic polyelectrolytes, which are used in shallow trench isolation chemical mechanical polishing with ceria abrasives. Specifically, the adsorption isotherms and chain conformation of anionic polyelectrolytes were studied in order to elucidate the difference in removal rates of silicon dioxide (SiO2) and silicon nitride (Si3N4) layers and the high selectivity characteristics of ceria slurry. Adsorption isotherms, FT-IR spectroscopy and contact angle measurements revealed that the anionic polyelectrolyte additives had much better adsorption affinities for the Si3N4 surface than for the SiO2 surface. Moreover, blanket wafer polishing results were successfully correlated with the adsorption isotherms of polyelectrolytes on the oxide particle suspensions. PMID:18078949

  17. Particle-surface interactions in chemical mechanical polishing

    SciTech Connect

    Dugger, M.T.; Adkins, C.L.J.; Resnick, P.J.; Jeon, J.S.; Raghavan, S.

    1996-10-01

    Material removal in chemical mechanical polishing (CMP) occurs by a pressure accentuated chemical attack of the surface. The polishing slurry typically consists of abrasive particles and reactive chemicals that may or may not include an oxidant. Post-CMP cleaning processes must remove both the ionic contaminants and any remaining polishing slurry particles. Central to the effectiveness of a clean is the use of conditions that will minimize the binding force between the residual particles and the wafer surface. The morphology and composition of the particle, the surface from which it must be removed, and the environment surrounding the wafer will determine the magnitude of forces that hold a particle to the wafer surface. At the Sandia/SEMATECH Center for Contamination Free Manufacturing, two techniques--atomic force microscopy (AFM) and electrokinetic deposition--are being used to explore these interactions for CMP of both oxide and tungsten surfaces. A basic understanding of particle-surface interaction forces and how they are affected by the chemical/physical environment of the particle and surface is the objective of this task. Modification of the binding forces between particles and wafer surfaces may be used to maximize post-CMP cleaning effectiveness.

  18. In situ electrochemical investigation of tungsten electrochemical behavior during chemical mechanical polishing

    SciTech Connect

    Stein, D.J.; Cecchi, J.L.; Hetherington, D.; Guilinger, T.

    1998-09-01

    The electrochemical behavior of tungsten during chemical mechanical polishing (CMP) was observed in order to investigate a proposed blanket passivation and abrasion mechanism for tungsten removal. The experiments were performed in a cell that allowed electrochemical measurements to be made during polish. Polish rates were determined from the same samples used in the cell. Alumina-based polish slurries containing potassium iodate, ferric nitrate, or ammonium persulfate were used. DC polarization experiments show no evidence of passive film formation on the tungsten during polish. Tungsten oxidation rates measured during polish account for removal rates that are 1 to 2 orders of magnitude below the measured polish rate. Values of the charge-transfer resistance (measured by ac impedance spectroscopy) during polish are 1 to 2 orders of magnitude higher than expected from the polish rate, thus corroborating the dc-based data. Polish rates under potentiostatic conditions were also measured. The current required to maintain the metal anodic of the open-circuit potential is well below the current expected from measured polish rates, assuming complete oxidation of the tungsten. The polish rate during cathodic potentiostatic conditions ({minus}0.5 V with regard to the open-circuit potential) was similar to the polish rate at open circuit. The authors conclude that the formation of a blanket passive layer does not significantly contribute to tungsten removal during CMP.

  19. Material removal mechanism of copper chemical mechanical polishing in a periodate-based slurry

    NASA Astrophysics Data System (ADS)

    Cheng, Jie; Wang, Tongqing; He, Yongyong; Lu, Xinchun

    2015-05-01

    The material removal mechanism of copper in a periodate-based slurry during barrier layer chemical mechanical polishing (CMP) has not been intensively investigated. This paper presents a study of the copper surface film chemistry and mechanics in a periodate-based slurry. On this basis, the controlling factor of the copper CMP material removal mechanism is proposed. The results show that the chemical and electrochemical reaction products on the copper surface are complex and vary considerably as a function of the solution pH. Under acidic conditions (pH 4) the copper surface underwent strong chemical dissolution while the corrosion was mild and uniform under alkaline conditions (pH 11). The corrosion effect was the lowest in near neutral solutions because the surface was covered with non-uniform Cu(IO3)2·H2O/Cu-periodate/copper oxides films, which had better passivation effect. The surface film thickness and mechanical removal properties were studied by AES and AFM nano-scratch tests. Based on the combined surface film analysis and CMP experiment results, it can be concluded that the controlling factor during copper CMP in a periodate-based slurry is the chemical-enhanced mechanical removal of the surface films. The periodate-based slurry should be modified by the addition of corrosion inhibitors and complexing agents to achieve a good copper surface quality with moderate chemical dissolution.

  20. Chemical-mechanical polishing of metal and dielectric films for microelectronic applications

    NASA Astrophysics Data System (ADS)

    Hegde, Sharath

    The demand for smaller, faster devices has led the integrated circuit (IC) industry to continually increase the device density on a chip while simultaneously reducing feature dimensions. Copper interconnects and multilevel metallization (MLM) schemes were introduced to meet some of these challenges. With the employment of MLM in the ultra-large-scale-integrated (ULSI) circuit fabrication technology, repeated planarization of different surface layers with tolerance of a few nanometers is required. Presently, chemical-mechanical planarization (CMP) is the only technique that can meet this requirement. Damascene and shallow trench isolation processes are currently used in conjunction with CMP in the fabrication of multilevel copper interconnects and isolation of devices, respectively, for advanced logic and memory devices. These processes, at some stage, require simultaneous polishing of two different materials using a single slurry that offers high polish rates, high polish selectivity to one material over the other and good post-polish surface finish. Slurries containing one kind of abrasive particles do not meet most of these demands due mainly to the unique physical and chemical properties of each abrasive. However, if a composite particle is formed that takes the advantages of different abrasives while mitigating their disadvantages, the CMP performance of resulting abrasives would be compelling. It is demonstrated that electrostatic interactions between ceria and silica particles at pH 4 can be used to produce composite particles with enhanced functionality. Zeta potential measurement and TEM images used for particle characterization show the presence of such composite particles with smaller shell particles attached onto larger core particles. Slurries containing ceria (core)/silica (shell) and silica (core)/ceria (shell) composite particles when used to polish metal and dielectric films, respectively, yield both enhanced metal and dielectric film removal rates

  1. An investigation into chemical-mechanical polishing process of zinc selenide

    NASA Astrophysics Data System (ADS)

    Yao, Hongyu

    2001-12-01

    An analysis of chemical-mechanical polishing (CMP) under fixed polishing conditions and different polishing times has been performed on ZnSe single crystals. The morphology of finishing surface was monitored by atomic force microscopy (AFM) and differential interference contrast (DIC) optical microscopy. Novel X-ray diffraction techniques such as grazing incidence X-ray diffraction (GIXD), asymmetric inclined plane X-ray diffraction (AIPXD), and symmetric inclined plane X-ray diffraction (SIPXD) were employed to study the surface and subsurface structural damages in ZnSe after polishing. Surface chemical analysis was carried out utilizing X-ray photoelectron spectroscopy (XPS) for polished ZnSe samples. Consistent improvement of surface and subsurface structure as well as surface morphology with increased polishing time was noticed. A large number of Se nanoprecipitates were observed appearing on ZnSe surface after CMP. A statistical CMP model based on Yates' algorithm was developed in this study. This model was used to systematically investigate the effects of specific polishing variables on the sodium hypochlorite (NaOCl) based CMP process of ZnSe. The force applied on the samples and the NaOCl concentration in the polishing slurry were found to be the most critical individual polishing parameters. In addition, maintaining an appropriate balance between the mechanical polishing component and the chemical etching component in the CMP process was found to be a crucial factor in determining the surface quality of polished ZnSe samples.

  2. Mechanical aspects of the material removal mechanism in chemical mechanical polishing (CMP)

    NASA Astrophysics Data System (ADS)

    Moon, Yongsik

    The chemical mechanical polishing (CMP) process has become a primary planarization technique required for the manufacture of advanced integrated circuit (IC) devices. As the feature size of IC chips shrinks down to 0.18 mum and below, the role of CMP as a robust planarization process becomes increasingly important. In this dissertation, mechanical aspects of the material removal mechanism in CMP are investigated analytically and experimentally as part of a fundamental study on CMP. The role of consumables, which include the polishing pad and abrasive particles in the slurry, in CMP performance is evaluated, and tribological characteristics (lubrication, friction, and wear) of CMP are also analyzed. To evaluate the role of slurry, the influence of chemistry of the slurry on the mechanical aspects of the material removal mechanism is examined. The mechanical and chemical contributions to material removal are studied to determine the key mechanism of material removal in CMP. From this study, it is shown that the material removal rate of the wafers is inversely proportional to the pad density and proportional to the pad compressibility and surface roughness. This is due to the fact that the material removal for a wafer in CMP is closely related to the actual pad contact area of the wafer. This is an indication of the probability of abrasives contacting the wafer surface. The material removal rate of silicon wafers is also proportional to the friction force between the workpiece and the polishing pad. The effect of the slurry film thickness variation on CMP performance, defined in terms of material removal, planarization, surface defects, and surface roughness, is significant. From the Stribeck curve, the lubrication condition under the wafer in CMP is closer to boundary or elasto-hydrodynamic lubrication than to hydrodynamic lubrication. It is also shown that the chemically reacted silicon layer causes the extension of the brittle/ductile transition depth, and the

  3. Mechanism of Ge2Sb2Te5 chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Wang, Liangyong; Song, Zhitang; Zhong, Min; Liu, Weili; Yan, Weixia; Qin, Fei; He, Aodong; Liu, Bo

    2012-04-01

    We report the exploration of Ge2Sb2Te5 (GST) chemical mechanical polishing (CMP) mechanism. Static etching experiments of GST film were first conducted in two typical silica-based slurries (pH 2 and pH 11). To investigate the chemical nature of GST in different chemical environments, solubility of GST in slurries and also the zeta potentials of GST powders vs pH were measured. We further compared the polishing performance to the removal rate (RR), surface roughness, polishing selectivity of GST over oxide, and influence on the phase change property by using the two typical slurries. Then measurements were done for the hardness of GST films before and after polishing, particle size of the slurry during polishing, and also the open circuit potential (OCP) of GST in the two slurries. On the basis of the aforementioned results, we proposed a possible mechanism for GST CMP including reaction formulas, removal of GST as molecules instead of as a lump, surface hydration in alkaline region and electrochemical process, which was partially supported by residue analysis for 8″ patterned wafers using energy dispersive spectroscopy (EDS) under transmission electron microscope (TEM).

  4. Electrochemical and mechanical polishing and shaping method and system

    NASA Technical Reports Server (NTRS)

    Engelhaupt, Darell E. (Inventor); Gubarev, Mikhail V. (Inventor); Jones, William David (Inventor); Ramsey, Brian D. (Inventor); Benson, Carl M. (Inventor)

    2011-01-01

    A method and system are provided for the shaping and polishing of the surface of a material selected from the group consisting of electrically semi-conductive materials and conductive materials. An electrically non-conductive polishing lap incorporates a conductive electrode such that, when the polishing lap is placed on the material's surface, the electrode is placed in spaced-apart juxtaposition with respect to the material's surface. A liquid electrolyte is disposed between the material's surface and the electrode. The electrolyte has an electrochemical stability constant such that cathodic material deposition on the electrode is not supported when a current flows through the electrode, the electrolyte and the material. As the polishing lap and the material surface experience relative movement, current flows through the electrode based on (i) adherence to Faraday's Law, and (ii) a pre-processing profile of the surface and a desired post-processing profile of the surface.

  5. Application of chemical mechanical polishing process on titanium based implants.

    PubMed

    Ozdemir, Z; Ozdemir, A; Basim, G B

    2016-11-01

    Modification of the implantable biomaterial surfaces is known to improve the biocompatibility of metallic implants. Particularly, treatments such as etching, sand-blasting or laser treatment are commonly studied to understand the impact of nano/micro roughness on cell attachment. Although, the currently utilized surface modification techniques are known to improve the amount of cell attachment, it is critical to control the level of attachment due to the fact that promotion of bioactivity is needed for prosthetic implants while the cardiac valves, which are also made of titanium, need demotion of cells attachment to be able to function. In this study, a new alternative is proposed to treat the implantable titanium surfaces by chemical mechanical polishing (CMP) technique. It is demonstrated that the application of CMP on the titanium surface helps in modifying the surface roughness of the implant in a controlled manner (inducing nano-scale smoothness or controlled nano/micro roughness). Simultaneously, it is observed that the application of CMP limits the bacteria growth by forming a protective thin surface oxide layer on titanium implants. It is further shown that there is an optimal level of surface roughness where the cell attachment reaches a maximum and the level of roughness is controllable through CMP. PMID:27524033

  6. Functions of Trilon® P as a polyamine in copper chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Jiang, Liang; Lan, Yongqing; He, Yongyong; Li, Yuzhuo; Luo, Jianbin

    2014-01-01

    In this paper, as a representative of the polyamines, Trilon® P was used as a critical additive in copper slurries to improve the copper chemical mechanical polishing (CMP) performance, and high copper removal rate (RR), low copper static etching rate (SER), low dishing and low dielectric erosion were realized by CMP tests on the copper patterned wafers. The chelating reactions between Trilon® P and cupric ions are revealed, and it is found that the reaction product Cu-Trilon® P complex has dual functions for copper RR and SER: the negative one is from the weak passivation and the lubrication while the positive one is from the complexation with cupric ions and the facilitation of (*OH) formation, and the final polishing result depends on the competition between the above two functions. In addition, the adsorption of Trilon® P on the plasma enhanced tetraethylorthosilicate (PETEOS) surface helps form a lubricating thin film, which relieves the severe mechanical stress on the PETEOS pattern, and thus results in low dielectric erosion.

  7. Research on influences of contact force in chemical mechanical polishing (CMP) process

    NASA Astrophysics Data System (ADS)

    Han, Lei; Zhao, Hongwei; Zhang, Qixun; Jin, Mingjun; Zhang, Lin; Zhang, Peng

    2015-04-01

    A series of simulations of chemical mechanical polishing (CMP) were conducted to investigate the contact force between abrasive particles and specimens by using the finite element method (FEM). In this paper, a micro-contact model, which only involves the mechanical interactions, was set up to simulate the polishing process by changing the processing parameters, including the downward pressure, abrasive size, and polishing speed. Simulation results show that the contact force becomes larger when the downward pressure increases. In addition, when the downward pressure and abrasive size increase, the fluctuation of the contact force becomes large, whereas it declines with decreases in the polishing speed. In addition, corresponding CMP experiments were done to investigate the material removal rate (MRR) and polished average roughness (Ra) under different simulation conditions. Through the establishment of the contact force properties in the simulation and the MRR and Ra in the CMP experiment, qualitative research has been done on the relationship between the contact force in the simulation and experimental results. Experimental results indicate that the MRR and surface roughness are influenced by the contact force. A high MRR can be obtained by a large contact force and dramatic fluctuations can lead to poor surface-finish quality. The investigation contributes to obtaining higher polishing efficiency and lower surface roughness through optimization of the polishing parameters.

  8. Surface topography in mechanical polishing of 6H-SiC (0001) substrate

    NASA Astrophysics Data System (ADS)

    Yin, Ling; Huang, Han

    2007-12-01

    Silicon carbide (SiC) single crystals have been used as the substrates of a new generation of wide band-gap semiconductors due to their unparalleled combination of high breakdown voltage, extreme temperature tolerance, mobility and radiation hardness. For their applications, the SiC substrates need to be machined with nanometric surface quality as well as high form accuracy. However, the superior properties of the materials render their machinability extremely difficult. In this paper, we report the form error and surface roughness of the 6H-SiC (0001) substrate mechanically polished using 3 μm diamond powders in two different polishing processes. One process was concentrated-load polishing; the other was surface polishing. The polished surfaces were evaluated using white light interferometry and atomic force microscopy (AFM) for assessment of two- and three-dimensional topographies including form error and surface roughness. We found that a large form error was produced on the 6H-SiC (0001) substrate in the concentrated-load polishing. The root-mean-square (RMS) surface roughness of approximately 4 nm was resulted. Surface polishing of the 6H-SiC (0001) substrate remarkably improved form accuracy. The RMS surface roughness of approximately 2.5 nm was obtained.

  9. Treating chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation process with surfactant.

    PubMed

    Hu, C Y; Lo, S L; Li, C M; Kuan, W H

    2005-04-11

    The effect of surfactants on the treatment of chemical mechanical polishing (CMP) wastewater by electro-coagulation-flotation (ECF) process was studied. Two surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) were employed in this study to compare the effect of cationic (CTAB) and anodic (SDS) surfactants on ECF. The cationic surfactant can enhance the removal of the turbidity, but anodic surfactant cannot. It can be explained by the hetero-coagulation theory. Moreover, the addition of CTAB in CMP wastewater can reduce the sludge volume and the flotation/sedimentation time in ECF process. The residual turbidity and dissolved silicon dropped with the increase of charge loading. No CTAB pollution problem exists after the ECF process. PMID:15811659

  10. Chemical Mechanical Polishing with Nanocolloidal Ceria Slurry for Low-Damage Planarization of Dielectric Films

    NASA Astrophysics Data System (ADS)

    Ryuzaki, Daisuke; Hoshi, Yosuke; Machii, Yoichi; Koyama, Naoyuki; Sakurai, Haruaki; Ashizawa, Toranosuke

    2012-03-01

    New chemical mechanical polishing processes using nanocolloidal ceria slurry are proposed for high-precision and low-damage planarization of silicon-dioxide-based dielectric films. In the polishing process of a shallow trench isolation structure, a hard pad and a cationic polymer additive are used in combination with the slurry. The new process is effective in improving the planarity and reducing the microscratch count in comparison with a conventional polishing process with calcined ceria slurry and a standard pad. In the polishing process of an interconnect structure with ultralow-k interlayer dielectrics (ULK-ILDs), the standard pad should be used since the ULK-ILDs are easily damaged. By employing a spin-on-type ULK-ILD having a self-planarizing effect, a high planarity is obtained when using the nanocolloidal ceria slurry with the standard pad. The electrical measurement of the interconnect structure indicates that dielectric damage due to the process is successfully suppressed.

  11. Particle size and surfactant effects on chemical mechanical polishing of glass using silica-based slurry

    SciTech Connect

    Zhang Zefang; Liu Weili; Song Zhitang

    2010-10-01

    This study explores the effect of particle size and surfactant on the chemical mechanical polishing (CMP) of glass using colloidal silica-based slurry. It was found that the material removal rate strongly depends on the particle size and the types of surfactants and that the rms roughness was independent of particle size and correlated to surfactants. On the basis of polishing results, it was concluded that the main polishing mechanism was changed from indentation mechanism to surface-area mechanism, with the variation of particle size. In addition, the molecular structure, charge type, and lubricating effect of the surfactants play an important role in the dispersion of abrasive particles and in the CMP performance.

  12. Gallic Acid as a Complexing Agent for Copper Chemical Mechanical Polishing Slurries at Neutral pH

    NASA Astrophysics Data System (ADS)

    Kim, Yung Jun; Kang, Min Cheol; Kwon, Oh Joong; Kim, Jae Jeong

    2011-05-01

    Gallic acid was investigated as a new complexing agent for copper (Cu) chemical mechanical polishing slurries at neutral pH. Addition of 0.03 M gallic acid and 1.12 M H2O2 at pH 7 resulted in a Cu removal rate of 560.73±17.49 nm/min, and the ratio of the Cu removal rate to the Cu dissolution rate was 14.8. Addition of gallic acid improved the slurry performance compared to glycine addition. X-ray photoelectron spectroscopy analysis and contact angle measurements showed that addition of gallic acid enhanced the Cu polishing behavior by suppressing the formation of surface Cu oxide.

  13. Chemical mechanical polishing: An enabling fabrication process for surface micromachining technologies

    SciTech Connect

    Sniegowski, J.J.

    1998-08-01

    Chemical-Mechanical-Polishing (CMP), first used as a planarization technology in the manufacture of multi-level metal interconnects for high-density Integrated Circuits (IC), is readily adapted as an enabling technology in MicroElectroMechanical Systems (MEMS) fabrication, particularly polysilicon surface micromachining. The authors have demonstrated that CMP enhances the design and manufacturability of MEMS devices by eliminating several photolithographic definition and film etch issues generated by severe topography. In addition, CMP planarization readily allows multi-level polysilicon structures comprised of 4- or more levels of polysilicon, eliminates design compromise generated by non-planar topography, and provides an avenue for integrating different process technologies. A recent investigation has also shown that CMP is a valuable tool for assuring acceptable optical flatness of micro-optical components such as micromirrors. Examples of these enhancements include: an extension of polysilicon surface-micromachining fabrication to a 5-level technology, a method of monolithic integration of electronics and MEMS, and optically flat micromirrors.

  14. Mirror smooth superconducting RF cavities by mechanical polishing with minimal acid use

    SciTech Connect

    Cooper, C.A.; Cooley, L.D.; /Fermilab

    2011-02-01

    A new mechanical technique for polishing the inside surface of niobium superconducting RF (SRF) cavities has been developed. Mirror-like finishes, the smoothest observed in cavities so far, were produced after fine polishing, with < 15 nm RMS roughness over 1 mm{sup 2} scan area. This is an order of magnitude less than the typical roughness produced by electropolishing. The processing equipment has advantages of modest installed and operating costs, simple associated technology, and no large quantities of acutely toxic chemicals or special handling procedures. Cavity quality factors above 10{sup 10} were maintained well above the 35 MV m{sup -1} benchmark for electropolished cavities, and this was achieved with an intermediate finish not as smooth as the final polish. Repair of a weld defect, which is intrinsic to this process, was also demonstrated. These transformational aspects could enable a new SRF cavity processing paradigm for future large scale particle accelerators such as the International Linear Collider.

  15. Comparison of ceria nanoparticle concentrations in effluent from chemical mechanical polishing of silicon dioxide.

    PubMed

    Zazzera, Larry; Mader, Brian; Ellefson, Mark; Eldridge, Jess; Loper, Steve; Zabasajja, John; Qian, Julie

    2014-11-18

    This work measured and compared the effluent from the chemical mechanical polishing (CMP) of silicon dioxide using ceria slurry and ceria fixed abrasive. CMP waste streams were tested for total solids, cerium, silicon, and 6 nm to 20 μm diameter particles. The concentration of cerium and total solids in the effluent were very different for the two polishes studied. The fixed abrasive polish produced 94% less CeO2 emissions per SiO2 removed. The higher ceria levels in the slurry effluent are associated with 99-279 nm particles, and attributed to ceria abrasive. The lower concentration of ceria in the effluent from the fixed abrasive process is due to the lower wear rate of mineral from the fixed abrasive, compared to the more environmentally mobile mineral in the slurry. These results support the "bonded" nature of the abrasive particles in fixed abrasive polishing and are relevant to sustainability strategies that seek to reduce particle emissions in surface conditioning technology. PMID:25317965

  16. Planar surface-micromachined pressure sensors by chemical-mechanical polishing

    SciTech Connect

    Eaton, W.P.; Smith, J.H.

    1996-11-01

    Planar, surface micromachined pressure sensors have been fabricated by an extension of the chemical-mechanical polishing (CMP) process. CMP eliminates many of the fabrication problems associated with the photolithography, dry etch, and metallization of non-planar devices. Furthermore, CMP adds additional design flexibility. The sensors are based upon deformable, silicon nitride diaphragms with polysilicon piezoresistors. Absolute pressure is detected by virtue of reference pressure cavities underneath the diaphragms.

  17. Chemical mechanical polishing of steel substrate using colloidal silica-based slurries

    NASA Astrophysics Data System (ADS)

    Jiang, Liang; He, Yongyong; Luo, Jianbin

    2015-03-01

    AISI 52100 steel has been widely used in the mechanical industry due to its excellent mechanical properties and high availability. In some cases, an ultra-smooth surface of AISI 52100 steel is needed and is even indispensable for the satisfactory performance of devices. In this paper, chemical mechanical polishing technique was employed to prepare the ultra-smooth surface of AISI 52100 steel. Colloidal silica was used as the abrasive. The effects of pH, complexing agent such as glycine, H2O2 and benzotriazole (BTA) on the polishing performance were studied. It is revealed that, with the increase of pH, the static etching rate (SER) and the material removal rate (MRR) are both gradually reduced, and the post-CMP surface roughness Ra decreases. This is attributed to the fact that compact and passive iron oxides, especially Fe(III) oxides, gradually form on the top surface. At pH 4.00, in the presence of glycine, and with the increase of the H2O2 concentration, the SER is further suppressed, and the surface roughness Ra gradually decreases; the MRR initially dramatically increases due to the fact that, with the addition of small amount of H2O2, the porous iron oxide layer with relatively low mechanical strength can be rapidly formed on the surface. Moreover, glycine intensifies the chemical dissolution by chelating iron ions, especially Fe(II) ions, and thereby the mechanical strength of the oxide layer further weakens. Then, after reaching the peak value, the MRR gradually decreases when the H2O2 concentration further increases since the compactness of the oxide layer gradually increases. With the increase of the BTA concentration, the MRR is gradually suppressed and the surface roughness Ra decreases due to the formation of Fe-BTA passivating film on the top surface. Finally, a two-step polishing process was developed. The polishing results show that, within 20 min, a rough surface of AISI 52100 steel with the Ra value of 188 nm can be polished into an ultra

  18. Effects of catalyst concentration and ultraviolet intensity on chemical mechanical polishing of GaN

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Wang, Tongqing; Pan, Guoshun; Lu, Xinchun

    2016-08-01

    Effects of catalyst concentration and ultraviolet intensity on chemical mechanical polishing (CMP) of GaN were deeply investigated in this paper. Working as an ideal homogeneous substrate material in LED industry, GaN ought to be equipped with a smooth and flat surface. Taking the strong chemical stability of GaN into account, photocatalytic oxidation technology was adopted in GaN CMP process to realize efficient removal. It was found that, because of the improved reaction rate of photocatalytic oxidation, GaN material removal rate (MRR) increases by a certain extent with catalyst concentration increasing. Cross single line analysis on the surface after polishing by Phase Shift MicroXAM-3D was carried out to prove the better removal effect with higher catalyst concentration. Ultraviolet intensity field in H2O2-SiO2-based polishing system was established and simulated, revealing the variation trend of ultraviolet intensity around the outlet of the slurry. It could be concluded that, owing to the higher planarization efficiency and lower energy damage, the UV lamp of 125 W is the most appropriate lamp in this system. Based on the analysis, defects removal model of this work was proposed to describe the effects of higher catalyst concentration and higher power of UV lamp.

  19. Chemical mechanical polishing characteristics of ITO thin film prepared by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Lee, Kang-Yeon; Choi, Gwon-Woo; Kim, Yong-Jae; Choi, Youn-Ok; Kim, Nam-Oh

    2012-02-01

    Indium-tin-oxide (ITO) thin films have attracted intensive interest because of their unique properties of good conductivity, high optical transmittance over the visible region and easy patterning ability. ITO thin films have found many applications in anti-static coatings, thermal heaters, solar cells, flat panel displays (FPDs), liquid crystal displays (LCDs), electroluminescent devices, sensors and organic light-emitting diodes (OLEDs). ITO thin films are generally fabricated by using various methods, such as spraying, chemical vapor deposition (CVD), evaporation, electron gun deposition, direct current electroplating, high frequency sputtering, and reactive sputtering. In this research, ITO films were grown on glass substrates by using a radio-frequency (RF) magnetron sputtering method. In order to achieve a high transmittance and a low resistivity, we examined the various film deposition conditions, such as substrate temperature, working pressure, annealing temperature, and deposition time. Next, in order to improve the surface quality of the ITO thin films, we performed a chemical mechanical polishing (CMP) with different process parameters and compared the electrical and the optical properties of the polished ITO thin films. The best CMP conditions with a high removal rate, low nonuniformity, low resistivity and high transmittance were as follows: platen speed, head speed, polishing time, and slurry flow rate of 30 rpm, 30 rpm, 60 sec, and 60 ml/min, respectively.

  20. Chemical mechanical polishing of Indium phosphide, Gallium arsenide and Indium gallium arsenide films and related environment and safety aspects

    NASA Astrophysics Data System (ADS)

    Matovu, John Bogere

    As scaling continues with advanced technology nodes in the microelectronic industry to enhance device performance, the performance limits of the conventional substrate materials such as silicon as a channel material in the front-end-of-the-line of the complementary metal oxide semiconductor (CMOS) need to be surmounted. These challenges have invigorated research into new materials such as III-V materials consisting of InP, GaAs, InGaAs for n-channel CMOS and Ge for p-channels CMOS to enhance device performance. These III-V materials have higher electron mobility that is required for the n-channel while Ge has high hole mobility that is required for the p-channel. Integration of these materials in future devices requires chemical mechanical polishing (CMP) to achieve a smooth and planar surface to enable further processing. The CMP process of these materials has been associated with environment, health and safety (EH&S) issues due to the presence of P and As that can lead to the formation of toxic gaseous hydrides. The safe handling of As contaminated consumables and post-CMP slurry waste is essential. In this work, the chemical mechanical polishing of InP, GaAs and InGaAs films and the associated environment, health and safety (EH&S) issues are discussed. InP removal rates (RRs) and phosphine generation during the CMP of blanket InP films in hydrogen peroxide-based silica particle dispersions in the presence and absence of three different multifunctional chelating carboxylic acids, namely oxalic acid, tartaric acid, and citric acid are reported. The presence of these acids in the polishing slurry resulted in good InP removal rates (about 400 nm min-1) and very low phosphine generation (< 15 ppb) with very smooth post-polish surfaces (0.1 nm RMS surface roughness). The optimized slurry compositions consisting of 3 wt % silica, 1 wt % hydrogen peroxide and 0.08 M oxalic acid or citric acid that provided the best results on blanket InP films were used to evaluate

  1. Achievement of Prolonged Oxygen Detection in Room-Temperature Ionic Liquids on Mechanically Polished Platinum Screen-Printed Electrodes.

    PubMed

    Lee, Junqiao; Arrigan, Damien W M; Silvester, Debbie S

    2016-05-17

    The demonstration of prolonged amperometric detection of oxygen in room-temperature ionic liquids (RTILs) was achieved by the use of mechanical polishing to activate platinum screen-printed electrodes (Pt-SPEs). The RTILs studied were 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) and N-butyl-N-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpyrr][NTf2]). It was found that voltammetry on polished Pt-SPEs exhibited less deterioration (in terms of voltammogram shapes, stability of peak currents, and appearance of contaminant peaks) from long-term consecutive cycling under 100% vol oxygen flow in both RTILs. The detection capability of these RTIL/Pt-SPE systems, initially subjected to long-term consecutive voltammetric cycling, was also investigated by cyclic voltammetry (CV) and long-term chronoamperometry (LTCA). Current versus concentration plots were linear on both unpolished and polished electrodes for 10-100% vol O2 (using CV) and 0.1-5% vol O2 (using LTCA). However, sensitivities and limits of detection (LODs) from CV were found to improve significantly on polished electrodes compared to unpolished electrodes, particularly in [C2mim][NTf2], but also moderately in [C4mpyrr][NTf2]. The lowest LODs (of ca. 0.1% vol O2) were found on polished SPEs using LTCA, with the most stable responses observed in [C4mpyrr][NTf2]. Calibration graphs could not be obtained on unpolished electrodes in both RTILs using LTCA. The results show that polishing markedly improves the analytical performances of Pt-SPEs for oxygen sensing in RTILs. The reusability of such disposable Pt-SPEs, after the surfaces had been experimentally fouled, was also demonstrated through the use of polishing. Mechanical polishing of Pt-SPE devices offers a viable approach to performance improvement for amperometric gas sensing. PMID:27063949

  2. Magnetoreological Fluid Template for Basic Studies of Mechanical-Chemical Effects During Polishing

    SciTech Connect

    Miao, C.; Bristol, K. M.; Marino, A.E.; Shafrir, S.N.; DeGroote, J.E.; Jacobs, S.D.

    2008-01-07

    We developed a new magnetorheological (MR) fluid for studying the relative contributions of mechanics and chemistry in polishing hard materials. The base carrier fluid is a mixture of two non-aqueous liquids. At conventional carbonyl iron (CI) magnetic particle concentrations, removal rates with this formulation were unacceptably low for the polycrystalline optical ceramic aluminum oxynitride (ALON). We overcame this problem by creating a high magnetic solids concentration suspension consisting of blend of large and small CI particles. Our test bed for experiments was a magnetorheological finishing (MRF) spot-taking machine (STM) that can only polish spots into a non-rotating part. We demonstrated that, using this new MR fluid formation, we could substantially increase peak removal rates on ALON with small additions of nonmagnetic, nanodiamond abrasives. Material removal with this fluid was assumed to be predominately driven by mechanics. With the addition of small amounts of DI water to the base fluid containing nanodiamonds, the peak removal rate showed an additional increase, presumably due to the altered fluid rheology and possibly chemical interactions. In this paper we describe the difficult fluid viscosity issues that were addressed in creating a viable, high removal rate, non-aqueous MR fluid template that could be pumped in the STM for several days of experiments.

  3. A novel approach of chemical mechanical polishing for cadmium zinc telluride wafers.

    PubMed

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Kang, Renke; Zhang, Bi; Guo, Dongming

    2016-01-01

    A novel approach of chemical mechanical polishing (CMP) is developed for cadmium zinc telluride (CdZnTe or CZT) wafers. The approach uses environment-friendly slurry that consists of mainly silica, hydrogen peroxide, and citric acid. This is different from the previously reported slurries that are usually composed of strong acid, alkali, and bromine methanol, and are detrimental to the environment and operators. Surface roughness 0.5 nm and 4.7 nm are achieved for Ra and peak-to-valley (PV) values respectively in a measurement area of 70 × 50 μm(2), using the developed novel approach. Fundamental polishing mechanisms are also investigated in terms of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Hydrogen peroxide dominates the passivating process during the CMP of CZT wafers, indicating by the lowest passivation current density among silica, citric acid and hydrogen peroxide solution. Chemical reaction equations are proposed during CMP according to the XPS and electrochemical measurements. PMID:27225310

  4. A novel approach of chemical mechanical polishing for cadmium zinc telluride wafers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Kang, Renke; Zhang, Bi; Guo, Dongming

    2016-05-01

    A novel approach of chemical mechanical polishing (CMP) is developed for cadmium zinc telluride (CdZnTe or CZT) wafers. The approach uses environment-friendly slurry that consists of mainly silica, hydrogen peroxide, and citric acid. This is different from the previously reported slurries that are usually composed of strong acid, alkali, and bromine methanol, and are detrimental to the environment and operators. Surface roughness 0.5 nm and 4.7 nm are achieved for Ra and peak-to-valley (PV) values respectively in a measurement area of 70 × 50 μm2, using the developed novel approach. Fundamental polishing mechanisms are also investigated in terms of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Hydrogen peroxide dominates the passivating process during the CMP of CZT wafers, indicating by the lowest passivation current density among silica, citric acid and hydrogen peroxide solution. Chemical reaction equations are proposed during CMP according to the XPS and electrochemical measurements.

  5. A novel approach of chemical mechanical polishing for cadmium zinc telluride wafers

    PubMed Central

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Kang, Renke; Zhang, Bi; Guo, Dongming

    2016-01-01

    A novel approach of chemical mechanical polishing (CMP) is developed for cadmium zinc telluride (CdZnTe or CZT) wafers. The approach uses environment-friendly slurry that consists of mainly silica, hydrogen peroxide, and citric acid. This is different from the previously reported slurries that are usually composed of strong acid, alkali, and bromine methanol, and are detrimental to the environment and operators. Surface roughness 0.5 nm and 4.7 nm are achieved for Ra and peak-to-valley (PV) values respectively in a measurement area of 70 × 50 μm2, using the developed novel approach. Fundamental polishing mechanisms are also investigated in terms of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Hydrogen peroxide dominates the passivating process during the CMP of CZT wafers, indicating by the lowest passivation current density among silica, citric acid and hydrogen peroxide solution. Chemical reaction equations are proposed during CMP according to the XPS and electrochemical measurements. PMID:27225310

  6. Effects of chemo-mechanical polishing on CdZnTe X-ray and gamma-ray detectors

    DOE PAGESBeta

    Egarievwe, Stephen E.; Hossain, Anwar; Okwechime, Ifechukwude O.; Gul, Rubi; James, Ralph B.

    2015-06-23

    Here, mechanically polishing cadmium zinc telluride (CdZnTe) wafers for x-ray and gamma-ray detectors often is inadequate in removing surface defects caused by cutting them from the ingots. Fabrication-induced defects, such as surface roughness, dangling bonds, and nonstoichiometric surfaces, often are reduced through polishing and etching the surface. In our earlier studies of mechanical polishing with alumina powder, etching with hydrogen bromide in hydrogen peroxide solution, and chemomechanical polishing with bromine–methanol–ethylene glycol solution, we found that the chemomechanical polishing process produced the least surface leakage current. In this research, we focused on using two chemicals to chemomechanically polish CdZnTe wafers aftermore » mechanical polishing, viz. bromine–methanol–ethylene glycol (BME) solution, and hydrogen bromide (HBr) in a hydrogen peroxide and ethylene–glycol solution. We used x-ray photoelectron spectroscopy (XPS), current–voltage (I–V) measurements, and Am-241 spectral response measurements to characterize and compare the effects of each solution. The results show that the HBr-based solution produced lower leakage current than the BME solution. Results from using the same chemomechanical polishing solution on two samples confirmed that the surface treatment affects the measured bulk current (a combination of bulk and surface currents). XPS results indicate that the tellurium oxide to tellurium peak ratios for the mechanical polishing process were reduced significantly by chemomechanical polishing using the BME solution (78.9% for Te 3d5/2O2 and 76.7% for Te 3d3/2O2) compared with the HBr-based solution (27.6% for Te 3d5/2O2 and 35.8% for Te 3d3/2O2). Spectral response measurements showed that the 59.5-keV peak of Am-241 remained under the same channel number for all three CdZnTe samples. While the BME-based solution gave a better performance of 7.15% full-width at half-maximum (FWHM) compared with 7.59% FWHM

  7. Effects of chemo-mechanical polishing on CdZnTe X-ray and gamma-ray detectors

    SciTech Connect

    Egarievwe, Stephen E.; Hossain, Anwar; Okwechime, Ifechukwude O.; Gul, Rubi; James, Ralph B.

    2015-06-23

    Here, mechanically polishing cadmium zinc telluride (CdZnTe) wafers for x-ray and gamma-ray detectors often is inadequate in removing surface defects caused by cutting them from the ingots. Fabrication-induced defects, such as surface roughness, dangling bonds, and nonstoichiometric surfaces, often are reduced through polishing and etching the surface. In our earlier studies of mechanical polishing with alumina powder, etching with hydrogen bromide in hydrogen peroxide solution, and chemomechanical polishing with bromine–methanol–ethylene glycol solution, we found that the chemomechanical polishing process produced the least surface leakage current. In this research, we focused on using two chemicals to chemomechanically polish CdZnTe wafers after mechanical polishing, viz. bromine–methanol–ethylene glycol (BME) solution, and hydrogen bromide (HBr) in a hydrogen peroxide and ethylene–glycol solution. We used x-ray photoelectron spectroscopy (XPS), current–voltage (I–V) measurements, and Am-241 spectral response measurements to characterize and compare the effects of each solution. The results show that the HBr-based solution produced lower leakage current than the BME solution. Results from using the same chemomechanical polishing solution on two samples confirmed that the surface treatment affects the measured bulk current (a combination of bulk and surface currents). XPS results indicate that the tellurium oxide to tellurium peak ratios for the mechanical polishing process were reduced significantly by chemomechanical polishing using the BME solution (78.9% for Te 3d5/2O2 and 76.7% for Te 3d3/2O2) compared with the HBr-based solution (27.6% for Te 3d5/2O2 and 35.8% for Te 3d3/2O2). Spectral response measurements showed that the 59.5-keV peak of Am-241 remained under the same channel number for all three CdZnTe samples. While the BME-based solution gave a better

  8. Particles detection and analysis of hard disk substrate after cleaning of post chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Huang, Yating; Lu, Xinchun; Pan, Guoshun; Lee, Bill; Luo, Jianbin

    2009-08-01

    Scrub, ultrasonic and megasonic are widely used in industry as post-CMP (chemical mechanical polishing/planarization) cleaning procedure. In this paper experiments and results are described to analyze the particle contaminations of hard disk substrate after each process of post-CMP cleaning. A scatter spot method has been exploited to detect the location and characteristics of the particles. SEM with EDX is used to observe and analyze the particles' shape and size as well as the elements. The results indicate that brush scrub process can remove 99% contaminations after CMP but not that efficient for submicron particle. Megasonic is a refined method for cleaning nano-particles. However, contaminations like metallic particles and bacteria from the equipment may cause pollution. The abrasive particles embedded in the plating pits cannot be removed by mechanical force. Pollution in the dryer is also discussed.

  9. The intrinsically high pitting corrosion resistance of mechanically polished nitinol in simulated physiological solutions.

    PubMed

    Bai, Zhijun; Rotermund, Harm H

    2011-10-01

    Nitinol wires have been widely used in many biomedical applications, such as cardiovascular stent due to their superelasticity and shape memory effect. However, their corrosion properties and the related biocompatibility are not well understood, and the reported results are controversial. In this study, we evaluate the pitting corrosion property of nitinol, titanium, nickel, and 316L stainless steel (316LSS) wires with different surface roughnesses in a saline solution at 37 °C. The cyclic potentiodynamic polarization results show that mechanically polished nitinol and Ti wires are highly resistant to pitting corrosion, while Ni and 316LSS wires are susceptible to pitting corrosion. Electrochemical impedance spectroscopy is used to study the interface of oxide film/solution and all mechanically polished nitinol wires are covered by 2-3 nm thick films formed under open circuit potential. Furthermore, the electronic structures and semiconducting properties of passive films on nitinol, Ti and Ni wires are studied by Mott-Schottky analysis. Passive films formed on nitinol and Ti exhibit n-type semiconducting characteristics, whereas films on Ni show p-type semiconducting characteristics. Scanning Kelvin Microscopy is used to measure the surface potential difference between common inclusions from the nitinol matrix and the results indicate that the inclusions are more electrochemically noble than the nitinol matrix. Band energy theory is used to model the electrochemical interface between the passive films of nitinol and the solution under different applied potential conditions. A mechanism for the strong pitting corrosion resistance of nitinol in saline solution is proposed. PMID:21648066

  10. Tunable removal rates of silicon dioxide, silicon nitride and polysilicon films during chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Dandu, Veera P. R.

    Achieving a high Si3N4 removal rate and a relatively low SiO2 removal rate, which is challenging but promising for emerging applications for sub-32 nm node devices, was investigated. This was thought to be impossible as the removal of Si3N4 usually follows a two-step mechanism in which silicon nitride is hydrolyzed first and then removed during CMP. Therefore, additives normally used to suppress the SiO 2 removal rate would tend to suppress the S3N4 removal rate as well. However, it was shown that by using a specific type of a cationic polymer in ceria-based dispersions, a low SiO2 removal rate (<2 nm/min) and relatively high Si3N4 removal rate (˜120 nm/min) can be achieved. These results have been extended to processes involved in MEMS and FinFET fabrication, where a polysilicon layer has to be selectively polished/protected with respect to silicon dioxide and/or silicon nitride layers. Several dispersions were identified which yield tunable removal rates of polysilicon (from <2 nm/min to ˜1 microm/min), silicon dioxide (<2 nm/min to ˜500 nm/min) and silicon nitride (<2 nm/min to ˜120 nm/min) films. This has been made possible by using several additives in ceria and silica based dispersions with and without surface functionalization at different pH values. A fundamental investigation of the interaction of the additive(s) with the abrasives, SiO2 Si3N4, and polysilicon films was also carried out in order to elucidate the removal mechanisms. Zeta potential measurements, UV-Vis Spectroscopy, adsorption isotherms and thermo gravimetric analysis were performed to understand the adsorption behavior of these additives on abrasives and polishing films at different pH values. It was observed that the Ce3+ on the surface of the ceria abrasives is reacting with the silicon dioxide and suboxide on the silicon nitride surfaces during polishing. Also, it appears that electrostatic interactions in conjunction with the reactivity of the active sites on the surface of

  11. Frictional Characterization of Chemical-Mechanical Polishing Pad Surface and Diamond Conditioner Wear

    NASA Astrophysics Data System (ADS)

    Yamada, Yohei; Kawakubo, Masanori; Hirai, Osamu; Konishi, Nobuhiro; Kurokawa, Syuhei; Doi, Toshiro

    2008-08-01

    We evaluated a contact metrology instrument used in chemical-mechanical polishing (CMP) systems for high-volume manufacture and examined in situ coefficient of friction (COF) monitoring to identify the tribology of CMP, and subsequently to determine the useful lifespan of consumables. The results showed that the direct measurement of the wear of the pad allowed for an accurate determination of both pad thickness and the ideal time to replace the pad and conditioner disk based on pad wear rate. We also presented a clear correlation between the working grid area of the conditioner disk and the tribological behavior of the pad break-in procedure, leading to the result showing that the variation in tungsten film removal rate decreased as the working grid density of the conditioner disk increased. This study has proven the effectiveness of measuring friction force for better CMP control.

  12. Efficient polishing of aspheric optics

    SciTech Connect

    Taylor, J.S.; Piscotty, M.A.; Nguyen, N.Q.; Landram, C.S.; Ng, L.C.

    1997-04-15

    The objectives of this project are to develop, evaluate, and optimize novel designs for a polishing tool intended for ultra-precise figure corrections on aspheric optics with tolerances typical of those required for use in extreme ultraviolet (EUV) projection lithography. This work may lead to an enhanced US industrial capability for producing optics for EUV, x-ray and, other high precision applications. LLNL benefits from developments in computer-controlled polishing and the insertion of fluid mechanics modeling into the precision manufacturing area. Our accomplishments include the numerical estimation of the hydrodynamic shear stress distribution for a new polishing tool that directs and controls the interaction of an abrasive slurry with an optical surface. A key milestone is in establishing a correlation between the shear stress predicted using our fluid mechanics model and the observed removal footprint created by a prototype tool. In addition, we demonstrate the ability to remove 25 nm layers of optical glass in a manner qualitatively similar to macroscopic milling operations using a numerically- controlled machine tool. Other accomplishments include the development of computer control software for directing the polishing tool and the construction of a polishing testbed.

  13. Use of chemical-mechanical polishing for fabricating photonic bandgap structures

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Hetherington, Dale L.; Smith, Bradley K.

    1999-01-01

    A method is disclosed for fabricating a two- or three-dimensional photonic bandgap structure (also termed a photonic crystal, photonic lattice, or photonic dielectric structure). The method uses microelectronic integrated circuit (IC) processes to fabricate the photonic bandgap structure directly upon a silicon substrate. One or more layers of arrayed elements used to form the structure are deposited and patterned, with chemical-mechanical polishing being used to planarize each layer for uniformity and a precise vertical tolerancing of the layer. The use of chemical-mechanical planarization allows the photonic bandgap structure to be formed over a large area with a layer uniformity of about two-percent. Air-gap photonic bandgap structures can also be formed by removing a spacer material separating the arrayed elements by selective etching. The method is useful for fabricating photonic bandgap structures including Fabry-Perot resonators and optical filters for use at wavelengths in the range of about 0.2-20 .mu.m.

  14. Iron trichloride as oxidizer in acid slurry for chemical mechanical polishing of Ge2Sb2Te5

    NASA Astrophysics Data System (ADS)

    Yan, Wei-Xia; Wang, Liang-Yong; Zhang, Ze-Fang; Liu, Wei-Li; Song, Zhi-Tang

    2014-04-01

    The effect of iron trichloride (FeCl3) on chemical mechanical polishing (CMP) of Ge2Sb2Te5 (GST) film is investigated in this paper. The polishing rate of GST increases from 38 nm/min to 144 nm/min when the FeCl3 concentration changes from 0.01 wt% to 0.15 wt%, which is much faster than 20 nm/min for the 1 wt% H2O2-based slurry. This polishing rate trends are inversely correlated with the contact angle data of FeCl3-based slurry on the GST film surface. Thus, it is hypothesized that the hydrophilicity of the GST film surface is associated with the polishing rate during CMP. Atomic force microscope (AFM) and optical microscope (OM) are used to characterize the surface quality after CMP. The chemical mechanism is studied by potentiodynamic measurements such as Ecorr and Icorr to analyze chemical reaction between FeCl3 and GST surface. Finally, it is verified that slurry with FeCl3 has no influence on the electrical property of the post-CMP GST film by the resistivity-temperature (RT) tests.

  15. Brush Scrub Cleaning after Spraying Ozonized Water on Si Wafer Treated by Chemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Kurokawa, Yoshiaki; Hayashi, Kounosuke; Nishimura, Eriko; Saito, Reiko; Maki, Kunisuke

    2008-09-01

    To clean the surface of 300-mm-diameter silicon wafers treated by chemical mechanical polishing (CMP), the following steps were performed: (1) the wafer surfaces were first terminated with hydrogen using an etching solution of hydrofluoric acid, and (2) the wafers were then spun while ozonized water was sprayed before brush scrub cleaning was performed. The number of particles more than 100 nm in diameter remaining on the wafer decreased linearly with increasing time after spraying ozonized water for approximately 5 s before brush scrub cleaning. The wafers had fewer than 10 particles after spraying ozonized water for approximately 15 s followed by brush scrub cleaning. Such a cleaning effect was not accomplished when the ozonized water was not sprayed. A model of the brush scrub cleaning process is discussed from the view point that an oxide film is first formed on the wafer surface where no particles are adhered, and then grows laterally beneath the particles. The force then applied by the brush scrubber overcomes the adhesion force between the particles and the wafer, which results in their removal when the oxide layer reaches a sufficient thickness. The growth of the oxide film was confirmed by observing the spectra obtained by attenuated total reflectance spectroscopy (ATR) using a Fourier transform infrared spectroscope (FTIR) and by X-ray photoelectron spectroscopy (XPS).

  16. The way to zeros: The future of semiconductor device and chemical mechanical polishing technologies

    NASA Astrophysics Data System (ADS)

    Tsujimura, Manabu

    2016-06-01

    For the last 60 years, the development of cutting-edge semiconductor devices has strongly emphasized scaling; the effort to scale down current CMOS devices may well achieve the target of 5 nm nodes by 2020. Planarization by chemical mechanical polishing (CMP), is one technology essential for supporting scaling. This paper summarizes the history of CMP transitions in the planarization process as well as the changing degree of planarity required, and, finally, introduces innovative technologies to meet the requirements. The use of CMP was triggered by the replacement of local oxidation of silicon (LOCOS) as the element isolation technology by shallow trench isolation (STI) in the 1980s. Then, CMP’s use expanded to improving embedability of aluminum wiring, tungsten (W) contacts, Cu wiring, and, more recently, to its adoption in high-k metal gate (HKMG) and FinFET (FF) processes. Initially, the required degree of planarity was 50 nm, but now 0 nm is required. Further, zero defects on a post-CMP wafer is now the goal, and it is possible that zero psi CMP loading pressure will be required going forward. Soon, it seems, everything will have to be “zero” and perfect. Although the process is also chemical in nature, the CMP process is actually mechanical with a load added using slurry particles several tens of nm in diameter. Zero load in the loading process, zero nm planarity with no trace of processing, and zero residual foreign material, including the very slurry particles used in the process, are all required. This article will provide an overview of how to achieve these new requirements and what technologies should be employed.

  17. Effect of mechanical polishing on corrosion behavior of Hastelloy C22 coating prepared by high power diode laser cladding

    NASA Astrophysics Data System (ADS)

    Wang, Qin-Ying; Bai, Shu-Lin; Zhao, Yun-Hong; Liu, Zong-De

    2014-06-01

    Hastelloy C22 coatings were prepared on mild steel by high power diode laser cladding technique. In order to investigate the effect of mechanical polishing on corrosion behavior, the coatings with original surface (coating C1) and new surfaces after mechanical polishing away of 0.3 mm (coating C2) and 0.6 mm (coating C3) in depth were studied. Their microstructures and compositions were measured, and corrosion resistance in seawater was studied. The planar, cellular and dendritic solidifications were found from the coating/substrate interface to the top surface of coatings. In coating C1, smallest size primary solidification containing mainly Ni and largest quantity of eutectic networks composed of Cr, Mo and W are dominant, and harmful carbide M(Cr, W)2C is found. While Mo6Ni6C phase exists only in coatings C2 and C3. The open circuit potential and electrochemical impedance spectroscopy of coating C1 are higher within two days, and then lower later than the other two coatings. Coatings C2 and C3 display larger stable radius of capacitive loop and lower corrosion current density owing to higher contents of Cr and Mo, as well as no harmful carbide at surface, which reveals higher corrosion resistance and lower corrosion rate than coating C1. Consequently, properly mechanical polishing of original coating surface is beneficial for improving its corrosion resistance.

  18. Suppression of blister formation and deuterium retention on tungsten surface due to mechanical polishing and helium pre-exposure

    NASA Astrophysics Data System (ADS)

    Nishijima, D.; Iwakiri, H.; Amano, K.; Ye, M. Y.; Ohno, N.; Tokunaga, K.; Yoshida, N.; Takamura, S.

    2005-07-01

    Low-energy deuterium (D) plasma exposure on tungsten (W), which is an important material for ITER, results in blister formation on the surface. Blister formation increases both micron-sized dust production and D retention. Blister formation depends greatly on surface pre-treatment. Deuterium plasma exposure on mirror-finished powder metallurgy W at 500 K for 3 h forms a blister with a diameter of a few hundred micrometres on the surface. Blister formations on the mechanically-polished and helium-pre-exposed surfaces are drastically suppressed. Deuterium retention is also reduced on both the mechanically-polished surface and the helium-pre-exposed surface compared with that on the mirror-finished surface. The suppressive effect of blister formation on the mechanically-polished surface is maintained for 50 h. The size of blisters and D retention on mirror-finished surface exposed for 50 h increases by some degrees (<~500 µm, 7 × 1020 m-2) compared with that on mirror-finished surface exposed for 3 h (<~200 µm, 5 × 1020 m-2), but is not proportional to the exposure time. The saturation level of D retention even on blister-rich surfaces seems to be lower than an order of 1021 D2 m-2.

  19. A novel approach of chemical mechanical polishing using environment-friendly slurry for mercury cadmium telluride semiconductors

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Guo, Dongming; Kang, Renke; Zhang, Bi

    2016-03-01

    A novel approach of chemical mechanical polishing (CMP) is developed for mercury cadmium telluride (HgCdTe or MCT) semiconductors. Firstly, fixed-abrasive lapping is used to machine the MCT wafers, and the lapping solution is deionized water. Secondly, the MCT wafers are polished using the developed CMP slurry. The CMP slurry consists of mainly SiO2 nanospheres, H2O2, and malic and citric acids, which are different from previous CMP slurries, in which corrosive and toxic chemical reagents are usually employed. Finally, the polished MCT wafers are cleaned and dried by deionized water and compressed air, respectively. The novel approach of CMP is environment-friendly. Surface roughness Ra, and peak-to-valley (PV) values of 0.45, and 4.74 nm are achieved, respectively on MCT wafers after CMP. The first and second passivating processes are observed in electrochemical measurements on MCT wafers. The fundamental mechanisms of CMP are proposed according to the X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Malic and citric acids dominate the first passivating process, and the CMP slurry governs the second process. Te4+3d peaks are absent after CMP induced by the developed CMP slurry, indicating the removing of oxidized films on MCT wafers, which is difficult to achieve using single H2O2 and malic and citric acids solutions.

  20. A novel approach of chemical mechanical polishing using environment-friendly slurry for mercury cadmium telluride semiconductors

    PubMed Central

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Guo, Dongming; Kang, Renke; Zhang, Bi

    2016-01-01

    A novel approach of chemical mechanical polishing (CMP) is developed for mercury cadmium telluride (HgCdTe or MCT) semiconductors. Firstly, fixed-abrasive lapping is used to machine the MCT wafers, and the lapping solution is deionized water. Secondly, the MCT wafers are polished using the developed CMP slurry. The CMP slurry consists of mainly SiO2 nanospheres, H2O2, and malic and citric acids, which are different from previous CMP slurries, in which corrosive and toxic chemical reagents are usually employed. Finally, the polished MCT wafers are cleaned and dried by deionized water and compressed air, respectively. The novel approach of CMP is environment-friendly. Surface roughness Ra, and peak-to-valley (PV) values of 0.45, and 4.74 nm are achieved, respectively on MCT wafers after CMP. The first and second passivating processes are observed in electrochemical measurements on MCT wafers. The fundamental mechanisms of CMP are proposed according to the X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Malic and citric acids dominate the first passivating process, and the CMP slurry governs the second process. Te4+3d peaks are absent after CMP induced by the developed CMP slurry, indicating the removing of oxidized films on MCT wafers, which is difficult to achieve using single H2O2 and malic and citric acids solutions. PMID:26926622

  1. A novel approach of chemical mechanical polishing using environment-friendly slurry for mercury cadmium telluride semiconductors.

    PubMed

    Zhang, Zhenyu; Wang, Bo; Zhou, Ping; Guo, Dongming; Kang, Renke; Zhang, Bi

    2016-01-01

    A novel approach of chemical mechanical polishing (CMP) is developed for mercury cadmium telluride (HgCdTe or MCT) semiconductors. Firstly, fixed-abrasive lapping is used to machine the MCT wafers, and the lapping solution is deionized water. Secondly, the MCT wafers are polished using the developed CMP slurry. The CMP slurry consists of mainly SiO2 nanospheres, H2O2, and malic and citric acids, which are different from previous CMP slurries, in which corrosive and toxic chemical reagents are usually employed. Finally, the polished MCT wafers are cleaned and dried by deionized water and compressed air, respectively. The novel approach of CMP is environment-friendly. Surface roughness Ra, and peak-to-valley (PV) values of 0.45, and 4.74 nm are achieved, respectively on MCT wafers after CMP. The first and second passivating processes are observed in electrochemical measurements on MCT wafers. The fundamental mechanisms of CMP are proposed according to the X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Malic and citric acids dominate the first passivating process, and the CMP slurry governs the second process. Te(4+)3d peaks are absent after CMP induced by the developed CMP slurry, indicating the removing of oxidized films on MCT wafers, which is difficult to achieve using single H2O2 and malic and citric acids solutions. PMID:26926622

  2. Precision machining, polishing and measurement of mechanical and toxicological properties of lead tungstate crystals for the CMS electromagnetic calorimeter

    SciTech Connect

    Wuest, C.R.; Fuchs, B.A.; Shi, X.

    1995-08-01

    We have developed new machining and polishing techniques that have previously been applied to large scintillating crystal arrays for high energy physics experiments such as the Barium Fluoride Electromagnetic Calorimeter for the GEM Detector at SSCL, the LCsI Electromagnetic Calorimeter for the BaBar Detector at PEP-II B Factory at SLAC and the 110,000 crystal CMS Lead Tungstate Electromagnetic Calorimeter at LHC at CERN. We discuss earlier results achieved with diamond machining and polishing methods and present new results on diamond machining of lead tungstate crystals. Additionally we present new results on mechanical properties of lead tungstate including toxicological data important for the safe handling and processing of this material.

  3. Cleaning by Brush-Scrubbing of Chemical Mechanical Polished Silicon Surfaces Using Ozonized Water and Diluted HF

    NASA Astrophysics Data System (ADS)

    Kurokawa, Yoshiaki; Hirose, Harumichi; Moriya, Takahiko; Kimura, Chouichi

    1999-09-01

    A new process for scrubbing chemical-mechanical-polished silicon wafer surfaces with a brush (brush-scrubbing process) was developed. The scrubbing is performed in two stages; the first stage involves a wet treatment using ozonized water and dilute HF. The second stage involves scrubbing with a Poly(vinyl alcohol)(PVA) brush. After scrubbing, the number of residual particles, metal and carbonaceous contamination, and surface roughness of the silicon wafer surface were evaluated. It was determined that this new brush-scrubbing process efficiently removed particles from chemical mechanical polishedsilicon surfaces. Finally, a model explaining the new brush-scrubbingprocess is constructed.

  4. RNA-Seq and iTRAQ Reveal the Dwarfing Mechanism of Dwarf Polish Wheat (Triticum polonicum L.)

    PubMed Central

    Wang, Yi; Xiao, Xue; Wang, Xiaolu; Zeng, Jian; Kang, Houyang; Fan, Xing; Sha, Lina; Zhang, Haiqin; Zhou, Yonghong

    2016-01-01

    The dwarfing mechanism of Rht-dp in dwarf Polish wheat (DPW) is unknown. Each internode of DPW was significantly shorter than it in high Polish wheat (HPW), and the dwarfism was insensitive to photoperiod, abscisic acid (ABA), gibberellin (GA), cytokinin (CK), auxin and brassinolide (BR). To understand the mechanism, three sets of transcripts, DPW, HPW, and a chimeric set (a combination of DPW and HPW), were constructed using RNA sequencing (RNA-Seq). Based on the chimeric transcripts, 2,446 proteins were identified using isobaric tags for relative and absolute quantification (iTRAQ). A total of 108 unigenes and 12 proteins were considered as dwarfism-related differentially expressed genes (DEGs) and differentially expressed proteins (DEPs), respectively. Among of these DEGs and DEPs, 6 DEGs and 6 DEPs were found to be involved in flavonoid and S-adenosyl-methionine (SAM) metabolisms; 5 DEGs and 3 DEPs were involved in cellulose metabolism, cell wall plasticity and cell expansion; 2 DEGs were auxin transporters; 2 DEPs were histones; 1 DEP was a peroxidase. These DEGs and DEPs reduced lignin and cellulose contents, increased flavonoid content, possibly decreased S-adenosyl-methionine (SAM) and polyamine contents and increased S-adenosyl-L-homocysteine hydrolase (SAHH) content in DPW stems, which could limit auxin transport and reduce extensibility of the cell wall, finally limited cell expansion (the cell size of DPW was significantly smaller than HPW cells) and caused dwarfism in DPW. PMID:27194943

  5. RNA-Seq and iTRAQ Reveal the Dwarfing Mechanism of Dwarf Polish Wheat (Triticum polonicum L.).

    PubMed

    Wang, Yi; Xiao, Xue; Wang, Xiaolu; Zeng, Jian; Kang, Houyang; Fan, Xing; Sha, Lina; Zhang, Haiqin; Zhou, Yonghong

    2016-01-01

    The dwarfing mechanism of Rht-dp in dwarf Polish wheat (DPW) is unknown. Each internode of DPW was significantly shorter than it in high Polish wheat (HPW), and the dwarfism was insensitive to photoperiod, abscisic acid (ABA), gibberellin (GA), cytokinin (CK), auxin and brassinolide (BR). To understand the mechanism, three sets of transcripts, DPW, HPW, and a chimeric set (a combination of DPW and HPW), were constructed using RNA sequencing (RNA-Seq). Based on the chimeric transcripts, 2,446 proteins were identified using isobaric tags for relative and absolute quantification (iTRAQ). A total of 108 unigenes and 12 proteins were considered as dwarfism-related differentially expressed genes (DEGs) and differentially expressed proteins (DEPs), respectively. Among of these DEGs and DEPs, 6 DEGs and 6 DEPs were found to be involved in flavonoid and S-adenosyl-methionine (SAM) metabolisms; 5 DEGs and 3 DEPs were involved in cellulose metabolism, cell wall plasticity and cell expansion; 2 DEGs were auxin transporters; 2 DEPs were histones; 1 DEP was a peroxidase. These DEGs and DEPs reduced lignin and cellulose contents, increased flavonoid content, possibly decreased S-adenosyl-methionine (SAM) and polyamine contents and increased S-adenosyl-L-homocysteine hydrolase (SAHH) content in DPW stems, which could limit auxin transport and reduce extensibility of the cell wall, finally limited cell expansion (the cell size of DPW was significantly smaller than HPW cells) and caused dwarfism in DPW. PMID:27194943

  6. Development of highly-mechanically polished metal-substrate for neutron supermirrors

    NASA Astrophysics Data System (ADS)

    Takeda, Shin; Guo, Jiang; Morita, Shinya; Ono, Hirohisa; Oda, Tatsuro; Kato, Junichi; Sato, Hirotaka; Hino, Masahiro; Yamagata, Yutaka; Furusaka, Michihiro

    2014-07-01

    A small-angle neutron scattering instrument using an ellipsoidal focusing mirror has been developed at Hokkaido University and a prototype machine (mfSANS) has been installed at the JRR-3 research reactor at Japan Atomic Energy Agency (JAEA). They are based on an ellipsoidal focusing mirror on a borosilicate glass substrate. It turned out that borosilicate glass was very brittle and difficult to machine or polish it to the required surface-finishing process. In order to improve this situation, we decided to develop a method to create a metal substrate based ellipsoidal focusing mirror. As the first step, test pieces of flat and ellipsoidal surface neutron supermirrors using metal substrates were fabricated. They were first roughly shaped by a conventional numerically controlled (NC) cutting machine and amorphous NiP was plated. They were then machined using an ultrahigh precision cutting (UPC) method and finished by NC polishing techniques. Surface roughness of Ra ≈ 0.78 nm and surface figure error of submicrometer were realized so far.

  7. Corrosion Investigations of Ruthenium in Potassium Periodate Solutions Relevant for Chemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Cheng, Jie; Wang, Tongqing; Pan, Jinshan; Lu, Xinchun

    2016-05-01

    Ruthenium is the most promising material for the barrier layer used for the sub 14 nm technology node in integrated circuits manufacturing. Potassium periodate (KIO4)-based slurry is used in the chemical mechanical planarization (CMP) process of the barrier layer. However, the electrochemical and corrosion properties of ruthenium have not been investigated in such slurry. In this paper, the electrochemical and corrosion behaviors of ruthenium in KIO4 solutions were investigated under static conditions but at different pH values by potentiodynamic polarization and electrochemical impedance spectroscopy measurements, combined with surface chemical analysis using auger electron spectroscopy. Moreover, to study wear enhanced corrosion during CMP, tribocorrosion experiments were carried out to monitor the current density changes during and after mechanical scratching. The results show that at pH 6, ruthenium forms a relatively thick and heterogeneous surface film composed of RuO2·2H2O/RuO3, showing a high corrosion resistance and it exhibits a quick repassivation after mechanical scratching. At pH 4, ruthenium shows a passivation behavior with formation of a uniform and conductive oxide like RuO2·2H2O. It should be noted that there is a possible formation of RuO4 toxic gas under this condition, which should be avoided in the actual production. However, at pH 11, ruthenium exhibits no considerable passivity and the corrosion proceeds uniformly.

  8. Corrosion Investigations of Ruthenium in Potassium Periodate Solutions Relevant for Chemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Cheng, Jie; Wang, Tongqing; Pan, Jinshan; Lu, Xinchun

    2016-08-01

    Ruthenium is the most promising material for the barrier layer used for the sub 14 nm technology node in integrated circuits manufacturing. Potassium periodate (KIO4)-based slurry is used in the chemical mechanical planarization (CMP) process of the barrier layer. However, the electrochemical and corrosion properties of ruthenium have not been investigated in such slurry. In this paper, the electrochemical and corrosion behaviors of ruthenium in KIO4 solutions were investigated under static conditions but at different pH values by potentiodynamic polarization and electrochemical impedance spectroscopy measurements, combined with surface chemical analysis using auger electron spectroscopy. Moreover, to study wear enhanced corrosion during CMP, tribocorrosion experiments were carried out to monitor the current density changes during and after mechanical scratching. The results show that at pH 6, ruthenium forms a relatively thick and heterogeneous surface film composed of RuO2·2H2O/RuO3, showing a high corrosion resistance and it exhibits a quick repassivation after mechanical scratching. At pH 4, ruthenium shows a passivation behavior with formation of a uniform and conductive oxide like RuO2·2H2O. It should be noted that there is a possible formation of RuO4 toxic gas under this condition, which should be avoided in the actual production. However, at pH 11, ruthenium exhibits no considerable passivity and the corrosion proceeds uniformly.

  9. Control of adhesion force between ceria particles and polishing pad in shallow trench isolation chemical mechanical planarization.

    PubMed

    Seo, Jihoon; Moon, Jinok; Bae, Jae-Young; Yoon, Kwang Seob; Sigmund, Wolfgang; Paik, Ungyu

    2014-06-01

    The adhesion force between ceria and polyurethane (PU) pad was controlled to remove the step height from cell region to peripheral region during Shallow Trench Isolation Chemical Mechanical Planarization (STI-CMP) for NAND flash. Picolinic acid was found to be adsorbed on ceria particles at pH 4.5 following a Langmuir isotherm with the maximum adsorbed amount of 0.36 mg/m2. The ceria suspension with full surface coverage of picolinic acid showed a threefold increase in the number of adhered ceria particles on the PU pad over non-coated ceria particles. It was shown that the coverage percent of picolinic acid on ceria corresponds well with the amount percent of adsorbed ceria on PU pad. The change in adsorbed particles was directly reflected in the CMP polishing process where significant improvements were achieved. Particularly, convex areas on the chip experienced higher friction force from the attached abrasives on the PU pad than concave areas. As a result, the convex areas have increased removal rate of step height compared to the ceria suspension without picolinic acid. The changing profiles of convex areas are reported during the step height reduction as a function of polishing time. PMID:24738395

  10. Tribo-mechanical properties of thin boron coatings deposited on polished cobalt alloy surfaces for orthopedic applications

    PubMed Central

    Klepper, C. C.; Williams, J. M.; Truhan, J.J.; Qu, J.; Riester, L.; Hazelton, R. C.; Moschella, J.J.; Blau, P.J.; Anderson, J.P.; Popoola, O.O.; Keitz, M.D.

    2008-01-01

    This paper presents experimental evidence that thin (<∼200 nm) boron coatings, deposited with a (vacuum) cathodic arc technique on pre-polished Co-Cr-Mo surfaces, could potentially extend the life of metal-on-polymer orthopedic devices using cast Co-Cr-Mo alloy for the metal component. The primary tribological test used a linear, reciprocating pin-on-disc arrangement, with pins made of ultra-high molecular weight polyethylene. The disks were cast Co-Cr-Mo samples that were metallographically polished and then coated with boron at a substrate bias of 500 V and at about 100 °C. The wear tests were carried out in a saline solution to simulate the biological environment. The improvements were manifested by the absence of a detectable wear track scar on the coated metal component, while significant polymer transfer film was detected on the uncoated (control) samples tested under the same conditions. The polymer transfer track was characterized with both profilometry and Rutherford Backscattering Spectroscopy. Mechanical characterization of the thin films included nano-indentation, as well as additional pin-on-disk tests with a steel ball to demonstrate adhesion, using ultra-high frequency acoustic microscopy to probe for any void occurrence at the coating-substrate interface. PMID:19340285

  11. Tribo-mechanical properties of thin boron coatings deposited on polished cobalt alloy surfaces for orthopedic applications.

    PubMed

    Klepper, C C; Williams, J M; Truhan, J J; Qu, J; Riester, L; Hazelton, R C; Moschella, J J; Blau, P J; Anderson, J P; Popoola, O O; Keitz, M D

    2008-03-31

    This paper presents experimental evidence that thin (< approximately 200 nm) boron coatings, deposited with a (vacuum) cathodic arc technique on pre-polished Co-Cr-Mo surfaces, could potentially extend the life of metal-on-polymer orthopedic devices using cast Co-Cr-Mo alloy for the metal component. The primary tribological test used a linear, reciprocating pin-on-disc arrangement, with pins made of ultra-high molecular weight polyethylene. The disks were cast Co-Cr-Mo samples that were metallographically polished and then coated with boron at a substrate bias of 500 V and at about 100 degrees C. The wear tests were carried out in a saline solution to simulate the biological environment. The improvements were manifested by the absence of a detectable wear track scar on the coated metal component, while significant polymer transfer film was detected on the uncoated (control) samples tested under the same conditions. The polymer transfer track was characterized with both profilometry and Rutherford Backscattering Spectroscopy. Mechanical characterization of the thin films included nano-indentation, as well as additional pin-on-disk tests with a steel ball to demonstrate adhesion, using ultra-high frequency acoustic microscopy to probe for any void occurrence at the coating-substrate interface. PMID:19340285

  12. Effects of Calcination and Milling Process Conditions for Ceria Slurry on Shallow-Trench-Isolation Chemical-Mechanical Polishing Performance

    NASA Astrophysics Data System (ADS)

    Kim, Jun-Seok; Kang, Hyun-Goo; Kanemoto, Manabu; Paik, Ungyu; Park, Jea-Gun

    2007-12-01

    To improve the performance of shallow trench isolation chemical-mechanical polishing (STI-CMP) in terms of the removal selectivity of oxide and nitride films and the formation of surface defects, we investigated the effects of the calcination and milling process conditions during ceria slurry synthesis. We have focused on the effects of particle size distribution, the large-particle size, and the dispersion stability in a ceria slurry. We determined the optimum bead size for milling and appropriate calcination temperatures in order to obtain a reasonable particle distribution, with lower numbers of fine primary particles and large, agglomerated particles, in ceria slurry. This was achieved by reducing the quantity of aggregated particles during milling and two-step calcination process generating higher-density particles. These results can be qualitatively explained by abrasive collisions occurring between the milling beads and the decarbonation of cerium carbonate through diffusion during the manufacturing process used for the ceria slurry.

  13. A nano-scale mirror-like surface of Ti–6Al–4V attained by chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Chenliang, Liang; Weili, Liu; Shasha, Li; Hui, Kong; Zefang, Zhang; Zhitang, Song

    2016-05-01

    Metal Ti and its alloys have been widely utilized in the fields of aviation, medical science, and micro-electro-mechanical systems, for its excellent specific strength, resistance to corrosion, and biological compatibility. As the application of Ti moves to the micro or nano scale, however, traditional methods of planarization have shown their short slabs. Thus, we introduce the method of chemical mechanical polishing (CMP) to provide a new way for the nano-scale planarization method of Ti alloys. We obtain a mirror-like surface, whose flatness is of nano-scale, via the CMP method. We test the basic mechanical behavior of Ti–6Al–4V (Ti64) in the CMP process, and optimize the composition of CMP slurry. Furthermore, the possible reactions that may take place in the CMP process have been studied by electrochemical methods combined with x-ray photoelectron spectroscopy (XPS). An equivalent circuit has been built to interpret the dynamic of oxidation. Finally, a model has been established to explain the synergy of chemical and mechanical effects in the CMP of Ti–6Al–4V. Project supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period of China (Grant No. 2009ZX02030-1), the National Natural Science Foundation of China (Grant No. 51205387), the Support by Science and Technology Commission of Shanghai City, China (Grant No. 11nm0500300), and the Science and Technology Commission of Shanghai City, China (Grant No. 14XD1425300).

  14. Preparation of Fe-doped colloidal SiO(2) abrasives and their chemical mechanical polishing behavior on sapphire substrates.

    PubMed

    Lei, Hong; Gu, Qian; Chen, Ruling; Wang, Zhanyong

    2015-08-20

    Abrasives are one of key influencing factors on surface quality during chemical mechanical polishing (CMP). Silica sol, a widely used abrasive in CMP slurries for sapphire substrates, often causes lower material removal rate (MRRs). In the present paper, Fe-doped colloidal SiO2 composite abrasives were prepared by a seed-induced growth method in order to improve the MRR of sapphire substrates. The CMP performance of Fe-doped colloidal SiO2 abrasives on sapphire substrates was investigated using UNIPOL-1502 CMP equipment. Experimental results indicate that the Fe-doped colloidal SiO2 composite abrasives exhibit lower surface roughness and higher MRR than pure colloidal SiO2 abrasives for sapphire substrates under the same testing conditions. Furthermore, the acting mechanism of Fe-doped colloidal SiO2 composite abrasives in sapphire CMP was analyzed by x-ray photoelectron spectroscopy. Analytical results show that the Fe in the composite abrasives can react with the sapphire substrates to form aluminum ferrite (AlFeO3) during CMP, which promotes the chemical effect in CMP and leads to improvement of MRR. PMID:26368752

  15. Atomistic Mechanisms of Chemical Mechanical Polishing of a Cu Surface in Aqueous H2O2: Tight-Binding Quantum Chemical Molecular Dynamics Simulations.

    PubMed

    Kawaguchi, Kentaro; Ito, Hiroshi; Kuwahara, Takuya; Higuchi, Yuji; Ozawa, Nobuki; Kubo, Momoji

    2016-05-11

    We applied our original chemical mechanical polishing (CMP) simulator based on the tight-binding quantum chemical molecular dynamics (TB-QCMD) method to clarify the atomistic mechanism of CMP processes on a Cu(111) surface polished with a SiO2 abrasive grain in aqueous H2O2. We reveal that the oxidation of the Cu(111) surface mechanically induced at the friction interface is a key process in CMP. In aqueous H2O2, in the first step, OH groups and O atoms adsorbed on a nascent Cu surface are generated by the chemical reactions of H2O2 molecules. In the second step, at the friction interface between the Cu surface and the abrasive grain, the surface-adsorbed O atom intrudes into the Cu bulk and dissociates the Cu-Cu bonds. The dissociation of the Cu-Cu back-bonds raises a Cu atom from the surface that is mechanically sheared by the abrasive grain. In the third step, the raised Cu atom bound to the surface-adsorbed OH groups is removed from the surface by the generation and desorption of a Cu(OH)2 molecule. In contrast, in pure water, there are no geometrical changes in the Cu surface because the H2O molecules do not react with the Cu surface, and the abrasive grain slides smoothly on the planar Cu surface. The comparison between the CMP simulations in aqueous H2O2 and pure water indicates that the intrusion of a surface-adsorbed O atom into the Cu bulk is the most important process for the efficient polishing of the Cu surface because it induces the dissociation of the Cu-Cu bonds and generates raised Cu atoms that are sheared off by the abrasive grain. Furthermore, density functional theory calculations show that the intrusion of the surface-adsorbed O atoms into the Cu bulk has a high activation energy of 28.2 kcal/mol, which is difficult to overcome at 300 K. Thus, we suggest that the intrusion of surface-adsorbed O atoms into the Cu bulk induced by abrasive grains at the friction interface is a rate-determining step in the Cu CMP process. PMID:27092706

  16. Ultrasonic Polishing

    NASA Technical Reports Server (NTRS)

    Gilmore, Randy

    1993-01-01

    The ultrasonic polishing process makes use of the high-frequency (ultrasonic) vibrations of an abradable tool which automatically conforms to the work piece and an abrasive slurry to finish surfaces and edges on complex, highly detailed, close tolerance cavities in materials from beryllium copper to carbide. Applications range from critical deburring of guidance system components to removing EDM recast layers from aircraft engine components to polishing molds for forming carbide cutting tool inserts or injection molding plastics. A variety of materials including tool steels, carbides, and even ceramics can be successfully processed. Since the abradable tool automatically conforms to the work piece geometry, the ultrasonic finishing method described offers a number of important benefits in finishing components with complex geometries.

  17. FY07 LDRD Final Report A Fracture Mechanics and Tribology Approach to Understanding Subsurface Damage on Fused Silica during Grinding and Polishing

    SciTech Connect

    Suratwala, T I; Miller, P E; Menapace, J A; Wong, L L; Steele, R A; Feit, M D; Davis, P J; Walmer, C D

    2008-02-05

    The objective of this work is to develop a solid scientific understanding of the creation and characteristics of surface fractures formed during the grinding and polishing of brittle materials, specifically glass. In this study, we have experimentally characterized the morphology, number density, and depth distribution of various surface cracks as a function of various grinding and polishing processes (blanchard, fixed abrasive grinding, loose abrasive, pitch polishing and pad polishing). Also, the effects of load, abrasive particle (size, distribution, foreign particles, geometry, velocity), and lap material (pitch, pad) were examined. The resulting data were evaluated in terms of indentation fracture mechanics and tribological interactions (science of interacting surfaces) leading to several models to explain crack distribution behavior of ground surfaces and to explain the characteristics of scratches formed during polishing. This project has greatly advanced the scientific knowledge of microscopic mechanical damage occurring during grinding and polishing and has been of general interest. This knowledge-base has also enabled the design and optimization of surface finishing processes to create optical surfaces with far superior laser damage resistance. There are five major areas of scientific progress as a result of this LDRD. They are listed in Figure 1 and described briefly in this summary below. The details of this work are summarized through a number of published manuscripts which are included this LDRD Final Report. In the first area of grinding, we developed a technique to quantitatively and statistically measure the depth distribution of surface fractures (i.e., subsurface damage) in fused silica as function of various grinding processes using mixtures of various abrasive particles size distributions. The observed crack distributions were explained using a model that extended known, single brittle indentation models to an ensemble of loaded, sliding

  18. Effect of strain rate and temperature on mechanical properties of selected building Polish steels

    NASA Astrophysics Data System (ADS)

    Moćko, Wojciech; Kruszka, Leopold

    2015-09-01

    Currently, the computer programs of CAD type are basic tool for designing of various structures under impact loading. Application of the numerical calculations allows to substantially reduce amount of time required for the design stage of such projects. However, the proper use of computer aided designing technique requires input data for numerical software including elastic-plastic models of structural materials. This work deals with the constitutive model developed by Rusinek and Klepaczko (RK) applied for the modelling of mechanical behaviour of selected grades structural St0S, St3SX, 18GS and 34GS steels and presents here results of experimental and empirical analyses to describe dynamic elastic-plastic behaviours of tested materials at wide range of temperature. In order to calibrate the RK constitutive model, series of compression tests at wide range of strain rates, including static, quasi-static and dynamic investigations at lowered, room and elevated temperatures, were carried out using two testing stands: servo-hydraulic machine and split Hopkinson bar. The results were analysed to determine influence of temperature and strain rate on visco-plastic response of tested steels, and show good correlation with experimental data.

  19. Development of High-Speed Copper Chemical Mechanical Polishing Slurry for Through Silicon Via Application Based on Friction Analysis Using Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Amanokura, Jin; Ono, Hiroshi; Hombo, Kyoko

    2011-05-01

    In order to obtain a high-speed copper chemical mechanical polishing (CMP) process for through silicon vias (TSV) application, we developed a new Cu CMP slurry through friction analysis of Cu reaction layer by an atomic force microscope (AFM) technique. A lateral modulation friction force microscope (LM-FFM) is able to measure the friction value properly giving a vibration to the layer. We evaluated the torsional displacement between the probe of the LM-FFM and the Cu reaction layer under a 5 nm vibration to cancel the shape effect of the Cu reaction layer. The developed Cu CMP slurry forms a frictionally easy-removable Cu reaction layer.

  20. Enhancing non-classicality in mechanical systems

    NASA Astrophysics Data System (ADS)

    Li, Jie; Gröblacher, Simon; Paternostro, Mauro

    2013-03-01

    We study the effects of post-selection measurements on both the non-classicality of the state of a mechanical oscillator and the entanglement between two mechanical systems that are part of a distributed optomechanical network. We address the cases of both Gaussian and non-Gaussian measurements, identifying in which cases simple photon counting and Geiger-like measurements are effective in distilling a strongly non-classical mechanical state and enhancing the purely mechanical entanglement between two elements of the network.

  1. Anodization of electrolytically polished Ta surfaces for enhancement of carrier injection into organic field-effect transistors

    SciTech Connect

    Ueno, Keiji; Abe, Shigeomi; Onoki, Ryo; Saiki, Koichiro

    2005-12-01

    Electrolytically polished surfaces of Ta sheets were anodized in an aqueous KI solution to form Ta{sub 2}O{sub 5} films with a relatively high dielectric constant and a high breakdown electric field. Organic field-effect transistors (OFETs) were fabricated on these Ta{sub 2}O{sub 5}/Ta substrates with a bottom gate configuration. The Ta{sub 2}O{sub 5} films anodized at 100 V were about 200 nm thick, and the dielectric strength was as high as 5 MV/cm. A p-type pentacene OFET fabricated on this bottom gate showed the good field-effect mobility of 0.35 cm{sup 2}/V s. By using this high-k gate substrate, it becomes possible to inject a higher amount of charge carriers into organic active layers than on the SiO{sub 2}/Si gate conventionally used in most OFETs.

  2. Study of impurity distribution in mechanically polished, chemically treated and high vacuum degassed pure niobium samples using the TOFSIMS technique

    NASA Astrophysics Data System (ADS)

    Bose, A.; Joshi, S. C.

    2015-07-01

    The performance of superconducting radio frequency (SRF) cavities is strongly influenced by various impurities within the penetration depth (∼50 nm) of niobium (Nb), which in turn depends on the applied surface treatments. The effect of these surface treatments on the impurities of Nb has been explored using various surface analytical techniques. However, the results are still inadequate in many aspects and the effect of sequential SRF treatments on the impurity distribution has not been explored. The present study analyzes various impurities within the penetration depth of Nb samples, treated by SRF cavity processing techniques such as colloidal silica polishing (simulating centrifugal barrel polishing), buffer chemical polishing (BCP), high pressure rinsing (HPR) and degassing under a high vacuum (HV) condition at 600 °C for 10 h. Static, dynamic and slow sputtering modes of the time of flight secondary ion mass spectrometry (TOFSIMS) technique were employed to study the effect of the above treatments on interstitial impurities, hydrocarbons, oxides, acidic residues, reaction products and metallic contaminations. The study confirms that the impurity distribution in Nb is not only sensitive to the surface treatments, but also to their sequence. Varying the treatment sequence prior to HV degassing treatments affected the final impurity levels in HV degassed bulk Nb samples. The HV degassing treatment was capable of reducing hydrogen contamination, but oxygen, carbon and metallic impurities were introduced into bulk Nb due to poor isolation from furnace contamination. On the other hand, BCP treated samples exhibited minimum hydrocarbon and metallic contamination along with the thinnest oxide layer at ∼2.8 nm, but led to extensive contamination of the oxide layer with residuals and reaction products of acids used in the BCP solution. HPR treatment, on the other hand, was effective in reducing the acidic impurities on the top surface. Variability of the

  3. Laser polishing of niobium for SRF applications

    SciTech Connect

    Zhao, Liang; Klopf, J. Michael; Reece, Charles E.; Kelley, Michael

    2013-09-01

    Smooth interior surfaces are desired for niobium SRF cavities, now obtained by buffered chemical polish (BCP) and/or electropolish (EP). Laser polishing is a potential alternative, having advantages of speed, freedom from chemistry and in-process inspection. Here we show that laser polishing can produce smooth topography with Power Spectral Density (PSD) measurements similar to that obtained by EP. We studied the influence of the laser power density and laser beam raster rate on the surface topography. These two factors need to be combined carefully to smooth the surface without damaging it. Computational modeling was used to simulate the surface temperature and explain the mechanism of laser polishing.

  4. Bio-inspired Fillers for Mechanical Enhancement

    NASA Astrophysics Data System (ADS)

    Korley, Lashanda

    2012-02-01

    An examination of natural materials has offered a new perspective on the development of multi-functional materials with enhanced mechanical properties. One important lesson from nature is the utilization of composite structures to impart improved mechanical behavior and enhanced functionality using nanofillers. A relatively unexplored expansion of this bio-inspired, nanoscale filler approach to high performance materials is the incorporation of responsive, multi-functional reinforcing elements in polymeric composites with the goal of combining superior mechanical behavior that can be tuned with additional functionality, such as sensing and bioactivity. One approach is the use of self-assembling small molecules that form uniform, one-dimensional nanostructures as an emerging class of filler components. Another pathway toward mechanical enhancement is the incorporation of stimuli-responsive and high-modulus electrospun nanofibers. We have probed the utilization of high-aspect ratio, self-assembled small molecules and responsive electrospun nanofibers as all-organic nanofillers to achieve significant modulus changes within elastomeric matrices. The influence of matrix-filler interactions and the role of hierarchical organization in these nature-inspired composites will be discussed. Potential applications in barrier technology and drug delivery have also been explored.

  5. Plasmonic Enhancement Mechanisms in Solar Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Cushing, Scott K.

    Semiconductor photovoltaics (solar-to-electrical) and photocatalysis (solar-to-chemical) requires sunlight to be converted into excited charge carriers with sufficient lifetimes and mobility to drive a current or photoreaction. Thin semiconductor films are necessary to reduce the charge recombination and mobility losses, but thin films also limit light absorption, reducing the solar energy conversion efficiency. Further, in photocatalysis, the band edges of semiconductor must straddle the redox potentials of a photochemical reaction, reducing light absorption to half the solar spectrum in water splitting. Plasmonics transforms metal nanoparticles into antennas with resonances tuneable across the solar spectrum. If energy can be transferred from the plasmon to the semiconductor, light absorption in the semiconductor can be increased in thin films and occur at energies smaller than the band gap. This thesis investigates why, despite this potential, plasmonic solar energy harvesting techniques rarely appear in top performing solar architectures. To accomplish this goal, the possible plasmonic enhancement mechanisms for solar energy conversion were identified, isolated, and optimized by combining systematic sample design with transient absorption spectroscopy, photoelectrochemical and photocatalytic testing, and theoretical development. Specifically, metal semiconductor nanostructures were designed to modulate the plasmon's scattering, hot carrier, and near field interactions as well as remove heating and self-catalysis effects. Transient absorption spectroscopy then revealed how the structure design affected energy and charge carrier transfer between metal and semiconductor. Correlating this data with wavelength-dependent photoconversion efficiencies and theoretical developments regarding metal-semiconductor interactions identified the origin of the plasmonic enhancement. Using this methodology, it has first been proven that three plasmonic enhancement routes are

  6. Plasmonic Enhancement Mechanisms in Solar Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Cushing, Scott K.

    Semiconductor photovoltaics (solar-to-electrical) and photocatalysis (solar-to-chemical) requires sunlight to be converted into excited charge carriers with sufficient lifetimes and mobility to drive a current or photoreaction. Thin semiconductor films are necessary to reduce the charge recombination and mobility losses, but thin films also limit light absorption, reducing the solar energy conversion efficiency. Further, in photocatalysis, the band edges of semiconductor must straddle the redox potentials of a photochemical reaction, reducing light absorption to half the solar spectrum in water splitting. Plasmonics transforms metal nanoparticles into antennas with resonances tuneable across the solar spectrum. If energy can be transferred from the plasmon to the semiconductor, light absorption in the semiconductor can be increased in thin films and occur at energies smaller than the band gap. This thesis investigates why, despite this potential, plasmonic solar energy harvesting techniques rarely appear in top performing solar architectures. To accomplish this goal, the possible plasmonic enhancement mechanisms for solar energy conversion were identified, isolated, and optimized by combining systematic sample design with transient absorption spectroscopy, photoelectrochemical and photocatalytic testing, and theoretical development. Specifically, metal semiconductor nanostructures were designed to modulate the plasmon's scattering, hot carrier, and near field interactions as well as remove heating and self-catalysis effects. Transient absorption spectroscopy then revealed how the structure design affected energy and charge carrier transfer between metal and semiconductor. Correlating this data with wavelength-dependent photoconversion efficiencies and theoretical developments regarding metal-semiconductor interactions identified the origin of the plasmonic enhancement. Using this methodology, it has first been proven that three plasmonic enhancement routes are

  7. Atomic-scale and pit-free flattening of GaN by combination of plasma pretreatment and time-controlled chemical mechanical polishing

    SciTech Connect

    Deng, Hui; Endo, Katsuyoshi; Yamamura, Kazuya

    2015-08-03

    Chemical mechanical polishing (CMP) combined with atmospheric-pressure plasma pretreatment was applied to a GaN (0001) substrate. The irradiation of a CF{sub 4}-containing plasma was proven to be very useful for modifying the surface of GaN. When CMP was conducted on a plasma-irradiated surface, a modified layer of GaF{sub 3} acted as a protective layer on GaN by preventing the formation of etch pits. Within a short duration (8 min) of CMP using a commercially available CeO{sub 2} slurry, an atomically flat surface with a root mean square (rms) roughness of 0.11 nm was obtained. Moreover, etch pits, which are inevitably introduced in conventional CMP, could not be observed at the dislocation sites on the polished GaN surface. It was revealed that CMP combined with the plasma pretreatment was very effective for obtaining a pit-free and atomically flat GaN surface.

  8. Defectless Monolithic Low-k/Cu Interconnects Produced by Chemically Controlled Chemical Mechanical Polishing Process with In situ End-Point-Detection Technique

    NASA Astrophysics Data System (ADS)

    Ueki, Makoto; Onodera, Takahiro; Ishikawa, Akira; Hoshino, Susumu; Hayashi, Yoshihiro

    2009-04-01

    Defectless monolithic low-k/Cu interconnects have been obtained for low-power LSIs by a chemically controlled local chemical mechanical polishing (CMP) process to remove a Cu/TaN barrier on hydrophobic SiOCH low-k films. In the first step, Cu-CMP, a unique end-point-detection (EDP) method is implemented to detect a very thin Cu layer (˜100 nm) that remains on the TaN barrier by in situ white-light interferometry, which is implemented in the local CMP apparatus where the wafers undergoing polishing are oriented face-up. In the second step, TaN-CMP, a SiO2 hard-mask (HM) layer on the low-k film is selectively removed to reduce the nonuniformity of the Cu line thickness, and accordingly, those of the resistance and capacitance. Here, a CMP slurry with an oxidizer is used to change the low-k surface from a hydrophobic condition to a hydrophilic condition, improving wettability and reducing the number of scratches and abrasive particles. In the post-CMP cleaning, an alkaline rinse solution with an oxidation-reduction potential (ORP) of less than -0.5 V vs a normal hydrogen electrode (NHE) produces a clean low-k surface resulting in monolithic low-k/Cu interconnects with excellent dielectric properties comparable to those of SiO2/Cu interconnects.

  9. Outline of Polish Morphology.

    ERIC Educational Resources Information Center

    Bidwell, Charles E.

    This volume, one of a series of concise but relatively exhaustive descriptions of the grammatical structures of the principal standard Slavic languages, contains an outline of Polish morphology. The four major sections are morphophonemics, nominal inflection, the Polish verb (Part 1--stem alternation and conjugation, and the Polish verb (Part…

  10. Mechanisms of polyhalogenated biphenyl enhancement of endotoxicity

    SciTech Connect

    Hoglen, N.C.

    1993-01-01

    Polyhalogenated aromatic hydrocarbons (PHAHs) are a class of environmental contaminants that can produce a number of toxic responses. Many of their toxicities are thought to be mediated by a cytosolic receptor called the aryl hydrocarbon (Ah) receptor. Among the most toxic compounds in this class, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3,3[prime],4,4[prime]-tetrabromobiphenyl (TBB), have been shown to markedly increase the sensitivity of rodents to lipopolysaccharide (LPS)-mediated hepatotoxicity and lethality. The purpose of this study was to define what mechanisms are involved in PHAH-enhancement of endotoxicity and hepatotoxicity using TBB and a related PHAH, 3,3[prime],4,4[prime],5-pentachlorobiphenyl (PeCB). A number of findings were demonstrated. First, it was confirmed that TBB markedly enhanced LPS-mediated hepatotoxicity and lethality, and this enhancement was greatest when LPS was administered one day after the PHAH. In addition, the TBB markedly elevated peak serum activity of tumor necrosis factor (TNF), a cytotoxic cytokine produced by macrophages after LPS exposure. However, increased TNF after LPS was seen at all time points after TBB treatment. Dexamethasone blocked both increased TNF production and hepatotoxicity. PeCB also markedly enhanced LPS-mediated hepatotoxicity/lethality with similar increases in TNF. In addition to increasing TNF, it was demonstrated that PeCB could sensitize the liver to TNF hepatotoxicity. Studies using 3-methylcholanthrene (3MC), a compound that binds as avidly to the Ah receptor as the PeCB, found no enhancement of endotoxicity, suggesting that Ah receptor activation alone does not mediate PHAH enhancement. 3MC did, however, increase LPS-stimulated serum TNF levels. 2,2[prime],4,4[prime],5,5[prime]-Hexachlorobiphenyl, a PHAH that does not bind to the Ah receptor, did not enhance endotoxicity or TNF production.

  11. Synthesis of Fe metal precipitated colloidal silica and its application to W chemical mechanical polishing (CMP) slurry.

    PubMed

    Kang, Young-Jae; Prasad, Y Nagendra; Kim, In-Kwon; Jung, Seok-Jo; Park, Jin-Goo

    2010-09-01

    The objective of this paper is to develop a new method of Fe (metal) precipitation on colloidal silica to overcome the stability problem, which would be responsible in producing defects, with commercially available fumed silica slurry containing Fe ions. The slurry was developed by using sodium silicate (Na(2)SiO(3)) as a raw material and the concentration of precipitation of metal was controlled by addition of Fe salt (Fe(NO(3))(3)). To compare the concentration of precipitated Fe with directly added Fe ions in slurry solutions, static electrochemical and peroxide decomposition experiments were performed. Although the performance of the Fe precipitation appeared to be lower than Fe ion addition during these experiments, nearly equal removal rate was observed due to the dynamic condition during polishing. The Fe precipitated colloidal silica particles at the concentration of 52ppm showed the similar W removal rate and selectivity of W to TEOS (tetraethylorthosilicate) to commercially available fumed silica slurry containing externally added Fe ions. The introduction of Fe particle precipitation on colloidal silica particles would result in a longer shelf life time and hence lower defect level in W CMP. PMID:20546766

  12. A facile chemical-mechanical polishing lift-off transfer process toward large scale Cu(In,Ga)Se2 thin-film solar cells on arbitrary substrates

    NASA Astrophysics Data System (ADS)

    Tseng, Kuan-Chun; Yen, Yu-Ting; Thomas, Stuart R.; Tsai, Hung-Wei; Hsu, Cheng-Hung; Tsai, Wen-Chi; Shen, Chang-Hong; Shieh, Jia-Min; Wang, Zhiming M.; Chueh, Yu-Lun

    2016-02-01

    The fabrication of Cu(In,Ga)Se2 (CIGS) solar cells on flexible substrates is a non-trivial task due to thermal and ion diffusion related issues. In order to circumvent these issues, we have developed a chemical-mechanical polishing lift-off (CMPL) transfer process, enabling the direct transfer of CIGS solar cells from conventional soda-lime glass (SLG) onto arbitrary flexible substrates up to 4 cm2 in size. The structural and compositional nature of the pre- and post-transferred films is examined using electron microscopy, X-ray diffraction analysis, Raman and photoluminescence spectroscopy. We demonstrate the fabrication of solar cells on a range of flexible substrates while being able to maintain 75% cell efficiency (η) when compared to pre-transferred solar cells. The results obtained in this work suggest that our transfer process offers a highly promising approach toward large scale fabrication of CIGS-based solar cells on a wide variety of flexible substrates, suitable for use in the large scale CIGS photovoltaic industry.The fabrication of Cu(In,Ga)Se2 (CIGS) solar cells on flexible substrates is a non-trivial task due to thermal and ion diffusion related issues. In order to circumvent these issues, we have developed a chemical-mechanical polishing lift-off (CMPL) transfer process, enabling the direct transfer of CIGS solar cells from conventional soda-lime glass (SLG) onto arbitrary flexible substrates up to 4 cm2 in size. The structural and compositional nature of the pre- and post-transferred films is examined using electron microscopy, X-ray diffraction analysis, Raman and photoluminescence spectroscopy. We demonstrate the fabrication of solar cells on a range of flexible substrates while being able to maintain 75% cell efficiency (η) when compared to pre-transferred solar cells. The results obtained in this work suggest that our transfer process offers a highly promising approach toward large scale fabrication of CIGS-based solar cells on a wide

  13. Effect of FA/O complexing agents and H2O2 on chemical mechanical polishing of ruthenium in weakly alkaline slurry

    NASA Astrophysics Data System (ADS)

    Bo, Duan; Weijing, An; Jianwei, Zhou; Shuai, Wang

    2015-07-01

    This paper investigated the effect of FA/O and hydrogen peroxide (H2O2) on ruthenium (Ru) removal rate (RR) and static etching rate (SER). It was revealed that Ru RR and SER first linearly increased then slowly decreaseed with the increasing H2O2 probably due to the formation of uniform Ru oxides on the surface during polishing. Their corrosion behaviors and states of surface oxidation were analyzed. In addition, FA/O could chelate Ru oxides (such as (RuO4)2- and RuO4- changed into soluble amine salts [R(NH3)4] (RuO4)2) and enhance Ru RR. The non-ionic surfactant AD was used to improve the Ru CMP performance. In particular, the addition of AD can lead to significant improvement of the surface roughness. Project supported by the Special Project Items No. 2 in National Long-Term Technology Development Plan (No. 2009ZX02308), the Natural Science Foundation of Hebei Province (No. E2013202247), the Science and Technology Plan Project of Hebei Province (Nos. Z2010112, 10213936), the Hebei Provincial Department of Education Fund (No. 2011128), and the Scientific Research Fund of Hebei Provincial Education (No. QN2014208).

  14. Microbial Mechanisms Enhancing Soil C Storage

    SciTech Connect

    Zak, Donald

    2015-09-24

    Human activity has globally increased the amount of nitrogen (N) entering ecosystems, which could foster higher rates of C sequestration in the N-limited forests of the Northern Hemisphere. Presently, these ecosystems are a large global sink for atmospheric CO2, the magnitude of which could be influenced by the input of human-derived N from the atmosphere. Nevertheless, empirical studies and simulation models suggest that anthropogenic N deposition could have either an important or inconsequential effect on C storage in forests of the Northern Hemisphere, a set of observations that continues to fuel scientific discourse. Although a relatively simple set of physiological processes control the C balance of terrestrial ecosystems, we still fail to understand how these processes directly and indirectly respond to greater N availability in the environment. The uptake of anthropogenic N by N-limited forest trees and a subsequent enhancement of net primary productivity have been the primary mechanisms thought to increase ecosystem C storage in Northern Hemisphere forests. However, there are reasons to expect that anthropogenic N deposition could slow microbial activity in soil, decrease litter decay, and increase soil C storage. Fungi dominate the decay of plant detritus in forests and, under laboratory conditions, high inorganic N concentrations can repress the transcription of genes coding for enzymes which depolymerize lignin in plant detritus; this observation presents the possibility that anthropogenic N deposition could elicit a similar effect under field conditions. In our 18-yr-long field experiment, we have been able to document that simulated N deposition, at a rate expected in the near future, resulted in a significant decline in cellulolytic and lignolytic microbial activity, slowed plant litter decay, and increased soil C storage (+10%); this response is not portrayed in any biogeochemical model simulating the effect of atmospheric N deposition on ecosystem C

  15. Directly polished lightweight aluminum mirror

    NASA Astrophysics Data System (ADS)

    ter Horst, Rik; Tromp, Niels; de Haan, Menno; Navarro, Ramon; Venema, Lars; Pragt, Johan

    2008-07-01

    During the last ten years, Astron has been a major contractor for the design and manufacturing of astronomical instruments for Space- and Earth based observatories, such as VISIR, MIDI, SPIFFI, X-Shooter and MIRI. The collaboration between optical- and mechanical designers at Astron led to new design philosophies and strategies. Driven by the need to reduce the weight of optically ultra-stiff structures, two promising techniques have been developed in the last years: ASTRON Extreme Lightweighting for mechanical structures and an improved Polishing Technique for Aluminum Mirrors. Using one single material for both optical components and mechanical structure simplifies the design of a cryogenic instrument significantly, it is very beneficial during instrument test and verification, and makes the instrument insensitive to temperature changes. Aluminum has been the main material used for cryogenic optical instruments, and optical aluminum mirrors are generally diamond turned. The application of a polishable hard top coating like nickel removes excess stray light caused by the groove pattern, but limits the degree of lightweighting of the mirrors due to the bi-metal effect. By directly polishing the aluminum mirror surface, the recent developments at Astron allow for using a non-exotic material for light weighted yet accurate optical mirrors, with a lower surface roughness (~1nm RMS), higher surface accuracy and reduced light scattering. This paper presents the techniques, obtained results and a global comparison with alternative lightweight mirror solutions.

  16. Micro-structural analysis of local damage introduced in subsurface regions of 4H-SiC wafers during chemo-mechanical polishing

    NASA Astrophysics Data System (ADS)

    Sako, Hideki; Matsuhata, Hirofumi; Sasaki, Masayuki; Nagaya, Masatake; Kido, Takanori; Kawata, Kenji; Kato, Tomohisa; Senzaki, Junji; Kitabatake, Makoto; Okumura, Hajime

    2016-04-01

    The surface morphology and lattice defect structures in the subsurface regions of 4H-SiC wafers introduced during chemo-mechanical polishing (CMP) were studied by scanning electron microscopy and transmission electron microscopy. It is known that local damage consisting of high-density lattice defects is introduced in the wafers during the current CMP, however, optical microscopy showed that the surface was very flat and clean without any presence of surface defects. Specifically, this study focused on the detailed analysis of such lattice defect structures. The high-density lattice defects locally introduced in the subsurface regions consisted of nano-scale surface scratches, high-density basal-plane dislocation loops, Shockley-type stacking faults, and Y-shaped defects. Two types of dislocation loops were introduced near the scratches that were selected for further study: nearly perfect basal-plane dislocations, which were accompanied by narrow stacking faults, and apparent partial basal-plane dislocations, which were accompanied by wide stacking faults. A Y-shaped defect was observed in the local damage along the [ 11 2 ¯ 0 ] direction, but not in the local damage along the [ 1 ¯100 ] direction. It was also found that the directions of the Burgers vectors for the basal-plane dislocations clearly depended on the directions of the introduced scratch-like defects.

  17. A facile chemical-mechanical polishing lift-off transfer process toward large scale Cu(In,Ga)Se2 thin-film solar cells on arbitrary substrates.

    PubMed

    Tseng, Kuan-Chun; Yen, Yu-Ting; Thomas, Stuart R; Tsai, Hung-Wei; Hsu, Cheng-Hung; Tsai, Wen-Chi; Shen, Chang-Hong; Shieh, Jia-Min; Wang, Zhiming M; Chueh, Yu-Lun

    2016-03-01

    The fabrication of Cu(In,Ga)Se2 (CIGS) solar cells on flexible substrates is a non-trivial task due to thermal and ion diffusion related issues. In order to circumvent these issues, we have developed a chemical-mechanical polishing lift-off (CMPL) transfer process, enabling the direct transfer of CIGS solar cells from conventional soda-lime glass (SLG) onto arbitrary flexible substrates up to 4 cm(2) in size. The structural and compositional nature of the pre- and post-transferred films is examined using electron microscopy, X-ray diffraction analysis, Raman and photoluminescence spectroscopy. We demonstrate the fabrication of solar cells on a range of flexible substrates while being able to maintain 75% cell efficiency (η) when compared to pre-transferred solar cells. The results obtained in this work suggest that our transfer process offers a highly promising approach toward large scale fabrication of CIGS-based solar cells on a wide variety of flexible substrates, suitable for use in the large scale CIGS photovoltaic industry. PMID:26878109

  18. Preparation of monodisperse polystyrene/silica core-shell nano-composite abrasive with controllable size and its chemical mechanical polishing performance on copper

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Wang, Haibo; Zhang, Zefang; Qin, Fei; Liu, Weili; Song, Zhitang

    2011-11-01

    Monodisperse silica-coated polystyrene (PS) nano-composite abrasives with controllable size were prepared via a two-step process. Monodisperse positively charged PS colloids were synthesized via polymerization of styrene by using a cationic initiator. In the subsequent coating process, silica formed shell on the surfaces of core PS particles via the ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane. Neither centrifugation/water wash/redispersion cycle process nor surface modification or addition surfactant was needed in the whole process. The morphology of the abrasives was characterized by scanning electron microscope. Transmission electron microscope and energy dispersive X-ray analysis results indicated that silica layer was successfully coated onto the surfaces of PS particles. Composite abrasive has a core-shell structure and smooth surface. The chemical mechanical polishing performances of the composite abrasive and conventional colloidal silica abrasive on blanket copper wafers were investigated. The root mean square roughness decreases from 4.27 nm to 0.56 nm using composite abrasive. The PS/SiO2 core-shell composite abrasives exhibited little higher material removal rate than silica abrasives.

  19. The Application of Bileaflet Mechanical Heart Valves in the Polish Ventricular Assist Device: Physical and Numerical Study and First Clinical Usage.

    PubMed

    Malota, Zbigniew; Sadowski, Wojciech; Krzyskow, Marek; Stolarzewicz, Bogdan

    2016-03-01

    The Polish ventricular assist device (Polvad) has been used successfully in clinical contexts for many years. The device contains two single-disc valves, one at the inlet and one at the outlet connector of the pneumatic pump. Unfortunately, in recent years, a problem has occurred with the availability of single-disc valves. This article presents the possibility of using bileaflet mechanical heart valve prostheses in the Polvad to avoid a discontinuity in clinical use. The study is based on experimental and numerical simulations and comparison of the distribution of flow, pressure, and stress (wall, shear, and turbulent) inside the Polvad chamber and the inlet/outlet connectors fitted with Sorin Monodisc and Sorin Bicarbon Fitline valves. The type and orientation of the inlet valve affects valve performance and flow distribution inside the chamber. Near-wall flow is observed for single-disc valves. In the case of bileaflet valves, the main jet is directed more centrally, with lower shear stress but higher turbulent stress in comparison with single-disc valves. For clinical usage, a 45° orientation of the bileaflet inlet valve was chosen, as this achieves good washing of the inlet area near the membrane paste surface. The Polvad with bileaflet valves has now been used successfully in our clinic for over a year and will continue to be used until new assist devices for heart support are developed. PMID:26365391

  20. Nano-scale stick-slip friction model for the chatter scratch generated by chemical mechanical polishing process.

    PubMed

    Kim, Hong Jin; Yang, Ji Chul; Yoon, Bo Un; Lee, Hyeon-Deok; Kim, Taesung

    2012-07-01

    Although Chemical Mechanical Planarization (CMP) process is a still promising technology for the fabrication of the next generation devices, CMP-induced defects tackle further development of CMP process. In particular, even nano-sized scratches generated by CMP process kill the device directly. However mechanism of scratch formation was not clearly understood yet. CMP-induced scratches are classified as razor, chatter mark and skipping scratch. Among them, chatter mark scratch (or chatter scratch) is the most critical defect for the device yield loss. Chatter scratch has a periodic pattern of scars, which is reminiscent of a stick-slip friction pattern. Based on that similarity, stick-slip model was proposed in this paper in order to explain how chatter scratch is formed. And controlling parameters for chatter scratch are defined. During stick period the friction force that exceeds the yield strength of wafer surface makes chatter scratch and the distance between chatter marks is determined by slip period. PMID:22966633

  1. Rediscovery of Polish meteorites

    NASA Astrophysics Data System (ADS)

    Tymiński, Z.; Stolarz, M.; Żołądek, P.; Wiśniewski, M.; Olech, A.

    2016-01-01

    The total number of Polish registered meteorites (by July 2016) including the meteoritical artifacts as Czestochowa Raków I and II is 22. Most of them are described by the pioneer of Polish Meteoritics Jerzy Pokrzywnicki who also identified the meteorite fall locations. In recent years prospectors found impressive specimens of known Polish meteorites such as Morasko: 34 kg, 50 kg, 164 kg, 174 kg and 261 kg or Pultusk: 1578 g, 1576 g, 1510 g, 610 g and 580 g expanding and determining precisely the known meteorite strewn fields.

  2. Sublingual immunotherapy (SLIT)--indications, mechanism, and efficacy: Position paper prepared by the Section of Immunotherapy, Polish Society of Allergy.

    PubMed

    Jutel, Marek; Bartkowiak-Emeryk, Małgorzata; Bręborowicz, Anna; Cichocka-Jarosz, Ewa; Emeryk, Andrzej; Gawlik, Radosław; Gonerko, Paweł; Rogala, Barbara; Nowak-Węgrzyn, Anna; Samoliński, Bolesław

    2016-01-01

    SLIT (sublingual immunotherapy,) induces allergen-specific immune tolerance by sublingual administration of a gradually increasing dose of an allergen. The mechanism of SLIT is comparable to those during SCIT (subcutaneous immunotherapy), with the exception of local oral dendritic cells, pre-programmed to elicit tolerance. In the SLIT dose, to achieve the same efficacy as in SCIT, it should be 50-100 times higher with better safety profile. The highest quality evidence supporting the efficacy of SLIT lasting 1-3 years has been provided by the large scale double-blind, placebo-controlled (DBPC) trials for grass pollen extracts, both in children and adults with allergic rhinitis. Current indications for SLIT are allergic rhinitis (and conjunctivitis) in both children and adults sensitized to pollen allergens (trees, grass, Parietaria), house dust mites (Dermatophagoides pteronyssinus, Dermatophagoides farinae), cat fur, as well as mild to moderate controlled atopic asthma in children sensitized to house dust mites. There are positive findings for both asthma and new sensitization prevention. Severe adverse events, including anaphylaxis, are very rare, and no fatalities have been reported. Local adverse reactions develop in up to 70 - 80% of patients. Risk factors for SLIT adverse events have not been clearly identified. Risk factors of non-adherence to treatment might be dependent on the patient, disease treatment, physician-patient relationship, and variables in the health care system organization. PMID:27012173

  3. The effect of hydrogen peroxide on polishing removal rate in CMP with various abrasives

    NASA Astrophysics Data System (ADS)

    Manivannan, R.; Ramanathan, S.

    2009-01-01

    The effect of hydrogen peroxide in chemical mechanical planarization slurries for shallow trench isolation was investigated. The various abrasives used in this study were ceria, silica, alumina, zirconia, titania, silicon carbide, and silicon nitride. Hydrogen peroxide suppresses the polishing of silicon dioxide and silicon nitride surfaces by ceria abrasives. The polishing performances of other abrasives were either unaffected or enhanced slightly with the addition of hydrogen peroxide. The ceria abrasives were treated with hydrogen peroxide, and the polishing of the work surfaces with the treated abrasive shows that the inhibiting action of hydrogen peroxide is reversible. It was found that the effect of hydrogen peroxide as an additive is a strong function of the nature of the abrasive particle.

  4. Polished polymide substrate

    DOEpatents

    Farah, John; Sudarshanam, Venkatapuram S.

    2003-05-13

    Polymer substrates, in particular polyimide substrates, and polymer laminates for optical applications are described. Polyimide substrates are polished on one or both sides depending on their thickness, and single-layer or multi-layer waveguide structures are deposited on the polished polyimide substrates. Optical waveguide devices are machined by laser ablation using a combination of IR and UV lasers. A waveguide-fiber coupler with a laser-machined groove for retaining the fiber is also disclosed.

  5. Elastic emission polishing

    SciTech Connect

    Loewenthal, M.; Loseke, K.; Dow, T.A.; Scattergood, R.O.

    1988-12-01

    Elastic emission polishing, also called elastic emission machining (EEM), is a process where a stream of abrasive slurry is used to remove material from a substrate and produce damage free surfaces with controlled surface form. It is a noncontacting method utilizing a thick elasto-hydrodynamic film formed between a soft rotating ball and the workpiece to control the flow of the abrasive. An apparatus was built in the Center, which consists of a stationary spindle, a two-axis table for the workpiece, and a pump to circulate the working fluid. The process is controlled by a programmable computer numerical controller (CNC), which presently can operate the spindle speed and movement of the workpiece in one axis only. This apparatus has been used to determine material removal rates on different material samples as a function of time, utilizing zirconium oxide (ZrO{sub 2}) particles suspended in distilled water as the working fluid. By continuing a study of removal rates the process should become predictable, and thus create a new, effective, yet simple tool for ultra-precision mechanical machining of surfaces.

  6. Polish artificial heart program.

    PubMed

    El Fray, Miroslawa; Czugala, Monika

    2012-01-01

    Despite significant advances in the development of artificial heart substitutes, anthrombogenic materials and surfaces remain to be the main challenge for implants, which can prevent thrombosis that leads to rejection. The goal of material engineering is essentially to design polymeric materials of high durability and optimal thrombogenicity in mechanical heart prosthesis, being developed recently in a frame of the polish artificial heart program. For these reasons, various surface modifications are being continuously developed for a 'gold standard' material, which is a polyurethane (PU) thermoplastic elastomer and they will be shortly reviewed. However, new polymeric materials can meet medical word's attention if they are able to provide similar or better characteristics in term of bulk and surface properties. Specifically, if they will show appropriate surface topography, which is the most influential in determining the response of live tissues toward biomaterials. Nanostructured polyester thermoplastic elastomers of high biodurability as an alternative to PU materials for artificial heart are challenging new materials, and they will be discussed briefly. PMID:22110047

  7. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  8. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, U.

    1995-04-25

    A composition and method are disclosed of preparing YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T{sub c}. About 5-20% additions give rise to substantially improved mechanical properties.

  9. The effect of mechanical load cycling and polishing time on microleakage of class V glass-ionomer and composite restorations: A scanning electron microscopy evaluation

    PubMed Central

    Mirzaie, Mansoreh; Yasini, Esmail; Kermanshah, Hamid; Omidi, Baharan Ranjbar

    2014-01-01

    Background: Microleakage is one of the challenging concerns in direct filling restorations. Understanding of its related factors is important in clinical practice. The aim of this study was scanning electron microscopy (SEM) evaluation of marginal integrity in three types of tooth-colored restorative materials in class V cavity preparations and the effect of load cycling and polishing time on the microleakage. Materials and Methods: In this in vitro experimental study, class V cavity preparations were prepared on the buccal and lingual surfaces of 60 bovine incisors. The specimens were divided into three groups each containing 20 teeth: group 1: Filtek Z350, Group 2: Fuji IX/G Coat Plus, Group 3: Fuji II LC/GC varnish. In each group, 2 subgroups (n = 20) were established based on finishing time (immediate or delayed by 24 h). All specimens were thermocycled (×2,000, 5-50°C). In each sub groups, half of the teeth were load cycled. Epoxy resin replicas of 24 specimens were evaluated under field emission-SEM and interfacial gaps were measured. All teeth were then immersed in 0.5% basic fuchsin dye for 24 h, sectioned and observed under stereomicroscope. Data were analyzed with Kruskal-Wallis’ test and Mann-Whitney U test and a comparison between incisal and cervical microleakage was made with Wilcoxon test. P < 0.05 was considered as significant. Results: Load cycling and filling material had a significant effect on microleakage, but polishing time did not. Cervical microleakage in Z350/load cycle/immediate polish and Fuji IX/load cycle/immediate or delayed polish and Fuji IX/no load cycle/immediate polish were significantly higher than incisal microleakage. Conclusion: It was concluded that the cervical sealing ability of Fuji IX under load cycling was better than Fuji II LC. Under load cycling and immediate polishing Z350 showed better marginal integrity than both Fuji II LC and Fuji IX. The immediate polishing didn’t cause a statistically significant increase

  10. Polishing performances of different optics with different size powder and different pH value slurries during CMP polishing

    NASA Astrophysics Data System (ADS)

    Cao, Jun; Wei, Chaoyang; Liu, Shijie; Dun, Aihuan; Yang, Minghong; Xu, Xueke; Shao, Jianda

    2015-10-01

    Different size polishing powder and different pH value ceria slurries were used to polish fused silica glass K9 glass and Nd-doped glass on pitch plate. Material removal rates (MRR) of glass polished with different size powder and various pH value slurries, and textures of each sample were characterized. The results show that powder size has an effect on glass polishing performance: scratch densities increase with the increase of polishing powder size; surface textures become rougher with the increase of the size of polishing powder. The slurry pH value also affects glass polishing performance: MRR of fused silica glass are lowest under any pH value slurry while Nd-doped glass has the largest MRR; removal rates of all three kinds of glass will rise under both acidic and alkaline condition. Near neutral polishing environment and smaller size powder are useful for the surface polishing process. The results further reveal polishing mechanism and provide the guidance for glass surface process.

  11. Laminar Tendon Composites with Enhanced Mechanical Properties

    PubMed Central

    Alberti, Kyle A.; Sun, Jeong-Yun; Illeperuma, Widusha R.; Suo, Zhigang; Xu, Qiaobing

    2015-01-01

    Purpose A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called “bioskiving” to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. Methods In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. Results We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. Conclusions The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications. PMID:25691802

  12. Enhancing Mechanics Learning through Cognitively Appropriate Instruction

    ERIC Educational Resources Information Center

    Espinoza, Fernando

    2004-01-01

    The unquestionably central role of physics in the development of scientific literacy is undermined by its perceived difficulty. An investigation of high school students' use of the concepts of momentum and force suggests that, in the case of mechanics, the reason for physics' unpopularity and image as a "hard" subject is largely due to an…

  13. System Enhancements for Mechanical Inspection Processes

    NASA Technical Reports Server (NTRS)

    Hawkins, Myers IV

    2011-01-01

    Quality inspection of parts is a major component to any project that requires hardware implementation. Keeping track of all of the inspection jobs is essential to having a smooth running process. By using HTML, the programming language ColdFusion, and the MySQL database, I created a web-based job management system for the 170 Mechanical Inspection Group that will replace the Microsoft Access based management system. This will improve the ways inspectors and the people awaiting inspection view and keep track of hardware as it is in the inspection process. In the end, the management system should be able to insert jobs into a queue, place jobs in and out of a bonded state, pre-release bonded jobs, and close out inspection jobs.

  14. [History of Polish pharmacy].

    PubMed

    Okuda, J; Okuda, R

    1993-01-01

    Doctoral thesis (in French) by Monika Debska-Donnet, entitled "History of pharmacy and pharmaceutical art collections in Poland" which was presented to Paris XI University (Faculty of Pharmaceutical and Biological Sciences) in 1991, was translated into Japanese and summarized. In this report, histories of pharmacy education, pharmacists, community pharmacies, pharmacopoeiae, pharmaceutical industries in Poland were described, and four representative Polish museums of history of pharmacy were also explained. PMID:11639718

  15. Enhanced nonlinear interactions in quantum optomechanics via mechanical amplification

    NASA Astrophysics Data System (ADS)

    Lemonde, Marc-Antoine; Didier, Nicolas; Clerk, Aashish A.

    2016-04-01

    The quantum nonlinear regime of optomechanics is reached when nonlinear effects of the radiation pressure interaction are observed at the single-photon level. This requires couplings larger than the mechanical frequency and cavity-damping rate, and is difficult to achieve experimentally. Here we show how to exponentially enhance the single-photon optomechanical coupling strength using only additional linear resources. Our method is based on using a large-amplitude, strongly detuned mechanical parametric drive to amplify mechanical zero-point fluctuations and hence enhance the radiation pressure interaction. It has the further benefit of allowing time-dependent control, enabling pulsed schemes. For a two-cavity optomechanical set-up, we show that our scheme generates photon blockade for experimentally accessible parameters, and even makes the production of photonic states with negative Wigner functions possible. We discuss how our method is an example of a more general strategy for enhancing boson-mediated two-particle interactions and nonlinearities.

  16. Thermally mediated mechanism to enhance magnetoelectric coupling in multiferroics.

    PubMed

    Chang, C-M; Mani, B K; Lisenkov, S; Ponomareva, I

    2015-05-01

    The main roadblock on the way to practical realization of magnetoelectric devices is the lack of multiferroics with strong magnetoelectric coupling. We propose an unusual route to dramatically enhance this coupling through a thermally mediated mechanism. Such a thermally mediated magnetoelectric effect is quantified by an isentropic rather than isothermal magnetoelectric response and is computed here from first principles. A robust enhancement of the magnetoelectric coupling is predicted for both naturally occurring and heterostructured materials. PMID:25978260

  17. Efficiency of Fatty Acids as Chemical Penetration Enhancers: Mechanisms and Structure Enhancement Relationship

    PubMed Central

    Ibrahim, Sarah A.; Li, S. Kevin

    2010-01-01

    Purpose The present study evaluated the effects of fatty acids commonly present in cosmetic and topical formulations on permeation enhancement across human epidermal membrane (HEM) lipoidal pathway when the fatty acids saturated the SC lipid domain without cosolvents (Emax). Methods HEM was treated with neat fatty acids or fatty acid suspensions to determine Emax. A volatile solvent system was used to deposit fatty acids on HEM surface to compare fatty acid enhancer efficiency in topical volatile formulations with Emax. To elucidate permeation enhancement mechanism(s), estradiol (E2β) uptake into fatty acid-treated SC lipid domain was determined. Results Emax of fatty acids was shown to increase with their octanol solubilities and decrease with their lipophilicities, similar to our previous findings with other enhancers. Emax of solid fatty acids was shown to depend on their melting points, an important parameter to the effectiveness of the enhancers. The E2β uptake results suggest that enhancer-induced permeation enhancement across HEM is related to enhanced permeant partitioning into the SC lipid domain. Conclusions The results suggest Emax as a model for studying the permeation enhancement effect of the fatty acids and their structure enhancement relationship. PMID:19911256

  18. Surface Roughness of Commercial Composites after Different Polishing Protocols: An Analysis with Atomic Force Microscopy

    PubMed Central

    Giacomelli, Luca; Derchi, Giacomo; Frustaci, Andrea; Bruno, Orlando; Covani, Ugo; Barone, Antonio; De Santis, Daniele; Chiappelli, Francesco

    2010-01-01

    Background and Aims: Polishing may increase the surface roughness of composites, with a possible effect on bacterial growth and material properties. This preliminary in vitro study evaluates the effect of three different polishing systems (PoGo polishers, Enhance, Venus Supra) on six direct resin composites (Gradia Direct, Venus, Venus Diamond, Enamel Plus HFO, Tetric Evoceram, Filtek Supreme XT). Materials and Methods: For each composite, 12 square specimens were prepared: 9 specimens were polished, three for each different method, while three specimens were used as controls. Surface roughness was determined with AFM by measuring Root Mean Square (RMS) of average height. Results: PoGo polisher determined a significantly rougher surface, versus controls, in 5 out of 6 composites evaluated. Some significant differences from unpolished controls were observed also for Enhance polishing. Polishing with Venus Supra did not result in any significant difference in surface roughness versus controls. No differences were observed between different polishing systems. Conclusions: These preliminary results suggest that Venus Supra polishing system could determine a smoother composite surface if compared to the other polishing systems tested. On this basis, we are conducting an in vivo study to evaluate bacterial colonization on some combinations of composites and polishing protocols. PMID:21228920

  19. Issues in tokamak/stellarator transport and confinement enhancement mechanisms

    SciTech Connect

    Perkins, F.W.

    1990-08-01

    At present, the mechanism for anomalous energy transport in low-{beta} toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E {times} B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs.

  20. Application of Composite Mechanics to Composites Enhanced Concrete Structures

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Gotsis, Pascal K.

    2006-01-01

    A new and effective method is described to design composites to repair damage or enhance the overload strength of concrete infrastructures. The method is based on composite mechanics which is available in computer codes. It is used to simulate structural sections made from reinforced concrete which are typical in infrastructure as well as select reinforced concrete structures. The structural sections are represented by a number of layers through the thickness where different layers are used in concrete, and for the composite. The reinforced concrete structures are represented with finite elements where the element stiffness parameters are from the structural sections which are represented by composite mechanics. The load carrying capability of the structure is determined by progressive structural fracture. Results show up to 40 percent improvements for damage and for overload enhancement with relatively small laminate thickness for the structural sections and up to three times for the composite enhanced select structures (arches and domes).

  1. Femtosecond laser polishing of optical materials

    NASA Astrophysics Data System (ADS)

    Taylor, Lauren L.; Qiao, Jun; Qiao, Jie

    2015-10-01

    Technologies including magnetorheological finishing and CNC polishing are commonly used to finish optical elements, but these methods are often expensive, generate waste through the use of fluids or abrasives, and may not be suited for specific freeform substrates due to the size and shape of finishing tools. Pulsed laser polishing has been demonstrated as a technique capable of achieving nanoscale roughness while offering waste-free fabrication, material-specific processing through direct tuning of laser radiation, and access to freeform shapes using refined beam delivery and focusing techniques. Nanosecond and microsecond pulse duration radiation has been used to perform successful melting-based polishing of a variety of different materials, but this approach leads to extensive heat accumulation resulting in subsurface damage. We have experimentally investigated the ability of femtosecond laser radiation to ablate silicon carbide and silicon. By substituting ultrafast laser radiation, polishing can be performed by direct evaporation of unwanted surface asperities with minimal heating and melting, potentially offering damage-free finishing of materials. Under unoptimized laser processing conditions, thermal effects can occur leading to material oxidation. To investigate these thermal effects, simulation of the heat accumulation mechanism in ultrafast laser ablation was performed. Simulations have been extended to investigate the optimum scanning speed and pulse energy required for processing various substrates. Modeling methodologies and simulation results will be presented.

  2. Plasmon resonance enhanced mechanical detection of ligand binding

    SciTech Connect

    Ariyaratne, Amila; Zocchi, Giovanni

    2015-01-05

    Small molecule binding to the active site of enzymes typically modifies the mechanical stiffness of the enzyme. We exploit this effect, in a setup which combines nano-mechanics and surface plasmon resonance (SPR) enhanced optics, for the label free detection of ligand binding to an enzyme. The large dynamic range of the signal allows to easily obtain binding curves for small ligands, in contrast to traditional SPR methods which rely on small changes in index of refraction. Enzyme mechanics, assessed by nano-rheology, thus emerges as an alternative to electronic and spin resonances, assessed by traditional spectroscopies, for detecting ligand binding.

  3. Correlation-enhanced Metrology with Mechanical Parametric Amplifiers

    NASA Astrophysics Data System (ADS)

    Cheung, Hil Fung Harry; Chang, Laura; Patil, Yogesh Sharad; Chakram, Srivatsan; Vengalattore, Mukund

    2015-05-01

    Quantum correlations between the two arms of a mechanical parametric amplifier can be used to realize sensing beyond the standard quantum limit. We use nondegenerate mechanical parametric oscillators made of silicon nitride membrane resonators to demonstrate mechanical amplitude squeezing. This is the acoustic equivalent of intensity difference squeezing observed in optical parametric oscillators. We use the strong correlations between the nondegenerate modes to realize sub-thermal force sensitivities through noise cancellation and signal enhancement schemes. Our classical realization of enhanced metrology in a platform amenable to quantum optomechanics and nonclassical state preparation paves the way for quantum nonlinear sensing. This work is supported by the DARPA QuASAR program through a grant from the ARO and an NSF INSPIRE award.

  4. Reel-to-reel substrate tape polishing system

    DOEpatents

    Selvamanickam, Venkat; Gardner, Michael T.; Judd, Raymond D.; Weloth, Martin; Qiao, Yunfei

    2005-06-21

    Disclosed is a reel-to-reel single-pass mechanical polishing system (100) suitable for polishing long lengths of metal substrate tape (124) used in the manufacture of high-temperature superconductor (HTS) coated tape, including multiple instantiations of a polishing station (114) in combination with a subsequent rinsing station (116) arranged along the axis of the metal substrate tape (124) that is translating between a payout spool (110a) and a take-up spool (110b). The metal substrate tape obtains a surface smoothness that is suitable for the subsequent deposition of a buffer layer.

  5. Enhancing the mechanical properties of single-crystal CVD diamond.

    PubMed

    Liang, Qi; Yan, Chih-Shiue; Meng, Yufei; Lai, Joseph; Krasnicki, Szczesny; Mao, Ho-Kwang; Hemley, Russell J

    2009-09-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness (∼78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond. PMID:21832321

  6. Prosodic cues enhance rule learning by changing speech segmentation mechanisms

    PubMed Central

    de Diego-Balaguer, Ruth; Rodríguez-Fornells, Antoni; Bachoud-Lévi, Anne-Catherine

    2015-01-01

    Prosody has been claimed to have a critical role in the acquisition of grammatical information from speech. The exact mechanisms by which prosodic cues enhance learning are fully unknown. Rules from language often require the extraction of non-adjacent dependencies (e.g., he plays, he sings, he speaks). It has been proposed that pauses enhance learning because they allow computing non-adjacent relations helping word segmentation by removing the need to compute adjacent computations. So far only indirect evidence from behavioral and electrophysiological measures comparing learning effects after exposure to speech with and without pauses support this claim. By recording event-related potentials during the acquisition process of artificial languages with and without pauses between words with embedded non-adjacent rules we provide direct evidence on how the presence of pauses modifies the way speech is processed during learning to enhance segmentation and rule generalization. The electrophysiological results indicate that pauses as short as 25 ms attenuated the N1 component irrespective of whether learning was possible or not. In addition, a P2 enhancement was present only when learning of non-adjacent dependencies was possible. The overall results support the claim that the simple presence of subtle pauses changed the segmentation mechanism used reflected in an exogenously driven N1 component attenuation and improving segmentation at the behavioral level. This effect can be dissociated from the endogenous P2 enhancement that is observed irrespective of the presence of pauses whenever non-adjacent dependencies are learned. PMID:26483731

  7. Mechanical enhancement of nanofibrous scaffolds through polyelectrolyte complexation

    NASA Astrophysics Data System (ADS)

    Xu, Jia; Cai, Ning; Xu, Weixiu; Xue, Yanan; Wang, Zelong; Dai, Qin; Yu, Faquan

    2013-01-01

    Optimization of mechanical properties is required in applications of tissue-engineered scaffolds. In this study, a polyelectrolyte complexation approach is proposed to improve the mechanical properties of the nanofibrous scaffolds. Through an electrospun chitosan/gelatin (CG) model system, it is demonstrated that the storage modulus of CG nanofiber-based complex membranes is over 103-fold higher than that of neat chitosan or gelatin membranes. Further, an annealing process was found to promote the conjugation of the oppositely charged polymers and thus the tensile modulus of CG membranes is 1.9-fold elevated. When the molar ratio of aminoglucoside units in chitosan to carboxyl units in gelatin is 1:1, the complex nanofiber-based membranes (CG2) display the highest mechanical strength. In addition, the complex membranes reveal an excellent swelling capacity. By comparing the CG membranes electrospun with cast, it is deduced that the complexation is one of the main contributing factors to the improvement in mechanical properties. FTIR and DSC analyses confirm that more molecular interactions took place in the complexation. SEM observation clearly displays the electrospinnability of the complex. Therefore, polyelectrolyte complexation is an effective strategy for enhancing mechanical properties of nanofibrous scaffolds. These mechanically enhanced chitosan/gelatin nanofibrous membranes have wider applications than wound dressing.

  8. Polishing technique for beryllium mirror

    NASA Technical Reports Server (NTRS)

    Froechtenigt, J. F.

    1976-01-01

    Performance tests, accomplished by inserting entire X ray telescope and polished mirror into vacuum line 67 m long and taking photographs of an X ray resolution source, indicate that polishing increases mirror efficiency from 0.06 percent for X rays at 0.8 nm and increases resolution from 15 to 3.75 arc-seconds.

  9. EFFECT OF DIFFERENT POLISHING SYSTEMS ON THE SURFACE ROUGHNESS OF MICROHYBRID COMPOSITES

    PubMed Central

    Scheibe, Kristine Guará Brusaca Almeida; Almeida, Karoline Guará Brusaca; Medeiros, Igor Studart; Costa, José Ferreira; Alves, Cláudia Maria Coêlho

    2009-01-01

    The use of composite resins in dentistry is well accepted for restoring anterior and posterior teeth. Many polishing protocols have been evaluated for their effect on the surface roughness of restorative materials. This study compared the effect of different polishing systems on the surface roughness of microhybrid composites. Thirty-six specimens were prepared for each composite [Charisma® (Heraeus Kulzer), Fill Magic® (Vigodent), TPH Spectrum® (Dentsply), Z100® (3M/ESPE) and Z250® (3M/ESPE)] and submitted to surface treatment with Enhance® and PoGo® (Dentsply) points, sequential Sof-Lex XT® aluminum oxide disks (3M/ESPE), and felt disks (TDV) combined with Excel® diamond polishing paste (TDV). Average surface roughness (Ra) was measured with a mechanical roughness tester. The data were analyzed by two-way ANOVA with repetition of the factorial design and the Tukey-Kramer test (p<0.01). The F-test result for treatments and resins was high (p<0.0001 for both), indicating that the effect of the treatment applied to the specimen surface and the effect of the type of resin on surface roughness was highly significant. Regarding the interaction between polishing system and type of resin used, a p value of 0.0002 was obtained, indicating a statistically significant difference. A Ra of 1.3663 was obtained for the Sof-Lex/TPH Spectrum interaction. In contrast, the Ra for the felt disk+paste/Z250 interactions was 0.1846. In conclusion, Sof-Lex polishing system produced a higher surface roughness on TPH Spectrum resin when compared to the other interactions. PMID:19148401

  10. Enhanced Mechanical Stability of Gold Nanotips through Carbon Nanocone Encapsulation

    NASA Astrophysics Data System (ADS)

    Cano-Marquez, Abraham G.; Schmidt, Wesller G.; Ribeiro-Soares, Jenaina; Gustavo Cançado, Luiz; Rodrigues, Wagner N.; Santos, Adelina P.; Furtado, Clascidia A.; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvão, Douglas S.; Jorio, Ado

    2015-06-01

    Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance. Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices. Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability. Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp2 carbon at the nanoscale.

  11. Enhanced Mechanical Stability of Gold Nanotips through Carbon Nanocone Encapsulation

    PubMed Central

    Cano-Marquez, Abraham G.; Schmidt, Wesller G.; Ribeiro-Soares, Jenaina; Gustavo Cançado, Luiz; Rodrigues, Wagner N.; Santos, Adelina P.; Furtado, Clascidia A.; Autreto, Pedro A.S.; Paupitz, Ricardo; Galvão, Douglas S.; Jorio, Ado

    2015-01-01

    Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance. Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices. Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability. Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp2 carbon at the nanoscale. PMID:26083864

  12. Mechanisms for training security inspectors to enhance human performance

    SciTech Connect

    Burkhalter, H.E.; Sessions, J.C.

    1988-01-01

    The Department of Energy (DOE) has established qualification standards for protective force personnel employed at nuclear facilities (10 CFR Part 1046 (Federal Register)). Training mechanisms used at Los Alamos to enhance human performance in meeting DOE standards include, but are not limited to, the following: for cardio-respiratory training, they utilize distance running, interval training, sprint training, pacing, indoor aerobics and circuit training; for muscular strength, free weights, weight machines, light hand weights, grip strength conditioners, and calistenics are employed; for muscular endurance, participants do high repetitions (15 - 40) using dumbbells, flex weights, resistive rubber bands, benches, and calisthenics; for flexibility, each training session devotes specific times to stretch the muscles involved for a particular activity. These training mechanisms with specific protocols can enhance human performance.

  13. Correlation between contact surface and friction during the optical glass polishing

    NASA Astrophysics Data System (ADS)

    Belkhir, N.; Aliouane, T.; Bouzid, D.

    2014-01-01

    This study aims to determine the correlation between the contact surface, the polishing pressure and the friction coefficient during the optical glass polishing. For this purpose, BK7 optical glass samples were polished and the mentioned parameters were measured to find a correlation between them. Several methods of characterization have been used; the mechanical profilometer, the AFM, and in addition setups for measuring forces and the contact surface have been developed and adapted to the polishing machine. The found results have shown the existence of a close relationship between the three parameters and the influence of each other. This have allowed to deduce that during the polishing process it is very important to control the contact pressure and the polisher form according to the pressure distribution in order to guarantee a very high quality of the polished surface.

  14. Enhanced mechanical properties of nanocomposites at low graphene content.

    PubMed

    Rafiee, Mohammad A; Rafiee, Javad; Wang, Zhou; Song, Huaihe; Yu, Zhong-Zhen; Koratkar, Nikhil

    2009-12-22

    In this study, the mechanical properties of epoxy nanocomposites with graphene platelets, single-walled carbon nanotubes, and multi-walled carbon nanotube additives were compared at a nanofiller weight fraction of 0.1 +/- 0.002%. The mechanical properties measured were the Young's modulus, ultimate tensile strength, fracture toughness, fracture energy, and the material's resistance to fatigue crack propagation. The results indicate that graphene platelets significantly out-perform carbon nanotube additives. The Young's modulus of the graphene nanocomposite was approximately 31% greater than the pristine epoxy as compared to approximately 3% increase for single-walled carbon nanotubes. The tensile strength of the baseline epoxy was enhanced by approximately 40% with graphene platelets compared to approximately 14% improvement for multi-walled carbon nanotubes. The mode I fracture toughness of the nanocomposite with graphene platelets showed approximately 53% increase over the epoxy compared to approximately 20% improvement for multi-walled carbon nanotubes. The fatigue resistance results also showed significantly different trends. While the fatigue suppression response of nanotube/epoxy composites degrades dramatically as the stress intensity factor amplitude is increased, the reverse effect is seen for graphene-based nanocomposites. The superiority of graphene platelets over carbon nanotubes in terms of mechanical properties enhancement may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface, as well as the two-dimensional (planar) geometry of graphene platelets. PMID:19957928

  15. Enhanced nonlinear interactions in quantum optomechanics via mechanical amplification

    PubMed Central

    Lemonde, Marc-Antoine; Didier, Nicolas; Clerk, Aashish A.

    2016-01-01

    The quantum nonlinear regime of optomechanics is reached when nonlinear effects of the radiation pressure interaction are observed at the single-photon level. This requires couplings larger than the mechanical frequency and cavity-damping rate, and is difficult to achieve experimentally. Here we show how to exponentially enhance the single-photon optomechanical coupling strength using only additional linear resources. Our method is based on using a large-amplitude, strongly detuned mechanical parametric drive to amplify mechanical zero-point fluctuations and hence enhance the radiation pressure interaction. It has the further benefit of allowing time-dependent control, enabling pulsed schemes. For a two-cavity optomechanical set-up, we show that our scheme generates photon blockade for experimentally accessible parameters, and even makes the production of photonic states with negative Wigner functions possible. We discuss how our method is an example of a more general strategy for enhancing boson-mediated two-particle interactions and nonlinearities. PMID:27108814

  16. Use of two surface analyzers to evaluate the surface roughness of four esthetic restorative materials after polishing.

    PubMed

    Joniot, Sabine; Salomon, Jean Pierre; Dejou, Jacques; Grégoire, Geneviève

    2006-01-01

    This study had two aims: determine how well four esthetic restorative materials lent themselves to polishing and compare the results obtained using two different techniques for evaluating surface roughness. The four materials used were two composites modified by the addition of resin, Dyract AP (Dentsply) and Dyract Flow (Dentsply); one composite designed for posterior restorations, SureFil (Dentsply) and one universal micromatrix composite, Esthet-X (Dentsply). Five test pieces were made with each product by inserting the material into cylindrical molds and polymerizing it layer by layer. A single operator polished the specimens on the same day using the Enhance system (Dentsply) and two aluminum oxide pastes. The surfaces were studied successively by means of two surface analyzers: a high-resolution optical profilometer (Nanosurf 488, SAS Technology) and a mechanical profilometer (Mitutoyo Surftest-SV 402). These measurements gave the mean roughness of the surface (Ra). Ten zones were examined for each specimen, and the specimens were observed under an optical microscope (PMG3 inverted metallographic microscope) at 50x magnification. The qualitative and quantitative analyses of the results showed good surface states for all materials. However, the composites based on nano- and micro-filler technology gave the smoothest surfaces after polishing. A comparison of the values obtained with each method of observation showed that mechanical profilometry tended to show roughness caused by polishing, while optical profilometry brought out roughness due to the structure of the material itself. PMID:16536192

  17. Lethal and sublethal effects of rice polishing process on Sitophilus oryzae (Coleoptera: Curculionidae).

    PubMed

    Lucas, E; Riudavets, J

    2000-12-01

    The mechanical impact of rice polishingon the rice weevil, Sitophilus oryzae (L.), and the subsequent postpolishing effects associated with rice quality were studied. "Brown" rice (not polished), "White (infest then polish)" rice, and "White (polish then infest)" rice were used with different polishing process intensities and different initial weevil densities. Weevil progeny were more numerous in Brown than in White (infest then polish) or White (polish then infest) rice. Polishing corresponding to a weight loss of 11% in rice generated an immediate mortality of approximately 40%; the subsequent mortality caused by rice quality was also 40% (total >80%). A polishing process corresponding to 14 and 16% of rice weight loss generated a drastic mortality in the weevil population (>95%). The progeny per adult weevil was similar with high and low initial weevil densities. The development of weevil progeny was also delayed by about 1 wk in White (infest then polish) rice compared with Brown rice. Furthermore, weevil adults of the progeny were significantly heavier in Brown than in White (infest then polish) or White (polish then infest) rice. PMID:11142320

  18. Mechanical oscillations enhance gene delivery into suspended cells

    PubMed Central

    Zhou, Z. L.; Sun, X. X.; Ma, J.; Man, C. H.; Wong, A. S. T.; Leung, A. Y.; Ngan, A. H. W.

    2016-01-01

    Suspended cells are difficult to be transfected by common biochemical methods which require cell attachment to a substrate. Mechanical oscillations of suspended cells at certain frequencies are found to result in significant increase in membrane permeability and potency for delivery of nano-particles and genetic materials into the cells. Nanomaterials including siRNAs are found to penetrate into suspended cells after subjecting to short-time mechanical oscillations, which would otherwise not affect the viability of the cells. Theoretical analysis indicates significant deformation of the actin-filament network in the cytoskeleton cortex during mechanical oscillations at the experimental frequency, which is likely to rupture the soft phospholipid bilayer leading to increased membrane permeability. The results here indicate a new method for enhancing cell transfection. PMID:26956215

  19. Molecular mechanisms underlying progesterone-enhanced breast cancer cell migration.

    PubMed

    Wang, Hui-Chen; Lee, Wen-Sen

    2016-01-01

    Progesterone (P4) was demonstrated to inhibit migration in vascular smooth muscle cells (VSMCs), but to enhance migration in T47D breast cancer cells. To investigate the mechanism responsible for this switch in P4 action, we examined the signaling pathway responsible for the P4-induced migration enhancement in breast cancer cell lines, T47D and MCF-7. Here, we demonstrated that P4 activated the cSrc/AKT signaling pathway, subsequently inducing RSK1 activation, which in turn increased phosphorylation of p27 at T198 and formation of the p27pT198-RhoA complex in the cytosol, thereby preventing RhoA degradation, and eventually enhanced migration in T47D cells. These findings were confirmed in the P4-treated MCF-7. Comparing the P4-induced molecular events in between breast cancer cells and VSMCs, we found that P4 increased p27 phosphorylation at T198 in breast cancer cells through RSK1 activation, while P4 increased p27 phosphorlation at Ser10 in VSMCs through KIS activation. P27pT198 formed the complex with RhoA and prevented RhoA degradation in T47D cells, whereas p-p27Ser10 formed the complex with RhoA and caused RhoA degradation in VSMCs. The results of this study highlight the molecular mechanism underlying P4-enhanced breast cancer cell migration, and suggest that RSK1 activation is responsible for the P4-induced migration enhancement in breast cancer cells. PMID:27510838

  20. Molecular mechanisms underlying progesterone-enhanced breast cancer cell migration

    PubMed Central

    Wang, Hui-Chen; Lee, Wen-Sen

    2016-01-01

    Progesterone (P4) was demonstrated to inhibit migration in vascular smooth muscle cells (VSMCs), but to enhance migration in T47D breast cancer cells. To investigate the mechanism responsible for this switch in P4 action, we examined the signaling pathway responsible for the P4-induced migration enhancement in breast cancer cell lines, T47D and MCF-7. Here, we demonstrated that P4 activated the cSrc/AKT signaling pathway, subsequently inducing RSK1 activation, which in turn increased phosphorylation of p27 at T198 and formation of the p27pT198-RhoA complex in the cytosol, thereby preventing RhoA degradation, and eventually enhanced migration in T47D cells. These findings were confirmed in the P4-treated MCF-7. Comparing the P4-induced molecular events in between breast cancer cells and VSMCs, we found that P4 increased p27 phosphorylation at T198 in breast cancer cells through RSK1 activation, while P4 increased p27 phosphorlation at Ser10 in VSMCs through KIS activation. P27pT198 formed the complex with RhoA and prevented RhoA degradation in T47D cells, whereas p-p27Ser10 formed the complex with RhoA and caused RhoA degradation in VSMCs. The results of this study highlight the molecular mechanism underlying P4-enhanced breast cancer cell migration, and suggest that RSK1 activation is responsible for the P4-induced migration enhancement in breast cancer cells. PMID:27510838

  1. [Lysenkoism in Polish botany].

    PubMed

    Köhler, Piotr

    2008-01-01

    Lysenkoism in Poland was never an autonomous phenomenon. The whole array of reasons for which it appeared in Polish science would require a separate study--here it only needs to be pointed out that the major reasons included terror on the part of the security service, lawlessness, the ubiquitous atmosphere of intimidation and terror, censorship, the diminishing sphere of civil liberties, political show trials, propaganda and denunciations. An important role in facilitating the introduction of Lysenkoism was played also by the reorganization of science after World War Two, the isolation of Polish science from science in the West, as well as the damage it had suffered during the war. At first, Lysenkoism was promoted in Poland by a small group of enthusiastic and uncritical proponents. A overview of the events connected with the ten years of Lysenkoism in Poland (end of 1948--beginning of 1958) shows a two-tier picture of how the 'idea' was propagated. The first tier consisted in the activities of the Association of Marxist Naturalists [Koło Przyrodników-Marksistów], which it engaged in since the end of 1948. The Association was later transformed into a Union of Marxist Naturalists, and this in turn merged, in 1952, with the Copernican Society of Polish Naturalists [Polskie Towarzystwo Przyrodników im. Kopernika]. It was that society which promoted Lysenkoism longest, until the end of 1956. The propaganda and training activities of the circle and the society prepared ground for analogous activities of the newly formed Polish Academy of Science (PAN), which--since its very establishment in 1952--engaged in promoting Lysenkoism through its Second Division. These activities were aimed at naturalists, initially at those who were prominent scientists (eg. the conference at Kuźnice, 1950/1951), and then at those who were only starting their academic career (including national courses in new biology at Dziwnów, 1952, or Kortowo, 1953 and 1955). The end to promoting

  2. Oxidized Metal Powders for Mechanical Shock and Crush Safety Enhancers

    SciTech Connect

    GARINO, TERRY J.

    2002-01-01

    The use of oxidized metal powders in mechanical shock or crush safety enhancers in nuclear weapons has been investigated. The functioning of these devices is based on the remarkable electrical behavior of compacts of certain oxidized metal powders when subjected to compressive stress. For example, the low voltage resistivity of a compact of oxidized tantalum powder was found to decrease by over six orders of magnitude during compaction between 1 MPa, where the thin, insulating oxide coatings on the particles are intact, to 10 MPa, where the oxide coatings have broken down along a chain of particles spanning the electrodes. In this work, the behavior of tantalum and aluminum powders was investigated. The low voltage resistivity during compaction of powders oxidized under various conditions was measured and compared. In addition, the resistivity at higher voltages and the dielectric breakdown strength during compaction were also measured. A key finding was that significant changes in the electrical properties persist after the removal of the stress so that a mechanical shock enhancer is feasible. This was verified by preliminary shock experiments. Finally, conceptual designs for both types of enhancers are presented.

  3. Mechanisms underlying the social enhancement of vocal learning in songbirds.

    PubMed

    Chen, Yining; Matheson, Laura E; Sakata, Jon T

    2016-06-14

    Social processes profoundly influence speech and language acquisition. Despite the importance of social influences, little is known about how social interactions modulate vocal learning. Like humans, songbirds learn their vocalizations during development, and they provide an excellent opportunity to reveal mechanisms of social influences on vocal learning. Using yoked experimental designs, we demonstrate that social interactions with adult tutors for as little as 1 d significantly enhanced vocal learning. Social influences on attention to song seemed central to the social enhancement of learning because socially tutored birds were more attentive to the tutor's songs than passively tutored birds, and because variation in attentiveness and in the social modulation of attention significantly predicted variation in vocal learning. Attention to song was influenced by both the nature and amount of tutor song: Pupils paid more attention to songs that tutors directed at them and to tutors that produced fewer songs. Tutors altered their song structure when directing songs at pupils in a manner that resembled how humans alter their vocalizations when speaking to infants, that was distinct from how tutors changed their songs when singing to females, and that could influence attention and learning. Furthermore, social interactions that rapidly enhanced learning increased the activity of noradrenergic and dopaminergic midbrain neurons. These data highlight striking parallels between humans and songbirds in the social modulation of vocal learning and suggest that social influences on attention and midbrain circuitry could represent shared mechanisms underlying the social modulation of vocal learning. PMID:27247385

  4. Polishing gold and gold-alloy crystals

    NASA Technical Reports Server (NTRS)

    Doty, J. P.

    1976-01-01

    Sawed cross-section samples are rough polished at minimum pressure with 14 micron grit. After saw marks are polished away, polishing grit is changed to 0.05 micron. When smooth appearance is attained, surface is then chemically polished by hand in dust free room.

  5. Lysenko affair and Polish botany.

    PubMed

    Köhler, Piotr

    2011-01-01

    This article describes the slight impact of Lysenkoism upon Polish botany. I begin with an account of the development of plant genetics in Poland, as well as the attitude of scientists and the Polish intelligentsia toward Marxist philosophy prior to the World War II. Next I provide a short history of the introduction and demise of Lysenkoism in Polish science, with a focus on events in botany, in context with key events in Polish science from 1939 to 1958. The article outlines the little effects of Lysenkoism upon botanists and their research, as well as how botanists for the most part rejected what was often termed the "new biology." My paper shows that though Lysenko's theories received political support, and were actively promoted by a small circle of scientists and Communist party activists, they were never accepted by most botanists. Once the political climate in Poland altered after the events of 1956, Lysenko's theories were immediately abandoned. PMID:20665091

  6. Tooth polishing: The current status

    PubMed Central

    Sawai, Madhuri Alankar; Bhardwaj, Ashu; Jafri, Zeba; Sultan, Nishat; Daing, Anika

    2015-01-01

    Healthy teeth and gums make a person feel confident and fit. As people go about their daily routines and with different eating and drinking habits, the tooth enamel turns yellowish or gets stained. Polishing traditionally has been associated with the prophylaxis procedure in most dental practices, which patients know and expect. However, with overzealous use of polishing procedure, there is wearing of the superficial tooth structure. This would lead to more accumulation of local deposits. Also, it takes a long time for the formation of the fluoride-rich layer of the tooth again. Hence, now-a-days, polishing is not advised as a part of routine oral prophylaxis procedure but is done selectively based on the patients’ need. The article here, gives an insight on the different aspects of the polishing process along with the different methods and agents used for the same. PMID:26392683

  7. Mechanism based approaches for rescuing and enhancing cognition

    PubMed Central

    Lynch, Gary; Gall, Christine M.

    2013-01-01

    Progress toward pharmacological means for enhancing memory and cognition has been retarded by the widely discussed failure of behavioral studies in animals to predict human outcomes. As a result, a number of groups have targeted cognition-related neurobiological mechanisms in animal models, with the assumption that these basic processes are highly conserved across mammals. Here we survey one such approach that begins with a form of synaptic plasticity intimately related to memory encoding in animals and likely operative in humans. An initial section will describe a detailed hypothesis concerning the signaling and structural events (a “substrate map”) that convert learning associated patterns of afferent activity into extremely stable increases in fast, excitatory transmission. We next describe results suggesting that all instances of intellectual impairment so far tested in rodent models involve a common endpoint failure in the substrate map. This will be followed by a clinically plausible proposal for obviating the ultimate defect in these models. We then take up the question of whether it is reasonable to expect, from either general principles or a very limited set of experimental results, that enhancing memory will expand the cognitive capabilities of high functioning brains. The final section makes several suggestions about how to improve translation of behavioral results from animals to humans. Collectively, the material covered here points to the following: (1) enhancement, in the sense of rescue, is not an unrealistic possibility for a broad array of neuropsychiatric disorders; (2) serendipity aside, developing means for improving memory in normals will likely require integration of information about mechanisms with new behavioral testing strategies; (3) a shift in emphasis from synapses to networks is a next, logical step in the evolution of the cognition enhancement field. PMID:23966908

  8. Mechanism based approaches for rescuing and enhancing cognition.

    PubMed

    Lynch, Gary; Gall, Christine M

    2013-01-01

    Progress toward pharmacological means for enhancing memory and cognition has been retarded by the widely discussed failure of behavioral studies in animals to predict human outcomes. As a result, a number of groups have targeted cognition-related neurobiological mechanisms in animal models, with the assumption that these basic processes are highly conserved across mammals. Here we survey one such approach that begins with a form of synaptic plasticity intimately related to memory encoding in animals and likely operative in humans. An initial section will describe a detailed hypothesis concerning the signaling and structural events (a "substrate map") that convert learning associated patterns of afferent activity into extremely stable increases in fast, excitatory transmission. We next describe results suggesting that all instances of intellectual impairment so far tested in rodent models involve a common endpoint failure in the substrate map. This will be followed by a clinically plausible proposal for obviating the ultimate defect in these models. We then take up the question of whether it is reasonable to expect, from either general principles or a very limited set of experimental results, that enhancing memory will expand the cognitive capabilities of high functioning brains. The final section makes several suggestions about how to improve translation of behavioral results from animals to humans. Collectively, the material covered here points to the following: (1) enhancement, in the sense of rescue, is not an unrealistic possibility for a broad array of neuropsychiatric disorders; (2) serendipity aside, developing means for improving memory in normals will likely require integration of information about mechanisms with new behavioral testing strategies; (3) a shift in emphasis from synapses to networks is a next, logical step in the evolution of the cognition enhancement field. PMID:23966908

  9. Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue

    PubMed Central

    Rojas, Julio C.; Bruchey, Aleksandra K.; Gonzalez-Lima, F.

    2011-01-01

    This paper provides the first review of the memory-enhancing and neuroprotective metabolic mechanisms of action of methylene blue in vivo. These mechanisms have important implications as a new neurobiological approach to improve normal memory and to treat memory impairment and neurodegeneration associated with mitochondrial dysfunction. Methylene blue’s action is unique because its neurobiological effects are not determined by regular drug-receptor interactions or drug-response paradigms. Methylene blue shows a hormetic dose-response, with opposite effects at low and high doses. At low doses, methylene blue is an electron cycler in the mitochondrial electron transport chain, with unparalleled antioxidant and cell respiration-enhancing properties that affect the function of the nervous system in a versatile manner. A major role of the respiratory enzyme cytochrome oxidase on the memory-enhancing effects of methylene blue is supported by available data. The memory-enhancing effects have been associated with improvement of memory consolidation in a network-specific and use-dependent fashion. In addition, low doses of methylene blue have also been used for neuroprotection against mitochondrial dysfunction in humans and experimental models of disease. The unique auto-oxidizing property of methylene blue and its pleiotropic effects on a number of tissue oxidases explain its potent neuroprotective effects at low doses. The evidence reviewed supports a mechanistic role of low-dose methylene blue as a promising and safe intervention for improving memory and for the treatment of acute and chronic conditions characterized by increased oxidative stress, neurodegeneration and memory impairment. PMID:22067440

  10. [The Polish Medical Association, Londyn].

    PubMed

    Nowak, K

    1994-01-01

    The Polish Medical Association, founded in 1944 in London and celebrating its Golden Jubilee in 1944, is a unique organisation of doctors brought together by the shared experience of serving in the Polish armed forces on the fronts of the II World War. Preparing themselves for the return to a free Poland and later facing the realities of the emigré existence, they formed an association based on an identity with patriotic ideals and espousing a loyalty to the national cause, solidarity with the aspirations and goals of the expatriate community and commitment to the integrity in the performance of their professional duties. It was created against a background of the already existing Polish Medical Faculty at the University of Edinburgh and supported by strong lobbying on the part of the Polish Government and the favourable political climate. The need for a professional body of Polish doctors became evident. During the first few years the Association, originally called the Polish Medical Association in the British Empire, numbered over 700 doctors and achieved notable succeses for its members. The most significant were the endeavours which contributed to the inclusion of the so-called Clause 5 of the Polish Resettlement Act 1947, which in practice allowed Polish doctors serving in the Polish forces under British command to obtain full medical registration. Almost 800 doctors benefitted from this legislature and by coincidence, with the introduction of the National Health Service, they constituted the single most significant injection of non-British doctors into the British health care system. Throughout the years the Association, which originally comprised doctors with an Army background acquired more and more civilian members. The second generation followed, smaller waves of post-war emigration brought in new members from Poland. With time the administrative structure of the Association--initially comprising ten divisions in the UK and overseas--has changed; the

  11. Electrochemical polishing of notches

    DOEpatents

    Kephart, Alan R.; Alberts, Alfred H.

    1989-01-01

    An apparatus and method are disclosed for the selective electrochemical polishing of a lateral tip of a deep longitudinal notch in a work piece used to test crack initiation properties of materials. A DC power source is connected to the work piece and to an electrode disposed laterally along the distal end of an insulated body which is inserted in the longitudinal notch. The electrode and distal end of the body are disposed along the tip of the notch, but are spaced from the notch so as to provide a lateral passage for an electrolyte. The electrolyte is circulated through the passage so that the electrolyte only contacts the work piece adjacent the passage. Conveniently, the electrolyte is circulated by use of an inlet tube and an outlet tube provided at opposite ends of the passage. These tubes are preferably detachably located adjacent the ends of the passage and suitable seals are provided. A holding device including arms to which the tubes are attached is conveniently used to rapidly and easily locate the test specimen with the passage aligned with the tubes. The electrode is preferably a wire which is located in grooves along the distal end of the insulated body and up one side of the body or a plastic sheath insulated thin metal strip.

  12. Electrochemical polishing of notches

    DOEpatents

    Kephart, A.R.; Alberts, A.H.

    1989-02-21

    An apparatus and method are disclosed for the selective electrochemical polishing of a lateral tip of a deep longitudinal notch in a work piece used to test crack initiation properties of materials. A DC power source is connected to the work piece and to an electrode disposed laterally along the distal end of an insulated body which is inserted in the longitudinal notch. The electrode and distal end of the body are disposed along the tip of the notch, but are spaced from the notch so as to provide a lateral passage for an electrolyte. The electrolyte is circulated through the passage so that the electrolyte only contacts the work piece adjacent the passage. Conveniently, the electrolyte is circulated by use of an inlet tube and an outlet tube provided at opposite ends of the passage. These tubes are preferably detachably located adjacent the ends of the passage and suitable seals are provided. A holding device including arms to which the tubes are attached is conveniently used to rapidly and easily locate the test specimen with the passage aligned with the tubes. The electrode is preferably a wire which is located in grooves along the distal end of the insulated body and up one side of the body or a plastic sheath insulated thin metal strip. 4 figs.

  13. XXXVI Polish Astronomical Society Meeting

    NASA Astrophysics Data System (ADS)

    Różańska, Agata; Bejger, Michał

    2014-12-01

    XXXVI meeting of Polish Astronomical Society was held in Warsaw on Sept. 11-14, 2013. The conference brought together 150 astronomers working in different institutes in Poland and abroad. The highlight of the Congress was the first awarding of the Paczynski's Medal. The first laureate of the Medal is Professor Martin Rees from University of Cambridge. Medal was given by the President of the Polish Astronomical Society prof. Bozena Czerny.

  14. Enhanced Sensitivity of Micro Mechanical Chemical Sensors Through Structural Variation

    SciTech Connect

    Harris, J.C.

    2001-04-16

    Chemical detection devices are very effective; however, their bulkiness makes them undesirable for portable applications. The next generation of chemical detectors is microscopic mechanical devices capable of measuring trace amounts of chemical vapor within the environment. The chemicals do not react directly with the detector, instead intermolecular forces cause chemicals to adhere to the surface. This surface adhesion of the chemical creates surface stress on the detectors leading to measurable movement. Modifications to the structural design of these microstructures have resulted in signal enhancement to over seven hundred percent.

  15. The enhancement mechanism of thin plasma layer on antenna radiation

    SciTech Connect

    Wang, Chunsheng Jiang, Binhao; Li, Xueai

    2015-03-09

    A model of plasma-antenna is carried out to study the radiation enhancement mechanism of antenna covered by thin plasma layer. The results show when the radiation intensity achieves maximum, a region of equal electric field is formed due to the reflection of electric field at the interface of plasma and air. The plasma layer acted as an extension of the antenna. Furthermore, the shape of plasma layer is changed to verify the effect of plasma boundary on antenna radiation. The study shows the effect of thin plasma layer on electromagnetic field and provides a type of plasma antenna.

  16. Enhancement of sleep slow waves: underlying mechanisms and practical consequences

    PubMed Central

    Bellesi, Michele; Riedner, Brady A.; Garcia-Molina, Gary N.; Cirelli, Chiara; Tononi, Giulio

    2014-01-01

    Even modest sleep restriction, especially the loss of sleep slow wave activity (SWA), is invariably associated with slower electroencephalogram (EEG) activity during wake, the occurrence of local sleep in an otherwise awake brain, and impaired performance due to cognitive and memory deficits. Recent studies not only confirm the beneficial role of sleep in memory consolidation, but also point to a specific role for sleep slow waves. Thus, the implementation of methods to enhance sleep slow waves without unwanted arousals or lightening of sleep could have significant practical implications. Here we first review the evidence that it is possible to enhance sleep slow waves in humans using transcranial direct-current stimulation (tDCS) and transcranial magnetic stimulation. Since these methods are currently impractical and their safety is questionable, especially for chronic long-term exposure, we then discuss novel data suggesting that it is possible to enhance slow waves using sensory stimuli. We consider the physiology of the K-complex (KC), a peripheral evoked slow wave, and show that, among different sensory modalities, acoustic stimulation is the most effective in increasing the magnitude of slow waves, likely through the activation of non-lemniscal ascending pathways to the thalamo-cortical system. In addition, we discuss how intensity and frequency of the acoustic stimuli, as well as exact timing and pattern of stimulation, affect sleep enhancement. Finally, we discuss automated algorithms that read the EEG and, in real-time, adjust the stimulation parameters in a closed-loop manner to obtain an increase in sleep slow waves and avoid undesirable arousals. In conclusion, while discussing the mechanisms that underlie the generation of sleep slow waves, we review the converging evidence showing that acoustic stimulation is safe and represents an ideal tool for slow wave sleep (SWS) enhancement. PMID:25389394

  17. Simultaneous ion sputter polishing and deposition

    NASA Technical Reports Server (NTRS)

    Rutledge, S.; Banks, B.; Brdar, M.

    1981-01-01

    Results of experiments to study ion beam sputter polishing in conjunction with simultaneous deposition as a mean of polishing copper surfaces are presented. Two types of simultaneous ion sputter polishing and deposition were used in these experiments. The first type utilized sputter polishing simultaneous with vapor deposition, and the second type utilized sputter polishing simultaneous with sputter deposition. The etch and deposition rates of both techniques were studied, as well as the surface morphology and surface roughness.

  18. Enhanced Graphene Mechanical Properties through Ultrasmooth Copper Growth Substrates.

    PubMed

    Griep, Mark H; Sandoz-Rosado, Emil; Tumlin, Travis M; Wetzel, Eric

    2016-03-01

    The combination of extraordinary strength and stiffness in conjunction with exceptional electronic and thermal properties in lightweight two-dimensional materials has propelled graphene research toward a wide array of applications including flexible electronics and functional structural components. Tailoring graphene's properties toward a selected application requires precise control of the atomic layer growth process, transfer, and postprocessing procedures. To date, the mechanical properties of graphene are largely controlled through postprocess defect engineering techniques. In this work, we demonstrate the role of varied catalytic surface morphologies on the tailorability of subsequent graphene film quality and breaking strength, providing a mechanism to tailor the physical, electrical, and mechanical properties at the growth stage. A new surface planarization methodology that results in over a 99% reduction in Cu surface roughness allows for smoothness parameters beyond that reported to date in literature and clearly demonstrates the role of Cu smoothness toward a decrease in the formation of bilayer graphene defects, altered domain sizes, monolayer graphene sheet resistance values down to 120 Ω/□ and a 78% improvement in breaking strength. The combined electrical and mechanical enhancements achieved through this methodology allows for the direct growth of application quality flexible transparent conductive films with monolayer graphene. PMID:26882091

  19. Gurney flap—Lift enhancement, mechanisms and applications

    NASA Astrophysics Data System (ADS)

    Wang, J. J.; Li, Y. C.; Choi, K.-S.

    2008-01-01

    Since its invention by a race car driver Dan Gurney in 1960s, the Gurney flap has been used to enhance the aerodynamics performance of subsonic and supercritical airfoils, high-lift devices and delta wings. In order to take stock of recent research and development of Gurney flap, we have carried out a review of the characteristics and mechanisms of lift enhancement by the Gurney flap and its applications. Optimum design of the Gurney flap is also summarized in this paper. For the Gurney flap to be effective, it should be mounted at the trailing edge perpendicular to the chord line of airfoil or wing. The flap height must be of the order of local boundary layer thickness. For subsonic airfoils, an additional Gurney flap increases the pressure on the upstream surface of the Gurney flap, which increases the total pressure of the lower surface. At the same time, a long wake downstream of the flap containing a pair of counter-rotating vortices can delay or eliminate the flow separation near the trailing edge on the upper surface. Correspondingly, the total suction on the airfoil is increased. For supercritical airfoils, the lift enhancement of the Gurney flap mainly comes from its ability to shift the shock on the upper surface in the downstream. Applications of the Gurney flap to modern aircraft design are also discussed in this review.

  20. Composite adaptive control of belt polishing force for aero-engine blade

    NASA Astrophysics Data System (ADS)

    Zhsao, Pengbing; Shi, Yaoyao

    2013-09-01

    The existing methods for blade polishing mainly focus on robot polishing and manual grinding. Due to the difficulty in high-precision control of the polishing force, the blade surface precision is very low in robot polishing, in particular, quality of the inlet and exhaust edges can not satisfy the processing requirements. Manual grinding has low efficiency, high labor intensity and unstable processing quality, moreover, the polished surface is vulnerable to burn, and the surface precision and integrity are difficult to ensure. In order to further improve the profile accuracy and surface quality, a pneumatic flexible polishing force-exerting mechanism is designed and a dual-mode switching composite adaptive control(DSCAC) strategy is proposed, which combines Bang-Bang control and model reference adaptive control based on fuzzy neural network(MRACFNN) together. By the mode decision-making mechanism, Bang-Bang control is used to track the control command signal quickly when the actual polishing force is far away from the target value, and MRACFNN is utilized in smaller error ranges to improve the system robustness and control precision. Based on the mathematical model of the force-exerting mechanism, simulation analysis is implemented on DSCAC. Simulation results show that the output polishing force can better track the given signal. Finally, the blade polishing experiments are carried out on the designed polishing equipment. Experimental results show that DSCAC can effectively mitigate the influence of gas compressibility, valve dead-time effect, valve nonlinear flow, cylinder friction, measurement noise and other interference on the control precision of polishing force, which has high control precision, strong robustness, strong anti-interference ability and other advantages compared with MRACFNN. The proposed research achieves high-precision control of the polishing force, effectively improves the blade machining precision and surface consistency, and

  1. AIBA as Free Radical Initiator for Abrasive-Free Polishing of Hard Disk Substrate

    NASA Astrophysics Data System (ADS)

    Lei, Hong; Ren, Xiaoyan

    2015-04-01

    In order to optimize the existing slurry for abrasive-free polishing (AFP) of a hard disk substrate, a water-soluble free radical initiator, 2,2'-azobis (2-methylpropionamidine) dihydrochloride (AIBA) was introduced into H2O2-based slurry in the present work. Polishing experiment results with AIBA in the H2O2 slurry indicate that the material removal rate (MRR) increases and the polished surface has a lower surface roughness. The mechanism of AIBA in AFP was investigated using electron spin-resonance spectroscopy and UV-Visible analysis, which showed that the concentration of hydroxyl radical (a stronger oxidizer than H2O2) in the slurry was enhanced in the present of AIBA. The structure of the film formed on the substrate surface was investigated by scanning electron microscopy, auger electron spectroscopy and electrochemical impedance spectroscopy technology, showing that a looser and porous oxide film was found on the hard disk substrate surface when treated with the H2O2-AIBA slurry. Furthermore, potentiodynamic polarization tests show that the H2O2-AIBA slurry has a higher corrosion current density, implying that a fast dissolution reaction can occur on the substrate surface. Therefore, we can conclude that the stronger oxidation ability, loose oxide film on the substrate surface, and the higher corrosion-wear rate of the H2O2-AIBA slurry lead to the higher MRR.

  2. Effect of Polishing on the Friction Behaviors and Cutting Performance of Boron-Doped Diamond Films on WC-Co Inserts

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Shen, Bin; Sun, Fanghong; Zhang, Zhiming

    2014-04-01

    Boron doped (B-doped) diamond films are deposited onto WC-Co inserts by HFCVD with the mixture of acetone, trimethyl borate (C3H9BO3) and H2. The as-deposited B-doped diamond films are characterized with scanning electron microscope (SEM), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, 3D surface topography based on white-light interferometry and Rockwell hardness tester. The effects of mechanical polishing on the friction behavior and cutting performance of B-doped diamond are evaluated by ball-on-plate type reciprocating tribometer and turning of aluminum alloy 7075 materials, respectively. For comparison, the same tests are also conducted for the bare WC-Co inserts with smooth surface. Friction tests suggest that the unpolished and polished B-doped diamond films possess relatively low fluctuation of friction coefficient than as-received bare WC-Co samples. The average stable friction coefficient for B-doped diamond films decreases apparently after mechanical polishing. The values for WC-Co sample, unpolished and polished B-doped diamond films are approximately 0.38, 0.25 and 0.11, respectively. The cutting results demonstrate that the low friction coefficient and high adhesive strength of B-doped diamond films play an essential role in the cutting performance enhancement of the WC-Co inserts. However, the mechanical polishing process may lower the adhesive strength of B-doped diamond films. Consequently, the polished B-doped diamond coated inserts show premature wear in the machining of adhesive aluminum alloy materials.

  3. Laser polishing of niobium for superconducting radio-frequency accelerator applications

    SciTech Connect

    Zhao, Liang; Klopf, John M.; Reece, Charles E.; Kelley, Michael J.

    2014-08-01

    Interior surfaces of niobium cavities used in superconducting radio frequency accelerators are now obtained by buffered chemical polish and/or electropolish. Laser polishing is a potential alternative, having advantages of speed, freedom from noxious chemistry and availability of in-process inspection. We studied the influence of the laser power density and laser beam raster rate on the surface topography. These two factors need to be combined carefully to smooth the surface without damage. Computational modeling was used to estimate the surface temperature and gain insight into the mechanism of laser polishing. Power spectral density analysis of surface topography measurements shows that laser polishing can produce smooth topography similar to that obtained by electropolish. This is a necessary first step toward introducing laser polishing as an alternative to the currently practiced chemical polishing.

  4. Sensing roughness and polish direction

    NASA Astrophysics Data System (ADS)

    Jakobsen, M. L.; Olesen, A. S.; Larsen, H. E.; Stubager, J.; Hanson, S. G.; Pedersen, T. F.; Pedersen, H. C.

    2016-04-01

    As a part of the work carried out on a project supported by the Danish council for technology and innovation, we have investigated the option of smoothing standard CNC machined surfaces. In the process of constructing optical prototypes, involving custom-designed optics, the development cost and time consumption can become relatively large numbers in a research budget. Machining the optical surfaces directly is expensive and time consuming. Alternatively, a more standardized and cheaper machining method can be used, but then the object needs to be manually polished. During the polishing process the operator needs information about the RMS-value of the surface roughness and the current direction of the scratches introduces by the polishing process. The RMS-value indicates to the operator how far he is from the final finish, and the scratch orientation is often specified by the customer in order to avoid complications during the casting process. In this work we present a method for measuring the RMS-values of the surface roughness while simultaneously determining the polishing direction. We are mainly interested in the RMS-values in the range from 0 - 100 nm, which corresponds to the finish categories of A1, A2 and A3. Based on simple intensity measurements we estimates the RMS-value of the surface roughness, and by using a sectioned annual photo-detector to collect the scattered light we can determine the direction of polishing and distinguish light scattered from random structures and light scattered from scratches.

  5. Quantification of microscopic surface features of single point diamond turned optics with subsequent chemical polishing

    NASA Astrophysics Data System (ADS)

    Cardenas, Nelson; Kyrish, Matthew; Taylor, Daniel; Fraelich, Margaret; Lechuga, Oscar; Claytor, Richard; Claytor, Nelson

    2015-03-01

    Electro-Chemical Polishing is routinely used in the anodizing industry to achieve specular surface finishes of various metals products prior to anodizing. Electro-Chemical polishing functions by leveling the microscopic peaks and valleys of the substrate, thereby increasing specularity and reducing light scattering. The rate of attack is dependent of the physical characteristics (height, depth, and width) of the microscopic structures that constitute the surface finish. To prepare the sample, mechanical polishing such as buffing or grinding is typically required before etching. This type of mechanical polishing produces random microscopic structures at varying depths and widths, thus the electropolishing parameters are determined in an ad hoc basis. Alternatively, single point diamond turning offers excellent repeatability and highly specific control of substrate polishing parameters. While polishing, the diamond tool leaves behind an associated tool mark, which is related to the diamond tool geometry and machining parameters. Machine parameters such as tool cutting depth, speed and step over can be changed in situ, thus providing control of the spatial frequency of the microscopic structures characteristic of the surface topography of the substrate. By combining single point diamond turning with subsequent electro-chemical etching, ultra smooth polishing of both rotationally symmetric and free form mirrors and molds is possible. Additionally, machining parameters can be set to optimize post polishing for increased surface quality and reduced processing times. In this work, we present a study of substrate surface finish based on diamond turning tool mark spatial frequency with subsequent electro-chemical polishing.

  6. Fiber Optic Connector Polishing Fixture Assembly

    NASA Technical Reports Server (NTRS)

    Kolasinski, John R. (Inventor); Moszcziewski, Joseph Roch (Inventor)

    2003-01-01

    A fiber optic connector polishing fixture assembly for sup- porting a terminus of a fiber optic cable before a polishing surface. The assembly comprises: a fiber optic polishing fixture adapted to support the terminus before the polishing surface; a fixture support connected to the fixture for sup- porting the fixture before the polishing surface; and an adjustable connection between the fixture and the fixture support having user accessible adjustment controls for allowing a user to operate the controls to shift the fixture and fixture support relative to one another for substantially eliminating an apex offset of the terminus with respect to the polishing surface.

  7. Early bilingualism enhances mechanisms of false-belief reasoning.

    PubMed

    Kovács, Agnes Melinda

    2009-01-01

    In their first years, children's understanding of mental states seems to improve dramatically, but the mechanisms underlying these changes are still unclear. Such 'theory of mind' (ToM) abilities may arise during development, or have an innate basis, developmental changes reflecting limitations of other abilities involved in ToM tasks (e.g. inhibition). Special circumstances such as early bilingualism may enhance ToM development or other capacities required by ToM tasks. Here we compare 3-year-old bilinguals and monolinguals on a standard ToM task, a modified ToM task and a control task involving physical reasoning. The modified ToM task mimicked a language-switch situation that bilinguals often encounter and that could influence their ToM abilities. If such experience contributes to an early consolidation of ToM in bilinguals, they should be selectively enhanced in the modified task. In contrast, if bilinguals have an advantage due to better executive inhibitory abilities involved in ToM tasks, they should outperform monolinguals on both ToM tasks, inhibitory demands being similar. Bilingual children showed an advantage on the two ToM tasks but not on the control task. The precocious success of bilinguals may be associated with their well-developed control functions formed during monitoring and selecting languages. PMID:19120412

  8. A proposed mechanism for turbulent enhancement of broadcast spawning efficiency

    NASA Astrophysics Data System (ADS)

    Crimaldi, J. P.; Browning, H. S.

    2004-08-01

    The broadcast spawning reproductive strategy relies on turbulent-stirring processes in the flow to bring together gametes previously released by adult males and females. The subsequent fertilization rate depends on the product of co-occurring concentrations of egg and sperm. Turbulent mixing produces a strong average dilution in these concentrations, suggesting that an increase in turbulence would reduce the average local fertilization rate. However, turbulent dilution occurs at time scales that may be long compared to those associated with fertilization. Therefore, the instantaneous structure of egg and sperm filaments at shorter time scales must be considered. In this paper, a mechanism is proposed whereby coherent turbulent structures in the velocity field cause coalescence between high-concentration filaments of egg and sperm, significantly enhancing the average fertilization rate. Simple analytical and numerical models are used to demonstrate how the mechanism works, and to make qualitative estimates of its effect on the resulting fertilization rate. The results suggest that the efficiency of broadcast spawning is a consequence of features in the instantaneous turbulent field, and that this efficiency is not captured by models that consider only time-averaged features of the flow.

  9. Biodegradable HEMA-based hydrogels with enhanced mechanical properties.

    PubMed

    Moghadam, Mohamadreza Nassajian; Pioletti, Dominique P

    2016-08-01

    Hydrogels are widely used in the biomedical field. Their main purposes are either to deliver biological active agents or to temporarily fill a defect until they degrade and are followed by new host tissue formation. However, for this latter application, biodegradable hydrogels are usually not capable to sustain any significant load. The development of biodegradable hydrogels presenting load-bearing capabilities would open new possibilities to utilize this class of material in the biomedical field. In this work, an original formulation of biodegradable photo-crosslinked hydrogels based on hydroxyethyl methacrylate (HEMA) is presented. The hydrogels consist of short-length poly(2-hydroxyethyl methacrylate) (PHEMA) chains in a star shape structure, obtained by introducing a tetra-functional chain transfer agent in the backbone of the hydrogels. They are cross-linked with a biodegradable N,O-dimethacryloyl hydroxylamine (DMHA) molecule sensitive to hydrolytic cleavage. We characterized the degradation properties of these hydrogels submitted to mechanical loadings. We showed that the developed hydrogels undergo long-term degradation and specially meet the two essential requirements of a biodegradable hydrogel suitable for load bearing applications: enhanced mechanical properties and low molecular weight degradation products. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1161-1169, 2016. PMID:26061346

  10. Mechanisms for Enhanced Hydrophobicity by Atomic-Scale Roughness.

    PubMed

    Katasho, Yumi; Liang, Yunfeng; Murata, Sumihiko; Fukunaka, Yasuhiro; Matsuoka, Toshifumi; Takahashi, Satoru

    2015-01-01

    It is well known that the close-packed CF3-terminated solid surface is among the most hydrophobic surfaces in nature. Molecular dynamic simulations show that this hydrophobicity can be further enhanced by the atomic-scale roughness. Consequently, the hydrophobic gap width is enlarged to about 0.6 nm for roughened CF3-terminated solid surfaces. In contrast, the hydrophobic gap width does not increase too much for a rough CH3-terminated solid surface. We show that the CF3-terminated surface exists in a microscopic Cassie-Baxter state, whereas the CH3-terminated surface exists as a microscopic Wenzel state. This finding elucidates the underlying mechanism for the different widths of the observed hydrophobic gap. The cage structure of the water molecules (with integrated hydrogen bonds) around CH3 terminal assemblies on the solid surface provides an explanation for the mechanism by which the CH3-terminated surface is less hydrophobic than the CF3-terminated surface. PMID:26337567

  11. Surfactant-enhanced spreading: Experimental achievements and possible mechanisms.

    PubMed

    Kovalchuk, N M; Trybala, A; Arjmandi-Tash, O; Starov, V

    2016-07-01

    Surfactants are broadly used to improve wetting properties of aqueous formulations. The improvement is achieved by essential reduction of liquid/air and solid/liquid interfacial tensions resulting in the decrease of contact angle. For moderately hydrophobic substrates, there is a range of surfactants providing complete wetting of substrate. With the decrease of substrate surface energy, this range of surfactants reduces very quickly and only trisiloxane surfactant solutions are capable to wet completely such highly hydrophobic substrates as polypropylene and parafilm. That is why these surfactants are referred to as superspreaders. The most intriguing feature of wetting surfactant solutions is their ability to spread much faster than pure liquids with spread area, S, being proportional to time, t, S~t, as compared to S~t(0.2) for pure liquids, which wet completely the solid substrate. Trisiloxane surfactant solutions spread faster than other aqueous surfactant solutions, which also provide complete wetting, being superspreaders in the sense of spreading rate as well. The mechanism of fast spreading of surfactant solutions on hydrophobic substrates and much higher spreading rates for trisiloxane solutions are to be explained. Below the available experimental data on superspreading and surfactant-enhanced spreading are analysed/summarised, and possible mechanisms governing the fast spreading are discussed. PMID:26282600

  12. Mechanisms for Enhanced Hydrophobicity by Atomic-Scale Roughness

    PubMed Central

    Katasho, Yumi; Liang, Yunfeng; Murata, Sumihiko; Fukunaka, Yasuhiro; Matsuoka, Toshifumi; Takahashi, Satoru

    2015-01-01

    It is well known that the close-packed CF3-terminated solid surface is among the most hydrophobic surfaces in nature. Molecular dynamic simulations show that this hydrophobicity can be further enhanced by the atomic-scale roughness. Consequently, the hydrophobic gap width is enlarged to about 0.6 nm for roughened CF3-terminated solid surfaces. In contrast, the hydrophobic gap width does not increase too much for a rough CH3-terminated solid surface. We show that the CF3-terminated surface exists in a microscopic Cassie–Baxter state, whereas the CH3-terminated surface exists as a microscopic Wenzel state. This finding elucidates the underlying mechanism for the different widths of the observed hydrophobic gap. The cage structure of the water molecules (with integrated hydrogen bonds) around CH3 terminal assemblies on the solid surface provides an explanation for the mechanism by which the CH3-terminated surface is less hydrophobic than the CF3-terminated surface. PMID:26337567

  13. Polishing compound for plastic surfaces

    DOEpatents

    Stowell, Michael S.

    1995-01-01

    A polishing compound for plastic surfaces. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS.TM., LEXAN.TM., LUCITE.TM., polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired.

  14. Polishing compound for plastic surfaces

    DOEpatents

    Stowell, M.S.

    1995-08-22

    A polishing compound for plastic surfaces is disclosed. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS{trademark}, LEXAN{trademark}, LUCITE{trademark}, polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired. 5 figs.

  15. Graphite Composite Panel Polishing Fixture

    NASA Technical Reports Server (NTRS)

    Hagopian, John; Strojny, Carl; Budinoff, Jason

    2011-01-01

    The use of high-strength, lightweight composites for the fixture is the novel feature of this innovation. The main advantage is the light weight and high stiffness-to-mass ratio relative to aluminum. Meter-class optics require support during the grinding/polishing process with large tools. The use of aluminum as a polishing fixture is standard, with pitch providing a compliant layer to allow support without deformation. Unfortunately, with meter-scale optics, a meter-scale fixture weighs over 120 lb (.55 kg) and may distort the optics being fabricated by loading the mirror and/or tool used in fabrication. The use of composite structures that are lightweight yet stiff allows standard techniques to be used while providing for a decrease in fixture weight by almost 70 percent. Mounts classically used to support large mirrors during fabrication are especially heavy and difficult to handle. The mount must be especially stiff to avoid deformation during the optical fabrication process, where a very large and heavy lap often can distort the mount and optic being fabricated. If the optic is placed on top of the lapping tool, the weight of the optic and the fixture can distort the lap. Fixtures to support the mirror during fabrication are often very large plates of aluminum, often 2 in. (.5 cm) or more in thickness and weight upwards of 150 lb (68 kg). With the addition of a backing material such as pitch and the mirror itself, the assembly can often weigh over 250 lb (.113 kg) for a meter-class optic. This innovation is the use of a lightweight graphite panel with an aluminum honeycomb core for use as the polishing fixture. These materials have been used in the aerospace industry as structural members due to their light weight and high stiffness. The grinding polishing fixture consists of the graphite composite panel, fittings, and fixtures to allow interface to the polishing machine, and introduction of pitch buttons to support the optic under fabrication. In its

  16. Polishing compound for plastic surfaces

    SciTech Connect

    Stowell, M.S.

    1993-01-01

    A polishing compound for plastic surfaces is disclosed. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains colloidal silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS{sup TM}, LEXAN{sup TM}, LUCITE{sup TM}, polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired.

  17. Dissolved air flotation of polishing wastewater from semiconductor manufacturer.

    PubMed

    Liu, J C; Lien, C Y

    2006-01-01

    The feasibility of the dissolved air flotation (DAF) process in treating chemical mechanical polishing (CMP) wastewater was evaluated in this study. Wastewater from a local semiconductor manufacturer was sampled and characterised. Nano-sized silica (77.6 nm) with turbidity of 130 +/- 3 NTU was found in the slightly alkaline wastewater with traces of other pollutants. Experimental results indicated removal efficiency of particles, measured as suspended particle or turbidity, increased with increasing concentration of cationic collector cetyltrimethyl ammonium bromide (CTAB). When CTAB concentration was 30 mg/L, pH of 6.5 +/- 0.1 and recycle ratio of 30%, very effective removal of particles (> 98%) was observed in saturation pressure range of 4 to 6 kg/cm2, and the reaction proceeded faster under higher pressure. Similarly, the reaction was faster under the higher recycle ratio, while final removal efficiency improved slightly as the recycle ratio increased from 20 to 40%. An insignificant effect of pH on treatment efficiency was found as pH varied from 4.5 to 8.5. The presence of activator, Al3+ and Fe3+, enhanced the system performance. It is proposed that CTAB adsorbs on silica particles in polishing wastewater through electrostatic interaction and makes particles more hydrophobic. The increase in hydrophobicity results in more effective bubble-particle collisions. In addition, flocculation of silica particles through bridging effect of collector was found; it is believed that flocculation of particles also contributed to flotation. Better attachment between gas bubble and solid, higher buoyancy and higher air to solid ratio all lead to effective flotation. PMID:16752774

  18. Laser measurement and analysis of reposition error in polishing systems

    NASA Astrophysics Data System (ADS)

    Liu, Weisen; Wang, Junhua; Xu, Min; He, Xiaoying

    2015-10-01

    In this paper, robotic reposition error measurement method based on laser interference remote positioning is presented, the geometric error is analyzed in the polishing system based on robot and the mathematical model of the tilt error is presented. Studies show that less than 1 mm error is mainly caused by the tilt error with small incident angle. Marking spot position with interference fringe enhances greatly the error measurement precision, the measurement precision of tilt error can reach 5 um. Measurement results show that reposition error of the polishing system is mainly from the tilt error caused by the motor A, repositioning precision is greatly increased after polishing system improvement. The measurement method has important applications in the actual error measurement with low cost, simple operation.

  19. Surface roughness and morphology of resin composites polished with two-step polishing systems.

    PubMed

    Can Say, Esra; Yurdagüven, Haktan; Yaman, Batu Can; Özer, Füsun

    2014-01-01

    The purpose of this study was to investigate surface roughness (Ra) and morphology of supra-nanofilled [Estelite Omega (EO), Estelite ∑ Quick (EQ)], micro-hybrid [Esthet.X HD (EHD), G-aenial (GAE)] and nano-hybrid [Clearfil Majesty Posterior (CMP), Charisma Diamond (CD), Beautifil II (BII)] composites polished with two-step polishing systems [Enhance/PoGo (EP); Venus Supra (VS)]. Composite discs, 30 of each type, were prepared. Each composite group was divided into three subgroups: Mylar (control), EP and VS. Ra was evaluated with profilometer. In each composite group, the control had the lowest Ra. With both polishing systems, EO and EQ had significantly the lowest Ra, whereas CMP and BII had the highest. Except for GAE, CD and BII, the differences in Ra between EP and VS in each composite group were significant, showing smoother surfaces for EP. Supra-nanofilled composites created smoother surfaces than nano-hybrids, and their performance was similar or slightly better than that of micro-hybrids. PMID:24598241

  20. Chemical Enhancer Solubility in Human Stratum Corneum Lipids and Enhancer Mechanism of Action on Stratum Corneum Lipid Domain

    PubMed Central

    Ibrahim, Sarah A.; Li, S. Kevin

    2010-01-01

    Previously, chemical enhancer-induced permeation enhancement on human stratum corneum (SC) lipoidal pathway at enhancer thermodynamic activities approaching unity in the absence of cosolvents (defined as Emax) was determined and hypothesized to be related to the enhancer solubilities in the SC lipid domain. The objectives of the present study were to (a) quantify enhancer uptake into SC lipid domain at saturation, (b) elucidate enhancer mechanism(s) of action, and (c) study the SC lipid phase behavior at Emax. It was concluded that direct quantification of enhancer uptake into SC lipid domain using intact SC was complicated. Therefore a liposomal model of extracted human SC lipids was used. In the liposome study, enhancer uptake into extracted human SC lipid liposomes (EHSCLL) was shown to correlate with Emax. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC) were used to evaluate lipid phase alterations in enhancer-treated intact SC. IR spectra demonstrated an increase in the lipid domain fluidity and DSC thermograms indicated a decrease in the phase transition temperature with increasing Emax. These results suggest that the enhancer mechanism of action is through enhancer intercalation into SC intercellular lipids and subsequent lipid lamellae fluidization related to enhancer lipid concentration. PMID:19747970

  1. Experimental Study on the Effects of Alumina Abrasive Particle Behavior in MR Polishing for MEMS Applications

    PubMed Central

    Kim, Dong-Woo; Cho, Myeong-Woo; Seo, Tae-Il; Shin, Young-Jae

    2008-01-01

    Recently, the magnetorheological (MR) polishing process has been examined as a new ultra-precision polishing technology for micro parts in MEMS applications. In the MR polishing process, the magnetic force plays a dominant role. This method uses MR fluids which contains micro abrasives as a polishing media. The objective of the present research is to shed light onto the material removal mechanism under various slurry conditions for polishing and to investigate surface characteristics, including shape analysis and surface roughness measurement, of spots obtained from the MR polishing process using alumina abrasives. A series of basic experiments were first performed to determine the optimum polishing conditions for BK7 glass using prepared slurries by changing the process parameters, such as wheel rotating speed and electric current. Using the obtained results, groove polishing was then performed and the results are investigated. Outstanding surface roughness of Ra=3.8nm was obtained on the BK7 glass specimen. The present results highlight the possibility of applying this polishing method to ultra-precision micro parts production, especially in MEMS applications.

  2. Mechanism involved in enhancement of osteoblast differentiation by hyaluronic acid

    SciTech Connect

    Kawano, Michinao; Ariyoshi, Wataru; Iwanaga, Kenjiro; Okinaga, Toshinori; Habu, Manabu; Yoshioka, Izumi; Tominaga, Kazuhiro; Nishihara, Tatsuji

    2011-02-25

    Research highlights: {yields} In this study was to investigate the effects of HA on osteoblast differentiation induced by BMP-2. {yields} MG63 cells were incubated with BMP-2 and HA for various time periods. {yields} Phosphorylation of Smad 1/5/8, p38, and ERK proteins was determined by western blot analysis. To elucidate the nuclear translocation of phosphorylated Smad 1/5/8, stimulated cells were subjected to immunofluorescence microscopy. {yields} HA enhanced BMP-2 induces osteoblastic differentiation in MG63 cells via down-regulation of BMP-2 antagonists and ERK phosphorylation. -- Abstract: Objectives: Bone morphogenetic protein-2 (BMP-2) is expected to be utilized to fill bone defects and promote healing of fractures. However, it is unable to generate an adequate clinical response for use in bone regeneration. Recently, it was reported that glycosaminoglycans, including heparin, heparan sulfate, keratan sulfate, dermatan sulfate, chondroitin-4-sulfate, chondroitin-6-sulfate, and hyaluronic acid (HA), regulate BMP-2 activity, though the mechanism by which HA regulates osteogenic activities has not been fully elucidated. The aim of this study was to investigate the effects of HA on osteoblast differentiation induced by BMP-2. Materials and methods: Monolayer cultures of osteoblastic lineage MG63 cells were incubated with BMP-2 and HA for various time periods. To determine osteoblastic differentiation, alkaline phosphatase (ALP) activity in the cell lysates was quantified. Phosphorylation of Smad 1/5/8, p38, and ERK proteins was determined by Western blot analysis. To elucidate the nuclear translocation of phosphorylated Smad 1/5/8, stimulated cells were subjected to immunofluorescence microscopy. To further elucidate the role of HA in enhancement of BMP-2-induced Smad signaling, mRNA expressions of the BMP-2 receptor antagonists noggin and follistatin were detected using real-time RT-PCR. Results: BMP-2-induced ALP activation, Smad 1/5/8 phosphorylation, and

  3. Reading Authentic Polish, Volume I.

    ERIC Educational Resources Information Center

    Walczynski, Waldemar

    This book of instructional materials for reading in Polish are intended for college-level students, and are designed to bring native English-speakers from an 0+ (Novice High) to a 1+ (Intermediate High) language proficiency level on the American Council on the Teaching of Foreign Languages/Interagency Language Roundtable proficiency scale. The…

  4. Shaken and stirred: mechanisms of ultrasound-enhanced thrombolysis

    PubMed Central

    Bader, Kenneth B.; Gruber, Matthew J.; Holland, Christy K.

    2014-01-01

    The use of ultrasound and microbubbles as an effective adjuvant to thrombolytics has been demonstrated in vitro, ex vivo, and in vivo. However, the specific mechanisms of ultrasound-enhanced thrombolysis (UET) have yet to be elucidated. We present visual observations illustrating two mechanisms of UET: acoustic cavitation and radiation force. An in vitro flow model was developed to observe human whole blood clots exposed to human fresh-frozen plasma, rt-PA (0, 0.32, 1.58, or 3.15 μg/mL), and the ultrasound contrast agent Definity® (2 μL/mL). Intermittent, continuous-wave, ultrasound (120 kHz, 0.44 MPa peak-to-peak pressure) was used to insonify the perfusate. Ultraharmonic (UH) emissions indicative of stable cavitation were monitored with a passive cavitation detector. The clot was observed with an inverted microscope, and images were recorded with a charge-coupled device (CCD) camera. The images were post processed to determine the time-dependent clot diameter and root-mean-square velocity of the clot position. Clot lysis occurred preferentially surrounding large, resonant-sized bubbles undergoing stable oscillations. UH emissions from stable cavitation were found to correlate with the lytic rate. Clots were observed to translate synchronously with the initiation and cessation of the ultrasound exposure. The root-mean-square velocity of the clot correlated with the lytic rate. These data provide visual documentation of stable cavitation activity and radiation force during sub-megahertz sonothrombolysis. The observations of this study suggest that the process of clot lysis is complex, and both stable cavitation and radiation force are mechanistically responsible for this beneficial bioeffect in this in vitro model. PMID:25438846

  5. The Polish People: The Challenge of Sponsorship.

    ERIC Educational Resources Information Center

    Li, Gertraude Roth; Johnson, Winston

    This report provides background information on Polish refugees that may be of use to sponsors involved in Polish refugee resettlement in the United States. The report discusses economic and social conditions in Poland; the social values and political attitudes of modern Polish refugees as opposed to those of Poles who settled in the United States…

  6. Polishability of thin electrolytic and electroless NiP layers

    NASA Astrophysics Data System (ADS)

    Kinast, Jan; Beier, Matthias; Gebhardt, Andreas; Risse, Stefan; Tünnermann, Andreas

    2015-10-01

    Ultra-precise metal optics are key components of sophisticated scientific instrumentation in astronomy and space applications, covering a wide spectral range. Especially for applications in the visible or ultra-violet spectral ranges, a low roughness of the optics is required. Therefore, a polishable surface is necessary. State of the art is an amorphous nickel-phosphorus (NiP) layer, which enables several polishing techniques achieving a roughness of <1 nm RMS. Typically, these layers are approximately 30 μm to 60 μm thick. Deposited on Al6061, the bimetallic effect leads to a restricted operational temperature, caused by different coefficients of thermal expansion of Al6061 and NiP. Thinner NiP layers reduce the bimetallic effect. Hence, the possible operating temperature range. A deterministic shape correction via Magnetorheological Finishing of the substrate Al6061 leads to low shape deviations prior to the NiP deposition. This allows for depositing thin NiP-layers, which are polishable via a chemical mechanical polishing technique aiming at ultra-precise metal optics. The present article shows deposition processes and polishability of electroless and electrolytic NiP layers with thicknesses between 1 μm and 10 μm.

  7. Vibrationally enhanced tunneling as a mechanism for enzymatic hydrogen transfer.

    PubMed Central

    Bruno, W J; Bialek, W

    1992-01-01

    We present a theory of enzymatic hydrogen transfer in which hydrogen tunneling is mediated by thermal fluctuations of the enzyme's active site. These fluctuations greatly increase the tunneling rate by shortening the distance the hydrogen must tunnel. The average tunneling distance is shown to decrease when heavier isotopes are substituted for the hydrogen or when the temperature is increased, leading to kinetic isotope effects (KIEs)--defined as the factor by which the reaction slows down when isotopically substituted substrates are used--that need be no larger than KIEs for nontunneling mechanisms. Within this theory we derive a simple KIE expression for vibrationally enhanced ground state tunneling that is able to fit the data for the bovine serum amine oxidase (BSAO) system, correctly predicting the large temperature dependence of the KIEs. Because the KIEs in this theory can resemble those for nontunneling dynamics, distinguishing the two possibilities requires careful measurements over a range of temperatures, as has been done for BSAO. PMID:1420907

  8. Nondiffusive mechanisms enhance protein uptake rates in ion exchange particles

    PubMed Central

    Dziennik, S. R.; Belcher, E. B.; Barker, G. A.; DeBergalis, M. J.; Fernandez, S. E.; Lenhoff, A. M.

    2003-01-01

    Scanning confocal fluorescence microscopy and multiphoton fluorescence microscopy were used to image the uptake of the protein lysozyme into individual ion exchange chromatography particles in a packed bed in real time. Self-sharpening concentration fronts penetrating into the particles were observed at low salt concentrations in all of the adsorbents studied, but persisted to 100 mM ionic strength only in some materials. In other adsorbents, diffuse profiles were seen at these higher salt concentrations, with the transition region exhibiting a pronounced fluorescence peak at the front at intermediate salt concentrations. These patterns in the uptake profiles are accompanied by significant increases in protein uptake rates that are also seen macroscopically in batch uptake experiments. The fluorescence peak appears to be a concentration overshoot that may develop, in part, from an electrokinetic contribution to transport that also enhances the uptake rate. Further evidence for an electrokinetic origin is that the effect is correlated with high adsorbent surface charge densities. Predictions of a mathematical model incorporating the electrokinetic effect are in qualitative agreement with the observations. These findings indicate that mechanisms other than diffusion contribute to protein transport in oppositely charged porous materials and may be exploited to achieve rapid uptake in process chromatography. PMID:12522150

  9. The short-range mechanism of surface enhanced raman scattering

    NASA Astrophysics Data System (ADS)

    Furtak, T. E.; Roy, D.

    1985-07-01

    In addition to the electromagnetic influences which increase the local field at the surface of suitably rough free-electron-like metals, molecule and site specific electronic resonances are also frequently operative. This leads to enhanced scattering beyond that caused by the electromagnetic mechanism alone. The electronic resonances involve charge-transfer excitation between members of an active complex M wAg xCl y(H 2O) z which involves the probe molecule M and, in the electrochemical environment, the constituents of the solution. These complexes allow the resonance to be communicated to Raman transitions in all members of the complex. The stability of the complexes are sensitive to changes in the environment, such as the applied voltage and to the presence of foreign metal ions, through induced changes in y, the number of halide or pseudo-halide ions in the complex. Through analysis of the vibrational signature of the probe molecule under various environmental influences we are able to observe subtle changes in the character of the bonding between that molecule and the rest of the complex. These changes can also be interpreted as indirect results of changes in the value of y.

  10. Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

    NASA Astrophysics Data System (ADS)

    Li, Xin-nan; Zhang, Hai-ying; Cui, Xiang-qun; Jiang, Zi-bo; Zheng, Yi; Liu, Xing-tao; Ni, Hou-kun

    2012-10-01

    A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope.

  11. HyDRa: polishing with a vortex.

    PubMed

    Sohn, Erika; Ruiz, Elfego; Salas, Luis; Luna, Esteban; Herrera, Joel

    2013-09-01

    We present a hydrodynamic, deterministic polishing tool (HyDRa) based on the fluid-jet polishing (FJP) principle. In contrast to other FJP methods, the polishing flux is accelerated with pressurized air and then expelled at high velocity, forming a radial, grazing abrasive pattern that exerts no net force of the tool on the surface to be polished, since the vacuum and thrust forces that are created at the tool's output balance each other out. The grazing effect minimizes microroughness, making it appropriate for finishing high-quality surfaces. The principle of operation as well as polishing results of a series of small etalon plates are presented. PMID:24085071

  12. Metal-enhanced chemiluminescence from chromium, copper, nickel, and zinc nanodeposits: Evidence for a second enhancement mechanism in metal-enhanced fluorescence

    SciTech Connect

    Weisenberg, Micah; Zhang Yongxia; Geddes, Chris D.

    2010-09-27

    Over the past decade metal-fluorophore interactions, metal-enhanced fluorescence, have attracted significant research attention, with the technology now becoming common place in life science applications. In this paper, we address the underlying mechanisms of metal-enhanced fluorescence (MEF) and experimentally show using chemiluminescence solutions that MEF is indeed underpinned by two complimentary mechanisms, consistent with the recent reports by Geddes and co-workers [Zhang et al., J. Phys. Chem. C 113, 12095 (2009)] and their enhanced fluorescence hypothesis.

  13. Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance

    PubMed Central

    Gao, Chengde; Liu, Tingting; Shuai, Cijun; Peng, Shuping

    2014-01-01

    Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications. PMID:24736662

  14. Mechanisms of enhanced taurine release under Ca2+ depletion.

    PubMed

    Molchanova, Svetlana M; Oja, Simo S; Saransaari, Pirjo

    2005-10-01

    The sulfur-containing amino acid taurine is an inhibitory neuromodulator in the brain of mammals, as well as a key substance in the regulation of cell volumes. The effect of Ca(2+) on extracellular taurine concentrations is of special interest in the context of the regulatory mechanisms of taurine release. The aim of this study was to characterize the basal release of taurine in Ca(2+)-free medium using in vivo microdialysis of the striatum of anesthetized rats. Perfusion of Ca(2+)-free medium via a microdialysis probe evoked a sustained release of taurine (up to 180 % compared to the basal levels). The Ca(2+) chelator EGTA (1mM) potentiated Ca(2+) depletion-evoked taurine release. The substitution of CaCl(2) by choline chloride did not alter the observed effect. Ca(2+)-free solution did not significantly evoke release of taurine from tissue loaded with the competitive inhibitor of taurine transporter guanidinoethanesulfonate (1mM), suggesting that in Ca(2+) depletion taurine is released by the transporter operating in the outward direction. The volume-sensitive chloride channel blocker diisothiocyanostilbene-2,2'-disulfonate (1mM) did not attenuate the taurine release evoked by Ca(2+) depletion. The non-specific blocker of voltage-sensitive Ca(2+) channels NiCl(2) (0.65 mM) enhanced taurine release in the presence of Ca(2+). CdCl(2) (0.25 mM) had no effect under these conditions. However, both CdCl(2) and NiCl(2) attenuated the effect of Ca(2+)-free medium on the release of taurine. The data obtained imply the involvement of both decreased influx of Ca(2+) and increased non-specific influx of Na(+) through voltage-sensitive calcium channels in the regulation of transporter-mediated taurine release in Ca(2+) depletion. PMID:15982785

  15. Computerized approaches to enhance understanding of organic reaction mechanisms: CAN reaction mechanisms and CPLEX prelaboratory methodology

    NASA Astrophysics Data System (ADS)

    Al-Shammari, Abdulrahman G. Alhamzani

    2008-10-01

    Two approaches to enhance the understanding of organic reaction mechanisms are described. First, a new method for teaching organic reaction mechanisms that can be used in a Computer-Assisted Instruction (CAI) environment is proposed and tested (Chapter 1). The method concentrates upon the important intermediate structures, which are assumed to be on the reaction coordinate, and which can be evaluated and graded by currently available computer techniques. At the same time, the "curved arrows" that show the electron flow in a reaction mechanism are neglected, since they cannot be evaluated and graded with currently available computer techniques. By allowing student practice for learning organic reaction mechanisms using the Curved Arrow Neglect (CAN) method within a "Practice Makes Perfect" CAI method, student performance in the drawing of traditional reaction mechanisms, in which students had to include the "curved arrows" on their written classroom exams, was significantly enhanced. Second, computerized prelaboratory experiments (CPLEX) for organic chemistry laboratory 1 & 2 courses have been created, used, and evaluated (Chapters 2 and 3). These computerized prelabs are unique because they combine both "dry lab" actions with detailed animations of the actual chemistry occurring at the molecular level. The "dry lab" serves to simulate the actual physical manipulations of equipment and chemicals that occur in the laboratory experiment through the use of drag-and-drop computer technology. At the same time, these physical actions are accompanied on a separate part of the computer screen by animations showing the chemistry at the molecular level that is occurring in the experiment. These CPLEX modules were made into Internet accessible modules. The students were allowed to access the CPLEX modules prior to performing the actual laboratory experiment. A detailed evaluation of students' perception of the modules was accomplished via survey methodology during the entire

  16. A Common Molecular Motif Characterizes Extracellular Allosteric Enhancers of GPCR Aminergic Receptors and Suggests Enhancer Mechanism of Action

    PubMed Central

    Bernstein, Robert Root; Dillon, Patrick F

    2014-01-01

    Several classes of compounds that have no intrinsic activity on aminergic systems nonetheless enhance the potency of aminergic receptor ligands three-fold or more while significantly increasing their duration of activity, preventing tachyphylaxis and reversing fade. Enhancer compounds include ascorbic acid, ethylenediaminetetraacetic acid, cortico-steroids, opioid peptides, opiates and opiate antagonists. This paper provides the first review of aminergic enhancement, demonstrating that all enhancers have a common, inobvious molecular motif and work through a common mechanism that is manifested by three common characteristics. First, aminergic enhancers bind directly to the amines they enhance, suggesting that the common structural motif is reflected in common binding targets. Second, one common target is the first extracellular loop of aminergic receptors. Third, at least some enhancers are antiphosphodiesterases. These observations suggest that aminergic enhancers act on the extracellular surface of aminergic receptors to keep the receptor in its high affinity state, trapping the ligand inside the receptor. Enhancer binding produces allosteric modifications of the receptor structure that interfere with phosphorylation of the receptor, thereby inhibiting down-regulation of the receptor. The mechanism explains how enhancers potentiate aminergic activity and increase duration of activity and makes testable predictions about additional compounds that should act as aminergic enhancers. PMID:25174918

  17. Post cleaning of chemical mechanical polishing process

    NASA Astrophysics Data System (ADS)

    Liu, Chi-Wen; Dai, Bau-Tong; Yeh, Ching-Fa

    1996-02-01

    We describe a study on the effect of the electrostatic nature in silica particles on the post CMP cleaning behavior. A fall-off for the zeta potential of silica particles is observed as the pH of dip solutions is increased. In this study, we also observed that particle counts on the SiO 2 and the Si 3N 4 dielectric films had a similar dependence on the pH. Furthermore, we confirmed that surface hardness of the wafer is an important factor for particles physically embedded in different dielectric materials during and after the CMP process. The nanoscale surface hardness of dielectric films was measured by the nanoindentation technique. Experimental results showed that particles had difficulty attaching to a harder surface of the dielectric film.

  18. Polishing compound for plastic surfaces

    DOEpatents

    Stowell, M.S.

    1991-01-01

    This invention is comprised of a polishing compound for plastic materials. The compound includes approximately by approximately by weight 25 to 80 parts at least one petroleum distillate lubricant, 1 to 12 parts mineral spirits, 50 to 155 parts abrasive paste, and 15 to 60 parts water. Preferably, the compound includes approximately 37 to 42 parts at least one petroleum distillate lubricant, up to 8 parts mineral spirits, 95 to 110 parts abrasive paste, and 50 to 55 parts water. The proportions of the ingredients are varied in accordance with the particular application. The compound is used on PLEXIGLAS{trademark}, LEXAN{trademark}, LUCITE{trademark}, polyvinyl chloride (PVC), and similar plastic materials whenever a smooth, clear polished surface is desired.

  19. Energy savings in Polish buildings

    SciTech Connect

    Markel, L.C.; Gula, A.; Reeves, G.

    1995-12-31

    A demonstration of low-cost insulation and weatherization techniques was a part of phase 1 of the Krakow Clean Fossil Fuels and Energy Efficient Project. The objectives were to identify a cost-effective set of measures to reduce energy used for space heating, determine how much energy could be saved, and foster widespread implementation of those measures. The demonstration project focused on 4 11-story buildings in a Krakow housing cooperative. Energy savings of over 20% were obtained. Most important, the procedures and materials implemented in the demonstration project have been adapted to Polish conditions and applied to other housing cooperatives, schools, and hospitals. Additional projects are being planned, in Krakow and other cities, under the direction of FEWE-Krakow, the Polish Energie Cities Network, and Biuro Rozwoju Krakowa.

  20. Evaluation of the surface roughness in dental ceramics submitted to different finishing and polishing methods.

    PubMed

    Vieira, Alex C; Oliveira, Mario C S; Lima, Emilena M C X; Rambob, Isabel; Leite, Mariana

    2013-09-01

    Ceramic restorations have been widely used in dentistry. These restorations often require intraoral adjustment with diamond burs after their cementation causing increasing roughness of the ceramic surface. Consequently some finishing and polishing methods have been used to minimize this occurrence. The aim of this study is to evaluate the roughness of the ceramic surfaces submitted to different finishing and polishing methods. 144 specimens of VITAVM(®)7, VM(®)9 and VM(®)13 (VITA Zahnfabrik) ceramics were fabricated and submitted to grinding using diamond burs. They were then divided into 15 groups (five of each ceramic type). Groups 1, 6 and 11-positive control (Glaze); Groups 2, 7 and 12-negative control (no polishing); Groups 3, 8 and 13-polished with abrasive rubbers (Edenta), felt disc and diamond polishing past; Groups 4, 9 and 14-polished with abrasive rubbers (Shofu), felt disc and diamond polishing past; Groups 5, 10 and 15-polished with aluminum oxide discs (Sof-Lex, 3M-ESPE), felt disc and diamond polishing paste. The roughness of the samples surfaces were measured using the rugosimeter Surfcorder SE 1700 and the data were submitted to statistical analysis using ANOVA and Tukey test at a level of significance of 5 %. There was statistically significance difference between the positive control groups and the other groups in all the ceramic types. Mechanical finishing and polishing methods were not able to provide a surface as smooth as the glazed surface for the tested ceramics. To assist dental practitioners to select the best finishing and polishing methods for the final adjustment of the ceramic restorations. PMID:24431749

  1. Stress polishing demonstrator for ELT M1 segments and industrialization

    NASA Astrophysics Data System (ADS)

    Hugot, Emmanuel; Bernard, Anaïs.; Laslandes, Marie; Floriot, Johan; Dufour, Thibaut; Fappani, Denis; Combes, Jean Marc; Ferrari, Marc

    2014-07-01

    After two years of research and development under ESO support, LAM and Thales SESO present the results of their experiment for the fast and accurate polishing under stress of ELT 1.5 meter segments as well as the industrialization approach for mass production. Based on stress polishing, this manufacturing method requires the conception of a warping harness able to generate extremely accurate bending of the optical surface of the segments during the polishing. The conception of the warping harness is based on finite element analysis and allowed a fine tuning of each geometrical parameter of the system in order to fit an error budget of 25nm RMS over 300μm of bending peak to valley. The optimisation approach uses the simulated influence functions to extract the system eigenmodes and characterise the performance. The same approach is used for the full characterisation of the system itself. The warping harness has been manufactured, integrated and assembled with the Zerodur 1.5 meter segment on the LAM 2.5meter POLARIS polishing facility. The experiment consists in a cross check of optical and mechanical measurements of the mirrors bending in order to develop a blind process, ie to bypass the optical measurement during the final industrial process. This article describes the optical and mechanical measurements, the influence functions and eigenmodes of the system and the full performance characterisation of the warping harness.

  2. Surface roughness of a dental ceramic after polishing with different vehicles and diamond pastes.

    PubMed

    Camacho, Guilherme Brião; Vinha, Dionísio; Panzeri, Heitor; Nonaka, Tomio; Gonçalves, Mariane

    2006-01-01

    During fabrication of bonded ceramic restorations, cervical adaptation, occlusal adjustment and final finishing/polishing are procedures to be performed at the dental office after adhesive cementation. Final adjustments may result in loss of ceramic glaze, which requires new polishing of the ceramic surface, with special attention for selection of adequate materials and instruments. The purpose of this study was to evaluate the efficiency of different vehicles associated with diamond pastes indicated for dental ceramic polishing. Two polishing pastes (Crystar Paste and Diamond Excell) associated with four vehicles (rubber cup, Robinson bristle brush, felt wheel and buff disc) were evaluated. Disc-shaped specimens were fabricated from Ceramco II dental ceramic. Surface roughness means (Ra) of the ceramic specimens were determined with a rugosimeter. Data were analyzed statistically by two-way ANOVA and Tukey's test at 5% significance level. There was no statistically significant difference (p>0.01) between the polishing pastes. However, there were statistically significant differences (p<0.01) among the tested vehicles. Vehicle-paste interaction showed statistically significant difference (p<0.05) as well. It may be concluded that: 1) Robinson bristle brush, felt wheel and buff disc were efficient vehicles to be used in association with a diamond polishing paste; 2) The use of rubber cup as a vehicle showed poor efficiency for mechanical polishing of the ceramic surfaces; 3) Both pastes provided similar and efficient polishing and may be recommended for use with an appropriated vehicle. PMID:17262123

  3. Implications of Polishing Techniques in Quantitative X-Ray Microanalysis

    PubMed Central

    Rémond, Guy; Nockolds, Clive; Phillips, Matthew; Roques-Carmes, Claude

    2002-01-01

    Specimen preparation using abrasives results in surface and subsurface mechanical (stresses, strains), geometrical (roughness), chemical (contaminants, reaction products) and physical modifications (structure, texture, lattice defects). The mechanisms involved in polishing with abrasives are presented to illustrate the effects of surface topography, surface and subsurface composition and induced lattice defects on the accuracy of quantitative x-ray microanalysis of mineral materials with the electron probe microanalyzer (EPMA). PMID:27446758

  4. Side polished twin-core fiber coupler

    NASA Astrophysics Data System (ADS)

    Wang, Xianbin; Yuan, Libo

    2015-07-01

    A novel optical fiber coupler was proposed and fabricated for coupling each core of a twin-core fiber (TCF) with a single-core fiber (SCF) core simultaneously and accessing independently both cores of the TCF. The coupler is mainly composed of two sides polished SCF and a side polished TCF. Each optical field launched from the TCF could be coupled into the side polished SCF. The coupler has a simple structure and less cross-talk between the two cores.

  5. Challenges to ART market: a Polish case.

    PubMed

    Alichniewicz, Anna; Michałowska, Monika

    2015-02-01

    In the paper we are analyzing the Polish ART market. It can be noticed that the lack of legal regulation has resulted in many discrepancies among the policies adopted by various ART agencies. The social acceptance of ART procedures available mostly in private clinics led to growing commercialization of the Polish ART market. Additionally, the language of gift and altruistic rhetoric that are overwhelmingly employed by ART agencies reveals hypocrisy of the Polish ART market. PMID:24889400

  6. Enhancing medicine price transparency through price information mechanisms

    PubMed Central

    2014-01-01

    Background Medicine price information mechanisms provide an essential tool to countries that seek a better understanding of product availability, market prices and price compositions of individual medicines. To be effective and contribute to cost savings, these mechanisms need to consider prices in their particular contexts when comparing between countries. This article discusses in what ways medicine price information mechanisms can contribute to increased price transparency and how this may affect access to medicines for developing countries. Methods We used data collected during the course of a WHO project focusing on the development of a vaccine price and procurement information mechanism. The project collected information from six medicine price information mechanisms and interviewed data managers and technical experts on key aspects as well as observed market effects of these mechanisms. The reviewed mechanisms were broken down into categories including objective and target audience, as well as the sources, types and volumes of data included. Information provided by the mechanisms was reviewed according to data available on medicine prices, product characteristics, and procurement modalities. Results We found indications of positive effects on access to medicines resulting from the utilization of the reviewed mechanisms. These include the uptake of higher quality medicines, more favorable results from contract negotiations, changes in national pricing policies, and the decrease of prices in certain segments for countries participating in or deriving data from the various mechanisms. Conclusion The reviewed mechanisms avoid the methodological challenges observed for medicine price comparisons that only use national price databases. They work with high quality data and display prices in the appropriate context of procurement modalities as well as the peculiarities of purchasing countries. Medicine price information mechanisms respond to the need for increased

  7. Polish Foundation for Energy Efficiency

    SciTech Connect

    1995-12-31

    The Polish Foundation for Energy Efficiency (FEWE) was established in Poland at the end of 1990. FEWE, as an independent and non-profit organization, has the following objectives: to strive towards an energy efficient national economy, and to show the way and methods by use of which energy efficiency can be increased. The activity of the Foundation covers the entire territory of Poland through three regional centers: in Warsaw, Katowice and Cracow. FEWE employs well-known and experienced specialists within thermal and power engineering, civil engineering, economy and applied sciences. The organizer of the Foundation has been Battelle Memorial Institute - Pacific Northwest Laboratories from the USA.

  8. Serotonergic mechanism underlying tranylcypromine enhancement of nicotine self-administration

    PubMed Central

    Villégier, Anne-Sophie; Belluzzi, James D.; Leslie, Frances M.

    2010-01-01

    Although nicotine is generally considered to be the main psychoactive component of tobacco, growing evidence highlights the importance of non-nicotine compounds in smoking reinforcement. Monoamine oxidase (MAO) inhibition is a major consequence of smoking and MAO inhibitors, such as tranylcypromine, increase nicotine reinforcement. Tranylcypromine has multiple pharmacological effects, increasing monoamine release for a few hours immediately after its administration and blocking MAO activity for several days. To assess the relative role of these two actions, adult male rats were tested in consecutive daily 3-hr sessions for self-administration of nicotine (3μg/kg/inj, i.v.) either 20 hr or 1hr following administration of tranylcypromine (3 mg/kg). Both paradigms were shown to produce highly significant inhibition of MAO activity. However, whereas animals readily acquired self-administration when pretreated with tranylcypromine 1hr prior to testing, they did not with the longer pretreatment interval. Such animals did immediately acquire nicotine self-administration when the tranylcypromine pretreatment interval was switched to 1hr prior to testing on day 4, indicating that an acute effect of the MAO inhibitor was responsible for enhanced nicotine reinforcement. Several lines of evidence implicate serotonin (5-HT) as the mediator of this enhancement: (1) Tranyclypromine-enhanced nicotine reinforcement was blocked by the 5-HT2 receptor antagonists, ritanserin and ketanserin; (2) parachloroamphetamine (PCA), a 5-HT releaser, also enhanced nicotine self-administration in animals in which MAO activity was inhibited; (3) pretreatment with tranylcypromine increased PCA-induced 5-HT overflow in the nucleus accumbens. These findings suggest that MAO inhibition enhances serotonergic transmission, which serves a critical role in the reinforcing effects of nicotine. PMID:20936688

  9. Perceptions of and Attitudes towards Regional Varieties of Polish: Views from Two Polish Provinces

    ERIC Educational Resources Information Center

    Milobog, Magdalena; Garrett, Peter

    2011-01-01

    This paper reports a study of perceptions and attitudes relating to regional varieties of Polish. The methodology followed folk linguistic approaches to attitudes research. Respondents in two Polish provinces were asked to draw on a map of Poland where they thought the main regional varieties of Polish were spoken, and then to name and…

  10. Profilometric analysis of two composite resins’ surface repolished after tooth brush abrasion with three polishing systems

    PubMed Central

    Uppal, Mudit; Ganesh, Arathi; Balagopal, Suresh; Kaur, Gurleen

    2013-01-01

    Aim: To evaluate the effect of three polishing protocols that could be implemented at recall on the surface roughness of two direct esthetic restorative materials. Materials and Methods: Specimens (n = 40) measuring 8 mm (length) × 5 mm (width) × 4 mm (height) were fabricated in an acrylic mold using two light-cured resin-based materials (microfilled composite and microhybrid composite). After photopolymerization, all specimens were finished and polished with one of three polishing protocols (Enhance, One Gloss, and Sof-Lex polishing systems). The average surface roughness of each treated specimen was determined using 3D optical profilometer. Next all specimens were brushed 60,000 times with nylon bristles at 7200 rpm using crosshead brushing device with equal parts of toothpaste and water used as abrasive medium. The surface roughness of each specimen was measured after brushing followed by repolishing with one of three polishing protocols, and then, the final surface roughness values were determined. Results: The data were analyzed using one-way and two-factor analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD). Significant difference (P < 0.05) in surface roughness was observed. Simulated brushing following initial polishing procedure significantly roughened the surface of restorative material (P < 0.05). Conclusion: Polishing protocols can be used to restore a smooth surface on esthetic restorative materials following simulated tooth brushing. PMID:23956531

  11. The effect of three polishing systems on surface roughness of flowable, microhybrid, and packable resin composites

    PubMed Central

    Hassan, Ahmed Mohammed; Nabih, Sameh Mahmoud; Mossa, Hossam Mohammed; Baroudi, Kusai

    2015-01-01

    Objectives: The aim of this study was to evaluate the effects of three different polishing systems on the surface roughness of three types of resin composite materials. Materials and Methods: Three types of resin composites (Heliomolar flow, TPH spectrum, and Tetric Ceram HB) and three polishing systems (Astropol, Enhance, and Soflex) were used. A total number of 40 samples were prepared from each one of the restorative materials and divided randomly into four groups (n = 10) according to the polishing procedure. The first group underwent no treatment and was used as a control group. Each one of the remaining groups was polished with one of the tested polishing systems. After completion of sample preparation, the mean surface roughness (Ra) value was measured using a surface profilometer. Data were analyzed using one-way analysis of variance (ANOVA). Results: The control group of each material recorded the lowest Ra value. Among the tested polishing systems, the groups finished with Soflex system exhibited the lowest Ra value. Among the resin composites, Heliomolar flow exhibited the lowest Ra value, regardless of the polishing system used. Conclusions: The smoothest surface of all types of resin composite was achieved under Mylar strip. PMID:26236686

  12. Apatite accumulation enhances the mechanical property of anammox granules.

    PubMed

    Lin, Y M; Lotti, T; Sharma, P K; van Loosdrecht, M C M

    2013-09-01

    The strength of granular sludge is essential for the mechanical stability of the granules. Inorganic precipitants form a major factor influencing the strength of the granules. To check the possibility of apatite accumulation in anammox granules, and study its contribution to the mechanical strength of granules, anammox granular sludge was collected from Dokhaven municipal wastewater treatment plant, the Netherlands. Mineral precipitation inside the granules was visualized by micro-computed tomography, and apatite was identified by electron probe microanalysis and X-ray powder diffraction. The mechanical strength of anammox granules was measured by a low load compression tester. The contribution of apatite to the mechanical strength was evaluated by the generalized Maxwell model. Ca-PO4 minerals are reported to accumulate in anammox granules. A transformation of Ca-PO4 happens, and apatite is the final stable form. The accumulation of apatite increases the mechanical strength of anammox granules. A fast method to monitor and evaluate the accumulation of minerals in anammox granules was proposed. PMID:23764605

  13. Gene activation by metazoan enhancers: Diverse mechanisms stimulate distinct steps of transcription.

    PubMed

    Beagrie, Robert A; Pombo, Ana

    2016-09-01

    Enhancers can stimulate transcription by a number of different mechanisms which control different stages of the transcription cycle of their target genes, from recruitment of the transcription machinery to elongation by RNA polymerase. These mechanisms may not be mutually exclusive, as a single enhancer may act through different pathways by binding multiple transcription factors. Multiple enhancers may also work together to regulate transcription of a shared target gene. Most of the evidence supporting different enhancer mechanisms comes from the study of single genes, but new high-throughput experimental frameworks offer the opportunity to integrate and generalize disparate mechanisms identified at single genes. This effort is especially important if we are to fully understand how sequence variation within enhancers contributes to human disease. PMID:27452946

  14. Buffered Electrochemical Polishing of Niobium

    SciTech Connect

    Gianluigi Ciovati; Tian, Hui; Corcoran, Sean

    2011-03-01

    The standard preparation of superconducting radio-frequency (SRF) cavities made of pure niobium include the removal of a 'damaged' surface layer, by buffered chemical polishing (BCP) or electropolishing (EP), after the cavities are formed. The performance of the cavities is characterized by a sharp degradation of the quality factor when the surface magnetic field exceeds about 90 mT, a phenomenon referred to as 'Q-drop.' In cavities made of polycrystalline fine grain (ASTM 5) niobium, the Q-drop can be significantly reduced by a low-temperature (? 120 °C) 'in-situ' baking of the cavity if the chemical treatment was EP rather than BCP. As part of the effort to understand this phenomenon, we investigated the effect of introducing a polarization potential during buffered chemical polishing, creating a process which is between the standard BCP and EP. While preliminary results on the application of this process to Nb cavities have been previously reported, in this contribution we focus on the characterization of this novel electrochemical process by measuring polarization curves, etching rates, surface finish, electrochemical impedance and the effects of temperature and electrolyte composition. In particular, it is shown that the anodic potential of Nb during BCP reduces the etching rate and improves the surface finish.

  15. Early Bilingualism Enhances Mechanisms of False-Belief Reasoning

    ERIC Educational Resources Information Center

    Kovacs, Agnes Melinda

    2009-01-01

    In their first years, children's understanding of mental states seems to improve dramatically, but the mechanisms underlying these changes are still unclear. Such "theory of mind" (ToM) abilities may arise during development, or have an innate basis, developmental changes reflecting limitations of other abilities involved in ToM tasks (e.g.…

  16. Holding fixture for metallographic mount polishing

    SciTech Connect

    Barth, C.H.; Cramer, C.E.

    1996-12-31

    A fixture for holding mounted specimens for polishing, having an arm; a body attached to one end of the arm, the body having at least one flange having an opening to accommodate a mounted specimen; and a means applying pressure against the outer surface of the mounted specimen to hold the specimen in contact with the polishing surface.

  17. Holding fixture for metallographic mount polishing

    DOEpatents

    Barth, C.H.; Cramer, C.E.

    1997-12-30

    A fixture is described for holding mounted specimens for polishing, having an arm; a body attached to one end of the arm, the body having at least one flange having an opening to accommodate a mounted specimen; and a means applying pressure against the outer surface of the mounted specimen to hold the specimen in contact with the polishing surface. 3 figs.

  18. BEGINNING POLISH, VOLUME ONE. YALE LINGUISTIC SERIES.

    ERIC Educational Resources Information Center

    SCHENKER, ALEXANDER M.

    BASED ON A MODERN LINGUISTIC ANALYSIS OF THE POLISH LANGUAGE, THIS TWO-VOLUME TEXT IS APPROPRIATE FOR A ONE-YEAR INTENSIVE COURSE. VOLUME I INCLUDES 25 LESSONS, EACH DIVIDED INTO--SENTENCES (DIALOGS), GRAMMAR, EXERCISES, AND VOCABULARY LISTS. THE INTRODUCTION PRESENTS A BRIEF CONTRASTIVE ANALYSIS OF POLISH AND RUSSIAN, AND THERE IS INCLUDED A…

  19. Holding fixture for metallographic mount polishing

    DOEpatents

    Barth, Clyde H.; Cramer, Charles E.

    1997-01-01

    A fixture for holding mounted specimens for polishing, having an arm; a body attached to one end of the arm, the body having at least one flange having an opening to accommodate a mounted specimen; and a means applying pressure against the outer surface of the mounted specimen to hold the specimen in contact with the polishing surface.

  20. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1983-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  1. Method of polishing nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1981-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  2. Cratering mechanics on Venus - Pressure enhancement by the atmospheric 'ocean'

    NASA Technical Reports Server (NTRS)

    Brackett, Robert A.; Mckinnon, William B.

    1992-01-01

    The impedance match technique and EOSs of equations of state (EOSs) of geologically relevant materials are used to investigate cratering mechanics on Venus, specifically, the coupling of impactor kinetic energy and momentum into the target surface. These EOSs are modified to account for multiple shocks. Peak impact pressures from both first reflection and later reverberations are determined. These are compared to values obtained using an atmosphereless model, and the differences between and implications for atmosphere-affected and atmosphereless impacts are discussed.

  3. Resolving the electromagnetic mechanism of surface-enhanced light scattering at single hot spots

    PubMed Central

    Alonso-González, P.; Albella, P.; Schnell, M.; Chen, J.; Huth, F.; García-Etxarri, A.; Casanova, F.; Golmar, F.; Arzubiaga, L.; Hueso, L.E.; Aizpurua, J.; Hillenbrand, R.

    2012-01-01

    Light scattering at nanoparticles and molecules can be dramatically enhanced in the 'hot spots' of optical antennas, where the incident light is highly concentrated. Although this effect is widely applied in surface-enhanced optical sensing, spectroscopy and microscopy, the underlying electromagnetic mechanism of the signal enhancement is challenging to trace experimentally. Here we study elastically scattered light from an individual object located in the well-defined hot spot of single antennas, as a new approach to resolve the role of the antenna in the scattering process. We provide experimental evidence that the intensity elastically scattered off the object scales with the fourth power of the local field enhancement provided by the antenna, and that the underlying electromagnetic mechanism is identical to the one commonly accepted in surface-enhanced Raman scattering. We also measure the phase shift of the scattered light, which provides a novel and unambiguous fingerprint of surface-enhanced light scattering. PMID:22353715

  4. Optically enhanced photon recycling in mechanically stacked multijunction solar cells

    DOE PAGESBeta

    Steiner, Myles A.; Geisz, John F.; Ward, J. Scott; Garcia, Ivan; Friedman, Daniel J.; King, Richard R.; Chiu, Philip T.; France, Ryan M.; Duda, Anna; Olavarria, Waldo J.; et al

    2015-11-09

    Multijunction solar cells can be fabricated by mechanically bonding together component cells that are grown separately. Here, we present four-junction four-terminal mechanical stacks composed of GaInP/GaAs tandems grown on GaAs substrates and GaInAsP/GaInAs tandems grown on InP substrates. The component cells were bonded together with a low-index transparent epoxy that acts as an angularly selective reflector to the GaAs bandedge luminescence, while simultaneously transmitting nearly all of the subbandgap light. As determined by electroluminescence measurements and optical modeling, the GaAs subcell demonstrates a higher internal radiative limit and, thus, higher subcell voltage, compared with GaAs subcells without the epoxy reflector.more » The best cells demonstrate 38.8 ± 1.0% efficiency under the global spectrum at 1000 W/m2 and ~ 42% under the direct spectrum at ~100 suns. As a result, eliminating the series resistance is the key challenge for further improving the concentrator cells.« less

  5. Optically enhanced photon recycling in mechanically stacked multijunction solar cells

    SciTech Connect

    Steiner, Myles A.; Geisz, John F.; Ward, J. Scott; Garcia, Ivan; Friedman, Daniel J.; King, Richard R.; Chiu, Philip T.; France, Ryan M.; Duda, Anna; Olavarria, Waldo J.; Young, Michelle; Kurtz, Sarah R.

    2015-11-09

    Multijunction solar cells can be fabricated by mechanically bonding together component cells that are grown separately. Here, we present four-junction four-terminal mechanical stacks composed of GaInP/GaAs tandems grown on GaAs substrates and GaInAsP/GaInAs tandems grown on InP substrates. The component cells were bonded together with a low-index transparent epoxy that acts as an angularly selective reflector to the GaAs bandedge luminescence, while simultaneously transmitting nearly all of the subbandgap light. As determined by electroluminescence measurements and optical modeling, the GaAs subcell demonstrates a higher internal radiative limit and, thus, higher subcell voltage, compared with GaAs subcells without the epoxy reflector. The best cells demonstrate 38.8 ± 1.0% efficiency under the global spectrum at 1000 W/m2 and ~ 42% under the direct spectrum at ~100 suns. As a result, eliminating the series resistance is the key challenge for further improving the concentrator cells.

  6. Feedback-Enhanced Parametric Squeezing of Mechanical Motion

    NASA Astrophysics Data System (ADS)

    Vinante, A.; Falferi, P.

    2013-11-01

    We present a single-quadrature feedback scheme able to overcome the conventional 3 dB limit on parametric squeezing. The method is experimentally demonstrated in a micromechanical system based on a cantilever with a magnetic tip. The cantilever is detected at low temperature by a SQUID susceptometer, while parametric pumping is obtained by modulating the magnetic field gradient at twice the cantilever frequency. A maximum squeezing of 11.5 dB and 11.3 dB is observed, respectively, in the response to a sinusoidal test signal and in the thermomechanical noise. So far, the maximum squeezing factor is limited only by the maximum achievable parametric modulation. The proposed technique might be used to squeeze one quadrature of a mechanical resonator below the quantum noise level, even without the need for a quantum limited detector.

  7. Laser treatment of aluminum copper alloys: A mechanical enhancement

    SciTech Connect

    De Mol van Otterloo, J.L.; De Hosson, J.T. . Dept. of Applied Physics)

    1994-02-15

    Aluminum-copper alloys are commonly used as structural components for the car and aircraft industry. They combine low density, high strength, high fracture toughness and good machinability. Moreover, the strength and wear-resistance of the surface of alloys are improved by a high power laser beam. In this way the molten surface will be self-quenched by conduction of heat into the bulk. This technique ensures solidification velocities of 0.01--1 m/s. These high solidification velocities have a significant influence on the size and distribution of the morphology. This work concentrates on Al-Cu alloys, in which the Cu content ranges between 0--40 wt.%, and is aimed at describing the mechanical and microstructural properties of these alloys upon variation of the laser scan velocity in the range of 0.0125 to 0.125 m/s.

  8. NanoClusters Enhance Drug Delivery in Mechanical Ventilation

    NASA Astrophysics Data System (ADS)

    Pornputtapitak, Warangkana

    The overall goal of this thesis was to develop a dry powder delivery system for patients on mechanical ventilation. The studies were divided into two parts: the formulation development and the device design. The pulmonary system is an attractive route for drug delivery since the lungs have a large accessible surface area for treatment or drug absorption. For ventilated patients, inhaled drugs have to successfully navigate ventilator tubing and an endotracheal tube. Agglomerates of drug nanoparticles (also known as 'NanoClusters') are fine dry powder aerosols that were hypothesized to enable drug delivery through ventilator circuits. This Thesis systematically investigated formulations of NanoClusters and their aerosol performance in a conventional inhaler and a device designed for use during mechanical ventilation. These engineered powders of budesonide (NC-Bud) were delivered via a MonodoseRTM inhaler or a novel device through commercial endotracheal tubes, and analyzed by cascade impaction. NC-Bud had a higher efficiency of aerosol delivery compared to micronized stock budesonide. The delivery efficiency was independent of ventilator parameters such as inspiration patterns, inspiration volumes, and inspiration flow rates. A novel device designed to fit directly to the ventilator and endotracheal tubing connections and the MonodoseRTM inhaler showed the same efficiency of drug delivery. The new device combined with NanoCluster formulation technology, therefore, allowed convenient and efficient drug delivery through endotracheal tubes. Furthermore, itraconazole (ITZ), a triazole antifungal agent, was formulated as a NanoCluster powder via milling (top-down process) or precipitation (bottom-up process) without using any excipients. ITZ NanoClusters prepared by wet milling showed better aerosol performance compared to micronized stock ITZ and ITZ NanoClusters prepared by precipitation. ITZ NanoClusters prepared by precipitation methods also showed an amorphous state

  9. Microstructure engineering from metallic powder blends for enhanced mechanical properties

    NASA Astrophysics Data System (ADS)

    Langlois, P.; Fagnon, N.; Dirras, G.

    2010-07-01

    The present work focuses on the transformation of high-purity Ni powder blends of controlled volume fractions (40 and 60 %) of nanometre-sized (100 nm) and micrometre-sized (544 nm) particles into bulk samples as part of a strategy for producing ultrafine-grained materials usefully exhibiting both strength and ductility. The process involved cold isostatic pressing at 1.5 GPa and sintering. The resulting bulk samples had relative densities near 95 %, were texture-free, and exhibited two different grain size distributions with an average value of 600 ± 30 nm. The mechanical properties were investigated by compression and microhardness tests, both at room temperature, and compared to the behaviour of a sample processed from micrometre-sized powder only. Samples prepared from the blends exhibited high yield stresses of 440 and 550 MPa after compression, and they did sustain work hardening. Tests conducted before and after compression up to 50 % deformation showed the same relative amount of hardness increase around 20 %, which was three times lower than that of the monolithic sample for which a decrease of the average grain size close to 26 % was measured.

  10. Aggregation-Induced Resonance Raman Optical Activity (AIRROA): A New Mechanism for Chirality Enhancement.

    PubMed

    Zajac, Grzegorz; Kaczor, Agnieszka; Pallares Zazo, Ana; Mlynarski, Jacek; Dudek, Monika; Baranska, Malgorzata

    2016-05-01

    Raman optical activity (ROA) spectroscopy is hampered by low sensitivity, with limited possibilities for enhancing the signal. In the present study, we report a new mechanism whereby chirality is enhanced using the resonance resulting from supramolecular aggregation. We have named this mechanism aggregation-induced resonance Raman optical activity (AIRROA). As an example, we study J-aggregates of astaxanthin (AXT), which show strong absorption of circularly polarized light in the range of ROA excitation. The implications of aggregation-induced signal enhancement for chiroptical spectroscopy are discussed. PMID:27057926

  11. Resource-Oriented Teams: Key Infrastructure Mechanisms for Enhancing Education Supports. A Center Report.

    ERIC Educational Resources Information Center

    California Univ., Los Angeles. Center for Mental Health in Schools.

    The Center for Mental Health in Schools has explored new infrastructure mechanisms designed to ensure that schools pay more systematic attention to how they use resources for addressing barriers to student learning and promoting healthy development. This report highlights key infrastructure mechanisms for enhancing education supports and stresses…

  12. Applicability of random sequential adsorption algorithm for simulation of surface plasma polishing kinetics

    NASA Astrophysics Data System (ADS)

    Minárik, Stanislav; Vaňa, Dušan

    2015-11-01

    Applicability of random sequential adsorption (RSA) model for the material removal during a surface plasma polishing is discussed. The mechanical nature of plasma polishing process is taken into consideration in modified version of RSA model. During the plasma polishing the surface layer is aligned such that molecules of material are removed from the surface mechanically as a consequence of the surface deformation induced by plasma particles impact. We propose modification of RSA technique to describe the reduction of material on the surface provided that sequential character of molecules release from the surface is maintained throughout the polishing process. This empirical model is able to estimate depth profile of material density on the surface during the plasma polishing. We have shown that preliminary results obtained from this model are in good agreement with experimental results. We believe that molecular dynamics simulation of the polishing process, possibly also other types of surface treatment, can be based on this model. However influence of material parameters and processing conditions (including plasma characteristics) must be taken into account using appropriate model variables.

  13. Mechanism of Growth Enhancement of Plants Induced by Active Species in Plasmas

    NASA Astrophysics Data System (ADS)

    Watanabe, Satoshi; Ono, Reoto; Hayashi, Nobuya

    2015-09-01

    Plant growth enhances when seeds are irradiated by plasma. However the mechanism of the growth enhancement by plasma has not been clarified. In this study, growth enhancement of plants using various active species and variation of plant cells are investigated. RF plasma is generated under conditions where pressure is 60 Pa and input electrical power is 60 W. Irradiation period varies from 0 (control) to 75 min. Air plasma shows maximum growth of plants with irradiation period of 60 min on the other hand, oxygen plasma shows the maximum growth with irradiation period of 15 min. From change of gaseous species and pressure dependence, growth enhancing factor is expected to be active oxygen species produced in plasma. According to gene expression analysis of Arabidopsis, there are two speculated mechanism of plant growth enhancement. The first is acceleration of cell cycle by gene expressions of photosynthesis and glycolytic pathway, and the second is increase of cell size via plant hormone production.

  14. A mechanism for the abundance enhancements of heavy nuclei in solar flare particle events

    NASA Technical Reports Server (NTRS)

    Cartwright, B. G.; Mogro-Campero, A.

    1973-01-01

    A mechanism is proposed to account for the recently reported abundance enhancements of heavy nuclei in solar flares. The mechanism requires two acceleration stages for its operation: First, fully stripped ions are accelerated to suprathermal energies, and subsequently, a fraction of these ions are Fermi accelerated to higher energies. It is shown that because injection into Fermi acceleration is rigidity dependent and the ions may pick up electrons during transport to the Fermi acceleration region, an enhancement of the abundances of heavy nuclei can occur. The degree of the enhancement depends on a number of factors particular to each flare, so that the degree of enhancement may be variable from flare to flare, or may be a function of time within a given flare. In some flares, conditions may be such that no enhancement would be expected.

  15. Super-polishing of Zerodur aspheres by means of conventional polishing technology

    NASA Astrophysics Data System (ADS)

    Polak, Jaroslav; Klepetková, Eva; Pošmourný, Josef; Šulc, Miroslav; Procháska, František; Tomka, David; Matoušek, Ondřej; Poláková, Ivana; Šubert, Eduard

    2015-01-01

    This paper describes a quest to find simple technique to superpolish Zerodur asphere (55μm departure from best fit sphere) that could be employed on old fashion way 1-excenter optical polishing machine. The work focuses on selection of polishing technology, study of different polishing slurries and optimization of polishing setup. It is demonstrated that either by use of fine colloidal CeO2 slurry or by use of bowl-feed polishing setup with CeO2 charged pitch we could reach 0.4nm RMS roughness while removing <30nm of surface layer. This technique, although not optimized, was successfully used to improve surface roughness on already prepolished Zerodur aspheres without necessity to involve sophisticated super-polishing technology and highly trained manpower.

  16. Polish women's experiences of breastfeeding in Ireland.

    PubMed

    Szafranska, Marcelina; Gallagher, Louise

    2016-01-01

    Exclusive breastfeeding among Polish mothers at three-four months (38.6 per cent) is in keeping with the low rates of breastfeeding in Ireland overall (Begley et al 2008), and suggests that Polish women have begun to adopt the infant feeding practices of Irish women. Therefore, the aim of this study was to explore the factors that influence Polish women's decisions to initiate and continue breastfeeding in Ireland. A descriptive qualitative approach was utilised to explore participants' perspectives of breastfeeding. Results showed that professional and family support are key to a successful breastfeeding experience for these mothers. Recommendations include further individualised support in order to meet the needs of Polish women breastfeeding in Ireland. PMID:26975131

  17. Deterministic polishing from theory to practice

    NASA Astrophysics Data System (ADS)

    Hooper, Abigail R.; Hoffmann, Nathan N.; Sarkas, Harry W.; Escolas, John; Hobbs, Zachary

    2015-10-01

    Improving predictability in optical fabrication can go a long way towards increasing profit margins and maintaining a competitive edge in an economic environment where pressure is mounting for optical manufacturers to cut costs. A major source of hidden cost is rework - the share of production that does not meet specification in the first pass through the polishing equipment. Rework substantially adds to the part's processing and labor costs as well as bottlenecks in production lines and frustration for managers, operators and customers. The polishing process consists of several interacting variables including: glass type, polishing pads, machine type, RPM, downforce, slurry type, baume level and even the operators themselves. Adjusting the process to get every variable under control while operating in a robust space can not only provide a deterministic polishing process which improves profitability but also produces a higher quality optic.

  18. Using FEM technology for optical surfaces polishing

    NASA Astrophysics Data System (ADS)

    Procháska, F.; Polák, J.; Tomka, D.; Šubert, E.

    2013-04-01

    The aim of this article is optical surfaces polishing on the 6-axis computer-controlled (CCM) machine Optotech MCP 250 CNC using FEM technology, which is suitable for aspheric elements polishing. The main attention is dedicated to the choice and to the precise adjustment of major process parameters. The possibility of usage the multi wave interferometer Luphoscan as a data source for the 2D surface correction is solved too.

  19. Ultrasound Microbubble Treatment Enhances Clathrin-Mediated Endocytosis and Fluid-Phase Uptake through Distinct Mechanisms

    PubMed Central

    Fekri, Farnaz; Delos Santos, Ralph Christian; Karshafian, Raffi

    2016-01-01

    Drug delivery to tumors is limited by several factors, including drug permeability of the target cell plasma membrane. Ultrasound in combination with microbubbles (USMB) is a promising strategy to overcome these limitations. USMB treatment elicits enhanced cellular uptake of materials such as drugs, in part as a result of sheer stress and formation of transient membrane pores. Pores formed upon USMB treatment are rapidly resealed, suggesting that other processes such as enhanced endocytosis may contribute to the enhanced material uptake by cells upon USMB treatment. How USMB regulates endocytic processes remains incompletely understood. Cells constitutively utilize several distinct mechanisms of endocytosis, including clathrin-mediated endocytosis (CME) for the internalization of receptor-bound macromolecules such as Transferrin Receptor (TfR), and distinct mechanism(s) that mediate the majority of fluid-phase endocytosis. Tracking the abundance of TfR on the cell surface and the internalization of its ligand transferrin revealed that USMB acutely enhances the rate of CME. Total internal reflection fluorescence microscopy experiments revealed that USMB treatment altered the assembly of clathrin-coated pits, the basic structural units of CME. In addition, the rate of fluid-phase endocytosis was enhanced, but with delayed onset upon USMB treatment relative to the enhancement of CME, suggesting that the two processes are distinctly regulated by USMB. Indeed, vacuolin-1 or desipramine treatment prevented the enhancement of CME but not of fluid phase endocytosis upon USMB, suggesting that lysosome exocytosis and acid sphingomyelinase, respectively, are required for the regulation of CME but not fluid phase endocytosis upon USMB treatment. These results indicate that USMB enhances both CME and fluid phase endocytosis through distinct signaling mechanisms, and suggest that strategies for potentiating the enhancement of endocytosis upon USMB treatment may improve targeted

  20. Ultrasound Microbubble Treatment Enhances Clathrin-Mediated Endocytosis and Fluid-Phase Uptake through Distinct Mechanisms.

    PubMed

    Fekri, Farnaz; Delos Santos, Ralph Christian; Karshafian, Raffi; Antonescu, Costin N

    2016-01-01

    Drug delivery to tumors is limited by several factors, including drug permeability of the target cell plasma membrane. Ultrasound in combination with microbubbles (USMB) is a promising strategy to overcome these limitations. USMB treatment elicits enhanced cellular uptake of materials such as drugs, in part as a result of sheer stress and formation of transient membrane pores. Pores formed upon USMB treatment are rapidly resealed, suggesting that other processes such as enhanced endocytosis may contribute to the enhanced material uptake by cells upon USMB treatment. How USMB regulates endocytic processes remains incompletely understood. Cells constitutively utilize several distinct mechanisms of endocytosis, including clathrin-mediated endocytosis (CME) for the internalization of receptor-bound macromolecules such as Transferrin Receptor (TfR), and distinct mechanism(s) that mediate the majority of fluid-phase endocytosis. Tracking the abundance of TfR on the cell surface and the internalization of its ligand transferrin revealed that USMB acutely enhances the rate of CME. Total internal reflection fluorescence microscopy experiments revealed that USMB treatment altered the assembly of clathrin-coated pits, the basic structural units of CME. In addition, the rate of fluid-phase endocytosis was enhanced, but with delayed onset upon USMB treatment relative to the enhancement of CME, suggesting that the two processes are distinctly regulated by USMB. Indeed, vacuolin-1 or desipramine treatment prevented the enhancement of CME but not of fluid phase endocytosis upon USMB, suggesting that lysosome exocytosis and acid sphingomyelinase, respectively, are required for the regulation of CME but not fluid phase endocytosis upon USMB treatment. These results indicate that USMB enhances both CME and fluid phase endocytosis through distinct signaling mechanisms, and suggest that strategies for potentiating the enhancement of endocytosis upon USMB treatment may improve targeted

  1. Efficacy of chemical treatments in eliminating Salmonella and Escherichia coli O157:H7 on scarified and polished alfalfa seeds.

    PubMed

    Holliday, S L; Scouten, A J; Beuchat, L R

    2001-10-01

    Alfalfa seeds are sometimes subjected to a scarification treatment to enhance water uptake, which results in more rapid and uniform germination during sprout production. It has been hypothesized that this mechanical abrasion treatment diminishes the efficacy of chemical treatments used to kill or remove pathogenic bacteria from seeds. A study was done to compare the effectiveness of chlorine (20,000 ppm), H2O, (8%), Ca(OH)2 (1%), Ca(OH)2 (1%) plus Tween 80 (1%), and Ca(OH)2 (1%) plus Span 20 (1%) treatments in killing Salmonella and Escherichia coli O157:H7 inoculated onto control, scarified, and polished alfalfa seeds obtained from two suppliers. The influence of the presence of organic material in the inoculum carrier on the efficacy of sanitizers was investigated. Overall, treatment with 1% Ca(OH)2 was the most effective in reducing populations of the pathogens. Reduction in populations of pathogens on seeds obtained from supplier I indicate that chemical treatments are less efficacious in eliminating the pathogens on scarified seeds compared to control seeds. However, the effectiveness of chemical treatment in removing Salmonella and E. coli O157:H7 from seeds obtained from supplier 2 was not markedly affected by scarification or polishing. The presence of organic material in the inoculum carrier did not have a marked influence on the efficacy of chemicals in reducing populations of test pathogens. Additional lots of control, scarified, and polished alfalfa seeds of additional varieties need to be tested before conclusions can be drawn concerning the impact of mechanical abrasion on the efficacy of chemical treatment in removing or killing Salmonella and E. coli O157:H7. PMID:11601695

  2. HyDRa: control of parameters for deterministic polishing.

    PubMed

    Ruiz, E; Salas, L; Sohn, E; Luna, E; Herrera, J; Quiros, F

    2013-08-26

    Deterministic hydrodynamic polishing with HyDRa requires a precise control of polishing parameters, such as propelling air pressure, slurry density, slurry flux and tool height. We describe the HyDRa polishing system and prove how precise, deterministic polishing can be achieved in terms of the control of these parameters. The polishing results of an 84 cm hyperbolic mirror are presented to illustrate how the stability of these parameters is important to obtain high-quality surfaces. PMID:24105579

  3. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Not Available

    1980-05-28

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels is described. The chemical attack polich comprises FeNO/sub 3/, concentrated CH/sub 3/COOH, concentrated H/sub 2/SO/sub 4/ and H/sub 2/O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  4. The local enhancement conundrum: in search of the adaptive value of a social learning mechanism.

    PubMed

    Arbilly, Michal; Laland, Kevin N

    2014-02-01

    Social learning mechanisms are widely thought to vary in their degree of complexity as well as in their prevalence in the natural world. While learning the properties of a stimulus that generalize to similar stimuli at other locations (stimulus enhancement) prima facie appears more useful to an animal than learning about a specific stimulus at a specific location (local enhancement), empirical evidence suggests that the latter is much more widespread in nature. Simulating populations engaged in a producer-scrounger game, we sought to deploy mathematical models to identify the adaptive benefits of reliance on local enhancement and/or stimulus enhancement, and the alternative conditions favoring their evolution. Surprisingly, we found that while stimulus enhancement readily evolves, local enhancement is advantageous only under highly restricted conditions: when generalization of information was made unreliable or when error in social learning was high. Our results generate a conundrum over how seemingly conflicting empirical and theoretical findings can be reconciled. Perhaps the prevalence of local enhancement in nature is due to stimulus enhancement costs independent of the learning task itself (e.g. predation risk), perhaps natural habitats are often characterized by unreliable yet highly rewarding payoffs, or perhaps local enhancement occurs less frequently, and stimulus enhancement more frequently, than widely believed. PMID:24044984

  5. Dual effects and mechanism of TiO2 nanotube arrays in reducing bacterial colonization and enhancing C3H10T1/2 cell adhesion

    PubMed Central

    Peng, Zhaoxiang; Ni, Jiahua; Zheng, Kang; Shen, Yandong; Wang, Xiaoqing; He, Guo; Jin, Sungho; Tang, Tingting

    2013-01-01

    Competition occurs between the osteoblasts in regional microenvironments and pathogens introduced during surgery, on the surface of bone implants, such as joint prostheses. The aim of this study was to modulate bacterial and osteoblast adhesion on implant surfaces by using a nanotube array. Titanium oxide (TiO2) nanotube arrays, 30 nm or 80 nm in diameter, were prepared by a two-step anodization on titanium substrates. Mechanically polished and acid-etched titanium samples were also prepared to serve as control groups. The standard strains of Staphylococcus epidermidis (S. epidermidis, American Type Culture Collection [ATCC]35984) and mouse C3H10T1/2 cell lines with osteogenic potential were used to evaluate the different responses to the nanotube arrays, in bacteria and eukaryotic cells. We found that the initial adhesion and colonization of S. epidermidis on the surface of the TiO2 nanotube arrays were significantly reduced and that the adhesion of C3H10T1/2 cells on the surface of the TiO2 nanotube arrays was significantly enhanced when compared with the control samples. Based on a surface analysis of all four groups, we observed increased surface roughness, decreased water contact angles, and an enhanced concentration of oxygen and fluorine atoms on the TiO2 nanotube surface. We conclude that the TiO2 nanotube surface can reduce bacterial colonization and enhance C3H10T1/2 cell adhesion; multiple physical and chemical properties of the TiO2 nanotube surface may contribute to these dual effects. PMID:23983463

  6. Mechanical property enhancement in laminates through control of morphology and crystal orientation

    NASA Astrophysics Data System (ADS)

    Zeilinger, A.; Daniel, R.; Stefenelli, M.; Sartory, B.; Chitu, L.; Burghammer, M.; Schöberl, T.; Kolednik, O.; Keckes, J.; Mitterer, C.

    2015-07-01

    This article shows the successful implementation of biological design principles into synthetic laminate materials in order to enhance their mechanical properties. We demonstrate and provide a strategy for laminate thin films, which reveals that the control of local crystal anisotropy across laminates together with the optimized layered arrangement are essential for their mechanical behavior. By the example of a laminate consisting of brittle CrN and ductile Cr layers, enhanced material properties are achieved by taking advantage of the self assembly mechanisms of the heterogeneous material during film growth. The usage of local microstructure analysis by a synchrotron based technique as well as miniature mechanical tests allow to understand the relationship between the apparent local microstructure and the accompanied mechanical properties. A crystallographic orientation relationship between Cr and CrN is elucidated, which leads to decisive mechanical enhancement due to microstructural benefits in terms of texture. This results in enhanced strength and fracture toughness of the laminate compared to its single constituents. The systematic approach gives an insight into the complex coherences of laminate materials, where the used techniques and design principles are universally applicable.

  7. Quantitative evaluation of blinking in surface enhanced resonance Raman scattering and fluorescence by electromagnetic mechanism

    NASA Astrophysics Data System (ADS)

    Itoh, Tamitake; Iga, Mitsuhiro; Tamaru, Hiroharu; Yoshida, Ken-ichi; Biju, Vasudevanpillai; Ishikawa, Mitsuru

    2012-01-01

    We analyze blinking in surface enhanced resonance Raman scattering (SERRS) and surface enhanced fluorescence (SEF) of rhodamine 6G molecules as intensity and spectral instability by electromagnetic (EM) mechanism. We find that irradiation of intense NIR laser pulses induces blinking in SERRS and SEF. Thanks to the finding, we systematically analyze SERRS and SEF from stable to unstable using single Ag nanoparticle (NP) dimers. The analysis reveals two physical insights into blinking as follows. (1) The intensity instability is inversely proportional to the enhancement factors of decay rate of molecules. The estimation using the proportionality suggests that separation of the molecules from Ag NP surfaces is several angstroms. (2) The spectral instability is induced by blueshifts in EM enhancement factors, which have spectral shapes similar to the plasmon resonance. This analysis provides us with a quantitative picture for intensity and spectral instability in SERRS and SEF within the framework of EM mechanism.

  8. Depth profiling of polishing-induced contamination on fused silica surfaces

    SciTech Connect

    Kozlowski, M.R.; Carr, J.; Hutcheon, I,; Torres, R.; Sheehan, L. Camp, D.; Yan, M.

    1997-12-20

    Laser-induced damage on optical surfaces is often associated with absorbing contaminants introduced by the polishing process. This is particularly the case for UV optics. Here secondary ion mass spectroscopy (SIMS) was used to measure depth profiles of finished process contamination on fused silica surfaces. Contaminants detected include the major polishing compound components (Ce or Zr from CeO2 or ZrO2), Al presently largely because of the use of Al2O3 in the final cleaning process (Fe, Cu,Cr) incorporated during the polishing step or earlier grinding steps. Depth profile data typically showed an exponential decay of contaminant concentration to a depth of 100-200 nm. This depth is consistent with a polishing redeposition layers formed during the chemo-mechanical polishing of fused silica. Peak contaminant levels are typically in the 10-100 ppm range, except for Al with exceeds 1000 ppm. A strong correlation has been shown between the presence of a gray haze damage morphology and the use of CeO2 polishing compound. No strong correlation was found however between high levels of Ce, or any other contaminant and the low damage threshold was observed. In fact one of the strongest indications of a correlation is between increased damage thresholds and increased Zr contamination. This suggests that the correlation between redeposition layer and laser damage threshold is not simple an absorbing contaminant issue.

  9. [Review on the main microorganisms and their metabolic mechanisms in enhanced biological phosphorus removal (EBPR) systems].

    PubMed

    Sun, Xue; Zhu, Wei-Jing; Wang, Liang; Wu, Wei-Xiang

    2014-03-01

    Enhanced biological phosphorus removal (EBPR) process is applied widely for removing phosphorus from wastewater. Studies on functional microorganisms and their metabolic mechanisms are fundamental to effective regulation for stable operation and performance improvement of EBPR process. Two main types of microorganisms in EBPR systems, polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) were selected to summarize their metabolic mechanisms such as substrate uptake mechanisms, glycogen degradation pathways, extent of TCA cycle involvement and metabolic similarity between PAOs and GAOs. Application of molecular biology techniques in microbiology and metabolic mechanisms involved in the EBPR system was evaluated. Potential future research areas for the EBPR system and process optimization were also proposed. PMID:24984512

  10. Energetic composite and system with enhanced mechanical sensitivity to initiation of self-sustained reaction

    DOEpatents

    Gash, Alexander E.; Barbee, Jr., Troy W.

    2012-05-29

    An energetic composition and system using amassed energetic multilayer pieces which are formed from the division, such as for example by cutting, scoring, breaking, crushing, shearing, etc., of a mechanically activatable monolithic energetic multilayer(s) (e.g. macro-scale sheets of multilayer films), for enhancing the sensitivity of the energetic composite and system to mechanical initiation of self-sustained reaction. In particular, mechanical initiation of the energetic composition may be achieved with significantly lower mechanical energy inputs than that typically required for initiating the monolithic energetic multilayers from which it is derived.

  11. Mechanisms of enhanced total organic carbon elimination from oxalic acid solutions by electro-peroxone process.

    PubMed

    Wang, Huijiao; Yuan, Shi; Zhan, Juhong; Wang, Yujue; Yu, Gang; Deng, Shubo; Huang, Jun; Wang, Bin

    2015-09-01

    Electro-peroxone (E-peroxone) is a novel electrocatalytic ozonation process that combines ozonation and electrolysis process to enhance pollutant degradation during water and wastewater treatment. This enhancement has been mainly attributed to several mechanisms that increase O3 transformation to ·OH in the E-peroxone system, e.g., electro-generation of H2O2 from O2 at a carbon-based cathode and its subsequent peroxone reaction with O3 to ·OH, electro-reduction of O3 to ·OH at the cathode, and O3 decomposition to ·OH at high local pH near the cathode. To get more insight how these mechanisms contribute respectively to the enhancement, this study investigated total organic carbon (TOC) elimination from oxalic acid (OA) solutions by the E-peroxone process. Results show that the E-peroxone process significantly increased TOC elimination rate by 10.2-12.5 times compared with the linear addition of the individual rates of corresponding ozonation and electrolysis process. Kinetic analyses reveal that the electrochemically-driven peroxone reaction is the most important mechanism for the enhanced TOC elimination rate, while the other mechanisms contribute minor to the enhancement by a factor of 1.6-2.5. The results indicate that proper selection of electrodes that can effectively produce H2O2 at the cathode is critical to maximize TOC elimination in the E-peroxone process. PMID:25989593

  12. Mechanism of enhanced hydrogen adsorption on palladium-doped nanoporous carbon fibers

    SciTech Connect

    Contescu, Cristian I; Gallego, Nidia C; Wu, Xianxian; Tekinalp, Halil; Edie, Dan; Thies, Mark C; Baker, Frederick S

    2007-01-01

    Recent work at Oak Ridge National Laboratory was directed towards adsorptive storage of hydrogen in nanoporous carbon fibers in which palladium was incorporated prior to spinning and carbonization/activation of the fibers. Palladium doped carbon fibers exhibited enhanced hydrogen uptake compared to the corresponding palladium-free nanoporous carbon fibers (at room temperature and 2 MPa pressure). However, the mechanism responsible for the enhanced hydrogen uptake is not fully understood. New findings are presented in this paper in support of a mechanism that encompasses both hydrogen spillover on palladium metal sites and hydrogen physisorption on nanostructured carbon sites.

  13. Design Considerations of Polishing Lap for Computer-Controlled Cylindrical Polishing Process

    NASA Technical Reports Server (NTRS)

    Khan, Gufran S.; Gubarev, Mikhail; Arnold, William; Ramsey, Brian D.

    2009-01-01

    This paper establishes a relationship between the polishing process parameters and the generation of mid spatial-frequency error. The consideration of the polishing lap design to optimize the process in order to keep residual errors to a minimum and optimization of the process (speeds, stroke, etc.) and to keep the residual mid spatial-frequency error to a minimum, is also presented.

  14. Internet Use of Polish by Polish Melburnians: Implications for Maintenance and Teaching

    ERIC Educational Resources Information Center

    Fitzgerald, Michael; Debski, Robert

    2006-01-01

    The Internet has become an important communication medium and it is having a significant impact on language use. The present study takes a "snapshot" of how the Polish language is currently used with modern communications technologies by Polish-Australians living in Melbourne. Through a questionnaire, it surveys which communications technologies…

  15. Mechanisms Of Residual Force Enhancement In Skeletal Muscle: Insights From Experiments And Mathematical Models.

    PubMed

    Campbell, Stuart G; Campbell, Kenneth S

    2011-12-01

    A skeletal muscle that is stretched while contracting will produce more force at steady state than if it is stretched passively and then stimulated to contract. This phenomenon is known as residual force enhancement and has been widely studied since its description more than sixty years ago. The idea that the mechanical properties of a muscle are governed not just by its present length but also by its length at earlier time points has far reaching implications since muscles stretch and shorten routinely in normal use. In this review, we present the experimental and theoretical advances that have been made toward understanding the mechanisms that underlie residual force enhancement. In the past ten years, experiments and models have focused on essentially three candidate mechanisms for residual force enhancement: (half-) sarcomere inhomogeneity, activity of so-called 'passive' mechanical elements in the sarcomere (titin), and the intrinsic properties of myosin crossbridges. Evidence, both computational and experimental, is accumulating for each of these mechanisms such that a final description of the phenomenon seems attainable in the near future. We conclude that computational models that incorporate more than one putative mechanism may ultimately facilitate reconciliation of the growing number of ideas and experimental data in this field. PMID:22180761

  16. Superconductivity Induced by Surface Polishing in CeIrSi3

    NASA Astrophysics Data System (ADS)

    Iida, Hiroki; Sato, Masashi; Kimura, Noriaki

    2016-07-01

    We show that superconductivity observed in the antiferromagnetic state of CeIrSi3, a pressure-induced heavy fermion superconductor, is mainly due to a surface layer induced by mechanical polishing. The superconducting reduction of the electrical resistivity in the antiferromagnetic state strongly depends on the strength of the applied electrical current and dissipates after a heat treatment. These results indicate that mechanical polishing causes an inhomogeneous distortion on the surface of the sample and locally produces a high-pressure region in which the bulk superconductivity arises.

  17. Burial and exhumation history of the Polish Outer Carpathians: Discriminating the role of thrusting and post-thrusting extension

    NASA Astrophysics Data System (ADS)

    Andreucci, B.; Castelluccio, A.; Jankowski, L.; Mazzoli, S.; Szaniawski, R.; Zattin, M.

    2013-11-01

    Several tectonic processes have been proposed to be important in the Alpine to the recent evolution of the Polish Outer Carpathians, i.e., Paleogene-Neogene thrusting, post-thrusting extension, Quaternary reactivation of compression. This work tests the effect of these processes on exhumation of the wedge, in order to verify their timing and relative role in shaping the Polish Outer Carpathians. AFT, AHe and ZHe analyses were performed on samples collected along the study region. This allowed the reconstruction of their post-depositional minimum heating, depth of burial and timing of cooling and exhumation. After deposition samples from the innermost units were heated up to temperatures of ca. 60-120 °C (ca. 4-9 km), whereas samples from the outer units were heated to temperatures lower than 60 °C (ca. 4 km). Cooling and exhumation occurred progressively later from west to east (between ca. 25 and 10 Ma in the western sector, between ca. 15 and 5 Ma in the eastern sector). These results have been put in relationship with single structural features to understand the relative role of thrusts and normal faults. In the eastern sector of the study region samples at the footwall of significant normal faults show a higher degree of reset and younger ages than samples located at the hangingwall. This implies that, in this sector, extensional tectonics played an important role in exhumation. However, proper tectonic exhumation only had a minor role, the major exhumation mechanism being erosion, which is enhanced in the footwalls and reduced in the hangingwalls. In the western sector of the Polish Outer Carpathians only in few cases evidence of enhanced erosion to the footwall of major normal faults could be observed based on the present data. In this region the wedge exhumed mainly as a response to thrusting and normal faulting only played a minor role, locally modifying the pattern of erosion. Finally no major exhumation events occurred after Miocene, pointing to a minor

  18. The driving mechanism of roAp stars : effects of local metallicity enhancement

    NASA Astrophysics Data System (ADS)

    Théado, S.; Dupret, M.-A.; Noels, A.

    2009-07-01

    We have investigated the influence of a local metallicity enhancement on the excitation mechanism of roAp star pulsations. Our computations show that such accumulations poorly affect the position of the theoretical roAp star instability strip although the opacity in the driving region of roAp modes is affected by metal accumulation.

  19. Mechanisms for enhanced packaging and/or burn-in total dose sensitivity in microelectronics

    SciTech Connect

    Pease, R.L.; Shaneyfelt, M.; Winokur, P.

    1997-03-01

    The ionizing radiation response of several semiconductor process technologies has been shown to be enhanced by plastic packaging and/or pre-conditioning (burn-in). Potential mechanisms for this effect are discussed and data on bipolar linear circuits are presented.

  20. Experimental and theoretical demonstrations for the mechanism behind enhanced microbial electron transfer by CNT network.

    PubMed

    Liu, Xian-Wei; Chen, Jie-Jie; Huang, Yu-Xi; Sun, Xue-Fei; Sheng, Guo-Ping; Li, Dao-Bo; Xiong, Lu; Zhang, Yuan-Yuan; Zhao, Feng; Yu, Han-Qing

    2014-01-01

    Bioelectrochemical systems (BESs) share the principle of the microbially catalyzed anodic substrate oxidation. Creating an electrode interface to promote extracellular electron transfer from microbes to electrode and understanding such mechanisms are crucial for engineering BESs. In this study, significantly promoted electron transfer and a 10-times increase in current generation in a BES were achieved by the utilization of carbon nanotube (CNT) network, compared with carbon paper. The mechanisms for the enhanced current generation with the CNT network were elucidated with both experimental approach and molecular dynamic simulations. The fabricated CNT network was found to be able to substantially enhance the interaction between the c-type cytochromes and solid electron acceptor, indicating that the direct electron transfer from outer-membrane decaheme c-type cytochromes to electrode might occur. The results obtained in this study will benefit for the optimized design of new materials to target the outer membrane proteins for enhanced electron exchanges. PMID:24429552

  1. Water filling and electric field-induced enhancement in the mechanical property of carbon nanotubes.

    PubMed

    Ye, H F; Zheng, Y G; Zhang, Z Q; Chen, Z; Zhang, H W

    2015-01-01

    The effects of water filling and electric field on the mechanical property of carbon nanotubes (CNTs) are investigated with molecular dynamics simulations. The simulation results indicate that the water filling and electric field could enhance the elastic modulus but reduce the Poisson's ratio of the CNTs. As for the buckling behaviors, a significant enhancement could be observed in the yield stress and average post-buckling stress of the CNTs. In particular, the enhancement in the yield stress induced by the water filling and electric field could be even higher than that resulted from the solid filling. Moreover, a transition mechanism from the rod instability to shell buckling is shown to explain the nonmonotonic variation of yield stress, and the critical diameter can be tuned through filling the water molecules and applying the electric field. The present findings provide a valuable route for the optimized design and application of the nanoscale functional devices based on the water-filled CNTs. PMID:26621767

  2. Laboratory evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    NASA Astrophysics Data System (ADS)

    Candela, Thibault; Brodsky, Emily E.; Marone, Chris; Elsworth, Derek

    2014-04-01

    It is well-established that seismic waves can increase the permeability in natural systems, yet the mechanism remains poorly understood. We investigate the underlying mechanics by generating well-controlled, repeatable permeability enhancement in laboratory experiments. Pore pressure oscillations, simulating dynamic stresses, were applied to intact and fractured Berea sandstone samples under confining stresses of tens of MPa. Dynamic stressing produces an immediate permeability enhancement ranging from 1 to 60%, which scales with the amplitude of the dynamic strain (7×10-7 to 7×10-6) followed by a gradual permeability recovery. We investigated the mechanism by: (1) recording deformation of samples both before and after fracturing during the experiment, (2) varying the chemistry of the water and therefore particle mobility, (3) evaluating the dependence of permeability enhancement and recovery on dynamic stress amplitude, and (4) examining micro-scale pore textures of the rock samples before and after experiments. We find that dynamic stressing does not produce permanent deformation in our samples. Water chemistry has a pronounced effect on the sensitivity to dynamic stressing, with the magnitude of permeability enhancement and the rate of permeability recovery varying with ionic strength of the pore fluid. Permeability recovery rates generally correlate with the permeability enhancement sensitivity. Microstructural observations of our samples show clearing of clay particulates from fracture surfaces during the experiment. From these four lines of evidence, we conclude that a flow-dependent mechanism associated with mobilization of fines controls both the magnitude of the permeability enhancement and the recovery rate in our experiments. We also find that permeability sensitivity to dynamic stressing increases after fracturing, which is a process that generates abundant particulate matter in situ. Our results suggest that fluid permeability in many areas of the

  3. The best of both worlds: automated CMP polishing of channel-cut monochromators

    SciTech Connect

    Kasman, Elina; Erdmann, Mark; Stoupin, Stanislav

    2015-09-03

    The use of a channel-cut monochromator is the most straightforward method to ensure that the two reflection surfaces maintain alignment between crystallographic planes without the need for complicated alignment mechanisms. Three basic characteristics that affect monochromator performance are: subsurface damage which contaminates spectral purity; surface roughness which reduces efficiency due to scattering; and surface figure error which imparts intensity structure and coherence distortion in the beam. Standard chemical-mechanical polishing processes and equipment are used when the diffracting surface is easily accessible, such as for single-bounce monochromators. Due to the inaccessibly of the surfaces inside a channel-cut monochromator for polishing, these optics are generally wet-etched for their final processing. This results in minimal subsurface damage, but very poor roughness and figure error. A new CMP channel polishing instrument design is presented which allows the internal diffracting surface quality of channel-cut crystals to approach that of conventional single-bounce monochromators

  4. The best of both worlds: automated CMP polishing of channel-cut monochromators

    NASA Astrophysics Data System (ADS)

    Kasman, Elina; Erdmann, Mark; Stoupin, Stanislav

    2015-09-01

    The use of a channel-cut monochromator is the most straightforward method to ensure that the two reflection surfaces maintain alignment between crystallographic planes without the need for complicated alignment mechanisms. Three basic characteristics that affect monochromator performance are: subsurface damage which contaminates spectral purity; surface roughness which reduces efficiency due to scattering; and surface figure error which imparts intensity structure and coherence distortion in the beam. Standard chemical-mechanical polishing processes and equipment are used when the diffracting surface is easily accessible, such as for single-bounce monochromators. Due to the inaccessibly of the surfaces inside a channel-cut monochromator for polishing, these optics are generally wet-etched for their final processing. This results in minimal subsurface damage, but very poor roughness and figure error. A new CMP channel polishing instrument design is presented which allows the internal diffracting surface quality of channel-cut crystals to approach that of conventional single-bounce monochromators.

  5. Modeling shear failure and permeability enhancement due to coupled Thermal-Hydrological-Mechanical processes in Enhanced Geothermal Reservoirs

    SciTech Connect

    Kelkar, Sharad

    2011-01-01

    The connectivity and accessible surface area of flowing fractures, whether natural or man-made, is possibly the single most important factor, after temperature, which determines the feasibility of an Enhanced Geothermal System (EGS). Rock deformation and in-situ stress changes induced by injected fluids can lead to shear failure on preexisting fractures which can generate microseismic events, and also enhance the permeability and accessible surface area of the geothermal formation. Hence, the ability to accurately model the coupled thermal-hydrologic-mechanical (THM) processes in fractured geological formations is critical in effective EGS reservoir development and management strategies. The locations of the microseismic events can serve as indicators of the zones of enhanced permeability, thus providing vital information for verification of the coupled THM models. We will describe a general purpose computational code, FEHM, developed for this purpose, that models coupled THM processes during multiphase fluid flow and transport in fractured porous media. The code incorporates several models of fracture aperture and stress behavior combined with permeability relationships. We provide field scale examples of applications to geothermal systems to demonstrate the utility of the method.

  6. Standards of the Polish Ultrasound Society – update. Spleen examination

    PubMed Central

    Walas, Maria Krystyna

    2013-01-01

    Ultrasound scan of the spleen is an integral part of the overall abdominal examination. Due to its anatomical position, physical examination of the spleen is frequently supplemented with an ultrasound which plays a special role in the differential diagnostics of splenic diseases and facilitates the determination of further diagnostic and therapeutic procedures. Similarly to other types of ultrasound scans, the examiner should be familiar with all significant clinical information as well as results of examinations and tests conducted so far. This enables to narrow the scope of search for etiological factors and indicate specific disease entities in the findings as well as allows for accurate assessment of coexistent pathologies. The article presents the standards of the Polish Ultrasound Society concerning the apparatus, preparation for the examination, technique and description of the findings. The authors discuss the normal anatomy of the spleen and the most common pathologies ranging from splenomegaly to splenic traumas. The indications for the contrast-enhanced ultrasound and characteristic patterns of enhancement of individual focal lesions are presented. This article is supplemented with photographic documentation, which provides images of the discussed lesions. The ultrasound examination, if carried out in compliance with current standards, allows for accurate interpretation of detected changes. This article has been prepared on the basis of the Ultrasound Examination Standards of the Polish Ultrasound Society (2011) and updated with the current knowledge. PMID:26672802

  7. [Study of pure titanium electrolytic polishing].

    PubMed

    Morita, N

    1990-03-01

    This study attempted to polish pure titanium test pieces electrolytically to mirror surface at the size of cast denture frames. Electrolytic polishing of pure titanium could be done on an area of 30 cm2 with a non-aqueous electrolyte. Small pure titanium plates could be polished electrolytically, but a uniformly smooth surface could not be obtained easily with large testpiece. The optimal electrolytic conditions were 30 V for 6 min at 25 degrees C using a solution consisting of 70 ml ethyl alcohol, 30 ml iso-propyl alcohol, 6 g aluminum chloride, and 25 g zinc chloride. The solution was safe and had less restriction of frequency of use. PMID:2135513

  8. Using synthetic bacterial enhancers to reveal a looping-based mechanism for quenching-like repression

    NASA Astrophysics Data System (ADS)

    Brunwasser-Meirom, Michal; Pollak, Yaroslav; Goldberg, Sarah; Levy, Lior; Atar, Orna; Amit, Roee

    2016-02-01

    We explore a model for `quenching-like' repression by studying synthetic bacterial enhancers, each characterized by a different binding site architecture. To do so, we take a three-pronged approach: first, we compute the probability that a protein-bound dsDNA molecule will loop. Second, we use hundreds of synthetic enhancers to test the model's predictions in bacteria. Finally, we verify the mechanism bioinformatically in native genomes. Here we show that excluded volume effects generated by DNA-bound proteins can generate substantial quenching. Moreover, the type and extent of the regulatory effect depend strongly on the relative arrangement of the binding sites. The implications of these results are that enhancers should be insensitive to 10-11 bp insertions or deletions (INDELs) and sensitive to 5-6 bp INDELs. We test this prediction on 61 σ54-regulated qrr genes from the Vibrio genus and confirm the tolerance of these enhancers' sequences to the DNA's helical repeat.

  9. Assessment of subsurface damage in polished II-VI semiconductors by ion channeling

    NASA Astrophysics Data System (ADS)

    Lucca, D. A.; Wetteland, C. J.; Misra, A.; Klopfstein, M. J.; Nastasi, M.; Maggiore, C. J.; Tesmer, J. R.

    2004-06-01

    Surfaces of bulk single crystal CdS, ZnSe and ZnO were prepared by mechanical polishing with 1 and 1/4 μm diamond abrasive slurries and by chemomechanical polishing with sodium hypochlorite:colloidal silica. Etched surfaces, indicative of original crystalline quality were also prepared. Near surface damage was investigated by ion channeling with He ions using incident beam energies of 2 and 5 MeV and detector positions of 75° and 13°. Damage depths were found to be significantly higher for ZnSe when compared to CdS or ZnO. The chemomechanical polishing process was seen to introduce small but measurable subsurface damage in CdS and ZnSe. However, channeling was unable to detect any damage for the chemomechanically polished ZnO surfaces, a result which was supported by cross-section transmission electron microscopy (XTEM). The presence of damage beyond that identified by the surface peak for the mechanically polished ZnSe surfaces was indicated by the dechanneling behavior below the surface.

  10. Effects of fibrillation on the wood fibers' enzymatic hydrolysis enhanced by mechanical refining.

    PubMed

    Liu, Wei; Wang, Bing; Hou, Qingxi; Chen, Wei; Wu, Ming

    2016-04-01

    The hardwood bleached kraft pulp (HBKP) fibers were pretreated by PFI mill to obtain the substrates, the effects of fibrillation on HBKP fibers' enzymatic hydrolysis was studied. The results showed that the enzymatic hydrolysis efficiency was enhanced obviously by mechanical refining. The mechanical refining alterated the fibers' characteristics such as fibrillation degree, specific surface area, swelling ability, crystallinity, fiber length and fines content. All these factors correlating to the enzymatic hydrolysis were evaluated through mathematical analysis. Among these factors, the fibrillation degree has the profoundest impact on the enzymatic hydrolysis of wood fibers. Consequently, the mechanical refining aiming for a high fibrillation degree was feasible to enhance the enzymatic hydrolysis of lignocellulosic biomass. PMID:26851576

  11. Occupational lung fibrosis in an aluminium polisher.

    PubMed

    De Vuyst, P; Dumortier, P; Rickaert, F; Van de Weyer, R; Lenclud, C; Yernault, J C

    1986-02-01

    An aluminium polisher developed severe lung fibrosis complicated by bronchial carcinoma. Although he was not submitted to the exposure risks usually described in aluminium lung (bauxite smelting, use of aluminium powders, aluminium welding), he worked in a high concentration of aluminium dust. This was demonstrated by mineralogical analyses which revealed large amounts of small metallic aluminium particles (0.5 micron - 5 micron) in bronchoalveolar lavage, lung tissue and lymph nodes 5 years after the end of exposure. Aluminium polishing seems to be a potential cause of aluminium lung. PMID:3699115

  12. Repetitive mechanical strain suppresses macrophage uptake of immunoglobulin G complexes and enhances cyclic adenosine monophosphate synthesis.

    PubMed Central

    Mattana, J.; Sankaran, R. T.; Singhal, P. C.

    1995-01-01

    Uptake of immunoglobulin G (IgG) complexes by macrophages (M phi) may play an important role in disease states characterized by increased levels of circulating immune complexes. In sites such as the glomerular mesangium M phi may be subjected to repetitive mechanical strain, although in vitro studies of M phi endocytosis are typically carried out with cells grown on rigid surfaces. We undertook the present study to determine whether repetitive mechanical strain could modulate M phi endocytosis of IgG complexes. IgG complex uptake was significantly diminished in M phi that were subjected to repetitive mechanical strain using parameters corresponding to peak and minimal intraglomerular pressures compared with control, and uptake varied according to the amount of mechanical strain applied. There was no significant difference in surface binding of IgG between M phi subjected to strain and those not. Mechanical strain did not significantly influence the rate of IgG complex degradation. Inhibition of nitric oxide synthase and guanylate cyclase activity did not alter the effect of mechanical strain, although this effect was potentiated by 3-isobutyl-1-methylxanthine (IBMX). Angiotensin II, which has been shown to reduce adenosine 3',5'-cyclic monophosphate (cAMP) production in M phi, significantly attenuated the suppressive effect of mechanical strain on IgG complex uptake as well as another inhibitor of cAMP generation, indomethacin. Enzyme immunoassay demonstrated significantly enhanced levels of cAMP in M phi that were subjected to mechanical strain compared with control, an effect that was potentiated by IBMX and attenuated by angiotensin II and indomethacin. These results demonstrate that repetitive mechanical strain significantly reduces IgG complex uptake by M phi, most likely by enhancing cAMP synthesis. Such an effect might play a significant role in macromolecule handling by M phi in sites in which they are subjected to repetitive mechanical deformation such as

  13. Three-dimensional evaluation of surface roughness of resin composites after finishing and polishing

    PubMed Central

    Nair, Veena S; Sainudeen, Shan; Padmanabhan, Prabeesh; Vijayashankar, L V; Sujathan, Unu; Pillai, Rajesh

    2016-01-01

    Aim: This study aims to investigate the effects of finishing and polishing procedures on four novel resin composites using three-dimensional optical profilometer. Materials and Methods: Four composites classified according to their filler size, were selected: Filtek™ Z350 XT/Nanofill (3M™ ESPE™), Esthet-X HD/Hybrid (Dentsply Caulk), Te Econom/Microfill (Ivoclar Vivadent®), Tetric EvoCeram® /Nanohybrid (Ivoclar Vivadent®). Composite specimens were made in Plexiglass mold and polished with Soflex (3M ESPE), Enhance + Pogo (Dentsply Caulk). Both the systems were used according to the manufacturers’ instructions, and the polished surfaces were assessed with an optical profilometer. Statistical Analysis Used: Kruskal-Wallis test and further pairwise comparison were performed by Mann-Whitney test. Results: The smoothest surfaces for all the resin composites tested were obtained from the Mylar strip; statistically significant differences were observed among them (P = 0.001). The order of composites was ranked from the lowest to highest surface roughness; Filtek Z350 XT < Te Econom < Tetric EvoCeram < Esthet XHD. Pairwise multiple comparison with Mann-Whitney test showed Filtek Z350 to have the smoothest surface and the least with Teric EvoCeram. Among the polishing systems, Soflex showed the smoothest surface and was significantly different from Pogo (P = 0.046). Conclusions: The effectiveness of the polishing systems seems to be dependent on the material used, treatment modality and also on the filler particle size. PMID:26957802

  14. Stress “deafness” in a Language with Fixed Word Stress: An ERP Study on Polish

    PubMed Central

    Domahs, Ulrike; Knaus, Johannes; Orzechowska, Paula; Wiese, Richard

    2012-01-01

    The aim of the present contribution was to examine the factors influencing the prosodic processing in a language with predictable word stress. For Polish, a language with fixed penultimate stress but several well-defined exceptions, difficulties in the processing and representation of prosodic information have been reported (e.g., Peperkamp and Dupoux, 2002). The present study utilized event-related potentials (ERPs) to investigate the factors influencing prosodic processing in Polish. These factors are (i) the predictability of stress and (ii) the prosodic structure in terms of metrical feet. Polish native speakers were presented with correctly and incorrectly stressed Polish words and instructed to judge the correctness of the perceived stress patterns. For some stress violations, an early negativity was found which was interpreted as a reflection of an error-detection mechanism. In addition, exceptional stress patterns (=antepenultimate stress) and post-lexical (=initial) stress evoked a task-related positivity effect (P300) whose amplitude and latency is correlated with the degree of anomaly and deviation from an expectation. In contrast, violations involving the default (=penultimate stress) did not produce such an effect. This asymmetrical result is interpreted to reflect that Polish native speakers are less sensitive to the default pattern than to the exceptional or post-lexical patterns. Behavioral results are orthogonal to the electrophysiological results showing that Polish speakers had difficulties to reject any kind of stress violation. Thus, on a meta-linguistic level Polish speakers appeared to be stress-“deaf” for any kind of stress manipulation, whereas the neural reactions differentiate between the default and lexicalized patterns. PMID:23125839

  15. Enhancing mechanical toughness of aluminum surfaces by nano-boron implantation: An ab initio study

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen; Kwon, Dae-Gyeon; Kwon, Young-Kyun; Tománek, David

    2015-01-01

    Searching for ways to enhance surface hardness of aluminum, we study the equilibrium structure, stability, elastic properties and formation dynamics of a boron-enriched surface using ab initio density functional calculations. We used molecular dynamics simulations to model the implantation of energetic boron nanoparticles in Al and identify structural arrangements that optimize the formation of strong covalent Bsbnd Al bonds. Nano-indentation simulations based on constrained optimization suggest that presence of boron nanostructures in the subsurface region enhances significantly the mechanical hardness of aluminum surfaces.

  16. Polishing procedure and surface characterization lead tungstate crystal scintillator Road No. 723 and No. 754

    SciTech Connect

    Kellam, M

    1996-05-01

    Step by step procedures are given for polishing the scintillator rods. A Strasbaugh spindle polishing machine was used along with visual inspection and hand polishing. Extensive data is given on pre-polish surface characterization, profilometry, microphotography, and interferometry.

  17. Surface Roughness, Microhardness, and Microleakage of a Silorane-Based Composite Resin after Immediate or Delayed Finishing/Polishing.

    PubMed

    Lins, Fernanda Carvalho Rezende; Ferreira, Raquel Conceição; Silveira, Rodrigo Richard; Pereira, Carolina Nemésio Barros; Moreira, Allyson Nogueira; Magalhães, Claudia Silami

    2016-01-01

    Objective. This study evaluated the effect of immediate or delayed finishing/polishing using different systems on the surface roughness, hardness, and microleakage of a silorane-based composite. Material and Methods. Specimens were made with silorane-based composite (Filtek P90, 3M ESPE) and assigned to the treatments: control (light-cured); aluminum oxide discs (Sof-Lex, 3M ESPE); diamond-impregnated silicone tips (Astropol, Ivoclar Vivadent); aluminum oxide-impregnated silicone tips (Enhance, Dentsply). Half of the specimens were finished/polished immediately and the rest after 7 days. Surface roughness (Ra, μm; n = 20) and Vickers microhardness (50 g; 45 s; n = 10) were measured. Cavities were prepared in bovine incisors and filled with Filtek P90. The fillings received immediate or delayed finishing/polishing (n = 10) and were subjected to dye penetration test (0.5% basic fuchsin, 24 h). Data were analyzed by ANOVA and Scheffe, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). Results. The finishing/polishing system significantly influenced roughness and microhardness (p < 0.0001). For enamel, microleakage was not affected by the finishing/polishing system (p = 0.309). For dentin, Sof-Lex discs and Astropol points promoted greater microleakage than Enhance points (p = 0.033). Conclusion. Considering roughness, microhardness, and microleakage together, immediate finishing/polishing of a silorane-based composite using aluminum oxide discs may be recommended. PMID:26977150

  18. Surface Roughness, Microhardness, and Microleakage of a Silorane-Based Composite Resin after Immediate or Delayed Finishing/Polishing

    PubMed Central

    Lins, Fernanda Carvalho Rezende; Ferreira, Raquel Conceição; Silveira, Rodrigo Richard; Pereira, Carolina Nemésio Barros; Moreira, Allyson Nogueira; Magalhães, Claudia Silami

    2016-01-01

    Objective. This study evaluated the effect of immediate or delayed finishing/polishing using different systems on the surface roughness, hardness, and microleakage of a silorane-based composite. Material and Methods. Specimens were made with silorane-based composite (Filtek P90, 3M ESPE) and assigned to the treatments: control (light-cured); aluminum oxide discs (Sof-Lex, 3M ESPE); diamond-impregnated silicone tips (Astropol, Ivoclar Vivadent); aluminum oxide-impregnated silicone tips (Enhance, Dentsply). Half of the specimens were finished/polished immediately and the rest after 7 days. Surface roughness (Ra, μm; n = 20) and Vickers microhardness (50 g; 45 s; n = 10) were measured. Cavities were prepared in bovine incisors and filled with Filtek P90. The fillings received immediate or delayed finishing/polishing (n = 10) and were subjected to dye penetration test (0.5% basic fuchsin, 24 h). Data were analyzed by ANOVA and Scheffe, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). Results. The finishing/polishing system significantly influenced roughness and microhardness (p < 0.0001). For enamel, microleakage was not affected by the finishing/polishing system (p = 0.309). For dentin, Sof-Lex discs and Astropol points promoted greater microleakage than Enhance points (p = 0.033). Conclusion. Considering roughness, microhardness, and microleakage together, immediate finishing/polishing of a silorane-based composite using aluminum oxide discs may be recommended. PMID:26977150

  19. Mechanisms of action of novel skin penetration enhancers: phospholipid versus skin lipid liposomes.

    PubMed

    El Maghraby, Gamal M M; Campbell, Michael; Finnin, Barrie C

    2005-11-23

    Employing thermal analysis, we investigated the mechanism of action of novel enhancers and probed phospholipid (PL) versus stratum corneum lipid (SCL) liposomes as model membranes. The enhancers included octyl salicylate (OS), padimate O (PADO) and 2-(1-nonyl)-1,3-dioxolane (ND). The negative controls were the empty liposomes. Positive controls employed dimethylsulfoxide (DMSO) and Azone (AZ). For PL liposomes, DMSO sharpened the transitions. AZ abolished the pre-transition, broadened the main transition and linearly reduced its transition temperature (T(m)). OS or PADO reduced T(m) and size of pre-transition, broadened the main transition and decreased its T(m) (non-linearly). ND abolished the pre-transition but increased T(m) of the main endotherm, suggesting retardation rather than enhancement. The results of SCL correlated with PL liposomes except for ND. In SCL liposomes, ND reduced T(m) and broadened the peaks indicating lipid disruption, which indicated its enhancing effects. In conclusion, OS, PADO and ND can enhance drugs by disrupting intercellular lipid domain but they differ from AZ in terms of the relationship between efficacy and concentration. Although PL liposomes are simple model membranes with sharp transitions which give detailed information about the effects of enhancers, they can provide misleading results. Simultaneous use of other models like SCL liposomes is recommended. PMID:16199131

  20. Improving the durability of a drag-reducing nanocoating by enhancing its mechanical stability.

    PubMed

    Cheng, Mengjiao; Zhang, Songsong; Dong, Hongyu; Han, Shihui; Wei, Hao; Shi, Feng

    2015-02-25

    The durability of superhydrophobic surface is a major problem to restrict industrial application of superhydrophobic materials from laboratory research, which can be attributed to a more general issue of mechanical stability for superhydrophobic coatings. Therefore, in order to handle this issue, we have fabricated a mechanically stable drag-reducing coating composed of elastic polydimethylsiloxane (PDMS) and hydrophobic copper particles on model ships, which can resist mechanical abrasion and has displayed a durable drag-reducing effect. In comparison with normal Au superhydrophobic coatings, the as-prepared PDMS/copper coatings showed durable drag reduction performance with a similar drag-reducing rate before (26%) and after (24%) mechanical abrasion. The mechanism for the enhanced mechanical stability and maintained drag reduction of the superhydrophobic surfaces was investigated through characterizations of surface morphology, surface wettability, and water adhesive force evaluation before and after abrasion. This is the first demonstration to realize the application of durable drag reduction by improving the mechanical stability of superhydrophobic coatings. We do believe that superhydrophobic surfaces with good resistance to mechanical abrasion or scratching may draw wide attention and gain significant applications with durable drag-reducing properties. PMID:25644454

  1. Polish Students after the Decline of Communism.

    ERIC Educational Resources Information Center

    Wnuk-Lipinska, Elzbieta

    1990-01-01

    The report describes Polish student and teacher surveys that indicate, over time, a lower level of student interest in studying and low levels of cognitive need and professional ambition. Findings are applied to possibilities for change in Poland's new social, political, and economic situation. Similarities of student attitudes in Poland and in…

  2. Knowledge Mobilisation in the Polish Education System

    ERIC Educational Resources Information Center

    Fazlagic, Jan; Erkol, Arif

    2015-01-01

    Poland has made substantial progress in improving the quality of its education system in recent years. This paper aims to describe the situation of the Polish education system from a knowledge management perspective and, to some extent, through innovation policies in education. The many challenges, this paper argues, can be tackled only through…

  3. Freeform grinding and polishing with PROSurf

    NASA Astrophysics Data System (ADS)

    Wolfs, Franciscus; Fess, Edward; DeFisher, Scott; Torres, Josh; Ross, James

    2015-10-01

    Recently, the desire to use freeform optics has been increasing, including shapes such as torics and anamorphic aspheres. Freeform optics can be used to expand capabilities of optical systems. They can compensate for limitations in rotationally symmetric optics. These same traits that give freeform optics the ability to improve optical systems also makes them more challenging to manufacture. This holds true for grinding, polishing, and metrology. As freeform optics become more prevalent in the industry, tolerances will become more stringent, requiring deterministic manufacturing processes. To generate freeforms, it is crucial to have control over all aspects of the process. Controlling the surface definition is important for achieving a better surface finish during processing. Metrology will be required to adjust tool paths at various stages in manufacturing. During grinding, metrology will be used to adjust tool positions relative to the nominal tool path to compensate for repeatable machine and tooling error. For polishing, metrology will be used to deterministically adjust dwell relative to the amount of the error in different surface locations, allowing for convergence towards the desired surface at a uniform rate. OptiPro has developed PROSurf, a CAM software package for creating freeform tool paths and applying metrology-based corrections. The software can be used for both grinding and polishing freeform optics. The software has flexibility to allow for different methods of modelling the surface: mathematical equations, solid models, and point clouds. The software is designed to make it easier to manufacture and polish complex freeform optics.

  4. Polish Complementary Schools in Iceland and England

    ERIC Educational Resources Information Center

    Zielinska, Malgorzata; Kowzan, Piotr; Ragnarsdóttir, Hanna

    2014-01-01

    Since 2004, the opening of labour markets has spurred a considerable number of Poles to emigrate e.g. to Iceland and England. Families with school age children have had the challenge of adapting to foreign environments and school systems. Polish complementary schools have played an important, albeit ambivalent, role in this process. Through focus…

  5. Sexual Health of Polish Athletes with Disabilities

    PubMed Central

    Plinta, Ryszard; Sobiecka, Joanna; Drosdzol-Cop, Agnieszka; Nowak-Brzezińska, Agnieszka; Kobiołka, Agnieszka; Skrzypulec-Plinta, Violetta

    2015-01-01

    The purpose of this study was to determine sexual functioning of Polish athletes with disabilities (including paralympians). The study encompassed 218 people with physical disabilities, aged between 18 and 45 (149 men and 69 women). The entire research population was divided into three groups: Polish paralympians (n = 45), athletes with disabilities (n = 126) and non-athletes with disabilities (n = 47). The quality of sexual life of Polish paralympians was measured by using the Polish version of Female Sexual Function Index and International Index of Erectile Function. Clinically significant erectile dysfunctions were most often diagnosed in non-athletes (83.33%) with 50% result of severe erectile dysfunctions, followed by athletes and paralympians with comparable results of 56.98% and 54.17% respectively (p = 0.00388). Statistically significant clinical sexual dysfunctions concerned lubrication, orgasm as well as pain domains, and prevailed among female non-athletes (68.42%, 68.42% and 57.89%). Practising sports at the highest level has a favourable effect on the sexuality of men and women with physical disabilities. Men with physical disabilities manifest more sexual disorders than women, an aspect which should be considered by health-care professionals working with people with disabilities. PMID:26133132

  6. Polish Youth: A Dychotomic World of Values.

    ERIC Educational Resources Information Center

    Bodnar, Artur; Zelichowski, Ryszard

    Research results show a skepticism among Polish youth concerning the possibility of implementing the accepted socialist values in political practice and denote a steady erosion of socialism's image. Youth organizations are many and varied, but it appears that most join because of the opportunity to meet friends, not because of political…

  7. Interface enhancement of glass fiber reinforced vinyl ester composites with flame-synthesized carbon nanotubes and its enhancing mechanism.

    PubMed

    Liao, Lingmin; Wang, Xiao; Fang, Pengfei; Liew, Kim Meow; Pan, Chunxu

    2011-02-01

    Interface enhancement with carbon nanotubes (CNTs) provides a promising approach for improving shock strength and toughness of glass fiber reinforced plastic (GFRP) composites. The effects of incorporating flame-synthesized CNTs (F-CNTs) into GFRP were studied, including on hand lay-up preparation, microstructural characterization, mechanical properties, fracture morphologies, and theoretical calculation. The experimental results showed that: (1) the impact strength of the GFRP modified by F-CNTs increased by more than 15% over that of the GFRP modified by CNTs from chemical vapor deposition; and (2) with the F-CNT enhancement, no interfacial debonding was observed at the interface between the fiber and resin matrix on the GFRP fracture surface, which indicated strong adhesive strength between them. The theoretical calculation revealed that the intrinsic characteristics of the F-CNTs, including lower crystallinity with a large number of defects and chemical functional groups on the surface, promoted their surface activity and dispersibility at the interface, which improved the interfacial bond strength of GFRP. PMID:21291279

  8. 21 CFR 872.6030 - Oral cavity abrasive polishing agent.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Oral cavity abrasive polishing agent. 872.6030... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in paste or powder...

  9. 21 CFR 872.6030 - Oral cavity abrasive polishing agent.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Oral cavity abrasive polishing agent. 872.6030... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in paste or powder...

  10. 21 CFR 872.6030 - Oral cavity abrasive polishing agent.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Oral cavity abrasive polishing agent. 872.6030... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in paste or powder...

  11. 21 CFR 872.6030 - Oral cavity abrasive polishing agent.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Oral cavity abrasive polishing agent. 872.6030... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in paste or powder...

  12. 21 CFR 872.6030 - Oral cavity abrasive polishing agent.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Oral cavity abrasive polishing agent. 872.6030... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6030 Oral cavity abrasive polishing agent. (a) Identification. An oral cavity abrasive polishing agent is a device in paste or powder...

  13. Analysis of using EMG and mechanical sensors to enhance intent recognition in powered lower limb prostheses

    NASA Astrophysics Data System (ADS)

    Young, A. J.; Kuiken, T. A.; Hargrove, L. J.

    2014-10-01

    Objective. The purpose of this study was to determine the contribution of electromyography (EMG) data, in combination with a diverse array of mechanical sensors, to locomotion mode intent recognition in transfemoral amputees using powered prostheses. Additionally, we determined the effect of adding time history information using a dynamic Bayesian network (DBN) for both the mechanical and EMG sensors. Approach. EMG signals from the residual limbs of amputees have been proposed to enhance pattern recognition-based intent recognition systems for powered lower limb prostheses, but mechanical sensors on the prosthesis—such as inertial measurement units, position and velocity sensors, and load cells—may be just as useful. EMG and mechanical sensor data were collected from 8 transfemoral amputees using a powered knee/ankle prosthesis over basic locomotion modes such as walking, slopes and stairs. An offline study was conducted to determine the benefit of different sensor sets for predicting intent. Main results. EMG information was not as accurate alone as mechanical sensor information (p < 0.05) for any classification strategy. However, EMG in combination with the mechanical sensor data did significantly reduce intent recognition errors (p < 0.05) both for transitions between locomotion modes and steady-state locomotion. The sensor time history (DBN) classifier significantly reduced error rates compared to a linear discriminant classifier for steady-state steps, without increasing the transitional error, for both EMG and mechanical sensors. Combining EMG and mechanical sensor data with sensor time history reduced the average transitional error from 18.4% to 12.2% and the average steady-state error from 3.8% to 1.0% when classifying level-ground walking, ramps, and stairs in eight transfemoral amputee subjects. Significance. These results suggest that a neural interface in combination with time history methods for locomotion mode classification can enhance intent

  14. Absence of Cx43 selectively from osteocytes enhances responsiveness to mechanical force in mice.

    PubMed

    Bivi, Nicoletta; Pacheco-Costa, Rafael; Brun, Lucas R; Murphy, Thomas R; Farlow, Nathan R; Robling, Alexander G; Bellido, Teresita; Plotkin, Lilian I

    2013-07-01

    The osteocyte network is crucial for the response of bone to mechanical force. Within this network, connexin43 (Cx43) is thought to mediate the communication of osteocytes and osteoblasts among themselves and the exchange of small molecules with the extracellular milieu. Despite recent advances in understanding Cx43 role for the response of bone cells to mechanical stimulation, the contribution of Cx43 specifically in osteocytes to mechanotransduction in vivo is not well-known. We examined the anabolic response to ulnar axial loading of mice lacking Cx43 in osteocytes (Cx43(ΔOt)). Loading induced a greater increase in periosteal bone formation rate in Cx43(ΔOt) mice compared to control littermates, resulting from higher mineralizing surface and enhanced mineral apposition rate. Expression of β-catenin protein, a molecule implicated in mechanotransduction, was higher in bones from Cx43(ΔOt) mice, compared to littermate controls. In addition, MLO-Y4 osteocytic cells knocked-down for Cx43 exhibited higher β-catenin protein expression and enhanced response to mechanical stimulation. These findings suggest that osteocytes lacking Cx43 are "primed" to respond to mechanical stimulation and that absence of Cx43 in osteocytes unleashes bone formation, by a mechanism that might involve accumulation of β-catenin. PMID:23483620

  15. A self-enhanced transport mechanism through long noncoding RNAs for X chromosome inactivation

    PubMed Central

    Li, Chunhe; Hong, Tian; Webb, Chiu-Ho; Karner, Heather; Sun, Sha; Nie, Qing

    2016-01-01

    X-chromosome inactivation (XCI) is the mammalian dosage compensation strategy for balancing sex chromosome content between females and males. While works exist on initiation of symmetric breaking, the underlying allelic choice mechanisms and dynamic regulation responsible for the asymmetric fate determination of XCI remain elusive. Here we combine mathematical modeling and experimental data to examine the mechanism of XCI fate decision by analyzing the signaling regulatory circuit associated with long noncoding RNAs (lncRNAs) involved in XCI. We describe three plausible gene network models that incorporate features of lncRNAs in their localized actions and rapid transcriptional turnovers. In particular, we show experimentally that Jpx (a lncRNA) is transcribed biallelically, escapes XCI, and is asymmetrically dispersed between two X’s. Subjecting Jpx to our test of model predictions against previous experimental observations, we identify that a self-enhanced transport feedback mechanism is critical to XCI fate decision. In addition, the analysis indicates that an ultrasensitive response of Jpx signal on CTCF is important in this mechanism. Overall, our combined modeling and experimental data suggest that the self-enhanced transport regulation based on allele-specific nature of lncRNAs and their temporal dynamics provides a robust and novel mechanism for bi-directional fate decisions in critical developmental processes. PMID:27527711

  16. Graphene oxide papers modified by divalent ions-enhancing mechanical properties via chemical cross-linking.

    PubMed

    Park, Sungjin; Lee, Kyoung-Seok; Bozoklu, Gulay; Cai, Weiwei; Nguyen, Sonbinh T; Ruoff, Rodney S

    2008-03-01

    Significant enhancement in mechanical stiffness (10-200%) and fracture strength (approximately 50%) of graphene oxide paper, a novel paperlike material made from individual graphene oxide sheets, can be achieved upon modification with a small amount (less than 1 wt %) of Mg(2+) and Ca(2+). These results can be readily rationalized in terms of the chemical interactions between the functional groups of the graphene oxide sheets and the divalent metals ions. While oxygen functional groups on the basal planes of the sheets and the carboxylate groups on the edges can both bond to Mg(2+) and Ca(2+), the main contribution to mechanical enhancement of the paper comes from the latter. PMID:19206584

  17. Precision machining and polishing of scintillating crystals for large calorimeters and hodoscopes

    NASA Astrophysics Data System (ADS)

    Wuest, C. R.; Fuchs, B. A.; Holdener, F. R.; Heck, J. L., Jr.

    1994-04-01

    New machining and polishing techniques have been developed for large scintillating crystal arrays such as the Barium Fluoride Electromagnetic Calorimeter for the GEM Detector at SSCL, the Crystal Clear Collaboration's cerium fluoride or lead tungstenate calorimeter at the proposed LHC and CERN, the PHENIX Detector at RHIC (barium fluoride), and the cesium iodide Calorimeter for the BaBar Detector at PEP-2 B Factory at SLAC. The machining and polishing methods to be presented in this paper provide crystalline surfaces without sub-surface damage or deformation as verified by Rutherford Back-scattering (RBS) analysis. Surface roughness of about 10-20 A and sub-micron mechanical tolerances have been demonstrated on large barium fluoride crystal samples. Mass production techniques have also been developed for machining the proper angled surfaces and polishing up to five 50 cm long crystals at one time. These techniques utilize kinematic mount technology developed at LLNL to allow precision machining and polishing of complex surfaces. They will present this technology along with detailed surface studies of barium fluoride and cerium fluoride crystals polished with this technique.

  18. Path planning and parameter optimization of uniform removal in active feed polishing

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Wang, Shaozhi; Zhang, Chunlei; Zhang, Linghua; Chen, Huanan

    2015-06-01

    A high-quality ultrasmooth surface is demanded in short-wave optical systems. However, the existing polishing methods have difficulties meeting the requirement on spherical or aspheric surfaces. As a new kind of small tool polishing method, active feed polishing (AFP) could attain a surface roughness of less than 0.3 nm (RMS) on spherical elements, although AFP may magnify the residual figure error or mid-frequency error. The purpose of this work is to propose an effective algorithm to realize uniform removal of the surface in the processing. At first, the principle of the AFP and the mechanism of the polishing machine are introduced. In order to maintain the processed figure error, a variable pitch spiral path planning algorithm and the dwell time-solving model are proposed. For suppressing the possible mid-frequency error, the uniformity of the synthesis tool path, which is generated by an arbitrary point at the polishing tool bottom, is analyzed and evaluated, and the angular velocity ratio of the tool spinning motion to the revolution motion is optimized. Finally, an experiment is conducted on a convex spherical surface and an ultrasmooth surface is finally acquired. In conclusion, a high-quality ultrasmooth surface can be successfully obtained with little degradation of the figure and mid-frequency errors by the algorithm.

  19. Precision machining and polishing of scintillating crystals for large calorimeters and hodoscopes. Revision 1

    SciTech Connect

    Wuest, C.R.; Fuchs, B.A.; Holdener, F.R.; Heck, J.L. Jr.

    1994-04-01

    New machining and polishing techniques have been developed for large scintillating crystal arrays such as the Barium Fluoride Electromagnetic Calorimeter for the GEM Detector at SSCL, the Crystal Clear Collaboration`s cerium fluoride or lead tungstenate calorimeter at the proposed LHC and CERN, the PHENIX Detector at RHIC (barium fluoride), and the cesium iodide Calorimeter for the BaBar Detector at PEP-2 B Factory at SLAC. The machining and polishing methods to be presented in this paper provide crystalline surfaces without sub-surface damage or deformation as verified by Rutherford Back-scattering (RBS) analysis. Surface roughness of about 10--20 angstroms and sub-micron mechanical tolerances have been demonstrated on large barium fluoride crystal samples. Mass production techniques have also been developed for machining the proper angled surfaces and polishing up to five 50 cm long crystals at one time. These techniques utilize kinematic mount technology developed at LLNL to allow precision machining and polishing of complex surfaces. They will present this technology along with detailed surface studies of barium fluoride and cerium fluoride crystals polished with this technique.

  20. Strongly enhanced tunable photoluminescence in polymorphous silicon carbon thin films via excitation-transfer mechanism

    SciTech Connect

    Wang Junzhuan; Suendo, V.; Abramov, A.; Yu Linwei; Roca i Cabarrocas, Pere

    2010-11-29

    Here, we investigate the enhanced tunable photoluminescence (PL) of hydrogenated polymorphous silicon carbon (pm-Si{sub 1-x}C{sub x}:H) thin films fabricated in a plasma enhanced chemical vapor deposition system. The silicon nanocrystal (nc-Si) inclusions are formed during gas-phase nucleation and incorporated in the hydrogenated amorphous silicon carbon (a-SiC:H) matrix. The nc-Si provides high-quality recombination centers for the photogenerated carriers in the pm-Si{sub 1-x}C{sub x}:H material, while the a-SiC:H matrix plays a role of sensitizer. We elucidate and provide experimental evidence for this excitation-transfer mechanism. Strongly enhanced PL performance can be achieved by effective matrix passivation that favors a diffusion-driven carrier recombination in the nc-Si centers.

  1. Molecular mechanisms of enhanced wound healing by copper oxide-impregnated dressings.

    PubMed

    Borkow, Gadi; Gabbay, Jeffrey; Dardik, Rima; Eidelman, Arthur I; Lavie, Yossi; Grunfeld, Yona; Ikher, Sergey; Huszar, Monica; Zatcoff, Richard C; Marikovsky, Moshe

    2010-01-01

    ABSTRACT Copper plays a key role in angiogenesis and in the synthesis and stabilization of extracellular matrix skin proteins, which are critical processes of skin formation. We hypothesized that introducing copper into wound dressings would enhance wound repair. Application of wound dressings containing copper oxide to wounds inflicted in genetically engineered diabetic mice (C57BL/KsOlaHsd-Lepr(db)) resulted in increased gene and in situ up-regulation of proangiogenic factors (e.g., placental growth factor, hypoxia-inducible factor-1 alpha, and vascular endothelial growth factor), increased blood vessel formation (p<0.05), and enhanced wound closure (p<0.01) as compared with control dressings (without copper) or commercial wound dressings containing silver. This study proves the capacity of copper oxide-containing wound dressings to enhance wound healing and sheds light onto the molecular mechanisms by which copper oxide-impregnated dressings stimulate wound healing. PMID:20409151

  2. Lymphoid Cell-Glioma Cell Interaction Enhances Cell Coat Production by Human Gliomas: Novel Suppressor Mechanism

    NASA Astrophysics Data System (ADS)

    Dick, Steven J.; Macchi, Beatrice; Papazoglou, Savvas; Oldfield, Edward H.; Kornblith, Paul L.; Smith, Barry H.; Gately, Maurice K.

    1983-05-01

    Certain human glioma lines produce mucopolysaccharide coats that impair the generation of cytolytic lymphocytes in response to these lines in vitro. Coat production is substantially enhanced by the interaction of glioma cells with a macromolecular factor released by human peripheral blood mononuclear cells in culture. This interaction thus constitutes an unusual mechanism by which inflammatory cells may nonspecifically suppress the cellular immune response to at least one class of solid tumors in humans.

  3. Air-side flow and heat transfer in compact heat exchangers: A discussion of enhancement mechanisms

    SciTech Connect

    Jacobi, A.M.; Shah, R.K.

    1998-10-01

    The behavior of air flows in complex heat exchanger passages is reviewed with a focus on the heat transfer effects of boundary-layer development, turbulence, spanwise and streamwise vortices, and wake management. Each of these flow features is discussed for the plain, wavy, and interrupted passages found in contemporary compact heat exchanger designs. Results from the literature are used to help explain the role of these mechanisms in heat transfer enhancement strategies.

  4. Wastewater polishing by a channelized macrophyte-dominated wetland and anaerobic digestion of the harvested phytomass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    : Constructed wetlands (CW) offer a mechanism to meet regulatory standards for wastewater treatment while minimizing energy inputs. To optimize CW wastewater polishing activities and investigate integration of CW with energy production from anaerobic digestion we constructed a pair of three-tier ch...

  5. Freeform correction polishing for optics with semi-kinematic mounting

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Yao; Kuo, Ching-Hsiang; Peng, Wei-Jei; Yu, Zong-Ru; Ho, Cheng-Fang; Hsu, Ming-Ying; Hsu, Wei-Yao

    2015-10-01

    Several mounting configurations could be applied to opto-mechanical design for achieving high precise optical system. The retaining ring mounting is simple and cost effective. However, it would deform the optics due to its unpredictable over-constraint forces. The retaining ring can be modified to three small contact areas becoming a semi-kinematic mounting. The semi-kinematic mounting can give a fully constrained in lens assembly and avoid the unpredictable surface deformation. However, there would be still a deformation due to self-weight in large optics especially in vertical setup applications. The self-weight deformation with a semi-kinematic mounting is a stable, repeatable and predictable combination of power and trefoil aberrations. This predictable deformation can be pre-compensated onto the design surface and be corrected by using CNC polisher. Thus it is a freeform surface before mounting to the lens cell. In this study, the freeform correction polishing is demonstrated in a Φ150 lens with semi-kinematic mounting. The clear aperture of the lens is Φ143 mm. We utilize ANSYS simulation software to analyze the lens deformation due to selfweight deformation with semi-kinematic mounting. The simulation results of the self-weight deformation are compared with the measurement results of the assembled lens cell using QED aspheric stitching interferometer (ASI). Then, a freeform surface of a lens with semi-kinematic mounting due to self-weight deformation is verified. This deformation would be corrected by using QED Magnetorheological Finishing (MRF® ) Q-flex 300 polishing machine. The final surface form error of the assembled lens cell after MRF figuring is 0.042 λ in peak to valley (PV).

  6. Experimental investigation and mechanism of critical heat flux enhancement in pool boiling heat transfer with nanofluids

    NASA Astrophysics Data System (ADS)

    Kamatchi, R.; Venkatachalapathy, S.; Nithya, C.

    2015-12-01

    In the present study, reduced graphene oxide (rGO) is synthesized from graphite using modified Hummer and chemical reduction methods. Various characterizations techniques are carried out to study the in-plane crystallite size, number of layers, presence of functional groups and surface morphology. Different concentrations of 0.01, 0.1, and 0.3 g/l of rGO/water nanofluids are prepared by dispersing the flakes in DI water. The colloidal stability of 0.3 g/l concentration is measured after 5 days using Zetasizer and found to be stable. The rGO/water nanofluids are then used to study the effect on the enhancement of critical heat flux (CHF) in pool boiling heat transfer. Results indicate an enhancement in CHF ranging from 145 to 245 % for the tested concentrations. The mechanisms of CHF enhancement are analyzed based on surface wettability, surface roughness, and porous layer thickness. The macrolayer dryout model sufficiently supports the mechanism of CHF enhancement of thin wire with rGO deposits, which is not reported yet.

  7. Evaluation of the mechanism of skin enhancing surfactants on the biomembrane of shed snake skin.

    PubMed

    Wonglertnirant, Nanthida; Ngawhirunpat, Tanasait; Kumpugdee-Vollrath, Mont

    2012-01-01

    The aim of the present work was to investigate the effects of different surfactants at various concentrations as a skin penetration enhancer through the biomembrane of the shed skin of Naja kaouthia. Additionally, the enhancer mechanism(s) of each class of surfactants were evaluated using physical characterization techniques, such as scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and small and wide angle X-ray scattering (SWAXS). Our results showed that skin permeability increased with increasing concentrations of surfactants and the degree of increase was higher for the model hydrophilic permeant, deuterium dioxide (D(2)O), than the lipophilic permeant, ketoprofen (KP). Ionic surfactants, sodium lauryl sulfate (SLS) and cetyl trimethyl ammonium bromide (CTAB), demonstrated higher enhancement ability than the polyoxyethylene (20) sorbitan mono-oleate (Tween 80) non-ionic surfactant, which was consistent with the results from physical characterization studies. Increasing amounts of permeated drug resulted in an increase in membrane interactions. From our observations, it can be assumed that SLS and CTAB can be localized inside the biomembrane and thereby enhance drug permeation mainly through interactions with intercellular lipids in the stratum corneum (SC) and the creation of a perturbed microenvironment among lipid alkyl chains and polar head groups. PMID:22466556

  8. Design Considerations of Polishing Lap for Computer-Controlled Cylindrical Polishing Process

    NASA Technical Reports Server (NTRS)

    Khan, Gufran S.; Gubarev, Mikhail; Speegle, Chet; Ramsey, Brian

    2010-01-01

    The future X-ray observatory missions, such as International X-ray Observatory, require grazing incidence replicated optics of extremely large collecting area (3 m2) in combination with angular resolution of less than 5 arcsec half-power diameter. The resolution of a mirror shell depends ultimately on the quality of the cylindrical mandrels from which they are being replicated. Mid-spatial-frequency axial figure error is a dominant contributor in the error budget of the mandrel. This paper presents our efforts to develop a deterministic cylindrical polishing process in order to keep the mid-spatial-frequency axial figure errors to a minimum. Simulation studies have been performed to optimize the operational parameters as well as the polishing lap configuration. Furthermore, depending upon the surface error profile, a model for localized polishing based on dwell time approach is developed. Using the inputs from the mathematical model, a mandrel, having conical approximated Wolter-1 geometry, has been polished on a newly developed computer-controlled cylindrical polishing machine. We report our first experimental results and discuss plans for further improvements in the polishing process.

  9. High Speed Surface Micro-Polishing for Spurious Reduction of Small Quartz Crystal Blanks

    NASA Astrophysics Data System (ADS)

    Hatsuzawa, Takeshi; Hamano, Hisashi; Saito, Masashi; Yanagida, Yasuko

    Surface polishing is required for small crystal blanks to eliminate frequency spurious generated by the infinite rectangular shape. From the productivity viewpoint, bi-convex or plano-cylindrical surface are generally used to realize the energy trapping at the central part of the blanks. So far barrel polishing is the common fabrication technology to obtain bi-convex surface, however, the surface is finished insufficiently and fabrication process takes longer time as the blank size becomes small. To solve this difficulty, two types of new surface micro-polishing mechanisms with fixed abrasive and arrayed blank arrangement are experimentally examined to obtain plano-cylindrical surface. The fastest finishing time of 10 s for a blank is achieved together with the spurious elimination.

  10. Investigation of the mechanism of enhanced skin penetration by ultradeformable liposomes

    PubMed Central

    Subongkot, Thirapit; Pamornpathomkul, Boonnada; Rojanarata, Theerasak; Opanasopit, Praneet; Ngawhirunpat, Tanasait

    2014-01-01

    This study aimed to determine the mechanism by which ultradeformable liposomes (ULs) with terpenes enhance skin penetration for transdermal drug delivery of fluorescein sodium, using transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). Skin treated with ULs containing d-limonene, obtained from in vitro skin penetration studies, was examined via TEM to investigate the effect of ULs on ultrastructural changes of the skin, and to evaluate the mechanism by which ULs enhance skin penetration. The receiver medium collected was analyzed by TEM and CLSM to evaluate the mechanism of the drug carrier system. Our findings revealed that ULs could enhance penetration by denaturing intracellular keratin, degrading corneodesmosomes, and disrupting the intercellular lipid arrangement in the stratum corneum. As inferred from the presence of intact vesicles in the receiver medium, ULs are also able to act as a drug carrier system. CLSM images showed that intact vesicles of ULs might penetrate the skin via a transappendageal pathway, potentially a major route of skin penetration. PMID:25114524

  11. Enhancement of tunability of MAPK cascade due to coexistence of processive and distributive phosphorylation mechanisms.

    PubMed

    Sun, Jianqiang; Yi, Ming; Yang, Lijian; Wei, Wenbin; Ding, Yiming; Jia, Ya

    2014-03-01

    The processive phosphorylation mechanism becomes important when there is macromolecular crowding in the cytoplasm. Integrating the processive phosphorylation mechanism with the traditional distributive one, we propose a mixed dual-site phosphorylation (MDP) mechanism in a single-layer phosphorylation cycle. Further, we build a degree model by applying the MDP mechanism to a three-layer mitogen-activated protein kinase (MAPK) cascade. By bifurcation analysis, our study suggests that the crowded-environment-induced pseudoprocessive mechanism can qualitatively change the response of this biological network. By adjusting the degree of processivity in our model, we find that the MAPK cascade is able to switch between the ultrasensitivity, bistability, and oscillatory dynamical states. Sensitivity analysis shows that the theoretical results remain unchanged within a reasonably chosen variation of parameter perturbation. By scaling the reaction rates and also introducing new connections into the kinetic scheme, we further construct a proportion model of the MAPK cascade to validate our findings. Finally, it is illustrated that the spatial propagation of the activated MAPK signal can be improved (or attenuated) by increasing the degree of processivity of kinase (or phosphatase). Our research implies that the MDP mechanism makes the MAPK cascade become a flexible signal module, and the coexistence of processive and distributive phosphorylation mechanisms enhances the tunability of the MAPK cascade. PMID:24606945

  12. Mechanisms underlying the prereversal enhancement of the vertical plasma drift in the low-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Eccles, J. V.; St. Maurice, J. P.; Schunk, R. W.

    2015-06-01

    The evening prereversal enhancement (PRE) of the vertical plasma drift has important consequences for the Appleton density anomaly and the stability of the nighttime ionosphere. Simplified simulations were used to review the three competing theories of the PRE origin, to explore their relative importance, and to indentify their interdependence. The mechanisms involved in the generation and climatology of the PRE are, first, a curl-free electric field response to rapid changes in the vertical electric field associated with the nighttime F region dynamo; second, a divergence of Hall currents in the E region away from the magnetic equator; and, third, the moderating effect of the large Cowling conductivities in the equatorial E region. The simulations indicate that the equatorial Cowling conductivity creates an important current path that limits the other two mechanisms prior to equatorial sunset and releases them after equatorial sunset. The curl-free mechanism is the dominant mechanism when the terminator and magnetic meridian are aligned in part due to the accelerating F region zonal wind. When the solar terminator is not aligned with the magnetic meridian, there is an interaction involving all three mechanisms contributing to the magnitude and timing of the PRE. Finally, the altitude profile of the PRE decays more quickly with altitude when the curl-free mechanism dominates as compared to when the Hall current mechanism dominates.

  13. The effect of one-step polishing system on the surface roughness of three esthetic resin composite materials.

    PubMed

    Türkün, L S; Türkün, M

    2004-01-01

    Proper finishing of restorations is desirable not only for aesthetic considerations but also for oral health. The primary goal of finishing is to obtain a restoration that has good contour, occlusion, healthy embrasure forms and a smooth surface. This study investigated: 1) analyzing the surface roughness of three resin composites finished and polished with a new one-step and two conventional multi-step polishing systems and 2) evaluating the effectiveness of one-step polishing system and surface morphology using scanning electron microscope analysis (SEM). Specimens (N = 72) measuring 8-mm in diameter x 2-mm in thickness were fabricated in a plexiglass mold covered with a Mylar strip using three esthetic resin composites. After polymerization six specimens per resin composite received no finishing treatment and served as a control. Fifty-four specimens were randomly polished with Sof-Lex discs, Enhance disc with polishing paste or PoGo for 30 seconds after being ground wet with a 1200 grit silicon carbide paper. The average surface roughness of each polished specimen was determined with a profilometer (Surtronic 4). The data were analyzed using repeated measures ANOVA and Scheffe's post-hoc test of multiple comparisons (p < or = 0.01). Representative samples of the mentioned finishing procedures were selected and examined using a scanning electron microscope (SEM). There was no surface roughness in all resin composites tested against Mylar strip. The results showed no difference between the surfaces of Clearfil ST and Esthet-X polished with PoGo and the Mylar group (p > or = 0.01). Among all the polishing systems tested, PoGo exhibited the smoothest finish for all resin composites. The combination of Enhance and Prisma Gloss polishing paste exhibited the highest roughness values for Filtek A110 and Clearfil ST; however, it gave the same Ra values as PoGo for Esthet-X (p < or = 0.01). SEM analysis of Esthet-X samples confirmed the profilometer's results. The

  14. Between Polish Positivism and American Capitalism: The Educational Agents' Experiment in the Polish-American Community, 1889-1914

    ERIC Educational Resources Information Center

    Jaroszynska-Kirchmann, Anna D.

    2008-01-01

    "Ameryka-Echo" was one of the most popular Polish-language weeklies, published in the United States between 1889 and 1972. Its founder and owner, Antoni A. Paryski, consciously sought to transplant ideas of Polish Positivism to the Polish-American immigrant communities in the United States. Reading was a central concept of self-education, promoted…

  15. Chemical mechanism of surface-enhanced Raman scattering via charge transfer in fluorenone-Ag complex.

    PubMed

    Wang, Jing; Li, Yafei; Wu, Shiwei; Song, Peng; Xia, Lixin

    2016-06-01

    The intermolecular interaction between fluorenone (FN) and silver surfaces was investigated experimentally and theoretically. The structural, electronic and optical properties of the FN-Ag complex indicate that the carbonyl group O atom in FN molecules is the adsorbed position site to attach the silver substrate through the weak bond O…Ag. The analysis of vibrational modes and Raman activity of the largely enhanced Raman peaks using two FN-Ag4-x (x  =  l, s) complex models reveals that only the a1 vibrational modes with C 2v symmetry are selectively enhanced, from the point view of the change of dipole moment and polarizability induced by the interaction between FN and Ag4 substrate. Furthermore, the direct visualized evidence of the surface-enhanced Raman scattering (SERS) chemical enhancement mechanism for the FN-Ag complex is presented. The results reveal that only the intermolecular charge transfer with π-π transition characterization between FN and an Ag4 cluster facilitates the resonance Raman process and is directly responsible for chemical enhancement of Raman scattering of the FN-Ag complex. PMID:27147706

  16. Chemical mechanism of surface-enhanced Raman scattering via charge transfer in fluorenone–Ag complex

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Li, Yafei; Wu, Shiwei; Song, Peng; Xia, Lixin

    2016-06-01

    The intermolecular interaction between fluorenone (FN) and silver surfaces was investigated experimentally and theoretically. The structural, electronic and optical properties of the FN–Ag complex indicate that the carbonyl group O atom in FN molecules is the adsorbed position site to attach the silver substrate through the weak bond O…Ag. The analysis of vibrational modes and Raman activity of the largely enhanced Raman peaks using two FN–Ag4-x (x  =  l, s) complex models reveals that only the a1 vibrational modes with C 2v symmetry are selectively enhanced, from the point view of the change of dipole moment and polarizability induced by the interaction between FN and Ag4 substrate. Furthermore, the direct visualized evidence of the surface-enhanced Raman scattering (SERS) chemical enhancement mechanism for the FN–Ag complex is presented. The results reveal that only the intermolecular charge transfer with π–π transition characterization between FN and an Ag4 cluster facilitates the resonance Raman process and is directly responsible for chemical enhancement of Raman scattering of the FN–Ag complex.

  17. Precision machining and polishing of scintillating crystals for large calorimeters and hodoscopes

    SciTech Connect

    Wuest, C.R.; Fuchs, B.A.

    1993-05-01

    New machining and polishing techniques have been developed for large barium fluoride scintillating crystals that provide crystalline surfaces without sub-surface damage or deformation as verified by Atomic Force Microscopy (AFM) and Rutherford Back-scattering (RBS) analyses. Surface roughness of about 10--20 angstroms and sub-micron mechanical tolerances have been demonstrated on large crystal samples. Mass production techniques have also been developed for machining and polishing up to five 50 cm long crystals at one time. We present this technology along with surface studies of barium fluoride crystals polished with this technique. This technology is applicable for a number of new crystal detectors proposed at Colliders including the Barium Fluoride Electromagnetic Calorimeter at SSC, the Crystal Clear Collaboration`s cerium fluoride calorimeter at LHC, and the KTeV and PHENIX scintillating hodoscopes at Fermilab, and RHIC, respectively. Lawrence Livermore National Laboratory (LLNL) has an active program of study on barium fluoride scintillating crystals for the Barium Fluoride Electromagnetic Calorimeter Collaboration and cerium fluoride and lead fluoride for the Crystal Clear Collaboration. This program has resulted in a number of significant improvements in the mechanical processing, polishing and coating of fluoride crystals. Techniques have been developed using diamond-loaded pitch lapping that can produce 15 angstrom RMS surface finishes over large areas. Also, special polishing fixtures have been designed based on mounting technology developed for the 1.1 m diameter optics used in LLNL`s Nova Laser. These fixtures allow as many as five 25--50 cm long crystals to be polished and lapped at the same time with tolerances satisfying the stringent requirements of crystal calorimeters. We also discuss results on coating barium fluoride with UV reflective layers of magnesium fluoride and aluminum.

  18. Polishing Material Removal Correlation on PMMA - FEM Simulation

    NASA Astrophysics Data System (ADS)

    Almeida, R.; Börret, R.; Rimkus, W.; Harrison, D. K.; DeSilva, A. K. M.

    2016-02-01

    The complexity of polishing is very high and experience in this field is required to achieve reproducible deterministic results concerning shape accuracy. The goal of this work is to predict the material removal of the polishing process on PMMA (Polymethylmethacrylate) using an industrial robot polisher. In order to predict the material removal, a FEM Model was created representing the polishing process. This model will help to predict the material removal when polishing parameters are changed. Experiments were carried out and compared to the results obtained from the different parameters tested in the simulation.

  19. Enhanced nano-mechanical and wear properties of polycarbosilane derived SiC coating on silicon

    NASA Astrophysics Data System (ADS)

    Mukherjee, Jonaki; Ghosh, Sujan; Ghosh, Arnab; Ranjan, Ashok; Saxena, Arvind K.; Das, Probal K.; Banerjee, Rajat

    2015-01-01

    Liquid Polycarbosilane derived β-SiC and α-SiC coating was deposited at three differently moderate high temperatures by CVD method on Silicon wafers. The nano-mechanical properties such as hardness, reduced Young's modulus, elastic recovery and plasticity index of the coatings were evaluated and compared at different deposition temperature. It was observed that with the increase in deposition temperature the nano-mechanical property of the coating enhances, the reason being the increase in crystallinity along with good adherence at higher temperature. Moreover the tribological properties of the coated samples show similar trends with increase in deposition temperature although it were found to be much better for the β-SiC than that of the α-SiC coated samples. All the coated samples shows brittle mode of failure during tribological testing. It was found that the 900 °C deposited film has better nano-mechanical as well as good tribological properties compared to other temperature of deposition due to better crystallinity and adherence. Thus the enhanced mechanical and tribological properties of this coating can be used as protective films on silicon for application in micrometers and other micro devices.

  20. Enhanced transparency, mechanical durability, and antibacterial activity of zinc nanoparticles on glass substrate

    PubMed Central

    Choi, Hyung-Jin; Choi, Jin-Seok; Park, Byeong-Ju; Eom, Ji-Ho; Heo, So-Young; Jung, Min-Wook; An, Ki-Seok; Yoon, Soon-Gil

    2014-01-01

    Homogeneously distributed zinc nanoparticles (NPs) on the glass substrate were investigated for the transmittance, mechanical durability, and antibacterial effect. The buffered Ti NPs between Zn NPs and glass substrate were studied for an enhancement of the transmittance and mechanical endurance. The Ti NPs buffered Zn NPs showed a high transmittance of approximately 91.5% (at a wavelength of 550 nm) and a strong antibacterial activity for Staphylococcus aureus and Escherichia coli bacteria. The buffered Ti NPs are attractive for an excellent mechanical endurance of the Zn NPs. The Zn NPs did not require the protection layer to prevent the degradation of the performance for both the antibacterial effect and the transmittance. PMID:25183360

  1. Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Tan, Dunlin; Zhang, Bowei; Tok, Alfred Iing Yoong; Teo, Edwin Hang Tong

    Vertically aligned carbon nanotube (CNT) array is one of the most promising energy dissipating materials due to its excellent temperature invariant mechanical property. However, the CNT arrays with desirable recoverability after compression is still a challenge. Here, we report on the mechanical enhancement of the CNT arrays reinforced by coating with boron nitride (BN) layers. These BN coated CNT (BN/CNT) arrays exhibit excellent compressive strength and recoverability as compared to those of the as-prepared CNT arrays which totally collapsed after compression. In addition, the BN coating also provides better resistance to oxidation due to its intrinsic thermal stability. This work presented here opens a new pathway towards tuning mechanical behavior of any arbitrary CNT arrays for promising potential such as damper, vibration isolator and shock absorber applications.

  2. Peptide-Graphene Interactions Enhance the Mechanical Properties of Silk Fibroin.

    PubMed

    Cheng, Yuan; Koh, Leng-Duei; Li, Dechang; Ji, Baohua; Zhang, Yingyan; Yeo, Jingjie; Guan, Guijian; Han, Ming-Yong; Zhang, Yong-Wei

    2015-10-01

    Studies reveal that biomolecules can form intriguing molecular structures with fascinating functionalities upon interaction with graphene. Then, interesting questions arise. How does silk fibroin interact with graphene? Does such interaction lead to an enhancement in its mechanical properties? In this study, using large-scale molecular dynamics simulations, we first examine the interaction of graphene with several typical peptide structures of silk fibroin extracted from different domains of silk fibroin, including pure amorphous (P1), pure crystalline (P2), a segment from N-terminal (P3), and a combined amorphous and crystalline segment (P4), aiming to reveal their structural modifications. Our study shows that graphene can have intriguing influences on the structures formed by the peptides with sequences representing different domains of silk fibroin. In general, for protein domains with stable structure and strong intramolecular interaction (e.g., β-sheets), graphene tends to compete with the intramolecular interactions and thus weaken the interchain interaction and reduce the contents of β-sheets. For the silk domains with random or less ordered secondary structures and weak intramolecular interactions, graphene tends to enhance the stability of peptide structures; in particular, it increases the contents of helical structures. Thereafter, tensile simulations were further performed on the representative peptides to investigate how such structure modifications affect their mechanical properties. It was found that the strength and resilience of the peptides are enhanced through their interaction with graphene. The present work reveals interesting insights into the interactions between silk peptides and graphene, and contributes in the efforts to enhance the mechanical properties of silk fibroin. PMID:26364925

  3. Enhanced mathematical modeling of the displacement amplification ratio for piezoelectric compliant mechanisms

    NASA Astrophysics Data System (ADS)

    Ling, Mingxiang; Cao, Junyi; Zeng, Minghua; Lin, Jing; Inman, Daniel J.

    2016-07-01

    Piezo-actuated, flexure hinge-based compliant mechanisms have been frequently used in precision engineering in the last few decades. There have been a considerable number of publications on modeling the displacement amplification behavior of rhombus-type and bridge-type compliant mechanisms. However, due to an unclear geometric approximation and mechanical assumption between these two flexures, it is very difficult to obtain an exact description of the kinematic performance using previous analytical models, especially when the designed angle of the compliant mechanisms is small. Therefore, enhanced theoretical models of the displacement amplification ratio for rhombus-type and bridge-type compliant mechanisms are proposed to improve the prediction accuracy based on the distinct force analysis between these two flexures. The energy conservation law and the elastic beam theory are employed for modeling with consideration of the translational and rotational stiffness. Theoretical and finite elemental results show that the prediction errors of the displacement amplification ratio will be enlarged if the bridge-type flexure is simplified as a rhombic structure to perform mechanical modeling. More importantly, the proposed models exhibit better performance than the previous models, which is further verified by experiments.

  4. Voriconazole Enhances the Osteogenic Activity of Human Osteoblasts In Vitro through a Fluoride-Independent Mechanism

    PubMed Central

    Allen, Kahtonna C.; Sanchez, Carlos J.; Niece, Krista L.; Wenke, Joseph C.

    2015-01-01

    Periostitis, which is characterized by bony pain and diffuse periosteal ossification, has been increasingly reported with prolonged clinical use of voriconazole. While resolution of clinical symptoms following discontinuation of therapy suggests a causative role for voriconazole, the biological mechanisms contributing to voriconazole-induced periostitis are unknown. To elucidate potential mechanisms, we exposed human osteoblasts in vitro to voriconazole or fluconazole at 15 or 200 μg/ml (reflecting systemic or local administration, respectively), under nonosteogenic or osteogenic conditions, for 1, 3, or 7 days and evaluated the effects on cell proliferation (reflected by total cellular DNA) and osteogenic differentiation (reflected by alkaline phosphatase activity, calcium accumulation, and expression of genes involved in osteogenic differentiation). Release of free fluoride, vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) was also measured in cell supernatants of osteoblasts exposed to triazoles, with an ion-selective electrode (for free fluoride) and enzyme-linked immunosorbent assays (ELISAs) (for VEGF and PDGF). Voriconazole but not fluconazole significantly enhanced the proliferation and differentiation of osteoblasts. In contrast to clinical observations, no increases in free fluoride levels were detected following exposure to either voriconazole or fluconazole; however, significant increases in the expression of VEGF and PDGF by osteoblasts were observed following exposure to voriconazole. Our results demonstrate that voriconazole can induce osteoblast proliferation and enhance osteogenic activity in vitro. Importantly, and in contrast to the previously proposed mechanism of fluoride-stimulated osteogenesis, our findings suggest that voriconazole-induced periostitis may also occur through fluoride-independent mechanisms that enhance the expression of cytokines that can augment osteoblastic activity. PMID:26324277

  5. Voriconazole Enhances the Osteogenic Activity of Human Osteoblasts In Vitro through a Fluoride-Independent Mechanism.

    PubMed

    Allen, Kahtonna C; Sanchez, Carlos J; Niece, Krista L; Wenke, Joseph C; Akers, Kevin S

    2015-12-01

    Periostitis, which is characterized by bony pain and diffuse periosteal ossification, has been increasingly reported with prolonged clinical use of voriconazole. While resolution of clinical symptoms following discontinuation of therapy suggests a causative role for voriconazole, the biological mechanisms contributing to voriconazole-induced periostitis are unknown. To elucidate potential mechanisms, we exposed human osteoblasts in vitro to voriconazole or fluconazole at 15 or 200 μg/ml (reflecting systemic or local administration, respectively), under nonosteogenic or osteogenic conditions, for 1, 3, or 7 days and evaluated the effects on cell proliferation (reflected by total cellular DNA) and osteogenic differentiation (reflected by alkaline phosphatase activity, calcium accumulation, and expression of genes involved in osteogenic differentiation). Release of free fluoride, vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) was also measured in cell supernatants of osteoblasts exposed to triazoles, with an ion-selective electrode (for free fluoride) and enzyme-linked immunosorbent assays (ELISAs) (for VEGF and PDGF). Voriconazole but not fluconazole significantly enhanced the proliferation and differentiation of osteoblasts. In contrast to clinical observations, no increases in free fluoride levels were detected following exposure to either voriconazole or fluconazole; however, significant increases in the expression of VEGF and PDGF by osteoblasts were observed following exposure to voriconazole. Our results demonstrate that voriconazole can induce osteoblast proliferation and enhance osteogenic activity in vitro. Importantly, and in contrast to the previously proposed mechanism of fluoride-stimulated osteogenesis, our findings suggest that voriconazole-induced periostitis may also occur through fluoride-independent mechanisms that enhance the expression of cytokines that can augment osteoblastic activity. PMID:26324277

  6. Water filling and electric field-induced enhancement in the mechanical property of carbon nanotubes

    PubMed Central

    Ye, H. F.; Zheng, Y. G.; Zhang, Z. Q.; Chen, Z.; Zhang, H. W.

    2015-01-01

    The effects of water filling and electric field on the mechanical property of carbon nanotubes (CNTs) are investigated with molecular dynamics simulations. The simulation results indicate that the water filling and electric field could enhance the elastic modulus but reduce the Poisson’s ratio of the CNTs. As for the buckling behaviors, a significant enhancement could be observed in the yield stress and average post-buckling stress of the CNTs. In particular, the enhancement in the yield stress induced by the water filling and electric field could be even higher than that resulted from the solid filling. Moreover, a transition mechanism from the rod instability to shell buckling is shown to explain the nonmonotonic variation of yield stress, and the critical diameter can be tuned through filling the water molecules and applying the electric field. The present findings provide a valuable route for the optimized design and application of the nanoscale functional devices based on the water-filled CNTs. PMID:26621767

  7. On the mechanism for nanoplasmonic enhancement of photon to electron conversion in nanoparticle sensitized hematite films.

    PubMed

    Iandolo, Beniamino; Antosiewicz, Tomasz J; Hellman, Anders; Zorić, Igor

    2013-04-14

    Hematite (Fe2O3) is a promising candidate for hydrogen production via water splitting despite the difference in the characteristic lengths for photon absorption and charge carrier transport. Metallic nanoparticles supporting localized surface plasmon resonances (LSPRs), i.e. collective, non-propagating oscillations of electrons excited by an external electric field, are well-suited to improve the optoelectronic properties of hematite, in particular for ultra-thin films. Several mechanisms have been proposed to explain the observed LSPR mediated performance enhancement. In this work, the improvement of incident photon-to-electron conversion efficiency (IPCE) of ultra-thin hematite photoanodes functionalized with Au nanodisks was investigated. The improvement in IPCE at wavelengths close to the bandgap in hematite was found to correlate well with the increase in optical extinction owing to the excitation of LSPR in the nanodisks. Finite-difference time-domain calculations of the near-field distribution around the nanodisks enabled us to elucidate the mechanism behind the IPCE enhancement and its variations with the position of the plasmonic resonance with respect to the bandgap of hematite. Both were attributed to an increased charge generation close to the hematite-electrolyte interface caused by the electric field enhancement in hematite. The results presented here are directly applicable to other semiconductors with similar properties to hematite and are expected to be helpful in future design of optimized photoanodes, where, for instance, functionalization with metallic nanoparticles is combined with material doping and nanostructuring. PMID:23439980

  8. Revealing the Mechanism of the Low-Energy Electron Yield Enhancement from Sensitizing Nanoparticles

    NASA Astrophysics Data System (ADS)

    Verkhovtsev, Alexey V.; Korol, Andrei V.; Solov'yov, Andrey V.

    2015-02-01

    We provide a physical explanation for the enhancement of the low-energy electron production by sensitizing nanoparticles due to irradiation by fast ions. It is demonstrated that a significant increase in the number of emitted electrons arises from the collective electron excitations in the nanoparticle. We predict a new mechanism of the yield enhancement due to the plasmon excitations and quantitatively estimate its contribution to the electron production. Revealing the nanoscale mechanism of the electron yield enhancement, we provide an efficient tool for evaluating the yield of the emitted electron from various sensitizers. It is shown that the number of low-energy electrons generated by the gold and platinum nanoparticles of a given size exceeds that produced by the equivalent volume of water and by other metallic (e.g., gadolinium) nanoparticles by an order of magnitude. This observation emphasizes the sensitization effect of the noble-metal nanoparticles and endorses their application in novel technologies of cancer therapy with ionizing radiation.

  9. Revealing the mechanism of the low-energy electron yield enhancement from sensitizing nanoparticles.

    PubMed

    Verkhovtsev, Alexey V; Korol, Andrei V; Solov'yov, Andrey V

    2015-02-13

    We provide a physical explanation for the enhancement of the low-energy electron production by sensitizing nanoparticles due to irradiation by fast ions. It is demonstrated that a significant increase in the number of emitted electrons arises from the collective electron excitations in the nanoparticle. We predict a new mechanism of the yield enhancement due to the plasmon excitations and quantitatively estimate its contribution to the electron production. Revealing the nanoscale mechanism of the electron yield enhancement, we provide an efficient tool for evaluating the yield of the emitted electron from various sensitizers. It is shown that the number of low-energy electrons generated by the gold and platinum nanoparticles of a given size exceeds that produced by the equivalent volume of water and by other metallic (e.g., gadolinium) nanoparticles by an order of magnitude. This observation emphasizes the sensitization effect of the noble-metal nanoparticles and endorses their application in novel technologies of cancer therapy with ionizing radiation. PMID:25723219

  10. Rock Mechanics and Enhanced Geothermal Systems: A DOE-sponsored Workshop to Explore Research Needs

    SciTech Connect

    Francois Heuze; Peter Smeallie; Derek Elsworth; Joel L. Renner

    2003-10-01

    This workshop on rock mechanics and enhanced geothermal systems (EGS) was held in Cambridge, Mass., on June 20-21 2003, before the Soil and Rock America 2003 International Conference at MIT. Its purpose was to bring together experts in the field of rock mechanics and geothermal systems to encourage innovative thinking, explore new ideas, and identify research needs in the areas of rock mechanics and rock engineering applied to enhanced geothermal systems. The agenda is shown in Appendix A. The workshop included experts in the fields of rock mechanics and engineering, geological engineering, geophysics, drilling, the geothermal energy production from industry, universities and government agencies, and laboratories. The list of participants is shown is Appendix B. The first day consisted of formal presentations. These are summarized in Chapter 1 of the report. By the end of the first day, two broad topic areas were defined: reservoir characterization and reservoir performance. Working groups were formed for each topic. They met and reported in plenary on the second day. The working group summaries are described in Chapter 2. The final session of the workshop was devoted to reaching consensus recommendations. These recommendations are given in Chapter 3. That objective was achieved. All the working group recommendations were considered and, in order to arrive at a practical research agenda usable by the workshop sponsors, workshop recommendations were reduced to a total of seven topics. These topics were divided in three priority groups, as follows. First-priority research topics (2): {sm_bullet} Define the pre-existing and time-dependent geometry and physical characteristics of the reservoir and its fracture network. That includes the identification of hydraulically controlling fractures. {sm_bullet} Characterize the physical and chemical processes affecting the reservoir geophysical parameters and influencing the transport properties of fractures. Incorporate those

  11. A review of porous media enhanced vapor-phase diffusion mechanisms, models, and data: Does enhanced vapor-phase diffusion exist?

    SciTech Connect

    Ho, C.K.; Webb, S.W.

    1996-05-01

    A review of mechanisms, models, and data relevant to the postulated phenomenon of enhanced vapor-phase diffusion in porous media is presented. Information is obtained from literature spanning two different disciplines (soil science and engineering) to gain a diverse perspective on this topic. Findings indicate that while enhanced vapor diffusion tends to correct the discrepancies observed between past theory and experiments, no direct evidence exists to support the postulated processes causing enhanced vapor diffusion. Numerical modeling analyses of experiments representative of the two disciplines are presented in this paper to assess the sensitivity of different systems to enhanced vapor diffusion. Pore-scale modeling is also performed to evaluate the relative significance of enhanced vapor diffusion mechanisms when compared to Fickian diffusion. The results demonstrate the need for additional experiments so that more discerning analyses can be performed.

  12. Flexural strength of sapphire: Weibull statistical analysis of stressed area, surface coating, and polishing procedure effects

    NASA Astrophysics Data System (ADS)

    Klein, Claude A.

    2004-09-01

    The results of fracture testing are usually reported in terms of a measured strength, σM=σi¯±Δσi¯, where σi¯ is the average of the recorded peak stresses at failure, and Δσi¯ represents the standard deviation. This "strength" does not provide an objective measure of the intrisic strength since σM depends on the test method and the size of the volume or the surface subjected to tensile stresses. We first clarify issues relating to Weibull's theory of brittle fracture and then make use of the theory to assess the results of equibiaxial flexure testing that was carried out on a variety of sapphire specimens, at three mechanical test facilities. Specifically, we describe the failure probability distribution in terms of a characteristic strength σC—i.e., the effective strength of a uniformly stressed 1cm2 area—which allows us to predict the average stress at failure of a uniformly loaded "window" if the Weibull modulus m is available. A Weibull statistical analysis of biaxial-flexure strength data thus amounts to obtaining the parameters σC and m, which is best done by directly fitting estimated cumulative failure probabilities to the appropriate expression derived from Weibull's theory. We demonstrate that: (a) measurements performed on sapphire test specimens originating from two suppliers confirm the applicability of the area scaling law; for mechanically polished c- and r-plane sapphire, we obtain σC≃975MPa, m =3.40 and σC≃550MPa, m =4.10, respectively. (b) Strongly adhering compressive coatings can augment the characteristic strength by as much as 60%, in accord with predictions based on fracture-mechanics considerations, but degrade the Weibull modulus, which mitigates the benefit of this approach. And (c) Measurements performed at 600°C on chemomechanically polished c-plane test specimens indicate that proper procedures may enhance the characteristic strength by as much as 150%, with no apparent degradation of the Weibull modulus.

  13. Mechanism of the enhanced degradation of pentachlorophenol by ultrasound in the presence of elemental iron.

    PubMed

    Dai, Youzhi; Li, Fenfang; Ge, Fei; Zhu, Fei; Wu, Lanyan; Yang, Xiangzheng

    2006-10-11

    Ultrasound combined with elemental iron (US/Fe(0)) is effective in oxidizing organic contaminants in water. The sonolysis degradation of pentachlorophenol (PCP) was significantly enhanced by a factor of 4.2 with the addition of elemental iron, mainly via reaction with hydroxyl radicals (OH radicals), and the synergistic mechanism of the enhancement in the combined system was investigated. Experiments were performed with (1) sole ultrasonic treatment; (2) ultrasound in presence of iron; (3) ultrasound combined with copper powder as the same particle size as iron powder; (4) ultrasound in presence of Fe(II). It was observed that PCP degradation and OH radicals production were both enhanced in these combined methods, and the pitting on the sonicated iron surface was apparent. These results indicated that the rate enhancements in US/Fe(0) system were attributed to (1) the iron solid effect and the catalysis of Fe(II) produced from corroded-iron with promoting the production of OH radicals; (2) the increased surface area of iron particles by acoustic cavitation with promoting the adsorption process. PMID:16762499

  14. Using synthetic bacterial enhancers to reveal a looping-based mechanism for quenching-like repression.

    PubMed

    Brunwasser-Meirom, Michal; Pollak, Yaroslav; Goldberg, Sarah; Levy, Lior; Atar, Orna; Amit, Roee

    2016-01-01

    We explore a model for 'quenching-like' repression by studying synthetic bacterial enhancers, each characterized by a different binding site architecture. To do so, we take a three-pronged approach: first, we compute the probability that a protein-bound dsDNA molecule will loop. Second, we use hundreds of synthetic enhancers to test the model's predictions in bacteria. Finally, we verify the mechanism bioinformatically in native genomes. Here we show that excluded volume effects generated by DNA-bound proteins can generate substantial quenching. Moreover, the type and extent of the regulatory effect depend strongly on the relative arrangement of the binding sites. The implications of these results are that enhancers should be insensitive to 10-11 bp insertions or deletions (INDELs) and sensitive to 5-6 bp INDELs. We test this prediction on 61 σ(54)-regulated qrr genes from the Vibrio genus and confirm the tolerance of these enhancers' sequences to the DNA's helical repeat. PMID:26832446

  15. Using synthetic bacterial enhancers to reveal a looping-based mechanism for quenching-like repression

    PubMed Central

    Brunwasser-Meirom, Michal; Pollak, Yaroslav; Goldberg, Sarah; Levy, Lior; Atar, Orna; Amit, Roee

    2016-01-01

    We explore a model for ‘quenching-like' repression by studying synthetic bacterial enhancers, each characterized by a different binding site architecture. To do so, we take a three-pronged approach: first, we compute the probability that a protein-bound dsDNA molecule will loop. Second, we use hundreds of synthetic enhancers to test the model's predictions in bacteria. Finally, we verify the mechanism bioinformatically in native genomes. Here we show that excluded volume effects generated by DNA-bound proteins can generate substantial quenching. Moreover, the type and extent of the regulatory effect depend strongly on the relative arrangement of the binding sites. The implications of these results are that enhancers should be insensitive to 10–11 bp insertions or deletions (INDELs) and sensitive to 5–6 bp INDELs. We test this prediction on 61 σ54-regulated qrr genes from the Vibrio genus and confirm the tolerance of these enhancers' sequences to the DNA's helical repeat. PMID:26832446

  16. Condensate polishers add operating reliability and flexibility

    SciTech Connect

    Layman, C.M.; Bennett, L.L.

    2008-08-15

    Many of today's advanced steam generators favour either an all-volatile treatment or oxygenated treatment chemistry programme, both of which require strict maintenance of an ultra-pure boiler fedwater ro condensate system. Those requirements are many times at odds with the lower-quality water sources, such as greywater, available for plant makeup and cooling water. Adding a condensate polisher can be a simple, cost-effective solution. 4 figs.

  17. First years of the Polish Fireball Network

    NASA Astrophysics Data System (ADS)

    Zoladek, P.

    2012-01-01

    The first attempts of video and photographic meteor observations in Poland are presented. The Polish Fireball Network (PFN) was estabilished in 2004 after a succesfull Leonid campaign and the appearance of the Laskarzew fireball. Typical fireball stations were equiped with CCTV systems, with METREC software running. The first digital fireball stations have been created in 2005. Currently, PFN consists of 20 fireball stations and uses 54 CCTV cameras.

  18. Subaperture approaches for asphere polishing and metrology

    NASA Astrophysics Data System (ADS)

    Tricard, Marc; Dumas, Paul; Forbes, Greg

    2005-02-01

    This paper summarizes some of QED Technologies" latest developments in the field of high-precision polishing and metrology. Magneto-Rheological Finishing (MRF) is a deterministic sub-aperture polishing process that overcomes many of the fundamental limitations of traditional finishing. MRF has demonstrated the ability to produce optical surfaces with accuracies better than 30 nm peak-to-valley (PV) and surface micro-roughness less than 0.5 nm rms on a wide variety of optical glasses, single crystals, and glass-ceramics. The MR fluid forms a polishing tool that is perfectly conformal and therefore can polish a variety of shapes, including flats, spheres, aspheres, prisms, and cylinders, with either round or rectangular apertures. QED"s Sub-aperture Stitching Interferometer (SSI) complements MRF by extending the effective aperture, accuracy, resolution, and dynamic range of a phase-shifting interferometer. This workstation performs automated sub-aperture stitching measurements of spheres, flats, and mild aspheres. It combines a six-axis precision stage system, a commercial Fizeau interferometer, and specially developed software that automates measurement design, data acquisition, and the reconstruction of the full-aperture map of figure error. Aside from the correction of sub-aperture placement errors (such as tilts, optical power, and registration effects), our software also accounts for reference-wave error, distortion, and other aberrations in the interferometer"s imaging optics. By addressing these matters up front, we avoid limitations encountered in earlier stitching work and significantly boost reproducibility beyond that of the integrated interferometer on its own.

  19. Nanocomposite films based on xylan-rich hemicelluloses and cellulose nanofibers with enhanced mechanical properties.

    PubMed

    Peng, Xin-wen; Ren, Jun-li; Zhong, Lin-xin; Sun, Run-cang

    2011-09-12

    Interest in xylan-rich hemicelluloses (XH) film is growing, and efforts have been made to prepare XH films with improved mechanical properties. This work described an effective approach to produce nanocomposite films with enhanced mechanical properties by incorporation of cellulose nanofibers (CNFs) into XH. Aqueous dispersions of XH (64-75 wt %), sorbitol (16-25 wt %), and CNF (0-20 wt %) were cast at a temperature of 23 °C and 50% relative humidity. The surface morphology of the films was revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties and crystal structure of the films were evaluated by thermal analysis (TG) and X-ray diffraction (XRD). The surface of XH films with and without CNF was composed primarily of nanonodules, and CNFs were embedded in the XH matrix. Freeze-dried XH powder was amorphous, whereas the films with and without CNF showed a distinct peak at around 2θ = 18°, which suggested that XH molecules aggregated or reordered in the casting solution or during water evaporation. Furthermore, the nanocomposite films had improved thermal stability. XH film with 25 wt % plasticizer (sorbitol, based on dry XH weight) showed poor mechanical properties, whereas incorporation of CNF (5-20 wt %, based on the total dry mixture) into the film resulted in enhanced mechanical properties due to the high aspect ratio and mechanical strength of CNF and strong interactions between CNF and XH matrix. This effective method makes it possible to produce hemicellulose-based biomaterials of high quality. PMID:21815695

  20. Enhanced autophagy as a potential mechanism for the improved physiological function by simvastatin in muscular dystrophy.

    PubMed

    Whitehead, Nicholas P

    2016-04-01

    Autophagy has recently emerged as an important cellular process for the maintenance of skeletal muscle health and function. Excessive autophagy can trigger muscle catabolism, leading to atrophy. In contrast, reduced autophagic flux is a characteristic of several muscle diseases, including Duchenne muscular dystrophy, the most common and severe inherited muscle disorder. Recent evidence demonstrates that enhanced reactive oxygen species (ROS) production by CYBB/NOX2 impairs autophagy in muscles from the dmd/mdx mouse, a genetic model of Duchenne muscular dystrophy. Statins decrease CYBB/NOX2 expression and activity and stimulate autophagy in skeletal muscle. Therefore, we treated dmd/mdx mice with simvastatin and showed decreased CYBB/NOX2-mediated oxidative stress and enhanced autophagy induction. This was accompanied by reduced muscle damage, inflammation and fibrosis, and increased muscle force production. Our data suggest that increased autophagy may be a potential mechanism by which simvastatin improves skeletal muscle health and function in muscular dystrophy. PMID:26890413

  1. Exploring vortex enhancement and manipulation mechanisms in jellyfish that contributes to energetically efficient propulsion

    PubMed Central

    Gemmell, Brad J; Costello, John H; Colin, Sean P

    2014-01-01

    The ability of animals to propel themselves efficiently through a fluid medium is ecologically advantageous. Flexible components that influence vortex interactions are widespread among animal propulsors. However the mechanisms by which vortices are enhanced and appropriately positioned for thrust generation are still poorly understood. Here, we describe how kinematic propulsor movements of a jellyfish can enhance and reposition a vortex ring that allows the recapture of wake energy for secondary thrust generation and efficient locomotion. We use high-speed video and digital particle image velocimetry (DPIV) to resolve kinematics simultaneously with fluid structures. These results provide new insight into how animals can manipulate fluid structures to reduce metabolic energy demands of swimming muscles and may have implications in bio-inspired design. PMID:25346796

  2. ZnO three-dimensional hedgehog-like nanostructure: synthesis, growth mechanism and optical enhancement

    NASA Astrophysics Data System (ADS)

    Liu, Huiqiang; Chu, Sheng; Peng, Rufang; Chu, Shijin; Jin, Bo

    2014-07-01

    The 3D hedgehog-like ZnO nanostructures were synthesized on Si substrate through chemical vapor deposition process. The morphology and structure of the products were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, as well as transmission electron microscopy. The ZnO 3D hedgehog-like architectures were found to consist of a central nucleus and multiple side-growing nanowires with diameter of 100-250 nm and length up to 10 µm. The growth mechanism of the hedgehog-like ZnO nanostructures was studied. It revealed a three-step process during the entire growth. Finally, room temperature photoluminescence spectra of ZnO 3D nanostructures showed that the center excitation would render much stronger PL emission intensity. Furthermore, simulation results indicated that the enhanced emission came from light-trapping-induced excitation light field enhancement.

  3. Duplication of holograms by using fingernail polish

    NASA Astrophysics Data System (ADS)

    Toxqui-López, S.; Olivares-Pérez, A.; Fuentes-Tapia, I.; Quintero-Romo, A.

    2007-08-01

    In this manuscript, we report the results of a research effort in finding an innovative recorder material which utilized fingernail polish (Super Oro One Coat®) information by means of the control of temperature as a parameter induced by hand rubbing. Analogical and computer holograms were replicated, resulting in a high quality behavior of fingernail polish through coating the polish with an average thickness of 10-15 μm, which contains some components of polyester resin with nitrocellulose. Through this material we obtained a high absolute diffraction efficiency, which was approximately equal to 90%, with gratings of 100 lines/mm. For a copy of conventional holograms at high frequencies (holographic ranges) the diffraction efficiency parameter is in the neighborhood of 22% at first order or more, depending on diffraction efficiency of the pattern of the hologram. The hologram is elaborated in the absence of any development of any process and does not need to have carefully controlled environmental conditions. Following this process, the hologram is obtained at standard atmospheric conditions of pressure and temperature. Another advantage is that it is possible to obtain a hologram at a lower cost; furthermore, the property of applicability to any substrate that it has is remarkable.

  4. Super-smooth polishing on aspherical surfaces (II): achievement of a super-smooth polishing

    NASA Astrophysics Data System (ADS)

    Ando, Manabu; Negishi, Mahito; Takimoto, Masafumi; Deguchi, Akinobu; Nakamura, Nobuo

    1995-08-01

    This paper discusses super-smooth polishing technology for excimer lasers, soft X-rays, and other short-wavelength light applications. Short-wavelength light elements require surface quality and contour accuracy superior to traditional specifications, as well as free-form contours. For this reason, our target for free-form contours of a 500 mm diameter was set to 0.08 mm PV for contour accuracy, and 0.2 nm RMS for surface roughness. To improve surface quality we employed local pitch polishing, utilizing a flexible tool laminated with an elastic sheet, which adapts well to various contours. For greater contour accuracy, we developed the CSSP (Canon Super-Smooth Polisher), which polishes 500 mm diameter optical elements. The CSSP polishing process achieves a contour accuracy of 0.078 mm PV and a surface roughness of 0.13 nm RMS on a 500 mm diameter fused silica toroidal mirror. We also fabricated both CaF2 and CVD-SiC, materials widely used in short-wavelength light elements.

  5. Mechanical Vectors Enhance Fungal Entomopathogen Reduction of the Grasshopper Pest Camnula pellucida (Orthoptera: Acrididae).

    PubMed

    Kistner, Erica J; Saums, Marielle; Belovsky, Gary E

    2015-02-01

    Mounting scientific evidence indicates that pathogens can regulate insect populations. However, limited dispersal and sensitivity to abiotic conditions often restricts pathogen regulation of host populations. While it is well established that arthropod biological vectors increase pathogen incidence in host populations, few studies have examined whether arthropod mechanical vectors (an organism that transmits pathogens but is not essential to the life cycle of the pathogen) influence host-pathogen dynamics. The importance of mechanical dispersal by ant scavengers, Formica fusca (L.), in a grasshopper-fungal entomopathogen system was investigated. We examined the ability of ants to mechanically disperse and transmit the pathogen, Entomophaga grylli (Fresenius) pathotype 1, to its host, the pest grasshopper Camnula pellucida (Scudder), in a series of laboratory experiments. Fungal spores were dispersed either externally on the ant's body surface or internally through fecal deposition. In addition, a third of all grasshoppers housed with fungal-inoculated ants became infected, indicating that ants can act as mechanical vectors of E. grylli. The effect of ant mechanical vectors on E. grylli incidence was also examined in a field experiment. Ant access to pathogen-exposed experimental grasshopper populations was restricted using organic ant repellent, thereby allowing us to directly compare mechanical and natural transmission. Ants increased grasshopper pathogen mortality by 58%, which led to greater pathogen reductions of grasshopper survival than natural transmission. Taken together, our results indicate that ants enhance E. grylli reduction of grasshopper pest numbers. Therefore, mechanical transmission of pathogens may be an important overlooking component of this grasshopper-fungal pathogen system. PMID:26308817

  6. 3C-SiC/ZnS heterostructured nanospheres with high photocatalytic activity and enhancement mechanism

    SciTech Connect

    Zhang, J.; Wu, X. L. E-mail: paul.chu@cityu.edu.hk; Liu, L. Z.; Yang, L.; Gan, Z. X.; Chu, Paul K. E-mail: paul.chu@cityu.edu.hk

    2015-03-15

    3C-SiC/n-type ZnS heterostructured nanospheres synthesized hydrothermally deliver enhanced photocatalytic performance under visible light excitation. The heterostructured catalysts consisting of 3C-SiC and ZnS nanocrystals with a mean size being less than 5 nm exhibit extended light absorption to the visible range. The proper band structure of the 3C-SiC and ZnS nanocrystals and intrinsic electric field induced by the heterojunction promote separation of photoexcited electrons and holes in the ZnS and 3C-SiC nanocrystals resulting in the increased photocatalytic efficiency. The associated mechanism is studied and proposed.

  7. New Mechanism for the Enhancement of sd Dominance in Interacting Boson Models

    NASA Astrophysics Data System (ADS)

    Dukelsky, J.; Pittel, S.

    2001-05-01

    We introduce an exactly solvable model for interacting bosons that extend up to high spin and interact through a repulsive pairing force. The model exhibits a phase transition to a state with almost complete sd dominance. The repulsive pairing interaction that underlies the model has a natural microscopic origin in the Pauli exclusion principle between constituent nucleons. As such, repulsive pairing between bosons seems to provide a new mechanism for the enhancement of sd dominance, giving further support for the validity of the sd interacting boson model.

  8. Chromatic stability of acrylic resins of artificial eyes submitted to accelerated aging and polishing

    PubMed Central

    GOIATO, Marcelo Coelho; dos SANTOS, Daniela Micheline; SOUZA, Josiene Firmino; MORENO, Amália; PESQUEIRA, Aldiéris Alves

    2010-01-01

    Esthetics and durability of materials used to fabricate artificial eyes has been an important eissue since artificial eyes are essential to restore esthetics and function, protect the remaining tissues and help with patients' psychological therapy. However, these materials are submitted to degrading effects of environmental agents on the physical properties of the acrylic resin. Objective This study assessed the color stability of acrylic resins used to fabricate sclera in three basic shades (N1, N2 and N3) when subjected to accelerated aging, mechanical and chemical polishing. Material and methods Specimens of each resin were fabricated and submitted to mechanical and chemical polishing. Chromatic analysis was performed before and after accelerated aging through ultraviolet reflection spectrophotometry. Results All specimens revealed color alteration following polishing and accelerated aging. The resins presented statistically significant chromatic alteration (p<0.01) between the periods of 252 and 1008 h. Conclusions Both polishing methods presented no significant difference between the values of color derivatives of resins. PMID:21308298

  9. Characterization and Streptococcus mutans adhesion on air polishing dentin.

    PubMed

    Tada, Kazuhiro; Oda, Hirotake; Inatomi, Michitomo; Sato, Soh

    2014-07-01

    Air polishing is known as an effective and time saving tooth cleaning method. However, this method increased surface roughness and bacterial adhesion on dentin surface. The aim of this study was to characterize and examine Streptococcus mutans adhesion on dentin surface after air polishing as compared to the conventional method. The dentin blocks (4 × 4 × 1 mm) were polished by a rubber cup with polishing material (Polishing) and air-polished by 25 μm glycine (G25), 65 μm glycine (G65), and 65 μm sodium bicarbonate (NHC65) microparticles. Surface roughness (Ra) was measured by a laser electron microscope. The amount of adhered S. mutans was quantified using a resazurin reduction assay (alamarBlue(®)). The Ra of G25 and G65 was significantly (p < 0.01) smaller than that of NHC65 and greater than that of Polishing. However, there was no significant difference in S. mutans adhesion among Polishing, G25, and G65, while NHC65 showed significantly (p < 0.01) higher S. mutans adhesion. Within the limitations of this in vitro study, air polishing using glycine microparticles conditioned S. mutans adhesion on dentin surface in a similar fashion than the conventional method, and less than air polishing using sodium bicarbonate microparticles. PMID:23744363

  10. Multiwavelength digital holography for polishing tool shape measurement

    NASA Astrophysics Data System (ADS)

    Lédl, Vít.; Psota, Pavel; Václavík, Jan; Doleček, Roman; Vojtíšek, Petr

    2013-09-01

    Classical mechano-chemical polishing is still a valuable technique, which gives unbeatable results for some types of optical surfaces. For example, optics for high power lasers requires minimized subsurface damage, very high cosmetic quality, and low mid spatial frequency error. One can hardly achieve this with use of subaperture polishing. The shape of the polishing tool plays a crucial role in achieving the required form of the optical surface. Often the shape of the polishing tool or pad is not known precisely enough during the manufacturing process. The tool shape is usually premachined and later is changed during the polishing procedure. An experienced worker could estimate the shape of the tool indirectly from the shape of the polished element, and that is why he can achieve the required shape in few reasonably long iterative steps. Therefore the lack of the exact tool shape knowledge is tolerated. Sometimes, this indirect method is not feasible even if small parts are considered. Moreover, if processes on machines like planetary (continuous) polishers are considered, the incorrect shape of the polishing pad could extend the polishing times extremely. Every iteration step takes hours. Even worse, polished piece could be wasted if the pad has a poor shape. The ability of the tool shape determination would be very valuable in those types of lengthy processes. It was our primary motivation to develop a contactless measurement method for large diffusive surfaces and demonstrate its usability. The proposed method is based on application of multiwavelength digital holographic interferometry with phase shift.

  11. EFFECTS OF POLISHING PROCEDURES ON COLOR STABILITY OF COMPOSITE RESINS

    PubMed Central

    Güler, Ahmet Umut; Güler, Eda; Yücel, Ali Çagin; ERTA§, Ertan

    2009-01-01

    The purpose of this study was to investigate the effect of different polishing methods on color stability of posterior, universal and nanohybrid composite resin restorative materials upon exposure to a staining agent. Twenty-five specimens were prepared for each of 5 different composite resins (Filtek Z250, Filtek P60, Quadrant LC, Grandio and Filtek Supreme). Specimens were divided into 5 groups and different polishing procedures, including polishing discs (Pd), polishing discs then diamond polishing paste (PdP), polishing discs then a liquid polishing system (Biscover) (PdB), and combinations of these (PdPB) were used. Unpolished specimens served as the control (C). The specimens were stored for 48 h in a coffee solution. The color of all specimens was measured before and after exposure with a colorimeter, and total color change ∆E*) were calculated. The data were analyzed with a two-way ANOVA and the means were compared by Tukey HSD test (α=0.05). The lowest color difference was observed in the groups PdP and C, while the highest color difference was observed in PdPB, and PdB. When comparing the five different restorative materials, no significant difference was observed between FiltekP60 and FiltekZ250, and these materials demonstrated significantly less color change than Quadrant LC and the nanohybrid materials (Grandio, Filtek Supreme). The posterior (Filtek P60) and universal (Filtek Z250) composite resin restorative materials, which do not contain tetraethyleneglycol dimethacrylate (TEGDMA), were found to be less stainable than the nanohybrid (Grandio, Filtek Supreme) and universal (Quadrant LC) composite resins, which contain TEGDMA. The use of diamond polishing paste after polishing with polishing discs significantly decreased staining when compared to the groups that used polishing discs alone, for all restorative materials tested. The highest color change values were obtained for the specimens that were polished with the Biscover liquid polish system

  12. Phospholipids that contain polyunsaturated fatty acids enhance neuronal cell mechanics and touch sensation

    PubMed Central

    Vásquez, Valeria; Krieg, Michael; Lockhead, Dean; Goodman, Miriam B.

    2014-01-01

    Summary Mechano-electrical transduction (MeT) channels embedded in neuronal cell membranes are essential for touch and proprioception. Little is understood about the interplay between native MeT channels and membrane phospholipids, in part because few techniques are available for altering plasma membrane composition in vivo. Here, we leverage genetic dissection, chemical complementation, and optogenetics to establish that arachidonic acid (AA), an omega-6 polyunsaturated fatty acid, enhances touch sensation and mechanoelectrical transduction activity while incorporated into membrane phospholipids in C. elegans touch receptor neurons (TRNs). Because dynamic force spectroscopy reveals that AA modulates the mechanical properties of TRN plasma membranes, we propose that this PUFA is needed for MeT channel activity. These findings establish that polyunsaturated phospholipids are crucial determinants of both the biochemistry and mechanics of mechanoreceptor neurons and reinforce the idea that sensory mechanotransduction in animals relies on a cellular machine composed of both proteins and membrane lipids. PMID:24388754

  13. Ester-free Thiol-X Resins: New Materials with Enhanced Mechanical Behavior and Solvent Resistance

    PubMed Central

    Podgórski, Maciej; Becka, Eftalda; Chatani, Shunsuke; Claudino, Mauro

    2015-01-01

    A series of thiol-Michael and radical thiol-ene network polymers were successfully prepared from ester-free as well as ester-containing monomer formulations. Polymerization reaction rates, dynamic mechanical analysis, and solvent resistance experiments were performed and compared between compositions with varied ester loading. The incorporation of ester-free alkyl thiol, vinyl sulfone and allylic monomers significantly improved the mechanical properties when compared with commercial, mercaptopropionate-based thiol-ene or thiol-Michael networks. For polymers with no hydrolytically degradable esters, glass transition temperatures (Tg's) as high as 100 °C were achieved. Importantly, solvent resistance tests demonstrated enhanced stability of ester-free formulations over PETMP-based polymers, especially in concentrated basic solutions. Kinetic analysis showed that glassy step-growth polymers are readily formed at ambient conditions with conversions reaching 80% and higher. PMID:25893009

  14. Enhanced Mechanical Properties of Nanoparticle Networks Cross-Linked by Biomimetic Catch Bonds

    NASA Astrophysics Data System (ADS)

    Mbanga, Badel L.; Iyer, Balaji V. S.; Yashin, Victor V.; Balazs, Anna C.

    2015-03-01

    The tunable behavior of cross-linked networks of Polymer-Grafted Nanoparticles (PGNs) makes them excellent candidates for designing novel materials with enhanced mechanical properties. The building block of a PGN network is a nanoparticle with grafted polymer chains whose free ends' reactive groups can form bonds with the end chains on the nearby particles. We use computer modeling to study the tensile behavior of 3D samples, in which some fraction of cross-links is formed through the biomimetic ``catch'' bonds. In contrast to conventional ``slip'' bonds, the catch bonds might become stronger under an applied force due to transitions between two conformational states. The mechanical properties of the PGN networks are shown to exhibit a drastic improvement upon introduction of the catch bonds into the network. We discuss how ductility, toughness, and rate of strain recovery of the network depend on the catch bond content.

  15. Mechanisms of Odor-Tracking: Multiple Sensors for Enhanced Perception and Behavior

    PubMed Central

    Gomez-Marin, Alex; Duistermars, Brian J.; Frye, Mark A.; Louis, Matthieu

    2010-01-01

    Early in evolution, the ability to sense and respond to changing environments must have provided a critical survival advantage to living organisms. From bacteria and worms to flies and vertebrates, sophisticated mechanisms have evolved to enhance odor detection and localization. Here, we review several modes of chemotaxis. We further consider the relevance of a striking and recurrent motif in the organization of invertebrate and vertebrate sensory systems, namely the existence of two symmetrical olfactory sensors. By combining our current knowledge about the olfactory circuits of larval and adult Drosophila, we examine the molecular and neural mechanisms underlying robust olfactory perception and extend these analyses to recent behavioral studies addressing the relevance and function of bilateral olfactory input for gradient detection. Finally, using a comparative theoretical approach based on Braitenberg's vehicles, we speculate about the relationships between anatomy, circuit architecture and stereotypical orientation behaviors. PMID:20407585

  16. Cold plasma welding of polyaniline nanofibers with enhanced electrical and mechanical properties.

    PubMed

    Ye, Dong; Yu, Yao; Liu, Lin; Lu, Xinpei; Wu, Yue

    2015-12-11

    Joining conducting polymer (CP) nanofibers into an interconnected porous network can result in good mechanical and electrical contacts between nanofibers that can be beneficial for the high performance of CP-based devices. Here, we demonstrate the cold welding of polyaniline (PAni) nanofiber loose ends with cold plasma. The room-temperature and atmospheric-pressure helium micro-plasma jet launches highly charged ion bullets at a PAni nanofiber target with high precision and the highly charged ion bullet selectively induces field emission at the sharp nanofiber loose ends. This technique joins nanofiber tips without altering the morphology of the film and protonation thus leading to significantly enhanced electrical and mechanical properties. In addition, this technique has high spatial resolution and is able to selectively weld and dope regions of nanofiber film with promising novel device applications. PMID:26574401

  17. Cold plasma welding of polyaniline nanofibers with enhanced electrical and mechanical properties

    NASA Astrophysics Data System (ADS)

    Ye, Dong; Yu, Yao; Liu, Lin; Lu, Xinpei; Wu, Yue

    2015-12-01

    Joining conducting polymer (CP) nanofibers into an interconnected porous network can result in good mechanical and electrical contacts between nanofibers that can be beneficial for the high performance of CP-based devices. Here, we demonstrate the cold welding of polyaniline (PAni) nanofiber loose ends with cold plasma. The room-temperature and atmospheric-pressure helium micro-plasma jet launches highly charged ion bullets at a PAni nanofiber target with high precision and the highly charged ion bullet selectively induces field emission at the sharp nanofiber loose ends. This technique joins nanofiber tips without altering the morphology of the film and protonation thus leading to significantly enhanced electrical and mechanical properties. In addition, this technique has high spatial resolution and is able to selectively weld and dope regions of nanofiber film with promising novel device applications.

  18. Mechanism of Enhanced Activity of Liposome-Entrapped Aminoglycosides against Resistant Strains of Pseudomonas aeruginosa

    PubMed Central

    Mugabe, Clement; Halwani, Majed; Azghani, Ali O.; Lafrenie, Robert M.; Omri, Abdelwahab

    2006-01-01

    Pseudomonas aeruginosa is inherently resistant to most conventional antibiotics. The mechanism of resistance of this bacterium is mainly associated with the low permeability of its outer membrane to these agents. We sought to assess the bactericidal efficacy of liposome-entrapped aminoglycosides against resistant clinical strains of P. aeruginosa and to define the mechanism of liposome-bacterium interactions. Aminoglycosides were incorporated into liposomes, and the bactericidal efficacies of both free and liposomal drugs were evaluated. To define the mechanism of liposome-bacterium interactions, transmission electron microscopy (TEM), flow cytometry, lipid mixing assay, and immunocytochemistry were employed. Encapsulation of aminoglycosides into liposomes significantly increased their antibacterial activity against the resistant strains used in this study (MICs of ≥32 versus ≤8 μg/ml). TEM observations showed that liposomes interact intimately with the outer membrane of P. aeruginosa, leading to the membrane deformation. The flow cytometry and lipid mixing assays confirmed liposome-bacterial membrane fusion, which increased as a function of incubation time. The maximum fusion rate was 54.3% ± 1.5% for an antibiotic-sensitive strain of P. aeruginosa and 57.8% ± 1.9% for a drug-resistant strain. The fusion between liposomes and P. aeruginosa significantly enhanced the antibiotics' penetration into the bacterial cells (3.2 ± 2.3 versus 24.2 ± 6.2 gold particles/bacterium, P ≤ 0.001). Our data suggest that liposome-entrapped antibiotics could successfully resolve infections caused by antibiotic-resistant P. aeruginosa through an enhanced mechanism of drug entry into the bacterial cells. PMID:16723560

  19. Mechanism of enhanced activity of liposome-entrapped aminoglycosides against resistant strains of Pseudomonas aeruginosa.

    PubMed

    Mugabe, Clement; Halwani, Majed; Azghani, Ali O; Lafrenie, Robert M; Omri, Abdelwahab

    2006-06-01

    Pseudomonas aeruginosa is inherently resistant to most conventional antibiotics. The mechanism of resistance of this bacterium is mainly associated with the low permeability of its outer membrane to these agents. We sought to assess the bactericidal efficacy of liposome-entrapped aminoglycosides against resistant clinical strains of P. aeruginosa and to define the mechanism of liposome-bacterium interactions. Aminoglycosides were incorporated into liposomes, and the bactericidal efficacies of both free and liposomal drugs were evaluated. To define the mechanism of liposome-bacterium interactions, transmission electron microscopy (TEM), flow cytometry, lipid mixing assay, and immunocytochemistry were employed. Encapsulation of aminoglycosides into liposomes significantly increased their antibacterial activity against the resistant strains used in this study (MICs of > or =32 versus < or =8 microg/ml). TEM observations showed that liposomes interact intimately with the outer membrane of P. aeruginosa, leading to the membrane deformation. The flow cytometry and lipid mixing assays confirmed liposome-bacterial membrane fusion, which increased as a function of incubation time. The maximum fusion rate was 54.3% +/- 1.5% for an antibiotic-sensitive strain of P. aeruginosa and 57.8% +/- 1.9% for a drug-resistant strain. The fusion between liposomes and P. aeruginosa significantly enhanced the antibiotics' penetration into the bacterial cells (3.2 +/- 2.3 versus 24.2 +/- 6.2 gold particles/bacterium, P < or = 0.001). Our data suggest that liposome-entrapped antibiotics could successfully resolve infections caused by antibiotic-resistant P. aeruginosa through an enhanced mechanism of drug entry into the bacterial cells. PMID:16723560

  20. Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

    NASA Astrophysics Data System (ADS)

    Lee, Min Wook; An, Seongpil; Song, Kyo Yong; Joshi, Bhavana N.; Jo, Hong Seok; Al-Deyab, Salem S.; Yoon, Sam S.; Yarin, Alexander L.

    2015-12-01

    Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex.

  1. Motion amplification using a flextensional compliant mechanism for enhanced energy harvesting

    NASA Astrophysics Data System (ADS)

    Abdelnaby, Mohammed A.; Arafa, Mustafa

    2016-04-01

    In vibration-based energy harvesting, ambient vibration often occurs in such small amplitudes that it cannot be used to drive electrical generators directly. To maximize the amount of output power, the input motion is usually amplified before being used for power generation. This work presents a non-resonant piezoelectric energy harvester that relies on a compliant mechanism to amplify a given persistent input motion in order to enhance the power output. The device can be used in situations where a small cyclic relative motion occurs between two surfaces, and where a device can be fitted to extract energy. The use of a compliant mechanism, as opposed to conventional gear drives or linkages, alleviates problems of excessive clearances, friction and power losses. A finite element model is developed to investigate the effect of the various design parameters on the system performance in terms of the amplification ratio, stiffness and output voltage. Findings of the present work are verified both numerically and experimentally on a cam-driven polymer mechanism. A parametric study is conducted to investigate the most influential variables in an attempt to optimize the design parameters for maximum power output. A magnetically bistable piezoelectric beam, driven by the compliant mechanism, is finally presented and provides substantially greater amounts of output power.

  2. Preparation, Characterization, and Enhanced Thermal and Mechanical Properties of Epoxy-Titania Composites

    PubMed Central

    Rubab, Zakya; Siddiqi, Humaira M.; Saeed, Shaukat

    2014-01-01

    This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4 as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress. PMID:24578638

  3. Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

    SciTech Connect

    Lee, Min Wook; An, Seongpil; Song, Kyo Yong; Joshi, Bhavana N.; Jo, Hong Seok; Yoon, Sam S. E-mail: ayarin@uic.edu; Al-Deyab, Salem S.; Yarin, Alexander L. E-mail: ayarin@uic.edu

    2015-12-28

    Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex.

  4. Would increased interstitial fluid flow through in situ mechanical stimulation enhance bone remodeling?

    PubMed

    Letechipia, J E; Alessi, A; Rodriguez, G; Asbun, J

    2010-08-01

    Bone accommodates to changes in its functional environment ensuring that sufficient skeletal mass is appropriately positioned to withstand the mechanical loads that result from functional activities. Increasing physical activity will result in increased bone mass, while the removal of functional loading would result in bone loss. Bone is a composite material made up of a collagen-hydroxyapatite matrix and a complex network of lacunae-canaliculi channels occupied by osteocyte and osteoblast processes, immersed in interstitial fluid. There are strong indications that changes in interstitial fluid flow velocity or pressure are the means by which an external load signal is communicated to the cell. In vitro studies indicate that shear stress, induced by interstitial fluid flow, is a potent bone cell behavior regulator. One of the forms of altering interstitial fluid flow is through the mechanical deformation of skeletal tissue in response to applied loads. Other methods include increased intramedullary pressure, negative-pressure tissue regeneration, or external mechanical stimulation. Analysis of these methods poses the question of process effectiveness. The efficacy of each method theoretically will depend on the mechanical efficiency of transmitting an external load and converting it into changes in interstitial fluid flow. In this paper, we combine recent knowledge on the effect of the bone's interstitial fluid flow, different fluid patterns, the role of gap junctions, and the concept of mechanical effectiveness of different methods that influence interstitial fluid flow within bone, and we hypothesize that the efficiency of bone remodeling can be improved if a small mechanical percussion device could be placed directly in contact with the bone, thus inducing local interstitial fluid flow variations. Enhancement of bone repair and remodeling through controlled interstitial fluid flow possesses many clinical applications. Further investigations and in vivo

  5. cAMP enhances BMP2-signaling through PKA and MKP1-dependent mechanisms

    SciTech Connect

    Ghayor, Chafik; Ehrbar, Martin; Miguel, Blanca San; Graetz, Klaus W.; Weber, Franz E.

    2009-04-03

    Recent studies suggest that the elevation of intracellular cyclic adenosine monophosphate (cAMP) and the activation of the protein kinase A regulate BMP-induced osteogenesis. However, the precise mechanisms underlying the enhancing effect of cAMP on BMP2 signaling were not completely revealed. In this study we investigated the effect of elevated cAMP level and PKA activation on the BMP2-induced osteoblastic differentiation in pluripotent C2C12 cells. Alkaline phosphatase activity and its mRNA were consistently induced by BMP2 treatment. The pretreatment of C2C12 cells with Forskolin, a cAMP generating agent, dbcAMP, an analogue of cAMP, or IBMX (3-isobutyl 1-methyl xanthine), and a nonspecific inhibitor of phosphodiesterases elicited further activation of alkaline phosphatase. Furthermore, elevated intracellular cAMP level increased BMP2-induced MKP1. On the other hand, BMP2-induced Erk phosphorylation (p44/p42) and cell proliferation were suppressed in the presence of cAMP. Thus, cAMP might enhance BMP2-induced osteoblastic differentiation by a MKP1-Erk-dependent mechanism.

  6. Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy.

    PubMed

    Girard, A; Gehan, H; Crut, A; Mermet, A; Saviot, L; Margueritat, J

    2016-06-01

    Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nanoparticles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle "supermolecules", that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diameter and sensitive to the elastic properties of the interstitial polymer. The latter dependence as well as finite element simulations suggest that this mode corresponds to the out-of-phase semirigid translation (l = 1 Lamb mode) of each nanoparticle of a dimer inside the matrix, activated by the mechanical coupling between the nanoparticles. These observations were permitted only thanks to the resonant excitation with the coupling plasmon excitation, leading to an enhancement up to 10(4) of the scattering by these vibrations. This enhanced ultralow frequency Raman scattering thus opens a new route to probe the local elastic properties of the surrounding medium. PMID:27176093

  7. Electrically and mechanically enhanced Ag nanowires-colorless polyimide composite electrode for flexible capacitive sensor

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Gon; Kim, Jiwan; Jung, Seung-Boo; Kim, Young-Sung; Kim, Jong-Woong

    2016-09-01

    Silver nanowire (AgNW) network is known for its low percolation threshold, high conductivity and good flexibility, therefore, considered one of the best candidates for fabrication of flexible and transparent electrodes. However, a general approach to make the AgNWs-based electrodes, an overcoating of nanowire dispersion onto a transparent polymer, should make an issue of poor mechanical stability, mainly caused by low adhesion between the nanowires and polymer. In addition, a thin insulating layer of polyvinylpyrrolidone (PVP) formed on the surface of AgNWs deteriorates the conductivity of their network, which means that a post-processing such as high temperature annealing is essentially needed. Here we employed a plasma treatment with an inert gas to remove the residual PVP layer, so that the conductivity could be enhanced without employing any high temperature processing. Interestingly, the optical transmittance in the wavelength near 400 nm was also increased, resulting in more neutral coloration of the electrode. An inverted layer processing made the nanowires to be partially buried at the surface of colorless polyimide (cPI), so that the enhancement of mechanical stability and connectivity with overlying materials were simultaneously achieved.

  8. Reduced silanized graphene oxide/epoxy-polyurethane composites with enhanced thermal and mechanical properties

    NASA Astrophysics Data System (ADS)

    Lin, Jing; Zhang, Peipei; Zheng, Cheng; Wu, Xu; Mao, Taoyan; Zhu, Mingning; Wang, Huaquan; Feng, Danyan; Qian, Shuxuan; Cai, Xianfang

    2014-10-01

    This paper describes the synthesis of reduced silanized graphene oxide/epoxy-polyurethane (EPUAs/R-Si-GEO) composites with enhanced thermal and mechanical properties. Graphene oxide (GEO), prepared from natural graphite flakes, was modified with methacryloxypropyltrimethoxysilane to prepare silanized GEO (Si-GEO), and was then reduced by NaHSO3 to prepare R-Si-GEO (partially reduced Si-GEO). EPAc/R-Si-GEO (R-Si-GEO/epoxy acrylate copolymers) was synthesized via an in situ polymerization of R-Si-GEO and epoxy acrylic monomers. EPUAs/R-Si-GEO was obtained by curing reaction between EPAc/R-Si-GEO and an isocyanate curing agent. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were used to characterize the surface and crystal structure of the modified graphene and EPUAs/R-Si-GEO. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize their morphology. Thermal gravimetric analysis (TGA), tensile strength, elongation at break, and cross-linking density measurements showed that the thermal stability and mechanical properties of EPUAs/R-Si-GEO were greatly enhanced by the addition of R-Si-GEO.

  9. Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models. Final report

    SciTech Connect

    Gangloff, R.P.; Kim, S.

    1993-09-01

    This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

  10. Mechanisms of enhanced osteoblast gene expression in the presence of hydroxyapatite coated iron oxide magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Tran, Nhiem; Hall, Douglas; Webster, Thomas J.

    2012-11-01

    Hydroxyapatite (HA) coated iron oxide (Fe3O4) magnetic nanoparticles have been shown to enhance osteoblast (bone forming cells) proliferation and osteoblast differentiation into calcium depositing cells (through increased secretion of alkaline phosphatase, collagen and calcium deposition) compared to control samples without nanoparticles. Such nanoparticles are, thus, very promising for numerous orthopedic applications including magnetically directed osteoporosis treatment. The objective of the current study was to elucidate the mechanisms of the aforementioned improved osteoblast responses in the presence of HA coated Fe3O4 nanoparticles. Results demonstrated large amounts of fibronectin (a protein known to increase osteoblast functions) adsorption on HA coated Fe3O4 nanoparticles. Specifically, fibronectin adsorption almost doubled when HA coated Fe3O4 nanoparticle concentrations increased from 12.5 to 100 μg ml-1, and from 12.5 to 200 μg ml-1, a four fold increase was observed. Results also showed greater osteoblast gene regulation (specifically, osteocalcin, type I collagen and cbfa-1) in the presence of HA coated Fe3O4 nanoparticles. Collectively, these results provide a mechanism for the observed enhanced osteoblast functions in the presence of HA coated iron oxide nanoparticles, allowing their further investigation for a number of orthopedic applications.

  11. Self aligning electron beam gun having enhanced thermal and mechanical stability

    DOEpatents

    Scarpetti, R.D. Jr.; Parkison, C.D.; Switzer, V.A.; Lee, Y.J.; Sawyer, W.C.

    1995-05-16

    A compact, high power electron gun is disclosed having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the ``triple point`` where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques. 12 Figs.

  12. Self aligning electron beam gun having enhanced thermal and mechanical stability

    DOEpatents

    Scarpetti, Jr., Raymond D.; Parkison, Clarence D.; Switzer, Vernon A.; Lee, Young J.; Sawyer, William C.

    1995-01-01

    A compact, high power electron gun having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the "triple point" where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques.

  13. Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Kim, Sang-Shik

    1993-01-01

    This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on 'stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

  14. Molecular dynamics simulation of effective thermal conductivity and study of enhanced thermal transport mechanism in nanofluids

    NASA Astrophysics Data System (ADS)

    Sarkar, Suranjan; Selvam, R. Panneer

    2007-10-01

    Nanofluids have been proposed as a route for surpassing the performance of currently available heat transfer liquids in the near future. In this study an equilibrium molecular dynamics simulation was used to model a nanofluid system. The thermal conductivity of the base fluid and nanofluid was computed using the Green-Kubo method for various volume fractions of nanoparticle loadings. This study showed the ability of molecular dynamics to predict the enhanced thermal conductivity of nanofluids. Through molecular dynamics calculation of mean square displacements for liquid phase in base fluid and for liquid and solid phases in nanofluid, this study tried to investigate the mechanisms involved in thermal transport of nanofluids at the atomic level. The result showed that the thermal transport enhancement of nanofluids was mostly due to the increased movement of liquid atoms in the presence of nanoparticle. Diffusion coefficients were also calculated for base fluid and nanofluids. Similarity of enhancement in thermal conductivity and diffusion coefficient for nanofluids indicates similar transport process for mass and heat.

  15. Chromate enhanced visible light driven TiO₂ photocatalytic mechanism on Acid Orange 7 photodegradation.

    PubMed

    Wang, Yeoung-Sheng; Shen, Jyun-Hong; Horng, Jao-Jia

    2014-06-15

    When hexavalent chromium (Cr(VI)) is added to a TiO2 photocatalytic reaction, the decolorization and mineralization efficiencies of azo dyes Acid Orange 7 (AO7) are enhanced even though the mechanism is unclear. This study used 5,5-dimethyl-l-pyrroline-N-oxide (DMPO) as the scavenger and the analysis of Electron Spin Resonance (ESR) to investigate this enhancement effect by observing the hydroxyl radical (OH) generation of the Cr(VI)/TiO2 system under UV and visible light (Vis) irradiation. With Cr(VI), the decolorization efficiencies were approximately 95% and 62% under UV and Vis, and those efficiencies were 25% less in the absence of Cr(VI). The phenomena of the DMPO-OH signals during the ESR analysis under Vis 405 and 550 nm irradiation were obviously the enhancement effects of Cr(VI) in aerobic conditions. In anoxic conditions, the catalytic effects of Cr(VI) could not be achieved due to the lack of a redox reaction between Cr(VI) and the adsorbed oxygen at the oxygen vacancy sites on the TiO2 surfaces. The results suggest that by introducing the agents of redox reactions such as chromate ions, we could lower the photoenergy of TiO2 needed and allow Vis irradiation to activate photocatalysis. PMID:24806871

  16. Innovative mechanisms of action for pharmaceutical cognitive enhancement: A systematic review.

    PubMed

    Fond, Guillaume; Micoulaud-Franchi, Jean-Arthur; Brunel, Lore; Macgregor, Alexandra; Miot, Stéphanie; Lopez, Régis; Richieri, Raphaëlle; Abbar, Mocrane; Lancon, Christophe; Repantis, Dimitris

    2015-09-30

    Pharmacological cognitive enhancement refers to improvement in cognitive functions after drug use in healthy individuals. This popular topic attracts attention both from the general public and the scientific community. The objective was to explore innovative mechanisms of psychostimulant's action, whose potential effectiveness was assessed in randomized placebo-controlled trials (RCTs). A systematic review was carried out, using the words "attention", "memory", "learning", "executive functions", and "vigilance/wakefulness" combined to "cognitive enhancer" or "smart drug". Methylphenidate, amphetamines, modafinil, nicotine, acetylcholine esterase inhibitors and antidepressants were extensively studied in previous meta-analyses and were not included in the present work. Drugs were classified according to their primary mode of action, namely catecholaminergic drugs (tolcapone, pramipexole, guanfacine), cholinergic drugs (anticholinergics), glutamatergic drugs (ampakines), histaminergic drugs, and non-specified (glucocorticoids). Overall, 50 RCTs were included in the present review. In conclusion, a number of new active drugs were found to improve some cognitive functions, in particular verbal episodic memory. However the number of RCTs was limited, and most of the studies found negative results. Future studies should assess both effectiveness and tolerance of repeated doses administration, and individual variability in dose response (including baseline characteristics and potential genetic polymorphisms). One explanation for the limited number of recent RCTs with new psychostimulants seems to be the ethical debate surrounding pharmaceutical cognitive enhancement in healthy subjects. PMID:26187342

  17. Molecular Mechanisms of Enhanced Bacterial Growth on Hexadecane with Red Clay.

    PubMed

    Jung, Jaejoon; Jang, In-Ae; Ahn, Sungeun; Shin, Bora; Kim, Jisun; Park, Chulwoo; Jee, Seung Cheol; Sung, Jung-Suk; Park, Woojun

    2015-11-01

    Red clay was previously used to enhance bioremediation of diesel-contaminated soil. It was speculated that the enhanced degradation of diesel was due to increased bacterial growth. In this study, we selected Acinetobacter oleivorans DR1, a soil-borne degrader of diesel and alkanes, as a model bacterium and performed transcriptional analysis using RNA sequencing to investigate the cellular response during hexadecane utilization and the mechanism by which red clay promotes hexadecane degradation. We confirmed that red clay promotes the growth of A. oleivorans DR1 on hexadecane, a major component of diesel, as a sole carbon source. Addition of red clay to hexadecane-utilizing DR1 cells highly upregulated β-oxidation, while genes related to alkane oxidation were highly expressed with and without red clay. Red clay also upregulated genes related to oxidative stress defense, such as superoxide dismutase, catalase, and glutaredoxin genes, suggesting that red clay supports the response of DR1 cells to oxidative stress generated during hexadecane utilization. Increased membrane fluidity in the presence of red clay was confirmed by fatty acid methyl ester analysis at different growth phases, suggesting that enhanced growth on hexadecane could be due to increased uptake of hexadecane coupled with upregulation of downstream metabolism and oxidative stress defense. The monitoring of the bacterial community in soil with red clay for a year revealed that red clay stabilized the community structure. PMID:25956940

  18. Modeling permeability enhancement due to coupled Thermal-Hydrological-Mechanical processes in Geothermal Reservoirs

    NASA Astrophysics Data System (ADS)

    Rapaka, S.; Kelkar, S.; Zyvoloski, G.; Pawar, R. J.

    2010-12-01

    The connectivity and accessible surface area of flowing fractures, whether natural or man-made, is possibly the single most important factor, after temperature, which determines the feasibility of a geothermal reservoir. Rock deformation and in-situ stress changes induced by injected fluids can enhance the permeability and accessible surface area of the geothermal formation, while simultaneously increasing the likelihood of premature thermal breakthrough. Hence, the ability to accurately model the fracture-stress interaction in the presence of variations in temperature and fluid pressure is critical in effective reservoir development and management strategies. We will describe a general purpose computational code, FEHM, developed for this purpose, that models coupled thermal-hydrological-mechanical processes during multi-phase fluid flow and transport in fractured porous media. The code incorporates several models of fracture aperture and stress behavior combined with permeability relationships. We provide field scale examples of applications to geothermal systems to demonstrate the utility of the method. The first example studies the role played by thermal and pore-pressure effects in enhancing the permeability in the near-wellbore region. In the second example, we will study permeability enhancement due to shear stresses farther away from the wellbore.

  19. Reduced expression IRF7 in nasal epithelial cells from smokers as a potential mechanism mediating enhanced susceptibility to influenza

    EPA Science Inventory

    Rationale: Smokers are more susceptible to viral infections, including influenza virus, yet the mechanisms mediating this effect are not known. Methods: We have established an in vitro model of differentiated nasal epithelial cells from smokers, which maintain enhanced levels...

  20. Electromagnetic modelling of Raman enhancement from nanoscale substrates: a route to estimation of the magnitude of the chemical enhancement mechanism in SERS.

    PubMed

    Brown, Richard J C; Wang, Jian; Tantra, Ratna; Yardley, Rachel E; Milton, Martin J T

    2006-01-01

    Despite widespread use for more than two decades, the SERS phenomenon has defied accurate physical and chemical explanation. The relative contributions from electronic and chemical mechanisms are difficult to quantify and are often not reproduced under nominally similar experimental conditions. This work has used electromagnetic modelling to predict the Raman enhancement expected from three configurations: metal nanoparticles, structured metal surfaces, and sharp metal tips interacting with metal surfaces. In each case, parameters such as artefact size, artefact separation and incident radiation wavelength have been varied and the resulting electromagnetic field modelled. This has yielded an electromagnetic description of these configurations with predictions of the maximum expected Raman enhancement, and hence a prediction of the optimum substrate configuration for the SERS process. When combined with experimental observations of the dependence of Raman enhancement with changing ionic strength, the modelling results have allowed a novel estimate of the size of the chemical enhancement mechanism to be produced. PMID:16833118

  1. Integrated Surface Topography Characterization of Variously Polished Niobium for Superconducting Particle Accelerators

    SciTech Connect

    Hui Tian, Charles Reece, Michael Kelley, G. Ribeill

    2009-05-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro-and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents flow. Interior surface chemical polishing (BCP/EP) to remove mechanical damage leaves surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely-used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is being used to distinguish the scale-dependent smoothing effects. The topographical evolution of the Nb surface as a function of different steps of EP is reported, resulting in a novel qualitative and quantitative description of Nb surface topography.

  2. Enhanced mechanical strength and electrical conductivity of carbon-nanotube/TiC hybrid fibers

    NASA Astrophysics Data System (ADS)

    Yi, Qinghua; Dai, Xiao; Zhao, Jie; Sun, Yinghui; Lou, Yanhui; Su, Xiaodong; Li, Qingwen; Sun, Baoquan; Zheng, Honghe; Shen, Mingrong; Wang, Qinghua; Zou, Guifu

    2013-07-01

    We report the synthesis of carbon nanotube/TiC hybrid fibers using a polymer-assisted chemical solution approach. Ti metal ions are bound to aqueous polyethyleneimine (PEI) to form precursor solution. Amphiphilic PEI with Ti easily permeates the CNT fibers. Upon annealing in a controlled atmosphere, a homogeneous TiC network is formed in the CNT fibers. The obtained CNT/TiC hybrid fibers show prominent enhancement in mechanical strength and electrical conductivity. The tensile strength and conductivity of CNT/TiC fibers can be improved to 0.67 GPa and 1650 S cm-1 at room temperature, respectively. More importantly, a tensile modulus as high as 420 GPa has been achieved for the CNT/TiC fibers. Analysis shows that the cross-linking matrix of hard TiC plays a significant role in the improvement of mechanical strength. Furthermore, the electrons are transported in the CNT/TiC fiber by a three dimensional hopping mechanism.We report the synthesis of carbon nanotube/TiC hybrid fibers using a polymer-assisted chemical solution approach. Ti metal ions are bound to aqueous polyethyleneimine (PEI) to form precursor solution. Amphiphilic PEI with Ti easily permeates the CNT fibers. Upon annealing in a controlled atmosphere, a homogeneous TiC network is formed in the CNT fibers. The obtained CNT/TiC hybrid fibers show prominent enhancement in mechanical strength and electrical conductivity. The tensile strength and conductivity of CNT/TiC fibers can be improved to 0.67 GPa and 1650 S cm-1 at room temperature, respectively. More importantly, a tensile modulus as high as 420 GPa has been achieved for the CNT/TiC fibers. Analysis shows that the cross-linking matrix of hard TiC plays a significant role in the improvement of mechanical strength. Furthermore, the electrons are transported in the CNT/TiC fiber by a three dimensional hopping mechanism. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01857a

  3. Compound antimalarial ethosomal cataplasm: preparation, evaluation, and mechanism of penetration enhancement.

    PubMed

    Shen, Shuo; Liu, Shu-Zhi; Zhang, Yu-Shi; Du, Mao-Bo; Liang, Ai-Hua; Song, Li-Hua; Ye, Zu-Guang

    2015-01-01

    Malaria is still a serious public health problem in some parts of the world. The problems of recurrence and drug resistance are increasingly more serious. Thus, it is necessary to develop a novel antimalarial agent. The objectives of this study were to construct a novel compound antimalarial transdermal nanosystem-ethosomal cataplasm, to investigate its characteristics and efficiency, and to systematically explore the penetration-enhancing mechanisms of ethosomal cataplasm. Artesunate-loaded ethosomes and febrifugine-loaded ethosomes were prepared, and their characteristics were evaluated. Drug-loaded ethosomes were incorporated in the matrix of cataplasm to form the compound antimalarial ethosomal cataplasm. With the help of ethosomal technology, the accumulated permeation quantity of artesunate significantly increased at 8 hours after administration, which was 1.57 times as much as that of conventional cataplasm. Soon after administration, the ethosomal cataplasm could make a large quantity of antimalarial drug quickly penetrate through skin, then the remaining drug in the ethosomal cataplasm could be steadily released. These characteristics of ethosomal cataplasm are favorable for antimalarial drugs to kill Plasmodium spp. quickly and prevent the resurgence of Plasmodium spp. As expected, the ethosomal cataplasm showed good antimalarial efficiency in this experiment. The negative conversion rates were 100% and the recurrence rates were 0% at all dosages. The mechanism of penetration enhancement of the ethosomal cataplasm was systematically explored using an optics microscope, polarization microscope, and transmission electron microscopy. The microstructure, ultrastructure, and birefringent structure in skin were observed. Data obtained in this study showed that the application of ethosomal technology to antimalarial cataplasm could improve the transdermal delivery of drug, enhance the efficacy, and facilitate practical application in clinic. PMID:26170661

  4. Compound antimalarial ethosomal cataplasm: preparation, evaluation, and mechanism of penetration enhancement

    PubMed Central

    Shen, Shuo; Liu, Shu-Zhi; Zhang, Yu-Shi; Du, Mao-Bo; Liang, Ai-Hua; Song, Li-Hua; Ye, Zu-Guang

    2015-01-01

    Malaria is still a serious public health problem in some parts of the world. The problems of recurrence and drug resistance are increasingly more serious. Thus, it is necessary to develop a novel antimalarial agent. The objectives of this study were to construct a novel compound antimalarial transdermal nanosystem–ethosomal cataplasm, to investigate its characteristics and efficiency, and to systematically explore the penetration-enhancing mechanisms of ethosomal cataplasm. Artesunate-loaded ethosomes and febrifugine-loaded ethosomes were prepared, and their characteristics were evaluated. Drug-loaded ethosomes were incorporated in the matrix of cataplasm to form the compound antimalarial ethosomal cataplasm. With the help of ethosomal technology, the accumulated permeation quantity of artesunate significantly increased at 8 hours after administration, which was 1.57 times as much as that of conventional cataplasm. Soon after administration, the ethosomal cataplasm could make a large quantity of antimalarial drug quickly penetrate through skin, then the remaining drug in the ethosomal cataplasm could be steadily released. These characteristics of ethosomal cataplasm are favorable for antimalarial drugs to kill Plasmodium spp. quickly and prevent the resurgence of Plasmodium spp. As expected, the ethosomal cataplasm showed good antimalarial efficiency in this experiment. The negative conversion rates were 100% and the recurrence rates were 0% at all dosages. The mechanism of penetration enhancement of the ethosomal cataplasm was systematically explored using an optics microscope, polarization microscope, and transmission electron microscopy. The microstructure, ultrastructure, and birefringent structure in skin were observed. Data obtained in this study showed that the application of ethosomal technology to antimalarial cataplasm could improve the transdermal delivery of drug, enhance the efficacy, and facilitate practical application in clinic. PMID:26170661

  5. A Novel Mechanism of Inherited TBG Deficiency: Mutation in a Liver-Specific Enhancer

    PubMed Central

    Ferrara, Alfonso Massimiliano; Pappa, Theodora; Fu, Jiao; Brown, Christopher D.; Peterson, April; Moeller, Lars C.; Wyne, Kathleen; White, Kevin P.; Pluzhnikov, Anna; Trubetskoy, Vassily; Nobrega, Marcelo; Weiss, Roy E.; Dumitrescu, Alexandra M.

    2015-01-01

    Context: T4-binding globulin (TBG), a protein secreted by the liver, is the main thyroid hormone (TH) transporter in human serum. TBG deficiency is characterized by reduced serum TH levels, but normal free TH and TSH and absent clinical manifestations. The inherited form of TBG deficiency is usually due to a mutation in the TBG gene located on the X-chromosome. Objective: Among the 75 families with X-chromosome-linked TBG deficiency identified in our laboratory, no mutations in the TBG gene were found in four families. The aim of the study was to identify the mechanism of TBG deficiency in these four families using biochemical and genetic studies. Design: Observational cohort, prospective. Setting: University research center. Patients: Four families with inherited TBG deficiency and no mutations in the TBG gene. Intervention: Clinical evaluation, thyroid function tests, and targeted resequencing of 1 Mb of the X-chromosome. Results: Next-generation sequencing identified a novel G to A variant 20 kb downstream of the TBG gene in all four families. In silico analysis predicted that the variant resides within a liver-specific enhancer. In vitro studies confirmed the enhancer activity of a 2.2-kb fragment of genomic DNA containing the novel variant and showed that the mutation reduces the activity of this enhancer. The affected subjects share a haplotype of 8 Mb surrounding the mutation, and the most recent common ancestor among the four families was estimated to be 19.5 generations ago (95% confidence intervals, 10.4–37). Conclusions: To our knowledge, the present study is the first report of an inherited endocrine disorder caused by a mutation in an enhancer region. PMID:25361180

  6. Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

    2015-12-01

    The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during substorms. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during substorms. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner magnetosphere. We obtained the following results. (1) Just after the substorm onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.

  7. HyDRa: polishing process convergence rate optimization.

    PubMed

    Salas, Luis; Luna, Esteban; Sohn, Erika; Ruiz, Elfego; Herrera, Joel

    2013-10-01

    In an effort to optimize the hydrodynamic radial (HyDRa) polishing process for applications where the amount of material that has to be removed implies long polishing times, we have developed a method to determine the optimum correction fraction that has to be made for a given error map, in terms of the level of determinism of the process, the number of iterations, and their associated polishing runs as well as run times. PMID:24085216

  8. Formation of a deposit on workpiece surface in polishing nonmetallic materials

    NASA Astrophysics Data System (ADS)

    Filatov, Yu. D.; Monteil, G.; Sidorko, V. I.; Filatov, O. Y.

    2013-05-01

    During the last decades in the theory of machining nonmetallic materials some serious advances have been achieved in the field of applying fundamental scientific approaches to the grinding and polishing technologies for high-quality precision surfaces of electronic components, optical systems, and decorative articles made of natural and synthetic stone [1-9]. These achievements include a cluster model of material removal in polishing dielectric workpieces [1-3, 6-7] and a physical-statistical model of formation of debris (wear) particles and removal thereof from a workpiece surface [8-10]. The aforesaid models made it possible to calculate, without recourse to Preston's linear law, the removal rate in polishing nonmetallic materials and the wear intensity for bound-abrasive tools. Equally important for the investigation of the workpiece surface generation mechanism and formation of debris particles are the kinetic functions of surface roughness and reflectance of glass and quartz workpiece surfaces, which have been established directly in the course of polishing. During the in situ inspection of a workpiece surface by laser ellipsometry [11] and reflectometry [12] it was found out that the periodic change of the light reflection coefficient of a workpiece surface being polished is attributed to the formation of fragments of a deposit consisting of work material particles (debris particles) and tool wear particles [13, 14]. The subsequent studies of the mechanism of interaction between the debris particles and wear particles in the tool-workpiece contact zone, which were carried out based on classical concepts [15, 16], yielded some unexpected results. It was demonstrated that electrically charged debris and wear particles, which are located in the coolant-filled gap between a tool and a workpiece, move by closed circular trajectories enclosed in spheres measuring less than one fifth of the gap thickness. This implies that the probability of the debris and wear

  9. Surface characteristics of posterior composites after polishing and toothbrushing.

    PubMed

    van Dijken, J W; Ruyter, I E

    1987-10-01

    The surface characteristics of eight posterior and two anterior composite resins were studied by SEM and profilometric tracings. The materials included both chemically cured and light-cured resin systems. Two posterior materials were microfilled composites; the others were conventional or hybrid types. The anterior composites were of conventional and hybrid types. At various steps in the procedures the following polishing/brushing treatments were evaluated: 1) dry polishing with Sof-lex discs followed by brushing with toothpaste; and 2) wet polishing with diamond pastes of increasing fineness, followed by brushing with toothpaste. The base line before the polishing/brushing procedures was obtained by wet polishing on silicon-carbide paper (4000 grit). All materials could be polished to a comparable smoothness by the Sof-lex discs, but this polishing procedure was associated with the development of an amorphous surface layer. Polishing with diamond pastes gave various results, with a 20-fold difference in surface roughness values from the smoothest to the roughest material. Toothbrushing after polishing with the Sof-lex system increased the surface roughness for all materials, but to various degrees. The two microfilled and four of the conventional posterior composites showed comparable surface roughness values, whereas two remaining posterior and the two anterior materials showed two to three times higher surface roughness values after toothbrushing. PMID:3478939

  10. Enhancing the mechanical properties of cement paste by growing in-situ fiber reinforcement during hydration

    NASA Astrophysics Data System (ADS)

    Constantinides, Margarita

    Efforts to improve the mechanical properties of concrete by modifying the cement paste matrix have focused entirely on strength enhancement. But the intrinsic brittleness of the cement paste matrix limits the possible improvement in the mechanical properties of concrete, and in particular the toughness of the material. Increasing the toughness of the cement paste matrix could lead to a reduction in flaw sensitivity by delaying unstable crack propagation. Consequently, the resistance of the material to cracking due to drying shrinkage, thermal shrinkage, expansive deterioration processes, and applied loads could increase considerably. The goal of this study was to grow in-situ fiber reinforcement in cement paste, a technique never before applied to cement-based materials, to enhance the toughness of the material. Ettringite, an existing, fiber-like hydration product was selected as the fiber reinforcement. Ettringite met all the necessary criteria to act as reinforcement in cement paste: adequate distribution in the matrix; adjustable volume fraction, aspect ratio and size; high stiffness along the fiber length; and finally compatibility with existing hydration products. Alkali-free accelerators were selected as the admixtures used to grow the ettringite in the cement paste. X-ray diffraction and scanning electron microscopy experiments were performed to study the volume fraction, distribution, size, and morphology of the ettringite crystals in the cement paste matrix (both plain and accelerator-containing). Mechanical tests (compression, splitting tension, flexural, compact tension) were used to evaluate the effect of the accelerators on the strength and toughness of cement paste. Microindentations on the surface of the cement paste matrix were performed to study the morphology of the cracks and the toughening mechanisms taking place. Through the characterization tests we identified that while more ettringite forms with the addition of the alkali-free accelerators

  11. Robotic Automation in Computer Controlled Polishing

    NASA Astrophysics Data System (ADS)

    Walker, D. D.; Yu, G.; Bibby, M.; Dunn, C.; Li, H.; Wu, Y.; Zheng, X.; Zhang, P.

    2016-02-01

    We first present a Case Study - the manufacture of 1.4 m prototype mirror-segments for the European Extremely Large Telescope, undertaken by the National Facility for Ultra Precision Surfaces, at the OpTIC facility operated by Glyndwr University. Scale-up to serial-manufacture demands delivery of a 1.4 m off-axis aspheric hexagonal segment with surface precision < 10 nm RMS every four days, compared with a typical year or more for an one-off part. This requires a radically-new approach to large optics fabrication, which will inevitably propagate into wider industrial optics. We report on how these ambitious requirements have stimulated an investigation into the synergy between robots and computer numerically controlled ('CNC') polishing machines for optical fabrication. The objective was not to assess which is superior. Rather, it was to understand for the first time their complementary properties, leading us to operate them together as a unit, integrated in hardware and software. Three key areas are reported. First is the novel use of robots to automate currently-manual operations on CNC polishing machines, to improve work-throughput, mitigate risk of damage to parts, and reduce dependence on highly-skilled staff. Second is the use of robots to pre-process surfaces prior to CNC polishing, to reduce total process time. The third draws the threads together, describing our vision of the automated manufacturing cell, where the operator interacts at cell rather than machine level. This promises to deliver a step-change in end-to-end manufacturing times and costs, compared with either platform used on its own or, indeed, the state-of-the-art used elsewhere.

  12. Enhanced mechanical strength and electrical conductivity of carbon-nanotube/TiC hybrid fibers.

    PubMed

    Yi, Qinghua; Dai, Xiao; Zhao, Jie; Sun, Yinghui; Lou, Yanhui; Su, Xiaodong; Li, Qingwen; Sun, Baoquan; Zheng, Honghe; Shen, Mingrong; Wang, Qinghua; Zou, Guifu

    2013-08-01

    We report the synthesis of carbon nanotube/TiC hybrid fibers using a polymer-assisted chemical solution approach. Ti metal ions are bound to aqueous polyethyleneimine (PEI) to form precursor solution. Amphiphilic PEI with Ti easily permeates the CNT fibers. Upon annealing in a controlled atmosphere, a homogeneous TiC network is formed in the CNT fibers. The obtained CNT/TiC hybrid fibers show prominent enhancement in mechanical strength and electrical conductivity. The tensile strength and conductivity of CNT/TiC fibers can be improved to 0.67 GPa and 1650 S cm(-1) at room temperature, respectively. More importantly, a tensile modulus as high as 420 GPa has been achieved for the CNT/TiC fibers. Analysis shows that the cross-linking matrix of hard TiC plays a significant role in the improvement of mechanical strength. Furthermore, the electrons are transported in the CNT/TiC fiber by a three dimensional hopping mechanism. PMID:23787809

  13. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties.

    PubMed

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-06-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ∼4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (∼60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications. PMID:27227818

  14. Development of Chitosan Scaffolds with Enhanced Mechanical Properties for Intestinal Tissue Engineering Applications

    PubMed Central

    Zakhem, Elie; Bitar, Khalil N.

    2015-01-01

    Massive resections of segments of the gastrointestinal (GI) tract lead to intestinal discontinuity. Functional tubular replacements are needed. Different scaffolds were designed for intestinal tissue engineering application. However, none of the studies have evaluated the mechanical properties of the scaffolds. We have previously shown the biocompatibility of chitosan as a natural material in intestinal tissue engineering. Our scaffolds demonstrated weak mechanical properties. In this study, we enhanced the mechanical strength of the scaffolds with the use of chitosan fibers. Chitosan fibers were circumferentially-aligned around the tubular chitosan scaffolds either from the luminal side or from the outer side or both. Tensile strength, tensile strain, and Young’s modulus were significantly increased in the scaffolds with fibers when compared with scaffolds without fibers. Burst pressure was also increased. The biocompatibility of the scaffolds was maintained as demonstrated by the adhesion of smooth muscle cells around the different kinds of scaffolds. The chitosan scaffolds with fibers provided a better candidate for intestinal tissue engineering. The novelty of this study was in the design of the fibers in a specific alignment and their incorporation within the scaffolds. PMID:26473937

  15. How actin crosslinking and bundling proteins cooperate to generate an enhanced cell mechanical response

    NASA Technical Reports Server (NTRS)

    Tseng, Yiider; Kole, Thomas P.; Lee, Jerry S H.; Fedorov, Elena; Almo, Steven C.; Schafer, Benjamin W.; Wirtz, Denis

    2005-01-01

    Actin-crosslinking proteins organize actin filaments into dynamic and complex subcellular scaffolds that orchestrate important mechanical functions, including cell motility and adhesion. Recent mutation studies have shown that individual crosslinking proteins often play seemingly non-essential roles, leading to the hypothesis that they have considerable redundancy in function. We report live-cell, in vitro, and theoretical studies testing the mechanical role of the two ubiquitous actin-crosslinking proteins, alpha-actinin and fascin, which co-localize to stress fibers and the basis of filopodia. Using live-cell particle tracking microrheology, we show that the addition of alpha-actinin and fascin elicits a cell mechanical response that is significantly greater than that originated by alpha-actinin or fascin alone. These live-cell measurements are supported by quantitative rheological measurements with reconstituted actin filament networks containing pure proteins that show that alpha-actinin and fascin can work in concert to generate enhanced cell stiffness. Computational simulations using finite element modeling qualitatively reproduce and explain the functional synergy of alpha-actinin and fascin. These findings highlight the cooperative activity of fascin and alpha-actinin and provide a strong rationale that an evolutionary advantage might be conferred by the cooperative action of multiple actin-crosslinking proteins with overlapping but non-identical biochemical properties. Thus the combination of structural proteins with similar function can provide the cell with unique properties that are required for biologically optimal responses.

  16. Enhanced densification, strength and molecular mechanisms in shock compressed porous silicon

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Vogler, Tracy J.

    2015-06-01

    In most porous materials, void collapse during shock compression couples mechanical energy to thermal energy. Increased temperature drives up pressures and lowers densities in the final Hugoniot states as compared to full-density samples. Some materials, however, exhibit an anomalous enhanced densification in their Hugoniot states when porosity is introduced. We have recently shown that silicon is such a material, and demonstrated a molecular mechanism for the effect using molecular simulation. We will review results from large-scale non-equilibrium molecular dynamics (NEMD) and Hugoniotstat simulations of shock compressed porous silicon, highlighting the mechanism by which porosity produces local shear which nucleate partial phase transition and localized melting at shock pressures below typical thresholds in these materials. Further, we will characterize the stress states and strength of the material as a function of porosity from 5 to 50 percent and with various porosity microstructures. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. Terminology extraction from medical texts in Polish

    PubMed Central

    2014-01-01

    Background Hospital documents contain free text describing the most important facts relating to patients and their illnesses. These documents are written in specific language containing medical terminology related to hospital treatment. Their automatic processing can help in verifying the consistency of hospital documentation and obtaining statistical data. To perform this task we need information on the phrases we are looking for. At the moment, clinical Polish resources are sparse. The existing terminologies, such as Polish Medical Subject Headings (MeSH), do not provide sufficient coverage for clinical tasks. It would be helpful therefore if it were possible to automatically prepare, on the basis of a data sample, an initial set of terms which, after manual verification, could be used for the purpose of information extraction. Results Using a combination of linguistic and statistical methods for processing over 1200 children hospital discharge records, we obtained a list of single and multiword terms used in hospital discharge documents written in Polish. The phrases are ordered according to their presumed importance in domain texts measured by the frequency of use of a phrase and the variety of its contexts. The evaluation showed that the automatically identified phrases cover about 84% of terms in domain texts. At the top of the ranked list, only 4% out of 400 terms were incorrect while out of the final 200, 20% of expressions were either not domain related or syntactically incorrect. We also observed that 70% of the obtained terms are not included in the Polish MeSH. Conclusions Automatic terminology extraction can give results which are of a quality high enough to be taken as a starting point for building domain related terminological dictionaries or ontologies. This approach can be useful for preparing terminological resources for very specific subdomains for which no relevant terminologies already exist. The evaluation performed showed that none of the

  18. Precision non-contact polishing tool

    DOEpatents

    Taylor, John S.

    1997-01-01

    A non-contact polishing tool that combines two orthogonal slurry flow geometries to provide flexibility in altering the shape of the removal footprint. By varying the relative contributions of the two flow geometries, the footprint shape can be varied between the characteristic shapes corresponding to the two independent flow regimes. In addition, the tool can include a pressure activated means by which the shape of the brim of the tool can be varied. The tool can be utilized in various applications, such as x-ray optical surfaces, x-ray lithography, lenses, etc., where stringent shape and finish tolerances are required.

  19. Precision non-contact polishing tool

    DOEpatents

    Taylor, J.S.

    1997-01-07

    A non-contact polishing tool is disclosed that combines two orthogonal slurry flow geometries to provide flexibility in altering the shape of the removal footprint. By varying the relative contributions of the two flow geometries, the footprint shape can be varied between the characteristic shapes corresponding to the two independent flow regimes. In addition, the tool can include a pressure activated means by which the shape of the brim of the tool can be varied. The tool can be utilized in various applications, such as x-ray optical surfaces, x-ray lithography, lenses, etc., where stringent shape and finish tolerances are required. 5 figs.

  20. An experimental study of electrochemical polishing for micro-electro-discharge-machined stainless-steel stents.

    PubMed

    Lappin, Derry; Mohammadi, Abdolreza Rashidi; Takahata, Kenichi

    2012-02-01

    This paper reports electrochemical polishing (EP) of 316L stainless-steel structures patterned using micro-electro-discharge machining (μEDM) for application to stents including intelligent stents based on micro-electro-mechanical-systems technologies. For the process optimization, 10 μm deep cavities μEDMed on the planar material were polished in a phosphoric acid-based electrolyte with varying current densities and polishing times. The EP condition with a current density of 1.5 A/cm(2) for an EP time of 180 s exhibited the highest surface quality with an average roughness of 28 nm improved from~400 nm produced with high-energy μEDM. The EP of μEDMed surfaces was observed to produce almost constant smoothness regardless of the initial roughness determined by varying discharge energies. Energy-dispersive X-ray spectroscopy was performed on the μEDMed surfaces before and after EP. A custom rotational apparatus was used to polish tubular test samples including stent-like structures created using μEDM, demonstrating uniform removal of surface roughness and sharp edges from the structures. PMID:22183790

  1. Experimental Quantization of Surface and Sub-Surface Structure in Float Polished Crystalline Quartz

    NASA Astrophysics Data System (ADS)

    Soãres, Schubert; Namba, Yoshiharu

    Float polishing produces extremely flat (<λ/20) surfaces to atomic conformity over large areas. This process was applied to develop robust AT-cut, premium-Q, cultured, crystalline-quartz acoustic oscillators, which are normally highly susceptible to fracture from mechanical shock. The fabrication process was optimized to eliminate sub-surface damage, and to maximize the flexural strength of the crystals. We report premium results of a near-bulk value of stress-fracture threshold of 620 MPa, and a surface roughness of less than 0.2nm rms for 6.35mm diameter, 103.8µm thick samples float polished with colloidal silica. The remarkable surface quality produced by float polishing is combined with a 10-fold improvement in strength over blanks manufactured by the conventional CeO2 process. We also report on the characterization of the surfaces by atomic force microscopy, scatterometry, and photo acoustic spectroscopy where we see that deep 100µm removal eliminates damage from processing prior to the final float polish. These results are a significant improvement over the performance of commercially available resonators in equivalent tests.

  2. Evidence for enhanced cross-field transport mechanisms in the TCV Snowflake divertor

    NASA Astrophysics Data System (ADS)

    Vijvers, Wouter

    2015-11-01

    TCV experiments demonstrate that cross-field plasma transport is enhanced in the Snowflake divertor (SFD) compared to a standard single-null divertor (SND). This enhanced cross-field transport spreads the exhaust power over a larger surface area than can be achieved by magnetic geometry alone and, thereby, reduces the peak heat flux. Comparison of the experiments with modelling identifies steepened radial gradients, ExB drift effects, and βp-driven instabilities as the responsible transport mechanisms. The uncovered physics is also relevant to the SND and may help improve predictive models for the target profiles in ITER and DEMO. In SFD variants with an X-point in the scrape-off layer (SOL), part of the heat flux profile is split off and redirected to an additional target. The resulting steepened radial gradients enhance cross-field diffusion. This is confirmed by EMC3-Eirene simulations, which show a factor two reduction of the parallel heat flux, even if diffusivities remain constant. Theoretical analysis predicts enhanced ExB drifts in the SFD by increased poloidal gradients of the temperature and density. The predictions are confirmed by target heat and particle flux measurements in dedicated experiments with both toroidal field directions. Cross-field convection by curvature-driven modes at high βp (``churning modes'') explains the large fluxes into the private flux region of the SFD. This activates the extra targets and reduces the peak power to the primary targets up to a factor four. This mechanism is expected to be most effective when the divertor conditions are most severe: near the separatrix of a narrow, high-pressure SOL of a large tokamak. These and other alternative divertor configurations thus provide potential solutions to the power exhaust challenge, as well as laboratories to study SOL transport, one of the most important topics in tokamak research. This project was carried out with financial support from NWO. The work was carried out within

  3. Evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    NASA Astrophysics Data System (ADS)

    Candela, T.; Brodsky, E. E.; Marone, C.; Elsworth, D.

    2013-12-01

    Dynamic permeability change by seismic waves is a well-established natural phenomenon yet the mechanism remains poorly understood. We investigate the mechanism by generating well-controlled repeatable permeability enhancement in a laboratory experiment. Each experiment proceeded as: (1) pore pressure oscillations, simulating dynamic stresses, were applied at one end of intact Berea sandstone samples under triaxial stresses of tens of megapascals, (2) samples were fractured within the apparatus, and (3) pore pressure oscillations resumed post-fracturing. In this way, both the fracture and porous media response to the dynamic stresses were investigated. In addition, we controled the mobility of fine particles by adjusting the pore fluid chemistry (deionized water, and brines of: NaCl 5%, NaCl 35%, CaCl2 5%). Our results are consistent with natural observations. Dynamic stressing produces an immediate permeability enhancement ranging from 1-60%, which scales with the amplitude of the dynamic strain, 7*10^-7 to 7*10^-6, followed by a progressive permeability recovery. In our experiments a flow-dependent mechanism associated with mobilization of fines appears to control both the magnitude of the permeability enhancement and the recovery rate. Both processes operate at two time scales, i.e., fast flushing/unclogging of the fines during the pore pressure oscillations and progressive clogging of the pore throats by particle migration, and were influenced by the fluid chemistry. The dynamic permeability changes were not associated with permanent deformation. We show that: 1) injection of unequilibrated fluids favors particle mobilization, and 2) transient permeability change results from the migration of fines which in turn results from dynamic stressing. Our results suggest that areas where pore fluids are in disequilibrium should be more sensitive to dynamic stressing. Interestingly, early observations of dynamic earthquake-triggering revealed preferential triggering in

  4. Paper-like graphene-Ag composite films with enhanced mechanical and electrical properties.

    PubMed

    Gao, Rungang; Hu, Nantao; Yang, Zhi; Zhu, Qirong; Chai, Jing; Su, Yanjie; Zhang, Liying; Zhang, Yafei

    2013-01-01

    In this paper, we have reported that paper-like graphene-Ag composite films could be prepared by a facile and novel chemical reduction method at a large scale. Using ascorbic acid as a reducing agent, graphene oxide films dipped in Ag+ aqueous solutions can be easily reduced along with the decoration of different sizes of Ag particles distributed uniformly. The results reveal that the obtained films exhibit improved mechanical properties with the enhancement of tensile strength and Young's modulus by as high as 82% and 136%, respectively. The electrical properties of graphene-Ag composite films were studied as well, with the sheet resistance of which reaching lower than approximately 600 Ω/□. The graphene-Ag composite films can be expected to find interesting applications in the area of nanoelectronics, sensors, transparent electrodes, supercapacitors, and nanocomposites. PMID:23324465

  5. Controlled Thermal-Mechanical Processing of Tubes and Pipes for Enhanced Manufacturing and Performance

    SciTech Connect

    Kolarik, Robert V.

    2005-11-11

    The Alloy Steel Business of The Timken Company won an award for the controlled thermo-mechanical processing (CTMP) project and assembled a strong international public/private partnership to execute the project. The premise of the CTMP work was to combine Timken's product understanding with its process expertise and knowledge of metallurgical and deformation fundamentals developed during the project to build a predictive process design capability. The CTMP effort succeeded in delivering a pc-based capability in the tube optimization model, with a virtual pilot plant (VPP) feature to represent the desired tube making process to predict the resultant microstructure tailored for the desired application. Additional tasks included a system for direct, online measurement of grain size and demonstration of application of CTMP via robotically enhanced manufacturing.

  6. Flow in porous media, phase and ultralow interfacial tensions: Mechanisms of enhanced petroleum recovery

    SciTech Connect

    Davis, H.T.; Scriven, L.E.

    1991-07-01

    A major program of university research, longer-ranged and more fundamental in approach than industrial research, into basic mechanisms of enhancing petroleum recovery and into underlying physics, chemistry, geology, applied mathematics, computation, and engineering science has been built at Minnesota. The original focus was surfactant-based chemical flooding, but the approach taken was sufficiently fundamental that the research, longer-ranged than industrial efforts, has become quite multidirectional. Topics discussed are volume controlled porosimetry; fluid distribution and transport in porous media at low wetting phase saturation; molecular dynamics of fluids in ultranarrow pores; molecular dynamics and molecular theory of wetting and adsorption; new numerical methods to handle initial and boundary conditions in immiscible displacement; electron microscopy of surfactant fluid microstructure; low cost system for animating liquid crystallites viewed with polarized light; surfaces of constant mean curvature with prescribed contact angle.

  7. Micro-electro-mechanically tunable metamaterial with enhanced electro-optic performance

    SciTech Connect

    Pitchappa, Prakash; Pei Ho, Chong; Lin, Yu-Sheng; Lee, Chengkuo; Kropelnicki, Piotr; Singh, Navab; Huang, Chia-Yi

    2014-04-14

    We experimentally demonstrate a micro-electro-mechanically tunable metamaterial with enhanced electro-optical performance by increasing the number of movable cantilevers in the symmetrical split ring resonator metamaterial unit cell. Simulations were carried out to understand the interaction of the incident terahertz radiation with out-of-plane deforming metamaterial resonator. In order to improve the overall device performance, the number of released cantilever in a unit cell was increased from one to two, and it was seen that the tunable range was doubled and the switching contrast improved by a factor of around five at 0.7 THz. This simple design approach can be adopted for a wide range of high performance electro-optical devices such as continuously tunable filters, modulators, and electro-optic switches to enable future photonic circuit applications.

  8. Engineering the Cyanobacterial Carbon Concentrating Mechanism for Enhanced CO2 Capture and Fixation

    SciTech Connect

    Sandh, Gustaf; Cai, Fei; Shih, Patrick; Kinney, James; Axen, Seth; Salmeen, Annette; Zarzycki, Jan; Sutter, Markus; Kerfeld, Cheryl

    2011-06-02

    In cyanobacteria CO2 fixation is localized in a special proteinaceous organelle, the carboxysome. The CO2 fixation enzymes are encapsulated by a selectively permeable protein shell. By structurally and functionally characterizing subunits of the carboxysome shell and the encapsulated proteins, we hope to understand what regulates the shape, assembly and permeability of the shell, as well as the targeting mechanism and organization of the encapsulated proteins. This knowledge will be used to enhance CO2 fixation in both cyanobacteria and plants through synthetic biology. The same strategy can also serve as a template for the production of modular synthetic bacterial organelles. Our research is conducted using a variety of techniques such as genomic sequencing and analysis, transcriptional regulation, DNA synthesis, synthetic biology, protein crystallization, Small Angle X-ray Scattering (SAXS), protein-protein interaction assays and phenotypic characterization using various types of cellular imaging, e.g. fluorescence microscopy, Transmission Electron Microscopy (TEM), and Soft X-ray Tomography (SXT).

  9. CO/sub 2/-laser polishing of fused silica surfaces for increased laser damage resistance at 1. 06. mu. m

    SciTech Connect

    Temple, P.A.; Milam, D.; Lowdermilk, W.H.

    1980-04-03

    Bare fused silica surfaces were prepared by subjecting the mechanically polished surface to a rastered cw CO/sub 2/ laser beam. Analysis shows that this processing causes: (a) removal of a uniform layer of fused silica; and (b) a probable re-fusing or healing of existing subsurface fractures. The fused silica removal rate is found to be a function of the laser intensity and scan rate. These surfaces are seen to have very low scatter and to be very smooth. In addition, they have exhibited entrance surface damage thresholds at 1.06 ..mu..m, and 1 nsec, which are substantially above those seen on the mechanically polished surface. When damage does occur, it tends to be at a few isolated points rather than the general uniform damage seen on the mechanicaly polished part. In addition to the damage results, we will discuss an observational technique used for viewing these surfaces which employs dark-field illumination.

  10. Mechanisms Mediating Enhanced Neutralization Efficacy of Staphylococcal Enterotoxin B by Combinations of Monoclonal Antibodies*

    PubMed Central

    Dutta, Kaushik; Varshney, Avanish K.; Franklin, Matthew C.; Goger, Michael; Wang, Xiaobo; Fries, Bettina C.

    2015-01-01

    Staphylococcal enterotoxin B (SEB) is a superantigen that cross-links the major histocompatibility complex class II and specific V-β chains of the T-cell receptor, thus forming a ternary complex. Developing neutralizing mAb to disrupt the ternary complex and abrogate the resulting toxicity is a major therapeutic challenge because SEB is effective at very low concentrations. We show that combining two SEB-specific mAbs enhances their efficacy, even though one of the two mAbs by itself has no effect on neutralization. Crystallography was employed for fine-mapping conformational epitopes in binary and ternary complexes between SEB and Fab fragments. NMR spectroscopy was used to validate and identify subtle allosteric changes induced by mAbs binding to SEB. The mapping of epitopes established that a combination of different mAbs can enhance efficacy of mAb-mediated protection from SEB induced lethal shock by two different mechanisms: one mAb mixture promoted clearance of the toxin both in vitro and in vivo by FcR-mediated cross-linking and clearance, whereas the other mAb mixture induced subtle allosteric conformational changes in SEB that perturbed formation of the SEB·T-cell receptor·major histocompatibility complex class II trimer. Finally structural information accurately predicted mAb binding to other superantigens that share conformational epitopes with SEB. Fine mapping of conformational epitopes is a powerful tool to establish the mechanism and optimize the action of synergistic mAb combinations. PMID:25572397

  11. Mechanisms mediating enhanced neutralization efficacy of staphylococcal enterotoxin B by combinations of monoclonal antibodies.

    PubMed

    Dutta, Kaushik; Varshney, Avanish K; Franklin, Matthew C; Goger, Michael; Wang, Xiaobo; Fries, Bettina C

    2015-03-13

    Staphylococcal enterotoxin B (SEB) is a superantigen that cross-links the major histocompatibility complex class II and specific V-β chains of the T-cell receptor, thus forming a ternary complex. Developing neutralizing mAb to disrupt the ternary complex and abrogate the resulting toxicity is a major therapeutic challenge because SEB is effective at very low concentrations. We show that combining two SEB-specific mAbs enhances their efficacy, even though one of the two mAbs by itself has no effect on neutralization. Crystallography was employed for fine-mapping conformational epitopes in binary and ternary complexes between SEB and Fab fragments. NMR spectroscopy was used to validate and identify subtle allosteric changes induced by mAbs binding to SEB. The mapping of epitopes established that a combination of different mAbs can enhance efficacy of mAb-mediated protection from SEB induced lethal shock by two different mechanisms: one mAb mixture promoted clearance of the toxin both in vitro and in vivo by FcR-mediated cross-linking and clearance, whereas the other mAb mixture induced subtle allosteric conformational changes in SEB that perturbed formation of the SEB·T-cell receptor·major histocompatibility complex class II trimer. Finally structural information accurately predicted mAb binding to other superantigens that share conformational epitopes with SEB. Fine mapping of conformational epitopes is a powerful tool to establish the mechanism and optimize the action of synergistic mAb combinations. PMID:25572397

  12. Mechanism of Selenium-Induced Inhibition of Arsenic-Enhanced UVR Carcinogenesis in Mice

    PubMed Central

    Burns, Fredric J.; Rossman, Toby; Vega, Katherine; Uddin, Ahmed; Vogt, Stefan; Lai, Barry; Reeder, Richard J.

    2008-01-01

    Background Hairless mice that ingested arsenite in drinking water exhibited more than a 5-fold enhancement of ultraviolet radiation (UVR) carcinogenesis, whereas arsenite alone was carcinogenically inactive. Dietary organoselenium blocked the cancer enhancement effect of arsenic but not cancer induction by UVR. Objective In this study we sought to explain selenium blockage of As enhancement by establishing the extent that As and Se tissue distributions are coincident or divergent. Methods We used the X-ray fluorescence microprobe at the Advanced Photon Source (Argonne National Laboratory) to probe sections of skin and liver from hairless mice exposed to a) UVR, b) UVR + As, c) UVR + organoselenium, or d) UVR + As + organoselenium. Results We found elevated levels of As in the skin epithelium (hair follicles and epidermis) and diffusely in the liver of mice exposed to UVR + As. Arsenic was entirely absent in skin in mice exposed to UVR + As + organoselenium, but a diffuse low level was seen in the liver. As and Se locations were consistently divergent in skin; As was more diffusely distributed, whereas Se was strongly associated with membranes. X-ray absorption near-edge spectra are consistent with the presence of the seleno-bis(S-glutathionyl) arsinium ion in the liver. Conclusions Supplemental Se was uncommonly effective at preventing even a trace of As in skin at 14 or 196 days of continuous exposure to As in drinking water. Traces of the seleno-bis(S-glutathionyl) arsinium ion in the liver suggested that formation of this compound was more likely to be responsible for the As-blocking effect of Se than was a mechanism based on antioxidation. PMID:18560523

  13. Computer-based creativity enhanced conceptual design model for non-routine design of mechanical systems

    NASA Astrophysics Data System (ADS)

    Li, Yutong; Wang, Yuxin; Duffy, Alex H. B.

    2014-11-01

    Computer-based conceptual design for routine design has made great strides, yet non-routine design has not been given due attention, and it is still poorly automated. Considering that the function-behavior-structure(FBS) model is widely used for modeling the conceptual design process, a computer-based creativity enhanced conceptual design model(CECD) for non-routine design of mechanical systems is presented. In the model, the leaf functions in the FBS model are decomposed into and represented with fine-grain basic operation actions(BOA), and the corresponding BOA set in the function domain is then constructed. Choosing building blocks from the database, and expressing their multiple functions with BOAs, the BOA set in the structure domain is formed. Through rule-based dynamic partition of the BOA set in the function domain, many variants of regenerated functional schemes are generated. For enhancing the capability to introduce new design variables into the conceptual design process, and dig out more innovative physical structure schemes, the indirect function-structure matching strategy based on reconstructing the combined structure schemes is adopted. By adjusting the tightness of the partition rules and the granularity of the divided BOA subsets, and making full use of the main function and secondary functions of each basic structure in the process of reconstructing of the physical structures, new design variables and variants are introduced into the physical structure scheme reconstructing process, and a great number of simpler physical structure schemes to accomplish the overall function organically are figured out. The creativity enhanced conceptual design model presented has a dominant capability in introducing new deign variables in function domain and digging out simpler physical structures to accomplish the overall function, therefore it can be utilized to solve non-routine conceptual design problem.

  14. Mechanism of multivalent nanoparticle encounter with HIV-1 for potency enhancement of peptide triazole virus inactivation.

    PubMed

    Rosemary Bastian, Arangassery; Nangarlia, Aakansha; Bailey, Lauren D; Holmes, Andrew; Kalyana Sundaram, R Venkat; Ang, Charles; Moreira, Diogo R M; Freedman, Kevin; Duffy, Caitlin; Contarino, Mark; Abrams, Cameron; Root, Michael; Chaiken, Irwin

    2015-01-01

    Entry of HIV-1 into host cells remains a compelling yet elusive target for developing agents to prevent infection. A peptide triazole (PT) class of entry inhibitor has previously been shown to bind to HIV-1 gp120, suppress interactions of the Env protein at host cell receptor binding sites, inhibit cell infection, and cause envelope spike protein breakdown, including gp120 shedding and, for some variants, virus membrane lysis. We found that gold nanoparticle-conjugated forms of peptide triazoles (AuNP-PT) exhibit substantially more potent antiviral effects against HIV-1 than corresponding peptide triazoles alone. Here, we sought to reveal the mechanism of potency enhancement underlying nanoparticle conjugate function. We found that altering the physical properties of the nanoparticle conjugate, by increasing the AuNP diameter and/or the density of PT conjugated on the AuNP surface, enhanced potency of infection inhibition to impressive picomolar levels. Further, compared with unconjugated PT, AuNP-PT was less susceptible to reduction of antiviral potency when the density of PT-competent Env spikes on the virus was reduced by incorporating a peptide-resistant mutant gp120. We conclude that potency enhancement of virolytic activity and corresponding irreversible HIV-1 inactivation of PTs upon AuNP conjugation derives from multivalent contact between the nanoconjugates and metastable Env spikes on the HIV-1 virus. The findings reveal that multispike engagement can exploit the metastability built into virus the envelope to irreversibly inactivate HIV-1 and provide a conceptual platform to design nanoparticle-based antiviral agents for HIV-1 specifically and putatively for metastable enveloped viruses generally. PMID:25371202

  15. Probing Mechanisms for Enzymatic Activity Enhancement of Organophosphorus Hydrolase in Functionalized Mesoporous Silica

    SciTech Connect

    Chen, Baowei; Lei, Chenghong; Shin, Yongsoon; Liu, Jun

    2009-12-25

    We have previously reported that organophosphorus hydrolase (OPH) can be spontaneously entrapped in functionalized mesoporous silica (FMS) with HOOC - as the functional groups and the entrapped OPH in HOOC-FMS showed enhanced enzyme specific activity. This work is to study the mechanisms that why OPH entrapped in FMS displayed the enhanced activity in views of OPH-FMS interactions using spectroscopic methods. The circular dichroism (CD) spectra show that, comparing to the secondary structure of OPH free in solution, OPH in HOOC-FMS displayed increased a-helix/b-strand transition of OPH with increased OPH loading density. The fluorescence emission spectra of Trp residues were used to assess the tertiary structural changes of the enzyme. There was a 42% increase in fluorescence. This is in agreement with the fact that the fluorescence intensity of OPH was increased accompanying with the increased OPH activity when decreasing urea concentrations in solution. The steady-state anisotropy was increased after OPH entrapping in HOOC-FMS comparing to the free OPH in solution, indicating that protein mobility was reduced upon entrapment. The solvent accessibility of Trp residues of OPH was probed by using acrylamide as a collisional quencher. Trp residues of OPH-FMS had less solvent exposure comparing with free OPH in solution due to its electrostatical binding to HOOC-FMS thereby displaying the increased fluorescence intensity. These results suggest the interactions of OPH with HOOC-FMS resulted in the protein immobilization and a favorable conformational change for OPH in the crowded confinement space and accordingly the enhanced activity.

  16. Vortex mechanism of heat transfer enhancement in a channel with spherical and oval dimples

    NASA Astrophysics Data System (ADS)

    Turnow, J.; Kornev, N.; Isaev, S.; Hassel, E.

    2011-03-01

    Vortex mechanism of heat transfer enhancement in a narrow channel with dimples has been investigated numerically using LES and URANS methods. The flow separation results in a formation of vortex structures which significantly enhance heat transfer on dimpled surfaces leading to a small increase in pressure loss. The heat transfer can be significantly increased by rounding the dimple edge and use of oval dimples. To get a deep insight into flow physics LES is performed for single phase flow in a channel with a spherical dimple. The instantaneous vortex formation and separation are investigated in and around the dimple area. Considered are Reynolds numbers (based on dimple print diameter) ReD = 20,000 and ReD = 40,000 the depth to print diameter ratio of Δ = 0.26. Frequency analysis of LES data revealed the presence of dominating frequencies in unsteady flow oscillations. Direct analysis of the flow field revealed the presence of coherent vortex structure inclined to the mean flow. The structure changes its orientation in time causing the long period oscillations with opposite-of-phase motion. Three dimensional proper orthogonal decomposition (POD) analysis is carried out on LES pressure and velocity fields to identify spatio-temporal structures hidden in the random fluctuations. Tornado-like spatial POD structures have been determined inside dimples.

  17. Emission enhancement mechanism of GaN:Eu by Mg codoping

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Hiroto; Takagi, Yasufumi; Otani, Tatsuki; Okada, Hiroshi; Wakahara, Akihiro

    2013-01-01

    Mg codoping into Eu-doped GaN strongly affects the two dominant optical sites A (620.3 nm) and B (622.3 nm) and dramatically improves the optical characteristics obtained from Eu3+ ions. To clarify the mechanism of the enhanced emission, the effects of the Mg concentration on the excitation and emission processes were evaluated by considering the excitation power dependence of photoluminescence (PL) and time-resolved PL at various temperatures. The excitation cross section σex, which reflected the excitation process, did not depend on the Mg concentration but strongly on the optical site, which was attributed to the different energy transfer processes of the two optical sites. σex for site A was three times larger than that for site B, indicating higher excitation efficiency for site A. Mg codoping dramatically increased the number of Eu ions in site A that remain active at room temperature (RT) and the 5D0 lifetime at RT, indicating the suppression of nonradiative components during the emission process. Therefore, the optical properties were markedly enhanced by Mg codoping.

  18. Chitosan nanocomposite films: enhanced electrical conductivity, thermal stability, and mechanical properties.

    PubMed

    Marroquin, Jason B; Rhee, K Y; Park, S J

    2013-02-15

    A novel, high-performance Fe(3)O(4)/MWNT/Chitosan nanocomposite has been prepared by a simple solution evaporation method. A significant synergistic effect of Fe(3)O(4) and MWNT provided enhanced electrical conductivity, mechanical properties, and thermal stability on the nanocomposites. A 5% (wt) loading of Fe(3)O(4)/MWNT in the nanocomposite increased conductivity from 5.34×10(-5) S/m to 1.49×10(-2) S/m compared to 5% (wt) MWNT loadings. The Fe(3)O(4)/MWNT/Chitosan films also exhibited increases in tensile strength and modulus of 70% and 155%, respectively. The integral procedure decomposition temperature (IPDT) was enhanced from 501 °C to 568 °C. These effects resulted from a number of factors: generation of a greater number of conductive channels through interactions between MWNT and Fe(3)O(4) surfaces, a higher relative crystallinity, the antiplasticizing effects of Fe(3)O(4), a restricted mobility and hindrance of depolymerization of the Chitosan chain segments, as well as uniform distribution, improved dispersion, and strong interfacial adhesion between the MWNT and Chitosan matrix. PMID:23399220

  19. Enhanced thermoelectric properties of bismuth sulfide polycrystals prepared by mechanical alloying and spark plasma sintering

    SciTech Connect

    Zhao Lidong; Zhang Boping Liu Weishu; Zhang Hailong; Li Jingfeng

    2008-12-15

    Bismuth sulfide powders were synthesized by mechanical alloying (MA) and then consolidated by spark plasma sintering (SPS) technique. In order to improve the electrical transport properties of bismuth sulfides, the carrier concentration was optimized by modifying chemical composition of sulfur through producing sulfur vacancies, and the carrier mobility was enhanced by a two-step SPS as a hot-forging process through increasing grain orientation. The electrical resistivity of bismuth sulfides was reduced to 10{sup -4} from 10{sup -2} {omega} m by optimizing sulfur content, and further lowered by hot-forging, whereby the power factor was significantly increased from 91 to 254 {mu}W/mK{sup 2}. The hot-forged Bi{sub 2}S{sub 2.90} sample showed the highest ZT=0.11 (at 523 K), which is higher than the reported value. The present work revealed that bismuth sulfide compounds as a promising candidate of thermoelectric materials can be synthesized by a simple process. - Abstract: Electrical properties of bismuth sulfides were improved by optimizing carrier concentration through modifying compositions of sulfur and enhancing carrier mobility through SPSed hot-forging. The ZT value of 0.11 was obtained, which is the maximum reported so far . Display Omitted.

  20. Enhancing combined biological nitrogen and phosphorus removal from wastewater by applying mechanically disintegrated excess sludge.

    PubMed

    Zubrowska-Sudol, Monika; Walczak, Justyna

    2015-06-01

    The goal of the study was to evaluate the possibility of applying disintegrated excess sludge as a source of organic carbon to enhance biological nitrogen and phosphorus removal. The experiment, performed in a sequencing batch reactor, consisted of two two-month series, without and with applying mechanically disintegrated excess sludge, respectively. The effects on carbon, nitrogen and phosphorus removal were observed. It was shown that the method allows enhancement of combined nitrogen and phosphorus removal. After using disintegrated sludge, denitrification effectiveness increased from 49.2 ± 6.8% to 76.2 ± 2.3%, which resulted in a decline in the NOx-N concentration in the effluent from the SBR by an average of 21.4 mg NOx-N/L. Effectiveness of biological phosphorus removal increased from 28.1 ± 11.3% to 96.2 ± 2.5%, thus resulting in a drop in the [Formula: see text] concentration in the effluent by, on average, 6.05 mg PO4(3-)-P/L. The application of disintegrated sludge did not deteriorate effluent quality in terms of COD and NH4(+)-N. The concentration of NH4(+)-N in both series averaged 0.16 ± 0.11 mg NH4(+)-N/L, and the concentration of COD was 15.36 ± 3.54 mg O2/L. PMID:25776916

  1. The Mechanism of Methylated Seed Oil on Enhancing Biological Efficacy of Topramezone on Weeds

    PubMed Central

    Zhang, Jinwei; Jaeck, Ortrud; Menegat, Alexander; Zhang, Zongjian; Gerhards, Roland; Ni, Hanwen

    2013-01-01

    Methylated seed oil (MSO) is a recommended adjuvant for the newly registered herbicide topramezone in China and also in other countries of the world, but the mechanism of MSO enhancing topramezone efficacy is still not clear. Greenhouse and laboratory experiments were conducted to determine the effects of MSO on efficacy, solution property, droplet spread and evaporation, active ingredient deposition, foliar absorption and translocation of topramezone applied to giant foxtail (Setaria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medic.). Experimental results showed that 0.3% MSO enhanced the efficacy of topramezone by 1.5-fold on giant foxtail and by 1.0-fold on velvetleaf. When this herbicide was mixed with MSO, its solution surface tension and leaf contact angle decreased significantly, its spread areas on weed leaf surfaces increased significantly, its wetting time was shortened on giant foxtail but not changed on velvetleaf, and less of its active ingredient crystal was observed on the treated weed leaf surfaces. MSO increased the absorption of topramezone by 68.9% for giant foxtail and by 45.9% for velvetleaf 24 hours after treatment. It also apparently promoted the translocation of this herbicide in these two weeds. PMID:24086329

  2. Micelle-enhanced and terbium-sensitized spectrofluorimetric determination of gatifloxacin and its interaction mechanism

    NASA Astrophysics Data System (ADS)

    Guo, Changchuan; Wang, Lei; Hou, Zhun; Jiang, Wei; Sang, Lihong

    2009-05-01

    A terbium-sensitized spectrofluorimetric method using an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), was developed for the determination of gatifloxacin (GFLX). A coordination complex system of GFLX-Tb 3+-SDBS was studied. It was found that SDBS significantly enhanced the fluorescence intensity of the complex (about 11-fold). Optimal experimental conditions were determined as follows: excitation and emission wavelengths of 331 and 547 nm, pH 7.0, 2.0 × 10 -4 mol l -1 terbium (III), and 2.0 × 10 -4 mol l -1 SDBS. The enhanced fluorescence intensity of the system (Δ If) showed a good linear relationship with the concentration of GFLX over the range of 5.0 × 10 -10 to 5.0 × 10 -8 mol l -1 with a correlation coefficient of 0.9996. The detection limit (3 σ) was determined as 6.0 × 10 -11 mol l -1. This method has been successfully applied to the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most of other methods reported, the rapid and simple procedure proposed in the text offers higher sensitivity, wider linear range, and better stability. The interaction mechanism of the system is also studied by the research of ultraviolet absorption spectra, surface tension, solution polarity and fluorescence polarization.

  3. Hippocampal molecular mechanisms involved in the enhancement of fear extinction caused by exposure to novelty.

    PubMed

    de Carvalho Myskiw, Jociane; Furini, Cristiane Regina Guerino; Benetti, Fernando; Izquierdo, Ivan

    2014-03-25

    Exposure to a novel environment enhances the extinction of contextual fear. This has been explained by tagging of the hippocampal synapses used in extinction, followed by capture of proteins from the synapses that process novelty. The effect is blocked by the inhibition of hippocampal protein synthesis following the novelty or the extinction. Here, we show that it can also be blocked by the postextinction or postnovelty intrahippocampal infusion of the NMDA receptor antagonist 2-amino-5-phosphono pentanoic acid; the inhibitor of calcium/calmodulin-dependent protein kinase II (CaMKII), autocamtide-2-related inhibitory peptide; or the blocker of L-voltage-dependent calcium channels (L-VDCCs), nifedipine. Inhibition of proteasomal protein degradation by β-lactacystin has no effect of its own on extinction or on the influence of novelty thereon but blocks the inhibitory effects of all the other substances except that of rapamycin on extinction, suggesting that their action depends on concomitant synaptic protein turnover. Thus, the tagging-and-capture mechanism through which novelty enhances fear extinction involves more molecular processes than hitherto thought: NMDA receptors, L-VDCCs, CaMKII, and synaptic protein turnover. PMID:24591622

  4. Mechanisms of action of hESC-secreted proteins that enhance human and mouse myogenesis.

    PubMed

    Yousef, Hanadie; Conboy, Michael J; Mamiya, Hikaru; Zeiderman, Matthew; Schlesinger, Christina; Schaffer, David V; Conboy, Irina M

    2014-08-01

    Adult stem cells grow poorly in vitro compared to embryonic stem cells, and in vivo stem cell maintenance and proliferation by tissue niches progressively deteriorates with age. We previously reported that factors produced by human embryonic stem cells (hESCs) support a robust regenerative capacity for adult and old mouse muscle stem/progenitor cells. Here we extend these findings to human muscle progenitors and investigate underlying molecular mechanisms. Our results demonstrate that hESC-conditioned medium enhanced the proliferation of mouse and human muscle progenitors. Furthermore, hESC-produced factors activated MAPK and Notch signaling in human myogenic progenitors, and Delta/Notch-1 activation was dependent on MAPK/pERK. The Wnt, TGF-β and BMP/pSmad1,5,8 pathways were unresponsive to hESC-produced factors, but BMP signaling was dependent on intact MAPK/pERK. c-Myc, p57, and p18 were key effectors of the enhanced myogenesis promoted by the hECS factors. To define some of the active ingredients of the hESC-secretome which may have therapeutic potential, a comparative proteomic antibody array analysis was performed and identified several putative proteins, including FGF2, 6 and 19 which as ligands for MAPK signaling, were investigated in more detail. These studies emphasize that a "youthful" signaling of multiple signaling pathways is responsible for the pro-regenerative activity of the hESC factors. PMID:25109702

  5. Molecular mechanisms of hyperthermia-induced apoptosis enhanced by withaferin A.

    PubMed

    Cui, Zheng-Guo; Piao, Jin-Lan; Rehman, Mati U R; Ogawa, Ryohei; Li, Peng; Zhao, Qing-Li; Kondo, Takashi; Inadera, Hidekuni

    2014-01-15

    Hyperthermia is a good therapeutic tool for non-invasive cancer therapy; however, its cytotoxic effects are not sufficient. In the present study, withaferin A (WA), a steroidal lactone derived from the plant Withania somnifera Dunal, has been investigated for its possible enhancing effects on hyperthermia-induced apoptosis. In HeLa cells, treatment with 0.5 or 1.0μM WA at 44°C for 30min induced significant apoptosis accompanied by decreased intracellular GSH/GSSG ratio and caspase-3 activation, while heat or WA alone did not induce such changes. The upregulation in apoptosis was significantly inhibited by glutathione monoethyl ester, a cell permeable glutathione precursor. Mitochondrial transmembrane potentials were dramatically decreased by the combined treatment, with increases in pro-apoptotic Bcl-2-family proteins tBid and Noxa, and downregulation of antiapoptotic Bcl-2 and Mcl-1. Combined treatment with hyperthermia and WA induced significant increases in JNK phosphorylation (p-JNK), and decreases in the phosphorylation of ERK (p-ERK) compared with either treatment alone. These results suggest that WA enhances hyperthermia-induced apoptosis via a mitochondria-caspase-dependent pathway; its underlying mechanism involves elevated intracellular oxidative stress, mitochondria dysfunction, and JNK activation. PMID:24321857

  6. Mechanisms of Enhanced Cell Killing at Low Doses: Implications for Radiation Risk

    SciTech Connect

    Dr. Peter J. Johnston; Dr. George D. Wilson

    2003-10-15

    We have shown that cell lethality actually measured after exposure to low-doses of low-LET radiation, is markedly enhanced relative to the cell lethality previously expected by extrapolation of the high-dose cell-killing response. Net cancer risk is a balance between cell transformation and cell kill and such enhanced lethality may more than compensate for transformation at low radiation doses over a least the first 10 cGy of low-LET exposure. This would lead to a non-linear, threshold, dose-risk relationship. Therefore our data imply the possibility that the adverse effects of small radiation doses (<10 cGy) could be overestimated in specific cases. It is now important to research the mechanisms underlying the phenomenon of low-dose hypersensitivity to cell killing, in order to determine whether this can be generalized to safely allow an increase in radiation exposure limits. This would have major cost-reduction implications for the whole EM program.

  7. Enhanced mechanical stability of interlayer dielectrics with self-organized molecular pores

    NASA Astrophysics Data System (ADS)

    Pandey, Akanksha

    final product. It has been shown in this thesis that the pores introduced through structural arrangement of atoms can provide much better mechanical and chemical reliability during the fabrication process as compared to the pores introduced through removal of large segments of material from the sample. Electrical properties of the material are measured using ellipsometer and changes in properties with processes like annealing and plasma exposure are discussed in detail. Mechanical properties of the material are measured using nano-indentation and ball indentation tests. To study the molecular structure and changes in molecular structure with processes like annealing, FTIR and XPS techniques are used. An alternative curing method for traditional subtractive films has also been proposed to enhance the material's resistance to viscoplastic deformation.

  8. Deterministic Computer-Controlled Polishing Process for High-Energy X-Ray Optics

    NASA Technical Reports Server (NTRS)

    Khan, Gufran S.; Gubarev, Mikhail; Speegle, Chet; Ramsey, Brian

    2010-01-01

    A deterministic computer-controlled polishing process for large X-ray mirror mandrels is presented. Using tool s influence function and material removal rate extracted from polishing experiments, design considerations of polishing laps and optimized operating parameters are discussed

  9. Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement.

    PubMed

    Takarada, Y; Hirano, Y; Ishige, Y; Ishii, N

    1997-11-01

    The relation between the eccentric force developed during a countermovement and the mechanical power output was studied in squatting exercises under nominally isotonic load (50% of 1-repetition maximum). The subjects (n = 5) performed squatting exercises with a countermovement at varied deceleration rates before lifting the load. The ground reaction force and video images were recorded to obtain the power output of the body. Net muscle moments acting at hip, knee, and ankle joints were calculated from video recordings by using inverse dynamics. When an intense deceleration was taken at the end of downward movement, large eccentric force was developed, and the mechanical power subsequently produced during the lifting movement was consistently larger than that produced without the countermovement. Both maximal and mean power outputs during concentric actions increased initially with the eccentric force, whereas they began to decline when the eccentric force exceeded approximately 1.4 times the sum of load and body weight. Video-image analysis showed that this characteristic relation was predominantly determined by the torque around the knee joint. Electromyographic analyses showed no consistent increase in time-averaged integrated electromyograph from vastus lateralis with the power output, suggesting that the enhancement of power output is primarily caused by the prestretch-induced improvement of an intrinsic force-generating capability of the agonist muscle. PMID:9375347

  10. The targeting mechanism of DHA ligand and its conjugate with Gemcitabine for the enhanced tumor therapy.

    PubMed

    Li, Siwen; Qin, Jingyi; Tian, Caiping; Cao, Jie; Fida, Guissi; Wang, Zhaohui; Chen, Haiyan; Qian, Zhiyu; Chen, Wei R; Gu, Yueqing

    2014-06-15

    Docosahexaenoic acid (DHA), an omega-3 C22 natural fatty acid serving as a precursor for metabolic and biochemical pathways, was reported as a targeting ligand of anticancer drugs. However, its tumor targeting ability and mechanism has not been claimed. Here we hypothesized that the uptake of DHA by tumor cells is related to the phosphatidylethanolamine (PE) contents in cell membranes. Thus, in this manuscript, the tumor-targeting ability of DHA was initially demonstrated in vitro and in vivo on different tumor cell lines by labeling DHA with fluorescence dyes. Subsequently, the tumor targeting ability was then correlated with the contents of PE in cell membranes to study the uptake mechanism. Further, DHA was conjugated with anticancer drug gemcitabine (DHA-GEM) for targeted tumor therapy. Our results demonstrated that DHA exhibited high tumor targeting ability and PE is the main mediator, which confirmed our hypothesis. The DHA-GEM displayed enhanced therapeutic efficacy than that of GEM itself, indicating that DHA is a promising ligand for tumor targeted therapy. PMID:25004114

  11. Security Enhancement Mechanism Based on Contextual Authentication and Role Analysis for 2G-RFID Systems

    PubMed Central

    Tang, Wan; Chen, Min; Ni, Jin; Yang, Ximin

    2011-01-01

    The traditional Radio Frequency Identification (RFID) system, in which the information maintained in tags is passive and static, has no intelligent decision-making ability to suit application and environment dynamics. The Second-Generation RFID (2G-RFID) system, referred as 2G-RFID-sys, is an evolution of the traditional RFID system to ensure better quality of service in future networks. Due to the openness of the active mobile codes in the 2G-RFID system, the realization of conveying intelligence brings a critical issue: how can we make sure the backend system will interpret and execute mobile codes in the right way without misuse so as to avoid malicious attacks? To address this issue, this paper expands the concept of Role-Based Access Control (RBAC) by introducing context-aware computing, and then designs a secure middleware for backend systems, named Two-Level Security Enhancement Mechanism or 2L-SEM, in order to ensure the usability and validity of the mobile code through contextual authentication and role analysis. According to the given contextual restrictions, 2L-SEM can filtrate the illegal and invalid mobile codes contained in tags. Finally, a reference architecture and its typical application are given to illustrate the implementation of 2L-SEM in a 2G-RFID system, along with the simulation results to evaluate how the proposed mechanism can guarantee secure execution of mobile codes for the system. PMID:22163983

  12. Shaped Apertures in Photoresist Films Enhance the Lifetime and Mechanical Stability of Suspended Lipid Bilayers

    PubMed Central

    Kalsi, Sumit; Powl, Andrew M.; Wallace, B.A.; Morgan, Hywel; de Planque, Maurits R.R.

    2014-01-01

    Planar lipid bilayers suspended in apertures provide a controlled environment for ion channel studies. However, short lifetimes and poor mechanical stability of suspended bilayers limit the experimental throughput of bilayer electrophysiology experiments. Although bilayers are more stable in smaller apertures, ion channel incorporation through vesicle fusion with the suspended bilayer becomes increasingly difficult. In an alternative bilayer stabilization approach, we have developed shaped apertures in SU8 photoresist that have tapered sidewalls and a minimum diameter between 60 and 100 μm. Bilayers formed at the thin tip of these shaped apertures, either with the painting or the folding method, display drastically increased lifetimes, typically >20 h, and mechanical stability, being able to withstand extensive perturbation of the buffer solution. Single-channel electrical recordings of the peptide alamethicin and of the proteoliposome-delivered potassium channel KcsA demonstrate channel conductance with low noise, made possible by the small capacitance of the 50 μm thick SU8 septum, which is only thinned around the aperture, and unimpeded proteoliposome fusion, enabled by the large aperture diameter. We anticipate that these shaped apertures with micrometer edge thickness can substantially enhance the throughput of channel characterization by bilayer lipid membrane electrophysiology, especially in combination with automated parallel bilayer platforms. PMID:24739164

  13. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    SciTech Connect

    Altuntas, Halit E-mail: biyikli@unam.bilkent.edu.tr; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  14. Security enhancement mechanism based on contextual authentication and role analysis for 2G-RFID systems.

    PubMed

    Tang, Wan; Chen, Min; Ni, Jin; Yang, Ximin

    2011-01-01

    The traditional Radio Frequency Identification (RFID) system, in which the information maintained in tags is passive and static, has no intelligent decision-making ability to suit application and environment dynamics. The Second-Generation RFID (2G-RFID) system, referred as 2G-RFID-sys, is an evolution of the traditional RFID system to ensure better quality of service in future networks. Due to the openness of the active mobile codes in the 2G-RFID system, the realization of conveying intelligence brings a critical issue: how can we make sure the backend system will interpret and execute mobile codes in the right way without misuse so as to avoid malicious attacks? To address this issue, this paper expands the concept of Role-Based Access Control (RBAC) by introducing context-aware computing, and then designs a secure middleware for backend systems, named Two-Level Security Enhancement Mechanism or 2L-SEM, in order to ensure the usability and validity of the mobile code through contextual authentication and role analysis. According to the given contextual restrictions, 2L-SEM can filtrate the illegal and invalid mobile codes contained in tags. Finally, a reference architecture and its typical application are given to illustrate the implementation of 2L-SEM in a 2G-RFID system, along with the simulation results to evaluate how the proposed mechanism can guarantee secure execution of mobile codes for the system. PMID:22163983

  15. Mechanically-enhanced three-dimensional scaffold with anisotropic morphology for tendon regeneration.

    PubMed

    Wu, Yang; Wang, Zuyong; Fuh, Jerry Ying Hsi; Wong, Yoke San; Wang, Wilson; Thian, Eng San

    2016-07-01

    Tissue engineering has showed promising results in restoring diseased tendon tissue functions. Herein, a hybrid three-dimensional (3D) porous scaffold comprising an outer portion rolled from an electrohydrodynamic jet printed poly(ɛ-caprolactone) (PCL) fiber mesh, and an inner portion fabricated from uniaxial stretching of a heat-sealed PCL tube, was developed for tendon tissue engineering (TE) application. The outer portion included three layers of micrometer-scale fibrous bundles (fiber diameter: ~25 µm), with an interconnected spacing and geometric anisotropy along the scaffold length. The inner portion showed orientated micro-ridges/grooves in a parallel direction to that of the outer portion. Owning to the addition of the inner portion, the as-fabricated scaffold exhibited comparable mechanical properties to those of the human patellar tendon in terms of Young's modulus (~227 MPa) and ultimate tensile stress (~50 MPa). Compared to the rolled electrospun fibers, human tenocytes cultured in the tendon scaffolds showed increased cellular metabolism. Furthermore, the 3D tendon scaffold resulted in up-regulated cell alignment, cell elongation and formation of collagen type I. These results demonstrated the potential of mechanically-enhanced 3D fibrous scaffold for applications in tendon TE, with desired cell alignment and functional differentiation. PMID:27215211

  16. BI-1 enhances Fas-induced cell death through a Na+/H+-associated mechanism

    PubMed Central

    Lee, Geum-Hwa; Kim, Hyung-Ryong; Chae, Han-Jung

    2014-01-01

    The role of Bax inhibitor-1 (BI-1) in the protective mechanism against apoptotic stimuli has been studied; however, as little is known about its role in death receptor-mediated cell death, this study was designed to investigate the effect of BI-1 on Fas-induced cell death, and the underlying mechanisms. HT1080 adenocarcinoma cells were cultured in high concentration of glucose media and transfected with vector alone (Neo cells) or BI-1-vector (BI-1 cells), and treated with Fas. In cell viability, apoptosis, and caspase-3 analyses, the BI-1 cells showed enhanced sensitivity to Fas. Fas significantly decreased cytosolic pH in BI-1 cells, compared with Neo cells, and this decrease correlated with BI-1 oligomerization, mitochondrial Ca2+ accumulation, and significant inhibition of sodium-hydrogen exchanger (NHE) activity. Compared with Neo cells, a single treatment of BI-1 cells with the NHE inhibitor EIPA or siRNA against NHE significantly increased cell death, which suggests that the viability of BI-1 cells is affected by the maintenance of intracellular pH homeostasis through NHE. [BMB Reports 2014; 47(7): 393-398] PMID:24314142

  17. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  18. POLISHING EFFLUENT FROM A PERCHLORATE-REDUCING ANAEROBIC BIOLOGICAL CONTACTOR

    EPA Science Inventory

    The U.S. Environmental Protection Agency undertook at 3 ½ year pilot-scale biological perchlorate treatment study that included two long (311 and 340 days) examinations of anaerobic effluent polishing. The polishing system consisted of hydrogen peroxide addition and aeration, fo...

  19. Ethnic Identity and the Polish Immigrant in America.

    ERIC Educational Resources Information Center

    Mostwin, Danuta

    1988-01-01

    Examines the ethnic identity of Polish Americans, and the issues that Polish immigrants face. The following are components of the conceptual structure of identity: (1) genetically inherited characteristics; (2) characteristics acquired through family socialization; and (3) characteristics acquired through re-socialization. (BJV)

  20. Social Obstacles Towards Success of Pupils in Polish Primary Schools.

    ERIC Educational Resources Information Center

    Nakielska, Zofia

    In 1973, the Polish Minister of Education ordered objective competitions at the primary school level in the fields of Polish studies, Russian language, and math. In order to determine whether such subject competitions were justified and if they contributed equally to the development of interests and abilities among the rural and urban and…

  1. Decreased aperture surface energy enhances electrical, mechanical, and temporal stability of suspended lipid membranes.

    PubMed

    Bright, Leonard K; Baker, Christopher A; Agasid, Mark T; Ma, Lin; Aspinwall, Craig A

    2013-11-27

    The development of next-generation transmembrane protein-based biosensors relies heavily on the use of black lipid membranes (BLMs); however, electrical, mechanical, and temporal instability of BLMs poses a limiting challenge to biosensor development. In this work, micrometer-sized glass apertures were modified with silanes of different chain length and fluorine composition, including 3-cyanopropyldimethychlorosilane (CPDCS), ethyldimethylchlorosilane (EDCS), n-octyldimethylchlorosilane (ODCS), (tridecafluoro-1, 1, 2, 2-tetrahydrooctyl)dimethylchlorosilane (PFDCS), or (heptadecafluoro-1,1,2,2-tetrahydrodecyl)dimethylchlorosilane (PFDDCS), to explore the effect of substrate surface energy on BLM stability. Low energy silane-modified surfaces promoted enhanced lipid-substrate interactions that facilitate the formation of low-leakage, stable BLMs. The surface energies of silane-modified substrates were 30 ± 3, 16 ± 1, 14 ± 2, 11 ± 1, and 7.1 ± 2 mJ m(-2) for CDCS, EDCS, ODCS, PFDCS, and PFDDCS, respectively. Decreased surface energy directly correlated to improved electrical, mechanical, and temporal BLM stability. Amphiphobic perfluorinated surface modifiers yielded superior performance compared to traditional hydrocarbon modifiers in terms of stability and BLM formation, with only marginal effects on BLM membrane permeability. Leakage currents obtained for PFDCS and PFDDCS BLMs were elevated only 10-30%, though PFDDCS modification yielded >5-fold increase in electrical stability as indicated by breakdown voltage (> 2000 mV vs 418 ± 73 mV), and >25-fold increase in mechanical stability as indicated by air-water transfers (> 50 vs 2 ± 0.2) when compared to previously reported CPDCS modification. Importantly, the dramatically improved membrane stabilities were achieved with no deleterious effects on reconstituted ion channel function, as evidenced by α-hemolysin activity. Thus, this approach provides a simple, low cost, and broadly applicable alternative for

  2. Framework for assessing key variable dependencies in loose-abrasive grinding and polishing

    SciTech Connect

    Taylor, J.S.; Aikens, D.M.; Brown, N.J.

    1995-12-01

    This memo describes a framework for identifying all key variables that determine the figuring performance of loose-abrasive lapping and polishing machines. This framework is intended as a tool for prioritizing R&D issues, assessing the completeness of process models and experimental data, and for providing a mechanism to identify any assumptions in analytical models or experimental procedures. Future plans for preparing analytical models or performing experiments can refer to this framework in establishing the context of the work.

  3. Pad polishing for rapid production of large flats

    NASA Astrophysics Data System (ADS)

    Berggren, Ralph R.; Schmell, Rodney A.

    1997-10-01

    Pad polishing is an efficient technique for polishing-out a ground surface and reaching a figure better than one wave, ready for completion with less than an hour on a planetary polisher. Recent work has shown success on 350 mm square parts; current work involves scaling the process to 1.4 meter diameter. For the 350 mm square piece of BK7, removal was one micrometer every 10 minutes. Polishing-out from a 5 micrometer grind took less than 3 hours, to a surface smoothness of one nm rms. Other tests verified that the pad leaves no unusual subsurface damage. Following completion on a pitch planetary polisher, surface finish is the same as obtained for conventional processing.

  4. The invisible community: undocumented Polish workers in Athens.

    PubMed

    Romaniszyn, K

    1996-04-01

    "This article describes the development of an economic migration from Poland to Greece and the creation of a migrant community in Athens. It presents the development of a new migration route by political immigrants. It then describes how the Polish political emigrants heading for Greece in the mid-1980s established the pillar institutions which were inherited by the Polish undocumented workers who have followed, and which have served the latter well. The article proceeds to highlight the work milieu of the Polish undocumented workers in Athens, and discusses the role played by the ¿Polish church', i.e., the Roman Catholic church to which Poles were given access. It concludes by considering the future prospects of this migration and of the Polish migrant community in Greece." PMID:12179815

  5. Precision technique for side-polished fiber fabrication

    NASA Astrophysics Data System (ADS)

    Mishakov, Gennadi V.; Sokolov, Victor I.

    2002-04-01

    The precision technique for side polishing of single-mode quartz fibers is developed. The technique comprises cutting curved groove in silica block, gluing a section of bare fiber into the groove, and subsequent grinding and polishing of the silica block/fiber assembly. We succeeded in fabricating up to six side-polished fibers in one block with effective interaction length 2-4 mm. The accuracy of polishing depth was achieved at 1 micrometers using in-situ monitoring of transmission of 1.3 micrometers laser light through the fiber. The developed technique combines high accuracy, reproducibility and low cost in commercial production. Side- polished single-mode fibers fabricated with this technique can find application as elements of Bragg grating transmission filters, narrowband reflectors, optical add/drop multiplexers, couplers, polarizers, sensors, etc.

  6. Polish device for FOCCoS/PFS slit system

    NASA Astrophysics Data System (ADS)

    de Oliveira, Antonio Cesar; de Oliveira, Ligia Souza; de Arruda, Marcio V.; Souza Marrara, Lucas; dos Santos, Leandro Henrique; Ferreira, Décio; dos Santos, Jesulino Bispo; de Paiva Vilaça, Rodrigo; Rosa, Josimar Aparecido; Sodré Junior, Laerte; de Oliveira, Claudia Mendes

    2014-07-01

    The Fiber Optical Cable and Connector System, "FOCCoS", for the Prime Focus Spectrograph, "PFS", is responsible for transporting light from the Subaru Telescope focal plane to a set of four spectrographs. Each spectrograph will be fed by a convex curved slit with 616 optical fibers organized in a linear arrangement. The slit frontal surface is covered with a special dark composite, made with refractory oxide, which is able to sustain its properties with minimum quantities of abrasives during the polishing process; this stability is obtained This stability is obtained by the detachment of the refractory oxide nanoparticles, which then gently reinforce gently the polishing process and increase its the efficiency. The surface roughness measured in several samples after high performance polishing was about 0.01 microns. Furthermore, the time for obtaining a polished surface with this quality is about 10 times less than the time required for polishing a brass, glass or ceramic surface of the same size. In this paper, we describe the procedure developed for high quality polishing of this type of slit. The cylindrical polishing described here, uses cylindrical concave metal bases on which glass paper is based. The polishing process consists to use grid sequences of 30μm, 12μm, 9μm, 5μm, 3μm, 1μm and, finally, a colloidal silica on a chemical cloth. To obtain the maximum throughput, the surface of the fibers should be polished in such a way that they are optically flat and free from scratches. The optical fibers are inspected with a microscope at all stages of the polishing process to ensure high quality. The efficiency of the process may be improved by using a cylindrical concave composite base as a substrate suitable for diamond liquid solutions. Despite this process being completely by hand, the final result shows a very high quality.

  7. Nanofibers of Elastin and Hydrophilic Segmented Polyurethane Solution Blends Show Enhanced Mechanical Properties through Intermolecular Protein-Polymer H Bonding.

    PubMed

    Heiny, Markus; Shastri, V Prasad

    2016-04-11

    Combining mechanical properties with enhanced cell interaction is highly desirable in a biomaterial. In this study, a new paradigm for enhancing the mechanical properties of segmented polyurethanes (SPUs) through solution blending with a biopolymer is presented. This noncovalent approach is based on the premise that molecular level blending of SPUs rich in hydrogen bonding (H bonding) domains with a biopolymer capable of H bonding will promote H-bond bridges between the components, leading to molecular annealing and modification of the physicochemical properties of the SPU. We demonstrate that by solution-blending solubilized elastin with a triblock copolymer-derived SPU, a 5-fold increase in tensile modulus of electrospun constructs of the SPU can be achieved, with concomitant enhancement in human endothelial cell attachment. Spectroscopic and calorimetric analysis confirm the role of H bonding in the enhancement, thus providing the impetus to further explore blending with biopolymers as a means of improving the property profiles of synthetic polymeric biomaterials. PMID:26940665

  8. Latest developments in Polish Fireball Network

    NASA Astrophysics Data System (ADS)

    Wiśniewski, M.; Żołądek, P.

    2015-01-01

    The Polish Fireball Network started in March 2004. Most of its observers are amateurs, members of the Comets and Meteors Workshop. The network consists of 40 continuously working stations, where nearly 70 sensitive CCTV video and digital cameras operate. The new cameras for digital meteor spectroscopy were tested. We use technology of crossed grids to have better chances to register a meteor spectrum. A resolution of 8 A/pixel + 5.5 A/pixel was achieved. For the meteor patrol we have chosen the DMK 23GX236 with a chip resolution of 1920x1200 pixels. Two new cameras will be able to cover almost the whole sky with a resolution 4'/pixel.

  9. Polished Downhole Transducer Having Improved Signal Coupling

    DOEpatents

    Hall, David R.; Fox, Joe

    2006-03-28

    Apparatus and methods to improve signal coupling in downhole inductive transmission elements to reduce the dispersion of magnetic energy at the tool joints and to provide consistent impedance and contact between transmission elements located along the drill string. A transmission element for transmitting information between downhole tools is disclosed in one embodiment of the invention as including an annular core constructed of a magnetically conductive material. The annular core forms an open channel around its circumference and is configured to form a closed channel by mating with a corresponding annular core along an annular mating surface. The mating surface is polished to provide improved magnetic coupling with the corresponding annular core. An annular conductor is disposed within the open channel.

  10. A Generic Mechanism for Enhanced Cytokine Signaling via Cytokine-Neutralizing Antibodies

    PubMed Central

    Shulgin, Boris; Helmlinger, Gabriel; Kosinsky, Yuri

    2016-01-01

    Enhancement or inhibition of cytokine signaling and corresponding immune cells responses are critical factors in various disease treatments. Cytokine signaling may be inhibited by cytokine-neutralizing antibodies (CNAs), which prevents further activation of cytokine receptors. However, CNAs may result in enhanced—instead of inhibitory—cytokine signaling (an “agonistic effect”) in various in vitro and in vivo experiments. This may lead to lack of efficacy or adverse events for cytokine-inhibiting based medicines. Alternatively, cytokine-antibody complexes may produce stronger signaling vs. cytokine alone, thereby increasing the efficacy of stimulating cytokine-based drugs, at equal or lower cytokine doses. In this paper, the effect of cytokine signaling enhancement by a CNA was studied in a generic mathematical model of interleukin-4 (IL-4) driven T-cell proliferation. The occurrence of the agonistic effect depends upon the antibody-to-cytokine binding affinity and initial concentrations of antibody and cytokine. Model predictions were in agreement with experimental studies. When the cytokine receptor consists of multiple subunits with substantially differing affinities (e.g., IL-4 case), the choice of the receptor chain to be blocked by the antibody is critical, for the agonistic effect to appear. We propose a generic mechanism for the effect: initially, binding of the CNA to the cytokine reduces free cytokine concentration; yet, cytokine molecules bound within the cytokine-CNA complex—and released later and over time—are “rescued” from earlier clearance via cellular internalization. Hence, although free cytokine-dependent signalling may be less potent initially, it will also be more sustained over time; and given non-linear dynamics, it will lead ultimately to larger cellular effector responses, vs. the same amount of free cytokine in the absence of CNA. We suggest that the proposed mechanism is a generic property of {cytokine, CNA, receptor

  11. Mechanical and Vascular Cues Synergistically Enhance Osteogenesis in Human Mesenchymal Stem Cells.

    PubMed

    Steward, Andrew J; Cole, Jacqueline H; Ligler, Frances S; Loboa, Elizabeth G

    2016-08-01

    Development and maintenance of a vascular network are critical for bone growth and homeostasis; strategies that promote vascular function are critical for clinical success of tissue-engineered bone constructs. Co-culture of endothelial cells (ECs) with mesenchymal stem cells (MSCs) and exposure to 10% cyclic tensile strain have both been shown to regulate osteogenesis in isolation, but potential synergistic effects have yet to be explored. The objective of this study was to expose an MSC-EC co-culture to 10% cyclic tensile strain to examine the role of this mechanical stimulus on MSC-EC behavior. We hypothesized that paracrine signaling from ECs would stimulate osteogenesis of MSCs, and exposure to 10% cyclic tensile strain would enhance this anabolic signal. Human umbilical vein ECs and human bone marrow-derived MSCs were either monocultured or co-cultured at a 1:1 ratio in a mixed osteo/angiogenic medium, exposed to 10% cyclic tensile strain at 1 Hz for 4 h/day for 2 weeks, and biochemically and histologically analyzed for endothelial and osteogenic markers. While neither 10% cyclic tensile strain nor co-culture alone had a significant effect on osteogenesis, the concurrent application of strain to an MSC-EC co-culture resulted in a significant increase in calcium accretion and mineral deposition, suggesting that co-culture and strain synergistically enhance osteogenesis. Neither co-culture, 10% cyclic tensile strain, nor a combination of these stimuli affected endothelial markers, indicating that the endothelial phenotype remained stable, but unresponsive to the stimuli evaluated in this study. This study is the first to investigate the role of cyclic tensile strain on the complex interplay between ECs and MSCs in co-culture. The results of this study provide key insights into the synergistic effects of 10% cyclic tensile strain and co-culture on osteogenesis. Understanding mechanobiological factors affecting MSC-EC crosstalk will help enhance strategies for

  12. Patient's autonomy of will in Polish law.

    PubMed

    Swiderska, Małgorzata

    2012-09-01

    A principle of Polish legislation is that the evidence of legality for any medical intervention is the patient's consent. The issue is directly referred to by both the Patient's Rights Act from 2008 and the Medical Profession Act from 1996. The patient's consent may be given after obtaining reliable, accessible and thorough information about all stages of medical intervention: diagnosis, therapy prospects or rehabilitation. The extent of information about the potential risk of medical treatment should include the typically foreseeable results, which usually brings the matter down to typical risk. However, there are interventions, which bear greater risk, and even though it can't be considered typical, it should also be mentioned, despite the fact that the postulate of tactfulness should be respected here. The burden of proof that appropriate information has been given lies upon the doctor. Thus default consent, especially one given on being admitted to hospital, to all medical actions isn't valid in legal terms. The role of forms including standard information for giving consent is limited. Polish law doesn't regulate this issue, and other forms of indirect communication are used as auxiliary and cannot replace direct contact between a patient and a doctor. According to the Patient's Rights Act, in case of deliberate breach of those rights, the court can grant the aggrieved party with an appropriate sum as financial compensation for the harm sustained or an appropriate sum of money for the charity chosen by the aggrieved party. It is a legal basis for claiming compensation for non-material harm in case of a breach of the patient's right to give consent. It is possible both in case of liability in tort, as well as contractual claims. PMID:23248839

  13. Droughts in historical times in Polish territory

    NASA Astrophysics Data System (ADS)

    Limanowka, Danuta; Cebulak, Elzbieta; Pyrc, Robert; Doktor, Radoslaw

    2015-04-01

    Climate change is one of the key environmental, social and economical issues, and it is also followed by political consequences. Impact of climate conditions on countries' economy is increasingly recognized, and a lot of attention is given, both in the global scale and by the individual national governments. In years 2008-2010, at the Poland -Institute of Meteorology and Water Management-National Research Institute was realized the KLIMAT Project on Impact of climate change on environment, economy and society (changes, effects and methods of reducing them, conclusions for science, engineering practice and economic planning) No. POIG01-03-01-14-011/08. The project was financed by the European Union and Polish state budget in frame of Innovative Economy Operational Programme. A very wide range of research was carried out in the different thematic areas. One of them was "Natural disasters and internal safety of the country (civil and economical)." The problem of drought in Poland was developed in terms of meteorology and hydrology. "Proxy" Data Descriptions very often inform about dry years and seasons, hot periods without precipitation. Analysis of historical material allowed to extract the years that have experienced prolonged periods of high temperatures and rainfall shortages. Weather phenomenon defined as drought belongs to extreme events. This information was very helpful in the process of indexing and thus to restore the course and intensity of climatic elements in the past. The analysis covered the period from year 1000 to modern times. Due to the limited information from the period of 1000-1500 the authors focused primarily on the period from 1500 to 2010. Analysis of the collected material has allowed the development of a highly precise temporal structure of the possible occurrence of dry periods to Polish territory.

  14. Determination and optimization of Vitamin B complex in xylanase enzyme treated polished rice by response surface methodology.

    PubMed

    Kothakota, Anjineyulu; Pandey, J P; Ahmad, A H; Kumar, Anil; Ahmad, Wasif

    2016-07-01

    The present study provides information about the concentrations of Vitamin B (thiamine, riboflavin, pyridoxine and niacin) in polished brown rice treated with xylanase. Xylanase enzyme was produced from Aspergillus awamori MTCC 9166. Brown rice was treated with 60-100% enzyme (40 ml of buffer -undiluted) for 30 to 150 min (with variation of 30 min) at 30 degrees C to 50 degrees C (with variation of 5 degrees C) to attain a saturated moisture level of 35.5 g100(-1)g .The enzyme acted upon selective degradation (polishing time 10-50 sec) of bran layer facilitating retention of more vital nutrients along with the vitamins. Vitamin B content, detected through HPLC and optimized by response surface methodology (RSM) with central composite design (CCRD), demonstrated that selective degradation of bran layers for polished rice facilitated increase of thiamine (57%), riboflavin (48%), pyridoxine (90%) and niacin (55%) concentration in bio polished rice over normally milled rice.Enzyme treated bio-polished rice was considered to be better source of vitamin B complex than mechanically milled rice, hence more nutritionally efficacious. PMID:27498499

  15. Combined quantum mechanics (TDDFT) and classical electrodynamics (Mie theory) methods for calculating surface enhanced Raman and hyper-Raman spectra.

    PubMed

    Mullin, Jonathan; Valley, Nicholas; Blaber, Martin G; Schatz, George C

    2012-09-27

    Multiscale models that combine quantum mechanics and classical electrodynamics are presented, which allow for the evaluation of surface-enhanced Raman (SERS) and hyper-Raman scattering spectra (SEHRS) for both chemical (CHEM) and electrodynamic (EM) enhancement mechanisms. In these models, time-dependent density functional theory (TDDFT) for a system consisting of the adsorbed molecule and a metal cluster fragment of the metal particle is coupled to Mie theory for the metal particle, with the surface of the cluster being overlaid with the surface of the metal particle. In model A, the electromagnetic enhancement from plasmon-excitation of the metal particle is combined with the chemical enhancement associated with a static treatment of the molecule-metal structure to determine overall spectra. In model B, the frequency dependence of the Raman spectrum of the isolated molecule is combined with the enhancements determined in model A to refine the enhancement estimate. An equivalent theory at the level of model A is developed for hyper-Raman spectra calculations. Application to pyridine interacting with a 20 nm diameter silver sphere is presented, including comparisons with an earlier model (denoted G), which combines plasmon enhanced fields with gas-phase Raman (or hyper-Raman) spectra. The EM enhancement factor for spherical particles at 357 nm is found to be 10(4) and 10(6) for SERS and SEHRS, respectively. Including both chemical and electromagnetic mechanisms at the level of model A leads to enhancements on the order of 10(4) and 10(9) for SERS and SEHRS. PMID:22946645

  16. Absence of TNF-α enhances inflammatory response in the newborn lung undergoing mechanical ventilation.

    PubMed

    Ehrhardt, Harald; Pritzke, Tina; Oak, Prajakta; Kossert, Melina; Biebach, Luisa; Förster, Kai; Koschlig, Markus; Alvira, Cristina M; Hilgendorff, Anne

    2016-05-15

    Bronchopulmonary dysplasia (BPD), characterized by impaired alveolarization and vascularization in association with lung inflammation and apoptosis, often occurs after mechanical ventilation with oxygen-rich gas (MV-O2). As heightened expression of the proinflammatory cytokine TNF-α has been described in infants with BPD, we hypothesized that absence of TNF-α would reduce pulmonary inflammation, and attenuate structural changes in newborn mice undergoing MV-O2 Neonatal TNF-α null (TNF-α(-/-)) and wild type (TNF-α(+/+)) mice received MV-O2 for 8 h; controls spontaneously breathed 40% O2 Histologic, mRNA, and protein analysis in vivo were complemented by in vitro studies subjecting primary pulmonary myofibroblasts to mechanical stretch. Finally, TNF-α level in tracheal aspirates from preterm infants were determined by ELISA. Although MV-O2 induced larger and fewer alveoli in both, TNF-α(-/-) and TNF-α(+/+) mice, it caused enhanced lung apoptosis (TUNEL, caspase-3/-6/-8), infiltration of macrophages and neutrophils, and proinflammatory mediator expression (IL-1β, CXCL-1, MCP-1) in TNF-α(-/-) mice. These differences were associated with increased pulmonary transforming growth factor-β (TGF-β) signaling, decreased TGF-β inhibitor SMAD-7 expression, and reduced pulmonary NF-κB activity in ventilated TNF-α(-/-) mice. Preterm infants who went on to develop BPD showed significantly lower TNF-α levels at birth. Our results suggest a critical balance between TNF-α and TGF-β signaling in the developing lung, and underscore the critical importance of these key pathways in the pathogenesis of BPD. Future treatment strategies need to weigh the potential benefits of inhibiting pathologic cytokine expression against the potential of altering key developmental pathways. PMID:27016588

  17. Efficacy and Pharmacological Mechanism of Pronase-Enhanced Low-Dose Antibiotics for Helicobacter pylori Eradication

    PubMed Central

    Liu, Kai Y.; Du, Fang C.; Fu, Qiang; Zhang, Wei J.; Sun, Hong W.; Zhang, Yi; Gan, Le L.; Yue, Zhi Y.

    2014-01-01

    This study examined the efficacy and pharmacological mechanism of pronase-assisted low-dose antibiotics for eradication of Helicobacter pylori. Mongolian gerbils infected with H. pylori received 7-day treatment (omeprazole, different concentrations of pronase, amoxicillin, and clarithromycin), and the efficacy was assessed using the eradication rate and the colonization of H. pylori. In Mongolian gerbils orally administered pronase, the thickness of the gastric mucous layer (GML) was examined using immunohistochemical and alcian blue staining, and the concentrations of amoxicillin in gastric tissue and serum were detected using high-performance liquid chromatography (HPLC). The eradication rates were 80.0% (12/15) in the high-pronase quadruple group (HPQG) and 86.7% (13/15) in the high-antibiotic group (HAG) (P = 1.000). The antibiotic dose in the HPQG was only 1/20 that in the HAG. Thirty minutes after oral treatment with pronase, the sticky protein of the GML was hydrolyzed, and the GML became thinner. Higher amoxicillin concentrations in both the gastric tissue and serum were observed in the pronase group than in the Am10 group. The concentration of amoxicillin in the Am10-plus-Pr108 group in gastric tissue was 3.8 times higher than in the Am10 group in 5 min. Together, these data suggest that pronase significantly reduced the dose of antibiotics used in H. pylori eradication. The pharmacological mechanism is likely pronase removal of the mucus layer, promoting chemical factor (i.e., gastric acid and pepsinogen) distribution and increasing the antibiotic concentrations in the deep GML, which acted on H. pylori collectively. Thus, pronase may enhance the level of antibiotics for eradication of H. pylori in the clinic. PMID:24687504

  18. Nanocrystals for dermal penetration enhancement - Effect of concentration and underlying mechanisms using curcumin as model.

    PubMed

    Vidlářová, Lucie; Romero, Gregori B; Hanuš, Jaroslav; Štěpánek, František; Müller, Rainer H

    2016-07-01

    Nanocrystals have received considerable attention in dermal application due to their ability to enhance delivery to the skin and overcome bioavailability issues caused by poor water and oil drug solubility. The objective of this study was to investigate the effect of nanocrystals on the mechanism of penetration behavior of curcumin as a model drug. Curcumin nanocrystals were produced by the smartCrystals® process, i.e. bead milling followed by high pressure homogenization. The mean particle size of the curcumin crystals was about 200nm. Stabilization was performed with alkyl polyglycoside surfactants. The distribution of curcumin within the skin was determined in vitro on cross-sections of porcine skin and visualized by fluorescent microscopy. The skin penetration profile was analyzed for the curcumin nanosuspension with decreasing concentrations (2%, 0.2%, 0.02% and 0.002% by weight) and compared to nanocrystals in a viscous hydroxypropylcellulose (HPC) gel. This study demonstrated there was minor difference between low viscous nanosuspension and the gel, but low viscosity seemed to favor skin penetration. Localization of curcumin was observed in the hair follicles, also contributing to skin uptake. Looking at the penetration of curcumin from formulations with decreasing nanocrystal concentration, formulations with 2%, 0.2% and 0.02% showed a similar penetration profile, whereas a significantly weaker fluorescence was observed in the case of a formulation containing 0.002% of curcumin nanocrystals. In this study we have shown that curcumin nanocrystals prepared by the smartCrystal® process are promising carriers in dermal application and furthermore, we identified the ideal concentration of 0.02% nanocrystals in dermal formulations. The comprehensive study of decreasing curcumin concentration in formulations revealed that the saturation solubility (Cs) is not the only determining factor for the penetration. A new mechanism based also on the concentration of the

  19. Oral non-typable Haemophilus influenzae enhances physiological mechanism of airways protection.

    PubMed

    Clancy, R L; Dunkley, M L

    2010-07-01

    Oral immunotherapy with inactivated non-typeable Haemophilus influenzae (NTHi) prevents exacerbations of chronic obstructive pulmonary disease, but the mechanism is unclear. The aim of this study was to determine the mechanism of protection. This was a placebo versus active prospective study over 3 months in 64 smokers. The active treatment was three courses of oral NTHi given at monthly intervals, followed by measurement of bacteriological and immunological parameters. The results can be summarized: (i) NTHi-specific T cells increased in the placebo treatment group over time (P<0.05); (ii) the T cell response in the oral NTHi group started earlier than that in the placebo group (P<0.05); and (iii) serum NTHi-specific immunoglobulin (Ig)G had significantly greater variation in the placebo group (P<0.0001). The increase in antibody in placebos over time correlated with exposure to live H. influenzae (P<0.05) determined from culture of gargles; (iv) reduction in saliva lysozyme over time (P<0.05) was detected only in the oral NTHi treatment group. These data are consistent with T cell priming of gut lymphoid tissue by aspiration of bronchus content into the gut, with oral immunotherapy augmenting this process leading to enhanced bronchus protection. The evidence for protection was a stable IgG antibody level through the study in the oral NTHi treatment group, contrasting with an increase in antibody correlating with exposure of the airways to H. influenzae in the placebo group. Saliva lysozyme was a useful biomarker of mucosal inflammation, falling after oral NTHi consistent with a reduction in the level of intralumenal inflammation. PMID:20408861

  20. How Polish Children Switch from One Case to Another when Using Novel Nouns: Challenges for Models of Inflectional Morphology

    ERIC Educational Resources Information Center

    Krajewski, Grzegorz; Theakston, Anna L.; Lieven, Elena V. M.; Tomasello, Michael

    2011-01-01

    The two main models of children's acquisition of inflectional morphology--the Dual-Mechanism approach and the usage-based (schema-based) approach--have both been applied mainly to languages with fairly simple morphological systems. Here we report two studies of 2-3-year-old Polish children's ability to generalise across case-inflectional endings…

  1. Efficiency Enhancement Mechanism for Poly(3, 4-ethylenedioxythiophene):Poly(styrenesulfonate)/Silicon Nanowires Hybrid Solar Cells Using Alkali Treatment

    NASA Astrophysics Data System (ADS)

    Jiang, Yurong; Gong, Xiu; Qin, Ruiping; Liu, Hairui; Xia, Congxin; Ma, Heng

    2016-05-01

    The efficiency enhancement mechanism of the alkali-treated Si nanowire (SiNW) solar cells is discussed and analyzed in detail, which is important to control the useful photovoltaic process. All the results demonstrate that the photovoltaic performance enhancement of alkali-treated SiNW device steps from the formation of the good core-shell heterojunction, which consequently enhances the junction area, promotes fast separating and transporting of electron and hole pairs, and reduces the carrier surface combination. It also indicates that alkali treatment for SiNWs is a promising processing as an economical method for the formation of good core-shell SiNW/polymer heterojunction.

  2. Combined effects of crystallography, heat treatment and surface polishing on blistering in tungsten exposed to high-flux deuterium plasma

    NASA Astrophysics Data System (ADS)

    Zayachuk, Y.; Tanyeli, I.; Van Boxel, S.; Bystrov, K.; Morgan, T. W.; Roberts, S. G.

    2016-08-01

    For tungsten exposed to low-energy hydrogen-plasmas, it has been thought that grains with < \\text{1} \\text{1} \\text{1}> surface normal are most susceptible to blistering while those with < \\text{0} \\text{0} \\text{1}> surface normal are virtually impervious to it. Here, we report results showing that non-uniformity of blister distribution depends on the state of the surface due to polishing. In electrochemically polished material blisters appear on the grains with all orientations, while in mechanically polished material blister-free areas associated with particular orientations emerge. On the other hand, blistering is shown to have a strong dependence on the level of deformation within particular grains in partially recrystallized material.

  3. Mechanisms of Polyelectrolyte Enhanced Surfactant Adsorption at the Air-Water Interface

    PubMed Central

    Stenger, Patrick C.; Palazoglu, Omer A.; Zasadzinski, Joseph A.

    2009-01-01

    Chitosan, a naturally occurring cationic polyelectrolyte, restores the adsorption of the clinical lung surfactant Survanta to the air-water interface in the presence of albumin at much lower concentrations than uncharged polymers such as polyethylene glycol. This is consistent with the positively charged chitosan forming ion pairs with negative charges on the albumin and lung surfactant particles, reducing the net charge in the double-layer, and decreasing the electrostatic energy barrier to adsorption to the air-water interface. However, chitosan, like other polyelectrolytes, cannot perfectly match the charge distribution on the surfactant, which leads to patches of positive and negative charge at net neutrality. Increasing the chitosan concentration further leads to a reduction in the rate of surfactant adsorption consistent with an over-compensation of the negative charge on the surfactant and albumin surfaces, which creates a new repulsive electrostatic potential between the now cationic surfaces. This charge neutralization followed by charge inversion explains the window of polyelectrolyte concentration that enhances surfactant adsorption; the same physical mechanism is observed in flocculation and re-stabilization of anionic colloids by chitosan and in alternate layer deposition of anionic and cationic polyelectrolytes on charged colloids. PMID:19366599

  4. Injectable thermosensitive chitosan hydrogels with controlled gelation kinetics and enhanced mechanical resistance.

    PubMed

    Assaad, Elias; Maire, Marion; Lerouge, Sophie

    2015-10-01

    The use of injectable hydrogels is presently limited by the difficulty to achieve rapid gelation, high mechanical resistance and excellent cytocompatibility. In our study, high-strength injectable thermosensitive hydrogels of unmodified chitosan (CH) were obtained by combining sodium hydrogen carbonate (SHC) with phosphate buffer (PB) or beta-glycerophosphate (BGP) as gelling agents. A synergic effect led to the acceleration of gelation and a remarkable improvement of the storage modulus (G') of the hydrogels. Furthermore, the new hydrogels exhibited drastically enhanced Young moduli and resistance in compression as compared to conventional hydrogels prepared with BGP, PB or their combination. This was achieved while reducing the total salt concentration in the hydrogels. The gelation was rapid and the hydrogels presented porous structures and physiological pH, and did not show any cytotoxicity to L929 fibroblast cells in vitro. Overall, these new hydrogels provide interesting alternatives for use as blood vessel embolizing agents or as injectable scaffolds for drug delivery and/or cell seeding in tissue engineering strategies. PMID:26076604

  5. Enhanced hydrogen storage from nanostructured graphene and nickel hybrids based on spillover mechanism

    NASA Astrophysics Data System (ADS)

    Wei, Lin; Mao, Yuanbing

    2015-03-01

    As a fascinating 2-dimentional carbon material, graphene has been decorated with metal nanoparticles to enhance its hydrogen storage performance based on the spillover mechanism. In this work, Ni and Ni alloys have been used to decorate the surface of graphene. Graphene oxide was fabricated from graphite by improved Hummer method. To form Ni/graphene and Ni/Pd/graphene hybrids, the graphene oxide water dispersion was mixted with nickel chloride (and palladium chloride). Ni(OH)2/graphene and Ni(OH)2/Pd(OH)2/graphene hybrids were synthesized through hydrothermal treatment, using water as a solvent and HMT as a capping agent. After heat treatment and in situ reduction with hydrogen flow, the nanostructured Ni/graphene and Ni/Pd graphene hybrids were obtained. The nanostructured Ni/Pd/Ag/graphene hybrid was synthesized from graphene oxide in the ethylene glycol solution and metal nitrates using similar reactions. XRD, Raman, SEM, AFM were used to characterize these products. ASAP 2020 was used to test the hydrogen adsorption and desorption capacities.

  6. Enhanced bioactivity, biocompatibility and mechanical behavior of strontium substituted bioactive glasses.

    PubMed

    Arepalli, Sampath Kumar; Tripathi, Himanshu; Hira, Sumit Kumar; Manna, Partha Pratim; Pyare, Ram; S P Singh

    2016-12-01

    Strontium contained biomaterials have been reported as a potential bioactive material for bone regeneration, as it reduces bone resorption and stimulates bone formation. In the present investigation, the bioactive glasses were designed to partially substitute SrO for SiO2 in Na2O-CaO-SrO-P2O5-SiO2 system. This work demonstrates that the substitution of SrO for SiO2 has got significant benefit than substitution for CaO in the bioactive glass. Bioactivity was assessed by the immersion of the samples in simulated body fluid for different intervals. The formation of hydroxy carbonate apatite layer was identified by X-ray diffractometry, scanning electron microscopy (SEM) and energy dispersive spectroscopy. The elastic modulus of the bioactive glasses was measured and found to increase with increasing SrO for SiO2. The blood compatibility of the samples was evaluated. In vitro cell culture studies of the samples were performed using human osteosarcoma U2-OS cell lines and found a significant improvement in cell viability and proliferation. The investigation showed enhancement in bioactivity, mechanical and biological properties of the strontia substituted for silica in glasses. Thus, these bioactive glasses would be highly potential for bone regeneration. PMID:27612694

  7. Mechanisms of enhanced mobilisation of trace metals by anionic surfactants in soil.

    PubMed

    Hernández-Soriano, Maria del Carmen; Degryse, Fien; Smolders, Erik

    2011-03-01

    Long-term applications of small concentrations of surfactants in soil via wastewater irrigation or pesticide application may enhance trace metal solubility. Mechanisms by which anionic surfactants (Aerosol 22, SDS and Biopower) affect trace metal solubility were assessed using batch, incubation and column experiments. In batch experiments on seven soils, the concentrations of Cu, Cd, Ni and Zn in the dissolved fraction of soils increased up to 100-fold at the high application rates, but increased less than 1.5-fold below the critical micelle concentration. Dissolved metal concentrations were less than 20% affected by surfactants in long-term incubations (70 days) up to the largest dose of 200 mg C kg(-1) soil. Leaching soil columns with A22 (100-1000 mg C L(-1)) under unsaturated conditions increased trace metal concentrations in the leachates 2-4 fold over the control. Correlation analysis and speciation modelling showed that the increased solubility of metals upon surfactant application was more related to the solubilisation of soil organic matter from soil than to complexation of the metals with the surfactant. Organic matter from soil was solubilised in response to a decrease of solution Ca(2+) as a result of Ca-surfactant precipitation. At environmentally relevant concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility. PMID:21163562

  8. Enhancement of Mechanical and Thermal Properties of Polycaprolactone/Chitosan Blend by Calcium Carbonate Nanoparticles

    PubMed Central

    Abdolmohammadi, Sanaz; Siyamak, Samira; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Rahman, Mohamad Zaki Ab; Azizi, Susan; Fatehi, Asma

    2012-01-01

    This study investigates the effects of calcium carbonate (CaCO3) nanoparticles on the mechanical and thermal properties and surface morphology of polycaprolactone (PCL)/chitosan nanocomposites. The nanocomposites of PCL/chitosan/CaCO3 were prepared using a melt blending technique. Transmission electron microscopy (TEM) results indicate the average size of nanoparticles to be approximately 62 nm. Tensile measurement results show an increase in the tensile modulus with CaCO3 nanoparticle loading. Tensile strength and elongation at break show gradual improvement with the addition of up to 1 wt% of nano-sized CaCO3. Decreasing performance of these properties is observed for loading of more than 1 wt% of nano-sized CaCO3. The thermal stability was best enhanced at 1 wt% of CaCO3 nanoparticle loading. The fractured surface morphology of the PCL/chitosan blend becomes more stretched and homogeneous in PCL/chitosan/CaCO3 nanocomposite. TEM micrograph displays good dispersion of CaCO3 at lower nanoparticle loading within the matrix. PMID:22605993

  9. Ultrasound-stimulated microbubble enhancement of radiation treatments: endothelial cell function and mechanism

    PubMed Central

    Al-Mahrouki, Azza A.; Wong, Emily; Czarnota, Gregory J.

    2015-01-01

    Endothelial cell death caused by novel microbubble-enhanced ultrasound cancer therapy leads to secondary tumour cell death. In order to characterize and optimize these treatments, the molecular mechanisms resulting from the interaction with endothelial cells were investigated here. Endothelial cells (HUVEC) were treated with ultrasound-stimulated microbubbles (US/MB), radiation (XRT), or a combination of US/MB+XRT. Effects on cells were evaluated at 0, 3, 6, and 24 hours after treatment. Experiments took place in the presence of modulators of sphingolipid-based signalling including ceramide, fumonisin B1, monensin, and sphingosine-1-phosphate. Experimental outcomes were evaluated using histology, TUNEL, clonogenic survival methods, immuno-fluorescence, electron microscopy, and endothelial cell blood-vessel-like tube forming assays. Fewer cells survived after treatment using US/MB+XRT compared to either the control or XRT. The functional ability to form tubes was only reduced in the US/ MB+XRT condition in the control, the ceramide, and the sphingosine-1-phosphate treated groups. The combined treatment had no effect on tube forming ability in either the fumonisin B1 or in the monensin exposed groups, since both interfere with ceramide production at different cellular sites. In summary, experimental results supported the role of ceramide signalling as a key element in cell death initiation with treatments using US/MB+XRT to target endothelial cells. PMID:26909363

  10. Cyclical mechanical stretch enhances degranulation and IL-4 secretion in RBL-2H3 mast cells.

    PubMed

    Komiyama, Hidenori; Miyake, Koichi; Asai, Kuniya; Mizuno, Kyoichi; Shimada, Takashi

    2014-01-01

    Mast cells are widely distributed in the body and affect their surrounding environment through degranulation and secretion of cytokines. Conversely, mast cells are influenced by environmental stimuli such as cyclical mechanical stretch (CMS), such as that induced by heartbeat and respiration. Peripherally distributed mast cells are surrounded by extracellular matrix, where they bind IgE on their surface by expressing the high-affinity Fc receptor for IgE (FcεRI), and they release mediators after cross-linking of surface-bound IgE by allergen. To analyse how CMS affects mast cell responses, we examined the effect of applying CMS on the behaviour of IgE-bound mast cells (RBL-2H3 cell line) adhering to fibronectin as a substitute for extracellular matrix. We found that CMS enhanced FcεRI-mediated secretion in the presence of antigen (2,4-dinitrophenol-bovine serum albumin). CMS increased expression of IL-4 mRNA and secretion of IL-4 protein. Western blot analysis showed that CMS changes the signal transduction in mitogen-activated protein kinases and AKT, which in turn alters the regulation of IL-4 and increases the secretion of IL-4. These results suggest that CMS modulates the effect of mast cells on inflammation and resultant tissue remodelling. Understanding how CMS affects mast cell responses is crucial for developing therapies to treat mast cell-related diseases. PMID:23584980

  11. Examination of mechanisms underlying enhanced memory performance in action video game players: a pilot study

    PubMed Central

    Li, Xianchun; Cheng, Xiaojun; Li, Jiaying; Pan, Yafeng; Hu, Yi; Ku, Yixuan

    2015-01-01

    Previous studies have shown enhanced memory performance resulting from extensive action video game playing. The mechanisms underlying the cognitive benefit were investigated in the current study. We presented two types of retro-cues, with variable intervals to memory array (Task 1) or test array (Task 2), during the retention interval in a change detection task. In Task 1, action video game players demonstrated steady performance while non-action video game players showed decreased performance as cues occurred later, indicating their performance difference increased as the cue-to-memory-array intervals became longer. In Task 2, both participant groups increased their performance at similar rates as cues presented later, implying the performance difference in two groups were irrespective of the test-array-to-cue intervals. These findings suggested that memory benefit from game plays is not attributable to the higher ability of overcoming interference from the test array, but to the interactions between the two processes of protection from decay and resistance from interference, or from alternative hypotheses. Implications for future studies were discussed. PMID:26136720

  12. A novel thermo-mechanical system enhanced transdermal delivery of hydrophilic active agents by fractional ablation.

    PubMed

    Sintov, Amnon C; Hofmann, Maja A

    2016-09-25

    The Tixel is a novel device based on a thermo-mechanical ablation technology that combines a sophisticated motion and a temperature control. The fractional technology is used to transfer a very precise thermal energy to the skin thereby creating an array of microchannels, accompanying by no signs of pain or inconvenience. This study aimed to evaluate the effect of the Tixel on the skin permeability of three hydrophilic molecular models: verapamil hydrochloride, diclofenac sodium, and magnesium ascorbyl phosphate. Tixel's gold-platted stainless steel tip heated to a temperature of 400°C was applied on skin for 8ms or 9ms at a protrusion of 400μm (the distance in which the tip protrudes beyond the distance gauge). The experiments were carried out partly in vivo in humans using a fluorescent dye and a confocal microscopy and partly in vitro using porcine skin and a Franz diffusion cell system. The results obtained in this study have shown that (a) no significant collateral damage to the skin tissue and no necrosis or dermal coagulation have been noted, (b) the microchannels remained open and endured for at least 6h, and (c) the skin permeability of hydrophilic molecules, which poorly penetrate the lipophilic stratum corneum barrier, was significantly enhanced by using Tixel's pretreatment. PMID:27480396

  13. Heavy-ion radiobiology: new approaches to delineate mechanisms underlying enhanced biological effectiveness.

    PubMed

    Blakely, E A; Kronenberg, A

    1998-11-01

    Shortly after the discovery of polonium and radium by Marie Curie and her husband and colleague, Pierre Curie, it was learned that exposure to these alpha-particle emitters produced deleterious biological effects. The mechanisms underlying the increased biological effectiveness of densely ionizing radiations, including alpha particles, neutrons and highly energetic heavy charged particles, remain an active area of investigation. In this paper, we review recent advances in several areas of the radiobiology of these densely ionizing radiations, also known as heavy ions. Advances are described in the areas of DNA damage and repair, chromosome aberrations, mutagenesis, neoplastic transformation in vitro, genomic instability, normal tissue radiobiology and carcinogenesis in vivo. We focus on technical innovations, including novel applications of pulsed-field gel electrophoresis, fluorescence in situ hybridization (FISH), linkage analysis, and studies of gene expression and protein expression. We also highlight the use of new cellular and animal systems, including those with defined DNA repair deficiencies, as well as epithelial cell model systems to assess neoplastic transformation both in vitro and in vivo. The studies reviewed herein have had a substantial impact on our understanding of the genotoxic effects of heavy ions as well as their distinct effects on tissue homeostasis. The use of these radiations in cancer therapy is also discussed. The use of both heavy-ion and proton therapy is on the upswing in several centers around the world, due to their unique energy deposition characteristics that enhance the therapeutic effect and help reduce damage to normal tissue. PMID:9806616

  14. Mechanisms controlling soil carbon turnover and their potential application for enhancing carbon sequestration

    SciTech Connect

    Jastrow, Julie D.; Amonette, James E.; Bailey, Vanessa L.

    2007-01-01

    Two major mechanisms, (bio)chemical alteration and physicochemical protection, stabilize soil organic carbon (SOC) and thereby control soil carbon turnover. With (bio)chemical alteration, SOC is transformed by biotic and abiotic processes to chemical forms that are more resistant to decomposition and, in some cases, more easily retained by sorption to soil solids. With physicochemical protection, biochemical attack of SOC is inhibited by organomineral interactions at molecular to millimeter scales. Stabilization of otherwise decomposable SOM can occur via sorption to soil surfaces, complexation with soil minerals, occlusion within aggregates, and deposition in pores inaccessible to decomposers and extracellular enzymes. Soil structure (i.e., the arrangement of solids and pores in the soil) is a master integrating variable that both controls and indicates the SOC stabilization status of a soil. To enhance SOC sequestration, the best option is to modify the soil physicochemical environment to favor the activities of fungi. Specific practices that accomplish this include minimizing tillage, maintaining a near-neutral soil pH and an adequate base cation exchange capacity (particularly Ca), ensuring adequate drainage, and minimizing erosion by water and wind. In some soils, amendments with various high-specific-surface micro- and mesoporous sorbents such as fly ash or charcoal can be beneficial.

  15. Heavy-ion radiobiology: new approaches to delineate mechanisms underlying enhanced biological effectiveness

    NASA Technical Reports Server (NTRS)

    Blakely, E. A.; Kronenberg, A.; Chatterjee, A. (Principal Investigator)

    1998-01-01

    Shortly after the discovery of polonium and radium by Marie Curie and her husband and colleague, Pierre Curie, it was learned that exposure to these alpha-particle emitters produced deleterious biological effects. The mechanisms underlying the increased biological effectiveness of densely ionizing radiations, including alpha particles, neutrons and highly energetic heavy charged particles, remain an active area of investigation. In this paper, we review recent advances in several areas of the radiobiology of these densely ionizing radiations, also known as heavy ions. Advances are described in the areas of DNA damage and repair, chromosome aberrations, mutagenesis, neoplastic transformation in vitro, genomic instability, normal tissue radiobiology and carcinogenesis in vivo. We focus on technical innovations, including novel applications of pulsed-field gel electrophoresis, fluorescence in situ hybridization (FISH), linkage analysis, and studies of gene expression and protein expression. We also highlight the use of new cellular and animal systems, including those with defined DNA repair deficiencies, as well as epithelial cell model systems to assess neoplastic transformation both in vitro and in vivo. The studies reviewed herein have had a substantial impact on our understanding of the genotoxic effects of heavy ions as well as their distinct effects on tissue homeostasis. The use of these radiations in cancer therapy is also discussed. The use of both heavy-ion and proton therapy is on the upswing in several centers around the world, due to their unique energy deposition characteristics that enhance the therapeutic effect and help reduce damage to normal tissue.

  16. Examination of mechanisms underlying enhanced memory performance in action video game players: a pilot study.

    PubMed

    Li, Xianchun; Cheng, Xiaojun; Li, Jiaying; Pan, Yafeng; Hu, Yi; Ku, Yixuan

    2015-01-01

    Previous studies have shown enhanced memory performance resulting from extensive action video game playing. The mechanisms underlying the cognitive benefit were investigated in the current study. We presented two types of retro-cues, with variable intervals to memory array (Task 1) or test array (Task 2), during the retention interval in a change detection task. In Task 1, action video game players demonstrated steady performance while non-action video game players showed decreased performance as cues occurred later, indicating their performance difference increased as the cue-to-memory-array intervals became longer. In Task 2, both participant groups increased their performance at similar rates as cues presented later, implying the performance difference in two groups were irrespective of the test-array-to-cue intervals. These findings suggested that memory benefit from game plays is not attributable to the higher ability of overcoming interference from the test array, but to the interactions between the two processes of protection from decay and resistance from interference, or from alternative hypotheses. Implications for future studies were discussed. PMID:26136720

  17. Mechanism of enhanced antipseudomonal activity of BO-2727, a new injectable 1-beta-methyl carbapenem.

    PubMed Central

    Hazumi, N; Fuse, A; Matsuda, K; Hashizume, T; Sanada, M

    1995-01-01

    The mechanism of the enhanced activity of BO-2727 against imipenem-resistant Pseudomonas aeruginosa was studied by using a set of four isogenic strains derived from beta-lactamase-deficient P. aeruginosa PAO4089 (blaJ blaP). Complementation of the blaJ and blaP mutations conferred greater resistance to biapenem, panipenem, and imipenem than to BO-2727 and meropenem, most notably in the outer membrane protein D2-deficient strain. The higher levels of resistance to biapenem, panipenem, and imipenem can be explained by the slow but significant hydrolysis by beta-lactamase, whereas the reduced levels of resistance to BO-2727 and meropenem would be attributable to their stability in the presence of high levels of beta-lactamase and the fact that they cause only low induction of beta-lactamase. It is also noted that the activity of BO-2727 against the beta-lactamase-deficient strain was less affected by the loss of the D2 porin than was that of meropenem, indicating that BO-2727 in comparison with meropenem can overcome an intrinsic resistance caused by the loss of D2. Moreover, comparative in vitro resistance studies have shown that BO-2727 and meropenem selected fewer resistant cells than other carbapenems. In conclusion, BO-2727 exhibited improved activity against imipenem-resistant P. aeruginosa, probably because of its ability to overcome loss of the D2 porin and beta-lactamase hydrolysis. PMID:7793876

  18. Enhanced long-term nitrogen removal and its quantitative molecular mechanism in tidal flow constructed wetlands.

    PubMed

    Zhi, Wei; Yuan, Li; Ji, Guodong; He, Chunguang

    2015-04-01

    Tidal flow constructed wetlands (TF CWs) have recently been studied as a sustainable technology to achieve enhanced nitrogen removal; however, the underlying mechanisms responsible for removing ammonium (NH4(+)) and nitrate (NO3(-)) have not been compared and quantified at the molecular level (genes) in controlled TF CWs. In this study, two TF CWs T1 (treating NH4(+) wastewater) and T2 (treating NO3(-) wastewater) achieved high removal efficiencies for chemical oxygen demand (COD, 92 ± 2.7% and 95 ± 2.4%, respectively), NH4(+)/NO3(-) (76 ± 3.9% and 97 ± 2.2%, respectively), and total nitrogen (TN, 81 ± 3.5% and 93 ± 2.3%, respectively). Combined analyses revealed that the presence of simultaneous nitrification, anammox, and denitrification processes and the coupling of dissimilatory nitrate reduction to ammonium, ammonia oxidation, and anammox were the primary reason accounted for the robust treatment performance in T1 and T2, respectively. Results from stepwise regression analysis suggested that the NH4(+) removal rate in T1 was collectively controlled by amoA, nxrA, and anammox, while the NO3(-) removal rate in T2 was governed by nxrA and narG gene. PMID:25781063

  19. CVD growth of carbon nanostructures from zirconia: mechanisms and a method for enhancing yield.

    PubMed

    Kudo, Akira; Steiner, Stephen A; Bayer, Bernhard C; Kidambi, Piran R; Hofmann, Stephan; Strano, Michael S; Wardle, Brian L

    2014-12-24

    By excluding metals from synthesis, growth of carbon nanostructures via unreduced oxide nanoparticle catalysts offers wide technological potential. We report new observations of the mechanisms underlying chemical vapor deposition (CVD) growth of fibrous carbon nanostructures from zirconia nanoparticles. Transmission electron microscope (TEM) observation reveals distinct differences in morphological features of carbon nanotubes and nanofibers (CNTs and CNFs) grown from zirconia nanoparticle catalysts versus typical oxide-supported metal nanoparticle catalysts. Nanofibers borne from zirconia lack an observable graphitic cage consistently found with nanotube-bearing metal nanoparticle catalysts. We observe two distinct growth modalities for zirconia: (1) turbostratic CNTs 2-3 times smaller in diameter than the nanoparticle localized at a nanoparticle corner, and (2) nonhollow CNFs with approximately the same diameter as the nanoparticle. Unlike metal nanoparticle catalysts, zirconia-based growth should proceed via surface-bound kinetics, and we propose a growth model where initiation occurs at nanoparticle corners. Utilizing these mechanistic insights, we further demonstrate that preannealing of zirconia nanoparticles with a solid-state amorphous carbon substrate enhances growth yield. PMID:25487041

  20. Low-power feedback-enhanced electro-mechanical impedance (FEMI) sensors

    NASA Astrophysics Data System (ADS)

    Jang, Ji Eun; Yue, C. Patrick

    2008-03-01

    Electro-mechanical impedance (EMI) method utilizing smart piezoelectric sensors has emerged as a promising technology for structural health monitoring in civil, mechanical and aerospace engineering. However, two major limiting factors have prevented field deployment of this method in real life. First, smart piezoelectric sensors, such as Lead Zirconate Titanate (PZT) patches, are highly sensitive to environmental changes such as temperature, humidity, and vibration. Secondly, bulky and expensive equipment is needed for performing impedance measurement. This paper proposes a feedback-enhanced electro-mechanical impedance (FEMI) technique for improving robustness against environmental variations and a design of a low-power EMI sensor with built-in measurement circuitries based on this new technique. The proposed FEMI technique employs a feedback scheme to amplify the peaking characteristics of the natural resonance frequencies in the EMI frequency response. The feedback loop includes a phase-locked loop (PLL) and a transimpedance amplifier (TIA). An analog EMI measurement circuit is developed to replace bulky EMI measurement instruments. To keep the power consumption low, the proposed system does not require any analog-to-digital conversion or DSP circuit blocks, but uses a simple analog mixer to multiply input and output waveforms of the PZT sensor, and then extract the EMI amplitude by passing the mixer output through a low-pass filter (LPF). The performance of the proposed FEMI sensor is verified by simulations using MATLAB. Simulated natural frequency peaks in the EMI spectrum are noticeably sharper with the feedback scheme than the one without feedback. As a result, the natural frequency shift due to any structural change can be more easily detected. To quantify the shift of these natural frequency peaks, the root mean square deviation (RMSD) of the difference between cases with and without damage is calculated. The simulation results show that the RMSD with

  1. New perspectives in hydrodynamic radial polishing techniques for optical surfaces

    NASA Astrophysics Data System (ADS)

    Ruiz, Elfego; Sohn, Erika; Luna, Esteban; Salas, Luis; Cordero, Alberto; González, Jorge; Núñez, Manuel; Salinas, Javier; Cruz-González, Irene; Valdés, Jorge; Cabrera, Victor; Martínez, Benjamín

    2004-09-01

    In order to overcome classic polishing techniques, a novel hydrodynamic radial polishing tool (HyDRa) is presented; it is useful for the corrective lapping and fine polishing of diverse materials by means of a low-cost abrasive flux and a hydrostatic suspension system that avoids contact of the tool with the working surface. This tool enables the work on flat or curved surfaces of currently up to two and a half meters in diameter. It has the advantage of avoiding fallen edges during the polishing process as well as reducing tool wear out and deformation. The functioning principle is based on the generation of a high-velocity, high-pressure, abrasive emulsion flux with radial geometry. The polishing process is repeatable by means of the control of the tool operational parameters, achieving high degrees of precision and accuracy on optical and semiconductor surfaces, with removal rates of up to 9 mm3/hour and promising excellent surface polishing qualities. An additional advantage of this new tool is the possibility to perform interferometric measurements during the polishing process without the need of dismounting the working surface. A series of advantages of this method, numerical simulations and experimental results are described.

  2. Estimation of the dietary acrylamide exposure of the Polish population.

    PubMed

    Mojska, Hanna; Gielecińska, Iwona; Szponar, Lucjan; Ołtarzewski, Maciej

    2010-01-01

    The objective of our study was to determine acrylamide content in the Polish foods and to assess the average dietary acrylamide exposure of the Polish population. We analysed the acrylamide content in Polish food using GCQ-MS/MS method. The daily dietary acrylamide exposure was computed using a probabilistic approach for the total Polish population (1-96 years) and for the following age groups: 1-6, 7-18 and 19-96, using Monte Carlo simulation technique. To assess the Polish population exposure to acrylamide present in food, food consumption data was taken from the 'Household Food Consumption and Anthropometric Survey in Poland'. The mean content of acrylamide in tested 225 samples of foodstuffs taken randomly all over Poland, ranged widely from 11 to 3647 microg/kg of product. For the total Polish population (1-96 years) the estimated acrylamide mean exposure is 0.43 microg/kg of body weight per day. The main sources of dietary acrylamide in Polish population were as follow: bread--supplied 45% of total dietary acrylamide intake, French fries and potato crisps--23%, roasted coffee--19%. PMID:20470853

  3. Evaluation and analysis of polished fused silica subsurface quality by the nanoindenter technique

    SciTech Connect

    Ma Bin; Shen Zhengxiang; He Pengfei; Sha Fei; Wang Chunliang; Wang Bin; Ji Yiqin; Liu Huasong; Li Weihao; Wang Zhanshan

    2011-03-20

    We evaluate the subsurface quality of polished fused silica samples using the nanoindenter technique. Two kinds of samples, consisting of hundreds of nanometers and micrometers of subsurface damage layers, are fabricated by controlling the grinding and polishing processes, and the subsurface quality has been verified by the chemical etching method. Then several nanoindentation experiments are performed using the Berkovich tip to investigate the subsurface quality. Some differences are found by relative measurements in terms of the relationship between the total penetration and the peak load on the surfaces, the modulus calculated over the defined depths and from unload, and the indented morphology at a constant load near the surface collapse threshold. Finally, the capabilities of such a mechanical method for detecting subsurface flaws are discussed and analyzed.

  4. Effect of texture of polishing particle on the surface roughness of a cobalt-chromium alloy using a centrifugal shooting type polishing machine.

    PubMed

    Ono, Takahiro; Ishikawa, Kaori; Yamaba, Osamu; Nokubi, Takashi

    2005-12-01

    In a previous report, we investigated the influence of the shooting angle of polishing particle on the surface roughness of a cobalt-chromium (Co-Cr) alloy using a centrifugal shooting type polishing machine. In the present work, we examined the effects of the texture of polishing particle and polishing time on the surface roughness of Co-Cr alloy cast specimens. Nine different textures of polishing particle were investigated with respect to core material and particle abrasiveness: three different elastic body cores (core A, hard chloroprene rubber; core B, soft chloroprene rubber; core C, natural rubber) and three different green carborundum powders as abrasives (#800, #3000, and #6000). Polishing was performed under a fixed shooting angle of 30 degrees for six different polishing times (1, 2, 3, 5, 7, and 10 minutes). Surface roughness (Ra, Sm) and cutting depth on the polished surface were measured after each polishing stage. Surface roughness was significantly improved within three minutes, particularly using a polishing particle with rough carborundum powder (#800 or #3000) and a heavy core (core A or core B). Cutting depth increased in proportion to polishing time and roughness of carborundum powder, and was least with core C. These results suggested that a polishing particle composed of core B and #3000 carborundum paste was superior for the intermediate polishing of a Co-Cr alloy, and that polishing time should be limited to within three minutes. PMID:16445008

  5. Notch signaling enhances FcεRI-mediated cytokine production by mast cells through direct and indirect mechanisms.

    PubMed

    Nakano, Nobuhiro; Nishiyama, Chiharu; Yagita, Hideo; Hara, Mutsuko; Motomura, Yasutaka; Kubo, Masato; Okumura, Ko; Ogawa, Hideoki

    2015-05-01

    Th2-type cytokines and TNF-α secreted by activated mast cells upon cross-linking of FcεRI contribute to the development and maintenance of Th2 immunity to parasites and allergens. We have previously shown that cytokine secretion by mouse mast cells is enhanced by signaling through Notch receptors. In this study, we investigated the molecular mechanisms by which Notch signaling enhances mast cell cytokine production induced by FcεRI cross-linking. FcεRI-mediated production of cytokines, particularly IL-4, was significantly enhanced in mouse bone marrow-derived mast cells by priming with Notch ligands. Western blot analysis showed that Notch signaling augmented and prolonged FcεRI-mediated phosphorylation of MAPKs, mainly JNK and p38 MAPK, through suppression of the expression of SHIP-1, a master negative regulator of FcεRI signaling, resulting in the enhanced production of multiple cytokines. The enhancing effect of Notch ligand priming on multiple cytokine production was abolished by knockdown of Notch2, but not Notch1, and FcεRI-mediated production of multiple cytokines was enhanced by retroviral transduction with the intracellular domain of Notch2. However, only IL-4 production was enhanced by both Notch1 and Notch2. The enhancing effect of Notch signaling on IL-4 production was lost in bone marrow-derived mast cells from mice lacking conserved noncoding sequence 2, which is located at the distal 3' element of the Il4 gene locus and contains Notch effector RBP-J binding sites. These results indicate that Notch2 signaling indirectly enhances the FcεRI-mediated production of multiple cytokines, and both Notch1 and Notch2 signaling directly enhances IL-4 production through the noncoding sequence 2 enhancer of the Il4 gene. PMID:25821223

  6. Advanced manufacturing technologies for light-weight post- polished snap-together reflective optical system designs

    NASA Astrophysics Data System (ADS)

    Sweeney, Michael N.

    2002-09-01

    Fast, light weight, off-axis, aspheric, reflective optical designs are increasingly being designed and built for space-based remote sensing, fire control systems, aerial reconnaissance, cryovac instrumentation and laser scanning. Diamond point turning (DPT) is the technology of first resort for many of these applications. In many cases the best diamond machining technologies available cannot meet the desired requirements for system wavefront error and scatter. Aluminum, beryllium, AlBeMet and silicon carbide mirrors, layered with thin films of electroless nickel or silicon can be first diamond machined and then post polished to achieve greatly enhanced performance levels for surface scatter, wavefront error (WFE), and alignment registration. By application of post polishing using precise null testing techniques, the objectives of snap-together, or limited compensation alignment of aggressive reflective optical systems can be achieved that are well beyond the performance envelope achievable by diamond machining alone. This paper discusses the tradeoffs among materials and processes selection for post polished reflective systems and illustrates actual applications including telescopes for earth and Mars orbit, and a commercial, high speed, flat field scan engine.

  7. 42 CFR 433.112 - FFP for design, development, installation or enhancement of mechanized claims processing and...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... FFP. (7) The costs of the system are determined in accordance with 45 CFR 74.171. (8) The Medicaid... 42 Public Health 4 2010-10-01 2010-10-01 false FFP for design, development, installation or... Retrieval Systems § 433.112 FFP for design, development, installation or enhancement of mechanized...

  8. Surface polishing of niobium for superconducting radio frequency (SRF) cavity applications

    SciTech Connect

    Zhao, Liang

    2014-08-01

    Niobium cavities are important components in modern particle accelerators based on superconducting radio frequency (SRF) technology. The interior of SRF cavities are cleaned and polished in order to produce high accelerating field and low power dissipation on the cavity wall. Current polishing methods, buffered chemical polishing (BCP) and electro-polishing (EP), have their advantages and limitations. We seek to improve current methods and explore laser polishing (LP) as a greener alternative of chemical methods. The topography and removal rate of BCP at different conditions (duration, temperature, sample orientation, flow rate) was studied with optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Differential etching on different crystal orientations is the main contributor to fine grain niobium BCP topography, with gas evolution playing a secondary role. The surface of single crystal and bi-crystal niobium is smooth even after heavy BCP. The topography of fine grain niobium depends on total removal. The removal rate increases with temperature and surface acid flow rate within the rage of 0~20 °C, with chemical reaction being the possible dominate rate control mechanism. Surface flow helps to regulate temperature and avoid gas accumulation on the surface. The effect of surface flow rate on niobium EP was studied with optical microscopy, atomic force microscopy (AFM), and power spectral density (PSD) analysis. Within the range of 0~3.7 cm/s, no significant difference was found on the removal rate and the macro roughness. Possible improvement on the micro roughness with increased surface flow rate was observed. The effect of fluence and pulse accumulation on niobium topography during LP was studied with optical microscopy, SEM, AFM, and PSD analysis. Polishing on micro scale was achieved within fluence range of 0.57~0.90 J/cm2, with pulse accumulation adjusted accordingly. Larger area treatment was proved possible by

  9. Pain-enhancing mechanism through interaction between TRPV1 and anoctamin 1 in sensory neurons

    PubMed Central

    Takayama, Yasunori; Uta, Daisuke; Furue, Hidemasa; Tominaga, Makoto

    2015-01-01

    The capsaicin receptor transient receptor potential cation channel vanilloid 1 (TRPV1) is activated by various noxious stimuli, and the stimuli are converted into electrical signals in primary sensory neurons. It is believed that cation influx through TRPV1 causes depolarization, leading to the activation of voltage-gated sodium channels, followed by the generation of action potential. Here we report that the capsaicin-evoked action potential could be induced by two components: a cation influx-mediated depolarization caused by TRPV1 activation and a subsequent anion efflux-mediated depolarization via activation of anoctamin 1 (ANO1), a calcium-activated chloride channel, resulting from the entry of calcium through TRPV1. The interaction between TRPV1 and ANO1 is based on their physical binding. Capsaicin activated the chloride currents in an extracellular calcium-dependent manner in HEK293T cells expressing TRPV1 and ANO1. Similarly, in mouse dorsal root ganglion neurons, capsaicin-activated inward currents were inhibited significantly by a specific ANO1 antagonist, T16Ainh-A01 (A01), in the presence of a high concentration of EGTA but not in the presence of BAPTA [1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid]. The generation of a capsaicin-evoked action potential also was inhibited by A01. Furthermore, pain-related behaviors in mice treated with capsaicin, but not with αβ-methylene ATP, were reduced significantly by the concomitant administration of A01. These results indicate that TRPV1–ANO1 interaction is a significant pain-enhancing mechanism in the peripheral nervous system. PMID:25848051

  10. Mechanisms of enhanced osteoclastogenesis in girls and young women with Turner's Syndrome.

    PubMed

    Faienza, Maria Felicia; Brunetti, Giacomina; Ventura, Annamaria; Piacente, Laura; Messina, Maria Francesca; De Luca, Filippo; Ciccarelli, Maria; Oranger, Angela; Mori, Giorgio; Natale, Maria Pia; Gigante, Margherita; Ranieri, Elena; Gesualdo, Loreto; Colucci, Silvia; Cavallo, Luciano; Grano, Maria

    2015-12-01

    Subjects with hypergonadotropic hypogonadism due to Turner's syndrome show low cortical mineral density, osteoporosis and risk of fractures. It is not clear if this bone fragility derives from chromosomal abnormalities or is the result of inadequate bone formation due to estrogen deficiency. The aim of this study was to investigate the cellular mechanisms underlying bone fragility in subjects with Turner's syndrome before induction of puberty and after hormonal replacement therapy (HRT). For this purpose, we have evaluated the osteoclastogenic potential of non-fractioned and T-cell depleted cultures of peripheral blood mononuclear cells (PBMCs) belonging to girls with Turner's syndrome who had not been treated with HRT yet, girls and young women who were on HRT and age-matched controls. Untreated subjects showed high FSH serum levels, whereas the other subjects displayed normal FSH serum levels. T-cell immunophenotype was analyzed through flow cytometry. Biochemical and DXA analyses were performed. Spontaneous osteoclastogenesis in non-fractioned and T-cell depleted cultures of PBMC belonging to girls with high FSH levels was more evident than in cultures of subjects with normal FSH levels. In the former, osteoclastogenesis was sustained by monocytes expressing high levels of c-fms, TNF-α and RANK, and T-cells producing high RANKL and TNF-α; in the latter it was supported by T-cells expressing high RANKL levels. CD4(+)CD25(high) T-cells were reduced in all subjects, whereas CD3(+)/CD16(+)/CD56(+) NKT-cells were increased in those with high FSH levels. High RANKL and CTX levels were detected in the sera. Bone impairment was already detectable by DXA in subjects aged under 10, although it became more evident with aging. In conclusion, our results demonstrated that bone fragility in subjects with Turner's syndrome is associated to enhanced osteoclastogenesis. This process seems to be due to high FSH serum levels before HRT, whereas it is caused by high RANKL during

  11. New insights into the molecular mechanisms of thrombosis from high resolution surface enhanced Raman microscopy

    NASA Astrophysics Data System (ADS)

    Keyes, Tia E.; Leane, Deirdre; Forster, Robert J.; Moran, Niamh; Kenny, Dermot

    2005-06-01

    Occlusion of a blood vessel due to thrombosis can reduce or completely stop blood supply to different tissues or organs with the clinical consequences of myocardial infarction or stroke. Platelets are the cellular component which initiate thrombus formation, they activate in response to a variety of signals, such as interactions with a damaged blood vessel. αIIbβ3 is a membrane bound integrin protein responsible for regulating adhesion of the activated platelet to damaged blood vessels. It exists in both activated and non-activated states displaying high and low affinity respectively for ligands such as fibrinogen. αIIbβ3 determines the "stickiness" of the blood platelet and is therefore, a logical target for therapeutic measures to control thrombus formation. During the past decade considerable progress has been made to identify the role of the αIIbβ3 complex in platelet-mediated thrombus formation and the structure of αIIbβ3 has been extrapolated from the crystal structure of related integrins. However, despite these advances, the bimolecular mechanisms underlying the activation of αIIbβ3 remain poorly understood. In this contribution, we describe methodologies of deriving surface enhanced Raman spectroscopy of αIIbβ3 on nanostructured metal surfaces, fabricated by a number of methods. We compare activation of αIIbβ3 by SERS using a range of known activation conditions including Mn(II), EDTA and dithiotheritol (DTT). By studying the behaviour of the disulfide and CS marker vibrations in the spectral region 400 to 800 cm-1 using SERS we confirm that activation results in significant conformational change in the protein, and most interestingly, that the response is not the same for every agonist. This mechanistic difference has implications for the biochemical study of this protein (and indeed for understanding the role of this integrin in response to different agonists).

  12. ON THE POSSIBLE MECHANISMS OF TWO GROUND-LEVEL ENHANCEMENT EVENTS

    SciTech Connect

    Firoz, Kazi A.; Islam, Jamal N.; Moon, Y.-J.; Park, S.-H.; Kudela, K.; Dorman, Lev I.

    2011-12-20

    We have carried out a case study on the possible mechanism of ground-level enhancement (GLE) occurrence. For this, we have considered two GLE events (GLE69 and GLE70) and scrutinized their relationships with simultaneous soft/hard X-rays as well as solar energetic particle (SEP) fluxes of different energy bands. Although most of the energy bands of the flares maintain strong correlations (r {>=} 0.8) with the GLEs, depending only on this evidence we could not precisely imply that GLEs can be caused by solar flares. So, we have attempted to understand possible relativistic energies of the GLEs, which have been determined by availing the relativistic traversing time and velocities of the particles along the nominal path of Archimedean spiral magnetic field lines. Results suggest that the energy released from accelerated particles in high-energy ({gamma}-ray) solar flares might sometimes cause the GLE. We found that during hard X-ray flares {<=}7 MeV, the relativistic energy ({<=}0.23 GeV) of GLE69 was much less than 1 GeV whereas during SEP flares >30 MeV the possible relativistic energy of GLE69 amounts to {approx}2.78 GeV, and this makes us believe that GLE69 might be caused by the energy released from particle accelerations in high-energy solar flares. On the contrary, during hard X-ray ({<=}7 MeV) as well as {gamma}-ray solar flares (>30 MeV) the relativistic energy of GLE70 amounts to {<=}{approx}0.35 GeV, indicating that the GLE70 was presumably not caused by the released energy from accelerated particles in the solar flare. Alternatively, the released energy from particle accelerations in solar radio emission type II burst concomitant coronal-mass-ejection-driven shocks seems to have been responsible for causing the GLE70.

  13. Enhanced spontaneous locomotor activity in bovine GH transgenic mice involves peripheral mechanisms.

    PubMed

    Bohlooly-Y, M; Olsson, B; Gritli-Linde, A; Brusehed, O; Isaksson, O G; Ohlsson, C; Söderpalm, B; Törnell, J; Ola, B

    2001-10-01

    Clinical and experimental studies indicate a role for GH in mechanisms related to anhedonia/hedonia, psychic energy, and reward. Recently we showed that transgenic mice with general overexpression of bovine GH display increased spontaneous locomotor activity. In the present study, we investigated whether this behavioral change is owing to a direct action of GH in the central nervous system or to peripheral GH actions. A transgenic construct, containing the glial fibrillary acidic protein promoter directing specific expression of bovine GH to the central nervous system, was designed. The central nervous system-specific expression of bovine GH in the glial fibrillary acidic protein-bovine GH transgenic mice was confirmed, but no effect on spontaneous locomotor activity was observed. Serum bovine GH levels were increased in glial fibrillary acidic protein-bovine GH transgenic mice but clearly lower than in transgenic mice with general overexpression of bovine GH. In contrast to the transgenic mice with general overexpression of bovine GH, glial fibrillary acidic protein-bovine GH mice did not display any difference in serum IGF-I levels. The levels of free T(3) and the conversion of the free T(4) to free T(3) were only increased in transgenic mice with general overexpression of bovine GH, but serum corticosterone levels were similarly increased in both transgenic models. These results suggest that free T(3) and/or IGF-I, affecting dopamine and serotonin systems in the central nervous system, may mediate the enhanced locomotor activity observed in transgenic mice with general overexpression of bovine GH. PMID:11564723

  14. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    SciTech Connect

    Li, Yingjie; Go, David B.

    2014-09-14

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

  15. Wastewater polishing by a channelized macrophyte-dominated wetland and anaerobic digestion of the harvested phytomass.

    PubMed

    Cohen, Michael F; Hare, Caden; Kozlowski, John; McCormick, Rachel S; Chen, Lily; Schneider, Linden; Parish, Meghan; Knight, Zane; Nelson, Timothy A; Grewell, Brenda J

    2013-01-01

    Constructed wetlands (CW) offer a mechanism to meet increasingly stringent regulatory standards for wastewater treatment while minimizing energy inputs. Additionally, harvested wetland phytomass subjected to anaerobic digestion can serve as a source of biogas methane. To investigate CW wastewater polishing activities and potential energy yield we constructed a pair of secondary wastewater-fed channelized CW modules designed to retain easily harvestable floating aquatic vegetation and maximize exposure of water to roots and sediment. Modules that were regularly harvested averaged a nitrate removal rate of 1.1 g N m(-2) d(-1); harvesting, sedimentation and gasification were responsible for 30.5%, 8.0% and 61.5% of the N losses, respectively. Selective harvesting of a module to maintain dominance of filamentous algae had no effect on nitrate removal rate but lowered productivity by one-half. The average monthly productivity for unselectively harvested modules was 9.3 ± 1.7 g dry wt. m(-2) d(-1) (±SE). Cessation of harvesting in one module resulted in a significant increase in nitrate removal rate and decrease in phosphate removal rate. Compared to the influent, the effluent of the harvested module had significantly lower levels of estrogenic activity, as determined by a quantitative PCR-based juvenile trout bioassay, and significantly lower densities of E. coli. In mixed vertical-flow reactors anaerobic co-digestion of equal dry weight proportions of harvested aquatic vegetation, wine yeast lees and dairy manure was greatly improved when the manure was replaced with the crude glycerol by-product of biodiesel production. Remaining solids were vermicomposted for use as a soil amendment. Our results indicate that incorporation of constructed wetlands into an integrated treatment system can simultaneously enhance the economic and energetic feasibility of wastewater and organic waste treatment processes. PMID:23245307

  16. CNC subaperture polishing process arrangement for microroughness minimisation

    NASA Astrophysics Data System (ADS)

    Prochaska, F.; Matousek, O.; Tomka, D.; Polak, J.; Poláková, I.

    2015-01-01

    The aim of this study was to determine the optimal subaperture polishing procedure for aspherical surfaces on the Optotech MCP 250 CNC machine. Due to the fact that the CNC subaperture polishing process runs along well defined paths, certain frequencies develop on the polished surface, which can be limiting for the resulting microroughness. A proper sequence of polishing steps in different tool motion control modes can minimize these frequencies and help to substantially reduce microroughness. In this context, various tool motion control modes ("Spiral spindle mode", "Spiral axis mode" and "Raster mode") in combination with different tools were tested. The resulting microroughness values were observed in the defined mid-frequency and high-frequency areas. The best results, i.e. the lowest microroughness values were obtained using a combination of the processes "Ball spiral axis mode", "FEM raster mode", "spiral spindle 2D FEM correction mode" and "AFJ spiral axis mode"

  17. High quality optically polished aluminum mirror and process for producing

    NASA Technical Reports Server (NTRS)

    Lyons, III, James J. (Inventor); Zaniewski, John J. (Inventor)

    2002-01-01

    A new technical advancement in the field of precision aluminum optics permits high quality optical polishing of aluminum monolith, which, in the field of optics, offers numerous benefits because of its machinability, lightweight, and low cost. This invention combines diamond turning and conventional polishing along with india ink, a newly adopted material, for the polishing to accomplish a significant improvement in surface precision of aluminum monolith for optical purposes. This invention guarantees the precise optical polishing of typical bare aluminum monolith to surface roughness of less than about 30 angstroms rms and preferably about 5 angstroms rms while maintaining a surface figure accuracy in terms of surface figure error of not more than one-fifteenth of wave peak-to-valley.

  18. High quality optically polished aluminum mirror and process for producing

    NASA Technical Reports Server (NTRS)

    Lyons, III, James J. (Inventor); Zaniewski, John J. (Inventor)

    2005-01-01

    A new technical advancement in the field of precision aluminum optics permits high quality optical polishing of aluminum monolith, which, in the field of optics, offers numerous benefits because of its machinability, lightweight, and low cost. This invention combines diamond turning and conventional polishing along with india ink, a newly adopted material, for the polishing to accomplish a significant improvement in surface precision of aluminum monolith for optical purposes. This invention guarantees the precise optical polishing of typical bare aluminum monolith to surface roughness of less than about 30 angstroms rms and preferably about 5 angstroms rms while maintaining a surface figure accuracy in terms of surface figure error of not more than one-fifteenth of wave peak-to-valley.

  19. Why won't Polish women birth at home?

    PubMed

    Pendleton, John

    2015-09-01

    Polish women living in the United Kingdom (UK) are statistically more likely to have normal births than their British counterparts, yet anecdotally, do not choose to birth their babies at home. A medicalised approach to birth in their country of origin means women are unaware of the benefits of midwifery-led care, which they often perceive as sub-standard. Affordable travel means Polish women can access care in both countries and compounds the difficulties in acclimatising to UK maternity services. Online discussion groups and Internet forums represent an opportunity for midwives to engage with women to promote their services. This is increasingly important with rising numbers of both Polish migrants to the UK and Polish residents applying for British citizenship. PMID:26547999

  20. DEMONSTRATION BULLETIN: COLLOID POLISHING FILTER METHOD - FILTER FLOW TECHNOLOGY, INC.

    EPA Science Inventory

    The Filter Flow Technology, Inc. (FFT) Colloid Polishing Filter Method (CPFM) was tested as a transportable, trailer mounted, system that uses sorption and chemical complexing phenomena to remove heavy metals and nontritium radionuclides from water. Contaminated waters can be pro...