A Two-Fluid, MHD Coronal Model

NASA Technical Reports Server (NTRS)

Suess, S. T.; Wang, A.-H.; Wu, S. T.; Poletto, G.; McComas, D. J.

1999-01-01

We describe first results from a numerical two-fluid MHD model of the global structure of the solar Corona. The model is two-fluid in the sense that it accounts for the collisional energy exchange between protons and electrons. As in our single-fluid model, volumetric heat and Momentum sources are required to produce high speed wind from Corona] holes, low speed wind above streamers, and mass fluxes similar to the empirical solar wind. By specifying different proton and electron heating functions we obtain a high proton temperature in the coronal hole and a relatively low proton temperature above the streamer (in comparison with the electron temperature). This is consistent with inferences from SOHO/UltraViolet Coronagraph Spectrometer instrument (UVCS), and with the Ulysses/Solar Wind Observations Over the Poles of the Sun instrument (SWOOPS) proton and electron temperature measurements which we show from the fast latitude scan. The density in the coronal hole between 2 and 5 solar radii (2 and 5 R(sub S)) is similar to the density reported from SPARTAN 201.-01 measurements by Fisher and Guhathakurta [19941. The proton mass flux scaled to 1 AU is 2.4 x 10(exp 8)/sq cm s, which is consistent with Ulysses observations. Inside the closed field region, the density is sufficiently high so that the simulation gives equal proton and electron temperatures due to the high collision rate. In open field regions (in the coronal hole and above the streamer) the proton and electron temperatures differ by varying amounts. In the streamer the temperature and density are similar to those reported empirically by Li et al. [1998], and the plasma beta is larger than unity everywhere above approx. 1.5 R(sub S), as it is in all other MHD coronal streamer models [e.g., Steinolfson et al., 1982; also G. A. Gary and D. Alexander, Constructing the coronal magnetic field, submitted to Solar Physics, 1998].

F"orster-type mechanism of the redox-driven proton pump

NASA Astrophysics Data System (ADS)

Mourokh, Lev; Smirnov, Anatoly; Nori, Franco

2007-03-01

We propose a model to describe an electronically-driven proton pump in the cytochrome c oxidase (CcO). We examine the situation when the electron transport between the two sites embedded into the inner membrane of the mitochondrion occurs in parallel with the proton transfer from the protonable site that is close to the negative (inner) side of the membrane to the other protonable site located nearby the positive (outer) surface of the membrane. In addition to the conventional electron and proton tunnelings between the sites, the Coulomb interaction between electrons and protons localized on the corresponding sites leads to so-called F"orster transfer, i.e. to the process when the simultaneous electron and proton tunnelings are accompanied by the resonant energy transfer between the electrons and protons. Our calculations based on reasonable parameters have demonstrated that the F"orster process facilitates the proton pump at physiological temperatures. We have examined the effects of an electron voltage build-up, external temperature, and molecular electrostatics driving the electron and proton energies to the resonant conditions, and have shown that these parameters can control the proton pump operation.

Protonation enthalpies of metal oxides from high temperature electrophoresis

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

Rodriguez-Santiago, V; Fedkin, Mark V.; Lvov, Serguei N.

2012-01-01

Surface protonation reactions play an important role in the behavior of mineral and colloidal systems, specifically in hydrothermal aqueous environments. However, studies addressing the reactions at the solid/liquid interface at temperatures above 100 C are scarce. In this study, newly and previously obtained high temperature electrophoresis data (up to 260 C) zeta potentials and isoelectric points for metal oxides, including SiO2, SnO2, ZrO2, TiO2, and Fe3O4, were used in thermodynamic analysis to derive the standard enthalpies of their surface protonation. Two different approaches were used for calculating the protonation enthalpy: one is based on thermodynamic description of the 1-pKa modelmore » for surface protonation, and another one on a combination of crystal chemistry and solvation theories which link the relative permittivity of the solid phase and the ratio of the Pauling bond strength and bond length to standard protonation enthalpy. From this analysis, two expressions relating the protonation enthalpy to the relative permittivity of the solid phase were obtained.« less

Protonation enthalpies of metal oxides from high temperature electrophoresis.

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

Rodriguez-Santiago, V; Fedkin, Mark V; Lvov, Serguei N.

2012-01-01

Surface protonation reactions play an important role in the behavior of mineral and colloidal systems, specifically in hydrothermal aqueous environments. However, studies addressing the reactions at the solid/liquid interface at temperatures above 100 C are scarce. In this study, newly and previously obtained high temperature electrophoresis data (up to 260 C) - zeta potentials and isoelectric points - for metal oxides, including SiO{sub 2}, SnO{sub 2}, ZrO{sub 2}, TiO{sub 2}, and Fe{sub 3}O{sub 4}, were used in thermodynamic analysis to derive the standard enthalpies of their surface protonation. Two different approaches were used for calculating the protonation enthalpy: one ismore » based on thermodynamic description of the 1-pKa model for surface protonation, and another one - on a combination of crystal chemistry and solvation theories which link the relative permittivity of the solid phase and the ratio of the Pauling bond strength and bond length to standard protonation enthalpy. From this analysis, two expressions relating the protonation enthalpy to the relative permittivity of the solid phase were obtained.« less

Accurate MR thermometry by hyperpolarized 129 Xe.

PubMed

Zhang, Le; Burant, Alex; McCallister, Andrew; Zhao, Victor; Koshlap, Karl M; Degan, Simone; Antonacci, Michael; Branca, Rosa Tamara

2017-09-01

To investigate the temperature dependence of the resonance frequency of lipid-dissolved xenon (LDX) and to assess the accuracy of LDX-based MR thermometry. The chemical shift temperature dependence of water protons, methylene protons, and LDX was measured from samples containing tissues with varying fat contents using a high-resolution NMR spectrometer. LDX results were then used to acquire relative and absolute temperature maps in vivo and the results were compared with PRF-based MR thermometry. The temperature dependence of proton resonance frequency (PRF) is strongly affected by the specific distribution of water and fat. A redistribution of water and fat compartments can reduce the apparent temperature dependence of the water chemical shift from -0.01 ppm/°C to -0.006 ppm, whereas the LDX chemical shift shows a consistent temperature dependence of -0.21 ppm/°C. The use of the methylene protons resonance frequency as internal reference improves the accuracy of LDX-based MR thermometry, but degrades that of PRF-based MR thermometry, as microscopic susceptibility gradients affected lipid and water spins differently. The LDX resonance frequency, with its higher temperature dependence, provides more accurate and precise temperature measurements, both in vitro and in vivo. More importantly, the resonance frequency of nearby methylene protons can be used to extract absolute temperature information. Magn Reson Med 78:1070-1079, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Proton trapping in yttrium-doped barium zirconate

NASA Astrophysics Data System (ADS)

Yamazaki, Yoshihiro; Blanc, Frédéric; Okuyama, Yuji; Buannic, Lucienne; Lucio-Vega, Juan C.; Grey, Clare P.; Haile, Sossina M.

2013-07-01

The environmental benefits of fuel cells have been increasingly appreciated in recent years. Among candidate electrolytes for solid-oxide fuel cells, yttrium-doped barium zirconate has garnered attention because of its high proton conductivity, particularly in the intermediate-temperature region targeted for cost-effective solid-oxide fuel cell operation, and its excellent chemical stability. However, fundamental questions surrounding the defect chemistry and macroscopic proton transport mechanism of this material remain, especially in regard to the possible role of proton trapping. Here we show, through a combined thermogravimetric and a.c. impedance study, that macroscopic proton transport in yttrium-doped barium zirconate is limited by proton-dopant association (proton trapping). Protons must overcome the association energy, 29 kJ mol-1, as well as the general activation energy, 16 kJ mol-1, to achieve long-range transport. Proton nuclear magnetic resonance studies show the presence of two types of proton environment above room temperature, reflecting differences in proton-dopant configurations. This insight motivates efforts to identify suitable alternative dopants with reduced association energies as a route to higher conductivities.

Proton trapping in yttrium-doped barium zirconate.

PubMed

Yamazaki, Yoshihiro; Blanc, Frédéric; Okuyama, Yuji; Buannic, Lucienne; Lucio-Vega, Juan C; Grey, Clare P; Haile, Sossina M

2013-07-01

The environmental benefits of fuel cells have been increasingly appreciated in recent years. Among candidate electrolytes for solid-oxide fuel cells, yttrium-doped barium zirconate has garnered attention because of its high proton conductivity, particularly in the intermediate-temperature region targeted for cost-effective solid-oxide fuel cell operation, and its excellent chemical stability. However, fundamental questions surrounding the defect chemistry and macroscopic proton transport mechanism of this material remain, especially in regard to the possible role of proton trapping. Here we show, through a combined thermogravimetric and a.c. impedance study, that macroscopic proton transport in yttrium-doped barium zirconate is limited by proton-dopant association (proton trapping). Protons must overcome the association energy, 29 kJ mol(-1), as well as the general activation energy, 16 kJ mol(-1), to achieve long-range transport. Proton nuclear magnetic resonance studies show the presence of two types of proton environment above room temperature, reflecting differences in proton-dopant configurations. This insight motivates efforts to identify suitable alternative dopants with reduced association energies as a route to higher conductivities.

Temperature dependence of partial conductivities of the BaZr0.7Ce0.2Y0.1O3-δ proton conductor

NASA Astrophysics Data System (ADS)

Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

2017-10-01

Partial conductivities are presented for BaZr0.7Ce0.2Y0.1O3-δ, an important proton conductor for protonic-ceramic fuel cells and membrane reactors. Atmospheric dependencies of impedance performed in humidified and dry O2, air, N2 and H2(10%)/N2(90%) in the temperature range 300-900 °C, supported by the modified emf method, confirm significant electron-hole and protonic contributions to transport. For very reducing and wet atmospheres, the conductivity is predominantly ionic, with a higher participation of protons with decreasing temperature and increasing water-vapour partial pressure (pH2O). From moderately reducing conditions of wet N2 to wet O2, however, the conductivity is considerably influenced by electron holes as revealed by a significant dependence of total conductivity on oxygen partial pressure (pO2). With higher pH2O, proton transport increases, with a concomitant decrease of holes and oxygen vacancies. However, the effect of pH2O is also influenced by temperature, with a greater protonic contribution at both lower temperature and pO2. Values of proton transport number tH ≈ 0.63 and electronic transport number th ≈ 0.37 are obtained at 600 °C for pH2O = 0.022 atm and pO2 = 0.2 atm, whereas tH ≈ 0.95 and th ≈ 0.05 for pO2 = 10-5 atm. A hydration enthalpy of -109 kJ mol-1 is obtained in the range 600-900 °C.

Standing shocks in a two-fluid solar wind

NASA Technical Reports Server (NTRS)

Habbal, Shadia R.; Hu, You Qiu; Esser, Ruth

1994-01-01

We present a numerical study of the formation of standing shocks in the solar wind using a two-fluid time-dependent model in the presence of Alfven waves. Included in this model is the adiabatic cooling and thermal conduction of both electrons and protons. In this study, standing shocks develop in the flow when additional critical points form as a result of either localized momentum addition or rapid expansion of the flow tube below the existing sonic point. While the flow speed and density exhibit the same characteristics as found in earlier studies of the formation of standing shocks, the inclusion of electron and proton heat conduction produces different signatures in the electron and proton temperature profiles across the shock layer. Owing to the strong heat conduction, the electron temperature is nearly continuous across the shock, but its gradient has a negative jump across it, thus producing a net heat flux out of the shock layer. The proton temperature exhibits the same characteristics for shocks produced by momentum addition but behaves differently when the shock is formed by the rapid divergence of the flow tube. The adiabatic cooling in a rapidly diverging flow tube reduces the proton temperature so substantially that the proton heat conduction becomes negligible in the vicinity of the shock. As a result, protons experience a positive jump in temperature across the shock. While Alfven waves do not affect the formation of standing shocks, they contribute to the change of the mmomentum and energy balance across them. We also find that for this solar wind model the inclusion of thermal conduction and adiabatic cooling for the elctrons and protons increases significantly the range of parameters characterizing the formation of standing shocks over those previously found for isothermal and polytropic models.

Room temperature synthesis of protonated layered titanate sheets using peroxo titanium carbonate complex solution.

PubMed

Sutradhar, Narottam; Sinhamahapatra, Apurba; Pahari, Sandip Kumar; Bajaj, Hari C; Panda, Asit Baran

2011-07-21

We report the synthesis of peroxo titanium carbonate complex solution as a novel water-soluble precursor for the direct synthesis of layered protonated titanate at room temperature. The synthesized titanates showed excellent removal capacity for Pb(2+) and methylene blue. Based on experimental observations, a probable mechanism for the formation of protonated layered dititanate sheets is also discussed.

New High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

NASA Technical Reports Server (NTRS)

Kinder, James D.

2004-01-01

Fuel cells are receiving a considerable amount of attention for potential use in a variety of areas, including the automotive industry, commercial power generation, and personal electronics. Research at the NASA Glenn Research Center has focused on the development of fuel cells for use in aerospace power systems for aircraft, unmanned air vehicles, and space transportation systems. These applications require fuel cells with higher power densities and better durability than what is required for nonaerospace uses. In addition, membrane cost is a concern for any fuel cell application. The most widely used membrane materials for proton exchange membrane (PEM) fuel cells are based on sulfonated perfluorinated polyethers, typically Nafion 117, Flemion, or Aciplex. However, these polymers are costly and do not function well at temperatures above 80 C. At higher temperatures, conventional membrane materials dry out and lose their ability to conduct protons, essential for the operation of the fuel cell. Increasing the operating temperature of PEM fuel cells from 80 to 120 C would significantly increase their power densities and enhance their durability by reducing the susceptibility of the electrode catalysts to carbon monoxide poisoning. Glenn's Polymers Branch has focused on developing new, low-cost membranes that can operate at these higher temperatures. A new series of organically modified siloxane (ORMOSIL) polymers were synthesized for use as membrane materials in a high-temperature PEM fuel cell. These polymers have an organic portion that can allow protons to transport through the polymer film and a cross-linked silica network that gives the polymers dimensional stability. These flexible xerogel polymer films are thermally stable, with decomposition onset as high as 380 C. Two types of proton-conducting ORMOSIL films have been produced: (1) NASA-A, which can coordinate many highly acid inorganic salts that facilitate proton conduction and (2) NASA-B, which has been produced and which incorporates strongly acidic (proton donating) functional groups into the polymer backbone. Both of these polymer films have demonstrated significantly higher proton conductivity than Nafion at elevated temperatures and low relative humidities. An added advantage is that these polymers are very inexpensive to produce because their starting materials are commodity chemicals that are commercially available in large volumes.

High temperature proton exchange membranes with enhanced proton conductivities at low humidity and high temperature based on polymer blends and block copolymers of poly(1,3-cyclohexadiene) and poly(ethylene glycol)

DOE PAGES

Deng, Shawn; Hassan, Mohammad K.; Nalawade, Amol; ...

2015-09-16

Hot (at 120 °C) and dry (20% relative humidity) operating conditions benefit fuel cell designs based on proton exchange membranes (PEMs) and hydrogen due to simplified system design and increasing tolerance to fuel impurities. In this paper, presented are preparation, partial characterization, and multi-scale modeling of such PEMs based on cross-linked, sulfonated poly(1,3-cyclohexadiene) (xsPCHD) blends and block copolymers with poly(ethylene glycol) (PEG). These low cost materials have proton conductivities 18 times that of current industry standard Nafion at hot, dry operating conditions. Among the membranes studied, the blend xsPCHD-PEG PEM displayed the highest proton conductivity, which exhibits a morphology withmore » higher connectivity of the hydrophilic domain throughout the membrane. Simulation and modeling provide a molecular level understanding of distribution of PEG within this hydrophilic domain and its relation to proton conductivities. Finally, this study demonstrates enhancement of proton conductivity at high temperature and low relative humidity by incorporation of PEG and optimized sulfonation conditions.« less

Mixing the Solar Wind Proton and Electron Scales: Effects of Electron Temperature Anisotropy on the Oblique Proton Firehose Instability

NASA Technical Reports Server (NTRS)

Maneva, Y.; Lazar, M.; Vinas, A.; Poedts, S.

2016-01-01

The double adiabatic expansion of the nearly collisionless solar wind plasma creates conditions for the firehose instability to develop and efficiently prevent the further increase of the plasma temperature in the direction parallel to the interplanetary magnetic field. The conditions imposed by the firehose instability have been extensively studied using idealized approaches that ignore the mutual effects of electrons and protons. Recently, more realistic approaches have been proposed that take into account the interplay between electrons and protons,? unveiling new regimes of the parallel oscillatory modes. However, for oblique wave propagation the instability develops distinct branches that grow much faster and may therefore be more efficient than the parallel firehose instability in constraining the temperature anisotropy of the plasma particles. This paper reports for the first time on the effects of electron plasma properties on the oblique proton firehose (PFH) instability and provides a comprehensive vision of the entire unstable wave-vector spectrum, unifying the proton and the smaller electron scales. The plasma ß and temperature anisotropy regimes considered here are specific for the solar wind and magnetospheric conditions, and enable the electrons and protons to interact via the excited electromagnetic fluctuations. For the selected parameters, simultaneous electron and PFH instabilities can be observed with a dispersion spectrum of the electron firehose (EFH) extending toward the proton scales. Growth rates of the PFH instability are markedly boosted by the anisotropic electrons, especially in the oblique direction where the EFH growth rates are orders of magnitude higher.

MIXING THE SOLAR WIND PROTON AND ELECTRON SCALES: EFFECTS OF ELECTRON TEMPERATURE ANISOTROPY ON THE OBLIQUE PROTON FIREHOSE INSTABILITY

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

Maneva, Y.; Lazar, M.; Poedts, S.

2016-11-20

The double adiabatic expansion of the nearly collisionless solar wind plasma creates conditions for the firehose instability to develop and efficiently prevent the further increase of the plasma temperature in the direction parallel to the interplanetary magnetic field. The conditions imposed by the firehose instability have been extensively studied using idealized approaches that ignore the mutual effects of electrons and protons. Recently, more realistic approaches have been proposed that take into account the interplay between electrons and protons, unveiling new regimes of the parallel oscillatory modes. However, for oblique wave propagation the instability develops distinct branches that grow much fastermore » and may therefore be more efficient than the parallel firehose instability in constraining the temperature anisotropy of the plasma particles. This paper reports for the first time on the effects of electron plasma properties on the oblique proton firehose (PFH) instability and provides a comprehensive vision of the entire unstable wave-vector spectrum, unifying the proton and the smaller electron scales. The plasma β and temperature anisotropy regimes considered here are specific for the solar wind and magnetospheric conditions, and enable the electrons and protons to interact via the excited electromagnetic fluctuations. For the selected parameters, simultaneous electron and PFH instabilities can be observed with a dispersion spectrum of the electron firehose (EFH) extending toward the proton scales. Growth rates of the PFH instability are markedly boosted by the anisotropic electrons, especially in the oblique direction where the EFH growth rates are orders of magnitude higher.« less

Nanostructure-based proton exchange membrane for fuel cell applications at high temperature.

PubMed

Li, Junsheng; Wang, Zhengbang; Li, Junrui; Pan, Mu; Tang, Haolin

2014-02-01

As a clean and highly efficient energy source, the proton exchange membrane fuel cell (PEMFC) has been considered an ideal alternative to traditional fossil energy sources. Great efforts have been devoted to realizing the commercialization of the PEMFC in the past decade. To eliminate some technical problems that are associated with the low-temperature operation (such as catalyst poisoning and poor water management), PEMFCs are usually operated at elevated temperatures (e.g., > 100 degrees C). However, traditional proton exchange membrane (PEM) shows poor performance at elevated temperature. To achieve a high-performance PEM for high temperature fuel cell applications, novel PEMs, which are based on nanostructures, have been developed recently. In this review, we discuss and summarize the methods for fabricating the nanostructure-based PEMs for PEMFC operated at elevated temperatures and the high temperature performance of these PEMs. We also give an outlook on the rational design and development of the nanostructure-based PEMs.

Ionic Liquids and New Proton Exchange Membranes for Fuel Cells

NASA Technical Reports Server (NTRS)

Belieres, Jean-Philippe

2004-01-01

There is currently a great surge of activity in fuel cell research as laboratories across the world seek to take advantage of the high energy capacity provided by &el cells relative to those of other portable electrochemical power systems. Much of this activity is aimed at high temperature fie1 cells, and a vital component of such &el cells must be the availability of a high temperature stable proton-permeable membrane. NASA Glenn Research Center is greatly involved in developing this technology. Other approaches to the high temperature fuel cell involve the use of single- component or almost-single-component electrolytes that provide a path for protons through the cell. A heavily researched case is the phosphoric acid fuel cell, in which the electrolyte is almost pure phosphoric acid and the cathode reaction produces water directly. The phosphoric acid fie1 cell delivers an open circuit voltage of 0.9 V falling to about 0.7 V under operating conditions at 170 C. The proton transport mechanism is mainly vehicular in character according to the viscosity/conductance relation. Here we describe some Proton Transfer Ionic Liquids (PTILs) with low vapor pressure and high temperature stability that have conductivities of unprecedented magnitude for non-aqueous systems. The first requirement of an ionic liquid is that, contrary to experience with most liquids consisting of ions, it must have a melting point that is not much above room temperature. The limit commonly suggested is 100 C. PTILs constitute an interesting class of non-corrosive proton-exchange electrolyte, which can serve well in high temperature (T = 100 - 250 C) fuel cell applications. We will present cell performance data showing that the open circuit voltage output, and the performance of a simple H2(g)Pt/PTIL/Pt/O2(g) fuel cell may be superior to those of the equivalent phosphoric acid electrolyte fuel cell both at ambient temperature and temperatures up to and above 200 C. My work at NASA Glenn Research Center during this summer is to develop and characterize proton exchange membranes doped with ionic liquids. The main techniques used to characterize these materials are: Impedance Spectroscopy, NMR, DSC, TGA, DMA, IR, and SEM ...

Acceleration and heating of two-fluid solar wind by Alfven waves

NASA Technical Reports Server (NTRS)

Sandbaek, Ornulf; Leer, Egil

1994-01-01

Earlier model studies of solar wind driven by thermal pressure and Alfven waves have shown that wave amplitudes of 20-30 km/s at the coronal base are sufficient to accelerate the flow to the high speeds observed in quasi-steady streams emanating from large coronal holes. We focus on the energy balance in the proton gas and show that heat conduction from the region where the waves are dissipated may play an important role in determining the proton temperature at the orbit of Earth. In models with 'classical' heat conduction we find a correlation between high flow speed, high proton temperature, and low electron temperature at 1 AU. The effect of wave heating on the development of anisotropies in the solar wind proton gas pressure is also investigated in this study.

Comparative study of energy-transducing properties of cytoplasmic membranes from mesophilic and thermophilic Bacillus species.

PubMed Central

De Vrij, W; Bulthuis, R A; Konings, W N

1988-01-01

The properties of enzymes involved in energy transduction from a mesophilic (Bacillus subtilis) and a thermophilic (B. stearothermophilus) bacterium were compared. Membrane preparations of the two organisms contained dehydrogenases for NADH, succinate, L-alpha-glycerophosphate, and L-lactate. Maximum NADH and cytochrome c oxidation rates were obtained at the respective growth temperatures of the two bacteria. The enzymes involved in the oxidation reactions in membranes of the thermophilic species were more thermostable than those of the mesophilic species. The apparent microviscosities of the two membrane preparations were studied at different temperatures. At the respective optimal growth temperatures, the apparent microviscosities of the membranes of the two organisms were remarkably similar. The transition from the gel to the liquid-crystalline state occurred at different temperatures in the two species. In the two species, the oxidation of physiological (NADH) and nonphysiological (N,N,N',N'-tetramethyl-p-phenylenediamine or phenazine methosulfate) electron donors led to generation of a proton motive force which varied strongly with temperature. At increasing temperatures, the efficiency of energy transduction declined because of increasing H+ permeability. At the growth temperature, the efficiency of energy transduction was lower in B. stearothermophilus than in the mesophilic species. Extremely high respiratory activities enabled B. stearothermophilus to maintain a high proton motive force at elevated temperatures. The pH dependence of proton motive force generation appeared to be similar in the two membrane preparations. The highest proton motive forces were generated at low external pH, mainly because of a high pH gradient. At increasing external pH, the proton motive force declined. PMID:2834342

Surface Protonics Promotes Catalysis

PubMed Central

Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

2016-01-01

Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. PMID:27905505

Stepwise Internal Energy Control for Protonated Methanol Clusters by Using the Inert Gas Tagging

NASA Astrophysics Data System (ADS)

Shimamori, Takuto; Kuo, Jer-Lai; Fujii, Asuka

2016-06-01

Preferred isomer structures of hydrogen-bonded clusters should depend on their temperature because of the entropy term in the free energy. To observe such temperature dependence, we propose a new approach to control the internal energy (vibrational temperature) of protonated clusters in the gas phase. We performed IR spectroscopy of protonated methanol clusters, H+ (CH{_3}OH) {_n}, n= 5 and 7, with the tagging by various inert gas species (Ar, CO{_2}, CO, CS{_2}, C{_2}H{_2}, and C{_6}H{_6}). We found that vibrational temperature of the tagged clusters raises with increase of the interaction energy with the tag species, and the observed cluster structures follow the theoretical prediction of the temperature dependence of the isomer population.

Crystalline polyoxometalate (POM)–polyethylene glycol (PEG) composites aimed as non-humidified intermediate-temperature proton conductors

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

Tsuboi, Masaki; Hibino, Mitsuhiro; Mizuno, Noritaka

2016-02-15

Crystalline polyoxometalate (POM)–polyethylene glycol (PEG) composites aimed as non-humidified intermediate-temperature proton conductors were synthesized and characterized by single crystal and powder XRD, solid state MASNMR, and TG-DTA measurements. Among the POM–PEG composites, Cs{sub 2.7}H{sub 0.3}[PW{sub 12}O{sub 40}]·1.2PEG1000 (CsHPW-PEG1000) possessed one-dimensional channels with diameters of ca. 6 and 8 Å, where PEG probably resided, and showed the best performance as a proton conductor (1.2×10{sup −5} S cm{sup −1} at 443 K). Proton conductivities of POM–PEG composites decreased by the increase in molecular weights of PEG (CsHPW-PEG12,000) or anion charges (CsHSiW-PEG1000). Variable contact time {sup 13}C-CP (cross polarization) MASNMR revealed that localmore » mobility (i.e., segmental motion) of PEG is related to the trends in proton conductivities. These results show that amount of acidic protons (H{sup +}) is not the primary factor in proton conduction and that segmental motion of PEG assists the proton hopping among POMs in the crystal lattice of POM–PEG composites. - Graphical abstract: Non-humidified intermediate-temperature proton conduction in crystalline polyoxometalate (POM)–polyethylene (PEG) composites are assisted by the segmental motion of PEG. - Highlights: • Crystalline polyoxometalate–polyethlene glycol (PEG) composites were synthesized. • CsHPW-PEG1000 possessed one-dimensional channels and showed the highest proton conductivity. • {sup 13}C CPMASNMR revealed that segmental motion of PEG is related to the proton conduction.« less

Unique Proton Transportation Pathway in a Robust Inorganic Coordination Polymer Leading to Intrinsically High and Sustainable Anhydrous Proton Conductivity.

PubMed

Gui, Daxiang; Dai, Xing; Tao, Zetian; Zheng, Tao; Wang, Xiangxiang; Silver, Mark A; Shu, Jie; Chen, Lanhua; Wang, Yanlong; Zhang, Tiantian; Xie, Jian; Zou, Lin; Xia, Yuanhua; Zhang, Jujia; Zhang, Jin; Zhao, Ling; Diwu, Juan; Zhou, Ruhong; Chai, Zhifang; Wang, Shuao

2018-05-16

Although comprehensive progress has been made in the area of coordination polymer (CP)/metal-organic framework (MOF)-based proton-conducting materials over the past decade, searching for a CP/MOF with stable, intrinsic, high anhydrous proton conductivity that can be directly used as a practical electrolyte in an intermediate-temperature proton-exchange membrane fuel cell assembly for durable power generation remains a substantial challenge. Here, we introduce a new proton-conducting CP, (NH 4 ) 3 [Zr(H 2/3 PO 4 ) 3 ] (ZrP), which consists of one-dimensional zirconium phosphate anionic chains and fully ordered charge-balancing NH 4 + cations. X-ray crystallography, neutron powder diffraction, and variable-temperature solid-state NMR spectroscopy suggest that protons are disordered within an inherent hydrogen-bonded infinite chain of acid-base pairs (N-H···O-P), leading to a stable anhydrous proton conductivity of 1.45 × 10 -3 S·cm -1 at 180 °C, one of the highest values among reported intermediate-temperature proton-conducting materials. First-principles and quantum molecular dynamics simulations were used to directly visualize the unique proton transport pathway involving very efficient proton exchange between NH 4 + and phosphate pairs, which is distinct from the common guest encapsulation/dehydration/superprotonic transition mechanisms. ZrP as the electrolyte was further assembled into a H 2 /O 2 fuel cell, which showed a record-high electrical power density of 12 mW·cm -2 at 180 °C among reported cells assembled from crystalline solid electrolytes, as well as a direct methanol fuel cell for the first time to demonstrate real applications. These cells were tested for over 15 h without notable power loss.

In Situ Solid-State Reactions Monitored by X-ray Absorption Spectroscopy: Temperature-Induced Proton Transfer Leads to Chemical Shifts.

PubMed

Stevens, Joanna S; Walczak, Monika; Jaye, Cherno; Fischer, Daniel A

2016-10-24

The dramatic colour and phase alteration with the solid-state, temperature-dependent reaction between squaric acid and 4,4'-bipyridine has been probed in situ with X-ray absorption spectroscopy. The electronic and chemical sensitivity to the local atomic environment through chemical shifts in the near-edge X-ray absorption fine structure (NEXAFS) revealed proton transfer from the acid to the bipyridine base through the change in nitrogen protonation state in the high-temperature form. Direct detection of proton transfer coupled with structural analysis elucidates the nature of the solid-state process, with intermolecular proton transfer occurring along an acid-base chain followed by a domino effect to the subsequent acid-base chains, leading to the rapid migration along the length of the crystal. NEXAFS thereby conveys the ability to monitor the nature of solid-state chemical reactions in situ, without the need for a priori information or long-range order. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Proton Order-Disorder Phenomena in a Hydrogen-Bonded Rhodium-η(5)-Semiquinone Complex: A Possible Dielectric Response Mechanism.

PubMed

Mitsumi, Minoru; Ezaki, Kazunari; Komatsu, Yuuki; Toriumi, Koshiro; Miyatou, Tatsuya; Mizuno, Motohiro; Azuma, Nobuaki; Miyazaki, Yuji; Nakano, Motohiro; Kitagawa, Yasutaka; Hanashima, Takayasu; Kiyanagi, Ryoji; Ohhara, Takashi; Nakasuji, Kazuhiro

2015-06-26

A newly synthesized one-dimensional (1D) hydrogen-bonded (H-bonded) rhodium(II)-η(5)-semiquinone complex, [Cp*Rh(η(5)-p-HSQ-Me4)]PF6 ([1]PF6; Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; HSQ = semiquinone) exhibits a paraelectric-antiferroelectric second-order phase transition at 237.1 K. Neutron and X-ray crystal structure analyses reveal that the H-bonded proton is disordered over two sites in the room-temperature (RT) phase. The phase transition would arise from this proton disorder together with rotation or libration of the Cp* ring and PF6(-) ion. The relative permittivity εb' along the H-bonded chains reaches relatively high values (ca., 130) in the RT phase. The temperature dependence of (13)C CP/MAS NMR spectra demonstrates that the proton is dynamically disordered in the RT phase and that the proton exchange has already occurred in the low-temperature (LT) phase. Rate constants for the proton exchange are estimated to be 10(-4)-10(-6) s in the temperature range of 240-270 K. DFT calculations predict that the protonation/deprotonation of [1](+) leads to interesting hapticity changes of the semiquinone ligand accompanied by reduction/oxidation by the π-bonded rhodium fragment, producing the stable η(6)-hydroquinone complex, [Cp*Rh(3+)(η(6)-p-H2Q-Me4)](2+) ([2](2+)), and η(4)-benzoquinone complex, [Cp*Rh(+)(η(4)-p-BQ-Me4)] ([3]), respectively. Possible mechanisms leading to the dielectric response are discussed on the basis of the migration of the protonic solitons comprising of [2](2+) and [3], which would be generated in the H-bonded chain. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrode materials: a challenge for the exploitation of protonic solid oxide fuel cells

PubMed Central

Fabbri, Emiliana; Pergolesi, Daniele; Traversa, Enrico

2010-01-01

High temperature proton conductor (HTPC) oxides are attracting extensive attention as electrolyte materials alternative to oxygen-ion conductors for use in solid oxide fuel cells (SOFCs) operating at intermediate temperatures (400–700 °C). The need to lower the operating temperature is dictated by cost reduction for SOFC pervasive use. The major stake for the deployment of this technology is the availability of electrodes able to limit polarization losses at the reduced operation temperature. This review aims to comprehensively describe the state-of-the-art anode and cathode materials that have so far been tested with HTPC oxide electrolytes, offering guidelines and possible strategies to speed up the development of protonic SOFCs. PMID:27877342

Effect of water on the low temperature conductivity of polymer electrolytes.

PubMed

Siu, Ana; Schmeisser, Jennifer; Holdcroft, Steven

2006-03-30

The proton conductivity of radiation-grafted ethylenetetrafluoroethylene-grafted-poly(styrene sulfonic) acid (ETFE-g-PSSA) and Nafion 117 membranes between 25 and -37 degrees C is reported. The freezing of water in the membranes, which strongly depends on the internal acid concentration, results in a 4-fold decrease in proton conductivity. The activation energies before and after the freezing of the membranes are approximately 0.15 and 0.4 eV, consistent with proton transport through liquid water and strongly bound water, respectively. Differential scanning calorimetry data show that up to 14 H(2)O molecules per H(+)/SO(3)(-) group remain unfrozen at subzero temperatures and are believed to be responsible for the low temperature conductivity that is observed. These results indicate that proton conductivity in membranes may be achieved via strongly bound and highly polarized water.

H3PO4 imbibed polyacrylamide-graft-chitosan frameworks for high-temperature proton exchange membranes

NASA Astrophysics Data System (ADS)

Yuan, Shuangshuang; Tang, Qunwei; He, Benlin; Chen, Haiyan; Li, Qinghua; Ma, Chunqing; Jin, Suyue; Liu, Zhichao

2014-03-01

Proton exchange membrane (PEM), transferring protons from anode to cathode, is a key component in a PEM fuel cell. In the current work, a new class of PEMs are synthesized benefiting from the imbibition behavior of three-dimensional (3D) polyacrylamide-graft-chitosan (PAAm-graft-chitosan) frameworks to H3PO4 aqueous solution. Interconnected 3D framework of PAAm-graft-chitosan provides tremendous space for holding proton-conducting H3PO4. The highest anhydrous proton conductivity of 0.13 S cm-1 at 165 °C is obtained. A fuel cell using a thick membrane as a PEM showed a peak power density of 405 mW cm-2 with O2 and H2 as the oxidant and fuel, respectively. Results indicate that the interconnected 3D framework provides superhighway for proton conduction. The valued merits on anhydrous proton conductivity, huge H3PO4 loading, and easy synthesis promise the new membranes to be good alternatives as high-temperature PEMs.

Morphology and Proton Transport in Sulfonated Block Copolymer and Mesoporous Polymer Electrolyte Membranes

NASA Astrophysics Data System (ADS)

Chen, Chelsea; Wong, David; Beers, Keith; Balsara, Nitash

2013-03-01

In an effort to understand the fundamentals of proton transport in polymer electrolyte membranes (PEMs), we have developed a series of poly(styrene-b-ethylene-b-styrene) (SES) membranes. The SES membranes were subsequently sulfonated to yield proton conducting S-SES membranes. We examine the effects of sulfonation level, temperature and thermal history on the morphology of S-SES membranes in both dry and hydrated states. The effects of these parameters on water uptake and proton transport characteristics of the membranes are also examined. Furthermore, building upon the strategy we deployed in sulfonating the SES membranes, we fabricated mesoporous S-SES membranes, with pores lined up with the proton conducting channels. These membranes have three distinct phases: structural block, proton-conducting block, and void. We examine the effects of pore size, domain structure and sulfonation level on water uptake and proton conductivity of the mesoporous PEMs at different temperatures. This work is funded by Department of Energy.

High Temperature Protonic Conductors

NASA Technical Reports Server (NTRS)

Dynys, Fred; Berger, Marie-Helen; Sayir, Ali

2007-01-01

High Temperature Protonic Conductors (HTPC) with the perovskite structure are envisioned for electrochemical membrane applications such as H2 separation, H2 sensors and fuel cells. Successive membrane commercialization is dependent upon addressing issues with H2 permeation rate and environmental stability with CO2 and H2O. HTPC membranes are conventionally fabricated by solid-state sintering. Grain boundaries and the presence of intergranular second phases reduce the proton mobility by orders of magnitude than the bulk crystalline grain. To enhanced protonic mobility, alternative processing routes were evaluated. A laser melt modulation (LMM) process was utilized to fabricate bulk samples, while pulsed laser deposition (PLD) was utilized to fabricate thin film membranes . Sr3Ca(1+x)Nb(2-x)O9 and SrCe(1-x)Y(x)O3 bulk samples were fabricated by LMM. Thin film BaCe(0.85)Y(0.15)O3 membranes were fabricated by PLD on porous substrates. Electron microscopy with chemical mapping was done to characterize the resultant microstructures. High temperature protonic conduction was measured by impedance spectroscopy in wet air or H2 environments. The results demonstrate the advantage of thin film membranes to thick membranes but also reveal the negative impact of defects or nanoscale domains on protonic conductivity.

Voyager observations of solar wind proton temperature - 1-10 AU

NASA Technical Reports Server (NTRS)

Gazis, P. R.; Lazarus, A. J.

1982-01-01

Simultaneous measurements are made of the solar wind proton temperatures by the Voyager 1 and 2 spacecraft, far from earth, and the IMP 8 spacecraft in earth orbit. This technique permits a separation of radial and temporal variations of solar wind parameters. The average value of the proton temperature between 1 and 9 AU is observed to decrease as r (the heliocentric radius) to the -(0.7 + or - 0.2). This is slower than would be expected for adiabatic expansion. A detailed examination of the solar wind stream structure shows that considerable heating occurs at the interface between high and low speed streams.

In Situ Neutron Diffraction of Rare-Earth Phosphate Proton Conductors Sr/Ca-doped LaPO4 at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Al-Wahish, Amal; Al-Binni, Usama; Bridges, C. A.; Huq, A.; Bi, Z.; Paranthaman, M. P.; Tang, S.; Kaiser, H.; Mandrus, D.

Acceptor-doped lanthanum orthophosphates are potential candidate electrolytes for proton ceramic fuel cells. We combined neutron powder diffraction (NPD) at elevated temperatures up to 800° C , X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to investigate the crystal structure, defect structure, thermal stability and surface topography. NPD shows an average bond length distortion in the hydrated samples. We employed Quasi-Elastic Neutron Scattering (QENS) and electrochemical impedance spectroscopy (EIS) to study the proton dynamics of the rare-earth phosphate proton conductors 4.2% Sr/Ca-doped LaPO4. We determined the bulk diffusion and the self-diffusion coefficients. Our results show that QENS and EIS are probing fundamentally different proton diffusion processes. Supported by the U.S. Department of Energy.

Pressure and temperature fluctuation simulation of J-PARC cryogenic hydrogen system

NASA Astrophysics Data System (ADS)

Tatsumoto, H.; Ohtsu, K.; Aso, T.; Kawakami, Y.

2015-12-01

The J-PARC cryogenic hydrogen system provides supercritical cryogenic hydrogen to the moderators at a pressure of 1.5 MPa and temperature of 18 K and removes 3.8 kW of nuclear heat from the 1 MW proton beam operation. We prepared a heater for thermal compensation and an accumulator, with a bellows structure for volume control, to mitigate the pressure fluctuation caused by switching the proton beam on and off. In this study, a 1-D simulation code named DiSC-SH2 was developed to understand the propagation of pressure and temperature propagations through the hydrogen loop due to on and off switching of the proton beam. We confirmed that the simulated dynamic behaviors in the hydrogen loop for 300-kW and 500-kW proton beam operations agree well with the experimental data under the same conditions.

Radiation effects in heteroepitaxial InP solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Curtis, H. B.; Swartz, C. K.; Brinker, D. J.; Vargas-Aburto, C.

1993-01-01

Heteroepitaxial InP solar cells, with GaAs substrates, were irradiated by 0.5 and 3 MeV protons and their performance, temperature dependency, and carrier removal rates determined as a function of fluence. The radiation resistance of the present cells was significantly greater than that of non-heteroepitaxial InP cells at both proton energies. A clear difference in the temperature dependency of V(sub oc), was observed between heteroepitaxial and homoepitaxial InP cells. The analytically predicted dependence of dV(sub oc)/dT on Voc was confirmed by the fluence dependence of these quantities. Carrier removal was observed to increase with decreasing proton energy. The results obtained for performance and temperature dependency were attributed to the high dislocation densities present in the heteroepitaxial cells while the energy dependence of carrier removal was attributed to the energy dependence of proton range.

Experimental nanocalorimetry of protonated and deprotonated water clusters

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

Boulon, Julien; Braud, Isabelle; Zamith, Sébastien

2014-04-28

An experimental nanocalorimetric study of mass selected protonated (H{sub 2}O){sub n}H{sup +} and deprotonated (H{sub 2}O){sub n−1}OH{sup −} water clusters is reported in the size range n = 20–118. Water cluster's heat capacities exhibit a change of slope at size dependent temperatures varying from 90 to 140 K, which is ascribed to phase or structural transition. For both anionic and cationic species, these transition temperatures strongly vary at small sizes, with higher amplitude for protonated than for deprotonated clusters, and change more smoothly above roughly n ≈ 35. There is a correlation between bonding energies and transition temperatures, which ismore » split in two components for protonated clusters while only one component is observed for deprotonated clusters. These features are tentatively interpreted in terms of structural properties of water clusters.« less

Mesospheric Dynamical Changes Induced by the Solar Proton Events in October-November 2003

NASA Technical Reports Server (NTRS)

Jackman, Charles H.; Roble, Raymond G.; Fleming, Eric L.

2007-01-01

The very large solar storms in October-November 2003 caused solar proton events (SPEs) at the Earth that impacted the upper atmospheric polar cap regions. The Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME-GCM) was used to study the atmospheric dynamical influence of the solar protons that occurred in Oct-Nov 2003, the fourth largest period of SPEs measured in the past 40 years. The highly energetic solar protons caused ionization, as well as dissociation processes, and ultimately produced odd hydrogen (HOx) and odd nitrogen (NOy). Significant short-lived ozone decreases (10-70%) followed these enhancements of HOx and NOy and led to a cooling of most of the lower mesosphere. This cooling caused an atmospheric circulation change that led to adiabatic heating of the upper mesosphere. Temperature changes up to plus or minus 2.6 K were computed as well as wind (zonal, meridional, vertical) perturbations up to 20-25% of the background winds as a result of 22 the solar protons. The solar proton-induced mesospheric temperature and wind perturbations diminished over a period of 4-6 weeks after the SPEs. The Joule heating in the mesosphere, induced by the solar protons, was computed to be relatively insignificant for these solar storms with most of the temperature and circulation perturbations caused by ozone depletion in the sunlit hemisphere.

Temperature dependence of (+)-catechin pyran ring proton coupling constants as measured by NMR and modeled using GMMX search methodology

Treesearch

Fred L. Tobiason; Stephen S. Kelley; M. Mark Midland; Richard W. Hemingway

1997-01-01

The pyran ring proton coupling constants for (+)-catechin have been experimentally determined in deuterated methanol over a temperature range of 213 K to 313 K. The experimental coupling constants were simulated to 0.04 Hz on the average at a 90 percent confidence limit using a LAOCOON method. The temperature dependence of the coupling constants was reproduced from the...

Intermediate temperature proton conductors for PEM fuel cells based on phosphonic acid as protogenic group: a progress report.

PubMed

Steininger, H; Schuster, M; Kreuer, K D; Kaltbeitzel, A; Bingöl, B; Meyer, W H; Schauff, S; Brunklaus, G; Maier, J; Spiess, H W

2007-04-21

The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with phosphonic acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the phosphonic acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the "spacer concept", which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of phosphonic acid functionalized polymers. Instead, a very high concentration of phosphonic acid functional groups forming "bulky" hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in phosphonic acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl phosphonic acid) and poly(meta-phenylene phosphonic acid) are discussed. Though both polymers exhibit a substantial concentration of phosphonic acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below sigma = 10(-3) S cm(-1) at T = 150 degrees C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat phosphonic acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for phosphonic acid functionalized ionomers (IEC >10 meq g(-1)) may allow for high proton conductivities in the intermediate temperature range (T approximately 120 -160 degrees C).

SU-E-T-354: Peak Temperature Ratio of TLD Glow Curves to Investigate the Spatial Dependence of LET in a Clinical Proton Beam

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

Reft, C; Pankuch, M; Ramirez, H

Purpose: Use the ratio of the two high temperature peaks (HTR) in TLD 700 glow curves to investigate spatial dependence of the linear energy transfer (LET) in proton beams. Studies show that the relative biological effectiveness (RBE) depends upon the physical dose as well as its spatial distribution. Although proton therapy uses a spatially invariant RBE of 1.1, studies suggest that the RBE increases in the distal edge of a spread out Bragg peak (SOBP) due to the increased LET. Methods: Glow curve studies in TLD 700 show that the 280 C temperature peak is more sensitive to LET radiationmore » than the 210 C temperature peak. Therefore, the areas under the individual temperature peaks for TLDs irradiated in a proton beam normalized to the peak ratio for 6 MV photons are used to determine the HTR to obtain information on its LET. TLD 700 chips with dimensions 0.31×0.31×0.038 cc are irradiated with 90 MeV protons at varying depths in a specially designed blue wax phantom to investigate LET spatial dependence. Results: Five TLDs were placed at five different depths of the percent depth dose curve (PDD) of range 16.2 cm: center of the SOPB and approximately at the 99% distal edge, 90%, 75% and 25% of the PDD, respectively. HTR was 1.3 at the center of the SOBP and varied from 2.2 to 3.9 which can be related to an LET variation from 0.5 to 18 KeV/μ via calibration with radiation beams of varying LET. Conclusion: HTR data show a spatially invariant LET slightly greater than the 6 MV radiations in the SOBP, but a rapidly increasing LET at the end of the proton range. These results indicate a spatial variation in RBE with potential treatment consequences when selecting treatment margins to minimize the uncertainties in proton RBE.« less

Proton Tolerance of SiGe Precision Voltage References for Extreme Temperature Range Electronics

NASA Astrophysics Data System (ADS)

Najafizadeh, Laleh; Bellini, Marco; Prakash, A. P. Gnana; Espinel, Gustavo A.; Cressler, John D.; Marshall, Paul W.; Marshall, Cheryl J.

2006-12-01

A comprehensive investigation of the effects of proton irradiation on the performance of SiGe BiCMOS precision voltage references intended for extreme environment operational conditions is presented. The voltage reference circuits were designed in two distinct SiGe BiCMOS technology platforms (first generation (50 GHz) and third generation (200 GHz)) in order to investigate the effect of technology scaling. The circuits were irradiated at both room temperature and at 77 K. Measurement results from the experiments indicate that the proton-induced changes in the SiGe bandgap references are minor, even down to cryogenic temperatures, clearly good news for the potential application of SiGe mixed-signal circuits in emerging extreme environments

The relationship between kappa and temperature in energetic ion spectra at Jupiter

NASA Technical Reports Server (NTRS)

Collier, Michael R.; Hamilton, D. C.

1995-01-01

A universal energy per charge kappa function fit is simultaneously applied to the spectra of Voyager 2 Low Energy Charged Particle (LECP) proton, helium, oxygen, sulfur, and carbon ions during 33 Jovian plasma sheet crossings from 26 to 160 R(sub J). The fits yield an approximately linear relationship between high energy spectral index, kappa, and core proton temperature of the form kappa (T(sub H)) approximately = eta dot T(sub H) + kappa(sub 0) with eta = 0.080 ke/V, kappa(sub 0) = 2.86, and T(sub H) measured in keV. Core proton temperatures range from 5 to 35 keV with spectral indices ranging from 3 to 6.

Spin-spin relaxation of protons in ferrofluids characterized with a high-Tc superconducting quantum interference device-detected magnetometer in microtesla fields

NASA Astrophysics Data System (ADS)

Liao, Shu-Hsien; Liu, Chieh-Wen; Yang, Hong-Chang; Chen, Hsin-Hsien; Chen, Ming-Jye; Chen, Kuen-Lin; Horng, Herng-Er; Wang, Li-Min; Yang, Shieh-Yueh

2012-06-01

In this work, the spin-spin relaxation of protons in ferrofluids is characterized using a high-Tc SQUID-based detector in microtesla fields. We found that spin-spin relaxation rate is enhanced in the presence of superparamagnetic nanoparticles. The enhanced relaxation rates are attributed to the microscopic field gradients from magnetic nanoparticles that dephase protons' spins nearby. The relaxation rates decrease when temperatures increase. Additionally, the alternating current magnetic susceptibility was inversely proportional to temperature. Those characteristics explained the enhanced Brownian motion of nanoparticles at high temperatures. Characterizing the relaxation will be helpful for assaying bio-molecules and magnetic resonance imaging in microtesla fields.

Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC

NASA Astrophysics Data System (ADS)

Mäntysaari, Heikki; Schenke, Björn; Shen, Chun; Tribedy, Prithwish

2017-09-01

Results for particle production in √{ s} = 5.02TeV p + Pb collisions at the Large Hadron Collider within a combined classical Yang-Mills and relativistic viscous hydrodynamic calculation are presented. We emphasize the importance of sub-nucleon scale fluctuations in the proton projectile to describe the experimentally observed azimuthal harmonic coefficients vn, demonstrating their sensitivity to the proton shape. We stress that the proton shape and its fluctuations are not free parameters in our calculations. Instead, they have been constrained using experimental data from HERA on exclusive vector meson production. Including temperature dependent shear and bulk viscosities, as well as UrQMD for the low temperature regime, we present results for mean transverse momenta, harmonic flow coefficients for charged hadrons and identified particles, as well as Hanbury-Brown-Twiss radii.

Disorder in KHCO3 as studied by EPR and DTA in Cu2+ doped and gamma-irradiated single crystals

NASA Astrophysics Data System (ADS)

Koksal, F.; Karabulut, B.; Demir, D.; Icbudak, H.; Koseoglu, R.

2005-08-01

Kalicinite (KHCO3) single crystals were investigated by the electron paramagnetric resonance (EPR) technique in their Cu2+ doped and gamma- irradiated states. It is observed that the behavior of the spectrum is the same at ambient and low temperatures down to 113 K in consistence with the monoclinic symmetry of the crystal. However, when the temperature is increased to 313 K, only one site signals were observed at all orientations of the magnetic field for the Cu2+ doped samples as the site splitted signals overlap at this temperature. Furthermore, for the gamma-irradiated crystals, two sites were observed for the induced H(C)over dot O-3 and (C)over dot O-2(-) radicals at ambient temperature for an arbitrary orientation of the magnetic field. However, when the temperature is increased to 348 K, the signals due to the H(C)over dot O-3 radical overlap indicating only one site, but the signals due to (C)over dot O-2(-) the radical do not and continue to indicate the presence of the two sites. Therefore, we conclude that this one site transition at 313 K is due to the disordering of the proton vacancies, as the charge compensation of Cu2+ is fulfilled by K+ and proton holes. This indicates that the proton vacancies come to disorder at 313 K and the protons get disordered at 348 K. The differential thermal analysis results show two small endothermic peaks for the Cu2+ doped and gamma-irradiated samples at 313 and 348 K that were attributed to the disorder of the proton vacancies and protons, in consistency with the EPR results.

Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells.

PubMed

Duan, Chuancheng; Kee, Robert J; Zhu, Huayang; Karakaya, Canan; Chen, Yachao; Ricote, Sandrine; Jarry, Angelique; Crumlin, Ethan J; Hook, David; Braun, Robert; Sullivan, Neal P; O'Hayre, Ryan

2018-05-01

Protonic ceramic fuel cells, like their higher-temperature solid-oxide fuel cell counterparts, can directly use both hydrogen and hydrocarbon fuels to produce electricity at potentially more than 50 per cent efficiency 1,2 . Most previous direct-hydrocarbon fuel cell research has focused on solid-oxide fuel cells based on oxygen-ion-conducting electrolytes, but carbon deposition (coking) and sulfur poisoning typically occur when such fuel cells are directly operated on hydrocarbon- and/or sulfur-containing fuels, resulting in severe performance degradation over time 3-6 . Despite studies suggesting good performance and anti-coking resistance in hydrocarbon-fuelled protonic ceramic fuel cells 2,7,8 , there have been no systematic studies of long-term durability. Here we present results from long-term testing of protonic ceramic fuel cells using a total of 11 different fuels (hydrogen, methane, domestic natural gas (with and without hydrogen sulfide), propane, n-butane, i-butane, iso-octane, methanol, ethanol and ammonia) at temperatures between 500 and 600 degrees Celsius. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (less than 1.5 per cent degradation per 1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. Large fluctuations in temperature are tolerated, and coking is not observed even after thousands of hours of continuous operation. Finally, sulfur, a notorious poison for both low-temperature and high-temperature fuel cells, does not seem to affect the performance of protonic ceramic fuel cells when supplied at levels consistent with commercial fuels. The fuel flexibility and long-term durability demonstrated by the protonic ceramic fuel cell devices highlight the promise of this technology and its potential for commercial application.

Effect of temperature on the protonation of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid in aqueous solutions: Potentiometric and calorimetric studies

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

Li, Xingliang; Zhang, Zhicheng; Endrizzi, Francesco

2015-06-01

The TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) has been demonstrated in several pilot-scale operations to be effective at separating trivalent actinides (An 3+) from trivalent lanthanides (Ln 3+). However, fundamental studies have revealed undesired aspects of TALSPEAK, such as the significant partitioning of Na +, lactic acid, and water into the organic phase, thermodynamically unpredictable pH dependence, and the slow extraction kinetics. In the modified TALSPEAK process, the combination of the aqueous holdback complexant HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid) with the extractant HEH[EHP] (2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester) in the organic phase has been found tomore » exhibit a nearly flat pH dependence between 2.5 and 4.5 and more rapid phase transfer kinetics for the heavier lanthanides. To help understand the speciation of Ln 3+ and An 3+ in the modified TALSPEAK, systematic studies are underway on the thermodynamics of major reactions in the HEDTA system under conditions relevant to the process (e.g., higher temperatures). Thermodynamics of the protonation and complexation of HEDTA with Ln 3+ were studied at variable temperatures. Equilibrium constants and enthalpies were determined by a combination of techniques including potentiometry and calorimetry. This paper presents the protonation constants of HEDTA at T = (25 to 70) °C. The potentiometric titrations have demonstrated that, stepwise, the first two protonation constants decrease and the third one slightly increases with the increase of temperature. This trend is in good agreement with the enthalpy of protonation directly determined by calorimetry. The results of NMR analysis further confirm that the first two protonation reactions occur on the diamine nitrogen atoms, while the third protonation reaction occurs on the oxygen of a carboxylate group. These data, in conjunction with the thermodynamic parameters of Ln 3+/An 3+ complexes with HEDTA at different temperatures, will help to predict the speciation and temperature-dependent behavior of Ln 3+/An 3+ in the modified TALSPEAK process.« less

Electrolysis-induced protonation of VO2 thin film transistor for the metal-insulator phase modulation

NASA Astrophysics Data System (ADS)

Katase, Takayoshi; Endo, Kenji; Ohta, Hiromichi

2016-02-01

Compared to state-of-the-art modulation techniques, protonation is the most ideal to control the electrical and optical properties of transition metal oxides (TMOs) due to its intrinsic non-volatile operation. However, the protonation of TMOs is not typically utilized for solid-state devices because of imperative high-temperature annealing treatment in hydrogen source. Although one solution for room temperature (RT) protonation of TMOs is liquid-phase electrochemistry, it is unsuited for practical purposes due to liquid-leakage problem. Herein we demonstrate solid-state RT-protonation of vanadium dioxide (VO2), which is a well-known thermochromic TMO. We fabricated the three terminal thin-film-transistor structure on an insulating VO2 film using a water-infiltrated nanoporous glass, which serves as a solid electrolyte. For gate voltage application, water electrolysis and protonation/deprotonation of VO2 film surface occurred, leading to reversible metal-insulator phase conversion of ~11-nm-thick VO2 layer. The protonation was clearly accompanied by the structural change from an insulating monoclinic to a metallic tetragonal phase. Present results offer a new route for the development of electro-optically active solid-state devices with TMO materials by engineering RT protonation.

A comparative study of nano-SiO2 and nano-TiO2 fillers on proton conductivity and dielectric response of a silicotungstic acid-H3PO4-poly(vinyl alcohol) polymer electrolyte.

PubMed

Gao, Han; Lian, Keryn

2014-01-08

The effects of nano-SiO2 and nano-TiO2 fillers on a thin film silicotungstic acid (SiWA)-H3PO4-poly(vinyl alcohol) (PVA) proton conducting polymer electrolyte were studied and compared with respect to their proton conductivity, environmental stability, and dielectric properties, across a temperature range from 243 to 323 K. Three major effects of these fillers have been identified: (a) barrier effect; (b) intrinsic dielectric constant effect; and (c) water retention effect. Dielectric analyses were used to differentiate these effects on polymer electrolyte-enabled capacitors. Capacitor performance was correlated to electrolyte properties through dielectric constant and dielectric loss spectra. Using a single-ion approach, proton density and proton mobility of each polymer electrolyte were derived as a function of temperature. The results allow us to deconvolute the different contributions to proton conductivity in SiWA-H3PO4-PVA-based electrolytes, especially in terms of the effects of fillers on the dynamic equilibrium of free protons and protonated water in the electrolytes.

Fractal diffusion in high temperature polymer electrolyte fuel cell membranes

NASA Astrophysics Data System (ADS)

Hopfenmüller, Bernhard; Zorn, Reiner; Holderer, Olaf; Ivanova, Oxana; Lehnert, Werner; Lüke, Wiebke; Ehlers, Georg; Jalarvo, Niina; Schneider, Gerald J.; Monkenbusch, Michael; Richter, Dieter

2018-05-01

The performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution. Time of flight spectroscopy and backscattering spectroscopy have been combined to cover a broad dynamic range. In order to selectively observe the diffusion of protons potentially contributing to the ion conductivity, two samples were prepared, where in one of the samples the phosphoric acid was used with hydrogen replaced by deuterium. The scattering data from the two samples were subtracted in a suitable way after measurement. Thereby subdiffusive behavior of the proton diffusion has been observed and interpreted in terms of a model of fractal diffusion. For this purpose, a scattering function for fractal diffusion has been developed. The fractal diffusion dimension dw and the Hausdorff dimension df have been determined on the length scales covered in the neutron scattering experiments.

Proton core-beam system in the expanding solar wind: Hybrid simulations

NASA Astrophysics Data System (ADS)

Hellinger, Petr; Trávníček, Pavel M.

2011-11-01

Results of a two-dimensional hybrid expanding box simulation of a proton beam-core system in the solar wind are presented. The expansion with a strictly radial magnetic field leads to a decrease of the ratio between the proton perpendicular and parallel temperatures as well as to an increase of the ratio between the beam-core differential velocity and the local Alfvén velocity creating a free energy for many different instabilities. The system is indeed most of the time marginally stable with respect to the parallel magnetosonic, oblique Alfvén, proton cyclotron and parallel fire hose instabilities which determine the system evolution counteracting some effects of the expansion and interacting with each other. Nonlinear evolution of these instabilities leads to large modifications of the proton velocity distribution function. The beam and core protons are slowed with respect to each other and heated, and at later stages of the evolution the two populations are not clearly distinguishable. On the macroscopic level the instabilities cause large departures from the double adiabatic prediction leading to an efficient isotropization of effective proton temperatures in agreement with Helios observations.

Transfer of a proton between H2 and O2.

PubMed

Kluge, Lars; Gärtner, Sabrina; Brünken, Sandra; Asvany, Oskar; Gerlich, Dieter; Schlemmer, Stephan

2012-11-13

The proton affinities of hydrogen and oxygen are very similar. Therefore, it has been discussed that the proton transfer from the omnipresent H(3)(+) to molecular oxygen in the near thermoneutral reaction H(3)(+) + O(2) <--> O(2)H(+) + H(2) effectively binds the interstellar oxygen in O(2)H(+). In this work, the proton transfer reaction has been investigated in a low-temperature 22-pole ion trap from almost room temperature (280 K) down to the lowest possible temperature limited by freeze out of oxygen gas (about 40 K at a low pressure). The Arrhenius behaviour of the rate coefficient for the forward reaction shows that it is subject to an activation energy of E(A)/k=113 K. Thus, the forward reaction can proceed only in higher temperature molecular clouds. Applying laser-induced reactions to the given reaction (in the backward direction), a preliminary search for spectroscopic signatures of O(2)H(+) in the infrared was unsuccessful, whereas the forward reaction has been successfully used to probe the population of the lowest ortho and para levels of H(3)(+).

Two-proton capture on the 68Se nucleus with a new self-consistent cluster model

NASA Astrophysics Data System (ADS)

Hove, D.; Garrido, E.; Jensen, A. S.; Sarriguren, P.; Fynbo, H. O. U.; Fedorov, D. V.; Zinner, N. T.

2018-07-01

We investigate the two-proton capture reaction of the prominent rapid proton capture waiting point nucleus, 68Se, that produces the borromean nucleus 70Kr (68Se + p + p). We apply a recently formulated general model where the core nucleus, 68Se, is treated in the mean-field approximation and the three-body problem of the two valence protons and the core is solved exactly. We compare using two popular Skyrme interactions, SLy4 and SkM*. We calculate E2 electromagnetic two-proton dissociation and capture cross sections, and derive the temperature dependent capture rates. We vary the unknown 2+ resonance energy without changing any of the structures computed self-consistently for both core and valence particles. We find rates increasing quickly with temperature below 2-4 GK after which we find rates varying by about a factor of two independent of 2+ resonance energy. The capture mechanism is sequential through the f5/2 proton-core resonance, but the continuum background contributes significantly.

A quasilinear kinetic model for solar wind electrons and protons instabilities

NASA Astrophysics Data System (ADS)

Sarfraz, M.; Yoon, P. H.

2017-12-01

In situ measurements confirm the anisotropic behavior in temperatures of solar wind species. These anisotropies associated with charge particles are observed to be relaxed. In collionless limit, kinetic instabilities play a significant role to reshape particles distribution. The linear analysis results are encapsulated in inverse relationship between anisotropy and plasma beta based observations fittings techniques, simulations methods, or solution of linearized Vlasov equation. Here amacroscopic quasilinear technique is adopted to confirm inverse relationship through solutions of set of self-consistent kinetic equations. Firstly, for a homogeneous and non-collisional medium, quasilinear kinetic model is employed to display asymptotic variations of core and halo electrons temperatures and saturations of wave energy densities for electromagnetic electron cyclotron (EMEC) instability sourced by, T⊥}>T{∥ . It is shown that, in (β ∥ , T⊥}/T{∥ ) phase space, the saturations stages of anisotropies associated with core and halo electrons lined up on their respective marginal stability curves. Secondly, for case of electrons firehose instability ignited by excessive parallel temperature i.e T⊥}>T{∥ , both electrons and protons are allowed to dynamically evolve in time. It is also observed that, the trajectories of protons and electrons at saturation stages in phase space of anisotropy and plasma beta correspond to proton cyclotron and firehose marginal stability curves, respectively. Next, the outstanding issue that most of observed proton data resides in nearly isotropic state in phase space is interpreted. Here, in quasilinear frame-work of inhomogeneous solar wind system, a set of self-consistent quasilinear equations is formulated to show a dynamical variations of temperatures with spatial distributions. On choice of different initial parameters, it is shown that, interplay of electron and proton instabilities provides an counter-balancing force to slow down the protons away from marginal stability states. As we are dealing both, protons and electrons for radially expanding solar wind plasma, our present approach may eventually be incorporated in global-kinetic models of the solar wind species.

Excited state of protonated benzene and toluene

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

Esteves-López, Natalia; Dedonder-Lardeux, Claude; Jouvet, Christophe, E-mail: Christophe.jouvet@univ-amu.fr

We present photo-fragmentation electronic spectra of the simplest protonated aromatic molecules, protonated benzene and toluene, recorded under medium resolution conditions and compared with the photo-fragmentation spectrum of protonated pyridine. Despite the resolution and cold temperature achieved in the experiment, the electronic spectra of protonated benzene and toluene are structure-less, thus intrinsically broadened. This is in agreement with the large geometrical changes and the fast dynamic toward internal conversion predicted by ab initio calculations for protonated benzene [Rode et al., J. Phys. Chem. A 113, 5865–5873 (2009)].

Warm and cold pasta phase in relativistic mean field theory

NASA Astrophysics Data System (ADS)

Avancini, S. S.; Menezes, D. P.; Alloy, M. D.; Marinelli, J. R.; Moraes, M. M. W.; Providência, C.

2008-07-01

In the present article we investigate the onset of the pasta phase with different parametrizations of the nonlinear Walecka model. At zero temperature two different methods are used, one based on coexistent phases and the other on the Thomas-Fermi approximation. At finite temperature only the coexistence phases method is used. npe matter with fixed proton fractions and in β equilibrium is studied. The pasta phase decreases with the increase of temperature. The internal pasta structure and the beginning of the homogeneous phase vary depending on the proton fraction (or the imposition of β equilibrium), on the method used, and on the chosen parametrization. It is shown that a good parametrization of the surface tension with dependence on the temperature, proton fraction, and geometry is essential to describe correctly large isospin asymmetries and the transition from pasta to homogeneous matter.

Flow properties of the solar wind obtained from white light data and a two-fluid model

NASA Technical Reports Server (NTRS)

Habbal, Shadia Rifai; Esser, Ruth; Guhathakurta, Madhulika; Fisher, Richard

1994-01-01

The flow properties of the solar wind from 1 R(sub s) to 1 AU were obtained using a two fluid model constrained by density and scale height temperatures derived from white light observations, as well as knowledge of the electron temperature in coronal holes. The observations were obtained with the white light coronographs on SPARTAN 201-1 and at Mauna Loa (Hawaii), in a north polar coronal hole from 1.16 to 5.5 R(sub s) on 11 Apr. 1993. By specifying the density, temperature, Alfven wave velocity amplitude and heating function at the coronal base, it was found that the model parameters fit well the constraints of the empirical density profiles and temperatures. The optimal range of the input parameters was found to yield a higher proton temperature than electron temperature in the inner corona. The results indicate that no preferential heating of the protons at larger distances is needed to produce higher proton than electron temperatures at 1 AU, as observed in the high speed solar wind.

Low-temperature nanodoping of protonated LiNbO3 crystals by univalent ions

NASA Astrophysics Data System (ADS)

Borodin, Yu. V.

2015-01-01

In the nanocomposite model developed here, crystals are treated as subordinate aggregate of pro- ton-selected structural elements, their blocks, and proton-containing quantum sublattices with preferred transport effects separating them. The formation of stratified reversible hexagonal structures is accompanied with protonation and formation of a dense network of H-bonds ensuring the nanocomposite properties. Nanodoping with H+ ions occurs during processing of crystals and glasses in melts as well as in aqueous solutions of Ag, Tl, Rb, and Cs salts. The isotope exchange H+ ↔ D+ and ion exchange H+ ↔ M+ lead to nanodoping of protonated materials with D+ and M+ ions. This is manifested especially clearly in Li-depleted nonequilibrium LiNbO3 and LiTaO3 crystals. Low-temperature proton-ion nanodoping over superlattices is a basically new approach to analysis of the structure and properties of extremely nonequilibrium materials.

Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC

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

Mantysaari, Heikki; Schenke, Bjorn; Shen, Chun

Results for particle production inmore » $$\\sqrt{s}$$ = 5.02 TeV p+Pb collisions at the Large Hadron Collider within a combined classical Yang-Mills and relativistic viscous hydrodynamic calculation are presented. We emphasize the importance of sub-nucleon scale fluctuations in the proton projectile to describe the experimentally observed azimuthal harmonic coefficients v n, demonstrating their sensitivity to the proton shape. We stress that the proton shape and its fluctuations are not free parameters in our calculations. Instead, they have been constrained using experimental data from HERA on exclusive vector meson production. Including temperature dependent shear and bulk viscosities, as well as UrQMD for the low temperature regime, we present results for mean trans-verse momenta, harmonic flow coefficients for charged hadrons and identified particles, as well as Hanbury-Brown-Twiss radii.« less

Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC

DOE PAGES

Mantysaari, Heikki; Schenke, Bjorn; Shen, Chun; ...

2017-07-21

Results for particle production inmore » $$\\sqrt{s}$$ = 5.02 TeV p+Pb collisions at the Large Hadron Collider within a combined classical Yang-Mills and relativistic viscous hydrodynamic calculation are presented. We emphasize the importance of sub-nucleon scale fluctuations in the proton projectile to describe the experimentally observed azimuthal harmonic coefficients v n, demonstrating their sensitivity to the proton shape. We stress that the proton shape and its fluctuations are not free parameters in our calculations. Instead, they have been constrained using experimental data from HERA on exclusive vector meson production. Including temperature dependent shear and bulk viscosities, as well as UrQMD for the low temperature regime, we present results for mean trans-verse momenta, harmonic flow coefficients for charged hadrons and identified particles, as well as Hanbury-Brown-Twiss radii.« less

A determination of relativistic shock jump conditions using Monte Carlo techniques

NASA Technical Reports Server (NTRS)

Ellison, Donald C.; Reynolds, Stephen P.

1991-01-01

Monte Carlo techniques are used, assuming isotropic elastic scattering of all particles, to calculate jump conditions in parallel relativistic collisionless shocks in the absence of Fermi acceleration. The shock velocity and compression ratios are shown for arbitrary flow velocities and for any upstream temperature. Both single-component electron-positron plasma and two-component proton-electron plasmas are considered. It is shown that protons and electrons must share energy, directly or through the mediation of plasma waves, in order to satisfy the basic conservation conditions, and the electron and proton temperatures are determined for a particular microscopic, kinetic-theory model, namely, that protons always scatter elastically. The results are directly applicable to shocks in which waves of scattering superthermal particles are absent.

Analysis of proton irradiated n- and p-type strained FinFETs at low temperatures down to 100 K

NASA Astrophysics Data System (ADS)

Vicentis Caparroz, Luis Felipe; Mendes Bordallo, Caio Cesar; Martino, Joao Antonio; Simoen, Eddy; Claeys, Cor; Ghedini Der Agopian, Paula

2018-06-01

This paper studies the main low temperature electrical parameters of SOI n- and p-type FinFETs, standard and strained devices, submitted to proton irradiation. The study covers the range from room temperature down to 100 K, focusing on the threshold voltage (VTH), subthreshold swing (SS), the Early voltage VEA, transistor efficiency and the intrinsic gain voltage (AV) for 3 different channel widths. The p-channel devices showed a greater immunity to radiation than the n-channel ones, when considering the basic parameters thanks to the back conduction turn-off tendency, while from the analog parameters point of view, both transistor types presented a similar response to proton radiation at strong inversion.

Correlation between coordinated water content and proton conductivity in Ca-BTC-based metal-organic frameworks.

PubMed

Mallick, Arijit; Kundu, Tanay; Banerjee, Rahul

2012-09-11

Proton conductivity of five Ca-based MOFs which depends on the amount of water molecules coordinated to the Ca-centres has been reported. These MOFs show high temperature proton conductivity due to the strong hydrogen bonding between the lattice and coordinated water molecules.

Proton Conduction in Grain-Boundary-Free Oxygen-Deficient BaFeO2.5+δ Thin Films

PubMed Central

Benes, Alexander; Molinari, Alan; Kruk, Robert; Brötz, Joachim; Chellali, Reda; Hahn, Horst

2017-01-01

Reduction of the operating temperature to an intermediate temperature range between 350 °C and 600 °C is a necessity for Solid Oxide Fuel/Electrolysis Cells (SOFC/SOECs). In this respect the application of proton-conducting oxides has become a broad area of research. Materials that can conduct protons and electrons at the same time, to be used as electrode catalysts on the air electrode, are especially rare. In this article we report on the proton conduction in expitaxially grown BaFeO2.5+δ (BFO) thin films deposited by pulsed laser deposition on Nb:SrTiO3 substrates. By using Electrochemical Impedance Spectroscopy (EIS) measurements under different wet and dry atmospheres, the bulk proton conductivity of BFO (between 200 °C and 300 °C) could be estimated for the first time (3.6 × 10−6 S cm−1 at 300 °C). The influence of oxidizing measurement atmosphere and hydration revealed a strong dependence of the conductivity, most notably at temperatures above 300 °C, which is in good agreement with the hydration behavior of BaFeO2.5 reported previously. PMID:29286321

Advanced Hybrid Membranes for Next Generation PEMFC Automotive Applications.

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

Herring, Andrew M; Motz, Andrew R; Kuo, Mei-Chen

The objective of this proposal is to fabricate a low cost high performance hybrid inorganic/polymer membrane that has a proton area specific resistance (ASR) < 0.02 ohm cm2 at the operating temperature of an automotive fuel cell stack (95 - 120°C) at low inlet RH <50% with good mechanical and chemical durability. Additionally the membrane will be optimized for low hydrogen and oxygen crossover with high electrical ASR at all temperatures and adequate proton ASR at lower temperatures. We also seek to gain valuable insights into rapid proton transport at the limit of proton hydration. Additional research will be performedmore » to incorporate the membrane into a 50 cm2 membrane electrode assembly (MEA). The materials at the start of this project are at a TRL of 2, as we have shown that they have proton conductivity under high and dry conditions, but we have not yet consistently shown that they will function in an operational fuel cell. At the project’s end the materials will be at a TRL of 4 and will be integrated into an MEA, demonstrating that they can function with electrodes as a single fuel cell.« less

Structure and Dynamics Investigations of Sr/Ca-Doped LaPO 4 Proton Conductors

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

al-Wahish, Amal; al-Binni, U.; Tetard, L.

Proton conductors loom out of the pool of candidate materials with great potential to boost hydrogen alternatives to fossil-based resources for energy. Acceptor doped lanthanum orthophosphates are considered for solid oxide fuel cells (SOFCs) for their potential stability and conductivity at high temperature. By exploring the crystal and defect structure of x% Sr/Ca-doped LaPO 4 with different nominal Sr/Ca concentrations (x = 0 – 10) with Neutron powder diffraction (NPD) and X-ray powder diffraction (XRD), we confirm that Sr/Ca-doped LaPO 4 can exist as self-supported structures at high temperatures during solid oxide fuel cell operation. Thermal stability, surface topography, sizemore » distribution are also studied to better understand the proton conductivity for dry and wet compounds obtained at sintering temperatures ranging from 1200 to 1400 °C using a combination of scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). In conclusion, the results suggest that Sr doped samples exhibit the highest proton conductivity of our samples and illustrate the impact of material design and versatile characterization schemes on the development of proton conductors with superior functionality.« less

High-Temperature Proton-Conducting Ceramics Developed

NASA Technical Reports Server (NTRS)

Sayir, Ali; Dynys, Frederick W.; Berger, M. H.

2005-01-01

High-temperature protonic conductors (HTPC) are needed for hydrogen separation, hydrogen sensors, fuel cells, and hydrogen production from fossil fuels. The HTPC materials for hydrogen separation at high temperatures are foreseen to be metal oxides with the perovskite structure A(sup 2+)B(sup 4+)C(sup 2-, sub 3) and with the trivalent cation (M(sup 3+)) substitution at the B(sup 4+)-site to introduce oxygen vacancies. The high affinity for hydrogen ions (H(sup +)) is advantageous for protonic transport, but it increases the reactivity toward water (H2O) and carbon dioxide (CO2), which can lead to premature membrane failure. In addition, there are considerable technological challenges related to the processing of HTPC materials. The high melting point and multi-cation chemistry of HTPC materials creates difficulties in in achieving high-density, single-phase membranes by solid-state sintering. The presence of secondary phases and grain-boundary interfaces are detrimental to the protonic conduction and environmental stability of polycrystalline HTPC materials.

New membranes based on ionic liquids for PEM fuel cells at elevated temperatures

NASA Astrophysics Data System (ADS)

Ye, H.; Huang, J.; Xu, J. J.; Kodiweera, N. K. A. C.; Jayakody, J. R. P.; Greenbaum, S. G.

Proton exchange membrane (PEM) fuel cells operating at elevated temperature, above 120 °C, will yield significant benefits but face big challenges for the development of suitable PEMs. The objectives of this research are to demonstrate the feasibility of the concept and realize [acid/ionic liquid/polymer] composite gel-type membranes as such PEMs. Novel membranes consisting of anhydrous proton solvent H 3PO 4, the protic ionic liquid PMIH 2PO 4, and polybenzimidazole (PBI) as a matrix have been prepared and characterized for PEM fuel cells intended for operation at elevated temperature (120-150 °C). Physical and electrochemical analyses have demonstrated promising characteristics of these H 3PO 4/PMIH 2PO 4/PBI membranes at elevated temperature. The proton transport mechanism in these new membranes has been investigated by Fourier transform infrared and nuclear magnetic resonance spectroscopic methods.

Plasma properties of driver gas following interplanetary shocks observed by ISEE-3

NASA Technical Reports Server (NTRS)

Zwickl, R. D.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Smith, E. J.

1983-01-01

Plasma fluid parameters calculated from solar wind and magnetic field data to determine the characteristic properties of driver gas following a select subset of interplanetary shocks were studied. Of 54 shocks observed from August 1978 to February 1980, 9 contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature. While helium enhancements were present downstream of the shock in all 9 of these events, only about half of them contained simultaneous changes in the two quantities. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance, by a small decrease in the variance of the bulk velocity, and by an increase in the ratio of parallel to perpendicular temperature. The cold driver gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

Plasma properties of driver gas following interplanetary shocks observed by ISEE-3

NASA Technical Reports Server (NTRS)

Zwickl, R. D.; Ashbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Smith, E. J.

1982-01-01

Plasma fluid parameters calculated from solar wind and magnetic field data obtained on ISEE 3 were studied. The characteristic properties of driver gas following interplanetary shocks was determined. Of 54 shocks observed from August 1978 to February 1980, nine contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature across a tangential discontinuity. While helium enhancements were present in all of nine of these events, only about half of them contained simultaneous changes in the two quantities. Often the He/H ratio changed over a period of minutes. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance and by an increase in the ratio of parallel to perpendicular temperature. The drive gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

Analysis of Deactivation Mechanism on a Multi-Component Sulfur-Tolerant Steam Reforming Catalyst

DTIC Science & Technology

2010-08-01

Alkaline Fuel Cells (AFC) .............................................................................. 4 1.1.2. Proton Exchange Membrane Fuel Cells ( PEMFC ...temperature fuel cells. Alkaline Fuel Cell (AFC), Proton Exchange Membrane Fuel Cell ( PEMFC ), DMFC and Phosphoric Acid Fuel Cell (PAFC) are low...1960s. 1.1.2. Proton Exchange Membrane Fuel Cells ( PEMFC ) Proton exchange membrane fuel cells are said to be the best type of fuel cells to replace

The effects of fasting and cold exposure on metabolic rate and mitochondrial proton leak in liver and skeletal muscle of an amphibian, the cane toad Bufo marinus.

PubMed

Trzcionka, M; Withers, K W; Klingenspor, M; Jastroch, M

2008-06-01

Futile cycling of protons across the mitochondrial inner membrane contributes significantly to standard metabolic rate in a variety of ectothermic and endothermic animals, but adaptations of the mitochondrial bioenergetics to different environmental conditions have rarely been studied in ectotherms. Changes in ambient temperature and nutritional status have a great effect on the physiological demands of ectothermic amphibians and may require the adjustment of mitochondrial efficiency. In order to investigate the effect of temperature and nutritional status on the mitochondrial level, we exposed male cane toads to either 10 degrees C or 30 degrees C and fasted half of the animals in each group. Cold exposure resulted in a fourfold reduction of the resting metabolic rate whereas nutritional status had only minor effects. The mitochondrial adjustments to each condition were observed by comparing the proton leak kinetics of isolated liver and skeletal muscle mitochondria at 25 degrees C. In response to cold exposure, liver mitochondria showed a decrease in proton conductance while skeletal muscle mitochondria were unchanged. Additional food deprivation had minor effects in skeletal muscle, but in liver we uncovered surprising differences in energy saving mechanisms between the acclimation temperatures: in warm-acclimated toads, fasting resulted in a decrease of the proton conductance whereas in cold-acclimated toads, the activity of the respiratory chain was reduced. To investigate the molecular mechanism underlying mitochondrial proton leakage, we determined the adenine-nucleotide transporter (ANT) content, which explained tissue-specific differences in the basal proton leak, but neither the ANT nor uncoupling protein (UCP) gene expression correlated with alterations of the proton leak in response to physiological stimuli.

Preparation of nano-structured polymeric proton conducting membranes for use in fuel cells.

PubMed

Alberti, Giulio; Casciola, Mario; Pica, Monica; Di Cesare, Giusi

2003-03-01

We briefly discuss the state of the art of polymer electrolyte membrane fuel cells and suggest that the main obstacles to the commercial development of these fuel cells are essentially the high costs and poor characteristics of present proton conducting membranes. A strategy for the preparation of improved nanocomposite membranes based on the introduction of proton conducting lamell? in the polymeric matrix of present ionomeric membranes is then discussed. Due to their high proton conductivity (in some cases even higher than 10(-1) S cm(-1)), tailor made lamellae obtained by exfoliation of superacid metal (IV) phosphonates are particularly suitable for the preparation of these hybrid membranes. The expected positive influence of the dispersed lamellae on important properties of proton conducting membranes, such as swelling, mechanical resistance, proton transport, and diffusion of methanol, are also discussed. The methods used to obtain good lamellar dispersions into ionomeric polymers and the preparation and main characteristics of some hybrid membranes are also briefly described. The presence of nanoparticles of metal phosphonates in the electrodic interfaces Nafion/Pt already considerably improves the electrochemical characteristics of fuel cells in the temperature range 80-130 degrees C. The increased working temperature of the fuel cell considerably reduces CO poisoning of the platinum electrodes and allows better control of the cooling system, thus overcoming important obstacles to the development of medium temperature PEM fuel cells.

Fractal diffusion in high temperature polymer electrolyte fuel cell membranes

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

Hopfenmuller, Bernhard; Zorn, Reiner; Holderer, Olaf

In this paper, the performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution. Time of flight spectroscopy and backscattering spectroscopy have been combined to cover a broad dynamic range. In order to selectively observe the diffusion of protons potentially contributing to the ion conductivity,more » two samples were prepared, where in one of the samples the phosphoric acid was used with hydrogen replaced by deuterium. The scattering data from the two samples were subtracted in a suitable way after measurement. Thereby subdiffusive behavior of the proton diffusion has been observed and interpreted in terms of a model of fractal diffusion. For this purpose, a scattering function for fractal diffusion has been developed. The fractal diffusion dimension d w and the Hausdorff dimension d f have been determined on the length scales covered in the neutron scattering experiments.« less

Fractal diffusion in high temperature polymer electrolyte fuel cell membranes

DOE PAGES

Hopfenmuller, Bernhard; Zorn, Reiner; Holderer, Olaf; ...

2018-05-29

In this paper, the performance of fuel cells depends largely on the proton diffusion in the proton conducting membrane, the core of a fuel cell. High temperature polymer electrolyte fuel cells are based on a polymer membrane swollen with phosphoric acid as the electrolyte, where proton conduction takes place. We studied the proton diffusion in such membranes with neutron scattering techniques which are especially sensitive to the proton contribution. Time of flight spectroscopy and backscattering spectroscopy have been combined to cover a broad dynamic range. In order to selectively observe the diffusion of protons potentially contributing to the ion conductivity,more » two samples were prepared, where in one of the samples the phosphoric acid was used with hydrogen replaced by deuterium. The scattering data from the two samples were subtracted in a suitable way after measurement. Thereby subdiffusive behavior of the proton diffusion has been observed and interpreted in terms of a model of fractal diffusion. For this purpose, a scattering function for fractal diffusion has been developed. The fractal diffusion dimension d w and the Hausdorff dimension d f have been determined on the length scales covered in the neutron scattering experiments.« less

Composite electrolyte with proton conductivity for low-temperature solid oxide fuel cell

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

Raza, Rizwan, E-mail: razahussaini786@gmail.com; Department of Energy Technology, Royal Institute of Technology, KTH, Stockholm 10044; Ahmed, Akhlaq

In the present work, cost-effective nanocomposite electrolyte (Ba-SDC) oxide is developed for efficient low-temperature solid oxide fuel cells (LTSOFCs). Analysis has shown that dual phase conduction of O{sup −2} (oxygen ions) and H{sup +} (protons) plays a significant role in the development of advanced LTSOFCs. Comparatively high proton ion conductivity (0.19 s/cm) for LTSOFCs was achieved at low temperature (460 °C). In this article, the ionic conduction behaviour of LTSOFCs is explained by carrying out electrochemical impedance spectroscopy measurements. Further, the phase and structure analysis are investigated by X-ray diffraction and scanning electron microscopy techniques. Finally, we achieved an ionic transport numbermore » of the composite electrolyte for LTSOFCs as high as 0.95 and energy and power density of 90% and 550 mW/cm{sup 2}, respectively, after sintering the composite electrolyte at 800 °C for 4 h, which is promising. Our current effort toward the development of an efficient, green, low-temperature solid oxide fuel cell with the incorporation of high proton conductivity composite electrolyte may open frontiers in the fields of energy and fuel cell technology.« less

Temperature dependent fluorescence spectra arise from change in excited-state intramolecular proton transfer potential of 4‧-N,N-dimethylamino-3-hydroxyflavone-doped acetonitrile crystals

NASA Astrophysics Data System (ADS)

Furukawa, Kazuki; Yamamoto, Norifumi; Hino, Kazuyuki; Sekiya, Hiroshi

2016-01-01

The effect of intermolecular interaction on excited-state intramolecular proton transfer (ESIPT) in 4‧-N,N-dimethylamino-3-hydroxyflavone (DMHF) doped in acetonitrile crystals was investigated by measuring the temperature dependence of fluorescence excitation and fluorescence spectra. A solid/solid phase transition of DMHF-doped acetonitrile crystals occurred in the temperature between 210 and 218 K. Significant differences in the spectral profiles and shifts in the fluorescence spectra were observed in the low- and high-temperature regions of the phase transition. The temperature dependence of the ESIPT potential of DMHF is discussed.

Proton NMR study of α-MnH 0.06

NASA Astrophysics Data System (ADS)

Soloninin, A. V.; Skripov, A. V.; Buzlukov, A. L.; Antonov, V. E.; Antonova, T. E.

2004-07-01

Proton nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates for the solid solution α-MnH 0.06 have been measured over the temperature range 11-297 K and the resonance frequency range 20-90 MHz. A considerable shift and broadening of the proton NMR line and a sharp peak of the spin-lattice relaxation rate are observed near 130 K. These effects are attributed to the onset of antiferromagnetic ordering below the Néel temperature TN≈130 K. The proton NMR line does not disappear in the antiferromagnetic phase; this suggests a small magnitude of the local magnetic fields at H-sites in α-MnH 0.06. The spin-lattice relaxation rate in the paramagnetic phase is dominated by the effects of spin fluctuations.

A HIGH-LEVEL CALCULATION OF THE PROTON AFFINITY OF DIBORANE

EPA Science Inventory

The experimental proton affinity of diborane (B2H6) is based on an unstable species, B2H,+, 4 which has been observed only at low temperatures. The present work calculates the proton 5 affinity of diborane using the Gaussian-3 method and other high-level compound ab initio 6 met...

Harvesting electricity from human hair.

PubMed

Tulachan, Brindan; Singh, Sushil K; Philip, Deepu; Das, Mainak

2016-01-01

Electrical conductivity of human hair is a debatable issue among hair experts and scientists. There are unsubstantiated claims that hair conducts electricity. However, hair experts provided ample evidence that hair is an insulator. Although wet hair exhibited drastic reduction in resistivity; scientists regarded hair as a proton semiconductor at the best. Here, we demonstrate that hair filaments generate electricity on absorbing water vapor between 50 degrees and 80 degrees C. This electricity can operate low power electronic systems. Essentially, we are exposing the hydrated hair polymer to a high temperature (50 degrees-80 degrees C). It has long been speculated that when certain biopolymers are simultaneously hydrated and exposed to high temperature, they exhibit significant proton hopping at a specific temperature regime. This happens due to rapid movement of water molecules on the polymer surface. This lead us to speculate that the observed flow of current is partly ionic and partly due to "proton hopping" in the hydrated nano spaces of hair filament. Such proton hopping is exceptionally high when the hydrated hair polymer is exposed to a temperature between 50 degrees and 80 degrees C. Differential scanning calorimetry data further corroborated the results and indicated that indeed at this temperature range, there is an enormous movement of water molecules on the hair polymer surface. This enormously rapid movement of water molecules lead to the "making and breaking" of innumerable hydrogen bonds and thus resulting in hopping of the protons. What is challenging is "how to tap these hopping protons to obtain useful electricity?" We achieved this by placing a bundle of hair between two different electrodes having different electro negativities, and exposing it to water vapor (water + heat). The two different electrodes offered directionality to the hopping protons and the existing ions and thus resulting in the generation of useful current. Further, by continuously hydrating the polymer with water vapor, we prolonged the process. If this interesting aspect of polymer is exploited further and fine tuned, then it will open new avenues for development of sophisticated polymer-based systems, which could be used to harvest electricity from waste heat.

The kinetics of the decompositions of the proton bound dimers of 1,4-dimethylpyridine and dimethyl methylphosphonate from atmospheric pressure ion mobility spectra

NASA Astrophysics Data System (ADS)

Ewing, R. G.; Eiceman, G. A.; Harden, C. S.; Stone, J. A.

2006-09-01

The rate constants for the dissociations, A2H+ --> AH+ + A, of the symmetrical proton bound dimers of 2,4-dimethylpyridine and dimethyl methylphosphonate have been determined using an ion mobility spectrometer operating with air as drift gas at ambient pressure. Reaction time was varied by varying the drift electric field. The rate constants were derived from the mobility spectra by determining the rate at which ions decomposed in the drift region. Arrhenius plots with a drift gas containing water vapor at 5 ppmv gave the following activation energies and pre-exponential factors: 2,4-dimethylpyridine, 94 +/- 2 kJ mol-1, log A (s-1) = 15.9 +/- 0.4; dimethyl methylphosphonate, 127 +/- 3 kJ mol-1, log A (s-1) = 15.6 +/- 0.3. The enthalpy changes for the decompositions calculated from the activation energies are in accord with literature values for symmetrical proton bound dimers of oxygen and nitrogen bases. The results for dimethyl methylphosphonate were obtained over the temperature range 478-497 K and are practically independent of water concentration (5-2000 ppmv). The activation energy for 2,4-dimethylpyridine, obtained over the temperature range 340-359 K, decreased to 31 kJ mol-1 in the presence of 2.0 x 103 ppmv of water. At the low temperature, a displacement reaction involving water may account for the decrease. The reduced mobilities of the protonated molecules and the proton bound dimers have been determined over a wide temperature range. While the values for the dimers are essentially independent of the water concentration in the drift gas, those of the protonated molecules show a strong dependence.

Theoretical analysis of the unusual temperature dependence of the kinetic isotope effect in quinol oxidation.

PubMed

Ludlow, Michelle K; Soudackov, Alexander V; Hammes-Schiffer, Sharon

2009-05-27

In this paper we present theoretical calculations on model biomimetic systems for quinol oxidation. In these model systems, an excited-state [Ru(bpy)(2)(pbim)](+) complex (bpy = 2,2'-dipyridyl, pbim = 2-(2-pyridyl)benzimidazolate) oxidizes a ubiquinol or plastoquinol analogue in acetonitrile. The charge transfer reaction occurs via a proton-coupled electron transfer (PCET) mechanism, in which an electron is transferred from the quinol to the Ru and a proton is transferred from the quinol to the pbim(-) ligand. The experimentally measured average kinetic isotope effects (KIEs) at 296 K are 1.87 and 3.45 for the ubiquinol and plastoquinol analogues, respectively, and the KIE decreases with temperature for plastoquinol but increases with temperature for ubiquinol. The present calculations provide a possible explanation for the differences in magnitudes and temperature dependences of the KIEs for the two systems and, in particular, an explanation for the unusual inverse temperature dependence of the KIE for the ubiquinol analogue. These calculations are based on a general theoretical formulation for PCET reactions that includes quantum mechanical effects of the electrons and transferring proton, as well as the solvent reorganization and proton donor-acceptor motion. The physical properties of the system that enable the inverse temperature dependence of the KIE are a stiff hydrogen bond, which corresponds to a high-frequency proton donor-acceptor motion, and small inner-sphere and solvent reorganization energies. The inverse temperature dependence of the KIE may be observed if the 0/0 pair of reactant/product vibronic states is in the inverted Marcus region, while the 0/1 pair of reactant/product vibronic states is in the normal Marcus region and is the dominant contributor to the overall rate. In this case, the free energy barrier for the dominant transition is lower for deuterium than for hydrogen because of the smaller splittings between the vibronic energy levels for deuterium, and the KIE increases with increasing temperature. The temperature dependence of the KIE is found to be very sensitive to the interplay among the driving force, the reorganization energy, and the vibronic coupling in this regime.

High Temperature Thermosetting Polyimide Nanocomposites Prepared with Reduced Charge Organoclay

NASA Technical Reports Server (NTRS)

Campbell, Sandi; Liang, Margaret I.

2005-01-01

The naturally occurring sodium and calcium cations found in bentonite clay galleries were exchanged with lithium cations. Following the cation exchange, a series of reduced charge clays were prepared by heat treatment of the lithium bentonite at 130 C, 150 C, or 170 C. Inductively coupled plasma (ICP) analysis showed that heating the lithium clay at elevated temperatures reduced its cation exchange capacity. Ion exchange of heat-treated clays with either a protonated alkyl amine or a protonated aromatic diamine resulted in decreasing amounts of the organic modifier incorporated into the lithium clay. The level of silicate dispersion in a thermosetting polyimide matrix was dependent upon the temperature of Li-clay heat treatment as well as the organic modification. In general, clays treated at 150 C or 170 C, and exchanged with protonated octadcylamine or protonated 2,2'-dimethlybenzidine (DMBZ) showed a higher degree of dispersion than clays treated at 130 C, or exchanged with protonated dodecylamine. Dynamic mechanical analysis showed little change in the storage modulus or T(sub g) of the nanocomposites compared to the base resin. However, long term isothermal aging of the samples showed a significant decrease in the resin oxidative weight loss. Nanocomposite samples aged in air for 1000 hours at 288 C showed of to a decrease in weight loss compared to that of the base resin. This again was dependent on the temperature at which the Li-clay was heated and the choice of organic modification.

Doubling of the Critical Current Density of 2G-YBCO Coated Conductors through proton irradiation

NASA Astrophysics Data System (ADS)

Welp, Ulrich; Jia, Ying; Kwok, Wai-Kwong; Rupich, Marty; Fleshler, Steven; Kayani, Asfghar

2013-03-01

We report on magnetization and transport measurements of the critical current density of commercial 2G YBCO coated conductors before and after proton irradiation. The samples were irradiated along the c-axis with 4 MeV protons to a fluence of 1.5x1016 p/cm2. We find that at temperatures below 50 K, proton irradiation increases Jc by a factor of 2 in low fields and increases up to 2.5 in fields of 7 T. At 77 K, proton irradiation is less effective in enhancing the critical current. Doubling of Jc in fields of several Tesla and at temperatures below 50 K will be highly beneficial for applications of coated conductors in rotating machinery, generators and magnet coils. - Work supported by the US DoE-BES funded Energy Frontier Research Center (YJ), and by Department of Energy, Office of Science, Office of Basic Energy Sciences (UW, WKK), under Contract No. DE-AC02-06CH11357.

Majority of Solar Wind Intervals Support Ion-Driven Instabilities

NASA Astrophysics Data System (ADS)

Klein, K. G.; Alterman, B. L.; Stevens, M. L.; Vech, D.; Kasper, J. C.

2018-05-01

We perform a statistical assessment of solar wind stability at 1 AU against ion sources of free energy using Nyquist's instability criterion. In contrast to typically employed threshold models which consider a single free-energy source, this method includes the effects of proton and He2 + temperature anisotropy with respect to the background magnetic field as well as relative drifts between the proton core, proton beam, and He2 + components on stability. Of 309 randomly selected spectra from the Wind spacecraft, 53.7% are unstable when the ion components are modeled as drifting bi-Maxwellians; only 4.5% of the spectra are unstable to long-wavelength instabilities. A majority of the instabilities occur for spectra where a proton beam is resolved. Nearly all observed instabilities have growth rates γ slower than instrumental and ion-kinetic-scale timescales. Unstable spectra are associated with relatively large He2 + drift speeds and/or a departure of the core proton temperature from isotropy; other parametric dependencies of unstable spectra are also identified.

Periodic annealing of radiation damage in GaAs solar cells

NASA Technical Reports Server (NTRS)

Loo, R. Y.; Knechtli, R. C.; Kamath, G. S.

1980-01-01

Continuous annealing of GaAs solar cells is compared with periodic annealing to determine their relative effectiveness in minimizing proton radiation damage. It is concluded that continuous annealing of the cells in space at 150 C can effectively reduce the proton radiation damage to the GaAs solar cells. Periodic annealing is most effective if it can be initiated at relatively low fluences (approximating continuous annealing), especially if low temperatures of less than 200 C are to be used. If annealing is started only after the fluence of the damaging protons has accumulated to a high value 10 to the 11th power sq/pcm), effective annealing is still possible at relatively high temperatures. Finally, since electron radiation damage anneals even more easily than proton radiation damage, substantial improvements in GaAs solar cell life can be achieved by incorporating the proper annealing capabilities in solar panels for practical space missions where both electron and proton radiation damage have to be minimized.

Towards the next generation of solid oxide fuel cells operating below 600 °c with chemically stable proton-conducting electrolytes.

PubMed

Fabbri, Emiliana; Bi, Lei; Pergolesi, Daniele; Traversa, Enrico

2012-01-10

The need for reducing the solid oxide fuel cell (SOFC) operating temperature below 600 °C is imposed by cost reduction, which is essential for widespread SOFC use, but might also disclose new applications. To this aim, high-temperature proton-conducting (HTPC) oxides have gained widespread interest as electrolyte materials alternative to oxygen-ion conductors. This Progress Report describes recent developments in electrolyte, anode, and cathode materials for protonic SOFCs, addressing the issue of chemical stability, processability, and good power performance below 600 °C. Different fabrication methods are reported for anode-supported SOFCs, obtained using state-of-the-art, chemically stable proton-conducting electrolyte films. Recent findings show significant improvements in the power density output of cells based on doped barium zirconate electrolytes, pointing out towards the feasibility of the next generation of protonic SOFCs, including a good potential for the development of miniaturized SOFCs as portable power supplies. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Majority of Solar Wind Intervals Support Ion-Driven Instabilities.

PubMed

Klein, K G; Alterman, B L; Stevens, M L; Vech, D; Kasper, J C

2018-05-18

We perform a statistical assessment of solar wind stability at 1 AU against ion sources of free energy using Nyquist's instability criterion. In contrast to typically employed threshold models which consider a single free-energy source, this method includes the effects of proton and He^{2+} temperature anisotropy with respect to the background magnetic field as well as relative drifts between the proton core, proton beam, and He^{2+} components on stability. Of 309 randomly selected spectra from the Wind spacecraft, 53.7% are unstable when the ion components are modeled as drifting bi-Maxwellians; only 4.5% of the spectra are unstable to long-wavelength instabilities. A majority of the instabilities occur for spectra where a proton beam is resolved. Nearly all observed instabilities have growth rates γ slower than instrumental and ion-kinetic-scale timescales. Unstable spectra are associated with relatively large He^{2+} drift speeds and/or a departure of the core proton temperature from isotropy; other parametric dependencies of unstable spectra are also identified.

Moving protons with pendant amines: proton mobility in a nickel catalyst for oxidation of hydrogen.

PubMed

O'Hagan, Molly; Shaw, Wendy J; Raugei, Simone; Chen, Shentan; Yang, Jenny Y; Kilgore, Uriah J; DuBois, Daniel L; Bullock, R Morris

2011-09-14

Proton transport is ubiquitous in chemical and biological processes, including the reduction of dioxygen to water, the reduction of CO(2) to formate, and the production/oxidation of hydrogen. In this work we describe intramolecular proton transfer between Ni and positioned pendant amines for the hydrogen oxidation electrocatalyst [Ni(P(Cy)(2)N(Bn)(2)H)(2)](2+) (P(Cy)(2)N(Bn)(2) = 1,5-dibenzyl-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane). Rate constants are determined by variable-temperature one-dimensional NMR techniques and two-dimensional EXSY experiments. Computational studies provide insight into the details of the proton movement and energetics of these complexes. Intramolecular proton exchange processes are observed for two of the three experimentally observable isomers of the doubly protonated Ni(0) complex, [Ni(P(Cy)(2)N(Bn)(2)H)(2)](2+), which have N-H bonds but no Ni-H bonds. For these two isomers, with pendant amines positioned endo to the Ni, the rate constants for proton exchange range from 10(4) to 10(5) s(-1) at 25 °C, depending on isomer and solvent. No exchange is observed for protons on pendant amines positioned exo to the Ni. Analysis of the exchange as a function of temperature provides a barrier for proton exchange of ΔG(‡) = 11-12 kcal/mol for both isomers, with little dependence on solvent. Density functional theory calculations and molecular dynamics simulations support the experimental observations, suggesting metal-mediated intramolecular proton transfers between nitrogen atoms, with chair-to-boat isomerizations as the rate-limiting steps. Because of the fast rate of proton movement, this catalyst may be considered a metal center surrounded by a cloud of exchanging protons. The high intramolecular proton mobility provides information directly pertinent to the ability of pendant amines to accelerate proton transfers during catalysis of hydrogen oxidation. These results may also have broader implications for proton movement in homogeneous catalysts and enzymes in general, with specific implications for the proton channel in the Ni-Fe hydrogenase enzyme.

Ferromagnetism in proton irradiated 4H-SiC single crystal

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

Zhou, Ren-Wei; Wang, Hua-Jie; Chen, Wei-Bin

Room-temperature ferromagnetism is observed in proton irradiated 4H-SiC single crystal. An initial increase in proton dose leads to pronounced ferromagnetism, accompanying with obvious increase in vacancy concentration. Further increase in irradiation dose lowers the saturation magnetization with the decrease in total vacancy defects due to the defects recombination. It is found that divacancies are the mainly defects in proton irradiated 4H-SiC and responsible for the observed ferromagnetism.

Effect of proton irradiation on superconductivity in optimally doped BaFe 2 ( As 1 - x P x ) 2 single crystals

DOE PAGES

Smylie, M. P.; Leroux, M.; Mishra, V.; ...

2016-03-10

In this paper, irradiation with 4 MeV protons was used to systematically introduce defects in single crystals of the iron-arsenide superconductor BaFe 2(As 1-xP x) 2, x = 0.33. The effect of disorder on the low-temperature behavior of the London penetration depth λ(T) and transition temperature T c was investigated. In nearly optimally doped samples with T c ~ 29 K, signatures of a superconducting gap with nodes were observed. Contrary to previous reports on electron-irradiated crystals, we do not see a disorder-driven lifting of accidental nodes, and we observe that proton-induced defects are weaker pair breakers than electron-induced defects.more » Finally, we attribute our findings to anisotropic electron scattering caused by proton irradiation defects.« less

Better Proton-Conducting Polymers for Fuel-Cell Membranes

NASA Technical Reports Server (NTRS)

Narayan, Sri; Reddy, Prakash

2012-01-01

Polyoxyphenylene triazole sulfonic acid has been proposed as a basis for development of improved proton-conducting polymeric materials for solid-electrolyte membranes in hydrogen/air fuel cells. Heretofore, the proton-conducting membrane materials of choice have been exemplified by a family of perfluorosulfonic acid-based polymers (Nafion7 or equivalent). These materials are suitable for operation in the temperature of 75 to 85 C, but in order to reduce the sizes and/or increase the energy-conversion efficiencies of fuel-cell systems, it would be desirable to increase temperatures to as high as 120 C for transportation applications, and to as high as 180 C for stationary applications. However, at 120 C and at relative humidity values below 50 percent, the loss of water from perfluorosulfonic acid-based polymer membranes results in fuel-cell power densities too low to be of practical value. Therefore, membrane electrolyte materials that have usefully high proton conductivity in the temperature range of 180 C at low relative humidity and that do not rely on water for proton conduction at 180 C would be desirable. The proposed polyoxyphenylene triazole sulfonic acid-based materials have been conjectured to have these desirable properties. These materials would be free of volatile or mobile acid constituents. The generic molecular structure of these materials is intended to exploit the fact, demonstrated in previous research, that materials that contain ionizable acid and base groups covalently attached to thermally stable polymer backbones exhibit proton conduction even in the anhydrous state.

Why do proton conducting polybenzimidazole phosphoric acid membranes perform well in high-temperature PEM fuel cells?

PubMed

Melchior, Jan-Patrick; Majer, Günter; Kreuer, Klaus-Dieter

2016-12-21

Transport properties and hydration behavior of phosphoric acid/(benz)imidazole mixtures are investigated by diverse NMR techniques, thermogravimetric analysis (TGA) and conductivity measurements. The monomeric systems can serve as models for phosphoric acid/poly-benzimidazole membranes which are known for their exceptional performance in high temperature PEM fuel cells. 1 H- and 31 P-NMR data show benzimidazole acting as a strong Brønsted base with respect to neat phosphoric acid. Since benzimidazole's nitrogens are fully protonated with a low rate for proton exchange with phosphate species, proton diffusion and conduction processes must take place within the hydrogen bond network of phosphoric acid only. The proton exchange dynamics between phosphate and benzimidazole species pass through the intermediate exchange regime (with respect to NMR line separations) with exchange times being close to typical diffusion times chosen in PFG-NMR diffusion measurements (ms regime). The resulting effects, as described by the Kärger equation, are included into the evaluation of PFG-NMR data for obtaining precise proton diffusion coefficients. The highly reduced proton diffusion coefficient within the phosphoric acid part of the model systems compared to neat phosphoric acid is suggested to be the immediate consequence of proton subtraction from phosphoric acid. This reduces hydrogen bond network frustration (imbalance of the number of proton donors and acceptors) and therefore also the rate of structural proton diffusion, phosphoric acid's acidity and hygroscopicity. Reduced water uptake, shown by TGA, goes along with reduced electroosmotic water drag which is suggested to be the reason for PBI-phosphoric acid membranes performing better in fuel cells than other phosphoric-acid-containing electrolytes with higher protonic conductivity.

Solar wind proton temperature-velocity relationship

NASA Technical Reports Server (NTRS)

Lopez, R. E.; Freeman, J. W.

1986-01-01

Helios 1 data are analyzed to find an experimental fit for the temperature-velocity relationship at 1 AU. It is shown that the proton temperature-velocity changes at a velocity of approximately 500 km/s. Interplanetary dynamic processes, i.e., stream interactions, are shown to affect the temperature-velocity relationships less than 22 percent; the functional form of these relationships appears to be preserved throughout the solar cycle. It is pointed out that any comprehensive model of the solar wind will have to address the difference in the temperature-velocity relationship between the low- and high-speed wind, since this is a product of the acceleration and subsequent heating process generating the solar wind.

Effect of proton irradiation on the normal-state low-energy excitations of Ba(Fe 1-xRh x) 2As 2 superconductors

DOE PAGES

Moroni, M.; Gozzelino, L.; Ghigo, G.; ...

2017-09-19

Here, we present a 75As nuclear magnetic resonance (NMR) and resistivity study of the effect of 5.5 MeV proton irradiation on the optimal electron doped (x = 0.068) and overdoped (x = 0.107) Ba(Fe 1–xRh x) 2As 2 iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual resistivity in both compositions, sizable broadening of the NMR spectra was observed in all the irradiated samples at low temperature. The effect is significantly stronger in the optimally doped sample where the Curie Weiss temperature dependence of the line width suggests the onset of ferromagneticmore » correlations coexisting with superconductivity at the nanoscale. 1/T 2 measurements revealed that the energy barrier characterizing the low energy spin fluctuations of these compounds is enhanced upon proton irradiation, suggesting that the defects are likely slowing down the fluctuations between (0,π) and (π,0) nematic ground states.« less

Effect of proton irradiation on the normal-state low-energy excitations of Ba(Fe 1-xRh x) 2As 2 superconductors

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

Moroni, M.; Gozzelino, L.; Ghigo, G.

Here, we present a 75As nuclear magnetic resonance (NMR) and resistivity study of the effect of 5.5 MeV proton irradiation on the optimal electron doped (x = 0.068) and overdoped (x = 0.107) Ba(Fe 1–xRh x) 2As 2 iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual resistivity in both compositions, sizable broadening of the NMR spectra was observed in all the irradiated samples at low temperature. The effect is significantly stronger in the optimally doped sample where the Curie Weiss temperature dependence of the line width suggests the onset of ferromagneticmore » correlations coexisting with superconductivity at the nanoscale. 1/T 2 measurements revealed that the energy barrier characterizing the low energy spin fluctuations of these compounds is enhanced upon proton irradiation, suggesting that the defects are likely slowing down the fluctuations between (0,π) and (π,0) nematic ground states.« less

Numerical studies on alpha production from high energy proton beam interaction with Boron

NASA Astrophysics Data System (ADS)

Moustaizis, S. D.; Lalousis, P.; Hora, H.; Korn, G.

2017-05-01

Numerical investigations on high energy proton beam interaction with high density Boron plasma allows to simulate conditions concerning the alpha production from recent experimental measurements . The experiments measure the alpha production due to p11B nuclear fusion reactions when a laser-driven high energy proton beam interacts with Boron plasma produced by laser beam interaction with solid Boron. The alpha production and consequently the efficiency of the process depends on the initial proton beam energy, proton beam density, the Boron plasma density and temperature, and their temporal evolution. The main advantage for the p11B nuclear fusion reaction is the production of three alphas with total energy of 8.9 MeV, which could enhance the alpha heating effect and improve the alpha production. This particular effect is termed in the international literature as the alpha avalanche effect. Numerical results using a multi-fluid, global particle and energy balance, code shows the alpha production efficiency as a function of the initial energy of the proton beam, the Boron plasma density, the initial Boron plasma temperature and the temporal evolution of the plasma parameters. The simulations enable us to determine the interaction conditions (proton beam - B plasma) for which the alpha heating effect becomes important.

Friedel-Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery.

PubMed

Merle, Géraldine; Ioana, Filipoi Carmen; Demco, Dan Eugen; Saakes, Michel; Hosseiny, Seyed Schwan

2013-12-30

Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel-Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion.

Block Copolymers for Alkaline Fuel Cell Membrane Materials

DTIC Science & Technology

2014-07-30

temperature fuel cells including proton exchange membrane fuel cell ( PEMFC ) and alkaline fuel cell (AFC) with operation temperature usually lower than 120...advantages over proton exchange membrane fuel cells ( PEMFCs ) resulting in the popularity of AFCs in the US space program.[8-11] The primary benefit AFC...offered over PEMFC is better electrochemical kinetics on the anode and cathode under the alkaline environment, which results in the ability to use

Electron-ion temperature equilibration in warm dense tantalum

DOE PAGES

Doppner, T; LePape, S.; Ma, T.; ...

2014-11-05

We present measurements of electron-ion temperature equilibration in proton-heated tantalum, under warm dense matter conditions. Our results agree with theoretical predictions for metals calculated using input data from ab initio simulations. Furthermore, the fast relaxation observed in the experiment contrasts with much longer equilibration times found in proton heated carbon, indicating that the energy flow pathways in warm dense matter are far from being fully understood.

Exploring proton transfer in 1,2,3-triazole-triazolium dimer with ab initio method

NASA Astrophysics Data System (ADS)

Li, Ailin; Yan, Tianying; Shen, Panwen

Ab initio calculations are utilized to search for transition state structures for proton transfer in the 1,2,3-triazole-triazolium complexes on the basis of optimized dimers. The result suggests six transition state structures for single proton transfer in the complexes, most of which are coplanar. The energy barriers, between different stable and transition states structures with zero point energy (ZPE) corrections, show that proton transfer occurs at room temperature with coplanar configuration that has the lowest energy. The results clearly support that reorientation gives triazole flexibility for proton transfer.

Use of multi-functional flexible micro-sensors for in situ measurement of temperature, voltage and fuel flow in a proton exchange membrane fuel cell.

PubMed

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased.

Epoxy-crosslinked sulfonated poly (phenylene) copolymer proton exchange membranes

DOEpatents

Hibbs, Michael; Fujimoto, Cy H.; Norman, Kirsten; Hickner, Michael A.

2010-10-19

An epoxy-crosslinked sulfonated poly(phenylene) copolymer composition used as proton exchange membranes, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cell, in electrode casting solutions and electrodes, and in sulfur dioxide electrolyzers. These improved membranes are tougher, have higher temperature capability, and lower SO.sub.2 crossover rates.

Proton Transports in Pure Liquid Water Characterized by Melted Ice Lattice Model

NASA Astrophysics Data System (ADS)

Jie, Binbin; Sah, Chihtang

Basic water properties have not been understood for 200 years. Our Melted Ice Lattice model accounts for the 2 basic properties of pure water, the ion product (pH) and mobilities. It has HCP primitive unit cells, each with 4H2O, based on the 1933 Bernal-Fowler model, verified by 1935 Pauling residual entropy theory of 1928-1935 Giauque experimental low temperature specific heat measurements. Our 2 ion species are point-mass protons p + and p-, for mass and electricity transport. Three protonic thermal activation energies are obtained from pH and p + and p- mobilities vs T (0-100OC). Proton transport is analyzed in 3 proton-phonon collision steps: proton detrapping by protonic phonon absorption, proton scattering by oxygenic (water) phonons, and proton trapping with protonic phonon emission. Distinction between Potential and Kinetic Energy Bands of protons (Fermions) and phonons (Bosons) is noted. Experimental protonic activation energies are the phonon energies given by the spring-mass vibration frequencies of lattice, wn = (kn/mn)1/2 . n is the proton-mass unit of the synchronized vibrating particles in the primitive unit cells.

A highly stable two-dimensional copper(II)-organic framework for proton conduction and ammonia impedance sensing.

PubMed

Sun, Zhibing; Yu, Shihang; Zhao, Lili; Wang, Jifeng; Li, Zifeng; Li, Gang

2018-05-22

This work reports on the design and fabrication of a proton conductive 2D MOF, [Cu(p-IPhHIDC)]n (1) (p-IPhH3IDC = 2-(p-N-imidazol-1-yl)-phenyl-1H-imidazole-4,5dicarboxylic acid) as an advanced ammonia impedance sensor at room temperature and 68-98% RHs. MOF 1 shows the optimized proton conductivity value of 1.51 × 10-3 S·cm-1 at 100 C and 98% RH. Its temperature-dependent and humidity-dependent proton conduction properties have been explored. The large amount of uncoordinated carboxylate groups between the layers play a vital role in the resultant conductivity. Distinctly, the fabricated MOF-based sensor displays the required stability to NH3, enhanced sensitivity and notable selectivity to NH3 gas. At room temperature and 68% RH, it indicates a remarkable gas response of 8620% to 130 ppm of NH3 gas and lower detection limit (2 ppm) towards NH3 gas. It is also found that the gas response of the ammonia sensor increases linearly with the increase of NH3 gas concentration under 68-98% RHs and room temperature. Moreover, the sensor indicates excellent reversibility and selectivity toward NH3 vs N2, H2, O2, CO, CO2, benzene and MeOH. Based on structural analyses, activation energy calculations, water and NH3 vapor absorptions, and PXRD determinations, the proton conduction and NH3 sensing mechanisms are suggested. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NMR studies of double proton transfer in hydrogen bonded cyclic N,N'-diarylformamidine dimers: conformational control, kinetic HH/HD/DD isotope effects and tunneling.

PubMed

Lopez, Juan Miguel; Männle, Ferdinand; Wawer, Iwona; Buntkowsky, Gerd; Limbach, Hans-Heinrich

2007-08-28

Using dynamic NMR spectroscopy, the kinetics of the degenerate double proton transfer in cyclic dimers of polycrystalline (15)N,(15)N'-di-(4-bromophenyl)-formamidine (DBrFA) have been studied including the kinetic HH/HD/DD isotope effects in a wide temperature range. This transfer is controlled by intermolecular interactions, which in turn are controlled by the molecular conformation and hence the molecular structure. At low temperatures, rate constants were determined by line shape analysis of (15)N NMR spectra obtained using cross-polarization (CP) and magic angle spinning (MAS). At higher temperatures, in the microsecond time scale, rate constants and kinetic isotope effects were obtained by a combination of longitudinal (15)N and (2)H relaxation measurements. (15)N CPMAS line shape analysis was also employed to study the non-degenerate double proton transfer of polycrystalline (15)N,(15)N'-diphenyl-formamidine (DPFA). The kinetic results are in excellent agreement with the kinetics of DPFA and (15)N,(15)N'-di-(4-fluorophenyl)-formamidine (DFFA) studied previously for solutions in tetrahydrofuran. Two large HH/HD and HD/DD isotope effects are observed in the whole temperature range which indicates a concerted double proton transfer mechanism in the domain of the reaction energy surface. The Arrhenius curves are non-linear indicating a tunneling mechanism. Arrhenius curve simulations were performed using the Bell-Limbach tunneling model. The role of the phenyl group conformation and hydrogen bond compression on the barrier of the proton transfer is discussed.

Electron Heating in Low-Mach-number Perpendicular Shocks. I. Heating Mechanism

NASA Astrophysics Data System (ADS)

Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

2017-12-01

Recent X-ray observations of merger shocks in galaxy clusters have shown that the postshock plasma has two temperatures, with the protons hotter than the electrons. By means of two-dimensional particle-in-cell simulations, we study the physics of electron irreversible heating in low-Mach-number perpendicular shocks, for a representative case with sonic Mach number of 3 and plasma beta of 16. We find that two basic ingredients are needed for electron entropy production: (1) an electron temperature anisotropy, induced by field amplification coupled to adiabatic invariance; and (2) a mechanism to break the electron adiabatic invariance itself. In shocks, field amplification occurs at two major sites: at the shock ramp, where density compression leads to an increase of the frozen-in field; and farther downstream, where the shock-driven proton temperature anisotropy generates strong proton cyclotron and mirror modes. The electron temperature anisotropy induced by field amplification exceeds the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance and allows for efficient entropy production. For our reference run, the postshock electron temperature exceeds the adiabatic expectation by ≃ 15 % , resulting in an electron-to-proton temperature ratio of ≃ 0.45. We find that the electron heating efficiency displays only a weak dependence on mass ratio (less than ≃ 30 % drop, as we increase the mass ratio from {m}i/{m}e=49 up to {m}i/{m}e=1600). We develop an analytical model of electron irreversible heating and show that it is in excellent agreement with our simulation results.

A combined experimental and numerical approach for the control and monitoring of the SPES target during operation at high temperature

NASA Astrophysics Data System (ADS)

Ballan, Michele; Manzolaro, Mattia; Meneghetti, Giovanni; Andrighetto, Alberto; Monetti, Alberto; Bisoffi, Giovanni; Prete, Gianfranco

2016-06-01

The SPES project at INFN-LNL aims at the production of neutron-rich Radioactive Ion Beams (RIBs) using the ISOL (Isotope Separation On Line) technique. A 40 MeV 200 μA proton beam will directly impinge a uranium carbide target, generating approximately 1013 fissions per second. The target system is installed under vacuum inside a water-cooled chamber, and have to maintain high working temperatures, close to 2000 °C. During operation the proton beam provides the heating power required to keep the target at the desired temperature level. As a consequence, its characteristics have to be strictly controlled in order to avoid undesired overheating. According to the original design of the control system, the proton beam can be suddenly interrupted in case of out of range vacuum or cooling water flow levels. With the aim to improve the reliability of the control system a set of temperature sensors has been installed close to the target. Their types and installation positions were defined taking into consideration the detailed information coming from a dedicated thermal-electric model that allowed to investigate the most critical and inaccessible target hot-spots. This work is focused on the definition and experimental validation of the aforementioned numerical model. Its results were used to appropriately install two type C thermocouples, a PT100 thermo-resistance and a residual primary beam current detector. In addition the numerical model will be used for the definition of appropriate thresholds for each installed temperature sensor, since it allows to define a relationship between the locally measured values with the overall calculated temperature field. In case of over temperatures the monitoring system will send warning signals or in case interrupt the proton beam.

High-temperature annealing of proton irradiated beryllium – A dilatometry-based study

DOE PAGES

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; ...

2016-04-07

S—200 F grade beryllium has been irradiated with 160 MeV protons up to 1.2 10 20 cm –2 peak fluence and irradiation temperatures in the range of 100–200 °C. To address the effect of proton irradiation on dimensional stability, an important parameter in its consideration in fusion reactor applications, and to simulate high temperature irradiation conditions, multi-stage annealing using high precision dilatometry to temperatures up to 740 °C were conducted in air. X-ray diffraction studies were also performed to compliment the macroscopic thermal study and offer a microscopic view of the irradiation effects on the crystal lattice. The primary objectivemore » was to qualify the competing dimensional change processes occurring at elevated temperatures namely manufacturing defect annealing, lattice parameter recovery, transmutation 4He and 3H diffusion and swelling and oxidation kinetics. Further, quantification of the effect of irradiation dose and annealing temperature and duration on dimensional changes is sought. Here, the study revealed the presence of manufacturing porosity in the beryllium grade, the oxidation acceleration effect of irradiation including the discontinuous character of oxidation advancement, the effect of annealing duration on the recovery of lattice parameters recovery and the triggering temperature for transmutation gas diffusion leading to swelling.« less

The photochemical cycle of bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lozier, R. H.; Niederberger, W.

1977-01-01

The reaction cycle of bacteriorhodopsin in the purple membrane isolated from Halobacterium halobium has been studied by optical absorption spectroscopy using low-temperature and flash kinetic techniques. After absorption of light, bacteriorhodopsin passes through at least five distinct intermediates. The temperature and pH dependence of the absorbance changes suggests that branch points and/or reversible steps exist in this cycle. Flash spectroscopy in the presence of a pH-indicating dye shows that the transient release of a proton accompanies the photoreaction cycle. The proton release occurs from the exterior and the uptake is on the cytoplasmic side of the membrane, as required by the function of bacteriorhodopsin as a light-driven proton pump. Proton translocating steps connecting release and uptake are indicated by deuterium isotope effects on the kinetics of the cycle. The rapid decay of a light-induced linear dichroism shows that a chromophore orientation change occurs during the reaction cycle.

Nuclear-plus-interference-scattering effect on the energy deposition of multi-MeV protons in a dense Be plasma.

PubMed

Wang, Zhigang; Fu, Zhenguo; He, Bin; Hu, Zehua; Zhang, Ping

2016-09-01

The nuclear plus interference scattering (NIS) effect on the stopping power of hot dense beryllium (Be) plasma for multi-MeV protons is theoretically investigated by using the generalized Brown-Preston-Singleton (BPS) model, in which a NIS term is taken into account. The analytical formula of the NIS term is detailedly derived. By using this formula, the density and temperature dependence of the NIS effect is numerically studied, and the results show that the NIS effect becomes more and more important with increasing the plasma temperature or density. Different from the cases of protons traveling through the deuterium-tritium plasmas, for a Be plasma, a prominent oscillation valley structure is observed in the NIS term when the proton's energy is close to E_{p}=7MeV. Furthermore, the penetration distance is remarkably reduced when the NIS term is considered.

Influence of La/W ratio on electrical conductivity of lanthanum tungstate with high La/W ratio

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

Kojo, Gen; Shono, Yohei; Ushiyama, Hiroshi

The proton-conducting properties of lanthanum tungstates (LWOs) with high La/W ratios were investigated using electrochemical measurements and quantum chemical calculations. Single phases of LWOs with high La/W ratios (6.3≤La/W≤6.7) were synthesized by high-temperature sintering at around 1700 °C. The electrical conductivity of LWO increased with increasing La/W ratio in the single-phase region. The LWO synthesized at the optimum sintering temperature and time, and with the optimum La/W ratio gave the maximum conductivity, i.e., 2.7×10{sup −3} S cm{sup −1} with La/W=6.7 at 500 °C. Density functional theory calculations, using the nudged elastic band method, were performed to investigate the proton diffusionmore » barrier. The results suggest that the proton diffusion paths around La sites have the lowest proton diffusion barrier. These findings improve our understanding of LWO synthesis and the proton-conducting mechanism and provide a strategy for improving proton conduction in LWOs. - Graphical abstract: The LWOs with high La/W ratios were synthesized for the first time. The optimum La/W ratio gave the maximum conductivity with La/W=6.7 at 500 °C. The proton diffusion paths were also considered with density functional theory calculations. - Highlights: • The proton-conducting properties of lanthanum tungstates (LWOs) were investigated. • Single phase LWOs with high La/W ratios (6.3≤La/W≤6.7) were synthesized successfully. • LWOs with the high La/W ratios showed high proton conductivity. • The DFT calculation suggested the lowest proton diffusion barrier in the path around La sites.« less

High Temperature Protonic Conductors by Melt Growth

DTIC Science & Technology

2006-11-21

A.R. de Arellano-López, A. Sayir. “Microestructura y Comportamiento Plástico de Perovsquitas Conductoras Protónicas de Alta Temperatura ”. Bol. Soc...Conductores Protónicos de Alta Temperatura Crecidos por Fusión de Zona Flotante”. VII Reunión Nacional y VI Conferencia Iberoamericana (Electrocerámica...Fernández Departamento de Física de la Materia Condensada University of Seville, Sevilla, SPAIN High temperature protonic conductors (HTPC) were

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects.

PubMed

Lemke, Sonja; Handle, Philip H; Plaga, Lucie J; Stern, Josef N; Seidl, Markus; Fuentes-Landete, Violeta; Amann-Winkel, Katrin; Köster, Karsten W; Gainaru, Catalin; Loerting, Thomas; Böhmer, Roland

2017-07-21

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping. The kinetics of the HDA to LDA transformation lacks a proton/deuteron isotope effect, revealing that this process is dominated by the restructuring of the oxygen network. The x-ray diffraction experiments performed on samples at intermediate transition stages reflect a linear combination of the LDA and HDA patterns implying a macroscopic phase separation, instead of a local intermixing of the two amorphous states.

Electron heating at interplanetary shocks

NASA Technical Reports Server (NTRS)

Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Zwickl, R. D.

1982-01-01

Data for 41 forward interplanetary shocks show that the ratio of downstream to upstream electron temperatures, T/sub e/(d/u) is variable in the range between 1.0 (isothermal) and 3.0. On average, (T/sub e/(d/u) = 1.5 with a standard deviation, sigma e = 0.5. This ratio is less than the average ratio of proton temperatures across the same shocks, (T/sub p/(d/u)) = 3.3 with sigma p = 2.5 as well as the average ratio of electron temperatures across the Earth's bow shock. Individual samples of T/sub e/(d/u) and T/sub p/(d/u) appear to be weakly correlated with the number density ratio. However the amounts of electron and proton heating are well correlated with each other as well as with the bulk velocity difference across each shock. The stronger shocks appear to heat the protons relatively more efficiently than they heat the electrons.

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects

NASA Astrophysics Data System (ADS)

Lemke, Sonja; Handle, Philip H.; Plaga, Lucie J.; Stern, Josef N.; Seidl, Markus; Fuentes-Landete, Violeta; Amann-Winkel, Katrin; Köster, Karsten W.; Gainaru, Catalin; Loerting, Thomas; Böhmer, Roland

2017-07-01

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping. The kinetics of the HDA to LDA transformation lacks a proton/deuteron isotope effect, revealing that this process is dominated by the restructuring of the oxygen network. The x-ray diffraction experiments performed on samples at intermediate transition stages reflect a linear combination of the LDA and HDA patterns implying a macroscopic phase separation, instead of a local intermixing of the two amorphous states.

Electrocatalysis-induced elasticity modulation in a superionic proton conductor probed by band-excitation atomic force microscopy.

PubMed

Papandrew, A B; Li, Q; Okatan, M B; Jesse, S; Hartnett, C; Kalinin, S V; Vasudevan, R K

2015-12-21

Variable temperature band-excitation atomic force microscopy in conjunction with I-V spectroscopy was used to investigate the crystalline superionic proton conductor CsHSO4 during proton exchange induced by a Pt-coated conductive scanning probe. At a sample temperature of 150 °C and under an applied bias <1 V, reduction currents of up to 1 nA were observed. Simultaneously, we show that the electrochemical reactions are accompanied by a reversible decrease in the elastic modulus of CsHSO4, as seen by a contact resonance shift, and find evidence for superplasticity during scanning. These effects were not observed in the room-temperature phase of CsHSO4 or in the case of catalytically inactive conductive probes, proving the utility of this technique for monitoring electrochemical processes on the nanoscale, as well as the use of local contact stiffness as a sensitive indicator of electrochemical reactions.

Use of d-3He proton spectroscopy as a diagnostic of shell rho r in capsule implosion experiments with approximately 0.2 NIF scale high temperature Hohlraums at Omega.

PubMed

Delamater, N D; Wilson, D C; Kyrala, G A; Seifter, A; Hoffman, N M; Dodd, E; Singleton, R; Glebov, V; Stoeckl, C; Li, C K; Petrasso, R; Frenje, J

2008-10-01

We present the calculations and preliminary results from experiments on the Omega laser facility using d-(3)He filled plastic capsule implosions in gold Hohlraums. These experiments aim to develop a technique to measure shell rho r and capsule unablated mass with proton spectroscopy and will be applied to future National Ignition Facility (NIF) experiments with ignition scale capsules. The Omega Hohlraums are 1900 microm length x 1200 microm diameter and have a 70% laser entrance hole. This is approximately a 0.2 NIF scale ignition Hohlraum and reaches temperatures of 265-275 eV similar to those during the peak of the NIF drive. These capsules can be used as a diagnostic of shell rho r, since the d-(3)He gas fill produces 14.7 MeV protons in the implosion, which escape through the shell and produce a proton spectrum that depends on the integrated rho r of the remaining shell mass. The neutron yield, proton yield, and spectra change with capsule shell thickness as the unablated mass or remaining capsule rho r changes. Proton stopping models are used to infer shell unablated mass and shell rho r from the proton spectra measured with different filter thicknesses. The experiment is well modeled with respect to Hohlraum energetics, neutron yields, and x-ray imploded core image size, but there are discrepancies between the observed and simulated proton spectra.

Reply to the 'Comment on "Proton transport in barium stannate: classical, semi-classical and quantum regime"'.

PubMed

Geneste, Grégory; Hermet, Jessica; Dezanneau, Guilhem

2017-08-09

We respond to the erroneous criticisms about our modeling of proton transport in barium stannate [G. Geneste et al., Phys. Chem. Chem. Phys., 2015, 17, 19104]. In this previous work, we described, on the basis of density-functional calculations, proton transport in the classical and semi-classical regimes, and provided arguments in favor of an adiabatic picture for proton transfer at low temperature. We re-explain here our article (with more detail and precision), the content of which has been distorted in the Comment, and reiterate our arguments in this reply. We refute all criticisms. They are completely wrong in the context of our article. Even though a few of them are based on considerations probably true in some metals, they make no sense here since they do not correspond to the content of our work. It has not been understood in the Comment that two competitive configurations, associated with radically different transfer mechanisms, have been studied in our work. It has also not been understood in the Comment that the adiabatic regime described for transfer occurs in the protonic ground state, in a very-low barrier configuration with the protonic ground state energy larger than the barrier. Serious confusion has been made in the Comment with the case of H in metals like Nb or Ta, leading to the introduction of the notion of (protonic) "excited-state proton transfer", relevant for H in some metals, but (i) that does not correspond to the (ground state) adiabatic transfers here described, and (ii) that does not correspond to what is commonly described as the "adiabatic limit for proton transfer" in the scientific literature. We emphasize, accordingly, the large differences between proton transfer in the present oxide and hydrogen jumps in metals like Nb or Ta, and the similarities between proton transfer in the present oxide and in acid-base solutions. We finally describe a scenario for proton transfer in the present oxide regardless of the temperature regime.

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

Mautner, M.M.N.

The ionization energy of ferrocene (Cp{sub 2}Fe) was measured by charge-transfer equilibria as 6.81 {plus minus} 0.07 eV (157.1 {plus minus} 1.6 kcal/mol). The proton affinity was obtained from equilibrium temperature studies as 207 {plus minus} 1 kcal/mol. The protonation of Cp{sub 2}Fe also involves a significant entropy change of +6.3 cal/mol{center dot}K. Deuteration experiments show that, in the protonation of Cp{sub 2}Fe, the incoming proton goes to a sterically unique position and does not exchange with the ring protons. This is consistent with protonation on iron, but ring protonation exclusively in an exo position or an agostic ring-to-iron bridgedmore » structure are also possible. The results suggest that the proton affinity at Fe is greater by at least 5 kcal/mol than for ring protonation. The solvation energies of Cp{sub 2}Fe{sup +} and Cp{sub 2}FeH{sup +} by a CH{sub 3}CN molecule, 11.4 and 12.9 kcal/mol, respectively, are weaker than those of most gas-phase cations, and the attachment energies of dimethyl ether and benzene, <9 kcal/mol, are even weaker. These results support that the weak solution basicity of Cp{sub 2}Fe is due to inefficient ion solvation. The kinetics of proton transfer between Cp{sub 2}Fe and some cyclic compounds is unusually slow, with reaction efficiencies of 0.1-0.01, without significant temperature dependence. These are the first proton-transfer reactions to show such behavior, which may be due to a combination of an energy barrier and steric hindrance. Proton transfer is also observed from (RCN){sub 2}H{sup +} dimer ions to Cp{sub 2}Fe. These reactions may be direct or involve ligand switching, and in several cases either mechanism is endothermic and entropy-driven.« less

Pickup protons and pressure-balanced structures: Voyager 2 observations in merged interaction regions near 35 AU

NASA Astrophysics Data System (ADS)

Burlaga, L. F.; Ness, N. F.; Belcher, J. W.; Szabo, A.; Isenberg, P. A.; Lee, M. A.

1994-11-01

Five pressure-balanced structures, each with a scale of the order of a few hundredths of an astonomical unit (AU), were identified in two merged interaction regions (MIRs) near 35 AU in the Voyager 2 plasma and magnetic field data. They include a tangential discontinuity, simple and complex magnetic holes, slow correlated variations among the plasma and magnetic field parameters, and complex uncorrelated variations among the parameters. The changes in the magnetic pressure in these events are balanced by changes in the pressure of interstellar pickup protons. Thus the pickup protons probably play a major role in the dynamics of the MIRs. The solar wind proton and electron pressures are relatively unimportant in the MIRs at 35 AU and beyond. The region near 35 AU is transition region: the Sun is the source of the magnetic field, but the interstellar medium in source of pickups protons. Relative to the solar wind proton guyroadius, the thicknesses of the discontinuities and simple magnetic holes observed near 35 AU are at least an order of magnitude greater than those observed at 1 AU. However, the thicknesses of the tangential discontinuity and simple magnetic holes observed near 35 AU (in units of the pickup proton Larmor radius) are comparable to those observed at 1 AU (in units of the solar wind proton gyroradius). Thus the gyroradius of interstellar pickup protons controls the thickness of current sheets near 35 AU. We determine the interstellar pickup proton pressure in the PBSs. Using a model for the pickup proton temperature, we estimate that the average interstellar pickup proton pressure, temperature, and density in the MIRs at 35 AU are (0.53 +/- 0.14) x 10-12 erg/cu cm, (5.8 +/- 0.4) x 106 K and (7 +/- 2) x 10-4/cu cm.

Three-dimensional protonic conductivity in porous organic cage solids.

PubMed

Liu, Ming; Chen, Linjiang; Lewis, Scott; Chong, Samantha Y; Little, Marc A; Hasell, Tom; Aldous, Iain M; Brown, Craig M; Smith, Martin W; Morrison, Carole A; Hardwick, Laurence J; Cooper, Andrew I

2016-09-13

Proton conduction is a fundamental process in biology and in devices such as proton exchange membrane fuel cells. To maximize proton conduction, three-dimensional conduction pathways are preferred over one-dimensional pathways, which prevent conduction in two dimensions. Many crystalline porous solids to date show one-dimensional proton conduction. Here we report porous molecular cages with proton conductivities (up to 10(-3) S cm(-1) at high relative humidity) that compete with extended metal-organic frameworks. The structure of the organic cage imposes a conduction pathway that is necessarily three-dimensional. The cage molecules also promote proton transfer by confining the water molecules while being sufficiently flexible to allow hydrogen bond reorganization. The proton conduction is explained at the molecular level through a combination of proton conductivity measurements, crystallography, molecular simulations and quasi-elastic neutron scattering. These results provide a starting point for high-temperature, anhydrous proton conductors through inclusion of guests other than water in the cage pores.

Three-dimensional protonic conductivity in porous organic cage solids

NASA Astrophysics Data System (ADS)

Liu, Ming; Chen, Linjiang; Lewis, Scott; Chong, Samantha Y.; Little, Marc A.; Hasell, Tom; Aldous, Iain M.; Brown, Craig M.; Smith, Martin W.; Morrison, Carole A.; Hardwick, Laurence J.; Cooper, Andrew I.

2016-09-01

Proton conduction is a fundamental process in biology and in devices such as proton exchange membrane fuel cells. To maximize proton conduction, three-dimensional conduction pathways are preferred over one-dimensional pathways, which prevent conduction in two dimensions. Many crystalline porous solids to date show one-dimensional proton conduction. Here we report porous molecular cages with proton conductivities (up to 10-3 S cm-1 at high relative humidity) that compete with extended metal-organic frameworks. The structure of the organic cage imposes a conduction pathway that is necessarily three-dimensional. The cage molecules also promote proton transfer by confining the water molecules while being sufficiently flexible to allow hydrogen bond reorganization. The proton conduction is explained at the molecular level through a combination of proton conductivity measurements, crystallography, molecular simulations and quasi-elastic neutron scattering. These results provide a starting point for high-temperature, anhydrous proton conductors through inclusion of guests other than water in the cage pores.

Theoretical and computational studies of renewable energy materials: Room temperature ionic liquids and proton exchange membranes

NASA Astrophysics Data System (ADS)

Feng, Shulu

2011-12-01

Two kinds of renewable energy materials, room temperature ionic liquids (RTILs) and proton exchange membranes (PEMs), especially Nafion, are studied by computational and theoretical approaches. The ultimate purpose of the present research is to design novel materials to meet the future energy demands. To elucidate the effect of alkyl side chain length and anion on the structure and dynamics of the mixtures, molecular dynamics (MD) simulations of three RTILs/water mixtures at various water mole fractions: 1-butyl-3-methylimidazolium (BMIM+)/BF4-, 1-octyl-3-methylimidazolium (OMIM+)/BF4-, and OMIM +/Cl- are performed. Replacing the BMIM + cation with OMIM+ results in stronger aggregation of the cations as well as a slower diffusion of the anions, and replacing the BF4- anion with Cl- alters the water distribution at low water mole fractions and slows diffusion of the mixtures. Potential experimental manifestations of these behaviors in both cases are provided. Proton solvation properties and transport mechanisms are studied in hydrated Nafion, by using the self-consistent multistate empirical valence bond (SCI-MS-EVB) method. It is found that by stabilizing a more Zundel-like (H5O 2+) structure in the first solvation shells, the solvation of excess protons, as well as the proton hydration structure are both influenced by the sulfonate groups. Hydrate proton-related hydrogen bond networks are observed to be more stable than those with water alone. In order to characterize the nature of the proton transport (PT), diffusive motion, Arrhenius activation energies, and transport pathways are calculated and analyzed. Analysis of diffusive motion suggests that (1) a proton-hopping mechanism dominates the proton transport for the studied water loading levels and (2) there is an obvious degree of anti-correlation between the proton hopping and the vehicular transport. The activation energy drops rapidly with an increasing water content when the water loading level is smaller than ˜ 10 H2O/SO 3-, which is consistent with experimental observations. The sulfonate groups are also found to have influence on the proton hopping directions. The temperature and water content effects on the PT pathways are also investigated. The morphological effects on proton solvation and transport in hydrated Nafion are investigated, by using the SCI-MS-EVB method. Two of the most significant morphological models of Nafion, the lamellar model and the cylinder model, are selected. The two models exhibit distinct PT patterns, which result in different proton diffusion rates. In both models, the interaction between protons and the sulfonate groups are proven to be the key to determining PT behavior. The proton solvation structure change as a function of the distance between protons and sulfonate groups has been analyzed. It is found that the increase of water cylinder radius or water layer height leads to the presence of more protons around the sulfonate groups. Furthermore, at a lower hydration level, the increased amount of protons around the sulfonate groups consists of more Zundel-like structures, which is influenced by the distinct morphological structures of Nafion.

Oriented MOF-polymer Composite Nanofiber Membranes for High Proton Conductivity at High Temperature and Anhydrous Condition

PubMed Central

Wu, Bin; Pan, Jiefeng; Ge, Liang; Wu, Liang; Wang, Huanting; Xu, Tongwen

2014-01-01

The novel oriented electrospun nanofiber membrane composed of MOFs and SPPESK has been synthesized for proton exchange membrane fuel cell operating at high temperature and anhydrous conditions. It is clear that the oriented nanofiber membrane displays the higher proton conductivity than that of the disordered nanofiber membrane or the membrane prepared by conventional solvent-casting method (without nanofibers). Nanofibers within the membranes are significantly oriented. The proton conductivity of the oriented nanofiber membrane can reach up to (8.2 ± 0.16) × 10−2 S cm−1 at 160°C under anhydrous condition for the highly orientation of nanofibers. Moreover, the oxidative stability and resistance of methanol permeability of the nanofibers membrane are obviously improved with an increase in orientation of nanofibers. The observed methanol permeability of 0.707 × 10−7 cm2 s−1 is about 6% of Nafion-115. Consequently, orientated nanofibers membrane is proved to be a promising material as the proton exchange membrane for potential application in direct methanol fuel cells. PMID:25082522

Self-consistent model of the interstellar pickup protons, Alfvenic turbulence, and core solar wind in the outer heliosphere

DOE PAGES

Gamayunov, Konstantin V.; Zhang, Ming; Pogorelov, Nikolai V.; ...

2012-09-05

In this study, a self-consistent model of the interstellar pickup protons, the slab component of the Alfvénic turbulence, and core solar wind (SW) protons is presented for r ≥ 1 along with the initial results of and comparison with the Voyager 2 (V2) observations. Two kinetic equations are used for the pickup proton distribution and Alfvénic power spectral density, and a third equation governs SW temperature including source due to the Alfvén wave energy dissipation. A fraction of the pickup proton free energy, fD , which is actually released in the waveform during isotropization, is taken from the quasi-linear considerationmore » without preexisting turbulence, whereas we use observations to specify the strength of the large-scale driving, C sh, for turbulence. The main conclusions of our study can be summarized as follows. (1) For C sh ≈ 1-1.5 and f D ≈ 0.7-1, the model slab component agrees well with the V2 observations of the total transverse magnetic fluctuations starting from ~8 AU. This indicates that the slab component at low-latitudes makes up a majority of the transverse magnetic fluctuations beyond 8-10 AU. (2) The model core SW temperature agrees well with the V2 observations for r ≳ 20 AU if f D ≈ 0.7-1. (3) A combined effect of the Wentzel-Kramers-Brillouin attenuation, large-scale driving, and pickup proton generated waves results in the energy sink in the region r ≲ 10 AU, while wave energy is pumped in the turbulence beyond 10 AU. Without energy pumping, the nonlinear energy cascade is suppressed for r ≲ 10 AU, supplying only a small energy fraction into the k-region of dissipation by the core SW protons. A similar situation takes place for the two-dimensional turbulence. (4) The energy source due to the resonant Alfvén wave damping by the core SW protons is small at heliocentric distances r ≲ 10 AU for both the slab and the two-dimensional turbulent components. As a result, adiabatic cooling mostly controls the model SW temperature in this region, and the model temperature disagrees with the V2 observations in the region r ≲ 20 AU.« less

Proton beam generation of whistler waves in the earth's foreshock

NASA Technical Reports Server (NTRS)

Wong, H. K.; Goldstein, M. L.

1987-01-01

It is shown that proton beams, often observed upstream of the earth's bow shock and associated with the generation of low-frequency hydromagnetic fluctuations, are also capable of generating whistler waves. The waves can be excited by an instability driven by two-temperature streaming Maxwellian proton distributions which have T (perpendicular)/T(parallel) much greater than 1. It can also be excited by gyrating proton beam distributions. These distributions generate whistler waves with frequencies ranging from 10 to 100 times the proton cyclotron frequency (in the solar wind reference frame) and provide another mechanism for generating the '1-Hz' waves often seen in the earth's foreshock.

Stable transport in proton driven fast ignition

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

Bret, A.

2009-09-15

Proton beam transport in the context of proton driven fast ignition is usually assumed to be stable due to proton high inertia, but an analytical analysis of the process is still lacking. The stability of a charge and current neutralized proton beam passing through a plasma is therefore conducted here, for typical proton driven fast ignition parameters. In the cold regime, two fast growing modes are found, with an inverse growth rate much smaller than the beam time of flight to the target core. The stability issue is thus not so obvious, and kinetic effects are investigated. One unstable modemore » is found stabilized by the background plasma proton and electron temperatures. The second mode is also damped, providing the proton beam thermal spread is larger than {approx}10 keV. In fusion conditions, the beam propagation should therefore be stable.« less

Influence of the Proton Pressure Tensor on the Turbulent Velocity Spectrum at Ion Kinetic Scales

NASA Astrophysics Data System (ADS)

Vasquez, B. J.; Markovskii, S.

2011-12-01

Numerical hybrid simulations with particle protons and fluid electrons are presented for turbulent fluctuations with spatial variations in a plane perpendicular to the background magnetic field. The steepened portion of the proton bulk velocity spectrum is found at smaller wavenumbers for larger background proton temperature. The velocity spectrum is determined, in part, by the proton pressure tensor. The proton pressure tensor is shown to possess non-gyrotropic and finite off-diagonal components in the places where the turbulent fluctuations have developed strong gradients. Proton demagnetization at these places is a factor in the departure from a Maxwellian velocity distribution function. How demagnetization could connect with both reversible and effectively irreversible aspects of the pressure tensor is considered. The effectively irreversible aspect corresponds to the net heating of the protons and to the dissipation of the turbulent energy cascade.

Proton irradiated graphite grades for a long baseline neutrino facility experiment

NASA Astrophysics Data System (ADS)

Simos, N.; Nocera, P.; Zhong, Z.; Zwaska, R.; Mokhov, N.; Misek, J.; Ammigan, K.; Hurh, P.; Kotsina, Z.

2017-07-01

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140-180 MeV, to peak fluence of ˜6.1 ×1020 p /cm2 and irradiation temperatures between 120 - 200 °C . The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use as a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young's modulus. The proton fluence level of ˜1020 cm-2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ˜5 ×1020 cm-2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.

Proton irradiated graphite grades for a long baseline neutrino facility experiment

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

Simos, N.; Nocera, P.; Zhong, Z.

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140–180 MeV, to peak fluence of ~6.1×10 20 p/cm 2 and irradiation temperatures between 120–200 °C. The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use asmore » a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young’s modulus. The proton fluence level of ~10 20 cm -2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ~5×10 20 cm -2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.« less

Proton irradiated graphite grades for a long baseline neutrino facility experiment

DOE PAGES

Simos, N.; Nocera, P.; Zhong, Z.; ...

2017-07-24

In search of a low-Z pion production target for the Long Baseline Neutrino Facility (LBNF) of the Deep Underground Neutrino Experiment (DUNE) four graphite grades were irradiated with protons in the energy range of 140–180 MeV, to peak fluence of ~6.1×10 20 p/cm 2 and irradiation temperatures between 120–200 °C. The test array included POCO ZXF-5Q, Toyo-Tanso IG 430, Carbone-Lorraine 2020 and SGL R7650 grades of graphite. Irradiation was performed at the Brookhaven Linear Isotope Producer. Postirradiation analyses were performed with the objective of (a) comparing their response under the postulated irradiation conditions to guide a graphite grade selection for use asmore » a pion target and (b) understanding changes in physical and mechanical properties as well as microstructure that occurred as a result of the achieved fluence and in particular at this low-temperature regime where pion graphite targets are expected to operate. A further goal of the postirradiation evaluation was to establish a proton-neutron correlation damage on graphite that will allow for the use of a wealth of available neutron-based damage data in proton-based studies and applications. Macroscopic postirradiation analyses as well as energy dispersive x-ray diffraction of 200 KeV x rays at the NSLS synchrotron of Brookhaven National Laboratory were employed. The macroscopic analyses revealed differences in the physical and strength properties of the four grades with behavior however under proton irradiation that qualitatively agrees with that reported for graphite under neutrons for the same low temperature regime and in particular the increase of thermal expansion, strength and Young’s modulus. The proton fluence level of ~10 20 cm -2 where strength reaches a maximum before it begins to decrease at higher fluences has been identified and it agrees with neutron-induced changes. X-ray diffraction analyses of the proton irradiated graphite revealed for the first time the similarity in microstructural graphite behavior to that under neutron irradiation and the agreement between the fluence threshold of ~5×10 20 cm -2 where the graphite lattice undergoes a dramatic change. The confirmed similarity in behavior and agreement in threshold fluences for proton and neutron irradiation effects on graphite reported for the first time in this study will enable the safe utilization of the wealth of neutron irradiation data on graphite that extends to much higher fluences and different temperature regimes by the proton accelerator community searching for multi-MW graphite targets.« less

Use of Multi-Functional Flexible Micro-Sensors for in situ Measurement of Temperature, Voltage and Fuel Flow in a Proton Exchange Membrane Fuel Cell

PubMed Central

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased. PMID:22163545

Theoretical study of interactions between 2,2-Bis (ethylferrocenyl) propane and ammonium perchlorate at low temperature

NASA Astrophysics Data System (ADS)

Zhou, Junhong; Zhang, Wei; Yang, Jun; Jiang, Benzheng; Chen, Weiming

2016-05-01

In order to explore the interaction mechanism between 2,2-Bis (ethylferrocenyl) propane (GFP) and ammonium perchlorate (AP) at low temperature (below 250 °C), all the possible intermolecular interactions between GFP and AP were calculated. The calculations were performed in single molecule, cluster and slab models. The calculation results show that the interactions between GFP and AP at low temperature mainly come from GFP:-H+ and GFP-NH4+ pair interactions. We speculate that the interaction mechanism between GFP and AP at low temperature is that GFP/H+ or GFP/NH4+ interactions cause GFP to be protonated, and then protonated GFP is to further oxidized.

Defining the Operational Conditions for High Temperature Polymer Fuel Cells in Naval Environments

DTIC Science & Technology

2008-12-31

benefits of both Proton Exchange Membrane Fuel Cells ( PEMFCs ) and phosphoric acid fuel cell technologies: a solid polymer electrolyte, the PBI...membrane, but with higher temperature (160°C) operation. PBI membrane technology is far less developed than that for PEMFCs , but it is rapidly emerging as...how air contaminants affect the properties of proton exchange membrane fuel cells ( PEMFCs ). PEMFCs operate at 80 °C, and are the present choice of fuel

Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery

PubMed Central

Merle, Géraldine; Ioana, Filipoi Carmen; Demco, Dan Eugen; Saakes, Michel; Hosseiny, Seyed Schwan

2014-01-01

Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion. PMID:24957118

Operational characteristics of the J-PARC cryogenic hydrogen system for a spallation neutron source

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

Tatsumoto, Hideki; Ohtsu, Kiichi; Aso, Tomokazu

2014-01-29

The J-PARC cryogenic hydrogen system provides supercritical hydrogen with the para-hydrogen concentration of more than 99 % and the temperature of less than 20 K to three moderators so as to provide cold pulsed neutron beams of a higher neutronic performance. Furthermore, the temperature fluctuation of the feed hydrogen stream is required to be within ± 0.25 K. A stable 300-kW proton beam operation has been carried out since November 2012. The para-hydrogen concentrations were measured during the cool-down process. It is confirmed that para-hydrogen always exists in the equilibrium concentration because of the installation of an ortho-para hydrogen convertor.more » Propagation characteristics of temperature fluctuation were measured by temporarily changing the heater power under off-beam condition to clarify the effects of a heater control for thermal compensation on the feed temperature fluctuation. The experimental data gave an allowable temperature fluctuation of ± 1.05 K. It is clarified through a 286-kW and a 524-kW proton beam operations that the heater control would be applicable for the 1-MW proton beam operation by extrapolating from the experimental data.« less

Phosphoric acid functionalized pre-sintered meso-silica for high temperature proton exchange membrane fuel cells.

PubMed

Zeng, Jie; He, Beibei; Lamb, Krystina; De Marco, Roland; Shen, Pei Kang; Jiang, San Ping

2013-05-21

An inorganic proton exchange membrane based on sintered mesoporous silica and phosphoric acid was developed with a high proton conductivity of 0.06 S cm(-1) at 200 °C, achieving an excellent power output of 689 mW cm(-2) in H2 at 190 °C and 200 mW cm(-2) in methanol at 200 °C with no external humidification.

Protic Salt Polymer Membranes: High-Temperature Water-Free Proton-Conducting Membranes

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

Gervasio, Dominic Francis

2010-09-30

This research on proton-containing (protic) salts directly addresses proton conduction at high and low temperatures. This research is unique, because no water is used for proton ionization nor conduction, so the properties of water do not limit proton fuel cells. A protic salt is all that is needed to give rise to ionized proton and to support proton mobility. A protic salt forms when proton transfers from an acid to a base. Protic salts were found to have proton conductivities that are as high as or higher than the best aqueous electrolytes at ambient pressures and comparable temperatures without ormore » with water present. Proton conductivity of the protic salts occurs providing two conditions exist: i) the energy difference is about 0.8 eV between the protic-salt state versus the state in which the acid and base are separated and 2) the chemical constituents rotate freely. The physical state of these proton-conducting salts can be liquid, plastic crystal as well as solid organic and inorganic polymer membranes and their mixtures. Many acids and bases can be used to make a protic salt which allows tailoring of proton conductivity, as well as other properties that affect their use as electrolytes in fuel cells, such as, stability, adsorption on catalysts, environmental impact, etc. During this project, highly proton conducting (~ 0.1S/cm) protic salts were made that are stable under fuel-cell operating conditions and that gave highly efficient fuel cells. The high efficiency is attributed to an improved oxygen electroreduction process on Pt which was found to be virtually reversible in a number of liquid protic salts with low water activity (< 1% water). Solid flexible non-porous composite membranes, made from inorganic polymer (e.g., 10%indium 90%tin pyrophosphate, ITP) and organic polymer (e.g., polyvinyl pyridinium phosphate, PVPP), were found that give conductivity and fuel cell performances similar to phosphoric acid electrolyte with no need for hydration at ambient pressures. Synthesis and processing of these protic salts into proton-conducting membrane is far from optimized. This protic salt approach has great promise for more improvements in proton conducting membranes for making practical compact, lightweight and inexpensive fuel cells with uses ranging from small electronics (Power = 1 to 100 Watts) to transportation (kiloWatts) to stationary applications (>100 kiloWatts). This work clearly showed that proton can be conducted without water using protoic ionic liquids which are Bronsted salts which contain a proton and whose acid and base moieties have pK separated by more than 4 units and less than 14. A key finding is that the base used should be significantly different than the basicity of water or else water displaces the base and an ordinary acid membrane is left behind. This is the case where the acid moiety is sulfonic acid found on perfluorinated polymeric membranes. This PI suggests that a fruitful route for attaining highly proton-conductive stable protic salt membranes is to use the STABLE poly-phosphazene (-P=N-) polymer backbone with electrochemically STABLE pendant acid or base units on the phosphorous of poly-phosphazene and with suitable pK so the base is NOT the same pK as water. From this work this should give stable water-free proton conductors which should allow for stable fuel cells with Pt catalysts and possible with non-platinum catalyst for the hydrogen anode and oxygen cathode.« less

High-temperature supercapacitor with a proton-conducting metal pyrophosphate electrolyte

PubMed Central

Hibino, Takashi; Kobayashi, Kazuyo; Nagao, Masahiro; Kawasaki, Shinji

2015-01-01

Expanding the range of supercapacitor operation to temperatures above 100°C is important because this would enable capacitors to operate under the severe conditions required for next-generation energy storage devices. In this study, we address this challenge by the fabrication of a solid-state supercapacitor with a proton-conducting Sn0.95Al0.05H0.05P2O7 (SAPO)-polytetrafluoroethylene (PTFE) composite electrolyte and a highly condensed H3PO4 electrode ionomer. At a temperature of 200°C, the SAPO-PTFE electrolyte exhibits a high proton conductivity of 0.02 S cm−1 and a wide withstanding voltage range of ±2 V. The H3PO4 ionomer also has good wettability with micropore-rich activated carbon, which realizes a capacitance of 210 F g−1 at 200°C. The resulting supercapacitor exhibits an energy density of 32 Wh kg−1 at 3 A g−1 and stable cyclability after 7000 cycles from room temperature to 150°C. PMID:25600936

Some notes on hydrogen-related point defects and their role in the isotope exchange and electrical conductivity in olivine

NASA Astrophysics Data System (ADS)

Karato, Shun-ichiro

2015-11-01

Nominally anhydrous minerals such as olivine dissolve hydrogen in a variety of forms including free (or interstitial) proton (Hrad) and two protons trapped at the M-site ((2 H)M×). The strength of chemical bonding between protons and the surrounding atoms are different among different species, and consequently protons belonging to different species likely have different mobility (diffusion coefficients). I discuss the role of diffusion of protons in different species in the isotope exchange and hydrogen-assisted electrical conductivity adding a few notes to the previous work by Karato (2013) including a new way to test the model. I conclude that in the case of isotope exchange, the interaction among these species is strong because diffusion is heterogeneous, whereas there is no strong interaction among different species in electrical conduction where diffusion is homogeneous (in an infinite crystal). Consequently, the slowest diffusing species controls the rate of isotope exchange, whereas the fastest diffusing species controls electrical conductivity leading to a different temperature dependence of activation energy and anisotropy. This model explains the differences in the activation energy and anisotropy between isotope diffusion and electrical conductivity, and predicts that the mechanism of electrical conductivity changes with temperature providing an explanation for most of the discrepancies among different experimental observations at different temperatures except for those by Poe et al. (2010) who reported anomalously high water content dependence and highly anisotropic activation energy. When the results obtained at high temperatures are used, most of the geophysically observed high and highly anisotropic electrical conductivity in the asthenosphere can be explained without invoking partial melting.

Production and Extraction of [10C]-CO2 From Proton Bombardment of Molten 10B2O3

NASA Astrophysics Data System (ADS)

Schueller, M. J.; Nickles, R. J.; Roberts, A. D.; Jensen, M.

2003-08-01

This work describes the production of 10C (t1/2 = 19 s) from an enriched 10B2O3 target using a CTI RDS-112 11 MeV proton cyclotron. Proton beam heating is used to raise the target to a molten state (˜ 1300 °C), enabling the activity to diffuse to the surface of the melt. An infrared thermocouple monitors the melt temperature. Helium sweep gas then transports the activity to flow-through chemistry processing for human inhalation of 10CO2 for blood flow imaging with Positron Emission Tomography. The temperature-related diffusion of activity out of the white-hot molten glass target is discussed.

Polymer and Composite Membranes for Proton-Conducting, High-Temperature Fuel Cells: A Critical Review

PubMed Central

Quartarone, Eliana; Angioni, Simone; Mustarelli, Piercarlo

2017-01-01

Polymer fuel cells operating above 100 °C (High Temperature Polymer Electrolyte Membrane Fuel Cells, HT-PEMFCs) have gained large interest for their application to automobiles. The HT-PEMFC devices are typically made of membranes with poly(benzimidazoles), although other polymers, such as sulphonated poly(ether ether ketones) and pyridine-based materials have been reported. In this critical review, we address the state-of-the-art of membrane fabrication and their properties. A large number of papers of uneven quality has appeared in the literature during the last few years, so this review is limited to works that are judged as significant. Emphasis is put on proton transport and the physico-chemical mechanisms of proton conductivity. PMID:28773045

Polymer and Composite Membranes for Proton-Conducting, High-Temperature Fuel Cells: A Critical Review.

PubMed

Quartarone, Eliana; Angioni, Simone; Mustarelli, Piercarlo

2017-06-22

Polymer fuel cells operating above 100 °C (High Temperature Polymer Electrolyte Membrane Fuel Cells, HT-PEMFCs) have gained large interest for their application to automobiles. The HT-PEMFC devices are typically made of membranes with poly(benzimidazoles), although other polymers, such as sulphonated poly(ether ether ketones) and pyridine-based materials have been reported. In this critical review, we address the state-of-the-art of membrane fabrication and their properties. A large number of papers of uneven quality has appeared in the literature during the last few years, so this review is limited to works that are judged as significant. Emphasis is put on proton transport and the physico-chemical mechanisms of proton conductivity.

Molecular dynamics analysis of stabilities of the telomeric Watson-Crick duplex and the associated i-motif as a function of pH and temperature.

PubMed

Panczyk, Tomasz; Wolski, Pawel

2018-06-01

This work deals with a molecular dynamics analysis of the protonated and deprotonated states of the natural sequence d[(CCCTAA) 3 CCCT] of the telomeric DNA forming the intercalated i-motif or paired with the sequence d[(CCCTAA) 3 CCCT] and forming the Watson-Crick (WC) duplex. By utilizing the amber force field for nucleic acids we built the i-motif and the WC duplex either with native cytosines or using their protonated forms. We studied, by applying molecular dynamics simulations, the role of hydrogen bonds between cytosines or in cytosine-guanine pairs in the stabilization of both structures in the physiological fluid. We found that hydrogen bonds exist in the case of protonated i-motif and in the standard form of the WC duplex. They, however, vanish in the case of the deprotonated i-motif and protonated form of the WC duplex. By determining potentials of mean force in the enforced unwrapping of these structures we found that the protonated i-motif is thermodynamically the most stable. Its deprotonation leads to spontaneous and observed directly in the unbiased calculations unfolding of the i-motif to the hairpin structure at normal temperature. The WC duplex is stable in its standard form and its slight destabilization is observed at the acidic pH. However, the protonated WC duplex unwraps very slowly at 310 K and its decomposition was not observed in the unbiased calculations. At higher temperatures (ca. 400 K or more) the WC duplex unwraps spontaneously. Copyright © 2018. Published by Elsevier B.V.

Proton Content and Nature in Perovskite Ceramic Membranes for Medium Temperature Fuel Cells and Electrolysers

PubMed Central

Colomban, Philippe; Zaafrani, Oumaya; Slodczyk, Aneta

2012-01-01

Recent interest in environmentally friendly technology has promoted research on green house gas-free devices such as water steam electrolyzers, fuel cells and CO2/syngas converters. In such applications, proton conducting perovskite ceramics appear especially promising as electrolyte membranes. Prior to a successful industrial application, it is necessary to determine/understand their complex physical and chemical behavior, especially that related to proton incorporation mechanism, content and nature of bulk protonic species. Based on the results of quasi-elastic neutron scattering (QNS), thermogravimetric analysis (TGA), Raman and IR measurements we will show the complexity of the protonation process and the importance of differentiation between the protonic species adsorbed on a membrane surface and the bulk protons. The bulk proton content is very low, with a doping limit (~1–5 × 10−3 mole/mole), but sufficient to guarantee proton conduction below 600 °C. The bulk protons posses an ionic, covalent bond free nature and may occupy an interstitial site in the host perovskite structure. PMID:24958293

Empirical Constraints on Proton and Electron Heating in the Fast Solar Wind

NASA Technical Reports Server (NTRS)

Cranmer, Steven R.; Matthaeus, William H.; Breech, Benjamin A.; Kasper, Justin C.

2009-01-01

This paper presents analyses of measured proton and electron temperatures in the high-speed solar wind that are used to calculate the separate rates of heat deposition for protons and electrons. It was found that the protons receive about 60% of the total plasma heating in the inner heliosphere, and that this fraction increases to approximately 80% by the orbit of Jupiter. The empirically derived partitioning of heat between protons and electrons is in rough agreement with theoretical predictions from a model of linear Vlasov wave damping. For a modeled power spectrum consisting only of Alfvenic fluctuations, the best agreement was found for a distribution of wavenumber vectors that evolves toward isotropy as distance increases.

Stability and linearity of luminescence imaging of water during irradiation of proton-beams and X-ray photons lower energy than the Cerenkov light threshold

NASA Astrophysics Data System (ADS)

Yamamoto, Seiichi; Koyama, Shuji; Yabe, Takuya; Komori, Masataka; Tada, Junki; Ito, Shiori; Toshito, Toshiyuki; Hirata, Yuho; Watanabe, Kenichi

2018-03-01

Luminescence of water during irradiations of proton-beams or X-ray photons lower energy than the Cerenkov-light threshold is promising for range estimation or the distribution measurements of beams. However it is not yet obvious whether the intensities and distributions are stable with the water conditions such as temperature or addition of solvable materials. It remains also unclear whether the luminescence of water linearly increases with the irradiated proton or X-ray energies. Consequently we measured the luminescence of water during irradiations of proton-beam or X-ray photons lower energy than the Cerenkov-light threshold with different water conditions and energies to evaluate the stability and linearity of luminescence of water. We placed a water phantom set with a proton therapy or X-ray system, luminescence images of water with different conditions and energies were measured with a high-sensitivity cooled charge coupled device (CCD) camera during proton or X-ray irradiations to the water phantom. In the stability measurements, imaging was made for different temperatures of water and addition of inorganic and organic materials to water. In the linearity measurements for the proton, we irradiated with four different energies below Cerenkov light threshold. In the linearity measurements for the X-ray, we irradiated X-ray with different supplied voltages. We evaluated the depth profiles for the luminescence images and evaluated the light intensities and distributions. The results showed that the luminescence of water was quite stable with the water conditions. There were no significant changes of intensities and distributions with the different temperatures. Results from the linearity experiments showed that the luminescence of water linearly increased with their energies. We confirmed that luminescence of water is stable with conditions of water. We also confirmed that the luminescence of water linearly increased with their energies.

Enhancement in Proton Conductivity and Thermal Stability in Nafion Membranes Induced by Incorporation of Sulfonated Carbon Nanotubes.

PubMed

Yin, Chongshan; Li, Jingjing; Zhou, Yawei; Zhang, Haining; Fang, Pengfei; He, Chunqing

2018-04-25

Proton exchange membrane fuel cell (PEMFC) is one of the most promising green power sources, in which perfluorinated sulfonic acid ionomer-based membranes (e.g., Nafion) are widely used. However, the widespread application of PEMFCs is greatly limited by the sharp degradation in electrochemical properties of the proton exchange membranes under high temperature and low humidity conditions. In this work, the high-performance sulfonated carbon nanotubes/Nafion composite membranes (Su-CNTs/Nafion) for the PEMFCs were prepared and the mechanism of the microstructures on the macroscopic properties of membranes was intensively studied. Microstructure evolution in Nafion membranes during water uptake was investigated by positron annihilation lifetime spectroscopy, and results strongly showed that the Su-CNTs or CNTs in Nafion composite membranes significantly reinforced Nafion matrices, which influenced the development of ionic-water clusters in them. Proton conductivities in Su-CNTs/Nafion composite membranes were remarkably enhanced due to the mass formation of proton-conducting pathways (water channels) along the Su-CNTs. In particular, these pathways along Su-CNTs in Su-CNTs/Nafion membranes interconnected the isolated ionic-water clusters at low humidity and resulted in less tortuosity of the water channel network for proton transportation at high humidity. At a high temperature of 135 °C, Su-CNTs/Nafion membranes maintained high proton conductivity because the reinforcement of Su-CNTs on Nafion matrices reduced the evaporation of water molecules from membranes as well as the hydrophilic Su-CNTs were helpful for binding water molecules.

Solid-state proton conductors

NASA Astrophysics Data System (ADS)

Jewulski, J. R.; Osif, T. L.; Remick, R. J.

1990-12-01

The purpose of this program was to survey the field of solid-state proton conductors (SSPC), identify conductors that could be used to develop solid-state fuel cells suitable for use with coal derived fuel gases, and begin the experimental research required for the development of these fuel cells. This document covers the following topics: the history of developments and current status of the SSPC, including a review of proton conducting electrolyte structures, the current status of the medium temperature SSPC development, electrodes for moderate temperature (SSPC) fuel cell, basic material and measurement techniques applicable for SSPC development, modeling, and optimization studies. Correlation and optimization studies are described which include correlation studies on proton conduction and oxide cathode optimization for the SSPC fuel cell. Experiments with the SSPC fuel cells are presented which include the fabrication of the electrolyte disks, apparatus for conducting measurements, the strontium-cerium based electrolyte, the barium-cerium based electrolyte with solid foil electrodes, the barium-cerium based electrolyte with porous electrodes, and conduction mechanisms.

Methods for measuring exchangeable protons in glycosaminoglycans.

PubMed

Beecher, Consuelo N; Larive, Cynthia K

2015-01-01

Recent NMR studies of the exchangeable protons of GAGs in aqueous solution, including those of the amide, sulfamate, and hydroxyl moieties, have demonstrated potential for the detection of intramolecular hydrogen bonds, providing insights into secondary structure preferences. GAG amide protons are observable by NMR over wide pH and temperature ranges; however, specific solution conditions are required to reduce the exchange rate of the sulfamate and hydroxyl protons and allow their detection by NMR. Building on the vast body of knowledge on detection of hydrogen bonds in peptides and proteins, a variety of methods can be used to identify hydrogen bonds in GAGs including temperature coefficient measurements, evaluation of chemical shift differences between oligo- and monosaccharides, and relative exchange rates measured through line shape analysis and EXSY spectra. Emerging strategies to allow direct detection of hydrogen bonds through heteronuclear couplings offer promise for the future. Molecular dynamic simulations are important in this effort both to predict and confirm hydrogen bond donors and acceptors.

The Long-term Middle Atmospheric Influence of Very Large Solar Proton Events

NASA Technical Reports Server (NTRS)

Jackman, Charles H.; Marsh, Daniel R.; Vitt, Francis M.; Garcia, Rolando R.; Randall, Cora E.; Fleming, Eric L.; Frith, Stacey M.

2008-01-01

Long-term variations in ozone have been caused by both natural and humankind related processes. The humankind or anthropogenic influence on ozone originates from the chlorofluorocarbons and halons (chlorine and bromine) and has led to international regulations greatly limiting the release of these substances. Certain natural ozone influences are also important in polar regions and are caused by the impact of solar charged particles on the atmosphere. Such natural variations have been studied in order to better quantify the human influence on polar ozone. Large-scale explosions on the Sun near solar maximum lead to emissions of charged particles (mainly protons and electrons), some of which enter the Earth's magnetosphere and rain down on the polar regions. "Solar proton events" have been used to describe these phenomena since the protons associated with these solar events sometimes create a significant atmospheric disturbance. We have used the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model (WACCM) to study the long-term (> few months) influences of solar proton events from 1963 through 2004 on stratospheric ozone and temperature. There were extremely large solar proton events in 1972, 1989,2000,2001, and 2003. These events caused very distinctive polar changes in layers of the Earth's atmosphere known as the stratosphere (12-50 km; -7-30 miles) and mesosphere (50-90 km; 30-55 miles). The solar protons connected with these events created hydrogen- and nitrogen-containing compounds, which led to the polar ozone destruction. The nitrogen-containing compounds, called odd nitrogen, lasted much longer than the hydrogen-containing compounds and led to long-lived stratospheric impacts. An extremely active period for these events occurred in the five-year period, 2000- 2004, and caused increases in odd nitrogen which lasted for several months after individual events. Associated stratospheric ozone decreases of >lo% were calculated to last for up to five months past the largest events. However, the computed total column ozone and stratospheric temperature changes connected with the solar events were not found to be statistically significant. Thus, solar proton events do not likely contribute significantly to measured total column ozone fluctuations and stratospheric temperature changes.

Proton radiation damage experiment on P-Channel CCD for an X-ray CCD camera onboard the ASTRO-H satellite

NASA Astrophysics Data System (ADS)

Mori, Koji; Nishioka, Yusuke; Ohura, Satoshi; Koura, Yoshiaki; Yamauchi, Makoto; Nakajima, Hiroshi; Ueda, Shutaro; Kan, Hiroaki; Anabuki, Naohisa; Nagino, Ryo; Hayashida, Kiyoshi; Tsunemi, Hiroshi; Kohmura, Takayoshi; Ikeda, Shoma; Murakami, Hiroshi; Ozaki, Masanobu; Dotani, Tadayasu; Maeda, Yukie; Sagara, Kenshi

2013-12-01

We report on a proton radiation damage experiment on P-channel CCD newly developed for an X-ray CCD camera onboard the ASTRO-H satellite. The device was exposed up to 109 protons cm-2 at 6.7 MeV. The charge transfer inefficiency (CTI) was measured as a function of radiation dose. In comparison with the CTI currently measured in the CCD camera onboard the Suzaku satellite for 6 years, we confirmed that the new type of P-channel CCD is radiation tolerant enough for space use. We also confirmed that a charge-injection technique and lowering the operating temperature efficiently work to reduce the CTI for our device. A comparison with other P-channel CCD experiments is also discussed. We performed a proton radiation damage experiment on a new P-channel CCD. The device was exposed up to 109 protons cm-2 at 6.7 MeV. We confirmed that it is radiation tolerant enough for space use. We confirmed that a charge-injection technique reduces the CTI. We confirmed that lowering the operating temperature also reduces the CTI.

Effects of low temperature periodic annealing on the deep-level defects in 200 keV proton irradiated AlGaAs-GaAs solar cells

NASA Technical Reports Server (NTRS)

Li, S. S.; Chiu, T. T.; Loo, R. Y.

1981-01-01

The GaAs solar cell has shown good potential for space applications. However, degradation in performance occurred when the cells were irradiated by high energy electrons and protons in the space environment. The considered investigation is concerned with the effect of periodic thermal annealing on the deep-level defects induced by the 200 keV protons in the AlGaAs-GaAs solar cells. Protons at a fluence of 10 to the 11th P/sq cm were used in the irradiation cycle, while annealing temperatures of 200 C (for 24 hours), 300 C (six hours), and 400 C (six hours) were employed. The most likely candidate for the E(c) -0.71 eV electron trap observed in the 200 keV proton irradiated samples may be due to GaAs antisite, while the observed E(v) +0.18 eV hole trap has been attributed to the gallium vacancy related defect. The obtained results show that periodic annealing in the considered case does not offer any advantages over the one time annealing process.

Temperature controls oxidative phosphorylation and reactive oxygen species production through uncoupling in rat skeletal muscle mitochondria.

PubMed

Jarmuszkiewicz, Wieslawa; Woyda-Ploszczyca, Andrzej; Koziel, Agnieszka; Majerczak, Joanna; Zoladz, Jerzy A

2015-06-01

Mitochondrial respiratory and phosphorylation activities, mitochondrial uncoupling, and hydrogen peroxide formation were studied in isolated rat skeletal muscle mitochondria during experimentally induced hypothermia (25 °C) and hyperthermia (42 °C) compared to the physiological temperature of resting muscle (35 °C). For nonphosphorylating mitochondria, increasing the temperature from 25 to 42 °C led to a decrease in membrane potential, hydrogen peroxide production, and quinone reduction levels. For phosphorylating mitochondria, no temperature-dependent changes in these mitochondrial functions were observed. However, the efficiency of oxidative phosphorylation decreased, whereas the oxidation and phosphorylation rates and oxidative capacities of the mitochondria increased, with increasing assay temperature. An increase in proton leak, including uncoupling protein-mediated proton leak, was observed with increasing assay temperature, which could explain the reduced oxidative phosphorylation efficiency and reactive oxygen species production. Copyright © 2015 Elsevier Inc. All rights reserved.

Correction of Proton Resonance Frequency Shift Temperature Maps for Magnetic Field Disturbances Caused by Breathing

NASA Astrophysics Data System (ADS)

Shmatukha, Andriy V.; Bakker, Chris J. G.

2006-05-01

Respiratory Induced Resonance Offset (RIRO) is a periodic disturbance of the magnetic field due to breathing. Such disturbances handicap the accuracy of the Proton Resonance Frequency Shift (PRFS) method of MRI temperature mapping in anatomies situated nearby the lungs and chest wall. In this work, we propose a method capable of minimizing errors caused by RIRO in PRFS temperature maps. In this method, a set of baseline images characterizing RIRO at a variety of respiratory cycle instants is acquired before the thermal treatment starts. During the treatment, the temperature evolution is found from two successive images. Then, the calculated temperature changes are corrected for the additional contribution caused by RIRO using the pre-treatment baseline images acquired at the identical instances of the respiratory cycle. Our method is shown to improve the accuracy and stability of PRFS temperature maps in the presence of RIRO and motion in phantom and volunteer experiments.

[Effects of exogenous spermidine on lipid peroxidation and membrane proton pump activity of cucumber seedling leaves under high temperature stress].

PubMed

Tian, Jing; Guo, Shi-Rong; Sun, Jin; Wang, Li-Ping; Yang, Yan-Juan; Li, Bin

2011-12-01

Taking a relatively heat-resistant cucumber (Cucumis sativus) cultivar 'Jinchun No. 4' as test material, a sand culture experiment was conducted in growth chamber to investigate the effects of foliar spraying spermidine (Spd) on the lipid peroxidation, membrane proton pump activity, and corresponding gene expression of cucumber seedling leaves under high temperature stress. Compared with the control, foliar spraying Spd increased the plant height, stem diameter, dry and fresh mass, and leaf area significantly, and inhibited the increase of leaf relative conductivity, malondialdehyde (MDA) content, and lipoxygenase (LOX) activity effectively. Foliar spraying Spd also helped to the increase of leaf plasma membrane- and tonoplast H(+)-ATPase activity, but no significant difference was observed in the gene expression levels. These results suggested that exogenous Spd could significantly decrease the leaf lipid peroxidation and increase the proton pump activity, and thus, stabilize the leaf membrane structure and function, alleviate the damage induced by high temperature stress, and enhance the heat tolerance of cucumber seedlings.

Thermalization of Heavy Ions in the Solar Wind

NASA Astrophysics Data System (ADS)

Tracy, Patrick J.; Kasper, Justin C.; Zurbuchen, Thomas H.; Raines, Jim M.; Shearer, Paul; Gilbert, Jason

2015-10-01

Observations of velocity distribution functions from the Advanced Composition Explorer/Solar Wind Ion Composition Spectrometer heavy ion composition instrument are used to calculate ratios of kinetic temperature and Coulomb collisional interactions of an unprecedented 50 ion species in the solar wind. These ions cover a mass per charge range of 1-5.5 amu/e and were collected in the time range of 1998-2011. We report the first calculation of the Coulomb thermalization rate between each of the heavy ion (A > 4 amu) species present in the solar wind along with protons (H+) and alpha particles (He2+). From these rates, we find that protons are the dominant source of Coulomb collisional thermalization for heavy ions in the solar wind and use this fact to calculate a collisional age for those heavy ion populations. The heavy ion thermal properties are well organized by this collisional age, but we find that the temperature of all heavy ions does not simply approach that of protons as Coulomb collisions become more important. We show that He2+ and C6+ follow a monotonic decay toward equal temperatures with protons with increasing collisional age, but O6+ shows a noted deviation from this monotonic decay. Furthermore, we show that the deviation from monotonic decay for O6+ occurs in solar wind of all origins, as determined by its Fe/O ratio. The observed differences in heavy ion temperature behavior point toward a local heating mechanism that favors ions depending on their charge and mass.

Optomechanical characterization of proton-exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Jalani, Nikhil H.; Mizar, Shivananda P.; Choi, Pyoungho; Furlong, Cosme; Datta, Ravindra

2004-08-01

Nafion is widely used as the polymer electrolyte in proton exchange membrane (PEM) fuel cells. The properties that make the Nafion membrane indispensable are the combination of good water uptake, ion-exchange capacity, proton conductivity, gas permeability, and excellent electrochemical stability. The amount of water sorbed in the Nafion membrane is critical as the proton conductivity depends directly on the water content of the membrane which determines the fuel cell performance. The factors which affect the extent of the solvent uptake by Nafion are temperature, ion-exchange capacity, pretreatment of membrane, and the physical state of absorbing water, whether it is in liquid or vapor phase. The water sorption in the membrane is explained in terms of thermodynamic equilibrium of water in the vapor and absorption phases. As the membrane imbibes more water, the membrane matrix expands and exerts a pressure on the pore liquid which affects its chemical potential and limits extent of swelling. The extent of matrix expansion of the membranes depends on the elastic modulus, E, of the membrane, which directly affects the sorption. Hence, it is important to understand the variation of E for Nafion membrane with relative humidity (RH) and temperature. Optoelectronic holography (OEH) techniques are applied to perform quantitative, noninvasive, full field of view investigations to determine temperature and water activity dependence of E. The results obtained confirm that with the increase in temperature, E decreases and the membranes imbibes more water. Such results will allow optimization and realization of fuel cells with improved efficiency and performance.

Thermal decomposition of solid phase nitromethane under various heating rates and target temperatures based on ab initio molecular dynamics simulations.

PubMed

Xu, Kai; Wei, Dong-Qing; Chen, Xiang-Rong; Ji, Guang-Fu

2014-10-01

The Car-Parrinello molecular dynamics simulation was applied to study the thermal decomposition of solid phase nitromethane under gradual heating and fast annealing conditions. In gradual heating simulations, we found that, rather than C-N bond cleavage, intermolecular proton transfer is more likely to be the first reaction in the decomposition process. At high temperature, the first reaction in fast annealing simulation is intermolecular proton transfer leading to CH3NOOH and CH2NO2, whereas the initial chemical event at low temperature tends to be a unimolecular C-N bond cleavage, producing CH3 and NO2 fragments. It is the first time to date that the direct rupture of a C-N bond has been reported as the first reaction in solid phase nitromethane. In addition, the fast annealing simulations on a supercell at different temperatures are conducted to validate the effect of simulation cell size on initial reaction mechanisms. The results are in qualitative agreement with the simulations on a unit cell. By analyzing the time evolution of some molecules, we also found that the time of first water molecule formation is clearly sensitive to heating rates and target temperatures when the first reaction is an intermolecular proton transfer.

XFEL structures of the influenza M2 proton channel: Room temperature water networks and insights into proton conduction

DOE PAGES

Thomaston, Jessica L.; Woldeyes, Rahel A.; Nakane, Takanori; ...

2017-08-23

The M2 proton channel of influenza A is a drug target that is essential for the reproduction of the flu virus. It is also a model system for the study of selective, unidirectional proton transport across a membrane. Ordered water molecules arranged in “wires” inside the channel pore have been proposed to play a role in both the conduction of protons to the four gating His37 residues and the stabilization of multiple positive charges within the channel. To visualize the solvent in the pore of the channel at room temperature while minimizing the effects of radiation damage, data were collectedmore » to a resolution of 1.4 Å using an X-ray free-electron laser (XFEL) at three different pH conditions: pH 5.5, pH 6.5, and pH 8.0. Data were collected on the Inward open state, which is an intermediate that accumulates at high protonation of the His37 tetrad. At pH 5.5, a continuous hydrogen-bonded network of water molecules spans the vertical length of the channel, consistent with a Grotthuss mechanism model for proton transport to the His37 tetrad. This ordered solvent at pH 5.5 could act to stabilize the positive charges that build up on the gating His37 tetrad during the proton conduction cycle. The number of ordered pore waters decreases at pH 6.5 and 8.0, where the Inward open state is less stable. Furthermore, these studies provide a graphical view of the response of water to a change in charge within a restricted channel environment.« less

The General Base in the Thymidylate Synthase Catalyzed Proton Abstraction

PubMed Central

Ghosh, Ananda K.; Islam, Zahidul; Krueger, Jonathan; Abeysinghe, Don Thelma; Kohen, Amnon

2015-01-01

The enzyme thymidylate synthase (TSase), an important chemotherapeutic drug target, catalyzes the formation of 2′-deoxythymidine-5′-monophosphate (dTMP), a precursor of one of the DNA building blocks. TSase catalyzes a multi-step mechanism that includes the abstraction of a proton from the C5 of the substrate 2′-deoxyuridine-5′-monophosphate (dUMP). Previous studies on ecTSase proposed that an active-site residue, Y94 serves the role of the general base abstracting this proton. However, since Y94 is neither very basic, nor connected to basic residues, nor located close enough to the pyrimidine proton to be abstracted, the actual identity of this base remains enigmatic. Based on crystal structures, an alternative hypothesis is that the nearest potential proton-acceptor of C5 of dUMP is a water molecule that is part of a hydrogen bond (H-bond) network comprised of several water molecules and several protein residues including H147, E58, N177, and Y94. Here, we examine the role of the residue Y94 in the proton abstraction step by removing its hydroxyl group (Y94F mutant). We investigated the effect of the mutation on the temperature dependence of intrinsic kinetic isotope effects (KIEs) and found that these KIEs are more temperature dependent than those of the wild-type enzyme (WT). These results suggest that the phenolic –OH of Y94 is a component of the transition state for the proton abstraction step. The findings further support the hypothesis that no single functional group is the general base, but a network of bases and hydroxyls (from water molecules and tyrosine) sharing H-bonds across the active site can serve the role of the general base to remove the pyrimidine proton. PMID:25912171

Classical and quantum theories of proton disorder in hexagonal water ice

NASA Astrophysics Data System (ADS)

Benton, Owen; Sikora, Olga; Shannon, Nic

2016-03-01

It has been known since the pioneering work of Bernal, Fowler, and Pauling that common, hexagonal (Ih) water ice is the archetype of a frustrated material: a proton-bonded network in which protons satisfy strong local constraints (the "ice rules") but do not order. While this proton disorder is well established, there is now a growing body of evidence that quantum effects may also have a role to play in the physics of ice at low temperatures. In this paper, we use a combination of numerical and analytic techniques to explore the nature of proton correlations in both classical and quantum models of ice Ih. In the case of classical ice Ih, we find that the ice rules have two, distinct, consequences for scattering experiments: singular "pinch points," reflecting a zero-divergence condition on the uniform polarization of the crystal, and broad, asymmetric features, coming from its staggered polarization. In the case of the quantum model, we find that the collective quantum tunneling of groups of protons can convert states obeying the ice rules into a quantum liquid, whose excitations are birefringent, emergent photons. We make explicit predictions for scattering experiments on both classical and quantum ice Ih, and show how the quantum theory can explain the "wings" of incoherent inelastic scattering observed in recent neutron scattering experiments [Bove et al., Phys. Rev. Lett. 103, 165901 (2009), 10.1103/PhysRevLett.103.165901]. These results raise the intriguing possibility that the protons in ice Ih could form a quantum liquid at low temperatures, in which protons are not merely disordered, but continually fluctuate between different configurations obeying the ice rules.

XFEL structures of the influenza M2 proton channel: Room temperature water networks and insights into proton conduction

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

Thomaston, Jessica L.; Woldeyes, Rahel A.; Nakane, Takanori

The M2 proton channel of influenza A is a drug target that is essential for the reproduction of the flu virus. It is also a model system for the study of selective, unidirectional proton transport across a membrane. Ordered water molecules arranged in “wires” inside the channel pore have been proposed to play a role in both the conduction of protons to the four gating His37 residues and the stabilization of multiple positive charges within the channel. To visualize the solvent in the pore of the channel at room temperature while minimizing the effects of radiation damage, data were collectedmore » to a resolution of 1.4 Å using an X-ray free-electron laser (XFEL) at three different pH conditions: pH 5.5, pH 6.5, and pH 8.0. Data were collected on the Inward open state, which is an intermediate that accumulates at high protonation of the His37 tetrad. At pH 5.5, a continuous hydrogen-bonded network of water molecules spans the vertical length of the channel, consistent with a Grotthuss mechanism model for proton transport to the His37 tetrad. This ordered solvent at pH 5.5 could act to stabilize the positive charges that build up on the gating His37 tetrad during the proton conduction cycle. The number of ordered pore waters decreases at pH 6.5 and 8.0, where the Inward open state is less stable. Furthermore, these studies provide a graphical view of the response of water to a change in charge within a restricted channel environment.« less

Anomalous enhancement of proton conductivity for water molecular clusters stabilized in interstitial spaces of porous molecular crystals.

PubMed

Tadokoro, Makoto; Ohhata, Yuki; Shimazaki, Yuriko; Ishimaru, Shin'ichi; Yamada, Teppei; Nagao, Yuki; Sugaya, Tomoaki; Isoda, Kyosuke; Suzuki, Yuta; Kitagawa, Hiroshi; Matsui, Hiroshi

2014-10-13

In an investigation into the proton conductivity of crystallized water clusters confined within low-dimensional nanoporous materials, we have found that water-stable nanoporous crystals are formed by complementary hydrogen bonding between [Co(III) (H2 bim)3 ](3+) (H2 bim: 2,2'-biimidazole) and TATC(3-) (1,3,5- tricarboxyl-2,4,6-triazinate); the O atoms in the -COO(-) groups of TATC(3-) in the porous outer wall are strongly hydrogen bonded with H2 O, forming two types of WMCs (water molecular clusters): a spirocyclic tetramer chain (SCTC) that forms infinite open 1D channels, and an isolated cyclic tetramer (ICT) present in the void space. The ICT is constructed from four H2 O molecules as a novel C2 -type WMC, which are hydrogen bonded with four-, three-, and two-coordination spheres, respectively. The largest structural fluctuation is observed at elevated temperatures from the two-coordinated H2 O molecules, which begin to rapidly and isotropically fluctuate on heating. This behavior can be rationalized by a simple model for the elucidation of pre-melting phenomena, similar to those in ice surfaces as the temperature increases. Moreover, high proton conductivity of SCTCs (ca. 10(-5) S cm(-1) at 300 K with an activation energy of 0.30 eV) through a proton-hole mechanism was observed for pellet samples using the alternating impedance method. The proton conductivity exhibits a slight enhancement of about 0.1×10(-5) S cm(-1) at 274 K due to a structural transition upon approaching this temperature that elongates the unit cell along the b-axis. The proton-transfer route can be predicted in WMCs, as O(4) of an H2 O molecule at the center of an SCTC shows a motion that rotates the dipole in the b-axis direction, but not the c-axis; the thermal ellipsoids of O(4) based on anisotropic temperature factors obtained by X-ray crystallography reflect a structural fluctuation along the b-axis direction induced by [Co(III) (H2 bim)3 ](3+) . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-temperature superconductivity using a model of hydrogen bonds.

PubMed

Kaplan, Daniel; Imry, Yoseph

2018-05-29

Recently, there has been much interest in high-temperature superconductors and more recently in hydrogen-based superconductors. This work offers a simple model that explains the behavior of the superconducting gap based on naive BCS (Bardeen-Cooper-Schrieffer) theory and reproduces most effects seen in experiments, including the isotope effect and [Formula: see text] enhancement as a function of pressure. We show that this is due to a combination of the factors appearing in the gap equation: the matrix element between the proton states and the level splitting of the proton.

Non-cooperative immobilization of residual water bound in lyophilized photosynthetic lamellae.

PubMed

Harańczyk, Hubert; Baran, Ewelina; Nowak, Piotr; Florek-Wojciechowska, Małgorzata; Leja, Anna; Zalitacz, Dorota; Strzałka, Kazimierz

2015-12-01

This study applied 1H-NMR in time and in frequency domain measurements to monitor the changes that occur in bound water dynamics at decreased temperature and with increased hydration level in lyophilizates of native wheat photosynthetic lamellae and in photosynthetic lamellae reconstituted from lyophilizate. Proton relaxometry (measured as free induction decay = FID) distinguishes a Gaussian component S within the NMR signal (o). This comes from protons of the solid matrix of the lamellae and consists of (i) an exponentially decaying contribution L1 from mobile membrane protons, presumably from lipids, and from water that is tightly bound to the membrane surface and thus restricted in mobility; and (ii) an exponentially decaying component L2 from more mobile, loosely bound water pool. Both proton relaxometry data and proton spectroscopy show that dry lyophilizate incubated in dry air, i.e., at a relative humidity (p/p0) of 0% reveals a relatively high hydration level. The observed liquid signal most likely originates from mobile membrane protons and a tightly bound water fraction that is sealed in pores of dry lyophilizate and thus restricted in mobility. The estimations suggest that the amount of sealed water does not exceed the value characteristic for the main hydration shell of a phospholipid. Proton spectra collected for dry lyophilizate of photosynthetic lamellae show a continuous decrease in the liquid signal component without a distinct freezing transition when it is cooled down to -60ºC, which is significantly lower than the homogeneous ice nucleation temperature [Bronshteyn, V.L. et al. Biophys. J. 65 (1993) 1853].

Ab-initio calculations of the proton location in topaz-OH, Al2SiO4(OH)2

NASA Astrophysics Data System (ADS)

Churakov, S. V.; Wunder, B.

The position of hydrogen in the structure of topaz-OH was determined by means of ab-initio quantum-mechanic calculations. Static lattice energy calculations predict the existence of four non-equivalent positions of protons, which are characterized by O4-H1... O1, O4-H2... O2, O4-H3... O3 and O4-H4... O4 hydrogen bonds. The distribution of the protons between positions of local equilibrium is controlled by the proton-proton avoidance rule and the strength of the hydrogen bonds. The most favourable configuration of hydrogen atoms is achieved for adjacent protons, which form O4-H3... O3 and O4-H4... O4 hydrogen bonds, respectively. The thermal excitation of atoms at a temperature of 55 K is large enough for the hydrogen atoms occasionally to change their positions to form O4-H1... O1 and O4-H2... O2 bonds. At ambient pressures and higher temperatures the protons are in a dynamic exchange between the allowed positions of local minima. As a consequence, for nearly room-temperature conditions, the dynamic change between different structural configurations leads to the violation of all possible symmetry elements and with that to space group #E5/E5#1. The flipping of the protons between different sites is achieved by simple rotation of the OH-dipole and does not produce any significant distortion of the framework of topaz, whose symmetry remains that of the space group Pbnm. Therefore, no reduction of symmetry has been observed in former X-ray studies on topaz-OH. Calculated IR absorption spectra of topaz-OH were found to be in good agreement with measured spectra. According to the calculations, the two favourable configurations of protons might correspond to the measured peak splitting within the OH-stretching range. An experimentally observed low-frequency band at 3520 cm-1 was assigned to the OH-stretching of the O4-H3... O3 bond, while the band at 3600 cm-1 was attributed to OH-stretching of the O4-H4... O4 hydrogen bond. The broad peak in FAR-IR frequency range at 100-150 cm-1 is attributed to the stretching of H3... O3 and H4... O4 contacts. The rate of proton exchange at 670 K among different sites was estimated by ab-inito molecular dynamic simulations. The calculations predict that flipping of adjacent protons between O4-H3... O3 and O4-H4... O4 bonds at 670 K occur at a rate of about 1.96 THz.

The tensile and fatigue properties of DIN 1.4914 martensitic stainless steel after 590 MeV proton irradiation

NASA Astrophysics Data System (ADS)

Marmy, P.; Victoria, M.

1992-09-01

Tensile and low cycle fatigue subsize specimens of DIN 1.4914 martensitic steel (MANET) have been irradiated with 590 MeV protons to doses up to 1 dpa and at temperatures between 363 and 703 K. The helium produced by spallation reactions was measured as 130 appm/dpa. A strong radiation hardening is found, which decreases as the irradiation temperature increases. The tensile elongation is reduced after irradiation, but the fracture mode is always ductile and transgranular. The radition hardening produced at low irradiation temperatures is recovered after annealing at higher temperatures. Continous softening is observed during low cycle fatigue testing. The rate of softening of the irradiated material is stonger than that of the unirradiated material and tends to reach the saturation level of the latter. The irradiation badly affects the fatigue life, particularly in the temperature domain of dynamic strain ageing between 553 and 653 K.

Phosphorus-doped glass proton exchange membranes for low temperature direct methanol fuel cells

NASA Astrophysics Data System (ADS)

Prakash, Shruti; Mustain, William E.; Park, SeongHo; Kohl, Paul A.

Phosphorus-doped silicon dioxide thin films were used as ion exchange membranes in low temperature proton exchange membrane fuel cells. Phosphorus-doped silicon dioxide glass (PSG) was deposited via plasma-enhanced chemical vapor deposition (PECVD). The plasma deposition of PSG films allows for low temperature fabrication that is compatible with current microelectronic industrial processing. SiH 4, PH 3 and N 2O were used as the reactant gases. The effect of plasma deposition parameters, substrate temperature, RF power, and chamber pressure, on the ionic conductivity of the PSG films is elucidated. PSG conductivities as high as 2.54 × 10 -4 S cm -1 were realized, which is 250 times higher than the conductivity of pure SiO 2 films (1 × 10 -6 S cm -1) under identical deposition conditions. The higher conductivity films were deposited at low temperature, moderate pressure, limited reactant gas flow rate, and high RF power.

Cross-linked sulfonated aromatic ionomers via SO2 bridges: Conductivity properties

NASA Astrophysics Data System (ADS)

Di Vona, M. L.; Pasquini, L.; Narducci, R.; Pelzer, K.; Donnadio, A.; Casciola, M.; Knauth, P.

2013-12-01

The proton conductivity of SPEEK membranes in situ cross-linked by thermal treatment at 180 °C for various times was investigated by impedance spectroscopy. The conductivity measurements were made on fully humidified membranes between 25 and 65 °C and on membranes exposed to different relative humidity between 80 and 140 °C. The Ionic Exchange Capacity (IEC) was determined by acid-base titration and the water uptake by gravimetry. The proton conductivity was determined as function of temperature, IEC, degree of cross-linking and hydration number. A curve of proton conductivity vs. hydration number allows predicting that in order to reach a value of 0.1 S/cm at 100 °C a hydration number above 20 is necessary. The measured conductivity at this temperature is 0.16 S/cm for a hydration number of 60.

Magnetically aligned nanodomains: application in high-performance ion conductive membranes.

PubMed

Hasani-Sadrabadi, Mohammad Mahdi; Majedi, Fatemeh Sadat; Coullerez, Géraldine; Dashtimoghadam, Erfan; VanDersarl, Jules John; Bertsch, Arnaud; Moaddel, Homayoun; Jacob, Karl I; Renaud, Philippe

2014-05-28

Polyelectrolyte-coated magnetic nanoparticles were prepared by decorating the surface of superparamagnetic iron oxide nanoparticles (SPIONs) with crosslinked chitosan oligopolysaccharide (CS). These positively charged particles (CS-SPIONs) were then added to a negatively charged polymer (Nafion), and cast into membranes under an applied magnetic field. TEM and SAXS measurements confirmed this process created aligned, cylindrical nanodomains in the membranes. This was also indirectly confirmed by proton conductivity values. The strong electrostatic interaction between chitosan and Nafion prevented oxygen permeability and water evaporation at elevated temperatures through the proton conductive channels. The resultant proton exchange membranes showed lower conduction dependency to relative humidity, which is highly desirable for hydrogen fuel cells. The fuel cell performance tests were performed on the designed polyelectrolyte membrane by hydrogen-oxygen single cells at elevated temperature (120 °C) and low relative humidity.

Proton dynamics in oxides: insight into the mechanics of proton conduction from quasielastic neutron scattering.

PubMed

Karlsson, Maths

2015-01-07

This article is concerned with the use of quasielastic neutron scattering as a technique for investigation of the dynamical properties of proton conducting oxides. Currently, the main interest in these materials comes from their promise as electrolytes in future electrochemical devices and particularly through their use as electrolytes in next-generation, intermediate-temperature, fuel cells. However, the realization of such devices depends critically on the development of new, more highly proton conducting oxides. Such a development depends on increasing the current understanding of proton conduction in oxides and for this purpose quasielastic neutron scattering is an important mean. The aim of this article is to introduce the non-specialist reader to the basic principles of quasielastic neutron scattering, its advantages and disadvantages, to summarize the work that has been done on proton conducting oxides using this technique, as well as to discuss future opportunities within this field of research.

Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

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

Palani, P. Bahavan, E-mail: bahavanpalani@gmail.com; Abidin, K. Sainul; Kannan, R., E-mail: rksrsrk@gmail.com

2016-05-23

The highest proton conductivity value of 0.0802 Scm{sup −1} is obtained at 6 wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na{sup +} MMT was modified (protonated) to H{sup +} MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranesmore » were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.« less

Electronic properties of deep-level defects in proton irradiated AlGaAs-GaAs solar cells

NASA Technical Reports Server (NTRS)

Li, S. S.

1981-01-01

Deep level transient spectroscopy and capacitance voltage techniques as well as analysis of the forward current voltage (I-V) characteristics and SEM-EIC data were carried out for proton irradiated GaAs solar cells over a wide range of proton energies and proton fluences. Defect and recombination parameters such as defect energy levels and density, carrier capture cross sections and lifetimes as well as diffusion lengths in the undoped n-GaAs LPE layers were determined. Good correlation between these defect parameters and solar cell performance parameters was obtained for GaAs solar cells irradiated by 200 and 290 KeV protons. It was found that 200 to 290 KeV protons will produce the most defects and damages to the GaAs solar cell structure used. The influence of the low temperature (200 to 400 C) periodic thermal annealing on the deep level defects and the performance of the 200 KeV proton irradiated cells is discussed.

Method of generating hydrogen by catalytic decomposition of water

DOEpatents

Balachandran, Uthamalingam; Dorris, Stephen E.; Bose, Arun C.; Stiegel, Gary J.; Lee, Tae-Hyun

2002-01-01

A method for producing hydrogen includes providing a feed stream comprising water; contacting at least one proton conducting membrane adapted to interact with the feed stream; splitting the water into hydrogen and oxygen at a predetermined temperature; and separating the hydrogen from the oxygen. Preferably the proton conducting membrane comprises a proton conductor and a second phase material. Preferable proton conductors suitable for use in a proton conducting membrane include a lanthanide element, a Group VIA element and a Group IA or Group IIA element such as barium, strontium, or combinations of these elements. More preferred proton conductors include yttrium. Preferable second phase materials include platinum, palladium, nickel, cobalt, chromium, manganese, vanadium, silver, gold, copper, rhodium, ruthenium, niobium, zirconium, tantalum, and combinations of these. More preferably second phase materials suitable for use in a proton conducting membrane include nickel, palladium, and combinations of these. The method for generating hydrogen is preferably preformed in the range between about 600.degree. C. and 1,700.degree. C.

Hydrolysis of N3-methyl-2'-deoxycytidine: model compound for reactivity of protonated cytosine residues in DNA.

PubMed

Sowers, L C; Sedwick, W D; Shaw, B R

1989-11-01

Protonation of cytosine residues at physiological pH may occur in DNA as a consequence of both alkylation and aberrant base-pair formation. When cytosine derivatives are protonated, they undergo hydrolysis reactions at elevated rates and can either deaminate to form the corresponding uracil derivatives or depyrimidinate generating abasic sites. The kinetic parameters for reaction of protonated cytosine are derived by studying the hydrolysis of N3-methyl-2'-deoxycytidine (m3dC), a cytosine analogue which is predominantly protonated at physiological pH. Both deamination and depyrimidimation reaction rates are shown to be linearly dependent upon the fraction of protonated molecules. We present here thermodynamic parameters which allow determination of hydrolysis rates of m3dC as functions of pH and temperature. Protonation of cytosine residues in DNA, as induced by aberrant base-pair formation or base modification, may accelerate the rate of both deamination and depyrimidation up to several thousand-fold under physiological conditions.

Aqueous proton transfer across single-layer graphene

DOE PAGES

Achtyl, Jennifer L.; Unocic, Raymond R.; Xu, Lijun; ...

2015-03-17

Proton transfer across single-layer graphene proceeds with large computed energy barriers and is thought to be unfavourable at room temperature unless nanoscale holes or dopants are introduced, or a potential bias is applied. Here we subject single-layer graphene supported on fused ​silica to cycles of high and low pH, and show that protons transfer reversibly from the aqueous phase through the graphene to the other side where they undergo acid–base chemistry with the silica hydroxyl groups. After ruling out diffusion through macroscopic pinholes, the protons are found to transfer through rare, naturally occurring atomic defects. Computer simulations reveal low energymore » barriers of 0.61–0.75 eV for aqueous proton transfer across hydroxyl-terminated atomic defects that participate in a Grotthuss-type relay, while ​pyrylium-like ether terminations shut down proton exchange. In conclusion, unfavourable energy barriers to helium and ​hydrogen transfer indicate the process is selective for aqueous protons.« less

Conductivity equations of protons transporting through 2D crystals obtained with the rate process theory and free volume concept

NASA Astrophysics Data System (ADS)

Hao, Tian; Xu, Yuanze; Hao, Ting

2018-04-01

The Eyring's rate process theory and free volume concept are employed to treat protons (or other particles) transporting through a 2D (two dimensional) crystal like graphene and hexagonal boron nitride. The protons are assumed to be activated first in order to participate conduction and the conduction rate is dependent on how much free volume available in the system. The obtained proton conductivity equations show that only the number of conduction protons, proton size and packing structure, and the energy barrier associated with 2D crystals are critical; the quantization conductance is unexpectedly predicted with a simple Arrhenius type temperature dependence. The predictions agree well with experimental observations and clear out many puzzles like much smaller energy barrier determined from experiments than from the density function calculations and isotope separation rate independent of the energy barrier of 2D crystals, etc. Our work may deepen our understandings on how protons transport through a membrane and has direct implications on hydrogen related technology and proton involved bioprocesses.

Enhanced Proton Conductivity in Y-Doped BaZrO3 via Strain Engineering.

PubMed

Fluri, Aline; Marcolongo, Aris; Roddatis, Vladimir; Wokaun, Alexander; Pergolesi, Daniele; Marzari, Nicola; Lippert, Thomas

2017-12-01

The effects of stress-induced lattice distortions (strain) on the conductivity of Y-doped BaZrO 3 , a high-temperature proton conductor with key technological applications for sustainable electrochemical energy conversion, are studied. Highly ordered epitaxial thin films are grown in different strain states while monitoring the stress generation and evolution in situ. Enhanced proton conductivity due to lower activation energies is discovered under controlled conditions of tensile strain. In particular, a twofold increased conductivity is measured at 200 °C along a 0.7% tensile strained lattice. This is at variance with conclusions coming from force-field simulations or the static calculations of diffusion barriers. Here, extensive first-principles molecular dynamic simulations of proton diffusivity in the proton-trapping regime are therefore performed and found to agree with the experiments. The simulations highlight that compressive strain confines protons in planes parallel to the substrate, while tensile strain boosts diffusivity in the perpendicular direction, with the net result that the overall conductivity is enhanced. It is indeed the presence of the dopant and the proton-trapping effect that makes tensile strain favorable for proton conduction.

Blister formation at subcritical doses in tungsten irradiated by MeV protons

NASA Astrophysics Data System (ADS)

Gavish Segev, I.; Yahel, E.; Silverman, I.; Makov, G.

2017-12-01

The material response of tungsten to irradiation by MeV protons has been studied experimentally, in particular with respect to bubble and blister formation. Tungsten samples were irradiated by 2.2 MeV protons at the Soreq Applied Research Accelerator Facility (SARAF) to doses of the order of 1017 protons/cm2 which are below the reported critical threshold for blister formation derived from keV range irradiation studies. Large, well-developed blisters are observed indicating that for MeV range protons the critical threshold is at least an order of magnitude lower than the lowest value reported previously. The effects of fluence, flux, and corresponding temperature on the distribution and characteristics of the obtained blisters were studied. FIB cross sections of several blisters exposed their depth and structure.

Hydroxy protons as structural probes to reveal hydrogen bonding properties of polyols in aqueous solution by NMR spectroscopy

NASA Astrophysics Data System (ADS)

Oruc, Gizem; Varnali, Tereza; Bekiroglu, Somer

2018-05-01

The solution properties of ethylene glycol (ethane-1,2-diol), glycerol (propane-1,2,3-triol), erythritol ((2R,3S)-butane-1,2,3,4-tetraol), D-xylitol ((2R,3r,4S)-pentane-1,2,3,4,5-pentaol), D-mannitol ((2R,3R,4R,5R)-hexane-1,2,3,4,5,6-hexaol), and D-sorbitol ((2S,3R,4R,5R)-hexane-1,2,3,4,5,6-hexaol), constituting a subgroup of polyalcohols/polyols of maximum six carbon atoms have been investigated using 1H NMR chemical shifts, coupling constants, temperature coefficients, and chemical exchange rates of hydroxy protons in aqueous medium. Relative within a molecule, minimum two-fold difference in rate of exchange values and higher temperature dependence of chemical shifts of the hydroxy protons on terminal carbon atoms confirm that sustainable hydrogen bonding interactions is accentuated for the hydroxyl groups on secondary carbons. Compared to the primary carbons i.e. terminal ones, the hydroxy protons on second and third carbon atoms exhibit much lower rate of exchange and smaller temperature coefficients, indicating that they are further involved in transient hydrogen bonding interactions. Scalar 3JOH,CH-couplings ranging between 3.9 and 7.2 Hz imply that the hydroxyl groups are practically in free rotation regime. Examination of the chemical shift differences with respect to the shift of glycol hydroxy proton reveals that the disparity between terminal and inner hydroxyl groups disclosed by the exchange rates and temperature coefficients is sustained with the exception of 0.003 and 0.053 ppm for O(3)H of mannitol and O(5)H of sorbitol respectively. The experimental findings have been augmented by quantum chemical calculations targeting theoretical NMR chemical shifts, as well as the conformational analysis of the structures.

Interplay between protons and electrons in a firehose-unstable plasma: Particle-in-cell simulations

NASA Astrophysics Data System (ADS)

Bourdin, Philippe-A.; Maneva, Yana

2017-04-01

Kinetic plasma instabilities originating from unstable, non-Maxwellian shapes of the velocity distribution functions serve as internal degrees of freedom in plasma dynamics, and play an important role near solar current sheets and in solar wind plasmas. In the presence of strong temperature anisotropy (different thermal spreads in the velocity space with respect to the mean magnetic field), plasmas are unstable either to the firehose mode or to the mirror mode in the case of predominant parallel and perpendicular temperatures, respectively. The growth rates of these instabilities and their thresholds depend on plasma properties, such as the temperature anisotropy and the plasma beta. The physics of the temperature anisotropy-driven instabilities becomes even more diverse for various shapes of velocity distribution functions and the particle species of interest. Recent studies based on a linear instability analysis show an interplay in the firehose instability between protons and electrons when the both types of particle species are prone to unstable velocity distribution functions and their instability thresholds. In this work we perform for the first time 3D nonlinear PIC (particle-in-cell) numerical simulations to test for the linear-theory prediction of the simultaneous proton-electron firehose instability. The simulation setup allows us not only to evaluate the growth rate of each firehose instability, but also to track its nonlinear evolution and the related wave-particle interactions such as the pitch-angle scattering or saturation effects. The specialty of our simulation is that the magnetic and electric fields have a low numerical noise level by setting a sufficiently large number of super-particles into the simulation box and enhancing the statistical significance of the velocity distribution functions. We use the iPIC3D code with fully periodic boundaries under various conditions of the electron-to-proton mass ratio, which gives insight into the instability interplay at the intermediate electron-proton and on the scaling of our results towards more realistic particle settings.

Demonstrating the potential of yttrium-doped barium zirconate electrolyte for high-performance fuel cells.

PubMed

Bae, Kiho; Jang, Dong Young; Choi, Hyung Jong; Kim, Donghwan; Hong, Jongsup; Kim, Byung-Kook; Lee, Jong-Ho; Son, Ji-Won; Shim, Joon Hyung

2017-02-23

In reducing the high operating temperatures (≥800 °C) of solid-oxide fuel cells, use of protonic ceramics as an alternative electrolyte material is attractive due to their high conductivity and low activation energy in a low-temperature regime (≤600 °C). Among many protonic ceramics, yttrium-doped barium zirconate has attracted attention due to its excellent chemical stability, which is the main issue in protonic-ceramic fuel cells. However, poor sinterability of yttrium-doped barium zirconate discourages its fabrication as a thin-film electrolyte and integration on porous anode supports, both of which are essential to achieve high performance. Here we fabricate a protonic-ceramic fuel cell using a thin-film-deposited yttrium-doped barium zirconate electrolyte with no impeding grain boundaries owing to the columnar structure tightly integrated with nanogranular cathode and nanoporous anode supports, which to the best of our knowledge exhibits a record high-power output of up to an order of magnitude higher than those of other reported barium zirconate-based fuel cells.

Stimulated Mirror Instability From the Interplay of Anisotropic Protons and Electrons, and their Suprathermal Populations

NASA Astrophysics Data System (ADS)

Shaaban, S. M.; Lazar, M.; Astfalk, P.; Poedts, S.

2018-03-01

Mirror instability driven by the temperature anisotropy of protons can offer a plausible explanation for the mirror-like fluctuations observed in planetary magnetosheaths. In the present paper we invoke a realistic kinetic approach which can reproduce nonthermal features of plasma particles reported by the observations, i.e., temperature anisotropies and suprathermal populations. Seeking accuracy, a numerical analysis is performed using an advanced code named DSHARK, recently proposed to resolve the linear dispersion and stability for an arbitrary propagation in bi-Kappa distributed electron-proton plasmas. The stimulating effect of the anisotropic bi-Maxwellian electrons reported in Remya et al. (2013, https://doi.org/10.1002/jgra.50091) is markedly enhanced in the presence of suprathermal electrons described by the bi-Kappa distribution functions. The influence of suprathermal protons is more temperate, but overall, present results demonstrate that these sources of free energy provide natural conditions for a stimulated mirror instability, more efficient than predicted before and capable to compete with other instabilities (e.g., the electromagnetic ion-cyclotron instability) and mechanisms of relaxation.

Effects of temperature and cadmium exposure on the mitochondria of oysters (Crassostrea virginica) exposed to hypoxia and subsequent reoxygenation.

PubMed

Ivanina, Anna V; Kurochkin, Ilya O; Leamy, Larry; Sokolova, Inna M

2012-09-15

Intertidal bivalves are commonly exposed to multiple stressors including periodic hypoxia, temperature fluctuations and pollution, which can strongly affect energy metabolism. We used top-down control and elasticity analyses to determine the interactive effects of intermittent hypoxia, cadmium (Cd) exposure and acute temperature stress on mitochondria of the eastern oyster Crassostrea virginica. Oysters were acclimated at 20°C for 30 days in the absence or presence of 50 μg l(-1) Cd and then subjected to a long-term hypoxia (6 days at <0.5% O(2) in seawater) followed by normoxic recovery. Mitochondrial function was assessed at the acclimation temperature (20°C), or at elevated temperature (30°C) mimicking acute temperature stress in the intertidal zone. In the absence of Cd or temperature stress, mitochondria of oysters showed high resilience to transient hypoxia. In control oysters at 20°C, hypoxia/reoxygenation induced elevated flux capacity of all three studied mitochondrial subsystems (substrate oxidation, phosphorylation and proton leak) and resulted in a mild depolarization of resting mitochondria. Elevated proton conductance and enhanced capacity of phosphorylation and substrate oxidation subsystems may confer resistance to hypoxia/reoxygenation stress in oyster mitochondria by alleviating production of reactive oxygen species and maintaining high aerobic capacity and ATP synthesis rates during recovery. Exposure to environmental stressors such as Cd and elevated temperatures abolished the putative adaptive responses of the substrate oxidation and phosphorylation subsystems, and strongly enhanced proton leak in mitochondria of oysters subjected to hypoxia/reoxygenation stress. Our findings suggest that Cd exposure and acute temperature stress may lead to the loss of mitochondrial resistance to hypoxia and reoxygenation and thus potentially affect the ability of oysters to survive periodic oxygen deprivation in coastal and estuarine habitats.

A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin-lattice relaxation data for the methyl groups in solids.

PubMed

Bernatowicz, Piotr; Shkurenko, Aleksander; Osior, Agnieszka; Kamieński, Bohdan; Szymański, Sławomir

2015-11-21

The theory of nuclear spin-lattice relaxation in methyl groups in solids has been a recurring problem in nuclear magnetic resonance (NMR) spectroscopy. The current view is that, except for extreme cases of low torsional barriers where special quantum effects are at stake, the relaxation behaviour of the nuclear spins in methyl groups is controlled by thermally activated classical jumps of the methyl group between its three orientations. The temperature effects on the relaxation rates can be modelled by Arrhenius behaviour of the correlation time of the jump process. The entire variety of relaxation effects in protonated methyl groups have recently been given a consistent quantum mechanical explanation not invoking the jump model regardless of the temperature range. It exploits the damped quantum rotation (DQR) theory originally developed to describe NMR line shape effects for hindered methyl groups. In the DQR model, the incoherent dynamics of the methyl group include two quantum rate (i.e., coherence-damping) processes. For proton relaxation only one of these processes is relevant. In this paper, temperature-dependent proton spin-lattice relaxation data for the methyl groups in polycrystalline methyltriphenyl silane and methyltriphenyl germanium, both deuterated in aromatic positions, are reported and interpreted in terms of the DQR model. A comparison with the conventional approach exploiting the phenomenological Arrhenius equation is made. The present observations provide further indications that incoherent motions of molecular moieties in the condensed phase can retain quantum character over much broader temperature range than is commonly thought.

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

Tracy, Patrick J.; Kasper, Justin C.; Zurbuchen, Thomas H.

Observations of velocity distribution functions from the Advanced Composition Explorer/Solar Wind Ion Composition Spectrometer heavy ion composition instrument are used to calculate ratios of kinetic temperature and Coulomb collisional interactions of an unprecedented 50 ion species in the solar wind. These ions cover a mass per charge range of 1–5.5 amu/e and were collected in the time range of 1998–2011. We report the first calculation of the Coulomb thermalization rate between each of the heavy ion (A > 4 amu) species present in the solar wind along with protons (H{sup +}) and alpha particles (He{sup 2+}). From these rates, wemore » find that protons are the dominant source of Coulomb collisional thermalization for heavy ions in the solar wind and use this fact to calculate a collisional age for those heavy ion populations. The heavy ion thermal properties are well organized by this collisional age, but we find that the temperature of all heavy ions does not simply approach that of protons as Coulomb collisions become more important. We show that He{sup 2+} and C{sup 6+} follow a monotonic decay toward equal temperatures with protons with increasing collisional age, but O{sup 6+} shows a noted deviation from this monotonic decay. Furthermore, we show that the deviation from monotonic decay for O{sup 6+} occurs in solar wind of all origins, as determined by its Fe/O ratio. The observed differences in heavy ion temperature behavior point toward a local heating mechanism that favors ions depending on their charge and mass.« less

Conductivity and spectroscopic investigation of bis(trifluoromethanesulfonyl)imide solution in ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

PubMed

Yu, Lei; Pizio, Benjamin S; Vaden, Timothy D

2012-06-07

Protic ionic liquids (PILs) are promising alternatives to water for swelling Nafion as a fuel cell proton exchange membrane (PEM). PILs can significantly improve the high-temperature performance of a PEM. The proton dissociation and solvation mechanisms in a PIL, which are keys to understanding the proton transportation and conductivity, have not been fully explored. In this paper, we used FTIR, Raman, and electronic spectroscopy with computational simulation techniques to explore the spectroscopic properties of bis(trifluoromethanesulfonyl)imide (HTFSI) solutions in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) ionic liquid at concentrations from ∼0.1 to as high as ∼1.0 M. Solution conductivities were measured at room temperature and elevated temperatures up to ∼65 °C. The solution structure and properties depend on the concentration of HTFSI. At lower concentration, around 0.1 M, the HTFSI solution has higher conductivity than pure BMITFSI. However, the conductivity decreases when the concentration increases from 0.1 to 1.0 M. Temperature-dependent conductivities followed the Vogel-Fulcher-Tamman equation at all concentrations. Conductivity and spectroscopy results elucidate the complicated ionization and solvation mechanism of HTFSI in BMITFSI solutions. Raman spectroscopy and density functional theory (DFT) calculations are consistent with the complete ionization of HTFSI to generate solvated H(+) at low concentrations. FTIR, Raman, and electronic spectroscopic results as well as DFT computational simulation indicated that when the concentration is as high as 1.0 M, a significant amount of TFSI(-) is protonated, most likely at the imide nitrogen.

THE COUPLED EVOLUTION OF ELECTRONS AND IONS IN CORONAL MASS EJECTION-DRIVEN SHOCKS

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

Manchester IV, W. B.; Van der Holst, B.; Toth, G.

2012-09-01

We present simulations of coronal mass ejections (CMEs) performed with a new two-temperature coronal model developed at the University of Michigan, which is able to address the coupled thermodynamics of the electron and proton populations in the context of a single fluid. This model employs heat conduction for electrons, constant adiabatic index ({gamma} = 5/3), and includes Alfven wave pressure to accelerate the solar wind. The Wang-Sheeley-Arge empirical model is used to determine the Alfven wave pressure necessary to produce the observed bimodal solar wind speed. The Alfven waves are dissipated as they propagate from the Sun and heat protonsmore » on open magnetic field lines to temperatures above 2 MK. The model is driven by empirical boundary conditions that includes GONG magnetogram data to calculate the coronal field, and STEREO/EUVI observations to specify the density and temperature at the coronal boundary by the Differential Emission Measure Tomography method. With this model, we simulate the propagation of fast CMEs and study the thermodynamics of CME-driven shocks. Since the thermal speed of the electrons greatly exceeds the speed of the CME, only protons are directly heated by the shock. Coulomb collisions low in the corona couple the protons and electrons allowing heat exchange between the two species. However, the coupling is so brief that the electrons never achieve more than 10% of the maximum temperature of the protons. We find that heat is able to conduct on open magnetic field lines and rapidly propagates ahead of the CME to form a shock precursor of hot electrons.« less

Effects of proton irradiation on structural and electrochemical charge storage properties of TiO 2 nanotube electrodes for lithium-ion batteries

DOE PAGES

Smith, Kassiopeia A.; Savva, Andreas I.; Deng, Changjian; ...

2017-03-23

The effects of proton irradiation on nanostructured metal oxides have been investigated. Recent studies suggest that the presence of structural defects (e.g. vacancies and interstitials) in metal oxides may enhance the material's electrochemical charge storage capacity. A new approach to introduce defects in electrode materials is to use ion irradiation as it can produce a supersaturation of point defects in the target material. In this work we report the effect of low-energy proton irradiation on amorphous TiO 2 nanotube electrodes at both room temperature and high temperature (250 °C). Upon room temperature irradiation the nanotubes demonstrate an irradiation-induced phase transformationmore » to a mixture of amorphous, anatase, and rutile domains while showing a 35% reduction in capacity compared to anatase TiO 2. On the other hand, the high temperature proton irradiation induced a disordered rutile phase within the nanotubes as characterized by Raman spectroscopy and transmission electron microscopy, which displays an improved capacity by 20% at ~240 mA h g –1 as well as improved rate capability compared to an unirradiated anatase sample. Voltammetric sweep data were used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation had more contributions from diffusion in lithium charge storage. Finally, our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for designing advanced electrode materials.« less

Effects of proton irradiation on structural and electrochemical charge storage properties of TiO 2 nanotube electrodes for lithium-ion batteries

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

Smith, Kassiopeia A.; Savva, Andreas I.; Deng, Changjian

The effects of proton irradiation on nanostructured metal oxides have been investigated. Recent studies suggest that the presence of structural defects (e.g. vacancies and interstitials) in metal oxides may enhance the material's electrochemical charge storage capacity. A new approach to introduce defects in electrode materials is to use ion irradiation as it can produce a supersaturation of point defects in the target material. In this work we report the effect of low-energy proton irradiation on amorphous TiO 2 nanotube electrodes at both room temperature and high temperature (250 °C). Upon room temperature irradiation the nanotubes demonstrate an irradiation-induced phase transformationmore » to a mixture of amorphous, anatase, and rutile domains while showing a 35% reduction in capacity compared to anatase TiO 2. On the other hand, the high temperature proton irradiation induced a disordered rutile phase within the nanotubes as characterized by Raman spectroscopy and transmission electron microscopy, which displays an improved capacity by 20% at ~240 mA h g –1 as well as improved rate capability compared to an unirradiated anatase sample. Voltammetric sweep data were used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation had more contributions from diffusion in lithium charge storage. Finally, our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for designing advanced electrode materials.« less

Isotope effects associated with tunneling and double proton transfer in the hydrogen bonds of benzoic acid

NASA Astrophysics Data System (ADS)

Xue, Q.; Horsewill, A. J.; Johnson, M. R.; Trommsdorff, H. P.

2004-06-01

The isotope effects associated with double proton transfer in the hydrogen bonds of benzoic acid (BA) dimers have been measured using field-cycling 1H NMR relaxometry and quasielastic neutron scattering. By studying mixed isotope (hydrogen and deuterium) samples, the dynamics of three isotopologues, BA-HH, BA-HD, and BA-DD, have been investigated. Low temperature measurements provide accurate measurements of the incoherent tunneling rate, k0. This parameter scales accurately with the mass number, m, according to the formula k0=(E/m)e-F√m providing conclusive evidence that the proton transfer process is a strongly correlated motion of two hydrons. Furthermore, we conclude that the tunneling pathway is the same for the three isotopologue species. Measurements at higher temperatures illuminate the through barrier processes that are mediated via intermediate or excited vibrational states. In parallel with the investigation of proton transfer dynamics, the theoretical and experimental aspects of studying spin-lattice relaxation in single crystals of mixed isotope samples are investigated in depth. Heteronuclear dipolar interactions between 1H and 2H isotopes contribute significantly to the overall proton spin-lattice relaxation and it is shown that these must be modeled correctly to obtain accurate values for the proton transfer rates. Since the sample used in the NMR measurements was a single crystal, full account of the orientation dependence of the spin-lattice relaxation with respect to the applied B field was incorporated into the data analysis.

Nanocomposite membranes based on polybenzimidazole and ZrO2 for high-temperature proton exchange membrane fuel cells.

PubMed

Nawn, Graeme; Pace, Giuseppe; Lavina, Sandra; Vezzù, Keti; Negro, Enrico; Bertasi, Federico; Polizzi, Stefano; Di Noto, Vito

2015-04-24

Owing to the numerous benefits obtained when operating proton exchange membrane fuel cells at elevated temperature (>100 °C), the development of thermally stable proton exchange membranes that demonstrate conductivity under anhydrous conditions remains a significant goal for fuel cell technology. This paper presents composite membranes consisting of poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI4N) impregnated with a ZrO2 nanofiller of varying content (ranging from 0 to 22 wt %). The structure-property relationships of the acid-doped and undoped composite membranes have been studied using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray scattering, infrared spectroscopy, and broadband electrical spectroscopy. Results indicate that the level of nanofiller has a significant effect on the membrane properties. From 0 to 8 wt %, the acid uptake as well as the thermal and mechanical properties of the membrane increase. As the nanofiller level is increased from 8 to 22 wt % the opposite effect is observed. At 185 °C, the ionic conductivity of [PBI4N(ZrO2 )0.231 ](H3 PO4 )13 is found to be 1.04×10(-1)  S cm(-1) . This renders membranes of this type promising candidates for use in high-temperature proton exchange membrane fuel cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature dependence of proton NMR relaxation times at earth's magnetic field

NASA Astrophysics Data System (ADS)

Niedbalski, Peter; Kiswandhi, Andhika; Parish, Christopher; Ferguson, Sarah; Cervantes, Eduardo; Oomen, Anisha; Krishnan, Anagha; Goyal, Aayush; Lumata, Lloyd

The theoretical description of relaxation processes for protons, well established and experimentally verified at conventional nuclear magnetic resonance (NMR) fields, has remained untested at low fields despite significant advances in low field NMR technology. In this study, proton spin-lattice relaxation (T1) times in pure water and water doped with varying concentrations of the paramagnetic agent copper chloride have been measured from 6 to 92oC at earth's magnetic field (1700 Hz). Results show a linear increase of T1 with temperature for each of the samples studied. Increasing the concentration of the copper chloride greatly reduced T1 and reduced dependence on temperature. The consistency of the results with theory is an important confirmation of past results, while the ability of an ultra-low field NMR system to do contrast-enhanced magnetic resonance imaging (MRI) is promising for future applicability to low-cost medical imaging and chemical identification. This work is supported by US Dept of Defense Award No. W81XWH-14-1-0048 and the Robert A. Welch Foundation Grant No. AT-1877.

Initial results from a cryogenic proton irradiation of a p-channel CCD

NASA Astrophysics Data System (ADS)

Gow, J. P. D.; Wood, D.; Burt, D.; Hall, D. J.; Dryer, B.; Holland, A. D.; Murray, N. J.

2015-08-01

The displacement damage hardness that can be achieved using p-channel charge coupled devices (CCD) was originally demonstrated in 1997 and since then a number of other studies have demonstrated an improved tolerance to radiationinduced CTI when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. This study describes the initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with a 10 MeV equivalent proton fluences of 1.24×109 and 1.24×1011 protons.cm-2. The number of defects identified using trap pumping, dark current and cosmetic quality immediately after irradiation and over a period of 150 hours after the irradiation with the device held at 153 K and then after different periods of time at room temperature are described. The device also exhibited a flatband voltage shift of around 30 mV per krad, determined by the reduction in full well capacity.

Paired-pulse facilitation achieved in protonic/electronic hybrid indium gallium zinc oxide synaptic transistors

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

Guo, Li Qiang, E-mail: guoliqiang@ujs.edu.cn; Ding, Jian Ning; Huang, Yu Kai

2015-08-15

Neuromorphic devices with paired pulse facilitation emulating that of biological synapses are the key to develop artificial neural networks. Here, phosphorus-doped nanogranular SiO{sub 2} electrolyte is used as gate dielectric for protonic/electronic hybrid indium gallium zinc oxide (IGZO) synaptic transistor. In such synaptic transistors, protons within the SiO{sub 2} electrolyte are deemed as neurotransmitters of biological synapses. Paired-pulse facilitation (PPF) behaviors for the analogous information were mimicked. The temperature dependent PPF behaviors were also investigated systematically. The results indicate that the protonic/electronic hybrid IGZO synaptic transistors would be promising candidates for inorganic synapses in artificial neural network applications.

Memory and learning behaviors mimicked in nanogranular SiO2-based proton conductor gated oxide-based synaptic transistors

NASA Astrophysics Data System (ADS)

Wan, Chang Jin; Zhu, Li Qiang; Zhou, Ju Mei; Shi, Yi; Wan, Qing

2013-10-01

In neuroscience, signal processing, memory and learning function are established in the brain by modifying ionic fluxes in neurons and synapses. Emulation of memory and learning behaviors of biological systems by nanoscale ionic/electronic devices is highly desirable for building neuromorphic systems or even artificial neural networks. Here, novel artificial synapses based on junctionless oxide-based protonic/electronic hybrid transistors gated by nanogranular phosphorus-doped SiO2-based proton-conducting films are fabricated on glass substrates by a room-temperature process. Short-term memory (STM) and long-term memory (LTM) are mimicked by tuning the pulse gate voltage amplitude. The LTM process in such an artificial synapse is due to the proton-related interfacial electrochemical reaction. Our results are highly desirable for building future neuromorphic systems or even artificial networks via electronic elements.In neuroscience, signal processing, memory and learning function are established in the brain by modifying ionic fluxes in neurons and synapses. Emulation of memory and learning behaviors of biological systems by nanoscale ionic/electronic devices is highly desirable for building neuromorphic systems or even artificial neural networks. Here, novel artificial synapses based on junctionless oxide-based protonic/electronic hybrid transistors gated by nanogranular phosphorus-doped SiO2-based proton-conducting films are fabricated on glass substrates by a room-temperature process. Short-term memory (STM) and long-term memory (LTM) are mimicked by tuning the pulse gate voltage amplitude. The LTM process in such an artificial synapse is due to the proton-related interfacial electrochemical reaction. Our results are highly desirable for building future neuromorphic systems or even artificial networks via electronic elements. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02987e

Proton irradiation effects on beryllium – A macroscopic assessment

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

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong

Beryllium, due to its excellent neutron multiplication and moderation properties, in conjunction with its good thermal properties, is under consideration for use as plasma facing material in fusion reactors and as a very effective neutron reflector in fission reactors. While it is characterized by unique combination of structural, chemical, atomic number, and neutron absorption cross section it suffers, however, from irradiation generated transmutation gases such as helium and tritium which exhibit low solubility leading to supersaturation of the Be matrix and tend to precipitate into bubbles that coalesce and induce swelling and embrittlement thus degrading the metal and limiting itsmore » lifetime. Utilization of beryllium as a pion production low-Z target in high power proton accelerators has been sought both for its low Z and good thermal properties in an effort to mitigate thermos-mechanical shock that is expected to be induced under the multi-MW power demand. To assess irradiation-induced changes in the thermal and mechanical properties of Beryllium, a study focusing on proton irradiation damage effects has been undertaken using 200 MeV protons from the Brookhaven National Laboratory Linac and followed by a multi-faceted post-irradiation analysis that included the thermal and volumetric stability of irradiated beryllium, the stress-strain behavior and its ductility loss as a function of proton fluence and the effects of proton irradiation on the microstructure using synchrotron X-ray diffraction. The mimicking of high temperature irradiation of Beryllium via high temperature annealing schemes has been conducted as part of the post-irradiation study. This study focuses on the thermal stability and mechanical property changes of the proton irradiated beryllium and presents results of the macroscopic property changes of Beryllium deduced from thermal and mechanical tests.« less

Proton irradiation effects on beryllium – A macroscopic assessment

DOE PAGES

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; ...

2016-07-01

Beryllium, due to its excellent neutron multiplication and moderation properties, in conjunction with its good thermal properties, is under consideration for use as plasma facing material in fusion reactors and as a very effective neutron reflector in fission reactors. While it is characterized by unique combination of structural, chemical, atomic number, and neutron absorption cross section it suffers, however, from irradiation generated transmutation gases such as helium and tritium which exhibit low solubility leading to supersaturation of the Be matrix and tend to precipitate into bubbles that coalesce and induce swelling and embrittlement thus degrading the metal and limiting itsmore » lifetime. Utilization of beryllium as a pion production low-Z target in high power proton accelerators has been sought both for its low Z and good thermal properties in an effort to mitigate thermos-mechanical shock that is expected to be induced under the multi-MW power demand. To assess irradiation-induced changes in the thermal and mechanical properties of Beryllium, a study focusing on proton irradiation damage effects has been undertaken using 200 MeV protons from the Brookhaven National Laboratory Linac and followed by a multi-faceted post-irradiation analysis that included the thermal and volumetric stability of irradiated beryllium, the stress-strain behavior and its ductility loss as a function of proton fluence and the effects of proton irradiation on the microstructure using synchrotron X-ray diffraction. The mimicking of high temperature irradiation of Beryllium via high temperature annealing schemes has been conducted as part of the post-irradiation study. This study focuses on the thermal stability and mechanical property changes of the proton irradiated beryllium and presents results of the macroscopic property changes of Beryllium deduced from thermal and mechanical tests.« less

Proton irradiation effects on beryllium - A macroscopic assessment

NASA Astrophysics Data System (ADS)

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; Camino, Fernando

2016-10-01

Beryllium, due to its excellent neutron multiplication and moderation properties, in conjunction with its good thermal properties, is under consideration for use as plasma facing material in fusion reactors and as a very effective neutron reflector in fission reactors. While it is characterized by unique combination of structural, chemical, atomic number, and neutron absorption cross section it suffers, however, from irradiation generated transmutation gases such as helium and tritium which exhibit low solubility leading to supersaturation of the Be matrix and tend to precipitate into bubbles that coalesce and induce swelling and embrittlement thus degrading the metal and limiting its lifetime. Utilization of beryllium as a pion production low-Z target in high power proton accelerators has been sought both for its low Z and good thermal properties in an effort to mitigate thermos-mechanical shock that is expected to be induced under the multi-MW power demand. To assess irradiation-induced changes in the thermal and mechanical properties of Beryllium, a study focusing on proton irradiation damage effects has been undertaken using 200 MeV protons from the Brookhaven National Laboratory Linac and followed by a multi-faceted post-irradiation analysis that included the thermal and volumetric stability of irradiated beryllium, the stress-strain behavior and its ductility loss as a function of proton fluence and the effects of proton irradiation on the microstructure using synchrotron X-ray diffraction. The mimicking of high temperature irradiation of Beryllium via high temperature annealing schemes has been conducted as part of the post-irradiation study. This paper focuses on the thermal stability and mechanical property changes of the proton irradiated beryllium and presents results of the macroscopic property changes of Beryllium deduced from thermal and mechanical tests.

Isotope Induced Proton Ordering in Partially Deuterated Aspirin

NASA Astrophysics Data System (ADS)

Schiebel, P.; Papoular, R. J.; Paulus, W.; Zimmermann, H.; Detken, A.; Haeberlen, U.; Prandl, W.

1999-08-01

We report the nuclear density distribution of partially deuterated aspirin, C8H5O4-CH2D, at 300 and 15 K, as determined by neutron diffraction coupled with maximum entropy method image reconstruction. While fully protonated and fully deuterated methyl groups in aspirin are delocalized at low temperatures due to quantum mechanical tunneling, we provide here direct evidence that in aspirin- CH2D at 15 K the methyl hydrogens are localized, while randomly distributed over three sites at 300 K. This is the first observation by diffraction methods of low-temperature isotopic ordering in condensed matter.

Nonthermal turbulent heating in the solar envelope.

NASA Technical Reports Server (NTRS)

Papadopoulos, K.

1973-01-01

It is shown that MHD pulses, in the form of fast magnetosonic waves or solitons, can produce a strong electron-ion coupling capable of maintaining electron-proton temperature equilibrium in the solar envelope. The mechanism producing the nonthermal heating is the fluid-like modified two-stream instability, which, since it is essentially independent of the electron-proton temperature ratio and the value of beta, becomes a prime candidate for the anomalous collisions required by the fluid models inside a distance less than 30 solar radii, in order to explain the dominant features of the solar-wind flow.

A proton-exchange membrane prepared by the radiation grafting of styrene and silica into polytetrafluoroethylene films

NASA Astrophysics Data System (ADS)

Yu, Hongyan; Shi, Jianheng; Zeng, Xinmiao; Bao, Mao; Zhao, Xinqing

2009-07-01

A polytetrafluoroethylene (PTFE) based organic-inorganic hybrid proton-exchange membrane was prepared from simultaneous radiation grafting of styrene (St) into porous PTFE membrane with the in situ sol-gel reaction of tetraethoxysilane (TEOS) followed by sulfonation in fuming sulfonic acid. The effect of radiation on the sol-gel reaction was studied. The results show that radiation promotes the sol-gel reaction with the help of St at room temperature. Incorporated silica gel helps to produce higher degree of grafting (DOG). SEM analysis was conducted to confirm that the inorganic silicon oxide was introduced to produce hybrid membrane in this work. The proton conductivity of membrane evaluated using electrochemical impedance spectroscopy is much higher (14.3×10 -2 S cm -1) than that of Nafion ® 117 at temperature of 80 °C with acceptable water uptake 51 wt%.

Pressure control of a proton beam-irradiated water target through an internal flow channel-induced thermosyphon.

PubMed

Hong, Bong Hwan; Jung, In Su

2017-07-01

A water target was designed to enhance cooling efficiency using a thermosyphon, which is a system that uses natural convection to induce heat exchange. Two water targets were fabricated: a square target without any flow channel and a target with a flow channel design to induce a thermosyphon mechanism. These two targets had the same internal volume of 8 ml. First, visualization experiments were performed to observe the internal flow by natural convection. Subsequently, an experiment was conducted to compare the cooling performance of both water targets by measuring the temperature and pressure. A 30-MeV proton beam with a beam current of 20 μA was used to irradiate both targets. Consequently, the target with an internal flow channel had a lower mean temperature and a 50% pressure drop compared to the target without a flow channel during proton beam irradiation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pulsed electron nuclear double resonance studies of the photoexcited triplet state of pentacene in p-terphenyl crystals at room temperature.

PubMed

Yago, Tomoaki; Link, Gerhard; Kothe, Gerd; Lin, Tien-Sung

2007-09-21

Pulsed electron nuclear double resonance (ENDOR) using a modified Davies-type [Phys. Lett. 47A, 1 (1974)] sequence is employed to study the hyperfine (HF) structure of the photoexcited triplet state of pentacene dispersed in protonated and deuterated p-terphenyl single crystals. The strong electron spin polarization and long phase memory time of triplet pentacene enable us to perform the ENDOR measurements on the S=1 spin system at room temperature. Proton HF tensor elements and spin density values of triplet pentacene are extracted from a detailed angular-dependent study in which the orientation of the magnetic field is varied systematically in two different pentacene planes. Analysis reveals that the pentacene molecule is no longer planar in the p-terphenyl host lattice. The distortion is more pronounced in the deuterated crystal where the unit cell dimensions are slightly smaller than those of the protonated crystal.

Inverted Fuel Cell: Room-Temperature Hydrogen Separation from an Exhaust Gas by Using a Commercial Short-Circuited PEM Fuel Cell without Applying any Electrical Voltage.

PubMed

Friebe, Sebastian; Geppert, Benjamin; Caro, Jürgen

2015-06-26

A short-circuited PEM fuel cell with a Nafion membrane has been evaluated in the room-temperature separation of hydrogen from exhaust gas streams. The separated hydrogen can be recovered or consumed in an in situ olefin hydrogenation when the fuel cell is operated as catalytic membrane reactor. Without applying an outer electrical voltage, there is a continuous hydrogen flux from the higher to the lower hydrogen partial pressure side through the Nafion membrane. On the feed side of the Nafion membrane, hydrogen is catalytically split into protons and electrons by the Pt/C electrocatalyst. The protons diffuse through the Nafion membrane, the electrons follow the short-circuit between the two brass current collectors. On the cathode side, protons and electrons recombine, and hydrogen is released. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Protonic Conduction of BaCe0.85YO. 1503 Doped with SrTiO3

NASA Technical Reports Server (NTRS)

Dynys, Frederick W.; Sayir, Ali

2005-01-01

Reformers based on ceramic membrane technology potentially offer hydrogen production that is comparable to the cost of fossil fuels. Protonic conducting ceramic with the chemical formula AB03 offers the promise of highly selective hydrogen separation at intermediate temperature (400-800 C). Among different perovskite-type oxides, BaCe03 and SrCe03 based compositions show high protonic conductivities but strong resistance to densification. X-ray diffraction studies on sintered specimens of BaCe0.85Y0.1503-6 show multi-phase formation which was found to show dependence upon powder synthesis method. Doping with SrTiO3 suppresses multi-phase formation and enhances grain growth. Conductivity measurements in temperature range of 200 to 1000 C were performed by ac impedance spectroscopy under dry and wet conditions. Sintering behavior, phase formation and conductivity results will be reported.

Superconductivity and fast proton transport in nanoconfined water

NASA Astrophysics Data System (ADS)

Johnson, K. H.

2018-04-01

A real-space molecular-orbital density-wave description of Cooper pairing in conjunction with the dynamic Jahn-Teller mechanism for high-Tc superconductivity predicts that electron-doped water confined to the nanoscale environment of a carbon nanotube or biological macromolecule should superconduct below and exhibit fast proton transport above the transition temperature, Tc ≅ 230 K (-43 °C).

Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions

NASA Astrophysics Data System (ADS)

Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

2016-12-01

In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavor particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p -p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of ‘thermometers’ or ‘thermometric scales’ and ‘speedometers’. A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature (T) curve as a function of particle’s rest mass (m 0) when plotting T versus m 0, and the mean transverse flow velocity from the slope of the mean transverse momentum (< {p}T> ) curve as a function of mean moving mass (\\overline{m}) when plotting < {p}T> versus \\overline{m}.

Proton Conductivity in Phosphoric Acid: The Role of Quantum Effects

DOE PAGES

Heres, M.; Wang, Y.; Griffin, P. J.; ...

2016-10-07

Phosphoric acid has one of the highest intrinsic proton conductivities of any known liquids, and the mechanism of this exceptional conductivity remains a puzzle. In our detailed experimental studies we discovered a strong isotope effect in the conductivity of phosphoric acids caused by (i) a strong isotope shift of the glass transition temperature and (ii) a significant reduction of the energy barrier by zero-point quantum fluctuations. Our results suggest that the high conductivity in phosphoric acids is caused by a very efficient proton transfer mechanism, which is strongly assisted by quantum effects.

Memory device using movement of protons

DOEpatents

Warren, W.L.; Vanheusden, K.J.R.; Fleetwood, D.M.; Devine, R.A.B.

1998-11-03

An electrically written memory element is disclosed utilizing the motion of protons within a dielectric layer surrounded by layers on either side to confine the protons within the dielectric layer with electrode means attached to the surrounding layers to change the spatial position of the protons within the dielectric layer. The device is preferably constructed as a silicon-silicon dioxide-silicon layered structure with the protons being introduced to the structure laterally through the exposed edges of the silicon dioxide layer during a high temperature anneal in an atmosphere containing hydrogen gas. The device operates at low power, is preferably nonvolatile, is radiation tolerant, and is compatible with convention silicon MOS processing for integration with other microelectronic elements on the same silicon substrate. With the addition of an optically active layer, the memory element becomes an electrically written, optically read optical memory element. 19 figs.

Memory device using movement of protons

DOEpatents

Warren, William L.; Vanheusden, Karel J. R.; Fleetwood, Daniel M.; Devine, Roderick A. B.

1998-01-01

An electrically written memory element utilizing the motion of protons within a dielectric layer surrounded by layers on either side to confine the protons within the dielectric layer with electrode means attached to the surrounding layers to change the spatial position of the protons within the dielectric layer. The device is preferably constructed as a silicon-silicon dioxide-silicon layered structure with the protons being introduced to the structure laterally through the exposed edges of the silicon dioxide layer during a high temperature anneal in an atmosphere containing hydrogen gas. The device operates at low power, is preferably nonvolatile, is radiation tolerant, and is compatible with convention silicon MOS processing for integration with other microelectronic elements on the same silicon substrate. With the addition of an optically active layer, the memory element becomes an electrically written, optically read optical memory element.

Memory device using movement of protons

DOEpatents

Warren, William L.; Vanheusden, Karel J. R.; Fleetwood, Daniel M.; Devine, Roderick A. B.

2000-01-01

An electrically written memory element utilizing the motion of protons within a dielectric layer surrounded by layers on either side to confine the protons within the dielectric layer with electrode means attached to the surrounding layers to change the spatial position of the protons within the dielectric layer. The device is preferably constructed as a silicon-silicon dioxide-silicon layered structure with the protons being introduced to the structure laterally through the exposed edges of the silicon dioxide layer during a high temperature anneal in an atmosphere containing hydrogen gas. The device operates at low power, is preferably nonvolatile, is radiation tolerant, and is compatible with convention silicon MOS processing for integration with other microelectronic elements on the same silicon substrate. With the addition of an optically active layer, the memory element becomes an electrically written, optically read optical memory element.

The effects of electron and proton radiation on GaSb infrared solar cells

NASA Technical Reports Server (NTRS)

Gruenbaum, P. E.; Avery, J. E.; Fraas, L. M.

1991-01-01

Gallium antimonide (GaSb) infrared solar cells were exposed to 1 MeV electrons and protons up to fluences of 1 times 10(exp 15) cm (-2) and 1 times 10(exp 12) cm (-2) respectively. In between exposures, current voltage and spectral response curves were taken. The GaSb cells were found to degrade slightly less than typical GaAs cells under electron irradiation, and calculations from spectral response curves showed that the damage coefficient for the minority carrier diffusion length was 3.5 times 10(exp 8). The cells degraded faster than GaAs cells under proton irradiation. However, researchers expect the top cell and coverglass to protect the GaSb cell from most damaging protons. Some annealing of proton damage was observed at low temperatures (80 to 160 C).

Density Functional Theory Investigation of Proton Diffusion in Tungsten Oxide And Its Hydrates

NASA Astrophysics Data System (ADS)

Lin, Hao

Fast proton conduction mechanism is of key importance for achieving high performance in fuel cell membranes, batteries, supercapacitors, and electrochromic materials. Enhanced proton diffusion is often observed in hydrated materials where it is thought to occur via the famous Grotthuss mechanism through pathways formed by structural water. Using first-principles calculations, we demonstrate that proton diffusion in tungsten oxide dihydrate (WO3·2H 2O), a known good proton conductor, takes place within the layers of corner-sharing WO6 octahedra without direct involvement of structural water. The calculated proton migration barrier in WO3·2H 2O is in good agreement with the experimental value inferred from the temperature dependence of conductivity. The preferred proton diffusion path in WO3·2H2O is essentially the same as in gamma-WO 3. In contrast to the small intercalation voltages calculated for WO 3 and WO3·2H2O, we find that proton absorption in the monohydrate WO3·H2O is energetically highly favorable. However, strong proton-proton repulsion limits the equilibrium H content at zero voltage. We find a fast one-dimensional diffusion channel in WO3·H2O at dilute proton concentrations, but much higher barriers are expected at near-equilibrium concentrations due to strong repulsive interactions with other protons. Our results illustrate that low proton diffusion barriers and low insertion voltages both contribute to fast proton transport in bulk WO3·2H2O and gamma-WO 3.

Conductivity Analysis of Membranes for High-Temperature PEMFC Applications

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

Reed, R.; Turner, J.A.

2005-01-01

Low-temperature operation requirements for per-fluorinated membranes are one factor that limits the viability of current fuel cell technology for transportation and other uses. Because of this, high-temperature membrane materials are being researched. The protonic conductivity of organic/inorganic hybrid composites, Nafion® analog material, and heteropoly acid doped Nafion membranes were studied using a BekkTech® conductivity test cell as a hydrogen pump. The goal was to find a high-temperature membrane with sufficient enough conductive properties to replace the currently implemented low-temperature membranes, such as Nafion. Four-point conductivity measurements were taken using a hydrogen pump experiment. Results showed that one of the organic/inorganicmore » membranes that we tested had similar protonic conductivity to Nafion. Nafion analog membranes were shown to have similar to slightly better conductivity than Nafion at high-temperatures. However, like Nafion, performance dropped upon dehydration of the membrane at higher temperatures. Of the heteropoly acid doped Nafion membranes studied, silicotungstic acid was found to be, overall, the most promising for use as a dopant.« less

A flexible metal-organic framework with a high density of sulfonic acid sites for proton conduction

NASA Astrophysics Data System (ADS)

Yang, Fan; Xu, Gang; Dou, Yibo; Wang, Bin; Zhang, Heng; Wu, Hui; Zhou, Wei; Li, Jian-Rong; Chen, Banglin

2017-11-01

The design of stable electrolyte materials with high proton conductivity for use in proton exchange membrane fuel cells remains a challenge. Most of the materials explored have good conductivity at high relative humidity (RH), but significantly decreased conductivity at reduced RH. Here we report a chemically stable and structurally flexible metal-organic framework (MOF), BUT-8(Cr)A, possessing a three-dimensional framework structure with one-dimensional channels, in which high-density sulfonic acid (-SO3H) sites arrange on channel surfaces for proton conduction. We propose that its flexible nature, together with its -SO3H sites, could allow BUT-8(Cr)A to self-adapt its framework under different humid environments to ensure smooth proton conduction pathways mediated by water molecules. Relative to other MOFs, BUT-8(Cr)A not only has a high proton conductivity of 1.27 × 10-1 S cm-1 at 100% RH and 80 °C but also maintains moderately high proton conductivity at a wide range of RH and temperature.

In-situ Monitoring of Internal Local Temperature and Voltage of Proton Exchange Membrane Fuel Cells

PubMed Central

Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

2010-01-01

The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm2, and that with a sensor is 426 mW/cm2. Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse. PMID:22163556

In-situ monitoring of internal local temperature and voltage of proton exchange membrane fuel cells.

PubMed

Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

2010-01-01

The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm(2), and that with a sensor is 426 mW/cm(2). Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse.

Effects of high-energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films

NASA Astrophysics Data System (ADS)

Sylva, G.; Bellingeri, E.; Ferdeghini, C.; Martinelli, A.; Pallecchi, I.; Pellegrino, L.; Putti, M.; Ghigo, G.; Gozzelino, L.; Torsello, D.; Grimaldi, G.; Leo, A.; Nigro, A.; Braccini, V.

2018-05-01

In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm‑2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.

Vibrational renormalisation of the electronic band gap in hexagonal and cubic ice

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

Engel, Edgar A., E-mail: eae32@cam.ac.uk; Needs, Richard J.; Monserrat, Bartomeu

2015-12-28

Electron-phonon coupling in hexagonal and cubic water ice is studied using first-principles quantum mechanical methods. We consider 29 distinct hexagonal and cubic ice proton-orderings with up to 192 molecules in the simulation cell to account for proton-disorder. We find quantum zero-point vibrational corrections to the minimum electronic band gaps ranging from −1.5 to −1.7 eV, which leads to improved agreement between calculated and experimental band gaps. Anharmonic nuclear vibrations play a negligible role in determining the gaps. Deuterated ice has a smaller band-gap correction at zero-temperature of −1.2 to −1.4 eV. Vibrations reduce the differences between the electronic band gapsmore » of different proton-orderings from around 0.17 eV to less than 0.05 eV, so that the electronic band gaps of hexagonal and cubic ice are almost independent of the proton-ordering when quantum nuclear vibrations are taken into account. The comparatively small reduction in the band gap over the temperature range 0 − 240 K of around 0.1 eV does not depend on the proton ordering, or whether the ice is protiated or deuterated, or hexagonal, or cubic. We explain this in terms of the atomistic origin of the strong electron-phonon coupling in ice.« less

Strangeness Production in the ALICE Experiment at the LHC

NASA Astrophysics Data System (ADS)

Johnson, Harold; Fenner, Kiara; Harton, Austin; Garcia-Solis, Edmundo; Soltz, Ron

2015-04-01

The study of strange particle production is an important tool in understanding the properties of a hot and dense medium, the quark-gluon plasma, created in heavy-ion collisions at ultra-relativistic energies. This quark-gluon plasma (QGP) is believed to have been present just after the big bang. The standard model of physics contains six types of quarks. Strange quarks are not among the valence quarks found in protons and neutrons. Strange quark production is sensitive to the extremely high temperatures of the QGP. CERN's Large Hadron Collider accelerates particles to nearly the speed of light before colliding them to create this QGP state. In the results of high-energy particle collisions, hadrons are formed out of quarks and gluons when cooling from extremely high temperatures. Jets are a highly collimated cone of particles coming from the hadronization of a single quark or gluon. Understanding jet interactions may give us clues about the QGP. Using FastJet (a popular jet finder algorithm), we extracted strangeness, or strange particle characteristics of jets contained within proton-proton collisions during our research at CERN. We have identified jets with and without strange particles in proton-proton collisions and we will present a comparison of pT spectra in both cases. This material is based upon work supported by the National Science Foundation under grants PHY-1305280 and PHY-1407051.

Proton transport, water uptake and hydrogen permeability of nanoporous hematite ceramic membranes

NASA Astrophysics Data System (ADS)

Colomer, M. T.

2011-10-01

For the first time, mesoporous acid-free hematite ceramic membranes have been studied as proton conductors. The xerogels after calcination at 300 °C for 1 h were mesoporous, as is mentioned above, with a BET surface area of 130 ± 2 m2 g-1, an average pore diameter of 3.8 nm and a pore volume of 0.149 ± 0.001 cc g-1. A sigmoidal dependence of the conductivity and the water uptake with the RH at a constant temperature was observed. The conductivity of the ceramic membranes increased linearly with temperature for all relative humidities studied. The highest value of proton conductivity was found to be 2.76 × 10-3 S cm-1 at 90 °C and 81% RH. According to the activation energy values, proton migration in this kind of materials could be dominated by the Grotthuss mechanism in the whole range of RH. The low cost and high hydrophilicity of these ceramic membranes make them potential substitutes for perfluorosulfonic polymeric membranes in proton exchange membrane (PEMFCs). In addition, since hydrogen permeability values are in the range of 10-9 to 10-10 mol cm-1 s Pa, in order to fabricate oxide-based PEMs that are capable of keeping streams of H2 and O2 from mixing, a separation layer with pore sizes <2 nm whose pores are filled with water will be needed.

Cationic Covalent Organic Frameworks: A Simple Platform of Anionic Exchange for Porosity Tuning and Proton Conduction.

PubMed

Ma, Heping; Liu, Bailing; Li, Bin; Zhang, Liming; Li, Yang-Guang; Tan, Hua-Qiao; Zang, Hong-Ying; Zhu, Guangshan

2016-05-11

Mimicking proton conduction mechanism of Nafion to construct novel proton-conducting materials with low cost and high proton conductivity is of wide interest. Herein, we have designed and synthesized a cationic covalent organic framework with high thermal and chemical stability by combining a cationic monomer, ethidium bromide (EB) (3,8-diamino-5-ethyl-6-phenylphenanthridinium bromide), with 1,3,5-triformylphloroglucinol (TFP) in Schiff base reactions. This is the first time that the stable cationic crystalline frameworks allowed for the fabrication of a series of charged COFs (EB-COF:X, X = F, Cl, Br, I) through ion exchange processes. Exchange of the extra framework ions can finely modulate the COFs' porosity and pore sizes at nanoscale. More importantly, by introducing PW12O40(3-) into this porous cationic framework, we can greatly enhance the proton conductivity of ionic COF-based material. To the best of our knowledge, EB-COF:PW12 shows the best proton conductivity at room temperature among ever reported porous organic materials.

Energetics and mechanisms for the unimolecular dissociation of protonated trioses and relationship to proton-mediated formaldehyde polymerization to carbohydrates in interstellar environments.

PubMed

Simakov, Anton; Sekiguchi, Osamu; Bunkan, Arne Joakim C; Uggerud, Einar

2011-12-28

We report the unimolecular decomposition of protonated glyceraldehyde, [HOCH(2)CH(OH)CHO]H(+), and protonated dihydroxyacetone, [HOCH(2)C(O)CH(2)OH]H(+). On the basis of mass spectrometric experiments and computational quantum chemistry, we have found that these isomeric ions interconvert freely at energies below that required for their unimolecular decompositions. The losses of formaldehyde and water (the latter also followed by CO loss) are the dominating processes, with formaldehyde loss having the lower energetic threshold. The reverse of the formaldehyde loss, namely, the addition of formaldehyde to protonated glycolaldehyde, appears to be an inefficient reaction at low temperature and pressure in the gas phase, leading to dissociation products. The relevance of these findings to interstellar chemistry and prebiotic chemistry is discussed, and it is concluded that the suggestion made in the literature that successive addition of formaldehyde by proton-assisted reactions should account for interstellar carbohydrates most likely is incorrect. © 2011 American Chemical Society

Enhanced proton transport in nanostructured polymer electrolyte/ionic liquid membranes under water-free conditions.

PubMed

Kim, Sung Yeon; Kim, Suhan; Park, Moon Jeong

2010-10-05

Proton exchange fuel cells (PEFCs) have the potential to provide power for a variety of applications ranging from electronic devices to transportation vehicles. A major challenge towards economically viable PEFCs is finding an electrolyte that is both durable and easily passes protons. In this article, we study novel anhydrous proton-conducting membranes, formed by incorporating ionic liquids into synthetic block co-polymer electrolytes, poly(styrenesulphonate-b-methylbutylene) (S(n)MB(m)), as high-temperature PEFCs. The resulting membranes are transparent, flexible and thermally stable up to 180 °C. The increases in the sulphonation level of S(n)MB(m) co-polymers (proton supplier) and the concentration of the ionic liquid (proton mediator) produce an overall increase in conductivity. Morphology effects were studied by X-ray scattering and electron microscopy. Compared with membranes having discrete ionic domains (including Nafion 117), the nanostructured membranes revealed over an order of magnitude increase in conductivity with the highest conductivity of 0.045 S cm(-1) obtained at 165 °C.

Crystal structure of acetanilide at 15 and 295 K by neutron diffraction. Lack of evidence for proton transfer along the N-H...O hydrogen bond

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

Johnson, S.W.; Eckert, J.; Barthes, M.

1995-11-02

The crystal structure of acetanilide C{sub 8}H{sub 9}NO, M{sub r} = 135.17, orthorhombic, space group Pbca, Z=8, has been determined from neutron diffraction data at 15 and 295 K. The crystal data obtained are presented. This new investigation of the structure of acetanilide has been undertaken in order to assess a recent suggestion that confirmational substates in the amide proton position may be responsible for the vibrational anomalies. We found no evidence for multiple conformations or transfer along the N-H...O hydrogen bond of the amide proton at either temperature. However the intramolecular O...H6 distance from O to the nearest phenylmore » ring proton is unusually short and the amide proton has relatively close contacts with one of the phenyl and one of the methyl protons, which may well affect the vibrational parameters of the respective molecular groups. 44 refs., 6 figs., 5 tabs.« less

Analysis of coronal H I Lyman alpha measurements from a rocket flight on 1979 April 13

NASA Technical Reports Server (NTRS)

Withbroe, G. L.; Kohl, J. L.; Weiser, H.; Noci, G.; Munro, R. H.

1982-01-01

It is noted that measurements of the profiles of resonantly scattered hydrogen Lyman-alpha coronal radiation have been used in determining hydrogen kinetic temperatures from 1.5 to 4 solar radii from sun center in a quiet region of the corona. Proton temperatures derived using the line widths decrease with height from 2.6 x 10 to the 6th K at 1.5 solar radii to 1.2 x 10 to the 6th K at 4 solar radii. These measurements, together with temperatures for lower heights determined from earlier Skylab and eclipse data, suggest that there is a maximum in the quiet coronal proton temperature at about 1.5 solar radii. Comparison of measured Lyman-alpha intensities with those calculated using a representative model for the radial variation of the coronal electron density yields information on the magnitude of the electron temperature gradient and suggests that the solar wind flow was subsonic for distances less than 4 solar radii.

Evaluating the time and temperature dependent biaxial strength of Gore-Select ® series 57 proton exchange membrane using a pressure loaded blister test

NASA Astrophysics Data System (ADS)

Grohs, Jacob R.; Li, Yongqiang; Dillard, David A.; Case, Scott W.; Ellis, Michael W.; Lai, Yeh-Hung; Gittleman, Craig S.

Temperature and humidity fluctuations in operating fuel cells impose significant biaxial stresses in the constrained proton exchange membranes (PEMs) of a fuel cell stack. The strength of the PEM, and its ability to withstand cyclic environment-induced stresses, plays an important role in membrane integrity and consequently, fuel cell durability. In this study, a pressure loaded blister test is used to characterize the biaxial strength of Gore-Select ® series 57 over a range of times and temperatures. Hencky's classical solution for a pressurized circular membrane is used to estimate biaxial strength values from burst pressure measurements. A hereditary integral is employed to construct the linear viscoelastic analog to Hencky's linear elastic exact solution. Biaxial strength master curves are constructed using traditional time-temperature superposition principle techniques and the associated temperature shift factors show good agreement with shift factors obtained from constitutive (stress relaxation) and fracture (knife slit) tests of the material.

Electron Heating in Low Mach Number Perpendicular Shocks. II. Dependence on the Pre-shock Conditions

NASA Astrophysics Data System (ADS)

Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

2018-05-01

Recent X-ray observations of merger shocks in galaxy clusters have shown that the post-shock plasma is two-temperature, with the protons being hotter than the electrons. In this work, the second of a series, we investigate the efficiency of irreversible electron heating in perpendicular low Mach number shocks, by means of two-dimensional particle-in-cell simulations. We consider values of plasma beta (the ratio of thermal and magnetic pressures) in the range 4 ≲ β p0 ≲ 32, and sonic Mach number (the ratio of shock speed to pre-shock sound speed) in the range 2 ≲ M s ≲ 5, as appropriate for galaxy cluster shocks. As shown in Paper I, magnetic field amplification—induced by shock compression of the pre-shock field, or by strong proton cyclotron and mirror modes accompanying the relaxation of proton temperature anisotropy—can drive the electron temperature anisotropy beyond the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance, and allows for efficient entropy production. We find that the post-shock electron temperature T e2 exceeds the adiabatic expectation {T}e2,{ad} by an amount ({T}e2-{T}e2,{ad})/{T}e0≃ 0.044 {M}s({M}s-1) (here, T e0 is the pre-shock temperature), which depends only weakly on the plasma beta over the range 4 ≲ β p0 ≲ 32 that we have explored, as well as on the proton-to-electron mass ratio (the coefficient of ≃0.044 is measured for our fiducial {m}i/{m}e=49, and we estimate that it will decrease to ≃0.03 for the realistic mass ratio). Our results have important implications for current and future observations of galaxy cluster shocks in the radio band (synchrotron emission and Sunyaev–Zel’dovich effect) and at X-ray frequencies.

Proton irradiation of simple gas mixtures: Influence of irradiation parameters

NASA Technical Reports Server (NTRS)

Sack, Norbert J.; Schuster, R.; Hofmann, A.

1990-01-01

In order to get information about the influence of irradiation parameters on radiolysis processes of astrophysical interest, methane gas targets were irradiated with 6.5 MeV protons at a pressure of 1 bar and room temperature. Yields of higher hydrocarbons like ethane or propane were found by analysis of irradiated gas samples using gas chromatography. The handling of the proton beam was of great experimental importance for determining the irradiation parameters. In a series of experiments current density of the proton beam and total absorbed energy were shown to have a large influence on the yields of produced hydrocarbons. Mechanistic interpretations of the results are given and conclusions are drawn with regard to the chemistry and the simulation of various astrophysical systems.

Formation of (HCOO – )(H 2 SO 4 ) Anion Clusters: Violation of Gas-Phase Acidity Predictions

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

Hou, Gao-Lei; Wang, Xue-Bin; Valiev, Marat

2017-08-10

Sulfuric acid is commonly known to be a strong acid and, by all counts, should readily donate its proton to formate, which has much higher proton affinity. This conventional wisdom is challenged in this work, where temperature-dependent negative ion photoelectron spectroscopy (NIPES) and theoretical studies demonstrate the existence of (HCOO?)(H2SO4) pair at the energy slightly below the conventional (HCOOH)(HSO4?) structure. Analysis of quantum-mechanical calculations indicates that large proton affinity barrier (~36 kcal/mol), favoring proton transfer to formate, is offset by the gain in inter-molecular interaction energy between HCOO? and H2SO4 through the formation of two strong hydrogen bonds. However, thismore » stabilization comes with severe entropic penalty, requiring the two species in the precise align-ment. As a result, the population of (HCOO?)(H2SO4) drops significantly at higher temperatures, rendering (HCOOH)(HSO4?) to be the dominant species. This phe-nomenon is consistent with the NIPES data, which shows depletion in the spectra assigned to (HCOO?)(H2SO4), and has also been verified by ab initio molecular dynamics simulations.« less

Boosting laser-ion acceleration with multi-picosecond pulses

PubMed Central

Yogo, A.; Mima, K.; Iwata, N.; Tosaki, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Johzaki, T.; Sentoku, Y.; Nishimura, H.; Sagisaka, A.; Matsuo, K.; Kamitsukasa, N.; Kojima, S.; Nagatomo, H.; Nakai, M.; Shiraga, H.; Murakami, M.; Tokita, S.; Kawanaka, J.; Miyanaga, N.; Yamanoi, K.; Norimatsu, T.; Sakagami, H.; Bulanov, S. V.; Kondo, K.; Azechi, H.

2017-01-01

Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 1018 W cm−2, the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines. PMID:28211913

On the idea of low-energy nuclear reactions in metallic lattices by producing neutrons from protons capturing "heavy" electrons

NASA Astrophysics Data System (ADS)

Tennfors, Einar

2013-02-01

The present article is a critical comment on Widom and Larsens speculations concerning low-energy nuclear reactions (LENR) based on spontaneous collective motion of protons in a room temperature metallic hydride lattice producing oscillating electric fields that renormalize the electron self-energy, adding significantly to the effective electron mass and enabling production of low-energy neutrons. The frequency and mean proton displacement estimated on the basis of neutron scattering from protons in palladium and applied to the Widom and Larsens model of the proton oscillations yield an electron mass enhancement less than one percent, far below the threshold for the proposed neutron production and even farther below the mass enhancement obtained by Widom and Larsen assuming a high charge density. Neutrons are not stopped by the Coulomb barrier, but the energy required for the neutron production is not low.

Synthesis, crystal structure and antitumor activities of water soluble protonated salt of 20(S)-camptothecin

NASA Astrophysics Data System (ADS)

Lu, Wen; Wang, Yong; Wang, Luna; Zhao, Fengyi; Yang, Shilong; Xi, Chengjie; Yang, Yu; Xu, Li; Chi, Xingwei

2018-03-01

A water soluble camptothecin protonated salt has been synthesized; single crystals were grown by slow evaporation solution growth technique at room temperature and characterized by single crystal X-ray diffraction, FT-IR and 1H NMR. The CPT was protonated as (CPT+H+) cations, the cationic protonation occurred on the N position at pyridine group, which fromed a cation-anion compound with perchlorate ion that determined by X-Ray diffraction. Its activities against Hela (cervix), MCF-7 (breast), A549 (lung), HepG2 (liver) and HUVEC (umbilical vein, normal cell) were investigated. The toxicity of the protonated salt was slightly lower than camptothecin. IC50 values of 7.01 μM against HepG-2 cell, 8.61 μM against A549 cell, 17.82 μM against McF-7 cell, all of them are lower than the IC50 values of CPT against these cells except Hela cell.

Primary and aggregate color centers in proton irradiated LiF crystals and thin films for luminescent solid state detectors

NASA Astrophysics Data System (ADS)

Piccinini, M.; Ambrosini, F.; Ampollini, A.; Bonfigli, F.; Libera, S.; Picardi, L.; Ronsivalle, C.; Vincenti, M. A.; Montereali, R. M.

2015-04-01

Proton beams of 3 MeV energy, produced by the injector of a linear accelerator for proton therapy, were used to irradiate at room temperature lithium fluoride crystals and polycrystalline thin films grown by thermal evaporation. The irradiation fluence range was 1011-1015 protons/cm2. The proton irradiation induced the stable formation of primary and aggregate color centers. Their formation was investigated by optical absorption and photoluminescence spectroscopy. The F2 and F3+ photoluminescence intensities, carefully measured in LiF crystals and thin films, show linear behaviours up to different maximum values of the irradiation fluence, after which a quenching is observed, depending on the nature of the samples (crystals and films). The Principal Component Analysis, applied to the absorption spectra of colored crystals, allowed to clearly identify the formation of more complex aggregate defects in samples irradiated at highest fluences.

Toward real-time temperature monitoring in fat and aqueous tissue during magnetic resonance-guided high-intensity focused ultrasound using a three-dimensional proton resonance frequency T1 method.

PubMed

Diakite, Mahamadou; Odéen, Henrik; Todd, Nick; Payne, Allison; Parker, Dennis L

2014-07-01

To present a three-dimensional (3D) segmented echoplanar imaging (EPI) pulse sequence implementation that provides simultaneously the proton resonance frequency shift temperature of aqueous tissue and the longitudinal relaxation time (T1 ) of fat during thermal ablation. The hybrid sequence was implemented by combining a 3D segmented flyback EPI sequence, the extended two-point Dixon fat and water separation, and the double flip angle T1 mapping techniques. High-intensity focused ultrasound (HIFU) heating experiments were performed at three different acoustic powers on excised human breast fat embedded in ex vivo porcine muscle. Furthermore, T1 calibrations with temperature in four different excised breast fat samples were performed, yielding an estimate of the average and variation of dT1 /dT across subjects. The water only images were used to mask the complex original data before computing the proton resonance frequency shift. T1 values were calculated from the fat-only images. The relative temperature coefficients were found in five fat tissue samples from different patients and ranged from 1.2% to 2.6%/°C. The results demonstrate the capability of real-time simultaneous temperature mapping in aqueous tissue and T1 mapping in fat during HIFU ablation, providing a potential tool for treatment monitoring in organs with large fat content, such as the breast. Copyright © 2013 Wiley Periodicals, Inc.

The temperature dependence of the hydroxyl deuterium quadrupole coupling parameter and the rotational correlation time of the OD internuclear vector in neat ethanol-d

NASA Astrophysics Data System (ADS)

Ferris, Thomas D.; Farrar, Thomas C.

The temperature dependence of the hydroxyl proton chemical shift and deuterium quadrupolar relaxation time of neat ethanol were measured over the temperature range 190-350 K. The proton isotropic chemical shift varies from 6.2 ppm at 190 K to 4.7 ppm at 350 K. The deuterium NMR relaxation time in ethanol- d 1 varies from 6.2 ms to 309 ms over the same range. Ab initio calculations performed on various ethanol clusters ranging in size from monomer to hexamer show a linear correlation ( R 2 = 0.99) between ≤D, the deuterium quadrupole coupling parameter, and δH, the isotropic proton chemical shift in ppm relative to TMS: ≤D(kHz) = 297.60 - 15.28 δH. The temperature dependence of ≤D ranges from 199.5 kHz at 190 K to 221.4 kHz at 350 K. Using the values for ≤D and the relaxation time data, the temperature dependence of the OD rotational correlation time was found to vary from 282 ps at 190 K to 4.5 ps near the boiling point (350 K). Using these correlation times and bulk viscosity data, the Gierer-Wirtz model predicts a supramolecular cluster volume of about 317 A 3 , the approximate volume of a cyclic pentamer cluter of ethanol molecules. The cluster volume was nearly constant from 340 K to about 290 K.

PREFACE: Transport phenomena in proton conducting media Transport phenomena in proton conducting media

NASA Astrophysics Data System (ADS)

Eikerling, Michael

2011-06-01

Proton transport phenomena are of paramount importance for acid-base chemistry, energy transduction in biological organisms, corrosion processes, and energy conversion in electrochemical systems such as polymer electrolyte fuel cells. The relevance for such a plethora of materials and systems, and the ever-lasting fascination with the highly concerted nature of underlying processes drive research across disciplines in chemistry, biology, physics and chemical engineering. A proton never travels alone. Proton motion is strongly correlated with its environment, usually comprised of an electrolyte and a solid or soft host material. For the transport in nature's most benign proton solvent and shuttle, water that is, insights from ab initio simulations, matured over the last 15 years, have furnished molecular details of the structural diffusion mechanism of protons. Excess proton movement in water consists of sequences of Eigen-Zundel-Eigen transitions, triggered by hydrogen bond breaking and making in the surrounding water network. Nowadays, there is little debate about the validity of this mechanism in water, which bears a stunning resemblance to the basic mechanistic picture put forward by de Grotthuss in 1806. While strong coupling of an excess proton with degrees of freedom of solvent and host materials facilitates proton motion, this coupling also creates negative synergies. In general, proton mobility in biomaterials and electrochemical proton conducting media is highly sensitive to the abundance and structure of the proton solvent. In polymer electrolyte membranes, in which protons are bound to move in nano-sized water-channels, evaporation of water or local membrane dehydration due to electro-osmotic coupling are well-known phenomena that could dramatically diminish proton conductivity. Contributions in this special issue address various vital aspects of the concerted nature of proton motion and they elucidate important structural and dynamic effects of solvent, charge-bearing species at interfaces and porous host materials on proton transport properties. As a common thread, articles in this special issue contribute to understanding the functionality provided by complex materials, beyond hydrogen bond fluctuations in water. The first group of articles (Smirnov et al, Henry et al, Medvedev and Stuchebrukhov) elucidates various aspects of the impact of local structural fluctuations, hydrogen bonding and long-range electrostatic forces on proton transfer across and at the surface of mitochondrial membranes. The second group of articles (Ilhan and Spohr, Allahyarov et al and Idupulapati et al) employ molecular dynamics simulations to rationalize vital dependencies of proton transport mechanisms in aqueous-based polymer electrolyte membranes on the nanoporous, phase-separated ionomer morphology, and on the level of hydration. The articles by Gebel et al, Boillat et al, and Aleksandrova et al employ small angle neutron scattering, neutron radiography, and electrochemical atomic force microscopy, respectively, to obtain detailed insights into the kinetics of water sorption, water distribution, water transport properties, as well as spatial maps of proton conductivity in fuel cell membranes. The contribution of Paschos et al provides a comprehensive review of phosphate-based solid state protonic conductors for intermediate temperature fuel cells. The topic of proton conductive materials for high-temperature, water-free operation of fuel cells is continued in the article of Verbraeken et al which addresses synthesis and characterization of a proton conducting perovskite. The guest editor wishes to acknowledge and thank all contributing authors for their commitment to this special issue. Moreover, I would like to thank the staff at IOP Publishing for coordinating submission and refereeing processes. Finally, for the readers, I hope that this special issue will be a valuable and stimulating source of insights into the versatile and eminently important field of transport phenomena in proton conducting media. Complex dynamics of fluids in disordered and crowded environments contents Electrostatic models of electron-driven proton transfer across a lipid membrane Anatoly Yu Smirnov, Lev G Mourokh and Franco Nori Molecular basis of proton uptake in single and double mutants of cytochrome c oxidase Rowan M Henry, David Caplan, Elisa Fadda and Régis Pomès Proton diffusion along biological membranes E S Medvedev and A A Stuchebrukhov Ab initio molecular dynamics of proton networks in narrow polymer electrolyte pores Mehmet A Ilhan and Eckhard Spohr A simulation study of field-induced proton-conduction pathways in dry ionomers Elshad Allahyarov, Philip L Taylor and Hartmut Löwen Molecular structure and transport dynamics in perfluoro sulfonyl imide membranes Nagesh Idupulapati, Ram Devanathan and Michel Dupuis The kinetics of water sorption in Nafion membranes: a small-angle neutron scattering study Gérard Gebel, Sandrine Lyonnard, Hakima Mendil-Jakani and Arnaud Morin Using 2H labeling with neutron radiography for the study of solid polymer electrolyte water transport properties P Boillat, P Oberholzer, B C Seyfang, A Kästner, R Perego, G G Scherer, E H Lehmann and A Wokaun Spatial distribution and dynamics of proton conductivity in fuel cell membranes: potential and limitations of electrochemical atomic force microscopy measurements E Aleksandrova, S Hink, R Hiesgen and E Roduner A review on phosphate based, solid state, protonic conductors for intermediate temperature fuel cells O Paschos, J Kunze, U Stimming and F Maglia A structural study of the proton conducting B-site ordered perovskite Ba3Ca1.18Ta1.82O8.73 Maarten C Verbraeken, Hermenegildo A L Viana, Philip Wormald and John T S Irvine

Dielectric 1/f noise of proton glass on a hydrated protein surface

NASA Astrophysics Data System (ADS)

Careri, Giorgio; Consolini, Giuseppe

2000-09-01

From nonexponentiality of dielectric relaxation detected in hydrated lysozyme powder we evaluate the power spectrum x2ω of the fluctuating dipole moment x¯2 of one macromolecule, due to the glass of protons migrating on the protein surface. Near room temperature, the contribution to the total dipole moment by the integrated strength of the 1/fα noise in the frequency range from 104 to 106 Hz, is well consistent with early Kirkwood's predictions in solution and more recent computations. The biochemical significance of the nonequilibrium region near the Vogel-Fulcher temperature T0~268 K calls for further investigations.

Pasta Nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

NASA Astrophysics Data System (ADS)

Caplan, Matthew; Horowitz, Charles; da Silva Schneider, Andre; Berry, Donald

2014-09-01

We simulate the decompression of cold dense nuclear matter, near the nuclear saturation density, in order to study the role of nuclear pasta in r-process nucleosynthesis in neutron star mergers. Our simulations are performed using a classical molecular dynamics model with 51 200 and 409 600 nucleons, and are run on GPUs. We expand our simulation region to decompress systems from initial densities of 0.080 fm-3 down to 0.00125 fm-3. We study proton fractions of YP = 0.05, 0.10, 0.20, 0.30, and 0.40 at T = 0.5, 0.75, and 1 MeV. We calculate the composition of the resulting systems using a cluster algorithm. This composition is in good agreement with nuclear statistical equilibrium models for temperatures of 0.75 and 1 MeV. However, for proton fractions greater than YP = 0.2 at a temperature of T = 0.5 MeV, the MD simulations produce non-equilibrium results with large rod-like nuclei. Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.

In-Situ Measurement of High-Temperature Proton Exchange Membrane Fuel Cell Stack Using Flexible Five-in-One Micro-Sensor

PubMed Central

Lee, Chi-Yuan; Weng, Fang-Bor; Kuo, Yzu-Wei; Tsai, Chao-Hsuan; Cheng, Yen-Ting; Cheng, Chih-Kai; Lin, Jyun-Ting

2016-01-01

In the chemical reaction that proceeds in a high-temperature proton exchange membrane fuel cell stack (HT-PEMFC stack), the internal local temperature, voltage, pressure, flow and current nonuniformity may cause poor membrane material durability and nonuniform fuel distribution, thus influencing the performance and lifetime of the fuel cell stack. In this paper micro-electro-mechanical systems (MEMS) are utilized to develop a high-temperature electrochemical environment-resistant five-in-one micro-sensor embedded in the cathode channel plate of an HT-PEMFC stack, and materials and process parameters are appropriately selected to protect the micro-sensor against failure or destruction during long-term operation. In-situ measurement of the local temperature, voltage, pressure, flow and current distributions in the HT-PEMFC stack is carried out. This integrated micro-sensor has five functions, and is favorably characterized by small size, good acid resistance and temperature resistance, quick response, real-time measurement, and the goal is being able to be put in any place for measurement without affecting the performance of the battery. PMID:27763559

In-Situ Measurement of High-Temperature Proton Exchange Membrane Fuel Cell Stack Using Flexible Five-in-One Micro-Sensor.

PubMed

Lee, Chi-Yuan; Weng, Fang-Bor; Kuo, Yzu-Wei; Tsai, Chao-Hsuan; Cheng, Yen-Ting; Cheng, Chih-Kai; Lin, Jyun-Ting

2016-10-18

In the chemical reaction that proceeds in a high-temperature proton exchange membrane fuel cell stack (HT-PEMFC stack), the internal local temperature, voltage, pressure, flow and current nonuniformity may cause poor membrane material durability and nonuniform fuel distribution, thus influencing the performance and lifetime of the fuel cell stack. In this paper micro-electro-mechanical systems (MEMS) are utilized to develop a high-temperature electrochemical environment-resistant five-in-one micro-sensor embedded in the cathode channel plate of an HT-PEMFC stack, and materials and process parameters are appropriately selected to protect the micro-sensor against failure or destruction during long-term operation. In-situ measurement of the local temperature, voltage, pressure, flow and current distributions in the HT-PEMFC stack is carried out. This integrated micro-sensor has five functions, and is favorably characterized by small size, good acid resistance and temperature resistance, quick response, real-time measurement, and the goal is being able to be put in any place for measurement without affecting the performance of the battery.

SSH2S: Hydrogen storage in complex hydrides for an auxiliary power unit based on high temperature proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Baricco, Marcello; Bang, Mads; Fichtner, Maximilian; Hauback, Bjorn; Linder, Marc; Luetto, Carlo; Moretto, Pietro; Sgroi, Mauro

2017-02-01

The main objective of the SSH2S (Fuel Cell Coupled Solid State Hydrogen Storage Tank) project was to develop a solid state hydrogen storage tank based on complex hydrides and to fully integrate it with a High Temperature Proton Exchange Membrane (HT-PEM) fuel cell stack. A mixed lithium amide/magnesium hydride system was used as the main storage material for the tank, due to its high gravimetric storage capacity and relatively low hydrogen desorption temperature. The mixed lithium amide/magnesium hydride system was coupled with a standard intermetallic compound to take advantage of its capability to release hydrogen at ambient temperature and to ensure a fast start-up of the system. The hydrogen storage tank was designed to feed a 1 kW HT-PEM stack for 2 h to be used for an Auxiliary Power Unit (APU). A full thermal integration was possible thanks to the high operation temperature of the fuel cell and to the relative low temperature (170 °C) for hydrogen release from the mixed lithium amide/magnesium hydride system.

Target depth dependence of damage rate in metals by 150 MeV proton irradiation

NASA Astrophysics Data System (ADS)

Yoshiie, T.; Ishi, Y.; Kuriyama, Y.; Mori, Y.; Sato, K.; Uesugi, T.; Xu, Q.

2015-01-01

A series of irradiation experiments with 150 MeV protons was performed. The relationship between target depth (or shield thickness) and displacement damage during proton irradiation was obtained by in situ electrical resistance measurements at 20 K. Positron annihilation lifetime measurements were also performed at room temperature after irradiation, as a function of the target thickness. The displacement damage was found to be high close to the beam incident surface area, and decreased with increasing target depth. The experimental results were compared with damage production calculated with an advanced Monte Carlo particle transport code system (PHITS).

Advanced Materials for PEM-Based Fuel Cell Systems

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

James E. McGrath; Donald G. Baird; Michael von Spakovsky

2005-10-26

Proton exchange membrane fuel cells (PEMFCs) are quickly becoming attractive alternative energy sources for transportation, stationary power, and small electronics due to the increasing cost and environmental hazards of traditional fossil fuels. Two main classes of PEMFCs include hydrogen/air or hydrogen/oxygen fuel cells and direct methanol fuel cells (DMFCs). The current benchmark membrane for both types of PEMFCs is Nafion, a perfluorinated sulfonated copolymer made by DuPont. Nafion copolymers exhibit good thermal and chemical stability, as well as very high proton conductivity under hydrated conditions at temperatures below 80 degrees C. However, application of these membranes is limited due tomore » their high methanol permeability and loss of conductivity at high temperatures and low relative humidities. These deficiencies have led to the search for improved materials for proton exchange membranes. Potential PEMs should have good thermal, hydrolytic, and oxidative stability, high proton conductivity, selective permeability, and mechanical durability over long periods of time. Poly(arylene ether)s, polyimides, polybenzimidazoles, and polyphenylenes are among the most widely investigated candidates for PEMs. Poly(arylene ether)s are a promising class of proton exchange membranes due to their excellent thermal and chemical stability and high glass transition temperatures. High proton conductivity can be achieved through post-sulfonation of poly(arylene ether) materials, but this most often results in very high water sorption or even water solubility. Our research has shown that directly polymerized poly(arylene ether) copolymers show important advantages over traditional post-sulfonated systems and also address the concerns with Nafion membranes. These properties were evaluated and correlated with morphology, structure-property relationships, and states of water in the membranes. Further improvements in properties were achieved through incorporation of inorganic fillers, such as phosphotungstic acid and zirconium hydrogen phosphate. Block copolymers were also studied due to the possibility to achieve a desired combination of homopolymer properties as well as the unique morphologies that are possible with block copolymers. Bezoyl substituted poly(p-phenylene) blocks were combined with poly(arylene ether) blocks to merge the structural rigidity of the poly(p-phenylene) with the ductility and high protonic conductivity of the poly(arylene ether)s. As evidenced by our many refereed publications and preprints, the research that we have conducted over the past several years has made a valuable and significant contribution to the literature and to the state of understanding of proton exchange membranes. Our early efforts at scale-up have suggested that the directly polymerized disulfonated poly(arylene ether sulfone) copolymers are commercially viable alternatives for proton exchange membranes. A new process for bipolar plates was developed and is described. An important single domain PEMFC model was developed and is documented in herein.« less

Preparation, characterization and application of novel proton conducting ceramics

NASA Astrophysics Data System (ADS)

Wang, Siwei

Due to the immediate energy shortage and the requirement of environment protection nowadays, the efficient, effective and environmental friendly use of current energy sources is urgent. Energy conversion and storage is thus an important focus both for industry and academia. As one of the hydrogen energy related materials, proton conducting ceramics can be applied in solid oxide fuel cells and steam electrolysers, as well as high temperature hydrogen separation membranes and hydrogen sensors. For most of the practical applications, both high proton conductivity and chemical stability are desirable. However, the state-of-the-art proton conducting ceramics are facing great challenges in simultaneously fulfilling conductivity and stability requirements for practical applications. Consequently, understanding the properties for the proton conducting ceramics and developing novel materials that possess both high proton conductivity and enhanced chemical stability have both scientific and practical significances. The objective of this study is to develop novel proton conducting ceramics, either by evaluating the doping effects on the state-of-the-art simple perovskite structured barium cerates, or by investigating novel complex perovskite structured Ba3Ca1.18Nb1.82O 9-delta based proton conductors as potential proton conducting ceramics with improved proton conductivity and enhanced chemical stability. Different preparation methods were compared, and their influence on the structure, including the bulk and grain boundary environment has been investigated. In addition, the effects of microstructure on the electrical properties of the proton conducting ceramics have also been characterized. The solid oxide fuel cell application for the proton conducting ceramics performed as electrolyte membranes has been demonstrated.

Vortex dynamics in β-FeSe single crystals: effects of proton irradiation and small inhomogeneous stress

NASA Astrophysics Data System (ADS)

Amigó, M. L.; Haberkorn, N.; Pérez, P.; Suárez, S.; Nieva, G.

2017-12-01

We report on the critical current density J c and the vortex dynamics of pristine and 3 MeV proton irradiated (cumulative dose equal to 2× {10}16 cm-2) β-FeSe single crystals. We also analyze a remarkable dependence of the superconducting critical temperature T c, J c and the flux creep rate S on the sample mounting method. Free-standing crystals present T c = 8.4(1) K, which increases to 10.5(1) K when they are fixed to the sample holder by embedding them with GE-7031 varnish. On the other hand, the irradiation has a marginal effect on T c. The pinning scenario can be ascribed to twin boundaries and random point defects. We find that the main effect of irradiation is to increase the density of random point defects, while the embedding mainly reduces the density of twin boundaries. Pristine and irradiated crystals present two outstanding features in the temperature dependence of the flux creep rate: S(T) presents large values at low temperatures, which can be attributed to small pinning energies, and a plateau at intermediate temperatures, which can be associated with glassy relaxation. From Maley analysis, we observe that the characteristic glassy exponent μ changes from ˜1.7 to 1.35-1.4 after proton irradiation.

Hydrogen Donor-Acceptor Fluctuations from Kinetic Isotope Effects: A Phenomenological Model

PubMed Central

Roston, Daniel; Cheatum, Christopher M.; Kohen, Amnon

2012-01-01

Kinetic isotope effects (KIEs) and their temperature dependence can probe the structural and dynamic nature of enzyme-catalyzed proton or hydride transfers. The molecular interpretation of their temperature dependence requires expensive and specialized QM/MM calculations to provide a quantitative molecular understanding. Currently available phenomenological models use a non-adiabatic assumption that is not appropriate for most hydride and proton-transfer reactions, while others require more parameters than the experimental data justify. Here we propose a phenomenological interpretation of KIEs based on a simple method to quantitatively link the size and temperature dependence of KIEs to a conformational distribution of the catalyzed reaction. The present model assumes adiabatic hydrogen tunneling, and by fitting experimental KIE data, the model yields a population distribution for fluctuations of the distance between donor and acceptor atoms. Fits to data from a variety of proton and hydride transfers catalyzed by enzymes and their mutants, as well as non-enzymatic reactions, reveal that steeply temperature-dependent KIEs indicate the presence of at least two distinct conformational populations, each with different kinetic behaviors. We present the results of these calculations for several published cases and discuss how the predictions of the calculations might be experimentally tested. The current analysis does not replace molecular quantum mechanics/molecular mechanics (QM/MM) investigations, but it provides a fast and accessible way to quantitatively interpret KIEs in the context of a Marcus-like model. PMID:22857146

Modeling solubility, acid-base properties and activity coefficients of amoxicillin, ampicillin and (+)6-aminopenicillanic acid, in NaCl(aq) at different ionic strengths and temperatures.

PubMed

Crea, Francesco; Cucinotta, Daniela; De Stefano, Concetta; Milea, Demetrio; Sammartano, Silvio; Vianelli, Giuseppina

2012-11-20

The total solubility of three penicillin derivatives was determined, in pure water and NaCl aqueous solutions at different salt concentrations (from ∼0.15 to 1.0 mol L(-1) for ampicillin and amoxicillin, and from ∼0.05 to 2.0 mol L(-1) for (+)6-aminopenicillanic acid), using the shake-flask method for generating the saturated solutions, followed by potentiometric analysis. The knowledge of the pH of solubilization and of the protonation constants determined in the same experimental conditions, allowed us to calculate, by means of the mass balance equations, the solubility of the neutral species at different ionic strength values, to model its dependence on the salt concentration and to determine the corresponding values at infinite dilution. The salting parameter and the activity coefficients of the neutral species were calculated by the Setschenow equation. The protonation constants of ampicillin and amoxicillin, determined at different temperatures (from T=288.15 to 318.15K), from potentiometric and spectrophotometric measurements, were used to calculate, by means of the Van't Hoff equation, the temperature coefficients at different ionic strength values and the corresponding protonation entropies. The protonation enthalpies of the (+)6-aminopenicillanic acid were determined by isoperibol calorimetric titrations at T=298.15K and up to I=2.0 mol L(-1). The dependence of the protonation constants on ionic strength was modeled by means of the Debye-Hückel and SIT (Specific ion Interaction Theory) approaches, and the specific interaction parameters of the ionic species were determined. The hydrolysis of the β-lactam ring was studied by spectrophotometric and H NMR investigations as a function of pH, ionic strength and time. Potentiometric measurements carried out on the hydrolyzed (+)6-aminopenicillanic acid allowed us to highlight that the opened and the closed β-lactam forms of the (+)6-aminopenicillanic acid have quite different acid-base properties. An analysis of literature solubility, protonation constants, enthalpies and activity coefficients is reported too. Copyright © 2012 Elsevier B.V. All rights reserved.

Proton emission from cone-in-shell fast-ignition experiments at Omega

NASA Astrophysics Data System (ADS)

Sinenian, N.; Theobald, W.; Frenje, J. A.; Stoeckl, C.; Séguin, F. H.; Li, C. K.; Petrasso, R. D.; Stephens, R. B.

2012-11-01

Measurements of energetic protons from cone-in-shell fast-igniton implosions at Omega have been conducted. In these experiments, charged-particle spectrometers were used to measure a significant population (>1013) of energetic protons (7.5 MeV max.), indicating the presence of strong electric fields. These energetic protons, observed in directions both transverse and forward relative to the direction of the short-pulse laser beam, have been used to study aspects of coupling efficiency of the petawatt fast-ignitior beam. Approximately 5% of the laser energy coupled to hot electrons was lost to fast ions. Forward going protons were less energetic and showed no dependence on laser intensity or whether the cone tip was intact when the short-pulse laser was fired. Maximum energies of protons emitted transverse to the cone-in-shell target scale with incident on-target laser intensity (2-6×1018W-cm-2), as described by the ponderomotive scaling (∝I1/2). It is shown that these protons are accelerated from the entire cone, rather than from the cone tip alone. These protons were used to estimate the lower limit on the hot-electron temperature, which was found to be hotter than the ponderomotive scaling by factors of 2-3.

Stability of proton-bound clusters of alkyl alcohols, aldehydes and ketones in Ion Mobility Spectrometry.

PubMed

Jurado-Campos, Natividad; Garrido-Delgado, Rocío; Martínez-Haya, Bruno; Eiceman, Gary A; Arce, Lourdes

2018-08-01

Significant substances in emerging applications of ion mobility spectrometry such as breath analysis for clinical diagnostics and headspace analysis for food purity include low molar mass alcohols, ketones, aldehydes and esters which produce mobility spectra containing protonated monomers and proton-bound dimers. Spectra for all n- alcohols, aldehydes and ketones from carbon number three to eight exhibited protonated monomers and proton-bound dimers with ion drift times of 6.5-13.3 ms at ambient pressure and from 35° to 80 °C in nitrogen. Only n-alcohols from 1-pentanol to 1-octanol produced proton-bound trimers which were sufficiently stable to be observed at these temperatures and drift times of 12.8-16.3 ms. Polar functional groups were protected in compact structures in ab initio models for proton-bound dimers of alcohols, ketones and aldehydes. Only alcohols formed a V-shaped arrangement for proton-bound trimers strengthening ion stability and lifetime. In contrast, models for proton-bound trimers of aldehydes and ketones showed association of the third neutral through weak, non-specific, long-range interactions consistent with ion dissociation in the ion mobility drift tube before arriving at the detector. Collision cross sections derived from reduced mobility coefficients in nitrogen gas atmosphere support the predicted ion structures and approximate degrees of hydration. Copyright © 2018 Elsevier B.V. All rights reserved.

Hybrid sulfur cycle operation for high-temperature gas-cooled reactors

DOEpatents

Gorensek, Maximilian B

2015-02-17

A hybrid sulfur (HyS) cycle process for the production of hydrogen is provided. The process uses a proton exchange membrane (PEM) SO.sub.2-depolarized electrolyzer (SDE) for the low-temperature, electrochemical reaction step and a bayonet reactor for the high-temperature decomposition step The process can be operated at lower temperature and pressure ranges while still providing an overall energy efficient cycle process.

A new screening method for flunitrazepam in vodka and tequila by fluorescence spectroscopy.

PubMed

Leesakul, Nararak; Pongampai, Sirintip; Kanatharana, Proespichaya; Sudkeaw, Pravit; Tantirungrotechai, Yuthana; Buranachai, Chittanon

2013-01-01

A new screening method for flunitrazepam in colourless alcoholic beverages based on a spectroscopic technique is proposed. Absorption and steady-state fluorescence of flunitrazepam and its protonated form with various acids were investigated. The redshift of the wavelength of maximum absorption was distinctively observed in protonated flunitrazepam. An emissive fluorescence at 472 nm was detected in colourless spirits (vodka and tequila) at room temperature. 2-M perchloric acid was the most appropriated proton source. By using electron ionization mass spectrometry and time-dependent density functional theory calculations, the possible structure of protonated flunitrazepam was identified to be 2-nitro-N-methylacridone, an acridone derivative as opposed to 2-methylamino-5-nitro-2'-fluorobenzophenone, a benzophenone derivative. Copyright © 2012 John Wiley & Sons, Ltd.

CO2 laser annealing of 50-microns-thick silicon solar cells

NASA Technical Reports Server (NTRS)

Walker, F. E.

1979-01-01

A test program is conducted to determine thin solar cell annealing effects using a laser energy source. A CO2 continuous-wave laser was used in annealing experiments on 50 micrometers-thick silicon solar cells after proton irradiation. Test cells were irradiated to a fluence of 1.0 x 10 to the 12th power protons/sq cm with 1.9 MeV protons. After irradiation, those cells receiving full proton dosage were degraded by an average of 30% in output power. In annealing tests laser beam exposure times on the solar cell varied from 2 seconds to 16 seconds reaching cell temperatures of from 400 C to 500 C. Under those conditions annealing test results showed recovery in cell output power of from 33% to 90%.

Towards fast and accurate temperature mapping with proton resonance frequency-based MR thermometry

PubMed Central

Yuan, Jing; Mei, Chang-Sheng; Panych, Lawrence P.; McDannold, Nathan J.; Madore, Bruno

2012-01-01

The capability to image temperature is a very attractive feature of MRI and has been actively exploited for guiding minimally-invasive thermal therapies. Among many MR-based temperature-sensitive approaches, proton resonance frequency (PRF) thermometry provides the advantage of excellent linearity of signal with temperature over a large temperature range. Furthermore, the PRF shift has been shown to be fairly independent of tissue type and thermal history. For these reasons, PRF method has evolved into the most widely used MR-based thermometry method. In the present paper, the basic principles of PRF-based temperature mapping will be reviewed, along with associated pulse sequence designs. Technical advancements aimed at increasing the imaging speed and/or temperature accuracy of PRF-based thermometry sequences, such as image acceleration, fat suppression, reduced field-of-view imaging, as well as motion tracking and correction, will be discussed. The development of accurate MR thermometry methods applicable to moving organs with non-negligible fat content represents a very challenging goal, but recent developments suggest that this goal may be achieved. If so, MR-guided thermal therapies may be expected to play an increasingly-important therapeutic and palliative role, as a minimally-invasive alternative to surgery. PMID:22773966

Sulfonated graphene oxide/nafion composite membrane for vanadium redox flow battery.

PubMed

Kim, Byung Guk; Han, Tae Hee; Cho, Chang Gi

2014-12-01

Nafion is the most frequently used as the membrane material due to its good proton conductivity, and excellent chemical and mechanical stabilities. But it is known to have poor barrier property due to its well-developed water channels. In order to overcome this drawback, graphene oxide (GO) derivatives were introduced for Nafion composite membranes. Sulfonated graphene oxide (sGO) was prepared from GO. Both sGO and GO were treated each with phenyl isocyanate and transformed into corresponding isGO and iGO in order to promote miscibility with Nafion. Then composite membranes were obtained, and the adaptability as a membrane for vanadium redox flow battery (VRFB) was investigated in terms of proton conductivity and vanadium permeability. Compared to a pristine Nafion, proton conductivities of both isGO/Nafion and iGO/Nafion membranes showed less temperature sensitivity. Both membranes also showed quite lower vanadium permeability at room temperature. Selectivity of the membrane was the highest for isGO/Nafion and the lowest for the pristine Nafion.

An Unusual Coronal Mass Ejection: First Solar Wind Electron, Proton, Alpha Monitor (SWEPAM) Results from the Advanced Composition Explorer. Appendix 6

NASA Technical Reports Server (NTRS)

McComas, D. J.; Bame, S. J.; Barker, P. L.; Delapp, D. M.; Gosling, J. T.; Skoug, R. M.; Tokar, R. L.; Riley, P.; Feldman, W. C.; Santiago, E.

2001-01-01

This paper reports the first scientific results from the Solar Wind Electron Proton Alpha Monitor (SWEPAM) instrument on board the Advanced Composition Explorer (ACE) spacecraft. We analyzed a coronal mass ejection (CME) observed in the solar wind using data from early February, 1998. This event displayed several of the common signatures of CMEs, such as counterstreaming halo electrons and depressed ion and electron temperatures, as well as some unusual features. During a portion of the CME traversal, SWEPAM measured a very large helium to proton abundance ratio. Other heavy ions, with a set of ionization states consistent with normal (1 to 2x10(exp 6) K) coronal temperatures, were proportionately enhanced at this time. These observations suggest a source for at least some of the CME material, where heavy ions are initially concentrated relative to hydrogen and then accelerated up into the solar wind, independent of their mass and first ionization potential.

Experimental study of fusion neutron and proton yields produced by petawatt-laser-irradiated D₂-³He or CD₄-³He clustering gases.

PubMed

Bang, W; Barbui, M; Bonasera, A; Quevedo, H J; Dyer, G; Bernstein, A C; Hagel, K; Schmidt, K; Gaul, E; Donovan, M E; Consoli, F; De Angelis, R; Andreoli, P; Barbarino, M; Kimura, S; Mazzocco, M; Natowitz, J B; Ditmire, T

2013-09-01

We report on experiments in which the Texas Petawatt laser irradiated a mixture of deuterium or deuterated methane clusters and helium-3 gas, generating three types of nuclear fusion reactions: D(d,^{3}He)n, D(d,t)p, and ^{3}He(d,p)^{4}He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model using known cross sections and measured plasma parameters. Within our measurement errors, the fusion products were isotropically distributed. Plasma temperatures, important for the cross sections, were determined by two independent methods: (1) deuterium ion time of flight and (2) utilizing the ratio of neutron yield to proton yield from D(d,^{3}He)n and ^{3}He(d,p)^{4}He reactions, respectively. This experiment produced the highest ion temperature ever achieved with laser-irradiated deuterium clusters.

A parameter study of the two-fluid solar wind

NASA Technical Reports Server (NTRS)

Sandbaek, Ornulf; Leer, Egil; Holzer, Thomas E.

1992-01-01

A two-fluid model of the solar wind was introduced by Sturrock and Hartle (1966) and Hartle and Sturrock (1968). In these studies the proton energy equation was integrated neglecting the heat conductive term. Later several authors solved the equations for the two-fluid solar wind model keeping the proton heat conductive term. Methods where the equations are integrated simultaneously outward and inward from the critical point were used. The equations were also integrated inward from a large heliocentric distance. These methods have been applied to cases with low coronal base electron densities and high base temperatures. In this paper we present a method of integrating the two-fluid solar wind equations using an iteration procedure where the equations are integrated separately and the proton flux is kept constant during the integrations. The technique is applicable for a wide range of coronal base densities and temperatures. The method is used to carry out a parameter study of the two-fluid solar wind.

A novel layered perovskite cathode for proton conducting solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Ding, Hanping; Xue, Xingjian; Liu, Xingqin; Meng, Guangyao

BaZr 0.1Ce 0.7Y 0.2O 3- δ (BZCY7) exhibits adequate proton conductivity as well as sufficient chemical and thermal stability over a wide range of SOFC operating conditions, while layered SmBa 0.5Sr 0.5Co 2O 5+ δ (SBSC) perovskite demonstrates advanced electrochemical properties based on doped ceria electrolyte. This research fully takes advantage of these advanced properties and develops novel protonic ceramic membrane fuel cells (PCMFCs) of Ni-BZCY7|BZCY7|SBSC. The results show that the open-circuit potential of 1.015 V and maximum power density of 533 mW cm -2 are achieved at 700 °C. With temperature increase, the total cell resistance decreases, among which electrolyte resistance becomes increasingly dominant over polarization resistance. The results also indicate that SBSC perovskite cathode is a good candidate for intermediate temperature PCMFC development, while the developed Ni-BZCY7|BZCY7|SBSC cell is a promising functional material system for next generation SOFCs.

Two-component Fermi-liquid theory - Equilibrium properties of liquid metallic hydrogen

NASA Technical Reports Server (NTRS)

Oliva, J.; Ashcroft, N. W.

1981-01-01

It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.

Determination of regional brain temperature using proton magnetic resonance spectroscopy to assess brain-body temperature differences in healthy human subjects.

PubMed

Childs, Charmaine; Hiltunen, Yrjö; Vidyasagar, Rishma; Kauppinen, Risto A

2007-01-01

Proton magnetic resonance spectroscopy ((1)H MRS) was used to determine brain temperature in healthy volunteers. Partially water-suppressed (1)H MRS data sets were acquired at 3T from four different gray matter (GM)/white matter (WM) volumes. Brain temperatures were determined from the chemical-shift difference between the CH(3) of N-acetyl aspartate (NAA) at 2.01 ppm and water. Brain temperatures in (1)H MRS voxels of 2 x 2 x 2 cm(3) showed no substantial heterogeneity. The volume-averaged temperature from single-voxel spectroscopy was compared with body temperatures obtained from the oral cavity, tympanum, and temporal artery regions. The mean brain parenchyma temperature was 0.5 degrees C cooler than readings obtained from three extra-brain sites (P < 0.01). (1)H MRS imaging (MRSI) data were acquired from a slice encompassing the single-voxel volumes to assess the ability of spectroscopic imaging to determine regional brain temperature within the imaging slice. Brain temperature away from the center of the brain determined by MRSI differed from that obtained by single-voxel MRS in the same brain region, possibly due to a poor line width (LW) in MRSI. The data are discussed in the light of proposed brain-body temperature gradients and the use of (1)H MRSI to monitor brain temperature in pathologies, such as brain trauma.

Effects of target plasma electron-electron collisions on correlated motion of fragmented protons.

PubMed

Barriga-Carrasco, Manuel D

2006-02-01

The objective of the present work is to examined the effects of plasma target electron-electron collisions on H2 + protons traversing it. Specifically, the target is deuterium in a plasma state with temperature Te=10 eV and density n=10(23) cm(-3), and proton velocities are vp=vth, vp=2vth, and vp=3vth, where vth is the electron thermal velocity of the target plasma. Proton interactions with plasma electrons are treated by means of the dielectric formalism. The interactions among close protons through plasma electronic medium are called vicinage forces. It is checked that these forces always screen the Coulomb explosions of the two fragmented protons from the same H2 + ion decreasing their relative distance. They also align the interproton vector along the motion direction, and increase the energy loss of the two protons at early dwell times while for longer times the energy loss tends to the value of two isolated protons. Nevertheless, vicinage forces and effects are modified by the target electron collisions. These collisions enhance the calculated self-stopping and vicinage forces over the collisionless results. Regarding proton correlated motion, when these collisions are included, the interproton vector along the motion direction overaligns at slower proton velocities (vp=vth) and misaligns for faster ones (vp=2vth, vp=3vth). They also contribute to a great extend to increase the energy loss of the fragmented H2 + ion. This later effect is more significant in reducing projectile velocity.

Temperature of the plasmasphere from Van Allen Probes HOPE

NASA Astrophysics Data System (ADS)

Genestreti, K. J.; Goldstein, J.; Corley, G. D.; Farner, W.; Kistler, L. M.; Larsen, B. A.; Mouikis, C. G.; Ramnarace, C.; Skoug, R. M.; Turner, N. E.

2017-01-01

We introduce two novel techniques for estimating temperatures of very low energy space plasmas using, primarily, in situ data from an electrostatic analyzer mounted on a charged and moving spacecraft. The techniques are used to estimate proton temperatures during intervals where the bulk of the ion plasma is well below the energy bandpass of the analyzer. Both techniques assume that the plasma may be described by a one-dimensional E→×B→ drifting Maxwellian and that the potential field and motion of the spacecraft may be accounted for in the simplest possible manner, i.e., by a linear shift of coordinates. The first technique involves the application of a constrained theoretical fit to a measured distribution function. The second technique involves the comparison of total and partial-energy number densities. Both techniques are applied to Van Allen Probes Helium, Oxygen, Proton, and Electron (HOPE) observations of the proton component of the plasmasphere during two orbits on 15 January 2013. We find that the temperatures calculated from these two order-of-magnitude-type techniques are in good agreement with typical ranges of the plasmaspheric temperature calculated using retarding potential analyzer-based measurements—generally between 0.2 and 2 eV (2000-20,000 K). We also find that the temperature is correlated with L shell and hot plasma density and is negatively correlated with the cold plasma density. We posit that the latter of these three relationships may be indicative of collisional or wave-driven heating of the plasmasphere in the ring current overlap region. We note that these techniques may be easily applied to similar data sets or used for a variety of purposes.

Mechanism of the enhancement of the Bohr effect in mammalian hemoglobins by diphosphoglycerate.

PubMed

Riggs, A

1971-09-01

The number of protons released from several mammalian hemoglobins as a consequence of oxygenation is greater in the presence of low concentrations of 2,3-diphosphoglycerate than in its absence. A mechanism for this enhancement of proton release is proposed. The basis of this mechanism is that 2,3-diphosphoglycerate binds primarily between the protonated alpha-NH(2) terminal groups of the two beta chains in deoxyhemoglobin. This binding will shift the ionization equilibria in favor of the protonation of the deoxyhemoglobin. Partial release of 2,3-diphosphoglycerate upon oxygenation of the hemoglobin is then accompanied by a release of protons. The apparent enthalpy of diphosphoglycerate binding appears to be close to zero. The previously reported temperature dependence appears to be due entirely to the associated protonation reaction. If only a single diphosphoglycerate binding site is assumed, the intrinsic association constant is estimated to be 3.9 x 10(5) M(-1) for deoxyhemoglobin and 1.05 x 10(4) M(-1) for oxyhemoglobin at 20 degrees C in 0.1 M NaCl.

Mechanism of the Enhancement of the Bohr Effect in Mammalian Hemoglobins by Diphosphoglycerate

PubMed Central

Riggs, Austen

1971-01-01

The number of protons released from several mammalian hemoglobins as a consequence of oxygenation is greater in the presence of low concentrations of 2,3-diphosphoglycerate than in its absence. A mechanism for this enhancement of proton release is proposed. The basis of this mechanism is that 2,3-diphosphoglycerate binds primarily between the protonated α-NH2 terminal groups of the two β chains in deoxyhemoglobin. This binding will shift the ionization equilibria in favor of the protonation of the deoxyhemoglobin. Partial release of 2,3-diphosphoglycerate upon oxygenation of the hemoglobin is then accompanied by a release of protons. The apparent enthalpy of diphosphoglycerate binding appears to be close to zero. The previously reported temperature dependence appears to be due entirely to the associated protonation reaction. If only a single diphosphoglycerate binding site is assumed, the intrinsic association constant is estimated to be 3.9 × 105 M-1 for deoxyhemoglobin and 1.05 × 104 M-1 for oxyhemoglobin at 20°C in 0.1 M NaCl. PMID:5289365

FIRE HOSE INSTABILITY DRIVEN BY ALPHA PARTICLE TEMPERATURE ANISOTROPY

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

Matteini, L.; Schwartz, S. J.; Hellinger, P.

We investigate properties of a solar wind-like plasma, including a secondary alpha particle population exhibiting a parallel temperature anisotropy with respect to the background magnetic field, using linear and quasi-linear predictions and by means of one-dimensional hybrid simulations. We show that anisotropic alpha particles can drive a parallel fire hose instability analogous to that generated by protons, but that, remarkably, can also be triggered when the parallel plasma beta of alpha particles is below unity. The wave activity generated by the alpha anisotropy affects the evolution of the more abundant protons, leading to their anisotropic heating. When both ion speciesmore » have sufficient parallel anisotropies, both of them can drive the instability, and we observe the generation of two distinct peaks in the spectra of the fluctuations, with longer wavelengths associated to alphas and shorter ones to protons. If a non-zero relative drift is present, the unstable modes propagate preferentially in the direction of the drift associated with the unstable species. The generated waves scatter particles and reduce their temperature anisotropy to a marginally stable state, and, moreover, they significantly reduce the relative drift between the two ion populations. The coexistence of modes excited by both species leads to saturation of the plasma in distinct regions of the beta/anisotropy parameter space for protons and alpha particles, in good agreement with in situ solar wind observations. Our results confirm that fire hose instabilities are likely at work in the solar wind and limit the anisotropy of different ion species in the plasma.« less

Neutrinos in astrophysics and cosmology

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

Balantekin, A. B.

Neutrinos play a crucial role in many aspects of astrophysics and cosmology. Since they control the electron fraction, or equivalently neutron-to-proton ratio, neutrino properties impact yields of r-process nucleosynthesis. Similarly the weak decoupling temperature in the Big Bang Nucleosynthesis epoch is exponentially dependent on the neutron-to-proton ratio. In these conference proceedings, I briefly summarize some of the recent work exploring the role of neutrinos in astrophysics and cosmology.

COLLABORATIVE RESEARCH AND DEVELOPMENT (CR&D) Delivery Order 0067: Molecular Simulations for Hydrated Polymer Fuel Membranes

DTIC Science & Technology

2007-11-01

proton transfer. 1. INTRODUCTION While polymer electrolyte membrane fuel cells ( PEMFCs ) hold out the possibility for providing several important...Among the broader aims of the research is to develop PEMFC systems which can operate at higher temperatures than presently achievable while still...efforts have provided insight into the mechanisms which enable proton conduction in PEMFCs . Hydrated membranes are two-phase systems, an

Humidity Effects on Fragmentation in Plasma-Based Ambient Ionization Sources

NASA Astrophysics Data System (ADS)

Newsome, G. Asher; Ackerman, Luke K.; Johnson, Kevin J.

2016-01-01

Post-plasma ambient desorption/ionization (ADI) sources are fundamentally dependent on surrounding water vapor to produce protonated analyte ions. There are two reports of humidity effects on ADI spectra. However, it is unclear whether humidity will affect all ADI sources and analytes, and by what mechanism humidity affects spectra. Flowing atmospheric pressure afterglow (FAPA) ionization and direct analysis in real time (DART) mass spectra of various surface-deposited and gas-phase analytes were acquired at ambient temperature and pressure across a range of observed humidity values. A controlled humidity enclosure around the ion source and mass spectrometer inlet was used to create programmed humidity and temperatures. The relative abundance and fragmentation of molecular adduct ions for several compounds consistently varied with changing ambient humidity and also were controlled with the humidity enclosure. For several compounds, increasing humidity decreased protonated molecule and other molecular adduct ion fragmentation in both FAPA and DART spectra. For others, humidity increased fragment ion ratios. The effects of humidity on molecular adduct ion fragmentation were caused by changes in the relative abundances of different reagent protonated water clusters and, thus, a change in the average difference in proton affinity between an analyte and the population of water clusters. Control of humidity in ambient post-plasma ion sources is needed to create spectral stability and reproducibility.

Humidity Effects on Fragmentation in Plasma-Based Ambient Ionization Sources.

PubMed

Newsome, G Asher; Ackerman, Luke K; Johnson, Kevin J

2016-01-01

Post-plasma ambient desorption/ionization (ADI) sources are fundamentally dependent on surrounding water vapor to produce protonated analyte ions. There are two reports of humidity effects on ADI spectra. However, it is unclear whether humidity will affect all ADI sources and analytes, and by what mechanism humidity affects spectra. Flowing atmospheric pressure afterglow (FAPA) ionization and direct analysis in real time (DART) mass spectra of various surface-deposited and gas-phase analytes were acquired at ambient temperature and pressure across a range of observed humidity values. A controlled humidity enclosure around the ion source and mass spectrometer inlet was used to create programmed humidity and temperatures. The relative abundance and fragmentation of molecular adduct ions for several compounds consistently varied with changing ambient humidity and also were controlled with the humidity enclosure. For several compounds, increasing humidity decreased protonated molecule and other molecular adduct ion fragmentation in both FAPA and DART spectra. For others, humidity increased fragment ion ratios. The effects of humidity on molecular adduct ion fragmentation were caused by changes in the relative abundances of different reagent protonated water clusters and, thus, a change in the average difference in proton affinity between an analyte and the population of water clusters. Control of humidity in ambient post-plasma ion sources is needed to create spectral stability and reproducibility.

Individual Basepair Stability of DNA and RNA Studied by NMR-Detected Solvent Exchange

PubMed Central

Steinert, Hannah S.; Rinnenthal, Jörg; Schwalbe, Harald

2012-01-01

In this study, we have optimized NMR methodology to determine the thermodynamic parameters of basepair opening in DNA and RNA duplexes by characterizing the temperature dependence of imino proton exchange rates of individual basepairs. Contributions of the nuclear Overhauser effect to exchange rates measured with inversion recovery experiments are quantified, and the influence of intrinsic and external catalysis exchange mechanisms on the imino proton exchange rates is analyzed. Basepairs in DNA and RNA have an approximately equal stability, and the enthalpy and entropy values of their basepair dissociation are correlated linearly. Furthermore, the compensation temperature, Tc, which is derived from the slope of the correlation, coincides with the melting temperature, and duplex unfolding occurs at that temperature where all basepairs are equally thermodynamically stable. The impact of protium-deuterium exchange of the imino hydrogen on the free energy of RNA basepair opening is investigated, and it is found that two A·U basepairs show distinct fractionation factors. PMID:22713572

Carbon composite bipolar plate for high-temperature proton exchange membrane fuel cells (HT-PEMFCs)

NASA Astrophysics Data System (ADS)

Lee, Dongyoung; Lee, Dai Gil

2016-09-01

A carbon/epoxy composite bipolar plate is an ideal substitute for the brittle graphite bipolar plate for lightweight proton exchange membrane fuel cells (PEMFCs) because of its high specific strength and stiffness. However, conventional carbon/epoxy composite bipolar plates are not applicable for high-temperature PEMFCs (HT-PEMFCs) because these systems are operated at higher temperatures than the glass transition temperatures of conventional epoxies. Therefore, in this study, a cyanate ester-modified epoxy is adopted for the development of a carbon composite bipolar plate for HT-PEMFCs. The composite bipolar plate with exposed surface carbon fibers is produced without any surface treatments or coatings to increase the productivity and is integrated with a silicone gasket to reduce the assembly cost. The developed carbon composite bipolar plate exhibits not only superior electrical properties but also high thermo-mechanical properties. In addition, a unit cell test is performed, and the results are compared with those of the conventional graphite bipolar plate.

Real-Time Remote Monitoring of Temperature and Humidity Within a Proton Exchange Membrane Fuel Cell Using Flexible Sensors

PubMed Central

Kuo, Long-Sheng; Huang, Hao-Hsiu; Yang, Cheng-Hao; Chen, Ping-Hei

2011-01-01

This study developed portable, non-invasive flexible humidity and temperature microsensors and an in situ wireless sensing system for a proton exchange membrane fuel cell (PEMFC). The system integrated three parts: a flexible capacitive humidity microsensor, a flexible resistive temperature microsensor, and a radio frequency (RF) module for signal transmission. The results show that the capacitive humidity microsensor has a high sensitivity of 0.83 pF%RH−1 and the resistive temperature microsensor also exhibits a high sensitivity of 2.94 × 10−3 °C−1. The established RF module transmits the signals from the two microsensors. The transmission distance can reach 4 m and the response time is less than 0.25 s. The performance measurements demonstrate that the maximum power density of the fuel cell with and without these microsensors are 14.76 mW·cm−2 and 15.90 mW·cm−2, with only 7.17% power loss. PMID:22164099

Development of a Ne gas target for {sup 22}Na production by proton irradiation

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

Mandal, Bidhan Ch., E-mail: mechbidhan@gmail.com; Pal, Gautam; Barua, Luna

2016-03-15

The article presents the design and development of a neon gas target for the production of {sup 22}Na using a proton beam from the room temperature cyclotron in Variable Energy Cyclotron Centre, Kolkata. The target design is made to handle a beam power of 85 W (17 MeV, 5 μA). The design is based on simulation using the computer code FLUKA for the beam dump and CFD-CFX for target cooling. The target has been successfully used for the production of {sup 22}Na in a 6 day long 17 MeV, 5 μA proton irradiation run.

Holography and hydrodynamics in small systems

NASA Astrophysics Data System (ADS)

Chesler, Paul M.

2016-12-01

Using holographic duality, we present results for the off-center collision of Gaussian wave packets in strongly coupled N = 4 supersymmetric Yang-Mills theory. The wave packets are thin along the collision axis and superficially at least resemble Lorentz contracted colliding protons. The collision results in the formation of a droplet of liquid of size R ∼ 1 /Teff where Teff is the effective temperature, which is the characteristic microscopic scale in strongly coupled plasma. These results demonstrate the applicability of hydrodynamics to microscopically small systems and bolster the notion that hydrodynamics can be applied to heavy-light ion collisions as well as proton-proton collisions.

Modeling torque versus speed, shot noise, and rotational diffusion of the bacterial flagellar motor.

PubMed

Mora, Thierry; Yu, Howard; Wingreen, Ned S

2009-12-11

We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E. coli motor at various pH and temperature conditions. In particular, the dramatic drop of torque at high rotation speeds (the "knee") is shown to arise from saturation of the proton flux. Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads. This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions.

New Measurement of the 1 S -3 S Transition Frequency of Hydrogen: Contribution to the Proton Charge Radius Puzzle

NASA Astrophysics Data System (ADS)

Fleurbaey, Hélène; Galtier, Sandrine; Thomas, Simon; Bonnaud, Marie; Julien, Lucile; Biraben, François; Nez, François; Abgrall, Michel; Guéna, Jocelyne

2018-05-01

We present a new measurement of the 1 S -3 S two-photon transition frequency of hydrogen, realized with a continuous-wave excitation laser at 205 nm on a room-temperature atomic beam, with a relative uncertainty of 9 ×10-13. The proton charge radius deduced from this measurement, rp=0.877 (13 ) fm , is in very good agreement with the current CODATA-recommended value. This result contributes to the ongoing search to solve the proton charge radius puzzle, which arose from a discrepancy between the CODATA value and a more precise determination of rp from muonic hydrogen spectroscopy.

Varying stopping and self-focusing of intense proton beams as they heat solid density matter

NASA Astrophysics Data System (ADS)

Kim, J.; McGuffey, C.; Qiao, B.; Wei, M. S.; Grabowski, P. E.; Beg, F. N.

2016-04-01

Transport of intense proton beams in solid-density matter is numerically investigated using an implicit hybrid particle-in-cell code. Both collective effects and stopping for individual beam particles are included through the electromagnetic fields solver and stopping power calculations utilizing the varying local target conditions, allowing self-consistent transport studies. Two target heating mechanisms, the beam energy deposition and Ohmic heating driven by the return current, are compared. The dependences of proton beam transport in solid targets on the beam parameters are systematically analyzed, i.e., simulations with various beam intensities, pulse durations, kinetic energies, and energy distributions are compared. The proton beam deposition profile and ultimate target temperature show strong dependence on intensity and pulse duration. A strong magnetic field is generated from a proton beam with high density and tight beam radius, resulting in focusing of the beam and localized heating of the target up to hundreds of eV.

Varying stopping and self-focusing of intense proton beams as they heat solid density matter

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

Kim, J.; McGuffey, C., E-mail: cmcguffey@ucsd.edu; Qiao, B.

2016-04-15

Transport of intense proton beams in solid-density matter is numerically investigated using an implicit hybrid particle-in-cell code. Both collective effects and stopping for individual beam particles are included through the electromagnetic fields solver and stopping power calculations utilizing the varying local target conditions, allowing self-consistent transport studies. Two target heating mechanisms, the beam energy deposition and Ohmic heating driven by the return current, are compared. The dependences of proton beam transport in solid targets on the beam parameters are systematically analyzed, i.e., simulations with various beam intensities, pulse durations, kinetic energies, and energy distributions are compared. The proton beam depositionmore » profile and ultimate target temperature show strong dependence on intensity and pulse duration. A strong magnetic field is generated from a proton beam with high density and tight beam radius, resulting in focusing of the beam and localized heating of the target up to hundreds of eV.« less

Global Simulation of Proton Precipitation Due to Field Line Curvature During Substorms

NASA Technical Reports Server (NTRS)

Gilson, M. L.; Raeder, J.; Donovan, E.; Ge, Y. S.; Kepko, L.

2012-01-01

The low latitude boundary of the proton aurora (known as the Isotropy Boundary or IB) marks an important boundary between empty and full downgoing loss cones. There is significant evidence that the IB maps to a region in the magnetosphere where the ion gyroradius becomes comparable to the local field line curvature. However, the location of the IB in the magnetosphere remains in question. In this paper, we show simulated proton precipitation derived from the Field Line Curvature (FLC) model of proton scattering and a global magnetohydrodynamic simulation during two substorms. The simulated proton precipitation drifts equatorward during the growth phase, intensifies at onset and reproduces the azimuthal splitting published in previous studies. In the simulation, the pre-onset IB maps to 7-8 RE for the substorms presented and the azimuthal splitting is caused by the development of the substorm current wedge. The simulation also demonstrates that the central plasma sheet temperature can significantly influence when and where the azimuthal splitting takes place.

Quantum simulation of thermally-driven phase transition and oxygen K-edge x-ray absorption of high-pressure ice

PubMed Central

Kang, Dongdong; Dai, Jiayu; Sun, Huayang; Hou, Yong; Yuan, Jianmin

2013-01-01

The structure and phase transition of high-pressure ice are of long-standing interest and challenge, and there is still a huge gap between theoretical and experimental understanding. The quantum nature of protons such as delocalization, quantum tunneling and zero-point motion is crucial to the comprehension of the properties of high-pressure ice. Here we investigated the temperature-induced phase transition and oxygen K-edge x-ray absorption spectra of ice VII, VIII and X using ab initio path-integral molecular dynamics simulations. The tremendous difference between experiments and the previous theoretical predictions is closed for the phase diagram of ice below 300 K at pressures up to 110 GPa. Proton tunneling assists the proton-ordered ice VIII to transform into proton-disordered ice VII where only thermal activated proton-transfer cannot occur. The oxygen K edge with its shift is sensitive to the order-disorder transition, and therefore can be applied to diagnose the dynamics of ice structures. PMID:24253589

A Study of influence on sulfonated TiO2-Poly (Vinylidene fluoride-co-hexafluoropropylene) nano composite membranes for PEM Fuel cell application

NASA Astrophysics Data System (ADS)

kumar, K. Selva; Rajendran, S.; Prabhu, M. Ramesh

2017-10-01

The present work describes the sulfonated Titania directly blended with Poly (Vinylidene fluoride-co-hexafluoropropylene) as a host polymer by solvent casting technique for PEM fuel cell application. Characterization studies such as FT-IR, SEM, EDX, AFM, Proton conductivity, contact angle measurement, IEC, TG, water uptake, tensile strength were performed by for synthesized proton conducting polymer electrolytes. The maximum proton conductivity value was found to be 3.6 × 10-3S/cm for 25 wt% sulfonated Titania based system at 80 °C. The temperature dependent proton conductivity of the polymer electrolyte follows an Arrhenius relationship. Surface morphology of the composite membranes was investigated by tapping mode. Thermal stability of the system was studied by TG analysis. The fabricated composite membranes with high proton conductivity, good water uptake and IEC parameters exhibited a maximum fuel cell power density of 85 Mw/cm2for PEM fuel cell application.

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells

PubMed Central

Matsuzaki, Yoshio; Tachikawa, Yuya; Somekawa, Takaaki; Hatae, Toru; Matsumoto, Hiroshige; Taniguchi, Shunsuke; Sasaki, Kazunari

2015-01-01

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC). PMID:26218470

Magnetic penetration-depth measurements of a suppressed superfluid density of superconducting Ca0.5Na0.5Fe2As2 single crystals by proton irradiation

NASA Astrophysics Data System (ADS)

Kim, Jeehoon; Haberkorn, N.; Graf, M. J.; Usov, I.; Ronning, F.; Civale, L.; Nazaretski, E.; Chen, G. F.; Yu, W.; Thompson, J. D.; Movshovich, R.

2012-10-01

We report on the dramatic effect of random point defects, produced by proton irradiation, on the superfluid density ρs in superconducting Ca0.5Na0.5Fe2As2 single crystals. The magnitude of the suppression is inferred from measurements of the temperature-dependent magnetic penetration depth λ(T) using magnetic force microscopy. Our findings indicate that a radiation dose of 2×1016 cm-2 produced by 3 MeV protons results in a reduction of the superconducting critical temperature Tc by approximately 10%. In contrast, ρs(0) is suppressed by approximately 60%. This breakdown of the Abrikosov-Gorkov theory may be explained by the so-called “Swiss cheese model,” which accounts for the spatial suppression of the order parameter near point defects similar to holes in Swiss cheese. Both the slope of the upper critical field and the penetration depth λ(T/Tc)/λ(0) exhibit similar temperature dependences before and after irradiation. This may be due to a combination of the highly disordered nature of Ca0.5Na0.5Fe2As2 with large intraband and simultaneous interband scattering as well as the s±-wave nature of short coherence length superconductivity.

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells.

PubMed

Matsuzaki, Yoshio; Tachikawa, Yuya; Somekawa, Takaaki; Hatae, Toru; Matsumoto, Hiroshige; Taniguchi, Shunsuke; Sasaki, Kazunari

2015-07-28

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC).

Infrared Spectroscopy of the Mass 31 Cation: Protonated Formaldehyde VS. The Triplet Methoxy Cation

NASA Astrophysics Data System (ADS)

Mosley, J. D.; Cheng, T. C.; Duncan, M. A.

2012-06-01

The m/z=31 cation is produced by ionization and fragmentation of methanol, ethanol, dimethyl ether, etc. Two structures have been proposed, protonated formaldehyde (^1CH_2OH^+) and the triplet methoxy cation (^3CH_3O^+). The infrared spectrum of the mass 31 cation is obtained using infrared photodissociation spectroscopy with Ar tagging. The spectrum reveals the presence of two stable isomers, protonated formaldehyde (^1CH_2OH^+) and the triplet methoxy cation (^3CH_3O^+). The triplet methoxy cation has been studied extensively and is predicted to interconvert to protonated formaldehyde through an essentially barrierless process on a timescale much faster than our experiment (>100 μs). The presence of two structural isomers is verified by comparison of spectra from different precursors and spectra of different temperature ions from the same precursor.

Artificial synapse network on inorganic proton conductor for neuromorphic systems.

PubMed

Zhu, Li Qiang; Wan, Chang Jin; Guo, Li Qiang; Shi, Yi; Wan, Qing

2014-01-01

The basic units in our brain are neurons, and each neuron has more than 1,000 synapse connections. Synapse is the basic structure for information transfer in an ever-changing manner, and short-term plasticity allows synapses to perform critical computational functions in neural circuits. Therefore, the major challenge for the hardware implementation of neuromorphic computation is to develop artificial synapse network. Here in-plane lateral-coupled oxide-based artificial synapse network coupled by proton neurotransmitters are self-assembled on glass substrates at room-temperature. A strong lateral modulation is observed due to the proton-related electrical-double-layer effect. Short-term plasticity behaviours, including paired-pulse facilitation, dynamic filtering and spatiotemporally correlated signal processing are mimicked. Such laterally coupled oxide-based protonic/electronic hybrid artificial synapse network proposed here is interesting for building future neuromorphic systems.

A mini-type hydrogen generator from aluminum for proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Wang, Er-Dong; Shi, Peng-Fei; Du, Chun-Yu; Wang, Xiao-Rui

A safe and simple hydrogen generator, which produced hydrogen by chemical reaction of aluminum and sodium hydroxide solution, was proposed for proton exchange membrane fuel cells. The effects of concentration, dropping rate and initial temperature of sodium hydroxide solution on hydrogen generation rate were investigated. The results showed that about 38 ml min -1 of hydrogen generation rate was obtained with 25 wt.% concentration and 0.01 ml s -1 dropping rate of sodium hydroxide solution. The cell fueled by hydrogen from the generator exhibited performance improvement at low current densities, which was mainly due to the humidified hydrogen reduced the protonic resistivity of the proton exchange membrane. The hydrogen generator could stably operate a single cell under 500 mA for nearly 5 h with about 77% hydrogen utilization ratio.

Proton conducting sol-gel sulfonated membranes produced from 2-allylphenol, 3-glycidoxypropyl trimethoxysilane and tetraethyl orthosilicate

NASA Astrophysics Data System (ADS)

Mosa, J.; Durán, A.; Aparicio, M.

An important research area in proton exchange membrane fuel cells (PEMFC) is devoted to the development of low cost membranes able to work at temperatures higher than 100 °C. In this work, homogeneous, transparent and crack-free hybrid membranes have been synthesized using tetraethyl orthosilicate (TEOS), 3-glycidoxipropyl trimethoxysilane (GPTMS) and 2-allylphenol (AP) as precursors. The synthesis of proton conducting membranes was performed by a post-sulfonation method using trimethylsilyl chlorosulfonate as a mild sulfonating agent. The water retention properties provided by sulfonate and hydroxyl groups and the high porosity leads to relatively high proton conductivity (maximum values around 1.3 × 10 -3 S cm -1 at 140 °C and 100% RH) for membranes treated at 180 °C and sulfonated for 2 h.

Nanostructured polymer membranes for proton conduction

DOEpatents

Balsara, Nitash Pervez; Park, Moon Jeong

2013-06-18

Polymers having an improved ability to entrain water are characterized, in some embodiments, by unusual humidity-induced phase transitions. The described polymers (e.g., hydrophilically functionalized block copolymers) have a disordered state and one or more ordered states (e.g., a lamellar state, a gyroid state, etc.). In one aspect, the polymers are capable of undergoing a disorder-to-order transition while the polymer is exposed to an increasing temperature at a constant relative humidity. In some aspects the polymer includes a plurality of portions, wherein a first portion forms proton-conductive channels within the membrane and wherein the channels have a width of less than about 6 nm. The described polymers are capable of entraining and preserving water at high temperature and low humidity. Surprisingly, in some embodiments, the polymers are capable of entraining greater amounts of water with the increase of temperature. The polymers can be used in Polymer Electrolyte Membranes in fuel cells.

Hardness of AISI type 410 martensitic steels after high temperature irradiation via nanoindentation

NASA Astrophysics Data System (ADS)

Waseem, Owais Ahmed; Jeong, Jong-Ryul; Park, Byong-Guk; Maeng, Cheol-Soo; Lee, Myoung-Goo; Ryu, Ho Jin

2017-11-01

The hardness of irradiated AISI type 410 martensitic steel, which is utilized in structural and magnetic components of nuclear power plants, is investigated in this study. Proton irradiation of AISI type 410 martensitic steel samples was carried out by exposing the samples to 3 MeV protons up to a 1.0 × 1017 p/cm2 fluence level at a representative nuclear reactor coolant temperature of 350 °C. The assessment of deleterious effects of irradiation on the micro-structure and mechanical behavior of the AISI type 410 martensitic steel samples via transmission electron microscopy-energy dispersive spectroscopy and cross-sectional nano-indentation showed no significant variation in the microscopic or mechanical characteristics. These results ensure the integrity of the structural and magnetic components of nuclear reactors made of AISI type 410 martensitic steel under high-temperature irradiation damage levels up to approximately 5.2 × 10-3 dpa.

Crystal structure and vibrational spectra of melaminium arsenate

NASA Astrophysics Data System (ADS)

Anbalagan, G.; Marchewka, M. K.; Pawlus, K.; Kanagathara, N.

2015-01-01

The crystals of the new melaminium arsenate (MAS) [C3H7N6+ṡH2AsO4-] were obtained by the slow evaporation of an aqueous solution at room temperature. Single crystal X-ray diffraction analysis reveals that the crystal belongs to triclinic system with centro symmetric space group P-1. The crystals are built up from single protonated melaminium residues and single dissociated arsenate H2AsO4- anions. The protonated melaminium ring is almost planar. A combination of ionic and donor-acceptor hydrogen-bond interactions linking together the melaminium and arsenate residues forms a three-dimensional network. Vibrational spectroscopic analysis is reported on the basis of FT-IR and FT-Raman spectra recorded at room temperature. Hydrogen bonded network present in the crystal gives notable vibrational effect. DSC has also been performed for the crystal shows no phase transition in the studied temperature range (113-293 K).

Structural stability of anhydrous proton conducting SrZr0.9Er0.1O3-δ perovskite ceramic vs. protonation/deprotonation cycling: Neutron diffraction and Raman studies

NASA Astrophysics Data System (ADS)

Slodczyk, Aneta; Colomban, Philippe; Upasen, Settakorn; Grasset, Frédéric; André, Gilles

2015-08-01

Long-term chemical and structural stability of an ion conducting ceramic is one of the main criteria for its selection as an electrolytic membrane in energy plant devices. Consequently, medium density SrZr0.9Er0.1O3-δ (SZE) anhydrous proton conducting ceramic - a potential electrolyte of SOFC/PCFC, was analysed by neutron diffraction between room temperature and 900 °C. After the first heating/cooling cycle, the ceramic pieces were exposed to water vapour pressure in an autoclave (500 °C, 40 bar, 7 days) in order to incorporate protonic species; the protonated compound was then again analysed by neutron diffraction. This procedure was repeated two times. At each step, the sample was also controlled by TGA and Raman spectroscopy. These studies allow the first comprehensive comparison of structural and chemical stability during the protonation/deprotonation cycling. The results reveal good structural stability, although an irreversible small contraction of the unit-cell volume and local structure modifications near Zr/ErO5[] octahedra are detected after the first protonation. After the second protonation easy ceramic crumbling under a stress is observed because of the presence of secondary phases (SrCO3, Sr(OH)2) well detected by Raman scattering and TGA. The role of crystallographic purity, substituting element and residual porosity in the proton conducting perovskite electrolyte stability is discussed.

The effect of pH and concentration upon aggregation transitions in aqueous solutions of poloxamine T701.

PubMed

Armstrong, J K; Chowdhry, B Z; Snowden, M J; Dong, J; Leharne, S A

2001-10-23

Thermally induced aggregation transitions have been investigated for aqueous solutions of the poloxamine block copolymer T701-(OE(4)OP(13))(2)NCH(2)CH(2)N(OP(13)OE(4))(2)-using differential scanning calorimetry. The calorimetric signals obtained were fitted to a mass action model description of aggregation using a previously reported analytical procedure (Patterson et al., Langmuir 13 (1997) 2219). The presence of a central ethylene diamine moiety in the molecular structure renders the T701 molecule basic; this was confirmed and measured by acid/base titration. Basicity is shown to have an important impact upon aggregation. At low pH (2.5), the poloxamine exists in its protonated form and the bulk solution proton concentration is sufficient to suppress de-protonation, aggregation-as a consequence-is shifted to a higher temperature range. Any increase in pH reduces the temperature range over which aggregation occurs. The derived experimental calorimetric parameters, obtained from model fitting procedures, can be used to compute the fraction of poloxamine existing in an aggregated form, at any particular temperature. The data sets obtained were interpolated to show that at human body temperature (310.6 K) the fraction of poloxamine found in its aggregated form is zero at a pH of 2.5. However at a pH of 6.8, the percentage aggregation increases to about 85%. These aggregation characteristics of T701 have important implications for the design of drug delivery systems, which incorporate poloxamines.

Atmospheric pressure chemical ionization of fluorinated phenols in atmospheric pressure chemical ionization mass spectrometry, tandem mass spectrometry, and ion mobility spectrometry

NASA Technical Reports Server (NTRS)

Eiceman, G. A.; Bergloff, J. F.; Rodriguez, J. E.; Munro, W.; Karpas, Z.

1999-01-01

Atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) for fluorinated phenols (C6H5-xFxOH Where x = 0-5) in nitrogen with Cl- as the reagent ion yielded product ions of M Cl- through ion associations or (M-H)- through proton abstractions. Proton abstraction was controllable by potentials on the orifice and first lens, suggesting that some proton abstraction occurs through collision induced dissociation (CID) in the interface region. This was proven using CID of adduct ions (M Cl-) with Q2 studies where adduct ions were dissociated to Cl- or proton abstracted to (M-H)-. The extent of proton abstraction depended upon ion energy and structure in order of calculated acidities: pentafluorophenol > tetrafluorophenol > trifluorophenol > difluorophenol. Little or no proton abstraction occurred for fluorophenol, phenol, or benzyl alcohol analogs. Ion mobility spectrometry was used to determine if proton abstraction reactions passed through an adduct intermediate with thermalized ions and mobility spectra for all chemicals were obtained from 25 to 200 degrees C. Proton abstraction from M Cl- was not observed at any temperature for phenol, monofluorophenol, or difluorophenol. Mobility spectra for trifluorophenol revealed the kinetic transformations to (M-H)- either from M Cl- or from M2 Cl- directly. Proton abstraction was the predominant reaction for tetra- and penta-fluorophenols. Consequently, the evidence suggests that proton abstraction occurs from an adduct ion where the reaction barrier is reduced with increasing acidity of the O-H bond in C6H5-xFxOH.

Proton Translocation in Cytochrome c Oxidase: Insights from Proton Exchange Kinetics and Vibrational Spectroscopy

PubMed Central

Ishigami, Izumi; Hikita, Masahide; Egawa, Tsuyoshi; Yeh, Syun-Ru; Rousseau, Denis L.

2014-01-01

Cytochrome c oxidase is the terminal enzyme in the electron transfer chain. It reduces oxygen to water and harnesses the released energy to translocate protons across the inner mitochondrial membrane. The mechanism by which the oxygen chemistry is coupled to proton translocation is not yet resolved owing to the difficulty of monitoring dynamic proton transfer events. Here we summarize several postulated mechanisms for proton translocation, which have been supported by a variety of vibrational spectroscopic studies. We recently proposed a proton translocation model involving proton accessibility to the regions near the propionate groups of the heme a and heme a3 redox centers of the enzyme based by hydrogen/deuterium (H/D) exchange Raman scattering studies (Egawa et al., PLOS ONE 2013). To advance our understanding of this model and to refine the proton accessibility to the hemes, the H/D exchange dependence of the heme propionate group vibrational modes on temperature and pH was measured. The H/D exchange detected at the propionate groups of heme a3 takes place within a few seconds under all conditions. In contrast, that detected at the heme a propionates occurs in the oxidized but not the reduced enzyme and the H/D exchange is pH-dependent with a pKa of ~8.0 (faster at high pH). Analysis of the thermodynamic parameters revealed that, as the pH is varied, entropy/enthalpy compensation held the free energy of activation in a narrow range. The redox dependence of the possible proton pathways to the heme groups is discussed. PMID:25268561

Perfluoroalkyl phosphonic and phosphinic acids as proton conductors for anhydrous proton-exchange membranes.

PubMed

Herath, Mahesha B; Creager, Stephen E; Kitaygorodskiy, Alex; DesMarteau, Darryl D

2010-09-10

A study of proton-transport rates and mechanisms under anhydrous conditions using a series of acid model compounds, analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, sulfonic, and carboxylic acid protogenic groups, is reported. Model compounds are characterized with respect to proton conductivity, viscosity, proton, and anion (conjugate base) self-diffusion coefficients, and Hammett acidity. The highest conductivities, and also the highest viscosities, are observed for the phosphonic and phosphinic acid model compounds. Arrhenius analysis of conductivity and viscosity for these two acids reveals much lower activation energies for ion transport than for viscous flow. Additionally, the proton self-diffusion coefficients are much higher than the conjugate-base self-diffusion coefficients for these two acids. Taken together, these data suggest that anhydrous proton transport in the phosphonic and phosphinic acid model compounds occurs primarily by a structure-diffusion, hopping-based mechanism rather than a vehicle mechanism. Further analysis of ionic conductivity and ion self-diffusion rates by using the Nernst-Einstein equation reveals that the phosphonic and phosphinic acid model compounds are relatively highly dissociated even under anhydrous conditions. In contrast, sulfonic and carboxylic acid-based systems exhibit relatively low degrees of dissociation under anhydrous conditions. These findings suggest that fluoroalkyl phosphonic and phosphinic acids are good candidates for further development as anhydrous, high-temperature proton conductors.

Interplanetary medium data book, appendix

NASA Technical Reports Server (NTRS)

King, J. H.

1977-01-01

Computer generated listings of hourly average interplanetary plasma and magnetic field parameters are given. Parameters include proton temperature, proton density, bulk speed, an identifier of the source of the plasma data for the hour, average magnetic field magnitude and cartesian components of the magnetic field. Also included are longitude and latitude angles of the vector made up of the average field components, a vector standard deviation, and an identifier of the source of magnetic field data.

Solvent Dependence of Double Proton Transfer in the Formic Acid-Formamidine Complex: Path Integral Molecular Dynamics Investigation.

PubMed

Kungwan, Nawee; Ngaojampa, Chanisorn; Ogata, Yudai; Kawatsu, Tsutomu; Oba, Yuki; Kawashima, Yukio; Tachikawa, Masanori

2017-10-05

Solvent dependence of double proton transfer in the formic acid-formamidine (FA-FN) complex at room temperature was investigated by means of ab initio path integral molecular dynamics (AIPIMD) simulation with taking nuclear quantum and thermal effects into account. The conductor-like screening model (COSMO) was applied for solvent effect. In comparison with gas phase, double proton delocalization between two heavy atoms (O and N) in FA-FN were observed with reduced proton transfer barrier height in low dielectric constant medium (<4.8). For dielectric constant medium at 4.8, the chance of finding these two protons are more pronounced due to the solvent effect which completely washes out the proton transfer barrier. In the case of higher dielectric constant medium (>4.8), the ionic species becomes more stable than the neutral ones and the formate anion and formamidium cation are thermodynamically stable. For ab initio molecular dynamics simulation, in low dielectric constant medium (<4.8) a reduction of proton transfer barrier with solvent effect is found to be less pronounced than the AIPIMD due to the absence of nuclear quantum effect. Moreover, the motions of FA-FN complex are significantly different with increasing dielectric constant medium. Such a difference is revealed in detail by the principal component analysis.

Spectrally edited 2D 13Csbnd 13C NMR spectra without diagonal ridge for characterizing 13C-enriched low-temperature carbon materials

NASA Astrophysics Data System (ADS)

Johnson, Robert L.; Anderson, Jason M.; Shanks, Brent H.; Fang, Xiaowen; Hong, Mei; Schmidt-Rohr, Klaus

2013-09-01

Two robust combinations of spectral editing techniques with 2D 13Csbnd 13C NMR have been developed for characterizing the aromatic components of 13C-enriched low-temperature carbon materials. One method (exchange with protonated and nonprotonated spectral editing, EXPANSE) selects cross peaks of protonated and nearby nonprotonated carbons, while the other technique, dipolar-dephased double-quantum/single-quantum (DQ/SQ) NMR, selects signals of bonded nonprotonated carbons. Both spectra are free of a diagonal ridge, which has many advantages: Cross peaks on the diagonal or of small intensity can be detected, and residual spinning sidebands or truncation artifacts associated with the diagonal ridge are avoided. In the DQ/SQ experiment, dipolar dephasing of the double-quantum coherence removes protonated-carbon signals; this approach also eliminates the need for high-power proton decoupling. The initial magnetization is generated with minimal fluctuation by combining direct polarization, cross polarization, and equilibration by 13C spin diffusion. The dipolar dephased DQ/SQ spectrum shows signals from all linkages between aromatic rings, including a distinctive peak from polycondensed aromatics. In EXPANSE NMR, signals of protonated carbons are selected in the first spectral dimension by short cross polarization combined with dipolar dephasing difference. This removes ambiguities of peak assignment to overlapping signals of nonprotonated and protonated aromatic carbons, e.g. near 125 ppm. Spin diffusion is enhanced by dipolar-assisted rotational resonance. Before detection, Csbnd H dipolar dephasing by gated decoupling is applied, which selects signals of nonprotonated carbons. Thus, only cross peaks due to magnetization originating from protonated C and ending on nearby nonprotonated C are retained. Combined with the chemical shifts deduced from the cross-peak position, this double spectral editing defines the bonding environment of aromatic, COO, and Cdbnd O carbons, which is particularly useful for identifying furan and arene rings. The Cdbnd O carbons, whose chemical shifts vary strongly (between 212 and 165 ppm) and systematically depend on their two bonding partners, show particularly informative cross peaks, given that one bonding partner is defined by the other frequency coordinate of the cross peak. The new techniques and the information content of the resulting spectra are validated on sulfuric-acid treated low-temperature carbon materials and on products of the Maillard reaction. The crucial need for spectral editing for correct peak assignment is demonstrated in an example.

Composite polymer electrolyte containing ionic liquid and functionalized polyhedral oligomeric silsesquioxanes for anhydrous PEM applications.

PubMed

Subianto, Surya; Mistry, Mayur K; Choudhury, Namita Roy; Dutta, Naba K; Knott, Robert

2009-06-01

A new type of supported liquid membrane was made by combining an ionic liquid (IL) with a Nafion membrane reinforced with multifunctional polyhedral oligomeric silsesquioxanes (POSSs) using a layer-by-layer strategy for anhydrous proton-exchange membrane (PEM) application. The POSS was functionalized by direct sulfonation, and the sulfonated POSS (S-POSS) was incorporated into Nafion 117 membranes by the infiltration method. The resultant hybrid membrane shows strong ionic interaction between the Nafion matrix and the multifunctional POSS, resulting in increased glass transition temperature and thermal stability at very low loadings of S-POSS (1%). The presence of S-POSS has also improved the proton conductivity especially at low humidities, where it shows a marked increase due to its confinement in the ionic domains and promotes water uptake by capillary condensation. In order to achieve anhydrous conductivity, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI) was incorporated into these membranes to provide proton conduction in the absence of water. Although the incorporation of an IL shows a plasticizing effect on the Nafion membrane, the S-POSS composite membrane with an IL shows a higher modulus at high temperatures compared to Nafion 117 and a Nafion-IL membrane, with significantly higher proton conductivity (5 mS/cm at 150 degrees C with 20% IL). This shows the ability of the multifunctional POSS and IL to work symbiotically to achieve the desirable proton conductivity and mechanical properties of such membranes by enhancing the ionic interaction within the material.

Pressure-assisted cold denaturation of hen egg white lysozyme: the influence of co-solvents probed by hydrogen exchange nuclear magnetic resonance.

PubMed

Vogtt, K; Winter, R

2005-08-01

COSY proton nuclear magnetic resonance was used to measure the exchange rates of amide protons of hen egg white lysozyme (HEWL) in the pressure-assisted cold-denatured state and in the heat-denatured state. After dissolving lysozyme in deuterium oxide buffer, labile protons exchange for deuterons in such a way that exposed protons are substituted rapidly, whereas "protected" protons within structured parts of the protein are substituted slowly. The exchange rates k obs were determined for HEWL under heat treatment (80 degrees C) and under high pressure conditions at low temperature (3.75 kbar, -13 degrees C). Moreover, the influence of co-solvents (sorbitol, urea) on the exchange rate was examined under pressure-assisted cold denaturation conditions, and the corresponding protection factors, P, were determined. The exchange kinetics upon heat treatment was found to be a two-step process with initial slow exchange followed by a fast one, showing residual protection in the slow-exchange state and P-factors in the random-coil-like range for the final temperature-denatured state. Addition of sorbitol (500 mM) led to an increase of P-factors for the pressure-assisted cold denatured state, but not for the heat-denatured state. The presence of 2 M urea resulted in a drastic decrease of the P-factors of the pressure-assisted cold denatured state. For both types of co-solvents, the effect they exert appears to be cooperative, i.e., no particular regions within the protein can be identified with significantly diverse changes of P-factors.

Water-Free Proton-Conducting Membranes for Fuel Cells

NASA Technical Reports Server (NTRS)

Narayanan, Sekharipuram; Yen, Shiao-Pin

2007-01-01

Poly-4-vinylpyridinebisulfate (P4VPBS) is a polymeric salt that has shown promise as a water-free proton-conducting material (solid electrolyte) suitable for use in membrane/electrode assemblies in fuel cells. Heretofore, proton-conducting membranes in fuel cells have been made from perfluorinated ionomers that cannot conduct protons in the absence of water and, consequently, cannot function at temperatures >100 C. In addition, the stability of perfluorinated ionomers at temperatures >100 C is questionable. However, the performances of fuel cells of the power systems of which they are parts could be improved if operating temperatures could be raised above 140 C. What is needed to make this possible is a solid-electrolyte material, such as P4VPBS, that can be cast into membranes and that both retains proton conductivity and remains stable in the desired higher operating temperature range. A family of solid-electrolyte materials different from P4VPBS was described in Anhydrous Proton-Conducting Membranes for Fuel Cells (NPO-30493), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), page 48. Those materials notably include polymeric quaternized amine salts. If molecules of such a polymeric salt could be endowed with flexible chain structures, it would be possible to overcome the deficiencies of simple organic amine salts that must melt before being able to conduct protons. However, no polymeric quaternized amine salts have yet shown to be useful in this respect. The present solid electrolyte is made by quaternizing the linear polymer poly- 4-vinylpyridine (P4VP) to obtain P4VPBS. It is important to start with P4VP having a molecular weight of 160,000 daltons because P4VPBS made from lower-molecular-weight P4VP yields brittle membranes. In an experimental synthesis, P4VP was dissolved in methanol and then reacted with an excess of sulfuric acid to precipitate P4VPBS. The precipitate was recovered, washed several times with methanol to remove traces of acid, and dried to a white granular solid. In another synthesis, nanoparticles of silica rich with surface hydroxyl groups were added to P4VP in methanol solution, which was then reacted with excess sulfuric acid to precipitate granules of a composite that most probably had the composition (P4VPBS)-SiO2-SiO(HSO4)2. The granular P4VPBS produced in the first-mentioned synthesis was dissolved in water to make a glue-like, turbid solution; the granular P4VPBS/silica composite produced in the second-mentioned synthesis was mixed with water to make a turbid, glue-like suspension. The proportions of polymer salt to water in such preparations can be varied; it was found that approximately equal parts of water and polymer salt yield a solution or suspension amenable to further processing.

Ionic liquids and ionic liquid acids with high temperature stability for fuel cell and other high temperature applications, method of making and cell employing same

DOEpatents

Angell, C Austen [Mesa, AZ; Xu, Wu [Broadview Heights, OH; Belieres, Jean-Philippe [Chandler, AZ; Yoshizawa, Masahiro [Tokyo, JP

2011-01-11

Disclosed are developments in high temperature fuel cells including ionic liquids with high temperature stability and the storage of inorganic acids as di-anion salts of low volatility. The formation of ionically conducting liquids of this type having conductivities of unprecedented magnitude for non-aqueous systems is described. The stability of the di-anion configuration is shown to play a role in the high performance of the non-corrosive proton-transfer ionic liquids as high temperature fuel cell electrolytes. Performance of simple H.sub.2(g) electrolyte/O.sub.2(g) fuel cells with the new electrolytes is described. Superior performance both at ambient temperature and temperatures up to and above 200.degree. C. are achieved. Both neutral proton transfer salts and the acid salts with HSO.sup.-.sub.4 anions, give good results, the bisulphate case being particularly good at low temperatures and very high temperatures. The performance of all electrolytes is improved by the addition of a small amount of involatile base of pK.sub.a value intermediate between those of the acid and base that make the bulk electrolyte. The preferred case is the imidazole-doped ethylammonium hydrogensulfate which yields behavior superior in all respects to that of the industry standard phosphoric acid electrolyte.

Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion

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

Soudackov, Alexander V.; Hammes-Schiffer, Sharon

2015-11-21

Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at highmore » temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton transfer and proton-coupled electron transfer in chemical and biological processes.« less

Freezing Temperatures, Ice Nanotubes Structures, and Proton Ordering of TIP4P/ICE Water inside Single Wall Carbon Nanotubes.

PubMed

Pugliese, P; Conde, M M; Rovere, M; Gallo, P

2017-11-16

A very recent experimental paper importantly and unexpectedly showed that water in carbon nanotubes is already in the solid ordered phase at the temperature where bulk water boils. The water models used so far in literature for molecular dynamics simulations in carbon nanotubes show freezing temperatures lower than the experiments. We present here results from molecular dynamics simulations of water inside single walled carbon nanotubes using an extremely realistic model for both liquid and icy water, the TIP4P/ICE. The water behavior inside nanotubes of different diameters has been studied upon cooling along the isobars at ambient pressure starting from temperatures where water is in a liquid state. We studied the liquid/solid transition, and we observed freezing temperatures higher than in bulk water and that depend on the diameter of the nanotube. The maximum freezing temperature found is 390 K, which is in remarkable agreement with the recent experimental measurements. We have also analyzed the ice structure called "ice nanotube" that water forms inside the single walled carbon nanotubes when it freezes. The ice forms observed are in agreement with previous results obtained with different water models. A novel finding, a partial proton ordering, is evidenced in our ice nanotubes at finite temperature.

Improved Electrodes for High Temperature Proton Exchange Membrane Fuel Cells using Carbon Nanospheres.

PubMed

Zamora, Héctor; Plaza, Jorge; Cañizares, Pablo; Lobato, Justo; Rodrigo, Manuel A

2016-05-23

This work evaluates the use of carbon nanospheres (CNS) in microporous layers (MPL) of high temperature proton exchange membrane fuel cell (HT-PEMFC) electrodes and compares the characteristics and performance with those obtained using conventional MPL based on carbon black. XRD, hydrophobicity, Brunauer-Emmett-Teller theory, and gas permeability of MPL prepared with CNS were the parameters evaluated. In addition, a short life test in a fuel cell was carried out to evaluate performance under accelerated stress conditions. The results demonstrate that CNS is a promising alternative to traditional carbonaceous materials because of its high electrochemical stability and good electrical conductivity, suitable to be used in this technology. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel proton conducting polymer electrolytes based on polyparabanic acid doped with H 3PO 4 for high temperature fuel cell

NASA Astrophysics Data System (ADS)

Aihara, Yuichi; Sonai, Atsuo

Three novel proton conducting polymer electrolytes based on polyparabanic acid doped with H 3PO 4 were synthesized and their use in high temperature fuel cells characterized. The precursor polymers, PMD-Im, POD-Im and PDMDP-Im, were synthesized by cyclization polymerization of diisocynanates. After doping with H 3PO 4, the ionic conductivity and the thermal degradation were studied by using the AC impedance method and thermal gravimetric analysis, respectively. These membranes showed high ionic conductivity of the order of 10 -2 S cm -1 at 423 K with good thermal stability. Their application to fuel cells was demonstrated and polarization curves were obtained at 423 K were obtained without humidification.

Enhanced production of multi-strange hadrons in high-multiplicity proton-proton collisions

NASA Astrophysics Data System (ADS)

Adam, J.; Adamová, D.; Aggarwal, M. M.; Rinella, G. Aglieri; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; Aiola, S.; Akindinov, A.; Alam, S. N.; Albuquerque, D. S. D.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Molina, R. Alfaro; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Prado, C. Alves Garcia; An, M.; Andrei, C.; Andrews, H. A.; Andronic, A.; Anguelov, V.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Arnaldi, R.; Arnold, O. W.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Balasubramanian, S.; Baldisseri, A.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Camejo, A. Batista; Batyunya, B.; Batzing, P. C.; Bearden, I. 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F.; Grosso, R.; Gruber, L.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hamon, J. C.; Harris, J. W.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Hellbär, E.; Helstrup, H.; Herghelegiu, A.; Corral, G. Herrera; Herrmann, F.; Hess, B. A.; Hetland, K. F.; Hillemanns, H.; Hippolyte, B.; Horak, D.; Hosokawa, R.; Hristov, P.; Hughes, C.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Inaba, M.; Incani, E.; Ippolitov, M.; Irfan, M.; Isakov, V.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacak, B.; Jacazio, N.; Jacobs, P. M.; Jadhav, M. B.; Jadlovska, S.; Jadlovsky, J.; Jahnke, C.; Jakubowska, M. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Bustamante, R. T. Jimenez; Jones, P. G.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kang, J. H.; Kaplin, V.; Kar, S.; Uysal, A. Karasu; Karavichev, O.; Karavicheva, T.; Karayan, L.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Khan, M. Mohisin; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Khatun, A.; Kileng, B.; Kim, D. W.; Kim, D. J.; Kim, D.; Kim, H.; Kim, J. S.; Kim, J.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Klewin, S.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Kofarago, M.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kopcik, M.; Kour, M.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Meethaleveedu, G. Koyithatta; Králik, I.; Kravčáková, A.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kuhn, C.; Kuijer, P. G.; Kumar, A.; Kumar, J.; Kumar, L.; Kumar, S.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; de Guevara, P. Ladron; Fernandes, C. Lagana; Lakomov, I.; Langoy, R.; Lapidus, K.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, S.; Lehas, F.; Lehner, S.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; Monzón, I. León; Vargas, H. León; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loginov, V.; Loizides, C.; Lopez, X.; Torres, E. López; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Lupi, M.; Lutz, T. H.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Cervantes, I. Maldonado; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manko, V.; Manso, F.; Manzari, V.; Mao, Y.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martinengo, P.; Martínez, M. I.; García, G. Martínez; Pedreira, M. Martinez; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzilli, M.; Mazzoni, M. A.; McDonald, D.; Meddi, F.; Melikyan, Y.; Menchaca-Rocha, A.; Meninno, E.; Pérez, J. Mercado; Meres, M.; Mhlanga, S.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Mishra, T.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Zetina, L. Montaño; Montes, E.; de Godoy, D. A. Moreira; Moreno, L. A. P.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Mulligan, J. D.; Munhoz, M. G.; Münning, K.; Munzer, R. H.; Murakami, H.; Murray, S.; Musa, L.; Musinsky, J.; Naik, B.; Nair, R.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; da Luz, H. Natal; Nattrass, C.; Navarro, S. R.; Nayak, K.; Nayak, R.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; de Oliveira, R. A. Negrao; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Noris, J. C. C.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Oleniacz, J.; da Silva, A. C. Oliveira; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Orava, R.; Oravec, M.; Velasquez, A. Ortiz; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, D.; Pagano, P.; Paić, G.; Pal, S. K.; Palni, P.; Pan, J.; Pandey, A. K.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Patra, R. N.; Paul, B.; Pei, H.; Peitzmann, T.; Peng, X.; da Costa, H. Pereira; Peresunko, D.; Lezama, E. Perez; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pimentel, L. O. D. L.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Poppenborg, H.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Rami, F.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Ravasenga, I.; Read, K. F.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Cahuantzi, M. Rodríguez; Manso, A. Rodriguez; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Montero, A. J. Rubio; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Saarinen, S.; Sadhu, S.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Šándor, L.; Sandoval, A.; Sano, M.; Sarkar, D.; Sarkar, N.; Sarma, P.; Scapparone, E.; Scarlassara, F.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schmidt, M.; Schuchmann, S.; Schukraft, J.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Šefčík, M.; Seger, J. E.; Sekiguchi, Y.; Sekihata, D.; Selyuzhenkov, I.; Senosi, K.; Senyukov, S.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, M.; Sharma, M.; Sharma, N.; Sheikh, A. I.; Shigaki, K.; Shou, Q.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singhal, V.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Sozzi, F.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Stachel, J.; Stan, I.; Stankus, P.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Suljic, M.; Sultanov, R.; Šumbera, M.; Sumowidagdo, S.; Swain, S.; Szabo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Tabassam, U.; Takahashi, J.; Tambave, G. J.; Tanaka, N.; Tarhini, M.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Muñoz, G. Tejeda; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thakur, D.; Thomas, D.; Tieulent, R.; Tikhonov, A.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trombetta, G.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vala, M.; Palomo, L. Valencia; van der Maarel, J.; van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vyvre, P. Vande; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Doce, O. Vázquez; Vechernin, V.; Veen, A. M.; Velure, A.; Vercellin, E.; Limón, S. Vergara; Vernet, R.; Vickovic, L.; Viinikainen, J.; Vilakazi, Z.; Baillie, O. Villalobos; Tello, A. Villatoro; Vinogradov, A.; Vinogradov, L.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Watanabe, D.; Watanabe, Y.; Weber, M.; Weber, S. G.; Weiser, D. F.; Wessels, J. P.; Westerhoff, U.; Whitehead, A. M.; Wiechula, J.; Wikne, J.; Wilk, G.; Wilkinson, J.; Willems, G. A.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yalcin, S.; Yang, P.; Yano, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yoon, J. H.; Yurchenko, V.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zardoshti, N.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhang, C.; Zhang, Z.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.

2017-06-01

At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark-gluon plasma (QGP). Such an exotic state of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions, is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions, but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p-Pb collision results, indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.

Quantum free energy landscapes from ab initio path integral metadynamics: Double proton transfer in the formic acid dimer is concerted but not correlated.

PubMed

Ivanov, Sergei D; Grant, Ian M; Marx, Dominik

2015-09-28

With the goal of computing quantum free energy landscapes of reactive (bio)chemical systems in multi-dimensional space, we combine the metadynamics technique for sampling potential energy surfaces with the ab initio path integral approach to treating nuclear quantum motion. This unified method is applied to the double proton transfer process in the formic acid dimer (FAD), in order to study the nuclear quantum effects at finite temperatures without imposing a one-dimensional reaction coordinate or reducing the dimensionality. Importantly, the ab initio path integral metadynamics technique allows one to treat the hydrogen bonds and concomitant proton transfers in FAD strictly independently and thus provides direct access to the much discussed issue of whether the double proton transfer proceeds via a stepwise or concerted mechanism. The quantum free energy landscape we compute for this H-bonded molecular complex reveals that the two protons move in a concerted fashion from initial to product state, yet world-line analysis of the quantum correlations demonstrates that the protons are as quantum-uncorrelated at the transition state as they are when close to the equilibrium structure.

New Measurement of the 1S-3S Transition Frequency of Hydrogen: Contribution to the Proton Charge Radius Puzzle.

PubMed

Fleurbaey, Hélène; Galtier, Sandrine; Thomas, Simon; Bonnaud, Marie; Julien, Lucile; Biraben, François; Nez, François; Abgrall, Michel; Guéna, Jocelyne

2018-05-04

We present a new measurement of the 1S-3S two-photon transition frequency of hydrogen, realized with a continuous-wave excitation laser at 205 nm on a room-temperature atomic beam, with a relative uncertainty of 9×10^{-13}. The proton charge radius deduced from this measurement, r_{p}=0.877(13)  fm, is in very good agreement with the current CODATA-recommended value. This result contributes to the ongoing search to solve the proton charge radius puzzle, which arose from a discrepancy between the CODATA value and a more precise determination of r_{p} from muonic hydrogen spectroscopy.

A description of electron heating with an electrostatic potential jump in a parallel, collisionless, fire hose shock

NASA Technical Reports Server (NTRS)

Ellison, Donald C.; Jones, Frank C.

1988-01-01

The electron heating required if protons scatter elastically in a parallel, collisionless shock is calculated. Near-elastic proton scattering off large amplitude background magnetic field fluctuations might be expected if the waves responsible for the shock dissipation are generated by the fire hose instability. The effects of an electrostatic potential jump in the shock layer are included by assuming that the energy lost by protons in traversing the potential jump is converted into electron thermal pressure. It is found that the electron temperature increase is a strong function of the potential jump. Comparison is made to the parallel shock plasma simulation of Quest (1987).

How big are the smallest drops of quark-gluon plasma?

NASA Astrophysics Data System (ADS)

Chesler, Paul M.

2016-03-01

Using holographic duality, we present results for both head-on and off-center collisions of Gaussian shock waves in strongly coupled {N}=4 supersymmetric Yang-Mills theory. The shock waves superficially resemble Lorentz contracted colliding protons. The collisions results in the formation of a plasma whose evolution is well described by viscous hydrodynamics. The size of the produced droplet is R ˜ 1 /T eff where T eff is the effective temperature, which is the characteristic microscopic scale in strongly coupled plasma. These results demonstrate the applicability of hydrodynamics to microscopically small systems and bolster the notion that hydrodynamics can be applied to heavy-light ion collisions as well as some proton-proton collisions.

Modeling Torque Versus Speed, Shot Noise, and Rotational Diffusion of the Bacterial Flagellar Motor

PubMed Central

Mora, Thierry; Yu, Howard; Wingreen, Ned S.

2010-01-01

We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E. coli motor at various pH and temperature conditions. In particular, the dramatic drop of torque at high rotation speeds (the “knee”) is shown to arise from saturation of the proton flux. Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads. This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions. PMID:20366231

Planetary quarantine in the solar system. Survival rates of some terrestrial organisms under simulated space conditions by proton irradiation

NASA Astrophysics Data System (ADS)

Koike, J.; Oshima, T.

We have been studying the survival rates of some species of terrestrial unicellular and multicellular organism (viruses, bacteria, yeasts, fungi, algae, etc.) under simulated interstellar conditions, in connection with planetary quarantine. The interstellar environment in the solar system has been simulated by low temperature, high vacuum (77 K, 4 × 10 -8 torr), and proton irradiation from a Van de Graaff generator. After exposure to a barrage of protons corresponding to about 250 years of irradiation in solar space, tobacco mosaic virus, Bacillus subtilis spores, Staphylococcus aureus, Micrococcus flavus, Aspergillus niger spores, and Clostridium mangenoti spores showed survival rates of 82, 45, 74, 13, 28, and 25%, respectively.

Fluoroquinolone resistance of Serratia marcescens: sucrose, salicylate, temperature, and pH induction of phenotypic resistance.

PubMed

Begic, Sanela; Worobec, Elizabeth A

2007-11-01

Serratia marcescens is a nosocomial agent with a natural resistance to a broad spectrum of antibiotics, making the treatment of its infections very challenging. This study examines the influence of salicylate, sucrose, temperature, and pH variability on membrane permeability and susceptibility of S. marcescens to norfloxacin (hydrophilic fluoroquinolone) and nalidixic acid (hydrophobic quinolone). Resistance of wild-type S. marcescens UOC-67 (ATCC 13880) to norfloxacin and nalidixic acid was assessed by minimal inhibitory concentration (MIC) assays after growth in the presence of various concentrations of sucrose and salicylate and different temperatures and pH values. Norfloxacin and nalidixic acid accumulation was determined in the absence and presence of (i) carbonyl cyanide m-chlorophenylhydrazone (CCCP), a proton-motive-force collapser, and (ii) Phe-Arg beta-naphthylamide (PAbetaN), an efflux pump inhibitor. Accumulation of norfloxacin decreased when S. marcescens was grown in high concentrations of salicylate (8 mmol/L) and sucrose (10% m/v), at high temperature (42 degrees C), and at pH 6, and it was restored in the presence of CCCP because of the collapse of proton-gradient-dependent efflux in S. marcescens. Although nalidixic acid accumulation was observed, it was not affected by salicylate, sucrose, pH, or temperature changes. In the absence of PAbetaN, and either in the presence or absence of CCCP, a plateau was reached in the nalidixic acid accumulation for all environmental conditions. With the addition of 20 mg/L PAbetaN nalidixic acid accumulation is restored for all environmental conditions, suggesting that this quinolone is recognized by a yet to be identified S. marcescens pump that does not use proton motive force as its energy source.

Nonhumidified intermediate temperature fuel cells using protic ionic liquids.

PubMed

Lee, Seung-Yul; Ogawa, Atsushi; Kanno, Michihiro; Nakamoto, Hirofumi; Yasuda, Tomohiro; Watanabe, Masayoshi

2010-07-21

In this paper, the characterization of a protic ionic liquid, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), as a proton conductor for a fuel cell and the fabrication of a membrane-type fuel cell system using [dema][TfO] under nonhumidified conditions at intermediate temperatures are described in detail. In terms of physicochemical and electrochemical properties, [dema][TfO] exhibits high activity for fuel cell electrode reactions (i.e., the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR)) at a Pt electrode, and the open circuit voltage (OCV) of a liquid fuel cell is 1.03 V at 150 degrees C, as has reported in ref 27. However, diethylmethylammonium bis(trifluoromethane sulfonyl)amide ([dema][NTf(2)]) has relatively low HOR and ORR activity, and thus, the OCV is ca. 0.7 V, although [dema][NTf(2)] and [dema][TfO] have an identical cation ([dema]) and similar thermal and bulk-transport properties. Proton conduction occurs mainly via the vehicle mechanism in [dema][TfO] and the proton transference number (t(+)) is 0.5-0.6. This relatively low t(+) appears to be more disadvantageous for a proton conductor than for other electrolytes such as hydrated sulfonated polymer electrolyte membranes (t(+) = 1.0). However, fast proton-exchange reactions occur between ammonium cations and amines in a model compound. This indicates that the proton-exchange mechanism contributes to the fuel cell system under operation, where deprotonated amines are continuously generated by the cathodic reaction, and that polarization of the cell is avoided. Six-membered sulfonated polyimides in the diethylmethylammonium form exhibit excellent compatibility with [dema][TfO]. The composite membranes can be obtained up to a [dema][TfO] content of 80 wt % and exhibit good thermal stability, high ionic conductivity, and mechanical strength and gas permeation comparable to those of hydrated Nafion. H(2)/O(2) fuel cells prepared using the composite membranes can successfully operate at temperatures from 30 to 140 degrees C under nonhumidified conditions, and a current density of 250 mA cm(-2) is achieved at 120 degrees C. The protic ionic liquid and its composite membrane are a possible candidate for an electrolyte of a H(2)/O(2) fuel cell that operates under nonhumidified conditions.

TEM characterization of irradiated microstructure of Fe-9%Cr ODS and ferritic-martensitic alloys

NASA Astrophysics Data System (ADS)

Swenson, M. J.; Wharry, J. P.

2018-04-01

The objective of this study is to evaluate the effects of irradiation dose and dose rate on defect cluster (i.e. dislocation loops and voids) evolution in a model Fe-9%Cr oxide dispersion strengthened steel and commercial ferritic-martensitic steels HCM12A and HT9. Complimentary irradiations using Fe2+ ions, protons, or neutrons to doses ranging from 1 to 100 displacements per atom (dpa) at 500 °C are conducted on each alloy. The irradiated microstructures are characterized using transmission electron microscopy (TEM). Dislocation loops exhibit limited growth after 1 dpa upon Fe2+ and proton irradiation, while any voids observed are small and sparse. The average size and number density of loops are statistically invariant between Fe2+, proton, and neutron irradiated specimens at otherwise fixed irradiation conditions of ∼3 dpa, 500 °C. Therefore, we conclude that higher dose rate charged particle irradiations can reproduce the neutron irradiated loop microstructure with temperature shift governed by the invariance theory; this temperature shift is ∼0 °C for the high sink strength alloys studied herein.

A reliable confirmation of the chemical structure of synthetic oligonucleotides: Detection of active protons in DNA oligomers by low-temperature FT infrared spectroscopy

NASA Astrophysics Data System (ADS)

Rozenberg, M.; Shoham, G.

2009-01-01

Cooling the samples allowed us to characterize solid oligonucleotides such as dimers, trimers and pentamers of cytidine, for the first time, in the IR range of the out-of-plane bending molecular modes (1000-400 cm -1) at 20 K. Especially interesting are the narrow IR bands of the out-of-plane bending ν4 NH 2 proton mode, which are apparently invisible at room temperature. This unequivocally defined and well-resolved NH 2 bending band should provide important information on the exact chemical form and hydrogen bonding interactions of cytidine amine groups. As such, this unique IR spectroscopy is suggested as a practical analytical tool to validate and characterize synthetic DNA bases and oligonucleotides. Using an approach of this type it was found that desalted oligonucleotide samples of the same nominal composition, but which had been produced by three different manufacturers, differ significantly in their IR spectra. These data suggest that the presumably identical oligonucleotides are in fact different, at least with respect to the content and nature of their NH protons.

A reliable confirmation of the chemical structure of synthetic oligonucleotides: detection of active protons in DNA oligomers by low-temperature FT infrared spectroscopy.

PubMed

Rozenberg, M; Shoham, G

2009-01-01

Cooling the samples allowed us to characterize solid oligonucleotides such as dimers, trimers and pentamers of cytidine, for the first time, in the IR range of the out-of-plane bending molecular modes (1000-400 cm(-1)) at 20K. Especially interesting are the narrow IR bands of the out-of-plane bending nu(4) NH(2) proton mode, which are apparently invisible at room temperature. This unequivocally defined and well-resolved NH(2) bending band should provide important information on the exact chemical form and hydrogen bonding interactions of cytidine amine groups. As such, this unique IR spectroscopy is suggested as a practical analytical tool to validate and characterize synthetic DNA bases and oligonucleotides. Using an approach of this type it was found that desalted oligonucleotide samples of the same nominal composition, but which had been produced by three different manufacturers, differ significantly in their IR spectra. These data suggest that the presumably identical oligonucleotides are in fact different, at least with respect to the content and nature of their NH protons.

Hydrogen-bonded ring closing and opening of protonated methanol clusters H(+)(CH3OH)(n) (n = 4-8) with the inert gas tagging.

PubMed

Li, Ying-Cheng; Hamashima, Toru; Yamazaki, Ryoko; Kobayashi, Tomohiro; Suzuki, Yuta; Mizuse, Kenta; Fujii, Asuka; Kuo, Jer-Lai

2015-09-14

The preferential hydrogen bond (H-bond) structures of protonated methanol clusters, H(+)(MeOH)n, in the size range of n = 4-8, were studied by size-selective infrared (IR) spectroscopy in conjunction with density functional theory calculations. The IR spectra of bare clusters were compared with those with the inert gas tagging by Ar, Ne, and N2, and remarkable changes in the isomer distribution with the tagging were found for clusters with n≥ 5. The temperature dependence of the isomer distribution of the clusters was calculated by the quantum harmonic superposition approach. The observed spectral changes with the tagging were well interpreted by the fall of the cluster temperature with the tagging, which causes the transfer of the isomer distribution from the open and flexible H-bond network types to the closed and rigid ones. Anomalous isomer distribution with the tagging, which has been recently found for protonated water clusters, was also found for H(+)(MeOH)5. The origin of the anomaly was examined by the experiments on its carrier gas dependence.

Magnetic properties of point defects in proton irradiated diamond

NASA Astrophysics Data System (ADS)

Makgato, T. N.; Sideras-Haddad, E.; Ramos, M. A.; García-Hernández, M.; Climent-Font, A.; Zucchiatti, A.; Muñoz-Martin, A.; Shrivastava, S.; Erasmus, R.

2016-09-01

We investigate the magnetic properties of ultra-pure type-IIa diamond following irradiation with proton beams of ≈1-2 MeV energy. SQUID magnetometry indicate the formation of Curie type paramagnetism according to the Curie law. Raman and Photoluminescence spectroscopy measurements show that the primary structural features created by proton irradiation are the centers: GR1, ND1, TR12 and 3H. The Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulations together with SQUID observations show a strong correlation between vacancy production, proton fluence and the paramagnetic factor. At an average surface vacancy spacing of ≈1-1.6 nm and bulk (peak) vacancy spacing of ≈0.3-0.5 nm Curie paramagnetism is induced by formation of ND1 centres with an effective magnetic moment μeff~(0.1-0.2)μB. No evidence of long range magnetic ordering is observed in the temperature range 4.2-300 K.

Evolution of energy metabolism. Proton permeability of the inner membrane of liver mitochondria is greater in a mammal than in a reptile.

PubMed Central

Brand, M D; Couture, P; Else, P L; Withers, K W; Hulbert, A J

1991-01-01

Standard metabolic rate is 7-fold greater in the rat (a typical mammal) than in the bearded dragon, Amphibolurus vitticeps (a reptile with the same body mass and temperature). Rat hepatocytes respire 4-fold faster than do hepatocytes from the lizard. The inner membrane of isolated rat liver mitochondrial has a proton permeability that is 4-5-fold greater than the proton permeability of the lizard liver mitochondrial membrane per mg of mitochondrial protein. The greater permeability of rat mitochondria is not caused by differences in the surface area of the mitochondrial inner membrane, but differences in the fatty acid composition of the mitochondrial phospholipids may be involved in the permeability differences. Greater proton permeability of the mitochondrial inner membrane may contribute to the greater standard metabolic rate of mammals. PMID:1850242

Measurement of proton momentum distributions using a direct geometry instrument

NASA Astrophysics Data System (ADS)

Senesi, R.; Kolesnikov, A. I.; Andreani, C.

2014-12-01

We report the results of inelastic neutron scattering measurements on bulk water and ice using the direct geometry SEQUOIA chopper spectrometer at the Spallation Neutron Source (USA), with incident energy Ei= 6 eV. In this set up the measurements allow to access the Deep Inelastic Neutron Scattering regime. The scattering is centred at the proton recoil energy given by the impulse approximation, and the shape of the recoil peak conveys information on the proton momentum distribution in the system. The comparison with the performance of inverse geometry instruments, such as VESUVIO at the ISIS source (UK), shows that complementary information can be accessed by the use of direct and inverse geometry instruments. Analysis of the neutron Compton profiles shows that the proton kinetic energy in ice at 271 K is larger than in room temperature liquid water, in agreement with previous measurements on VESUVIO.

Synthesis and high proton conductive performance of a quaternary vanadomolybdotungstosilicic heteropoly acid.

PubMed

Cai, Huaxue; Wu, Xuefei; Wu, Qingyin; Yan, Wenfu

2016-09-28

A new vanadium and molybdenum-substituted quaternary silicon-containing heteropoly acid H6SiW9MoV2O40·15H2O has been synthesized in this paper by the stepwise acidification and the stepwise addition of elemental solutions. The structural feature and hydration of this product were characterized by IR, UV, XRD and TG-DTA, and its proton conductivity was measured by electrochemical impedance spectroscopy (EIS). The result of EIS shows that H6SiW9MoV2O40·15H2O is a solid high-proton conductor with a conductivity of 6.01 × 10(-3) S cm(-1) at 22 °C and 80% relative humidity, which increases at higher temperatures. Its conductive activation energy is 27.5 kJ mol(-1), which suggests that the mechanism of proton conduction is dominated by the vehicle mechanism.

Quantum tunneling of thermal protons through pristine graphene.

PubMed

Poltavsky, Igor; Zheng, Limin; Mortazavi, Majid; Tkatchenko, Alexandre

2018-05-28

Engineering of atomically thin membranes for hydrogen isotope separation is an actual challenge which has a broad range of applications. Recent experiments [M. Lozada-Hidalgo et al., Science 351, 68 (2016)] unambiguously demonstrate an order-of-magnitude difference in permeabilities of graphene-based membranes to protons and deuterons at ambient conditions, making such materials promising for novel separation technologies. Here we demonstrate that the permeability mechanism in such systems changes from quantum tunneling for protons to quasi-classical transport for heavier isotopes. Quantum nuclear effects exhibit large temperature and mass dependence, modifying the Arrhenius activation energy and Arrhenius prefactor for protons by more than 0.5 eV and by seven orders of magnitude correspondingly. Our findings not only shed light on the separation process for hydrogen isotope ions passing through pristine graphene but also offer new insights for controlling ion transport mechanisms in nanostructured separation membranes by manipulating the shape of the barrier and transport process conditions.

The response of CR-39 nuclear track detector to 1-9 MeV protons

DOE PAGES

Sinenian, N.; Rosenberg, M. J.; Manuel, M.; ...

2011-10-28

The response of CR-39 nuclear track detector (TasTrak®) to protons in the energy range of 0.92-9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. The effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather thanmore » the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.« less

Enhanced target normal sheath acceleration of protons from intense laser interaction with a cone-tube target

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

Xiao, K. D.; Huang, T. W.; Zhou, C. T., E-mail: zcangtao@iapcm.ac.cn

2016-01-15

Laser driven proton acceleration is proposed to be greatly enhanced by using a cone-tube target, which can be easily manufactured by current 3D-print technology. It is observed that energetic electron bunches are generated along the tube and accelerated to a much higher temperature by the combination of ponderomotive force and longitudinal electric field which is induced by the optical confinement of the laser field. As a result, a localized and enhanced sheath field is produced at the rear of the target and the maximum proton energy is about three-fold increased based on the two-dimentional particle-in-cell simulation results. It is demonstratedmore » that by employing this advanced target scheme, the scaling of the proton energy versus the laser intensity is much beyond the normal target normal sheath acceleration (TNSA) case.« less

A nuclear magnetic double resonance study of N-beta-bis-(beta'-chloroethyl) phosphonylethyl-DL-phenylalanine.

PubMed

Friedman, M; Boyd, W A

1977-01-01

Studies were carried out on the effect of decoupling, deuterium labeling, concentration, temperature, and solvent media on the NMR parameters of the vinyl phosphonate adduct of phenylalanine, C6H5CH2CH(COO-)NH2+CH2CH2PO(OCH2CH2C1)2. The results permit assignments of chemical shifts and coupling constants to the various protons of this molecule which contains unique structural features. The NH2+-CH2-protons are deshielded by more than 1 ppm than the CH2-PO-protons. The -OCH2-protons are nonequivalent exhibiting a fine split. Possible sources of the fine split include NH...O=P hydrogen bonding. The deuterium-labeling method should be applicable for synthesizing deuterium-and tritium-labeled crosslinked amino acids such as lysinoalanine and lanthionine and demonstrating analgous dehydroalanine-alpha-amino group-crosslinking.

Isochoric Heating of Solid-Density Matter with an Ultrafast Proton Beam

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

Key, M H; Mackinnon, A J; Patel, P K

A new technique is described for the isochoric heating (i.e., heating at constant volume) of matter to high energy-density plasma states (>10{sup 5} J/g) on a picosecond timescale (10{sup -12} sec). An intense, collimated, ultrashort-pulse beam of protons--generated by a high-intensity laser pulse--is used to isochorically heat a solid density material to a temperature of several eV. The duration of heating is shorter than the timescale for significant hydrodynamic expansion to occur, hence the material is heated to a solid density warm dense plasma state. Using spherically-shaped laser targets a focused proton beam is produced and used to heat amore » smaller volume to over 20 eV. The technique described of ultrafast proton heating provides a unique method for creating isochorically heated high-energy density plasma states.« less

Damage evaluation of proton irradiated titanium deuteride thin films to be used as neutron production targets

NASA Astrophysics Data System (ADS)

Suarez Anzorena, Manuel; Bertolo, Alma A.; Gagetti, Leonardo; Gaviola, Pedro A.; del Grosso, Mariela F.; Kreiner, Andrés J.

2018-06-01

Titanium deuteride thin films have been manufactured under different conditions specified by deuterium gas pressure, substrate temperature and time. The films were characterized by different techniques to evaluate the deuterium content and the homogeneity of such films. Samples with different concentrations of deuterium, including non deuterated samples, were irradiated with a 150 keV proton beam. Both deposits, pristine and irradiated, were characterized by optical profilometry and scanning electron microscopy.

Phase-Equilibria and Nanostructure Formation in Charged Rigid-Rod Polymers and Carbon Nanotubes

DTIC Science & Technology

2002-11-10

or liquid crystalline) and the crystalline polymer state. The form-I crystal solvate, identi- fied as a cocrystal of the protonated polymer and the...dissolution temperature, below 100 °C.12,13 The form-II crystal solvate, considered a polymer-solvent cocrystal in which the polymer is deprotonated,11,12...solvate that is a cocrystal of protonated PBZT and PPA anions. As previously mentioned, the fact that these two extreme cases result in similar

Durability and Performance of Polystyrene-b-Poly(vinylbenzyl trimethylammonium) Diblock Copolymer and Equivalent Blend Anion Exchange Membranes

DTIC Science & Technology

2015-01-01

requiring circulation of the electrolyte to filter out the carbonate solids. The superior power density of proton exchange membrane fuel cells ( PEMFC ...without requir- ing a CO2 free oxidant stream, prevented commercial develop- ment of the liquid AFC, allowing PEMFCs to dominate low temperature fuel...cell research and development. PEMFCs employ a solid acidic polymer to transport protons from anode to cathode. PEMs have been researched heavily the

The viscosity and temperature dependence of 1H T1-NMRD of the Gd(H 2O) 83+ complex

NASA Astrophysics Data System (ADS)

Zhou, Xiangzhi; Westlund, Per-Olof

2005-11-01

Water proton T1-NMRD profiles of the Gd(H 2O) 83+ complex have been recorded at three temperatures and at four concentrations of glycerol. The analysis is performed using both the generalized Solomon-Bloembergen-Morgan (GSBM) theory [J. Magn. Reson. 167(2004), 147-160], and the stochastic Liouville approach (SLA). The GSBM approach uses a two processes dynamic model of the zero-field splitting (ZFS) correlation function whereas SLA uses a single process model. Both models reproduce the proton T1-NMRD profiles well. However, the model parameters extracted from the two analyses, yield different ESR X-band spectra which moreover do not reproduce the experimental ESR spectra. It is shown that the analyses of the proton T1-NMRD profiles recorded for a solution Gd(H 2O) 83+ ions are relatively insensitive to the slow modulation part of dynamic model of the ZFS interaction correlation function. The description of the electron spin system results in a very small static ZFS, while recent ESR lineshape analysis indicates that the contribution from the static ZFS is important. Analysis of proton T1-NMRD profiles of Gd(H 2O) 83+ complex do result in a description of the electron spin system but these microscopic parameters are uncertain unless they also are tested in a ESR-lineshape analysis.

Chemicals and energy co-generation from direct hydrocarbons/oxygen proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Li, W. S.; Lu, D. S.; Luo, J. L.; Chuang, K. T.

A proton exchange membrane fuel cell for chemicals and energy co-generation was set up with hydrocarbons ethane, propane and butane as fuels, and the electrochemical performance of the cell was studied by using linear potential sweep, alternating current impedance and gas chromatography. The cell performance can be improved to a great extent by increasing the platinum load in the catalyst, by treating the membrane with phosphoric acid and by elevating temperature. The improvement of cell performance by the increase of platinum load is ascribed to the increase of reaction sites for hydrocarbon oxidation, that by phosphoric acid treatment to the increase of proton conductivity in Nafion membrane, and that by elevating temperature to the improvement in thermodynamic as well as kinetic aspects. Only a small fraction of the hydrocarbon is converted to carbon dioxide in this cell during its power generation. The current efficiency is 5% for the conversion of ethane to carbon dioxide in the ethane/oxygen fuel cell with 20% carbon-supported platinum as catalyst and phosphoric acid-treated membrane as proton exchange membrane at 0.2 V, 80 °C and ambient pressure. The reaction activity of hydrocarbons at the anode is in the order of propane, butane and ethane. The possible chemicals produced from the cell were hydrocarbons with more than six carbons, which are inactive at the anode under cell conditions.

Coupling of the coronal helium abundance to the solar wind

NASA Technical Reports Server (NTRS)

Hansteen, Viggo H.; Leer, Egil; Holzer, Thomas E.

1994-01-01

Models of the transition region-corona-solar wind system are investigated in order to find the coronal helium abundance and to study the role played by coronal helium in controlling the solar wind proton flux. The thermal force on alpha-particles in the transition region sets the flow of helium into the corona. The frictional coupling between alpha-particles and protons and/or the electric polarization field determines the proton flux in the solar wind as well as the fate of the coronal helium content. The models are constructed by solving the time-dependent population and momentum equations for all species of hydrogen and helium in an atmosphere with a given temperature profile. Several temperature profiles are considered in order to very the roles of frictional coupling and electric polarization field in the solar wind, and the thermal force in the transition region. Steady-state solutions are found for coronae with a hydrogen flux at 1 AU of 1.0 x 10(exp 9)/cm(exp 2)/sec or larger. For coronae with lower hydrogen fluxes, the helium flux into the corona is larger than the flux 'pulled out' by the solar wind protons, and solutions with increasing coronal helium content are found. The timescale for forming a helium-filled corona, that may allow for a steady outflow, is long compared to the mixing time for the corona.

A Ta/W mixed addenda heteropolyacid with excellent acid catalytic activity and proton-conducting property

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

Li, Shujun; Peng, Qingpo; Chen, Xuenian, E-mail: xnchen@htu.edu.cn

A new HPAs H{sub 20}[P{sub 8}W{sub 60}Ta{sub 12}(H{sub 2}O){sub 4}(OH){sub 8}O{sub 236}]·125H{sub 2}O (H-1) which comprises a Ta/W mixed addenda heteropolyanion, 20 protons, and 125 crystalline water molecules has been prepared through ion-exchange method. The structure and properties of H-1 have been explored in detail. AC impedance measurements indicate that H-1 is a good solid state proton conducting material at room temperature with a conductivity value of 7.2×10{sup −3} S cm{sup −1} (25 °C, 30% RH). Cyclic voltammograms of H-1 indicate the electrocatalytic activity towards the reduction of nitrite. Hammett acidity constant H{sub 0} of H-1 in CH{sub 3}CN ismore » −2.91, which is the strongest among the present known HPAs. Relatively, H-1 exhibits excellent catalytic activities toward acetal reaction. - Highlights: • A Ta/W mixed addenda Heteropolyacid (H-1) was isolated. • Hammett acidity constant H{sub 0} of H-1 is the strongest among the present known HPAs. • H-1 exhibits excellent catalytic activities toward acetal reaction. • H-1 is a good solid state proton conducting material at room temperature.« less

Diffusion length damage coefficient and annealing studies in proton-irradiated InP

NASA Technical Reports Server (NTRS)

Hakimzadeh, Roshanak; Vargas-Aburto, Carlos; Bailey, Sheila G.; Williams, Wendell

1993-01-01

We report on the measurement of the diffusion length damage coefficient (K(sub L)) and the annealing characteristics of the minority carrier diffusion length (L(sub n)) in Czochralski-grown zinc-doped indium phosphide (InP), with a carrier concentration of 1 x 10(exp l8) cm(exp -3). In measuring K(sub L) irradiations were made with 0.5 MeV protons with fluences ranging from 1 x 10(exp 11) to 3 x 10(exp 13) cm(exp -2). Pre- and post-irradiation electron-beam induced current (EBIC) measurements allowed for the extraction of L(sub n) from which K(sub L) was determined. In studying the annealing characteristics of L(sub n) irradiations were made with 2 MeV protons with fluence of 5 x 10(exp 13) cm(exp -2). Post-irradiation studies of L(sub n) with time at room temperature, and with minority carrier photoinjection and forward-bias injection were carried out. The results showed that recovery under Air Mass Zero (AMO) photoinjection was complete. L(sub n) was also found to recover under forward-bias injection, where recovery was found to depend on the value of the injection current. However, no recovery of L(sub n) after proton irradiation was observed with time at room temperature, in contrast to the behavior of 1 MeV electron-irradiated InP solar cells reported previously.

Inorganic-based proton conductive composite membranes for elevated temperature and reduced relative humidity PEM fuel cells

NASA Astrophysics Data System (ADS)

Wang, Chunmei

Proton exchange membrane (PEM) fuel cells are regarded as highly promising energy conversion systems for future transportation and stationary power generation and have been under intensive investigations for the last decade. Unfortunately, cutting edge PEM fuel cell design and components still do not allow economically commercial implementation of this technology. The main obstacles are high cost of proton conductive membranes, low-proton conductivity at low relative humidity (RH), and dehydration and degradation of polymer membranes at high temperatures. The objective of this study was to develop a systematic approach to design a high proton conductive composite membrane that can provide a conductivity of approximately 100 mS cm-1 under hot and dry conditions (120°C and 50% RH). The approach was based on fundamental and experimental studies of the proton conductivity of inorganic additives and composite membranes. We synthesized and investigated a variety of organic-inorganic Nafion-based composite membranes. In particular, we analyzed their fundamental properties, which included thermal stability, morphology, the interaction between inorganic network and Nafion clusters, and the effect of inorganic phase on the membrane conductivity. A wide range of inorganic materials was studied in advance in order to select the proton conductive inorganic additives for composite membranes. We developed a conductivity measurement method, with which the proton conductivity characteristics of solid acid materials, zirconium phosphates, sulfated zirconia (S-ZrO2), phosphosilicate gels, and Santa Barbara Amorphous silica (SBA-15) were discussed in detail. Composite membranes containing Nafion and different amounts of functionalized inorganic additives (sulfated inorganics such as S-ZrO2, SBA-15, Mobil Composition of Matter MCM-41, and S-SiO2, and phosphonated inorganic P-SiO2) were synthesized with different methods. We incorporated inorganic particles within Nafion clusters either by mixing inorganic gels or solutions with Nafion solution followed by membrane casting or by blending inorganic powders with Nafion solution. The membrane properties, such as acidity, swelling, water uptake, thermostability, proton conductivity, and electrochemical performance, were explored in depth. We characterized the inorganic phase inside composite membranes and its interaction with the Nafion matrix by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, we discussed the effect of these inorganic conductors' properties, such as particle size, conductivity, and interaction between functional groups and the Nafion, on the membrane conductivity. The contribution of hydrophilic inorganic particles in improving the membrane fuel cell performance was numerically analyzed by Tafel plot. Finally, the proton conductivity phenomena in composite membranes were simulated with two proton-transport models; one was based on the rule of mixtures, and the other was described by generalized Stefan-Maxwell equations. In the simulation, we proposed a new route in rational design of high proton-conductive composite membranes.

Ensemble Simulations of Proton Heating in the Solar Wind via Turbulence and Ion Cyclotron Resonance

NASA Astrophysics Data System (ADS)

Cranmer, Steven R.

2014-07-01

Protons in the solar corona and heliosphere exhibit anisotropic velocity distributions, violation of magnetic moment conservation, and a general lack of thermal equilibrium with the other particle species. There is no agreement about the identity of the physical processes that energize non-Maxwellian protons in the solar wind, but a traditional favorite has been the dissipation of ion cyclotron resonant Alfvén waves. This paper presents kinetic models of how ion cyclotron waves heat protons on their journey from the corona to interplanetary space. It also derives a wide range of new solutions for the relevant dispersion relations, marginal stability boundaries, and nonresonant velocity-space diffusion rates. A phenomenological model containing both cyclotron damping and turbulent cascade is constructed to explain the suppression of proton heating at low alpha-proton differential flow speeds. These effects are implemented in a large-scale model of proton thermal evolution from the corona to 1 AU. A Monte Carlo ensemble of realistic wind speeds, densities, magnetic field strengths, and heating rates produces a filled region of parameter space (in a plane described by the parallel plasma beta and the proton temperature anisotropy ratio) similar to what is measured. The high-beta edges of this filled region are governed by plasma instabilities and strong heating rates. The low-beta edges correspond to weaker proton heating and a range of relative contributions from cyclotron resonance. On balance, the models are consistent with other studies that find only a small fraction of the turbulent power spectrum needs to consist of ion cyclotron waves.

Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion

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

Soudackov, Alexander; Hammes-Schiffer, Sharon

2015-11-17

Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency regimes for the proton donor-acceptor vibrational mode. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term does not significantly impact the rate constants derived using the cumulant expansion approachmore » in any of the regimes studied. The effects of the quadratic term may become significant when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant, however, particularly at high temperatures and for proton transfer interfaces with extremely soft proton donor-acceptor modes that are associated with extraordinarily weak hydrogen bonds. Even with the thermal averaging procedure, the effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances, and the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton transfer and proton-coupled electron transfer in chemical and biological processes. We are grateful for support from National Institutes of Health Grant GM056207 (applications to enzymes) and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (applications to molecular electrocatalysts).« less

Free-Energy Landscape and Proton Transfer Pathways in Oxidative Deamination by Methylamine Dehydrogenase.

PubMed

Zelleke, Theodros; Marx, Dominik

2017-01-18

The rate-determining step in the reductive half-reaction of the bacterial enzyme methylamine dehydrogenase, which is proton abstraction from the native substrate methylamine, is investigated using accelerated QM/MM molecular dynamics simulations at room temperature. Generation of the multidimensional thermal free-energy landscape without restriction of the degrees of freedom beyond a multidimensional reaction subspace maps two rather similar pathways for the underlying proton transfer to one of two aspartate carboxyl oxygen atoms, termed OD1 and OD2, which hydrogen bond with Thr122 and Trp108, respectively. Despite significant large-amplitude motion perpendicular to the one-dimensional proton transfer coordinate, due to fluctuations of the donor-acceptor distance of about 3 Å, it is found that the one-dimensional proton transfer free-energy profiles are essentially identical to the minimum free-energy pathways on the multidimensional free-energy landscapes for both proton transfer channels. Proton transfer to one of the acceptor oxygen atoms-the OD2 site-is slightly favored in methylamine dehydrogenase by approximately 2 kcal mol -1 , both kinetically and thermodynamically. Mechanistic analyses reveal that the hydrogen bond between Thr122β and OD1 is always present in the transition state independently of the proton transfer channel. Population analysis confirms that the electronic charge gained upon oxidation of the substrate is delocalized within the ring systems of the tryptophan tryptophylquinone cofactor. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature effects on the mechanical properties of candidate SNS target container materials after proton and neutron irradiation

NASA Astrophysics Data System (ADS)

Byun, T. S.; Farrell, K.; Lee, E. H.; Mansur, L. K.; Maloy, S. A.; James, M. R.; Johnson, W. R.

2002-05-01

This report presents the tensile properties of EC316LN austenitic stainless steel and 9Cr-2WVTa ferritic/martensitic steel after 800 MeV proton and spallation neutron irradiation to doses in the range 0.54-2.53 dpa at 30-100 °C. Tensile testing was performed at room temperature (20 °C) and 164 °C. The EC316LN stainless steel maintained notable strain-hardening capability after irradiation, while the 9Cr-2WVTa ferritic/martensitic steel posted negative hardening in the engineering stress-strain curves. In the EC316LN stainless steel, increasing the test temperature from 20 to 164 °C decreased the strength by 13-18% and the ductility by 8-36%. The effect of test temperature for the 9Cr-2WVTa ferritic/martensitic steel was less significant than for the EC316LN stainless steel. In addition, strain-hardening behaviors were analyzed for EC316LN and 316L stainless steels. The strain-hardening rate of the 316 stainless steels was largely dependent on test temperature. A calculation using reduction of area measurements and stress-strain data predicted positive strain hardening during plastic instability.

Acid-Group-Content-Dependent Proton Conductivity Mechanisms at the Interlayer of Poly(N-dodecylacrylamide-co-acrylic acid) Copolymer Multilayer Nanosheet Films.

PubMed

Sato, Takuma; Tsukamoto, Mayu; Yamamoto, Shunsuke; Mitsuishi, Masaya; Miyashita, Tokuji; Nagano, Shusaku; Matsui, Jun

2017-11-14

The effect of the content of acid groups on the proton conductivity at the interlayer of polymer-nanosheet assemblies was investigated. For that purpose, amphiphilic poly(N-dodecylacrylamide-co-acrylic acid) copolymers [p(DDA/AA)] with varying contents of AA were synthesized by free radical polymerization. Surface pressure (π)-area (A) isotherms of these copolymers indicated that stable polymer monolayers are formed at the air/water interface for AA mole fraction (n) ≤ 0.49. In all cases, a uniform dispersion of the AA groups in the polymer monolayer was observed. Subsequently, polymer monolayers were transferred onto solid substrates using the Langmuir-Blodgett (LB) technique. X-ray diffraction (XRD) analyses of the multilayer films showed strong Bragg diffraction peaks, suggesting a highly uniform lamellar structure for the multilayer films. The proton conductivity of the multilayer films parallel to the direction of the layer planes were measured by impedance spectroscopy, which revealed that the conductivity increased with increasing values of n. Activation energies for proton conduction of ∼0.3 and 0.42 eV were observed for n ≥ 0.32 and n = 0.07, respectively. Interestingly, the proton conductivity of a multilayer film with n = 0.19 did not follow the Arrhenius equation. These results were interpreted in terms of the average distance between the AA groups (l AA ), and it was concluded that, for n ≥ 0.32, an advanced 2D hydrogen bonding network was formed, while for n = 0.07, l AA is too long to form such hydrogen bonding networks. The l AA for n = 0.19 is intermediate to these extremes, resulting in the formation of hydrogen bonding networks at low temperatures, and disruption of these networks at high temperatures due to thermally induced motion. These results indicate that a high proton conductivity with low activation energy can be achieved, even under weakly acidic conditions, by arranging the acid groups at an optimal distance.

Lanthanide ion (III) complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP8−) for dual biosensing of pH with CEST (chemical exchange saturation transfer) and BIRDS (biosensor imaging of redundant deviation in shifts)

PubMed Central

Huang, Yuegao; Coman, Daniel; Ali, Meser M.; Hyder, Fahmeed

2014-01-01

Relaxivity based magnetic resonance of phosphonated ligands chelated with gadolinium (Gd3+) shows promise for pH imaging. However instead of monitoring the paramagnetic effect of lanthanide complexes on the relaxivity of water protons, biosensor (or molecular) imaging with magnetic resonance is also possible by detecting either the non-exchangeable or the exchangeable protons on the lanthanide complexes themselves. The non-exchangeable protons (e.g., –CHx, where 3≥x≥1) are detected using a three-dimensional chemical shift imaging method called Biosensor Imaging of Redundant Deviation in Shifts (BIRDS), whereas the exchangeable protons (e.g., –OH or –NHy, where 2≥y≥1) are measured with Chemical Exchange Saturation Transfer (CEST) contrast. Here we tested the feasibility of BIRDS and CEST for pH imaging of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP8−) chelated with thulium (Tm3+) and ytterbium (Yb3+). BIRDS and CEST experiments show that both complexes are responsive to pH and temperature changes. Higher pH and temperature sensitivities are obtained with BIRDS for either complex when using the chemical shift difference between two proton resonances vs. using the chemical shift of a single proton resonance, thereby eliminating the need to use water resonance as reference. While CEST contrast for both agents is linearly dependent on pH within a relatively large range (i.e., 6.3-7.9), much stronger CEST contrast is obtained with YbDOTA-4AmP5− than with TmDOTA-4AmP5−. In addition, we demonstrate the prospect of using BIRDS to calibrate CEST as new platform for quantitative pH imaging. PMID:24801742

Lanthanide ion (III) complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate for dual biosensing of pH with chemical exchange saturation transfer (CEST) and biosensor imaging of redundant deviation in shifts (BIRDS).

PubMed

Huang, Yuegao; Coman, Daniel; Ali, Meser M; Hyder, Fahmeed

2015-01-01

Relaxivity-based magnetic resonance of phosphonated ligands chelated with gadolinium (Gd(3+)) shows promise for pH imaging. However instead of monitoring the paramagnetic effect of lanthanide complexes on the relaxivity of water protons, biosensor (or molecular) imaging with magnetic resonance is also possible by detecting either the nonexchangeable or the exchangeable protons on the lanthanide complexes themselves. The nonexchangeable protons (e.g. -CHx, where 3 ≥ x ≥ 1) are detected using a three-dimensional chemical shift imaging method called biosensor imaging of redundant deviation in shifts (BIRDS), whereas the exchangeable protons (e.g. -OH or -NHy , where 2 ≥ y ≥ 1) are measured with chemical exchange saturation transfer (CEST) contrast. Here we tested the feasibility of BIRDS and CEST for pH imaging of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaminophosphonate (DOTA-4AmP(8-)) chelated with thulium (Tm(3+) ) and ytterbium (Yb(3+)). BIRDS and CEST experiments show that both complexes are responsive to pH and temperature changes. Higher pH and temperature sensitivities are obtained with BIRDS for either complex when using the chemical shift difference between two proton resonances vs using the chemical shift of a single proton resonance, thereby eliminating the need to use water resonance as reference. While CEST contrast for both agents is linearly dependent on pH within a relatively large range (i.e. 6.3-7.9), much stronger CEST contrast is obtained with YbDOTA-4AmP(5-) than with TmDOTA-4AmP(5-). In addition, we demonstrate the prospect of using BIRDS to calibrate CEST as new platform for quantitative pH imaging. Copyright © 2014 John Wiley & Sons, Ltd.

A parametric study of the linear growth of magnetospheric EMIC waves in a hot plasma

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

Wang, Qi; Cao, Xing; Gu, Xudong, E-mail: guxudong@whu.edu.cn, E-mail: bbni@whu.edu.cn

2016-06-15

Since electromagnetic ion cyclotron (EMIC) waves in the terrestrial magnetosphere play a crucial role in the dynamic losses of relativistic electrons and energetic protons and in the ion heating, it is important to pursue a comprehensive understanding of the EMIC wave dispersion relation under realistic circumstances, which can shed significant light on the generation, amplification, and propagation of magnetospheric EMIC waves. The full kinetic linear dispersion relation is implemented in the present study to evaluate the linear growth of EMIC waves in a multi-ion (H{sup +}, He{sup +}, and O{sup +}) magnetospheric plasma that also consists of hot ring currentmore » protons. Introduction of anisotropic hot protons strongly modifies the EMIC wave dispersion surface and can result in the simultaneous growth of H{sup +}-, He{sup +}-, and O{sup +}-band EMIC emissions. Our parametric analysis demonstrates that an increase in the hot proton concentration can produce the generation of H{sup +}- and He{sup +}-band EMIC waves with higher possibility. While the excitation of H{sup +}-band emissions requires relatively larger temperature anisotropy of hot protons, He{sup +}-band emissions are more likely to be triggered in the plasmasphere or plasmaspheric plume where the background plasma is denser. In addition, the generation of He{sup +}-band waves is more sensitive to the variation of proton temperature than H{sup +}-band waves. Increase of cold heavy ion (He{sup +} and O{sup +}) density increases the H{sup +} cutoff frequency and therefore widens the frequency coverage of the stop band above the He{sup +} gyrofrequency, leading to a significant damping of H{sup +}-band EMIC waves. In contrast, O{sup +}-band EMIC waves characteristically exhibit the temporal growth much weaker than the other two bands, regardless of all considered variables, suggesting that O{sup +}-band emissions occur at a rate much lower than H{sup +}- and He{sup +}-band emissions, which is consistent with the observations.« less

Modeling solubility and acid-base properties of some amino acids in aqueous NaCl and (CH3)4NCl aqueous solutions at different ionic strengths and temperatures.

PubMed

Bretti, Clemente; Giuffrè, Ottavia; Lando, Gabriele; Sammartano, Silvio

2016-01-01

New potentiometric experiments have been performed in NaCl and in (CH3)4NCl media, to determine the protonation constants, the protonation enthalpy changes and the solubility of six natural α-amino acids, namely Glycine (Gly), Alanine (Ala), Valine (Val), Leucine (Leu), Serine (Ser) and Phenylalanine (Phe). The aim of the work is the rationalization of the protonation thermodynamics (log [Formula: see text], solubility and [Formula: see text]) in NaCl, determining recommended, tentative or provisional values in selected experimental conditions and to report, for the first time, data in a weak interacting medium, as (CH3)4NCl. Literature data analysis was performed selecting the most reliable values, analyzed together with new data here reported. Significant trends and similarities were observed in the behavior of the six amino acids, and in some cases it was possible to determine common parameters for the ionic strength and temperature dependence. In general, the first protonation step, relative to the amino group, is significantly exothermic (average value is [Formula: see text] = -44.5 ± 0.4 kJ mol(-1) at infinite dilution and T = 298.15 K), and the second, relative to the carboxylate group, is fairly close to zero ([Formula: see text] = -2.5 ± 1.6, same conditions). In both cases, the main contribution to the proton binding reaction is mainly entropic in nature. For phenylalanine and leucine, solubility measurements at different concentrations of supporting electrolyte allowed to determine total and specific solubility values, then used to obtain the Setschenow and the activity coefficients of all the species involved in the protonation equilibria. The values of the first protonation constant in (CH3)4NCl are lower than the corresponding values in NaCl, due to the weak interaction between the deprotonated amino group and (CH3)4N(+). In this light, differences between the protonation functions in NaCl and (CH3)4NCl were used for the quantification of the stability of the weak [(CH3)4N(+)-L(-)] complexes that resulted log K = -0.38 ± 0.07 as an average value for the six amino acids.

The evolution of solid density within a thermal explosion. I. Proton radiography of pre-ignition expansion, material motion, and chemical decomposition

NASA Astrophysics Data System (ADS)

Smilowitz, L.; Henson, B. F.; Romero, J. J.; Asay, B. W.; Saunders, A.; Merrill, F. E.; Morris, C. L.; Kwiatkowski, K.; Grim, G.; Mariam, F.; Schwartz, C. L.; Hogan, G.; Nedrow, P.; Murray, M. M.; Thompson, T. N.; Espinoza, C.; Lewis, D.; Bainbridge, J.; McNeil, W.; Rightley, P.; Marr-Lyon, M.

2012-05-01

We report proton transmission images obtained during direct heating of a sample of PBX 9501 (a plastic bonded formulation of the explosive nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) prior to the ignition of a thermal explosion. We describe the application of proton radiography using the 800 MeV proton accelerator at Los Alamos National Laboratory to obtain transmission images in these thermal explosion experiments. We have obtained images at two spatial magnifications and viewing both the radial and the transverse axes of a solid cylindrical sample encased in aluminum. During heating we observe the slow evolution of proton transmission through the samples, with particular detail during material flow associated with the HMX β-δ phase transition. We also directly observe the loss of solid density to decomposition associated with elevated temperatures in the volume defining the ignition location in these experiments. We measure a diameter associated with this volume of 1-2 mm, in agreement with previous estimations of the diameter using spatially resolved fast thermocouples.

Coordination-chemistry control of proton conductivity in the iconic metal-organic framework material HKUST-1.

PubMed

Jeong, Nak Cheon; Samanta, Bappaditya; Lee, Chang Yeon; Farha, Omar K; Hupp, Joseph T

2012-01-11

HKUST-1, a metal-organic framework (MOF) material containing Cu(II)-paddlewheel-type nodes and 1,3,5-benzenetricarboxylate struts, features accessible Cu(II) sites to which solvent or other desired molecules can be intentionally coordinated. As part of a broader investigation of ionic conductivity in MOFs, we unexpectedly observed substantial proton conductivity with the "as synthesized" version of this material following sorption of methanol. Although HKUST-1 is neutral, coordinated water molecules are rendered sufficiently acidic by Cu(II) to contribute protons to pore-filling methanol molecules and thereby enhance the alternating-current conductivity. At ambient temperature, the chemical identities of the node-coordinated and pore-filling molecules can be independently varied, thus enabling the proton conductivity to be reversibly modulated. The proton conductivity of HKUST-1 was observed to increase by ~75-fold, for example, when node-coordinated acetonitrile molecules were replaced by water molecules. In contrast, the conductivity became almost immeasurably small when methanol was replaced by hexane as the pore-filling solvent. © 2011 American Chemical Society

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

Ivanov, Sergei D., E-mail: sergei.ivanov@unirostock.de; Grant, Ian M.; Marx, Dominik

With the goal of computing quantum free energy landscapes of reactive (bio)chemical systems in multi-dimensional space, we combine the metadynamics technique for sampling potential energy surfaces with the ab initio path integral approach to treating nuclear quantum motion. This unified method is applied to the double proton transfer process in the formic acid dimer (FAD), in order to study the nuclear quantum effects at finite temperatures without imposing a one-dimensional reaction coordinate or reducing the dimensionality. Importantly, the ab initio path integral metadynamics technique allows one to treat the hydrogen bonds and concomitant proton transfers in FAD strictly independently andmore » thus provides direct access to the much discussed issue of whether the double proton transfer proceeds via a stepwise or concerted mechanism. The quantum free energy landscape we compute for this H-bonded molecular complex reveals that the two protons move in a concerted fashion from initial to product state, yet world-line analysis of the quantum correlations demonstrates that the protons are as quantum-uncorrelated at the transition state as they are when close to the equilibrium structure.« less

Effect of end-group cross-linking on transport properties of sulfonated poly(phenylene sulfide nitrile)s for proton exchange membranes

NASA Astrophysics Data System (ADS)

Kang, Na Rae; Lee, So Young; Shin, Dong Won; Hwang, Doo Sung; Lee, Kang Hyuck; Cho, Doo Hee; Kim, Ji Hoon; Lee, Young Moo

2016-03-01

A series of end-group cross-linked membranes (Az-XESPSN) were prepared by click reaction to investigate the effects of cross-linking on the morphology and proton transport properties of proton exchange membranes. The morphological transformations resulting from thermal annealing and cross-linking were observed by means of atomic force microscopy (AFM) and transmission electron microscopy (TEM). Compared to the non-cross-linked ESPSN membranes, the Az-XESPSN membranes exhibited lower water uptake and improved mechanical and chemical stabilities. In addition, the Az-XESPSN membranes exhibited higher proton conductivities (0.018-0.028 S cm-1) compared to those of the ESPSN membranes (0.0044-0.0053 S cm-1) and Nafion 212 (0.0061 S cm-1), particularly in conditions of elevated temperature (120 °C) and low relative humidity (35%). Such enhancements can be attributed to a synergistic effect of well-defined hydrophilic ionic clusters and triazole groups that function as proton carriers under anhydrous conditions. Furthermore, the Az-XESPSN membranes exhibited significantly enhanced single cell performance and long-term stability compared to those of ESPSN membranes.

Some challenging points in the identification of defects in floating-zone n-type silicon irradiated with 8 and 15 MeV protons

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

Emtsev, V. V., E-mail: emtsev@mail.ioffe.ru; Abrosimov, N. V.; Kozlovskii, V. V.

2016-10-15

Electrical properties of defects formed in n-Si(FZ) following 8 and 15 MeV proton irradiation are investigated by Hall effect measurements over the wide temperature range of T ≈ 25 to 300 K. Close attention is paid to the damaging factor of proton irradiation, leaving aside passivation effects by hydrogen. The concept of defect production and annealing processes being accepted in the literature so far needs to be reconsidered. Contrary to expectations the dominant impurity-related defects produced by MeV protons turn out to be electrically neutral in n-type material. Surprisingly, radiation acceptors appear to play a minor role. Annealing studies ofmore » irradiated samples of such complex defects as a divacancy tied to a phosphorus atom and a vacancy tied to two phosphorus atoms. The latter defect features high thermal stability. Identification of the dominant neutral donors, however, remains unclear and will require further, more detailed, studies. The electric properties of the material after proton irradiation can be completely restored at T = 800°C.« less

Accelerated radiation damage test facility using a 5 MV tandem ion accelerator

NASA Astrophysics Data System (ADS)

Wady, P. T.; Draude, A.; Shubeita, S. M.; Smith, A. D.; Mason, N.; Pimblott, S. M.; Jimenez-Melero, E.

2016-01-01

We have developed a new irradiation facility that allows to perform accelerated damage tests of nuclear reactor materials at temperatures up to 400 °C using the intense proton (<100 μA) and heavy ion (≈10 μA) beams produced by a 5 MV tandem ion accelerator. The dedicated beam line for radiation damage studies comprises: (1) beam diagnosis and focusing optical components, (2) a scanning and slit system that allows uniform irradiation of a sample area of 0.5-6 cm2, and (3) a sample stage designed to be able to monitor in-situ the sample temperature, current deposited on the sample, and the gamma spectrum of potential radio-active nuclides produced during the sample irradiation. The beam line capabilities have been tested by irradiating a 20Cr-25Ni-Nb stabilised stainless steel with a 3 MeV proton beam to a dose level of 3 dpa. The irradiation temperature was 356 °C, with a maximum range in temperature values of ±6 °C within the first 24 h of continuous irradiation. The sample stage is connected to ground through an electrometer to measure accurately the charge deposited on the sample. The charge can be integrated in hardware during irradiation, and this methodology removes uncertainties due to fluctuations in beam current. The measured gamma spectrum allowed the identification of the main radioactive nuclides produced during the proton bombardment from the lifetimes and gamma emissions. This dedicated radiation damage beam line is hosted by the Dalton Cumbrian Facility of the University of Manchester.

Advanced Materials for PEM-Based Fuel Cell Systems

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

James E. McGrath

2005-10-26

Proton exchange membrane fuel cells (PEMFCs) are quickly becoming attractive alternative energy sources for transportation, stationary power, and small electronics due to the increasing cost and environmental hazards of traditional fossil fuels. Two main classes of PEMFCs include hydrogen/air or hydrogen/oxygen fuel cells and direct methanol fuel cells (DMFCs). The current benchmark membrane for both types of PEMFCs is Nafion, a perfluorinated sulfonated copolymer made by DuPont. Nafion copolymers exhibit good thermal and chemical stability, as well as very high proton conductivity under hydrated conditions at temperatures below 80 °C. However, application of these membranes is limited due to theirmore » high methanol permeability and loss of conductivity at high temperatures and low relative humidities. These deficiencies have led to the search for improved materials for proton exchange membranes. Potential PEMs should have good thermal, hydrolytic, and oxidative stability, high proton conductivity, selective permeability, and mechanical durability over long periods of time. Poly(arylene ether)s, polyimides, polybenzimidazoles, and polyphenylenes are among the most widely investigated candidates for PEMs. Poly(arylene ether)s are a promising class of proton exchange membranes due to their excellent thermal and chemical stability and high glass transition temperatures. High proton conductivity can be achieved through post-sulfonation of poly(arylene ether) materials, but this most often results in very high water sorption or even water solubility. Our research has shown that directly polymerized poly(arylene ether) copolymers show important advantages over traditional post-sulfonated systems and also address the concerns with Nafion membranes. These properties were evaluated and correlated with morphology, structure-property relationships, and states of water in the membranes. Further improvements in properties were achieved through incorporation of inorganic fillers, such as phosphotungstic acid and zirconium hydrogen phosphate. Block copolymers were also studied due to the possibility to achieve a desired combination of homopolymer properties as well as the unique morphologies that are possible with block copolymers. Bezoyl substituted poly(p-phenylene) blocks were combined with poly(arylene ether) blocks to merge the structural rigidity of the poly(p-phenylene) with the ductility and high protonic conductivity of the poly(arylene ether)s. As evidenced by our many refereed publications and preprints, the research that we have conducted over the past several years has made a valuable and significant contribution to the literature and to the state of understanding of proton exchange membranes. Our early efforts at scale-up have suggested that the directly polymerized disulfonated poly(arylene ether sulfone) copolymers are commercially viable alternatives for proton exchange membranes. A new process for bipolar plates was developed and is described. An important single domain PEMFC model was developed and is documented in this final report.« less

Proton conductivity in ampullae of Lorenzini jelly

PubMed Central

Josberger, Erik E.; Hassanzadeh, Pegah; Deng, Yingxin; Sohn, Joel; Rego, Michael J.; Amemiya, Chris T.; Rolandi, Marco

2016-01-01

In 1678, Stefano Lorenzini first described a network of organs of unknown function in the torpedo ray—the ampullae of Lorenzini (AoL). An individual ampulla consists of a pore on the skin that is open to the environment, a canal containing a jelly and leading to an alveolus with a series of electrosensing cells. The role of the AoL remained a mystery for almost 300 years until research demonstrated that skates, sharks, and rays detect very weak electric fields produced by a potential prey. The AoL jelly likely contributes to this electrosensing function, yet the exact details of this contribution remain unclear. We measure the proton conductivity of the AoL jelly extracted from skates and sharks. The room-temperature proton conductivity of the AoL jelly is very high at 2 ± 1 mS/cm. This conductivity is only 40-fold lower than the current state-of-the-art proton-conducting polymer Nafion, and it is the highest reported for a biological material so far. We suggest that keratan sulfate, identified previously in the AoL jelly and confirmed here, may contribute to the high proton conductivity of the AoL jelly with its sulfate groups—acid groups and proton donors. We hope that the observed high proton conductivity of the AoL jelly may contribute to future studies of the AoL function. PMID:27386543

Long-term Trends in the Solar Wind Proton Measurements

NASA Astrophysics Data System (ADS)

Elliott, Heather A.; McComas, David J.; DeForest, Craig E.

2016-11-01

We examine the long-term time evolution (1965-2015) of the relationships between solar wind proton temperature (T p) and speed (V p) and between the proton density (n p) and speed using OMNI solar wind observations taken near Earth. We find a long-term decrease in the proton temperature-speed (T p-V p) slope that lasted from 1972 to 2010, but has been trending upward since 2010. Since the solar wind proton density-speed (n p-V p) relationship is not linear like the T p-V p relationship, we perform power-law fits for n p-V p. The exponent (steepness in the n p-V p relationship) is correlated with the solar cycle. This exponent has a stronger correlation with current sheet tilt angle than with sunspot number because the sunspot number maxima vary considerably from cycle to cycle and the tilt angle maxima do not. To understand this finding, we examined the average n p for different speed ranges, and found that for the slow wind n p is highly correlated with the sunspot number, with a lag of approximately four years. The fast wind n p variation was less, but in phase with the cycle. This phase difference may contribute to the n p-V p exponent correlation with the solar cycle. These long-term trends are important since empirical formulas based on fits to T p and V p data are commonly used to identify interplanetary coronal mass ejections, but these formulas do not include any time dependence. Changes in the solar wind density over a solar cycle will create corresponding changes in the near-Earth space environment and the overall extent of the heliosphere.

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type

NASA Astrophysics Data System (ADS)

Baret, P.; Beaujolais, V.; Bougault, C.; Gaude, D.; Pierre, J.-L.

1998-01-01

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type are described. The study of the gallium complex emphasizes: (i) that the inversion of the octahedral center is not observed and: (ii) the absence of exchange between free ligand and complex, at room temperature. In the case of the iron complex, assignments of the hyperfine shifted resolved resonances are achieved, based on temperature-behavior studies, which evidence the D3 symmetry of the complex. These assignments are in complete agreement with measured T1 values and proton-to-iron distances obtained from molecular modelling. Les complexes du gallium (III) et du fer (III) d'un ligand macrobicyclique chiral impliquant trois sous-unités de type binaphtol sont étudiés en RMN du proton en solution méthanolique. L'étude du complexe (diamagnétique) du gallium permet de montrer que le complexe : (i) ne subit pas d'inversion de la configuration (Δ/Λ) du site octaédrique et : (ii) qu'il n'y a pas d'échange entre ligand libre et complexe à la température ambiante. L'évolution du spectre du complexe paramagnétique du fer avec la température permet une attribution des protons du ligand et met en évidence la symétrie D3 du complexe. Une bonne corrélation est obtenue entre la distance fer-proton (donnée par la modélisation moléculaire) et le T1 du proton considéré.

Molecular dynamics in stiff ionene below glass transition.

PubMed

Makrocka-Rydzyk, M; Glowinkowski, S; Jurga, S; Meyer, W H

1995-08-01

Temperature dependences of proton and fluorine second moments and spin-lattice relaxation time T1 below glass transition were measured in glassy "I-Do,Pip-Me-BF4" ionene. The existence of motions of methyl groups and segments linking the cationic centers, namely piperidinium rings and trimethylene groups, for the polymeric part of ionene were established. Isotropic rotation of the counter-ion was evidenced and its limited diffusion suggested. To interpret the proton and fluorine relaxation data, a Davidson-Cole distribution of correlation times was assumed.

Method of synthesis of proton conducting materials

DOEpatents

Garzon, Fernando Henry; Einsla, Melinda Lou; Mukundan, Rangachary

2010-06-15

A method of producing a proton conducting material, comprising adding a pyrophosphate salt to a solvent to produce a dissolved pyrophosphate salt; adding an inorganic acid salt to a solvent to produce a dissolved inorganic acid salt; adding the dissolved inorganic acid salt to the dissolved pyrophosphate salt to produce a mixture; substantially evaporating the solvent from the mixture to produce a precipitate; and calcining the precipitate at a temperature of from about 400.degree. C. to about 1200.degree. C.

Model for energy transfer in the solar wind: Model results

NASA Technical Reports Server (NTRS)

Barnes, A. A., Jr.; Hartle, R. E.

1972-01-01

A description is given of the results of solar wind flow in which the heating is due to (1) propagation and dissipation of hydromagnetic waves generated near the base of the wind, and (2) thermal conduction. A series of models is generated for fixed values of density, electron and proton temperature, and magnetic field at the base by varying the wave intensity at the base of the model. This series of models predicts the observed correlation between flow speed and proton temperature for a large range of velocities. The wave heating takes place in a shell about the sun greater than or approximately equal to 10 R thick. We conclude that large-scale variations observed in the solar wind are probably due mainly to variation in the hydromagnetic wave flux near the sun.

Hydrogen content and mechanical stress in glow discharge amorphous silicon

NASA Astrophysics Data System (ADS)

Paduschek, P.; Eichinger, P.; Kristen, G.; Mitlehner, H.

1982-08-01

The hydrogen content of plasma deposited amorphous silicon thin films on silicon has been determined as a function of annealing parameters (200-700°C, 12 h) using the proton-proton scattering method. It is shown that hydrogen is released with an activation energy of 1.3 eV. Different deposition temperatures are compared with respect to the hydrogen evolution. The mechanical stress of the layers on silicon substrates has been measured by interferometric techniques for each annealing step. As the hydrogen content decreases monotonically with rising annealing temperature the mechanical stress converts from compressive to tensile. While only a weak correlation exists between the total hydrogen content and the mechanical stress, the bound hydrogen as determined by IR absorption displays a linear relation with the measured mechanical stress.

Quantum Effects at a Proton Relaxation at Low Temperatures

NASA Astrophysics Data System (ADS)

Kalytka, V. A.; Korovkin, M. V.

2016-11-01

Quantum effects during migratory polarization in multi-well crystals (including multi-well silicates and crystalline hydrates) are investigated in a variable electric field at low temperatures by direct quantum-mechanical calculations. Based on analytical solution of the quantum Liouville kinetic equation in the linear approximation for the polarizing field, the non-stationary density matrix is calculated for an ensemble of non-interacting protons moving in the field of one-dimensional multi-well crystal potential relief of rectangular shape. An expression for the complex dielectric constant convenient for a comparison with experiment and calculation of relaxer parameters is derived using the nonequilibrium polarization density matrix. The density matrix apparatus can be used for analytical investigation of the quantum mechanism of spontaneous polarization of a ferroelectric material (KDP and DKDP).

Water-Mediated Proton Hopping on an Iron Oxide Surface

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

Merte, L. R.; Peng, Guowen; Bechstein, Ralf

2012-05-18

The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H3O+-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO2(110), where water dissociationmore » is a key step in proton diffusion.« less

The resolved layer of a collisionless, high beta, supercritical, quasi-perpendicular shock wave. I - Rankine-Hugoniot geometry, currents, and stationarity

NASA Technical Reports Server (NTRS)

Scudder, J. D.; Aggson, T. L.; Mangeney, A.; Lacombe, C.; Harvey, C. C.

1986-01-01

Data collected by the ISEE dual-spacecraft mission (on November 7, 1977) on a slowly moving, supercritical, high-beta, quasi-perpendicular bow shock are presented, and the local geometry, spatial scales, and stationarity of this shock wave are assessed in a self-consistent Rankine-Hugoniot-constrained frame of reference. Included are spatial profiles of the ac and dc magnetic and electric fields, electron and proton fluid velocities, current densities, electron and proton number densities, temperatures, pressures, and partial densities of the reflected protons. The observed layer profile is shown to be nearly phase standing and one-dimensional in a Rankine-Hugoniot frame, empirically determined by the magnetofluid parameters outside the layer proper.

Deprotonation of hydrogen bonded Schiff bases by three strong nitrogen bases

NASA Astrophysics Data System (ADS)

Schilf, Wojciech; Cmoch, Piotr; Szady-Chełmieniecka, Anna; Grech, Eugeniusz

2009-03-01

Three Schiff bases obtained from substituted salicylaldehydes and 2-hydroxy-1-naphthaldehyde and aliphatic amines were investigated in terms of possible withdrawal of tautomeric proton from intramolecular hydrogen bridge. Three strong nitrogen bases: 1,8-bis(dimethylamino)naphtalene (DMAN), 1,1,3,3-tetramethylguanidine (TMG) and 1,8-bis(tetramethylguanidino)naphthalene (TMGN) were used as deprotonating agents in acetonitrile solution at room temperature. In the specified conditions it was found that only in the case of 5-nitrosalicylaldehyde and isopropyl amine derivative this process could be performed using TMG and TMGN as a base. The other derivatives, where bridged proton is shifted to oxygen or nitrogen atom, do not undergo such reaction. The deprotonation process was monitored by nitrogen and proton NMR measurements.

Infrared study of OH(-) defects in KTiOPO4 crystals

NASA Astrophysics Data System (ADS)

Morris, P. A.; Crawford, M. K.; Jones, B.

1992-12-01

Variations in the concentrations and distributions of the OH(-) defects present in flux and hydrothermal KTiOPO4 (KTP) crystals, measured by infrared spectroscopy of single crystals, are attributed to differences in the growth environments and other nonhydrogenic defects present in the crystals. The concentrations of OH(-) have been estimated from the infrared data to be approximately 400 ppma (parts per million atomic) (3.0 x 10 exp 19/cu cm) in the flux crystals, 1100-1500 ppma (0.74-1.1 x 10 exp 20/cu cm) in the high-temperature hydrothermal and 600 ppma (4.3 x 10 exp 19/cu cm) in the low-temperature hydrothermal crystals. A 3566/cm peak and a 3575/cm band are observed in all crystals. The integrated intensity of the OH(-) absorption band at 3566/cm increases at the expense of the 3575/cm band at higher temperatures in the high-temperature hydrothermal crystals. Several OH(-) peaks (3490, 3455, 3428, 3420, and 3333/cm), which have strongly temperature-dependent linewidths, are present in the hydrothermally grown KTP crystals. The temperature dependencies of their peak frequencies and widths are consistent with the presence of mobile protons in the lattice. The protons located in the 3490 and 3428/cm sites are believed to contribute to the ionic conductivity of the high-conductivity high-temperature hydrothermal crystals.

Constraints on models for the flagellar rotary motor.

PubMed Central

Berg, H C

2000-01-01

Most bacteria that swim are propelled by flagellar filaments, each driven at its base by a rotary motor embedded in the cell wall and cytoplasmic membrane. A motor is about 45 nm in diameter and made up of about 20 different kinds of parts. It is assembled from the inside out. It is powered by a proton (or in some species, a sodium-ion) flux. It steps at least 400 times per revolution. At low speeds and high torques, about 1000 protons are required per revolution, speed is proportional to protonmotive force, and torque varies little with temperature or hydrogen isotope. At high speeds and low torques, torque increases with temperature and is sensitive to hydrogen isotope. At room temperature, torque varies remarkably little with speed from about -100 Hz (the present limit of measurement) to about 200 Hz, and then it declines rapidly reaching zero at about 300 Hz. These are facts that motor models should explain. None of the existing models for the flagellar rotary motor completely do so. PMID:10836502

Numerical simulation of proton exchange membrane fuel cells at high operating temperature

NASA Astrophysics Data System (ADS)

Peng, Jie; Lee, Seung Jae

A three-dimensional, single-phase, non-isothermal numerical model for proton exchange membrane (PEM) fuel cell at high operating temperature (T ≥ 393 K) was developed and implemented into a computational fluid dynamic (CFD) code. The model accounts for convective and diffusive transport and allows predicting the concentration of species. The heat generated from electrochemical reactions, entropic heat and ohmic heat arising from the electrolyte ionic resistance were considered. The heat transport model was coupled with the electrochemical and mass transport models. The product water was assumed to be vaporous and treated as ideal gas. Water transportation across the membrane was ignored because of its low water electro-osmosis drag force in the polymer polybenzimidazole (PBI) membrane. The results show that the thermal effects strongly affect the fuel cell performance. The current density increases with the increasing of operating temperature. In addition, numerical prediction reveals that the width and distribution of gas channel and current collector land area are key optimization parameters for the cell performance improvement.

Nafion/silane nanocomposite membranes for high temperature polymer electrolyte membrane fuel cell.

PubMed

Ghi, Lee Jin; Park, Na Ri; Kim, Moon Sung; Rhee, Hee Woo

2011-07-01

The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both potable and stationary applications because it can offer high power density and be used only hydrogen and oxygen as environment-friendly fuels. Nafion which is widely used has mechanical and chemical stabilities as well as high conductivity. However, there is a drawback that it can be useless at high temperatures (> or = 90 degrees C) because proton conducting mechanism cannot work above 100 degrees C due to dehydration of membrane. Therefore, PEMFC should be operated for long-term at high temperatures continuously. In this study, we developed nanocomposite membrane using stable properties of Nafion and phosphonic acid groups which made proton conducting mechanism without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion and then its aminopropyl group was chemically modified to phosphonic acid groups. The nanocomposite membrane showed very high conductivity (approximately 0.02 S/cm at 110 degrees C, <30% RH).

Proton Relaxivity and Magnetic Hyperthermia Evaluation of Gadolinium Doped Nickel Ferrite Nanoparticles as Potential Theranostic Agents.

PubMed

Yadavalli, Tejabhiram; Raja, Paradeep; Ramaswamy, Shivaraman; Chandrasekharan, Gopalakrishnan; Chennakesavulu, Ramasamy

2017-02-01

This paper outlines the preparation of gadolinium doped nickel ferrite nanoparticles as potential magnetic carriers and longitudinal magnetic resonance imaging contrast agents using hydrothermal method with gadolinium concentration varying from 10% to 40%. A concise effect on the crystal structure was observed at 10% and 20% gadolinium doping, while gadolinium oxide was observed to leach at concentrations exceeding 20%. Further, gadolinium doped nickel ferrites were analyzed for their morphological, magnetic, proton relaxation and magnetic hyperthermia heating properties to understand their potential role as magnetic carrier agents. Low temperature and room temperature magnetic studies conducted on the samples showed comparatively high magnetic saturation with low remanent magnetization. Further, relaxometry studies revealed a high relaxation rate of 6.63 s−1 at a concentration of 0.1 mg/mL. Magnetic hyperthermia studies of the samples at a concentration of 1 mg/mL, assessed that the samples attained a temperature of 68 °C in 240 seconds.

Proton-Coupled Electron Transfer and Substituent Effects in Catechol-Based Deep Eutectic Solvents: Gross and Fine Tuning of Redox Activity.

PubMed

Smith, Parker J; Goeltz, John C

2017-12-07

The 1,2-diol moiety in a variety of substituted catechols allows formation of room temperature ionic melts in a 2:1 ratio with choline chloride or choline dihydrogen citrate. These deep eutectic solvents were 4.3-6.6 M in redox active catechols. Substituents on 3- and 4-substituted catechols shift both E° and pK a such that Hammett parameters predict the observed E p for oxidation in square wave voltammetry. The proton acceptor for the proton-coupled oxidation shifts the observed E p more strongly than the substituents within the substituents and acceptors reported here. The shift is predicted well by the pK a of the conjugate acid of the proton acceptor, i.e., water in aqueous solutions or chloride or dihydrogen citrate in the DESs in this study. Together, the substituent and the proton acceptor allow gross and fine-tuning of the oxidation potential for catechol over 750 mV, the first demonstration of control of the thermodynamics of proton-coupled electron transfer in deep eutectic solvents. Changing the substituents on the HBD affords fine control in tens of millivolts, while changing the base strength of the anion of the organic salt affords gross control across hundreds of millivolts.

Eucalypt smoke and wildfires

NASA Astrophysics Data System (ADS)

Maleknia, Simin D.; Bell, Tina L.; Adams, Mark A.

2009-01-01

Eucalypt contributions to biogenic sources of volatile organic compounds (VOCs) in Australia are estimated at teragram (Tg = 1012 g) amounts each year. Biogenic VOCs include plant-specific isoprenoids (isoprene and a range of terpenes) and other reactive organic compounds (i.e., acids, aldehydes and ketones). Atmospheric reactions of VOCs are numerous and many have significant environmental impact. Wildfires increase both the amounts of VOCs released and the complexity of their reactions. Proton-transfer reaction mass spectrometry (PTR-MS), gas chromatography mass spectrometry (GCMS) and direct analysis in real time (DART) mass spectrometry were applied to analyze release of VOCs as a function of temperatures ranging from ambient to combustion. PTR-MS enabled trace level analysis of VOCs from a complex forest atmosphere and revealed the release of terpenes associated with leaf damage during a storm. Temperature profile studies revealed ion abundances (i.e., emissions of VOCs) could be correlated with boiling points and vapor pressures of specific compounds. PTR-MS analysis of VOCs resulting from heating fresh leaf (E. grandis) material suggested that emissions of protonated methanol (m/z 33) and protonated acetaldehyde (m/z 45) were greatest at ~60 °C while m/z 137 and 153 (associated with a series of terpenes) showed monotonic increases in ion abundance over a wide temperature range from ambient to 200 °C. GCMS analysis of fresh and senescent leaves of E. grandis showed that a series of VOCs (ethylvinylketone, diethylketone, 2-ethylfuran, hexanal and hexenals) are present only in fresh leaves while several terpenes ([alpha] and [beta] pinenes, [alpha]-phellandrene, eucalyptol, [gamma]-terpinene) were common in both. DART analysis of fresh leaf and stem of E. sideroxylon identified tissue-specific VOCs (e.g., methanol and ethanol were more abundant in stems). PTR-MS combustion studies of senescent leaves (E. grandis) identified two distinct, temperature-dependent VOC compositions. Before the appearance of smoke, the composition of VOCs remained consistent and correlated well with various naturally occurring isoprenoids, as observed in temperature profile studies. Sampling of eucalypt smoke suggested ions (m/z 75, 85, 87, 99, 111 and 125) correlated with protonated mass of oxygenated aldehydes, ketones, furans and substituted benzenes, and were due to pyrolysis of polycarbohydrates (cellulose and lignin) that are common in many types of wood.

Evolution of Proton and Alpha Particle Velocities through the Solar Cycle

NASA Astrophysics Data System (ADS)

Ďurovcová, T.; Šafránková, J.; Němeček, Z.; Richardson, J. D.

2017-12-01

Relative properties of solar wind protons and α particles are often used as indicators of a source region on the solar surface, and analysis of their evolution along the solar wind path tests our understanding of physics of multicomponent magnetized plasma. The paper deals with the comprehensive analysis of the difference between proton and α particle bulk velocities at 1 au with a special emphasis on interplanetary coronal mass ejections (ICMEs). A comparison of about 20 years of Wind observations at 1 au with Helios measurements closer to the Sun (0.3-0.7 au) generally confirms the present knowledge that (1) the differential speed between both species increases with the proton speed; (2) the differential speed is lower than the local Alfvén speed; (3) α particles are faster than protons near the Sun, and this difference decreases with the increasing distance. However, we found a much larger portion of observations with protons faster than α particles in Wind than in Helios data and attributed this effect to a preferential acceleration of the protons in the solar wind. A distinct population characterized by a very small differential velocity and nearly equal proton and α particle temperatures that is frequently observed around the maximum of solar activity was attributed to ICMEs. Since this population does not exhibit any evolution with increasing collisional age, we suggest that, by contrast to the solar wind from other sources, ICMEs are born in an equilibrium state and gradually lose this equilibrium due to interactions with the ambient solar wind.

Shape evolution of 72,74Kr with temperature in covariant density functional theory

NASA Astrophysics Data System (ADS)

Zhang, Wei; Niu, Yi-Fei

2017-09-01

The rich phenomena of deformations in neutron-deficient krypton isotopes, such as shape evolution with neutron number and shape coexistence, have attracted the interest of nuclear physicists for decades. It is interesting to study such shape phenomena using a novel way, e.g. by thermally exciting the nucleus. In this work, we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach, and apply this approach for the study of shape evolution in 72,74Kr with increasing temperature. For 72Kr, with temperature increasing, the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T ˜0.9 MeV, and then changes from oblate to spherical at T ˜2.1 MeV. For 74Kr, its global minimum is at quadrupole deformation β 2 ˜ -0.14 and abruptly changes to spherical at T˜ 1.7 MeV. The proton pairing transition occurs at critical temperature 0.6 MeV following the rule T c=0.6Δ p(0), where Δ p(0) is the proton pairing gap at zero temperature. The signatures of the above pairing transition and shape changes can be found in the specific heat curve. The single-particle level evolutions with temperature are presented. Supported by National Natural Science Foundation of China (11105042, 11305161, 11505157), Open Fund of Key Laboratory of Time and Frequency Primary Standards, CAS, and Support from Henan Administration of Foreign Experts Affairs

Active-site protein dynamics and solvent accessibility in native Achromobacter cycloclastes copper nitrite reductase.

PubMed

Sen, Kakali; Horrell, Sam; Kekilli, Demet; Yong, Chin W; Keal, Thomas W; Atakisi, Hakan; Moreau, David W; Thorne, Robert E; Hough, Michael A; Strange, Richard W

2017-07-01

Microbial nitrite reductases are denitrifying enzymes that are a major component of the global nitrogen cycle. Multiple structures measured from one crystal (MSOX data) of copper nitrite reductase at 240 K, together with molecular-dynamics simulations, have revealed protein dynamics at the type 2 copper site that are significant for its catalytic properties and for the entry and exit of solvent or ligands to and from the active site. Molecular-dynamics simulations were performed using different protonation states of the key catalytic residues (Asp CAT and His CAT ) involved in the nitrite-reduction mechanism of this enzyme. Taken together, the crystal structures and simulations show that the Asp CAT protonation state strongly influences the active-site solvent accessibility, while the dynamics of the active-site 'capping residue' (Ile CAT ), a determinant of ligand binding, are influenced both by temperature and by the protonation state of Asp CAT . A previously unobserved conformation of Ile CAT is seen in the elevated temperature series compared with 100 K structures. DFT calculations also show that the loss of a bound water ligand at the active site during the MSOX series is consistent with reduction of the type 2 Cu atom.

Effects of Alternating Hydrogenated and Protonated Segments in polymers on their Wettability.

NASA Astrophysics Data System (ADS)

Smith, Dennis; Traiphol, Rakchart; Cheng, Gang; Perahia, Dvora

2003-03-01

Polymers consisting of alternating hydrogenated and fluorinated segments exhibit unique interfacial characteristics governed by the components that dominate the interface. Presence of fluorine reduces the interfacial energy and is expected to decrease the adhesion to the polymer surface. Thin liquid crystalline (LC) layers of 4,4?-octyl-cyanobiphenyl, cast on top of a polymeric layer consisting of alternating methylstylbine protonated segments bridged by a fluorinated group was used as a mechanistic tool to study of interfacial effects on three parameters: wetting, interfacial alignment and surface induces structures. The liquid crystal cast on a low interfacial energy fluorinated polymeric film exhibits bulk homeotropic alignment as expected. However it fully wetted the polymer surface despite the incompatibility of the protonated LC and mainly fluorinated polymer interface. Further more, it was found to stabilize the interfacial Semitic layers to a higher temperature and induce different surface ordering that was not observed at the same temperature neither in the bulk nor at the interfaces with silicon or glass surface. These results indicate that the interfacial interactions of polymers with liquid crystals are a complex function of both surface energies and the interfacial structure of the polymer.

Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

NASA Astrophysics Data System (ADS)

Téllez Lozano, Helena; Druce, John; Cooper, Samuel J.; Kilner, John A.

2017-12-01

18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H216O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity ( 1.3 × 10-11 cm2s-1) at this temperature and that the presence of water (2H216O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of 3. The 2H distribution, as inferred from the 2H216O- SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials.

NMR based solvent exchange experiments to understand the conformational preference of intrinsically disordered proteins using FG-nucleoporin peptide as a model

PubMed Central

Heisel, Kurt A.; Krishnan, V. V.

2014-01-01

The conformational preference of a peptide with three phenylalanine-glycine (FG) repeats from the intrinsically disordered domain of nucleoporin 159 (nup159) from the yeast nucleopore complex (NPC) is studied. Conformational states of this FG-peptide in dimethyl sulfoxide (DMSO), a non-native solvent are first studied. A solvent exchange scheme is designed and performed to understand how the conformational preferences of the peptide are altered as the solvent shifts from DMSO to water. An ensemble of structures of a 19-residue peptide is determined based on 13Cα, 1Hα, and 1HN chemical shifts and with inter-proton distances. An experimental model is then presented where chemical shifts and amide-proton temperature dependence is probed at changing DMSO to water ratios. These co-solvent experiments provide evidence of a conformational change as the fraction of water increases by the stark change in the behavior of amide protons under varied temperature. This investigation provides a NMR based experimental method in the field of intrinsically disordered proteins to realize conformational transitions from a non-native set of structures (in DMSO) to a native set of disordered conformers (in water). PMID:24037535

Crosslinked polybenzimidazoles containing branching structure as membrane materials with excellent cell performance and durability for fuel cell applications

NASA Astrophysics Data System (ADS)

Hu, Meishao; Ni, Jiangpeng; Zhang, Boping; Neelakandan, Sivasubramaniyan; Wang, Lei

2018-06-01

Crosslinking is an effective method to improve the properties of high temperature proton exchange membranes based on polybenzimidazole. However, the compact structure of crosslinked polybenzimidazole hinders the phosphoric acid absorption of the membranes, resulting in a relatively poor fuel cell performance. Recently, we find that branched polymers can absorb more phosphoric acid with a larger free volume, but suffer from deteriorated mechanical strength. In this work, a new method is proposed to obtain excellent over-all properties of high temperature proton exchange membranes. A series of crosslinked polybenzimidazoles containing branching structure as membrane materials are successfully prepared for the first time. Compared with conventional crosslinked membranes, these crosslinked polybenzimidazole membranes containing branching structure exhibit a higher phosphoric acid doping level and proton conductivity, improved durability, lower swelling rate and comparable mechanical strength. In particular, the fuel cell base on the crosslinked and branched membrane with a 10% ratio of crosslinker in non-humidified hydrogen/air at 160 °C achieves a power density of 404 mW cm-2. The results indicate that the combination of crosslinking and branching is an effective approach to improve the properties of polybenzimidazole membrane materials.

A Deeper Understanding of Stability in the Solar Wind: Applying Nyquist's Instability Criterion to Wind Faraday Cup Data

NASA Astrophysics Data System (ADS)

Alterman, B. L.; Klein, K. G.; Verscharen, D.; Stevens, M. L.; Kasper, J. C.

2017-12-01

Long duration, in situ data sets enable large-scale statistical analysis of free-energy-driven instabilities in the solar wind. The plasma beta and temperature anisotropy plane provides a well-defined parameter space in which a single-fluid plasma's stability can be represented. Because this reduced parameter space can only represent instability thresholds due to the free energy of one ion species - typically the bulk protons - the true impact of instabilities on the solar wind is under estimated. Nyquist's instability criterion allows us to systematically account for other sources of free energy including beams, drifts, and additional temperature anisotropies. Utilizing over 20 years of Wind Faraday cup and magnetic field observations, we have resolved the bulk parameters for three ion populations: the bulk protons, beam protons, and alpha particles. Applying Nyquist's criterion, we calculate the number of linearly growing modes supported by each spectrum and provide a more nuanced consideration of solar wind stability. Using collisional age measurements, we predict the stability of the solar wind close to the sun. Accounting for the free-energy from the three most common ion populations in the solar wind, our approach provides a more complete characterization of solar wind stability.

Dissolving Hydroxyolite: A DNA Molecule into Its Hydroxyapatite Mold.

PubMed

Bertran, Oscar; Revilla-López, Guillermo; Casanovas, Jordi; Del Valle, Luis J; Turon, Pau; Puiggalí, Jordi; Alemán, Carlos

2016-05-04

In spite of the clinical importance of hydroxyapatite (HAp), the mechanism that controls its dissolution in acidic environments remains unclear. Knowledge of such a process is highly desirable to provide better understanding of different pathologies, as for example osteoporosis, and of the HAp potential as vehicle for gene delivery to replace damaged DNA. In this work, the mechanism of dissolution in acid conditions of HAp nanoparticles encapsulating double-stranded DNA has been investigated at the atomistic level using computer simulations. For this purpose, four consecutive (multi-step) molecular dynamics simulations, involving different temperatures and proton transfer processes, have been carried out. Results are consistent with a polynuclear decalcification mechanism in which proton transfer processes, from the surface to the internal regions of the particle, play a crucial role. In addition, the DNA remains protected by the mineral mold and transferred proton from both temperature and chemicals. These results, which indicate that biomineralization imparts very effective protection to DNA, also have important implications in other biomedical fields, as for example in the design of artificial bones or in the fight against osteoporosis by promoting the fixation of Ca(2+) ions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PLASMA TURBULENCE AND KINETIC INSTABILITIES AT ION SCALES IN THE EXPANDING SOLAR WIND

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

Hellinger, Petr; Trávnícek, Pavel M.; Matteini, Lorenzo

The relationship between a decaying strong turbulence and kinetic instabilities in a slowly expanding plasma is investigated using two-dimensional (2D) hybrid expanding box simulations. We impose an initial ambient magnetic field perpendicular to the simulation box, and we start with a spectrum of large-scale, linearly polarized, random-phase Alfvénic fluctuations that have energy equipartition between kinetic and magnetic fluctuations and vanishing correlation between the two fields. A turbulent cascade rapidly develops; magnetic field fluctuations exhibit a power-law spectrum at large scales and a steeper spectrum at ion scales. The turbulent cascade leads to an overall anisotropic proton heating, protons are heatedmore » in the perpendicular direction, and, initially, also in the parallel direction. The imposed expansion leads to generation of a large parallel proton temperature anisotropy which is at later stages partly reduced by turbulence. The turbulent heating is not sufficient to overcome the expansion-driven perpendicular cooling and the system eventually drives the oblique firehose instability in a form of localized nonlinear wave packets which efficiently reduce the parallel temperature anisotropy. This work demonstrates that kinetic instabilities may coexist with strong plasma turbulence even in a constrained 2D regime.« less

The Interaction of Coronal Mass Ejections with Alfvénic Turbulence

NASA Astrophysics Data System (ADS)

Manchester, Ward, IV; Van Der Holst, Bart

2017-09-01

We provide a first attempt to understand the interaction between Alfvén wave turbulence, kinetic instabilities and temperature anisotropies in the environment of a fast coronal mass ejection (CME) near the Sun. The impact of a fast CME on the solar corona causes turbulent energy, thermal energy and dissipative heating to increase by orders of magnitude, and produces conditions suitable for a host of kinetic instabilities. We study these CME-induced effects with the recently developed Alfvén Wave Solar Model, with which we are able to self-consistently simulate the turbulent energy transport and dissipation as well as isotropic electron heating and anisotropic proton heating. Furthermore, the model also offers the capability to address the effects of fire hose, mirror mode, and cyclotron kinetic instabilities on proton energy partitioning all in a global-scale numerical simulation. We find amplified turbulent energy in the CME sheath, along with strong wave reflection at the shock combine to cause wave dissipation rates to increase by more than a factor of 100. In contrast, wave energy is greatly diminished by adiabatic expansion in the flux rope. Finally, we find proton temperature anisotropies are limited by kinetic instabilities to a level consistent with solar wind observations.

The Interaction of Coronal Mass Ejections with Alfvenic Turbulence

NASA Astrophysics Data System (ADS)

Manchester, W.; van der Holst, B.

2017-12-01

We provide a first attempt to understand the interaction between Alfven wave turbulence, kinetic instabilities and temperature anisotropies in the environment of a fast coronal mass ejection (CME). The impact of a fast CME on the solar corona causes turbulent energy, thermal energy and dissipative heating to increase by orders of magnitude, and produces conditions suitable for a host of kinetic instabilities. We study these CME-induced effects with the recently developed Alfven Wave Solar Model, with which we are able to self-consistently simulate the turbulent energy transport and dissipation as well as isotropic electron heating and anisotropic proton heating. Furthermore, the model also offers the capability to address the effects of firehose, mirror mode, and cyclotron kinetic instabilities on proton energy partitioning, all in a global-scale numerical simulation. We find turbulent energy greatly enhanced in the CME sheath, strong wave reflection at the shock, which leads to wave dissipation rates increasing by more than a factor of 100. In contrast, wave energy is greatly diminished by adiabatic expansion in the flux rope. Finally, we find proton temperature anisotropies are limited by kinetic instabilities to a level consistent with solar wind observations.

Hydrogen Diffusion and Trapping in α -Iron: The Role of Quantum and Anharmonic Fluctuations

NASA Astrophysics Data System (ADS)

Cheng, Bingqing; Paxton, Anthony T.; Ceriotti, Michele

2018-06-01

We investigate the thermodynamics and kinetics of a hydrogen interstitial in magnetic α -iron, taking account of the quantum fluctuations of the proton as well as the anharmonicities of lattice vibrations and hydrogen hopping. We show that the diffusivity of hydrogen in the lattice of bcc iron deviates strongly from an Arrhenius behavior at and below room temperature. We compare a quantum transition state theory to explicit ring polymer molecular dynamics in the calculation of diffusivity. We then address the trapping of hydrogen by a vacancy as a prototype lattice defect. By a sequence of steps in a thought experiment, each involving a thermodynamic integration, we are able to separate out the binding free energy of a proton to a defect into harmonic and anharmonic, and classical and quantum contributions. We find that about 30% of a typical binding free energy of hydrogen to a lattice defect in iron is accounted for by finite temperature effects, and about half of these arise from quantum proton fluctuations. This has huge implications for the comparison between thermal desorption and permeation experiments and standard electronic structure theory. The implications are even greater for the interpretation of muon spin resonance experiments.

Proton transfer pathways, energy landscape, and kinetics in creatine-water systems.

PubMed

Ivchenko, Olga; Whittleston, Chris S; Carr, Joanne M; Imhof, Petra; Goerke, Steffen; Bachert, Peter; Wales, David J

2014-02-27

We study the exchange processes of the metabolite creatine, which is present in both tumorous and normal tissues and has NH2 and NH groups that can transfer protons to water. Creatine produces chemical exchange saturation transfer (CEST) contrast in magnetic resonance imaging (MRI). The proton transfer pathway from zwitterionic creatine to water is examined using a kinetic transition network constructed from the discrete path sampling approach and an approximate quantum-chemical energy function, employing the self-consistent-charge density-functional tight-binding (SCC-DFTB) method. The resulting potential energy surface is visualized by constructing disconnectivity graphs. The energy landscape consists of two distinct regions corresponding to the zwitterionic creatine structures and deprotonated creatine. The activation energy that characterizes the proton transfer from the creatine NH2 group to water was determined from an Arrhenius fit of rate constants as a function of temperature, obtained from harmonic transition state theory. The result is in reasonable agreement with values obtained in water exchange spectroscopy (WEX) experiments.

Electromagnetic ion cyclotron waves stimulated by modest magnetospheric compressions

NASA Technical Reports Server (NTRS)

Anderson, B. J.; Hamilton, D. C.

1993-01-01

AMPTE/CCE magnetic field and particle data are used to test the suggestion that increased hot proton temperature anisotropy resulting from convection during magnetospheric compression is responsible for the enhancement in Pc 1 emission via generation of electromagnetic ion cyclotron (EMIC) waves in the dayside outer equatorial magnetosphere. The relative increase in magnetic field is used to gauge the strength of the compression, and an image dipole model is used to estimate the motion of the plasma during compression. Proton data are used to analyze the evolution of the proton distribution and the corresponding changes in EMIC wave activity expected during the compression. It is suggested that enhancements in dynamic pressure pump the energetic proton distributions in the outer magnetosphere, driving EMIC waves. Waves are expected to be generated most readily close to the magnetopause, and transient pressure pulses may be associated with bursts of EMIC waves, which would be observed on the ground in association with ionospheric transient signatures.

Nuclear Reaction Rates and the Production of Light P-Process Isotopes in Fast Expansions of Proton-Rich Matter

NASA Astrophysics Data System (ADS)

Jordan, G. C., IV; Meyer, B. S.

2004-09-01

We study nucleosynthesis in rapid expansions of proton-rich matter such as might occur in winds from newly-born neutron stars. For rapid enough expansion, the system fails to maintain an equilibrium between neutrons and protons and the abundant 4He nuclei. This leads to production of quite heavy nuclei early in the expansion. As the temperature falls, the system attempts to re-establish the equilibrium between free nucleons and 4He. This causes the abundance of free neutrons to drop and the heavy nuclei to disintegrate. If the disintegration flows quench before the nuclei reach the iron group, a distribution of p-process nuclei remains. We briefly discuss the possibility of this process as the mechanism of production of light p-process isotopes (specifically 92Mo, 94Mo, 96Ru, and 98Ru), and we provide a qualitative assessment of the impact of nuclear reaction rates of heavy, proton rich isotopes on the production of these astrophysically important nuclides.

Multiple Ions Resonant Heating and Acceleration by Alfven/cyclotron Fluctuations in the Solar Wind

NASA Astrophysics Data System (ADS)

Xie, H.; Ofman, L.

2003-12-01

We study the interaction between protons, and multiple minor ions (O5+, He++) and a given cyclotron resonant spectra in coronal hole plasma. One-dimensional hybrid simulations are performed in initially homogeneous, collisionless, magnetized plasma with waves propagating parallel to the background magnetic field. The self-consistent hybrid simulations are used to study how multiple minor species may affect the resonance interaction between a spectrum of waves and the solar wind protons. The results of the simulations provide a clear picture of wave-particle interaction under various coronal conditions, which can explain 1) how multiple minor ions affect the resonant heating and the temperature anisotropy of the solar wind protons by a given wave spectrum; 2) how energy is distributed and transferred among waves and different ion species; 3) the growth and damping of different beam microinstability modes, including both inward and outward waves; 4) the formation of proton double-peak distribution in the solar wind.

High conductive, long-term durable, anhydrous proton conductive solid-state electrolyte based on a metal-organic framework impregnated with binary ionic liquids: Synthesis, characteristic and effect of anion

NASA Astrophysics Data System (ADS)

Chen, Hui; Han, Shu-Yan; Liu, Rui-Heng; Chen, Teng-Fei; Bi, Kai-Lun; Liang, Jian-Bo; Deng, Yu-Heng; Wan, Chong-Qing

2018-02-01

Incorporating ionic liquids (abbreviated as ILs) into porous metal-organic framework (MOF) to obtain ILs@MOF nanocomposites is documented as a feasible method to achieve new type of anhydrous proton conductor with high performance. We newly synthesized a series of ILs with different acid counter anions (R-SO3-) and their ILs@MOF hybrid materials, i.e. SA-EIMS@MIL-101, MSA-EIMS@MIL-101 and PTSA-EIMS@MIL-101 (SA = sulfate acid, MSA = methanesulfonate acid, PTSA = p-toluenesulfonate acid, EIMS = 1-(1-ethyl-3-imidazolium)propane-3-sulfonate). Such hybrid materials displayed as anhydrous proton conduction with long-term durability even heated at 150 °C open to air. σ value of SA-EIMS@MIL-101 is up to 1.89 × 10-3 S cm-1, being in the range of the most conductive MOF-based materials. MOF support exhibited favorable proton transport and long-term retention for ILs. Anion volumes of R-SO3- displayed significant effects on the proton conductivity of such hybrid ILs@MOF materials. The smaller the van der Waals volume of R-SO3- is, the higher the conductivity of ILs@MOF is. This work suggests that the combination of a variety of the incorporated ILs and a MOF framework would afford high proton transport and gives an idea to explore the safe, anhydrous, solid-state electrolyte for high temperature proton exchange membrane fuel cell.

Solid hydrogen target for laser driven proton acceleration

NASA Astrophysics Data System (ADS)

Perin, J. P.; Garcia, S.; Chatain, D.; Margarone, D.

2015-05-01

The development of very high power lasers opens up new horizons in various fields, such as laser plasma acceleration in Physics and innovative approaches for proton therapy in Medicine. Laser driven proton acceleration is commonly based on the so-called Target Normal Sheath Acceleration (TNSA) mechanisms: a high power laser is focused onto a solid target (thin metallic or plastic foil) and interact with matter at very high intensity, thus generating a plasma; as a consequence "hot" electrons are produced and move into the forward direction through the target. Protons are generated at the target rear side, electrons try to escape from the target and an ultra-strong quasi-electrostatic field (~1TV/m) is generated. Such a field can accelerate protons with a wide energy spectrum (1-200 MeV) in a few tens of micrometers. The proton beam characteristics depend on the laser parameters and on the target geometry and nature. This technique has been validated experimentally in several high power laser facilities by accelerating protons coming from hydrogenated contaminant (mainly water) at the rear of metallic target, however, several research groups are investigating the possibility to perform experiments by using "pure" hydrogen targets. In this context, the low temperature laboratory at CEA-Grenoble has developed a cryostat able to continuously produce a thin hydrogen ribbon (from 40 to 100 microns thick). A new extrusion concept, without any moving part has been carried out, using only the thermodynamic properties of the fluid. First results and perspectives are presented in this paper.

In situ resistivity measurements of RAFM base alloys at cryogenic temperatures: The effect of proton irradiation

NASA Astrophysics Data System (ADS)

Gómez-Ferrer, B.; Vila, R.; Jiménez-Rey, D.; Ortiz, C. J.; Mota, F.; García, J. M.; Rodríguez, A.

2014-04-01

A four-probe technique for measurement of electrical resistance on low-temperature ion-irradiated metallic sheets is described. The design, temperature control system, preparation method of samples and the resistivity measurements are described in detail. The resistivity recovery (RR) curve has been measured on a Fe-5%Cr model alloy irradiated with 5 MeV protons. The procedure to obtain the RR derivative curve is outlined and experimental errors are identified and quantified. Special care has been taken to use a sample with very low impurity content and low dislocation density (1.2 × 108 cm-2). Thus, effects in recovery spectrum of the Fe-5%Cr alloy are only due to the presence of Cr and irradiation defects, which will be mainly Frenkel Pairs (FPs) given that the mean energy of the Primary Knock-on Atoms (PKA) is close to 0.35 keV. The results obtained for the Fe-5%Cr under 5 MeV proton irradiation are found to be in overall agreement with previous experimental measurements performed under electron irradiation although some differences appear probably due to the different spatial distribution of the created defects and the higher temperature resolution of annealing steps. The RR spectrum obtained reveals the appearance of the structure of stages I and II and also a partial suppression of the stage III peak with respect to previous results obtained after electron irradiation. The stage III suppression is explained as a superposition of vacancy recombination effects and short-range ordering (SRO) effects which are apparently dependent on the spatial distribution of defects created during irradiation. Moreover, recombination phenomena are observed beyond stage III up to 500 K.

Performance and temperature dependencies of proton irradiated n/p and p/n GaAs and n/p silicon cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.

1985-01-01

n/p homojunction GaAs cells are found to be more radiation resistant than p/n heteroface GaAs under 10 MeV proton irradiation. Both GaAs cell types outperform conventional silicon n/p cells under the same conditions. An increased temperature dependency of maximum power for the GaAs n/p cells is attributed to differences in Voc between the two GaAs cell types. These results and diffusion length considerations are consistent with the conclusion that p-type GaAs is more radiation resistant than n-type and therefore that the n/p configuration is possibly favored for use in the space radiation environment. However, it is concluded that additional work is required in order to choose between the two GaAs cell configurations.

Performance and temperature dependencies of proton irradiated n/p GaAs and n/p silicon cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.

1985-01-01

The n/p homojunction GaAs cell is found to be more radiation resistant than p/nheteroface GaAs under 10 MeV proton irradiation. Both GaAs cell types outperform conventional silicon n/p cells under the same conditions. An increase temperature dependency of maximum power for the GaAs n/p cells is attributed largely to differences in Voc between the two GaAs cell types. These results and diffusion length considerations are consistent with the conclusion that p-type GaAs is more radiation resistant than n-type and therefore that the n/p configuration is possibly favored for use in the space radiation environment. However, it is concluded that additional work is required in order to choose between the two GaAs cell configurations.

Quantum coherence and temperature dependence of the anomalous state of nanoconfined water in carbon nanotubes

DOE PAGES

Reiter, George F.; Deb, Aniruddha; Sakurai, Y.; ...

2016-10-17

X-ray Compton scattering measurements of the electron momentum distribution in water confined in both single-walled and double-walled carbon nanotubes (SWNT and DWNT), as a function of temperature and confinement size are presented here together with earlier measurements of the proton momentum distribution in the same systems using neutron Compton scattering. These studies provide a coherent picture of an anomalous state of water that exists because of nanoconfinement. This state cannot be described by the weakly interacting molecule picture. It has unique transport properties for both protons and water molecules. In conclusion, we suggest that knowledge of the excitation spectrum ofmore » this state is needed to understand the enhanced flow of water in cylinders with diameters on the order of 20 Å.« less

Self-Healing of Proton Damage in Lithium Niobite LiNbO2

NASA Astrophysics Data System (ADS)

Shank, Joshua C.; Tellekamp, M. Brooks; Zhang, En Xia; Bennett, W. Geoff; McCurdy, Michael W.; Fleetwood, Daniel M.; Alles, Michael L.; Schrimpf, Ronald D.; Doolittle, W. Alan

2015-04-01

Proton radiation damage and short-term annealing are investigated for lithium niobite (LiNbO2) mixed electronic-ionic memristors. Radiation damage and short-term annealing were characterized using Electrochemical Impedance Spectroscopy (EIS) to determine changes in the device resistance and the lithium ion mobility. The radiation damage resulted in a 0.48% change in the resistance at a fluence of 1014 cm-2. In-situ short-term annealing at room temperature reduced the net detrimental effect of the damage with a time constant of about 9 minutes. The radiation damage mechanism is attributed predominantly to displacement damage at the niobium and oxygen sites trapping lithium ions that are responsible for induced polarization within the material. Short term annealing is attributed to room temperature thermal annealing of these defects, freeing the highly mobile lithium ions.

Thermal conduction study of warm dense aluminum by proton differential heating

NASA Astrophysics Data System (ADS)

Ping, Y.; Kemp, G.; McKelvey, A.; Fernandez-Panella, A.; Shepherd, R.; Collins, G.; Sio, H.; King, J.; Freeman, R.; Hua, R.; McGuffey, C.; Kim, J.; Beg, F.

2016-10-01

A differential heating platform has been developed for thermal conduction study (Ping et al. PoP 2015), where a temperature gradient is induced and subsequent heat flow is probed by time-resolved diagnostics. An experiment using proton differential heating has been carried out at Titan laser for Au/Al targets. Two single-shot time-resolved diagnostics are employed, SOP (streaked optical pyrometry) for surface temperature and FDI (Fourier Domain Interferometry) for surface expansion. Hydrodynamic simulations show that after 15ps, absorption in underdense plasma needs to be taken into account to correctly interpret SOP data. Comparison between simulations with different thermal conductivity models and a set of data with varying target thickness will be presented. This work was performed under DOE contract DE-AC52-07NA27344 with support from OFES Early Career program and LLNL LDRD program.

Lipidic cubic phase serial millisecond crystallography using synchrotron radiation

PubMed Central

Nogly, Przemyslaw; James, Daniel; Wang, Dingjie; White, Thomas A.; Zatsepin, Nadia; Shilova, Anastasya; Nelson, Garrett; Liu, Haiguang; Johansson, Linda; Heymann, Michael; Jaeger, Kathrin; Metz, Markus; Wickstrand, Cecilia; Wu, Wenting; Båth, Petra; Berntsen, Peter; Oberthuer, Dominik; Panneels, Valerie; Cherezov, Vadim; Chapman, Henry; Schertler, Gebhard; Neutze, Richard; Spence, John; Moraes, Isabel; Burghammer, Manfred; Standfuss, Joerg; Weierstall, Uwe

2015-01-01

Lipidic cubic phases (LCPs) have emerged as successful matrixes for the crystallization of membrane proteins. Moreover, the viscous LCP also provides a highly effective delivery medium for serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs). Here, the adaptation of this technology to perform serial millisecond crystallography (SMX) at more widely available synchrotron microfocus beamlines is described. Compared with conventional microcrystallography, LCP-SMX eliminates the need for difficult handling of individual crystals and allows for data collection at room temperature. The technology is demonstrated by solving a structure of the light-driven proton-pump bacteriorhodopsin (bR) at a resolution of 2.4 Å. The room-temperature structure of bR is very similar to previous cryogenic structures but shows small yet distinct differences in the retinal ligand and proton-transfer pathway. PMID:25866654

Ion-/proton-conducting apparatus and method

DOEpatents

Yates, Matthew [Penfield, NY; Liu, Dongxia [Rochester, NY

2011-05-17

A c-axis-oriented HAP thin film synthesized by seeded growth on a palladium hydrogen membrane substrate. An exemplary synthetic process includes electrochemical seeding on the substrate, and secondary and tertiary hydrothermal treatments under conditions that favor growth along c-axes and a-axes in sequence. By adjusting corresponding synthetic conditions, an HAP this film can be grown to a controllable thickness with a dense coverage on the underlying substrate. The thin films have relatively high proton conductivity under hydrogen atmosphere and high temperature conditions. The c-axis oriented films may be integrated into fuel cells for application in the intermediate temperature range of 200-600.degree. C. The electrochemical-hydrothermal deposition technique may be applied to create other oriented crystal materials having optimized properties, useful for separations and catalysis as well as electronic and electrochemical applications, electrochemical membrane reactors, and in chemical sensors.

Protein conformational modifications and kinetics of water-protein interactions in milk protein concentrate powder upon aging: effect on solubility.

PubMed

Haque, Enamul; Bhandari, Bhesh R; Gidley, Michael J; Deeth, Hilton C; Møller, Sandie M; Whittaker, Andrew K

2010-07-14

Protein conformational modifications and water-protein interactions are two major factors believed to induce instability of protein and eventually affect the solubility of milk protein concentrate (MPC) powder. To test these hypotheses, MPC was stored at different water activities (a(w) 0.0-0.85) and temperatures (25 and 45 degrees C) for up to 12 weeks. Samples were examined periodically to determine solubility, change in protein conformation by Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA), and water status (interaction of water with the protein molecule/surface) by measuring the transverse relaxation time (T(2)) with proton nuclear magnetic resonance ((1)H NMR). The solubility of MPC decreased significantly with aging, and this process was enhanced by increasing water activity (a(w)) and storage temperature. Minor changes in protein secondary structure were observed with FTIR, which indicated some degree of unfolding of protein molecules. PCA of the FTIR data was able to discriminate samples according to moisture content and storage period. Partial least-squares (PLS) analysis showed some correlation between FTIR spectral feature and solubility. The NMR T(2) results indicated the presence of three distinct populations of water molecules, and the proton signal intensity and T(2) values of proton fractions varied with storage conditions (humidity, temperature) and aging. Results suggest that protein/protein interactions may be initiated by unfolding of protein molecules that eventually affects solubility.

Wind and IMP 8 Solar Wind, Magnetosheath and Shock Data

NASA Technical Reports Server (NTRS)

2004-01-01

The purpose of this project was to provide the community access to magnetosheath data near Earth. We provided 27 years of IMP 8 magnetosheath proton velocities, densities, and temperatures with our best (usually 1-min.) time resolution. IMP 8 crosses the magnetosheath twice each 125 day orbit, and we provided magnetosheath data for the roughly 27 years of data for which magnetometer data are also available (which are needed to reliably pick boundaries). We provided this 27 years of IMP 8 magnetosheath data to the NSSDC; this data is now integrated with the IMP 8 solar wind data with flags indicating whether each data point is in the solar wind, magnetosheath, or at the boundary between the two regions. The plasma speed, density, and temperature are provided for each magnetosheath point. These data are also available on the MIT web site ftp://space .mit.edu/pub/plasma/imp/www/imp.html. We provide ASCII time-ordered rows of data giving the observation time, the spacecraft position in GSE, the velocity is GSE, the density and temperature for protons. We also have analyzed and archived on our web site the Wind magnetosheath plasma parameters. These consist of ascii files of the proton and alpha densities, speeds, and thermal speeds. These data are available at ftp://space.mit.edu/pub/plasma/wind/sheath These are the two products promised in the work statement and they have been completed in full.

Contribution of Proton Capture Reactions to the Ascertained Abundance of Fluorine in the Evolved Stars of Globular Cluster M4, M22, 47 Tuc and NGC 6397

NASA Astrophysics Data System (ADS)

Mahanta, Upakul; Goswami, Aruna; Duorah, H. L.; Duorah, K.

2017-12-01

The origin of the abundance pattern and also the (anti)correlation present among the elements found in stars of globular clusters (GCs) remains unimproved until date. The proton-capture reactions are presently recognised in concert of the necessary candidates for that sort of observed behaviour in the second generation stars. We tend to propose a reaction network of a nuclear cycle namely carbon-nitrogen-oxygen-fluorine (CNOF) at evolved stellar condition since fluorine (^{19}F) is one such element which gets plagued by proton capture reactions. The stellar temperature thought about here ranges from 2× 107 to 10× 107 K and there has been an accretion occuring, with material density being 102 g/cm3 and 103 g/cm3. Such kind of temperature density conditions are probably going to be prevailing within the H-burning shell of evolved stars. The estimated abundances of ^{19}F are then matched with the info that has been determined for a few some metal-poor giants of GC M4, M22, 47 Tuc as well as NGC 6397. As far as the comparison between the observed and calculated abundances is concerned, it is found that the abundance of ^{19}F have shown an excellent agreement with the observed abundances with a correlation coefficent above 0.9, supporting the incidence of that nuclear cycle at the adopted temperature density conditions.

Kinetic insights over a PEMFC operating on stationary and oscillatory states.

PubMed

Mota, Andressa; Gonzalez, Ernesto R; Eiswirth, Markus

2011-12-01

Kinetic investigations in the oscillatory state have been carried out in order to shed light on the interplay between the complex kinetics exhibited by a proton exchange membrane fuel cell fed with poisoned H(2) (108 ppm of CO) and the other in serie process. The apparent activation energy (E(a)) in the stationary state was investigated in order to clarify the E(a) observed in the oscillatory state. The apparent activation energy in the stationary state, under potentiostatic control, rendered (a) E(a) ≈ 50-60 kJ mol(-1) over 0.8 V < E < 0.6 V and (b) E(a) ≈ 10 kJ mol(-1) at E = 0.3 V. The former is related to the H(2) adsorption in the vacancies of the surface poisoned by CO and the latter is correlated to the process of proton conductivity in the membrane. The dependence of the period-one oscillations on the temperature yielded a genuine Arrhenius dependence with two E(a) values: (a) E(a) around 70 kJ mol(-1), at high temperatures, and (b) E(a) around 10-15 kJ mol(-1), at lower temperatures. The latter E(a) indicates the presence of protonic mass transport coupled to the essential oscillatory mechanism. These insights point in the right direction to predict spatial couplings between anode and cathode as having the highest strength as well as to speculate the most likely candidates to promote spatial inhomogeneities. © 2011 American Chemical Society

Low temperature FTIR spectra and hydrogen bonds in polycrystalline cytidine.

PubMed

Rozenberg, M; Jung, C; Shoham, G

2004-08-01

FTIR spectra of polycrystalline samples of cytidine, pure and containing a small quantity of N(O)H or N(O)D groups (<20%), were measured in KBr pellets from 4000 to 400 cm(-1) at temperatures from 300 to 20K. For the first time the bands of the narrow isotopically decoupled proton stretching vibration mode (nu(1)) of OH- and NH- groups were found; their number corresponds to the number of H-bonds in crystal according to structural data. The FTIR spectra at low temperature in the out-of-plane bending nu(4) proton mode range (lower than 1000 cm(-1)) of N(O)H groups revealed narrow bands, which correspond to nu(1) bands together with several "extra" bands, which are influenced by the isotopic exchange and (or) cooling. All of them have their counterparts in the N(O)D-substance spectrum with an isotopic frequency ratio of 1.30-1.40. The "extra" bands are assigned to the H-bound OH and NH protons, which are disordered and cannot be seen with X-ray crystal structure analysis. The peak positions of both mode bands (expressed as the red shift of nu(1) or blue shift of nu(4) modes relatively free molecules) were used for the estimation of the energy of different H-bonds using previously established empirical correlations between spectral and thermodynamic parameters of hydrogen bonds. The correlation of the red shift and H-bond length is also confirmed for all five H-bonds of cytidine.

Nonhumidified High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

NASA Technical Reports Server (NTRS)

Kinder, James D.

2005-01-01

Fuel cells are being considered for a wide variety of aerospace applications. One of the most versatile types of fuel cells is the proton-exchange-membrane (PEM) fuel cell. PEM fuel cells can be easily scaled to meet the power and space requirements of a specific application. For example, small 100-W PEM fuel cells are being considered for personal power for extravehicular activity suit applications, whereas larger PEM fuel cells are being designed for primary power in airplanes and in uninhabited air vehicles. Typically, PEM fuel cells operate at temperatures up to 80 C. To increase the efficiency and power density of the fuel cell system, researchers are pursuing methods to extend the operating temperature of the PEM fuel cell to 180 C. The most widely used membranes in PEM fuel cells are Nafion 112 and Nafion 117--sulfonated perfluorinated polyethers that were developed by DuPont. In addition to their relatively high cost, the properties of these membranes limit their use in a PEM fuel cell to around 80 C. The proton conductivity of Nafion membranes significantly decreases above 80 C because the membrane dehydrates. The useful operating range of Nafion-based PEM fuel cells can be extended to over 100 C if ancillary equipment, such as compressors and humidifiers, is added to maintain moisture levels within the membrane. However, the addition of these components reduces the power density and increases the complexity of the fuel cell system.

Thermal stability of deep level defects induced by high energy proton irradiation in n-type GaN

NASA Astrophysics Data System (ADS)

Zhang, Z.; Farzana, E.; Sun, W. Y.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; McSkimming, B.; Kyle, E. C. H.; Speck, J. S.; Arehart, A. R.; Ringel, S. A.

2015-10-01

The impact of annealing of proton irradiation-induced defects in n-type GaN devices has been systematically investigated using deep level transient and optical spectroscopies. Moderate temperature annealing (>200-250 °C) causes significant reduction in the concentration of nearly all irradiation-induced traps. While the decreased concentration of previously identified N and Ga vacancy related levels at EC - 0.13 eV, 0.16 eV, and 2.50 eV generally followed a first-order reaction model with activation energies matching theoretical values for NI and VGa diffusion, irradiation-induced traps at EC - 0.72 eV, 1.25 eV, and 3.28 eV all decrease in concentration in a gradual manner, suggesting a more complex reduction mechanism. Slight increases in concentration are observed for the N-vacancy related levels at EC - 0.20 eV and 0.25 eV, which may be due to the reconfiguration of other N-vacancy related defects. Finally, the observed reduction in concentrations of the states at EC - 1.25 and EC - 3.28 eV as a function of annealing temperature closely tracks the detailed recovery behavior of the background carrier concentration as a function of annealing temperature. As a result, it is suggested that these two levels are likely to be responsible for the underlying carrier compensation effect that causes the observation of carrier removal in proton-irradiated n-GaN.

Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade.

PubMed

Kolmogorov, A; Atoian, G; Davydenko, V; Ivanov, A; Ritter, J; Stupishin, N; Zelenski, A

2014-02-01

The RHIC polarized H(-) ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

Separation of certain carboxylic acids utilizing cation exchange membranes

DOEpatents

Chum, H.L.; Sopher, D.W.

1983-05-09

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100/sup 0/C and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Separation of certain carboxylic acids utilizing cation exchange membranes

DOEpatents

Chum, Helena L.; Sopher, David W.

1984-01-01

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Proton threshold states in the Na22(p,γ)Mg23 reaction and astrophysical implications

NASA Astrophysics Data System (ADS)

Comisel, H.; Hategan, C.; Graw, G.; Wolter, H. H.

2007-04-01

Proton threshold states in Mg23 are important for the astrophysically relevant proton capture reaction Na22(p,γ)Mg23. In the indirect determination of the resonance strength of the lowest states, which were not accessible by direct methods, some of the spin-parity-assignments remained experimentally uncertain. We have investigated these states with shell model, Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison of calculated and observed properties, we relate the lowest relevant resonance state at Ex=7643 keV to an excited 3/2+ state in accordance with a recent experimental determination by Jenkins From this we deduce significantly improved values for the Na22(p,γ)Mg23 reaction rate at stellar temperatures below T9=0.1 K.

Evaluation of Space Radiation Effects on HgCdTe Avalanche Photodiode Arrays for Lidar Applications

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Abshire, James B.; Lauenstein, Jean-Marie; Sullivan, William III; Beck, Jeff; Hubbs, John E.

2018-01-01

We report the results from proton and gamma ray radiation testing of HgCdTe avalanche photodiode (APD) arrays developed by Leonardo DRS for space lidar detectors. We tested these devices with both approximately 60 MeV protons and gamma rays, with and without the read out integrated circuit (ROIC). We also measured the transient responses with the device fully powered and with the APD gain from unity to greater than 1000. The detectors produced a large current impulse in response to each proton hit but the response completely recovered within 1 microsecond. The devices started to have persistent damage at a proton fluence of 7e10 protons/cm2, equivalent to 10 krad(Si) total ionization dose. The dark current became much higher after the device was warmed to room temperature and cooled to 80K again, but it completely annealed after baking at 85 C for several hours. These results showed the HgCdTe APD arrays are suitable for use in space lidar for typical Earth orbiting and planetary missions provided that provisions are made to heat the detector chip to 85 C for several hours after radiation damage becomes evident that system performance is impacted.

Proton, Deuteron and Helion Spectra from Central Au+Au collisions at the AG

NASA Astrophysics Data System (ADS)

Baumgart, Stephen

2002-10-01

The AGS E895 experiment ran Au+Au collisions at bombarding energies of 2, 4, 6 and 8 AGeV. For central collisions, particle spectra have been measured for pions, kaons, protons, deuterons, and helions. From these spectra, the dN/dy distributions have been determined across a rapidity range from approximately -1.5 to 1.5 at maximum beam energy. Integration of the rapidity densities gives the total yields of each particle species. The final charge of the system can be calculated from the total yields to show that all of the initial charge is accounted for. The conclusions from the analyses of the condensate particle spectra will be presented. Fits to the spectra determine the freeze-out temperatures, radial flow velocities, and chemical potentials. The rapidity density distributions are used to estimate the longitudinal flow. The proton phase space density can be estimated by combining the proton spectra with the gaussian freeze-out radii intrepreted from a coalescence model employing the yields of protons, deuterons, tritons, and helions. Comparisons of the above results will be made to the experimental evidence from SIS, the AGS, the SPS, and RHIC.

Novel structure design of composite proton exchange membranes with continuous and through-membrane proton-conducting channels

NASA Astrophysics Data System (ADS)

Wang, Hang; Tang, Chenxiao; Zhuang, Xupin; Cheng, Bowen; Wang, Wei; Kang, Weimin; Li, Hongjun

2017-10-01

The primary goal of this study is to develop a high-performanced proton exchange membrane with the characteristics of through-membrane and continuous solution blown nanofibers as proton-conducting channels. The curled sulfonated phenolphthalein poly (ether sulfone) and poly (vinylidene fluoride) nanofibers were separately fabricated through the solution blowing process which is a new nanofiber fabricating method with high productivity, then they were fabricated into a sandwich-structured mat. Then this sandwich-structured mat was hot-pressed to form the designed structure using different melting temperatures of the two polymers by melting and making poly (vinylidene fluoride) flow into the phenolphthalein poly (ether sulfone) nanofiber mat. The characteristics of the composite membrane, such as morphology and performance of the membrane, were investigated. The characterization results proved the successful preparation of the membrane structure. Performance results showed that the novel structured membrane with through-membrane nanofibers significantly improved water swelling and methanol permeability, though its conductivity is lower than that of Nafion, the cell performance showed comparable results. Therefore, the novel structure design can be considered as a promising method for preparing of proton exchange membranes.

A-Site Cation Substitutions in Strained Y-Doped BaZrO 3 Multilayer Films Leading to Fast Proton Transport Pathways

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

Aruta, Carmela; Han, Chu; Zhou, Si

Proton-conducting perovskite oxides form a class of solid electrolytes for novel electrochemical devices operating at moderate temperatures. Here, we use hard X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and density functional theory calculations to investigate the structure and elucidate the origin of the fast proton transport properties of strained ultrathin films of Y-doped BaZrO 3 grown by pulsed lased deposition on NdGaO 3. Our study shows that our BaZr 0.8Y 0.2O 3 films incorporate a significant amount of Y dopants, and to a lesser extent also Zr ions, substituting for Ba 2+, and that these substitutional defects agglomerate forming columnarmore » regions crossing vertically from the surface to the interface the entire film. In conclusion, our calculations also show that, in regions rich in Y substitutions for both Zr and Ba, the proton transfer process involves nearly zero-energy barriers, indicating that A-site cation substitutions by Y lead to fast transport pathways and hence are responsible for the previously observed enhanced values of the proton conductivity of these perovskite oxide films.« less

Proton radiation effect on performance of InAs/GaSb complementary barrier infrared detector

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

Soibel, Alexander; Rafol, Sir B.; Khoshakhlagh, Arezou

In this work, we investigated the effect of proton irradiation on the performance of long wavelength infrared InAs/GaSb photodiodes (λ{sub c} = 10.2 μm), based on the complementary barrier infrared detector design. We found that irradiation with 68 MeV protons causes a significant increase of the dark current from j{sub d} = 5 × 10{sup −5} A/cm{sup 2} to j{sub d} = 6 × 10{sup −3} A/cm{sup 2}, at V{sub b} = 0.1 V, T = 80 K and fluence 19.2 × 10{sup 11 }H{sup +}/cm{sup 2}. Analysis of the dark current as a function of temperature and bias showed that the dominant contributor to the dark current in these devices changes from diffusion current to tunneling current after proton irradiation.more » This change in the dark current mechanism can be attributed to the onset of surface leakage current, generated by trap-assisted tunneling processes in proton displacement damage areas located near the device sidewalls.« less

New synthesis of nanopowders of proton conducting materials. A route to densified proton ceramics

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

Khani, Zohreh; Taillades-Jacquin, Melanie; Taillades, Gilles

2009-04-15

Low temperature routes have been developed for the preparation of BaCe{sub 0.9}Y{sub 0.1}O{sub 2.95} (BCY10) and BaZr{sub 0.9}Y{sub 0.1}O{sub 2.95} (BZY10) in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell. These methods make use on the one hand of the chelation of metal (II), (III) and (IV) ions by acrylates (hydrogelation route) and on the other of the destabilisation and precipitation of micro-emulsions. Both routes lead to single phase yttrium doped barium cerate or zirconate perovskites, as observed by X-ray diffraction, after thermal treatment at 900 deg. C for 4more » h for BCY10 and 800 deg. C for BZY10. These temperatures, lower than those usually used for preparation of barium cerate or zirconate, lead to oxide nanoparticles of size <40 nm. Dense ceramics (>=95%) are obtained by sintering BCY10 pellets at 1350 deg. C and BZY10 pellets at 1500 deg. C for 10 h. The water uptake of compacted samples at 500 deg. C is 0.14 wt% for BCY10 and 0.26 wt% for BZY10. Total conductivities in the range 300-600 deg. C were determined using impedance spectroscopy in a humidified nitrogen atmosphere. The total conductivity was 1.8x10{sup -2} S/cm for BCY10 and 2x10{sup -3} S/cm for BZY10 at 600 deg. C. The smallest perovskite nanoparticles and highest conductivities were obtained by hydrogelation of precursor barium, zirconium, cerium and yttrium acrylates. - Graphical Abstract: Low temperature hydrogelation and micro-emulsion routes have been developed for the preparation of rare earth doped barium and zirconium cerates in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell.« less

The effect of deuteration and doping on the phase transition temperature of grown glycine phosphite single crystals

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

Perumal, R., E-mail: perumal-cgc@yahoo.co.uk; Chandru, A. Lakshmi; Babu, S. Moorthy

The Glycinium Phosphite (GPI) compound is a representative of hydrogen-bonded ferroelectric crystals. The ordering of protons could be expected below the room temperature (225 K). Crystals grown from the milipore water as well as deuterated solvents respectively. The corresponding hydrogen bond distance was stretched out due to the effect of isotopic substitution that increase the phase transition temperature. Further to improve the phase transition temperature, GPI crystal was doped with organic complexing agent and various metals and the obtained results are presented.

Accreting X-ray pulsar atmospheres heated by Coulomb deceleration of protons

NASA Technical Reports Server (NTRS)

Meszaros, P.; Harding, A. K.; Kirk, J. G.; Galloway, D. J.

1983-01-01

Results are presented from detailed self-consistent models of accreting magnetized neutron star atmospheres, heated by the gradual deceleration of infalling protons via Coulomb encounters. The temperature and density gradients are calculated assuming momentum and energy balance, coupled with the radiative transfer for two polarizations. The cyclotron resonance effects were treated approximately. These models are characterized by power-law energy spectra, with single pulses at higher frequencies and multiple pulses at lower ones for some aspect angles, as well as a phase-dependent spectral index.

Quantitative Magnetic Resonance Thermometry and Its Use with MR-Guided Focused Ultrasound

NASA Astrophysics Data System (ADS)

Pauly, Kim

2014-03-01

Focused ultrasound (FUS) uses a large area array, typically outside the body, that is geometrically or electronically focused to a point deep in the body. Such focusing provides amplification of the ultrasound intensity, thereby allowing heating of tissue to the point of coagulation at the focus, without damage to the intervening tissue. Guidance of FUS treatments deep in the body can be done quantitatively with magnetic resonance (MR) thermometry, termed MRgFUS. The physics behind MR thermometry lie in the changes in hydrogen bonding with temperature. As tissue temperature rises, hydrogen bonds break, allowing the return of the electron cloud to shield water protons, reducing the magnetic field seen by the protons, and the resonant frequency. The change in resonant frequency is -0.01 ppm per degree C and is the same for all aqueous tissues. The result of the shift in proton resonant frequency is seen in the phase of gradient echo images. Subtraction of the phase of images acquired before and during heating allows the removal of background phase from other sources, yielding quantitative temperature maps. Temperature standard deviations less than 1 degree C are readily achievable and thermal dose maps are easily calculated. Thermal dose is found from a conversion of the whole temperature-time curve to an equivalent number of minutes at 43 degrees C. A thermal dose of 240 minutes is often taken as the threshold for tissue damage. MR thermometry is complicated by the motion of the target tissue and/or motion of other organs such as occurs during respiration. More sophisticated algorithms than the simple baseline subtraction take advantage of the facts that motion can be repetitive (in the case of respiratory motion) and/or the fact that the focal region in MRgFUS is small, allowing for extraction of the heat from the phase profile without subtraction of a background phase.

Triaspartate: a model system for conformationally flexible DDD motifs in proteins.

PubMed

Duitch, Laura; Toal, Siobhan; Measey, Thomas J; Schweitzer-Stenner, Reinhard

2012-05-03

Understanding the interactions that govern turn formation in the unfolded state of proteins is necessary for a complete picture of the role that these turns play in both normal protein folding and functionally relevant yet disordered linear motifs. It is still unclear, however, whether short peptides can adopt stable turn structures in aqueous environments in the absence of any nonlocal interactions. To explore the effect that nearest-neighbor interactions and the local peptide environment have on the turn-forming capability of individual amino acid residues in short peptides, we combined vibrational (IR, Raman, and VCD), UV-CD, and (1)H NMR spectroscopies in order to probe the conformational ensemble of the central aspartic acid residue of the triaspartate peptide (DDD). The study was motivated by the recently discovered turn propensities of aspartic acid in GDG (Hagarman; et al. Chem.-Eur. J. 2011, 17, 6789). We investigated the DDD peptide under both acidic and neutral conditions in order to elucidate the effect that side-chain protonation has on the conformational propensity of the central aspartic acid residue. Amide I' profiles were analyzed in terms of two-dimensional Gaussian distributions representing conformational subdistributions in Ramachandran space. Interestingly, our results show that while the protonated form of the DDD peptide samples various turn-like conformations similar to GDG, deprotonation of the peptide eliminates this propensity for turns, causing the fully ionized peptide to exclusively sample pPII and β-strand-like structures. To further explore the factors stabilizing these more extended conformations in fully ionized DDD, we analyzed the temperature dependence of both the UV-CD spectrum and the (3)J(H(N),H(α)) coupling constants of the two amide protons (N- and C-terminal) in terms of a simple two-state (pPII-β) thermodynamic model. Thus, we were able to obtain the enthalpic and entropic differences between the pPII and β-strand conformations of the central and C-terminal residue. For the central residue, we obtained ΔH(3) = -12.0 kJ/mol and ΔS(3) = -73.8 J/mol·K, resulting in a much larger room-temperature Gibbs free energy of 10.0 kJ/mol, which effectively locks the C-terminal in a β-like conformation. A comparison of the temperature dependence of the chemical shifts reveals that there is indeed some type of protection of the amide protons from solvent in ionized DDD. This finding and several other lines of evidence suggest that both conformations of ionized DDD are stabilized by hydrogen bonding between the carboxylate groups of the central and C-terminal residue and the respective amide protons. These hydrogen bonds can be expected to be eliminated by side-chain protonation and substituted by hydrogen bonds between the N-terminal amide proton and the C-terminal carbonyl group as well as between the central aspartate side chain and the N-terminal amide proton. Hence, our results are indicative of a pH-induced switch in hydrogen-bonding patterns of aspartic acid motifs.

Temperature dependence of the symmetry energy and neutron skins in Ni, Sn, and Pb isotopic chains

NASA Astrophysics Data System (ADS)

Antonov, A. N.; Kadrev, D. N.; Gaidarov, M. K.; Sarriguren, P.; de Guerra, E. Moya

2017-02-01

The temperature dependence of the symmetry energy for isotopic chains of even-even Ni, Sn, and Pb nuclei is investigated in the framework of the local density approximation (LDA). The Skyrme energy density functional with two Skyrme-class effective interactions, SkM* and SLy4, is used in the calculations. The temperature-dependent proton and neutron densities are calculated through the hfbtho code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. In addition, two other density distributions of 208Pb, namely the Fermi-type density determined within the extended Thomas-Fermi (TF) method and symmetrized-Fermi local density obtained within the rigorous density functional approach, are used. The kinetic energy densities are calculated either by the hfbtho code or, for a comparison, by the extended TF method up to second order in temperature (with T2 term). Alternative ways to calculate the symmetry energy coefficient within the LDA are proposed. The results for the thermal evolution of the symmetry energy coefficient in the interval T =0 -4 MeV show that its values decrease with temperature. The temperature dependence of the neutron and proton root-mean-square radii and corresponding neutron skin thickness is also investigated, showing that the effect of temperature leads mainly to a substantial increase of the neutron radii and skins, especially in the more neutron-rich nuclei, a feature that may have consequences on astrophysical processes and neutron stars.

Two different types of channels exhibiting distinct proton transport behavior in an open-framework aluminophosphate

NASA Astrophysics Data System (ADS)

Xue, Chen; Zou, Yang; Liu, Shao-Xian; Ren, Xiao-Ming; Tian, Zheng-Fang

2018-02-01

A three-dimensional open-framework aluminophosphate, (NH4)2Al4(PO4)4(HPO4)·H2O (1), shows two types of eight-membered polyhedral ring channels. The lattice water molecules occupy within the channel with (HO)PO3 tetrahedra (channel-I), whilst the ammonium ions reside in another type of channel (channel-II). This aluminophosphate shows superior stability to water and NaOH aqueous solution, but unstable to H2SO4 aqueous solution. The proton conductance of 1 has been investigated under anhydrous condition and various relative humidity, indicating rather low conductivity under anhydrous condition even at elevated temperature (σdc = 9.05 × 10-13 S cm-1 at 343 K and 4.25 × 10-10 S cm-1 even at 473 K), and this situation demonstrates that both the ammonium ions and the protons in (HO)PO3 tetrahedra have quite low mobility. The conductivity of 1 reaches to 4.0 × 10-5 S cm-1 at 299 K, 2.57 × 10-4 S cm-1 at 343 K under 99%RH, respectively. The greatly enhancement of proton conductivity at 99%RH is due to the formation of H-bond between H2O molecules and (HO)PO3 tetrahedra in the channel-I to assist proton hopping process, while the ammonium ions show negligible contribution to enhancement of proton conductivity.

1H NMR studies of the 5-(hydroxymethyl)-2'-deoxyuridine containing TF1 binding site.

PubMed

Pasternack, L B; Bramham, J; Mayol, L; Galeone, A; Jia, X; Kearns, D R

1996-07-15

The pyrimidine base 5-(hydroxymethyl)-2'-deoxyuridine (HmU) is a common nucleotide in SPO1 phage DNA. Numerous transcriptional proteins bind HmU-containing DNA preferentially implicating a regulatory function of HmU. We have investigated the conformation and dynamics of d-(5'-CHmUCHmUACACGHmUGHmUAGAG-OH-3')2 (HmU-DNA). This oligonucleotide mimics the consensus sequence of Transcription Factor 1 (TF1). The HmU-DNA was compared to the thymine-containing oligonucleotide. NOESY and DQF COSY spectroscopy provided resonance assignments of nonexchangeable and exchangeable protons, intranucleotide, internucleotide and intrastrand proton-proton distances, and dihedral angle constraints. Methylene protons of the hydroxymethyl group are nonequivalent protons and the hydroxymethyl group is not freely rotating. The hydroxymethyl group adopts a specific orientation with the OH group oriented on the 3' side of the plane of the base. Analysis of imino proton resonances and NOEs indicates additional end base pair fraying and a temperature-induced transition to a conformation in which the internal HmU-A base pairs are disrupted or have reduced lifetimes. Orientation of the hydroxymethyl group indicates the presence of internucleotide intrastrand hydrogen bonding between the HmU12C5 hydroxyl group and A13. All sugars in both DNAs show a C2'endo conformation (typical of B-DNA).

Influence of High-Energy Proton Irradiation on β-Ga2O3 Nanobelt Field-Effect Transistors.

PubMed

Yang, Gwangseok; Jang, Soohwan; Ren, Fan; Pearton, Stephen J; Kim, Jihyun

2017-11-22

The robust radiation resistance of wide-band gap materials is advantageous for space applications, where the high-energy particle irradiation deteriorates the performance of electronic devices. We report on the effects of proton irradiation of β-Ga 2 O 3 nanobelts, whose energy band gap is ∼4.85 eV at room temperature. Back-gated field-effect transistor (FET) based on exfoliated quasi-two-dimensional β-Ga 2 O 3 nanobelts were exposed to a 10 MeV proton beam. The proton-dose- and time-dependent characteristics of the radiation-damaged FETs were systematically analyzed. A 73% decrease in the field-effect mobility and a positive shift of the threshold voltage were observed after proton irradiation at a fluence of 2 × 10 15 cm -2 . Greater radiation-induced degradation occurs in the conductive channel of the β-Ga 2 O 3 nanobelt than at the contact between the metal and β-Ga 2 O 3 . The on/off ratio of the exfoliated β-Ga 2 O 3 FETs was maintained even after proton doses up to 2 × 10 15 cm -2 . The radiation-induced damage in the β-Ga 2 O 3 -based FETs was significantly recovered after rapid thermal annealing at 500 °C. The outstanding radiation durability of β-Ga 2 O 3 renders it a promising building block for space applications.

High temperature polymers for proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Einsla, Brian Russel

Novel proton exchange membranes (PEMs) were investigated that show potential for operating at higher temperatures in both direct methanol (DMFC) and H 2/air PEM fuel cells. The need for thermally stable polymers immediately suggests the possibility of heterocyclic polymers bearing appropriate ion conducting sites. Accordingly, monomers and random disulfonated poly(arylene ether) copolymers containing either naphthalimide, benzoxazole or benzimidazole moieties were synthesized via direct copolymerization. The ion exchange capacity (IEC) was varied by simply changing the ratio of disulfonated monomer to nonsulfonated monomer in the copolymerization step. Water uptake and proton conductivity of cast membranes increased with IEC. The water uptake of these heterocyclic copolymers was lower than that of comparable disulfonated poly(arylene ether) systems, which is a desirable improvement for PEMs. Membrane electrode assemblies were prepared and the initial fuel cell performance of the disulfonated polyimide and polybenzoxazole (PBO) copolymers was very promising at 80°C compared to the state-of-the-art PEM (NafionRTM); nevertheless these membranes became brittle under operating conditions. Several series of poly(arylene ether)s based on disodium-3,3'-disulfonate-4,4 '-dichlorodiphenylsulfone (S-DCDPS) and a benzimidazole-containing bisphenol were synthesized and afforded copolymers with enhanced stability. Selected properties of these membranes were compared to separately prepared miscible blends of disulfonated poly(arylene ether sulfone) copolymers and polybenzimidazole (PBI). Complexation of the sulfonic acid groups with the PBI structure reduced water swelling and proton conductivity. The enhanced proton conductivity of NafionRTM membranes has been proposed to be due to the aggregation of the highly acidic side-chain sulfonic acid sites to form ion channels. A series of side-chain sulfonated poly(arylene ether sulfone) copolymers based on methoxyhydroquinone was synthesized in order to investigate this possible advantage and to couple this with the excellent hydrolytic stability of poly(arylene ether)s. The methoxy groups were deprotected to afford reactive phenolic sites and nucleophilic substitution reactions with functional aryl sulfonates were used to prepare simple aryl or highly acidic fluorinated sulfonated copolymers. The proton conductivity and water sorption of the resulting copolymers increased with the ion exchange capacity, but changing the acidity of the sulfonic acid had no apparent effect.

NMR detection of pH-dependent histidine-water proton exchange reveals the conduction mechanism of a transmembrane proton channel.

PubMed

Hu, Fanghao; Schmidt-Rohr, Klaus; Hong, Mei

2012-02-29

The acid-activated proton channel formed by the influenza M2 protein is important for the life cycle of the virus. A single histidine, His37, in the M2 transmembrane domain (M2TM) is responsible for pH activation and proton selectivity of the channel. Recent studies suggested three models for how His37 mediates proton transport: a shuttle mechanism involving His37 protonation and deprotonation, a H-bonded imidazole-imidazolium dimer model, and a transporter model involving large protein conformational changes in synchrony with proton conduction. Using magic-angle-spinning (MAS) solid-state NMR spectroscopy, we examined the proton exchange and backbone conformational dynamics of M2TM in a virus-envelope-mimetic membrane. At physiological temperature and pH, (15)N NMR spectra show fast exchange of the imidazole (15)N between protonated and unprotonated states. To quantify the proton exchange rates, we measured the (15)N T(2) relaxation times and simulated them for chemical-shift exchange and fluctuating N-H dipolar fields under (1)H decoupling and MAS. The exchange rate is 4.5 × 10(5) s(-1) for Nδ1 and 1.0 × 10(5) s(-1) for Nε2, which are approximately synchronized with the recently reported imidazole reorientation. Binding of the antiviral drug amantadine suppressed both proton exchange and ring motion, thus interfering with the proton transfer mechanism. By measuring the relative concentrations of neutral and cationic His as a function of pH, we determined the four pK(a) values of the His37 tetrad in the viral membrane. Fitting the proton current curve using the charge-state populations from these pK(a)'s, we obtained the relative conductance of the five charge states, which showed that the +3 channel has the highest time-averaged unitary conductance. At physiologically relevant pH, 2D correlation spectra indicated that the neutral and cationic histidines do not have close contacts, ruling out the H-bonded dimer model. Moreover, a narrowly distributed nonideal helical structure coexists with a broadly distributed ideal helical conformation without interchange on the sub-10 ms time scale, thus excluding the transporter model in the viral membrane. These data support the shuttle mechanism of proton conduction, whose essential steps involve His-water proton exchange facilitated by imidazole ring reorientations. © 2011 American Chemical Society

On two alternative mechanisms of ethane activation over ZSM-5 zeolite modified by Zn2+ and Ga1+ cations.

PubMed

Kazansky, V B; Subbotina, I R; Rane, N; van Santen, R A; Hensen, E J M

2005-08-21

The activation of ethane over zinc- and gallium-modified HZSM-5 dehydrogenation catalysts was studied by diffuse reflectance infrared spectroscopy. Hydrocarbon activation on HZSM-5 modified by bivalent Zn and univalent Ga cations proceeds via two distinctly different mechanisms. The stronger molecular adsorption of ethane by the acid-base pairs formed by distantly separated cationic Zn2+ and basic oxygen sites results already at room temperature in strong polarizability of adsorbed ethane and subsequent heterolytic dissociative adsorption at moderate temperatures. In contrast, molecular adsorption of ethane on Ga+ cations is weak. At high temperatures dissociative hydrocarbon adsorption takes place, resulting in the formation of ethyl and hydride fragments coordinating to the cationic gallium species. Whereas in the zinc case a Brønsted acid proton is formed upon ethane dissociation, decomposition of the ethyl fragment on gallium results in gallium dihydride species and does not lead to Brønsted acid protons. This difference in alkane activation has direct consequences for hydrocarbon conversions involving dehydrogenation.

Impact of heat and water management on proton exchange membrane fuel cells degradation in automotive application

NASA Astrophysics Data System (ADS)

Nandjou, F.; Poirot-Crouvezier, J.-P.; Chandesris, M.; Blachot, J.-F.; Bonnaud, C.; Bultel, Y.

2016-09-01

In Proton Exchange Membrane Fuel Cells, local temperature is a driving force for many degradation mechanisms such as hygrothermal deformation and creep of the membrane, platinum dissolution and bipolar plates corrosion. In order to investigate and quantify those effects in automotive application, durability testing is conducted in this work. During the ageing tests, the local performance and temperature are investigated using in situ measurements of a printed circuit board. At the end of life, post-mortem analyses of the aged components are conducted. The experimental results are compared with the simulated temperature and humidity in the cell obtained from a pseudo-3D multiphysics model in order to correlate the observed degradations to the local conditions inside the stack. The primary cause of failure in automotive cycling is pinhole/crack formation in the membrane, induced by high variations of its water content over time. It is also observed that water condensation largely increases the probability of the bipolar plates corrosion while evaporation phenomena induce local deposits in the cell.

Improving a free air breathing proton exchange membrane fuel cell through the Maximum Efficiency Point Tracking method

NASA Astrophysics Data System (ADS)

Higuita Cano, Mauricio; Mousli, Mohamed Islam Aniss; Kelouwani, Sousso; Agbossou, Kodjo; Hammoudi, Mhamed; Dubé, Yves

2017-03-01

This work investigates the design and validation of a fuel cell management system (FCMS) which can perform when the fuel cell is at water freezing temperature. This FCMS is based on a new tracking technique with intelligent prediction, which combined the Maximum Efficiency Point Tracking with variable perturbation-current step and the fuzzy logic technique (MEPT-FL). Unlike conventional fuel cell control systems, our proposed FCMS considers the cold-weather conditions, the reduction of fuel cell set-point oscillations. In addition, the FCMS is built to respond quickly and effectively to the variations of electric load. A temperature controller stage is designed in conjunction with the MEPT-FL in order to operate the FC at low-temperature values whilst tracking at the same time the maximum efficiency point. The simulation results have as well experimental validation suggest that propose approach is effective and can achieve an average efficiency improvement up to 8%. The MEPT-FL is validated using a Proton Exchange Membrane Fuel Cell (PEMFC) of 500 W.

Pumpless thermal management of water-cooled high-temperature proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Song, Tae-Won; Choi, Kyoung-Hwan; Kim, Ji-Rae; Yi, Jung S.

2011-05-01

Proton exchange membrane fuel cells (PEMFCs) have been considered for combined heat and power (CHP) applications, but cost reduction has remained an issue for commercialization. Among various types of PEMFC, the high-temperature (HT) PEMFC is gaining more attention due to the simplicity of the system, that will make the total system cost lower. A pumpless cooling concept is introduced to reduce the number of components of a HT PEMFC system even further and also decrease the parasitic power required for operating the system. In this concept, water is used as the coolant, and the buoyancy force caused by the density difference between vapour and liquid when operated above boiling temperate is utilized to circulate the coolant between the stack and the cooling device. In this study, the basic parameters required to design the cooling device are discussed, and the stable operation of the HT PEMFC stack in both the steady-state and during transient periods is demonstrated. It found that the pumpless cooling method provides more uniform temperature distribution within the stack, regardless of the direction of coolant flow.

Alternating current breakdown voltage of ice electret

NASA Astrophysics Data System (ADS)

Oshika, Y.; Tsuchiya, Y.; Okumura, T.; Muramoto, Y.

2017-09-01

Ice has low environmental impact. Our research objectives are to study the availability of ice as a dielectric insulating material at cryogenic temperatures. We focus on ferroelectric ice (iceXI) at cryogenic temperatures. The properties of iceXI, including its formation, are not clear. We attempted to obtain the polarized ice that was similar to iceXI under the applied voltage and cooling to 77 K. The polarized ice have a wide range of engineering applications as electronic materials at cryogenic temperatures. This polarized ice is called ice electret. The structural difference between ice electret and normal ice is only the positions of protons. The effects of the proton arrangement on the breakdown voltage of ice electret were shown because electrical properties are influenced by the structure of ice. We observed an alternating current (ac) breakdown voltage of ice electret and normal ice at 77 K. The mean and minimum ac breakdown voltage values of ice electret were higher than those of normal ice. We considered that the electrically weak part of the normal ice was improved by applied a direct electric field.

Postirradiation behavior of p-channel charge-coupled devices irradiated at 153 K

NASA Astrophysics Data System (ADS)

Gow, Jason P. D.; Wood, Daniel; Murray, Neil J.; Burt, David; Hall, David J.; Dryer, Ben; Holland, Andrew D.

2016-04-01

The displacement damage hardness that can be achieved using p-channel charge-coupled devices (CCD) was originally demonstrated in 1997, and since then a number of other studies have demonstrated an improved tolerance to radiation-induced charge transfer inefficiency when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. The initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with 10-MeV equivalent proton fluences of 1.24×109 and 1.24×1011 protons cm-2 is described. The dark current, cosmetic quality, and the number of defects identified using trap pumping immediately were monitored after the irradiation for a period of 150 h with the device held at 153 K and then after different periods of time at room temperature. The device also exhibited a flatband voltage shift of around 30 mV/krad, determined by the reduction in full well capacity.

Deep proton tunneling in the electronically adiabatic and non-adiabatic limits: Comparison of the quantum and classical treatment of donor-acceptor motion in a protein environment

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

Benabbas, Abdelkrim; Salna, Bridget; Sage, J. Timothy

2015-03-21

Analytical models describing the temperature dependence of the deep tunneling rate, useful for proton, hydrogen, or hydride transfer in proteins, are developed and compared. Electronically adiabatic and non-adiabatic expressions are presented where the donor-acceptor (D-A) motion is treated either as a quantized vibration or as a classical “gating” distribution. We stress the importance of fitting experimental data on an absolute scale in the electronically adiabatic limit, which normally applies to these reactions, and find that vibrationally enhanced deep tunneling takes place on sub-ns timescales at room temperature for typical H-bonding distances. As noted previously, a small room temperature kinetic isotopemore » effect (KIE) does not eliminate deep tunneling as a major transport channel. The quantum approach focuses on the vibrational sub-space composed of the D-A and hydrogen atom motions, where hydrogen bonding and protein restoring forces quantize the D-A vibration. A Duschinsky rotation is mandated between the normal modes of the reactant and product states and the rotation angle depends on the tunneling particle mass. This tunnel-mass dependent rotation contributes substantially to the KIE and its temperature dependence. The effect of the Duschinsky rotation is solved exactly to find the rate in the electronically non-adiabatic limit and compared to the Born-Oppenheimer (B-O) approximation approach. The B-O approximation is employed to find the rate in the electronically adiabatic limit, where we explore both harmonic and quartic double-well potentials for the hydrogen atom bound states. Both the electronically adiabatic and non-adiabatic rates are found to diverge at high temperature unless the proton coupling includes the often neglected quadratic term in the D-A displacement from equilibrium. A new expression is presented for the electronically adiabatic tunnel rate in the classical limit for D-A motion that should be useful to experimentalists working near room temperature. This expression also holds when a broad protein conformational distribution of D-A equilibrium distances dominates the spread of the D-A vibrational wavefunction.« less

Deep proton tunneling in the electronically adiabatic and non-adiabatic limits: comparison of the quantum and classical treatment of donor-acceptor motion in a protein environment.

PubMed

Benabbas, Abdelkrim; Salna, Bridget; Sage, J Timothy; Champion, Paul M

2015-03-21

Analytical models describing the temperature dependence of the deep tunneling rate, useful for proton, hydrogen, or hydride transfer in proteins, are developed and compared. Electronically adiabatic and non-adiabatic expressions are presented where the donor-acceptor (D-A) motion is treated either as a quantized vibration or as a classical "gating" distribution. We stress the importance of fitting experimental data on an absolute scale in the electronically adiabatic limit, which normally applies to these reactions, and find that vibrationally enhanced deep tunneling takes place on sub-ns timescales at room temperature for typical H-bonding distances. As noted previously, a small room temperature kinetic isotope effect (KIE) does not eliminate deep tunneling as a major transport channel. The quantum approach focuses on the vibrational sub-space composed of the D-A and hydrogen atom motions, where hydrogen bonding and protein restoring forces quantize the D-A vibration. A Duschinsky rotation is mandated between the normal modes of the reactant and product states and the rotation angle depends on the tunneling particle mass. This tunnel-mass dependent rotation contributes substantially to the KIE and its temperature dependence. The effect of the Duschinsky rotation is solved exactly to find the rate in the electronically non-adiabatic limit and compared to the Born-Oppenheimer (B-O) approximation approach. The B-O approximation is employed to find the rate in the electronically adiabatic limit, where we explore both harmonic and quartic double-well potentials for the hydrogen atom bound states. Both the electronically adiabatic and non-adiabatic rates are found to diverge at high temperature unless the proton coupling includes the often neglected quadratic term in the D-A displacement from equilibrium. A new expression is presented for the electronically adiabatic tunnel rate in the classical limit for D-A motion that should be useful to experimentalists working near room temperature. This expression also holds when a broad protein conformational distribution of D-A equilibrium distances dominates the spread of the D-A vibrational wavefunction.

Reversible hydrogen storage using CO2 and a proton-switchable iridium catalyst in aqueous media under mild temperatures and pressures.

PubMed

Hull, Jonathan F; Himeda, Yuichiro; Wang, Wan-Hui; Hashiguchi, Brian; Periana, Roy; Szalda, David J; Muckerman, James T; Fujita, Etsuko

2012-03-18

Green plants convert CO(2) to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO(2) and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO(2), formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong π-donor, and is rationalized by theoretical and experimental studies.

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

Luo, Langli; Su, Mao; Yan, Pengfei

The presence of water vapor, intentional or unavoidable, is crucial to many materials applications, such as steam generator, turbine engine, fuel cell, catalyst, and corrosion 1-6. Phenomenologically, water vapor has been noticed to accelerate oxidation of metals/alloys 7,8, however, the atomistic mechanisms remain elusive. Herein, through direct in situ atomic-scale transmission electron microscopy observation and density functional theory calculation, we reveal that water vapor enhanced oxidation of Ni-Cr alloy is associated with proton dissolution promoted vacancy formation, migration and clustering. Protons derived from water dissociation occupy interstitial position in the oxide lattice, which consequently leads to the lowering of bothmore » vacancy formation energy and the cation diffusion barrier. The atomic scale observations reveal a water vapor derived proton mediated oxide growth mechanism, which provides insights for reckoning many technological processes concerning materials in moist environment at elevated temperatures.« less

Magnetic properties, water proton relaxivities, and in-vivo MR images of paramagnetic nanoparticles

NASA Astrophysics Data System (ADS)

Lee, Gang Ho; Chang, Yongmin

2015-07-01

In this mini review, magnetic resonance imaging (MRI) contrast agents based on lanthanideoxide (Ln2O3) nanoparticles are described. Ln2O3 (Ln = Gd, Dy, Ho, and Er) nanoparticles are paramagnetic, but show appreciable magnetic moments at room temperature and even at ultrasmall particle diameters. Among Ln2O3 nanoparticles, Gd2O3 nanoparticles show larger longitudinal water proton relaxivity (r1) values than Gd-chelates because of the large amount of Gd in the nanoparticle, and the other Ln2O3 nanoparticles (Ln = Dy, Ho, and Er) show appreciable transverse water proton relaxivity (r2) values. Therefore, Gd2O3 nanoparticles are potential T1 MRI contrast agents while the other Ln2O3 nanoparticles are potential T2 MRI contrast agents at high MR fields.

Wave and particle evolution downstream of quasi-perpendicular shocks

NASA Technical Reports Server (NTRS)

Mckean, M. E.; Omidi, N.; Krauss-Varban, D.; Karimabadi, H.

1995-01-01

Distributions of ions heated in quasi-perpendicular bow shocks have large perpendicular temperature anisotropies that provide free energy for the growth of Alfven ion cyclotron (AIC) and mirror waves. These modes are often obsreved in the Earth's magnetosheath. Using two-dimensional hybrid simulations, we show that these waves are produced near the shock front and convected downstream rather than being produced locally downstream. The wave activity reduces the proton anisotropy to magnetosheath levels within a few tens of gyroradii of the shock but takes significantly longer to reduce the anisotropy of He(++) ions. The waves are primarily driven by proton anisotropy and the dynamics of the helium ions is controlled by the proton waves. Downstream of high Mach number shocks, mirror waves compete effectively with AIC waves. Downstream of low Mach number shocks, AIC waves dominate.

Stimulated Emission and Optical Properties of Solid Solutions of Cu(In,Ga)Se2 Direct Band Gap Semiconductors

NASA Astrophysics Data System (ADS)

Svitsiankou, I. E.; Pavlovskii, V. N.; Lutsenko, E. V.; Yablonskii, G. P.; Mudryi, A. V.; Borodavchenko, O. M.; Zhivulko, V. D.; Yakushev, M. V.; Martin, R.

2018-05-01

Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of 20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of 20 kW/cm2. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se2 thin films.

Plasma distribution and spacecraft charging modeling near Jupiter

NASA Technical Reports Server (NTRS)

Goldstein, R.; Divine, N.

1977-01-01

To assess the role of spacecraft charging near Jupiter, the plasma distribution in Jupiter's magnetosphere was modeled using data from the plasma analyzer experiments on Pioneer 10 (published results) and on Pioneer 11 (preliminary results). In the model, electron temperatures are kT = 4 eV throughout, whereas proton temperatures range over 100 or equal to kT or equal to 400 eV. The model fluxes and concentrations vary over three orders of magnitude among several corotating regions, including, in order to increasing distance from Jupiter, a plasma void, plasma sphere, sporadic zone, ring current, current sheet, high latitude plasma and magnetosheath. Intermediate and high energy electrons and protons (to 100 MeV) are modeled as well. The models supply the information for calculating particle fluxes to a spacecraft in the Jovian environment. The particle balance equations (including effects of secondary and photoemission) then determine the spacecraft potential.

Analysis performance of proton exchange membrane fuel cell (PEMFC)

NASA Astrophysics Data System (ADS)

Mubin, A. N. A.; Bahrom, M. H.; Azri, M.; Ibrahim, Z.; Rahim, N. A.; Raihan, S. R. S.

2017-06-01

Recently, the proton exchange membrane fuel cell (PEMFC) has gained much attention to the technology of renewable energy due to its mechanically ideal and zero emission power source. PEMFC performance reflects from the surroundings such as temperature and pressure. This paper presents an analysis of the performance of the PEMFC by developing the mathematical thermodynamic modelling using Matlab/Simulink. Apart from that, the differential equation of the thermodynamic model of the PEMFC is used to explain the contribution of heat to the performance of the output voltage of the PEMFC. On the other hand, the partial pressure equation of the hydrogen is included in the PEMFC mathematical modeling to study the PEMFC voltage behaviour related to the input variable input hydrogen pressure. The efficiency of the model is 33.8% which calculated by applying the energy conversion device equations on the thermal efficiency. PEMFC’s voltage output performance is increased by increasing the hydrogen input pressure and temperature.

Proton fire hose instabilities in the expanding solar wind: Role of oblique magnetic field

NASA Astrophysics Data System (ADS)

Hellinger, Petr

2016-04-01

The double adiabatic (CGL) approximation for the ideal (Parker) interplanetary magnetic field (IMF) predicts generation of the parallel particle temperature anisotropy (T∥ > T⊥) for a nearly radial magnetic field whereas for a strongly oblique IMF generation of the opposite temperature anisotropy is expected. The transition between the two behaviours is expected at around 45o, i.e. around 1 AU in the solar wind in the ecliptic plane. We investigate properties of a proton-electron plasma system in the solar wind using hybrid expanding box simulations starting with an oblique IMF. The simulated system becomes unstable with respect to the parallel and oblique fire hose instabilities and is forced to stay around the corresponding marginal stability. Rotation of the IMF reduces the time system stays near the marginal stability regions and for a strongly transverse IMF the system moves away from the regions unstable with respect to the fire hose instabilities.

Influence of flow constraints on the properties of the critical endpoint of symmetric nuclear matter

NASA Astrophysics Data System (ADS)

Ivanytskyi, A. I.; Bugaev, K. A.; Sagun, V. V.; Bravina, L. V.; Zabrodin, E. E.

2018-06-01

We propose a novel family of equations of state for symmetric nuclear matter based on the induced surface tension concept for the hard-core repulsion. It is shown that having only four adjustable parameters the suggested equations of state can, simultaneously, reproduce not only the main properties of the nuclear matter ground state, but the proton flow constraint up its maximal particle number densities. Varying the model parameters we carefully examine the range of values of incompressibility constant of normal nuclear matter and its critical temperature, which are consistent with the proton flow constraint. This analysis allows us to show that the physically most justified value of nuclear matter critical temperature is 15.5-18 MeV, the incompressibility constant is 270-315 MeV and the hard-core radius of nucleons is less than 0.4 fm.

Magnetic resonance imaging using chemical exchange saturation transfer

NASA Astrophysics Data System (ADS)

Park, Jaeseok

2012-10-01

Magnetic resonance imaging (MRI) has been widely used as a valuable diagnostic imaging modality that exploits water content and water relaxation properties to provide both structural and functional information with high resolution. Chemical exchange saturation transfer (CEST) in MRI has been recently introduced as a new mechanism of image contrast, wherein exchangeable protons from mobile proteins and peptides are indirectly detected through saturation transfer and are not observable using conventional MRI. It has been demonstrated that CEST MRI can detect important tissue metabolites and byproducts such as glucose, glycogen, and lactate. Additionally, CEST MRI is sensitive to pH or temperature and can calibrate microenvironment dependent on pH or temperature. In this work, we provide an overview on recent trends in CEST MRI, introducing general principles of CEST mechanism, quantitative description of proton transfer process between water pool and exchangeable solute pool in the presence or absence of conventional magnetization transfer effect, and its applications

Scalings of Alfvén-cyclotron and ion Bernstein instabilities on temperature anisotropy of a ring-like velocity distribution in the inner magnetosphere

DOE PAGES

Min, Kyungguk; Liu, Kaijun; Gary, S. Peter

2016-03-18

Here, a ring-like proton velocity distribution with ∂f p(v ⊥)/∂v ⊥>0 and which is sufficiently anisotropic can excite two distinct types of growing modes in the inner magnetosphere: ion Bernstein instabilities with multiple ion cyclotron harmonics and quasi-perpendicular propagation and an Alfvén-cyclotron instability at frequencies below the proton cyclotron frequency and quasi-parallel propagation. Recent particle-in-cell simulations have demonstrated that even if the maximum linear growth rate of the latter instability is smaller than the corresponding growth of the former instability, the saturation levels of the fluctuating magnetic fields can be greater for the Alfvén-cyclotron instability than for the ion Bernsteinmore » instabilities. In this study, linear dispersion theory and two-dimensional particle-in-cell simulations are used to examine scalings of the linear growth rate and saturation level of the two types of growing modes as functions of the temperature anisotropy T ⊥/T || for a general ring-like proton distribution with a fixed ring speed of 2v A, where v A is the Alfvén speed. For the proton distribution parameters chosen, the maximum linear theory growth rate of the Alfvén-cyclotron waves is smaller than that of the fastest-growing Bernstein mode for the wide range of anisotropies (1≤T ⊥/T ||≤7) considered here. Yet the corresponding particle-in-cell simulations yield a higher saturation level of the fluctuating magnetic fields for the Alfvén-cyclotron instability than for the Bernstein modes as long as inline image. Since fast magnetosonic waves with ion Bernstein instability properties observed in the magnetosphere are often not accompanied by electromagnetic ion cyclotron waves, the results of the present study indicate that the ring-like proton distributions responsible for the excitation of these fast magnetosonic waves should not be very anisotropic.« less

SU-E-T-486: In Vivo Skin Dosimetry Using the Exradin W1 Plastic Scintillation Detector for Passively Scattered Proton Beam Therapy

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

Alsanea, F; Kudchadker, R; Usama, M

Purpose: To evaluate the accuracy and usefulness of plastic scintillation detectors used for skin dosimetry of patients undergoing passive scatter proton therapy. Methods: Following an IRB approved protocol, six patients undergoing passively scattered proton beam therapy for prostate cancer were selected for in vivo skin dosimetry using the Exradin W1 plastic scintillator. The detector was calibrated on a Cobalt-60 unit, and phantom measurements in the proton beam with the W1 and a calibrated parallel plate ion chamber were used to account for the under-response due to high LET at energies used for treatment. Measurements made in a heated water tankmore » were used to account for temperature dependence. For in vivo measurements, the W1 is fixed to the patient’s skin with medical tape in the center of each of two laterally opposed treatment fields. Measurements will be performed once per week for each patient for the duration of treatment, for a total of thirty six measurements. The measured dose will be compared to the expected dose, extracted from the Eclipse treatment planning system. The average difference over all measurements and per-patient will be computed, as well as standard deviations. Results: The calibrated detector exhibited a 7% under-response in 225 and 250 MeV beams, and a 4% under-response when used at 37 °C (relative to the response at the calibration temperature of 20 °C). Patient measurements are ongoing. Conclusion: The Exradin W1 plastic scintillator detector is a strong candidate for in vivo skin dosimetry in passively scattered proton beams as PSDs are water equivalent and very small (2mm in diameter), permitting accurate measurements that do not perturb the delivered dose. This project was supported in part by award number CA182450 from the National Cancer Institute.« less

Microstructured Electrolyte Membranes to Improve Fuel Cell Performance

NASA Astrophysics Data System (ADS)

Wei, Xue

Fuel cells, with the advantages of high efficiency, low greenhouse gas emission, and long lifetime are a promising technology for both portable power and stationary power sources. The development of efficient electrolyte membranes with high ionic conductivity, good mechanical durability and dense structure at low cost remains a challenge to the commercialization of fuel cells. This thesis focuses on exploring novel composite polymer membranes and ceramic electrolytes with the microstructure engineered to improve performance in direct methanol fuel cells (DMFCs) and solid oxide fuel cells (SOFCs), respectively. Polymer/particle composite membranes hold promise to meet the demands of DMFCs at lower cost. The structure of composite membranes was controlled by aligning proton conducting particles across the membrane thickness under an applied electric field. The field-induced structural changes caused the membranes to display an enhanced water uptake, proton conductivity, and methanol permeability in comparison to membranes prepared without an applied field. Although both methanol permeability and proton conductivity are enhanced by the applied field, the permeability increase is relatively lower than the proton conductivity improvement, which results in enhanced proton/methanol selectivity and improved DMFC performance. Apatite ceramics are a new class of fast ion conductors being studied as alternative SOFC electrolytes in the intermediate temperature range. An electrochemical/hydrothermal deposition method was developed to grow fully dense apatite membranes containing well-developed crystals with c-axis alignment to promote ion conductivity. Hydroxyapatite seed crystals were first deposited onto a metal substrate electrochemically. Subsequent ion substitution during the hydrothermal growth process promoted the formation of dense, fully crystalline films with microstructure optimal for ion transport. The deposition parameters were systematically investigated, such as reactant type, reagent concentration, solution pH, and reaction time. Dense apatite films were formed on palladium substrates that can serve as intermediate temperature fuel cell anodes. The novel apatite membrane structure is promising for fuel cell applications, as well as in improving the biocompatibility of orthopedic implants when coated on stainless steel or titanium substrates.

Fusion proton diagnostic for the C-2 field reversed configurationa)

NASA Astrophysics Data System (ADS)

Magee, R. M.; Clary, R.; Korepanov, S.; Smirnov, A.; Garate, E.; Knapp, K.; Tkachev, A.

2014-11-01

Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50 cm2), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (˜100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber.

Dynamic Nuclear Polarization Study of Inhibitor Binding to the M218–60 Proton Transporter from Influenza A

PubMed Central

Andreas, Loren B.; Barnes, Alexander B.; Corzilius, Björn; Chou, James J.; Miller, Eric A.; Caporini, Marc; Rosay, Melanie; Griffin, Robert G

2013-01-01

We demonstrate the use of dynamic nuclear polarization (DNP) to elucidate ligand binding to a membrane protein using dipolar recoupling magic angle spinning (MAS) NMR. In particular, we detect drug binding in the proton transporter M218–60 from influenza A using recoupling experiments at room temperature and with cryogenic DNP. The results indicate that the pore binding site of rimantadine is correlated with previously reported widespread chemical shift changes, suggesting functional binding in the pore. Futhermore, the 15N labeled ammonium of rimantadine was observed near A30 13Cβ and G34 13Cα suggesting a possible hydrogen bond to A30 Carbonyl. Cryogenic DNP was required to observe the weaker external binding site(s) in a ZF-TEDOR spectrum. This approach is generally applicable, particularly for weakly bound ligands, in which case the application of MAS NMR dipolar recoupling requires the low temperatures to quench dynamic exchange processes. For the fully protonated samples investigated, we observed DNP signal enhancements of ~10 at 400 MHz using only 4–6 mM of the polarizing agent TOTAPOL. At 600 MHz and with DNP, we measured a distance between the drug and the protein to a precision of 0.2 Å. PMID:23480101

Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

PubMed Central

Téllez Lozano, Helena; Druce, John; Cooper, Samuel J.; Kilner, John A.

2017-01-01

Abstract 18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H2 16O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity (~1.3 × 10−11 cm2s−1) at this temperature and that the presence of water (2H2 16O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of ~3. The 2H distribution, as inferred from the 2H2 16O− SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials. PMID:29383047

The Hydric Effect in Inorganic Nanomaterials for Nanoelectronics and Energy Applications.

PubMed

Sun, Xu; Guo, Yuqiao; Wu, Changzheng; Xie, Yi

2015-07-08

Protons, as one of the world's smallest ions, are able to trigger the charge effect without obvious lattice expansion inside inorganic materials, offering a unique and important test-bed for controlling their diverse functionalities. Arising from the high chemical reactivity of hydrogen (easily losing an electron) with various main group anions (easily accepting a proton), the hydric effect provides a convenient and environmentally benign route to bring about fascinating new physicochemical properties, as well as to create new inorganic structures based on the "old lattice" without dramatically destroying the pristine structure, covering most inorganic materials. Moreover, hydrogen atoms tend to bond with anions or to produce intrinsic defects, both of which are expected to inject extra electrons into lattice framework, promising advances in control of bandgap, spin behavior, and carrier concentration, which determine functionality for wide applications. In this review article, recently developed effective hydric strategies are highlighted, which include the conventional hydric reaction under high temperature or room temperature, proton irradiation or hydrogen plasma treatment, and gate-electrolyte-driven adsorption or doping. The diverse physicochemical properties brought by the hydric effect via modulation of the intrinsic electronic structure are also summarized, finding wide applications in nanoelectronics, energy applications, and catalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complex methyl group and hydrogen-bonded proton motions in terms of the Arrhenius and Schrödinger equations.

PubMed

Latanowicz, L

2008-01-01

Equations for the temperature dependence of the spectral densities J(is)(m)(momega(I) +/-omega(T)), where m=1, 2, omega(I) and omega(T) are the resonance and tunnel splitting angular frequencies, in the presence of a complex motion, have been derived. The spin pairs of the protons or deuterons of the methyl group perform a complex motion consisting of three component motions. Two of them involve mass transportation over the barrier and through the barrier. They are characterized by k((H)) (Arrhenius) and k((T)) (Schrödinger) rate constants, respectively. The third motion causes fluctuations of the frequencies (nomega(I)+/-omega(T)) and it is related to the lifetime of the methyl spin at the energy level influenced by the rotor-bath interactions. These interactions induce rapid transitions, changing the symmetry of the torsional sublevels either from A to E or from E(a) to E(b). The correlation function for this third motion (k((omega)) rate constant) has been proposed by Müller-Warmuth et al. The spectral densities of the methyl group hindered rotation (k((H)), k((T)) and k((omega)) rate constants) differ from the spectral densities of the proton transfer (k((H)) and k((T)) rate constants) because three compound motions contribute to the complex motion of the methyl group. The recently derived equation [Formula: see text] , where [Formula: see text] and [Formula: see text] are the fraction and energy of particles with energies from zero to E(H), is taken into account in the calculations of the spectral densities. This equation follows from Maxwell's distribution of thermal energy. The spectral densities derived are applied to analyse the experimental temperature dependencies of proton and deuteron spin-lattice relaxation rate in solids containing the methyl group. A wide range of temperatures from zero Kelvin up to the melting point is considered. It has been established that the motion characterized by k((omega)) influences the spin-lattice relaxation up to the temperature T(tun) only. This temperature is directly determined by the equation C(p)T=E(H) (thermal energy=activation energy), where C(p) is the molar heat capacity. Probably the cessation of the third motion is a result of the de Broglie wavelength related to this motion becoming too short. As shown recently, the potential barrier can be an obstacle for the de Broglie wave. The theoretical equations derived in this paper are compared to those known in the literature.

Synthesis, crystal structure, thermal analysis and dielectric properties of Rb4(SO4)(HSO4)2(H3AsO4) compound

NASA Astrophysics Data System (ADS)

Belhaj Salah, M.; Nouiri, N.; Jaouadi, K.; Mhiri, T.; Zouari, N.

2018-01-01

A new inorganic Rb4(SO4)(HSO4)2(H3AsO4) compound was prepared. It was found to crystallize in the monoclinic system (P21 space group) with the following lattice parameters: a = 5868 (1) Å, b = 13,579(2) Å, c = 11,809 (3) Å and β = 94,737 (1)°. The structure is characterized by SO42-, HSO4- and H3AsO4 tetrahedra connected by hydrogen bridge to form two types of dimmer (H(8)S(2)O4- … S(1)O42- and H(12)S(2)O4- … H3AsO4). These dimmers are interconnected by both hydrogen bonds O(14)sbnd H(14)· · ·O(4) and O(15)sbnd H(15)· · ·O(2). They are also linked by the hydrogen bridge assured by the hydrogen atoms H(2), H(3) and H(4) of the H3AsO4 group to build the chain S(1)O4⋯H3AsO4 which are parallel to the ''a'',direction. The rubidium cations are coordinated by eight oxygen atoms with Rbsbnd O distance ranging from 2893(8) to 3.415(6) Å. The existence of Osbnd H and (S/As)sbnd O bonds in the structure at room temperature has been confirmed by IR and Raman spectroscopy in the frequency ranges 4000-400 cm-1and 1200 - 50 cm-1, respectively. Thermal analysis of Rb4(HSO4)(HSO4)2(H3AsO4) showed that the transformation to high temperature phase occurs at 407 K by one-step process. Thermal decomposition of the product takes place at much higher temperatures, with an onset of approximately 522 K. The first transition detected by differential scanning calorimetry (DSC) was also analyzed by dielectric and conductivity measurements using the impedance spectroscopy techniques. The conductivity in the high temperature phase at 428 K is 1.04 × 10-3 Ω-1 cm-1, and the activation energy for the proton transport is 0.36 eV. The conductivity relaxation parameters associated with the high disorder protonic conduction have been examined from analysis of the M"/M"max spectrum measured in a wide temperature range. Transport properties of this material appear to be due to the proton hopping mechanism. The obtained results show that this transition is protonic by nature.

Nonlinear Evolution of Observed Fast Streams in the Solar Wind - Micro-instabilities and Energy Exchange between Protons and Alpha Particles

NASA Astrophysics Data System (ADS)

Maneva, Y. G.; Poedts, S.

2017-12-01

Non-thermal kinetic components such as deformed velocity distributions, temperature anisotropies and relative drifts between the multiple ion populations are frequently observed features in the collisionless fast solar wind streams near the Earth whose origin is still to be better understood. Some of the traditional models consider the formation of the temperature anisotropies through the effect of the solar wind expansion, while others assume in situ heating and particle acceleration by local fluctuations, such as plasma waves, or by spacial structures, such as advected or locally generated current sheets. In this study we consider the evolution of initial ion temperature anisotropies and relative drifts in the presence of plasma oscillations, such as ion-cyclotron and kinetic Alfven waves. We perform 2.5D hybrid simulations to study the evolution of observed fast solar wind plasma parcels, including the development of the plasma micro-instabilities, the field-particle correlations and the energy transfer between the multiple ion species. We consider two distinct cases of highly anisotropic and quickly drifting protons which excite ion-cyclotron waves and of moderately anisotropic slower protons, which co-exist with kinetic Alfven waves. The alpha particles for both cases are slightly anisotropic in the beginning and remain anisotropic throughout the simulation time. Both the imposed magnetic fluctuations and the initial differential streaming decrease in time for both cases, while the minor ions are getting heated. Finally we study the effects of the solar wind expansion and discuss its implications for the nonlinear evolution of the system.

In Situ Flow MAS NMR Spectroscopy and Synchrotron PDF Analyses of the Local Response of the Brønsted Acidic Site in SAPO-34 during Hydration at Elevated Temperatures.

PubMed

Kalantzopoulos, Georgios N; Lundvall, Fredrik; Checchia, Stefano; Lind, Anna; Wragg, David S; Fjellvåg, Helmer; Arstad, Bjørnar

2018-02-19

In situ flow magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and synchrotron-based pair distribution function (PDF) analyses were applied to study water's interactions with the Brønsted acidic site and the surrounding framework in the SAPO-34 catalyst at temperatures up to 300 °C for NMR spectroscopy and 700 °C for PDF. 29 Si enrichment of the sample enabled detailed NMR spectroscopy investigations of the T-atom generating the Brønsted site. By NMR spectroscopy, we observed dehydration above 100 °C and a coalescence of Si peaks due to local framework adjustments. Towards 300 °C, the NMR spectroscopy data indicated highly mobile acidic protons. In situ total X-ray scattering measurements analyzed by PDF showed clear changes in the Al local environment in the 250-300 °C region, as the Al-O bond lengths showed a sudden change. This fell within the same temperature range as the increased Brønsted proton mobility. We suggest that the active site in this catalyst under industrial conditions comprises not only the Brønsted proton but also SiO 4 . To the best of our knowledge, this is the first work proposing a structural model of a SAPO catalyst by atomic PDF analysis. The combination of synchrotron PDF analysis with in situ NMR spectroscopy is promising in revealing the dynamic features of a working catalyst. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Steam electrolysis by solid oxide electrolysis cells (SOECs) with proton-conducting oxides.

PubMed

Bi, Lei; Boulfrad, Samir; Traversa, Enrico

2014-12-21

Energy crisis and environmental problems caused by the conventional combustion of fossil fuels boost the development of renewable and sustainable energies. H2 is regarded as a clean fuel for many applications and it also serves as an energy carrier for many renewable energy sources, such as solar and wind power. Among all the technologies for H2 production, steam electrolysis by solid oxide electrolysis cells (SOECs) has attracted much attention due to its high efficiency and low environmental impact, provided that the needed electrical power is generated from renewable sources. However, the deployment of SOECs based on conventional oxygen-ion conductors is limited by several issues, such as high operating temperature, hydrogen purification from water, and electrode stability. To avoid these problems, proton-conducting oxides are proposed as electrolyte materials for SOECs. This review paper provides a broad overview of the research progresses made for proton-conducting SOECs, summarizing the past work and finding the problems for the development of proton-conducting SOECs, as well as pointing out potential development directions.

A Rare Terminal Dinitrogen Complex of Chromium

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

Mock, Michael T.; Chen, Shentan; Rousseau, Roger J.

The reduction of dinitrogen to ammonia from N2 and H2 is currently carried out by the Haber-Bosch process, an energy intensive process that requires high pressures and high temperatures and accounts for the production of millions of tons of ammonia per year. The development of a catalytic, energy-efficient process for N2 reduction is of great interest and remains a formidable challenge. In this communication, we are reporting the preparation, characterization and computational electronic structure analysis of a rare 'Chatt-type' ((P-P)2M(N2)2, P-P = diphosphine ligand) complex of chromium, cis-[Cr(N2)2(PPh2NBn2)2] and its reactivity with CO. This complex is supported by the diphosphinemore » ligand PPh2NBn2, containing non-coordinating pendant amine bases, to serve as proton relays. Future studies for this complex are aimed at answering fundamental questions regarding the role of proton relays in the second coordination sphere in their ability to facilitate proton movement from an external acid to metal-bound dinitrogen ligands in the challenging multi-proton/electron reduction of N2 to ammonia.« less

Collisionless Isotropization of the Solar-Wind Protons by Compressive Fluctuations and Plasma Instabilities

NASA Astrophysics Data System (ADS)

Verscharen, D.; Chandran, B. D. G.; Klein, K. G.; Quataert, E.

2016-12-01

Compressive fluctuations are a minor yet significant component of astrophysical plasma turbulence. In the solar wind, long-wavelength compressive slow-mode fluctuations lead to changes in β∥p ≡ 8πnpkBT∥p/B2 and in Rp ≡ T⊥p/T∥p, where T⊥p and T∥p are the perpendicular and parallel temperatures of the protons, B is the magnetic field strength, and np is the proton density. If the amplitude of the compressive fluctuations is large enough, Rp crosses one or more instability thresholds for anisotropy-driven micro-instabilities. The enhanced field fluctuations from these micro-instabilities scatter the protons so as to reduce the anisotropy of the pressure tensor, driving the average value of Rp away from the marginal stability boundary until the fluctuating value of Rp stops crossing the boundary. We model this "fluctuating-anisotropy effect" using linear Vlasov-Maxwell theory to describe the large-scale compressive fluctuations. We show that this effect can explain why, in the nearly collisionless solar wind, the average value of Rp is close to unity.

Enhanced critical currents of commercial 2G superconducting coated conductors through proton irradiation

NASA Astrophysics Data System (ADS)

Welp, Ulrich; Leroux, M.; Kihlstrom, K. J.; Kwok, W.-K.; Koshelev, A. E.; Miller, D. J.; Rupich, M. W.; Fleshler, S.; Malozemoff, A. P.; Kayani, A.

2015-03-01

We report on magnetization and transport measurements of the critical current density, Jc, of commercial 2G YBCO coated conductors before and after proton irradiation. The samples were irradiated along the c-axis with 4 MeV protons. Proton irradiation produces a mixed pinning landscape composed of pre-existing rare earth particles and a uniform distribution of irradiation induced nm-sized defects. This pinning landscape strongly reduces the suppression of Jc in magnetic fields resulting in a doubling of Jc in a field of ~ 4T. The irradiation dose-dependence of Jc is characterized by a temperature and field dependent sweat spot that at 5 K and 6 T occurs around 20x1016 p/cm2. Large-scale time dependent Ginzburg-Landau simulations yield a good description of our results. This work supported by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. D.O.E., Office of Science, Office of Basic Energy Sciences (KK, ML, AEK) and by the D.O.E, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 (UW, WKK).

New insights into proton surface mobility processes in PEMFC catalysts using isotopic exchange methods.

PubMed

Ferreira-Aparicio, Paloma

2009-09-01

The surface chemistry and the adsorption/desorption/exchange behavior of a proton-exchange membrane fuel cell catalyst are analyzed as a case study for the development of tailor-made support materials of enhanced performance and stability. By using H2, D2, and CO as probe molecules, the relevance of some surface functional groups of the catalyst support on several diffusion processes taking place during the adsorption is shown. Sulfonic groups associated with the vulcanized carbon black surface have been detected by means of spectroscopic techniques (X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy) and by analysis of the desorbed products during temperature-programmed desorption tests by mass spectrometry. Such hydrophilic species have been observed to favor proton surface mobility and exchange with Pt-adsorbed deuterium even in the presence of adsorbed CO. This behavior is relevant both for the proper characterization of these kinds of catalysts using adsorption probes and for the design of new surface-modified carbon supports, enabling alternative proton-transfer pathways throughout the catalytic layers toward the membrane.

Freeze-out conditions in proton-proton collisions at the highest energies available at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider

NASA Astrophysics Data System (ADS)

Das, Sabita; Mishra, Debadeepti; Chatterjee, Sandeep; Mohanty, Bedangadas

2017-01-01

The freeze-out conditions in proton-proton collisions at √{sNN}=200 , 900, and 7000 GeV have been extracted by fits to the mean hadron yields at midrapidity within the framework of the statistical model of an ideal gas of hadrons and resonances in the grand canonical ensemble. The variation of the extracted freeze-out thermal parameters and the goodness of the fits with √{sN N} are discussed. We find the extracted temperature and baryon chemical potential of the freeze-out surface to be similar in p +p and heavy-ion collisions. On the other hand, the thermal behavior of the strange hadrons is qualitatively different in p +p as compared to A +A collisions. We find an additional parameter accounting for nonequilibrium strangeness production is essential for describing the p +p data. This is in contrast to A +A where the nonequilibrium framework could be successfully replaced by a sequential and complete equilibrium model with an early freeze-out of the strange hadrons.

Heterogeneous Coordination Environments in Lithium-Neutralized Ionomers Identified Using 1H and 7Li MAS NMR

PubMed Central

Alam, Todd M.; Jenkins, Janelle E.; Bolintineanu, Dan S.; Stevens, Mark J.; Frischknecht, Amalie L.; Buitrago, C. Francisco; Winey, Karen I.; Opper, Kathleen L.; Wagener, Kenneth B.

2012-01-01

The carboxylic acid proton and the lithium coordination environments for precise and random Li-neutralized polyethylene acrylic acid P(E-AA) ionomers were explored using high speed solid-state 1H and 7Li MAS NMR. While the 7Li NMR revealed only a single Li coordination environment, the chemical shift temperature variation was dependent on the precise or random nature of the P(E-AA) ionomer. The 1H MAS NMR revealed two different carboxylic acid proton environments in these materials. By utilizing 1H-7Li rotational echo double resonance (REDOR) MAS NMR experiments, it was demonstrated that the proton environments correspond to different average 1H-7Li distances, with the majority of the protonated carboxylic acids having a close through space contact with the Li. Molecular dynamics simulations suggest that the shortest 1H-7Li distance corresponds to un-neutralized carboxylic acids directly involved in the coordination environment of Li clusters. These solid-state NMR results show that heterogeneous structural motifs need to be included when developing descriptions of these ionomer materials.

Two-Step Reactive Aid Sintering of BaZr0.8Y0.2O3- δ Proton-Conducting Ceramics

NASA Astrophysics Data System (ADS)

Wang, Siwei; Chen, Yan; Zhang, Lingling; Ren, Cong; Chen, Fanglin; Brinkman, Kyle S.

2015-12-01

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr0.8Y0.2O3- δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. In this paper, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO3 and B2O3-Li2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improved to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. The bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.

Two-Step Reactive Aid Sintering of BaZr 0.8Y 0.2O 3-δ Proton-Conducting Ceramics

DOE PAGES

Wang, Siwei; Chen, Yan; Zhang, Lingling; ...

2015-10-14

Ceramic-based proton conductors enable high-temperature hydrogen economy applications such as hydrogen separation membranes, fuel cells, and steam electrolyzers. BaZr 0.8Y 0.2O 3-δ (BZY) proton-conducting oxide possesses the highest level of proton conductivity reported to date, but poor sinterability hinders its widespread utilization. Here, we report a two-step reactive aid sintering (TRAS) method involving the introduction of BaCO 3 and B 2O 3-Li 2O for the preparation of dense BZY ceramics sintered at 1500°C. The resulting BZY samples showed a pure perovskite structure with a dramatic increase in the relative density to 91.5%. In addition, the shrinkage during sintering was improvedmore » to 19.3% by a TRAS method as compared to 2.6% by the conventional solid date reaction method. Moreover, the bulk conductivity was improved due to enhanced densification, while the grain boundary conductivity decreased due to the blocking behavior of the sintering aid resulting in a decrease in the total conductivity of the samples.« less

Implications inferred from anisotropy parameter of proton distributions related to EMIC waves in the inner magnetosphere.

NASA Astrophysics Data System (ADS)

Noh, S. J.; Lee, D. Y.

2017-12-01

In the classic theory of wave-particle resonant interaction, anisotropy parameter of proton distribution is considered as an important factor to determine an instability such as ion cyclotron instability. The particle distribution function is often assumed to be a bi-Maxwellian distribution, for which the anisotropy parameter can be simplified to temperature anisotropy (T⊥/T∥-1) independent of specific energy of particles. In this paper, we studied the proton anisotropy related to EMIC waves using the Van Allen Probes observations in the inner magnetosphere. First, we found that the real velocity distribution of protons is usually not expressed with a simple bi-Maxwellian distribution. Also, we calculated the anisotropy parameter using the exact formula defined by Kennel and Petschek [1966] and investigated the linear instability criterion of them. We found that, for majority of the EMIC wave events, the threshold anisotropy condition for proton cyclotron instability is satisfied in the expected range of resonant energy. We further determined the parallel plasma beta and its inverse relationship with the anisotropy parameter. The inverse relationship exists both during the EMIC wave times and non-EMIC wave times, but with different slopes. Based on this result, we demonstrate that the parallel plasma beta can be a critical factor that determines occurrence of EMIC waves.

Design study of an YBCO-coated beam screen for the super proton-proton collider bending magnets

NASA Astrophysics Data System (ADS)

Gan, Pingping; Zhu, Kun; Fu, Qi; Li, Haipeng; Lu, Yuanrong; Easton, Matt; Liu, Yudong; Tang, Jingyu; Xu, Qingjin

2018-04-01

In order to reduce the beam impedance and refrigeration power dramatically, we have designed a high temperature superconductor (HTS) coated beam screen to screen the cold chamber walls of the super proton-proton collider bending magnets from beam-induced heat loads. It employs an absorber, inspired by the future circular collider studies, to absorb the immense synchrotron radiation power of 12.8 W/m emitted from the 37.5 TeV proton beams. Such a structure has the advantage of decreasing the electron cloud effect and improving the beam vacuum. We have compared the critical magnetic field and current density and accessibility of two potential HTS materials for the beam screen, TlBa2Ca2Cu3O9-δ (Tl-1223) and Yttrium Barium Copper Oxide (YBCO) and finally chose YBCO for coating. The beam screen is tentatively designed to work at 55-70 K because of the limited development of the YBCO material. The thermal analysis with oxygen cooling fluid indicates that the YBCO conductor can maintain its superconductivity even if the synchrotron radiation hits the YBCO-coated surface and the mechanical analysis shows that the structure has the ability to resist the Lorenz force during magnet quenches.

Pendant dual sulfonated poly(arylene ether ketone) proton exchange membranes for fuel cell application

NASA Astrophysics Data System (ADS)

Nguyen, Minh Dat Thinh; Yang, Sungwoo; Kim, Dukjoon

2016-10-01

Poly(arylene ether ketone) (PAEK) possessing carboxylic groups at the pendant position is synthesized, and the substitution degree of pendant carboxylic groups is controlled by adjusting the ratio of 4,4-bis(4-hydroxyphenyl)valeric acid and 2,2-bis(4-hydroxyphenyl)propane. Dual sulfonated 3,3-diphenylpropylamine (SDPA) is grafted onto PAEK as a proton-conducting moiety via the amidation reaction with carboxylic groups. The transparent and flexible membranes with different degrees of sulfonation are fabricated so that we can test and compare their structure and properties with a commercial Nafion® 115 membrane for PEMFC applications. All prepared PAEK-SDPA membranes exhibit good oxidative and hydrolytic stability from Fenton's and high temperature water immersion test. SAXS analysis illustrates an excellent phase separation between the hydrophobic backbone and hydrophilic pendant groups, resulting in big ionic clusters. The proton conductivity was measured at different relative humidity, and its behavior was analyzed by hydration number of the membrane. Among a series of membranes, some samples (including B20V80-SDPA) show not only higher proton conductivity, but also higher integrated cell performance than those of Nafion® 115 at 100% relative humidity, and thus we expect these to be good candidate membranes for proton exchange membrane fuel cells (PEMFCs).

Visualization of the Diffusion Pathway of Protons in (NH4)2Si0.5Ti0.5P4O13 as an Electrolyte for Intermediate-Temperature Fuel Cells.

PubMed

Sun, Chunwen; Chen, Lanli; Shi, Siqi; Reeb, Berthold; López, Carlos Alberto; Alonso, José Antonio; Stimming, Ulrich

2018-01-16

We demonstrate that (NH 4 ) 2 Si 0.5 Ti 0.5 P 4 O 13 is an excellent proton conductor. The crystallographic information concerning the hydrogen positions is unraveled from neutron-powder-diffraction (NPD) data for the first time. This study shows that all the hydrogen atoms are connected though H bonds, establishing a two-dimensional path between the [(Si 0.5 Ti 0.5 )P 4 O 13 2- ] n layers for proton diffusion across the crystal structure by breaking and reconstructing intermediate H-O═P bonds. This transient species probably reduces the potential energy of the H jump from an ammonium unit to the next neighboring NH 4 + unit. Both theoretical and experimental results support an interstitial-proton-conduction mechanism. The proton conductivities of (NH 4 ) 2 Si 0.5 Ti 0.5 P 4 O 13 reach 0.0061 and 0.024 S cm -1 in humid air at 125 and 250 °C, respectively. This finding demonstrates that (NH 4 ) 2 Si 0.5 Ti 0.5 P 4 O 13 is a promising electrolyte material operating at 150-250 °C. This work opens up a new avenue for designing and fabricating high-performance inorganic electrolytes.

Clinical evaluation of MR temperature monitoring of laser-induced thermotherapy in human liver using the proton-resonance-frequency method and predictive models of cell death.

PubMed

Kickhefel, Antje; Rosenberg, Christian; Weiss, Clifford R; Rempp, Hansjörg; Roland, Joerg; Schick, Fritz; Hosten, Norbert

2011-03-01

To assess the feasibility, precision, and accuracy of real-time temperature mapping (TMap) during laser-induced thermotherapy (LITT) for clinical practice in patients liver with a gradient echo (GRE) sequence using the proton resonance frequency (PRF) method. LITT was performed on 34 lesions in 18 patients with simultaneous real-time visualization of relative temperature changes. Correlative contrast-enhanced T1-weighted magnetic resonance (MR) images of the liver were acquired after treatment using the same slice positions and angulations as TMap images acquired during LITT. For each slice, TMap and follow-up images were registered for comparison. Afterwards, segmentation based on temperature (T) >52°C on TMap and based on necrosis seen on follow-up images was performed. These segmented structures were overlaid and divided into zones where the TMap was found to either over- or underestimate necrosis on the postcontrast images. Regions with T>52°C after 20 minutes were defined as necrotic tissue based on data received from two different thermal dose models. The average intersecting region of TMap and necrotic zone was 87% ± 5%, the overestimated 13% ± 4%, and the underestimated 13% ± 5%. This study demonstrates that MR temperature mapping appears reasonably capable of predicting tissue necrosis on the basis of indicating regions having greater temperatures than 52°C and could be used to monitor and adjust the thermal therapy appropriately during treatment. Copyright © 2011 Wiley-Liss, Inc.

Pulsed Laser Deposition of High Temperature Protonic Films

NASA Technical Reports Server (NTRS)

Dynys, Fred W.; Berger, M. H.; Sayir, Ali

2006-01-01

Pulsed laser deposition has been used to fabricate nanostructured BaCe(0.85)Y(0.15)O3- sigma) films. Protonic conduction of fabricated BaCe(0.85)Y(0.15)O(3-sigma) films was compared to sintered BaCe(0.85)Y(0.15)O(3-sigma). Sintered samples and laser targets were prepared by sintering BaCe(0.85)Y(0.15)O(3-sigma) powders derived by solid state synthesis. Films 1 to 8 micron thick were deposited by KrF excimer laser on porous Al2O3 substrates. Thin films were fabricated at deposition temperatures of 700 to 950 C at O2 pressures up to 200 mTorr using laser pulse energies of 0.45 - 0.95 J. Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe(0.85)Y(0.15)O(3-sigma) films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C to 900 C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 oC; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied

A comparison of the temperature and density structure in high and low speed thermal proton flows

NASA Technical Reports Server (NTRS)

Raitt, W. J.; Schunk, R. W.; Banks, P. M.

1975-01-01

Steady-state altitude profiles of H(+) density, drift velocity, and temperature and O(+) density and temperature were deduced for a wide range of H(+) outflow velocities from subsonic to supersonic flow for plasma densities typical of both undisturbed and trough regions of the ionsophere. Allowance was made for the effects of inertia, parallel stress, and the velocity dependence of the H(+) collision frequencies. It was found that at supersonic outflow velocities there is a decrease in H(+) temperature with increasing outflow velocity. The H(+) temperatures are substantially increased above the O(+) temperatures when H(+) is flowing, with T(H+)/T(O+) reaching a maximum ratio of about 3:1.

Coulomb collisions in the solar wind

NASA Technical Reports Server (NTRS)

Klein, L. W.; Ogilvie, K. W.; Burlaga, L. F.

1985-01-01

A major improvement of the present investigation over previous studies of the subject is related to the use of helium temperatures obtained from helium ion measurements uncontaminated by the high-velocity tail of the proton distribution. More observations, covering a large parameter range, were employed, and the effects of interspecies drift were taken into account. It is shown in a more definite way than has been done previously, that Coulomb collisions provide the most important mechanism bringing about equilibrium between helium and protons in the solar wind. Other mechanisms may play some part in restricted regions, but Coulomb collisions are dominant on the macroscale.

Anodes for protonic ceramic fuel cells (PCFCs) =

NASA Astrophysics Data System (ADS)

Nasani, Narendar

One of the more promising possibilities for future "green" electrical energy generation is the protonic ceramic fuel cell (PCFC). PCFCs offer a low-pollution technology to generate electricity electrochemically with high efficiency. Reducing the operating temperature of solid oxide fuel cells (SOFCs) to the 500-700°C range is desirable to reduce fabrication costs and improve overall longevity. This aim can be achieved by using protonic ceramic fuel cells (PCFCs) due to their higher electrolyte conductivity at these temperatures than traditional ceramic oxide-ion conducting membranes. This thesis deals with the state of the art Ni-BaZr0.85Y0.15O3-delta cermet anodes for PCFCs. The study of PCFCs is in its initial stage and currently only a few methods have been developed to prepare suitable anodes via solid state mechanical mixing of the relevant oxides or by combustion routes using nitrate precursors. This thesis aims to highlight the disadvantages of these traditional methods of anode preparation and to, instead, offer a novel, efficient and low cost nitrate free combustion route to prepare Ni-BaZr0.85Y0.15O3-delta cermet anodes for PCFCs. A wide range of techniques mainly X-ray diffraction (XRD), scanning electron microscopy (SEM), environmental scanning electron microscopy, (ESEM) and electrochemical impedance spectroscopy (EIS) were employed in the cermet anode study. The work also offers a fundamental examination of the effect of porosity, redox cycling behaviour, involvement of proton conducting oxide phase in PCFC cermet anodes and finally progresses to study the electrochemical performance of a state of the art anode supported PCFC. The polarisation behaviour of anodes has been assessed as a function of temperature (T), water vapour (pH2O), hydrogen partial pressures (pH2) and phase purity for electrodes of comparable microstructure. The impedance spectra generally show two arcs at high frequency R2 and low frequency R3 at 600 °C, which correspond to the electrode polarisation resistance. Work shows that the R2 and R3 terms correspond to proton transport and dissociative H2 adsorption on electrode surface, respectively. The polarization resistance of the cermet anode (Rp) was shown to be significantly affected by porosity, with the PCFC cermet anode with the lowest porosity exhibiting the lowest Rp under standard operating conditions. This result highlights that porogens are not required for peak performance in PCFC anodes, a result contrary to that of their oxide-ion conducting anode counterparts. In-situ redox cycling studies demonstrate that polarisation behaviour was drastically impaired by redox cycling. In-situ measurements using an environmental scanning electron microscopy (ESEM) reveal that degradation proceeds due to volume expansion of the Ni-phase during the re-oxidation stage of redox cycling.The anode supported thin BCZY44 based protonic ceramic fuel cell, formed using a peak performing Ni-BaZr0.85Y0.15O3-delta cermet anode with no porogen, shows promising results in fuel cell testing conditions at intermediate temperatures with good durability and an overall performance that exceeds current literature data.

Proton tunneling in low dimensional cesium silicate LDS-1

NASA Astrophysics Data System (ADS)

Matsui, Hiroshi; Iwamoto, Kei; Mochizuki, Dai; Osada, Shimon; Asakura, Yusuke; Kuroda, Kazuyuki

2015-07-01

In low dimensional cesium silicate LDS-1 (monoclinic phase of CsHSi2O5), anomalous infrared absorption bands observed at 93, 155, 1210, and 1220 cm-1 are assigned to the vibrational mode of protons, which contribute to the strong hydrogen bonding between terminal oxygen atoms of silicate chain (O-O distance = 2.45 Å). The integrated absorbance (oscillator strength) for those modes is drastically enhanced at low temperatures. The analysis of integrated absorbance employing two different anharmonic double-minimum potentials makes clear that proton tunneling through the potential barrier yields an energy splitting of the ground state. The absorption bands at 93 and 155 cm-1, which correspond to the different vibrational modes of protons, are attributed to the optical transition between the splitting levels (excitation from the ground state (n = 0) to the first excited state (n = 1)). Moreover, the absorption bands at 1210 and 1220 cm-1 are identified as the optical transition from the ground state (n = 0) to the third excited state (n = 3). Weak Coulomb interactions in between the adjacent protons generate two types of vibrational modes: symmetric mode (93 and 1210 cm-1) and asymmetric mode (155 and 1220 cm-1). The broad absorption at 100-600 cm-1 reveals an emergence of collective mode due to the vibration of silicate chain coupled not only with the local oscillation of Cs+ but also with the proton oscillation relevant to the second excited state (n = 2).

Novel proton exchange membranes based on structure-optimized poly(ether ether ketone ketone)s and nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Ni, Chuangjiang; Wei, Yingcong; Zhao, Qi; Liu, Baijun; Sun, Zhaoyan; Gu, Yan; Zhang, Mingyao; Hu, Wei

2018-03-01

Two sulfonated fluorenyl-containing poly(ether ether ketone ketone)s (SFPEEKKs) were synthesized as the matrix of composite proton exchange membranes by directly sulfonating copolymer precursors comprising non-sulfonatable fluorinated segments and sulfonatable fluorenyl-containing segments. Surface-modified nanocrystalline cellulose (NCC) was produced as the "performance-enhancing" filler by treating the microcrystalline cellulose with acid. Two families of SFPEEKK/NCC nanocomposite membranes with various NCC contents were prepared via a solution-casting procedure. Results revealed that the insertion of NCC at a suitable ratio could greatly enhance the proton conductivity of the pristine membranes. For example, the proton conductivity of SFPEEKK-60/NCC-4 (SFPEEKK with 60% fluorenyl segments in the repeating unit, and inserted with 4% NCC) composite membrane was as high as 0.245 S cm-1 at 90 °C, which was 61.2% higher than that of the corresponding pure SFPEEKK-60 membrane. This effect could be attributed to the formation of hydrogen bond networks and proton conduction paths through the interaction between -SO3H/-OH groups on the surface of NCC particles and -SO3H groups on the SFPEEKK backbones. Furthermore, the chemically modified NCC filler and the optimized chemical structure of the SFPEEKK matrix also provided good dimensional stability and mechanical properties of the obtained nanocomposites. In conclusion, these novel nanocomposites can be promising proton exchange membranes for fuel cells at moderate temperatures.

An influence of solar activity on latitudinal distribution of atmospheric ozone and temperature in 2-D radiative-photochemical model

NASA Technical Reports Server (NTRS)

Dyominov, I. G.

1989-01-01

On the basis of the 2-D radiative-photochemical model of the ozone layer at heights 0 to 60 km in the Northern Hemisphere there are revealed and analyzed in detail the characteristic features of the season-altitude-latitude variations of ozone and temperature due to changes of the solar flux during the 11 year cycle, electron and proton precipitations.

Cationic Polymers Developed for Alkaline Fuel Cell Applications

DTIC Science & Technology

2015-01-20

into five categories: proton exchange membrane fuel cell ( PEMFC ), alkaline fuel cell (AFC), molten carbonate fuel cell (MCFC), solid oxide fuel...SOFC and PAFC belong to high temperature fuel cell, which can be applied in stationary power generation. PEMFC and AFC belong to low temperature fuel...function of the polymer electrolyte is to serve as electrolyte to transport ions between electrodes. PEMFC uses a polymer as electrolyte and works

Temperature dependence of broadline NMR spectra of water-soaked, epoxy-graphite composites

NASA Astrophysics Data System (ADS)

Lawing, David; Fornes, R. E.; Gilbert, R. D.; Memory, J. D.

1981-10-01

Water-soaked, epoxy resin-graphite fiber composites show a waterline in their broadline proton NMR spectrum which indicates a state of intermediate mobility between the solid and free water liquid states. The line is still present at -42 °C, but shows a reversible decrease in amplitude with decreasing temperature. The line is isotropic upon rotation of the fiber axis with respect to the external magnetic field.