Spin-locking versus chemical exchange saturation transfer MRI for investigating chemical exchange process between water and labile metabolite protons.

Science.gov (United States)

Jin, Tao; Autio, Joonas; Obata, Takayuki; Kim, Seong-Gi

2011-05-01

Chemical exchange saturation transfer (CEST) and spin-locking (SL) experiments were both able to probe the exchange process between protons of nonequivalent chemical environments. To compare the characteristics of the CEST and SL approaches in the study of chemical exchange effects, we performed CEST and SL experiments at varied pH and concentrated metabolite phantoms with exchangeable amide, amine, and hydroxyl protons at 9.4 T. Our results show that: (i) on-resonance SL is most sensitive to chemical exchanges in the intermediate-exchange regime and is able to detect hydroxyl and amine protons on a millimolar concentration scale. Off-resonance SL and CEST approaches are sensitive to slow-exchanging protons when an optimal SL or saturation pulse power matches the exchanging rate, respectively. (ii) Offset frequency-dependent SL and CEST spectra are very similar and can be explained well with an SL model recently developed by Trott and Palmer (J Magn Reson 2002;154:157-160). (iii) The exchange rate and population of metabolite protons can be determined from offset-dependent SL or CEST spectra or from on-resonance SL relaxation dispersion measurements. (iv) The asymmetry of the magnetization transfer ratio (MTR(asym)) is highly dependent on the choice of saturation pulse power. In the intermediate-exchange regime, MTR(asym) becomes complicated and should be interpreted with care. Copyright © 2010 Wiley-Liss, Inc.

Guanidinium chloride induction of partial unfolding in amide proton exchange in RNase A.

Science.gov (United States)

Mayo, S L; Baldwin, R L

1993-11-05

Amide (NH) proton exchange rates were measured in 0.0 to 0.7 M guanidinium chloride (GdmCl) for 23 slowly exchanging peptide NH protons of ribonuclease A (RNase A) at pH* 5.5 (uncorrected pH measured in D2O), 34 degrees C. The purpose was to find out whether GdmCl induces exchange through binding to exchange intermediates that are partly or wholly unfolded. It was predicted that, when the logarithm of the exchange rate is plotted as a function of the molarity of GdmCl, the slope should be a measure of the amount of buried surface area exposed to GdmCl in the exchange intermediate. The results indicate that these concentrations of GdmCl do induce exchange by means of a partial unfolding mechanism for all 23 protons; this implies that exchange reactions can be used to study the unfolding and stability of local regions. Of the 23 protons, nine also show a second mechanism of exchange at lower concentrations of GdmCl, a mechanism that is nearly independent of GdmCl concentration and is termed "limited structural fluctuation."

Inter- and intra-annular proton exchange in gaseous benzylbenzenium ions (protonated diphenylmethane)

OpenAIRE

Kuck, Dietmar; Bäther, Wolfgang

1986-01-01

Two distinct proton exchange reactions occur in metastable gaseous benzylbenzenium ions, generated by isobutane chemical ionization of diphenylmethane and four deuterium-labelled analogues. Whereas the proton ring-walk at the benzenium moiety is fast giving rise to a completely random intraannular proton exchange, the interannular proton exchange is surprisingly slow and competes with the elimination of benzene. A kinetic isotope effect of kH/kD= 5 has been determined for the interannular pro...

Electro-oxidation of methanol diffused through proton exchange membrane on Pt surface: crossover rate of methanol

International Nuclear Information System (INIS)

Jung, Inhwa; Kim, Doyeon; Yun, Yongsik; Chung, Suengyoung; Lee, Jaeyoung; Tak, Yongsug

2004-01-01

Methanol crossover rate through proton exchange membrane (Nafion 117) was investigated with a newly designed electrochemical stripping cell. Nanosize Pt electrode was prepared by the electroless deposition. Distinct electrocatalytic oxidation behaviors of methanol inside membrane were similar to the methanol oxidation in aqueous electrolyte, except adsorption/desorption of hydrogen. The amount of methanol diffused through membrane was calculated from the charge of methanol oxidation during repetitive cyclic voltammetry (CV) and methanol crossover rate was estimated to be 0.69 nmol/s

NMR studies of proton exchange kinetics in aqueous formaldehyde solutions.

Science.gov (United States)

Rivlin, Michal; Eliav, Uzi; Navon, Gil

2014-05-01

Aqueous solutions of formaldehyde, formalin, are commonly used for tissue fixation and preservation. Treatment with formalin is known to shorten the tissue transverse relaxation time T2. Part of this shortening is due to the effect of formalin on the water T2. In the present work we show that the shortening of water T2 is a result of proton exchange between water and the major constituent of aqueous solutions of formaldehyde, methylene glycol. We report the observation of the signal of the hydroxyl protons of methylene glycol at 2ppm to high frequency of the water signal that can be seen at low temperatures and at pH range of 6.0±1.5 and, at conditions where it cannot be observed by the single pulse experiment, it can be detected indirectly through the water signal by the chemical exchange saturation transfer (CEST) experiment. The above finding made it possible to obtain the exchange rate between the hydroxyl protons of the methylene glycol and water in aqueous formaldehyde solutions, either using the dispersion of the spin-lattice relaxation rate in the rotating frame (1/T1ρ) or, at the slow exchange regime, from the line width hydroxyl protons of methylene glycol. The exchange rate was ∼10(4)s(-1) at pH 7.4 and 37°C, the activation energy, 50.2kJ/mol and its pH dependence at 1.1°C was fitted to: k (s(-1))=520+6.5×10(7)[H(+)]+3.0×10(9)[OH(-)]. Copyright © 2014. Published by Elsevier Inc.

Aprotic solvent systems provide mechanistic windows for biomolecular reactions: nucleic acid proton exchange

International Nuclear Information System (INIS)

McConnell, B.; Tan, A.

1986-01-01

Detection of general acid-base catalysis of proton transfer reactions in aqueous cytidine (or adenosine) is completely obscured by the highly reactive endocyclic protonated species of the nucleobase, whose amino proton lifetime is much shorter than that of the neutral form. In aqueous solution, protonation of the nucleobase always accompanies protonation of the buffer catalyzing exchange. However, in DMSO/water mixtures this is not the case; aqueous protonated acetate or chloroacetate can be added to cytidine in DMSO solutions without further dissociation of the buffer or significant protonation of cytidine N-3. Under these conditions general acid catalysis is observed, which involves an H-bonded complex between cytidine (N-3) and the buffer acid. Increased amino proton exchange in response to H-bond donation to C(N-3) is further suggested by increased 1 H NMR saturation-recovery rates with the formation of G-C base-pairs in DMSO and by the inverse dependence of amino proton exchange on nucleoside concentration

Proton channels and exchangers in cancer.

Science.gov (United States)

Spugnini, Enrico Pierluigi; Sonveaux, Pierre; Stock, Christian; Perez-Sayans, Mario; De Milito, Angelo; Avnet, Sofia; Garcìa, Abel Garcìa; Harguindey, Salvador; Fais, Stefano

2015-10-01

Although cancer is characterized by an intratumoral genetic heterogeneity, a totally deranged pH control is a common feature of most cancer histotypes. Major determinants of aberrant pH gradient in cancer are proton exchangers and transporters, including V-ATPase, Na+/H+ exchanger (NHE), monocarboxylate transporters (MCTs) and carbonic anhydrases (CAs). Thanks to the activity of these proton transporters and exchangers, cancer becomes isolated and/or protected not only from the body reaction against the growing tumor, but also from the vast majority of drugs that when protonated into the acidic tumor microenvironment do not enter into cancer cells. Proton transporters and exchangers represent a key feature tumor cells use to survive in the very hostile microenvironmental conditions that they create and maintain. Detoxifying mechanisms may thus represent both a key survival option and a selection outcome for cells that behave as unicellular microorganisms rather than belonging to an organ, compartment or body. It is, in fact, typical of malignant tumors that, after a clinically measurable yet transient initial response to a therapy, resistant tumor clones emerge and proliferate, thus bursting a more malignant behavior and rapid tumor progression. This review critically presents the background of a novel and efficient approach that aims to fight cancer through blocking or inhibiting well characterized proton exchangers and transporters active in human cancer cells. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. Copyright © 2014 Elsevier B.V. All rights reserved.

Advantages of chemical exchange-sensitive spin-lock (CESL) over chemical exchange saturation transfer (CEST) for hydroxyl- and amine-water proton exchange studies.

Science.gov (United States)

Jin, Tao; Kim, Seong-Gi

2014-11-01

The chemical exchange (CE) rate of endogenous hydroxyl and amine protons with water is often comparable to the difference in their chemical shifts. These intermediate exchange processes have been imaged by the CE saturation transfer (CEST) approach with low-power and long-duration irradiation. However, the sensitivity is not optimal and, more importantly, the signal is contaminated by slow magnetization transfer processes. Here, the properties of CEST signals are compared with those of a CE-sensitive spin-lock (CESL) technique irradiating at the labile proton frequency. First, using a higher power and shorter irradiation in CE-MRI, we obtain: (i) an increased selectivity to faster CE rates via a higher sensitivity to faster CEs and a lower sensitivity to slower CEs and magnetization transfer processes; and (ii) a decreased in vivo asymmetric magnetization transfer contrast measured at ±15 ppm. The sensitivity gain of CESL over CEST is higher for a higher power and shorter irradiation. Unlike CESL, CEST signals oscillate at a very high power and short irradiation. Second, time-dependent CEST and CESL signals are well modeled by analytical solutions of CE-MRI with an asymmetric population approximation, which can be used for quantitative CE-MRI and validated by simulations of Bloch-McConnell equations and phantom experiments. Finally, the in vivo amine-water proton exchange contrast measured at 2.5 ppm with ω1 = 500 Hz is 18% higher in sensitivity for CESL than CEST at 9.4 T. Overall, CESL provides better exchange rate selectivity and sensitivity than CEST; therefore, CESL is more suitable for CE-MRI of intermediate exchange protons. Copyright © 2014 John Wiley & Sons, Ltd.

Proton exchange membrane fuel cells

CERN Document Server

Qi, Zhigang

2013-01-01

Preface Proton Exchange Membrane Fuel CellsFuel CellsTypes of Fuel CellsAdvantages of Fuel CellsProton Exchange Membrane Fuel CellsMembraneCatalystCatalyst LayerGas Diffusion MediumMicroporous LayerMembrane Electrode AssemblyPlateSingle CellStackSystemCell Voltage Monitoring Module (CVM)Fuel Supply Module (FSM)Air Supply Module (ASM)Exhaust Management Module (EMM)Heat Management Module (HMM)Water Management Module (WMM)Internal Power Supply Module (IPM)Power Conditioning Module (PCM)Communications Module (COM)Controls Module (CM)SummaryThermodynamics and KineticsTheoretical EfficiencyVoltagePo

Advantages of Chemical Exchange-Sensitive Spin-Lock (CESL) Over Saturation Transfer (CEST) for Hydroxyl- and Amine-Water Proton Exchange Studies

Science.gov (United States)

Jin, Tao; Kim, Seong-Gi

2014-01-01

The chemical exchange (CE) rate of endogenous hydroxyl and amine protons with water is often comparable to the difference in their chemical shifts. These intermediate exchange (IMEX) processes have been imaged by the CE saturation transfer (CEST) approach with low-power and long-duration irradiation. However, its sensitivity is not optimal, and more importantly, the signal is contaminated by slow magnetization transfer processes. Here, the property of CEST signals is compared to a CE-sensitive spin-locking (CESL) technique irradiating at the labile proton frequency. Firstly, using a higher power and shorter irradiation in CE-MRI yields i) increasing selectivity to faster chemical exchange rates by higher sensitivity to faster exchanges and less sensitivity to slower CE and magnetization transfer processes, and ii) decreasing in vivo asymmetric magnetization transfer contrast measured at ±15 ppm. The sensitivity gain of CESL over CEST is higher for a higher-power and shorter irradiation. Unlike CESL, CEST signals oscillate at a very high power and short irradiation. Secondly, time-dependent CEST and CESL signals are well modeled by analytical solutions of CE-MRI with asymmetric population approximation (CEAPA), which can be used for quantitative CE-MRI, and validated by simulations of Bloch-McConnell equations and phantom experiments. Lastly, in vivo amine-water proton exchange contrast measured at 2.5 ppm with ω1 of 500 Hz is 18% higher in sensitivity for CESL than CEST at 9.4 T. Overall, CESL provides better exchange rate selectivity and sensitivity than CEST; therefore, CESL is more suitable for CE-MRI of IMEX protons. PMID:25199631

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca exchangers.

Science.gov (United States)

Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

2008-05-01

Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+)exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H(+)-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca(2+)/H(+) exchangers and H(+) pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca(2+) flux. These results suggest cautious interpretation of mutant Ca(2+)/H(+) exchanger phenotypes that may be due to either perturbed Ca(2+) or H(+) transport.

Quantitation of chemical exchange rates using pulsed-field-gradient diffusion measurements

International Nuclear Information System (INIS)

Andrec, Michael; Prestegard, James H.

1997-01-01

A new approach to the quantitation of chemical exchange rates is presented, and its utility is illustrated with application to the exchange of protein amide protons with bulk water. The approach consists of a selective-inversion exchange HMQC experiment in which a short spin echo diffusion filter has been inserted into the exchange period. In this way, the kinetics of exchange are encoded directly in an apparent diffusion coefficient which is a function of the position of the diffusion filter in the pulse sequence. A detailed theoretical analysis of this experiment indicates that, in addition to the measurement of simple exchange rates, the experiment is capable of measuring the effect of mediated exchange, e.g. the transfer of magnetization from bulk water to an amide site mediated by an internal bound water molecule or a labile protein side-chain proton in fast exchange with bulk water. Experimental results for rapid water/amide exchange in acyl carrier protein are shown to be quantitatively consistent with the exchange rates measured using a selective-inversion exchange experiment

Moessbauer study of proton-exchanged LiNbO3:Fe

International Nuclear Information System (INIS)

Engelmann, H.; Andler, G.; Dezsi, I.

1990-01-01

Topotactic proton exchange (Li against H) can be achieved by treating LiBnO 3 with appropriate acids. In order to investigate the effect of proton exchange on Fe-impurities we studied LiNbO 3 :Fe powder material treated in sulphuric acid and LiNbO 3 :Fe single crystals treated in benzoic acid by Moessbauer spectroscopy. During the topotactic ion exchange only the Li-ions are exchanged for protons, whereas the Fe-impurities are retained in the material. (orig.)

Hydrogen-exchange kinetics of the indole NH proton of the buried tryptophan in the constant fragment of the immunoglobulin light chain

International Nuclear Information System (INIS)

Kawata, Y.; Goto, Y.; Hamaguchi, K.; Hayashi, F.; Kobayashi, Y.; Kyogoku, Y.

1988-01-01

The constant fragment of the immunoglobulin light chain (type λ) has two trytophyl residues at positions 150 and 187. Trp-150 is buried in the interior, and Trp-187 lies on the surface of the molecule. The hydrogen-deuterium exchange kinetics of the indole NH proton Trp-150 were studied at various pH values at 25 0 C by 1 H nuclear magnetic resonance. Exchange rates were approximately first order in hydroxyl ion dependence above pH 8, were relatively independent of pH between pH 7 and 8, and decreased below pH 7. On the assumption that the exchange above pH 8 proceeds through local fluctuations of the protein molecule, the exchange rates between pH 7 and 8 through global unfolding were estimated. The exchange rate constant within this pH range at 25 0 C thus estimated was consistent with that of the global unfolding of the constant fragment under the same conditions as those reported previously. The activation energy for the exchange process at pH 7.8 was the same as that for the unfolding process by 2 M guanidine hydrochloride. The exchange rates of backbone NH protons were almost the same as that of the indole NH proton of Trp-150 at pH 7.l. These observations also indicated that the exchange between pH 7 and 8 occurs through global unfolding of the protein molecule and is rate-limited by the unfolding. At around pH 9, on the other hand, the activation energy for the exchange process of the indole NH proton of Trp-150 was smaller than that for the unfolding process, and the exchange rates differed according to the different signals of backbone NH protons. These findings together with the pH dependence of the rate constant indicated that exchange due to local fluctuations is predominant above pH 8

Proton Conductive Channel Optimization in Methanol Resistive Hybrid Hyperbranched Polyamide Proton Exchange Membrane

Directory of Open Access Journals (Sweden)

Liying Ma

2017-12-01

Full Text Available Based on a previously developed polyamide proton conductive macromolecule, the nano-scale structure of the self-assembled proton conductive channels (PCCs is adjusted via enlarging the nano-scale pore size within the macromolecules. Hyperbranched polyamide macromolecules with different size are synthesized from different monomers to tune the nano-scale pore size within the macromolecules, and a series of hybrid membranes are prepared from these two micromoles to optimize the PCC structure in the proton exchange membrane. The optimized membrane exhibits methanol permeability low to 2.2 × 10−7 cm2/s, while the proton conductivity of the hybrid membrane can reach 0.25 S/cm at 80 °C, which was much higher than the value of the Nafion 117 membrane (0.192 S/cm. By considering the mechanical, dimensional, and the thermal properties, the hybrid hyperbranched polyamide proton exchange membrane (PEM exhibits promising application potential in direct methanol fuel cells (DMFC.

Protein proton-proton dynamics from amide proton spin flip rates

International Nuclear Information System (INIS)

Weaver, Daniel S.; Zuiderweg, Erik R. P.

2009-01-01

Residue-specific amide proton spin-flip rates K were measured for peptide-free and peptide-bound calmodulin. K approximates the sum of NOE build-up rates between the amide proton and all other protons. This work outlines the theory of multi-proton relaxation, cross relaxation and cross correlation, and how to approximate it with a simple model based on a variable number of equidistant protons. This model is used to extract the sums of K-rates from the experimental data. Error in K is estimated using bootstrap methodology. We define a parameter Q as the ratio of experimental K-rates to theoretical K-rates, where the theoretical K-rates are computed from atomic coordinates. Q is 1 in the case of no local motion, but decreases to values as low as 0.5 with increasing domination of sidechain protons of the same residue to the amide proton flips. This establishes Q as a monotonous measure of local dynamics of the proton network surrounding the amide protons. The method is applied to the study of proton dynamics in Ca 2+ -saturated calmodulin, both free in solution and bound to smMLCK peptide. The mean Q is 0.81 ± 0.02 for free calmodulin and 0.88 ± 0.02 for peptide-bound calmodulin. This novel methodology thus reveals the presence of significant interproton disorder in this protein, while the increase in Q indicates rigidification of the proton network upon peptide binding, confirming the known high entropic cost of this process

Characterization of creatine guanidinium proton exchange by water-exchange (WEX) spectroscopy for absolute-pH CEST imaging in vitro.

Science.gov (United States)

Goerke, Steffen; Zaiss, Moritz; Bachert, Peter

2014-05-01

Chemical exchange saturation transfer (CEST) enables indirect detection of small metabolites in tissue by MR imaging. To optimize and interpret creatine-CEST imaging we characterized the dependence of the exchange-rate constant k(sw) of creatine guanidinium protons in aqueous creatine solutions as a function of pH and temperature T in vitro. Model solutions in the low pH range (pH = 5-6.4) were measured by means of water-exchange (WEX)-filtered ¹H NMR spectroscopy on a 3 T whole-body MR tomograph. An extension of the Arrhenius equation with effective base-catalyzed Arrhenius parameters yielded a general expression for k(sw) (pH, T). The defining parameters were identified as the effective base-catalyzed rate constant k(b,eff) (298.15 K) = (3.009 ± 0.16) × 10⁹  Hz l/mol and the effective activation energy E(A,b,eff)  = (32.27 ± 7.43) kJ/mol at a buffer concentration of c(buffer)  = (1/15) M. As expected, a strong dependence of k(sw) on temperature was observed. The extrapolation of the exchange-rate constant to in vivo conditions (pH = 7.1, T = 37 °C) led to the value of the exchange-rate constant k(sw)  = 1499 Hz. With the explicit function k(sw) (pH, T) available, absolute-pH CEST imaging could be realized and experimentally verified in vitro. By means of our calibration method it is possible to adjust the guanidinium proton exchange-rate constant k(sw) to any desired value by preparing creatine model solutions with a specific pH and temperature. Copyright © 2014 John Wiley & Sons, Ltd.

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca(2+) exchangers

Science.gov (United States)

Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+) exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recen...

Imade-imide cross-linked PEEK proton exchange membrane.

CSIR Research Space (South Africa)

Luo, H

2009-08-01

Full Text Available The proton exchange membrane is a key component of polymer electrolyte membrane fuel cell (PEMFC). It plays an important role, conducts protons and separates the fuel from oxidant in PEMFC. DuPont’s Nafion is a perfluorinated sulfonic acid polymer...

Influence of the rated power in the performance of different proton exchange membrane (PEM) fuel cells

International Nuclear Information System (INIS)

San Martin, J.I.; Zamora, I.; San Martin, J.J.; Aperribay, V.; Torres, E.; Eguia, P.

2010-01-01

Fuel cells are clean generators that provide both electrical and thermal energy with a high global efficiency level. The characteristics of these devices depend on numerous parameters such as: temperature, fuel and oxidizer pressures, fuel and oxidizer flows, etc. Therefore, their influence should be evaluated to appropriately characterize behaviour of the fuel cell, in order to enable its integration in the electric system. This paper presents a theoretical and experimental analysis of the performance of two commercial Proton Exchange Membrane (PEM) fuel cells of 40 and 1200 W, and introduces the application of the principle of geometrical similarity. Using the principle of geometrical similarity it is possible to extrapolate the results obtained from the evaluation of one fuel cell to other fuel cells with different ratings. An illustrating example is included.

On the proton exchange contribution to electron-hydrogen atom elastic scattering

International Nuclear Information System (INIS)

Mignaco, J.A.; Tort, A.C.

1979-05-01

It is shown that the exchange contribution to the electron-proton potential Born term in elastic electron-hydrogen atom scattering arises as the non relativistic limit from the exchange of a proton between the two participant electrons - calculated from quantum electrodynamics including properly bound states (as solution of Bethe - Salpeter equation). (Author) [pt

Proton exchange in systems: Glucose-water and uric acid-water

International Nuclear Information System (INIS)

Maarof, S.

2007-01-01

It is clear that formation of glucose-water and uric acid-water solutions is related in principle to interaction accepter - donor between hydrogen atom in water and oxygen atom in glucose or uric acid. The proton exchange in hydrogen bond system is an integral process and it goes by tunnel mechanism (transfer of proton within the hydrogen bridge in these structures). Proton exchange process goes very quickly at low concentrations for glucose and uric acid solutions, because these compounds are able to form more than one hydrogen bond, which helps the proton transfer within obtained structure. However, at its high concentrations, the process becomes very slow due to higher viscosity of its solutions, which result in break down of the structures, and more hydrogen bonds. (author)

Stereochemistry-Dependent Proton Conduction in Proton Exchange Membrane Fuel Cells.

Science.gov (United States)

Thimmappa, Ravikumar; Devendrachari, Mruthyunjayachari Chattanahalli; Kottaichamy, Alagar Raja; Tiwari, Omshanker; Gaikwad, Pramod; Paswan, Bhuneshwar; Thotiyl, Musthafa Ottakam

2016-01-12

Graphene oxide (GO) is impermeable to H2 and O2 fuels while permitting H(+) shuttling, making it a potential candidate for proton exchange membrane fuel cells (PEMFC), albeit with a large anisotropy in their proton transport having a dominant in plane (σIP) contribution over the through plane (σTP). If GO-based membranes are ever to succeed in PEMFC, it inevitably should have a dominant through-plane proton shuttling capability (σTP), as it is the direction in which proton gets transported in a real fuel-cell configuration. Here we show that anisotropy in proton conduction in GO-based fuel cell membranes can be brought down by selectively tuning the geometric arrangement of functional groups around the dopant molecules. The results show that cis isomer causes a selective amplification of through-plane proton transport, σTP, pointing to a very strong geometry angle in ionic conduction. Intercalation of cis isomer causes significant expansion of GO (001) planes involved in σTP transport due to their mutual H-bonding interaction and efficient bridging of individual GO planes, bringing down the activation energy required for σTP, suggesting the dominance of a Grotthuss-type mechanism. This isomer-governed amplification of through-plane proton shuttling resulted in the overall boosting of fuel-cell performance, and it underlines that geometrical factors should be given prime consideration while selecting dopant molecules for bringing down the anisotropy in proton conduction and enhancing the fuel-cell performance in GO-based PEMFC.

Quantification of protein backbone hydrogen-deuterium exchange rates by solid state NMR spectroscopy

International Nuclear Information System (INIS)

Lopez del Amo, Juan-Miguel; Fink, Uwe; Reif, Bernd

2010-01-01

We present the quantification of backbone amide hydrogen-deuterium exchange rates (HDX) for immobilized proteins. The experiments make use of the deuterium isotope effect on the amide nitrogen chemical shift, as well as on proton dilution by deuteration. We find that backbone amides in the microcrystalline α-spectrin SH3 domain exchange rather slowly with the solvent (with exchange rates negligible within the individual 15 N-T 1 timescales). We observed chemical exchange for 6 residues with HDX exchange rates in the range from 0.2 to 5 s -1 . Backbone amide 15 N longitudinal relaxation times that we determined previously are not significantly affected for most residues, yielding no systematic artifacts upon quantification of backbone dynamics (Chevelkov et al. 2008b). Significant exchange was observed for the backbone amides of R21, S36 and K60, as well as for the sidechain amides of N38, N35 and for W41ε. These residues could not be fit in our previous motional analysis, demonstrating that amide proton chemical exchange needs to be considered in the analysis of protein dynamics in the solid-state, in case D 2 O is employed as a solvent for sample preparation. Due to the intrinsically long 15 N relaxation times in the solid-state, the approach proposed here can expand the range of accessible HDX rates in the intermediate regime that is not accessible so far with exchange quench and MEXICO type experiments.

Probing water structure and transport in proton exchange membranes

NARCIS (Netherlands)

Ling, X.

2018-01-01

Proton exchange membrane fuel cells (PEMFCs) have attracted tremendous attention as alternative energy sources because of their high energy density and practically zero greenhouse gas emission - water is their only direct by-product. Critical to the function of PEMFCs is fast proton and water

Rethinking the Combination of Proton Exchanger Inhibitors in Cancer Therapy.

Science.gov (United States)

Iessi, Elisabetta; Logozzi, Mariantonia; Mizzoni, Davide; Di Raimo, Rossella; Supuran, Claudiu T; Fais, Stefano

2017-12-23

Microenvironmental acidity is becoming a key target for the new age of cancer treatment. In fact, while cancer is characterized by genetic heterogeneity, extracellular acidity is a common phenotype of almost all cancers. To survive and proliferate under acidic conditions, tumor cells up-regulate proton exchangers and transporters (mainly V-ATPase, Na⁺/H⁺ exchanger (NHE), monocarboxylate transporters (MCTs), and carbonic anhydrases (CAs)), that actively extrude excess protons, avoiding intracellular accumulation of toxic molecules, thus becoming a sort of survival option with many similarities compared with unicellular microorganisms. These systems are also involved in the unresponsiveness or resistance to chemotherapy, leading to the protection of cancer cells from the vast majority of drugs, that when protonated in the acidic tumor microenvironment, do not enter into cancer cells. Indeed, as usually occurs in the progression versus malignancy, resistant tumor clones emerge and proliferate, following a transient initial response to a therapy, thus giving rise to more malignant behavior and rapid tumor progression. Recent studies are supporting the use of a cocktail of proton exchanger inhibitors as a new strategy against cancer.

Preparation and characterization of self-crosslinked organic/inorganic proton exchange membranes

Science.gov (United States)

Zhong, Shuangling; Cui, Xuejun; Dou, Sen; Liu, Wencong

A series of silicon-containing sulfonated polystyrene/acrylate (Si-sPS/A) nanoparticles are successfully synthesized via simple emulsion polymerization method. The Si-sPS/A latexes show good film-forming capability and the self-crosslinked organic/inorganic proton exchange membranes are prepared by pouring the Si-sPS/A nanoparticle latexes into glass plates and drying at 60 °C for 10 h and 120 °C for 2 h. The potential of the membranes in direct methanol fuel cells (DMFCs) is characterized preliminarily by studying their thermal stability, ion-exchange capacity, water uptake, methanol diffusion coefficient, proton conductivity and selectivity (proton conductivity/methanol diffusion coefficient). The results indicate that these membranes possess excellent thermal stability and methanol barrier due to the existence of self-crosslinked silica network. In addition, the proton conductivity of the membranes is in the range of 10 -3-10 -2 S cm -1 and all the membranes show much higher selectivity in comparison with Nafion ® 117. These results suggest that the self-crosslinked organic/inorganic proton exchange membranes are particularly promising in DMFC applications.

Proton exchange between oxymethyl radical and acids and bases: semiempirical quantum-chemical study

Directory of Open Access Journals (Sweden)

Irina Pustolaikina

2016-12-01

Full Text Available The reactions with proton participation are widely represented in the analytical, technological and biological chemistry. Quantum-chemical study of the exchange processes in hydrogen bonding complexes will allow us to achieve progress in the understanding of the elementary act mechanism of proton transfer in hydrogen bonding chain as well as the essence of the acid-base interactions. Oxymethyl radical •CH2ОН is small in size and comfortable as a model particle that well transmits protolytic properties of paramagnetic acids having more complex structure. Quantum-chemical modeling of proton exchange reaction oxymethyl radical ∙CH2OH and its diamagnetic analog CH3OH with amines, carboxylic acids and water was carried out using UAM1 method with the help of Gaussian-2009 program. QST2 method was used for the search of transition state, IRC procedure was applied for the calculation of descents along the reaction coordinate. The difference in the structure of transition states of ∙CH2OH/ CH3OH with bases and acids has been shown. It has been confirmed that in the case of bases, consecutive proton exchange mechanism was fixed, and in the case of complexes with carboxylic acids parallel proton exchange mechanism was fixed. The similarity in the reaction behavior of paramagnetic and diamagnetic systems in the proton exchange has been found. It was suggested that the mechanism of proton exchange reaction is determined by the structure of the hydrogen bonding cyclic complex, which is, in turn, depends from the nature of the acid-base interactions partners.

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

Science.gov (United States)

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

Rapid and accurate processing method for amide proton exchange rate measurement in proteins

International Nuclear Information System (INIS)

Koskela, Harri; Heikkinen, Outi; Kilpelaeinen, Ilkka; Heikkinen, Sami

2007-01-01

Exchange between protein backbone amide hydrogen and water gives relevant information about solvent accessibility and protein secondary structure stability. NMR spectroscopy provides a convenient tool to study these dynamic processes with saturation transfer experiments. Processing of this type of NMR spectra has traditionally required peak integration followed by exponential fitting, which can be tedious with large data sets. We propose here a computer-aided method that applies inverse Laplace transform in the exchange rate measurement. With this approach, the determination of exchange rates can be automated, and reliable results can be acquired rapidly without a need for manual processing

Proton exchange in acid–base complexes induced by reaction coordinates with heavy atom motions

International Nuclear Information System (INIS)

Alavi, Saman; Taghikhani, Mahdi

2012-01-01

Highlights: ► Proton exchange in acid–base complexes is studied. ► The structures, binding energies, and normal mode vibrations are calculated. ► Transition state structures of proton exchange mechanism are determined. ► In the complexes studied, the reaction coordinate involves heavy atom rocking. ► The reaction coordinate is not simply localized in the proton movements. - Abstract: We extend previous work on nitric acid–ammonia and nitric acid–alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid–strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are −1 . This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm −1 . Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

Exchange rate policy

Directory of Open Access Journals (Sweden)

Plačkov Slađana

2013-01-01

Full Text Available Small oscillations of exchange rate certainly affect the loss of confidence in the currency (Serbian dinar, CSD and because of the shallow market even the smallest change in the supply and demand leads to a shift in exchange rate and brings uncertainty. Some economists suggest that the course should be linked to inflation and thus ensure predictable and stable exchange rates. Real exchange rate or slightly depressed exchange rate will encourage the competitiveness of exporters and perhaps ensure the development of new production lines which, in terms of overvalued exchange rate, had no economic justification. Fixed exchange rate will bring lower interest rates, lower risk and lower business uncertainty (uncertainty avoidance, but Serbia will also reduce foreign exchange reserves by following this trend. On the other hand, a completely free exchange rate, would lead to a (real fall of Serbian currency, which in a certain period would lead to a significant increase in exports, but the consequences for businessmen and citizens with loans pegged to the euro exchange rate, would be disastrous. We will pay special attention to the depreciation of the exchange rate, as it is generally favorable to the export competitiveness of Serbia and, on the other hand, it leads to an increase in debt servicing costs of the government as well as of the private sector. Oscillations of the dinar exchange rate, appreciation and depreciation, sometimes have disastrous consequences on the economy, investors, imports and exports. In subsequent work, we will observe the movement of the dinar exchange rate in Serbia, in the time interval 2009-2012, in order to strike a balance and maintain economic equilibrium. A movement of foreign currencies against the local currency is controlled in the foreign exchange market, so in case economic interests require, The National Bank of Serbia (NBS, on the basis of arbitrary criteria, can intervene in the market.

Multi-block sulfonated poly(phenylene) copolymer proton exchange membranes

Science.gov (United States)

Fujimoto, Cy H [Albuquerque, NM; Hibbs, Michael [Albuquerque, NM; Ambrosini, Andrea [Albuquerque, NM

2012-02-07

Improved multi-block sulfonated poly(phenylene) copolymer compositions, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cells, in electrode casting solutions and electrodes. The multi-block architecture has defined, controllable hydrophobic and hydrophilic segments. These improved membranes have better ion transport (proton conductivity) and water swelling properties.

Study of proton polarization in charge exchange process on optically oriented sodium atoms

International Nuclear Information System (INIS)

Zelenskij, A.N.; Kokhanovskij, S.A.

1984-01-01

Using high-power adjustable dye lasers for electron spin orientation in a charge-exchange target enables to significantly increase the proton polarization efficiency. A device is described that permits to avoid growth of the polarized proton beam emittance in a charge-exchange process in a strong magnetic field. The devise main feature is the use of an intensive source of neutral hydrogen atoms and the presence of a helium additional charge-exchange target which actualy is a proton ''source''. The helium charge-exchange cell is placed in the same magnetic field of a solenoid where a cell with oriented sodium is placed, a polarized electron being captured by a proton in the latter cell. In this case the beam at the solenoid inlet and outlet is in a neutral state; emittance growth related to the effect of end magnetic fields is not observed. The device after all prouduces polarized protons, their polarization degree is measured and the effect of various factors on polarization degree is studied. The description of the laser source and laser system is given. Measurement results have shown the beam intensity of neutral 7 keV atoms which passed through a polarizer to be 2 mA. The proton current doesn't depend. On the beeld fin the region of chrge exchange for the 8 kGs magnetic field. The degree of sodium polarization was 80% and polarized proton current approximately 70 μA at a temperature of the polarized sodium cell corresponding to the density of sodium vapar approximately 3x10 13 at/cm 2

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca2+ exchangers

OpenAIRE

Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

2008-01-01

Tonoplast-localised proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a ...

Proton exchange membranes based on PVDF/SEBS blends

Energy Technology Data Exchange (ETDEWEB)

Mokrini, A.; Huneault, M.A. [Industrial Materials Institute, National Research Council of Canada, 75 de Mortagne Blvd., Boucherville, Que. (Canada J4B 6Y4)

2006-03-09

Proton-conductive polymer membranes are used as an electrolyte in the so-called proton exchange membrane fuel cells. Current commercially available membranes are perfluorosulfonic acid polymers, a class of high-cost ionomers. This paper examines the potential of polymer blends, namely those of styrene-(ethylene-butylene)-styrene block copolymer (SEBS) and polyvinylidene fluoride (PVDF), in the proton exchange membrane application. SEBS/PVDF blends were prepared by twin-screw extrusion and the membranes were formed by calendering. SEBS is a phase-segregated material where the polystyrene blocks can be selectively functionalized offering high ionic conductivity, while PVDF insures good dimensional stability and chemical resistance to the films. Proton conductivity of the films was obtained by solid-state grafting of sulfonic acid moieties. The obtained membranes were characterized in terms of conductivity, ionic exchange capacity and water uptake. In addition, the membranes were characterized in terms of morphology, microstructure and thermo-mechanical properties to establish the blends morphology-property relationships. Modification of interfacial properties between SEBS and PVDF was found to be a key to optimize the blends performance. Addition of a methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer (MMA-BA-MMA) was found to compatibilize the blend by reducing the segregation scale and improving the blend homogeneity. Mechanical resistance of the membranes was also improved through the addition of this compatibilizer. As little as 2wt.% compatibilizer was sufficient for complete interfacial coverage and lead to improved mechanical properties. Compatibilized blend membranes also showed higher conductivities, 1.9x10{sup -2} to 5.5x10{sup -3}Scm{sup -1}, and improved water management. (author)

Tritium-proton exchange on fresh and oxidized lecithin

International Nuclear Information System (INIS)

Schreiber, J.

1978-01-01

A method for exchange labelling of acid protons in lecithin and for their quantitative determination is described. The suitability of the method is discussed using both lecithin monohydrate and autoxidation products as examples. (author)

Cross-lined PEEK proton exchange membranes for fuel cell - Conference Poster

CSIR Research Space (South Africa)

Luo, H

2009-07-01

Full Text Available The low-cost cross-linked Polyetheretherketone (PEEK) proton exchange membranes were prepared via the simple route. The membranes exhibited similar electrochemical properties as compared with commercial Nafion. The membranes were highly proton...

Proton magnetic resonance study of the influence of chemical modification, mutation, quaternary state, and ligation state on dynamic stability of the heme pocket in hemoglobin as reflected in the exchange of the proximal histidyl ring labile proton

International Nuclear Information System (INIS)

Han, K.H.; La Mar, G.N.; Nagai, K.

1989-01-01

Proton nuclear magnetic resonance spectroscopy has been utilized to investigate the rates of exchange with deuterium of the proximal histidyl ring protons in a series of chemically modified and mutated forms of Hb A. Differences in rates of exchange are related to differences in the stability of the deformed or partially unfolded intermediates from which exchange with bulk solvent takes place. Each modified/mutated Hb exhibited kinetic subunit heterogeneity in the reduced ferrous state, with the alpha subunit exhibiting faster exchange than the beta subunit. Modification or mutation resulted in significant increases in the His F8 ring NH exchange rates primarily for the affected subunit and only if the modification/mutation occurs at the allosterically important alpha 1 beta 2 subunit interface. Moreover, this enhancement in exchange rate is observed primarily in that quaternary state of the modified/mutated Hb in which the modified/substituted residue makes the intersubunit contact. This confirms the importance of allosteric constraints in determining the dynamic properties of the heme pocket. Using modified or mutated Hbs that can switch between the alternate quaternary states within a given ligation state or ligate within a given quaternary state, we show that the major portion of the enhanced exchange rate in R-state oxy Hb relative to T-state deoxy Hb originates from the quaternary switch rather than from ligation. However, solely ligation effects are not negligible. The exchange rates of the His F8 ring labile protons increase dramatically upon oxidizing the iron to the ferric state, and both the subunit kinetic heterogeneity and the allosteric sensitivity to the quaternary state are essentially abolished

Proton exchange mechanism of synthesizing CdS quantum dots in nafion

International Nuclear Information System (INIS)

Nandakumar, P.; Vijayan, C.; Murti, Y.V.G.S.; Dhanalakshmi, K.; Sundararajan, G.

1999-01-01

Nanocrystals of CdS are synthesized in the proton exchange membrane nafion in different sizes in the range 1.6 to 6 nm. To understand the process leading to the formation of these quantum dots, we have probed the proton exchange by ac conductance measurements in the frequency range 100 Hz to 13 MHz. Nafion shows good electrical conductivity due to proton transport probably via the Grothus mechanism. Incorporation of cadmium ions by replacement of the hydrogen ions in the sulphonic acid group resulted in a large decrease in conductance indicating the reduction of the mobile carrier density. The conductivity plots all show strong frequency dependence with higher conductance towards the higher frequencies where a near-flat frequency response is seen. After the formation of CdS clusters, there is a partial recovery of conductance corresponding to the reinstatement of the protonic carriers on the side groups. The conductivity of the nafion films embedded with the semiconductor quantum dots exhibits a size-dependence with the highest conductivity obtained for the largest clusters. These findings lend clear experimental evidence for the model of synthesis of quantum dots in nafion by the exchange mechanism. (author)

Interest Rate Rules, Exchange Market Pressure, and Successful Exchange Rate Management

NARCIS (Netherlands)

Klaassen, F.; Mavromatis, K.

2016-01-01

Central banks with an exchange rate objective set the interest rate in response to what they call ''pressure.'' Instead, existing interest rate rules rely on the exchange rate minus its target. To stay closer to actual policy, we introduce a rule that uses exchange market pressure (EMP), the

Composite proton exchange membrane based on sulfonated organic nanoparticles

Science.gov (United States)

Pitia, Emmanuel Sokiri

As the world sets its sight into the future, energy remains a great challenge. Proton exchange membrane (PEM) fuel cell is part of the solution to the energy challenge because of its high efficiency and diverse application. The purpose of the PEM is to provide a path for proton transport and to prevent direct mixing of hydrogen and oxygen at the anode and the cathode, respectively. Hence, PEMs must have good proton conductivity, excellent chemical stability, and mechanical durability. The current state-of-the-art PEM is a perfluorosulfonate ionomer, Nafion®. Although Nafion® has many desirable properties, it has high methanol crossover and it is expensive. The objective of this research was to develop a cost effective two-phase, composite PEM wherein a dispersed conductive organic phase preferentially aligned in the transport direction controls proton transport, and a continuous hydrophobic phase provides mechanical durability to the PEM. The hypothesis that was driving this research was that one might expect better dispersion, higher surface to volume ratio and improved proton conductivity of a composite membrane if the dispersed particles were nanometer in size and had high ion exchange capacity (IEC, = [mmol sulfonic acid]/gram of polymer). In view of this, considerable efforts were employed in the synthesis of high IEC organic nanoparticles and fabrication of a composite membrane with controlled microstructure. High IEC, ~ 4.5 meq/g (in acid form, theoretical limit is 5.4 meq/g) nanoparticles were achieved by emulsion copolymerization of a quaternary alkyl ammonium (QAA) neutralized-sulfonated styrene (QAA-SS), styrene, and divinylbenzene (DVB). The effects of varying the counterion of the sulfonated styrene (SS) monomer (alkali metal and QAA cations), SS concentration, and the addition of a crosslinking agent (DVB) on the ability to stabilize the nanoparticles to higher IECs were assessed. The nanoparticles were ion exchanged to acid form. The extent of ion

Development of proton exchange membranes fuel cells with sulfonated HTPB-phenol; Desenvolvimento de membranas polimericas trocadoras de protons utilizando PBLH-fenol

Energy Technology Data Exchange (ETDEWEB)

Ferraz, Fernando A.; Oliveira, Angelo R.S.; Cesar-Oliveira, Maria Aparecida F. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Quimica. Lab. de Polimeros Sinteticos], e-mail: ferraz@quimica.ufpr.br; Cantao, Mauricio P. [LACTEC - Instituto de Tecnologia para o Desenvolvimento, Curitiba, PR (Brazil). Centro Politecnico

2007-07-01

Proton exchange membrane fuel cells (PEMFC) have been paid attention as promising candidates for vehicle and portable applications. PEMFC employ proton exchange polymer membrane which serves as an electrolyte between anode and cathode. Nafion{sup R} (DuPont), perfluorosulfonic acid/PTFE copolymer membranes are typically used as the polymer electrolyte in PEMFC due to their good chemical and mechanical properties as well as high proton conductivity. However, high cost of these materials is one of main obstacles for commercialization of PEMFC. Extensive efforts have been devoted to develop alternative polymer electrolyte membranes. Our group have investigated the development of proton exchange membranes fuel cells using sulfonated HTPB-Phenyl ether (HTPB-Phenol), making possible the formation of membranes with sulfonated groups amount of 2,4, 2,5 and 2,8 mmol/g of dry polymer from HTPB-Phenol 80, 98 and 117 respectively. These results mean a bigger values than those of the Nafion{sup R} membranes, that possess an ion exchange capacity of 0,67 up to 1,25 mmol/g of sulfonated groups. (author)

Quantitative description of proton exchange processes between water and endogenous and exogenous agents for WEX, CEST, and APT experiments.

Science.gov (United States)

Zhou, Jinyuan; Wilson, David A; Sun, Phillip Zhe; Klaus, Judith A; Van Zijl, Peter C M

2004-05-01

The proton exchange processes between water and solutes containing exchangeable protons have recently become of interest for monitoring pH effects, detecting cellular mobile proteins and peptides, and enhancing the detection sensitivity of various low-concentration endogenous and exogenous species. In this work, the analytic expressions for water exchange (WEX) filter spectroscopy, chemical exchange-dependent saturation transfer (CEST), and amide proton transfer (APT) experiments are derived by the use of Bloch equations with exchange terms. The effects of the initial states for the system, the difference between a steady state and a saturation state, and the relative contributions of the forward and backward exchange processes are discussed. The theory, in combination with numerical calculations, provides a useful tool for designing experimental schemes and assessing magnetization transfer (MT) processes between water protons and solvent-exchangeable protons. As an example, the case of endogenous amide proton exchange in the rat brain at 4.7 T is analyzed in detail. Copyright 2004 Wiley-Liss, Inc.

Determination of the equilibrium micelle-inserting position of the fusion peptide of gp41 of human immunodeficiency virus type 1 at amino acid resolution by exchange broadening of amide proton resonances

International Nuclear Information System (INIS)

Chang, D.-K.; Cheng, S.-F.

1998-01-01

The exchange broadening of backbone amide proton resonances of a 23-mer fusion peptide of the transmembrane subunit of HIV-1 envelope glycoprotein gp41, gp41-FP, was investigated at pH 5 and 7 at room temperature in perdeuterated sodium dodecyl sulfate (SDS) micellar solution. Comparison of resonance peaks for these pHs revealed an insignificant change in exchange rate between pH 5 and 7 for amide protons of residues 4 through 14, while the exchange rate increase at neutral pH was more prominent for amide protons of the remaining residues, with peaks from some protons becoming undetectable. The relative insensitivity to pH of the exchange for the amide protons of residues 4 through 14 is attributable to the drastic reduction in [OH-] in the micellar interior, leading to a decreased exchange rate. The A15-G16 segment represents a transition between these two regimes. The data are thus consistent with the notion that the peptide inserts into the hydrophobic core of a membrane-like structure and the A15-G16 dipeptide is located at the micellar-aqueous boundary

Proton-proton reaction rates at extreme energies

International Nuclear Information System (INIS)

Nagano, Motohiko

1993-01-01

Results on proton-antiproton reaction rates (total cross-section) at collision energies of 1.8 TeV from experiments at Fermilab have suggested a lower rate of increase with energy compared to the extrapolation based on results previously obtained at CERN's proton-antiproton collider (CERN Courier, October 1991). Now an independent estimate of the values for the proton-proton total cross-section for collision energies from 5 to 30 TeV has been provided by the analysis of cosmic ray shower data collected over ten years at the Akeno Observatory operated by the Institute for Cosmic Ray Research of University of Tokyo. These results are based on the inelastic cross-section for collisions of cosmic ray protons with air nuclei at energies in the range10 16-18 eV. A new extensive air shower experiment was started at Akeno, 150 km west of Tokyo, in 1979 with a large array of detectors, both on the ground and under a 1-metre concrete absorber. This measured the total numbers of electrons and muons of energies above 1GeV for individual showers with much better accuracy than before. Data collection was almost continuous for ten years without any change in the triggering criteria for showers above10 16 eV. The mean free path for proton-air nuclei collisions has been determined from the zenith angle of the observed frequency of air showers which have the same effective path length for development in the atmosphere and the same primary energy

Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST)

Science.gov (United States)

Friedman, Joshua I.; Xia, Ding; Regatte, Ravinder R.; Jerschow, Alexej

2015-07-01

Chemical Exchange Saturation Transfer (CEST) magnetic resonance experiments have become valuable tools in magnetic resonance for the detection of low concentration solutes with far greater sensitivity than direct detection methods. Accurate measures of rates of chemical exchange provided by CEST are of particular interest to biomedical imaging communities where variations in chemical exchange can be related to subtle variations in biomarker concentration, temperature and pH within tissues using MRI. Despite their name, however, traditional CEST methods are not truly selective for chemical exchange and instead detect all forms of magnetization transfer including through-space NOE. This ambiguity crowds CEST spectra and greatly complicates subsequent data analysis. We have developed a Transfer Rate Edited CEST experiment (TRE-CEST) that uses two different types of solute labeling in order to selectively amplify signals of rapidly exchanging proton species while simultaneously suppressing 'slower' NOE-dominated magnetization transfer processes. This approach is demonstrated in the context of both NMR and MRI, where it is used to detect the labile amide protons of proteins undergoing chemical exchange (at rates ⩾ 30 s-1) while simultaneously eliminating signals originating from slower (∼5 s-1) NOE-mediated magnetization transfer processes. TRE-CEST greatly expands the utility of CEST experiments in complex systems, and in-vivo, in particular, where it is expected to improve the quantification of chemical exchange and magnetization transfer rates while enabling new forms of imaging contrast.

The mass balance of a Proton Exchange Membrane Fuel Cell (PEMFC)

International Nuclear Information System (INIS)

Miloud, S.; Kamaruzzaman Sopian; Wan Ramli Wan Daud

2006-01-01

A Proton Exchange Membrane Fuel Cell (PEMFC), operating at low temperature uses a simple chemical process to combine hydrogen and oxygen into water, producing electric current and heat during the electrochemical reaction. This work concern on the theoretical consideration of the mass balance has been evaluated to predict the mass flow rate of the both gases (hydrogen/oxygen), the water mass balance, and the heat transfer in order to design a single cell PEMFC stack with a better flow field distributor on the performance of Polymer Electrolyte membrane fuel cells

Covalently cross-linked polyetheretherketone proton exchange membrane for DMFC

CSIR Research Space (South Africa)

Luo, H

2009-05-01

Full Text Available -7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application....

Correlation of the antimicrobial activity of salicylaldehydes with broadening of the NMR signal of the hydroxyl proton. Possible involvement of proton exchange processes in the antimicrobial activity.

Science.gov (United States)

Elo, Hannu; Kuure, Matti; Pelttari, Eila

2015-03-06

Certain substituted salicylaldehydes are potent antibacterial and antifungal agents and some of them merit consideration as potential chemotherapeutic agents against Candida infections, but their mechanism of action has remained obscure. We report here a distinct correlation between broadening of the NMR signal of the hydroxyl proton of salicylaldehydes and their activity against several types of bacteria and fungi. When proton NMR spectra of the compounds were determined using hexadeuterodimethylsulfoxide as solvent and the height of the OH proton signal was measured, using the signal of the aldehyde proton as an internal standard, it was discovered that a prerequisite of potent antimicrobial activity is that the proton signal is either unobservable or relatively very low, i.e. that it is extremely broadened. Thus, none of the congeners whose OH proton signal was high were potent antimicrobial agents. Some congeners that gave a very low OH signal were, however, essentially inactive against the microbes, indicating that although drastic broadening of the OH signal appears to be a prerequisite, also other (so far unknown) factors are needed for high antimicrobial activity. Because broadening of the hydroxyl proton signal is related to the speed of the proton exchange process(es) involving that proton, proton exchange may be involved in the mechanism of action of the compounds. Further studies are needed to analyze the relative importance of different factors (such as electronic effects, strength of the internal hydrogen bond, co-planarity of the ring and the formyl group) that determine the rates of those processes. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

RADIATION STABILITY OF NAFION MEMBRANES USED FOR ISOTOPE SEPARATION BY PROTON EXCHANGE MEMBRANE ELECTROLYSIS

International Nuclear Information System (INIS)

Fox, E.

2009-01-01

Proton Exchange Membrane Electrolyzers have potential interest for use for hydrogen isotope separation from water. In order for PEME to be fully utilized, more information is needed on the stability of Nafion when exposed to radiation. This work examines Nafion 117 under varying exposure conditions, including dose rate, total dosage and atmospheric condition. Analytical tools, such as FT-IR, ion exchange capacity, DMA and TIC-TOC were used to characterize the exposed membranes. Analysis of the water from saturated membranes can provide important data on the stability of the membranes during radiation exposure. It was found that the dose rate of exposure plays an important role in membrane degradation. Potential mechanisms for membrane degradation include peroxide formation by free radicals

RADIATION STABILITY OF NAFION MEMBRANES USED FOR ISOTOPE SEPARATION BY PROTON EXCHANGE MEMBRANE ELECTROLYSIS

Energy Technology Data Exchange (ETDEWEB)

Fox, E

2009-05-15

Proton Exchange Membrane Electrolyzers have potential interest for use for hydrogen isotope separation from water. In order for PEME to be fully utilized, more information is needed on the stability of Nafion when exposed to radiation. This work examines Nafion 117 under varying exposure conditions, including dose rate, total dosage and atmospheric condition. Analytical tools, such as FT-IR, ion exchange capacity, DMA and TIC-TOC were used to characterize the exposed membranes. Analysis of the water from saturated membranes can provide important data on the stability of the membranes during radiation exposure. It was found that the dose rate of exposure plays an important role in membrane degradation. Potential mechanisms for membrane degradation include peroxide formation by free radicals.

Internal humidifying of PEM [Proton Exchange Membrane] fuel cells

Energy Technology Data Exchange (ETDEWEB)

Staschewski, D [Karlsruhe Research Center (FZK), Karlsruhe (Germany). Inst. for Neutron Physics and Reactor Technics

1996-12-01

Hydrogen fuel cells (FC) for vehicular traction should stand out for a car-specific lightweight design. As regards PEMFC systems containing proton exchange membranes, this quality can be considerably improved by introducing porous bipolar plates which are conditioned by a water loop and deliver hot humidifying water to the adjacent membrane-electrode assembly (MEA). According to the principle of internal humidification here indicated special fuel cells based on sintered fiber and powder graphite were manufactured at FZK on a semi-technical scale. Self-made Pt/C electrodes hotpressed onto Nafion resulted in currents up to 200 A with pure oxygen as oxidant, providing the precondition for detailed studies of turnover and drainage rates within a monocell test arrangement. (author)

A new ion exchange behavior of protonated titanate nanotubes after deprotonation and the study on their morphology and optical properties

International Nuclear Information System (INIS)

Zhang Huibin; Cao Lixin; Liu Wei; Su Ge

2012-01-01

Graphical abstract: The morphological transformation of protonated titanate nanotubes under alkali solution before ion exchange (a) and after ion exchange (b). Highlights: ► A novel ion exchange behavior of protonated titanate nanotubes after deprotonation. ► The exchangeability of protonated titanate nanotubes are not as inert as past reported. ► The tube walls of H 2 Ti 3 O 7 nanotubes is observed to get loosened after ion exchange. ► The paper proves a new and easy way to modify protonated titanate nanotubes. - Abstract: After the deprotonation of protonated titanate nanotubes (H 2 Ti 3 O 7 ), we observed a novel ion exchange behavior on them. In the past literatures, protonated titanate nanotubes prepared via hydrothermal method have been reported with a poor exchangeability which may due to the chemical bonding of interlayer protons to nearby oxygen atoms. However, in this experiment under alkali environment (pH > 10), protonated titanate nanotubes exhibited a vast ion exchange capacity toward [Co(NH 3 ) 6 ] 2+ . This interesting phenomenon is contrary to the past reports which found protonated titanate nanotubes hardly could be ionexchanged by objective cations. This paper proves the deprotonation process on H 2 Ti 3 O 7 nanotubes sufficiently facilitates the diffusion of metal complex cations into protonated titanate nanotubes and significantly changes their ion exchange capacity. As a consequence of cabalt intercalting via ion exchange, the tube wall of H 2 Ti 3 O 7 nanotubes is observed to get loosened. Additionally, the exciton concentrations corresponding to the nanotube surface states are discussed in the paper.

Correlation between morphology, water uptake, and proton conductivity in radiation-grafted proton-exchange membranes

DEFF Research Database (Denmark)

Balog, Sandor; Gasser, Urs; Mortensen, Kell

2010-01-01

An SANS investigation of hydrated proton exchange membranes is presented. Our membranes were synthesized by radiation-induced grafting of ETFE with styrene in the presence of a crosslinker, followed by sulfonation of the styrene. The contrast variation method was used to understand the relationship...

Stimulated-healing of proton exchange membrane fuel cell catalyst

NARCIS (Netherlands)

Latsuzbaia, R.; Negro, E.; Koper, G.J.M.

2013-01-01

Platinum nanoparticles, which are used as catalysts in Proton Exchange Membrane Fuel Cells (PEMFC), tend to degrade after long-term operation. We discriminate the following mechanisms of the degradation: poisoning, migration and coalescence, dissolution, and electrochemical Ostwald ripening. There

An artificial neural network ensemble method for fault diagnosis of proton exchange membrane fuel cell system

International Nuclear Information System (INIS)

Shao, Meng; Zhu, Xin-Jian; Cao, Hong-Fei; Shen, Hai-Feng

2014-01-01

The commercial viability of PEMFC (proton exchange membrane fuel cell) systems depends on using effective fault diagnosis technologies in PEMFC systems. However, many researchers have experimentally studied PEMFC (proton exchange membrane fuel cell) systems without considering certain fault conditions. In this paper, an ANN (artificial neural network) ensemble method is presented that improves the stability and reliability of the PEMFC systems. In the first part, a transient model giving it flexibility in application to some exceptional conditions is built. The PEMFC dynamic model is built and simulated using MATLAB. In the second, using this model and experiments, the mechanisms of four different faults in PEMFC systems are analyzed in detail. Third, the ANN ensemble for the fault diagnosis is built and modeled. This model is trained and tested by the data. The test result shows that, compared with the previous method for fault diagnosis of PEMFC systems, the proposed fault diagnosis method has higher diagnostic rate and generalization ability. Moreover, the partial structure of this method can be altered easily, along with the change of the PEMFC systems. In general, this method for diagnosis of PEMFC has value for certain applications. - Highlights: • We analyze the principles and mechanisms of the four faults in PEMFC (proton exchange membrane fuel cell) system. • We design and model an ANN (artificial neural network) ensemble method for the fault diagnosis of PEMFC system. • This method has high diagnostic rate and strong generalization ability

Preparations of an inorganic-framework proton exchange nanochannel membrane

Science.gov (United States)

Yan, X. H.; Jiang, H. R.; Zhao, G.; Zeng, L.; Zhao, T. S.

2016-09-01

In this work, a proton exchange membrane composed of straight and aligned proton conducting nanochannels is developed. Preparation of the membrane involves the surface sol-gel method assisted with a through-hole anodic aluminum oxide (AAO) template to form the framework of the PEM nanochannels. A monomolecular layer (SO3Hsbnd (CH2)3sbnd Sisbnd (OCH3)3) is subsequently added onto the inner surfaces of the nanochannels to shape a proton-conducting pathway. Straight nanochannels exhibit long range order morphology, contributing to a substantial improvement in the proton mobility and subsequently proton conductivity. In addition, the nanochannel size can be altered by changing the surface sol-gel condition, allowing control of the active species/charge carrier selectivity via pore size exclusion. The proton conductivity of the nanochannel membrane is reported as high as 11.3 mS cm-1 at 70 °C with a low activation energy of 0.21 eV (20.4 kJ mol-1). First-principle calculations reveal that the activation energy for proton transfer is impressively low (0.06 eV and 0.07 eV) with the assistance of water molecules.

Two-dimensional analytical model of a proton exchange membrane fuel cell

International Nuclear Information System (INIS)

Liu, Jia Xing; Guo, Hang; Ye, Fang; Ma, Chong Fang

2017-01-01

In this study, a two-dimensional full cell analytical model of a proton exchange membrane fuel cell is developed. The analytical model describes electrochemical reactions on the anode and cathode catalyst layer, reactants diffusion in the gas diffusion layer, and gases flow in the gas channel, etc. The analytical solution is derived according to the basic physical equations. The performance predicted by the model is in good agreement with the experimental data. The results show that the polarization mainly occurs in the cathode side of the proton exchange membrane fuel cell. The anodic overpotential cannot be neglected. The hydrogen and oxygen concentrations decrease along the channel flow direction. The hydrogen and oxygen concentrations in the catalyst layer decrease with the current density. As predicted by the model, concentration polarization mainly occurs in the cathode side. - Highlights: • A 2D full cell analytical model of a proton exchange membrane fuel cell is developed. • The analytical solution is deduced according to the basic equations. • The anode overpotential is not so small that it cannot be neglected. • Species concentration distributions in the fuel cell is obtained and analyzed.

Transfer Rate Edited experiment for the selective detection of Chemical Exchange via Saturation Transfer (TRE-CEST).

Science.gov (United States)

Friedman, Joshua I; Xia, Ding; Regatte, Ravinder R; Jerschow, Alexej

2015-07-01

Chemical Exchange Saturation Transfer (CEST) magnetic resonance experiments have become valuable tools in magnetic resonance for the detection of low concentration solutes with far greater sensitivity than direct detection methods. Accurate measures of rates of chemical exchange provided by CEST are of particular interest to biomedical imaging communities where variations in chemical exchange can be related to subtle variations in biomarker concentration, temperature and pH within tissues using MRI. Despite their name, however, traditional CEST methods are not truly selective for chemical exchange and instead detect all forms of magnetization transfer including through-space NOE. This ambiguity crowds CEST spectra and greatly complicates subsequent data analysis. We have developed a Transfer Rate Edited CEST experiment (TRE-CEST) that uses two different types of solute labeling in order to selectively amplify signals of rapidly exchanging proton species while simultaneously suppressing 'slower' NOE-dominated magnetization transfer processes. This approach is demonstrated in the context of both NMR and MRI, where it is used to detect the labile amide protons of proteins undergoing chemical exchange (at rates⩾30s(-1)) while simultaneously eliminating signals originating from slower (∼5s(-1)) NOE-mediated magnetization transfer processes. TRE-CEST greatly expands the utility of CEST experiments in complex systems, and in-vivo, in particular, where it is expected to improve the quantification of chemical exchange and magnetization transfer rates while enabling new forms of imaging contrast. Copyright © 2015 Elsevier Inc. All rights reserved.

Exchange rate rebounds after foreign exchange market interventions

Science.gov (United States)

Hoshikawa, Takeshi

2017-03-01

This study examined the rebounds in the exchange rate after foreign exchange intervention. When intervention is strongly effective, the exchange rate rebounds at next day. The effect of intervention is reduced slightly by the rebound after the intervention. The exchange rate might have been 67.12-77.47 yen to a US dollar without yen-selling/dollar-purchasing intervention of 74,691,100 million yen implemented by the Japanese government since 1991, in comparison to the actual exchange rate was 103.19 yen to the US dollar at the end of March 2014.

The role of charge-exchange cross-section for pickup protons and neutrals in the inner heliosheath

Science.gov (United States)

Chalov, S. V.

2018-06-01

The process of deceleration of the solar wind downstream of the termination shock is studied on the basis of a one-dimensional multi-component model. It is assumed that the solar wind consists of thermal protons, electrons and interstellar pickup protons. The protons interact with interstellar hydrogen atoms by charge-exchange. Two cases are considered. In the first one, the charge-exchange cross-section for thermal protons and hydrogen atoms is the same as for pickup protons and atoms. Under this condition, there is a strong dependence of the solar wind velocity on the downstream temperature of pickup protons. When the proton temperature is close to 10 keV, the change in the velocity with the distance from the termination shock is similar to that measured on the Voyager 1 spacecraft: linear velocity decrease is accompanied by an extended transition region with near-zero velocity. However, with a more careful approach to the choice of the charge-exchange cross-section, the situation changes dramatically. The strong dependence of the solar wind speed on the pickup proton temperature disappears and the transition region in the heliosheath disappears as well, at least at reasonable distances from the TS.

Proton Conductivity of Proton Exchange Membrane Synergistically Promoted by Different Functionalized Metal-Organic Frameworks.

Science.gov (United States)

Rao, Zhuang; Tang, Beibei; Wu, Peiyi

2017-07-12

In this study, two functionalized metal-organic frameworks (MOFs), UiO-66-SO 3 H and UiO-66-NH 2 , were synthesized. Then, different composite proton exchange membranes (PEMs) were prepared by single doping and codoping of these two MOFs, respectively. It was found that codoping of these two MOFs with suitable sizes was more conducive to the proton conductivity enhancement of the composite PEM. A synergistic effect between these two MOFs led to the the formation of more consecutive hydration channels in the composite PEM. It further greatly promoted the proton conductivity of the composite PEM. The proton conductivity of the codoped PEM reached up to 0.256 S/cm under 90 °C, 95% RH, which was ∼1.17 times higher than that of the recast Nafion (0.118 S/cm). Besides, the methanol permeability of the codoped PEM was prominently decreased owing to the methanol trapping effect of the pores of these two MOFs. Meanwhile, the high water and thermal stabilities of these two MOFs were beneficial to the high proton conductivity stability of the codoped PEM under high humidity and high temperature. The proton conductivity of the codoped PEM was almost unchanged throughout 3000 min of testing under 90 °C, 95% RH. This work provides a valuable reference for designing different functionalized MOFs to synergistically promote the proton conductivities of PEMs.

Bretton Woods Fixed Exchange Rate System versus Floating Exchange Rate System

OpenAIRE

Geza, Paula; Giurca Vasilescu, Laura

2011-01-01

One of the most important issues of monetary policy is to find out whether the state should intervene among the exchange rates, taking into account the fact that changes in the exchange rates represent a significant transmission channel of the effects generated by the monetary policy. Taking into consideration the failure of fixed exchange rate regimes and the recent improvement of financial markets, the return in the near future to such a regime – as for example the Bretton Woods system –...

Automated exchange transfusion and exchange rate.

Science.gov (United States)

Funato, M; Shimada, S; Tamai, H; Taki, H; Yoshioka, Y

1989-10-01

An automated blood exchange transfusion (BET) with a two-site technique has been devised by Goldmann et al and by us, using an infusion pump. With this method, we successfully performed exchange transfusions 189 times in the past four years on 110 infants with birth weights ranging from 530 g to 4,000 g. The exchange rate by the automated method was compared with the rate by Diamond's method. Serum bilirubin (SB) levels before and after BET and the maximal SB rebound within 24 hours after BET were: 21.6 +/- 2.4, 11.5 +/- 2.2, and 15.0 +/- 1.5 mg/dl in the automated method, and 22.0 +/- 2.9, 11.2 +/- 2.5, and 17.7 +/- 3.2 mg/dl in Diamond's method, respectively. The result showed that the maximal rebound of the SB level within 24 hours after BET was significantly lower in the automated method than in Diamond's method (p less than 0.01), though SB levels before and after BET were not significantly different between the two methods. The exchange rate was also measured by means of staining the fetal red cells (F cells) both in the automated method and in Diamond's method, and comparing them. The exchange rate of F cells in Diamond's method went down along the theoretical exchange curve proposed by Diamond, while the rate in the automated method was significantly better than in Diamond's, especially in the early stage of BET (p less than 0.01). We believe that the use of this automated method may give better results than Diamond's method in the rate of exchange, because this method is performed with a two-site technique using a peripheral artery and vein.

On the importance of exchangeable NH protons in creatine for the magnetic coupling of creatine methyl protons in skeletal muscle

NARCIS (Netherlands)

Kruiskamp, M.J.; Nicolaij, K.

2001-01-01

The methyl protons of creatine in skeletal muscle exhibit a strong off-resonance magnetization transfer effect. The mechanism of this process is unknown. We previously hypothesized that the exchangeable amide/amino protons of creatine might be involved. To test this the characteristics of the

Resonance charge exchange between excited states in slow proton-hydrogen collisions

International Nuclear Information System (INIS)

Tolstikhina, Inga Yu.; Kato, Daiji

2010-01-01

The theory of resonance charge exchange in slow collisions of a proton with a hydrogen atom in the excited state is developed. It extends the Firsov-Demkov theory of resonance charge exchange to the case of degenerate initial and final states. The theory is illustrated by semiclassical and quantum calculations of charge exchange cross sections between states with n=2 in parabolic and spherical coordinates. The results are compared with existing close-coupling calculations.

Is a more stable exchange rate associated with reduced exchange rate pass-through?

OpenAIRE

Mark J. Holmes

2007-01-01

Pass-through from the nominal effective exchange rate to import prices is modelled within a regime-switching environment. Evidence suggests that exchange rate pass through can be characterised as regime-specific where the probability of switching between regimes is influenced by the extent of exchange rate volatility.

Proton exchange membrane fuel cells modeling

CERN Document Server

Gao, Fengge; Miraoui, Abdellatif

2013-01-01

The fuel cell is a potential candidate for energy storage and conversion in our future energy mix. It is able to directly convert the chemical energy stored in fuel (e.g. hydrogen) into electricity, without undergoing different intermediary conversion steps. In the field of mobile and stationary applications, it is considered to be one of the future energy solutions.Among the different fuel cell types, the proton exchange membrane (PEM) fuel cell has shown great potential in mobile applications, due to its low operating temperature, solid-state electrolyte and compactness.This book pre

Hydrogen/deuterium exchange of multiply-protonated cytochrome c ions

International Nuclear Information System (INIS)

Wood, T.D.; Guan, Ziqiang; O'Connor, P.B.

1995-01-01

Low resolution measurements show gaseous multiply-protonated cytochrome c ions undergo hydrogen/deuterium (H/D) exchange with pseudo first-order kinetics at three distinct exchange levels, suggesting the co-existence of gaseous protein conformations. Although exchange levels first increase with increasing charge values, they decrease at the highest charge values, consistent with solution-phase behavior of cytochrome c, where the native structure unfolds with decreasing pH until folding into a compact A-state at lowest pH. High resolution measurements indicate the presence of at least six H/D exchange levels. Infrared (IR) laser heating and fast collisions via quadrupolar excitation (QE) increase H/D exchange levels (unfolding) while charge-stripping ions to lower charge values can increase or decrease H/D exchange levels (unfolding or folding). Wolynes has suggested studying proteins in vacuo could play an important role in delineating the contributions various forces play in the protein folding process, provided appropriate comparisons can be made between gas-phase and solution-phase structures

Exchange-Mediated Contrast in CEST and Spin-Lock Imaging

Science.gov (United States)

Cobb, Jared Guthrie; Li, Ke; Xie, Jingping; Gochberg, Daniel F.; Gore, John C.

2014-01-01

PURPOSE Magnetic resonance images of biological media based on chemical exchange saturation transfer (CEST) show contrast that depends on chemical exchange between water and other protons. In addition, spin-lattice relaxation rates in the rotating frame (R1ρ) are also affected by exchange, especially at high fields, and can be exploited to provide novel, exchange-dependent contrast. Here, we evaluate and compare the factors that modulate the exchange contrast for these methods using simulations and experiments on simple, biologically relevant samples. METHODS Simulations and experimental measurements at 9.4T of rotating frame relaxation rate dispersion and CEST contrast were performed on solutions of macromolecules containing amide and hydroxyl exchanging protons. RESULTS The simulations and experimental measurements confirm that both CEST and R1ρ measurements depend on similar exchange parameters, but they manifest themselves differently in their effects on contrast. CEST contrast may be larger in the slow and intermediate exchange regimes for protons with large resonant frequency offsets (e.g. > 2ppm). Spin-locking techniques can produce larger contrast enhancement when resonant frequency offsets are small (exchange is in the intermediate to fast regime. The image contrasts scale differently with field strength, exchange rate and concentration. CONCLUSION CEST and R1ρ measurements provide different and somewhat complementary information about exchange in tissues. Whereas CEST can depict exchange of protons with specific chemical shifts, appropriate R1ρ dependent acquisitions can be employed to selectively portray protons of specific exchange rates. PMID:24239335

Exchange-mediated contrast in CEST and spin-lock imaging.

Science.gov (United States)

Cobb, Jared Guthrie; Li, Ke; Xie, Jingping; Gochberg, Daniel F; Gore, John C

2014-01-01

Magnetic resonance images of biological media based on chemical exchange saturation transfer (CEST) show contrast that depends on chemical exchange between water and other protons. In addition, spin-lattice relaxation rates in the rotating frame (R1ρ) are also affected by exchange, especially at high fields, and can be exploited to provide novel, exchange-dependent contrast. Here, we evaluate and compare the factors that modulate the exchange contrast for these methods using simulations and experiments on simple, biologically relevant samples. Simulations and experimental measurements at 9.4 T of rotating frame relaxation rate dispersion and CEST contrast were performed on solutions of macromolecules containing amide and hydroxyl exchanging protons. The simulations and experimental measurements confirm that both CEST and R1ρ measurements depend on similar exchange parameters, but they manifest themselves differently in their effects on contrast. CEST contrast may be larger in the slow and intermediate exchange regimes for protons with large resonant frequency offsets (e.g. >2 ppm). Spin-locking techniques can produce larger contrast enhancement when resonant frequency offsets are small (exchange is in the intermediate-to-fast regime. The image contrasts scale differently with field strength, exchange rate and concentration. CEST and R1ρ measurements provide different and somewhat complementary information about exchange in tissues. Whereas CEST can depict exchange of protons with specific chemical shifts, appropriate R1ρ-dependent acquisitions can be employed to selectively portray protons of specific exchange rates. © 2013.

Thermo-economic analysis of proton exchange membrane fuel cell fuelled with methanol and methane

International Nuclear Information System (INIS)

Suleiman, B.; Abdulkareem, A.S.; Musa, U.; Mohammed, I.A.; Olutoye, M.A.; Abdullahi, Y.I.

2016-01-01

Highlights: • Modified proton exchange membrane fuel cell was reported. • Thermolib software was used for the simulation of PEM fuel cell configurations. • Optimal operating parameters at 50 kW output of each process were determined. • Thermo-economic analysis is the most efficient way of process selection. • Methane system configuration has been identified as the best preferred PEM fuel cell. - Abstract: Exergy and economic analysis is often used to find and identify the most efficient process configuration for proton exchange membrane fuel cell from the thermo-economic point of view. This work gives an explicit account of the synergetic effect of exergetic and economic analysis of proton exchange membrane fuel cell (PEMFC) using methanol and methane as fuel sources. This was carried out through computer simulation using Thermolib simulation toolbox. Data generated from the simulated model were subsequently used for the thermodynamic and economic analysis. Analysis of energy requirement for the two selected processes revealed that the methane fuelled system requires the lower amount of energy (4.578 kJ/s) in comparison to the methanol fuelled configuration which requires 180.719 J/s. Energy analysis of both configurations showed that the principle of energy conservation was satisfied while the result of the exergy analysis showed high exergetic efficiency around major equipment (heat exchangers, compressors and pumps) of methane fuelled configuration. Higher irreversibility rate were observed around the burner, stack, and steam reformer. These trends of exergetic efficiency and irreversibility rate were observed around equipment in the methanol fuelled system but with lower performance when compared with the methane fuelled process configuration. On the basis of overall exergetic efficiency and lost work, the methanol system was more efficient with lower irreversibility rate of 547.27 kJ/s and exergetic efficiency of 34.44% in comparison with the methane

Two-photon exchange corrections in elastic lepton-proton scattering

Energy Technology Data Exchange (ETDEWEB)

Tomalak, Oleksandr; Vanderhaeghen, Marc [Johannes Gutenberg Universitaet Mainz (Germany)

2015-07-01

The measured value of the proton charge radius from the Lamb shift of energy levels in muonic hydrogen is in strong contradiction, by 7-8 standard deviations, with the value obtained from electronic hydrogen spectroscopy and the value extracted from unpolarized electron-proton scattering data. The dominant unaccounted higher order contribution in scattering experiments corresponds to the two photon exchange (TPE) diagram. The elastic contribution to the TPE correction was studied with the fixed momentum transfer dispersion relations and compared to the hadronic model with off-shell photon-nucleon vertices. A dispersion relation formalism with one subtraction was proposed. Theoretical predictions of the TPE elastic contribution to the unpolarized elastic electron-proton scattering and polarization transfer observables in the low momentum transfer region were made. The TPE formalism was generalized to the case of massive leptons and the elastic contribution was evaluated for the kinematics of upcoming muon-proton scattering experiment (MUSE).

Predicting Ionization Rates from SEP and Solar Wind Proton Precipitation into the Martian Atmosphere

Science.gov (United States)

Jolitz, R.; Dong, C.; Lee, C. O.; Curry, S.; Lillis, R. J.; Brain, D.; Halekas, J. S.; Larson, D. E.; Bougher, S. W.; Jakosky, B. M.

2017-12-01

Precipitating energetic particles ionize planetary atmospheres and increase total electron content. At Mars, the solar wind and solar energetic particles (SEPs) can precipitate directly into the atmosphere because solar wind protons can charge exchange to become neutrals and pass through the magnetosheath, while SEPs are sufficiently energetic to cross the magnetosheath unchanged. In this study we will present predicted ionization rates and resulting electron densities produced by solar wind and SEP proton ionization during nominal solar activity and a CME shock front impact event on May 16 2016. We will use the Atmospheric Scattering of Protons and Energetic Neutrals (ASPEN) model to compare ionization by SEP and solar wind protons currently measured by the SWIA (Solar Wind Ion Analyzer) and SEP instruments aboard the MAVEN spacecraft. Results will help to quantify how the ionosphere responds to extreme solar events during solar minimum.

Double cross-linked polyetheretherketone proton exchange membrane for fuel cell

CSIR Research Space (South Africa)

Luo, H

2012-04-01

Full Text Available and separating the fuel from oxidant. A polyperfluorosulfonic acid ionomer Nafion? (developed by Dupont) is the mostly used proton exchange membrane in PEMFCs, because of its high proton conductivity and excellent chemical stability [3, 4]. However, the high...-Methyl-2-pyrrolidinone. After the solution was homogenized by stirring, the polymer solution was cast on a glass Petri dish. The solvent was then removed in a vacuum oven at 130 ?C. The membrane was peeled off from the Petri dish. Thereafter...

Arene-mercury complexes stabilized by gallium chloride: relative rates of H/D and arene exchange.

Science.gov (United States)

Branch, Catherine S; Barron, Andrew R

2002-11-27

We have previously proposed that the Hg(arene)(2)(GaCl(4))(2) catalyzed H/D exchange reaction of C(6)D(6) with arenes occurs via an electrophilic aromatic substitution reaction in which the coordinated arene protonates the C(6)D(6). To investigate this mechanism, the kinetics of the Hg(C(6)H(5)Me)(2)(GaCl(4))(2) catalyzed H/D exchange reaction of C(6)D(6) with naphthalene has been studied. Separate second-order rate constants were determined for the 1- and 2-positions on naphthalene; that is, the initial rate of H/D exchange = k(1i)[Hg][C-H(1)] + k(2i)[Hg][C-H(2)]. The ratio of k(1i)/k(2i) ranges from 11 to 2.5 over the temperature range studied, commensurate with the proposed electrophilic aromatic substitution reaction. Observation of the reactions over an extended time period shows that the rates change with time, until they again reach a new and constant second-order kinetics regime. The overall form of the rate equation is unchanged: final rate = k(1f)[Hg][C-H(1)] + k(2f)[Hg][C-H(2)]. This change in the H/D exchange is accompanied by ligand exchange between Hg(C(6)D(6))(2)(GaCl(4))(2) and naphthalene to give Hg(C(10)H(8))(2)(GaCl(4))(2,) that has been characterized by (13)C CPMAS NMR and UV-visible spectroscopy. The activation parameters for the ligand exchange may be determined and are indicative of a dissociative reaction and are consistent with our previously calculated bond dissociation for Hg(C(6)H(6))(2)(AlCl(4))(2). The initial Hg(arene)(2)(GaCl(4))(2) catalyzed reaction of naphthalene with C(6)D(6) involves the deuteration of naphthalene by coordinated C(6)D(6); however, as ligand exchange progresses, the pathway for H/D exchange changes to where the protonation of C(6)D(6) by coordinated naphthalene dominates. The site selectivity for the H/D exchange is initially due to the electrophilic aromatic substitution of naphthalene. As ligand exchange occurs, this selectivity is controlled by the activation of the naphthalene C-H bonds by mercury.

Choice of exchange rate regimes for African countries: Fixed or Flexible Exchange rate regimes?

OpenAIRE

Simwaka, Kisu

2010-01-01

The choice of an appropriate exchange rate regime has been a subject of ongoing debate in international economics. The majority of African countries are small open economies and thus where the choice of the exchange rate regime is an important policy issue. Aside from factors such as interest rates and inflation, the exchange rate is one of the most important determinants of a country’s relative level of economic health. For this reason, exchange rates are among the most watched analyzed and ...

An Investigation of Proton Conductivity of Vinyltriazole-Grafted PVDF Proton Exchange Membranes Prepared via Photoinduced Grafting

OpenAIRE

Sezgin, Sinan; Sinirlioglu, Deniz; Muftuoglu, Ali Ekrem; Bozkurt, Ayhan

2014-01-01

Proton exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for clean and efficient power generation in the twenty-first century. In this study, high performance of poly(vinylidene fluoride) (PVDF) and proton conductivity of poly(1-vinyl-1,2,4-triazole) (PVTri) were combined in a graft copolymer, PVDF-g-PVTri, by the polymerization of 1-vinyl-1,2,4-triazole on a PVDF based matrix under UV light in one step. The polymers were doped with triflic acid (TA) at differe...

Backbone dynamics of a model membrane protein: measurement of individual amide hydrogen-exchange rates in detergent-solubilized M13 coat protein using 13C NMR hydrogen/deuterium isotope shifts

International Nuclear Information System (INIS)

Henry, G.D.; Weiner, J.H.; Sykes, B.D.

1987-01-01

Hydrogen-exchange rates have been measured for individual assigned amide protons in M13 coat protein, a 50-residue integral membrane protein, using a 13 C nuclear magnetic resonance (NMR) equilibrium isotope shift technique. The locations of the more rapidly exchanging amides have been determined. In D 2 O solutions, a peptide carbonyl resonance undergoes a small upfield isotope shift (0.08-0.09 ppm) from its position in H 2 O solutions; in 1:1 H 2 O/D 2 O mixtures, the carbonyl line shape is determined by the exchange rate at the adjacent nitrogen atom. M13 coat protein was labeled biosynthetically with 13 C at the peptide carbonyls of alanine, glycine, phenylalanine, proline, and lysine, and the exchange rates of 12 assigned amide protons in the hydrophilic regions were measured as a function of pH by using the isotope shift method. This equilibrium technique is sensitive to the more rapidly exchanging protons which are difficult to measure by classical exchange-out experiments. In proteins, structural factors, notably H bonding, can decrease the exchange rate of an amide proton by many orders of magnitude from that observed in the freely exposed amides of model peptides such as poly(DL-alanine). With corrections for sequence-related inductive effects, the retardation of amide exchange in sodium dodecyl sulfate solubilized coat protein has been calculated with respect to poly(DL-alanine). The most rapidly exchanging protons, which are retarded very little or not at all, are shown to occur at the N- and C-termini of the molecule. A model of the detergent-solubilized coat protein is constructed from these H-exchange data which is consistent with circular dichroism and other NMR results

An Empirical Investigation into Exchange Rate Regime Choice and Exchange Rate Volatility

OpenAIRE

Helge Berger; Jan-Egbert Sturm; Jakob de Haan

2000-01-01

We test a simple model of exchange rate regime choice with data for 65 non-OECD countries covering the period 1980-94. We find that the variance of output at home and in potential target c ountries as well as the correlation between home and foreign real activity are powerful and robust predictors of exchange rate regime choice. Surprisingly, a more volatile foreign economy can be an argument in favor of a fixed exchange rate regime once similarities in the business cycle are taken into accou...

Advanced proton-exchange materials for energy efficient fuel cells.

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, Cy H.; Grest, Gary Stephen; Hickner, Michael A.; Cornelius, Christopher James; Staiger, Chad Lynn; Hibbs, Michael R.

2005-12-01

The ''Advanced Proton-Exchange Materials for Energy Efficient Fuel Cells'' Laboratory Directed Research and Development (LDRD) project began in October 2002 and ended in September 2005. This LDRD was funded by the Energy Efficiency and Renewable Energy strategic business unit. The purpose of this LDRD was to initiate the fundamental research necessary for the development of a novel proton-exchange membranes (PEM) to overcome the material and performance limitations of the ''state of the art'' Nafion that is used in both hydrogen and methanol fuel cells. An atomistic modeling effort was added to this LDRD in order to establish a frame work between predicted morphology and observed PEM morphology in order to relate it to fuel cell performance. Significant progress was made in the area of PEM material design, development, and demonstration during this LDRD. A fundamental understanding involving the role of the structure of the PEM material as a function of sulfonic acid content, polymer topology, chemical composition, molecular weight, and electrode electrolyte ink development was demonstrated during this LDRD. PEM materials based upon random and block polyimides, polybenzimidazoles, and polyphenylenes were created and evaluated for improvements in proton conductivity, reduced swelling, reduced O{sub 2} and H{sub 2} permeability, and increased thermal stability. Results from this work reveal that the family of polyphenylenes potentially solves several technical challenges associated with obtaining a high temperature PEM membrane. Fuel cell relevant properties such as high proton conductivity (>120 mS/cm), good thermal stability, and mechanical robustness were demonstrated during this LDRD. This report summarizes the technical accomplishments and results of this LDRD.

Reversible Heterolytic Cleavage of the H-H Bond by Molybdenum Complexes: Controlling the Dynamics of Exchange Between Proton and Hydride

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shaoguang; Appel, Aaron M.; Bullock, R. Morris

2017-05-18

Controlling the heterolytic cleavage of the H-H bond of dihydrogen is critically important in catalytic hydrogenations and in the catalytic oxidation of H2. We show how the rate of reversible heterolytic cleavage of H2 can be controlled over nearly four orders of magnitude at 25 °C, from 2.1 × 103 s-1 to ≥107 s-1. Bifunctional Mo complexes, [CpMo(CO)(κ3-P2N2)]+ (P2N2 = 1,5-diaza-3,7-diphosphacyclooctane with alkyl/aryl groups on N and P), have been developed for heterolytic cleavage of H2 into a proton and a hydride, akin to Frustrated Lewis Pairs. The H-H bond cleavage is enabled by the basic amine in the second coordination sphere. The products of heterolytic cleavage of H2, Mo hydride complexes bearing protonated amines, [CpMo(H)(CO)(P2N2H)]+, were characterized by spectroscopic studies and by X-ray crystallography. Variable temperature 1H, 15N and 2-D 1H-1H ROESY NMR spectra indicated rapid exchange of the proton and hydride. The exchange rates are in the order [CpMo(H)(CO)(PPh2NPh2H)]+ > [CpMo(H)(CO)(PtBu2NPh2H)]+ > [CpMo(H)(CO)(PPh2NBn2H)]+ > [CpMo(H)(CO)(PtBu2NBn2H)]+ > [CpMo(H)(CO)(PtBu2NtBu2H)]+. The pKa values determined in acetonitrile range from 9.3 to 17.7, and show a linear correlation with the logarithm of the exchange rates. Thus the exchange dynamics are controlled through the relative acidity of the [CpMo(H)(CO)(P2N2H)]+ and [CpMo(H2)(CO)(P2N2)]+ isomers, providing a design principle for controlling heterolytic cleavage of H2.

CAPSTONE SENIOR DESIGN - SUPRAMOLECULAR PROTON EXCHANGE MEMBRANES FOR FUEL CELLS

Science.gov (United States)

In order to assume a leading role in the burgeoning hydrogen economy, new infrastructure will be required for fuel cell manufacturing and R&D capabilities. The objective of this proposal is the development of a new generation of advanced proton exchange membrane (PEM) technol...

Cooperation between bound waters and hydroxyls in controlling isotope-exchange rates

Science.gov (United States)

Panasci, Adele F.; McAlpin, J. Gregory; Ohlin, C. André; Christensen, Shauna; Fettinger, James C.; Britt, R. David; Rustad, James R.; Casey, William H.

2012-02-01

Mineral oxides differ from aqueous ions in that the bound water molecules are usually attached to different metal centers, or vicinal, and thus separated from one another. In contrast, for most monomeric ions used to establish kinetic reactivity trends, such as octahedral aquo ions (e.g., Al(H 2O) 63+), the bound waters are closely packed, or geminal. Because of this structural difference, the existing literature about ligand substitution in monomer ions may be a poor guide to the reactions of geochemical interest. To understand how coordination of the reactive functional groups might affect the rates of simple water-exchange reactions, we synthesized two structurally similar Rh(III) complexes, [Rh(phen) 2(H 2O) 2] 3+ [ 1] and [Rh(phen) 2(H 2O)Cl] 2+ [ 2] where (phen) = 1,10-phenanthroline. Complex [ 1] has two adjacent, geminal, bound waters in the inner-coordination sphere and [ 2] has a single bound water adjacent to a bound chloride ion. We employed Rh(III) as a trivalent metal rather than a more geochemically relevant metal like Fe(III) or Al(III) to slow the rate of reaction, which makes possible measurement of the rates of isotopic substitution by simple mass spectrometry. We prepared isotopically pure versions of the molecules, dissolved them into isotopically dissimilar water, and measured the rates of exchange from the extents of 18O and 16O exchange at the bound waters. The pH dependency of rates differ enormously between the two complexes. Pseudo-first-order rate coefficients at 298 K for water exchanges from the fully protonated molecules are close: k0298 = 5 × 10 -8(±0.5 × 10 -8) s -1 for [ 1] and k0298 = 2.5 × 10 -9(±1 × 10 -9) for [ 2]. Enthalpy and entropy activation parameters (Δ H‡ and Δ S‡) were measured to be 119(±3) kJ mol -1, and 14(±1) J mol -1 K -1, respectively for [ 1]. The corresponding parameters for the mono-aquo complex, [ 2], are 132(±3) kJ mol -1 and 41.5(±2) J mol -1 K -1. Rates increase by many orders of magnitude

Hydrogen exchange rate of tyrosine hydroxyl groups in proteins as studied by the deuterium isotope effect on C(zeta) chemical shifts.

Science.gov (United States)

Takeda, Mitsuhiro; Jee, Jungoo; Ono, Akira Mei; Terauchi, Tsutomu; Kainosho, Masatsune

2009-12-30

We describe a new NMR method for monitoring the individual hydrogen exchange rates of the hydroxyl groups of tyrosine (Tyr) residues in proteins. The method utilizes (2S,3R)-[beta(2),epsilon(1,2)-(2)H(3);0,alpha,beta,zeta-(13)C(4);(15)N]-Tyr, zeta-SAIL Tyr, to detect and assign the (13)C(zeta) signals of Tyr rings efficiently, either by indirect (1)H-detection through 7-8 Hz (1)H(delta)-(13)C(zeta) spin couplings or by direct (13)C(zeta) observation. A comparison of the (13)C(zeta) chemical shifts of three Tyr residues of an 18.2 kDa protein, EPPIb, dissolved in H(2)O and D(2)O, revealed that all three (13)C(zeta) signals in D(2)O appeared at approximately 0.13 ppm ( approximately 20 Hz at 150.9 MHz) higher than those in H(2)O. In a H(2)O/D(2)O (1:1) mixture, however, one of the three signals for (13)C(zeta) appeared as a single peak at the averaged chemical shifts, and the other two appeared as double peaks at exactly the same chemical shifts in H(2)O and D(2)O, in 50 mM phosphate buffer (pH 6.6) at 40 degrees C. These three peaks were assigned to Tyr-36, Tyr-120, and Tyr-30, from the lower to higher chemical shifts, respectively. The results indicate that the hydroxyl proton of Tyr-120 exchanges faster than a few milliseconds, whereas those of Tyr-30 and Tyr-36 exchange more slowly. The exchange rate of the Tyr-30 hydroxyl proton, k(ex), under these conditions was determined by (13)C NMR exchange spectroscopy (EXSY) to be 9.2 +/- 1.1 s(-1). The Tyr-36 hydroxyl proton, however, exchanges too slowly to be determined by EXSY. These profound differences among the hydroxyl proton exchange rates are closely related to their relative solvent accessibility and the hydrogen bonds associated with the Tyr hydroxyl groups in proteins.

Exchange rate regulation, the behavior of exchange rates, and macroeconomic stability in Brazil

Directory of Open Access Journals (Sweden)

Francisco Eduardo Pires de Souza

2011-12-01

Full Text Available In the last two decades an entirely new set of rules governing the foreign exchange transactions was established in Brazil, substituting for the framework inherited from the 1930s. Foreign exchange controls were dismantled and a floating exchange rate regime replaced different forms of peg. In this paper we argue that although successful by comparison to previous experiences, the current arrangement has important flaws that should be addressed. We discuss how it first led to high volatility and extremely high interest rates, which, when overcome, gave way to a long lasting appreciation of the real exchange rate with adverse consequences to industry.

Effective Exchange Rate Classifications and Growth

OpenAIRE

Justin M. Dubas; Byung-Joo Lee; Nelson C. Mark

2005-01-01

We propose an econometric procedure for obtaining de facto exchange rate regime classifications which we apply to study the relationship between exchange rate regimes and economic growth. Our classification method models the de jure regimes as outcomes of a multinomial logit choice problem conditional on the volatility of a country's effective exchange rate, a bilateral exchange rate and international reserves. An `effective' de facto exchange rate regime classification is then obtained by as...

Hydrogen--deuterium exchanges in nucleosides and nucleotides. A mechanism for exchange of the exocyclic amino hydrogens of adenosine

International Nuclear Information System (INIS)

Cross, D.G.; Brown, A.; Fisher, H.F.

1975-01-01

The pH dependence of the apparent first-order rate constant for the exchange of the exocyclic amino hydrogens of adenosine with deuterium from the solvent was measured by stopped-flow ultraviolet spectroscopy. This dependence shows acid catalysis, base catalysis, and spontaneous exchange at neutral pH values. A study of the effect of several buffers on the rates of exchange reveals both general acid and general base catalytic behavior for the exchange process. We propose a general mechanism for the exchange which requires N-1 protonated adenosine as an intermediate for the acid-catalyzed exchange and amidine anion for the base-catalyzed exchange. In both cases the rate-limiting step is the base-catalyzed abstraction of a proton from the exocyclic amino moiety. Evaluation of the rate constants predicts the equilibrium for the exocyclic amino/imino tautomers to be 6.3 x 10 3 :1. (U.S.)

Exchange rate smoothing in Hungary

OpenAIRE

Karádi, Péter

2005-01-01

The paper proposes a structural empirical model capable of examining exchange rate smoothing in the small, open economy of Hungary. The framework assumes the existence of an unobserved and changing implicit exchange rate target. The central bank is assumed to use interest rate policy to obtain this preferred rate in the medium term, while market participants are assumed to form rational expectations about this target and influence exchange rates accordingly. The paper applies unobserved varia...

DeVelopment of the high-intensity polarized H- source with proton charge exchange on sodium optically oriented atoms

International Nuclear Information System (INIS)

Zelenskij, A.N.; Kokhanovskij, S.A.

1982-01-01

The results of experimental study on the source of polarized H - ions at polarized electron capture by proton from optically oriented sodium atoms are presented. Circular-polarized dye laser radiation with lamp pumping is used for polarization of highly dense sodium vapors in the pulsed mode. A facility for polarization measurement in the ion source is described. Dependence of the counting rate of metastables for the right and left circular radiation polarization in respect to wave length is presented. The results of measuring the degree of polarization under change of sodium density are revealed. The measurements have disclosed that obtaining of high polarization degree at 20-30% charge exchange effectiveness is possible but large radiation power is required. Use of a dense charge exchange target provides high effectiveness of hte whole polarization process. Yield of polarized H - ions can approach 10 μA/1 mA of the initial proton current

Application of Proton Exchange Membrane Fuel Cell for Lift Trucks

DEFF Research Database (Denmark)

Hosseinzadeh, Elham; Rokni, Masoud

2011-01-01

In this study a general PEMFC (Proton Exchange Membrane Fuel Cell) model has been developed to take into account the effect of pressure losses, water crossovers, humidity aspects and voltage over potentials in the cells. The model is zero dimensional and it is assumed to be steady state. The effect...

Model-based fault detection for proton exchange membrane fuel cell ...

African Journals Online (AJOL)

In this paper, an intelligent model-based fault detection (FD) is developed for proton exchange membrane fuel cell (PEMFC) dynamic systems using an independent radial basis function (RBF) networks. The novelty is that this RBF networks is used to model the PEMFC dynamic systems and residuals are generated based ...

New insights into proton surface mobility processes in PEMFC catalysts using isotopic exchange methods.

Science.gov (United States)

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.

Exchange Rate Policy in Philippine Development

OpenAIRE

Bautista, Romeo M.

2003-01-01

This paper examines the conduct of exchange rate policy in the Philippines since the early 1980s, paying particular attention to the influence of exchange rate adjustments on relative production incentives. While primary interest is in the exchange rate regime and its incentive effects, the role of trade policy has to be simultaneously analyzed in view of its influence on the conduct of exchange rate policy as well as its direct effect on the real exchange rate. Moreover, there are analytical...

15NH/D-SOLEXSY experiment for accurate measurement of amide solvent exchange rates: application to denatured drkN SH3

International Nuclear Information System (INIS)

Chevelkov, Veniamin; Xue, Yi; Krishna Rao, D.; Forman-Kay, Julie D.; Skrynnikov, Nikolai R.

2010-01-01

Amide solvent exchange rates are regarded as a valuable source of information on structure/dynamics of unfolded (disordered) proteins. Proton-based saturation transfer experiments, normally used to measure solvent exchange, are known to meet some serious difficulties. The problems mainly arise from the need to (1) manipulate water magnetization and (2) discriminate between multiple magnetization transfer pathways that occur within the proton pool. Some of these issues are specific to unfolded proteins. For example, the compensation scheme used to cancel the Overhauser effect in the popular CLEANEX experiment is not designed for use with unfolded proteins. In this report we describe an alternative experimental strategy, where amide 15 N is used as a probe of solvent exchange. The experiment is performed in 50% H 2 O-50% D 2 O solvent and is based on the (HACACO)NH pulse sequence. The resulting spectral map is fully equivalent to the conventional HSQC. To fulfill its purpose, the experiment monitors the conversion of deuterated species, 15 N D , into protonated species, 15 N H , as effected by the solvent exchange. Conceptually, this experiment is similar to EXSY which prompted the name of 15 N H/D -SOLEXSY (SOLvent EXchange SpectroscopY). Of note, our experimental scheme, which relies on nitrogen rather than proton to monitor solvent exchange, is free of the complications described above. The developed pulse sequence was used to measure solvent exchange rates in the chemically denatured state of the drkN SH3 domain. The results were found to correlate well with the CLEANEX-PM data, r = 0.97, thus providing a measure of validation for both techniques. When the experimentally measured exchange rates are converted into protection factors, most of the values fall in the range 0.5-2, consistent with random-coil behavior. However, elevated values, ca. 5, are obtained for residues R38 and A39, as well as the side-chain indole of W36. This is surprising, given that high

Effect of Nafion ionometer content on proton conductivity in the catalyst layer of proton exchange fuel cell

Energy Technology Data Exchange (ETDEWEB)

Ozalevlia, Cihan Cemil; Jian Xie; Xu, Fan [METU MS Mechanical Engineering (United States)], email: cihan.ozalevli@metu.edu.tr, email: jianxie@iupui.edu, email: fanxu@iupui.edu

2011-07-01

In the energy conversion sector, proton exchange fuel cells (PEFC's) are among the most promising technologies for the future. The Nafion ionometer is the most important part of the membrane electrode assembly (MEA) which is the core technology of the system. The Nafion ionometer is both a proton conductor and a binder for the catalyst layer in the technology. The aim of this study is to assess the effect of the Nafion content in the cathode catalyst layer on the proton conductivity of the MEA. Two MEAs with different Nafion content were prepared following the LANL process and the proton conductivity of the catalyst layer was measured. Results showed a much higher performance of the 28wt. % Nafion MEA than the 10wt. %. This study demonstrated that when the Nafion ionometer content decreases, the performance of the fuel cell decreases; further investigations should be undertaken with Nafion ionometer amounts of 15wt. % to 20wt. %.

Proton exchange membranes prepared by grafting of styrene/divinylbenzene into crosslinked PTFE membranes

International Nuclear Information System (INIS)

Li Jingye; Ichizuri, Shogo; Asano, Saneto; Mutou, Fumihiro; Ikeda, Shigetoshi; Iida, Minoru; Miura, Takaharu; Oshima, Akihiro; Tabata, Yoneho; Washio, Masakazu

2005-01-01

Thin PTFE membranes were prepared by coating the PTFE dispersion onto the aluminum films. Thus the thin crosslinked PTFE (RX-PTFE) membranes were obtained by means of electron beam irradiation above the melting temperature of PTFE under oxygen-free atmosphere. The RX-PTFE membranes were pre-irradiated and grafted by styrene with or without divinylbenzene (DVB) in liquid phase. The existence of DVB accelerated the initial grafting rate. The styrene grafted RX-PTFE membranes are white colored, on the other hand, the styrene/DVB grafted RX-PTFE membranes are colorless. The proton exchange membranes (PEMs) were obtained by sulfonating the grafted membranes using chlorosulfonic acid. The ion exchange capacity (IEC) values of the PEMs ranging from 1.5 to 2.8 meq/g were obtained. The PEMs made from the styrene/DVB grafted membranes showed higher chemical stability than those of the styrene grafted membranes under oxidative circumstance

High temperature proton exchange membranes prepared from epoxycyclohexylethyltrimethoxysilane and amino trimethylene phosphonic acid as anhydrous proton conductors

International Nuclear Information System (INIS)

Chen, Cheng; Shen, Chunhui; Kong, Gengjin; Gao, Shanjun

2013-01-01

High temperature anhydrous proton exchange membranes based on phosphonic acid were prepared from epoxycyclohexylethyltrimethoxysilane (EHTMS) and amino trimethylene phosphonic acid (ATMP) by sol–gel process. The structures and properties of membranes with different phosphonic acid content were extensively characterized by FTIR, TG-DSC and XRD. Their proton conductivity under dry condition was also investigated under different temperature. The results show that the proton conductivity of the prepared membranes strongly depends on temperature, and the proton conductivity ranges from 8.81 × 10 −5 S cm −1 at 20 °C to 4.65 × 10 −2 S cm −1 at 140 °C under anhydrous condition. It indicates that the increasing temperature is favorable for congregating of the grafted–PO 3 H 2 and increasing of the proton mobility. In addition, from the results of AFM images, it was confirmed that the continuous distribution of phosphonic acid groups is favorable for the formation of the proton transport channel, which can significantly enhance the proton conductivity of the membranes. Highlights: ► Hybrid membranes of Epoxycyclohexylethyltrimethoxysilane and Amino trimethylene phosphonic acid. ► The proton conductivity is 4.65 × 10 −2 S cm −1 at 140 °C under anhydrous condition. ► Continuous uniform distributions of phosphonic acid groups can be observed by AFM. ► There could be hydrogen bond network within high temperature membranes

High temperature proton exchange membranes prepared from epoxycyclohexylethyltrimethoxysilane and amino trimethylene phosphonic acid as anhydrous proton conductors

Energy Technology Data Exchange (ETDEWEB)

Chen, Cheng [Department of Polymer Materials and Engineering, School of Material Science and Engineering, Wuhan University of Technology, No. 122 Luoshi Road, Wuhan 430070 (China); Shen, Chunhui, E-mail: shenchunhui@whut.edu.cn [Department of Polymer Materials and Engineering, School of Material Science and Engineering, Wuhan University of Technology, No. 122 Luoshi Road, Wuhan 430070 (China); Kong, Gengjin; Gao, Shanjun [Department of Polymer Materials and Engineering, School of Material Science and Engineering, Wuhan University of Technology, No. 122 Luoshi Road, Wuhan 430070 (China)

2013-06-15

High temperature anhydrous proton exchange membranes based on phosphonic acid were prepared from epoxycyclohexylethyltrimethoxysilane (EHTMS) and amino trimethylene phosphonic acid (ATMP) by sol–gel process. The structures and properties of membranes with different phosphonic acid content were extensively characterized by FTIR, TG-DSC and XRD. Their proton conductivity under dry condition was also investigated under different temperature. The results show that the proton conductivity of the prepared membranes strongly depends on temperature, and the proton conductivity ranges from 8.81 × 10{sup −5} S cm{sup −1} at 20 °C to 4.65 × 10{sup −2} S cm{sup −1} at 140 °C under anhydrous condition. It indicates that the increasing temperature is favorable for congregating of the grafted–PO{sub 3}H{sub 2} and increasing of the proton mobility. In addition, from the results of AFM images, it was confirmed that the continuous distribution of phosphonic acid groups is favorable for the formation of the proton transport channel, which can significantly enhance the proton conductivity of the membranes. Highlights: ► Hybrid membranes of Epoxycyclohexylethyltrimethoxysilane and Amino trimethylene phosphonic acid. ► The proton conductivity is 4.65 × 10{sup −2} S cm{sup −1} at 140 °C under anhydrous condition. ► Continuous uniform distributions of phosphonic acid groups can be observed by AFM. ► There could be hydrogen bond network within high temperature membranes.

Power ramp rate capabilities of a 5 kW proton exchange membrane fuel cell system with discrete ejector control

Science.gov (United States)

Nikiforow, K.; Pennanen, J.; Ihonen, J.; Uski, S.; Koski, P.

2018-03-01

The power ramp rate capabilities of a 5 kW proton exchange membrane fuel cell (PEMFC) system are studied theoretically and experimentally for grid support service applications. The fuel supply is implemented with a fixed-geometry ejector and a discrete control solution without any anode-side pressure fluctuation suppression methods. We show that the stack power can be ramped up from 2.0 kW to 4.0 kW with adequate fuel supply and low anode pressure fluctuations within only 0.1 s. The air supply is implemented with a centrifugal blower. Air supply ramp rates are studied with a power increase executed within 1 and 0.2 s after the request, the time dictated by grid support service requirements in Finland and the UK. We show that a power ramp-up from 2.0 kW to 3.7 kW is achieved within 1 s with an initial air stoichiometry of 2.5 and within 0.2 s with an initial air stoichiometry of 7.0. We also show that the timing of the power ramp-up affects the achieved ancillary power capacity. This work demonstrates that hydrogen fueled and ejector-based PEMFC systems can provide a significant amount of power in less than 1 s and provide valuable ancillary power capacity for grid support services.

Chemical exchange rotation transfer imaging of intermediate-exchanging amines at 2 ppm.

Science.gov (United States)

Zu, Zhongliang; Louie, Elizabeth A; Lin, Eugene C; Jiang, Xiaoyu; Does, Mark D; Gore, John C; Gochberg, Daniel F

2017-10-01

Chemical exchange saturation transfer (CEST) imaging of amine protons exchanging at intermediate rates and whose chemical shift is around 2 ppm may provide a means of mapping creatine. However, the quantification of this effect may be compromised by the influence of overlapping CEST signals from fast-exchanging amines and hydroxyls. We aimed to investigate the exchange rate filtering effect of a variation of CEST, named chemical exchange rotation transfer (CERT), as a means of isolating creatine contributions at around 2 ppm from other overlapping signals. Simulations were performed to study the filtering effects of CERT for the selection of transfer effects from protons of specific exchange rates. Control samples containing the main metabolites in brain, bovine serum albumin (BSA) and egg white albumen (EWA) at their physiological concentrations and pH were used to study the ability of CERT to isolate molecules with amines at 2 ppm that exchange at intermediate rates, and corresponding methods were used for in vivo rat brain imaging. Simulations showed that exchange rate filtering can be combined with conventional filtering based on chemical shift. Studies on samples showed that signal contributions from creatine can be separated from those of other metabolites using this combined filter, but contributions from protein amines may still be significant. This exchange filtering can also be used for in vivo imaging. CERT provides more specific quantification of amines at 2 ppm that exchange at intermediate rates compared with conventional CEST imaging. Copyright © 2017 John Wiley & Sons, Ltd.

Modeling Of Proton Exchange Membrane Fuel Cell Systems

DEFF Research Database (Denmark)

Nielsen, Mads Pagh

The objective of this doctoral thesis was to develop reliable steady-state and transient component models suitable to asses-, develop- and optimize proton exchange membrane (PEM) fuel cell systems. Several components in PEM fuel cell systems were characterized and modeled. The developed component...... cell systems. Consequences of indirectly fueling PEM stacks with hydrocarbons using reforming technology were investigated using a PEM stack model including CO poisoning kinetics and a transient Simulink steam reforming system model. Aspects regarding the optimization of PEM fuel cell systems...

Can Exchange Rates Be Predicted?

OpenAIRE

Siriwutiset, Trin

2007-01-01

Foreign exchange rates produce significant impacts on both the macroeconomic and microeconomic scale. Countries� government and multinational companies have been seeking ways to stabilize the exchange rates for a few decades. However, there is no perfect consensus on methods to control and stabilize the exchange rates. In fact, there are several occasions in history where turbulence movements caused crisis in the economies. There are several factors that are identified by economis...

Exchange Rate Determinants in Russia; 1992-1993

OpenAIRE

Vincent Koen; Eric Meyermans

1994-01-01

This paper examines the evolution of the exchange rate of the ruble vis-à-vis the U.S. dollar from exchange rate unification, in July 1992, to the end of 1993. The expected and actual paths of the exchange rate are related to the exchange and trade regime and to the stance of financial and exchange rate policies. An econometric analysis based on weekly data is offered, which suggests that monetary factors have a significant impact on the short run behavior of the exchange rate.

Exchange Rate Pass-Through in Turkey

OpenAIRE

Marco Rossi; Daniel Leigh

2002-01-01

In light of the strong correlation between exchange rate movements and domestic prices in Turkey, it is important to assess the impact of the exchange rate on domestic prices, in particular as Turkey moves to an inflation targeting regime. This paper uses a recursive vector autoregression model to investigate the impact of exchange rate movements on prices in Turkey. We find that (i) the impact of the exchange rate on prices is over after about a year, but is mostly felt in the first four mon...

Tandem cathode for proton exchange membrane fuel cells

DEFF Research Database (Denmark)

Siahrostami, Samira; Björketun, Mårten E.; Strasser, Peter

2013-01-01

The efficiency of proton exchange membrane fuel cells is limited mainly by the oxygen reduction reaction at the cathode. The large cathodic overpotential is caused by correlations between binding energies of reaction intermediates in the reduction of oxygen to water. This work introduces a novel...... to identify potentially active and selective materials for both catalysts. Co-porphyrin is recommended for the first step, formation of hydrogen peroxide, and three different metal oxides – SrTiO3(100), CaTiO3(100) and WO3(100) – are suggested for the subsequent reduction step....

The foreign exchange rate rate exposure of nations

OpenAIRE

Entorf, Horst; Moebert, Jochen; Sonderhof, Katja

2007-01-01

Following the well-known approach by Adler and Dumas (1984) we evaluate the foreign exchange rate exposure of nations. Results based on data from 27 countries show that national foreign exchange rate exposures are significantly related to the current trade balance variables of corresponding economies.

Real exchange rate misalignments

OpenAIRE

Terra, Maria Cristina T.; Valladares, Frederico Estrella Carneiro

2003-01-01

This paper characterizes episodes of real appreciations and depreciations for a sample of 85 countries, approximately from 1960 to 1998. First, the equilibrium real exchange rate series are constructed for each country using Goldfajn and Valdes (1999) methodology (cointegration with fundamentals). Then, departures from equilibrium real exchange rate (misalignments) are obtained, and a Markov Switching Model is used to characterize the misalignments series as stochastic autor...

Molecular dynamics simulation of radiation grafted FEP films as proton exchange membranes: Effects of the side chain length

DEFF Research Database (Denmark)

Li, Xue; Zhao, Yang; Li, Weiwei

2017-01-01

In order to study the microstructure of the prepared potential proton exchange membrane (PEM), molecular dynamics (MD) simulations were used to lucubrate the transport behavior of water molecules and hydronium ions inside the hydrated sulfonated styrene grafted fluorinated ethylene propylene (FEP...... whereas larger water clusters formed. The results of the mean square displacements (MSDs) show that the proton conductivities of the membranes with the proposed side chain lengths were about three fifths of the experimental data, of which the membrane with side chain length of 7 sulfonic styrene units...... was supposed to exhibit the highest proton conductivity, that is 115.69 mS cm-1. All of the supposed membrane models presented good proton conductivity that could definitely meet the application requirements of the proton exchange membranes. The MD simulations can provide an insight to the chain structure...

Exchange-rate forecasts and asymmetric loss: empirical evidence for the yen/dollar exchange rate

DEFF Research Database (Denmark)

Stadtmann, Georg; Pierdzioch; Rülke

2012-01-01

We used the yen/dollar exchange-rate forecasts of the Wall Street Journal (WSJ) poll to analyse whether exchange-rate forecasters have an asymmetric loss function. To this end, we applied an approach recently developed by Elliott et al. (2005). We found that only few forecasters seem to form...

The determinants of exchange rate in Croatia

Directory of Open Access Journals (Sweden)

Manuel BENAZIC

2016-06-01

Full Text Available The dilemma for every country with an independent monetary policy is which kind of exchange rate arrangement should be applied. Through the exchange rate policy, countries can influence their economies, i.e. price stability and export competiveness. Croatia is a new EU member state, it has its own monetary policy and currency but it is on the way to euro introduction. Regarding the experiences from the beginning of the 1990s when Croatia was faced with serious monetary instabilities and hyperinflation, the goal of Croatian National Bank (CNB is to ensure price stability and one way to do so is through exchange rate policy. Croatia, as a small and open economy, has applied a managed floating exchange rate regime. The exchange rate is determined primarily by the foreign exchange supply and demand on the foreign exchange market, with occasional market interventions by the CNB. Therefore, in order to maintain exchange rate stability, policymakers must be able to recognize how changes in these factors affect changes in the exchange rate. This research aims to find a relationship among the main sources of foreign currency inflow and outflow and the level of exchange rate in Croatia. The analysis is carried out by using the bounds testing (ARDL approach for co-integration. The results indicate the existence of a stable co-integration relationship between the observed variables, whereby an increase in the majority of variables leads to an exchange rate appreciation.

Synthesis and Characterization of Sulfonated Graphene Oxide Reinforced Sulfonated Poly (Ether Ether Ketone (SPEEK Composites for Proton Exchange Membrane Materials

Directory of Open Access Journals (Sweden)

Ning Cao

2018-03-01

Full Text Available As a clean energy utilization device, full cell is gaining more and more attention. Proton exchange membrane (PEM is a key component of the full cell. The commercial-sulfonated, tetrafluoroethylene-based fluoropolymer-copolymer (Nafion membrane exhibits excellent proton conductivity under a fully humidified environment. However, it also has some disadvantages in practice, such as high fuel permeability, a complex synthesis process, and high cost. To overcome these disadvantages, a low-cost and novel membrane was developed. The sulfonated poly (ether ether ketone (SPEEK was selected as the base material of the proton exchange membrane. Sulfonated graphene (SG was cross-linked with SPEEK through the elimination reaction of hydrogen bonds. It was found that the sulfonic acid groups and hydrophilic oxygen groups increased obviously in the resultant membrane. Compared with the pure SPEEK membrane, the SG-reinforced membrane exhibited better proton conductivity and methanol permeability prevention. The results indicate that the SG/SPEEK could be applied as a new proton exchange membrane in fuel cells.

Rapid and quantitative chemical exchange saturation transfer (CEST) imaging with magnetic resonance fingerprinting (MRF).

Science.gov (United States)

Cohen, Ouri; Huang, Shuning; McMahon, Michael T; Rosen, Matthew S; Farrar, Christian T

2018-05-13

To develop a fast magnetic resonance fingerprinting (MRF) method for quantitative chemical exchange saturation transfer (CEST) imaging. We implemented a CEST-MRF method to quantify the chemical exchange rate and volume fraction of the N α -amine protons of L-arginine (L-Arg) phantoms and the amide and semi-solid exchangeable protons of in vivo rat brain tissue. L-Arg phantoms were made with different concentrations (25-100 mM) and pH (pH 4-6). The MRF acquisition schedule varied the saturation power randomly for 30 iterations (phantom: 0-6 μT; in vivo: 0-4 μT) with a total acquisition time of ≤2 min. The signal trajectories were pattern-matched to a large dictionary of signal trajectories simulated using the Bloch-McConnell equations for different combinations of exchange rate, exchangeable proton volume fraction, and water T 1 and T 2 relaxation times. The chemical exchange rates of the N α -amine protons of L-Arg were significantly (P exchange using saturation power method. Similarly, the L-Arg concentrations determined using MRF were significantly (P exchange rate was well fit (R 2  = 0.9186) by a base catalyzed exchange model. The amide proton exchange rate measured in rat brain cortex (34.8 ± 11.7 Hz) was in good agreement with that measured previously with the water exchange spectroscopy method (28.6 ± 7.4 Hz). The semi-solid proton volume fraction was elevated in white (12.2 ± 1.7%) compared to gray (8.1 ± 1.1%) matter brain regions in agreement with previous magnetization transfer studies. CEST-MRF provides a method for fast, quantitative CEST imaging. © 2018 International Society for Magnetic Resonance in Medicine.

A perturbative treatment of double gluon exchange in γ*-proton DIS

International Nuclear Information System (INIS)

Kharraziha, H.

2000-04-01

A new model for the exchange of two gluons between the virtual photon and the proton, in non-diffractive deeply inelastic electron-proton scattering, is developed and studied. This model relies on a perturbative calculation, previously applied to diffraction, and a general result from Regge theory. As a first application of the model, we study corrections to the momentum transfer to the quark-anti-quark pair, at the photon-vertex. We find a significant enhancement of the cross-section at ∝Q 2 momentum transfers, and large negative corrections for small momentum transfers. The implication of this result for jet-distributions measured at HERA, is discussed. (orig.)

Interest Rates and Exchange Rate Relationship in BRIC-T Countries

OpenAIRE

Selim KAYHAN; Tayfur BAYAT; Ahmet UGUR

2013-01-01

This study examines the dynamic relationships between the real exchange rate and the real interest rate in the BRIC-T (Brazil, Russia, India, China and Turkey) countries by employing monthly data from the beginning of flexible exchange rate regime to July 2011. For this aim, non-linear causality test and frequency domain causality test approaches are used. According to frequency domain causality test results, interest rate affects exchange rate in only China and this effect exist only in the ...

Annealed proton exchanged optical waveguides in lithium niobate differences between the X- and Z-cuts

CERN Document Server

Nekvindova, P; Cervena, J; Budnar, M; Razpet, A; Zorko, B; Pelicon, P; 10.1016/S0925-3467(01)00186-0

2002-01-01

Summarizes results and assessments of our systematic fabrication and characterization of proton exchanged (PE) and annealed proton exchanged (APE) waveguides in lithium niobate. This study focused on different behavior of crystallographically diverse X(1120) and Z (0001) substrate cuts during waveguide fabrication, and differences in characteristics of the resulting waveguides. Non-toxic adipic acid was used as a proton source, and the waveguides properties were defined by mode spectroscopy (waveguide characteristics) and neutron depth profiling (NDP, lithium concentration and distribution), infrared vibration spectra and elastic recoil detection analysis (ERDA, concentration and depth distribution of hydrogen). It was discovered that the X-cut structure is more permeable for moving particles (lithium and hydrogen ions), which leads to a higher effectiveness of the PE process within the X-cut. The explanation of this phenomenon is based on fitting X-cut orientation towards cleavage planes of lithium niobate c...

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

Science.gov (United States)

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.

Amide proton solvent protection in amylin fibrils probed by quenched hydrogen exchange NMR.

Directory of Open Access Journals (Sweden)

Andrei T Alexandrescu

Full Text Available Amylin is an endocrine hormone that accumulates in amyloid plaques in patients with advanced type 2 diabetes. The amyloid plaques have been implicated in the destruction of pancreatic β-cells, which synthesize amylin and insulin. To better characterize the secondary structure of amylin in amyloid fibrils we assigned the NMR spectrum of the unfolded state in 95% DMSO and used a quenched hydrogen-deuterium exchange technique to look at amide proton solvent protection in the fibrils. In this technique, partially exchanged fibrils are dissolved in 95% DMSO and information about amide proton occupancy in the fibrils is determined from DMSO-denatured monomers. Hydrogen exchange lifetimes at pH 7.6 and 37°C vary between ∼5 h for the unstructured N-terminus to 600 h for amide protons in the two β-strands that form inter-molecular hydrogen bonds between amylin monomers along the length of the fibril. Based on the protection data we conclude that residues A8-H18 and I26-Y37 comprise the two β-strands in amylin fibrils. There is variation in protection within the β-strands, particularly for strand β1 where only residues F15-H18 are strongly protected. Differences in protection appear to be due to restrictions on backbone dynamics imposed by the packing of two-layers of C2-symmetry-related β-hairpins in the protofilament structure, with strand β1 positioned on the surface and β2 in the interior.

Exchange rate regimes and monetary arrangements

Directory of Open Access Journals (Sweden)

Ivan Ribnikar

2005-06-01

Full Text Available There is a close relationship between a country’s exchange rate regime and monetary arrangement and if we are to examine monetary arrangements then exchange rate regimes must first be analysed. Within the conventional and most widely used classification of exchange rate regimes into rigid and flexible or into polar regimes (hard peg and float on one side, and intermediate regimes on the other there, is a much greater variety among intermediate regimes. A more precise and, as will be seen, more useful classification of exchange rate regimes is the first topic of the paper. The second topic is how exchange rate regimes influence or determine monetary arrangements and monetary policy or monetary policy regimes: monetary autonomy versus monetary nonautonomy and discretion in monetary policy versus commitment in monetary policy. Both topics are important for countries on their path to the EU and the euro area

Towards neat methanol operation of direct methanol fuel cells: a novel self-assembled proton exchange membrane.

Science.gov (United States)

Li, Jing; Cai, Weiwei; Ma, Liying; Zhang, Yunfeng; Chen, Zhangxian; Cheng, Hansong

2015-04-18

We report here a novel proton exchange membrane with remarkably high methanol-permeation resistivity and excellent proton conductivity enabled by carefully designed self-assembled ionic conductive channels. A direct methanol fuel cell utilizing the membrane performs well with a 20 M methanol solution, very close to the concentration of neat methanol.

The effects of real exchange rate misalignment and real exchange volatility on exports

OpenAIRE

Diallo, Ibrahima Amadou

2011-01-01

This paper uses panel data cointegration techniques to study the impacts of real exchange rate misalignment and real exchange rate volatility on total exports for a panel of 42 developing countries from 1975 to 2004. The results show that both real exchange rate misalignment and real exchange rate volatility affect negatively exports. The results also illustrate that real exchange rate volatility is more harmful to exports than misalignment. These outcomes are corroborated by estimations on s...

A Case for Intermediate Exchange-Rate Regimes

OpenAIRE

Agnès Bénassy-Quéré; Véronique Salins

2010-01-01

Despite increasing capital mobility and the subsequent difficulty in controlling exchange rates, intermediate exchange-rate regimes have remained widespread, especially in emerging and developing economies. This piece of evidence hardly fits the "impossible Trinity" theory arguing that it becomes difficult to control the exchange rate without a "hard" device when capital flows are freed. Calvo and Reinhart (2000) have suggested several explanations for such "fear of floating": exchange rate p...

Carbon nanofiber growth on carbon paper for proton exchange membrane fuel cells

NARCIS (Netherlands)

Celebi, S.; Nijhuis, T.A.; Schaaf, van der J.; Bruijn, de F.A.; Schouten, J.C.

2011-01-01

Homogeneous deposition precipitation (HDP) of nickel has been investigated for the growth of carbon nanofibers (CNFs) on carbon paper for use in proton exchange membrane fuel cells as a gas diffusion layer. Selective CNF growth on only one side of carbon paper is required to transfer the generated

Floating Exchange Rate Regime

OpenAIRE

Quader, Syed Manzur

2004-01-01

In recent years, many developing countries having a history of high inflation, unfavorable balance of payment situation and a high level of foreign currencies denominated debt, have switched or are in the process of switching to a more flexible exchange rate regime. Therefore, the stability of the exchange rate and the dynamics of its volatility are more crucial than before to prevent financial crises and macroeconomic disturbances. This paper is designed to find out the reasons behind Bangla...

Approaches to proton single-event rate calculations

International Nuclear Information System (INIS)

Petersen, E.L.

1996-01-01

This article discusses the fundamentals of proton-induced single-event upsets and of the various methods that have been developed to calculate upset rates. Two types of approaches are used based on nuclear-reaction analysis. Several aspects can be analyzed using analytic methods, but a complete description is not available. The paper presents an analytic description for the component due to elastic-scattering recoils. There have been a number of studies made using Monte Carlo methods. These can completely describe the reaction processes, including the effect of nuclear reactions occurring outside the device-sensitive volume. They have not included the elastic-scattering processes. The article describes the semiempirical approaches that are most widely used. The quality of previous upset predictions relative to space observations is discussed and leads to comments about the desired quality of future predictions. Brief sections treat the possible testing limitation due to total ionizing dose effects, the relationship of proton and heavy-ion upsets, upsets due to direct proton ionization, and relative proton and cosmic-ray upset rates

Inflation Targeting and Exchange Rate Management in Korea

Directory of Open Access Journals (Sweden)

Won-Am Park

2008-06-01

Full Text Available This paper investigates the experience of inflation targeting in Korea with an emphasis on exchange rate management. The Korean call rate responded to not only expected inflation, but also to output gap and changes in the real effective exchange rate of the Korean won, when we estimated the call rate reaction function over the period of 1999-2007. It was found that the call rate responded to changes in real effective exchange rate more than it did to expected inflation. We also examined whether Korean inflation targeting was actually centered on the exchange rate by estimating the Singaporean style of exchange rate reaction function. It was found that Korean monetary policy was not exchange-rate- centered, since the nominal effective exchange rate of the Korean won responded modestly to inflation and output gap, far less than did the Singaporean dollar.

Preparation of new proton exchange membranes using sulfonated poly(ether sulfone) modified by octylamine (SPESOS)

International Nuclear Information System (INIS)

Mabrouk, W.; Ogier, L.; Matoussi, F.; Sollogoub, C.; Vidal, S.; Dachraoui, M.; Fauvarque, J.F.

2011-01-01

Highlights: → New, simple and cheap way to synthesize a membrane. → The membranes combine good proton conductivities with good mechanical properties. → The membrane performances in a fuel cell are similar to the Nafion 117. - Abstract: Sulfonated poly(arylene ether sulfone) (SPES) has received considerable attention in membrane preparation for proton exchange membrane fuel cell (PEMFC). But such membranes are brittle and difficult to handle in operation. We investigated new membranes using SPES grafted with various degrees of octylamine. Five new materials made from sulfonated polyethersulfone sulfonamide (SPESOS) were synthetized with different grades of grafting. They were made from SPES, with initially an ionic exchange capacity (IEC) of 2.4 meq g -1 (1.3 H + per monomer unit). Pristine SPES with that IEC is water swelling and becomes soluble at 80 deg. C, its proton conductivity is in the range of 0.1 S cm -1 at room temperature in aqueous H 2 SO 4 1 M, similar to that of Nafion. After grafting with various amounts of octylamine, the material is water insoluble; membranes are less brittle and show sufficient ionic conductivity. Proton transport numbers were measured close to 1.

Measuring the costs of exchange rate volatility

OpenAIRE

Paul R. Bergin

2004-01-01

Many countries go to great lengths to manage their exchange rates. Probably the most prominent recent example is the European Monetary Union, where all the members abandoned their national currencies and adopted the euro. A number of developing countries maintain other kinds of regimes of managed exchange rates, even though they face potent market pressures to let their exchange rates float. One of the main motives for these arrangements stems from the extreme volatility of exchange rates. Th...

Rapid deuterium exchange-in time for probing conformational change

International Nuclear Information System (INIS)

Dharmasiri, K.; Smith, D.L.

1995-01-01

Isotopic exchange of protein backbone amide hydrogens has been used extensively as a sensitive probe of protein structure. One of the salient features of hydrogen exchange is the vast range of exchange rates in one protein. Isotopic exchange methods have been used to study the structural features including protein folding and unfolding (1), functionally different forms of proteins (2), protein-protein complexation (3), and protein stability parameter. Many backbone amide protons that are surface accessible and are not involved in hydrogen bonding undergo rapid deuterium exchange. In order to study, fast exchanging amide protons, fast exchange-in times are necessary

Where Would the EUR/CHF Exchange Rate be Without the SNB's Minimum Exchange Rate Policy?

DEFF Research Database (Denmark)

Hanke, Michael; Poulsen, Rolf; Weissensteiner, Alex

2015-01-01

Since its announcement made on September 6, 2011, the Swiss National Bank (SNB) has been pursuing the goal of a minimum EUR/CHF exchange rate of 1.20, promising to intervene on currency markets to prevent the exchange rate from falling below this level.We use a compound option pricing approach...

Modified nanocrystal cellulose/fluorene-containing sulfonated poly(ether ether ketone ketone) composites for proton exchange membranes

Science.gov (United States)

Wei, Yingcong; Shang, Yabei; Ni, Chuangjiang; Zhang, Hanyu; Li, Xiaobai; Liu, Baijun; Men, Yongfeng; Zhang, Mingyao; Hu, Wei

2017-09-01

Highly sulfonated poly(ether ether ketone ketone)s (SFPEEKKs) with sulfonation degrees of 2.34 (SFPEEKK5) and 2.48 (SFPEEKK10) were synthesized through the direct sulfonation of a fluorene-containing poly(ether ether ketone ketone) under a relatively mild reaction condition. Using the solution blending method, sulfonated nanocrystal cellulose (sNCC)-enhanced SFPEEKK composites (SFPEEKK/sNCC) were successfully prepared for investigation as proton exchange membranes. Transmission electron microscopy showed that sNCC was uniformly distributed in the composite membranes. The properties of the composite membranes, including thermal stability, mechanical properties, water uptake, swelling ratio, oxidative stability and proton conductivity were thoroughly evaluated. Results indicated that the insertion of sNCC could contribute to water management and improve the mechanical performance of the membranes. Notably, the proton conductivity of SFPEEKK5/sNCC-5 was as high as 0.242 S cm-1 at 80 °C. All data proved the potential of SFPEEKK/sNCC composites for proton exchange membranes in medium-temperature fuel cells.

Empirical Studies of Exchange Rates: Price Behavior, Rate Determinationand Market Efficiency

OpenAIRE

Richard M. Levich

1983-01-01

Theoretical and empirical research completed over the last decade has dramatically increased our understanding of exchange rate behavior. The major insight to come from this decade of research is that foreign exchange is a financial asset. In an asset pricing framework, current exchange rates reflect the expected values of future exogenous variables. The purpose of this paper is to survay the empirical evidence on exchange rate behavior, market efficiency and related topics. Section 2 present...

Role of Exchange Rate Volatility in Exchange Rate Pass-Through to Import Prices: Some Evidence from Japan

OpenAIRE

Guneratne Banda Wickremasinghe; Param Silvapulle

2004-01-01

This paper investigates the effect of exchange rate volatility on the degree of exchange rate pass-through in Japan for the period January 1975 to June 1997. Although several studies put forward theoretical arguments for the volatility-domestic import price relationship, only a very few studies produced empirical evidence. The volatility of contractual currency based exchange rate index returns was modelled using GARCH-type processes with skewed student t-distribution, capturing the typical n...

Detection of the sulfhydryl groups in proteins with slow hydrogen exchange rates and determination of their proton/deuteron fractionation factors using the deuterium-induced effects on the 13C(beta) NMR signals.

Science.gov (United States)

Takeda, Mitsuhiro; Jee, JunGoo; Terauchi, Tsutomu; Kainosho, Masatsune

2010-05-05

A method for identifying cysteine (Cys) residues with sulfhydryl (SH) groups exhibiting slow hydrogen exchange rates has been developed for proteins in aqueous media. The method utilizes the isotope shifts of the C(beta) chemical shifts induced by the deuteration of the SH groups. The 18.2 kDa E. coli peptidyl prolyl cis-trans isomerase b (EPPIb), which was selectively labeled with [3-(13)C;3,3-(2)H(2)]Cys, showed much narrower line widths for the (13)C(beta) NMR signals, as compared to those of the proteins labeled with either [3-(13)C]Cys or (3R)-[3-(13)C;3-(2)H]Cys. The (13)C(beta) signals of the two Cys residues of EPPIb, i.e. Cys-31 and Cys-121, labeled with [3-(13)C;3,3-(2)H(2)]Cys, split into four signals in H(2)O/D(2)O (1:1) at 40 degrees C and pH 7.5, indicating that the exchange rates of the side-chain SH's and the backbone amides are too slow to average the chemical shift differences of the (13)C(beta) signals, due to the two- and three-bond isotope shifts. By virtue of the well-separated signals, the proton/deuteron fractional factors for both the SH and amide groups of the two Cys residues in EPPIb could be directly determined, as approximately 0.4-0.5 for [SD]/[SH] and 0.9-1.0 for [ND]/[NH], by the relative intensities of the NMR signals for the isotopomers. The proton NOE's of the two slowly exchanging SH's were clearly identified in the NOESY spectra and were useful for the determining the local structure of EPPIb around the Cys residues.

Search for a new exchange-rate regime.

Science.gov (United States)

Williamson, J

1987-07-31

The regime of unmanaged floating exchange rates was implicitly judged a failure when, with the Plaza Agreement, attempts at cooperative exchange-rate management were reintroduced primarily because of concern at the size of misalignments. Any satisfactory successor regime will need to limit misalignments while retaining the genuine social benefits of exchange-rate flexibility. It is argued that a system of target zones for exchange rates, ideally embedded in a more comprehensive set of guidelines for international economic policy coordination, could best reconcile these needs.

On equilibrium real exchange rates in euro area: Special focus on behavioral equilibrium exchange rates in Ireland and Greece

Directory of Open Access Journals (Sweden)

Klára Plecitá

2012-01-01

Full Text Available This paper focuses on the intra-euro-area imbalances. Therefore the first aim of this paper is to identify euro-area countries exhibiting macroeconomic imbalances. The subsequent aim is to estimate equilibrium real exchange rates for these countries and to compute their degrees of real exchange rate misalignment. The intra-area balance is assessed using the Cluster Analysis and the Principle Component Analysis; on this basis Greece and Ireland are selected as the two euro-area countries with largest imbalances in 2010. Further the medium-run equilibrium exchange rates for Greece and Ireland are estimated applying the Behavioral Equilibrium Exchange Rate (BEER approach popularised by Clark and MacDonald (1998. In addition, the long-run equilibrium exchange rates are estimated using the Permanent Equilibrium Exchange Rate (PEER model. Employing the BEER and PEER approaches on quarterly time series of real effective exchange rates (REER from 1997: Q1 to 2010: Q4 we identify an undervaluation of the Greek and Irish REER around their entrance to the euro area. For the rest of the period analysed their REER is broadly in line with estimated BEER and PEER levels.

An Econometric Diffusion Model of Exchange Rate Movements within a Band - Implications for Interest Rate Differential and Credibility of Exchange Rate Policy

OpenAIRE

Rantala, Olavi

1992-01-01

The paper presents a model ofexchange rate movements within a specified exchange rate band enforced by central bank interventions. The model is based on the empirical observation that the exchange rate has usually been strictly inside the band, at least in Finland. In this model the distribution of the exchange rate is truncated lognormal from the edges towards the center of the band and hence quite different from the bimodal distribution of the standard target zone model. The model is estima...

Searching for an Appropriate Exchange Rate Regime

Directory of Open Access Journals (Sweden)

Yunjong Wang

2001-06-01

Full Text Available This paper attempts to survey current debates on the choice of exchange rate regime in emerging market economies. The issue of choosing an appropriate exchange rate regime is being actively discussed since the recent Asian crisis. As a lesson from the recent crises, one widely shared conclusion is that soft peg exchange rate regimes are extremely vulnerable in a world of volatile capital movements. Consequently, new orthodoxy based on the impossible trinity hypothesis favours two corner solutions ― greater flexibility or credible institutional assurance, like a currency board system or dollarization. Nevertheless, questions whether such corner solutions are adequate for developing countries are rising of late. "Fear of floating" is still conspicuous in many developing countries having adopted nominally a free-floating exchange rate regime. Developing countries are sensitive to exchange rate fluctuations because the cost of exchange rate volatility is greater than the benefit when compared to developed countries. Monitoring bands is a compromise solution, but it still needs further enhancement of estimation techniques for fundamental equilibrium exchange rates in order to make those estimation results more workable in practice. Other alternatives include the creation of soft peg of the G-3 currencies. Despite counterarguments, the stability of G-3 currencies could prove to be beneficial to emerging market economies.

Mathematical modeling of water mass balance for proton exchange membrane fuel cell

International Nuclear Information System (INIS)

Wan Ramli Wan Daud; Kamaruzzaman Sopian; Jaafar Sahari; Nik Suhaimi Mat Hassan

2006-01-01

Gas and water management are key to achieving good performance from a proton exchange membrane fuel cell (PEMFC) stack. Water plays a critical role in PEMFC. The proton conductivity is increase with the water content. In order to achieve enough hydration, water is normally introduced into the cell externally by a variety of methods such as liquid injection, steam introduction, and humidification of reactants by passing them through humidifiers before entering the cell. In this paper, mathematical modeling of water mass balance for PEMFC at anode and cathode side are proposed by using external humidification and assume that steady state, constant pressure, constant temperature and gases distribution are uniform

A nuclear magnetic relaxation study of hydrogen exchange and water dynamics in aqueous systems

International Nuclear Information System (INIS)

Lankhorst, D.

1983-01-01

In this thesis exchange of water protons in solutions of some weak electrolytes and polyelectrolytes is studied. Also the dynamical behaviour of water molecules in pure water is investigated. For these purposes nuclear magnetic resonance relaxation measurements, in solutions of oxygen-17 enriched water, are interpreted. The exchange rate of the water protons is derived from the contribution of 1 H- 17 O scalar coupling to the proton transverse relaxation rate. This rate is measured by the Carr-Purcell technique. (Auth.)

The Deceptive Resilience of Fixed Exchange Rates

OpenAIRE

Mushin, Jerry

2004-01-01

This paper is an examination of the experience of exchange-rate systems since 1978. Despite the accelerating trend in favour of floating exchange rates, a substantial minority of IMF members have continued to fix the value of their currencies. The recent incidence of each of the principal types of exchange-rate peg is described.

Sulfonation of cPTFE Film grafted Styrene for Proton Exchange Membrane Fuel Cell

Directory of Open Access Journals (Sweden)

Yohan Yohan

2010-10-01

Full Text Available Sulfonation of γ-ray iradiated and styrene-grafted crosslinked polytetrafluoroethylene film (cPTFE-g-S film have been done. The aim of the research is to make hydropyl membrane as proton exchange membrane fuel cell. Sulfonation was prepared with chlorosulfonic acid in chloroethane under various conditions. The impact of the percent of grafting, the concentration of chlorosulfonic acid, the reaction time,and the reaction temperature on the properties of sulfonated film is examinated. The results show that sulfonation of surface-grafted films is incomplete at room  temperature. The increasing of concentration of chlorosulfonic acid and reaction temperature accelerates the reaction but they also add favor side reactions. These will lead to decreasing of the ion-exchange capacity, water uptake, and proton conductivity but increasing the resistance to oxidation in a perhidrol solution. The cPTFE-g-SS membrane which is resulted has stability in a H2O2 30% solution for 20 hours.

Management of exchange rate regimes in emerging Asia

Directory of Open Access Journals (Sweden)

Ramkishen S. Rajan

2012-04-01

Full Text Available This paper revisits the issue of exchange rate regimes in emerging Asia over the decade 1999–2009. It finds that while Asia is home to a wide array of exchange rate regimes, there are signs of gradual movement toward somewhat greater exchange rate flexibility in many of the regional countries. There appears to be evidence of an apparent “fear of appreciation” which is manifested in asymmetric exchange rate intervention—i.e., a willingness to allow depreciations but reluctance to allow appreciations. This policy of effective exchange rate undervaluation is rather unorthodox from a neoclassical sense, but is consistent with a development policy centered on suppressing the price of non-tradable goods relative to tradables (i.e., real exchange rate undervaluation.

Modeling Real Exchange Rate Persistence in Chile

Directory of Open Access Journals (Sweden)

Leonardo Salazar

2017-07-01

Full Text Available The long and persistent swings in the real exchange rate have for a long time puzzled economists. Recent models built on imperfect knowledge economics seem to provide a theoretical explanation for this persistence. Empirical results, based on a cointegrated vector autoregressive (CVAR model, provide evidence of error-increasing behavior in prices and interest rates, which is consistent with the persistence observed in the data. The movements in the real exchange rate are compensated by movements in the interest rate spread, which restores the equilibrium in the product market when the real exchange rate moves away from its long-run benchmark value. Fluctuations in the copper price also explain the deviations of the real exchange rate from its long-run equilibrium value.

Phosphoric acid doped imidazolium polysulfone membranes for high temperature proton exchange membrane fuel cells

DEFF Research Database (Denmark)

Yang, Jingshuai; Li, Qingfeng; Jensen, Jens Oluf

2012-01-01

A novel acid–base polymer membrane is prepared by doping of imidazolium polysulfone with phosphoric acid for high temperature proton exchange membrane fuel cells. Polysulfone is first chloromethylated, followed by functionalization of the chloromethylated polysulfone with alkyl imidazoles i.e. me...

Interdependence and Exchange Rate Regimes in East Asia: Intra-regional Transmissions of Exchange Rate Policies after the Crisis (in Japanese)

OpenAIRE

OHNO Sanae; FUKUDA Shin-ichi

2003-01-01

Since the onset of the Asian crisis, what characterizes the East Asian exchange rates has been a topic of considerable discussion. In the pre-crisis period, the de facto pegs to the U.S. dollar sometimes destabilized the real "effective" exchange rates of these currencies. Several economists have, thus, proposed the desirability of intermediate exchange rate regimes in East Asia that might stabilize their effective exchange rates. The post-crisis experience in East Asia, however, taught us th...

Two-Photon Exchange Effects in Elastic Electron-Proton Scattering

Energy Technology Data Exchange (ETDEWEB)

Johnson, Myriam James [Argonne National Lab. (ANL), Argonne, IL (United States)

2013-08-01

Two methods, Rosenbluth separation and polarization transfer, can be used to extract the proton form factor ratio μp G_Ep/G_Mp, but they do not yield the same results. It is thought that the disagreement is due to two photon exchange corrections to the differential cross sections. High precision proton Rosenbluth extractions were carried out at 102 kinematics points spanning 16 values of momentum transfer Q², from 0.40 to 5.76 GeV². Reduced cross sections were found to 1.1% or better for Q² less than 3 GeV² increasing to 4% at 5.76 GeV² The form factor ratios were determined to 1:5-3% for Q² < 1.5 GeV², increasing to 9% by 3 GeV² and rapidly above. Our data agrees with prior Rosenbluth, improving upon it the 1.0 - 2.0 GeV² range to conclusively show a separation from polarization transfer where it had not been certain before. In addition, reduced cross sections at each Q² were tested for nonlinearity in the angular variable. Such a departure from linearity would be a signature of two photon exchange effects, and prior data had not been sufficiently precise to show nonzero curvature. Our data begins to hint at negative curvature but does not yet show a significant departure from zero.

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

Science.gov (United States)

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.

Modelling and validation of Proton exchange membrane fuel cell (PEMFC)

Science.gov (United States)

Mohiuddin, A. K. M.; Basran, N.; Khan, A. A.

2018-01-01

This paper is the outcome of a small scale fuel cell project. Fuel cell is an electrochemical device that converts energy from chemical reaction to electrical work. Proton Exchange Membrane Fuel Cell (PEMFC) is one of the different types of fuel cell, which is more efficient, having low operational temperature and fast start up capability results in high energy density. In this study, a mathematical model of 1.2 W PEMFC is developed and simulated using MATLAB software. This model describes the PEMFC behaviour under steady-state condition. This mathematical modeling of PEMFC determines the polarization curve, power generated, and the efficiency of the fuel cell. Simulation results were validated by comparing with experimental results obtained from the test of a single PEMFC with a 3 V motor. The performance of experimental PEMFC is little lower compared to simulated PEMFC, however both results were found in good agreement. Experiments on hydrogen flow rate also been conducted to obtain the amount of hydrogen consumed to produce electrical work on PEMFC.

Kinetics for exchange of imino protons in the d(C-G-C-G-A-A-T-T-C-G-C-G) double helix and in two similar helices that contain a G . T base pair, d(C-G-T-G-A-A-T-T-C-G-C-G), and an extra adenine, d(C-G-C-A-G-A-A-T-T-C-G-C-G).

Science.gov (United States)

Pardi, A; Morden, K M; Patel, D J; Tinoco, I

1982-12-07

The relaxation lifetimes of imino protons from individual base pairs were measured in (I) a perfect helix, d(C-G-C-G-A-A-T-T-C-G-C-G), (II) this helix with a G . C base pair replaced with a G . T base pair, d(C-G-T-G-A-A-T-T-C-G-C-G), and (III) the perfect helix with an extra adenine base in a mismatch, d(C-G-C-A-G-A-A-T-T-C-G-C-G). The lifetimes were measured by saturation recovery proton nuclear magnetic resonance experiments performed on the imino protons of these duplexes. The measured lifetimes of the imino protons were shown to correspond to chemical exchange lifetimes at higher temperatures and spin-lattice relaxation times at lower temperatures. Comparison of the lifetimes in these duplexes showed that the destabilizing effect of the G . T base pair in II affected the opening rate of only the nearest-neighbor base pairs. For helix III, the extra adenine affected the opening rates of all the base pairs in the helix and thus was a larger perturbation for opening of the base pairs than the G . T base pair. The temperature dependence of the exchange rates of the imino proton in the perfect helix gives values of 14-15 kcal/mol for activation energies of A . T imino protons. These relaxation rates were shown to correspond to exchange involving individual base pair opening in this helix, which means that one base-paired imino proton can exchange independent of the others. For the other two helices that contain perturbations, much larger activation energies for exchange of the imino protons were found, indicating that a cooperative transition involving exchange of at least several base pairs was the exchange mechanism of the imino protons. The effects of a perturbation in a helix on the exchange rates and the mechanisms for exchange of imino protons from oligonucleotide helices are discussed.

On exchange rate misalignments in the Eurozone's peripheral countries

Science.gov (United States)

Grochová, Ladislava; Plecitá, Klára

2013-10-01

In this paper we model equilibrium exchange rates for the Eurozone's countries on the basis of the Behavioural Equilibrium Exchange Rate approach, which assumes, that equilibrium exchange rates are in the long run affected by economic fundamentals. To assess the degree of exchange rate misalignment for the Eurozone's peripheral countries - Portugal, Ireland, Greece and Spain - the gap between the actual and the modelled equilibrium exchange rate value is calculated. Our results show that Spain, Portugal and Ireland had their real exchange rates in equilibrium when they joined the Eurozone; however their real exchange rates have been persistently overvalued since the beginning of the 2000s. Greece, on the other hand, has experienced diminishing undervaluation at the beginning of its membership in the Eurozone and since 2009 has exhibited an overvalued real exchange rate.

Proton Exchange Membrane Fuel Cells Applied for Transport Sector

DEFF Research Database (Denmark)

Hosseinzadeh, Elham; Rokni, Masoud

2010-01-01

A thermodynamic analysis of a PEMFC (proton exchange membrane fuel cell) is investigated. PEMFC may be the most promising technology for fuel cell automotive systems, which is operating at quite low temperatures, (between 60 to 80℃). In this study the fuel cell motive power part of a lift truck has...... been investigated. The fuel cell stack used in this model is developed using a Ballard PEMFC [1], so that the equations used in the stack modeling are derived from the experimental data. The stack can produce 3 to 15 kilowatt electricity depending on the number of cells used in the stack. Some...

Low stoichiometry operation of a proton exchange membrane fuel cell employing the interdigitated flow field

DEFF Research Database (Denmark)

Berning, Torsten; Kær, Søren Knudsen

2012-01-01

A multiphase fuel cell model based on computational fluid dynamics is used to investigate the possibility of operating a proton exchange membrane fuel cell at low stoichiometric flow ratios (ξ gases. A case study...

Review of low pressure plasma processing of proton exchange membrane fuel cell electrocatalysts

OpenAIRE

Brault , Pascal

2016-01-01

Review article; International audience; The present review is describing recent advances in plasma deposition and treatment of low temperature proton exchange membrane fuel cells electrocatalysts. Interest of plasma processing for growth of platinum based, non-precious and metal free electrocatalysts is highlighted. Electrocatalysts properties are tentatively correlated to plasma parameters.

Multiphase Simulations and Design of Validation Experiments for Proton Exchange Membrane Fuel Cells

DEFF Research Database (Denmark)

Berning, Torsten

2013-01-01

Proton exchange membrane fuel cells directly convert into electricity the chemical energy of hydrogen and oxygen from air. The by-products are just water and waste heat. Depending on the operating conditions the water may be in the liquid or gas phase, and liquid water can hence plug the porous m...

A new assessment of floating exchange rates

OpenAIRE

Waimann, D. R.

1981-01-01

The switch to floating exchange rates during the 1970s has given economists the first comprehensive opportunity to assess the arguments for and against floating. Much new work has been done on various aspects of floating exchange rate behaviour. This article attempts a limited survey of the evidence concerning two important issues—whether floating exchange rates are inherently unstable and whether they harm international trade.

Model Uncertainty and Exchange Rate Forecasting

NARCIS (Netherlands)

Kouwenberg, R.; Markiewicz, A.; Verhoeks, R.; Zwinkels, R.C.J.

2017-01-01

Exchange rate models with uncertain and incomplete information predict that investors focus on a small set of fundamentals that changes frequently over time. We design a model selection rule that captures the current set of fundamentals that best predicts the exchange rate. Out-of-sample tests show

Model Uncertainty and Exchange Rate Forecasting

NARCIS (Netherlands)

R.R.P. Kouwenberg (Roy); A. Markiewicz (Agnieszka); R. Verhoeks (Ralph); R.C.J. Zwinkels (Remco)

2013-01-01

textabstractWe propose a theoretical framework of exchange rate behavior where investors focus on a subset of economic fundamentals. We find that any adjustment in the set of predictors used by investors leads to changes in the relation between the exchange rate and fundamentals. We test the

14 CFR 65.43 - Rating privileges and exchange.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Rating privileges and exchange. 65.43... § 65.43 Rating privileges and exchange. (a) The holder of a senior rating on August 31, 1970, may at any time after that date exchange his rating for a facility rating at the same air traffic control...

Accelerating parameter identification of proton exchange membrane fuel cell model with ranking-based differential evolution

International Nuclear Information System (INIS)

Gong, Wenyin; Cai, Zhihua

2013-01-01

Parameter identification of PEM (proton exchange membrane) fuel cell model is a very active area of research. Generally, it can be treated as a numerical optimization problem with complex nonlinear and multi-variable features. DE (differential evolution), which has been successfully used in various fields, is a simple yet efficient evolutionary algorithm for global numerical optimization. In this paper, with the objective of accelerating the process of parameter identification of PEM fuel cell models and reducing the necessary computational efforts, we firstly present a generic and simple ranking-based mutation operator for the DE algorithm. Then, the ranking-based mutation operator is incorporated into five highly-competitive DE variants to solve the PEM fuel cell model parameter identification problems. The main contributions of this work are the proposed ranking-based DE variants and their application to the parameter identification problems of PEM fuel cell models. Experiments have been conducted by using both the simulated voltage–current data and the data obtained from the literature to validate the performance of our approach. The results indicate that the ranking-based DE methods provide better results with respect to the solution quality, the convergence rate, and the success rate compared with their corresponding original DE methods. In addition, the voltage–current characteristics obtained by our approach are in good agreement with the original voltage–current curves in all cases. - Highlights: • A simple and generic ranking-based mutation operator is presented in this paper. • Several DE (differential evolution) variants are used to solve the parameter identification of PEMFC (proton exchange membrane fuel cells) model. • Results show that our method accelerates the process of parameter identification. • The V–I characteristics are in very good agreement with experimental data

The feasibility of a fixed exchange rate regime for new EU-members: evidence from real exchange rates

NARCIS (Netherlands)

Candelon, B.; Kool, C.J.M.; Raabe, K.; van Veen, T.

2005-01-01

In this paper, we estimate fundamental bilateral real exchange rates for a group of eight accession countries using a panel-cointegration approach for the period 1993-2003. We document a significant positive link between productivity levels and the corresponding real exchange rate levels. Future

The feasibility of a fixed exchange rate regime for new EU-members : Evidence from real exchange rates

NARCIS (Netherlands)

Candelon, B.; Kool, C.J.M.; Raabe, K.; Veen, van A.P. (Tom)

2005-01-01

In this paper, we estimate fundamental bilateral real exchange rates for a group of eight accession countries using a panel-cointegration approach for the period 1993-2003. We document a significant positive link between productivity levels and the corresponding real exchange rate levels. Future

Does oxidative stress affect the activity of the sodium-proton exchanger?

Science.gov (United States)

Bober, Joanna; Kedzierska, Karolina; Kwiatkowska, Ewa; Stachowska, Ewa; Gołembiewska, Edyta; Mazur, Olech; Staniewicz, Zdzisław; Ciechanowski, Kazimierz; Chlubek, Dariusz

2010-01-01

Accumulation of reactive oxygen species (ROS) takes place in patients with chronic renal failure (CRF). Oxidative stress causes disorders in the activity of the sodium-proton exchanger (NHE). Studies on NHE in CRF produced results that are discrepant and difficult to interpret. The aim of this study was to demonstrate that oxidative stress had an effect on the activity of NHE. We enrolled 87 subjects divided into 4 groups: patients with CRF treated conservatively; patients with CRF hemodialyzed without glucose--HD-g(-); patients with CRF hemodialyzed with glucose--HD-g(+); controls (C). The activity of NHE, the rate of proton efflux V(max), Michaelis constant (Km), and the concentration of thiobarbituric acid-reactive substances (TBARS, an indicator of oxidative stress) in plasma, as well as the concentration of reduced glutathione in blood were determined. The concentration of TBARS was significantly higher in hemodialyzed patients before and after dialysis and in patients with CRF on conservative treatment in comparison with group C. TBARS in plasma correlated negatively with VpH(i)6.4 in group C and with V(max) and VpH(i)6.4 after HD in group HD-g(-). We found that the concentration of creatinine correlated with TBARS (p < 0.0001; r = +0.51) in the conservatively treated group. We observed a marked oxidative stress and decreased NHE activity when dialysis was done without glucose, whereas patients dialyzed with glucose demonstrated a relatively low intensity of oxidative stress.

Water-Protein Hydrogen Exchange in the Micro-Crystalline Protein Crh as Observed by Solid State NMR Spectroscopy

International Nuclear Information System (INIS)

Boeckmann, Anja; Juy, Michel; Bettler, Emmanuel; Emsley, Lyndon; Galinier, Anne; Penin, Francois; Lesage, Anne

2005-01-01

We report site-resolved observation of hydrogen exchange in the micro-crystalline protein Crh. Our approach is based on the use of proton T 2 ' -selective 1 H- 13 C- 13 C correlation spectra for site-specific assignments of carbons nearby labile protein protons. We compare the proton T 2 ' selective scheme to frequency selective water observation in deuterated proteins, and discuss the impacts of deuteration on 13 C linewidths in Crh. We observe that in micro-crystalline proteins, solvent accessible hydroxyl and amino protons show comparable exchange rates with water protons as for proteins in solution, and that structural constraints, such as hydrogen bonding or solvent accessibility, more significantly reduce exchange rates

Proton exchange membrane fuel cell operation and degradation in short-circuit.

OpenAIRE

Silva , R.E.; Harel , F.; Jemei , S.; Gouriveau , Rafael; Hissel , Daniel; Boulon , L.; Agbossou , K.

2013-01-01

International audience; Hybridization of proton exchange membrane fuel cells (PEMFC) and ultra capacitors (UC) are considered as an alternative way to implement high autonomy, high dynamic, and reversible energy sources. PEMFC allow high efficiency and high autonomy, however their dynamic response is limited and this source does not allow recovering energy. UC appears to be a complementary source to fuel cell systems (FCS) due to their high power density, fast dynamics, and reversibility. A d...

A re-examination of the exchange rate overshooting hypothesis ...

African Journals Online (AJOL)

Southern African Business Review ... This finding is inconsistent with the monetary model of exchange rate determination, which asserts that there is a long-run relationship between the exchange rate ... Key words: Exchange rates, monetary model, autoregressive distributed lag, cointegration, exchange rate overshooting ...

Exchange Rate Regime in Russia, Evaluation and Recommendations

OpenAIRE

Olga, Vasilevskaya

2009-01-01

This paper studies exchange rate choice in Russia with respect to social, economic and political determinants. The study deliberately narrowed the scope of the discussion to two extreme cases, i.e. fixed and floating exchange rate. Today Russia applies managed floating exchange rate arrangement and it is important to determine the direction of the further monetary policy development either towards fixed or floating exchange rate. The paper argues that the logical extension of the historical t...

KRW/USD Exchange Rate Volatility and Efficient Risk Management

Directory of Open Access Journals (Sweden)

Sang-Yong Joo

1999-03-01

Full Text Available This thesis analyzes the relationship between the exchange rate of Korean Won and US dollar and the amount of foreign exchange, and studies the direction of the amendment of the risk control of foreign exchange. The GARCH (Generalized Auto Regressive Conditional Heteroscedasticity model which visually embodies the auto-regress of the wave of exchange rate shows that the amount of trade will enhance the fluidity of the exchange rate, that is, the various expects of the participators of the market affect the amount of trade and the fluidity, so in the process of trading, the trader who is in the dry tree of information bears more trading expenditure. It is predicted that the liberalization of foreign exchange rate and fluctuated exchange rate system will jointly bring the enhancement of the fluidity of the exchange rate and the amount of exchange trade. The change of this system will bring the rise of participators in foreign exchange market; meanwhile, it will also initiate superfluous fluidity of foreign exchange market. In order to overcome this problem, the government needs to implement the development strategy of the understructure of the foreign exchange market and the enterprises need to carry through systemic exchange rate risk control.

Modeling inflation rates and exchange rates in Ghana: application of multivariate GARCH models.

Science.gov (United States)

Nortey, Ezekiel Nn; Ngoh, Delali D; Doku-Amponsah, Kwabena; Ofori-Boateng, Kenneth

2015-01-01

This paper was aimed at investigating the volatility and conditional relationship among inflation rates, exchange rates and interest rates as well as to construct a model using multivariate GARCH DCC and BEKK models using Ghana data from January 1990 to December 2013. The study revealed that the cumulative depreciation of the cedi to the US dollar from 1990 to 2013 is 7,010.2% and the yearly weighted depreciation of the cedi to the US dollar for the period is 20.4%. There was evidence that, the fact that inflation rate was stable, does not mean that exchange rates and interest rates are expected to be stable. Rather, when the cedi performs well on the forex, inflation rates and interest rates react positively and become stable in the long run. The BEKK model is robust to modelling and forecasting volatility of inflation rates, exchange rates and interest rates. The DCC model is robust to model the conditional and unconditional correlation among inflation rates, exchange rates and interest rates. The BEKK model, which forecasted high exchange rate volatility for the year 2014, is very robust for modelling the exchange rates in Ghana. The mean equation of the DCC model is also robust to forecast inflation rates in Ghana.

Essays on exchange rate policy in developing countries

OpenAIRE

Khamfula, Y.A.

1999-01-01

The breakdown of the Bretton Woods system of pegged exchange rates has since 1971 given developing countries a wider range of choice with regard to their exchange rate regimes than had previously existed. With the emergence of a variety of exchange rate regimes, increasing attention has been given to the rationale for choosing one type of regime over another and how the variations in the nominal or real exchange rate affect the economies of these countries. This Ph.D. thesis is a combination ...

Exchange Rate Volatility, Inflation Uncertainty and Foreign Direct ...

African Journals Online (AJOL)

This article examines the effect of exchange rate volatility and inflation uncertainty on foreign direct investment in Nigeria. The investigation covers the period between 1970 and 2005. Exchange rate volatility and inflation uncertainty were estimated using the GARCH model. Estimation results indicated that exchange rate ...

Fiscal Policy and Welfare under Different Exchange Rate Regimes

DEFF Research Database (Denmark)

Østrup, Finn

a representativeindividual's utility, it is demonstrated that there are differences betweenexchange rate regimes with respect to the level of government spending. Thesedifferences arise first because a rise in government spending affects macroeconomicvariables differently under different exchange rate regimes......, and secondbecause the government's inclination to expand government spending is affectedby inflation which depends on the exchange rate regime. At low rates of inflation,the government is inclined to set a higher level of government spending under afixed exchange rate regime than under a floating exchange rate...... regime in whichthe monetary authority optimises preferences which include an employment targetand an inflation target. As government spending affects the representativeindividual's utility, the choice of exchange rate regime has an impact on welfare.Keywords: exchange rate regimes; fiscal policy...

EFECT OF FOREIGN EXCHANGE RATE FLUCTUATIONS ON NIGERIAN ECONOMY

Directory of Open Access Journals (Sweden)

Lawrence Olisaemeka UFOEZE

2018-03-01

Full Text Available This study investigated the effect of exchange rate fluctuations on Nigerian economy. The fixed and floating exchange eras were compared to know the exchange rate system in which the economy has fairly better. The time period covered was 1970 to 2012. The study employed the ordinary least square (OLS multiple regression technique for the analysis. The coefficient of determination (R2, F-test, t-test, beta and Durbin-Watson were used in the interpretation of the results. The resulted revealed that about 85% of the changes in macroeconomic indicators are explained in the fixed exchange era. In the floating exchange era, 99% was explained while the whole periods has 73% explanatory power, hence the floating exchange era (1986 to date is more effective in explaining economic trend in Nigeria. Also, exchange rate has significant positive effect on GDP during the fixed exchange rate era and negative effect the eras floating and all-time; inflation has insignificant negative effect on GDP during the fixed exchange era; significant effect in floating era and significant negative effect in the all-time period; money supply has insignificant negative effect GDP in fixed exchange era; and significant positive effect during the floating and all-time period; and oil revenue has significant positive effect on the GDP in all the exchange rate regimes (floating, fixed and all-time in Nigeria.  The study thus conclude that exchange rate movement is a good indicator for monitoring Nigerian economic growth. So far exchange rate has always been a key economic indicator for Nigeria. The floating exchange period has outperformed the fixed exchange rate in terms of contribution inflation, money supply and oil revenue to economic growth. This indicate that the floating exchange rate has been a better economic regime for sustainable economic growth in Nigeria. From the findings, it is evident that oil revenue has positive effect in Nigeria and has remained the mainstay

China; Sources of Real Exchange Rate Fluctuations

OpenAIRE

Tao Wang

2004-01-01

This paper reviews the evolution of China's real effective exchange rate between 1980 and 2002, and uses a structural vector autoregression model to study the relative importance of different types of macroeconomic shocks for fluctuations in the real exchange rate. The structural decomposition shows that relative real demand and supply shocks account for most of the variations in real exchange rate changes during the estimation period. The paper also finds that supply shocks are as important ...

Charge exchange in a divertor plasma with excited particles

International Nuclear Information System (INIS)

Krasheninnikov, S.I.; Lisitsa, V.S.; Pigarov, A.Y.

1988-01-01

A model is constructed for the dynamics of neutral atoms and multicharged ions in a tokamak plasma. The influence of cascade excitation on charge exchange and ionization is taken into account. The effective rates of the resonant charge exchange of a proton with a hydrogen atom, the nonresonant charge exchange of a helium atom with a proton, and that of an α particle with atomic hydrogen are calculated as functions of the parameters of the divertor plasma in a tokamak. The charge exchange H + +He→H+He + can represent a significant fraction (∼30%) of the total helium ionization rate. Incorporating the charge exchange of He 2+ with atomic hydrogen under the conditions prevailing in the divertor plasma of the INTOR reactor can lead to substantial He 2+ →He + conversion and thereby reduce the sputtering of the divertor plates by helium ions

Essays on exchange rate policy in developing countries

NARCIS (Netherlands)

Khamfula, Y.A.

1999-01-01

The breakdown of the Bretton Woods system of pegged exchange rates has since 1971 given developing countries a wider range of choice with regard to their exchange rate regimes than had previously existed. With the emergence of a variety of exchange rate regimes, increasing attention has been given

Impulse Response of the Exchange Rate Volatility to a Foreign Exchange Intervention Shock

OpenAIRE

Hoshikawa, Takeshi

2009-01-01

This paper uses Lin's technique (1997) to report on the impulse response function analysis that traces the dynamics of exchange rate volatility from innovations in Japanese foreign exchange intervention. Using a multivariate GARCH model, we employed a volatility impulse response function based on Lin (1997) to detect the impulse response of exchange rate volatility on a one-unit foreign exchange intervention shock. The main findings of t his paper are as follows: (1) a foreign exchange inter...

Charge-exchange processes in a divertor plasma with account for excited particles

International Nuclear Information System (INIS)

Krasheninnikov, S.I.; Lisitsa, V.S.; Pigarov, A.Yu.

1988-01-01

A model describing dynamics of neutral atoms and multicharge ions in tokamak plasma, taking account of cascade excitation effect on charge exchange and ionization processes, is constructed. Dependences of effective rate of processes of proton charge exchange on hydrogen atom and non-resonance helium atom charge exchange on proton and α-particle- on atomic hydrogen on tokamak divertor plasma parameters are calculated. It is shown that H + +He→H-He + charge exchange can make up a notable shave (∼30%) in full helium ionization rate. Accounting for Ge 2+ charge exchange on atomic hydrogen under INTOR reactor divertor plasma conditions can lead to substantial He 2+ →He + conversion and thus increase diverter plate sputtering by helium ions

Increasing Stability in the Mix of Exchange-rate Policies.

OpenAIRE

Mushin, Jerry

2008-01-01

This paper is an examination of the experience of exchange-rate policy systems since 1996 and a comparison with the experience of 1978 to 1995. Exchange-rate policy has become more stable than it was in the earlier period. In addition, it has become polarized, with almost all countries choosing either a fixed exchange-rate regime (especially in low-GDP countries) or a floating exchange-rate regime (especially in high-GDP countries). Limited-flexibility exchange-rate systems have become unimpo...

Carbon Corrosion at Pt/C Interface in Proton Exchange Membrane Fuel Cell Environment

International Nuclear Information System (INIS)

Choi, Min Ho; Beam, Won Jin; Park, Chan Jin

2010-01-01

This study examined the carbon corrosion at Pt/C interface in proton exchange membrane fuel cell environment. The Pt nano particles were electrodeposited on carbon substrate, and then the corrosion behavior of the carbon electrode was examined. The carbon electrodes with Pt nano electrodeposits exhibited the higher oxidation rate and lower oxidation overpotential compared with that of the electrode without Pt. This phenomenon was more active at 75 .deg. C than 25 .deg. C. In addition, the current transients and the corresponding power spectral density (PSD) of the carbon electrodes with Pt nano electrodeposits were much higher than those of the electrode without Pt. The carbon corrosion at Pt/C interface was highly accelerated by Pt nano electrodeposits. Furthermore, the polarization and power density curves of PEMFC showed degradation in the performance due to a deterioration of cathode catalyst material and Pt dissolution

Real Exchange Rates in Advanced Transition Economies

Directory of Open Access Journals (Sweden)

Sanja Grubacic

2015-10-01

Full Text Available The recent evidence from Eastern Europe suggests that one of the major obstacles towards the adoption of euro may lie in the impact that the recession of 2008 exerted on the trajectory of real exchange rates in new member countries (European Commission, 2015.  This paper aims to establish and explain the relationship between the external shocks derived from the global financial crisis and recession of 2008 and equilibrium real exchange rate in advanced transition economies of Eastern Europe. The interplay between the external and internal balances is explained by developing an inter-temporal optimizing model of the real exchange rate determination in a small open economy with structural distortions. The results of our model suggest that, in the aftermath of recession, if the Eastern European economies attempt to restore and maintain the balance between the consumption, saving, and investment, the equilibrium real exchange rate will tend to reverse its trajectory from appreciation to depreciation over time in order to encourage a greater production in the future. The equilibrium real exchange rate depreciation in the future may obtain either as a result of an increase in the direct subsidies on investment or as a result of reduced subsidies on the "net-of-investment" income.  The deprecation of countries’ real exchange rate, however, may continue to act as an effective constraint against the adoption of euro.

The influence of interest rates on the exchange rate and exchange rate volatility

OpenAIRE

Florin MAVRIS; Dumitru-Cristian OANEA

2014-01-01

The dynamic of interest rates has been the subject of attention by both traders and researchers. We see in what manner different factors that depend on the actions of central banks that influence them by using a GARCH type model and we compare its performance with other models to see what approach explains and predicts the movement of the exchange rate. To better understand the type of model that is applicable the data is tested for heteroskedasticity, and only after that the model is impleme...

Construction and evaluation of a proton exchange fuel cell

International Nuclear Information System (INIS)

Gutierrez, Omar; Monsalve, Carlos; Trujillo, Gonzalo; Hoyos, Bibian; Sanchez, Carlos; Gonzalez, Javier

2005-01-01

One design of a hydrogen proton exchange membrane fuel cell (PEMFC) is proposed. Porous carbon supported platinum electrodes were manufactured by impregnation, reduction and hot-press methods; noble metal loading of 0.4 mg/cm 2 was achieved. The conditions to obtain the porous support were: composition of 15 % Teflon and 85 % carbon, pressure of 100 Kgf/cm 2 , temperature of 300 Celsius degrade and 20 minutes of hot-pressing. The pattern of gas flow distribution was made possible by machined interdigitated channels into conductor graphite plates. Several tests were run varying the load resistance to obtain the polarization curves. Comparison with a commercial PEMFC is also made

Exchange rate policy under sovereign default risk

OpenAIRE

Schabert, Andreas

2011-01-01

We examine monetary policy options for a small open economy where sovereign default might occur due to intertemporal insolvency. Under interest rate policy and floating exchange rates the equilibrium is indetermined. Under a fixed exchange rate the equilibrium is uniquely determined and independent of sovereign default.

THE USE OF CHLOROSULFONIC ACID ON SULFONATION OF cPTFE FILM GRAFTED STYRENE FOR PROTON EXCHANGE MEMBRANE

Directory of Open Access Journals (Sweden)

Yohan Yohan

2010-06-01

Full Text Available Sulfonation of g-ray iradiated and styrene-grafted crosslinked polytetrafluoro ethylene film (cPTFE-g-S film have been done. The aim of the research was to make hydrophyl membrane as proton exchange membrane fuel cell. Sulfonation was prepared by using chlorosulfonic acid in chloroethane under various conditions. The impact of the percentage of grafting, the concentration of chlorosulfonic acid, the reaction time,and the reaction temperature on the properties of sulfonated film were examined. The results show that sulfonation of surface-grafted films was incomplete at room temperature. Increasing concentration of chlorosulfonic acid and reaction temperature accelerate the reaction but they also favor side reactions. These lead to the decrease of the ion-exchange capacity, water uptake, and proton conductivity but the increase of the resistance to oxidation in a perhydrol solution. The resulted cPTFE-g-SS membraneis stabile in a H2O2 30% solution for 20 h.   Keywords: Chorosulfonic acid, sulfonation, PTFE film, proton excange membrane.

Sparseness and Roughness of Foreign Exchange Rates

Science.gov (United States)

Vandewalle, N.; Ausloos, M.

An accurate multiaffine analysis of 23 foreign currency exchange rates has been performed. The roughness exponent H1 which characterizes the excursion of the exchange rate has been numerically measured. The degree of intermittency C1 has been also estimated. In the (H1,C1) phase diagram, the currency exchange rates are dispersed in a wide region around the Brownian motion value (H1=0.5,C1=0) and have a significantly intermittent component (C1≠0).

The determinants of exchange rates and the movements of EUR/RON exchange rate via non-linear stochastic processes

Directory of Open Access Journals (Sweden)

Petrică Andreea-Cristina

2017-07-01

Full Text Available Modeling exchange rate volatility became an important topic for research debate starting with 1973, when many countries switched to floating exchange rate system. In this paper, we focus on the EUR/RON exchange rate both as an economic measure and present the implied economic links, and also as a financial investment and analyze its movements and fluctuations through two volatility stochastic processes: the Standard Generalized Autoregressive Conditionally Heteroscedastic Model (GARCH and the Exponential Generalized Autoregressive Conditionally Heteroscedastic Model (EGARCH. The objective of the conditional variance processes is to capture dependency in the return series of the EUR/RON exchange rate. On this account, analyzing exchange rates could be seen as the input for economic decisions regarding Romanian macroeconomics - the exchange rates being influenced by many factors such as: interest rates, inflation, trading relationships with other countries (imports and exports, or investments - portfolio optimization, risk management, asset pricing. Therefore, we talk about political stability and economic performance of a country that represents a link between the two types of inputs mentioned above and influences both the macroeconomics and the investments. Based on time-varying volatility, we examine implied volatility of daily returns of EUR/RON exchange rate using the standard GARCH model and the asymmetric EGARCH model, whose parameters are estimated through the maximum likelihood method and the error terms follow two distributions (Normal and Student’s t. The empirical results show EGARCH(2,1 with Asymmetric order 2 and Student’s t error terms distribution performs better than all the estimated standard GARCH models (GARCH(1,1, GARCH(1,2, GARCH(2,1 and GARCH(2,2. This conclusion is supported by the major advantage of the EGARCH model compared to the GARCH model which consists in allowing good and bad news having different impact on the

Measuring real exchange rate misalignment in Croatia: cointegration approach

Directory of Open Access Journals (Sweden)

Irena Palić

2014-12-01

Full Text Available The purpose of the paper is to analyze misalignment of the real exchange rate in Croatia. The misalignment analysis is conducted using the permanent equilibrium exchange rate approach. The equilibrium real exchange rate is computed using the cointegration approach whereby the real exchange rate and its fundamentals, namely terms of trade, net foreign assets and the ratio of prices of tradables to non-tradables are included in cointegration analysis. The Hodrick and Prescott filter is used to obtain permanent values of the equilibrium real exchange rate. The real exchange rate misalignment is computed as the deviation of the RER from its permanent equilibrium level. Four overvaluation periods and three undervaluation periods are recorded in Croatia in the observed period. Overvaluation periods are more often and of longer duration than undervaluation periods. However, the real exchange rate does not deviate largely from its estimated equilibrium value in the observed period, and it is neither overvalued nor undervalued constantly, but the periods alternate. Considering the results of the analysis, together with the empirical characteristics of Croatian economy, namely the high foreign currency indebtedness, highly euroized economy and underdeveloped export oriented sector, the depreciation of the real exchange rate is not recommended to economic policy makers and the current Croatian exchange rate policy is appropriate.

Proton conduction based on intracrystalline chemical reaction

International Nuclear Information System (INIS)

Schuck, G.; Lechner, R.E.; Langer, K.

2002-01-01

Proton conductivity in M 3 H(SeO 4 ) 2 crystals (M=K, Rb, Cs) is shown to be due to a dynamic disorder in the form of an intracrystalline chemical equilibrium reaction: alternation between the association of the monomers [HSeO 4 ] 1- and [SeO 4 ] 2- resulting in the dimer [H(SeO 4 ) 2 ] 3- (H-bond formation) and the dissociation of the latter into the two monomers (H-bond breaking). By a combination of quasielastic neutron scattering and FTIR spectroscopy, reaction rates were obtained, as well as rates of proton exchange between selenate ions, leading to diffusion. The results demonstrate that this reaction plays a central role in the mechanism of proton transport in these solid-state protonic conductors. (orig.)

Exchange Rate Regimes – A periodical overview and a critical analysis of exchange rate regimes in Kosovo

Directory of Open Access Journals (Sweden)

Flamur Bunjaku

2015-03-01

Full Text Available Exchange rate regimes and the monetary policy are the key instruments governments use to achieve their economic and financial objectives. Moreover, due to global financial crisis the latter instruments get more importance. Empirical evidences show that exchange rate regimes in Kosovo and its monetary policy throughout their development were mainly influenced by different political and historical developments. In regard of Euroisation of monetary system in Kosovo it was found that this action generated macro - financial stability in terms of inflation and price fluctuation. However, in terms of microeconomic aspects, the unilateral adaptation of Euro as the official currency of Kosovo failed to provide microeconomic advantages such as to export stimulation, and so forth. The main exchange rate regime systems were discussed focusing in their advantages and disadvantages, and it was concluded that there is no commonly accepted theory regarding the optimality of exchange rate regimes. In addition, the global financial crisis impact in the financial system of Kosovo is also discussed and it was found that negative impacts of global financial crisis were moderate and indirect.

Double agents and secret agents: the emerging fields of exogenous chemical exchange saturation transfer and T2-exchange magnetic resonance imaging contrast agents for molecular imaging.

Science.gov (United States)

Daryaei, Iman; Pagel, Mark D

2015-01-01

Two relatively new types of exogenous magnetic resonance imaging contrast agents may provide greater impact for molecular imaging by providing greater specificity for detecting molecular imaging biomarkers. Exogenous chemical exchange saturation transfer (CEST) agents rely on the selective saturation of the magnetization of a proton on an agent, followed by chemical exchange of a proton from the agent to water. The selective detection of a biomarker-responsive CEST signal and an unresponsive CEST signal, followed by the ratiometric comparison of these signals, can improve biomarker specificity. We refer to this improvement as a "double-agent" approach to molecular imaging. Exogenous T 2 -exchange agents also rely on chemical exchange of protons between the agent and water, especially with an intermediate rate that lies between the slow exchange rates of CEST agents and the fast exchange rates of traditional T 1 and T 2 agents. Because of this intermediate exchange rate, these agents have been relatively unknown and have acted as "secret agents" in the contrast agent research field. This review exposes these secret agents and describes the merits of double agents through examples of exogenous agents that detect enzyme activity, nucleic acids and gene expression, metabolites, ions, redox state, temperature, and pH. Future directions are also provided for improving both types of contrast agents for improved molecular imaging and clinical translation. Therefore, this review provides an overview of two new types of exogenous contrast agents that are becoming useful tools within the armamentarium of molecular imaging.

Exchange-rate regimes and economic growth: An empirical evaluation

OpenAIRE

Simón Sosvilla-Rivero; María del Carmen Ramos-Herrera

2014-01-01

Based on a dataset of 123 economies, this paper empirically investigates the relation between exchange-rate regimes and economic growth. We find that growth performance is best under intermediate exchange rate regimes, while the smallest growth rates are associated with flexible exchange rates. Nevertheless, this conclusion is tempered when we analyze the countries by income level: even though countries that adopt intermediate exchange-rate regimes are characterized by higher economic growth,...

An Investigation of Proton Conductivity of Vinyltriazole-Grafted PVDF Proton Exchange Membranes Prepared via Photoinduced Grafting

Directory of Open Access Journals (Sweden)

Sinan Sezgin

2014-01-01

Full Text Available Proton exchange membrane fuel cells (PEMFCs are considered to be a promising technology for clean and efficient power generation in the twenty-first century. In this study, high performance of poly(vinylidene fluoride (PVDF and proton conductivity of poly(1-vinyl-1,2,4-triazole (PVTri were combined in a graft copolymer, PVDF-g-PVTri, by the polymerization of 1-vinyl-1,2,4-triazole on a PVDF based matrix under UV light in one step. The polymers were doped with triflic acid (TA at different stoichiometric ratios with respect to triazole units and the anhydrous polymer electrolyte membranes were prepared. All samples were characterized by FTIR and 1H-NMR spectroscopies. Their thermal properties were examined by thermogravimetric analysis (TGA and differential scanning calorimetry (DSC. TGA demonstrated that the PVDF-g-PVTri and PVDF-g-PVTri-(TAx membranes were thermally stable up to 390°C and 330°C, respectively. NMR and energy dispersive X-ray spectroscopy (EDS results demonstrated that PVDF-g-PVTri was successfully synthesized with a degree of grafting of 21%. PVDF-g-PVTri-(TA3 showed a maximum proton conductivity of 6×10-3 Scm−1 at 150°C and anhydrous conditions. CV study illustrated that electrochemical stability domain for PVDF-g-PVTri-(TA3 extended over 4.0 V.

Novel proton exchange membranes based on structure-optimized poly(ether ether ketone ketone)s and nanocrystalline cellulose

Science.gov (United States)

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.

Exchange rate behavior with negative interest rates: Some early negative observations

OpenAIRE

Hameed, Allaudeen S.; Rose, Andrew

2017-01-01

This paper examines exchange rate behavior during the recent period with negative nominal interest rates. We use a daily panel of data on 61 currencies from January 2010 through May 2016, during which five economies - Denmark, the European Economic and Monetary Union, Japan, Sweden, and Switzerland - experienced negative nominal interest rates. We examine both effective exchange rates and bilateral rates; the latter typically measured against the Swiss franc since Switzerland has had the long...

Exchange Rate Fluctuation and the Nigeria Economic Growth

Directory of Open Access Journals (Sweden)

Lawal Adedoyin Isola

2016-11-01

Full Text Available The aim of this study is to investigate the impact of exchange rate fluctuation on economic growth in Nigeria within the context of four profound theories: purchasing power parity; monetary model of exchange rates; the portfolio balance approach; and the optimal currency area theory. Data was collected from the CBN statistical bulletin in Nigeria from 2003– 2013and the Autoregressive Distributed Lag (ARDL model was employed to estimate the model. In the model, real GDP (RGDP was used as the proxy for economic growth while Inflation rate (IF, Exchange rate (EXC, Interest rate (INT and Money Supply(M2 as proxies for other macroeconomic variables. The empirical results show that exchange rate fluctuation has no effect on economic growth in the long run though a short run relationship exist between the two. Based on these findings, this paper recommends that the Central bank for policy purposes should ensure that stern foreign exchange control policies are put in place in order to help in appropriate determination of the value of the exchange rate. This will in the long run help to strengthen the value of the Naira.

Helium Ion Microscopy of proton exchange membrane fuel cell electrode structures

DEFF Research Database (Denmark)

Chiriaev, Serguei; Dam Madsen, Nis; Rubahn, Horst-Günter

2017-01-01

electrode interface structure dependence on ionomer content, systematically studied by Helium Ion Microscopy (HIM). A special focus was on acquiring high resolution images of the electrode structure and avoiding interface damage from irradiation and tedious sample preparation. HIM demonstrated its....... In the hot-pressed electrodes, we found more closed contact between the electrode components, reduced particle size, polymer coalescence and formation of nano-sized polymer fiber architecture between the particles. Keywords: proton exchange membrane fuel cells (PEMFCs); Helium Ion Microscopy (HIM...

Modeling the Volatility of Exchange Rates: GARCH Models

Directory of Open Access Journals (Sweden)

Fahima Charef

2017-03-01

Full Text Available The modeling of the dynamics of the exchange rate at a long time remains a financial and economic research center. In our research we tried to study the relationship between the evolution of exchange rates and macroeconomic fundamentals. Our empirical study is based on a series of exchange rates for the Tunisian dinar against three currencies of major trading partners (dollar, euro, yen and fundamentals (the terms of trade, the inflation rate, the interest rate differential, of monthly data, from jan 2000 to dec-2014, for the case of the Tunisia. We have adopted models of conditional heteroscedasticity (ARCH, GARCH, EGARCH, TGARCH. The results indicate that there is a partial relationship between the evolution of the Tunisian dinar exchange rates and macroeconomic variables.

38 CFR 3.32 - Exchange rates for foreign currencies.

Science.gov (United States)

2010-07-01

... Exchange rates for foreign currencies. When determining the rates of pension or parents' DIC or the amounts... parents' DIC. (1) Because exchange rates for foreign currencies cannot be determined in advance, rates of... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Exchange rates for...

Determining the Exchange Rate: Purchasing Power Parity – PPP

Directory of Open Access Journals (Sweden)

Bangun WIDOYOKO

2018-05-01

Full Text Available This study aimed to examine the effect of inflation on the issue of exchange rate determination of the forward exchange rate on the exchange rate of RMB (Renminbi to Rupiah. Inflation has been chosen as an independent variable because of its close relation to PPP (purchasing power parity theory. Analyses in this research have used logistic analysis with time series data. The data that has been used include exchange rate data with the period 2007-2017 with a sample size of 132 data. The results of this study have shown that inflation is effective in determining the exchange rate.

Does Exchange Rate Volatility Affect Korea's Seaborne Import Volume?

Directory of Open Access Journals (Sweden)

Chang Beom Kim

2017-03-01

Full Text Available This study used monthly data from 2000 to 2015 to analyze the effects of USD/KRW exchange rate volatility on seaborne import volume in Korea. The results of an autoregressive distributed lag (ARDL analysis indicate that USD/KRW exchange rate volatility has a statistically significant negative influence on Korea's seaborne import volume. Moreover, the results of a vector error correction model (VECM analysis found that the USD/KRW exchange rate volatility exhibited short-term unidirectional causality on import volume and real income, and confirmed bidirectional causality between the real effective exchange rate and exchange rate volatility.

Epoxides cross-linked hexafluoropropylidene polybenzimidazole membranes for application as high temperature proton exchange membranes

International Nuclear Information System (INIS)

Yang, Jingshuai; Xu, Yixin; Liu, Peipei; Gao, Liping; Che, Quantong; He, Ronghuan

2015-01-01

Covalently cross-linked hexafluoropropylidene polybenzimidazole (F 6 PBI) was prepared and used to fabricate high temperature proton exchange membranes with enhanced mechanical strength against thermoplastic distortion. Three different epoxides, i.e. bisphenol A diglycidyl ether (R 1 ), bisphenol A propoxylate diglycidyl ether (R 2 ) and poly(ethylene glycol) diglycidyl ether (R 3 ), were chosen as the cross-linkers to investigate the influence of their structures on the properties of the cross-linked F 6 PBI membranes. All the cross-linked F 6 PBI membranes displayed excellent stability towards the radical oxidation. Comparing with the pure F 6 PBI membrane, the cross-linked F 6 PBI membranes showed high acid doping level but less swelling after doping phosphoric acid at elevated temperatures. The mechanical strength at 130 °C was improved from 0.4 MPa for F 6 PBI membrane to a range of 0.8–2.0 MPa for the cross-linked F 6 PBI membranes with an acid doping level as high as around 14, especially for that crosslinking with the epoxide (R 3 ), which has a long linear structure of alkyl ether. The proton conductivity of the cross-linked membranes was increased accordingly due to the high acid doping levels. Fuel cell tests demonstrated the technical feasibility of the acid doped cross-linked F 6 PBI membranes for high temperature proton exchange membrane fuel cells

Exchange Rate and the PRC Foreign Trade

Directory of Open Access Journals (Sweden)

Izotov D. A.

2009-09-01

Full Text Available The stages of exchange rate regulation and foreign trade systems reforming in PRC during the period 1978-2008 are examined. A quantitative assessment of PRC foreign trade parameters reactions to the currency rate dynamics on the national and regional levels is made. Also the import and export impact of potential exchange rate changes is estimated

Effect of glycidyl methacrylate (GMA) incorporation on water uptake and conductivity of proton exchange membranes

Science.gov (United States)

Sproll, Véronique; Schmidt, Thomas J.; Gubler, Lorenz

2018-03-01

The aim of this work was to investigate how hygroscopic moieties like hydrolyzed glycidyl methacrylate (GMA) influence the properties of sulfonated polysytrene based proton exchange membranes (PEM). Therefore, several membranes were synthesized by electron beam treatment of the ETFE (ethylene-alt-tetrafluoroethylene) base film with a subsequent co-grafting of styrene and GMA at different ratios. The obtained membranes were sulfonated to introduce proton conducting groups and the epoxide moiety of the GMA unit was hydrolyzed for a better water absorption. The PEM was investigated regarding its structural composition, water uptake and through-plane conductivity. It could be shown that the density of sulfonic acid groups has a higher influence on the proton conductivity of the PEM than an increased water uptake.

Exchange rate volatility and international trade: The option approach

OpenAIRE

Franke, Günter

1986-01-01

Usually it is argued that an increase in exchange rate volatility reduces the volume of international trade since trading firms are risk averse. This paper shows for risk neutral firms that the expected international trade volume in standardized commodities grows with exchange rate volatility. The firms adjust their trade volume to the exchange rate level. The more favorable the exchange rate is, the higher is the export volume. If the rate drops below some level, exports are stopped. Thus in...

ψ (2 S ) versus J /ψ suppression in proton-nucleus collisions from factorization violating soft color exchanges

Science.gov (United States)

Ma, Yan-Qing; Venugopalan, Raju; Watanabe, Kazuhiro; Zhang, Hong-Fei

2018-01-01

We argue that the large suppression of the ψ (2 S ) inclusive cross section relative to the J /ψ inclusive cross section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the color glass condensate (CGC) effective field theory and employ an improved color evaporation model (ICEM) to describe their hadronization into quarkonium at large distances. The combined CGC+ICEM model provides a quantitative description of J /ψ and ψ (2 S ) data in proton-proton (p+p) collisions from both RHIC and the LHC. Factorization breaking effects in hadronization, due to additional parton comovers in the nucleus, are introduced heuristically by imposing a cutoff Λ , representing the average momentum kick from soft color exchanges, in the ICEM. Such soft exchanges have no perceptible effect on J /ψ suppression in p+A collisions. In contrast, the interplay of the physics of these soft exchanges at large distances, with the physics of semihard rescattering at short distances, causes a significant additional suppression of ψ (2 S ) yields relative to that of the J /ψ . A good fit of all RHIC and LHC J /ψ and ψ (2 S ) data, for transverse momenta P⊥≤5 GeV in p+p and p+A collisions, is obtained for Λ ˜10 MeV.

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

Science.gov (United States)

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 high 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

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

International Nuclear Information System (INIS)

Soudackov, Alexander V.; Hammes-Schiffer, Sharon

2015-01-01

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 high 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

Overcoming Fear of Floating: Exchange Rate Policies in Chile.

OpenAIRE

Jose De Gregorio; Andrea Tokman R.

2004-01-01

The paper reviews the exchange rate management experience in Chile, with particular emphasis on the floating exchange rate regime and its two forex intervention episodes. It presents evidence on Chile’s favorable conditions to face exchange rate shocks: a well-developed financial sector, that offers hedging opportunities taken up by the corporate sector to decrease its vulnerability through balance sheet effects; and a low and decreasing level of passthrough from the exchange rate to prices. ...

The tail index of exchange rate returns

NARCIS (Netherlands)

C.G. Koedijk (Kees); M. Schafgans (Marcia); C.G. de Vries (Casper)

1990-01-01

textabstractIn the literature on the empirical distribution of foreign exchange rates there is now consensus that exchange rate yields are fat-tailed. Three problems, however, persist: (1) Which class of distribution functions is most appropriate? (2) Are the parameters of the distribution invariant

The Foreign Exchange Rate Exposure of Nations

OpenAIRE

Entorf, Horst; Moebert, Jochen; Sonderhof, Katja

2007-01-01

Following the well-known approach by Adler and Dumas (1984), we evaluate the foreign exchange rate exposure of nations. Results based on data from 27 countries show that national foreign exchange rate exposures are significantly related to the current trade balance variables of corresponding economies.

PRO-QUEST: a rapid assessment method based on progressive saturation for quantifying exchange rates using saturation times in CEST.

Science.gov (United States)

Demetriou, Eleni; Tachrount, Mohamed; Zaiss, Moritz; Shmueli, Karin; Golay, Xavier

2018-03-05

To develop a new MRI technique to rapidly measure exchange rates in CEST MRI. A novel pulse sequence for measuring chemical exchange rates through a progressive saturation recovery process, called PRO-QUEST (progressive saturation for quantifying exchange rates using saturation times), has been developed. Using this method, the water magnetization is sampled under non-steady-state conditions, and off-resonance saturation is interleaved with the acquisition of images obtained through a Look-Locker type of acquisition. A complete theoretical framework has been set up, and simple equations to obtain the exchange rates have been derived. A reduction of scan time from 58 to 16 minutes has been obtained using PRO-QUEST versus the standard QUEST. Maps of both T 1 of water and B 1 can simply be obtained by repetition of the sequence without off-resonance saturation pulses. Simulations and calculated exchange rates from experimental data using amino acids such as glutamate, glutamine, taurine, and alanine were compared and found to be in good agreement. The PRO-QUEST sequence was also applied on healthy and infarcted rats after 24 hours, and revealed that imaging specificity to ischemic acidification during stroke was substantially increased relative to standard amide proton transfer-weighted imaging. Because of the reduced scan time and insensitivity to nonchemical exchange factors such as direct water saturation, PRO-QUEST can serve as an excellent alternative for researchers and clinicians interested to map pH changes in vivo. © 2018 International Society for Magnetic Resonance in Medicine.

Optimization of 7-T Chemical Exchange Saturation Transfer Parameters for Validation of Glycosaminoglycan and Amide Proton Transfer of Fibroglandular Breast Tissue

NARCIS (Netherlands)

Dula, Adrienne N.; Dewey, Blake E.; Arlinghaus, Lori R.; Williams, Jason M.; Klomp, DWJ; Yankeelov, Thomas E.; Smith, Seth

Purpose: To (a) implement simulation-optimized chemical exchange saturation transfer (CEST) measurements sensitive to amide proton transfer (APT) and glycosaminoglycan (GAG) hydroxyl proton transfer effects in the human breast at 7 T and (b) determine the reliability of these techniques for

Exchange rates and climate change: An application of fund

NARCIS (Netherlands)

Tol, R.S.J.

2006-01-01

As economic and emissions scenarios assume convergence of per capita incomes, they are sensitivity to the exchange rate used for international comparison. Particularly, developing countries are project to grow slower with a purchasing power exchange rate than with a market exchange rate. Different

Exchange rate predictability and state-of-the-art models

OpenAIRE

Yeșin, Pınar

2016-01-01

This paper empirically evaluates the predictive performance of the International Monetary Fund's (IMF) exchange rate assessments with respect to future exchange rate movements. The assessments of real trade-weighted exchange rates were conducted from 2006 to 2011, and were based on three state-of-the-art exchange rate models with a medium-term focus which were developed by the IMF. The empirical analysis using 26 advanced and emerging market economy currencies reveals that the "diagnosis" of ...

Exchange-Rate Unification with Black Market Leakages; Russia 1992

OpenAIRE

Linda S. Goldberg

1993-01-01

In 1992 Russia unified the multiple exchange rates that had applied to international transactions. This paper describes the multiple exchange rate system that existed in Russia prior to mid-1992 and undertakes a theoretical exploration of the effects of the exchange rate unification that took place in July 1992. The model developed here allows for leakages between official and black markets and permits flexibility of the exchange rates in both official and parallel currency markets. Within th...

Side-chain dynamics of a detergent-solubilized membrane protein: Measurement of tryptophan and glutamine hydrogen-exchange rates in M13 coat protein by 1H NMR spectroscopy

International Nuclear Information System (INIS)

O'Neil, J.D.J.; Sykes, B.D.

1989-01-01

M13 coat protein is a small (50 amino acids) lipid-soluble protein that becomes an integral membrane protein during the infection stage of the life cycle of the M13 phage and is therefore used as a model membrane protein. To study side-chain dynamics in the protein, the authors have measured individual hydrogen-exchange rates for a primary amide in the side chain of glutamine-15 and for the indole amine of tryptophan-26. The protein was solubilized with the use of perdeuteriated sodium dodecyl sulfate (SDS), and hydrogen-exchange rates were measured by using 1 H nuclear magnetic resonance spectroscopy. The glutamine-15 syn proton exchanged at a rate identical with that in glutamine model peptides except that the pH corresponding to minimum exchange was elevated by about 1.5 pH units. The tryptophan-26 indole amine proton exchange was biphasic, suggesting that two populations of tryptophan-26 exist. It is suggested that the two populations may reflect protein dimerization or aggregation in the SDS micelles. The pH values of minimum exchange for tryptophan-26 in both environments were also elevated by 1.3-1.9 pH units. This phenomenon is reproduced when small tryptophan- and glutamine-containing hydrophobic peptides are dissolved in the presence of SDS micelles. The electrostatic nature of this phenomenon is proven by showing that the minimum pH for exchange can be reduced by dissolving the hydrophobic peptides in the positively charged detergent micelle dodecyltrimethylammonium bromide

KRW/USD Exchange Rate Volatility and Efficient Risk Management

OpenAIRE

Sang-Yong Joo; Chae-Shick Chung; Young-Woo Lee

1999-01-01

This thesis analyzes the relationship between the exchange rate of Korean Won and US dollar and the amount of foreign exchange, and studies the direction of the amendment of the risk control of foreign exchange. The GARCH (Generalized Auto Regressive Conditional Heteroscedasticity) model which visually embodies the auto-regress of the wave of exchange rate shows that the amount of trade will enhance the fluidity of the exchange rate, that is, the various expects of the participators of the ma...

Fluctuation Dynamics of Exchange Rates on Indian Financial Market

Science.gov (United States)

Sarkar, A.; Barat, P.

Here we investigate the scaling behavior and the complexity of the average daily exchange rate returns of the Indian Rupee against four foreign currencies namely US Dollar, Euro, Great Britain Pound and Japanese Yen. Our analysis revealed that the average daily exchange rate return of the Indian Rupee against the US Dollar exhibits a persistent scaling behavior and follow Levy stable distribution. On the contrary the average daily exchange rate returns of the other three foreign currencies show randomness and follow Gaussian distribution. Moreover, it is seen that the complexity of the average daily exchange rate return of the Indian Rupee against US Dollar is less than the other three exchange rate returns.

Forecasting Exchange Rate Volatility in the Presence of Jumps

DEFF Research Database (Denmark)

Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

We study measures of foreign exchange rate volatility based on high-frequency (5-minute) $/DM exchange rate returns using recent nonparametric statistical techniquesto compute realized return volatility and its separate continuous sample path and jumpcomponents, and measures based on prices...... of exchange rate futures options, allowingcalculation of option implied volatility. We find that implied volatility is an informationallyefficient but biased forecast of future realized exchange rate volatility. Furthermore,we show that log-normality is an even better distributional approximation...... for impliedvolatility than for realized volatility in this market. Finally, we show that the jump componentof future realized exchange rate volatility is to some extent predictable, and thatoption implied volatility is the dominant forecast of the future jump component....

A Range-Based Multivariate Model for Exchange Rate Volatility

NARCIS (Netherlands)

B. Tims (Ben); R.J. Mahieu (Ronald)

2003-01-01

textabstractIn this paper we present a parsimonious multivariate model for exchange rate volatilities based on logarithmic high-low ranges of daily exchange rates. The multivariate stochastic volatility model divides the log range of each exchange rate into two independent latent factors, which are

MONETARY MODELS AND EXCHANGE RATE DETERMINATION ...

African Journals Online (AJOL)

Power Party [PPP] based on the law of one price asserts that the change in the exchange rate between .... exchange in international economic transactions has made it vitally evident that the management of ... One lesson from this episode is to ...

Exchange Rate Volatility and Investment: A Panel Data Cointegration Approach

Directory of Open Access Journals (Sweden)

Ibrahima Amadou DIALLO

2015-05-01

Full Text Available This paper examines the link between real exchange rate volatility and domestic investment by using panel data cointegration techniques. We study the empirical connection between real effective exchange rate volatility and investment for 51 developing countries (23 low-income and 28 middle-income countries. The theoretical relationship between investment and real exchange rate volatility predicts that the effects of exchange rate uncertainty on profits are ambiguous. The empirical results illustrate that real effective exchange rate volatility has a strong negative impact on investment. This outcome is robust in low income and middle income countries, and by using an alternative measurement of exchange rate volatility.

The Skill-Biased Effects of Exchange Rate Fluctuations

OpenAIRE

Boris Kaiser; Michael Siegenthaler

2015-01-01

This paper examines the linkages between real exchange rate movements and firms' skill demand. Real exchange rate movements may affect unskilled workers differently than skilled workers because of skill-specific adjustment costs, or because exchange rates lead to changes in relative factor prices and firms' competition intensity. Using panel data on Swiss manufacturers, we find that an appreciation increases high-skilled and reduces low-skilled employment in most firms, while total employment...

Asymmetric Exchange Rate Exposure - Research in Southeast Asian Countries

Directory of Open Access Journals (Sweden)

Minh Thi Hong Le

2017-04-01

Full Text Available The study aims to analyse the impact of exchange rate exposure on stock returns in six countries representative of Southeast Asia, including Indonesia, Malaysia, Philippines, Singapore, Thailand and Vietnam from 2009 to 2014. Both nominal and real exchange rates are taken into account for evaluating exchange rate fluctuations via panel data. In order to achieve this goal, a panel regressive estimation approach is proposed in which a GLS model is firstly used to treat heteroscedasticity in the panel data and, then, a GMM estimator is employed to ensure the consistency of the estimates. The results point out that the exchange rate exposure of these countries is asymmetric. At market level, for a rise in the exchange rate (or local currency depreciates, the average stock returns tend to decrease. However, due to the favourable impact of currency depreciation on the net export position, the reduction speed of stock returns is faster than the rising speed of the exchange rate.

Triangular arbitrage as an interaction among foreign exchange rates

Science.gov (United States)

Aiba, Yukihiro; Hatano, Naomichi; Takayasu, Hideki; Marumo, Kouhei; Shimizu, Tokiko

2002-07-01

We first show that there are in fact triangular arbitrage opportunities in the spot foreign exchange markets, analyzing the time dependence of the yen-dollar rate, the dollar-euro rate and the yen-euro rate. Next, we propose a model of foreign exchange rates with an interaction. The model includes effects of triangular arbitrage transactions as an interaction among three rates. The model explains the actual data of the multiple foreign exchange rates well.

Causes and Results of Exchange Rate Intervention Under Inflation Targeting

Directory of Open Access Journals (Sweden)

Bora Suslu

2012-06-01

Full Text Available Under inflation targeting, central banks exchange rate interventions are discussed frequently in the economic literature recently. Effectiveness of intervention in exchange rate under inflation targeting are examined from three perspectives. These are expectations of the actors and the impact on the variance, reserve accumulation and the cost of sterilization. Since 2003 the Central Bank of Turkey has intervened exchange rate with both direct and indirect methods. The purpose of this study is to examine the results of these three aspects of the CBRT and the foreign exchange interventions. We found that by logit analysis under the inflation targeting of CBRT as a result of the intervention of exchange rate is effect expectations of economic unit and reduce of exchange rate the variance; after thes intervention the variance of exchange rate and cost of sterilization are increased. In this respect, the effectiveness of the intervention of the Central Bank exchange rate market is only reserve accumulation

Novel membranes for proton exchange membrane fuel cell operation above 120°C. Final report for period October 1, 1998 to December 31, 1999

Energy Technology Data Exchange (ETDEWEB)

Srinivasan, Supramaniam [Princeton Univ., NJ (United States); Lee, Seung-Jae [Princeton Univ., NJ (United States); Costamagna, Paola [Princeton Univ., NJ (United States); Yang, Christopher [Princeton Univ., NJ (United States); Adjemian, Kevork [Princeton Univ., NJ (United States); Bocarsly, Andrew [Princeton Univ., NJ (United States); Ogden, Joan M. [Princeton Univ., NJ (United States); Benziger, Jay [Princeton Univ., NJ (United States)

2000-05-01

In this project we investigated the experimental performance of three new classes of membranes, composites of perfluorosulfonic acid polymers with heteropolyacides, hydrated oxides and fast proton conducting glasses, which are promising candidates as electrolytes for proton exchange membrane fuel cells (PEMFCs), capable of operation at temperatures above 120°C. The motivations for PEMFC's operation at this temperature are to: 1) minimize the CO poisoning problem (adsorption of CO onto the platinum catalyst is greatly reduced at these temperatures), 2) find better solutions for the water and thermal management problems in proton exchange membrane fuel cells, 3) find potentially lower cost materials for proton exchange membranes. We prepared and characterized a variety of novel membrane materials. The most promising of these have been evaluated for performance in a single, small area (5cm²) fuel cell run on hydrogen and oxygen. Our results establish the technical feasibility of PEMFC operation above 120°C.

What determines the exchange rate: economic factors or market sentiment?

OpenAIRE

Gregory P. Hopper

1997-01-01

Do economic factors influence exchange rates? Or does market sentiment play a bigger role? Are short-run exchange rates predictable? Greg Hopper reviews exchange-rate economics, focusing on what is predictable and what isn't. He also examines the practical implications of exchange-rate theories for currency option pricing, risk management, and portfolio selection.

Halogen–Metal Exchange on Bromoheterocyclics with Substituents Containing an Acidic Proton via Formation of a Magnesium Intermediate

Directory of Open Access Journals (Sweden)

Qingqiang Tian

2017-11-01

Full Text Available A selective and practical bromine–metal exchange on bromoheterocyclics bearing substituents with an acidic proton under non-cryogenic conditions was developed by a simple modification of an existing protocol. Our protocol of using a combination of i-PrMgCl and n-BuLi has not only solved the problem of intermolecular quenching that often occurred when using alkyl lithium alone as the reagent for halogen–lithium exchange, but also offered a highly selective method for performing bromo–metal exchange on dibrominated arene compounds through chelation effect.

Determination of the Optimal Exchange Rate Via Control of the Domestic Interest Rate in Nigeria

Directory of Open Access Journals (Sweden)

Virtue U. Ekhosuehi

2014-01-01

Full Text Available An economic scenario has been considered where the government seeks to achieve a favourable balance-of-payments over a fixed planning horizon through exchange rate policy and control of the domestic interest rate. The dynamics of such an economy was considered in terms of a bounded optimal control problem where the exchange rate is the state variable and the domestic interest rate is the control variable. The idea of balance-of-payments was used as a theoretical underpinning to specify the objective function. By assuming that, changes in exchange rates were induced by two effects: the impact of the domestic interest rate on the exchange rate and the exchange rate system adopted by the government. Instances for both fixed and flexible optimal exchange rate regimes have been determined. The use of the approach has been illustrated employing data obtained from the Central Bank of Nigeria (CBN statistical bulletin. (original abstract

Water Soluble Polymers as Proton Exchange Membranes for Fuel Cells

Directory of Open Access Journals (Sweden)

Bing-Joe Hwang

2012-03-01

Full Text Available The relentless increase in the demand for useable power from energy-hungry economies continues to drive energy-material related research. Fuel cells, as a future potential power source that provide clean-at-the-point-of-use power offer many advantages such as high efficiency, high energy density, quiet operation, and environmental friendliness. Critical to the operation of the fuel cell is the proton exchange membrane (polymer electrolyte membrane responsible for internal proton transport from the anode to the cathode. PEMs have the following requirements: high protonic conductivity, low electronic conductivity, impermeability to fuel gas or liquid, good mechanical toughness in both the dry and hydrated states, and high oxidative and hydrolytic stability in the actual fuel cell environment. Water soluble polymers represent an immensely diverse class of polymers. In this comprehensive review the initial focus is on those members of this group that have attracted publication interest, principally: chitosan, poly (ethylene glycol, poly (vinyl alcohol, poly (vinylpyrrolidone, poly (2-acrylamido-2-methyl-1-propanesulfonic acid and poly (styrene sulfonic acid. The paper then considers in detail the relationship of structure to functionality in the context of polymer blends and polymer based networks together with the effects of membrane crosslinking on IPN and semi IPN architectures. This is followed by a review of pore-filling and other impregnation approaches. Throughout the paper detailed numerical results are given for comparison to today’s state-of-the-art Nafion® based materials.

Molecular simulations of hydrated proton exchange membranes. The structure

Energy Technology Data Exchange (ETDEWEB)

Marcharnd, Gabriel [Duisburg-Essen Univ., Essen (Germany). Lehrstuhl fuer Theoretische Chemie; Bordeaux Univ., Talence (France). Dept. of Chemistry; Bopp, Philippe A. [Bordeaux Univ., Talence (France). Dept. of Chemistry; Spohr, Eckhard [Duisburg-Essen Univ., Essen (Germany). Lehrstuhl fuer Theoretische Chemie

2013-01-15

The structure of two hydrated proton exchange membranes for fuel cells (PEMFC), Nafion {sup registered} (Dupont) and Hyflon {sup registered} (Solvay), is studied by all-atom molecular dynamics (MD) computer simulations. Since the characteristic times of these systems are long compared to the times for which they can be simulated, several different, but equivalent, initial configurations with a large degree of randomness are generated for different water contents and then equilibrated and simulated in parallel. A more constrained structure, analog to the newest model proposed in the literature based on scattering experiments, is investigated in the same way. One might speculate that a limited degree of entanglement of the polymer chains is a key feature of the structures showing the best agreement with experiment. Nevertheless, the overall conclusion remains that the scattering experiments cannot distinguish between the several, in our view equally plausible, structural models. We thus find that the characteristic features of experimental scattering curves are, after equilibration, fairly well reproduced by all systems prepared with our method. We thus study in more detail some structural details. We attempt to characterize the spatial and size distribution of the water rich domains, which is where the proton diffusion mostly takes place, using several clustering algorithms. (orig.)

Modelling Exchange Rate Volatility by Macroeconomic Fundamentals in Pakistan

OpenAIRE

Munazza Jabeen; Saud Ahmad Khan

2014-01-01

What drives volatility in foreign exchange market in Pakistan? This paper undertakes an analysis of modelling exchange rate volatility in Pakistan by potential macroeconomic fundamentals well-known in the economic literature. For this, monthly data on Pak Rupee exchange rates in the terms of major currencies (US Dollar, British Pound, Canadian Dollar and Japanese Yen) and macroeconomics fundamentals is taken from April, 1982 to November, 2011. The results show thatthe PKR-USD exchange rate vo...

The Determinants of won/dollar Exchange Rate Volatility and Policy Recommendations

Directory of Open Access Journals (Sweden)

Chae-Shick Chung

1998-09-01

Full Text Available This thesis analyzed the feature and different points of the changing of the exchange rate of Korea won against US dollar, then discussed the direction of the completion of Korea exchange rate system. The prediction result of the model GARCH which vividly shows the phenomenon of the auto-regression of the exchange rate has indicated the level of the exchange rate yesterday could explain the circumstance of the change of exchange rate today. Meanwhile, the policy of the US exchange rate will affect the exchange rate of Korea won against US dollar and the volatility of foreign exchange rate. In the present situation of Korean economy in which the liberalization of capital and the independence of the central bank has been established, the choosing range of the exchange system could only be completely changeable exchange rate system or exchange rate system of multilateral arrangement like Europe. However, in terms of the condition of the world economy, the introduction of the latter system is too early. There is an idea that under the changeable exchange rate system which is the only choice, it is the right time to activate the main body of private economy, the financial derivatives market in which the exchange risk could be trade-off. Government should work on and create a policy that would be able to satisfy the expectations of the market participants.

[Effect of high magnesium ion concentration on the electron transport rate and proton exchange in thylakoid membranes in higher plants].

Science.gov (United States)

Ignat'ev, A R; Khorobrykh, S A; Ivanov, B N

2001-01-01

The effects of magnesium ion concentration on the rate of electron transport in isolated pea thylakoids were investigated in the pH range from 4.0 up to 8.0. In the absence of magnesium ions in the medium and in the presence of 5 mM MgCl2 in the experiments not only without added artificial acceptors but also with ferricyanide or methylviologen as an acceptor, this rate had a well-expressed maximum at pH 5.0. It was shown that, after depression to minimal values at pH 5.5-6.5, it gradually rose with increasing pH. An increase in magnesium ion concentration up to 20 mM essentially affected the electron transfer rate: it decreased somewhat at pH 4.0-5.0 but increased at higher pH values. At this magnesium ion concentration, the maximum rate was at pH 6.0-6.5 and the minimum, at pH 7.0. Subsequent rise upon increasing pH to 8.0 was expressed more sharply. The influence of high magnesium ion concentration on the rate of electron transport was not observed in the presence of gramicidin D. It was found that without uncoupler, the changes in the electron transfer rate under the influence of magnesium ions correlated to the changes in the first-order rate constant of the proton efflux from thylakoids. It is supposed that the change in the ability of thylakoids to keep protons by the action of magnesium ions is the result of electrostatic interactions of these ions with the charges on the external surface of membranes. A possible role of regulation of the electron transport rate by magnesium ions in vivo is discussed.

The Exchange Rate Exposure of Danish Non-Financial Companies

DEFF Research Database (Denmark)

Aabo, Tom

1999-01-01

of the extra-market exchange rate exposure of individual companies. As such, only a minority of companies has significant exposures when using the effective Danish exchange rate in an OLS regression analysis while half of the companies have significant exposures when using five main exchange rates. A GARCH(1......A shortcut to measuring exchange rate exposure at the company level can be to exploit the information content in the stock prices. A regression analysis is conducted for the main Danish non-financial companies. The use of one all-comprising exchange rate indicator fails to address the complexity......,1) regression analysis is shown to further improve the detection of exposures. The success in identifying exposures for Danish non-financial companies is in contrast to earlier US studies and is relevant in a European context....

Chartist Trading in Exchange Rate Theory

OpenAIRE

Selander, Carina

2006-01-01

This thesis consists of four papers, of which paper 1 and 4 are co-written with Mikael Bask. Paper [1] implements chartists trading in a sticky-price monetary model for determining the exchange rate. It is demonstrated that chartists cause the exchange rate to "overshoot the overshooting equilibrium" of a sticky-price monetary model. Chartists base their trading on a short-long moving average. The importance of technical trading depends inversely on the time horizon in currency trade. The exc...

Labour Demand and Exchange Rate Volatility

OpenAIRE

Udo Broll; Sabine Hansen

2004-01-01

The purpose of this paper is to assess under what conditions exchange rate volatility exerts a positive effect on a firm's labour demand. As the exchange rate volatility increases, so does the value of the export option provided the firm under study is flexible. Flexibility is important because it gives the firm option value. Higher volatility increases the potential gains from trade and may increase the demand for labour. This may explain part of the mixed empirical findings regarding the ef...

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

Science.gov (United States)

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.

Synthesis, crystal structure, and H/D exchange of the inside protonated form of the cage imine 4,8,12-triaza-1-azoniatricyclo[6.6.3.2(4,12)]nonadec-1(15)-ene. A model for proton transfer through an aliphatic membrane

DEFF Research Database (Denmark)

Springborg, Johan; Nielsen, Bente; Olsen, Carl Erik

2002-01-01

belonging to the triazacyclononane entity. The imine double bond is situated between the N-atom of the triazacyclononane entity and the C-atom belonging to one of the three trimethylene bridges. The imine 2 is stable in acidic solution and the inside coordinated proton is very robust in acidic solution......, which gave K-im = 1.57(1) x 10(-5) M at 25 degreesC, DeltaSdegrees = -83(1) J mol(-1) K-1 and DeltaHdegrees = 2,6(3) kJ mol(-1) at 1 = 1.0 M (NaCl). The inside coordinated proton in 3 is labile in basic solution and the rate for NH/ND exchange was determined by H-1 NMR at three different temperatures....... The reaction followed the expression k(obs) = k(ex)[OD-] with k(ex) = 0.0978(30) dm(3) mol (1) s(-1) at 25 degreesC, DeltaSdegrees = 87(4) J mol(-1) K-1, and DeltaHdegrees = 104.9(11) kJ mol(-1) at I = 1.0 M (NaCl). The exchange rate is more than 5 x 106 times faster than that of the parent saturated cage 1...

real exchange rate misalignment and economic performance in ...

African Journals Online (AJOL)

... effects of real exchange rate misalignment on economic performance in Nigeria. .... main factors that impacts on real exchange rate in India .... financial assets and ignores non-economic factor such as .... and fiscal policies to control inflation.

Basic Exchange Rate Theories

NARCIS (Netherlands)

J.G.M. van Marrewijk (Charles)

2005-01-01

textabstractThis four-chapter overview of basic exchange rate theories discusses (i) the elasticity and absorption approach, (ii) the (long-run) implications of the monetary approach, (iii) the short-run effects of monetary and fiscal policy under various economic conditions, and (iv) the transition

Monetary policy and exchange rate dynamics: the exchange rate as a shock absorber

Czech Academy of Sciences Publication Activity Database

Audzei, Volha; Brázdik, F.

2015-01-01

Roč. 65, č. 5 (2015), s. 391-410 ISSN 0015-1920 Institutional support: PRVOUK-P23 Keywords : Czech Republic * exchange rates * sign restrictions Subject RIV: AH - Economics Impact factor: 0.449, year: 2015 http://journal.fsv.cuni.cz/storage/1340_audzei.pdf

Current Account and Real Exchange Rate Dynamics in Indonesia

Directory of Open Access Journals (Sweden)

Firman Mochtar

2015-07-01

Full Text Available We analyze the role of both permanent and temporary factors in affecting the Indonesian current account and real exchange dynamics before and after 2000. Adopting Lee and Chinn (1998; 2006 approach as well as Chinn et al. (2007, two results stand out. First, we confirm that the behavior of the real exchange rate has altered since 2000. Identifications show that permanent shocks are the primary causes for the movement of the real exchange rate after 2000, while in the period before 2000, the Indonesian real exchange rate changes are characterized by greater dominance of temporary shocks. The apparent change in the real exchange rate behavior may be strongly justified by the implementation of free-floating exchange rate system since August 1997. Second, the shift of the real exchange rate behavior after 2000 does not necessarily affect the current account dynamics. Empirical evidence confirms that the variance of current account post 2000 remains largely due to temporary shocks. Albeit having increasing influence, permanent shocks have insignificant effect in explaining fluctuations of the current account. In this sense, the current account surplus after 2000 is attributed largely to nominal variables such as price increase, while the impact of productivity improvement is still limited.

Real Exchange Rate Dynamics in a Small, Primary-Exporting Country

OpenAIRE

Mohsin S. Khan; Peter J. Montiel

1987-01-01

Although the nominal exchange rate is often used as a policy instrument in small, primary-commodity-exporting countries, the real exchange rate is an endogenous variable that responds to both exogenous and policyinduced shocks. This paper examines the dynamic effects on the real exchange rate of various shocks, such as devaluation, fiscal and trade policies, and changes in the terms of trade and foreign real interest rates. Because the path of the real exchange rate differs for different type...

Deep-inelastic electron-proton diffraction

International Nuclear Information System (INIS)

Dainton, J.B.

1995-11-01

Recent measurements by the H1 collaboration at HERA of the cross section for deep-inelastic electron-proton scattering in which the proton interacts with minimal energy transfer and limited 4-momentum transfer squared are presented in the form of the contribution F 2 D(3) to the proton structure function F 2 . By parametrising the cross section phenomenologically in terms of a leading effective Regge pole exchange and comparing the result with a similar parametrisation of hadronic pp physics, the proton interaction is demonstrated to be dominantly of a diffractive nature. The quantitative interpretation of the parametrisation in terms of the properties of an effective leading Regge pole exchange, the pomeron (IP), shows that there is no evidence for a 'harder' BFKL-motivated IP in such deep-inelastic proton diffraction. The total contribution of proton diffraction to deep-inelastic electron-proton scattering is measured to be ∝10% and to be rather insensitive to Bjorken-x and Q 2 . A first measurement of the partonic structure of diffractive exchange is presented. It is shown to be readily interpreted in terms of the exchange of gluons, and to suggest that the bulk of diffractive momentum transfer is carried by a leading gluon. (orig.)

Fear of Floating: Exchange Rate Flexibility Indices

OpenAIRE

Reinhart, Carmen

2001-01-01

Many emerging market countries have suffered financial crises. One view blames soft pegs for these crises. Adherents to that view suggest that countries move to corner solutions--hard pegs or floating exchange rates. We analyze the behavior of exchange rates, reserves, and interest rates to assess whether there is evidence that country practice is moving toward corner solutions. We focus on whether countries that claim they are floating are indeed doing so. We find that countries that say th...

Degradation modeling and operational optimization for improving the lifetime of high-temperature PEM (proton exchange membrane) fuel cells

International Nuclear Information System (INIS)

Kim, Jintae; Kim, Minjin; Kang, Taegon; Sohn, Young-Jun; Song, Taewon; Choi, Kyoung Hwan

2014-01-01

High-temperature PEMFCs (proton exchange membrane fuel cells) using PA (phosphoric acid)-doped PBI (polybenzimidazole) membranes have received attention as a potential solution to several of the issues with traditional low-temperature PEMFCs. However, the durability of high-temperature PEMFCs deteriorates rapidly with increasing temperature, although its performance improves. This characteristic makes it difficult to select the proper operating temperature to achieve its target lifetime. In this paper, to resolve this problem, models were developed to predict the performance and durability of the high-temperature PEMFC as a function of operating temperature. The optimal operating temperature was then determined for a variety of lifetimes. Theoretical model to estimate cell performance and empirical model to predict the degradation rate of cell performance were constructed, respectively. The prediction results of the developed models agreed well with the experimental data. From the simulation, we could obtain higher average cell performances by optimizing the operating temperature for the given target lifetime compared to the cell performance at some temperatures determined using an existing rule of thumb. It is expected that the proposed methodologies will lead to the more rapid commercialization of this technology in such applications as stationary and automotive fuel cell systems. - Highlights: • High-temperature PEMFCs (proton exchange membrane fuel cells). • Operational optimization for improving the lifetime. • Development of the degradation modeling for high-temperature PEMFCs

Rate of oxygen isotope exchange between selenate and water.

Science.gov (United States)

Kaneko, Masanori; Poulson, Simon R

2012-04-17

The rate of oxygen isotope exchange between selenate and water was investigated at conditions of 10 to 80 °C and pH -0.6 to 4.4. Oxygen isotope exchange proceeds as a first-order reaction, and the exchange rate is strongly affected by reaction temperature and pH, with increased rates of isotope exchange at higher temperature and lower pH. Selenate speciation (HSeO(4)(-) vs SeO(4)(2-)) also has a significant effect on the rate of isotope exchange. The half-life for isotope exchange at example natural conditions (25 °C and pH 7) is estimated to be significantly in excess of 10(6) years. The very slow rate of oxygen isotope exchange between selenate and water under most environmental conditions demonstrates that selenate-δ(18)O signatures produced by biogeochemical processes will be preserved and hence that it will be possible to use the value of selenate-δ(18)O to investigate the biogeochemical behavior of selenate, in an analogous fashion to the use of sulfate-δ(18)O to study the biogeochemical behavior of sulfate.

A concise guide to sustainable PEMFCs: recent advances in improving both oxygen reduction catalysts and proton exchange membranes.

Science.gov (United States)

Scofield, Megan E; Liu, Haiqing; Wong, Stanislaus S

2015-08-21

The rising interest in fuel cell vehicle technology (FCV) has engendered a growing need and realization to develop rational chemical strategies to create highly efficient, durable, and cost-effective fuel cells. Specifically, technical limitations associated with the major constituent components of the basic proton exchange membrane fuel cell (PEMFC), namely the cathode catalyst and the proton exchange membrane (PEM), have proven to be particularly demanding to overcome. Therefore, research trends within the community in recent years have focused on (i) accelerating the sluggish kinetics of the catalyst at the cathode and (ii) minimizing overall Pt content, while simultaneously (a) maximizing activity and durability as well as (b) increasing membrane proton conductivity without causing any concomitant loss in either stability or as a result of damage due to flooding. In this light, as an example, high temperature PEMFCs offer a promising avenue to improve the overall efficiency and marketability of fuel cell technology. In this Critical Review, recent advances in optimizing both cathode materials and PEMs as well as the future and peculiar challenges associated with each of these systems will be discussed.

Choice of optimal exchange rate system For the Republic of Croatia

Directory of Open Access Journals (Sweden)

Dražen Koški

2008-12-01

Full Text Available The aim of research whose results are presented in this article was to choose the optimal system of exchange rate for the Republic of Croatia, of course before its accession to EU. The analyzed exchange rate systems here range from free-floating exchange rate to system without domestic currency in circulation. Naturally, the classification of International Monetary Fond is included in it. After that, the comparison of basic economic advantages and disadvantages of the fixed exchange rate in relation to floating exchange rate were carried out. Although the question is about the extreme systems, disregarding the system without domestic currency in circulation, their comparison makes possible completely satisfactory basis for the right conclusions on the choice of optimal exchange rate system for the Republic of Croatia. Considering its economic particularities, the system of managed-floating exchange rate without proclaimed exchange direction in advance is certainly optimal for the Republic of Croatia. Namely, within the framework of this system the limited floating exchange rates decrease the foreign exchange risk allowing to monetary authorities, at least partly, the independent monetary policy

DOES CURRENCY SUBSTITUTION AFFECT EXCHANGE RATE VOLATILITY?

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Hisao Kumamoto

2014-10-01

Full Text Available This study investigates the impacts of the degree of currency substitution on nominal exchange rate volatility in seven countries (Indonesia, the Philippines, the Czech Republic, Hungary, Poland, Argentina, and Peru. We use the Threshold ARCH model to consider the ratchet effect of currency substitution and sample periods in the 2000s, during which time the economies of the sample countries stabilized, while the U.S. dollar and euro depreciated against other major currencies following the recent global financial crisis. The presented empirical analyses show that the degree of currency substitution has significant positive effects on the conditional variance of the depreciation rate of the nominal exchange rate in most sample countries. Moreover, a shock to the depreciation rate of the nominal exchange rate has asymmetric effects on the conditional variance, depending on the sign. One possible explanation for these differential effects is the existence of the ratchet effect of currency substitution.

Exchange-rate-based stabilization in Argentina and Chile : a fresh look

OpenAIRE

Kiguel, Miguel A.; Liviatan, Nissan

1994-01-01

Exchange-rate-based stabilization is designed to reduce inflation by using the exchange rate as the main nominal anchor. This does not necessarily mean a fixed exchange rate. A crawling peg with a low rate of depreciation or a pre-announced gradual reduction in the rate of devaluation are alternative ways to use the exchange rate as a nominal anchor. Exchange-rate-based stabilization (ERBS) has been widely used in the high-inflation economies of Latin America. Argentina, Chile, and Uruguay ad...

Genome-Wide Identification and Analysis of Arabidopsis Sodium Proton Antiporter (NHX and Human Sodium Proton Exchanger (NHE Homologs in Sorghum bicolor

Directory of Open Access Journals (Sweden)

P. Hima Kumari

2018-05-01

Full Text Available Na+ transporters play an important role during salt stress and development. The present study is aimed at genome-wide identification, in silico analysis of sodium-proton antiporter (NHX and sodium-proton exchanger (NHE-type transporters in Sorghum bicolor and their expression patterns under varied abiotic stress conditions. In Sorghum, seven NHX and nine NHE homologs were identified. Amiloride (a known inhibitor of Na+/H+ exchanger activity binding motif was noticed in both types of the transporters. Chromosome 2 was found to be a hotspot region with five sodium transporters. Phylogenetic analysis inferred six ortholog and three paralog groups. To gain an insight into functional divergence of SbNHX/NHE transporters, real-time gene expression was performed under salt, drought, heat, and cold stresses in embryo, root, stem, and leaf tissues. Expression patterns revealed that both SbNHXs and SbNHEs are responsive either to single or multiple abiotic stresses. The predicted protein–protein interaction networks revealed that only SbNHX7 is involved in the calcineurin B-like proteins (CBL- CBL interacting protein kinases (CIPK pathway. The study provides insights into the functional divergence of SbNHX/NHE transporter genes with tissue specific expressions in Sorghum under different abiotic stress conditions.

Visibility graph approach to exchange rate series

Science.gov (United States)

Yang, Yue; Wang, Jianbo; Yang, Huijie; Mang, Jingshi

2009-10-01

By means of a visibility graph, we investigate six important exchange rate series. It is found that the series convert into scale-free and hierarchically structured networks. The relationship between the scaling exponents of the degree distributions and the Hurst exponents obeys the analytical prediction for fractal Brownian motions. The visibility graph can be used to obtain reliable values of Hurst exponents of the series. The characteristics are explained by using the multifractal structures of the series. The exchange rate of EURO to Japanese Yen is widely used to evaluate risk and to estimate trends in speculative investments. Interestingly, the hierarchies of the visibility graphs for the exchange rate series of these two currencies are significantly weak compared with that of the other series.

Development of the sulphonated poly(2,6-Dimethyl-1,4-Phenylene Oxide) membranes for proton exchange membranes fuel cells

International Nuclear Information System (INIS)

Ebrasu, Daniela; Petreanu, Irina; Iordache, Ioan; Stefanescu, Ioan; Gaspar, Costinela-Laura; Militaru, Daniela

2008-01-01

Full text: Fuel cells have the potential to become an important energy conversion technology. Research efforts directed toward the widespread commercialization of fuel cells have accelerated the developing of new types of Proton Exchange Membranes (also termed 'polymer electrolyte membranes') (PEM). Common issues critical to all high performance proton exchange membranes include: - high protonic conductivity; - low electronic conductivity; - low permeability to fuel and oxidant; - low water transport through diffusion and electro-osmosis; - oxidative and hydrolytic stability; - good mechanical properties in both the dry and hydrated states; - cost; and capability for fabrication into Membrane Electrode Assemblies (MEAs). In this sense we choose to use poly(2,6-Dimethyl-1,4-Phenylene Oxide) (PPO) as basis for development of new PEM membranes. The membranes were prepared by lamination from solution (Doctor Balde) method in controlled atmosphere (preliminary vacuum 0.003 Torr and/or nitrogen). FTIR spectra of the sulphonated polymers prove the sulphonic groups presence according the literature. Ionic exchange capacity (IEC) have the values 1.15-3.6 meq/g. TGA-DSC analysis put in evidence the thermal degradation of the sulphonated polymers at about 120 deg. C. These properties of the sulphonated PPO are in accordance of the requirements for PEM membranes and indicate that this polymer is suitable for PEM Fuel cells. (authors)

Exchange rate risks and their impact upon the energy market

Directory of Open Access Journals (Sweden)

Abed Al-Zabidi

2007-04-01

Full Text Available The expansion of international business in Slovakia brought not only the opening of markets and expansion of enterprise possibilities but also an increase in the competition and new risks. One of such risks is also the exchange rate risk. The business that realizes a financial transaction exceeding borders of the state or derives his buying or selling prices in Slovak crowns from the foreign currency, is subjected to the exchange rate risks. The exchange rate risks are caused by volatility of exchange courses of Slovak crowns related to foreign currencies. The progress of exchange rates can considerably influence a real result of a transaction negatively; therefore it is important for enterprises to identify possible risks resulting from changes in exchange rates, so they could react accordingly.The proposed article is aimed at the explanation of basic techniques of minimizing exchange rate risks with the use of financial tools available on the financial market.

Fluorinated poly(ether sulfone) ionomers with disulfonated naphthyl pendants for proton exchange membrane applications

Science.gov (United States)

Hu, Zhaoxia; Lu, Yao; Zhang, Xulve; Yan, Xiaobo; Li, Na; Chen, Shouwen

2018-06-01

Proton exchange membranes based on fluorinated poly(ether sulfone)s with disulfonated naphthyl pendants (sSPFES) have been successfully prepared by post functionalization through polymeric SNAr reaction. Copolymer structure was confirmed by H-nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy, the physico-chemical properties of the sSPFES membranes were evaluated by thermogravimetric analysis, gel permeation chromatography, electro-chemical impedance spectroscopy, atomic force microscopy, Fenton, water-swelling and fuel cell test. The pendant grafting degree was controlled by varying the feeding amount of the disulfonaphthols, resulting in the ion exchange capacity about 1.28-1.73 mmol/g. The obtained sSPFES membranes were thermal stable, mechanical ductile, and exhibited dimensional change less than 17%, water uptake below 70%, and proton conductivity as high as 0.17-0.28 S/cm at 90°C in water. In a single H2/O2 fuel cell test at 80°C, the sSPFES-B-3.2 membrane (1.61 mmol/g) showed the maximum power output of 593-658 mW/cm2 at 60%-80% relative humidity, indicating their rather promising potential for fuel cell applications.

Exchange Rate and International Trade: Case From Indonesian Manufacturing Sector

Directory of Open Access Journals (Sweden)

Anung Yoga Anindhita

2017-07-01

Full Text Available Exchange rate fluctuation in Floating Exchange Rate Regime is considered to Exchange rate fluctuation in Floating Exchange Rate Regime is considered to have impacts on the international trade through its adjustment to the price and its volatility to the trade risk. This paper is aimed at estimating those impacts on the international trade of manufacturing sector in Indonesia for period 2007 to 2014. To conduct estimation, it uses multiple regression analysis on two models: First, the import of raw-and-auxiliary materials; Second, the export of manufacturing sector. The results show that the exchange rate impacts both work significantly on the import of raw-and-auxiliary materials. The finding implies that, through the import of raw-and-auxiliary materials, manufacturing sector is very susceptible to the shock caused by exchange rate changes. Meanwhile, the export of manufacturing sector is not able to take advantage of the depreciation of the exchange rate due to the lack of competitiveness.DOI: 10.15408/sjie.v6i2.5210

Econometric Analysis of Croatia’s Proclaimed Foreign Exchange Rate

Directory of Open Access Journals (Sweden)

Mance Davor

2015-04-01

Full Text Available The officially proclaimed foreign exchange policy of the Croatian National Bank (CNB is a managed float with a discretionary right of intervention on the Croatian kuna/euro foreign exchange (FX market in order to maintain price stability. This paper examines the validity of three monetary policy hypotheses: the stability of the nominal exchange rate, the stability of exchange rate changes, and the exchange rate to inflation pass-through effect. The CNB claims a direct FX to inflation rate pass-through channel for which we find no evidence, but we find a strong link between FX rate changes and changes in M4, as well as between M4 changes and inflation. Changes in foreign investment Granger cause changes in monetary aggregates that further Granger cause inflation. Changes in FX rate Granger cause a reaction in M4 that indirectly Granger causes a further rise in inflation. Vector Autoregression Impulse Response Functions of changes in FX rate, M1, M4, and CPI confirm the Granger causalities in the established order.

Impact of exchange rates on the world uranium market

International Nuclear Information System (INIS)

Fulton, M.E.; Combs, G.F. Jr.

1986-01-01

A preliminary analysis of the relationship between exchange rates and US uranium prices and product ion is presented. This analysis supplements the discussions on the broader topic of fuel prices, exchange rates and other international economic phenomena scheduled during the 1985 EPRI Fuel Supply Seminar. By varying exchange rate assumptions in the recently developed Uranium Market Model, estimates of the magnitude and timing of price and production effects were obtained. These effects do indeed appear to be large and have implications in procurement, fuel planning and commodity policy. While analysts may differ on details, the inescapable conclusion is that exchange rates matter a great deal in the uranium market. The case described is for a scenario of exchange rates with other currencies returning to their 1980 levels. A second case, an across the board weakening of the dollar by 25%, the results of which are somewhat less dramatic is also examined

Effects of air exchange, temperature and slurry management on odorant emissions from pig production units and slurry tanks studied by proton-transfer-reaction mass spectrometry (PTR-MS)

Energy Technology Data Exchange (ETDEWEB)

Feilberg, A.; Adamsen, A.P.S.; Liu, D.; Hansen, M.J.; Bildsoe, P. [Aarhus Univ., Tjele (Denmark). Dept. of Biosystems Engineering

2010-07-01

The factors affecting the variability of odorant emissions from intensive pig production facilities were examined using proton-transfer-reaction mass spectrometry (PTR-MS) to monitor emissions of odorants. Quantitative and time-resolved results for protonated ions representing hydrogen sulphide (H{sub 2}S), volatile organic sulphur compounds, organic amines, volatile carboxylic acids, carbonyls, phenols and indoles can be obtained. This study presented the results from PTRMS measurements of odorant emissions from finisher pig houses and finisher manure storage tanks. The measurements were performed at an experimental full-scale pig section with mechanical ventilation and at an experimental manure storage facility with controlled air exchange. Field measurements were taken during variable air exchange rates and temperatures, during finisher growth, and during emptying of the slurry pit. The results revealed a pronounced diurnal variation in emissions of odorants from the pig section with peaks in daytime coinciding with the highest ventilation rates and highest room temperatures. The highest emission rates were observed for H{sub 2}S and carboxylic acids. Based on odour threshold values, methanethiol and 4-methylphenol were estimated to contribute considerably to the odour nuisance. Discharging of the slurry pit led to reduced H{sub 2}S emissions, but peaks of H{sub 2}S were observed during manure handling.

Misalignment under different exchange rate regimes: the case of Turkey

OpenAIRE

Dağdeviren, Sengül; Ogus Binatli, Ayla; Sohrabji, Niloufer

2011-01-01

The paper examines misalignment of the Turkish lira between 1998 to 2008. Misalignment, specifically overvaluation has been linked to fixed exchange rate regimes. By studying the case of Turkey during this period which covers both a fixed and floating exchange rate regime, we contribute to the literature on the relation between misalignment and exchange rate regimes. We first estimate the equilibrium real exchange rate for Turkey, then compute misalignment and finally test for structural brea...

The Estimation of the Equilibrium Real Exchange Rate for Romania

OpenAIRE

Bogdan Andrei Dumitrescu; Vasile Dedu

2009-01-01

This paper aims to estimate the equilibrium real exchange rate for Romania, respectively the real exchange rate consistent with the macroeconomic balance, which is achieved when the economy is operating at full employment and low inflation (internal balance) and has a current account that is sustainable (external balance). This equilibrium real exchange rate is very important for an economy because deviations of the real exchange rate from its equilibrium value can affect the competitiveness ...

Exchange Rate and Inflation Dynamics

OpenAIRE

Eatzaz Ahmad; Saima Ahmed Ali

1999-01-01

This paper studies simultaneous determination of nominal exchange rate and domestic price level in Pakistan. The estimated model contains sufficient built-in dynamics to trace the pattern and speed of adjustment in the two variables in response to temporary or permanent shocks. The two domestic shocks considered in the paper are monetary and real shocks, while the three external shocks considered are import price, export price and foreign exchange reserves shocks. The study finds that the imp...

Exchange Rate Changes and Inflation in Post-Crisis Asian Economies: VAR Analysis of the Exchange Rate Pass-Through

OpenAIRE

Takatoshi Ito; Kiyotaka Sato

2006-01-01

Macroeconomic consequences of a large currency depreciation among the crisis-hit Asian economies had varied from one country to another. Inflation did not soar in most Asian countries, including Thailand and Korea, after the exchange rate depreciated during the crisis. Indonesia, however, suffered very high inflation following a very large nominal depreciation of the rupiah. As a result, price competitive advantage by the rupiah depreciation was lost in the real exchange rate terms. The objec...

On the necessity of taking into account the contribution of multiphoton exchanges into electron-proton deep inelastic scattering

International Nuclear Information System (INIS)

Savrin, V.I.

1979-01-01

The hypothesis that the multiphoton exchanges give a substantial contribution to the electron-proton inclusive scattering is formulated. The hypothesis explains the observed violation of the Bjorken scaling law. As it is shown, the mechanism of such intensification of multiple exchanges may by connected with the properties of the processes of hadron multiproduction in the deep inelastic field. This results in the necessity to calculate the inclusive cross section in all electromagnetic coupling constant orders. This has been done in the framework of the density matrix method. As a result the deep inelastic scattering cross section calculated without application of the perturbation theory reveals a new property of the scaling invariance and leads to the natural relationship of structural functions with electromagnetic proton form-factors on the exclusive threshold

Exchange rate formation in Ukraine and its impact on macroeconomic indicators

OpenAIRE

Koroliuk Tatiana Aleksandrovna

2014-01-01

The factors of exchange rate formation in Ukraine are analyzes in this paper, the influence of exchange rate on macroeconomic indicators of development and the main priorities of the exchange rate policy are determined exchange.

Relationship between indoor radon concentrations and air exchange rate

International Nuclear Information System (INIS)

Wang Jingshu; Liu Yuyu; Yao Xiaohua; Meng Jianfeng; Zhang Yongyi; Wang Xiaohe; Yu Xiufen.

1995-01-01

The indoor concentration of radon and the air exchange rate were simultaneously measured in four empty rooms, made of brick and cement, which were located in different floors of dwelling houses in Taiyuan, Shanxi, China. SF 6 tracer gas decay method was used to measure the air exchange rate. Indoor radon was collected with the dimembrane method. When the ventilation rate increased, the concentration of radon dropped rapidly. Regression analysis indicated that the indoor concentration of radon was equal to the outdoor level of radon when the air exchange rate was greater than 3-4. SF 6 decay method was an effective and convenient method for measuring the air exchange rate. There was no marked difference in measurements obtained in different locations of a room. (N.K.)

Exporter Price Response to Exchange Rate Changes

DEFF Research Database (Denmark)

Fosse, Henrik Barslund

Firms exporting to foreign markets face a particular challenge: to price their exports in a foreign market when the exchange rate changes. This paper takes on pricing- to-market using a unique data set that covers rm level monthly trade at great detail. As opposed to annual trade ows, monthly trade...... theoretical contributions to the litterature on pricing-to-market and exchange rate pass-through....

The determinants of real exchange rate volatility in Nigeria | Ajao ...

African Journals Online (AJOL)

This study recommends that the central monetary authority should institute policies that will minimize the magnitude of exchange rate volatility while the federal government exercises control of viable macroeconomic variables which have direct influence on exchange rate fluctuation. Keywords: Exchange Rate, Volatility, ...

Political pressures and exchange rate stability in emerging market economies

OpenAIRE

Ester Faia; Massimo Giuliodori; Michele Ruta

2008-01-01

This paper presents a political economy model of exchange rate policy. The theory is based on a common agency approach with rational expectations. Financial and exporter lobbies exert political pressures to influence the government’s choice of exchange rate policy, before shocks to the economy are realized. The model shows that political pressures affect exchange rate policy and create an over-commitment to exchange rate stability. This helps to rationalize the empirical evidence on fear of l...

Examining the volatility of exchange rate: Does monetary policy matter?

OpenAIRE

Lim, Shu Yi; Sek, Siok Kun

2014-01-01

We conduct empirical analysis on examining the changes in exchange rate volatility under two monetary policy regimes, i.e. the pre- and post- inflation targeting (IT) regimes. In addition, we also investigate if the monetary decisions can have impacts on the volatility of exchange rate. The study is focused in four Asian countries that experienced drastic in the switch of monetary policy from the rigid exchange rate to flexible exchange rate and inflation targeting after the Asian financial c...

The case for regional exchange rate arrangement in East Asia

OpenAIRE

Takuji Kinkyo

2004-01-01

The Asian crisis highlighted the difficulties for developing countries to actively manage exchange rates in an environment of high capital mobility. Now it became fashionable to argue that the exchange rate should be either allowed to float freely or irrevocably fixed. This paper examines the case for regional exchange rate arrangements as an instrument to enhance the manageability of exchange rates and discusses the options in East Asia. It critically assess the existing proposal of common b...

THE EFFECT OF EXCHANGE RATE VOLATILITY ON WHEAT TRADE WORLDWIDE

OpenAIRE

Sun, Changyou; Kim, Mina; Koo, Won W.; Cho, Guedae; Jin, Hyun Joung

2002-01-01

A modified gravity-type model was employed to evaluate the effect of exchange rate volatility on wheat exports worldwide. Special attention was given to the econometric properties of the gravity model within panel framework. Short and long-term measures of exchange rate volatility were constructed and compared. Both measures of exchange rate volatility have exhibited a negative effect on world wheat trade and the long-term effect was even larger. This result implies that exchange rate volatil...

Exchange Rate Effects on International Commercial Trade Competitiveness

Directory of Open Access Journals (Sweden)

Ionel Bostan

2018-04-01

Full Text Available This study is meant to be an evaluation sustained by theoretical and empirical considerations of the exchange rate impact on international commercial trade competitiveness. In this respect, the study aims to find how the exchange rate influences Romanian competitiveness through assessing the effects generated on exports and imports. The main purpose of the study is to assess the complex action of the exchange rate on international commercial trade competitiveness in contemporaneity and the connections between these variables. The empirical part contains a regression analysis where exports and imports are dependent variables influenced by a series of determinants.

A Range-Based Multivariate Model for Exchange Rate Volatility

OpenAIRE

Tims, Ben; Mahieu, Ronald

2003-01-01

textabstractIn this paper we present a parsimonious multivariate model for exchange rate volatilities based on logarithmic high-low ranges of daily exchange rates. The multivariate stochastic volatility model divides the log range of each exchange rate into two independent latent factors, which are interpreted as the underlying currency specific components. Due to the normality of logarithmic volatilities the model can be estimated conveniently with standard Kalman filter techniques. Our resu...

Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

Science.gov (United States)

Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

2016-08-01

The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

CHANGES IN EXCHANGE RATE REGIMES

Directory of Open Access Journals (Sweden)

Carmen SANDU (TODERASCU

2014-06-01

Full Text Available The experience of recentyears showsthat it hasa fundamentalroleformation mechanismof the exchange rateinmacroeconomic stabilization. Global economiccrises, oil shockshave shownthe difficultyoffloatingsustainabilitybyparticipants in the system. EuropeanMonetary System, focused onconcertedfloatingcurrenciestoECU, was formedunder the conditionsin which somecountries have adoptedregional monetaryarrangements(EU countries, with suchbasescurrencyregimeshybridthat combinesspecific mechanismsto those offixedratefree floating. This paperaims to demonstratethe important role thatithasthe choice ofexchange rateregimeas abasic elementin thefoundationofmacroeconomic stabilizationinstruments. Consideredan expression of thestateof the domestic economyandinternationalcompetitiveness, the exchange rate is determined bya complex set ofexternal factorsorinternalstabilityisa prerequisite forthe crisis.

Design of flow-field patterns for proton exchange membrane fuel cell application

International Nuclear Information System (INIS)

Rosli, M.I.; Wan Ramli Wan Daud; Kamaruzzaman Sopian; Jaafar Sahari

2006-01-01

Fuel cells are electrochemical devices that produce electricity at high efficiency without combustion. Fuel cells are emerging as viable candidates as power sources in many applications, including road vehicles, small-scale power stations, and possibly even portable electronics. This paper addresses the design of flow-field patterns for proton exchange membrane fuel cell (PEMFC). The PEMFC is a low-temperature fuel cell, in which a proton conductive polymer membrane is used as the electrolyte. In PEMFC, flow-field pattern is one important thing that effects the performance of PEMFC. This paper present three types of flow-field pattern that will be consider to be testing using CFD analysis and by experimental. The design look detail on to their shape and dimension to get the best pattern in term of more active electrode area compare to electrode area that will be used. Another advantage and disadvantage for these three type of flow-field patterns from literature also compared in this paper

Employing Hot Wire Anemometry to Directly Measure the Water Balance of a Commercial Proton Exchange Membrane Fuel Cell Stack

DEFF Research Database (Denmark)

Shakhshir, Saher Al; Berning, Torsten

2016-01-01

Proton exchange membrane fuel cells (PEMFC’s) are currently being commercialized for various applications ranging from automotive (e.g. the Toyota Mirai) to stationary such as powering telecom backup units. In PEMFC’s, oxygen from air is internally combined with hydrogen to form water and produce...... and increased degradation rates. Clearly, a fundamental understanding of all aspects of water management in PEMFC is imperative. This includes the fuel cell water balance, i.e. which fraction of the product water leaves the fuel cell via the anode channels versus the cathode channel. Our research group...... signal received gives valuable insight into heat and mass transfer phenomena in a PEMFC....

Martingale Regressions for a Continuous Time Model of Exchange Rates

OpenAIRE

Guo, Zi-Yi

2017-01-01

One of the daunting problems in international finance is the weak explanatory power of existing theories of the nominal exchange rates, the so-called “foreign exchange rate determination puzzle”. We propose a continuous-time model to study the impact of order flow on foreign exchange rates. The model is estimated by a newly developed econometric tool based on a time-change sampling from calendar to volatility time. The estimation results indicate that the effect of order flow on exchange rate...

Investigating the effects of liquidity and exchange rate on Tehran Stock Exchange

Directory of Open Access Journals (Sweden)

Younos Vakil Alroaia

2014-08-01

Full Text Available This paper presents an empirical investigation to study the effects of two macroeconomic factors; namely exchange rate and liquidity on stock index. The proposed study was applied in Iran and on major index of Tehran Stock Exchange over the period 2001-2011. They reported that the currency exchange maintained negative impact on stock exchange for the period of investigation. This is due to the fact that when currency devalued, working capital decreases and firms did not enough money to purchase raw materials, pay wages, etc. In addition, liquidity marinated a direct and positive relationship with exchange index. However, the impact of liquidity seems to be bigger than currency exchange.

VOLATILITY OF EXCHANGE RATE IN THE CONTEXT OF FOREIGN TRADE

Directory of Open Access Journals (Sweden)

Oleg STRATULAT

2016-09-01

Full Text Available Moderate fluctuation of the exchange rate, basically in its floating regime is considered normality. Meanwhile,excessive volatility of the exchange rate is an issue for many countries. Its elimination is directed to foreign trade, which, through essential exports, followed by significant currency inflows, contribute to the stability of exchange rates. Unfortunately, Moldova’s foreign trade has become a key factor in maintaining the stability of foreign exchange.

Brazilian exchange rate complexity: Financial crisis effects

Science.gov (United States)

Piqueira, José Roberto C.; Mortoza, Letícia Pelluci D.

2012-04-01

With the financial market globalization, foreign investments became vital for the economies, mainly in emerging countries. In the last decades, Brazilian exchange rates appeared as a good indicator to measure either investors' confidence or risk aversion. Here, some events of global or national financial crisis are analyzed, trying to understand how they influenced the "dollar-real" rate evolution. The theoretical tool to be used is the López-Mancini-Calbet (LMC) complexity measure that, applied to real exchange rate data, has shown good fitness between critical events and measured patterns.

Influence of reactor irradiation on the protons intercalation and stability of barium cerates and strontium cerates

International Nuclear Information System (INIS)

Aksenova, T.I.; Khromushin, I.V.; Zhotabaev, Zh.R.; Kornienko, P.A.; Munasbaeva, K.K.

2005-01-01

The work is devoted to study of reactor irradiation influence on the gas-solid exchange processes in the high-temperature proton semiconductors on the base of cerates and strontium. A number of new regularities of influence of content of some proton semiconductors on the gas-solid exchange processes was established. It is shown, that increase of rate of cation doping rate leads to considerable lowering in its of carbonic gas content, and therefore to improvement their tribological properties. It is revealed, that irradiation of polycrystalline samples leads to growth of oxygen amount desorbed from samples, whereas irradiation of monocrystalline samples practically does not has effect on the desorbed oxygen amount. It was found, that character of relation of intercalated in the sample protons depend on sample doping rate

Controlling fuel crossover and hydration in ultrathin proton exchange membrane-based fuel cells using Pt-nanosheet catalysts

DEFF Research Database (Denmark)

Wang, Rujie; Zhang, Wenjing (Angela); He, Gaohong

2014-01-01

and provided in situ hydration inside Nafion membranes to maintain their proton conductivity level. Furthermore, LDH nanosheets reinforced the Nafion membranes, with 181% improvement in tensile modulus and 166% improvement in yield strength. In a hydrogen fuel cell running with dry fuel, the membrane......An ultra-thin proton exchange membrane with Pt-nanosheet catalysts was designed for a self-humidifying fuel cell running on H2 and O2. In this design, an ultra-thin Nafion membrane was used to reduce ohmic resistance. Pt nanocatalysts were uniformly anchored on exfoliated, layered double hydroxide...

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice

International Nuclear Information System (INIS)

Ware, J.H.; Rusek, A.; Sanzari, J.; Avery, S.; Sayers, C.; Krigsfeld, G.; Nuth, M.; Wan, X.S.; Kennedy, A.R.

2010-01-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice.

Science.gov (United States)

Ware, J H; Sanzari, J; Avery, S; Sayers, C; Krigsfeld, G; Nuth, M; Wan, X S; Rusek, A; Kennedy, A R

2010-09-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Fiscal deficits, exchange rate crises and inflation.

NARCIS (Netherlands)

van Wijnbergen, S.J.G.

1991-01-01

This article extends earlier work on unsustainable monetary policies by endogenizing the regime switch that ultimately restores sustainability. Within this framework we analyze exchange rate based stabilization programs and shows how constraints on Central Bank borrowing during an exchange crisis

Jump spillover between oil prices and exchange rates

Science.gov (United States)

Li, Xiao-Ping; Zhou, Chun-Yang; Wu, Chong-Feng

2017-11-01

In this paper, we investigate the jump spillover effects between oil prices and exchange rates. To identify the latent historical jumps for exchange rates and oil prices, we use a Bayesian MCMC approach to estimate the stochastic volatility model with correlated jumps in both returns and volatilities for each. We examine the simultaneous jump intensities and the conditional jump spillover probabilities between oil prices and exchange rates, finding strong evidence of jump spillover effects. Further analysis shows that the jump spillovers are mainly due to exogenous events such as financial crises and geopolitical events. Thus, the findings have important implications for financial risk management.

Asymmetric Exchange Rate Exposure - Research in Southeast Asian Countries

OpenAIRE

Minh Thi Hong Le; Ha Thi Cam Huynh; Hong Thi Thu Dinh

2017-01-01

The study aims to analyse the impact of exchange rate exposure on stock returns in six countries representative of Southeast Asia, including Indonesia, Malaysia, Philippines, Singapore, Thailand and Vietnam from 2009 to 2014. Both nominal and real exchange rates are taken into account for evaluating exchange rate fluctuations via panel data. In order to achieve this goal, a panel regressive estimation approach is proposed in which a GLS model is firstly used to treat heteroscedasticity in the...

HOGEN{trademark} proton exchange membrane hydrogen generators: Commercialization of PEM electrolyzers

Energy Technology Data Exchange (ETDEWEB)

Smith, W.F.; Molter, T.M. [Proton Energy Systems, Inc., Rocky Hill, CT (United States)

1997-12-31

PROTON Energy Systems` new HOGEN series hydrogen generators are Proton Exchange Membrane (PEM) based water electrolyzers designed to generate 300 to 1000 Standard Cubic Feet Per Hour (SCFH) of high purity hydrogen at pressures up to 400 psi without the use of mechanical compressors. This paper will describe technology evolution leading to the HOGEN, identify system design performance parameters and describe the physical packaging and interfaces of HOGEN systems. PEM electrolyzers have served US and UK Navy and NASA needs for many years in a variety of diverse programs including oxygen generators for life support applications. In the late 1970`s these systems were advocated for bulk hydrogen generation through a series of DOE sponsored program activities. During the military buildup of the 1980`s commercial deployment of PEM hydrogen generators was de-emphasized as priority was given to new Navy and NASA PEM electrolysis systems. PROTON Energy Systems was founded in 1996 with the primary corporate mission of commercializing PEM hydrogen generators. These systems are specifically designed and priced to meet the needs of commercial markets and produced through manufacturing processes tailored to these applications. The HOGEN series generators are the first step along the path to full commercial deployment of PEM electrolyzer products for both industrial and consumer uses. The 300/1000 series are sized to meet the needs of the industrial gases market today and provide a design base that can transition to serve the needs of a decentralized hydrogen infrastructure tomorrow.

Proton Exchange Membrane Fuel Cell Modelling Using Moving Least Squares Technique

Directory of Open Access Journals (Sweden)

Radu Tirnovan

2009-07-01

Full Text Available Proton exchange membrane fuel cell, with low polluting emissions, is a great alternative to replace the traditional electrical power sources for automotive applications or for small stationary consumers. This paper presents a numerical method, for the fuel cell modelling, based on moving least squares (MLS. Experimental data have been used for developing an approximated model of the PEMFC function of the current density, air inlet pressure and operating temperature of the fuel cell. The method can be applied for modelling others fuel cell sub-systems, such as the compressor. The method can be used for off-line or on-line identification of the PEMFC stack.

Investigation of water distribution in proton exchange membrane fuel cells via Terahertz imaging

International Nuclear Information System (INIS)

Thamboon, P.; Buaphad, P.; Thongbai, C.; Saisud, J.; Kusoljariyakul, K.; Rhodes, M.W.; Vilaithong, T.

2011-01-01

Coherent transition radiation in a THz regime generated from a femtosecond electron bunch is explored for its potential use in imaging applications. Due to water sensitivity, the THz imaging experiment is performed on a proton exchange membrane fuel cell (PEMFC) to assess the ability to quantify water in the flow field of the cell. In this investigation, the PEMFC design and the experimental setup for the THz imaging is described. The results of the THz images in the flow field are also discussed.

Dynamic Model of the High Temperature Proton Exchange Membrane Fuel Cell Stack Temperature

DEFF Research Database (Denmark)

Andreasen, Søren Juhl; Kær, Søren Knudsen

2009-01-01

The present work involves the development of a model for predicting the dynamic temperature of a high temperature proton exchange membrane (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system co...... elements for start-up, heat conduction through stack insulation, cathode air convection, and heating of the inlet gases in the manifold. Various measurements are presented to validate the model predictions of the stack temperatures....

Compact modeling of a telecom back-up unit powered by air-cooled proton exchange membrane fuel cell

DEFF Research Database (Denmark)

Gao, Xin; Kær, Søren Knudsen

2018-01-01

Applications of proton exchange membrane fuel cells (PEMFC’s) are expanding in portable, automotive and stationary markets. One promising application is the back-up power for telecommunication applications in remote areas where usually air-cooled PMEFC’s are used. An air-cooled PEMFC system is much...

An empirical study of exchange rate pass-through in China

Directory of Open Access Journals (Sweden)

Jin Xiaowen

2012-01-01

Full Text Available This paper seeks to estimate exchange rate pass-through in China and investigate its relationship with monetary policy. Linear and VAR models are applied to analyze robustness. The linear model shows that, over the long run, a 1% appreciation of NEER causes a decline in the CPI inflation rate of 0.132% and PPI inflation rate of 0.495%. The VAR model supports the results of the linear model, suggesting a fairly low CPI pass-through and relatively higher PPI pass-through. Furthermore, this paper finds that, with the fixed exchange rate regime, CPI pass-through remains higher. The exchange rate regimes influence on CPI pass through, combined with the fact that appreciation diminishes inflation, suggests that the Chinese government could pursue a more flexible exchange rate policy. In addition, reasons for low exchange rate pass-through for CPI are analyzed. The analysis considers price control, basket and weight of Chinese price indices, distribution cost, and imported and non-tradable share of inputs.

Protein folding kinetics by combined use of rapid mixing techniques and NMR observation of individual amide protons

International Nuclear Information System (INIS)

Roder, H.; Wuethrich, K.

1986-01-01

A method to be used for experimental studies of protein folding introduced by Schmid and Baldwin, which is based on the competition between amide hydrogen exchange and protein refolding, was extended by using rapid mixing techniques and 1 H NMR to provide site-resolved kinetic information on the early phases of protein structure acquisition. In this method, a protonated solution of the unfolded protein is rapidly mixed with a deuterated buffer solution at conditions assuring protein refolding in the mixture. This simultaneously initiates the exchange of unprotected amide protons with solvent deuterium and the refolding of protein segments which can protect amide groups from further exchange. After variable reaction times the amide proton exchange is quenched while folding to the native form continues to completion. By using 1 H NMR, the extent of exchange at individual amide sites is then measured in the refolded protein. Competition experiments at variable reaction times or variable pH indicate the time at which each amide group is protected in the refolding process. This technique was applied to the basic pancreatic trypsin inhibitor, for which sequence-specific assignments of the amide proton NMR lines had previously been obtained. For eight individual amide protons located in the beta-sheet and the C-terminal alpha-helix of this protein, apparent refolding rates in the range from 15 s-1 to 60 s-1 were observed. These rates are on the time scale of the fast folding phase observed with optical probes

Development and Validation of a Simple Analytical Model of the Proton Exchange Membrane Fuel Cell (Pemfc) in a Fork-Lift Truck Power System

DEFF Research Database (Denmark)

Hosseinzadeh, Elham; Rokni, Masoud

2013-01-01

In this study, a general proton exchange membrane fuel cell (PEMFC) model has been developed in order to investigate the balance of plant of a fork-lift truck thermodynamically. The model takes into account the effects of pressure losses, water crossovers, humidity aspects, and voltage overpotent......In this study, a general proton exchange membrane fuel cell (PEMFC) model has been developed in order to investigate the balance of plant of a fork-lift truck thermodynamically. The model takes into account the effects of pressure losses, water crossovers, humidity aspects, and voltage...

A New Approach to Forecasting Exchange Rates

OpenAIRE

Kenneth W Clements; Yihui Lan

2006-01-01

Building on purchasing power parity theory, this paper proposes a new approach to forecasting exchange rates using the Big Mac data from The Economist magazine. Our approach is attractive in three aspects. Firstly, it uses easily-available Big Mac prices as input. These prices avoid several serious problems associated with broad price indexes, such as the CPI, that are used in conventional PPP studies. Secondly, this approach provides real-time exchange-rate forecasts at any forecast horizon....

Introducing False EUR and False EUR exchange rates

Science.gov (United States)

Ausloos, M.; Ivanova, K.

2000-10-01

The Euro ( EUR) is a new currency introduced by the European Community. Its exchange rate is very puzzling. We have invented a false Euro ( FEUR) dating back to 1993 and have derived the exchange rates of the FEUR with respect to currencies not belonging to the EUR, i.e., DKK, CHF, JPY and USD. This allows us to search for correlations between the fluctuations preexisting to the introduction of EUR and present ones in such financial data. The detrended fluctuation analysis ( DFA) statistical method is used. This leads to assume a power-law behavior, i.e., a scaling hypothesis, through an exponent α. The latter has demonstrated its usefulness for the investigations of long-range power-law correlations in several types of financial sequences. Our findings show that the α exponent interestingly characterizes fractional Brownian motion of the currency exchange rates between EUR and DKK over a 25 day interval, and usual Brownian motion otherwise and for the three other investigated exchange rates. We can devise an investment strategy based on the localα technique and obtain appreciable gains for the time being.

The Determinants of Real Exchange Rate Volatility in Nigeria

African Journals Online (AJOL)

Rahel

magnitude of exchange rate volatility while the federal government exercises control of ... objectives in the area of price stability and economic growth. Volatile real ..... Exchange rate shocks and instability is a common feature of emerging.

Self assembled 12-tungstophosphoric acid-silica mesoporous nanocomposites as proton exchange membranes for direct alcohol fuel cells.

Science.gov (United States)

Tang, Haolin; Pan, Mu; Jiang, San Ping

2011-05-21

A highly ordered inorganic electrolyte based on 12-tungstophosphoric acid (H(3)PW(12)O(40), abbreviated as HPW or PWA)-silica mesoporous nanocomposite was synthesized through a facile one-step self-assembly between the positively charged silica precursor and negatively charged PW(12)O(40)(3-) species. The self-assembled HPW-silica nanocomposites were characterized by small-angle XRD, TEM, nitrogen adsorption-desorption isotherms, ion exchange capacity, proton conductivity and solid-state (31)P NMR. The results show that highly ordered and uniform nanoarrays with long-range order are formed when the HPW content in the nanocomposites is equal to or lower than 25 wt%. The mesoporous structures/textures were clearly presented, with nanochannels of 3.2-3.5 nm in diameter. The (31)P NMR results indicates that there are (≡SiOH(2)(+))(H(2)PW(12)O(40)(-)) species in the HPW-silica nanocomposites. A HPW-silica (25/75 w/o) nanocomposite gave an activation energy of 13.0 kJ mol(-1) and proton conductivity of 0.076 S cm(-1) at 100 °C and 100 RH%, and an activation energy of 26.1 kJ mol(-1) and proton conductivity of 0.05 S cm(-1) at 200 °C with no external humidification. A fuel cell based on a 165 μm thick HPW-silica nanocomposite membrane achieved a maximum power output of 128.5 and 112.0 mW cm(-2) for methanol and ethanol fuels, respectively, at 200 °C. The high proton conductivity and good performance demonstrate the excellent water retention capability and great potential of the highly ordered HPW-silica mesoporous nanocomposites as high-temperature proton exchange membranes for direct alcohol fuel cells (DAFCs).

Apparent exchange rate for breast cancer characterization.

Science.gov (United States)

Lasič, Samo; Oredsson, Stina; Partridge, Savannah C; Saal, Lao H; Topgaard, Daniel; Nilsson, Markus; Bryskhe, Karin

2016-05-01

Although diffusion MRI has shown promise for the characterization of breast cancer, it has low specificity to malignant subtypes. Higher specificity might be achieved if the effects of cell morphology and molecular exchange across cell membranes could be disentangled. The quantification of exchange might thus allow the differentiation of different types of breast cancer cells. Based on differences in diffusion rates between the intra- and extracellular compartments, filter exchange spectroscopy/imaging (FEXSY/FEXI) provides non-invasive quantification of the apparent exchange rate (AXR) of water between the two compartments. To test the feasibility of FEXSY for the differentiation of different breast cancer cells, we performed experiments on several breast epithelial cell lines in vitro. Furthermore, we performed the first in vivo FEXI measurement of water exchange in human breast. In cell suspensions, pulsed gradient spin-echo experiments with large b values and variable pulse duration allow the characterization of the intracellular compartment, whereas FEXSY provides a quantification of AXR. These experiments are very sensitive to the physiological state of cells and can be used to establish reliable protocols for the culture and harvesting of cells. Our results suggest that different breast cancer subtypes can be distinguished on the basis of their AXR values in cell suspensions. Time-resolved measurements allow the monitoring of the physiological state of cells in suspensions over the time-scale of hours, and reveal an abrupt disintegration of the intracellular compartment. In vivo, exchange can be detected in a tumor, whereas, in normal tissue, the exchange rate is outside the range experimentally accessible for FEXI. At present, low signal-to-noise ratio and limited scan time allows the quantification of AXR only in a region of interest of relatively large tumors. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

Synthesis and properties of hexafluoroisopropylidene-containing sulfonated poly(arylene thioether phosphine oxide)s for proton exchange membranes

Energy Technology Data Exchange (ETDEWEB)

Gui, Longyong; Zhang, Chunjie; Kang, Sen; Tan, Ning; Xiao, Guyu; Yan, Deyue [College of Chemistry and Chemical Engineering, The State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

2010-03-15

A series of novel sulfonated poly(arylene thioether phosphine oxide)s with hexafluoroisopropylidene moieties (sPTPOF) were prepared by polycondensation of sulfonated bis(4-fluorophenyl)phenyl phosphine oxide and bis(4-fluorophenyl)phenyl phosphine oxide with 4,4'-(hexafluoroisopropylidene) diphenthiol. The incorporation of hexafluoroisopropylidene moieties to the resulting polymers is effective to increase the hydrophobicity of non-sulfonated segments and to decrease the swelling while maintaining high proton conductivity. For instance, sPTPOF-100 showed a proton conductivity of 0.090 S/cm as well as a swelling of 5.3% at 80 C. In addition, the sPTPOF polymers exhibited excellent thermal properties and oxidative stability. AFM phase images illustrated that the sPTPOF membranes show a special nanophase-separated morphology, namely, the connectivity of ionic channels increased obviously but their width only slightly increased with increasing sulfonation degree. This special microstructure is favorable for promoting proton transport and restraining the swelling. The sPTPOF polymers are a promising material for proton exchange membranes. (author)

Exchange rate regimes and inflation: Evidence from India.

OpenAIRE

Mohanty, Biswajit; Bhanumurthy, N.R.

2014-01-01

Exchange rate stability is crucial for inflation management as a stable rate is expected to reduce domestic inflation pressures through a `policy discipline effect'- restricting money supply growth, and a `credibility effect'- inducing higher money demand and reduced velocity of money. Alternatively, the impossibility trillema predicts that in the presence of an open capital account, a stable exchange rate may lead to lack of control on monetary policy and, hence, higher inflation. Using a mo...

Charge-exchange breakup of the deuteron with the production of two protons and spin structure of the amplitude of the nucleon charge transfer reaction

International Nuclear Information System (INIS)

Glagolev, V.V.; Lyuboshits, V.L.; Lyuboshits, V.V.; Piskunov, N.M.

1999-01-01

In the framework of the impulse approximation, the relation between the effective cross section of the charge-exchange breakup of a fast deuteron d + a → (pp) + b and the effective cross section of the charge transfer process n + a → p + b is discussed. In doing so, the effects of the proton identity (Fermi-statistics) and of the Coulomb and strong interactions of protons in the final state are taken into account. The distribution over relative momenta of the protons, produced in the charge-exchange process d + p → (pp) + n in the forward direction, is investigated. At the transfer momenta being close to zero the effective cross section of the charge-exchange breakup of a fast deuteron, colliding with the proton target, is determined only by the spin-flip part of the amplitude of the charge transfer reaction n + p → p + n at the zero angle. It is shown that the study of the process d + p → (pp) + n in a beam of the polarized (aligned) deuterons allows one, in principle, to separate two spin-dependent terms in the amplitude of the charge transfer reaction n + p → p + n, one of which does not conserve and the other one conserves the projection of the nucleon spin onto the direction of momentum at the transition of the neutron into the proton

Effects of interest rate, exchange rate and their volatilities on stock prices: evidence from banking industry of Pakistan

Directory of Open Access Journals (Sweden)

Syed Tehseen JAWAID

2012-08-01

Full Text Available This study investigates the effects of exchange rate, interest rates, and their volatilities on stock prices of banking industry of Pakistan. Cointegration results suggests the existance of significant negative long run relationship between exchange rate and short term interest rate with stock prices. On the other hand, positive and significant relationship exists between volatilities of exchange rate and interest rate with stock prices. Causality analysis confirms bidirectional causality between exchange rate and stock prices. Whereas, unidirectional causality runs from short term interest rate to stock prices. Sensitivity analysis confirms that the results are robust. It is suggested that investors should invest in banking sector stocks when exchange rate and interest rates are highly volatile. The result also supports the view that exchange rate and interest rate can be used as an indicator for investment decision making in banking sector stocks.

Novel high-performance nanocomposite proton exchange membranes based on poly (ether sulfone)

Energy Technology Data Exchange (ETDEWEB)

Hasani-Sadrabadi, Mohammad Mahdi [Polymer Engineering Department, Amirkabir University of Technology, Tehran (Iran); Biomedical Engineering Department, Amirkabir University of Technology, Tehran (Iran); Dashtimoghadam, Erfan; Ghaffarian, Seyed Reza [Polymer Engineering Department, Amirkabir University of Technology, Tehran (Iran); Hasani Sadrabadi, Mohammad Hossein [Faculty of Social and Economics Science, Alzahra University, Tehran (Iran); Heidari, Mahdi [Graduate School of Management and Economics, Sharif University of Technology, Tehran (Iran); Moaddel, Homayoun [Department of Materials Science and Engineering, University of California, Los Angeles, CA (United States)

2010-01-15

In the present research, proton exchange membranes based on partially sulfonated poly (ether sulfone) (S-PES) with various degrees of sulfonation were synthesized. It was found that the increasing of sulfonation degree up to 40% results in the enhancement of water uptake, ion exchange capacity and proton conductivity properties of the prepared membranes to 28.1%, 1.59 meq g{sup -1}, and 0.145 S cm{sup -1}, respectively. Afterwards, nanocomposite membranes based on S-PES (at the predetermined optimum sulfonation degree) containing various loading weights of organically treated montmorillonite (OMMT) were prepared via the solution intercalation technique. X-ray diffraction patterns revealed the exfoliated structure of OMMT in the macromolecular matrices. The S-PES nanocomposite membrane with 3.0 wt% of OMMT content showed the maximum selectivity parameter of about 520,000 S s cm{sup -3} which is related to the high conductivity of 0.051 S cm{sup -1} and low methanol permeability of 9.8 x 10{sup -8} cm{sup 2} s{sup -1}. Furthermore, single cell DMFC fuel cell performance test with 4 molar methanol concentration showed a high power density (131 mW cm{sup -2}) of the nanocomposite membrane at the optimum composition (40% of sulfonation and 3.0 wt% of OMMT loading) compared to the Nafion {sup registered} 117 membrane (114 mW cm{sup -2}). Manufactured nanocomposite membranes thanks to their high selectivity, ease of preparation and low cost could be suggested as the ideal candidate for the direct methanol fuel cell applications. (author)

On equilibrium real exchange rates in euro area: Special focus on behavioral equilibrium exchange rates in Ireland and Greece

OpenAIRE

Klára Plecitá; Luboš Střelec

2012-01-01

This paper focuses on the intra-euro-area imbalances. Therefore the first aim of this paper is to identify euro-area countries exhibiting macroeconomic imbalances. The subsequent aim is to estimate equilibrium real exchange rates for these countries and to compute their degrees of real exchange rate misalignment. The intra-area balance is assessed using the Cluster Analysis and the Principle Component Analysis; on this basis Greece and Ireland are selected as the two euro-area countries with ...

Exchange rate policy and devaluation in Malawi:

OpenAIRE

Pauw, Karl; Dorosh, Paul A.; Mazunda, John

2013-01-01

This study demonstrates why devaluation was ultimately necessary in Malawi and also what its eventual impact might be in terms of prices, income distribution, and domestic production. Our approach is to use a computable general equilibrium (CGE) model to evaluate the economywide impacts of foreign exchange shortages in Malawi under two alternative exchange rate regimes. The foreign exchange shortages are modeled by simulating the effect of actual shocks, including tobacco price declines and r...

3ON PAK RUPEE EXCHANGE RATES: WHETHER STOCK OR FLOW MATTERS?

Directory of Open Access Journals (Sweden)

Razzaque H Bhatti

2011-01-01

Full Text Available This paper examines whether the monetary model or the flow model of exchange rate explains the long-run movements in Pak rupee exchange rates vis-à-vis the four major currencies – the US dollar, British pound, Swiss franc and Japanese yen – over the period 1983q1-2009q4. Results obtained by employing the Johansen and Juselius (1990 technique of cointegration are supportive of the monetary model in two Pak rupee exchange rates vis-à-vis the US dollar and the Swiss franc when both short- and long-run interest rates are used and of the flow model in three exchange rates vis-à-vis the British pound, Swiss franc and Japanese yen when the short-run interest rate is used. These results show that both stock equilibrium in capital markets and flow equilibrium in foreign exchange markets determine Pak rupee exchange rates.

THE DETERMINATION OF THE COSTA RICA COLON/USD EXCHANGE RATE

OpenAIRE

Yu Hsing

2009-01-01

The purpose of this paper is to compare four major exchange rate models for the Costa Rica Colon. We examine exchange rate data for the Costa Rica/U.S. dollar relationship from 1981-2007 and find that monetary models have a higher explanatory ability whereas the Mundell-Fleming model performs better in forecasting exchange rates than other models. The coefficient of the interest rate differential in the uncovered interest parity model has a wrong sign.

Effects of Monetary Shocks on Exchange Rate: Empirical Evidence from India

Directory of Open Access Journals (Sweden)

Sharma Chandan

2017-08-01

Full Text Available This paper examines the effect of monetary policy shocks on exchange rate in a Multiple Indicator Approach (MIA framework. This study has employed a monetary policy index of key monetary policy instruments in India (Bank rate, Cash Reserve Ratio, Repo and Reverse Repo rates. The study finds the empirical evidence for puzzling behavior of price level and exchange rate. Both price and exchange rate increase initially in response to a contractionary policy shock. Policy shocks affect output, inflation and exchange rate to an appreciable extent over a forecasting horizon of one year.

Empirical Correction for Differences in Chemical Exchange Rates in Hydrogen Exchange-Mass Spectrometry Measurements.

Science.gov (United States)

Toth, Ronald T; Mills, Brittney J; Joshi, Sangeeta B; Esfandiary, Reza; Bishop, Steven M; Middaugh, C Russell; Volkin, David B; Weis, David D

2017-09-05

A barrier to the use of hydrogen exchange-mass spectrometry (HX-MS) in many contexts, especially analytical characterization of various protein therapeutic candidates, is that differences in temperature, pH, ionic strength, buffering agent, or other additives can alter chemical exchange rates, making HX data gathered under differing solution conditions difficult to compare. Here, we present data demonstrating that HX chemical exchange rates can be substantially altered not only by the well-established variables of temperature and pH but also by additives including arginine, guanidine, methionine, and thiocyanate. To compensate for these additive effects, we have developed an empirical method to correct the hydrogen-exchange data for these differences. First, differences in chemical exchange rates are measured by use of an unstructured reporter peptide, YPI. An empirical chemical exchange correction factor, determined by use of the HX data from the reporter peptide, is then applied to the HX measurements obtained from a protein of interest under different solution conditions. We demonstrate that the correction is experimentally sound through simulation and in a proof-of-concept experiment using unstructured peptides under slow-exchange conditions (pD 4.5 at ambient temperature). To illustrate its utility, we applied the correction to HX-MS excipient screening data collected for a pharmaceutically relevant IgG4 mAb being characterized to determine the effects of different formulations on backbone dynamics.

A Review on Cold Start of Proton Exchange Membrane Fuel Cells

Directory of Open Access Journals (Sweden)

Zhongmin Wan

2014-05-01

Full Text Available Successful and rapid startup of proton exchange membrane fuel cells (PEMFCs at subfreezing temperatures (also called cold start is of great importance for their commercialization in automotive and portable devices. In order to maintain good proton conductivity, the water content in the membrane must be kept at a certain level to ensure that the membrane remains fully hydrated. However, the water in the pores of the catalyst layer (CL, gas diffusion layer (GDL and the membrane may freeze once the cell temperature decreases below the freezing point (Tf. Thus, methods which could enable the fuel cell startup without or with slight performance degradation at subfreezing temperature need to be studied. This paper presents an extensive review on cold start of PEMFCs, including the state and phase changes of water in PEMFCs, impacts of water freezing on PEMFCs, numerical and experimental studies on PEMFCs, and cold start strategies. The impacts on each component of the fuel cell are discussed in detail. Related numerical and experimental work is also discussed. It should be mentioned that the cold start strategies, especially the enumerated patents, are of great reference value on the practical cold start process.

On the Effect of Clamping Pressure and Method on the Current Mapping of Proton Exchange Membrane Water Electrolysis

DEFF Research Database (Denmark)

Al Shakhshir, Saher; Zhou, Fan; Kær, Søren Knudsen

The degradation of the electrochemical reaction of the proton exchange membrane water electrolysis (PEMWE) can be characterized using in-situ current mapping measurements (CMM). CMM is significantly affected by the amount of clamping pressure and method. In this work the current is mapped...

A panel data investigation of real exchange rate misalignment and growth

Directory of Open Access Journals (Sweden)

Flávio Vilela Vieira

2012-09-01

Full Text Available The paper investigates the role of real exchange rate misalignment on long-run growth for a set of ninety countries using time series data from 1980 to 2004. We first estimate a panel data model (fixed and random effects for the real exchange rate in order to produce estimates of the equilibrium real exchange rate and this is then used to construct measures of real exchange rate misalignment. We provide an alternative set of estimates of RER misalignment using panel cointegration methods. The results for the two-step System GMM panel growth models indicate that the coefficients for real exchange rate misalignment are positive for different model specification and samples, which means that a more depreciated (appreciated real exchange rate helps (harms long-run growth. The estimated coefficients are higher for developing and emerging countries.

Equilibrium amide hydrogen exchange and protein folding kinetics

International Nuclear Information System (INIS)

Bai Yawen

1999-01-01

The classical Linderstrom-Lang hydrogen exchange (HX) model is extended to describe the relationship between the HX behaviors (EX1 and EX2) and protein folding kinetics for the amide protons that can only exchange by global unfolding in a three-state system including native (N), intermediate (I), and unfolded (U) states. For these slowly exchanging amide protons, it is shown that the existence of an intermediate (I) has no effect on the HX behavior in an off-pathway three-state system (I↔U↔N). On the other hand, in an on-pathway three-state system (U↔I↔N), the existence of a stable folding intermediate has profound effect on the HX behavior. It is shown that fast refolding from the unfolded state to the stable intermediate state alone does not guarantee EX2 behavior. The rate of refolding from the intermediate state to the native state also plays a crucial role in determining whether EX1 or EX2 behavior should occur. This is mainly due to the fact that only amide protons in the native state are observed in the hydrogen exchange experiment. These new concepts suggest that caution needs to be taken if one tries to derive the kinetic events of protein folding from equilibrium hydrogen exchange experiments

Exchange Rate Instability: Japan's Micro-Macro Experiences and Implications for China

Institute of Scientific and Technical Information of China (English)

Mamoru Ishida

2006-01-01

Since 1985, the yen-dollar exchange rates repeatedly fluctuated and climbed to a level that could not be justified by economic fundamentals. The impacts on the Japanese economy were serious and far-reaching.Since 21 July 2005, China has been moving toward a more flexible exchange rate regime. Keeping RMB exchange rates basically stable and providing Chinese industries with means to hedge exchange rate risks are essential for China's sound economic development.

Exchange Rate Expectations, Currency Crises, and the Pricing of American Depositary Receipts

OpenAIRE

Eichler, Stefan

2012-01-01

I.1 Motivation Exchange rates are a key issue in international economics and politics. While the determinants of exchange rates have been extensively studied in previous works, this dissertation contributes to the literature by deriving exchange rate expectations from stock market (ADR) data and analyzing their determinants. This exercise is done for three cases where one has to resort to exchange rate expectations since the national exchange rate is either manipulated by the central bank...

Real exchange rate persistence and the excess return puzzle

DEFF Research Database (Denmark)

Juselius, Katarina; Assenmacher, Katrin

2017-01-01

The PPP puzzle refers to the wide swings of nominal exchange rates around their long-run equilibrium values whereas the excess return puzzle represents the persistent deviation of the domestic-foreign interest rate differential from the expected change in the nominal exchange rate. Using the I(2......) cointegrated VAR model, much of the excess return puzzle disappears when an uncertainty premium in the foreign exchange market, proxied by the persistent PPP gap, is introduced. Self-reinforcing feedback mechanisms seem to cause the persistence in the Swiss-US parity conditions. These results support imperfect...

Protonic conductors for proton exchange membrane fuel cells: An overview

Directory of Open Access Journals (Sweden)

Jurado Ramon Jose

2002-01-01

Full Text Available At present, Nation, which is a perfluorinated polymer, is one of the few materials that deliver the set of chemical and mechanical properties required to perform as a good electrolyte in proton exchange membrane fuel cells (PEMFCs. However, Nation presents some disadvantages, such as limiting the operational temperature of the fuel system (So°C, because of its inability to retain water at higher temperatures and also suffers chemical crossover. In addition to these restrictions, Nation membranes are very expensive. Reducing costs and using environmentally friendly materials are good reasons to make a research effort in this field in order to achieve similar or even better fuel-cell performances. Glass materials of the ternary system SiO2-ZrO2-P2O5, hybrid materials based on Nation, and nanopore ceramic membranes based on SiO2 TiO2, Al2O3, etc. are considered at present, as promising candidates to replace Nation as the electrolyte in PEMFCs. These types of materials are generally prepared by sol-gel processes in order to tailor their channel-porous structure and pore size. In this communication, the possible candidates in the near future as electrolytes (including other polymers different than Nation in PEMFCs are briefly reviewed. Their preparation methods, their electrical transport properties and conduction mechanisms are considered. The advantages and disadvantages of these materials with respect to Nation are also discussed.

Exchange Rate and Interest Rate in the Monetary Policy Reaction Function

Directory of Open Access Journals (Sweden)

Krušković Borivoje D.

2017-01-01

Full Text Available In recent years there has been a particular interest in the relation between exchange rates and interest rates both in developed countries and emerging countries. This is understandable given the important role that these variables have in determining the movement of nominal and real economic variables, including the movement of domestic inflation, real output, exports and imports, foreign exchange reserves, etc. To realized the importance of the given instruments selected macroeconomic indicators, data analysis (monthly data relating to Serbia was made on the basis of the Transfer Function Model, a data analysis (annual data relating to emerging countries was done on the basis of the Stepvise Multiple Regression model. In the transfer function model we used the Maximum Likelihood method for assessing unknown coefficients. In the gradual multiple regression model we used the Least Square method for the evaluation of unknown coefficients. All indicator values were used in the original unmodified form, i.e. there was no need for a variety of transformations. Empirical analysis showed that the exchange rate is a more significant transmission mechanism than the interest rate both in emerging markets and Serbia.

Direct sorbitol proton exchange membrane fuel cell using moderate catalyst loadings

International Nuclear Information System (INIS)

Oyarce, Alejandro; Gonzalez, Carlos; Lima, Raquel Bohn; Lindström, Rakel Wreland; Lagergren, Carina; Lindbergh, Göran

2014-01-01

Highlights: •The performance of a direct sorbitol fuel cell was evaluated at different temperatures. •The performance was compared to the performance of a direct glucose fuel cell. •The mass specific peak power density of the direct sorbitol fuel cell was 3.6 mW mg −1 totalcatalystloading at 80 °C. •Both sorbitol and glucose fuel cell suffer from deactivation. -- Abstract: Recent progress in biomass hydrolysis has made it interesting to study the use of sorbitol for electricity generation. In this study, sorbitol and glucose are used as fuels in proton exchange membrane fuel cells having 0.9 mg cm −2 PtRu/C at the anode and 0.3 mg cm −2 Pt/C at the cathode. The sorbitol oxidation was found to have slower kinetics than glucose oxidation. However, at low temperatures the direct sorbitol fuel cell shows higher performance than the direct glucose fuel cell, attributed to a lower degree of catalyst poisoning. The performance of both fuel cells is considerably improved at higher temperatures. High temperatures lower the poisoning, allowing the direct glucose fuel cell to reach a higher performance than the direct sorbitol fuel cell. The mass specific peak power densities of the direct sorbitol and direct glucose fuel cells at 65 °C was 3.2 mW mg −1 catalyst and 3.5 mW mg −1 catalyst , respectively. Both of these values are one order of magnitude larger than mass specific peak power densities of earlier reported direct glucose fuel cells using proton exchange membranes. Furthermore, both the fuel cells showed a considerably decrease in performance with time, which is partially attributed to sorbitol and glucose crossover poisoning the Pt/C cathode

Study of Hydrogen Consumption by Control System in Proton Exchange Membrane Fuel Cell

International Nuclear Information System (INIS)

Ros Emilia Rosli; Edy Herianto Majlan; Siti Afiqah Abd Hamid; Wan Ramli Wan Daud; Ramizi Mohamed; Dedi Rohendi

2016-01-01

Efficient operation results from a proper control strategy. In the operation and performance of a Proton Exchange Membrane Fuel Cell (PEMFC), the hydrogen gas flow rate is one of the most essential control parameter in addition to operating pressure, water management, temperature and humidity. This is because of the high cost and amount of energy are required to produce the purity hydrogen gas. In this paper, a Proportional Integral Derivative (PID) feedback control system is used to control the hydrogen flow rate. A strategy is adapted to balance the hydrogen use based on the loading requirements, especially during start-ups and sudden power demands. This system is implemented using National Instrument (NI) devices powered by the LabVIEW program. This is due to its simplicity and customization flexibility for measuring, processing and recording data. Designed structure allows the real-time implementation of a robust control law that is able to address the related nonlinearities and uncertainties without incurring a heavy computational load for the controller algorithm. While it facilitating a fast sampling rate according to the needs of the power system. Test results from the controller show that the new fuel control system provides good performance by reducing the amount of wasted hydrogen gas compared with that of the previous open loop system by 30 % to over 80 % saved by the varied load. This improvement is beneficial for any PEMFC that experiences fluctuating power demand, especially for vehicle applications. (author)

The Effect of Exchange Rate Volatility on Iran’s Raisin Export

OpenAIRE

2014-01-01

Exchange rate volatility is one of the effective and ambiguous factors in agricultural product export. Considering the importance of agricultural trade to avoid single-product economy, the main aim of this study was to investigate the impact of exchange rate volatility on the Raisin export of Iran during the years1959-2011. For this purpose, exchange rate volatility index was estimated using Moving Average Standard Deviation (MASD). Then, the impact of exchange rate volatility on the value of...

Mapping {sup 15}O Production Rate for Proton Therapy Verification

Energy Technology Data Exchange (ETDEWEB)

Grogg, Kira; Alpert, Nathaniel M.; Zhu, Xuping [Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts (United States); Min, Chul Hee [Department of Radiological Science, College of Health Science, Yonsei University, Wonju, Kangwon (Korea, Republic of); Testa, Mauro; Winey, Brian [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts (United States); Normandin, Marc D. [Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts (United States); Shih, Helen A.; Paganetti, Harald; Bortfeld, Thomas [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts (United States); El Fakhri, Georges, E-mail: elfakhri@pet.mgh.harvard.edu [Center for Advanced Radiological Sciences, Nuclear Medicine and Molecular Imaging, Radiology Department, Massachusetts General Hospital, Boston, Massachusetts (United States)

2015-06-01

Purpose: This work was a proof-of-principle study for the evaluation of oxygen-15 ({sup 15}O) production as an imaging target through the use of positron emission tomography (PET), to improve verification of proton treatment plans and to study the effects of perfusion. Methods and Materials: Dynamic PET measurements of irradiation-produced isotopes were made for a phantom and rabbit thigh muscles. The rabbit muscle was irradiated and imaged under both live and dead conditions. A differential equation was fitted to phantom and in vivo data, yielding estimates of {sup 15}O production and clearance rates, which were compared to live versus dead rates for the rabbit and to Monte Carlo predictions. Results: PET clearance rates agreed with decay constants of the dominant radionuclide species in 3 different phantom materials. In 2 oxygen-rich materials, the ratio of {sup 15}O production rates agreed with the expected ratio. In the dead rabbit thighs, the dynamic PET concentration histories were accurately described using {sup 15}O decay constant, whereas the live thigh activity decayed faster. Most importantly, the {sup 15}O production rates agreed within 2% (P>.5) between conditions. Conclusions: We developed a new method for quantitative measurement of {sup 15}O production and clearance rates in the period immediately following proton therapy. Measurements in the phantom and rabbits were well described in terms of {sup 15}O production and clearance rates, plus a correction for other isotopes. These proof-of-principle results support the feasibility of detailed verification of proton therapy treatment delivery. In addition, {sup 15}O clearance rates may be useful in monitoring permeability changes due to therapy.

Correlated photon-pair generation in a periodically poled MgO doped stoichiometric lithium tantalate reverse proton exchanged waveguide

NARCIS (Netherlands)

Lobino, M.; Marshall, G.D.; Xiong, C.; Clark, A.S.; Bonneau, D.; Natarajan, C.M.; Tanner, M.G.; Hadfield, R.H.; Dorenbos, S.N.; Zijlstra, T.; Zwiller, V.; Marangoni, M.; Ramponi, R.; Thompson, M.G.; Eggleton, B.J.; O'Brien, J.L.

2011-01-01

We demonstrate photon-pair generation in a reverse proton exchanged waveguide fabricated on a periodically poled magnesium doped stoichiometric lithium tantalate substrate. Detected pairs are generated via a cascaded second order nonlinear process where a pump laser at wavelength of 1.55 ?m is first

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

Science.gov (United States)

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.

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

Directory of Open Access Journals (Sweden)

K. Vogtt

2005-08-01

Full Text Available 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 (80ºC and under high pressure conditions at low temperature (3.75 kbar, -13ºC. 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.

Exchange rate stabilization under imperfect credibility

OpenAIRE

Calvo, Guillermo; Vegh, Carlos

1991-01-01

This paper analyzes stabilization policy under predetermined exchange rates in a cash-in-advance, staggered-prices model. Under full credibility, a reduction in the rate of devaluation results in an immediate and permanent reduction in the inflation rate, with no effect on output or consumption. In contrast, a non-credible stabilization results in an initial expansion of output, followed by a later recession. The inflation rate of home goods remains above the rate of devaluation throughout...

Exchange rate policy and external debt in emerging economies: an empirical analysis

OpenAIRE

Cebir, Bilgen

2012-01-01

In this thesis, we empirically analyze the e ects of exchange rate policy on external debt accumulation in emerging market economies with a sample of 15 countries over the period 1998-2010. The exchange rate policy is captured by the de facto exchange rate classi cation of Ilzetzki, Reinhart, and Rogo (2008). This classification is based on the actual exchange rate behavior rather than the officially declared regimes. Therefore, it is expected to better reflect the exchange rate policies act...

A review on the effect of proton exchange membranes in microbial fuel cells

Directory of Open Access Journals (Sweden)

Mostafa Rahimnejad

2014-03-01

Full Text Available Microorganisms in microbial fuel cells (MFC liberate electrons while the electron donors are consumed. In the anaerobic anode compartment, substrates such as carbohydrates are utilized and as a result bioelectricity is produced in the MFC. MFCs may be utilized as electricity generators in small devices such as biosensors. MFCs still face practical barriers such as low generated power and current density. Recently, a great deal of attention has been given to MFCs due to their ability to operate at mild conditions and using different biodegradable substrates as fuel. The MFC consists of anode and cathode compartments. Active microorganisms are actively catabolized to carbon sources, therefore generating bioelectricity. The produced electron is transmitted to the anode surface but the generated protons must pass through the proton exchange membrane (PEM in order to reach the cathode compartment. PEM as a key factor affecting electricity generation in MFCs has been investigated here and its importance fully discussed.

Proton exchange membrane materials for the advancement of direct methanol fuel-cell technology

Science.gov (United States)

Cornelius, Christopher J [Albuquerque, NM

2006-04-04

A new class of hybrid organic-inorganic materials, and methods of synthesis, that can be used as a proton exchange membrane in a direct methanol fuel cell. In contrast with Nafion.RTM. PEM materials, which have random sulfonation, the new class of materials have ordered sulfonation achieved through self-assembly of alternating polyimide segments of different molecular weights comprising, for example, highly sulfonated hydrophilic PDA-DASA polyimide segment alternating with an unsulfonated hydrophobic 6FDA-DAS polyimide segment. An inorganic phase, e.g., 0.5 5 wt % TEOS, can be incorporated in the sulfonated polyimide copolymer to further improve its properties. The new materials exhibit reduced swelling when exposed to water, increased thermal stability, and decreased O.sub.2 and H.sub.2 gas permeability, while retaining proton conductivities similar to Nafion.RTM.. These improved properties may allow direct methanol fuel cells to operate at higher temperatures and with higher efficiencies due to reduced methanol crossover.

Cross-correlations between RMB exchange rate and international commodity markets

Science.gov (United States)

Lu, Xinsheng; Li, Jianfeng; Zhou, Ying; Qian, Yubo

2017-11-01

This paper employs multifractal detrended analysis (MF-DFA) and multifractal detrended cross-correlation analysis (MF-DCCA) to study cross-correlation behaviors between China's RMB exchange rate market and four international commodity markets, using a comprehensive set of data covering the period from 22 July 2005 to 15 March 2016. Our empirical results from MF-DFA indicate that the RMB exchange rate is the most inefficient among the 4 selected markets. The results from quantitative analysis have testified the existence of cross-correlations and the result from MF-DCCA have further confirmed a strong multifractal behavior between RMB exchange rate and international commodity markets. We also demonstrate that the recent financial crisis has significant impact on the cross-correlated behavior. Through the rolling window analysis, we find that the RMB exchange rates and international commodity prices are anti-persistent cross-correlated. The main sources of multifractality in the cross-correlations are long-range correlations between RMB exchange rate and the aggregate commodity, energy and metals index.

Influence of Silica/Sulfonated Polyether-Ether Ketone as Polymer Electrolyte Membrane for Hydrogen Fueled Proton Exchange Membrane Fuel Cells

Directory of Open Access Journals (Sweden)

Sri Handayani

2011-12-01

Full Text Available The operation of non-humidified condition of proton exchange membrane fuel cell (PEMFC using composite sPEEK-silica membrane is reported. Sulfonated membrane of PEEK is known as hydrocarbon polyelectrolyte membrane for PEMFC and direct methanol fuel cell (DMFC. The state of the art of fuel cells is based on the perluorosulfonic acid membrane (Nafion. Nafion has been the most used in both PEMFC and DMFC due to good performance although in low humidified condition showed poor current density. Here we reported the effect of silica in hydrocarbon sPEEK membrane that contributes for a better water management system inside the cell, and showed 0.16 W/cm2 of power density which is 78% higher than that of non-silica modified [Keywords: composite membrane, polyether-ether ketone, silica, proton exchange membrane fuel cell].

Statistical Analysis of the Exchange Rate of Bitcoin.

Science.gov (United States)

Chu, Jeffrey; Nadarajah, Saralees; Chan, Stephen

2015-01-01

Bitcoin, the first electronic payment system, is becoming a popular currency. We provide a statistical analysis of the log-returns of the exchange rate of Bitcoin versus the United States Dollar. Fifteen of the most popular parametric distributions in finance are fitted to the log-returns. The generalized hyperbolic distribution is shown to give the best fit. Predictions are given for future values of the exchange rate.

EXCHANGE-RATES FORECASTING: EXPONENTIAL SMOOTHING TECHNIQUES AND ARIMA MODELS

Directory of Open Access Journals (Sweden)

Dezsi Eva

2011-07-01

Full Text Available Exchange rates forecasting is, and has been a challenging task in finance. Statistical and econometrical models are widely used in analysis and forecasting of foreign exchange rates. This paper investigates the behavior of daily exchange rates of the Romanian Leu against the Euro, United States Dollar, British Pound, Japanese Yen, Chinese Renminbi and the Russian Ruble. Smoothing techniques are generated and compared with each other. These models include the Simple Exponential Smoothing technique, as the Double Exponential Smoothing technique, the Simple Holt-Winters, the Additive Holt-Winters, namely the Autoregressive Integrated Moving Average model.

New load cycling strategy for enhanced durability of high temperature proton exchange membrane fuel cell

DEFF Research Database (Denmark)

Thomas, Sobi; Jeppesen, Christian; Steenberg, Thomas

2017-01-01

The objective of this paper is to develop a new operational strategy to increase the lifetime of a high temperature proton exchange membrane (HT-PEMFCs) fuel cell system by using load cycling patterns to reduce the phosphoric acid loss from the fuel cell. Four single cells were operated under.......8 Acm-2 for the higher end, were selected for the load cycling operation. The relaxation time, which is the period of time spent at low current density operation, is varied to understand how the performance over prolonged period behaves. The duration of the high current density operation is selected...... based on the relaxation time in order to have the same average current density of (0.55 Acm-2 ) for all the cells. Cell 5, with a relaxation time of 2 min performs best and shows lower degradation rate of 36 μVh-1 compared to other load cycling cells with smaller relaxation times. The cell operated...

Latitudinal and longitudinal dispersion of energetic auroral protons

Directory of Open Access Journals (Sweden)

D. A. Lorentzen

Full Text Available Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300-350 km and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.

Key words. Ionosphere (auroral ionosphere; · particle precipitation · Space plasma physics · (transport processes

Latitudinal and longitudinal dispersion of energetic auroral protons

Directory of Open Access Journals (Sweden)

D. A. Lorentzen

2000-01-01

Full Text Available Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300-350 km and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.Key words. Ionosphere (auroral ionosphere; · particle precipitation · Space plasma physics · (transport processes

Estimating Exchange Market Pressure and the Degree of Exchange Market Intervention for Finland during the Floating Exchange Rate Regime

OpenAIRE

Pösö, Mika; Spolander, Mikko

1997-01-01

In this paper, we use a fairly simple monetary macro model to calculate the quarterly measures of exchange market pressure and the degree of the Bank of Finland's intervention during the time the markka was floated. Exchange market pressure measures the size of the exchange rate change that would have occurred if the central bank had unexpectedly refrained from intervening in the foreign exchange market. Intervention activity of the central bank is measured as the proportion of exchange marke...

Dynamic behavior of liquid water transport in a tapered channel of a proton exchange membrane fuel cell cathode

NARCIS (Netherlands)

Akhtar, N.; Kerkhof, P.J.A.M.

2011-01-01

A numerical model of a proton exchange membrane fuel cell (PEMFC) cathode with a tapered channel design has been developed in order to examine the dynamic behavior of liquid water transport. Three-dimensional, transient simulations employing the level-set method (available in COMSOL 3.5a, a

Predicting liquid water saturation through differently structured cathode gas diffusion media of a proton exchange Membrane Fuel Cell

NARCIS (Netherlands)

Akhtar, N.; Kerkhof, P.J.A.M.

2012-01-01

The role of gas diffusion media with differently structured properties have been examined with emphasis on the liquid water saturation within the cathode of a proton exchange membrane fuel cell (PEMFC). The cathode electrode consists of a gas diffusion layer (GDL), a micro-porous layer and a

Recommended data on proton-ion collision rate coefficients for Fe X-Fe XV ions

International Nuclear Information System (INIS)

Skobelev, I.; Murakami, I.; Kato, T.

2006-01-01

The proton-ion collisions are important for excitation of some ion levels in a high-temperature low density plasma. In the present work evaluation of data obtained for proton-induced transitions in Fe X - Fe XV ions with the help of different theoretical methods is carried out. It is suggested a simple analytical formula with 7 parameters allowing to describe dependency of proton rate coefficient on proton temperature in an enough wide temperature range. The values of free parameters have been determined by fitting of approximation formula to numerical data and are presented for recommended data together with fitting accuracies. By comparing of proton collision rates with electron ones it is shown that proton impact excitation processes may be important for Fe X, XI, XIII-XV ions. The results obtained can be used for plasma kinetics calculations and for development of spectroscopy methods of plasma diagnostics. (author)

A re-examination of the exchange rate overshooting hypothesis

African Journals Online (AJOL)

kirstam

Studies on exchange rate overshooting on the Zambian foreign exchange rate market are .... depreciation between 2008 and 2009 during the great recession. Figure 2 shows ...... manufacturing sector in Nigeria', European Journal of Business and Management, 5(22):. 67–73 .... paper. Washington, DC: IMF Working Paper.

Correlation of infrared spectra and phase transitions in annealed proton-exchanged MgO doped LiNbO3

International Nuclear Information System (INIS)

Sun, Jian; Xu, Chang-qing

2015-01-01

Infrared spectra of OH − groups in annealed proton-exchanged (APE) 5 mol. % MgO-doped LiNbO 3 (MgO:LiNbO 3 ) crystals were studied using the Fourier transform infrared spectroscopy technique. Samples were prepared by benzoic acid proton-exchange followed with thermal annealing in oxygen. Evolutions of absorption peaks in APE MgO:LiNbO 3 crystals were recorded and analyzed. Comparing with none-doped APE LiNbO 3 crystals, a different phase transition behavior was found during thermal annealing. A periodically poled MgO:LiNbO 3 slab waveguide was prepared using identical procedures, and the second harmonic generation (SHG) signals were measured. Comparing the obtained SHG results with the infrared spectra, relationships between the phase transitions and the recovery of second-order nonlinear coefficients during thermal annealing were investigated. Finally, a method for optimizing the performance of MgO:LiNbO 3 waveguides was proposed

Application for Determination of the Forward Exchange Rate in Access 2003

Directory of Open Access Journals (Sweden)

Loredana MOCEAN

2006-01-01

Full Text Available The exchange rate set the present rate for a foreign currency transaction with payment or delivery at some future date. Forward rates are calculated by using the current exchange rate for the currency pair and the interest rates for the two currencies and allow you to lock in rate now for a future. This paper describes the formulas which determinate the forward exchange rate and how can we implement them in a short, but efficient informatics application.

The Brazilian experience in managing interest-exchange rate nexus

OpenAIRE

Ricardo Carneiro; Pedro Rossi

2013-01-01

This paper addresses four main questions: firstly, it discusses some theoretical background related to the interest-exchange rate nexus; secondly, it makes an attempt to explain why the interest rate in Brazil is so high, examining briefly the main explanations for it; thirdly, it describes Brazil’s foreign exchange markets, their size and hierarchy; and lastly, it explains the carry trade dynamics considering the institutionalism of the Brazilian foreign exchange market and also the govern...

Real Exchange Rate and Productivity in an OLG Model

OpenAIRE

Thi Hong Thinh DOAN; Karine GENTE

2013-01-01

This article develops an overlapping generations model to show how demography and savings affect the relationship between real exchange rate (RER) and productivity. In high-saving (low-saving) countries and/or low-population-growth-rate countries, a rise in productivity leads to a real depreciation (appreciation) whereas the RER may appreciate or depreciate in highproduction-growth-rate. Using panel data, we conclude that a rise in productivity generally causes a real exchange rate appreciati...

Exchange Rate Regime and External Adjustment in CEE Countries