Intermediate Exchange Research Articles

Nafion/IL Intermediate Temperature Proton Exchange Membranes Improved by Mesoporous Hollow Silica Spheres

AbstractA novel polyelectrolyte composite membrane was designed and prepared for intermediate temperature proton exchange membrane fuel cells (PEMFCs). It was composed of perfluorosulfonic acid resin (Nafion®), protic ionic liquid (IL, [dema][TfO]) and mesoporous hollow silica spheres (MHSi). The morphologies of MHSi and Nafion‐based composite membranes were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of MHSi on proton conductivity of the composite membranes versus relative humidity (RH) and temperature (100–140 °C) were investigated. The results indicated, that the Nafion/IL/MHSi composite membranes exhibited excellent proton conductivity even under 30% RH or high temperature (above 100 °C). A high proton conductivity (5.41 mS cm−1) of the composite membrane at 30 °C and 30% RH can be observed from the test result, which was five times higher than that of the pristine Nafion. The N‐IL‐12S composite membrane showed an outstanding proton conductivity, as far as 14.7 mS cm−1 under 140 °C and low RH, which was almost two orders higher than that of the pristine Nafion membrane. Moreover, the unique hollow and mesoporous structure of MHSi improved IL retention rate of the membrane evidently. Together with high thermal stability of the composite membrane confirmed by thermogravimetric analysis (TGA), the Nafion/IL composite membrane improved by MHSi is a potential candidate in intermediate temperature PEMFC.

Nematic quantum phases in the bilayer honeycomb antiferromagnet

The spin$-1/2$ Heisenberg antiferromagnet on the honeycomb bilayer lattice is shown to display a rich variety of semiclassical and genuinely quantum phases, controlled by the interplay between intralayer frustration and interlayer exchange. Employing a complementary set of techniques, comprising spin rotationally invariant Schwinger boson mean field theory, bond operators, and series expansions we unveil the quantum phase diagram, analyzing low-energy excitations and order parameters. By virtue of Schwinger bosons we scan the complete range of exchange parameters, covering both long range ordered as well as quantum disordered ground states and reveal the existence of an extended, frustration induced lattice nematic phase in a range of intermediate exchange unexplored so far.

Ligand Proton Pseudocontact Shifts Determined from Paramagnetic Relaxation Dispersion in the Limit of NMR Intermediate Exchange.

Delineation of protein-ligand interaction modes is key for rational drug discovery. The availability of complex crystal structures is often limited by the aqueous solubility of the compounds, while lead-like compounds with micromolar affinities normally fall into the NMR intermediate exchange regime, in which severe line broadening to beyond the detection of interfacial resonances limits NMR applications. Here, we developed a new method to retrieve low-populated bound-state 1H pseudocontact shifts (PCSs) using paramagnetic relaxation dispersion (RD). We evaluated using a 1H PCS-RD approach in a BRM bromodomain lead-like inhibitor to filter molecular docking poses using multiple intermolecular structural restraints. Considering the universal presence of proton atoms in druglike compounds, our work will have wide application in structure-guided drug discovery even under an extreme condition of NMR intermediate exchange and low aqueous solubility of ligands.

Substrate Binding Drives Active-Site Closing of Human Blood Group B Galactosyltransferase as Revealed by Hot-Spot Labeling and NMR Spectroscopy Experiments.

Crystallography has shown that human blood group A (GTA) and B (GTB) glycosyltransferases undergo transitions between "open", "semiclosed", and "closed" conformations upon substrate binding. However, the timescales of the corresponding conformational reorientations are unknown. Crystal structures show that the Trp and Met residues are located at "conformational hot spots" of the enzymes. Therefore, we utilized 15 N side-chain labeling of Trp residues and 13 C-methyl labeling of Met residues to study substrate-induced conformational transitions of GTB. Chemical-shift perturbations (CSPs) of Met and Trp residues in direct contact with substrate ligands reflect binding kinetics, whereas the CSPs of Met and Trp residues at remote sites reflect conformational changes of the enzyme upon substrate binding. Acceptor binding is fast on the chemical-shift timescale with rather small CSPs in the range of less than approximately 20 Hz. Donor binding matches the intermediate exchange regime to yield an estimate for exchange rate constants of approximately 200-300 Hz. Donor or acceptor binding to GTB saturated with acceptor or donor substrate, respectively, is slow (<10 Hz), as are coupled protein motions, reflecting mutual allosteric control of donor and acceptor binding. Remote CSPs suggest that substrate binding drives the enzyme into the closed state required for catalysis. These findings should contribute to better understanding of the mechanism of glycosyl transfer of GTA and GTB.

Liquidity risk in sequential trading networks

This paper studies a model of intermediated exchange with liquidity-constrained traders. Intermediaries are embedded in a trading network and their financial capacities are private information. We characterize our model's monotone, pure-strategy equilibrium. Agents earn positive intermediation rents in equilibrium. An experimental investigation supports the model's baseline predictions concerning agents' strategies, price dynamics, and the division of surplus. While private financial constraints inject uncertainty into the trading environment, our experiment suggests they are also a behavioral speed-bump, preventing traders from experiencing excessive losses due to overbidding.

One-Pot Synthesis of Deuterated Aldehydes from Arylmethyl Halides.

A facile, one-pot approach for synthesizing deuterated aldehydes from arylmethyl halides was developed using D2O as the deuterium source. The efficient process is realized by a sequence of formation, H/D exchange, and oxidation of pyridinium salt intermediates. The mild and air-compatible reaction conditions enable efficient synthesis of diverse deuterated aldehydes with high deuterium incorporation.

The Phase Behavior and Organization of Sphingomyelin/Cholesterol Membranes: A Deuterium NMR Study

We have studied the dependence of the phase and domain characteristics of sphingomyelin (SM)/cholesterol model membranes on sterol content and temperature using deuterium nuclear magnetic resonance. NMR spectra of N-palmitoyl(D31)-D-erythro-sphingosylphosphorylcholine (PSM-d31) were taken for temperatures from 25 to 70°C and cholesterol concentrations of 0–40%. Analogous experiments were performed using 1-palmitoyl,2-palmitoyl(D31)-sn-glycero-3-phosphocholine (DPPC-d31)/cholesterol membranes to carefully compare the data obtained using palmitoyl chains that have similar “kinked” conformations. The constructed phase diagrams exhibit both solid-ordered (so) + liquid-ordered (lo) and liquid-disordered (ld) + lo phase-coexistence regions with a clear three-phase line. Macroscopic (micron-sized) coexistence of ld and lo phases was not observed; instead, line-broadening in the ld+lo region was characterized by intermediate exchange of lipids between the two types of domains. The length scales associated with the domains were estimated to be 75–150 nm for PSM-d31/cholesterol and DPPC-d31/cholesterol model membranes.

Heterogeneous Co(OH)2 nanoplates/Co3O4 nanocubes enriched with oxygen vacancies enable efficient oxygen evolution reaction electrocatalysis.

Heterogeneous Co(OH)2 nanoplate/Co3O4 nanocube hybrids with rich oxygen vacancies have been constructed through a controllable approach. The high surface areas of such unique nanohybrids together with abundant oxygen vacancies provide more surface active sites, which can facilitate the charge transfer and boost the exchange of intermediates. Specifically, the resultant Co(OH)2 nanoplate/Co3O4 nanocube hybrids display outstanding oxygen evolution reaction (OER) performances with a low overpotential of 281 mV at 10 mA cm-2 and excellent durability after continuous CV of 3000 cycles, shedding light for large-scale applications in practical water splitting.

Lateral Exchange Markets: How Social Platforms Operate in a Networked Economy

Lateral exchange markets (LEMs) are sites of technologically intermediated exchange between actors occupying equivalent network positions. To develop an enriched understanding of these markets, the authors develop a more broad-based and differentiated understanding of peer-to-peer, sharing, and access-based markets. They focus on two key axes: the extent of (1) consociality and (2) platform intermediation. Drawing on these attributes, the authors theoretically deduce four ideal types—Forums, Enablers, Matchmakers, and Hubs. Each type provides value in a different way: Forums connect actors, Enablers equip actors, Matchmakers pair actors, and Hubs centralize exchange. Twenty organizational cases reveal insights into the failure, adaptation, and success of LEMs. Lateral exchange markets shift responsibility for personal and exchange security to relevant personal actors, to institutions, or to the governing algorithms of technology platforms. Extending the general proposition that sociality increasingly infuses market logics, the findings suggest a new frontier in which social resources and software platform algorithms interact as operand resources whose negative consequences (e.g., opportunism) require careful management through assurances and institutional arrangements matched to the type of LEM operation.

Film, Performance, and the Spaces Between: The Collaborative Works of Mara Mattuschka and Chris Haring

This article takes as its starting point five collaborative experimental films by choreographer Chris Haring and filmmaker Mara Mattuschka. Transposing live stage performances into self-contained cinematic worlds, these works represent compelling examples of intermedial exchange. The article draws on intermedial discourse, performance theory, dance film, and theories of space, body, and voice to illustrate how the films self-consciously stage their own process of transformation through an emphasis on the physical, sensual, and metaphorical spaces between.

Cost of Banking Crises: Does the Policy Framework Matter?

This paper empirically investigates how the stringency of macroeconomic policy frameworks impacts the unconditional cost of banking crises. We consider monetary, fiscal and exchange rate policies. A restrictive policy framework may promote stronger banking stability, by enhancing discipline and credibility, and by giving financial room to policymakers. At the same time though, tying the hands of policymakers may be counterproductive and procyclical, especially if it prevents them from responding properly to financial imbalances and crises. Our analysis considers a sample of 146 countries over the period 1970-2013, and reveals that extremely restrictive policy frameworks are likely to increase the expected cost of banking crises. By contrast, by combining discipline and flexibility, some policy arrangements such as budget balance rules with an easing clause, intermediate exchange rate regimes or an inflation targeting framework may significantly contain the cost of banking crises. As such, we provide evidence on the benefits of “constrained discretion” for the real impact of banking crises.

Choosing the Exchange Rate Regime-a Case for Intermediate Regimes for Emerging and Developing Economies

The main objective of the paper is to verify the vanishing interim regime hypothesis (so-called bipolar view) and to analyse factors that may influence the probability of use of intermediate exchange rate regimes, especially in emerging and developing economies. In order to accomplish the research objectives the evolution of exchange rate regimes is presented with the special consideration of decisions of IMF member states in this respect. Next a logistic regression model that estimates the probability of use of an intermediate regime is applied. The results achieved allow a challenge to the vanishing interim regime hypothesis. Empirical observations support this hypothesis only in advanced countries and not in their emerging and developing peers.

Porous cobalt oxide nanoplates enriched with oxygen vacancies for oxygen evolution reaction

Porous cobalt oxide nanoplates enriched with oxygen vacancies are synthesized using a ligand-assisted polyol reduction method. This method enables large-scale synthesis that offers superior uniformity, solution dispersity and controllable concentration of oxygen vacancies on surface. The large surface area of porous cobalt oxide nanoplates together with enriched oxygen vacancies provide more active sites, which promote faster exchange of intermediates and more efficient electron transfer. The as prepared cobalt oxide nanoplates manifest oxygen evolution reaction (OER) overpotential as low as 306mV at 10mA/cm2 in 1M KOH, which is superior to the values of most reported Co-based electrocatalysts.

Unemployment and optimal exchange rate in an open economy

China has been criticized for adopting a low yuan policy to take unfair advantage of its trading partners. This paper considers the optimal exchange rate policy of a Keynesian open economy with unemployed resources. In the case of Cobb-Douglas utility and production functions, indirect utility is monotone-increasing and concave in the exchange rate. Yuan devaluation is shown to reduce unemployment. Moreover, the optimal exchange rate is one which guarantees full employment. The United States may want to choose a different rate which ensures full employment. The two countries could negotiate an intermediate exchange rate for which some unemployment exists in both countries.

Fluorine Pseudocontact Shifts Used for Characterizing the Protein-Ligand Interaction Mode in the Limit of NMR Intermediate Exchange.

The characterization of protein-ligand interaction modes becomes recalcitrant in the NMR intermediate exchange regime as the interface resonances are broadened beyond detection. Here, we determined the 19 F low-populated bound-state pseudocontact shifts (PCSs) of mono- and di-fluorinated inhibitors of the BRM bromodomain using a highly skewed protein/ligand ratio. The bound-state 19 F PCSs were retrieved from 19 F chemical exchange saturation transfer (CEST) in the presence of the lanthanide-labeled protein, which was termed the 19 F PCS-CEST approach. These PCSs enriched in spatial information enabled the identification of best-fitting poses, which agree well with the crystal structure of a more soluble analog in complex with the BRM bromodomain. This approach fills the gap of the NMR structural characterization of lead-like inhibitors with moderate affinities to target proteins, which are essential for structure-guided hit-to-lead evolution.

Fluorine Pseudocontact Shifts Used for Characterizing the Protein–Ligand Interaction Mode in the Limit of NMR Intermediate Exchange

AbstractThe characterization of protein–ligand interaction modes becomes recalcitrant in the NMR intermediate exchange regime as the interface resonances are broadened beyond detection. Here, we determined the 19F low‐populated bound‐state pseudocontact shifts (PCSs) of mono‐ and di‐fluorinated inhibitors of the BRM bromodomain using a highly skewed protein/ligand ratio. The bound‐state 19F PCSs were retrieved from 19F chemical exchange saturation transfer (CEST) in the presence of the lanthanide‐labeled protein, which was termed the 19F PCS‐CEST approach. These PCSs enriched in spatial information enabled the identification of best‐fitting poses, which agree well with the crystal structure of a more soluble analog in complex with the BRM bromodomain. This approach fills the gap of the NMR structural characterization of lead‐like inhibitors with moderate affinities to target proteins, which are essential for structure‐guided hit‐to‐lead evolution.

Three‐chamber Bioelectrochemical System for Biogas Upgrading and Nutrient Recovery

AbstractHere, an innovative three‐chamber bioelectrochemical system configuration is proposed to combine COD, CO2 and NH4+ removal into a single device. In the proposed process, while COD oxidation and CO2 reduction occurred, respectively, in the anodic and cathodic chamber, the consequent current generation promoted the migration of target ionic species towards an intermediate accumulation chamber, across cation and anion exchange membranes, respectively. Under this configuration, COD removal proceeded in the anode chamber with an average removal rate of 841 mgCOD L−1 d−1 while the cathode was able to remove 2.1 gCO2 L−1 d−1 and produce 60 meq L−1 d−1 of CH4. Around 90% of the removed CO2 was contained in the concentrated spill (at around 20 g L−1 of bicarbonate), which was recovered from the intermediate accumulation chamber and also contained the removed nitrogen as ammonium ion (around 32% removal and around 4‐fold concentration with respect to the anode influent). Methane generation allowed a partial recovery of energy of overall energy consumption costs of both COD and CO2 removal. This study confirms the possibility to combine three processes into a single bioelectrochemical device.

Constraints on nonstandard intermediate boson exchange models from neutrino-electron scattering

Constraints on couplings of several Beyond Standard Model Physics scenarios, mediated by massive intermediate particles including (1) Extra Z-prime, (2) New Light Spin-1 Boson, and (3) Charged Higgs Boson, are placed via neutrino-electron scattering channel to test Standard Model at low energy-momentum transfer regime. Data on $\bar{\nu}_{e}-e$ and $\nu_{e}-e$ scattering from the TEXONO and LSND Experiments, respectively, are used. Upper bounds to coupling constants of Flavor Conserving and Flavor Violating New Light Spin-1 Boson and Charged Higgs Boson with respect to different mediator masses are determined. The relevant parameter spaces are extended by allowing light mediators. New lower mass limits for extra Z-prime gauge boson models are also placed.

The effects of real exchange rate volatility on sectoral export flows under intermediate and flexible exchange rate regimes: Empirical evidence from Turkey

The aim of this paper is to analyse empirically the effects of real exchange rate volatility on sectoral exports in Turkey under intermediate and flexible exchange rate regimes. The cointegration test and error correction models are used to test the long-run relationship and short-run effects, respectively. The estimation results show that the real exchange rate volatility has negative and significant effects on sectoral exports in both intermediate and flexible exchange rate regimes. These empirical results are consistent with the theory. However, the impact of real exchange rate and foreign income appeared to be quite different for the two exchange rate regimes. Further, research is required to analyse the impacts of real exchange rate and foreign income on sectoral exports. Keywords: Real exchange rate volatility, real exchange rate, intermediate exchange rate regime, flexible exchange rate regime, sectoral export.

Real Exchange Rate Volatility and Sectoral Export Flows Under Intermediate and Flexible Exchange Rate Regimes: Empirical Evidence From Turkey

Real Exchange Rate Volatility and Sectoral Export Flows Under Intermediate and Flexible Exchange Rate Regimes: Empirical Evidence From Turkey