Symptom burden guiding invasive electrophysiological study in paroxysmal supraventricular tachycardia: The believe SVT registry.

BACKGROUND AND OBJECTIVE: Patients with palpitations clinically suggestive of paroxysmal supraventricular tachycardia (PSVT) are often managed conservatively until ECG-documentation of the tachycardia, leading to high impact on life quality and healthcare resource utilization. We evaluated results of electrophysiological study (EPS), and ablation when appropriate, among these patients, with special focus on gender differences in management. METHODS: BELIEVE SVT is a European multicenter, retrospective registry in tertiary hospitals performing EPS in patients with palpitations, without ECG-documentation of tachycardia or preexcitation, and considered highly suggestive of PSVT by a cardiologist or cardiac electrophysiologist. We analyzed clinical characteristics, results of EPS and ablation, complications, and clinical outcomes during follow-up. RESULTS: Six-hundred eighty patients from 20 centers were included. EPS showed sustained tachycardia in 60.9% of patients, and substrate potentially enabling AVNRT in 14.7%. No major/permanent complications occurred. Minor/transient complications were reported in 0.84% of patients undergoing diagnostic-only EPS and 1.8% when followed by ablation. During a 3.4-year follow-up, 76.2% of patients remained free of palpitations recurrence. Ablation (OR: 0.34, P < .01) and male gender (OR: 0.58, P = .01) predicted no recurrence. Despite a higher female proportion among patients with recurrence, (77.2% vs 63.5% among those asymptomatic during follow-up, P < .01), 73% of women in this study reported no recurrence of palpitations after EPS. CONCLUSIONS: EPS and ablation are safe and effective in preventing recurrence of nondocumented palpitations clinically suggestive of PSVT. Despite a lower efficacy, this strategy is also highly effective among women and warrants no gender differences in management.

Challenges of modeling nanostructured materials for photocatalytic water splitting.

Understanding the water splitting mechanism in photocatalysis is a rewarding goal as it will allow producing clean fuel for a sustainable life in the future. However, identifying the photocatalytic mechanisms by modeling photoactive nanoparticles requires sophisticated computational techniques based on multiscale modeling. In this review, we will survey the strengths and drawbacks of currently available theoretical methods at different length and accuracy scales. Understanding the surface-active site through Density Functional Theory (DFT) using new, more accurate exchange-correlation functionals plays a key role for surface engineering. Larger scale dynamics of the catalyst/electrolyte interface can be treated with Molecular Dynamics albeit there is a need for more generalizations of force fields. Monte Carlo and Continuum Modeling techniques are so far not the prominent path for modeling water splitting but interest is growing due to the lower computational cost and the feasibility to compare the modeling outcome directly to experimental data. The future challenges in modeling complex nano-photocatalysts involve combining different methods in a hierarchical way so that resources are spent wisely at each length scale, as well as accounting for excited states chemistry that is important for photocatalysis, a path that will bring devices closer to the theoretical limit of photocatalytic efficiency.

Carbon Dioxide Capture Enhanced by Pre-Adsorption of Water and Methanol in UiO-66.

The rapidly rising level of carbon dioxide in the atmosphere resulting from human activity is one of the greatest environmental problems facing our civilization today. Most technologies are not yet sufficiently developed to move existing infrastructure to cleaner alternatives. Therefore, techniques for capturing carbon dioxide from emission sources may play a key role at the moment. The structure of the UiO-66 material not only meets the requirement of high stability in contact with water vapor but through the water pre-adsorbed in the pores, the selectivity of carbon dioxide adsorption is increased. We successfully applied the recently developed methodology for water adsorption modelling. It allowed to elucidate the influence of water on CO2 adsorption and study the mechanism of this effect. We showed that water is adsorbed in octahedral cage and stands for promotor for CO2 adsorption in less favorable space than tetrahedral cages. Water plays a role of a mediator of adsorption, what is a general idea of improving affinity of adsorbate. On the basis of pre-adsorption of methanol as another polar solvent, we have shown that the adsorption sites play a key role here, and not, as previously thought, only the interaction between the solvent and quadrupole carbon dioxide. Overall, we explained the mechanism of increased CO2 adsorption in the presence of water and methanol, as polar solvents, in the UiO-66 pores for a potential post-combustion carbon dioxide capture application.

New Features of the Open Source Monte Carlo Software Brick-CFCMC: Thermodynamic Integration and Hybrid Trial Moves.

We present several new major features added to the Monte Carlo (MC) simulation code Brick-CFCMC for phase- and reaction equilibria calculations (https://gitlab.com/ETh_TU_Delft/Brick-CFCMC). The first one is thermodynamic integration for the computation of excess chemical potentials (µex). For this purpose, we implemented the computation of the ensemble average of the derivative of the potential energy with respect to the scaling factor for intermolecular interactions (⟨∂U∂λ⟩). Efficient bookkeeping is implemented so that the quantity ∂U∂λ is updated after every MC trial move with negligible computational cost. We demonstrate the accuracy and reliability of the calculation of µex for sodium chloride in water. Second, we implemented hybrid MC/MD translation and rotation trial moves to increase the efficiency of sampling of the configuration space. In these trial moves, short Molecular Dynamics (MD) trajectories are performed to collectively displace or rotate all molecules in the system. These trajectories are accepted or rejected based on the total energy drift. The efficiency of these trial moves can be tuned by changing the time step and the trajectory length. The new trial moves are demonstrated using MC simulations of a viscous fluid (deep eutectic solvent).

Multi-scale Entropy Evaluates the Proarrhythmic Condition of Persistent Atrial Fibrillation Patients Predicting Early Failure of Electrical Cardioversion.

Atrial fibrillation (AF) is nowadays the most common cardiac arrhythmia, being associated with an increase in cardiovascular mortality and morbidity. When AF lasts for more than seven days, it is classified as persistent AF and external interventions are required for its termination. A well-established alternative for that purpose is electrical cardioversion (ECV). While ECV is able to initially restore sinus rhythm (SR) in more than 90% of patients, rates of AF recurrence as high as 20-30% have been found after only a few weeks of follow-up. Hence, new methods for evaluating the proarrhythmic condition of a patient before the intervention can serve as efficient predictors about the high risk of early failure of ECV, thus facilitating optimal management of AF patients. Among the wide variety of predictors that have been proposed to date, those based on estimating organization of the fibrillatory (f-) waves from the surface electrocardiogram (ECG) have reported very promising results. However, the existing methods are based on traditional entropy measures, which only assess a single time scale and often are unable to fully characterize the dynamics generated by highly complex systems, such as the heart during AF. The present work then explores whether a multi-scale entropy (MSE) analysis of the f-waves may provide early prediction of AF recurrence after ECV. In addition to the common MSE, two improved versions have also been analyzed, composite MSE (CMSE) and refined MSE (RMSE). When analyzing 70 patients under ECV, of which 31 maintained SR and 39 relapsed to AF after a four week follow-up, the three methods provided similar performance. However, RMSE reported a slightly better discriminant ability of 86%, thus improving the other multi-scale-based outcomes by 3-9% and other previously proposed predictors of ECV by 15-30%. This outcome suggests that investigation of dynamics at large time scales yields novel insights about the underlying complex processes generating f-waves, which could provide individual proarrhythmic condition estimation, thus improving preoperative predictions of ECV early failure.

Homochiral Metal-Organic Frameworks for Enantioselective Separations in Liquid Chromatography.

Selective separation of enantiomers is a substantial challenge for the pharmaceutical industry. Chromatography on chiral stationary phases is the standard method, but at a very high cost for industrial-scale purification due to the high cost of the chiral stationary phases. Typically, these materials are poorly robust, expensive to manufacture, and often too specific for a single desired substrate, lacking desirable versatility across different chiral analytes. Here, we disclose a porous, robust homochiral metal-organic framework (MOF), TAMOF-1, built from copper(II) and an affordable linker prepared from natural l-histidine. TAMOF-1 has shown to be able to separate a variety of model racemic mixtures, including drugs, in a wide range of solvents of different polarity, outperforming several commercial chiral columns for HPLC separations. Although not exploited in the present article, it is worthy to mention that the preparation of this new material is scalable to the multikilogram scale, opening unprecedented possibilities for low-energy chiral separation at the industrial scale.

Intermediate states approach for adsorption studies in flexible metal-organic frameworks.

Adsorption studies in flexible metal-organic frameworks are challenging and time-consuming. It is mainly because the mechanism of adsorption, defined by structural framework properties, is constantly modified during the process, as the framework transformation depends on the adsorption uptake. We propose here a new approach to investigate adsorption in such complex systems, in which the simulations of adsorption in a deforming framework are replaced by the analysis of adsorption in intermediate rigid structures. As a proof of concept we analyze carbon dioxide, hexane, and methane adsorption in MIL-53. 19 intermediate structures were generated using geometrical interpolation between the open and the closed MOF forms and optimized with quantum DFT calculations. The grand canonical Monte Carlo method was applied to calculate adsorption isotherms in all intermediate structures. The comparison with experimental results enabled the identification of the intermediate adsorption states. The analysis of the microscopic configurations of the adsorbed molecules in these structures allowed us to propose a new mechanism of adsorbate evolution over the entire process.

Phase Transition Induced by Gas Adsorption in Metal-Organic Frameworks.

We present a molecular simulation study with the aim of investigating the structural phase transition of ZJU-198 metal-organic framework. This material has been recently synthetized with the appropriate control of window size, which performs well for the separation of mixtures of gases containing nitrogen and methane. We find that the adsorption of small gases in this structure is unusual, and provide an explanation of the molecular mechanisms involved. Using molecular simulation, we analyze the structural distortions exerted by the adsorption of carbon dioxide, nitrogen, methane, acetylene, and ethene. We found that the separation of mixtures composed of these gases in ZJU-198 is due to the organic linker of the structure. The rotation of this linker causes the expansion of the cavities and enhances gas separation by allowing the adsorption of molecules that a priori are too big to be adsorbed.

Influence of Flexibility on the Separation of Chiral Isomers in STW-Type Zeolite.

Molecular simulation, through the computation of adsorption isotherms, is a useful predictive tool for the selective capacity of nanoporous materials. Generally, adsorbents are modelled as rigid frameworks, as opposed to allowing for vibrations of the lattice, and this approximation is assumed to have negligible impact on adsorption. In this work, this approach was tested in an especially challenging system by computing the adsorption of the chiral molecules 2-pentanol, 2-methylbutanol and 3-methyl-2-butanol in the all-silica and germanosilicate chiral zeolites STW and studying their lattice vibrations upon adsorption. The analysis of single- and multicomponent adsorption isotherms showed the suitability of STW-type zeolites as molecular sieves for chiral separation processes, which pose a challenging task in the chemical and pharmaceutical industries. Moreover, new experimental adsorption data validate the force field employed. The results reveal that the lattice vibrations of the all-silica framework are sorbate-independent, while those of germanosilicate STW show host-guest coupling modulated by uptake and sorbate type that disrupts the chiral recognition sites. This study indicates that the effects of intrinsic flexibility on the selective capacity of nanoporous materials may range from low to high impact, and some of them could not have been foreseen even after examination of the structural dynamics of an empty framework.

Adsorption of Cyclohexane in Pure Silica Zeolites: High-Throughput Computational Screening Validated by Experimental Data.

Adsorption of cyclohexane in pure silica zeolites was studied experimentally and by molecular simulations. Based on the adsorption isobars obtained from the quasi-equilibrated temperature adsorption and desorption (QE-TPDA) measurements and reported adsorption isotherms for high-silica zeolites Y, ZSM-5, and ZSM-11 we refined Lennard-Jones parameters for guest-host interactions available in the literature. Adsorption of cyclohexane from equimolar mixture of twisted-boat and chair conformations has been screened in 171 pure silica zeolitic structures using grand canonical Monte Carlo simulations. Almost 20 frameworks showing extraordinary preference for adsorption of the chair conformation over the twisted boat one or vice versa were found. This selectivity was attributed to the geometry of channels and cavities present in the pore structures, as all t-boat selective structures possess channels or cavities of 8.3-9.1 Å. We also differentiated ways of chair-selectivity depending on the size and shape of the channels or cavities and also on the arrangement of the guest molecules in the pores.

Molecular Dynamics Analysis of Charge Transport in Ionic-Liquid Electrolytes Containing Added Salt with Mono, Di, and Trivalent Metal Cations.

Among many other applications, room-temperature ionic liquids (ILs) are used as electrolytes for storage and energy-conversion devices. In this work, we investigate, at the microscopic level, the structural and dynamical properties of 1-methyl-1-butyl-pyrrolidinium bis(trifluoromethanesulfonyl) imide [C4 PYR]+ [Tf2 N]- IL-based electrolytes for metal-ion batteries. We carried out molecular dynamics simulations of electrolytes mainly composed of [C4 PYR]+ [Tf2 N]- IL with the addition of Mn+ -[Tf2 N]- metal salts (M=Li+ , Na+ , Ni2+ , Zn2+ , Co2+ , Cd2+ , and Al3+ , n=1, 2, and 3) dissolved in the IL. The addition of low salt concentrations lowers the charge transport and conductivity of the electrolytes. This effect is due to the strong interaction of the metal cations with the [Tf2 N]- anions, which allows for molecular aggregation between them. We analyze how the conformation of the [Tf2 N]- anions surrounding the metal cations determine the charge-transport properties of the electrolyte. We found two main conformations based on the size and charge of the metal cation: monodentate and bidentate (number of oxygen atoms of the anion pointing to the metal atoms). The microscopic local structure of the Mn+ -[Tf2 N]- aggregates influences the microscopic charge transport as well as the macroscopic conductivity of the total electrolyte.

Stepped Propane Adsorption in Pure-Silica ITW Zeolite.

Gas adsorption over zeolites is at the basis of important applications of this class of microporous crystalline solids, notably as separation media and catalysts, but it may also be complex and not straightforward to understand. Here we report that for temperature below 323 K propane adsorption on the small-pore pure-silica zeolite ITW exhibits a clear step (pseudosaturation). This is absent in the case of propene and the other small linear alkanes. An intermediate plateau, clearly observed in the 293 K isotherm, always occurs when one molecule of propane is loaded in every other cage, i.e., at half-saturation. The simulation results show a swelling of the ITW structure upon propane adsorption. The strong dependence of available pore volume on the adsorbate loading level implies that adsorption cannot occur on the void structure while saturation can only be reached on highly loaded structures. To account for this unprecedented adsorption phenomenon, we propose the term "guest-modulated effect".

Unravelling the influence of carbon dioxide on the adsorptive recovery of butanol from fermentation broth using ITQ-29 and ZIF-8.

The vapor phase adsorption of butanol from ABE fermentation at the head space of the fermenter is an interesting route for the efficient recovery of biobutanol. The presence of gases such as carbon dioxide that are produced during the fermentation process causes a stripping of valuable compounds from the aqueous into the vapor phase. This work studies the effect of the presence of carbon dioxide on the adsorption of butanol at a molecular level. With this aim in mind Monte Carlo simulations were employed to study the adsorption of mixtures containing carbon dioxide, butanol and ethanol. Molecular models for butanol and ethanol that reproduce experimental properties of the molecules such as polarity, vapor-liquid coexistence or liquid density have been developed. Pure component isotherms and heats of adsorption have been computed and compared to experimental data to check the accuracy of the interacting parameters. Adsorption of butanol/ethanol mixtures has been studied in absence and presence of CO2 on two representative materials, a pure silica LTA zeolite and a hydrophobic metal-organic framework ZIF-8. To get a better understanding of the molecular mechanism that governs the adsorption of the targeted mixture in the selected materials, the distribution of the molecules inside the structures was analyzed. The combination of these features allows obtaining a deeper understanding of the process and to identify the role of carbon dioxide in the butanol purification process.

Potential of polarizable force fields for predicting the separation performance of small hydrocarbons in M-MOF-74.

The separation of light olefins from paraffins via cryogenic distillation is a very energy intensive process. Solid adsorbents and especially metal-organic frameworks with open metal sites have the potential to significantly lower the required energy. Specifically, M-MOF-74 has drawn considerable attention for application in olefin/paraffin separation. To investigate how the separation proceeds on a molecular level and to design better materials, molecular simulation can be a useful tool. Unfortunately, it is still a challenge to model the adsorption behavior of many adsorbates in metal-organic frameworks with open metal sites. Previously, the inclusion of explicit polarization has been suggested to improve the quality of classical force fields for such systems. Here, the potential of polarizable force fields for the description of olefins and paraffins in metal-organic frameworks with open metal sites is investigated. In particular, heats of adsorption, binding geometries, and adsorption isotherms are calculated for C2H4, C2H6, C3H6, and C3H8 in M-MOF-74 (with M = Co, Mn, Fe, and Ni). In this study, no force field parameters are adjusted to improve the model. The results show that including explicit polarization significantly improves the description of the adsorption in comparison to non-polarizable generic force fields which do not consider explicit polarization. The study also reveals that simulation predictions are sensitive to the assigned repulsive potential and framework charges. A fully re-parametrized polarizable force field may have the capability to improve the predictions even further.

Fitting electron density as a physically sound basis for the development of interatomic potentials of complex alloys.

The development of new interatomic potentials to model metallic systems is a difficult task, due in part to the dependence between the parameters that describe the electron density and the short-range interactions. Parameter search methods are prone to false convergence. To solve this problem, we have developed a methodology for obtaining the electron density parameters independently of the short-range interactions, so that physically sound parameters can be obtained to describe the electron density, after which the short-range parameters can be fitted, thus reducing the complexity of the process and yielding better interatomic potentials. With the new method we can develop self-consistent, accurate force fields, using solely calculations, without the need to fit to experimental data. Density functional theory calculations are used to compute the observables with which the potential is fit. We applied the method to a Ni-based Inconel 625 superalloy (IN625), modelled here as Ni, Cr, Mo and Fe solid solution alloys. The capability of the force fields developed using this new method is validated, by comparing the structural and thermo-elastic properties predicted with the force fields, with the corresponding experimental data, both for single crystals and polycrystalline alloys.

Cadmium-BINOL Metal-Organic Framework for the Separation of Alcohol Isomers.

The large-scale isolation of specific isomers of amyl alcohols for applications in the chemical, pharmaceutical, and biochemical industries represents a challenging task due to the physicochemical similarities of these structural isomers. The homochiral metal-organic framework cadmium-BINOL (BINOL=1,1'-bi-2-naphthol) is suitable for the separation of pentanol isomers, combining adsorption selectivities above 5 with adsorption capacities of around 4.5 mol kg-1 . Additionally, a slight ability for separation of racemic mixtures of 2-pentanol is also detected. This behavior is explained based on matching shapes, strength of host-guest interactions, and on the network of hydrogen bonds. The last of these explains both the relative success and shortfalls of prediction methods at high loadings (ideal adsorbed solution theory) or at low coverage (separation factors), which are therefore useful here at a qualitative level, but not accurate in quantitative terms. Finally, the high selectivity of cadmium-BINOL for 1-pentanol over its isomers offers prospects for practical applications and some room for optimizing conditions.

Highly Selective Zeolite Topologies for Flue Gas Separation.

The separation of carbon dioxide from flue gas is essential for the reduction of greenhouse gas emissions. In adsorptive methods, the challenge lies in the choice of suitable porous materials. Among all zeolite topologies, a number of adsorbents with pore dimensions in the range of the guest molecules were identified to allow an excellent separation by diffusion, and MRE and AFO zeolite topologies appear to be the best candidates based on equilibrium adsorption. Also, it was found that the behavior of this gas mixture in DFT and APD zeolites differed from the normal behavior.

Critical Role of Dynamic Flexibility in Ge-Containing Zeolites: Impact on Diffusion.

Incorporation of germanium in zeolites is well known to confer static flexibility to their framework, by stabilizing the formation of small rings. In this work, we show that the flexibility associated to Ge atoms in zeolites goes beyond this static effect, manifesting also a clear dynamic nature, in the sense that it leads to enhanced molecular diffusion. Our study combines experimental and theoretical methods providing evidence for this effect, which has not been described previously, as well as a rationalization for it, based on atomistic grounds. We have used both pure-silica and silico-germanate ITQ-29 (LTA topology) zeolites as a case study. Based on our simulations, we identify the flexibility associated to the pore breathing-like behavior induced by the Ge atoms, as the key factor leading to the enhanced diffusion observed experimentally in Ge-containing zeolites.

Aqueous Solutions of Ionic Liquids: Microscopic Assembly.

Aqueous solutions of ionic liquids are of special interest, due to the distinctive properties of ionic liquids, in particular, their amphiphilic character. A better understanding of the structure-property relationships of such systems is hence desirable. One of the crucial molecular-level interactions that influences the macroscopic behavior is hydrogen bonding. In this work, we conduct molecular dynamics simulations to investigate the effects of ionic liquids on the hydrogen-bond network of water in dilute aqueous solutions of ionic liquids with various combinations of cations and anions. Calculations are performed for imidazolium-based cations with alkyl chains of different lengths and for a variety of anions, namely, [Br](-), [NO3](-), [SCN](-) [BF4](-), [PF6](-), and [Tf2N](-). The structure of water and the water-ionic liquid interactions involved in the formation of a heterogeneous network are analyzed by using radial distribution functions and hydrogen-bond statistics. To this end, we employ the geometric criterion of the hydrogen-bond definition and it is shown that the structure of water is sensitive to the amount of ionic liquid and to the anion type. In particular, [SCN](-) and [Tf2N](-) were found to be the most hydrophilic and hydrophobic anions, respectively. Conversely, the cation chain length did not influence the results.

Quantum and Classical Molecular Dynamics of Ionic Liquid Electrolytes for Na/Li-based Batteries: Molecular Origins of the Conductivity Behavior.

Compositional effects on the charge-transport properties of electrolytes for batteries based on room-temperature ionic liquids (RTILs) are well-known. However, further understanding is required about the molecular origins of these effects, in particular regarding the replacement of Li by Na. In this work, we investigate the use of RTILs in batteries, by means of both classical molecular dynamics (MD), which provides information about structure and molecular transport, and ab initio molecular dynamics (AIMD), which provides information about structure. The focus has been placed on the effect of adding either Na(+) or Li(+) to 1-methyl-1-butyl-pyrrolidinium [C4 PYR](+) bis(trifluoromethanesulfonyl)imide [Tf2 N](-) . Radial distribution functions show excellent agreement between MD and AIMD, which ensures the validity of the force fields used in the MD. This is corroborated by the MD results for the density, the diffusion coefficients, and the total conductivity of the electrolytes, which reproduce remarkably well the experimental observations for all studied Na/Li concentrations. By extracting partial conductivities, it is demonstrated that the main contribution to the conductivity is that of [C4 PYR](+) and [Tf2 N](-) . However, addition of Na(+) /Li(+) , although not significant on its own, produces a dramatic decrease in the partial conductivities of the RTIL ions. The origin of this indirect effect can be traced to the modification of the microscopic structure of the liquid as observed from the radial distribution functions, owing to the formation of [Na(Tf2 N)n ]((n-1)-) and [Li(Tf2 N)n ]((n-1)-) clusters at high concentrations. This formation hinders the motion of the large ions, hence reducing the total conductivity. We demonstrate that this clustering effect is common to both Li and Na, showing that both ions behave in a similar manner at a microscopic level in spite of their distinct ionic radii. This is an interesting finding for extending Li-ion and Li-air technologies to their potentially cheaper Na-based counterparts.