Gender-specific differences in comorbidities, in-hospital complications and outcomes in emergency patients with ethanol intoxication with and without multisubstance use.

AIMS OF THE STUDY: To analyse gender-specific differences in comorbidities, multisubstance abuse, in-hospital complications, intensive care unit transfers and referrals to psychiatric wards of emergency department patients with ethanol intoxication. Several lines of evidence suggest an influence of gender differences on diagnostic and therapeutic approaches to various diseases. METHODS: Over a period of 7 years, all patients with signs or symptoms of ethanol intoxication and a positive blood ethanol test admitted for the first time to the emergency department of a Swiss regional tertiary referral hospital were prospectively enrolled. Patients were categorised into two subgroups: patients without additional drug use were considered ethanol-only cases, whereas patients who had also ingested other substances (as determined from bystanders, physicians and urine drug screening) were considered multisubstance cases. A retrospective analysis of this database evaluated gender-specific differences in comorbidities, multisubstance abuse, in-hospital complications, intensive care unit transfers and referrals to psychiatric wards within these two subgroups. Statistical analysis included Fisher's exact test for categorical data and Wilcoxon rank sum test for continuous data. RESULTS: Of 409 enrolled patients, 236 cases were ethanol-only and 173 were multisubstance cases. The three most common comorbidities in multisubstance patients showed significant gender differences: psychiatric disorders (43% males vs 61% females; p = 0.022), chronic ethanol abuse (55% males vs 32% females; p = 0.002) and drug addiction (44% males vs 17% females; p = 0.001). Gender differences were also found for the most frequently co-ingested substances: benzodiazepines (35% males vs 43% females; p = 0.014), cannabis (45% males vs 24% females; p = 0.006) and cocaine (24% males vs 6% females; p = 0.001). Male and female ethanol-only patients were transferred to the intensive care unit in 8% of cases. In multisubstance cases, 32% of male and 43% of female patients were transferred to the intensive care unit (no significant gender difference). The psychiatric ward referral rate in male (30%) and female (48%) patients with multisubstance abuse was significantly different (p = 0.028). No significant gender difference in psychiatric ward referral rates was observed for ethanol-only patients (12% males, 17% females). CONCLUSION: Among emergency department patients admitted with ethanol intoxication, gender differences in comorbidities, substance use and psychiatric ward referrals were highly significant among patients who presented with multisubstance abuse. Rates of intensive care unit transfer for patients with ethanol intoxication are substantial for both genders, reflecting relevant disease burden and resource demand, as well as the need for further preventive efforts.

Fluids and Electrolytes under Confinement in Single-Digit Nanopores.

Confined fluids and electrolyte solutions in nanopores exhibit rich and surprising physics and chemistry that impact the mass transport and energy efficiency in many important natural systems and industrial applications. Existing theories often fail to predict the exotic effects observed in the narrowest of such pores, called single-digit nanopores (SDNs), which have diameters or conduit widths of less than 10 nm, and have only recently become accessible for experimental measurements. What SDNs reveal has been surprising, including a rapidly increasing number of examples such as extraordinarily fast water transport, distorted fluid-phase boundaries, strong ion-correlation and quantum effects, and dielectric anomalies that are not observed in larger pores. Exploiting these effects presents myriad opportunities in both basic and applied research that stand to impact a host of new technologies at the water-energy nexus, from new membranes for precise separations and water purification to new gas permeable materials for water electrolyzers and energy-storage devices. SDNs also present unique opportunities to achieve ultrasensitive and selective chemical sensing at the single-ion and single-molecule limit. In this review article, we summarize the progress on nanofluidics of SDNs, with a focus on the confinement effects that arise in these extremely narrow nanopores. The recent development of precision model systems, transformative experimental tools, and multiscale theories that have played enabling roles in advancing this frontier are reviewed. We also identify new knowledge gaps in our understanding of nanofluidic transport and provide an outlook for the future challenges and opportunities at this rapidly advancing frontier.

Multiframe Imaging of Micron and Nanoscale Bubble Dynamics.

Here, we report on the direct sequential imaging of laser-induced cavitation of micron and nanoscale bubbles using Movie-Mode Dynamic Transmission Electron Microscopy (MM-DTEM). A 532 nm laser pulse (∼12 ns) was used to excite gold nanoparticles inside a ∼1.2 µm layer of water, and the resulting bubbles were observed with a series of nine electron pulses (∼10 ns) separated by as little as 40 ns peak to peak. Isolated nanobubbles were observed to collapse in less than 50 ns, while larger (∼2-3 µm) bubbles were observed to grow and collapse in less than 200 ns. Temporal profiles were generally asymmetric, possibly indicating faster growth than collapse dynamics, and the collapse time scale was found to be consistent with modeling and literature data from other techniques. More complex behavior was also observed for bubbles within proximity to each other, with interaction leading to longer lifetimes and more likely rebounding after collapse.

Ion Solvation and Transport in Narrow Carbon Nanotubes: Effects of Polarizability, Cation-π Interaction, and Confinement.

Understanding ion solvation and transport under confinement is critical for a wide range of emerging technologies, including water desalination and energy storage. While molecular dynamics (MD) simulations have been widely used to study the behavior of confined ions, considerable deviations between simulation results depending on the specific treatment of intermolecular interactions remain. In the following, we present a systematic investigation of the structure and dynamics of two representative solutions, that is, KCl and LiCl, confined in narrow carbon nanotubes (CNTs) with a diameter of 1.1 and 1.5 nm, using a combination of first-principles and classical MD simulations. Our simulations show that the inclusion of both polarization and cation-π interactions is essential for the description of ion solvation under confinement, particularly for large ions with weak hydration energies. Beyond the variation in ion solvation, we find that cation-π interactions can significantly influence the transport properties of ions in CNTs, particularly for KCl, where our simulations point to a strong correlation between ion dehydration and diffusion. Our study highlights the complex interplay between nanoconfinement and specific intermolecular interactions that strongly control the solvation and transport properties of ions.

Similarities and differences between potassium and ammonium ions in liquid water: a first-principles study.

Understanding ion solvation in liquid water is critical in optimizing materials for a wide variety of emerging technologies, including water desalination and purification. In this work, we report a systematic investigation and comparison of solvated K+ and NH4+ using first-principles molecular dynamics simulations. Our simulations reveal a strong analogy in the solvation properties of the two ions, including the size of the solvation shell as well as the solvation strength. On the other hand, we find that the local water structure in the ion solvation is significantly different; specifically, NH4+ yields a smaller number of water molecules and a more ordered water structure in the first solvation shell due to the formation of hydrogen bonds between the ion and water molecules. Finally, our simulations indicate that a comparable solvation strength of the two ions is a result of an interplay between the nature of ion-water interaction and number of water molecules that can be accommodated in the ion solvation shell.

Electronic structure of aqueous solutions: Bridging the gap between theory and experiments.

Predicting the electronic properties of aqueous liquids has been a long-standing challenge for quantum mechanical methods. However, it is a crucial step in understanding and predicting the key role played by aqueous solutions and electrolytes in a wide variety of emerging energy and environmental technologies, including battery and photoelectrochemical cell design. We propose an efficient and accurate approach to predict the electronic properties of aqueous solutions, on the basis of the combination of first-principles methods and experimental validation using state-of-the-art spectroscopic measurements. We present results of the photoelectron spectra of a broad range of solvated ions, showing that first-principles molecular dynamics simulations and electronic structure calculations using dielectric hybrid functionals provide a quantitative description of the electronic properties of the solvent and solutes, including excitation energies. The proposed computational framework is general and applicable to other liquids, thereby offering great promise in understanding and engineering solutions and liquid electrolytes for a variety of important energy technologies.

Structure and dynamics of aqueous solutions from PBE-based first-principles molecular dynamics simulations.

Establishing an accurate and predictive computational framework for the description of complex aqueous solutions is an ongoing challenge for density functional theory based first-principles molecular dynamics (FPMD) simulations. In this context, important advances have been made in recent years, including the development of sophisticated exchange-correlation functionals. On the other hand, simulations based on simple generalized gradient approximation (GGA) functionals remain an active field, particularly in the study of complex aqueous solutions due to a good balance between the accuracy, computational expense, and the applicability to a wide range of systems. Such simulations are often performed at elevated temperatures to artificially "correct" for GGA inaccuracies in the description of liquid water; however, a detailed understanding of how the choice of temperature affects the structure and dynamics of other components, such as solvated ions, is largely unknown. To address this question, we carried out a series of FPMD simulations at temperatures ranging from 300 to 460 K for liquid water and three representative aqueous solutions containing solvated Na+, K+, and Cl- ions. We show that simulations at 390-400 K with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional yield water structure and dynamics in good agreement with experiments at ambient conditions. Simultaneously, this computational setup provides ion solvation structures and ion effects on water dynamics consistent with experiments. Our results suggest that an elevated temperature around 390-400 K with the PBE functional can be used for the description of structural and dynamical properties of liquid water and complex solutions with solvated ions at ambient conditions.

Exploring the free energy surface using ab initio molecular dynamics.

Efficient exploration of configuration space and identification of metastable structures in condensed phase systems are challenging from both computational and algorithmic perspectives. In this regard, schemes that utilize a set of pre-defined order parameters to sample the relevant parts of the configuration space [L. Maragliano and E. Vanden-Eijnden, Chem. Phys. Lett. 426, 168 (2006); J. B. Abrams and M. E. Tuckerman, J. Phys. Chem. B 112, 15742 (2008)] have proved useful. Here, we demonstrate how these order-parameter aided temperature accelerated sampling schemes can be used within the Born-Oppenheimer and the Car-Parrinello frameworks of ab initio molecular dynamics to efficiently and systematically explore free energy surfaces, and search for metastable states and reaction pathways. We have used these methods to identify the metastable structures and reaction pathways in SiO2 and Ti. In addition, we have used the string method [W. E, W. Ren, and E. Vanden-Eijnden, Phys. Rev. B 66, 052301 (2002); L. Maragliano et al., J. Chem. Phys. 125, 024106 (2006)] within the density functional theory to study the melting pathways in the high pressure cotunnite phase of SiO2 and the hexagonal closed packed to face centered cubic phase transition in Ti.

Behavior of P85 and P188 Poloxamer Molecules: Computer Simulations Using United-Atom Force-Field.

To study the interaction between poloxamer molecules and lipid bilayers using molecular dynamics simulation technique with the united-atom resolution, we augmented the GROMOS force-field to include poloxamers. We validated the force-field by calculating the radii of gyration of two poloxamers, P85 and P188, solvated in water and by considering the poloxamer density distributions at the air/water interface. The emphasis of our simulations was on the study of the interaction between poloxamers and lipid bilayer. At the water/lipid bilayer interface, we observed that both poloxamers studied, P85 and P188, behaved like surfactants: the hydrophilic blocks of poloxamers became adsorbed at the polar interface, while their hydrophobic block penetrated the interface into the aliphatic tail region of the lipid bilayer. We also observed that when P85 and P188 poloxamers interacted with damaged membranes that contained pores, the hydrophobic blocks of copolymers penetrated into the membrane in the vicinity of the pore and compressed the membrane. Due to this compression, water molecules were evacuated from the pore.

Shock Wave-Induced Damage of a Protein by Void Collapse.

In this study, we report on a series of molecular dynamics simulations that were used to examine the effects of shock waves on a membrane-bound ion channel. A planar shock wave was found to compress the ion channel upon impact, but the protein geometry resembles the crystal structure as soon as the solvent density begins to dissipate. When a void was placed in close proximity to the membrane, the shock wave proved to be more destructive to the protein due to formation of a nanojet that results from the asymmetric collapse of the void. The nanojet was able to cause significant structural changes to the protein even at low piston velocities that are not able to directly cause poration of the membrane.

Interfacial effects on the band edges of functionalized si surfaces in liquid water.

By combining ab initio molecular dynamics simulations and many-body perturbation theory calculations of electronic energy levels, we determined the band edge positions of functionalized Si(111) surfaces in the presence of liquid water, with respect to vacuum and to water redox potentials. We considered surface terminations commonly used for Si photoelectrodes in water splitting experiments. We found that, when exposed to water, the semiconductor band edges were shifted by approximately 0.5 eV in the case of hydrophobic surfaces, irrespective of the termination. The effect of the liquid on band edge positions of hydrophilic surfaces was much more significant and determined by a complex combination of structural and electronic effects. These include structural rearrangements of the semiconductor surfaces in the presence of water, changes in the orientation of interfacial water molecules with respect to the bulk liquid, and charge transfer at the interfaces, between the solid and the liquid. Our results showed that the use of many-body perturbation theory is key to obtain results in agreement with experiments; they also showed that the use of simple computational schemes that neglect the detailed microscopic structure of the solid-liquid interface may lead to substantial errors in predicting the alignment between the solid band edges and water redox potentials.

Hydrogen-bond dynamics of water at the interface with InP/GaP(001) and the implications for photoelectrochemistry.

We investigate the structure, topology, and dynamics of liquid water at the interface with natively hydroxylated (001) surfaces of InP and GaP photoelectrodes. Using ab initio molecular dynamics simulations, we show that contact with the semiconductor surface enhances the water hydrogen-bond strength at the interface. This leads to the formation of an ice-like structure, within which dynamically driven water dissociation and local proton hopping are amplified. Nevertheless, the structurally similar and isovalent InP and GaP surfaces generate qualitatively different interfacial water dynamics. This can be traced to slightly more covalent-like character in the binding of surface adsorbates to GaP, which results in a more rigid hydrogen-bond network that limits the explored topological phase space. As a consequence, local proton hopping can give rise to long-range surface proton transport on InP, whereas the process is kinetically limited on GaP. This allows for spatial separation of individual stages of hydrogen-evolving, multistep reactions on InP(001). Possible implications for the mechanisms of cathodic water splitting and photocorrosion on the two surfaces are considered in light of available experimental evidence.

Ligand-mediated modification of the electronic structure of CdSe quantum dots.

X-ray absorption spectroscopy and ab initio modeling of the experimental spectra have been used to investigate the effects of surface passivation on the unoccupied electronic states of CdSe quantum dots (QDs). Significant differences are observed in the unoccupied electronic structure of the CdSe QDs, which are shown to arise from variations in specific ligand-surface bonding interactions.

Persistent medium-range order and anomalous liquid properties of Al(1-x)Cu(x) alloys.

The development of short-to-medium-range order in atomic arrangements has generally been observed in noncrystalline solid systems such as metallic glasses. Whether such medium-range order (MRO) can exist in materials at well above their melting or glass-transition temperature has been a long-standing important scientific issue. Here, using ab initio molecular dynamics simulations, we show that a novel, persistent MRO exists in liquid Al-Cu alloys near the composition of CuAl3. The correlated atomic motions associated with the MRO give rise to a substantially enhanced viscosity in the vicinity of the composition. The component of the MRO liquid state gradually decreases with increasing temperature, and it disappears above a crossover temperature T(LLC). The continuous liquid-liquid crossover through a percolationlike transition leads to a pronounced heat capacity peak at T(LLC).

Local structural models of complex oxygen- and hydroxyl-rich GaP/InP(001) surfaces.

We perform density-functional theory calculations on model surfaces to investigate the interplay between the morphology, electronic structure, and chemistry of oxygen- and hydroxyl-rich surfaces of InP(001) and GaP(001). Four dominant local oxygen topologies are identified based on the coordination environment: M-O-M and M-O-P bridges for the oxygen-decorated surface; and M-[OH]-M bridges and atop M-OH structures for the hydroxyl-decorated surface (M = In, Ga). Unique signatures in the electronic structure are linked to each of the bond topologies, defining a map to structural models that can be used to aid the interpretation of experimental probes of native oxide morphology. The M-O-M bridge can create a trap for hole carriers upon imposition of strain or chemical modification of the bonding environment of the M atoms, which may contribute to the observed photocorrosion of GaP/InP-based electrodes in photoelectrochemical cells. Our results suggest that a simplified model incorporating the dominant local bond topologies within an oxygen adlayer should reproduce the essential chemistry of complex oxygen-rich InP(001) or GaP(001) surfaces, representing a significant advantage from a modeling standpoint.

Probing the Structure of Salt Water under Confinement with First-Principles Molecular Dynamics and Theoretical X-ray Absorption Spectroscopy.

We investigated the structure of liquid water around cations (Na(+)) and anions (Cl(-)) confined inside of a (19,0) carbon nanotube with first-principles molecular dynamics and theoretical X-ray absorption spectroscopy (XAS). We found that the ions preferentially reside near the interface between the nanotube and the liquid. Upon confinement, the XAS signal of water molecules surrounding Na(+) exhibits enhanced pre-edge and reduced post-edge features with respect to that of pure water, at variance with the solvation shell of Na(+) in bulk water. Conversely, the first solvation shell of confined Cl(-) has a main-edge intensity comparable to that of bulk solvated Cl(-), likely as a result of a high number of acceptor hydrogen bonds in the first solvation shell. Confined nonsolvating water molecules exhibit bulk-like or water-monomer-like properties, depending on whether they belong to core or interfacial layers, respectively.

Local effects in the X-ray absorption spectrum of salt water.

Both first-principles molecular dynamics and theoretical X-ray absorption spectroscopy have been used to investigate the aqueous solvation of cations in 0.5 M MgCl(2), CaCl(2), and NaCl solutions. We focus here on the species-specific effects that Mg(2+), Ca(2+), and Na(+) have on the X-ray absorption spectrum of the respective solutions. For the divalent cations, we find that the hydrogen-bonding characteristics of the more rigid magnesium first-shell water molecules differ from those in the more flexible solvation shell surrounding calcium. In particular, the first solvation shell water molecules of calcium are able to form acceptor hydrogen bonds, and this results in an enhancement of a post-edge peak near 540 eV. The absence of acceptor hydrogen bonds for magnesium first shell water molecules provides an explanation for the experimental and theoretical observation of a lack of enhancement at the post-main-edge peak. For the sodium monovalent cation we find that the broad tilt angle distribution results in a broadening of postedge features, despite populations in donor-and-acceptor configurations consistent with calcium. We also present the reaveraged spectra of the MgCl(2), CaCl(2), and NaCl solutions and show that trends apparent with increasing concentration (0.5, 2.0, 4.0 M) are consistent with experiment. Finally, we examine more closely both the effect that cation coordination number has on the hydrogen-bonding network and the relative perturbation strength of the cations on lone pair oxygen orbitals.

Evidence for a first-order liquid-liquid transition in high-pressure hydrogen from ab initio simulations.

Using quantum simulation techniques based on either density functional theory or quantum Monte Carlo, we find clear evidence of a first-order transition in liquid hydrogen, between a low conductivity molecular state and a high conductivity atomic state. Using the temperature dependence of the discontinuity in the electronic conductivity, we estimate the critical point of the transition at temperatures near 2,000 K and pressures near 120 GPa. Furthermore, we have determined the melting curve of molecular hydrogen up to pressures of 200 GPa, finding a reentrant melting line. The melting line crosses the metalization line at 700 K and 220 GPa using density functional energetics and at 550 K and 290 GPa using quantum Monte Carlo energetics.