Using the Multicomponent Aerosol FORmation Model (MAFOR) to Determine Improved VOC Emission Factors in Ship Plumes.

International shipping's particulate matter primary emissions have a share in global anthropogenic emissions of between 3% and 4%. Ship emissions of volatile organic compounds (VOCs) can play an important role in the formation of fine particulate matter. Using an aerosol box model for the near-plume scale, this study investigated how the changing VOC emission factor (EF) for ship engines impacts the formation of secondary PM2.5 in ship exhaust plumes that were detected during a measurement campaign. The agreement between measured and modeled particle number size distribution was improved by adjusting VOC emissions, in particular of intermediate-, low-, and extremely low-volatility compounds. The scaling of the VOC emission factor showed that the initial emission factor, based on literature data, had to be multiplied by 3.6 for all VOCs. Information obtained from the box model was integrated into a regional-scale chemistry transport model (CTM) to study the influence of changed VOC ship emissions over the Mediterranean Sea. The regional-scale CTM run with adjusted ship emissions indicated a change in PM2.5 of up to 5% at the main shipping routes and harbor cities in summer. Nevertheless, overall changes due to a change in the VOC EF were rather small, indicating that the size of grid cells in CTMs leads to a fast dilution.

Synchrony in the periphery: inter-subject correlation of physiological responses during live music concerts.

While there is an increasing shift in cognitive science to study perception of naturalistic stimuli, this study extends this goal to naturalistic contexts by assessing physiological synchrony across audience members in a concert setting. Cardiorespiratory, skin conductance, and facial muscle responses were measured from participants attending live string quintet performances of full-length works from Viennese Classical, Contemporary, and Romantic styles. The concert was repeated on three consecutive days with different audiences. Using inter-subject correlation (ISC) to identify reliable responses to music, we found that highly correlated responses depicted typical signatures of physiological arousal. By relating physiological ISC to quantitative values of music features, logistic regressions revealed that high physiological synchrony was consistently predicted by faster tempi (which had higher ratings of arousing emotions and engagement), but only in Classical and Romantic styles (rated as familiar) and not the Contemporary style (rated as unfamiliar). Additionally, highly synchronised responses across all three concert audiences occurred during important structural moments in the music-identified using music theoretical analysis-namely at transitional passages, boundaries, and phrase repetitions. Overall, our results show that specific music features induce similar physiological responses across audience members in a concert context, which are linked to arousal, engagement, and familiarity.

Bridges of Calcium Bicarbonate Tightly Couple Dipolar Lipid Membranes.

The interaction between lipid membranes and ions is associated with a range of key physiological processes. Most earlier studies have focused on the interaction of lipids with cations, while the specific effects of the anions have been largely overlooked. Owing to dissolved atmospheric carbon dioxide, bicarbonate is an important ubiquitous anion in aqueous media. In this paper, we report on the effect of bicarbonate anions on the interactions between dipolar lipid membranes in the presence of previously adsorbed calcium cations. Using a combination of solution X-ray scattering, osmotic stress, and molecular dynamics simulations, we followed the interactions between 1,2-didodecanoyl-sn-glycero-3-phosphocholine (DLPC) lipid membranes that were dialyzed against CaCl2 solutions in the presence and absence of bicarbonate anions. Calcium cations adsorbed onto DLPC membranes, charge them, and lead to their swelling. In the presence of bicarbonate anions, however, the calcium cations can tightly couple one dipolar DLPC membrane to the other and form a highly condensed and dehydrated lamellar phase with a repeat distance of 3.45 ± 0.02 nm. Similar tight condensation and dehydration has only been observed between charged membranes in the presence of multivalent counterions. Bridging between bilayers by calcium bicarbonate complexes induced this arrangement. Furthermore, in this condensed phase, lipid molecules and adsorbed ions were arranged in a two-dimensional oblique lattice.

Elucidating the catalytic degradation of enrofloxacin by copper oxide nanoparticles through the identification of the reactive oxygen species.

Copper oxide nanoparticles (CuO-NPs) have been suggested as effective catalysts to degrade many persistent organic contaminants. In parallel, CuO-NPs are considered toxic to soil microorganisms, plants and human cells, possibly because they induce oxidative stress and generation of reactive oxygen species (ROS). However, the mechanism of the catalytic process and the generated ROS are poorly understood. Here we discuss the reaction mechanism of CuO-NPs during the catalytic degradation of enrofloxacin - an antibiotic pharmaceutical used in this study as a representative persistent organic compound. The degradation of an aqueous solution of the enrofloxacin exposed to CuO-NPs and hydrogen peroxide was studied showing fast removal of the enrofloxacin at ambient conditionsns. ROS production was identified by electron spin resonance and a spin trapping technique. The distribution of the free radical species indicated production of a high percentage of superoxide (O2-.) radicals as well as hydroxyl radicals; this production is similar to the "radical production" activity of the superoxide dismutase (SOD) enzyme in the presence of hydrogen peroxide. This activity was also tested in the opposite direction, to examine if CuO-NPs show reactivity that potentially mimics the classical SOD enzymatic activity. The CuO-NPs were found to catalyze the dismutation of superoxide to hydrogen peroxide and oxygen in a set of laboratory experiments.

Structure and Interactions between Charged Lipid Membranes in the Presence of Multivalent Ions.

When aqueous salt solutions contain multivalent ions (like Ca2+ or Mg2+), strong correlation effects may lead to ion-bridging, net attraction, and tight-coupling between like-charged interfaces. To examine the effects of surface charge density, temperature, salt type, and salt concentration on the structures of tightly coupled charged interfaces, we have used mixed lipid membranes, containing either saturated or unsaturated tails in the presence of multivalent ions. We discovered that tightly coupled membrane lamellar phases, dominated by attractive interactions, coexisted with weakly coupled lamellar phases, dominated by repulsive interactions. To control the membrane charge density, we mixed lipids with negatively charged headgroups, DLPS and DOPS, with their zwitterionic analogue having the same tails, DLPC and DOPC, respectively. Using solution X-ray scattering we measured the lamellar repeat distance, D, at different ion concentrations, temperatures, and membrane charge densities. The multivalent ions tightly coupled the mixed lipid bilayers whose charged lipid molar fraction was between 0.1 and 1. The repeat distance of the tightly coupled phase was about 4 nm for the DLPS/DLPC mixtures and about 5 nm for the DOPS/DOPC mixtures. In this phase, the repeat distance slightly increased with increasing temperature and decreased with increasing charge density. When the molar fraction of charged lipid was 0.1 or 0.25, a less tightly coupled phase coexisted with the tightly coupled phase. The weakly coupled lamellar phase had significantly larger D values, although they were consistently shorter than the D values in monovalent salt solutions with similar screening lengths.

D+: software for high-resolution hierarchical modeling of solution X-ray scattering from complex structures.

This paper presents the computer program D+ (https://scholars.huji.ac.il/uriraviv/book/d-0), where the reciprocal-grid (RG) algorithm is implemented. D+ efficiently computes, at high-resolution, the X-ray scattering curves from complex structures that are isotropically distributed in random orientations in solution. Structures are defined in hierarchical trees in which subunits can be represented by geometric or atomic models. Repeating subunits can be docked into their assembly symmetries, describing their locations and orientations in space. The scattering amplitude of the entire structure can be calculated by computing the amplitudes of the basic subunits on 3D reciprocal-space grids, moving up in the hierarchy, calculating the RGs of the larger structures, and repeating this process for all the leaves and nodes of the tree. For very large structures (containing over 100 protein subunits), a hybrid method can be used to avoid numerical artifacts. In the hybrid method, only grids of smaller subunits are summed and used as subunits in a direct computation of the scattering amplitude. D+ can accurately analyze both small- and wide-angle solution X-ray scattering data. This article describes how D+ applies the RG algorithm, accounts for rotations and translations of subunits, processes atomic models, accounts for the contribution of the solvent as well as the solvation layer of complex structures in a scalable manner, writes and accesses RGs, interpolates between grid points, computes numerical integrals, enables the use of scripts to define complicated structures, applies fitting algorithms, accounts for several coexisting uncorrelated populations, and accelerates computations using GPUs. D+ may also account for different X-ray energies to analyze anomalous solution X-ray scattering data. An accessory tool that can identify repeating subunits in a Protein Data Bank file of a complex structure is provided. The tool can compute the orientation and translation of repeating subunits needed for exploiting the advantages of the RG algorithm in D+. A Python wrapper (https://scholars.huji.ac.il/uriraviv/book/python-api) is also available, enabling more advanced computations and integration of D+ with other computational tools. Finally, a large number of tests are presented. The results of D+ are compared with those of other programs when possible, and the use of D+ to analyze solution scattering data from dynamic microtubule structures with different protofilament number is demonstrated. D+ and its source code are freely available for academic users and developers (https://bitbucket.org/uriraviv/public-dplus/src/master/).

Osmotic Stress Induced Desorption of Calcium Ions from Dipolar Lipid Membranes.

The interaction between multivalent ions and lipid membranes with saturated tails and dipolar (net neutral) headgroups can lead to adsorption of the ions onto the membrane. The ions charge the membranes and contribute to electrostatic repulsion between them, in a similar manner to membranes containing charged lipids. Using solution X-ray scattering and the osmotic stress method, we measured and modeled the pressure-distance curves between partially charged membranes containing mixtures of charged (1,2-dilauroyl-sn-glycero-3-phospho-l-serine, DLPS) and dipolar (1,2-dilauroyl-sn-glycero-3-phosphocholine, DLPC) lipids over a wide range of membrane charge densities. We then compared these pressure-distance curves with those of DLPC membranes in the presence of 10 mM CaCl2. Our data and modeling show that when low osmotic stress is applied to the DLPC bilayers, the membrane charge density is equivalent to that of a charged membrane containing ca. 4 mol % DLPS and 96 mol % DLPC. As the osmotic stress increased, the charge density of the DLPC membrane decreased and resembled that of a membrane containing ca. 1 mol % DLPS. These data are consistent with desorption of the calcium ions from the DLPC membrane with increasing osmotic stress.

Critical Conditions for Adsorption of Calcium Ions onto Dipolar Lipid Membranes.

Dipolar lipid membranes may adsorb multivalent ions. The binding constant depends on the type of lipid and ions. In this paper, we focus on the adsorption of calcium ions onto 1,2-dilauroylphosphatidylcholine (DLPC) membrane. Using small-angle-X-ray scattering we found that at ambient room temperature ca. 0.6 mM CaCl2 is a critical concentration at which calcium ions adsorbed to 30 mg/mL (ca. 48 mM) DLPC membrane. We then determined the structure of the lamellar phases formed at CaCl2 concentrations below and above the critical concentration and characterized the effect of temperature and incubation time on the adsorption process. Our findings suggest that calcium adsorption to DLPC membranes requires an initial nucleation phase.

Charging and softening, collapse, and crystallization of dipolar phospholipid membranes by aqueous ionic liquid solutions.

Ionic liquids have a variety of unique controllable structures and properties. These properties may be used to tailor the self-assembly of charged and dipolar biomolecules. Using solution X-ray scattering, we measured the structure of Dilauryl(C12:0)-sn-glycero-3-phospho-l-choline (DLPC), a dipolar (or zwitterionic) lipid, in the water-soluble room temperature ionic liquid Ethyl Methyl Imidazolium Ethyl Sulfate (EMIES) and mixtures of EMIES and water. We find that the interaction between the lipid bilayers is dominated by the balance between the charging of the polar headgroups by the ionic liquid, softening of the bilayer, and the osmotic pressure induced by the solvent. This balance leads to the following changes with increasing ionic liquid concentration: an incomplete unbinding transition from an attractive regime to a swollen regime of the lamellar phase formed by the bilayers. The swollen phase is followed by a collapse of the bilayers into a highly desolvated lamellar phase at some critical EMIES concentration, and eventually formation of lipid-crystalline phase, at very high EMIES concentrations. The latter phase is revealed by wide-angle X-ray scattering (WAXS) from the lipid solutions, showing multiple Bragg peaks, consistent with highly ordered structures. These structures were not observed in any other type of aqueous solutions containing monovalent or multivalent ions. The kinetics and temperature dependence of these transitions were also determined.

Enrofloxacin oxidative degradation facilitated by metal oxide nanoparticles.

The activity of copper oxide, titanium carbide and silicon nitride nanoparticles for the oxidative degradation of environmentally relevant concentrations (µg L(-1) range) of enrofloxacin - an important veterinary antibiotic drug - in aqueous solutions was investigated. With hydrogen peroxide as an oxidative agent, both copper oxide and titanium carbide decrease the concentration of enrofloxacin by more than 90% over 12 h. Addition of sodium halide salts strongly increases the reaction rate of copper oxide nanoparticles. The mechanism for the formation of Reactive Oxygen Species (ROS) was investigated by Electron Spin Resonance (ESR).