Chemically Resolved Evaporation Dynamics of Dicarboxylic Acid Mixtures in Solid Particles.

The evaporation rate and corresponding vapor pressure of dicarboxylic acids have been the subject of numerous scientific studies over the years, with reported values spanning several orders of magnitude. Recent work has identified the importance of considering the phase state of the material during evaporation, likely accounting for some of the variability in measured vapor pressures. In the homologous series of dicarboxylic acids, the phase state under dry conditions may be crystalline or amorphous, with particles of odd-carbon-numbered acids exhibiting tendencies to remain amorphous and spherical. Although measurements of vapor pressures for pure components make up most of the available literature data, for many applications, these compounds are not present in isolation. Additionally, many systems containing a semi-volatile material exist in a solid state, especially under dry and low relative humidity conditions. In this work, we explore the evaporation of compounds present in mixed solid-state particles. Specifically, we use single particle levitation coupled with mass spectrometry to measure the evolving composition of solid particles containing mixtures of glutaric acid and succinic acid, glutaric acid and adipic acid, and malonic acid and succinic acid. Under dry conditions, these systems exhibit non-spherical geometries consistent with crystallization of one or both components into an organic crystal. Our measurements allow the evaporation of each component in the mixture to be characterized independently and effective vapor pressures of the pure components to be inferred. The resulting vapor pressures are compared against pure component vapor pressures. We demonstrate that these mixtures exhibit thermodynamic ideality but can be influenced by limited diffusion in the solid phase. These are the first results in the literature that explore the thermodynamic and kinetic factors that control the evaporative evolution of mixed solid-state particles.

Connecting the Phase State and Volatility of Dicarboxylic Acids at Elevated Temperatures.

The partitioning of semivolatile organic molecules between condensed phases and the vapor phase has broad application across a range of scientific disciplines, with significant impacts in atmospheric chemistry for regulating the evolving composition of aerosol particles. Vapor partitioning depends on the molecular interactions and phase state of the condensed material and shows a well-established dependence on temperature. The phase state of solid organic material is not always well-defined, and many examples can be found for the formation of amorphous subcooled liquid states rather than crystalline solids. This can lead to significant changes to vapor equilibrium processes by modifying the thermodynamics and kinetics of evaporation. Here, we explore the influence of phase state on the evaporation dynamics of a series of straight-chain dicarboxylic acids across a range of above-ambient temperatures. These molecules show an odd/even alteration in some of their properties based on the number of carbon atoms that may be connected to their phase state under dry conditions. Using a newly developed linear-quadrupole electrodynamic balance, we levitate single particles containing the sample and expose them to dry conditions across a range of temperatures (ambient to ∼350 K). Using the rate of evaporation measured from the change in the size or relative mass, we derive the vapor pressure and enthalpy of vaporization. Light scattering data allows for unambiguous identification of the phase of the particles (crystal vs amorphous) allowing the vapor equilibrium properties to be attributed to a particular state. This work highlights a new experimental method for characterizing vapor pressures of low volatility substances and extends the temperature range of available data for the vapor pressure of terminal dicarboxylic acids. These measurements show that crystalline and subcooled liquid states persist at elevated temperatures and provide a direct comparison between subcooled and crystal phases under the same experimental conditions.

Efficacy of Cefazolin versus Ceftriaxone for Extremity Open Fracture Management at a Level 1 Trauma Center.

Background: Antibiotic agents have been shown to improve outcomes in open extremity fractures. The first-generation cephalosporins, which are used most often, are often under-dosed based on weight and recommended frequency. Ceftriaxone offers a broader coverage and a decreased frequency of administration. Our institution began utilizing ceftriaxone for open fracture management in 2017 to address those concerns. Objective: To examine the efficacy of cefazolin versus ceftriaxone for open fracture management of extremity trauma. Patients and Methods: Retrospective study from 2015-2019 of patients who sustained open extremity fractures. Patients were stratified by antibiotic administered and Gustilo-Anderson grade. Outcomes included non-union/malunion, superficial surgical site infection (SSI), deep SSI, osteomyelitis, re-operation after index hospital visit, re-admission due to prior injury, limb loss, and death. Subgroup analysis stratified each antibiotic group by Gustilo-Anderson grade 1 or 2 and grade 3. Results: Data was collected from 2015 to 2019. Of the 1,149 patients, 619 patients met inclusion criteria. Three hundred fifty-five patients received cefazolin and 264 patients received ceftriaxone. There were no statistically significant differences between groups on specified outcomes. No statistically significant differences existed during subgroup analysis for the specified outcomes. Multivariable analysis demonstrated increased Gustilo-Anderson grade increased risk of infectious outcome. Conclusions: Ceftriaxone is a safe and effective alternative for open fracture extremity management that offers the advantage of 24-hour dosing and single antibiotic coverage for grade 3 open fractures. It does not increase infectious complications and offers benefits of resource efficiency.

Hygroscopic Growth, Phase Morphology, and Optical Properties of Model Aqueous Brown Carbon Aerosol.

Brown carbon aerosol in the atmosphere contain light-absorbing chromophores that influence the optical scattering properties of the particles. These chromophores may be hydrophobic, such as PAHs, or water soluble, such as nitroaromatics, imidazoles, and other conjugated oxygen-rich molecules. Water-soluble chromophores are expected to exist in aqueous solution in the presence of sufficient water and will exhibit physical properties (e.g., size, refractive index, and phase morphology) that depend on the environmental relative humidity (RH). In this work, we characterize the RH-dependent properties of 4-nitrocatechol (4-NC) and its mixtures with ammonium sulfate, utilizing a single-particle levitation platform coupled with Mie resonance spectroscopy to probe the size, real part of the complex refractive index (RI), and phase morphology of individual micron-sized particles. We measure the hygroscopic growth properties of pure 4-NC and apply mixing rules to characterize the growth of mixtures with ammonium sulfate. We report the RI at 589 nm for these samples as a function of RH and explore the wavelength dependence of the RI at non-absorbing wavelengths. The real part of the RI at 589 nm was found to vary in the range 1.54-1.59 for pure 4-NC from 92.5 to 75% RH, with an estimated pure component RI of 1.70. The real part of the RI was also measured for mixtures of AS and 4-NC and ranged from 1.39 to 1.51 depending on the component ratio and RH. We went on to characterize phase transitions in mixed particles, identifying the onset RH of liquid-liquid phase separation (LLPS) and efflorescence transitions. Mixtures showed LLPS in the range of 85-76% RH depending on the molar ratio, while efflorescence typically fell between 22 and 42% RH. Finally, we characterized the imaginary part of the complex RI using an effective oscillator model to capture the wavelength-dependent absorption properties of the system.

Validating a Novel Emotional Intelligence Instrument for Resident Physicians.

To construct and validate a scale of emotional intelligence (EI) for the medical field, n = 80 resident physicians responded to a 69-item self-report measure during the pilot phase of development of the Scale of Emotional Functioning: Medicine (SEF:MED). Based on multiple-phase item and structural analyses, a final 36-item version was created based on data from n = 321 respondent residents. Initially exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) supported the expected three-factor solution as did additional CFA from a second sample of n = 113 participants. Internal consistency reliabilities obtained from the original n = 321 residents for the three SEF:MED subscales of Interpersonal Skills (IS), Emotional Awareness (EA), and Emotional Management (EM) were 0.81, 0.82, and 0.84, respectively. Alphas for the second CFA data set were 0.89, 0.87, and 0.88 for IS, EM, and EA, respectively. In addition, the SEF:MED was validated by comparing it to related measures (i.e., the Profile of Emotional Competence (PEC) and the Maslach Burnout Inventory-Human Services Survey for Medical Personnel [MBI-HSS (MP)]); Correlation coefficients between the Total EI composite on the SEF:MED and the PEC global scales ranged from r = 0.64 to 0.68. Finally, correlation coefficients from the Total EI composite on the SEF:MED significantly related to the MBI-HSS (MP) Emotional Exhaustion (EE), Depersonalization (DP), and Personal Accomplishment (PA) scales (r = -0.50, -0.44, and 0.52, respectively). The SEF:MED may provide useful data to physicians and other medical professionals as they consider their own well-being and how it may affect care of their patients.

Hygroscopic growth of simulated lung fluid aerosol particles under ambient environmental conditions.

The hygroscopicity of respiratory aerosol determines their particle size distribution and regulates solute concentrations to which entrained microorganisms are exposed. Here, we report the hygroscopicity of simulated lung fluid (SLF) particles. While the response of aqueous particles follow simple mixing rules based on composition, we observe phase hysteresis with increasing and decreasing relative humidity (RH) and clear uptake of water prior to deliquescence. These results indicate that RH history may control the state of respiratory aerosol in the environment and influence the viability of microorganisms.

Ion-molecule interactions enable unexpected phase transitions in organic-inorganic aerosol.

Atmospheric aerosol particles are commonly complex, aqueous organic-inorganic mixtures, and accurately predicting the properties of these particles is essential for air quality and climate projections. The prevailing assumption is that aqueous organic-inorganic aerosols exist predominately with liquid properties and that the hygroscopic inorganic fraction lowers aerosol viscosity relative to the organic fraction alone. Here, in contrast to those assumptions, we demonstrate that increasing inorganic fraction can increase aerosol viscosity (relative to predictions) and enable a humidity-dependent gel phase transition through cooperative ion-molecule interactions that give rise to long-range networks of atmospherically relevant low-mass oxygenated organic molecules (180 to 310 Da) and divalent inorganic ions. This supramolecular, ion-molecule effect can drastically influence the phase and physical properties of organic-inorganic aerosol and suggests that aerosol may be (semi)solid under more conditions than currently predicted. These observations, thus, have implications for air quality and climate that are not fully represented in atmospheric models.

Simultaneous Retrieval of the Size and Refractive Index of Suspended Droplets in a Linear Quadrupole Electrodynamic Balance.

Single-particle trapping is an effective strategy to explore the physical and optical properties of aerosol with high precision. Laser-based methods are commonly used to probe the size, optical properties, and composition of nonlight-absorbing droplets in optical and electrodynamic traps. However, these methods cannot be applied to droplets containing photoactive chromophores, and thus, single-particle methods have been restricted to only a subset of atmospherically relevant particle compositions. In this work, we explore the application of a broadband light scattering approach, Mie resonance spectroscopy, to simultaneously probe the size and the refractive index (RI) of droplets in a linear quadrupole electrodynamic balance. We examine the evaporation of poly(ethylene glycol)s and compare the calculated vapor pressures with literature values to benchmark the size accuracy without prior constraint on the RI. We then explore the hygroscopic growth and deliquescence of sodium chloride droplets, measuring RI at the deliquescence relative humidity and demonstrating agreement to literature values. These data allow the wavelength dependence of the RI of aqueous NaCl to be determined using a first-order Cauchy equation, and we effectively reproduce literature data from multiple techniques. We finally discuss measurements from a light-absorbing aqueous droplet containing humic acid and interpret the spectra via the imaginary component of the RI. The approach described here allows the radius of nonabsorbing droplets to be determined within 0.1%, the refractive index within 0.2%, and the first-order term in the Cauchy dispersion equation within ∼5%.

Computational investigation of LiF containing hypersalts.

This study explores the design of possible hypersalts starting from the hyperhalogen Li3F4 plus a Li atom and the hyperalkali Li4F3 plus a F atom. The investigation uses a multistep composite computational job that follows the same setup of the CBS-QB3 method, and uses B3LYP in combination with the CBSB7 + basis set for geometry optimizations. Adiabatic ionization energies (AIE), adiabatic electron affinities (AEA), HOMO-LUMO energy gaps, and NBO's are calculated for each presented species. Results confirm that the newly constructed hyperalkalis Li4F3, which has two isomers A and B, result in even lower AIE (3.83 eV and 3.65 eV for hyperalkali A and B, respectively) than the starting superalkali Li2F. The study also confirms the structures for the designed hyperhalogens Li3F4 (two isomers A and B) with higher AEA (7.70 eV and 5.63 eV for hyperhalogen A and B, respectively) than the superhalogen LiF2 building block. Hyperhalogens A and B in combination with a Li atom and hyperalkali A and B in combination with a F atom are used to create hypersalts. This yields three possible hypersalts A, B(C), and D with the formula Li4F4. Hypersalt A has the larger binding energy for dissociation into neutral fragments equal to 7.82 eV. Hypersalt C has the lower binding energy for dissociation into neutrals of 7.17 eV and hypersalt D the larger binding energy for dissociation into ions.

Low-Temperature Synchrotron Photoionization Study of 2-Methyl-3-buten-2-ol (MBO) Oxidation Initiated by O(3P) Atoms in the 298-650 K Range.

This work studies the oxidation of 2-methyl-3-buten-2-ol initiated by O(3P) atoms. The oxidation was investigated at room temperature, 550, and 650 K. Using the synchrotron radiation from the Advanced Light Source (ALS) of the Lawrence Berkley National Laboratory, reaction intermediates and products were studied by multiplexed photoionization mass spectrometry. Mass-to-charge ratios, kinetic time traces, photoionization spectra, and adiabatic ionization energies for each primary reaction species were obtained and used to characterize their identity. Using electronic structure calculations, potential energy surface scans of the different species produced throughout the oxidation were examined and presented in this paper to further validate the primary chemistry occurring. Branching fractions of primary products at all three temperatures were also provided. At room temperature only three primary products formed: ethenol (26.6%), acetaldehyde (4.2%), and acetone (53.4%). At 550 and 650 K the same primary products were observed in addition to propene (5.1%, 11.2%), ethenol (18.1%, 2.8%), acetaldehyde (8.9%, 5.7%), cyclobutene (1.6%, 10.8%), 1-butene (2.0%, 10.9%), trans-2-butene (3.2%, 23.1%), acetone (50.4%, 16.8%), 3-penten-2-one (1.0%, 11.5%), and 3-methyl-2-butenal (0.9%, 2.5%), where the first branching fraction value in parentheses corresponds to the 550 K data. At the highest temperature, a small amount of propyne (1.0%) was also observed.

Absolute photoionization cross sections of two cyclic ketones: cyclopentanone and cyclohexanone.

Absolute photoionization cross sections for cyclopentanone and cyclohexanone, as well as partial ionization cross sections for the dissociative ionized fragments, are presented in this investigation. Experiments are performed via a multiplexed photoionization mass spectrometer utilizing vacuum ultraviolet (VUV) synchrotron radiation supplied by the Advanced Light Source of Lawrence Berkeley National Laboratory. These results allow the quantification of these species that is relevant to investigate the kinetics and combustion reactions of potential biofuels. The CBS-QB3 calculated values for the adiabatic ionization energies agree well with the experimental values, and the identification of possible dissociative fragments is discussed for both systems. Copyright © 2017 John Wiley & Sons, Ltd.