True digestibility of tryptophan in plant and animal protein.

BACKGROUND: Protein quality, evaluated using Digestible Indispensable Amino Acid Score (DIAAS) requires ileal digestibility values of individual indispensable amino acids (IAA) in each protein. However, true tryptophan (Trp) digestibility has rarely been quantified in humans. OBJECTIVE: To measure the true Trp digestibility and DIAAS of 2H-intrinsically labelled plant and animal protein sources in humans, using the dual isotope tracer technique. METHODS: The true Trp digestibility of 2H intrinsically labelled plant proteins such as whole mung bean (n=6) and dehulled mung bean (n=6), chickpea (n=5), and yellow pea (n=5), and protein from animal source foods such as egg white (n=6), whole egg (n=6), chicken meat (n=6) and goat milk (n=7) was determined against the known digestibility of U-13C spirulina whole cell protein as reference, except for goat milk protein which was measured against free crystalline 13C-Trp as reference. Banked samples from earlier studies conducted to determine true IAA digestibility of different protein sources were used for the analysis. DIAAS was calculated for each test protein using digestibility corrected IAA scores (mg IAA/g of protein) in comparison to the IAA requirement score for adults. RESULTS: The true Trp digestibility of whole mung bean, dehulled mung bean, chickpea, yellow pea, egg white, whole egg, chicken meat, and goat milk were 67.6±3.7%, 74.5±4.4%, 72.6±2.3%, 72.5±2.2%, 89.7±2.5%, 91.4±2.6%, 95.9±2.2%, and 92.8±2.9% respectively. The true Trp digestibility of plant protein sources was significantly lower than that of animal protein sources (p<0.05). Trp was not a limiting IAA in all the tested proteins. CONCLUSION: The true Trp digestibility determined in the present study ranged from 67.6±3.7% to 95.9 ± 2.2% for whole mung bean and chicken meat respectively, and adds to the database of individual true IAA digestibility of different protein sources. This study was registered in Clinical Trials Registry of India (CTRI) with registration number: CTRI/2017/11/010468, CTRI/2020/04/024512, CTRI/2018/03/012265.

Decomposing the late positive potential to cannabis cues in regular cannabis users: A temporal-spatial principal component analysis.

Cannabis use disorder (CUD) is increasing in the United States, yet, specific neural mechanisms of CUD are not well understood. Disordered substance use is characterized by heightened drug cue incentive salience, which can be measured using the late positive potential (LPP), an event-related potential (ERP) evoked by motivationally significant stimuli. The drug cue LPP is typically quantified by averaging the slow wave's scalp-recorded amplitude across its entire time course, which may obscure distinct underlying factors with differential predictive validity; however, no study to date has examined this possibility. In a sample of 105 cannabis users, temporo-spatial Principal Component Analysis was used to decompose cannabis cue modulation of the LPP into its underlying factors. Acute stress was also inducted to allow for identification of specific cannabis LPP factors sensitive to stress. Factor associations with CUD severity were also explored. Eight factors showed significantly increased amplitudes to cannabis images relative to neutral images. These factors spanned early (~372 ms), middle (~824 ms), and late (>1000 ms) windows across frontal, central, and parietal-occipital sites. CUD phenotype individual differences were primarily associated with frontal, middle/late latency factor amplitudes. Acute stress effects were limited to one early central and one late frontal factor. Taken together, results suggest that the cannabis LPP can be decomposed into distinct, temporal-spatial factors with differential responsivity to acute stress and CUD phenotype variability. Future individual difference studies examining drug cue modulation of the LPP should consider (1) frontalcentral poolings in addition to conventional central-parietal sites, and (2) later LPP time windows.

The revised Clinician-Administered PTSD scale for DSM-5 (CAPS-5-R): Initial psychometric evaluation in a trauma-exposed community sample.

The Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) is a widely used, well-validated structured interview for posttraumatic stress disorder (PTSD). It was recently revised to improve various aspects of administration and scoring. We conducted a psychometric evaluation of the revised version, known as the CAPS-5-R. Participants were 73 community residents with mixed trauma exposure (e.g., sexual assault, physical assault, transportation accident, the unnatural death of a loved one). CAPS-5-R PTSD diagnosis demonstrated good test-retest reliability, кs = .73-.79; excellent interrater reliability, кs = .86-.93; and good-to-excellent alternate forms reliability with the CAPS-5, кs = .79-.93. In addition, the CAPS-5-R total PTSD severity score demonstrated excellent test-retest reliability, intraclass correlation coefficient (ICC) = .86; interrater reliability, ICC = .98; and alternate forms reliability with the CAPS-5, r = .95. Further, the CAPS-5-R demonstrated good convergent validity with other measures of PTSD and good discriminant validity with measures of other constructs (e.g., depression, anxiety, alcohol problems, somatic concerns, mania). Given its strong psychometric performance in this study, as well as its improvements in administration and scoring, the CAPS-5-R appears to be a valuable update of the current CAPS-5.

Photochemically Driven Peptide Formation in Supersaturated Aerosol Droplets.

The condensation of amino acids into peptides plays a crucial role in protein synthesis and is thus essential for understanding the origins of life. However, the spontaneous formation of peptides from amino acids in bulk aqueous media is energetically unfavorable, posing a challenge for elucidating plausible abiotic mechanisms. In this study, we investigate the formation of amide bonds between amino acids within highly supersaturated aerosol droplets containing dicyandiamide (DCD), a cyanide derivative potentially present on primordial Earth. Metastable states, i.e. supersaturation, within individual micron-sized droplets are studied using both an optical trap and a linear quadrupole electrodynamic balance. When irradiated with intense visible light, amide bond formation is observed to occur and can be monitored using vibrational bands in Raman spectra. The reaction rate is found to be strongly influenced by droplet size and kinetic modelling suggests that it is driven by the photochemical product of a DCD self-reaction. Our results highlight the potential of atmospheric aerosol particles as reaction environments for peptide synthesis and have potential implications for the prebiotic chemistry of early Earth.

Clinical Manifestations and Genomic Evaluation of Melioidosis Outbreak among Children after Sporting Event, Australia.

Melioidosis, caused by the environmental gram-negative bacterium Burkholderia pseudomallei, usually develops in adults with predisposing conditions and in Australia more commonly occurs during the monsoonal wet season. We report an outbreak of 7 cases of melioidosis in immunocompetent children in Australia. All the children had participated in a single-day sporting event during the dry season in a tropical region of Australia, and all had limited cutaneous disease. All case-patients had an adverse reaction to oral trimethoprim/sulfamethoxazole treatment, necessitating its discontinuation. We describe the clinical features, environmental sampling, genomic epidemiologic investigation, and public health response to the outbreak. Management of this outbreak shows the potential benefits of making melioidosis a notifiable disease. The approach used could also be used as a framework for similar outbreaks in the future.

Direct LiF imaging diagnostics on refractive X-ray focusing at the EuXFEL High Energy Density instrument.

The application of fluorescent crystal media in wide-range X-ray detectors provides an opportunity to directly image the spatial distribution of ultra-intense X-ray beams including investigation of the focal spot of free-electron lasers. Here the capabilities of the micro- and nano-focusing X-ray refractive optics available at the High Energy Density instrument of the European XFEL are reported, as measured in situ by means of a LiF fluorescent detector placed into and around the beam caustic. The intensity distribution of the beam focused down to several hundred nanometers was imaged at 9 keV photon energy. A deviation from the parabolic surface in a stack of nanofocusing Be compound refractive lenses (CRLs) was found to affect the resulting intensity distribution within the beam. Comparison of experimental patterns in the far field with patterns calculated for different CRL lens imperfections allowed the overall inhomogeneity in the CRL stack to be estimated. The precise determination of the focal spot size and shape on a sub-micrometer level is essential for a number of high energy density studies requiring either a pin-size backlighting spot or extreme intensities for X-ray heating.

A von Hámos spectrometer for diamond anvil cell experiments at the High Energy Density Instrument of the European X-ray Free-Electron Laser.

A von Hámos spectrometer has been implemented in the vacuum interaction chamber 1 of the High Energy Density instrument at the European X-ray Free-Electron Laser facility. This setup is dedicated, but not necessarily limited, to X-ray spectroscopy measurements of samples exposed to static compression using a diamond anvil cell. Si and Ge analyser crystals with different orientations are available for this setup, covering the hard X-ray energy regime with a sub-eV energy resolution. The setup was commissioned by measuring various emission spectra of free-standing metal foils and oxide samples in the energy range between 6 and 11 keV as well as low momentum-transfer inelastic X-ray scattering from a diamond sample. Its capabilities to study samples at extreme pressures and temperatures have been demonstrated by measuring the electronic spin-state changes of (Fe0.5Mg0.5)O, contained in a diamond anvil cell and pressurized to 100 GPa, via monitoring the Fe Kß fluorescence with a set of four Si(531) analyser crystals at close to melting temperatures. The efficiency and signal-to-noise ratio of the spectrometer enables valence-to-core emission signals to be studied and single pulse X-ray emission from samples in a diamond anvil cell to be measured, opening new perspectives for spectroscopy in extreme conditions research.

A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell.

An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X-ray Free Electron Laser (European XFEL). Advantage was taken of the high repetition rate of the European XFEL (up to 4.5 MHz) to collect pulse-resolved MHz X-ray diffraction data from samples as they are dynamically compressed at intermediate strain rates (≤103 s-1), where up to 352 diffraction images can be collected from a single pulse train. The set-up employs piezo-driven dDACs capable of compressing samples in ≥340 µs, compatible with the maximum length of the pulse train (550 µs). Results from rapid compression experiments on a wide range of sample systems with different X-ray scattering powers are presented. A maximum compression rate of 87 TPa s-1 was observed during the fast compression of Au, while a strain rate of ∼1100 s-1 was achieved during the rapid compression of N2 at 23 TPa s-1.

Damage threshold of LiF crystal irradiated by femtosecond hard XFEL pulse sequence.

Here we demonstrate the results of investigating the damage threshold of a LiF crystal after irradiating it with a sequence of coherent femtosecond pulses using the European X-ray Free Electron Laser (EuXFEL). The laser fluxes on the crystal surface varied in the range ∼ 0.015-13 kJ/cm2 per pulse when irradiated with a sequence of 1-100 pulses (tpulse ∼ 20 fs, Eph = 9 keV). Analysis of the surface of the irradiated crystal using different reading systems allowed the damage areas and the topology of the craters formed to be accurately determined. It was found that the ablation threshold decreases with increasing number of X-ray pulses, while the depth of the formed craters increases non-linearly and reaches several hundred nanometers. The obtained results have been compared with data already available in the literature for nano- and picosecond pulses from lasers in the soft X-ray/VUV and optical ranges. A failure model of lithium fluoride is developed and verified with simulation of material damage under single-pulse irradiation. The obtained damage threshold is in reasonably good agreement with the experimentally measured one.

Measurement of True Indispensable Amino Acid Digestibility by the Dual Isotope Tracer Technique: A Methodological Review.

The digestible indispensable amino acid score uses ileal digestibility of each indispensable amino acid (IAA) of a dietary protein to calculate its protein quality. However, true ileal digestibility, which is the exclusive sum of digestion and absorption of a dietary protein up to the terminal ileum, is difficult to measure in humans. It is traditionally measured using invasive oro-ileal balance methods but can be confounded by endogenous secreted protein in the intestinal lumen, although the use of intrinsically labeled protein corrects for this. A recent, minimally invasive dual isotope tracer technique is now available to measure true IAA digestibility of dietary protein sources. This method involves simultaneous ingestion of 2 intrinsically but differently (stable) isotopically labeled proteins, a (2H or 15N-labeled) test protein and (13C-labeled) reference protein whose true IAA digestibility is known. Using a plateau-feeding protocol, the true IAA digestibility is determined by comparing the steady state ratio of blood to meal test protein IAA enrichment to the similar reference protein IAA ratio. The use of intrinsically labeled protein also distinguishes between IAA of endogenous and dietary origin. The collection of blood samples makes this method minimally invasive. As the α-15N and α-2H atoms of AAs of the intrinsically labeled protein are prone to label loss because of transamination, underestimation of digestibility, appropriate correction factors need to be employed when using 15N or 2H labeled test protein. The true IAA digestibility values of highly digestible animal protein by the dual isotope tracer technique are comparable to that measured by direct oro-ileal balance measurements, but no data are yet available for proteins with lower digestibility. A major advantage is that the minimally invasive method allows for true IAA digestibility measurement in humans across different age groups and physiological conditions.

Determination of Indispensable Amino Acid Digestibility of the Red Kidney Bean in Humans Using a Dual Stable Isotope Tracer Method.

BACKGROUND: Protein quality of the red kidney bean (RKB), a common source of dietary protein, has been assessed using the protein digestibility-corrected amino acid score (PDCAAS) determined in animal models using mainly oro-fecal digestibility. More recently, the FAO recommended to use digestible indispensable amino acid score (DIAAS) instead of PDCAAS but highlighted insufficient data on true ileal indispensable amino acid (IAA) digestibility of proteins because amino acids are absorbed in the ileum. OBJECTIVES: Using a recently developed dual stable isotope tracer method, we aimed to measure each IAA digestibility as representation of true ileal digestibility of the RKB, Phaseolus vulgaris, in humans consuming a typical Jamaican meal. METHODS: RKB-IAAs were intrinsically labeled by adding 2H2O to the plants. Uniformly labeled-[13C]-spirulina (standard protein) was added to a meal prepared with the labeled RKB and fed to 10 healthy adults (5 males, 5 females) in a nonrandomized trial as primed/intermittent doses to achieve a steady state IAA enrichment in plasma. Enrichment of 2H- and 13C-labeled IAA in plasma and the bean was measured by mass spectrometry. Each IAA digestibility (except tryptophan and histidine) was calculated as the ratio of plasma 2H-IAA to meal 2H-IAA divided by the ratio of plasma 13C-IAA to meal 13C-IAA adjusted for loss of 2H-atom during transamination and digestibility of spirulina. RESULTS: Adequate IAA labeling (>1000 ppm 2H excess) and plasma plateau isotopic enrichment were achieved. Mean RKB-IAA digestibility (%) was 79.4 ± 0.5, ranging from 69.0 ± 1.2 (threonine) to 85.7 ± 1.7 (lysine). CONCLUSION: The dual stable isotope tracer digestibility data are similar to published oro-fecal digestibility supporting substantial nitrogen exchange in the colon. The individual IAA digestibility is useful to derive DIAAS to replace PDCAAS. Using published RKB-IAA composition, extrapolated DIAAS was 0.63 based on the lowest score for methionine. CLINICAL TRIAL REGISTRATION: https://register. CLINICALTRIALS: gov; ID: NCT-04118517.

Impact of pH on Gas-Particle Partitioning of Semi-Volatile Organics in Multicomponent Aerosol.

The partitioning of semivolatile organic compounds (SVOCs) between the condensed and gas phases can have significant implications for the properties of aerosol particles. In addition to affecting size and composition, this partitioning can alter radiative properties and impact cloud activation processes. We present measurements and model predictions on how activity and pH influence the evaporation of SVOCs from particles to the gas phase, specifically investigating aqueous inorganic particles containing dicarboxylic acids (DCAs). The aerosols are studied at the single-particle level by using optical trapping and cavity-enhanced Raman spectroscopy. Optical resonances in the spectra enable precise size tracking, while vibrational bands allow real-time monitoring of pH. Results are compared to a Maxwell-type model that accounts for volatile and nonvolatile solutes in aqueous droplets that are held at a constant relative humidity. The aerosol inorganic-organic mixture functional group activity coefficients thermodynamic model and Debye-Hückel theory are both used to calculate the activities of the species present in the droplet. For DCAs, we find that the evaporation rate is highly sensitive to the particle pH. For acidity changes of approximately 1.5 pH units, we observe a shift from a volatile system to one that is completely nonvolatile. We also observe that the pH itself is not constant during evaporation; it increases as DCAs evaporate, slowing the rate of evaporation until it eventually ceases. Whether a DCA evaporates or remains a stable component of the droplet is determined by the difference between the lowest pKa of the DCA and the pH of the droplet.

Optical trapping and light scattering in atmospheric aerosol science.

Aerosol particles are ubiquitous in the atmosphere, and currently contribute a large uncertainty to climate models. Part of the endeavour to reduce this uncertainty takes the form of improving our understanding of aerosol at the microphysical level, thus enabling chemical and physical processes to be more accurately represented in larger scale models. In addition to modeling efforts, there is a need to develop new instruments and methodologies to interrogate the physicochemical properties of aerosol. This perspective presents the development, theory, and application of optical trapping, a powerful tool for single particle investigations of aerosol. After providing an overview of the role of aerosol in Earth's atmosphere and the microphysics of these particles, we present a brief history of optical trapping and a more detailed look at its application to aerosol particles. We also compare optical trapping to other single particle techniques. Understanding the interaction of light with single particles is essential for interpreting experimental measurements. In the final part of this perspective, we provide the relevant formalism for understanding both elastic and inelastic light scattering for single particles. The developments discussed here go beyond Mie theory and include both how particle and beam shape affect spectra. Throughout the entirety of this work, we highlight numerous references and examples, mostly from the last decade, of the application of optical trapping to systems that are relevant to the atmospheric aerosol.

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.

Temperature-Controlled Dual-Beam Optical Trap for Single Particle Studies of Organic Aerosol.

An optical trapping cell that is capable of suspending particles using two counter-propagating beams in a temperature-controlled environment is reported here. With this dual-beam optical trap, we are able to hold single micron-sized droplets at temperatures down to 253 K (-20 °C) for hours at a time and in metastable (supercooled) states. As particles are trapped at the shared focal points of two intense beams, strong cavity-enhanced Raman scattering (CERS) is observed and allows for high precision measurements of physical properties. Here, the evaporation of highly oxygenated organic systems was monitored using CERS and was used to determine temperature-dependent vapor pressures and enthalpies of vaporization. The wavelength- and temperature-dependent optical properties were also simultaneously retrieved using CERS.

Optical deformation of single aerosol particles.

Advancements in designing complex models for atmospheric aerosol science and aerosol-cloud interactions rely vitally on accurately measuring the physicochemical properties of microscopic particles. Optical tweezers are a laboratory-based platform that can provide access to such measurements as they are able to isolate individual particles from an ensemble. The surprising ability of a focused beam of light to trap and hold a single particle can be conceptually understood in the ray optics regime using momentum transfer and Newton's second law. The same radiation pressure that results in stable trapping will also exert a deforming optical stress on the surface of the particle. For micron-sized aqueous droplets held in the air, the deformation will be on the order of a few nanometers or less, clearly not observable through optical microscopy. In this study, we utilize cavity-enhanced Raman scattering and a phenomenon known as thermal locking to measure small deformations in optically trapped droplets. With the aid of light-scattering calculations and a model that balances the hydrostatic pressure, surface tension, and optical pressure across the air-droplet interface, we can accurately determine surface tension from our measurements. Our approach is applied to 2 systems of atmospheric interest: aqueous organic and inorganic aerosol.

Cognitive reappraisal, emotional suppression, and depressive and anxiety symptoms in later life: The moderating role of gender.

OBJECTIVES: Although socioemotional selectivity (SST) suggests that people experience more positive affect as they age, symptoms of anxiety and depression persist and are often greater in older women than men. Coping strategies may influence the extent to which older adults experience these symptoms. The purpose of the current study is to examine possible gender differences in the use of an adaptive (cognitive reappraisal (CR) and a maladaptive (emotive suppression (ES) emotion regulation strategy in relation to depressive and anxiety symptoms. METHOD: Our study uses cross-sectional data drawn from a community sample of older adults (60+; n = 906). We used OLS regression and moderation analyses to test our study hypotheses. RESULTS: Gender moderated the association between CR in both depressive and anxiety symptoms. Women reported greater use of CR relative to men. Further, CR use was negatively related to symptoms of anxiety and depression in women, but not men. In contrast, men used ES more frequently than women, though older men and women's use of ES was unrelated to anxiety or depressive symptoms. CONCLUSION: Our findings provide initial evidence that greater CR use in older women is related to lower symptoms of both anxiety and depression relative to older men. Age-related increases in CR use (e.g. SST) among women may serve to decrease anxiety and depression symptoms. Findings suggest decreasing anxiety and depressive symptoms via CR may benefit older women more than older men. Future research is needed to identify the coping strategies that are most beneficial for men.

Isolated & Combined Wearable Technology Underestimate the Total Energy Expenditure of Professional Young Rugby League Players; A Doubly Labelled Water Validation Study.

ABSTRACT: Costello, N, Deighton, K, Cummins, C, Whitehead, S, Preston, T, and Jones, B. Isolated & combined wearable technology underestimate the total energy expenditure of professional young rugby league players; a doubly labelled water validation study. J Strength Cond Res 36(12): 3398-3403, 2022-Accurately determining total energy expenditure (TEE) enables the precise manipulation of energy balance within professional collision-based sports. Therefore, this study investigated the ability of isolated or combined wearable technology to determine the TEE of professional young rugby league players across a typical preseason and in-season period. Total energy expenditure was measured via doubly labelled water, the criterion method, across a fourteen-day preseason ( n = 6) and 7-day in-season ( n = 7) period. Practical measures of TEE included SenseWear Pro3 Armbands in isolation and combined with metabolic power derived from microtechnology units. SenseWear Pro3 Armbands significantly under-reported preseason (5.00 [2.52] MJ·d -1 ; p = 0.002) and in-season (2.86 [1.15] MJ·d -1 ; p < 0.001) TEE, demonstrating a large and extremely large standardized mean bias, and a very large and large typical error, respectively. Combining metabolic power with SenseWear Pro3 Armbands almost certainly improved preseason (0.95 [0.15] MJ·d -1 ; Effect size = 0.32 ± 0.04; p < 0.001) and in-season (1.01 [0.15] MJ·d -1 ; ES = 0.88 ± 1.05; p < 0.001) assessment. However, SenseWear Pro3 Armbands combined with metabolic power continued to significantly under-report preseason (4.04 [2.38] MJ·d -1 ; p = 0.004) and in-season (2.18 [0.96] MJ·d -1 ; p = 0.002) expenditure, demonstrating a large and very large standardized mean bias, and a very large and large typical error, respectively. These findings demonstrate the limitations of utilizing isolated or combined wearable technology to accurately determine the TEE of professional collision-based sport athletes across different stages of the season.

The High Energy Density Scientific Instrument at the European XFEL.

The European XFEL delivers up to 27000 intense (>1012 photons) pulses per second, of ultrashort (≤50 fs) and transversely coherent X-ray radiation, at a maximum repetition rate of 4.5 MHz. Its unique X-ray beam parameters enable groundbreaking experiments in matter at extreme conditions at the High Energy Density (HED) scientific instrument. The performance of the HED instrument during its first two years of operation, its scientific remit, as well as ongoing installations towards full operation are presented. Scientific goals of HED include the investigation of extreme states of matter created by intense laser pulses, diamond anvil cells, or pulsed magnets, and ultrafast X-ray methods that allow their diagnosis using self-amplified spontaneous emission between 5 and 25 keV, coupled with X-ray monochromators and optional seeded beam operation. The HED instrument provides two target chambers, X-ray spectrometers for emission and scattering, X-ray detectors, and a timing tool to correct for residual timing jitter between laser and X-ray pulses.

Hygroscopicity of Microplastic and Mixed Microplastic Aqueous Ammonium Sulfate Systems.

A growing body of research suggests the presence and long-range transport of microplastics in the atmosphere. However, the interactions between these microplastics and atmospheric aerosol are poorly understood. Environmental microplastics vary in color, morphology, and chemical composition and become oxidized over time by UV, mechanical, and biological action. Once introduced to the atmosphere, these microplastics will likely become mixed with atmospheric aerosol. Determining how microplastics interact with aerosol particles and how they may alter aerosol physical properties, including water uptake and loss, is necessary to understand the impact of these microplastics on our environment. Herein, we investigate the effect of microplastics on the water activity of bulk water and ammonium sulfate solutions. We compare a variety of plastic compositions and microplastic morphologies including plastics that have been aged by UV irradiation and mechanical forces in the lab. In addition, we investigate the water uptake and loss in microplastic samples through dynamic vapor sorption. We find an increase in total water sorption for UV-aged plastics compared to pristine plastics. Finally, we investigate the effect of fractional surface coverage on the equilibration time scale.