Temperature-Dependent Kinetics of the Reactions of the Criegee Intermediate CH2OO with Aliphatic Aldehydes

Criegee intermediates, formed by alkene ozonolysis in the troposphere, can react with volatile organic compounds (VOCs). The temperature-dependent kinetics of the reactions between the Criegee intermediate CH2OO and three aliphatic aldehydes, RCHO where R = H, CH3, and C2H5 (formaldehyde, acetaldehyde, and propionaldehyde, respectively), have been studied using a laser flash-photolysis transient absorption spectroscopy technique. The experimental measurements are supported by ab initio calculations at various composite levels of theory that characterize stationary points on the reaction potential and free energy surfaces. As with other reactions of CH2OO with organic carbonyls, the mechanisms involve 1,3-dipolar cycloaddition at the C=O group, over submerged barriers, leading to the formation of 1,2,4-trioxolane secondary ozonides. The bimolecular rate constants of all three reactions decrease with increasing temperature over the range 275-335 K and are characterized by equations of Arrhenius form: k(T) = (7.1 ± 1.5) × 10-14exp((1160 ± 60)/T), (8.9 ± 1.7) × 10-15exp((1530 ± 60)/T), and (5.3 ± 1.3) × 10-14exp((1210 ± 70)/T) cm3 s-1 for HCHO, CH3CHO, and C2H5CHO, respectively. Based on estimated concentrations of CH2OO, the reactions with aldehydes are unlikely to play a significant role in the atmosphere

The Degradation of Acetaldehyde in Estuary Waters in Southern California, USA

Acetaldehyde plays an important role in oxidative cycles in the troposphere. Estimates of its air-water flux are important in global models. Biological degradation is believed to be the dominant loss process in water, but there have been few measurements, none in estuaries. Acetaldehyde degradation rates were measured in surface waters at the inflow to the Upper Newport Back Bay estuary in Orange County, Southern California, USA, over a 6-month period including the rainy winter season. Deuterated acetaldehyde was added to filtered and unfiltered water samples incubated in glass syringes, and its loss analyzed by purge and trap gas chromatography mass spectrometry. Filtered samples showed no significant degradation, suggesting that particle-mediated degradation is the dominant removal process. Correlation between measured degradation rate constants in unfiltered incubations and bacteria counts suggests the loss is due to microorganisms. Degradation in unfiltered samples followed first-order kinetics, with rate constants ranging from 0.0006 to 0.025 min-1 (k; average 0.0043 ± 0.006 min-1). Turnover (1/k) ranged from 40 to 1667 min, consistent with prior studies in coastal waters. Acetaldehyde concentrations in the estuary are estimated to range from 30 to ~500 nM (average ~250 nM). Results suggest the estuary is a source of acetaldehyde to the atmosphere

Chromophoric Dissolved Organic Matter and Dissolved Organic Carbon in Lakes Across an Elevational Gradient From the Mountains to the Sea

Dissolved organic matter (DOM) in lakes across elevation gradients is a complex function of topography, climate, vegetation coverage, land use, and lake properties. To examine sources and processing of DOM from sea level to mountain lakes (3–1,574 m), we measured dissolved organic carbon (DOC) concentrations and chromophoric dissolved organic matter (CDOM) optical properties, lake characteristics, and water quality parameters in 62 freshwater lakes in the Pacific Northwest, USA. Higher elevation lakes had lower DOC concentrations and absorbance. These lakes had higher forest cover and minimal wetlands in their watershed, in addition to low nutrients, water temperatures, and chlorophyll a in the lake itself. Two humic-like and one protein-like fluorescent component were identified from excitation-emission matrix spectroscopy. The index of recent autochthonous contribution (BIX), fluorescence index (FIX), and SR optical indices showed that most lakes were dominated by terrestrially derived material. The humification index (HIX) and specific ultra-violet absorbance (SUVA254) were consistent with more aromatic humic CDOM at lower elevations. The lower fluorescence of humic-like components at higher elevation was attributed to lower inputs from vegetation. The relative contribution of the protein-like component increased at higher elevation. This may be due to reduced allochthonous terrestrial inputs relative to in situ production of autochthonous material or increased photochemical/biological degradation of allochthonous material. Differences in optical characteristics associated with the amount and source of CDOM were observed across the elevational gradient. These differences were driven by characteristics at both within-lake and watershed scales

Changes in the gut microbiome and fermentation products concurrent with enhanced longevity in acarbose-treated mice.

BACKGROUND: Treatment with the α-glucosidase inhibitor acarbose increases median lifespan by approximately 20% in male mice and 5% in females. This longevity extension differs from dietary restriction based on a number of features, including the relatively small effects on weight and the sex-specificity of the lifespan effect. By inhibiting host digestion, acarbose increases the flux of starch to the lower digestive system, resulting in changes to the gut microbiota and their fermentation products. Given the documented health benefits of short-chain fatty acids (SCFAs), the dominant products of starch fermentation by gut bacteria, this secondary effect of acarbose could contribute to increased longevity in mice. To explore this hypothesis, we compared the fecal microbiome of mice treated with acarbose to control mice at three independent study sites. RESULTS: Microbial communities and the concentrations of SCFAs in the feces of mice treated with acarbose were notably different from those of control mice. At all three study sites, the bloom of a single bacterial taxon was the most obvious response to acarbose treatment. The blooming populations were classified to the largely uncultured Bacteroidales family Muribaculaceae and were the same taxonomic unit at two of the three sites. Propionate concentrations in feces were consistently elevated in treated mice, while the concentrations of acetate and butyrate reflected a dependence on study site. Across all samples, Muribaculaceae abundance was strongly correlated with propionate and community composition was an important predictor of SCFA concentrations. Cox proportional hazards regression showed that the fecal concentrations of acetate, butyrate, and propionate were, together, predictive of mouse longevity even while controlling for sex, site, and acarbose. CONCLUSION: We observed a correlation between fecal SCFAs and lifespan in mice, suggesting a role of the gut microbiota in the longevity-enhancing properties of acarbose. Treatment modulated the taxonomic composition and fermentation products of the gut microbiome, while the site-dependence of the responses illustrate the challenges facing reproducibility and interpretation in microbiome studies. These results motivate future studies exploring manipulation of the gut microbial community and its fermentation products for increased longevity, testing causal roles of SCFAs in the observed effects of acarbose

Fluorescent lifetimes of oils and oil distillates in artificial seawater

Supporting data associated with a study of the fluorescent lifetimes of eleven oil and oil distillates in artificial seawater are given. The table is a list of the oil and oil distillate names along with the associated sample numbers used in this study and their API densities. The excel data file contains lifetimes as a function of emission wavelength for different oils and oil products shown by sample number. The lifetimes were measured with a Horiba DeltaFlex Lifetime System that uses pulsed diode light sources. There is a separate sheet for each excitation source: 268, 285 and 348 nm. Lifetimes were well fit to a tri-exponential model with 3 lifetime components: an intermediate T1, a long-lived T2 and a short-lived T3. These data tables also include the fractional population B for each lifetime component and the chi squared values for the fit. Average values and standard deviations are reported. The figure shows the excitation-emission matrix spectra of oils and oil products in artificial seawater acquired with a Horiba Aqualog fluorometer. Excitation wavelength is on the x-axis and emission wavelength is on the y-axis. The color scale is fluorescence intensity in microvolts ranging from low (blue) to high (red). The wavelength range used here is that typically used in studies of dissolved organic matter (DOM). The oils show peaks in what is typically assigned to protein peaks in DOM spectra (excitation = 270-280 nm; emission 300-380 nm). A table with the oil sample names and numbers is available through the blue download button at the top of the page. More files are available below

Impact of the Macrophyte Nymphaea odorata (Lily Pads) on Dissolved Organic Matter (DOM) in a Lake

(Files are available for download below.) Macrophytes are a potential source of dissolved organic matter (DOM) in lakes. To probe the contribution of Nymphaea odorata (lily pads), dissolved organic carbon concentrations (DOC) and optical properties of chromophoric DOM were measured in a lake in the Pacific Northwest, United States over a year. Lily pads are prevalent around the shoreline during summer, dying back in fall. Indices of recent autochthonous contribution (BIX), fluorescence (FIX) and SR showed the lake was dominated by terrestrially-derived material. DOC concentrations were not correlated with rainfall, but were positively correlated with absorption coefficients. Values were highest in the summer dry season and decreased in the winter wet season, suggesting a source in the lake being diluted by precipitation rather than a dominant source from watershed runoff. Humic-like and protein-like fluorescent components were identified from excitation-emission matrix spectroscopy in lake waters and lily pad leachates. The protein-like component was highest during the summer, indicative of an in situ autochthonous source. Lily pad leachates had BIX, FIX, and SR values characteristic of terrestrial material and lake samples. However, leachates had lower humification index (HIX), specific ultraviolet absorbance (SUVA), flu/abs ratios and spectral slope (S) values. Higher absorption coefficients and DOC concentrations in the lake in summer were correlated with lower HIX, SUVA, flu/abs and S values, consistent with material leaching from lily pads. Seasonal trends in optical indices, absorption coefficients and DOC concentrations are consistent with lily pads being a significant DOM source in the lake, particularly in the summer dry season with low watershed runoff. This is for the supporting data for the paper in Limnology and Oceanography, specifically the absorbance and fluorescence spectra of the Lake Louise water samples (taken weekly over the course of a year). These files include large spreadsheets with raw and corrected absorbance and fluorescence intensity data as a function of wavelength, as well as the raw and corrected absorbance and fluorescence 3D excitation-emission matrix spectra (EEMs). These files are in .opj format, which is readable with commercially available Origin graphing software. Data includes tables with optical parameters and indices for absorbance and fluorescence for the weekly lake water samples, and spreadsheets with raw and corrected absorbance and fluorescence intensity data as a function of wavelength, as well as raw and corrected absorbance and fluorescence 3D excitation-emission matrix spectra (EEMs)

Supporting Information for Chromophoric Dissolved Organic Matter (CDOM) Across an Elevational Gradient from Sea Level to Mountain Lakes in the Pacific Northwest

This dataset is in support of Juetten et al., which has been submitted to the Journal of Geophysical Research Biogeosciences for consideration for publication. Chromophoric dissolved organic matter (CDOM) in lakes across elevation gradients is a complex function of topography, climate, vegetation coverage, land use, and lake properties. To examine sources and processing of CDOM from sea level to mountain lakes (3 to 1574 m), we measured CDOM optical properties, lake characteristics, and water quality parameters in 62 freshwater lakes in the Pacific Northwest, USA. Higher elevation lakes had lower dissolved organic carbon (DOC) and absorbance. These lakes had higher forest cover, minimal wetlands or crops, low nutrients, cooler water temperatures, and low chlorophyll a. Two humic-like and one protein-like fluorescent component were identified from excitation-emission matrix spectroscopy (EEMs). The index of recent autochthonous contribution (BIX), fluorescence index (FIX) and SR optical indices indicated that most lakes were dominated by terrestrially-derived material. The humification index (HIX) and specific ultra-violet absorbance (SUVA) were consistent with more aromatic humic CDOM at lower elevations. Fluorescence of humic-like components was lower at higher elevation, indicating reduced amounts of CDOM, attributed to lower inputs from vegetation. The relative contribution of the protein-like component increased at higher elevation, because allochthonous terrestrial inputs are reduced relative to in situ production of autochthonous material or higher photochemical and biological degradation of allochthonous material. Differences in optical characteristics associated with CDOM levels and some characteristics associated with CDOM source and quality were observed across the elevational gradient. These differences were driven by characteristics at both within-lake and watershed scales, suggesting a more complete understanding of CDOM patterns can be gained by examining factors at multiple spatial scales. The dataset available below is supplementary information to the paper in a Word file format. This includes: a figure corresponding to the RDA Figure 6 in the manuscript giving the lake names; a table giving sampling dates, elevations, locations and watershed characteristics for the lakes; a table comparing water quality parameters for deep vs, surface water samples from Lake Padden in 2011; and a table giving the measured water quality parameters for the lakes from summer 2018

Paleomagnetism. Solar nebula magnetic fields recorded in the Semarkona meteorite.

Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constraints on the intensity of these fields. Here we show that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 microteslas. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the Sun. This implies that background magnetic fields in the terrestrial planet-forming region were likely 5 to 54 microteslas, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.This is the accepted manuscript. The final version is available from Science at http://www.sciencemag.org/content/346/6213/1089.abstract

Internal and external cooling methods and their effect on body temperature, thermal perception and dexterity

© 2018 The Authors. Published by PLOS. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1371/journal.pone.0191416© 2018 Maley et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Objective The present study aimed to compare a range of cooling methods possibly utilised by occupational workers, focusing on their effect on body temperature, perception and manual dexterity. Methods Ten male participants completed eight trials involving 30 min of seated rest followed by 30 min of cooling or control of no cooling (CON) (34C, 58% relative humidity). The cooling methods utilised were: ice cooling vest (CV0), phase change cooling vest melting at 14C (CV14), evaporative cooling vest (CVEV), arm immersion in 10C water (AI), portable water-perfused suit (WPS), heliox inhalation (HE) and ice slushy ingestion (SL). Immediately before and after cooling, participants were assessed for fine (Purdue pegboard task) and gross (grip and pinch strength) manual dexterity. Rectal and skin temperature, as well as thermal sensation and comfort, were monitored throughout. Results Compared with CON, SL was the only method to reduce rectal temperature (P = 0.012). All externally applied cooling methods reduced skin temperature (P0.05). Conclusion The present study observed that ice ingestion or ice applied to the skin produced the greatest effect on rectal and skin temperature, respectively. AI should not be utilised if workers require subsequent fine manual dexterity. These results will help inform future studies investigating appropriate pre-cooling methods for the occupational worker.This project is financially supported by the US Government through the Technical Support Working Group within the Combating Terrorism Technical Support Office.Published versio