RESUMEN
Isoprene has the highest atmospheric emissions of any nonmethane hydrocarbon, and isoprene epoxydiols (IEPOX) are well-established oxidation products and the primary contributors forming isoprene-derived secondary organic aerosol (SOA). Highly acidic particles (pH 0-3) widespread across the lower troposphere enable acid-driven multiphase chemistry of IEPOX, such as epoxide ring-opening reactions forming methyltetrol sulfates through nucleophilic attack of sulfate (SO42-). Herein, we systematically demonstrate an unexpected decrease in SOA formation from IEPOX on highly acidic particles (pH < 1). While IEPOX-SOA formation is commonly assumed to increase at low pH when more [H+] is available to protonate epoxides, we observe maximum SOA formation at pH 1 and less SOA formation at pH 0.0 and 0.4. This is attributed to limited availability of SO42- at pH values below the acid dissociation constant (pKa) of SO42- and bisulfate (HSO4-). The nucleophilicity of HSO4- is 100× lower than SO42-, decreasing SOA formation and shifting particulate products from low-volatility organosulfates to higher-volatility polyols. Current model parameterizations predicting SOA yields for IEPOX-SOA do not properly account for the SO42-/HSO4- equilibrium, leading to overpredictions of SOA formation at low pH. Accounting for this underexplored acidity-dependent behavior is critical for accurately predicting SOA concentrations and resolving SOA impacts on air quality.
Asunto(s)
Aerosoles , Compuestos Epoxi/química , Concentración de Iones de Hidrógeno , Equilibrio Ácido-BaseRESUMEN
Radioactive iodine is a highly effective treatment for thyroid cancer and has now been used in clinical practice for more than 80 years. In general, the treatment is well tolerated. However, it can be logistically quite complex for patients due to the need to reduce iodine intake and achieve high levels of thyroid-stimulating hormone prior to treatment. Radiation protection precautions must also be taken to protect others from unnecessary radiation exposure following treatment. It has been well documented by thyroid cancer patient support groups that there is significant variation in practice across the UK. It is clear that some patients are being asked to observe unnecessarily burdensome restrictions that make it more difficult for them to tolerate the treatment. At the instigation of these support groups, a multidisciplinary group was assembled to examine the evidence and generate guidance on best practice for the preparation of patients for this treatment and the management of subsequent radiation protection precautions, with a focus on personalising the advice given to individual patients. The guidance includes advice about managing particularly challenging situations, for example treating patients who require haemodialysis. We have also worked together to produce a patient information leaflet covering these issues. We hope that the guidance document and patient information leaflet will assist centres in improving our patients' experience of receiving radioactive iodine. The patient information sheet is available as Supplementary Material to this article.
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Protección Radiológica , Neoplasias de la Tiroides , Humanos , Adulto , Neoplasias de la Tiroides/radioterapia , Neoplasias de la Tiroides/tratamiento farmacológico , Radioisótopos de Yodo/efectos adversos , Tirotropina , Reino UnidoRESUMEN
Acid-driven multiphase chemistry of isoprene epoxydiols (IEPOX) with inorganic sulfate aerosols contributes substantially to secondary organic aerosol (SOA) formation, which constitutes a large mass fraction of atmospheric fine particulate matter (PM2.5). However, the atmospheric chemical sinks of freshly generated IEPOX-SOA particles remain unclear. We examined the role of heterogeneous oxidation of freshly generated IEPOX-SOA particles by gas-phase hydroxyl radical (â¢OH) under dark conditions as one potential atmospheric sink. After 4 h of gas-phase â¢OH exposure (â¼3 × 108 molecules cm-3), chemical changes in smog chamber-generated IEPOX-SOA particles were assessed by hydrophilic interaction liquid chromatography coupled with electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (HILIC/ESI-HR-QTOFMS). A comparison of the molecular-level compositional changes in IEPOX-SOA particles during aging with or without â¢OH revealed that decomposition of oligomers by heterogeneous â¢OH oxidation acts as a sink for â¢OH and maintains a reservoir of low-volatility compounds, including monomeric sulfate esters and oligomer fragments. We propose tentative structures and formation mechanisms for previously uncharacterized SOA constituents in PM2.5. Our results suggest that this â¢OH-driven renewal of low-volatility products may extend the atmospheric lifetimes of particle-phase IEPOX-SOA by slowing the production of low-molecular weight, high-volatility organic fragments and likely contributes to the large quantities of 2-methyltetrols and methyltetrol sulfates reported in PM2.5.
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Contaminantes Atmosféricos , Sulfatos , Sulfatos/química , Atmósfera/química , Hemiterpenos , Butadienos , Aerosoles/química , Material Particulado/análisis , Polvo/análisis , Oxidación-Reducción , Estrés Oxidativo , Contaminantes Atmosféricos/análisisRESUMEN
Aerosol acidity increases secondary organic aerosol (SOA) formed from the reactive uptake of isoprene-derived epoxydiols (IEPOX) by enhancing condensed-phase reactions within sulfate-containing submicron particles, leading to low-volatility organic products. However, the link between the initial aerosol acidity and the resulting physicochemical properties of IEPOX-derived SOA remains uncertain. Herein, we show distinct differences in the morphology, phase state, and chemical composition of individual organic-inorganic mixed particles after IEPOX uptake to ammonium sulfate particles with different initial atmospherically relevant acidities (pH = 1, 3, and 5). Physicochemical properties were characterized via atomic force microscopy coupled with photothermal infrared spectroscopy (AFM-PTIR) and Raman microspectroscopy. Compared to less acidic particles (pH 3 and 5), reactive uptake of IEPOX to the most acidic particles (pH 1) resulted in 50% more organosulfate formation, clearer phase separation (core-shell), and more irregularly shaped morphologies, suggesting that the organic phase transitioned to semisolid or solid. This study highlights that initial aerosol acidity may govern the subsequent aerosol physicochemical properties, such as viscosity and morphology, following the multiphase chemical reactions of IEPOX. These results can be used in future studies to improve model parameterizations of SOA formation from IEPOX and its properties, toward the goal of bridging predictions and atmospheric observations.
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Atmósfera , Hemiterpenos , Ácidos/química , Aerosoles/química , Atmósfera/química , Butadienos , Concentración de Iones de HidrógenoRESUMEN
BACKGROUND: Item response theory (IRT) methods for addressing differential item functioning (DIF) can detect group differences in responses to individual items (e.g., bias). IRT and DIF-detection methods have been used increasingly often to identify bias in cognitive test performance by characteristics (DIF grouping variables) such as hearing impairment, race, and educational attainment. Previous analyses have not considered the effect of missing data on inferences, although levels of missing cognitive data can be substantial in epidemiologic studies. METHODS: We used data from Visit 6 (2016-2017) of the Atherosclerosis Risk in Communities Neurocognitive Study (N = 3,580) to explicate the effect of artificially imposed missing data patterns and imputation on DIF detection. RESULTS: When missing data was imposed among individuals in a specific DIF group but was unrelated to cognitive test performance, there was no systematic error. However, when missing data was related to cognitive test performance and DIF group membership, there was systematic error in DIF detection. Given this missing data pattern, the median DIF detection error associated with 10%, 30%, and 50% missingness was -0.03, -0.08, and -0.14 standard deviation (SD) units without imputation, but this decreased to -0.02, -0.04, and -0.08 SD units with multiple imputation. CONCLUSIONS: Incorrect inferences in DIF testing have downstream consequences for the use of cognitive tests in research. It is therefore crucial to consider the effect and reasons behind missing data when evaluating bias in cognitive testing.
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Sesgo , Humanos , Pruebas NeuropsicológicasRESUMEN
OBJECTIVES: Vision and hearing impairments affect 55% of people aged 60+ years and are associated with lower cognitive test performance; however, tests rely on vision, hearing, or both. We hypothesized that scores on tests that depend on vision or hearing are different among those with vision or hearing impairments, respectively, controlling for underlying cognition. METHODS: Leveraging cross-sectional data from the Baltimore Longitudinal Study of Aging (BLSA) and the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS), we used item response theory to test for differential item functioning (DIF) by vision impairment (better eye presenting visual acuity worse than 20/40) and hearing impairment (better ear .5-4 kHz pure-tone average > 25 decibels). RESULTS: We identified DIF by vision impairment for tests whose administrations do not rely on vision [e.g., Delayed Word Recall both in ARIC-NCS: .50 logit difference between impaired and unimpaired (p = .04) and in BLSA: .62 logits (p = .02)] and DIF by hearing impairment for tests whose administrations do not rely on hearing [Digit Symbol Substitution test in BLSA: 1.25 logits (p = .001) and Incidental Learning test in ARIC-NCS: .35 logits (p = .001)]. However, no individuals had differences between unadjusted and DIF-adjusted measures of greater than the standard error of measurement. CONCLUSIONS: DIF by sensory impairment in cognitive tests was independent of administration characteristics, which could indicate that elevated cognitive load among persons with sensory impairment plays a larger role in test performance than previously acknowledged. While these results were unexpected, neither of these samples are nationally representative and each has unique selection factors; thus, replication is critical.
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Aterosclerosis , Disfunción Cognitiva , Pérdida Auditiva , Anciano , Envejecimiento , Aterosclerosis/complicaciones , Baltimore , Disfunción Cognitiva/complicaciones , Disfunción Cognitiva/etiología , Estudios Transversales , Pérdida Auditiva/complicaciones , Pérdida Auditiva/diagnóstico , Pérdida Auditiva/psicología , Humanos , Estudios Longitudinales , Pruebas NeuropsicológicasRESUMEN
A moderately halophilic and strictly aerobic bacterium was isolated from a human stool as part of a study on the diagnosis of childhood malnutrition in Mali. Strain Marseille-Q1616T is a Gram-stain-positive, rod-shaped, catalase-positive and oxidase-negative bacterium. It has a genome size of 3.91 Mbp with 39.79% G+C content, which contains 3954 protein-coding genes including genes encoding phosphomycin resistance and Listeria monocytogenes, 16 rRNA genes and 64 tRNA genes. Strain Marseille-Q1616T exhibited a 96.3% 16S rRNA gene sequence similarity and shared an OrthoANI value of 70.64% (the highest observed) with Virgibacillus kekensis, the phylogenetically closest validly published species. Based on phenotypic and phylogenetic evidence and genomic average nucleotide identity values, we suggest the creation of a new species within the Virgibacillus genus, named Virgibacillus doumboii sp. nov., type strain Marseille-Q1616T (= CSURQ1616).
RESUMEN
Strain Marseille-P3248Ñ is a new species from the order Actinomycetales that was isolated from the urine sample of a girl aged 20 months with rotavirus gastroenteritis. It is a facultative anaerobic Gram-positive rod-shaped bacterium. Strain Marseille-P3248Ñ exhibits 94.73% sequence similarity with Arcanobacterium pluranimalium strain M430/94/2, a phylogenetically related species with standing in nomenclature. Its genome size is 1 667 964 bp with 49.1% G + C content. Strain Marseille-P3248Ñ (= CSURP3248) is the type strain of the new species Arcanobacterium urinimassiliense sp. nov.
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An anaerobic facultative Gram-stain positive bacterium was isolated from human gut microbiota. Strain Marseille-P5551T was considered to be a new genus within the phylum Firmicutes, as it exhibits a 91.87% similarity level with Faecalicatena orotica (NR_117129.1), the phylogenetically closest related species. The draft genome size of strain Marseille-P5551T is 4 142 938 bp with 44.4% of G + C content. We hereby suggest the creation of Luxibacter massiliensis gen. nov., sp. nov., as a new bacterial genus.
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Using the taxonogenomics method, we describe Gracilibacillus phocaeensis strain Marseille-P3801, a new species previously isolated from a salty stool of a 20-year-old man from N'Diop, Senegal. It is a Gram-positive, aerobic and motile bacillus. The major fatty acids are C15:0-anteiso (59%), C16:0 (16%) and C17:0-anteiso (11%). Strain Marseille-P3801 exhibits a 98.45% sequence similarity with Gracilibacillus thailandensis strain TP2-8, the phylogenetically closest species. Its genome is 4.66 Mb with 39.6 mol% G + C content.
RESUMEN
Varibaculum massiliense sp. nov. strain Marseille-P2802T (= CSUR P2802 = DSM 103074) is a new species within the genus Varibaculum in the phylum Actinobacteria that was isolated from the urine of a 59-year-old man treated with chronic haemodialysis for diabetic nephropathy.
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Strain Marseille-P5643T was isolated from a vaginal sample of a healthy Senegalese woman. It is an anaerobic Gram-negative, rod-shaped bacterium. Strain Marseille-P5643T exhibits 93.7% similarity levels with the Facklamia hominis strain ATCC 700628T, the phylogenetically closest related species with standing in nomenclature. The draft genome size of strain Marseille-P5643T is 1.79 Mb with 39.0 mol% of G+C content. We propose here the creation of Vaginisenegalia massiliensis gen. nov., sp. nov., as a new bacterial genus from the phylum Firmicutes.
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Parabacteroides massiliensis sp. nov., strain Marseille-P2231T (= CSURP2231 = DSM 101860) is a new species within the family Tannerellaceae. It was isolated from a stool specimen of a 25-year-old healthy woman. Its genome was 5 013 798 bp long with a 45.7 mol% G+C content. The closest species based on 16S rRNA sequence was Parabacteroides merdae strain JCM 9497T with 98.19% sequence similarity. Considering phenotypic features and comparative genome studies, we proposed the strain Marseille-P2231T as the type strain of Parabacteroides massiliensis sp. nov., a new species within the genus Parabacteroides.
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[This corrects the article DOI: 10.1155/2018/1453173.].
RESUMEN
OBJECTIVES: Methanogenic Archaea are considered as extremely oxygen-sensitive organisms, and their culture is fastidious, requiring specific equipment. We report here conditions allowing the cultivation of Methanobrevibacter smithii in an anaerobic chamber without the addition of hydrogen. METHODS: We first enriched the stool sample in an anaerobic liquid medium. To cultivate M. smithii with Bacteroides thetaiotaomicron and other hydrogen-producing bacteria on solid medium in an anaerobic chamber, we divided the agar plates into two compartments and seeded each strain on each compartment. Methane production was assessed by gas chromatography, and the growing colonies were authenticated by MALDI-TOF MS. RESULTS: We successfully cultured M. smithii from a liquid culture medium inoculated with stool collected from a healthy donor in an anaerobic chamber. The isolation in pure culture permitted successful culture on agar medium by our performing a co-culture with B. thetaiotaomicron. We also successfully tested the co-cultivation of M. smithii with other known hydrogen-producing bacteria. Gas chromatographic tests showed that these strains produced hydrogen in different amounts. Agar colonies of methanogens were obtained by co-culture with these bacteria, and methane production was detected. CONCLUSIONS: We propose a new approach to isolate and cultivate new strains of M. smithii by using a co-culture-based technique that can facilitate and make available the isolation of new methanogenic Archaea strains in clinical microbiology laboratories.
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Bacterias/metabolismo , Hidrógeno/metabolismo , Methanobrevibacter/crecimiento & desarrollo , Methanobrevibacter/aislamiento & purificación , Adulto , Agar , Anaerobiosis , Bacterias/clasificación , Bacterias/crecimiento & desarrollo , Técnicas de Cocultivo , Medios de Cultivo , Heces/microbiología , Femenino , Voluntarios Sanos , Humanos , Metano/análisis , Metano/biosíntesis , Methanobrevibacter/metabolismoRESUMEN
Strain Marseille-P4006T, a Gram-stain-positive, rod-shaped, non-sporulating, facultatively anaerobic bacterium, was isolated from the vaginal swab of a 45-year-old woman with recurrent bacterial vaginosis. We studied its phenotypic characteristics and sequenced its whole genome. The major fatty acids were C16:0 (48%), C19:1n9 (14%) and C18:0 (11%). The 3 070 142-bp-long genome contains 2855 protein-coding genes and 68 RNAs. Strain Marseille-P4006T exhibited 98.1% 16S rRNA similarity with Lactobacillus farraginis, the closest species phylogenetically. Thus, strain Marseille-P4006 is distinct enough to represent a new species for which we propose the name Lactobacillus raoultii sp. nov. The type strain is Marseille-P4006T.
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Four strains isolated by microbial culturomics from breast milk of healthy mothers from Mali were not identified and characterized by taxono-genomics. This led us to propose the new genera and species Lactimicrobium massiliense, Anaerolactibacter massiliensis and Galactobacillus timonensis containing type strain Marseille-P4301T (CSUR P4301T), Marseille-P4302T (CSUR P4302T) and Marseille-P4641T (CSUR P4641T), respectively. The strain Marseille-P4482 represents a novel species, Acidipropionibacterium timonense, in a previously known genus with type strain being Marseille-P4482T (CSUR P4482T).
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A new bacterium, strain AT3T, was isolated by microbial culturomics from a faecal sample from a Frenchman after bariatric surgery. The isolate exhibited 96.6% 16S ribosomal RNA gene nucleotide sequence similarity with Anaerotruncus colihominis strain WAL 14565T = CCUG 45055T = CIP 107754T. Phenotypic and genomic characteristics showed that the new strain represents a novel species, for which the name Anaerotruncus massiliensis sp. nov. is proposed. The type strain is strain AT3T = CSUR P2007T = DSM 100567T.
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Using the strategy of taxonogenomics, we described Clostridium pacaense sp. nov. strain Marseille-P3100T, a Gram-variable, nonmotile, spore-forming anaerobic bacillus. This strain was isolated from a 3.3-month-old Senegalese girl with clinical aspects of marasmus. The closest species based on 16S ribosomal RNA was Clostridium aldenense, with a similarity of 98.4%. The genome length was 2 672 129 bp, with a 50% GC content; 2360 proteins were predicted. Finally, predominant fatty acids were hexadecanoic acid, tetradecanoic acid and 9-hexadecenoic acid.