Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols.

The complexation of iron(III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron(II) and the carbon dioxide anion radical. Importantly, iron(III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown. This study utilizes glycolaldehyde as a model organic species to examine the oxidation pathways and evolution of organic aerosol initiated by the photodissociation of aqueous iron(III) oxalate complexes. Hanging droplets (radius 1 mm) containing iron(III), oxalic acid, glycolaldehyde, and ammonium sulfate (pH ∼3) are exposed to irradiation at 365 nm and sampled at discrete time points utilizing field-induced droplet ionization mass spectrometry (FIDI-MS). Glycolaldehyde is found to undergo rapid oxidation to form glyoxal, glycolic acid, and glyoxylic acid, but the formation of high molecular weight oligomers is not observed. For comparison, particle-phase experiments conducted in a laboratory chamber explore the reactive uptake of gas-phase glycolaldehyde onto aqueous seed aerosol containing iron and oxalic acid. The presence of iron oxalate in seed aerosol is found to inhibit aerosol growth. These results suggest that photodissociation of iron(III) oxalate can lead to the formation of volatile oxidation products in tropospheric aqueous aerosols.

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

Isoprene NO3 Oxidation Products from the RO2 + HO2 Pathway.

We describe the products of the reaction of the hydroperoxy radical (HO(2)) with the alkylperoxy radical formed following addition of the nitrate radical (NO(3)) and O(2) to isoprene. NO(3) adds preferentially to the C(1) position of isoprene (>6 times more favorably than addition to C(4)), followed by the addition of O(2) to produce a suite of nitrooxy alkylperoxy radicals (RO(2)). At an RO(2) lifetime of ∼30 s, δ-nitrooxy and ß-nitrooxy alkylperoxy radicals are present in similar amounts. Gas-phase product yields from the RO(2) + HO(2) pathway are identified as 0.75-0.78 isoprene nitrooxy hydroperoxide (INP), 0.22 methyl vinyl ketone (MVK) + formaldehyde (CH(2)O) + hydroxyl radical (OH) + nitrogen dioxide (NO(2)), and 0-0.03 methacrolein (MACR) + CH(2)O + OH + NO(2). We further examined the photochemistry of INP and identified propanone nitrate (PROPNN) and isoprene nitrooxy hydroxyepoxide (INHE) as the main products. INHE undergoes similar heterogeneous chemistry as isoprene dihydroxy epoxide (IEPOX), likely contributing to atmospheric secondary organic aerosol formation.

The effects of α-pinene versus toluene-derived secondary organic aerosol exposure on the expression of markers associated with vascular disease.

To investigate the toxicological effects of biogenic- versus anthropogenic-source secondary organic aerosol (SOA) on the cardiovascular system, the Secondary Particulate Health Effects Research program irradiation chamber was used to expose atherosclerotic apolipoprotein E null (Apo E-/-) mice to SOA from the oxidation of either α-pinene or toluene for 7 days. SOA atmospheres were produced to yield 250-300 µg/m(3) of particulate matter and ratios of 10:1:1 α-pinene:nitrogen oxide (NOx):ammonia (NH3); 10:1:1:1 α-pinene:NOx:NH3:sulfur dioxide (SO2) or 10:1:1 toluene:NOx:NH3; and 10:1:1:1 toluene:NOx:NH3:SO2. Resulting effects on the cardiovascular system were assessed by measurement of vascular lipid peroxidation (thiobarbituric acid reactive substance (TBARS)), as well as quantification of heme-oxygenase (HO)-1, endothelin (ET)-1, and matrix metalloproteinase (MMP)-9 mRNA expression for comparison to previous program exposure results. Consistent with similar previous studies, vascular TBARS were not increased significantly with any acute SOA exposure. However, vascular HO-1, MMP-9, and ET-1 observed in Apo E-/- mice exposed to α-pinene + NOx + NH3 + SO2 increased statistically, while α-pinene + NOx + NH3 exposure to either toluene + NOx + NH3 or toluene +NOx + NH3 + SO2 resulted in a decreased expression of these vascular factors. Such findings suggest that the specific chemistry created by the presence or absence of acidic components may be important in SOA-mediated toxicity in the cardiovascular system and/or progression of cardiovascular disease.

Secondary organic aerosol formation from low-NO(x) photooxidation of dodecane: evolution of multigeneration gas-phase chemistry and aerosol composition.

The extended photooxidation of and secondary organic aerosol (SOA) formation from dodecane (C(12)H(26)) under low-NO(x) conditions, such that RO(2) + HO(2) chemistry dominates the fate of the peroxy radicals, is studied in the Caltech Environmental Chamber based on simultaneous gas and particle-phase measurements. A mechanism simulation indicates that greater than 67% of the initial carbon ends up as fourth and higher generation products after 10 h of reaction, and simulated trends for seven species are supported by gas-phase measurements. A characteristic set of hydroperoxide gas-phase products are formed under these low-NO(x) conditions. Production of semivolatile hydroperoxide species within three generations of chemistry is consistent with observed initial aerosol growth. Continued gas-phase oxidation of these semivolatile species produces multifunctional low volatility compounds. This study elucidates the complex evolution of the gas-phase photooxidation chemistry and subsequent SOA formation through a novel approach comparing molecular level information from a chemical ionization mass spectrometer (CIMS) and high m/z ion fragments from an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Combination of these techniques reveals that particle-phase chemistry leading to peroxyhemiacetal formation is the likely mechanism by which these species are incorporated in the particle phase. The current findings are relevant toward understanding atmospheric SOA formation and aging from the "unresolved complex mixture," comprising, in part, long-chain alkanes.

Best methods for evaluating educational impact: a comparison of the efficacy of commonly used measures of library instruction.

OBJECTIVES AND BACKGROUND: Libraries are increasingly called upon to demonstrate student learning outcomes and the tangible benefits of library educational programs. This study reviewed and compared the efficacy of traditionally used measures for assessing library instruction, examining the benefits and drawbacks of assessment measures and exploring the extent to which knowledge, attitudes, and behaviors actually paralleled demonstrated skill levels. METHODS: An overview of recent literature on the evaluation of information literacy education addressed these questions: (1) What evaluation measures are commonly used for evaluating library instruction? (2) What are the pros and cons of popular evaluation measures? (3) What are the relationships between measures of skills versus measures of attitudes and behavior? Research outcomes were used to identify relationships between measures of attitudes, behaviors, and skills, which are typically gathered via attitudinal surveys, written skills tests, or graded exercises. RESULTS AND CONCLUSIONS: Results provide useful information about the efficacy of instructional evaluation methods, including showing significant disparities between attitudes, skills, and information usage behaviors. This information can be used by librarians to implement the most appropriate evaluation methods for measuring important variables that accurately demonstrate students' attitudes, behaviors, or skills.

Calcium promotes exopolysaccharide phase variation and biofilm formation of the resulting phase variants in the human pathogen Vibrio vulnificus.

Vibrio vulnificus is a Gram-negative bacterium found in estuaries and coastal waters and is associated with human disease caused by ingestion of raw shellfish. Pathogenesis is directly related to the presence of capsular polysaccharide (CPS). Encapsulated virulent strains exhibit an opaque colony phenotype, while unencapsulated attenuated strains appear translucent. A third colony type, rugose, is caused by expression of rugose extracellular polysaccharide (rEPS) and forms robust biofilms. Vibrio vulnificus undergoes phase variation associated with altered levels of CPS and rEPS, and we show here that calcium (Ca²(+) ) significantly increases the rate of CPS and rEPS phase variation in this species. Interestingly, multiple phenotypic responses to increased [Ca²(+) ] were observed among strains, which suggests the existence of underlying cognate genetic or epigenetic differences. Certain translucent isolates contained deletions at the group I CPS operon, inferring increased [Ca²(+) ] upregulates existing phase variation mechanisms. Expanding on a previous observation (Kierek and Watnick, Proc. Natl. Acad. Sci. USA 100: 14357-14362, 2003), increased [Ca²(+) ] also enhanced biofilm formation for all phase variants. Our results show that Ca²(+) promotes both polysaccharide phase variation and biofilm formation of the resulting phase variants, thereby likely serving a dual role in persistence of V. vulnificus in the environment.

An accessible method for screening aerosol filtration identifies poor-performing commercial masks and respirators.

BACKGROUND: The COVID-19 pandemic has presented an acute shortage of regulation-tested masks. Many of the alternatives available to hospitals have not been certified, leaving uncertainty about their ability to properly protect healthcare workers from SARS-CoV-2 transmission. OBJECTIVE: For situations where regulatory methods are not accessible, we present experimental methods to evaluate mask filtration and breathability quickly via cost-effective approaches (e.g., ~$2000 USD) that could be replicated in communities of need without extensive infrastructure. We demonstrate the need for screening by evaluating an existing diverse inventory of masks/respirators from a local hospital. METHODS: Two experimental approaches are presented to examine both aerosol filtration and flow impedance (i.e., breathability). For one of the approaches ("quick assessment"), screening for appropriate filtration could be performed under 10 min per mask, on average. Mask fit tests were conducted in tandem but are not the focus of this study. RESULTS: Tests conducted of 47 nonregulation masks reveal variable performance. A number of commercially available masks in hospital inventories perform similarly to N95 masks for aerosol filtration of 0.2 µm and above, but there is a range of masks with relatively lower filtration efficiencies (e.g., <90%) and a subset with poorer filtration (e.g., <70%). All masks functioned acceptably for breathability, and impedance was not correlated with filtration efficiency. SIGNIFICANCE: With simplified tests, organizations with mask/respirator shortages and uncertain inventories can make informed decisions about use and procurement.

An intervention to improve communication between breast cancer survivors and their physicians.

Breast cancer survivors often use clues to convey their concerns to their oncologists. The authors conducted a randomized trial of a communication coaching intervention in which 22 female breast cancer survivors were randomized to the coaching and 22 to treatment as usual. They hypothesized that the intervention would increase breast cancer self-efficacy, improve mood, and reduce fears of recurrence. Through a series of ANCOVAs they found that the intervention led to increases in self-efficacy. Changes in self-efficacy predicted changes in anxiety, depression, and womanhood fears. This coaching intervention shows promise but requires additional studies to establish is efficacy and effectiveness.

An interactive web-based curriculum on evidence-based medicine: design and effectiveness.

BACKGROUND AND OBJECTIVES: Medical education experts have called for improved training in evidence-based medicine (EBM) and the increased use of e-learning technologies in medical education. In response, we developed an interactive, Web-based curriculum on key aspects of EBM in family medicine. METHODS: Students participating in a 6-week family medicine clerkship (n=238) were randomly assigned to intervention (n=134) or control (n=104) groups. Both groups participated in the traditional clerkship experience, but intervention group students received additional training via an on-line curriculum that included learning modules in MEDLINE searching skills, EBM skills, and the calculation of the number needed to treat (NNT) statistic. The on-line curriculum was evaluated using a case-control design with a test case at the clerkship's end. RESULTS: Results suggested that the on-line curriculum was effective, with experimental group students outperforming control group participants on a variety of measures, including the number of MEDLINE searches conducted during the clerkship (13 searches versus 3 searches) and the quality of literature search strategies on an evaluation patient case study (2.9 versus 2.1 on a 1=poor to 4=excellent scale). Intervention group students reported greater confidence and enjoyment in searching the biomedical journal literature via MEDLINE and were more likely to identify the best articles (randomized controlled trials or meta-analyses) for the evaluation case from among those retrieved (60% versus 34%). In addition, intervention group students' abilities to correctly calculate the NNT were significantly higher than those of control group participants (73% versus 27%). Intervention group students were more likely than control subjects to report learning from other students during the clerkship. CONCLUSIONS: This study demonstrates that an e-learning approach to educating medical students to effectively search MEDLINE for articles meeting the criteria for evidence-based practice can result in higher-quality literature search strategies, identification of higher-quality evidence, and improved confidence in information retrieval and analysis skills.

Capsular polysaccharide production and serum survival of Vibrio vulnificus are dependent on antitermination control by RfaH.

The human pathogen Vibrio vulnificus undergoes phase variation among colonial morphotypes, including a virulent opaque form which produces capsular polysaccharide (CPS) and a translucent phenotype that produces little or no CPS and is attenuated. Here, we found that a V. vulnificus mutant defective for RfaH antitermination control showed a diminished capacity to undergo phase variation and displayed significantly reduced distal gene expression within the Group I CPS operon. Moreover, the rfaH mutant produced negligible CPS and was highly sensitive to killing by normal human serum, results which indicate that RfaH is likely essential for virulence in this bacterium.

Manganese is an additional cation that enhances colonial phase variation of Vibrio vulnificus.

Vibrio vulnificus, an inhabitant of marine and estuarine environments around the world, is the leading cause of reported seafood-related deaths in the United States. Disease is caused by opaque colony-forming strains that produce capsular polysaccharide, loss of which results in an unencapsulated translucent phenotype with diminished virulence potential. Rugose is a third phenotypic variant of V. vulnificus, and produces a separate exopolysaccharide that results in a dry, wrinkled appearance and the ability to form profuse biofilms. Phase variation among these three phenotypes is influenced by several environmental factors, including the presence of calcium in the medium (Garrison-Schilling et al.). In this study, we have identified a second cation, manganese, which substantially increases the propensity of opaque V. vulnificus strains to switch to translucent or rugose phenotypes. In comparative studies, manganese and calcium promoted switching to the same phenotype for some strains but to different phenotypes for others, results of which indicate that the two cations do not always promote the same changes in underlying gene expression. The data here provide further evidence that exposure of V. vulnificus to select cations results in phenotypic changes that impact both virulence capacity and ecology of the organism.

Genome-wide mapping of furfural tolerance genes in Escherichia coli.

Advances in genomics have improved the ability to map complex genotype-to-phenotype relationships, like those required for engineering chemical tolerance. Here, we have applied the multiSCale Analysis of Library Enrichments (SCALEs; Lynch et al. (2007) Nat. Method.) approach to map, in parallel, the effect of increased dosage for >10(5) different fragments of the Escherichia coli genome onto furfural tolerance (furfural is a key toxin of lignocellulosic hydrolysate). Only 268 of >4,000 E. coli genes (∼ 6%) were enriched after growth selections in the presence of furfural. Several of the enriched genes were cloned and tested individually for their effect on furfural tolerance. Overexpression of thyA, lpcA, or groESL individually increased growth in the presence of furfural. Overexpression of lpcA, but not groESL or thyA, resulted in increased furfural reduction rate, a previously identified mechanism underlying furfural tolerance. We additionally show that plasmid-based expression of functional LpcA or GroESL is required to confer furfural tolerance. This study identifies new furfural tolerant genes, which can be applied in future strain design efforts focused on the production of fuels and chemicals from lignocellulosic hydrolysate.

Genetic analysis and prevalence studies of the brp exopolysaccharide locus of Vibrio vulnificus.

Phase variation in the Gram-negative human pathogen Vibrio vulnificus involves three colonial morphotypes- smooth opaque colonies due to production of capsular polysaccharide (CPS), smooth translucent colonies as the result of little or no CPS expression, and rugose colonies due to production of a separate extracellular polysaccharide (EPS), which greatly enhances biofilm formation. Previously, it was shown that the brp locus, which consists of nine genes arranged as an operon, is up-regulated in rugose strains in a c-di-GMP-dependent manner, and that plasmid insertions into the locus resulted in loss of rugosity and efficient biofilm production. Here, we have used non-polar mutagenesis to assess the involvement of individual brp genes in production of EPS and related phenotypes. Inactivation of genes predicted to be involved in various stages of EPS biosynthesis eliminated both the rugose colonial appearance and production of EPS, while knockout of a predicted flippase function involved in EPS transport resulted in a dry, lightly striated phenotype, which was associated with a reduction of brp-encoded EPS on the cell surface. All brp mutants retained the reduced motility characteristic of rugose strains. Lastly, we provide evidence that the brp locus is highly prevalent among strains of V. vulnificus.

Barriers and benefits associated with nurses information seeking related to patient education needs on clinical nursing units.

The purpose of this study was to answer the following two questions: What are clinical nurses' rationales for their approaches to finding patient educational materials on the web? What are perceived barriers and benefits associated with the use of web-based information resources for patient education in the context of nursing clinical practice?Over 179 individual data units were analyzed to understand clinical nurses' rationales for their approaches to find patient educational materials on the web. Rationales were defined as those underlying catalysts or activators leading to an information need. Analyses found that the primary reasons why clinical nurses conducted web-based information searches included direct patient requests ( 9 requests), colleague requests (6 requests), building patient materials collections (4), patients' family requests (3), routine teaching (1), personal development (1), or staff development (1). From these data, four broad themes emerged: professional reasons, personal reasons, technology reasons, and organization reasons for selecting information resources. Content analysis identified 306 individual data units representing either 'benefits' (178 units) or 'barriers' (128) to the nurses' use of web resources for on-unit patient care. Inter-rater reliability was assessed and found to be excellent (r = 0.943 to 0.961). The primary themes that emerged as barriers to the used of web-based resources included: 1) time requirements to perform a search, 2) nurses' experience and knowledge about the resources or required technology, 3) specific characteristics of individuals electronic information resources, and 4) organizational procedures and policies. Three primary themes that represented the benefits of using web-based resources were also identified: 1) past experiences and knowledge of a specific resource or the required technologies, 2) availability and accessibility on the unit, and 3) specific characteristics of individual information tool. In many cases, nurses commented on specific characteristics or features of favorite information resources. Favorite sites included a variety or reputable health care organizations that displayed context in text, audio, and/or video. In addition such sites were described as easy-to read and provided content related to patient-focused information or specific content such as toll free telephone contact numbers.Information searching is the interaction between and among information users and computer-based information systems. Information seeking is becoming an important part of the knowledge work of nurses. Information seeking and searching intersects with the field of human computer interaction (HCI), which focuses on all aspects of human, and computer interactions. Users of an information system are understood as "actors" in situations, with a set of skills and shared practices based on work experiences with others. Designing better tools and developing information searching strategies that support, extend, and transform practices, begins by asking: Who are the users? What are the tasks? What is the interplay between the technology and the organization of the task? This study contributes fundamental data and information about the rationales nurses use in information seeking tasks. In addition it provides empirical evidences regarding barriers and benefits of information seeking in the context of patient education needs in inpatient clinical settings.