Production of HO2 and OH radicals from near-UV irradiated airborne TiO2 nanoparticles.

The production of gas-phase hydroperoxyl radicals, HO2, is observed directly from sub-micron airborne TiO2 nanoparticles irradiated by 300-400 nm radiation. The rate of HO2 production as a function of O2 pressure follows Langmuir isotherm behaviour suggesting O2 is involved in the production of HO2 following its adsorption onto the surface of the TiO2 aerosol. Reduction of adsorbed O2 by photogenerated electrons is likely to be the initial step followed by reaction with a proton produced via oxidation of adsorbed water with a photogenerated hole. The rate of HO2 production decreased significantly over the range of relative humidities between 8.7 and 36.9%, suggesting competitive adsorption of water vapour inhibits HO2 production. From the data, the adsorption equilibrium constants were calculated to be: KO2 = 0.27 ± 0.02 Pa-1 and KH2O = 2.16 ± 0.12 Pa-1 for RH = 8.7%, decreasing to KO2 = 0.18 ± 0.01 Pa-1 and KH2O = 1.33 ± 0.04 Pa-1 at RH = 22.1%. The increased coverage of H2O onto the TiO2 aerosol surface may inhibit HO2 production by decreasing the effective surface area of the TiO2 particle and lowering the binding energy of O2 on the aerosol surface, hence shortening its desorption lifetime. The maximum yield (i.e. when [O2] is projected to atmospherically relevant levels) for production of gas-phase HO2, normalised for surface area and light intensity, was found to be at a RH of 8.7% for the 80% anatase and 20% rutile formulation of TiO2 used here. This yield decreased to as the RH was increased to 22.1%. Using this value, the rate of production of HO2 from TiO2 surfaces under atmospheric conditions was estimated to be in the range 5 × 104-1 × 106 molecule cm-3 s-1 using observed surface areas of mineral dust at Cape Verde, and assuming a TiO2 fraction of 4.5%. For the largest loadings of dust in the troposphere, the rate of this novel heterogeneous production mechanism begins to approach that of HO2 production from the gas-phase reaction of OH with CO in unpolluted regions. The production of gas-phase OH radicals could only be observed conclusively at high aerosol surface areas, and was attributed to the decomposition of H2O2 at the surface by photogenerated electrons.

Comment on "Methanol dimer formation drastically enhances hydrogen abstraction from methanol by OH at low temperature" by W. Siebrand, Z. Smedarchina, E. Martínez-Núñez and A. Fernández-Ramos, Phys. Chem. Chem. Phys., 2016, 18, 22712.

The article "Methanol dimer formation drastically enhances hydrogen abstraction from methanol by OH at low temperature" proposes a dimer mediated mechanism in order to explain the large low temperature rate coefficients for the OH + methanol reaction measured by several groups. It is demonstrated here theoretically that under the conditions of these low temperature experiments, there are insufficient dimers formed for the proposed new mechanism to apply. Experimental evidence is also presented to show that dimerization of the methanol reagent does not influence the rate coefficients reported under the conditions of methanol concentration used for the kinetics studies. It is also emphasised that the low temperature experiments have been performed using both the Laval nozzle expansion and flow-tube methods, with good agreement found for the rate coefficients measured using these two distinct techniques.

Significant OH production under surface cleaning and air cleaning conditions: Impact on indoor air quality.

We report measurements of hydroxyl (OH) and hydroperoxy (HO2 ) radicals made by laser-induced fluorescence spectroscopy in a computer classroom (i) in the absence of indoor activities (ii) during desk cleaning with a limonene-containing cleaner (iii) during operation of a commercially available "air cleaning" device. In the unmanipulated environment, the one-minute averaged OH concentration remained close to or below the limit of detection (6.5×105  molecule cm-3 ), whilst that of HO2 was 1.3×107  molecule cm-3 . These concentrations increased to ~4×106 and 4×108  molecule cm-3 , respectively during desk cleaning. During operation of the air cleaning device, OH and HO2 concentrations reached ~2×107 and ~6×108  molecule cm-3 respectively. The potential of these OH concentrations to initiate chemical processing is explored using a detailed chemical model for indoor air (the INDCM). The model can reproduce the measured OH and HO2 concentrations to within 50% and often within a few % and demonstrates that the resulting secondary chemistry varies with the cleaning activity. Whilst terpene reaction products dominate the product composition following surface cleaning, those from aromatics and other VOCs are much more important during the use of the air cleaning device.

Potential arsenic exposures in 25 species of zoo animals living in CCA-wood enclosures.

Animal enclosures are often constructed from wood treated with the pesticide chromated copper arsenate (CCA), which leaches arsenic (As) into adjacent soil during normal weathering. This study evaluated potential pathways of As exposure in 25 species of zoo animals living in CCA-wood enclosures. We analyzed As speciation in complete animal foods, dislodgeable As from CCA-wood, and As levels in enclosure soils, as well as As levels in biomarkers of 9 species of crocodilians (eggs), 4 species of birds (feathers), 1 primate species (hair), and 1 porcupine species (quills). Elevated soil As in samples from 17 enclosures was observed at 1.0-110mg/kg, and enclosures housing threatened and endangered species had As levels higher than USEPA's risk-based Eco-SSL for birds and mammals of 43 and 46mg/kg. Wipe samples of CCA-wood on which primates sit had dislodgeable As residues of 4.6-111µg/100cm(2), typical of unsealed CCA-wood. Inorganic As doses from animal foods were estimated at 0.22-7.8µg/kg bw/d. Some As levels in bird feathers and crocodilian eggs were higher than prior studies on wild species. However, hair from marmosets had 6.37mg/kg As, 30-fold greater than the reference value, possibly due to their inability to methylate inorganic As. Our data suggested that elevated As in soils and dislodgeable As from CCA-wood could be important sources of As exposure for zoo animals.

Measurements of the HO2 uptake coefficients onto single component organic aerosols.

Measurements of HO2 uptake coefficients (γ) were made onto a variety of organic aerosols derived from glutaric acid, glyoxal, malonic acid, stearic acid, oleic acid, squalene, monoethanol amine sulfate, monomethyl amine sulfate, and two sources of humic acid, for an initial HO2 concentration of 1 × 10(9) molecules cm(-3), room temperature and at atmospheric pressure. Values in the range of γ < 0.004 to γ = 0.008 ± 0.004 were measured for all of the aerosols apart from the aerosols from the two sources of humic acid. For humic acid aerosols, uptake coefficients in the range of γ = 0.007 ± 0.002 to γ = 0.09 ± 0.03 were measured. Elevated concentrations of copper (16 ± 1 and 380 ± 20 ppb) and iron (600 ± 30 and 51 000 ± 3000 ppb) ions were measured in the humic acid atomizer solutions compared to the other organics that can explain the higher uptake values measured. A strong dependence upon relative humidity was also observed for uptake onto humic acid, with larger uptake coefficients seen at higher humidities. Possible hypotheses for the humidity dependence include the changing liquid water content of the aerosol, a change in the mass accommodation coefficient or in the Henry's law constant.

Low temperature kinetics of the CH3OH + OH reaction.

The rate constant of the reaction between methanol and the hydroxyl radical has been studied in the temperature range 56-202 K by pulsed laser photolysis-laser induced fluorescence in two separate experiments using either a low temperature flow tube coupled to a time-of-flight mass spectrometer or a pulsed Laval nozzle apparatus. The two independent techniques yield rate constants that are in mutual agreement and consistent with the results reported previously below 82 K [Shannon et al. Nat. Chem. 2013, 5, 745-749] and above 210 K [Dillon et al. Phys. Chem. Chem. Phys. 2005, 7, 349-355], showing a very sharp increase with decreasing temperature with an onset around 180 K. This onset is also signaled by strong chemiluminescence tentatively assigned to formaldehyde, which is consistent with the formation of the methoxy radical at low temperature by quantum tunnelling, and its subsequent reaction with H and OH. Our results add confidence to the previous low temperature rate constant measurements and consolidate the experimental reference data set for further theoretical work required to describe quantitatively the tunnelling mechanism operating in this reaction. An additional measurement of the rate constant at 56 K yielded a value of (4.9 ± 0.8) × 10(-11) cm(3) molecule(-1) s(-1) (2σ), showing that the rate constant is increasing less rapidly at temperatures below 70 K.

A combined experimental and theoretical study of reactions between the hydroxyl radical and oxygenated hydrocarbons relevant to astrochemical environments.

The kinetics of the reactions of the hydroxyl radical (OH) with acetone and dimethyl ether (DME) have been studied between 63-148 K and at a range of pressures using laser-flash photolysis coupled with laser induced fluorescence detection of OH in a pulsed Laval nozzle apparatus. For acetone, a large negative temperature dependence was observed, with the rate coefficient increasing from k1 = (1.6 ± 0.8) × 10(-12) cm(3) molecule(-1) s(-1) at 148 K to (1.0 ± 0.1) × 10(-10) cm(3) molecule(-1) s(-1) at 79 K, and also increasing with pressure. For DME, a similar behaviour was found, with the rate coefficient increasing from k2 = (3.1 ± 0.5) × 10(-12) cm(3) molecule(-1) s(-1) at 138 K to (1.7 ± 0.1) × 10(-11) cm(3) molecule(-1) s(-1) at 63 K, and also increasing with pressure. The temperature and pressure dependence of the experimental rate coefficients are rationalised for both reactions by the formation and subsequent stabilisation of a hydrogen bonded complex, with a non-zero rate coefficient extrapolated to zero pressure supportive of quantum mechanical tunnelling on the timescale of the experiments leading to products. In the case of DME, experiments performed in the presence of O2 provide additional evidence that the yield of the CH3OCH2 abstraction product, which can recycle OH in the presence of O2, is ≥50%. The experimental data are modelled using the MESMER (Master Equation Solver for Multi Energy Well Reactions) code which includes a treatment of quantum mechanical tunnelling, and uses energies and structures of transition states and complexes calculated by ab initio methods. Good agreement is seen between experiment and theory, with MESMER being able to reproduce for both reactions the temperature behaviour between ~70-800 K and the pressure dependence observed at ~80 K. At the limit of zero pressure, the model predicts a rate coefficient of ~10(-11) cm(3) molecule(-1) s(-1) for the reaction of OH with acetone at 20 K, providing evidence that the reaction can proceed quickly in those regions of space where both species have been observed. The results and modelling build considerably on our previous experimental study performed under a much more limited range of conditions (Shannon et al., Phys. Chem. Chem. Phys., 2010, 12, 13511-13514).

Measurements of uptake coefficients for heterogeneous loss of HO2 onto submicron inorganic salt aerosols.

Laboratory studies were conducted to investigate the kinetics of HO2 radical uptake onto submicron inorganic salt aerosols. HO2 reactive uptake coefficients were measured at room temperature using an aerosol flow tube and the Fluorescence Assay by Gas Expansion (FAGE) technique that allowed for measurements to be conducted under atmospherically relevant HO2 concentrations ([HO2] = 10(8) to 10(9) molecule cm(-3)). The uptake coefficient for HO2 uptake onto dry inorganic salt aerosols was consistently below the detection limit (γ(HO2) < 0.004). The mass accommodation coefficient of HO2 radicals onto Cu(II)-doped (NH4)2SO4 aerosols was measured to be α(HO2) = 0.4 ± 0.3 representing the kinetic upper limit to γ. For aqueous (NH4)2SO4, NaCl and NH4NO3 aerosols not containing traces of transition metal ions, a range of γ(HO2) = 0.003-0.02 was measured. These values were much lower than γ values previously measured on aqueous (NH4)2SO4 and NaCl aerosols and also those typically used in atmospheric models (γ(HO2) = 0.1-1.0). Evidence is presented showing that the HO2 uptake coefficients onto aqueous salt aerosol particles are dependent both on the exposure time to the aerosol and on the HO2 concentration used.

The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo.

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.

A laser induced fluorescence study relating to physical properties of the iodine monoxide radical.

The dispersed fluorescence spectra originating from the v' = 2 and v' = 0 levels of the A(2)Pi(3/2) state of iodine monoxide (IO) have been recorded for the first time after laser induced fluorescence (LIF) excitation in the A(2)Pi(3/2)<-- X(2)Pi(3/2) electronic transition. The results are used to obtain relative Franck-Condon factors for various v'-->v'' transitions in the A(2)Pi(3/2)--> X(2)Pi(3/2) system up to v'' = 12 and compared with theoretical predictions. A fluorescence quenching study of the A(2)Pi(3/2) state of IO has also been performed, revealing that collisional quenching and rotational energy transfer (RET) are rapid in the A(2)Pi(3/2) state of IO. The J'-dependence to fluorescence quenching of the A(2)Pi(3/2) (v' = 2) state of IO by N(2) suggests a collisional predissociation mechanism.

A kinetic and spectroscopic study of the CH3I-Cl and ICH2I-Cl adducts.

Laser-induced fluorescence from the CH3I-Cl and ICH2I-Cl adducts formed in association reactions between chlorine atoms and CH3I and CH2I2 has been observed for the first time. The LIF excitation and dispersed fluorescence spectra have been measured in the range 345-375 nm and 380-480 nm, respectively, at 204 and 296 K. The excitation spectra exhibit vibrational fine structure, and a semiquantitative analysis of the spectra yields a similar binding energy for both adducts of approximately 60 kJ mol(-1). The adduct fluorescence is efficiently quenched by N2 and exhibits a zero-pressure lifetime of approximately 25-30 ns. Using LIF excited from the CH3I-Cl and ICH2I-Cl adducts, the kinetics of the reactions of atomic chlorine with methyl iodide and diiodomethane have been investigated, the results showing that both reactions proceed via two independent channels, an association reaction to form the adduct and a bimolecular abstraction reaction. At T approximately 200 K, the association reaction is predominant, and CH3I-Cl formation is irreversible, with rate coefficients for adduct formation found to be pressure-dependent and in reasonable agreement with the literature. At approximately 200 K, removal of the adduct is dominated by reaction with radical species (CH3 and ClSO) and by self-reaction, which proceed at close to the gas kinetic limit. At 296 K, CH3I-Cl formation is reversible, and the equilibrium constant, K(p) = (70.9 +/- 27.4) x 10(3) atm(-1), was determined, which is in excellent agreement with the literature, and the adduct does not significantly react with CH3I. The uncertainty is at the 95% confidence level (2sigma) and includes systematic errors. At approximately 200 K, the ICH2I-Cl adduct is again stabilized, with pressure-dependent rate coefficients reaching the high pressure limit at lower pressures than for the Cl + CH3I reaction. At room temperature, the ICH2I-Cl adduct is removed via an additional unimolecular decomposition channel, which dominates over the reversible decomposition channel to reform Cl + CH2I2. Neither adduct was observed to undergo significant reaction with molecular oxygen at approximately 200 or 296 K, with an upper limit rate coefficient determined as k < 10(-16) cm(3) molecule(-1) s(-1).

Measurement and modelling of air pollution and atmospheric chemistry in the U.K. West Midlands conurbation: overview of the PUMA Consortium project.

The PUMA (Pollution of the Urban Midlands Atmosphere) Consortium project involved intensive measurement campaigns in the Summer of 1999 and Winter of 1999/2000, respectively, in which a wide variety of air pollutants were measured in the UK West Midlands conurbation including detailed speciation of VOCs and major component analysis of aerosol. Measurements of the OH and HO2 free radicals by the FAGE technique demonstrated that winter concentrations of OH were approximately half of those measured during the summer despite a factor of 15 reduction in production through the photolysis of ozone. Detailed box modelling of the fast reaction chemistry revealed the decomposition of Criegee intermediates formed from ozone-alkene reactions to be responsible for the majority of the formation of hydroxyl in both the summer and winter campaigns, in contrast to earlier rural measurements in which ozone photolysis was predominant. The main sinks for hydroxyl are reactions with NO2, alkenes and oxygenates. Concentrations of the more stable hydrocarbons were found to be relatively invariant across the conurbation, but the impacts of photochemistry were evident through analyses of formaldehyde which showed the majority to be photochemical in origin as opposed to emitted from road traffic. Measurements on the upwind and downwind boundaries of the conurbation revealed substantial enhancements in NOx as a result of emissions within the conurbation, especially during westerly winds which carried relatively clean air. Using calcium as a tracer for crustal particles, it proved possible to reconstruct aerosol mass from the major chemical components with a fairly high degree of success. The organic to elemental carbon ratios showed a far greater influence of photochemistry in summer than winter, presumably resulting mainly from the greater availability of biogenic precursors during the summer campaign. Two urban airshed models were developed and applied to the conurbation, one Eulerian, the other Lagrangian. Both were able to give a good simulation of concentrations of both primary and secondary pollutants at urban background locations.

Paramyxovirus infection in caiman lizards (Draecena guianensis).

Three separate epidemics occurred in caiman lizards (Dracaena guianensis) that were imported into the USA from Peru in late 1998 and early 1999. Histologic evaluation of tissues from necropsied lizards demonstrated a proliferative pneumonia. Electron microscopic examination of lung tissue revealed a virus that was consistent with members of the family Paramyxoviridae. Using a rabbit polyclonal antibody against an isolate of ophidian (snake) paramyxovirus, an immunoperoxidase staining technique demonstrated immunoreactivity within pulmonary epithelial cells of 1 lizard. Homogenates of lung, brain, liver, or kidney from affected lizards were placed in flasks containing monolayers of either terrapene heart cells or viper heart cells. Five to 10 days later, syncytial cells formed. When Vero cells were inoculated with supernatant of infected terrapene heart cells, similar syncytial cells developed. Electron microscopic evaluation of infected terrapene heart cells revealed intracytoplasmic inclusions consisting of nucleocapsid strands. Using negative-staining electron microscopy, abundant filamentous nucleocapsid material with a herringbone structure typical of the Paramyxoviridae was observed in culture medium of infected viper heart cells. Seven months following the initial epizootic, blood samples were collected from surviving group 1 lizards, and a hemagglutination inhibition assay was performed to determine presence of specific antibody against the caiman lizard isolate. Of the 17 lizards sampled, 7 had titers of < or =1:20 and 10 had titers of >1:20 and < or =1:80. This report is only the second of a paramyxovirus identified in a lizard and is the first to snow the relationship between histologic and ultrastructural findings and virus isolation.

Reptile anesthesia.

Successful reptile anesthesia requires patience, planning, and understanding of normal anatomy and physiology in health and disease. Reptiles make good anesthetic patients because of their physiologic resilience. New drugs that are not only safe and efficacious, but also result in relatively short recovery times, have greatly enhanced the design of anesthetic regimens. Further studies are required to quantitatively evaluate the physiologic effects of drugs used and validate available monitoring modalities for use in a wide variety of reptiles.

The effect of time at which plasma separation occurs on biochemical values in small island flying foxes (Pteropus hypomelanus).

Heparinized blood samples from 15 adult small island flying foxes (Pteropus hypomelanus) were stored at 22 degrees C for 0-, 6-, and 24-hr intervals prior to centrifugation and separation of plasma from erythrocytes. Mean plasma biochemical values of 16 analytes were determined from all samples. Mean values of blood urea nitrogen, creatinine, total protein, albumin, globulin, alkaline phosphatase, alanine transaminase, aspartate transaminase, cholesterol, calcium, sodium, and bilirubin did not change significantly over 24 hr at 22 degrees C. Glucose was decreased at 6 and 24 hr. Potassium and phosphorus increased and chloride decreased, respectively, between 6 and 24 hr.

The National Health Service Corps for the 21st century.

The National Health Service Corps (NHSC) was created in 1970 to provide primary health care clinicians for the underserved. The article includes a review of the peer-reviewed and intragovernmental literature on the NHSC program from 1971 to 1998 and also presents a current profile of the program. Despite significant increases in NHSC field strength since 1991, the 2,439 clinicians meet only 12% of the need for primary health care providers in underserved areas. While the NHSC has successfully addressed clinician diversity and retention issues, community and site development remain barriers to increasing access. Most communities in need are not ready to recruit and support clinicians. The NHSC of the next millennium must work with the neediest communities to reach the appropriate stage of readiness. Only after completing the necessary "preplacement" activities can the NHSC assist in the recruitment and placement of clinicians to increase access.

Bringing decision support to nurse managers.

Modern hospital nursing management requires timely and accurate information to allow nurse managers to adjust resources to patient requirements. We report an experience using production theory to provide the framework for the development of Decision Support Objects: graphic displays of nursing hours budgeted, scheduled, and worked within institution-specific control limits. Every month, nurse managers follow an analytic algorithm to understand nursing resources and trends on their units. Exception reporting closes the accountability loop. The essentials of education for nurse managers include skill training in the use of the decision-support tools and supportive lecture/seminars for understanding the managerial implications of using them.

Human ERRgamma, a third member of the estrogen receptor-related receptor (ERR) subfamily of orphan nuclear receptors: tissue-specific isoforms are expressed during development and in the adult.

The nuclear receptor protein superfamily is a large group of transcription factors involved in many aspects of animal development, tissue differentiation, and homeostasis in the higher eukaryotes. A subfamily of receptors, ERRalpha and beta (estrogen receptor-related receptor alpha and beta), closely related to the ER, were among the first orphan nuclear receptors identified. These receptors can bind DNA as monomers and are thought to activate transcription constitutively, unaffected by beta-estradiol. Studies of the expression patterns of ERRalpha and gene disruption experiments of ERRbeta indicate that they play an important role in the development and differentiation of specific tissues in the mouse. In this work we demonstrate the existence in humans of a third member of this subfamily of receptors, termed ERRgamma, which is highly expressed in a number of diverse fetal and adult tissues including brain, kidney, pancreas, and placenta. The ERRgamma mRNA is highly alternatively spliced at the 5'-end, giving rise to a number of tissue-specific RNA species, some of which code for protein isoforms differing in the N-terminal region. Like ERRalpha and beta, ERRgamma binds as a monomer to an ERRE. A GAL4-ERRgamma fusion protein activates transcription in a ligand-independent manner in transfected HEK293 cells to a greater degree than either the GAL4-ERRalpha or -beta fusion proteins.