Particle water and pH are predicted using meteorological observations (relative humidity (RH), temperature (T)), gas/particle composition, and thermodynamic modeling (ISORROPIA-II). A comprehensive ...uncertainty analysis is included, and the model is validated. We investigate mass concentrations of particle water and related particle pH for ambient fine-mode aerosols sampled in a relatively remote Alabama forest during the Southern Oxidant and Aerosol Study (SOAS) in summer and at various sites in the southeastern US during different seasons, as part of the Southeastern Center for Air Pollution and Epidemiology (SCAPE) study. Particle water and pH are closely linked; pH is a measure of the particle H+ aqueous concentration and depends on both the presence of ions and amount of particle liquid water. Levels of particle water, in turn, are determined through water uptake by both the ionic species and organic compounds. Thermodynamic calculations based on measured ion concentrations can predict both pH and liquid water but may be biased since contributions of organic species to liquid water are not considered. In this study, contributions of both the inorganic and organic fractions to aerosol liquid water were considered, and predictions were in good agreement with measured liquid water based on differences in ambient and dry light scattering coefficients (prediction vs. measurement: slope = 0.91, intercept = 0.5 μg m−3, R2 = 0.75). ISORROPIA-II predictions were confirmed by good agreement between predicted and measured ammonia concentrations (slope = 1.07, intercept = −0.12 μg m−3, R2 = 0.76). Based on this study, organic species on average contributed 35% to the total water, with a substantially higher contribution (50%) at night. However, not including contributions of organic water had a minor effect on pH (changes pH by 0.15 to 0.23 units), suggesting that predicted pH without consideration of organic water could be sufficient for the purposes of aqueous secondary organic aerosol (SOA) chemistry. The mean pH predicted in the Alabama forest (SOAS) was 0.94 ± 0.59 (median 0.93). pH diurnal trends followed liquid water and were driven mainly by variability in RH; during SOAS nighttime pH was near 1.5, while daytime pH was near 0.5. pH ranged from 0.5 to 2 in summer and 1 to 3 in the winter at other sites. The systematically low pH levels in the southeast may have important ramifications, such as significantly influencing acid-catalyzed reactions, gas–aerosol partitioning, and mobilization of redox metals and minerals. Particle ion balances or molar ratios, often used to infer pH, do not consider the dissociation state of individual ions or particle liquid water levels and do not correlate with particle pH.
The TET (ten-eleven translocation) family of α-ketoglutarate (α-KG)-dependent dioxygenases catalyzes the sequential oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), ...5-formylcytosine and 5-carboxylcytosine, leading to eventual DNA demethylation. The TET2 gene is a bona fide tumor suppressor frequently mutated in leukemia, and TET enzyme activity is inhibited in IDH1/2-mutated tumors by the oncometabolite 2-hydroxyglutarate, an antagonist of α-KG, linking 5mC oxidation to cancer development. We report here that the levels of 5hmC are dramatically reduced in human breast, liver, lung, pancreatic and prostate cancers when compared with the matched surrounding normal tissues. Associated with the 5hmC decrease is the substantial reduction of the expression of all three TET genes, revealing a possible mechanism for the reduced 5hmC in cancer cells. The decrease of 5hmC was also observed during tumor development in different genetically engineered mouse models. Together, our results identify 5hmC as a biomarker whose decrease is broadly and tightly associated with tumor development.
We investigate, for two water models displaying a liquid-liquid critical point, the relation between changes in dynamic and ther-modynamic anomalies arising from the presence of the liquid-liquid ...critical point. We find a correlation between the dynamic crossover and the locus of specific heat maxima$C_{P}^{max}$("Widom line") emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between$C_{P}^{max}$and dynamic crossover is not limited to the case of water, a hydrogen bond network-forming liquid, but is a more general feature of crossing the Widom line. Specifically, we also study the Jagla potential, a spherically symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions.
Organic aerosol (OA) represents a large fraction of submicron aerosols in the
megacity of Beijing, yet long-term characterization of its sources and
variations is very limited. Here we present an ...analysis of in situ
measurements of OA in submicrometer particles with an aerosol chemical
speciation monitor (ACSM) for 2 years from July 2011 to May 2013. The sources
of OA are analyzed with a multilinear engine (ME-2) by constraining three
primary OA factors including fossil-fuel-related OA (FFOA), cooking OA (COA),
and biomass burning OA (BBOA). Two secondary OAs (SOA), representing a less
oxidized oxygenated OA (LO-OOA) and a more oxidized (MO-OOA), are identified
during all seasons. The monthly average concentration OA varied from 13.6 to
46.7 µg m−3 with a strong seasonal pattern that is usually
highest in winter and lowest in summer. FFOA and BBOA show similarly
pronounced seasonal variations with much higher concentrations and
contributions in winter due to enhanced coal combustion and biomass burning
emissions. The contribution of COA to OA, however, is relatively stable
(10–15 %) across different seasons, yet presents significantly higher
values at low relative humidity levels (RH < 30 %),
highlighting the important role of COA during clean periods. The two SOA
factors present very different seasonal variations. The pronounced
enhancement of LO-OOA concentrations in winter indicates that emissions from
combustion-related primary emissions could be a considerable source of SOA
under low-temperature (T) conditions. Comparatively, MO-OOA shows high
concentrations consistently at high RH levels across different T levels,
and the contribution of MO-OOA to OA is different seasonally with lower
values occurring more in winter (30–34 %) than other seasons
(47–64 %). Overall, SOA (= LO-OOA + MO-OOA) dominates OA
composition during all seasons by contributing 52–64 % of the total OA
mass in the heating season and 65–75 % in non-heating seasons. The
variations in OA composition as a function of OA mass loading further
illustrate the dominant role of SOA in OA across different mass loading
scenarios during all seasons. However, we also observed a large increase in
FFOA associated with a corresponding decrease in MO-OOA during periods with
high OA mass loadings in the heating season, illustrating an enhanced role of
coal combustion emissions during highly polluted episodes. Potential source
contribution function analysis further shows that the transport from the
regions located to the south and southwest of Beijing within ∼ 250 km
can contribute substantially to high FFOA and BBOA concentrations in the
heating season.
A new alpha-emitting isotope U-214, produced by the fusion-evaporation reaction W-182(Ar-36,4n) U-214, was identified by employing the gas-filled recoil separator SHANS and the recoil-a correlation ...technique. More precise a-decay properties of even-even nuclei U-216,U-218 were also measured in the reactions of Ar-40, Ca-40 beams with W-180,W-182,W- 184 targets. By combining the experimental data, improved alpha-decay reduced widths delta(2) for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N = 126 are deduced. Their systematic trends are discussed in terms of the N-p N-n scheme in order to study the influence of protonneutron interaction on a decay in this region of nuclei. It is strikingly found that the reduced widths of( 214,216)U are significantly enhanced by a factor of two as compared with the NpNn systematics for the 84 <= Z <= 90 and N < 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the pi 1f (7/2) and nu 1f(5/2) spin-orbit partner orbits, which is supported by the large-scale shell model calculation.
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We show for the first time quantitative online measurements of five nitrated phenol (NP) compounds in ambient air (nitrophenol C6H5NO3, methylnitrophenol C7H7NO3, nitrocatechol C6H5NO4, ...methylnitrocatechol C7H7NO4, and dinitrophenol C6H4N2O5) measured with a micro-orifice volatilization impactor (MOVI) high-resolution chemical ionization mass spectrometer in Detling, United Kingdom during January–February, 2012. NPs absorb radiation in the near-ultraviolet (UV) range of the electromagnetic spectrum and thus are potential components of poorly characterized light-absorbing organic matter (“brown carbon”) which can affect the climate and air quality. Total NP concentrations varied between less than 1 and 98 ng m–3, with a mean value of 20 ng m–3. We conclude that NPs measured in Detling have a significant contribution from biomass burning with an estimated emission factor of 0.2 ng (ppb CO)−1. Particle light absorption measurements by a seven-wavelength aethalometer in the near-UV (370 nm) and literature values of molecular absorption cross sections are used to estimate the contribution of NP to wood burning brown carbon UV light absorption. We show that these five NPs are potentially important contributors to absorption at 370 nm measured by an aethalometer and account for 4 ± 2% of UV light absorption by brown carbon. They can thus affect atmospheric radiative transfer and photochemistry and with that climate and air quality.
SnO2–ZnO hetero-nanofibers were fabricated by a facile electrospinning method and calcination in this study. The SnO2–ZnO nanofibers were characterized by scanning electron microscopy (SEM), ...transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD). The gas sensor prepared by the SnO2–ZnO hetero-nanofibers revealed better ethanol sensing performance than pure ZnO and pure SnO2 nanofibers, good stability and excellent selectivity at the optimum temperature of 300°C. The response and recovery time to 100ppm ethanol were about 25s and 9s, respectively. The growth mechanism of the hetero-nanofibers was discussed, as well as the ethanol adsorption–desorption mechanism.
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