Diurnal cycle of fossil and nonfossil carbon using radiocarbon analyses during CalNex

Radiocarbon (14C) analysis is a unique tool to distinguish fossil/nonfossil sources of carbonaceous aerosols. We present 14C measurements of organic carbon (OC) and total carbon (TC) on highly time resolved filters (3–4 h, typically 12 h or longer have been reported) from 7 days collected during California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 in Pasadena. Average nonfossil contributions of 58% ± 15% and 51% ± 15% were found for OC and TC, respectively. Results indicate that nonfossil carbon is a major constituent of the background aerosol, evidenced by its nearly constant concentration (2–3 μgC m−3). Cooking is estimated to contribute at least 25% to nonfossil OC, underlining the importance of urban nonfossil OC sources. In contrast, fossil OC concentrations have prominent and consistent diurnal profiles, with significant afternoon enhancements (~3 μgC m−3), following the arrival of the western Los Angeles (LA) basin plume with the sea breeze. A corresponding increase in semivolatile oxygenated OC and organic vehicular emission markers and their photochemical reaction products occurs. This suggests that the increasing OC is mostly from fresh anthropogenic secondary OC (SOC) from mainly fossil precursors formed in the western LA basin plume. We note that in several European cities where the diesel passenger car fraction is higher, SOC is 20% less fossil, despite 2–3 times higher elemental carbon concentrations, suggesting that SOC formation from gasoline emissions most likely dominates over diesel in the LA basin. This would have significant implications for our understanding of the on-road vehicle contribution to ambient aerosols and merits further study.

Eculizumab hepatotoxicity in pediatric aHUS.

BACKGROUND Eculizumab is a humanized anti-C5 antibody approved for the treatment of atypical hemolytic uremic syndrome (aHUS). Its use is increasing in children following reports of its safety and efficacy. METHODS We reviewed biochemical and clinical data related to possible drug-induced liver injury in 11 children treated with eculizumab for aHUS in a single center. RESULTS Elevated aminotransferases were observed in 7 children aged 6 to 11 years following eculizumab treatment for aHUS. Internationally accepted liver enzyme thresholds for drug-induced liver injury were exceeded in 5 cases. In all cases, liver injury was classified as mixed hepatocellular and cholestatic. Infectious and other causes were excluded in each case. One patient with no pre-existing liver disease developed tender hepatomegaly and liver enzyme derangement exceeding 20 times the upper limit of normal following initiation of eculizumab. Recurrent liver injury following re-challenge with eculizumab necessitated its discontinuation and transition to plasma therapy. CONCLUSIONS Hepatotoxicity in association with eculizumab is a potentially important yet previously unreported adverse event. We recommend monitoring liver enzymes in all patients receiving eculizumab. Further research is required to clarify the impact of this adverse event, to characterize the mechanism of potential hepatotoxicity, and to identify which patients are most at risk.

Hormonal Contraception and the Risk of HIV Acquisition: An Individual Participant Data Meta-analysis.

BACKGROUND Observational studies of a putative association between hormonal contraception (HC) and HIV acquisition have produced conflicting results. We conducted an individual participant data (IPD) meta-analysis of studies from sub-Saharan Africa to compare the incidence of HIV infection in women using combined oral contraceptives (COCs) or the injectable progestins depot-medroxyprogesterone acetate (DMPA) or norethisterone enanthate (NET-EN) with women not using HC. METHODS AND FINDINGS Eligible studies measured HC exposure and incident HIV infection prospectively using standardized measures, enrolled women aged 15-49 y, recorded ≥15 incident HIV infections, and measured prespecified covariates. Our primary analysis estimated the adjusted hazard ratio (aHR) using two-stage random effects meta-analysis, controlling for region, marital status, age, number of sex partners, and condom use. We included 18 studies, including 37,124 women (43,613 woman-years) and 1,830 incident HIV infections. Relative to no HC use, the aHR for HIV acquisition was 1.50 (95% CI 1.24-1.83) for DMPA use, 1.24 (95% CI 0.84-1.82) for NET-EN use, and 1.03 (95% CI 0.88-1.20) for COC use. Between-study heterogeneity was mild (I2 < 50%). DMPA use was associated with increased HIV acquisition compared with COC use (aHR 1.43, 95% CI 1.23-1.67) and NET-EN use (aHR 1.32, 95% CI 1.08-1.61). Effect estimates were attenuated for studies at lower risk of methodological bias (compared with no HC use, aHR for DMPA use 1.22, 95% CI 0.99-1.50; for NET-EN use 0.67, 95% CI 0.47-0.96; and for COC use 0.91, 95% CI 0.73-1.41) compared to those at higher risk of bias (pinteraction = 0.003). Neither age nor herpes simplex virus type 2 infection status modified the HC-HIV relationship. CONCLUSIONS This IPD meta-analysis found no evidence that COC or NET-EN use increases women's risk of HIV but adds to the evidence that DMPA may increase HIV risk, underscoring the need for additional safe and effective contraceptive options for women at high HIV risk. A randomized controlled trial would provide more definitive evidence about the effects of hormonal contraception, particularly DMPA, on HIV risk.

Determinanten kognitiver Angstmanifestation während schulischer Tests: Eine Längsschnittstudie

Theoretischer Hintergrund und Fragestellung: Schulische Tests dienen der Feststellung von Wissen und Können. Wie jede Messung kann auch diese durch Störvariablen verzerrt werden. Während Tests erlebte Angst ist ein solcher potentieller Störeinfluss: Angst kann Testleistungen beinträchtigen, da sie sich hinderlich auf die Informationsverarbeitung auswirken kann (Störung des Wissensabrufs und des Denkens; Zeidner, 1998). Dieser kognitiven Angstmanifestation (Rost & Schermer, 1997) liegt die angstbedingte automatische Aufmerksamkeitsorientierung auf aufgaben-irrelevante Gedanken während der Testbearbeitung zugrunde (Eysenck, Derakshan, Santos & Calvo, 2007). Es hat sich allerdings gezeigt, dass Angst nicht grundsätzlich mit Testleistungseinbußen einhergeht (Eysenck et al., 2007). Wir gehen davon aus, dass die Kapazität zur Selbstkontrolle bzw. Aufmerksamkeitsregulation (Baumeister, Muraven & Tice, 2000; Schmeichel & Baumeister, 2010) ein Faktor ist, der bedingt, wie stark kognitive Angstmanifestation während Tests und damit zusammenhängende Leistungseinbußen auftreten. Ängstliche Lernende mit höherer Aufmerksamkeitsregulationskapazität sollten ihrer automatischen Aufmerksamkeitsorientierung auf aufgaben-irrelevante Gedanken erfolgreicher entgegensteuern und ihre Aufmerksamkeit weiterhin auf die Aufgabenbearbeitung richten können. Dem entsprechend sollten sie trotz Angst weniger kognitive Angstmanifestation während Tests erleben als ängstliche Lernende mit geringerer Aufmerksamkeitsregulationskapazität. Auch die Selbstwirksamkeitserwartung und das Selbstwertgefühl sind Variablen, die in der Vergangenheit mit der Bewältigung von Angst und Stress in Verbindung gebracht wurden (Bandura, 1977; Baumeister, Campbell, Krueger & Vohs, 2003). Daher wurden diese Variablen als weitere Prädiktoren berücksichtigt. Es wurde die Hypothese getestet, dass die dispositionelle Aufmerksamkeitsregulationskapazität über die dispositionelle Selbstwirksamkeitserwartung und das dispositionelle Selbstwertgefühl hinaus Veränderungen in der kognitiven Angstmanifestation während Mathematiktests in einer Wirtschaftsschülerstichprobe vorhersagt. Es wurde des Weiteren davon ausgegangen, dass eine indirekte Verbindung zwischen der Aufmerksamkeitsregulationskapazität und der Veränderung in den Mathematiknoten, vermittelt über die Veränderung in der kognitiven Angstmanifestation, besteht. Methode: Einhundertachtundfünfzig Wirtschaftsschüler bearbeiteten im September 2011 (T1) einen Fragebogen, der die folgenden Messungen enthielt:-Subskala Kognitive Angstmanifestation aus dem Differentiellen Leistungsangstinventar (Rost & Schermer, 1997) bezogen auf Mathematiktests (Sparfeldt, Schilling, Rost, Stelzl & Peipert, 2005); Alpha = .90; -Skala zur dispositionellen Aufmerksamkeitsregulationskapazität (Bertrams & Englert, 2013); Alpha = .88; -Skala zur Selbstwirksamkeitserwartung (Schwarzer & Jerusalem, 1995); Alpha = .83; -Skala zum Selbstwertgefühl (von Collani & Herzberg, 2003); Alpha = .83; -Angabe der letzten Mathematikzeugnisnote. Im Februar 2012 (T2), also nach 5 Monaten und kurz nach dem Erhalt des Halbjahreszeugnisses, gaben die Schüler erneut ihre kognitive Angstmanifestation während Mathematiktests (Alpha = .93) und ihre letzte Mathematikzeugnisnote an. Ergebnisse: Die Daten wurden mittels Korrelationsanalyse, multipler Regressionsanalyse und Bootstrapping ausgewertet. Die Aufmerksamkeitsregulationskapazität, die Selbstwirksamkeitserwartung und das Selbstwertgefühl (alle zu T1) waren positiv interkorreliert, r= .50/.59/.59. Diese Variablen wurden gemeinsam als Prädiktoren in ein Regressionsmodell zur Vorhersage der kognitiven Angstmanifestation zu T2 eingefügt. Gleichzeitig wurde die kognitive Angstmanifestation zu T1 konstant gehalten. Es zeigte sich, dass die Aufmerksamkeitsregulationskapazität erwartungskonform die Veränderungen in der kognitiven Angstmanifestation vorhersagte, Beta = -.21, p= .02. Das heißt, dass höhere Aufmerksamkeitsregulationskapazität zu T1 mit verringerter kognitiver Angstmanifestation zu T2 einherging. Die Selbstwirksamkeitserwartung, Beta = .12, p= .14, und das Selbstwertgefühl, Beta = .05, p= .54, hatten hingegen keinen eigenen Vorhersagewert für die Veränderungen in der kognitiven Angstmanifestation. Des Weiteren ergab eine Mediationsanalyse mittels Bootstrapping (bias-corrected bootstrap 95% confidence interval, 5000 resamples; siehe Hayes & Scharkow, in press), dass die Aufmerksamkeitsregulationskapazität (T1), vermittelt über die Veränderung in der kognitiven Angstmanifestation, indirekt mit der Veränderung in der Mathematikleistung verbunden war (d.h. das Bootstrap-Konfidenzintervall schloss nicht die Null ein; CI [0.01, 0.24]). Für die Selbstwirksamkeitserwartung und das Selbstwertgefühl fand sich keine analoge indirekte Verbindung zur Mathematikleistung. Fazit: Die Befunde verweisen auf die Bedeutsamkeit der Aufmerksamkeitsregulationskapazität für die Bewältigung kognitiver Angstreaktionen während schulischer Tests. Losgelöst von der Aufmerksamkeitsregulationskapazität scheinen positive Erwartungen und ein positives Selbstbild keine protektive Wirkung hinsichtlich der leistungsbeeinträchtigenden kognitiven Angstmanifestation während Mathematiktests zu besitzen.

Modeling the formation and aging of secondary organic aerosols during CalNex 2010

Four different literature parameterizations for the formation and evolution of urban secondary organic aerosol (SOA) frequently used in 3-D models are evaluated using a 0-D box model representing the Los Angeles metropolitan region during the California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle- and gas-phase observations from the CalNex Pasadena ground site. That site provides a unique opportunity to study aerosol formation close to anthropogenic emission sources with limited recirculation. The model SOA that formed only from the oxidation of VOCs (V-SOA) is insufficient to explain the observed SOA concentrations, even when using SOA parameterizations with multi-generation oxidation that produce much higher yields than have been observed in chamber experiments, or when increasing yields to their upper limit estimates accounting for recently reported losses of vapors to chamber walls. The Community Multiscale Air Quality (WRF-CMAQ) model (version 5.0.1) provides excellent predictions of secondary inorganic particle species but underestimates the observed SOA mass by a factor of 25 when an older VOC-only parameterization is used, which is consistent with many previous model–measurement comparisons for pre-2007 anthropogenic SOA modules in urban areas. Including SOA from primary semi-volatile and intermediate-volatility organic compounds (P-S/IVOCs) following the parameterizations of Robinson et al. (2007), Grieshop et al. (2009), or Pye and Seinfeld (2010) improves model–measurement agreement for mass concentration. The results from the three parameterizations show large differences (e.g., a factor of 3 in SOA mass) and are not well constrained, underscoring the current uncertainties in this area. Our results strongly suggest that other precursors besides VOCs, such as P-S/IVOCs, are needed to explain the observed SOA concentrations in Pasadena. All the recent parameterizations overpredict urban SOA formation at long photochemical ages (3 days) compared to observations from multiple sites, which can lead to problems in regional and especially global modeling. However, reducing IVOC emissions by one-half in the model to better match recent IVOC measurements improves SOA predictions at these long photochemical ages. Among the explicitly modeled VOCs, the precursor compounds that contribute the greatest SOA mass are methylbenzenes. Measured polycyclic aromatic hydrocarbons (naphthalenes) contribute 0.7% of the modeled SOA mass. The amounts of SOA mass from diesel vehicles, gasoline vehicles, and cooking emissions are estimated to be 16–27, 35–61, and 19–35 %, respectively, depending on the parameterization used, which is consistent with the observed fossil fraction of urban SOA, 71(+-3) %. The relative contribution of each source is uncertain by almost a factor of 2 depending on the parameterization used. In-basin biogenic VOCs are predicted to contribute only a few percent to SOA. A regional SOA background of approximately 2.1 μgm-3 is also present due to the long-distance transport of highly aged OA, likely with a substantial contribution from regional biogenic SOA. The percentage of SOA from diesel vehicle emissions is the same, within the estimated uncertainty, as reported in previous work that analyzed the weekly cycles in OA concentrations (Bahreini et al., 2012; Hayes et al., 2013). However, the modeling work presented here suggests a strong anthropogenic source of modern carbon in SOA, due to cooking emissions, which was not accounted for in those previous studies and which is higher on weekends. Lastly, this work adapts a simple two-parameter model to predict SOA concentration and O/C from urban emissions. This model successfully predicts SOA concentration, and the optimal parameter combination is very similar to that found for Mexico City. This approach provides a computationally inexpensive method for predicting urban SOA in global and climate models. We estimate pollution SOA to account for 26 Tg yr-1 of SOA globally, or 17% of global SOA, one third of which is likely to be non-fossil.