A confidence framing effect: Flexible use of evidence in metacognitive monitoring.

Human behavior is flexibly regulated by specific goals of cognitive tasks. One notable example is goal-directed modulation of metacognitive behavior, where logically equivalent decision-making problems can yield different patterns of introspective confidence depending on the frame in which they are presented. While this observation highlights the important heuristic nature of metacognitive monitoring, computational mechanisms underlying this phenomenon remain elusive. We confirmed the confidence framing effect in two-alternative dot-number discrimination and in previously published preference-choice data, demonstrating distinctive confidence patterns between "choose more" or "choose less" frames. Formal model comparisons revealed a simple confidence heuristic behind this phenomenon, which assigns greater weight to chosen than unchosen stimulus evidence. This computation appears to be based on internal evidence constituted under specific task demands rather than physical stimulus intensity itself, a view justified in terms of ecological rationality. These results shed light on the adaptive nature of human decision-making and metacognitive monitoring.

Potential Factors Contributing to Ozone Production in AQUAS-Kyoto Campaign in Summer 2020: Natural Source-Related Missing OH Reactivity and Heterogeneous HO2/RO2 Loss.

This study presents total OH reactivity, ancillary trace species, HO2 reactivity, and complex isoprene-derived RO2 reactivity due to ambient aerosols measured during the air quality study (AQUAS)-Kyoto campaign in September, 2020. Observations were conducted during the coronavirus disease (COVID-19) pandemic (associated with reduced anthropogenic emissions). The spatial distribution of missing OH reactivity highlights that the origin of volatile organic compounds (VOCs) may be from natural-emission areas. For the first time, the real-time loss rates of HO2 and RO2 onto ambient aerosols were measured continuously and alternately. Ozone production sensitivity was investigated considering unknown trace species and heterogeneous loss effects of XO2 (≡HO2 + RO2) radicals. Missing OH reactivity enhanced the ozone production potential by a factor of 2.5 on average. Heterogeneous loss of radicals could markedly suppress ozone production under low NO/NOx conditions with slow gas-phase reactions of radicals and change the ozone regime from VOC- to NOx-sensitive conditions. This study quantifies the relationship of missing OH reactivity and aerosol uptake of radicals with ozone production in Kyoto, a low-emission suburban area. The result has implications for future NOx-reduction policies. Further studies may benefit from the combination of chemical transport models and inverse modeling over a wide spatiotemporal range.

Decomposition of multifunctionalized α-alkoxyalkyl-hydroperoxides derived from the reactions of Criegee intermediates with diols in liquid phases.

The oxidation of volatile organic compounds in the atmosphere produces organic hydroperoxides (ROOHs) that typically possess not only -OOH but also other functionalities such as -OH and -C(O). Because of their high hydrophilicity and low volatility, such multifunctionalized ROOHs are expected to be taken up in atmospheric condensed phases such as aerosols and fog/cloud droplets. However, the characteristics of ROOHs that control their fates and lifetimes in liquid phases are poorly understood. Here, we report a study of the liquid-phase decomposition kinetics of multifunctionalized α-alkoxyalkyl-hydroperoxides (α-AHs) that possessed an ether, a carbonyl, a hydroperoxide, and two hydroxy groups. These ROOHs were synthesized by ozonolysis of α-terpineol in water in the presence of 1,3-propanediol, 1,4-butanediol, or 1,5-pentanediol. Their decomposition products were detected as chloride anion adducts by electrospray mass spectrometry as a function of reaction time. Experiments using H218O and D2O revealed that hemiacetal species were α-AH decomposition products that further transformed into other products. The result that the rate coefficients (k) of the decomposition of C15 α-AHs increased exponentially from pH 5.0 to 3.9 was consistent with an H+-catalyzed decomposition mechanism. The temperature dependence of k and an Arrhenius plot yielded activation energies (Ea) of 15.7 ± 0.8, 15.0 ± 2.4, and 15.9 ± 0.3 kcal mol-1 for the decomposition of α-AHs derived from the reaction of α-terpineol CIs with 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, respectively. The determined Ea values were compared with those of related ROOHs. We found that alkyl chain length is not a critical factor for the decomposition mechanism, whereas the presence of additional -OH groups would modulate the reaction barriers to decomposition via the formation of hydrogen-bonding with surrounding water molecules. The derived Ea values for the decomposition of the multifunctionalized, terpenoid-derived α-AHs will facilitate atmospheric modeling by serving as representative values for ROOHs in atmospheric condensed phases.

On the assumptions behind metacognitive measurements: Implications for theory and practice.

Theories of visual confidence have largely been grounded in the gaussian signal detection framework. This framework is so dominant that idiosyncratic consequences from this distributional assumption have remained unappreciated. This article reports systematic comparisons of the gaussian signal detection framework to its logistic counterpart in the measurement of metacognitive accuracy. Because of the difference in their distribution kurtosis, these frameworks are found to provide different perspectives regarding the efficiency of confidence rating relative to objective decision (the logistic model intrinsically gives greater meta-d'/d' ratio than the gaussian model). These frameworks can also provide opposing conclusions regarding the metacognitive inefficiency along the internal evidence continuum (whether meta-d' is larger or smaller for higher levels of confidence). Previous theories developed on these lines of analysis may need to be revisited as the gaussian and logistic metacognitive models received somewhat equivalent support in our quantitative model comparisons. Despite these discrepancies, however, we found that across-condition or across-participant comparisons of metacognitive measures are relatively robust against the distributional assumptions, which provides much assurance to conventional research practice. We hope this article promotes the awareness for the significance of hidden modeling assumptions, contributing to the cumulative development of the relevant field.

[A Case of Laparoscopic Gastrojejunal Bypass Surgery for Malignant Stenosis after Chemoradiotherapy for Esophageal Cancer].

We report a case of malignant stenosis due to recurrence of lymph node metastasis treated with laparoscopic gastrojejunal bypass. A 83-year-old man who underwent chemoradiotherapy for esophageal cancer(cT3N2M0). About 3 and half years after chemoradiotherapy, he was referred to hospital for vomiting. As a result of the examination, we diagnosed malignant stenosis of descending part of duodenum due to retroperitoneum lymph node recurrence of esophageal cancer. We performed laparoscopic gastrojejunal bypass operation because we suggested self-expandable metallic stent make easy to migrate into anal side of the duodenum. The postoperative course was good. He was enrolled in oncology department on the 21 days after the operation. Gastroduodenal stenosis is common pathology by malignant tumor. Gastrojejunostomy and placement of self-expandable metallic stent is commonly performed for malignant gastroduodenal obstruction. Endoscopic metallic stent placement is minimally invasive treatment for malignant stenosis of the intestine, however sometime the stent placement will make easy to migrate by extra compression. Gastrojejunostomy mat be more safety than endoscopic stent placement for the malignant gastroduodenal obstruction.

Aerosol Liquid Water Promotes the Formation of Water-Soluble Organic Nitrogen in Submicrometer Aerosols in a Suburban Forest.

Water-soluble organic nitrogen (WSON) affects the formation, chemical transformations, hygroscopicity, and acidity of organic aerosols as well as biogeochemical cycles of nitrogen. However, large uncertainties exist in the origins and formation processes of WSON. Submicrometer aerosol particles were collected at a suburban forest site in Tokyo in summer 2015 to investigate the relative impacts of anthropogenic and biogenic sources on WSON formations and their linkages with aerosol liquid water (ALW). The concentrations of WSON (ave. 225 ± 100 ngN m-3) and ALW exhibited peaks during nighttime, which showed a significant positive correlation, suggesting that ALW significantly contributed to WSON formation. Further, the thermodynamic predictions by ISORROPIA-II suggest that ALW was primarily driven by anthropogenic sulfate. Our analysis, including positive matrix factorization, suggests that aqueous-phase reactions of ammonium and reactive nitrogen with biogenic volatile organic compounds (VOCs) play a key role in WSON formation in submicrometer particles, which is particularly significant in nighttime, at the suburban forest site. The formation of WSON associated with biogenic VOCs and ALW was partly supported by the molecular characterization of WSON. The overall result suggests that ALW is an important driver for the formation of aerosol WSON through a combination of anthropogenic and biogenic sources.

Increased expression of tripartite motif (TRIM) like 2 promotes tumoral growth in human oral cancer.

Tripartite motif family-like 2 (TRIML2), a member of the TRIM proteins family, is closely related to Alzheimer's disease, however, no studies of TRIML2 have been published in the cancer research literature. In the current study, we investigated the expression level of TRIML2 and its molecular mechanisms in human oral squamous cell carcinoma (OSCC); reverse transcriptase-quantitative polymerase chain reaction, immunoblot analysis, and immunohistochemistry showed that TRIML2 is up-regulated significantly in OSCCs in vitro and in vivo. TRIML2 knockdown OSCC cells showed decreased cellular proliferation by cell-cycle arrest at G1 phase that resulted from down-regulation of CDK4, CDK6, and cyclin D1 and up-regulation of p21Cip1 and p27Kip1. Surprisingly, resveratrol, a polyphenol, led to not only down-regulation of TRIML2 but also cell-cycle arrest at G1 phase similar to TRIML2 knockdown experiments. Taken together, we concluded that TRIML2 might play a significant role in tumoral growth and that resveratrol may be a new drug for treating OSCC by interfering with TRIML2 function.

UNC93B1 promotes tumoral growth by controlling the secretion level of granulocyte macrophage colony-stimulating factor in human oral cancer.

Unc-93 homolog B1 (UNC93B1), a transmembrane protein, is correlated with immune diseases, such as influenza, herpes simplex encephalitis, and the pathogenesis of systemic lupus erythematosus; however, the role of UNC93B1 in cancers including human oral squamous cell carcinomas (OSCCs) remains unknown. In the current study, we investigated the UNC93B1expression level in OSCCs using quantitative reverse transcription-polymerase chain reaction, immunoblot analysis, and immunohistochemistry. Our data showed that UNC93B1 mRNA and protein expressions increased markedly (p < 0.05) in OSCCs compared with normal cells and tissues and that high expression of UNC93B1 in OSCCs was related closely to tumoral size. UNC93B1 knockdown (shUNC93B1) OSCC cells showed decreased cellular proliferation by cell-cycle arrest in the G1 phase with up-regulation of p21Cip1 and down-regulation of CDK4, CDK6, cyclin D1, and cyclin E. We also found that granulocyte macrophage colony-stimulating factor (GM-CSF) was down-regulated significantly (p < 0.05) in shUNC93B1 OSCC cells. Moreover, inactivation of GM-CSF using neutralization antibody led to cell-cycle arrest at the G1 phase similar to the phenotype of the shUNC93B1 cells. The current findings indicated that UNC93B1 might play a crucial role in OSCC by controlling the secretion level of GM-CSF involved in tumoral growth and could be a potential therapeutic target for OSCCs.

Relative and Absolute Sensitivity Analysis on Ozone Production in Tsukuba, a City in Japan.

The change in the ozone production rate on reducing its precursors, namely, ozone production sensitivity, is important information for developing a strategy to reduce ozone. We expanded a conventional sensitivity analysis theory by including peroxy radical loss by uptake onto particle surfaces in the aim of examining their potential impact. We also propose a new concept of absolute sensitivity that enables us to evaluate the quantitative effectiveness of precursor reduction toward mitigating ozone production over a given period and area. This study applies the theory to observations in Tsukuba, a city in Japan. The relative sensitivity analysis shows that ozone production was more sensitive to volatile organic compounds (VOCs) in the morning and evening, and it became more sensitive to NOx in the afternoon. NO depletion was a main trigger in this sensitivity regime transition. The absolute sensitivity analysis indicates that the VOC-sensitive period in the morning determines the total ozone production sensitivity in a day. While particles did not have significant impact on regime classification in Tsukuba, they have a potential to decrease the mitigating effect of VOC reduction on ozone production and to moderate the enhancement effect of NOx reduction depending upon uptake coefficients. A further study will benefit from a combination with an observation-constrained box model simulation or chemical transport modeling system, which may provide sensitivity analysis over a large spatial and temporal range.

Multiple coagulation factor deficiency protein 2 as a crucial component in metastasis of human oral cancer.

Multiple coagulation factor deficiency protein 2 (MCFD2), a binding partner of lectin mannose binding 1 (LMAN1), causes combined deficiencies of coagulation factors V and VIII. MCFD2 function in inherited hematologic disorders is well elucidated; however, little is known about its role in human tumorigenesis. The aim of the current study was to investigate the states of MCFD2 in oral squamous cell carcinoma (OSCC). The expression of MCFD2 was up-regulated significantly in all cell lines examined. Evaluation of the cellular functions associated with tumoral metastasis showed that MCFD2 knockdown (shMCFD2) cells exhibited significantly lower cellular invasiveness and migration and higher cellular adhesion compared with shControl cells. Of note, shMCFD2 cells also showed weak immunoreactivity of LMAN1 and a lower secretion level of galactoside-binding soluble 3 binding protein (LGALS3BP). In addition to in vitro validation, clinical data on 70 patients with OSCC indicated that state of MCFD2 expression level is associated with regional lymph node metastasis. Altogether, we have demonstrated that MCFD2 promotes cancer metastasis by regulating LMAN1 and LGALS3BP expression levels. Hence, MCFD2 may represent a promising candidate for a novel therapeutic target for patients with metastatic OSCCs.

FBLIM1 enhances oral cancer malignancy via modulation of the epidermal growth factor receptor pathway.

Filamin-binding LIM protein 1 (FBLIM1) is related to regulation of inflammatory responses, such as chronic recurrent multifocal osteomyelitis; however, the relevance of FBLIM1 in oral squamous cell carcinoma (OSCC) is unknown. The aim of the current study was to elucidate the possible role of FBLIM1 in the carcinogenesis of OSCC. We analyzed FBLIM1 expression using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), immunoblot analysis, and immunohistochemistry. The expression levels of FBLIM1 were up-regulated significantly (P < 0.05) in OSCC-derived cell lines and primary OSCCs specimens compared with normal counterparts. FBLIM1 expression also was correlated with the primary tumoral size (P < 0.05) and vascular invasion (P < 0.05). We then assessed tumoral progression after treatment with FBLIM1 siRNA and clopidogrel, an antiplatelet agent. Similar to the FBLIM1 knockdown effect, clopidogrel-treated cells had attenuated functions of proliferation, migration, and invasiveness. Interestingly, clopidogrel treatment led to down-regulation of epidermal growth factor receptor (EGFR) and FBLIM1. These findings identify FBLIM1 as a putative therapeutic target by using clopidogrel for inhibiting over activation of EGFR signaling to prevent OSCC malignancy.

Controlling factors of oligomerization at the water surface: why is isoprene such a unique VOC?

Recent studies have shown that atmospheric particles are sufficiently acidic to enhance the uptake of unsaturated volatile organic compounds (VOCs) by triggering acid-catalyzed oligomerization. Controlling factors of oligomerization at the aqueous surfaces, however, remain to be elucidated. Herein, isoprene (2-methyl-1,3-butadiene, ISO), 1,3-butadiene (1,3-b), 1,4-pentadiene (1,4-p), 1-pentene (1-p), and 2-pentene (2-p) vapors are exposed to an acidic water microjet (1 ≤ pH ≤ 5), where cationic products are generated on its surface within ∼10 µs and directly detected using surface-sensitive mass spectrometry. We found that carbocations form at the air-water interface in all the cases, whereas the extent of oligomerization largely depends on the structure in the following order: ISO ≫ 1,3-b > 1,4-p ≫ 1-p ≈ 2-p. Importantly, the cationic oligomerization of ISO yields a protonated decamer ((ISO)10H+, a C50 species of m/z 681.6), while the pentenes 1-p/2-p remain as protonated monomers. We suggest that ISO oligomerization is uniquely facilitated by (1) the resonance stabilization of (ISO)H+ through the formation of a tertiary carbocation with a conjugated C[double bond, length as m-dash]C bond pair, and (2) π-electron enrichment induced by the neighboring methyl group. Experiments in D2O and D2O : H2O mixtures revealed that ISO oligomerization on the acidic water surface proceeds via two competitive mechanisms: chain-propagation and proton-exchange reactions. Furthermore, we found that ISO carbocations undergo addition to relatively inert 1-p, generating hitherto uncharacterized co-oligomers.

Kinetics Study of Heterogeneous Bromine Release from the Reaction between Gaseous Ozone and Aqueous Bromide Solution.

The heterogeneous release of molecular bromine, Br2, from the reaction between gaseous ozone and aqueous bromide ion in seawater ice and sea salt aerosols is considered to be an initial source of reactive bromine species in the troposphere. Recent studies have demonstrated that the uptake of ozone by aqueous bromide solution is promoted by reactions at the gas-liquid interface. The present work investigated the heterogeneous reaction between gaseous ozone and aqueous bromide solution at atmospheric pressure and room temperature using a wetted wall flow reactor combined with a chemical ionization mass spectrometer. The emission rate of Br2 was measured as a function of gaseous ozone concentration, aqueous bromide concentration, and pH. In addition, we conducted a simple kinetics model simulation that included only bulk aqueous-phase reactions and compared the theoretical values with the experimentally determined values. The Br2 emission rates measured experimentally differ from the simulated rates at relatively high bromide concentration, as well as in the pH region of 6-9. These differences might be explained by different Br- concentration and/or deprotonation efficiency near the interface region and those in the bulk solution.

SIPA1 promotes invasion and migration in human oral squamous cell carcinoma by ITGB1 and MMP7.

Signal-induced proliferation-associated protein 1 (SIPA1) is known to be a GTPase activating protein. Overexpressed SIPA1 is related to metastatic progression in breast and prostate cancers; however, the relevance of SIPA1 in oral squamous cell carcinoma (OSCC) is still unknown. The aim of this study was to examine SIPA1 expression and its functional mechanisms in OSCC. SIPA1 mRNA and protein expressions were analyzed by quantitative reverse transcriptase-polymerase chain reaction, Western blot analysis, and immunohistochemistry. The expressions of SIPA1 were up-regulated significantly in vitro and in vivo. Moreover, SIPA1 expression was correlated with regional lymph node metastasis. We next assessed the cellular functions associated with tumoral metastasis using SIPA1 knockdown (shSIPA1) cells and analyzed the downstream molecules of SIPA1, i.e., bromodomain containing protein 4(BRD4), integrin beta1 (ITGB1), and matrix metalloproteinase 7 (MMP7). The shSIPA1 cells showed decreased invasiveness and migratory activities, however cellular adhesion ability was maintained at a high level. In addition, ITGB1 expression was greater in shSIPA1 cells, whereas MMP7 expression was lower than in control cells. This research is the first to establish that SIPA1 promotes cancer metastasis by regulating the ITGB1 and MMP7. Therefore, SIPA1 might be a novel therapeutic target for patients with lymph node metastasis of OSCC.

UBE2S associated with OSCC proliferation by promotion of P21 degradation via the ubiquitin-proteasome system.

Ubiquitin-conjugating enzyme E2S (UBE2S), a family of E2 protein in the ubiquitin-proteasome system, is highly expressed in several types of cancers; however, its roles in oral squamous cell carcinoma (OSCC) have not yet been well elucidated. The purpose of this study was to clarify the functional activities of UBE2S in OSCCs. We analyzed the expression levels of UBE2S in nine OSCC cell lines and primary OSCC tissues by quantitative reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry (IHC). The correlations between UBE2S expression and clinical classifications of OSCCs were analyzed using the IHC scoring system. We also used UBE2S knockdown OSCC cells for functional assays (proliferation assay, flow cytometry, and Western blotting). UBE2S was overexpressed in OSCCs in vitro and in vivo and was correlated significantly (P < 0.05) with the primary tumoral size. The cellular growth was decreased and the cell-cycle was arrested in the G2/M phase in the UBE2S knockdown (shUBE2S) cells. The expression level of P21, a target of the ubiquitin-proteasome system, was increased in the shUBE2S cells because of lower anaphase activity that promotes complex subunit 3 (APC3), an E3 ubiquitin ligase, compared with shMock cells. These findings might promote the understanding of the relationship between UBE2S overexpression and oral cancer proliferation, indicating that UBE2S would be a potential biomarker of and therapeutic target in OSCCs.

Novel mechanism of aberrant ZIP4 expression with zinc supplementation in oral tumorigenesis.

Zrt-Irt-like protein 4 (ZIP4) is critical molecule for proper mammalian development and releasing zinc from vesicular compartments. Recent studies suggested that ZIP4 plays an important role of tumor progression in pancreatic, prostate, and hepatocellular cancers, however, little is known about the detail mechanism of ZIP4 in their cancers. In the present study, we examined the possibility of ZIP4 as a new molecular target for oral squamous cell carcinoma (OSCC). We evaluated ZIP4 expression in OSCC-derived cell lines and primary OSCC samples by quantitative RT-PCR, immunoblotting, and immunohistochemistry (IHC). We also analyzed the clinical correlation between ZIP4 status and clinical behaviors in patients with OSCC. In addition, ZIP4 knockdown cells (shZIP4 cells) and ZnCl2 treatment were used for functional experiments, including cellular proliferation assay, zinc uptake assay, and cell-cycle analysis. ZIP4 mRNA and protein were up-regulated significantly in OSCCs compared with normal counterparts in vitro and in vivo. IHC showed that ZIP4 expression in the primary OSCC was positively correlated with primary tumoral size. The shZIP4 cells showed decrease accumulation of intercellular zinc and decreased cellular growth by cell-cycle arrest at the G1 phase, resulting from up-regulation of cyclin-dependent kinase inhibitors and down-regulation of cyclins and cyclin-dependent kinases. Since cellular growth of OSCC cells after treatment with zinc was significantly greater than control cells, we speculated that intercellular ZnCl2 accumulation is an important factor for cellular growth. Consistent with our hypothesis, not only decreased zinc uptake by ZIP4 knockdown but also chelating agent, N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), showed inhibitory effects of cellular proliferation. Therefore, our data provide evidence for an essential role of ZIP4 and intracellular zinc for tumoral growth in OSCC, suggesting that zinc uptake might be a potential therapeutic targeting event for OSCCs.

TEAD4-YAP interaction regulates tumoral growth by controlling cell-cycle arrest at the G1 phase.

TEA domain transcription factor 4 (TEAD4), which has critical functions in the process of embryonic development, is expressed in various cancers. However, the important role of TEAD4 in human oral squamous cell carcinomas (OSCCs) remain unclear. Here we investigated the TEAD4 expression level and the functional mechanism in OSCC using quantitative reverse transcriptase-polymerase chain reaction, Western blot analysis, and immunohistochemistry. Furthermore, TEAD4 knockdown model was used to evaluate cellular proliferation, cell-cycle analysis, and the interaction between TEAD4 and Yes-associated protein (YAP) which was reported to be a transcription coactivator of cellular proliferation. In the current study, we found that TEAD4 expression increased significantly in vitro and in vivo and correlated with tumoral size in OSCC patients. TEAD4 knockdown OSCC cells showed decreased cellular proliferation resulting from cell-cycle arrest in the G1 phase by down-regulation of cyclins, cyclin-dependent kinases (CDKs), and up-regulation of CDK inhibitors. We also found that the TEAD4-YAP complex in the nuclei may be related closely to transcriptions of G1 arrest-related genes. Taken together, we concluded that TEAD4 might play an important role in tumoral growth and have potential to be a therapeutic target in OSCCs.

Water vapour effects on secondary organic aerosol formation in isoprene ozonolysis.

Secondary organic aerosol (SOA) formation from isoprene ozonolysis was investigated using a Teflon bag reactor under dry and humid conditions. Both the number and volume concentrations of SOA were found to be decreased by the addition of water vapour. Gas- and particle-phase product analyses with a negative ion chemical ionization mass spectrometer show that oligomers composed of stabilized Criegee intermediates as the chain units contribute to the SOA formation and that water vapour inhibits stabilized Criegee intermediates from forming the oligomers, resulting in the suppression of SOA formation. Additionally, it is suggested that a portion of stabilized Criegee intermediates other than CH2OO have low reactivity toward H2O, and thus can be involved in the oligomer and SOA formation even under humid conditions. Volatility estimation predicts that the oligomers containing even one or two stabilized Criegee intermediates can be partitioned into the aerosol phase.

Relative Reactivity Measurements of Stabilized CH2OO, Produced by Ethene Ozonolysis, Toward Acetic Acid and Water Vapor Using Chemical Ionization Mass Spectrometry.

We investigated the relative reactivity of stabilized CH2OO, produced by ethene ozonolysis, toward acetic acid and water vapor at a temperature of 298 ± 2 K and atmospheric pressure. Hydroperoxymethyl acetate produced through the reaction between stabilized CH2OO and acetic acid was monitored using a chemical ionization mass spectrometer as a function of the acetic acid concentration at different relative humidities. The rate of the reaction between CH2OO and water vapor depended quadratically on the water vapor concentration, suggesting that CH2OO reacted with water dimers in preference to water monomers. We obtained the bimolecular rate constant for the reaction between CH2OO and water dimer relative to the rate constant for the reaction between CH2OO and acetic acid, k3/k1, of (6.3 ± 0.4) × 10-2. The k3 value of (8.2 ± 0.8) × 10-12 cm3 molecule-1 s-1 was derived by combining with a k1 value of (1.3 ± 0.1) × 10-10 cm3 molecule-1 s-1, which has been previously reported by direct kinetic studies. The k3 value thus obtained is consistent with the absolute rate constants measured directly, suggesting that the reactivity of CH2OO is irrespective of the CH2OO generation method, namely, ethene ozonolysis or diiodomethane photolysis. We indirectly determined the yield of stabilized CH2OO from the ozonolysis of ethene of 0.59 ± 0.17 and 0.55 ± 0.16 under dry and humid (relative humidity 23-24%) conditions, respectively, suggesting that the yield is independent of the water vapor concentration. Our results suggest that hydroperoxymethyl acetate is the sole product of the reaction between stabilized CH2OO and acetic acid. The approach presented here can likely be extended to studies of the reactivities of more complicated and atmospherically relevant stabilized Criegee intermediates.

Reactive Uptake of Gaseous Sesquiterpenes on Aqueous Surfaces.

Sesquiterpenes emitted from biogenic sources play important roles in atmospheric HOx cycles and new particle formation. Current atmospheric models, however, fail to account for their fates, possibly due to missing heterogeneous sinks. Here we apply interface-specific mass spectrometry to detect carbocation products of the reactive uptake of gaseous sesquiterpenes C15H24 (ß-caryophyllene (ß-C), α-humulene (α-H), and alloaromadendrene (a-d)) on the surface of aqueous microjets as functions of water acidity and gas concentration. We find that these gases are effectively protonated to C15H25+ upon colliding with the surface of pH < 5 water microjets. We determine inflection points from plots of product yields vs bulk pH: pH1/2 = 4.17 ± 0.05, 4.28 ± 0.06, and 4.36 ± 0.19, and kinetic isotope effects (KIEs) from H2O/D2O (1:1 = vol/vol) experiments: KIE = 2.31 ± 0.08, 1.95 ± 0.05, and 2.71 ± 0.11, for ß-C, α-H, and a-d, respectively. These results are analyzed vis-a-vis previous reports on isoprene and monoterpenes experiments. We estimate 6.2 × 10-5 ≤ γ ≤ 3.1 × 10-4 for the reactive uptake of gaseous sesquiterpenes on acidic (1 < pH < 3) water surfaces. The atmospheric implications of present findings are discussed.