Formation rates of complex organics in UV irradiated CH3OH-rich ices I: Experiments

(Abridged) Gas-phase complex organic molecules are commonly detected in the warm inner regions of protostellar envelopes. Recent models show that photochemistry in ices followed by desorption may explain the observed abundances. This study aims to experimentally quantify the broad-band UV-induced production rates of complex organics in CH3OH-rich ices at 20-70 K under ultra-high vacuum conditions. The reaction products are mainly identified by RAIRS and TPD experiments. Complex organics are readily formed in all experiments, both during irradiation and during a slow warm-up of the ices to 200 K after the UV lamp is turned off. The relative abundances of photoproducts depend on the UV fluence, the ice temperature, and whether pure CH3OH ice or CH3OH:CH4/CO ice mixtures are used. C2H6, CH3CHO, CH3CH2OH, CH3OCH3, HCOOCH3, HOCH2CHO and (CH2OH)2 are all detected in at least one experiment. The derived product-formation yields and their dependences on different experimental parameters, such as the initial ice composition, are used to estimate the CH3OH photodissociation branching ratios in ice and the relative diffusion barriers of the formed radicals. The experiments show that ice photochemistry in CH3OH ices is efficient enough to explain the observed abundances of complex organics around protostars and that ratios of complex molecules can be used to constrain their formation pathway.Comment: Accepted for publication in A&A. 65 pages including appendice

Dissociating task difficulty from incongruence in face-voice emotion integration

In the everyday environment, affective information is conveyed by both the face and the voice. Studies have demonstrated that a concurrently presented voice can alter the way that an emotional face expression is perceived, and vice versa, leading to emotional conflict if the information in the two modalities is mismatched. Additionally, evidence suggests that incongruence of emotional valence activates cerebral networks involved in conflict monitoring and resolution. However, it is currently unclear whether this is due to task difficulty—that incongruent stimuli are harder to categorize—or simply to the detection of mismatching information in the two modalities. The aim of the present fMRI study was to examine the neurophysiological correlates of processing incongruent emotional information, independent of task difficulty. Subjects were scanned while judging the emotion of face-voice affective stimuli. Both the face and voice were parametrically morphed between anger and happiness and then paired in all audiovisual combinations, resulting in stimuli each defined by two separate values: the degree of incongruence between the face and voice, and the degree of clarity of the combined face-voice information. Due to the specific morphing procedure utilized, we hypothesized that the clarity value, rather than incongruence value, would better reflect task difficulty. Behavioral data revealed that participants integrated face and voice affective information, and that the clarity, as opposed to incongruence value correlated with categorization difficulty. Cerebrally, incongruence was more associated with activity in the superior temporal region, which emerged after task difficulty had been accounted for. Overall, our results suggest that activation in the superior temporal region in response to incongruent information cannot be explained simply by task difficulty, and may rather be due to detection of mismatching information between the two modalities

A hybrid moment equation approach to gas-grain chemical modeling

[Context] The stochasticity of grain chemistry requires special care in modeling. Previously methods based on the modified rate equation, the master equation, the moment equation, and Monte Carlo simulations have been used. [Aims] We attempt to develop a systematic and efficient way to model the gas-grain chemistry with a large reaction network as accurately as possible. [Methods] We present a hybrid moment equation approach which is a general and automatic method where the generating function is used to generate the moment equations. For large reaction networks, the moment equation is cut off at the second order, and a switch scheme is used when the average population of certain species reaches 1. For small networks, the third order moments can also be utilized to achieve a higher accuracy. [Results] For physical conditions in which the surface reactions are important, our method provides a major improvement over the rate equation approach, when benchmarked against the rigorous Monte Carlo results. For either very low or very high temperatures, or large grain radii, results from the rate equation are similar to those from our new approach. Our method is faster than the Monte Carlo approach, but slower than the rate equation approach. [Conclusions] The hybrid moment equation approach with a cutoff and switch scheme is applicable to large gas-grain networks, and is accurate enough to be used for astrochemistry studies. The layered structure of the grain mantle could also be incorporated into this approach, although a full implementation of the grain micro-physics appears to be difficult.Comment: 11 pages, 4 figures. Accepted for publication in Astronomy and Astrophysic

Time Preferences, Land Tenure Security and the Adoption of Sustainable Land Management Practices in Southeast Nigeria

Sustainable land management (SLM) practices are important for tackling agricultural land degradation. This study investigates the association between farmers’ time preferences and their adoption of SLM practices (agroforestry, terracing, and land fallow practices) with intertemporal benefits, and further documents the moderating role of land tenure security in this relationship. The analysis in the paper is based on data from a survey of 480 farmers in south-east Nigeria, complemented by semi-structured interviews. Farmers’ time preferences were elicited using both a survey and experiments with hypothetical payouts. Land tenure was conceptualised as a composite concept to suit the legally pluralistic context of the study area. This study found that many of the sampled farmers have high discount rates. The result further shows that farmers’ time preferences are negatively associated with their adoption of agroforestry and land fallow practices. Moreover, the result shows that both legal and de facto tenure security encourage the adoption of SLM practices. Other factors influencing the adoption of SLM practices include gender, household size, education, credit constraints, marital status, risk attitude, farming experience, and farm characteristics (e.g., erosion problems and steepness of slope). Furthermore, this study found that the security-enhancing effect of land tenure security (de facto) can alleviate the negative influence of time preferences on farmers’ adoption of SLM practices. The findings suggest that farmers with higher discount rates, who have secure tenure rights to land, are more likely to adopt SLM practices, compared to similar farmers without tenure security

Molecular marketing, personalised information and willingness-to-pay for functional foods: Vitamin D enriched eggs

Increasingly, the health claims made by food products focus on the marketing of specific molecular enrichments. Research exploring consumers’ willingness to pay (WTP) for health claims assumes that individuals hold perfect information on the benefits of the enrichment, and that their valuations depend solely on whether or not they need to improve their health. While health interventions are aimed at individuals at higher health risk, consumers may be unaware of the health risks that they face, limiting the effectiveness of a generic targeting strategy. Using an orthogonal experimental design, we explore the impact of two factors on the WTP for vitamin D enrichment in eggs: whether the information is person-specific or generic; and the presence of a health claim explaining the vitamin D enrichment. Results indicate that it is the provision of information, not the health claim, that influences WTP. Both generic and personalised information lead to similar increases in the WTP for vitamin D enrichment. While we only observe a direct effect of generic information on the WTP for vitamin D enrichment, personal information may also operate by increasing the perceived risk of vitamin D deficiency. Our results support the use of personalised health information during the choice task as a means of increasing the sales of healthy products

Analysis of the enabling environment for delivering land degradation neutrality in Nigeria: perspectives from the sub-national to local level

The discourse around the planning, monitoring, and assessment of land degradation neutrality (LDN) has been communicated strongly on global and national scales; however, there is relatively little information on the enabling environment that will support the achievement of LDN targets locally. Recognising the dearth of studies that apply the LDN concept at the local scale, this study investigated local stakeholders’ perspectives on the progress towards, and challenges around, establishing the enabling environment for achieving LDN. It developed and used an extended LDN enabler framework that incorporates the gender component of LDN. The data for this study were collected from stakeholders from sub-national and local institutions concerned with LDN in Nigeria. The study findings indicate the presence of several relevant institutions and policy instruments to support progress towards LDN. However, this did not create an enabling environment for land users due to the lack of sufficient funding, weak systemic capacities of the relevant institutions, and the operational challenges for delivering policy incentives. Moreover, shortcomings in the regulatory framework give rise to land tenure insecurity and gender-biased land administration systems. Also, the findings indicate that entrenched traditional norms are a major challenge in achieving gender-balanced LDN outcomes. The extended LDN-enabler framework developed in this study will extend the scope of future studies examining progress toward LDN at regional and local scales

Complex molecules toward low-mass protostars: the Serpens core

Gas-phase complex organic molecules are commonly detected toward high-mass protostellar hot cores. Detections toward low-mass protostars and outflows are comparatively rare, and a larger sample is key to investigate how the chemistry responds to its environment. Guided by the prediction that complex organic molecules form in CH3OH-rich ices and thermally or non-thermally evaporate with CH3OH, we have identified three sight-lines in the Serpens core - SMM1, SMM4 and SMM4-W - which are likely to be rich in complex organics. Using the IRAM 30m telescope, narrow lines (FWHM of 1-2 km s-1) of CH3CHO and CH3OCH3 are detected toward all sources, HCOOCH3 toward SMM1 and SMM4-W, and C2H5OH not at all. Beam-averaged abundances of individual complex organics range between 0.6 and 10% with respect to CH3OH when the CH3OH rotational temperature is applied. The summed complex organic abundances also vary by an order of magnitude, with the richest chemistry toward the most luminous protostar SMM1. The range of abundances compare well with other beam-averaged observations of low-mass sources. Complex organic abundances are of the same order of magnitude toward low-mass protostars and high-mass hot cores, but HCOOCH3 is relatively more important toward low-mass protostars. This is consistent with a sequential ice photochemistry, dominated by CHO-containing products at low temperatures and early times.Comment: 20 pages, including 5 figures. Accepted for publication in Ap

Cold gas as an ice diagnostic toward low mass protostars

Up to 90% of the chemical reactions during star formation occurs on ice surfaces, probably including the formation of complex organics. Only the most abundant ice species are however observed directly by infrared spectroscopy. This study aims to develop an indirect observational method of ices based on non-thermal ice desorption in the colder part of protostellar envelopes. For that purpose the IRAM 30m telescope was employed to observe two molecules that can be detected both in the gas and the ice, CH3 OH and HNCO, toward 4 low mass embedded protostars. Their respective gas-phase column densities are determined using rotational diagrams. The relationship between ice and gas phase abundances is subsequently determined. The observed gas and ice abundances span several orders of magnitude. Most of the CH3OH and HNCO gas along the lines of sight is inferred to be quiescent from the measured line widths and the derived excitation temperatures, and hence not affected by thermal desorption close to the protostar or in outflow shocks. The measured gas to ice ratio of ~10-4 agrees well with model predictions for non-thermal desorption under cold envelope conditions and there is a tentative correlation between ice and gas phase abundances. This indicates that non-thermal desorption products can serve as a signature of the ice composition. A larger sample is however necessary to provide a conclusive proof of concept.Comment: accepted by A&A letters, 10 pages including 5 figure

Detection of the hydroperoxyl radical HO2 toward \rho Oph A: Additional constraints on the water chemical network

Context: Hydrogen peroxide (HOOH) was recently detected toward \rho Oph A. Subsequent astrochemical modeling that included reactions in the gas phase and on the surface of dust grains was able to explain the observed abundance, and highlighted the importance of grain chemistry in the formation of HOOH as an intermediate product in water formation. This study also predicted that the hydroperoxyl radical HO2, the precursor of HOOH, should be detectable. Aims: We aim at detecting the hydroperoxyl radical HO2 in \rho Oph A. Methods: We used the IRAM 30m and the APEX telescopes to target the brightest HO2 lines at about 130 and 260 GHz. Results: We detect five lines of HO2 (comprising seven individual molecular transitions). The fractional abundance of HO2 is found to be about 1e-10, a value similar to the abundance of HOOH. This observational result is consistent with the prediction of the above mentioned astrochemical model, and thereby validates our current understanding of the water formation on dust grains. Conclusions: This detection, anticipated by a sophisticated gas-grain chemical model, demonstrates that models of grain chemistry have improved tremendously and that grain surface reactions now form a crucial part of the overall astrochemical network.Comment: 5 pages, 4 figures, accepted for publication as a Letter to the Editor in Astronomy and Astrophysic