Gas phase formation of the prebiotic molecule formamide: insights from new quantum computations

New insights into the formation of interstellar formamide, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction NH2 + H2CO -> NH2CHO + H. Contrarily to what previously suggested, this reaction is essentially barrierless and can, therefore, occur under the low temperature conditions of interstellar objects thus providing a facile formation route of formamide. The rate coefficient parameters for the reaction channel leading to NH2CHO + H have been calculated to be A = 2.6x10^{-12} cm^3 s^{-1}, beta = -2.1 and gamma = 26.9 K in the range of temperatures 10-300 K. Including these new kinetic data in a refined astrochemical model, we show that the proposed mechanism can well reproduce the abundances of formamide observed in two very different interstellar objects: the cold envelope of the Sun-like protostar IRAS16293-2422 and the molecular shock L1157-B2. Therefore, the major conclusion of this Letter is that there is no need to invoke grain-surface chemistry to explain the presence of formamide provided that its precursors, NH2 and H2CO, are available in the gas-phase.Comment: MNRAS Letters, in pres

New quantum chemical computations of formamide deuteration support a gas-phase formation of this prebiotic molecule

Based on recent work, formamide might be a potentially very important molecule in the emergence of terrestrial life. Although detected in the interstellar medium for decades, its formation route is still debated, whether in the gas phase or on the dust grain surfaces. Molecular deuteration has proven to be, in other cases, an efficient way to identify how a molecule is synthesised. For formamide, new published observations towards the IRAS16293-2422 B hot corino show that its three deuterated forms have all the same deuteration ratio, 2--5%, and that this is a factor 3--8 smaller than that measured for H2CO towards the IRAS16293-2422 protostar. Following a previous work on the gas-phase formamide formation via the reaction NH2 + H2CO -> HCONH2 + H, we present here new calculations of the rate coefficients for the production of monodeuterated formamide through the same reaction, starting from monodeuterated NH2 or H2CO. Some misconceptions regarding our previous treatment of the reaction are also cleared up. The results of the new computations show that, at the 100 K temperature of the hot corino, the rate of deuteration of the three forms is the same, within 20%. On the contrary, the reaction between non-deuterated species proceeds three times faster than that with deuterated ones. These results confirm that a gas-phase route for the formation of formamide is perfectly in agreement with the available observations.Comment: MNRAS in pres

Optimizing prediction of binge eating episodes : a comparison approach to test alternative conceptualizations of the affect regulation model

Background : Although a wealth of studies have tested the link between negative mood states and likelihood of a subsequent binge eating episode, the assumption that this relationship follows a typical linear dose&ndash;response pattern (i.e., that risk of a binge episode increases in proportion to level of negative mood) has not been challenged. The present study demonstrates the applicability of an alternative, non-linear conceptualization of this relationship, in which the strength of association between negative mood and probability of a binge episode increases above a threshold value for the mood variable relative to the slope below this threshold value (threshold dose response model). Methods : A sample of 93 women aged 18 to 40 completed an online survey at random intervals seven times per day for a period of one week. Participants self-reported their current mood state and whether they had recently engaged in an eating episode symptomatic of a binge. Results : As hypothesized, the threshold approach was a better predictor than the linear dose&ndash;response modeling of likelihood of a binge episode. The superiority of the threshold approach was found even at low levels of negative mood (3 out of 10, with higher scores reflecting more&nbsp; negative mood). Additionally, severity of negative mood beyond this threshold value appears to be useful for predicting time to onset of a binge episode. Conclusions : Present findings suggest that simple dose&ndash;response formulations for the association between&nbsp; negative mood and onset of binge episodes miss vital aspects of this relationship. Most&nbsp; notably, the impact of mood on binge eating appears to depend on whether a threshold value&nbsp; of negative mood has been breached, and elevation in mood beyond this point may be useful&nbsp; for clinicians and researchers to identify time to onset. <br /

on a coupled system of shallow water equations admitting travelling wave solutions

We consider three inviscid, incompressible, irrotational fluids that are contained between the rigid wallsy=−h1andy=h+Hand that are separated by two free interfacesη1andη2. A generalized nonlocal spectral (NSP) formulation is developed, from which asymptotic reductions of stratified fluids are obtained, including coupled nonlinear generalized Boussinesq equations and(1+1)-dimensional shallow water equations. A numerical investigation of the(1+1)-dimensional case shows the existence of solitary wave solutions which have been investigated for different values of the characteristic parameters

Quantum chemical computations of gas-phase glycolaldehyde deuteration and constraints to its formation route

Despite the detection of numerous interstellar complex organic molecules (iCOMs) for decades, it is still a matter of debate whether they are synthesized in the gas-phase or on the icy surface of interstellar grains. In the past, molecular deuteration has been used to constrain the formation paths of small and abundant hydrogenated interstellar species. More recently, the deuteration degree of formamide, one of the most interesting iCOM, has also been explained in the hypothesis that it is formed by the gas-phase reaction NH$_2$ + H$_2$CO. In this article, we aim at using molecular deuteration to constrain the formation of another iCOM, glycolaldehyde, which is an important prebiotic species. More specifically, we have performed dedicated electronic structure and kinetic calculations to establish the glycolaldehyde deuteration degree in relation to that of ethanol, which is its possible parent species according to the suggestion of Skouteris et al. (2018). We found that the abundance ratio of the species containing one D-atom over the all-protium counterpart depends on the produced D isotopomer and varies from 0.9 to 0.5. These theoretical predictions compare extremely well with the monodeuterated isotopomers of glycolaldehyde and that of ethanol measured towards the Solar-like protostar IRAS 16293-2422, supporting the hypothesis that glycolaldehyde could be produced in the gas-phase for this source. In addition, the present work confirms that the deuterium fractionation of iCOMs cannot be simply anticipated based on the deuterium fractionation of the parent species but necessitates a specific study, as already shown for the case of formamide.Comment: Accepted by Ap

Promoting healthy eating, active play and sustainability consciousness in early childhood curricula, addressing the Ben10™ problem: a randomised control trial

Background: This paper details the research protocol for a study funded by the Australian Research Council. An integrated approach towards helping young children respond to the significant pressures of &lsquo;360 degree marketing&rsquo; on their food choices, levels of active play, and sustainability consciousness via the early childhood curriculum is lacking. The overall goal of this study is to evaluate the efficacy of curriculum interventions that educators design when using a pedagogical communication strategy on children&rsquo;s knowledge about healthy eating, active play and the sustainability consequences of their toy food and toy selections. Methods/Design: This cluster-randomised trial will be conducted with 300, 4 to 5 year-old children attending pre-school. Early childhood educators will develop a curriculum intervention using a pedagogical communication strategy that integrates content knowledge about healthy eating, active play and sustainability consciousness and deliver this to their pre-school class. Children will be interviewed about their knowledge of healthy eating, active play and the sustainability consequences of their food and toy selections. Parents will complete an Eating and Physical Activity Questionnaire rating their children&rsquo;s food preferences, digital media viewing and physical activity habits. All measures will be administered at baseline, the end of the intervention and 6 months post intervention. Informed consent will be obtained from all parents and the pre-school classes will be allocated randomly to the intervention or wait-list control group. Discussion: This study is the first to utilise an integrated pedagogical communication strategy developed specifically for early childhood educators focusing on children&rsquo;s healthy eating, active play, and sustainability consciousness. The significance of the early childhood period, for young children&rsquo;s learning about healthy eating, active play and sustainability, is now unquestioned. The specific teaching and learning practices used by early childhood educators, as part of the intervention program, will incorporate a sociocultural perspective on learning; this perspective emphasises building on the play interests of children, that are experienced within the family and home context, as a basis for curriculum provision. Trial Registration: Australian New Zealand Clinical Trials Registry ACTRN12614000363684: Date registered: 07/04/201

Person-centred care in interventions to limit weight gain in pregnant women with obesity - a systematic review

Background Person-centred care, asserting that individuals are partners in their care, has been associated with care satisfaction but the value of using it to support women with obesity during pregnancy is unknown. Excessive gestational weight gain is associated with increased risks for both mother and baby and weight gain therefore is an important intervention target. The aims of this review was to 1) explore to what extent and in what manner interventions assessing weight in pregnant women with obesity use person-centred care and 2) assess if interventions including aspects of person-centred care are more effective at limiting weight gain than interventions not employing person-centred care. Methods Ten databases were systematically searched in January 2014. Studies had to report an intervention offered to pregnant women with obesity and measure gestational weight gain to be included. All included studies were independently double coded to identify to what extent they included three defined aspects of person-centred care: 1) “initiate a partnership” including identifying the person’s circumstances and motivation; 2) “working the partnership” through sharing the decision-making regarding the planned action and 3) “safeguarding the partnership through documentation” of care preferences. Information on gestational weight gain, study quality and characteristics were also extracted. Results Ten studies were included in the review, of which five were randomised controlled trials (RCT), and the remaining observational studies. Four interventions included aspects of person-centred care; two observational studies included both “initiating the partnership”, and “working the partnership”. One observational study included “initiating the partnership” and one RCT included “working the partnership”. No interventions included “safeguarding the partnership through documentation”. Whilst all studies with person-centred care aspects showed promising findings regarding limiting gestational weight gain, so did the interventions not including person-centred care aspects. Conclusions The use of an identified person-centred care approach is presently limited in interventions targeting gestational weight gain in pregnant women with obesity. Hence to what extent person-centred care may improve health outcomes and care satisfaction in this population is currently unknown and more research is needed. That said, our findings suggest that use of routines incorporating person-centredness are feasible to include within these interventions

Investigating the Efficiency of Explosion Chemistry as a Source of Complex Organic Molecules in TMC-1

Many species of complex organic molecules (COMs) have been observed in several astrophysical environments but it is not clear how they are produced, particularly in cold, quiescent regions. One process that has been proposed as a means to enhance the chemical complexity of the gas phase in such regions is the explosion of the ice mantles of dust grains. In this process, a build up of chemical energy in the ice is released, sublimating the ices and producing a short lived phase of high density, high temperature gas. The gas–grain chemical code UCLCHEM has been modified to treat these explosions in order to model the observed abundances of COMs toward the TMC1 region. It is found that, based on our current understanding of the explosion mechanism and chemical pathways, the inclusion of explosions in chemical models is not warranted at this time. Explosions are not shown to improve the model’s match to the observed abundances of simple species in TMC-1. Further, neither the inclusion of surface diffusion chemistry, nor explosions, results in the production of COMs with observationally inferred abundances

Computer software for understanding resonances and resonance-related phenomena in chemical reactions

In numerical modelling of chemical reactions one calculates the scattering matrix for the required values of energy and angular momentum. Having done so, one still faces the non-trivial task of extracting detailed information about the reaction mechanism. We discuss the methods and numerical tools for such an analysis in terms of resonance poles and semiclassical trajectories. Our approach avoids calculating the scattering matrix in semiclassical approximation, and employs its numerical values computed previously by an accurate scattering code