Benzene formation in the inner regions of protostellar disks

Benzene (c-C6H6) formation in the inner 3 AU of a protostellar disk can be efficient, resulting in high abundances of benzene in the midplane region. The formation mechanism is different to that found in interstellar clouds and in protoplanetary nebulae, and proceeds mainly through the reaction between allene (C3H4) and its ion. This has implications for PAH formation, in that some fraction of PAHs seen in the solar system could be native rather than inherited from the interstellar medium.Comment: 9 pages, 2 colour figures, to be published in the Astrophysical Journal Letter

A new astrobiological model of the atmosphere of Titan

We present results of an investigation into the formation of nitrogen-bearing molecules in the atmosphere of Titan. We extend a previous model (Li et al. 2015, 2016) to cover the region below the tropopause, so the new model treats the atmosphere from Titan's surface to an altitude of 1500 km. We consider the effects of condensation and sublimation using a continuous, numerically stable method. This is coupled with parameterized treatments of the sedimentation of the aerosols and their condensates, and the formation of haze particles. These processes affect the abundances of heavier species such as the nitrogen-bearing molecules, but have less effect on the abundances of lighter molecules. Removal of molecules to form aerosols also plays a role in determining the mixing ratios, in particular of HNC, HC3N and HCN. We find good agreement with the recently detected mixing ratios of C2H5CN, with condensation playing an important role in determining the abundance of this molecule below 500 km. Of particular interest is the chemistry of acrylonitrile (C2H3CN) which has been suggested by Stevenson et al. (2015) as a molecule that could form biological membranes in an oxygen-deficient environment. With the inclusion of haze formation we find good agreement of our model predictions of acrylonitrile with the available observations.Comment: 17 pages, 6 figures, Accepted by Ap

Chemical Processes in Protoplanetary Disks

We have developed a high resolution combined physical and chemical model of a protoplanetary disk surrounding a typical T Tauri star. Our aims were to use our model to calculate the chemical structure of disks on small scales (sub-milli-arcsecond in the inner disk for objects at the distance of Taurus, ~ 140 pc) to investigate the various chemical processes thought to be important in disks and to determine potential molecular tracers of each process. Our gas-phase network was extracted from the UMIST Database for Astrochemistry to which we added gas-grain interactions including freeze out and thermal and non-thermal desorption (cosmic-ray induced desorption, photodesorption and X-ray desorption) and a grain-surface network. We find that cosmic-ray induced desorption has the least effect on our disk chemical structure while photodesorption has a significant effect, enhancing the abundances of most gas-phase molecules throughout the disk and affecting the abundances and distribution of HCN, CN and CS, in particular. In the outer disk, we also see enhancements in the abundances of H2O and CO2. X-ray desorption is a potentially powerful mechanism in disks, acting to homogenise the fractional abundances of gas-phase species across the depth and increasing the column densities of most molecules although there remain significant uncertainties in the rates adopted for this process. The addition of grain-surface chemistry enhances the fractional abundances of several small complex organic molecules including CH3OH, HCOOCH3 and CH3OCH3 to potentially observable values (i.e. a fractional abundance of >~ 1.0E-11).Comment: 24 pages, 13 figures, accepted for publication in Ap

An encounter group approach to psychological care during pregnancy : a thesis presented in partial fulfillment of the requirements for the degree of Master of Arts in Psychology at Massey University

Pregnancy is seen as a time of psychological change in the normal woman. Supportive antenatal care is beneficial in decreasing stress in the mother and in promoting future mental health in the whole family. Fifty-two women attending a suburban General Practice at which encounter groups were offered as part of routine antenatal care, were studied during the last trimester of pregnancy with the general aim of providing information necessary for the improvement of antenatal health care services. A series of questionnaires were completed by the women prior to their being invited to join the encounter groups, and again two weeks prior to their estimated date of delivery. These included I.P.A.T. Neuroticism Scale Questionnaire, and the use of a semantic differential technique to assess attitudes. It was found that pregnant women show a much higher level of neuroticism than would be expected in the normal population of women, and this was most marked in multigravidae. The profile was typified, by an increased score on E (submissiveness) component, and a decreased score on the I (tendermindedness) component. These were interpreted as being changes beneficial to the psychological health of the mother. The most important underlying factor in the attitudes of the pregnant woman was related to the perception of the husband. Only half of the women had planned their pregnancies, but almost all had a positive attituds towards motherhood. The majority hoped to have their husbands present at delivery, and a large proportion intended to breastfeed. None of the women had taken full advantage of the methods of preparation for parenthood available to them, and many had not discussed childbirth with their friends or mothers. The thirty-two women who attended the encounter groups were characterised by higher I (tendermindedness) scores on tho N.S.Q., and primigravidae were more likely to attend than multigravidae. Multigravidae who did attend differed from multigravidae who did not, both on the N.S.Q. and on the basis of their previous obstetric history, having had shorter labours and having produced larger babies previously. The principal functions of the encounter group were to provide information and companionship, and to increase self-confidence. Members gained maximum reassurance from seeing others return safely with their infants after delivery. The use of groups such as these in training workers in the field of maternal health care to empathise with their patients is stressed

Deuterium chemistry in protoplanetary disks II The inner 30 AU

We present the results of models of the chemistry, including deuterium, in the inner regions of protostellar disks. We find good agreement with recent gas phase observations of several (non--deuterated) species. We also compare our results with observations of comets and find that in the absence of other processing e.g. in the accretion shock at the surface of the disk, or by mixing in the disk, the calculated D/H ratios in ices are higher than measured and reflect the D/H ratio set in the molecular cloud phase. Our models give quite different abundances and molecular distributions to other inner disk models because of the differences in physical conditions in the model disk. This emphasizes how changes in the assumptions about the density and temperature distribution can radically affect the results of chemical models.Comment: Accepted by Astrophysical Journa