High pressure cosmochemistry applied to major planetary interiors: Experimental studies

The overall goal of this project is to determine properties of the H-He-C-N-O system, as represented by small molecules composed of these elements, that are needed to constrain theoretical models of the interiors of the major planets. Much of our work now concerns the H2O-NH3 system. This project is the first major effort to measure phase equilibria in binary fluid-solid systems in diamond anvil cells. Vibrational spectroscopy, direct visual observations, and X-ray crystallography of materials confined in externally heated cells are our primary experimental probes. We also are collaborating with the shockwave physics group at Lawrence Livermore Laboratory in studies of the equation of state of a synthetic Uranus fluid and molecular composition of this and other H-C-N-O materials under planetary conditions

A Study of the SP Geophysical Technique in a Campus Setting

The self potential (SP) method is a simple and inexpensive geophysical surveying technique, which involves measuring electrical potentials on the surface due to charge separations in the subsurface. These charge separations can arise from a number of different physical and electrochemical processes, and hence interpretations tend to be qualitative. Small anomalies are typically neglected as transient, inexplicable, or uninteresting. In contrast, large negative anomalies associated with ore bodies are noted for their constancy. In this study, an area on the campus of Memorial University was repeatedly surveyed in order to determine which natural and anthropogenic features generated SP anomalies, and whether these anomalies were constant or transient. We found anomalies associated with a building, a buried metallic pipe, trees, and subtler ground variations. The locations of anomalies, both large and small, were notably unvarying over a period of days and weeks. The building always generated a significant negative anomaly, but the sign of other anomalies (including that associated with the pipe) and the magnitude of all anomalies varied with time. In a second area dominated by a shallow sewer pipe, SP data allowed modeling of the burial depth and charge distribution of the pipe. Our results show that SP can be a useful and reliable method for shallow ground surveys, but that the time-varying nature of both sign and magnitude of small to moderate anomalies should be taken into account in data collection and interpretation. Résumé La méthode des potentiels spontanés est une technique d’exécution de levés géophysiques simple et peu dispendieuse consistant à mesurer les potentiels électriques à la surface liés aux séparations des charges dans le sous-sol. Ces séparations des charges peuvent découler d’un certain nombre de processus physiques et électrochimiques différents, de sorte que les interprétations données ont tendance à être qualitatives. On néglige généralement les petites anomalies, les considérant comme des anomalies transitoires, inexplicables ou peu intéressantes. En revanche, on note les anomalies négatives poussées qui sont associées aux corps minéralisés en raison de leur constance. Dans le cadre de cette étude, on a réalisé des levés répétés dans un secteur du campus de l’Université Memorial pour déterminer quelles particularités naturelles et artificielles produisaient des anomalies des PS et si ces anomalies étaient constantes ou transitoires. Nous avons découvert des anomalies associées à un bâtiment, à un tuyau en métal enfoui, à des arbres et à des irrégularités du terrain plus subtiles. Fait remarquable, les emplacements des anomalies, tant prononcées que minimes, n’ont pas changé au cours d’une période de plusieurs jours et semaines. Le bâtiment a toujours produit une anomalie négative marquée, mais le signal d’autres anomalies (notamment celle associée au tuyau) et la magnitude de toutes les anomalies ont varié au fil du temps. Dans un second secteur où était surtout présent un tuyau d’égout peu profond, les données des PS ont permis la modélisation de la profondeur d’enfouissement et de la distribution des charges du tuyau. Nos résultats révèlent que la polarisation spontanée peut s’avérer une méthode utile et fiable pour les levés terrestres peu profonds, mais qu’il faudrait tenir compte de la nature variable des signaux et de la magnitude des anomalies minimes à moyennes lors de la collecte et de l’interprétation des données. [Traduit par la redaction

Balloon-borne radiometer measurement of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years

Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990–2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and global optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. This suggests that, to within the errors of the 1990 measurements, there has been no significant change in the HNO3 summer mid-latitude profile

The role of psychological flexibility in the relationship between self-concealment and disordered eating symptoms

The present cross-sectional study investigated whether psychological flexibility mediates the association between self-concealment and disordered eating (DE) symptoms among non-clinical college students. Data of 209 male and female participants (nfemale = 165), aged 18-22 years old, were used for analyses. Self-concealment was found to be positively associated with DE symptoms (i.e., general eating disorder symptoms and eating disorder-related cognitions) and negatively associated with psychological flexibility. Psychological flexibility was inversely associated with DE symptoms. Finally, psychological flexibility was found to mediate the association between self-concealment and DE symptoms after accounting for gender, ethnic background, and body mass index (BMI)

Derivation of tropospheric methane from TCCON CH₄ and HF total column observations

The Total Carbon Column Observing Network (TCCON) is a global ground-based network of Fourier transform spectrometers that produce precise measurements of column-averaged dry-air mole fractions of atmospheric methane (CH₄). Temporal variability in the total column of CH₄ due to stratospheric dynamics obscures fluctuations and trends driven by tropospheric transport and local surface fluxes that are critical for understanding CH₄ sources and sinks. We reduce the contribution of stratospheric variability from the total column average by subtracting an estimate of the stratospheric CH₄ derived from simultaneous measurements of hydrogen fluoride (HF). HF provides a proxy for stratospheric CH₄ because it is strongly correlated to CH₄ in the stratosphere, has an accurately known tropospheric abundance (of zero), and is measured at most TCCON stations. The stratospheric partial column of CH₄ is calculated as a function of the zonal and annual trends in the relationship between CH₄ and HF in the stratosphere, which we determine from ACE-FTS satellite data. We also explicitly take into account the CH₄ column averaging kernel to estimate the contribution of stratospheric CH₄ to the total column. The resulting tropospheric CH₄ columns are consistent with in situ aircraft measurements and augment existing observations in the troposphere

Stratospheric Lifetimes of CFC-12, CCl4, CH4, CH3CL and N20 from Measurements Made By The Atmospheric Chemistry Experiment-Fourier Transform Spectrometer

Long lived halogen-containing compounds are important atmospheric constituents since they can act both as a source of chlorine radicals, which go on to catalyse ozone loss, and as powerful greenhouse gases. The long-term impact of these species on the ozone layer is dependent on their stratospheric lifetimes. Using observations from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) we present calculations of the stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O. The lifetimes were calculated using the slope of the tracer-tracer correlation of these species with CFC-11 at the tropopause. The correlation slopes were corrected for the changing atmospheric concentrations of each species based on age of air and CFC-11 measurements from samples taken aboard the Geophysica aircraft - along with the effective linear trend of the volume mixing ratio (VMR) from tropical ground based AGAGE (Advanced Global Atmospheric Gases Experiment) sites. Stratospheric lifetimes were calculated using a CFC-11 lifetime of 45 yr. These calculations produced values of 113 + (-) 26 (18) yr (CFC-12), 35 + (-) 11 (7) yr (CCl4), 69 + (-) 65 (23) yr (CH3Cl), 123 + (-) 53 (28) yr (N2O) and 195 + (-) 75 (42) yr (CH4). The errors on these values are the weighted 1 sigma non-systematic errors. Systematic errors were estimated by recalculating lifetimes using VMRs which had been modified to reflect differences between ACE-FTS retrieved VMRs and those from other instruments. The results of these calculations, including systematic errors, were as follows: 113 + (-) 32 (20) for CFC-12, 123 + (-) 83 (35) for N2O, 195 + (-) 139 (57) for CH4, 35 + (-) 14 (8) for CCl4 and 69 + (-) 2119 (34) yr for CH3Cl. For CH3Cl & CH4 this represents the first calculation of the stratospheric lifetime using data from a space based instrument