The structure of flame filaments in chaotic flows

The structure of flame filaments resulting from chaotic mixing within a combustion reaction is considered. The transverse profile of the filaments is investigated numerically and analytically based on a one-dimensional model that represents the effect of stirring as a convergent flow. The dependence of the steady solutions on the Damkohler number and Lewis number is treated in detail. It is found that, below a critical Damkohler number Da(crit), the flame is quenched by the flow. The quenching transition appears as a result of a saddle-node bifurcation where the stable steady filament solution collides with an unstable one. The shape of the steady solutions for the concentration and temperature profiles changes with the Lewis number and the value of Da(crit) increases monotonically with the Lewis number. Properties of the solutions are studied analytically in the limit of large Damkohler number and for small and large Lewis number.Comment: 17 pages, 13 figures, to be published in Physica

ALMA data suggest the presence of a spiral structure in the inner wind of CW Leo

(abbreviated) We aim to study the inner wind of the well-known AGB star CW Leo. Different diagnostics probing different geometrical scales have pointed toward a non-homogeneous mass-loss process: dust clumps are observed at milli-arcsec scale, a bipolar structure is seen at arcsecond-scale and multi-concentric shells are detected beyond 1". We present the first ALMA Cycle 0 band 9 data around 650 GHz. The full-resolution data have a spatial resolution of 0".42x0".24, allowing us to study the morpho-kinematical structure within ~6". Results: We have detected 25 molecular lines. The emission of all but one line is spatially resolved. The dust and molecular lines are centered around the continuum peak position. The dust emission has an asymmetric distribution with a central peak flux density of ~2 Jy. The molecular emission lines trace different regions in the wind acceleration region and suggest that the wind velocity increases rapidly from about 5 R* almost reaching the terminal velocity at ~11 R*. The channel maps for the brighter lines show a complex structure; specifically for the 13CO J=6-5 line different arcs are detected within the first few arcseconds. The curved structure present in the PV map of the 13CO J=6-5 line can be explained by a spiral structure in the inner wind, probably induced by a binary companion. From modeling the ALMA data, we deduce that the potential orbital axis for the binary system lies at a position angle of ~10-20 deg to the North-East and that the spiral structure is seen almost edge-on. We infer an orbital period of 55 yr and a binary separation of 25 au (or ~8.2 R*). We tentatively estimate that the companion is an unevolved low-mass main-sequence star. The ALMA data hence provide us for the first time with the crucial kinematical link between the dust clumps seen at milli-arcsecond scale and the almost concentric arcs seen at arcsecond scale.Comment: 22 pages, 18 Figures, Astronomy & Astrophysic

Models for Dense Molecular Cloud Cores

We present a detailed model for the thermal balance, chemistry, and radiative transfer within quiescent dense molecular cloud cores that contain a central protostar. Large variations in the gas temperature are expected to affect the gas-phase chemistry dramatically; with the predicted H2O abundance varying by more than a factor of 1000 within cloud cores. Based on our predicitions for the thermal and chemical structure of the cores, we have constructed self-consistent radiative transfer models to compute line strengths and profiles for transitions of various isotopomers of CO, H2O, and OI. We predict the high lying transitions of water to be in absorption, and low gain maser emission at 183 GHz. We predict the 63 micron line of OI to be in absorption against the continuum for many sources. Finally, our model can also account successfully for recent ISO observations of absorption in rovibrational transitions of water toward the source AFGL 2591.Comment: 36 pages, 18 figures, LaTex, Accepted for publication by ApJ (11/97

Disruptive Knowledge in Education for Reconciliation: The Effects of Indigenous Course Requirements on Non-Indigenous Students’ Attitudes

Following the Truth and Reconciliation Commission of Canada, various institutions have embarked on diverse educational initiatives in the name of creating equitable and respectful relationships between Indigenous and non-Indigenous Peoples. One such initiative is the University of Winnipeg’s mandate that all undergraduate students fulfill an Indigenous Course Requirement (ICR). Using the framework of disruptive knowledge, this mixed-methods study investigated the impact of select ICR courses on non-Indigenous students’ attitudes. Results revealed increased recognition of discriminations facing Indigenous Peoples, increased support for systemic change, and self-described behavioural changes. At the same time, these results highlight the limitations of such courses within a settler-colonial context.À la suite de la Commission de vérité et réconciliation du Canada (CVR), diverses institutions se sont lancées dans des initiatives éducatives variées au nom de la création de relations équitables et respectueuses entre les peuples autochtones et non autochtones. L›une de ces initiatives est le mandat de l›Université de Winnipeg, selon lequel tous les étudiants de premier cycle suivent un cours obligatoire qui répondra à une exigence de cours autochtone (ECA). En utilisant la théorie des connaissances perturbatrices, cette étude à méthodes-mixtes a examiné l›impact de certains cours (ECA) sur les attitudes des étudiants non autochtones. Les résultats ont révélé une reconnaissance amplifiée des discriminations auxquelles les peuples autochtones sont confrontés, un soutien développé aux initiatives d›équité du gouvernement et des changements de comportement et de pensées auto-décrits. En même temps, ces résultats mettent en évidence les limites de tels cours dans un contexte de colonisation

Electromagnetic corrections in the anomaly sector

Chiral perturbation theory in the anomaly sector for $N_f=2$ is extended to include dynamical photons, thereby allowing a complete treatment of isospin breaking. A minimal set of independent chiral lagrangian terms is determined and the divergence structure is worked out. There are contributions from irreducible and also from reducible one-loop graphs, a feature of ChPT at order larger than four. The generating functional is non-anomalous at order $e^2p^4$, but not necessarily at higher order in $e^2$. Practical applications to $\gamma\pi\to\pi\pi$ and to the $\pi^0\to2\gamma$ amplitudes are considered. In the latter case, a complete discussion of the corrections beyond current algebra is presented including quark mass as well as electromagnetic effects.Comment: 26 pages, 3 figure

High-resolution absorption spectroscopy of the OH 2Pi 3/2 ground state line

The chemical composition of the interstellar medium is determined by gas phase chemistry, assisted by grain surface reactions, and by shock chemistry. The aim of this study is to measure the abundance of the hydroxyl radical (OH) in diffuse spiral arm clouds as a contribution to our understanding of the underlying network of chemical reactions. Owing to their high critical density, the ground states of light hydrides provide a tool to directly estimate column densities by means of absorption spectroscopy against bright background sources. We observed onboard the SOFIA observatory the 2Pi3/2, J = 5/2 3/2 2.5 THz line of ground-state OH in the diffuse clouds of the Carina-Sagittarius spiral arm. OH column densities in the spiral arm clouds along the sightlines to W49N, W51 and G34.26+0.15 were found to be of the order of 10^14 cm^-2, which corresponds to a fractional abundance of 10^-7 to 10^-8, which is comparable to that of H_2O. The absorption spectra of both species have similar velocity components, and the ratio of the derived H_2O to OH column densities ranges from 0.3 to 1.0. In W49N we also detected the corresponding line of ^18OH

Arterial Oxygen Tension in Relation to Age in Hospital Subjects

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111097/1/j.1532-5415.1973.tb00840.x.pd

Pesticide Analysis in Vegetables Using QuEChERS Extraction and Colorimetric Detection

A novel combination of extraction and detection methods is demonstrated for pesticide residue analysis in vegetable samples. Acetylcholinesterase (AChE) inhibition was used as a simple colorimetric test for organophosphates/carbamates (OP/C), and was tested with extracts from the widely-used QuEChERS extraction method. In the absence of pesticide, diluted (50% with water) acetonitrile did not inhibit enzyme activity, demonstrating the compatibility of this extraction solvent with the AChE inhibition test. QuEChERS extraction of chlorpyrifos-spiked tomato, spinach and lettuce samples indicated a high sensitivity to OP/C, with AChE inhibition occurring in the ppb range. The applicability of this method combination was tested by screening tomatoes from 18 different sources, including private gardens, farmer’s market venders, and local supermarkets. Tomatoes from one private garden, three “certified naturally grown” farmer’s market venders and two “organic” supermarket source had AChE inhibition significantly above nominally pesticide-free controls, suggesting the presence of OP/C residue. These residues were likely below levels of health concern, as indicated by lack of complete AChE inhibition, and the absence of inhibition upon sample dilution. This study demonstrates that the combination of QuEChERS extraction and AChE-inhibition detection provides a relatively simple and inexpensive alternative for detection of OP/C in vegetable samples

A multi-transition submillimeter water maser study of evolved stars - detection of a new line near 475 GHz

Context: Maser emission from the H2O molecule probes the warm, inner circumstellar envelopes of oxygen-rich red giant and supergiant stars. Multi-maser transition studies can be used to put constraints on the density and temperature of the emission regions. Aims: A number of known H2O maser lines were observed toward the long period variables R Leo and W Hya and the red supergiant VY CMa. A search for a new, not yet detected line near 475 GHz was conducted toward these stars. Methods: The Atacama Pathfinder Experiment telescope was used for a multi-transition observational study of submillimeter H2O lines. Results: The 5_33-4_40 transition near 475 GHz was clearly detected toward VY CMa and W Hya. Many other H2O lines were detected toward all three target stars. Relative line intensity ratios and velocity widths were found to vary significantly from star to star. Conclusions: Maser action is observed in all but one line for which it was theoretically predicted. In contrast, one of the strongest maser lines, in R Leo by far the strongest, the 437 GHz 7_53-6_60 transition, is not predicted to be inverted. Some other qualitative predictions of the model calculations are at variance with our observations. Plausible reasons for this are discussed. Based on our findings for W Hya and VY CMa, we find evidence that the H2O masers in the AGB star W Hya arise from the regular circumstellar outflow, while shock excitation in a high velocity flow seems to be required to excite masers far from the red supergiant VY CMa.Comment: 9 pages, 4 figures, Astronomy and Astrophyics (in press

Intermittency in two-dimensional Ekman-Navier-Stokes turbulence

We study the statistics of the vorticity field in two-dimensional Navier-Stokes turbulence with a linear Ekman friction. We show that the small-scale vorticity fluctuations are intermittent, as conjectured by Nam et al. [Phys. Rev. Lett. vol.84 (2000) 5134]. The small-scale statistics of vorticity fluctuations coincides with the one of a passive scalar with finite lifetime transported by the velocity field itself.Comment: 4 pages, 7 figure