Cosmic choruses: Metaphor and performance

In this chapter, Renaud Gagné pursues a chronologically wide-ranging study of how the motion of the heavenly bodies was thought about through the idea of choral dance. This chapter compares various unrelated, self-reflexive usages of the astral chorus metaphor in three genres of poetry and briefly considers how each illuminates the others. Instead of a teleological narrative, a dialogue of commonalities and contrasts is sought in the juxtaposition of comparable case studies. The striking image of the astral chorus was, among many other things, a powerful catalyst for thinking mimesis in action. A vision of the cosmic order is used in all three texts to reflect on the boundaries of poetic representation. The first text is a short epigram from Marcus Argentarius (AP 9.270 = G.-P. XXVI). The second passage is the ecphrasis of Dionysus’s shield in the Dionysica of Nonnus of Panopolis (25.380-572). The third text is another shield ecphrasis, that one from the first stasimon of Euripides’ Electra (432-486). The readings illustrate how a key figure of cosmic harmony was revisited to ponder the limits of poetic representation. Projecting itself on the cosmos, the idea of the choral dance could also reflect the cosmos back on song itself

Diagnostics Of Disks Around Hot Stars

We discuss three different observational diagnostics related to disks around hot stars: absorption line determinations of rotational velocities of Be stars; polarization diagnostics of circumstellar disks; and X-ray line diagnostics of one specific magnetized hot star, theta(1) Ori C. Some common themes that emerge from these studies include (a) the benefits of having a specific physical model as a framework for interpreting diagnostic data; (b) the importance of combining several different types of observational diagnostics of the same objects; and (c) that while there is often the need to reinterpret traditional diagnostics in light of new theoretical advances, there are many new and powerful diagnostics that are, or will soon be, available for the study of disks around hot stars

Gold( i )-catalyzed addition of aldehydes to cyclopropylidene bearing 6-aryl-1,5-enynes

A diastereoselective, gold-catalyzed cascading cycloisomerization of alkylidene cyclopropane bearing 1,5-enynes that terminates in a cyclo-addition of aldehydes has been developed

Probing the Source of Enhanced Activity in Multiborylated Silsesquioxane Catalysts for C-O Bond Reduction

A family of variably borylated silsesquioxanes can be conveniently synthesized by the hydroboration of vinyl- and allyl-modified silsesquioxanes using Piers' borane (HB­(C6F5)2). The catalytic activity of these Lewis acidic catalysts has been examined for the reduction of isochroman with 1,1,3,3-tetramethyldisiloxane, and loadings as low as 0.05 mol % boron are feasible. Despite scaling all catalytic reactions to the boron Lewis acid, the multiborylated silsesquioxanes showed exceptional catalytic activity compared to the monoborylated silsesquioxanes. Even at a catalyst loading of 0.05 mol %, the multiborylated catalyst could achieve a TOF of 7 min-1. The ideal position for boron on the silsesquioxanes was at the C2 position, as this position did not inhibit Lewis acidity via the β-silicon effect (at C1) or limit the inductive electron-withdrawing ability of the silsesquioxane core (at C3). The high catalyst activity is attributed to the increased Lewis acidity of the multiborylated silsesquioxanes

{Bis[2-(diphenyl­phosphan­yl)eth­yl]phenyl­phosphane-κ3 P,P′,P′′}[(Z)-8-mesityl­cyclo­oct-4-en-1-yl]platinum(II) tetra­fluorido­borate dichloro­methane disolvate

In the title ionic compound, [Pt(C17H23)(C34H33P3)](BF4)·2CH2Cl2, the PtII atom adopts a square-planar coordination geometry with the large (Z)-8-mesityl­cyclo­oct-4-en-1-yl group occupying the fourth coordination site. The (triphos)Pt moiety and the mesityl group are attached to the cyclo­oct-4-ene motif at the 1- and 8-position in a syn configuration. The (BF4)− anion and one of the dichloromethane solvate molecules each are disordered over two sets of sites

Influence of permafrost extent on photochemical reactivity, functional group composition, and geochemical cycling of a subarctic discontinuous permafrost Alaskan watershed

Thesis (Ph.D.) University of Alaska Fairbanks, 2020Sub-Arctic Alaskan boreal forests are currently extremely susceptible to permafrost thaw caused by increases in atmospheric temperatures in the region. Upon thaw, permafrost soil organic matter can leach out organic matter, nitrogen, and metals. It is important to observe the effects the leaching of permafrost may have on photoreactivity, functional group composition, and metal introduction. Photoproduced reactive oxygen species may affect metal fate and transport through mechanisms such as the photo-Fenton reaction. Functional group analysis allows for differences in natural organic matter source and ability to complex metals throughout a watershed. Additionally, permafrost soils may have the ability to leach in metals through lateral flow of surface waters as observed in other studies. These metals could then complex to organic matter and alter the geochemical cycling within the watershed. Organic matter is a nutrient source, and metals (e.g., As) may increase the toxicity of surface waters through the thaw of permafrost. The influx of sequestered organic matter and metals to surface waters has the potential to drastically alter ecosystem processes. This study observes how permafrost leaching affects water composition, including its overall photoreactivity and functional group composition. The data obtained was then used to observe and deduce conclusions on how permafrost thaw influences surface water photoreactivity and functional group composition. Finally, trace metal analysis was conducted on a whole watershed scale over three years to observe how permafrost influences the geochemical composition of three main thermokarst surface waters with varying degrees of permafrost degradation. Overall, permafrost was determined to be heterogeneous and highly photoreactive both inter- and intra- watershed. Additionally, the functional group composition of surface waters influenced by permafrost thaw was different between summer and winter, indicating that winter is an important period to sample. Due to this change in functional group composition, the photoreactivity of winter samples was higher than summer with regard to the production of reactive oxygen species. Metal concentrations also increased during the winter for lakes identified to be undergoing active permafrost thaw. Finally, this case study found that metal concentration data combined with optical indices provided important information for resolving the possible extent of permafrost beneath thermokarst lakes.Chapter 1. Composition and photoreactivity of natural organic matter leached from discontinuous permafrost in sub-Arctic Alaska -- Chapter 2. Permafrost thaw impact on natural organic matter photoreactivity and chemical composition in sub-Arctic Alaskan thermokarst lakes -- Chapter 3. Seasonal geochemistry cycles in a sub-Arctic watershed underlain by discontinuous permafrost -- General conclusions

Chandra HETGS Multiphase Spectroscopy Of The Young Magnetic O Star Theta(1) Orionis C

We report on four Chandra grating observations of the oblique magnetic rotator theta(1) Ori C (O5.5 V), covering a wide range of viewing angles with respect to the star\u27s 1060 G dipole magnetic field. We employ line-width and centroid analyses to study the dynamics of the X-ray - emitting plasma in the circumstellar environment, as well as line-ratio diagnostics to constrain the spatial location, and global spectral modeling to constrain the temperature distribution and abundances of the very hot plasma. We investigate these diagnostics as a function of viewing angle and analyze them in conjunction with new MHD simulations of the magnetically channeled wind shock mechanism on theta(1) Ori C. This model fits all the data surprisingly well, predicting the temperature, luminosity, and occultation of the X-ray - emitting plasma with rotation phase

The Search for Low-mass Companions of B Stars in the Carina Nebula Cluster Trumpler 16

We have developed lists of likely B3--A0 stars (called "late B" stars) in the young cluster Trumpler 16. The following criteria were used: location within 3' of Eta Car, an appropriate V and B-V combination, and proper motion (where available). Color and magnitude cuts have been made assuming an E(B-V) =0.55 mag +/- 0.1, which is a good approximation close to the center of Trumpler 16. These lists have been cross-correlated with X-ray sources found in the Chandra Carina Complex Project (CCCP). Previous studies have shown that only very rarely (if at all) do late main sequence B stars produce X-rays. We present evidence that the X-ray detected sources are binaries with low-mass companions, since stars less massive than 1.4 Msun are strong X-ray sources at the age of the cluster. Both the median X-ray energies and X-ray luminosities of these sources are in good agreement with values for typical low-mass coronal X-ray sources. We find that 39% of the late B stars based on a list with proper motions have low-mass companions. Similarly, 32% of a sample without proper motions have low-mass companions. We discuss the X-ray detection completeness. These results on low-mass companions of intermediate mass stars are complementary to spectroscopic and interferometric results, and probe new parameter space of low mass companions at all separations. They do not support a steeply rising distribution of mass ratios to low masses for intermediate-mass (5 Msun) primaries, such as would be found by random pairing from the Initial Mass Function.Comment: Accepted for the ApJS Special Issue on the Chandra Carina Complex Project (CCCP), scheduled for publication in May 2011. All 16 CCCP Special Issue papers are available at http://cochise.astro.psu.edu/Carina_public/special_issue.html through 2011 at leas

Observation of Replica Symmetry Breaking in the 1D Anderson Localization Regime in an Erbium-Doped Random Fiber Laser

The analogue of the paramagnetic to spin-glass phase transition in disordered magnetic systems, leading to the phenomenon of replica symmetry breaking, has been recently demonstrated in a two-dimensional random laser consisting of an organic-based amorphous solid-state thin film. We report here the first demonstration of replica symmetry breaking in a one-dimensional photonic system consisting of an erbium-doped random fiber laser operating in the continuous-wave regime based on a unique random fiber grating system, which plays the role of the random scatterers and operates in the Anderson localization regime. The clear transition from a photonic paramagnetic to a photonic spin glass phase, characterized by the probability distribution function of the Parisi overlap, was verified and characterized. In this unique system, the radiation field interacts only with the gain medium, and the fiber grating, which provides the disordered feedback mechanism, does not interfere with the pump

A nearby young M dwarf with a wide, possibly planetary-mass companion

We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the $\sim$45 Myr old Tucana Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708~\AA~absorption consistent with M dwarfs younger than TucHor but older than the $\sim$10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the $\sim$24 Myr old $\beta$ Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6--15 M$_J$ for the secondary. It is thus likely 2MASS J21265040-8140293short is the widest orbit planetary mass object known ($>$4500AU) and its estimated mass, age, spectral type, and $T_{eff}$ are similar to the well-studied planet $\beta$ Pictoris b. Because of their extreme separation and youth, this low-mass pair provide an interesting case study for very wide binary formation and evolution.Peer reviewedFinal Accepted Versio