Majorite-Garnet Partitioning of the Highly Siderophile Elements: New Results and Application to Mars

HSE and Os isotopes are used to constrain processes such as accretion, mantle evolution, crustal recycling, and core-mantle mixing, and to constrain the timing and depth of differentiation of Mars. Although showed that the HSE contents of the martian mantle could have been established by metal-silicate equilibrium in early Mars, the role of a cooling magma ocean and associated crystallization in further fractionating the HSEs is unclear. Garnet is thought to have played an important role in controlling trace element concentrations in the martian mantle reservoirs. However, testing these models, including Os isotopes, has been hindered by a dearth of partitioning data for the HSE in deep mantle phases - majorite, wadsleyite, ringwoodite, akimotoite - that may be present in the martian mantle. We examine the partitioning behavior of HSEs between majorite garnet (gt), olivine (oliv), and silicate liquid (melt)

Origin of Volatiles in Earth: Indigenous Versus Exogenous Sources Based on Highly Siderophile, Volatile Siderophile, and Light Volatile Elements

Origin of Earth's volatiles has traditionally been ascribed to late accretion of material after major differentiation events - chondrites, comets, ice or other exogenous sources. A competing theory is that the Earth accreted its volatiles as it was built, thus water and other building blocks were present early and during differentiation and core formation (indigenous). Here we discuss geochemical evidence from three groups of elements that suggests Earth's volatiles were acquired during accretion and did not require additional sources after differentiation

On carbon and oxygen isotope ratios in starburst galaxies: New data from NGC253 and Mrk231 and their implications

Using the IRAM 30-m telescope, CN and CO isotopologues have been measured toward the central regions of the nearby starburst galaxy NGC253 and the prototypical ultraluminous infrared galaxy Mrk231. In NGC253, the 12C/13C ratio is 40+-10. Assuming that the ratio also holds for the CO emitting gas, this yields 16O/18O = 145+-36 and 16O/17O = 1290+-365 and a 32S/34S ratio close to that measured for the local interstellar medium (20-25). No indication for vibrationally excited CN is found. Peak line intensity ratios between NGC253 and Mrk231 are ~100 for 12C16O and 12C18O J=1-0, while the ratio for 13C16O J=1-0 is ~250. This and similar 13CO and C18O line intensities in the J=1-0 and 2-1 transitions of Mrk231 suggest 12C/13C ~ 100 and 16O/18O ~ 100, in agreement with values obtained for the less evolved ultraluminous merger Arp220. Also accounting for other extragalactic data, 12C/13C ratios appear to vary over a full order of magnitude, from >100 in ultraluminous high redshift galaxies to ~100 in more local such galaxies to ~40 in weaker starbursts not undergoing a large scale merger to 25 in the Central Molecular Zone of the Milky Way. With 12C being predominantly synthesized in massive stars, while 13C is mostly ejected by longer lived lower mass stars at later times, this is qualitatively consistent with our results of decreasing carbon isotope ratios with time and rising metallicity. It is emphasized, however, that both infall of poorly processed material, initiating a nuclear starburst, as well as the ejecta from newly formed massive stars (in particular in case of a top-heavy stellar initial mass function) can raise the carbon isotope ratio for a limited amount of time.Comment: Accepted by Astronomy & Astrophysics, 6 figures, 4 table

The cosmic history of hot gas cooling and radio active galactic nucleus activity in massive early-type galaxies

We study the X-ray properties of 393 optically selected early-type galaxies (ETGs) over the redshift range of z≈ 0.0–1.2 in the Chandra Deep Fields (CDFs). To measure the average X-ray properties of the ETG population, we use X-ray stacking analyses with a subset of 158 passive ETGs (148 of which were individually undetected in X-ray). This ETG subset was constructed to span the redshift ranges of z= 0.1–1.2 in the ≈4 Ms CDF-South and ≈2 Ms CDF-North and z= 0.1–0.6 in the ≈250 ks Extended-CDF-South where the contribution from individually undetected active galactic nuclei (AGN) is expected to be negligible in our stacking. We find that 55 of the ETGs are detected individually in X-ray, and 12 of these galaxies have properties consistent with being passive hot-gas-dominated systems (i.e. systems not dominated by an X-ray bright AGN). On the basis of our analyses, we find little evolution in the mean 0.5–2 keV to B-band luminosity ratio (LX/LB∝ [1 +z]1.2) since z≈ 1.2, implying that some heating mechanism prevents the gas from cooling in these systems. We consider that feedback from radio-mode AGN activity could be responsible for heating the gas. We select radio AGN in the ETG population using their far-infrared/radio flux ratio. Our radio observations allow us to constrain the duty cycle history of radio AGN activity in our ETG sample. We estimate that if scaling relations between radio and mechanical power hold out to z≈ 1.2 for the ETG population being studied here, the average mechanical power from AGN activity is a factor of ≈1.4–2.6 times larger than the average radiative cooling power from hot gas over the redshift range z≈ 0–1.2. The excess of inferred AGN mechanical power from these ETGs is consistent with that found in the local Universe for similar types of galaxies

Seesaw Extended MSSM and Anomaly Mediation without Tachyonic Sleptons

Superconformal anomalies provide an elegant and economical way to understand the soft breaking parameters in SUSY models; however, implementing them leads to the several undesirable features including: tachyonic sleptons and electroweak symmetry breaking problems in both the MSSM and the NMSSM. Since these two theories also have the additonal problem of massless neutrinos, we have reconsidered the AMSB problems in a class of models that extends the NMSSM to explain small neutrino masses via the seesaw mechanism. In a recent paper, we showed that for a class of minimal left-right extensions, a built-in mechanism exists which naturally solves the tachyonic slepton problem and provides new alternatives to the MSSM that also have automatic R-parity conservation. In this paper, we discuss how electroweak symmetry breaking arises in this model through an NMSSM-like low energy theory with a singlet VEV, induced by the structure of the left-right extension and of the right magnitude. We then study the phenomenological issues and find: the LSP is an Higgsino-wino mix, new phenomenology for chargino decays to the LSP, degenerate same generation sleptons and a potential for a mild squark-slepton degeneracy. We also discuss possible collider signatures and the feasibility of dark matter in this model.Comment: 40 pages, 10 figures, 5 tables; v3: Added addendum and three new references; v4: Added reference that was inadvertently omitte

Cestode Species Identification on Waterfowl: Parasitology Class Project 2022

Parasites can have a significant effect on an ecosystem if they become too abundant due to the multitude of animals that play a role in their life cycle. This research is a part of a larger class project for BIO 462 identifying parasites that are commonly found in or on waterfowl from around the Winona, Minnesota area. Ducks were donated from hunters and dissected to collect their endo and ectoparasites. Parasite specimens were stained and mounted to look for morphological characteristics that ultimately helped identify the parasites using light microscopy. DNA was extracted from the individual cestodes, and PCR was used to amplify select genes of the DNA. The DNA was then sequenced then compared to other DNA samples in GenBank which determined if the parasites was already classified or if a new species was found. More specimens will be processed to obtain additional results and obtain proper identification. These findings could help identify not only what parasites are common in certain species of ducks, but also provide additional information to the abundance of parasites within waterfowl in our local area

Survey of Canadian Animal-Based Researchers' Views on the Three Rs: Replacement, Reduction and Refinement

The ‘Three Rs’ tenet (replacement, reduction, refinement) is a widely accepted cornerstone of Canadian and international policies on animal-based science. The Canadian Council on Animal Care (CCAC) initiated this web-based survey to obtain greater understanding of ‘principal investigators’ and ‘other researchers’ (i.e. graduate students, post-doctoral researchers etc.) views on the Three Rs, and to identify obstacles and opportunities for continued implementation of the Three Rs in Canada. Responses from 414 participants indicate that researchers currently do not view the goal of replacement as achievable. Researchers prefer to use enough animals to ensure quality data is obtained rather than using the minimum and potentially waste those animals if a problem occurs during the study. Many feel that they already reduce animal numbers as much as possible and have concerns that further reduction may compromise research. Most participants were ambivalent about re-use, but expressed concern that the practice could compromise experimental outcomes. In considering refinement, many researchers feel there are situations where animals should not receive pain relieving drugs because it may compromise scientific outcomes, although there was strong support for the Three Rs strategy of conducting animal welfare-related pilot studies, which were viewed as useful for both animal welfare and experimental design. Participants were not opposed to being offered “assistance” to implement the Three Rs, so long as the input is provided in a collegial manner, and from individuals who are perceived as experts. It may be useful for animal use policymakers to consider what steps are needed to make replacement a more feasible goal. In addition, initiatives that offer researchers greater practical and logistical support with Three Rs implementation may be useful. Encouragement and financial support for Three Rs initiatives may result in valuable contributions to Three Rs knowledge and improve welfare for animals used in science