The Magellanic Stream: break up and accretion onto the hot Galactic corona

The Magellanic HI Stream (~2x10^9 Msun [d/55 kpc]^2) encircling the Galaxy at a distance 'd' is arguably the most important tracer of what happens to gas accreting onto a disk galaxy. Recent observations reveal that the Stream's mass is in fact dominated (3:1) by its ionised component. Here we revisit the origin of the mysterious H-alpha recombination emission observed along much of its length that is overly bright (~150-200 milli-Rayleigh) for the known Galactic ultraviolet background (~20-40 mR / [d/55 kpc]^2). In an earlier model, we proposed that a slow shock cascade was operating along the Stream due to its interaction with the extended Galactic hot corona. We find that, for a smooth coronal density profile, this model can explain the bright H-alpha emission if the coronal density satisfies 2 < (n / 10^{-4} cm^{-3}) < 4 at d = 55 kpc. But in view of updated parameters for the Galactic halo and mounting evidence that most of the Stream must lie far beyond the Magellanic Clouds (d>55 kpc), we revisit the shock cascade model in detail. At lower densities, the HI gas is broken down by the shock cascade but mostly mixes with the hot corona without significant recombination. At higher densities, the hot coronal mass (including the other baryonic components) exceeds the baryon budget of the Galaxy. If the H-alpha emission arises from the shock cascade, the upper limit on the smooth coronal density constrains the Stream's mean distance to < 75 kpc. If, as some models indicate, the Stream is even further out, either the shock cascade is operating in a regime where the corona is substantially mass-loaded with recent gas debris, or an entirely different ionization mechanism is responsible.Comment: Significant expansion of the parameter space explored in response to referee's comments. ApJ accepte

Degeneracies between Modified Gravity and Baryonic Physics

In order to determine the observable signatures of modified gravity theories, it is important to consider the effect of baryonic physics. We use a modified version of the ISIS code to run cosmological hydrodynamic simulations to study degeneracies between modified gravity and radiative hydrodynamical processes. Of these, one was the standard $\Lambda$CDM model and four were variations of the Symmetron model. For each model we ran three variations of baryonic processes: non-radiative hydrodynamics; cooling and star formation; and cooling, star formation, and supernova feedback. We construct stacked gas density, temperature, and dark matter density profiles of the halos in the simulations, and study the differences between them. We find that both radiative variations of the models show degeneracies between their processes and at least two of the three parameters defining the Symmetron model.Comment: 9 pages, 4 figures, matches version accepted to A&

Transgenerational effects alleviate severe fecundity loss during ocean acidification in a ubiquitous planktonic copepod

Ocean acidification (OA) caused by anthropogenic CO2 emission is projected for thousands of years to come, and significant effects are predicted for many marine organisms. While significant evolutionary responses are expected during such persistent environmental change, most studies consider only short-term effects. Little is known about the transgenerational effects of parental environments or natural selection on the capacity of populations to counter detrimental OA effects. In this study, six laboratory populations of the calanoid copepod Pseudocalanus acuspes were established at three different CO2 partial pressures (pCO2 of 400, 900 and 1550 μatm) and grown for two generations at these conditions. Our results show evidence of alleviation of OA effects as a result of transgenerational effects in P. acuspes. Second generation adults showed a 29% decrease in fecundity at 900 μatm CO2 compared to 400 μatm CO2. This was accompanied by a 10% increase in metabolic rate indicative of metabolic stress. Reciprocal transplant tests demonstrated that this effect was reversible and the expression of phenotypic plasticity. Furthermore, these tests showed that at a pCO2 exceeding the natural range experienced by P. acuspes (1550 μatm), fecundity would have decreased by as much as 67% compared to at 400 μatm CO2 as a result of this plasticity. However, transgenerational effects partly reduced OA effects so that the loss of fecundity remained at a level comparable to that at 900 μatm CO2. This also relieved the copepods from metabolic stress, and respiration rates were lower than at 900 μatm CO2. These results highlight the importance of tests for transgenerational effects to avoid overestimation of the effects of OA

Economic Analysis of Incentives for Foreign Direct Investment in Beef Systems in Argentina and Uruguay

The European Union's (EU) ban of hormone-treated beef products in 1989 has virtually eliminated beef exports to the EU from countries where cattle are routinely implanted with growth hormones. This study examined whether or not foreign direct investment in beef systems in Argentina and Uruguay would provide a profitable method for investors who want to export beef to the EU. The results indicate that while investment in these systems is potentially profitable, government interventions designed to keep domestic beef prices low inject considerable risk into the investment decision.Investment in beef systems, South America, risk, cointegration, International Relations/Trade, Livestock Production/Industries,

Student preferences impact outcome of flipped classroom in dental education: Students favoring flipped classroom benefited more

Many reports in dental education showed that student learning improved with the flipped classroom method. However, there are few reports that describe how different subsets of students may benefit from the flipped classroom. In this study, we investigated how students’ preference for the flipped classroom impacted their learning outcome. We used a flipped classroom module on the physiology of the autonomic nervous system taught to year one Doctor of Dental Surgery students to test the hypothesis that students who favored the flipped classroom performed better on assessment quizzes. The module was composed of pre-class activity, out-of-class assignment, in-class discussion, and two in-class quizzes. Quiz 1 was given after students self-studied the foundational content online through the pre-class activity, and Quiz 2 was at the end of the module. Students filled out a survey to report learning experiences and preferences. Fewer students scored below 75% on Quiz 2 than on Quiz 1. Students’ self-evaluated understanding of content significantly improved after finishing the assignment and discussion compared to finishing the pre-class activity alone. Moreover, students who preferred to learn through the flipped classroom scored higher in Quiz 2. Students with higher overall grades in the course preferred the flipped classroom more than low performers. Our results indicated that students favoring the flipped classroom method spent more time on the assignment, understood the content better, and performed better on assessments than students who prefer traditional lectures

Metformin Activity against Breast Cancer: Mechanistic Differences by Molecular Subtype and Metabolic Conditions

Obesity and type 2 diabetes increase the risk of and reduce survival in breast cancer (BC) patients. Metformin is the only anti-diabetic drug that alters this risk, with a reduction in BC incidence and improved outcomes. Metformin has AMP-kinase (AMPK) dependent and independent mechanisms of action, most notably affecting the liver and skeletal muscle. We and others have shown that metformin also downregulates protein and lipid synthesis; deactivates various receptor tyrosine kinases; alters cell cycle transcription/translation; modulates mitochondrial respiration and miRNA activation; targets key metabolic molecules; induces stem cell death and may induce apoptosis or autophagy in BC cells. Many of these anti-cancer effects are molecular subtype-specific. Metformin is most potent against triple negative (basal), followed by luminal BCs. The efficacy of metformin, as well as dose needed for the activity, is also modulated by the extracellular glucose concentration, cellular expression of the glucose transporter protein 1 (GLUT1), and the organic cation transporter protein 1 (OCT1, which transports metformin into cells). This chapter summarizes the diverse clinical and preclinical data related to the anti-cancer effects of metformin, focused against breast cancer

Century-scale trends and seasonality in pH and temperature for shallow zones of the Bering Sea

No records exist to evaluate long-term pH dynamics in high-latitude oceans, which have the greatest probability of rapid acidification from anthropogenic CO2 emissions. We reconstructed both seasonal variability and anthropogenic change in seawater pH and temperature by using laser ablation high-resolution 2D images of stable boron isotopes (δ11B) on a long-lived coralline alga that grew continuously through the 20th century. Analyses focused on four multiannual growth segments. We show a long-term decline of 0.08 ± 0.01 pH units between the end of the 19th and 20th century, which is consistent with atmospheric CO2 records. Additionally, a strong seasonal cycle (∼0.22 pH units) is observed and interpreted as episodic annual pH increases caused by the consumption of CO2 during strong algal (kelp) growth in spring and summer. The rate of acidification intensifies from –0.006 ± 0.007 pH units per decade (between 1920s and 1960s) to –0.019 ± 0.009 pH units per decade (between 1960s and 1990s), and the episodic pH increases show a continuous shift to earlier times of the year throughout the centennial record. This is indicative of ecosystem shifts in shallow water algal productivity in this high-latitude habitat resulting from warming and acidification

Robot acting on moving bodies (RAMBO): Preliminary results

A robot system called RAMBO is being developed. It is equipped with a camera, which, given a sequence of simple tasks, can perform these tasks on a moving object. RAMBO is given a complete geometric model of the object. A low level vision module extracts and groups characteristic features in images of the object. The positions of the object are determined in a sequence of images, and a motion estimate of the object is obtained. This motion estimate is used to plan trajectories of the robot tool to relative locations nearby the object sufficient for achieving the tasks. More specifically, low level vision uses parallel algorithms for image enchancement by symmetric nearest neighbor filtering, edge detection by local gradient operators, and corner extraction by sector filtering. The object pose estimation is a Hough transform method accumulating position hypotheses obtained by matching triples of image features (corners) to triples of model features. To maximize computing speed, the estimate of the position in space of a triple of features is obtained by decomposing its perspective view into a product of rotations and a scaled orthographic projection. This allows the use of 2-D lookup tables at each stage of the decomposition. The position hypotheses for each possible match of model feature triples and image feature triples are calculated in parallel. Trajectory planning combines heuristic and dynamic programming techniques. Then trajectories are created using parametric cubic splines between initial and goal trajectories. All the parallel algorithms run on a Connection Machine CM-2 with 16K processors