Strong late-time circumstellar interaction in the peculiar supernova iPTF14hls

We present a moderate-resolution spectrum of the peculiar Type II supernova iPTF14hls taken on day 1153 after discovery. This spectrum reveals the clear signature of shock interaction with dense circumstellar material (CSM). We suggest that this CSM interaction may be an important clue for understanding the extremely unusual photometric and spectroscopic evolution seen over the first 600 days of iPTF14hls. The late-time spectrum shows a double-peaked intermediate-width H-alpha line indicative of expansion speeds around 1000 km/s, with the double-peaked shape hinting at a disc-like geometry in the CSM. If the CSM was highly asymmetric, perhaps in a disc or torus that was ejected from the star 3-6 years prior to explosion, then the CSM interaction could have been overrun and hidden below the SN ejecta photosphere from a wide range of viewing angles. In that case, CSM interaction luminosity would have been thermalized well below the photosphere, possibly sustaining the high luminosity without exhibiting the traditional observational signatures of strong CSM interaction (narrow H-alpha emission and X-rays). Variations in density structure of the CSM could account for the multiple rebrightenings of the lightcurve. We propose that enveloped CSM interaction as seen in some recent SNe, rather than an entirely new explosion mechanism, may be adequate to explain the peculiar evolution of iPTF14hls.Comment: 6 pages, 5 figures, submitted to MNRAS with referee respons

Massive stars dying alone: The extremely remote environment of SN 2009ip

We present late-time HST images of the site of supernova (SN) 2009ip taken almost 3 yr after its bright 2012 luminosity peak. SN 2009ip is now slightly fainter in broad filters than the progenitor candidate detected by HST in 1999. The current source continues to be dominated by ongoing late-time CSM interaction that produces strong H-alpha emission and a weak pseudo-continuum, as found previously for 1-2 yr after explosion. The intent of these observations was to search for evidence of recent star formation in the local (1kpc; 10 arcsec) environment around SN 2009ip, in the remote outskirts of its host spiral galaxy NGC 7259. We can rule out the presence of any massive star-forming complexes like 30 Dor or the Carina Nebula at the SN site or within a few kpc. If the progenitor of SN 2009ip was really a 50-80 Msun star as archival HST images suggested, then it is strange that there is no sign of this type of massive star formation anywhere in the vicinity. A possible explanation is that the progenitor was the product of a merger or binary mass transfer, rejuvenated after a lifetime that was much longer than 4-5 Myr, allowing its natal H II region to have faded. A smaller region like the Orion Nebula would be an unresolved but easily detected point source. This is ruled out within 1.5 kpc around SN 2009ip, but a small H II region could be hiding in the glare of SN 2009ip itself. Later images after a few more years have passed are needed to confirm that the progenitor candidate is truly gone and to test for the presence of a small H II region or cluster at the SN position.Comment: 8 pages, 5 figs. submitted to MNRA

The Role of Slp-76 Phosphotyrosines in TCR Signal Transduction and T Cell Differentiation

The cytosolic adapter protein src homology 2(SH2) domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) lacks enzymatic activity but nucleates a multi-molecular signaling complex that links early T cell receptor (TCR)-induced phosphorylation events into multiple downstream signaling pathways. The N-terminus of SLP-76 contains three tyrosines at residues 112,128 and 145 that are phosphorylated following TCR ligation and, although the mechanisms are not entirely clear, they are required for optimal TCR signal transduction. TCR signals are required for T cell proliferation, cytokine production, and effector and memory differentiation. The experiments described in this dissertation have first tested the biochemical mechanisms by which the SLP-76 tyrosines transmit signals and second tested how alterations in the TCR signals transmitted through SLP-76 tyrosines influence T cell differentiation and effector function. Experiments were performed using two genomic knock-in (KI) mice that express tyrosine to phenylalanine mutations at residue 145 (Y145F) or 112 and 128 together (Y112/128F). Using biochemistry-, flow cytometry- and microscopy-based approaches we show that mutations in the tyrosines of SLP-76 result in graded defects in TCR-induced signals and function depending on the tyrosine(s) affected. Surprisingly, localization of SH2 domain containing effector proteins to mutant SLP-76-nucleated signaling complexes was not lost and therefore could not account for the observed signaling defects. Infection of SLP-76 KI mice with lymphocytic choriomeningitis virus (LCMV) resulted in normal CD8 expansion but graded enhancement of memory differentiation consistent with a model in which weaker TCR signals preferentially promote memory versus effector differentiation. Furthermore CD8+ effector and memory KI T cells failed to produce appropriate cytokine upon antigen restimulation. Similarly, in vitro polarized KI Th17 and Th2 cells failed to produce IL17a and IL4, respectively, following TCR restimulation. Taken together our data show that SLP-76 tyrosines are essential for optimal TCR signal transduction and, moreover, TCR signals sufficient to promote T cell differentiation are different than those required to elicit inflammatory cytokine production

Effects of reduced dissolved oxygen concentrations on physiology and fluorescence of hermatypic corals and benthic algae.

While shifts from coral to seaweed dominance have become increasingly common on coral reefs and factors triggering these shifts successively identified, the primary mechanisms involved in coral-algae interactions remain unclear. Amongst various potential mechanisms, algal exudates can mediate increases in microbial activity, leading to localized hypoxic conditions which may cause coral mortality in the direct vicinity. Most of the processes likely causing such algal exudate induced coral mortality have been quantified (e.g., labile organic matter release, increased microbial metabolism, decreased dissolved oxygen availability), yet little is known about how reduced dissolved oxygen concentrations affect competitive dynamics between seaweeds and corals. The goals of this study were to investigate the effects of different levels of oxygen including hypoxic conditions on a common hermatypic coral Acropora yongei and the common green alga Bryopsis pennata. Specifically, we examined how photosynthetic oxygen production, dark and daylight adapted quantum yield, intensity and anatomical distribution of the coral innate fluorescence, and visual estimates of health varied with differing background oxygen conditions. Our results showed that the algae were significantly more tolerant to extremely low oxygen concentrations (2-4 mg L(-1)) than corals. Furthermore corals could tolerate reduced oxygen concentrations, but only until a given threshold determined by a combination of exposure time and concentration. Exceeding this threshold led to rapid loss of coral tissue and mortality. This study concludes that hypoxia may indeed play a significant role, or in some cases may even be the main cause, for coral tissue loss during coral-algae interaction processes

Best Practices for English Learners with Disabilities in US Schools – A Systematic Review

This systematic review investigated best practices for enhancing academic achievement among English Learners with Disabilities (ELDs) in US schools. By examining 17 peer-reviewed articles and comparing them to the CEC 2014 Quality Indicators, the study identifies significant practices, including culturally responsive methods, technology integration, evidence-based strategies, addressing service delivery challenges, and improving assessment tools. This review has limitations related to inconsistent terminology and highlights the need for standardized language and continued research. It recommends integrating culturally responsive practices, leveraging technology, and refining inclusive assessment tools. This review provides educators, policymakers, and researchers insights, emphasizing ongoing teacher development and policy alignment to optimize support for ELDs’ academic success

A new method to measure galaxy bias

We present a new approach for modelling galaxy/halo bias that utilizes the full non-linear information contained in the moments of the matter density field, which we derive using a set of numerical simulations. Although our method is general, we perform a case study based on the local Eulerian bias scheme truncated to second order. Using 200 N-body simulations covering a total comoving volume of 675 h-3 Gpc3, we measure several two- and three-point statistics of the halo distribution to unprecedented accuracy. We use the bias model to fit the halo-halo power spectrum, the halo-matter cross-spectrum and the corresponding three bispectra for wavenumbers in the range 0.04 ≲ k ≲ 0.12 h Mpc-1. We find that the constraints on the bias parameters obtained using the full non-linear information differ significantly from those derived using standard perturbation theory at leading order. Hence, neglecting the full non-linear information leads to biased results for this particular scale range. We also test the validity of the second-order Eulerian local biasing scheme by comparing the parameter constraints derived from different statistics. Analysis of the halo-matter cross-correlation coefficients defined for the two- and three-point statistics reveals further inconsistencies contained in the second-order Eulerian bias scheme, suggesting it is too simple a model to describe halo bias with high accuracy

Modelling large-scale halo bias using the bispectrum

We study the relation between the density distribution of tracers for large-scale structure and the underlying matter distribution - commonly termed bias - in the Λ cold dark matter framework. In particular, we examine the validity of the local model of biasing at quadratic order in the matter density. This model is characterized by parameters b1 and b2. Using an ensemble of N-body simulations, we apply several statistical methods to estimate the parameters. We measure halo and matter fluctuations smoothed on various scales. We find that, whilst the fits are reasonably good, the parameters vary with smoothing scale. We argue that, for real-space measurements, owing to the mixing of wavemodes, no smoothing scale can be found for which the parameters are independent of smoothing. However, this is not the case in Fourier space. We measure halo and halo-mass power spectra and from these construct estimates of the effective large-scale bias as a guide for b1. We measure the configuration dependence of the halo bispectra Bhhh and reduced bispectra Qhhh for very large-scale k-space triangles. From these data, we constrain b1 and b2, taking into account the full bispectrum covariance matrix. Using the lowest order perturbation theory, we find that for Bhhh the best-fitting parameters are in reasonable agreement with one another as the triangle scale is varied, although the fits become poor as smaller scales are included. The same is true for Qhhh. The best-fitting values were found to depend on the discreteness correction. This led us to consider halo-mass cross-bispectra. The results from these statistics supported our earlier findings. We then developed a test to explore whether the inconsistency in the recovered bias parameters could be attributed to missing higher order corrections in the models. We prove that low-order expansions are not sufficiently accurate to model the data, even on scales k1∼ 0.04 h Mpc−1. If robust inferences concerning bias are to be drawn from future galaxy surveys, then accurate models for the full non-linear bispectrum and trispectrum will be essentia