Pseudo-Riemannian geodesic foliations by circles

We investigate under which assumptions an orientable pseudo-Riemannian geodesic foliations by circles is generated by an $S^1$-action. We construct examples showing that, contrary to the Riemannian case, it is not always true. However, we prove that such an action always exists when the foliation does not contain lightlike leaves, i.e. a pseudo-Riemannian Wadsley's Theorem. As an application, we show that every Lorentzian surface all of whose spacelike/timelike geodesics are closed, is finitely covered by $S^1\times \R$. It follows that every Lorentzian surface contains a non-closed geodesic.Comment: 14 page

The Chemical and Dynamical Evolution of Isolated Dwarf Galaxies

Using a suite of simulations (Governato et al. 2010) which successfully produce bulgeless (dwarf) disk galaxies, we provide an analysis of their associated cold interstellar media (ISM) and stellar chemical abundance patterns. A preliminary comparison with observations is undertaken, in order to assess whether the properties of the cold gas and chemistry of the stellar components are recovered successfully. To this end, we have extracted the radial and vertical gas density profiles, neutral hydrogen velocity dispersion, and the power spectrum of structure within the ISM. We complement this analysis of the cold gas with a brief examination of the simulations' metallicity distribution functions and the distribution of alpha-elements-to-iron.Comment: To appear in the proceedings of the JENAM 2010 Symposium "Dwarf Galaxies: Keys to Galaxy Formation and Evolution" (Lisbon, 9-10 September 2010), P. Papaderos, S. Recchi, G. Hensler (eds.), Springer Verlag (2011), in pres

Faint AGN and the Ionizing Background

We determine the evolution of the faint, high-redshift, optical luminosity function (LF) of AGN implied by several observationally-motivated models of the ionizing background. Our results depend crucially on whether we use the total ionizing rate measured by the proximity effect technique or the lower determination from the flux decrement distribution of Ly alpha forest lines. Assuming a faint-end LF slope of 1.58 and the SDSS estimates of the bright-end slope and normalization, we find that the LF must break at M_B*=-24.2,-22.3, -20.8 at z=3,4, 5 if we adopt the lower ionization rate and assume no stellar contribution to the background. The break must occur at M_B*=-20.6,-18.7, -18.7 for the proximity effect background estimate. These values brighten by as much as ~2 mag if high-z galaxies contribute to the background with an escape fraction of ionizing photons consistent with recent estimates: f_e=0.16. By comparing to faint AGN searches, we find that the typically-quoted proximity effect estimates of the background imply an over-abundance of faint AGN (even with f_e=1). Even adopting the lower bound on proximity effect measurements, the stellar escape fraction must be high: f_e>0.2. Conversely, the lower flux- decrement-derived background requires a limited stellar contribution: f_e<0.05. Our derived LFs together with the locally-estimated black hole density suggest that the efficiency of converting mass to light in optically-unobscured AGN is somewhat lower than expected, <0.05. Comparison with similar estimates based on X-ray counts suggests that more than half of all AGN are obscured in the UV/optical. We also derive lower limits on typical AGN lifetimes and obtain >10^7 yrs for favored cases.Comment: 19 pages, 16 figures. Accepted by Astrophysical Journa

The Formation of a Realistic Disk Galaxy in Lambda Dominated Cosmologies

We simulate the formation of a realistic disk galaxy within the hierarchical scenario of structure formation and study its internal properties to the present epoch. We compare results from a LambdaCDM simulation with a LambdaWDM (2keV) simulation that forms significantly less small scale structure. We show how high mass and force resolution in both the gas and dark matter components play an important role in solving the angular momentum catastrophe claimed from previous simulations of galaxy formation within the hierarchical framework. The stellar material in the disk component has a final specific angular momentum equal to 40% and 90% of that of the dark halo in the LambdaCDM and LambdaWDM models respectively. The LambdaWDM galaxy has a drastically reduced satellite population and a negligible stellar spheroidal component. Encounters with satellites play only a minor role in disturbing the disk. Satellites possess a variety of star formation histories linked to mergers and pericentric passages along their orbit around the primary galaxy. In both cosmologies, the galactic halo retains most of the baryons accreted and builds up a hot gas phase with a substantial X-ray emission. Therefore, while we have been successful in creating a realistic stellar disk in a massive galaxy within the LambdaCDM scenario, energy injection emerges as necessary ingredient to reduce the baryon fraction in galactic halos, independent of the cosmology adopted. (abridged)Comment: ApJ in press. Images and movies at http://hpcc.astro.washington.edu/faculty/fabio/galform.html Significantly expanded revised version. (9 pages vs the original 4

Systematic review of health-related quality of life following thyroid cancer.

This systematic review provides a summary of all studies published between 2000 and 2019 using a health-related quality of life (HRQOL) patient-completed questionnaire to report outcomes following diagnosis and treatment of thyroid cancer. The search terms were "thyroid cancer" or "thyroid carcinoma," "quality of life" or "health related quality of life," and "questionnaire" or "patient reported outcome." EMBASE, PubMed, Medline, PsycINFO, CINAHL, and HaNDLE-On-QOL search engines were searched between 2 February and 23 February 2020. A total of 811 identified articles were reduced to 314 when duplicates were removed. After exclusion criteria (not thyroid specific, no quality of life questionnaires, and conference abstracts) were applied, 92 remained. Hand searching identified a further 2 articles. Of the 94 included, 16 had a surgical, 26 a primarily medical, and 52 a general focus. There were articles from 27 countries. A total of 49 articles were published from 2015 through 2019 inclusive. A total of 72 questionnaires were used among the articles and a range of 7 to 2215 participants were included within each article. This review demonstrated an increasing number of publications annually. The scope of enquiry into aspects of HRQOL following thyroid cancer is broad, with relatively few addressing surgical aspects and many focusing on the impact of radio-iodine. More research is required into shared decision-making in initial management decisions and HRQOL and interventions aimed specifically at addressing long-term HRQOL difficulties

Clinically Actionable Insights into Initial and Matched Recurrent Glioblastomas to Inform Novel Treatment Approaches

© 2019 H. P. Ellis et al. Glioblastoma is the most common primary adult brain tumour, and despite optimal treatment, the median survival is 12-15 months. Patients with matched recurrent glioblastomas were investigated to try to find actionable mutations. Tumours were profiled using a validated DNA-based gene panel. Copy number variations (CNVs) and single nucleotide variants (SNVs) were examined, and potentially pathogenic variants and clinically actionable mutations were identified. The results revealed that glioblastomas were IDH-wildtype (IDHWT; n = 38) and IDH-mutant (IDHMUT; n = 3). SNVs in TSC2, MSH6, TP53, CREBBP, and IDH1 were variants of unknown significance (VUS) that were predicted to be pathogenic in both subtypes. IDHWT tumours had SNVs that impacted RTK/Ras/PI(3)K, p53, WNT, SHH, NOTCH, Rb, and G-protein pathways. Many tumours had BRCA1/2 (18%) variants, including confirmed somatic mutations in haemangioblastoma. IDHWT recurrent tumours had fewer pathways impacted (RTK/Ras/PI(3)K, p53, WNT, and G-protein) and CNV gains (BRCA2, GNAS, and EGFR) and losses (TERT and SMARCA4). IDHMUT tumours had SNVs that impacted RTK/Ras/PI(3)K, p53, and WNT pathways. VUS in KLK1 was possibly pathogenic in IDHMUT. Recurrent tumours also had fewer pathways (p53, WNT, and G-protein) impacted by genetic alterations. Public datasets (TCGA and GDC) confirmed the clinical significance of findings in both subtypes. Overall in this cohort, potentially actionable variation was most often identified in EGFR, PTEN, BRCA1/2, and ATM. This study underlines the need for detailed molecular profiling to identify individual GBM patients who may be eligible for novel treatment approaches. This information is also crucial for patient recruitment to clinical trials