Intrinsic and extrinsic geometries of a tidally deformed black hole

A description of the event horizon of a perturbed Schwarzschild black hole is provided in terms of the intrinsic and extrinsic geometries of the null hypersurface. This description relies on a Gauss-Codazzi theory of null hypersurfaces embedded in spacetime, which extends the standard theory of spacelike and timelike hypersurfaces involving the first and second fundamental forms. We show that the intrinsic geometry of the event horizon is invariant under a reparameterization of the null generators, and that the extrinsic geometry depends on the parameterization. Stated differently, we show that while the extrinsic geometry depends on the choice of gauge, the intrinsic geometry is gauge invariant. We apply the formalism to solutions to the vacuum field equations that describe a tidally deformed black hole. In a first instance we consider a slowly-varying, quadrupolar tidal field imposed on the black hole, and in a second instance we examine the tide raised during a close parabolic encounter between the black hole and a small orbiting body.Comment: 27 pages, 4 figure

On the cross-section of Dark Matter using substructure infall into galaxy clusters

We develop a statistical method to measure the interaction cross-section of Dark Matter, exploiting the continuous minor merger events in which small substructures fall into galaxy clusters. We find that by taking the ratio of the distances between the galaxies and Dark Matter, and galaxies and gas in accreting sub-halos, we form a quantity that can be statistically averaged over a large sample of systems whilst removing any inherent line-of-sight projections. In order to interpret this ratio as a cross-section of Dark Matter we derive an analytical description of sub-halo infall which encompasses; the force of the main cluster potential, the drag on a gas sub-halo, a model for Dark Matter self-interactions and the resulting sub-halo drag, the force on the gas and galaxies due to the Dark Matter sub-halo potential, and finally the buoyancy on the gas and Dark Matter. We create mock observations from cosmological simulations of structure formation and find that collisionless Dark Matter becomes physically separated from X-ray gas by up to 20h^-1 kpc. Adding realistic levels of noise, we are able to predict achievable constraints from observational data. Current archival data should be able to detect a difference in the dynamical behaviour of Dark Matter and standard model particles at 6 sigma, and measure the total interaction cross-section sigma/m with 68% confidence limits of +/- 1cm2g^-1. We note that this method is not restricted by the limited number of major merging events and is easily extended to large samples of clusters from future surveys which could potentially push statistical errors to 0.1cm^2g^-1.Comment: 14 pages, 11 figure

Drought-related issues in forage, silage and baleage

Eric Bailey, beef extension specialist; Joe Horner, agricultural economics specialist; Robert Kallenbach, forage production and management specialist; Ray Massey, agricultural economics specialist; Craig Roberts, agronomy specialist; Peter Scharf, agronomy specialist; William Wiebold, agronomy specialistNew 8/12; Revised 8/18University of Missouri ExtensionThe extreme drought of 2018 in the Midwest region has forced livestock producers to be concerned with drought effects such as high levels of nitrates in forage and drought-damaged crops for silage and baleage. Many producers are now searching for alternative feeding options for livestock. In addition to safety and herd health issues, these factors affect the business decisions for each operation. In response to producers’ concerns, University of Missouri Extension has developed this list of producers’ questions answered by extension crop and forage specialists

Drought-related issues in forage, silage and baleage

"Drought often changes the composition of forages. Issues such as nitrate accumulation and reduced nutritive value often cause problems for farmers using drought-damaged forages. Many producers are now searching for alternative feeding options for livestock. In response to producers' concerns, University of Missouri Extension has developed this list of producers' questions answered by extension crop and forage specialists."--Page 1.Eric Bailey (Beef Extension Specialist), Joe Horner (Agricultural Economics Specialist), Robert Kallenbach (Forage Production and Management Specialist), Ray Massey (Agricultural Economics Specialist), Craig Roberts (Agronomy Specialist), Peter Scharf (Agronomy Specialist), William Wiebold (Agronomy Specialist

The Effect of Flipped Instruction on Special Education Preservice Teachers\u27 Perceptions

This study analyzes the flipped instruction model used in three special education educator preparation courses to examine which components preservice teachers perceived most contributed to their content knowledge, motivation, and engagement (n=50). Weekly pre-class asynchronous assignments included the use of educational technology tools such as an interactive e-textbook site, Perusall, and online academic activities such as Khan Academy to strengthen their content knowledge. This allowed more time for a student-centered approach during synchronous instruction to incorporate tools such as Nearpod, Pear Deck, Flipgrid and digital badges to strength-en their motivation and engagement. Data were collected through a post-course survey; results indicate that preservice teachers perceived this model was motivating, engaging, and contributed significantly to their content knowledge. They also identified hands-on activities during class as a significant component of their learning. This article discusses the project, limitations, and implications for future flipped instruction research in special education educator preparation programs

The Effect of Flipped Instruction on Special Education Preservice Teachers\u27 Perceptions

This study analyzes the flipped instruction model used in three special education educator preparation courses to examine which components preservice teachers perceived most contributed to their content knowledge, motivation, and engagement (n=50). Weekly pre-class asynchronous assignments included the use of educational technology tools such as an interactive e-textbook site, Perusall, and online academic activities such as Khan Academy to strengthen their content knowledge. This allowed more time for a student-centered approach during synchronous instruction to incorporate tools such as Nearpod, Pear Deck, Flipgrid and digital badges to strength-en their motivation and engagement. Data were collected through a post-course survey; results indicate that preservice teachers perceived this model was motivating, engaging, and contributed significantly to their content knowledge. They also identified hands-on activities during class as a significant component of their learning. This article discusses the project, limitations, and implications for future flipped instruction research in special education educator preparation programs

The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827

Galaxy cluster Abell 3827 hosts the stellar remnants of four almost equally bright elliptical galaxies within a core of radius 10kpc. Such corrugation of the stellar distribution is very rare, and suggests recent formation by several simultaneous mergers. We map the distribution of associated dark matter, using new Hubble Space Telescope imaging and VLT/MUSE integral field spectroscopy of a gravitationally lensed system threaded through the cluster core. We find that each of the central galaxies retains a dark matter halo, but that (at least) one of these is spatially offset from its stars. The best-constrained offset is 1.62+/-0.48kpc, where the 68% confidence limit includes both statistical error and systematic biases in mass modelling. Such offsets are not seen in field galaxies, but are predicted during the long infall to a cluster, if dark matter self-interactions generate an extra drag force. With such a small physical separation, it is difficult to definitively rule out astrophysical effects operating exclusively in dense cluster core environments - but if interpreted solely as evidence for self-interacting dark matter, this offset implies a cross-section sigma/m=(1.7+/-0.7)x10^{-4}cm^2/g x (t/10^9yrs)^{-2}, where t is the infall duration.Comment: 15 pages, 9 figure

Context-Dependent Cell Cycle Checkpoint Abrogation by a Novel Kinase Inhibitor

Checkpoint kinase 1 and 2 (Chk1/Chk2), and the Aurora kinases play a critical role in the activation of the DNA damage response and mitotic spindle checkpoints. We have identified a novel inhibitor of these kinases and utilized this molecule to probe the functional interplay between these two checkpoints.Fragment screening, structure guided design, and kinase cross screening resulted in the identification of a novel, potent small molecule kinase inhibitor (VER-150548) of Chk1 and Chk2 kinases with IC(50)s of 35 and 34 nM as well as the Aurora A and Aurora B kinases with IC(50)s of 101 and 38 nM. The structural rationale for this kinase specificity could be clearly elucidated through the X-ray crystal structure. In human carcinoma cells, VER-150548 induced reduplication and the accumulation of cells with >4N DNA content, inhibited histone H3 phosphorylation and ultimately gave way to cell death after 120 hour exposure; a phenotype consistent with cellular Aurora inhibition. In the presence of DNA damage induced by cytotoxic chemotherapeutic drugs, VER-150548 abrogated DNA damage induced cell cycle checkpoints. Abrogation of these checkpoints correlated with increased DNA damage and rapid cell death in p53 defective HT29 cells. In the presence of DNA damage, reduplication could not be observed. These observations are consistent with the Chk1 and Chk2 inhibitory activity of this molecule.In the presence of DNA damage, we suggest that VER-150548 abrogates the DNA damage induced checkpoints forcing cells to undergo a lethal mitosis. The timing of this premature cell death induced by Chk1 inhibition negates Aurora inhibition thereby preventing re-entry into the cell cycle and subsequent DNA reduplication. This novel kinase inhibitor therefore serves as a useful chemical probe to further understand the temporal relationship between cell cycle checkpoint pathways, chemotherapeutic agent induced DNA damage and cell death

Efficacy and safety of tiotropium Respimat® SMI in COPD in two 1-year randomized studies

Two 1-year studies evaluated the long-term efficacy and safety of tiotropium 5 or 10 μg versus placebo, inhaled via the Respimat® Soft Mist™ Inhaler (SMI). The two studies were combined and had 4 co-primary endpoints (trough FEV1 response, Mahler Transition Dyspnea Index [TDI] and St George’s Respiratory Questionnaire scores all at week 48, and COPD exacerbations per patient-year). A total of 1990 patients with COPD participated (mean FEV1: 1.09 L). The mean trough FEV1 response of tiotropium 5 or 10 μg relative to placebo was 127 or 150 mL, respectively (both P < 0.0001). The COPD exacerbation rate was significantly lower with tiotropium 5 μg (RR = 0.78; P = 0.002) and tiotropium 10 μg (RR = 0.73; P = 0.0008); the health-related quality of life and Mahler TDI co-primary endpoints were significantly improved with both doses (both P < 0.0001). Adverse events were generally balanced except anticholinergic class effects, which were more frequent with active treatment. Fatal events occurred in 2.4% (5 μg), 2.7% (10 μg), and 1.6% (placebo) of patients; these differences were not significant. Tiotropium Respimat® SMI 5 μg demonstrated sustained improvements in patients with COPD relative to placebo and similar to the 10 μg dose but with a lower frequency of anticholinergic adverse events