THEMIS: A Parameter Estimation Framework for the Event Horizon Telescope

The Event Horizon Telescope (EHT) provides the unprecedented ability to directly resolve the structure and dynamics of black hole emission regions on scales smaller than their horizons. This has the potential to critically probe the mechanisms by which black holes accrete and launch outflows, and the structure of supermassive black hole spacetimes. However, accessing this information is a formidable analysis challenge for two reasons. First, the EHT natively produces a variety of data types that encode information about the image structure in nontrivial ways; these are subject to a variety of systematic effects associated with very long baseline interferometry and are supplemented by a wide variety of auxiliary data on the primary EHT targets from decades of other observations. Second, models of the emission regions and their interaction with the black hole are complex, highly uncertain, and computationally expensive to construct. As a result, the scientific utilization of EHT observations requires a flexible, extensible, and powerful analysis framework. We present such a framework, Themis, which defines a set of interfaces between models, data, and sampling algorithms that facilitates future development. We describe the design and currently existing components of Themis, how Themis has been validated thus far, and present additional analyses made possible by Themis that illustrate its capabilities. Importantly, we demonstrate that Themis is able to reproduce prior EHT analyses, extend these, and do so in a computationally efficient manner that can efficiently exploit modern high-performance computing facilities. Themis has already been used extensively in the scientific analysis and interpretation of the first EHT observations of M87

SYMBA: An end-to-end VLBI synthetic data generation pipeline: Simulating Event Horizon Telescope observations of M 87

Context. Realistic synthetic observations of theoretical source models are essential for our understanding of real observational data. In using synthetic data, one can verify the extent to which source parameters can be recovered and evaluate how various data corruption effects can be calibrated. These studies are the most important when proposing observations of new sources, in the characterization of the capabilities of new or upgraded instruments, and when verifying model-based theoretical predictions in a direct comparison with observational data. Aims. We present the SYnthetic Measurement creator for long Baseline Arrays (SYMBA), a novel synthetic data generation pipeline for Very Long Baseline Interferometry (VLBI) observations. SYMBA takes into account several realistic atmospheric, instrumental, and calibration effects. Methods. We used SYMBA to create synthetic observations for the Event Horizon Telescope (EHT), a millimetre VLBI array, which has recently captured the first image of a black hole shadow. After testing SYMBA with simple source and corruption models, we study the importance of including all corruption and calibration effects, compared to the addition of thermal noise only. Using synthetic data based on two example general relativistic magnetohydrodynamics (GRMHD) model images of M 87, we performed case studies to assess the image quality that can be obtained with the current and future EHT array for different weather conditions. Results. Our synthetic observations show that the effects of atmospheric and instrumental corruptions on the measured visibilities are significant. Despite these effects, we demonstrate how the overall structure of our GRMHD source models can be recovered robustly with the EHT2017 array after performing calibration steps, which include fringe fitting, a priori amplitude and network calibration, and self-calibration. With the planned addition of new stations to the EHT array in the coming years, images could be reconstructed with higher angular resolution and dynamic range. In our case study, these improvements allowed for a distinction between a thermal and a non-thermal GRMHD model based on salient features in reconstructed images

A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows

We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT

First sagittarius A* Event Horizon Telescope results. VI. Testing the black hole metric

Galaxie

First Sagittarius A* Event Horizon Telescope results. I. The shadow of the supermassive black hole in the center of the Milky Way

Galaxie

Temperature Effect On The Measurement Of Stresses In Pipelines Using Ultrasonic Lcr Waves

Stress measurement using ultrasonic techniques has emerging as one of the simplest, low cost, and fast technologies for integrity evaluation. The method consists of relating the ultrasonic wave speed with mechanical stress. Critically refracted longitudinal wave, also called Lcr wave, is the kind of wave which is most sensitive to strain and stress. Taking such technique to the field requires the knowledge about how non-controllable factors influence the measurement. Previous works identified the temperature as the main influence variable. This work deals with the magnitude of such influence. Samples of API 5L×70 steel, which is one of the most used materials for pipelines, were cut from an as-manufactured sheet and tested inside a room with controlled temperature. The magnitude of the temperature was allowed to change between 20 and 25°C. Care was taken to control the remaining influence factors. The measurement of the time-of-flight was performed using two ultrasonic transducers placed in a probe specially built for stress measuring with Lcr waves. For such probe, wave speed is proportional to time-of-flight. The same kind of transducers was used in all measurements, but their natural frequencies varied: 2.25, 3.5 and 5.0 MHz. The results showed that the time-of-flight is highly influenced by the temperature and that the coefficient of variation is between 14 and 18 ns/°C or equivalent to 50 MPa/°C. Considering that the method can measure stresses as low as 25 MPa, the temperature effect is very important and must be taken account for measurements in the field. Copyright © 2008 by ASME.16361367VIOTTI, M.R., SUTÉRIO, R., ALBERTAZZI, JR, A., KAUFMANN, G.H., Residual stress measurement using a radial in-plane speckle interferometer and laser annealing preliminary results (2004) Optics and Lasers in Engineering, 42 (1), pp. 71-84. , ELSEVIER, vLU, J., JAMES, M.R., MORDFIN, L., (1996) Comparative Study of Different Techniques, pp. 225-231. , Handbook of Measurement Residual Stresses. Lilburn: Fairmont Press, Cap. 9, pFRAGA, R.S., 2007, Avaliação da profundidade de penetração de ondas longitudinals criticamente refratadas. Master Thesis. University of Campinas - Unicamp, Campinas, SP, Brazil. 142 p. fin Portuguese]ANDRINO, M.H., Aplicação de ondas longitudinals criticamente refratadas para a medição de tensões em dutos (2007), Ph.D. Dissertation. University of Campinas, Unicamp, Campinas, SP, Brazil. 227 p, in PortuguesePAO, Y., WU, T., GAMER, U., Acoustoelastic birefringences in plastically deformed solids: Part I - Theory (1991) Journal of Applied Mechanics, 58, pp. 11-17MINICUCCI, D.J., SANTOS, A.A., ANDRINO, M.H., SANTOS, F.C., Stress Evaluation of Railroad Forged Wheels by Ultrasonic Testing (2007) Journal of Testing and Evaluation, 35 (I)BRAY, D.E., STANLEY, R.K., (1997) Nondestructive Evaluation, A Tool for Design, Service and Manufacture, , Revised Edition CRC Press. ISBN 0-8493-2655-9ROSE, J. L., 1999, Ultrasonic Waves in solid media. Cambridge University Press, Chapters 7, 18 e 19, pp. 288-306BRAY, D.E., STANLEY, R.K., Nondestructive Evaluation (1997) A tool in Design, Manufacturing, and Service, , CRC Press, Florida: Boca RatonCAETANO, S. F., 2003, Determinação das Constantes Acustoelásticas para Aço API 5L X70 para Gasodutos, University of Campinas - Unicamp, Campinas, SP, Brazil, 167 PSANTOS, R.A., Temperature Effect on Stress Measurement by Lcr Waves in API 5L X70 Steel (2007), Master Thesis. University of Campinas, Unicamp, Campinas, SP, Brazil. 150pMONTGOMERY, D.C., (2005) Design and Analysis of Experiments, , John Wiley & Sons, 643 p. ISBN: 0471316

Composição nutricional e avaliação de rótulo de rações secas para cães comercializadas em Jaboticabal-SP

Avaliaram-se 49 marcas de rações para cães adultos e filhotes comercializadas em Jaboticabal-SP. Os alimentos foram divididos em três segmentos: econômico, standard e super-premium. Nessa ordem, as rações para cães adultos apresentaram, em média, 16,9%, 20,9% e 27,8% de proteína, 9,7%, 10,5% e 15% de gordura, 6,4%, 2,9% e 1,1% de fibra e 1,9%, 1,9% e 1,4% de Ca. Para filhotes, os produtos standard e super-premium apresentaram, respectivamente, 26,1% e 31,0% de proteína, 10,8% e 15,2% de gordura, 2,6% e 2,4% de fibra, 2,1% e 1,7% de Ca e 1,6% e 1,3% de P. A porcentagem de rações cujos teores nutricionais declarados no rótulo não estavam de acordo com os encontrados nas análises de laboratório foi, para os produtos super-premium para filhotes, 80,0% para o Ca e 60,0% para a gordura; para os produtos standard para filhotes, 28,6% para proteína e 57,2% para o cálcio; para os produtos econômicos para cães adultos, 44,0% para a fibra e 33,0% para a proteína; para os produtos standard para cães adultos de 33,0% para a gordura e 50,0% para o Ca; e para os produtos super-premium para cães adultos, 50,0% para o cálcio e 33,0% para a gordura. Foram encontradas inadequações nutricionais em produtos, como teores insuficientes de proteína e altas concentrações de fibra, cálcio e fósforo.Fortynine food products for adult or juvenile dogs, commercially available in Jaboticabal, São Paulo, Brazil, were tested for nutrient composition. The products were divided into three categories: low-cost, standard and super-premium. In that order, average compositions for adult foods were 16.9%, 20.9% and 27.8% protein, 9.7%, 10.5% and 15% fat, 6.4%, 2.9% and 1.1% fiber, and 1.9%, 1.9% and 1.4% calcium. For puppy foods, the average compositions of standard and super-premium foods were 26.1% and 31% protein, 10.8% and 15.2% fat, 2.6% and 2.4% fiber, 2.1% and 1.7% Ca, and 1.6% and 1.3% P, respectively. The percentages of products whose published label values were in disagreement with laboratory results were: super-premium products for puppies, 80% for Ca and 60% for fat; standard products for puppies, 28.6% for protein and 57.2% for Ca; low-cost products for adults, 44% for fiber and 33% for protein; standard products for adults, 33% for fat and 50% for Ca; super-premium products for adults, 50% for calcium and 33% for fat. Products with nutritional shortcomings were found, such as insufficient protein content and too high levels of fiber, calcium, and phosphorus