Remarks on a normal subgroup of GA_n

We show that the subgroup generated by locally finite polynomial automorphisms of k^n is normal in GA_n. Also, some properties of normal subgroups of GA_n containing all diagonal automorphisms are given.Comment: 5 page

TESS unveils the phase curve of WASP-33b. Characterization of the planetary atmosphere and the pulsations from the star

We present the detection and characterization of the full-orbit phase curve and secondary eclipse of the ultra-hot Jupiter WASP-33b at optical wavelengths, along with the pulsation spectrum of the host star. We analyzed data collected by the Transiting Exoplanet Survey Satellite (TESS) in sector 18. WASP-33b belongs to a very short list of highly irradiated exoplanets that were discovered from the ground and were later visited by TESS. The host star of WASP-33b is of delta Scuti-type and shows nonradial pulsations in the millimagnitude regime, with periods comparable to the period of the primary transit. These completely deform the photometric light curve, which hinders our interpretations. By carrying out a detailed determination of the pulsation spectrum of the host star, we find 29 pulsation frequencies with a signal-to-noise ratio higher than 4. After cleaning the light curve from the stellar pulsations, we confidently report a secondary eclipse depth of 305.8 +/- 35.5 parts-per-million (ppm), along with an amplitude of the phase curve of 100.4 +/- 13.1 ppm and a corresponding westward offset between the region of maximum brightness and the substellar point of 28.7 +/- 7.1 degrees, making WASP-33b one of the few planets with such an offset found so far. Our derived Bond albedo, A_B = 0.369 +/- 0.050, and heat recirculation efficiency, epsilon = 0.189 +/- 0.014, confirm again that he behavior of WASP-33b is similar to that of other hot Jupiters, despite the high irradiation received from its host star. By connecting the amplitude of the phase curve to the primary transit and depths of the secondary eclipse, we determine that the day- and nightside brightness temperatures of WASP-33b are 3014 +/- 60 K and 1605 +/- 45 K, respectively. From the detection of photometric variations due to gravitational interactions, we estimate a planet mass of M_P = 2.81 +/- 0.53 M$_J.Comment: 19 pages, 15 figure

Vector Theory of Gravity

We proposed a gravitation theory based on an analogy with electrodynamics on the basis of a vector field. For the first time, to calculate the basic gravitational effects in the framework of a vector theory of gravity, we use a Lagrangian written with gravitational radiation neglected and generalized to the case of ultra-relativistic speeds. This allows us to accurately calculate the values of all three major gravity experiments: the values of the perihelion shift of Mercury, the light deflection angle in the gravity field of the Sun and the value of radar echo delay. The calculated values coincide with the observed ones. It is shown that, in this theory, there exists a model of an expanding Universe.Comment: 9 page

Learning-based Ensemble Average Propagator Estimation

By capturing the anisotropic water diffusion in tissue, diffusion magnetic resonance imaging (dMRI) provides a unique tool for noninvasively probing the tissue microstructure and orientation in the human brain. The diffusion profile can be described by the ensemble average propagator (EAP), which is inferred from observed diffusion signals. However, accurate EAP estimation using the number of diffusion gradients that is clinically practical can be challenging. In this work, we propose a deep learning algorithm for EAP estimation, which is named learning-based ensemble average propagator estimation (LEAPE). The EAP is commonly represented by a basis and its associated coefficients, and here we choose the SHORE basis and design a deep network to estimate the coefficients. The network comprises two cascaded components. The first component is a multiple layer perceptron (MLP) that simultaneously predicts the unknown coefficients. However, typical training loss functions, such as mean squared errors, may not properly represent the geometry of the possibly non-Euclidean space of the coefficients, which in particular causes problems for the extraction of directional information from the EAP. Therefore, to regularize the training, in the second component we compute an auxiliary output of approximated fiber orientation (FO) errors with the aid of a second MLP that is trained separately. We performed experiments using dMRI data that resemble clinically achievable $q$-space sampling, and observed promising results compared with the conventional EAP estimation method.Comment: Accepted by MICCAI 201

Broad-band spectrophotometry of the hot Jupiter HAT-P-12b from the near-UV to the near-IR

The detection of trends or gradients in the transmission spectrum of extrasolar planets is possible with observations at very low spectral resolution. Transit measurements of sufficient accuracy using selected broad-band filters allow for an initial characterization of the atmosphere of the planet. We obtained time series photometry of 20 transit events and analyzed them homogeneously, along with eight light curves obtained from the literature. In total, the light curves span a range from 0.35 to 1.25 microns. During two observing seasons over four months each, we monitored the host star to constrain the potential influence of starspots on the derived transit parameters. We rule out the presence of a Rayleigh slope extending over the entire optical wavelength range, a flat spectrum is favored for HAT-P-12b with respect to a cloud-free atmosphere model spectrum. A potential cause of such gray absorption is the presence of a cloud layer at the probed latitudes. Furthermore, in this work we refine the transit parameters, the ephemeris and perform a TTV analysis in which we found no indication for an unseen companion. The host star showed a mild non-periodic variability of up to 1%. However, no stellar rotation period could be detected to high confidence.Comment: 13 pages, 6 figures, Accepted for publication in A&

Comprehensive maximum likelihood estimation of diffusion compartment models towards reliable mapping of brain microstructure

open4siDiffusion MRI is a key in-vivo non invasive imaging capability that can probe the microstructure of the brain. However,its limited resolution requires complex voxelwise generative models of the diffusion. Diffusion Compartment (DC) models divide the voxel into smaller compartments in which diffusion is homogeneous. We present a comprehensive framework for maximum likelihood estimation (MLE) of such models that jointly features ML estimators of (i) the baseline MR signal,(ii) the noise variance,(iii) compartment proportions,and (iv) diffusion-related parameters. ML estimators are key to providing reliable mapping of brain microstructure as they are asymptotically unbiased and of minimal variance. We compare our algorithm (which efficiently exploits analytical properties of MLE) to alternative implementations and a state-of-theart strategy. Simulation results show that our approach offers the best reduction in computational burden while guaranteeing convergence of numerical estimators to the MLE. In-vivo results also reveal remarkably reliable microstructure mapping in areas as complex as the centrum semiovale. Our ML framework accommodates any DC model and is available freely for multi-tensor models as part of the ANIMA software (https://github.com/Inria-Visages/Anima-Public/wiki).Stamm, Aymeric; Commowick, Olivier; Warfield, Simon K.; Vantini, SimoneStamm, Aymeric; Commowick, Olivier; Warfield, Simon K.; Vantini, Simon

One-loop self-energy correction to the 1s and 2s hyperfine splitting in H-like systems

The one-loop self-energy correction to the hyperfine splitting of the 1s and 2s levels in H-like low-Z atoms is evaluated to all orders in Z\alpha. The results are compared to perturbative calculations. The residual higher-order contribution is evaluated. Implications to the specific difference of the hyperfine structure intervals 8\Delta \nu_2 - \Delta \nu_1 in He^+ are investigated.Comment: 17 pages, RevTeX, 3 figure

Persistent high burden and mortality associated with advanced HIV disease in rural Tanzania despite uptake of World Health Organization "test and treat" guidelines

BACKGROUND: Information about burden, characteristics, predictors, and outcomes of advanced human immunodeficiency virus disease (AHD) is scarce in rural settings of sub-Saharan Africa. Human immunodeficiency virus (HIV) infections and associated deaths remain high despite specific guidelines issued by the World Health Organization (WHO). METHODS: Burden of AHD and 6-month death/loss to follow-up (LTFU) were described among 2498 antiretroviral therapy (ART)-naive nonpregnant people with HIV (PWH) aged >15 years enrolled in the Kilombero Ulanga Antiretroviral Cohort in rural Tanzania between 2013 and 2019. Baseline characteristics associated with AHD and predictors of death/LTFU among those with AHD were analyzed using multivariate logistic and Cox regression, respectively. RESULTS: Of the PWH, 62.2% had AHD at diagnosis (66.8% before vs 55.7% after national uptake of WHO "test and treat" guidelines in 2016). At baseline, older age, male sex, lower body mass index, elevated aminotransferase aspartate levels, severe anemia, tachycardia, decreased glomerular filtration rate, clinical complaints, impaired functional status, and enrollment into care before 2018 were independently associated with AHD. Among people with AHD, incidence of mortality, and LTFU were 16 and 34 per 100 person-years, respectively. WHO clinical stage 3 or 4, CD4 counts <100 cells/microL, severe anemia, tachypnea, and liver disease were associated with death/LTFU. CONCLUSIONS: More than 50% of PWH enrolled in our cohort after test and treat implementation still had AHD at diagnosis. Increasing HIV testing and uptake and implementation of the WHO-specific guidelines on AHD for prevention, diagnosis, treatment of opportunistic infections, and reducing the risks of LTFU are urgently needed to reduce morbidity and mortality

Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen

While measurements of the hyperfine structure of hydrogen-like atoms are traditionally regarded as test of bound-state QED, we assume that theoretical QED predictions are accurate and discuss the information about the electromagnetic structure of protons that could be extracted from the experimental values of the ground state hyperfine splitting in hydrogen and muonic hydrogen. Using recent theoretical results on the proton polarizability effects and the experimental hydrogen hyperfine splitting we obtain for the Zemach radius of the proton the value 1.040(16) fm. We compare it to the various theoretical estimates the uncertainty of which is shown to be larger that 0.016 fm. This point of view gives quite convincing arguments in support of projects to measure the hyperfine splitting of muonic hydrogen.Comment: Submitted to Phys. Rev.