Sub-second periodicity in a fast radio burst

The origin of fast radio bursts (FRBs), millisecond-duration flashes of radio waves that are visible at distances of billions of light-years, remains an open astrophysical question. Here we report the detection of the multi-component FRB 20191221A with the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB), and the identification of a periodic separation of 216.8(1) ms between its components with a significance of 6.5 sigmas. The long (~ 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the FRB population. We also report two additional FRBs, 20210206A and 20210213A, whose multi-component pulse profiles show some indication of periodic separations of 2.8(1) and 10.7(1) ms, respectively, suggesting the possible existence of a group of FRBs with complex and periodic pulse profiles. Such short periodicities provide strong evidence for a neutron-star origin of these events. Moreover, our detections favour emission arising from the neutron-star magnetosphere, as opposed to emission regions located further away from the star, as predicted by some models. Possible explanations for the observed periodicity include super-giant pulses from a neutron star that are possibly related to a magnetar outburst and interacting neutron stars in a binary system.

Postprandial effects of macronutrient composition meals on metabolic responses and arterial stiffness indexes in lean and obese men adults; a protocol study (Preprint)

BACKGROUND Background: Prior studies have shown that meal composition is capable of effect on metabolic response and arterial stiffness indexes. OBJECTIVE Objective: A three-phase parallel study will design to investigate the effects of meal composition on metabolic parameters and arterial stiffness indexes among lean and obese adult. The planned study protocol is presented METHODS Methods/design: This is a parallel clinical trial targeting adults (aged 18–35 years, free from any diseases) selected by inclusion and exclusion criteria at Mashhad University Medical Sciences. Each subject will complete three interventions with a washout period of one week: high carbohydrate, high protein and high fat meal. The postprandial effect will be assessed during 360 minutes from each meal including energy expenditure component, pulse wave analysis and pulse wave velocity and blood sampling. RESULTS N/A CONCLUSIONS Metabolic Responses, Macronutrients Composition, Arterial Stiffness, Study Protocol: The differences in postprandial response due to different meal composition could affect of metabolic and vascular parameters. This could provide necessary information for the establishment of new strategies in terms of nutritional education and metabolic and vascular improvement. CLINICALTRIAL Trial registration: Iranian Registry of Clinical Trials: IRCT20190818044552N1. Registered on August 26, 2019

Фазово-модулированный двухкомпонентный импульс в диспергирующей среде

A theory of optical two-component pulse of self-induced transparency in a dispersive medium has been developed. Using the generalized version of the perturbative expansion method, the system of material equations for an ensemble of two-level atoms and the wave equation in a dispersive medium are reduced to coupled nonlinear Schrödinger equations. A solution in the form of a phase-modulated two-component $$0\pi $$ pulse is obtained. The pulse components oscillate at the sum and difference frequencies in the vicinity of the carrier-wave frequency. Explicit analytical expressions for the parameters and formation conditions of a nonlinear wave, which depend on the dispersive properties of the medium, are presented. Known results are obtained for a particular case.

Separation of integrated pulse shapes into unique sub-components

Average pulse profiles are generally separable into several components whereas individual components can be described by a Gaussian shape. One generally distinguishes betweencoreandconalcomponents, although it is yet unclear whether core and conal components originate from the same (Lyne & Manchester 1988) or a different emission mechanism (Rankin 1983). Investigating this problem, we studied the behaviour of individual components observed in about 200 profiles of 18 pulsars measured at three different frequencies, i.e. at 1.4 GHz, 4.75 GHz and 10.55 GHz. We unambiguously determined the number, location, width, flux density and spectral index of individual components using a special technique (Kramer et al. 1994). The applied method ensures that only intrinsic features of the pulse profiles are fitted by comparing off-pulse noise statistics and post-fit residuals as a goodness-of-fit estimator. As a first result, we note that all high S/N pulsar profiles can be accurately described by using only a small number (usually ≤ 5) of gaussian components, although we also find an example of a seven component pulse shape (B0740–28). Fitted components determined for different observations of the same pulsar were averaged, producing a grand mean profile which is completely noise-free and thus suitable for a reliable flux density measurement of individual components, for an accurate determination of the pulse width to calculate opening angles, ρ, of the emission cone, or for use as a template for obtaining pulse arrival times.