Identifying the Etiology of Post-acute Sequelae SARS-CoV-2 (PASC) Infection

The viral illness coronavirus disease 2019 (COVID-19) has affected millions worldwide since its initial discovery in late 2019. After recovering from the primary viral infection, many have found themselves suffering new, ongoing, or recurrent COVID-19 symptoms in a condition referred to as long COVID or post-acute sequelae SARS-CoV-2 (PASC) infection. Presently, little is understood regarding the etiology of PASC. This literature review analyzes current theories of PASC development in adult humans after initial COVID-19 disease. An understanding of PASC’s developmental mechanism will pave the way for better-targeted therapies to treat patients diagnosed with this illness. Proposed PASC origin theories for discussion include: (1) persistent SARS-CoV-2 remains after initial COVID-19 infection; (2) immunosuppression during COVID-19 disease leads to hyperinflammation and subsequent symptoms; (3) microclots cause organ damage. The interplay between these theories reveals future study directions and implications. A deeper understanding of these PASC mechanisms allows research progression towards treatments that directly target the illness at its source

What Types of Jets does Nature Make: A New Population of Radio Quasars

We use statistical results from a large sample of about 500 blazars, based on two surveys, the Deep X-ray Radio Blazar Survey (DXRBS), nearly complete, and the RASS-Green Bank survey (RGB), to provide new constraints on the spectral energy distribution of blazars, particularly flat-spectrum radio quasars (FSRQ). This reassessment is prompted by the discovery of a population of FSRQ with spectral energy distribution similar to that of high-energy peaked BL Lacs. The fraction of these sources is sample dependent, being ~ 10% in DXRBS and ~ 30% in RGB (and reaching ~ 80% for the Einstein Medium Sensitivity Survey). We show that these ``X-ray strong'' radio quasars, which had gone undetected or unnoticed in previous surveys, indeed are the strong-lined counterparts of high-energy peaked BL Lacs and have synchrotron peak frequencies, nu_peak, much higher than ``classical'' FSRQ, typically in the UV band for DXRBS. Some of these objects may be 100 GeV - TeV emitters, as are several known BL Lacs with similar broadband spectra. Our large, deep, and homogeneous DXRBS sample does not show anti-correlations between nu_peak and radio, broad line region, or jet power, as expected in the so-called ``blazar sequence'' scenario. However, the fact that FSRQ do not reach X-ray-to-radio flux ratios and nu_peak values as extreme as BL Lacs and the elusiveness of high nu_peak - high-power blazars suggest that there might be an intrinsic, physical limit to the synchrotron peak frequency that can be reached by strong-lined, powerful blazars. Our findings have important implications for the study of jet formation and physics and its relationship to other properties of active galactic nuclei.Comment: 15 pages, 12 figures. Accepted for publication in The Astrophysical Journal (May 1 2003 issue). Postscript file also available at http://www.stsci.edu/~padovani/unif_papers.htm

Blazar surveys with WMAP and Swift

We present the preliminary results from two new surveys of blazars that have direct implications on the GLAST detection of extragalactic sources from two different perspectives: microwave selection and a combined deep X-ray/radio selection. The first one is a 41 GHz flux-limited sample extracted from the WMAP 3-yr catalog of microwave point sources. This is a statistically well defined sample of about 200 blazars and radio galaxies, most of which are expected to be detected by GLAST. The second one is a new deep survey of Blazars selected among the radio sources that are spatially coincident with serendipitous sources detected in deep X-ray images (0.3-10 keV) centered on the Gamma Ray Bursts (GRB) discovered by the Swift satellite. This sample is particularly interesting from a statistical viewpoint since a) it is unbiased as GRBs explode at random positions in the sky, b) it is very deep in the X-ray band (\fx \simgt $10^{-15}$ \ergs) with a position accuracy of a few arc-seconds, c) it will cover a fairly large (20-30 square deg.) area of sky, d) it includes all blazars with radio flux (1.4 GHz) larger than 10 mJy, making it approximately two orders of magnitude deeper than the WMAP sample and about one order of magnitude deeper than the deepest existing complete samples of radio selected blazars, and e) it can be used to estimate the amount of unresolved GLAST high latitude gamma-ray background and its anisotropy spectrum.Comment: 3 pages, 3 figures, to appear in Proc. of the 1st GLAST Symposium, Feb 5-8, 2007, Stanford, AIP, Eds. S. Ritz, P. F. Michelson, and C. Meega

TRAINING STRATEGIES TO MAXIMISE RECOVERY AND PERFORMANCE IN SOCCER PLAYERS

Introduction: In soccer, the long duration of the competitive season and the large number of games require a careful organization of the training load and a maximization of the training stimuli. The presence of close matches (from 7 to 3 days) requires a careful control of accumulated fatigue and the use of training stimuli aimed at improving different aspects of the soccer physical performance. However, to date in soccer, there is little information about the characteristics of tapering during the microcycle, while the knowledge concerning the specificity of the training methods remains confused. Purpose: the aims of the present investigation were threefold: i) to examine the effect of in-week tapering strategy (reduction in training load 24 h before a match) on player preparedness; ii) to compare the physiological response and mechanical profile of different training strategies, and iii) to compare their effects on soccer-related physical performance. Methods: For these training studies three soccer teams were involved, with a total of 41 players. In the first study, a cross-over experimental design was used, and the participants performed two simulated match-week microcycles, with the same workload, except for the experimental week where a further reduction of ~33% of the volume (time) was performed the day before the match. In the second study was used a parallel two-group, work-matched, longitudinal (Baseline-Test Post-test) experimental design. Two different speed endurance training protocols were compared before and after four weeks of training. In the third study, the acute physical and physiological response of two training approaches (speed endurance vs. repeat sprint training) were compared. Results: In the first study, it was found that a further 33% of training-load reduction the eve of the match improved the height of a countermovement jump, sprint time over a 20 m and repeated sprint ability, enhancing preparedness, while Yo-Yo IR1 performance was maintained. The second study showed that 10-seconds sprint was associated with a possibly greater effect on repeat-sprint total time, higher power output, as well as lower blood lactate concentration, compared to 20-seconds sprint. In the third study, we showed that repeated sprint exercise is associated with a higher mechanical load and heart rate response, while speed endurance training is associated with a higher speed average and a higher blood lactate concentration at the end of the exercise. Conclusion: A further volume reduction during tapering provides an improvement of jump and sprint performances. Additionally, the assessment of the sprint duration (during repeated sprint) has shown that short-time sprint generates higher power demand and higher mechanical load. Conversely, long-sprint duration generates higher speed and high level of blood lactate concentration. However, both short and long-sprint duration have a positive effect on soccer-related performances. Therefore, the manipulation of the training load during tapering together with the type of training stimulus led to increasing soccer-physical performance

Log-parabolic spectra and particle acceleration in blazars. III: SSC emission in the TeV band from Mkn 501

Curved broad-band spectral distributions of non-thermal sources like blazars are described well by a log-parabolic (LP) law where the second degree term measures the curvature. LP energy spectra can be obtained for relativistic electrons by means of a statistical acceleration mechanism whose probability of acceleration depends on energy. In this paper we compute the spectra radiated by an electron population via synchrotron (S) and Synchro-Self Compton(SSC) processes to derive the relations between the LP parameters. These spectra were obtained by means of an accurate numerical code. We found that the ratio between the curvature parameters of the S spectrum to that of the electrons is equal to about 0.2 instead of 0.25, the value foreseen in the delta approximation. Inverse Compton spectra are also intrinsically curved and can be approximated by a log-parabola only in limited ranges. The curvature parameter, estimated around the SED peak, may vary from a lower value than that of the S spectrum up to that of emitting electrons depending on whether the scattering is in the Thomson or in the Klein-Nishina regime. We applied this analysis to computing the SSC emission from the BL Lac object Mkn 501 during the large flare of April 1997. We fit simultaneous BeppoSAX and CAT data and reproduced intensities and spectral curvatures of both components with good accuracy. The large curvature observed in the TeV range was found to be mainly intrinsic, and therefore did not require a large pair production absorption against the extragalactic background. We regard this finding as an indication that the Universe is more transparent at these energies than previously assumed by several models found in the literature. This conclusion is supported by recent detection of two relatively high redshift blazars with H.E.S.S.Comment: Comments: 12 pages, 11 figures. Accepted for publication in the Astronomy and Astrophysic

Log-parabolic spectra and particle acceleration in blazars - II: The BeppoSAX wide band X-ray spectra of Mkn 501

We present the results of a spectral and temporal study of the complete set of BeppoSAX NFI (11) and WFC (71) observations of the BL Lac object Mkn 501. The WFC 2-28 keV data, reported here for the first time, were collected over a period of about five years, from September 1996 to October 2001. These observations, although not evenly distributed, show that Mkn 501, after going through a very active phase from spring 1997 to early 1999, remained in a low brightness state until late 2001. The data from the LECS, MECS and PDS instruments, covering the wide energy interval 0.1-150 keV, have been used to study in detail the spectral variability of the source. We show that the X-ray energy distribution of Mkn 501 is well described by a log-parabolic law in all luminosity states. This model allowed us to obtain good estimates of the SED synchrotron peak energy and of its associated power. The strong spectral variability observed, consisting of strictly correlated changes between the synchrotron peak energy and bolometric flux, suggests that the main physical changes are not only due to variations of the maximum Lorentz factor of the emitting particles but that other quantities must be varying as well. During the 1997 flare the high energy part of the spectrum of Mkn 501 shows evidence of an excess above the best fit log-parabolic law suggesting the existence of a second emission component that may be responsible for most of the observed variability.Comment: Accepted for publication in Astronomy & Astrophysics (11 pages, 7 figures