Microscopic, kinetic and hydrodynamic hybrid models of collective motions with chemotaxis: a numerical study

A general class of hybrid models has been introduced recently, gathering the advantages multiscale descriptions. Concerning biological applications, the particular coupled structure fits to collective cell migrations and pattern formation scenarios. In this context, cells are modelled as discrete entities and their dynamics is given by ODEs, while the chemical signal influencing the motion is considered as a continuous signal which solves a diffusive equation. From the analytical point of view, this class of model has been proved to have a mean-field limit in the Wasserstein distance towards a system given by the coupling of a Vlasov-type equation with the chemoattractant equation. Moreover, a pressureless nonlocal Euler-type system has been derived for these models, rigorously equivalent to the Vlasov one for monokinetic initial data. In the present paper, we present a numerical study of the solutions to the Vlasov and Euler systems, exploring general settings for inital data, far from the monokinetic ones

Kinetic description and macroscopic limit of swarming dynamics with continuous leader-follower transitions

In this paper, we derive a kinetic description of swarming particle dynamics in an interacting multi-agent system featuring emerging leaders and followers. Agents are classically characterized by their position and velocity plus a continuous parameter quantifying their degree of leadership. The microscopic processes ruling the change of velocity and degree of leadership are independent, non-conservative and non-local in the physical space, so as to account for long-range interactions. Out of the kinetic description, we obtain then a macroscopic model under a hydrodynamic limit reminiscent of that used to tackle the hydrodynamics of weakly dissipative granular gases, thus relying in particular on a regime of small non-conservative and short-range interactions. Numerical simulations in one- and two-dimensional domains show that the limiting macroscopic model is consistent with the original particle dynamics and furthermore can reproduce classical emerging patterns typically observed in swarms.Comment: 30 pages, 7 figure

Preventing congestion in crowd dynamics caused by reversing flow

In this paper we devise a microscopic (agent-based) mathematical model for reproducing crowd behaviour in a specific scenario: a number of pedestrians, consisting of numerous social groups, flow along a corridor until a gate located at the end of the corridor closes. People are not informed about the closure of the gate and perceive the blockage observing dynamically the local crowd conditions. Once people become aware of the new conditions, they stop and then decide either to stay, waiting for reopening, or to go back and leave the corridor for ever. People going back hit against newly incoming people who are not yet aware of the blockage or have already decided to stay. This creates a dangerous counter-flow which can easily lead to accidents. We run several numerical simulations varying parameters which control the crowd behaviour, in order to understand the factors which have the greatest impact on the dynamics. We conclude with some useful suggestions directed to the organizers of mass events

CARDIAC “BALL OF WOOL”: A rare case of a solid interventricular hydatid cyst

A 49 years old Romanian lady was admitted to the department of infectious diseases because of dyspnoea, malaise and mild fever. Chest X-ray was normal. A 12 lead ECG demonstrated right bundle branch block, and a transthoracic echocardiography showed a mass in the mid inter-ventricular septum, measuring 40x25 mm, protruding into the right ventricular chamber. The mass had the appearance of a solid lesion iso-echoic with the myocardium with hypo-echoic zones inside, resembling a “ball of wool” (Figure 1), suggesting a myxoma. Otherwise, all echocardiographic parameters were normal, except a mild pulmonary hypertension (PAPs 35 mmHg). During laboratory investigations, serum antiechinococcus antibodies was positive. Various imaging investigations including CT scanning and echocardiography were undertaken, but no cysts were detected in the abdomen or chest, respectively. The cardiac mass was then studied in more detail: a three-dimensional echocardiography was performed to better appreciate the shape and the location of the mass for a cardio-surgical view (Figure 2). A cardiac magnetic resonance didn’t show specific features and indicated a probable tumour, such as echocardiography (Figure 3)

Large left ventricular pseudoaneurysm

Left ventricular pseudoaneurysm (LVPA) can complicate 4% of myocardial infarction ; it forms when rupture of the myocardium is contained by adherent pericardium or scar tissue. The diagnosis of a LVPA can be very difficult because of nonspecific signs and symptoms. Transthoracic twodimensional echocardiography (TTE) is the first applied investigation, although often can be non-diagnostic. TTE, contrast ventriculography, cardiac magnetic resonance (CMR) and three-dimensional echocardiography (3DE) are useful tools in pre-surgical assessment, allowing the differentiation between LV aneurysm and pseudoaneurysm, and the evaluation of LVPA size and spatial distribution. We report a case of a patient with a post-infarction LVPA that was detected initially by TTE and then cofirmed by ventriculography, 3DE and CMR. The patient was successfully treated surgically and then monitored by TTE

Case Report: Two Case Reports of Acute Myopericarditis After mRNA COVID-19 Vaccine

BackgroundCases of myocarditis and myopericarditis after mRNA COVID-19 vaccines have been reported, especially after the second dose and in young males. Their course is generally benign, with symptoms onset after 24-72 h from the dose. Case SummaryWe report two cases of myopericarditis after the second dose of the mRNA-1273 COVID-19 vaccine in two young males. Both the patients were administered the mRNA-1273 COVID-19 vaccine from the same batch on the same day and experienced fever on the same day of the vaccine, and symptoms consisted of myopericarditis 3 days after the dose. DiscussionMyopericarditis is usually considered an uncommon adverse reaction after various vaccinations, reported also after the mRNA COVID-19 vaccine. Several explanations have been proposed, including an abnormal activation of the immune system leading to a pro-inflammatory cascade responsible for myocarditis development. Both patients experienced the same temporal onset as well as the same symptoms, it is also useful to underscore that both vaccines belonged to the same batch of vaccines. However, despite these cases, vaccination against COVID-19 far outweighs the risk linked to COVID-19 infection and remains the best option to overcome this disease

Concordance between Observations and Simulations in the Evolution of the Mass Relation between Supermassive Black Holes and Their Host Galaxies

International audienceWe carry out a comparative analysis of the relation between the mass of supermassive black holes (BHs) and the stellar mass of their host galaxies at 0.2 < z < 1.7 using well-matched observations and multiple state-of-the-art simulations (e.g., MassiveBlackII, Horizon-AGN, Illustris, TNG, and a semianalytic model). The observed sample consists of 646 uniformly selected Sloan Digital Sky Survey quasars (0.2 < z < 0.8) and 32 broad-line active galactic nuclei (AGNs; 1.2 < z < 1.7) with imaging from Hyper Suprime-Cam (HSC) for the former and Hubble Space Telescope (HST) for the latter. We first add realistic observational uncertainties to the simulation data and then construct a simulated sample in the same manner as the observations. Over the full redshift range, our analysis demonstrates that all simulations predict a level of intrinsic scatter of the scaling relations comparable to the observations that appear to agree with the dispersion of the local relation. Regarding the mean relation, Horizon-AGN and TNG are in closest agreement with the observations at low and high redshift (z ∼ 0.2 and 1.5, respectively), while the other simulations show subtle differences within the uncertainties. For insight into the physics involved, the scatter of the scaling relation, seen in the SAM, is reduced by a factor of two and closer to the observations after adopting a new feedback model that considers the geometry of the AGN outflow. The consistency in the dispersion with redshift in our analysis supports the importance of both quasar- and radio-mode feedback prescriptions in the simulations. Finally, we highlight the importance of increasing the sensitivity (e.g., using the James Webb Space Telescope), thereby pushing to lower masses and minimizing biases due to selection effects

Heart transplantation and anti‐HLA antibodY: myocardial dysfunction and prognosis ‐ HeartLAy study

Abstract Aims The presence of anti‐human leucocyte antigen (HLA) antibodies has been implicated in a higher incidence of complications as well as mortality rate in heart transplantation. The aim of the study was to identify through non‐invasive parameters early signs of myocardial dysfunction in the presence of anti‐HLA antibodies but without evidence of antibody‐mediated rejection (AMR) and its possible prognostic impact. Methods and results A total of 113 heart‐transplanted patients without acute cellular rejection (ACR) and AMR or cardiac allograft vasculopathy (CAV) were prospectively enrolled and divided into two groups [‘HLA+’ (50 patients) and ‘HLA−’ (63 patients)], based on the presence of anti‐HLA antibodies. Each patient was followed for 2 years after the enrolment, recording episodes of AMR, ACR, CAV, and mortality. Clinical characteristics were similar between the two groups. Among laboratory data, N‐terminal pro‐B‐type natriuretic peptide and high‐sensitivity cardiac troponin values were significantly higher in the presence of anti‐HLA antibodies (P < 0.001 and P = 0.003, respectively). The echocardiographic parameters that showed a statistically significant difference between the two groups were deceleration time of E wave (DecT E, P < 0.001), left ventricular global longitudinal strain (P < 0.001), tricuspid annular plane systolic excursion (P = 0.011), tricuspid S′ wave (P = 0.002), and free wall right ventricular longitudinal strain (fwRVLS, P = 0.027), whereas left atrial strain did not differ significantly (P = 0.408). Univariate analysis showed that anti‐HLA antibodies were associated with the development of CAV at both 1 and 2 year follow‐up [odds ratio (OR) 11.90, 95% confidence interval (CI) 1.43–90.79, P = 0.022 and OR 3.37, 95% CI 1.78–9.67, P = 0.024, respectively]. Bivariate analysis demonstrated that both fwRVLS and DecT E were predictors of CAV development independently from HLA status. Conclusions The presence of circulating anti‐HLA antibodies is correlated with a mild cardiac dysfunction, even in the absence of AMR, and CAV development. Interestingly, reduced values of DecT E and fwRVLS were predictors of future development of CAV, independently from anti‐HLA antibody