The comprehensive clinic, laboratory, and instrumental evaluation of children with COVID-19: a 6-months prospective study

Objectives: To perform a comprehensive clinic, laboratory, and instrumental evaluation of children affected by coronavirus disease (COVID-19). Methods: Children with a positive result of nasopharyngeal swab for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) underwent laboratory tests, anal and conjunctival swab, electrocardiography, lung, abdomen, and cardiac ultrasound. Twenty-four-hour ambulatory blood pressure monitoring was performed if abnormal basal blood pressure. Patients were followed-up for 6 months. Results: Three hundred and sixteen children were evaluated; 15 were finally included. Confirmed family member SARS-CoV-2 infection was present in all. Twenty-seven percent were asymptomatic. Anal and conjunctival swabs tests resulted negative in all. Patients with lower body mass index (BMI) presented significantly higher viral loads. Main laboratory abnormalities were: lactate dehydrogenase increasing (73%), low vitamin D levels (87%), hematuria (33%), proteinuria (26%), renal hyperfiltration (33%), and hypofiltration (13%). Two of the patients with hyperfiltration exhibited high blood pressure levels at diagnosis, and persistence of prehypertension at 6-month follow-up. No abnormalities were seen at ultrasound, excepting for one patient who exhibited B-lines at lung sonography. Immunoglobulin G seroconversion was observed in all at 1-month. Conclusions: Our study confirm that intra-family transmission is important. The significant higher viral loads recorded among patients with lower BMI, together with low vitamin D levels, support the impact of nutritional status on immune system. Renal involvement is frequent even among children with mild COVID-19, therefore prompt evaluation and identification of patients with reduced renal function reserve would allow a better stratification and management of patients. Seroconversion occurs also in asymptomatic children, with no differences in antibodies titer according to age, sex and clinical manifestations

Work-related injuries in young workers: an Italian multicentric epidemiological survey

Emergency departments records from 33 hospitals were reviewed to disclose work-related injuries occurred in teen-subjects living in 14 Italian cities. During January-June 2000, 317 work-related injuries were reported. Male subjects, 17 year old, working in the industrial field, resulted the most affected, probably due to the fact that among young workers this sex and age class is the most represented one. Cluster analysis identified two groups of work-related injuries: one includes mainly transportation injuries causing lower extremities or multiple body sites traumas. The other is more strictly related to specific working tasks and includes mostly traumas and cut wounds in hand/wrist and head, together with eye lesions. A more intensive supervision on the use of protective equipment, a more appropriate training in hazard recognition and safe work practices, including operation of vehicles in the work site, must be implemented to reduce work-related injuries

Work-related injuries in young workers: an Italian multicentric epidemiological survey.

Emergency departments records from 33 hospitals were reviewed to disclose work-related injuries occurred in teen-subjects living in 14 Italian cities. During January-June 2000, 317 work-related injuries were reported. Male subjects, 17 year old, working in the industrial field, resulted the most affected,probably due to the fact that among young workers this sex and age class is the most represented one. Cluster analysis identified two groups of work-related injuries: one includes mainly transportation injuries causing lower extremities or multiple body sites traumas. The other is more strictly related to specific working tasks and includes mostly traumas and cut wounds in hand/wrist and head, together with eye lesions. A more intensive supervision on the use of protective equipment, a more appropriate training in hazard recognition and safe work practices, including operation of vehicles in the work site, must be implemented to reduce work-related injuries

On the characteristics of optimal transfers.

In the past 50 years the scientists have been developing and analysing methods and new algorithms that optimise an interplanetary trajectory according to one or more objectives. Within this field, in 1963 Lawden derived, from Pontryagin's minimum principle, the so-called `primer vector theory'. The main goal of this thesis is to develop a theoretical understanding of Lawden's theory, getting an insight into the optimality of a trajectory when mid-course corrections need to be applied. The novelty of the research is represented by a different approach to the primer vector theory, which simplifies the structure of the problem

Optimisation modelling of mid-course corrections along interplanetary transfers

The primer vector theory, firstly proposed by Lawden, defines a set of necessary conditions to characterise whether a transfer trajectory is optimum with respect to propellant usage, within a two-body problem context. If the conditions are not satisfied, one or more potential intermediate impulses are performed along the transfer trajectory, in order to lower the overall cost. The method is based on the propagation of the state transition matrix and on the solution of a boundary value problem, which leads to a mathematical and computational complexity. A novel propagator has been developed and it is based on the decoupling between the in-plane and out-of-plane components of the primer vector on the orbital plane. It reduces the mathematical complexity and the computational cost of the problem presented by Lawden. In this paper it is proved how the method is independent from the semi-major axis of the transfer orbit. A case that exploits the properties of the novel propagator is also presented. The optimality has been analysed keeping the transfer arc fixed, while the departure and arrival trajectories are varying. The search space is defined only by the boundary conditions on the transfer orbit and its eccentricity

Novel Approach on the Optimisation of Mid-Course Corrections Along Interplanetary Trajectories

The primer vector theory, firstly proposed by Lawden, defines a set of necessary conditions to characterise whether an impulsive thrust trajectory is optimal with respect to propellant usage, within a two-body problem context. If the conditions are not satisfied, one or more potential intermediate impulses are performed along the transfer arc, in order to lower the overall cost. The method is based on the propagation of the state transition matrix and on the solution of a boundary value problem, which leads to a mathematical and computational complexity.In this paper, a different approach is introduced. It is based on a polar coordinates transformation of the primer vector which allows the decoupling between its in-plane and out-of-plane components. The out-of-plane component is solved analytically while for the in-plane ones a Hamiltonian approximation is made.The novel procedure reduces the mathematical complexity and the computational cost of Lawden’s problem and gives also a different perspective about the optimisation of a transfer trajector

Geometric Approach to the Perpendicular Thrust Case for Trajectory Optimization

For the case of impulsive thrust trajectories, Lawden’s primer vector theory gives a set of necessary conditions that determines if intermediate impulses have to be applied in order to obtain a fuel optimal trajectory. In this paper, a novel approach is presented in which, through the representation of the primer vector in polar coordinates, a separation of the in-plane and out-of-plane components occurs. This procedure gives a complete analytic solution for the out-of-plane component of the primer vector, which is shown to be independent of the semimajor axis of the transfer orbit. In the case where the initial and final thrusts are both perpendicular to the orbital plane, the optimality of the transfer arc is fully analyzed. The analytic correlations between the boundary conditions on the transfer orbit and the profile of the primer vector are derived. In particular, the novel approach allows the development of a simple procedure based on a graphical representation from which, given only the initial and final position vectors, the optimality of the transfer orbit can be determined

Modelling mid-course corrections for optimality conditions along interplanetary transfers

Within the field of trajectory optimisation, Lawden developed the primer vector theory, which defines a set of necessary conditions to characterise whether a transfer trajectory, in the two-body problem context, is optimum with respect to propellant usage. If the conditions are not satisfied, a region of the transfer trajectory is identified in which one or more potential intermediate impulses are performed in order to lower the overall cost. The method is computationally complex owing to having to solve a boundary value problem. In this paper is presented a new propagator that reduces the mathematical complexity and the computational cost of the problem, in particular it exploits a separation between the in-plane and out-of-plane components of the primer vector along the transfer trajectory. Using this propagator, the optimality of the transfer arc has been investigated, varying the departure and arrival orbits. In particular, keeping fixed the transfer trajectory, the optimality has been extensively analysed varying both the initial and final positions on the orbit, together with the directions of the initial and final thrust impulses