Modified SIQR model for the COVID-19 outbreak in several countries.

In this paper, we propose a modified Susceptible-Infected-Quarantine-Recovered (mSIQR) model, for the COVID-19 pandemic. We start by proving the well-posedness of the model and then compute its reproduction number and the corresponding sensitivity indices. We discuss the values of these indices for epidemiological relevant parameters, namely, the contact rate, the proportion of unknown infectious, and the recovering rate. The mSIQR model is simulated, and the outputs are fit to COVID-19 pandemic data from several countries, including France, US, UK, and Portugal. We discuss the epidemiological relevance of the results and provide insights on future patterns, subjected to health policies.

Time-varying pharmacodynamics in a simple non-integer HIV infection model.

In this paper we study the effect of time-varying drug exposure in the dynamics of a fractional order model for the human immunodeficiency virus infection. We compute the reproduction number of the model and verify the stability of the disease-free equilibrium. The model is simulated for parameters directly modelling the pharmacodynamics of HIV, namely the slope of the dose-response curve, the drug's half-life, and the dosing interval. The later affect in a significant way the infection patterns. The order of the fractional derivative is also a key player of the model, adding more information, which could be useful for a deeper understanding of the pharmacodynamics of HIV, necessary for more accurate therapeutic regimens.

Laboratory diagnosis of chronic kidney disease in adults: an overview of hospitals inserted in the Portuguese National Health System / Diagnóstico laboratorial de doença renal crônica em adultos: visão geral dos hospitais inseridos no Sistema Nacional de Saúde de Portugal

ABSTRACT Introduction: The laboratory diagnosis of chronic kidney disease (CKD) is a simple and cost-effective procedure that allows the detection of early stages of the disease, which is essential to avoid kidney damage and a life threateaning event. It consists of measuring serum creatinine concentration, urinary albumin concentration and calculating the estimated glomerular filtration rate (eGFR). In 2012, the guidelines for laboratory evaluation of the CKD were published by the Kidney Disease: Improving Global Outcomes (KDIGO). Objectives: This study aimed to evaluate whether the laboratories in hospitals of the Portuguese National Health System follow these guidelines and provide a correct diagnosis of CKD. Material and method: A questionnaire composed of 32 questions was sent to the Clinical Pathology Services of all hospitals inserted in the System. Results: All 49 labs responded that measure serum creatinine, 18 reported measurering eGFR. Ten reported measuring eGFR only if specifically ordered. Forty-four measure total protein and albumin in the urine, three only protein, one albumin alone, and one measure none of them. The type of samples, methods, reagents, equipment, expression units of results and reference intervals varied. Conclusion: There is great variability among laboratories in relation to the methodology of measuring serum creatinine, albumin and total protein in the urine. There are wide variations in the release of results. Most laboratories do not follow the guidelines recommended by the KDIGO 2012. This work indicates that there is a need to develop education and alignment processes in the laboratory diagnosis of CKD in the laboratories installed in hospitals inserted in the Portuguese National Health System.

RESUMO Introdução: O diagnóstico laboratorial de doença renal crônica (DRC) é simples e econômico e permite a detecção de estágios iniciais da doença, o que é essencial para evitar danos renais e risco de morte. Consiste em medir a concentração de creatinina sérica e albumina urinária e calcular a taxa de filtração glomerular (eTFG). Em 2012, as diretrizes para avaliação laboratorial da DRC foram divulgadas pela Kidney Disease: Improving Global Outcomes (KDIGO). Objetivos: Os objetivos deste estudo são avaliar se os laboratórios em hospitais do Sistema Nacional de Saúde Português seguem essas diretrizes e se fornecem diagnóstico correto de DRC. Material e método: Um questionário com 32 perguntas foi enviado aos serviços de patologia clínica de todos os hospitais inseridos no sistema. Resultados: Todos os 49 laboratórios responderam que medem creatinina e 18, eTFG. Dez disseram que medem a eTFG apenas se especificamente solicitado. Quarenta e quatro medem proteínas totais e albumina urinária; três, apenas proteínas; um, somente albumina; e um não mede nenhuma delas. Tipo de amostras, métodos, reagentes, equipamentos, unidades de expressão dos resultados e intervalos de referência variaram. Conclusão: Existe grande variabilidade entre laboratórios em relação às metodologias de medida da creatinina sérica, albumina e proteínas totais na urina. Há grandes variações quanto à liberação dos resultados. A maioria dos laboratórios não segue as diretrizes recomendadas pela KDIGO 2012. Este trabalho indica que existe necessidade de serem desenvolvidos processos de educação e harmonização no diagnóstico laboratorial de DRC nos laboratórios instalados em hospitais inseridos no Sistema Nacional de Saúde Português.

Effects of dynamic quarantine and nonlinear infection rate in a model for computer worms propagation.

We propose a new model for computer worms propagation, using dynamic quarantine and a nonlinear infection rate. The dynamic quarantine is based in epidemic disease control methods and in the principle 'assume guilty before proven inocent'. This means that the host is blocked whenever its behavior looks suspicious. After a short time, the quarantined computer is released. The nonlinear infection rate is used to capture the dynamics of overcrowded infectious networks and high viral loads. We simulate numerically the model for distinct values of the quarantine times. We observe that increasing the quarantine time decreases the number of infectious hosts in the network.

A coinfection model for HIV and HCV.

We study a mathematical model for the human immunodeficiency virus (HIV) and hepatites C virus (HCV) coinfection. The model predicts four distinct equilibria: the disease free, the HIV endemic, the HCV endemic, and the full endemic equilibria. The local and global stability of the disease free equilibrium was calculated for the full model and the HIV and HCV submodels. We present numerical simulations of the full model where the distinct equilibria can be observed. We show simulations of the qualitative changes of the dynamical behavior of the full model for variation of relevant parameters. From the results of the model, we infer possible measures that could be implemented in order to reduce the number of infected individuals.

Equivalence of human odometry by walk and run is indifferent to self-selected speed.

Humans and other animals can measure distances nonvisually by legged locomotion. Experiments typically employ an outbound measure (M) and an inbound report (R) phase. Previous research has found distance reproduction to be maximally accurate, when gait symmetry and speed of M and R are of like kind: Successful human odometry manifests at the level of the M-R system. In the present work, M was an experimenter-set distance produced by a blindfolded participant using a primary gait (walk, run). R was always by walk. Fast and slow versions of walk and run were adopted by participants, such that when M was fast R was slow, and vice versa. Distance was underestimated when M was slower than R and overestimated when M was faster than R. However, the pattern of participant-adopted velocities indicated that it was the instructions, not the speed as such, that yielded the pattern of results. The results are interpretable through a dynamical perspective and indicate speed is an imperfection parameter acting on the attractors of the M-R system.

Central pattern generators for bipedal locomotion.

Golubitsky, Stewart, Buono and Collins proposed two models for the achitecture of central pattern generators (CPGs): one for bipeds (which we call leg) and one for quadrupeds (which we call quad). In this paper we use symmetry techniques to classify the possible spatiotemporal symmetries of periodic solutions that can exist in leg (there are 10 nontrivial types) and we explore the possibility that coordinated arm/leg rhythms can be understood, on the CPG level, by a small breaking of the symmetry in quad, which leads to a third CPG architecture arm. Rhythms produced by leg correspond to the bipedal gaits of walk, run, two-legged hop, two-legged jump, skip, gallop, asymmetric hop, and one-legged hop. We show that breaking the symmetry between fore and hind limbs in quad, which yields the CPG arm, leads to periodic solution types whose associated leg rhythms correspond to seven of the eight leg gaits found in leg; the missing biped gait is the asymmetric hop. However, when arm/leg coordination rhythms are considered, we find the correct rhythms only for the biped gaits of two-legged hop, run, and gallop. In particular, the biped gait walk, along with its arm rhythms, cannot be obtained by a small breaking of symmetry of any quadruped gait supported by quad.