Risk factors associated with COVID-19 mortality in Mexico.

BACKGROUND: On December 31, 2019, one of the most serious pandemics in recent times made its appearance. Certain health conditions, such as obesity and diabetes mellitus, have been described to be related to COVID-19 unfavorable outcomes. OBJECTIVE: To identify factors associated with mortality in patients with COVID-19. MATERIAL AND METHODS: Retrospective cohort of 998,639 patients. Patient sociodemographic and clinical characteristics were analyzed, with survivors being compared with the deceased individuals. Cox proportional hazards model was used to identify variables predictive of COVID-19-associated mortality. RESULTS: Among the deceased patients, men accounted for 64.3%, and women, for 35.7%, with the difference being statistically significant. Subjects older than 80 years had a 13-fold higher risk of dying from COVID-19 (95% CI = 12,469, 13,586), while chronic kidney disease entailed a risk 1.5 times higher (95% CI = 1,341, 1,798), and diabetes mellitus involved a risk 1.25 times higher (95% CI = 1.238,1.276). CONCLUSIONS: Age, sex, diabetes mellitus and obesity were found to be predictors of COVID-19 mortality. Further research related to chronic obstructive pulmonary disease, cardiovascular diseases, smoking and pregnancy is suggested.

ANTECEDENTES: El 31 de diciembre de 2019, se inició una de las pandemias más graves de los últimos tiempos. Se ha descrito que ciertas condiciones de salud, como la obesidad y la diabetes mellitus, están relacionadas con desenlaces desfavorables por COVID-19. OBJETIVO: Identificar factores asociados a mortalidad en pacientes con COVID-19. MATERIAL Y MÉTODOS: Cohorte retrospectiva de 998 639 pacientes. Se analizaron las características sociodemográficas y clínicas de los pacientes, y se compararon supervivientes con fallecidos. Se utilizó el modelo de riesgos proporcionales de Cox para la identificación de variables predictivas de defunción por COVID-19. RESULTADOS: Entre los fallecidos, los hombres representaron 64.3 % y las mujeres 35.7 %, diferencia que resultó estadísticamente significativa. Las personas con más de 80 años presentaron un riesgo 13 veces mayor de morir por COVID-19 (IC 95 % = 12.469,13.586) y la enfermedad renal crónica, un riesgo de 1.5 (IC 95 % = 1.341, 1.798); la diabetes mellitus tuvo un riesgo de 1.25 (IC 95 % = 1.238,1.276). CONCLUSIONES: La edad, el sexo, la diabetes mellitus y la obesidad resultaron ser entidades predictivas de muerte por COVID-19. Se sugiere más investigación relacionada con enfermedad pulmonar obstructiva crónica, enfermedades cardiovasculares, tabaquismo y embarazo.

Effects of the Temperature-Time Regime of Curing of Composite Patch on Repair Process Efficiency.

Repair procedures with the use of composite patches are considered to be the most effective among the current technologies of repair of the structures of various applications. In the process of moulding-on of a patch made of polymeric composite material by means of curing, technological stresses arise in the patch. Determination of residual technological stresses is a priority task for the modelling of the repair process. Reduction of residual stresses can be achieved by optimization of the mode of repair patch curing. For meeting this objective, the method for determination of technological stresses, which arise in the structure under repair in the process of curing of a composite patch, has been developed. The method takes into account the shrinkage, change in physico-mechanical characteristics, rheological processes occurring in the binder during moulding process, and determination of stresses in the structure under repair at any time. Therefore, premature failure of the repair joint at the stage of repair can be avoided. It is shown that the method adequately describes the level of deformations and stresses in the structure being repaired at the stage of heating and holding of the composite patch. Increase in the moulding temperature leads to a reduction in residual stresses in the structure under repair. However, current stresses at the stages of heating and temperature holding are increased significantly. Reliability of assumptions and developed method is confirmed by the comparison with the experimental data. The obtained experimental graph of total deformation of the composite patch allowed us to clearly determine the moment of residual stress occurrence in the structure under repair. This moment matches quite exactly (with the discrepancy not exceeding 5 min) the gel point determined analytically based on dependence of the degree of curing on the moulding mode. Consequently, the research together with the results previously obtained allows making an integrated choice of geometric parameters of the repair composite patch and temperature-time regime of its curing in order to ensure the specified level of strength and stiffness of the structure under repair.

Stress-Strain Behaviour of Reparable Composite Panel with Step-Variable Thickness.

There is an urgent problem of finding an economically viable method of maintenance and restoration of the bearing capacity of structures of various applications. Repair of structures with patches made of polymeric composite materials is one of the most promising repair technologies. However, an improper choice of parameters of the composite patch leads to unjustified increase in the structure mass and the cost of its further operation. These situations result from the lack of reliable methods for developing the repair process, which take into account the influence of the patch geometry and conditions for performance of repair works on the bearing capacity of the repaired structure. The mathematical model of the reparable composite shell-type panel taking into account inhomogeneity of transverse shear deformations at stepped variation of its thickness has been developed. In contrast to the classical theory of layered shells, the model allows simplifying a three-dimensional problem by setting of the displacement field on the layers' interfaces and their linear interpolation over thickness of the panel, as well as considering the transverse shear deformations resulting from the strength, temperature, or shrinkage loading. According to results, the maximum rise in stresses in the case of a notched panel occurs in the weakened layer, and it is from this layer the failure of the structure will start. In the event of the patch, the panel surface opposite the reinforcement is the most loaded (i.e., susceptible to failure) surface. To confirm the reliability of the developed model, we compared the analytical calculations with the results of experimental and numerical studies of the deformed state of a panel of step-variable thickness by the method of holographic interferometry and modelling by the finite element method. Displacement fields available from experiments correspond to the predicted theoretical results. The resulting maximum error does not exceed 7%. The data obtained during numerical modelling allowed us to conclude that the accuracy of theoretical calculations is sufficient for engineering practice. Results of the work can be used to solve the practical problems such as determination of stress-strain behaviour of a damaged structure or structure after repair, specification of the permissible delamination dimensions, and defining of parameters of the bonded repair process.

Self-Heating Mould for Composite Manufacturing.

The shipbuilding industry, engine manufacturing, aviation, rocket and space technology are promising fields of application for polymeric composite materials. Shape-generating moulding tools with internal heating are used for the creation of a more economically viable method of moulding of internally heated composite structures. The use of a fine-fibered resistive structure in the heated tools allows implementation of effective heating of the composite and elimination of the need for expensive and energy-intensive heating equipment. The aim of this paper was the reduction of energy consumption for internally heated moulding tools by choosing the optimal parameters for their resistive layer. A method for determination of the parameters of the moulding tool resistive layer was developed. This method allows calculation of the heating layer parameters and implementation of the specified time-temperature regime for moulding of the composite structure. It was shown that energy saving for the heated fiberglass shape-generating moulding tools was from 40 to 60%. It was found that the increase in the thickness of the moulded package of the polymeric composite material resulted not only in a higher supplied power for the heating system, but also in a complication of the method for system control, because of the growing exothermic effect of the binder curing reaction. For composite products based on Hysol EA 9396 binder, thicknesses more than 4 mm are critical, because it is not possible to cope with the self-heating effect only by cooling with ambient air already utilized at the twentieth minute of the moulding process. The influence of the physical and mechanical characteristics of the moulding tool material and stiffening ribs was analysed in terms of energy consumption and controllability of the heating system. Fiberglass shows the lowest energy consumption. Heating of the aluminium and steel moulding tools for the same purpose will require 20% and 45% more power, respectively. An increase in the number of stiffening ribs has a strong effect on the heat removal of the heating system. With a small number of aluminium ribs it is not possible to maintain the specified temperature-time regime for a fiberglass moulded package of 5 mm thick with the use of the equipment. However, when the number of stiffeners is increased to 10, the exothermic effect of the reaction becomes smoother and then the heating equipment can cope with the task. An experimental prototype of heating equipment of moulding tools for the manufacturing of structures of polymeric composite materials, as well as a flexible thermal blanket for repair of non-separable structures, were developed. The results can be the basis for a new method of optimal design of parameters of moulding tool structure at minimal heat removal to the environment.

Health schools as an organizational form of realization of the "life course health development" concept.

This study was conducted to evaluate the effectiveness of health education in the Tatarstan Republic by establishing educational programs - Health Schools - for groups of patients with a high risk of developing potentially fatal cardiac and respiratory conditions. The concept of "Life Course Health Development" implies the development of mechanisms for personalized health management. The goal of the study is to explore the effectiveness of the specialized Health Schools in Tatarstan. For the comparative study of health education effects on the overall state of personal health, 590 patients were surveyed in a randomized controlled trial. The groups of patients were compared in relation to their health education; their health status was observed prior to and afterward undergoing the educative preventative programs and estimated in comparison between the two groups. Extrapolation of the data on Tatarstan's patient population was obtained through this study, taking into account the state of health of the Health Schools students, obtaining the regression equations of population mortality and the effects of training on it. The effectiveness of Health Schools for patients with cardiovascular pathology has been proven. However, additional efforts are required to involve a wider range of patients and increase learning effectiveness to critical levels of awareness by introducing new forms of education in Health Schools since it statistically significantly increased the awareness level regarding disease nature and preventive measures.

Neurophysiological mechanisms of complex arithmetic task solving.

A new method for identification of stages in arithmetic task solving has been presented. Solving of addition tasks induced formation of EEG foci in delta-theta-band were formed in fronto-central and parietal regions of the left hemisphere and in parietal-temporal and frontal areas of right hemisphere. In multiplication tasks, delta-theta-foci were formed in frontal, central and parietal regions of the left hemisphere as well as in temporal areas of the right hemisphere. When solving addition tasks, the coherence asymmetry was increased in left hemisphere between frontal, parietal and temporal areas in delta-theta-band as well as between frontal and parietal regions in alpha-band. The neurophysiological mechanisms of complex addition and multiplication arithmetic task solving is discussed.