Association between COVID-19 and the incidence of type 1 diabetes in Portugal - a registry study.

BACKGROUND: Viral respiratory infections may precipitate type 1 diabetes (T1D). A possible association between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for COVID-19, and the incidence of T1D is being determined. This study was carried out using Portuguese registries, aiming at examining temporal trends between COVID-19 and T1D. METHODS: Hospital data, comparing the incidence before and during the COVID-19 pandemic, from children and young adults diagnosed with new-onset T1D, was acquired beginning in 2017 and until the end of 2022. Data was obtained from nine different Portuguese hospital units. The impact of the COVID-19 pandemic, beginning in March 2020, was assessed comparing the annual numbers of new-onset T1D cases. The annual median levels of glucose, glycated hemoglobin (HbA1c) and fasting C-peptide at T1D diagnosis were compared. The annual number of diabetic ketoacidosis (DKA) episodes among new T1D cases was also assessed at two centers. RESULTS: In total, data from 574 newly diagnosed T1D patients was analyzed, including 530 (92.3%) children. The mean ages for child and adult patients were 9.1 (SD 4.4) and 32.8 (SD 13.6) years, respectively. 57.8% (331/573) were male, one patient had unknown sex. The overall median (25-75 percentiles) levels of glucose, HbA1c and fasting C-peptide at diagnosis were 454 mg/dL (356-568), 11.8% (10.1-13.4) and 0.50 µg/L (0.30-0.79), respectively. DKA at T1D diagnosis was present in 48.4% (76/157). For eight centers with complete 2018 to 2021 data (all calendar months), no overall significant increase in T1D cases was observed during the COVID-19 pandemic, i.e. 90 cases in 2018, 90 cases in 2019, 112 in 2020 and 100 in 2021 (P for trend = 0.36). Two of the centers, Faro (CHUA) and Dona Estefânia (CHULC) hospitals, did however see an increase in T1D from 2019 to 2020. No significant changes in glucose (P = 0.32), HbA1c (P = 0.68), fasting C-peptide (P = 0.20) or DKA frequency (P = 0.68) at the time of T1D diagnosis were observed over the entire study period. CONCLUSION: The T1D incidence did not increase significantly, when comparing the years before and during the COVID-19 pandemic, nor did key metabolic parameters or number of DKA episodes change.

Evaluation of the Resistance of a Polypropylene Geotextile Against Ultraviolet Radiation.

The exposure to solar radiation (mainly due to the action of ultraviolet radiation) is one of the main causes for the premature failure of many polymeric materials, including the geotextiles. In this work, a nonwoven polypropylene geotextile (stabilized with a known amount of a hindered amine light stabilizer) was exposed to ultraviolet-aging tests, both in the laboratory (accelerated conditions) and outdoors (natural conditions). The damage occurred in the geotextile (caused by the ultraviolet-aging tests) was evaluated quantitatively (by monitoring changes in its mass per unit area, thickness, and tensile properties) and qualitatively (by scanning electron microscopy). The results, among other findings, showed that: (1) the ultraviolet-aging tests (both in the laboratory and outdoors) induced relevant damage in the polypropylene fibers of the geotextile (transverse cracks), leading to the deterioration of its tensile behavior, (2) the amount of degradation increased with the increase of the ultraviolet radiant energy, (3) the laboratory tests caused a faster deterioration of the polypropylene fibers than the outdoor tests, and (4) the degradation found by scanning electron microscopy in the polypropylene fibers correlated well with the deterioration occurred in the tensile behavior of the geotextile.

Tensile and Tearing Properties of a Geocomposite Mechanically Damaged by Repeated Loading and Abrasion.

The behaviour of geosynthetics can be affected by many agents, both in the short and long term. Mechanical damage caused by repeated loading or abrasion are examples of agents that may induce undesirable changes in the properties of geosynthetics. The research conducted in this work complemented previous studies and consisted of submitting a geocomposite, isolated and successively, to two degradation tests: mechanical damage under repeated loading and abrasion. The geocomposite (a nonwoven geotextile reinforced with polyethylene terephthalate filaments) was tested on both sides (with or without filaments) and directions (machine and cross-machine). The impact of the degradation tests on the geocomposite was quantified by monitoring changes in its tensile and tearing behaviour. The results showed that, in most cases, the degradation tests caused the deterioration of the tensile and tearing behaviour of the geocomposite, affecting its reinforcement function. The decline in tensile strength correlated reasonably well with the decline in tearing strength. Changing the side and direction tested influenced, in some cases (those involving abrasion), the degradation experienced by the geocomposite. The reduction factors (referring to tensile and tearing strength) for the combined effect of the degradation agents tended to be lower when determined by using the common method (compared to those resulting directly from the successive exposure to both agents).

Effect of Sustained Loading on the Direct Shear Behaviour of Recycled C&D Material-Geosynthetic Interfaces.

Recycled construction and demolition (C&D) wastes have been pointed out as a feasible alternative to traditional backfill materials of geosynthetic-reinforced structures, but the current knowledge about the interface behaviour between these unconventional (recycled) materials and the reinforcement is still limited, particularly as far as the time-dependent response is concerned. In this study, a series of large-scale direct shear tests was conducted using an innovative multistage method to evaluate the influence of shear creep loading on the direct shear response of the interfaces between a fine-grained C&D material and two different geosynthetic reinforcements (high-strength geotextile and geogrid). The peak and large-displacement interface shear strength parameters obtained from tests involving sustained loading were compared with those from conventional interface tests. Test results have shown that the shear creep deformation of the interfaces increased with the magnitude of sustained loading. The test specimens experienced additional vertical contraction during the creep stage, which tended to increase with the applied normal stress. For the recycled C&D material-geotextile interface, the sustained loading induced a reduction in the apparent cohesion and a slight increase in the friction angle, when compared to the values estimated from conventional tests. In turn, for the geogrid interface, the apparent cohesion values increased, whereas the friction angle did not significantly change upon shear creep loading.

Weathering of a Nonwoven Polypropylene Geotextile: Field vs. Laboratory Exposure.

Like other plastic materials, geosynthetics can undergo changes in their properties due to weathering. These changes must be known and, if necessary, duly accounted for in the design phase. This work evaluates the resistance of a nonwoven polypropylene geotextile to weathering, both in the field (under natural degradation conditions) and in the laboratory (under accelerated degradation conditions). The damage experienced by the geotextile in the field weathering tests was evaluated by monitoring changes in its physical (mass per unit area and thickness), mechanical (tensile, tearing and puncture behaviour) and hydraulic (water permeability normal to the plane) properties. Microscopic damage was assessed by scanning electron microscopy. In the laboratory weathering tests, only the tensile behaviour of the geotextile was monitored. The results showed that all geotextile properties were affected by weathering. The mechanical strength of the geotextile decreased in the field weathering tests. Microscopic transverse cracks were found in the weathered polypropylene fibres, which may explain the reduction in mechanical strength. The accumulation of dirt on the nonwoven structure altered the physical and hydraulic properties of the geotextile. Comparing the field and laboratory weathering tests, the reduction in tensile strength found after 24 months outdoors (roughly 30%) was very similar to that observed after 4000 h in the laboratory. This relationship may not be valid for other geotextiles or other exposure locations.

Influence of Mechanical Damage under Repeated Loading on the Resistance of Geogrids against Abrasion.

Geogrids are building materials widely used for soil reinforcement that can be affected by the action of many degradation agents throughout their service life. The potential negative effect of the degradation agents should be properly estimated and accounted for during the design phase. The main aim of this work was to study the influence of mechanical damage under repeated loading on the resistance of geogrids against abrasion. Three geogrids (one extruded and two woven) were exposed in isolation to mechanical damage under repeated loading and abrasion tests, followed by the successive exposure to both degradation tests. The damage suffered by the geogrids was evaluated by visual inspection and by tensile tests. Based on the changes found in tensile strength, reduction factors were determined. The reduction factors obtained directly from the successive exposure were compared to those resulting from a method in which the reduction factors obtained for the isolated effect of each degradation agent were multiplied. Results indicated that the abrasion process tended to be affected by a previous exposure to mechanical damage under repeated loading and that the multiplication of the reduction factors obtained for the isolated effects of the degradation agents may not correctly represent their combined effect.

Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode.

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

Laboratory Study of the Ultraviolet Radiation Effect on an HDPE Geomembrane.

High-density polyethylene (HDPE) geomembranes are polymeric geosynthetic materials usually applied as a liner in environmental facilities due to their good mechanical properties, good welding conditions, and excellent chemical resistance. A geomembrane's field performance is affected by different conditions and exposures, including ultraviolet radiation, thermal and oxidative exposure, and chemical contact. This article presents an experimental study with a 1.0 mm-thick HDPE virgin geomembrane exposed by the Xenon arc weatherometer for 2160 h and the ultraviolet fluorescent weatherometer for 8760 h to understand the geomembrane's behavior under ultraviolet exposure. The evaluation was performed using the melt flow index (MFI) test, oxidative-induction time (OIT) tests, tensile test, differential scanning calorimetry (DSC) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. The sample exposed in the Xenon arc equipment showed a tendency to increase the MFI values during the exposure time. This upward trend may indicate morphological changes in the polymer. The tensile behavior analysis showed a tendency of the sample to lose ductility, without showing brittle behavior. The samples' OIT test results under both device exposures showed faster antioxidant depletion for the standard OIT test than the high-pressure OIT test. The DSC and FTIR analyses did not demonstrate the polymer's changes.

Effect of Different Aggregates on the Mechanical Damage Suffered by Geotextiles.

The installation process of geosynthetics can be, in some applications, one of the most relevant degradation mechanisms of these construction materials, affecting their performance and useful lifetime. In this work, three nonwoven geotextiles with different masses per unit area were submitted to mechanical damage under repeated loading tests with corundum and with different natural aggregates. The damage occurred in the geotextiles was evaluated by visual inspection and by monitoring changes in their short-term tensile and puncture behaviors (mechanical properties) and in their water permeability behavior normal to the plane (hydraulic property). The mechanical damage under repeated loading tests provoked relevant changes in the mechanical and hydraulic properties of the geotextiles. These changes depended on the mass per unit area of the geotextiles and on the characteristics of the aggregates. The results enabled the establishment of a correlation between the loss of mechanical strength and the variation of the water permeability normal to the plane of the geotextiles.

Resistance of Geosynthetics against the Isolated and Combined Effect of Mechanical Damage under Repeated Loading and Abrasion.

The behaviour of materials used for developing engineering structures should be properly foreseen during the design phase. Regarding geosynthetics, which are construction materials used in a wide range of engineering structures, the installation on site and the action of many degradation agents during service life may promote changes in their properties, endangering the structures in which they are applied. The evaluation of the damage suffered by geosynthetics, like installation damage or abrasion, is often carried out through laboratory tests. This work studied the behaviour of five geosynthetics (three geotextiles and two geogrids) after being individually and successively exposed to two degradation tests: mechanical damage under repeated loading and abrasion. The short-term mechanical and hydraulic behaviours of the geosynthetics were analysed by performing tensile tests and water permeability normal to the plane tests. Reduction factors were determined based on the changes occurred in the tensile strength of the geosynthetics. Findings showed that mechanical damage under repeated loading and abrasion tended to affect the mechanical and hydraulic properties of the geosynthetics and that the reduction factors calculated according to the traditional method may not be able to represent accurately the damage suffered by the materials when exposed successively to the degradation mechanisms.