This work is devoted to study the existence of periodic solutions for a class of ε-family of discontinuous differential systems with many zones. We show that the averaged functions at any order ...control the existence of crossing limit cycles for systems in this class. We also provide some examples dealing with nonsmooth perturbations of nonlinear centers.
•We provide the averaging theory at any order for a class of discontinuous systems.•The main theorem allows to study the limit cycles of these systems.•The main result is applied to study nonsmooth perturbations of nonlinear centers.•For these centers we estimate the number of limit cycles.
Alzheimer’s disease (AD) is a progressive and neurodegenerative disorder of the cortex and hippocampus, which eventually leads to cognitive impairment. Although the etiology of AD remains unclear, ...the presence of β-amyloid (Aβ) peptides in these learning and memory regions is a hallmark of AD. Therefore, the inhibition of Aβ peptide aggregation has been considered the primary therapeutic strategy for AD treatment. Many studies have shown that resveratrol has antioxidant, anti-inflammatory, and neuroprotective properties and can decrease the toxicity and aggregation of Aβ peptides in the hippocampus of AD patients, promote neurogenesis, and prevent hippocampal damage. In addition, the antioxidant activity of resveratrol plays an important role in neuronal differentiation through the activation of silent information regulator-1 (SIRT1). SIRT1 plays a vital role in the growth and differentiation of neurons and prevents the apoptotic death of these neurons by deacetylating and repressing p53 activity; however, the exact mechanisms remain unclear. Resveratrol also has anti-inflammatory effects as it suppresses M1 microglia activation, which is involved in the initiation of neurodegeneration, and promotes Th2 responses by increasing anti-inflammatory cytokines and SIRT1 expression. This review will focus on the antioxidant and anti-inflammatory neuroprotective effects of resveratrol, specifically on its role in SIRT1 and the association with AD pathophysiology.
•PVLD crowns exhibited lower transient and residual stresses than PVZ crowns.•Slow cooling significantly reduced transient stresses but not residual stresses.•PVZ crowns were more sensitive to layer ...thickness ratio than PVLD crowns.•Material properties responsible for the deleterious tensile stresses were identified.•Associations between stress distribution and clinical fractures were made by VFEM.
To understand the stress development in porcelain-veneered zirconia (PVZ) and porcelain-veneered lithium disilicate (PVLD) crowns with different veneer/core thickness ratios and cooling rates. To provide design guidelines for better performing bilayer restorations with the aid of Viscoelastic Finite Element Method (VFEM).
The VFEM was validated by comparing the predicted residual stresses with experimental measurements. Then, the model was used to predict transient and residual stresses in the two bilayer systems. Models with two different veneer/core thickness ratios were prepared (2:1 and 1:1) and two cooling protocols were simulated (Fast: ∼300 °C/min, Slow: ∼30 °C/min) using the heat transfer module, followed by stress analysis in ABAQUS. The physical properties of zirconia, lithium disilicate, and the porcelains used for the simulations were determined as a function of temperature.
PVLD showed lower residual stresses than PVZ. The maximum tensile stresses in PVZ were observed in the cusp area, whereas those in PVLD were located in the central fossa. The 1:1 thickness ratio decreased stresses in both layers of PVZ. Slow cooling slightly decreased residual stresses in both systems. However, the cooling rate effect was more evident in transient stresses.
Slow cooling is preferable for both systems. A thinner porcelain layer over zirconia lowers stresses throughout the restoration. The different stress distributions between PVZ and PVLD may affect their failure modes. Smaller mismatches in modulus, CTE, and specific heat between the constituents, and the use of low Tg porcelains can effectively reduce the deleterious transient and residual tensile stresses in bilayer restorations.
Glutathione and aged garlic extract are sulfur-containing products that play important protective and regulatory roles within the immune system and in oxidative processes. Hydrogen sulfide (H₂S), an ...endogenous, gaseous, signaling transmitter, has also been shown to be involved in the regulation of inflammation. Recent studies have shown that sulfur-containing compounds from garlic have beneficial effects in attenuating outcomes associated with cardiovascular disease and inflammation by a mechanism that may be related to the H₂S signaling pathway. In this review, we summarize the main functions of glutathione (GSH), garlic derivatives and H₂S and their role in the immune response and impact on health and disease.
Acute kidney injury (AKI), characterized by a sharp drop in glomerular filtration, continues to be a significant health burden because it is associated with high initial mortality, morbidity, and ...substantial health-care costs. There is a strong connection between AKI and mechanisms of senescence activation. After ischemic or nephrotoxic insults, a wide range of pathophysiological events occur. Renal tubular cell injury is characterized by cell membrane damage, cytoskeleton disruption, and DNA degradation, leading to tubular cell death by necrosis and apoptosis. The senescence mechanism involves interstitial fibrosis, tubular atrophy, and capillary rarefaction, all of which impede the morphological and functional recovery of the kidneys, suggesting a strong link between AKI and the progression of chronic kidney disease. During abnormal kidney repair, tubular epithelial cells can assume a senescence-like phenotype. Cellular senescence can occur as a result of cell cycle arrest due to increased expression of cyclin kinase inhibitors (mainly p21), downregulation of Klotho expression, and telomere shortening. In AKI, cellular senescence is aggravated by other factors including oxidative stress and autophagy. Given this scenario, the main question is whether AKI can be repaired and how to avoid the senescence process. Stem cells might constitute a new therapeutic approach. Mesenchymal stem cells (MSCs) can ameliorate kidney injury through angiogenesis, immunomodulation, and fibrosis pathway blockade, as well as through antiapoptotic and promitotic processes. Young umbilical cord–derived MSCs are better at increasing Klotho levels, and thus protecting tissues from senescence, than are adipose-derived MSCs. Umbilical cord–derived MSCs improve glomerular filtration and tubular function to a greater degree than do those obtained from adult tissue. Although senescence-related proteins and microRNA are upregulated in AKI, they can be downregulated by treatment with umbilical cord–derived MSCs. In summary, stem cells derived from young tissues, such as umbilical cord–derived MSCs, could slow the post-AKI senescence process.
Objectives
Diet can play a role in caries disease and the consumption of ultra‐processed foods has increased over the years. The purpose was to propose predictive models on the relation between ...caries experience, diet, sex, and oral health aspects.
Methods
This cross‐sectional study included 5213 schoolchildren aged 2–11 years and a questionnaire based on WHO Oral Health Survey was applied to assess the intake of sugary foods, oral hygiene practices, access to health services and parents' perception; dmft/DMFT index, biofilm accumulation and orthodontic treatment need were assessed by 6 calibrated dentists.
Results
The logistic model showed that female sex and presence of biofilm increased the chance of having early childhood caries; besides, this chance increased by 17% for each additional day of sweetened drink intake. In children aged 6–11 years, a negative binomial regression model showed that the absence of biofilm and frequency of toothbrushing were related to lower caries index, while male sex and the consumption of salty snacks and cake/cookies were related to higher dmft+DMFT index. Disagreement or weak agreement between caregivers' perception of the presence of dental caries and children's need for dental treatment was found.
Conclusion
Early childhood caries was dependent on the consumption of sweetened drinks and the presence of biofilm, while in older children the caries experience was predicted by the consumption of snacks, cakes and biscuits, biofilm accumulation and toothbrushing frequency, emphasizing the need of health education to encourage healthy eating habits and oral care with an approach to parents/caregivers to prevent dental caries development.
This study focuses on the effects of reducing the diameter of rivets used in Friction Riveting due to the need for downscaling when joining assemblies on a smaller scale. The Friction Riveting ...process has shown promising feasibility for a variety of material combinations and applications in the transportation industry. Recent research has explored the potential application of this technique in electronics, specifically for the assembly of printed circuit boards (PCBs), using AA-2024-T351 rivets on thin glass-fiber-reinforced epoxy substrates (FR4). The joint formation of joints produced with PCBs was investigated in terms of process temperature evolution, microstructural changes, and mechanical properties. Joints were obtained at process temperatures ranging from 285 ºC to 368 ºC. The use of 4 mm rivets resulted in extensive delamination, weak joint mechanisms, and cracking, impaired by the different coefficients of thermal expansion of the materials involved. Reducing the rivet diameter to 3 mm significantly improved joint quality. A further reduction to 2.5 mm minimized delamination but led to insufficient anchorage and cracking. Joints produced with a 3 mm rivet diameter achieved the highest ultimate tensile force of 276 N. This study sets the foundation for applying the Friction Riveting process to practical PCB assemblies, demonstrating that optimizing the process parameters to the diameter-to-thickness ratio can balance sufficient rivet anchoring, minimize delamination, and reduce cracking.
Na segunda metade do século XX, o médico foniatra e escritor Pedro Bloch (1914-2004) publicou livros infantis e tratados sobre a voz e a fala de crianças. Bloch ouvia os pequenos e registrava suas ...interpretações do mundo, que soavam engraçadas. Neste artigo analisamos como fontes seus dois dicionários infantis (1998 e 2001), partindo da hipótese de que eles marcam o surgimento de uma nova posição da criança na cultura e na sociedade, na qual ela passa a exercer papel de interlocutora legítima. Metodologicamente nossa leitura se escora no ideário de autores como R. Darnton, J. Huizinga, R. Williams e, especialmente, da História cultural do humor de J. Bremmer e H. Roodenburg, que apostam na comicidade como chave para a compreensão de fenômenos históricos e culturais, o que concluímos ter ocorrido nesses volumes que consideram o posicionamento infantil e apontam a possibilidade de uma nova escrita da história da criança.
Depression is a serious and widespread mental health disorder. Although effective treatment does exist, a significant proportion of patients with depression fail to respond to antidepressant ...treatment trials, a condition named treatment-resistant depression. Efficient approach should be given this condition in order to revert the burden caused by depression. Clinical practice guidelines (CPGs) are evidence-based health promotion instruments to improve diagnosis and treatment. CPGs recommendations for treatment-resistant depression must be trustworthy. The objective of the proposed study is to systematically identify, appraise the quality of CPGs for the treatment of depression and elaborate a synthesis of recommendations for treatment-resistant depression of CPGs considered to be of high quality and with high quality recommendations.
We will search the databases of organizations, such as PubMed, Embase, Cochrane Library, PsycInfo, and the Virtual Health Library, and organizations that develop CPGs. Three independent researchers will assess the quality of the CPGs and their recommendations using the AGREE II and AGREE-REX instruments, respectively. Given the identification of divergences and convergences as well as weak and strong points among high quality CPGs, our work may help developers, clinicians and eventually patients.
No ethical approval is required for a systematic review, as no patient data will be used. The research results will be disseminated in conferences and submitted to a peer reviewed journal.
•The interfacial strength between various layers of multi-layer zirconias has been examined.•Multi-layer zirconias with different yttria contents showed a trade-off between strength and ...translucency.•The Enamel and Dentin layers exhibited similar flexural strength for a given material class.•The strength of the cross-sectional multi-layer beams was ∼30% lower than that of Enamel or Dentin layers.•Major errors in measuring flexural strength of short beams are friction and accuracy in determining loading span distances.
The rapidly increasing use of zirconia-based CAD/CAM multi-layer structures in dentistry calls for a thorough evaluation of their mechanical integrity. This work examines the effect of the multi-layering architecture as well as variations in composition and inclusion of pigments among the layers on the flexural strength of multi-layer zirconias.
A modified 4-point bending test, aided by a Finite Element Analysis (FEA), was used to probe the interfacial strength of 3 classes of yttria-partially-stabilized zirconia: Ultra Translucent Multi-Layer (UTML—5Y-PSZ), Super Translucent Multi-Layer (STML—4Y-PSZ), Multi-Layer (ML—3Y-PSZ). In accord with the size limitation (22-mm height) of CAD/CAM pucks, test samples were prepared in the form of “long” (25×2×3mm) and “short” (17.8×1.5×2mm) beams. Homogeneous beams (both long and short) were produced from either the Enamel (the lightest shade) or Dentin (the darkest shade) layer, whereas multi-layer beams (short beam only) were obtained by cutting the pucks along their thickness direction, where the material components of various shades were stacked.
The Enamel and Dentin layers exhibited similar flexural strength for a given material class, with ML amassing the highest strength (800–900MPa) followed by STML (560–650MPa) and UTML (470–500MPa). The 3 classes of multi-layer zirconia showed a trade-off between strength and translucency, reflecting different yttria contents in these materials. The failure stress of the cross-sectional multi-layer beams was, however, ∼30% lower than that of their Enamel or Dentin layer counterparts, regardless of material tested.
The weakness of interfaces is a drawback in these materials. Additionally, when measuring strength using short beam flexure, friction between the specimen and supporting pins and accuracy in determining loading span distances may lead to major errors.
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