Simulation of the corrosion-induced damage on aluminum alloy 2024 specimens with equivalent surface notches

The effect of corrosion environment aggressiveness on the tensile mechanical properties degradation of AA2024-T3 was investigated. Tensile speci­­mens were pre-corroded for various exposure times to different corrosive solutions, i.e., exfoliation corrosion (EXCO) and 3.5 wt. % NaCl. Then they were tested mechanically. In non-corroded specimens, surface notches of vari­ous depths were machined to simulate the de­gra­dation of the tensile mechanical properties due to the presence of artificial surface defects. A mechanical model was developed to correlate the corrosion-induced tensile ductility degradation due to pitting and possible hydrogen embrittle­ment with the equivalent arti­fici­al­ly induced surface notches. The cases studied for this physical cor­re­la­tion were: a) EXCO exposure with artificial notches, b) EXCO with 3.5 wt.% NaCl ex­posure and c) 3.5 wt.% NaCl ex­posure with artificial notches. Higher corre­la­tion was noticed for short exposure times for all cases where the dominant de­gradation mechanism is slight pitting form­ation. It was found that 1 h EXCO ex­­posure is equivalent to 92 h exposure to NaCl solution re­gard­ing the tensile duc­tility degradation while 24 h EXCO exposure has the same effect on duc­til­ity decrease with a 240 μm surface notch or 4000 h exposure to NaCl solution

Analysis of shared heritability in common disorders of the brain

ience, this issue p. eaap8757 Structured Abstract INTRODUCTION Brain disorders may exhibit shared symptoms and substantial epidemiological comorbidity, inciting debate about their etiologic overlap. However, detailed study of phenotypes with different ages of onset, severity, and presentation poses a considerable challenge. Recently developed heritability methods allow us to accurately measure correlation of genome-wide common variant risk between two phenotypes from pools of different individuals and assess how connected they, or at least their genetic risks, are on the genomic level. We used genome-wide association data for 265,218 patients and 784,643 control participants, as well as 17 phenotypes from a total of 1,191,588 individuals, to quantify the degree of overlap for genetic risk factors of 25 common brain disorders. RATIONALE Over the past century, the classification of brain disorders has evolved to reflect the medical and scientific communities' assessments of the presumed root causes of clinical phenomena such as behavioral change, loss of motor function, or alterations of consciousness. Directly observable phenomena (such as the presence of emboli, protein tangles, or unusual electrical activity patterns) generally define and separate neurological disorders from psychiatric disorders. Understanding the genetic underpinnings and categorical distinctions for brain disorders and related phenotypes may inform the search for their biological mechanisms. RESULTS Common variant risk for psychiatric disorders was shown to correlate significantly, especially among attention deficit hyperactivity disorder (ADHD), bipolar disorder, major depressive disorder (MDD), and schizophrenia. By contrast, neurological disorders appear more distinct from one another and from the psychiatric disorders, except for migraine, which was significantly correlated to ADHD, MDD, and Tourette syndrome. We demonstrate that, in the general population, the personality trait neuroticism is significantly correlated with almost every psychiatric disorder and migraine. We also identify significant genetic sharing between disorders and early life cognitive measures (e.g., years of education and college attainment) in the general population, demonstrating positive correlation with several psychiatric disorders (e.g., anorexia nervosa and bipolar disorder) and negative correlation with several neurological phenotypes (e.g., Alzheimer's disease and ischemic stroke), even though the latter are considered to result from specific processes that occur later in life. Extensive simulations were also performed to inform how statistical power, diagnostic misclassification, and phenotypic heterogeneity influence genetic correlations. CONCLUSION The high degree of genetic correlation among many of the psychiatric disorders adds further evidence that their current clinical boundaries do not reflect distinct underlying pathogenic processes, at least on the genetic level. This suggests a deeply interconnected nature for psychiatric disorders, in contrast to neurological disorders, and underscores the need to refine psychiatric diagnostics. Genetically informed analyses may provide important "scaffolding" to support such restructuring of psychiatric nosology, which likely requires incorporating many levels of information. By contrast, we find limited evidence for widespread common genetic risk sharing among neurological disorders or across neurological and psychiatric disorders. We show that both psychiatric and neurological disorders have robust correlations with cognitive and personality measures. Further study is needed to evaluate whether overlapping genetic contributions to psychiatric pathology may influence treatment choices. Ultimately, such developments may pave the way toward reduced heterogeneity and improved diagnosis and treatment of psychiatric disorders

Piezoresistive Properties of Natural Hydraulic Lime Binary Pastes with Incorporated Carbon-Based Nanomaterials under Cyclic Compressive Loadings

Natural Hydraulic Limes (NHL) are extensively used for the restoration of Monuments of Cultural Heritage, often combined with pozzolanic materials, such as natural pozzolans and metakaolin etc. In the present study, five (5) different cases of binary lime-based pastes composed of a specific type of NHL (NHL5) and metakaolin as pozzolanic addition were examined, that were reinforced with carbon nanostructures, namely graphene and carbon nanotubes. For the first time in restoration mortars, the incorporation of carbon nanostructures was investigated, aiming to produce materials with adequate piezoresistive response, so that they have the potential to be exploited for in situ structural health monitoring. The compressive strength, flexural strength, electrical resistance and piezoresistive response of the composite pastes was examined. The results showed that all modified carbon nanostructures lead to a significant reduction in electrical resistance. The pastes reinforced with 2D nanostructures (graphene family) displayed up to 30% increase in compressive strength and the pastes reinforced with 1D nanostructures (carbon nanotubes) displayed enhanced flexural strength (up to 100% increase). Piezoresistivity was attained for almost all investigated pastes, nevertheless the graphene oxide (GO) was considered as optimal reinforcement as the sensing ability of such pastes was found to be almost proportional to the applied compressive load level

Microstructural and Mechanical Characterization of the Aging Response of Wrought 6156 (Al-Mg-Si) Aluminum Alloy

The impact of the artificial aging response on the microstructure and tensile mechanical properties of aluminum alloy 6156 was investigated. Specimens were artificially aged at three different artificial aging temperatures and for various holding times to investigate all possible aging conditions, including the under-aged (UA), peak-aged (PA) and over-aged (OA) tempers. Microstructural investigation as well as tensile tests were performed immediately after the isothermal artificial aging heat treatment. An almost 50% increase in yield stress (around 340 MPa) was noticed in the PA temper and this was attributed to the precipitation of β′ and Q′ phases, consistent with the modelling predictions. This high yield stress value is accompanied by high values of elongation at fracture (>10%) that is essential for damage tolerance applications. The lack of large or interconnected grain boundary precipitates contributes to this high elongation. Slanted fracture was noticed for both UA and PA tempers, exhibiting a typical ductile and shear fracture mechanism. At the OA temper, coarsening of the precipitates along with broadening of the precipitate free zones resulted in a reduction in the strengthening effectiveness of the precipitates, and a small increase in the tensile ductility of approximately 12% was noticed

Mechanical properties degradation of (Al-Cu-Li) 2198 alloy due to corrosion exposure

AbstractThe present work investigates the corrosion resistance of the innovative Al-Cu-Li (2198) aluminum alloy; a comparison against Al-Cu (2024) alloy is attempted. Tensile specimens were pre-corroded for different exposure times to exfoliation corrosion solution and immediately afterwards they were tested in tension. For small exposure times (< 12 h) small pits could be found on the corroded surfaces; pitting was also noticed at the small side surfaces (thickness) of the tensile specimens. Corrosion exposure seems not to essentially decrease the yield stress of AA2198 even for high exposure times, while this was not the case for AA2024. After heavy corrosion exposure (>12 h), AA2024 lost almost 30% of its initial ultimate tensile strength, while for AA2198 the respective value was only 11%. Al-Cu-Li alloy shows superior corrosion resistance in terms of maintaining higher percentages of tensile ductility; AA2198 exhibited higher remaining elongation at fracture values due to corrosion degradation for all investigated exposure times

Dispersion of Multi-Walled Carbon Nanotubes into White Cement Mortars: The Effect of Concentration and Surfactants

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a superplasticizer were examined to reinforce, at the nanoscale, a white cement mortar typically used for the restoration of monuments of cultural heritage. It was shown that sodium dodecylbenzenesulfonate (SDBS) and Triton X-100 surfactants slightly decreased the white cement mortars&rsquo; electrical resistivity (by an average of 10%), however, the mechanical properties were essentially decreased by an average of 60%. The most suitable dispersion agent for the MWCNTs proved to be the superplasticizer Ceresit CC198, and its optimal concentration was investigated for different MWCNT concentrations. Carboxylation of the MWCNT surface with nitric acid did not improve the mechanical performance of the white cement nanocomposites. The parametric experimental study showed that the optimum combination of 0.8 wt% of cement superplasticizer and 0.2 wt% of cement MWCNTs resulted in a 60% decrease in the electrical resistivity; additionally, the flexural and compressive strengths were both increased by approximately 25% and 10%, respectively

Epidemiological Profile among Greek CrossFit Practitioners

CrossFit (CF) is a popular and rapidly expanding training program in Greece and worldwide. However, there is a lack of scientific evidence on the risk of musculoskeletal injuries related to CF in the Greek population. A self-administered survey of 1224 Greek CF practitioners aged 18 to 59 was conducted and analyzed using the Statistical Package for Social Sciences (SPSS) software. The highest percentage of the participants (34%) practiced 5 days per week for 60 min (42.2%) and had 2 days per week of rest (41.7%). A total of 273 individuals (23%) participated in CF competitions and 948 (77%) did not. The results showed that the most common injuries were muscle injuries (51.3%), followed by tendinopathies (49.6%) and joint injuries (26.6%). The shoulders (56.6%; n = 303), knees (31.8%; n = 170), and lumbar spine (33.1%; n = 177) were the most commonly injured locations. The logistic regression model showed that participation in competitions (p = 0.001), rest per week (p = 0.01), duration of training per session (p = 0.001), and frequency of training per week (p = 0.03) were statistically significant factors for injury. Training level was not a statistically significant factor for injury (p = 0.43). As CF continues to gain popularity on a global scale and the number of athletes gradually increases, it is important to monitor the safety of practitioners. Clinicians should consider participation in competitions, rest, training duration, and frequency in order to make CF safer

Non-destructive damage characterization of marble subjected to bending

Μη διαθέσιμη περίληψηNot available summarizationPresented on