A FULLY IMPLICIT MATERIAL RESPONSE CODE WITH ABLATION AND PYROLYSIS FOR SIMULATION OF THERMAL PROTECTION SYSTEMS

The purpose of this paper is to introduce and describe a 2-D fully implicit numerical simulation tool capable of evaluating the behaviour of an ablative charring thermal protection system during atmospheric entry. In particular, the computational tool can model the heat transfer inside a solid porous material and the decomposition of the latter, pyrolysis gas density, pressure and speed distributions and surface recession. The governing equations are fully coupled and are integrated using a time-implicit scheme. The grid can contract to simulate the recession phenomenon and the recession rate can be evaluated using different ablation models, depending on the problem and on the available data. Spatial and temporal convergence tests demonstrated that the tool is second order accurate in space and time and comparisons with available numerical results are shown here for code verification

Bond strength and morphology of enamel using self-etching adhesive systems with different acidities

OBJECTIVES: To assess the bond strength and the morphology of enamel after application of self-etching adhesive systems with different acidities. The tested hypothesis was that the performance of the self-etching adhesive systems does not vary for the studied parameters. MATERIAL AND METHODS: Composite resin (Filtek Z250) buildups were bonded to untreated (prophylaxis) and treated (bur-cut or SiC-paper) enamel surfaces of third molars after application of four self-etching and two etch-and-rinse adhesive systems (n=6/condition): Clearfil SE Bond (CSE); OptiBond Solo Plus Self-Etch (OP); AdheSe (AD); Tyrian Self Priming Etching (TY), Adper Scotchbond Multi-Purpose Plus (SBMP) and Adper Single Bond (SB). After storage in water (24 h/37°C), the bonded specimens were sectioned into sticks with 0.8 mm² cross-sectional area and the microtensile bond strength was tested at a crosshead speed of 0.5 mm/min. The mean bond strength values (MPa) were subjected to two-way ANOVA and Tukey's test (α=0.05). The etching patterns of the adhesive systems were also observed with a scanning electron microscope. RESULTS: The main factor adhesive system was statistically significant (

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

Modeling and Numerical Simulation of the Behavior of Charring Ablators During Atmospheric Re-Entry

During the atmospheric entry of a blunt body, a bow shock wave is generated on the nose of the vehicle, originating a zone at the wall where gaseous species are in thermochemical non-equilibrium. In fact, the large kinetic energy of the flow is converted through the shock into internal energy causing an increase in temperature, especially close to the nose. The temperature rise occurring near the stagnation region may excite the vibrational energy of the gas molecules and may also lead to dissociation and even to ionization. Thus, a hypersonic flow is frequently a chemically reacting flow. Another important high-temperature effect is the radiative heating from the flow to the body. The most important consequence of high temperatures, from a technological point of view, is the resultant high heat transfer rates to the surface. Thus, in order to protect the vehicle's substructure against the heat loads coming from the boundary layer, it is necessary to provide an accurate design of the heat shield that has the task to isolate the interior of the space vehicle from the high temperatures in the shock layer. Therefore, the accurate prediction of the thermal response of the Thermal Protection System (TPS) is essential to accurately design the heat shield with the aim of optimizing its thickness and shape. Thermal protection systems able to endure very high temperatures are made up of materials called surface ablators, that lose mass when subjected to high thermal loads. There can be different causes of mass loss such as phase change, chemical erosion, oxidation and mechanical removal. In general, the mass loss is part of a process called ablation through which the material rejects energy by means of a density variation. Another type of ablative materials are the so called charring or decomposing ablators that undergo both surface ablation and in-depth decomposition. The surface ablators are usually metals, graphite or carbon-carbon, while the charring ablators are resin/binder composites. The main goal of this research has been the development of a computational tool able to accurately simulate the behavior of a non-reusable heat shield during the atmospheric re-entry of a space vehicle. The final tool can study both the behavior of the ablative thermal protection system and its interaction with the boundary layer through a strong coupling with a CFD solver. The main features that can be considered during the computation are the decomposition of the resin and the consequent generation of pyrolysis gas inside the pore space, in addition to the ablation phenomenon. For instance, the pyrolysis effects related to the inner decomposition within a porous charring ablator can be studied, including in-depth gas flux, porosity and pore pressure. This information can be used to predict in-depth damage or mechanical removal caused by large pressure gradients inside the pore spaces. Our numerical simulation tool is also able to simulate the recession of the material and different ablation models can be used to evaluate the recession rate at the wall. Moreover the ablators (unlike the ceramic tiles) strongly affect the flow field through the ablation phenomenon and the pyrolysis gas injection into the boundary layer. Consequently, the coupling with a Navier-Stokes code allows us to study the gas/solid interaction at the wall

Violência contra a mulher

Inclui bibliografia.Traz o tema da violência contra a mulher, mais especificamente da violência doméstica. Aborda questões como o papel da mulher na sociedade, o ciclo da violência doméstica e como romper esse ciclo, onde buscar ajuda e os direitos assegurados pela Lei Maria da Penha que, pouco mais de uma década após sua aprovação, tem sido utilizada na elaboração de políticas voltadas ao combate à violência contra as mulheres

R25C mutation in the NKX2.5 gene in Italian patients affected with non-syndromic and syndromic congenital heart disease

AIMS: Heterozygous mutations in the transcription factor Nkx2.5 indicate a genetic cause for congenital heart diseases (CHDs) in human beings. The present study aimed to assess the prevalence of NKX2.5 mutations in Italian patients with sporadic non-syndromic and syndromic CHD, as well as to appraise any genotype-phenotype correlations. METHODS: One hundred Italian patients affected with CHD (90 had sporadic non-syndromic CHD and 10 had syndromic CHD) were screened for NKX2.5 mutations. The coding region and flanking regions involved in gene splicing of the CSX/NKX2.5 gene were amplified from genomic DNA by PCR, and mutational analysis was performed using denaturing high performance liquid chromatography and DNA sequencing. RESULTS: One previously reported NKX2.5 mutation (c.73C>T, p.R25C) was identified in two of the 100 CHD patients (2%). We have detected the p.R25C alteration in a woman showing aneurysm of the membranous septum, aortic coarctation and bicuspid aortic valve, that was a different phenotype from those previously reported, and for the first time in a patient with syndromic CHD with Down's syndrome (posterior ventricular septal defect, atrial septal defect, left superior cava vein ' sinus, and patent ductus arteriosus). CONCLUSION: Our results confirm that NKX2.5 mutations are not a common cause of CHD; furthermore, the p.R25C variation may increase susceptibility to development of CHD in patients with and without chromosomal abnormalities