•A fracture mechanics approach to assess the impact performance of AHSS is presented.•Fracture resistance is evaluated through the essential work of fracture methodology.•Toughness is measured in ...terms of crack initiation and propagation resistance.•Crash resistance of AHSS is described according to a cracking pattern in crash tests.•Steels with higher essential work of fracture, we, present better crash performance.
Automotive industry players have devoted large efforts to identify the material parameters governing the crash resistance of Advanced High Strength Steels (AHSS). Such knowledge is essential to improve impact performance prediction and optimize new steel development. Nevertheless, there is still an open discussion about which are the most relevant properties on AHSS crashworthiness. In this work, the authors investigate the correlation between the fracture toughness of different AHSS and their crash failure behaviour. Fracture toughness is measured in the frame of fracture mechanics, through the essential work of fracture methodology. Two fracture resistance parameters are characterized: the fracture toughness at cracking initiation, wei, and the essential work of fracture, we. Toughness values are compared with the results of axial impact tests, which are evaluated according to the energy absorbed and the cracking behaviour observed in crash boxes. Results show that fracture toughness permits to describe different crash events in terms of crack initiation and crack propagation and allows ranking AHSS impact resistance; steels with higher we present better crash performance. Therefore, fracture toughness is proposed as a key material property to predict the crash resistance of AHSS and as a relevant design parameter for crash resistant parts.
•Self-healing UHPCs are developed by using a set of two additions.•Healing additions reduce the mechanical performance but refine the microporosity.•An effective autonomous self-healing capacity is ...assessed in the fabricated UHPC.•Self-healing capacity is not improved when increasing the additions content used.•The crack width and the healing period influence the self-healing efficacy.
UHPC are developed in present paper incorporating an innovative self-healing system based on two micro/nano-additions: silica microcapsules containing epoxy sealing compound (CAP) and amine functionalised silica nanoparticles. Although CAP are well integrated within the cementitious matrix, their inclusion promotes a reduction in the mechanical performance so CAP could act as weak points. However, the inclusion of these additions refines pore distribution thus increasing the expected durability in aggressive media. An effective autonomous self-healing capacity is assessed/confirmed which is unexpectedly higher in the concretes with the lower healing additions content studied. This capacity depends on the crack width and the healing period considered.
A Fe–20.1Mn–1.23Si–1.72Al–0.5C TWIP steel with ultrafine grain structure was successfully processed through equal channel angular pressing (ECAP) at warm temperature up to four passes following the
B
...C
route. The microstructure evolution was characterized by electron backscattered diffraction to obtain the grain maps, which revealed an obvious reduction in grain size, as well as a decrease in the twin fraction, with increasing number of ECAP passes. The texture evolution during ECAP was analyzed by orientation distribution function. The results show that the annealed material presents brass (
B
) as dominant component. After ECAP, the one pass sample presents
A
1
* and
A
2
* as the strongest components, while the two passes and four passes samples change gradually toward
B
/
B
¯
components. TEM analysis shows that all samples present twins. The twin thickness is reduced with increasing the number of ECAP passes. Nano-twins, as a result of secondary twinning, are also observed in the one and two passes samples. In the four passes sample, the microstructure is extensively refined by the joint action of ultrafine subgrains, grains and twins. The mechanical behavior was studied by tensile samples, and it was found that the yield strength and the ultimate tensile strength are significantly enhanced at increasing number of ECAP passes. Although the ductility and strain hardening capability are reduced with ECAP process, the present TWIP steel shows significant uniform deformation periods with positive work hardening rates.
Seasonal "common-cold" human coronaviruses are widely spread throughout the world and are mainly associated with mild upper respiratory tract infections. The emergence of highly pathogenic ...coronaviruses MERS-CoV, SARS-CoV, and most recently SARS-CoV-2 has prompted increased attention to coronavirus biology and immunopathology, but the T-cell response to seasonal coronaviruses remains largely uncharacterized. Here we report the repertoire of viral peptides that are naturally processed and presented upon infection of a model cell line with seasonal coronavirus OC43. We identified MHC-bound peptides derived from each of the viral structural proteins (spike, nucleoprotein, hemagglutinin-esterase, membrane, and envelope) as well as non-structural proteins nsp3, nsp5, nsp6, and nsp12. Eighty MHC-II bound peptides corresponding to 14 distinct OC43-derived epitopes were identified, including many at very high abundance within the overall MHC-II peptidome. Fewer and less abundant MHC-I bound OC43-derived peptides were observed, possibly due to MHC-I downregulation induced by OC43 infection. The MHC-II peptides elicited low-abundance recall T-cell responses in most donors tested. In vitro assays confirmed that the peptides were recognized by CD4+ T cells and identified the presenting HLA alleles. T-cell responses cross-reactive between OC43, SARS-CoV-2, and the other seasonal coronaviruses were confirmed in samples of peripheral blood and peptide-expanded T-cell lines. Among the validated epitopes, spike protein S903-917 presented by DPA1*01:03/DPB1*04:01 and S1085-1099 presented by DRB1*15:01 shared substantial homology to other human coronaviruses, including SARS-CoV-2, and were targeted by cross-reactive CD4 T cells. Nucleoprotein N54-68 and hemagglutinin-esterase HE128-142 presented by DRB1*15:01 and HE259-273 presented by DPA1*01:03/DPB1*04:01 are immunodominant epitopes with low coronavirus homology that are not cross-reactive with SARS-CoV-2. Overall, the set of naturally processed and presented OC43 epitopes comprise both OC43-specific and human coronavirus cross-reactive epitopes, which can be used to follow CD4 T-cell cross-reactivity after infection or vaccination, and to guide selection of epitopes for inclusion in pan-coronavirus vaccines.
The deformation behavior of IN718 superalloy was investigated using the hot compression tests in the temperature range of 950–1100°C, and strain rates covering the quasi-static to the quasi-dynamic ...regions (0.001–10s−1). The shape of flow curves as well as the corresponding work hardening rates analysis was utilized to reveal the dynamic recrystallization (DRX) phenomena. DRX was the dominant restoration mechanism in the whole temperature and strain rate domains, which was characterized by the optical and EBSD images. Extended flow softening was observed at high strain rates due to the adiabatic heating and dislocations interaction. In addition to the assessment the capability of Sellars equations, a new constitutive equation based on the multiple variable regression analysis was proposed for modeling the peak stress as a function of strain rate and temperature. Besides the simple form of the proposed model, it has a good accuracy for predicting the peak stress.
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•The inflection analysis proved the occurrence of DRX.•Adiabatic heating and strong dislocations interaction cause more softening at 10s−1.•For showing the constitutive equation, the power expression is the best.•A new constitutive equation based on multivariable regression analysis was proposed.•The proposed model showed a good accuracy for predicting the peak stress.
We report on the surface and bulk chemistry of Li x Mn2O4 (0 ≤ x ≤ 1) spinel oxide electrode for the selective extraction of LiCl from natural salt lake brines using an electrochemical method based ...on LiMn2O4 (LMO) lithium intercalation electrode and polypyrrole (PPy) reversible chloride electrode. Both the surface composition and insertion/release of Li ions into/from the crystal structure have been studied with pulsed laser deposited (PLD) thin Li x Mn2O4 films and composite LMO/carbon black electrodes. Cyclic voltammetry (CV), XPS/UPS, XRD, chrono-amperometry, and galvanostatic intermittent titration technique (GITT) experiments in model LiNO3 solutions and natural brines from Salar de Olaroz (Jujuy, Argentina) have been used. Repetitive CV and GITT experiments showed reversible extraction/intercalation of Li ions in LMO with high selectivity and electrode stability in natural brine, while PPy is reversible to chloride ions. Chronoamperometry for time-bound diffusion in small nanocrystals with interference of concentration profiles yielded D Li + ∼ 10–10 cm2·s–1. Photoelectron spectroscopy showed Mn/O surface stoichiometry close to 1:2 and initial 1:1 MnIV/MnIII ratio with MnIII depletion during oxidation at 1.1 V vs Ag/AgCl and recovery of surface MnIII after reduction at 0.4 V. Coadsorption of Na+ was detected which resulted in slower ion exchange of Li ions, but there was no evidence of Na+ intercalation in the Mn oxide electrode.
One of the most accepted engineering construction concepts of underground repositories for high radioactive waste considers the use of low-pH cementitious materials. This paper deals with the design ...of those based on Ordinary Portland Cements with high contents of silica fume and/or fly ashes that modify most of the concrete "standard" properties, the pore fluid composition and the microstructure of the hydrated products. Their resistance to long-term groundwater aggression is also evaluated. The results show that the use of OPC cement binders with high silica content produces low-pH pore waters and the microstructure of these cement pastes is different from the conventional OPC ones, generating C-S-H gels with lower CaO/SiO sub(2) ratios that possibly bind alkali ions. Leaching tests show a good resistance of low-pH concretes against groundwater aggression although an altered front can be observed.
Vaccines are one of the most cost effective methods to control infectious diseases and at the same time one of the most complex products of the pharmaceutical industry. In contrast to other drugs, ...vaccines are used mainly in healthy individuals, often in children. For this reason, very high standards are set for their production. Subunit vaccines, especially peptide vaccines, can provide a safe and cost-effective alternative to vaccines produced from attenuated or inactivated pathogen preparations. Biochemical and structural studies of class II MHC-peptide complexes are beginning to provide a conceptual foundation for the rational design of subunit and peptide vaccines. In this review, we show how analysis of peptide-class II MHC complexes together with developing understanding of antigen processing pathways has opened the door to understanding the major rules that govern selection of T cell epitopes. We review progress towards computational prediction of such epitopes, and efforts to evaluate algorithms that incorporate various structural and/or biochemical aspects of the MHC-peptide interaction. Finally, using malaria as a model, we describe the development of a minimal subunit vaccine for the human malaria parasite Plasmodium falciparum.
•This work researches the properties of self-stressing SCC for structural elements.•Expansive additives influence self-compacting properties and compressive strength.•Without watering, type G ...additives promote larger total longitudinal expansion.•The cement chemical composition influences the type K additive efficacy.•Different microstructural mechanisms are responsible for the obtained expansion.
Self-stressing self-compacting concretes were developed for structural elements, considering two types of expansive additives (types K and G) and two cement types. The influence of different parameters in their performance was evaluated. The addition of expansive additives resulted in compressive strength reductions that mainly depended on the total expansion reached. This total expansion depended on the alumina and sulfates contents of cement when using type K additive and, without watering, type G promoted larger total longitudinal expansion by forming amorphous calcium hydrated agglomerates. In contrast, when using type K additive, an indiscriminate formation of ettringite was observed.
This research work studies the influence of single microalloying elements (Nb and Mo) and the solidification route on the hot ductility behavior of a high-manganese austenitic Twinning Induced ...Plasticity (TWIP) steel. For this purpose uniaxial hot tensile tests in the temperature range of 700–1100°C under a constant true strain rate (10−3s−1) were carried out to evaluate the hot ductility as a function of reduction in area (%RA). In general, results revealed a beneficial influence of Nb and Mo additions to TWIP steels on the hot ductility behavior, particularly in the intermediate temperature range of 800–900°C, where the reduction of area (RA) value can be as high as 73%. The hot ductility behavior of the present TWIP steels is discussed in terms of solid-solution strengthening, solute drag phenomenon, dynamic recrystallization (DRX) and grain boundary precipitation. Ductile fracture type was recognized as the material failure surface containing many dimples in almost all the studied cases.
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