Atomic scale modeling of the thermodynamic and kinetic properties of dilute alloys driven by forced atomic relocations

Sustained external forces acting on a material provide additional mechanisms to evolve the state of the system, and these mechanisms do not necessarily obey the microscopic detailed balance. Therefore, standard methods to compute the thermodynamic and kinetic properties do not apply in such driven systems. The competition between these mechanisms and the standard thermally activated jumps leads to non-equilibrium steady states. We extend the Self-Consistent Mean Field theory to take into account forced atomic relocations (FARs) as a model of these additional kinetic mechanisms. The theory is applied to the atomic-scale modelling of radiation damage. Using a first-shell approximation of the theory, we highlight the violation of Onsager reciprocal relations in driven systems. An implementation of the extended theory into the KineCluE code yields calculations of the effective Onsager coefficients in agreement with Monte Carlo simulations. A systematic parametric study is performed to emphasize the effect of FAR distances and the solute-defect interaction on the diffusion properties. The effect of FAR on the vacancy-solute flux coupling and the solute tracer diffusivity is non-negligible when: (i) the solute-vacancy thermodynamic attraction is large, (ii) the magnitude of the thermal jump frequencies is lower or comparable to the frequencies of FAR, and (iii) the range of interactions between vacancies and solute atoms is close to FAR distances.Comment: typos corrected, references added, revised arguments in Introduction and Modeling section

QoS-Aware Middleware for Web Services Composition

The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online Business-to-Business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different Quality of Service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming

The role of tumor-associated macrophages in glioma cohort: through both traditional RNA sequencing and single cell RNA sequencing

Gliomas are the leading cause in more than 50% of malignant brain tumor cases. Prognoses, recurrences, and mortality are usually poor for gliomas that have malignant features. In gliomas, there are four grades, with grade IV gliomas known as glioblastomas (GBM). Currently, the primary methods employed for glioma treatment include surgical removal, followed by chemotherapy after the operation, and targeted therapy. However, the outcomes of these treatments are unsatisfactory. Gliomas have a high number of tumor-associated macrophages (TAM), which consist of brain microglia and macrophages, making them the predominant cell group in the tumor microenvironment (TME). The glioma cohort was analyzed using single-cell RNA sequencing to quantify the genes related to TAMs in this study. Furthermore, the ssGSEA analysis was utilized to assess the TAM-associated score in the glioma group. In the glioma cohort, we have successfully developed a prognostic model consisting of 12 genes, which is derived from the TAM-associated genes. The glioma cohort demonstrated the predictive significance of the TAM-based risk model through survival analysis and time-dependent ROC curve. Furthermore, the correlation analysis revealed the significance of the TAM-based risk model in the application of immunotherapy for individuals diagnosed with GBM. Ultimately, the additional examination unveiled the prognostic significance of PTX3 in the glioma group, establishing it as the utmost valuable prognostic indicator in patients with GBM. The PCR assay revealed the PTX3 is significantly up-regulated in GBM cohort. Additionally, the assessment of cell growth further confirms the involvement of PTX3 in the GBM group. The analysis of cell proliferation showed that the increased expression of PTX3 enhanced the ability of glioma cells to proliferate. The prognosis of glioblastomas and glioma is influenced by the proliferation of tumor-associated macrophages

Polysaccharide Extracted from Laminaria japonica

This study aimed to determine the effect of topically applied Laminaria polysaccharide (LP) on skin aging. We applied ointment containing LP (10, 25, and 50 μg/g) or vitamin E (10 μg/g) to the dorsal skin of aging mice for 12 months and young control mice for 4 weeks. Electron microscopy analysis of skin samples revealed that LP increased dermal thickness and skin collagen content. Tissue inhibitor of metalloprotease- (TIMP-) 1 expression was upregulated while that of matrix metalloproteinase- (MMP-) 1 was downregulated in skin tissue of LP-treated as compared to untreated aging mice. Additionally, phosphorylation of c-Jun N-terminal kinase (JNK) and p38 was higher in aging skin than in young skin, while LP treatment suppressed phospho-JNK expression. LP application also enhanced the expression of antioxidative enzymes in skin tissue, causing a decrease in malondialdehyde levels and increases in superoxide dismutase, catalase, and glutathione peroxidase levels relative to those in untreated aging mice. These results indicate that LP inhibits MMP-1 expression by preventing oxidative stress and JNK phosphorylation, thereby delaying skin collagen breakdown during aging

Modélisation multi-échelle de la ségrégation induite par irradiation dans des alliages dilués base nickel et base fer

Nous présentons une modélisation quantitative de la redistribution des défauts ponctuels (DPs) et de la ségrégation induite par irradiation (SII) sur les défauts étendus, dans des alliages modèles dilués Ni(B ≡ Ti, Cr) et Fe(B ≡ P, Mn, Cr, Si, Ni, Cu). Le changement de composition chimique au voisinage des défauts étendus joue un rôle décisif sur l’évolution de la microstructure et les propriétés mécaniques d’un matériau. L’irradiation génère des défauts ponctuels, qui diffusent en s’échangeant avec les atomes voisins, s’annihilent en se recombinant entre eux ou en interagissant avec des défauts étendus (qui agissent comme des puits de DPs). Les flux de DPs vers les puits induisent des flux atomiques dans le même sens ou le sens opposé des flux de DPs, produisant ainsi la SII aux puits. Nous étendons la théorie de champ moyen auto-cohérent aux déplacements atomiques forcés (DAF), mécanismes de diffusion athermiques générés par une cascade de déplacements sous irradiation. L’implémentation de nos développements théoriques dans le code KineCluE, nous permet de calculer les flux de DPs et d’atomes, et leurs couplages. A partir du calcul des flux en fonction de la température, de la composition, et du champ de déformation ; et d’un traitement de type cinétique chimique des réactions de production et d’annihilation des DPs, nous obtenons les profils stationnaires de SII. Dans chacun des régimes cinétiques particuliers pour lequel, l’une des réactions des DPs domine par rapport aux autres, nous obtenons les expressions analytiques des profils stationnaires des DPs et solutés sur les puits planaires. Pour rendre compte de l’effet du champ de déformation généré par une dislocation coin sur la SII et sur les taux d’élimination des DPs sur la dislocation, nous résolvons numériquement les équations d’élastodiffusion. A partir d’une base de données ab initio des énergies de liaison, des dipôles élastiques, et des fréquences d’échange atome-DP dans, nous réalisons une étude systématique des effets de la microstructure et des conditions d’irradiation sur les propriétés de diffusion, les taux d’élimination des DPs aux puits, et la SII. Nous montrons que : (i) les boucles de dislocations sont enrichies en Ni dans Fe(Ni) et appauvries en Ti dans Ni(Ti), et les quantités ségrégées sont en bon accord avec les valeurs expérimentales mesurées dans les alliages modèles Fe(Ni) et Ni(Ti) irradiés aux ions ; (ii) à fort flux, basse température, et grande force de puits de la microstructure, les évènements DAF réduisent sensiblement la SII, tout particulièrement dans les alliages base Ni ; (iii) les décalages en température calculés pour simuler les effets d’une irradiation aux neutrons par une irradiation aux ions, peuvent être très différents selon le phénomène induit par irradiation que l’on étudie, le régime cinétique dans lequel le système évolue, et la nature chimique de l’alliage étudié ; (iv) l’interaction entre les DPs et les atomes de soluté modifie le facteur de biais d’absorption entre lacunes et interstitiels d’une dislocation coin. Ainsi l’ajout de Ni produit un biais négatif alors que l’ajout de Mn augmente le facteur de biais (jusqu’à 200% de la valeur dans Fe pur sous contrainte), suivant la température et la composition ; (v) la contrainte augmente significativement la quantité de la ségrégation de soluté dans Fe(Ni) (par exemple, 400% de la valeur sans élasticité à 400K), et change le signe de la SII dans Fe(Cr).We present a quantitative modeling of the point-defect (PD) redistribution and solute radiation-induced segregation (RIS) at extended defects in dilute Ni(B ≡ Ti, Cr) and Fe(B ≡ P, Mn, Cr, Si, Ni, Cu) alloys. The change in chemical composition, in the vicinity of extended defects, plays a decisive role on the evolution of the microstructure and mechanical properties of materials. Irradiation produces PDs, that diffuse by exchanging with neighboring atoms, annihilate by mutual recombination or by interacting with extended defects (that act as PD sinks). The fluxes of PDs towards sinks lead to atomic fluxes in the same or opposite direction of the PD flux; thereby producing RIS at sinks. We extend the self-consistent mean-field theory to forced atomic relocations (FARs), athermal diffusion mechanisms generated by displacement cascades under irradiation. The implementation of the extended theory in the KineCluE code allows us to compute PD and atomic fluxes, and their couplings. From the calculation of fluxes as a function of temperature, composition, and strain field; and a mean-field treatment of the production and annihilation reactions of PDs, we obtain the steady-state RIS profiles. In each of the particular kinetic regimes for which one of the PD reactions dominates over the others, we derive analytical expressions of steady-state profiles of PDs and solute atoms at planar sinks. To account for the effect of strain generated by an edge dislocation on the RIS and PD elimination rates, we numerically solve the elastodiffusion equations. Based on an ab initio database of binding energies, elastic dipoles, and atom-PD exchange frequencies, we perform a systematic study of the effects of the microstructure and irradiation conditions on diffusion properties, PD elimination rates at sinks, and RIS. We show that: (i) the dislocation loops are enriched in Ni in Fe(Ni) and depleted in Ti in Ni(Ti), and the calculated amounts of RIS are in good agreement with the experimental values measured in model Fe(Ni) and Ni(Ti) alloys irradiated by ions; (ii) at high flux, low temperature, and high sink strength, forced atomic relocations significantly reduce RIS, especially in Ni-based alloys; (iii) the temperature shifts calculated to simulate the effects of neutron irradiation by ion irradiation can be very different depending on the radiation-induced phenomenon, the kinetic regime in which the system evolves, and the chemical nature of the investigated alloy; (iv) the interactions between PDs and solute atoms change the absorption bias between vacancies and interstitials of an edge dislocation, as for instance, the addition of Ni leads to a negative bias while the addition of Mn increases the bias factor (up to 200% of the strained pure Fe value), depending on temperature and composition; (v) the dislocation strain field significantly increases Ni RIS (e.g., about 400% of the strain-free value at 400K) in Fe(Ni), and changes the sign of RIS in Fe(Cr)

Effect of substitutional Ni atoms on the Snoek relaxation in ferrite and martensite Fe-C alloys: An atomistic investigation

International audienceQuantitative simulations of the carbon-induced internal friction in ferrite/martensite Fe-C and Fe-Ni-C alloys are performed by combining a mean-field elastic model and the atomistic kinetic Monte Carlo based on a pair interaction model to describe the composition-dependent carbon migration. The simulation is validated by experimental data and a thermo-kinetic theory. Our results predict that (i) additional peaks occur in the internal friction profiles of Fe-C and Fe-Ni-C due to C-C and Ni-C pair interactions; (ii) the Ni-alloying shifts the internal friction peak to lower temperature than in Fe-C alloys; (iii) the peak temperature is not simply related to the most frequent carbon jumps during the relaxation process; (iv) the internal friction behavior in martensite depends on the excitation direction with respect to the carbon ordering direction

Atomistic simulation of the collective carbon motion in body-centered tetragonal iron: A new insight into the martensite ageing

Thermodynamic and kinetic properties of carbon (C) atoms in body-centered tetragonal iron (Fe) are investigated by using Monte Carlo (MC) simulations. Pairwise interactions between carbon atoms are obtained by combining the linear elasticity theory and the state-of-the-art results from density functional theory (DFT). This energy database is applied to MC simulations to predict the equilibrium carbon configuration and the collective kinetic motion of carbon atoms in an as-quenched martensite. From the metropolis MC simulation, we obtain a novel equilibrium phase of Fe 6 C 2 structure. However, according to the kinetic MC simulations, it is difficult to reach this equilibrium phase during the martensite ageing because, at room temperature or below, the carbon diffusivity is so slow that it will take an unrealistically long time for the system to achieve the equilibrium; and at higher temperature, even though the kinetics are accelerated, the carbon concentration of the predicted equilibrium phase is so high that other metastable carbides can be formed before such equilibrium is reached. Moreover, the effects of the temperature, the applied stress, and the initial state on the ageing kinetics are highlighted. The evolution of the carbon cluster concentration and the time scale of the ageing kinetics are in good agreement with some existing experimental results