Oriented colorings of partial 2-trees

A homomorphism from an oriented graph G to an oriented graph H is an arc-preserving mapping f from V(G) to V(H), that is f(x)f(y) is an arc in H whenever xy is an arc in G. The oriented chromatic number of G is the minimum order of an oriented graph H such that G has a homomorphism to H. In this paper, we determine the oriented chromatic number of the class of partial 2-trees for every girth g?3. We also give an upper bound for the oriented chromatic number of planar graphs with girth at least 11.     

The development of a thermodynamic model for Al2O3–MgO refractory castable corrosion by secondary metallurgy steel ladle slags

Alumina magnesia in situ spinel castables are used as ladle refractory lining in the steel industry. In contact with slag, they suffer degradations which limits their performance. The purpose of this article is to predict the thermochemical attack of a slag on alumina magnesia refractory using Factsage^® thermodynamic modeling. To evaluate the reliability of the thermodynamic results, a validation step was carried out, which supported that the database was well adapted to the alumina magnesia spinel system. The corrosion phenomenon was then computed for a simple to a complete system to understand the mechanism and the influence of specific oxides. The model was also compared to corroded microstructures from a steel ladle to evaluate the contribution of each constituent in the castable. The aggregates of alumina react with slag to produce monomineral layers of lime aluminates (CA6 and CA2), while complex spinels (Mg, Fe, Mn)O (Fe₂, Al₂)O₃ are formed from the reaction of the slag with the matrix of the castable. Several oxides (MnO, FeO, Fe₂O₃) from the slag contribute to the formation of the spinel structures. The microstructures of refractories used in steel ladles confirm the main conclusions and the thermodynamic approach.     

Nature, Environment and Quantification of Titanium Species in TiSiBEA Zeolites Investigated by XRD, NMR, DR UV–Vis and XPS

Ti _x SiBEA zeolites (x = 1.5, 3.2 and 5.8 Ti wt%) are prepared by a two-step postsynthesis method involving (1) dealumination of TEABEA zeolite by nitric acid leading to nests of SiO–H groups in vacant T-atom sites and (2) incorporation of Ti into SiBEA zeolite by reacting TiCl₄ vapor with those silanol groups. The incorporation of Ti into the SiBEA framework is evidenced by XRD, ²⁹Si MAS NMR, ¹H–²⁹Si CP MAS NMR and ¹H MAS NMR. DR UV–vis and XPS investigations show that, for low Ti content, mainly framework tetrahedral Ti(IV) ions are present in Ti _x SiBEA zeolites. On the basis of XPS data, the quantification of framework tetrahedral Ti(IV) and framework and/or extra-framework octahedral Ti(IV) ions is followed as a function of Ti content.     

Dynamic characterization of machining robot and stability analysis

Machining robots have major advantages over cartesian machine tools because of their flexibility, their ability to reach inaccessible areas on a complex part, and their important workspace. However, their lack of rigidity and precision is still a limit for precision tasks. Innovations and design optimization of robotic structure, links, and power transmission allow robot manufacturers to propose business solutions for machining applications. Beyond accuracy problems, it is also necessary to quantify the vibration phenomena that may affect, as in machine tools, the quality of machined parts and the tools and spindle lifespan. These vibrations occurred at specific machining conditions depending on robot and spindle dynamic properties. The robot’s posture evolved significantly in its workspace and induces dynamic’s changes observed at the tool tip that in turn impact the stability of the machining process. The objective of this paper is to quantify the dynamic behavior’s variation of an ABB IRB 6660 robot equipped with a high-speed machining (HSM) spindle in its workspace and analyze the consequences in terms of machining stability. Through an experimental modal characterization, significant variability of modal parameters is observed at the tool tip and impacts the stability of machining. The results show that an adjustment of the cutting conditions must accompany the change of robot posture during machining to ensure stability.     

Synthesis and in vitro and in vivo Antifungal Activity of the Hydroxy Metabolites of Saperconazole

Herein we describe the scalable diastereoselective and enantioselective syntheses of eight enantiomers of hydroxy metabolites of saperconazole. The in vitro antifungal activity of the eight stereoisomers (compounds 1 – 8 ) was compared against a broad panel of Candida spp. (n=93), Aspergillus spp. (n=10), Cryptococcus spp. (n=19), and dermatophytes (n=27). The four 2S isomers 1 – 4 of the new agent were generally slightly more active than the four 2R isomers 5 – 8 . All eight isomers were tested in a model of experimental A. fumigatus infection in guinea pigs by intravenous inoculation of the fungal conidia. Treatment doses were 1.25 mg kg^?1 and 2.5 mg kg^?1 per day. Infection severity was measured in terms of mean survival time (MST) after infection and mean tissue burdens in brain, liver, spleen, and kidney at postmortem examination. Among the eight isomers, the 2S diastereomers 1 – 4 showed a generally higher level of activity than the 2R diastereomers 5 – 8 , revealing compounds 1 and 4 as the most potent overall in eradicating tissue burden and MST. Compared with reference compounds itraconazole and saperconazole, the hydroxy isomers 1 – 8 are less potent inhibitors of the growth of A. fumigatus in vitro and of ergosterol biosynthesis in both A. fumigatus and C. albicans.     

Synthesis,Microstructure, and Mechanical Properties of Ti3Sn(1−x)AlxC2 MAX Phase Solid Solutions

Ti₃Sn_(1−x)Al_xC₂ MAX phase solid solutions are successfully synthesized from different reactant mixtures. Rietveld refinement allows to carefully characterize their structures and the ocathedra and trigonal prims distortion parameters as a function of the Al content. Mechanical properties of solid solutions are studied from nanoindentation experiments and dynamic resonant method. It is shown that solid solution hardening is not operative in this system. Elastic modulus is found to increase from Ti₃SnC₂ to Ti₃AlC₂, and such a result is discussed in terms of Ti–A bond stiffness.     

Bio-Sourced Poly l-Lactide-Flax Composites with Close to Maximum Stiffness at Low Fiber Content through Two-Stage Annealing

Poly l -Lactide (PLLA) composites with short flax fibers (from 0 to 10 wt/wt%) with close to maximum theoretical stiffness are prepared by melt-compounding and injection-molding followed by a two-step isothermal crystallization protocol that fully separates the nucleation and growth stages (Tammann). The use of fast chip scanning calorimetry for thermal characterization avoids the complicating issues of crystal reorganization during the cooling and heating steps between the isothermal stages. Flax fibers are very efficient and selective nucleating agents of PLLA favoring the ordered α form. The resulting morphology exhibits trans-crystallization on the fibers surface, predominantly at fiber defects, with a clear reduction of crystal size and a very strong fiber matrix cohesion. Efficient nucleation further leads to a large reduction of the overall crystallization time. Avrami analysis evidences a reduction of crystal growth dimensionality, consistent with both optical and scanning electron microscopy. The high modulus of the composites is unambiguously related to the strong orientation of the fibers in the tensile direction, to their high aspect ratio and to the excellent matrix-fibers cohesion. On the other hand, the tensile strength and hardness appear isotropic within experimental uncertainty and are unfavorably influenced by the presence of the fibers and by the two-stage annealing.     

Cultivation of Head and Neck Squamous Cell Carcinoma Cells with Wound Fluid Leads to Cisplatin Resistance via Epithelial-Mesenchymal Transition Induction

Locoregional recurrence is a major reason for therapy failure after surgical resection of head and neck squamous cell carcinoma (HNSCC). The physiological process of postoperative wound healing could potentially support the proliferation of remaining tumor cells. The aim of this study was to evaluate the influence of wound fluid (WF) on the cell cycle distribution and a potential induction of epithelial-mesenchymal transition (EMT). To verify this hypothesis, we incubated FaDu and HLaC78 cells with postoperative WF from patients after neck dissection. Cell viability in dependence of WF concentration and cisplatin was measured by flow cytometry. Cell cycle analysis was performed by flow cytometry and EMT-marker expression by rtPCR. WF showed high concentrations of interleukin (IL)-6, IL-8, IL-10, CCL2, MCP-1, EGF, angiogenin, and leptin. The cultivation of tumor cells with WF resulted in a significant increase in cell proliferation without affecting the cell cycle. In addition, there was a significant enhancement of the mesenchymal markers Snail 2 and vimentin, while the expression of the epithelial marker E-cadherin was significantly decreased. After cisplatin treatment, tumor cells incubated with WF showed a significantly higher resistance compared with the control group. The effect of cisplatin-resistance was dependent on the WF concentration. In summary, proinflammatory cytokines are predominantly found in WF. Furthermore, the results suggest that EMT can be induced by WF, which could be a possible mechanism for cisplatin resistance.     

Skeletal Ryanodine Receptors Are Involved in Impaired Myogenic Differentiation in Duchenne Muscular Dystrophy Patients

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting following repeated muscle damage and inadequate regeneration. Impaired myogenesis and differentiation play a major role in DMD as well as intracellular calcium (Ca²⁺) mishandling. Ca²⁺ release from the sarcoplasmic reticulum is mostly mediated by the type 1 ryanodine receptor (RYR1) that is required for skeletal muscle differentiation in animals. The study objective was to determine whether altered RYR1-mediated Ca²⁺ release contributes to myogenic differentiation impairment in DMD patients. The comparison of primary cultured myoblasts from six boys with DMD and five healthy controls highlighted delayed myoblast differentiation in DMD. Silencing RYR1 expression using specific si-RNA in a healthy control induced a similar delayed differentiation. In DMD myotubes, resting intracellular Ca²⁺ concentration was increased, but RYR1-mediated Ca²⁺ release was not changed compared with control myotubes. Incubation with the RYR-calstabin interaction stabilizer S107 decreased resting Ca²⁺ concentration in DMD myotubes to control values and improved calstabin1 binding to the RYR1 complex. S107 also improved myogenic differentiation in DMD. Furthermore, intracellular Ca²⁺ concentration was correlated with endomysial fibrosis, which is the only myopathologic parameter associated with poor motor outcome in patients with DMD. This suggested a potential relationship between RYR1 dysfunction and motor impairment. Our study highlights RYR1-mediated Ca²⁺ leakage in human DMD myotubes and its key role in myogenic differentiation impairment. RYR1 stabilization may be an interesting adjunctive therapeutic strategy in DMD.