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Intersection homotopy, refinements and coarsenings
No full textIn previous works, we studied intersection homotopy groups associated to a Goresky and MacPherson perversity and a filtered space. They are defined as the homotopy groups of simplicial sets introduced by P. Gajer. We particularized to locally conical spaces of Siebenmann (called CS sets) and established a topological invariance for them when the regular part remains unchanged.Here, we consider coarsenings, made of two structures of CS sets on the same topological space, the strata of one being a union of strata of the other. We endow them with a general perversity and its pushforward, where the adjective ``general'' means that the perversities are defined on the poset of the strata and not only according to their codimension. If the perversity verifies a growing property analogous to that of the original perversities of Goresky and MacPherson, we also find an invariance theorem for the intersection homotopy groups of a coarsening, under the above restriction on the regular parts. An invariance is shown too in some cases where singular strata become regular in the coarsening, for Thom-Mather spaces
Comprehensive investigation of WO<sub>3-x</sub> thin films: Structural, optical, and electrical insights, with application in photodegradation of dyes
No full textInternational audienceTungsten oxide WO₃₋ₓ thin films were synthesized using the spray pyrolysis technique on glass substrates heated to 350 °C, employing tungsten hexachloride (WCl₆) as the precursor. The films were annealed at the same temperature for 5 h. Their structural properties were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis revealed that the as-deposited films crystallized in a monoclinic W₁₈O₄₉ (WO2.72) phase, while annealing induced a phase transformation to tetragonal W₅O₁₄ (WO2.8). Optical measurements indicated a wide direct optical band gap of 3.56 eV for WO2.72, which increased to 3.79 eV for WO2.8 after annealing, accompanied by a reduction in Urbach energy. Electrical properties were analyzed using impedance spectroscopy in the frequency range of 100 kHz–13 MHz at temperatures between 200 and 275 °C. Nyquist plot fitting revealed contributions from both grain interiors and grain boundaries to the relaxation process, with a non-Debye poly-dispersive behavior. Additionally, the activation energy decreased post-annealing. The as-deposited films exhibited excellent photocatalytic performance in the degradation of methylene blue under solar irradiation. This enhanced activity was attributed to the presence of oxygen vacancies and a comparatively lower band gap relative to the annealed films. This study not only highlights the phase transformation of WO₃₋ₓ to WO₃ induced by thermal annealing but also demonstrates the potential of WO2.72 thin films in photocatalytic dye degradation applications
Antiferromagnetism, Anion Disorder, and Lattice Defects in the S = 5/2 [Bi2O2][Mn2+F4] Aurivillius Compound
No full textInternational audience[Bi2O2][MnF4] is an Aurivillius oxyfluoride phase with Mn2+ cations filling the one-layer perovskite subunits. Its synthesis as a single-phase material by a high-temperature solid-state route is complicated by the high volatility of fluorine in the used precursors and by its limited thermal stability above 400 °C. Its crystal structure was determined using synchrotron and neutron diffraction data. It shows structural singularities, highlighted by the anion positional disorder inherent to the I4/mmm space group, despite the evidence of strong local axial and equatorial octahedral tilts along with clues for ideal F– and O2– total segregation in the two-layered subunits. Contrarily to the M = Ni2+, Co2+, and Fe2+/3+ analogs, where similar tilts order in various supercells, for M = Mn2+ only short-range ordering (SRO) was detected by electron diffraction. This was rationalized in terms of the d5 ion isotropic nature for which weak distortions of the crystal field do not have an energy penalty and favor local octahedral defects acting as antiphase boundaries between nanometric SRO domains. DFT calculations validate equiprobable tilted [MnF6] arrangements in the perovskite layers and suggest the possibility for an O ↔ F exchange between the [Bi2O2] and [MnF4] modules, supported by HAADF imaging. The presence of oxygen and vacancies in the perovskite slabs was also detected in samples prepared at higher temperatures. [Bi2O2][MnF4] magnetic structure shows a colinear antiferromagnetic arrangement below TN = 19.8 K, with Mn2+ spins (S = 5/2, L = 0) aligned parallel to the c-axis (Mz = 3.8(2) μB/Mn). This is again in contrast with the systematic spin-canting responsible for weak ferromagnetism in the previous M2+ Aurivillius compounds. Finally, the modest fluoride ionic mobility was measured in a small temperature range, restricted by the stability of the compound in air
Artificial Intelligence for Environmental Profiling: Improving Spatial Analysis by Capturing Local Specificities
No full textInternational audienc
NovaMatic Industries: Investment Timing and Real Options Valuation
No full textThe Case Centre, case study 125-0033-1, teaching note 125-0033-8, teaching note supplement 125-0033-8BThis case introduces students to real options analysis through a strategic investment decision at NovaMatic Industries. The firm must evaluate whether to invest immediately in a USD150.8 million automated production facility or delay the decision by two years to gain more market clarity, despite potential cost escalation. Students compare the two strategies using traditional NPV analysis, decision tree modeling, the Black-Scholes option pricing framework, and Monte Carlo simulation. The case highlights the limitations of static valuation under uncertainty and demonstrates how the value of flexibility can be quantified. Designed for courses that integrate corporate finance with programming, the case requires students to build Python-based models and translate analytical results into managerial recommendations. Through this process, students gain practical experience in modeling risk, valuing timing options, and interpreting simulation results. The teaching package includes a fully documented solution notebook to support implementation and facilitate in-class discussion. This case is well-suited for master's-level courses in finance, financial engineering, or analytics that emphasize applied problem solving, data-driven decision-making, and communication of investment insights
A Rectification-Based Approach for Distilling Boosted Trees into Decision Trees
No full textWe present a new approach for distilling boosted trees into decision trees, in the objective of generating an ML model offering an acceptable compromise in terms of predictive performance and interpretability. We explain how the correction approach called rectification can be used to implement such a distillation process. We show empirically that this approach provides interesting results, in comparison with an approach to distillation achieved by retraining the model
Estigma contra Educação a Distância é problema real que impacta desempenhos e precisa ser combatido
No full textInternational audienc
Sediments as renewable raw earth for producing unfired bricks and mortars
No full textInternational audienc
Preoperative anxiety assessment in orthopaedic surgery: a systematic review and meta-analysis
No full textInternational audiencePurpose: Preoperative anxiety (Pop-Anx) is highly prevalent among patients undergoing orthopaedic surgery. Pop-Anx can stem from fears related to the procedure, anaesthesia, or the recovery process. It has been linked to poorer postoperative outcomes, including greater pain, reduced function, and a lower quality of life. Despite its clinical significance, Pop-Anx is inconsistently assessed due to a lack of standardized tools and clear guidelines. The objective was to identify instruments used for measuring Pop-Anx in patients undergoing orthopaedic surgeries.Methods: A systematic search was conducted across five databases up to September 2024, following PRISMA guidelines. Data on anxiety assessment tools, timing, administration, and related outcomes were extracted. Meta-analyses were conducted on studies with a low risk of bias using random-effects models.Results: Screening of the literature revealed that 42 studies assessed Pop-Anx, involving a total of 115,380 patients. Ten different tools were used to measure Pop-Anx, with the Hospital Anxiety and Depression Scale (HADS) being the most frequent. Significant variability was observed in assessment timing and methodology. A meta-analysis showed that Pop Anx was positively correlated with postoperative anxiety (z = 0.60) and pain (z = 0.22) and negatively correlated with joint function (z = -0.25). Females reported higher Pop-Anx (g = 0.38). The timing of outcome assessment did not significantly moderate these relationships.Conclusion: Although Pop-Anx is associated with worse postoperative outcomes, it is assessed using heterogeneous and sometimes inadequate tools. Standardized, context-specific assessment methods are needed. Despite its clinical relevance, Pop-Anx remains underassessed in some common orthopaedic procedures
