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A robust determination of the effective thermal conductivity of a multilayer Si3N4/SiO2 stack using multiple heater geometries in the 3-omega method
No full textInternational audienceMultilayer dielectric thin films are fundamental components in modern microelectronic and photonic devices where thermal management is critical. This work presents a robust methodological framework for accurately determining the cross-plane effective thermal conductivity (κeff,⊥) of such complex systems using the 3-omega method. We use a five-layer Si3N4/SiO2 stack fabricated by plasma-enhanced chemical vapor deposition as a case study. The analysis combines experimental data from multiple heater geometries with a 3D finite element method based inverse analysis. We first demonstrate, through a frequency-dependent sensitivity analysis, that a direct multi-parameter fit for intrinsic layer properties is an ill-posed problem. This analysis provides a clear, quantitative justification for adopting a simpler and more robust effective medium model (EMA). The validity and application boundaries of the EMA are then rigorously established through a numerical study on a series of “virtual samples.” Finally, applying this validated framework to our experimental data, the thermal conductivity of a fused silica substrate was determined to be 1.287 ± 0.030 W/(m K), and the effective thermal conductivity of the 1288 nm thick stack was reliably determined to be 0.621 ± 0.008 W/(m K). This work provides not only a key thermophysical property for Si3N4/SiO2 multilayers but also a comprehensive and validated workflow for reliably characterizing complex thin film systems where standard analytical solutions fail
Ultrasonic maging of layer on substrate structures using high-frequency acoustic field correlation
No full textInternational audienceLayer on substrate structures are often subject to various types of defects, particularly those resulting from manufacturing process during thin-film growth. Currently, onemethod of inspecting such structures involves the use of IDT transducers for excitation and laser vibrometry for reception. In this work, we propose a complementaryapproach inspired by passive noise correlation imaging methods initially developed in geophysics. This technique is applied here to image layered structures on substrates byexploiting the correlation of diffuse acoustic waves and the associated principle of passive Green’s function reconstruction, enabling the detection and imaging of defects.The analysis was performed using numerical simulations and preliminary experiments on silicon wafers (3 mm thick). IDTs (10-25) MHz were used to generatesurface waves, and the resulting displacement field was captured using laser vibrometry. Simulations and measurements were carried out on both defect-free and defectcontaining cases. Correlation matrices were calculated on Full Matrix Capture mode. Finally, a beamforming algorithm was applied to localize defects, taking into accountsilicon’s anisotropy
Les droits d’auteur en danger ? Ce que l’affaire « Bartz contre Anthropic » risque de changer aux États-Unis… et ailleurs
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Sovereign credit rating provision and financial development
No full textInternational audienceThis paper examines the impact of obtaining a sovereign credit rating for the first time on financial development in 50 emerging countries. Controlling for endogeneity and selection bias, we show that receiving an initial sovereign credit rating significantly transforms domestic financial systems. Rated countries experience a reallocation of bank assets, reduced reliance on domestic bank financing, and increased access to international bond markets, enabling expanded private-sector credit. Sovereign ratings also stimulate local currency bond market development and enhance foreign currency bond issuance. Additionally, they attract portfolio equity inflows and foster the internationalization of domestic banks, though their effects on direct debt flows and FDI are less pronounced. Overall, our findings highlight the critical role of sovereign credit ratings in advancing financial development and integration in emerging markets
Conversion Rate Optimization at Quantor Networks: Leveraging A/B Testing
No full textThe Case Centre, case study 525-0070-1, teaching note 525-0070-8In 2024, Mark, Digital Marketing Manager at Quantor Networks - a B2B provider of IT security solutions - faced growing pressure to deliver results. Recent digital advertising campaigns had successfully driven relevant traffic to the company's website. But there was a problem: while traffic increased substantially, conversions of visitors into leads did not. With customer acquisition costs rising and his boss demanding answers, Mark needed to figure out what was going wrong. Identifying the website as the bottleneck, Mark began exploring conversion rate optimization (CRO). He realized he needed a more structured, evidence-based approach - not only to understand what was blocking conversions, but also to justify his proposed changes. Facing internal skepticism and high expectations, Mark turned to A/B testing to support his recommendations with real data. The case follows Mark as he shifts to a structured testing mindset. Students are tasked with helping him apply A/B testing more systematically - prioritizing elements to test, analyzing results for significance, and developing a roadmap for improving website performance beyond the initial test.2025
Enfants atteints de psoriasis de la cohorte Secu-Ped : les patients utilisant des anti-interleukines 17 dans la vie réelle sont-ils éligibles pour les études cliniques de phase III ?
No full textInternational audienceIntroductionLes essais cliniques de phase III des biothérapies pour les enfants souffrant de psoriasis modéré à sévère sont dessinés pour une population sélectionnée. Cette population peut différer des enfants vus dans notre pratique quotidienne.Notre objectif était d’évaluer la proportion d’enfants atteints de psoriasis ayant reçu un anti-interleukine 17, sécukinumab (SECU) ou ixékizumab (IXE), dans la cohorte internationale en vie courante « Secu-Ped » (anti-interleukin 17 in children with psoriasis), qui auraient pu être inclus dans les trois essais cliniques de phase III de ces traitements.Matériel et méthodesLes données au début de la 1re biothérapie des 152 enfants (âge moyen : 12,9 ± 3,4 ans ; filles : 54% ; psoriasis en plaques : 58 % ; rhumatisme psoriasique : 9,9 %) inclus dans 7 pays ont été analysées, 134 enfants avaient reçu du SECU et 24 de l’IXE.L’inéligibilité a été évaluée après application des critères d’inclusion (CI) et d’exclusion (CE) utilisés dans les essais de phase III du SECU et du l’IXE, après analyse des publications et du registre des essais thérapeutiques ClinicalTrials.gov. Une analyse pas-à-pas a été effectuée, en démarrant par l’âge, puis le type clinique, les scores de sévérité et les autres paramètres, quand disponibles.RésultatsPour les deux essais thérapeutiques du SECU, seuls quatre paramètres étaient identifiables (âge, forme clinique, PASI et PGA). Aucun autre CI et CE n’était pas disponible. Dans l’essai portant sur le psoriasis sévère (Bodemer C, et al.), 12 enfants (9,0 %) auraient pu être inclus. Dans l’étude sur le psoriasis modéré à sévère (Magnolo N, et al.), 43 (32,1 %) auraient pu être inclus.Pour l’essai sur l’IXE (Paller A, et al.) tous les critères étaient disponibles, notamment l’antériorité des traitements. Quatre enfants (11,2 %) auraient été éligibles à cet essai.DiscussionSur cette grande cohorte en vie courante, moins d’un tiers des enfants étudiés aurait été éligible aux essais thérapeutiques essentiellement du fait de leur forme clinique et de la sévérité du psoriasis à l’inclusion. Il est probable que nous ayons surévalué ce taux car pour le SECU de nombreux CI et CE n’étant pas disponibles, et donc n’ont pas pu être analysés. D’autre part, nous avons inclus les enfants pour lesquels le paramètre analysé (ex : PASI, PGA) n’était pas disponible (donnée manquante) et considéré comme incluables dans les essais.ConclusionCe type d’analyse souligne la nécessité de cohortes prospectives ou rétrospectives d’enfants psoriasiques sous biothérapie, en vie courante, tant la différence par rapport aux enfants inclus dans les essais est importante
Cannabis growers as gardeners: results from a survey among Italian and British small-scale growers
No full textInternational audienceBackgroundThe horticultural nature of growing cannabis is often overlooked in the study of cannabis production, and subsequent policies. Little is known about whether growers' horticultural expertise influences cannabis cultivation methods, the growing of other psychoactive plants, substance use behaviors, or interactions with the criminal justice system. The trajectory of cultivation, in terms of whether cannabis is a gateway to more general gardening, or vice versa, is also unexplored. Studying individuals who combine cannabis cultivation with other gardening activities is valuable because it provides insights into the motivations and practices of cannabis growers as illegal drug market participants.MethodsData from 1302 small-scale cannabis growers in Italy and the UK was collected through an online survey from 2020 to 2021. We ran two regressions to compare (1) those who only grow cannabis with those who also grow other plants and; (2) those who started growing cannabis and then grew other plants and vice versa.ResultsMost people in our sample grew cannabis and other plants (General Gardeners; 82 %). In comparison with the Only-cannabis group (OCG), General Gardeners (GG) tended to be older, more educated, and more likely to be in a relationship. GG grew more cannabis crops outdoors, and the purposes for growing were more related to ecological or medical reasons rather than selling cannabis. The OCG group had higher odds of using stimulant drugs and meeting cannabis use dependence criteria compared to GG. Among GG, the majority (71 %) started growing other plants and later moved to cannabis.ConclusionGardening other plants is common among cannabis growers and precedes cultivating cannabis far more than the reverse pathway. As general gardeners appear focused on cannabis alone, concerns about spillover to growing other psychoactive plants or fungi may be overstated. Given the lower expected harms associated with general gardening, it could serve as a proxy for reduced supply involvement in legal assessments