Rethink Baseline of Integrated Gradients from the Perspective of Shapley Value

Numerous approaches have attempted to interpret deep neural networks (DNNs) by attributing the prediction of DNN to its input features. One of the well-studied attribution methods is Integrated Gradients (IG). Specifically, the choice of baselines for IG is a critical consideration for generating meaningful and unbiased explanations for model predictions in different scenarios. However, current practice of exploiting a single baseline fails to fulfill this ambition, thus demanding multiple baselines. Fortunately, the inherent connection between IG and Aumann-Shapley Value forms a unique perspective to rethink the design of baselines. Under certain hypothesis, we theoretically analyse that a set of baseline aligns with the coalitions in Shapley Value. Thus, we propose a novel baseline construction method called Shapley Integrated Gradients (SIG) that searches for a set of baselines by proportional sampling to partly simulate the computation path of Shapley Value. Simulations on GridWorld show that SIG approximates the proportion of Shapley Values. Furthermore, experiments conducted on various image tasks demonstrate that compared to IG using other baseline methods, SIG exhibits an improved estimation of feature's contribution, offers more consistent explanations across diverse applications, and is generic to distinct data types or instances with insignificant computational overhead.Comment: 12 page

Synthesis of conjugated polymers via direct C–H/C–Cl coupling reactions using a Pd/Cu binary catalytic system

Direct arylation polycondensation is regarded as an efficient synthetic method for conjugated polymers. This methodology is difficult to apply to dichloroaryl monomers because of the low reactivity of the C–Cl bonds compared to that of the C–Br bonds in dibromoaryl monomers, which have been widely used in direct arylation polycondensation. In this research, direct arylation polycondensation of dichloroaryl monomers was achieved by the use of a Pd/Cu binary catalytic system. Optimisation of the molar ratio of the Pd and Cu catalyst resulted in the formation of high-molecular-weight polymers in good yields. Structural defects of the polymer at the terminal unit were minimised by logical choice of the monomer ratio on the basis of the reaction mechanism. The obtained polymer with relatively low structural defects showed a higher quantum efficiency of photoluminescence and electroluminescence than that of the polymer with irregular terminal structures

Synthesis of new 2′-deoxy-2′-fluoro-4′-azido nucleoside analogues as potent anti-HIV agents

We prepared 1-(4′-azido-2′-deoxy-2′-fluoro-β -D-arabinofuranosyl)cytosine (10) and its hydrochloride salt (11) as potential antiviral agents based on the favorable antiviral profiles of 4′-substituted nucleosides. Compounds 10 and 11 were synthesized from 1,3,5-O-tribenzoyl-2-deoxy-2-fluoro-D-arabinofuranoside in multiple steps, and their structures were unequivocally established by IR, 1H NMR, 13C NMR, and 19F NMR spectroscopy, HRMS, and X-ray crystallography. Compounds 10 and 11 exhibited potent anti-HIV-1 activity (EC50: 0.3 and 0.13 nM, respectively) without significant cytotoxicity in concentrations up to 100 μM. Compound 11 exhibited extremely potent anti-HIV activity against NL4-3 (wild-type), NL4-3 (K101E), and RTMDR viral strains, with EC50 values of 0.086, 0.15, and 0.11 nM, respectively. Due to the high potency of 11, it was also screened against an NIH Reagent Program NRTI-resistant virus panel containing eleven mutated viral strains and for cytotoxicity against six different human cell lines. The results of this screening indicated that 11 is a novel NRTI that could be developed as an anti-AIDS clinical trial candidate to overcome drug-resistance issues

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Recherche de la production de 4 quark tops dans le modèle standard avec des états finaux de même signe di-lepton et multi-lepton à 13 TeV avec le détecteur ATLAS au LHC

This thesis presents the latest results of the Standard Model four-top-quark search in the same sign di-lepton and multi-lepton channel. The analysis uses the full Run2 proton-proton collision dataset at sqrt(s)=13 TeV collected with the ATLAS detector, which corresponds to an integrated luminosity of 139 fb⁻¹. Events with two same sign leptons or three or more leptons, plus multiple jets and b-tagged jets in the final states are considered in the analysis. Further event and kinematic selections are performed in separate signal and background control regions with proper background modelling. Boosting Decision Tree (BDT) based Multi-Variate Analysis (MVA) method is then used to enhance signal and background separation. Finally, a simultaneous likelihood fit is performed on the BDT discriminant across all the signal and background control regions to measure the four-top-quark production cross section and the signal strength (defined as the ratio of the measured cross section over the SM prediction). The measured four-top-quark production cross section is δtttt=24+5-5(stat)+5-4(syst)fb=24+7-6 fb, which is in consistent with the standard model prediction within 2 standard deviations. The corresponding signal strength is μ=2.0+0.4-0.4(stat)+0.7-0.4(syst)=2.0+0.8-0.6. The observed (expected) significance of the four-top-quark signal is 4.3 (2.4) σ, which provides the first evidence for the SM four-top-quark production.Cette thèse présente les résultats sur la recherche de la production de quatre quarks top dans le canal deux leptons de même signe ou multilepton. L’analyse utilise l’ensemble des collisions proton-proton du Run 2 du LHC à sqrt(s)=13 TeV collecté avec le détecteur ATLAS, ce qui correspond à une luminosité de 139 fb⁻¹. Les événements avec deux leptons de même signe ou au moins trois leptons avec de nombreux jets en particulier provenant de quarks b sont considérés. Les événements sont sélectionnés en région de signal et régions de contrôle avec une modélisation du bruit de fond appropriée. Un arbre de décision boosté (BDT), qui est une méthode multivariée, est alors utilisé pour augmenter la séparation entre le signal et le bruit de fond. Enfin un ajustement par maximum de vraisemblance est effectué sur la sortie du BDT simultanément sur les régions de signal et de contrôle pour mesurer la section efficace de production de quatre quarks top et la force du signal (définie comme le rapport entre la section efficace mesurée et la prédiction du modèle standard). La section efficace mesurée est : δtttt=24+5-5(stat)+5-4(syst)fb=24+7-6 fb, ce qui est compatible avec la prédiction du modèle standard à 1.7 déviations standard. La force du signal correspondante est : μ=2.0+0.4-0.4(stat)+0.7-0.4(syst)=2.0+0.8-0.6. La signification statistique observée (attendue) du signal quatre quarks top est 4.3 (2.4) σ, ce qui représente la première mise en évidence de ce processus