Publications by Wei Li | EPFL Graph Search

Second Virtual International Symposium on Cellular and Organismal Stress Responses, September 8-9, 2022

Paolo De Los Rios, Pierre Goloubinoff, Wei Li

The Second International Symposium on Cellular and Organismal Stress Responses took place virtually on September 8-9, 2022. This meeting was supported by the Cell Stress Society International (CSSI) and organized by Patricija Van OostenHawle and Andrew Truman (University of North Carolina at Charlotte, USA) and Mehdi Mollapour (SUNY Upstate Medical University, USA). The goal of this symposium was to continue the theme from the initial meeting in 2020 by providing a platform for established researchers, new investigators, postdoctoral fellows, and students to present and exchange ideas on various topics on cellular stress and chaperones. We will summarize the highlights of the meeting here and recognize those that received recognition from the CSSI.

SPRINGER2023

Molecular Electronic Study of Spiro-[cyclopenta[1,2-b:5,4-b ']dithiophene-4,9 '-fluorene] Derivatives: Route to Decent Hole-Transporting Materials

Peng Gao, Wei Li, Mohammad Khaja Nazeeruddin, Michael Saliba

Spiro-type molecules have been extensively explored as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). However, a closer look at the rule of design of such molecules is missing, and a combined experimental and theoretical study is needed. In this work, three spiro-[cyclopenta[1,2-b:5,4-b ']dithiophene-4,9 '-fluorene] (SDTF) derivatives decorated with triphenylamine have been designed and synthesized. The thermal and optoelectronic properties, single-crystal structures, and charge -transport properties have been extensively investigated to reveal the impact of the linkage position of triphenylamine groups by combining experimental and theoretical methods, and the results are consistent with each other. Moreover, transfer integrals and reorganization energies in these molecules are also calculated to predict hole mobility. Our comprehensive studies show that SDTF-2 with a suitable energy alignment, good hole injection/ transportability, and high theoretical hole mobility can be employed for efficient perovskite solar cells, achieving a high power conversion efficiency of 19.3%. In addition, first-principle calculations reveal that the strong interactions between SDTF-2 and the perovskite surface can facilitate fast hole extraction. Our way of study has provided useful information as part of the Materials Genome Initiative. We hope our investigation will offer a reliable path to predict or find the potential of novel spiro-type HTMs to become the alternative choice of spiro-OMeTAD.

AMER CHEMICAL SOC2022

Search for relativistic fractionally charged particles in space

Johan Juul Chang, Jie Chen, Jennifer Maria Frieden, Ming Gao, Wei Li, Xuan Li, Junqiu Liu, Hao Liu, Shuai Liu, Chiara Perrina, Arshia Ruina, Jian Wang, Siyuan Wang, Yi Wang, Xiao Wang, Songmei Wu, Zhirui Xu, Yong Yang, Yi Zhang, Yan Zhang

More than a century after the performance of the oil drop experiment, the possible existence of fractionally charged particles (FCPs) still remains unsettled. The search for FCPs is crucial for some extensions of the Standard Model in particle physics. Most of the previously conducted searches for FCPs in cosmic rays were based on experiments underground or at high altitudes. However, there have been few searches for FCPs in cosmic rays carried out in orbit other than AMS-01 flown by a space shuttle and BESS by a balloon at the top of the atmosphere. In this study, we conduct an FCP search in space based on on -orbit data obtained using the Dark Matter Particle Explorer (DAMPE) satellite over a period of five years. Unlike underground experiments, which require an FCP energy of the order of hundreds of GeV, our FCP search starts at only a few GeV. An upper limit of 6.2 x 10-10 cm-2 sr-1 s-1 is obtained for the flux. Our results demonstrate that DAMPE exhibits higher sensitivity than experiments of similar types by three orders of magnitude that more stringently restricts the conditions for the existence of FCP in primary cosmic rays.

2022

Zn(II) and Cu(II) tetrakis(diarylamine)phthalocyanines as hole-transporting materials for perovskite solar cells

Cansu Igci, Hiroyuki Kanda, Nadja Isabelle Desiree Klipfel, Wei Li, Mohammad Khaja Nazeeruddin, Kasparas Rakstys, Jianxing Xia

Finding new hole-transporting materials (HTMs) suitable for replacing the state-of-the-art spiro-OMe-TAD is still challenging. In this work, newly synthesized diarylamine-substituted metal phthalocyanines (MPcs, M 1/4 Zn(II) or Cu(II)) functionalized with either linear or branched alkoxy chains are evaluated as HTMs in perovskite solar cells. Both the nature of the alkoxy chains and that of the coordinated metal species were found to influence the functional properties of the new MPcs. In particular, devices based on a ZnPc featuring four n-butoxy side chains exhibited the highest power conversion efficiencies (PCEs). A PCE of 20.00% was reached for triple cation perovskite devices, and a PCE up to 20.18% could be achieved for double cation devices. (C) 2022 The Authors. Published by Elsevier Ltd.

ELSEVIER SCI LTD2022

Search for light pseudoscalar boson pairs produced from decays of the 125 GeV Higgs boson in final states with two muons and two nearby tracks in pp collisions at $\sqrt{s}=$ 13 TeV

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Thomas Berger, Michele Bianco, Xin Chen, Yixing Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Ajay Kumar, Sanjeev Kumar, Vineet Kumar, Ekaterina Kuznetsova, Jing Li, Lei Li, Wei Li, Ho Ling Li, Zhen Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Kun Shi, Wei Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Siyuan Wang, Zheng Wang, Mingkui Wang, Xiao Wang, Hui Wang, Jian Wang, Qian Wang, Yi Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang

A search is presented for pairs of light pseudoscalar bosons, in the mass range from 4 to 15 GeV, produced from decays of the 125 GeV Higgs boson. The decay modes considered are final states that arise when one of the pseudoscalars decays to a pair of tau leptons, and the other one either into a pair of tau leptons or muons. The search is based on proton-proton collisions collected by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV that correspond to an integrated luminosity of 35.9 fb−1 . The 2μ2τ and 4 τ channels are used in combination to constrain the product of the Higgs boson production cross section and the branching fraction into 4 τ final state, σB , exploiting the linear dependence of the fermionic coupling strength of pseudoscalar bosons on the fermion mass. No significant excess is observed beyond the expectation from the standard model. The observed and expected upper limits at 95% confidence level on σB , relative to the standard model Higgs boson production cross section, are set respectively between 0.022 and 0.23 and between 0.027 and 0.19 in the mass range probed by the analysis.

2020

A multi-dimensional search for new heavy resonances decaying to boosted WW, WZ, or ZZ boson pairs in the dijet final state at 13 TeV

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Thomas Berger, Michele Bianco, Alessandro Caratelli, Xin Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Sebastiana Gianì, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Wei Li, Lei Li, Jing Li, Yiming Li, Zhen Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Amr Mohamed, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Jessica Prisciandaro, Quentin Python, Andrea Rizzi, Paolo Ronchese, Valérie Scheurer, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Mingkui Wang, Yi Wang, Qian Wang, Zheng Wang, Jian Wang, Siyuan Wang, Xiao Wang, Hui Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang, Yi Zhang

A search in an all-jet final state for new massive resonances decaying to WW, WZ, or ZZ boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an integrated luminosity of 77.3 fb

^{-1}

recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13 TeV. The search is focussed on potential resonances with masses above 1.2 TeV, where the decay products of each W or Z boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector triplet model, spin-1 Z' and W' resonances with masses below 3.5 and 3.8 TeV, respectively, are excluded at 95% confidence level. In a narrow-width bulk graviton model, upper limits on cross sections are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2 TeV, respectively. The limits presented in this paper are the best to date in the dijet final state.

2019

A search for pair production of new light bosons decaying into muons in proton-proton collisions at 13 TeV

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Michele Bianco, Xin Chen, Yixing Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Sanjeev Kumar, Ajay Kumar, Vineet Kumar, Ekaterina Kuznetsova, Jing Li, Ho Ling Li, Wei Li, Lei Li, Zhen Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Amr Mohamed, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Varun Sharma, Ashish Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Zheng Wang, Siyuan Wang, Yi Wang, Qian Wang, Hui Wang, Xiao Wang, Jian Wang, Mingkui Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang

A search for new light bosons decaying into muon pairs is presented using a data sample corresponding to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at a center-of-mass energy s=13TeV , collected with the CMS detector at the CERN LHC. The search is model independent, only requiring the pair production of a new light boson and its subsequent decay to a pair of muons. No significant deviation from the predicted background is observed. A model independent limit is set on the product of the production cross section times branching fraction to dimuons squared times acceptance as a function of new light boson mass. This limit varies between 0.15 and 0.39 fb over a range of new light boson masses from 0.25 to 8.5 GeV. It is then interpreted in the context of the next-to-minimal supersymmetric standard model and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. In both cases, there is significant improvement over previously published limits.

2019

A search for the standard model Higgs boson decaying to charm quarks

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Thomas Berger, Michele Bianco, Alessandro Caratelli, Xin Chen, Yixing Chen, Tian Cheng, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Sebastiana Gianì, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Federica Legger, Wei Li, Lei Li, Yiming Li, Jing Li, Zhen Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Amr Mohamed, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Jessica Prisciandaro, Quentin Python, Andrea Rizzi, Paolo Ronchese, Valérie Scheurer, Sourav Sen, Varun Sharma, Ashish Sharma, Lesya Shchutska, Wei Shi, Kun Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Jian Wang, Qian Wang, Siyuan Wang, Xiao Wang, Hui Wang, Mingkui Wang, Zheng Wang, Yi Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang, Yi Zhang

A direct search for the standard model Higgs boson, H, produced in association with a vector boson, V (W or Z), and decaying to a charm quark pair is presented. The search uses a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb

^{-1}

, collected by the CMS experiment at the LHC in 2016, at a centre-of-mass energy of 13 TeV. The search is carried out in mutually exclusive channels targeting specific decays of the vector bosons: W

\to \ell \nu

, Z

\to \ell\ell

, and Z

\to \nu\nu

, where

\ell

is an electron or a muon. To fully exploit the topology of the H boson decay, two strategies are followed. In the first one, targeting lower vector boson transverse momentum, the H boson candidate is reconstructed via two resolved jets arising from the two charm quarks from the H boson decay. A second strategy identifies the case where the two charm quark jets from the H boson decay merge to form a single jet, which generally only occurs when the vector boson has higher transverse momentum. Both strategies make use of novel methods for charm jet identification, while jet substructure techniques are also exploited to suppress the background in the merged-jet topology. The two analyses are combined to yield a 95% confidence level observed (expected) upper limit on the cross section

\sigma

(H)

\mathcal{B}

(H

\to \mathrm{c\bar{c}}

) of 4.5 (2.4

^{+1.0}_{-0.7}

) pb, corresponding to 70 (37) times the standard model prediction.

2019

AIM 2019 Challenge on Image Extreme Super-Resolution: Methods and Results

Majed El Helou, Muhammad Haris, Wei Li, Hanwen Liu, Radu Timofte, Xin Yang, Peng Yi, Jia Yu, Ruofan Zhou

This paper reviews the AIM 2019 challenge on extreme image super-resolution, the problem of restoring of rich details in a low resolution image. Compared to previous, this challenge focuses on an extreme upscaling factor, x16, and employs the novel DIVerse 8K resolution (DIV8K) dataset. This report focuses on the proposed solutions and final results. The challenge had 2 tracks. The goal in Track 1 was to generate a super-resolution result with high fidelity, using the conventional PSNR as the primary metric to evaluate different methods. Track 2 instead focused on generating visually more pleasant super-resolution results, evaluated using subjective opinions. The two tracks had 71 and 52 registered participants, respectively, and 9 teams competed in the final testing phase. This report gauges the experimental protocol and baselines for the extreme image super-resolution task.

IEEE COMPUTER SOC2019

An embedding technique to determine $\tau\tau$ backgrounds in proton-proton collision data

Muhammad Ahmad, Benjamin William Allen, Georgios Anagnostou, Konstantin Androsov, Tagir Aushev, Michele Bianco, Yixing Chen, Xin Chen, Tian Cheng, Davide Cieri, Giuseppe Codispoti, Pratyush Das, Abhisek Datta, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Daniel Gonzalez, Ruchi Gupta, Seungkyu Ha, Csaba Hajdu, Peter Hansen, Ali Harb, Miao Hu, Alexis Kalogeropoulos, Viktor Khristenko, Donghyun Kim, Ji Hyun Kim, Sanjeev Kumar, Ajay Kumar, Vineet Kumar, Ekaterina Kuznetsova, Wei Li, Jing Li, Lei Li, Ho Ling Li, Zhen Liu, Hao Liu, Werner Lustermann, Bibhuprasad Mahakud, Maren Tabea Meinhard, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Kun Shi, Wei Shi, Muhammad Shoaib, Jan Steggemann, Marco Trovato, Andromachi Tsirou, David Vannerom, Joao Varela, Siyuan Wang, Zheng Wang, Mingkui Wang, Xiao Wang, Hui Wang, Jian Wang, Qian Wang, Yi Wang, Muhammad Waqas, Matthias Weber, Matthias Wolf, Fan Xia, Meng Xiao, Yong Yang

An embedding technique is presented to estimate standard model ττ backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed μμ events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS . Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at √s=13 TeV corresponding to an integrated luminosity of 41.5 fb−1.

2019