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Institution

École normale supérieure de Cachan

EducationCachan, Île-de-France, France
About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Finite element method. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.


Papers
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Journal ArticleDOI
TL;DR: A drastic enhancement of the fluorescence quantum yield-in an "off- on" fashion comparable to that seen in photoinduced electron transfer (PET) molecular sensors-was observed.
Abstract: The syntheses and properties of two calixarene-based fluorescent molecular sensors are reported. These comprise tert-butylcalix[4]arene either with one appended fluorophore and three ester groups (Calix-AMN1), or with four appended fluorophores (Calix-AMN4). The fluorophore is 6-acyl-2-methoxynaphthalene (AMN), which contains an electron-donating substituent (methoxy group) conjugated to an electron-withdrawing substituent (carbonyl group); this allows photoinduced charge transfer (PCT) to occur upon excitation. The investigated fluoroionophores thus belong to the family of PCT fluorescent molecular sensors. In addition to the expected red shifts of the absorption and emission spectra upon cation binding, a drastic enhancement of the fluorescence quantum yield—in an “off–on” fashion comparable to that seen in photoinduced electron transfer (PET) molecular sensors—was observed. For Calix-AMN1, it increases from 10−3 for the free ligand to 0.68 for the complex with Ca2+. This exceptional behaviour can be interpreted in terms of the relative locations of the nπ* and ππ* levels, which depend on the charge density of the bound cation. For Calix-AMN4, in addition to the photophysical effects observed for Calix-AMN1, interactions between the chromophores by complexation with some cations have been found in the ground state (hypochromic effect) and in the excited state (excimer formation). Steady-state fluorescence anisotropy measurements for the system Na+⊂Calix-AMN4, show a depolarization effect due to energy transfer (homotransfer) between the fluorophores. Regarding the complexing properties, a high selectivity for Na+ over K+, Li+, Ca2+ and Mg2+ was observed in ethanol and ethanol–water mixtures. The selectivity (Na+/other cations) expressed as the ratio of the stability constants was found to be more than 400.

106 citations

Proceedings ArticleDOI
04 Oct 2010
TL;DR: It is shown how to extract sensitive cryptographic keys from a variety of commercially available tamper resistant cryptographic security tokens, exploiting vulnerabilities in their RSA PKCS#11 based APIs, using Tookan, an automated tool developed.
Abstract: We show how to extract sensitive cryptographic keys from a variety of commercially available tamper resistant cryptographic security tokens, exploiting vulnerabilities in their RSA PKCS#11 based APIs. The attacks are performed by Tookan, an automated tool we have developed, which reverse-engineers the particular token in use to deduce its functionality, constructs a model of its API for a model checker, and then executes any attack trace found by the model checker directly on the token. We describe the operation of Tookan and give results of testing the tool on 17 commercially available tokens: 9 were vulnerable to attack, while the other 8 had severely restricted functionality. One of the attacks found by the model checker has not previously appeared in the literature. We show how Tookan may be used to verify patches to insecure devices, and give a secure configuration that we have implemented in a patch to a software token simulator. This is the first such configuration to appear in the literature that does not require any new cryptographic mechanisms to be added to the standard. We comment on lessons for future key management APIs.

106 citations

Journal ArticleDOI
TL;DR: The device analysis suggests that the main concern is the moderate redox stability of the complexes under high applied driving currents, leading to devices with moderate stabilities pointing to a proof-of-concept for further development.
Abstract: This study presents the influence of various substituents on the photophysical features of heteroleptic copper(I) complexes bearing both N-heterocyclic carbene (NHC) and dipyridylamine (dpa = dipyridylamine skeleton corresponding to ligand L1) ligands. The luminescent properties have been compared to our recently reported archetypal blue emitting [Cu(IPr)(dpa)][PF6] complex. The choice of the substituents on both ligands has been guided to explore the effect of the electron donor/acceptor and "push-pull" on the emission wavelengths and photoluminescence quantum yields. A selection of the best candidates in terms of their photophysical features were applied for developing the first blue light-emitting electrochemical cells (LECs) based on copper(I) complexes. The device analysis suggests that the main concern is the moderate redox stability of the complexes under high applied driving currents, leading to devices with moderate stabilities pointing to a proof-of-concept for further development. Nevertheless, under low applied driving currents the blue emission is stable, showing performance levels competitive to those reported for blue LECs based on iridium(III) complexes. Overall, this work provides valuable guidelines to tackle the design of enhanced NHC copper complexes for lighting applications in the near future.

106 citations

Journal ArticleDOI
TL;DR: Current knowledge relating to both delivery systems and combinations of inducing factors including chemicals which are used to generate human iPS cells are covered.
Abstract: The unlimited proliferation capacity of embryonic stem cells (ESCs) combined with their pluripotent differentiation potential in various lineages raised great interest in both the scientific community and the public at large with hope for future prospects of regenerative medicine. However, since ESCs are derived from human embryos, their use is associated with significant ethical issues preventing broad studies and therapeutic applications. To get around this bottleneck, Takahashi and Yamanaka have recently achieved the conversion of adult somatic cells into ES-like cells via the forced expression of four transcription factors: Oct3/4, Sox2, Klf4 and c-Myc. This first demonstration attracted public attention and opened a new field of stem cells research with both cognitive – such as disease modeling - and therapeutic prospects. This pioneer work just received the 2012 Nobel Prize in Physiology or Medicine. Many methods have been reported since 2006, for the generation of induced pluripotent stem (iPS) cells. Most strategies currently under use are based on gene delivery via gamma-retroviral or lentiviral vectors; some experiments have also been successful using plasmids or transposons-based systems and few with adenovirus. However, most experiments involve integration in the host cell genome with an identified risk for insertional mutagenesis and oncogenic transformation. To circumvent such risks which are deemed incompatible with therapeutic prospects, significant progress has been made with transgene-free reprogramming methods based on e.g.: sendai virus or direct mRNA or protein delivery to achieve conversion of adult cells into iPS. In this review we aim to cover current knowledge relating to both delivery systems and combinations of inducing factors including chemicals which are used to generate human iPS cells. Finally, genetic instability resulting from the reprogramming process is also being considered as a safety bottleneck for future clinical translation and stem cell-therapy prospects based on iPS.

105 citations

Journal ArticleDOI
TL;DR: This paper presents a class containing the piecewise affine functions which are ultimately pseudo-periodic and can be finitely described, which enables us to propose some algorithms for each of the network calculus operations.
Abstract: Network calculus offers powerful tools to analyze the performances in communication networks, in particular to obtain deterministic bounds. This theory is based on a strong mathematical ground, notably by the use of (min,+) algebra. However, the algorithmic aspects of this theory have not been much addressed yet. This paper is an attempt to provide some efficient algorithms implementing network calculus operations for some classical functions. Some functions which are often used are the piecewise affine functions which ultimately have a constant growth. As a first step towards algorithmic design, we present a class containing these functions and closed under the main network calculus operations (min, max, +, -, convolution, subadditive closure, deconvolution): the piecewise affine functions which are ultimately pseudo-periodic. They can be finitely described, which enables us to propose some algorithms for each of the network calculus operations. We finally analyze their computational complexity.

105 citations


Authors

Showing all 2722 results

NameH-indexPapersCitations
Shi Xue Dou122202874031
Olivier Hermine111102643779
John R. Reynolds10560750027
Shaul Mukamel95103040478
Tomás Torres8862528223
Ifor D. W. Samuel7460523151
Serge Abiteboul7327824576
Stéphane Roux6862719123
Zeger Debyser6740416531
Louis Nadjo6426412596
Praveen K. Thallapally6419012110
Andrew Travers6319313537
Shoji Takeuchi6369214704
Bineta Keita6327412053
Yves Mély6236813478
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20233
202222
202121
202029
201958
201879