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Erebor and Durian: Full Anonymous Ring Signatures from Quaternions and Isogenies

We construct two efficient post-quantum ring signatures with anonymity against full key exposure from isogenies, addressing the limitations of existing isogeny-based ring signatures. First, we present an efficient concrete distinguisher for the SQIsign simulator when the signing key is provided using one transcript. This shows that turning SQIsign into an efficient full anonymous ring signature requires some new ideas. Second, we propose a variant of SQIsign (Asiacrypt'20) that is resistant to the distinguisher attack with only a x1.4 increase in size and we render it to a ring signature, that we refer to as Erebor. This variant introduces a new zero-knowledge assumption that ensures full anonymity. The efficiency of Erebor remains comparable to that of SQIsign, with only a proportional increase due to the ring size. This results in a signature size of 0.71 KB for 4 users and 1.41 KB for 8 users, making it the most compact post-quantum ring signature for up to 29 users. Third, we revisit the GPS signature scheme (Asiacrypt'17), developing efficient subroutines to make the scheme more efficient and significantly reduce the resulting signature size. By integrating our scheme with the paradigm by Beullens, Katsumata, and Pintore (Asiacrypt’20), we achieve an efficient logarithmic ring signature, that we call Durian, resulting in a signature size of 9.87 KB for a ring of size 1024.

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Open Access
Partial rejuvenation of the spermatogonial stem cell niche after gender-affirming hormone therapy in trans women

Although the impact of gender-affirming hormone therapy (GAHT) on spermatogenesis in trans women has already been studied, data on its precise effects on the testicular environment is poor. Therefore, this study aimed to characterize, through histological and transcriptomic analysis, the spermatogonial stem cell niche of 106 trans women who underwent standardized GAHT, comprising estrogens and cyproterone acetate. A partial dedifferentiation of Sertoli cells was observed, marked by the co-expression of androgen receptor and anti-Müllerian hormone which mirrors the situation in peripubertal boys. The Leydig cells also exhibited a distribution analogous to peripubertal tissue, accompanied by a reduced insulin-like factor 3 expression. Although most peritubular myoid cells expressed alpha-smooth muscle actin 2, the expression pattern was disturbed. Besides this, fibrosis was particularly evident in the tubular wall and the lumen was collapsing in most participants. A spermatogenic arrest was also observed in all participants. The transcriptomic profile of transgender tissue confirmed a loss of mature characteristics - a partial rejuvenation - of the spermatogonial stem cell niche and, in addition, detected inflammation processes occurring in the samples. The present study shows that GAHT changes the spermatogonial stem cell niche by partially rejuvenating the somatic cells and inducing fibrotic processes. These findings are important to further understand how estrogens and testosterone suppression affect the testis environment, and in the case of orchidectomized testes as medical waste material, their potential use in research.

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Open Access
Representation of Imprecision in Deep Neural Networks for Image Classification.

Quantification and reduction of uncertainty in deep-learning techniques have received much attention but ignored how to characterize the imprecision caused by such uncertainty. In some tasks, we prefer to obtain an imprecise result rather than being willing or unable to bear the cost of an error. For this purpose, we investigate the representation of imprecision in deep-learning (RIDL) techniques based on the theory of belief functions (TBF). First, the labels of some training images are reconstructed using the learning mechanism of neural networks to characterize the imprecision in the training set. In the process, a label assignment rule is proposed to reassign one or more labels to each training image. Once an image is assigned with multiple labels, it indicates that the image may be in an overlapping region of different categories from the feature perspective or the original label is wrong. Second, those images with multiple labels are rechecked. As a result, the imprecision (multiple labels) caused by the original labeling errors will be corrected, while the imprecision caused by insufficient knowledge is retained. Images with multiple labels are called imprecise ones, and they are considered to belong to meta-categories, the union of some specific categories. Third, the deep network model is retrained based on the reconstructed training set, and the test images are then classified. Finally, some test images that specific categories cannot distinguish will be assigned to meta-categories to characterize the imprecision in the results. Experiments based on some remarkable networks have shown that RIDL can improve accuracy (AC) and reasonably represent imprecision both in the training and testing sets.

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CRI

Summary La Nature (1873–1962) is a French popular science magazine that spanned a large time period and a large range of topics. It is available via ocerized archives so that it forms a corpus that is simultaneously diachronous, heterogeneous, and noisy. Although these characteristics make it complex to analyze, La Nature is of great interest for digital humanities studies on the evolution of thoughts in science, technology, and even politics. The work presented in this article is part of research on the semantic annotation of these archives, which is discovering clues for exploring them. One type of clue that has not been explored in a complex corpus such as La Nature is binomial names, or more specifically, the named entities that refer to the Linnean classification of life, e.g., Escherichia coli. To overcome this complexity, the concept of a Competent Reader, who can detect binomial names even when obsolete, non-standard or defaced by OCR, is introduced. By imitating a Competent Reader, our approach, which we call the Competent Reader Imitator (CRI), involves combining a rule-based approach with a frequency argument. We show that this innovative method is robust to numerous variations and consistently achieves an F-measure of about 70% despite diachronicity, heterogeneity, and noise, which are all known to impede named entity recognition. Our method has many potential applications, such as in the study of chemical names and names of scientific and technical artifacts, which could benefit from the Competent Reader imitation approach. Beyond our work on La Nature, we hope this paper provides a set of tools and methods that are easily understandable, frugal, and usable for a general public interested in exploring similar historical corpus.

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Ultrafast spectroscopy of coherent phonons across the pressure driven insulator to metal phase transition in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Nowadays, materials science is moving towards the understanding and control of materials in nonequilibrium states by making use of perturbative techniques to investigate their dynamical responses. From this perspective, the use of ultrashort light pulses seems to be a relevant approach as it can selectively address different degrees of freedom in solid-state systems and more particularly electrons. Such a method can help to decipher the physical phenomena arising from electronic correlations and complements a more conventional methodology where the phase diagrams of materials are investigated at thermodynamical equilibrium. Here, we combine femtosecond optical spectroscopy and a high-pressure setup to monitor the ultrafast out-of-equilibrium photo response of a V2O3 thin film across the pressure driven insulator-to-metal transition. The experimental results demonstrate the possibility to use the spectroscopy of coherent phonons as a thermodynamical phase marker in V2O3 thin films. In addition, the frequency behavior of the ultrafast coherent phonon mode (A1g character) seems to reflect the manifestation of a strong coupling between the lattice and electronic degrees of freedom near first-order transition lines with a pronounced drop in frequency around the critical pressure. Published by the American Physical Society 2024

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Open Access