Explaining Dynamic Graph Neural Networks via Relevance Back-propagation

Graph Neural Networks (GNNs) have shown remarkable effectiveness in capturing abundant information in graph-structured data. However, the black-box nature of GNNs hinders users from understanding and trusting the models, thus leading to difficulties in their applications. While recent years witness the prosperity of the studies on explaining GNNs, most of them focus on static graphs, leaving the explanation of dynamic GNNs nearly unexplored. It is challenging to explain dynamic GNNs, due to their unique characteristic of time-varying graph structures. Directly using existing models designed for static graphs on dynamic graphs is not feasible because they ignore temporal dependencies among the snapshots. In this work, we propose DGExplainer to provide reliable explanation on dynamic GNNs. DGExplainer redistributes the output activation score of a dynamic GNN to the relevances of the neurons of its previous layer, which iterates until the relevance scores of the input neuron are obtained. We conduct quantitative and qualitative experiments on real-world datasets to demonstrate the effectiveness of the proposed framework for identifying important nodes for link prediction and node regression for dynamic GNNs

Effects of Cations and PH on Antimicrobial Activity of Thanatin and s-Thanatin against _Escherichia coli_ ATCC25922 and _B. subtilis_ ATCC 21332

Thanatin and s-thanatin were insect antimicrobial peptides which have shown potent antimicrobial activities on a variety of microbes. In order to investigate the effect of cations and pH on the activity of these peptides against Gram-negative bacteria and Gram-positive bacteria, the antimicrobial activities of both peptides were studied in increasing concentrations of monovalent cations (K^+^ and Na^+^), divalent cations (Ca^2+^ and Mg^2+^) and H^+^. The NCCLS broth microdilution method showed that both peptides were sensitive to the presence of cations. The divalent cations showed more antagonized effect on the activity against Gram-negative bacteria than the monovalent cations, since the two peptides lost the ability to inhibit bacterial growth at a very low concentration. In addition, the activities of both peptides tested were not significantly affected by pH. Comparing to studies of other antibacterial peptide activities, our data support a hypothesis that positive ions affect the sensitivity to cation peptides

NGC 5846-UDG1: A Galaxy Formed Mostly by Star Formation in Massive, Extremely Dense Clumps of Gas

It has been shown that ultra-diffuse galaxies (UDGs) have higher specific frequencies of globular clusters, on average, than other dwarf galaxies with similar luminosities. The UDG NGC 5846-UDG1 is among the most extreme examples of globular cluster-rich galaxies found so far. Here we present new Hubble Space Telescope observations and analysis of this galaxy and its globular cluster system. We find that NGC 5846-UDG1 hosts 54 ± 9 globular clusters, three to four times more than any previously known galaxy with a similar luminosity and higher than reported in previous studies. With a galaxy luminosity of L V,gal ≈ 6 × 107 L ⊙ (M ⋆ ≈ 1.2 × 108 M ⊙) and a total globular cluster luminosity of L V,GCs ≈ 7.6 × 106 L ⊙, we find that the clusters currently comprise ∼13% of the total light. Taking into account the effects of mass loss from clusters during their formation and throughout their lifetime, we infer that most of the stars in the galaxy likely formed in globular clusters, and very little to no normal low-density star formation occurred. This result implies that the most extreme conditions during early galaxy formation promoted star formation in massive and dense clumps, in contrast to the dispersed star formation observed in galaxies today

Tidal Distortions in NGC1052-DF2 and NGC1052-DF4: Independent Evidence for a Lack of Dark Matter

Two ultra diffuse galaxies in the same group, NGC1052-DF2 and NGC1052-DF4, have been found to have little or no dark matter and to host unusually luminous globular cluster populations. Such low mass diffuse objects in a group environment are easily disrupted and are expected to show evidence of tidal distortions. In this work we present deep new imaging of the NGC1052 group obtained with the Dragonfly Telephoto Array to test this hypothesis. We find that both galaxies show strong position angle twists and are significantly more elongated in their outskirts than in their interiors. The group's central massive elliptical NGC1052 is the most likely source of these tidal disturbances. The observed distortions imply that the galaxies have a low total mass or are very close to NGC1052. Considering constraints on the galaxies' relative distances, we infer that the dark matter halo masses of these galaxies cannot be much greater than their stellar masses. Calculating pericenters from the distortions, we find that the galaxies are on highly elliptical orbits, with a ratio of pericenter to present-day radius Rperi/R0~0.1 if the galaxies are dark matter-free and Rperi/R0~0.01 if they have a normal dark halo. Our findings provide strong evidence, independent of kinematic constraints, that both galaxies are dark matter deficient. Furthermore, the similarity of the tidal features in NGC1052-DF2 and NGC1052-DF4 strongly suggests that they arose at comparable distances from NGC1052. In Appendix A, we describe sbcontrast, a robust method to determine the surface brightness limits of images.Comment: Resubmitted to ApJ after incorporating the referee's comments. The revised version includes a new Appendix A which describes sbcontrast, a method for determining the surface brightness depth of image

Subject function and double subject construction in mandarin chinese

L'identification du sujet en chinois mandarin est une question qui fait depuis longtemps l'objet de controverses. Dans une première partie nous présentons les trois positions qui s'opposent. Dans la deuxième partie , nous examinons ces positions dans le cadre de la grammaire fonctionnelle , telle qu'elle à été présentée par Dik (1978, 1980). Dans la troisième partie, nous soutenons qu'il est nécessaire d'introduire la notion de "Fonction de sujet mineur" pour rendre ccrpte de ce qu'on appelle "construction à double sujet" en mandarin. Enfin, dans la dernière partie, on discute deux solutions alternatives, en notant leurs implications pour la théorie.Shen Jiaxuan. Subject function and double subject construction in mandarin chinese. In: Cahiers de linguistique - Asie orientale, vol. 16 2, 1987. pp. 195-211

A Brief Introduction to the Institute of Linguistics and to Linguistic Studies in China

Jiaxuan Shen. A Brief Introduction to the Institute of Linguistics and to Linguistic Studies in China . In: Bulletin de la Classe des lettres et des sciences morales et politiques, tome 12, n°7-12, 2001. pp. 381-385

Study on disc cutter chipping of TBM based on field data and particle flow code simulation

Using tunnel boring machines to excavate high-strength intact rock masses is becoming more common. Due to the interactions between disc cutters and rocks, abnormal wear of disc cutters, especially cutter chipping, has become a common phenomenon. Existing research has mainly focused on normal wear of disc cutters without addressing abnormal wear cases. This study used the disc cutter consumption data of a tunnel project in China to investigate the abovementioned problem based on field research. According to the failure patterns and fracture surface characteristics, the cutter chipping patterns were mainly categorized into four types: granule chipping, patch chipping, primary collapse, and secondary collapse. To further simulate the evolution of disc cutter chipping, based on the linear plastic bond model, a new contact model called the modified plastic bond (MPB) model was proposed to solve the metal simulation problem in Particle Flow Code software. To this end, a set of uniaxial tensile and compressive tests were initially conducted to verify the applicability of the MPB model. Then, a series of three-dimensional rock-cutting simulation tests were conducted to reflect the evolutionary processes involved in each type of cutter chipping. The cutter chipping mechanism and morphological characteristics were classified and summarized in detail. The results revealed that the cutting speed and penetration growth led to a rising trend in the probability and intensity of the cutter chipping. The presence of initial defects also induced an adverse effect on the service life of the cutter. The results indicated suitable working conditions for the cutter and suggested ways to control tunneling parameters and avoid frequent cutter chipping cases

A Secure and Fair Double Auction Framework for Cloud Virtual Machines

Double auction is one of the most promising solutions to allocate virtual machine (VM) resources in two-sided cloud markets, which can increase the utilization rate of VM resources. However, most cloud auction mechanisms simply assume that the auctioneer is fully trusted while ignoring bid-privacy preservation and trade fairness in the process of auction. Previous studies have indicated that some cryptographic tools can be used to resolve the above issues, but the poor performance makes those techniques difficult to practice. In this paper, we propose a Secure and Fair Double AuCtion framework (named SF-DAC) for cloud virtual machines, which performs cloud auction efficiently while guaranteeing both bid privacy and trade fairness. We design secure 3-party computation protocols that support secure comparison and secure sorting, which enable us to construct a secure double auction scheme that outperforms all prior comparable solutions. Furthermore, we propose a fair trading mechanism based on smart contracts to prevent the bidders from halting the auction without financial penalties. The extensive experiments demonstrate that SF-DAC achieves an order of magnitude reduction in computation and communication costs than prior arts

Abscisic acid and polyamines coordinately regulate strawberry drought responses

Abscisic acid (ABA) and polyamines (PAs) play an important role in plant stress responses; however, their cooperative mechanisms are not fully understood. Here, using the detached-, PEG 6000- and pot-drought strawberry leaves, we investigated the expression changes of genes key to ABA and PA homeostasis by a combination of qRT-PCR, western blotting, RNA-sequencing, physiological analyses, and pharmacological tests. The results showed that early drought may promote the production of both putrescine (Put) by FaADC1 and ABA by FaNCED1, then these productions could be further facilitated by the accumulated Put. Meanwhile, the high accumulation of ABA not only further accelerated ABA biosynthesis by FaNCED3, but also controlled PA homeostasis by a decrease in FaADC1 expression and an increase in FaSAMDC1 and FaPAO5 expression. Based on our RNA-seq data, Put was involved in photosynthesis and oxidative phosphorylation, while ABA was implicated in sugar and flavonoid metabolism, both of which were linked to auxin (IAA). Altogether, in response to strawberry drought stress, FaNCED1/3 and FaADC1/FaSAMDC1 participated separately in ABA and PA accumulation, mostly FaNCED1/FaADC1 was induced by stress and FaNCED3/FaSAMDC1 was induced by ABA. Finally, a balance between ABA and PAs for the cooperative control of plant growth and adaptation is proposed through IAA, photosynthesis, oxidative phosphorylation, and flavonoid metabolism, among which ABA may act in a Put-dependent manner