Federated Learning Backdoor Attack Based on Frequency Domain Injection.

Federated learning (FL) is a distributed machine learning framework that enables scattered participants to collaboratively train machine learning models without revealing information to other participants. Due to its distributed nature, FL is susceptible to being manipulated by malicious clients. These malicious clients can launch backdoor attacks by contaminating local data or tampering with local model gradients, thereby damaging the global model. However, existing backdoor attacks in distributed scenarios have several vulnerabilities. For example, (1) the triggers in distributed backdoor attacks are mostly visible and easily perceivable by humans; (2) these triggers are mostly applied in the spatial domain, inevitably corrupting the semantic information of the contaminated pixels. To address these issues, this paper introduces a frequency-domain injection-based backdoor attack in FL. Specifically, by performing a Fourier transform, the trigger and the clean image are linearly mixed in the frequency domain, injecting the low-frequency information of the trigger into the clean image while preserving its semantic information. Experiments on multiple image classification datasets demonstrate that the attack method proposed in this paper is stealthier and more effective in FL scenarios compared to existing attack methods.

Two consecutive aza-amino acids in peptides promote stable ß-turn formation in water.

Studies on the synthetic methodologies and the structural propensity of peptides containing consecutive aza-amino acids are still in their infancy. Here, details of the synthesis and conformational analysis of tripeptides containing two consecutive aza-amino acids are provided. The demonstration that the type I ß-turn folding is induced, even in aqueous media, by the introduction of one or two lateral chains on the diaza-peptide unit is of particular importance for the design of peptidomimetics of biological interest.

The Positive Side of the Alzheimer's Disease Amyloid Cross-Interactions: The Case of the Aß 1-42 Peptide with Tau, TTR, CysC, and ApoA1.

Alzheimer's disease (AD) represents a progressive amyloidogenic disorder whose advancement is widely recognized to be connected to amyloid-ß peptides and Tau aggregation. However, several other processes likely contribute to the development of AD and some of them might be related to protein-protein interactions. Amyloid aggregates usually contain not only single type of amyloid protein, but also other type of proteins and this phenomenon can be rationally explained by the process of protein cross-seeding and co-assembly. Amyloid cross-interaction is ubiquitous in amyloid fibril formation and so a better knowledge of the amyloid interactome could help to further understand the mechanisms of amyloid related diseases. In this review, we discuss about the cross-interactions of amyloid-ß peptides, and in particular Aß1-42, with other amyloids, which have been presented either as integrated part of Aß neurotoxicity process (such as Tau) or conversely with a preventive role in AD pathogenesis by directly binding to Aß (such as transthyretin, cystatin C and apolipoprotein A1). Particularly, we will focus on all the possible therapeutic strategies aiming to rescue the Aß toxicity by taking inspiration from these protein-protein interactions.

Achieving Practical Venue Recycle of Waste Oil-Based Drilling Fluids with Vacuum Distillation Technology.

Drilling fluids are essential operating additives for extracting oil and shale gas. Thus, their pollution control and recycling utilization are significant to petrochemical development. Vacuum distillation technology was used in this research to handle waste oil-based drilling fluids and achieve reutilization. Briefly, recycled oil and recovered solids can be obtained from waste oil-based drilling fluids whose density is 1.24-1.37 g/cm3 by vacuum distillation under the condition of an external heat transfer oil temperature of 270 ± 5 °C and a reaction pressure below 5 × 103 Pa. Meanwhile, recycled oil has excellent apparent viscosity (AV, 21 mPa·s) and plastic viscosity (PV, 14 mPa·s), which could be used as a substitute for 3# white oil. Furthermore, PF-ECOSEAL prepared by recycled solids exhibited better rheological properties (27.5 mPa·s AV, 18.5 mPa·s PV, and 9 Pa yield point) and plugging performance (32 mL V0, 1.90 mL/min1/2Vsf) than drilling fluids prepared with the conventional plugging agent PF-LPF. Our work confirmed that vacuum distillation is a valid technology in innocuity treatment and resource utilization of drilling fluids and has great value in industrial applications.

Proteolytically Stable Diaza-Peptide Foldamers Mimic Helical Hot Spots of Protein-Protein Interactions and Act as Natural Chaperones.

A novel class of peptidomimetic foldamers based on diaza-peptide units are reported. Circular dichroism, attenuated total reflection -Fourier transform infrared, NMR, and molecular dynamics studies demonstrate that unlike the natural parent nonapeptide, the specific incorporation of one diaza-peptide unit at the N-terminus allows helical folding in water, which is further reinforced by the introduction of a second unit at the C-terminus. The ability of these foldamers to resist proteolysis, to mimic the small helical hot spot of transthyretin-amyloid ß (Aß) cross-interaction, and to decrease pathological Aß aggregation demonstrates that the introduction of diaza-peptide units is a valid approach for designing mimics or inhibitors of protein-protein interaction and other therapeutic peptidomimetics. This study also reveals that small peptide foldamers can play the same role as physiological chaperone proteins and opens a new way to design inhibitors of amyloid protein aggregation, a hallmark of more than 20 serious human diseases such as Alzheimer's disease.

Adversarial CAPTCHAs.

Following the principle of to set one's own spear against one's own shield, we study how to design adversarial completely automated public turing test to tell computers and humans apart (CAPTCHA) in this article. We first identify the similarity and difference between adversarial CAPTCHA generation and existing hot adversarial example (image) generation research. Then, we propose a framework for text-based and image-based adversarial CAPTCHA generation on top of state-of-the-art adversarial image generation techniques. Finally, we design and implement an adversarial CAPTCHA generation and evaluation system, called aCAPTCHA, which integrates 12 image preprocessing techniques, nine CAPTCHA attacks, four baseline adversarial CAPTCHA generation methods, and eight new adversarial CAPTCHA generation methods. To examine the performance of aCAPTCHA, extensive security and usability evaluations are conducted. The results demonstrate that the generated adversarial CAPTCHAs can significantly improve the security of normal CAPTCHAs while maintaining similar usability. To facilitate the CAPTCHA security research, we also open source the aCAPTCHA system, including the source code, trained models, datasets, and the usability evaluation interfaces.

Design, Synthesis, and Biological Evaluation of Novel DNA Gyrase-Inhibiting Spiropyrimidinetriones as Potent Antibiotics for Treatment of Infections Caused by Multidrug-Resistant Gram-Positive Bacteria.

Spiropyrimidinetriones are a novel class of antibacterial agents that target the bacterial type II topoisomerase via a new mode of action. Compound ETX0914 is thus far the only drug from this class that is being evaluated in clinical trials. To improve the antibacterial activity and pharmacokinetic properties of ETX0914, we carried out systematic structural modification of this compound, and a number of compounds with increased potency were obtained. The most promising compound 33e, with incorporation of a spirocyclopropane at the oxazolidinone 5 position reduced metabolism, exhibited excellent antibacterial activity against Gram-positive pathogens and a good pharmacokinetic profile combined with high aqueous solubility. In addition, compound 33e exhibited good selectivity for Staphylococcus aureus gyrase over human Topo IIα. In a murine model of systemic methicillin-resistant S. aureus infection, 33e exhibited superior in vivo efficacy (ED50 = 3.87 mg/kg) compared to ETX0914 (ED50 = 11.51 mg/kg).