The spin Hall effect of radiofrequency waves in magnetic-fusion devices

In inhomogeneous media, electromagnetic-wave rays deviate from the trajectories predicted by the leading-order geometrical optics. This effect, called the spin Hall effect of light, is typically neglected in ray-tracing codes used for modeling waves in plasmas. Here, we demonstrate that the spin Hall effect can be significant for radiofrequency waves in toroidal fusion plasmas. For example, an electron-cyclotron wave beam can deviate by as large as ten wavelengths ($\sim 0.1\,\text{m}$) relative to the lowest-order ray trajectory in the poloidal direction. We calculate this displacement using gauge-invariant ray equations of extended geometrical optics, and we also compare our theoretical predictions with full-wave simulations

Siamese-DETR for Generic Multi-Object Tracking

The ability to detect and track the dynamic objects in different scenes is fundamental to real-world applications, e.g., autonomous driving and robot navigation. However, traditional Multi-Object Tracking (MOT) is limited to tracking objects belonging to the pre-defined closed-set categories. Recently, Open-Vocabulary MOT (OVMOT) and Generic MOT (GMOT) are proposed to track interested objects beyond pre-defined categories with the given text prompt and template image. However, the expensive well pre-trained (vision-)language model and fine-grained category annotations are required to train OVMOT models. In this paper, we focus on GMOT and propose a simple but effective method, Siamese-DETR, for GMOT. Only the commonly used detection datasets (e.g., COCO) are required for training. Different from existing GMOT methods, which train a Single Object Tracking (SOT) based detector to detect interested objects and then apply a data association based MOT tracker to get the trajectories, we leverage the inherent object queries in DETR variants. Specifically: 1) The multi-scale object queries are designed based on the given template image, which are effective for detecting different scales of objects with the same category as the template image; 2) A dynamic matching training strategy is introduced to train Siamese-DETR on commonly used detection datasets, which takes full advantage of provided annotations; 3) The online tracking pipeline is simplified through a tracking-by-query manner by incorporating the tracked boxes in previous frame as additional query boxes. The complex data association is replaced with the much simpler Non-Maximum Suppression (NMS). Extensive experimental results show that Siamese-DETR surpasses existing MOT methods on GMOT-40 dataset by a large margin

A New Family of Nucleophiles for Photoinduced, Copper-Catalyzed Cross-Couplings via Single-Electron Transfer: Reactions of Thiols with Aryl Halides Under Mild Conditions (0 °C)

Building on the known photophysical properties of well-defined copper–carbazolide complexes, we have recently described photoinduced, copper-catalyzed N-arylations and N-alkylations of carbazoles. Until now, there have been no examples of the use of other families of heteroatom nucleophiles in such photoinduced processes. Herein, we report a versatile photoinduced, copper-catalyzed method for coupling aryl thiols with aryl halides, wherein a single set of reaction conditions, using inexpensive CuI as a precatalyst without the need for an added ligand, is effective for a wide range of coupling partners. As far as we are aware, copper-catalyzed C–S cross-couplings at 0 °C have not previously been achieved, which renders our observation of efficient reaction of an unactivated aryl iodide at −40 °C especially striking. Mechanistic investigations are consistent with these photoinduced C–S cross-couplings following a SET/radical pathway for C–X bond cleavage (via a Cu(I)–thiolate), which contrasts with nonphotoinduced, copper-catalyzed processes wherein a concerted mechanism is believed to occur

Oxygen nucleophiles as reaction partners in photoinduced, copper-catalyzed cross-couplings: O-arylations of phenols at room temperature

Most copper-catalyzed cross-couplings require an elevated reaction temperature. Recently, a photoinduced variant has been developed that enables C–X bond-forming reactions of certain nitrogen and sulfur nucleophiles to proceed under unusually mild conditions (−40 °C to room temperature). In view of the importance of carbon–oxygen bond construction in organic chemistry, the expansion of this photochemical approach to oxygen nucleophiles is an important objective. In this report, we establish that, in the presence of light and an inexpensive copper pre-catalyst (CuI), a wide array of phenols and aryl iodides can be coupled to generate diaryl ethers under mild conditions (room temperature) in the presence of a variety of functional groups. Our studies indicate that a Cu(I)–phenoxide complex is a viable intermediate in photoinduced C–O bond-formation

Backbone Interactions Between Transcriptional Activator ExsA and Anti-Activator ExsD Facilitate Regulation of the Type III Secretion System in \u3cem\u3ePseudomonas aeruginosa\u3c/em\u3e

The type III secretion system (T3SS) is a pivotal virulence mechanism of many Gram-negative bacteria. During infection, the syringe-like T3SS injects cytotoxic proteins directly into the eukaryotic host cell cytoplasm. In Pseudomonas aeruginosa, expression of the T3SS is regulated by a signaling cascade involving the proteins ExsA, ExsC, ExsD, and ExsE. The AraC-type transcription factor ExsA activates transcription of all T3SS-associated genes. Prior to host cell contact, ExsA is inhibited through direct binding of the anti-activator protein ExsD. Host cell contact triggers secretion of ExsE and sequestration of ExsD by ExsC to cause the release of ExsA. ExsA does not bind ExsD through the canonical ligand binding pocket of AraC-type proteins. Using site-directed mutagenesis and a specific in vitro transcription assay, we have now discovered that backbone interactions between the amino terminus of ExsD and the ExsA beta barrel constitute a pivotal part of the ExsD-ExsA interface. Follow-up bacterial two-hybrid experiments suggest additional contacts create an even larger protein–protein interface. The discovered role of the amino terminus of ExsD in ExsA binding explains how ExsC might relieve the ExsD-mediated inhibition of T3SS gene expression, because the same region of ExsD interacts with ExsC following host cell contact

A mechanistic investigation of the photoinduced, copper-mediated cross-coupling of an aryl thiol with an aryl halide

Photoinduced, copper-catalyzed cross-coupling can offer a complementary approach to thermal (non-photoinduced) methods for generating C–X (X = C, N, O, S, etc.) bonds. In this report, we describe the first detailed mechanistic investigation of one of the processes that we have developed, specifically, the (stoichiometric) coupling of a copper–thiolate with an aryl iodide. In particular, we focus on the chemistry of a discrete [Cu^I(SAr)_2]− complex (Ar = 2,6-dimethylphenyl), applying a range of techniques, including ESI-MS, cyclic voltammetry, transient luminescence spectroscopy, optical spectroscopy, DFT calculations, Stern–Volmer analysis, EPR spectroscopy, actinometry, and reactivity studies. The available data are consistent with the viability of a pathway in which photoexcited [Cu^I(SAr)_2]−* serves as an electron donor to an aryl iodide to afford an aryl radical, which then reacts in cage with the newly generated copper(II)–thiolate to furnish the cross-coupling product in a non-chain process