A repeating fast radio burst associated with a persistent radio source.

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately [Formula: see text] parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications.

A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber.

Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

CTLA-4 and CD86 genetic variants and haplotypes in patients with rheumatoid arthritis in southeastern China.

The cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and costimulatory molecule (CD80/CD86) genes are important susceptibility genes associated with autoimmune diseases. CTLA-4 polymorphisms have been found to be associated with various autoimmune diseases. However, the association data are inconsistent for rheumatoid arthritis (RA). We investigated the genetic association of CTLA-4 and CD86 polymorphisms with RA in a Chinese population. Four single nucleotide polymorphisms (SNPs) (rs5742909 and rs231775 in CTLA-4, and rs17281995 and rs1129055 in CD86) were genotyped in 213 patients with RA and 303 healthy controls using polymerase chain reaction-restriction fragment length polymorphism. The genotype and allele distributions of rs5742909 differ significantly between RA patients and controls (P < 0.05) and the dominant model was found to be the best inheritance model. Stratification studies showed that CTLA-4 gene polymorphisms were more significantly associated with rheumatoid factor-negative and anti-cyclic citrullinated peptide-negative subgroups in the southeastern Han Chinese population. We also found that the haplotype of 2 CTLA-4 SNPs showed significant association with the disease (P = 0.0025) with the T-A (OR = 1.88, 95%CI = 1.12-3.15) and T-G (OR = 3.45, 95%CI = 1.10-10.87) haplotypes being observed more frequently in cases than in controls. We failed to find any significant association of the 2 CD86 SNPs with RA. These results indicate that the polymorphisms of CTLA-4 (rs5742909) may be important genetic factors for RA risk in the southeastern Han Chinese population.