Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer graphene sheets with a twist between them. Gate voltages applied to top and back gates of a tDBG device tune both the flatness and topology of the electronic bands, enabling an unusual level of experimental control. Metallic states with broken spin and valley symmetries have been observed in tDBG devices with twist angles in the range 1.2–1.3°, but the topologies and order parameters of these states have remained unclear. We report the observation of an anomalous Hall effect in the correlated metal state of tDBG, with hysteresis loops spanning hundreds of mT in out-of-plane magnetic field (B⊥) that demonstrate spontaneously broken time-reversal symmetry. The B⊥ hysteresis persists for in-plane fields up to several Tesla, suggesting valley (orbital) ferromagnetism. At the same time, the resistivity is strongly affected by even mT-scale values of in-plane magnetic field, pointing to spin-valley coupling or to a direct orbital coupling between in-plane field and the valley degree of freedom.

Amicoumacin group of antibiotics, such as baciphelacin, 1 amicoumacins, 2 AI-77s, 3 xenocoumacins, 4 Y-05460M-A, 5 PM-94128, 6 Sg17-1-4, 7 bacilosarcins A, B 8 and lipoamicoumacins A-D, 9 is a small family of isocoumarin, which possesses the common chromophore, 3, 4-dihydro-8-hydroxyisocoumarin. Most members of amicoumacin group of antibiotics are produced by the genus Bacillus and exhibit various important bioactivities. The chromophore shows specific UV absorbance at 247 and 314 nm in methanol. Thus, a project based on HPLC-diode array screening and HPLC-MS dereplication was carried out to find new amicoumacin analogues from the secondary metabolites of Bacillus spp. As a result, PJS (1), a new isocoumarin antibiotic was discovered from the fermentation broth of Bacillus subtilis PJS. In this study, we wish to report the fermentation, isolation, physico Àchemical properties, structural elucidation and biological activities of (1) ( Figure 1).The producing strain Bacillus subtilis PJS was isolated from the leaf of an unidentified plant collected at Luopu county, Hetian area, Xinjiang Province, People's Republic of China. On the basis of analysis of 16S rRNA, it was identified as Bacillus subtilis subsp. inaquosorum. A stock culture of the strain Bacillus subtilis PJS was maintained on modified Gause's no. 1 agar slant consisting of soluble starch (Beijing Qi Te Xin Chemical Co. Ltd. China) 20.0 g, NaCl 50.0 g, K 2 HPO 4 0.5 g, KNO 3 1.0 g, MgSO 4 1.0 g, FeSO 4 0.02 g, glucose 1.0 g, peptone 0.5 g, tryptone 0.3 g and agar 20.0 g in 1.0 l distilled water (pH 8.0) at 4 1C. The stock culture was inoculated into 250 ml Erlenmeyer flasks containing 50 ml of seed medium, which was the same modified Gause's no.1 liquid medium as above, but no agar. The culture was incubated on a rotary shaker (180 r.p.m.) at 28 1C for 24 h. Fifty millilitres of the seed culture was transferred to a 5000 ml Erlenmeyer flask containing 1000 ml of the producing medium, which was the same as the seed medium. The fermentation was carried out at 28 1C for 48 h on a rotary shaker (180 r.p.m.).Eighty liters of the fermentation broth was centrifuged at 4500 r.p.m. for 20 min, then, the supernatant was obtained and was extracted twice with 40 l of ethyl acetate each time. The organic layer was pooled and concentrated under reduced pressure at 37 1C to give yellow syrup (2.3 g). It was then separated by preparative thin layer chromatography on 10 Â 10 cm plates (silica gel 60F 254 , Merck KGaA, Darmstadt, Germany) using CHCl 3 -MeOH, 65:35 (v/v) as the developing solvent. Under UV 365 nm, bands with light blue fluorescence at R f ¼ 0.35 were scraped and then eluted with methanol to yield a semipurified sample (260 mg). After dissolved in 1 ml methanol, the sample was filtered through a 0.22 mm membrane and was further purified by HPLC on a shim-Pack PRC-ODS column (250 Â 20 mm, Shimadzu Corp., Tokyo, Japan) with MeOH-H 2 O, 55:45 (v/v) at 2 ml min À1 . Peak at R t ¼ 26 min, showed UV absorbance at 247 and 314 nm detected by prominence diode array ...

No abstract