A study of the interaction between inverted cucurbit[7]uril and symmetric viologens

The interaction between inverted cucuribit[7]uril (iQ[7]) and a series of symmetric viologen derivatives bearing aliphatic substituents of variable length, namely dicationic dialkyl-4,4′-bipyridinium guests where the alkyl is CH₃(CH₂)n with n = 0 to 6, has been studied in aqueous solution by ¹H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. In the case of both n = 5 (HV ²⁺) and 6 (SV²⁺), single crystal X-ray diffraction revealed the composition to be [(iQ[7])₂(HV)₂][CdCl₃Br][H₃O+]₂[H₂O]₁₂.₅ and (iQ[7])₂(C7-SV)₁.₅[CdCl₄]₄(H₃O⁺)₅(H₂O)₈, respectively, with both adopting an external B-type structure (the alkyl chains of the viologen reside within the iQ[7])

Supramolecular assembly of cucurbit[6]uril and N-butyl-4-pyrrolidinopyridine

The nature of the supramolecular host-guest complex involving 4-pyrrolidinopyridine (BuPC4) and cucurbit[6]uril (Q[6]) has been investigated by NMR and UV spectroscopy, MALDI-TOF mass spectrometry, X-ray crystallography and isothermal titration calorimetry (ITC). The results revealed that the alkyl chain of the guest BuPC4 is located inside the cavity of the Q[6] host, whereas the other section of the BuPC4 guest remains outside of the portal

Magnetic Borophenes from an Evolutionary Search

A computational methodology based on ab initio evolutionary algorithms and spin-polarized density functional theory was developed to predict two-dimensional magnetic materials. Its application to a model system borophene reveals an unexpected rich magnetism and polymorphism. A metastable borophene with nonzero thickness is an antiferromagnetic semiconductor from first-principles calculations, and can be further tuned into a half-metal by finite electron doping. In this borophene, the buckling and coupling among three atomic layers are not only responsible for magnetism, but also result in an out-of-plane negative Poisson\u27s ratio under uniaxial tension, making it the first elemental material possessing auxetic and magnetic properties simultaneously

Isometric 3D Adversarial Examples in the Physical World

3D deep learning models are shown to be as vulnerable to adversarial examples as 2D models. However, existing attack methods are still far from stealthy and suffer from severe performance degradation in the physical world. Although 3D data is highly structured, it is difficult to bound the perturbations with simple metrics in the Euclidean space. In this paper, we propose a novel $\epsilon$-isometric ($\epsilon$-ISO) attack to generate natural and robust 3D adversarial examples in the physical world by considering the geometric properties of 3D objects and the invariance to physical transformations. For naturalness, we constrain the adversarial example to be $\epsilon$-isometric to the original one by adopting the Gaussian curvature as a surrogate metric guaranteed by a theoretical analysis. For invariance to physical transformations, we propose a maxima over transformation (MaxOT) method that actively searches for the most harmful transformations rather than random ones to make the generated adversarial example more robust in the physical world. Experiments on typical point cloud recognition models validate that our approach can significantly improve the attack success rate and naturalness of the generated 3D adversarial examples than the state-of-the-art attack methods.Comment: NeurIPS 202

Magnetar Flare-Driven Bumpy Declining Light Curves in Hydrogen-poor Superluminous Supernovae

Recent observations indicate that hydrogen-poor superluminous supernovae often display bumpy declining light curves. However, the cause of these undulations remains unclear. In this paper, we have improved the magnetar model, which includes flare activities. We present a systematic analysis of a well-observed SLSNe-I sample with bumpy light curves in the late-phase. These SLSNe-I were identified from multiple transient surveys, such as the Pan-STARRS1 Medium Deep Survey (PS1 MDS) and the Zwicky Transient Facility (ZTF). Our study provides a set of magnetar-powered model light curve fits for five SLSNe-I, which accurately reproduce observed light curves using reasonable physical parameters. By extracting essential characteristics of both explosions and central engines, these fits provide valuable insights into investigating their potential association with gamma ray burst engines. We found that the SLSN flares tend to be the dim and long extension of the GRB flares in the peak luminosity versus peak time plane. Conducting large-scale, high cadence surveys in the near future could enhance our comprehension of both SLSN undulation properties and their potential relationship with GRBs by modeling their light curve characteristics.Comment: 10 pages, 5 figures. Accepted for publication in the Astrophysical Journa