Collective iteration behavior for online social networks

Understanding the patterns of collective behavior in online social network (OSNs) is critical to expanding the knowledge of human behavior and tie relationship. In this paper, we investigate a specific pattern called social signature in Facebook and Wiki users’ online communication behaviors, capturing the distribution of frequency of interactions between different alters over time in the ego network. The empirical results show that there are robust social signatures of interactions no matter how friends change over time, which indicates that a stable commutation pattern exists in online communication. By comparing a random null model, we find the that commutation pattern is heterogeneous between ego and alters. Furthermore, in order to regenerate the pattern of the social signature, we present a preferential interaction model, which assumes that new users intend to look for the old users with strong ties while old users have tendency to interact with new friends. The experimental results show that the presented model can reproduce the heterogeneity of social signature by adjusting 2 parameters, the number of communicating targets m and the max number of interactions n, for Facebook users, m=n=5, for Wiki users, m=2 and n=8. This work helps in deeply understanding the regularity of social signature

Effect of user tastes on personalized recommendation

In this paper, based on a weighted projection of the user-object bipartite network, we study the effects of user tastes on the mass-diffusion-based personalized recommendation algorithm, where a user's tastes or interests are defined by the average degree of the objects he has collected. We argue that the initial recommendation power located on the objects should be determined by both of their degree and the users' tastes. By introducing a tunable parameter, the user taste effects on the configuration of initial recommendation power distribution are investigated. The numerical results indicate that the presented algorithm could improve the accuracy, measured by the average ranking score, more importantly, we find that when the data is sparse, the algorithm should give more recommendation power to the objects whose degrees are close to the users' tastes, while when the data becomes dense, it should assign more power on the objects whose degrees are significantly different from user's tastes.Comment: 8 pages, 4 figure

Thailandepsin A

Thailandepsin A [systematic name: (E)-(1S,5S,6R,9S,20R)-6-[(2S)-butan-2-yl]-5-hy­droxy-20-[2-(meth­yl­sulfan­yl)eth­yl]-2-oxa-11,12-dithia-7,19,22-triaza­bicyclo­[7.7.6]docosa-15-ene-3,8,18,21-tetra­one], C23H37N3O6S3, is a newly reported [Wang et al. (2011). J. Nat. Prod. doi:10.1021/np200324x] bicyclic depsipeptide that has potent histone deacetyl­ase inhibitory activity and broad-spectrum anti­proliferative activity. The absolute configuration of thailandepsin A has been determined from the anomalous dispersion and the stereochemistry of all chiral C atoms. Intra­molecular N—H⋯O and N—H⋯S hydrogen bonds occur. Inter­molecular N—H⋯O and O—H⋯O hydrogen bonds are observed in the crystal structure

Exploring dark matter spike distribution around the Galactic centre with stellar orbits

Precise measurements of the stellar orbits around Sagittarius A* have established the existence of a supermassive black hole (SMBH) at the Galactic centre (GC). Due to the interplay between the SMBH and dark matter (DM), the DM density profile in the innermost region of the Galaxy, which is crucial for the DM indirect detection, is still an open question. Among the most popular models in the literature, the theoretical spike profile proposed by Gondolo and Silk (1999; GS hereafter) is well adopted. In this work, we investigate the DM spike profile using updated data from the Keck and VLT telescopes considering that the presence of such an extended mass component may affect the orbits of the S-stars in the Galactic center. We examine the radius and slope of the generalized NFW spike profile, analyze the Einasto spike, and discuss the influence of DM annihilation on the results. Our findings indicate that an initial slope of $\gamma \gtrsim 0.92$ for the generalized NFW spike profile is ruled out at a 95% confidence level. Additionally, the spike radius $R_{\rm sp}$ larger than 21.5 pc is rejected at 95% probability for the Einasto spike with $\alpha=0.17$, which also contradicts the GS spike model. The constraints with the VLT/GRAVITY upper limits are also projected. Although the GS NFW spike is well constrained by the Keck and VLT observation of S2, an NFW spike with a weak annihilation cusp may still be viable, as long as the DM annihilation cross section satisfies \left \gtrsim 7.7\times 10^{-27}~{\rm cm^3\,s^{-1}} (m_{\rm DM}/100~{\rm GeV}) at 95% level.Comment: 12 pages, 10 figures and 1 table. Accepted for publication in MNRA

Constraints on peculiar velocity distribution of binary black holes using gravitational waves with GWTC-3

The peculiar velocity encodes rich information about the formation, dynamics, evolution, and merging history of binary black holes. In this work, we employ a hierarchical Bayesian model to infer the peculiar velocity distribution of binary black holes for the first time using GWTC-3 by assuming a Maxwell-Boltzmann distribution for the peculiar velocities. The constraint on the peculiar velocity distribution parameter is rather weak and uninformative with the current GWTC-3 data release. However, the measurement of the peculiar velocity distribution can be significantly improved with the next-generation ground-based gravitational wave detectors. For instance, the uncertainty on the peculiar velocity distribution parameter will be measured within $\sim$ 10\% with $10^3$ golden binary black hole events for the Einstein Telescope. We, therefore, conclude that our statistical approach provides a robust inference for the peculiar velocity distribution.Comment: 15 pages, 2 figures

2-Methyl­sulfanyl-4-(3-pyrid­yl)pyrimidine

In the title compound, C10H9N3S, the dihedral angle between the aromatic rings is 8.09 (14)°. In the crystal, a C—H⋯N interaction links the molecules, forming chains