2,878 research outputs found
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 for the generalized NFW spike profile is
ruled out at a 95% confidence level. Additionally, the spike radius larger than 21.5 pc is rejected at 95% probability for the Einasto spike
with , 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 10\%
with 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
- …