191 research outputs found
An Army of Me: Sockpuppets in Online Discussion Communities
In online discussion communities, users can interact and share information
and opinions on a wide variety of topics. However, some users may create
multiple identities, or sockpuppets, and engage in undesired behavior by
deceiving others or manipulating discussions. In this work, we study
sockpuppetry across nine discussion communities, and show that sockpuppets
differ from ordinary users in terms of their posting behavior, linguistic
traits, as well as social network structure. Sockpuppets tend to start fewer
discussions, write shorter posts, use more personal pronouns such as "I", and
have more clustered ego-networks. Further, pairs of sockpuppets controlled by
the same individual are more likely to interact on the same discussion at the
same time than pairs of ordinary users. Our analysis suggests a taxonomy of
deceptive behavior in discussion communities. Pairs of sockpuppets can vary in
their deceptiveness, i.e., whether they pretend to be different users, or their
supportiveness, i.e., if they support arguments of other sockpuppets controlled
by the same user. We apply these findings to a series of prediction tasks,
notably, to identify whether a pair of accounts belongs to the same underlying
user or not. Altogether, this work presents a data-driven view of deception in
online discussion communities and paves the way towards the automatic detection
of sockpuppets.Comment: 26th International World Wide Web conference 2017 (WWW 2017
Transmission of a Symmetric Light Pulse through a Wide QW
The reflection, transmission and absorption of a symmetric electromagnetic
pulse, which carrying frequency is close to the frequency of an interband
transition in a QW (QW), are obtained. The energy levels of a QW are assumed
discrete, one exited level is taken into account. The case of a wide QW is
considered when a length of the pulse wave, appropriate to the carrying
frequency, is comparable to the QW's width. In figures the time dependencies of
the dimensionless reflection, absorption are transmission are represented. It
is shown, that the spatial dispersion and a distinction in refraction indexes
influence stronger reflection.Comment: 8 pages,8 figures with caption
Influence of Anomalous Dispersion on Optical Characteristics of Quantum Wells
Frequency dependencies of optical characteristics (reflection, transmission
and absorption of light) of a quantum well are investigated in a vicinity of
interband resonant transitions in a case of two closely located excited energy
levels. A wide quantum well in a quantizing magnetic field directed normally to
the quantum-well plane, and monochromatic stimulating light are considered.
Distinctions between refraction coefficients of barriers and quantum well, and
a spatial dispersion of the light wave are taken into account. It is shown that
at large radiative lifetimes of excited states in comparison with nonradiative
lifetimes, the frequency dependence of the light reflection coefficient in the
vicinity of resonant interband transitions is defined basically by a curve,
similar to the curve of the anomalous dispersion of the refraction coefficient.
The contribution of this curve weakens at alignment of radiative and
nonradiative times, it is practically imperceptible at opposite ratio of
lifetimes . It is shown also that the frequency dependencies similar to the
anomalous dispersion do not arise in transmission and absorption coefficients.Comment: 10 pages, 6 figure
Effect of Defoliation Frequency on Forage Yield from Intensive Silvopastoral Systems Compared to a Monoculture Grassland
Livestock production in the tropical regions of the world faces serious constraints as a result of climate change. Monoculture based pastures require the use of large amounts of nitrogen fertilizers to sustain production throughout the year. In general terms, tropical grasses are of low quality and when consumed by ruminant species, contribute to the emission of greenhouse gases (methane, carbon dioxide and nitrous oxide) (Herrero et al. 2009; Place et al. 2009). The establishment of intensive silvopastoral systems (iSPS) with associated shrubs legumes and grasses can increase the yield and quality of forage as well as fixation and transfer of atmospheric nitrogen (N) (Murgueitio et al. 2011). Therefore, the costs of nitrogen fertilizers and the emissions of greenhouse gases under practical conditions can be reduced. The intensive silvopastoral system is a kind of agroforestal practice that it is environmentally friendly and at the same time improves productivity of livestock systems. However, several aspects of its management have not been fully evaluated.
This is the case of the response to defoliation, which is an important management factor associated to the overall biomass productivity (Solorio 2005)
Binding Mechanism of Metalâ‹…NTP Substrates and Stringent-Response Alarmones to Bacterial DnaG-Type Primases
SummaryPrimases are DNA-dependent RNA polymerases found in all cellular organisms. In bacteria, primer synthesis is carried out by DnaG, an essential enzyme that serves as a key component of DNA replication initiation, progression, and restart. How DnaG associates with nucleotide substrates and how certain naturally prevalent nucleotide analogs impair DnaG function are unknown. We have examined one of the earliest stages in primer synthesis and its control by solving crystal structures of the S. aureus DnaG catalytic core bound to metal ion cofactors and either individual nucleoside triphosphates or the nucleotidyl alarmones, pppGpp and ppGpp. These structures, together with both biochemical analyses and comparative studies of enzymes that use the same catalytic fold as DnaG, pinpoint the predominant nucleotide-binding site of DnaG and explain how the induction of the stringent response in bacteria interferes with primer synthesis
- …