26,736 research outputs found
A model of rotating hotspots for 3:2 frequency ratio of HFQPOs in black hole X-ray binaries
We propose a model to explain a puzzling 3:2 frequency ratio of high
frequency quasi-periodic oscillations (HFQPOs) in black hole (BH) X-ray
binaries, GRO J1655-40, GRS 1915+105 and XTE J1550-564. In our model a
non-axisymmetric magnetic coupling (MC) of a rotating black hole (BH) with its
surrounding accretion disc coexists with the Blandford-Znajek (BZ) process. The
upper frequency is fitted by a rotating hotspot near the inner edge of the
disc, which is produced by the energy transferred from the BH to the disc, and
the lower frequency is fitted by another rotating hotspot somewhere away from
the inner edge of the disc, which arises from the screw instability of the
magnetic field on the disc. It turns out that the 3:2 frequency ratio of HFQPOs
in these X-ray binaries could be well fitted to the observational data with a
much narrower range of the BH spin. In addition, the spectral properties of
HFQPOs are discussed. The correlation of HFQPOs with jets from microquasars is
contained naturally in our model.Comment: 8 pages, 4 figures. accepted by MNRA
Negative Link Prediction in Social Media
Signed network analysis has attracted increasing attention in recent years.
This is in part because research on signed network analysis suggests that
negative links have added value in the analytical process. A major impediment
in their effective use is that most social media sites do not enable users to
specify them explicitly. In other words, a gap exists between the importance of
negative links and their availability in real data sets. Therefore, it is
natural to explore whether one can predict negative links automatically from
the commonly available social network data. In this paper, we investigate the
novel problem of negative link prediction with only positive links and
content-centric interactions in social media. We make a number of important
observations about negative links, and propose a principled framework NeLP,
which can exploit positive links and content-centric interactions to predict
negative links. Our experimental results on real-world social networks
demonstrate that the proposed NeLP framework can accurately predict negative
links with positive links and content-centric interactions. Our detailed
experiments also illustrate the relative importance of various factors to the
effectiveness of the proposed framework
Topology and topological sequence entropy
Let be a compact metric space and be continuous. Let be the supremum of topological sequence entropies of over all subsequences of and be the set of the values for all continuous maps on . It is known that . Only three possibilities for have been observed so far, namely , and . In this paper we completely solve the problem of finding all possibilities for by showing that in fact for every set there exists a one-dimensional continuum with . In the construction of we use Cook continua. This is apparently the first application of these very rigid continua in dynamics. We further show that the same result is true if one considers only homeomorphisms rather than con\-ti\-nuous maps. The problem for group actions is also addressed. For some class of group actions (by homeomorphisms) we provide an analogous result, but in full generality this problem remains open. The result works also for an analogous class of semigroup actions (by continuous maps)
CAT: enhancing multimodal large language model to answer questions in dynamic audio-visual scenarios
This paper focuses on the challenge of answering questions
in scenarios that are composed of rich and complex dynamic audiovisual components. Although existing Multimodal Large Language Models (MLLMs) can respond to audio-visual content, these responses are
sometimes ambiguous and fail to describe specific audio-visual events. To
overcome this limitation, we introduce the CAT, which enhances MLLM
in three ways: 1) besides straightforwardly bridging audio and video, we
design a clue aggregator that aggregates question-related clues in dynamic audio-visual scenarios to enrich the detailed knowledge required
for large language models. 2) CAT is trained on a mixed multimodal
dataset, allowing direct application in audio-visual scenarios. Notably,
we collect an audio-visual joint instruction dataset named AVinstruct,
to further enhance the capacity of CAT to model cross-semantic correlations. 3) we propose AI-assisted ambiguity-aware direct preference
optimization, a strategy specialized in retraining the model to favor the
non-ambiguity response and improve the ability to localize specific audiovisual objects. Extensive experimental results demonstrate that CAT
outperforms existing methods on multimodal tasks, especially in AudioVisual Question Answering (AVQA) tasks. The codes and the collected
instructions are released at https://github.com/rikeilong/Bay-CA
DAMA/LIBRA results and perspectives
The DAMA/LIBRA experiment, running at the Gran Sasso National Laboratory of
the I.N.F.N. in Italy, has a sensitive mass of about 250 kg highly radiopure
NaI(Tl). It is mainly devoted to the investigation of Dark Matter (DM)
particles in the Galactic halo by exploiting the model independent DM annual
modulation signature. The present DAMA/LIBRA experiment and the former DAMA/NaI
one (the first generation experiment having an exposed mass of about 100 kg)
have released so far results corresponding to a total exposure of 1.17 ton yr
over 13 annual cycles. They provide a model independent evidence of the
presence of DM particles in the galactic halo at 8.9 sigma C.L.. A short
summary of the obtained results is presented and future perspectives of the
experiment mentioned.Comment: 12 pages, Proceed. of the 15th Bled Workshop "What Comes Beyond
Standard Models" (December 2012), Vol. 13, No.
Observation of orbital ordering and origin of the nematic order in FeSe
To elucidate the origin of nematic order in FeSe, we performed
field-dependent 77Se-NMR measurements on single crystals of FeSe. We observed
orbital ordering from the splitting of the NMR spectra and Knight shift and a
suppression of it with magnetic field B0 up to 16 T applied parallel to the
Fe-planes. There is a significant change in the distribution and magnitude of
the internal magnetic field across the orbital ordering temperature Torb while
stripe-type antiferromagnetism is absent. Giant antiferromagnetic (AFM) spin
fluctuations measured by the NMR spin-lattice relaxation are gradually
developed starting at ~ 40 K, which is far below the nematic ordering
temperature Tnem. These results demonstrate that orbital ordering is the origin
of the nematic order, and the AFM spin fluctuation is the driving mechanism of
superconductivity in FeSe under the presence of the nematic order.Comment: 6 pages, 4 figure
Bottom-Up versus Top-Down Induction of Sleep by Zolpidem Acting on Histaminergic and Neocortex Neurons
Zolpidem, a GABAA receptor-positive modulator, is the gold-standard drug for treating insomnia. Zolpidem prolongs IPSCs to decrease sleep latency and increase sleep time, effects that depend on α2 and/or α3 subunit-containing receptors. Compared with natural NREM sleep, zolpidem also decreases the EEG power, an effect that depends on α1 subunit-containing receptors, and which may make zolpidem-induced sleep less optimal. In this paper, we investigate whether zolpidem needs to potentiate only particular GABAergic pathways to induce sleep without reducing EEG power. Mice with a knock-in F77I mutation in the GABAA receptor γ2 subunit gene are zolpidem-insensitive. Using these mice, GABAA receptors in the frontal motor neocortex and hypothalamic (tuberomammillary nucleus) histaminergic-neurons of γ2I77 mice were made selectively sensitive to zolpidem by genetically swapping the γ2I77 subunits with γ2F77 subunits. When histamine neurons were made selectively zolpidem-sensitive, systemic administration of zolpidem shortened sleep latency and increased sleep time. But in contrast to the effect of zolpidem on wild-type mice, the power in the EEG spectra of NREM sleep was not decreased, suggesting that these EEG power-reducing effects of zolpidem do not depend on reduced histamine release. Selective potentiation of GABAA receptors in the frontal cortex by systemic zolpidem administration also reduced sleep latency, but less so than for histamine neurons. These results could help with the design of new sedatives that induce a more natural sleep
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