3,629 research outputs found
Radial Angular Momentum Transfer and Magnetic Barrier for Short-Type Gamma-Ray Burst Central Engine Activity
Soft extended emission (EE) following initial hard spikes up to 100 seconds
was observed with {\em Swift}/BAT for about half of short-type gamma-ray bursts
(SGRBs). This challenges the conversional central engine models of SGRBs, i.e.,
compact star merger models. In the framework of the black hole-neutron star
merger models, we study the roles of the radial angular momentum transfer in
the disk and the magnetic barrier around the black hole for the activity of
SGRB central engines. We show that the radial angular momentum transfer may
significantly prolong the lifetime of the accretion process and multiple
episodes may be switched by the magnetic barrier. Our numerical calculations
based on the models of the neutrino-dominated accretion flows suggest that the
disk mass is critical for producing the observed EE. In case of the mass being
, our model can reproduce the observed timescale and
luminosity of both the main and EE episodes in a reasonable parameter set. The
predicted luminosity of the EE component is lower than the observed EE with
about one order of magnitude and the timescale is shorter than 20 seconds if
the disk mass being . {\em Swift}/BAT-like instruments may
be not sensitive enough to detect the EE component in this case. We argue that
the EE component would be a probe for merger process and disk formation for
compact star mergers.Comment: 9 pages, 3 figures, accepted for publication in Ap
Meta contrastive label correction for financial time series
Financial applications such as stock price forecasting, usually face an issue
that under the predefined labeling rules, it is hard to accurately predict the
directions of stock movement. This is because traditional ways of labeling,
taking Triple Barrier Method, for example, usually gives us inaccurate or even
corrupted labels. To address this issue, we focus on two main goals. One is
that our proposed method can automatically generate correct labels for noisy
time series patterns, while at the same time, the method is capable of boosting
classification performance on this new labeled dataset. Based on the
aforementioned goals, our approach has the following three novelties: First, we
fuse a new contrastive learning algorithm into the meta-learning framework to
estimate correct labels iteratively when updating the classification model
inside. Moreover, we utilize images generated from time series data through
Gramian angular field and representative learning. Most important of all, we
adopt multi-task learning to forecast temporal-variant labels. In the
experiments, we work on 6% clean data and the rest unlabeled data. It is shown
that our method is competitive and outperforms a lot compared with benchmarks
Isolation and characterization of a novel Bacillus subtilis WD23 exhibiting laccase activity from forest soil
The strain Bacillus sp. WD23 exhibiting laccase activity was screened from forest soil. The M9 medium containing Cu2+ was used for enriching and isolating bacterial strains capable of oxidizing syringaldazine. One isolated strain was identified as Bacillus subtilis WD23 based on the results of physiological and biochemical tests and 16S rDNA sequence analysis. The strain WD23 could grow at temperatures ranging from 20 to 55°C and showed optimum growth temperature and pH at 25°C and 7.0, respectively. The sporulation rate of the strain clearly correlated well with the laccase activity. The temperature half-life of the spore laccase was 2.5 h at 80°C and the pH half life time was 15 d at pH 9.0. Its spore laccase could decolorize 50 - 90% of Remazol brilliant blue R (RBBR), alizarin red, congo red, methyl orange and methyl violet, which suggests the potential application of spore laccase in dyestuff treatment.Keywords: Bacterial laccase, Bacillus subtilis, spore, decolorizationAfrican Journal of Biotechnology Vol. 9(34), pp. 5496-5502, 23 August, 201
<Abstract of published report>Diastereoselective Alkylation of Chiral Tin(II) Enolates onto Cyclic Acyl Iminium Ions. : Asymmetric Total Syuthesis of (-)-Supinidine.
<Abstract of annual report>New General Asymmetric Synthesis of Versatile γ-Alkylated Butenolides and Its Application to Expeditious Synthesis of the Chiral Geissman-Waiss Lactones Useful for (+)-Retronecine Synthesis.
Impacts of residual aluminum from aluminate flocculant on the morphological and physiological characteristics of Vallisneria natans and Hydrilla verticillata
Aluminate is generally used as a flocculent in water and wastewater treatment processes, but the residual aluminum (Al) may have toxic effects on aquatic organisms when the concentration accumulates beyond a threshold level. The in situ and laboratory tests were conducted to evaluate the impact of residual Al on submerged macrophytes in West Lake, Hangzhou, China, which receives Al flocculant-purified water diverted from the Qiantang River. The responses of Vallisneria natans and Hydrilla verticillata were investigated based on their morphological and physiological parameters in pot culture and aquarium simulation experiments. In the pot culture experiments, the biomass, seedling number, plant height, stolon number, stolon length, and root weight were significantly higher at a site located 150 m from the inlet compared with those at a site located 15 m from the inlet (P < 0.05), thereby indicating that the residual Al significantly inhibited the morphological development of V. natans and H. verticillata. The variations in the chlorophyll-a, protein, and malondialdehyde contents of the two species in both the pot culture and aquarium simulation experiments also demonstrated that the two submerged macrophytes were stressed by residual Al. V. natans and H. verticillata accumulated 0.052-0.227 mg of Al per gram of plant biomass (fresh weight, mg/g FW) and 0.045-0.205 mg Al/g FW in the in situ experiments, respectively, where the amounts of Al were significantly higher in the plants in the treatment aquaria during the laboratory experiments than those in the controls. These results may have important implications for the restoration of submerged macrophytes and ecological risk assessments in Al-exposed lakes. It is recommended that the Al salt concentration used for the control of lake eutrophication should be reduced to an appropriate level.</p
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