Accretion onto Intermediate Mass Black Holes Regulated by Radiative Feedback I. Parametric Study for Spherically Symmetric Accretion

We study the effect of radiative feedback on accretion onto intermediate mass black holes (IMBHs) using the hydrodynamical code ZEUS-MP with a radiative transfer algorithm. In this paper, the first of a series, we assume accretion from a uniformly dense gas with zero angular momentum and extremely low metallicity. Our 1D and 2D simulations explore how X-ray and UV radiation emitted near the black hole regulates the gas supply from large scales. Both 1D and 2D simulations show similar accretion rate and period between peaks in accretion, meaning that the hydro-instabilities that develop in 2D simulations do not affect the mean flow properties. We present a suite of simulations exploring accretion across a large parameter space, including different radiative efficiencies and radiation spectra, black hole masses, density and temperature, $T_\infty$, of the neighboring gas. In agreement with previous studies we find regular oscillatory behavior of the accretion rate, with duty cycle $\sim 6$, mean accretion rate 3% $(T_{\infty}/10^4 {\rm K})^{2.5}$ of the Bondi rate and peak accretion $\sim 10$ times the mean for $T_{\infty}$ ranging between 3000K and 15000K. We derive parametric formulas for the period between bursts, the mean accretion rate and the peak luminosity of the bursts and thus provide a formulation of how feedback regulated accretion operates. The temperature profile of the hot ionized gas is crucial in determining the accretion rate, while the period of the bursts is proportional to the mean size of the Str\"{o}mgren sphere and we find qualitatively different modes of accretion in the high vs. low density regimes. We also find that softer spectrum of radiation produces higher mean accretion rate.Comment: 16 pages, 12 figures, accepted for publication in Ap

An Enhanced Multimodal Stacking Scheme for Online Pornographic Content Detection

An enhanced multimodal stacking scheme is proposed for quick and accurate online detection of harmful pornographic contents on the Internet. To accurately detect harmful contents, the implicative visual features (auditory features) are extracted using a bi-directional RNN (recurrent neural network) with VGG-16 (a multilayered dilated convolutional network) to implicitly express the signal change patterns over time within each input. Using only the implicative visual and auditory features, a video classifier and an audio classifier are trained, respectively. By using both features together, one fusion classifier is also trained. Then, these three component classifiers are stacked in the enhanced ensemble scheme to reduce the false negative errors in a serial order of the fusion classifier, video classifier, and audio classifier for a quick online detection. The proposed multimodal stacking scheme yields an improved true positive rate of 95.40% and a false negative rate of 4.60%, which are superior values to previous studies. In addition, the proposed stacking scheme can accurately detect harmful contents up to 74.58% and an average rate of 62.16% faster than the previous stacking scheme. Therefore, the proposed enhanced multimodal stacking scheme can be used to quickly and accurately filter out harmful contents in the online environments

A Person Re-Identification Scheme Using Local Multiscale Feature Embedding with Dual Pyramids

In this paper, we propose a new person re-identification scheme that uses dual pyramids to construct and utilize the local multiscale feature embedding that reflects different sizes and shapes of visual feature elements appearing in various areas of a person image. In the dual pyramids, a scale pyramid reflects the visual feature elements in various sizes and shapes, and a part pyramid selects elements and differently combines them for the feature embedding per each region of the person image. In the experiments, the performance of the cases with and without each pyramid were compared to verify that the proposed scheme has an optimal structure. The state-of-the-art studies known in the field of person re-identification were also compared for accuracy. According to the experimental results, the method proposed in this study showed a maximum of 99.25% Rank-1 accuracy according to the dataset used in the experiments. Based on the same dataset, the accuracy was determined to be about 3.55% higher than the previous studies, which used only person images, and about 1.25% higher than the other studies using additional meta-information besides images of persons

Chemical Recycling of Polycarbonate and Polyester without Solvent and Catalyst: Mechanochemical Methanolysis

In this study, we present a green and economical approach to chemical recycling of commercial polycarbonates and poly-esters, specifically poly(bisphenol A carbonate), poly(ethylene terephthalate), and poly(lactic acid). Our method involves mechanochemical ball-milling of a heterogeneous mixture of plastic and methanol, resulting in quantitative depolymeriza-tion to yield monomers or useful chemical units that already have high demands. We found that the energy-intensive step is forming physical contact between the reactants, rather than the chemical methanolysis itself. Mechanochemical ball-milling facilitates sufficient physical contact and energy transfer between plastics and methanol, eliminating the need for solvents and catalysts. Our study demonstrates a practical and sustainable process with minimal chemical input and simple output for the chemical recycling of these plastics

Recent Organic Transformations with Silver Carbonate as a Key External Base and Oxidant

Silver carbonate (Ag2CO3), a common transition metal-based inorganic carbonate, is widely utilized in palladium-catalyzed C–H activations as an oxidant in the redox cycle. Silver carbonate can also act as an external base in the reaction medium, especially in organic solvents with acidic protons. Its superior alkynophilicity and basicity make silver carbonate an ideal catalyst for organic reactions with alkynes, carboxylic acids, and related compounds. This review describes recent reports of silver carbonate-catalyzed and silver carbonate-mediated organic transformations, including cyclizations, cross-couplings, and decarboxylations

Copper-Catalyzed Selective Arylations of Benzoxazoles with Aryl Iodides

A copper-catalyzed direct ring-opening double <i>N</i>-arylation of benzoxazoles with aryl iodides has been developed. The present system exhibits high selectivity despite competition from <i>C</i>-arylation. The selectivity between ring-opening <i>N</i>-arylation and <i>C</i>-arylation was controlled by the choice of reaction vessel. The nitrile bound bis­(triphenylphosphine)­copper cyanide was identified as the active catalytic species for both reactions, and when combined with a nitrile-containing solvent, enhanced the reaction efficiency

A Polysomnography Study of Snoring and Obstructive Sleep Apnea in Relation to Chronic Bronchitis

Background and Objective Reportedly, snoring is associated with chronic bronchitis. This association warrants further studies including polysomnographic evaluations because of few epidemiologic studies on the association. Via a polysomnography study, we evaluated the associations of snoring, obstructive sleep apnea, and systemic inflammation with chronic bronchitis among 442 participants from a population-based cohort. Methods At baseline, we assessed participants’ serum levels of C-reactive protein, a biomarker of systemic inflammation. Over a 5-year period, we conducted overnight polysomnography and identified any new cases of chronic bronchitis. Results After taking into account age, smoking, and other potential risk factors, the multivariate odds ratio (95% CI) for chronic bronchitis was 2.9 (95% CI, 1.3–6.4) for snorers with cumulative duration of snoring episodes ≥ 1 hour as compared with those snoring < 1 hour. This association did not change after further adjustment for the presence of apnea. Obstructive sleep apnea had no association with chronic bronchitis. A higher level of serum C-reactive protein was associated with chronic bronchitis (p value for trend < 0.05). In a joint analysis of snoring and C-reactive protein, longer cumulative duration of snoring episodes accompanied by systemic inflammation was associated with a 10-fold (95% CI, 2.9 to 37.4) increase in the multivariate odds of chronic bronchitis. Conclusions This polysomnography study provides additional data supporting the hypothesis that snoring is associated with chronic bronchitis implying that snoring-related local and systemic inflammation may play roles in the development of chronic bronchitis