Supermassive black holes are not only common in the present-day galaxies, but billion solar masses black holes also powered z ≥ 6 quasars. One efficient way to form such black holes is the collapse ...of a massive primordial gas cloud into a so-called direct collapse black hole. The main requirement for this scenario is the presence of large accretion rates of ≥ 0.1 M⊙ yr− 1 to form a supermassive star. It is not yet clear how and under what conditions such accretion rates can be obtained. The prime aim of this work is to determine the mass accretion rates under non-isothermal collapse conditions. We perform high-resolution cosmological simulations for three primordial haloes of a few times 107 M⊙ illuminated by an external UV flux, J
21 = 100–1000. We find that a rotationally supported structure of about parsec size is assembled, with an aspect ratio between 0.25 and 1 depending upon the thermodynamical properties. Rotational support, however, does not halt collapse, and mass inflow rates of ∼ 0.1 M⊙ yr− 1 can be obtained in the presence of even a moderate UV background flux of strength J
21 ≥ 100. To assess whether such large accretion rates can be maintained over longer time-scales, we employed sink particles, confirming the persistence of accretion rates of ∼ 0.1 M⊙ yr− 1. We propose that complete isothermal collapse and molecular hydrogen suppression may not always be necessary to form supermassive stars, precursors of black hole seeds. Sufficiently high inflow rates can be obtained for UV flux J
21 = 500–1000, at least for some cases. This value brings the estimate of the abundance of direct collapse black hole seeds closer to that high-redshift quasars.
This research presents a tracking formation by multiple mobile robots. The formation used is leader follower approach. Formation control is designed based on the robot kinematics model. Follower is ...controlled to track the position of the specified formation. Triangle shape is used to the goal formation. Experiments carried out with two scenarios. First, leader moves to a point with linear motion. Second, leader moves along the circular trajectory. Leader motion is constantly with the aim that the formation is rigidly formed while moving towards the goal. Experiments show that robots can perform and maintain formation while achieving goals.
In this investigation, we aimed to fabricate easy separable composite microbeads for efficient adsorption of tetracycline (TC) drug. MIL-125(Ti)/MIL-53(Fe) binary metal organic framework (MOF) was ...synthetized and incorporated with carbon nanotube (CNT) into alginate (Alg) microbeads to form MIL-125(Ti)/MIL-53(Fe)/CNT@Alg composite microbeads. Various tools including FTIR, XRD, SEM, BET, Zeta potential and XPS were applied to characterize the composite microbeads. It was found that the specific surface area of MIL-125(Ti)/MIL-53(Fe)/CNT@Alg microbeads was 273.77 m
/g. The results revealed that the adsorption of TC augmented with rising CNT proportion up to 15 wt% in the microbeads matrix. In addition, the adsorption process followed the pseudo-second-order and well-fitted to Freundlich and Langmuir models with a maximum adsorption capacity of 294.12 mg/g at 25 ◦C and pH 6. Furthermore, thermodynamic study clarified that the TC adsorption process was endothermic, random and spontaneous. Besides, reusability test signified that MIL-125(Ti)/MIL-53(Fe)/CNT@Alg composite microbeads retained superb adsorption properties for six consecutive cycles, emphasizing its potentiality for removing of pharmaceutical residues.
•Faster decolorization of AB-14 dye by AO and EC and follow pseudo-first order kinetic.•Faster and similar decolorization by EC and AO due to the generation of strong oxidant OH in the bulk.•Current ...density (j), Initial dye conc. (Co), NaCl conc. (CN), and pH affect the oxidation efficiency.•Synergy between coagulation and oxidation by OH and active chlorine species.
In this study, a laboratory scale for the treatment of a recalcitrant and toxic synthetic wastewater containing diazo dye, acid brown 14 (AB-14) has been comparatively performed by two electro-catalytic treatment processes, namely anodic oxidation (AO) and electrocoagulation (EC) using a new batch electrochemical cell. Additionally, the influence of several operating parameters such as; current density (j), initial dye concentration (Co), NaCl concentration (CN), and pH on the color removal efficiency and chemical oxygen demand (COD) are evaluated. The powerful capability of the AO and EC of AB-14 which related to the mechanistic reaction pathway is shown. The poor degradation is ascribed to higher Co and pH, while the enhancement of j and CN is responsible for better degradation of AB-14 dye. The results indicate that the EC is more effective than AO under the same operational condition. A kinetic model is developed for evaluation of the pseudo-first-order-rate constant (kapp) as a function of various operational parameters. The results emphasize the high efficiency of AO and EC and the clean processes which are hopeful alternative for the treatment of the large volume wastewater of the textile industry.
A growing trend for nutraceutical and gluten-free cereal-based products highlights the need for development of new products. Buckwheat is one of the potential candidates for such products and the ...present paper reviews the functional and nutraceutical compounds present in common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tataricum). The vital functional substances in buckwheat are flavonoids, phytosterols, fagopyrins, fagopyritols, phenolic compounds, resistant starch, dietary fibre, lignans, vitamins, minerals and antioxidants, which make it a highly active biological pseudocereal. Cholesterol-lowering effects that lessen the problems of constipation and obesity are important health benefits that can be achieved through the functional substances of buckwheat.
Co‐infections commonly arise when two or multiple different pathogens infect the same host, either as simultaneous or as secondary concurrent infection. This potentiates their pathogenic effects and ...leads to serious negative consequences on the exposed host. Numerous studies on the occurrence of the bacterial, parasitic, fungal and viral co‐infections were conducted in various tilapia species. Co‐infections have been associated with serious negative impacts on susceptible fish because they increase the fish susceptibility to diseases and the likelihood of outbreaks in the affected fish. Co‐infections can alter the disease course and increase the severity of disease through synergistic and, more rarely, antagonistic interactions. In this review, reports on the synergistic co‐infections and their impacts on the affected tilapia species are highlighted. Additionally, their pathogenic mechanisms are briefly discussed. Tilapia producers should be aware of the possible occurrence of co‐infections and their effects on the affected tilapia species and in particular of the clinical signs and course of the disease. To date, there is still limited information regarding the pathogenicity mechanisms and pathogen interactions during these co‐infections. This is generally due to low awareness regarding co‐infections, and in many cases, a dominant pathogen is perceived to be of vital importance and hence becomes the target of treatment while the treatment of the co‐infectious agents is neglected. This review article aimed at raising awareness regarding co‐infections and helping researchers and fish health specialists pay greater attention to these natural cases, leading to increased research and more consistent diagnosis of co‐infectious outbreaks in order to improve control strategies to protect tilapia when infected with multiple pathogens.
Witnessing the birth of a supermassive protostar Latif, M. A; Schleicher, D. R. G; Hartwig, T
Monthly notices of the Royal Astronomical Society,
05/2016, Letnik:
458, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The detection of z > 6 quasars reveals the existence of supermassive black holes of a few 109 M⊙. One of the potential pathways to explain their formation in the infant universe is the so-called ...direct collapse model which provides massive seeds of 105–106 M⊙. An isothermal direct collapse mandates that haloes should be of a primordial composition and the formation of molecular hydrogen remains suppressed in the presence of a strong Lyman Werner flux. In this study, we perform high resolution cosmological simulations for two massive primordial haloes employing a detailed chemical model which includes H− cooling as well as realistic opacities for both the bound–free H− emission and the Rayleigh scattering of hydrogen atoms. We are able to resolve the collapse up to unprecedentedly high densities of ∼10−3 g cm−3 and to scales of about 10−4 au. Our results show that the gas cools down to ∼5000 K in the presence of H− cooling, and induces fragmentation at scales of about 8000 au in one of the two simulated haloes, which may lead to the formation of a binary. In addition, fragmentation also occurs on the au scale in one of the haloes but the clumps are expected to merge on short time-scales. Our results confirm that H− cooling does not prevent the formation of a supermassive star and the trapping of cooling radiation stabilizes the collapse on small scales.
Immobilized eggshell with a polymer mixture of alginate and polyvinyl alcohol was applied as a biocomposite adsorbent (ESC) for the adsorption of C.I. Remazol Reactive Red 198 from aqueous solution. ...ESC was characterized using XRD, TGA, FTIR and SEM. The Red dye adsorption onto the ESC was investigated in a batch system with respect to initial dye concentration, pH, contact time, agitation speed, solution temperature and biocomposite dosage. The prepared biocomposite exhibits high efficiency for red dye adsorption and the equilibrium states could be achieved in 3
h for the different studied initial dye concentrations. The equilibrium isotherm study indicated that sorption data were analyzed and fitted well by both Langmuir and Temkin models compared to Freundlich model. The maximum monolayer dye adsorption capacity (at the optimum pH 1.0) was estimated to be 46.9
mg/g at 22
°C. The kinetic study revealed that pseudo-second order model fitted well the kinetic data, while both the intraparticle diffusion and Boyd kinetic model indicated that intraparticle diffusion was the main rate determining step in the biosorption process. The negative values of both the enthalpy (ΔH°) and Gibbs free energy (ΔG°) changes indicate exothermic as well as feasible and spontaneous nature of the biosorption process respectively.
► Biocomposite eggshell was applied for the adsorption of Reactive dye. ► The sorption data were fitted well by both Langmuir and Temkin models. ► The kinetic data was fitted well with pseudo-second order model. ► Intraparticle diffusion was the main rate determining step. ► The negative values of ΔH° and ΔG° indicate exothermic and spontaneous nature.
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