Simulating Rayleigh-Taylor induced magnetohydrodynamic turbulence in prominences

Solar prominences represent large-scale condensations suspended against gravity within the solar atmosphere. The Rayleigh-Taylor (RT) instability is proposed to be one of the important fundamental processes leading to the generation of dynamics at many spatial and temporal scales within these long-lived, cool, and dense structures amongst the solar corona. We run 2.5D ideal magnetohydrodynamic (MHD) simulations with the open-source MPI-AMRVAC code far into the nonlinear evolution of an RT instability perturbed at the prominence-corona interface. Our simulation achieves a resolution down to $\sim 23$ km on a 2D $(x,y)$ domain of size 30 Mm $\times$ 30 Mm. We follow the instability transitioning from a multi-mode linear perturbation to its nonlinear, fully turbulent state. Over the succeeding $\sim 25$ minute period, we perform a statistical analysis of the prominence at a cadence of $\sim 0.858$ s. We find the dominant guiding $B_z$ component induces coherent structure formation predominantly in the vertical velocity $V_y$ component, consistent with observations, demonstrating an anisotropic turbulence state within our prominence. We find power-law scalings in the inertial range for the velocity, magnetic, and temperature fields. The presence of intermittency is evident from the probability density functions of the field fluctuations, which depart from Gaussianity as we consider smaller and smaller scales. In exact agreement, the higher-order structure functions quantify the multifractality, in addition to different scale characteristics and behavior between the longitudinal and transverse directions. Thus, the statistics remain consistent with the conclusions from previous observational studies, enabling us to directly relate the RT instability to the turbulent characteristics found within quiescent prominence.Comment: 21 pages, 17 figures, Accepted for publication in Astronomy and Astrophysic

A one-pot route to tunable sugar-derived sulfonated carbon catalysts for sustainable production of biodiesel by fatty acid esterification

Carbon-based solid acid catalysts possessing up to 1.29 mmol g-1 –SO3H active centers were synthesized from glucose via an efficient one-pot hydrothermal carbonization-sulfonation without the need for high temperatures. Catalysts combined aromatic structure with hydrophilic –OH and –COOH groups and a high density of –SO3H centers (up to a total acid density of 5.31 mmol g-1). The level of –SO3H (0.81-1.29 mmol g-1) proved synthetically tunable. The relevance of the catalyst to the production of more sustainable fuels was tested using oleic acid (a free fatty acid whose esterification can be employed as a model for biodiesel production). Optimizing catalyst and conditions (20:1 MeOH:oleic acid molar ratio, 5 wt. % catalyst loading wrt oleic acid, 80 °C, 120 min.) enabled oleic acid esterification to the corresponding methyl oleate (a biodiesel component) with 97.50.4% conversion and a low 37.6 kJ mol-1 activation energy. Activity loss upon re-use of the catalyst was proved to be by de-sulfonation and could be completely reversed. Hence, re-sulfonation of spent catalyst by a one-step process again delivered a 97.4+/-0.5 % conversion of oleic acid

Comparative Study on the Rearing Performance of Muga Silkworm

Muga silkworm, Antheraea assamensis Helfer, generally reared outdoor on standing host trees for which it is always under pressure of vagaries of weather conditions causing substantial loss. Attempts were made to rear the silkworm under indoor conditions during different seasons. In first attempt, the worms were reared from brushing till spinning and in second, worms were first reared under indoor conditions up to 2nd in star and then transferred to outdoor condition. Rearing performance, larval and cocoon parameters were compared with complete indoor and outdoor conditions. Throughout all the seasons, survival per cent of worms, effective rate of rearing, mature larval weight, cocoon weight, pupal weight and shell weight was significantly higher when the worms were reared for first two instars under indoor conditions compared to either complete indoor or outdoor rearing. The study suggests that, it is beneficial to rear muga silkworms inside up to second instar and then rear outside for reducing mortality of worms during chawki instars and for production of higher and good quality cocoons.</p

A reusable magnetic nanocatalyst for bio-fuel additives: The ultrasound-assisted synthesis of solketal

We report an efficient ultrasound-assisted room temperature synthesis of solketal by acetalization of glycerol with acetone.</p

A mesoporous polysulfonic acid-formaldehyde polymeric catalyst for biodiesel production from Jatropha curcas oil

A highly reactive acid-functionalized polymer is prepared by the simple condensation of aqueous formaldehyde and p-phenolsulfonic acid and used as a solid catalyst in concerted (trans)esterification. This yields biodiesel from Jatropha oil without the need to remove water by-product from the reaction mixture. An isolated biodiesel yield of 982 % is achieved using a catalyst loading of 10 wt. %, methanol:oil ratio of 12:1, temperature of 90 °C, and reaction time of 6 h. The high activity of our catalyst is attributed to its porous nature and the co-inclusion of reactive SO3H sites and phenolic OH groups. Advantageously, these groups are hydrophilic, allowing the catalyst to remain highly active in the presence of H2O. Nine methyl ester components are identified in the biodiesel product, with 9-octadecanoic acid methyl ester (C18:2, 64.92 %) and hexadecanoic acid methyl ester (C16:0, 16.44 %) as the major constituents. The catalyst is evaluated over 4 cycles, maintaining a 922 % isolated yield. Physicochemical analysis of the spent catalyst by SEM-EDX suggests this decrease is due to some loss of mesoporosity and sulfur content

BxC: a swift generator for 3D magnetohydrodynamic turbulence

Magnetohydrodynamic turbulence is central to laboratory and astrophysical plasmas, and is invoked for interpreting many observed scalings. Verifying predicted scaling law behaviour requires extreme-resolution direct numerical simulations (DNS), with needed computing resources excluding systematic parameter surveys. We here present an analytic generator of realistically looking turbulent magnetic fields, that computes 3D ${\cal{O}}(1000^3)$ solenoidal vector fields in minutes to hours on desktops. Our model is inspired by recent developments in 3D incompressible fluid turbulence theory, where a Gaussian white noise vector subjected to a non-linear transformation results in an intermittent, multifractal random field. Our $B\times C$ model has only few parameters that have clear geometric interpretations. We directly compare a (costly) DNS with a swiftly $B\times C$-generated realization, in terms of its (i) characteristic sheet-like structures of current density, (ii) volume-filling aspects across current intensity, (iii) power-spectral behaviour, (iv) probability distribution functions of increments for magnetic field and current density, structure functions, spectra of exponents, and (v) partial variance of increments. The model even allows to mimic time-evolving magnetic and current density distributions and can be used for synthetic observations on 3D turbulent data cubes.Comment: 18 pages, 14 figures, Accepted for publication in Physical Review

A magnetically separable acid-functionalized nanocatalyst for biodiesel production

A robust, magnetically recoverable Fe3O4@SiO2-SO3H core@shell nanoparticulate acid catalyst was successfully synthesized by a stepwise co-precipitation, coating, and functionalization. It was utilized as a heterogeneous catalyst for the transesterification and esterification of triglycerides and free fatty acids in Jatropha curcas oil (JCO) to a fatty acid methyl ester (FAME) mixture. This product conformed to ASTM standards for biodiesel. The as-prepared catalyst had a magnetic saturation of 30.94 emu g-1, surface area of 32.88 m2g-1, acidity of 0.76 mmol g-1, and pore diameter of 3.48 nm. The catalyst showed 98±1% conversion using the optimized reaction conditions of methanol:oil molar ratio of 9:1, 8 wt.% catalyst loading, 80 °C, and 3.5 h. The transesterification of JCO to FAME using the present catalyst benefitted from a very low activation energy of 37.0 kJ mol-1. The solid acid catalyst exhibited excellent chemical and thermal stability, and also reusability based on easy separation from the reaction mixture due to its inherently magnetic nature. Modest deterioration in oil conversion after multiple uses was offset by one-pot, quantitative regeneration of catalyst active sites. This enabled identical performance in JCO methyl transesterification and esterification in the 1st and 10th catalytic cycles

Green biodiesel production from Jatropha curcas oil using a carbon-based solid acid catalyst: A process optimization study

Biodiesel production from low cost, inedible oil represents an increasingly important target for reasons of both sustainability and cost. In this work, we comprehensively verify the batch reproducibility of a sulfonic acid functionalized carbonaceous material (SAFACAM) as catalyst for biodiesel production from inedible feedstock Jatropha curcas oil (JCO) using a heterogeneous biomass-based carbonaceous solid acid catalyst. The current catalyst benefits the environment through its atom-efficient, one-pot preparation from an abundant natural biomass derivative (glucose) and has the potential to reduce the overall biodiesel production cost by converting inexpensive raw materials. In this context, JCO has emerged as a crop of interest to energy sector, potentially providing a reliable and renewable energy source for many countries. Through a central composite design (CCD) approach using response surface methodology (RSM), a 98.70.6 % conversion of biodiesel is achieved (methanol-to-oil molar ratio 20:1, reaction time 50 mins, reaction temperature 120 °C and catalyst loading 9 wt. % (with respect to oil)). The chemically satisfactory composition of the biodiesel product has been verified, the reusability of catalyst has been tested, and a significant enhancement in performance when using microwave heating demonstrated. An 83.00.8 % conversion of JCO is reported in the fifth cycle of reuse

Horizontal Transfer of miR-643 from Cisplatin-Resistant Cells Confers Chemoresistance to Recipient Drug-Sensitive Cells by Targeting APOL6

Acquisition of resistance to cisplatin is a major impediment to the success of cisplatin-based combination therapies for cancer. Recent studies indicate that exosomal miRNAs derived from drug-resistant tumour cells can confer resistance properties to recipient cells by a horizontal transfer mechanism. Although the role of horizontal transfer of a few miRNAs has been described, little is known about the concerted action of horizontal transfer of miRNAs in conferring cisplatin resistance. The present study was designed to identify the role of miR-643, which is one of the most significantly increased miRNA in exosomes released from cisplatin-resistant Heptocarcinoma cells, in altering the cisplatin resistance properties of recipient cells. Drug-sensitivity assays involving miR-643 revealed that ectopic expression of miR-643 can desensitise the cells towards cisplatin. Furthermore, we identified APOL6 as a major target of miR-643. Further mechanistic studies showed that miR-643 can modulate APOL6 mRNA and protein levels, leading to a reversal of APOL6-mediated apoptosis. Altogether, our results suggest an APOL6-dependent mechanism for miR-643 mediated cisplatin resistance upon the horizontal transfer across cell types