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International audience; In our previous work, macroscopic models for multi-species diffusion/heterogeneous reaction with different diffusion coefficients in porous media were derived from the homogenization technique based on a spectral approach ( Le et al. , Applied Mathematical Modelling, 104 , 666-681, 2022 ). This work aims to analyze numerically the properties of the eigenvalues and eigenfunctions of the spectral problem, the solution of the closure problems and the effective coefficients as a function of key parameters such as the Damkohler number, the ratios of the reaction rates and diffusion coefficients. This provides in-depth understanding of the role of the coefficients involved in the macroscopic models in the whole range of the Damkohler number. Simulation results of the macroscopic equations are compared with direct numerical simulations in unsteady regime, showing a very satisfactory agreement and thus numerically validating the proposed models. (c) 2022 Published by Elsevier Inc.

International audience; Macroscopic models for diffusion and heterogeneous reversible reaction of two species in porous media are developed by using coupled homogenization technique and spectral approach. Three representative cases related to the order of magnitude of the macroscopic Damköhler number DaL, namely predominating reaction, diffusion-reaction of the same order and dominating diffusion, are considered. The concentrations are developed as time series in an eigenfunctions basis associated with periodic spectral problems formulated in the unit-cell, thus forming a new microscopic problem to be homogenized. Such an approach represents a powerful tool to upscale diffusion-reaction microscopic problems, especially for high Damköhler number values where classical asymptotic development fails. It enables to capture the physics at very short times, when the characteristic time of reaction involved is much faster than the diffusion one. This work allows us to formulate the complex macroscopic laws describing the heterogeneous diffusion/reaction problem for two species in high Damköhler number regime.

Background: In recent years, the study of the structure and biological activity of medicinal plants has been particularly important to search for diabetes medicine. Ruellia tuberosa is used to treat various diseases such as diabetes by inhibiting the activity of α-glucosidase. Objective: In this study, an experiment was designed to isolatedisolate and identifiedidentifyα-glucosidase inhibitory extracts and compounds from Ruellia tuberosa L. through bio-assay guided isolation. Method: Dry powder of Ruellia tuberosa L. was extracted with 70% ethanol, followed by liquidliquid partition with n-hexane, ethyl acetate and butanol, respectively. The extracts were evaluated withα-glucosidase inhibition. The potential extracts were isolated to identifynew compounds. The effects of these compounds on the α-glucosidase inhibitory were evaluated. Results: The a-glucosidase inhibitory activities showed that the n-hexane, ethyl acetate and the butanol extract had the α-glucosidase inhibition with an IC50 of 46.2 ± 0.9, 6.6 ± 2.9 and 8.9 ± 0.9 μg/mL, respectively. From the n-hexane and ethyl acetate extracts, the structures of four compounds were elucidated by NMR spectroscopic method, including lupeol (1), syringaresinol (2), apigenin (3), verbascoside (4). The a-glucosidase inhibitory activities showed that all isolated compounds were more active than the positive control - acarbose with an IC50 of 37.5 ± 0.4; 19.5 ± 0.2; 20.1 ± 0.3; 69.3 ± 0.2 μg/mL, respectively. Conclusion: The ethyl acetate extract showed strong activity about 19 times more than the positive control - acarbose. The compound syringaresinol (2) was the most powerful α-glucosidase inhibitor. Therefore, Ruellia tuberosa L. contains many compounds that can inhibit α-glucosidase activity.

This work is dedicated to a multi-scale modelling of coupled diffusion and reaction in a porous microelectrode operating in the Direct Electron Transfer mode. The pore-scale physico-electrochemical unsteady model is developed considering the oxygen reduction, catalyzed by an enzyme coating the pores of the electrode, coupled to the diffusion of oxygen and mass balance of enzymes. This model is formally upscaled to obtain an original closed unsteady macroscopic model operating at the electrode scale, together with the associated closure providing the effective diffusivity tensor. A validation of this model is carried out from a comparison with the solution of the initial 3D pore-scale governing equations considering the bilirubin oxydase as the catalyst. The relevance and accuracy of the macroscale model are proved allowing a considerable simulation speedup. It is further employed to successfully predict experimental voltammetry results obtained with porous gold electrodes functionnalized with a bilirubin oxidase mutant (BOD S362C). This model represents a breakthrough by providing an operational simple way of understanding and further optimizing porous electrodes functioning in DET mode.

The current mining operation of mineral resources in QuangNinh province-Vietnam is increasingly complicated. Correspondingly, themanagement of the mine sites becomes more difficult. Records anddocuments of minerals and mine sites are archived in different forms.Database systems are stored dispersedly and insufficiently; in many caseslack accuracy, topicality and have not been linked to each othersystematically. These lead to many difficulties in accessing and extractinginformation for the implementation of management as well as for investorsand people with related interest. In this paper an advanced software hasbeen developed for the management of mineral resources and has beenapplied for Quang Ninh province. The software has improved thesupervision and administration of the mining operation in the province.

Underground coal mining in Vietnam plays an important role tonot only the sustainable coal industry but also the energy and social securityin this country. Although the Vietnam coal industry has produced 35–45million tonnes of raw coal per annum in past ten years, a great volume ofcoal resources remains distributed in complex geo-mining conditions andmostly unmined. This paper presents a brief review of the current andpotential technologies for cutting coal and controlling roof in Vietnamunderground coal mines. From the review, it is concluded that there is anurgent demand on improvement of current technologies as well as oninvestigation for effective application of more advanced mining methodsinto the industry, especially for deep mining at Red River Delta—the largestcoal basin in Vietnam.

Longwall mining is one of the most productive methods forextracting underground coal seams. Although the understanding of longwallmining-associated geotechnical mechanisms has been significantlyimproved that contributes to better ground control, roof rock/top coal fallahead of support (roof fall) has not been fully understood that causes severedamage to equipment and casualty at face. Empirical, theoretical andmodelling methods were successfully used in past studies to understand themechanisms driving roof fall; however, key mechanisms and theirinteractions during the fall were not satisfactorily investigated due tolimitation of each method. This study aims to gain a systematicunderstanding of roof fall mechanisms in longwall operation. A review ofpast studies on roof fall is implemented with emphasis on the principles ofapplied research methods. The study confirms that the interaction betweenroof strata, coal seam and face support largely controls roof fall whilenumerical modelling shows great potential in studying roof fall complexmechanisms. The paper’s findings provide mining engineers/scientists witha systematic understanding on roof fall from which more effective roofcontrol strategies can be further developed.

A new hopan-type triterpenoic peracid, tinctoride A (1), together with three known compounds, zeorin (2), 6β,22-dihydroxyhopane (3), and ergosterol peroxide (4), was isolated from Parmotrema tinctorum (Despr. ex Nyl.) Hale. Their chemical structures were identified by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy and compared with those reported in the literature. The enzyme inhibitory potential of compounds 1–3 against α-glucosidase was investigated, exhibiting nil to weak inhibitory activity.

At present, according to the extraction plan in the year 2020 of Duong Huy Coal Company -Vinacomin, the mining is divided into three main zones: Central Zone extracts 06 faces; South Zoneextracts 2 faces and Northeast Zone extracts 2 faces. The designated total production of all zones is1,880,000 tons/year. To ensure the production of each mining zone, exhaust fan stations are installed atventilation roadway adits with a total of 05 main fan stations. However, in the near future, to ensure andmaintain production activities, the mine is being planned and operated using 03 main fan stations. Thecalculation results for the reasonable working mode of fan stations are as follows: for fan station FBCDZ-8-№32B at level +47 m, airflow is 167.69 m3/s and air pressure is 243.74 mm H2O; for fan station 2K56-№30 level +40 m, airflow is 123.37 m3/s and air pressure is 324.79 mm H2O; for fan station FBCDZ-8-№32B at level +44 m, airflow is 167.69 m3/s and air pressure is 354.99 mm H2O.

Support plans and operation schemes of mine faces are critical technical documents inunderground coal mining management. The development and selection of a reasonable support plan andoperation scheme of the face are complicated because they involve many factors. In specific miningconditions, developing and selecting an appropriate support plan and operation scheme will improve theworking efficiency of equipment, increase labor productivity, and ensure workers' safety. This articleresearched a mining technology for the thin seams, focusing on coal seam 10T in Nam Khe Tam coalmine, 86 Coal Company. From the analysis of geo-mining conditions, the article developed and selecteda reasonable support plan and operation scheme for the face in coal seam 10T. After being used in thefield, the support plan and operation scheme have brought the face efficiency and safety.

Quang Ninh underground coal mines are currently in the phase of finishing up the mineralreserves located near the surface. Also, in this phase, a number of coal mines have opened and preparednew mine sites for the extraction of the reserves at greater depth. Several mines have mined at -350 mdepth and are driving opening excavations at -500 m depth below sea level. The mining at greater depthfaces many difficulties, such as a significant increase in support and excavation pressures. The longwallface pressure is mostly manifested in great magnitude that causes support overloaded and jumped andface spall/roof fall. This paper, based on the geological condition of the Seam 11 Ha Lam coal mine,uses the numerical program UDEC for studying the impact of mining depth on stress distribution aroundthe longwall face. The results show that the deeper the mining is, the greater the plastic deformationzone is. The peak front abutment stress moves closer to the coal wall, mainly concentrating on theimmediate roof and top coal. The top coal is greatly broken, and its bearing capacity is decreased. Somesolutions to the stability of roof strata are proposed, and a proper working resistance of support isdetermined. Additionally, the paper suggests that the starting depth for deep mining in Quang Ninhunderground coal mines should be -350 m below sea level.