Joint roughness coefficients (JRCs) influence the shear and characteristic strengths of structural planes; however, the relationship model of this influence is yet to be derived. This study ...investigates 11 numerical simulation programs using a realistic failure process analysis software. The influence of size and JRC on the shear strengths of the structural planes was studied. The stress-strain curves of different JRCs and their sizes were analyzed. Mathematical models of the shear strength of structural planes and JRC and sizes were formulated and proposed, and their expressions were obtained. Moreover, mathematical models of JRC and the characteristic size and strength of the structural planes were established.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Microwave-assisted methane DHA reaction rate model developed.•Dynamic data reconciliation and optimal parameter estimation undertaken.•Multi-physics, multi-scale model of a fixed bed reactor model ...developed.•MW power absorption is modeled by Maxwell’s equation.•Model used to investigate complex heat and mass transfer inside catalysts particle.
In this paper, dynamic data reconciliation and parameter estimation has been performed for the microwave-assisted methane dehydroaromatization reaction system using the in-house experimental data. A custom reaction rate model has been developed including a model for coke formation and a model for the catalyst deactivation. A multi-physics, multi-scale reactor model is developed by developing a model for the microwave absorption in the metal and support sites in the catalyst and coupling the catalysts level model with the bulk scale model. For estimating microwave power absorption in the metal and support particles, a detailed model using the Maxwell’s equation as well as a reduced order model are developed. Analysis of operation frequency shows that 2.45 GHz frequency has a better reactor performance. It is also observed that the temperature differences between the metal and support sites are unlikely to be high for the methane dehydroaromatization reaction system as opposed to the traditional belief for MW-assisted reactive systems.
Abstract
Sirtuin 3 (SIRT3) is an NAD+-dependent deacetylase linked to a broad range of physiological and pathological processes, including aging and aging-related diseases. However, the role of SIRT3 ...in regulating human stem cell homeostasis remains unclear. Here we found that SIRT3 expression was downregulated in senescent human mesenchymal stem cells (hMSCs). CRISPR/Cas9-mediated depletion of SIRT3 led to compromised nuclear integrity, loss of heterochromatin and accelerated senescence in hMSCs. Further analysis indicated that SIRT3 interacted with nuclear envelope proteins and heterochromatin-associated proteins. SIRT3 deficiency resulted in the detachment of genomic lamina-associated domains (LADs) from the nuclear lamina, increased chromatin accessibility and aberrant repetitive sequence transcription. The re-introduction of SIRT3 rescued the disorganized heterochromatin and the senescence phenotypes. Taken together, our study reveals a novel role for SIRT3 in stabilizing heterochromatin and counteracting hMSC senescence, providing new potential therapeutic targets to ameliorate aging-related diseases.
This study presented an approach to overcome diffusion limitation and imbalance between Brønsted and Lewis acidities that affect conversion and aromatic yield in alkane nonoxidative ...dehydroaromatization (DHA) conversion. Three different Ga-promoted ZSM-5 catalysts were synthesized for the ethane DHA reaction. The hierarchical galloaluminosilicate Meso-GaZSM-5 was prepared by the solid-state crystallization technique wherein Ga was introduced through the in situ synthesis process. The microporous galloaluminosilicate Micro-GaZSM-5 was synthesized by the hydrothermal technique wherein Ga was introduced in situ during zeolite formation. The hierarchically structured Ga-Meso-ZSM-5 was synthesized by the solid-state crystallization method, but the Ga was introduced by the incipient wetness method. Additional Pt was incorporated by the incipient wetness technique for all three catalysts to enhance the DHA activity. The solid-state crystallization technique created the hierarchical structure without using a template. With the in situ technique, Ga species replaced the Al framework, reducing the strong Brønsted acidity. Meanwhile, they created the extraframework GaO+, introducing the strong Lewis acid sites into catalysts. Due to better synergistic interaction between the oxidation state of metals, acidic properties, and catalyst porosity, Pt-Meso-GaZSM-5 showed higher C2H6 conversion and aromatic selectivity. The improvement on diffusivity not only reduces the effect of channel blockage but also improves the utilization of active sites. This work sheds light on the direct, nonoxidative conversion of shale gas without going through the syngas route.
Direct nonoxidative conversion of ethane to aromatics has become an effective way of upgrading shale gas. Metal-promoted shape selective zeolite catalysts are often used for aromatization. Although ...the coking issue of the catalysts in ethane aromatization has been reported, the deactivation mechanism and the performance of regenerated Ga–Pt promoted HZSM-5 needs to be further investigated. The objective of this study is to elucidate deactivation mechanism of Ga–Pt promoted HZSM-5 and investigate the feasibility of regenerating deactivated catalysts for commercial viability. When using lower concentration of oxygen (2 vol %) for regeneration, decreased catalyst deactivation rate was observed. The metal particle size, crystalline structures, and acidity are characterized by various analytical instrumentations (TEM, XRD, NH3-TPD). The change of Bronsted acidity was observed on regenerated catalysts. The results showed that metal agglomeration and leaching of Pt from homogeneous Ga–Pt particle were the main causes of deactivation other than coke deposition, indicating that stabilization of bimetallic metal particles on zeolite surface is critical.
Abstract
Organismal aging is driven by interconnected molecular changes encompassing internal and extracellular factors. Combinational analysis of high-throughput ‘multi-omics’ datasets (gathering ...information from genomics, epigenomics, transcriptomics, proteomics, metabolomics and pharmacogenomics), at either populational or single-cell levels, can provide a multi-dimensional, integrated profile of the heterogeneous aging process with unprecedented throughput and detail. These new strategies allow for the exploration of the molecular profile and regulatory status of gene expression during aging, and in turn, facilitate the development of new aging interventions. With a continually growing volume of valuable aging-related data, it is necessary to establish an open and integrated database to support a wide spectrum of aging research. The Aging Atlas database aims to provide a wide range of life science researchers with valuable resources that allow access to a large-scale of gene expression and regulation datasets created by various high-throughput omics technologies. The current implementation includes five modules: transcriptomics (RNA-seq), single-cell transcriptomics (scRNA-seq), epigenomics (ChIP-seq), proteomics (protein–protein interaction), and pharmacogenomics (geroprotective compounds). Aging Atlas provides user-friendly functionalities to explore age-related changes in gene expression, as well as raw data download services. Aging Atlas is freely available at https://bigd.big.ac.cn/aging/index.
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•Ammonia was steadily produced with a microwave reactor at 320 °C within 11 min after reduction over 24 h of testing.•Dispersion and bond strength of active metal sites on support ...linked to activity and microwave efficiency.•Ru/MgO catalyst able to produce 0.25 gamm/gcat/day and suitable for on-demand ammonia production for small scale applications.
In this work a fixed frequency (2.45 GHz) microwave (MW) was used to synthesis ammonia over Ru/MgO catalysts under ambient atmospheric pressure at 320 °C. The loading of Ru catalyst over MgO was varied at 4 wt% and 10 wt%. The metal support interaction was found to play an important role not only catalytically but also altering the microwave-catalyst interaction affecting the ammonia formation rate. The higher metal loading (10 wt%) produced the most activity, stability, and energy efficiency. It was found the Ru was better dispersed at higher loading which decreased the sintering of the catalyst due to lower microwave energy needed to maintain the reaction temperature. Additional effects from the microwave can include enhanced electron movement and/or electric fields formed between the metal sites of the catalyst. The microwave reactor offers a quick on/off catalyst recovery, within 11 min, compared to thermal convectional Haber Bosch (HB) technology.
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The efficient aerobic oxidative condensation of renewable furfural and ethanol in the presence of a nano Au catalyst and potassium carbonate has been developed and a 70.6% yield of ...furan-2-acrolein is obtained .
•A catalytic system is developed for the volarization of renewable furfural.•Oxidative condensation of furfural with ethanol to furan-2-acrolein is achieved.•The catalyst system is composed of Au nanoparticle and potassium carbonate.•A 94.1% furfural conversion in 75.0% selectivity of furan-2-acrolein is obtained.
A specialty chemical compound, furan-2-acrolein, can be produced from renewable feedstock via furfural. An efficient catalytic process related to oxidative condensation of furfural and ethanol using supported Au catalyst has been developed. A series of solid catalysts including Au/Al2O3, Au/CeO2, Au/Fe3O4, Au/HTc (hydrotalcite calcined) and Au/Nb2O5 are prepared and their catalytic activities in oxidative condensation of furfural with ethanol are compared. Moreover, the influence of the presence of base promoters, such as K2CO3, on Au catalyst performance is investigated. The physical properties of these catalysts are characterized by XRD, TEM, SEM, UV–vis and BET techniques. The impact of reaction variables on catalyst performance is measured. It has been found that, in the presence of Au/Al2O3 and potassium carbonate, 94.1% conversion of furfural and 75.0% selectivity to furan-2-acrolein are obtained under the conditions of 140°C, 0.3MPa of O2 and reaction time of 4h.
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•Direct non-oxidative conversion of stranded gas to aromatics is economically feasible.•Transition metal-promoted ZSM-5 zeolite is active for stranded gas conversion.•Catalyst ...stability and regeneration are major challenges to stranded gas aromatization.•Ethylene is a key intermediates in aromatic formation.•Indirect natural gas conversion has higher capital cost then direct approach.
Ethane aromatization was carried out using metal promoted ZSM-5 catalysts. Desired products including ethylene and aromatics were obtained over Pt and Mo promoted ZSM-5 zeolite under reaction conditions of 600°C, 0.1MPa and GHSV=1000h−1. Results indicated that aromatics were formed via ethylene intermediate. Although ethane conversion and selectivity to aromatics were influenced by metal promoters, the distribution of benzene, toluene, xylenes and C9 aromatics depends mainly on the shape selective property of the ZSM-5. Ethane aromatization catalyst deactivated over time due to carbon deposition and metal leaching. Although oxidative regeneration could recovered 90% activity, the catalyst deactivated even faster after regeneration. For the purpose of economic comparison between direct and indirect natural gas conversion, the performance of edge coated Co-Re/γ-Al2O3 Fischer-Tropsch synthesis catalyst was presented. Even with capital savings on downstream refining, indirect natural gas conversion shows lower internal rate of return (IRR), largely because of higher capital and operating costs in syngas production.
In this study, an alternative approach based on microwave-enhanced ammonia synthesis for Haber-Bosch process was carried out under moderate pressure of 0.1–0.65 MPa and temperature range of ...280–400 °C over a stable CsRu/CeO2 catalyst. The ammonia production rate is significantly improved under microwave conditions. At 0.65 MPa and 320 °C, maximum ammonia production rate was achieved at H2/N2 ratio of 1/1. Stable performance was obtained in a 6-cycles of startup-shutdown operation for cumulative on-line time of 80 h. The work demonstrates the potential of microwave catalytic technology for the distributed ammonia synthesis using renewable power having intermittent nature of energy supply.
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•Microwave-enhanced NH3 synthesis is a promising alternative for H-B process.•High pressure quartz reactor was designed and used in MW NH3 synthesis.•NH3 production rate were enhanced by increasing pressure and lowering H2/N2 ratio.•Effects of process parameters for NH3 production rate are systematic investigated.•MW catalytic is a potential technology for the NH3 synthesis using renewable power.
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