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Shell and tube horizontal thermosyphon reboilers (STHTs) find wide applications in the process industry particularly due to their inherent advantages in handling large duties, high viscosity fluids and low fouled susceptibility. However, current design commercial packages suffer from obvious limitations including extensive user manipulations, trial-and-error necessity, increased human factor influence. To overcome these limitations, we develop in this work a rigorous MINLP model for STHT sizing, by achieving automated selection of detailed exchanger geometries with optimal overall heat transfer coefficient. The corrected minimum cross-flow area in shell-side is incorporated to accommodate full cross-flow patterns in tube bundle, thus handling popular service of X shell without baffle construction. A dependable convective boiling heat transfer model is proposed to obtain the shell-side heat transfer coefficient, validated with Aspen EDR. The critical variable, heat flux, which affects nucleate boiling heat transfer performance, is optimized through a simultaneous equation-solving process using a global solver, reducing excessive unit overdesign. Pressure balance between STHT and distillation column is fully considered by a proposed optimization model incorporating pressure drop and pipe sizing. By employing global optimization techniques and automating the design process, this innovative approach minimizes manual adjustments and provides more accurate and cost-effective designs. • A novel mathematical model is proposed for the design of shell and tube horizontal thermosyphon reboiler. • The formulation for two-phase shell-side boiling heat transfer is presented in detail. • Reboiler geometries associated with heat transfer performance are optimized through a global optimization strategy. • Systemic pressure balance is carried out to maintain stability in horizontal thermosyphon reboiler operation. [ABSTRACT FROM AUTHOR]

Abstract Two dimensional (2D) p–n heterostructures are demonstrated to be promising candidates for future integrated electronics and optoelectronics ascribing to their unique physical, optical and electrical properties. In this work, for the first time, we report the successful synthesis of high quality vertically stacked Sb 2 Te 3 /MoS 2 heterostructures via van der Waals (vdW) epitaxial growth. Due to the p-type nature of Sb 2 Te 3 and n-type nature of MoS 2 , the constructed Sb 2 Te 3 /MoS 2 heterostructure-based devices can function as high performance rectifying diodes, and be further used as photodetectors and photovoltaics. As a result, the achieved p–n heterojunctions exhibit ultra-high current rectification ratio up to 106 and typical photon-to-electron conversion efficiency reaching 4.5%, both of which are much higher than all the previously reported 2D vdW heterojunctions grown by vapor deposition routes. Moreover, remarkable photoresponsivity (330 A/W) and fast photoresponse speed (<500 μs) are achieved, which also represent the highest values reported so far in similar systems. Combing the excellent electrical and optoelectrical properties, the achieved Sb 2 Te 3 /MoS 2 heterostructures may find broad applications in future integrated electronics and optoelectronics devices and systems. Graphical abstract High-quality and large scale vertically stacked Sb 2 Te 3 /MoS 2 heterostructures are achieved with van der Waals epitaxial growth method. Benefiting from the p-type nature of the Sb 2 Te 3 and n-type nature of the MoS 2 , p–n junction is formed at the interface, which shows excellent rectifying behaviors (rectification ratio up to 106) and typical photovoltaic properties (power conversion efficiency up to 4.5%). fx1 Highlights • Vertical Sb 2 Te 3 /MoS 2 p–n heterojunctions are constructed for the first time. • The achieved Sb 2 Te 3 /MoS 2 p–n heterojunctions possess very sharp interfaces. • Efficient charge carriers separation and transfer process were observed. • The p–n diodes exhibit ultra-high current rectification ratio up to 106. • The p–n diodes show excellent photovoltaic properties. [ABSTRACT FROM AUTHOR]

Abstract: The salt-tolerant green alga Dunaliella has remarkable capability to survive in some extreme environments such as nitrogen starvation, which makes Dunaliella be a proper model for mining novel genes on nitrogen uptake or assimilation. In this study, a glutamine synthetase (GS) gene DvGS2 with amino acid identity of 72% to other homologous GS proteins, was isolated and characterized from Dunaliella viridis. Phylogenetic comparison with other GSs revealed that DvGS2 occupied an independent phylogenetic position. Expressional analysis in D. viridis cells under nitrogen starvation confirmed that DvGS2 increased its mRNA level in 12h. Subcellular localization study and functional analysis in a GS-deficient Escherichia coli mutant proved that DvGS2 was a chloroplastic and functional GS enzyme. In order to investigate the potential application of DvGS2 in higher plants, the transgenic studies of DvGS2 in Arabidopsis thaliana were carried out. Results showed that the transgenic lines expressed the DvGS2 gene and demonstrated obviously enhanced root length (29%), fresh weight (40%–48% at two concentrations of nitrate supplies), stem length (21%), leaf size (39%) and silique number (44%) in contrast with the wild-type Arabidopsis. Furthermore, the transgenic lines had higher total nitrogen content (35%–43%), total GS activity (39%–45%) and soluble protein concentration (23%–24%) than the wild type. These results indicated that the overexpression of DvGS2 in A. thaliana resulted in higher biomass and the improvement of the host's nitrogen use efficiency. [Copyright &y& Elsevier]

Summary: Methanogenesis from the biomass in the anoxic biogas reactors is catalyzed by syntrophic cooperation between anaerobic bacteria, syntrophic acetogenic bacteria and methanogenic archaea. Understanding of microbial community composition within the biogas reactors may improve the methane production from biomass fermentation. In this study, methanogenic archaea diverity of a biogas reactor supplied with swine feces as mono-substrate under mesophilic conditions was investigated. Community composition was determined by analysis of methyl coenzyme reductase subunit A gene (mcrA) clone library consisting of 123 clones. Statistical analysis of mcrA library indicated that all major groups of methanogens from our biogas reactor were detected. In the library, 57.7% clones were affiliated to Methanobacteriales, 34.2% to Methanomicrobiales, 2.4% to Methanosarcinales and about 5.7% clones belonged to unclassified euryarchaeota. Over 90% of the methanogenic archaea from our biogas reactor were postulated to be hydrogenotrophic methanogens. Comparing with other previous studies reporting that hydrogenotrophic methanogens are dominant species in the biogas plants, this study firstly reported that Methanobacteriales instead of Methanomicrobiales are the most predominant methanogenic archaea in the biogas reactor fed with swine feces as sole substrate. [ABSTRACT FROM AUTHOR]

Development of one-step processes combining hierarchical porous architecture with heteroatom doping control has remained a challenge. This is especially important for structure-engineered graphene materials as high performance active electrodes for energy and advanced applications. Herein, we present a facile and general approach for synthesizing patternable, nitrogen-doped and hierarchical porous graphene from graphene oxide/urea mixture using high-repetition picosecond laser in ambient air. Impressively, the highest areal capacitance of laser-induced nitrogen-doped graphene (LING) is 60.7 mF/cm2, which is about 3 times that of undoped porous graphene. After 25,000 consecutive cycles of galvanostatic charge-discharge at a current density of 10 mA/cm2, the optimized LING electrode maintained 98.7% of its original capacitance. Most importantly, the as-prepared LING electrode material has high energy and power density due to the synergistic effect of hierarchical porous structure, nitrogen-doping and engineering defects. The proposed laser one-step synthesis of LING may also be applied to other heteroatom-doped hierarchical porous graphene-based electrodes for high-performance electrochemical energy storage. This work presents an extremely facile and versatile strategy for the synthesis of defective nitrogen-doped hierarchically porous graphene as a high performance storage electrode material on self-assembled graphene oxide/urea mixture film via high-repetition picosecond laser. Image 1 [ABSTRACT FROM AUTHOR]

Development of rapid processes combining the preparation of porous structures with the control of their properties has remained a challenge. This is particularly true for applications of graphitized hierarchically porous carbon nanosheets (GHPCNs) predominantly focus on fields of energy storage and conversion materials, electronics, sensors, separation and detection. Here we report a one-step approach to transform commercial bakelite into three-dimensional high electrical conductivity GHPCNs using the high-repetition picosecond infrared laser scribing in nitrogen atmosphere. The GHPCNs with mesopores and macropores can be rapidly induced on bakelite plate by the transient laser heating due to thermal accumulation effect. Studies reveal that the in-plane topological defects of the bakelite-based GHPCNs flakes contain pentagon-heptagon structures. The local controllable laser patterning technique enables porous structures and shapes to be controlled in highly GHPCNs films with variable properties. The methodology developed here have great potential to stimulate both research and industrial interest in the development of bakelite-derived GHPCNs electronic and energy storage micro-devices. [ABSTRACT FROM AUTHOR]

This work mainly focuses on exploring carbon coated ε-MnO 2 (ε-MnO 2 /C) with 3D hierarchical structures for degradation of gaseous toluene under visible light. Influence of C-coating on surface adsorption, visible-light activity and photocatalytic activities of C-coated MnO 2 have been investigated. The results indicate that the C-coating behave as the adsorption and electron-transfer system, and the resulting C-coated ε-MnO 2 could extend the optical response from UV to visible light region, which can generate more electron − hole pairs. The photocatalyst ε-MnO 2 /0.45C exhibited excellent visible-light photocatalytic activities, with degradation rate of toluene up to 87.34% in 70 min, but no photocatalytic activity could be observed for the pure ε-MnO 2 . The PL spectra and photocurrent response results indicate that the composite structure can not only enhance the utilization of visible light but also consequently reduce electron (e − )-hole (h + ) pair recombination, which improve the photocatalytic efficiency of the composite photocatalyst. This work provides a facile and economic approach for fabricating photocatalysts with high efficiency for degradation of VOCs under visible light at room temperature. [ABSTRACT FROM AUTHOR]

• Designed a combustion experiment platform that can simulate high-altitude environment. • Revealed the intrinsic effect of pressure on the fluorination and oxidation of Mg. • Provided further insight into micro-scale combustion process of Mg particles. • Heterogeneous condensation reactions are innovatively treated in combustion simulation. The exploration of condensed combustion products (CCPs) is essential to reveal the ignition, combustion, and infrared radiation mechanisms of Mg-based (Magnesium/polytetrafluoroethylene/Viton) solid fuels that have been considerably employed in the field of aerospace. Systematic experiments and numerical simulations are performed with the physicochemical properties (including morphology, element distribution, phase composition and particle size distribution) and flow field distribution characteristics of CCPs, respectively. The effects of formulation and pressure on the combustion behaviors of pyrotechnic compositions are thoroughly investigated based on thermal analysis measurements, laser ignition, optical diagnosis and CCPs collection. The results demonstrated that the major solid products for all cases are MgF 2 agglomerates and MgO smoke oxide particles (SOPs). Increasing the Mg content in the formulation is simultaneously beneficial for the reduction of large agglomerates and SOPs. As the pressure is decreased from 0.1 MPa to 0.02 MPa, the volume weighted mean diameter of CCPs increases significantly due to the decrease in burning rate. The numerical model established in this paper better approximates the realistic combustion process by coupling the heterogeneous condensation reactions, and is adopted to predict the distribution of CCPs in the combustion flow field under different experimental conditions. Numerical results reveal that the MgF 2 is mainly distributed in the anaerobic combustion core zone immediately above the burning surface, while MgO is located in the peripheral aerobic combustion diffusion zone. The negative pressure environment has more profound influence on the oxidation reaction of Mg than fluorination reaction. The scientific findings are expected to facilitate the development of more complete combustion and infrared radiation models, while theoretically providing in-depth guidance for the increasing military and civilian application of Mg-based solid fuels. [ABSTRACT FROM AUTHOR]

• Designed a small-scale negative pressure combustion experiment system. • Revealed the effect of pressure on flame structure and temperature. • Demonstrated the pressure sensitivity of the burning rate under 0.02–0.1 MPa. • Predicted the combustion products distribution characteristics. The present study is devoted to comprehensively evaluating the combustion performance of Mg-based (Magnesium/polytetrafluoroethylene/Viton) solid fuels in high-altitude operating environments. A small-scale sealed CO 2 laser ignition experiment system is designed to produce different negative pressure environments. A high-speed camera (HSC) and an infrared thermal imager are used to cooperatively capture the burning process. The results obtained demonstrate that the area of the flame core zone and the flame temperature increase significantly as the pressure increases. It is conducive to the heat feedback of the gas phase reaction zone to the solid phase heating zone, resulting in an increase in the burning rate. As the Mg content increases, the flame temperature is decreased and the burning rate is increased. The burning rate for the Mg-based solid fuels is found to increase monotonically with ambient pressure and to follow the Vieille's law in the pressure range of 0.02–0.1 MPa. Based on the experiment, a three-dimensional combustion-flow coupling solution model is established including the detailed aerobic combustion reaction kinetic model and the eddy dissipation concept (EDC) model. Numerical simulation results reveal that the content of incompletely reacted Mg increases as the pressure decreases. Conversely, the decreasing behavior of oxygen partial pressure at low pressure reduces the probability of reaction of Mg with O 2 , resulting in a dramatical decrease in the mass fraction of MgO. The scientific findings provide useful insight for the deep understanding of the combustion behavior of Mg-based solid fuels, and support for the increasing demands for both military and civilian applications. [ABSTRACT FROM AUTHOR]

Abstract: The thermal properties and combustion characteristics of KClO4/Mg–50%Al, KClO4/Mg–50%Al with additives such as nitrocellulose (NC), urotropine and guanidine nitrate (GN) were studied experimentally using differential thermal analysis (DTA) and thermogravimetry (TG) and closed bomb experiments. The results of DTA–TG analysis revealed that additives could affect thermal stability and the decomposition temperature of KClO4/Mg–50%Al alloy. The order of the ignition temperatures of mixtures (T i) is KP/Mg–50%Al/urotropine (2#, 557.7°C)>KP/Mg–50%Al/GN(3#, 553.6°C)>KP/Mg–50%Al (1#, 538.8°C)>KP/Mg–50%Al/NC (4#, 536.5°C). On the other hand, the results of the closed bomb experiments confirm that the combustion pressures were all increased with the addition of additives. The ignition delay times of these mixtures are in the order KClO4/Mg–50%Al (1#)>KClO4/Mg–50%Al/GN (3#)>KClO4/Mg50%Al/NC (4#)>KClO4/Mg–50%Al/urotropine (2#). [ABSTRACT FROM AUTHOR]