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Abstract: Bacterial cellulose (BC) was used as a raw material to produce freestanding carbon aerogels (CAs). The CAs were further decorated with Ni and MnO2/Ni(OH)2 hybrid via electrodeposition and redox reaction to produce carbon nanofiber networks decorated with electrochemically active metal and metal compounds. The properties of this novel material as supercapacitor electrodes were investigated. The electrochemical performance of the electrodes was examined in 1 M Na2SO4 electrolyte using cyclic voltammetry (CV), cyclic charge-discharge (CCD), and electrochemical impedance spectroscopy (EIS) tests. The results showed that a specific capacitance of 109 F g−1 was achieved at the current density of 1 A g−1. The electrodes could deliver an energy density of 9.4 Wh kg−1 and a power density of 4 KW kg−1 and demonstrated a high cyclability. These results showed great potential of this new material for supercapacitor electrodes. A flexible solid-state supercapacitor prototype was prepared using this material to demonstrate its function as a power source for a LED light. This study provided a new way to use BC as a biobased low-cost material for the fabrication of energy storage devices.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Although turbulent flow is generally needed for good suspension of photocatalysts, lower flow rates are preferred from an economic viewpoint for energy-efficient operation. However, no experimental work has been conducted to reveal how photocatalyst particles move and distribute in a tubular photocatalytic reactor under mild operating conditions, which is critical for reactor design and configuration of the light concentration. In our study, the photocatalyst itself was employed as a tracer particle for Particle Image Velocity (PIV) measurement. PIV combined with a new laser sheet image analysis (LSIA) technology was employed to investigate both the particle velocity and number distribution in the tubular reactor. It was found that, in the inlet, a higher velocity distribution of fluid generally occurred in the lower part of the tube. However, in the middle and outlet regions of the tube, a higher velocity distribution existed in the upper part of the tube. LSIA investigation showed that the transport capacity of the fluid and the initial particle size distribution are two essential factors influencing particle number distribution in the suspension. Regardless of the particle size, the middle part of the reactor holds the maximum number of particles while the outlet has the minimum number of particles. In the inlet, both small and large particles show similar number distribution trends against the flow rate. However, in the middle part of the tube, the number of small particles decreases with the flow rate while the number of the large particles shows the opposite trend. The difference in velocity distribution along the radial direction also significantly affects the particle distribution. One interesting finding is that, regardless of the particle size, the number of particles in the upper part of the tube is always higher than that in centre. Stokes’ drag law and the Saffman lift force were employed to explain this experimental finding. In the last section, the correlation between particle distribution and optical properties was numerically investigated by a modified differential approximation (MDA) method. [ABSTRACT FROM AUTHOR]

Bubbles evolving from electrode surface are the results of the multi-processes, interfacial mass transfer, chemical reaction, micro fluid flow, etc. In this paper, the investigations on the bubble growth mechanism during photoelectrochemical and electrochemical conversions are carried out. The experimental results show two different growth laws during photoelectrochemical and electrochemical conversions, which are chemical reaction and diffusion controlled respectively, caused by the difference in the effective surface area of the electrode. And mathematical models for bubble growth describing the two effects are established. [ABSTRACT FROM AUTHOR]

Nanofluids as thermal absorption media or optical filters have showed great potential for application in direct absorption solar collector or hybrid photovoltaic/thermal (PV/T) collectors. Due to their nanoscale size and high surface energy, particles in nanofluid have a great tendency to aggregate into large secondary agglomerate, even in the presence of the anti-agglomeration agent, which could in turn lead to significant change in the thermal and optical properties of the nanofluid. However, rare work has been carried out to investigate the relation between the aggregation and optical properties of the nanofluid, which in our view, is of great importance for the enhanced performance of the nanofluid in solar collectors. In this study, taken alumina nanofluids with controlled particle aggregation properties as example, we were able to investigate the underlying correlation between the size distribution of the aggregate in nanofluid and their resulting absorption coefficients. It was found that inhibited aggregation and resultant smaller aggregated particle size could lead to larger absorption coefficient. Both Rayleigh scattering and Mie scattering theories have been attempted to predict the optical properties of the nanofluid after particle aggregation. The results indicate that values obtained by Rayleigh scattering theory are several orders higher than experimental values but that predicted by Mie scattering theory can reasonably match with the experimental results. Specially, it was demonstrated that by introducing the projected areas of the nanoparticle aggregate corresponding to smallest sphere enclosing diameter, more accurate absorption coefficient prediction based on Mie theory can be obtained. Our study is expected to provide a valuable guidance for the regulation of the optical properties of nanofluids and to improve their performance in solar collectors. [ABSTRACT FROM AUTHOR]

Abstract: Corrosion protective coatings are known to degrade due to moisture exposure. To predict coatings service lifetime, acceleration tests are necessary. We employ flowing deionized water to accelerate coating degradation. Coating barrier properties are found, via electrochemical impedance spectroscopy (EIS), to decrease as flow rate (Q) increases, similar to findings for coatings in NaCl solution. EIS modulus decreases more for coatings in deionized water than those in electrolyte solution. Topographical characterizations show severe coating blistering in deionized water immersion with higher Q, but not in electrolyte solutions. Deionized water is thus believed to accelerate more aggressively the degradation than electrolyte solution. [Copyright &y& Elsevier]

Abstract: Resveratrol is a polyphenolic compound produced by a few higher plants when under attack by pathogens such as bacteria or fungi. Besides antioxidant benefits to humans, this health-promoting compound has been reported to extend longevity in yeasts, flies, worms, fishes and obesity mice. Here we utilized the synthetic scaffolds strategy to improve resveratrol production in Saccharomyces cerevisiae. We observed a 5.0-fold improvement over the non-scaffolded control, and a 2.7-fold increase over the previous reported with fusion protein. This work demonstrated the synthetic scaffolds can be used for the optimization of engineered metabolic pathway. [Copyright &y& Elsevier]

In this study, we experimentally investigate the large-scale vortex pair formed by droplets in the spanwise direction of the flow field of a hollow cone spray injected transversely into a gaseous crossflow. Experiments are conducted in a square channel for a wide range of spray and crossflow conditions. The spatial and velocity distributions of the spray droplets for different cross-sections of the flow field in terms of different flow conditions are measured through flow visualization. Three parameters, namely, vortex vorticity, depth of vortex core, and distance between both vortex cores, are used to characterize the counter-rotating vortex pair (CVP) formed by droplets. The crossflow Reynolds number, (initial atomized) droplet Reynolds number, and number of droplets injected per unit time are all found to significantly influence the features of droplets CVP. We newly define the spray-to-crossflow momentum flux ratio ( J ∗) based on the injected momentum flux of initial atomized droplets. Accordingly, we develop a set of correlations for predicting the features of droplets CVP based on experimental measurements and the Buckingham π theorem. The results show that these correlations well predict all measured conditions. The results of this study should provide insights into the dynamics of spray droplets in a crossflow and an understanding of the large-scale mixing between a hollow cone spray and a crossflow. [ABSTRACT FROM AUTHOR]

In this study, evolution and final state of particle size distribution (PSD) of TiO 2 /water suspension were described by a modified population balance equation considering both natural convection and Brownian motion. The calculation was verified by experimental measurement of scanning electron microscope and Laser particle analyzer. Based on the predicted PSD, Rayleigh scattering theory (for d < 4 λ ) and Fraunhofer diffraction theory (for d > 4 λ ) were then employed to determine the scattering and absorption coefficients of TiO 2 /water suspensions with various particle concentrations and at various light wavelengths. UV–Vis investigation showed that the predicted optical properties of TiO 2 /water suspension considering PSD are in much better agreement with the experimental results than that without considering PSD, at all particle concentrations investigated. It is traditionally accepted that for colloid suspension the scattering coefficient can be neglected compared to the absorption coefficient and therefore the extinction, which is the combination of the absorption and scattering coefficients, can be approximately replaced by the absorption coefficient. However, our finding indicates that, when particle aggregation is considered, the scattering coefficient of TiO 2 /water suspension could be much higher than the absorption coefficient. Consequently, using the absorption coefficient alone to replace the extinction coefficient even at long wavelengths could result in significant calculation errors and is not recommended. [ABSTRACT FROM AUTHOR]

• Yarrowia has shown the potential for producing complex terpenoids. • Yarrowia may hold multiple cytosolic acetyl-CoA and NADPH generation pathways. • Metabolite channeling is a key consideration in terpene pathway engineering. • Knowledge gaps exist in compartment-specific fluxes for utilizing alternative carbon sources (e.g., lipids). • Metabolic shift, genetic stability, and dimorphism in large-scale Yarrowia fermentation need further studies. Yarrowia lipolytica has emerged as an important non-model host for terpene production. However, three main challenges remain in industrial production using this yeast. First, considerable knowledge gaps exist in metabolic flux across multiple compartments, cofactor generation, and catabolism of non-sugar carbon sources. Second, many enzymatic steps in the complex-terpene synthesis pathway can pose rate-limitations, causing accumulation of toxic intermediates and increased metabolic burdens. Third, metabolic shifts, morphological changes, and genetic mutations are poorly characterized under industrial fermentation conditions. To overcome these challenges, systems metabolic analysis, protein engineering, novel pathway engineering, model-guided strain design, and fermentation optimization have been attempted with some successes. Further developments that address these challenges are needed to advance the Yarrowia lipolytica platform for industrial-scale production of high-value terpenes, including those with highly complex structures such as anticancer molecules withanolides and insecticidal limonoids. [ABSTRACT FROM AUTHOR]

• The phase interface in the upstream horizontal section was reconstructed using ECVT. • Upstream interface drop and slugging are induced by the flow in the riser. • Lockhart-Martinelli model is found to be best and is used for improved correlation. • An improved void fraction prediction model is proposed for pipeline-riser systems. • This improved model leads to considerably reduced prediction errors. This paper introduces the application of void fraction prediction models (25 models total) from a simple horizontal pipe to a complex, real pipeline. The flow mechanism in the pipeline-riser system is explained based on the upstream phase interface and differential pressure in the downstream riser. The transition boundaries of "stratified to intermittent flow" and "stratified smooth to stratified wavy flow" in the horizontal section were predicted well by the models based on simple pipes. Electrical capacitance volume tomography was used to obtain the upstream void fraction just before the downstream gas-liquid eruption, α 1 , or during multiple cycles, α 2. The difference between α 1 and α 2 are ranging between −10 % and 5 %. Finally, an improved correlation is proposed based on the model found to be best (Lockhart and Martinelli, with error values (root mean square error (RMSE) and mean absolute percentage error (MAPE)) of about 12 % and 18 %); the corresponding error levels (RMSE and MAPE) amount roughly to 5 % and 10 %, respectively. The improved model also delivers a good prediction for α 1 when separating in two flow regimes. Overall, the finally proposed correlation reads and is found superior in terms of accuracy to all previously published correlations. [ABSTRACT FROM AUTHOR]

• SCW/CO 2 /N 2 mixture injection is proposed for heavy oil recovery. • A core experimental system of SCW/CO 2 /N 2 flooding is developed. • SCW/CO 2 /N 2 flooding is divided into three stages. • CO 2 and N 2 provide the driving force and eliminate gravity override. • SCW/CO 2 /N 2 flooding can both enhance oil recovery and upgrade oil quality. Exploitation of heavy oil is critical for mitigating the energy crisis. However, conventional thermal recovery methods cannot completely exploit the potential of heavy oil owing to its high viscosity and heavy distillates. A new technology is proposed with reference to CO 2 – and N 2 -assisted supercritical water (MGA-SCW) injection for heavy oil recovery. In this study, an experimental apparatus was developed to simulate the MGA-SCW flooding process and test its feasibility. MGA-SCW injection remarkably enhanced oil recovery, increased the oil production rate, and improved the oil quality. For MGA-SCW flooding at 25 MPa and 400 °C, the recovery factor approached 95 %, and the oil viscosity decreased by 32 %; the light distillate fraction (180–350 °C) increased from 11 to 15 %. The dynamic process of MGA-SCW flooding is divided into three stages: pressure difference, thermal, and miscible drives. This technology can be applied to the development and utilization of offshore heavy oil fields. [ABSTRACT FROM AUTHOR]

Numerical simulation of free surface multi-fluid flow is a challenging problem owning to the interaction between deformed interface and free surface. In this paper, a multiphase particle solver (free surface multiphase moving particle semi-implicit method, FS-MMPS) is developed to predict the early spreading flow of spilled oil where exist the oil–water interface and air–oil/air–water free surface. First, a multiphase virtual particle model is proposed to substitute the inaccurate free surface boundary condition for multiphase flow in conventional MPS methods. Specifically, virtual particles of different liquid phases are compensated outside free surface so that the pressure of free surface particles can be solved from pressure Poisson equation, thereby improving the accuracy of multi-fluid interaction at free surface. Meanwhile, a pressure gradient model based on the coupling of Taylor series expansion and dynamic specification of particle stabilizing term (PST) is proposed to simultaneously enhance accuracy and depress instability caused by multiphase virtual particles. Experiments of early spreading of thick oil slicks and continuous oil spill from a damaged tank are conducted for validation and demonstration of the accuracy and stability enhancements in 2D. Finally, the effects of traveling wave and continuous spilling on oil spreading are investigated to show the capability of the proposed method. The spreading of thick oil slicks is accelerated when wave height increases or wave length decreases, and the largest increase of spreading rate accelerated by traveling wave is 14%. [ABSTRACT FROM AUTHOR]

Direct contact condensation of jets in fluid has been widely applied in many industrial applications owing to the low requirement of driving potential and high efficiency of heat and mass transfer. Here, experiments are carried out to investigate the velocity field characteristics of the turbulent jet induced by direct contact condensation of steam jet in crossflow of water in a vertical pipe. Visual equipment is specially invented to investigate the velocity field characteristics by using Particle Image Velocimetry (PIV) measurement technique. The high intensity laser light reflected by the pure steam region just outside the nozzle-exit brings out severe damage to the CCD camera. To solve this technical problem, a black plate is adopted to shield the pure steam region. According to the contours of the velocity fields and streamlines, the influences of jet momentum ratio, jet Reynolds number and water temperature on the jet flow field are explored. The jet centerline trajectory equations in exponential form are established based on the local maximum mean velocity. By introducing the jet Reynolds number and jet momentum ratio, the correlation for prediction of jet centerline trajectory equations is proposed, and the predicted results are within 30% of the experimental data. The reciprocal of the local maximum mean velocity and the half-width of the jet are proportional to the downstream coordinate along the jet velocity centerline trajectory. The scaled velocity field complies with the self-similarity principle. [ABSTRACT FROM AUTHOR]

• The interface wave in the horizontal section before the riser was studied by an ECVT. • Flow regime transition boundaries shift to lower velocities due to the riser. • The period of hydraulic jump is consistent with that of severe slugging flow. • The hydraulic jump upstream is mainly caused by pressure fluctuations of the riser. This paper describes experiments conducted on the gas–liquid two-phase flow characteristics in a pipeline-riser system under 1 MPa. The hydraulic jump phenomenon (HJP) in the upstream horizontal section was quantitatively studied using electrical capacitance volume tomography (ECVT). Flow regime transition boundaries were shifted to lower gas and liquid velocities due to the impact of the riser at the end of the horizontal pipe. The HJP's period is consistent with that of severe slugging flow; additionally, the liquid slug production and the gas–liquid eruption stages always occur before the HJP in the upstream horizontal section. The Pearson correlation coefficient between the HJP upstream and the pressure fluctuations in the three main structures (horizontal, downward, and riser sections), the period consistency, and the sequential relationship between them were analyzed to verify that the pressure fluctuations in the downstream riser were the main cause of the HJP upstream. [ABSTRACT FROM AUTHOR]

Abstract: Mechanically flexible mats consisting of electrospun carbon nanofibers (ECNFs) were prepared by first electrospinning aqueous mixtures containing a natural product of alkali lignin together with polyvinyl alcohol (PVA) into composite nanofiber mats followed by stabilization in air and carbonization in an inert environment. Morphological and structural properties, as well as specific surface area, total pore volume, average pore size, and pore size distribution, of the lignin-based ECNF mats were characterized; and their electrochemical performances (i.e., capacitive behaviors) were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The lignin-based ECNF mats exhibited outstanding performance as free-standing and/or binder-free electrodes of supercapacitors. For example, the ECNFs made from the composite nanofibers with mass ratio of lignin/PVA being 70/30 (i.e., ECNFs (70/30)) had the average diameter of ∼100 nm and the Brunauer–Emmett–Teller (BET) specific surface area of ∼583 m2 g−1. The gravimetric capacitance of ECNFs (70/30) electrode in 6 M KOH aqueous electrolyte exhibited 64 F g−1 at current density of 400 mA g−1 and 50 F g−1 at 2000 mA g−1. The ECNFs (70/30) electrode also exhibited excellent cycling durability/stability, and the gravimetric capacitance merely reduced by ∼10% after 6000 cycles of charge/discharge. [Copyright &y& Elsevier]

• Monodispersed HCSs with tunable cavity size were synthesized through a thermal-etching process without template. • The "inside-out" oriented thermal etching process was induced by the "core-shell" differentiated chemical structures of CSs. • HCSs exhibited a SISG efficiency as high as 88.9%, which outperforms most of the previously reported carbon-based materials. • The delicate heat management contributes to the significantly improved SISG efficiency. Hollow carbon spheres (HCSs) with controllable morphology and structure have received considerable attention in the field of energy conversion and storage. Herein, monodispersed HCSs with cavity sizes tuned from 100 nm to 800 nm and shell thickness from 450 nm to 50 nm were successfully synthesized through a unique template-free thermal-etching method. It was evidenced that the dynamically controllable synthesis of HCSs was attributed to the "inside-out" oriented thermal oxidation etching of carbon spheres (CSs) induced by the differentiated "core-shell" chemical structures. Comparing to CSs, the obtained HCSs exhibited much increased efficiency for solar-driven interfacial steam generation (SISG), reaching as high as 88.9%, which outperforms most of the previously reported carbon-based materials. It was then demonstrated that the rational heat management for both photothermal and thermal-evaporation conversion is essential to achieve satisfying SISG efficiency. Depending on the increasing cavity sizes, HCSs presented gradual increases in both photothermal conversion and thermal-evaporation performances, mainly attributed to the improved light absorption and the delicate heat management, respectively. However, the further increase in cavity size resulted in excessive heat loss and presented decreased thermal-evaporation performance. This work provides an alternative and promising approach to the reasonable design of hollow nanostructures with delicate heat management for efficient SISG as well as other solar energy conversion applications. Hollow carbon spheres with tunable cavity was synthesized by an oriented thermal etching of hydrothermally synthesized carbon spheres, which exhibited excellent solar steam generation performances, with delicate heat management in both photothermal conversion and thermal-evaporation processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: β-Ionone is a fragrant terpenoid that generates a pleasant floral scent and is used in diverse applications as a cosmetic and flavoring ingredient. A growing consumer desire for natural products has increased the market demand for natural β-ionone. To date, chemical extraction from plants remains the main approach for commercial natural β-ionone production. Unfortunately, changing climate and geopolitical issues can cause instability in the β-ionone supply chain. Microbial fermentation using generally recognized as safe (GRAS) yeast offers an alternative method for producing natural β-ionone. Yarrowia lipolytica is an attractive host due to its oleaginous nature, established genetic tools, and large intercellular pool size of acetyl-CoA (the terpenoid backbone precursor). Results: A push–pull strategy via genome engineering was applied to a Y. lipolytica PO1f derived strain. Heterologous and native genes in the mevalonate pathway were overexpressed to push production to the terpenoid backbone geranylgeranyl pyrophosphate, while the carB and biofunction carRP genes from Mucor circinelloides were introduced to pull flux towards β-carotene (i.e., ionone precursor). Medium tests combined with machine learning based data analysis and 13C metabolite labeling investigated influential nutrients for the β-carotene strain that achieved > 2.5 g/L β-carotene in a rich medium. Further introduction of the carotenoid cleavage dioxygenase 1 (CCD1) from Osmanthus fragrans resulted in the β-ionone production. Utilization of in situ dodecane trapping avoided ionone loss from vaporization (with recovery efficiencies of ~ 76%) during fermentation operations, which resulted in titers of 68 mg/L β-ionone in shaking flasks and 380 mg/L in a 2 L fermenter. Both β-carotene medium tests and β-ionone fermentation outcomes indicated the last enzymatic step CCD1 (rather than acetyl-CoA supply) as the key bottleneck. Conclusions: We engineered a GRAS Y. lipolytica platform for sustainable and economical production of the natural aroma β-ionone. Although β-carotene could be produced at high titers by Y. lipolytica, the synthesis of β-ionone was relatively poor, possibly due to low CCD1 activity and non-specific CCD1 cleavage of β-carotene. In addition, both β-carotene and β-ionone strains showed decreased performances after successive sub-cultures. For industrial application, β-ionone fermentation efforts should focus on both CCD enzyme engineering and strain stability improvement. [ABSTRACT FROM AUTHOR]