Search

Elegant controllable protein degradation tools have great applications in metabolic engineering and synthetic biology designs. SspB-mediated ClpXP proteolysis system is well characterized, and SspB acts as an adaptor tethering ssrA-tagged substrates to the ClpXP protease. This degron was applied in metabolism optimization, but the efficiency was barely satisfactory. Limited high-quality tools are available for controllable protein degradation. By coupling structure-guided modeling and directed evolution, we establish state-of-the-art high-throughput screening strategies for engineering both degradation efficiency and SspB-ssrA binding specificity of this degron. The reliability of our approach is confirmed by functional validation of both SspB and ssrA mutants using fluorescence assays and metabolic engineering of itaconic acid or ferulic acid biosynthesis. Isothermal titration calorimetry analysis and molecular modeling revealed that an appropriate instead of excessively strong interaction between SspB and ssrA benefited degradation efficiency. Mutated SspB-ssrA pairs with 7-22-fold higher binding K

In this study, mixed fuel droplets of ethyl alcohol and biodiesel with different volumes or ratios were prepared and the related expansion, injection and micro-explosion phenomena were investigated...

The ignition, injection, and micro-explosion characteristics of aviation fuel (RP-3)/ethanol mixed droplets and biodiesel/ethanol mixed droplets at different proportions under high temperature conditions (420 °C) were compared using an experimental setup. A device for measuring small droplet volumes was designed using an infusion set and different types of needles, and a corresponding equation was established. Mixed droplets suspended on high-temperature resistance nichrome wire with a diameter of 0.2 mm were heated by sending them to a position approximately 2 mm from the forklift preheating plug using a moving rail. SLR and high-speed cameras were used to observe the flame structure as well as the injection and micro-explosion of the mixed droplets during combustion, respectively. Expansion, injection, and micro-explosion were observed in the biodiesel/ethanol mixed droplet experiments when the biodiesel content was 60%. Although the micro-explosion of mixed droplets of aviation fuel/ethanol was not observed, expansion and ejection of the droplets were observed. Image Pro-plus software was used to calculate the diameters at different times in the combustion cycle of the droplets. Through this analysis, the occurrence of micro-explosion was described, and a model for the calculation of micro-explosion strength was established.

This study investigated the combustion characteristics and kinetics of sewage sludge (SS), wheat straw (WS) and their blends using thermogravimetric analysis, under air condition. Combustion characteristic parameters of SS blended with 5%–50% WS was enhanced, especially revealed by an increase in comprehensive combustion index. A significant synergetic interaction was found in high temperature region through experiments. When proportion of WS was 50%, the synergetic interaction was strongest. And the catalytic effect of alkali metal oxides in WS ash on the combustion of SS residues at high temperature region had a strong effect on synergetic interaction. Metal oxides circulated in different oxide forms to transport oxygen to carbon surface, leading to catalytic effect. Activation energy was evaluated by two isoconversional method: Flynn-Wall-Ozawa and Vyazovkin method. The lowest average activation energies of the blends were obtained at 50% wheat straw blending ratio (89.29 kJ/mol by FWO and 87.48 kJ/mol by V, respectively). The thermodynamic parameters (Gibbs free energy, Entropy and Enthalpy) were also obtained. And two master plots methods were utilized to determine the appropriate fit kinetic model of combustion which can be described by Avarami-Erofeve (A2).

This study aimed at understanding the effects of co-flow condition on lift-off characteristics of the propane jet flame. A co-flow burner system was used to provide free jet condition, air co-flow condition and vitiated co-flow condition. In vitiated co-flow, methane was the co-flow fuel, and the co-flow equivalence ratios of methane/air mixtures changed from 0.5 to 0.7. On the basis of the results, the flame issuing into air-co-flow showed a higher lift-off height compared to the flame not issuing into a co-flow (i.e. free jet condition), with a faster increment rate simultaneously. In the vitiated co-flow condition, a conversion of lift-off height changing tendency was observed with the increment of flow rate and equivalence ratio of the co-flow. As the cases remained the same equivalence ratio, the cases with lower co-flow rates showed higher lift-off heights in the early combustion period. The lift-off height increased with the equivalence ratio in the cases with low co-flow rate, however, it decreased at high co-flow rate. It could be observed in the captured images that the ignition process was accelerated with the increment of equivalence ratio and co-flow rate.

The ignition characteristics and combustion processes of coal gangue pellets in O2/CO2 atmosphere were studied in a drop tube furnace with oxygen concentration range from 21% to 100%, the experimen...

The catalytic efficiency of CeO2 carriers and the catalytic properties of palladium (Pd) nanocrystals loaded on different morphology CeO2 carrier were studied for lean methane (CH4) combustion. The catalytic activity of simple CeO2 carriers was ranked in the order of rod-CeO2(r-CeO2) > cube-CeO2(c-CeO2) > octahedral-CeO2(o-CeO2). After the Pd species was loaded on CeO2, 90% of CH4 was converted at 348 °C catalyzed by Pd/octahedral-CeO2 (Pd/o-CeO2) with (1 1 1) crystal faces, which had much higher catalytic activity comparing with Pd loaded on c-CeO2 with (1 0 0) crystal faces and r-CeO2 with (1 1 0) and (1 0 0) crystal faces. The results of XRD, HRTEM, EDS, H2-TPR, XPS and elemental mapping showed that the Pd species in the form of Pd0 and PdO were highly dispersed on surface of all CeO2 carriers. Most importantly, quasi In-situ XPS results convinced that Ce3+/Ce4+ ion pairs played an important role in the catalytic combustion of low-concentration methane by adsorbing or releasing oxygen. Compared with r-CeO2 and c-CeO2, the concentration of Ce3+ on the surface of o-CeO2 carrier was greatly increased when the Pd species were present, which indirectly reflected that the concentration of oxygen vacancies on the carrier surface also increased. Consequently, the high catalytic activity of Pd/o-CeO2 is not only related to the high dispersion of Pd0 and PdO species on the surface of the catalyst, but also closely related to the synergistic interaction between Pd species and (1 1 1) specific faces of o-CeO2 exposing.

Spray characteristics of biodiesel-pentanol blends (with 0 v/v%, 10 v/v%, 20 v/v%, 30 v/v% and 40 v/v% pentanol) were investigated and compared with those of diesel in this work. Experiments under a variety of working conditions were carried out on a common-rail system and a constant volume chamber. High-speed Schlieren photography was used to capture the spray images. The analysis revealed that biodiesel and diesel showed the longest and the shortest spray tip penetration, the smallest and the largest spray cone angle, the smallest and the largest R (ratio between the liquid core area and the spray area), respectively. As the percentage of pentanol increased, the spray tip penetration of biodiesel-pentanol blends decreased, while the spray cone angle and R increased. BDP40 (60% biodiesel and 40% pentanol) showed similar spray characteristics as that of diesel. The comparison of tip velocities also showed that pentanol would reduce the initial axial momentum of injected fuels. Biodiesel showed the largest initial axial momentum while diesel owned the smallest one. Additionally, spray structures of blended fuels were more likely to fluctuate compared to biodiesel and diesel. The empirical equations of H-A model were used to verify the experimental results and showed great agreement between experimental results and predicts.

This paper reviews several important preparation methods, and several kinds of MnO2 composites, which is efficient in formaldehyde catalytic oxidation. The preparation of MnO2 composites discussed in this article refer to sol–gel method, rheological phase reaction method, micro-emulsion method, chemical coprecipitation method, solid-phase synthesis and template method. After a presentation of methods for the preparation of MnO2, a review of the performance on formaldehyde catalytic oxidation over (I) manganese oxides; (II) metal–MnO2 oxide composites; (III) graphene–MnO2 composites is provided. The mechanisms for catalytic oxidation of HCHO over MnO2 composites, future directions and potential hotspots are also discussed to facilitate understanding.

Proxies based on glycerol dialkyl glycerol tetraethers (GDGTs), a suite of membrane lipids occurring ubiquitously in soils, have generated increasing interest in quantitative paleo-environmental reconstruction. Hot and dry climates are likely to have occurred in the geological past; however, the limitations and applicability of these proxies to hot and dry environments are still unknown. In this study, we analyzed the GDGT distribution in the Turpan (TRP) basin of China, where the highest soil temperature can be approximately 70°C, and the mean annual precipitation (MAP) is 15.3 mm. We compared GDGT-based proxies among TRP soils, Nanyang (NY) soils, and Kunming (KM) soils; these three sites exhibit similar mean annual air temperature (MAAT) albeit contrasting temperature seasonality and MAP. Archaeal isoprenoidal GDGTs (isoGDGTs) dominate over bacterial branched GDGTs (brGDGTs) in most TRP soils; this is a characteristic GDGT distribution pattern for soils from dry regions globally. Another feature is the anomalously high GDGT-0/crenarchaeol ratio, which is generally attributed to the contribution of anaerobic methanogenic archaea by previous studies; however, these anaerobic archaea are unlikely to be highly abundant in the dry TRP soils, indicating that certain uncultured halophilic Euryarchaeota are likely to produce a significant amount of GDGT-0 that finally results in a high GDGT-0/Cren ratio. The changes in the salinity of the TRP soils appear to be an important factor affecting the MBT’5ME and the relative abundance of 6- vs. 5-methyl pentamethylated brGDGTs (IRIIa’). This is likely to introduce certain scatters in the correlations between MBT’5ME and MAAT and that between IRIIa’ and pH determined at the global scale. A comparison of the MBT’5ME-inferred temperature between TRP, NY, and KM soils does not indicate a significant bias toward summer temperature, indicating that brGDGT paleothermometers in soils could reflect the MAAT.

In this work, NiCo2O4 with a hierarchical porous flower-like structure was fabricated and used as catalyst support for Pd nanoparticles. The NiCo2O4 was composed of porous nanoplates without overlapping, and the Pd nanoparticles were uniformly distributed on these nanoplates. Pd–NiCo2O4 with the Pd loading of 2.0 wt% showed extremely high activity and stability, methane (1.0% CH4/Air) can be totally oxidized at 330 °C and the T90 is 309 °C, which is much lower than that of pure NiCo2O4 (T90 = 405 °C). At wet condition with the presence of 10 vol% water vapor, the catalytic activity was still acceptable with the T90 of 366 °C, and no activity decrease or permanent damage for the catalyst was observed after 35 h reaction, showing high stability. A series of techniques including TEM, SEM, XRD, H2-TPR, BET and especially quasi in situ XPS combined with in situ MS were used to characterize the catalysts and investigate the catalysis mechanism. Two pathways of CHO evolution were proved by the quasi in situ XPS and in situ MS results: OCHO intermediate dehydrogenation pathway at lower temperature and CO oxidation pathway of CHO at higher temperature.

This work aimed to figure out the liftoff characteristics of ethylene and ethane, which are both promising fuels in the new energy era for flames in coflow. A free jet condition, air coflow...

It is unclear whether or not the paleotemperature proxies based on the branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soil exhibits any seasonal bias in temperature reconstruction. To test this, we examined the brGDGT distributions and compared the mean annual air temperature (MAAT) estimates inferred from the brGDGT-based paleothermometers for surface soils from Nanyang (NY) and Kunming (KM), two sites in China with similar MAAT, but with contrasting climate seasonality (i.e. different summer and winter temperatures). If a significant bias towards summer or winter temperature were to occur, the soils from the locality with stronger seasonality would be expected to yield different temperature estimates than those from the other locality. The results show that, at a regional isothermal scale, the most important environmental control on the soil brGDGT distribution is pH at NY but soil water content (SWC) at KM, suggesting a regional difference in the key environmental control on the brGDGT distributions. MBT′ and CBT are both controlled primarily by pH at NY but by SWC at KM. In contrast, the MBT′5ME index, known to be dependent on MAAT alone, displays no relationship with pH or SWC at both sites, allowing us to evaluate the impact of temperature seasonality. MBT′5ME is statistically higher at the NY soils than at the KM soils; a MBT′5ME difference of 0.04 units is equivalent to a difference of ca. 1.3 °C in MAAT. Likewise, the MAATmr estimates produced from multiple linear regression calibration for the two soil sites differ by only 0.8 °C. This suggests that there is no significant bias towards summer temperature in the brGDGT-based paleothermometer as the mean summer temperature differs by 6.4 °C at the two soil sites. By extension, temperature reconstructed from the brGDGT-based proxies for the loess-paleosol sequences in the southern Chinese Loess Plateau is unlikely to be biased towards summer.

Combustion behaviors and carbon monoxide emission characteristics of four kinds of coals and their blends, which were shaped into pellets, were investigated in a drop-tube furnace with vari...

The methylation index (MBT or MBT′) of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils along altitudinal transects of some mountains, e.g. Mount (Mt.) Shennongjia and Mt. Gongga, exhibited no correlation with altitude or mean annual air temperature (MAT) alone. However, a significant correlation between MBT′, cyclization ratio (CBT) of brGDGTs and MAT for each transect could still be found. To investigate the reason, we reanalyzed the brGDGTs in soils from Mt. Shennongjia using an improved liquid chromatography method and examined whether the newly described 6-methyl brGDGTs were the main cause of the large scatter in the correlation between MBT′ and MAT. In contrast to MBT′, the MBT′5ME, based on 5-methyl brGDGTs alone, correlated significantly with MAT (R2 0.89, p

Edible insects have become a recognized alternative and sustainable source of high-quality proteins and fats for livestock or human consumption. In the production process of black soldier fly (BSF), (Hermetia illucens L. [Diptera: Stratiomyidae]), initial substrate pH is a critical parameter to ensure the best value of insect biomass, life history traits, and quality bio-fertilizer. This study examined the impact of initial pH values on BSF larvae production, development time, and adult longevity. The BSF were reared on artificial diet with initial pH of 2.0, 4.0, 6.0, 8.0, and 10.0; the control was set at 7.0. Final BSF larval weight was significantly greater in substrates having initial pH 6.0 (0.21 g), control 7.0 (0.20 g), and 10.0 (0.20 g) with no significant difference among them, whereas larval weight reared with initial pH 2.0 and 4.0 were lowest at 0.16 g (-23%). Prepupal weight was greatest when larvae were reared on substrates with initial pH 6.0 (0.18 g), control 7.0 (0.19 g), 8.0 (0.18 g), and 10.0 (0.18 g). In contrast, the prepupal weight of larvae reared on diets with initial pH 2.0 was lowest at 0.15 g (-22%). Larval development time was 21.19 d at pH 8.0, about 3 d (12.5%) shorter than that of those reared on diets with initial pH 6.0, 7.0 control, and 10.0. In all treatments, pH shifted to 5.7 after 3-4 d and 8.5 after 16-17 d except for two groups (2.0 and 4.0) where the pH remained slightly acidic 5.0 and 6.5, respectively.

A method to measure the volume of tiny droplets was designed, and 10 kinds of aviation fuel (RP-3), biodiesel and ethanol mixed droplets with the same volume and different proportions were prepared by using this method. Two kinds of experimental platforms (heating plate and tube furnace) for observing droplet micro-explosion were established. The expansion, ejection and micro-explosion characteristics of mixed droplets at high ambient temperature (480 °C) were studied by a heating plate experimental platform consisting of a combustion chamber composed of 7 heating plates, a controllable movable slide rail and other equipment. The BD10R20E70 and BD40R50E10 mixed droplets produced ejection and expansion phenomena in the experiment, other kinds of mixed droplets not only produced expansion and ejection, but also produced micro-explosion, but the intensity of these micro-explosion was different. Moreover, secondary micro-explosion of droplets was also observed in the heating experiment of BD40R10E50 droplet. The calculation equation of micro-explosion intensity was established and the micro-explosion intensity of 10 kinds of mixed droplets was calculated. Through the analysis of the micro-explosion intensity value, four different levels of micro-explosion intensity were distinguished. The micro-explosion characteristics of BD60R10E30 and BD60E40 mixed droplets were compared and analyzed by using a tubular furnace experimental platform. The reason for the difference in micro-explosion intensity between the two mixed droplets was analyzed, and the rationality of the division of micro-explosion strength was verified.

A novel method by integrating the color information and bilinear interpolation with the traditional fast tracking via spatio-temporal context learning (STC) called as C-STC is presented. Experimental results with variant videos show that the improved algorithm can track the object accurately compared with the traditional STC, Particle Filter (PF) and Multiple Instance Learning (MIL). Moreover, multi-core emulation experiments have been conducted based on TMDXEVM6678L. Synchronization and communication between cores are realized based on the MessageQ. Two modes of data transmission from PC to DSP are achieved. The results show that the transmission via network promotes the real-time performance, which laying the foundation for communication between the DSP and the gigabit ethernet camera.

With the bursting development of computer science and mobile devices, the combination of education and recent techniques is urgently needed. In view of the existing mobile learning system interactive poor, renewable resources, shortcomings and so on big data traffic, this paper puts forward a kind of mobile learning system based on Android platform. The system can not only solve the above problem, also can easily implement integration and extension. With the rapid popularization of smart mobile terminals, mobile study become a hot spot, the trend of traditional live remote education system puts forward a new challenge. Therefore, in this paper, we undertake research on British and American literature learning platform based on Android mobile systems. We modify the framework of the current Android system and re-design the user interface. The simulation result shows the system is user-friendly and stable.