代谢工程改造微生物固定二氧化碳研究进展

微生物固定CO₂是实现CO₂资源化利用的有效策略之一,为固碳减排、节能生产与绿色合成提供了借鉴。然而,微生物在固定CO₂过程中存在底物利用效率低、能量需求量大、路径难优化等问题。为了解决这些问题,本文总结了6种天然CO₂固定途径与5种人工CO₂固定途径,并从自养微生物、异养微生物和人工微生物三个方面系统分析了代谢工程改造微生物固定CO₂合成化学品的最新进展。在自养微生物固定CO₂方面,采用的策略主要包括提高CO₂固定途径效率、开发能量捕集系统与调节碳代谢流分布;在异养微生物固定CO₂方面,常用的方法主要有强化羧化途径、重构CO₂固定途径与优化能量供给;在人工微生物固定CO₂方面,主要的研究思路是设计人工CO₂固定途径与构建人工CO₂固定微生物。最后,从CO₂固定的关键酶、途径和微生物...     

Simulation of nitrogen in soil and winter wheat crops: Modelling nitrogen turnover through organic matter

A computer model is described that simulates leaching, organic matter turnover and nitrogen uptake by a winter wheat crop. The model is assessed against a data set from the Netherlands where winter wheat was grown in two seasons (1982–3 and 1983–4) on three different soils in two different parts of the country. The model satisfactorily simulated the growth, N uptake and production of grain. It also simulated the dynamics of indigenous soil N well but it did not always account for the fate of applied fertilizer N. Some possible reasons for this and ways of improving the model are discussed.     

Reproducibility of Turnover Rates in Heterogeneous Metal Catalysis: Compilation of Data and Guidelines for Data Analysis

The combination of turnover rate measurements and surface science techniques allows a firm quantification of rates in heterogeneous catalysis by metals. There are many examples of reactions where the turnover rates from different laboratories are the same. However, there are still problems, as in the isomerization and hydrogenolysis of hydrocarbons over noble metals, where the turnovers rates from different laboratories differ by many orders of magnitude. An explanation for this discrepancy is discussed. Guidelines for experimental work in heterogeneous catalysis that will help to minimize this wide scatter of turnover rates in the future are presented.

     

A general compartment‐based population balance model for particle coating and layered granulation

In this work, a general multidimensional population balance (PB) model is developed to predict the coating volume distribution on polydisperse particles as a function of time during particle coating in a paddle mixer. The model adopts a compartmental approach to account for coating variation caused by particle flow heterogeneity. Simulations show that for a realistic range of seed particle size polydispersity and coating mass applied, the coating volume distribution depends on the growth rate exponent and seed particle size distribute on, with the coating volume coefficient of variance (CoV) approaching an asymptotic value as the coating‐to‐particle volume ratio increases. These effects cannot be predicted by simpler one‐dimensional models. However, the full two‐dimensional PB and simpler one‐dimensional models such as Mann's equation do predict similar sensitivity of coating volume CoV to the variation in the compartment model parameters, i.e., to changes in the particle mixing behavior in the vessel. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

The effect of the addition of silica particles on linear spherulite growth rate of isotactic polypropylene and its explanation by lamellar cluster model

The effect of the addition of silica particles on spherulite growth rates of isotactic polypropylene has been investigated using an optical microscope. The spherulite growth rate remained constant with time and the growth rates decreased with increasing the silica content. The addition of silica particles generally causes a reduction of the average distance between adjacent silica particles and the linear growth rates become zero when the inter-particle distance reached to the end-to-end distance of the matrix chains. The reduction in the linear growth rate can be explained by assuming the lamellar clustering process that the precursor or solidified units with the single chain space, which spontaneously are built up from the melt, act as the crystallizing units and the diffusive mobility of the units was restricted by spatial confinement between adjacent silica particles.     

An extended Kalman filter for in situ sensing of yttria-stabilized zirconia in chemical vapor deposition

Chemical vapor deposition is widely used in integrated circuit fabrication. With the increasingly stringent requirements for product quality and yield, it is necessary to apply process monitoring, fault detection and eventually closed-loop control to the deposition process. The implementation of these tools requires an in situ sensor that can measure film properties in real time. This paper discusses an extended Kalman filter (EKF) based in situ sensor and its application in chemical vapor deposition of yttria-stabilized zirconia (YSZ) on a silicon substrate. The sensor measures reflectance from the film surface at 950 and 470 nm. The measurements were processed by the EKF to estimate film thickness, growth rate and surface roughness. The challenge with estimation of film microstructure like roughness lies in the process dynamic model for microstructure evolution at small scales, which in general is high-dimensional and nonlinear. In this work a simple but adaptive process dynamic model and a detailed optical sensor model were used to study how a simple process model could aid in estimation. Based on these models the observability of the process was discussed. The estimated film properties were verified with ex situ characterization using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Finally sensitivity and robustness of EKF were discussed, along with our perspectives on future work on in situ sensing for thin film deposition.     

A transient mathematical model for maximum respiration activity and oxygen diffusion coefficient estimation in non-steady-state biofilms

A transient mathematical model was established in order to evaluate oxygen diffusivity in non-steady-state biofilms. A submerged fixed bed biofilm system with efficient medium recirculation was investigated for p-toluenesulphonic acid degradation by Comamonas testosteroni T-2 in a multi-species biofilm. Static mixer elements (Sulzer Chemtech Ltd, Switzerland) were used as a support matrix for biofilm formation. Biofilm respiration was estimated using the dynamic gassing-out oxygen uptake method. Based on the dissolved oxygen concentration profiles, the oxygen diffusion coefficient and the maximum respiration activity were calculated. The values of the dissolved oxygen diffusion coefficient varied with biolfilm development and values reported here (2×10⁻¹⁰–1.2×10⁻⁹ m² s⁻¹) are in good agreement with literature data. Calculated oxygen consumption rates fit well with values obtained in respirometry tests with washed out biofilms. The knowledge of diffusivity changes in biofilms is particularly important for removal capacity estimation and appropriate reactor design. © 1998 Society of Chemical Industry     

Transient cooling of petroleum by natural convection in cylindrical storage tanks: A simplified heat loss model

The transient cooling by natural convection of a warm crude oil contained in a large vertical cylindrical storage tank located in a cold environment is investigated. The governing mass, momentum and energy equations utilizing a temperature-dependent apparent viscosity were solved numerically, and from the results a correlation is developed between the Nusselt number at the sidewall and the instantaneous Rayleigh number driving the time-dependent flow. A simplified heat loss model is developed to predict the mean tank temperature over time, utilizing this correlation to calculate a time-dependent heat transfer coefficient for the sidewall. The results from the simplified model are compared with the mean tank temperatures results from a simulation of the full natural convection equations for the cooling of a crude oil in a 60 m diameter tank, and excellent agreement is obtained.     

Contact resistances in spark plasma sintering: From in-situ and ex-situ determinations to an extended model for the scale up of the process

Heating in spark plasma sintering is a key point of this manufacturing process that requires advanced simulation to predict the thermal gradients present during the process and adjust them. Electric and thermal contact resistances have a prominent role in these gradients. Their determination is difficult as they vary with pressure and temperature. A calibration method is used to determine all of the contact resistances present within tools of different sizes. Ex situ measurements were also performed to validate the results of the in-situ calibrations. An extended predictive and scalable contacts model was developed and reveals the great importance and diversity of the contact resistances responsible for the general heating of the column and high thermal gradients between the parts. The ex/in situ comparison highlights a high lateral thermal contact resistance and the presence of a possible phenomenon of electric current facilitation across the lateral interface for the high temperatures.     

A-FABP in Metabolic Diseases and the Therapeutic Implications: An Update

Adipocyte fatty acid-binding protein (A-FABP), which is also known as ap2 or FABP4, is a fatty acid chaperone that has been further defined as a fat-derived hormone. It regulates lipid homeostasis and is a key mediator of inflammation. Circulating levels of A-FABP are closely associated with metabolic syndrome and cardiometabolic diseases with imminent diagnostic and prognostic significance. Numerous animal studies have elucidated the potential underlying mechanisms involving A-FABP in these diseases. Recent studies demonstrated its physiological role in the regulation of adaptive thermogenesis and its pathological roles in ischemic stroke and liver fibrosis. Due to its implication in various diseases, A-FABP has become a promising target for the development of small molecule inhibitors and neutralizing antibodies for disease treatment. This review summarizes the clinical and animal findings of A-FABP in the pathogenesis of cardio-metabolic diseases in recent years. The underlying mechanism and its therapeutic implications are also highlighted.     

A mathematical model for the production of biosurfactants by Pseudomonas aeuginosa CFTR-6: Production of biomass

The fermentation reaction producing biosurfactant using Pseudomonas aeruginosa CFTR-6 was studied. The progress of the bioreaction was monitored in terms of biomass production, product formation and substrate consumption in shake flask experiments using different initial sugar concentrations. A logistic model for biomass growth was found to be satisfactory. Average estimates of the specific growth rate, biomass yield coefficient and maintenance coefficients were obtained.     

CoMo sulfide-catalyzed hydrodeoxygenation of lignin model compounds: An extended reaction network for the conversion of monomeric and dimeric substrates

In the present work, extensive hydrodeoxygenation (HDO) studies with a commercial sulfided CoMo/Al₂O₃ catalyst were performed on a library of lignin model compounds at 50 bar hydrogen pressure and 300 °C in dodecane, using a batch autoclave system. The catalyst was activated under hydrogen atmosphere prior to the reaction, and the spent catalyst was analyzed using thermogravimetric analysis. An extended reaction network is proposed, showing that HDO, demethylation, and hydrogenation reactions take place simultaneously. HDO of mono-oxygenated substrates proved to be difficult at the applied conditions. Starting from most positions in the network, phenol, and cresols are therefore the main final products, suggesting the possibility of convergence on a limited number of products from a mixture of substrates. HDO of dimeric model compounds mimicking typical lignin linkages revealed that coumaran alkyl ethers and β-O-4 bonds can be broken, but 5–5′ linkages not.     

A mechanistic growth model for inorganic crystals: Solid‐state interactions

Growth shapes of inorganic crystalline solids govern material properties such as catalytic activity and selectivity, solar cell efficiency, and so forth. A systematic understanding of the crystal growth process and the solid‐state interactions within inorganic crystals should help to engineer crystal shapes. A general model that identifies periodic bond chains in inorganic crystals while accounting for the long‐range electrostatic interactions is presented. The variation in the electronic structure and the partial charges of growth units on the inorganic crystal surfaces has been captured using the bond valence model. The electrostatic interaction energies in the kink sites of inorganic crystals were calculated using a space partitioning method that is computationally efficient. This model provides a quantitative explanation for the asymmetric growth spirals formed on the surface of calcite. This methodology for studying solid‐state interactions can be used with a mechanistic growth model to predict the morphology of a wide variety of inorganic crystals. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3707–3719, 2014     

ZL50活性炭吸附脱除二氧化硫的吸附动力学模型(英文)

A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO2 in flue gas by carbon adsorbents for flue gas purification. The change in adsorption capacity and adsorption rate with time at different water vapor concentrations and different SO2 concentrations was studied. The model was in good agreement with experimental data. The surface reaction was probably the rate controlling step in the early stage for SO2 adsorption by ZL50 activated carbon. The parameters m and n in the nth order adsorption kinetic model were related to the magnitude of the time compensation and adsorption driving force, respectively. The change of parameter n with water vapor concentrations and sulfur dioxide concentrations was studied and some physical implications were given. The sum of square errors was less than 1.0 and the average absolute percentage deviations ranged from 0.5 to 3.2. The kinetic model was compared with other models in the literature.     

一种用于评价洗发水去屑功效的体外生物模型

以马拉色菌作为指示菌,建立了一种以猪皮为载体的生物模型。该生物模型可以用于评价头发护理产品的去屑功效。包含以下步骤:载体前处理;指示菌的接种;用洗发水处理猪皮模型,采用平板接触法进行抑菌效果测试;计算平板上马拉色菌的生长面积与平板面积之比作为有效指数P;以有效指数P评价产品的去屑功效。去屑剂评价结果表明,在0.1%~2.0%范围内,抑菌整体作用排序为BPTZPTOCT。洗发水评价结果表明:1种洗发水无去屑功效;3种洗发水有去屑功效;2种洗发水有较强去屑功效。     

An improved integral non-linear model for the contact of particles in distinct element simulations

In this paper we consider a non-linear model for the elastic-frictional contact of spherical particles based on a modification of the classical Hertz-Mindlin no-slip solution. The characteristics of the original model are described and discussed in terms of the capabilities to simulate collisions using the distinct element method (DEM). Perfectly elastic collisions in normal direction and elastic-frictional mechanisms in tangential direction are considered for impacts of a sphere with a flat wall at various angles. On this basis, we suggest a mathematical modification of Mindlin's tangential solution and demonstrate formally its advantages with respect to the commonly used model. We illustrate a comparison of the proposed model with other commonly used models and a validation of the models against experimental data, available under similar conditions (Kharaz et al., Powder Technology 120 (2001) 281). It is shown that an improved realism and consistency is obtained with our modification, especially regarding the tangential displacement and force-displacement relation, at the cost of a very simple modification of the model algorithm.     

An extended DEM–CFD model for char combustion in a bubbling fluidized bed combustor of inert sand

This paper proposes a transient three-phase numerical model for the simulation of multiphase flow, heat and mass transfer and combustion in a bubbling fluidized bed of inert sand. The gas phase is treated as a continuum and solved using the computational fluid dynamics (CFD) approach; the solid particles are treated as two discrete phases with different reactivity characteristics and solved on the individual particle scale using an extended discrete element model (DEM). A new char combustion submodel considering sand inhibitory effects is also developed to describe char particle combustion behavior in the fluidized bed. Two conditions, i.e. a single larger graphite particle and a batch of smaller graphite particles, are used to test the prediction capability of the model. The model is validated by comparing the predicted results with the previous measured results and conclusions in the literature in terms of bed hydrodynamics, individual particle temperature, char residence time and concentrations of the products. The effects of bed temperature, oxygen concentration and superficial velocity on char combustion behavior are also examined through model simulation. The results indicate that the proposed model provides a proximal approach to elucidate multiphase flow and combustion mechanisms in fluidized bed combustors.     

An integrated model for predicting the flame propagation in crimped ribbon flame arresters

Crimped ribbon flame arresters are important safety devices in the chemical industry,especially for the dangerous situations.Although proper design of arresters by the numerical simulation method is promising,its reliability and accuracy are dependent upon the mathematical model.In this work,an integrated mathematical model for the microchannel in the crimped ribbon flame arresters was set up;the fluid flow behavior and the sensitivities of four chemical kinetics mechanisms of propane-air on the accuracy were analysed.It is shown that turbulence is predominant in the microchannel of the crimped ribbon flame arresters under the deflagration and detonation conditions,and a new quenching criterion for the numerical simulation is proposed.The kinetics mechanism of Mansouri et al.among the four ones is the most accurate due to the best agreement of the predicted outlet temperature at the experimental flameproof velocity with the autoignition temperature of propane-air.The species mass fraction profiles and the temperature distribution,which are too difficult to measure due to the tiny dimension of the microchannel in experiments,are captured.The fundamental insights into chemical reactions and heat loss are well portrayed.It can be concluded that the integrated mathematical model established in this work can be used as a reliable tool for modeling,selecting and designing such type of crimped ribbon flame arresters with the propane-air medium in the future.     

An analytical two-temperature model for convection-diffusion in multilayered systems: Application to the thermal characterization of microchannel reactors

The main purpose of this paper is to implement some convenient analytical solutions of the two-dimensional convection-diffusion equations in a multilayered system, in the form of some relationships between average temperature fields, based on the thermal quadrupole formalism. Some equivalent analogical networks are proposed in order to implement the model in a more convenient form, based on the electrical analogy. The important advantage of such approach is to connect different layers through simple network connections between the respective interface variables. Special emphasis is laid on the case where the lateral boundary conditions correspond to insulated walls. The transient case is also presented, for non-insulated lateral boundary conditions, coupled with a third layer. Some examples are given in order to illustrate the suitability of the proposed model in the case of temperature field image processing in a microfluidic chip.