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化学示踪剂是研究干旱区地下水化学演化和补给来源追踪的有效手段之一。本文以Cl-为示踪剂,通过其他离子与Cl-的相互关系对石羊河流域地下水演化特征及影响因子进行分析:Br-/Cl-、Na+/Cl-、S042-/Cl-、HCO3-/Cl-、Ca2+/Cl-、Mg2+/Cl-相互关系指示了流域中游地区地下水与地表水补给关系密切,水质较好,水化学作用以溶滤为主,蒸发也起到一定作用,下游盆地地下水矿化度较高,不完全是现代降水的补给,石膏、方解石溶解和阳离子交换作用使得地下水富镁。总体而言,石羊河流域地下水演化在多种地球化学作用下进行,在以蒸发为主导动力的条件下,水岩相互作用和阳离子交换过程促使地下水演化为现代特征。 相似文献
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Hui Liu Xiaohua Li Xiaoping Liu Huanqing Wang 《Journal of The Franklin Institute》2019,356(15):8049-8079
In this paper, a novel decentralized adaptive neural control approach based on the backstepping technique is proposed to design a decentralized H∞ adaptive neural controller for a class of stochastic large-scale nonlinear systems with external disturbances and unknown nonlinear functions. RBF neural networks are utilized to approximate the packaged unknown nonlinearities. A novel concept with regard to bounded-H∞ performance is proposed. It can be applied to solve an H∞ control problem for a class of stochastic nonlinear systems. The constant terms appeared in stability analysis are dealt with by using Gronwall inequality, so that H∞ performance criterion is satisfied. The assumption that the approximation errors of neural networks must be square-integrable in some literature can be eliminated. The design process for decentralized bounded-H∞ controllers is given. The proposed control scheme guarantees that all the signals in the resulting closed-loop large-scale system are uniformly ultimately bounded in probability, and each subsystem possesses disturbance attenuation performance for external disturbances. Finally, the simulation results are provided to illustrate the effectiveness and feasibility of the proposed approach. 相似文献
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BackgroundFreeze-drying is known as one of the best methods to preserve bacterial strains. Protectant is the key factor affecting the survival rate of freeze-dried strains. In addition, salinity, bacterial suspension concentration, drying time, and other factors can also affect the survival rate of strains to varying degrees. At present, there are relatively few studies on freeze-drying preservation of marine bacteria. In the present study, we performed the freeze-drying protectant screening and optimized the preservation conditions for Pseudoalteromonas nigrifaciens, which is widely distributed in marine environment. The protective effects of the screened protectants were verified by 18 other marine bacterial strains.ResultsThe results indicated that the combination of 5.0% (w/v) lactose, 5.0% (w/v) mannitol, 5.0% (w/v) trehalose, 10.0% (w/v) skim milk powder, 0.5% (w/v) ascorbic acid and 0.5% (w/v) gelatin was the best choice for the preservation of P. nigrifaciens. The suggested salinity and concentration of initial cell suspension were 10 g/L NaCl and 1.0 × 109 CFU/mL, respectively. Furthermore, stationary-phase cells were the best choice for the freeze-drying process. The highest survival rate of P. nigrifaciens reached 52.8% when using 5–10% (w/v) skim milk as rehydration medium. Moreover, the other 18 marine strains belonging to Pseudoalteromonas, Vibrio, Photobacterium, Planomicrobium, Edwardsiella, Enterococcus, Bacillus, and Saccharomyces were freeze-dried under the abovementioned conditions. Their survival rates were 2.3–95.1%.ConclusionCollectively, our results supported that the protectant mixture and parameters were beneficial for lyophilization of marine bacteria.How to cite: Zhang Z, Yu Y, Wang Y, et al. Development of new protocol for freeze-drying preservation of Pseudoalteromonas nigrifaciens and its protective effect on other marine bacteria. Electron J Biotechnol 2020;44. https://doi.org/10.1016/j.ejbt.2019.12.006. 相似文献
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BackgroundLarge amounts of β-alanine are required in fine chemical and pharmaceutical synthesis and other fields. Profitable and green methods are required for the industrial production of β-alanine.ResultsReplacing endogenous panD of Escherichia coli with heterologous CgpanD from Corynebacterium glutamicum enabled β-alanine synthesis of 0.67 g/L by strain B0016-082BB. Overexpressing CgpanD on both plasmids and chromosomes to enhance the rate-limiting step improved the β-alanine titer to 4.25 g/L in strain B0016-083BB/pPL451-panD with a slighter metabolic burden. Growth factors were introduced by addition of yeast extract, and 6.65 g/L of β-alanine was synthesized by strain B0016-083BB/pPL451-panD in the M9-3Y medium.ConclusionsEnhancement of the rate-limiting steps in the β-alanine biosynthetic pathway, recruitment of the temperature-sensitive inducible pL promoter, and optimization of the fermentation process could efficiently increase β-alanine production in E. coli.How to cite: Xua J, Zhua Y, Zhou Z. Systematic engineering of the rate-limiting step of β-alanine biosynthesis in Escherichia col. Electron J Biotechnol 2021;51. https://doi.org/10.1016/j.ejbt.2021.03.002. 相似文献
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BackgroundIn industrial yeasts, selection and breeding for resistance to multiple stresses is a focus of current research. The objective of this study was to investigate the tolerance to multiple stresses of Saccharomyces cerevisiae obtained through an adaptive laboratory evolution strategy involving a repeated liquid nitrogen freeze–thaw process coupled with multi-stress shock selection. We also assessed the related resistance mechanisms and very high-gravity (VHG) bioethanol production of this strain.ResultsElite S. cerevisiae strain YF10-5, exhibiting improved VHG fermentation capacity and stress resistance to osmotic pressure and ethanol, was isolated following ten consecutive rounds of liquid nitrogen freeze–thaw treatment followed by plate screening under osmotic and ethanol stress. The ethanol yield of YF10-5 was 16% higher than that of the parent strain during 35% (w/v) glucose fermentation. Furthermore, there was upregulation of three genes (HSP26, HSP30, and HSP104) encoding heat-shock proteins involved in the stress response, one gene (TPS1) involved in the synthesis of trehalose, and three genes (ADH1, HXK1, and PFK1) involved in ethanol metabolism and intracellular trehalose accumulation in YF10-5 yeast cells, indicating increased stress tolerance and fermentative capacity. YF10-5 also showed excellent fermentation performance during the simultaneous saccharification and fermentation of VHG sweet potato mash, producing 13.40% (w/v) ethanol, which corresponded to 93.95% of the theoretical ethanol yield.ConclusionsA multiple-stress-tolerant yeast clone was obtained using adaptive evolution by a freeze–thaw method coupled with stress shock selection. The selected robust yeast strain exhibits potential for bioethanol production through VHG fermentation.How to cite: Zhang Q, Jin Y, Fang Y, et al. Adaptive evolution and selection of stress-resistant Saccharomyces cerevisiae for very high gravity bioethanol fermentation. Electron J Biotechnol 2019;41. https://doi.org/10.1016/j.ejbt.2019.06.003 相似文献
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A.A. Raptis 《Journal of The Franklin Institute》1983,316(6):445-449
This paper investigates the effects of a magnetic field on the free convective flow of a viscous, incompressible, dissipative fluid through a porous medium, occupying a semi-infinite region of the space bounded by an infinite vertical and porous plate. The plate is subjected to a normal suction velocity and the heat flux at the plate is constant. The magnetic field is of uniform strength and is applied perpendicular to the plate. An analytical solution to the problem is obtained. The influence of the magnetic parameter (M) and permeability parameter (K) is discussed for the case of air (P = 0.71) when the plate is subjected to a constant suction velocity and is being cooled by free convection currents. 相似文献
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BackgroundEthanol concentration (PE), ethanol productivity (QP) and sugar consumption (SC) are important values in industrial ethanol production. In this study, initial sugar and nitrogen (urea) concentrations in sweet sorghum stem juice (SSJ) were optimized for high PE (≥ 10%, v/v), QP, (≥ 2.5 g/L·h) and SC (≥ 90%) by Saccharomyces cerevisiae SSJKKU01. Then, repeated-batch fermentations under normal gravity (NG) and high gravity (HG) conditions were studied.ResultsThe initial sugar at 208 g/L and urea at 2.75 g/L were the optimum values to meet the criteria. At the initial yeast cell concentration of ~ 1 × 108 cells/mL, the PE, QP and SC were 97.06 g/L, 3.24 g/L·h and 95.43%, respectively. Repeated-batch fermentations showed that the ethanol production efficiency of eight successive cycles with and without aeration were not significantly different when the initial sugar of cycles 2 to 8 was under NG conditions (~ 140 g/L). Positive effects of aeration were observed when the initial sugar from cycle 2 was under HG conditions (180–200 g/L). The PE and QP under no aeration were consecutively lower from cycle 1 to cycle 6. Additionally, aeration affected ergosterol formation in yeast cell membrane at high ethanol concentrations, whereas trehalose content under all conditions was not different.ConclusionInitial sugar, sufficient nitrogen and appropriated aeration are necessary for promoting yeast growth and ethanol fermentation. The SSJ was successfully used as an ethanol production medium for a high level of ethanol production. Aeration was not essential for repeated-batch fermentation under NG conditions, but it was beneficial under HG conditions.How to cite: Sriputorn B, Laopaiboon P, Phukoetphim N, et al. Enhancement of ethanol production efficiency in repeated-batch fermentation from sweet sorghum stem juice: Effect of initial sugar, nitrogen and aeration. Electron J Biotechnol 2020;46. https://doi.org/10.1016/j.ejbt.2020.06.001 相似文献
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偶应力问题的非协调元分析 总被引：2，自引：0，他引：2
从偶应力弹性体势能泛函的驻值条件出发,得到了偶应力理论中非协调元体系的能量相容原理。基于其常应力(常偶应力)分片检验条件的强形式,对平面四结点单元的非协调试探内函数进行了优化,提出了一种稳定有效的非协调元方法。有限元列式中,微转动和宏观转动相等的约束条件通过罚因子的形式引入。分析了含中心圆孔的无限平板,在单轴拉伸以及纯剪状态时,偶应力的存在对孔周应力集中的影响。算例表明,该单元计算效率高,精度好,即使在材料本征长度很小时,仍然能够得到相当理想的结果 相似文献
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M. Sobral 《Journal of The Franklin Institute》1975,300(3):209-212
Given the linear system = Ax - bu, y = cTx, it is shown that, for a certain non-quadratic cost functional, the optimal control is given by uopt(x) = h(cTx), where the function h(y) must satisfy the conditions ky2?h(y)y>0 for y≠0, h(0) = 0 and existence of h-1 everywhere. The linear system considered must satisfy the Popov condition 1/k + (1 +?ωβ) G(?ω)>0 for all ω, G(s) being the y(s)/u(s) transfer function. 相似文献
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BackgroundThe 11S globulin from amaranth is the most abundant storage protein in mature seeds and is well recognized for its nutritional value. We used this globulin to engineer a new protein by adding a four valine-tyrosine antihypertensive peptide at its C-terminal end to improve its functionality. The new protein was named AMR5 and expressed in the Escherichia coli BL21-CodonPlus(DE3)-RIL strain using a custom medium (F8PW) designed for this work.ResultsThe alternative medium allowed for the production of 652 mg/L expressed protein at the flask level, mostly in an insoluble form, and this protein was subjected to in vitro refolding. The spectrometric analysis suggests that the protein adopts a β/α structure with a small increment of α-helix conformation relative to the native amaranth 11S globulin. Thermal and urea denaturation experiments determined apparent Tm and C1/2 values of 50.4°C and 3.04 M, respectively, thus indicating that the antihypertensive peptide insertion destabilized the modified protein relative to the native one. AMR5 hydrolyzed by trypsin and chymotrypsin showed 14- and 1.3-fold stronger inhibitory activity against angiotensin I-converting enzyme (IC50 of 0.034 mg/mL) than the unmodified protein and the previously reported amaranth acidic subunit modified with antihypertensive peptides, respectively.ConclusionThe inserted peptide decreases the structural stability of amaranth 11S globulin and improves its antihypertensive activity.How to cite: Espinosa-Hernández E, Morales-Camacho JI, Fernández-Velasco DA, et al. The insertion of bioactive peptides at the C terminal end of an 11S globulin changes the structural stability and improves the antihypertensive activity. Electron J Biotechnol 2019;37. https://doi.org/10.1016/j.ejbt.2018.11.001. 相似文献
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Mathematical results are derived, which enable one to find a vector of parameters k0 such that (P1(s,k0)?H)∩(P2(k0)=0), where P1(s,k) is a polynomial in s and in the components of k,P2(k) is a polynomial in the components of k, and H is the set of Hurwitz polynomials. The algorithm is based on an extension of the root locus technique to the multiparameter case. The design problem of coupling networks between a resistive generator and a passive load, under prescribed power gain characteristics, is translated into the above formulation. A numerical example is provided. 相似文献
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In this paper, fault detection and isolation (FDI) in linear uncertain dynamic systems is addressed. The main contributions consist of the formulation of the FDI problem as a filter-based multi-objective optimization problem and the study of the tools used for the solution. The design objectives are formulated in terms of H∞, H- and generalized H2 performance specifications as well as regional constraints on filter poles. The problem is solved using linear matrix inequality (LMI) and generalized structured singular value (μg) techniques. Special design features are illustrated through a simulation example and experimental results from a controlled hydraulic process are provided to demonstrate the potential of the proposed procedure. 相似文献
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Cong Liu Feng An Paria S M Gharavi Qinwen Lu Junkun Zha Chao Chen Liming Wang Xiaozhi Zhan Zedong Xu Yuan Zhang Ke Qu Junxiang Yao Yun Ou Zhiming Zhao Xiangli Zhong Dongwen Zhang Nagarajan Valanoor Lang Chen Tao Zhu Deyang Chen Xiaofang Zhai Peng Gao Tingting Jia Shuhong Xie Gaokuo Zhong Jiangyu Li 《国家科学评论(英文版)》2020,7(1):84
Complex oxides with tunable structures have many fascinating properties, though high-quality complex oxide epitaxy with precisely controlled composition is still out of reach. Here we have successfully developed solution-based single-crystalline epitaxy for multiferroic (1-x)BiTi(1-y)/2FeyMg(1-y)/2O3–(x)CaTiO3 (BTFM–CTO) solid solution in large area, confirming its ferroelectricity at the atomic scale with strong spontaneous polarization. Careful compositional tuning leads to a bulk magnetization of 0.07 ± 0.035 μB/Fe at room temperature, enabling magnetically induced polarization switching exhibiting a large magnetoelectric coefficient of 2.7–3.0 × 10−7 s/m. This work demonstrates the great potential of solution processing in large-scale complex oxide epitaxy and establishes novel room-temperature magnetoelectric coupling in epitaxial BTFM–CTO film, making it possible to explore a much wider space of composition, phase, and structure that can be easily scaled up for industrial applications. 相似文献
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BackgroundThe harmful effects of type 2 diabetes mellitus and its complications have become a major global public health problem. In this study, the effects of Momordica charantia saponins (MCS) on lipid metabolism, oxidative stress, and insulin signaling pathway in type 2 diabetic rats were investigated.ResultsMCS could attenuate the tendency of weight loss of the model rats. It could also improve glucose tolerance; reduce fasting blood glucose, nonesterified fatty acid, triglyceride, and total cholesterol; and increase the insulin content and insulin sensitivity index of the rats. The activity of superoxide dismutase and catalase increased, and the content of malondialdehyde decreased in the liver and pancreas tissues of rats in MCS-treated groups significantly. In addition, the expression of p-IRS-1 (Y612) and p-Akt (S473) increased, and the expression of p-IRS-1 (S307) decreased in the liver tissues and pancreas tissues of rats in MCS-treated groups significantly.ConclusionMCS has an antidiabetic effect, which may be related to its improving the lipid metabolism disorder, reducing oxidative stress level, and regulating the insulin signaling pathway.How to cite: Jiang S, Xu L, Xu X, et al. Anti-diabetic effect of Momordica charantia saponins in rats induced by high-fat diet combined with STZ. Electron J Biotechnol 2020;43. https://doi.org/10.1016/j.ejbt.2019.12.001. 相似文献
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BackgroundAgkistrodon acutus, a traditional Chinese medicine, clinically used in the treatment of rheumatism, tumor, and cardiovascular and cerebrovascular diseases. Due to the unique medicinal value and the difficulty of artificial breeding of Agkistrodon acutus, the supply of Agkistrodon acutus on the market exceeds the demand, and a large number of its adulterants are found on the market. In this study, the cytb gene sequences of Agkistrodon acutus and 9 snakes were compared and analyzed, specific primers were designed, and specific PCR methods were established to detect Agkistrodon acutus medicinal samples on the market.ResultsThis method was successfully applied to distinguish the snake from other adulterated species, and tested 18 Agkistrodon acutus samples randomly purchased from six cities. Twelve samples were counterfeit and six were genuine. The standard reference material of Agkistrodon acutus was cloned by molecular cloning and sequencing, and the gene sequence difference with other species was significant. It shows that the region could be used as the fingerprint region of the target species.ConclusionsThe proposed method can be used as a species-specific marker and can be highly distinguished from other adulterated snake species, which is helpful to effectively avoid the problem of false sale of Agkistrodon acutus.How to cite: Yingnuo L, Yanshuang W, Mingcheng Li, et al. Development of a species-specific PCR assay for authentication of Agkistrodon acutus based on mitochondrial cytochrome b gene. Electron J Biotechnol 2021;49. https://doi.org/10.1016/j.ejbt.2020.07.005 相似文献