共表达分子伴侣蛋白提高III型普鲁兰水解酶在短小芽孢杆菌中的分泌表达及发酵优化

本研究旨在通过共表达分子伴侣蛋白以及优化发酵条件来提高III型普鲁兰水解酶(TK-PUL)在短小芽孢杆菌中的分泌表达水平。通过构建共表达TK-PUL和分子伴侣蛋白的多种重组短小芽孢杆菌,并以胞外酶活为指标对其进行筛选,确定最有利于TK-PUL分泌表达的分子伴侣蛋白及对应的重组短小芽孢杆菌。在此基础上采用单因素实验和响应面法优化重组短小芽孢杆菌的发酵条件。结果表明,共表达分子伴侣蛋白PrsA^(Ba)的重组短小芽孢杆菌的胞外酶活达到98.79 U/mL,提高了0.31倍。该重组短小芽孢杆菌的最佳培养基包括19.65 g/L葡萄糖、21.46 g/L酵母提取物、12.01 g/L MgCl_(2)·6H_(2)O、9.02 g/L脯氨酸、0.01 g/L FeSO4·7H_(2)O、0.01 g/L MnSO4·4H_(2)O、0.001 g/L ZnSO4·7H_(2)O。在发酵温度为35℃、起始发酵pH为7.0的条件下,该重组短小芽孢杆菌于最佳培养基中培养66 h时,其胞外酶活达到192.68 U/mL,提高了1.56倍。本研究通过共表达分子伴侣蛋白和发酵优化实现了TK-PUL在短小芽孢杆菌的高效分泌表达,为TK-PUL的应用提供了基础。

混合牙列期骨性III类错合与骨性I类错合基骨及牙弓对比研究

目的:通过测量混合牙列期骨性III类错合患者与骨性I类错合患者的锥形束计算机断层扫描(Cone beam computed tomography, CBCT),对比分析上下颌牙弓、基骨弓长度与宽度差异及协调性,以期为替牙期骨性III类错合畸形治疗提供参考依据。方法:选择替牙列期骨性III类错合与骨性I类错合各30例,通过Dolphin软件处理收集到的DICOM (Digital Imaging and Communications in Medicine)医学图像数据,行三维重建并测量上下颌牙弓、基骨弓的长度与宽度,计算同一牙段牙弓宽度与基骨弓宽度之间的差值,比较骨性III类与骨性I类错牙合畸形牙弓与基骨弓宽度差值的差异。结果:1) 骨性III类错合组上颌牙弓及基骨弓长度均小于骨性I类错合组,下颌基骨弓长度大于骨性I类错合组,且差异有统计学意义(P 0.05)。2) 骨性III类错合组下颌前段及中段基骨弓宽度大于骨性I类错合组,差异有统计学意义(P 0.05)。3) 骨性III类错合组上颌牙弓与基骨弓宽度的差值均大于骨性I类错合组,下颌牙弓与基骨弓宽度的差值均小于骨性I类错合组,其中上颌后段牙弓宽度与基骨弓宽度差值差异有统计学意义(P < 0.05)。结论:混合牙列期骨性III类错合存在牙弓、基骨弓不调,上颌可扩大基骨弓,下颌可扩大牙弓,以期改善牙弓与基骨弓的协调性。

基于NSGA-III算法求解柔性作业车间调度问题

针对多目标柔性作业车间调度问题,提出一种改进NSGA-Ⅲ算法,以完工时间、机器总负荷、瓶颈机器负荷为目标建立调度模型。首先,为提高种群的多样性,提出一种基于惩罚的边界相交距离定义关联操作中种群个体与参考向量之间的距离;其次,为提高环境选择的计算效率,利用基于惩罚的边界相交距离消除机制来保护个体,降低了个体保护策略的计算成本;最后,为避免种群陷入局部最优,在遗传算子中采用一种改进的变异策略。运用两个评价指标与NSGA-Ⅲ算法进行比较,其收敛性与多样性均由于NSGA-Ⅲ算法。同时在4个Kacem算例上进行测试得出改进NSGA-Ⅲ算法解的质量较高,最后通过实际的生产实例证明改进的NSGA-Ⅲ算法优于或等同于现存在的方法,也证明了该方法在解决多目标柔性作业车间调度难题上的可操作性。

Spectrophotometric Determination of Water-Soluble Hexavalent Chromium and Determination of Total Hexavalent Chromium Content of Portland Cement in the Presence of Iron (III) and Titanium (IV) Using Derivative Ratio Spectrophotometry

A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement with 1, 2, 5, 8 Tetrahydroxyanthraquinone, (Quinalizarin, QINZ) at pH 1.5. The European Directive (2003/53/EC) limits the use of cements so that it contains no more than 2 mg.Kg-1 of water-soluble Cr (VI). The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement. The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances). The validity of the method is thoroughly examined and the proposed method gives satisfactory results. A derivative spectrophotometric method has been developed for the determination of total Cr (VI) in Portland cement in the presence of Fe (III) and Ti (IV). The hexavalent chromium complex formed at pH 1.5 allows precise and accurate determination of chromium (VI) over the concentration range 0.05 to 3.0 mg.L-1of chromium (VI). The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The MDL (at 95% confidence level) was found to be 25 ng/mL for chromium (VI) in National Institute of Standards and Technology (NIST) cement samples using the proposed method.

Evaluation of Acute Chromium (III) Toxicity in Relation to Daphnia Similis

Acute chromium (III) toxicity in relation to Daphnia similis, most appropriate for Brazilian environment has been evaluated. The preliminary toxicity test showed that the median effective concentration was 10 mg/l. After having performed the final test, the immobility percentage was calculated for each concentration in relation to the total number of the used organisms within the chosen pH range. It was shown that the proposed methodology rendered realistic results and the 48-h CE50 value under the test conditions is 3.24 mg/l. The minimum concentration that did not show any toxicity to Daphnia similis was 2.5 mg of chromium (III) per liter. The obtained level is superior to the maximum limit recommended by the Brazilian norms, 0.5 mg/l.

Synthesis of Chromium(III) Oxide Nanoparticles by Electrochemical Method and Mukia Maderaspatana Plant Extract, Characterization, KMnO₄Decomposition and Antibacterial Study

Chromium oxide nanoparticles were synthesized by the reduction of potassium dichromate solution with Mukia Maderaspatana plant extract. In electrochemical methods, Cr2O3 nanoparticles were synthesized by two ways, using platinum (Pt) electrodes and K2Cr2O7 solution with H2SO4 as medium in the first case. And chromium doped platinum electrode (Pt/Cr) in presence of NaHCO3 solution in second case. The resulting Cr2O3 nanoparticles were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-VIS absorption and Fourier-transform infrared (FTIR) spectroscopy. The enhancing influence of Cr2O3 nanoparticles as a catalyst for the decomposition of KMnO4 has been studied. The antibacterial effect of Cr2O3 nanoparticles against E. coli was investigated. These particles were shown to have an effective bactericide.

Trace amount of chromium（III） in waste water measured by extraction spectrophometry in H2CrO6-n-CsH11OH system

A novel, simple, rapid, economic and hypersensitive method of measuring Cr3＋ is described in this paper. Cr3＋ could be oxidated to H2CrO6, which is extracted by n-C5H11OH, so a trace amount of chromium is measured directly by spectrometers, Sandra sensitivity is S=6.40×10^-3 ug.cm-2.

The Electrode for Potentiometric Determinаtion of Chromium (III, VI) in Wаter Solutions

The possibility of determining of chromium (III, VI) ions was investigated in this paper. It is shown that the electrode on а basis of heаzlewoodite has high selectivity to chromium (III) ions. Also the stability constants of complexes, forming in system “Cr3+-Mohr’s salt-Ca(OH)2-PVA ÷ PAA” were determined by potentiometric titration with ion-selective electrode.

Removal of Chromium(III) from the Waste Solution of an Indian Tannery by Amberlite IR 120 Resin

The extraction of chromium(III) from a model waste solution and also from a waste solution of an Indian tannery with Amberlite IR 120 resin is described, and the performance of this resin is compared with other similar resins. The parameters that were optimized include effect of mixing time, pH, loading and elution behaviours of chromium(III) for this resin. Sorption of chromium(III) on Amberlite IR 120 followed Freundlich isotherm and Langmuir isotherm model, and the maximum sorption capacity was determined to be 142.86 mg Cr(III)/g of the resin. Higher Freundlich constant (Kf) values (6.30 and 13.46 for aqueous feed of 500 and 1000 ppm Cr(III)) indicated strong chemical interaction through ion exchange mechanism of the metal ion with the resin. The kinetic data showed good fit to the Lagergren first order model for extraction of chromium(III). Desorption of chromium(III) from the loaded resin increased with the increase in concentration of eluent (5-20% H2SO4). With 20% (v/v) sulphuric acid solution 94% chromium(III) was eluted in three stages. Elution of the Cr(III) in the column experiments was however, found to be lower (82%) than that of the shake flask data. In case of Indian tannery’s waste solution, it was observed that almost total chromium was extracted in four stages with Amberlite IR 120.

Kinetics and Mechanism of Interaction between Chromium(III) and Ethylenediaminetetra-3-Propinate in Aqueous Acidic Media

The kinetics of the formation of 1:1 complex of chromium(III) with ethylenediaminetetra-3-propinate (EDTP) was followed spectrophotometrically at lmax = 557 nm. The reaction was found to be first order in chromium(III) and was accelerated by EDTP. Increasing the pH from 3.3 to 4.7 accelerated the reaction rate, the reaction rate was retarded by increasing ionic strength and dielectric constant of the reaction medium. A mechanism was suggested to account for the results obtained which involves ion pair formation between the various species of the reactants. Values of the activation parameters obtained indicate an associative mechanism.

Removal and Recovery of Chromium(III) from Aqueous Chromium(III) Using <i>Arthrobacter nicotianae</i>Cells

The removal of Cr(III) from aqueous Cr(III) using Arthrobacter nicotianae cells was examined. Cr(III) removal was strongly affected by the pH of the solution and the amounts of Cr(III) removed increased as the pH (1 - 5) of the solution increased. The removal of Cr(III) using the cells was also strongly affected by the Cr(III) concentration of the solution, and obeyed the Langmuir isotherm. The percentage of Cr increased as the cell quantity increased, whereas the amount of Cr (μmol/g dry wt. cells) decreased. The removal of Cr(III) using the cells was very fast, and reached an equilibrium within 6 h from the supply of Cr(III) in the solution. A small amount of Cr(III) absorbed by immobilized cells was desorbed at 30oC;however, most was desorbed at reflux temperature using diluted HCl. Cr(III) adsorption-desorption cycles can be repeated 5 times using immobilized cells. These results have practical implications for industrial wastewater management.

Spectrophotometric Determination of Trace Chromium(VI) in Mass Chromium(III)

The method for the sepration and determination of trace Cr(VI) exiting in mass Cr(III) has been researched. The method is highly sensitive and less interference, but is simple and useful for analysis trace Cr(VI).

Thermodynamic Properties of Chromium (III) Ion Adsorption by Sweet Orange (<i>Citrus sinensis</i>) Peels

The adsorption of Cr (III) ion from aqueous solution using orange peels as adsorbent was investigated using batch equilibrium technique. The research is significant as it’s aimed at investigating the suitability of orange peel, a waste product as adsorbent for the adsorption of Cr (III) ions from aqueous solution. Orange peel as an adsorbent is resource-saving and has an environmental friendly behavior. Adsorption envelope experiment was conducted using a constant Cr (III) ion concentration of 0.1 M, adsorbent dose of 2.5 g and a temperature of 30°C at varying solution pH of 2, 4, 7, 9 and 12 respectively with pH of 2 having the highest adsorption and therefore it was selected for use in the adsorption isotherm experiment. Adsorption isotherm experiment was conducted at varying temperatures (30°C, 40°C, 50°C, 60°C), concentration (0.1 M, 0.2 M and 0.3 M) Cr(NO3)3. Thermodynamic parameters such as ΔG, ΔH, ΔHr, ΔA, and ΔS were calculated from the experimental data which showed that the adsorption process is feasible, spontaneous and followed physisorption mechanism 9H2O and adsorbent dosage (1 g, 1.5 g and 2 g) respectively. The experimental results were tested using Langmuir, Freundlich, Linear and Temkin adsorption isotherm models. The experimental data best fitted the Freundlich isotherm model. The experimental results revealed the suitability of orange peel which is a waste product as effective adsorbent for the sorption of chromium (III) ions from aqueous solution.

Periodate Oxidation of a Ternary Complex of Nitrilotriacetatochromium(III) Involving ß-Alanine as Co-Ligand

The kinetics of the periodate oxidation of chromium(III)-complex, [CrIII(NTA)(Ala)(H2O)]-(NTA = Nitrilotriacetate and Ala = &#223;-alanine) to Cr(VI) have been carried out for the temperature range 15°C - 35°C under pseudo-first order conditions, >>?[complex]. Reaction obeyed first order dependence with respect to and [Cr(III)], and the rate of reaction increases with increasing of pH for the range 3.40 - 4.45. Experimentally, the mechanism of this reaction is found to be consistent with the rate law in which the hydroxo species, [CrIII(NTA)(Ala)(OH)]2- is considerably much more reactive than their conjugate acid. ΔH* and ΔS* have been calculated. It is proposed that electron transfer occurs through an inner-sphere mechanism via coordination of to chromium(III).

Removal of Chromium(VI) from Aqueous Solution Using Persimmon Tannin Gel and Subsequent Recovery as Chromium(III)

This study herein was investigated the removal of chromium(VI) from an aqueous solution using persimmon tannin gel and its subsequent recovery as chromium(III). At pH 2, Cr(VI) was effectively adsorbed (~80% adsorption) and ppm solution was reduced to Cr(III) on the persimmon gel within 10 min. Although desorption of the Cr(III) species was challenging at 30°, it was increased upon increasing the temperature and was quantitatively desorbed in the presence of 1 M hydrochloric acid under reflux. In addition, although the quantity of retained Cr(VI) on the tannin gel increased upon increasing the chromium concentration of the original aqueous solution, all the desorbed chromium was successfully reduced to Cr(III). Finally, Cr(VI) removal and recovery as Cr(III) was repeated effectively 8 times using the same persimmon tannin gel sample, thus demonstrating the recyclability of this system.

A Chiral Three Dimensional Potassium(I)/Strontium(II)/Chromium(III) Oxalato-Bridged Coordination Polymer: Synthesis, Characterization and Thermal Analysis

A new compound of general formula {[(H2O)2K(μ-H2O)Sr]@[Cr(C2O4)3]}n (1) has been synthesized in water and characterized by elemental and thermal analyses, EDX, IR and UV-Vis spectroscopies and by single crystal X-ray structure determination. Compound 1 crystallizes in the chiral space group Fdd2 of orthorhombic system with a = 14.110 (4) ?, b = 36.074 (11)?, c =11.034 (3)? and Z = 16. Compound 1 is a coordination polymer in which the three-dimensional lattice framework is realized by the interconnectivity between K+ cations, Sr2+ cations, aqua ligands and [Cr(C2O4)3]3– complex anions. The asymmetric unit of 1 consists of one cationic motif formally written [(H2O)2K(μ-H2O)Sr]3+ and one anionic entity, [Cr(C2O4)3]3–. The K+ and Sr2+ ions in the cationic motif are both eight-coordinate while the Cr3+ ions in the anionic complex are six-coordinate in a distorted octahedral geometry. Coulombic interactions between the ionic motifs and the three-dimensional H-bonding involving aqua ligands help to consolidate the bulk structure. Thermogra-vimetric analysis (TGA) shows that compound 1 is stable to heat up to ca. 80℃.

Green-synthesized, biochar-supported nZVI from mango kernel residue for aqueous hexavalent chromium removal: Performance, mechanism and regeneration

A biochar-supported green nZVI(G-nZVI@MKB)composite was synthesized using mango kernel waste with“dual identity”as reductant and biomass of biochar.The G-nZVI@MKB with a Fe/C mass ratio of 2.0(G-nZVI@MKB2)was determined as the most favorable composite for hexavalent chromium(Cr(VI))removal.Distinct influencing parameters were discussed,and 99.0%of Cr(VI)removal occurred within 360 min under these optimized parameters.Pseudo-second order kinetic model and intra-particle diffusion model well depicted Cr(VI)removal process.The XRD,FTIR,SEM,and XPS analyses verified the key roles of G-nZVI and functional groups,as well as the primary removal mechanisms involving electrostatic attraction,reduction,and complexation.G-nZVI@MKB2 exhibited good stability and reusability with only a 16.4%decline in Cr(VI)removal after five cycles.This study offered evidence that mango kernel could be recycled as a beneficial resource to synthesize green nZVI-loaded biochar composite for efficient Cr(VI)elimination from water.

Enhanced visible-light-driven reduction of hexavalent chromium under neutral conditions using quasi-MOF photocatalysts via thiocyanate modulation

In order to address the issue that the photocatalytic reduction of hexavalent chromium(Cr(VI))is often limited by the inefficient utilization of electrons in photocatalysts,a quasi-MOF photocatalyst using thiocyanate(-SCN)was developed as a modulator to enhance the charge transfer properties of ZIF-L-based photocatalysts.The incorporation of-SCN introduced structural defects,which improved visible light absorption and the reduction ability of photogenerated electrons.-SCN significantly adjusted the electronic properties and established a stable electron release pathway,serving as active sites for reduction.The optimized quasi-MOF demonstrated a Cr(VI)reduction rate of 94.8%in neutral potassium thiocyanate solution under visible light without a hole scavenger.The reaction rate constant is 2.8 times that of the photocatalyst without defect modulation.This study offers a promising strategy for developing highly efficient photocatalysts for environmental remediation.

Solidification/Stabilization of Chromium in Red Mud-based Geopolymer

Up to 1.5wt%of Cr(Ⅲ)salts(CrCl_(3),and Cr_(2)O_(3))and Cr(Ⅵ)salts(Na_(2)CrO_(4),and CaCr_(2)O_(7))were incorporated into red mud-based geopolymers,respectively.The solidification/stabilization,compressive strength,and durability of the Cr-containing geopolymers were investigated.The experimental results indicate that the red mud-based geopolymer could effectively solidify/stabilize different types of Cr salts with solidification/stabilization rates of above 99.61%.Geopolymers are environmentally safe when the dosage of CaCr_(2)O_(7)is≤1.0wt%,or the dosage of CrCl_(3),Cr_(2)O_(3),and Na_(2)CrO_(4)is≤1.5wt%,respectively.The effects of Cr salts on the compressive strength varies with the type and content of Cr salts.The freeze-thaw cycle is more destructive to geopolymer properties than sulfate attack or acid rain erosion.The solidification/stabilization of Cr is mainly attributed to the following reasons:a)The chemical binding of Cr is related to the formation of Cr-containing hydrates(eg,magnesiochromite((Mg,Fe)(Cr,Al)_(2)O_(4)))and doping into N-A-S-H gel and C-A-S-H gel framework;b)The physical effect is related to the encapsulation by the hydration products(e g,N-A-S-H gel and C-A-S-H gel).This study provides a reference for the treatment of hazardous Cr-containing wastes by solid waste-based geopolymers.

基于改进NSGA-III算法的多无人机协同目标分配

武器-目标分配问题是战场环境下无人机对敌方执行打击任务的关键,其目的是基于目标的威胁、价值和我方武器的毁伤概率,寻找合理的武器目标分配方案,以提高作战效率。针对当前多目标优化算法解决静态武器-目标分配问题时收敛速度慢、收敛稳定性差,难以适应当前战场高度实时性的问题,提出一种改进的基于参考点的非支配排序遗传算法。通过二进制编码打击方案并优化初始种群,引入自适应变异与交叉策略以及种群寻优更新策略,基于对战场态势进行评估得到的威胁矩阵和优势矩阵,种群多次迭代后生成目标打击方案。最后计算满足约束条件的Pareto解集,并将Pareto前沿中的相对最优解作为多无人机的打击方案。多次实验证明,在较好情况下改进算法相比于原始算法的收敛时间减少46.74%,目标威胁值降低50.5%,总飞行航程减少26.46%,杀伤目标数增加11.76%,证明该算法在解决多无人机空对地打击任务目标分配问题时具有合理性和高效性。