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Cracking is a major reason for the failure of magnesium alloy joint. It would be often caused by stress concentration. In this study, a double side gas tungsten arc (GTA) welding of AZ61 magnesium alloy plate and finite element method (FEM) were conducted to investigate the effect of partial melting on the formation of stress cracking in the welded joint. The surface microstructure of cracking formed in the welded seam was characterized by scanning electron microscopy, and software, Sysweld, was used to simulate the thermal history and residual stresses distribution of the weldment. The results indicated that under the influence of stress concentration, the fusion of low melting point eutectic compound β-Mg 17 Al 12 along grain boundaries induced the cracking in the welded seam. This study has theoretical guiding significance to prevent the formation of stress cracking caused by fusion of eutectic compound β-Mg17Al12 , which is especially critical for the manufacturing of magnesium alloy welded components.

The natural transformation of Escherichia coli is a novel and recently developed system that has significance for genetic studies and the biological safety of genetic engineering. However, the mechanisms of transformation, including development of competence and DNA uptake, are not thoroughly understood. In this study, we demonstrated the effect of the general stress response regulator RpoS, which has been associated with E. coli transformation, on natural transformation performed in an “open system”. We find that RpoS is required for natural transformation but not to artificial transformation and RpoS mainly affect transformation in the liquid culture prior to plating. In the liquid culture, RpoS over-expression promotes natural transformation in early exponential phase and static incubation accumulates RpoS and promotes transformation to a limited extent. These findings provide detailed understanding of RpoS function on natural transformation.

Rh(III)-catalyzed C−H activation features mild reaction conditions, good functional group tolerance, high reaction efficiency, and regioselectivity. Recently, it has attracted tremendous attention and has been employed to synthesize various heterocycles, such as indoles, isoquinolines, isoquinolones, pyrroles, pyridines, and polyheterocycles, which are important privileged structures in biological molecules, natural products, and agrochemicals. In this short review, we attempt to present an overview of recent advances in Rh(III)-mediated C−H bond activation to generate diverse heterocyclic scaffolds with sp3 carbon centers.

Autonomously replicating sequences (ARSs) are essential for genome replication and can regulate gene expression as potential cis-elements; however, the mechanisms underlying this regulation are unclear. In order to understand these mechanisms, we first replaced genes adjacent to ARSs on chromosome III of Saccharomyces cerevisiae with an expression cassette containing the gene encoding red fluorescence protein (RFP) and verified that the relative fluorescence intensity of RFP was positively correlated with the activities of the adjacent ARSs. Then, to investigate the effect of ARSs on gene expression, we designed ARS-insertion and -deletion variants, finding that the insertion of a strongly active ARS adjacent to a weakly active ARS enhanced adjacent gene expression, whereas the deletion of a strongly active ARS reduced the expression of the flanking RFP; however, insertion of multiple strong ARSs did not show a synergistic effect on gene expression. Further analysis suggested that ARSs located in compact chromosomal regions exerted a stronger effect on gene expression than those in relaxed chromosomal regions. These results demonstrated that ARSs regulated S. cerevisiae gene expression by interacting with the chromosome structure and provide a potential strategy for regulating gene expression in synthetic biology and metabolic engineering studies using S. cerevisiae.

The construction quality is always the focus and aim of a project, and how to control and manage the quality of the project is an eternal theme. With the endless stream of new architectural design, increasingly diversity in functions and complexity in professional system, and massive tedious data information, quality and management are facing stern challenge in the new political, economic, social and technological environment. The emergence and popularization of BIM (Information Modeling Building) not only changed the production tools of practitioners, but also provided a new way for engineering quality management. This paper will conduct research and discussion in aspect of the construction quality management in the time of opportunity and challenge.

Compatibility between host cells and heterologous pathways is a challenge for constructing organisms with high productivity or gain of function. Designer yeast cells incorporating the Synthetic Chromosome Rearrangement and Modification by LoxP-mediated Evolution (SCRaMbLE) system provide a platform for generating genotype diversity. Here we construct a genetic AND gate to enable precise control of the SCRaMbLE method to generate synthetic haploid and diploid yeast with desired phenotypes. The yield of carotenoids is increased to 1.5-fold by SCRaMbLEing haploid strains and we determine that the deletion of YEL013W is responsible for the increase. Based on the SCRaMbLEing in diploid strains, we develop a strategy called Multiplex SCRaMbLE Iterative Cycling (MuSIC) to increase the production of carotenoids up to 38.8-fold through 5 iterative cycles of SCRaMbLE. This strategy is potentially a powerful tool for increasing the production of bio-based chemicals and for mining deep knowledge., The SCRaMbLE system integrated into Sc2.0’s synthetic yeast chromosome project allows rapid strain evolution. Here the authors use a genetic logic gate to control induction of recombination in a haploid and diploid yeast carrying synthetic chromosomes.

Vitamin D not only promotes the health of human bones and muscles but also has an important impact on the metabolism of extraskeletal tissues. As a steroid hormone, vitamin D possesses important physiological functions, including cell differentiation and proliferation and immune regulation. Research has shown that vitamin D insufficiency (VDI) or vitamin D deficiency (VDD) can make children susceptible to asthma. Vitamin D has important immunoregulatory functions associated with preventing the occurrence of asthma or the worsening of its symptoms, improving lung function and enhancing glucocorticoid (GCS) action. An increasing number of randomized controlled intervention studies have confirmed that vitamin D affects the occurrence and development of asthmatic diseases. In recent years, accumulating laboratory and clinical research has supported the use of vitamin D as an adjuvant treatment for asthma and has achieved good clinical results. But the clinical outcome of vitamin D in the treatment of asthma is not as impressive as experimental studies. In addition to the complexity of clinical research, it may be related to clinical application methods. In order to combine theory with clinical practice, focused on exploring and selecting the most effective vitamin D adjuvant treatment of asthma, and comprehensively optimizing and applying these methods is beneficial to improve the therapeutic effect. However, there are different opinions regarding the results of the studies.

QD biosynthesis affects the mechanical strength of yeast cells. The intracellular synthesis of CdSe QD in yeast cells incubated with Na2 SeO3 and subsequently with CdCl2 increases the glucan content of their cell walls, resulting in their enhanced mechanical strength.

As for the shortcomings of poor rigidity and strength of weak of thin-walled tube parts, a device of an adaptive PID controller which based on neural network has been proposed by regarding the thin-walled tube fixture system as the research object. The controller which integrates the characteristics of neural network and PID regulator can realize the self-tuning of PID parameters effectively and make the control system equip with the feature of fast response, small overshoot and strong robustness etc. Simulation results show that the controller can meet the system requirements commendably and it can implement the automatic chucking control of the thin-walled steel cutting process with fast and non-destructive in the experimental prototype.

TiC-TiB2 composite ceramics were successfully fabricated via planetary ball milling of 72 mass% Ti and 28 mass % B4C powders, followed by low temperature sintering process at 1200°C. The microstructure of the ball-milled powder mixtures and composite ceramics were characterized by Differential thermal analysis equipment (DTA), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that the ball-milled powder mixtures (Ti and B4C powders) were completely transformed to TiC-TiB2 composite ceramics as the powders were milled for 60 h and sintered at 1200°C for 1 h. The formation mechanism of the TiC-TiB2 composite was discussed. The high energy ball milling and necessary sintering for the powder mixtures plays an important role in the formation of the composites.

Titanium diboride (TiB2), which is characterized by a high melting potin,high stiffness, good wear resistance, has good structural and thermodynamiccompatibility with Al2O3. In this paper, Al2O3-TiB2 composite ceramics wereeffectively synthesized by mechanical alloying(MA), planetary ball milling of 26.25wt.% B2O3, 30 wt.% TiO2, 33.75 wt.% Al and 10 wt.% Ni. The phase transformationafter different milling time was conducted by X-ray diffractometry(XRD). The XRDanalyses exhibited that the Al2O3-TiB2 composite was formed after 12h milling time(BPR:10/1 and rotational speed of vial: 500 rpm). The results indicate that increasingmilling time up to 60 h had no significant effect other than refining the crystallite size.

Artificial plasmid DNA transformation of Escherichia coli induced by calcium chloride is a routine technique in molecular biology and genetic engineering processes, but its mechanism has remained elusive. Because adenosine monophosphate (AMP) has been found to regulate natural transformation in Haemophilus influenza, we aimed to investigate the effects of AMP and its derivatives on E. coli transformation by treating competence with different concentrations of them. Analysis of the transformation efficiencies revealed that AMP inhibited the artificial plasmid DNA transformation of E. coli in a concentration- and time-dependent manner. Furthermore, we found that AMP had no effect on the expression of the transformed gene but that the intracellular AMP level of the competent cells rose after a 6 h treatment. These results suggested that the intracellular AMP level had an important role in E. coli transformation. And these have useful implications for the further investigation of the mechanism of E. coli transformation.

Microbial cells have shown a great potential to biosynthesize inorganic nanoparticles within their orderly regulated intracellular environment. However, very little is known about the mechanism of nanoparticle biosynthesis. Therefore, it is difficult to control intracellular synthesis through the manipulation of biological processes. Here, we present a mechanism-oriented strategy for controlling the biosynthesis of fluorescent CdSe quantum dots (QDs) by means of metabolic engineering in yeast cells. Using genetic techniques, we demonstrated that the glutathione metabolic pathway controls the intracellular CdSe QD formation. Inspired from this mechanism, the controllability of CdSe QD yield was realized through engineering the glutathione metabolism in genetically modified yeast cells. The yeast cells were homogeneously transformed into more efficient cell-factories at the single-cell level, providing a specific way to direct the cellular metabolism toward CdSe QD formation. This work could provide the foundation for the future development of nanomaterial biosynthesis.

A single-layer zinc oxide (ZnO) nanorod array-based micro energy harvester was designed and integrated with a piezoelectric metacapacitor. The device presents outstanding low-frequency (1-10 Hz) mechanical energy harvesting capabilities. When compared with conventional pristine ZnO nanostructured piezoelectric harvesters or generators, both open-circuit potential and short-circuit current are significantly enhanced (up to 3.1 V and 124 nA cm-2) for a single mechanical knock (∼34 kPa). Higher electromechanical conversion efficiency (1.3 pC/Pa) is also observed. The results indicate that the integration of the piezoelectric metacapacitor is a crucial factor for improving the low-frequency energy harvesting performance. A double piezoelectric-driven mechanism is proposed to explain current higher output power, in which the metacapacitor plays the multiple roles of charge pumping, storing and transferring. An as-fabricated prototype device for lighting an LED demonstrates high power transference capability, with over 95% transference efficiency to the external load.

With the circumstances that emergencies happen more frequently and supply chain uncertainty increases, this paper researches that how does supply chain resume production quickly in supply disruption and keep the competitive advantages of the whole supply chain network. This research fills the theory of supply disruption management, meanwhile, constructs and perfects the contingency plan in supply disruption, regarding the four-echelon supply chain as research subject, assuming that supply disruption caused by force majeure. It analyzes the contingency plan model for two situations. One is single-supplier disruption; the other is multiple-supplier disruption. This paper also demonstrates the significance of supply disruption management, especially in cost control and proposes the countermeasure to solve that problem.

Biosynthesis of alkanes in microbial foundries offers a sustainable and green supplement to traditional fossil fuels. The dynamic equilibrium of fatty aldehydes, key intermediates, played a critical role in microbial alkanes production, due to the poor catalytic capability of aldehyde deformylating oxygenase (ADO). In our study, exploration of competitive pathway together with multi-modular optimization was utilized to improve fatty aldehydes balance and consequently enhance alkanes formation in Escherichia coli. Endogenous fatty alcohol formation was supposed to be competitive with alkane production, since both of the two routes consumed the same intermediate-fatty aldehyde. Nevertheless, in our case, alkanes production in E. coli was enhanced from trace amount to 58.8mg/L by the facilitation of moderate fatty alcohol biosynthesis, which was validated by deletion of endogenous aldehyde reductase (AHR), overexpression of fatty alcohol oxidase (FAO) and consequent transcriptional assay of aar, ado and adhP genes. Moreover, alkanes production was further improved to 81.8mg/L, 86.6mg/L or 101.7mg/L by manipulation of fatty acid biosynthesis, lipids degradation or electron transfer system modules, which directly referenced to fatty aldehydes dynamic pools. A titer of 1.31g/L alkanes was achieved in 2.5L fed-batch fermentation, which was the highest reported titer in E. coli. Our research has offered a reference for chemical overproduction in microbial cell factories facilitated by exploring competitive pathway.

At present, the finish machining process of workpiece with free-form surface has the disadvantages of complex trajectory planning, low machining efficiency and precision. To solve these problems, an idea of uniform ER finishing with changeable removal rate model is proposed in this paper. The rheological effect of ER fluid is used to change the magnetic field distribution in finishing areas; then the finishing pressure distribution is changed, that makes the material removal rate of every point in the contact area be approximately equal, so the aim of uniform removal is achieved. In this paper, the quantitative relationship between electric field intensity and finishing pressure is studied. Contrast experiments of finishing and removal effects are performed under the different conditions of electric field distribution. The ER finishing equipment is developed and the proposed finishing method is feasible and has the potential of obtaining the ultra precision.

In order to improve the information extraction technology of seismic damage assessment and information publishing of earthquake damage. Based on past earthquake experience it was constructed technical flow of earthquake damage assessment rapidly, This paper ,take Yushu earthquake as example, studies the framework and establishment of the information service system by means of ArcIMS and distributed database technology. It analysis some key technologies , build web publishing architecture of massive remote sensing images. The system implements joint application of remote sensing image processing technology, database technology and WebGIS technology, The result could provide the important basis for earthquake damage assessment ,emergency management and rescue mission.

A novel aluminum alloy which could react with water and generate hydrogen at room temperature was prepared via mechanical alloying (MA). The results shows that milling time, additives and mass ratio have a significant role in the hydrogen production rate. The highest hydrogen production rate of alloys reaches 95% of theoretical value. The velocity of hydrogen generation reaches more over 200 mL/min for a gram alloy. Active materials (Ga and In) included in the aluminum alloys can be recycled and used repeatedly. The hydrolysis reaction between aluminum and H2O will take place and release a large amount of heat, which contributes to increasing the velocity of hydrogen generation. The reaction products consist of AlO(OH) and hydrogen.

Weikun Tang,1 Junpeng Fan,1 Yide He,1 Bihai Huang,2 Huihui Liu,1 Daiwen Pang,2 Zhixiong Xie11College of Life Sciences, 2College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, People's Republic of ChinaAbstract: Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSe-core QDs (MAA–QDs) were investigated. After incubation with different concentrations of MAA–QDs (0.043, 0.13, 0.4, 1.2, and 3.6 µmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA–QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium–mercaptoacetic acid complex (Cd–MAA) that is formed in the solution of MAA–QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd–MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles.Keywords: genotoxicity, MAA CdSe quantum dots, cadmium–MAA complex, transformation assay, DNA&nbsp

The effect of extracellular DNA (eDNA) on bacterial attachment was characterized using Escherichia coli, DNase I, and several different kinds of DNA. Here, we showed that eDNA enhanced bacterial attachment to solid surface in a concentration-dependent way. Either plasmid DNA or chromosome DNA, even or eukaryotic DNA fragments showed the promotion effect, suggesting that the effect of DNA on bacterial attachment is nonspecific. This promotion effect of eDNA is separable from that of conjunctive pili. In a static culture system, biofilm can form even with the presence of active DNase I. DNase I impaired bacterium-to-bacterium adhesion and microcolony formation efficiently but had little effect on bacterial attachment to a solid surface and mature biofilm. Consequently, this study provides a rational description for the role of DNA in bacterial biofilm formation in natural environments.

Since the heavy current and frequent start-stop of portable electric tool, the special energy saving power assisted system is designed. The method for solving these problems is to make a binary power supply with super capacitor and lead-acid battery. The super capacitor provides power assistance to increase output current when starting and recycles inertia energy when stopping, the energy distribution is done by control system. In this paper, the operation principle and control circuit are described and the effect of the proposed system is tested by experiment. The experiment results show that the proposed system double the output current and save energy around 20%. In this way, the problems of short-lifetime and inefficient power take off are solved and this energy saving power assisted system is also appropriate to electric mobile and so on which employ secondary electric power supply as power.

Through simulation analysis of the blood cell by Abques under the function of the different pressures, the change of the cell’s axial diameter and the importance of the effect of external force and double concave shape on the erythrocyte’s deformability are obtained. It lays the foundation for the research artificial organs lubrication.

Based on the density functional pseudopotential method, the electronic structures and the optical properties for Ti doped ZnS are investigated in detail. The calculation results indicate that the doping of Ti widens the band gap of ZnS and the Fermi level shifts upward into the conduction band. The impurity elements form new highly localized impurity energy level at the bottom of the conduction band near the Fermi level.,.Meanwhile, blue shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change of band gaps.

TiB2-TiC complex phases coating deposited onto the surface of electrodes by electro-spark deposition (ESD) in order to prolong the life of single phase coated electrode (TiB2 or TiC) during resistance welding of galvanized steels. The microstructures and TiB2-TiC complex phases coatings were characterized by SEM and XRD. The results indicate that life of TiB2-TiC complex phases coated electrode is prolonged significantly than life of single-phase coated electrode （TiB2 or TiC ）, failure mechanism of TiB2-TiC complex phases coated electrode is mainly wear to cause diameter increase on electrode tip, which results in lower current density during welding process, and then nugget size cannot satisfy the requirement of resistance spot welding. The failure mechanism of TiB2-TiC complex phases coated electrode is obviously different from uncoated electrode, the failure mechanism of uncoated electrode is wear and alloying between electrode tip surface and molten Zn on galvanized steel weld surface.

Adsorption of DNA to bacterial surfaces plays a crucial role in biofilm formation, genetic transformation and bacterial survival in environments. The relevant features were determined performing adsorption isotherms of DNA to E. coli cells. The results suggest that DNA adsorbing to E. coli is in a source-nonspecific way; a same concentration of long linear DNA is easier to be adsorbed than short linear DNA; DNA adsorption is also influenced by bacterial growth phases and environmental conditions (e.g. temperature, salt type and concentration). To better understand the features of DNA adsorption to bacterial surfaces, the zeta potential of the bacteria was determined. The combined results from the adsorption isotherms and the measurement of zeta potential suggest the inhibition effect of the negative surface potential of E. coli on DNA adsorption. It implies further that the adsorption of DNA to bacterial surfaces is governed by not only DNA receptors but also the negatively charged components of bacterial outer membrane. A mathematical derivation of the experimental data suggests that the electrostatic self-repulsion of DNA may facilitate itself to overcome the electrostatic barrier near the bacterial surfaces to be adsorbed, but this effect is dependent on DNA length and concentration. Moreover, salt ions (e.g. NaCl and MgCl 2 ) can increase the adsorption to bacterial surfaces of DNA via screening the electrostatic potential near the negatively charged surfaces. These results provide important implications for understanding adsorption to bacteria of DNA in natural environments and the relevant bacterial behaviors.

Based on the research of dynamic characteristics of axial flow blood pump which is drove by the large gap magnetic drive system, a serial communication between PC and AT89C51 to realize the real-time process of the blood pump acceleration is proposed. The acceleration control parameters are decided by the analysis of blood pump speed control mechanism. As a result, Previous, the previous program which is modified to change the control parameters repeatedly is saluted by building the PC model. At the same time, the control of multiple control parameters could be achieved when a program on the microcontroller is addressed. What’s more, the more experiments will be realized, to provide more conveniences to the system.

The aggregate gradation and mechanical property of particle reinforced composite (resin and quartz sand composite ) were studied with test, the results show that: The more optimal scheme of aggregate gradation can be obtained with right ratio of larger particle quartz sand and small particle quartz plate , which can make the gradation resin content from the original 20% ~ 25% reduced to 12% ~ 14%, so as to reduce the cost and improve the economic benefit and guarantee bending strength of winding layer not decrease in the meantime

Quantum dots (QDs) are inorganic fluorescent nanocrystals with excellent properties such as tunable emission spectra and photo-bleaching resistance compared with organic dyes, which make them appropriate for applications in molecular beacons. In this work, quantum dot-based molecular beacons (QD-based MBs) were fabricated to specifically detect β-lactamase genes located in pUC18 which were responsible for antibiotic resistance in bacteria Escherichia coli (E. coli) DH5α. QD-based MBs were constructed by conjugating mercaptoacetic acid-quantum dots (MAA-QDs) with black hole quencher 2 (BHQ2) labeled thiol DNA vial metal-thiol bonds. Two types of molecular beacons, double-strands beacons and hairpin beacons, were observed in product characterization by gel electrophoresis. Using QD-based MBs, one-step FISH in tiny bacteria DH5α was realized for the first time. QD-based MBs retained their bioactivity when hybridizing with complementary target DNA, which showed excellent advantages of eliminating background noise caused by adsorption of non-specific bioprobes and achieving clearer focus of genes in plasmids pUC18, and capability of bacterial cell penetration and signal specificity in one-step in situ hybridization.

By using an LKB-2277 Bioactivity Monitor and cycle-flow method, the thermogenic curves of aerobic growth for Bacillus thuringiensis cry II strain at 28 °C have been obtained. The metabolic thermogenic curves of Bt cry II contain two distinct parts: the first part reflects the changes of bacterial growth phase and the second part corresponds to sporulation phase. From these thermogenic curves in the absence or presence of Sm3+, Dy3+ ions, the thermokinetic parameters such as the growth rate constants k, the interval time τI, the maximum power PMAX1 and heat-output QLOG for log phase, the maximum power PMAX2 and heat-output QSTAT for stationary phase, the heat-output QSPOR for sporulation phase and total heat effects QT were calculated. Sm3+ and Dy3+ ions have promoting action on the growth of Bt cry II in their lower concentration range, on the other hand, they have inhibitory action on the sporulation of Bt in their higher concentration range. It has also been found that the effects of Sm3+ and Dy3+ ions on Br firing the sporulation phase were far greater than those during the bacterial growth phase. It was concluded that the application of Bt for controlling insecticide could not be affected by the presence of the rare-earth elements in the environmental ecosystem.

There are currently some problems in the field of chemical synthesis, such as environmental impact, energy loss, and safety, that need to be tackled urgently. An interdisciplinary approach, based on different backgrounds, may succeed in solving these problems. Organisms can be chosen as potential platforms for materials fabrication, since biosystems are natural and highly efficient. Here, an example of how to solve some of these chemical problems through biology, namely, through a novel biological strategy of coupling intracellular irrelated biochemical reactions for controllable synthesis of multicolor CdSe quantum dots (QDs) using living yeast cells as a biosynthesizer, is demonstrated. The unique fluorescence properties of CdSe QDs can be utilized to directly and visually judge the biosynthesis phase to fully demonstrate this strategy. By such a method, CdSe QDs, emitting at a variety of single fluorescence wavelengths, can be intracellularly, controllably synthesized at just 30°C instead of at 300°C with combustible, explosive, and toxic organic reagents. This green biosynthetic route is a novel strategy of coupling, with biochemical reactions taking place irrelatedly, both in time and space. It involves a remarkable decrease in reaction temperature, from around 300 °C to 30 °C and excellent color controllability of CdSe photoluminescence. It is well known that to control the size of nanocrystals is a mojor challenge in the biosynthesis of high-quality nanomaterials. The present work demonstrates clearly that biological systems can be creatively utilized to realize controllable unnatural biosynthesis that normally does not exist, offering new insights for sustainable chemistry.

Ferrichrome is a kind of high-affinity iron(III) chelators and its complex with Fe3+ can be specifically recognized by the corresponding receptors located on the outer membrane of some bacterial ce...

The role of DNA in bacterial aggregation was determined using various types of DNA and Escherichia coli, a good model for investigating the correlation between added polymer and bacterial aggregation and adsorption of polymer to bacterial surfaces. The results of the aggregation assay suggest that extracellular DNA indeed increased the aggregation percentage of E. coli, but this effect was dependent on DNA concentration and length. Moreover, DNA promoted bacterial aggregation in a type-nonspecific way. The combined results of the aggregation assay and the adsorption assay show further that the promotion of E. coli aggregation by DNA occurred along with adsorption of DNA to E. coli. Consequently, the possible mechanisms for DNA-promoted bacterial aggregation are discussed. Using fluorescent-labeled DNA, we mapped DNA within the E. coli aggregates. Subsequently, introduction of DNase I broke up the DNA-involved E. coli aggregates. These results suggest that DNA functions as a molecular bridge to promote E. coli aggregation.

We report single molecule conductance measurement of 4,4‘-bipyridine (BPY), 1,2-di(pyridin-4-yl)ethene (BPY-EE), and 1,2-di(pyridin-4-yl)ethane (BPY-EA), in which the two pyridine rings sandwich the conjugated ethene group and the nonconjugated ethane group, respectively. The conductance measurements of the molecules bridged in two Au electrodes have been carried out in aqueous solutions using the scanning tunneling microscopy-based break junction (STM-BJ) technique. All three molecules show two sets of conductance values with the high conductance (HC) values about 8−10 times higher than the low conductance (LC) values. The HC values for BPY, BPY-EE, and BPY-EA are (4.7 ± 1.1) × 10-3 G0, (2.3 ± 0.9) × 10-3 G0, and (4.5 ± 2.2) × 10-4 G0, respectively, in an order of BPY > BPY-EE > BPY-EA. The decrease of conductance of BPY-EE can be attributed mainly to the length increase of the molecule, while the decrease of the conductance of BPY-EA reveals the degree of electron decoupling upon insertion of one CH2CH2...

In this article, the underpotential deposition (UPD) of Sb on Au(111) and Au(100) over a wide potential range in a BMIBF4 ionic liquid containing SbCl3 is investigated by cyclic voltammetry and in situ scanning tunneling microscopy (STM). The cyclic voltammograms of the two surfaces show similar features of Sb UPD, which is kinetically sluggish at high underpotential shift but rapid at low underpotential shift with a large and broad reduction peak. The total charge flux associated with the UPD suggests an equivalent of nearly 1 ML quantity of Sb deposit. In situ STM results showed precursor adsorption and several stages of the UPD. The prior UPD reversible adsorption of SbCl3 precursor occurs only on Au(111) with an ordered hexagonal array of six- and seven-membered clusters in (√31 × √31)R8.9° registration with the Au(111) surface. On both Au(111) and Au(100), the initial stage of Sb UPD (from −0.2 to −0.4 V) proceeds with the formation of similar short atomic strips of Sb atoms with a length of 2−2.5 nm...

Natural plasmid transformation of Escherichia coli is a complex process that occurs strictly on agar plates and requires the global stress response factor σ S . Here, we showed that additional carbon sources could significantly enhance the transformability of E. coli . Inactivation of phosphotransferase system genes ( ptsH , ptsG , and crr ) caused an increase in the transformation frequency, and the addition of cyclic AMP (cAMP) neutralized the promotional effect of carbon sources. This implies a negative role of cAMP in natural transformation. Further study showed that crp and cyaA mutations conferred a higher transformation frequency, suggesting that the cAMP-cAMP receptor protein (CRP) complex has an inhibitory effect on transformation. Moreover, we observed that rpoS is negatively regulated by cAMP-CRP in early log phase and that both crp and cyaA mutants show no transformation superiority when rpoS is knocked out. Therefore, it can be concluded that both the crp and cyaA mutations derepress rpoS expression in early log phase, whereby they aid in the promotion of natural transformation ability. We also showed that the accumulation of RpoS during early log phase can account for the enhanced transformation aroused by additional carbon sources. Our results thus demonstrated that the presence of additional carbon sources promotes competence development and natural transformation by reducing cAMP-CRP and, thus, derepressing rpoS expression during log phase. This finding could contribute to a better understanding of the relationship between nutrition state and competence, as well as the mechanism of natural plasmid transformation in E. coli . IMPORTANCE Escherichia coli , which is not usually considered to be naturally transformable, was found to spontaneously take up plasmid DNA on agar plates. Researching the mechanism of natural transformation is important for understanding the role of transformation in evolution, as well as in the transfer of pathogenicity and antibiotic resistance genes. In this work, we found that carbon sources significantly improve transformation by decreasing cAMP. Then, the low level of cAMP-CRP derepresses the general stress response regulator RpoS via a biphasic regulatory pattern, thereby contributing to transformation. Thus, we demonstrate the mechanism by which carbon sources affect natural transformation, which is important for revealing information about the interplay between nutrition state and competence development in E. coli .

It is a challenge for Web service composition to perceive dynamic changes of external environment and adapt to the changes of business process rapidly. In this paper, a context-aware adaptive Web service composition framework is presented and the functions of main modules are also described in detail. In this framework, BPEL is used to describe Web service composition process and a kind of special Web service called context service is defined to support context-awareness. Agent technology is introduced to enable context service to actively perceive and process contexts of Web service and Web service composition.

In recent years, context-awareness technology is introduced to Web Service Composition to solve the personalization problem in Web Service Composition, which makes the composition results more suitable to the user’s environment. The context-aware web service composition language called CA-CCML (Context-aware Cooperative Composition Modeling Language) is designed. This paper focuses on the research of CA-CCML interpreter, which is composed of CA-CCML Editor, Context Manager and Web Service Manager. Finally, an application case of a study hall searching system is presented to show the usability and validity of CA-CCML interpreter.

The paper constructs an evolutionary game model of enterprise and public in the intervention of government, so as to discuss the strategy choice that is whether enterprise fulfills social responsibility or public conduct supervision. Through establishing replicated dynamic equation of the game between enterprise and public, and using Jacobi matrix local stability analysis method to analyze the stability of the replicated dynamic system in local equilibrium, and further explore the dynamic evolution process of game under different incentives intensity of government. The result shows that when the government incentives intensity is large enough, the enterprises that have stronger brand awareness are more willing to fulfill social responsibility; on the contrary, low brand awareness enterprises do not have that strong motivation to fulfill social responsibility. In addition, in a long-term game, public could choose the policy of no supervision, and also indicate that under the condition of asymmetric information, the public have difficult to supervise the enterprise behaviors. According to the above analysis, this paper put forward specific suggestions from the level of government, the public and enterprise.

A novel transformation system, in which neither a nonphysiological concentration of Ca2+ and temperature shifts nor electronic shocks were required, was developed to determine whether Escherichia coli is naturally transformable. In the new protocol, E. coli was cultured normally to the stationary phase and then cultured statically at 37 degrees C in Luria-Bertani broth. After static culture, transformation occurred in bacteria spread on Luria-Bertani plates. The protein synthesis inhibitor chloramphenicol inhibited this transformation process. The need for protein synthesis in plated bacteria suggests that the transformation of E. coli in this new system is regulated physiologically.

Semiconductor quantum dots (QDs) as a kind of nonisotopic biological labeling material have many unique fluorescent properties relative to conventional organic dyes and fluorescent proteins, such as composition- and size-dependent absorption and emission, a broad absorption spectrum, photostability, and single-dot sensitivity. These properties make them a promising stable and sensitive label, which can be used for long-term fluorescent tracking and subcellular location of genes and proteins. Here, a simple approach for the construction of QD-labeled DNA probes was developed by attaching thiol-ssDNA to QDs via a metal-thiol bond. The as-prepared QD-labeled DNA probes had high dispersivity, bioactivity, and specificity for hybridization. Based on such a kind of probe with a sequence complementary to multiple clone sites in plasmid pUC18, fluorescence in situ hybridization of the tiny bacterium Escherichia coli has been realized for the first time.