Showing papers by "Wei Jiang published in 2010"
TL;DR: The determination of preferred assembly pathways as well as the formation of dead-end structures provides a clear picture of a rich kinetic behavior of the self-sorting systems under study.
Abstract: Three binary pseudorotaxanes, which are based on two different secondary ammonium/crown ether binding motifs, have been studied by 1H NMR and 1H,1H EXSY NMR experiments with respect to their thermodynamic stabilities and their axle exchange kinetics. The stability ranking does not follow the order of axle exchange rates, and the thermodynamically most stable axle−wheel combinations assemble only slowly. On the basis of these binding motifs, a series of self-sorting systems have been studied ranging from simple four-component mixtures through sequence-specific pseudorotaxanes to multiply threaded complexes. Because of the mismatch of kinetic and thermodynamic order, wrongly assembled structures are unavoidable, which require error-correction steps to yield the final thermodynamically controlled self-sorted products. These error-correction steps can easily be monitored by electrospray mass spectrometry, when a mixed-flow microreactor is coupled to the ion source to cover second time scales. Self-assembly in...
188 citations
TL;DR: This finding not only provides new insight into the origins of vesicles but also provides further understanding on the self-assembly kinetics of amphiphilic block copolymers in a selective solvent.
Abstract: In this study, the kinetics of vesicle formation of ABA amphiphilic triblock copolymers from an initially homogeneous state was theoretically and experimentally investigated by adding a selective solvent into the system. The pathway of spontaneous vesicle formation depended greatly on the selective solvent addition rate. At a slow addition rate, the pathway followed three stages: (1) the amphiphilic triblock copolymer combined into a large irregular aggregation; (2) the large irregular aggregation broke into big irregular spheres; and (3) some hydrophilic molecules in the big irregular spheres diffused toward the surface, and some hydrophilic molecules diffused toward the center, forming vesicles. However, at a fast addition rate, the pathway was as follows: (1) the amphiphilic triblock copolymer aggregated into many small spheres; (2) the small spheres merged to form rod-like micelles first and then oblate membranes; and (3) the oblate membranes closed up to form vesicles. This pathway difference for vesicle formation can be attributed to the existence of many metastable states in the system. This finding not only provides new insight into the origins of vesicles but also provides further understanding on the self-assembly kinetics of amphiphilic block copolymers in a selective solvent.
120 citations
TL;DR: In vivo optical imaging and luciferase assays demonstrated that systemic delivery of the folate-labeled polyplexes resulted in preferential accumulation of transgenes in folate receptor-positive tumors, and mcDNA mediated approach achieved 2.3 fold higher gene expressions in tumors than conventional plasmid.
84 citations
TL;DR: This study was performed to search for micro‐organisms possessing elevated tolerance to butanol that limits their butanol production during industrial‐scale fermentation process.
Abstract: Aims: Poor butanol tolerance of solventogenic stains directly limits their butanol production during industrial-scale fermentation process. This study was performed to search for micro-organisms possessing elevated tolerance to butanol.
Methods and Results: Two strains, which displayed higher butanol tolerance compared to commonly used solventogenic Clostridium acetobutylicum, were isolated by evolution and screening strategies. Both strains were identified as lactic acid bacteria (LAB). On this basis, a LAB culture collection was tested for butanol tolerance, and 60% of the strains could grow at a butanol concentration of 2·5% (v/v). In addition, an isolated strain with superior butanol tolerance was transformed using a certain plasmid.
Conclusions: The results indicate that many strains of LAB possessed inherent tolerance of butanol.
Significance and Impact of the Study: This study suggests that LAB strains may be capable of producing butanol to elevated levels following suitable genetic manipulation.
47 citations
TL;DR: This study elucidates the mechanism by which PMA activates and stabilizes IL-2 expression in T cells and demonstrates that PMA stimulation led to phosphorylation of NF90 at Ser647 via PKCβI.
Abstract: IL-2 is an important cytokine produced in T cells in response to Ag or mitogen stimulation. It is regulated at both transcriptional and posttranscriptional levels. One of the key regulators of IL-2 mRNA stability is NF90. Upon T cell activation, NF90 translocates from the nucleus into the cytoplasm, where it binds to the AU-rich element-containing 3' untranslated regions of IL-2 mRNA and stabilizes it. Our previous work showed that CD28 costimulation of T cells activated AKT to phosphorylate NF90 at Ser(647) and caused NF90 to undergo nuclear export and stabilize IL-2 mRNA. Phorbol ester (PMA) is a protein kinase C (PKC) activator. Through transcription activation and mRNA stabilization, IL-2 mRNA levels increase promptly when T cells are stimulated with PMA. However, how PMA stabilizes IL-2 mRNA was still unclear. In this study, we demonstrate that PMA stimulation led to phosphorylation of NF90 at Ser(647) via PKCβI. This phosphorylation was necessary for nuclear export of NF90 in response to PMA and for IL-2 mRNA stabilization. We show that phosphorylation at NF90-Ser(647) upregulated IL-2 production in response to PMA stimulation. Our results support a model in which PMA stimulation activates PKCβI to phosphorylate NF90-Ser(647), and this phosphorylation triggers NF90 relocation to the cytoplasm and stabilize IL-2 mRNA. Thus, our study elucidates the mechanism by which PMA activates and stabilizes IL-2 expression in T cells.
41 citations
TL;DR: A unique reversible transformation between toroidal and cylindrical assemblies was observed as discussed by the authors, where toroids can change to cylinders by elongation at higher temperature and upon cooling rate these cylinders can form toroids through pathway of cylinder-sphere-vesicle-ring or the end-to-end connection.
Abstract: A unique reversible transformation between toroidal and cylindrical assemblies was observed Toroids can change to cylinders by elongation at higher temperature Reversely, upon cooling rate these cylinders can form toroids through pathway of cylinder–sphere–vesicle–ring or the end-to-end connection
36 citations
TL;DR: In this article, the authors synthesize monodispersed magnetite (Fe3O4) in toluene with the particle size from 4 to 12 nm and obtain aqueous nanofluids by a simple one-step phase transfer.
Abstract: Magnetic nanofluids possess some unique properties that can significantly affect their thermal conductivity. We synthesize monodispersed magnetite (Fe3O4) nanofluids in toluene with the particle size from 4 to 12 nm and obtain aqueous nanofluids by a simple “one-step” phase transfer. Even without the effect of external field, the magnetic-interaction-induced self-assembled aggregation can still be significant in magnetite nanofluids. Investigation of the microstructures of self-assembled aggregation is carried out by the dynamic light scattering, which unveils the variation of aggregated configurations with particle concentration and time. Based on the calculation from the existing models, the aggregates decrease the thermal conductivity of both themselves and the entire system, mainly due to the less solid contents and weaker mobility compared with the single particles as well as the increase in interfacial thermal resistance. As the manifestation of the aggregation-structure variation, the measured ther...
28 citations
TL;DR: The ability of tandem mass spectrometry to deliver structural information on a series of self-sorted crown ether/ammonium pseudorotaxanes to establish well understood correlations between the complexes' gas-phase behavior and their solution structures is explored.
Abstract: The increasing complexity of self-assembled supramolecules generates the need for analytical techniques that can accurately elucidate their structures. Here, we explore the ability of tandem mass spectrometry to deliver structural information on a series of self-sorted crown ether/ammonium pseudorotaxanes. Of these intertwined molecules, different charge states are accessible and the effects of Coulomb interactions on the fragmentation pattern can be examined. Three different cases can be distinguished: (1) one or more counterions are present in the complex and compete with the crown for binding to the ammonium ion. This destabilizes the supramolecular bond. (2) In multiply charged complexes, charge repulsion significantly alters the fragmentation behavior as compared with singly charged ions. (3) If guest and host are both charged, the supramolecular bond becomes very weak. The different charge states provide different pieces of information about the supramolecules under study. Although singly charged complexes provide data on the building block connectivity, the doubly charged analogs are more reliable with respect to complex stoichiometry. As there are several factors which may cause differences in the gas phase and solution behavior of supramolecules (the presence and absence of solvation, changes in the strength of non-covalent interactions upon ionization), it is important to establish well understood correlations between the complexes' gas-phase behavior and their solution structures. A more detailed understanding will help to characterize the structures of even more complex supramolecular architectures by mass spectrometry.
28 citations
TL;DR: Oleic acid-modified CuS nanoparticles were chemically synthesized in this article to improve the anti-wear ability of the fabric/phenolic composite at varied loads and environmental temperatures.
Abstract: Oleic acid-modified CuS nanoparticles were chemically synthesized. The tribological properties of surface modified and unmodified CuS nanoparticles as additives in the hybrid polytetrafluoroethylene (PTFE)/Kevlar fabric/phenolic composite were investigated in detail. The experimental results indicated that the incorporation of modified CuS nanoparticles improved the antiwear ability of the fabric/phenolic composite at varied loads and environmental temperatures. The reasons for the enhanced wear properties of the fabric/phenolic composite filled with surface-modified CuS nanoparticles were discussed based on the results of scanning electron microscopy and Fourier transform infrared spectroscopy.
27 citations
TL;DR: In this article, the influence of flow rates of reactants, reactants concentrations, and surfactant concentrations on copper particle size and size distribution has been investigated and it was found that neither of them has much influence on particle size distribution of copper nanoparticles synthesized in microfluidic reactors.
Abstract: Copper nanofluids have been chemically synthesized by using home-made microfluidic reactors and by using a boiling flask-3-neck. The influence of flow rates of reactants, reactants concentrations, and surfactant concentrations on copper particle size and size distribution has been investigated. It has been found that neither of them has much influence on particle size and size distribution of copper nanoparticles synthesized in microfluidic reactors due to the fast and efficient mass diffusion in microscale dimension. The copper nanoparticles have an average size of about 3.4 nm with a relatively narrow size distribution of around 22% evaluated by the coefficient of variation. While the average size of copper nanoparticles synthesized by flask method changes from 2.7 to 4.9 nm with a coefficient of variation larger than 30%, depending on concentrations of [Cu(NH3)4]·(OH)2 and surfactant sodium dodecylbenzenesulfonate. In addition, by using microfluidic reactors the synthesis time of copper nanofluids can be reduced as much as one order of magnitude, from ~10 min to ~28 s.
27 citations
TL;DR: In this article, the tribological behavior of the spun Kevlar fabric composites filled with polyfluo wax (PFW) and LaF 3 were evaluated using a pin-on-disc friction and wear tester under variable applied load and rotating speed.
TL;DR: Two procedures for the synthesis of benzo-21-crown-7 have been explored and the [1+1] macrocyclization with KBF4 as the template was found to be more efficient than the intramolecular macrocyclized without template.
Abstract: Two procedures for the synthesis of benzo-21-crown-7 have been explored. The [1+1] macrocyclization with KBF4 as the template was found to be more efficient than the intramolecular macrocyclization without template. Pseudorotaxanes form with secondary ammonium ions bearing at least one alkyl chain narrow enough to slip into the crown ether. Substitution on benzo-21-crown-7 or on the secondary ammonium axle alters the binding affinity and binding mode. Compared to dibenzo-24-crown-8, the complexing properties of benzo-21-crown-7 turn out to be more susceptible to modifications at the crown periphery.
TL;DR: In this article, a facile method for forming a MWNT-based composite coating with behavior of the super-hydrophilic/superhydrophobic transition is demonstrated, where the change of the surface microstructure and the surface chemical composition arising from increasing temperatures determines the surface wettability of the resulting composite coating.
Abstract: A facile method for forming a MWNT-based composite coating with behavior of the superhydrophilic/superhydrophobic transition is demonstrated. The change of the surface microstructure and the surface chemical composition arising from increasing temperatures determines the surface wettability of the resulting composite coating. The coating surface shows the superhydrophobic property at 150, 200, and 360°, and displays superhydrophilic performance at 300°C.
TL;DR: In this paper, the effect of shear flow on the self-assembly of ABC amphiphilic copolymers in dilute selective solutions by changing the stirring rate and the composition of the triblock copolymer was studied.
TL;DR: In this article, the effect of shear on the crystallization behavior of the poly(ether ether ketone) (PEEK) has been investigated by means of ex situ wide-angle X-ray diffraction (WAXD), small-angle x-ray scattering, and differential scanning calorimetry (DSC).
Abstract: The effect of shear on the crystallization behavior of the poly(ether ether ketone) (PEEK) has been investigated by means of ex situ wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering, and differential scanning calorimetry (DSC). The changes of the intensity of WAXD patterns along shear direction of the PEEK induced by short-term shear were observed when the samples crystallized at 330 degrees C. The results showed that the dimensions of the crystallites perpendicular to the (110) and (111) planes reduced with the increase of shear rate, whereas the dimensions of the crystallites perpendicular to (200) plane increased with the increase of shear rate. Moreover, increasing shear rate can lead to the increase of the crystallinity as well as the average thickness of the crystalline layers. Correspondingly, a new melting peak at higher temperature was found during the subsequent DSC scanning when the shear rate was increased to 30 s(-1). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 220-225, 2010
01 Dec 2010
TL;DR: This paper presents a novel QoS-aware approach which adopts a two-phase graph search algorithm which effectively reduces the search space and significantly improves the accuracy of the search results.
Abstract: Automatic service composition has been an active research area in the field of service computing. Service engineers demand algorithms that not only synthesize the correct work plans but also meet the need of the overall qualities like response time, throughput, fee, etc. In this paper, we present a novel QoS-aware approach which adopts a two-phase graph search algorithm. This approach effectively reduces the search space and significantly improves the accuracy of the search results.
TL;DR: In this article, a novel one-step chemical reduction method is developed to fabricate nanofluids with very tiny spherical copper nanoparticles, and their chemical and colloidal stability is studied by adjusting their pH value with citric acid.
Abstract: A novel one-step chemical reduction method is developed to fabricate nanofluids with very tiny spherical copper nanoparticles. Their chemical and colloidal stability is studied by adjusting their pH value with citric acid. Their thermal conductivity is also measured by the transient hot-wire method. The particle size can be varied from 6.4 nm to 2.9 nm by changing the surfactant concentration. The thermal conductivity data show the existence of a critical particle size below which the nanoparticles cannot significantly enhance fluid conductivity due to the particle conductivity reduction and the solid-liquid interfacial thermal resistance increase as the particle size decreases. By considering these two factors, we have also made some theoretical analysis to find the possible critical particle size.
Patent•
17 Mar 2010
TL;DR: In this article, a double plug-and-socket supermolecular device with function of a molecular keyboard lock was presented. But it was not shown to be controllable.
Abstract: The invention provides a method for preparing a double plug-and-socket supermolecular device with function of a molecular keyboard lock. A donor anthryl bridge double crownether 1 and an acceptor naphthyl diimide bridged two-site object 2-2H.2PF6 can form stable pseudorotaxane through a mode of polyvalent bonding, and the formation and disassociation of a pseudorotaxane system can be realized through acid-alkali regulation and control; the reversible process is accompanied by solution color change and fluorescence change, and the plug-and-socket molecular device is controllable. The pseudorotaxane system not only can prevent anthryl groups in the double crownether from being influenced by photooxidation reaction, but also can be used as a logic functional device, i.e. a molecular keyboardlock; and the double plug-and-socket supermolecular device has wide application prospect in the technical fields of nanometer robots and nanometer information treatment.
TL;DR: Evaluating the safety and efficacy of E10A combined with paclitaxel/cisplatin chemotherapy in advanced head and neck carcinoma found it feasible and well-tolerated procedure that exerts mild antitumor effects.
Abstract: e16005 Background: E10A is an adenovirus containing human endostatin gene (Ad-rhE). The phase I clinical trial of E10A revealed that weekly intratumoral injection of up to 1 × 1012 VP of E10A to pa...
TL;DR: In this article, a stable superhydrophobic surface has been fabricated with poly(furfuryl alcohol) (PFA)/polytetrafluoroethylene (PTFE) composite coatings on steel substrates by using a facile method.
Abstract: A stable superhydrophobic surface have been fabricated with poly(furfuryl alcohol) (PFA)/polytetrafluoroethylene (PTFE) composite coatings on steel substrates by using a facile method. The observation of field emission scanning electron microscopy revealed that the hierarchical microstructures formed on the surfaces are controlled by varying the curing temperature. This method can be easily operated on substrates of steel, therefore is readily developed to other engineering metal substrates such as aluminum, copper, etc.
TL;DR: In this article, three kinds of modified multiwalled carbon nanotubes (MWNTs) with different length were obtained by grafting carboxylic groups on long MWNTs or copolymer groups on short and long WNTs.
Abstract: Three kinds of modified multiwalled carbon nanotubes (MWNTs) with different length were obtained by grafting carboxylic groups on long MWNTs or copolymer groups on short and long MWNTs. The modified MWNTs were examined by infrared spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy (FESEM). Afterward, the modified MWNTs were introduced into poly (furfuryl alcohol) (PFA), and the tribological behaviors of the resultant PFA composite coatings were investigated using a ring-on-block wear tester under dry friction condition. The dispersion of MWNTs in PFA composites and the worn surfaces were investigated by FESEM. The results indicated that the MWNTs dispersion and the tribological behaviors of PFA composite coatings could be obviously improved by modification with the copolymer. More significantly, under similarly uniform dispersion of MWNTs, the tribological properties of PFA composite coatings with short nanotubes presented better results when compared with those with long nanotubes because of the influence of nanotube length on the degree of modification of the MWNTs surfaces.