Showing papers by "Northeastern University (China) published in 2007"

Extraction of Proteins from Biological Fluids by Use of an Ionic Liquid/Aqueous Two-Phase System

Abstract: An ionic liquid/aqueous two-phase system based on the hydrophilic ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl) and K(2)HPO(4) has been employed for direct extraction of proteins from human body fluids for the first time. Proteins present at low levels were quantitatively extracted into the BmimCl-rich upper phase with a distribution ratio of about 10 between the upper and lower phase and an enrichment factor of 5. Addition of an appropriate amount of K(2)HPO(4) to the separated upper phase results in a further phase separation, giving rise to an improved enrichment factor of 20. FTIR and UV spectroscopy demonstrated that no chemical (bonding) interactions between the ionic liquid and the protein functional groups were identifiable, while no alterations of the natural properties of the proteins were observed. The partitioning of proteins in the two-phase system was assumed to have been facilitated by the electrostatic potential difference between the coexisting phases, as well as by salting out effects. The system could be applied successfully for the quantification of proteins in human urine after on-line phase separation in a flow system. The use of an ionic liquid, as a green solvent, offers clear advantages over traditional liquid-liquid extractions, in which the use of toxic organic solvents is unavoidable.

Guaranteed Cost Networked Control for T–S Fuzzy Systems With Time Delays

Abstract: This paper develops a guaranteed cost networked control (GCNC) method for Takagi-Sugeno (T-S) fuzzy systems with time delays. The state feedback controller is designed via the networked control system (NCS) theory. The stability of the overall fuzzy system using GCNC is also established. Network-induced delay in network transmission and packet dropout are analyzed. Some deductions are also extended to uncertain systems. Simulation results show the validity of the present control scheme

Direct Extraction of Double-Stranded DNA Into Ionic Liquid 1-Butyl-3-methylimidazolium Hexafluorophosphate and Its Quantification

Abstract: Ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), as a green solvent, was successfully used for the direct extraction of dsDNA The extraction efficiency and the distribution coefficient values indicated that trace amounts of DNA at the levels of <5 ng μL-1 facilitate quantitative fast extraction, while proteins and metal species do not interfere A total of 30% of the DNA in ionic liquid at ∼20 ng μL-1 was back extracted into aqueous phase in phosphate−citrate buffer with a single−stage extraction The extraction is demonstrated to be endothermic with an enthalpy of 343 kJ moL-1 The extraction mechanisms were proposed and verified by 31P NMR and FT-IR spectra Interactions between cationic 1-butyl-3-methylimidazolium (Bmim+) and P−O bonds of phosphate groups in the DNA strands take place both in the dissolved BmimPF6 in aqueous phase and at the interface of the two phases This interaction consequently led to the transformation of DNA conformations, along with a reduction of ethid

VGRAM: improving performance of approximate queries on string collections using variable-length grams

Abstract: Many applications need to solve the following problem of approximate string matching: from a collection of strings, how to find those similar to a given string, or the strings in another (possibly the same) collection of strings? Many algorithms are developed using fixed-length grams, which are substrings of a string used as signatures to identify similar strings. In this paper we develop a novel technique, called VGRAM, to improve the performance of these algorithms. Its main idea is to judiciously choose high-quality grams of variable lengths from a collection of strings to support queries on the collection. We give a full specification of this technique, including how to select high-quality grams from the collection, how to generate variable-length grams for a string based on the preselected grams, and what is the relationship between the similarity of the gram sets of two strings and their edit distance. A primary advantage of the technique is that it can be adopted by a plethora of approximate string algorithms without the need to modify them substantially. We present our extensive experiments on real data sets to evaluate the technique, and show the significant performance improvements on three existing algorithms.

Adaptive Synchronization Between Two Different Chaotic Neural Networks With Time Delay

Abstract: This letter presents an adaptive synchronization scheme between two different kinds of delayed chaotic neural networks (NNs) with partly unknown parameters. An adaptive controller is designed to guarantee the global asymptotic synchronization of state trajectories for two different chaotic NNs with time delay. An illustrative example is given to demonstrate the effectiveness of the present method.

Fuzzy XML data modeling with the UML and relational data models

Abstract: Information imprecision and uncertainty exist in many real-world applications and for this reason fuzzy data modeling has been extensively investigated in various data models. Currently, huge amounts of electronic data are available on the Internet, and XML has been the de facto standard of information representation and exchange over the Web. This paper focuses on fuzzy XML data modeling, which is mainly involved in the representation model of the fuzzy XML, its conceptual design, and its storage in databases. Based on ''possibility distribution theory'', we developed this fuzzy XML data model. We developed this fuzzy UML data model to design the fuzzy XML model conceptually. We investigated the formal conversions from the fuzzy UML model to the fuzzy XML model and the formal mapping from the fuzzy XML model to the fuzzy relational databases.

Adaptive Reliable $H_{\infty}$ Filtering Against Sensor Failures

Abstract: This paper is concerned with the adaptive reliable Hinfin filtering problem against sensor failures for continuous-time linear systems. An adaptive Hinfin performance index is defined to describe the disturbance attenuation performance of systems with time-varying parameter estimations. By combining the linear matrix inequality (LMI) approach for Hinfin filter design and adaptive method, a method of designing adaptive reliable Hinfin filters is proposed, where the filter parameter matrices are updated automatically to compensate the sensor failures effects on systems based on the online estimations of eventual faults. It is shown that the design condition for the newly proposed adaptive Hinfin filtering is more relaxed than that for the traditional fixed gain filter design based on LMI approach. An illustrative example and its simulation results are given to illustrate the effectiveness of the proposed design method.

Doping phosphoric acid in polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

Abstract: Polybenzimidazole (PBI) membranes were doped in phosphoric acid solutions of different concentrations at room temperature. The doping chemistry was studied using the Scatchard method. The energy distribution of the acid complexation in polymer membranes is heterogeneous, that is, there are two different types of sites in PBI for the acid doping. The protonation constants of PBI by phosphoric acid are found to be 12.7 L mol -1 (K 1 ) for acid complexing sites with higher affinity, and 0.19 L mol -1 (K 2 ) for the sites with lower affinity. The dissociation constants for the complexing acid onto these two types of PBI sites are found to be 5.4 X 10 -4 and 3.6 X 10 -2 , respectively, that is, about 10 times smaller than that of aqueous phosphoric acid in the first case but 5 times higher in the second. The proton conducting mechanism is also discussed.

Rear Vehicle Detection and Tracking for Lane Change Assist

Abstract: A monocular vision based rear vehicle detection and tracking system is presented for Lane Change Assist (LCA), which does not need road boundary and lane information. Our algorithm extracts regions of interest (ROI) using the shadow underneath a vehicle, and accurately localizes vehicle regions in ROI by vehicle features such as symmetry, edge and shadow underneath vehicles. The algorithm realizes vehicle verification by combining knowledge-based and learning-based methods. During vehicle tracking, templates are dynamically created on-line, tracking window is adaptively adjusted with motion estimation, and confidence is determined for tracked vehicle. The algorithm was tested under various traffic scenes at different daytime, the result illustrated good performance.

Effect of high current pulsed electron beam treatment on surface microstructure and wear and corrosion resistance of an AZ91HP magnesium alloy

Abstract: This paper reports an analysis of the microstructure and property modifications on a commercial Mg alloy AZ91HP treated by using High Current Pulsed Electron Beam (HCPEB). It is shown that, a thin layer consisting of nanograined MgO formed on the top surface after HCPEB (electron energy ∼ 30 keV, pulse duration 1 μs, energy density ∼ 3 J/cm2) treatment, below which is a melted layer with depth of about 8–10 μm. The heat affected zone (HAZ) underneath the melted layer and stress wave affected zone contains many stress induced deformation marks. Meantime, a nearly complete dissolution of the intermetallic phase Mg17Al12 in the melted layer is observed, leading to the formation of a super-saturated solid solution on the surface. This is due to the solute trapping effect occurred during the fast solidification process. As a result, the wear and corrosion resistance of the alloy were significantly improved as shown by sliding friction, wear and immersion tests.

Improvement in performance of MgO–CaO refractories by addition of nano-sized ZrO2

Abstract: MgO–CaO refractories added with different sized ZrO2 powders were sintered at 1600 °C, the effect of the ZrO2 powders on performance of MgO–CaO refractories was investigated. The results showed that the densification of the MgO–CaO refractories was appreciably promoted when a small amount of ZrO2 was added owing to the formation of small size CaZrO3 facilitated to sintering, and the densification was promoted further with increasing the amount of ZrO2 due to the volume expansion caused by the reaction of the added ZrO2 and CaO to form CaZrO3 in the refractories, and the addition of nano-sized ZrO2 was more effective. The thermal shock resistance of the MgO–CaO refractories was improved by modification of the microstructure due to the formed CaZrO3 particles that predominately located on the grain boundaries and triple points in the whole microstructure, and the addition of nano-sized ZrO2 was more effective attributed to its well dispersion and the critical addition amount was effectively decreased to 6%. The slaking resistance of the MgO–CaO refractories was appreciably improved by addition of ZrO2 due to its effect on decreasing the amount of free CaO in the refractories, promotion of densification as well as modification of microstructure, the nano-sized ZrO2 addition was more effective due to its higher activity. The slag corrosion resistance of the MgO–CaO refractories was enhanced by addition of ZrO2 due to the increase of the viscosity of the liquid phase and thus inhibited further penetration of slag at elevated temperatures.

Superconductivity in novel Ge-based skutterudites: {Sr,Ba}pt4Ge12.

Abstract: Combining experiments and ab initio models we report on ${\mathrm{SrPt}}_{4}{\mathrm{Ge}}_{12}$ and ${\mathrm{BaPt}}_{4}{\mathrm{Ge}}_{12}$ as members of a novel class of superconducting skutterudites, where Sr or Ba atoms stabilize a framework entirely formed by Ge atoms. Below ${T}_{c}=5.35$ and 5.10 K for ${\mathrm{BaPt}}_{4}{\mathrm{Ge}}_{12}$ and ${\mathrm{SrPt}}_{4}{\mathrm{Ge}}_{12}$, respectively, electron-phonon coupled superconductivity emerges, ascribed to intrinsic features of the Pt-Ge framework, where Ge-$p$ states dominate the electronic structure at the Fermi energy.