Showing papers by "Zhen Li published in 2008"
TL;DR: A new light-emitting polyacetylene bearing imidazole moieties in the side chain was conveniently prepared through a postfunctionalization strategy, as a sensory polymer to selectively report the presence of Cu2+ based on the fluorescence "turn-off".
290 citations
TL;DR: A label-free DNA assay system with a simple dye with aggregation-induced emission (AIE) characteristics as the fluorescent bioprobe that enables real-time monitoring of folding process of G1 in the absence of any pre-attached fluorogenic labels on the DNA strand.
Abstract: Biosensing processes such as molecular beacons require non-trivial effort to covalently label or mark biomolecules We report here a label-free DNA assay system with a simple dye with aggregation-induced emission (AIE) characteristics as the fluorescent bioprobe 1,1,2,2-Tetrakis[4-(2-bromoethoxy)phenyl]ethene is nonemissive in solution but becomes highly emissive when aggregated This AIE effect is caused by restriction of intramolecular rotation, as verified by a large increase in the emission intensity by increasing viscosity and decreasing temperature of the aqueous buffer solution of 1,1,2,2-tetrakis[4-(2-triethylammonioethoxy)phenyl]ethene tetrabromide (TTAPE) When TTAPE is bound to a guanine-rich DNA strand (G1) via electrostatic attraction, its intramolecular rotation is restricted and its emission is turned on When a competitive cation is added to the G1 solution, TTAPE is detached and its emission is turned off TTAPE works as a sensitive poststaining agent for poly(acrylamide) gel electrophoresis (PAGE) visualization of G1 The dye is highly affinitive to a secondary structure of G1 called the G-quadruplex The bathochromic shift involved in the G1 folding process allows spectral discrimination of the G-quadruplex from other DNA structures The strong affinity of TTAPE dye to the G-quadruplex structure is associated with a geometric fit aided by the electrostatic attraction The distinct AIE feature of TTAPE enables real-time monitoring of folding process of G1 in the absence of any pre-attached fluorogenic labels on the DNA strand TTAPE can be used as a K+ ion biosensor because of its specificity to K+-induced and -stabilized quadruplex structure
263 citations
TL;DR: An old and cheap compound, zincon (2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene), was found to be a "novel" highly sensitive and selective chemosensor for cyanide in pure aqueous solutions, with a detection limit of 0.13 ppm and a color change that could be observed by the naked eye.
210 citations
TL;DR: To develop sensitive and selective CN− chemosensors, a new imidazole-functionalized polyfluorene (P1) was designed and obtained conveniently, the fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 0.20 ppm in diluted solutions.
Abstract: To develop sensitive and selective CN− chemosensors, a new imidazole-functionalized polyfluorene (P1) was designed and obtained conveniently, the fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 0.20 ppm in diluted solutions. By utilizing the much higher stability constant of the complex of CN− and Cu2+, the quenched fluorescence of the solution of P1 by Cu2+ ions could recover upon the addition of trace CN− anions, with the detection limit down to 0.31 ppm, making P1 a novel, sensitive and selective cyanide probe.
184 citations
TL;DR: A series of nonlinear optical chromophores were successfully prepared, in which pyrrole moieties were the conjugated bridge, and thesechromophores demonstrated similar or enhanced NLO effects and interesting optical behavior.
Abstract: A series of nonlinear optical (NLO) chromophores were successfully prepared, in which pyrrole moieties were the conjugated bridge. In comparison with their analogues containing furan or thiophene groups as the bridge, these chromophores demonstrated similar or enhanced NLO effects (up to 3.3 times) and interesting optical behavior. While the acceptor groups were malononitrile (Mal), 3-phenyl-5-isoxazolone (Iso), and 1,3-diethylthiobarbituric acid (Bar), the chromophores exhibited much blue-shifted maximum absorption wavelengths (λmax) (up to 36 nm); however, the λmax of the chromophore containing tricyanovinyldihydrofuran (TCF) as acceptor became much longer than that of the analogue (up to 75 nm).
84 citations
TL;DR: The obtained experimental results indicated that the polymer backbone, in addition to the linked isolation moieties, could act as isolation spacers in some special cases and benefit the macroscopic NLO effect of the resultant polymers.
Abstract: Three indole-based nonlinear optical (NLO) chromophores with changeable isolation groups were successfully introduced into the polymer backbone to yield a series of main-chain polyurethanes. Thanks to the main-chain structure and the advantages of the indole-based chromophores, all of the polymers show excellent transparency, good processability, thermal stability, and relatively good NLO effects. The obtained experimental results indicated that the polymer backbone, in addition to the linked isolation moieties, could act as isolation spacers in some special cases. The tested NLO results demonstrated that the isolation groups with apparent site-isolation effect might not benefit the macroscopic NLO effect of the resultant polymers.
63 citations
TL;DR: In this article, a new series of azobenzene-containing polyfluorenes have been successfully prepared through polymer reactions by the utilization of "click" chemistry, and all the polymers were well characterized and soluble in common solvents.
Abstract: A new series of azobenzene-containing polyfluorenes have been successfully prepared through polymer reactions by the utilization of "click" chemistry. All the polymers were well characterized and soluble in common solvents. By the application of the concept of "suitable isolation group", the macroscopic nonlinear optical (NLO) properties of the polymers could be boosted to as large as three times that of the polymer without isolation moieties. Also, all the polymers were thermally stable, and demonstrated good procesability, coupled with improved optical transparency. Thus, they are good candidates for the practical applications as new photonic materials.
58 citations
TL;DR: A series of polyvinyl carbazole-based polymers containing sulfonyl-based nonlinear optical chromophores as the side chains were prepared conveniently through a postfunctionalization approach as mentioned in this paper.
Abstract: A series of poly(vinylcarbazole)-based polymers containing sulfonyl-based nonlinear optical chromophores as the side chains were prepared conveniently through a postfunctionalization approach. In the polymers, the subtle structure of the chromophore moieties could be easily modified by the introduction of different isolation group, to adjust the property of the resultant polymers. The polymers exhibited good optical transparency, besides their good processability and thermal stability. The poled polymer films exhibited large second harmonic generation (SHG) coefficients of d33 values (up to 28.6 pm/V) with excellent thermal stability (about 90% of the maximal SHG coefficients remain at ∼ 110 °C). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2983–2993, 2008
58 citations
TL;DR: In this article, a 3D ordered macro-porous structure with conducting polymers and magnetic inorganic compounds was obtained by water-assisted self-assembly method, and the morphologies of this honeycomb structure film were studied by transmission electron microscopic and atomic force microscropy, while the Fourier transform infrared spectra were obtained to illustrate its composition.
47 citations
01 Jan 2008
TL;DR: Three generalized systems for event detection are developed and evaluated, and two ad-hoc methods that were designed to specifically detect OpposingFlow and TakePicture events are introduced.
Abstract: We have developed and evaluated three generalized systems for event detection. The first system is a simple brute force search method, where each space-time location in the video is evaluated by a binary decision rule on whether it contains the event or not. The second system is build on top of a head tracker to avoid costly brute force searching. The decision stage is a combination of state of the art feature extractors and classifiers. Our third system has a probabilistic framework. From the observations, the pose of the people are estimated and used to determine the presence of event. Finally we introduce two ad-hoc methods that were designed to specifically detect OpposingFlow and TakePicture events. The results are promising as we are able to get good results on several event categories, while for all events we have gained valuable insights and experience.
38 citations
TL;DR: The results indicate the existence of a powerful polymer effect on dispersing CNTs and the attachment of a ferrocene pendant to a PPA backbone, followed by hybridization with C NTs, improved the thermal stability.
Abstract: A group of ferrocene-containing poly(phenylacetylene)s (PPAs) with different alkyl spacers were synthesized by using organorhodium complexes [Rh(diene)Cl]2 and Rh+(nbd)[C6H5B−(C6H5)3] as catalysts....
03 Dec 2008
TL;DR: A novel two-stage scheme of pornographic image detection is proposed, which first applies the content-based image retrieval technique to find out whether human are present in the images, and then a detailed skin color analysis is performed to affirm the presence of pornographic content.
Abstract: A novel two-stage scheme of pornographic image detection is proposed in this paper. Specifically, we first apply the content-based image retrieval technique to find out whether human are present in the images. Then a detailed skin color analysis is performed to affirm the presence of pornographic content in the images. Experimental results show that the proposed algorithm performs well and fast in detecting pornographic images.
TL;DR: In this article, a series of azobenzene-containing polyurethanes were prepared and post-azo coupling reactions were successfully used to modify the subtle structure of the chromophore moieties.
TL;DR: In this paper, two new indole-based chromophores were designed and successfully introduced to the polymeric system, the resultant polymers demonstrated enhanced NLO effects, good processability, thermal stability and nearly excellent transparency, indicating the advantages of "H" type chromophore moieties.
Abstract: Two new "H" type of indole-based chromophores were designed and successfully introduced to the polymeric system, the resultant polymers demonstrated enhanced NLO effects, good processability, thermal stability and nearly excellent transparency, indicating the advantages of "H" type chromophore moieties. And they could be promising candidates for the practical applications as new photonic materials.
TL;DR: In this article, a simple method of thermal evaporation to fabricate micro and nanostructures of zinc oxide was presented, which was characterized by techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and analytical transmission electron Microscope.
Abstract: A simple method of thermal evaporation to fabricate micro and nanostructures of zinc oxide was presented. ZnO micro and nanostructures, prepared under different quantity of O 2 , were characterized by techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and analytical transmission electron Microscope. The SEM images indicated that the products prepared under the condition of sufficient O 2 were needle-like microrods and the samples synthesized under the condition of deficient O 2 were nanorods and nanowires with very high aspect ratio. The results of XRD and Raman shifts revealed that the ZnO micro and nanostructures synthesized under different quantity of O 2 were both single crystalline with the hexagonal wurtzite structure. The HRTEM images indicated that the ZnO nanowire prepared under the condition of deficient O 2 was single crystalline and grown along the direction of [0 0 1]. Photoluminescence measurement was carried out and it showed that the spectra of ZnO micro and nanostructures prepared under different quantity of O 2 exhibited similar emission features. In addition, the growth mechanism of ZnO micro and nanostructures was preliminarily discussed.
TL;DR: In this paper, a new imidazole-containing disubstituted polyacetylene (P1) with strong green fluorescence was successfully prepared through polymer reaction, which was nearly impossible to be obtained from the direct polymerization of its corresponding monomer.
Abstract: new imidazole-containing disubstituted polyacetylene (P1) with strong green fluorescence was successfully prepared through polymer reaction, which was nearly impossible to be obtained from the direct polymerization of its corresponding monomer. The polymer was soluble in common organic solvents, and its strong green fluorescence could be quenched completely by the Cu 2+ and Co 2+ ions, at the concentrations as low as 1.33 and 1.67 x 10 -5 mol/L (0.85 and 0.92 ppm), respectively. Because of the high stability of the complex formed by cyanide and copper ions, the quenched green fluorescence of P1 by copper ions could be turned on upon the addition of trace cyanide (as low as 2.70 x 10 -5 mol/L, 0.70 ppm), making P1 a new sensitive cyanide chemosensor. The results thus provided a new opportunity to develop anion chemosensors based on good cation chemosensors.
TL;DR: In this paper, a series of second-order nonlinear optical polymers with fluorene moieties as isolation spacers were successfully prepared based on control experiments, and the tested NLO properties of the polymers demonstrated that the isolation groups with big size do not always benefit the resultant NLO effect.
TL;DR: In this paper, a new SOI high-voltage device with a step thickness sustained voltage layer (ST SOI) was proposed, where the electric field in the drift region is modulated, and that in the buried layer is enhanced by the variable-thickness SOI layer, resulting in enhancement of breakdown voltage (BV).
Abstract: A new SOI high-voltage device with a step thickness sustained voltage layer (ST SOI) is proposed. The electric field in the drift region is modulated, and that in the buried layer is enhanced by the variable-thickness SOI layer, resulting in enhancement of breakdown voltage (BV). BV for the ST SOI with two steps is twice as high as that of the conventional SOI, maintaining the low on-resistance (Ron).
TL;DR: Applications of atomic force microscopy (AFM) to the fabrication of chemical nanosensors are presented and the sensitive characteristic of such TiO2 nanowires to hydrogen is investigated.
TL;DR: It is demonstrated in this transgenic line that cre mRNA was specifically expressed in growing oocytes like endogenous zp3 mRNA, and it was confirmed that the cre line was capable of activating a loxP‐blocked EGFP reporter gene by both maternal and oocyte‐expressed Cre.
Abstract: In this communication, we report the generation of a cre transgenic zebrafish line under an oocyte-specific promoter, zp3. The transgenic line Tg(zp3:cre; krt8:rfp) also contains a co-integrated rfp transgene under the skin epithelial promoter krt8 to allow selection of cre transgenic fish based on RFP fluorescence in the skin. We demonstrated in this transgenic line that cre mRNA was specifically expressed in growing oocytes like endogenous zp3 mRNA. When Tg(zp3:cre; krt8:rfp) was crossed with a loxP transgenic line, the floxed DNA was specifically eliminated from female, but not male, germline. Tg(zp3:cre; krt8:rfp) fish also have maternal cre mRNA in early embryos to cause Cre-mediated recombination; this feature can be used to activate other loxP transgenic lines in early embryos. Furthermore, after crossing with another loxP transgenic line, Tg(EF:loxP-mCherry-loxP-egfp), we confirmed that our cre line was capable of activating a loxP-blocked EGFP reporter gene by both maternal and oocyte-expressed Cre. Developmental Dynamics 237:2955–2962, 2008. © 2008 Wiley-Liss, Inc.
TL;DR: In this paper, a probable mechanism for the formation of nanocrystalline PbS particles is proposed, which is based on electron beam irradiating poly(vinyl alcohol) (PVA)-thioacetamide (C 2 H 5 NS)-isopropyl alcohol (IPA) aqueous solution containing lead acetate (Pb(CH 3 COO) 2 ·3H 2 O) with the absorbed dose of 350 kGy at room temperature.
17 Dec 2008
TL;DR: A new data hiding method for 3D triangle meshes in the predictive VQ domain is presented that is reversible and enables the cover mesh data to be completely restored when the payload is removed from the VQ bitstream.
Abstract: In the digitized world nowadays, digital content (audio, images, video, 3D meshes, etc.) can be easily copied, manipulated and distributed. Copyright protection and integrity verification of digital content have become urgent problems for multimedia owners and distributors. In addition, to alleviate bandwidth requirements, vector quantization (VQ) is an effective and popular vertex data compression technique for triangle meshes. In this paper, we present a new data hiding method for 3D triangle meshes in the predictive VQ domain. The proposed method is reversible and enables the cover mesh data to be completely restored when the payload is removed from the VQ bitstream. The mechanism is embedding the payload by modifying the prediction rules during the VQ process. Besides, the hash of the cover mesh can be hidden for the self authentication purpose. Experimental results demonstrate the high capacity of the proposed data hiding scheme.
TL;DR: Based on the oxygen isotope ratio and microparticle record in ice cores recovered at Mt. Muztagata, Eastern Pamirs, the seasonal variations of atmospheric dust have been reconstructed for the past four decades.
Abstract: Based on the oxygen isotope ratio and microparticle record in ice cores recovered at Mt. Muztagata, Eastern Pamirs, the seasonal variations of atmospheric dust have been reconstructed for the past four decades. High dust concentrations and coarser particle grains have the similar trend with oxygen isotope value. Our statistical results indicate that 50%–60% high dust concentration samples occur during the season with high oxygen isotope values (summer), while low dust storm frequency during spring and winter. Back-trajectory analysis shows that the air mass hitting Muztagata predominately came from West Asia (such as Iran-Afghanistan Plateau) and Central Asia, which are the main dust source area for Muztagata. Dust storms in those source areas most frequently occur during summer (from May to August), while frequent dust storm events in northern China mainly occur during spring (March to May). Regions in the path of Asian dust transport, such as in Japan, the North Pacific, and Greenland, also show high dust concentrations during spring (from March to May). Our results indicate that dust storms have different seasonality in different regions within Asia.
TL;DR: In this article, the ammonium (NH4+) history recorded in an ice core from the East Pamir in Central Asia, which was drilled on the Mt. Muztagata at the elevation of 7010 m a.s.
Abstract: As a major alkaline gas in the atmosphere, ammonia (NH3) plays an important role in atmospheric chemistry. However, there is little knowledge about NH3 variations in the Central Asia. Here we analyzed the ammonium (NH4+) history recorded in an ice core from the East Pamir in Central Asia, which was drilled on the Mt. Muztagata at the elevation of 7010 m a.s.l. in 2003. The core was carefully dated and NH4+ concentration history during 1907–2002 was reconstructed. The result shows that NH4+ concentration remained approximately constant until the 1930s after a sudden decrease at the very beginning of the 20th century, followed by a minimum in 1940 before increasing steadily to the peak at the end of 1990s. It is found that the annual mean NH4+ concentration was strongly associated with the Northern Hemisphere temperature, suggesting the impact of temperature on NH3 emissions in the Central Asia. Moreover, an increase of NH4+ concentration after 1940 also reflects the enhancement of NH3 emissions from anthropogenic sources such as fertilizer applications and livestock wastes in the 20th century.
TL;DR: A new fast approach to the nearest codevector search for 3D mesh compression using an Orthonormal transformed codebook using the coefficients of an input vector along a set of orthonormal bases as the criteria to reject impossible codevectors.
Abstract: A new fast approach to the nearest codevector search for 3D mesh compression using an orthonormal transformed codebook is proposed. The algorithm uses the coefficients of an input vector along a set of orthonormal bases as the criteria to reject impossible codevectors. Compared to the full search algorithm, a great deal of computational time is saved without extra distortion and additional storage requirement. Simulation results demonstrate the effectiveness of the proposed algorithm in terms of computational complexity.
TL;DR: In this article, a novel method has been developed by electron beam irradiation to prepare nanocrystalline tin(II) selenide with an orthorhombic phase.
TL;DR: In this article, the influence of oxygen on the growth of carbon nanotubes (CNTs) using plasma-enhanced chemical vapour deposition has been studied, and the results showed that small cobalt oxide particles obtained by O2-etching were deoxidized back to Co catalyst particles with small size in the CH4/H2 atmosphere for the growth.
Abstract: The influence of oxygen on the growth of carbon nanotubes (CNTs) using plasma-enhanced chemical vapour deposition has been studied. The cobalt catalyst film and CNTs were characterized by scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscope, x-ray photoelectron spectroscopy and Raman spectroscopy. The results showed that small cobalt oxide particles obtained by O2-etching were deoxidized back to Co catalyst particles with small size in the CH4/H2 atmosphere for the growth of CNTs. Small Co particles and the inlet of oxygen in the stage of CNT growth enhanced the yield rate and purity of aligned CNTs.
TL;DR: A 16.8 m firn core of middle Himalayas was recovered on the col of Dasuopu glacier in August 2006, being 7000 m above sea level as mentioned in this paper, and a total of 317 samples were measured for stable oxygen isotope ratios and major ion concentrations.
Abstract: A 16.8 m firn core of middle Himalayas was recovered on the col of Dasuopu glacier in August 2006, being 7000 m above sea level. A total of 317 samples were measured for stable oxygen isotope ratios (δ
18O) and major ion concentrations (Na+, NH
4
+
, K+, Mg2+, Ca2+, Cl−, SO
4
2−
, and NO
3
−
). The firn core dating and seasonal partitioning were carried out based on the marked seasonal variations along the stable oxygen isotopes and crustal species (Ca2+, Mg2+) profiles. The multi-parameters and high-resolution glaciochemical data set of Dasuopu firn core recorded the detailed chemical characteristics of precipitation in high-elevation region, middle Himalayas, since 1991 A.D., which mainly originated from the crustal and anthropogenic sources, while the sea-salt contribution was minor. The seasonal variability of major ion concentrations was dominated by the seasonal alternation of the prevalent air mass, atmospheric circulation situation and precipitation regime. Linear regression analysis indicated that most of the variance in annual ionic fluxes can be explained by a linear dependence on snow accumulation rate.
TL;DR: In this article, a novel method has been developed by electron beam irradiation to prepare PbSe nanoparticles using 2 MeV 10mA GJ-2-II electronic accelerator as radiation source.
Abstract: A novel method has been developed by electron beam irradiation to prepare PbSe nanoparticles. 2 MeV 10mA GJ-2-II electronic accelerator was used as radiation source. Nanocrystalline PbSe was prepared rapidly at room temperature under atmospheric pressure without any kind of toxic reagents. The structure and morphology of prepared PbSe nanoparticles were analysed by X-ray diffraction, transmission electron microscope and atomic force microscope. The results indicated that the obtained materials were cubic nanocrystalline PbSe with an average grain size of 30 nm. The optical properties of prepared PbSe nanocrystalline were characterized by using photoluminescence spectroscopy. The possible mechanism of the PbSe grain growth by electron beam irradiation method is proposed.
07 Jul 2008
TL;DR: The method and result for the glacier identification integrated intensity of backscattering from Envisat/ASAR images, coherence coefficients of repeat pass interferometry from ASAR and ALOS/PalSAR, and full polarimetric SAR from PalSAR are demonstrated.
Abstract: For climatological and hydrological investigations, the areas covered by glacier and their spatial variability are important parameters, particularly in Qinghai-Tibetan Plateau. A interferometric SAR technique not only can produce a high-resolution digital elevation models but also can identify the surface object with coherence coefficients. This property of SAR polarimetry is particularly useful in classification. In this paper we analyze to demonstrate the method and result for the glacier identification integrated intensity of backscattering from Envisat/ASAR images, coherence coefficients of repeat pass interferometry from ASAR and ALOS/PalSAR, and full polarimetric SAR from PalSAR.