Showing papers by "Wuhan University published in 2010"

WLD: A Robust Local Image Descriptor

Abstract: Inspired by Weber's Law, this paper proposes a simple, yet very powerful and robust local descriptor, called the Weber Local Descriptor (WLD). It is based on the fact that human perception of a pattern depends not only on the change of a stimulus (such as sound, lighting) but also on the original intensity of the stimulus. Specifically, WLD consists of two components: differential excitation and orientation. The differential excitation component is a function of the ratio between two terms: One is the relative intensity differences of a current pixel against its neighbors, the other is the intensity of the current pixel. The orientation component is the gradient orientation of the current pixel. For a given image, we use the two components to construct a concatenated WLD histogram. Experimental results on the Brodatz and KTH-TIPS2-a texture databases show that WLD impressively outperforms the other widely used descriptors (e.g., Gabor and SIFT). In addition, experimental results on human face detection also show a promising performance comparable to the best known results on the MIT+CMU frontal face test set, the AR face data set, and the CMU profile test set.

Financial Reporting Quality and Investment Efficiency of Private Firms in Emerging Markets

Abstract: Prior research shows that financial reporting quality (FRQ) is positively related to investment efficiency for large U.S. publicly traded companies. We examine the role of FRQ in private firms from emerging markets, a setting in which extant research suggests that FRQ would be less conducive to the mitigation of investment inefficiencies. Earlier studies show that private firms have lower FRQ, presumably because of lower market demand for public information. Prior research also shows that FRQ is lower in countries with low investor protection, bank-oriented financial systems, and stronger conformity between tax and financial reporting rules. Using firm-level data from the World Bank, our empirical evidence suggests that FRQ positively affects investment efficiency. We further find that the relation between FRQ and investment efficiency is increasing in bank financing and decreasing in incentives to minimize earnings for tax purposes. Such a connection between tax-minimization incentives and the informational role of earnings has often been asserted in the literature. We provide explicit evidence in this regard.

Multi-electron reaction materials for high energy density batteries

Abstract: The need for high energy density batteries becomes increasingly important for the development of new and clean energy technologies, such as electric vehicles and electrical storage from wind and solar power. The search for new energetic materials of primary and secondary batteries with higher energy density has been highlighted in recent years. This review surveys recent advances in the research field of high energy density electrode materials with focus on multi-electron reaction chemistry of light-weight elements and compounds. In the first section, we briefly introduce the basic strategies for enhancement of the energy density of primary batteries based on multi-electron reactions. The following sections present overviews of typical electrode materials with multi-electron chemistry and their secondary battery applications in aqueous and non-aqueous electrolytes. Finally, the challenges and ongoing research strategies of these novel electrode materials and battery systems for high density energy storage and conversion are discussed.

Polyimides: Promising Energy‐Storage Materials

Abstract: Based on this redox mechanism, we developed a series of polyamides with different structures and investigated their electrochemical activity as cathode materials for rechargeable lithium batteries. The results show that the polymer framework endows these samples with excellent cycling stability. Additionally, their capacity and rate capability are also satisfactory. The five polyimides were obtained through a simple polycondensation between commonly used dianhydrides and diamines. Coin cells consisting of the cathode (polyimide: conductive carbon: PTFE= 6:3:1), lithium anode and electrolyte (1 M LiTFSI/DOL+DME) were used for cycling tests, with the cutoff voltage of 1.5~3.5 V. FTIR characterization confirms the obtaining of our target products. In the charge/discharge measurements, all the samples show efficiency close to 100%. The Table below summarizes the results of five typical products. The theoretical capacity is calculated based on a four-electron mechanism shown above. The strong resemblance in the average discharge voltage and voltage profile between the sample PI-1 and PI-2, PI-3 and PI-4 seems to imply that the average discharging voltage are mainly determined by the functional group adjacent to the carbonyl group rather than that attached to the nitrogen atom. Comparing the theoretical capacity and experimental value, it can be generalized that almost half of the active site is available to be attached by Li, which possibly suggests that two electrons have been transferred during the charge/discharge process. Considering the importance of cyclabilty and rate performance, polyimide containing NTCDA(1,4,5,8-naphthalenetetracarboxylic dianhydride) unit seems to be a promising energy-storage material. Authors would express their sincere thanks to the Nature Science Foundation of China (No. 20873094) for the financial support.

A genome-wide association study of cleft lip with and without cleft palate identifies risk variants near MAFB and ABCA4

Abstract: Case-parent trios were used in a genome-wide association study of cleft lip with and without cleft palate. SNPs near two genes not previously associated with cleft lip with and without cleft palate (MAFB, most significant SNP rs13041247, with odds ratio (OR) per minor allele = 0.704, 95% CI 0.635-0.778, P = 1.44 x 10(-11); and ABCA4, most significant SNP rs560426, with OR = 1.432, 95% CI 1.292-1.587, P = 5.01 x 10(-12)) and two previously identified regions (at chromosome 8q24 and IRF6) attained genome-wide significance. Stratifying trios into European and Asian ancestry groups revealed differences in statistical significance, although estimated effect sizes remained similar. Replication studies from several populations showed confirming evidence, with families of European ancestry giving stronger evidence for markers in 8q24, whereas Asian families showed stronger evidence for association with MAFB and ABCA4. Expression studies support a role for MAFB in palatal development.

Organocatalysis in Cross-Coupling: DMEDA-Catalyzed Direct C−H Arylation of Unactivated Benzene

Abstract: A striking breakthrough to the frame of traditional cross-couplings/C-H functionalizations using an organocatalyst remains unprecedented. We uncovered a conceptually different approach toward the biaryl syntheses by using DMEDA as the catalyst to promote the direct C-H arylation of unactivated benzene in the presence of potassium tert-butoxide. The arylation of unactivated benzene with aryl iodides, or aryl bromides and even chlorides under the assistance of an iodo-group, could simply take place at 80 °C. The new methodology presumably involves an aryl radical anion as an intermediate. This finding offers an option toward establishing a new horizon for direct C-H/cross-coupling reactions.

High‐Performance Alkaline Polymer Electrolyte for Fuel Cell Applications

Abstract: Although the proton exchange membrane fuel cell (PEMFC) has made great progress in recent decades, its commercialization has been hindered by a number of factors, among which is the total dependence on Pt-based catalysts. Alkaline polymer electrolyte fuel cells (APEFCs) have been increasingly recognized as a solution to overcome the dependence on noble metal catalysts. In principle, APEFCs combine the advantages of and alkaline fuel cell (AFC) and a PEMFC: there is no need for noble metal catalysts and they are free of carbonate precipitates that would break the waterproofing in the AFC cathode. However, the performance of most alkaline polyelectrolytes can still not fulfill the requirement offuel cell operations. In the present work, detailed information about the synthesis and physicochemical properties of the quaternary ammonia polysulfone (QAPS), a high-performance alkaline polymer electrolyte that has been successfully applied in the authors' previous work to demonstrate an APEFC completely free from noble metal catalysts (S. Lu, J. Pan, A. Huang, L. Zhuang, J. Lu, Proc. Natl. Acad. Sci. USA 2008, 105, 20611), is reported. Monitored by NMR analysis, the synthetic process of QAPS is seen to be simple and efficient. The chemical and thermal stability, as well as the mechanical strength of the synthetic QAPS membrane, are outstanding in comparison to commercial anion-exchange membranes. The ionic conductivity of QAPS at room temperature is measured to be on the order of 10 -2 S cm -1 Such good mechanical and conducting performances can be attributed to the superior microstructure of the polyelectrolyte, which features interconnected ionic channels in tens of nanometers diameter, as revealed by HRTEM observations. The electrochemical behavior at the Pt/ QAPS interface reveals the strong alkaline nature of this polyelectrolyte, and the preliminary fuel cell test verifies the feasibility of QAPS for fuel cell applications.

Assessing object-based classification: advantages and limitations

Abstract: The advantages of object-based classification over the traditional pixel-based approach are well documented. However, the potential limitations of object-based classification remain less explored. In this letter, we assess the advantages and limitations of an object-based approach to remote sensing image classification relative to a pixel-based approach. We first quantified the negative impacts of under-segmentation errors on the potential accuracy of object-based classification by developing a new segmentation accuracy measure. Then we evaluated the advantages and limitations of object-based classification by quantifying their overall effects relative to pixel-based classification, with respect to their classification units and features at multiple segmentation scales. The results based on a QuickBird satellite image indicate that (1) segmentation accuracies decrease with increasing segmentation scales and the negative impacts of under-segmentation errors become significantly large at large scales and (2...

Discrete plasticity in sub-10-nm-sized gold crystals

Abstract: Although deformation processes in submicron-sized metallic crystals are well documented, the direct observation of deformation mechanisms in crystals with dimensions below the sub-10-nm range is currently lacking. Here, through in situ high-resolution transmission electron microscopy (HRTEM) observations, we show that (1) in sharp contrast to what happens in bulk materials, in which plasticity is mediated by dislocation emission from Frank-Read sources and multiplication, partial dislocations emitted from free surfaces dominate the deformation of gold (Au) nanocrystals; (2) the crystallographic orientation (Schmid factor) is not the only factor in determining the deformation mechanism of nanometre-sized Au; and (3) the Au nanocrystal exhibits a phase transformation from a face-centered cubic to a body-centered tetragonal structure after failure. These findings provide direct experimental evidence for the vast amount of theoretical modelling on the deformation mechanisms of nanomaterials that have appeared in recent years.

Review on Estimation of Land Surface Radiation and Energy Budgets From Ground Measurement, Remote Sensing and Model Simulations

Abstract: Land surface radiation and energy budgets are critical components of any land surface models that characterize hydrological, ecological and biogeochemical processes. The estimates of their components generated from remote sensing data or simulations from numerical models have large uncertainties. This paper provides a comprehensive review of recent advances in estimating insolation, albedo, clear-sky longwave downward and upwelling radiation, all-wave net radiation and evapotranspiration from ground measurements, remote sensing algorithms and products, as well as numerical model simulations. The decadal variations of these components are also discussed.

Research on the architecture and key technology of Internet of Things (IoT) applied on smart grid

Abstract: Advances in the areas of embedded systems, computing, and networking are leading to an infrastructure composed of millions of heterogeneous devices. These devices will not simply convey information but process it in transit, connect peer to peer, and form advanced collaborations. This “Internet of Things (IoT)” infrastructure will be strongly integrated with the environment. This paper focuses on researching on the architecture and key technology of Internet of Things. Moreover, the applications of Internet of Things are interpreted in this paper. Especially, the application of IoT in smart grid is emphasized. The work presented here proposes the principal characteristics for an effective integration of the Internet of Things in smart grid.

Molecular mechanism of chemoresistance by miR-215 in osteosarcoma and colon cancer cells

Abstract: Translational control mediated by non-coding microRNAs (miRNAs) plays a key role in the mechanism of cellular resistance to anti-cancer drug treatment. Dihydrofolate reductase (DHFR) and thymidylate synthase (TYMS, TS) are two of the most important targets for antifolate- and fluoropyrimidine-based chemotherapies in the past 50 years. In this study, we investigated the roles of miR-215 in the chemoresistance to DHFR inhibitor methotrexate (MTX) and TS inhibitor Tomudex (TDX). The protein levels of both DHFR and TS were suppressed by miR-215 without the alteration of the target mRNA transcript levels. Interestingly, despite the down-regulation of DHFR and TS proteins, ectopic expression of miR-215 resulted in a decreased sensitivity to MTX and TDX. Paradoxically, gene-specific small-interfering RNAs (siRNAs) against DHFR or TS had the opposite effect, increasing sensitivity to MTX and TDX. Further studies revealed that over-expression of miR-215 inhibited cell proliferation and triggered cell cycle arrest at G2 phase, and that this effect was accompanied by a p53-dependent up-regulation of p21. The inhibitory effect on cell proliferation was more pronounced in cell lines containing wild-type p53, but was not seen in cells transfected with siRNAs against DHFR or TS. Moreover, denticleless protein homolog (DTL), a cell cycle-regulated nuclear and centrosome protein, was confirmed to be one of the critical targets of miR-215, and knock-down of DTL by siRNA resulted in enhanced G2-arrest, p53 and p21 induction, and reduced cell proliferation. Additionally, cells subjected to siRNA against DTL exhibited increased chemoresistance to MTX and TDX. Endogenous miR-215 was elevated about 3-fold in CD133+HI/CD44+HI colon cancer stem cells that exhibit slow proliferating rate and chemoresistance compared to control bulk CD133+/CD44+ colon cancer cells. Taken together, our results indicate that miR-215, through the suppression of DTL expression, induces a decreased cell proliferation by causing G2-arrest, thereby leading to an increase in chemoresistance to MTX and TDX. The findings of this study suggest that miR-215 may play a significant role in the mechanism of tumor chemoresistance and it may have a unique potential as a novel biomarker candidate.

Comparison of Dye Photodegradation and its Coupling with Light-to-Electricity Conversion over TiO2 and ZnO

Abstract: Through comparing the photocatalytic performance of microscale ZnO, nano ZnO, and Degussa P25 titania (P25), it was found that the microscale ZnO exhibited 2.6-35.7 times higher photocatalytic activity for the photodegradation of various dye pollutants than P25 under both UV-visible and visible irradiation and showed much better photostability than the nano ZnO. The photocatalysts were characterized with XRD, Raman, BET, DRUV-vis, adsorption of dye, photoelectrochemical measurement, and PL. The much higher photocataltyic activity of the microscale ZnO than P25 under UV-visible irradiation is attributed to the higher efficiency of generation, mobility, and separation of photoinduced electrons and holes. The much higher visible photocataltyic activity of the microscale ZnO than P25 is due to the higher photosensitization efficiency of electron transfer from an excited dye to the conduction band of the microscale ZnO than that of P25. The much better photostability of the microscale ZnO than the nano ZnO is due to its better crystallinity and lower defects. The photostability of the microscale ZnO is greatly improved by the surface modification of ZnO with a small amount of TiO(2). On the basis of the excellent photocatalytic performance of the microscale ZnO and TiO(2)-modified ZnO, a novel device of coupling photodegradation with light-to-electricity conversion was developed, which is a promising candidate for the photocatalytic removal of dye pollutants and a renewable energy source.

Synthesis of floriated ZnFe2O4 with porous nanorod structures and its photocatalytic hydrogen production under visible light

Abstract: Floriated ZnFe2O4 with porous nanorod structures were successfully synthesized via mild hydrothermal and calcination processes by using cetyltrimethylammonium bromide (CTABr) as a template-directing reagent. The resulting ZnFe2O4 was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS) and nitrogen adsorption measurement. It was found that the floriated ZnFe2O4 nanostructures were composed of porous nanorods with an average length of 122 nm and diameter of 29 nm. The obtained ZnFe2O4 with a bandgap of ∼1.94 eV was firstly used as a visible-light-driven photocatalyst for hydrogen production, and exhibits remarkable photostability in an aqueous suspension by using CH3OH as a sacrificial reagent. Moreover, the possible photo-reaction mechanism for the hydrogen production from CH3OH aqueous solution was proposed for better understanding the photocatalytic behavior of ZnFe2O4 without Pt-loading.

Synthesis of a novel hydrazone derivative and biophysical studies of its interactions with bovine serum albumin by spectroscopic, electrochemical, and molecular docking methods

Abstract: Hydrazone derivatives possess potential antitumor activities based on modulation of the iron metabolism in cancer cell. A novel hydrazone, N′-(2,4-dimethoxybenzylidene)-2-hydroxybenzohydrazide (DBH), has been synthesized and characterized, which is an analogue of 311 possessing potent anticancer activity. The interactions between DBH and bovine serum albumin (BSA) have been investigated systematically by fluorescence, molecular docking, circular dichroism (CD), UV−vis absorption, and electrochemical impedance spectroscopy (EIS) methods under physiological conditions. The fluorescence quenching observed is attributed to the formation of a complex between BSA and DBH, and the reverse temperature effect of the fluorescence quenching has been found and discussed. The primary binding pattern is determined by hydrophobic interaction occurring in Sudlow’s site I of BSA. DBH could slightly change the secondary structure and induce unfolding of the polypeptides of protein. An average binding distance of ∼4.0 nm ha...

TiO2 Immobilized in Cellulose Matrix for Photocatalytic Degradation of Phenol under Weak UV Light Irradiation

Abstract: TiO2/cellulose composite films have been prepared via a sol−gel method from the hydrolysis of a precursor TiO2 sol solution in the regenerated cellulose films prepared on the basis of cellulose dissolution at low temperature. The structure and properties of the composite films were characterized by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, FT-IR, UV−visible spectroscopy, and photocatalytic degradation tests. The micronanoporous structure and hydroxyl groups in the regenerated cellulose films at the wet state provided cavities and affinity for the creation and the immobilization of TiO2 nanoparticles in the cellulose matrix through electrostatic and hydrogen bonding interactions. The TiO2/cellulose composite films exhibited a good photocatalytic activity for photodegradation of phenol under weak UV light irradiation, leading to an important application in photodegradation of organic pollutant. This was a portable photocatalyst, wh...