Using the heat kernel, we derive first a local Gauss–Bonnet–Chern theorem for manifolds with a non-product metric near the
boundary. Then we establish an anomaly formula for Ray–Singer metrics defined by a Hermitian metric on a flat vector bundle
over a Riemannian manifold with boundary, not assuming that the Hermitian metric on the flat vector bundle is flat nor that
the Riemannian metric has product structure near the boundary.
Received: January 2004; Revision: February 2005; Accepted: September 2005 相似文献
A gold(I)-catalyzed three-component reaction of β-nitrostyrenes with 1,3-dicarbonyl compounds and primary amines to form polysubstituted pyrroles has been developed at room temperature in ethanol. The key advantages of the three-component reaction are the mild reaction conditions and environm entally safer solvent 相似文献
A novel method has been reported for 2,6-dichlorophenol using surface-enhanced Raman scattering (SERS). SiO2/gold composites were selected as the SERS substrates to provide the response of gold nanoparticles. Molecular imprinting was subsequently used for the development of a specific detector to 2,6-dichlorophenol with precipitation polymerization. The molecularly imprinted polymer provided sensitive and selective SERS detection for the determination of 2,6-dichlorophenol. The intensity and concentration obeyed a linear relationship from 1?×?10?5 to 1?×?10?9?mol?L?1 2,6-dichlorophenol. The sensitivity of SERS with the molecularly imprinted polymers provides a promising approach for practical analysis. 相似文献
A new method is described for the determination of the pesticide λ-cyhalothrin (LC). It combines SERS detection with molecular imprinting and largely improves selectivity. A multilayer surface imprinted nanocomposite was synthesized in two steps on a nanostructure of type SiO2@rGO@Ag acting as a substrates. Firstly, the surface of the SiO2@rGO@Ag composite was modified with self-polymerized dopamine. Secondly, surface-initiated polymerization was carried out to prepare a molecularly imprinted polymer (MIP) using LC as the template. The use of this SiO2@rGO@Ag-MIP allows for excellent SERS based detection and has high selectivity for LC. The Raman intensity and LC concentration present perfect linear relationship between 10?5 to 10?9 mol L?1 and the detection limit is 3.8×10?10 mol L?1. All the procedures are conducted in aqueous or ethanol solution.
Graphical abstract Schematic of a new method for determination of the pesticide λ-cyhalothrin. It combines SERS detection with molecular imprinting and largely improves selectivity. A multilayer surface imprinted nanocomposite was synthesized in two steps on a nanostructure of type SiO2@rGO@Ag acting as a substrates.
The alkaline hydrolysis of aromatic esters exhibits autocatalytic kinetics when performed under two-phase conditions without any mixing solvent. The molecular structures of such aromatic esters determine whether the autocatalysis occurs or not. It has been established that enhancing the solubility of the hydrophobic ester in water by the hydrotropic salts yielded by the hydrolysis itself accelerates the apparent reaction rate. By kinetically independent measurements, the solubilization process of the ester was verified to be the rate-determining step. It has been observed that the solubilization process can be influenced by factors such as the initial addition of hydrotropic salt, the volumetric ratio of the oil/aqueous phase, and the concentration of alkali. 相似文献
A divergent synthetic approach to six Ganoderma meroterpenoids, namely ganocins A–C, ganocochlearins C and D, and cochlearol T, has been developed for the first time. This synthetic route features a two-phase strategy which includes early-stage rapid construction of a common planar tricyclic intermediate followed by highly selective late-stage transformations into various Ganoderma meroterpenoids. Key to the strategy are a bioinspired intramolecular hetero-Diels–Alder reaction and Stahl-type oxidative aromatization, allowing efficient formation of the common tricyclic phenol intermediate. A nucleophilic dearomatization of the phenol unit, combined with a regioselective 1,4-reduction of the resulting dienone, enabled rapid access to ganocins B and C. Additionally, site-selective Mukaiyama hydration, followed by an intramolecular oxa-Michael addition/triflation cascade, served as a key strategic element in the chemical synthesis of ganocin A. 相似文献
We study the Berezin-Toeplitz quantization on symplectic manifolds making use of the full off-diagonal asymptotic expansion
of the Bergman kernel. We give also a characterization of Toeplitz operators in terms of their asymptotic expansion. The semi-classical
limit properties of the Berezin-Toeplitz quantization for non-compact manifolds and orbifolds are also established.
Second-named author partially supported by the SFB/TR 12. 相似文献
The influence of pH on the thixotropy of pure kaolinite suspension and magnesium aluminum hydroxide (Mg-AI-MMH)-kaolinite suspension was studied. The results show that the thixotropic type of pure kaolinite suspension was not affected by pH studied in the range of 3.60-12.00. The thixotropic type of Mg-AI-MMH-kaolinite suspension with mass ratio (R) value of MMH to kaolinite 0.029 transformed from complex thixotropy into positive thixotropy with increasing of pH in the range of pH 3.83-12.00, and the type of thixotropy of Mg-AI-MMH-kaolinite suspension with R = 0.129 transformed from positive thixotropy into complex thixotropy with increasing of pH in the range of pH 3.70-11.96. 相似文献
A wavelength modulation surface plasmon resonance biosensor based on ZnO-Au nanocomposites for the detection of human IgM was developed. Self-assembly technique has the advantages of flexibility, simplicity and the precise control of film component and was applied to the building of the sensor. The ZnO-Au nanocomposites are in a dumbbell-like shape and can be immobilized on the Au film through 1,6-hexanedithiol by covalent attachment. Meanwhile the activated ZnO nanocrystals can be used to connect protein. The biosensor based on ZnO-Au nanocomposites was used to detect human IgM. Some experimental conditions were examined and optimized. In the selected conditions, the modified biosensor exhibits a satisfactory response for human IgM in the concentration range of 0.30-20.00 μg mL−1. However, the biosensor without ZnO-Au nanocomposites shows a response for human IgM in the concentration range of 1.25-20.00 μg mL−1. Compared with the biosensor based on Au film, when the biosensor based on the ZnO-Au nanocomposites was applied, the sensitivity for determination of human IgM is significantly enhanced. 相似文献