The global pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus has necessitated rapid,easy-to-use,and accurate diagnostic methods to monitor the virus infection.Herein,a ratiometric flu...The global pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus has necessitated rapid,easy-to-use,and accurate diagnostic methods to monitor the virus infection.Herein,a ratiometric fluorescence enzyme-linked immunosorbent assay(ELISA)was developed using Si-fluorescein isothiocyanate nanoparticles(FITC NPs)for detecting SARSCoV-2 nucleocapsid(N)protein.Si-FITC NPs were prepared by a one-pot hydrothermal method using 3-aminopropyl triethoxysilane(APTES)-FITC as the Si source.This method did not need post-modification and avoided the reduction in quantum yield and stability.The p-nitrophenyl(pNP)produced by the alkaline phosphatase(ALP)-mediated hydrolysis of pnitrophenyl phosphate(pNPP)could quench Si fluorescence in Si-FITC NPs via the inner filter effect.In ELISA,an immunocomplex was formed by the recognition of capture antibody/N protein/reporter antibody.ALP-linked secondary antibody bound to the reporter antibody and induced pNPP hydrolysis to specifically quench Si fluorescence in Si-FITC NPs.The change in fluorescence intensity ratio could be used for detecting N protein,with a wide linearity range(0.01-10.0 and 50-300 ng/mL)and low detection limit(0.002 ng/mL).The concentration of spiked SARS-CoV-2 N protein could be determined accurately in human serum.Moreover,this proposed method can accurately distinguish coronavirus disease 2019(COVID-19)and non-COVID-19 patient samples.Therefore,this simple,sensitive,and accurate method can be applied for the early diagnosis of SARS-CoV-2 virus infection.展开更多
In this paper, the problem how to reduce the GB effect in SC filters is discussed. A new generalbiquadratic SC structure in which the GB effect is reduced is developed. The structure is stray-insensitiveand has very l...In this paper, the problem how to reduce the GB effect in SC filters is discussed. A new generalbiquadratic SC structure in which the GB effect is reduced is developed. The structure is stray-insensitiveand has very low W<sub>0</sub> and Q sensitivities. Using the low-pass SC filter for an example, method of reducingthe GB effect has been shown in detail.展开更多
Most existing reconstruction algorithms for photoacoustic imaging (PAI) assume that transducers used to receive ultrasound signals have infinite bandwidth. When transducers with finite bandwidth are used, this assumpt...Most existing reconstruction algorithms for photoacoustic imaging (PAI) assume that transducers used to receive ultrasound signals have infinite bandwidth. When transducers with finite bandwidth are used, this assumption may result in reduction of the imaging contrast and distortions of reconstructed images. In this paper, we propose a novel method to compensate the finite bandwidth effect in PAI by using an optimal filter in the Fourier domain. Simulation results demonstrate that the use of this method can improve the contrast of the reconstructed images with finite-bandwidth ultrasound transducers.展开更多
Variation of plastic viscosity and extrapolated shear yield stress with the concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 suspensions at 0.27 powder volume fraction was investigated at 294 K....Variation of plastic viscosity and extrapolated shear yield stress with the concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 suspensions at 0.27 powder volume fraction was investigated at 294 K. An optimum level of Dispex A40 for full deflocculation is found to be at 0.18% mass fraction of the powder, at which the rheological behaviour shows little different to that of adjusting the pH to 4 to obtain full deflocculation. It is demonstrated that the shear stress drop can roughly work as an index for the thixotropy in particular fixed conditions, and consequently an index for the deflocculation as the shear stress drop becomes larger when the level of the flocculation increases, and vice versa. It is also found that the addition of Dispex A40 can prevent the filter cakes from cracking, whereas the cakes at various pH values with polyvinyl alcohol as a sole polymer normally develop cracking during drying.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFA0910900)the National Natural Science Foundation(No.22104147)+4 种基金Youth Innovation Promotion Association CAS(No.2021359)the Natural Science Foundation of Guangdong(Nos.2018B030306046 and 2020A1515111130)Guangdong Provincial Key Laboratory of Synthetic Genomics(No.2019B030301006)Shenzhen Science and Technology Program(No.KQTD20180413181837372)Shenzhen Outstanding Talents Training Fund.
文摘The global pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)virus has necessitated rapid,easy-to-use,and accurate diagnostic methods to monitor the virus infection.Herein,a ratiometric fluorescence enzyme-linked immunosorbent assay(ELISA)was developed using Si-fluorescein isothiocyanate nanoparticles(FITC NPs)for detecting SARSCoV-2 nucleocapsid(N)protein.Si-FITC NPs were prepared by a one-pot hydrothermal method using 3-aminopropyl triethoxysilane(APTES)-FITC as the Si source.This method did not need post-modification and avoided the reduction in quantum yield and stability.The p-nitrophenyl(pNP)produced by the alkaline phosphatase(ALP)-mediated hydrolysis of pnitrophenyl phosphate(pNPP)could quench Si fluorescence in Si-FITC NPs via the inner filter effect.In ELISA,an immunocomplex was formed by the recognition of capture antibody/N protein/reporter antibody.ALP-linked secondary antibody bound to the reporter antibody and induced pNPP hydrolysis to specifically quench Si fluorescence in Si-FITC NPs.The change in fluorescence intensity ratio could be used for detecting N protein,with a wide linearity range(0.01-10.0 and 50-300 ng/mL)and low detection limit(0.002 ng/mL).The concentration of spiked SARS-CoV-2 N protein could be determined accurately in human serum.Moreover,this proposed method can accurately distinguish coronavirus disease 2019(COVID-19)and non-COVID-19 patient samples.Therefore,this simple,sensitive,and accurate method can be applied for the early diagnosis of SARS-CoV-2 virus infection.
文摘In this paper, the problem how to reduce the GB effect in SC filters is discussed. A new generalbiquadratic SC structure in which the GB effect is reduced is developed. The structure is stray-insensitiveand has very low W<sub>0</sub> and Q sensitivities. Using the low-pass SC filter for an example, method of reducingthe GB effect has been shown in detail.
文摘Most existing reconstruction algorithms for photoacoustic imaging (PAI) assume that transducers used to receive ultrasound signals have infinite bandwidth. When transducers with finite bandwidth are used, this assumption may result in reduction of the imaging contrast and distortions of reconstructed images. In this paper, we propose a novel method to compensate the finite bandwidth effect in PAI by using an optimal filter in the Fourier domain. Simulation results demonstrate that the use of this method can improve the contrast of the reconstructed images with finite-bandwidth ultrasound transducers.
文摘Variation of plastic viscosity and extrapolated shear yield stress with the concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 suspensions at 0.27 powder volume fraction was investigated at 294 K. An optimum level of Dispex A40 for full deflocculation is found to be at 0.18% mass fraction of the powder, at which the rheological behaviour shows little different to that of adjusting the pH to 4 to obtain full deflocculation. It is demonstrated that the shear stress drop can roughly work as an index for the thixotropy in particular fixed conditions, and consequently an index for the deflocculation as the shear stress drop becomes larger when the level of the flocculation increases, and vice versa. It is also found that the addition of Dispex A40 can prevent the filter cakes from cracking, whereas the cakes at various pH values with polyvinyl alcohol as a sole polymer normally develop cracking during drying.
