Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow meter.Recently,much interest is being paid on the measurement o...Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow meter.Recently,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS applications.However,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are lacking.In the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical nozzles.In computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 deg.The computational results are validated with some experimental data available.The results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical nozzles.It is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain value.This implies that the miniature critical nozzles should be carefully designed.展开更多
Background： DNA methylation has been suggested as a biomarker for early cancer detection and treatment. Varieties of technologies for detecting DNA methylation have been developed, but they are not sufficiently sensi...Background： DNA methylation has been suggested as a biomarker for early cancer detection and treatment. Varieties of technologies for detecting DNA methylation have been developed, but they are not sufficiently sensitive for use in diagnostic devices. The aim of this study was to determine the suitability of Raman spectroscopy for label-free detection of methylated DNA. Methods： The methylated promoter regions of cancer-related genes cadherin 1 （CDH1） and retinoic acid receptor beta （RARB） served as target DNA sequences. Based on bisulfite conversion, oligonucleotides ofmethylated or nonmethylated probes and targets were synthesized for the DNA methylation assay. Principal component analysis with linear discriminant analysis （PCA-DA） was used to discriminate the hybridization between probes and targets （methylated probe and methylated target or nonmethylated probe and nonmethylated target） of CDH! and RARB from nonhybridization between the probe and targets （methylated probe and nonmethylated target or nonmethylated probe and methylated target）. Results： This study revealed that the CDH1 and RARB oligo sets and their hybridization data could be classified using PCA-DA. The classification results for CDH1 methylated probe ＋ CDH1 methylated target versus CDH! methylated probe ＋ CDHI unmethylated target showed sensitivity, specificity, and error rates of 92%, 100%, and 8%, respectively. The classification results for the RARB methylated probe ＋ RARB methylated target versus RARB methylated probe ＋ RARB unmethylated target showed sensitivity, specificity, and error rates of 92%, 93%, and 11%, respectively. Conclusions： Label-free detection ofDNA methylation could be achieved using Raman spectroscopy with discriminant analysis.展开更多
文摘Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow meter.Recently,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS applications.However,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are lacking.In the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical nozzles.In computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 deg.The computational results are validated with some experimental data available.The results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical nozzles.It is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain value.This implies that the miniature critical nozzles should be carefully designed.
文摘Background： DNA methylation has been suggested as a biomarker for early cancer detection and treatment. Varieties of technologies for detecting DNA methylation have been developed, but they are not sufficiently sensitive for use in diagnostic devices. The aim of this study was to determine the suitability of Raman spectroscopy for label-free detection of methylated DNA. Methods： The methylated promoter regions of cancer-related genes cadherin 1 （CDH1） and retinoic acid receptor beta （RARB） served as target DNA sequences. Based on bisulfite conversion, oligonucleotides ofmethylated or nonmethylated probes and targets were synthesized for the DNA methylation assay. Principal component analysis with linear discriminant analysis （PCA-DA） was used to discriminate the hybridization between probes and targets （methylated probe and methylated target or nonmethylated probe and nonmethylated target） of CDH! and RARB from nonhybridization between the probe and targets （methylated probe and nonmethylated target or nonmethylated probe and methylated target）. Results： This study revealed that the CDH1 and RARB oligo sets and their hybridization data could be classified using PCA-DA. The classification results for CDH1 methylated probe ＋ CDH1 methylated target versus CDH! methylated probe ＋ CDHI unmethylated target showed sensitivity, specificity, and error rates of 92%, 100%, and 8%, respectively. The classification results for the RARB methylated probe ＋ RARB methylated target versus RARB methylated probe ＋ RARB unmethylated target showed sensitivity, specificity, and error rates of 92%, 93%, and 11%, respectively. Conclusions： Label-free detection ofDNA methylation could be achieved using Raman spectroscopy with discriminant analysis.
