Neural network methods have recently emerged as a hot topic in computed tomography(CT) imaging owing to their powerful fitting ability;however, their potential applications still need to be carefully studied because t...Neural network methods have recently emerged as a hot topic in computed tomography(CT) imaging owing to their powerful fitting ability;however, their potential applications still need to be carefully studied because their results are often difficult to interpret and are ambiguous in generalizability. Thus, quality assessments of the results obtained from a neural network are necessary to evaluate the neural network. Assessing the image quality of neural networks using traditional objective measurements is not appropriate because neural networks are nonstationary and nonlinear. In contrast, subjective assessments are trustworthy, although they are time-and energy-consuming for radiologists. Model observers that mimic subjective assessment require the mean and covariance of images, which are calculated from numerous image samples;however, this has not yet been applied to the evaluation of neural networks. In this study, we propose an analytical method for noise propagation from a single projection to efficiently evaluate convolutional neural networks(CNNs) in the CT imaging field. We propagate noise through nonlinear layers in a CNN using the Taylor expansion. Nesting of the linear and nonlinear layer noise propagation constitutes the covariance estimation of the CNN. A commonly used U-net structure is adopted for validation. The results reveal that the covariance estimation obtained from the proposed analytical method agrees well with that obtained from the image samples for different phantoms, noise levels, and activation functions, demonstrating that propagating noise from only a single projection is feasible for CNN methods in CT reconstruction. In addition, we use covariance estimation to provide three measurements for the qualitative and quantitative performance evaluation of U-net. The results indicate that the network cannot be applied to projections with high noise levels and possesses limitations in terms of efficiency for processing low-noise projections. U-net is more effective in improving the image quality of smooth regions compared with that of the edge. LeakyReLU outperforms Swish in terms of noise reduction.展开更多
On the basis of the survey of underground noise in Jinggezhuang and Donghuantuo mines, Kailuan Group, noise radiation intensity, noise propagation properties and noise frequency-spectrum characteristics of underground...On the basis of the survey of underground noise in Jinggezhuang and Donghuantuo mines, Kailuan Group, noise radiation intensity, noise propagation properties and noise frequency-spectrum characteristics of underground equipment were studied at different work conditions. The result indicates that the noise source intensity surpasses the noise limit requirement of 85 dBA completely. Nearly 70% noise sources exceed the noise limit of 90 dBA, and some are over 100 dBA. Noise attenua- tion in semi-free field environment on the ground is significantly different from underground far-field environment of noise source in coal mines. Noise of these regions, where staffs are long and highly concentrated, exceeds 85 dBA, the basic noise limit. The noise frequency-spectrum presents the wideband characteristics. Especially in the main frequency of the language communication 500, 1 000 and 2 000 Hz, the octave band of noise performs obviously.展开更多
Noise and noise propagation are inevitable and play a constructive role in various biological processes.The stability of cell homeostasis is also a critical issue.In the unidirectional transition cascade of colon cell...Noise and noise propagation are inevitable and play a constructive role in various biological processes.The stability of cell homeostasis is also a critical issue.In the unidirectional transition cascade of colon cells,stem cells(SCs)are the source.They differentiate into transit-amplifying cells(TACs),and TACs differentiate into fully differentiated cells(FDCs).Two differentiation processes are irreversible.The stability factor is introduced so that the noise propagation mechanism from the perspective of stability is studied according to the noise propagation formulas.It is found that the value of the stability factor corresponding to the minimum noise in FDCs may be the best choice to enable colon cells to maintain high stability and low noise of the cascade.Moreover,for the source cell,the total noise only includes intrinsic noise;for the downstream cell with self-proliferation capability,the total noise mainly depends on its intrinsic noise and transmitted noise from upstream cells,and its intrinsic noise is dominant.For the downstream cell without self-proliferation capability,the total noise is mainly determined by transmitted noises from upstream cells,and there is a minimum value.This work provides a new approach for studying the mechanism of noise propagation while considering the stability of cell homeostasis in biological systems.展开更多
Antimicrobial resistance is a growing concern in the field of microbiology.In a microbial community,the Susceptible Subpopulations(SSs)and the Non-genetically Resistant Subpopulations(NRSs)can switch between each othe...Antimicrobial resistance is a growing concern in the field of microbiology.In a microbial community,the Susceptible Subpopulations(SSs)and the Non-genetically Resistant Subpopulations(NRSs)can switch between each other,and NRSs can mutate to Genetically Resistant Subpopulations(GRSs).In order to quantitatively describe the relationship between noise and signal amplification in the subpopulations,a mathematical model for three subpopulations is proposed in this paper.The gain fluctuation relation is obtained by linear noise approximation of the master equation.Then,through the simulation of these theoretical results,the following conclusions are found.First,the indirect effects of the interaction between subpopulations are much greater than the direct effects,which may be one of the reasons that the infection is dificult to cure.This is consistent with the findings of Zhou et al.and indicates the reliability of our new model.Second,the intrinsic net growth rate of SSs can be chosen as the adjustment parameter,which can effectively exploit or avoid the strong correlation between SSs and the two resistant subpopulations,including NRSs and GRSs.Third,unlike unidirectional cascades,additional intrinsic noise in GRSs can propagate to NRSs.Similarly,although there is no direct interaction between SSs and GRSs,additional intrinsic noise in GRSs can propagate to SSs,and vice versa.Finally,both total noise and adjusted noise exhibit similar amplification properties in this population.It is worth noting that the noise is consistently amplified from NRSs to GRSs.These findings may provide new insights into antimicrobial therapy.展开更多
Feed-forward gene transcriptional regulatory networks, as a set of common signal motifs, are widely distributed in the biological systems. In this paper, the noise characteristics and propagation mechanism of various ...Feed-forward gene transcriptional regulatory networks, as a set of common signal motifs, are widely distributed in the biological systems. In this paper, the noise characteristics and propagation mechanism of various feed-forward gene transcriptional regulatory loops are investigated, including （i） coherent feed-forward loops with AND-gate, （ii） coherent feed-forward loops with OR-gate logic, and （iii） incoherent feed-forward loops with AND-gate logic. By introducing logarithmic gain coefficient and using linear noise approximation, the theoretical formulas of noise decomposition are derived and the theoretical results are verified by Gillespie simulation. From the theoretical and numerical results of noise decomposition algorithm, three general characteristics about noise transmission in these different kinds of feed-forward loops are observed, i） The two-step noise propagation of upstream factor is negative in the incoherent feed-forward loops with AND-gate logic, that is, upstream factor can indirectly suppress the noise of downstream factors, ii） The one-step propagation noise of upstream factor is non-monotonic in the coherent feed-forward loops with OR-gate logic, iii） When the branch of the feed-forward loop is negatively controlled, the total noise of the downstream factor monotonically increases for each of all feed-forward loops. These findings are robust to variations of model parameters. These observations reveal the universal rules of noise propagation in the feed-forward loops, and may contribute to our understanding of design principle of gene circuits.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62031020 and 61771279)。
文摘Neural network methods have recently emerged as a hot topic in computed tomography(CT) imaging owing to their powerful fitting ability;however, their potential applications still need to be carefully studied because their results are often difficult to interpret and are ambiguous in generalizability. Thus, quality assessments of the results obtained from a neural network are necessary to evaluate the neural network. Assessing the image quality of neural networks using traditional objective measurements is not appropriate because neural networks are nonstationary and nonlinear. In contrast, subjective assessments are trustworthy, although they are time-and energy-consuming for radiologists. Model observers that mimic subjective assessment require the mean and covariance of images, which are calculated from numerous image samples;however, this has not yet been applied to the evaluation of neural networks. In this study, we propose an analytical method for noise propagation from a single projection to efficiently evaluate convolutional neural networks(CNNs) in the CT imaging field. We propagate noise through nonlinear layers in a CNN using the Taylor expansion. Nesting of the linear and nonlinear layer noise propagation constitutes the covariance estimation of the CNN. A commonly used U-net structure is adopted for validation. The results reveal that the covariance estimation obtained from the proposed analytical method agrees well with that obtained from the image samples for different phantoms, noise levels, and activation functions, demonstrating that propagating noise from only a single projection is feasible for CNN methods in CT reconstruction. In addition, we use covariance estimation to provide three measurements for the qualitative and quantitative performance evaluation of U-net. The results indicate that the network cannot be applied to projections with high noise levels and possesses limitations in terms of efficiency for processing low-noise projections. U-net is more effective in improving the image quality of smooth regions compared with that of the edge. LeakyReLU outperforms Swish in terms of noise reduction.
基金Supported by the National Natural Science Foundation of China （50974061） the Natural Science Foundation of Hebei Province （E2009001420）
文摘On the basis of the survey of underground noise in Jinggezhuang and Donghuantuo mines, Kailuan Group, noise radiation intensity, noise propagation properties and noise frequency-spectrum characteristics of underground equipment were studied at different work conditions. The result indicates that the noise source intensity surpasses the noise limit requirement of 85 dBA completely. Nearly 70% noise sources exceed the noise limit of 90 dBA, and some are over 100 dBA. Noise attenua- tion in semi-free field environment on the ground is significantly different from underground far-field environment of noise source in coal mines. Noise of these regions, where staffs are long and highly concentrated, exceeds 85 dBA, the basic noise limit. The noise frequency-spectrum presents the wideband characteristics. Especially in the main frequency of the language communication 500, 1 000 and 2 000 Hz, the octave band of noise performs obviously.
基金Project supported by the National Natural Science Foundation of China(Grant No.11605014).
文摘Noise and noise propagation are inevitable and play a constructive role in various biological processes.The stability of cell homeostasis is also a critical issue.In the unidirectional transition cascade of colon cells,stem cells(SCs)are the source.They differentiate into transit-amplifying cells(TACs),and TACs differentiate into fully differentiated cells(FDCs).Two differentiation processes are irreversible.The stability factor is introduced so that the noise propagation mechanism from the perspective of stability is studied according to the noise propagation formulas.It is found that the value of the stability factor corresponding to the minimum noise in FDCs may be the best choice to enable colon cells to maintain high stability and low noise of the cascade.Moreover,for the source cell,the total noise only includes intrinsic noise;for the downstream cell with self-proliferation capability,the total noise mainly depends on its intrinsic noise and transmitted noise from upstream cells,and its intrinsic noise is dominant.For the downstream cell without self-proliferation capability,the total noise is mainly determined by transmitted noises from upstream cells,and there is a minimum value.This work provides a new approach for studying the mechanism of noise propagation while considering the stability of cell homeostasis in biological systems.
基金partial support provided by the National Natural Science Foundation of China(12062027/12162032)Interdisciplinary Innovation Team of Modern Applied Mathematics and Life Sciences(202405AS350003)+1 种基金Ten Thousand Talent Plans for Young Top-notch TalentsApplied Basic Research Foundation(LS21005)of Yunnan Province.
文摘Antimicrobial resistance is a growing concern in the field of microbiology.In a microbial community,the Susceptible Subpopulations(SSs)and the Non-genetically Resistant Subpopulations(NRSs)can switch between each other,and NRSs can mutate to Genetically Resistant Subpopulations(GRSs).In order to quantitatively describe the relationship between noise and signal amplification in the subpopulations,a mathematical model for three subpopulations is proposed in this paper.The gain fluctuation relation is obtained by linear noise approximation of the master equation.Then,through the simulation of these theoretical results,the following conclusions are found.First,the indirect effects of the interaction between subpopulations are much greater than the direct effects,which may be one of the reasons that the infection is dificult to cure.This is consistent with the findings of Zhou et al.and indicates the reliability of our new model.Second,the intrinsic net growth rate of SSs can be chosen as the adjustment parameter,which can effectively exploit or avoid the strong correlation between SSs and the two resistant subpopulations,including NRSs and GRSs.Third,unlike unidirectional cascades,additional intrinsic noise in GRSs can propagate to NRSs.Similarly,although there is no direct interaction between SSs and GRSs,additional intrinsic noise in GRSs can propagate to SSs,and vice versa.Finally,both total noise and adjusted noise exhibit similar amplification properties in this population.It is worth noting that the noise is consistently amplified from NRSs to GRSs.These findings may provide new insights into antimicrobial therapy.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant Nos.2662015QC041 and 2662014BQ069)the Huazhong Agricultural University Scientific&Technological Self-innovation Foundation,China(Grant No.2015RC021)the National Natural Science Foundation of China(Grant Nos.11675060,91730301,11547244,and 11474117)
文摘Feed-forward gene transcriptional regulatory networks, as a set of common signal motifs, are widely distributed in the biological systems. In this paper, the noise characteristics and propagation mechanism of various feed-forward gene transcriptional regulatory loops are investigated, including （i） coherent feed-forward loops with AND-gate, （ii） coherent feed-forward loops with OR-gate logic, and （iii） incoherent feed-forward loops with AND-gate logic. By introducing logarithmic gain coefficient and using linear noise approximation, the theoretical formulas of noise decomposition are derived and the theoretical results are verified by Gillespie simulation. From the theoretical and numerical results of noise decomposition algorithm, three general characteristics about noise transmission in these different kinds of feed-forward loops are observed, i） The two-step noise propagation of upstream factor is negative in the incoherent feed-forward loops with AND-gate logic, that is, upstream factor can indirectly suppress the noise of downstream factors, ii） The one-step propagation noise of upstream factor is non-monotonic in the coherent feed-forward loops with OR-gate logic, iii） When the branch of the feed-forward loop is negatively controlled, the total noise of the downstream factor monotonically increases for each of all feed-forward loops. These findings are robust to variations of model parameters. These observations reveal the universal rules of noise propagation in the feed-forward loops, and may contribute to our understanding of design principle of gene circuits.
