Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo b...Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo both in spatial and time-frequency domain. The conventional way to solve this problem would suffer from performance degradation when physical target(PT) and false target(FT) are superposed in time. In this paper, we propose a new spatial filter according to the different correlation characteristic between PT and FT. The filter takes the ratio of expected signal power to expected jamming and noise power as the objective function under the constant filter modulus constraint. The optimal filter coefficients are derived with a generalized rayleigh quotient approach. Moreover, we analytically compute the target detection probability and demonstrate the applicability of the proposed method to the correlation coefficient. Monte Carlo simulations are provided to corroborate the proposed studies. Furthermore, the proposed method has simple architecture and low computation complexity, making it easily applied in modern radar system.展开更多
Plasma-screening effects on positronium （Ps） formation for positron-hydrogen collisions in a Debye plasma environ- ment is further investigated using the screening approximation model with the inclusion of the modif...Plasma-screening effects on positronium （Ps） formation for positron-hydrogen collisions in a Debye plasma environ- ment is further investigated using the screening approximation model with the inclusion of the modified structure of Ps. More accurate Ps formation cross sections （n = 1,2） are obtained for various Debye lengths from the Ps formation thresh- olds to 50 eV. The influence of considering modified bound-state wave functions and eigenenergies for the Ps is found to result in the reduction of the Ps formation cross sections at low energies, whereas it cannot counteract the enhancement of the Ps formation by the Debye screening.展开更多
A thick-screen frequency selective surface （FSS） has not only a broad bandwidth but also the advantages of overcoming the multilayer FSS shortcoming of complex structure and low transmittance of centre frequency due...A thick-screen frequency selective surface （FSS） has not only a broad bandwidth but also the advantages of overcoming the multilayer FSS shortcoming of complex structure and low transmittance of centre frequency due to the cascade of FSSs, and this means it could potentially be applied in a stealth curved streamlined radome. However, there is an unsteadiness of centre frequency in a wide range of incident angles and another unsteadiness of polarization in a big incident angle. In order to solve these problems, in this paper we provide a novel four-legged loaded element thick-screen FSS. The structure is analysed and simulated using the mode matching method and moment method. The centre frequency, the transmittance of centre frequency, and bandwidth of the structure are investigated when some parameters including the polarization at a big incident angle and the incident angles of TE ＆： TM waves are changed. The novel four-legged loaded element thick-screen FSS has better transmission properties with a better steadiness of polarization and incident angle independence. The novel structure of the four-legged loaded element thick-screen FSS provides a valuable reference for their application in a stealth curved streamlined radome.展开更多
With ion implantation (N+, energy 10 keV and dosage 1.56×1015 N+cm-2), a high xylanase-producing strain Aspergillus niger N212 was selected. Based on an orthogonal experiment, an optimal fermentation condition wa...With ion implantation (N+, energy 10 keV and dosage 1.56×1015 N+cm-2), a high xylanase-producing strain Aspergillus niger N212 was selected. Based on an orthogonal experiment, an optimal fermentation condition was designed for this high-yield strain. The suitable medium was composed of 8% corncob; 1.0% wheat bran; 0.1%TWEEN20; 0.5% (NH4)2SO4; 0.5%NaNO3; 0.5%FeSO4, 7.5 × 10-4; MnSO4·H2O, 2.5 × 10-4; ZnSO4, 2.0 × 10-4; CoCl2, 3.0 × 10-4. At present, under our experiment condition, xylanase activity of Aspergillus niger N212 reached a level of 600 IU/ml, almost increased by 100% in xylanase production and the time of yielding xylanase was largely reduced to 12 h at 28℃.展开更多
Background: Fetal Alcohol Spectrum Disorders (FASDs) are a global public health concern with lifelong consequences for affected individuals. Recent prevalence studies suggest FASD prevalence rates range from 1-5% amon...Background: Fetal Alcohol Spectrum Disorders (FASDs) are a global public health concern with lifelong consequences for affected individuals. Recent prevalence studies suggest FASD prevalence rates range from 1-5% among school age children. Most people with FASD are not correctly diagnosed and inadequate screening to identify patients with increased risk may contribute to under-diagnosis. This study developed a 10-item screening tool for FASD and examined its feasibility. Methods: The sample consisted of 355 children who had been evaluated at an FASD clinic. Data from the 33-item Alcohol Related Neurodevelopmental Disorder Behavioral Checklist was used to develop a brief FASD screen by comparing the changes in Cronbach’s alpha for different combinations of items. The validity of the brief scale was then further examined using receiving operating characteristic analyses. Results: The 10-item screen demonstrated acceptable sensitivity, specificity, and accuracy to identify children at high risk for FASD. The percentage correctly classified was 91.3 and the area under the receiving operating characteristic curve was 0.971. Conclusions: This feasibility study demonstrated that a screen for FASD consisting of 10 items with yes or no responses can be completed in 3 - 4 minutes. The tool is brief, with a low administration burden and has acceptable epidemiologic performance characteristics including accuracy. Future research should examine the performance of this tool when used in larger, community-based populations where screening for FASD would be appropriate.展开更多
[目的]分析1992—2021年中国40~74岁结直肠癌筛查人群的疾病负担变化趋势,为优化结直肠癌筛查策略和降低疾病负担提供科学依据。[方法]基于2021年全球疾病负担(Global Burden of Disease,GBD)数据,选取1992—2021年中国40~74岁结直肠癌...[目的]分析1992—2021年中国40~74岁结直肠癌筛查人群的疾病负担变化趋势,为优化结直肠癌筛查策略和降低疾病负担提供科学依据。[方法]基于2021年全球疾病负担(Global Burden of Disease,GBD)数据,选取1992—2021年中国40~74岁结直肠癌的发病、死亡、伤残调整寿命年(disability-adjusted life years,DALY)等数据,采用Joinpoint和年龄-时期-队列模型分析发病和死亡趋势并计算平均年度变化百分比(average annual percentage change,AAPC)及其95%置信区间(confidence interval,CI),并进行分解分析。[结果] 1992—2021年,筛查人群结直肠癌发病、死亡和DALY数量均呈上升趋势,男性上升幅度超过女性。发病粗率和男性死亡、DALY粗率均呈上升趋势,而女性死亡和DALY粗率均呈下降趋势。发病标化率男性(AAPC=2.25%,95%CI:2.17%~2.32%)增长高于女性(AAPC=1.03%,95%CI:0.97%~1.07%);男女性死亡和DALY标化率均呈现下降趋势,男性(AAPC=-0.13%,95%CI:-0.18%~-0.09%)下降低于女性(AAPC=-1.41%,95%CI:-1.47%~-1.36%),男性(AAPC=-0.10%,95%CI:-0.14%~-0.06%)DALY标化率下降幅度也低于女性(AAPC=-1.47%,95%CI:-1.52%~-1.43%)。年龄-时期-队列分析显示,结直肠癌风险随年龄增长呈上升趋势,男性各年龄组发病和死亡风险均显著高于女性。2007年后男女性发病风险均持续升高,而女性死亡和DALY风险持续下降。男性发病风险从1920—1924年的0.50(95%CI:0.46~0.54)增加到1975—1979年2.25(95%CI:2.03~2.49)。分解分析表明,人口增长和老龄化是发病率增长的主要原因,流行病学变化对发病率呈正向贡献,占37.27%,而对死亡率和DALY率呈负向贡献,分别占-30.13%和-31.63%。[结论]我国结直肠癌筛查人群结直肠癌疾病负担呈现“发病数、死亡数及DALY数、发病率持续攀升而标化死亡率、DALY显著下降”的双重特征,且存在明显的性别、年龄和出生队列差异。展开更多
以高耐热性玉米品种郑单958、低耐热性玉米品种先玉335为试验材料,以正常生长条件为对照(CK),利用半自动伸缩高温棚进行花期高温胁迫(HT)处理,通过circRNA高通量测序筛选高温胁迫下不同玉米品种花粉中差异表达的环状RNA(circRNA),对其...以高耐热性玉米品种郑单958、低耐热性玉米品种先玉335为试验材料,以正常生长条件为对照(CK),利用半自动伸缩高温棚进行花期高温胁迫(HT)处理,通过circRNA高通量测序筛选高温胁迫下不同玉米品种花粉中差异表达的环状RNA(circRNA),对其来源基因进行GO和KEGG富集分析,并筛选具有miRNA结合位点的差异表达circRNA,预测其下游目的基因,分析玉米花粉中响应高温胁迫的潜在circRNA-miRNA-mRNA共表达调控网络,从多层面解析玉米花粉中调控高温胁迫的分子作用机制,为提高玉米品种的耐热性提供理论依据。结果表明,在郑单958、先玉335不同样本中共鉴定出1 843个不同的circRNA,它们在玉米染色体中的分布不同。每个circRNA所包含的外显子数目也不相同,其中,大多数(624个)circRNA只含有1个外显子。在郑单958花粉中共鉴定出1 563个circRNA,其中,CK958-1、CK958-2、CK958-3中分别鉴定出305、213、356个circRNA,HT958-1、HT958-2、HT958-3中分别鉴定出222、242、225个circRNA。在先玉335花粉中共鉴定出1 423个circRNA,其中,CK335-1、CK335-2、CK335-3中分别鉴定出272、188、229个circRNA,HT335-1、HT335-2、HT335-3中分别鉴定出259、237、238个circRNA。不同样本中占比最高的均为外显子circRNA。circRNA与其来源基因不是一一对应的关系,有748个circRNA来源基因通过反向剪接机制只形成1个circRNA,156个circRNA来源基因通过反向剪接机制各自形成2个circRNA。在郑单958高温胁迫花粉与对照花粉对比组(HT958 vs CK958)中共筛选到9个差异表达circRNA,其中2个circRNA呈上调表达,其来源基因显著富集到焦磷酸酶活性、核苷酸磷酸代谢过程、糖基磷脂酰肌醇(GPI)锚定代谢过程等17个GO条目,显著富集到GPI锚定生物合成、代谢途径等KEGG通路。在先玉335高温胁迫花粉与对照花粉对比组(HT335 vs CK335)中共筛选到1个差异表达circRNA,其来源基因没有显著富集到任何GO条目、KEGG通路。在郑单958高温胁迫花粉与先玉335高温胁迫花粉对比组(HT958 vs HT335)中共筛选到17个差异表达circRNA,其中6个circRNA呈上调表达,其来源基因显著富集到内质网系统、高尔基相关囊泡膜、膜蛋白水解等16个GO条目中,没有显著富集到任何KEGG代谢通路。5个circRNA具有miRNA结合位点,可以作为海绵岛吸附miRNA间接调控下游靶标基因的表达,构建了包括5个circRNA、5个不同家族miRNA、2个mRNA在内的circRNA-miRNA-mRNA共表达调控网络。筛选到了54个circRNA包含内部核糖体进入位点(IRES),可以翻译表达多肽或者蛋白质直接作用于靶标基因。展开更多
文摘Detecting target echo in the existence of self-screen jamming is a challenging work for radar system, especially when digital radio frequency memory(DRFM) technique is employed that mixes the jamming and target echo both in spatial and time-frequency domain. The conventional way to solve this problem would suffer from performance degradation when physical target(PT) and false target(FT) are superposed in time. In this paper, we propose a new spatial filter according to the different correlation characteristic between PT and FT. The filter takes the ratio of expected signal power to expected jamming and noise power as the objective function under the constant filter modulus constraint. The optimal filter coefficients are derived with a generalized rayleigh quotient approach. Moreover, we analytically compute the target detection probability and demonstrate the applicability of the proposed method to the correlation coefficient. Monte Carlo simulations are provided to corroborate the proposed studies. Furthermore, the proposed method has simple architecture and low computation complexity, making it easily applied in modern radar system.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404223,11447158,and 11604223)the Doctoral Program Foundation of Shenyang Aerospace University,China(Grant No.13YB26)
文摘Plasma-screening effects on positronium （Ps） formation for positron-hydrogen collisions in a Debye plasma environ- ment is further investigated using the screening approximation model with the inclusion of the modified structure of Ps. More accurate Ps formation cross sections （n = 1,2） are obtained for various Debye lengths from the Ps formation thresh- olds to 50 eV. The influence of considering modified bound-state wave functions and eigenenergies for the Ps is found to result in the reduction of the Ps formation cross sections at low energies, whereas it cannot counteract the enhancement of the Ps formation by the Debye screening.
文摘A thick-screen frequency selective surface （FSS） has not only a broad bandwidth but also the advantages of overcoming the multilayer FSS shortcoming of complex structure and low transmittance of centre frequency due to the cascade of FSSs, and this means it could potentially be applied in a stealth curved streamlined radome. However, there is an unsteadiness of centre frequency in a wide range of incident angles and another unsteadiness of polarization in a big incident angle. In order to solve these problems, in this paper we provide a novel four-legged loaded element thick-screen FSS. The structure is analysed and simulated using the mode matching method and moment method. The centre frequency, the transmittance of centre frequency, and bandwidth of the structure are investigated when some parameters including the polarization at a big incident angle and the incident angles of TE ＆： TM waves are changed. The novel four-legged loaded element thick-screen FSS has better transmission properties with a better steadiness of polarization and incident angle independence. The novel structure of the four-legged loaded element thick-screen FSS provides a valuable reference for their application in a stealth curved streamlined radome.
文摘With ion implantation (N+, energy 10 keV and dosage 1.56×1015 N+cm-2), a high xylanase-producing strain Aspergillus niger N212 was selected. Based on an orthogonal experiment, an optimal fermentation condition was designed for this high-yield strain. The suitable medium was composed of 8% corncob; 1.0% wheat bran; 0.1%TWEEN20; 0.5% (NH4)2SO4; 0.5%NaNO3; 0.5%FeSO4, 7.5 × 10-4; MnSO4·H2O, 2.5 × 10-4; ZnSO4, 2.0 × 10-4; CoCl2, 3.0 × 10-4. At present, under our experiment condition, xylanase activity of Aspergillus niger N212 reached a level of 600 IU/ml, almost increased by 100% in xylanase production and the time of yielding xylanase was largely reduced to 12 h at 28℃.
基金Acknowledgements： This work is supported by National Natural Science Foundation of China （No. 60673084） and Hunan Provincial Natural Science Foundation of China （No. 06JJ4075）.
文摘Background: Fetal Alcohol Spectrum Disorders (FASDs) are a global public health concern with lifelong consequences for affected individuals. Recent prevalence studies suggest FASD prevalence rates range from 1-5% among school age children. Most people with FASD are not correctly diagnosed and inadequate screening to identify patients with increased risk may contribute to under-diagnosis. This study developed a 10-item screening tool for FASD and examined its feasibility. Methods: The sample consisted of 355 children who had been evaluated at an FASD clinic. Data from the 33-item Alcohol Related Neurodevelopmental Disorder Behavioral Checklist was used to develop a brief FASD screen by comparing the changes in Cronbach’s alpha for different combinations of items. The validity of the brief scale was then further examined using receiving operating characteristic analyses. Results: The 10-item screen demonstrated acceptable sensitivity, specificity, and accuracy to identify children at high risk for FASD. The percentage correctly classified was 91.3 and the area under the receiving operating characteristic curve was 0.971. Conclusions: This feasibility study demonstrated that a screen for FASD consisting of 10 items with yes or no responses can be completed in 3 - 4 minutes. The tool is brief, with a low administration burden and has acceptable epidemiologic performance characteristics including accuracy. Future research should examine the performance of this tool when used in larger, community-based populations where screening for FASD would be appropriate.
文摘以高耐热性玉米品种郑单958、低耐热性玉米品种先玉335为试验材料,以正常生长条件为对照(CK),利用半自动伸缩高温棚进行花期高温胁迫(HT)处理,通过circRNA高通量测序筛选高温胁迫下不同玉米品种花粉中差异表达的环状RNA(circRNA),对其来源基因进行GO和KEGG富集分析,并筛选具有miRNA结合位点的差异表达circRNA,预测其下游目的基因,分析玉米花粉中响应高温胁迫的潜在circRNA-miRNA-mRNA共表达调控网络,从多层面解析玉米花粉中调控高温胁迫的分子作用机制,为提高玉米品种的耐热性提供理论依据。结果表明,在郑单958、先玉335不同样本中共鉴定出1 843个不同的circRNA,它们在玉米染色体中的分布不同。每个circRNA所包含的外显子数目也不相同,其中,大多数(624个)circRNA只含有1个外显子。在郑单958花粉中共鉴定出1 563个circRNA,其中,CK958-1、CK958-2、CK958-3中分别鉴定出305、213、356个circRNA,HT958-1、HT958-2、HT958-3中分别鉴定出222、242、225个circRNA。在先玉335花粉中共鉴定出1 423个circRNA,其中,CK335-1、CK335-2、CK335-3中分别鉴定出272、188、229个circRNA,HT335-1、HT335-2、HT335-3中分别鉴定出259、237、238个circRNA。不同样本中占比最高的均为外显子circRNA。circRNA与其来源基因不是一一对应的关系,有748个circRNA来源基因通过反向剪接机制只形成1个circRNA,156个circRNA来源基因通过反向剪接机制各自形成2个circRNA。在郑单958高温胁迫花粉与对照花粉对比组(HT958 vs CK958)中共筛选到9个差异表达circRNA,其中2个circRNA呈上调表达,其来源基因显著富集到焦磷酸酶活性、核苷酸磷酸代谢过程、糖基磷脂酰肌醇(GPI)锚定代谢过程等17个GO条目,显著富集到GPI锚定生物合成、代谢途径等KEGG通路。在先玉335高温胁迫花粉与对照花粉对比组(HT335 vs CK335)中共筛选到1个差异表达circRNA,其来源基因没有显著富集到任何GO条目、KEGG通路。在郑单958高温胁迫花粉与先玉335高温胁迫花粉对比组(HT958 vs HT335)中共筛选到17个差异表达circRNA,其中6个circRNA呈上调表达,其来源基因显著富集到内质网系统、高尔基相关囊泡膜、膜蛋白水解等16个GO条目中,没有显著富集到任何KEGG代谢通路。5个circRNA具有miRNA结合位点,可以作为海绵岛吸附miRNA间接调控下游靶标基因的表达,构建了包括5个circRNA、5个不同家族miRNA、2个mRNA在内的circRNA-miRNA-mRNA共表达调控网络。筛选到了54个circRNA包含内部核糖体进入位点(IRES),可以翻译表达多肽或者蛋白质直接作用于靶标基因。
