Mapping Qtls for Grain Yield and Yield Components in Kenyan Maize (<i>Zea mays</i>L.) Under Low Phosphorus Using Single Nucleotide Polymorphism (SNPS)

Selection for tolerance to low phosphorus (P) using morphological traits alone is slow and often confounded by environmental effects. This study identified some Quantitative Trait Loci (QTLs) associated with grain yield (GYLD), Plant (PHT) and Ear heights (EHT) under low P in maize using single nucleotide polymorphic markers. 228 F2:3 individuals derived from a cross between two contrasting maize inbred lines together with 239 SNPs were mapped onto ten linkage groups (LGs) spanning 2255 centiMorgans (cM) with an average inter-marker distance of 9.44 cM. Majority of the SNP markers (63%) followed the Mendelian segregation and were fairly distributed in all the LGs. Mean performance for all the traits in the F3 population was higher than the parental values, which suggested transgressive segregation for all traits. Low to moderate broad sense heritability (0.35 - 0.50) in the F3 population for GYLD, PHT and EHT indicated that tolerance to low P is controlled by complex multi genetic factors. A full multi-QTL model analysis suggested six QTLs (2 QTLs each for GYLD, PHT and EHT) located on chromosomes 1, 3, 4 and 8. The two QTLs for GYLD increased maize yield under low P soils by 173 kg/ha while the 2 QTLs for PHT increased plant growth by 18.14 cm. The % phenotypic variance explained by these QTLs under low P environments had a wide range (0.242% - 53.34%) and was much lower for GYLD compared to plant growth. Both additive and dominance gene actions contributed differentially to the observed phenotypic variance for tolerance to low P soils with dominance contributing more genetic effects compared additive effects for majority of the QTLs. The findings of this study will provide some basis for marker-assisted selection for yield improvement and further guide breeding strategies under low P soils of western Kenya.

The Effects of Low Phosphorus Stress on Morphological and Physiological Characteristics of Maize (Zea mays L.) Landraces

A field trial was conducted to investigate main morphological and physiological changes of different maize landraces to low-P stress at the stage of seedling. P-deficiency significantly decreased root volume, total leaf area, and plant dry weight, but greatly increased density of root hairs and root top ratio. In addition, P-deficiency induced the significant enhancement of phosphorus utilization efficiency and the amount of proline, malondialdehye （MDA）, acid phosphatase （APase）, peroxidase （POD） and superoxide dismutase （SOD）, but the significant reduction of P uptake and soluable protein content. Since P-deficiency had smaller effects on the P-tolerant maize landraces DP-44, DP-32 and DP-33 as compared with P-sensitive landraces DP-29 and DP-24, it was demonstrated that differences of tolerance to P-deficiency existed among different maize landraces. The results based on the correlation analysis showed that the economic yield of maize landraces had relationships with their morphological and physiological characteristics under P-deficiency.

A Perturbation Analysis of Low-Rank Matrix Recovery by Schatten p-Minimization

A number of previous papers have studied the problem of recovering low-rank matrices with noise, further combining the noisy and perturbed cases, we propose a nonconvex Schatten p-norm minimization method to deal with the recovery of fully perturbed low-rank matrices. By utilizing the p-null space property (p-NSP) and the p-restricted isometry property (p-RIP) of the matrix, sufficient conditions to ensure that the stable and accurate reconstruction for low-rank matrix in the case of full perturbation are derived, and two upper bound recovery error estimation ns are given. These estimations are characterized by two vital aspects, one involving the best r-approximation error and the other concerning the overall noise. Specifically, this paper obtains two new error upper bounds based on the fact that p-RIP and p-NSP are able to recover accurately and stably low-rank matrix, and to some extent improve the conditions corresponding to RIP.

用于GaN CMOS集成技术的p型GaN欧姆接触研究

通过金属叠层结构、蒸发-合金工艺条件的优化调整,实现了低接触电阻率、高稳定的p型GaN欧姆接触技术,并研究分析了电极金属在合金过程中的扩散行为。测试结果显示,改进后的p型GaN欧姆接触电阻为11.9Ω·mm,比导通电阻率为3.9×10^(-5)Ω·cm^(2),同时在250℃以内的高温环境中欧姆特性不会发生退化。在此基础上,采用低损伤凹槽栅刻蚀、叠层栅介质沉积等工艺研制出增强型p沟道GaN晶体管器件,器件的阈值电压为-1.2 V(V_(GS)=VDS,IDS=10μA/mm),漏极电流密度为-5.6 mA/mm,导通电阻为665Ω·mm(V_(GS)=-8 V,V_(DS)=-2 V)。优异的p型GaN欧姆接触技术为高性能GaN p沟道器件的研制以及GaN CMOS集成技术的小型化、智能化、高速化发展奠定了重要基础。

基于回火P参数的低碳贝氏体钢回火性能预测

以低碳贝氏体钢为研究对象,讨论了回火参数对材料硬度的影响,基于回火P参数理论建立了钢的回火性能预测模型,绘制了回火参数转换算图。硬度误差分析结果显示,误差在15%以内,此模型可以用于回火工艺参数的优化和回火性能的预测。

基于低场核磁共振技术PVC-P土工膜细观渗透机理研究

PVC-P土工膜的防渗性能是膜防渗结构乃至工程安全运行的关键。为避免传统上用渗透系数表征其渗透性能的弊端,运用多组渗透压力下土工膜垂直渗透试验数据和基于低场核磁共振技术获取的孔隙度,构建了渗透流量-孔隙度数学模型,结合孔隙和孔径动态分布探讨了用孔隙度评价其垂直渗透性能的适用性。结果表明:以1H原子为探针的低场核磁共振技术能够准确量测膜内孔隙和孔径分布;依据T2特征谱弛豫时间划分的微孔隙、中孔隙和大孔隙的占比以及孔隙范围内孔径的萎缩或发育是孔隙度变化的根本原因;孔隙度与渗透流量关联性较强,利用量测的饱和PVC-P土工膜孔隙度和构建的模型能够准确预测渗透流量。研究成果表明基于低场核磁共振技术测得的孔隙度可用于PVC-P土工膜防渗性能评价。

低填充P-Si基阻燃体系协效阻燃PA66的制备及性能

尼龙66(PA66)作为一种广泛使用的工程塑料,因其优异的力学性能和加工性能而备受青睐。然而,PA66的可燃性限制了其在某些安全要求较高的应用领域的发展。为了解决这一问题,可通过构建P-Si基协效阻燃体系,对PA66进行熔融共混改性,以期提高其阻燃性能、力学性能及热稳定性。采用熔融共混法制备PA66复合材料,利用二乙基次磷酸铝(ADP)、次磷酸铝(AHP)及纳米二氧化硅(SiO2)构建多元协效阻燃体系,并系统研究了ADP/AHP/SiO2协效阻燃体系对PA66性能的影响,对PA66复合材料的阻燃性能、力学性能及热稳定性进行了综合评价。实验结果表明,ADP/AHP/SiO2协效阻燃体系显著提升了PA66的阻燃性能,当添加总量为9份时,PA66复合材料的阻燃等级达到V-0级别,极限氧指数高达34.3%。此外,PA66复合材料的拉伸性能也得到了显著提升,拉伸强度和拉伸弹性模量分别提高了27%和36%。热重测试显示,PA66复合材料的热稳定性也有明显改善。ADP/AHP/SiO2协效阻燃体系不仅显著提高了PA66的阻燃性能,还有效改善了其力学性能和热稳定性。该体系的引入为PA66的工程应用提供了有力支持,具有重要的实际应用价值和市场前景。

基于DSOGI-PLL与ANF-LPF的i_(p)-i_(q)三相谐波检测方法

随着分布式电源大规模接入电网,电力系统中频率波动、电压不平衡以及谐波畸变等问题日益严重。在这样不平衡和失真的电网条件下,传统i_(p)-i_(q)谐波检测法已不能满足工程需要。为解决这一问题,文中提出一种基于DSOGI-PLL与ANF-LPF的i_(p)-i_(q)三相谐波检测方法。一方面,采用DSOGI-PLL提高复杂电网下提取基波相位的能力;另一方面,采用一种具有选择性谐波滤波能力的改进结构LPF,来提高谐波检测的抗干扰能力。结果表明,所提方法能够在复杂电网条件下完成三相谐波检测。

Analysis of the contribution of acid phosphatase to P efficiency in Brassica napus under low phosphorus conditions

To understand whether genotypic variation in acid phosphatase (APase) activity in rapeseed (Brassica napus L.) induced by phosphorus (P) deficiency has impact on P efficiency,soil APase activity in the rhizosphere for rapeseed P-efficient genotype 102 and P-inefficient genotype 105 was measured against organic and inorganic P sources in the pot experiment,and the activities of root-secreted APase and leaf intracellular APase were investigated in different P-starvation periods in the nutrient solution.Higher activity of root-secreted APase in B.napus was induced under low P conditions.However,P nutrition and P uptake efficiency of the plants supplied with organic P were not directly related to the activity of root-secreted APase due to several confounding factors affecting APase availability.The higher activity of leaf APase improved P remobilization in plants and played important roles in enhancing P use efficiency,shown by the significant correlation between leaf APase activity and P use efficiency in a rapeseed recombinant inbred population of 135 lines.

基于Low-rank分解的复杂TI介质纯qP波正演模拟与逆时偏移

近年来,面向实际应用的TI介质准P波正演模拟与逆时偏移成像技术受到空前的关注.基于常规耦合型传播方程的正演模拟方法不仅存在伪横波及频散假象干扰,而且还遭受模型参数限制(η>0)和不稳定影响;而纯qP波方程的推导繁琐,且由于方程中包含拟微分算子造成求解难度大且精度有限.为此,本文首先构建了一种适用于任意TI介质的纯qP波传播算子,然后借助Low-rank分解求取该算子中的空间-波数域矩阵,同时引入Cerjan衰减边界条件来压制边界反射干扰,最终实现了一种间接的纯qP波波场外推方案,并将其成功应用于复杂TI介质正演模拟与逆时偏移成像中.通过开展数值模拟,并与其他方法对比表明:①该方法既避免了纯qP波方程的繁琐推导,又克服了耦合型方程对模型参数的限制;②还彻底消除了残余伪横波噪音及数值频散;③且能适应较大时间或空间步长及高频震源,是一种相对准确且稳定的各向异性纵波正演与成像策略.

Phosphorus Nutrient Characteristics of Different Maize (Zea mays L.) Inbreds for Tolerance to Low-P Stress

Phosphorus nutrient characteristics of different maize inbred lines to low-P stress were studied at stages of seedling, steming, earing, silking under pot culture. In the periods of seedling and steming, P uptake efficiency was the main contributor to P tolerance, and the relative P content in P-tolerant genotypes, 99180 and 99239 were higher than that in sensitive genotype, 99152. At earing stage, P-tolerant genotypes, compared to P-sensitive ones, had higher accumulation of P in upper leaves. When came to the silking stage, P uptake and redistribution efficiency of P-tolerant genotypes were higher than those in 99152. The results also suggested that there are different mechanisms of P nutrient uptake and distribution in different P-tolerant genotypes. Inbred line 99239, according to the investigation, was considered as an efficient stock in the P-uptake while 99180 fallen to the efficient stock of P redistribution.

Some High-P-Subtype and Low-P-Subtype F-Rich Granites in South China

The F-rich granites in South China could be distinguished as the high-p subtype andthe low-p subtype according to their P2O5 contents. There are obvious differences in chemicalcomopition of these two subtypes. The high-p subtype is strongly peraluminous and characterized by low silica and very low REE contents, while the low-p subtype is weakly peraluminousand characterized by high silica and very high REE contents. There are also some differences inchemical compositions of feldspars and micas for these two subtypes. The phosphorus of thehigh-p subtype mainly appears to be in the feldspar structure as PAISi-2 substitution or subordinately in amblygonite as an accessory mineral, while the phosphorus of the low-p subtype ismainly in apatite and other phosphate minerals.

高原低氧环境下HDAC5在大鼠体内P-gp表达中的作用及对苯妥英钠药代影响

目的探究高原低氧环境下HDAC5在大鼠体内P-gp表达中的关键作用及对苯妥英钠药代的影响。方法Wistar大鼠运至海拔4010 m的青海玉树巴塘,每组6只。不同组分别给予苯妥英钠、苯妥英钠联用金丝桃素、苯妥英钠联用维拉帕米。在高原地区收集服药后不同时间的血浆和肝组织。采用UFLC-MS法测定血浆中苯妥英钠的浓度,计算药代动力学参数。Western blot检测肝组织中HDAC5、P-gp蛋白表达的变化。结果UFLC-MS结果表明,给予P-gp激动剂后,AUC(0-t)、AUC(0-∞)、MRT(0-t)、MRT(0-∞)、T_(1/2z)、CL_(z)/F、V_(z)/F增加;给予P-gp抑制剂后,AUC(0-t)、AUC(0-∞)、MRT(0-t)、MRT(0-∞)、T_(1/2z)降低。同时,高原低氧环境下,HDAC5参与P-gp表达的调控。当给予P-gp激动剂和抑制剂时,HDAC5与P-gp表达呈现相同变化趋势。结论高原低氧环境下,肝中转运体P-gp的表达影响了P-gp底物苯妥英钠的药代动力学,P-gp的变化水平与HDAC5有关。

Applicability of P/S amplitude ratios for the discrimination of low magnitude seismic events

Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events.

基于通用可调(p,q)阶Rife-Vincent自乘-卷积窗的改进四谱线插值高精度谐波分析算法

加窗快速傅里叶变换(WIFFT)是一类重要的谐波参数估计方法。然而,快速傅里叶变换固有的栅栏效应以及非同步采样产生的频谱泄漏对谐波参数的估计精度有较大影响。为此,利用具有最大旁瓣衰减特性的I类Rife-Vincent窗作为父窗,提出一种新型的通用可调(p,q)阶Rife-Vincent自乘-卷积窗(RVSMC p-q),其特点在于通过改变乘积阶数和卷积阶数可以灵活地改变窗函数的主瓣宽度、旁瓣峰值和衰减速度。在此基础上,提出一种基于RVSMC p-q窗的四谱线插值高精度谐波参数估计方法,利用最小二乘拟合原理给出谐波信号的幅值、频率及相位参数的低复杂度多项式估计公式。在复杂谐波、间谐波及基波频率波动的情况下对基于RVSMC p-q窗的四谱线插值谐波参数估计方法的效果进行仿真。研究结果表明:在较低的乘积和卷积阶数条件下,新算法可以获得比经典的基于自乘积窗或自卷积窗的WIFFT算法更为优越的参数估计精度,且算法复杂度较低。

各向异性介质Low-rank有限差分法纯qP波叠前平面波最小二乘逆时偏移

拟声波最小二乘逆时偏移是一种极具潜力的地震波成像工具,但该方法遭受各向异性拟声波近似的限制,TTI介质正演模拟不稳定、反偏移记录中遭受伪横波二次扰动及数值频散假象,另外拟声波最小二乘逆时偏移还面临计算效率低、收敛速度慢、对速度等模型参数依赖性高等问题.为了克服各向异性拟声波最小二乘逆时偏移的缺陷,在反演框架下,本文借助Low-rank有限差分算法首次提出并实现了TTI介质纯qP波线性正演模拟及纯qP波最小二乘逆时偏移;为了进一步提升反演成像效率,同时改善反演成像方法对模型参数误差的依赖性及对地震数据噪声的适应性,通过引入叠前平面波优化策略,发展了TTI介质纯qP波叠前平面波最小二乘逆时偏移成像方法.在编程实现方法的基础上,通过开展模型成像测试,展示了本方法的优势和潜力:一方面加快了反演成像效率,另一方面也提升了方法的抗噪性,同时还降低了方法对模型参数的依赖性.

Metabolism of polyphosphate-accumulating organisms(PAOs) in biological phosphorus removal process under P-limiting and low temperature conditions

Lower temperature or polyphosphate limitation is the favorable condition to enrich polyphosphate-accumulating organisms (PAOs) or glycogen accumulating organisms (GAOs) in biological phosphorus removal process. In this study,a sludge highly enriched in PAOs was used to investigate the metabolic pathways and carbon transformation in batch tests under the two conditions for elucidating the contradiction. The results showed that the PAOs are able to take up acetate and store it as polyhydroxyalkanoates (PHA) in anaerobic phase although the poly-P pool is emptied through washing with negligible P release. The stoichiometric ratios of the PHB and PHV production and glycogen degradation to the acetate uptake combined with the Nile blue staining indicated that the PAOs possess the anaerobic metabolism of GAOs using glycogen as the sole energy source,but no transformation of PAOs to GAOs is observed. After reconverting to the normal operation,phosphorus uptake and release are recovered the same as the parent reactor.

柱花草SgLPR1基因克隆与表达分析

植物的生长和发育受土壤磷有效性的影响。柱花草(Stylosanthes guianensis)是主要的热带豆科牧草,对低磷胁迫表现出优良的适应性。由LPR基因编码的多铜氧化酶被报道在调控植物根系生长和低磷响应方面发挥重要作用。本研究分析了低磷胁迫对两个柱花草基因型生长的影响,并对SgLPR1基因进行了克隆和表达分析。结果表明:相对柱花草基因型‘TF0285’,‘TF0277’具有较高的植株干重和磷吸收效率,且低磷处理促进了‘TF0277’根系的生长。基因克隆分析表明,SgLPR1基因全长为1713 bp,编码570个氨基酸残基,蛋白分子量为64.1 kDa,属于Cupredoxin家族成员,亚细胞定位预测SgLPR1蛋白定位于内质网上。实时定量聚合酶链反应(PCR)结果表明,SgLPR1基因在柱花草茎中表达量高于其他组织中的表达量,且在根尖大于1 cm的根段中表达量最高。相比对照处理,缺氮、缺磷和缺钾处理均增加了SgLPR1基因在柱花草叶和根中的表达量。此外,低磷处理增加了SgLPR1基因在柱花草‘TF0277’根中的表达,但其在‘TF0285’根中的表达无显著变化。本研究结果揭示了SgLPR1可能参与柱花草根系生长对低磷胁迫的应答。

应用球型差分模板的低秩有限差分法纯qP波逆时偏移

各向异性介质拟声波方程正演模拟及逆时偏移存在伪横波干扰及数值不稳定现象,成像质量不佳;同时计算效率也是各向异性逆时偏移的重要影响因素。为此,提出一种兼具成像质量和计算效率的纯qP波逆时偏移成像方法。首先,从波动方程伪解析解和各向异性精确频散关系出发,分别构建了VTI和TTI介质纯qP波伪解析解波场延拓公式,避免了推导显式波动方程,无需对频散关系做平方处理,由此消除了波场模拟存在的伪横波干扰;然后,通过设计三维球型或二维圆形差分模板,并借助低秩有限差分法求解与模型相适应的差分系数,推导了基于低秩有限差分的纯qP波波场延拓公式,在时间方向延拓时,无需进行多次Fourier变换,降低了计算复杂度;最后,在此基础上,利用GPU并行计算正、反向地震波场,提高了逆时偏移的成像效率。典型二维和三维模型试算结果表明:该方法能够消除伪横波干扰,保证计算过程稳定,在二维和三维各向异性介质中都具有较强的适应性和较高的计算效率。