针对卫星导航所需的高精度地球定向参数(EOP)中的 UT1-UTC 预报问题,提出了基于双差分 LS+AR 的 UT1-UTC 参数预报方法。对 UT1-UTC 观测数据进行跳秒检测、固体地球带谐潮汐项改正,然后对改正后的 UT1-UTC 数据进行双差分处理,增强数据平稳性；采用最小二乘拟合(LS)与自回归(AR)分析方法对差分处理后的数据进行分析与预报；对预报结果进行逆差分处理与潮汐项改正外推、跳秒恢复,获取高精度的 UT1-UTC 预报值。通过与国际 EOP_PCC 预报结果对比表明,UT1-UTC 短期预报精度与 EOP_PCC 较优的预报精度相当,其中1天 UT1-UTC 预报精度优于0.03 ms,优于 EOP_PCC 预报结果。介绍了北京航天飞行控制中心的 UT1-UTC每日例行预报情况。

This paper proposes a prediction method of UT1-UTC in Earth orientation parameters (EOP)by dual differential least-squares (LS)and autoregressive (AR)model.Firstly,leap seconds are removed in UT1-UTC observations,and Earth zonal harmonic tidal are corrected.Then,the corrected UT1-UTC are processed by dual differential method,the stationarity of polar motion parameters is improved.LS+AR method is utilized to analyze the dual differential UT1-UTC to obtain the preliminary prediction results.Finally,the preliminary prediction results are processed by inverse dual differential method,and tidal correction are extrapolated and leap seconds are recovered to obtain high accuracy UT1-UTC prediction results.The prediction results are compared with EOP prediction comparison campaign (EOP_PCC)results.It shows that the short-term UT1-UTC parameters prediction error is at the same level of EOP_PCC.The one day prediction accuracy of UT1-UTC is less than 0.03ms,which is better than EOP _ PCC

目的 探讨通过悬浮培养法富集乙醛脱氢酶1(ALDH-1)高表达的头颈部鳞癌肿瘤细胞的可行性,鉴定富集的细胞是否具有肿瘤干细胞特性.方法 将头颈肿瘤细胞株接种于低黏附平板,在10 ng/ml重组表皮生长因子和10 ng/ml碱性成纤维细胞生长因子的无血清培养基中形成细胞微球,通过ALDEFLUOR方法对ALDH-1的表达水平进行半定量分析,采用流式细胞术分选出ALDH-1高表达细胞,分析其生物学特性.结果 UD-SCC1、UT-SCC22、UM-SCC11B、UT-SCC9和UT-SCC24A细胞在无血清培养液中悬浮培养5～1Od后均能形成细胞微球.在UD-SCC1、UT-SCC22、UM-SCC11B、UT-SCC9和UT-SCC24A细胞株细胞微球来源的细胞(SDC)中,ALDH-1的表达水平均高于其贴壁生长细胞(均P＜0.05).ALDH-1高表达和低表达细胞形成的克隆细胞数分别为(197±47)个和(33±16)个(P＜0.01).单个ALDH-1高表达和低表达UT-SCC9细胞的克隆形成率分别为17.1％和0.7％,差异有统计学意义(P＜0.05);单个ALDH-1高表达和低表达UD-SCC1细胞的克隆形成率分别为19.3％和0,差异有统计学意义(P＜0.01).UD-SCC1、UT-SCC22、UM-SCC11B、UT-SCC9和UT-SCC24A细胞的SDC侵袭力均高于其贴壁细胞(均P＜0.05).在UD-SCC1、UT-SCC22、UM-SCC11B、UT-SCC9和UT-SCC24A细胞的SDC中,Nanog、Sox2和Oct-4 mRNA的表达水平均高于其贴壁细胞(均P＜0.05).UD-SCC1和UT-SCC24A细胞的SDC中,低活性氧簇(ROS)水平细胞比例分别为(26.3±4.9)％和(72.1±6.1)％,均高于UD-SCC1和UT-SCC24A细胞的贴壁细胞中低ROS水平细胞比例[分别为(8.6±1.7)％和(23.7±7.5)％,均P＜0.05].结论 悬浮培养法可有效富集头颈部鳞癌细胞系内的ALDH-1高表达细胞,富集后的细胞具有肿瘤干细胞特性.

Objective Initiation,growth,recurrence,and metastasis of head and neck squamous cell carcinoma (HNSCC) have been related to the cancer stem cells (CSC) that can be identified by their aldehyde-dehydrogenase-isoform-1 (ALDH-1) activity.In this study,we try to prove that suspension culture can enrich ALDH-1 high expression cells within HNSCC cell lines and the enriched cells possess cancer stem cell properties.Methods Cells from five HNSCC cell lines were cultured in ultra-low attachment plates in serum-free Quantum 263 medium supplemented with 10 ng/ml EGF and 10 ng/ml bFGF,and ALDH-1 expression level was evaluated by ALDEFLUOR assay.ALDH-1 high expression cells were separated by FACS sorting,and their phenotypical and functional properties were characterized.Results Spheroids can be formed from all five HNSCC cell lines (UD-SCC1,UT-SCC22,UM-SCC11B,UT-SCC9 and UTSCC24A) under anchorage independent culture condition.The proportion of ALDH1 high expression cells were highly increased in s

利用南极中山站和戴维斯站观测的感应式磁力计数据,运用互谱分析方法统计分析了2004年3、6、9、12月的Pc1-2波事件,研究了Pc1-2波出现频次、中心频率和振幅对季节和磁地方时的分布。结果共获得有效Pc1-2波事件2932件,其中,出现在3、9月较多,分别占51.4%和26.1%,12月次之,占18.6%,6月最少,占3.8%。两站的Pc1-2波事件有59.8%出现在磁中午(0800—1000 UT)附近,且在午后靠近磁中午的时候Pc1-2波的中心频率比在午前靠近磁中午的时候大,振幅则在0800 UT时出现最大值;此外,在6月,Pc1-2波的平均中心频率最大,而平均振幅则最小。这些结果表明,极隙区纬度Pc1-2波的传播在很大程度上受电离层电导率的影响。

We recorded induction magnetometer data from Zhongshan and Davis Stations in Antarctica , for March , June , September, and December in 2004.We used cross-spectrum analysis to statistically study Pc1-2 wave occurrence, center frequency , and amplitude variations with respect to the seasons and magnetic local time .Of 2 932 valid wave events, Pc1-2 waves had a higher occurrence in March (51.4%) and September (26.1%) than in December (18.6%) and June (3.8%), and occurred most frequently near the magnetic local noon (59.8%at 0800-1000 UT) .The wave center frequency was higher post-noon than pre-noon and the wave amplitude reached a maximum at 0800 UT.The maximal center frequency and minimal amplitude occurred in June .These results suggest that Pc1-2 wave properties near the cusp latitudes are strongly influenced by ionospheric conductivity .

本文利用广义条件对称方法对带源项的变系数非线性反应扩散方程 f(x)ut =(g(x)D(u)ux)x+h(x)P(u)ux+q(x)Q(u)进行研究.当扩散项D(u)取um(m=?1,0,1)和eu两种重要情形时,对该方程进行对称约化,得到了具有广义泛函分离变量形式的精确解.这些精确解包含了该方程对应常系数情况下的解.

The nonlinear diffusion-convection equation f(x)ut =(g(x)D(u)ux)x+h(x)P(u)ux+q(x)Q(u) with variable coefficients and source term has been studied. This equation is symmetrically reduced by the generalized conditional symmetry method. Some exact solutions to the resulting equations are constructed, with the diffusion terms D(u)=um(m=?1,0,1) and D(u)=eu. These exact solutions are also the generalized functional separable solutions. Solutions to the equation with constant coefficients are covered by those exact solutions to the equation with variable coefficients.

主要介绍了周日、半日地球自转变化研究进展。首先介绍了周日、半日地球自转变化的研究发展历程以及主要激发因素,近几十年来,由于GPS、VLBI、SLR等观测技术和分析精度的提高,已能用几小时甚至1～2 h的观测数据求解地球自转参数(极移和自转速率变化),并从中检测到明显的周日、半日自转变化。与海潮模型所预测的结果进行比较,在主要的周日、半日潮波频率上,两者的振幅和相位符合得较好,特别是对UT1,符合度为90%左右,极移为60%左右。目前,仍有30%的极移周日、半日激发因素没有确定。然后对20世纪80年代以来关于极移和UT 1的周日、半日变化研究应用,以及不同的全球海潮改正模型作了较为全面的综述,现有的海潮改正模型存在10%～20%的误差,需要进一步的精化。最后对周日、半日地球自转变化的未来研究工作作了简单的展望。

We mainly focus on the progress of research on high frequency changes in the earth rotation. Firstly, we review the development course and main motivating factors of the diurnal and semidiurnal earth rotation change. In recent decades, earth orientation has been monitored with increasing accuracy by advanced space-geodetic techniques, including lunar and satellite laser ranging, very long baseline interferometry and the global positioning system. We are able to obtain the Earth Rotation Parameters (ERP, polar motion and rotation rate changes) by even 1 to 2 hours observation data, form which obvious diurnal and semidiurnal signals can be detected, and compare them with the predicted results by the ocean model. Both the amplitude and phase are in good agreement in the main diurnal and semidiurnal wave frequency, especially for the UT1, whose compliance is 90%, and 60%for polar motion, there are 30%motivating factor of the diurnal and semidiurnal polar motion have not been identified. Th