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The endcap of time-of-flight (ETOF) detector in BES (Beijing Spectrometer) III is planned to be upgraded by using multi-gap resistive plate chambers (MRPCs) and the designed time resolution of the MRPCs is around 50 ps. Thus a time-zero (T0) detector needs to be built to offer a high quality reference time for the MRPCs beam test. So a T0 detector is built using plastic scintillator tiles (BC420) to couple with four fast phototubes (PMTs, Hamamatsu H6533). The timing properties of the detector is studied by using a cosmic ray test and factors related to the time resolution, such as plastic scintillator size, readout mode and angle effects, are discussed. T0 detector timing resolutions of ~41-62 ps are achieved, which means that the T0 detector can be used in the MRPC beam test.  相似文献   
3.
A domain-level gradient-based routing (DLR) algorithm for heterogeneous optical networks with syn- chronous digital hierarchy and optical transport network domains is proposed and experimentally vali- dated. This algorithm classifies domains into groups with incremental levels on the basis of domain-level partitioning, and guides paths level by level along a gradient on the basis of interdomain routing tree evolution. The proposed algorithm is implemented in the hierarchical path computation element-based control architecture for connection provisioning. Testbeds with commercial and emulated nodes are es- tablished to verify the feasibility and performance of the algorithm. Experimental and emulation results show that DLR effectively performs in terms of network blocking probability, real time characteristics, and scalability.  相似文献   
4.
该文建立了一种利用磷酰化修饰结合电喷雾质谱(ESI-Q-TOF)测定多肽氨基酸序列的有效方法。利用Atherton-Todd反应,以二丙基亚磷酰酯(DPP)为磷酰化试剂,应用生物质谱技术,对磷酰化修饰后的5种模型肽的磷酰化反应情况进行了系统研究,考察了磷酰化肽的二级质谱特征,并与未经磷酰化反应的肽的二级质谱特征对比。结果表明,经过磷酰化修饰后,肽的二级质谱中的a1离子信号强度明显增加,可以准确鉴定其N端氨基酸;b系列离子信息完整,信号强度增强,使得多肽C ID测序的谱图简单、清晰,有利于肽的氨基酸序列的测定;赖氨酸(K,128.10 u)和谷氨酰胺(Q,128.13 u)两种氨基酸质荷比相近,由于二者磷酰化修饰后的差异性,使其得到准确区分。经过5种已知氨基酸序列的模型肽的磷酰化后结合质谱技术进行氨基酸序列测定验证,结果表明该方法简单、快速、准确,提高了利用质谱技术进行多肽测序的准确度和灵敏度,可为蛋白质组学研究提供有效的技术手段。  相似文献   
5.
A position-sensitive detector is designed for neutron detection. It uses a single continuous screen of a self-made lithium glass scintillator, rather than discrete crystal implementations, coupling with a multi-anode PMT (MaPMT). The scintillator is fast and efficient; with a decay time of 34 ns and thermal neutron detection efficiency of around 95.8% for the 3 mm thick screen, and its light yield is around 5670 photons per neutron and 3768 photons per MeV γ rays deposition. The spatial resolution is around 1.6 mm (FWHM) with the energy resolution around 34.7% by using α (5.2 MeV) rays test.  相似文献   
6.
保守体系的微分方程可用Hamilton体系的方法描述,其特点是保辛。两个辛矩阵之和不能保辛,两个辛矩阵的乘积仍是辛矩阵。最常用的小参数摄动法用的是加法,因此对辛矩阵不能保辛。从保辛的角度,要用正则变换。本文针对非线性微分方程,运用自变量坐标变换,对原系统进行变换。由此推导出变换后系统的变分原理。引入Hamilton对偶变量,通过数学变换,得到变系数非线性方程。针对该方程,本文提出了保辛摄动算法。通过数值算例,对不同步长下,保辛摄动法、多尺度摄动法、龙格库塔法和精确解的结果做了比较。数值例题表明,对于非线性方程,本文提出的保辛摄动算法有良好的精度。在步长增大的情况下,保辛摄动保持了良好的稳定性。  相似文献   
7.
为了研究二代头孢类新药头孢呋辛赖氨酸在肝损伤大鼠体内的药代动力学过程,建立了采用超快速液相色谱-串联质谱(UFLC-MS/MS)快速测定肝损伤模型大鼠血浆中头孢呋辛含量的方法。血浆样品在酸性条件下用乙腈沉淀蛋白,采用Shim-pack XR-ODS色谱柱(75 mm×3.0 mm, 2.2 μm)为分析柱、乙腈-0.1%甲酸水溶液(40:60, v/v)为流动相、流速为400 μL/min进行色谱分离,采用电喷雾负离子(ESI~)模式电离、多反应监测(MRM)模式进行质谱检测,用于定量分析的离子对分别为m/z 423.2→206.8 (头孢呋辛)和m/z 454.1→238.4 (内标头孢噻肟)。结果表明,大鼠血浆中头孢呋辛的质量浓度在0.01~1 mg/L和1~400 mg/L范围内线性关系良好(r>0.99),定量限为0.01 mg/L,日内和日间精密度(以相对标准偏差(RSD)计)均小于11.5%,准确度(RE)为~7.1%~2.2%,平均萃取回收率大于83.5%,样品运行时间仅为3.0 min,能够满足生物样品的测定需求。该法简便、快速,已用于肝损伤大鼠静脉注射头孢呋辛赖氨酸的药代动力学预实验研究。  相似文献   
8.
LiYSiO4:Ce is a promising scintillator and some of its properties have been reported in previous papers. In this paper, samples doped with different concentrations of Ce are prepared and studied. First, the relative light yields of the samples are measured as 28.1%-37.1% compared with a standard anthracene crystal being irradiated by α particles and as ~ 27.2% compared with NaI being irradiated by X-rays. Second, the effects of sample thicknesses on light yields are presented. Finally the timing behaviors of samples with different doped concentrations being irradiated with alpha particles and X-rays are discussed. The result shows that LiYSiO4:Ce is a kind of fast scintillator ( ~ 30 ns) with a moderate light yield that can be used for neutron detection.  相似文献   
9.
以2,3,4,6-四-O-乙酰基-β-D-葡萄糖异硫氰酸酯(GITC)为柱前手性衍生化试剂,建立了柱前衍生化反相高效液相色谱(RP-HPLC)法测定盐酸托莫西汀中S-异构体杂质的方法。考察了碱化与衍生化试剂的浓度及反应时间对衍生化产率的影响,以及流动相组成对柱效、分离度、保留时间的影响,并讨论了结构因素对手性衍生和分离的影响。采用Agilent Zorbax SB-C18(250 mm×4.6 mm,5μm)色谱柱,以乙腈-四氢呋喃-水(体积比为41∶14∶45)为流动相,流速1.0 mL/min;检测波长254 nm,柱温35℃。在优化实验条件下,盐酸托莫西汀与S-异构体的分离度R1.5;S-异构体的检出限为0.15 mg/L,在0.5~8 mg/L范围内线性良好;精密度RSD为1.8%;按标准加入法计算,加标回收率为92%~99%;按外标法计算,加标回收率为94%~102%。该方法简便、可靠,可作为盐酸托莫西汀原料药中S-异构体杂质限量的质控方法。  相似文献   
10.
 利用制备高效液相色谱法从日本产杉材(Cryptomeria japonica D.Don)中分离制备倍半萜类化合物。在YWC-Pack C18柱上,以异丙醇-甲醇-正己烷-水(体积比为50∶35∶10∶5)为流动相,流速为5 mL/min,制备了2种倍半萜类化合物,经紫外光谱、红外光谱及核磁、质谱分析,确认它们分别为(-)-cubebol和(+)-2,7(14),10-bisa-bolatrien-1-ol-4-one。所制备的两个化合物的纯度分别为98.7%和99.1%。  相似文献   
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