钝顶螺旋藻藻胆体的稳定性研究   总被引：1，自引：0，他引：1  

张熙颖  刘鲁宁  陈秀兰  张玉忠  周百成 《海洋科学》2004,28(8):38-42

根据室温荧光发射光谱表征 ,研究了藻胆蛋白浓度、离子强度、pH和葡聚糖等因素对钝顶螺旋藻(Spirulinaplatensis)藻胆体的稳定性的影响。藻胆蛋白浓度为0.6～1.2g/L时 ,钝顶螺旋藻藻胆体的室温荧光发射峰在676～681nm之间 ,此时藻胆体的稳定性强 ,不易解离。在低离子强度(<0.75mol/L)条件下 ,钝顶螺旋藻藻胆体易解离 ,解离速度随离子强度的递减而加快。钝顶螺旋藻藻胆体在 pH7时稳定 ,而在 pH5,6,8,9时只有轻微解离 ,表明藻胆体在较宽的 pH范围内保持相对稳定。在钝顶螺旋藻藻胆体溶液中加入10%的葡聚糖 ,保存30d后藻胆体依然保持完整 ,说明葡聚糖对藻胆体的稳定性有保护作用  相似文献   

机载海洋激光荧光雷达叶绿素a测量性能模拟和初步机载实验     

张凯临  贺岩  李志刚 《中国海洋大学学报(自然科学版)》2006,36(5):790-794

发展机载激光荧光雷达系统测量叶绿素a的浓度,模拟了采用三倍频355 nm波长激光作为激发光,机载海洋激光荧光雷达在不同飞行高度和测量不同深度水层的情况下,测量海表叶绿素a浓度的相对误差。依据模拟的参数建立机载激光荧光雷达系统并进行初步机载实验,获得了同经验数据较为一致的测量结果。  相似文献   

硬X射线衍射增强峰位成像CT的几何失真纠正方法     

孙怡  朱佩平  刘明贺  于健 《CT理论与应用研究》2006,15(2):13-21

近年来X射线相位衬度成像技术作为一种新的成像方式凭借其空间分辨率高的优势已经成为生物、医学以及材料科学等领域一种新的独具本领的研究工具。本文针对平行束情况下应用相位衬度成像技术得到的放置在胶囊内的苍蝇及蜜蜂投影图片进行重建,对系统几何失真进行了分析和纠正,很好地提高了重建图像的质量,验证了利用目标自身的信息进行自动校正的可行性。  相似文献   

16排螺旋CT血管成像在上肢动脉疾病的应用   总被引：3，自引：0，他引：3  

么刚  孙建男  刘巍立  李雪岩  陈秀梅 《CT理论与应用研究》2006,15(4):26-29

目的:探讨16排CT血管成像在上肢动脉病变诊断中的价值.材料与方法:对13例临床怀疑上肢动脉阻塞性患者行16排CT扫描,采用容积再现(VR)、最大密度投影(MIP)、多平面重建(MPR)技术处理图像。结果:13例上肢CTA中,有9例锁骨下动脉狭窄,1例左侧肱动脉完全闭塞,1例右侧腋动脉动脉瘤,其中8例经DSA证实。结论16排CT上肢血管成像是一项高度准确的成像技术和非侵袭性检查方法。  相似文献   

溶解性有机碳耦合营养状态解析河流CO₂动态及驱动因素     

张羿  王晗  马永梅  杜佳杰  龙靖潇  郎家锐  倪茂飞 《湖泊科学》2024,36(3):794-806

为全面探索河流溶解性有机碳(DOC)与二氧化碳(CO₂)动态及驱动因素的相关关系,以我国三峡库区河流——澎溪河为对象,于雨季和旱季采集表层水体水样,分别通过原位和室内测定,明确水文参数(水温、pH、碱度和流速)、DOC浓度和营养元素(总氮(TN)和总磷(TP))浓度,并计算水体CO₂分压(pCO₂)、水—气界面CO₂交换通量和营养元素化学计量比(DOC:TN、DOC:TP和TN:TP)。以河流CO₂、DOC和营养状态动态变化为基础,通过对DOC、TN、TP、营养元素化学计量比和荧光峰(B、T、A、M、C、D和N)与河流pCO₂的多维分析建立及评估潜在的耦合关系,从而揭示特定区域河流CO₂的来源与驱动因素特征。结果显示,澎溪河水—气界面CO₂交换速率在3.75～22.9 m/d范围内,雨季((9.91±4.93)m/d)>旱季((6.69±4.30) m/(d),pCO₂在65.95～2...  相似文献   

Where are the X-ray quasi-periodic oscillations in active galaxies?     

S. Vaughan  P. Uttley 《Monthly notices of the Royal Astronomical Society》2005,362(1):235-244

In this paper, we address the question of whether existing X-ray observations of Seyfert galaxies are sufficiently sensitive to detect quasi-periodic oscillations (QPOs) similar to those observed in the X-ray variations of Galactic black holes (GBHs). We use data from XMM–Newton and simulated data based on the best Rossi X-ray Timing Explorer ( RXTE ) long-term monitoring light curves to show that if X-ray QPOs are present in Seyfert X-ray light curves – with similar shapes and strengths to those observed in GBHs, but at lower frequencies commensurate with their larger black hole masses – they would be exceedingly difficult to detect. Our results offer a simple explanation for the present lack of QPO detections in Seyferts. We discuss the improvements in telescope size and monitoring patterns needed to make QPO detections feasible. The most efficient type of future observatory for searching for X-ray QPOs in active Galactic nuclei (AGN) is an X-ray All-Sky Monitor (ASM). A sufficiently sensitive ASM would be ideally suited to detect low-frequency QPOs in nearby AGN. The detection of AGN QPOs would strengthen the AGN–GBH connection, and could serve as powerful diagnostics of the black hole mass and the structure of the X-ray emitting region in AGN.  相似文献   

Entropy amplification from energy feedback in simulated galaxy groups and clusters     

S. Borgani  A. Finoguenov  S. T. Kay  T. J. Ponman  V. Springel  P. Tozzi  G. M. Voit 《Monthly notices of the Royal Astronomical Society》2005,361(1):233-243

  相似文献   

Development of the HEFT and NuSTAR focusing telescopes     

Fiona A. Harrison  Finn E. Christensen  William Craig  Charles Hailey  Wayne Baumgartner  C. M. H. Chen  James Chonko  W. Rick Cook  Jason Koglin  Kristin-Kruse Madsen  Michael Pivavoroff  Steven Boggs  David Smith 《Experimental Astronomy》2005,20(1-3):131-137

Hard X-ray/soft gamma-ray astrophysics is on the verge of a major advance with the practical realization of technologies capable of efficiently focusing X-rays above 10 keV. Hard X-ray focusing telescopes can achieve orders of magnitude improvements in sensitivity compared to the instruments based on coded apertures and collimated detectors that have traditionally been employed in this energy band. Compact focal planes enable high-performance detectors with good spectral resolution to be employed in efficient, low-background configurations. We have developed multilayer coated grazing incidence optics and solid state Cadmium Zinc Telluride focal plane systems for the High Energy Focusing Telescope (HEFT) balloon-borne experiment, and for the Nuclear Spectroscopic Telescope Array (NuSTAR) Small Explorer satellite. In this paper we describe the technologies, telescope designs, and performance of both experiments.  相似文献   

Study of the fast X-ray transient XTE J1901+014 based on INTEGRAL,RXTE, and ROSAT data     

D. I. Karasev  A. A. Lutovinov  S. A. Grebenev 《Astronomy Letters》2007,33(3):159-167

The source XTE J1901+014 discovered by the RXTE observatory during an intense outburst of hard radiation and classified as a fast X-ray transient is studied. The source’s spectral characteristics in the quiescent state have been investigated for the first time both in the soft X-ray energy range (3–20 keV) based on ROSAT and RXTE data and in the hard energy range (>20 keV) based on INTEGRAL data. A timing analysis of the source’s properties has revealed weak nonperiodic bursts of activity on time scales of several tens of seconds and two intense (～0.5–1 Crab) outbursts more than several hundred seconds in duration. Certain assumptions about the nature of the object under study are made.  相似文献   

Photon Spectroscopy with Imaging X-Ray Instruments     

B. J. Labonte  K. P. Reardon 《Solar physics》2007,240(2):387-401

Individual X-ray photons in the keV energy range produce hundreds of photoelectrons in a single pixel of a CCD array detector. The number of photoelectrons produced is a linear function of the photon energy, allowing the measurement of spectral information with an imaging detector system. Most solar X-ray telescopes, such as Yohkoh/SXT and Hinode/XRT, use CCD detectors in an integrating mode and are designed to make temperature estimates from multiband filter photometry. We show how such instruments can be used in a new way to perform a limited type of this photon spectroscopy. By measuring the variance in intensity of a series of repeated images through a single filter of an X-ray source, the mean energy per detected photon can be determined. This energy is related to the underlying coronal spectrum, and hence it can be used to deduce the mean plasma temperature. We apply this technique to data from the Yohkoh Soft X-Ray Telescope and compare the temperatures obtained with this technique with the temperatures derived using the standard filter ratio method for a postflare loop system. Given the large dynamic range of the soft X-ray flux observed from the Sun, we describe the requirements for a future instrument that would be better suited to performing photon spectroscopy. B.J. Labonte deceased 24 October 2005.  相似文献