Recent progress on anomalous X-ray pulsars     

Victoria M. Kaspi 《Astrophysics and Space Science》2007,308(1-4):1-11

I review recent observational progress on Anomalous X-ray Pulsars, with an emphasis on timing, variability, and spectra. Highlighted results include the recent timing and flux stabilization of the notoriously unstable AXP 1E 1048.1–5937, the remarkable glitches seen in two AXPs, and the newly recognized variety of AXP variability types, including outbursts, bursts, flares, and pulse profile changes. I also discuss recent discoveries regarding AXP spectra, including their surprising hard X-ray and far-infrared emission, as well as the pulsed radio emission seen in one source. Much has been learned about these enigmatic objects over the past few years, with the pace of discoveries remaining steady. However additional work on both observational and theoretical fronts is needed before we have a comprehensive understanding of AXPs and their place in the zoo of manifestations of young neutron stars.   相似文献   

boldmath Investigation of inter-molecular hydrogen bonding in the binary mixture (acetone + water) by concentration dependent Raman study and ab initio calculations     

欧阳顺利  吴楠楠  孙成林  刘靖尧  里佐威  高淑琴 《海洋学报(英文版)》2010,29(9)

This paper reports that vibrational spectroscopic analysis on hydrogen-bonding between acetone and water comprises both experimental Raman spectra and ab initio calculations on structures of various acetone/water complexes with changing water concentrations. The optimised geometries and wavenumbers of the neat acetone molecule and its complexes are calculated by using ab initio method at the MP2 level with 6-311+G(d,p) basis set. Changes in wavenumber position and linewidth (fullwidth at half maximum) have been explained for neat as well as binary mixtures with different mole fractions of the reference system, acetone, in terms of intermolecular hydrogen bonding. The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the concentration dependent changes in the spectral features in terms of hydrogen bonding.  相似文献   

南海北部陆坡海域内波谱特征   总被引：1，自引：0，他引：1  

尚晓东  卢著敏  谢晓辉  陈桂英 《热带海洋学报》2009,28(3):16-20

本文对1998年南海季风实验中定点观测的声学多普勒流速剖面仪（Acoustic Doppler Current Profiler，ADCP）海流数据进行频谱分析，结果表明南海北部地区内波之间的非线性作用的强弱影响着该海域的内波谱特征。在季节性温跃层（水深22m和58m）中，由于存在着强的非线性作用，内波带的谱斜率趋于σ^-1和σ^-2之间，而且较高能量的潮谐波频率的峰值随着频率呈现少见的一。递减。在季节性温跃层（水深130m）以下，内波非线性相互作用较弱，观测的内波带谱特征与标准Garrett-Munk内波谱相似，均显示了σ^-2的谱斜率。  相似文献   

深海热液区主要成分的高温高压拉曼光谱分析     

马君  黄阳玉  曲业飞  史晓凤  于增慧  郑荣儿 《中国海洋大学学报(自然科学版)》2009,39(5)

模拟深海热液口环境(最高压力40 MPa,最高温度350℃),对深海热液区的主要成分CO2、CH4及其混合物的水溶液在不同压力和温度条件下的拉曼光谱进行探测和分析,结果显示:常温低压下CO2水溶液的Fermi双峰分别位于1 384.9 cm-1和1 278.3 cm-1处,CH4的水溶液拉曼峰υ1位于2 912.1 cm-1处,均比其气相的拉曼频移小;常温下CO2和CH4水溶液的拉曼特征峰随压力(≤40 MPa)的变化均不明显;在40 MPa的压力下随着温度的升高(≤350℃),CO2水溶液的Fermi双峰分别向高波数区移动了约3.4 cm-1和7.0 cm-1,而CH4水溶液的拉曼峰υ1向低波数区移动了约3.1cm-1;混合后升温过程中CO2的双峰分别向高波数区移动了约4.3 cm-1和3.8 cm-1,CH4的特征峰υ1向低波数区移动了4.5 cm-1。说明在室温到350℃范围内温度的变化对CO2和CH4水溶液拉曼频移有影响,频移量与温度线性相关,而压力在≤40 MPa范围内的改变对拉曼频移影响不明显。  相似文献   

一种基于多源遥感影像的亚端元光谱提取方法     

朱长富  吴波  吴逸人  高海燕 《测绘科学》2009,34(4)

提出一种利用多源影像来提取低分辨影像亚端元光谱的方法,该方法利用高分辨分类得到的组分与低分辨的光谱之间的线性混合关系,建立了反演出低分辨影像的亚端元光谱的线性模型,并提出一种快速鲁棒反演亚端元光谱的提取方法。利用IKONOS和ETM数据验证了本文提出方法,实验结果表明了该方法的有效性。  相似文献   

Large-scale dune erosion tests to study the influence of wave periods   总被引：1，自引：0，他引：1  

M.R.A. van Gent  J.S.M. van Thiel de Vries  E.M. Coeveld  J.H. de Vroeg  J. van de Graaff 《Coastal Engineering》2008,55(12):1041-1051

Large-scale physical model tests were performed to quantify the effects of the wave period on dune erosion. Attention was focussed on 2D cross-shore effects in a situation with sandy dunes and extreme water levels and wave conditions. Besides profile measurements, detailed measurements in time and space of water pressure, flow velocities and sediment concentrations were performed in the near near-shore area. It was concluded that a longer wave period leads to a larger dune erosion volume and to a larger landward retreat of the dune face. Tests with double-peaked wave spectra showed that the influence of the spectral shape on dune erosion was best represented by the T_m − 1,0 spectral mean wave period, better than the peak wave period, T_p. The effect of the wave period on dune erosion was implemented in a dune erosion prediction method that estimates erosion volumes during normative storm conditions for the Dutch coast. More details of the measurements and additional analyses of physical processes are described in an accompanying paper by Van Thiel de Vries et al. [Van Thiel de Vries, J.S.M., van Gent, M.R.A., Reniers, A.J.H.M. and Walstra, D.J.R., submitted for publication. Analysis of dune erosion processes in large scale flume experiments, In this volume of Coastal Engineering.].  相似文献   

光谱对许氏平鲉消化代谢节律及生理应激研究          下载免费PDF全文

房莹莹  陈璐璐  刘松涛  孙飞  吴燕玲  李鑫  刘鹰  马贺 《海洋科学》2023,47(10):94-111

为探究不同光谱下许氏平鲉的消化代谢水平及外周激素节律,在5种光谱(红光、绿光、黄光、蓝光、白光,光周期12L∶12D)下,通过对许氏平鲉的血清、肠道、肝脏进行24 h (8:00,12:00,16:00,20:00,24:00)取样,结果显示:不同的光谱下许氏平鲉的消化代谢酶活性除胰蛋白酶(TRY)外均具有节律性,红光、黄光下α-淀粉酶(α-AMS)、脂肪酶(LPS)活性的峰值相位与白光组相比左移;胰蛋白酶活性无时间差异性;在绿光、黄光及红光下乳酸脱氢酶(LDH)活性的峰值相位与白光组相比发生左移,在五种光谱环境中,红、黄光影响消化酶活性峰值提前出现;丙酮酸激酶(PK)活性在绿、蓝及红光下峰值相位左移;己糖激酶(HK)的活性在绿、蓝、黄光下,其峰值相位与白光组相比发生左移,在五种光谱环境中,绿、蓝光影响代谢酶活性类峰值提前出现。许氏平鲉血清中褪黑素含量呈现昼低夜高分泌水平;皮质醇的含量表现为在白天降低,午夜显著升高至最高值后又持续降低。峰值相位的改变预示着生理节律的变动,以上结果表明不同光谱可以影响鱼类的生理代谢节律,在今后养殖过程中需要充分考虑光谱对养殖生物的生物学作用,进而制定更为合理的光照条件。  相似文献   

大黄鱼病原副溶血弧菌拮抗菌的筛选   总被引：1，自引：1，他引：0       下载免费PDF全文

郭国军  覃映雪  陈强  邹文政  鄢庆枇 《海洋学报》2008,30(1):127-134

用点种法从大黄鱼肠道优势菌群中筛选出104株病原性副溶血弧菌的拮抗菌,进一步研究拮抗效果最好的11株拮抗菌的抗菌谱和生长曲线,其中NAC平板上筛选的4株拮抗菌的抗菌范围较广,锰营养琼脂培养基上筛选的3株拮抗菌具有生长优势。用BIOLOG板测定了抗菌谱较广、有一定生长优势3株拮抗菌(R22,Y58和J312)的碳源利用情况,结果表明,3株拮抗菌的碳源谱都比较广,都能利用糖类、有机酸和氨基酸等,而且与鱼类营养的竞争较小。16S rRNA基因同源性分析的结果显示与R22,Y58,J312同源性达99%以上的菌株分别来自弧菌属、芽孢杆菌属和假单胞菌属。进一步对R22,J312和Y58三株拮抗菌进行生化鉴定,结果显示R22为溶藻弧菌,J312为荧光假单胞菌,但Y58的种属未能得到确认。所得到的3株拮抗菌R22,Y58,J312在拮抗病原菌、抗菌谱、生长特性和营养利用等方面都初步满足益生菌的筛选条件,有待进一步检测其安全性和实用效果以便能够成为能实用的益生菌。  相似文献   

Large-scale variability in the profiles of Hα and Hβ in the spectrum of the Herbig B8e star MWC 419 and a model interpretation of it     

A. V. Kurchakov  M. A. Pogodin  F. K. Rspaev 《Astrophysics》2007,50(2):207-224

Spectroscopic data taken with a moderate resolution spectrograph in the region of the Hα and Hβ lines are presented for the Herbig B8e star MWC 419. The spectroscopic observations were accompanied by broad band BVR photometric measurements. The observations reveal a variability in the line profiles that is typical of Herbig Ae/Be stars with signs of a strong stellar wind. The greatest changes are observed in the region of the absorption components of the line profiles, which convert the profile from a type P CygII to P CygIII, as well as in the intensities of the central emission components. A model technique is used for quantitative interpretation of this variability and it shows that the P Cyg profile conversion of the absorption component can be explained in terms of a stellar wind model in which its distribution over latitude varies on a time scale of a few days. __________ Translated from Astrofizika, Vol. 50, No. 2, pp. 259–280 (May 2007).  相似文献   

Estimation of the Land Surface Emissivity in the Hinterland of Taklimakan Desert   总被引：3，自引：2，他引：1  

LIU Yong-qiang  Ali MAMTIMIN  HUO Wen  YANG Xing-hua  LIU Xin-chun  MENG Xian-yong  HE Qing 《山地科学学报》2014,(6):1543-1551

An accurate accounting of land surface emissivity(ε) is important both for the retrieval of surface temperatures and the calculation of the longwave surface energy budgets.Since ε is one of the important parameterizations in land surface models(LSMs),accurate accounting also improves the accuracy of surface temperatures and sensible heat fluxes simulated by LSMs.In order to obtain an accurate emissivity,this paper focuses on estimating ε from data collected in the hinterland of Taklimakan Desert by two different methods.In the first method,ε was derived from the surface broadband emissivity in the 8–14 μm thermal infrared atmospheric window,which was determined from spectral radiances observed by field measurements using a portable Fourier transform infrared spectrometer,the mean ε being 0.9051.The second method compared the observed and calculated heat fluxes under nearneutral atmospheric stability and estimated ε indirectly by minimizing the root-mean-square difference between them.The result of the second method found a mean value of 0.9042,which is consistent with the result by the first method.Although the two methods recover ε from different field experiments and data,the difference of meanvalues is 0.0009.The first method is superior to the indirect method,and is also more convenient.  相似文献