ENSO indices and analyses

New ENSO indices were developed and the spatial variability and temporal evolution of ENSO were analyzed based on the new indices and modeling experiments, as well as multiple data resources. The new indices, after being defined, were validated with their good diagnostic characteristics and correlation with wind and SST. In the analysis after the definition and validation of the new indices, ENSO feedbacks from wind, heat fluxes, and precipitation were spatially and temporally examined in order to understand ENSO variability and evolution with some emphasized points such as the interaction among the feedbacks, the role of westerly wind bursts and the transformation between zonal and meridional circulations in an ENSO cycle, and the typical pattern of modern ENSO.     

Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5 m to 760.1 m depth, and sections investigated here were retrieved from 619.9 m and 661.0 m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70-75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20-120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas.     

Early afterglows of short gamma-ray bursts

In the relativistic fireball model, the afterglow of a gamma-ray burst (GRB) is produced by synchrotron radiation of the electrons accelerated in the external shock that emerges as the relativistic flow moves. According to this model, the afterglow peaks on a time scale of ～10 s when observed in the soft gamma-ray band. The peak flux can be high enough to be detected by modern all-sky monitors. We investigate the emission from short (ΔT<1 s) GRBs on a time scale t≈10 s using BATSE/CGRO data. A significant flux is recorded for ～20% of the events. In most cases, the observed persistent emission can be explained in terms of the model as an early burst afterglow. No early afterglows of most short GRBs are observed. The model parameters for these bursts are constrained.     

Optical identification of the hard X-ray source IGR J18257-0707

We present the results of our optical identification of the hard X-ray source IGR J18257-0707 through its spectrophotometric observations with the optical RTT-150 telescope. The accurate position of the X-ray source determined using Chandra observations has allowed this source to be confidently associatedwith a faint optical object (m _R ≈ 20.4) whose optical spectrumexhibits a broad H _α emission line at redshift z = 0.037. Thus, the source IGR J18257-0707 is a type-1 Seyfert galaxy at redshift z = 0.037.     

肝脏多房环形强化病变的影像分析?

目的：分析肝脏多房环形强化的影像学特征,探讨肝脓肿、肝内胆管细胞癌、肝转移瘤的鉴别诊断要点。方法：回顾性分析31例肝脏病变表现为多房环形强化的影像学特征,其中肝脓肿15例,肝内胆管细胞癌7例,肝转移瘤9例。13例行上腹部 CT 平扫和三期增强检查,7例行 MRI 平扫及 LAVA 多期增强检查,11例同时行 CT 和 MRI 检查。结果：3种病变在环壁及分隔的强化征象有差异。肝脓肿环壁及分隔均匀、完整（P <0.05）,可见病灶缩小征（P <0.05）。胆管细胞癌环形强化呈向心性充填（P <0.05）,或出现肝包膜回缩（P <0.05）和扩张胆管壁的局限性增厚。环壁不规则中断或见强化的壁结节,是诊断转移瘤较有价值的征象。结论：肝脓肿、肝内胆管细胞癌、肝转移瘤 3种病变各有其影像特点,CT 及 MR 检查对三者的诊断与鉴别诊断有重要价值。     

Phonon density of states in iron at high pressures and high temperatures

The phonon density of states (DOS) in iron has been measured in situ by nuclear resonance inelastic X-ray scattering (NRIXS) at high pressures and high temperatures in a resistively heated diamond anvil cell. The DOS data provide a variety of thermodynamic and elastic parameters essential for characterizing iron at depth in the Earth interior, such as average sound velocity, Debye temperature, atomic mean square displacement, average kinetic energy, vibrational entropy and specific heat. The NRIXS data were collected at 6, 20, and 29 GPa and at temperatures up to 920 K. Temperatures were directly determined from the measured spectra by the ratio of intensities of the phonon creation/annihilation side bands that are determined only by the Boltzmann factor. The change of the DOS caused by the structural transition from -Fe to -Fe is small and not resolvable within the experimental precision. However, the phonon energies in -Fe are clearly shifted to lower values with respect to - and -Fe. The temperature dependence of derived thermodynamic parameters is presented and compared with those obtained by Debyes model. The Debye temperatures that best describe the data decrease slightly with increasing temperature.     

基于气体吸附法和X射线Micro-CT三维成像技术定量解析天然和电化学处理绿松石孔隙特征

绿松石是一种多孔材料,其孔隙特征直接影响其颜色、光泽、硬度、耐久性等性质,进而影响其市场价值,电化学处理的主要目的是降低绿松石孔隙度从而使其耐久、保色。采用全自动比表面仪、X射线显微CT(Micro-CT)等测试分析手段,对电化学处理前后绿松石的孔隙特征进行了对比研究。比表面仪研究发现,电化学处理后的绿松石总孔隙度、总孔体积、平均孔径及比表面积均有一定程度的变化;吸附-脱附曲线高压区域天然绿松石吸附曲线斜率变大,而电化学处理绿松石吸附曲线斜率变小;天然绿松石孔径分布曲线为类抛物线,而电化学处理绿松石孔径分布曲线呈内凹曲线状。Micro-CT研究结果表明:天然绿松石中出现的由表面贯穿至内部的大孔洞,经电化学处理后孔洞被不完全充填;天然绿松石存在“流纹状”结构,孔隙沿“流纹”分布,而电化学处理绿松石的“流纹状”结构消失,孔隙分布杂乱无章。本研究首次从孔隙特征角度入手,发现天然绿松石与电化学处理绿松石在高压区域吸附曲线特征、50 nm孔径以上孔隙分布曲线、孔隙充填情况和内部结构等方面存在明显差异。通过检测绿松石的钾(K)含量,并结合孔隙特征差异,可以有效地对绿松石是否经过电化学处理进行检验判定。     

肺脂肪栓塞综合征的X线及螺旋CT诊断

目的:探讨肺脂肪栓塞综合征的X线及CT特点。方法:回顾性分析8例被诊断为肺脂肪栓塞患者的影像资料,由两位放射科医师对患者的胸部X线片及多层螺旋CT图像进行评价。结果:行X线片扫描5例表现为双肺弥漫性分布的片状密度增高影,2例表现为双肺中下野分布为主的片状阴影,1例仅表现为肺纹理增强。行CT检查5例表现为磨玻璃样改变(3例弥漫性分布、1例呈“地图样”片状分布、1例合并肺小叶间膈增厚呈现网状阴影),3例表现为多发实变影或结节影,2例合并有双侧胸腔积液。结论:X线平片仍是诊断肺脂肪栓塞比较可靠的影像学检查方法,螺旋CT能够提供更多特征性的影像信息。     

主动脉夹层撕裂内膜走行规律在真假腔识别中的应用

目的：探讨主动脉夹层（AD）撕裂内膜走行规律在AD真假腔识别中的临床价值。方法：回顾性分析63例AD患者的MSCTA资料,在降主动脉不同节段轴位图像上测量夹层动脉撕裂内膜与管壁两个结合点的角度,计算真腔所处夹角角平分线（TLIAB）的角度以确定其所在象限,观测在血管不同节段、不同象限内TLIAB的数量。结果：63例夹层患者降主动脉不同节段所得TLIAB最多为126层,不同节段间TLIAB数量的差异有统计学意义（χ²=63.87,P<0.05）。相同节段、不同AD类型间TLIAB数量的差异无统计学意义。TLIAB在右前象限最多,以主动脉弓降部最明显,主动脉弓降部位于右前象限和左前象限的管腔88.89%为真腔。结论：根据主动脉夹层撕裂内膜走行规律识别真假腔是一种简便、快速、有效的方法。