Complex organic molecules in an early stage of protostellar evolution

We have detected the rotational lines of HCOOCH₃ toward a Class 0 low-mass protostar, NGC1333 IRAS4B, which is reported to be extremely young according to the dynamical age of the molecular outflow (a few 100 yr). This suggests that the complex organic molecules appear from the very early stage of protostellar evolution. On the other hand, the complex organic molecules are not detected in a more evolved protostar, L1527. We have also found a similar trend in a massive star forming region, NGC2264. The HCOOCH₃ emission is almost absent toward IRS1, whereas it is concentrated near MMS3, which is younger than IRS1. In addition, the HCOOCH₃ intensity peak is slightly shifted from the dust emission peak, as is seen in the Orion KL Compact Ridge, giving an important clue to solve its origin.     

CO abundances in a protostellar cloud: freeze-out and desorption in the envelope and outflow of L483

CO isotopes are able to probe the different components in protostellar clouds. These components, core, envelope and outflow have distinct physical conditions, and sometimes more than one component contributes to the observed line profile. In this study, we determine how CO isotope abundances are altered by the physical conditions in the different components. We use a 3D molecular line transport code to simulate the emission of four CO isotopomers, ¹²CO   J = 2 → 1, ¹³CO J = 2 → 1  , C¹⁸O   J = 2 → 1  and C¹⁷O   J = 2 → 1  from the Class 0/1 object L483, which contains a cold quiescent core, an infalling envelope and a clear outflow. Our models replicate James Clerk Maxwell Telescope (JCMT) line observations with the inclusion of freeze-out, a density profile and infall. Our model profiles of ¹²CO and ¹³CO have a large linewidth due to a high-velocity jet. These profiles replicate the process of more abundant material being susceptible to a jet. C¹⁸O and C¹⁷O do not display such a large linewidth as they trace denser quiescent material deep in the cloud.     

Seismic response of deep Quaternary sediments in historical center of L’Aquila City (central Italy)

On 6 April 2009 a M_w=6.1 earthquake produced severe destruction and damage over the historic center of L’Aquila City (central Italy), in which the accelerometer stations AQK and AQU recorded a large amount of near-fault ground motion data. This paper analyzes the recorded ground motions and compares the observed peak accelerations and the horizontal to vertical response spectral ratios with those revealed from numerical simulations. The finite element method is considered herein to perform dynamic modeling on the soil profile underlying the seismic station AQU. The subsurface model, which is based on the reviewed surveys that were carried out in previous studies, consists of 200–400 m of Quaternary sediments overlying a Meso-Cenozoic carbonate bedrock. The Martin-Finn-Seed's pore-water pressure model is used in the simulations. The horizontal to vertical response spectral ratio that is observed during the weak seismic events shows three predominant frequencies at about 14 Hz, 3 Hz and 0.6 Hz, which may be related to the computed seismic motion amplification occurring at the shallow colluvium, at the top and base of the fluvial-lacustrine sequence, respectively. During the 2009 L’Aquila main shock the predominant frequency of 14 Hz shifts to lower values probably due to a peculiar wave-field incidence angle. The predominant frequency of 3 Hz shifts to lower values when the earthquake magnitude increases, which may be associated to the progressive softening of soil due to the excess pore-water pressure generation that reaches a maximum value of about 350 kPa in the top of fluvial-lacustrine sequence. The computed vertical peak acceleration underestimates the experimental value and the horizontal to vertical peak acceleration ratio that is observed at station AQU decreases when the earthquake magnitude increases, which reveals amplification of the vertical component of ground motion probably due to near-source effects.     

中国猪毛菜属(Salsola L.)植物的地理分布特点

对中国猪毛菜属7组37种的地理分布的分析结果表明：亚洲荒漠植物亚区以种类的绝对优势及具有不同演化阶段的组成为中国猪毛菜属的分布中心,该区中以新疆为中心由西向东种类多样性递减：中闽猪毛菜属生境主要为旱生、盐生环境(占总种数的92％),分布海拔可从平原地区的260m上升到高山地带3500m,一些种成为群落中的建群种及优势种：中国猪毛菜属的地埋成分有6种类型,以伊朗．亚洲中部分布型及亚洲中部分布型为主(占总种数的78．38％),中国猪毛菜属与中亚地区的渊源关系十分密切,与东部地区的关系微弱,中国猪毛菜属种类是中亚地区的植物向东迁移形成的。     

利用PSInSAR时间序列研究拉奎拉地震位移场变化特征

对2009年4月6日意大利拉奎拉(LAquila)Mw6.3级地震9景ENVISAT重轨单视复数据采用双轨模式进行永久散射体(Persistent Scatterer,PS)处理,获得了此次地震时序位移场,结合PS位移场Delaunay算法数值分析,结果表明:1)Envisat干涉雷达完整而清晰地探测到了地震前后位移场变化过程及其在不同阶段与震源断裂相关的不同形变特征:震前蠕动位移-明显变形-震期快速突变-震后量级明显减缓的持续变形;2)在此次分析的约54×59km2区域内,震中以西为大面积上升区,视线向最大上升量为130mm;震中以东为下降区域,但下降集中在破裂区,主要在发震过程及震后形成,视线向最大下沉量为210mm,与GPS监测结果一致;3)地震产生的破裂主要分布在约22×14km2范围内,沿NW走向、SW倾斜的Paganica-S.Demetrio正断层展布,方向约135°;4)本文为探索利用PSInSAR时间序列进行地震趋势预测提供了一个较好的案例.     

Influence of limited soil on the root distribution and anchorage of Vitex negundo L.

Field pull-out and laboratory tests were applied to investigate the effect of metal bolts and wire netting on plant root distribution and anchorage characteristics of 9-year-old Vitex negundo L. growing on a weakly weathered rocky slope (38°). Root number, length and diameter were recorded and single root specimens were classified and tested for tensile strength. The results show that root anchorage is different between the two constructions by bolts and wire. Under limited soil condition, root anchorage ability is 80% lower than when there is sufficient soil due to the reduction of the diameter and number of all second-order lateral roots, as well as the reduction of the tensile strength of the embedded second-order and first-order lateral roots on limited soil. We conclude that the distribution and anchorage of Vitex negundo L. is affected by limited soil availability on rocky slopes.     

大叶藻(Zostera marina L.)胚的结构和种子萌发过程的研究

以采自山东荣成褚岛桑沟湾南岸成熟的大叶藻种子为材料,研究了种子的外部形态特征、胚乳成分及胚的解剖结构,并初步了解了大叶藻种子的萌发过程。结果表明,大叶藻种子是单子叶有胚乳的种子,呈暗褐色,椭圆形或长圆形,种皮革质且有17～20条纵肋,胚乳丰厚坚硬,胚乳细胞被淀粉粒充满;胚弯曲,由胚根、胚轴、胚芽和子叶组成,子叶U形棒状,其弯曲部有一裂缝,胚芽位于裂缝处,胚轴较短,其下是两个对生的胚根,有中央维管束贯穿胚根、胚轴、胚芽和子叶。在子叶出土萌发的植物类型中,大叶藻种子萌发过程是罕见的。萌发初期,子叶优先生长突破种皮而长出地面,此后胚根才开始生长并产生不定根。对大叶藻种子结构和萌发过程的研究,为探讨大叶藻种子萌发和幼苗更新的限制因素提供了一定的理论依据。     

粗糙海面L 和C 双波段的代价函数多参量遥感反演分析

利用代价函数(cost function)方法,通过分析粗糙海面L和C双波段多极化遥感亮温对海表盐度、温度、风速和有效波高等参数的敏感性以及L和C双波段多极化的代价函数收敛特性,建立了反演海表盐度、温度、风速和有效波高等多参数的L和C双波段多极化代价函数模式。双波段遥感模式分析结果表明:(1)对于双参数的联合反演,L和C双波段垂直极化代价函数联合反演海表盐度和温度可以获得较好的反演结果。(2)L波段垂直极化和C波段水平极化代价函数联合反演海表盐度和风速较好。(3)对于三参数联合反演,L波段垂直极化和C波段的双极化联合反演盐度、温度和风速的精度较高。(4)L波段亮温对有效波高的敏感性较低(C波段经验模式不含有效波高),使得有效波高反演误差较大,L和C波段经验模式不适合反演有效波高参数。另外,为了定量分析L和C双波段代价函数的多参量遥感反演结果,采用加性噪音模拟亮温方法,对上述L和C双波段多极化模式的盐度、温度和风速等多参数联合反演误差进行了分析,均得出较好的结果。结论表明L和C双波段代价函数联合反演多参量可以明显提高参量反演精度,为粗糙海表面多参量的反演提供了新的方法和途径。     

基于SB-DInSAR时间序列探测地震形变过程的研究

对2009年4月6日意大利拉奎拉6.3级地震9景ENVISAT重轨单视复数据采用双轨模式进行小基线（SB）干涉处理,获得了此次地震的SB-DInSAR时间序列干涉图、位移场以及位移速度场。结果表明：1)地震位移场形变过程为由震前的缓慢变化到震后的加速运动,速度明显由慢到快;2）震中以西为大面积隆起区,最大隆起量为140 mm;震中以东为大面积下沉区域,但形变集中在破裂区,主要在发震过程及震后形成,最大沉降量达185 mm;3）地震产生的破裂主要沿震中的东南方向传播,集中在约13.4 km×7.6 km、方向约135°的椭圆形区域内。