脉冲星星际闪烁的研究进展

综述了脉冲星星际闪烁观测研究的进展，对脉冲星星际闪烁现象，星际介质中电子密度涨落谱，散射等离子体在银河系中的分面等方面的最新研究结果作了介绍。星际闪烁现象和昨际介质的深入理解，使脉冲星星际闪烁已成为研究诸如脉冲星辐射区结构和脉冲星速度等脉冲星本身性质的重要工具。     

塔克拉玛干沙漠北缘过渡带紫外辐射和总辐射特征

利用塔克拉玛干沙漠北缘沙漠-绿洲过渡带肖塘地区2011年直接探测的辐射资料,对该地区紫外辐射、总辐射状况进行了初步分析。结果表明:紫外辐射、总辐射年变化位相基本相同,年曝辐量分别为242.62、5441.31 MJ\5m-2,分别比塔克拉玛干沙漠腹地少21%、10%,年平均日曝辐量分别为0.68、15.35 MJ\5m-2。总辐射辐照度最大值为1329.6 W\5m-2,紫外辐射辐照度最大值为62.7 W\5m-2,出现在6月。沙尘暴对紫外辐射的减弱作用最明显,扬沙次之,浮尘减弱作用最小。紫外辐射日平均曝辐量占总辐射日平均曝辐量的3.36%～7.25%,年平均曝辐量占4.45%。     

Flow variability in the Strait of Gibraltar: The Mediterranean adjustment to tidal forcing

The vertical structure of the flow variability through the Strait of Gibraltar is studied based on the Gibraltar Experiment and the Word Ocean Circulation Experiment data sets. An analysis of the leading modes of velocity and density variability at the Strait of Gibraltar showed an adjustment of the water masses exchanged through the Strait. Mediterranean mass variations resulting from the water exchanged by barotropic tidal oscillations generate changes of the baroclinic component of the flow that damp these mass variations. This adjustment explains the previously observed fortnightly variation of the shear. Moreover, the adjustment is found to operate for the subinertial time scale flow variability forced by the atmospheric pressure. An analytical model aimed at reproducing variations of the velocity with time and in the vertical is derived. The model includes a depth-varying parameterisation of friction and takes into account density gradient fluctuations across the Strait. The model reproduces the main features of the flow, in particular the shear and the interface depth variations with the tide phase.     

Effect of Pozzolanic Reactivity on Compressibility Characteristics of Stabilised Low Lime Fly Ashes

This paper presents the effects of addition of lime and lime along with gypsum on the compressibility behavior of two class F fly ashes. Since the fly ashes develop strength and exhibit lower compression, consolidation testing with conventional duration of load increment may not be appropriate. Hence, an attempt has been made to assess the minimum duration of load increment necessary to study the compressibility characteristics of such materials. Thus compressibility behavior of fly ashes with additives has been studied using conventional consolidation test with different durations of load increments varying from 30 min to 48 h. The results obtained indicated that 30 min of duration of load increment can be used to assess the compressibility behavior of such materials. The effect of lime which reduces the compression is seen to be maximum from the results obtained with the duration of load increment of 30 min but gradually reduces with higher durations of load increment. It has also been observed that the rate of decrease in the compressibility is maximum up to 2.5% lime and gradual thereafter. The compressibility of lime treated fly ashes further reduces when gypsum is incorporated, the optimum gypsum percentage being 2.5. This reduction in the compressibility of fly ashes enhanced by incorporating lime and gypsum makes them versatile in the construction of embankments and for structural fills, particularly reducing the time required in between laying of each lift.     

Costs related to drowning and near drowning in northern Iran (Guilan province)

In Iran and many other low- and middle-income countries, few studies have been carried out in order to assess which cost analysis methods should be undertaken at the household and community level in relation to incidences of drowning. In this study, we have attempted to develop a model for estimating the impact of the economic burden that drowning and near drowning events incur for victims’ families in the Guilan province in the north of Iran by using an incidence approach. During the financial year of March 2007 to 2008, the following cost-related aspects of drowning episodes were evaluated: (note: main cost elements were income adjusted by family and years) medical costs, productivity loss costs and death costs. A total of 137 drowning fatalities and 104 near drowning incidents were recorded. Males in the age span of 10-29 years constitute a majority of the epidemiology and economy data. When the number of variables included in cost analysis was expanded, the estimated burden of economic duress increased dramatically; however, drowning cost for one drowned victim was equivalent to 17 times the country’s gross domestic product(GDP) per capital. Identification of injured person-based costs in this study will enable development of more effective prevention programs and provide indicators of other costs related to drowning episodes such as property damage and the impact of these accidents on community services and the public health care system.     

A systematized review exploring the map of publications on the health impacts of drought

Natural Hazards - Climate change is likely to increase the risk of drought which impacts on health are not quite known well due to its creeping nature. This study maps the publications on the...     

Helical Eruptive Prominence Associated with a Pair of Overlapping CMEs on 21 April 2001

The eruption of limb prominence on 21 April 2001 associated with two coronal mass ejections (CMEs) is investigated. Hα images reveal two large-scale eruptions (a prominence body and a southern foot-point arch), both showing helical internal structure. These two eruptions are found to be spatially and temporally associated with the corresponding CMEs. The kinematics and the study of geometrical parameters of the prominence show that the eruption was quite impulsive (with peak acceleration ≈470 m s⁻²) and has taken place for relatively low pitch angle of helical threads, not exceeding tan θ≈1.2. The stability criteria of the prominence are revisited in the light of the model of Vršnak (1990, Solar Phys. 129, 295) and the analysis shows that the eruption violates the instability criteria of that model. Finally, the energy stored in the prominence circuit and the energies (kinetic, potential, and magnetic) of the associated CMEs are estimated and it is found that there was enough energy stored in the prominence to drive the two CMEs. S.S. Ali is on leave from Aligarh Muslim University, Aligarh, 202 002, India.     

Initial velocity model construction of seismic tomography in near-surface applications

The impact of initial velocity models on final image reconstruction results and how to construct a proper initial velocity model in near-surface tomography studies are investigated on a two-layer synthetic model with gradually increasing velocity with depth. Refraction initial velocity models and linear velocity function models are tested on both synthetic and field data to obtain images close to reality. It is concluded that velocity function type initial models should be preferred in soft alluvial deposits that exist within the investigated depths, whereas refraction initial models should be preferred in the groundwater table or with strong refractors' existence within the investigated depths to obtain optimum subsurface images in refraction–diving wave seismic tomography.     

Magnetic resistivity and Hall currents effects on the stability of a self-gravitating plasma of varying density in variable magnetic field

The effect of Hall currents have been studied on the instability of a stratified layer of a self-gravitating finitely conducting plasma of varying density. It is assumed that the plasma is permeated by a variable horizontal magnetic field stratified vertically. The stability analysis has been carried out for longitudinal mode of wave propagation. The solution has been obtained through integral equation approach. The dispersion relation has been derived and solved numerically. It is found that both the Hall currents and finite conductivity have a destabilizing influence on the growth rate of the unstable mode of disturbance.