ESR/U-series dating of teeth recovered from well-stratigraphically age-controlled sequences from Northern France

During the last two decades, extensive road-construction works in Northern France have allowed the discovery of numerous Middle Palaeolithic sites. Geological and multidisciplinary studies performed on these localities allowed the establishment of a precise chronostratigraphical and biostratigraphical framework of regional significance, which could be correlated to the global marine palaeoclimatic scale. Each human occupation layer has been linked to this regional framework, thus providing a stratigraphical age-control for the Middle Palaeolithic human settlements of this area.At the same time, a program of geochronological studies was developed using TL, OSL, U-series, ESR and, as often as possible, ESR/U-series methods. Hence, bones and teeth recovered from archaeological sites of Savy, Ault, Caours, Gentelles and La Celle-sur-Seine, were analyzed and the results compared to the chronostratigraphical ages. The age results are generally in good agreement with the geological data while bones and dental tissues display in some cases U-series ages higher that the EU-ESR ones, suggesting U-loss phenomena.     

Delineation of layer boundaries from smooth models obtained from the geoelectrical sounding data inversion

Two techniques have been presented for the delineation of boundaries from smooth models obtained by smooth inversion techniques of geoelectrical sounding data, such as straightforward inversion scheme, Occam’s and Zohdy’s methods. The smooth model consists of a large number of equally spaced layers, wherein the real geological boundaries are missing. The techniques proposed here suppress the geologically irrelevant boundaries and support the real structural boundaries present in the geoelectrical data. In the first technique, solution of linear inverse problem is improved iteratively through weighted minimum norm inverse, the weight being taken from the current solution. The technique is referred as Iterative Straightforward Inversion Scheme. The second method is analytical, based on the application of smoothing filter, referred in the literature as edge-preserving smoothing. A few examples of theoretical magnetotelluric, dc resistivity and field sounding data have been presented to demonstrate the capabilities of the techniques. The methodologies also reduce the conspicuous oscillations in the smooth solutions caused by the conversion of sharp boundaries to the smooth ones.     

Observations of eruption clouds from Sakura-zima volcano,Kyushu, Japan from Skylab 4

Hasselblad and Nikon stereographic photographs taken from Skylab between 9 June 1973 and 1 February 1974 give synoptic plan views of several entire eruption clouds emanating from Sakura-zima volcano in Kagoshima Bay, Kyushu, Japan. Analytical plots of these stereographic pairs, studied in combination with meteorological data, indicate that the eruption clouds did not penetrate the tropopause and thus did not create a stratospheric dust veil of long residence time. A horizontal eddy diffusivity of the order of 10⁶ cm² s^?1 and a vertical eddy diffusivity of the order of 10⁵ cm² s^?1 were calculated from the observed plume dimensions and from available meteorological data. These observations are the first, direct evidence that explosive eruption at an estimated energy level of about 10¹⁸ ergs per paroxysm may be too small under atmospheric conditions similar to those prevailing over Sakura-zima for volcanic effluents to penetrate low-level tropospheric temperature inversions and, consequently, the tropopause over northern middle latitudes. Maximum elevation of the volcanic clouds was determined to be 3.4 km. The cumulative thermal energy release in the rise of volcanic plumes for 385 observed explosive eruptions was estimated to be 10²⁰ to 10²¹ ergs (10¹³ to 10¹⁴ J), but the entire thermal energy release associated with pyroclastic activity may be of the order of 2.5 × 10²² ergs (2.5 × 10¹⁵ J).Estimation of the kinetic energy component of explosive eruptions via satellite observation and meteorological consideration of eruption clouds is thus useful in volcanology as an alternative technique to confirm the kinetic energy estimates made by ground-based geological and geophysical methods, and to aid in construction of physical models of potential and historical tephra-fallout sectors with implications for volcano-hazard prediction.     

利用固定台站分析长江激发气枪信号特征

“地学长江计划”安徽实验是以气枪震源为核心的大型主动源探测实验。通过在长江安徽段20个固定点定点激发气枪震源,结合109个固定台站、11条流动测线组成的观测网络,首次利用主动源实现了对长江流域安徽段约6万km2面积的三维地下结构探测。本文利用固定台站对长江激发气枪信号进行了分析,结果表明,长江中气枪信号激发效果良好,固定台记录中气枪信号可识别的最远距离达300km。对气枪信号绝对振幅的研究结果表明：① 50km处的气枪信号约为10nm量级,200km处的气枪信号小于1 nm;② 气枪信号强度的空间分布存在一定的方位各向异性,可能与长江的几何形状有关;③ 台站背景噪声对于提取气枪信号至关重要,高质量的固定台网为识别nm量级气枪信号提供了可能。     

Estimating seepage from a reservoir from change in hydraulic head

An investigation of seepage below floodwater-retarding structures conducted by the U.S.D.A. Science and Education Administration Federal Research resulted in a method for estimating seepage from a reservoir based upon change in head. A typical structure was selected for the study and physiographic and geologic features of the site were identified. Extensive hydrologic and hydrogeologic data were collected and analyzed for the site. A major inflow event was recorded in the reservoir in September 1965 and data from that event were used to develop an equation for estimating the amount of seepage lost from the structure in relation to the hydraulic head behind the structure. The method presented by the authors provides a physically based method for estimating the impact of a reservoir on the groundwater flow system assuming variable reservoir head conditions.     

Studies of radon emanation from clays

Analyses of literature data and the results of experimental studies were used to identify the forms of radon occurrence in clays and the major factors that affect the emanation (radon release into the environment) from clay soils and rocks. The coefficient of emanation from clays was shown to be determined by the specific microstructure of materials and, under natural conditions (at normal temperature and pressure), to be practically independent of variations in the ambient conditions.     

Determination of geometrical spreading from traveltimes

Geometrical spreading plays an important role for amplitude preserving migration, which is a very time-consuming process. In order to achieve efficiency in terms of computational time and, particularly, storage space, we propose a method to determine geometrical spreading from coarsely gridded traveltime tables. The method is based on a hyperbolic traveltime expansion and provides also a fast and accurate algorithm for the interpolation of traveltimes, including the interpolation of complete shots. Examples demonstrate the applicability of the method to isotropic and anisotropic media.     

Identification of sub-trends from hydro-meteorological series

In hydro-meteorological trend analysis, an alteration in the given variable is detected by considering the long-term series as a whole. Whereas the long-term trend may be absent, the significance of hidden (short-durational) sub-trends in the series may be important for environmental management practices. In this paper, a graphical approach of identifying trend or sub-trends using nonparametric cumulative rank difference (CRD) was proposed. To confirm the significance of the visualized trend, the CRD was translated from the graphical to a statistical metric. To assess its capability, the performance of the CRD method was compared with that of the well-known Mann–Kendall (MK) test. The graphical and statistical CRD techniques were applied to detect trends and sub-trends in the annual rainfall of 10 River Nile riparian countries (RNRCs). The co-occurrence of the trend evolutions in the rainfall with those of the large-scale ocean–atmosphere interactions was analyzed. The power of the CRD method was shown to closely agree with that of the MK test under the various circumstances of sample sizes, variations, linear trend slopes, and serial correlations. At the level of significance α = 5 %, the long-term trends were found present in 30 % of the RNRCs. However at α = 5 %, the main downward (upward) sub-trends were found significant in 30 (60 %) of the RNRCs. Generally at α = 1 %, linkages of the trend evolutions in the rainfall of the RNRCs were found to those of the influences from the Atlantic and Indian Oceans. At α = 5 %, influences from the Pacific Ocean on the rainfall trends of some countries were also evident.     

有限角度CT图像重建算法综述

本文主要介绍了处理有限角度CT图像重建的思路和方法。有限角度CT图像重建属于不完全数据重建范畴,由于不满足数据完备性条件,因此不能精确重建。其处理方法大致可以分为两类:基于变换的迭代-解析重建算法和基于级数展开的迭代-代数/统计重建算法。同时,有限角度重建等价于病态矩阵求逆问题,适当的约束条件、先验知识以及正则化因子对提高重建图像质量非常重要。     

Magnetisation of titanomagnetites from Bulgarian basalts

A number of basalt samples containing titanomagnetites, with varying degrees and modes of oxidation, have been collected from 13 sites in northern Bulgaria, the degree of oxidation being determined from Curie point and lattice parameter determination. The stability of natural remanent magnetization and artificially induced thermoremanences (TRM) has been studied in an attempt to determine whether the oxidized rocks carry a TRM inherited from their original, unoxidized state. From the samples studied, it appears that the intensity and direction of the original TRM's are retained, but that there is some loss in stability.     

Export of lead from salt marshes

Lead accumulates in shallow salt marsh sediments and is taken up by grasses. Since about half of the annual grass crop is transported to the sea after the grass dies, this may contribute to the movement of lead to deeper waters. Where nitrogen additions increase the biomass of grasses, or where very heavy lead contamination takes place, substantial amounts of lead may be removed by tides from the marsh surfaces.     

Observations of noctilucent clouds from Lithuania

We present an analysis of systematic visual and photographic observations of noctilucent clouds seen from Lithuania in the years 1973–2009. The main trends in the noctilucent cloud occurrence frequency and the mean brightness are derived from statistical and correlation analysis. A clear signature of the solar activity cycle is imprinted on the noctilucent cloud occurrence frequency and mean brightness, both showing distinct anti-correlation with the sunspot numbers; however, no statistically significant increase of either noctilucent cloud occurrence frequency or brightness has been detected at least over past 19 yr (1991–2009). The only statistically significant positive trend is established for the numbers of very bright noctilucent cloud displays in the years 1973–2009. The most recent noctilucent cloud observations are linked to variations of local mesospheric temperatures, measured by the Aura satellite.