A Sensitivity Analysis of the Waterline Method of Constructing a Digital Elevation Model for Intertidal Areas in ERS SAR scene of Eastern England

A sensitivity analysis of the waterline method of constructing a Digital Elevation Model (DEM) of an intertidal zone using remote sensing and hydrodynamic modelling is described. Variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ERS Synthetic Aperture Radar (SAR) images of the Humber/Wash area on the English east coast acquired between 1992 and 1994. Waterlines from these images are heighted using a hydrodynamic tide-surge model and interpolated using block kriging. On 1:500 slope beaches, an average block height estimation standard deviation of 18–22 cm is achieved. This rises to 27 cm on 1:100 slope beaches, and 32 cm on 1:30 slope beaches. The average heighting error at different slopes is decomposed into components due to waterline heighting error, inadequate sensor resolution and interpolation inaccuracy. It is shown that, at 1:500 slope, waterline heighting error and interpolation inaccuracy are the main error sources, whilst at 1:30 slope, errors due to inadequate sensor resolution become dominant. The ability of the technique to generate intertidal DEMs for almost the entire coastal zone in a complete ERS SAR scene covering 100×100 km is demonstrated.     

Atmospheric forcing of fine-sand transport on a low-energy inner shelf: south-central Louisiana,USA

Hydrodynamic and sediment transport measurements from instrumentation deployed during a 54-day winter period at two sites on the Louisiana inner shelf are presented. Strong extratropical storms, with wind speeds of 7.8 to 15.1 m s^-1, were the dominant forcing mechanism during the study. These typically caused mean oscillatory flows and shear velocities about 33% higher than fair weather (averaging 12.3 and 3.2 cm s^-1 at the landward site, and 11.4 and 2.7 cm s^-1 at the seaward site, respectively). These responses were coupled with mean near-bottom currents more than twice as strong as during fair weather (10.3 and 7.5 cm s^-1 at the landward and seaward sites, respectively). These flowed in approximately the same direction as the veering wind, causing a net offshore transport of fine sand. Weak storms were responsible for little sediment transport whereas during fair weather, onshore sand transport of approximately 25-75% of the storm values appears to have occurred. This contradicts previous predictions of negligible fair-weather sediment movement on this inner shelf.     

Prograde metamorphic sequence of REE minerals in pelitic rocks of the Central Alps: implications for allanite–monazite–xenotime phase relations from 250 to 610 °C

The distribution of REE minerals in metasedimentary rocks was investigated to gain insight into the stability of allanite, monazite and xenotime in metapelites. Samples were collected in the central Swiss Alps, along a well‐established metamorphic field gradient that record conditions from very low grade metamorphism (250 °C) to the lower amphibolite facies (～600 °C). In the Alpine metapelites investigated, mass balance calculations show that LREE are mainly transferred between monazite and allanite during the course of prograde metamorphism. At very low grade metamorphism, detrital monazite grains (mostly Variscan in age) have two distinct populations in terms of LREE and MREE compositions. Newly formed monazite crystallized during low‐grade metamorphism (<440 °C); these are enriched in La, but depleted in Th and Y, compared with inherited grains. Upon the appearance of chloritoid (～440–450 °C, thermometry based on chlorite–choritoid and carbonaceous material), monazite is consumed, and MREE and LREE are taken up preferentially in two distinct zones of allanite distinguishable by EMPA and X‐ray mapping. Prior to garnet growth, allanite acquires two growth zones of clinozoisite: a first one rich in HREE + Y and a second one containing low REE contents. Following garnet growth, close to the chloritoid–out zone boundary (～556–580 °C, based on phase equilibrium calculations), allanite and its rims are partially to totally replaced by monazite and xenotime, both associated with plagioclase (± biotite ± staurolite ± kyanite ± quartz). In these samples, epidote relics are located in the matrix or as inclusions in garnet, and these preserve their characteristic chemical and textural growth zoning, indicating that they did not experience re‐equilibration following their prograde formation. Hence, the partial breakdown of allanite to monazite offers the attractive possibility to obtain in situ ages, representing two distinct crystallization stages. In addition, the complex REE + Y and Th zoning pattern of allanite and monazite are essential monitors of crystallization conditions at relatively low metamorphic grade.     

Tectonic amalgamation of crustal blocks along Gadag-Mandya Shear Zone in Dharwar Craton of southern India

The crustal scale Shear Zone that can be traced from Gadag in the north to Mandya in the south in Dharwar Craton of southern India is considered as the boundary between two subcratonic blocks namely the Eastern Dharwar Craton (EDC) and the Western Dharwar Craton (WDC) in published literature. The present study on the Gadag-Mandya Shear Zone (GMSZ) in the Javanahalli-Hagalvadi sector has brought out a detailed account on the disposition, geometry and kinematics of the shear zone, and also the distinctive structural patterns of the two adjacent supracrustal belts, namely the Chitradurga schist belt (CSB) in the west and Javanahalli schist belt (JSB) in the east. The JSB has an overall N-S striking and gentle easterly dipping geometry, the structural features of which are indicative of a predominant noncoaxial deformation and westward transportation of the supracrustal assemblage. In contrast, deformation in the CSB, which is defined mainly by a flattening type of strain, has produced an overall verticality of the structures (dominant foliation, axial planes of regional folds).     

An experimental study of elastohydrodynamics of towed flexible cylinders aided by video image processing

Experimental studies of the elastohydrodynamics of towed flexible cylinders aided by video image processing are reported. A scale model of a prototype hydrophone array has been designed, fabricated, and tested in a speed range of 1.0 to 4.5 m/sec. The experiments were conducted in a 67-m long towing tank. The instrumented flexible member, 12.7 mm in diameter and 13.55 m long, was fixed at the one end and free at the other and was slightly lighter than neutrally bouyant. Three tail drogue configurations were employed. An integral part of the physical model tests was the development and utilization of a microcomputer based video image processing system for model configuration reconstitution. Instability characteristics, tail acceleration spectral densities, lift force due to curvature, and drag coefficients are quantified and discussed.     

Genetic variability of wild Agave angustifolia populations based on AFLP: A basic study for conservation

Agave angustifolia is taken from wild populations in the desert of Sonora, Mexico, to make the alcoholic drink known as “bacanora”. An increase in the demand for this beverage has led to overexploitation of these agaves. We used AFLP to measure the genetic variability within and between natural populations of the species. The fixation index (FST) and population genetic distances (GD) were determined for three populations of A. angustifolia. At the clonal level, the expected heterozygosis (HE), the proportion of polymorphic loci (P), and the genetic similarity indices (GSIs) were lower in one population. Total GSI for adults and offshoots was 0.924. There were no differences in the GSI within or between the populations and dendrogram showed three groups that partially reflect the geographical distribution of the populations. Some degree of genetic variation between mother plants and their vegetatively produced rhizomes was observed. At the species level, total expected heterozygosity was high (HT = 0.314) with a P value of 78%, and intermediate gene flow (Nm = 1.18), giving rise to a moderate fixation index (FST = 0.175). Nm, FST and GD values observed, indicate that urgent measures must be implemented to preserve the genetic diversity.     

Late Quaternary paleoenvironments of an ephemeral wetland in North Dakota,USA: relative interactions of ground-water hydrology and climate change

This study of fossils (pollen, plant macrofossils, stomata and fish) and sediments (lithostratigraphy and geochemistry) from the Wendel site in North Dakota, USA, emphasizes the importance of considering ground-water hydrology when deciphering paleoclimate signals from lakes in postglacial landscapes. The Wendel site was a paleolake from about 11,500 ¹⁴C yr BP to 11,100 ¹⁴C yr BP. Afterwards, the lake-level lowered until it became a prairie marsh by 9,300 ¹⁴C yr BP and finally, at 8,500 ¹⁴C yr BP, an ephemeral wetland as it is today. Meanwhile, the vegetation changed from a white spruce parkland (11,500 to 10,500 ¹⁴C yr BP) to deciduous parkland, followed by grassland at 9,300 ¹⁴C yr BP. The pattern and timing of these aquatic and terrestrial changes are similar to coeval kettle lake records from adjacent uplands, providing a regional aridity signal. However, two local sources of ground water were identified from the fossil and geochemical data, which mediated atmospheric inputs to the Wendel basin. First, the paleolake received water from the melting of stagnant ice buried under local till for about 900 years after glacier recession. Later, Holocene droughts probably caused the lower-elevation Wendel site to capture the ground water of up-gradient lakes.     

Entropy Analysis of Multiple Scale Causality and Qualitative Causal Shifts in Spatial Systems*

Spatial systems are typically characterized by multiple controlling factors and processes operating at different spatial and temporal scales (multiple scale causality [MSC]). An entropy decomposition‐based approach to MSC is presented here in two contexts. First, given maps or distributions of an observed phenomenon at two or more scales, the contribution at more local or global (relative to the primary scale of observation) controls to the observed entropy can be estimated. Second, a theoretical treatment of the entropy decomposition equations shows that as the range of scale is increased by broadening or narrowing resolutions or by incorporating more controls, the influence of larger or smaller‐scale influences not only changes, but may change qualitatively, e.g., in terms of having positive (entropy‐increasing) or negative (information‐increasing) effects. Such qualitative causal shifts have implications for efforts to use any single causal explanation across the molecular to planetary spatial and instantaneous to geological range of scales relevant to physical geography. The entropy decomposition method is illustrated with an application to soil landscapes in the Ouachita Mountains, Arkansas.     

野生二粒小麦 Triticum dicoccoides抗杀锈病基因 YrH52分子定位的初步研究(英文)

主要对以色列野生二粒小麦赫尔蒙种群中分离获得的一个抗条锈病基因进行了分子定位研究 ,将源于赫尔蒙山具抗杀锈病的种系 T.dicoccides H52与普通的栽培种 Langdon进行杂交并创建了 F2 代遗传图。研究发现 H52种系抗条锈病的能力由一种显性基因控制 ,将其暂定名为 Yr H52。从 1 2 0个微卫星标记中 ,已经检测到来自亲本 91 %的多态性 ,而且从其中 56个微卫星分子标记中产生了 79个分离的位点 ,有 9个位点显示出了与 Yr H 52基因连锁 ,其重组率 0 .0 2～ 0 .3 5,遗传距离 2 .0 0～ 4 3 .3 7cm之间 ,L OD值 3 .56～ 54.2 2。由 1 0个微卫星位点和 Yr H52构建的染色体 1 B遗传图 ,其图距全长为 1 0 1 .5cm。Yr H52基因位于 Xgwm2 64 a和 Xgwm2 64 c之间 ,且与 Xgwm2 64 a、Xgwm1 8紧密连锁 ,两侧依次分别与 Xgwm1 3 1 a、Xgwm63 6b、Xgwm2 64 c、Xgwm4 0 3 a、Xgwm1 53、Xgwm550 a和 Xgwm1 2 4连锁。同时 ,Yr H52也与 REL P标记物 N or1紧密连锁 ,图距 1 .4 cm,L OD2 9.62。这显然与野生二粒小麦另一个抗条锈病基因 Yr1 5不同 ,研究证明 Yr1 5与 N or1图距是 1 1 .0 cm。