Equipment and procedure improvements for a lightweight,inexpensive, percussion core sampling system

This paper describes improvements for an inexpensive, lightweight percussion core sampling system and presents examples of recovered core. The system has proven most effective in remote settings where the weight of a coring system may be a constraint. Cores of up to 5.5 m in length have been recovered and the system has functioned successfully in water depths to 200 m. The system weighs approximately 25 kg and costs less than $450.00 (US).The percussion corer is designed for operation from a stable ice-pack surface. The core barrel assembly is lowered through the water column and driven into sediment with a weighted driver. A secondary line is used to raise and drop the driver. The driver is guided to the core barrel assembly by the main line. Cores are retrieved by a simple pulley system anchored to the ice pack.     

Land-surface segmentation as a method to create strata for spatial sampling and its potential for digital soil mapping

Sampling efforts are constrained by limited availability of resources. Therefore, methods to reduce the number of samples, while still achieving reasonable accuracy are needed. Land-surface segmentation (LSS) has proven a powerful technique to partition digital elevation models (DEMs) and their derivatives into relatively homogeneous areas, which can be further employed as support in soil sampling. Though topography is one of the main soil forming factors, a robust assessment of the potential of this technique to digital soil mapping (DSM) is still missing. In this study, we aimed at evaluating the potential of LSS in stratifying a landscape into relatively homogeneous areas, which can be used as strata for guiding the selection of sampling points in DSM. The experiments were carried out in two study areas where soil samples were available. Land-surface derivatives were derived from DEMs and segmented with a tool based on the multiresolution segmentation algorithm, into objects considered as homogeneous soil-landscape divisions. Thus, one sample was randomly selected within each segment from the existing sample data, based on which predictions of soil classes/sub-orders and properties, i.e. soil texture and A-horizon thickness, were made. Results were compared with predictions based on simple random sampling (SRS) and conditioned Latin hypercube (cLHS). The segmentation-based sampling (SBS) scheme performed better than SRS and cLHS schemes in predicting the A-horizon thickness, soil texture fractions and soil classes, showing a high potential of LSS in stratifying a landscape for the purposes of DSM. The novelty of this study is in the way strata are constructed, rather than in the sampling design itself. Further research is needed to demonstrate the value of a SBS design for practical use. The analyses presented here further highlight the importance of considering locally adaptive techniques in optimization of sampling schemes and predictions of soil properties.     

The Mk II sampler: a device to collect sediment cores for analysis of uncontaminated DNA

We describe an improved piston corer, the Mk II, for sampling soft sediments for ancient DNA analysis. The original Mk I model, designed to minimize contamination and successfully used in New Zealand, was subsequently deployed on Easter Island where three problems arose. Two of these problems related to sediment and water entering the core barrel and contaminating samples. The other difficulty was that plant material accumulated ahead of the piston and blocked the corer aperture. Design improvements were made to the prototype model and eliminated these problems.     

A portable extruder for accurate and precise high-resolution subsampling of unconsolidated sediment cores

Journal of Paleolimnology - We developed a portable extruder for precise and accurate high-resolution subsampling of unconsolidated sediment cores. This extruder is capable of producing subsamples...     

Development of a model for ice core dating based on grain elongation

A simple quasi-empirical model is presented to calculate the deformation rate and age scale corresponding to ice core depth, where grain size and shape are determined only by grain growth and grain deformation processes. Given the size and elongation of grains as a function of ice core depth and the accumulation rate at the ice-sheet surface, it is possible to determine the ice core age scale. The model results are in good agreement with measured values of the rate of grain deformation and the age scale for the GIPS2 ice core at depths above 700 m.     

The moment of inertia of Mars and the existence of a core

Summary. A relation is obtained between the true value of the moment of inertia of a planet and the value calculated from the dynamical form factor, J ₂, on the assumption of hydrostatic equilibrium. The result is applied to Mars and it is shown that the difference between the true and calculated moments of inertia is probably insignificant in considering models of the interior of Mars and in particular does not affect an argument for a core based on models calculated by Lyttleton.     

A comparison of two methods to create tracks of moving objects: linear weighted distance and constrained random walk

As an object moves through space, it creates a track (or path) representing the object's past and present position and associated attributes. If data capture fails, then positions along the tracks are unknown. The particular problem we address in this paper is to create tracks of moving objects with missing data. We implement and test two techniques that create continuous tracks of two primate species (Ateles geoffroyi, the red spider monkey, and Cebus capucinus, the white-faced capuchin). Continuous tracks were needed to calculate home range and to analyze daily ranging patterns for each species. Establishing continuous tracks of primates through field data alone, however, was impossible due to challenging field conditions. The results of the analysis using tracks with interpolated positions helped establish that Ateles tend to move directly to their destination while Cebus tended to follow a more wandering track.     

经济全球化与农业区域发展：从自然同质的景观到网络中的异质区段

本文以台湾花卉苗木产业的发展为研究个案,探讨商品作物全球化的趋势下农业区域的新意义。台湾的花卉苗木产业崛起于1960年代末期,而于1990年代后期面临生产过剩危机。缓解危机的出路,一方面是产品结构向耐储运产品（盆花与苗木类）转移,另一方面生产与贸易向大陆内需市场转移,使台湾花卉苗木业者藉先发者的生产技术与通路优势,以跨界生产网络再结构其自身,也将台湾花卉产业进一步地镶嵌在更复杂,更动态,更不确定的全球经济的竞争中,从而挑战了传统的重粮主义的农业区域及其治理。     

A new sediment slicer for rapid sectioning of the uppermost sediment cores from marine and freshwater habitats

The new sediment slicer described herein provides an easy and time-efficient way of sectioning cores of varying length, diameter, and composition from a wide range of habitats and sediment types. It is designed to process sediments collected by means of any soft-sediment core sampler with the core tube detachable from the sampler head and trigger unit. It is useful for sectioning core samples that include both the undisturbed sediment/water interface and highly consolidated sediments. The slicer is composed of three parts: (1) a supporting block, (2) a gliding block with the incorporated 10 cm sub-sampler holder designed to glide freely in the grooves along the supporting block, and (3) a metal blade for sediment slicing.     

Comparison of radiocarbon and OSL dating methods for a Late Quaternary sediment core from Lake Ulaan,Mongolia

Both radiocarbon and optically stimulated luminescence (OSL) dating methods were applied to test their suitability for establishing a chronology of arid-zone lacustrine sediments using a 5.88-m-long core drilled from Lake Ulaan, southern Mongolia. Although the radiocarbon and OSL ages agree in some samples, the radiocarbon ages are older than the corresponding OSL ages at the 550-cm depth horizon (late Pleistocene) and in the 100–300-cm interval (early to late Holocene). In the early to late Holocene, radiocarbon ages are consistently older than OSL ages by 4,100–5,800 years, and in the late Pleistocene by 2,700–3,000 years. Grain-size analysis of early to late Holocene sediments and one late Pleistocene sediment sample (550-cm depth) indicates that eolian processes were the dominant sediment-transport mechanism. Also, two late Pleistocene sediments samples (from 400- to 500-cm depths) are interpreted to have been deposited by both eolian and glaciofluvial processes. Accordingly, the radiocarbon ages that were older than the corresponding OSL ages during the Holocene seem to have been a consequence of the influx of ¹⁴C-deficient carbon delivered from adjacent soils and Paleozoic carbonate rocks by the westerly winds, a process that is also active today. In addition to the input of old reworked carbon by eolian processes, the late Pleistocene sediments were also influenced by old carbon delivered by deglacial meltwater. The results of this study suggest that when eolian sediment transport is suspected, especially in lakes of arid environments, the OSL dating method is superior to the radiocarbon dating method, as it eliminates a common ‘old-carbon’ error problem.     

P- and S-velocity images of the lithosphere–asthenosphere system in the Central Andes from local-source tomographic inversion

About 50 000 P and S arrival times and 25 000 values of t * recorded at seismic arrays operated in the Central Andes between 20°S and 25°S in the time period from 1994 to 1997 have been used for locating more than 1500 deep and crustal earthquakes and creating 3-D P , S velocity and Qp models. The study volume in the reference model is subdivided into three domains: slab, continental crust and mantle wedge. A starting velocity distribution in each domain is set from a priori information: in the crust it is based on the controlled sources seismic studies; in slab and mantle wedge it is defined using relations between P and S velocities, temperature and composition given by mineral physics. Each iteration of tomographic inversion consists of the following steps: (1) absolute location of sources in 3-D velocity model using P and S arrival times; (2) double-difference relocation of the sources and (3) simultaneous determination of P and S velocity anomalies, P and S station corrections and source parameters by inverting one matrix. Velocity parameters are computed in a mesh with the density of nodes proportional to the ray density with double-sided nodes at the domain boundaries. The next iteration is repeated with the updated velocity model and source parameters obtained at the previous step. Different tests aimed at checking the reliability of the obtained velocity models are presented. In addition, we present the results of inversion for Vp and Vp/Vs parameters, which appear to be practically equivalent to Vp and Vs inversion. A separate inversion for Qp has been performed using the ray paths and source locations in the final velocity model. The resulting Vp , Vs and Qp distributions show complicated, essentially 3-D structure in the lithosphere and asthenosphere. P and S velocities appear to be well correlated, suggesting the important role of variations of composition, temperature, water content and degree of partial melting.     

Use of an expert system to map forest soils from a geographical information system

Abstract

Mapping forest soils using conventional methods is time consuming and expensive. An expert system is described and applied to the mapping of five forest soil-landscape units formed on a single granitoid parent material. Three thematic maps were considered important in influencing the distribution of soils. The first showed the distribution of nine classes of native eucalypt forests, and the second and third were derived from a digital elevation model and represented slope gradient and a soil wetness index combined with topographical position. These layers were input to a raster based geographical information system (GIS) and then geometrically co-registered to a regular 30 m grid. From a knowledge of soil distributions, the relationships between the soil-landscape units and the three data layers were quantified by an experienced soil scientist and used as rules in a rule based expert system. The thematic layers accessed from the GIS provided data for the expert system to infer the forest soil-landscape unit most likely to occur at any given pixel. The soil-landscape map output by the expert system compared favourably with a conventional soil-landscape map generated using interpretation of aerial photographs.     

Effects of dissipation and a liquid core on forced nutations in Hamiltonian theory

In a previous paper, the authors considered the free rotation of an earth model composed of a rigid mantle and a liquid core in the presence of dissipation and under the Hamiltonian formalism, obtaining analytical expressions for the free nutation modes.
In this paper we treat the forced motion. Approximate analytical solutions are worked out by means of Hori's perturbation method, the free solutions obtained in the former paper playing the role of the unperturbed solutions required in the application of the method. These solutions are consistent in the sense that, with the usual terminology, the rigid body solutions and the complex transfer functions are calculated with the same parameters.
Besides in-phase terms, the dissipation at the core–mantle boundary studied in this paper gives rise to out-of-phase terms. From a qualitative perspective, we discuss the issue of the resonance in this context. The presence of dissipation changes dramatically the character of the FCN wobble; that is, it is no longer a regular oscillation but a damped one. A strict resonance phenomenon cannot take place thereby, since the forcing perturbations are oscillations with a real (non-complex) frequency.     

Relocating resource peripheries to the core of economic geography's theorizing: rationale and agenda

Theorizing in economic geography has focused on core regions, industrial and non-industrial, old and new. Indeed, contemplation of the idea of globalization has reinforced this quest. This paper disputes this blinkered thinking that peripheralizes resource peripheries, and seeks to re-position and emphasize resource peripheries within economic geography's theoretical agenda, specifically that associated with the new 'institutional' approach. A truly 'global' economic geography cannot afford to ignore resource peripheries. In particular, we argue that characterizing resource peripheries, and making them distinct from cores, is the intersection of four sets of institutional values or dimensions which we summarize in terms of industrialism (economic dimension), environmentalism (environmental dimension), aboriginalism (cultural dimension) and imperialism (geopolitical dimension). This admittedly preliminary framework underlies our hypothesis that resource peripheries around the world have become deeply contested spaces, much more so than those found in cores.