A 31,000-year high-resolution record from two sediment cores off northwest Africa

Benthic foraminiferal assemblage compositions and sedimentary geochemical parameters were analyzed in two radiocarbon dated sediment cores from the upwelling area off NW Africa at 12°N, to reconstruct productivity changes during the last 31 kyr. High-latitude cold events and variations in low-latitude summer insolation influenced humidity, wind systems, and the position of the tropical rain belt over this time period. This in turn caused changes in intensity and seasonality of primary productivity off the southern Northwest African continental margin. High accumulation rates of benthic foraminifera, carbonate, and organic carbon during times of north Atlantic melt water events Heinrich 2 (25.4 to 24.3 kyr BP) and 1 (16.8 to 15.8 kyr BP) indicate high productivity. Dominance of infaunal benthic foraminiferal species and high numbers of deep infaunal specimens during that time indicate a strong and sustained supply of refractory organic matter reworked from the upper slope and shelf. A more southerly position of the tropical rainbelt and the Northeast trade wind belt during Heinrich 2 and 1 may have enhanced wind intensity and almost permanent upwelling, driving this scenario. A phytodetritus-related benthic fauna indicates seasonally pulsed input of labile organic matter but generally low year-round productivity during the Last Glacial Maximum (23 to 18 kyr BP). The tropical rainbelt is more expanded to the North than during Heinrich Events, and relatively weak NE trade winds resulted in seasonal and weak upwelling, thus lower productivity. High productivity characterized by a seasonally high input of labile organic matter, is indicated for times of orbital forced warming, such as the African Humid Period (9.8 to 7 kyr BP). An intensified African monsoon during boreal summer and the northernmost position of the tropical rainbelt within the last 31 kyr resulted in enhanced river discharge from the northward-extended drainage area (or river basin) initiating intense phytoplankton blooms. In the late Holocene (4 to 0 kyr BP) strong carbonate dissolution may have been caused by even more enhanced organic matter fluxes to the sea floor. Increasing aridity on the continent and stronger NE trade winds induced intensive, seasonal coastal upwelling.

High resolution study of sediment core GeoB3606-1

Based on a high-resolution analysis of the diatom signal and biogenic bulk components at site GeoB3606-1 (25°S, off Namibia), we describe rapid palaeoceanographic changes in the Benguela Upwelling System (BUS) from early MIS 3 through to the early Holocene (55 000 to 7 000 14C yr BP). Coastal upwelling strongly varied at 25°S from MIS 3 through to MIS 2. The abrupt decrease in the accumulation rate of biogenic silica and diatoms from MIS 3 into MIS 2 records rapid oceanographic changes in the BUS off Namibia. During MIS 3, leakage of excess H4SiO4 acid from the Southern Ocean into low-latitude surface waters, as indicated by the occurrence of Antarctic diatoms, enhanced the production of spores of Chaetoceros at the expense of calcareous phytoplankton. Furthermore, shallower Antarctic Intermediate Water (AAIW) would have enriched the thermocline off Namibia with silicate transported from the Southern Ocean. The strong decrease of the siliceous signal throughout MIS 2 represents a decrease in the nutrient input to the BUS, even though the diatom assemblage is still dominated by spores of the upwelling-associated diatom genus Chaetoceros. Depletion of silicate in the thermocline from the onset of MIS 2 through to the early Holocene reflects the shutdown of AAIW injection from the Southern Ocean into the BUS, causing upwelled waters to become reduced in silicate, hence less favourable for diatom production. The deglaciation and early Holocene are characterised by the replacement of the upwelling-associated flora by a non-upwelling-related diatom community, reflecting weakened upwelling, retraction of the seaward extension of the chlorophyll filament off Lüderitz, and dominance of warmer waters.

Characterization of the Abydos region through OSIRIS high-resolution images in support of CIVA measurements

Context. On 12 November 2014, the European mission Rosetta delivered the Philae lander on the nucleus of comet 67P /Churyumov-Gerasimenko (67P). After the first touchdown, the lander bounced three times before finally landing at a site named Abydos. Aims. We provide a morphologically detailed analysis of the Abydos landing site to support Philae's measurements and to give context for the interpretation of the images coming from the Comet Infrared and Visible Analyser (CIVA) camera system onboard the lander. Methods. We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 6 December 2014 to perform the analysis of the Abydos landing site, which provided the geomorphological map, the gravitational slope map, the size-frequency distribution of the boulders. We also computed the albedo and spectral reddening maps. Results. The morphological analysis of the region could suggest that Philae is located on a primordial terrain. The Abydos site is surrounded by two layered and fractured outcrops and presents a 0.02 km(2) talus deposit rich in boulders. The boulder size frequency distribution gives a cumulative power-law index of 4.0 + 0.3/0.4, which is correlated with gravitational events triggered by sublimation and /or thermal fracturing causing regressive erosion. The average value of the albedo is 5.8% at lambda(1) = 480.7 nm and 7.4% at lambda(2) = 649.2 nm, which is similar to the global albedos derived by OSIRIS and CIVA, respectively.

High-resolution mapping and isolation of a yeast artificial chromosome contig containing fw2.2: A major fruit weight quantitative trait locus in tomato

A high-resolution physical and genetic map of a major fruit weight quantitative trait locus (QTL), fw2.2, has been constructed for a region of tomato chromosome 2. Using an F2 nearly isogenic line mapping population (3472 individuals) derived from Lycopersicon esculentum (domesticated tomato) × Lycopersicon pennellii (wild tomato), fw2.2 has been placed near TG91 and TG167, which have an interval distance of 0.13 ± 0.03 centimorgan. The physical distance between TG91 and TG167 was estimated to be ≤ 150 kb by pulsed-field gel electrophoresis of tomato DNA. A physical contig composed of six yeast artificial chromosomes (YACs) and encompassing fw2.2 was isolated. No rearrangements or chimerisms were detected within the YAC contig based on restriction fragment length polymorphism analysis using YAC-end sequences and anchored molecular markers from the high-resolution map. Based on genetic recombination events, fw2.2 could be narrowed down to a region less than 150 kb between molecular markers TG91 and HSF24 and included within two YACs: YAC264 (210 kb) and YAC355 (300 kb). This marks the first time, to our knowledge, that a QTL has been mapped with such precision and delimited to a segment of cloned DNA. The fact that the phenotypic effect of the fw2.2 QTL can be mapped to a small interval suggests that the action of this QTL is likely due to a single gene. The development of the high-resolution genetic map, in combination with the physical YAC contig, suggests that the gene responsible for this QTL and other QTLs in plants can be isolated using a positional cloning strategy. The cloning of fw2.2 will likely lead to a better understanding of the molecular biology of fruit development and to the genetic engineering of fruit size characteristics.

Direct observation of iron-induced conformational changes of mitochondrial DNA by high-resolution field-emission in-lens scanning electron microscopy.

When respiring rat liver mitochondria are incubated in the presence of Fe(III) gluconate, their DNA (mtDNA) relaxes from the supercoiled to the open circular form dependent on the iron dose. Anaerobiosis or antioxidants fail to completely inhibit the unwinding. High-resolution field-emission in-lens scanning electron microscopy imaging, in concert with backscattered electron detection, pinpoints nanometer-range iron colloids bound to mtDNA isolated from iron-exposed mitochondria. High-resolution field-emission in-lens scanning electron microscopy with backscattered electron detection imaging permits simultaneous detailed visual analysis of DNA topology, iron dose-dependent mtDNA unwinding, and assessment of iron colloid formation on mtDNA strands.

High resolution spectroscopic characterization of the FGK stars in the Solar neighborhood

We present the most recent results of our ongoing long-term high resolution spectroscopic study of nearby (d ≤ 25 pc) FGK stars which aim is to characterize the local properties of the Galaxy, in particular the star-formation history. A through analysis has been carried out for 253 cool stars in the solar neighborhood. This includes radial and rotational velocities determinations, chromospheric activity levels inference, kinematic analysis, and age estimates. This study does not only shed new light on the issue of stellar formation history but also contributes to any present or future mission aiming to detect extra-solar planets. Exo-planets are likely to be found orbiting around nearby cool stars and their detection and characterization is highly dependent on the precise determination of fundamental stellar parameters such as age, activity levels. Therefore, our study is of paramount importance to ensure the success of any such mission.

Spatial and temporal characteristics of summer precipitation over Central Europe in a suite of high-resolution climate models

High-impact, localized intense rainfall episodes represent a major socio-economic problem for societies worldwide, and at the same time these events are notoriously difficult to simulate properly in climate models. Here, the authors investigate how horizontal resolution and model formulation influence this issue by applying the HARMONIE regional climate model (HCLIM) with three different setups; two using convection parameterization at 15 and 6.25 km horizontal resolution (the latter within the “grey-zone” scale), with lateral boundary conditions provided by ERA-Interim reanalysis and integrated over a pan-European domain, and one with explicit convection at 2 km resolution (HCLIM2) over the Alpine region driven by the 15 km model. Seven summer seasons were sampled and validated against two high-resolution observational data sets. All HCLIM versions underestimate the number of dry days and hours by 20-40%, and overestimate precipitation over the Alpine ridge. Also, only modest added value were found of “grey-zone” resolution. However, the single most important outcome is the substantial added value in HCLIM2 compared to the coarser model versions at sub-daily time scales. It better captures the local-to-regional spatial patterns of precipitation reflecting a more realistic representation of the local and meso-scale dynamics. Further, the duration and spatial frequency of precipitation events, as well as extremes, are closer to observations. These characteristics are key ingredients in heavy rainfall events and associated flash floods, and the outstanding results using HCLIM in convection-permitting setting are convincing and encourage further use of the model to study changes in such events in changing climates.

Quantifying ice-shelf basal melt and ice-stream dynamics using high-resolution DEM and GPS time series

Thesis (Ph.D.)--University of Washington, 2016-06

High resolution provenancing of long travelled dust deposited on the Southern Alps, New Zealand

On 7 February 2000 an atypical orange discolouration of snowfields in the central Southern Alps, New Zealand occurred following the passage of a cold front. Analysis of snow samples identified fine orangey-brown dust mixed with much coarser grey dust. Air parcel forward trajectories from dust sources in southern and central Australia, where dust storms were reported on 4 February 2000, were computed to identify the deposits source. Geochemical analyses of the dust deposit using 26 trace elements, unaffected by regional air pollution and gravitational sorting, indicate that 20% of the dust was sourced from western New South Wales, with 45% from the eastern Eyre Peninsula of South Australia and the remaining 35% was local New Zealand dust. This provenancing approach provides a spatial resolution of long travelled dust sourcing not previously achieved. (c) 2005 Elsevier B.V. All rights reserved.

Long-range and high-resolution correlation optical time-domain reflectometry utilizing an all optical chaotic source

A high resolution optical time domain reflectometry (OTDR) based on an all-fiber chaotic source is demonstrated. We analyze the key factors limiting the operational range of such an OTDR, e.g., integral Rayleigh backscattering and the fiber loss, which degrade the optical signal to noise ratio at the receiver side, and then the guideline for counter-act such signal fading is discussed. The experimentally demonstrated correlation OTDR presents ability of 100km sensing range and 8.2cm spatial resolution (1.2 million resolved points), as a verification of the theoretical analysis. To the best of our knowledge, this is the first time that correlation OTDR measurement is performed over such a long distance with such high precision.

High resolution optical time-domain reflectometry based on correlation utilizing an all-fiber chaotic source

We propose a high-resolution optical time domain reflectometry (OTDR) based on an all-fiber supercontinuum source. The source simply consists of a laser with moderate power and a section of fiber which has a zero dispersion wavelength near the laser's central wavelength. Spectrum and time domain properties of the source are investigated, showing that the source has great capability in nonlinear optics, such as correlation OTDR. We analyze one of the key factors limiting the operational range of such an OTDR, i.e., sampling time. Finally, we experimentally demonstrate a correlation OTDR with 25km sensing range and 5.3cm spatial resolution, as a verification of theoretical analysis.

Coarse-to-fine skeleton extraction for high resolution 3D meshes

This paper presents a novel algorithm for medial surfaces extraction that is based on the density-corrected Hamiltonian analysis of Torsello and Hancock [1]. In order to cope with the exponential growth of the number of voxels, we compute a first coarse discretization of the mesh which is iteratively refined until a desired resolution is achieved. The refinement criterion relies on the analysis of the momentum field, where only the voxels with a suitable value of the divergence are exploded to a lower level of the hierarchy. In order to compensate for the discretization errors incurred at the coarser levels, a dilation procedure is added at the end of each iteration. Finally we design a simple alignment procedure to correct the displacement of the extracted skeleton with respect to the true underlying medial surface. We evaluate the proposed approach with an extensive series of qualitative and quantitative experiments. © 2013 Elsevier Inc. All rights reserved.

An adaptive hierarchical approach to the extraction of high resolution medial surfaces

We introduce a novel algorithm for medial surfaces extraction that is based on the density-corrected Hamiltonian analysis. The approach extracts the skeleton directly from a triangulated mesh and adopts an adaptive octree-based approach in which only skeletal voxels are refined to a lower level of the hierarchy, resulting in robust and accurate skeletons at extremely high resolution. The quality of the extracted medial surfaces is confirmed by an extensive set of experiments. © 2012 IEEE.

Derivation of lake mixing and stratification indices from high-resolution lake buoy data

Lake Analyzer is a numerical code coupled with supporting visualization tools for determining indices of mixing and stratification that are critical to the biogeochemical cycles of lakes and reservoirs. Stability indices, including Lake Number, Wedderburn Number, Schmidt Stability, and thermocline depth are calculated according to established literature definitions and returned to the user in a time series format. The program was created for the analysis of high-frequency data collected from instrumented lake buoys, in support of the emerging field of aquatic sensor network science. Available outputs for the Lake Analyzer program are: water temperature (error-checked and/or down-sampled), wind speed (error-checked and/or down-sampled), metalimnion extent (top and bottom), thermocline depth, friction velocity, Lake Number, Wedderburn Number, Schmidt Stability, mode-1 vertical seiche period, and Brunt-Väisälä buoyancy frequency. Secondary outputs for several of these indices delineate the parent thermocline depth (seasonal thermocline) from the shallower secondary or diurnal thermocline. Lake Analyzer provides a program suite and best practices for the comparison of mixing and stratification indices in lakes across gradients of climate, hydro-physiography, and time, and enables a more detailed understanding of the resulting biogeochemical transformations at different spatial and temporal scales.

Evaluating High-Resolution Aerial Photography Acquired by Unmanned Aerial Systems for Use in Mapping Everglades Wetland Plant Associations

Mapping of vegetation patterns over large extents using remote sensing methods requires field sample collections for two different purposes: (1) the establishment of plant association classification systems from samples of relative abundance estimates; and (2) training for supervised image classification and accuracy assessment of satellite data derived maps. One challenge for both procedures is the establishment of confidence in results and the analysis across multiple spatial scales. Continuous data sets that enable cross-scale studies are very time consuming and expensive to acquire and such extensive field sampling can be invasive. The use of high resolution aerial photography (hrAP) offers an alternative to extensive, invasive, field sampling and can provide large volume, spatially continuous, reference information that can meet the challenges of confidence building and multi-scale analysis.