Facile Fabrication of Ultrafine Copper Nanoparticles in Organic Solvent

A facile chemical reduction method has been developed to fabricate ultrafine copper nanoparticles whose sizes can be controlled down to ca. 1 nm by using poly(N-vinylpyrrolidone) (PVP) as the stabilizer and sodium borohyrdride as the reducing agent in an alkaline ethylene glycol (EG) solvent. Transmission electron microscopy (TEM) results and UV–vis absorption spectra demonstrated that the as-prepared particles were well monodispersed, mostly composed of pure metallic Cu nanocrystals and extremely stable over extended period of simply sealed storage

Migration of the Antarctic Polar Front through the mid-Pleistocene transition: evidence and climatic implications

The Antarctic Polar Front is an important biogeochemical divider in the Southern Ocean. Laminated diatom mat deposits record episodes of massive flux of the diatom Thalassiothrix antarctica beneath the Antarctic Polar Front and provide a marker for tracking the migration of the Front through time. Ocean Drilling Program Sites 1091, 1093 and 1094 are the only deep piston cored record hitherto sampled from the sediments of the circumpolar biogenic opal belt. Mapping of diatom mat deposits between these sites indicates a glacial-interglacial front migration of up to 6 degrees of latitude in the early / mid Pleistocene. The mid Pleistocene transition marks a stepwise minimum 7 degree northward migration of the locus of the Polar Front sustained for about 450 kyr until an abrupt southward return to a locus similar to its modern position and further south than any mid-Pleistocene locus. This interval from a “900 ka event” that saw major cooling of the oceans and a ?13C minimum through to the 424 ka Mid-Brunhes Event at Termination V is also seemingly characterised by 1) sustained decreased carbonate in the subtropical south Atlantic, 2) reduced strength of Antarctic deep meridional circulation, 3) lower interglacial temperatures and lower interglacial atmospheric CO2 levels (by some 30 per mil) than those of the last 400 kyr, evidencing less complete deglaciation. This evidence is consistent with a prolonged period lasting 450 kyr of only partial ventilation of the deep ocean during interglacials and suggests that the mechanisms highlighted by recent hypotheses linking mid-latitude atmospheric conditions to the extent of deep ocean ventilation and carbon sequestration over glacial-interglacial cycles are likely in operation during the longer time scale characteristic of the Mid-Pleistocene Transition. The cooling that initiated the “900 ka event” may have been driven by minima in insolation amplitude related to eccentricity modulation of precession that also affected low latitude climates as marked by threshold changes in the African monsoon system. The major thresholds in earth system behaviour through the Mid-Pleistocene Transition were likely governed by an interplay of the 100 kyr and 400 kyr eccentricity modulation of precession

Phylogenetic relationships of cone snails endemic to Cabo Verde based on mitochondrial genomes

Background: Due to their great species and ecological diversity as well as their capacity to produce hundreds of different toxins, cone snails are of interest to evolutionary biologists, pharmacologists and amateur naturalists alike. Taxonomic identification of cone snails still relies mostly on the shape, color, and banding patterns of the shell. However, these phenotypic traits are prone to homoplasy. Therefore, the consistent use of genetic data for species delimitation and phylogenetic inference in this apparently hyperdiverse group is largely wanting. Here, we reconstruct the phylogeny of the cones endemic to Cabo Verde archipelago, a well-known radiation of the group, using mitochondrial (mt) genomes. Results: The reconstructed phylogeny grouped the analyzed species into two main clades, one including Kalloconus from West Africa sister to Trovaoconus from Cabo Verde and the other with a paraphyletic Lautoconus due to the sister group relationship of Africonus from Cabo Verde and Lautoconus ventricosus from Mediterranean Sea and neighboring Atlantic Ocean to the exclusion of Lautoconus endemic to Senegal (plus Lautoconus guanche from Mauritania, Morocco, and Canary Islands). Within Trovaoconus, up to three main lineages could be distinguished. The clade of Africonus included four main lineages (named I to IV), each further subdivided into two monophyletic groups. The reconstructed phylogeny allowed inferring the evolution of the radula in the studied lineages as well as biogeographic patterns. The number of cone species endemic to Cabo Verde was revised under the light of sequence divergence data and the inferred phylogenetic relationships. Conclusions: The sequence divergence between continental members of the genus Kalloconus and island endemics ascribed to the genus Trovaoconus is low, prompting for synonymization of the latter. The genus Lautoconus is paraphyletic. Lautoconus ventricosus is the closest living sister group of genus Africonus. Diversification of Africonus was in allopatry due to the direct development nature of their larvae and mainly triggered by eustatic sea level changes during the Miocene-Pliocene. Our study confirms the diversity of cone endemic to Cabo Verde but significantly reduces the number of valid species. Applying a sequence divergence threshold, the number of valid species within the sampled Africonus is reduced to half.Spanish Ministry of Science and Innovation [CGL2013-45211-C2-2-P, CGL2016-75255-C2-1-P, BES-2011-051469, BES-2014-069575, Doctorado Nacional-567]info:eu-repo/semantics/publishedVersio

Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa

There are multiple hypotheses for human responses to glacial cycling in the Late Pleistocene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5-6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenvironments explain some, but not all temporal technological variability at PP5-6.Social Science and Humanities Research Council of Canada; NORAM; American-Scandinavian Foundation; Fundacao para a Ciencia e Tecnologia [SFRH/BPD/73598/2010]; IGERT [DGE 0801634]; Hyde Family Foundations; Institute of Human Origins; National Science Foundation [BCS-9912465, BCS-0130713, BCS-0524087, BCS-1138073]; John Templeton Foundation to the Institute of Human Origins at Arizona State Universit

Photoacoustic Sentinel Lymph Node Imaging with Self-Assembled Copper Neodecanoate Nanoparticles

Photoacoustic tomography (PAT) is emerging as a novel, hybrid, and non-ionizing imaging modality because of its satisfactory spatial resolution and high soft tissue contrast. PAT combines the advantages of both optical and ultrasonic imaging methods. It opens up the possibilities for noninvasive staging of breast cancer and may replace sentinel lymph node (SLN) biopsy in clinic in the near future. In this work, we demonstrate for the first time that copper can be used as a contrast metal for near-infrared detection of SLN using PAT. A unique strategy is adopted to encapsulate multiple copies of Cu as organically soluble small molecule complexes within a phospholipid-entrapped nanoparticle. The nanoparticles assumed a size of 80–90 nm, which is the optimum hydrodynamic diameter for its distribution throughout the lymphatic systems. These particles provided at least 6-fold higher signal sensitivity in comparison to blood, which is a natural absorber of light. We also demonstrated that high SLN detection sensitivity with PAT can be achieved in a rodent model. This work clearly demonstrates for the first time the potential use of copper as an optical contrast agent

The Weddell Gyre, Southern Ocean: present knowledge and future challenges

The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide and global modeling efforts – thereby enhancing predictions of the WG in global ocean circulation and climate

High-latitude forcing of diatom productivity in the southern Agulhas Plateauduring the past 350kyr

The hydrography of the Indian-Atlantic Ocean gateway has been connected to high-latitude climate dynamics by oceanic and atmospheric teleconnections on orbital and suborbital timescales. A wealth of sedimentary records aiming at reconstructing the late Pleistocene paleoceanography around the southern African continent has been devoted to understanding these linkages. Most of the records are, however, clustered close to the southern South African tip, with comparatively less attention devoted to areas under the direct influence of frontal zones of the Southern Ocean/South Atlantic. Here we present data of the composition and concentration of the diatom assemblage together with bulk biogenic content and the alkenone-based sea surface temperature (SST) variations for the past 350?kyr in the marine sediment core MD02-2588 (approximately 41°S, 26°E) recovered from the southern Agulhas Plateau. Variations in biosiliceous productivity show a varying degree of coupling with Southern Hemisphere paleoclimate records following a glacial-interglacial cyclicity. Ecologically well-constrained groups of diatoms record the glacial-interglacial changes in water masses dynamics, nutrient availability, and stratification of the upper ocean. The good match between the glacial maxima of total diatoms concentration, Chaetoceros spores abundance, and opal content with the maximum seasonal cover of Antarctic ice and the atmospheric dust records points to a dominant Southern Hemisphere forcing of diatom production. Suborbital variability of SST suggests rapid latitudinal migrations of the Subtropical Front and associated water masses over the southern Agulhas Plateau, following millennial contractions and expansions of the subtropical gyres. Warmings of the upper ocean over site MD02-2588 during terminations IV to I occurred earlier than that in the Antarctic Vostok, which is indicative of a Northern Hemisphere lead. Our multiparameter reconstruction highlights how high-latitude atmospheric and hydrographic processes modulated orbital highs and lows in primary production and SST as triggered by northward transport of Si, eolian dust input, and latitudinal migrations of frontal zones