1,721,128 research outputs found
Dall’archeologia urbana all’archeologia pubblica: alcune riflessioni, From urban archaeology to public archaeology: some reflections
No full textUna sintesi della stagione dell'archeologia urbana in Italia e della recente affermazione dell'archeologia pubblic
Are productivity and stratification important to sapropel deposition? Microfossil evidence from late Pliocene i-cycle 180 at Vrica, Calabria
No full textThe first appearance of monothalamous foraminifera and the molecular clock, state of the art.
No full textWhen did foraminifera appear in the geological record? The traditional paleontological approach put the first
occurrence of Foraminifera in the Paleozoic, however the architectural complexity and design displayed by Lower
Cambrian foraminiferal assemblages joint to the low fossilization potential of soft-walled taxa, indicate that the fossil
record should not be interpreted so literally (Langer, 1999). In literature interpretations based on molecular sequencing
data (molecular clock), which use the genetic distance to estimate divergence times between lineages, suggest that the
initial appearance of foraminifera should date back to 1.1 billion years (Pawlowski et al., 2003). Finally recent
paleontological data have found also several evidence of taxa similar to soft walled saccamminids back in the post
Sturtian deposits of Namibia and Mongolia (Bosak et al., 2012). Other similar putatively organic structured organisms
are described in many other articles (Marti Mus & Moczydlowska, 2000; Porter et al., 2003; Maloof et al., 2010) and
also Late Ediacaran Agglutinated foraminifera have been found by Pazio (2012) in northern Norway, evidencing that
this topic deserve to be approached deeply, joining all the efforts in order to find new sites and fossils. Aim of this
presentation is to point out recent findings of organic walled forms which prove that a different approach in the
preparation of samples and the study of this early forms needs to be adopted
Monothalamous soft-shelled foraminiferal image dataset from the Kveithola Trough (NW Barents Sea)
Full text linkWe present an image dataset of monothalamous soft-shelled Foraminifera (Monothalamea, [1]), an important component of benthic foraminiferal assemblage in sediment cores collected during two oceanographic expeditions that contributed to the MSM30-CORIBAR project (Ice dynamics and meltwater deposits: coring in the Kveithola trough, NW Barents Sea). 9 subsamples of sediment cores were collected during different years (2013-2016) in the Kveithola Trough, a glacially carved system in the NW Barents Sea. Cores were retrieved using a multi-corer (MUC) and a giant box-corer (GBC) and the subcores for foraminiferal analyses were obtained using Plexiglas tubes inserted manually into the cores. These subcores were sliced at 0.5 cm intervals down to 2 cm sediment depth and then every 1 cm down to 10 cm. Two staining methods, Cell Tracker Green (CTG) and Rose Bengal (RB), were used to distinguish between living and dead individuals. Then, the fixed sediment samples were sieved through 63 and 150 μm mesh screens and preserved in 10 % borax-buffered formalin. Six species and 37 undescribed morphotypes were recognized and included in this image dataset. Relatively few species of soft-shelled, monothalamous foraminifera have been described compared to a much larger number of undescribed morphotypes recognised from across the marine realm. Few researchers study with their taxonomy because of the time and difficulties that morphological identification involves. In addition, because "soft", delicate monothalamids rarely fossilize, they are generally overlooked by micropaleontologists. However, they are abundant and diverse and represent an important faunal component of marine as well as freshwater ecosystems. Further information about these frequently overlooked protists will help to address important knowledge gaps and enhance our ability to manage and conserve the planet's resources responsibly. In particular, our image dataset highlights the importance of monothalamous soft-shelled foraminifera in this peculiar Arctic environment and contributes to the first species/morphotype checklist for the area. We hope it will serve to fill gaps in knowledge regarding the ecology and biodiversity of benthic foraminifera, helping users to identify monothalamids species and morphotypes in Arctic waters and beyond. This data article is associated with the research papers: "Benthic foraminiferal assemblages and environmental drivers along the Kveithola Trough (NW Barents Sea)" by [2]
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Abyssal benthic foraminifera in the Polar Front Region (Pacific Sector): faunal composition, standing stock and size structure.
No full textWe have evaluated the quantitative composition of Rose Bengal-stained benthic foraminiferal assemblages of surface samples from two box cores (ANTA98-28 bc; ANTA01-01 bc) collected at the Polar Front in the Pacific sector of the Southern Ocean. Size structure, faunal composition and standing stock were analysed for living (Rose Bengalstained) and dead foraminifera. The size fractions among 63-150, 150-250 and >250 μm were counted separately in order to study the foraminiferal size distribution and to compare our results with earlier Antarctic studies. The low organic carbon content of the sediment, and hence the limited food availability, is reflected by very low standing stocks and low diversity values. Calcareous taxa dominated dead foraminiferal assemblages that were more diverse than the stained assemblages. In the sediment samples of ANTA01-01 bc, the living fauna contained agglutinated taxa and soft-shelled monothalamous forms. Our data represent the southernmost record of benthic foraminiferal community (63° S) from the Polar Front region in the Pacific sector. These samples provide further evidence for the occurrence of meiofaunal foraminifera in extreme environments, like the Antarctic region, where the uncoupled annual variations in temperature and production cause strong effects on the structure of benthic communities
Accumulation and distribution of microplastics in coastal sediments from the inner Oslofjord, Norway
No full textMicroplastic presence in benthic marine systems is a widely discussed topic. The influence of the natural matrix on microplastic distribution within the sedimentary matrix is often overlooked. Marine sediments from the western inner Oslofjord, Norway, were investigated for temporal trends, with a particular focus on the relationship between sediment grain-sizes and microplastic distribution. Density separation, optical microscopy and chemical validation were used to categorize microplastics. Microplastic concentrations ranged from 0.02 to 1.71 MPs g −1 dry weight (dw). Fibres were the most common (76%), followed by fragments and films (18%, 6%). Common polymers were polyesters (50%), polypropylene (18%), polymethylmethacrylate (9%), rayon and viscose (5%) and elastane (4%). Microplastics appear to accumulate preferentially according to their morphology and polymer type in certain sediment grain-sizes. Microplastics inputs to the Oslofjord appear to derive from a wastewater treatment plant in the vicinity. Although, the redistribution of microplastics within the fjord needs further investigation
Distribution of recent benthic foraminifera, including soft-walled monothalamous taxa, in an Arctic fjord (Tempelfjord, Svalbard)
No full text- …
