Pollen and non-pollen palynomorphs (NPP) from the Early Neolithic settlement of La Draga have provided new palaeoenvironmental data concerning the establishment of the first farming societies in NE ...Iberian Peninsula. The analysis of samples from the archaeological profiles allowed the comprehension of several processes involved in the formation of this archaeological site and the reconstruction of environmental conditions in the different phases of occupation, in addition to obtaining new data about the ecological significance of NPP in archaeological levels. New NPP have been described, illustrated, and discussed.
The first farming societies settled at La Draga in a humid and densely forested area, with the predominance of deciduous trees (deciduous Quercus and Corylus) and Pinus and Abies in the surrounding mountains. Following their establishment at the site, abrupt changes in vegetation are recorded, in terms of deforestation of oak and riparian forests. Sedimentation dynamics involved in the formation of the archaeological site influenced the composition of the NPP spectra, reflected in the contraposition between waterlogged and subaerial layers, but especially, between organic peaty layers formed at local level and sediments transported by erosive processes in the layers belonging to the second phase of occupation.
•Pollen and NPP analysis evidence human impact in the Neolithic site of La Draga.•Carbonicolous/lignicolous fungi spores were documented in collapsed wooden structures.•Integration of pollen, NPP and LOI shows evidence of soil erosion episodes.•Coprophilous fungi spores indicate local evidence of animals within the settlement.
This paper focuses on high-resolution analysis of pollen and sedimentology and botanical macro-remains analysis in a core from Lake Banyoles (Girona, Spain). The core sequence comprises a high ...resolution mid-Holocene (ca. 8.9–3.35calkaBP) vegetation succession, and sedimentological, geochemical and geomorphological proxies are related to both climatic and anthropogenic causes. Deforestation processes affected natural vegetation development in the Early Neolithic (7.25–5.55calkaBP) and Late Neolithic (5.17–3.71calkaBP), in the context of broadleaf deciduous forest resilience against cooling and drying oscillations. Changes in sedimentation dynamics and in lake water level caused the emergence of dry land on the lake margin where riparian forest was established from 5.55calkaBP onwards. The data show that in the context of an increasing aridification process, Neolithic land-use played an important role in vegetation history and environmental evolution.
•Human-environment relationships are studied around Lake Banyoles (NE Spain).•Broadleaf deciduous forests were resilient against cooling and drying oscillations.•Riparian forest was established in emerged dry land due to changes in sedimentation.•Anthropic deforestation affected vegetation and lake sedimentation during Neolithic.
Summary
The future of nuclear energy in the energy mix faces a permanent scrutiny of safety aspects in conciliation with bridled costs, either fission‐ or fusion‐based. This affects to all the ...exciting milestones pursued in XXIst. To name few in the field of fission, the deployment of the IVth generation reactors is expected or the definitive solution to the radioactive wastes is sought. A mention apart is made to fusion technology, with ITER as the flagship project. It seeks a virtually infinite energy source, intrinsically safe and with reduced radioactive waste production with respect to fission the first commercial reactor. All these, and many other endeavors, share the operation of sophisticated devices in the presence of intense ionizing radiation fields. Humans and electronics must be protected to ensure safe and reliable performance, while shielding normally represents a large fraction of the budget. This involves nuclear analysis in the design phase to forecast the radiation conditions. The complexity of the simulation of 3D radiation fields that is computationally affordable nowadays is unprecedented. While sophistication in geometries and source definitions has become routine, the resulting complexity of these scalar fields makes their analysis increasingly difficult. The need of enhancement of the analysis techniques is evident today. Vector calculus is proposed following a physical interpretation of the field lines that boosts the analysis capabilities. It identifies the trajectories around which shielding is weakest in an automated errorless and effortless approach. Its power is illustrated with an example relevant to the ITER reactor.
The future of nuclear energy in the energy mix faces a permanent scrutiny of safety aspects in conciliation with bridled costs, either fission‐ or fusion‐based. Radiation shielding normally represents a large fraction of the budget.
Vector calculus is proposed following a physical interpretation of the field lines that boosts the radiation analysis capabilities. It identifies the trajectories around which shielding is weakest in an automated errorless and effortless approach.
It is illustrated with an example relevant to the ITER reactor.
MCNP model of the ITER Tokamak Complex López-Revelles, A.J.; Catalán, J.P.; Kolšek, A. ...
Fusion engineering and design,
11/2018, Letnik:
136
Journal Article
Recenzirano
•It is based on a conservative representation of the latest baseline design of the ITER Tokamak Complex.•It exhibits an extremely low particle loss rate and it uses the most stable MCNP geometry ...implementations, avoiding the use of universes and macrobodies.•It is a version controlled model, user-friendly and easy-to-update and maintain MCNP model of the ITER Tokamak Complex.•It is completely and clearly commented and the cells and surfaces of the model are strongly organized, resulting in a room-oriented arrangement, which allows an easy isolation of every room.•The methodology developed to create this model is recommended for the production of future MCNP reference models of ITER and other nuclear facilities.
The Tokamak Complex will accommodate the ITER tokamak and some of the plant systems needed for the machine operation. In order to obtain radiation maps in the Tokamak Complex, a new MCNP model was released on September 2016. This model, based on a conservative representation of the latest baseline design, represents a version controlled, computationally stable, user-friendly and easy-to-update and maintain MCNP input of the Tokamak Complex. Every modification of the initial CAD models was reviewed, recorded and version controlled. The MCNP model of the Tokamak Complex uses the most stable MCNP geometry implementations, avoiding the use of universes and macrobodies. The input exhibits a low particle loss rate (<10−9) when running in void with a dispersed isotropic source. It is strongly organized and profusely commented. Information about the level, building, room, system and material is provided in the definition of every cell. The 36862 cells and 57085 surfaces are arranged by levels and by buildings. The cells are also arranged by rooms and by systems, resulting in a room-oriented organization of the model, which allows an easy isolation of every room.
Sixty-two 14C dates are analyzed in combination with a recently established local floating tree-ring sequence for the Early Neolithic site of La Draga (Banyoles, northeast Iberian Peninsula). ...Archaeological data, radiometric and dendrochronological dates, as well as sedimentary and micro-stratigraphical information are used to build a Bayesian chronological model, using the ChronoModel 2.0 and OxCal 4.4 computer programs, and IntCal 2020 calibration curve. The dendrochronological sequence is analyzed, and partially fixed to the calendrical scale using a wiggle-matching approach. Depositional events and the general stratigraphic sequence are expressed in expanded Harris Matrix diagrams and ordered in a temporal sequence using Allen Algebra. Post-depositional processes affecting the stratigraphic sequence are related both to the phreatic water level and the contemporaneous lakeshore. The most probable chronological model suggests two main Neolithic occupations, that can be divided into no less than three different “phases,” including the construction, use and repair of the foundational wooden platforms, as well as evidence for later constructions after the reorganization of the ground surface using travertine slabs. The chronological model is discussed considering both the modern debate on the Climatic oscillations during the period 8000–4800 cal BC, and the origins of the Early Neolithic in the western Mediterranean region.
The analysis of non-pollen palynomorphs (NPP) provides useful information about local environmental conditions. The study of a core from Lake Banyoles (Girona, NE Iberia) enabled the reconstruction ...of ecological changes and assessment of human impact in a lakeshore environment during the Mid-Holocene. This work aims to fill the gap in knowledge about the ecological significance of NPP in lowland areas in NE Iberia, and provides descriptions and illustrations of new types documented.
Deforestation induced by Early Neolithic communities caused the proliferation of lignicolous fungi in decaying wood and an increase in soil erosion. The input of allochthonous mud led to higher turbidity in the lake water, causing a succession in aquatic organisms, from cyanobacteria to green algae. In that context, a group of erosion-associated fungal spore types were recorded. Indicators of soil disturbance and coprophilous fungi were recorded from 5000 to 4200cal BP, linked with local habitation during the Late Neolithic–Chalcolithic. The NPP analysis reflects the significant human impact that caused changing local environmental conditions, consistent with the signals based on pollen analysis.
•Increasing turbidity caused by soil erosion caused cyanobacteria-fresh water algae succession.•Anthropogenic deforestation and associated soil erosion caused local ecological changes.•The presence of lignicolous fungi linked with decaying wood transported by runoffs•New NPP types were described and illustrated from Lake Banyoles (NE Iberia).
A systematic search for different viable models of the dark energy universe, all of which give rise to finite-time, future singularities, is undertaken, with the purpose to try to find a solution to ...this common problem. After some work, a universal procedure to cure all future singularities is developed and carefully tested with the help of explicit examples corresponding to each one of the four different types of possible singularities, as classified in the literature. The cases of a fluid with an equation of state which depends on some parameter, of modified gravity non-minimally coupled to a matter Lagrangian, of non-local gravity, and of isotropic turbulence in a dark fluid universe theory are investigated in detail.
Cosmological models with Yang-Mills fields Elizalde, E.; López-Revelles, A. J.; Odintsov, S. D. ...
Physics of atomic nuclei,
08/2013, Letnik:
76, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Cosmological models with an
SU
(2) Yang-Mills field are studied. For a specific model with a minimally coupled Yang-Mills Lagrangian, which includes an arbitrary function of the second-order term and ...a fourth-order term, a corresponding reconstruction program is proposed. It is shown that the model with minimal coupling has no de Sitter solutions, for any nontrivial function of the second-order term. To get de Sitter solutions, a gravitational model with nonminimally coupled Yang-Mills fields is then investigated. It is shown that the model with non-minimal coupling has in fact a de Sitter solution, even in absence of the cosmological constant term.
The synthetic analysis of several pollen records from sub-Mediterranean lowland Pre-Pyrenean regions evidences expansion of forests during the Early Holocene in Northeastern Iberia and the ...establishment of dense deciduous broadleaf forests during the Holocene Climate Optimum. Pollen records show the broadleaf deciduous forests resilience against cooling phases during the Mid-Holocene period, with slight regressions of oak woodlands and expansion of conifers or xerophytic taxa contemporary to some cooling episodes (i.e. 8.2 and 7.2 kyr cal. BP). Major vegetation changes influenced by climate change occurred in the transition to the Late Holocene, in terms of the start of a succession from broadleaf deciduous forests to evergreen sclerophyllous woodlands.
The lack of evidence of previous occupation seems to support the Neolithisation of the NE Iberian Peninsula as a result of a process of migration of farming populations to uninhabited or sparsely inhabited territories. In that context, remarkable changes in vegetation were recorded from 7.3 kyr cal. BP onwards in the Lake Banyoles area, where the establishment of permanent farming settlements caused the deforestation of oak woodlands. In La Garrotxa region, short deforestation episodes affecting broadleaf deciduous forests, together with expansion of grasslands and presence of Cerealia-t were documented in the period 7.4–6.0 kyr cal. BP. Finally, in the coastal area, where less evidence of Early Neolithic occupations is recorded, evidence of Neolithic impact is reflected in the presence of Cerealia-t in 6.5–6.2 kyr cal. BP, but no strong human transformation of landscape was carried out until more recent chronologies.
•Climate and human impact influenced environmental changes in the Mid-Holocene.•Resilience of deciduous broadleaf forests in sub-Mediterranean areas until the Late Holocene.•Mid-Holocene cooling episodes and human impact interaction transformed the landscape.•The Neolithisation in Iberia occurred in the context of a cooler and drier climate.
A multi-proxy investigation of sediment cores has enabled us to reconstruct the coastal environmental evolution of East-Central Corsica (the sites of Saint Florent, Piantarella-Bonifacio and ...Palo-Solenzara) for the last 8000 years. The analytical methods comprise pollen (five original pollen diagrams), weight loss-on-ignition measurements, laser granulometry, and ostracod identification. In addition, 26 radiocarbon dates are used to provide a robust chronostratigraphy for the sedimentary sequences. The assessment of coastal landscape dynamics enables us to define the major morphological changes and to evaluate the complex interplay between climatic forcing and anthropogenic activity on the vegetation history of Corsica, within an archaeological context, since the early Neolithic period (∼7.4 cal kyr BP). The major findings are that the first farmers reached Corsica by sea, and they encountered a coastal environment mainly composed of freshwater ponds located close to the shoreline. This specific paleoenvironmental feature offered a favourable location for agriculture and for the development of permanent settlements where a subsistence economy was developed. Since the Middle Holocene, postglacial sea-level rise has caused major changes in local coastal environments, often characterized by salt intrusion into freshwater bodies. At the transition between the Mid and Late Holocene (∼4.0 cal kyr BP), an increase in both salinity and aridity caused substantial landscape changes, mainly characterized by a further expansion of saline marshland, mainly occupied by Chenopodiaceae. The results also provide new insights into the role of Erica in the original Holocene vegetation of Corsica. Our data clearly indicate that an Erica arborea - Quercus ilex forest transition occurred before 6.3 cal kyr BP, significantly earlier than previously proposed. Finally, the earliest evidence of cereal cultivation is at ∼7350 cal kyr BP, and in addition we are better able to constrain the role of humans in the landscape dynamics of Corsica since the early Neolithic.
•Erica arborea - Quercus ilex forest transition occurred before 6.3 cal kyr BP.•Earliest evidence of cereal cultivation in Corsica (∼7350 cal kyr BP).•Expansion of saline marshland in the Mid to Late Holocene transition.
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