216 research outputs found
Evidence of potassium fixation through mono and divalent ion exchange
Mono and divalent cation exchange in some algerian major soil types was studied following empirical ap¡
proach. The reaction 2 Na-Soil + Ca2+ = Ca-Soil + 2 Na+ did not show complete reversibility possibly
due to high Ca selectivity of soils. The soils exhibited divalent over monovalent ion affinity but for monovalent
ion exchange the affinity in few cases remained almost the same. Gapon's equation did not seem
to describe Ca-K exchange very satisfactorily because exchangeable potassium ratio (EKR) and potassium
adsorption ratio (KAR) are not related linearly. The latter seems to be due to potassium fixing ten¡
dency of soils investigated
Describing the adsorption of potential determining ions on variable charge mineral surfaces
A computer program was developed to elaborate the titration curves of amphoteric surfaces according to
the double layer theory. The zpc, identified from the intersection point of the titration curves carried out
at different ionic strengths, fell at pH 3.15, 9.45 and 7.65 for Si, AI and Fe hydroxides, respectively. The
Stern model described quite satisfactorily the relation between Ď0 and Ď0. Some problem was presented
by Si surfaces which were then treated by a different calculation procedure.
The δ values, the Stern layer thickness, were very high for the SI surfaces and increased with decreasing
ionic strength. A different behaviour was showed by AI and Fe hydroxides; in these cases δ values were
very low and increased with increasing electrolyte concentration. These results were discussed in terms
of surface structures and activity of the supporting electrolyte
Ostracod and Foraminifer Responses to Late PleistoceneâHolocene Volcanic Activity in Northern Victoria Land as Recorded in Ross Sea (Antarctica) Marine Sediments
The impacts on ostracods and foraminifers caused by three Late Quaternary ashfalls of
different intensities and recovered in the ANTA02-NW2 core sediments (Drygalski Basin, western
Ross Sea) were analysed for the first time. Albeit with different timing, both associations demonstrated
similar response patterns associated with the deposition of material from volcanic eruptions.
In particular, based on the palaeontological evidence, it was possible to divide the cores into four
intervals/phases recording the evolution of the ecosystem before and after the deposition events: (1)
Pre-extinction phase (high abundance and high diversity values). (2) Extinction phase, characterised
by the complete disappearance of ostracod fauna; the foraminiferal assemblage, although not entirely
absent, records extremely low values of abundance and diversity (survivor assemblage). (3)
Recovery phase (increasing abundance and diversity values), characterised by the recolonisation of
some opportunistic taxa; species such as Australicythere devexa and Australicythere polylyca dominate
the ostracod assemblage. (4) Post-extinction phase (high abundance and high diversity values), with
the return to an environmental equilibrium characterised by the colonisation of specialised taxa such
as Argilloecia sp., Cytheropteron sp., Echinocythereis sp., and Hemicytherura spp. Our results may aid
in the understanding of how communities (i.e., ostracods and foraminifers) recovered after the impact
of direct deposits of volcanic ash into ocean waters. The mechanisms by which disappearance
and/or mortality was induced are still not clear. The release of toxic metals during the reaction of
the volcanic ash with seawater, the resulting chemical alteration in the seawater, and the change in
pH, together with the possible suppression of planktonic organisms, may have caused the two main
extinction phases recorded by the ANTA02-NW2 core sediments
P-IOTA: A Cloud-Based Geographically Distributed Threat Alert System That Leverages P4 and IOTA
The recent widespread novel network technologies for programming data planes are remarkably enhancing the customization of data packet processing. In this direction, the Programming Protocol-independent Packet Processors (P4) is envisioned as a disruptive technology, capable of configuring network devices in a highly customizable way. P4 enables network devices to adapt their behaviors to mitigate malicious attacks (e.g., denial of service). Distributed ledger technologies (DLTs), such as blockchain, allow secure reporting alerts on malicious actions detected across different areas. However, the blockchain suffers from major scalability concerns due to the consensus protocols needed to agree on a global state of the network. To overcome these limitations, new solutions have recently emerged. IOTA is a next-generation distributed ledger engineered to tackle the scalability limits while still providing the same security capabilities such as immutability, traceability, and transparency. This article proposes an architecture that integrates a P4-based data plane software-defined network (SDN) and an IOTA layer employed to notify about networking attacks. Specifically, we propose a fast, secure, and energy-efficient DLT-enabled architecture that combines the IOTA data structure, named Tangle, with the SDN layer to detect and notify about network threats
Phenomenology of a Fake Inert Doublet Model
We introduce a new way of modeling the physics beyond the Standard Model by
considering fake, strictly off-shell degrees of freedom: the fakeons. To
demonstrate the approach and exemplify its reach, we re-analyze the
phenomenology of the Inert Doublet Model under the assumption that the second
doublet is a fakeon. Remarkably, the fake doublet avoids the most stringent
-pole constraints regardless of the chosen mass scale, thereby allowing for
the presence of new effects well below the electroweak scale. Furthermore, the
absence of on-shell propagation prevents fakeons from inducing missing energy
signatures in collider experiments. The distinguishing features of the model
appear at the loop level, where fakeons modify the Higgs boson
decay width and the Higgs trilinear coupling. The running of
Standard Model parameters proceeds as in the usual Inert Doublet Model case.
Therefore, the fake doublet can also ensure the stability of the Standard Model
vacuum. Our work shows that fakeons are a valid alternative to the usual tools
of particle physics model building, with the potential to shape a new paradigm,
where the significance of the existing experimental constraints towards new
physics must necessarily be reconsidered.Comment: 12 pages, 7 figures, version accepted by JHE
A young marathon runner with severe aortic coarctation and bicuspid aortic valve disease complicated by contained aortic rupture
Role of heart rate and stroke volume during muscle metaboreflex-induced cardiac output increase: differences between activation during and after exercise
We hypothesized that the role of stroke volume (SV) in the metaboreflex-induced cardiac output (CO) increase was blunted when the metaboreflex was stimulated by exercise muscle ischemia (EMI) compared with post-exercise muscle ischemia (PEMI), because during EMI heart rate (HR) increases and limits diastolic filling. Twelve healthy volunteers were recruited and their hemodynamic responses to the metaboreflex evoked by EMI, PEMI, and by a control dynamic exercise were assessed. The main finding was that the blood pressure increment was very similar in the EMI and PEMI settings. In both conditions the main mechanism used to raise blood pressure was a CO elevation. However, during the EMI test CO was increased as a result of HR elevation whereas during the PEMI test CO was increased as a result of an increase in SV. These results were explainable on the basis of the different HR behavior between the two settings, which in turn led to different diastolic time and myocardial performance
New insights on the systematics of echinoids belonging to the family Spatangidae Gray 1825 using a combined approach based on morphology, morphometry, and genetics.
Spatangoids are probably the least resolved group within echinoids, with known topological incongruencies between phylogenies derived from molecular (very scarce) and morphological data. The present work, based on the analysis of 270 specimens of Spatangidae (Echinoidea, Spatangoida) trawled in the Sardinian seas
(Western Mediterranean), allowed us to verify the constancy of some characters that we consider to be diagnostic at the genus level âsuch as the path of the subanal fasciole and the relationship between labrum and adjacent ambulacral plates âand to distinguish two distinct forms within the studied material. Based on
morphological characters, morphometrics, and molecular analyses (sequencing of two mitochondrial markers: cytochrome c oxidase subunit1 (COI) and 16S), most of the individuals were classified as morphotype A and attributed to the species Spatangus purpureus, the most common spatangoid in the Mediterranean Sea, while a few corresponded to a different morphotype (B), genetically close to the species Spatangus raschi. Preliminary morphological analyses seemed to indicate that morphotype B specimens from Sardinia are slightly different from S. raschi and from Spatangus subinermis individuals, the second species of the family known to occur in the Mediterranean Sea. On the basis of morpho-structural observations and molecular analyses, comparing Mediterranean living forms with species from other areas (Central Eastern Atlantic, North Sea and neighboring basins, South African Sea, Philippines and Indonesian Archipelago, New Zealand, and Hawaiian Islands), the clear distinction of S. purpureus from several other species classified as Spatangus was confirmed. Based on the morphological and genetic differences, we propose to maintain the genus Spatangus including in it only the type species S. purpureus among the living species and to establish the new genus Propespatagus nov. gen. to include several other species previously classified as Spatangus. The clear distinction among different genera was also detected in fossil forms of Spatangus, Propespatagus nov. gen., and Sardospatangus (â ) from the European Oligo-Miocene sedimentary rocks of Germany; the Miocene of Ukraine, Italy, and Spatangoids are probably the least resolved group within echinoids, with known topological incongruencies between phylogenies derived from molecular (very scarce) and morphological data. The present work, based on the analysis of 270 specimens of Spatangidae (Echinoidea, Spatangoida) trawled in the Sardinian seas (Western Mediterranean), allowed us to verify the constancy of some characters that we consider to be diagnostic at the genus level âsuch as the path of the subanal fasciole and the relationship between labrum and adjacent ambulacral plates âand to distinguish two distinct forms within the studied material. Based on morphological characters, morphometrics, and molecular analyses (sequencing of two mitochondrial markers: cytochrome c oxidase subunit1 (COI) and 16S), most
of the individuals were classified as morphotype A and attributed to the species Spatangus purpureus, the most common spatangoid in the Mediterranean Sea, while a few corresponded to a different morphotype (B), genetically close to the species Spatangus raschi. Preliminary morphological analyses seemed to indicate
that morphotype B specimens from Sardinia are slightly different from S. raschi and from Spatangus subinermis individuals, the second species of the family known to occur in the Mediterranean Sea. On the basis of morpho-structural observations and molecular analyses, comparing Mediterranean living forms with species from other areas (Central Eastern Atlantic, North Sea and neighboring basins, South African Sea, Philippines and Indonesian Archipelago, New Zealand, and Hawaiian Islands), the clear distinction of S. purpureus from several other species classified as Spatangus was confirmed. Based on the morphological and genetic differences, we propose to maintain the genus Spatangus including in it only the type species S.
purpureus among the living species and to establish the new genus Propespatagus nov. gen. to include several other species previously classified as Spatangus. The clear distinction among different genera was also detected in fossil forms of Spatangus, Propespatagus nov. gen., and Sardospatangus (â ) from the European Oligo-Miocene sedimentary rocks of Germany; the Miocene of Ukraine, Italy, and Spatangoids are probably the least resolved group within echinoids, with known topological incongruencies between phylogenies derived from molecular (very scarce) and morphological data. The present work, based on the analysis of 270 specimens of Spatangidae (Echinoidea, Spatangoida) trawled in the Sardinian seas (Western Mediterranean), allowed us to verify the constancy of some characters that we consider to be diagnostic at the genus level âsuch as the path of the subanal fasciole and the relationship between labrum and adjacent ambulacral plates âand to distinguish two distinct forms within the studied material. Based on morphological characters, morphometrics, and molecular analyses (sequencing of two mitochondrial markers: cytochrome c oxidase subunit1 (COI) and 16S), most of the individuals were classified as morphotype A and attributed to the species Spatangus purpureus, the most common spatangoid in the Mediterranean Sea, while a few corresponded to a different morphotype (B), genetically close to the
species Spatangus raschi. Preliminary morphological analyses seemed to indicate that morphotype B specimens from Sardinia are slightly different from S. raschi and from Spatangus subinermis individuals, the second species of the family known to occur in the Mediterranean Sea. On the basis of morpho-structural observations and molecular analyses, comparing Mediterranean living forms with species from
other areas (Central Eastern Atlantic, North Sea and neighboring basins, South African Sea, Philippines and Indonesian Archipelago, New Zealand, and Hawaiian Islands), the clear distinction of S. purpureus from several other species classified as Spatangus was confirmed. Based on the morphological and genetic differences, we propose to maintain the genus Spatangus including in it only the type species S. purpureus among the living species and to establish the new genus Propespatagus nov. gen. to include several other species previously classified as Spatangus. The clear distinction among different genera was also detected in fossil forms of Spatangus, Propespatagus nov. gen., and Sardospatangus (â ) from the European Oligo-Miocene sedimentary rocks of Germany; the Miocene of Ukraine, Italy, and North Africa; the Plio-Pleistocene of Italy; and the Mio-Pliocene of Florida (USA). The new data can help in addressing taxonomic ambiguities within echinoids, as well as in improving species identification, and hence biodiversity assessments in the Mediterranean region
Supportingâelectrolyteâfree electrochemical methoxymethylation of alcohols using a 3Dâprinted electrosynthesis continuous flow cell system
We describe the development of a novel lowâcost smallâfootprint 3Dâprinted electrosynthesis continuous flow cell system that was designed and adapted to fit a commercially available Electrasyn 2.0. The utility and effectiveness of the combined flow/electrochemistry system over the batch process was demonstrated in the development of an improved and supportingâelectrolyteâfree version of our anodic methoxymethylation of alcohols
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