169,772 research outputs found
U/Th dating of freshwater travertine from middle Velino Valley (Central Italy): paleoclimatic and geological implication
No full textSix travertine bodies outcropping along the Middle Velino Valley (Central Italy) have been studied and dated
using the U/Th method in order to obtain new chronological constraints for the recent geological evolution of the
area. The lithological and sedimentological characteristics of travertines have been described,showing that such
deposits can be referred to waterfall,pool terraces and gentle slopes environment. Travertines have formed during
warm periods and can be referred to marine oxygen isotope stages 5,3 and 1. Travertine deposition seems to stop
around 5 ka BP according to other European and Italian sites. Pollen stratigraphy and ostracod assemblages from the
close sequence of Valle di Castiglione,characterized by the same climatic conditions of Velino Valley, have confirmed
that periods of Velino Valley travertine deposition were effectively characterized by warm and wet climatic conditions.
Seismic activity strongly active in the area since the Middle Pleistocene has deeply influenced the location and the
discharge of springs which have deposited the travertines,influencing in turn the shape and size of travertine
bodies. 6 2002 Elsevier Science B.V. All rights reserved
U/Th dating of freshwater travertine from Middle velino Valley (Central Italy): geological and paleoclimatic implications
No full textSix travertine bodies outcropping along the Middle Velino Valley (Central Italy) have been studied and dated
using the U/Th method in order to obtain new chronological constraints for the recent geological evolution of the
area. The lithological and sedimentological characteristics of travertines have been described,showing that such
deposits can be referred to waterfall,pool terraces and gentle slopes environment. Travertines have formed during
warm periods and can be referred to marine oxygen isotope stages 5,3 and 1. Travertine deposition seems to stop
around 5 ka BP according to other European and Italian sites. Pollen stratigraphy and ostracod assemblages from the
close sequence of Valle di Castiglione,characterized by the same climatic conditions of Velino Valley, have confirmed
that periods of Velino Valley travertine deposition were effectively characterized by warm and wet climatic conditions.
Seismic activity strongly active in the area since the Middle Pleistocene has deeply influenced the location and the
discharge of springs which have deposited the travertines,influencing in turn the shape and size of travertine
bodies
The role of particulate matter in bronze corrosion: A novel method for assessment and prediction
No full textThe impact of particulate matter (PM) on the deterioration of outdoor cultural heritage is of increasing concern, given the recent trends in atmospheric emissions. This work presents a novel method for investigating the effects of PM on bronze corrosion by combining the collection of ambient PM directly on metal substrates and ageing under controlled laboratory conditions, with the development of a predictive model based on chemometrics. PM deposits of different mass and composition were collected and chemically characterised using Ionic Chromatography, Total Organic Carbon, and Atomic Absorption Spectroscopy. Accelerated ageing was then performed in a climatic chamber simulating daily and seasonal environmental conditions characteristic of Southern Europe. The morphology and distribution of the deposited PM, as well as surface changes after deposition and artificial ageing, were analysed using microscopic and spectroscopic techniques. The alloying metals contained in the patina formed during the corrosion process - either in the water soluble/poorly adherent or in the insoluble/adherent fractions - were also quantified. Based on the collected data and the analyses results, principal component analysis and partial least squares techniques were employed to infer the correlation between the concentration of nitrite, chloride, sulphate and nitrate in PM and bronze corrosion. Multivariate regression allowed the influence of the different ionic species to be estimated, highlighting the primary role of chloride and sulphate ions in determining higher mass loss, and to define a cross-validated model for predictive purposes. The novel method proposed here can improve the understanding and prediction of the role of PM in the corrosion of bronze, ultimately providing guidance for targeted interventions in the preservation of outdoor cultural heritage
Microwave spectrum of benzimidazole
No full textThe microwave spectra of benzimidazole and of its N-D monodeuterated isotopic species, obtained at 120°C, show the full planarity of the molecule. Information on the lower energy vibrational excited states, and on the dipole moment have also been obtained. © 1992
Evaluation of the effectiveness of coatings for the protection of outdoor terracotta artworks through artificial ageing
No full textChallenges and guidelines for artificial ageing testing of cultural heritage materials exposed to a changing troposphere
No full textOutdoor Cultural Heritage (CH) suffers severe damage due to the interaction triggered by physical and chemical atmospheric factors. To study the mechanisms of degradation of materials induced and to test the effectiveness of experimental protective treatments, accelerated ageing tests and artificial rains are widely used in the field of
material science and outdoor CH conservation. In a scenario where climate and tropospheric composition
are changing, the compositional variation of atmospheric deposition is likely to strongly contribute to the gap between the results obtained in laboratory with respect to those from real outdoor exposure. In order to reduce this gap, wet and dry formulations, representative of changed wet and dry depositions, seem necessary for material testing. Currently, no ready-to-use updated formulations are available on account of the mentioned atmospheric changes. The study herein presented aims at providing updated environmental parameters
for the formulation of synthetic depositions to fine-tune accelerated ageing test and so to set up better conservative and preventive strategies. Specifically, this work intends to provide a suitable range of particulate matter composition and hydrometeor ion concentrations to formulate both synthetic PM and precipitation, following their long-term evolution. Concerning the synthetic PM, a formulation is proposed based on the statistical elaboration of current urban PM compositional data from a wide bibliographical survey. The synthetic
rain formulation, instead, is based on the analysis of trends and sources of ions in atmospheric bulk depositions (1997-2019 period) collected in a typical highly polluted southern European location, Po Valley. Results are compared with other Mediterranean locations, to provide an effective compositional range for each chemical parameter valid for the southern European region
Pyridine-CF4: A Molecule with a Rotating Cap
No full textThe rotational spectrum of pyridine-CF4 has been investigated by molecular beam Fourier transform microwave spectroscopy in a supersonic expansion. The CF4 moiety is located as a cap over the pyridine nitrogen, and the two parts are freely rotating with respect to each other. For this reason, in a first approximation, in the m = 0 state only the pyridine ring is rotating along the a-axis, and the value of rotational constant A' is nearly the same of the constant A of isolated pyridine. The (NCCF4)-C-..., distance is 3.372(1) angstrom. The dissociation energy has been estimated, from the centrifugal distortion, to be ca. 10 kJ/mol
Late Pleistocene and Holocene geological evolution of the Majelama Valley alluvial fan (Velino Massi, Abruzzo)
No full textThe Velino Massif (approx. 42° N) with the Majelama Valley alluvial fan developing on its southern flank, consists mainly of meso-cenozoic carbonatic sediments. The valley, dominated by peaks reaching altitudes of 2,100+2,200 m, shows several clear glacial evidences; at its mouth, at 1,100+1,050 m, there are remains of a morainic amphitheater attributable to the upper Pleistocene last glacial maximum. During the course of such period the Majelama Valley glacier could reach more than 6 km in length. In the upper part of the valley occur the remnants of the moraines deposited during the glacier's still-stands that took place on the Velino Massif during the stadial recessional phases known as Apennine I, II and III Stadials. The fan at the valley outlet is complex and incised by a number of small water courses which in their turn have formed alluvial fans. At present there is no water flowing in their beds, except in very limited stretches, during exceptional rainfall events. The Late Pleistocene evolution of the Majelama Valley fan has been reconstructed by means of morphological and stratigraphic studies, supported by a number14C datings. It has been established that the main body of the fan is made up mainly of sediments of outwash fan origin, more recent than a sequence of depositional and erosive events after 31,220 ± 1,400 years B.P. and likely older than 14,580 ± 800 years B.P.14C. They form a complex of five fans: the youngest of these is linked to the last of the three phases of the Apennine Stadial I. Then there are subsequent fluvial fans, the last two of which may date to Holocene times. In several quarries it has been observed that the outwash fan deposits cover a sequence consisting of: - fluvial sediments older than 39,500 years B.P.14C; - pedogenized outwash fan deposits older than 33,140 ± 1,700 years B.P.14C; - a paleosol buried in a period between 33,140 ± 1,700 and 31,220 ±1,400 years B.P.14C; - a series of fluvial deposits and erosion surfaces more recent than the above mentioned paleosol. Fault-scarps, which affected the outwash fan deposits but do not appear to have influenced the evolution of the fan, being more recent than the main deposition phases, have been observed. On the whole the development of the fan seems to be linked to climatic and environmental causes. On the basis of the relationships between the sediments and the morphology and among the different fans, it has been possible to distinguish the following events: a) a rhexistasy phase: a period during which glacial bodies were established in the Majelama Valley. b) a biostasy phase: the soil developed and was buried between 33,140 ± 1,700 and 31,220 ± 1,400 years B.P. by14C. For its characteristics, the soil could have developed during an Atlantic-temperate type climatic phase in presence of strong vegetal cover. c) a bioclimatic crisis; occurring as result of a cold and dry climatic change. d) a rhexistasy phase: datable between the burying of the soil and 14,580 ± 800 years B.P. with14C method, during which the last glacial maximum occurred. This phase is characterized by three distinct periods: a first period (d1) corresponding to the establishment of glaciers in the upper valley; a second (d2) which could be of arid climate; a third period (d3) during which the climate fostered the maximum glacial expansion, e) a phase of prevalent biostasy: during this phase, the climate has been temperate and humid, but interrupted by relative arid phases or characterized by irregular rain fall events of strong intensity. Among the "d" rhexistasy phase and the "e" prevalent biostasy phase, a transition period took place
Tunnelling rate and barrier to the transfer of the protic group in dimethylether–HCl
No full textIn dimethylether–HCl, the HCl group is tunnelling between the two lone pairs of the ether oxygen at a rate of 8182(7) MHz,
through a barrier of 69 cm1, as deduced from the free jet millimetre wave absorption spectrum
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