207 research outputs found
Isotopic features of rivers and underground waters of the Parma Province (Northern Italy) and their relationships with precipitation
No full text
Oxygen Isotopes in Carbonate and Phosphate of Modern Mammal Bioapatite: New Data and Critical Revision after about 25 Years from the First Recognitions
No full textOxygen and carbon isotopes of well-preserved skeletal remains give relevant support to archaeological and environmental reconstructions. However, the preservation of the skeletal remains must be preliminarily checked. About twenty-five years ago, a diagnostic method based on the oxygen isotope ratio in the phosphate, (Formula presented.) and carbonate, (Formula presented.) of bioapatite of modern mammals was proposed: for well-preserved samples, the (Formula presented.) and (Formula presented.) should plot near the regression line (Formula presented.) on (Formula presented.) obtained for modern mammals. In the last twenty years, techniques of analysis have changed. In the past, (Formula presented.) or (Formula presented.) were precipitated from dissolved bioapatite and analysed with the fluorination technique, whereas at present, temperature reduction (HTR) in a glassy carbon reactor with (Formula presented.) release is commonly used. Taking into account the HTR technique, for some modern mammals, we report a new (Formula presented.) + 1 on (Formula presented.) + 1 regression line, and related dispersion of the data that, in addition to mineralogical and structural methods, may be used to select samples reliable for archaeological use. In the past, other similar regression lines on modern mammals were defined by several authors. However, statistical results indicate that data used for these regression lines cannot be pooled because the hypothesis of a similar elevation is rejected
Preliminary results of preliminary isotopic analyses in deep aquifers of Friuli Plain (NE Italy).
No full textRisultati preliminare delle indagini isotopiche svolte sulle acque delle falde profonde della bassa pianura Friulana
No full textdelta18O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material
No full textOxygen isotopic composition of fulgurites from the Egyptian Sahara and other locations
No full textRATIONALE: Fulgurites are glassy crusts or hollow glassy tubes formed by the impact of a lightning strike on a target
material on the Earth’s surface. The oxygen isotopic composition of fulgurites has never been measured and, consequently,
it is unknown whether or not isotopic fractionations take place between the target material and the fulgurite glass during
the lightning event which is an excellent natural example of extremely fast melting process.
METHODS: Followingwell-established procedures (high-temperature reaction of the fulguritematerial with BrF5, conversion
into CO2 of the evolved O2 and measurement of the18O/16O ratio on a Finnigan Delta Smass spectrometer) wemeasured for
the first time the oxygen isotopic composition of sets of fulgurites coming from various locations on the Earth’s surface.
RESULTS: The range of isotopic values is quite large, probably reflecting the oxygen isotopic values of the target materials.
In the case of fulgurites from the Sahara Desert the isotopic values obtained from the bulk material, quartz crystals sticking
to the fulgurite body, tiny samples of loose sand coming from fulgurite bubbles, and sand samples collected near the
fulgurites, are very close to one another.
CONCLUSIONS: Although we do not have indisputable evidence, we conclude that, at least in the case of oxygen, the
fusion process of the material struck by lightning, as well as all the extremely fast high-temperature fusion processes,
probably take place without any isotopic fractionation effect
Current Opinions in Open and Endovascular Treatment of Major Arterial Injuries in Pediatric Patient
No full textPediatric major arterial vascular injuries may belong to the same principal categories as adults, but have been poorly documented, with an estimated overall incidence of <2% of all vascular traumas. Open surgery has been the mainstay of treatment, but no clear guidelines have been developed to recommend the best practice patterns in terms of strategy or repair as well as postoperative pharmacological regimen. Herein, we report three cases and a narrative review of the available literature regarding the main aspects when dealing with pediatric arterial injuries based on the predominant series available from the most recent published literature
18/16O in water of concentrated liquid foodstuff: are the commonly determined values accurate?
No full textRationale: Oxygen isotope analysis of water molecules of liquid foodstuffs is commonly done under isotopic equilibrium between water in the solution and its vapour water assuming that the liquid water activity is equal to unit and that liquid water is an ideal mixture of H2O isotopologues. A priori this behaviour is not realistic for all foodstuffs, which frequently are very concentrated solutions. In this paper we prevalently consider “balsamic vinegar” with the aim of defining an appropriate procedure of oxygen isotope analysis of water molecules in these concentrated solutions.
Methods: IRMS measures of the oxygen isotopes, 18O, were carried out on CO2 equilibrated with water molecules at 22 0.1°C. Three independently calibrated very low salinity waters were used as standards.
Results: For grape must and wine vinegar (density < 1.15 g/cm3 ), the 18O values for water determined directly on these solutions are “true” values. On the contrary, for balsamic vinegar with density higher than about 1.20 g/cm3, the 18O values obtained directly on the solutions are systematically different from those obtained on water produced by distillation of the same samples at 70°C under vacuum.
Conclusions: In the case of balsamic vinegar with density higher than about 1.20 g/cm3, to avoid severe systematic errors, the isotopic analyses must be carried out on water obtained by distillation under stirring
- …
