1,002 research outputs found
Leaking And Non-leaking Systems: Study Of Natural CO2 Accumulations For Geological Sequestration
The potential risks of geological CO2 storage must be understood and geologists are required to
predict how CO2 may behave once stored underground. As natural geological accumulations of
carbon dioxide occur in many basins in Italy and volcanic and seismically active areas allow CO2
rich fluids to migrate to the near surface, many of these areas have been investigated in order to
study long-term geochemical processes that may occur following geological storage of
anthropogenic CO2. A study representing an example of "leaking" system is the Solfatara crater
(Campi Flegrei, Southern Italy) characterised by the presence of both CO2 rich-waters and
fumarole. Soil gas flux measurements show that the entire area discharges between 1200 and 1500
tons of CO2 a day. Most part of analysed waters is the effect of a mixing between a shallow
meteoric water and a deep thermal Na-Cl end-member and/or seawater, resulting in sodiumchloride
waters. A high dissolved CO2 content (max value 566.28 cc/l) is also present. Furthermore,
the Campi Flegrei frequently undergo bradyseism related to the elastic response of the shallow crust
to increasing pressure within a shallow magma chamber. The study of this phenomenon could be
useful to detect ground deformation linked to geomechanical changes in a geological CO2 reservoir.
In contrast, an example of "non-leaking" system is the Pisticci oil and gas Field (Southern Italy)
where a great variety of hydrocarbons traps are formed by horst and tilted blocks in the Mesozoic
carbonate substratum covered by an almost continuous sequence of Lower Pliocene marls and
Middle Pliocene-Pleistocene marly blue clays. Soil gas surveys were performed after a MD 4.5
earthquake and two years later to test the permanence of the gas distribution pattern. CO2
distribution in soil gas seems not to be affected by changes in stress, as suggested by the average
values of both surveys. The principal aim of our research has been to evaluate and mitigate risks for
local populations as the studied areas are densely populated. To date, the obtained results suggest
that gas uprising is generally well localised around restricted areas, often controlled by local
tectonics (faults and/or fractures). This implies that, in the frame of geological CO2 sequestration, it
is necessary to carefully assess the presence of pathways (fault and/or fractures) that might allow
the migration of CO2 out of the reservoir
SOFC Micro-CHP integration in residential buildings
SOFC technology has reached many of the performance goals that where indicated by scientific society and is providing several application that permits market penetration. One of the main targets is related to Micro Cogeneration Heat and Power (μ-CHP) for residential application. The integration of this system with a residential house has to be deeply investigated to individuate market targets in terms of costs and efficiency. This study evaluates the Italian market condition and analyzes the integration possibility with both thermal and electrical systems. Different solutions are investigated evaluating thermal and electrical driven logic for μ-CHP SOFC based unit and the opportunity of integration with local electrical grid. Evaluation on heat and electricity storage was also considered as integration strategy. The study is based on electrical and thermal loads in typical residential users and the evaluation is based on Italian technical standards and guidelines. Several operating conditions were evaluated and compared to obtain an optimized size and integration of μHP SOFC based solution
One-dimensional Ising ferromagnet frustrated by long-range interactions at finite temperatures
We consider a one-dimensional lattice of Ising-type variables where the
ferromagnetic exchange interaction J between neighboring sites is frustrated by
a long-ranged anti-ferromagnetic interaction of strength g between the sites i
and j, decaying as |i-j|^-alpha, with alpha>1. For alpha smaller than a certain
threshold alpha_0, which is larger than 2 and depends on the ratio J/g, the
ground state consists of an ordered sequence of segments with equal length and
alternating magnetization. The width of the segments depends on both alpha and
the ratio J/g. Our Monte Carlo study shows that the on-site magnetization
vanishes at finite temperatures and finds no indication of any phase
transition. Yet, the modulation present in the ground state is recovered at
finite temperatures in the two-point correlation function, which oscillates in
space with a characteristic spatial period: The latter depends on alpha and J/g
and decreases smoothly from the ground-state value as the temperature is
increased. Such an oscillation of the correlation function is exponentially
damped over a characteristic spatial scale, the correlation length, which
asymptotically diverges roughly as the inverse of the temperature as T=0 is
approached. This suggests that the long-range interaction causes the Ising
chain to fall into a universality class consistent with an underlying
continuous symmetry. The e^(Delta/T)-temperature dependence of the correlation
length and the uniform ferromagnetic ground state, characteristic of the g=0
discrete Ising symmetry, are recovered for alpha > alpha_0.Comment: 12 pages, 7 figure
Chemical and isotopic characterisation of gas and water in a scientific
see Abstract Volum
Spatial distribution of arsenic, uranium and vanadium in the volcanic-sedimentary aquifers of the Vicano–Cimino Volcanic District (Central Italy)
Arsenic concentrations were analysed for 328 water samples collected in the Vicano–Cimino Volcanic District
(VCVD), an areawhere severe contamination of groundwater has become a serious problemfollowing the recent
application of the EU Directive on the maximum allowable concentration level for As in drinking waters. In
addition, uranium and vanadium concentrations were also analysed in light of the enhanced interest on their
environmental toxicity. Waters were collected from springs and wells fed by cold and shallow volcanic–sedimentary
aquifers, which locally represent the main drinking water source. Thermal springs (≤63 °C) related
to an active hydrothermal reservoir and waters associated with a CO2-rich gas phase of deep provenance were
also analysed. The collected data showed that the As concentrations in the shallow aquifers varied in a wide
range (0.05–300 μg/L) and were primarily controlled by water–rock interaction processes. High As concentrations
(up to 300 μg/L) were measured in springs and wells discharging from the volcanic products, and about
66% exceeded the limit of 10 μg/L for drinkingwaters,whereaswaters circulatingwithin the sedimentary formations
displayed much lower values (0.05–13 μg/L; ~4% exceeding the threshold limit). Thermal waters showed
the highest As concentrations (up to 610 μg/L) as the result of the enhanced solubility of As-rich volcanic rocks
during water–rock interaction processes at high temperatures. Where the local structural setting favoured the
rise of fluids from the deep hydrothermal reservoir and their interaction with the shallow volcanic aquifer, relatively
higher concentrations were found. Moreover, well overexploitation likely caused the lateral inflow of
As-rich waters towards not contaminated areas.
Uraniumand vanadiumconcentrations ofwaters circulating in the volcanic rocks ranged from0.01 to 85 μg/L and
0.05 to 62 μg/L, respectively. Less than 2% of analysed samples exceeded theWorld Health Organization's provisional
guidelines for U (30 μg/L), while none of them was above the Italian limit value of V in drinking water
(120 μg/L). Lower U (0.07–22 μg/L and 0.02–13 μg/L, respectively) and V concentrations (0.05–24 μg/L and
0.18–17 μg/L, respectively) were measured in the water samples from the sedimentary aquifer and thermal
waters. Local lithology appeared as the main factor affecting the U and V contents in the shallow aquifers, due
to the high concentrations of these two elements in the volcanic formations when compared to the sedimentary
units. In addition, high U concentrations were found in correspondence with U mineralization occurring within
the VCVD, fromwhich U is released in solution mainly through supergene oxidative alteration. Redox conditions
seem to play amajor role in controlling the concentrations of U and V inwaters. Oxidizing conditions characterizing
the cold waters favour the formation of soluble U- and V-species, whereas thermal waters under anoxic
conditions are dominated by relatively insoluble species. Geostatistical techniques were used to draw contour
maps by using variogram models and kriging estimation aimed to define the areas of potential health risk characterized
by As, U and V-rich waters, thus providing a useful tool for water management in a naturally contaminated
area to local Authorities
Broad band X-ray spectral properties of Gamma-ray bursts with BeppoSAX
In about one year, five gamma-ray bursts were simultaneously observed with
the Wide Field Cameras and Gamma Ray Burst Monitor aboard the BeppoSAX
satellite. From some of them X-ray afterglow emission has been clearly detected
with the same satellite. In order to understand how GRB emission is related to
the X-ray afterglow, we are performing a systematic study of the spectral
properties of these events. We report here preliminary results of this study.Comment: 5 pages, 3 figures. To appear in the Proceedings of the 4th
Huntsville Gamma-ray Burst Symposiu
Scanning Electron Microscopy of the Small Intestine Mucosa in Children with Celiac Disease After Long-Term Dietary Treatment
Jejunal mucosal specimens from twenty children with celiac disease were studied by light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) after one year of dietary treatment. An ultrastructural morphometric study was performed in five patients who had an intestinal permeability (IP) test. Seventeen patients were tested for serum antigliadin antibodies (AGA). In ten children, in whom LM showed partial villous atrophy, SEM and TEM examination confirmed the lesion. In the second group (10 children) with normal morphology at routine LM, SEM showed lesions of variable degree in 70% of cases. The morphological ultrastructural investigation showed good correlation with the immunological and functional data (IP test): ultrastructural damage of the jejunal mucosa after one year of a gluten-free diet was found in patients with positive serum AGA and an abnormal IP test. Furthermore, the morphometric study of the ultrastructural alterations allowed a quantitative, closer correlation between morphological and functional data. Our results suggest: 1) SEM and TEM investigations offer additional and more complete information on celiac patients, over LM alone. 2) The morphometric evaluation of the ultrastructural alterations highlights quantitative and reproducible correlations between morphological and clinical data, not strengthened by the subjective, qualitative study
Magnitude and Duration of Elevated Gastric pH in Patients Infected with Human Immunodeficiency Virus After Administration of Chewable, Dispersible, Buffered Didanosine Tablets
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90191/1/phco.24.16.1539.50959.pd
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