Search results for "Thermal"

Numerical modelling of gas-water-rock interactions in volcanic-hydrothermal environment: the Ischia Island (Southern Italy) case study.

2012

Hydrothermal systems hosted within active volcanic systems represent an excellent opportunity to investigate the interactions between aquifer rocks, infiltrating waters and deep-rising magmatic fluids, and thus allow deriving information on the activity state of dormant volcanoes. From a thermodynamic perspective, gas-water-rock interaction processes are normally far from equilibrium, but can be represented by an array of chemical reactions, in which irreversible mass transfer occurs from host rock minerals to leaching solutions, and then to secondary hydrothermal minerals. While initially developed to investigate interactions in near-surface groundwater environments, the reaction path mode…

The Ischia Island hydrothermal system: an integrated multidisciplinary (geochemical, geophysical and geological) study

2011

Ischia Island is the emergent portion of a large volcanic complex on the Gulf of Naples (Southern Italy). Ischia volcano has undertaken a complex evolution since 150 ka b.p., with prolonged cycles of effusive and explosive eruptions alternated with quiescence periods (the most recent of which started after the 1302 A.D. Arso eruption). Currently, hot springs (with discharge temperature up to 90 C), fumarolic gas emissions with CO2 up to 97%, and diffuse soil degassing testify a persistent activity state of the Ischia volcano. Ischia Island is a very good example of an active volcano hosting a large hydrothermal system and, in particular, its south-western sector has long been known to be th…

Ecological effects of natural ocean acidification on benthic macroalgal communities

2012

The Coupled Magmatic and Hydrothermal Systems of the Restless Aluto Caldera, Ethiopia

2020

Seismicity can be used to better understand interactions between magma bodies, hydrothermal systems and their host rocks—key factors influencing volcanic unrest. Here, we use earthquake data to image, for the first time, the seismic velocity structure beneath Aluto, a deforming volcano in the Main Ethiopian Rift. Traveltime tomography is used to jointly relocate seismicity and image 3D P- and S-wave velocity structures and the ratio between them (V P/V S). At depths of 4–9 km, the seismicity maps the top of a large low velocity zone with high V P/V S, which we interpret as a more ductile and melt-bearing region. A shallow (<3 km) hydrothermal system exhibits low seismic velocities and ve…

Geochemical fingerprints of brannerite (UTi 2 O 6 ): an integrated study

2020

AbstractBrannerite (UTi2O6) is among the major uranium-bearing minerals found in ore deposits, however as it has been long considered as a refractory mineral for leaching it is currently disregarded in ore deposits. Brannerite is found in a variety of geological environments with the most common occurrences being hydrothermal and pegmatitic. On the basis of scanning electron microscopy observations coupled with electron probe micro-analyses and laser ablation inductively-coupled plasma mass spectrometer analyses, this study describes the morphological features and the major- and trace-element abundances of brannerite samples from five hydrothermal and five pegmatitic localities across the w…

Structural and Electrochemical Analysis of CIGS: Cr Crystalline Nanopowders and Thin Films Deposited onto ITO Substrates

2021

A new approach for the synthesis of nanopowders and thin films of CuInGaSe2 (CIGS) chalcopyrite material doped with different amounts of Cr is presented. The chalcopyrite material CuInxGa1 − xSe2 was doped using Cr to form a new doped chalcopyrite with the structure CuInxCryGa1 − x − ySe2, where x = 0.4 and y = 0.0, 0.1, 0.2, or 0.3. The electrical properties of CuInx CryGa1 − x − ySe2 are highly dependent on the Cr content and results show these materials as promising dopants for the fabrication thin film solar cells. The CIGS nano-precursor powder was initially synthesized via an autoclave method, and then converted into thin films over transparent substrates. Both crystalline precursor p…

Co-reductive fabrication of carbon nanodots with high quantum yield for bioimaging of bacteria

2018

A simple and straightforward synthetic approach for carbon nanodots (C-dots) is proposed. The strategy is based on a one-step hydrothermal chemical reduction with thiourea and urea, leading to high quantum yield C-dots. The obtained C-dots are well-dispersed with a uniform size and a graphite-like structure. A synergistic reduction mechanism was investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The findings show that using both thiourea and urea during the one-pot synthesis enhances the luminescence of the generated C-dots. Moreover, the prepared C-dots have a high distribution of functional groups on their surface. In this work, C-dots proved …

CoS2/TiO2 Nanocomposites for Hydrogen Production under UV Irradiation

2019

Transition metal chalcogenides have intensively focused on photocatalytic hydrogen production for a decade due to their stronger edge and the quantum confinement effect. This work mainly focuses on synthesis and hydrogen production efficiencies of cobalt disulfide (CoS2)-embedded TiO2 nanocomposites. Materials are synthesized by using a hydrothermal approach and the hydrogen production efficiencies of pristine CoS2, TiO2 nanoparticles and CoS2/TiO2 nanocomposites are compared under UV irradiation. A higher amount of hydrogen production (2.55 mmol g&minus

Daytime sensible heat flux estimation over heterogeneous surfaces using multitemporal land‐surface temperature observations

2016

Equations based on surface renewal (SR) analysis to estimate the sensible heat flux (H) require as input the mean ramp amplitude and period observed in the ramp‐like pattern of the air temperature measured at high frequency. A SR‐based method to estimate sensible heat flux (HSR‐LST) requiring only low‐frequency measurements of the air temperature, horizontal mean wind speed, and land‐surface temperature as input was derived and tested under unstable conditions over a heterogeneous canopy (olive grove). HSR‐LST assumes that the mean ramp amplitude can be inferred from the difference between land‐surface temperature and mean air temperature through a linear relationship and that the ramp freq…

Broad-band Spectral Evolution of Scorpius X-1 along its Color-Color Diagram

2007

We analyze a large collection of RXTE archive data from April 1997 to August 2003 of the bright X-ray source Scorpius X-1 in order to study the broadband spectral evolution of the source for different values of the inferred mass accretion rate by studying energy spectra from selected regions in the Z-track of its Color-Color Diagram. A two-component model, consisting of a soft thermal component interpreted as thermal emission from an accretion disk and a thermal Comptonization component, is unable to fit the whole 3--200 keV energy spectrum at low accretion rates. Strong residuals in the highest energy band of the spectrum require the addition of a third component that can be fitted with a …