196 research outputs found
Photoelectrocatalytic Performances of Nanostructured/Decorated TiO 2
The behaviour of TiO2 based electrodes was investigated during the photoelectrocatalytic water splitting process. TiO2 nanotubes and compact oxide structures were obtained by electrochemical oxidation of Ti foils. A subsequent hydrothermal process carried out at both the nanotubular and compact oxide structures allowed decorating the structure by TiO2 nanoparticles. The synthesized TiO2 samples worked as photoanodes both in a bulk three electrode cell and in a thin gap cell. The results from measurements of the photocurrent and from electrochemical impedance spectroscopy were used to highlight a combined effect of the wavelength of the incident light and the kind of cell configuration, on the global performance of the systems. The results indicate that the decoration process does not result only in a simple increase of the specific surface, but it also determines a different concentration of the bulk and superficial sites in the electrode. The different response of the sites at different wavelengths, along with the accessibility of the electrolyte to the porous structure are evocated to justify the experimental behaviour observed
Controlling the Er content of porous silicon using the doping current intensity
The results of an investigation on the Er doping of porous silicon are presented. Electrochemical impedance spectroscopy, optical reflectivity, and spatially resolved energy dispersive spectroscopy (EDS) coupled to scanning electron microscopy measurements were used to investigate on the transient during the first stages of constant current Er doping. Depending on the applied current intensity, the voltage transient displays two very different behaviors, signature of two different chemical processes. The measurements show that, for equal transferred charge and identical porous silicon (PSi) layers, the applied current intensity also influences the final Er content. An interpretative model is proposed in order to describe the two distinct chemical processes. The results can be useful for a better control over the doping process
analysis of photocurrent and capacitance of tio2 nanotube polyaniline hybrid composites synthesized through electroreduction of an aryldiazonium salt
TiO2 nanotube–polyaniline hybrid composites were synthesized using an aminophenyl under-layer electrochemically grafted on TiO2 obtaining improvements in photocurrent and capacitance
Investigation on the Adsorption and Photooxidation of Glycerol at TiO2 Nanotubular Arrays
A study is presented on the adsorption of glycerol at TiO2as well as on its oxidative process during the contemporary water Photoelectro-splitting for hydrogen production. A deepening in the understanding on the working mechanism of the TiO2nanotubular photoanodes and on the interactions between glycerol and these structures has been gained through photocurrent tests, voltammetric scans, and EIS analysis. A range of wavelength of the incident radiation is investigated from 340 to 400 nm at which the effect of glycerol on the photocurrent is measured. Quantitative analysis of the EIS results is performed by the equivalent circuit approach
Increase in 20–50 Hz (gamma frequencies) power spectrum and synchronization after chronic vagal nerve stimulation
Objective: Though vagus nerve stimulation (VNS) is an important option in pharmacoresistant epilepsy, its mechanism of action remains unclear. The observation that VNS desynchronised the EEG activity in animals suggested that this mechanism could be involved in VNS antiepileptic effects in humans. Indeed VNS decreases spiking bursts, whereas its effects on the EEG background remain uncertain. The objective of the present study is to investigate how VNS affects local and inter regional syncronization in different frequencies in pharmacoresistent partial epilepsy. Methods: Digital recordings acquired in 11 epileptic subjects 1 year and 1 week before VNS surgery were compared with that obtained 1 month and 1 year after VNS activation. Power spectrum and synchronization were then analyzed and compared with an epileptic group of 10 patients treated with AEDs only and with 9 non-epileptic patients. Results: VNS decreases the synchronization of theta frequencies (P!0.01), whereas it increases gamma power spectrum and synchronization (!0.001 and 0.01, respectively). Conclusions: The reduction of theta frequencies and the increase in power spectrum and synchronization of gamma bands can be related to VNS anticonvulsant mechanism. In addition, gamma modulation could also play a seizure-independent role in improving attentional performances. Significance: These results suggest that some antiepileptic mechanisms affected by VNS can be modulated by or be the reflection of EEG changes.2026-2036Pubblicat
Assessing the impact of design factors on the performance of two miniature microbial fuel cells
Every day, wastewater treatment requires large amounts of electricity. Microbial Fuel Cells (MFCs) can convert wastewater treatment plants from net power consumers into energy neutral/positive systems by generating electricity from wastewaters. We investigate here the design factors that have major impacts on the performance of two miniature MFCs, and, consequently, of the resulting stack of MFCs. A versatile mathematical model is provided, which simulates the complex MFC system by integrating fluid dynamic principles with mass transport phenomena and (bio)electrochemical reactions. The model is used to support an in-depth study of the two MFCs, which differ for electrode spacing, anodic volume and fluid pattern within the anodic chamber, and to associate any difference in performance to design factors. Finally, system scale-up is demonstrated by generating stacks of the two MFCs. Thanks to the versatility of the model developed, this study becomes a guide for the effective development of future miniature MFCs
Accurate dust temperature and star formation rate in the most luminous quasar in the HYPerluminous quasars at the Epoch of ReionizatION (HYPERION) sample
We present ALMA Band 9 continuum observation of the ultraluminous
quasi-stellar object (QSO) SDSS J0100+2802, providing a
detection at GHz. SDSS J0100+2802 is the brightest QSO with the most
massive super massive black hole (SMBH) known at , and we study its dust
spectral energy distribution in order to determine the dust properties and the
star formation rate (SFR) of its host-galaxy. We obtain the most accurate
estimate so far of the temperature, mass and emissivity index of the dust,
having K,
M, . This allows us to measure the SFR with the
smallest statistical error for this QSO, SFR.
Our results enable us to evaluate the relative growth of the SMBH and host
galaxy of J0100+2802, finding that the SMBH is dominating the process of
BH-galaxy growth in this QSO at , when the Universe was Myr old.
Such unprecedented constraints on the host galaxy SFR and dust temperature can
only be obtained through high frequency observations, and highlight the
importance of ALMA Band 9 to obtain a robust overview of the build-up of the
first quasars' host galaxies at .Comment: 10 pages, 4 figures, 1 table. Accepted for publication in ApJ
Early Results from GLASS-JWST. XXI: Rapid assembly of a galaxy at z=6.23 revealed by its C/O abundance
The abundance of carbon relative to oxygen (C/O) is a promising probe of star
formation history in the early universe, as the ratio changes with time due to
production of these elements by different nucleosynthesis pathways. We present
a measurement of (stat) (sys)
in a galaxy observed as part of the GLASS-JWST Early Release Science
Program. Notably, we achieve good precision thanks to the detection of the
rest-frame ultraviolet O III], C III], and C IV emission lines delivered by
JWST/NIRSpec. The C/O abundance is 0.8 dex lower than the solar value and
is consistent with the expected yield from core-collapse supernovae, indicating
that longer-lived intermediate mass stars have not fully contributed to carbon
enrichment. This in turn implies rapid buildup of a young stellar population
with age Myr in a galaxy seen 900 million years after the
Big Bang. Our chemical abundance analysis is consistent with spectral energy
distribution modeling of JWST/NIRCam photometric data, which indicates a
current stellar mass and specific star formation rate sSFR
Gyr. These results showcase the value of chemical abundances and C/O in
particular to study the earliest stages of galaxy assembly.Comment: 16 pages, 4 figures, 2 tables. Accepted for publication in ApJ
Early results from GLASS-JWST. III: Galaxy candidates at z9-15
We present the results of a first search for galaxy candidates at
z9--15 on deep seven-bands NIRCam imaging acquired as part of the
GLASS-JWST Early Release Science Program on a flanking field of the Frontier
Fields cluster A2744. Candidates are selected via two different renditions of
the Lyman-break technique, isolating objects at z9-11, and z9-15,
respectively, supplemented by photometric redshifts obtained with two
independent codes. We find six color-selected candidates at z9, plus one
additional candidate with photometric redshift z9. In particular,
we identify two bright candidates at that are
unambiguously placed at and , respectively. The
total number of galaxies discovered at is in line with the predictions of
a non-evolving LF. The two bright ones at are unexpected given the
survey volume, although cosmic variance and small number statistics limits
general conclusions. This first search demonstrates the unique power of JWST to
discover galaxies at the high redshift frontier. The candidates are ideal
targets for spectroscopic follow-up in cycle.Comment: Submitted to ApJL, 9 pages, 4 figure
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