130 research outputs found
Investigating the inclusive transverse spectra in high-energy collisions in the context of geometric scaling framework
The presence of geometric scaling within the spectra of produced
hadrons at high energy collisions using small- -factorization is
investigated. It is proposed a phenomenological parameterization for the
unintegrated gluon distribution in the scaling range which reproduces the
features of the differential cross section both in the saturated and dilute
perturbative QCD regimes. As the saturation scale acts as an effective
regulator of the infrared region (IR), the extension of the model to quantities
usually associated to soft physics is studied. The approach is applied to
compute the average and the rapidity distribution of produced gluons at
high energies.Comment: 11 pages, 9 figure
Nuclear Modification Factor in Small System Collisions within Perturbative QCD Including Thermal Effects
In this paper, dedicated to the memory of the late Prof. Jean Cleymans, the
nuclear modification factors, , are investigated for pion production in
small system collisions, measured by PHENIX experiment at RHIC (Relativistic
Heavy Ion Collider). The theoretical framework is the transverse momentum
-factorization formalism for hard processes at small momentum fraction,
. Evidence for collective expansion and thermal effects for pions, produced
at equilibrium, is studied based on phenomenological parametrization of
blast-wave type in the relaxation time approximation. The dependencies on the
centrality and on the projectile species are discussed in terms of the behavior
of Cronin peak and the suppression of at large transverse momentum,
. The multiplicity of produced particles, which is sensitive to the soft
sector of the spectra, is also included in the present analysis.Comment: 12 pages, 4 figures. Contribution to MDPI Physics Special Issue "Jean
Cleymans: A Life for Physics", dedicated to the memory of Professor Jean
Cleyman
Chemical functionalization of graphene surface as filler for rubber compounds
Over the last few years, the surface modification of fillers for high-level technological applications such as polymer composites for tyre industry, conductive inks and coatings has seen a considerable increase in interest since it can increase mechanical, electrical, and thermal properties of the final material. Nano-sized carbon allotropes such as graphene and carbon nanotubes are a suitable class of compounds for these purposes: high thermal and electrical conductivity along with considerable mechanical reinforcement are the main improvements that these fillers bring to the composite and their elevated surface area allows to reduce the filler volume ratio compared to more common alternatives. An efficient and reliable method to modify the surface of these nano-fillers is the so-called pyrrole methodology, a mild procedure that involves bio-sourced reagents to introduce functional groups on the graphitic planes and that has been recently employed in the fabrication of elastomeric composites with improved mechanical properties. In order to understand the mechanism beneath the interaction between the pyrrole and the substrate and thus the behavior of the functionalized filler, a more in-depth analysis is requested. A theoretical work based on molecular dynamics simulations and a DFT study were performed in order to investigate the interaction energy, the geometry of interaction and the mobility of N-substituted pyrrole molecules adsorbed on the graphene planes. This theoretical study at atomistic level can help design a new class of high-performance fillers by better understanding the interaction mechanism given the important role of supramolecular interactions
Investigating the diffractive gluon jet production in lepton-ion collisions
We study the diffractive jet production in electron-ion collisions in the
kinematical region where the mass of the diffractive final state is
larger than . Based on parton saturation framework predictions are done
for the kinematics of future or possible machines as the EIC, LHeC,
HE-LHeC and FCC-eA. We analyze the differential cross section as a function of
jet (gluon) transverse momentum and from the experimental point of view this
observable could be used to extract the saturation scale as a function of
.Comment: 8 pages, 5 figures. To be published in Physical Review
Proteomic insights on the metabolism in inflammatory bowel disease
Inflammatory bowel diseases (IBD) are chronic and relapsing inflammatory conditions of the gut that include Crohn's disease and ulcerative colitis. The pathogenesis of IBD is not completely unraveled, IBD are multi-factorial diseases with reported alterations in the gut microbiota, activation of different immune cell types, changes in the vascular endothelium, and alterations in the tight junctions\u2019 structure of the colonic epithelial cells. Proteomics represents a useful tool to enhance our biological understanding and to discover biomarkers in blood and intestinal specimens. It is expected to provide reproducible and quantitative data that can support clinical assessments and help clinicians in the diagnosis and treatment of IBD. Sometimes a differential diagnosis of Crohn's disease and ulcerative colitis and the prediction of treatment response can be deducted by finding meaningful biomarkers. Although some non-invasive biomarkers have been described, none can be considered as the \u201cgold standard\u201d for IBD diagnosis, disease activity and therapy outcome. For these reason new studies have proposed an \u201cIBD signature\u201d, which consists in a panel of biomarkers used to assess IBD. The above described approach characterizes \u201comics\u201d and in this review we will focus on proteomics
Role of nuclear gluon distribution on particle production in heavy ion collisions
The transverse momentum spectra of hadrons is calculated from the
unintegrated gluon distribution (UGD) within the -factorization framework
at small . Starting from collisions, the modification caused by the
nuclear medium is incorporated in the UGD at high energies, which is related to
the nuclear shadowing phenomenon. Moreover, we consider that particle
production from minijet decaying is not enough to explain the spectra in
collisions due to collective phenomena that take place after the hard
collision. The Boltzmann-Gibbs Blast Wave (BGBW) distribution is utilized in
order to evaluate the distribution of particle production in equilibrium. Data
from ALICE collaboration for collisions at TeV are
analyzed and the nuclear modification factor for pion production is computed.Comment: 8 pages, 5 figure
Dilepton production through timelike Compton scattering within the -factorization approach
In this work we consider the dilepton production via timelike Compton
scattering (TCS) in electron-proton and proton-proton collisions. In
particular, the differential cross section in terms of the dilepton invariant
mass and rapidity is computed within the -factorization approach. Besides,
we utilize distinct unintegrated gluon distributions (UGD) in order to compare
their impact on the differential cross section of TCS in () collisions
evaluated at the LHC (LHeC), HL-LHC (LHeC), HE-LHC (LHeC) and FCC-hh (eh)
center-of-mass energies.Comment: 9 pages, 4 figure
Anharmonic calculations of vibrational spectra for molecular adsorbates: A divide-and-conquer semiclassical molecular dynamics approach
The vibrational spectroscopy of adsorbates is becoming an important investigation tool for catalysis and material science. This paper presents a semiclassical molecular dynamics method able to reproduce the vibrational energy levels of systems composed by molecules adsorbed on solid surfaces. Specifically, we extend our divide-and-conquer semiclassical method for power spectra calculations to gas-surface systems and interface it with plane-wave electronic structure codes. The Born-Oppenheimer classical dynamics underlying the semiclassical calculation is full dimensional, and our method includes not only the motion of the adsorbate but also those of the surface and the bulk. The vibrational spectroscopic peaks related to the adsorbate are accounted together with the most coupled phonon modes to obtain spectra amenable to physical interpretations. We apply the method to the adsorption of CO, NO, and H2O on the anatase-TiO2 (101) surface. We compare our semiclassical results with the single-point harmonic estimates and the classical power spectra obtained from the same trajectory employed in the semiclassical calculation. We find that CO and NO anharmonic effects of fundamental vibrations are similarly reproduced by the classical and semiclassical dynamics and that H2O adsorption is fully and properly described in its overtone and combination band relevant components only by the semiclassical approach
Transition metal nanoparticles on pyrrole-decorated sp2 carbon allotropes for selective hydrogen isotopic exchange
Compared to homogeneous catalysts, heterogeneous systems possess more attractiveness in the chemical industry because of the easier separation from the reaction products, lower amount of wastes, larger recyclability and lower toxicity and corrosiveness. Preparation of supported metal nanoparticles often requires energy demanding techniques such as laser ablation, electrochemical reduction, and high temperature heat treatments. In this work we present a facile and sustainable method to functionalize multi-walled carbon nanotubes (MWCNTs) and exploit the novel surface reactivity to deposit Ruthenium nanoparticles. Serinol pyrrole (SP) was synthesized and, through a Domino reaction, grafted on carbon nanotubes’ surface. Mild reducing conditions were employed to decorate CNT-SP with Ruthenium nanoparticles. The latter adduct was characterized by means of X-ray diffraction and transmission electron microscopy. Ru/CNT-SP was then tested in the selective deuteration of quinoline. High selectivity and conversion, determined through H-NMR, were achieved compared to commercial Ru/C catalysts. The results obtained in this work led to the filing of two patent applications
Transition metal nanoparticles on pyrrole-decorated sp2 carbon allotropes for selective hydrogen isotopic exchange
Compared to homogeneous catalysts, heterogeneous systems possess more attractiveness in the chemical industry because of the easier separation from the reaction products, lower amount of wastes, larger recyclability, and lower toxicity and corrosiveness.
Objective of this research was to prepare more efficient and more selective heterogeneous catalysts, by anchoring transition metal cations and nanoparticles on nitrogen decorated sp2 carbon allotrope (CA), which were functionalized with pyrrole compounds. Triethylenetetramine pyrrole (TETAP) was selected as the pyrrole compound: it was synthesized and grafted onto multiwalled carbon nanotubes and high surface area graphite with efficient and viable methodology.
The CA/TEPAP adduct was used as the support of transition metal nanoparticles.
It is here reported the example of ruthenium supported catalyst, investigated by means of elemental and surface area analyses, X-ray diffraction, transmission electron microscopy. The catalyst was used for the Hydrogen Isotopic Exchange (HIE) of aromatic compounds of pharmaceutical interest.
Outstanding selectivity was obtained
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