164 research outputs found
Study of coherent interactions between charged particle beams and crystals for beam steering and intense electromagnetic radiation generation
The work presented in this thesis has been devoted to the investigation of new
schemes for beam steering and high-intense electromagnetic radiation generation through
coherent interactions of charged particle beams with crystals. A series of experiments was
carried out in two different laboratories, i.e., the Super Proton Synchrotron (SPS) at CERN
in Geneve and the MAinzer MIkrotron (MAMI) of the University of Mainz in Germany, by
different international and national collaborations, namely the UA9 experiment., the
European CUTE project and the INFN COHERENT and ICE-RAD experiments. The
experimental data have been analysed and critically compared with simulations.
First of all, the possibility of combining the efficient deflection and the intense
electromagnetic radiation production of ultrarelativistic electrons through channeling or
volume reflection in bent silicon crystals was investigated. Interesting results were
obtained in a wide range of beam energies, spanning from 0.855 GeV available at MAMI
to hundreds of GeV accessible at the H4 extracted beamline of SPS. It has been
demonstrated the possibility to use bent crystals for efficient deflection of electron beams
in the subGeV energy range. This range of energies was still unexplored due to the lack of
properly sized bent crystal for negative beams steering. Secondly, it has been shown that
the radiation accompanying single (VR) and multiple (MVROC) volume reflection in a bent
crystal has peculiar characteristics, such as higher intensity than for bremsstrahlung in an
amorphous material and a wide angular acceptance, that make this kind of radiation quite
interesting for applications. On the very high-energy side, crystal-aided collimation through
radiation accompanying VR and MVROC has been proposed for the future electronpositron
colliders, e.g., the International Linear Collider. On the other hand, in the subGeVGeV
energy range, which is accessible by most electron accelerators worldwide, the
radiation accompanying VR can be exploited as an high-intensity X- or Îł-sourse with poor
emittance beams.
In addition to the studies carried out with electrons, the investigation of new
schemes for manipulation of charged beams trajectories was carried out at the H8
beamline of SPS with the usage of 400 GeV/c protons. Firstly, a periodically bent crystal
was realized via the superficial grooving method and tested at the H8 line. The
effectiveness of this method in achieving perfectly periodic structures was demonstrated.
On the strength of these results, it has been proposed to test the crystal sample as a
positron-based crystalline undulator in the energy range of 10-20 GeV, as a source of
intense MeV photons. Finally, it has been experimentally demonstrated that even a
straight crystal, i.e., a crystal mirror, may be used for the steering of ultrarelativistic protons
in place of a bent crystal. Unlike the traditional scheme relying on mm-long curved
crystals, particle mirroring enables beam steering in high-energy accelerators via
interactions with ÎŒm-thin straight crystal. The main advantage of mirroring is the interaction
with a minimal amount of material along the beam, thereby decreasing unwanted nuclear
interactions.
Summarizing, all the experimental studies presented in this thesis lead us to
consider crystals, either bent or unbent, as reliable tools in particle accelerator physics for
different applications within a wide energy range
Steering efficiency of a ultrarelativistic proton beam in a thin bent crystal
Crystals with small thickness along the beam exhibit top performance for
steering particle beams through planar channeling. For such crystals, the
effect of nuclear dechanneling plays an important role because it affects their
efficiency. We addressed the problem through experimental work carried out with
400 GeV/c protons at fixed-target facilities of CERN-SPS. The dependence of
efficiency vs. curvature radius has been investigated and compared favourably
to the results of modeling. A realistic estimate of the performance of a
crystal designed for LHC energy including nuclear dechanneling has been
achieved.Comment: 16 pages, 6 figure
Relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal
An investigation on the mechanism of relaxation
of axially confined 400 GeV/c protons to planar channeling
in a bent crystal was carried out at the extracted line H8 from
CERN Super Proton Synchrotron. The experimental results
were critically compared to computer simulations, showing
a good agreement. We identified a necessary condition for
the exploitation of axial confinement or its relaxation for
particle beam manipulation in high-energy accelerators. We
introduce the idea of using a short bent crystal, aligned with
one of its main axis to the beam direction, as a beam steerer
or a beam splitter with adjustable intensity in the field of particle
accelerators. In particular, in the latter case, a complete
relaxation from axial confinement to planar channeling takes
place, resulting in beam splitting into the two strongest skew
planar channels.An investigation on the mechanism of relaxation of axially confined 400 GeV/c protons to planar channeling in a bent crystal was carried out at the extracted line H8 from CERN Super Proton Synchrotron. The experimental results were critically compared to computer simulations, showing a good agreement. We identified a necessary condition for the exploitation of axial confinement or its relaxation for particle beam manipulation in high-energy accelerators. We introduce the idea of using a short bent crystal, aligned with one of its main axis to the beam direction, as a beam steerer or a beam splitter with adjustable intensity in the field of particle accelerators. In particular, in the latter case, a complete relaxation from axial confinement to planar channeling takes place, resulting in beam splitting into the two strongest skew planar channels
Materials derived from the human elastin-like polypeptide fusion with an antimicrobial peptide strongly promote cell adhesion
Protein and peptide materials have attracted great interest in recent years, especially for biological applications, in light of their possibility to easily encode bioactivity whilst maintaining cytocompatibility and biodegradability. Heterologous recombinant expression to produce antimicrobial peptides is increasingly considered a convenient alternative for the transition from conventional methods to more sustainable production systems. The human elastin-like polypeptide (HELP) has proven to be a valuable fusion carrier, and due to its cutting-edge properties, biomimetic materials with antimicrobial capacity have been successfully developed. In this work, we have taken advantage of this platform to produce a difficult-to-synthesise sequence as that of the human ÎČ-defensin 1 (hBD1), an amphipathic cationic peptide with structural folding constraints relevant to its bioactivity. In the design of the gene, highly specific endoproteinases recognition sites were introduced to release the active forms of hBD1. After the expression and purification of the new fusion construct, its biological activity was evaluated. It was found that both the fusion biopolymer and the released active forms can inhibit the growth of Escherichia coli in redox environments. Remarkably, 2D and 3D materials derived from the biopolymer showed a strong cell adhesion-promoting activity. These results suggest that HELP represents a multitasking platform that not only facilitates the production of bioactive domains and derived materials but could also pave the way for the development of new approaches to study biological interactions at the molecular level
A European regulatory perspective on cystic fibrosis: current treatments, trends in drug development and translational challenges for CFTR modulators
In this article we analyse the current authorised treatments and trends in early drug development for cystic fibrosis (CF) in the European Union for the time period 2000â2016. The analysis indicates a significant improvement in the innovation and development of new potential medicines for CF, shifting from products that act on the symptoms of the disease towards new therapies targeting the cause of CF. However, within these new innovative medicines, results for CF transmembrane conductance regulator (CFTR) modulators indicate that one major challenge for turning a CF concept product into an actual medicine for the benefit of patients resides in the fact that, although pre-clinical models have shown good predictability for certain mutations, a good correlation to clinical end-points or biomarkers (e.g. forced expiratory volume in 1â
s and sweat chloride) for all mutations has not yet been achieved. In this respect, the use of alternative end-points and innovative nonclinical models could be helpful for the understanding of those translational discrepancies. Collaborative endeavours to promote further research and development in these areas as well as early dialogue with the regulatory bodies available at the European competent authorities are recommended
Physicochemical Characterization of a Biomimetic, Elastin-Inspired Polypeptide with Enhanced Thermoresponsive Properties and Improved Cell Adhesion
Genetic engineering allows fine-tuning and controlling protein properties, thus exploiting the new derivatives to obtain novel materials and systems with improved capacity to actively interact with biological systems. The elastin-like polypeptides are tunable recombinant biopolymers that have proven to be ideal candidates for realizing bioactive interfaces that can interact with biological systems. They are characterized by a thermoresponsive behavior that is strictly related to their peculiar amino acid sequence. We describe here the rational design of a new biopolymer inspired by elastin and the comparison of its physicochemical properties with those of another already characterized member of the same protein class. To assess the cytocompatibility, the behavior of cells of different origins toward these components was evaluated. Our study shows that the biomimetic strategy adopted to design new elastin-based recombinant polypeptides represents a versatile and valuable tool for the development of protein-based materials with improved properties and advanced functionality
Identification of stably expressed reference small non-coding RNAs for microRNA quantification in high-grade serous ovarian carcinoma tissues
MicroRNAs (miRNAs) belong to a family of small nonâcoding RNAs (sncRNAs) playing important roles in human carcinogenesis. Multiple investigations reported miRNAs aberrantly expressed in several cancers, including highâgrade serous ovarian carcinoma (HGSâOvCa). Quantitative PCR is widely used in studies investigating miRNA expression and the identification of reliable endogenous controls is crucial for proper data normalization. In this study, we aimed to experimentally identify the most stable reference sncRNAs for normalization of miRNA qPCR expression data in HGSâOvCa. Eleven putative reference sncRNAs for normalization (U6, SNORD48, miRâ92aâ3p, letâ7aâ5p, SNORD61, SNORD72, SNORD68, miRâ103aâ3p, miRâ423â3p, miRâ191â5p, miRâ16â5p) were analysed on a total of 75 HGSâOvCa and 30 normal tissues, using a highly specific qPCR. Both the normal tissues considered to initiate HGSâOvCa malignant transformation, namely ovary and fallopian tube epithelia, were included in our study. Stability of candidate endogenous controls was evaluated using an equivalence test and validated by geNorm and NormFinder algorithms. Combining results from the three different statistical approaches, SNORD48 emerged as stably and equivalently expressed between malignant and normal tissues. Among malignant samples, considering groups based on residual tumour, miRâ191â5p was identified as the most equivalent sncRNA. On the basis of our results, we support the use of SNORD48 as best reference sncRNA for relative quantification in miRNA expression studies between HGSâOvCa and normal controls, including the first time both the normal tissues supposed to be HGSâOvCa progenitors. In addition, we recommend miRâ191â5p as best reference sncRNA in miRNA expression studies with prognostic intent on HGSâOvCa tissues
Enhancement of the Inelastic Nuclear Interaction Rate in Crystals via Antichanneling
The interaction rate of a charged particle beam with the atomic nuclei of a target varies significantly if the target has a crystalline structure. In particular, under specific orientations of the target with respect to the incident beam, the probability of inelastic interaction with nuclei can be enhanced with respect to the unaligned case. This effect, which can be named antichanneling, can be advantageously used in the cases where the interaction between beam and target has to be maximized. Here we propose to use antichanneling to increase the radioisotope production yield via cyclotron. A dedicated set of experimental measurements was carried out at the INFN Legnaro Laboratories with the AN2000 and CN accelerators to prove the existence of the antichanneling effect. The variation of the interaction yield at hundreds of keV to MeV energies was observed by means of sapphire and indium phosphide crystals, achieving an enhancement of the interaction rate up to 73% and 25%, respectively. Such a result may pave the way to the development of a novel type of nozzle for the existing cyclotrons, which can exploit crystalline materials as targets for radioisotope production, especially to enhance the production rate for expensive prime materials with minor upgrades of the current instrumentation
Self-Assembly of Homo- and Hetero-Chiral Cyclodipeptides into Supramolecular Polymers towards Antimicrobial Gels
There is an increasing interest towards the development of new antimicrobial coatings, especially in light of the emergence of antimicrobial resistance (AMR) towards common antibiotics. Cyclodipeptides (CDPs) or diketopiperazines (DKPs) are attractive candidates for their ability to self-assemble into supramolecular polymers and yield gel coatings that do not persist in the environment. In this work, we compare the antimicrobial cyclo(Leu-Phe) with its heterochiral analogs cyclo(D-Leu-L-Phe) and cyclo(L-Leu-D-Phe), as well as cyclo(L-Phe-D-Phe), for their ability to gel. The compounds were synthesized, purified by HPLC, and characterized by 1H-NMR, 13C-NMR, and ESI-MS. Single-crystal X-ray diffraction (XRD) revealed details of the intermolecular interactions within the supramolecular polymers. The DKPs were then tested for their cytocompatibility on fibroblast cells and for their antimicrobial activity on S. aureus. Overall, DKPs displayed good cytocompatibility and very mild antimicrobial activity, which requires improvement towards applications
Geant4 simulation model of electromagnetic processes in oriented crystals for the accelerator physics
Electromagnetic processes of charged particles interaction with oriented
crystals provide a wide variety of innovative applications such as beam
steering, crystal-based extraction/collimation of leptons and hadrons in an
accelerator, a fixed-target experiment on magnetic and electric dipole moment
measurement, X-ray and gamma radiation source for radiotherapy and nuclear
physics and a positron source for lepton and muon colliders, a compact
crystalline calorimeter as well as plasma acceleration in the crystal media.
One of the main challenges is to develop an up-to-date, universal and fast
simulation tool to simulate these applications.
We present a new simulation model of electromagnetic processes in oriented
crystals implemented into Geant4, which is a toolkit for the simulation of the
passage of particles through matter. We validate the model with the
experimental data as well as discuss the advantages and perspectives of this
model for the applications of oriented crystals mentioned above.Comment: 18 pages, 9 figure
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