The Mercedes water Cherenkov detector Assis, P.; Bakalová, A.; Barres de Almeida, U. ...
European physical journal. C, Particles and fields,
10/2022, Letnik:
82, Številka:
10
Journal Article
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The concept of a small, single-layer water Cherenkov detector, with three photomultiplier tubes (PMTs), placed at its bottom in a
120
∘
star configuration (
Mercedes
Water Cherenkov Detector) is ...presented. The PMTs are placed near the lateral walls of the stations with an adjustable inclination and may be installed inside or outside the water volume. To illustrate the technical viability of this concept and obtain a first-order estimation of its cost, an engineering design was elaborated. The sensitivity of these stations to low energy Extensive Air Shower (EAS) electrons, photons and muons is discussed, both in compact and sparse array configurations. It is shown that the analysis of the intensity and time patterns of the PMT signals, using machine learning techniques, enables the tagging of muons, achieving an excellent gamma/hadron discrimination for TeV showers. This concept minimises the station production and maintenance costs, allowing for a highly flexible and fast installation. Mercedes Water Cherenkov Detectors (WCDs) are thus well-suited for use in high-altitude large gamma-ray observatories covering an extended energy range from the low energies, closing the gap between satellite and ground-based measurements, to very high energy regions, beyond the PeV scale.
Experimentally, steric and inductive effects have been suggested as key parameters in the adsorption and reactivity of alcohols on transition-metal (TM) surfaces, however, our atomistic understanding ...of the behavior of alcohols in catalysis is far from satisfactory, in particular, due to the role of hydroxy groups in the adsorption properties of C3 alcohols on TM surfaces. In this study, we investigated those effects through ab initio calculations based on density functional theory employing a semilocal exchange-correlation functional within van der Waals corrections (the D3 framework) for the adsorption of C3 alcohols with different numbers and positions of OH groups, namely, propane, 1-propanol, 2-propanol, 1,2-propanediol, 1,3-propanediol and glycerol, on the compact Ni(111), Pd(111) and Pt(111) surfaces. As expected, we found that the adsorption energy is affected by the number of hydroxy groups with similar values for each pair of regioisomers, which clearly indicates the effect of the number of OH groups. Based on Bader charge analysis, we found an effective charge transfer from the C3 molecules to the substrates, which can explain the reduction in the work function due to adsorption. Upon adsorption, the alpha carbon to the OH group closest to the surface and the central carbon are the most positively charged atoms, which increases the lability of their bonded H atoms. In addition, the depletion of electron density between the C-H and O-H bonds closer to the surfaces corroborated their stretching, suggesting that the proximity of the adsorbates to the surfaces affects the acidity of these H atoms, as well as inductive effects within the molecules.
Joint trauma is predisposing to the incidence of osteoarthritis (OA) of the knee. There is a limited knowledge on the impact of posttraumatic osteochondral defects on the whole joint. This study was ...designed to define a critical size osteochondral defect in the knee of rats and to investigate a possible association between osteochondral defects and degeneration of the surrounding joint surface.
Cylindrical osteochondral defects of different sizes were created in the knee joint of rats. The natural course of these lesions was studied by macroscopic observation, histology, and immunohistochemistry. Gene expression of the articular cartilage surrounding the defects in vivo and of articular chondrocytes cultured in vitro in IL1β and fibroblast growth factor 2 (FGF2) supplemented media was evaluated by quantitative polymerase chain reaction (qPCR).
In defects of 0.9 mm diameter, spontaneous joint surface healing was observed but also upward advancing of the subchondral bone plate at 16 weeks. Larger 1.4 mm diameter defects were critical size, not resulting in successful healing at any time point. Importantly, the articular cartilage surrounding the defects expressed FGF2 and IL1β, but not ACAN and Col2. Chondrocytes cultured in IL1β and FGF2 supplemented media lost the natural fibroblast growth factor receptors – FGFr1/FGFr3 balance and showed decreased viability.
A critical size osteochondral defect was defined as 1.4 mm in diameter in rat. Subchondral bone plate advancement occured rapidly. The articular cartilage surrounding osteochondral defects showed catabolic activity with expression of IL1β, FGF2 and a disturbed FGFr1/FGFr3 balance, potentially initiating a process of early osteoarthritic disease.
Chondrogenic mesenchymal stem cells (MSCs) have not yet been used to address the clinical demands of large osteochondral joint surface defects. In this study, self-assembling tissue intermediates ...(TIs) derived from human periosteum-derived stem/progenitor cells (hPDCs) were generated and validated for stable cartilage formation in vivo using two different animal models.
hPDCs were aggregated and cultured in the presence of a novel growth factor (GF) cocktail comprising of transforming growth factor (TGF)-β1, bone morphogenetic protein (BMP)2, growth differentiation factor (GDF)5, BMP6, and fibroblast growth factor (FGF)2. Quantitative polymerase chain reaction (PCR) and immunohistochemistry were used to study in vitro differentiation. Aggregates were then implanted ectopically in nude mice and orthotopically in critical-size osteochondral defects in nude rats and evaluated by microcomputed tomography (µCT) and immunohistochemistry.
Gene expression analysis after 28 days of in vitro culture revealed the expression of early and late chondrogenic markers and a significant upregulation of NOGGIN as compared to human articular chondrocytes (hACs). Histological examination revealed a bilayered structure comprising of chondrocytes at different stages of maturity. Ectopically, TIs generated both bone and mineralized cartilage at 8 weeks after implantation. Osteochondral defects treated with TIs displayed glycosaminoglycan (GAG) production, type-II collagen, and lubricin expression. Immunostaining for human nuclei protein suggested that hPDCs contributed to both subchondral bone and articular cartilage repair.
Our data indicate that in vitro derived osteochondral-like tissues can be generated from hPDCs, which are capable of producing bone and cartilage ectopically and behave orthotopically as osteochondral units.
GRASPs are proteins involved in cell processes that seem paradoxical: responsible for shaping the Golgi cisternae and involved in unconventional secretion mechanisms that bypass the Golgi. Despite ...its physiological relevance, there is still a considerable lack of studies on full-length GRASPs. Our group has previously reported an unexpected behavior of the full-length GRASP from the fungus C. neoformans: its intrinsically-disordered characteristic. Here, we generalize this finding by showing that it is also observed in the GRASP from S. cerevisae (Grh1), which strongly suggests it might be a general property within the GRASP family. Furthermore, Grh1 is also able to form amyloid-like fibrils either upon heating or when submitted to changes in the dielectric constant of its surroundings, a condition that is experienced by the protein when in close contact with membranes of cell compartments, such as the Golgi apparatus. Intrinsic disorder and fibril formation can thus be two structural properties exploited by GRASP during its functional cycle.
The adsorption of alcohols on transition-metal (TM) substrates has received the attention of many researchers due to the applications of alcohols in several technological fields. However, our ...atomic-level understanding is still far from satisfactory, in particular for the interaction of alcohols with finite-size TM clusters, where new effects can arise due to the presence of quantum-size effects. In this work, we report a theoretical investigation of the adsorption properties of methanol, ethanol, and ethylene glycol on 12 different 3d, 4d, and 5d TM
15
clusters based on density functional theory calculations within the semi-empirical D3 van der Waals corrections. From the correlation analysis of all the lowest- and high-energy configurations, we identified the adsorption modes of methanol, ethanol, and ethylene glycol on the TM
15
clusters, in which the OH group binds to the cationic TM sites
via
the O-TM and H-TM interactions. Due to the relatively weak alcohol-TM
15
interaction, the changes induced on the TM
15
clusters are small, except for Au
15
and Ru
15
, where the bare cluster changes its structure to a nearby minimum in the potential energy surface. The adsorption energy for the alcohol/TM
15
systems is correlated to the combination of several parameters, in which the main contribution is connected with the O-TM interaction and the HOTM angles. Furthermore, the TM electronegativity is an important descriptor for the methanol and ethanol adsorption energies, while charge transfer is important for ethylene glycol.
Adsorption modes of methanol, ethanol, and ethylene glycol on TM
15
clusters.
Supramolecular short peptide-based gels are promising materials for the controlled release of drugs (
e.g.
chemotherapeutic drugs) owing to the biocompatibility and similarity to cell matrix. ...However, the drug encapsulation and control over its release, mainly the hydrophilic drugs, can be a cumbersome task. This can be overcome through encapsulation/compartmentalization of drugs in liposomes, which can also enable spatiotemporal control and enhanced drug release through a trigger, such as photothermia. Having this in mind, we explored the assembly of silica-coated gold nanoparticles and liposomes (storage units) with dehydropeptide-based hydrogels as a proof-of-concept to afford peptide-based NIR light-responsive lipogels. Several liposomes compositions were assessed that displayed influence on the final assembly properties by combining with silica-coated gold nanorods (∼106 nm). Gold nanospheres (∼11 nm) were used to study the preparation method, which revealed the importance of initially combine liposomes with nanoparticles and then the gelator solution to achieve a closer proximity of the nanoparticles to the liposomes. The control over a hydrophilic model drug, 5(6)-carboxyfluorescein, was only achieved by its encapsulation in liposomes, in which the presence of silica-coated nanorods further enabled the use of photothermia to induce the liposomes phase transition and stimulate the drug release. Further, both composites, the liposomes and silica-coated gold nanorods, induced a lower elastic modulus, but also provided an enhanced gelation kinetics. Hereby, this work advances fabrication strategies for the development of short peptide-based hydrogels towards on-demand, sustained and controlled release of hydrophilic drugs through photothermia under NIR light irradiation.
The incorporation of silica-coated gold nanorods and liposomes (storage units) into dehydropeptide-based hydrogels afforded peptide-based NIR light-responsive lipogels with tuneable and controlled release of hydrophilic drug model.
This work aimed to study aluminium to stainless steel explosive welds produced using two different interlayers: carbon steel and niobium. The use of each interlayer was analysed and compared ...microstructurally and mechanically using many characterisation techniques. The final joints using both interlayers presented favourable interfacial microstructure: waves on both interfaces. However, the joint using the carbon steel interlayer showed the best mechanical properties compared to the joints using the niobium interlayer. All interfaces found on both welds were wavy. However, depending on the metallic alloy combination, the shape of the wave is completely different. The results suggest that the shape of the waves is influenced by the shock impedance mismatch of the materials being welded. The impedance mismatch parameter (IMP) developed for explosive welding in this work proved to be a compelling method to order metallic combinations in a single axis to estimate the tendency to form typical or curled waves. Typical symmetrical waves tend to develop less quantity of IMCs than curled waves. However, the mechanical tests performed did not detect differences that could have been caused by this difference.
Adsorption is a crucial preliminary step for the conversion of CO2 into higher-value chemicals, nonetheless, the atomistic understanding of how substrate particle size affects this step is still ...incomplete. In this study, we employed density functional theory to investigate the effects of particle size on the adsorption of model molecules involved in the CO2 transformations (CO2, CO, H2O and H2) on Con, Nin and Cun particles with different sizes (n = 13, 55, 147) and on the respective close-packed surfaces. We found significant size-dependence of the adsorption properties for physisorbed (linear) and chemisorbed (bent) CO2 on the substrates and distinct (symmetric or asymmetric) stretching of the C–O bonds, which can play a crucial role to understand the CO2 dissociation pathways. For CO and H2, some properties showed small oscillations, due to size effects that induced alternation of the adsorption site preference for different particle sizes; for H2O, the adsorption properties were almost independent of particle size. The presence of low-coordinated adsorption sites resulted in a trend for stronger adsorption and greater charge transfer for smaller clusters. Fixing the size-independent factors (e.g., type of metal), our results show that CO2 adsorption on transition-metal clusters is significantly affected by particle size, suggesting that substrate particle size could be a key factor to understand and control the catalytic transformations of CO2.
In this study, we report an ab initio screening, based on density functional theory calculations, of Pt-based transition-metal nanoalloys using physicochemical descriptors derived from the adsorption ...and activation of CO2 on 55-atom nanoclusters, namely, PtnTM55−n, with n = 0, 13, 42, 55, TM = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Au. From the adsorption on the unary and binary nanoclusters, at the chemisorption regime (bent CO2), we identified a linear correlation between the interaction energy and charge transfer from the nanoclusters towards CO2 and the bent CO2 angle; moreover, the interaction energy is enhanced for larger values of the molecular charge and angle. The alloying of Cu55, Ag55, and Au55 with Pt provides a path to change the CO2 adsorption from physisorption (linear, non-activated) to chemisorption (enhanced interaction energies, bent, activated), while the strong interaction energy of CO2 with Os55, Ru55, and Fe55 can be decreased by alloying with Pt using different structural configurations, i.e., the trends are similar for core–shell and segregated structures. Thus, based on our results and analyses, we can select different combinations of PtnTM55−n nanoalloys to yield the desired interaction strength and magnitude of the charge transfer towards the activated anionic CO2, which can help in the design of nanocatalysts for CO2 activation or different chemical reactions in which charge transfer plays a crucial role.
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