Comment on Ricci Collineations of Static Spherically Symmetric Spacetimes

We present a counter example to a theorem given by Amir {\em et al.} J. Math. Phys. {\bf 35}, 3005 (1994). We also comment on a misleading statements of the same reference.Comment: 4 pages,LaTex fil

Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger Observatory

The combined fit of the measured energy spectrum and shower maximum depth distributions of ultra-high-energy cosmic rays is known to constrain the parameters of astrophysical models with homogeneous source distributions. Studies of the distribution of the cosmic-ray arrival directions show a better agreement with models in which a fraction of the flux is non-isotropic and associated with the nearby radio galaxy Centaurus A or with catalogs such as that of starburst galaxies. Here, we present a novel combination of both analyses by a simultaneous fit of arrival directions, energy spectrum, and composition data measured at the Pierre Auger Observatory. The model takes into account a rigidity-dependent magnetic field blurring and an energy-dependent evolution of the catalog contribution shaped by interactions during propagation. We find that a model containing a flux contribution from the starburst galaxy catalog of around 20% at 40 EeV with a magnetic field blurring of around 20° for a rigidity of 10 EV provides a fair simultaneous description of all three observables. The starburst galaxy model is favored with a significance of 4.5σ (considering experimental systematic effects) compared to a reference model with only homogeneously distributed background sources. By investigating a scenario with Centaurus A as a single source in combination with the homogeneous background, we confirm that this region of the sky provides the dominant contribution to the observed anisotropy signal. Models containing a catalog of jetted active galactic nuclei whose flux scales with the γ-ray emission are, however, disfavored as they cannot adequately describe the measured arrival directions

AugerPrime surface detector electronics

Operating since 2004, the Pierre Auger Observatory has led to major advances in our understanding of the ultra-high-energy cosmic rays. The latest findings have revealed new insights that led to the upgrade of the Observatory, with the primary goal of obtaining information on the primary mass of the most energetic cosmic rays on a shower-by-shower basis. In the framework of the upgrade, called AugerPrime, the 1660 water-Cherenkov detectors of the surface array are equipped with plastic scintillators and radio antennas, allowing us to enhance the composition sensitivity. To accommodate new detectors and to increase experimental capabilities, the electronics is also upgraded. This includes better timing with up-to-date GPS receivers, higher sampling frequency, increased dynamic range, and more powerful local processing of the data. In this paper, the design characteristics of the new electronics and the enhanced dynamic range will be described. The manufacturing and test processes will be outlined and the test results will be discussed. The calibration of the SD detector and various performance parameters obtained from the analysis of thefirst commissioning data will also be presented

Sesterterpenoids in marine and terrestrial organisms: a relational database

Sesterterpenoids (SSTPs) are pentaprenyl terpenoids derived from the linear precursor geranylfarnesyl diphosphate, which have been isolated from fungi, bacteria, lichens, plants, insects, and various marine invertebrates, especially sponges. To define a schema of knowledge organization on this topic, it was necessary to collect skills from various disciplines such as chemistry, botany, biology, ecology, pharmacology and others. This joint effort led to the definition of a rather detailed conceptual model which was then instantiated in a logical diagram to define the database used in this project [1]. This database contains all the basic concepts, starting with the name of the molecule, the chemical class, the organisms from which it was first extracted, potential bioactivity properties, and major extraction method procedures. Bibliographic references are stored for each passage of information. A public website has been created to visualize and consult the collected material, to share database maintenance activities among managers, and to provide automatic links with other accredited databases for easy and timely updating of the information. Literature covers the years 1918 to 2023 and includes about 2000 SSTPs, classified according to their structural complexity, from linear pentaprenyl to carbocyclic and heterocyclic scaffolds. Marine and terrestrial organismal sources are reported, and also, when possible, the synthetic origin of their SSTPs repertoire. A variety of bioactivities were described, ranging from cytotoxicity against human cancer cells and inhibition of pathogenic microbes, to anti-inflammatory, antiprotozoal, antitubercular and antifeedant activities and modulation of neurodegenerative processes, as well as activity in the treatment of metabolic diseases such as type II diabetes, hypercholesterolemia and obesity, and as immunosuppressive molecules

Isolation of Acacetin from <i>Calea urticifolia</i> with Inhibitory Properties against Human Monoamine Oxidase‑A and -B

<i>Calea urticifolia</i> (Asteraceae: Asteroideae) has long been used as a traditional medicine in El Salvador to treat arthritis and fever, among other illnesses. The chloroform extract of the leaves of <i>C. urticifolia</i> showed potent inhibition of recombinant human monoamine oxidases (MAO-A and -B). Further bioassay-guided fractionation led to the isolation of a flavonoid, acacetin, as the most prominent MAO inhibitory constituent, with IC₅₀ values of 121 and 49 nM for MAO-A and -B, respectively. The potency of MAO inhibition by acacetin was >5-fold higher for MAO-A (0.121 μM vs 0.640 μM) and >22-fold higher for MAO-B (0.049 μM vs 1.12 μM) as compared to apigenin, the closest flavone structural analogue. Interaction and binding characteristics of acacetin with MAO-A and -B were determined by enzyme-kinetic assays, enzyme–inhibitor complex binding, equilibrium–dialysis dissociation analyses, and computation analysis. Follow-up studies showed reversible binding of acacetin with human MAO-A and -B, resulting in competitive inhibition. Acacetin showed more preference toward MAO-B than to MAO-A, suggesting its potential for eliciting selective pharmacological effects that might be useful in the treatment of neurological and psychiatric disorders. In addition, the binding modes of acacetin at the enzymatic site of MAO-A and -B were predicted through molecular modeling algorithms, illustrating the high importance of ligand interaction with negative and positive free energy regions of the enzyme active site

Ga-Promoted Photocatalytic H₂ Production over Pt/ZnO Nanostructures

Photocatalytic H₂ generation is investigated over a series of Ga-modified ZnO photocatalysts that were prepared by hydrothermal methods. It is found that the structural, textural, and optoelectronic properties remarkably depend on the Ga content. The photocatalytic activity is higher in samples with Ga content equal to or lower than 5.4 wt %, which are constituted by Zn_1–<i>x</i>Ga_<i>x</i>O phases. Structural, textural, and optoelectronic characterization, combined with theoretical calculations, reveals the effect of Ga in the doped ZnO structures. Higher Ga incorporation leads to the formation of an additional ZnGa₂O₄ phase with spinel structure. The presence of such a phase is detrimental for the textural and optoelectronic properties of the photocatalysts, leading to a decrease in H₂ production. When Pt is used as the cocatalyst, there is an increase of 1 order of magnitude in the activity with respect to the bare photocatalysts. This is a result of Pt acting as an electron scavenger, decreasing the electron–hole recombination rate and boosting the H₂ evolution reaction

Unraveling the Factors That Control Soft Landing of Small Silyl Ions on Fluorinated Self-Assembled Monolayers

Dynamics simulations were performed to study soft landing of SiNCS⁺ and (CH₃)₂SiNCS⁺ ions on a self-assembled monolayer of perfluorinated alkanethiols on gold (F-SAM). Using classical trajectories, the short-time collision dynamics (picosecond scale) were investigated to analyze trapping probabilities for these silyl ions. Thermal desorption of trapped ions was simulated by using “boxed molecular dynamics” (BXD). The simulations predict substantial ion trapping in the collisions of these ions with the F-SAM, especially when the projectile’s incident direction is normal to the surface. Desorption of the SiNCS⁺ ion occurs significantly faster than desorption of the methylated ion, which may explain why soft landing was experimentally observed for the latter ion only [Miller, S. A.; Luo, H.; Pachuta, S. J.; Cooks, R. G. <i>Science</i> <b>1997</b>, <i>275</i>, 1447–1450; Luo, H.; Miller, S. A.; Cooks, R. G.; Pachuta, S. J. <i>Int. J. Mass. Spectrom. Ion Processes</i> <b>1998</b>, <i>174</i>, 193–217]. The free energy profiles for desorption of these ions show minima at 15 Å above the gold slab, indicating that the silyl ion has a preference to reside on top of the monolayer. Deep penetration of the ion into the monolayer is prevented by a large free energy barrier. However, according to DFT calculations, if this process occurred, the SiNCS⁺ ion could strongly bind to the Au(111) surface that supports the perfluorinated alkanethiol chains