The extension of Standard Model made by inclusion of additional $U(1)$ gauge
$L_\mu-L_\tau$ symmetry can explain the difference between the measured and the
predicted value of the muon magnetic ...moment and solve the tension in $B$ meson
decays. This model predicts the existence of a new, light $Z^\prime$ vector
boson, predominantly coupled to second and third generation leptons, whose
interaction with electrons is due to a loop mechanism involving muons and taus.
In this work, we present a rigorous evaluation of the upper limits in the
$Z^\prime$ parameter space, obtained from the analysis of the data collected by
the NA64-$e$ experiment at CERN SPS, that performed a search for light dark
matter with $2.84\times10^{11}$ electrons impinging with 100 GeV on an active
thick target. The resulting limits, despite being included in a region already
investigated by neutrino experiments,touch the muon $g-2$ preferred band for
values of the $Z^\prime$ mass of order of 1 MeV. The sensitivity projections
for the future high-statistics NA64-$e$ runs demonstrate the power of the
electrons/positron beam approach in this theoretical scenario.
The tellurium oxyanion, tellurite, is extremely noxious to most living organisms. Its toxicity has been mainly related to the generation of reactive oxygen species (ROS) as well as to an unbalancing ...of the thiol:redox buffering system. Nevertheless, a few bacteria are capable of thriving at high tellurite concentrations. One mechanism of resistance is the enzymatic and non-enzymatic reduction of tellurite to the less toxic elemental tellurium. This reduction generates nano- to micrometric tellurium crystals that display different shapes and sizes.
To date, a very limited number of highly tellurite-resistant and tellurite-reducing bacterial species are available from international culture collections. In this work, we decided to look for tellurite-reducing bacteria from an extreme environment, Antarctica. This environment exhibits a combination of several extreme factors such as high UV-radiation and desiccation and freezing conditions that impact directly on the local biodiversity. Since, as does, all these factors induce ROS formation, we hypothesized that Antarctic bacteria could also exhibit tellurite-resistance. In this context, we isolated 123 tellurite-resistant bacteria, and characterized six new tellurite-resistant and tellurite-reducing bacterial strains from samples collected in Antarctica. These strains were identified according to their 16S rRNA gene sequence as Staphylococcus hameolyticus, Staphylococcus sciuri, Acinetobacter haemolyticus, Pseudomonas lini, and two strains of Psychrobacter immobilis.
The isolates display tellurite-resistance about 35- to 500-fold higher than Escherichia coli (Te-sensitive organism), and a high level of tellurite reduction which might be interesting for an application in the field of bioremediation or nanoparticle biosynthesis.
We report the results of a search for a light pseudoscalar particle $a$ that
couples to electrons and decays to $e^+e^-$ performed using the high-energy
CERN SPS H4 electron beam. If such ...pseudoscalar with a mass $\simeq 17$ MeV
exists, it could explain the ATOMKI anomaly. We used the NA64 data samples
collected in the "visible mode" configuration with total statistics
corresponding to $8.4\times 10^{10}$ electrons on target (EOT) in 2017 and
2018. In order to increase sensitivity to small coupling parameter $\epsilon$
we used also the data collected in 2016-2018 in the "invisible mode"
configuration of NA64 with a total statistics corresponding to $2.84\times
10^{11}$ EOT. A thorough analysis of both these data samples in the sense of
background and efficiency estimations was already performed and reported in our
previous papers devoted to the search for light vector particles and axion-like
particles (ALP). In this work we recalculate the signal yields, which are
different due to different cross section and life time of a pseudoscalar
particle $a$, and perform a new statistical analysis. As a result, the region
of the two dimensional parameter space $m_a - \epsilon$ in the mass range from
1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of
$\epsilon$ in the range $2.1 \times 10^{-4} < \epsilon < 3.2 \times 10^{-4}$
are excluded.
Phys. Rev. D 101, 071101 (2020) The improved results on a direct search for a new X(16.7 MeV) boson which
could explain the anomalous excess of $e^+e^-$ pairs observed in the excited
8Be nucleus ...decays ("Berillium anomaly") are reported. Due to its coupling to
electrons, the X boson could be produced in the bremsstrahlung reaction e-Z ->
e-ZX by a high-energy beam of electrons incident on active target in the NA64
experiment at the CERN SPS and observed through its subsequent decay into
$e^+e^-$ pair. No evidence for such decays was found from the combined analysis
of the data samples with total statistics corresponding to 8.4\times 10^{10}
electrons on target collected in 2017 and 2018. This allows to set the new
limits on the $X$--$e^-$ coupling in the range 1.2 \times 10^{-4} < \epsilon_e
< 6.8 \times 10^{-4}, excluding part of the parameter space favored by the
Berillium anomaly. We also set new bounds on the mixing strength of photons
with dark photons (A') from non-observation of the decay $A' \to e^+e^-$ of the
bremsstrahlung A' with a mass below 24 MeV.
Tellurite, the most soluble tellurium oxyanion, is extremely harmful for most microorganisms. Part of this toxicity is due to the generation of reactive oxygen species that in turn cause oxidative ...stress. However, the way in which tellurite interferes with cellular processes is not well understood to date. Looking for new cellular tellurite targets, we decided to evaluate the functioning of the electron transport chain in tellurite-exposed cells. In this communication we show that the
E. coli ndh
gene, encoding NDH-II dehydrogenase, is significantly induced in toxicant-exposed cells and that the enzyme displays tellurite-reducing activity that results in increased superoxide levels in vitro.
The tellurium oxyanion tellurite is harmful for most microorganisms. Since its toxicity occurs chiefly once the toxicant reaches the intracellular compartment, unveiling the toxicant uptake process ...is crucial for understanding the whole phenomenon of tellurium toxicity. While the PitA phosphate transporter is thought to be one of the main paths responsible for toxicant entry into Escherichia coli, genetic and physiological evidence have identified the ActP acetate carrier as the main tellurite importer in Rhodobacter capsulatus. In this work, new background on the role of these transporters in tellurite uptake by E. coli is presented. It was found that, similar to what occurs in R. capsulatus, ActP is able to mediate toxicant entry to this bacterium. Lower reactive oxygen species levels were observed in E. coli lacking the actP gene.
Antioxidant enzyme catalase and fumarase C activity was almost unchanged after short exposure of E. coli ΔactP to sublethal tellurite concentrations, suggesting a low antioxidant response. In this strain, tellurite uptake decreased significantly during the first 5min of exposure and inductively coupled plasma optical emission spectroscopy assays using an actP-overexpressing strain confirmed that this carrier mediates toxicant uptake. Relative gene expression experiments by qPCR showed that actP expression is enhanced at short times of tellurite exposure, while pitA and pitB genes are induced later. Summarizing, the results show that ActP is involved in tellurite entry to E. coli and that its participation occurs mainly at early stages of toxicant exposure.
In this study, we present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c momentum. The analysis was ...performed using data collected by the NA64-\(e\) experiment in 2022. Our study is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64-ECAL and NA64-HCAL detectors. We determined the intrinsic hadronic contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those obtained in a dedicated setup, in which only hadrons impinged on the detector. The significant differences in the experimental signatures of electrons and hadrons motivated our approach, resulting in a small and well-controlled systematic uncertainty for the measurement. Our study allowed us to precisely determine the intrinsic hadronic contamination, which represents a crucial parameter for the NA64 experiment in which the hadron contaminants may result in non-trivial backgrounds. Moreover, we performed dedicated Monte Carlo simulations for the hadron production induced by the primary T2 target. We found a good agreement between measurements and simulation results, confirming the validity of the applied methodology and our evaluation of the intrinsic hadronic contamination.
The extension of Standard Model made by inclusion of additional \(U(1)\) gauge \(L_\mu-L_\tau\) symmetry can explain the difference between the measured and the predicted value of the muon magnetic ...moment and solve the tension in \(B\) meson decays. This model predicts the existence of a new, light \(Z^\prime\) vector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. In this work, we present a rigorous evaluation of the upper limits in the \(Z^\prime\) parameter space, obtained from the analysis of the data collected by the NA64-\(e\) experiment at CERN SPS, that performed a search for light dark matter with \(2.84\times10^{11}\) electrons impinging with 100 GeV on an active thick target. The resulting limits, despite being included in a region already investigated by neutrino experiments,touch the muon \(g-2\) preferred band for values of the \(Z^\prime\) mass of order of 1 MeV. The sensitivity projections for the future high-statistics NA64-\(e\) runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario.
Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Here, we used 503 forest ...inventory plots (93,719 individuals ≥2.5 cm diameter, 2609 species) to explore the relationships between local abundance, regional frequency and spatial aggregation of dominant species in four main habitat types in western Amazonia. Although the abundance‐occupancy relationship is positive for the full dataset, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade‐off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs). Given the importance of dominant species as drivers of diversity and ecosystem functioning, unravelling different dominance patterns is a research priority to direct conservation efforts in Amazonian forests.
Dominance of neotropical tree communities by a few species is widely documented, but dominant trees show a variety of distributional patterns still poorly understood. Contrary to the widely supported positive abundance‐occupancy relationship in ecology, we found that among dominant Amazonian tree species, there is a strong negative relationship between local abundance and regional frequency and/or spatial aggregation across habitat types. Our findings suggest an ecological trade‐off whereby dominant species can be locally abundant (local dominants) or regionally widespread (widespread dominants), but rarely both (oligarchs).
We report the results of a search for a light pseudoscalar particle \(a\) that couples to electrons and decays to \(e^+e^-\) performed using the high-energy CERN SPS H4 electron beam. If such ...pseudoscalar with a mass \(\simeq 17\) MeV exists, it could explain the ATOMKI anomaly. We used the NA64 data samples collected in the "visible mode" configuration with total statistics corresponding to \(8.4\times 10^{10}\) electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter \(\epsilon\) we used also the data collected in 2016-2018 in the "invisible mode" configuration of NA64 with a total statistics corresponding to \(2.84\times 10^{11}\) EOT. A thorough analysis of both these data samples in the sense of background and efficiency estimations was already performed and reported in our previous papers devoted to the search for light vector particles and axion-like particles (ALP). In this work we recalculate the signal yields, which are different due to different cross section and life time of a pseudoscalar particle \(a\), and perform a new statistical analysis. As a result, the region of the two dimensional parameter space \(m_a - \epsilon\) in the mass range from 1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of \(\epsilon\) in the range \(2.1 \times 10^{-4} < \epsilon < 3.2 \times 10^{-4}\) are excluded.
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