172 research outputs found
Depleted 15N in hydrolysable-N of arctic soils and its implication for mycorrhizal fungi–plant interaction
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 97 (2009): 183-194, doi:10.1007/s10533-009-9365-1.Uptake of nitrogen (N) via root-mycorrhizal associations accounts for a significant portion of
total N supply to many vascular plants. Using stable isotope ratios (δ15N) and the mass balance
among N pools of plants, fungal tissues, and soils, a number of efforts have been made in recent
years to quantify the flux of N from mycorrhizal fungi to host plants. Current estimates of this
flux for arctic tundra ecosystems rely on the untested assumption that the δ15N of labile organic
N taken up by the fungi is approximately the same as the δ15N of bulk soil. We report here
hydrolysable amino acids are more depleted in 15N relative to hydrolysable ammonium and
amino sugars in arctic tundra soils near Toolik Lake, Alaska, USA. We demonstrate, using a
case study, that recognizing the depletion in 15N for hydrolysable amino acids (δ15N = -5.6 ‰ on
average) would alter recent estimates of N flux between mycorrhizal fungi and host plants in an
arctic tundra ecosystem.This study was funded by NSF-DEB-0423385and NSF-DEB 0444592.
Additional support was provided by Arctic Long Term Ecological Research program, funded by
National Science Foundation, Division of Environmental Biology
The Immune System in Stroke
Stroke represents an unresolved challenge for both developed and developing countries and has a huge socio-economic impact. Although considerable effort has been made to limit stroke incidence and improve outcome, strategies aimed at protecting injured neurons in the brain have all failed. This failure is likely to be due to both the incompleteness of modelling the disease and its causes in experimental research, and also the lack of understanding of how systemic mechanisms lead to an acute cerebrovascular event or contribute to outcome. Inflammation has been implicated in all forms of brain injury and it is now clear that immune mechanisms profoundly influence (and are responsible for the development of) risk and causation of stroke, and the outcome following the onset of cerebral ischemia. Until very recently, systemic inflammatory mechanisms, with respect to common comorbidities in stroke, have largely been ignored in experimental studies. The main aim is therefore to understand interactions between the immune system and brain injury in order to develop novel therapeutic approaches. Recent data from clinical and experimental research clearly show that systemic inflammatory diseases -such as atherosclerosis, obesity, diabetes or infection - similar to stress and advanced age, are associated with dysregulated immune responses which can profoundly contribute to cerebrovascular inflammation and injury in the central nervous system. In this review, we summarize recent advances in the field of inflammation and stroke, focusing on the challenges of translation between pre-clinical and clinical studies, and potential anti-inflammatory/immunomodulatory therapeutic approaches
Observation of Two New Excited Ξb0 States Decaying to Λb0 K-π+
Two narrow resonant states are observed in the Λb0K-π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb-1. The minimal quark content of the Λb0K-π+ system indicates that these are excited Ξb0 baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m[Ξb(6327)0]=6327.28-0.21+0.23±0.12±0.24 and m[Ξb(6333)0]=6332.69-0.18+0.17±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41-0.27+0.26±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξb(6327)0]<2.20(2.56) and Γ[Ξb(6333)0]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξb0 resonances
Precision measurement of violation in the penguin-mediated decay
A flavor-tagged time-dependent angular analysis of the decay
is performed using collision data collected
by the LHCb experiment at % at TeV, the center-of-mass energy of
13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The
-violating phase and direct -violation parameter are measured
to be rad and
, respectively, assuming the same values
for all polarization states of the system. In these results, the
first uncertainties are statistical and the second systematic. These parameters
are also determined separately for each polarization state, showing no evidence
for polarization dependence. The results are combined with previous LHCb
measurements using collisions at center-of-mass energies of 7 and 8 TeV,
yielding rad and . This is the most precise study of time-dependent violation
in a penguin-dominated meson decay. The results are consistent with
symmetry and with the Standard Model predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-001.html (LHCb
public pages
Measurement of the differential branching fraction
The branching fraction of the rare decay is measured for the first time, in the squared dimuon mass
intervals, , excluding the and regions. The data
sample analyzed was collected by the LHCb experiment at center-of-mass energies
of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of $9\
\mathrm{fb}^{-1}q^{2}q^{2} >15.0\
\mathrm{GeV}^2/c^4$, where theoretical predictions have the smallest model
dependence, agrees with the predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-050.html (LHCb
public pages
Search for beautiful tetraquarks in the <i>ϒ</i>(1<i>S</i>)μ<sup>+</sup>μ<sup>−</sup> invariant-mass spectrum
International audienceThe ϒ(1S)μμ invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two quarks, . The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range [2.0, 5.0], and the state has rapidity in the range [2.0, 4.5] and transverse momentum less than 15 GeV/c
Measurement of the CKM angle γ using<i> B</i><sup>±</sup> → <i>DK</i><sup>±</sup> with D → K <sub>S</sub> <sup>0</sup> π<sup>+</sup>π<sup>−</sup>, K <sub>S</sub> <sup>0</sup> K<sup>+</sup>K<sup>−</sup> decays
A binned Dalitz plot analysis of decays, with and , is used to perform a
measurement of the CP-violating observables and , which are
sensitive to the Cabibbo-Kobayashi-Maskawa angle . The analysis is
performed without assuming any decay model, through the use of information
on the strong-phase variation over the Dalitz plot from the CLEO collaboration.
Using a sample of proton-proton collision data collected with the LHCb
experiment in 2015 and 2016, and corresponding to an integrated luminosity of
2.0, the values of the CP violation parameters are found to
be , , , and . The first
uncertainty is statistical, the second is systematic, and the third is due to
the uncertainty on the strong-phase measurements. These values are used to
obtain \gamma = \left(87\,^{+11}_{-12}\right)^\circ, , and , where is the ratio
between the suppressed and favoured -decay amplitudes and is the
corresponding strong-interaction phase difference. This measurement is combined
with the result obtained using 2011 and 2012 data collected with the \lhcb
experiment, to give \gamma = \left(80\,^{+10}_{\,-9}\right)^\circ, , and .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2018-017.html.
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