10,340 research outputs found
Isospin dependence of nucleon effective mass in Dirac Brueckner-Hartree-Fock approach
The isospin dependence of the nucleon effective mass is investigated in the
framework of the Dirac Brueckner-Hartree-Fock (DBHF) approach. The definition
of nucleon scalar and vector effective masses in the relativistic approach is
clarified. Only the vector effective mass is the quantity related to the
empirical value extracted from the analysis in the nonrelatiistic shell and
optical potentials. In the relativistic mean field theory, where the nucleon
scalar and vector potentials are both energy independent, the neutron vector
potential is stronger than that of proton in the neutron rich nuclear matter,
which produces a smaller neutron vector effective mass than that of proton. It
is pointed out that the energy dependence of nucleon potentials has to be
considered in the analysis of the isospin dependence of the nucleon effective
mass. In the DBHF the neutron vector effective mass is larger than that of
proton once the energy dependence of nucleon potentials is considered. The
results are consistent with the analysis of phenomenological isospin dependent
optical potentials.Comment: 4 pages, 3 Postscript figure
Aging-associated Alteration in the Cardiac MIF-AMPK Cascade in Response to Ischemic Stress
An important role for a macrophage migration inhibitory factor (MIF)-AMP-activated protein kinase (AMPK) signaling pathway in ameliorating myocardial damage following ischemia/reperfusion has been described. An aging-associated reduction in AMPK activity may be associated with a decline in the ability of cardiac cells to activate the MIF-AMPK cascade, thereby resulting in reduced tolerance to ischemic insults. To test this hypothesis, _in vivo_ regional ischemia was induced by occlusion of the left anterior descending (LAD) coronary artery in young (4-6 months) and aged (24-26 months) mice. The ischemic AMPK activation response was impaired in aged hearts compared to young ones (p<0.01). Notably, cardiac MIF expression in aged hearts was lower than in young hearts (p<0.01). Dual staining data clearly demonstrated larger infarct size in aged hearts following ischemia and reperfusion compared to young hearts (p<0.05). Ischemia-induced AMPK activation in MIF knock out (MIF KO) hearts was blunted, leading to greater contractile dysfunction of MIF KO cardiomyocytes during hypoxia than that of wild type (WT) cardiomyocytes. Finally exogenous recombinant MIF significantly reversed the contractile dysfunction of aged cardiomyocytes in response to hypoxia. We conclude that an aging-associated reduction in ischemic AMPK activation contributes to ischemic intolerance in aged hearts
Deletion of annexin 2 light chain p11 in nociceptors causes deficits in somatosensory coding and pain behavior
The S100 family protein p11 (S100A10, annexin 2 light chain) is involved in the trafficking of the voltage-gated sodium channel Na(V)1.8, TWIK-related acid-sensitive K+ channel (TASK-1), the ligand-gated ion channels acid-sensing ion channel 1a (ASIC1a) and transient receptor potential vanilloid 5/6 (TRPV5/V6), as well as 5-hydroxytryptamine receptor 1B (5-HT1B), a G-protein-coupled receptor. To evaluate the role of p11 in peripheral pain pathways, we generated a loxP-flanked (floxed) p11 mouse and used the Cre-loxP recombinase system to delete p11 exclusively from nociceptive primary sensory neurons in mice. p11-null neurons showed deficits in the expression of NaV1.8, but not of annexin 2. Damage-sensing primary neurons from these animals show a reduced tetrodotoxin-resistant sodium current density, consistent with a loss of membrane-associated NaV1.8. Noxious coding in wide-dynamic-range neurons in the dorsal horn was markedly compromised. Acute pain behavior was attenuated in certain models, but no deficits in inflammatory pain were observed. A significant deficit in neuropathic pain behavior was also apparent in the conditional-null mice. These results confirm an important role for p11 in nociceptor function
Muon anomalous magnetic moment in technicolor models
Contributions to the muon anomalous magnetic moment are evaluated in the
technicolor model with scalars and topcolor assisted technicolor model. In the
technicolor model with scalars, the additional contributions come from the
loops of scalars, which were found sizable only for a very large
disfavored by the experiment of . The topcolor effect is also
found to be large only for an unnaturally large , and thus the
previously evaluated loop effects of extended technicolor bosons, suppressed by
, must be resorted to account for the E821 experiment. So,
if the E821 experiment result persists, it would be a challenge to technicolor
models.Comment: refs and comments adde
Gradient-less Federated Gradient Boosting Trees with Learnable Learning Rates
The privacy-sensitive nature of decentralized datasets and the robustness of
eXtreme Gradient Boosting (XGBoost) on tabular data raise the needs to train
XGBoost in the context of federated learning (FL). Existing works on federated
XGBoost in the horizontal setting rely on the sharing of gradients, which
induce per-node level communication frequency and serious privacy concerns. To
alleviate these problems, we develop an innovative framework for horizontal
federated XGBoost which does not depend on the sharing of gradients and
simultaneously boosts privacy and communication efficiency by making the
learning rates of the aggregated tree ensembles learnable. We conduct extensive
evaluations on various classification and regression datasets, showing our
approach achieves performance comparable to the state-of-the-art method and
effectively improves communication efficiency by lowering both communication
rounds and communication overhead by factors ranging from 25x to 700x.Comment: Accepted at the 3rd ACM Workshop on Machine Learning and Systems
(EuroMLSys), May 8th 2023, Rome, Ital
Non-universal gauge bosons and lepton flavor-violation tau decays
There are many models beyond the standard model predicting the existence of
non-universal gauge bosons , which can give rise to very rich
phenomena. We calculate the contributions of the non-universal gauge bosons
, predicted by topcolor-assisted technicolor (TC2) models and
flavor-universal TC2 models, to the lepton flavor-violation tau decays and . We find that the branching ratio
is larger than that of the process
in all of the parameter space. Over a sizable
region of the parameter space, we have , which may be detected in the future experiments.Comment: Final version to appear in Phys. Lett. B. References added and typos
correcte
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Using Design of Experiments in Finite Element Modeling to Identify Critical Variables for Laser Powder Bed Fusion
Input of accurate material and simulation parameters is critical for accurate predictions in
Laser Powder Bed Fusion (L-PBF) Finite Element Analysis (FEA). It is challenging and
resource consuming to run experiments that measure and control all possible material properties
and process parameters. In this research, we developed a 3-dimensional thermal L-PBF FEA
model for a single track laser scan on one layer of metal powder above a solid metal substrate.
We applied a design of experiments (DOE) approach which varies simulation parameters to
identify critical variables in L-PBF. DOE is an exploratory tool for examining a large number of
factors and alternative modeling approaches. It also determines which approaches can best
predict L-PBF process performance.Mechanical Engineerin
Topcolor assisted technicolor models and muon anomalous magnetic moment
We discuss and estimate the contributions of the new particles predicted by
topcolor assisted technicolor(TC2) models to the muon anomalous magnetic moment
. Our results show that the contributions of Pseudo Goldstone bosons
are very small which can be safely ignored. The main contributions come from
the ETC gauge boson and topcolor gauge boson . If we
demand that the mass of is consistent with other experimental
constrains, its contributions are smaller than that of . With
reasonable values of the parameters in TC2 models, the observed BNL results for
could be explained.Comment: latex file, 11 pages, several figures and references adde
HDX-guided EPR spectroscopy to interrogate membrane protein dynamics
This project was supported by a Biotechnology and Biological Sciences Research Council (BBSRC) grant (BB/S018069/1) to C.P., who also acknowledges support from the Wellcome Trust (WT) (219999/Z/19/Z) and the Chinese Scholarship Council (CSC) in the form of studentships for B.J.L. and B.W., respectively. A.N.C. is a Sir Henry Dale Fellow jointly funded by the WT and the Royal Society (220628/Z/20/Z). Funding from the BBSRC (BB/M012573/1) enabled the purchase of mass spectrometry equipment.Solvent accessibilities of and distances between protein residues measured by pulsed-EPR approaches provide high-resolution information on dynamic protein motions. We describe protocols for the purification and site-directed spin labeling of integral membrane proteins. In our protocol, peptide-level HDX-MS is used as a precursor to guide single-residue resolution ESEEM accessibility measurements and spin labeling strategies for EPR applications. Exploiting the pentameric MscL channel as a model, we discuss the use of cwEPR, DEER/PELDOR, and ESEEM spectroscopies to interrogate membrane protein dynamics. For complete details on the use and execution of this protocol, please refer to Wang et al. (2022).Publisher PDFPeer reviewe
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