Source localization and denoising: a perspective from the TDOA space

In this manuscript, we formulate the problem of denoising Time Differences of Arrival (TDOAs) in the TDOA space, i.e. the Euclidean space spanned by TDOA measurements. The method consists of pre-processing the TDOAs with the purpose of reducing the measurement noise. The complete set of TDOAs (i.e., TDOAs computed at all microphone pairs) is known to form a redundant set, which lies on a linear subspace in the TDOA space. Noise, however, prevents TDOAs from lying exactly on this subspace. We therefore show that TDOA denoising can be seen as a projection operation that suppresses the component of the noise that is orthogonal to that linear subspace. We then generalize the projection operator also to the cases where the set of TDOAs is incomplete. We analytically show that this operator improves the localization accuracy, and we further confirm that via simulation.Comment: 25 pages, 9 figure

Nonylphenol and octylphenol differently affect cell redox balance by modulating the nitric oxide signaling

Nonylphenol (NP) and octylphenol (OP) are pervasive environmental contaminants belonging to the broader class of compounds known as alkylphenols, with potential human toxic effects. Classified as "xenoestrogens," NP and OP are able to interfere with the cell endocrine physiology via a direct interaction with the estrogen receptors. Here, using HepG2 cells in culture, the changes of the cell redox balance and mitochondrial activity induced by OP and NP have been investigated at mu M concentrations, largely below those provoking acute toxicity, as those typical of environmental contaminants. Following 24 h cell exposure to both OP and NP, ROS production appeared significantly increased (p <= 0.01), together with the production of higher NO oxides (p = 0.003) and peroxynitrated protein-derivatives (NP versus CTR, p = 0.003). The mitochondrial proton electrochemical potential gradient instead was decreased (p <= 0.05), as the oxygen consumption by complex IV, particularly following incubation with NP (NP versus CTR, p = 0.017). Consistently, the RT-PCR and Western blot analyses proved that the OP and NP can modulate to a different extent the expression of the inducible NOS (NP versus CTR, p <= 0.01) and the endothelial NOS (OP versus CTR, p <= 0.05), with a significant variation of the coupling efficiency of the latter (NP versus CTR, p <= 0.05), a finding that may provide a novel clue to understand the specific xenoestrogenic properties of OP and NP

Freeze-out conditions from net-proton and net-charge fluctuations at RHIC

We calculate ratios of higher-order susceptibilities quantifying fluctuations in the number of net protons and in the net-electric charge using the Hadron Resonance Gas (HRG) model. We take into account the effect of resonance decays, the kinematic acceptance cuts in rapidity, pseudo-rapidity and transverse momentum used in the experimental analysis, as well as a randomization of the isospin of nucleons in the hadronic phase. By comparing these results to the latest experimental data from the STAR collaboration, we determine the freeze-out conditions from net-electric charge and net-proton distributions and discuss their consistency.Comment: 7 pages, 6 figures, particle ratio figure adde

Nitric oxide, cytochrome c oxidase and myoglobin: Competition and reaction pathways

AbstractIt is relevant to cell physiology that nitric oxide (NO) reacts with both cytochrome oxidase (CcOX) and oxygenated myoglobin (MbO2). In this respect, it has been proposed [Pearce, L.L., et al. (2002) J. Biol. Chem. 277, 13556–13562] that (i) CcOX in turnover out-competes MbO2 for NO, and (ii) NO bound to reduced CcOX is “metabolized” in the active site to nitrite by reacting with O2. In contrast, rapid kinetics experiments reported in this study show that (i) upon mixing NO with MbO2 and CcOX in turnover, MbO2 out-competes the oxidase for NO and (ii) after mixing nitrosylated CcOX with O2 in the presence of MbO2, NO (and not nitrite) dissociates from the enzyme causing myoglobin oxidation

Evidence for detrimental cross interactions between reactive oxygen and nitrogen species in Leber's hereditary optic neuropathy cells

Here we have collected evidence suggesting that chronic changes in the NO homeostasis and the rise of reactive oxygen species bioavailability can contribute to cell dysfunction in Leber’s hereditary optic neuropathy (LHON) patients.We report that peripheral blood mononuclear cells (PBMCs), derived froma female LHON patient with bilateral reduced vision and carrying the pathogenic mutation 11778/ND4, display increased levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS), as revealed by flow cytometry, fluorometric measurements of nitrite/nitrate, and 3-nitrotyrosine immunodetection. Moreover, viability assays with the tetrazolium dye MTT showed that lymphoblasts from the same patient are more sensitive to prolonged NO exposure, leading to cell death. Taken together these findings suggest that oxidative and nitrosative stress cooperatively play an important role in driving LHON pathology when excess NO remains available over time in the cell environment