94 research outputs found

    13[C]-Urea Breath Test as a Novel Point-of-Care Biomarker for Tuberculosis Treatment and Diagnosis

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    BACKGROUND: Pathogen-specific metabolic pathways may be detected by breath tests based on introduction of stable isotopically-labeled substrates and detection of labeled products in exhaled breath using portable infrared spectrometers. METHODOLOGY/PRINCIPAL FINDINGS: We tested whether mycobacterial urease activity could be utilized in such a breath test format as the basis of a novel biomarker and diagnostic for pulmonary TB. Sensitized New-Zealand White Rabbits underwent bronchoscopic infection with either Mycobacterium bovis or Mycobacterium tuberculosis. Rabbits were treated with 25 mg/kg of isoniazid (INH) approximately 2 months after infection when significant cavitary lung pathology was present. [(13)C] urea was instilled directly into the lungs of intubated rabbits at selected time points, exhaled air samples analyzed, and the kinetics of delta(13)CO(2) formation were determined. Samples obtained prior to inoculation served as control samples for background (13)CO(2) conversion in the rabbit model. (13)CO(2), from metabolic conversion of [(13)C]-urea by mycobacterial urease activity, was readily detectable in the exhaled breath of infected rabbits within 15 minutes of administration. Analyses showed a rapid increase in the rate of (13)CO(2) formation both early in disease and prior to treatment with INH. Following INH treatment, all evaluable rabbits showed a decrease in the rate of (13)CO(2) formation. CONCLUSIONS/SIGNIFICANCE: Urea breath testing may provide a useful diagnostic and biomarker assay for tuberculosis and for treatment response. Future work will test specificity for M. tuberculosis using lung-targeted dry powder inhalation formulations, combined with co-administering oral urease inhibitors together with a saturating oral dose of unlabeled urea, which would prevent the delta(13)CO(2) signal from urease-positive gastrointestinal organisms

    Event-by-event correlations between Λ\Lambda (Λˉ\bar{\Lambda}) hyperon global polarization and handedness with charged hadron azimuthal separation in Au+Au collisions at sNN=27 GeV\sqrt{s_{\text{NN}}} = 27 \text{ GeV} from STAR

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    Global polarizations (PP) of Λ\Lambda (Λˉ\bar{\Lambda}) hyperons have been observed in non-central heavy-ion collisions. The strong magnetic field primarily created by the spectator protons in such collisions would split the Λ\Lambda and Λˉ\bar{\Lambda} global polarizations (ΔP=PΛPΛˉ<0\Delta P = P_{\Lambda} - P_{\bar{\Lambda}} < 0). Additionally, quantum chromodynamics (QCD) predicts topological charge fluctuations in vacuum, resulting in a chirality imbalance or parity violation in a local domain. This would give rise to an imbalance (Δn=NLNRNL+NR0\Delta n = \frac{N_{\text{L}} - N_{\text{R}}}{\langle N_{\text{L}} + N_{\text{R}} \rangle} \neq 0) between left- and right-handed Λ\Lambda (Λˉ\bar{\Lambda}) as well as a charge separation along the magnetic field, referred to as the chiral magnetic effect (CME). This charge separation can be characterized by the parity-even azimuthal correlator (Δγ\Delta\gamma) and parity-odd azimuthal harmonic observable (Δa1\Delta a_{1}). Measurements of ΔP\Delta P, Δγ\Delta\gamma, and Δa1\Delta a_{1} have not led to definitive conclusions concerning the CME or the magnetic field, and Δn\Delta n has not been measured previously. Correlations among these observables may reveal new insights. This paper reports measurements of correlation between Δn\Delta n and Δa1\Delta a_{1}, which is sensitive to chirality fluctuations, and correlation between ΔP\Delta P and Δγ\Delta\gamma sensitive to magnetic field in Au+Au collisions at 27 GeV. For both measurements, no correlations have been observed beyond statistical fluctuations.Comment: 10 pages, 10 figures; paper from the STAR Collaboratio

    Hyperon polarization along the beam direction relative to the second and third harmonic event planes in isobar collisions at sNN\sqrt{s_{NN}} = 200 GeV

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    The polarization of Λ\Lambda and Λˉ\bar{\Lambda} hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at sNN\sqrt{s_{NN}} = 200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pTp_T dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagree with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pTp_T dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.Comment: 6 pages, 5 figures, Published in Physical Review Letter

    Observation of the electromagnetic field effect via charge-dependent directed flow in heavy-ion collisions at the Relativistic Heavy Ion Collider

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    The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Non-central collisions can produce strong magnetic fields on the order of 101810^{18} Gauss, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and anti-quarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v1(y)v_1(\mathsf{y}). Here we present the charge-dependent measurements of dv1/dydv_1/d\mathsf{y} near midrapidities for π±\pi^{\pm}, K±K^{\pm}, and p(pˉ)p(\bar{p}) in Au+Au and isobar (4496_{44}^{96}Ru+4496_{44}^{96}Ru and 4096_{40}^{96}Zr+4096_{40}^{96}Zr) collisions at sNN=\sqrt{s_{\rm NN}}= 200 GeV, and in Au+Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the v1v_1 signal on collision system, particle species, and collision centrality can be qualitatively and semi-quantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the uu and dd quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations

    Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

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    The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen with a significance of 1--3 standard deviations in mid-central (intermediate impact parameter) collisions. Significant residual background effects may, however, still be present.Comment: 8 pages, 3 figure
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