| 1. |
- Ablikim, M., et al.
(författare)
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Measurement of branching fractions for psi(3686) -> gamma eta ', gamma eta, and gamma pi(0)
- 2017
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 96:5
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Tidskriftsartikel (refereegranskat)abstract
- Using a data sample of 448 x 10(6) psi(3686) events collected with the BESIII detector operating at the BEPCII storage ring, the decays psi(3686) -> gamma eta and psi(3686) -> gamma pi(0) are observed with a statistical significance of 7.3 sigma and 6.7 sigma, respectively. The branching fractions are measured to be B(psi(3686) -> gamma eta) = (0.85 +/- 0.18 +/- 0.05) x 10(-6) and B(psi(3686) ->gamma pi(0)) = (0.95 +/- 0.16 +/- 0.05) x 10(-6). In addition, we measure the branching fraction of psi(3686) -> gamma eta' to be B(psi(3686) -> gamma eta') = (125.1 +/- 2.2 +/- 6.2)x10(-6), which represents an improvement of precision over previous results.
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| 14. |
- Lui, A. T. Y., et al.
(författare)
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Cluster observation of plasma flow reversal in the magnetotail during a substorm
- 2006
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Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 24:7, s. 2005-2013
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Tidskriftsartikel (refereegranskat)abstract
- We investigate in detail a reversal of plasma flow from tailward to earthward detected by Cluster at the downstream distance of similar to 19 RE in the midnight sector of the magnetotail on 22 August 2001. This flow reversal was accompanied by a sign reversal of the B-z component and occurred during the late substorm expansion phase as revealed by simultaneous global view of auroral activity from IMAGE. We examine the associated Hall current system signature, current density, electric field, Lorentz force, and current dissipation/dynamo term, the last two parameters being new features that have not been studied previously for plasma flow reversals. It is found that (1) there was no clear quadrupole Hall current system signature organized by the flow reversal time, (2) the x-component of the Lorentz force did not change sign while the other two did, (3) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source, (4) the electric field was occasionally dawnward, producing a dynamo effect, and (5) the electric field was occasionally larger at the high-latitude plasma sheet than near the neutral sheet. These observations are consistent with the current disruption model for substorms in which these disturbances are due to shifting dominance of multiple current disruption sites and turbulence at the observing location.
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| 15. |
- Lui, A. T. Y., et al.
(författare)
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Prelude to THEMIS tail conjunction study
- 2007
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Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 25:4, s. 1001-1009
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Tidskriftsartikel (refereegranskat)abstract
- A close conjunction of several satellites (LANL, GOES. Polar. Geotail, and Cluster) distributed from the geostationary altitude to about 16 R-E downstream in the tail occurred during substorm activity as indicated by global auroral imaging and ground-based magnetometer data. This constellation of satellites resembles what is planned for the THEMIS (Time History of Events and Macroscopic Interactions during Substorms) mission to resolve the substorm controversy on the location of the substorm expansion onset region. In this article, we show in detail the dipolarization and dynamic changes seen by these satellites associated with two onsets of substorm intensification activity. In particular, we find that dipolarization at similar to 16 R-E downstream in the tail can occur with dawnward electric field and without plasma flow, just like some near-Earth dipolarization events reported previously. The spreading of substorm disturbances in the tail coupled with complementary ground observations indicates that the observed time sequence on the onsets of substorm disturbances favors initiation in the near-Earth region for this THEMIS-like conjunction.
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| 16. |
- Zhang, L. Q., et al.
(författare)
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MMS Observation on the Cross-Tail Current Sheet Roll-up at the Dipolarization Front
- 2021
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 126:4
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Tidskriftsartikel (refereegranskat)abstract
- We perform a case study on the evolution of the current sheet in different regions around the dipolarization front (DF), including magnetic-dip preceding the DF, front at the DF, and magnetic pileup region (MPR) behind the DF based on magnetospheric multiscale (MMS) observation on July 31, 2017. In this event, MMS1 stays inside the current sheet during the whole bursty bulk flow (BBF) interval. Our analysis reveals that the cross-tail current sheet at the DF is rolled up, signified by the depression (-V-z/-B-z) at the dip and elevation (+V-z/+B-z) at the front. The minimum variance analysis on the magnetic field method is applied to obtain the normal direction of the current sheet. The result confirms the roll-up, that is, downward at the depressed current sheet and upward at the elevated current sheet. The current sheet roll-up at the DF is asymmetric, with steeper elevation than depression. The elevation angle of the elevated current sheet is evaluated to be similar to 30 degrees. Strong duskward and predominantly perpendicular J spike (similar to 90 nA/m(2)) concentrate at the interface between the dip and the front. The strength of the current of the J-spike is about nine/three times the current at the dip/front. The front is characterized by positive E center dot J. In the dip/MPR, no such preference is seen. Ion/Electron pitch angle distributions exhibit significant and different evolutions in the roll-up current sheet from dip to front, including their energy-dependence and distributions. Finally, the roll-up current sheet could decelerate BBF and change the flow structure. The potential significance of the roll-up current sheet on BBF evolution is emphasized.
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| 17. |
- Abdallah, H., et al.
(författare)
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Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with HESS
- 2016
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:11
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Tidskriftsartikel (refereegranskat)abstract
- The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using gamma-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant gamma-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section . These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach values of 6 x 10(-26) cm(3) s(-1) in the W+W- channel for a DM particle mass of 1.5 TeV, and 2 x 10(-26) cm(3) s(-1) in the tau(+)tau(-) channel for a 1 TeV mass. For the first time, ground-based gamma-ray observations have reached sufficient sensitivity to probe values expected from the thermal relic density for TeV DM particles.
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| 18. |
- Abramowski, A., et al.
(författare)
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Acceleration of petaelectronvolt protons in the Galactic Centre
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 531:7595, s. 476-479
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Tidskriftsartikel (refereegranskat)abstract
- Galactic cosmic rays reach energies of at least a few petaelectronvolts(1) (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators ('PeVatrons'), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies(2). Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 10(13) electronvolts) were inferred from recent gamma-ray observations(3). However, none of the currently known accelerators-not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays-has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of.-rays extending without a cut-off or a spectral break to tens of teraelectronvolts(4). Here we report deep.-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts(5) and an outflow from the Galactic Centre(6). Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 10(6)-10(7) years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.
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| 19. |
- Abramowski, A., et al.
(författare)
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Detailed spectral and morphological analysis of the shell type supernova remnant RCW 86
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 612
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We aim for an understanding of the morphological and spectral properties of the supernova remnant RCW 86 and for insights into the production mechanism leading to the RCW 86 very high-energy gamma-ray emission. Methods. We analyzed High Energy Spectroscopic System (H.E.S.S.) data that had increased sensitivity compared to the observations presented in the RCW 86 H.E.S.S. discovery publication. Studies of the morphological correlation between the 0.5-1 keV X-ray band, the 2-5 keV X-ray band, radio, and gamma-ray emissions have been performed as well as broadband modeling of the spectral energy distribution with two different emission models. Results. We present the first conclusive evidence that the TeV gamma-ray emission region is shell-like based on our morphological studies. The comparison with 2-5 keV X-ray data reveals a correlation with the 0.4-50 TeV gamma-ray emission. The spectrum of RCW 86 is best described by a power law with an exponential cutoff at E-cut = (3.5 +/- 1.2(stat)) TeV and a spectral index of Gamma approximate to 1.6 +/- 0.2. A static leptonic one-zone model adequately describes the measured spectral energy distribution of RCW 86, with the resultant total kinetic energy of the electrons above 1 GeV being equivalent to similar to 0.1% of the initial kinetic energy of a Type Ia supernova explosion (10(51) erg). When using a hadronic model, a magnetic field of B approximate to 100 mu G is needed to represent the measured data. Although this is comparable to formerly published estimates, a standard E-2 spectrum for the proton distribution cannot describe the gamma-ray data. Instead, a spectral index of Gamma(p) approximate to 1.7 would be required, which implies that similar to 7 x 10(49)/n(cm-3) erg has been transferred into high-energy protons with the effective density n(cm-3) = n/1 cm(-3). This is about 10% of the kinetic energy of a typical Type Ia supernova under the assumption of a density of 1 cm(-3).
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| 20. |
- Abramowski, A., et al.
(författare)
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Discovery of variable VHE gamma-ray emission from the binary system 1FGL J1018.6-5856
- 2015
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Ingår i: Astronomy and Astrophysics Supplement Series. - : EDP Sciences. - 0365-0138 .- 1286-4846. ; 577
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Tidskriftsartikel (refereegranskat)abstract
- Re-observations with the HESS telescope array of the very high-energy (VHE) source HESS J1018-589 A that is coincident with the Fermi-LAT γ-ray binary 1FGL J1018.6-5856 have resulted in a source detection significance of more than 9σ and the detection of variability (χ$^2$/ν of 238.3/155) in the emitted γ-ray flux. This variability confirms the association of HESS J1018-589 A with the high-energy γ-ray binary detected by Fermi-LAT and also confirms the point-like source as a new VHE binary system. The spectrum of HESS J1018-589 A is best fit with a power-law function with photon index Γ = 2.20 \plusmn 0.14$_stat$ \plusmn 0.2$_sys$. Emission is detected up to ~20 TeV. The mean differential flux level is (2.9 \plusmn 0.4) \times 10$^-13$ TeV$^-1$ cm$^-2$ s$^-1$ at 1 TeV, equivalent to ~1% of the flux from the Crab Nebula at the same energy. Variability is clearly detected in the night-by-night light curve. When folded on the orbital period of 16.58 days, the rebinned light curve peaks in phase with the observed X-ray and high-energy phaseograms. The fit of the HESS phaseogram to a constant flux provides evidence of periodicity at the level of N$_sigma$\gt 3σ. The shape of the VHE phaseogram and measured spectrum suggest a low-inclination, low-eccentricity system with amodest impact from VHE γ-ray absorption due to pair production (τ \lsim 1 at 300 GeV).
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| 21. |
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| 22. |
- Lui, A. T. Y., et al.
(författare)
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Breakdown of the frozen-in condition in the Earth's magnetotail
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:A4, s. A04215-
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Tidskriftsartikel (refereegranskat)abstract
- [1] We investigate in detail the breakdown of the frozen-in condition detected by Cluster at the downstream distance of similar to 19 R-E in the midnight sector of the magnetotail during a substorm expansion on 22 August 2001. It is found that the breakdown occurred ( 1) in a low-density environment with moderate to large proton plasma flow and significant fluctuations in electric and magnetic fields, ( 2) in regions with predominantly dissipation but occasionally dynamo effect, and ( 3) at times simultaneously at two Cluster satellites separated by more than 1000 km in both X- and Z-directions. Evaluation of the terms in the generalized Ohm's law indicates that the anomalous resistivity contribution arising from field fluctuations during this event is the most significant, followed by the Hall, electron viscosity, and inertial contributions in descending order of importance. This result demonstrates for the first time from observations that anomalous resistivity from field fluctuations ( implying kinetic instabilities) can play a substantial role in the breakdown of the frozen-in condition in the magnetotail during substorm expansions. Consideration of several observed features in the breakdown regions indicates that the breakdown occurs in a turbulent site resembling observed features found in current disruption and dipolarization sites.
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| 23. |
- Lui, A. T. Y., et al.
(författare)
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Evaluation of substorm models with Cluster observations of plasma flow reversal in the magnetotail
- 2008
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Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 41:10, s. 1611-1618
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate two prevailing substorm, models with an event of plasma flow reversal from tailward to Earthward detected by Cluster at the downstream distance of similar to 19 R-E in the magnetotail during a substorm. oil August 22, 2001. We use the unique capability of Cluster measurements in determining gradients to examine the associated current density, Lorentz force, and current dissipation/dynamo term. In association with plasma flow reversal, it is found that (1) there was no clear quadrupole magnetic perturbation signature, (2) the x-component of the Lorentz force did not change sign, (3) the y-component of the product of the current density and the electric field was occasionally negative indicative of a dynamo effect, and (4) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source. These observations are consistent with the near-Earth initiation model for substorms with multiple current disruption sites moving progressively tailward near the late stage of substorm expansion.
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| 24. |
- Ohtani, S., et al.
(författare)
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Cluster observations in the inner magnetosphere during the 18 April 2002 sawtooth event : Dipolarization and injection at r=4.6 R-E
- 2007
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 112:A8
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Tidskriftsartikel (refereegranskat)abstract
- The present study examines a sawtooth injection event that took place around 0800 UT on 18 April 2002 when the Cluster spacecraft were located in the inner magnetosphere in the premidnight sector. In association with this injection, Cluster, at a radial distance of 4.6 RE, observed that the local magnetic field became more dipolar and that both ion and electron fluxes increased without notable energy dispersion. These features were accompanied by intensifications of the equatorward component of a double- oval structure and also by an enhancement of the ring- current oxygen ENA flux. The event was also accompanied by large magnetic field ( a few tens of nT) and electric field ( a few tens of mV/ m) fluctuations with characteristic timescales of a few tens of seconds. These observations strongly suggest that this sawtooth injection extended not only widely in local time but also deeply into the inner magnetosphere. Interestingly, Cluster repeatedly observed dipolarization- like signatures afterward, which, however, were not associated with enhancements of local energetic ion flux or with geosynchronous dipolarization or injection signatures. Instead, these magnetic signatures were accompanied by oscillatory plasma motion in the radial direction with a characteristic timescale of about 10 min, which appears to be related to the westward propagation of a spatially periodic auroral structure. The associated azimuthal electric field component was well correlated with the time derivative of the north- south magnetic field component, suggesting that the observed electric field is inductive. These findings suggest that electromagnetic processes far inside geosynchronous orbit play an important role in energization of energetic ions and auroral dynamics during magnetospheric storms.
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| 25. |
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| 26. |
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| 27. |
- Zhang, L. Q., et al.
(författare)
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Vorticity Within Bursty Bulk Flows : Convective Versus Kinetic
- 2022
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 127:3
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Tidskriftsartikel (refereegranskat)abstract
- Based on four-point Magnetospheric Multiscale observation, we carefully analyze the vorticity field in the course of a reconnection jet on 27 June 2017. In this event, the convective electric field (E-c) is overwhelmed by the kinetic electric field (E-k). Accordingly, the omega-field in the course of the BBF is dominated by kinetic vorticity (omega(k)). The omega-field in the E-k-dominated bursty bulk flow (BBF) is characterized by perpendicular anisotropy. Comparison of velocity-curl vorticity (omega= backward difference xV $\mathbf{\omega }=\nabla \times \mathbf{V}$) with E/B induced vorticity confirms a greater contribution to the BBF vorticity by E (omega E=(B. backward difference )E/B2 ${\mathbf{\omega }}_{\mathbf{E}}=(\mathbf{B}\cdot \nabla )\boldsymbol{E}/{\boldsymbol{B}}<^>{2}$) than by B (omega B=(E. backward difference )B/B2 ${\mathbf{\omega }}_{\mathbf{B}}=(\mathbf{E}\cdot \nabla )\mathbf{B}/{\boldsymbol{B}}<^>{2}$). Power spectrum density reveals that in the E-k-dominated BBF, the E-c and E-k spectra have different power laws. E-c dominates the B-spectrum while E-k dominates the E-spectrum. The E-c(B) spectrum has a -5/3-like slope below 0.25 Hz but a -3-like above 0.25 Hz. The E-k(E) spectrum is -5/3-like at the low-frequency end (below 0.1 Hz) but -2-like at the high-frequency end (above 2 Hz). Within its medium frequency range, the spectrum is flat. Particularly, the E-k(E) spectrum exhibits the bump at 1-2 Hz in the frequency domain. The solitary/bipolar E-spikes, with typical temporal scale of 0.3-1 s, are likely responsible for the E-bump. Finally, we statistically analyze and compare the vorticity field in E-k-dominated and E-c -dominated BBFs. The result demonstrates that the E-k-dominated BBF tends to have stronger vorticity than the E-c -dominated BBF.
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| 28. |
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| 29. |
- Baumjohann, W., et al.
(författare)
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Dynamics of thin current sheets : Cluster observations
- 2007
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 25:6, s. 1365-1389
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Forskningsöversikt (refereegranskat)abstract
- The paper tries to sort out the specific signatures of the Near Earth Neutral Line (NENL) and the Current Disruption (CD) models. and looks for these signatures in Cluster data from two events. For both events transient magnetic si-natures are observed, together with fast ion flows. In the simplest form of NENL scenario, with a large-scale two-dimensional reconnection site, quasi-invariance along Y is expected. Thus the magnetic signatures in the S/C frame are interpreted as relative motions, along the X or Z direction, of a quasi-steady X-line, with respect to the S/C. In the simplest form of CD scenario an azimuthal modulation is expected. Hence the signatures in the S/C frame are interpreted as signatures of azimuthally (along Y) moving current system associated with low frequency fluctuations of J(y) and the corresponding field-aligned currents Event I covers a pseudo-breakup, developing only at high latitudes. First, a thin (H approximate to 2000Km approximate to 2 rho(i), with pi the ion gyroradius) Current Sheet (CS) is found to be quiet. A slightly thinner CS (H approximate to 1000-2000 km approximate to 1-2 rho(i)), crossed about 30 min later, is found to be active. with fast earthward ion flow bursts (300-600 km/s) and simultaneous large amplitude fluctuations (delta B/B similar to 1). In the quiet CS the current density J(y) is carried by ions. Conversely, in the active CS ions are moving eastward; the westward current is carried by electrons that move eastward, faster than ions. Similarly, the velocity of earthward flows (300-600 km/s), observed during the active period. maximizes near or at the CS center. During the active phase of Event I no signature of the crossing of an X-line is identified, but an X-line located beyond Cluster could account for the observed ion flows, provided that it is active for at least 20 min. Ion flow bursts can also be due to CD and to the corresponding dipolarizations which are associated with changes in the current density. Yet their durations are shorter than the duration of the active period. While the overall partial derivative Bz/partial derivative t is too weak to accelerate ions up to the observed velocities, short duration partial derivative B-z/partial derivative t can produce the azimuthal electric field requested to account for the observed ion flow bursts. The corresponding large amplitude perturbations are shown to move eastward. which suggests that the reduction in the tail current could be achieved via a series of eastward traveling partial dipolarisations/CD. The second event is much more active than the first one. The observed flapping of the CS corresponds to an azimuthally propagating wave. A reversal in the proton flow velocity, from 1000 to + 1000 km/s, is measured by CODIF. The overall flow reversal, the associated change in the sign of B-z and the relationship between B-x and B-y suggest that the spacecraft are moving with respect to an X-line and its associated Hall-structure. Yet, a simple tailward retreat of a large-scale X-line cannot account for all the observations, since several flow reversals are observed. These quasi-periodic flow reversals can also be associated with an azimuthal motion of the low frequency oscillations. Indeed, at the beginning of the interval B-y varies rapidly along the Y direction; the magnetic signature is three-dimensional and essentially corresponds to a structure of filamentary field-aligned current, moving eastward at similar to 200 km/s. The transverse size of the structure is similar to 1000 km. Similar structures are observed before and after. Thesefilamentary structures are consistent with an eastward propagation of an azimuthal modulation associated with a current system J(y), J(x). During Event 1, signatures of filamentary field-aligned current structures are also observed, in association with modulations of J(y). Hence, for both events the structure of the magnetic fields and currents is three-dimensional.
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| 30. |
- Koller-Smith, Louise I. M., et al.
(författare)
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Comparing very low birth weight versus very low gestation cohort methods for outcome analysis of high risk preterm infants
- 2017
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Ingår i: BMC Pediatrics. - : Springer Science and Business Media LLC. - 1471-2431. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Background: Compared to very low gestational age (<32 weeks, VLGA) cohorts, very low birth weight (<1500 g; VLBW) cohorts are more prone to selection bias toward small-for-gestational age (SGA) infants, which may impact upon the validity of data for benchmarking purposes. Method: Data from all VLGA or VLBW infants admitted in the 3 Networks between 2008 and 2011 were used. Two-thirds of each network cohort was randomly selected to develop prediction models for mortality and composite adverse outcome (CAO: mortality or cerebral injuries, chronic lung disease, severe retinopathy or necrotizing enterocolitis) and the remaining for internal validation. Areas under the ROC curves (AUC) of themodels were compared. Results: VLBW cohort (24,335 infants) had twice more SGA infants (20.4% vs. 9.3%) than the VLGA cohort (29,180 infants) and had a higher rate of CAO (36.5% vs. 32.6%). The two models had equal prediction power for mortality and CAO (AUC 0.83), and similarly for all other cross-cohort validations (AUC 0.81-0.85). Neither model performed well for the extremes of birth weight for gestation (<1500 g and >= 32 weeks, AUC 0.50-0.65; >= 1500 g and >= 32 weeks, AUC 0.60-0.62). Conclusion: There was no difference in prediction power for adverse outcome between cohorting VLGA or VLBW despite substantial bias in SGA population. Either cohorting practises are suitable for international benchmarking.
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| 31. |
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| 32. |
- Lew, H. P., et al.
(författare)
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Isolation of Alkaline-tolerant Bacteria from Primary Infected Root Canals
- 2015
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Ingår i: Journal of Endodontics. - : Elsevier BV. - 0099-2399. ; 41:4, s. 451-456
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Alkaline-tolerant bacteria in primary infected root canals could have enhanced survival capacity against antimicrobials commonly used in root canal treatment. The aims of this study were to isolate and characterize alkaline-tolerant bacteria before endodontic treatment (S1), after chemomechariital root canal preparation (S2), and after calcium hydroxide dressing (S3). Methods: Bacteriologic samples were obtained from 43 primary infected root canals. Samples were inoculated into culture media at a pH of 9 and incubated anaerobically. The identities of bacterial isolates were determined by 16S ribosomal RNA sequencing. Results: All S1 samples were culture positive, with 70% harboring bacteria tolerating a pH of 9. Gram-positive bacteria Pseudoramibacter alactolyticus and Streptococcus spp were the most frequently isolated strains with a prevalence of 54%. Of 13 culture-positive S2 samples, 8 isolates tolerated a pH of 9, namely Streptococcus sanguinis, Enterococcus faecalis, Enterobacter cancerogen us, Streptococcus oralis, and Fusobacterium nucleatum. Seven of these 8 isolates (88%) were correspondingly isolated at S1. All 3 culture-positive S3 samples tolerated a pH of 9, namely S. sanguinis and E. faecalis, which were also isolated in the corresponding S1 and S2 samples. Conclusions: We showed that the presence of alkaline-tolerant Streptococcus and Enterococcus spp in primary infected root canals could lead to their persistence during and after root canal treatment and could pose a challenge to current treatment efficacy.
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| 33. |
- Lui, A. T. Y., et al.
(författare)
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Internal structure of a magnetic flux rope from Cluster observations
- 2007
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:7, s. L07102-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a magnetic flux rope (MFR) observed by Cluster in the magnetotail during a substorm on 2001 August 22. The MFR was aligned with its principal axis closely along the dawn-dusk direction and had a small size of similar to 2 R-E with a total current of similar to 0.8 MA. The four spacecraft traversed the MFR at different distances from its center based on the magnetic field signature. This fortuitous situation reveals the irregular magnetic field structure in its inner core, which is a feature reported here for the first time. At the leading edge, the y-component of the electric field was dawnward against the current density direction ( dynamo action) and the x-component of the Lorentz force was Earthward. These parameters reversed in direction at its trailing edge (load).
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| 34. |
- Mander, B. A., et al.
(författare)
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Inflammation, tau pathology, and synaptic integrity associated with sleep spindles and memory prior to beta-amyloid positivity
- 2022
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Ingår i: Sleep. - : Oxford University Press (OUP). - 0161-8105 .- 1550-9109. ; 45:9
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Tidskriftsartikel (refereegranskat)abstract
- Study Objectives Fast frequency sleep spindles are reduced in aging and Alzheimer's disease (AD), but the mechanisms and functional relevance of these deficits remain unclear. The study objective was to identify AD biomarkers associated with fast sleep spindle deficits in cognitively unimpaired older adults at risk for AD. Methods Fifty-eight cognitively unimpaired, beta-amyloid-negative, older adults (mean +/- SD; 61.4 +/- 6.3 years, 38 female) enriched with parental history of AD (77.6%) and apolipoprotein E (APOE) epsilon 4 positivity (25.9%) completed the study. Cerebrospinal fluid (CSF) biomarkers of central nervous system inflammation, beta-amyloid and tau proteins, and neurodegeneration were combined with polysomnography (PSG) using high-density electroencephalography and assessment of overnight memory retention. Parallelized serial mediation models were used to assess indirect effects of age on fast frequency (13 to <16Hz) sleep spindle measures through these AD biomarkers. Results Glial activation was associated with prefrontal fast frequency sleep spindle expression deficits. While adjusting for sex, APOE epsilon 4 genotype, apnea-hypopnea index, and time between CSF sampling and sleep study, serial mediation models detected indirect effects of age on fast sleep spindle expression through microglial activation markers and then tau phosphorylation and synaptic degeneration markers. Sleep spindle expression at these electrodes was also associated with overnight memory retention in multiple regression models adjusting for covariates. Conclusions These findings point toward microglia dysfunction as associated with tau phosphorylation, synaptic loss, sleep spindle deficits, and memory impairment even prior to beta-amyloid positivity, thus offering a promising candidate therapeutic target to arrest cognitive decline associated with aging and AD.
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- Pan, Y, et al.
(författare)
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Characterization of chromosomal abnormalities in prostate cancer cell lines by spectral karyotyping
- 1999
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Ingår i: Cytogenetics and cell genetics. - : S. Karger AG. - 0301-0171. ; 87:3-4, s. 225-232
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Tidskriftsartikel (refereegranskat)abstract
- Human prostate cancer is characterized by multiple gross chromosome alterations involving several chromosome regions. However, the specific genes involved in the development of prostate tumors are still largely unknown. Here we have studied the chromosome composition of the three established prostate cancer cell lines, LNCaP, PC-3, and DU145, by spectral karyotyping (SKY). SKY analysis showed complex karyotypes for all three cell lines, with 87, 58/113, and 62 chromosomes, respectively. All cell lines were shown to carry structural alterations of chromosomes 1, 2, 4, 6, 10, 15, and 16; however, no recurrent breakpoints were detected. Compared to previously published findings on these cell lines using comparative genomic hybridization, SKY revealed several balanced translocations and pinpointed rearrangement breakpoints. The SKY analysis was validated by fluorescence in situ hybridization using chromosome-specific, as well as locus-specific, probes. Identification of chromosome alterations in these cell lines by SKY may prove to be helpful in attempts to clone the genes involved in prostate cancer tumorigenesis.
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- Zhang, L. Q., et al.
(författare)
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Anisotropic Vorticity Within Bursty Bulk Flow Turbulence
- 2020
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Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 125:10
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing Magnetospheric Multiscale (MMS) observation in the tail plasma sheet, we study the vorticity field (omega = del x V) of the plasma bulk (convective) velocity within the bursty bulk flow (BBF) in detailed. Two typical events are presented. In the event on 25 June 2017, E-y is the main component. In the other event on 6 July 2017, E-z is the main component. For both cases, the BBF electric field is dominated by the convective electric field (Ec = - V x B). Our case studies show clearly the existence of the convective vorticity field within the BBF. The vorticity field has prominent anisotropy (quantified by the anisotropic angle (theta aa = arctan(omega(perpendicular to)/omega(parallel to))). More often, the BBF omega field has stronger perpendicular vorticity (omega(perpendicular to)) than the parallel vorticity (omega(parallel to)). The dominance of vorticity by omega(perpendicular to)-dominating BBF is confirmed in the statistical sense. In particular, event on 25 June shows the significant evolution of the ion flux energy with the strength of the omega field. The strong omega field corresponds to the ion flux enhancement at high energy (above 10 keV), while the weak omega field corresponds to the ion flux enhancement at medium energy (2-5 keV). Investigation of the subset of channel from fast plasma investigation partial moment measurement reveals that the ion behaviors in the strong and decayed BBFs are distinctly different. The channeled ions form the narrow band distribution in the strong BBF but the multiple-layer distribution in the weak BBF. Finally, spectrum analysis indicates that the BBF omega(perpendicular to) and omega(parallel to) have a similar scaling about -2.0 (below 0.2 Hz).
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