626 research outputs found
The substorm current wedge and midnight sector partial ring current near substorm onset: A synthesis based on a magnetotail magnetic field geometry model
The Substorm Current Wedge (SCW) occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally was suggested to be the strong westward auroral electrojet (WEJ). However, the SCW-WEJ system has no viable generator current. Similarly, the asymmetric or Partial Ring Current (PRC) increases in strength during the growth phase, and is sometimes associated with an enhanced Region 2 field-aligned current (FAC) closing to the ionosphere, but specifics of that closure have been lacking. Here we present a unifying picture which includes the SCW post- and pre-midnight (AM and PM, respectively) currents and a generator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotail magnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types of closed field line regions-stretched lines in the central part of the plasmasheet (SPS) and dipolar lines (DPS) between the low latitude boundary layer (LLBL) regions and the SPS. There is also an important plasmasheet transition region (TPS) in which the dipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which the midnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which becomes part of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on the dawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the ionosphere. These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriate locations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and the final upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originally proposed SCW
<i>mito</i>-QC illuminates mitophagy and mitochondrial architecture <i>in vivo</i>
Autophagic turnover of mitochondria, termed mitophagy, is proposed to be an essential quality-control (QC) mechanism of pathophysiological relevance in mammals. However, if and how mitophagy proceeds within specific cellular subtypes in vivo remains unclear, largely because of a lack of tractable tools and models. To address this, we have developed âmito-QC,â a transgenic mouse with a pH-sensitive fluorescent mitochondrial signal. This allows the assessment of mitophagy and mitochondrial architecture in vivo. Using confocal microscopy, we demonstrate that mito-QC is compatible with classical and contemporary techniques in histochemistry and allows unambiguous in vivo detection of mitophagy and mitochondrial morphology at single-cell resolution within multiple organ systems. Strikingly, our model uncovers highly enriched and differential zones of mitophagy in the developing heart and within specific cells of the adult kidney. mito-QC is an experimentally advantageous tool of broad relevance to cell biology researchers within both discovery-based and translational research communities
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGOâs first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
Jets, Stickiness and Anomalous Transport
Dynamical and statistical properties of the vortex and passive particle
advection in chaotic flows generated by four and sixteen point vortices are
investigated. General transport properties of these flows are found anomalous
and exhibit a superdiffusive behavior with typical second moment exponent (\mu
\sim 1.75). The origin of this anomaly is traced back to the presence of
coherent structures within the flow, the vortex cores and the region far from
where vortices are located. In the vicinity of these regions stickiness is
observed and the motion of tracers is quasi-ballistic. The chaotic nature of
the underlying flow dictates the choice for thorough analysis of transport
properties. Passive tracer motion is analyzed by measuring the mutual relative
evolution of two nearby tracers. Some tracers travel in each other vicinity for
relatively large times. This is related to an hidden order for the tracers
which we call jets. Jets are localized and found in sticky regions. Their
structure is analyzed and found to be formed of a nested sets of jets within
jets. The analysis of the jet trapping time statistics shows a quantitative
agreement with the observed transport exponent.Comment: 17 pages, 17 figure
Rapid Diagnosis of Smear-Negative Tuberculosis Using Immunology and Microbiology with Induced Sputum in HIV-Infected and Uninfected Individuals
Rationale and Objectives. Blood-based studies have demonstrated the potential of immunological assays to detect tuberculosis. However lung fluid sampling may prove superior as it enables simultaneous microbiological detection of mycobacteria to be performed. Until now this has only been possible using the expensive and invasive technique of broncho-alveolar lavage. We sought to evaluate an immunoassay using non-invasive induced-sputum to diagnose active tuberculosis. Methods and Results. Prospective cohort study of forty-two spontaneous sputum smear-negative or sputum non-producing adults under investigation for tuberculosis. CD4 lymphocytes specific to purified-protein-derivative of Mycobacterium tuberculosis actively synthesising interferon-gamma were measured by flow cytometry and final diagnosis compared to immunoassay using a cut-off of 0.5%. Sixteen subjects (38%) were HIV-infected (median CD4 count [range] = 332 cells/mu l [103748]). Thirty-eight (90%) were BCG-vaccinated. In 27 subjects diagnosed with active tuberculosis, the median [range] percentage of interferon-gamma synthetic CD4+ lymphocytes was 2.77% [0-23.93%] versus 0% [0-2.10%] in 15 negative for active infection (p<0.0001). Sensitivity and specificity of the immunoassay versus final diagnosis of active tuberculosis were 89% (24 of 27) and 80% (12 of 15) respectively. The 3 positive assays in the latter group occurred in subjects diagnosed with quiescent/latent tuberculosis. Assay performance was unaffected by HIV-status, BCG-vaccination or disease site. Combining this approach with traditional microbiological methods increased the diagnostic yield to 93% (25 of 27) alongside acid-fast bacilli smear and 96% (26 of 27) alongside tuberculosis culture. Conclusions. These data demonstrate for the first time that a rapid immunological assay to diagnose active tuberculosis can be performed successfully in combination with microbiological methods on a single induced-sputum sample
Influence of Psychological Factors on Pain and Disability in Anterior Knee Pain Patients
AKP patients express chronic pain but also disability. However, the correlation between pain and disability is not complete and linear. Some patients with a lot of pain show mild disability while others with much less pain also show great disability. The disability is profoundly influenced by other emotional and cognitive factors that are associated with the perception of pain. Therefore, the clinical efforts do not have to be focused only on treating the pain as a feeling but on identifying and modifying these factor
Sensitivity of the Advanced LIGO detectors at the beginning of gravitational wave astronomy
The Laser Interferometer Gravitational Wave Observatory (LIGO) consists of two widely separated 4 km laser interferometers designed to detect gravitational waves from distant astrophysical sources in the frequency range from 10 Hz to 10 kHz. The first observation run of the Advanced LIGO detectors started in September 2015 and ended in January 2016. A strain sensitivity of better than 10â23/Hzââââ was achieved around 100 Hz. Understanding both the fundamental and the technical noise sources was critical for increasing the astrophysical strain sensitivity. The average distance at which coalescing binary black hole systems with individual masses of 30ââMâ could be detected above a signal-to-noise ratio (SNR) of 8 was 1.3 Gpc, and the range for binary neutron star inspirals was about 75 Mpc. With respect to the initial detectors, the observable volume of the Universe increased by a factor 69 and 43, respectively. These improvements helped Advanced LIGO to detect the gravitational wave signal from the binary black hole coalescence, known as GW150914
Search for post-merger gravitational waves from the remnant of the binary neutron star merger GW170817
In Advanced LIGO, detection and astrophysical source parameter estimation of the binary black hole merger GW150914 requires a calibrated estimate of the gravitational-wave strain sensed by the detectors. Producing an estimate from each detector's differential arm length control loop readout signals requires applying time domain filters, which are designed from a frequency domain model of the detector's gravitational-wave response. The gravitational-wave response model is determined by the detector's opto-mechanical response and the properties of its feedback control system. The measurements used to validate the model and characterize its uncertainty are derived primarily from a dedicated photon radiation pressure actuator, with cross-checks provided by optical and radio frequency references. We describe how the gravitational-wave readout signal is calibrated into equivalent gravitational-wave-induced strain and how the statistical uncertainties and systematic errors are assessed. Detector data collected over 38 calendar days, from September 12 to October 20, 2015, contain the event GW150914 and approximately 16 of coincident data used to estimate the event false alarm probability. The calibration uncertainty is less than 10% in magnitude and 10 degrees in phase across the relevant frequency band 20 Hz to 1 kHz
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