469 research outputs found
Altered expression of the voltage-gated calcium channel subunit α2δ-1: a comparison between two experimental models of epilepsy and a sensory nerve ligation model of neuropathic pain.
The auxiliary α2δ-1 subunit of voltage-gated calcium channels is up-regulated in dorsal root ganglion neurons following peripheral somatosensory nerve damage, in several animal models of neuropathic pain. The α2δ-1 protein has a mainly presynaptic localization, where it is associated with the calcium channels involved in neurotransmitter release. Relevant to the present study, α2δ-1 has been shown to be the therapeutic target of the gabapentinoid drugs in their alleviation of neuropathic pain. These drugs are also used in the treatment of certain epilepsies. In this study we therefore examined whether the level or distribution of α2δ-1 was altered in the hippocampus following experimental induction of epileptic seizures in rats, using both the kainic acid model of human temporal lobe epilepsy, in which status epilepticus is induced, and the tetanus toxin model in which status epilepticus is not involved. The main finding of this study is that we did not identify somatic overexpression of α2δ-1 in hippocampal neurons in either of the epilepsy models, unlike the upregulation of α2δ-1 that occurs following peripheral nerve damage to both somatosensory and motor neurons. However, we did observe local reorganisation of α2δ-1 immunostaining in the hippocampus only in the kainic acid model, where it was associated with areas of neuronal cell loss, as indicated by absence of NeuN immunostaining, dendritic loss, as identified by areas where microtubule-associated protein-2 immunostaining was missing, and reactive gliosis, determined by regions of strong OX42 staining
An m sin i = 24 Earth Mass Planetary Companion To The Nearby M Dwarf GJ 176
We report the detection of a planetary companion with a minimum mass of m sin
i = 0.0771 M_Jup = 24.5 M_Earth to the nearby (d = 9.4 pc) M2.5V star GJ 176.
The star was observed as part of our M dwarf planet search at the Hobby-Eberly
Telescope (HET). The detection is based on 5 years of high-precision
differential radial velocity (RV) measurements using the
High-Resolution-Spectrograph (HRS). The orbital period of the planet is 10.24
d. GJ 176 thus joins the small (but increasing) sample of M dwarfs hosting
short-periodic planets with minimum masses in the Neptune-mass range. Low mass
planets could be relatively common around M dwarfs and the current detections
might represent the tip of a rocky planet population.Comment: 13 pages preprint, 3 figures, submitted to Ap
Bayesian model comparison applied to the Explorer-Nautilus 2001 coincidence data
Bayesian reasoning is applied to the data by the ROG Collaboration, in which
gravitational wave (g.w.) signals are searched for in a coincidence experiment
between Explorer and Nautilus. The use of Bayesian reasoning allows, under well
defined hypotheses, even tiny pieces of evidence in favor of each model to be
extracted from the data. The combination of the data of several experiments can
therefore be performed in an optimal and efficient way. Some models for
Galactic sources are considered and, within each model, the experimental result
is summarized with the likelihood rescaled to the insensitivity limit value
(`` function''). The model comparison result is given in in terms of
Bayes factors, which quantify how the ratio of beliefs about two alternative
models are modified by the experimental observationComment: 16 pages, 4 figures. Presented at the GWDAW2002 conference, held in
Kyoto on Dec.,2002. This version includes comments by the referees of CQG,
which has accepted the paper for pubblication in the special issue of the
conference. In particular, note that in Eq. 12 there was a typeset error. As
suggested by one of the referees, a uniform prior in Log(alpha) has also been
considere
High-Frequency network activity, global increase in Neuronal Activity, and Synchrony Expansion Precede Epileptic Seizures In Vitro
How seizures start is a major question in epilepsy research. Preictal EEG changes occur in both human patients and animal models, but their underlying mechanisms and relationship with seizure initiation remain unknown. Here we demonstrate the existence, in the hippocampal CA1 region, of a preictal state characterized by the progressive and global increase in neuronal activity associated with a widespread buildup of low-amplitude high-frequency activity (HFA) (100 Hz) and reduction in system complexity.HFAis generated by the firing of neurons, mainly pyramidal cells, at much lower frequencies. Individual cycles ofHFAare generated by the near-synchronous (within 5 ms) firing of small numbers of pyramidal cells. The presence of HFA in the low-calcium model implicates nonsynaptic synchronization; the presence of very similar HFA in the high-potassium model shows that it does not depend on an absence of synaptic transmission. Immediately before seizure onset, CA1 is in a state of high sensitivity in which weak depolarizing or synchronizing perturbations can trigger seizures. Transition to seizure is haracterized by a rapid expansion and fusion of the neuronal populations responsible for HFA, associated with a progressive slowing of HFA, leading to a single, massive, hypersynchronous cluster generating the high-amplitude low-frequency activity of the seizure
Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
We present improved black hole masses for 35 active galactic nuclei (AGNs)
based on a complete and consistent reanalysis of broad emission-line
reverberation-mapping data. From objects with multiple line measurements, we
find that the highest precision measure of the virial product is obtained by
using the cross-correlation function centroid (as opposed to the
cross-correlation function peak) for the time delay and the line dispersion (as
opposed to full width half maximum) for the line width and by measuring the
line width in the variable part of the spectrum. Accurate line-width
measurement depends critically on avoiding contaminating features, in
particular the narrow components of the emission lines. We find that the
precision (or random component of the error) of reverberation-based black hole
mass measurements is typically around 30%, comparable to the precision attained
in measurement of black hole masses in quiescent galaxies by gas or stellar
dynamical methods. Based on results presented in a companion paper by Onken et
al., we provide a zero-point calibration for the reverberation-based black hole
mass scale by using the relationship between black hole mass and host-galaxy
bulge velocity dispersion. The scatter around this relationship implies that
the typical systematic uncertainties in reverberation-based black hole masses
are smaller than a factor of three. We present a preliminary version of a
mass-luminosity relationship that is much better defined than any previous
attempt. Scatter about the mass-luminosity relationship for these AGNs appears
to be real and could be correlated with either Eddington ratio or object
inclination.Comment: 61 pages, including 8 Tables and 16 Figures. Accepted for publication
in The Astrophysical Journa
A Planetary Companion to gamma Cephei A
We report on the detection of a planetary companion in orbit around the
primary star of the binary system Cephei. High precision radial
velocity measurements using 4 independent data sets spanning the time interval
1981--2002 reveal long-lived residual radial velocity variations superimposed
on the binary orbit that are coherent in phase and amplitude with a period or
2.48 years (906 days) and a semi-amplitude of 27.5 m s. We performed a
careful analysis of our Ca II H & K S-index measurements, spectral line
bisectors, and {\it Hipparcos} photometry. We found no significant variations
in these quantities with the 906-d period. We also re-analyzed the Ca II
8662 {\AA} measurements of Walker et al. (1992) which showed possible
periodic variations with the ``planet'' period when first published. This
analysis shows that periodic Ca II equivalent width variations were only
present during 1986.5 -- 1992 and absent during 1981--1986.5. Furthermore, a
refined period for the Ca II 8662 {\AA} variations is 2.14 yrs,
significantly less than residual radial velocity period. The most likely
explanation of the residual radial velocity variations is a planetary mass
companion with sin = 1.7 and an orbital semi-major axis
of 2.13 AU. This supports the planet hypothesis for the residual
radial velocity variations for Cep first suggested by Walker et al.
(1992). With an estimated binary orbital period of 57 years Cep is the
shortest period binary system in which an extrasolar planet has been found.
This system may provide insights into the relationship between planetary and
binary star formation.Comment: 19 pages, 15 figures, accepted in Ap. J. Includes additional data and
improved orbital solutio
Determination Of The Orbit Of The Planetary Companion To The Metal Rich Star HD 45350
We present the precise radial velocity (RV) data for the metal-rich star HD
45350 collected with the Harlan J. Smith (HJS) 2.7 m telescope and the
Hobby-Eberly Telescope (HET) at McDonald Observatory. This star was noticed by
us as a candidate for having a giant planetary companion in a highly eccentric
orbit, but the lack of data close to periastron left the amplitude and thus
mass of the planet poorly constrained. Marcy et al. (2005) announced the
presence of the planet based on their Keck/HIRES data, but those authors also
cautioned that the remaining uncertainties in the orbital solution might be
large due to insufficient data near periastron passage. In order to close this
phase gap we exploited the flexible queue scheduled observing mode of the HET
to obtain intensive coverage of the most recent periastron passage of the
planet. In combination with the long term data from the HJS 2.7 m telescope we
determine a Keplerian orbital solution for this system with a period of 962
days, an eccentricity of e=0.76 and a velocity semi-amplitude K of 57.4 m/s.
The planet has a minimum mass of m sin i = 1.82 +- 0.14 M_Jup and an orbital
semi-major axis of a = 1.92 +-0.07 AU.Comment: 9 pages preprint, 4 figures, accepted in A
Evidence for a Long-period Planet Orbiting Epsilon Eridani
High precision radial velocity (RV) measurements spanning the years
1980.8--2000.0 are presented for the nearby (3.22 pc) K2 V star Eri.
These data, which represent a combination of six independent data sets taken
with four different telescopes, show convincing variations with a period of
7 yrs. A least squares orbital solution using robust estimation
yields orbital parameters of period, = 6.9 yrs, velocity -amplitude
19 {\ms}, eccentricity 0.6, projected companion mass sin = 0.86
, and semi-major axis 3.3 AU. Ca II H&K S-index
measurements spanning the same time interval show significant variations with
periods of 3 and 20 yrs, yet none at the RV period. If magnetic activity were
responsible for the RV variations then it produces a significantly different
period than is seen in the Ca II data. Given the lack of Ca II variation with
the same period as that found in the RV measurements, the long-lived and
coherent nature of these variations, and the high eccentricity of the implied
orbit, Keplerian motion due to a planetary companion seems to be the most
likely explanation for the observed RV variations. The wide angular separation
of the planet from the star (approximately 1 arc-second) and the long orbital
period make this planet a prime candidate for both direct imaging and
space-based astrometric measurements.Comment: To appear in Astrophysical Journal Letters. 9 pages, 2 figure
Triage conducted by lay-staff and emergency training reduces paediatric mortality in the emergency department of a rural hospital in Northern Mozambique
Introduction
The majority of emergency paediatric death in African countries occur within the first 24 h of admission. A coloured triage system is widely implemented in high-income countries and the emergency triage and assessment treatment (ETAT) is recommended by the World Health Organization, but not put into practice in Mozambique. We implemented a three-colour triage system in a rural district hospital with lay-staff workers conducting the first triage.
Methods
A retrospective, before and after, mortality analysis was performed using routine patient files from the district hospital between 2014 and 2017. The triage system was implemented in August 2016. Inclusion criteria were children under 15 years of age that entered the emergency centre. Primary outcome was child mortality rate. Secondary outcomes included the percentage agreement between the clinical and non-clinical staff and the duration from triage to first treatment. We used a negative binomial model in STATA 15 to compare mortality rates, and Kappa statistics to estimate the agreement between clinical and non-clinical staff.
Results
4176 admissions were included. The mortality rate ratio (MMR) was 45% lower after the start of the intervention (2016; MRR = 0.55; 0.38, 0.81; p = 0.002), compared to before. To estimate the agreement between non-clinical and clinical staff, 548 (of the 671) patient files were included. The agreement was estimated at 88.7% (Kappa = 0.644; p < 0.001). The median waiting time decreased with urgency of the triage: 2 h33 for ‘green’/least serious (IQR 1 h58-3 h30), 21 min for yellow/serious (IQR 0 h10-0 h58) and nine minutes for ‘red’/urgent (IQR 2–40 min).
Conclusion
In a rural setting with nurse-led clinical care and non-clinician staff working at the triage reception, implementation of a three-coloured triage system was feasible. Triage and ETAT training was associated with a decrease of 45% of paediatric deaths. The impact on mortality, low cost, and ease of the implementation supports scaling this intervention in similar settings
- …