355 research outputs found
Small-Scale X-ray Variability in the Cassiopeia A Supernova Remnant
A comparison of X-ray observations of the Cassiopeia A supernova remnant
taken in 2000, 2002, and 2004 with the Chandra ACIS-S3 reveals the presence of
several small scale features (<= 10 arcsec) which exhibit significant intensity
changes over a 4 year time frame. Here we report on the variability of six
features, four of which show count rate increases from ~ 10% to over 90%, and
two which show decreases of ~ 30% -- 40%. While extracted 1-4.5 keV X-ray
spectra do not reveal gross changes in emission line strengths, spectral fits
using non-equilibrium ionization, metal-rich plasma models indicate increased
or decreased electron temperatures for features showing increasing or
decreasing count rates, respectively. Based on the observed count rate changes
and the assumption that the freely expanding ejecta has a velocity of ~ 5000
km/s at the reverse shock front, we estimate the unshocked ejecta to have
spatial scale variations of 0.02 - 0.03 pc, which is consistent with the X-ray
emitting ejecta belonging to a more diffuse component of the supernova ejecta
than that seen in the optically emitting ejecta, which have spatial scales ~
0.001 pc.Comment: 9 pages, 8 figures, to be published in Astronomical Journa
Treatment with a Substance P Receptor Antagonist Is Neuroprotective in the Intrastriatal 6-Hydroxydopamine Model of Early Parkinson's Disease
Neuroinflammation and blood brain barrier (BBB) dysfunction have been implicated in the pathogenesis of Parkinson's disease (PD). The neuropeptide substance P (SP) is an important mediator of both neuroinflammation and BBB dysfunction through its NK1 receptor in a process known as neurogenic inflammation. Increased SP content has previously been reported following 6-OHDA treatment in vitro, with the levels of SP correlating with cell death. The present study used an in vivo 6-OHDA lesion model to determine if dopaminergic degeneration was associated with increased SP in the substantia nigra and whether this degeneration could be prevented by using a SP, NK1 receptor antagonist. Unilateral, intrastriatal 6-OHDA lesions were induced and SP (10 µg/2 µL) or the NK1 receptor antagonists, N-acetyl-L-tryptophan (2 µL at 50 nM) or L-333,060 (2 µL at 100 nM), administered immediately after the neurotoxin. Nigral SP content was then determined using immunohistochemical and ELISA methods, neuroinflammation and barrier integrity was assessed using Iba-1, ED-1, GFAP and albumin immunohistochemistry, while dopaminergic cell loss was assessed with tyrosine hydroxylase immunohistochemistry. Motor function in all animals was assessed using the rotarod task. Intrastriatal 6-OHDA lesioning produced an early and sustained increase in ipsilateral nigral SP content, along with a breakdown of the BBB and activation of microglia and astrocytes. Further exacerbation of SP levels accelerated disease progression, whereas NK1 receptor antagonist treatment protected dopaminergic neurons, preserved barrier integrity, reduced neuroinflammation and significantly improved motor function. We propose that neurogenic inflammation contributes to dopaminergic degeneration in early experimental PD and demonstrate that an NK1 receptor antagonist may represent a novel neuroprotective therapy
Combination of N-Acetyl-L-Tryptophan and Magnesium Sulphate for the treatment of brain, spinal and nerve injury
This invention relates to a method of therapy of brain, spinal and nerve injury. There is also provided a formulation which is particularly useful in the method. Injury to the brain results in the development of motor and cognitive deficits that contribute to the significant morbidity experienced by survivors of brain injury. Moreover, it is an occurrence that has the highest incidence in younger members of society. Accordingly, injury to the brain is responsible for the greatest loss of productive life as compared to any other disease process. Despite this, there is no effective therapy to improve outcome after brain injury. Use of this therapy significantly improves both motor and cognitive outcome in mild to severe experimental brain injury and has also been found to have beneficial effect also for the treatment of spinal cord and nerve injuries
Salvage surgery for a giant melanoma on the back
We report a case of a giant melanoma on the back with a very extreme Breslow thickness. On physical examination a large odorous and ulcerating tumour was seen adjacent to two large crusted lesions, probably in transit metastases. In the right and left axilla enlarged lymph nodes were palpated. The patient underwent salvage surgery consisting of a complete wide excision of the tumors on the back as well as axillary lymph node dissection on both sides. Histopathology showed a malignant melanoma with a Breslow thickness of 48 mm. Four of fifteen nodes in the right axilla and one of nine nodes in the left axilla, were positive for metastatic disease. Also various in transit and subcutaneous metastases were found in the wide excision specimen. The interest of our observation relies in the rarity of a melanoma with such an extreme Breslow thickness and the difficulty in performing adequate palliative therapy that offers quality of life by means of tumor control
Hubble Space Telescope WFPC-2 Imaging of Cassiopeia A
The young SNR Cassiopeia A was imaged with WFPC-2 through four filters
selected to capture the complete velocity range of the remnant's main shell in
several important emission lines. Primary lines detected were [O III]
4959,5007, [N II] 6583, [S II] 6716,6731 + [O II] 7319,7330 + [O I] 6300,6364,
and [S III] 9069,9532. About 3/4th of the remnant's main shell was imaged in
all four filters. Considerable detail is observed in the reverse-shocked ejecta
with typical knot scale lengths of 0.2"-0.4" (1 - 2 x 10^16 cm). Both bright
and faint emission features appear highly clumped. Large differences in [S III]
and [O III] line intensities indicating chemical abundance differences are also
seen, particularly in knots located along the bright northern limb and near the
base of the northeast jet. A line of curved overlapping filament in the
remnant's northwestern rim appears to mark the location of the remnant's
reverse shock front in this region. Finger-like ejecta structures elsewhere
suggest cases where the reverse shock front is encountering the remnant's
clumped ejecta. Narrow-band [N II] images of the remnant's circumstellar knots
("QSFs") reveal them to be 0.1"-0.6" thick knots and filaments, often with
diffuse edges facing away from the center of expansion. Three color composite
images of the whole remnant and certain sections along with individual filter
enlargements of selected regions of the bright optical shell are presented and
discussed.Comment: 26 pages, 12 figures Accepted to the Astronomical Journa
Kinematics of X-ray Emitting Components in Cassiopeia A
We present high-resolution X-ray proper motion measurements of Cassiopeia A
using Chandra observations from 2000 and 2002. We separate the emission into
four spectrally distinct classes: Si-dominated, Fe-dominated,
low-energy-enhanced, and continuum-dominated. These classes also represent
distinct spatial and kinematic components. The Si- and Fe-dominated classes are
ejecta and have a mean expansion rate of 0.2%/yr. This is the same as for the
forward shock filaments but less than the 0.3%/yr characteristic of optical
ejecta. The low-energy-enhanced spectral class possibly illuminates a clumpy
circumstellar component and has a mean expansion rate of 0.05%/yr. The
continuum-dominated emission likely represents the forward shock and consists
of diffuse circumstellar material which is seen as a circular ring around the
periphery of the remnant as well as projected across the center.Comment: 15 pages, 3 figures, accepted to Ap
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