16,154 research outputs found
Omega-3 Fatty Acids Improve Recovery, whereas Omega-6 Fatty Acids Worsen Outcome, after Spinal Cord Injury in the Adult Rat
Spinal cord injury (SCI) is a cause of major neurological disability, and no satisfactory treatment is currently available. Evidence suggests that polyunsaturated fatty acids (PUFAs) could target some of the pathological mechanisms that underlie damage after SCI. We examined the effects of treatment with PUFAs after lateral spinal cord hemisection in the rat. The ω-3 PUFAs α-linolenic acid and docosahexaenoic acid (DHA) injected 30 min after injury induced significantly improved locomotor performance and neuroprotection, including decreased lesion size and apoptosis and increased neuronal and oligodendrocyte survival. Evidence showing a decrease in RNA/DNA oxidation suggests that the neuroprotective effect of ω-3 PUFAs involved a significant antioxidant function. In contrast, animals treated with arachidonic acid, an ω-6 PUFA, had a significantly worse outcome than controls. We confirmed the neuroprotective effect of ω-3 PUFAs by examining the effects of DHA treatment after spinal cord compression injury. Results indicated that DHA administered 30 min after spinal cord compression not only greatly increased survival of neurons but also resulted in significantly better locomotor performance for up to 6 weeks after injury.
This report shows a striking difference in efficacy between the effects of treatment with ω-3 and ω-6 PUFAs on the outcome of SCI, with ω-3 PUFAs being neuroprotective and ω-6 PUFAs having a damaging effect. Given the proven clinical safety of ω-3 PUFAs, our observations show that these PUFAs have significant therapeutic potential in SCI. In contrast, the use of preparations enriched in ω-6 PUFAs after injury could worsen outcome after SCI
The connection between the 15 GHz radio and gamma-ray emission in blazars
Since mid-2007 we have carried out a dedicated long-term monitoring programme
at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope. One of
the main goals of this programme is to study the relation between the radio and
gamma-ray emission in blazars and to use it as a tool to locate the site of
high energy emission. Using this large sample of objects we are able to
characterize the radio variability, and study the significance of correlations
between the radio and gamma-ray bands. We find that the radio variability of
many sources can be described using a simple power law power spectral density,
and that when taking into account the red-noise characteristics of the light
curves, cases with significant correlation are rare. We note that while
significant correlations are found in few individual objects, radio variations
are most often delayed with respect to the gamma-ray variations. This suggests
that the gamma-ray emission originates upstream of the radio emission. Because
strong flares in most known gamma-ray-loud blazars are infrequent, longer light
curves are required to settle the issue of the strength of radio-gamma
cross-correlations and establish confidently possible delays between the two.
For this reason continuous multiwavelength monitoring over a longer time period
is essential for statistical tests of jet emission models.Comment: To appear in the Proceedings of the IAU Symposium No. 313:
"Extragalactic jets from every angle," Galapagos, Ecuador, 15-19 September
2014, F. Massaro, C. C. Cheung, E. Lopez, and A. Siemiginowska (Eds.),
Cambridge University Pres
Why do some intermediate polars show soft X-ray emission? A survey of XMM-Newton spectra
We make a systematic analysis of the XMM-Newton X-ray spectra of intermediate
polars (IPs) and find that, contrary to the traditional picture, most show a
soft blackbody component. We compare the results with those from AM Her stars
and deduce that the blackbody emission arises from reprocessing of hard X-rays,
rather than from the blobby accretion sometimes seen in AM Hers. Whether an IP
shows a blackbody component appears to depend primarily on geometric factors: a
blackbody is not seen in those that have accretion footprints that are always
obscured by accretion curtains or are only visible when foreshortened on the
white-dwarf limb. Thus we argue against previous suggestions that the blackbody
emission characterises a separate sub-group of IPs which are more akin to AM
Hers, and develop a unified picture of the blackbody emission in these stars.Comment: 9 pages, 6 figures. Accepted for publication in Ap
New results on group classification of nonlinear diffusion-convection equations
Using a new method and additional (conditional and partial) equivalence
transformations, we performed group classification in a class of variable
coefficient -dimensional nonlinear diffusion-convection equations of the
general form We obtain new interesting cases of
such equations with the density localized in space, which have large
invariance algebra. Exact solutions of these equations are constructed. We also
consider the problem of investigation of the possible local trasformations for
an arbitrary pair of equations from the class under consideration, i.e. of
describing all the possible partial equivalence transformations in this class.Comment: LaTeX2e, 19 page
Updated Information on the Local Group
The present note updates the information published in my recent monograph on
\underline{The Galaxies of the Local Group}. Highlights include (1) the
addition of the newly discovered Cetus dwarf spheroidal as a certain member of
the Local Group, (2) an improved distance for SagDIG, which now places this
object very close to the edge of the Local Group zero-velocity surface, (3)
more information on the evolutionary histories of some individual Local Group
members, and (4) improved distance determinations to, and luminosities for, a
number of Local Group members. These data increase the number of certain (or
probable) Local Group members to 36. The spatial distribution of these galaxies
supports Hubble's claim that the Local Group ``is isolated in the general
field.'' Presently available evidence suggests that star formation continued
much longer in many dwarf spheroidals than it did in the main body of the
Galactic halo. It is suggested that ``young'' globular clusters, such as
Ruprecht 106, might have formed in now defunct dwarf spheroidals. Assuming
SagDIG, which is the most remote Local Group galaxy, to lie on, or just inside,
the zero-velocity surface of the Local Group yields a dynamical age \gtrsim
17.9 \pm 2.7 Gyr.Comment: 19 pages, 1 figure, to be published in the April 2000 issue of PAS
Electron Conditioning of Technical Aluminium Surfaces: Effect on the Secondary Electron Yield
The effect of electron conditioning on commercially aluminium alloys 1100 and
6063 were investigated. Contrary to the assumption that electron conditioning,
if performed long enough, can reduce and stabilize the SEY to low values (, value of many pure elements), the SEY of aluminium did not go lower than
1.8. In fact, it reincreases with continued electron exposure dose.Comment: 36 pages, 25 figures, submitted to JVST
Pauli Diagonal Channels Constant on Axes
We define and study the properties of channels which are analogous to unital
qubit channels in several ways. A full treatment can be given only when the
dimension d is a prime power, in which case each of the (d+1) mutually unbiased
bases (MUB) defines an axis. Along each axis the channel looks like a
depolarizing channel, but the degree of depolarization depends on the axis.
When d is not a prime power, some of our results still hold, particularly in
the case of channels with one symmetry axis. We describe the convex structure
of this class of channels and the subclass of entanglement breaking channels.
We find new bound entangled states for d = 3.
For these channels, we show that the multiplicativity conjecture for maximal
output p-norm holds for p=2. We also find channels with behavior not exhibited
by unital qubit channels, including two pairs of orthogonal bases with equal
output entropy in the absence of symmetry. This provides new numerical evidence
for the additivity of minimal output entropy
Solar cycle effects in planetary geomagnetic activity: Analysis of 36‐year long OMNI dataset
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94796/1/grl13462.pd
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