254 research outputs found
The published research paper: is it an important indicator of successful operational research at programme level?
Is a published research paper an important indicator of successful operational research at programme level in low-income countries? In academia, publishing in peer-reviewed scientific journals is highly encouraged and strongly pursued for academic recognition and career progression. In contrast, for those who engage in operational research at programme level, there is often no necessity or reward for publishing the results of research studies; it may even be criticized as being an unnecessary detraction from programme-related work. We present arguments to support publishing operational research from low-income countries; we highlight some of the main reasons for failure of publication at programme level and suggest ways forward
A comparison of incompressible limits for resistive plasmas
The constraint of incompressibility is often used to simplify the
magnetohydrodynamic (MHD) description of linearized plasma dynamics because it
does not affect the ideal MHD marginal stability point. In this paper two
methods for introducing incompressibility are compared in a cylindrical plasma
model: In the first method, the limit is taken, where
is the ratio of specific heats; in the second, an anisotropic mass
tensor is used, with the component parallel to the magnetic
field taken to vanish, . Use of resistive MHD reveals
the nature of these two limits because the Alfv\'en and slow magnetosonic
continua of ideal MHD are converted to point spectra and moved into the complex
plane. Both limits profoundly change the slow-magnetosonic spectrum, but only
the second limit faithfully reproduces the resistive Alfv\'en spectrum and its
wavemodes. In ideal MHD, the slow magnetosonic continuum degenerates to the
Alfv\'en continuum in the first method, while it is moved to infinity by the
second. The degeneracy in the first is broken by finite resistivity. For
numerical and semi-analytical study of these models, we choose plasma
equilibria which cast light on puzzling aspects of results found in earlier
literature.Comment: 14 pages, 10 figure
High loss to follow-up following obstetric fistula repair surgery in rural Burundi: is there a way forward?
Structure, Deformations and Gravitational Wave Emission of Magnetars
Neutron stars can have, in some phases of their life, extremely strong
magnetic fields, up to 10^15-10^16 G. These objects, named magnetars, could be
powerful sources of gravitational waves, since their magnetic field could
determine large deformations. We discuss the structure of the magnetic field of
magnetars, and the deformation induced by this field. Finally, we discuss the
perspective of detection of the gravitational waves emitted by these stars.Comment: 11 pages, 2 figures, prepared for 19th International Conference on
General Relativity and Gravitation (GR19), Mexico City, Mexico, July 5-9,
201
Misregulation of mitochondria-lysosome contact dynamics in Charcot-Marie-Tooth Type 2B disease Rab7 mutant sensory peripheral neurons
Inter-organelle contact sites between mitochondria and lysosomes mediate the crosstalk and bidirectional regulation of their dynamics in health and disease. However, mitochondria-lysosome contact sites and their misregulation have not been investigated in peripheral sensory neurons. Charcot-Marie-Tooth type 2B disease is an autosomal dominant axonal neuropathy affecting peripheral sensory neurons caused by mutations in the GTPase Rab7. Using live super-resolution and confocal time-lapse microscopy, we showed that mitochondria-lysosome contact sites dynamically form in the soma and axons of peripheral sensory neurons. Interestingly, Charcot-Marie-Tooth type 2B mutant Rab7 led to prolonged mitochondria-lysosome contact site tethering preferentially in the axons of peripheral sensory neurons, due to impaired Rab7 GTP hydrolysis-mediated contact site untethering. We further generated a Charcot-Marie-Tooth type 2B mutant Rab7 knock-in mouse model which exhibited prolonged axonal mitochondria-lysosome contact site tethering and defective downstream axonal mitochondrial dynamics due to impaired Rab7 GTP hydrolysis as well as fragmented mitochondria in the axon of the sciatic nerve. Importantly, mutant Rab7 mice further demonstrated preferential sensory behavioral abnormalities and neuropathy, highlighting an important role for mutant Rab7 in driving degeneration of peripheral sensory neurons. Together, this study identifies an important role for mitochondria-lysosome contact sites in the pathogenesis of peripheral neuropathy
On the significance of population II Li6 abundances
We explore possible depletion factors for Li6 in the three stars where it has
been detected. To this end, we assume that 6Li/H scales as 16O/H throughout the
galactic evolution, an assumption motivated by the observations of a similar
scaling for 9Be. We examine the uncertainties attached to this modeling of 6Li
galactic evolution; we also incorporate a recent evaluation of the primordial
production of 6Li. The depletion factor D6, for 6Li, in HD84937, is constrained
to be less than 4 at 95% c.l.. This depletion factor is an extreme upper limit
on the depletion factor for 7Li. We conclude that the primordial abundance of
7Li cannot be higher that twice the observed value, since no current stellar
model is able to reproduce the observed trends of 7Li with temperature and
metallicity, and yet deplete 7Li by more than a factor 2, while satisfying
D6<4. All three 6Li observations are in excellent agreement with all standard
expectations: Big-Bang nucleosynthesis with 2<<6.5, and standard
isochrones of 6Li survival. We discuss possible deviations from our assumption
of 6Li/H scaling with 16O/H, due to alpha-alpha creation of 6Li in various
sites. We notably reject stellar flares as a significant source of 6Li in
HD84937.Comment: 19 pages, 4 figures, LaTeX. To appear in Ap
Pion production in the inner disk around Cygnus X-1
Neutron production via ^{4}He breakup and p(p, n{pi}^+)p is considered in the
innermost region of an accretion disk surrounding a Kerr Black Hole. These
reactions occur in a plasma in Wien equilibrium, where (radiatively produced)
pair production equals annihilation. Cooling of the disk is assumed to be due
to unsaturated inverse Comptonization of external soft photons and to the
energy needed to ignite both nuclear reactions. Assuming matter composition of
90% Hydrogen and 10% He, it is shown that, close to the border of this region,
neutron production is essentially from ^{4}He breakup. Close to the horizon,
the contribution from p(p, n{pi}^+)p to the neutron production is comparable to
that from the breakup. It is shown that the viscosity generated by the
collisions of the accreting matter with the neutrons may drive stationary
accretion, for accretion rates below a critical value. In this case, solution
to the disk equations is double-valued and for both solutions protons
overnumber the pairs. It is claimed that these solutions may mimic the states
of high and low luminosity observed in Cygnus X-1 and related sources. This
would be explained either by the coupling of thermal instability to the
peculiar behavior of the viscosity parameter alpha with the ion temperature
that may intermittently switch accretion off or by the impossibility of a
perfect tuning for both thermal and pair equilibrium in the disk, a fact that
forces the system to undergo a kind of limit cycle behavior around the upper
solution.Comment: 23 pages, 11 figure
Band-width control in a perovskite-type 3d^1 correlated metal Ca_{1-x}Sr_xVO_3. I. Evolution of the electronic properties and effective mass
Single crystals of the perovskite-type metallic alloy system
CaSrVO were synthesized in order to investigate metallic
properties near the Mott transition. The substitution of a Ca ion for a
Sr ion reduces the band width due to a buckling of the V-O-V bond
angle from for SrVO to for CaVO. Thus,
the value of can be systematically controlled without changing the number
of electrons making CaSrVO: one of the most ideal systems for
studying band-width effects. The Sommerfeld-Wilson's ratio (), the
Kadowaki-Woods ratio (in the same region as heavy Fermion systems), and a large
term in the electric resistivity, even at 300 K, substantiate a large
electron correlation in this system, though the effective mass, obtained by
thermodynamic and magnetic measurements, shows only a systematic but moderate
increase in going from SrVO to CaVO, in contrast to the critical
enhancement expected from the Brinkmann-Rice picture. It is proposed that the
metallic properties observed in this system near the Mott transition can be
explained by considering the effect of a non-local electron correlation.Comment: 14 pages in a Phys. Rev. B camera-ready format with 10 EPS figures
embedded. LaTeX 2.09 source file using "camera.sty" and "prbplug.sty"
provided by N. Shirakawa. For OzTeX (Macintosh), use "ozfig.sty" instead of
"psfig.sty". "ozfig.sty" can be also obtained by e-mail request to N.
Shirakawa: . Submitted to Phys. Rev.
Bondi-Hoyle-Lyttleton Accretion Model for Low-luminosity X-ray Sources in Globular Clusters
We present a new model for low-luminosity X-ray sources in globular clusters,
with L_x < 10^34 erg/s. The model we propose is that of a single neutron star
accreting from cluster gas that has accumulated as a natural product of stellar
evolution. An analytic luminosity function is derived under the assumption that
the speed distribution of neutron stars in the central region of a cluster is
described by a Maxwellian, and that the density and temperature of the gas are
uniform. Predictions of the model and implications for the gas content of
globular clusters are discussed.Comment: Accepted by ApJ. Minor changes and expanded conclusions sectio
Applying the ICMJE authorship criteria to operational research in low-income countries: the need to engage programme managers and policy makers [letter]
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