200 research outputs found
La mucormycose nasosinusienne: Diagnostic et modalites therapeutiques
La mucormycose est une infection fongique rare qui touche essentiellement les sujets immunodéprimés et notamment diabétiques. La localisation de cette maladie est surtout nasosinusienne. Son pronostic reste mauvais malgré le développement des moyens de prise en charge. Nous rapportons deux cas de mucormycose nasosinusienne à travers lesquels nous discutons les aspects cliniques et radiologiques, ainsi que les moyens thérapeutiques de cette maladie. Il s’agit d’un homme et d’une femme âgés respectivement de 56 et 52 ans. Le premier était diabétique et la deuxième insuffisante rénale. L’évolution était lente dans le premier cas et très rapide dans le deuxième. Le diagnostic était dans les deux cas histologique. L’évolution était, dans le premier cas, favorable après traitement associant débridement chirurgical et amphotéricine B, et dans le second rapidement fatale. Conclusion : La mucormycose nasosinusienne est une affection grave dont le pronostic peut être mauvais malgré le traitement.Mots clés : Infection fongique, mucormycose rhinocérébrale, zygomycètes
Chemical synthesis and magnetic properties of monodisperse cobalt ferrite nanoparticles
In this work, a successful synthesis of magnetic cobalt ferrite (CoFe2O4)
nanoparticles is presented. The synthesized CoFe2O4 nanoparticles have a
spherical shape and highly monodisperse in the selected solvent. The effect of
different reaction conditions such as temperature, reaction time and varying
capping agents on the phase and morphology is studied. Scanning transmission
electron microscopy showed that the size of these nanoparticles can be
controlled by varying reaction conditions. Both X-ray diffraction and energy
dispersive X-ray spectroscopy corroborate the formation of CoFe2O4 spinel
structure with cubic symmetry. Due to optimized reaction parameters, each
nanoparticle was shown to be a single magnetic domain with diameter ranges from
6 to 16 nm. Finally, the magnetic investigations showed that the obtained
nanoparticles are superparamagnetic with a small coercivity value of about 315
Oe and a saturation magnetization of 58 emu/g at room temperature. These
results make the cobalt ferrite nanoparticles promising for advanced magnetic
nanodevices and biomagnetic applications.Comment: 10 pages, 9 figure
Electrocaloric effect in Ba(0.2)Ca(0.8)Ti(0.95)Ge(0.05)O(3) determined by a new pyroelectric method
The present letter explores the electrocaloric effect (ECE) in the lead free
oxide Ba0.8Ca0.2Ti0.95Ge0.05O3 ceramics (BCTG). The electrocaloric responsivity
(dT/dE) was determined by two different methods using the Maxwell relationship
(dT/dE)~(dP/dT)_E. In a first well-known indirect method, P-E hysteresis loops
were measured in a wide temperature range from which the pyroelectric
coefficient p_E=(dP/dT)_E and thus (dT/dE) were determined by derivation of
P(T,E) data. In the second novel method the pyroelectric coefficient p_E and
consequently the electrocaloric responsivity was determined by direct
measurements of the pyroelectric currents under different applied electric
fields. Within the experimental error good agreement was obtained between two
methods with an electrocaloric responsivity equal to 0.18 +/- 0.05 10-6 K.m.V-1
was obtained at about 410 KComment: 5 pages, 4 figure
Wigner's Dynamical Transition State Theory in Phase Space: Classical and Quantum
A quantum version of transition state theory based on a quantum normal form
(QNF) expansion about a saddle-centre-...-centre equilibrium point is
presented. A general algorithm is provided which allows one to explictly
compute QNF to any desired order. This leads to an efficient procedure to
compute quantum reaction rates and the associated Gamov-Siegert resonances. In
the classical limit the QNF reduces to the classical normal form which leads to
the recently developed phase space realisation of Wigner's transition state
theory. It is shown that the phase space structures that govern the classical
reaction d ynamicsform a skeleton for the quantum scattering and resonance
wavefunctions which can also be computed from the QNF. Several examples are
worked out explicitly to illustrate the efficiency of the procedure presented.Comment: 132 pages, 31 figures, corrected version, Nonlinearity, 21 (2008)
R1-R11
Structure and dynamics of ring polymers: entanglement effects because of solution density and ring topology
The effects of entanglement in solutions and melts of unknotted ring polymers
have been addressed by several theoretical and numerical studies. The system
properties have been typically profiled as a function of ring contour length at
fixed solution density. Here, we use a different approach to investigate
numerically the equilibrium and kinetic properties of solutions of model ring
polymers. Specifically, the ring contour length is maintained fixed, while the
interplay of inter- and intra-chain entanglement is modulated by varying both
solution density (from infinite dilution up to \approx 40 % volume occupancy)
and ring topology (by considering unknotted and trefoil-knotted chains). The
equilibrium metric properties of rings with either topology are found to be
only weakly affected by the increase of solution density. Even at the highest
density, the average ring size, shape anisotropy and length of the knotted
region differ at most by 40% from those of isolated rings. Conversely, kinetics
are strongly affected by the degree of inter-chain entanglement: for both
unknots and trefoils the characteristic times of ring size relaxation,
reorientation and diffusion change by one order of magnitude across the
considered range of concentrations. Yet, significant topology-dependent
differences in kinetics are observed only for very dilute solutions (much below
the ring overlap threshold). For knotted rings, the slowest kinetic process is
found to correspond to the diffusion of the knotted region along the ring
backbone.Comment: 17 pages, 11 figure
A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions
Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact
Human and Canine Echinococcosis Infection in Informal, Unlicensed Abattoirs in Lima, Peru
Echinococcus granulosus infections are a major public health problem in livestock-raising regions around the world. The life cycle of this tapeworm is sustained between dogs (definitive host, canine echinococcosis), and herbivores (intermediary host, cystic hydatid disease). Humans may also develop cystic hydatid disease. Echinococcosis is endemic in rural areas of Peru; nevertheless, its presence or the extension of the problem in urban areas is basically unknown. Migration into Lima, an 8-million habitant's metropolis, creates peripheral areas where animals brought from endemic areas are slaughtered without veterinary supervision. We identified eight informal, unlicensed abattoirs in a peripheral district of Lima and performed a cross-sectional study in to assess the prevalence of canine echinococcosis, evaluated by coproELISA followed by PCR evaluation and arecoline purge. Eight of 22 dogs (36%) were positive to coproELISA, and four (18%) were confirmed to be infected with E. granulosus tapeworms either by PCR or direct observation (purge). Later evaluation of the human population living in these abattoirs using abdominal ultrasound, chest X-rays and serology, found 3 out of 32 (9.3%) subjects with echinococcal cysts in the liver (two viable, one calcified), one of whom had also lung involvement and a strongly positive antibody response. Autochthonous transmission of E. granulosus is present in Lima. Informal, unlicensed abattoirs may be sources of infection to neighbouring people in this urban environment
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