1,402 research outputs found
Asymptotic Behavior of an Age-Structured Population Model and Optimal Maturation Age
AbstractA continuous age-structured population model with two population groups, juveniles and adults, and with a dynamics for the resource, is considered. The only density dependence is through a uniform increase of the death rates. A complete description of the asymptotic behavior of the population dynamics system is obtained showing under natural hypotheses the existence of a nontrivial (“ecological”) equilibrium which attracts any initial nonzero population with nonzero initial amount of resources. Assuming that the offspring production rate is an increasing function of the maturation age, the evolutionarily stable value of this variable is briefly discussed
Hématome post traumatique du muscle iléopsoas avec paralysie du nerf fémoral: à propos d’un cas et revue de la littérature
L'hématome compressif du muscle iliopsoas dans le petit bassin est une complication connue des traitements anticoagulants, mais reste rare enpost-traumatique. La présente observation illustre un cas de cet hématome chez un adolescent de 14 ans qui s'est présenté avec une douleur posttraumatique de la cuisse et un déficit actif d'extension de la jambe évoluant depuis plus de 3 mois. Un examen clinique a montré l'existence d'une paralysie complète du quadriceps. Une IRM du petit bassin a retrouvé un volumineux hématome du muscle iliopsoas comprimant le nerf fémoral.Un drainage chirurgical de l'hématome a été réalisé. La récupération musculaire était partielle après six mois de recul
IN VITRO EFFECT OF ACETYLSALICYLIC ACID ON CALCIUM OXALATE CRYSTALLIZATION: AN APPROACH TO ANTILITHIASIS
Objective: In recent years, significant progress has been made in identifying and counting physico-chemical processes involved in urinary stone formation. The ability of urine to inhibit calcium oxalate crystallization is considered an important mechanism against stone formation. Several natural substances were tested to inhibit calcium oxalate crystallization. In the present study, we evaluate the effects of acetylsalicylic acid, also known as Aspirin, as an inhibitor of calcium oxalate crystallization in vitro.Methods: The nucleation and aggregation of calcium oxalate crystals were studied using turbidimetric 400-sec time course measurements of optic density at 620 nm after mixing solutions containing calcium chloride and sodium oxalate at room temperature, pH 5.7. The formation of crystals is induced by the addition of the oxalate to calcium solution. The effects on calcium oxalate crystal growth of acetylsalicylic acid with various concentrations were examined. The maximum increase of optic density in the course of time reflects maximum rate of formation of new particles. After reaching equilibrium, a progressive decrease of optic density with time is observed. Rate of aggregation is derived from the maximum decrease in optic density.Results: The results showed that if a concentration of acetylsalicylic acid is more than 1,66 mM both rate of formations of new particles and Rate of aggregation decreased (P<0.05).Conclusion: acetylsalicylic acid has a significant effect on nucleation as well as on crystal growth stage; consequently, it inhibits the crystal formation of calcium oxalate urinary lithiasis.Ă‚Â Ă‚
Engineering the spatial confinement of exciton-polaritons in semiconductors
We demonstrate the spatial confinement of electronic excitations in a solid
state system, within novel artificial structures that can be designed having
arbitrary dimensionality and shape. The excitations under study are
exciton-polaritons in a planar semiconductor microcavity. They are confined
within a micron-sized region through lateral trapping of their photon
component. Striking signatures of confined states of lower and upper polaritons
are found in angle-resolved light emission spectra, where a discrete energy
spectrum and broad angular patterns are present. A theoretical model supports
unambiguously our observations
Soft-tissue metastasis revealing a pancreatic adenocarcinoma: One case report and a review of literature
Soft tissue metastases from pancreatic adenocarcinoma are rare lesions and can be the source of diagnostic confusion both clinically and pathologically. To our knowledge, one patient has been reported on with soft tissue lesions that ultimately disclose a pancreatic adenocarcinoma. We report here on a patient who presented with a metastatic soft tissue lesion in the trochanter, and the buttocks, as the initial manifestation of pancreatic adenocarcinoma. Soft tissue metastasis from pancreatic carcinoma is a rare finding. Clinicians should be aware that metastatic soft tissue lesions could be the initial presenting sign for pancreatic cancer. Also, the immunohistochemical staining for CK 7 and 19 may be helpful for the diagnosis of metastatic pancreatic adenocarcinoma
First Results on Zinc Oxide Thick Film Deposition by Inverted Magnetron Sputtering for Cyclotron Solid Targets Production
The magnetron sputtering technique has been investigated in recent years with ever-growing interest as a verifiable solid target manufacturing technology aimed at the production of medical radionuclides by using low-energy cyclotron accelerators. However, the possible loss of high-cost materials prevents access to work with isotopically enriched metals. The need for expensive materials for the supply of the growing demand for theranostic radionuclides makes the material-saving approach and recovery essential for the radiopharmaceutical field. To overcome the main magnetron sputtering drawback, an alternative configuration is proposed. In this work, an inverted magnetron prototype for the deposition of tens of (Formula presented.) m film onto different substrates is developed. Such configuration for solid target manufacturing has been proposed for the first time. Two (Formula presented.) depositions (20–30 (Formula presented.) m) onto (Formula presented.) backing were carried out and analysed by SEM (Scanning Electron Microscopy) and XRD (X-ray Diffractogram). Their thermomechanical stability under the proton beam of a medical cyclotron was tested as well. A possible improvement of the prototype and the perspective of its utilisation were discussed
Interplay between local structure and electronic properties on CuO under pressure
The electronic and local structural properties of CuO under pressure have
been investigated by means of X-ray absorption spectroscopy (XAS) at Cu K edge
and ab-initio calculations, up to 17 GPa. The crystal structure of CuO consists
of Cu motifs within CuO square planar units and two elongated apical Cu-O
bonds. The CuO square planar units are stable in the studied pressure
range, with Cu-O distances that are approximately constant up to 5 GPa, and
then decrease slightly up to 17 GPa. In contrast, the elongated Cu-O apical
distances decrease continuously with pressure in the studied range. An
anomalous increase of the mean square relative displacement (EXAFS Debye
Waller, \sigma) of the elongated Cu-O path is observed from 5 GPa up to 13
GPa, when a drastic reduction takes place in \sigma. This is interpreted in
terms of local dynamic disorder along the apical Cu-O path. At higher pressures
(P>13 GPa), the local structure of Cu changes from a 4-fold square
planar to a 4+2 Jahn-Teller distorted octahedral ion. We interpret these
results in terms of the tendency of the Cu ion to form favorable
interactions with the apical O atoms. Also, the decrease in Cu-O apical
distance caused by compression softens the normal mode associated with the
out-of-plane Cu movement. CuO is predicted to have an anomalous rise in
permittivity with pressure as well as modest piezoelectricity in the 5-13 GPa
pressure range. In addition, the near edge features in our XAS experiment show
a discontinuity and a change of tendency at 5 GPa. For P < 5 GPa the evolution
of the edge shoulder is ascribed to purely electronic effects which also affect
the charge transfer integral. This is linked to a charge migration from the Cu
to O, but also to an increase of the energy band gap, which show a change of
tendency occurring also at 5 GPa
- …