Small-scale effects on the radial vibration of an elastic nanosphere based on nonlocal strain gradient theory.

Nonlocal strain gradient theory is widely used when dealing with micro- and nano-structures. In such framework, small-scale effects cannot be ignored. In this paper a model of radial vibration of an isotropic elastic nanosphere is theoretically investigated. The frequency equation is obtained from a nonlocal elastic constitutive law, based on a mix between local and nonlocal strain. This model is composed of both the classical gradient model and the Eringen's nonlocal elasticity model. To check the validity and accuracy of this theoretical approach, a comparison is made with the literature in certain specific cases, which shows a good agreement. Numerical examples are finally conducted to show the impact of small-scale effects in the radial vibration, which need to be included in the nonlocal strain gradient theory of nanospheres. It reveals that the vibration behavior greatly depends on the nanosphere size and nonlocal and strain gradient parameters. Particularly, when the nanospheres radius is smaller than a critical radius, the small-scale effects play a key role. Thus, the obtained frequency equation for radial vibration is very useful to interpret the experimental measurements of vibrational characteristics of nanospheres.

Numerical Investigation of the Dynamical Behavior of a Fluid-Filled Microparticle Suspended in Human Arteriole.

The study of artificial microparticles (capsules and vesicles) has gained a growing interest with the emergence of bio-engineering. One of their promoting applications is their use as therapeutic vectors for drug delivery, when capsules and vesicles release their capacity in a targeted environment. The dynamic behavior of capsules and vesicles in confined or unbounded flows was widely studied in the literature and their mechanical response was truthfully described using constitutive laws with good agreement with experiences. However, in a context of biological application, to our knowledge, none of published studies investigating the mechanical response of deformable microparticle took into account the real physiological conditions: the rheological properties of blood such as carrying fluid and the mechanical properties of blood vessels. In this paper, we consider a hyperelastic microparticle suspended in human arteriole. We investigate the deformation of the microparticle resulting from its interaction with blood flow and the arteriolar wall using various capillary numbers and respecting physiological properties of blood and arterial wall. The influence of the blood viscosity model (Newtonian versus shear thinning) is investigated and a comparison with a rigid microchannel and a muscle-embedded arteriole is carried out. The fluid structure interaction (FSI) problem is solved using arbitrary Lagrangian Eulerian (ALE) method. Our simulations have revealed that the arteriolar wall distensibility deeply influences both the deformation and velocity of the microparticle: the deformation strongly increases while the velocity decreases in comparison to an infinitely rigid wall. In the context of therapeutic procedure of targeted drug-delivery, a particular attention should be addressed to these observations, in particular for their implication in the burst mechanism.

Dynamics of the aortic arch submitted to a shock loading: Parametric study with fluid-structure models.

This work aims to present some fluid-structure models for analyzing the dynamics of the aorta during a brusque loading. Indeed, various lesions may appear at the aortic arch during car crash or other accident such as brusque falling. Aortic stresses evolution are simulated during the shock at the cross section and along the aorta. One hot question was that if a brusque deceleration can generate tissue tearing, or a shock is necessary to provoke such a damage. Different constitutive laws of blood are then tested whereas the aorta is assumed linear and elastic. The overall shock model is inspired from an experimental jig. We show that the viscosity has strong influence on the stress and parietal moments and forces. The nonlinear viscosity has no significant additional effects for healthy aorta, but modifies the stress and parietal loadings for the stenotic aorta.

[Idiopathic segmental infarct of the omentum. Differential diagnosis in an obese patient]. / Infarctus segmentaire idiopathique du grand épiploon. Savoir y penser chez un patient obèse.

OBJECTIVE: Infarction of the greater omentum is a rare etiology of acute abdominal pain. The differential diagnosis, especially with appendicitis, is difficult to establish. CASE REPORT: A 29 years-old male presented with acute abdominal pain. He underwent a laparoscopic resection on the 5th hospital day because of persistant pain despite conservative management. Histopathological examination confirmed the diagnosis of omental infarction. DISCUSSION: Primary segmental necrosis of the omentum is a rare entity. Obesity and cardiovascular diseases are considered predisposing conditions. The infarctions tend to occur in the right side of the omentum. Abdominal pain is predominant in opposition to the patient's good general condition. Laboratory results are usually nonspecific. Abdominal ultrasound may show a solid, ovoid, hyperechoic lesion. CT-scan may depict a fatty oval-shaped mass below the right anterolateral parietal wall associated with a thickening of the anterior parietal peritoneum. CONCLUSION: The correct diagnosis of omental infarction is important to establish preoperatively in acute abdominal pain, as in uneventful courses surgery can be avoided.

[Cerebral ischemia and severe digestive manifestations during rheumatoid purpura]. / Ischémie cérébrale et manifestations digestives sévères au cours d'un purpura rhumatoïde.

A 14-year-old male patient with Schönlein-Henoch vasculitis developed neurologic manifestations including cortical blindness, seizures and CT scan evidence of occipital ischemia. These manifestations occurred concomitantly with severe bleeding from a duodenal ulcer seen at endoscopy. Corticosteroid therapy was initially rejected then finally given because of the severity of neurologic involvement. Both neurologic and digestive manifestations improved rapidly. A control digestive endoscopy performed 30 days later was normal.

[Infantile visceral leishmaniasis in Morocco. A review of 67 cases managed at the Rabat Hospital for children (1979-1988)]. / Leishmaniose viscérale infantile au maroc. Expérience de l'Hôpital d'Enfants de Rabat à propos de soixante-sept cas (1979-1988).

Sixty-seven cases of visceral leishmaniasis managed at the Rabat Hospital for Children from 1979 through 1988 were studied retrospectively. Mode of onset and outcome were analyzed. Clinical manifestations included enlargement of the spleen (60 cases), fever (45 cases), enlargement of the liver (38 cases), and weight loss (53 cases). Six patients had misleading onset manifestations including one case each of pigmentary lithiasis, severe marasmus without enlargement of the spleen, nephrotic syndrome, evidence of portal hypertension, jaundice, and an abdominal mass. Diagnosis was established by the bone marrow study (positive in 58 of 66 patients) or by indirect immunofluorescence (positive in 21 of 24 patients, including 6 with a negative bone marrow study). In one patient, the parasite was recovered from a jejunal biopsy specimen. Drugs used included N-methyl-glucamine in 86 cases, pentamidine in 26 cases, and sodium gluconate stibio in one case. Complete recovery was achieved in 24 patients. Seven patients failed to respond to therapy. There were 8 deaths, including 4 prior to initiation of therapy; among these four deaths, three were due to acute anemia. Another patient died after leaving the hospital despite the physician's advice to the contrary. The 3 remaining deaths were caused by toxicity of the drugs used. Thirty-one patients were lost to follow-up after initial improvement. The severity of this disease and cost of management make earlier diagnosis and faultless management imperative.

[The impact of National Vaccination Days in the Agadir province of Morocco]. / Etude de l'impact des journées nationales de vaccination du Maroc dans la province d'Agadir.

In many countries the realization of the vaccination programmes is prevented by the lack of motivation of the population. We report herewith the positive results of a programme of social mobilisation observed in the Agadir province following the organization of National Vaccination Days in Morocco.

Endocrine cells in the anal canal.

Endocrine cells are normal inhabitants of the anal canal. While numerous endocrine cells are distributed throughout anal ducts and crypts, few are dispersed in the anal transitional zone. All these cells were characterized as serotonin-storing cells, and this endocrine profile is quite distinctive from that of adjacent mucosae. Rectal epithelium contains serotonin, somatostatin, enteroglucagon, BPP and HPP immunoreactive cells; endocrine cells are lacking in the pectinal folds and perianal skin. It is suggested that this distinctive hormonal profile may be regarded as a specific marker of this anal territory. The same pattern is found in the fetal transitional lining of anal canal. Evidence of serotonin-storing cells in the transitional epithelium of anal glands and crypts and in the ATZ epithelium, reinforces the homology between these linings and urothelium. The presence of a similar fetal epithelium implies that ATZ epithelium in adults is not necessarily metaplastic. All derivatives of the cloaca may therefore share the same endocrine profile.