Origin of relationship between ferromagnetic response and damage in stretched systems

This article presents a study whose purpose is to elucidate the damage effects in thin films on their magnetic response. Co₄₀Fe₄₀B₂₀ and Ni₈₀Fe₂₀ films of different nanometric thicknesses were stretched by more than 10% and in situ probed by atomic force microscopy measurements to determine their irreversible mechanical behavior (multi-cracking, buckling). Once these phenomena have been well identified, magnetic behavior of these stretched systems has been studied by ferromagnetic resonance to measure resulting magnetic anisotropy and damping evolutions. All of these experimental studies show that the magnetic properties are mainly affected by the stresses generated during the damage but not by the local discontinuities induced by the numerous cracks and buckles. This is in particular confirmed by the almost zero sensitivity to the damage of the magnetic properties of Ni₈₀Fe₂₀ alloy which is known for its vanishing magnetostriction.

Controlled co-deposition of FePt nanoparticles embedded in MgO: a detailed investigation of structure and electronic and magnetic properties

Films of FePt nanoparticles (NPs) embedded in MgO were obtained by controlled co-deposition of FePt NPs pre-formed by a gas aggregation source and of Mg evaporated in an oxygen atmosphere. Assemblies of core-shell FePt@MgO NPs and films of FePt NPs embedded in MgO matrix could be obtained by varying FePt and Mg deposition rates. Transmission electron microscopy (TEM) and high resolution-TEM revealed the core-shell structure of the NPs, with an FePt core (of average diameter (d) = 4.75 nm) presenting a multitwinned icosahedral structure, and MgO partially in crystalline form. The functional effect of the MgO shell in shielding the FePt core from external oxidation was shown with XPS. Upon controlled annealing, a transition from A1 to L10 ordering could be obtained, with structural and morphological re-arrangement. The magnetic hysteresis loops obtained from alternating gradient field magnetometry at room temperature show a 'wasp-waist' shape, with small values of coercive field (Hc = 300-1400 Oe), decreasing at increasing amounts of co-deposited MgO.

Follow up in a developing country of patients with complete atrio-ventricular block

Aim

The purpose of the study was to assess the incidence and survival rate of patients with complete atrio-ventricular block in the cardiac centre of St Elizabeth Catholic General Hospital, Kumbo, Cameroon.

Methods

Between 2009 and 2011, 26 patients with complete atrio-ventricular block were diagnosed at our institution. Complete atrio-ventricular block was defined as complete heart block, diagnosed by echocardiographic or electrocardiographic documentation of the dissociation between electrical activity of the atria and ventricles. Hospital charts, electrocardiograms (ECG), echocardiography and chest radiography were reviewed.

Results

The triad of symptoms that pointed to the diagnosis of complete atrio-ventricular block was mainly fatigue, shortness of breath on mild physical exertion, and dizziness. The median age at diagnosis was 65 ± 15 years. The escape rhythm showed a narrow QRS complex in 35.2% of patients, whereas wide QRS complexes were seen in 64.8%. In only 15 patients were pacemakers implanted: dual-chamber in 10 and single-chamber in five cases, depending on the availability of the pacemakers. During the observational period, five non-implanted patients died, giving a mortality rate of 45%. We recorded no deaths in patients with pacemakers.

Conclusion

In developing countries, natural selection is observed in patients with complete atrio-ventricular block. Lack of infrastructure and early detection, and financial limitations are the main problems faced in the follow up of these patients. Re-organisation of the public health system, new programmes for the prevention of cardiovascular diseases, and government subsidisation are needed in our milieu.

Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension

Spontaneous intracranial hypotension (SIH) is a polyhedric syndrome whose common denominator is postural headache. We describe four cases of spontaneous intracranial hypotension, their clinical-iconographic aspects, and emphasize the use of morphological MRI in the diagnosis and follow-up of this condition. In addition, we propose 3D myelocisternography MRI as a further contribution in cerebrospinal fluid losses causing postural headache.

Dynamic breast magnetic resonance imaging without complications in a patient with dual-chamber demand pacemaker

Mammography and ultrasound indicated a cancer of the right breast in a 77-year-old woman with a dual-chamber demand pacemaker. The patient was not pacemaker-dependent. She underwent breast 1.5T magnetic resonance imaging (MRI) (dynamic gradient echo sequence with Gd-DOTA 0.1 mmol/kg). Before the patient entered the MR room, the configuration of the device was changed (the response to magnet was switched from asynchronous to off and the rate-responsive algorithm was disabled). No relevant modifications of heart rhythm or rate were observed during the MR examination. No symptom was reported. Immediately after the examination, the pacemaker interrogation showed neither program changes nor alert warnings. MRI detected a bifocal cancer in the right breast which allowed tailored breast-conserving treatment to be initiated. Histopathology confirmed a bifocal invasive ductal carcinoma.

In vivo animal demonstration of the effect of vasoactive drugs using 195mAu and gamma camera techniques

195mAu, an ultrashort-lived (physical half life = 30.5 s) generator-produced radionuclide, has been used in an animal model to study, by gamma camera techniques, the peripheral effects of the vasoactive drugs norepinephrine and sodium nitroprusside systemically administered or epinephrine (intraarterially) injected at various concentrations. According to the results obtained by the analysis of time activity curves generated from areas of interest drawn on the proximal and distal parts of the limbs, the well known hemodynamic changes induced by these drugs, vasoconstriction (resulting in a decrease of the distal activity recorded), or vasodilatation (shortening the time of radioactivity appearance), could be observed. It is concluded that gamma camera techniques using the ultrashort lived radionuclide 195mAu allow the in vivo study of the effects of vasoactive drugs in an animal model and potentially in clinical situations.