Phase transitions and interface phenomena in the cryogenic temperature domain of a niobate nanostructured ceramic.

Powder neutron diffraction and dielectric spectroscopy were used to investigate both crystallographic and dielectric permittivity properties of a Sr2KNb5O15 single phase ferroelectric oxide with nanosized grains ranging from 35 nm to 90 nm. Measurements were carried out in the temperature range from 10 K (cryogenic) to 550 K. All neutron diffraction data were indexed on the basis of a tetragonal double unit cell. From 10 K to room temperature the space group of the Sr2KNb5O15 ferroelectric phase was considered to be P4bm. The refinement of the paraelectric phase (at 550 K) was determined in the centrosymmetric space group P4/mbm. Dielectric spectroscopy measurements were performed in a thermal cycle. A set of four phase transitions non-related to symmetry changing was detected from Rietveld analysis of neutron powder diffraction data. During a thermal cycle, in the cryogenic temperature domain, strong thermal hysteresis is developed. Both phase transition and thermal hysteresis were correlated. These phenomena are associated with Nb-cation atomic displacements in the NbO6 octahedra along the c-axis direction and of the domain with different frequencies involving grains as well as an excess of interfaces ascribed to the grain boundary. The bulk/grain boundary interfaces in nanostructured ceramics are correlated with the thermal stability phenomenon.

CLOCK Genes and Circadian Rhythmicity in Alzheimer Disease.

Disturbed circadian rhythms with sleep problems and disrupted diurnal activity are often seen in patients suffering from Alzheimer disease (AD). Both endogenous CLOCK genes and external Zeitgeber are responsible for the maintenance of circadian rhythmicity in humans. Therefore, modifications of the internal CLOCK system and its interactions with exogenous factors might constitute the neurobiological basis for clinically observed disruptions in rhythmicity, which often have grave consequences for the quality of life of patients and their caregivers. Presently, more and more data are emerging demonstrating how alterations of the CLOCK gene system might contribute to the pathophysiology of AD and other forms of dementia. At the same time, the impact of neuropsychiatric medication on CLOCK gene expression is under investigation.

Magnetic phase diagram of the S = 1/2 triangular layered compound NaNiO(2): a single crystal study.

Using magnetic torque measurements on a NaNiO(2) single crystal, we have established the magnetic phase diagram of this triangular compound. It presents five different phases depending on the temperature (4-300 K) and magnetic field (0-22 T) revealing several spin reorientations coupled to different magnetic anisotropies.

[Cardiac pseudotumor revealing Behçet's disease]. / Pseudotumeur cardiaque révélant une maladie de Behçet.

INTRODUCTION: Cardiac thrombosis is a rare complication of Behçet's disease (BD), which may present as a cardiac tumor. Its discovery precedes, in half of the cases, the diagnosis of BD. The high mortality may be associated to postsurgical complications and/or an associated involvement of pulmonary arteries. CASE REPORT: We present the case of a 31 years old Caucasian French woman, with a history of venous thromboembolic disease, who had surgery after the discovery of a right ventricle tumor. That was an organised thrombus with endomyocardial fibrosis and a diagnosis of Behçet's disease was made after the surgery. The outcome was favourable under medical treatment associating corticosteroids, colchicine and antivitamin K (AVK), without relapse four years later. CONCLUSION: The discovery of an intracardiac mass in a young patient must evoke the diagnosis of cardiac thrombus and Behçet's disease, even in the absence of predisposing ethnic or geographic factor.

[Aortitis after G-CSF injections]. / Aortite après injections de G-CSF.

INTRODUCTION: Aortitis consists in aortic wall inflammation from infectious or non infectious cause. It may lead to aortic aneurysm with a risk of rupture, which is life-threatening and may justify surgical procedures. The cause of the aortitis is sometimes obscure. CASE REPORT: We report the case of a 55 years old woman who developed acute aortitis of the descending aorta after G-CSF (granulocyte-colony stimulating factor) injections for blood stem cells graft. No cause was found to the aortitis, the evolution was favorable after corticosteroid treatment, without aneurysm at six months. CONCLUSION: The present case rises the question of G-CSF (Neupogen responsibility in aortic lesions. Neutrophilic mediated diseases (Sweet's syndrome, pyoderma gangrenosum) and leukocytoclastic vasculitis were reported after G-CSF therapy. Neutrophils induced by G-CSF injections present functional abnormalities which may play a role in the pathogenesis of these diseases.

[Glutathione peroxidase, an oxidative stress biomarker, in the menstrual cycle]. / Glutation-peroxidaza, biomarker de stress oxidativ, in ciclul menstrual.

UNLABELLED: The oxygen, through his toxic effects, has determined the human organism to perfectionate multiple and efficient protection systems, especially the GSH-Px. OBJECTIVES: To study the activity of GSHPx activity in the 0, 14 and 28 days of the menstrual cycle in a group of women with psychiatric disorders. METHODS: The activity of GSH-Px was investigated in 24 women inpatients from the Psychiatric Department of Murgeni Hospital Vaslui. The GSH-Px level was determined in human serum using Fukuzawa method, modified in the Biochemistry Lab of the "Al. I. Cuza" University, Iasi. RESULTS: It has been no correlation between the type of psychiatric disorders and the level of GSHPx. This activity of GSHpx is in direct relationship with the concentration of sexual hormones, showing an hormone dependent enzymatic induction. A growth of the GSHPx activity from the day 0 to the 28th day of the menstrual cycle followed by a sudden decrease at menstruation time have been observed in all age groups. This fact demonstrated the existence of an enzymatic cycle.

Use of 19F nuclear magnetic resonance spectroscopy for probing substitution of Al for Ga in cloverite.

The synthesis of gallophosphate cloverite in the presence of aluminium leads to a partial substitution of Ga by Al. 27Al and 19F magic-angle spinning nuclear magnetic resonance (MAS NMR) studies on this material confirm this substitution. 27Al MAS NMR shows a broad line at 30 ppm which can be attributed to tetrahedrally coordinated Al in the solid. The 19F MAS NMR results are more complex. The spectrum presents five lines between -68 ppm and -95 ppm which can be assigned to fluorine in D4Rs with variable composition in Ga and Al. Two other lines, at -145.6 ppm and -178.2 ppm, may correspond to impurities and to a fluorine atom in a pseudo-sodalite cage environment, respectively.