Sound velocity and refractive index of pure N2 fluid and of equimolar N2-CO2 fluid mixture up to 15 GPa.

The sound velocity and refractive index of pure N2 and of the equimolar N2-CO2 mixture are measured up to 15 GPa and 700 K in a resistive heating diamond anvil cell. The refractive index vs pressure is obtained by an interferometric method. The adiabatic sound velocity is then determined from the measurement of the Brillouin frequency shift in the backscattering geometry and the refractive index data. No phase separation of the N2-CO2 fluid mixture is observed. The fluid mixture properties are discussed in terms of ideal mixing.

X-ray magnetic circular dichroism measurements in Ni up to 200 GPa: resistant ferromagnetism.

The structural stability of fcc Ni over a very large pressure range offers a unique opportunity to experimentally investigate how magnetism is modified by simple compression. K-edge x-ray magnetic circular dichroism (XMCD) shows that fcc Ni is ferromagnetic up to 200 GPa, contradicting recent predictions of an abrupt transition to a paramagnetic state at 160 GPa. Density functional theory calculations point out that the pressure evolution of the K-edge XMCD closely follows that of the p projected orbital moment rather than that of the total spin moment. The disappearance of magnetism in Ni is predicted to occur above 400 GPa.

Synthesis of FeH5: A layered structure with atomic hydrogen slabs.

High pressure promotes the formation of polyhydrides with unusually high hydrogen-to-metal ratios. These polyhydrides have complex hydrogenic sublattices. We synthesized iron pentahydride (FeH5) by a direct reaction between iron and H2 above 130 gigapascals in a laser-heated diamond anvil cell. FeH5 exhibits a structure built of atomic hydrogen only. It consists of intercalated layers of quasicubic FeH3 units and four-plane slabs of thin atomic hydrogen. The distribution of the valence electron density indicates a bonding between hydrogen and iron atoms but none between hydrogen atoms, presenting a two-dimensional metallic character. The discovery of FeH5 suggests a low-pressure path to make materials that approach bulk dense atomic hydrogen.

Intranasal infection with Bordetella bronchiseptica in gnotobiotic piglets.

Nineteen gnotobiotic piglets, four to six days old, from three different litters, were inoculated intranasally on three consecutive days with a pure culture of Bordetella bronchiseptica. Necropsy 10 to 30 days after inoculation revealed atrophic rhinitis lesions in all and pneumonia in 13 (73 per cent)infected piglets. One died of septicaemia two days after inoculation. Agglutinating antibodies were detected in the sera of all piglets necropsied from 17 to 30 days after inoculation. Five control piglets showed no lesions or serological changes.

In vitro effect of glucocorticoids on phagocytic function of sheep alveolar macrophages.

The potentiation of infection is a recognized adverse effect of steroids. This study examined the in vitro effect of glucocorticoids on sheep alveolar macrophage phagocytic function, an essential means of cellular defence in the lungs, by evaluating the phagocytosis of zymosan particles after 30 min of contact between alveolar macrophages and steroids. Hydrocortisone, dexamethasone phosphate and methylprednisolone significantly reduced the phagocytic capability of sheep alveolar macrophages, but the effects of dexamethasone isonicotinate, prednisolone and flumethasone were less marked.

Differential diagnosis of neurologically expressed disorders in Western European cattle.

A classification of neurological or neurologically expressed disorders that occur in Western European cattle aged 12 month and over has been established on the basis of aetiology, frequency and conditions of appearance, age and type of animals concerned and the main clinical signs observed. Neurologically expressed disorders have been classified according to different groups of causes: biological, non-biological and non-specific or unknown. Differential diagnosis of neurologically expressed disorders is an essential element in the clinical epidemiological surveillance of bovine spongiform encephalopathy. A growing number of aetiologies are described in the scientific literature. The identification and centralised management of neurological disorders will make it possible, one the one hand, to take account of the inherent variability in the clinical forms encountered and in the diagnostic approaches of the observers and, on the other hand, to identify new risk factors in order to control them.

Melting of iron at Earth's inner core boundary based on fast X-ray diffraction.

Earth's core is structured in a solid inner core, mainly composed of iron, and a liquid outer core. The temperature at the inner core boundary is expected to be close to the melting point of iron at 330 gigapascal (GPa). Despite intensive experimental and theoretical efforts, there is little consensus on the melting behavior of iron at these extreme pressures and temperatures. We present static laser-heated diamond anvil cell experiments up to 200 GPa using synchrotron-based fast x-ray diffraction as a primary melting diagnostic. When extrapolating to higher pressures, we conclude that the melting temperature of iron at the inner core boundary is 6230 ± 500 kelvin. This estimation favors a high heat flux at the core-mantle boundary with a possible partial melting of the mantle.

Population-level retrospective study of neurologically expressed disorders in ruminants before the onset of bovine spongiform encephalopathy (BSE) in Belgium, a BSE risk III country.

A retrospective epidemiological study (n = 7,875) of neurologically expressed disorders (NED) in ruminants before the onset of the bovine spongiform encephalopathy epidemic (years studied, 1980 to 1997) was carried out in Belgium. The archives of all veterinary laboratories and rabies and transmissible spongiform encephalopathy (TSE) epidemiosurveillance networks were consulted. For all species, a significantly higher number of NED with virological causes (rabies) was reported south of the Sambre-Meuse Valley. During the period 1992 to 1997, for which the data were complete, (i) the predicted annual incidence of NED varied significantly as a function of species and area (higher numbers in areas where rabies was present) but was always above 100 cases per million, and (ii) the mean incidence of suspected TSE cases and, among them, those investigated by histopathological examination varied significantly as a function of species and area. The positive predictive value of a presumptive clinical diagnosis of NED ranged from 0.13 (game) to 0.63 (sheep). Knowledge of the positive predictive value permits the definition of a reference point before certain actions (e.g., awareness and training campaigns) are undertaken. It also shows the usefulness of a systematic necropsy or complementary laboratory tests to establish an etiological diagnosis. TSE analysis of a small, targeted historical sampling (n = 48) permitted the confirmation of one case and uncovered another case of scrapie. The results of the present study help to develop and maintain the quality of the worldwide clinical epidemiological networks for TSE, especially in countries that in the past imported live animals, animal products, and feedstuffs from countries with TSE cases.

[Respiratory diseases of the fowl:principles of histopathological diagnosis]. / Elements du diagnostic histopathologique differentiel des principales affections respiratoires de la poule.

Groups of specific pathogen free chickens were inoculated with five strains of Newcastle disease virus, one strain of adenovirus, four strains of infectious bronchitis virus, one strain of Mycoplasma gallisepticum and with infectious bronchitis virus together with Mycoplasma gallisepticum. Lungs and tracheas were taken at regular intervals for histopathological examination. A diagnosis could be based on tracheal lesions at different periods of their development. Newcastle disease was distinguished by a necrotic and haemorrhagic tracheitis. Adenovirus infection caused epithelial degeneration with basophil intranuclear inclusion bodies and discrete infiltration of the lamina propria by lymphocytes and histiocytes. Infectious bronchitis was characterised by a strong hyperplasia of epithelial cells and Mycoplasmosis by a massive infiltration of the lamina propria by lymphocytes and histiocytes. Epithelial hyperplasia and cellular infiltration of tracheal mucosa were typical of mixed infection with infectious bronchitis virus and mycoplasma.

[Alveolar macrophages of sheep: purification and identification]. / Le macrophage alvéolaire de mouton: purification et identification.

Broncho-alveolar lavages of sheep lungs were performed for alveolar macrophage identification and purification. The total number of harvested cells was 1.5 x 10(8) cells per 600 ml fluid lavage, with a mean of 2.48 x 10(5) cells/ml. Cell viability was 97.14%. Alveolar macrophages represented 78% of cells harvested. Separation was carried out by adherence to plastic flasks followed by Percoll centrifugation. The best results (purity of macrophage population and cell viability) was obtained with Percoll solution and NaCl 1.5 mol.l-1 with a density of 1.033 and 1.050. Identification was carried out by the non specific esterase staining method. In conclusion, broncho-alveolar lavage of isolated sheep lung is a simple and reliable method of respiratory tract cell collection.