Muon tomography, or muography, stands out as a non-invasive technique for the scanning of big objects' internal structure. It relies on the measurement of the direction changes or absorption of ...atmospheric muons when crossing the studied object. Proposed several decades ago, the performance achieved in particle detectors in the last years, specially in terms of stability, robustness and precision, has enlarged the possible applications of this technique. Bulk Micromegas represent a well-known technology suitable for the construction of muon telescopes based on these detectors. Thus autonomous and portable instruments have been conceived and constructed at Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), being able to perform muography measurements in-situ, next to the studied objects. At present, a new muon telescope concept is being developed at CEA, combining a Time Projection Chamber (TPC) readout by a 2D multiplexed bulk Micromegas. This new generation of detectors will enlarge the possible application fields of muography, being specially interesting for geotechnics.
Mitochondrial ferritin is a recently identified protein precursor encoded by an intronless gene. It is specifically taken up by the mitochondria and processed to a mature protein that assembles into ...functional ferritin shells. The full mature recombinant protein and its S144A mutant were produced to study structural and functional properties. They yielded high quality crystals from Mg(II) solutions which diffracted up to 1.38
Å resolution. The 3D structures of the two proteins resulted very similar to that of human H-ferritin, to which they have high level of sequence identity (∼80%). Metal-binding sites were identified in the native crystals and in those soaked in Mn(II) and Zn(II) solutions. The ferroxidase center binds binuclear iron at the sites A and B, and the structures showed that the A site was always fully occupied by Mg(II), Mn(II) or Zn(II), while the occupancy of the B site was variable. In addition, distinct Mg(II) and Zn(II)-binding sites were found in the 3-fold axes to block the hydrophilic channels. Other metal-binding sites, never observed before in H-ferritin, were found on the cavity surface near the ferroxidase center and near the 4-fold axes. Mitochondrial ferritin showed biochemical properties remarkably similar to those of human H-ferritin, except for the difficulty in renaturing to yield ferritin shells and for a reduced (∼41%) rate in ferroxidase activity. This was partially rescued by the substitution of the bulkier Ser144 with Ala, which occurs in H-ferritin. The residue is exposed on a channel that connects the ferroxidase center with the cavity. The finding that the mutation increased both catalytic activity and the occupancy of the B site demonstrated that the channel is functionally important. In conclusion, the present data define the structure of human mitochondrial ferritin and provide new data on the iron pathways within the H-type ferritin shell.
An apparatus has been constructed to characterize the chemical intermediates and products of tribochemical reactions in situ by means of internal reflection spectroscopy. Diamond-like carbon (DLC) ...films were deposited by plasma chemical vapor deposition on rubbing substrates and on a germanium internal reflectance element. Spectra were taken in situ while rubbing the surfaces together under moderate loads (approximately 7.8 kPa pressure). The surface of the DLC was found to contain carbonyl groups immediately after deposition. Rubbing the surfaces in air and in water removed these groups. Rubbing also oxidized the surface, forming carbon-oxygen single bonds. A sporadic tribochemical reaction involved the formation of tertiary vinyl groups at the surface.
Abstract Objectives This study aimed to evaluate the frequency of diabetic ketoacidosis (DKA) and its associated factors at the diagnosis of type 1 diabetes (T1D) in French children and adolescents ...prior to launching a public-health campaign of information to prevent DKA. Patients and methods Over a 1-year period, 1299 youngsters (aged < 15 years) were diagnosed with T1D at 146 paediatric centres in all regions of France. Age, gender, duration of symptoms, patient's pathway to diagnosis, clinical and biological signs, and family history of T1D were collected for each newly diagnosed patient. DKA was defined as pH < 7.30 or bicarbonate < 15 mmol/L, and severe DKA as pH < 7.10 or bicarbonate < 5 mmol/L. Results At the time of diagnosis, 26% of the children were aged 0–5 years, 34% were 5–10 years and 40% were 10–15 years. The overall prevalence of DKA was 43.9% (0–5 years: 54.2%; 5–10 years: 43.4%; and 10–15 years: 37.1%) and 14.8% for severe DKA (0–5 years: 16.6%; 5–10 years: 14.4%; and 10–15 years: 13.9%; < 2 years: 25.3%). Severe DKA was more frequent when the child was hospitalized at the family's behest (26.6%) than when referred by a general practitioner (7.6%) or paediatrician (5.1%; 30.6%, 53.7% and 9.2%, respectively, by patients’ age group). The frequency of DKA decreased to 20.1% (severe DKA: 4.4%) in families with a history of T1D. Multivariate analysis showed that age, pathway to diagnosis, duration of polyuria/polydipsia (< 1 week) and family history of T1D were associated with the presence of DKA, while pathway to diagnosis and family history of T1D were associated with severe DKA. Conclusion DKA at the time of T1D diagnosis in children and adolescents is frequent and often severe. Patients’ age, pathway to hospitalization and family history of diabetes were the main factors associated with DKA. These data suggest that a public-health campaign to prevent DKA at diagnosis can help reduce the frequency of DKA and also provide baseline data for evaluating the efficacy of such a campaign.
In contrast with most inhalational anesthetics, the anesthetic gases xenon (Xe) and nitrous oxide (N
2O) act by blocking the
N-methyl-
d-aspartate (NMDA) receptor. Using x-ray crystallography, we ...examined the binding characteristics of these two gases on two soluble proteins as structural models: urate oxidase, which is a prototype of a variety of intracellular globular proteins, and annexin V, which has structural and functional characteristics that allow it to be considered as a prototype for the NMDA receptor. The structure of these proteins complexed with Xe and N
2O were determined. One N
2O molecule or one Xe atom binds to the same main site in both proteins. A second subsite is observed for N
2O in each case. The gas-binding sites are always hydrophobic flexible cavities buried within the monomer. Comparison of the effects of Xe and N
2O on urate oxidase and annexin V reveals an interesting relationship with the in vivo pharmacological effects of these gases, the ratio of the gas-binding sites’ volume expansion and the ratio of the narcotic potency being similar. Given these data, we propose that alterations of cytosolic globular protein functions by general anesthetics would be responsible for the early stages of anesthesia such as amnesia and hypnosis and that additional alterations of ion-channel membrane receptor functions are required for deeper effects that progress to “surgical” anesthesia.
Yttria-stabilized zirconia (YSZ) thin films with yttria content between 5 and 30 mol% were deposited onto r-plane (101 2) Al sub(2)O sub(3), c-plane (0001) Al sub(2)O sub(3) and Si (001) substrates ...by solid single-source metal organic chemical vapor deposition (MOCVD) from Y(thd) sub(3) and Zr(thd) sub(4) precursors in the temperature range 450-850 degree C at a pressure of 0.40 kPa. With this delivery technique, growth rates as high as 0.7 mu m min super(-1) and as low as 2 nm min super(-1) could be achieved reproducibly and controllably by varying the source feeding rate. The composition could be controlled precisely by varying the proportions of each precursor in the precursor mixture above a substrate temperature of 600 degree C. YSZ thin films exhibit highly aligned columnar or fine-grained microstructures below this value.
TiCxNy coatings were grown on graphite substrates in a computer-controlled, hot-wall chemical vapour deposition (CVD) reactor, using gas mixtures of TiCl4–CH4–N2–H2 at a total pressure of 10.7 kPa ...(80 torr) and at a temperature of 1400 K. Growth rate, composition, morphology and crystallographic texture of the TiCxNy coatings were investigated as a function of the CH4/CH4+N2 ratio in the range 0–1 at a constant CH4+N2 flow rate of 370 standard cubic centimeters per minute (sccm). The C/C+N ratio and growth rate of the TiCxNy coatings increased with increasing CH4/CH4+N2 ratio in the gas phase. The compositions of the coatings with C/C+N ratios in the range 0–1 were found to be between the thermodynamic and the kinetic predictions. Morphology and preferred orientation of the coatings were observed to be strongly affected by the CH4/CH4+N2 ratio in the gas phase.
Pyrolytic carbon coatings were deposited on a graphite substrate by chemical vapour deposition technique from impinging jets of ethylene gas. The growth and structure of the coatings were ...investigated as a function of gas flow velocity. The deposition rate of the coatings increased linearly with the square root of gas velocity or flow rate of ethylene. This behaviour was explained by a mass-transport theory. The coatings exhibited cone-like morphology at low gas velocities and cauliflower-like morphology at high gas velocities. Textural analyses revealed that all the coatings were preferentially oriented in the 〈001〉 direction perpendicular to the substrate.
The microstructure and mechanical properties of nanograin-sized WC-Co composites were investigated and compared with those of conventional cermets. The dislocation density in the nanometer-sized WC ...crystals is lower than in the conventional ones, and no inclusions are observed in them. Nanostructured composites have higher tungsten content in the binder phase and a higher
FCC
HCP
ratio of the cobalt. An amorphous phase is observed in the binder phase of the nanostructured samples. Hardness and surface toughness were investigated by performing Palmqvist indentations at loads from 0.025 to 40 Kg. The hardness increases with decreasing binder mean free path of dislocation in the binder phase. The high hardness of nanostructured cemented carbides results not only from the ultrafine microstructure, but also from alloy strengthening of the binder phase itself. The variations of hardness with load suggest that the finer grade conventional carbides have higher microfracture strength, and the nanostructured WC-Co composites are superior to the conventional ones in this respect. Bulkfracture toughness is related to cracks developing through the phases of the material. Palmqvist indentation toughness measurements show that the toughness decreases with increasing hardness in conventional composites, whereas the increase of hardness in nano-structured composites does not further reduce their bulk fracture toughness. This implies that different dominant toughening mechanisms exist in the conventional and nanostructured composites.
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