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Accurate models of X-ray absorption and re-emission in partly stripped ions are necessary to calculate the structure of stars, the performance of hohlraums for inertial confinement fusion and many other systems in high-energy-density plasma physics. Despite theoretical progress, a persistent discrepancy exists with recent experiments at the Sandia Z facility studying iron in conditions characteristic of the solar radiative–convective transition region. The increased iron opacity measured at Z could help resolve a longstanding issue with the standard solar model, but requires a radical departure for opacity theory. To replicate the Z measurements, an opacity experiment has been designed for the National Facility (NIF). The design uses established techniques scaled to NIF. A laser-heated hohlraum will produce X-ray-heated uniform iron plasmas in local thermodynamic equilibrium (LTE) at temperatures
eV and electron densities
. The iron will be probed using continuum X-rays emitted in a
diameter source from a 2 mm diameter polystyrene (CH) capsule implosion. In this design,
of the NIF beams deliver 500 kJ to the
mm diameter hohlraum, and the remaining
directly drive the CH capsule with 200 kJ. Calculations indicate this capsule backlighter should outshine the iron sample, delivering a point-projection transmission opacity measurement to a time-integrated X-ray spectrometer viewing down the hohlraum axis. Preliminary experiments to develop the backlighter and hohlraum are underway, informing simulated measurements to guide the final design.
The objective of this study was to assess the effectiveness of a catheter-related bloodstream infection (CR BSI) reduction programme and healthcare workers' compliance with recommendations. A 3-year surveillance programme of CR BSIs in all hospital settings was implemented. As part of the programme, there was a direct observation of insertion and maintenance of central venous catheters (CVCs) to determine performance. A total of 38 education courses were held over the study period and feedback reports with the results of surveillance and recommendations were delivered to healthcare workers every 6 months. A total of 6722 short-term CVCs were inserted in 4982 patients for 58 763 catheter-days. Improvements of compliance with hand hygiene was verified at the insertion (87·1–100%, P < 0·001) and maintenance (51·1–72·1%, P = 0·029) of CVCs; and the use of chlorhexidine for skin disinfection was implemented at insertion (35·7–65·4%, P < 0·001) and maintenance (33·3–45·9%, P < 0·197) of CVCs. There were 266 CR BSI incidents recorded with an annual incidence density of 5·75/1000 catheter-days in the first year, 4·38 in the second year [rate ratio (RR) 0·76, 95% confidence interval (CI) 0·57–1·01] and 3·46 in the third year (RR 0·60, 95% CI 0·44–0·81). The education programme clearly improved compliance with recommendations for CVC handling, and was effective in reducing the burden of CR BSIs.
Schizophrenia is a chronic brain disorder associated with structural brain abnormalities already present at the onset of the illness. Whether these brain abnormalities might progress over time is still under debate.
The aim of this study was to investigate likely progressive brain volume changes in schizophrenia during the first 3 years after initiating antipsychotic treatment. The study included 109 patients with a schizophrenia spectrum disorder and a control group of 76 healthy subjects. Subjects received detailed clinical and cognitive assessment and structural magnetic resonance imaging (MRI) at regular time points during a 3-year follow-up period. The effects of brain changes on cognitive and clinical variables were examined along with the impact of potential confounding factors.
Overall, patients and healthy controls exhibited a similar pattern of brain volume changes. However, patients showed a significant lower progressive decrease in the volume of the caudate nucleus than control subjects (F1,307.2 = 2.12, p = 0.035), with healthy subjects showing a greater reduction than patients during the follow-up period. Clinical and cognitive outcomes were not associated with progressive brain volume changes during the early years of the illness.
Brain volume abnormalities that have been consistently observed at the onset of non-affective psychosis may not inevitably progress, at least over the first years of the illness. Taking together with clinical and cognitive longitudinal data, our findings, showing a lack of brain deterioration in a substantial number of individuals, suggest a less pessimistic and more reassuring perception of the illness.
Trajectory patterns of positive, disorganized and negative dimension symptoms during antipsychotic treatment in drug-naive patients with first-episode psychosis have yet to be examined by using naturalistic data.
This pragmatic clinical trial randomized 161 drug-naive patients with a first episode of psychosis to olanzapine, risperidone or haloperidol. Patients were assessed with the Scale for the Assessment of Negative Symptoms (SANS) and Positive Symptoms (SAPS) at baseline and at the end of weeks 1, 2, 3, 4 and 6 of antipsychotic treatment. Censored normal models of response trajectories were developed with three dimensions of the SAPS-SANS scores (positive, disorganized and negative) in order to identify the different response trajectories. Diagnosis, cannabis use, duration of untreated psychosis (DUP), smoking and antipsychotic class were examined as possible predictive variables.
Patients were classified in five groups according to the positive dimension, three groups according to the disorganized dimension and five groups according to the negative dimension. Longer DUPs and cannabis use were associated with higher scores and poorer responses in the positive dimension. Cannabis use was associated with higher scores and poorer responses in the disorganized dimension. Only schizophrenia diagnosis was associated with higher scores and poorer responses in the negative dimension.
Our results illustrate the heterogeneity of short-term response to antipsychotics in patients with a first episode of psychosis and highlight markedly different patterns of response in the positive, disorganized and negative dimensions. DUP, cannabis use and diagnosis appeared to have a prognostic value in predicting treatment response with different implications for each dimension.
Heliciculture is an excellent alternative to obtain edible snails but its viability is seriously threatened by pathogens. A parasitological survey was conducted in 3 mixed system-based heliciculture farms in Galicia (NW Spain), with the species Tetrahymena rostrata, Tetrahymena limacis, Tetratrichomonas limacis, Cryptobia helicogenae, Brachylaima aspersae (metacercariae and sporocysts), Alloionema appendiculatum, Nemhelix bakeri, and Riccardoella limacum being commonly found infecting Helix aspersa aspersa (petit-gris) snails. With the exception of C. helicogenae, N. bakeri, and B. aspersae sporocysts, all species were also detected in Helix aspersa maxima (gros-gris) snails, although generally with lower parameters. Most monoxenous infections, and consequently multiple parasitism, exhibited a rising trend during the first 2 months of intensive mating, with tendencies being slowed down or even reversed during the third month as a result of accumulated mortality and a sampling-derived reduction in host density. No parasites were vertically transmitted and infections were initially acquired from invading gastropod and micromammal reservoirs during fattening. Finally, artificial hibernation reduced significantly the prevalence of most species. These results confirm the importance of parasites in heliciculture and emphasize the need to prevent the entry of wild reservoirs into the farms and to rapidly remove the carcasses of dead snails from the reproduction units and fattening pens.
This study examines part of the thick palaeoweathering mantle that formed on the northern area of the Spanish Central System. The study of a compound profile indicates that despite weathering processes, the primary structure of the metamorphic rocks is preserved, and is only partially lost in some intervals of the upper part of the compound profile. Macro/micromorphology, mineralogy and geochemical changes within the profiles revealed two weathering paths. In the first path, Fe-chlorite weathered to chlorite-smectite mixed-layer/smectite/kaolinite+ iron oxides. In the second path, biotite and/or muscovite weathered to kaolinite + iron oxides. The profiles show a progressive decrease, from base to top, in mica and mixed-layers and an increase in smectite and kaolinite. Thus, the profiles only comprise the lower or intermediate zones of the weathering mantle. The weathering occurred under humid climates; the lower zones of the profiles were poorly drained, whereas the topmost zones were better drained and more oxidizing. The results obtained indicate that detailed mineralogical studies are very useful to reconstruct the characteristics of the weathering mantles, and as palaeogeographic and palaeoclimatic indicators.
Suitable in situ techniques capable of sensing for the presence of a biofilm on metallic surfaces are becoming increasingly necessary, especially in order to maintain seawater pipe system performance. This study has investigated the detection of aerobic marine bacterial biofilms using electrochemical impedance spectroscopy by monitoring the interfacial response of Pseudoalteromonas sp. NCIMB 2021 attachment and growth in order to identify characteristic events on a 0.2 mm diameter gold electrode surface. Uniquely, the applicability of surface charge density has been proven to be valuable in determining biofilm attachment and cell enumeration over 72 h duration on a gold surface within a modified continuous culture flow cel(lsa controlled low laminar flow regime with a Reynolds number ≈ 1).In addition, the potential for biofilm disruption has been evaluated using 500 nM of the nitric oxide (NO) donor sodium nitroprusside (NO is important for the regulation of a number of diverse biological processes). Ex situ confocal microscopy studies were performed to confirm biofilm coverage and morphology, plus the determination and quantification of the NO biofilm dispersal effects. Overall, the capability of the sensor to electrochemically detect the presence of initial bacterial biofilm formation and extent has been established and shown to have potential for real-time biofilm monitoring.
Chemical reactions of metals and strongly interacting alloys such as Cu-Mn, Ni-Ti, Ni-Hf and Ni-Zr with oxygen and hydrogen play important roles in the preparation, activation, and regeneration of many important heterogeneous catalytic systems involving supported and unsupported metals and alloys. Recent advances in the understanding of metal and alloy oxidation is bringing new insight into the reactive design and activation of bi- and multi-metallic catalysts. By surface studies of oxidation, thermal annealing and reduction of selected alloys and their thin films and reaction layers and products we have been able to delineate the factors which are most important to the oxide formation processes and the oxide reduction processes. Reaction models developed from these results are permitting the design of new catalyst systems and providing long sought understanding to explain specific aspects of well established metallic catalysts.
The primary use of reticulated ceramics is in molten metal filtration. However, other applications have emerged which utilize the porous nature of these materials, including low mass kiln furniture, low NOx. infrared burners, gas diffusers, hot gas filters, sensors and catalyst supports. In this paper, the use of reticulated ceramics as catalyst supports will be reviewed with emphasis on the manufacture, structure and properties.
The thermolytic decomposition of Mo(CO)6 with hydrogen sulfide or ammonia vapor (in a He carrier stream) at temperatures ranging from 300 to 1100 °C produces high surface area molybdenum sulfides (MoS2 or Mo2S3) or molybdenum carbides (hexagonal Mo2C) and carbonitrides, (hexagonal MoN(C) or cubic Mo2N(C)), respectively. The MoS2 surface areas range from 16.7 to 82.0 m2/g, while the surface areas of molybdenum carbides and carbonitrides vary from 14.9 to 21.1 m2/g. The maximum surface area for MoS2 is achieved at 500 °C and decreases with increasing or decreasing temperature. The surface area of the carbonitrides formed from 300 to 800 °C increases with increasing temperature up to 950 °C, where lower surface area Mo2C is formed. Crystallographically pure hexagonal MoN is prepared by decomposing Mo(CO) 6 in pure ammonia. Fe(CO) 5 decompositions in ammonia produce FexZ (where 5.8≥x≥1.6 and Z=C and N), and in some cases elemental Fe. Hexagonal Fe3 N(C) forms when Fe(CO) 5 is thermolyzed in ammonia from 300 to 600 °C, with surface areas ranging from 9.5 to 13.7 m2/g, whereas orthorhombic Fe3C and cubic Fe are produced at 700, 800, 900 and 1000 °C with surface areas of 6.7, 7.6, 2.2 and 2.0 m2/g, respectively. Within the same phase, the surface areas of the carbonitrides increase with increasing reaction temperature. These iron and molybdenum carbonitrides catalyze the conversion of CO/H2 to alkanes and methanol. Based on preliminary catalytic studies, the highest rate of methane (2850 g/kg/hr at 374 °C) and methanol (440 g/kg/hr at 284 °C) formation was accomplished with an FeMo carbonitride prepared by decomposing Mo(CO)6 and Fe(CO)5 in ammonia at 800 °C.
A series of Au/MnOx catalysts with the Au content ranging from 0 to 10 at%, a 19.5 wt% Pt/SnOx catalyst and a commercially available 2 wt% Pt/SnOx catalyst have been examined for activity toward low-temperature CO oxidation. A 1 atm, 10 sccm stoichiometric mixture of CO (1 vol.%) and O2 in He were reacted at 55°C over 100 mg of each catalyst for time periods as long as 20,000 min. Under these conditions a 10 at% Au/MnOx catalyst exhibits the highest activity and the lowest decay. Outgassing experiments indicate that CO2 retention is primarily responsible for the activity decay of the Pt/SnOx catalysts and that the 10 at% Au/MnOx catalyst is not significantly affected by this process.
The transition metal sulfide clusters (MeCp)2Mo2(μ-SH)2(μ-S)2, (MeCp)2Mo2Co2(μ3-S)2(μ4-S)(CO)4 [MoCoS], and (MeCp)2Mo2 Fe2 (μ3-S)2(CO)8, (MeCp = methylcyclopentadienyl) were used to prepare γ-Al2O3-supported catalysts. For comparison, a series of supported materials was also prepared using conventional incipient wetness impregnation. Infrared spectroscopy of adsorbed species was used to characterize the sites in the clusterderived and conventionally prepared catalysts. Nitric oxide chemisorbed onto the MoCoS/A catalyst was associated initially only with Co sites and then upon gentle heating shifted to the Mo sites, indicating that Co and Mo were in close proximity. In contrast, NO adsorbed onto both Co and Mo sites in the conventionally prepared materials and desorbed independently from these two types of sites. Infrared spectra of adsorbed thiophene and pyridine were similar for the clusterderived and conventionally prepared catalysts. Thiophene reacted at 100 °C to produce both olefinic species. The most abundant products from thiophene HDS were 1-butene, cis-2-butene, and trans-2-butene. Displacement studies showed that thiophene, pyridine, and NO adsorbed to the same site. The most active sites for HDS and HDN contained both Mo and a late transition metal. The HDN product distributions suggested that Mo was selective for C=N bond cleavage while the late transition metals were more active for C=C hydrogenolysis.
Nanoscale and well dispersed catalyst particles offer a large number of advantages: no diffusion resistance, easy accessibility to reactants, and a large number of active sites. In coal liquefaction, highly dispersed catalysts are especially needed because the catalyst particles are only able to influence reactions within their immediate vicinity.
Na+ in the Preyssler heteropolytungstate anion [NaP5W30O110]14− can be exchanged for a trivalent lanthanide ion. The potential significance of this new class of lanthanide heteropolyanions relates to their applications in catalysis science. This view follows from the fact that Keggin heteropolyanions and their free acids are used as heterogeneous solid catalysts and homogeneous solution catalysts. We describe synthetic conditions that lead to the incorporation of Ce3+ and Pr3+ within the Preyssler anion, and the coprecipitation of Ce3+ and the Preyssler anion. Initial studies indicate that the latter, coprecipitated, material deserves study for bifunctional catalytic activity.
The new method of preparation of La1−xSrxMnO3 catalysts supported on ceramic foam materials was developed. The synthesized supported perovskite catalysts were examined by X-ray diffraction analysis and BET methods. It was shown that in coated samples there is a pure perovskite phase on the support surface up to temperatures of 1000°C.
Unsupported La1−xSrxMnO3 catalysts were synthesized applying co-precipitation technique using La, Sr and Mn acetylacetonates and were studied by X-ray diffraction analysis. Temperature programmed reduction method revealed that catalysts contain 2 types of active centers: low temperature (α) and high temperature (β), the quantity of these centers and correlation between them depend on the value of x. It was shown that supported perovskite catalysts, similarly to the massive ones, maintain two types of active centers (α and β).
The activity of La1−xSrxMnO3 on mullite foam was characterized in the methane oxidation reaction.
An unsupported sample of Mo2N has been subjected to a first-stage hydrocracking test. The evolution of the HDS and HDN performance indicated a transformation of Mo2N into MoS2. This was substantiated by XPS and TEM, the latter technique showing that the transformation is limited to only a few surface layers.
Catalytically grown carbon nanofibers have been prepared by the thermal decomposition of carbon containing gases over copper-nickel and iron surfaces. This material is found to be highly graphitic in nature when prepared from certain catalysts and gaseous reactants. In the as-grown state, carbon nanofibers have surface areas in the range 200 to 300 m2/g, and by following careful activation procedures this value can readily be increased to ˜700 m2/g. Electrical measurements indicate that the material has a conductivity approaching that of single crystal graphite. This material combines the attributes of active carbon and graphite and in addition, the physical form of carbon nanofibers offers some interesting opportunities for the design of unique catalyst systems.
High surface area silicon carbide (SiC) of 31 m2/g has been synthesized by the catalytic conversion of activated carbon. The thermal stability in non-oxidizing environments is shown to be excellent; no significant sintering has been observed after ageing in nitrogen for 4 hours at 1273 K. The presence of 2v% steam or the use of air results in SiC oxidation into SiO2 and considerable sintering at 1273 K. Air oxidation of SiC is shown to cause substantial SiC conversion, viz. 60 % after 10 hours at 1273 K. Complete conversion is achieved at 1080 K in about 100 days. This rate of oxidation agrees with reports on the oxidation of non-porous Acheson SiC and Chemical Vapour Deposited SiC coatings. The use of SiC based catalysts is, therefore, limited to (1) high temperature gas phase reactions operating in the absence of oxidizing constituents (O2 or H2O) and (2) liquid phase processes at demanding pH. Syntheses of highly dispersed and highly loaded Ni/SiC catalysts are feasible by applying an ion-exchange technique, resulting in supported nickel particles of 4 nm.