A simple, soft, and fast microwave-assisted hydrothermal method was used for the preparation of nanocrystalline cobalt ferrite powders from commercially-available Fe(NO3)3∙9H2O, Co(NO3)2∙6H2O, ...ammonium hydroxide, and tetrapropylammonium hydroxide (TPAH). The synthesis was conducted in a sealed-vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized by XRD, FE-SEM, TEM, and HR-TEM. After a systematic study of the influence of the microwave variables (temperature, reaction time and nature of the bases), highly crystalline CoFe2O4 nanoparticles with a high uniformity in morphology and size, were directly obtained by heating at 130 °C for 20 min using the base TPAH. Dense ceramics of cobalt ferrite were prepared by non-conventional, microwave sintering of synthesized nanopowders at temperatures of 850–900 °C. The magnetic properties of both the nanopowders and the sintered specimens were determined in order to establish their feasibility as a permanent magnet.
A simple, rapid, and effective synthesis methodology for the preparation of high-performance TiO
2
nanoparticles and thin films by combining colloidal sol-gel and microwave-assisted hydrothermal ...synthesis was developed. The obtained results indicate that the heating with microwaves at 180 °C for 20 min was enough to synthesize crystalline TiO
2
nanoparticles, presenting anatase as a major phase with a crystal size of ~ 7 nm and a specific surface area of 220 m
2
g
−1
. A secondary thermal treatment improved the crystallinity and induced the anatase-to-rutile transformation. The highest photocatalytic activity was found for the as-synthesized powder without any additional thermal treatment. Thin films were also prepared by dip-coating and its high photocatalytic activity showed a kinetic curve comparable to that of a thin film of commercial TiO
2
powder prepared under similar conditions.
Mullite is widely used as a structural material for applications like thermal and environmental barriers coatings. For some of these applications, thermal spray is a suitable technique due to its ...fast production time and versatility. This makes mullite a very interesting coating material for thermal spray industry. In the present work, the viability to produce coatings by thermal spray using mullite-CNFs agglomerated powders is analyzed. The stability of aqueous mullite and mullite-CNFs suspensions was studied in terms of zeta potential and rheological behaviour of concentrated slurries. Slurries were optimized in terms of dispersant concentration and solid content. The optimized suspensions were used for the granules preparation by spray drying technology. The obtained granules were characterized through the determination of particle size distribution and shape factor by field emission scanning electron microscopy and laser scattering. These granules were used to form the coatings by Atmospheric Plasma Spraying which were characterized by evaluating the composition, structure, shape, and thickness.
It is important to know the spectrum of the microbial aetiology of prosthetic joint infections (PJIs) to guide empiric treatment and establish antimicrobial prophylaxis in joint replacements. There ...are no available data based on large contemporary patient cohorts. We sought to characterize the causative pathogens of PJIs and to evaluate trends in the microbial aetiology. We hypothesized that the frequency of antimicrobial-resistant organisms in PJIs has increased in the recent years. We performed a cohort study in 19 hospitals in Spain, from 2003 to 2012. For each 2-year period (2003–2004 to 2011–2012), the incidence of microorganisms causing PJIs and multidrug-resistant bacteria was assessed. Temporal trends over the study period were evaluated. We included 2524 consecutive adult patients with a diagnosis of PJI. A microbiological diagnosis was obtained for 2288 cases (90.6%). Staphylococci were the most common cause of infection (1492, 65.2%). However, a statistically significant rising linear trend was observed for the proportion of infections caused by Gram-negative bacilli, mainly due to the increase in the last 2-year period (25% in 2003–2004, 33.3% in 2011–2012; p 0.024 for trend). No particular species contributed disproportionally to this overall increase. The percentage of multidrug-resistant bacteria PJIs increased from 9.3% in 2003–2004 to 15.8% in 2011–2012 (p 0.008), mainly because of the significant rise in multidrug-resistant Gram-negative bacilli (from 5.3% in 2003–2004 to 8.2% in 2011–2012; p 0.032). The observed trends have important implications for the management of PJIs and prophylaxis in joint replacements.
This paper examines total factor productivity differences between exporting and non-exporting firms. These differences are documented on the basis of a sample of Spanish manufacturing firms over the ...period 1991–1996. The paper also examines two complementary explanations for the greater productivity of exporting firms: (1) the market selection hypothesis, and (2) the learning hypothesis. Non-parametric tests are proposed and implemented for testing these hypotheses. Results indicate clearly higher levels of productivity for exporting firms than for non-exporting firms. With respect to the relative merits of the selection and the learning hypotheses, we find evidence supporting the self-selection of more productive firms in the export market. The evidence in favor of learning-by-exporting is rather weak, and limited to younger exporters.
We use a global magnetohydrodynamics simulation to analyze transient magnetic reconnection processes at the magnetopause. The solar wind conditions have been kept constant, and an interplanetary ...magnetic field with large duskward BY and southward BZ components has been imposed. Five flux transfer events (FTEs) with clear bipolar magnetic field signatures have been observed. We observed a peculiar structure defined as interlinked flux tubes (IFTs) in the first and fourth FTE, which had very different generation mechanisms. The first FTE originates as an IFTs and remains with this configuration until its final moment. However, the fourth FTE develops as a classical flux rope but changes its 3-D magnetic configuration to that of IFTs. This work studies the mechanism for generating IFTs. The growth of the resistive tearing instability has been identified as the cause for the first IFTs formation. We believe that the instability has been triggered by the accumulation of interplanetary magnetic field at the subsolar point where the grid resolution is very high. The evidence shows that two new reconnection lines form northward and southward of the subsolar region. The IFTs have been generated with all the classical signatures of a single flux rope. The other IFTs detected in the fourth FTE developed as a result of magnetic reconnection inside its complex and twisted magnetic fields, which leads to a change in the magnetic configuration from a flux rope of twisted magnetic field lines to IFTs.
Sex-dependent differences of infective endocarditis (IE) have been reported. Women suffer from IE less frequently than men and tend to present more severe manifestations. Our objective was to analyse ...the sex-based differences of IE in the clinical presentation, treatment, and prognosis.
We analysed the sex differences in the clinical presentation, modality of treatment and prognosis of IE in a national-level multicentric cohort between 2008 and 2018. All data were prospectively recorded by the GAMES cohort (Spanish Collaboration on Endocarditis).
A total of 3451 patients were included, of whom 1105 were women (32.0%). Women were older than men (mean age, 68.4 vs 64.5). The most frequently affected valves were the aortic valve in men (50.6%) and mitral valve in women (48.7%).
aetiology was more frequent in women (30.1% vs 23.1%; p<0.001).Surgery was performed in 38.3% of women and 50% of men. After propensity score (PS) matching for age and estimated surgical risk (European System for Cardiac Operative Risk Evaluation II (EuroSCORE II)), the analysis of the matched cohorts revealed that women were less likely to undergo surgery (OR 0.74; 95% CI 0.59 to 0.91; p=0.05).The observed overall in-hospital mortality was 32.8% in women and 25.7% in men (OR for the mortality of female sex 1.41; 95% CI 1.21 to 1.65; p<0.001). This statistical difference was not modified after adjusting for all possible confounders.
Female sex was an independent factor related to mortality after adjusting for confounders. In addition, women were less frequently referred for surgical treatment.
The aim of this study was to analyse the association between human immunodeficiency virus (HIV) related clinical and analytical parameters and the presence of subclinical atherosclerosis as well as ...endothelial dysfunction. This was a prospective cohort study of HIV-positive patients who underwent intima media thickness (IMT) determination and coronary artery calcium scoring to determine subclinical atherosclerosis. To detect endothelial dysfunction, the breath holding index, flow-mediated dilation and the concentration of endothelial progenitor cells (EPCs) were measured. Patients with an IMT ≥ 0.9 mm had an average of 559.3 ± 283.34 CD4/μl, and those with an IMT < 0.9 mm had an average of 715.4 ± 389.92 CD4/μl (p = 0.04). Patients with a low calcium score had a significantly higher average CD4 cell value and lower zenith viral load (VL) than those with a higher score (707.7 ± 377.5 CD4/μl vs 477.23 ± 235.7 CD4/μl (p = 0.01) and 7 × 10
± 5 × 10
copies/ml vs 23.4 × 104 ± 19 × 104 copies/ml (p = 0.02)). The number of early EPCs in patients with a CD4 nadir < 350/µl was lower than that in those with a CD4 nadir ≥ 350 (p = 0.03). In HIV-positive patients, low CD4 cell levels and high VL were associated with risk of developing subclinical atherosclerosis. HIV patients with CD4 cell nadir < 350/µl may have fewer early EPCs.
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