K0.5Na0.5Nb1-xTaxO3 (KNNT) (with x = 0.00, 0.05, 0.10, 0.20, 0.30, 0.50 and 1) ceramics are prepared by ball milling and two calcinations at 830 °C for 5 h. Subsequent sintering of centimeter size ...pellets, 1–2 mm thick, is studied using conventional and spark plasma sintering techniques with various conditions. X-Ray diffraction and Raman spectroscopy phase identification reveal orthorhombic to tetragonal phase transitions occurring at about x = 0.50, associated to chemical disorder. Scanning electron microscope observations and associated energy dispersive X-ray spectroscopy analysis reveal some composite aspect of the ceramics. Substitution of niobium by tantalum, corresponding to x increase, decreases significantly the grain size but also the densification of the ceramics sintered by conventional sintering, while, enhancement of the piezoelectric properties is observed for both sintering techniques. Thanks to parameters optimization of the spark plasma sintering process, temperature-time-pressure, significant improvement of the relative density over 96%, is obtained for all the compositions sintered between 920 and 960 °C, under 50 MPa, for 5–10 min with heating rates of 100 °C/min. High relative permittivity (εr = 1027), piezoelectric charge coefficient (d33 = 160 pC/N) and piezoelectric coupling factor (kp = 46%) are obtained in spark plasma sintered K0.5Na0.5Nb1-xTaxO3 composite ceramics, for x ranging between 0.10 and 0.30 and for some specific spark plasma sintering conditions. Thus, tantalum single element substitution on niobium site, combined with spark plasma sintering, is revealed to be a powerful combination for the optimization and the reliability of piezoelectric properties in KNN system.
•Readiness Potential (RP) dynamics have been studied during Libet’s clock task.•Impulsivity traits assessed by the Barratt Impulsiveness Scale (BIS-11).•RP shows an earlier rising and a greater ...amplitude for higher BIS-11 scores.•Trait impulsivity positively correlates with motor system excitability.•We hypothesize less effective preparatory inhibition in trait impulsivity.
Electrophysiological and neuroimaging studies suggest that our actions are initiated by unconscious mental processes long before awareness of intention to act. The time window between the awareness of the intention to move and the movement onset, which normally permits to exert a conscious “veto” on the impending action, is modulated by individual differences in trait impulsivity. In particular, trait impulsive people show a delayed awareness of the intention to act, probably exceeding the “point of no return”, after which the action can no longer be inhibited. In order to investigate if individual differences in the “veto” interval might be explained by differences in the readiness potential (RP) dynamics, nineteen healthy participants underwent an impulsivity trait assessment using the Barratt Impulsiveness Scale (BIS-11) and performed a task based on Libet’s clock paradigm, during EEG recordings of pre-movement neural activity. We observed a positive relationship between impulsive personality trait and motor system excitability during the preparation of self-initiated movements. In particular, the RP showed an earlier negative rising phase and a greater amplitude, with the increasing of BIS-11 scores. Based on present results, we conclude hypothesizing that trait impulsivity might be characterized by less effective preparatory inhibition mechanisms, which have a fundamental role in the control of behavior.
The positivity effect in the elderly consists of an attentional preference for positive information as well as avoidance of negative information. Extant theories predict either that the positivity ...effect depends on controlled attentional processes (socio-emotional selectivity theory), or on an automatic gating selection mechanism (dynamic integration theory). This study examined the role of automatic and controlled attention in the positivity effect. Two dot-probe tasks (with the duration of the stimuli lasting 100 ms and 500 ms, respectively) were employed to compare the attentional bias of 35 elderly people to that of 35 young adults. The stimuli used were expressive faces displaying neutral, disgusted, fearful, and happy expressions. In comparison to young people, the elderly allocated more attention to happy faces at 100 ms and they tended to avoid fearful faces at 500 ms. The findings are not predicted by either theory taken alone, but support the hypothesis that the positivity effect in the elderly is driven by two different processes: an automatic attention bias toward positive stimuli, and a controlled mechanism that diverts attention away from negative stimuli.
•Positivity effect in the elderly is driven by two different processes.•The attentional bias toward positive stimuli is an automatic process.•The attentional avoiding of negative stimuli is a controlled mechanism.
The spark plasma sintering (SPS) behaviour of pure SnO2 has been studied. Two different SnO2 powders have been studied: a commercial 50–200 nm one and 4–6 nm nanoparticles obtained by precipitation. ...It has demonstrated that it is not possible to keep pure SnO2 above 1223 K by SPS. Indeed, at 1248 K, SnO appears whereas at higher temperatures, samples are composed by SnO2 and metal Sn. Three different cycles have been developed that allow achieving high densities (≥94%). The study of the grain size shows that when the density increases the grain size increases to reach 60–70 nm for the high density samples. Therefore, SPS can be successfully used to produce dense nanostructured SnO2 ceramics without any sintering agent. Nanostructuring is very efficient to lower thermal conductivity as values as low as 6.59 and 3.99 W m−1.K−1 at 373 and 1000 K respectively, are measured in SPS nanostructured ceramics. Moreover, the transport properties of the dense ceramics are the best reported for undoped SnO2.
Over last fifty years, intravenous (iv) phenytoin (PHT) loading dose has been the treatment of choice for patients with benzodiazepine‐resistant convulsive status epilepticus and several guidelines ...recommended this treatment regimen with simultaneous iv diazepam. Clinical studies have never shown a better efficacy of PHT over other antiepileptic drugs. In addition, iv PHT loading dose is a complex and time‐consuming procedure which may expose patients to several risks, such as local cutaneous reactions (purple glove syndrome), severe hypotension and cardiac arrhythmias up to ventricular fibrillation and death, and increased risk of severe allergic reactions. A further disadvantage of PHT is that it is a strong enzymatic inducer and it may make ineffective several drugs that need to be used simultaneously with antiepileptic treatment. In patients with a benzodiazepine‐resistant status epilepticus, we suggest iv administration of levetiracetam as soon as possible. If levetiracetam would be ineffective, a further antiepileptic drug among those currently available for iv use (valproate, lacosamide, or phenytoin) can be added before starting third line treatment.
Before to conclude officially this workshop — far from me the idea to attempt some concluding remarks already dealt at the meeting with various burning by Joseph Patterson, Mariko Kato, Dmitry ...Bisikalo, and Rene Hudec —, I would like to comment few highlights coming out from our fruitful week of discussions about The Golden Age of Cataclysmic Variables and Related Objects - II, without any pretension of completeness.
Sintered intermetallic
Ag
3
Sn
powders by spark plasma sintering (SPS) have been studied in order to analyse the effect of the microstructure on the transport properties at room temperature. Firstly, ...we synthesized
Ag
3
Sn
submicronic particles by polyol process. Then, we sintered them by SPS at different temperature (473, 573 and 663 K) and pressure (20 and 100 MPa) using fixed dwelling time of 5 min. X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) show that all sintered samples remained single-phased according to the
Ag
3
Sn
orthorhombic crystal structure. Their corresponding grain size (
≈
0.65 to 1.75
μ
m) and relative density (
≈
88–98%) were calculated and show similar evolution respect to the sintering parameters. As a matter of fact, sintering temperature remains the key factor to affect the microstructure of the sintered material
s
. Finally, the thermal conductivity and the electrical resistivity were investigated at room temperature by using the Flash Laser technique and the Physical Property Measurement System (PPMS) respectively. The obtained values were highly dependent on densitiy and grain showing the key role of the microstructure and thereby confirming the fact that
Ag
3
Sn
compound is a good candidate for a lead-free die-attach material in power module devices.
We describe regularized methods for image reconstruction and focus on the question of hyperparameter and instrument parameter estimation, i.e. unsupervised and myopic problems. We developed a ...Bayesian framework that is based on the posteriordensity for all unknown quantities, given the observations. This density is explored by a Markov chain Monte-Carlo sampling technique based on a Gibbs loop and including a Metropolis-Hastings step. The numerical evaluation relies on the SPIRE instrument of the Herschel observatory. Using simulated and real observations, we show that the hyperparameters and instrument parameters are correctly estimated, which opens up many perspectives for imaging in astrophysics.
The white (K0.5Na0.5)NbO3 compound with a perovskite structure is largely studied as a lead free piezoelectric material. Pellets sintered by SPS present an oxygen deficiency and a lower resistivity. ...As other perovskite oxides such as SrTiO3 or CaMnO3 have already shown high thermoelectric properties, the thermoelectric properties of oxygen deficient (K0.5Na0.5)NbO3 dense ceramics sintered by SPS have been investigated and appears as very promising. Dimensionless figure of merit ZT at 1000K is 0.012.
•The Seebeck coefficient is high (−(600–700)µV/K).•The thermal conductivity is stable between 3.5 and 4Wm−1K−1 from 325 to 1000K.•Dimensionless figure of merit ZT at 1000K is 0.012.
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