5,684 research outputs found
Caractérisation de matériaux avancés à faible permittivité par Spectroscopie Temporelle d'Annihilation de Positons (PALS)
Cet exposé présente le principe et la réalisation d'un détecteur PALS (Positron Annihilation Lifetime Spectroscopy). Ce détecteur nous permettra de mesurer le temps de vie d'un positon dans un matériau poreux et de caractériser ainsi la taille des pores. Dans une deuxième partie, nous présentons les caractéristiques de ce détecteur et nous comparons ces performances temporelles avec celles des détecteurs existant
Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta
We report on a comparative study of spin Hall related effects and
magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements
allow to estimate the characteristic transport parameters of both Pt and Ta
layers juxtaposed to YIG: the spin mixing conductance
at the YIGnormal metal interface, the spin Hall angle , and the
spin diffusion length in the normal metal. The inverse spin Hall
voltages generated in Pt and Ta by the pure spin current pumped from YIG
excited at resonance confirm the opposite signs of spin Hall angles in these
two materials. Moreover, from the dependence of the inverse spin Hall voltage
on the Ta thickness, we extract the spin diffusion length in Ta, found to be
nm. Both the YIG|Pt and YIG|Ta systems
display a similar variation of resistance upon magnetic field orientation,
which can be explained in the recently developed framework of spin Hall
magnetoresistance.Comment: 8 pages, 5 figures, 1 tabl
Detection of the microwave spin pumping using the inverse spin Hall effect
We report electrical detection of the dynamical part of the spin pumping
current emitted during ferromagnetic resonance (FMR) using the inverse Spin
Hall Effect (ISHE). The experiment is performed on a YIGPt bilayer. The
choice of YIG, a magnetic insulator, ensures that no charge current flows
between the two layers and only pure spin current produced by the magnetization
dynamics are transferred into the adjacent strong spin-orbit Pt layer via spin
pumping. To avoid measuring the parasitic eddy currents induced at the
frequency of the microwave source, a resonance at half the frequency is induced
using parametric excitation in the parallel geometry. Triggering this nonlinear
effect allows to directly detect on a spectrum analyzer the microwave component
of the ISHE voltage. Signals as large as 30 V are measured for precession
angles of a couple of degrees. This direct detection provides a novel efficient
means to study magnetization dynamics on a very wide frequency range with great
sensitivity
Nanoscale Suppression of Magnetization at Atomically Assembled Manganite Interfaces
Using polarized X-rays, we compare the electronic and magnetic properties of
a La(2/3)Sr(1/3)MnO(3)(LSMO)/SrTiO(3)(STO) and a modified
LSMO/LaMnO(3)(LMO)/STO interface. Using the technique of X-ray resonant
magnetic scattering (XRMS), we can probe the interfaces of complicated layered
structures and quantitatively model depth-dependent magnetic profiles as a
function of distance from the interface. Comparisons of the average electronic
and magnetic properties at the interface are made independently using X-ray
absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The
XAS and the XMCD demonstrate that the electronic and magnetic structure of the
LMO layer at the modified interface is qualitatively equivalent to the
underlying LSMO film. From the temperature dependence of the XMCD, it is found
that the near surface magnetization for both interfaces falls off faster than
the bulk. For all temperatures in the range of 50K - 300K, the magnetic
profiles for both systems always show a ferromagnetic component at the
interface with a significantly suppressed magnetization that evolves to the
bulk value over a length scale of ~1.6 - 2.4 nm. The LSMO/LMO/STO interface
shows a larger ferromagnetic (FM) moment than the LSMO/STO interface, however
the difference is only substantial at low temperature.Comment: 4 pages, 4 figure
The speed of learning instructed stimulus-response association rules in human: experimental data and model.
Humans can learn associations between visual stimuli and motor responses from just a single instruction. This is known to be a fast process, but how fast is it? To answer this question, we asked participants to learn a briefly presented (200ms) stimulus-response rule, which they then had to rapidly apply after a variable delay of between 50 and 1300ms. Participants showed a longer response time with increased variability for short delays. The error rate was low and did not vary with the delay, showing that participants were able to encode the rule correctly in less than 250ms. This time is close to the fastest synaptic learning speed deemed possible by diffusive influx of AMPA receptors. Learning continued at a slower pace in the delay period and was fully completed in average 900ms after rule presentation onset, when response latencies dropped to levels consistent with basic reaction times. A neural model was proposed that explains the reduction of response times and of their variability with the delay by (i) a random synaptic learning process that generates weights of average values increasing with the learning time, followed by (ii) random crossing of the firing threshold by a leaky integrate-and-fire neuron model, and (iii) assuming that the behavioural response is initiated when all neurons in a pool of m neurons have fired their first spike after input onset. Values of m=2 or 3 were consistent with the experimental data. The proposed model is the simplest solution consistent with neurophysiological knowledge. Additional experiments are suggested to test the hypothesis underlying the model and also to explore forgetting effects for which there were indications for the longer delay conditions. This article is part of a Special Issue entitled Neural Coding 2012
Voltage and temperature dependence of the grain boundary tunneling magnetoresistance in manganites
We have performed a systematic analysis of the voltage and temperature
dependence of the tunneling magnetoresistance (TMR) of grain boundaries (GB) in
the manganites. We find a strong decrease of the TMR with increasing voltage
and temperature. The decrease of the TMR with increasing voltage scales with an
increase of the inelastic tunneling current due to multi-step inelastic
tunneling via localized defect states in the tunneling barrier. This behavior
can be described within a three-current model for magnetic tunnel junctions
that extends the two-current Julliere model by adding an inelastic,
spin-independent tunneling contribution. Our analysis gives strong evidence
that the observed drastic decrease of the GB-TMR in manganites is caused by an
imperfect tunneling barrier.Comment: to be published in Europhys. Lett., 8 pages, 4 figures (included
« C’est normal qu’on mollisse ou qu’on vieillisse » : faut-il aborder le déclin fonctionnel avec les personnes âgées en médecine de famille ?
Pour répondre au vieillissement de la population, des initiatives de dépistage et de prise en charge des problèmes de santé liés à l’âge sont mises en place, notamment en médecine de famille. Les résultats préliminaires d’une étude qualitative suggèrent que les personnes âgées sont ambivalentes face à la notion d’anticipation des problèmes, tendent à les banaliser et à être réticentes à en parler spontanément à leur médecin. Cependant, elles trouvent pertinent que ce dernier aborde le sujet avec des questions spécifiques, ceci permettant d’initier une discussion sur des problématiques sensibles. Les possibilités de prise en charge des syndromes gériatriques et du déclin fonctionnel semblent peu connues des patient-e-s. Le dépistage permet donc d’aborder ces problématiques et d’informer les patient-e-s au sujet de solutions existantes.
[Among the health strategies to respond to the aging of the population, initiatives for the screening and management of age-related health issues are implemented, including in family medicine. Preliminary results of a qualitative study suggest that elderly people are ambivalent about anticipating age-related issues, tend to trivialize them and to be reluctant to discuss them spontaneously with their doctors. However, they find relevant that their family doctor brings up the topic with specific questions, because that allows initiating a discussion about some of these sensitive issue. It appears that the awareness of the existing management of geriatric syndromes and functional decline possibilities is rather low. A screening initiative is therefore an opportunity to address these different issues and to inform patients about existing solutions.]]]>
fre
oai:serval.unil.ch:BIB_7917561D1F2C
2022-05-07T01:20:55Z
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https://serval.unil.ch/notice/serval:BIB_7917561D1F2C
Good and Bad Days: Fluctuations in the Burden of Informal Dementia Caregivers, an Experience Sampling Study.
info:doi:10.1097/NNR.0000000000000243
info:eu-repo/semantics/altIdentifier/doi/10.1097/NNR.0000000000000243
info:eu-repo/semantics/altIdentifier/pmid/29095373
Pihet, S.
Moses Passini, C.
Eicher, M.
info:eu-repo/semantics/article
article
2017
Nursing research, vol. 66, no. 6, pp. 421-431
info:eu-repo/semantics/altIdentifier/eissn/1538-9847
urn:issn:0029-6562
<![CDATA[Informal dementia caregivers (IDCs) are often confronted with important fluctuations in care-related burden, commonly described as "good and bad days." These fluctuations are overlooked by traditional questionnaires focusing on the average experience. The experience sampling method (ESM) is based on the repeated collection of data in everyday life, thereby allowing the description of day-to-day fluctuations in IDC burden, and the identification of their correlates. ESM studies are still scarce among IDCs, with none focusing on day-to-day fluctuations in burden.
This ESM study aimed to examine day-to-day fluctuations in the burden of IDCs and test their associations with six moment-to-moment predictors.
Primary IDCs (N = 26, median age = 68 years, 77% women, 73% spouses) volunteered to answer questions about their daily burdens, patients' memories and behavioral problems (MBP), caregivers' MBP-related distress, psychological distress, self-efficacy and positive affects, and relationship quality; volunteers did this every evening for 2 weeks on a touchpad, resulting in 206 measures. Data were analyzed with multilevel linear regression.
Day-to-day fluctuations covered about two thirds of the total variance for most study variables. All six predictors had a significant bivariate relation with daily burden, explaining 15%-32% of its fluctuations, with significant differences between caregivers in the strength of these relations. The best multivariate model explained 51% of the day-to-day fluctuations in burden. It included caregiver MBP-related distress, psychological distress, and relationship quality.
This innovative study of IDC burden shows that day-to-day fluctuations are an important part of caregivers' real-life experiences and that half of this variability is predicted by currently understudied factors. Inviting caregivers to monitor clinical outcomes daily over 1 or 2 weeks could help tailor interventions to their individual needs and also empower them
Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3
We present a magnetoresistive-photoresistive device based on the interaction
of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that
undergoes light-induced strain. The magnitude of the resistance and
magnetoresistance in the CoFe film can be controlled by the wavelength of the
incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic
magnetoresistance is detected due to an additional magnetoelastic contribution
to magnetic anisotropy of the CoFe film. This effect may find applications in
photo-sensing systems, wavelength detectors and can possibly open a research
development in light-controlled magnetic switching properties for next
generation magnetoresistive memory devices.Comment: 5 pages, 4 figures, journal pape
Magnetic resonance spectroscopy of perpendicularly magnetized permalloy multilayer disks
Using a Magnetic Resonance Force Microscope, we compare the ferromagnetic
resonance spectra of individual micron-size disks with identical diameter, 1
m, but different layer structures. For a disk composed of a single 43.3 nm
thick permalloy (Py) layer, the lowest energy mode in the perpendicular
configuration is the uniform precession. The higher energy modes are standing
spin-waves confined along the diameter of the disk. For a Cu(30)/Py(100)/Cu(30)
nm multilayer structure, it has been interpreted that the lowest energy mode
becomes a precession localized at the Cu/Py interfaces. When the multilayer is
changed to Py(100)/Cu(10)/Py(10) nm, this localized mode of the thick layer is
coupled to the precession of the thin layer
Photovoltaic response around a unique180° ferroelectric domain wall in single crystalline BiFeO3
Using an experimental setup designed to scan a submicron sized light spot and collect the photogenerated current through larger electrodes, we map the photovoltaic response in ferroelectric BiFeO3 single crystals. We study the effect produced by a unique 180° ferroelectric domain wall (DW) and show that the photocurrent maps are significantly affected by its presence and shape. The effect is large in its vicinity and in the Schottky barriers at the interface with the Au electrodes, but no extra photocurrent is observed when the illuminating spot touches the DW, indicating that this particular entity is not the heart of specific photo-electric properties. Using 3D modelling, we argue that the measured effect is due to the spatial distribution of internal fields which are significantly affected by the charge of the DW due to its distortion
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