Recently, several putative quantum spin liquid (QSL) states were
discovered in
{\tilde S} = 1/2
S
̃
=
1
/
2
rare-earth based triangular-lattice antiferromagnets (TLAF) with the
delafossite structure. ...In order to elucidate the conditions for a QSL to
arise, we report here the discovery of a long-range magnetic order in
the Ce-based TLAF KCeS
_2
2
below
T_{\mathrm N} = 0.38
T
N
=
0.38
K,
despite the same delafossite structure. Finally, combining various
experimental and computational methods, we characterize the crystal
electric field scheme, the magnetic anisotropy and the magnetic ground
state of KCeS
_2
2
.
Summary
Sleep of chronic insomniacs is often characterized by extensive night‐to‐night variability. To date, no study has examined this variability with long series of daily sleep data. The present ...study examined night‐to‐night variability with a sample of 106 participants meeting DSM‐IV diagnostic criteria for persistent primary insomnia. Participants completed daily sleep diaries for an average of 31 days (range: 18–56). Sleep efficiency, sleep onset latency and wake after sleep onset were derived from this measure. Despite evidence of extensive night variability, results showed that sleep patterns could be classified in three clusters. The first one was characterized by a high probability of having poor sleep, the second one by a low and decreasing probability, and the third one by a constant median probability of having a poor sleep, which is an unpredictable sleep pattern. In the first cluster, poor sleep was expected each night for patients with a predominance mixed insomnia including the three insomnia subtypes. In the second cluster, patients presented moderate insomnia, sleep‐onset latency below the threshold level and a predominance of sleep‐maintenance insomnia. In the third pattern, poor nights seemed unpredictable for patients with moderate to severe insomnia associated with the lowest proportion of sleep‐maintenance insomnia. Overall, sleep was predictable for about two‐thirds of individuals, whereas it was unpredictable for about one‐third. These findings confirm the presence of extensive variability in the sleep of chronic insomniacs and that poor sleep may be predictable for some of them. Additional research is needed to characterize those sleep patterns in terms of clinical features and temporal course.
Abstract
Introduction
Exposure to child abuse may lead to long-term adverse changes in hyperarousal, health, and stress regulation that may predispose the survivor to insomnia and other sleep ...disturbances in adulthood. This may be especially true when the bedroom is viewed as unsafe. The aim of the present study was to examine whether exposure to child abuse was associated with poor sleep in adulthood and how this was moderated by perceived bedroom safety.
Methods
A diverse sample of 1,002 community-based adults age 22–60 participated in the Sleep and Healthy Activity, Diet, Environment, and Socialization (SHADES) study. Participants completed measures of sleep - insomnia symptoms (ISI), sleep quality (PSQI) and typical sleep duration, their levels of current perceived bedroom safety (response categories yes or no) and indicated whether they had a history of childhood abuse (defined as either physical or sexual abuse - yes or no). Covariates included age, sex, race/ethnicity, education, and body mass index. Mediating influence of depression and anxiety were also examined.
Results
Of those who completed the survey, 204 (20.36%) indicated a history of childhood abuse and this was associated with poorer sleep in terms of insomnia symptoms, sleep quality and sleep duration. A safety-by-abuse interaction was significant for insomnia, sleep quality, and sleep duration. In stratified analyses, those who suffered abuse but perceived their sleep environment as safe reported worse insomnia (B=2.39, p<0.0001) and sleep quality (B=1.47, p<0.0001) and shorter sleep duration (B=-0.40, p=0.006) relative to those with no history of abuse. In those whose sleep environment was perceived as unsafe, the impact of abuse was 20% greater for insomnia, 52% greater for sleep quality and 38% reduced for sleep duration. When depression/anxiety were included in models, relationships were generally maintained.
Conclusion
The findings suggest that abuse history may impact presentation of insomnia, and appears to be amplified by perceiving the bedroom as an unsafe environment. Both history of abuse and perceived bedroom safety should be routinely asked and accounted for by sleep clinicians.
Support (If Any):
This study was designed to determine if the K-Complex reflects an arousal from sleep or a sleep protection mechanism. Ten participants were presented auditory stimuli every 20 s while asleep. Trials ...were sorted according to the presence or absence of a K-Complex. A fast Fourier Transformation of the data was computed on
EEG
segments prior to and following stimulus onset. The log power of activity in delta, theta, alpha, sigma, and beta bandwidths was computed. When a K-Complex was elicited, there were no differences in
EEG
activity prior to and following the stimulus. However, during slow wave sleep, when a K-Complex was not elicited, there was a significant overall increase in theta, alpha, sigma, and beta activity following stimulus. These results tend to support the notion that the K-Complex appears to prevent arousal.
Le Complexe-K est une composante de l'électroencéphalogramme (
EEG
) qui apparaît pendant le sommeil lent (les stades 2, 3 et 4) en réponse à un stimulus externe ou avec une spontanéité apparente. Il a préalablement été démontré que le Complexe-K évoqué répondait à la loi du tout-ou-rien, ses différentes composantes ne variant pas en amplitude ni en latence lors de variations dans les paramètres physiques de stimuli auditifs (
Bastien & Campbell, 1992
). Malgré ces résultats nous informant sur les antécédents du Complexe-K, le débat sur le rôle fonctionnel de celui-ci demeure vif. Certains auteurs considèrent le Complexe-K comme un signe d'éveil pendant le sommeil. D'autres lui assignent la fonction de mécanisme protecteur pendant le sommeil. L'objectif de la présente étude est de vérifier ces théories opposées. L'analyse des spectres de l'
EEG
qui précèdent et suivent la présentation d'un stimulus auditif est effectuée sur des essais où un Complexe-K est évoqué et des essais où un complexe-K n'est pas évoqué par la stimulation auditive. Si le Complexe-K est un signe d'éveil pendant le sommeil, les spectres de l'
EEG
démontreront une augmentation dans l'activité des fréquences élevées de l'
EEG
(par exemple, alpha et bêta). Cependant, si le Complexe-K reflète un mécanisme de protection du sommeil, une activité moins intense des spectres de fréquences élevées de l'
EEG
et/ou une augmentation dans les spectres de fréquences lentes de l'
EEG
(par exemple, delta) seront présentes. L'
EEG
de dix participants est enregistré pendant une nuit. Les stimuli auditifs consistarent en des sons (52 ms, 80 dB
SPL
, 2000 Hz) présentés à toutes les 20 s pendant le sommeil à ondes lentes (stades 2, 3 et 4). L'
EEG
fut fragmenté en intervalles de 4 s relatifs à la présentation du stimulus. Des transformations de Fourrier (
FFT
s) sont analysées pour les intervalles suivants: de 8.00 à 4.00 et 3.99 à 0.00 s avant la présentation du stimulus et, de 1.25 à 5.25 et 5.26 à 9.25 s à la suite de la présentation du stimulus. La valeur logarithmique des spectres de l'activité delta, thêta, alpha, sigma et bêta est obtenue. Lors des essais où un Complexe-K est évoqué, aucun changement n'est détecté dans l'activité spectrale des bandes de fréquences avant ou après la présentation des stimuli. Cependant, lorsqu'un Complexe-K n'est pas évoqué, une augmentation générale significative apparaît dans l'activité spectrale des bandes de fréquences thêta, alpha, sigma et bêta à la suite de la présentation du stimulus dans les stades 3 et 4 du sommeil. Cette augmentation n'apparaît pas en stade 2. Lorsque l'analyse spectrale de l'
EEG
est effectuée sur le premier stimulus de chaque bloc de présentation de stimuli, les résultats sont similaires à tous les essais additionnés. Ces résultats semblent supporter la théorie selon laquelle, pendant le sommeil à ondes lentes (3 et 4), le Complexe-K agirait en tant que filtre des stimuli perturbateurs en prévenant l'éveil qui apparaîtrait sinon à la suite de la présentation du stimulus.
The objective of the present study is 2-fold: (1) compare the time-estimation performance of chronic insomnia sufferers to that of good sleepers and (2) evaluate the severity of the sleep complaint ...in order to assess its association with the time-estimation performance.
Between subjects design.
The sample included 11 individuals suffering from chronic primary insomnia (7 women and 4 men, mean age = 44.64 years, SD = 12.71) and 11 good sleepers (5 women and 6 men, mean age = 48.00 years, SD = 7.86).
N/A.
All participants completed a time-estimation task, namely a finger-tapping task. The results indicate no significant between-group differences on time-estimation data, as well as no significant relationship between severity of insomnia complaint and estimation of time.
These results suggest that the tendency to misestimate sleep difficulties is not linked to impaired time estimation-specific processes in insomnia sufferers, as measured with the present task.
In the updated APOGEE-Kepler catalog, we have asteroseismic and spectroscopic data for over 3000 first ascent red giants. Given the size and accuracy of this sample, these data offer an unprecedented ...test of the accuracy of stellar models on the post-main-sequence. When we compare these data to theoretical predictions, we find a metallicity dependent temperature offset with a slope of around 100 K per dex in metallicity. We find that this effect is present in all model grids tested, and that theoretical uncertainties in the models, correlated spectroscopic errors, and shifts in the asteroseismic mass scale are insufficient to explain this effect. Stellar models can be brought into agreement with the data if a metallicity-dependent convective mixing length is used, with Δ ML,YREC ∼ 0.2 per dex in metallicity, a trend inconsistent with the predictions of three-dimensional stellar convection simulations. If this effect is not taken into account, isochrone ages for red giants from the Gaia data will be off by as much as a factor of two even at modest deviations from solar metallicity (Fe/H = −0.5).
Following the loss of wakeful consciousness, the averaging of responses to stimuli produce evoked potential waveforms with prominent components either unique to or greatly enhanced by non-REM sleep. ...In the sleep onset periods (stage 1) these are the P2 and N350. Following the establishment of stable sleep (stage 2 and SWS), the N550 and P900 are also prominent. Investigation of the EEG associated with individual responses indicates that a good proportion of stimuli elicit, K-complexes or vertex sharp waves (VSWs) and occasionally will elicit both. Recent work has indicated that the N550 in the averaged response is due to the presence of K-complexes and that the N350 is at least largely due to the presence of VSWs. The large size of these grapho-elements indicates that they are probably produced by a synchronized discharge of multiple neural units. Both are readily observed in the absence of external stimulation and occur as normal components of sleep, indeed the K-complex is used as one of the identifying features of the onset of stable non-REM sleep. The present review details the investigation of these features and their associated evoked potential components, in terms of stimulus features, brain states associated with their production, their scalp topography, and changes as a function of age.
Purpose
The Berlin definition for acute respiratory distress syndrome (ARDS) is a new proposal for changing the American-European consensus definition but has not been assessed prospectively as yet. ...In the present study, we aimed to determine (1) the prevalence and incidence of ARDS with both definitions, and (2) the initial characteristics of patients with ARDS and 28-day mortality with the Berlin definition.
Methods
We performed a 6-month prospective observational study in the ten adult ICUs affiliated to the Public University Hospital in Lyon, France, from March to September 2012. Patients under invasive or noninvasive mechanical ventilation, with PaO
2
/FiO
2
<300 mmHg regardless of the positive end-expiratory pressure (PEEP) level, and acute onset of new or increased bilateral infiltrates or opacities on chest X-ray were screened from ICU admission up to discharge. Patients with cardiogenic pulmonary edema were excluded. Patients were further classified into specific categories by using the American-European Consensus Conference and the Berlin definition criteria. The complete data set was measured at the time of inclusion. Patient outcome was measured at day 28 after inclusion.
Results
During the study period 3,504 patients were admitted and 278 fulfilled the American-European Consensus Conference criteria. Among them, 18 (6.5 %) did not comply with the Berlin criterion PEEP ≥ 5 cmH
2
O and 20 (7.2 %) had PaO
2
/FiO
2
ratio ≤200 while on noninvasive ventilation. By using the Berlin definition in the remaining 240 patients (
n
= 42 mild,
n
= 123 moderate,
n
= 75 severe), the overall prevalence was 6.85 % and it was 1.20, 3.51, and 2.14 % for mild, moderate, and severe ARDS, respectively (
P
> 0.05 between the three groups). The incidence of ARDS amounted to 32 per 100,000 population per year, with values for mild, moderate, and severe ARDS of 5.6, 16.3, and 10 per 100,000 population per year, respectively (
P
< 0.05 between the three groups). The 28-day mortality was 35.0 %. It amounted to 30.9 % in mild, 27.9 % in moderate, and 49.3 % in severe categories (
P
< 0.01 between mild or moderate and severe,
P
= 0.70 between mild and moderate). In the Cox proportional hazard regression analysis ARDS stage was not significantly associated with patient death at day 28.
Conclusions
The present study did not validate the Berlin definition of ARDS. Neither the stratification by severity nor the PaO
2
/FiO
2
at study entry was independently associated with mortality.
Access to scanners for magnetic resonance imaging (MRI) is typically limited by cost and by infrastructure requirements. Here, we report the design and testing of a portable prototype scanner for ...brain MRI that uses a compact and lightweight permanent rare-earth magnet with a built-in readout field gradient. The 122-kg low-field (80 mT) magnet has a Halbach cylinder design that results in a minimal stray field and requires neither cryogenics nor external power. The built-in magnetic field gradient reduces the reliance on high-power gradient drivers, lowering the overall requirements for power and cooling, and reducing acoustic noise. Imperfections in the encoding fields are mitigated with a generalized iterative image reconstruction technique that leverages previous characterization of the field patterns. In healthy adult volunteers, the scanner can generate T1-weighted, T2-weighted and proton density-weighted brain images with a spatial resolution of 2.2 × 1.3 × 6.8 mm
. Future versions of the scanner could improve the accessibility of brain MRI at the point of care, particularly for critically ill patients.
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