Interlayer Magnetic Frustration in Quasi-stoichiometric Li1-xNi1+xO2

Susceptibility, high-field magnetization and submillimeter wave electron spin resonance measurements of layered quasi-stoichiometric Li1-xNi1+xO2 are reported and compared to isomorphic NaNiO2. A new mechanism of magnetic frustration induced by the excess Ni ions always present in the Li layers is proposed. We finally comment on the possible realization of an orbital liquid state in this controversial compound.Comment: 4 pages, 5 figures, submitted to Phys.Rev.B, Rapid Com

Coercivity and squareness enhancement in ball-milled hard magnetic-antiferromagnetic composites

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.The room-temperature coercivity,HC, and squareness, MR/MS (remanence/saturation magnetizations), of permanent magnet,SmCo5powders have been enhanced by ball milling with antiferromagnetic NiO (with Néel temperature, TN=590 K). This enhancement is observed in the as-milled state. However, when the milling of SmCo5 is carried out with an antiferromagnet with TN below room temperature (e.g., for CoO, TN=290 K), the coercivity enhancement is only observed at low temperatures after field cooling through TN. The ferromagnetic-antiferromagnetic exchange coupling induced either by local heating during milling(SmCo5+NiO) or field cooling (SmCo5+CoO) is shown to be the origin of the HC increase

Quantitative features of multifractal subtleties in time series

Based on the Multifractal Detrended Fluctuation Analysis (MFDFA) and on the Wavelet Transform Modulus Maxima (WTMM) methods we investigate the origin of multifractality in the time series. Series fluctuating according to a qGaussian distribution, both uncorrelated and correlated in time, are used. For the uncorrelated series at the border (q=5/3) between the Gaussian and the Levy basins of attraction asymptotically we find a phase-like transition between monofractal and bifractal characteristics. This indicates that these may solely be the specific nonlinear temporal correlations that organize the series into a genuine multifractal hierarchy. For analyzing various features of multifractality due to such correlations, we use the model series generated from the binomial cascade as well as empirical series. Then, within the temporal ranges of well developed power-law correlations we find a fast convergence in all multifractal measures. Besides of its practical significance this fact may reflect another manifestation of a conjectured q-generalized Central Limit Theorem

Firefighters\u27 physical activity across multiple shifts of planned burn work

Little is currently known about the physical activity patterns of workers in physically demanding populations. The aims of this study were to (a) quantify firefighters\u27 physical activity and sedentary time within (2-h periods) and across planned burn shifts; and (b) examine whether firefighters\u27 activity levels during one shift or 2-h period was associated with their activity levels in the following shift or 2-h period. Thirty-four salaried firefighters (26 men, 8 women) wore an Actical accelerometer for 28 consecutive days. Time spent sedentary (SED) and in light- (LPA), moderate- (MPA) and vigorous-intensity physical activity (VPA) were derived using validated cut-points. Multilevel analyses (shift, participant) were conducted using generalised linear latent and mixed models. Firefighters spent the majority of a planned burn shift (average length 10.4 h) or 2-h period engaged in LPA (69% and 70%, respectively). No significant associations were observed between SED and physical activity levels between consecutive planned burned shifts or 2-h periods. The physical activity that a firefighter engaged in during one shift (or 2-h period) did not subsequently affect their physical activity levels in the subsequent shift (or 2-h period). Further research is needed to establish how workers in physically demanding populations are able to sustain their activity levels over long periods of time

Pressure dependence of electron distribution along the TCNQ columns in (TEDA)2TCNQ3

High-pressure infrared absorption has been measured in the single crystals of (TEDA)2TCNQ3 at room temperature. An energy gap of a direct type with the size of approximately 0.23 eV is observed at ambient pressure. In the molecular vibration region, the absorption peaks due to the C=C stretching are observed at 1518 and 1504 cm-1, suggesting that the excess electrons are less localized in this substance compared to other 2:3 TCNQ complexes. The behavior of these peaks suggests that a phase transition takes place at 1.0 GPa. In the high-pressure phase the excess electrons tend to be more localized instead of being delocalized as indicated by the increasing of the energy spacing of those modes. The charge transfer degrees of the TCNQ molecules are estimated to be 0.60 and 0.80 (low pressure) and 0.56 and 0.88 (high-pressure phase)

The SCOUT-O3 Darwin Aircraft Campaign: rationale and mateorology

An aircraft measurement campaign involving the Russian high-altitude aircraft M55 Geophysica and the German DLR Falcon was conducted in Darwin, Australia in November and December 2005 as part of the European integrated project SCOUT-O3. The overall objectives of the campaign were to study the transport of trace gases through the tropical tropopause layer (TTL), mechanisms of dehydration close to the tropopause, and the role of deep convection in these processes. In this paper a detailed roadmap of the campaign is presented, including rationales for each flight, and an analysis of the local and large-scale meteorological context in which they were embedded. The campaign took place during the pre-monsoon season which is characterized by a pronounced diurnal evolution of deep convection including a mesoscale system over the Tiwi Islands north of Darwin known as �\x83¢Â�Â�HectorâÂ�Â�. This allowed studying in detail the role of deep convection in structuring the tropical tropopause region, in situ sampling convective overshoots above storm anvils, and probing the structure of anvils and cirrus clouds by Lidar and a suite of in situ instruments onboard the two aircraft. The large-scale flow during the first half of the campaign was such that local flights, away from convection, sampled air masses downstream of the âÂ�Â�cold trapâÂ�Â� region over Indonesia. Abundant cirrus clouds enabled the study of active dehydration, in particular during two TTL survey flights. The campaign period also encompassed a Rossby wave breaking event transporting stratospheric air to the tropical middle troposphere and an equatorial Kelvin wave modulating tropopause temperatures and hence the conditions for dehydration

Parental Perspectives of a Wearable Activity Tracker for Children Younger Than 13 Years: Acceptability and Usability Study

Background: There is increasing availability of, and interest in, wearable activity trackers for children younger than 13 years. However, little is known about how children and parents use these activity trackers or perceive their acceptability.Objective: This study primarily aimed to ascertain parental perspectives on the acceptability and usability of wearables designed to monitor children’s physical activity levels. Secondary aims were to (1) identify practical considerations for future use in physical activity interventions and promotion initiatives; (2) determine use of different features and functions incorporated into the accompanying app; and (3) identify parents’ awareness of their child’s current physical activity levels.Methods: In total, 36 children (18 boys and 18 girls) aged 7-12 years were asked to wear a wrist-worn activity tracker (KidFit) for 4 consecutive weeks and to use the accompanying app with parental assistance and guidance. Each week, one parent from each family (n=25; 21 mothers and 4 fathers) completed a Web-based survey to record their child’s activity tracker use, app interaction, and overall experiences. At the end of the 4-week period, a subsample of 10 parents (all mothers) participated in face-to-face interviews exploring perceptions of the acceptability and usability of wearable activity trackers and accompanying apps. Quantitative and qualitative data were analyzed descriptively and thematically, respectively. Thematic data are presented using pen profiles, which were constructed from verbatim transcripts.Results: Parents reported that they and their children typically found the associated app easy to use for activity tracking, though only step or distance information was generally accessed and some difficulties interpreting the data were reported. Children were frustrated with not being able to access real-time feedback, as the features and functions were only available through the app, which was typically accessed by, or in the presence of, parents. Parents identified that children wanted additional functions including a visual display to track and self-monitor activity, access to the app for goal setting, and the option of undertaking challenges against schools or significant others. Other barriers to the use of wearable activity trackers included discomfort of wearing the monitor because of the design and the inability to wear for water- or contact-based sports.Conclusions: Most parents reported that the wearable activity tracker was easy for their child or children to use and a useful tool for tracking their children’s daily activity. However, several barriers were identified, which may impact sustained use over time; both the functionality and wearability of the activity tracker should therefore be considered. Overall, wearable activity trackers for children have the potential to be integrated into targeted physical activity promotion initiatives