Associations of novel 24-h accelerometer-derived metrics with adiposity in children and adolescents

Background Further research is required to explore the associations between 24-h movement behaviours and health outcomes in the paediatric population. Therefore, this study aimed to examine the associations between novel data-driven 24-h activity metrics and adiposity among children and adolescents. Methods The sample included 382 children (8–13 years) and 338 adolescents (14–18 years). The average acceleration (AvAcc) of activity, intensity gradient (IG), and metrics representing the initial acceleration for the most active time periods of the 24-h cycle were calculated from raw acceleration data. Adiposity measures included body mass index z-score, fat mass percentage (FM%), and visceral adipose tissue (VAT). Data analysis was performed using multiple linear regression adjusted for wear time, sex, maternal education level, and maternal overweight and obesity. Results Children demonstrated higher values in all 24-h activity metrics than did adolescents (p < 0.001 for all). For children, the initial acceleration for the most active 2, 5, 15, and 30 min of the 24-h cycle were negatively associated with FM% (p ≤ 0.043 for all) and VAT (p <0.001 for all), respectively. For adolescents, the IG was negatively associated with FM% (p = 0.002) and VAT (p = 0.007). Moreover, initial acceleration for the most active 2, 5, 15, 30, 60, and 120 min were associated with FM% (p ≤ 0.007 for all) and with VAT (p ≤ 0.023 for all). Conclusions The intensity distribution of activity and initial acceleration for the most active 2, 5, 15, 30, 60, and 120 min within the 24-h cycle are beneficial for the prevention of excess adiposity in the paediatric population.

Automatic detection of prosodic boundaries in spontaneous speech

Automatic speech recognition (ASR) and natural language processing (NLP) are expected to benefit from an effective, simple, and reliable method to automatically parse conversational speech. The ability to parse conversational speech depends crucially on the ability to identify boundaries between prosodic phrases. This is done naturally by the human ear, yet has proved surprisingly difficult to achieve reliably and simply in an automatic manner. Efforts to date have focused on detecting phrase boundaries using a variety of linguistic and acoustic cues. We propose a method which does not require model training and utilizes two prosodic cues that are based on ASR output. Boundaries are identified using discontinuities in speech rate (pre-boundary lengthening and phrase-initial acceleration) and silent pauses. The resulting phrases preserve syntactic validity, exhibit pitch reset, and compare well with manual tagging of prosodic boundaries. Collectively, our findings support the notion of prosodic phrases that represent coherent patterns across textual and acoustic parameters.

Early Onset Acceleration of Fetal Growth in Gestational Diabetes Mellitus: Deciding About When and Whom to Screen for Preventing Fetal Macrosomia

The precise time into pregnancy at which women are screened for gestational diabetes mellitus (GDM) is crucial for determining the benefits of diagnosis. However, this issue remains a source of intense debate among guidance authorities and there is no consensus about when and whom to screen. Since 2010, the IADPSG recommends universal screening with 75g OGTT at 24–28 weeks’ gestation (WG), due to evidence of a positive linear correlation between maternal blood glucose levels around 28 WG and risk of fetal macrosomia. Nonetheless, emerging evidence indicates that initial acceleration of fetal growth (FG) related to GDM, predicting fetal macrosomia, is already underway at 20 WG, thereby suggesting that screening strategies for GDM earlier than the recommended 24–28 WG should be reconsidered (1). By exploiting the routine 19–21 WG obstetrical assessment of FG (anomaly scan), along with the risk stratification system endorsed by the Italian NHS, which offers, in addition to the usual GDM screening test at 24–28 WG, an early 75g OGTT at 16–18 WG to women who are classified as at high risk (HR) for GDM (i.e. previous GDM, pre-gravid obesity, or FPG at first prenatal visit between 5.6–6.9 mmol/L), we aimed to verify whether an early onset acceleration of FG related to GDM would be observed in our pregnant population, and if reversion could occur with current screening recommendations. For this, 769 consecutive women in singleton pregnancies, subjected to both anomaly scan and GDM screening, were retrospectively enrolled at our Institution between Jan 2018-Feb 2020. At a mean time of 20.8 WG, the percentiles of estimated fetal weight (EFW) and abdominal circumference (AC) were significantly higher in women who tested positive for GDM at late screening than in women with normal glucose tolerance (NGT). However, while no differences in the birthweight (BW) percentiles of neonates born to non-HR women diagnosed with GDM at 24–28 WG, with respect to NGT women were observed (p=0.416), neonates born to HR women diagnosed with GDM at 24–28 WG (due to refusal to comply with early screening advices) were significantly heavier (p&lt;0.001). In contrast, both the EFW and AC percentiles, as well as the BW percentiles, were significantly lower in infants born to HR women diagnosed with GDM at 16–18 WG with respect to their late diagnosis counterparts (EFW p=0.001, AC p=0.002, BW p=0.048), and not dissimilar to those of NGT women (EFW p=0.824, AC p=0.873, BW p=0.242). These results were confirmed by regression analysis, while adjusting for maternal confounders. Although an initial acceleration of FG related to GDM can be detected at anomaly scan in non-HR women, reversion occurs with current screening recommendations. Earlier screening strategies should be reserved to HR women, as the acceleration of FG related to GDM in these cases is less responsive to treatment delays. (1) Ref: Li et al. Lancet Diabetes Endocrinol. 2020;8(4):292–300.

Lyman-alpha radiation pressure: an analytical exploration

ABSTRACT We study radiation pressure due to Ly α line photons, obtaining and exploring analytical expressions for the force-multiplier, MF(NH, Z) = Fα/(Lα/c), as a function of gas column density, NH, and metallicity, Z, for both dust-free and dusty media, employing a WKB approach for the latter case. Solutions for frequency offset emission to emulate non-static media moving with a bulk velocity v have also been obtained. We find that, in static media, Ly α pressure dominates over both photoionization and dust-mediated UV radiation pressure in a very wide parameter range (16 &lt; log NH &lt; 23; −4 &lt; log [Z/Z⊙] &lt; 0). For example, it overwhelms the other two forces by $\lower.5ex\hbox{$\,\, \buildrel\gt \over \sim \,\,$}10$ (300) times in standard (low-Z) star-forming clouds. Thus, in agreement with previous studies, we conclude that Ly α pressure plays a dominant role in the initial acceleration of the gas around luminous sources, and must be implemented in galaxy formation, evolution and outflow models and simulations.

Dynamics of liquid drop on a vibrating micro-perforated plate

The present work presents the behavior of a liquid drop placed onto a surface of the perforated plate experimentally. Micro holes were created on the brass plate by a laser marking method. The actuator made of brass and piezoelectric discs driven by a sine input voltage, and it bonded rigidly to the perforated plate. This study aimed to reveal the behavior of the drop placed on the perforated plate and the effects of the initial acceleration value on the rate of change in the drop projected area onto the surface. For this purpose, a frequency-response function of the dry micro-perforated plate was measured by a laser vibrometer, and the acceleration distribution was determined on the perforated plate. Further, the drop was excited with five different initial acceleration values, and the drop projected area onto the surface was recorded by a camera during the atomization process. It was observed that droplets were atomized at the air–liquid interface on two sides of the perforated plate. The time-varying function of the drop projected area onto the surface for each initial acceleration value was presented graphically. The polynomial function was fitted to the experimental data points for each acceleration value, and thus the effects of the initial acceleration on the varying drop size were analyzed. The authors emphasized that the drop projected area onto the surface first increased and then decreased during the atomization process. The rate of change in the drop projected area onto the surface increased as the initial acceleration increased. The drop was atomized both by ejecting from the surface and sucking through the holes.

An Elastic Collision Model for Impulsive Jumping by Small Planktonic Organisms

Many small marine planktonic organisms converge on similar propulsion mechanisms that involve impulsively generated viscous wake vortex rings, and small-scale fluid physics is key to mechanistically understanding the adaptive values of this important behavioral trait. Here, a theoretical fluid mechanics model is developed for plankton jumping, based on observations that the initial acceleration phase for a jumping plankter to attain its maximum speed is nearly impulsive, taking only a small fraction of the viscous timescale, and therefore can be regarded as nearly inviscid, analogous to a one-dimensional elastic collision. Flow circulation time-series data measured by particle image velocimetry (PIV) are input into the model and Froude propulsion efficiencies are calculated for several plankton species. Jumping by the tailed ciliate Pseudotontonia sp. has a high Froude propulsion efficiency ~0.9. Copepod jumping also has a very high efficiency, usually >0.95. Jumping by the squid Doryteuthis pealeii paralarvae has an efficiency of 0.44 ± 0.16 (SD). Jumping by the small medusa Sarsia tubulosa has an efficiency of 0.38 ± 0.26 (SD). Differences in the calculated efficiencies are attributed to the different ways by which these plankters impart momentum on the water during the initial acceleration phase as well as the accompanied different added mass coefficients.

The dual nature of the dead-water phenomenology: Nansen versus Ekman wave-making drags

A ship encounters a higher drag in a stratified fluid compared to a homogeneous one. Grouped under the same “dead-water” vocabulary, two wave-making resistance phenomena have been historically reported. The first, the Nansen wave-making drag, generates a stationary internal wake which produces a kinematic drag with a noticeable hysteresis. The second, the Ekman wave-making drag, is characterized by velocity oscillations caused by a dynamical resistance whose origin is still unclear. The latter has been justified previously by a periodic emission of nonlinear internal waves. Here we show that these speed variations are due to the generation of an internal dispersive undulating depression produced during the initial acceleration of the ship within a linear regime. The dispersive undulating depression front and its subsequent whelps act as a bumpy treadmill on which the ship would move back and forth. We provide an analytical description of the coupled dynamics of the ship and the wave, which demonstrates the unsteady motion of the ship. Thanks to dynamic calculations substantiated by laboratory experiments, we prove that this oscillating regime is only temporary: the ship will escape the transient Ekman regime while maintaining its propulsion force, reaching the asymptotic Nansen limit. In addition, we show that the lateral confinement, often imposed by experimental setups or in harbors and locks, exacerbates oscillations and modifies the asymptotic speed.

Kinematics of coronal mass ejections in the LASCO field of view

In this paper we present a statistical study of the kinematics of 28894 coronal mass ejections (CMEs) recorded by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory spacecraft from 1996 until mid-2017. The initial acceleration phase is characterized by a rapid increase in CME velocity just after eruption in the inner corona. This phase is followed by a non-significant residual acceleration (deceleration) characterized by an almost constant speed of CMEs. We demonstrate that the initial acceleration is in the range 0.24–2616 m s−2 with median (average) value of 57 m s−2 (34 m s−2) and it takes place up to a distance of about 28 RSUN with median (average) value of 7.8 RSUN (6 RSUN). Additionally, the initial acceleration is significant in the case of fast CMEs (V > 900 km s−1), where the median (average) values are about 295 m s−2 (251 m s−2), respectively, and much weaker in the case of slow CMEs (V < 250 km s−1), where the median (average) values are about 18 m s−2 (17 m s−2), respectively. We note that the significant driving force (Lorentz force) can operate up to a distance of 6 RSUN from the Sun during the first 2 hours of propagation. We found a significant anti-correlation between the initial acceleration magnitude and the acceleration duration, whereas the residual acceleration covers a range from −1224 to 0 m s−2 with a median (average) value of −34 m s−2 (−17 m s−2). One intriguing finding is that the residual acceleration is much smaller during the 24th cycle in comparison to the 23rd cycle of solar activity. Our study has also revealed that the considered parameters, initial acceleration (ACCINI), residual acceleration (ACCRES), maximum velocity (VMAX), and time at maximum velocity (TimeMAX) mostly follow solar cycles and the intensities of the individual cycle.

Post-disintegration evolution of the largest Larsen B tributary glaciers

&lt;p&gt;Crane and Hektoria glaciers, the major tributaries of the former Larsen B Ice Shelf, underwent major structural and ice flow changes in the aftermath of the ice shelf&amp;#8217;s disintegration in March, 2002. In addition to the widely reported initial acceleration (leading to speeds 3 to 6 times the pre-disintegration rate), the continued retreat led to the formation of significant ice cliffs. For Hektoria, this occurred as a seamless transition from ice shelf disintegration. Crane Glacier had a two-stage acceleration, first increasing in speed by 3x in the first few months after disintegration, then slowing through September 2004, and then a rapid additional acceleration in 2005-2006. Both glaciers developed significant ice cliffs during retreat, with peak ice-front heights of 105 m for Crane and 85 m for Hektoria.&lt;/p&gt;