Night-to-Night Associations Between Light Exposure and Sleep Health

Previous research has demonstrated that exposure to light preceding and during sleep is associated with poor sleep, but most research to date has utilized either experimental or cross-sectional designs. The current study expands upon prior studies by using a microlongitudinal design that examines the night-to-night associations between light and sleep health in a diverse sample of adults (pre-registered at osf.io/k5zgv). U.S. adults aged 18 to 87 from two parent studies (N= 124) wore an actiwatch for up to 10 nights. Light variables estimated from actigraphy include both average exposure and time above light threshold of 10 (TALT10) and 40 (TALT40) lux both during sleep and for the 1-hour preceding sleep. Actigraphy-based sleep variables included sleep offset, duration, percentage, and fragmentation index. Higher average light exposure during sleep was associated with a later sleep offset time, lower sleep percentage, and higher fragmentation index (all p <.01). More minutes of TALT10 during sleep was associated with later sleep timing, lower sleep percentage, and higher fragmentation index (all p < .01) and greater TALT40 during sleep was associated with lower sleep percentage. Light exposure was not related to sleep duration. In summary, greater light exposure during sleep was related to poorer sleep continuity and later wake time. The lack of association between light and sleep duration may be the result of compensating for sleep disruption by delaying wake time. Multi-level interventions to consistently reduce light levels during sleep should be considered.

Changes in Muscle Strategies During Landing Task in Subjects With and Without Knee Genu Varum

Introduction: Onset and offset activation of lower limb and trunk muscles may change the knee with genu varum during landing. These motor control strategies can be different from those in healthy subjects and contribute to more injuries in lower extremities. This study aimed to compare the delay time of the onset activity of the abdominal and lower limb muscles in the specific landing task. Materials and Methods: Ten females with genu varum deformity and ten females with normal knee participated in this case-control study. Genu varum deformity was measured by a camera capturing goniometer. The subjects were informed to land by preferred lower limb from a table (30 cm high) on a force plate. Vertical Ground Reaction Force (VGRF) was measured to clarify the onset of the landing task. Surface Electromyography (sEMG) of transverse abdominal/int. oblique (TA/IO), Vastus Medialis (VM), Vastus Lateralis (VL), Lateral Gastrocnemius (LG), and medial gastrocnemius (MG) muscles were recorded during landing. The difference between the onset activity of the above muscles and onset of VGRF was calculated as delay times and compared between muscles and between two groups. Also, the offset of activities and the intensity of muscle activation (normalized RMS) were compared between the two groups. Results: Lower limb and trunk muscles showed significantly different onset of activities in the genu varum group (P<0.05), whereas there was no significant difference in the onset of muscle activities in the healthy group. Results indicated significant differences between two groups in TA/IO, LG, and MG muscles and the genu varum group had longer delay time for motor control strategy (especially ankle strategy) in the landing task. Offset time of all muscles in the genu varum and healthy subjects had a significant difference between muscles, especially in gastrocnemius muscles (P<0.05). Also, there were significant changes between the two groups in LG and MG muscles (P<0.05). Normalized muscle activities (nRMS) generally indicated an increase in muscle activation of genu varum subjects (TA/IO, LG, MG) compared with the normal subjects (P<0.05). Conclusion: Motor control strategies in landing task is different in the genu varum group due to changes in biomechanics and properties of the knee joint. This variation may be due to changes in proprioception afferent pathways around the knee joint. An increase in muscle activation, delay, and offset time of muscle activities in these subjects, indicated that an increase in the degree of freedom may change motor control strategies. Internal anticipation and postural adjustment of the landing task in these subjects need more motor unit recruitment (an increase in nRMS). This deformity in the knee joint might affect some activities and possibly cause knee changes such as osteoarthritis.

Observed and predicted ages at peak height velocity in soccer players

The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status.

Challenges and procedures for experiments with steady and unsteady model velocities in a water towing tank

Challenges for steady and unsteady model motion in a large water towing tank and procedures to overcome them are the focus of the presented work. Some challenges are attributed to experiments conducted in water, whereas others are uniquely ascribed to a towing tank facility. Data convergence and outlier detection are studied based on the phase averaged pressure in order to ensure proper data quality. Pressure measurements are performed with non-surface mounted sensors. Therefore, inertia effects are detrimental when the attached tubing is not fully de-aired. A procedure for de-airing the pressure sensor cavity and its tubing is described. An iterative approach is developed that compensates for nonlinear distortion of the model’s velocity profile. Further, vibration effects are examined by distinguishing mechanical and flow-induced frequencies that scale with the instantaneous model velocity. Sloshing waves are excited, which are a function of the water basin size. The first sloshing mode defines the required sensor offset time in between test cases when prevailing sloshing waves have not fully decayed. This appropriate selection of sensor offset time reduces data scatter and enables a reasonable waiting time in between test cases. A skim plate installed just below the water surface offers a potential solution to alleviate surface wave effects over the model.

The use of a 3rd U/S or D/S sensor in Salt Dilution Flow Measurements

&lt;p&gt;Salt Dilution flow measurement is relatively accurate and easy way to measure flow in turbulent waterways.&amp;#160; However, it&amp;#8217;s accuracy and precision are governed by the Signal to Noise (SNR) Ratio, which can be very low in urban, sub-urban, and rural waterways due to a highly variable BackGround specific Electrical Conductivity (BG ECT) signal.&amp;#160; Conventionally, more salt is added to the waterway to overcome the noise in the BG ECT.&amp;#160; The &amp;#8220;noise&amp;#8221; is a combination of random noise, which is amplified by the typically high BGECT (&gt;500 uS/cm), but also lower frequency noise that changes on the same time scale as the salt breakthrough curve.&amp;#160; To compensate for the changing BG ECT, we have employed a 3&lt;sup&gt;rd&lt;/sup&gt; UpStream (U/S) probe to track the BG ECT, along with algorithms to transform the signal in 3 domains: magnitude (ECT offset), time (transit time of pulse), and frequency (to compensate for storage in the waterway).&amp;#160; Additionally, we have tested the use of a 3&lt;sup&gt;rd&lt;/sup&gt; DownStream (D/S) probe to measure cross-channel variance when mixing is not complete in order to achieve a reasonable flow estimate.&amp;#160; Results are compared and discussed.&lt;/p&gt;

Is Selective Late Na+ Current Inhibition Different From Class I/B Antiarrhythmic Action? Comparison of The Effects of GS967 to Mexiletine in Canine Ventricular Myocardium

Enhancement of the late Na+ current (INaL) increases arrhythmia propensity in the heart, while suppression of the current is antiarrhythmic. GS967 is an agent considered as a selective blocker of INaL. In the present study, effects of GS967 on INaL, on L-type calcium current (ICa), and on action potential (AP) morphology were studied in canine ventricular myocytes by using conventional voltage clamp, action potential voltage clamp and sharp microelectrode techniques. These effects of GS967 were compared to tetrodotoxin (TTX) and to the class I/B antiarrhythmic compound mexiletine. 1 µM GS967, 40 µM mexiletine, and 10 µM TTX dissected largely similarly shaped inward currents under action potential voltage clamp conditions. In case of GS967 and mexiletine, the amplitude and integral of this current was significantly smaller when measured in the presence of 1 µM nisoldipine, while no difference was observed in case of TTX. Under conventional voltage clamp conditions, INaL was significantly decreased by 1 µM GS967 and 40 µM mexiletine (79.0±3.0% and 63.3±2.7% reduction of current integrals, respectively). The integral of ICa was moderately but significantly diminished by both drugs (reduction of 9.3±3.3% and 14.1±1.5%, respectively). These changes were associated with acceleration of inactivation of ICa. Drug effects on peak Na+ current (INaP) were also assessed by recording AP upstroke in multicellular preparations. Both GS967 and mexiletine showed fast onset and offset kinetics: 110 ms and 289 ms offset time constants, respectively, as determined from V+max measurements in right ventricular papillary muscles, while the onset kinetics was characterized by 5.3 AP and 2.6 AP, respectively, at 2.5 Hz. Effects on beat-to-beat variability of AP duration (APD) was studied in isolated myocytes. Beat-to-beat variability was significantly decreased by both GS967 and mexiletine (reduction of 42.1±6.5% and 24.6±12.8%, respectively) while their shortening effect on APD was comparable. It is concluded that the electrophysiological effects of GS967 are similar to those of mexiletine, but with somewhat faster offset kinetics of V+max block. However, since GS967 depressed V+max and INaL at the same concentration, the current view that GS967 represents a new class of drugs that selectively block INaL has to be questiond and it is suggested that GS967 should be classified as a class I/B (or I/B + IV) antiarrhythmic agent.

Consecutive Days of Racing Does Not Affect Sleep in Professional Road Cyclists

Purpose: Professional road cycling races are physiologically demanding, involving successive days of racing over 1 to 3 weeks of competition. Anecdotal evidence indicates that cyclists’ sleep duration either increases or deteriorates during these competitions. However, sleep duration in professional cyclists during stage races has not been assessed. This study examined the amount/quality of sleep obtained by 14 professional cyclists competing in the Australian Tour Down Under. Methods: Sleep was assessed using wrist activity monitors and self-report sleep diaries on the night prior to start of the race and on each night during the race. The impact of each day of the race on sleep onset, sleep offset, time in bed, sleep duration, and wake duration was assessed using separate linear mixed effects models. Results: During the race, cyclists obtained an average of 6.8 (0.9) hours of sleep between 23:30 and 07:27 hours and spent 13.9% (4.7%) of time in bed awake. Minor differences in sleep onset (P = .023) and offset times (P ≤.001) were observed during the week of racing, but these did not affect the amount of sleep obtained by cyclists. Interestingly, the 3 best finishers in the general classification obtained more sleep than the 3 worst finishers (7.2 [0.3] vs 6.7 [0.3] h; P = .049). Conclusions: Contrary to anecdotal reports, the amount of sleep obtained by cyclists did not change over the course of the 1-week race and was just below the recommended target of 7 to 9 hours for adults.

A Bursts Contention Avoidance Scheme Based on Streamline Effect Awareness and Limited Intermediate Node Buffering in the Core Network

In an Optical Burst Switched (OBS) network, data packets sourced from peripheral networks are assembled into huge sized data bursts. For each assembled data burst, an associated control signal in the form of a burst control packet is (BCP) is generated and scheduled at an offset time ahead of the data burst. The offset timing is to allow for the pre-configuration of required resources at all subsequent intermediate nodes prior to the actual data burst’s arrival. In that way, the data burst will fly-by each node and hence no requirement for temporary buffering at all intermediate nodes. An operational requirement of an OBS network is that it be loss-less as in that way a consistent as well as acceptable quality of service (QoS) for all applications and services it serves as a platform can be guaranteed. Losses in such a network are mainly caused by improper provisioning as well as dimensioning of resources thus leading to contentions among bursts and consequently discarding of some of the contending data bursts. Key to both provisioning as well as proper dimensioning of the available resources in an optimized way is the implementation of effective routing and wavelength (RWA) that will seclude any data losses due to contention occurrences. On the basis of the effects of the streamline effect (SLE), that is, effectively secluding primary contention among flows (streams) in the network, we propose in this paper a limited intermediate buffering that couples with SLE aware prioritized RWA (LIB-PRWA) scheme that combats secondary contention as well. The scheme makes routing decisions such as selection of primary and deflection routes based on current resources states in the candidate paths. A performance comparison of the proposed scheme is carried out and simulation results demonstrate its comparative abilities to effectively reduce losses as well as maintaining both high network resources utilization as well as QoS.