Regular Breaks Research Articles

Origin of regular chiral fluctuation or symmetry breaking unique to preferential enrichment

Origin of regular chiral fluctuation or symmetry breaking unique to preferential enrichment

A clean environmental week: Let the nature breathe

High levels of CO2 emissions in the atmosphere and toxic pollutants in air, water and food have serious repercussions on all life's systems, including living beings, environment and economy. Everyone on the Earth is concerned by pollution in some way or another, no matter where and how the pollution is produced as airborne and foodborne pollutants could circulate around the world in different ways, through for example climate components (wind, rain) and/or import and export of foodstuffs. Similarly to living beings that take advantage of day-night circadian rhythms to recover after diurnal hardships, the environment in its entirety could also be seen as a complex living system that needs regular breaks to assimilate or ingest toxic pollutants produced during intensive and continuous industrial processes. If greenhouses gas emissions and pollution rates continue to increase at the same rates as they are nowadays, uncontrollable climate effects might be inevitable and the air quality in some crowded cities in the world might be hardly respirable in the future. A global “Clean Environmental Week” is discussed as an attempt toward reducing air pollution and CO2 emissions through the interruption or reduction of industrial polluting activities regularly, for a week or so per year, to let the nature ‘breathe’ and recover from environmentally challenging pollutions. A clean environmental period of 10 days per year could reduce CO2 emissions by about one billion tons of CO2 per annum.

How did the public respond to the 2015 expert consensus public health guidance statement on workplace sedentary behaviour? A qualitative analysis

BackgroundIn June 2015, an expert consensus guidance statement was published recommending that office workers accumulate 2–4 h of standing and light activity daily and take regular breaks from prolonged sitting. This paper describes public responses to media coverage of the guidance, so as to understand public acceptability of the recommendations within the guidance, and perceptions of sitting and standing as health behaviours.MethodsUK news media websites that had reported on the sedentary workplace guidance statement, and permitted viewers to post comments responding to the story, were identified. 493 public comments, posted in a one-month period to one of six eligible news media websites, were thematically analysed.ResultsThree themes were extracted: (1) challenges to the credibility of the sedentary workplace guidance; (2) challenges to the credibility of public health; and (3) the guidance as a spur to knowledge exchange. Challenges were made to the novelty of the guidance, the credibility of its authors, the strength of its evidence base, and its applicability to UK workplaces. Public health was commonly mistrusted and viewed as a tool for controlling the public, to serve a paternalistic agenda set by a conspiracy of stakeholders with hidden non-health interests. Knowledge exchanges focused on correcting others’ misinterpretations, raising awareness of historical or scientific context, debating current workplace health policies, and sharing experiences around sitting and standing.ConclusionsThe guidance provoked exchanges of health-promoting ideas among some, thus demonstrating the potential for sitting reduction messages to be translated into everyday contexts by lay champions. However, findings also demonstrated confusion, misunderstanding and misapprehension among some respondents about the health value of sitting and standing. Predominantly unfavourable, mistrusting responses reveal significant hostility towards efforts to displace workplace sitting with standing, and towards public health science more broadly. Concerns about the credibility and purpose of public health testify to the importance of public engagement in public health guidance development.

Understaffing and registered nurses’ turnover: The moderating role of regular rest breaks

Current demographic and occupational changes call for new interventions to promote staff retention, especially in nursing where understaffing promotes turnover by increasing workload and strain. Based on previous research examining recovery at work, we investigated whether well-designed rest breaks can function as a resource that buffers adverse consequences of understaffing in nursing. We used a cross-sectional, multi-method study design and assessed understaffing of registered nurses, their regularity of rest breaks, and their annual turnover behaviour in 80 German geriatric nursing teams. As expected, understaffing positively predicted turnover only in work conditions with irregular rest breaks. Hence, implementing regularly scheduled rest breaks can be considered as an effective intervention for improving retention of nurses even in a situation of understaffing.

The Attention Merchants: The Epic Scramble to Get Inside Our Heads

The Attention Merchants: The Epic Scramble to Get Inside Our Heads

Regional-scale probabilistic shoreline evolution modelling for flood-risk assessment

Rapid deterministic modelling of shoreline evolution at regional and coastal-scheme scale enables Monte-Carlo simulations by which long-term shoreline statistics can be estimated. This paper describes UnaLinea, a fast, accurate finite difference solver of the one-line sediment continuity equation. The model is verified for the evolution of an initially straight shoreline of a plane beach subject to regular breaking waves at constant angle of incidence in the presence of either a groyne or a continuous single-point feed of sediment. Grid convergence and stability tests are used to obtain accurate, stable results, with satisfactory computational efficiency. Influences of wave input filtering and event-based sediment loading are considered. The rapid deterministic model is applied to Monte-Carlo simulations of the evolution of the west coast of Calabria, Italy for different scenarios including increased sediment load from a river and selected beach nourishment. The potential role of probabilistic shoreline evolution in regional coastal flood-risk assessment is explored through application to an idealised stretch of the Holderness coastline, U.K., where flood depths and expected damage are estimated for a 1000 year return period event.

Incidence of Dry Eyes Amongst The Computer Users

Objective: The Study was aimed at finding the incidence and prevention of computers vision syndrome(CVS) particularly “dry eye” in regular computer users. Study design: Observational, cross-sectional study Place and duration of study: It was conducted at Combined Military hospital Lahore, from Dec 2014 to Nov 2015. Methodology: A questionnaire proforma was prepared and distributed to the willing candidates. It was based on symptoms of eye, sensitivity of eyes to various environmental conditions, history of medications contributing to eye, working hours on computers etc. The visual effects of various display characteristics such as lighting, glare, display quality, refresh rates, and radiation are also briefly discussed. Results: Out of 290 regular computer users, 88 (30.3%) were found to have problem. Conclusion Although the computers vision syndrome is associated with a variety of ocular symptoms related to computer use including eyestrain, tired eyes, irritation, redness, blurred/double vision, headache and shoulder pain, this article was primarily focused on dry eye the major contributor to computer vision syndrome symptoms. Management requires a multidirectional approach combining ocular therapy with adjustment of the workstation. Conclusion: Proper lighting, anti-glare filters, ergonomic positioning of computer monitor and regular work breaks may help improve visual comfort. Lubricating drops and special computer glasses help relieve ocular surface-related symptoms. A lot more work needs to be done to specifically define the processes that cause in computer vision syndrome and to develop and improve effective treatments that successfully address these causes.

The Effects of Spacing, Naps, and Fatigue on the Acquisition and Retention of Laparoscopic Skills

Earlier research has shown that laparoscopic skills are trained more efficiently on a spaced schedule compared to a massed schedule. The aim of the study was to estimate to what extent the spacing interval, naps, and fatigue influenced the effectiveness of spacing laparoscopy training. Overall 4 groups of trainees (aged 17-41y; 72% female; Nmassed = 40; Nbreak = 35; Nbreak-nap = 37; Nspaced = 37) without prior experience were trained in 3 laparoscopic tasks using a physical box trainer with different scheduling interventions. The first (massed) group received three 100-minute training sessions consecutively on a single day. The second (break) group received the sessions interrupted with two 45-minute breaks. The third (break-nap) group had the same schedule as the second group, but had two 35-minute powernap intervals during the breaks. The fourth (spaced) group had the 3 sessions on 3 consecutive days. A retention session was organized approximately 3 months after training. The results showed an overall pattern of superior performance at the end of training and at retention for the spaced group, followed by the break-nap, break, and massed group, respectively. The spaced and break-nap group significantly outperformed the break and massed group, with effect sizes ranging from 0.20 to 0.37. Spacing laparoscopic training over 3 consecutive days or weeks is superior to massed training, even if the massed training contains breaks. Breaks with sleep opportunity (i.e., lying, inactive, and muted sensory input) enhance performance over training with regular breaks and traditional massed training.

Research and Analysis on the Wave Transformation and Irregular Wave Breaking Criterion on the Shore

Within the surf zone which is the region extending from the seaward boundary of wave breaking to the limit of wave uprush, breaking waves are the dominant hydrodynamics acting as the key role for sediment transport and beach profile change. Breaking waves exhibit various patterns, principally depending on the incident wave steepness and the beach slope. Based on the equations of conservation of mass, momentum and energy, a theoretical model for wave transformation in and outside the surf zone was obtained, which is used to calculate the wave shoaling, wave set-up and set down and wave height distributions in and outside the surf zone. The analysis and comparison were made about the breaking point location and the wave height variation caused by the wave breaking and the bottom friction, and about the wave breaking criterion under regular and irregular breaking waves. Flume experiments relating to the regular and irregular breaking wave height distribution across the surf zone were conducted to verify the theoretical model. The agreement is good between the theoretical and experimental results.

Wave-induced uprush jet velocity on a vertical structure

A vertical wall with an overhanging horizontal cantilever slab was tested in a small-scale test setup (with a scale of 1:20) under wave impact (impulsive) loads. A single breaking wave creates two distinct sequential impacts on the vertical and horizontal parts of the cantilever. The breaking wave jet hits on the vertical wall then rises with an uprush jet velocity and creates the second impact on the horizontal cantilever. This upward water momentum depends on the uprush jet velocity. In this study, data from pressure sensors was used to analyze the average uprush jet velocity (uv_av) under regular breaking waves. A formula to predict the average uprush jet velocity on a vertical structure is proposed. Wave height at the toe of the foreshore (H1), water depth at the structure toe (hs), and wave period (T) were found to be the main parameters governing the average uprush jet velocity. In addition, the influence of geometric properties such as clearance between still water level and horizontal part of the cantilever (c′) were analyzed. The proposed formula is applicable within the range 0.45≤H1/hs≤1.2, 2.0s≤T≤2.8s and 0.75m≤hs≤1.65m.

Wave breaking in the surf zone and deep-water in a non-hydrostatic RANS model. Part 1: Organized wave motions

We examine wave-breaking predictions ranging from shallow- to deep-water conditions using a non-hydrostatic σ-coordinate RANS model NHWAVE as described in Derakhti et al. (2016a), comparing results both with corresponding experiments and with the results of a volume-of-fluid (VOF)/Navier-Stokes solver (Ma et al., 2011; Derakhti and Kirby, 2014a,b). Our study includes regular and irregular depth-limited breaking waves on planar and barred beaches as well as steepness-limited unsteady breaking focused wave packets in intermediate and deep water. In Part 1 of this paper, it is shown that the model resolves organized wave motions in terms of free-surface evolution, spectral evolution, organized wave velocity evolution and wave statistics, using a few vertical σ-levels. In addition, the relative contribution of modeled physical dissipation and numerical dissipation to the integral breaking-induced wave energy loss is discussed. In steepness-limited unsteady breaking focused wave packets, the turbulence model has not been triggered, and all the dissipation is imposed indirectly by the numerical scheme. Although the total wave-breaking-induced energy dissipation is underestimated in the unsteady wave packets, the model is capable of predicting the dispersive and nonlinear properties of different wave packet components before and after the break point, as well as the overall wave height decay and the evolution of organized wave velocity field and power spectrum density over the breaking region. In Part 2 (Derakhti et al., 2016b), model reproduction of wave-breaking-induced turbulence and mean circulation is examined in detail. The same equations and numerical methods are used for the various depth regimes, and no ad-hoc treatment, such as imposing hydrostatic conditions, is involved in triggering breaking. Vertical grid resolution in all simulated cases is at least an order of magnitude coarser than that of typical VOF-based simulations.

Assessment of classical and approximated models estimating regular waves kinematics

The planning and management of many coastal activities require the knowledge of the wave mechanics in a target area. Many theoretical models have been developed to describe the evolution of a regular wave, with different levels of accuracy, but it is hard to evaluate which model is the most suitable one to reproduce a precise marine process.In this regard, an experimental program, started up at the Technical University of Bari, aims to provide some useful references to practitioners in the field. The present work enriches the existing experimental dataset and analyzes two new experimental regular breaking waves, examined in the shoaling zone. Their cross-shore and vertical velocities have been measured together with their elevations by means of a 2D Laser Doppler Anemometer and a resistive gauge, respectively. Several classical theories and approximate methods have been used to reproduce the waves kinematics, in order to test their validity and applicability. Mainly, the study outlines that i) an increasing error in the reproduction of the wave kinematics is observed while increasing its non linearities; ii) approximate methods tend to better perform in comparison with classical theories, even if in some cases they are more sensitive to the surface boundary conditions.

NHWAVE: Consistent boundary conditions and turbulence modeling

Large-scale σ-coordinate ocean circulation models neglect the horizontal variation of σ in the calculation of stress terms and boundary conditions. Following this practice, the effects of surface and bottom slopes in the dynamic surface and bottom boundary conditions have been usually neglected in the available non-hydrostatic wave-resolving models using a terrain-following grid. In this paper, we derive consistent surface and bottom boundary conditions for the normal and tangential stress fields as well as a Neumann-type boundary condition for scalar fluxes. Further, we examine the role of surface slopes in the predicted near-surface velocity and turbulence fields in surface gravity waves. By comparing the predicted velocity field in a deep-water standing wave in a closed basin, we show that the consistent boundary conditions do not generate unphysical vorticity at the free surface, in contrast to commonly used, simplified stress boundary conditions developed by ignoring all contributions except vertical shear in the transformation of stress terms. In addition, it is shown that the consistent boundary conditions significantly improve predicted wave shape, velocity and turbulence fields in regular surf zone breaking waves, compared with the simplified case. A more extensive model-data comparison of various breaking wave properties in different types of surface breaking waves is presented in companion papers (Derakhti et al., 2016a,b).

3D flow measurements in regular breaking waves past a fixed submerged bar on an impermeable plane slope

The velocity fields induced by regular breaking waves past a fixed bar on a 1 : 10 rigid plane slope were measured and analysed using a volumetric particle-tracking velocimetry system. Under specific conditions, the interaction between waves and morphological features steepens the waves, which eventually break. The geometry of the boundaries of the present experiments is common in natural environments, where reefs, sand and gravel bars, and submerged coastal structures, interact with the incoming wave field, ‘affecting’ the transport budget of substances (sediment, nutrients and pollutants), with relevant consequences on the water quality. The aims of the present work are the analysis of the flow field in the breaker, and the quantification of the terms in the equations usually adopted for modelling the flow and the turbulence. Two sets of attacking monochromatic wave trains with different periods and heights were used to generate a data set of instantaneous velocity, which was further analysed to extract turbulence. The measurement volume extended from the wave crest to a portion of the domain below the wave trough. The balance of linear momentum for the average field and the balance of turbulence were scrutinized, and included all the terms in a three-dimensional (3D) approach. The analysed data and results are original and novel because they include all the contributions derived from the 3D structure of a real flow field, and constitute a huge data set for the calibration of numerical codes.

High-Order Boussinesq-Type Model for Integrated Nearshore Dynamics

AbstractA two-dimensional high-order Boussinesq-type model was derived to simulate wave propagation and relevant processes in the nearshore zone. Because of its enhanced nonlinear character, the model can describe more accurately the amplitude dispersion compared to its weakly nonlinear counterpart. Extension to the surf zone was accomplished using the eddy-viscosity concept for simulating breaking waves. Swash-zone dynamics were simulated by applying a modified narrow-slot technique. Bottom friction and subgrid turbulent mixing were also incorporated. The model can estimate the wave-induced current field, including the undertow effect. The numerical model relied on a generalized multistep predictor-corrector scheme, and the waves were generated using the source function method. Both the one-horizontal-dimensional (1DH) and two-horizontal-dimensional (2DH) versions were validated against a variety of experimental tests, including regular and irregular wave propagation and breaking on plane beaches and sub...

High indoor CO2 concentrations in an office environment increases the transcutaneous CO2 level and sleepiness during cognitive work

ABSTRACTThe purpose of this study is to perform a multiparametric analysis on the environmental factors, the physiological stress reactions in the body, the measured alertness, and the subjective symptoms during simulated office work. Volunteer male subjects were monitored during three 4-hr work meetings in an office room, both in a ventilated and a non-ventilated environment. The environmental parameters measured included CO2, temperature, and relative humidity. The physiological test battery consisted of measuring autonomic nervous system functions, salivary stress hormones, blood's CO2- content and oxygen saturation, skin temperatures, thermal sensations, vigilance, and sleepiness. The study shows that we can see physiological changes caused by high CO2 concentration. The findings support the view that low or moderate level increases in concentration of CO2 in indoor air might cause elevation in the blood's transcutaneously assessed CO2. The observed findings are higher CO2 concentrations in tissues, changes in heart rate variation, and an increase of peripheral blood circulation during exposure to elevated CO2 concentration. The subjective parameters and symptoms support the physiological findings. This study shows that a high concentration of CO2 in indoor air seem to be one parameter causing physiological effects, which can decrease the facility user's functional ability. The correct amount of ventilation with relation to the number of people using the facility, functional air distribution, and regular breaks can counteract the decrease in functional ability. The findings of the study suggest that merely increasing ventilation is not necessarily a rational solution from a technical-economical viewpoint. Instead or in addition, more comprehensive, anthropocentric planning of space is needed as well as instructions and new kinds of reference values for the design and realization of office environments.

Cardiac Autonomic Modulation in Preadolescents Following 4 and 8 Weeks of Play-based Summer Activity

Pediatric obesity is associated with a decrease in cardiac autonomic modulation and baroreflex sensitivity. Physical activity increases heart rate variability in adults, yet no study has elucidated the mode and intensity of exercise for beneficial effects on cardiac autonomic modulation in children. Objective: The purpose of our study was to examine the effectiveness of 4 and 8 weeks of supervised, play-based activity on blood pressure, heart rate variability and baroreflex sensitivity in preadolescents. Methods: Twenty-two recreationally active overweight, 8 to 12 year-old children were randomly divided into a 4- and 8-week activity group and an unsupervised control group (4w, n = 6, 8w, n = 6, and C, n = 10). 4w and 8w groups performed play-based activities 5 days per week, 4 hours a day while C group were instructed to maintain a regular summer break with no supervised intervention. Heart rate variability and baroreflex sensitivity were tested before and after exercise with a heads-up tilt test. Results: Systolic blood pressure was significantly lower in all three groups in post conditions (P = 0.02, eta2 = 6.86). Normalized low and high frequencies reported a significant group-by-time difference in both supine resting conditions and after heads-up tilt (P = 0.04, eta2 = 0.28 and P = 0.05, eta2 = 0.28, respectively) and total power in supine position (P = 0.04, eta2 = 0.29) between the 8w, and the 4w and C groups, while baroreflex sensitivity increased by only 3 ms/mmHg in the 8w group (P = 0.09). Conclusion: 8 weeks of supervised, play-based physical activity improved autonomic nervous system activation with favorable changes in sympathovagal balance in recreationally active overweight preadolescents during summer break.

Temporal and Spatial Analysis of the New World Screwworm (Cochliomyia hominivorax) in Darien and Embera, Panama (2001-2011).

Larvae (maggots) of Cochliomyia hominivorax, the New World Screwworm fly, are voracious consumers of living flesh that have a negative economic impact by decreasing productivity, predisposing to other pathogens, and, in severe cases, causing death of domestic livestock. Screwworm caused extensive financial losses to the livestock industry in North America prior to its eradication. Sterile insect technique (SIT) was used to eradicate screwworm throughout North and Central America and continues to be the main tool to control it in eastern Panama. The goal of this study was to evaluate the temporal and spatial trends of screwworm myiasis cases reported in the Province of Darien and Comarca Embera (border with Colombia), Panama, from 2001 to 2011. We hypothesized that screwworm cases would vary seasonally and be spatially clustered near Colombia as a result of effective eradication strategies in Panama and the presence of an autochthonous population of flies in western Colombia. Temporal and spatial data were retrieved from COPEG-USDA records (Panama) and analysed by anova, Ripley's K function, discrete Poisson spatial statistic scan and Getis-Ord Gi*. No significant temporal trend was found, but cases were spatially distributed in four clusters. One cluster of cases occurred from 2001 to 2003 and was considered a focal temporal and spatial cluster. One cluster occurred in 2001 and 2007 indicating more rare outbreaks in an area with fewer cattle. The two remaining clusters contained cases from 2004 to 2011 and 2001 to 2011 suggesting regular breaks in the control barrier due to occasional failures of the SIT programme, difficulties implementing border quarantine strategies, livestock smuggling or the movement of infested wildlife.

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains.

This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a ‘Berry force’. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose.

Impact of prolonged sitting on vascular function in young girls.

What is the central question of this study? Children are spending more than 60% of their waking day sedentary. The consequences of excessive sedentary behaviour are not well understood in the child, but there is growing evidence that with increasing sedentary time, cardiovascular risk in childhood also increases. What is the main finding and its importance? Our findings show that a 3h period of uninterrupted sitting causes a profound (33%) reduction in vascular function in young girls. Importantly, we also demonstrate that breaking up sitting with regular exercise breaks can prevent this. Excessive sedentary behaviour has serious clinical and public health implications; however, the physiological changes that accompany prolonged sitting in the child are not completely understood. Herein, we examined the acute effect a prolonged period of sitting has upon superficial femoral artery function in 7- to 10-year-old girls and the impact of interrupting prolonged sitting with exercise breaks. Superficial femoral artery endothelium-dependent flow-mediated dilatation, total shear rate, anterograde and retrograde shear rates and oscillatory shear index were assessed before and after two experimental conditions: a 3h uninterrupted period of sitting (SIT) and a 3h period of sitting interrupted each hour with 10min of moderate-intensity exercise (EX). A mixed-model analysis of variance was used to compare between-condition and within-condition main effects, controlling for the within-subject nature of the experiment by including random effects for participant. Superficial femoral artery endothelium-dependent flow-mediated dilatation decreased significantly from pre- to post-SIT (mean difference 2.2% flow-mediated dilatation; 95% confidence interval=0.60-2.94%, P<0.001). This relative decline of 33% was abolished in the EX intervention. Shear rates were not significantly different within conditions. Our data demonstrate the effectiveness of short but regular exercise breaks in offsetting the detrimental effects of uninterrupted sitting in young girls.