Time Variability Research Articles

Expiratory braking defines the breathing patterns of asphyxiated neonates during therapeutic hypothermia

IntroductionAlthough neonatal breathing patterns vary after perinatal asphyxia, whether they change during therapeutic hypothermia (TH) remains unclear. We characterized breathing patterns in infants during TH for hypoxic-ischemic encephalopathy (HIE) and normothermia after rewarming.MethodsIn seventeen spontaneously breathing infants receiving TH for HIE and in three who did not receive TH, we analyzed respiratory flow and esophageal pressure tracings for respiratory timing variables, pulmonary mechanics and respiratory effort. Breaths were classified as braked (inspiratory:expiratory ratio ≥1.5) and unbraked (<1.5).ResultsAccording to the expiratory flow shape braked breaths were chategorized into early peak expiratory flow, late peak expiratory flow, slow flow, and post-inspiratory hold flow (PiHF). The most braked breaths had lower rates, larger tidal volume but lower minute ventilation, inspiratory airway resistance and respiratory effort, except for the PiHF, which had higher resistance and respiratory effort. The braked pattern predominated during TH, but not during normothermia or in the uncooled infants.ConclusionsWe speculate that during TH for HIE low respiratory rates favor neonatal braked breathing to preserve lung volume. Given the generally low respiratory effort, it seems reasonable to leave spontaneous breathing unassisted. However, if the PiHF pattern predominates, ventilatory support may be required.

Analisis Produktivitas Alat Berat dalam Pengelolaan Sampah di Kecamatan Sukarami Kota Palembang

In Indonesia, solid waste has become a problem for municipalities, which could result in hygienic and aesthetically unpleasant issues. The high rate of population growth will have an impact on waste generation since it will change the needs and lifestyles of city dwellers. The collection, transportation, and final disposal of urban solid waste (TPA) require suitable facilities and infrastructure, particularly hefty equipment. Heavy equipment, specifically waste trucks, and heavy digging equipment, plays a significant part in supporting waste management activities. In particular, the Palembang City region is covered in this study's discussion of the productivity of heavy machinery used in waste management, which might begin with the collecting system, transportation system, and heavy equipment employed at the landfill. The study was conducted in Palembang City's Sukarami District, and data was collected by surveying and observing the current condition of the heavy equipment that was already in place, namely in terms of cycle time variables and the volume of waste that was served. The findings of the study indicate that direct communal and direct individual patterns characterize the region's waste-collecting practices. Dump trucks, which are used to transport waste, had a productivity range of 609.98 to 1266.13 kilograms per hour, while bulldozers and excavators had a range of 759.42 to 1166.17 kilograms per hour. This heavy equipment repair recommendation is targeted at bulldozers and excavators since a field investigation reveals that there are now only 2 pieces of bulldozer heavy equipment and 1 unit of excavator heavy equipment available.

Long term follow-up of heart rate variability in healthcare workers with mild COVID-19

IntroductionPrior investigations into post-COVID dysautonomia often lacked control groups or compared affected individuals solely to healthy volunteers. In addition, no data on the follow-up of patients with SARS-CoV-2-related autonomic imbalance are available.MethodsIn this study, we conducted a comprehensive clinical and functional follow-up on healthcare workers (HCWs) with former mild COVID-19 (group 1, n = 67), to delineate the trajectory of post-acute autonomic imbalance, we previously detected in a case–control study. Additionally, we assessed HCWs for which a test before SARS-CoV-2 infection was available (group 2, n = 29), who later contracted SARS-CoV-2, aiming to validate findings from our prior case–control investigation. We evaluated autonomic nervous system heart modulation by means of time and frequency domain heart rate variability analysis (HRV) in HCWs during health surveillance visits. Short-term electrocardiogram (ECG) recordings, were obtained at about 6, 13 months and both at 6 and 13 months from the negative SARS-CoV-2 naso-pharyngeal swab (NPS) for group 1 and at about 1-month from the negative NPS for group 2. HCWs who used drugs, had comorbidities that affected HRV, or were hospitalized with severe COVID-19 were excluded.ResultsGroup 1 was split into three subgroups clinically and functionally followed at, about 6 months (subgroup-A, n = 17), 13 months (subgroup-B, n = 37) and both at 6 and 13 months (subgroup-C, n = 13) from the negative SARS-CoV-2 NPS. In subgroup-A, at 6-month follow-up compared with baseline, the spectral components in the frequency domain HRV parameters, showed an increase in normalized high frequency power (nHF) (t = 2.99, p = 0.009), a decrease in the normalized low frequency power (nLF) (t = 2.98, p = 0.009) and in the LF/HF ratio (t = 3.13, p = 0.006). In subgroup B, the comparison of the spectral components in the frequency domain HRV parameters, at 13-month follow-up compared with baseline, showed an increase in nHF (t = 2.54, p = 0.02); a decrease in nLF (t = 2.62, p = 0.01) and in the LF/HF ratio (t = 4.00, p = 0.0003). In subgroup-C, at both 6 and 13-month follow-ups, the spectral components in the frequency domain HRV parameters were higher than baseline in nHF (t = 2.64, p = 0.02 and (t = 2.13, p = 0.05, respectively); lower in nLF (t = 2.64, p = 0.02 and (t = 2.13, p = 0.05, respectively), and in LF/HF (t = 1.92, p = 0.08 and (t = 2.43, p = 0.03, respectively). A significant proportion of HCWs reported persistent COVID-19 symptoms at both the 6 and 13-month follow-ups, seemingly unrelated to cardiac autonomic balance. In group 2 HCWs, at 1-month follow-up compared with baseline, the spectral components in the frequency domain HRV parameters, showed a decrease in nHF (t = 2.19, p = 0.04); an increase in nLF (t = 2.15, p = 0.04) and in LF/HF (t = 3.49, p = 0.002).ConclusionThese results are consistent with epidemiological data suggesting a higher risk of acute cardiovascular complications during the first 30 days after COVID-19. The SARS-CoV-2 associated autonomic imbalance in the post-acute phase after recovery of mild COVID-19 resolved 6 months after the first negative SARS-CoV-2 NPS. However, a significant proportion of HCWs reported long-term COVID-19 symptoms, which dot not seems to be related to cardiac autonomic balance. Future research should certainly further test whether autonomic imbalance has a role in the mechanisms of long-COVID syndrome.

A unifying representation of path integrals for fractional Brownian motions

Fractional Brownian motion (fBm) is an experimentally-relevant, non-Markovian Gaussian stochastic process with long-ranged correlations between the increments, parametrised by the so-called Hurst exponent H; depending on its value the process can be sub-diffusive (0<H<1/2) , diffusive (H=1/2) or super-diffusive (1/2<H<1) . There exist three alternative equally often used definitions of fBm—due to Lévy and due to Mandelbrot and van Ness (MvN), which differ by the interval on which the time variable is formally defined. Respectively, the covariance functions of these fBms have different functional forms. Moreover, the MvN fBms have stationary increments, while for the Lévy fBm this is not the case. One may therefore be tempted to conclude that these are, in fact, different processes which only accidentally bear the same name. Recently determined explicit path integral representations also appear to have very different functional forms, which only reinforces the latter conclusion. Here we develop a unifying equivalent path integral representation of all three fBms in terms of Riemann–Liouville fractional integrals, which links the fBms and proves that they indeed belong to the same family. We show that the action in such a representation involves the fractional integral of the same form and order (dependent on whether H<1/2 or H>1/2 ) for all three cases, and differs only by the integration limits.

TIMES, ARE THEY A–CHANGING? IMPLANTATION AND FOLLOW–UP EXPERIENCE WITH LEADLESS PACEMAKERS (MICRA) AT PISA UNIVERSITY HOSPITAL

Abstract Background Leadless pacing represents a pivotal advancement in cardiac stimulation. Eliminating traditional pacing leads, leadless devices offer reduced complications, a bailout strategy for many previously challenging cases and streamlined procedures. Purpose This retrospective study aimed to compare, starting from December 1st 2023, newer implants (within the 3 years preceding Dec 1st 2023) and older implants (&amp;gt;3 years before) in a single–center experience with M–TPS (Micra Transcatheter Pacing System) in terms of safety and efficacy, at baseline and in a short–term follow–up (6 months). Methods A comprehensive analysis was conducted on 195 patients who underwent leadless pacemaker implantation at our Center, and that were followed–up for a minimum of 6 months. The cohort was stratified into two groups: recent (n=73) and less recent implants (n=122). Procedural variables, patient demographics, and clinical outcomes were documented. Post–implantation follow–up data include pacing threshold, fluoroscopy time, and other relevant variables. Results Comparison between the two groups revealed significant differences fluoroscopy time. Newer implants demonstrated a reduced fluoroscopy time [8 (IQR 5–12) vs 10 minutes (IQR 7–14)], suggesting potential advancements in technique. No significant differences were observed in other procedural or electrical parameters. Discussion: The comparison between older and newer leadless pacemaker implants reveals reassuring constancy in most parameters, suggesting the reliability of the M–TPS. The reduced fluoroscopy time aligns with the evolving proficiency of implanters and improved procedural efficiency. The dependable consistency observed across various parameters strengthens the confidence in the M–TPS, reinforcing its status as a reliable and effective solution for pacing. Conclusion The implantation and follow–up experience at our center elucidates very few differences between newer and older implants. This nuanced analysis contributes to the ongoing evolution of leadless pacemaker technology, which heralds a transformative era in cardiac care. With several years of implementation, accumulated follow–up data unveils valuable insights into its sustained effectiveness, guiding clinicians in optimizing patient outcomes and solidifying leadless pacing as a breakthrough in the realm of cardiac rhythm management.

Time-frequency analysis of nonlinear structures under nonstationary excitation by directly solving structural dynamic equation through absolute displacement

The time-frequency evolution of seismic ground motion energy under strong earthquakes, which can be described by the evolutionary power spectral density (EPSD) matrix, will amplify the most unfavorable responses of members in nonlinear structural systems. However, the existing general finite element software fails to reduce the dimension of the EPSD matrix and then decouple time from frequency in frequency domain analysis. This failure greatly limits the simulation and calculation of multi-dimensional nonlinear structures with multiple degrees of freedom by the stochastic vibration theory. In this study, the pseudo excitation method (PEM), which can direct solve structural dynamic equations using absolute displacement, is used to derive the self-spectral and cross-spectral densities of seismic ground motions in one-dimensional and multi-dimensional cases. In MATLAB, the EPSD matrix is transformed into a four-dimensional uniform modulation excitation matrix independent of the time variable. Nonlinear iteration is conducted and the precise integration method (PIM) is employed through a transient analysis module. Furthermore, a simple one-dimensional example is presented to verify the correctness of the proposed algorithm herein. Finally, as an example, we select important parameters of the coherence model at different supports of a half-through three-span concrete-filled steel tubular (CFST) tied-arch bridge in view of real engineering conditions, and calculate the time-varying power spectrum and variance of the responses of arch ribs, arch feet and the bridge deck system. The results show that the theoretical derivation and the algorithm constructed in this paper can simulate the time-delay effect of the nonlinear structural system. This proves the feasibility of general finite element software in solving and analyzing random responses to multi-dimensional and multi-support non-stationary excitation of nonlinear structures.

Assessing downscaling methods to simulate hydrologically relevant weather scenarios from a global atmospheric reanalysis: case study of the upper Rhône River (1902–2009)

Abstract. We assess the ability of two modelling chains to reproduce, over the last century (1902–2009) and from large-scale atmospheric information only, the temporal variations in river discharges, low-flow sequences and flood events observed at different locations of the upper Rhône River catchment, an alpine river straddling France and Switzerland (10 900 km2). The two modelling chains are made up of a downscaling model, either statistical (Sequential Constructive Atmospheric Analogues for Multivariate weather Predictions – SCAMP) or dynamical (Modèle Atmosphérique Régional – MAR), and the Glacier and SnowMelt SOil CONTribution (GSM-SOCONT) model. Both downscaling models, forced by atmospheric information from the global atmospheric reanalysis ERA-20C, provide time series of daily scenarios of precipitation and temperature used as inputs to the hydrological model. With hydrological regimes ranging from highly glaciated ones in its upper part to mixed ones dominated by snow and rain downstream, the upper Rhône River catchment is ideal for evaluating the different downscaling models in contrasting and demanding hydro-meteorological configurations where the interplay between weather variables in both space and time is determinant. Whatever the river sub-basin considered, the simulated discharges are in good agreement with the reference ones, provided that the weather scenarios are bias-corrected. The observed multi-scale variations in discharges (daily, seasonal, and interannual) are reproduced well. The low-frequency hydrological situations, such as annual monthly discharge minima (used as low-flow proxy indicators) and annual daily discharge maxima (used as flood proxy indicators), are reproduced reasonably well. The observed increase in flood activity over the last century is also reproduced rather well. The observed low-flow activity is conversely overestimated, and its variations from one sub-period to another are only partially reproduced. Bias correction is crucial for both precipitation and temperature and for both downscaling models. For the dynamical one, a bias correction is also essential for getting realistic daily temperature lapse rates. Uncorrected scenarios lead to irrelevant hydrological simulations, especially for the sub-basins at high elevation, due mainly to irrelevant snowpack dynamic simulations. The simulations also highlight the difficulty in simulating precipitation dependency on elevation over mountainous areas.

Public perceptions on net zero energy houses in Japan

AbstractFor Japan, which has not operated nearly all of its nuclear power plants since 2011 and is dependent on thermal power generation, the introduction of renewable energy into homes is extremely important for the future formation of a sustainable society. However, the introduction of net zero energy house (ZEH) in detached houses, which account for 55% of all dwellings in Japan, has not progressed. To promote the introduction of ZEH, this study clarified the awareness of owners of detached houses regarding ZEH. We analyzed factors that influence such perception of solar photovoltaics (PV) technology using a 1000-sample online survey questionnaire. The survey was conducted in late January 2020 and included questions examining the public perception of solar installation and factors that were found to be important in previous research. We found that Japanese respondents who live in detached houses generally lack an understanding of renewables and that the level of interest in installing solar PV for the ZEH is low. We also found that awareness of renewables, such as knowing new energy policy and searching information on solar PV, is the critical factor of installing renewables. At the same time, most socio-demographic and neighborhood variables seem not to influence installing solar PV or other technologies for ZEH. This research will contribute to the Japanese government’s goal of strengthening education on renewable energy to promote ZEH.

Assessing the time variability of GIEMS-2 satellite-derived surface water extent over 30 years

Assessing the time variability of GIEMS-2 satellite-derived surface water extent over 30 years

Numerical approximations of groundwater flow problem using fractional variational iteration method with fractional derivative of singular and nonsingular kernels

This study aims to present the numerical approximations of groundwater flow problem, namely the time-fractional Boussinesq equation using the fractional variational iteration method. Fractional derivatives in time variable are taken in Caputo and Caputo–Fabrizio sense. This work compares the solutions of the time-fractional Boussinesq equation for the Caputo and Caputo–Fabrizio fractional operators. Graphical representation of the water table head’s behavior for different time values is shown.

Variability in Pubertal Timing Among Asian American, Native Hawaiian, and Pacific Islander Subgroups

Variability in Pubertal Timing Among Asian American, Native Hawaiian, and Pacific Islander Subgroups

Forecasting the Exceedances of PM2.5 in an Urban Area

Forecasting the Exceedances of PM2.5 in an Urban Area

A simulation-based genetic algorithm for a semi-automated warehouse scheduling problem with processing time variability

For warehouse operations, efficiently scheduling the available resources is crucial to improve the productivity and customer satisfaction. This paper proposes a simulation-based evolutionary algorithm for order scheduling and multi-robot task assignment in a robotic mobile fulfillment system. The algorithm proactively deals with the effects of the processing time variability by evaluating schedules based on both its system performance as well as its robustness under uncertain conditions. The algorithm implements an efficient resource allocation method and a variance reduction technique to reduce the overall computational burden. The experimental results show that the techniques to reduce the computational time are effective and can significantly reduce the amount of simulations required for the fitness evaluation. If a candidate schedule is allocated insufficient simulation replications it can lead to an inaccurate estimate of its long-term average performance. This could lead to an average performance loss of 7.3 %. Furthermore, the proactive scheduler is able to generate schedules that are more robust compared to deterministically generated. A reduction in the average operational cost of about 5 % can be reached, compared to a deterministically generated schedule. The paper reveals the relevance of identifying and modeling uncertainty when designing schedules in an operational system, rather than looking for optimal schedules for ideal scenarios.

Novel non-linear models for clinical trial analysis with longitudinal data: A tutorial using SAS for both frequentist and Bayesian methods.

Longitudinal data from clinical trials are commonly analyzed using mixed models for repeated measures (MMRM) when the time variable is categorical or linear mixed-effects models (ie, random effects model) when the time variable is continuous. In these models, statistical inference is typically based on the absolute difference in the adjusted mean change (for categorical time) or the rate of change (for continuous time). Previously, we proposed a novel approach: modeling the percentage reduction in disease progression associated with the treatment relative to the placebo decline using proportional models. This concept of proportionality provides an innovative and flexible method for simultaneously modeling different cohorts, multivariate endpoints, and jointly modeling continuous and survival endpoints. Through simulated data, we demonstrate the implementation of these models using SAS procedures in both frequentist and Bayesian approaches. Additionally, we introduce a novel method for implementing MMRM models (ie, analysis of response profile) using the nlmixed procedure.

Two-Dimensional System of Moment Equations and Macroscopic Boundary Conditions Depending on the Velocity of Movement and the Surface Temperature of a Body Moving in Fluid

This article is dedicated to the derivation of a two-dimensional system of moment equations depending on the velocity of movement and the surface temperature of a body submerged in fluid, and macroscopic boundary conditions for the system of moment equations approximating the Maxwell microscopic boundary condition for the particle distribution function. The initial-boundary value problem for the Boltzmann equation with the Maxwell microscopic boundary condition is approximated by a corresponding problem for the system of moment equations with macroscopic boundary conditions. The number of moment equations and the number of macroscopic boundary conditions are interconnected and depend on the parity of the approximation of the system of moment equations. The setting of the initial-boundary value problem for a non-stationary, nonlinear two-dimensional system of moment equations in the first approximation with macroscopic boundary conditions is presented, and the solvability of the above-mentioned problem in the space of functions continuous in time and square-integrable in spatial variables is proven.

The MOSAiC Distributed Network: Observing the coupled Arctic system with multidisciplinary, coordinated platforms

Central Arctic properties and processes are important to the regional and global coupled climate system. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Distributed Network (DN) of autonomous ice-tethered systems aimed to bridge gaps in our understanding of temporal and spatial scales, in particular with respect to the resolution of Earth system models. By characterizing variability around local measurements made at a Central Observatory, the DN covers both the coupled system interactions involving the ocean-ice-atmosphere interfaces as well as three-dimensional processes in the ocean, sea ice, and atmosphere. The more than 200 autonomous instruments (“buoys”) were of varying complexity and set up at different sites mostly within 50 km of the Central Observatory. During an exemplary midwinter month, the DN observations captured the spatial variability of atmospheric processes on sub-monthly time scales, but less so for monthly means. They show significant variability in snow depth and ice thickness, and provide a temporally and spatially resolved characterization of ice motion and deformation, showing coherency at the DN scale but less at smaller spatial scales. Ocean data show the background gradient across the DN as well as spatially dependent time variability due to local mixed layer sub-mesoscale and mesoscale processes, influenced by a variable ice cover. The second case (May–June 2020) illustrates the utility of the DN during the absence of manually obtained data by providing continuity of physical and biological observations during this key transitional period. We show examples of synergies between the extensive MOSAiC remote sensing observations and numerical modeling, such as estimating the skill of ice drift forecasts and evaluating coupled system modeling. The MOSAiC DN has been proven to enable analysis of local to mesoscale processes in the coupled atmosphere-ice-ocean system and has the potential to improve model parameterizations of important, unresolved processes in the future.

Fourth-order exponential time differencing Runge–Kutta scheme and local meshless method to investigate unsteady diffusion–convection problems of anisotropic functionally graded materials

The current article is devoted to proposing a local meshfree method for simulating the unsteady diffusion–convection problems of anisotropic functionally graded materials (AFGM). The first stage of the proposed numerical algorithm is based on discretizing the spatial variables by utilizing the direct meshless local Petrov–Galerkin (DMLPG) method. Then a system of ODEs is extracted which is associated to the time variable. Furthermore, the fourth-order exponential time differencing Runge–Kutta method is applied to solve the system of ODEs. The main aim of this work is to introduce a flexible and low-cost numerical procedure to solve unsteady diffusion–convection problems of AFGM on the complicated geometry. The new numerical technique has admissible resultants to simulate the studied model. This numerical formulation is applied to several examples with complex domains to check its ability.

CONSEQUENCES OF A TWO-TIME RELATIVISTIC BOHMIAN MODEL

Abstract Effects of a Bohmian type quantum-relativistic theory are explored. The model is obtained by introducing a new and independent time parameter whose relative motions are not directly observable and cause the quantum uncertainties of the physical observables. Unlike the usual de Broglie-Bohm theories, the Quantum Potential does not affect directly the observable motion but it determines that one relative to the new time variable. It turns out that the Zitterbewegung of a free particle, of which a more general law is obtained, is the key example of these hidden motions and, through it, it seems possible to give physical reality to the Feynman’s paths. A relativistic revision of the uncertainty principle also derives from the theory.

Routine, Routine, Routine: Sleep Regularity and its Association with Sleep Metrics in Professional Rugby Union Athletes

BackgroundMaintaining a consistent sleep and wake time is often reported as a key component of circadian rhythmicity and quality sleep. However, the impact of sleep onset and offset time variability on overall sleep outcomes are underreported in elite athlete populations. This study investigated the relationship between sleep onset and offset time variability using the sleep regularity index (SRI) and measures of sleep and well-being in professional rugby union athletes. Twenty-three professional male rugby union athletes (mean ± SD, age: 23 ± 3 y) underwent sleep monitoring via wrist actigraphy for three weeks during a pre-season phase of training and completed a daily wellness questionnaire. Median SRI was calculated and used to stratify the trainees into two quantile groups: >76.4 SRI (Regular, n = 11) and < 76.4 SRI (Irregular, n = 12).ResultsThe regular sleep group showed significantly longer total sleep duration (p = 0.02, d = 0.97) compared to the irregular group (7:42 ± 0:29 vs. 7:18 ± 0:20 h: min per night, respectively). Furthermore, while not statistically significant, the regular sleep group showed greater sleep efficiency and less wake episodes compared to irregular sleepers, as demonstrated by moderate effect sizes (d = 0.71 and 0.69, respectively).ConclusionsThe results from this study indicate that minimizing variability in sleep onset and offset time is beneficial for increasing sleep duration and may improve sleep efficiency during pre-season training in elite male rugby union athletes. This study provides evidence for the importance of including sleep-wake routines as a key component of sleep education interventions.

Impact of misdiagnosis on the treatment and prognosis of acute aortic syndrome

Abstract Funding Acknowledgements None. Introduction Acute aortic syndrome (AAS) embraces a spectrum of pathologies with relatively low prevalence but associated with high mortality. The clinical presentation of AAS is highly variable and the differential diagnosis with other much more common diseases such as myocardial infarction (AMI) or pulmonary embolism (PE) is often difficult to achieve. AAS detection requires a high index of suspicion and the delay in diagnosis is associated with increased morbidity and mortality. Purpose The aim of this study is to characterize the diagnostic approach to AAS patients in the emergency department (ED) and to study the impact of the initial diagnostic suspicion on the treatment and prognosis of patients with AAS. Methods The "Aorta Code" is an inter-hospital and interdisciplinary care protocol for the management of patients with AAS in a 4-Hospital network. Patients with AAS were prospectively and consecutively collected from 2019 to 2022. The sample was classified into two groups according to whether the initial suspicion was AAA or another clinical entity. The diagnosis of AAS was established by computed tomography in all patients. Time, clinical, treatment and prognostic variables were analyzed. Results A total of 113 patients with AAS were included. Of them, only 38% (34) were initially suspected of having an AAS (Figure). AMI and PE were the initial diagnosis in 34% of patients (Figure). There were no significant differences in age, history of hypertension or other cardiovascular risk factors between the groups (table). Anterior chest pain was more frequent in the "AAS-suspicion" group. The diagnostic time delay was longer in patients with initial misdiagnosis (table). Patients with type A AAS with initial misdiagnosis underwent surgery in a lower proportion (table). Although the differences were not significant, patients with initial misdiagnosis had more postoperative complications and higher mortality. Conclusion It is essential to maintain a high index of diagnostic suspicion for AAS in the ED. Initial misdiagnosis is associated with a delayed diagnosis, delayed surgical treatment and a lower rate of surgery. In addition, although it is a small sample size, this group of patients had more postoperative complications and higher mortality.