Load Trajectory Research Articles

Interplay of Neighborhood and Psychosocial Factors in Predicting Trajectories of Allostatic Load Among Latinx Adults in the United States

Research highlights the independent roles of neighborhood and psychosocial risk and protective factors for accelerated physiological aging. However, the combined role of neighborhood and psychosocial factors for allostatic load among Latinx adults in the U.S. remains unclear. Informed by the Health Disparities Framework, the study aims are to: (1) examine the direct associations between neighborhood (cohesion and disorder) and psychosocial (loneliness) factors, respectively, and allostatic load trajectories; and (2) determine whether family social support moderates the association between loneliness and allostatic load trajectories. Data for Latinx adults ages ≥50 ( n = 319) are from the Health and Retirement Study (waves 2006–2016). Linear mixed models estimated baseline and rate of change in allostatic load, adjusting for sociodemographics. Loneliness was positively associated with baseline allostatic load. This association persisted when we considered neighborhood factors. Family social support moderated the association between loneliness and allostatic load slope. As neighborhood features, loneliness, and physiological dysregulation are each associated with worse cognitive outcomes, findings underscore the protective role of family social support for physiological dysregulation, thereby promoting cognitive resilience.

Defining the Critical Requisites for Accurate Simulation of SARS-CoV-2 Viral Dynamics: Patient Characteristics and Data Collection Protocol.

Mathematical models of viral dynamics are crucial in understanding infection trajectories. However, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load data often includes limited sparse observations with significant heterogeneity. This study aims to: (1) understand the impact of patient characteristics in shaping the temporal viral load trajectory and (2) establish a data collection protocol (DCP) to reliably reconstruct individual viral load trajectories. We collected longitudinal viral load data for SARS-CoV-2 Delta and Omicron variants from 243 patients in Singapore (2021-2022). A viral dynamics model was calibrated using patients' age, symptom presence, and vaccination status. We accessed associations between these patient characteristics and aspects of viral dynamics using linear regression models. We evaluated the accuracy of viral load trajectory estimation under different simulated DCPs by varying patient numbers, test frequencies, and test intervals. Older unvaccinated individuals had a longer viral shedding duration due to lower infection and cell death rates. Higher peak viral loads were found in older, symptomatic, and vaccinated individuals, with earlier peaks in younger vaccinated individuals. Symptom presence and vaccination resulted in a shorter time from infection to diagnosis. To accurately estimate viral dynamics, more frequent tests, longer test intervals, and larger patient samples are required. For 500 patients, a 21-day follow-up with measurements every 3 days and an 8-day follow-up with daily measurements was optimal for the Delta and Omicron variants, respectively. Patient characteristics significantly impacted viral dynamics. Our analytic approach and recommended DCPs can enhance preparedness and response to emerging pathogens beyond SARS-CoV-2.

Predictors and prognostic significance of the volume load trajectory: a longitudinal study in patients on peritoneal dialysis

Volume overload in peritoneal dialysis patients is a common issue that can lead to poor prognosis. We employed a group trajectory model to categorize volume load trajectories and examined the factors associated with each trajectory class to explore the impact of different trajectory groups on clinical prognosis and residual renal function (RRF). This single-center prospective cohort study included 214 patients on maintenance peritoneal dialysis within a tertiary hospital. The ratio of extracellular water to total body water was measured using Bioimpedance analysis. The SAS 9.4 PROC Traj procedure was used to examine the group-based trajectory of the patients. A multivariate logistic regression model was used to calculate the adjusted odds ratios (aOR) of the associated factors to predict the trajectory class of participants. The average age of the included patients was 53.56 (SD: 11.77) years, with a male proportion of 46.7% and a median follow-up time of 6 months. The normal stable group accounted for 35.05% of the total population and maintained a normal and stable level, the moderate stable group accounted for 52.8% of the total population and showed a slightly higher and stable level, and the high fluctuation group accounted for 12.15% of the total population and showed a high and fluctuating level. A multivariate logistic regression analysis revealed that age, diabetes, and albumin levels are significant factors influencing the categorization of volume load trajectories. There were statistically significant differences in both the technical survival rate and the loss of residual renal function among the three trajectory groups.

Sex differences in allostatic load trajectories among midlife and older adults: Evidence from the China health and retirement longitudinal study.

The female advantage in life expectancy sits uneasily with female disadvantage in health and well-being in later life compared to their male counterparts. This health disparity has been suggested to rest on sex difference in allostatic load (AL). We aim to delineate the sex-specific age trajectories of AL among midlife and older adults in China and to interpret the contradiction between the female advantage in life expectancy and their disadvantage in health in later life from the perspective of physiological dysregulation. Using data from the China Health and Retirement Longitudinal Study (CHARLS) conducted in 2011 and 2015, we included 3,836 male and 3,308 female Chinese adults aged 45 and older. Two-level mixed-effects models were fitted to examine how AL changed over time. Missing values were addressed by performing multiple imputations using chained equations. Results show AL increases with age for both sexes, with a steeper rise in females and a slight decline in males after adjusting for the sex-age interaction. Older males born before the People's Republic of China (PRC) exhibited different AL trajectories from younger cohorts. The sex-specific trajectories converge around the late 60s, with females surpassing males, aligning with the life expectancy-health paradox. The presence of a healthier older male cohort in CHARLS suggests future studies should account for cohort effects.

A 50-year data-driven model of disability and lesion load trajectories in progressive multiple sclerosis.

This scientific commentary refers to 'A data-driven model of disability progression in progressive multiple sclerosis', by Garbarino et al. (https://doi.org/10.1093/braincomms/fcae434).

Piecewise Time Polynomials-Based Control Methods for Obstacle Avoidance and Precision Positioning of Tower Crane Systems with Varying Cable Lengths

During the hoisting and lowering operations of a tower crane, dynamic variations in cable lengths significantly influence the oscillation frequency and amplitude of the load. These variations complicate the oscillation characteristics, heightening the challenge of balancing obstacle avoidance with precise positioning. To tackle this issue, we propose a trajectory planning and tracking control method that integrates hoisting control to reduce the impact of varying cable lengths on load swinging and achieve accurate positioning during obstacle navigation. A novel definition of swing angle is introduced to model the crane’s rigid and swinging components separately, enhancing model accuracy while simplifying complexity. A piecewise polynomial constructs the load trajectory in a low-dimensional flat space, which is then mapped to a high-dimensional generalized state space through a homeomorphic transformation, ensuring trajectory smoothness and traceability. A fractional-order sliding mode controller is employed to facilitate rapid and precise tracking of the actuated degrees of freedom, suppressing load oscillation while maintaining positioning accuracy. Experimental validation on a tower crane platform shows that the proposed strategy enables smooth obstacle avoidance and precise target point reaching, even with varying cable lengths.

Autoantibodies to BACE1 promote Aβ accumulation and neurodegeneration in Alzheimer's disease.

The profile of autoantibodies is dysregulated in patients with Alzheimer's disease (AD). Autoantibodies to beta-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) are present in human blood. This study aims to investigate the clinical relevance and pathophysiological roles of autoantibodies to BACE1 in AD. Clinical investigations were conducted in two independent cohorts, the Chongqing cohort, and the Australian Imaging, Biomarkers, and Lifestyle (AIBL) cohort. The Chongqing cohort included 55 AD patients, 28 patients with non-AD dementia, and 70 cognitively normal subjects (CN). The AIBL cohort included 162 Aβ-PET- CN, 169 Aβ-PET+ cognitively normal subjects (preclinical AD), and 31 Aβ-PET+ cognitively impaired subjects (ClinicalAD). Plasma autoantibodies to BACE1 were determined by one-site Elisa. The associations of plasma autoantibodies to BACE1 with brain Aβ load and cognitive trajectory were investigated. The effects of autoantibodies to BACE1 on AD-type pathologies and underlying mechanisms were investigated in APP/PS1 mice and SH/APPswe/PS1wt cell lines. In the Chongqing cohort, plasma autoantibodies to BACE1 were higher in AD patients, in comparison with CN and non-AD dementia patients. In the AIBL cohort, plasma autoantibodies to BACE1 were highest in clinical AD patients, followed by preclinical AD and CN subjects. Higher autoantibodies to BACE1 were associated with an increased incidence of brain amyloid positivity conversion during follow-up. Autoantibodies to BACE1 exacerbated brain amyloid deposition and subsequent AD-type pathologies, including Tau hyperphosphorylation, neuroinflammation, and neurodegeneration in APP/PS1 mice. Autoantibodies to BACE1 increased Aβ production by promoting BACE1 expression through inhibiting PPARγ signaling. These findings suggest that autoantibodies to BACE1 are pathogenic in AD and the upregulation of these autoantibodies may promote the development of the disease. This study offers new insights into the mechanism of AD from an autoimmune perspective.

Acute-phase innate immune responses in SIVmac239-infected Mamu-B*08+ Indian rhesus macaques may contribute to the establishment of elite control.

Spontaneous control of chronic-phase HIV/SIV viremia is often associated with the expression of specific MHC class I allotypes. HIV/SIV-specific CD8+ cytotoxic T lymphocytes (CTLs) restricted by these MHC class I allotypes appear to be critical for viremic control. Establishment of the elite controller (EC) phenotype is predictable in SIVmac239-infected Indian rhesus macaques (RMs), with approximately 50% of Mamu-B*08+ RMs and 20% of Mamu-B*17+ RMs becoming ECs. Despite extensive characterization of EC-associated CTLs in HIV/SIV-infected individuals, the precise mechanistic basis of elite control remains unknown. Because EC and non-EC viral load trajectories begin diverging by day 14 post-infection, we hypothesized that hyperacute innate immune responses may contribute to viremic control. To gain insight into the immunological factors involved in the determination of EC status, we vaccinated 16 Mamu-B*08+ RMs with Vif and Nef to elicit EC-associated CTLs, then subjected these 16 vaccinees and an additional 16 unvaccinated Mamu-B*08+ controls to repeated intrarectal SIVmac239 challenges. We then performed whole-blood transcriptomic analysis of all 32 SIVmac239-infected Mamu-B*08+ RMs and eight SIVmac239-infected Mamu-B*08 - RMs during the first 14 days of infection. Vaccination did not provide protection against acquisition, but peak and setpoint viremia were significantly lower in vaccinees relative to controls. We did not identify any meaningful correlations between vaccine-induced CTL parameters and SIVmac239 acquisition rate or chronic-phase viral loads. Ultimately, 13 of 16 vaccinees (81%) and 7 of 16 controls (44%) became ECs (viremia ≤ 10,000 vRNA copies/mL plasma for ≥ 4 weeks). We identified subsets of immunomodulatory genes differentially expressed (DE) between RM groupings based on vaccination status, EC status, and MHC class I genotype. These DE genes function in multiple innate immune processes, including the complement system, cytokine/chemokine signaling, pattern recognition receptors, and interferon-mediated responses. A striking difference in the kinetics of differential gene expression among our RM groups suggests that Mamu-B*08-associated elite control is characterized by a robust, rapid innate immune response that quickly resolves. These findings indicate that, despite the association between MHC class I genotype and elite control, innate immune factors in hyperacute SIV infection preceding CTL response development may facilitate the establishment of the EC phenotype.

Modelling multiplex testing for outbreak control

During the SARS-CoV-2 pandemic, polymerase chain reaction (PCR) and lateral flow device (LFD) tests were frequently deployed to detect the presence of SARS-CoV-2. Many of these tests were singleplex, and only tested for the presence of a single pathogen. Multiplex tests can test for the presence of several pathogens using only a single swab, which can allow for: surveillance of more pathogens, targeting of antiviral interventions, a reduced burden of testing, and lower costs. Test sensitivity however, particularly in LFD tests, is highly conditional on the viral concentration dynamics of individuals. To inform the use of multiplex testing in outbreak detection it is therefore necessary to investigate the interactions between outbreak detection strategies and the differing viral concentration trajectories of key pathogens. Viral concentration trajectories are estimated for SARS-CoV-2, and Influenza A/B. Testing strategies for the first five symptomatic cases in an outbreak are then simulated and used to evaluate key performance indicators. Strategies that use a combination of multiplex LFD and PCR tests achieve; high levels of detection, detect outbreaks rapidly, and have the lowest burden of testing across multiple pathogens. Influenza B was estimated to have lower rates of detection due to its modelled viral concentration dynamics. Data availability statementThe SARS-CoV-2 viral load trajectory data may be accessed by contacting Killingley et. al. The influenza A/B viral load trajectory may be accessed at https://github.com/bcowling/pediatric-vaccine-trial/tree/master/data.

Clutaxis: an information-driven source search method balancing exploration and exploitation in turbulent environments

Locating unknown emission sources in turbulent environments is a challenging yet crucial task, particularly in emergency response scenarios. Existing studies have developed information-theoretic approaches to fuse intermittent information collected by mobile sensors regarding the sources. This fused information is then used to support source-term estimation (STE) in various search algorithms. Among these, the cognitive strategy—a promising information-driven search algorithm—leverages a reward-based action selection mechanism to balance exploration and exploitation during each search step. However, this mechanism is hampered by a high computational load and rigid search trajectories, limiting its application in real-world systems. To address these issues, this paper proposes a novel information-driven search method called Clutaxis, based on a global exploration and exploitation tradeoff principle. Specifically, a particle filter is leveraged to maintain the STE. After projecting the particle filter samples onto a 2D search scene, the density-based spatial clustering of applications with noise (DBSCAN) algorithm is used to extract the density information of the samples, which is then used to construct a belief source area (BSA). By leveraging the uncertainty of the BSA, Clutaxis adopts explorative or exploitative actions with no restrictions on motion direction. Through dedicated simulations, the experimental results demonstrate the robustness of Clutaxis to key parameters and its advantages in computational complexity and search performance compared to two state-of-the-art algorithms (Infotaxis and Entrotaxis) and two Clutaxis variants (Clutaxis_ER and Clutaxis_EI).

Brief Report: Group-Based Trajectory Modeling to Determine Long-Term HIV Viral Load Trends Among Children With HIV in Kenya.

Identifying determinants of longitudinal HIV viral load (VL) trajectories using group-based trajectory modeling (GBTM) can inform clinical strategies and mechanisms of nonadherence among children. Children under 12 months old who were newly diagnosed with HIV were enrolled in the Optimizing Pediatric HIV therapy cohort (NCT00428116) from 2007 to 2010. Children initiated antiretroviral therapy at enrollment, and VL was assessed every 3 months for 24 months post-antiretroviral therapy and every 6 months thereafter up to 8 years old. VL trajectory groups were defined using GBTM. Fisher's exact and Kruskal-Wallis tests were used to determine the correlates of each trajectory group compared with the sustained-low VL group. Five VL trajectory groups were identified among 89 children with 522 VL visits from 6 to 24 months: sustained-low (63% of children), sustained-very-high (16%), sustained-high (9%), low-to-high (7%), and high-with-periods-of-low (6%). Children in the sustained-high group were more frequently on a first-line protease inhibitor (PI)-based regimen (63% vs 38%; P = 0.03) and had younger caregivers (median: 22 vs 28 years; P = 0.02). Among 54 children with 560 VL visits followed from 48 to 96 months, 5 trajectory groups were identified: sustained-low (74%), mid-range (4%), periods-of-low (7%), high-to-low (7%), and sustained-high (7%). Those in the high-to-low group had younger caregivers (21 vs 29 years; P = 0.01). GBTM identified unique VL patterns among children with unsuppressed VL. Caregiver and regimen-related characteristics were associated with patterns of nonsuppression. Younger caregivers may benefit from tailored counseling to help them support child antiretroviral therapy adherence. Palatable regimens are necessary for viral suppression among children with HIV.

Pulmonary herpes simplex virus and cytomegalovirus in patients with acute respiratory distress syndrome related to COVID-19

PurposeHuman herpesviruses, particularly cytomegalovirus (CMV) and herpes simplex virus (HSV), frequently reactivate in critically ill patients, including those with acute respiratory distress syndrome (ARDS) related to coronavirus disease 2019 (COVID-19). The clinical interpretation of pulmonary herpesvirus reactivation is challenging and there is ongoing debate about its association with mortality and benefit of antiviral medication. We aimed to quantify the incidence and pathogenicity of pulmonary CMV and HSV reactivations in critically ill COVID-19 patients.MethodsMechanically ventilated COVID-19 patients seropositive for CMV or HSV were included in this observational cohort study. Diagnostic bronchoscopy with bronchoalveolar lavage was performed routinely and analyzed for alveolar viral loads and inflammatory biomarkers. Utilizing joint modeling, we explored the dynamic association between viral load trajectories over time and mortality. We explored alveolar inflammatory biomarker dynamics between reactivated and non-reactivated patients.ResultsPulmonary reactivation (> 104 copies/ml) of CMV occurred in 6% of CMV-seropositive patients (9/156), and pulmonary reactivation of HSV in 37% of HSV-seropositive patients (63/172). HSV viral load dynamics prior to or without antiviral treatment were associated with increased 90-day mortality (hazard ratio [HR] 1.24, 95% confidence interval [CI] 1.04–1.47). The alveolar concentration of several inflammatory biomarkers increased with HSV reactivation, including interleukin (IL)-6, IL-1β, granulocyte colony stimulating factor (G-CSF), and tumor necrosis factor (TNF).ConclusionIn mechanically ventilated COVID-19 patients, HSV reactivations are common, while CMV reactivations were rare. HSV viral load dynamics prior to or without antiviral treatment are associated with mortality. Alveolar inflammation is elevated after HSV reactivation.

Daily spiritual experiences and allostatic load trajectories: a longitudinal study of midlife African American women.

This study aimed to evaluate the association between daily spiritual experiences and allostatic load (AL) trajectories in midlife African American women. A longitudinal analysis of public-use data from 727 African American women in the Study of Women's Health Across the Nation (SWAN) was performed. We included African American women who completed the Daily Spiritual Experiences Scale at SWAN visit 4 (2000-2001) and had AL data at three or more study visits over 7 years. AL was calculated at each visit using 10 biomarkers: systolic and diastolic blood pressure, body mass index, C-reactive protein, high-density lipoprotein cholesterol, total cholesterol, waist-to-hip ratio, fasting serum glucose, triglycerides, and dehydroepiandrosterone. Group-based trajectory modeling identified women with similar patterns of AL. We used multinomial logistic regression to estimate associations between daily spiritual experiences (some days or less, most days, daily, many times a day) and AL trajectories. Our sample had a mean ± SD age of 49.9 ± 2.66 years, 47% were early perimenopausal, and 17% earned <$19,999 annually. The mean ± SD AL score was 2.52 ± 1.68. Three AL trajectories were identified: low (35.1%), moderate (44.7%), and high (20.2%). In age-adjusted models, women who reported daily comfort in religion and spirituality were less likely to follow a high AL trajectory (odds ratio, 0.41; 95% CI, 0.18-0.93); the association was attenuated when controlling for depressive symptoms (odds ratio, 0.48; 95% CI, 0.19-1.21). Findings from this study do not support an independent association between spirituality in African American women and AL trajectories in midlife. Studies with a larger sample and additional measures of spirituality are warranted in this population.

Heavily treatment-experienced persons living with HIV currently in care in Italy: characteristics, risk factors, and therapeutic options—the ICONA Foundation cohort study

ObjectivesHeavily treatment-experienced (HTE) people living with HIV (PLWH) pose unique challenges due to limited antiretroviral treatment (ART) options. Our study aimed to investigate the prevalence and features of HTE individuals followed up in the Italian Cohort Naïve Antiretrovirals (ICONA) cohort as of December 31, 2021. MethodsHTE were defined based on meeting specific conditions concerning their current ART and their ART history up to December 31, 2021. Descriptive statistics were performed by HTE status. Regression analyses explored factors associated with becoming HTE based on pre-ART patients' characteristics. Cluster dendrogram analysis provided insights into subgroups with inadequate responses based on clusters of differentiation (CD4) counts and viral load (VL) trajectories. ResultsAmong the 8758 PLWH actively followed in our cohort, 163 individuals (1.9%), mainly female, younger, Italian, and infected through heterosexual contact, met the HTE criteria. A lower CD4 count at ART initiation (odds ratio [OR] 1.60 per 100 cells/mmc lower CD4, 95% confidence interval [CI] 1.06-2.41, P = 0.03) and hepatitis C virus antibody positivity (OR 1.90, 95% CI 1.16-3.11, P = 0.01) were associated with higher HTE risk. Thirty PLWH exhibited ongoing immune-virological failure (18% of the HTE subgroup and 0.003% of the total population). Thirty PLWH exhibited ongoing immune-virological failure (i.e., with a current CD4 count <200 cells/mmc or VL>200 copies/mL). A cluster analysis identified 13 (43%) with a current CD4 count <200 cells/mmc. Also, notably, 19/30 (63%) had major acquired resistance-associated mutations to at least one antiretroviral drug class. ConclusionsHTE is rare in our cohort and tends to co-exist with major resistance mutations. A focused investigation into treatment history and immuno-virological response is warranted, particularly given the availability of new antiretroviral drugs.

Comparative study on fatigue evaluation of suspenders by introducing actual vehicle trajectory data

Suspenders play a crucial role in transmitting loads from the bridge deck to the main cable in a suspension bridge. They are susceptible to fatigue due to repeated dynamic loads, particularly traffic loads. Traffic Load Models (TLMs), typically created using Monte–Carlo simulation and Weigh-In-Motion (WIM) data, are employed to evaluate this fatigue. However, these models often overlook practical vehicle trajectories and spatio-temporal distribution, which compromises the precision of fatigue assessments. In this study, we introduce a novel 2D Intelligent Driver Model (2D-IDM) that incorporates actual vehicle trajectories, with a particular focus on transverse vehicle movement. This enhancement aims to improve the fidelity of existing TLMs. To provide a clear, qualitative, and quantitative understanding of the effects of fatigue evaluation with or without actual trajectory characteristics, we have structured this paper as a comparative study. We compare our proposed model, denoted as TLM S-3, with two observation-based models (O-1 and O-2) and two simulation-based models (S-1 and S-2). We conducted an experimental case study on a long-span suspension bridge, where the actual traffic load trajectory was obtained using a WIM-Vision integrated system. To calculate fatigue damage considering both longitudinal and transverse directions, we established a multi-scale Finite Element Model (FEM) using solid element types to simulate the bridge girder. This model can generate the stress influence surface of the bridge and has been verified in both static and dynamic aspects. Our detailed comparative analysis demonstrates the consistency of the proposed 2D-IDM with the actual measured traffic load trajectories. This indicates that our approach can enhance the fidelity and precision of fatigue evaluations for bridge suspenders.

Space-time reconstruction of a moving acoustic loading on a membrane by coupling the force analysis technique and full-field non-contact vibration measurements

Identifying acoustical and mechanical loadings on structures is a common problem in acoustics and vibration analysis and stationary loadings are mostly considered on plate-like structures. This work describes a proof of concept for reconstructing the trajectory of an acoustic source moving in front of a membrane. Compared with works focusing on precisely identifying a loading’s amplitude at a given location, the objective is to reconstruct the loading’s trajectory–Qualitative loading identification is sought rather than quantitative. The force analysis technique is used to recover a space-time varying loading on a structure, starting from time-resolved full-field non-contact vibration measurements conducted on a circular membrane. At the same time, a compact and tonal sound source is used to draw freehand shapes in front of the membrane. The loading trajectory, therefore, contains information that was “acoustically written”. Simple hand gestures that correspond to the drawing of a Greek letter (Σ), a capital letter (P), two shapes (♡, ⋆), and a 3-letter word (net) are recovered using the proposed procedure. The effect of various parameters on the reconstructed information is studied. Perspectives in terms of possible research areas and applications are finally discussed. These perspectives include, for example, the use of membranes to help reconstruct complex and space-time-varying loadings or even applications in musical acoustics on membranophones.

The Association Between Allostatic Load and Frailty Trajectories Among Adults Aged 50+ Years: Mediating Role of Physical Activity.

To identify frailty trajectories and examine its association with allostatic load (AL) and mediating effect of physical activity (PA). This study included 8,082 adults from the English Longitudinal Study of Aging over Waves 4-9. AL was calculated by 14 biological indicators, and a 53-item frailty index was used to evaluate frailty. Frailty trajectories were classified by group-based trajectory modeling, and the mediated effect of PA was tested by causal mediation analysis. Four frailty trajectories were identified: "Robustness" (n = 4,437, 54.9%), "Incident prefrailty" (n = 2,061, 25.5%), "Prefrailty to frailty" (n = 1,136, 14.1%), and "Frailty to severe frailty" (n = 448, 5.5%). High baseline AL was associated with increased odds of "Incident prefrailty," "Prefrailty to frailty," and "Frailty to severe frailty" trajectories. PA demonstrated significant mediated effects in aforementioned associations. AL is significantly associated with the onset and progression of frailty, and such associations are partially mediated by PA.

Efficacy of point source legislation quantified for a 64-year river water quality trajectory of phosphorus loading

Changes in river water quality often follow typical trajectories characterized by sequential phases of degradation and recovery induced by management measures, typically achieved with combinations of legislative and technological interventions. However, the key question about the effectiveness of the different types of legal interventions – source control, use-related, and end-of-pipe – remains poorly understood. With the case of phosphorus (P), which is a valuable indicator of surface water quality and a widespread target of legislation at various governance levels in order to control eutrophication of water bodies, we quantified the relation between point source loading of P and resulting river water quality for a multidecadal trajectory of the river Ruhr (Germany). In particular, we analysed P-related legislation targeting point source pollution enforced at EU, national, state, and local level and linked their development with measured total phosphorus (TP) concentrations in the river Ruhr (Germany). To this end, we combined archival data with information in the literature and conducted interviews with contemporary witnesses to describe and quantify the efficacy of each legislative approach. Although not specifically targeted at P reduction, end-of-pipe measures (sewer systems and wastewater treatment plants (WWTP)) reduced TP inputs to surface waters already in the 1960s and 1970s, curbing TP inputs to the Ruhr by 38% in 1980. The first targeted source control legislation – the banning of phosphates in textile detergents in 1981 – effectively reduced TP concentrations in WWTP influents by 36% since 1990. In combination with stronger end-of-pipe legislation focusing on P elimination in WWTP since the 1990s, TP concentrations in WWTP effluents were reduced by 86% at the end of the 1990s and by 92% in 2021. Complete and successful source control for textile detergents made use-related legislation redundant. Our study demonstrates that source control measures should be prioritized, because they are the fastest way to curb emissions. These findings provide insights that can inform efficient decision-making regarding water quality in a trajectory perspective of hierarchical governance and technological needs, as well as effective policy-making and management for other pollutants requiring control from point sources.

Comparison of critical plane models for multiaxial fatigue life prediction

Background. The operation of numerous machines and units takes place under conditions of multi-axial cyclic loading, which, as a rule, is non-proportional. Evaluating the fatigue durability of metal alloys under conditions of multi-axial non-proportional loading is a relevant task in modern engineering. Solving this problem requires fatigue calculation methods that would consider operating conditions and properties of structural materials, including factors such as the type of stress state, loading trajectory, material sensitivity to non-proportional loading, and so on.Objective. To conduct a comparative analysis of a range of fatigue life models based on the concept of the critical plane, including the Fatemi-Socie, Wang-Brown, Smith-Watson-Topper, Liu I, and Liu II approaches, and to identify the limits and peculiarities of their application.Methods. The fatigue lives calculated using the selected models were compared with experimental results obtained for various metal alloys subjected to uniaxial tension-compression, alternating torsion, and proportional and non-proportional multiaxial loading.Results. The applicability limits of fatigue life models based on the critical plane concept were analyzed for different metal alloys under conditions of proportional and non-proportional multiaxial loading.Conclusions. The research results demonstrated that models requiring the use of material constants obtained from tests in both tension-compression and alternating torsion provide reliable fatigue life estimates for various types of metal alloys. Calculations based solely on fatigue curves from alternating torsion better correlate with the results of tests on ductile materials, while calculations based on criteria utilizing fatigue curves from tension-compression align more closely with results from tests on brittle materials.

930. COVID-19 symptom and viral load rebound among individuals reporting nirmatrelvir/ritonavir use compared to propensity score matched individuals not taking COVID-19 treatment

930. COVID-19 symptom and viral load rebound among individuals reporting nirmatrelvir/ritonavir use compared to propensity score matched individuals not taking COVID-19 treatment