Time-varying Effects Research Articles

Industrial designs and firm performance: evidence from publicly traded Canadian companies, 1990–2014

ABSTRACT Industrial designs (IDs) are a specialized type of intellectual property that protects a product's form and presentational features, giving it uniqueness that differentiates it from other products. This paper estimates the effect on firm revenue and profitability of holding IDs. Using a unique data set linking Canadian ID holdings with Canadian publicly traded firms over the years 1990-2014, the authors use two methods to identify a positive association between holding IDs and firm revenue per employee and net income per employee. We contribute to the literature on IDs by introducing controls for patenting, R&D spending, and time-varying sector effects. To determine the marginal effect of each additional ID held, we use a fixed effects regression and find that a 1% increase in the stock of IDs increases revenue per employee by 0.19%. With a nearest-neighbor matching approach, we find a 10% total premium in revenue per employee and a 20% premium in net income per employee among firms holding at least one ID, compared to those with none.

Life years lost by childhood cancer treatment and health related late effects among childhood cancer survivors

BackgroundIdentifying risk factors contributing the most to mortality of childhood cancer survivors is essential to guide harm reduction efforts in childhood cancer treatments, and long-term follow-up of childhood cancer survivors. MethodsWe assessed Life Years Lost from childhood cancer treatments and their health-related late effects among the French Childhood Cancer Survivors Study, a cohort of 7670 5-year childhood cancer survivors. Using a landmark strategy, we also assessed time-varying effects of risk factors, and how the multi-morbidity affects life years lost. ResultsWe found subsequent malignant neoplasm (9.0 years [95 %CI: 4.3–13.7]), severe cardiac disease (8.0 years [95 %CI: 1.2–14.9]), and the use of radiotherapy (6.0 years [95 %CI: 4.7–7.3]) to be the highest contributors to Life Years Lost among childhood cancer survivors. We found no interaction impact on life years lost between health related late effects considered. ConclusionsThose findings suggest that radiotherapy is the root cause of early mortality among childhood cancer survivors. Moreover patients experiencing a subsequent malignant neoplasm or a cardiac disease should be monitored closely after the event, as comorbidity is common and causes premature deaths.

The impact of microplastics on lake communities: A mesocosm study

Plastics are pervasive pollutants that are being produced at an increasing rate to meet consumer demands. After entering the environment, plastics can break down, creating smaller fragments, including secondary microplastics. Microplastic contamination in lakes has been recorded worldwide, and the ingestion of microplastics has been documented in zooplankton, macroinvertebrates, and fish. Microplastic ingestion and exposure can cause varying deleterious effects on these organism groups, but the impact of realistic microplastic concentrations on whole freshwater food webs requires further study. We addressed these knowledge gaps by conducting an 8-week experiment factorially crossing microplastic addition at a concentration of 1.5 particles/L with a fish predator (perch, Perca fluviatilus) presence in 1200-L outdoor mesocosms. Microplastic exposure had time-varying effects on zooplankton abundance, with a lower abundance of zooplankton in plastic treatments at the end of the experiment. Although microplastics had no impact on total macroinvertebrate abundance, there were effects on individual taxa. In the presence of microplastics, the cased caddisfly Triplectides spp. had a significantly lower abundance, which may have led to an increase in the snail Gyraulus spp. in week eight. Across the benthic and pelagic invertebrate communities, there were near-significant compositional differences between control and plastic treatments. These findings indicate that microplastic exposure may negatively impact freshwater invertebrate communities, even at low, field-realistic concentrations representative of the densities currently found in lakes.

Are natural resource volatility curses or blessings for economic performance? Stories of resource-rich regions

This paper analyses the time-varying and non-linear effects of natural resource volatility on economic growth in 10 countries using the smooth transition regression (STR) model and further examines the long-run and short-run relationships using the autoregressive distributed lag (ARDL) cointegration approach. The conclusions exhibit that natural resource rents are linearly and non-linearly associated with economic growth in countries with different levels of economic development, and display long-term cointegration and short-term equilibrium state. This study provides guides for policymakers in considering differences in national development to implement management strategies that combine the long and short term.

Appraising the corrosion inhibitory efficacy and adsorption mechanism of leaf extract of Datura discolor on low-carbon steel in low pH media via gravimetric experiments and AFM analysis

BackgroundThe study investigated the inhibitory action of Datura discolor leaf extract against the corrosion of low-carbon steel in 0.5 M solutions of three acids. The purpose was to ascertain the effect of extract concentration, immersion time and temperature variation on corrosion inhibitory efficiency, and to relate to existing reports which show that organic molecules in most plant extracts inhibit corrosion. Extraction of the leaves was done by maceration using methanol, and solvent was removed by evaporation to dryness. Classical gravimetric (mass loss) experiments were used, and experimental data were fitted to adsorption isotherm models to ascertain the best approximation. Surface examination of the low-carbon steel substrates was carried out using the atomic force microscope.ResultsInhibitory protective efficiency of extract was found to appreciate with increasing Datura discolor leaf extract concentration at a fixed temperature, with values ranging 77.6–88.8%, 91.35–98.08% and 19.64–44.64% in H2SO4, HCl and HNO3 solutions respectively at 27 °C. Elevation of temperature was found to depreciate the inhibitor efficiency at constant inhibitor concentration. Best isotherm model fitting was obtained with Langmuir model both at 27 °C and 60 °C and in all the hostile media, while Temkin model gave good approximation only at 60 °C and in H2SO4 and HCl solutions only. The negative values of free energy of adsorption (ΔGads0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\Delta G_{{{\ ext{ads}}}}^{0} )$$\\end{document} suggested that the adsorptive interaction of the inhibitor with the substrate surface was very spontaneous. Values of ΔGads0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta G_{{{\ ext{ads}}}}^{0}$$\\end{document} were all consistent, fluctuating between − 16.35 and − 17.63 kJ mol−1 in both H2SO4 and HCl solutions, and between − 9.76 and − 10.25 kJ mol−1 in HNO3 solution, and this suggests that adsorption of the inhibitor molecules occurred via physisorption. Values of the activation energy of the corrosion reaction (Eact)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(E_{{{\ ext{act}}}} )$$\\end{document} are all < 40 kJ mol−1, suggesting that the inhibition occurred by a physical adsorption mechanism.ConclusionsThe study concludes that Datura discolor crude leaf extract suppressed the corrosion reactions, and the inhibition was found to arise from the physisorptive interaction of the organic molecules with the substrate/solution interface, forming a stabilize inhibitor film on the substrate surface as revealed by the atomic force micrographs.

Time-varying effects of the oil prices to the stock returns in Turkiye

Time-varying effects of the oil prices to the stock returns in Turkiye

Trends in the association between alcohol use and generalized anxiety in Finnish adolescents

Abstract Background During the past two decades, alcohol use has decreased among adolescents, but on the contrary, anxiety symptoms have increased (at least among females). These diverging trends set interesting opportunities to examine whether the strength of the well-known correlation/co-occurrence between alcohol use and anxiety has also changed. This study aims to examine changes in the co-occurrence and associations between heavy episodic drinking (HED) and generalized anxiety among adolescents in Finland from 2013 to 2023. Methods Data from the Finnish School Health Promotion Study between 2013-2023 covered 874 110 participants aged 13-20. Generalized anxiety was measured using Generalized Anxiety Disorder Scale (GAD-7) (range 0-21), and heavy episodic drinking was measured as reported heavy drunkenness once a month or more often versus less than once a month. Yearly prevalence estimates of co-occurrence were analyzed for those with moderate to severe anxiety symptoms (&amp;gt;10) and monthly or more frequent HED. Associations between anxiety and HED were analyzed using logistic regression and time-varying effect modelling. Interactions between time and anxiety predicting HED were also considered. Results The moderate to severe anxiety symptoms increased from 10.7% to 20.9% and HED decreased from 18.0% to 11.8% between 2013 and 2023. The proportion of those with both HED and moderate to severe anxiety increased from 2.9% in 2013 to 3.6% in 2023. The association between anxiety symptoms and HED was stable during the study period, with odds ratios ranging between 1.06 and 1.07. Conclusions During the past decade, diverging trends in generalized anxiety symptoms and heavy episodic drinking have not changed the association between them. The proportion of adolescents with these co-occurring health concerns has increased in females. This calls for continuous efforts to strengthen the integration of mental health and substance use prevention and services. Key messages • The association between generalized anxiety and heavy episodic drinking has not changed in adolescents in Finland between 2013 and 2023. • The proportion of those with both moderate to severe anxiety symptoms and heavy episodic drinking has increased in females and remained stable in males during the past decade (2.9% - 3.6%).

Time-Varying Spillover Effects Between Clean and Traditional Energy Under Multiple Uncertainty Risk: Evidence from the U.S. Market

The global energy landscape is undergoing an unprecedented transformation with the rapid development of clean energy and the continued significance of traditional energy creating a complex dynamic relationship. This study employs the TVP-QVAR-DY model to systematically examine the dynamic spillover effects between clean and traditional energy markets in the United States, focusing on the impacts of economic policy uncertainty (EPU) and geopolitical risk (GPR). The findings reveal (1) significant time-varying spillover effects between the two markets, with total spillover effects ranging from 30% to 50%, intensifying during extreme events; (2) increases in EPU and GPR exacerbate uncertainty in energy markets, particularly in the traditional energy sector, with spillover effects from crude oil to natural gas reaching 23.60% and vice versa at 24.30%; and (3) in the short term, the clean energy market is influenced by traditional energy, with spillover effects from oil to clean energy at 5.10%, while in the medium to long term it gradually becomes independent and inversely affects the traditional energy market, contributing 2.94% to oil spillovers. The results indicate that as the global energy transition deepens, the clean energy market is shifting from a risk receiver to a risk contributor. Based on these findings, the study proposes policy recommendations including accelerating energy structure transition, managing macroeconomic uncertainty risks, coordinating domestic and international energy markets, and leveraging market mechanisms.

Effect of Mixing Time Variation and Framing Time on the Quality of Coffee Grounds-based Solid Soap

The increase in public consumption of coffee has resulted in an increase in wasted coffee grounds. Coffee grounds have good content for the skin, so they can be reused as a basic ingredient in soap-making. In the soap making process, the mixing and framing stages can affect the quality of the soap. This study aims to determine the effect of mixing time of 24.5 minutes, 25 minutes, and 25.5 minutes as well as framing time of 3 days, 5 days, and 7 days on the physical and chemical quality of solid soap made from coffee grounds. The physical quality parameters observed are colour, texture, cracking, and foam power. The chemical quality parameters are foam stability, pH, moisture content, and free alkali. The method used was the questionnaire method followed by statistical analysis using the Kruskal Wallis test for physical quality tests and the experimental method followed by statistical analysis using the Two-Way ANOVA test for chemical quality tests. The results showed that all variations in mixing time and framing time had an effect on the physical and chemical quality of solid soap and there were significant differences. The panellists assessed the physical quality of the soap to be attractive, hard, with no cracks, and foamy, while the results of the chemical quality test, the soap produced is safe to use by the quality standards of solid soap with a foam stability range of 82%-97%, pH 10.3-11.8, moisture content 6%-14%, and alkali free 0.03%-0.09%.

On the Effects of Physical Climate Risks on the Chinese Energy Sector

We examine the impact of physical climate risks on energy markets in China, distinguishing between traditional energy and new energy stock markets, and the energy commodity market, utilizing a time-varying parameter vector autoregressive model with stochastic volatility (TVP-SV-VAR). Specifically, we investigate the dynamic effects of five specific subtypes of physical climate risks, namely waterlogging by rain, drought, typhoon, cryogenic freezing, and high temperature, on WTI oil prices and coal prices. The findings reveal that these physical climate risks exhibit time-varying similar effects on the returns of traditional energy and new energy stocks, but heterogeneous effects on the returns of WTI oil prices and coal prices. Finally, we categorize and examine the impact of both acute and chronic physical risks on the energy commodity market.

Estimating Time-Varying Exposure Effects Through Continuous-Time Modelling in Mendelian Randomization.

Mendelian randomization is an instrumental variable method that utilizes genetic information to investigate the causal effect of a modifiable exposure on an outcome. In most cases, the exposure changes over time. Understanding the time-varying causal effect of the exposure can yield detailed insights into mechanistic effects and the potential impact of public health interventions. Recently, a growing number of Mendelian randomization studies have attempted to explore time-varying causal effects. However, the proposed approaches oversimplify temporal information and rely on overly restrictive structural assumptions, limiting their reliability in addressing time-varying causal problems. This article considers a novel approach to estimate time-varying effects through continuous-time modelling by combining functional principal component analysis and weak-instrument-robust techniques. Our method effectively utilizes available data without making strong structural assumptions and can be applied in general settings where the exposure measurements occur at different timepoints for different individuals. We demonstrate through simulations that our proposed method performs well in estimating time-varying effects and provides reliable inference when the time-varying effect form is correctly specified. The method could theoretically be used to estimate arbitrarily complex time-varying effects. However, there is a trade-off between model complexity and instrument strength. Estimating complex time-varying effects requires instruments that are unrealistically strong. We illustrate the application of this method in a case study examining the time-varying effects of systolic blood pressure on urea levels.

Life-cycle seismic performance of bridges with thin-walled steel piers under bi-directional excitations

In corrosive environments, steel bridges demonstrate time-dependent seismic performance and varied directional responses to bi-directional excitation at different life-cycle stages. However, current seismic assessment methods for bridges have not adequately addressed the time-dependent effects of bi-directional excitation directionality on seismic responses throughout their entire life cycle. Thus, this study aims to investigate the time-varying directional effects of bi-directional seismic excitations on steel bridges with multiple parameters and to propose a method for predicting the range of critical incident angles while considering the aging effects of bridges. Initially, time-dependent functions that characterize steel corrosion are integrated into multiscale finite element models of the steel bridges to simulate corrosion progression across their life-cycle stages. Subsequently, a quantitative analysis of the bi-directional seismic response of steel bridges is conducted throughout their life cycle, accounting for the directionality of seismic excitation. Finally, a method and process for predicting the range of time-varying bi-directional critical incident angles with 95 % probability are derived by fitting the statistical probability distribution boundary values of the critical incident angle deviation index. The study's findings indicate that the aging effects of steel bridges amplify the displacement response under bi-directional seismic excitation, with the maximum displacement response difference exceeds 40 %. The service time may increase the sensitivity of steel bridges to changes in incident angles, potentially amplifying the displacement response by a factor of 1.69. The study's findings highlight the importance of considering aging effects and bi-directional excitation directionality in bridge seismic assessments.

Spatiotemporal multilevel joint modeling of longitudinal and survival outcomes in end-stage kidney disease.

Individuals with end-stage kidney disease (ESKD) on dialysis experience high mortality and excessive burden of hospitalizations over time relative to comparable Medicare patient cohorts without kidney failure. A key interest in this population is to understand the time-dynamic effects of multilevel risk factors that contribute to the correlated outcomes of longitudinal hospitalization and mortality. For this we utilize multilevel data from the United States Renal Data System (USRDS), a national database that includes nearly all patients with ESKD, where repeated measurements/hospitalizations over time are nested in patients and patients are nested within (health service) regions across the contiguous U.S. We develop a novel spatiotemporal multilevel joint model (STM-JM) that accounts for the aforementioned hierarchical structure of the data while considering the spatiotemporal variations in both outcomes across regions. The proposed STM-JM includes time-varying effects of multilevel (patient- and region-level) risk factors on hospitalization trajectories and mortality and incorporates spatial correlations across the spatial regions via a multivariate conditional autoregressive correlation structure. Efficient estimation and inference are performed via a Bayesian framework, where multilevel varying coefficient functions are targeted via thin-plate splines. The finite sample performance of the proposed method is assessed through simulation studies. An application of the proposed method to the USRDS data highlights significant time-varying effects of patient- and region-level risk factors on hospitalization and mortality and identifies specific time periods on dialysis and spatial locations across the U.S. with elevated hospitalization and mortality risks.

Evaluation on Preparation and Performance of a Low-Carbon Alkali-Activated Recycled Concrete under Different Cementitious Material Systems.

A green, low-carbon concrete is a top way to recycle waste in construction. This study uses industrial solid waste slag powder (S95) and fly ash (FA) as binders to completely replace cement. This study used recycled coarse aggregate (RCA) instead of natural coarse aggregate (NCA). This is to prepare alkali-activated recycled concrete (AARC) with different cementitious material systems. Alkali-activated concrete (AAC) mixtures are modified for strength and performance based on the mechanical qualities and durability of AARC. Also, the time-varying effects of the environment on AARC properties are explored. The results show that with the performance enhancement of RCA, the mechanical performance of AARC is significantly improved. As RCA's quality improves, so does AARC's compressive strength. At a cementitious material content of 550 kg/m3, AARC's 28d compressive strengths using I-, II-, and III-class RCA were reduced by 2.2%, 12.7%, and 21.8%, respectively. I-class AARC has characteristics similar to natural aggregate concrete (NAC) in terms of shrinkage, resistance to chloride penetration, carbonization, and frost resistance. AARC is a new type of green building material that uses industrial solid waste to prepare alkali-activated cementitious materials. It can effectively reduce the amount of cement and alleviate energy consumption. This is conducive to the reuse of resources, environmental protection, and sustainable development.

Innovative strategies for time-release PCE design and cement paste flowability control

Extending the retention time of cement paste flowability with the addition of admixtures containing slow-release components is standard practice for ensuring the continued building quality of cement-based materials. This study aims to control the release rate of PCE and enhance its time-varying dispersion effect in fresh cement paste by utilizing Time-dependent Release PCEs (TRPCEs) with varying side-chain structures. The structural characterization of the synthesized TRPCEs was investigated using GPC (Gel Permeation Chromatography), FTIR (Fourier Transform Infrared Spectroscopy), and 1H NMR (Proton Nuclear Magnetic Resonance) techniques. Furthermore, experiments were carried out on time-varying flowability with different dosages of TRPCEs to investigate the flowability changes under the time-varying release effect. The influence of TRPCEs on cement hydration was examined using isothermal calorimetry by measuring the early hydration heat of cement paste. The time-dependent adsorption behaviors of TRPCEs were also examined using a TOC (Total Organic Carbon) analyzer. The findings show that TRPCEs have a minor effect on the cement hydration process's rapid reaction period but little effect on its induction and acceleration periods because of variations in the initial dispersion effect. Additionally, the adsorption behaviors of TRPCEs on cement particles vary significantly due to the hydrolysis of slow-release groups. The varying adsorption and consumption of TRPCEs on cement particles and hydration products in different hydration phases are key controlling factors for the time-varying flowability changes in cement paste. Finally, this innovative approach offers a novel perspective for designing and preparing new types of PCEs with a strong capability for time-varying flowability retention.

Enhanced material removal modeling in cylindrical bonnet tool polishing: Incorporating time-dependent pad wear effects

To enhance the accuracy and stability of the material removal model for cylindrical bonnet tool polishing (CBTP), this study introduces a model incorporating the time-varying wear effect of the polishing pad. Initially, the functional principles of the CBTP method are systematically outlined. An advanced material removal model is then proposed, which accounts for the impact of pad wear on pressure and velocity distributions within the contact area. Experimental methods were employed to explore how pad wear affects the pad surface morphology, polishing quality, and material removal rates. Findings reveal that pad wear considerably influences both the depth of material removal and the quality of the polished surface. Validation experiments demonstrate that the enhanced model is accurate and stable. Including the time-varying factor, the discrepancy between the predicted and experimental values of the polishing spot size was 9.29 %, while the accuracy of the predicted material removal depth reached 90.74 %. Additionally, the removal profiles generated by the improved model closely matched those observed experimentally.

Econometric approaches to examine the onset and duration of temporal variations in pedestrian and bicyclist injury severity analysis

There is considerable evidence in existing safety literature that the exogenous variable effects are likely to be time-varying in the injury severity analysis. The majority of these earlier studies tested time-varying effects of exogenous variables by crash year. However, there might be variability in the variable effects within a year, while the same effect might carry over in some or all parts of the preceding years. Towards that end, in this study, we propose a flexible framework to identify when the time-varying effect is likely to occur (the onset of temporal variation) and how long such time-varying effect lasts (duration of temporal variation) in the model estimates. In the study design, we assume that the onset of temporal variation can be any quarter of a year under consideration, while the time-varying effect can continue over different quarters after the onset of temporal variation in a variable effect. The injury severity model is estimated by using Correlated Random Parameter Generalized Ordered Logit formulation with piecewise linear functions. The empirical analysis is demonstrated by employing active traveler (pedestrian and bicyclist) crash data from Queensland, Australia for the years 2015 through 2020. The estimation results are further augmented by computing elasticity effects. The results indicate that the time-varying effects are likely to be different across years for several variables, while for other variables, the onset of time-varying effects could be different than the start of a year. Such flexibility in model specification is likely to have significant implications for devising and implementing effective countermeasures since it allows us to understand how road traffic injuries are evolving over time and when a new road safety issue might be arising.

Time-Varying effects of extreme weather shocks on output growth of the United States

This study investigates the impact of a structural shock to a metric of extreme weather, identified using sign restrictions, on output growth (and inflation) in the United States (US) from 1961 to 2022, using a new class of time-varying parameter vector autoregressive (endogenous TVP-VAR) model, whereby the identified structural innovation is allowed to influence the dynamics of the coefficients in the model unlike in traditional TVP-VARs. Our results provided evidence that severe weather shocks adversely affect output growth (and inflation) over the forecast horizon of one- to twelve-quarter-ahead. More importantly, we find that the effect of extreme weather on the US macroeconomic variables is indeed time-varying, with the impacts becoming smaller in recent times, possibly due to improved adaptation to climate change.

Time-Varying Effects of Nurse and Family-Assisted Peritoneal Dialysis.

Time-Varying Effects of Nurse and Family-Assisted Peritoneal Dialysis.

A reassessment of graduation modeling for policy design

A vast and diverse literature estimates graduation chances using logistic models set in an arbitrary timeframe, where a graduation indicator is checked at a conventional point in time and associated with covariates measured at some date. Survival models emerged over time as a robust alternative, for being able to estimate time-to-degree and time-varying effects of predictors. This paper reconsiders the effectiveness of both modeling approaches in addressing policy-relevant questions, particularly in light of the increasingly automated and algorithm-based educational policies. We find that both methods exhibit blind spots and limitations, but that adopting a simple pragmatic approach logistic models can achieve a comparable level of effectiveness at depicting graduation dynamics while also being capable of answering questions that are problematic for survival models. We exploit a unique dataset and the nature of discrete-time survival models as combinations of logistic regressions run at different times to illustrate how arbitrary timeframes impact the estimates of a logistic model of graduation. Conversely, we illustrate how separately running and analyzing all the distinct logistic regressions provides insights that are unlikely to come from a survival model.