Search Results (483)

The non-repeatability of the internal combustion engine’s cycle-by-cycle (CCN-R) operation directly affects pollutant emissions, fuel consumption, and energy efficiency. Reducing this non-repeatability is an important part of efforts to improve the environmental performance of power units. Cycle variability analysis allows the identification of engine operating areas that promote unstable combustion and increased emissions of harmful exhaust components. The aim of the study was to quantitatively assess the cycle-to-cycle non-repeatability COV of selected operating parameters of the Perkins 1104D-E44TA diesel engine. The analyses covered the maximum cylinder pressure (p_max), the mean indicated pressure (IMEP), and the crankshaft rotation angle corresponding to the occurrence of maximum pressure (α). The measurements were carried out on an engine dynamometer at 25 operating points, covering speeds 1000–2200 r./min and load torques 200–400 N × m, recording 500 consecutive operating cycles at each point. The results showed that the most stable engine operation occurred at medium rotational speeds and moderate loads, where COV_pmax values did not exceed 0.5% and COV_IMEP values were lower than 1.0%. Increased pmax non-repeatability (up to 2.10%) and very high α angle variability (up to 100–140%) were observed at high rotational speeds and high loads. Only in the case of COV_IMEP was a significant reduction in repeatability observed compared to idling. The results obtained from cycle-by-cycle non-repeatability analyses can ultimately, after being supplemented with exhaust gas composition testing, be used as tools to support engine control optimization in order to reduce pollutant emissions and improve combustion efficiency. Full article

Background: Transmissible gastroenteritis virus (TGEV), a coronavirus (CoV) infecting pigs, uses its spike (S) glycoprotein to bind porcine aminopeptidase N (pAPN) for cell entry. Although structural studies have identified receptor-binding motifs (RBMs) within the receptor-binding domain (RBD) of the S protein, the functional relevance of individual residues for TGEV receptor recognition, cell entry, and infection remain unclear. Methods: In this study, we performed structure-guided mutagenesis of the TGEV RBD to evaluate the contribution of specific residues to receptor binding and viral infectivity. Results: Using soluble RBD proteins, we found that most of the RBD residues within the pAPN-binding interface contribute to the binding interaction. Nonetheless, TGEV reverse genetics experiments revealed that just three RBD residues (Gly527, Tyr528, and Trp571) were indispensable for viral cell entry. Mutations at these positions, which are conserved among group 1 alpha-CoVs abolished infectivity, highlighting their central role in the virus–receptor interface. Conclusions: Our findings provide a detailed functional map of the TGEV RBD and offer insights into the evolution of receptor recognition across CoV. Full article

The rapid evolution of coronaviruses (CoVs) requires researchers to develop specific yet broad-spectrum detection methods to monitor their constant genomic changes. The goal of the present study was to establish a current pan-coronavirus RT-PCR system capable of detecting a wide variety of CoVs and useful for the investigation of virus diversity and host spectrum. For optimization, one-step and two-step nested RT-PCRs with three RT enzymes were examined, amplifying a ~600 bp long product of the RNA-dependent RNA polymerase. As templates, the in vitro transcribed RNA of ten pathogenic CoVs (SARS-CoV, SARS-CoV-2, NL-63, OC43, feline CoV, porcine epidemic diarrhea virus or PEDV, transmissible gastroenteritis virus or TGEV, canine CoV, bat CoV, and infectious bronchitis virus) were applied instead of the often-used DNA standards. A limit of detection of 5–50 copies/reaction was achieved with a random hexamer-primed two-step RT-PCR and a touchdown cycling profile, representing a lower detection limit and higher specificity compared to previously published primer sets. Swine origin pooled samples (n = 121), collected from apparently healthy herds in Hungary, were tested with the novel RT-PCR system. Sequences of porcine respiratory CoV/TGEV and porcine hemagglutinating encephalomyelitis virus were identified in 24 oral fluid and nasal swab pools, demonstrating the circulation of these viruses in this country, as well as the suitability of the new PCR for their detection. The results highlighted the importance of adequate RT enzyme selection and the use of RNase inhibitors in sample preparation and conservation. Full article

This study presents a machine learning framework for predicting the axial compressive strength of circular concrete-filled steel tube (CFST) columns subjected to concentric and eccentrically applied axial loads. A harmonized database of 1287 test specimens was compiled, encompassing diverse material strengths, geometric configurations, and eccentricity levels. Among the trained models, the CatBoost (CatB) algorithm exhibited the highest predictive performance. A 300-run Monte Carlo simulation yielded a mean R² of 0.966 (Min: 0.804; Max: 0.996), with a mean RMSE of 588.8 kN and MAPE of 8.36%, demonstrating accuracy and robustness across repeated randomized splits. Comparative benchmarking against current design equations revealed that CatBoost substantially reduced prediction scatter, improving the mean ratio and reducing the COV from 70–75% (ACI/AIJ/Wang) to 5.43%, while maintaining a nearly unbiased mean prediction ratio of 1.00. In addition, inverse prediction models based on CatBoost achieved test-set R² values of 0.908 for compressive strength and 0.945, 0.900, and 0.816 for key design parameters (D, t, L), indicating promising capability for supporting preliminary sizing and parameter selection. The outcomes of this study highlight the potential of data-driven modelling to complement existing design provisions and assist engineers in early-stage decision-making for axially loaded circular CFST columns. Full article

Background/Objectives: To estimate (a) survival after SARS-CoV-2 infection by COVID-19 vaccination status, and (b) COVID-19 vaccine effectiveness in a middle-income country. Methods: In this retrospective cohort study, secondary analysis of data from the national surveillance and vaccination databases was conducted. The primary outcome was COVID-19 death classified based on the WHO criteria. Data were analysed by vaccination status, age, sex, geographic region, and wave period. Kaplan–Meier curves were plotted; log-rank followed by multiple comparison tests were used to compare survival probabilities. Cox proportional-hazards models with time-varying covariates estimated hazard ratios (HR). Vaccine effectiveness was computed as (1-HR) × 100. Results: A total of 55,299 COVID-19 cases were captured by the national surveillance system between 1 April and 31 December 2021. Of these, 45,774 (1581 vaccinated, 44,193 unvaccinated) were included in the analysis. After a follow-up of 327 days, there were 22 deaths (case fatality rate (CFR) 1.5%) among 1581 COVID-19 vaccinated cases and 1821 deaths (CFR 4.1%) among 44,193 unvaccinated cases. There was one COVID-19 death per 10,000 person days in vaccinated cases compared with 2.7 COVID-19 deaths per 10,000 person days in unvaccinated cases. After adjustment for age, sex, and geographic region, the effectiveness against COVID-19 death across all vaccine types (ChAdOx1 nCoV-19, BNT162b2, Ad26.COV2.S, or BBIBP-CorV) was 68% (95% CI: 51–79). Effectiveness was 75% (95% CI: 59–84) for ChAdOx1 nCoV-19. Vaccine effectiveness across all vaccine types was higher in younger cases, (82% (95% CI: 52–93), 18–64 years vs. 63% (95% CI: 41–77), ≥65 years), females (84% (95% CI: 63–93), females vs. 53% (95% CI: 24–71), males) and those vaccinated in the past 3 months (71% (95% CI: 47–85), past 0–3 months vs. 56% (95% CI: 23–75), 3–6 months). Conclusions: COVID-19 vaccines were effective in preventing COVID-19 death in a population with low vaccination coverage. Limitations of the analysis include the use of surveillance data (under-reporting of cases, missing data), exclusion of partially vaccinated cases, and insufficient data on important confounders (circulating variants and comorbidities). Full article

Background/Objectives: COVID-19 and long COVID remain prevalent, with household transmission being an important mode of spread. To quantify household transmission of subclinical SARS-COV-2 infection and identify sociodemographic risk factors that may explain disparities in transmission, we conducted a case-ascertained antibody surveillance study of households in Cincinnati, Ohio. Methods: A partnership was formed between the Cincinnati Health Department and Cincinnati Children’s Hospital Medical Center. The Health Department identified cases of COVID-19. Infected individuals, along with their household contacts (n = 245), completed multiple questionnaires about symptoms, demographics, psychosocial (Adverse Childhood Experiences Scale and Everyday Discrimination Scale) and social risk factors, and conditions before and during the pandemic. In addition, they completed a non-fasting blood draw for IgG, IgM, IgA, and nucleocapsid protein serology testing. Results: Household contacts experienced few symptoms of COVID-19. However, according to the presence of the nucleocapsid protein, nearly 50% contracted the SARS-CoV-2 virus. This rate was similar by vaccination status but it was higher for household contacts who experienced high levels of early life adversity compared with those with lower levels. Conclusions: Our results confirm the high transmission of subclinical disease among household contacts, which may vary due to psychosocial factors. This reinforces the importance of isolating cases to prevent transmission, regardless of vaccination status. Full article

There is a subgroup of people infected with the SARS-CoV-2 virus who manifest lingering sequelae (LongC), with neurological symptoms (nLongC). We recruited 86 COVID-19 volunteers, 35 of whom were fully recovered (Cov) and 51 who had neurological symptoms (nLongC) 4–53 months after infection and compared them to 51 healthy pre-pandemic controls (HC). Thirty-five percent of nLongC individuals carried the apolipoprotein E4 (APOE4) gene, compared to 11% of Cov. Four plasma proteins, interleukin 1 beta (IL-1β), interleukin 8 (IL-8), glial fibrillary acidic protein (GFAP), and hemopexin, continued to be elevated in both Cov and nLongC compared to HC. Soluble CD14 was elevated in nLongC but not Cov. As a group, IL-1β decreased over time in Cov but not nLongC. Two of the elevated proteins, IL-8 and GFAP, correlated with age, with both Cov and nLongC showing higher levels than HC. Using a combination of four plasma proteins, along with age, body mass index, and APOE4 presence, we were able to achieve an area under the curve (AUC) of 0.81. These results suggest that SARS-CoV-2 infection causes a low-grade inflammatory process that, even months or years after infection, does not return to pre-COVID-19 levels, which may contribute to neurologic sequelae and accelerated aging. Full article

Ischemic heart disease (IHD) is the leading cause of death worldwide. Although 90% of the intramyocardial blood volume resides in the microvasculature, clinical imaging methods cannot visualize the microvascular coronary network in vivo, and non-invasive hemodynamic estimates overlook patient-specific microcirculatory contributions. Herein, we present a multiscale framework to extend the epicardial coronary tree and generate 1D microvascular networks in the myocardium based on ferumoxytol-enhanced magnetic resonance coronary imaging and fractional myocardial blood volume (fMBV) maps. Synthetic arterial networks were constructed from MRI data belonging to three swine, four healthy volunteers, and one IHD patient using a modified multistage, adaptive constrained constructive optimization approach. Hemodynamic simulations were performed in synthetic arterial networks. Morphological parameters were compared with empirical models. In 126 arterial networks (n = 6000 terminal segments per subject per seed; six seeds per coronary vessel), the morphometry was strongly correlated with empirical data (r > 0.87), with low variability (CoV < 0.01) across multiple rounds of network simulations. Mixed-effects models and a Dynamic Time Warping analysis confirmed robustness and repeatability. In the IHD patient, simulated arterial networks (n = 15) reproduced tissue-dependent morphological and functional signatures consistent with coronary autoregulation in scar and hypoperfused tissues. The findings establish an early potential for patient-specific microvascular network synthesis and hemodynamic simulations from MRI data. Full article

Introduction: The COVID-19 pandemic posed additional challenges for this vulnerable population, such as Sjögren’s disease (SjD), underscoring the need for effective and safe vaccination strategies. Objective: To evaluate the immunogenicity and safety of COVID-19 vaccines in patients with SjD. Methods: This prospective, observational, longitudinal study included SjD patients from the SAFER cohort. Immunogenicity was assessed via anti-spike IgG (IgG-S) titers using chemiluminescence reported as geometric mean titers (GMT) and fold increase in GMT (FI-GMT). Disease activity was evaluated using the ESSDAI score. Adverse events and COVID-19 infections were also monitored. Assessments were conducted at four time points: pre-first dose (T1), pre-second dose (T2), pre-booster (T3), and four weeks post-booster (T4). Primary vaccination involved ChAdOx1 nCoV-19 or inactivated vaccine (CoronaVac), and boosters were either homologous (ChAdOx1 nCoV-19) or heterologous (BNT162b2). Results: Among 51 participants (mean age 46 years; 90% female), 41% had comorbidities and 27% (n = 14/51) were highly immunosuppressed. Among those 73% (n = 37/51) under low immunosuppression, n = 8/51 (13%) were not using any medication. At baseline, 11% (n = 4/35) showed moderate/high disease activity, which decreased to 6.5% (n = 2/31) at T4. Primary vaccination was ChAdOx1 in 94% (n = 48/51) and CoronaVac in 6% (n = 3/51); 73% (n = 37/51) received heterologous and 27% (n = 14/51) homologous boosters. COVID-19 infection post-booster occurred in 20% (n = 10/51). Seroconversion rates reached nearly 100% across all medication subgroups except for biologic users, who showed delayed but stable seroconversion by T4. IgG-S titers increased progressively through T4. Primary immunization induced an ascending GMT in both vaccine types. At T4, the GMT was significantly higher in the BNT162b2 group (2148.03 [1452.05–3155.84]; p < 0.001; 95% CI) than in the ChAdOx1 group (324.29 [107.92–974.48]; p < 0.001; 95% CI); the fold-increase in immune response was six times greater with BNT162b2 (5.98 [2.97–12.03]; p = 0.001; 95% CI). Seroconversion was 100% in the heterologous group versus 83% in the homologous group (p > 0.01). Those with prior infection showed significantly higher titers, particularly at T2 and T3 (p < 0.001 for T1–T3). Adverse events were mild and not statistically significant. Multivariate regression confirmed BNT162b2 as an independent factor for higher antibody titers. Conclusion: COVID-19 vaccination in patients with SjD was safe and induced high anti-spike antibody titers and seropositivity. Heterologous boosting, particularly with BNT162b2, demonstrated superior immunogenicity. No association was found between vaccination and SjD disease flares or worsening activity. Full article

Consider regression models where the response variable Y only depends on the $p\times 1$ vector of predictors $\mathit{x}={(x_1,\dots ,x_p)}^T$ through the sufficient predictor $SP=\alpha +{\mathit{x}}^T\mathit{\beta }$. Let the covariance vector $\mathrm{Cov}(\mathit{x},Y)={\mathbf{\Sigma }}_{\mathit{x}Y}$. Assume the cases ${({\mathit{x}}_i^T,Y_i)}^T$ are independent and identically distributed random vectors for $i=1,\dots ,n$. Then for many such regression models, $\mathit{\beta }=\mathbf{0}$ if and only if ${\mathbf{\Sigma }}_{\mathit{x}Y}=\mathbf{0}$ where 0 is the $p\times 1$ vector of zeroes. The test of $H_0:{\mathbf{\Sigma }}_{\mathit{x}Y}=\mathbf{0}$ versus $H_1:{\mathbf{\Sigma }}_{\mathit{x}Y}\ne \mathbf{0}$ is equivalent to the high dimensional one sample test $H_0:\mathit{\mu }=\mathbf{0}$ versus $H_A:\mathit{\mu }\ne \mathbf{0}$ applied to ${\mathit{w}}_1,\dots ,{\mathit{w}}_n$ where ${\mathit{w}}_i=({\mathit{x}}_i-{\mathit{\mu }}_{\mathit{x}})(Y_i-{\mu }_Y)$ and the expected values $E(\mathit{x})={\mathit{\mu }}_{\mathit{x}}$ and $E(Y)={\mu }_Y$. Since ${\mathit{\mu }}_{\mathit{x}}$ and ${\mu }_Y$ are unknown, the test of $H_0:\mathit{\beta }=\mathbf{0}$ versus $H_1:\mathit{\beta }\ne \mathbf{0}$ is implemented by applying the one sample test to ${\mathit{v}}_i=({\mathit{x}}_i-\overline{\mathit{x}})(Y_i-\overline{Y})$ for $i=1,\dots ,n$. This test has milder regularity conditions than its few competitors. For the multiple linear regression one component partial least squares and marginal maximum likelihood estimators, the test can be adapted to test $H_0:{({\beta }_{i_1},\dots ,{\beta }_{i_k})}^T=\mathbf{0}$ versus $H_1:{({\beta }_{i_1},\dots ,{\beta }_{i_k})}^T\ne \mathbf{0}$ where $1\le k\le p.$ Full article

Background: Dose-sparing approaches can be effective in maintaining immunogenicity and safety while expanding vaccine coverage. We previously demonstrated that a half dose of ChAdOx1 nCoV-19 is as effective and immunogenic for primary vaccination. Methods: This non-inferiority, non-randomized controlled trial evaluated the effectiveness, humoral, and cellular immune responses of a third booster dose—comparing half-dose and full-dose regimens—in individuals aged 18–49 years, with a 1-year follow-up. Results: A total of 2801 participants were enrolled: 2352 received half doses and 449 received full doses. The incidence rate of COVID-19 was 225.0 per 1000 person-years in the half-dose group and 173.8 in the full-dose group, with no significant difference in effectiveness (β = −0.05; 95% CrI: −0.24 to 0.15). No deaths occurred, and hospitalization rates were similar. In a subsample (n = 558), anti-S IgG levels peaked 28 days post-dose and declined by day 180 after the primary series [175 (121–252) vs. 121 (71–208) GMT, p < 0.001], but remained elevated after the booster [192.1 (124–297) vs. 550 (380–797) GMT, p < 0.001]. Booster antibody levels were similar between groups [592.4 (318–1140) vs. 550 (380–797) GMT]. The half-dose group showed high titers against Omicron and robust T/B-cell responses (e.g., EMCD4, EMCD8, IFN⁺CD4⁺, CD19⁺TNF⁺). Conclusions: Fractional half dose of ChAdOx nCov-19 was effective and non-inferior to a full booster dose. Homologous regimen with 3 half doses or 3 full doses induced a similar increase in antibody titers and robust cellular response. ClinicalTrials.gov (NCT05059106). Full article

Background: Cytokines participate in regulating the immune response of lymphocytes. Interleukin 2 (IL-2) is the main modulator of T lymphocyte development, homeostasis, and function, whereas interleukin 7 (IL-7) regulates the development and homeostasis of immune cells and plays a crucial role in the maintenance of memory cells. The study aims to assess the blood IL-2 and IL-7 concentration in relation to the obtained cellular and humoral response in adults, six months after vaccination against COVID-19. Methods: We measured the concentration of IL-2 and IL-7 with ELISA, CoV2-IgG with an indirect chemiluminescence test, and the levels of IFN-γ with interferon gamma release assay (IGRA) post SARS-CoV-2 antigen stimulation. The study group (n = 76; F = 66, M = 10) was divided into 41 individuals, who did not report any chronic disorder (ChrD-Neg), and 35, who did (ChrD-Pos). Results: ChrD-Pos group presented higher IL-7 compared to ChrD-Neg (p = 0.023). Negative correlations were observed in the entire study population between IL-2 and age (R = −0.252, p = 0.028), as well as between IL-7 and IFN-γ (R = −0.295, p = 0.010). We found a positive correlation between IL-2 and IL-7 concentrations in the entire study population (R = 0.305, p = 0.007) and the ChrD-Pos group (R = 0.358, p = 0.035), and people with a positive IGRA result (R = 0.359, p = 0.005). Conclusions: The interaction of IL-2 and IL-7 may be important for achieving post-vaccination immunity, especially in adults with chronic diseases. Age is a factor modifying the post-vaccination response (decreased IL-2), whereas IL-7 may be an important factor in achieving a satisfactory post-vaccine response in people with chronic diseases. Full article

Background: In the Kingdom of Saudi Arabia, various COVID-19 vaccines were administered during the pandemic. However, region-specific real-word comparative data on their immunogenicity remain limited. This study aimed to assess the serological responses to Pfizer-BioNTech (BNT162b2), Moderna (mRNA-1273), and AstraZeneca (ChAdOx1 nCoV-19) vaccines in a diverse population living in KSA. Methods: This observational study included 236 adults recruited from vaccination sites in Riyadh. Participants provided serum samples at predefined intervals: before the first dose, after the first dose, after the second dose, and post-vaccination infection (if applicable). IgG and neutralising antibodies were quantified using ELISA assays. Demographic and vaccination data, and their associations with antibody responses, were evaluated. Results: At baseline, 75.4% of participants were positive for SARS-CoV-2 IgG, suggesting high prior exposure. Marked incremental increases in IgG levels were observed after each vaccine dose. Both Moderna and Pfizer elicited stronger responses, with Pfizer inducing the strongest early response and Moderna achieving the highest overall titres. Among IgG-positive individuals, neutralising antibodies were detected in 98.1%. There were no statistically significant differences by age or gender, although males tended to show higher mean titres. Heterologous vaccine schedules induced comparable or enhanced immunogenicity relative to homologous schedules, supporting their use in flexible immunisation strategies. Conclusions: All COVID-19 vaccines administered in Saudi Arabia elicited robust antibody responses, particularly the mRNA-based vaccines. Our findings support their continued use and justify varied vaccination approaches, including mix-and-match booster strategies, to enhance community immunity. Full article

Urine-based immunoassay is a non-invasive method with demonstrated utility in detecting anti-SARS-CoV-2 antibodies in unvaccinated patients with COVID-19. To evaluate urine’s potential for serological surveys in a real-world setting, SARS-CoV-2 serology was performed on urine samples from vaccinated individuals, both with and without prior confirmed COVID-19. (1) Methods: An in-house indirect ELISA was used to measure antibodies against recombinant spike (S) and nucleocapsid (N) proteins of SARS-CoV-2 in urine and paired serum from 149 individuals vaccinated with Janssen AD26.COV2.S, an S protein-based COVID-19 vaccine. (2) Results: Anti-S and anti-N levels were higher in the urine and serum of participants with confirmed prior COVID-19 compared to those without prior infection. Urinary anti-S effectively distinguished vaccinated individuals with (AUC = 0.96) and without (AUC = 0.88) prior infection from negative controls (non-vaccinated, non-previously infected individuals) (p < 0.0001). Among vaccinated participants, urinary anti-S and anti-N identified prior infection, with AUC values of 0.73 (p < 0.0001) and 0.60 (p = 0.03), respectively, being recorded. (3) Conclusions: Findings indicate that urinary anti-SARS-CoV-2 antibodies reflect AD26.COV2.S vaccination and previous COVID-19. To further advance the methodology, studies with larger sample sizes and a greater diversity of COVID-19 vaccines are required. Full article

This paper develops a novel design formula to estimate the residual strength of corroded stiffened cylindrical structures. It extends a previously established ultimate strength formulation for intact cylinders by introducing a corrosion-induced strength reduction factor. The foundational formula considers failure mode interactions like yielding, local buckling, overall buckling, and stiffener tripping. This research utilizes recent experimental and numerical investigations on corroded ring-stiffened cylinder models. Experimental results validate the numerical analysis method, showing good agreement in collapse pressures (2–4% difference) and shapes. The validated numerical method is then subject to an extensive parametric study, systematically varying corrosion characteristics. Results indicate a clear relationship between corrosion volume and strength reduction, with overall buckling being more sensitive. Based on these comprehensive results, a new empirical strength reduction factor (${\rho }_c$) is derived as a function of the corrosion volume ratio ($V_{non}$). This factor is integrated into the existing ultimate strength formula, allowing direct residual strength estimation for corroded structures. The proposed formula is rigorously verified against experimental and numerical data, showing excellent agreement (mean 1.00, COV 5.86%). This research provides a practical, accurate design tool for assessing the integrity and service life of corroded stiffened cylindrical structures. Full article