Abdulmalik Altuwayjiri

This study aimed to develop a “toxicity wind rose” for Riyadh City to investigate the di-rectional distribution of toxic PM₁₀ (particulate matter with aerodynamic diameter ≤ 10 µm) in the ambient atmosphere. The data collection approach combined an online moni-toring system with an offline sampling method. The monitoring instruments operated continuously, recording concentrations of key air pollutants including PM₁₀, PM₂.₅, NO₂, and SO₂, as well as meteorological parameters such as wind direction, temperature, and relative humidity. Concurrently, PM₁₀ samples were collected using Teflon and quartz fil-ters for subsequent chemical and toxicological analysis. The sampling campaign spanned from December 2019 to August 2020, covering both warm and cool seasons. The chemical and dithiothreitol (DTT) activity data were integrated with hourly wind direction meas-urements to construct pollutant and toxicity wind rose diagrams. During the warm sea-son, PM₁₀ concentrations exceeded 350 µg/m³ from the northwest and east, while the cool season showed elevated concentrations from the northeast. In contrast, the highest levels of oxidative potential (DTT activity) were associated with air masses originating from the north and west during the warm season and from the north during the cool season. These results demonstrate that high PM₁₀ mass concentrations do not necessarily coincide with high toxicity, highlighting the importance of considering both quantity and oxidative ca-pacity in air quality assessments.

Steel I-beams may be subject to deviation from their normal path towards the lateral direction due to obstacles along their axis line. This deviation in the lateral direction, i.e., the out-of-plane distance, affects the behavior of the steel beams and may reduce their ultimate capacity. To obtain this effect, finite element modeling (FEM) was used to model these beams with and without an out-of-plane distance at the mid-span beam length with several different variables. These variables were the out-of-plane distance, cross-section dimensions, beam length, and steel yield stress. The reliability of using FEM simulation was confirmed by comparing the experimental test results of 25 available steel beams in previous studies. The results indicate the high accuracy of the simulation of this beam in terms of ultimate capacity, structural behavior, and deformation patterns. After verifying the results, 116 broad-flange I-beam (BFIB) steel beams with different out-of-plane distances were modeled. The results showed that using an out-of-plane distance equal to the flange width of the BFIB-300 cross-section caused a 60% decrease in the ultimate capacity. The reduction ratios in the ultimate moment capacity in out-of-plane steel beams were directly proportional to the out-of-plane distance, cross-sectional dimensions, and steel yield stress, while the beam length had no effect. Failure in beams containing an out-of-plane distance occurs as a result of a global buckling in the upper flange, which contains tensile stresses at the outer edge and compressive stresses at the inner edge, with stress concentration occurring at the point of contact of the out-of-plane part with the main beam. The prediction results of the design codes were compared with the results of experimental tests and the FEM analysis of the beams with and without out-of-plane distances. For all the beams with out-of-plane distances, all the design codes were unable to predict this ultimate capacity.

Inflammatory bowel disease (IBD) is an immunologically complex disorder involving genetic, microbial, and environmental risk factors. Its global burden has continued to rise since industrialization, with epidemiological studies suggesting that ambient particulate matter (PM) in air pollution could be a contributing factor. Prior animal studies have shown that oral PM₁₀ exposure promotes intestinal inflammation in a genetic IBD model and that PM_2.5 inhalation exposure can increase intestinal levels of pro-inflammatory cytokines. PM₁₀ and PM_2.5 include ultrafine particles (UFP), which have an aerodynamic diameter of 3, 6 h/day, 3–5 days/week, starting 7–10 days before disease induction. No differences in weight change, clinical disease activity, or histology were observed between the PM and FA-exposed groups. In conclusion, UFP inhalation exposure did not exacerbate intestinal inflammation in acute, chemically-induced colitis models.

In this study we investigated the effectiveness of air purifiers and in-line filters in ventilation systems working simultaneously inside various classrooms at the University of Southern California (USC) main campus. We conducted real-time measurements of particle mass (PM), particle number (PN), and carbon dioxide (CO₂) concentrations in nine classrooms from September 2021 to January 2022. The measurement campaign was carried out with different configurations of the purifier (i.e., different flow rates) while the ventilation system was continuously working. Our results showed that the ventilation systems in the classrooms were adequate in providing sufficient outdoor air to dilute indoor CO₂ concentrations due to the high air exchange rates (2.63–8.63 h⁻¹). The particle penetration coefficients (P) of the investigated classrooms were very low for PM (<0.2) and PN (<0.1), with the exception of one classroom, corroborating the effectiveness of in-line filters in the ventilation systems. Additionally, the results showed that the efficiency of the air purifier exceeded 95% in capturing ultrafine and coarse particles and ranged between 82–88% for particles in the accumulation range (0.3–2 µm). The findings of this study underline the effectiveness of air purifiers and ventilation systems equipped with efficient in-line filters in substantially reducing indoor air pollution.