Short-term associations between daily mortality and ambient particulate matter, nitrogen dioxide, and the air quality index in a Middle Eastern megacity.

There is limited evidence for short-term association between mortality and ambient air pollution in the Middle East and no study has evaluated exposure windows of about a month prior to death. We investigated all-cause non-accidental daily mortality and its association with fine particulate matter (PM2.5), nitrogen dioxide (NO2), and the Air Quality Index (AQI) from March 2011 through March 2014 in the megacity of Tehran, Iran. Generalized additive quasi-Poisson models were used within a distributed lag linear modeling framework to estimate the cumulative effects of PM2.5, NO2, and the AQI up to a lag of 45 days. We further conducted multi-pollutant models and also stratified the analyses by sex, age group, and season. The relative risk (95% confidence interval (CI)) for all seasons, both sexes and all ages at lag 0 for PM2.5, NO2, and AQI were 1.004 (1.001, 1.007), 1.003 (0.999, 1.007), and 1.004 (1.001, 1.007), respectively, per inter-quartile range (IQR) increment (18.8??g/m3 for PM2.5, 12.6?ppb for NO2, and 31.5 for AQI). In multi-pollutant models, the PM2.5 associations were almost independent from NO2. However, the RRs for NO2 were slightly attenuated after adjustment for PM2.5 but they were still largely independent from PM2.5. The cumulative relative risks (95% CI) per IQR increment reached maximum during the cooler months, including: 1.13 (1.06, 1.20) for PM2.5 at lag 0-31 (for females, all ages); 1.17 (1.10, 1.25) for NO2 at lag 0-45 (for males, all ages); and 1.13 (1.07, 1.20) for the AQI at lag 0-30 (for females, all ages). Generally, the RRs were slightly larger for NO2 than PM2.5 and AQI. We found somewhat larger RRs in females, age group >65 years of age, and in cooler months. In summary, positive associations were found in most models. This is the first study to report short-term associations between all-cause non-accidental mortality and ambient PM2.5 and NO2 in Iran

Triaxial shear behavior of a cement-treated sand–gravel mixture

A number of parameters, e.g. cement content, cement type, relative density, and grain size distribution, can influence the mechanical behaviors of cemented soils. In the present study, a series of conventional triaxial compression tests were conducted on a cemented poorly graded sand–gravel mixture containing 30% gravel and 70% sand in both consolidated drained and undrained conditions. Portland cement used as the cementing agent was added to the soil at 0%, 1%, 2%, and 3% (dry weight) of sand–gravel mixture. Samples were prepared at 70% relative density and tested at confining pressures of 50 kPa, 100 kPa, and 150 kPa. Comparison of the results with other studies on well graded gravely sands indicated more dilation or negative pore pressure in poorly graded samples. Undrained failure envelopes determined using zero Skempton's pore pressure coefficient (A¯=0) criterion were consistent with the drained ones. Energy absorption potential was higher in drained condition than undrained condition, suggesting that more energy was required to induce deformation in cemented soil under drained state. Energy absorption increased with increase in cement content under both drained and undrained conditions

Numerical investigation of thermal-hydraulic performance enhancement in helical coil heat exchangers with twisted tube geometries

This numerical study examines the thermal-hydraulic performance of helical coil heat exchangers (HCHEs) using twisted tubes versus conventional circular tubes. The effects of Reynolds number (Re = 10,000 to 100,000), pitch length (11, 7.2, 5.5, 3.6 mm), and twisted tube orientation (co-current, counter-current) on heat transfer efficiency and pressure drop were investigated. The results show that higher Reynolds numbers can reduce the Resistance factor by approximately 25 % and improve heat transfer by approximately 35 %. An optimal pitch length of 5.5 mm was found to balance enhanced heat transfer and manageable pumping costs. Twisted tubes demonstrate significant performance advantages at lower Re, with 20–33 % higher Performance Evaluation Criterion (PEC) values compared to circular tubes. However, the benefit diminishes at higher Re, with less than 10 % PEC increase. Implementing counter-current twisted tube configurations leads to approximately 13 % higher Nusselt number and 11 % higher Resistance factor, resulting in a 10 % overall PEC improvement. These findings highlight the superior thermal-hydraulic performance of twisted tubes in HCHE applications, especially at lower Reynolds numbers. Future work could explore different fluids, advanced optimization, energy analysis, cost assessment, and additional geometric parameters to further enhance twisted tube heat exchanger design and performance

Application of Knudsen thermal force for detection of inert gases

Recently, detection and analysis of gas mixtures have become significant for purifications and separation of the natural gas mixture. In the present work, Direct Simulation Monte Carlo (DSMC) method is applied to evaluate the performance of a new micro gas sensor (MIKRA) for mass analysis of three inert gases (Helium, Neon and Argon). This sensor applied the Knudsen force induced by temperature difference at the low-pressure condition to diagnose the main components of the mixture. Since this sensor works in low-pressure condition, Boltzmann equation is used to attain accurate outcomes. To solve these equations, Direct Simulation Monte Carlo (DSMC) approach is used as a robust method for the non-equilibrium flow field. This study performed comprehensive studies to disclose the primary process of force production and applied this for the analysis of the gas mixture. Hence, effects of the main parameter such as temperature gradient and the gap of arms are expansively examined in different ambient pressures. Furthermore, the influence of various mixtures of the (Helium, Neon and Argon) on force generation is also investigated. Our findings show that value of generating Knudsen force significantly varies when the component of the mixture is changed. According to obtained results, the Knudsen force declines as the molecular weight of the gas decreases. In addition, the induced force is highly proportional to the molecular weight rather than other characteristics. Therefore, the Knudsen force is a reliable method for the mass analysis of the mixtures. Keywords: Knudsen force, Mass analysis of gas mixture, DSMC, Low-pressure gas actuators, MEM

Heat transfer of swirling impinging jets ejected from Nozzles with twisted tapes utilizing CFD technique

This research investigated the forced convection heat transfer by using the swirling impinging jets. This study focused on nozzles, which equipped with twisted tapes via a numerical approach. The computational domain created by utilizing the fully structured meshes, which had very high quality from the viewpoint of aspect ratio and skewness. The numerical simulations were performed at four different jet-to-plate distances (L/D) of 2, 4, 6 and 8, four Reynolds numbers of 4000, 8000, 12,000 and 16,000, and also four different twist ratios (y/w) of 3, 4, 5 and 6. The mesh-independent tests were conducted based upon the average Nusselt number. The obtained results revealed good agreement with the available experimental data from the open literature. It was observed that for jet-to-plate distances of L/D=6 and L/D=8, the heat transfer rate of swirling jets was more than regular jets, and heat transfer rate at higher Reynolds numbers increased due to the greater rate of momentum transfer. Besides, the calculation done for a pair of jets, and the results shown that using two jets, instead of one, could increase the rate of heat transfer in the same air flow rate

Graphene : recent advances in engineering, medical and biological sciences, and future prospective

Graphene, a two dimensional carbon allotrope, has been appeared as an interesting material of the 21st century, and received world-wide attention due to its extraordinary thermal, optical, and mechanical properties. Graphene and its derivatives are being studied in different field of science from medicine and pharmaceutics to engineering and industries. Graphene materials have mainly been explored in electronics, clean energy devices, biosensors and environmental remediation also in biomedicine field, their antimicrobial activity and their capacity as drug delivery or gene delivery platforms and tissue engineering scaffold have been reported. This article provides an overview of graphene and its recent advances in different fields including biomedicine and industries

Functionalized graphene oxide with chitosan for protein nanocarriers to protect against enzymatic cleavage and retain collagenase activity

Proteins have short half-life because of enzymatic cleavage. Here, a new protein nanocarrier made of graphene oxide (GO) + Chitosan (CS) is proposed to successfully prevent proteolysis in protein and simultaneously retain its activity. Bovine serum albumin (BSA) and collagenase were loaded on GO and GO-CS to explore the stability and activity of proteins. SEM, AFM, TEM, DSC, UV-Vis, FT-IR, RBS, Raman, SDS-PAGE and zymography were utilized as characterization techniques. The protecting role of GO and GO-CS against enzymatic cleavage was probed by protease digestion analysis on BSA, where the protease solution was introduced to GO-BSA and GO-CS-BSA at 37 °C for 0.5-1-3-6 hours. Characterizations showed the successful synthesis of few layers of GO and the coverage by CS. According to gelatin zymographic analysis, the loaded collagenase on GO and GO-CS lysed the gelatin and created non-staining bands which confirmed the activity of loaded collagenase. SDS-PAGE analysis revealed no significant change in the intact protein in the GO-BSA and GO-CS-BSA solution after 30-minute and 1-hour exposure to protease; however, free BSA was completely digested after 1 hour. After 6 hours, intact proteins were detected in GO-BSA and GO-CS-BSA solutions, while no intact protein was detected in the free BSA solution

Physical modeling of the effect of shape, blockage, and flow variability on scour in culvert outlets.

The widespread use of culverts has prompted researchers to focus on developing precise designs to prevent their failure caused by scouring at the culvert outlet. This study employed physical modelling to investigate alternation in culvert outlets under different conditions, including variations in culvert shape, blockage, and flow discharge during steady and unsteady flow conditions. Box and circular culverts were examined with 0%, 15%, and 30% blockage rates at the culvert inlet. For unsteady flow conditions, two hydrographs were generated, each with nine distinct flow discharges, while for steady flow conditions, flow rates of up to 14 l/s and 22 l/s were used. The sediment and flow conditions were carefully selected to ensure clear water throughout the experiments. According to the study results, the scour profile exhibited more growth in the circular culvert compared to the box culvert across all cases. Furthermore, an increase in flow rate led to an increase in the scour hole dimension, and the scouring increased with a rise in hydrograph stepwise. However, when the degree of blockage was increased, a strictly proportional increase in scour depth was not observed across all cases. The results and data presented in this research can be used by other researchers in addition to being used by hydraulic designers

Numerical modeling of surface reaction kinetics in electrokinetically actuated microfluidic devices

We outline a comprehensive numerical procedure for modeling of species transport and surface reaction kinetics in electrokinetically actuated microfluidic devices of rectangular cross section. Our results confirm the findings of previous simplified approaches that a concentration wave is created for sufficiently long microreactors. An analytical solution, developed for the wave propagation speed, shows that, when normalizing with the fluid mean velocity, it becomes a function of three parameters comprising the channel aspect ratio, the relative adsorption capacity, and the kinetic equilibrium constant. Our studies also reveal that the reactor geometry idealized as a slit, instead of a rectangular shape, gives rise to the underestimation of the saturation time. The extent of this underestimation increases by increasing the Damkohler number or decreasing the dimensionless Debye–Hückel parameter. Moreover, increasing the values of the Damkohler number, the dimensionless Debye–Hückel parameter, the relative adsorption capacity, and the velocity scale ratio results in lower saturation times

Lipoamino Acid Coated Superparamagnetic Iron Oxide Nanoparticles Concentration and Time Dependently Enhanced Growth of Human Hepatocarcinoma Cell Line (Hep-G2)

Superparamagnetic iron oxide nanoparticles (SPION) have been widely used in medicine for magnetic resonance imaging, hyperthermia, and drug delivery applications. The effect of SPION on animal cells has been a controversial issue on which there are many contradictions. This study focused on preparation of SPION with novel biocompatible coatings, their characterization, and cytotoxicity evaluation. An amino acid (glycine) and two novel lipo-amino acids (2 amino-hexanoic acid and 2 amino-hexadecanoic acid) coated magnetic nanoparticles were characterized by various physicochemical means such as X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), differential scanning calorimetry (DSC), and infrared spectroscopy (FT-IR). The cytotoxicity profile of the synthesized nanoparticles on Hep-G2 cells as measured by MTT assay showed the nanoparticles are nontoxic and the cell growth is promoted by SPION. Moreover, lipoamino acid coating SPION appear more beneficial than the other ones. By increasing concentration of SPION, growth enhancing impact will attenuate and toxicity will appear. Although the aggregation of SPION can affect the results, the gradual delivery of ferric/ferrous ions into cells is the main cause of this growth promotion effect. Conclusively, this study shows that lipoamino acid coating SPION can be used for various biomedical purposes