Effects of Compression applied to Gas Diffusion Layers in PEM Fuel Cells

There is a global and urgent need to embrace alternative renewable power sources to mitigate the detrimental environmental effects of the greenhouse gases, in particular carbon dioxide. Proton electrolyte membrane (PEM) fuel cells have been an attractive clean technology to decarbonise a multitude of applications, particularly those in the automotive sector. Although PEM fuel cells have, compared to other types of fuel cells, high efficiency and low-operating temperature, there are still some very important challenges that need to be overcome so that the PEM has a wider application. One of the main issues that affect the lifetime of PEM fuel cells is the mechanical degradation of the gas diffusion layers (GDLs). Since GDLs are responsible for the transport of reacting gases, heat and electronic charge from/to the catalyst layers, any damage to their structure may have detrimental consequences on the above transport processes and, subsequently, the performance of the fuel cell. Typically, GDLs are subject to two types of compressive stresses: assembling and cyclic stresses. The assembling stress occurs due to the clamping pressure applied to assemble the various components of the fuel cell. The cyclic stress is due to the hydration/dehydration cycles of the membrane as it swells or shrinks. In this thesis, a novel and carefully designed compression test (mimicking the assembling and cyclic stresses that the GDL is subjected to within the fuel cell) has been performed on a set of commercially available GDLs. This was followed by a series of tests to examine the effects of compression on the mass transport (gas permeability test), morphology (SEM analysis), thermal stability (TGA analysis), and wettability (contact angle test) of the tested GDLs. Such tests and the related outcomes are of much importance to the researchers in the field, especially those who model PEM fuel cells as these tests provide much more accurate and realistic data for the physical properties being investigated. The same investigation was then performed in the presence of sealing gaskets in order to explore how the effects of compression are mitigated with the sealing gaskets. Finally, the experimental values for the GDL gas permeability and contact angle (before and after compression) were fed into a comprehensive three-dimensional PEM fuel cell model to investigate their effects on the overall performance of the cell. The key findings of the study are as follows: (i) the MPL-coated GDLs are more resistive to mechanical deformation than uncoated GDLs, (ii) the contact angle of the GDLs reduce by 3° - 15° after compression, (iii) GDLs are less deformed in presence of sealing gaskets, (iv) GDLs lose around 40% of its PTEF content after compression and (v) the performance of the modelled fuel cell is hardly affected by variation in GDL gas permeability

Antimicrobial Analysis of Biosynthesized Lectin-Conjugated Gold Nanoparticles

To enhance the bioactivity of molecules through nanoparticles is being tested which has potential use in sustained-release drug delivery systems and to enhance the therapeutic effectiveness of drugs. Our current investigation s is to conjugate lectin to that of a gold nanoparticle (GNP) surface without disturbing the bioactive properties and enhances the antibacterial activity of lectin. Au-lectin nanoparticles were checked for their hemagglutination activity, characterized by transmission electron microscopy (TEM) and UV-visible spectrophotometer. The antibacterial effect of nanoparticle lectin, Au salt nanoparticle, and conjugated Au-lectin was estimated by Kirby-Bauer disc method; MICs were determined by microbroth dilution and compared with ciprofloxacin. These tests were done using known species of bacterial strain of multidrug resistant. The hemagglutination activity of lectin was improved to fourfold after purification. Lectin and Au nanoparticles combined had a significant effect on the inhibition of bacterial growth. No significant differences were observed in the inhibition zone diameters from killed bacteria and its supernatant towards any of the tested organisms. Lectin-conjugated gold particles showed good efficacy as antimicrobial agents and the nanoparticle-killed bacteria to work against the viable population of the same bacterium and/or other bacterial species too

Synthetic nanocomposite MgH2/5 wt. % TiMn2 powders for solid-hydrogen storage tank integrated with PEM fuel cell

Abstract Storing hydrogen gas into cylinders under high pressure of 350 bar is not safe and still needs many intensive studies dedic ated for tank’s manufacturing. Liquid hydrogen faces also severe practical difficulties due to its very low density, leading to larger fuel tanks three times larger than traditional gasoline tank. Moreover, converting hydrogen gas into liquid phase is not an economic process since it consumes high energy needed to cool down the gas temperature to −252.8 °C. One practical solution is storing hydrogen gas in metal lattice such as Mg powder and its nanocomposites in the form of MgH2. There are two major issues should be solved first. One related to MgH2 in which its inherent poor hydrogenation/dehydrogenation kinetics and high thermal stability must be improved. Secondly, related to providing a safe tank. Here we have succeeded to prepare a new binary system of MgH2/5 wt. % TiMn2 nanocomposite powder that show excellent hydrogenation/dehydrogenation behavior at relatively low temperature (250 °C) with long cycle-life-time (1400 h). Moreover, a simple hydrogen storage tank filled with our synthetic nanocomposite powders was designed and tested in electrical charging a battery of a cell phone device at 180 °C through a commercial fuel cell

Silver Nanoparticles Loaded on Chitosan-g-PVA Hydrogel for the Wound-Healing Applications

Silver nanoparticle composites have abundant biomedical applications due to their unique antibacterial properties. In the current work, green tea leaf extract was used as a natural reducing agent to synthesize AgNPs (AgNPs) using microwave irradiation technology. Furthermore, microwave irradiation has been used for the preparation of AgNPs/chitosan (Ch) grafted polyvinyl alcohol (PVA) hydrogel samples. To approve the accomplishment of AgNPs hydrogel polymer, UV-spectrum, TEM, and FT-IR spectrum analyses and the release of silver ions, actions were taken. The wound-healing ability of the prepared hydrogel samples was measured via both the in vitro (fibroblast cells) and the in vivo using rat models. It was found that chitosan-grafted polyvinyl alcohol, including AgNPs, exhibited excellent antibacterial activity against E. coli and S. aureus using the agar diffusion method. It can be said that microwave irradiation was successful in creating a hydrogel that contained silver nanoparticles. A wound that was still open was successfully treated with these composites

Knowledge about the Risk of Cardiovascular Disease among Adults with Type 2 Diabetes Visiting the Outpatient Clinics at Tertiary Hospital in Riyadh, Saudi Arabia: A Cross-Sectional Study

Background: One of the primary goals of diabetes management is to prevent cardiovascular events. The rate of cardiovascular diseases (CVDs) is significantly high in the diabetic population. Inadequate knowledge of CVDs risk in diabetes may result in the failure of its early prevention, causing increased morbidity and mortality. The objectives of this study were to assess the CVD risk knowledge and determine the predictors of the knowledge among adults with type 2 diabetes. Methods: A cross-sectional study was conducted to examine the study objectives. Convenience sampling was used to recruit adults with type 2 diabetes mellitus (DM) who visited the King Saud University Medical City (KSUMC) outpatient clinics. Data were collected using the Heart Disease Fact Questionnaire. SPSS software (version 24.0) was used for data analysis. Results: A total of 383 patients were recruited. The level of CVD risk knowledge was high among all participants (19.04 ± 3.47). There were significant differences in knowledge scores between different groups, including age (p = 0.01), marital status (p = 0.01), and type of residence (p = 0.04). Participants who were older than 40 years, married, and lived in traditional houses had higher knowledge scores. Conclusion: The study findings indicated a high level of CVD risk knowledge in our study population. The presence of multidisciplinary intensive education programmes targeting type 2 DM patients, such as that conducted at KSUMC, might be responsible for the higher levels of knowledge among our study population. Thus, increasing the efforts towards the education of patients will improve the level of knowledge, including CVD risk knowledge

Self-directed learning readiness and online learning self-efficacy among undergraduate nursing students

Background: Self-efficacy is a key aspect to succeed in both online learning and self-directed learning readiness. Self-directed learning is described as learning on one's initiative, with the learner taking major responsibility for the effort's design, implementation, and evaluation. Aim: Assess the relationship between self-directed learning readiness and online learning self-efficacy among undergraduate nursing students in Saudi Arabia. Methods: A correlational descriptive research design among 282 nursing students from 3 selected nursing colleges in Saudi Arabia. One tool was developed includes self-directed learning readiness scale and online learning self-efficacy. Findings: The over-all mean score online learning self-efficacy of the students was 5.21 ± 1.26 which represents an expert. 39.4 % of the students show Above-average SDL readiness. There is a significant positive correlation between self-directed learning readiness and overall online learning self-efficacy (r = 0.641, p = 0.00*). Conclusion: The majority students’ self-directed learning readiness ranges between the average and above the average. The significant relationship between the two scales addresses how self-efficacy is an essential part of self-directed learning readiness

Knowledge and Attitude toward E-Cigarettes among First Year University Students in Riyadh, Saudi Arabia

Background: Electronic cigarettes are immensely popular among youths across the globe. However, knowledge, attitudes, and perceptions regarding their use vary by country. The present study investigated the knowledge and attitudes toward e-cigarette use among first-year university students in Saudi Arabia. Methods: A cross-sectional design was adopted, and an online, self-administered questionnaire assessing the knowledge of and attitudes toward e-cigarette use was utilized to conduct this study. The study population included students from all streams enrolled in their first year of university. Descriptive statistics were used to report percentages and frequencies, while advanced statistics, such as multiple logistic regression analyses, were used to determine associations. Results: The lifetime and current prevalence of e-cigarette use was 27.4% and 13.5%, respectively, among first-year university students. The mean age of smoking initiation was 16.4 ± 1.2 years. Of e-cigarette users, 31.3% smoked every day and 86.7% used flavored e-cigarettes. Knowledge of the harmful effects of e-cigarettes was high (addiction, 61.2%; asthma, 61%; nicotine content, 75.2%). However, when comparing e-cigarettes to regular cigarettes, only 22.5% and 48.4% of the students reported that they carry the same risk and contain the same chemicals as regular cigarettes do. There was a lack of knowledge (17.1%) regarding government regulations related to e-cigarettes. An attitude of support was observed regarding banning e-cigarettes (2.6 ± 1.5 on a scale of 0 to 4), while at the same time, some associated e-cigarette use with helping to reduce tobacco dependency (2.1 ± 1.2). Marketing adverts were agreed upon to positively influence youth (1.9 ± 1.4). However, the participants’ perceptions relating e-cigarette use to style were not well articulated. Significant gender differences were found: most of the women who participated in the study had better knowledge of e-cigarettes (p p = 0.013), being a current smoker (OR = 11.6; p p < 0.001) were strong predictors of e-cigarette use. Conclusions: These findings suggested the increasing popularity of e-cigarette use among male first-year university students. More educational campaigns and stricter regulations are needed to curb this trend

Knowledge and Attitude toward E-Cigarettes among First Year University Students in Riyadh, Saudi Arabia

Background: Electronic cigarettes are immensely popular among youths across the globe. However, knowledge, attitudes, and perceptions regarding their use vary by country. The present study investigated the knowledge and attitudes toward e-cigarette use among first-year university students in Saudi Arabia. Methods: A cross-sectional design was adopted, and an online, self-administered questionnaire assessing the knowledge of and attitudes toward e-cigarette use was utilized to conduct this study. The study population included students from all streams enrolled in their first year of university. Descriptive statistics were used to report percentages and frequencies, while advanced statistics, such as multiple logistic regression analyses, were used to determine associations. Results: The lifetime and current prevalence of e-cigarette use was 27.4% and 13.5%, respectively, among first-year university students. The mean age of smoking initiation was 16.4 &plusmn; 1.2 years. Of e-cigarette users, 31.3% smoked every day and 86.7% used flavored e-cigarettes. Knowledge of the harmful effects of e-cigarettes was high (addiction, 61.2%; asthma, 61%; nicotine content, 75.2%). However, when comparing e-cigarettes to regular cigarettes, only 22.5% and 48.4% of the students reported that they carry the same risk and contain the same chemicals as regular cigarettes do. There was a lack of knowledge (17.1%) regarding government regulations related to e-cigarettes. An attitude of support was observed regarding banning e-cigarettes (2.6 &plusmn; 1.5 on a scale of 0 to 4), while at the same time, some associated e-cigarette use with helping to reduce tobacco dependency (2.1 &plusmn; 1.2). Marketing adverts were agreed upon to positively influence youth (1.9 &plusmn; 1.4). However, the participants&rsquo; perceptions relating e-cigarette use to style were not well articulated. Significant gender differences were found: most of the women who participated in the study had better knowledge of e-cigarettes (p &lt; 0.001). Being male, having higher income status (OR = 1.67; p = 0.013), being a current smoker (OR = 11.6; p &lt; 0.001), and having intention for future use (OR = 3.45; p &lt; 0.001) were strong predictors of e-cigarette use. Conclusions: These findings suggested the increasing popularity of e-cigarette use among male first-year university students. More educational campaigns and stricter regulations are needed to curb this trend

Assessment of Physicochemical, Anticancer, Antimicrobial, and Biofilm Activities of N-Doped Graphene

Nanomedicine has been used as a precise treatment for many diseases. The advantage of using nanodrugs is that they have more permeability and less toxicity to cells, which enhances the drug delivery system. Graphene is well known for its potential biological applications in drug, food, and pharma industries. This study aimed to assess the productivity and potentiality of nitrogen-doped graphene (NDG) and to evaluate their anticancer, antimicrobial, and biofilm inhibition activity. Nitrogen-doped graphene was synthesized by using a one-pot facile synthesis of NDG, wherein the NDG was prepared by the reduction of graphene oxide (GO) in the presence of hydrazine hydrate as a reducing agent, while ammonium hydroxide was used as a source of nitrogen on the surface of graphene. As-synthesized NDG was characterized by various characterization techniques such as UV-Vis, FT-IR, XRD, XPS, TEM, and N2 sorption studies analysis. Antimicrobial, anticancer, and biofilm inhibition assays were performed by standard protocols. N-doped graphene (NDG) showed better activity against Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), Bacillus&nbsp;subtillis,&nbsp;Streptococcus pneumoniae, and Streptococcus mutans (p &le; 0.05), whereas there was no activity against Gram-negative strains in Klebsiella pneumoniae and Pseudomonas&nbsp;aeruginosa. Biofilm inhibition was also improved with NDG compared to the standard ampicillin. NDG showed better results in both MCF-7 and Hela cell lines with IC50 of 27.15 &micro;g/mL and 30.85 &micro;g/mL, respectively. In conclusion, NDG has the best ability for use as a biomolecule, and research studies focusing on proteomics, metabolomics, and in vivo studies are needed to increase the impact of NDG in the drug and pharma industry

Assessment of Physicochemical, Anticancer, Antimicrobial, and Biofilm Activities of N-Doped Graphene

Nanomedicine has been used as a precise treatment for many diseases. The advantage of using nanodrugs is that they have more permeability and less toxicity to cells, which enhances the drug delivery system. Graphene is well known for its potential biological applications in drug, food, and pharma industries. This study aimed to assess the productivity and potentiality of nitrogen-doped graphene (NDG) and to evaluate their anticancer, antimicrobial, and biofilm inhibition activity. Nitrogen-doped graphene was synthesized by using a one-pot facile synthesis of NDG, wherein the NDG was prepared by the reduction of graphene oxide (GO) in the presence of hydrazine hydrate as a reducing agent, while ammonium hydroxide was used as a source of nitrogen on the surface of graphene. As-synthesized NDG was characterized by various characterization techniques such as UV-Vis, FT-IR, XRD, XPS, TEM, and N2 sorption studies analysis. Antimicrobial, anticancer, and biofilm inhibition assays were performed by standard protocols. N-doped graphene (NDG) showed better activity against Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), Bacillus subtillis, Streptococcus pneumoniae, and Streptococcus mutans (p ≤ 0.05), whereas there was no activity against Gram-negative strains in Klebsiella pneumoniae and Pseudomonas aeruginosa. Biofilm inhibition was also improved with NDG compared to the standard ampicillin. NDG showed better results in both MCF-7 and Hela cell lines with IC50 of 27.15 µg/mL and 30.85 µg/mL, respectively. In conclusion, NDG has the best ability for use as a biomolecule, and research studies focusing on proteomics, metabolomics, and in vivo studies are needed to increase the impact of NDG in the drug and pharma industry