Chitosan/functionalized fruit stones as a highly efficient adsorbent biomaterial for adsorption of brilliant green dye: Comprehensive characterization and statistical optimization

In this research, a highly efficient adsorbent biomaterial (hereinafter, CTS/PPS-HS) of chitosan/functionalized fruit stones (peach and plum) with H2SO4 was produced for the adsorption of brilliant green (BG) dye from aquatic systems. The developed biomaterial was characterized by several techniques like SEM-EDX, FTIR, XRD, BET, and pHpzc. To systematically optimize the adsorption performance of CTS/PPS-HS, the Box-Behnken design (BBD) based on response surface methodology (RSM) was attained. The factors considered for optimization included A: CTS/PPS-HS dosage (0.02-0.08 g), B: pH (4-10), and C: removal time (10-60 min). The pseudo-first-order and Langmuir isotherm models exhibited excellent agreement with the experimental results of BG adsorption by CTS/PPS-HS. The outstanding adsorption capacity (409.63 mg/g) of CTS/PPS-HS was obtained. The remarkable adsorption of BG onto CTS/PPS-HS can be primarily attributed to electrostatic forces between the acidic sites of CTS/PPS-HS and the BG cations, accompanied by interactions such as π-π, Yoshida H-bonding, n-π, and H-bond interactions. The current data underscores the significant potential inherent in combining biomass with CTS polymer to create an exceptionally effective adsorbent biomaterial tailored for the elimination of cationic dyes.

Development of chitosan biopolymer by chemically modified orange peel for safranin O dye removal: A sustainable adsorbent and adsorption modeling using RSM-BBD

This study aimed to develop a biocomposite (hereinafter, CHI/OP-H2SO4) via the functionalization of chitosan (CHI) biopolymer by chemically modified orange peel (OP-H2SO4). The physicochemical characteristics of CHI/OP-H2SO4 were studied using methods such as pHpzc, XRD, FTIR, BET, and FESEM-EDX. The efficacy of the CHI/OP-H2SO4 biocomposite in removing cationic dye (safranin O, SAF-O) from aqueous solutions was assessed. The Box-Behnken Design (BBD) based on response surface methodology (RSM) was employed to optimize the adsorption performance of CHI/OP-H2SO4, considering factors such as A: CHI/OP-H2SO4 dose (0.02-0.08 g), B: pH (4-10), and C: time (10-60 min). The pseudo-first-order and Freundlich isotherm models align well with the experimental data of SAF-O adsorption by CHI/OP-H2SO4. The excellent adsorption capacity for CHI/OP-H2SO4 was recorded (321.2 mg/g). The notable adsorption of SAF-O onto CHI/OP-H2SO4 is attributed primarily to electrostatic forces between the acidic groups of CHI/OP-H2SO4 and the SAF-O cation, along with H-bonding, and n-π interactions. By transforming waste materials into valuable resources, this approach not only mitigates environmental impact but also produces a promising and sustainable adsorbent for the removal of cationic dyes, exemplified here by the effective removal of SAF-O dye.

Development of cashew nut shell lignin-acrylonitrile butadiene styrene 3D printed core and industrial hemp/aluminized glass fiber epoxy biocomposite for morphing wing and unmanned aerial vehicle applications

The aim of this study was to develop a lightweight epoxy based biocomposite for morphing wing and unmanned aerial vehicle (UAV) applications. The proposed composite was developed using a 3D printed high stiffness lignin-Acrylonitrile Butadiene Styrene (ABS) core and industrial hemp with aluminized glass fiber epoxy skin. The ABS was reinforced using lignin macromolecule derived from cashew nut shells via twin screw extruder and the core was printed using an industrial grade 3D printer. Furthermore, the composites were prepared by compression moulding with an ABS-lignin core and hemp/aluminized GF surface and characterized according to respective American society of testing and materials (ASTM) standards. The findings indicate that the addition of 30 vol% Al-glass and hemp fiber with lignin strengthened ABS core improved the mechanical properties. The composite material designated as "E2" exhibits the maximum mechanical properties, providing tensile strength, flexural strength, Izod impact, interlaminar shear strength (ILSS), and compression values of, 136 MPa, 168 MPa, 4.82 kJ/m2, 21 MPa, and 155 MPa respectively. The maximal energy absorbed by composite designation "E2," during drop load impact test is 20.6 J. Similarly, the composite designation "E2"gives fatigue life cycles of 33,709, 25,781 and 19,633 for 50 %, 70 % and 90 % of ultimate tensile strength (UTS) and 32.5 (K1c) MPa⋅m and 0.76 (G1c) MJ/m2 in fracture toughness and energy release rate respectively.

Mapping the Private Healthcare Sector in Riyadh Region: Size, Services, and Alignment with the Saudi Ministry of Health Priorities

Background

Mapping exercises are important to inform development of interventions aiming to enhance private sector's contribution towards achieving health systems objectives.

Objective

To map size, types, and distribution of private health institutions, and to identify the services they offer, and their alignment with Ministry of Health priorities.

Methods

A cross-sectional study targeted licensed, for-profit private health institutions in Riyadh Region, Saudi Arabia. Secondary data were collected from Department of Private Health Institutions in Riyadh and the Ministry of Health Year Statistical Book. Descriptive statistics were employed to analyze the collected data.

Results

Private hospitals increased from 40 (2017) to 46 (2021), with private sector hospital beds rising from 5,426 (2017) to 6,339 (2021). Pharmaceutical institutions comprised 55.4% of private health institutions, followed by polyclinics (23%) and supportive health services centers (17.1%). Laboratories, hospitals, and clinics represented 2%, 1%, and 0.5% of private health institutions respectively. Ambulance and radiology service centers were least available private health institutions at 0.1%. Home healthcare, remote care, telemedicine, family medicine, and long-term care were offered by 1.3%, 0.5%, 0.4%, and 0.1% of private health institutions respectively. Private hospitals accounted for 41.4% of total hospitals and private hospitals beds constituted 30.9% of Riyadh's total, with an average of 137.8 beds per hospital. Around 82% of private health institutions were in Riyadh city, with around 18% in peripheral provinces.

Conclusion

Private healthcare sector has witnessed substantial growth, primarily influenced by supply rather than demand dynamics. Incentives are essential to promote investment in Ministry of Health priorities.

Quasi‐static axial crushing of multi‐tubular foam‐filled carbon fiber reinforced composite structures

In automotive design, a key aspect in limiting injuries in the event of collision is the ability of vehicle's structures to absorb high quantities of energy. Recently, automobiles have been designed with materials such as carbon fiber‐reinforced polymers to replace the conventional metallic materials, to boost structural safety and fuel efficiency. In this study, various combinations of carbon fiber‐reinforced plastic and Kevlar‐reinforced polymer composite tubes were assembled to form multi‐tubular composites and their crushing properties were investigated under quasi‐static axial compression. A total of five different combinations were designed and tested. The results showed that the addition of intermediate tubing system in the hollow composite tubes significantly improved the load‐bearing and energy absorption capabilities of the composite tubes. In addition, these configurations were also filled with polyurethane (PU) foam. It was shown that, apart from specific energy absorption (SEA), all the other parameters, such as peak load, mean load, crushing force efficiency, and overall energy absorption ability, were enhanced with the addition of foam. The SEA parameter showed inconsistent behavior, and this was attributed to the weight addition caused by the addition of foam in the composite tubes.

Highlights

Exploring the effect of nanoclay addition on energy absorption capability of laterally loaded glass/epoxy composite tubes

The energy absorption capability of laterally loaded glass fiber reinforced polymer (GFRP) tubular components containing montmorillonite clay (MC) was explored in this article. GFRP components filled with 0, 1, 2, 3, and 4 wt% of MC were created using wet‐wrapping by hand lay‐up techniques. For the laterally loaded tubes, the crushing load and the energy absorption versus displacement responses were presented. In addition, deformation histories were tracked. The energy absorption analysis was carried out by evaluating the initial peak load (), total energy absorption, and specific absorbed energy. Also, a mathematical regression models were built to predict the energy absorption indicators. Furthermore, the optimal MC wt% is determined using a multi‐attribute decision making method called complex proportional assessment. Overall results demonstrated that the suggested GFRP tubes containing 4 wt% of MC exhibited unique energy absorption capability.

Highlights

Effect of Fiber Loading on Thermal Properties of Cellulosic Washingtonia Reinforced HDPE Biocomposites

In this research work, we aim to study the effect of the incorporation of vegetable fiber reinforcement on the thermo-mechanical and dynamic properties of a composite formed by a polymeric matrix reinforced with cellulosic fibers with the various Washingtonia fiber (WF) loadings (0%, 10%, 20%, and 30% by wt%) as reinforced material in high-density polyethylene (HDPE) Biocomposites to evaluate the optimum fiber loading of biocomposites. In addition, several characterization techniques (i.e., thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermal mechanical analysis (TMA)) were used to better understand the characteristics of the new composites prepared. With these techniques, we managed to verify the rigidity and thermal stability of the composites so elaborated, as well as the success of the polymer and the structural homogeneity of the obtained biocomposites. Hence, the biocomposite with the best ratio (HDPE/20WF) showed a loss modulus (E″) of 224 MPa, a storage modulus (E') of 2079 MPa, and a damping factor (Tanδ) of 0.270 to the glass transition (Tg) of 145 °C. In addition, thermomechanical analysis (TMA) of the biocomposite samples exhibited marginally higher Ts compared to the HDPE matrix. The best results were recorded with biocomposites with 20% WF, which showed better thermal properties. This composite material can be used as insulation in construction materials (buildings, false ceilings, walls, etc.).

Effect of Number of Tests on the Mechanical Characteristics of Agave sisalana Yarns for Composites Structures: Statistical Approach

A designer of sustainable biocomposite structures and natural ropes needs to have a high confidence interval (95% CI) for mechanical characteristics data of performance materials, yet qualities for plant-based fibers are very diverse. A comprehensive study of the elements that enhance the performance of biocomposites or sustainable ropes created from vegetable fibers is necessary. The current study included five groups with varying numbers (N) of tests of 20, 40, 60, 80, and 100 on the mechanical characteristics at room temperatures. The purpose of this study was to determine how changing N affects the mechanical properties of sisal yarn. These properties include its strength, Young's modulus, and deformation at rupture. A significance testing program including more than 100 tests was performed. Owing to the heterogeneity of the plant yarn, each group received more than 20 samples at a gauge length (GL) of 100 mm. The tensile strength characteristics of sisal yarns produced a wide range of findings, as is common for natural fibers, necessitating a statistical analysis. Its dispersion was explored and measured using the statistical methods. The Weibull distribution with two parameters and a prediction model with a 95% confidence level for maximum likelihood (ML) and least squares (LS) were used to investigate and quantify its dispersion.

Enhanced Open-Hole Strength and Toughness of Sandwich Carbon-Kevlar Woven Composite Laminates

Fiber-reinforced plastic composites are sensitive to holes, as they cut the main load-carrying member in the composite (fibers) and they induce out-of-plane stresses. In this study, we demonstrated notch sensitivity enhancement in a hybrid carbon/epoxy (CFRP) composite with a Kevlar core sandwich compared to monotonic CFRP and Kevlar composites. Open-hole tensile samples were cut using waterjet cutting at different width to diameter ratios and tested under tensile loading. We performed an open-hole tension (OHT) test to characterize the notch sensitivity of the composites via the comparison of the open-hole tensile strength and strain as well as the damage propagation (as monitored via CT scan). The results showed that hybrid laminate has lower notch sensitivity than CFRP and KFRP laminates because the strength reduction rate with hole size was lower. Moreover, this laminate showed no reduction in the failure strain by increasing the hole size up to 12 mm. At w/d = 6, the lowest drop in strength showed by the hybrid laminate was 65.4%, followed by the CFRP and KFRP laminates with 63.5% and 56.1%, respectively. For the specific strength, the hybrid laminate showed a 7% and 9% higher value as compared with CFRP and KFRP laminates, respectively. The enhancement in notch sensitivity was due to its progressive damage mode, which was initiated via delamination at the Kevlar-carbon interface, followed by matrix cracking and fiber breakage in the core layers. Finally, matrix cracking and fiber breakage occurred in the CFRP face sheet layers. The specific strength (normalized strength and strain to density) and strain were larger for the hybrid than the CFRP and KFRP laminates due to the lower density of Kevlar fibers and the progressive damage modes which delayed the final failure of the hybrid composite.

Mechanical, thermal, viscoelastic and hydrophobicity behavior of complex grape stalk lignin and bamboo fiber reinforced polyester composite

This work aims to investigate the degradation stability of bamboo fiber-reinforced polyester composite toughened with complex lignin biopolymer derived from the waste grape stalks. The properties like mechanical, wear, thermal, DMA, and hydrophobic were studied after the addition of lignin and analyzed how the lignin addition influenced these properties. Prior to composite making the fiber and lignin was treated with silane. According to the results obtained incorporating 40 vol% of bamboo fiber into the polyester resin, the mechanical and wear properties enhanced. Further, the composite containing 2.0 vol% of lignin has maximum tensile strength, tensile modulus, flexural strength, flexural modulus, and ILSS. Similarly, the composite designation having 4 vol% lignin revealed the improved wear loss stability of 0.007 mm³/Nm (sp. wear rate). The highest degradation temperature reported for composite designation UBL4 it was 520 °C, with a relatively lesser weight loss of 19 %. Likewise, the highest storage modulus was about 4.5 GPa, and the lowest loss factor was up to 0.3 for the composite designation UBL4. The contact angle investigation revealed that all composite designations are not fall below 70°, indicating their hydrophobic stability. These composites with enhanced stability against load, heat and water could be utilized in the industrial, automotive and defense sectors where high performance outcomes are required.

Study on Flexural Behavior of Glass Fiber Reinforced Plastic Sandwich Composites Using Liquid Thermoplastic Resin

Experimental and numerical studies of composite sandwich structures are warranted to reap the benefits of these materials when they are well designed. In the current research, new liquid thermoplastic and epoxy resins were used to fabricate four composite sandwich panels with two additional foam types and different densities in the wind turbine industry. A comprehensive comparison of three-point bending test results was made. Finite-element-based simulations using the ABAQUS program with Hashin’s damage criterion were conducted to examine the failure behavior of the GFRP sandwich composites. The flexural behavior of the glass-fiber-reinforced plastic (GFRP) sandwich panels was investigated and compared with the experiments. The results show that the GF/PVC/Elium composite panel gives the highest load absorption, flexural strength, flexural modulus, core shear ultimate strength, and facing stress due to effect of the core foam and resin types. For the PVC foam core sandwich panel, using thermoplastic resin increased the flexural strength by 18% compared to that of the epoxy resin. The simulation results show excellent agreement between the finite-element-predicted failure loads and the experimental results.

Bearing Properties of CFRP Composite Laminates Containing Spread-Tow Thin-Plies

With the development of spread-tow, thin-ply technology, ultra-thin composite laminates could be produced. Composite bolted joints are commonly used on aircraft’s load-bearing structures and are considered the main cause of stress concentration. The aim of this research is to investigate the bolted joint behavior of composite laminates that combine thin-plies and conventional thick-plies in a predetermined stacking sequence. The impact of thin-ply placement within the stack on bearing strength, including the onset of damages, is examined. The work involves mechanical tests and fractographic activities to understand the damage mechanisms of the plies and their interactions, and its reflections on the bearing load capacity of the joint for double-lap bolted joints. The results showed an improvement in the bearing strength of up to 19% by inserting the thin-plies inside the laminate. The visual examination of the specimens showed a bearing damage mode for all the tested specimens. The computed tomography scans showed damage mechanisms that mostly occurred with the normal plies, rather than breaking the thin-plies. For the specimens of traditional plies, delaminations were noticed at most of the interfaces. For the one with a block of thin-plies in the middle, all the delaminations were forced to the surface layers with an extra large size. Forspecimens with distributed thin-plies, a higher number of smaller delaminations was recognized.

Enhancing Impact Energy Absorption, Flexural and Crash Performance Properties of Automotive Composite Laminates by Adjusting the Stacking Sequences Layup

In response to the high demand for light automotive, manufacturers are showing a vital interest in replacing heavy metallic components with composite materials that exhibit unparalleled strength-to-weight ratios and excellent properties. Unidirectional carbon/epoxy prepreg was suitable for automotive applications such as the front part of the vehicle (hood) due to its excellent crash performance. In this study, UD carbon/epoxy prepreg with 70% and 30% volume fraction of reinforcement and resin, respectively, was used to fabricate the composite laminates. The responses of different three stacking sequences of automotive composite laminates to low-velocity impact damage and flexural and crash performance properties were investigated. Three-point bending and drop-weight impact tests were carried out to determine the flexural modulus, strength, and impact damage behavior of selected materials. Optical microscopy analysis was used to identify the failure modes in the composites. Scanning electron microscopy (SEM) and C-scan non-destructive methods were utilized to explore the fractures in the composites after impact tests. Moreover, the performance index and absorbed energy of the tested structures were studied. The results showed that the flexural strength and modulus of automotive composite laminates strongly depended on the stacking sequence. The highest crash resistance was noticed in the laminate with a stacking sequence of [[0, 90, 45, -45]₂, 0, 90]_S. Therefore, the fabrication of a composite laminate structure enhanced by selected stacking sequences is an excellent way to improve the crash performance properties of automotive composite structures.

Denial attitude towards COVID-19 among general population in Saudi Arabia

Introduction

During the current crisis of COVID 19, recent studies evident that it has a huge impact on public mental health and individuals’ behavior.

Objectives

Our study aimed to estimate the prevalence of high denial attitude towards the emerging pandemic of COVID 19 among the general population of Saudi Arabia.

Methods

A cross-sectional online survey was conducted from April 3, 2020 to May 5, 2020. All participants (N= 1817) were asked to complete an online questionnaire survey that included socio-demographic and other variables, and Denial Attitude Questionnaire towards COVID-19 pandemic (DAQ-COVID-19).

Results

High denial attitude was prevalent among 728 (40.1 %) of the participants. It was associated with old age, being married, having low educational level, working in a non-medical professions, do not have a past history of infectious diseases, spending less than one hour following COVID-19 news, satisfied with the government procedures for COVID-19, and highly depressed and anxious respondents, where p-values were 0.001, 0.019, <0.001, 0.027, <0.001, <0.001, 0.004, 0.008, and 0.026; respectively.

Conclusions

About two out of five participants had high denial attitude. To our knowledge, the current study is the first study that tries to evaluate a high denial attitude during the initial COVID 19 outbreaks, especially in Saudi Arabia. However, further exploration in this field is needed. We suggest conducting such a study at the end of the current pandemic or in the second wave of the outbreak