An immense problem affecting environmental pollution is the increase of waste tyre vehicles. In an attempt to decrease the magnitude of this issue, crumb rubber modifier (CRM) obtained from waste tyre rubber has gained interest in asphalt reinforcement. The use of crumb rubber in the reinforcement of asphalt is considered as a smart solution for sustainable development by reusing waste materials, and it is believed that crumb rubber modifier (CRM) could be an alternative polymer material in improving hot mix asphalt performance properties. In this paper, a critical review on the use of crumb rubber in reinforcement of asphalt pavement will be presented and discussed. It will also include a review on the effects of CRM on the stiffness, rutting, and fatigue resistance of road pavement construction.
In this study, a magnetic/polyetherimide-acrylonitrile composite nanofiber membrane with effective adsorption of nickel ions in an aqueous solution was created using a simple electrospinning method. Iron oxide nanoparticles (NPs) were stirred and ultrasonically dispersed into a polyetherimide-acrylonitrile solution to create a homogenous NPs suspension, which was placed in an electrospinning machine to produce a uniform and smooth nanofiber composite membrane. Nanoparticle incorporation into this membrane was confirmed using scanning electron microscope, energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and NPs aqueous stability from a leaching test. The high adsorption capability of the membrane on nickel ions was attributed to the combination of magnetic NPs, polyetherimide-acrylonitrile matrix, and the nanostructure of the membrane. A membrane containing magnetic NPs demonstrated the maximum adsorption capabilities (102 mg/g) of nickel ions in an aqueous solution. Various kinetic and isotherm models were applied to understand the adsorption behavior, such as pseudo-second-order kinetic and Langmuir isotherm models. A polyetherimide-acrylonitrile composite nanofiber membrane containing magnetic NPs could be used as an environmentally friendly and nontoxic adsorbent for the removal of nickel ions in an aqueous medium due to its ease of preparation and use and stability in aqueous mediums.
The advent of antimicrobials-resistant (AMR), including colistin-resistant bacteria, poses a significant challenge to animal and human health, food safety, socio-economic growth, and the global environment. This study aimed to ascertain the colistin resistance prevalence and molecular mechanisms of colistin resistance in Enterobacteriaceae. The colistin resistance was determined using broth microdilution assay, PCR; and Sanger sequencing of mcr genes responsible for colistin resistance in Enterobacteriaceae (n = 627), including Escherichia coli (436), Salmonella spp. (n = 140), and Klebsiella pneumoniae (n = 51), obtained from chicken and chicken meats. Out of 627 Enterobacteriaceae, 8.6% of isolates exhibited colistin resistance phenotypically. Among these colistin resistant isolates, 9.3% (n = 37) were isolated from chicken meat, 7.2% (n = 11) from the cloacal swab of chicken and 7.9% (n = 6) from the litter samples. Overall, 12.96% of colistin-resistant isolates were positive with mcr genes, in which mcr-1 and mcr-5 genes were determined in 11.11% and 1.85% of colistin-resistant isolates, respectively. The E. coli isolates obtained from chicken meats, cloacal swabs and litter samples were found positive for mcr-1, and Salmonella spp. originated from the chicken meat sample was observed with mcr-5, whereas no mcr genes were observed in K. pneumoniae strains isolated from any of the collected samples. The other colistin resistance genes, including mcr-2, mcr-3, mcr-4, mcr-6, mcr-7, mcr-8, mcr-9, and mcr-10 were not detected in the studied samples. The mcr-1 and mcr-5 genes were sequenced and found to be 100% identical to the mcr-1 and mcr-5 gene sequences available in the NCBI database. This is the first report of colistin resistance mcr-5 gene in Malaysia which could portend the emergence of mcr-5 harboring bacterial strains for infection. Further studies are needed to characterize the mr-5 harbouring bacteria for the determination of plasmid associated with mcr-5 gene.
Electrocatalytic water splitting is a promising alternative to produce high purity hydrogen gas as the green substitute for renewable energy. Thus, development of electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are vital to improve the efficiency of the water splitting process particularly based on transition metals which has been explored extensively to replace the highly active electrocatalytic activity of the iridium and ruthenium metals-based electrocatalysts. In situ growth of the material on a conductive substrate has also been proven to have the capability to lower down the overpotential value significantly. On top of that, the presence of substrate has given a massive impact on the morphology of the electrocatalyst. Among the conductive substrates that have been widely explored in the field of electrochemistry are the copper based substrates mainly copper foam, copper foil and copper mesh. Copper-based substrates possess unique properties such as low in cost, high tensile strength, excellent conductor of heat and electricity, ultraporous with well-integrated hierarchical structure and non-corrosive in nature. In this review, the recent advancements of HER and OER electrocatalysts grown on copper-based substrates has been critically discussed, focusing on their morphology, design, and preparation methods of the nanoarrays.
A pavement structure consists of several layers for the primary purpose of transmitting and distributing traffic loads to the subgrade. Rutting is one form of pavement distresses that may influence the performance of road pavements. Geosynthetics is one type of synthetic materials utilized for improving the performance of pavements against rutting. Various studies have been conducted on using different geosynthetic materials in pavement structures by different researchers. One of the practices is a reinforcing material in asphalt pavements. This paper intends to present and discuss the discoveries from some of the studies on utilizing geosynthetics in flexible pavements as reinforcement against permanent deformation (rutting).
Semi-flexible pavement surfacing is a composite pavement that utilizes the porous pavement structure of the flexible bituminous pavement, which is subsequently grouted with appropriate cementitious materials. This study aims to investigate the compressive strength, flexural strength, and workability performance of cementitious grout. The grout mixtures are designed to achieve high strength and maintain flow properties in order to allow the cement slurries to infiltrate easily through unfilled compacted skeletons. A paired-sample t-test was carried out to find out whether water/cement ratio, SP percentages, and use of silica fume influence the cementitious grout performance. The findings showed that the replacement of 5% silica fume with an adequate amount of superplasticizer and water/cement ratio was beneficial in improving the properties of the cementitious grout.
This study investigates the Covid-19 driven indiscriminate disposal of PPE wastes (mostly face mask and medical wastes) in Chittagong metropolitan area (CMA), Bangladesh. Based on the field monitoring, the mean PPE density (PPE/m2± SD) was calculated to be 0.0226 ± 0.0145, 0.0164 ± 0.0122, and 0.0110 ± 0.00863 for July, August, and September 2021, respectively (during the peak time of Covid-19 in Bangladesh). Moreover, gross information on PPE waste generation in the city was calculated using several parameters such as population density, face mask acceptance rate by urban population, total Covid-19 confirmed cases, quarantined and isolated patients, corresponding medical waste generation rate (kg/bed/day), etc. Moreover, the waste generated due to face mask and other PPEs in the CMA during the whole Covid-19 period (April 4, 2020 to September 5, 2021) were calculated to be 64183.03 and 128695.75 tons, respectively. It has been observed that the negligence of general people, lack of awareness about environmental pollution, and poor municipal waste management practices are the root causes for the contamination of the dwelling environment by PPE wastes. As a result, new challenges have emerged in solid waste management, which necessitates the development of an appropriate waste management strategy. The ultimate policies and strategies may help to achieve the SDG goals 3, 6, 11, 12, 13, and 15, and increase public perception on the use and subsequent disposal of PPEs, especially face masks.
The present study focuses on the indiscriminate disposal of personal protective equipment (PPEs) and resulting environmental contamination during the 3rd wave of COVID-19-driven global pandemic in the Chittagong metropolitan area, Bangladesh. Because of the very high rate of infection by the delta variant of this virus, the use of PPEs by the public is increased significantly to protect the ingestion/inhalation of respiratory droplets in the air. However, it is a matter of solicitude that general people throw away the PPEs to the dwelling environment unconsciously. With the increase of inappropriate disposal of PPEs (i.e., mostly the disposable face masks made from plastic microfibers), the possibility of transmission of the virus to the general public cannot be neglected completely. This is because this virus can survive for several days on the inanimate matter like plastics and fibers. At the same time, the result of environmental contamination by microplastic/microfiber has been widespread which eventually creates the worst impact on ecosystems and organisms. The present results may help to increase public perception of the use and subsequent disposal of PPEs, especially the face masks.
Xylitol production by bioconversion of xylose can be economically interesting if the raw material can be recovered from a cheap lignocellulosic biomass (LCB). Meranti wood sawdust (MWS) is a renewable and low-cost LCB that can be used as a promising and economic source of xylose, a starting raw material for the manufacture of several specialty chemicals, especially xylitol. This study aimed to optimize the hydrolysis process of MWS and to determine the influence of temperature, H2SO4 concentration, and residence time on xylose release and on by-product formation (glucose, arabinose, acetic acid, furfural, hydroxymethylfurfural (HMF), and lignin degradation products (LDPs)). Batch hydrolysis was conducted under various operating conditions, and response surface methodology was adopted to achieve the highest xylose yield. Xylose production was highly affected by temperature, acid concentration, and residence time. The optimum temperature, acid concentration, and time were determined to be 124 °C, 3.26 %, and 80 min, respectively. Under these optimum conditions, xylose yield and selectivity were attained at 90.6 % and 4.05 g/g, respectively.
A growing concern for public transit is its inability to shift passenger's mode from private to public transport. In order to overcome this problem, a more developed feeder bus network and matched schedules will play important roles. The present paper aims to review some of the studies performed on Feeder Bus Network Design and Scheduling Problem (FNDSP) based on three distinctive parts of the FNDSP setup, namely, problem description, problem characteristics, and solution approaches. The problems consist of different subproblems including data preparation, feeder bus network design, route generation, and feeder bus scheduling. Subsequently, descriptive analysis and classification of previous works are presented to highlight the main characteristics and solution methods. Finally, some of the issues and trends for future research are identified. This paper is targeted at dealing with the FNDSP to exhibit strategic and tactical goals and also contributes to the unification of the field which might be a useful complement to the few existing reviews.
Uncontrolled stormwater runoff not only creates drainage problems and flash floods but also presents a considerable threat to water quality and the environment. These problems can, to a large extent, be reduced by a type of stormwater management approach employing permeable pavement systems (PPS) in urban, industrial and commercial areas, where frequent problems are caused by intense undrained stormwater. PPS could be an efficient solution for sustainable drainage systems, and control water security as well as renewable energy in certain cases. Considerable research has been conducted on the function of PPS and their improvement to ensure sustainable drainage systems and water quality. This paper presents a review of the use of permeable pavement for different purposes. The paper focuses on drainage systems and stormwater runoff quality from roads, driveways, rooftops and parking lots. PPS are very effective for stormwater management and water reuse. Moreover, geotextiles provide additional facilities to reduce the pollutants from infiltrate runoff into the ground, creating a suitable environment for the biodegradation process. Furthermore, recently, ground source heat pumps and PPS have been found to be an excellent combination for sustainable renewable energy. In addition, this study has identified several gaps in the present state of knowledge on PPS and indicates some research needs for future consideration.
Today, rapid economic and industrial growth generates increasing amounts of waste materials such as waste tyre rubber. Attempts to inspire a green technology which is more environmentally friendly that can produce economic value are a major consideration in the utilization of waste materials. The aim of this study is to evaluate the effect of waste tyre rubber (crumb rubber modifier (CRM)), in stone mastic asphalt (SMA 20) performance. The virgin bitumen (80/100) penetration grade was used, modified with crumb rubber at four different modification levels, namely, 6%, 12%, 16%, and 20% by weight of the bitumen. The testing undertaken on the asphalt mix comprises the indirect tensile (dynamic stiffness), dynamic creep, and wheel tracking tests. By the experimentation, the appropriate amount of CRM was found to be 16% by weight of bitumen. The results show that the addition of CRM into the mixture has an obvious significant effect on the performance properties of SMA which could improve the mixture's resistance against permanent deformation. Further, higher correlation coefficient was obtained between the rut depth and permanent strain as compared to resilient modulus; thus dynamic creep test might be a more reliable test in evaluating the rut resistance of asphalt mixture.
The ageing of the bitumen during storage, mixing, transport and laying on the road, as well as in service life, are the most important problems presented by the use of bitumen in pavements. This paper investigates the possibility of using waste cooking oil (WCO), which is a waste material that pollutes landfills and rivers, as an alternative natural rejuvenating agent for aged bitumen to a condition that resembles the original bitumen. With this target, the physical and chemical properties of the original bitumen, aged bitumen and rejuvenated bitumen were measured and compared by the bitumen binder tests - softening point, penetration, Brookfield viscosity, dynamic shear rheometer and Fourier transform infrared spectroscopy. In addition, the behaviour of the WCO rejuvenated bitumen is investigated and compared with virgin bitumen after using the rolling thin film oven ageing process. In general, the results showed that using 3-4% of WCO the aged bitumen group 40/50 was rejuvenated to a condition that closely resembled the physical, rheological properties of the original bitumen (80/100), however, there was a difference in the tendency to ageing between the WCO rejuvenated bitumen and the virgin bitumen during mixing, transport and laying on the road.
Most highly motorized countries in the world have implemented different speed limits for light weight and heavy weight vehicles. The heavy vehicle speed limit is usually chosen to be lower than that of passenger cars due to the difficulty for the drivers to safely maneuver the heavy vehicle at high speed and greater impact during a crash. However, in many cases, the speed limit for heavy vehicle is set by only considering the vehicle size or category, mostly due to simplicity in enforcement. In this study, traffic and vehicular data for all vehicle types were collected using a weigh-in-motion system installed at Federal Route 54 in Malaysia. The first finding from the data showed that the weight variation for each vehicle category is considerable. Therefore, the effect of gross vehicle weight (GVW) and category of heavy vehicle on free flow speed and their interaction were analyzed using statistical techniques. Empirical analysis results showed that statistically for each type of heavy vehicle, there was a significant relationship between free flow speed of a heavy vehicle and GVW. Specifically, the results suggest that the mean and variance of free flow speed decrease with an increase GVW by the amount unrelated to size and shape for all GVW range. Then, based on the 85th percentile principle, the study proposed a new concept for setting the speed limit for heavy vehicle by incorporating GVW where a different speed limit is imposed to the heavy vehicle, not only based on vehicle classification, but also according to its GVW.
Road distress results in high maintenance costs. However, increased understandings of asphalt behaviour and properties coupled with technological developments have allowed paving technologists to examine the benefits of introducing additives and modifiers. As a result, polymers have become extremely popular as modifiers to improve the performance of the asphalt mix. This study investigates the performance characteristics of epoxidized natural rubber (ENR)-modified hot-mix asphalt. Tests were conducted using ENR-asphalt mixes prepared using the wet process. Mechanical testing on the ENR-asphalt mixes showed that the resilient modulus of the mixes was greatly affected by testing temperature and frequency. On the other hand, although rutting performance decreased at high temperatures because of the increased elasticity of the ENR-asphalt mixes, fatigue performance improved at intermediate temperatures as compared to the base mix. However, durability tests indicated that the ENR-asphalt mixes were slightly susceptible to the presence of moisture. In conclusion, the performance of asphalt pavement can be enhanced by incorporating ENR as a modifier to counter major road distress.
Toxoplasma gondii is an obligate intracellular protozoon which causes toxoplasmosis, an important zoonotic disease that is endemic worldwide. Common sources of T. gondii infection in humans are food or water contaminated with oocysts and raw or undercooked meat with cysts. In animals, common sources of infection include feed, water, or litter contaminated with oocysts. The diagnosis and molecular characterization of T. gondii infection in humans and animals is crucial due to public and veterinary health importance. Various traditional and serological methods have been used in clinical practice for toxoplasmosis diagnosis, but interpreting the results remains a challenge. Several molecular techniques have also been used for the detection and genetic characterization of T. gondii , but primarily in research settings. In this paper, we review the techniques that are currently used for the diagnosis and genetic characterization of T. gondii in humans and animals, along with their advantages and disadvantages. The techniques reviewed have laid the groundwork for the future development of more effective and precise detection and characterization of T. gondii . These advances will contribute to a better understanding of epidemiology, prevention and control of toxoplasmosis. Thus, this review would be of particular interest to clinical physicians, veterinarians and researchers.
Expression levels of the NAC gene family were studied in rice infected with Rice dwarf virus (RDV), Rice black-streaked dwarf virus (RBSDV), Rice grassy stunt virus (RGSV), Rice ragged stunt virus (RRSV), and Rice transitory yellowing virus (RTYV). Microarray analysis showed that 75 (68%) OsNAC genes were differentially regulated during infection with RDV, RBSDV, RGSV, and RRSV compared with the control. The number of OsNAC genes up-regulated was highest during RGSV infection, while the lowest number was found during RTYV infection. These phenomena correlate with the severity of the syndromes induced by the virus infections. Most of the genes in the NAC subgroups NAC22, SND, ONAC2, ANAC34, and ONAC3 were down-regulated for all virus infections. These OsNAC genes might be related to the health stage maintenance of the host plants. Interestingly, most of the genes in the subgroups TIP and SNAC were more highly expressed during RBSDV and RGSV infections. These results suggested that OsNAC genes might be related to the responses induced by the virus infection. All of the genes assigned to the TIP subgroups were highly expressed during RGSV infection when compared with the control. For RDV infection, the number of activated genes was greatest during infection with the S-strain, followed by the D84-strain and the O-strain, with seven OsNAC genes up-regulated during infection by all three strains. The Os12g03050 and Os11g05614 genes showed higher expression during infection with four of the five viruses, and Os11g03310, Os11g03370, and Os07g37920 genes showed high expression during at least three viral infections. We identified some duplicate genes that are classified as neofunctional and subfunctional according to their expression levels in different viral infections. A number of putative cis-elements were identified, which may help to clarify the function of these key genes in network pathways.
Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.
Recently, as a supplement of cement, the utilization of pozzolanic materials in cement and concrete manufacturing has increased significantly. This study investigates the scope to use pozzolanic wastes (slag, palm oil fuel ash and rice husk ash) as an alkali activated binder (AAB) that can be used as an alternative to cement. To activate these materials, sodium hydroxide solution was used at 1.0, 2.5 and 5.0 molar concentration added into the mortar, separately. The required solution was used to maintain the flow of mortar at 110% ± 5%. The consistency and setting time of the AAB-paste were determined. Mortar was tested for its flow, compressive strength, porosity, water absorption and thermal resistance (heating at 700 °C) and investigated by scanning electron microscopy. The experimental results reveal that AAB-mortar exhibits less flow than that of ordinary Portland cement (OPC). Surprisingly, AAB-mortars (with 2.5 molar solution) achieved a compressive strength of 34.3 MPa at 28 days, while OPC shows that of 43.9 MPa under the same conditions. Although water absorption and porosity of the AAB-mortar are slightly high, it shows excellent thermal resistance compared to OPC. Therefore, based on the test results, it can be concluded that in the presence of a chemical activator, the aforementioned pozzolans can be used as an alternative material for cement.