Analyses of pig genomes provide insight into porcine demography and evolution

For 10,000 years pigs and humans have shared a close and complex relationship. From domestication to modern breeding practices, humans have shaped the genomes of domestic pigs. Here we present the assembly and analysis of the genome sequence of a female domestic Duroc pig (Sus scrofa) and a comparison with the genomes of wild and domestic pigs from Europe and Asia. Wild pigs emerged in South East Asia and subsequently spread across Eurasia. Our results reveal a deep phylogenetic split between European and Asian wild boars ∼1 million years ago, and a selective sweep analysis indicates selection on genes involved in RNA processing and regulation. Genes associated with immune response and olfaction exhibit fast evolution. Pigs have the largest repertoire of functional olfactory receptor genes, reflecting the importance of smell in this scavenging animal. The pig genome sequence provides an important resource for further improvements of this important livestock species, and our identification of many putative disease-causing variants extends the potential of the pig as a biomedical model

An investigation into the design for rideability of small wheel single-track bicycles and e-scooters

Over the years, bicycles evolved as one of the most efficient means of transportation. A plethora of bicycles design is available in the market. However, the principal designs and most notably the wheel size has changed little ever since the evolution of the safety bicycles. The bicycles with bigger wheels (26-inch - 29-inch in diameter) have been the most common design and remained dominant over a long period. However, the desire for compact and portable means of transportation led to the invention of the small wheels and small-wheeled personal mobility devices (PMDs) like folding bicycles, kick scooters, e-scooters, Segway and so on. In recent decades, rapid urbanisation has created one of the biggest challenges in the transportation system: the first- and last-mile problem. Today, many modern cities, including Singapore, are restructuring their transport infrastructure to allow greater use of these bicycles and e-scooters to smoothen the first and last mile problem in urban mobility. Small wheel (≤20-inch diameter) bicycles and e-scooters are becoming increasingly popular in such modern cities because of their compactness, manoeuvrability and portability. However, the rideability (i.e. stability and handling) of these small wheelers has often been questioned. It is a well-known fact that the small wheel bicycles and e-scooters do not ride as good as its big wheel counterparts and their ride is often described as “less-stable”, “wobbly” and “twitchy”. Most believed that small wheelers are inherently unstable because of the smaller wheel size. Nonetheless, there has not been any comprehensive investigation to quantitatively compare the performance of the different wheel sized PMDs and suggest possible solutions to improve the current designs of small wheelers. On top of that, the growing popularity and the advent of the micro-mobility in last few years has also brought forth an alarming increase in PMDs related accidents and injuries. Therefore, there is a rising concern about the safety of the riders who use these small wheelers. A comprehensive investigation on the performance of the different wheel sized PMDs is the major objective of this study. The design philosophies, methodologies and available guidelines were analysed for different wheel sized PMDs. The rideability of 20-inch, 16-inch and 12-inch bicycles and 8-inch e-scooters have been studied and compared with that of 26-inch referenced big wheel bicycle based on the dynamic self-stability and handling characteristics. The inherent stability characteristics have been analysed based on the eigenvalues, self-stability velocity range and, the steer and lean oscillation behaviour. Furthermore, the obstacle rollover tendency and steady-state turning performances were considered for handling analysis. Finally, an improved and cost-effective methodology has been established to enhance the performance of small wheel PMDs by incorporating the dynamic models into the design process. Simple front steering design guidelines were developed using the improved design methodology. Prototype small wheel bicycles were fabricated, and their performance was compared analytically and experimentally to the current designs of big and small wheel bicycles. The analysis of current design practice revealed that most of the available design guidelines were developed for big wheel bicycles, and no specific design guidelines were found for designing the small wheelers. Therefore, a strong influence of big wheel bicycles’ design was observed in the designs of small wheel PMDs. Furthermore, the study has successfully confirmed that the current designs of the small wheel PMDs are indeed less stable and difficult to ride at normal speed. The analysis suggested that the available design guidelines for big wheel bicycles do not translate directly to the small wheelers and the performance discrepancy in big wheelers and small wheelers is not because of the smaller wheel sized, as per se but, lack of adequate design guidelines for small wheelers that resulted in lesser stability and poor readability. A good agreement was observed between the experimental and the analytical results for prototype bicycles developed using proposed design guidelines and the current bicycle designs. Therefore, the proposed design guidelines were successfully validated, both analytically and experimentally. Lastly, it has been successfully shown that the current designs of small wheel PMDs are yet to be optimised and performance could be improved by carefully tuning their design configurations such as front steering geometry and mass distribution.Doctor of Philosoph

Development of an improved design methodology and front steering design guideline for small-wheel bicycles for better stability and performance

The maneuverability and compactness of small-wheel and folding bicycles are greatly appreciated. Nonetheless, the performance of these small-wheel bicycles as compared to the big-wheel bicycles has always been questioned. They are often blamed for being less stable, wobbly, or twitchy. It is still unclear how the performance of the small-wheel bicycle designs can be improved. Both small- and big-wheel bicycles are designed with similar ergonomics; therefore, the focus has been on the front steering design. The steering design parameters of 91 big-wheel and 27 small-wheel bicycles were compared, bearing in mind the available front steering design guidelines to understand: (1) the influence of big-wheel bicycle’s frame design on small-wheel bicycles and (2) most common range of design parameters used in current bicycle designs. The analysis showed a strong influence of current big-wheel bicycle design practice on front frame parameter selection of small-wheel bicycles. Furthermore, the self-stability comparison over the most common design range confirmed the lesser stability in the current small-wheel bicycle designs at normal riding speed. However, it was also found that the lesser stability was not the result of small wheels per se, but rather owing to an inadequacy in the current design approach to addressing the complex influence of reducing wheel size and bicycle frame design on its stability and performance. Therefore, an improved design methodology was adopted by incorporating the bicycle dynamics into the current design approach and the front steering design guidelines for small-wheel bicycles have been developed. The guidelines contradict the current small-wheel bicycle design practice, as they recommend steeper headtube angles for small-wheel bicycles. The guidelines were validated with good agreement between the theoretical and experimental results on two prototype 20-inch-wheel bicycles having counter-intuitive steering geometry

Development of hybrid magnetorheological elastomers by 3D printing

Intelligent or smart materials have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as temperature, pH, electric or magnetic fields, etc. Magnetorheological (MR) materials are a class of smart materials whose properties can be varied by applying an external magnetic field. In this work, the possibility of employing a suitable 3D printing technology for the development of one of the smart MR materials, the magnetorheological elastomer (MRE) has been explored. In order to achieve such 3D printing, a multi-material printing is implemented, where a controlled volume of MR fluid is encapsulated within an elastomer matrix in the layer-by-layer fashion. The choice of printing materials determines the final structure of the 3D printed hybrid MR elastomer. Printing with a vulcanizing MR suspension produces the solid MR structure inside the elastomer matrix while printing with a non-vulcanizing MR suspension (MR fluid) results in the structures that the MR fluid is encapsulated inside the elastomer matrix. The 3D printability of different materials has been studied by measuring their rheological properties and we found that the highly shear thinning and thixotropic properties are important for 3D printability. The quality of the printed filaments strongly depends on the key printing parameters such as extrusion pressure, initial height and feed rate. The experimental results from the forced vibration testing show that the 3D printed MR elastomers could change their elastic and damping properties when exposed to the external magnetic field. Furthermore, the 3D printed MR elastomer also exhibits the anisotropic behavior when the direction of the magnetic field is changed with respect to the orientation of the printed filaments. This study has demonstrated that the 3D printing is viable for fabrication of hybrid MR elastomers with controlled structures of magnetic particles or MR fluids.MOE (Min. of Education, S’pore

A hybrid magnetorheological elastomer developed by encapsulation of magnetorheological fluid

A new hybrid MR elastomer was fabricated by encapsulating a magnetorheological fluid (MR fluid) within a UV-curable silicone elastomer. A strong magneto-deformation effect was observed where the hybrid MR elastomer changed its shape in the presence of a magnetic field. Furthermore, when a moderately strong magnetic field was applied, the elastic and damping properties of the hybrid MR elastomer changed obviously. The magnetic field strength, strain amplitude, strain rate, preload, and orientation of magnetic flux direction affected the behavior of the new hybrid MR elastomer. The hybrid MR elastomer also exhibited a higher MR effect when compared with conventional MR elastomer. The investigation also found that the combination of magnetic field strength and preload highly influenced the hybrid MR elastomer behavior. This MR fluid-encapsulated elastomer is expected to be a potential candidate for the tunable spring-damper element as well soft actuators.MOE (Min. of Education, S’pore

Dot-patterned hybrid magnetorheological elastomer developed by 3D printing

This article presents the development of dot-patterned magnetorheological (MR) elastomers (MREs) via 3D printing technology and their magnetorheological characterization. The 3D printed MR elastomer consists of three different materials; magnetic particles, magnetic particles carrier medium, and an elastomer. In such 3D printing, a controlled volume of MR fluid is encapsulated layer-by-layer within the elastomer matrix. The capability of 3D printing technology has been successfully demonstrated by developing the various dot patterns MR elastomers namely isotropic, anisotropic and configurations inspired from basic crystal structures such as BCC and FCC. The magneto-mechanical properties of such 3D printed MR elastomers (3DP-MREs) are studied using a cyclic compression and through a forced vibration testing. In the presence of a magnetic field, a clear change in stiffness of 3DP-MREs has been achieved. Moreover, the anisotropic behavior of 3DP-MREs has also been demonstrated. The experimental results suggested that the 3D printing method makes it possible to develop various structured MREs even without applying a magnetic field during the fabrication process.Ministry of Education (MOE)This work was supported by the Academic Research Funds (RG189/ 14) from the Ministry of Education, Singapore

Magnetic circuit analysis to obtain the magnetic permeability of magnetorheological elastomers

The magnetic permeability of magnetorheological elastomers must be known for their long-term use in the actual engineering systems. In this article, the magnetic permeability of both isotropic and anisotropic magnetorheological elastomers has been determined using a new method. The magnetic induction was measured and a closed magnetic circuit analysis was carried out to obtain the magnetic permeability of magnetorheological elastomers for both isotropic and anisotropic magnetorheological elastomers with 10%–50% volume concentration of carbonyl iron particles. The magnetic permeability was increased with increasing particle concentration for both isotropic and anisotropic magnetorheological elastomers as we could expect. The isotropic permeability is always lower than the anisotropic permeability. The maximum relative permeability value of 6.6 was obtained for 50% particle volume concentration. The experimental results also show a good agreement with theoretical predictions and previous investigations.MOE (Min. of Education, S’pore

Health literacy and associated factors among undergraduates: A university-based cross-sectional study in Nepal.

Health literacy is one of the most critical aspects of health promotion. Limited health literacy is also accounted for adverse health outcomes and a huge financial burden on society. However, a gap exists in the level of health literacy, especially among undergraduates. This study aimed to assess the levels of health literacy and its socio-demographic determinants among undergraduate students of Tribhuvan University, Nepal. A web-based cross-sectional survey was conducted among 469 undergraduate students from five institutes of Tribhuvan University, Nepal. The 16-item short version of the European Health Literacy Survey Questionnaire (HLS-EU-Q16) was used to measure students' health literacy levels. Associated factors were examined using Chi-square tests followed by multivariate logistic regression analyses at the level of significance of 0.05. Nearly 61% of students were found to have limited health literacy (24.5% had "inadequate" and 36.3% had "problematic" health literacy). Female students (aOR = 1.6, 95% CI: 1.1-2.5), students from non-health related majors (aOR = 1.9, 95% CI: 1.2-3.0), students with unsatisfactory health status (aOR = 2.8, 95% CI: 1.7-4.5), students with poor financial status (aOR = 2.9, 95% CI: 1.2-6.8) and students with low self-esteem (aOR = 2.5, 95% CI: 1.5-4.1) were significantly more likely to have limited health literacy. The majority of the undergraduates were found to have limited health literacy. Gender, sector of study, self-rated health status, self-rated financial status, and self-esteem were significantly associated with limited health literacy. This study indicates university students should not be assumed to be health-literate and interventions to improve students' health literacy especially for those whose majors are not health-related should be implemented. Further studies using a longer version of the health literacy survey questionnaire and qualitative methods to explore more on determinants of health literacy are recommended

Vibration Analysis of the Third Rail Structure of a Mass Rapid Transit System with Structural Defects

The third rail is a critical piece of railway infrastructure that provides a continuous supply of electricity to power mass rapid transit trains. The vibration of the third rail may excite different resonant modes and affect its structural integrity and reliability by degrading the mechanical properties leading to the damaged or missing structural components. This paper examines vibrational characteristics of the third rail of Singapore Mass Rapid Transit system with damaged and missing structural components. Using the mathematical model, the first five, pin-to-pin modes of vibration and natural frequencies were identified and compared with modal and harmonic response obtained from ANSYS finite element models. A good agreement was observed between the analytical and numerical solutions. The study was further extended to study the sagging of the third rail due to structural failure and its impact on collector shoes. It was found that the structural defects could produce resonance modes below 5 Hz. In addition, the sagging and contact force on collector shoes increased by multiple folds when more than 2 claw structures are broken. The methods and the results presented in this article can be used as a tool for predictive maintenance by detecting possible structural failure or defects