14 research outputs found
Chemical cleaning of RO membranes fouled by wastewater effluent: Achieving higher efficiency with dual-step cleaning
No full textThe effect of different modes of cleaning of RO membranes fouled by wastewater treatment plant effluent has been investigated. Characterization of the wastewater effluent revealed the presence of foulants containing carboxylic and phenolic functional groups as well as calcium ions. The chemical cleaning agents, sodium hydroxide (NaOH), ethylenediaminetetraacetic acid (EDTA), sodium dodecyl sulfate (SDS), and sodium chloride (NaCl), were selected as models for alkaline solutions, metal chelating agents, surfactants, and salt cleaning, respectively. Specifically, we examined the impact of a sequence or a combination of two cleaning agents compared to the use of single cleaning agents. Increased cleaning efficiency was demonstrated when two cleaning agents were applied in a certain order and mixture. In particular, it was shown that addition of NaOH can enhance the overall cleaning performance when introduced with other chemical agents, due to its ability to loosen the fouling layer. Cleaning efficiency as high as 94% was obtained by simply increasing the pH of an NaCl cleaning solution, compared to 65% in the case of the individual salt solution with no pH adjustment. On the other hand, combining chemical cleaning agents was not advantageous in some cases, possibly because of the competing cleaning mechanisms of some of the agents. The most and the least effective cleaning modes were highlighted, suggesting a rationale for the design of chemical cleaning of RO membranes fouled by wastewater effluent. This study demonstrates that careful selection of cleaning agents and the steps through which those agents are applied allows the regeneration of high water productivity after fouling while minimizing both the cleaning time and the amount of chemicals
Fouling and cleaning of RO membranes fouled by mixtures of organic foulants simulating wastewater effluent
No full textReport on industrial attachment with Land Transport Authority
No full textThe author was involved in several projects namely the North East Line (NEL) Platform Gap Filler, Seng Kang/Punggol Light Rail Transit (SPLRT) Grab Poles, Proposed design for the C651 Trains Platform Gap Filler, Noise Study and C151 Train Temperature Measurement. Finite Element Analysis (FEA) was performed on the NEL Platform Gap Filler and SPLRT Grab Poles. Five loading cases were considered in the analysis of NEL Platform Gap Filler. The maximum stresses of the five cases are within the allowable stress of the Aluminium L-bracket of 169.57 MPa. However, further testing would be desired to achieve a more accurate result. For the FEA of the SPLRT Grab Poles, the maximum stresses on the T-shaped and L-shaped grab poles are 104.2 MPa and 85.217 MPa respectively. Given an allowable stress of 217.39 MPa, both of the grab poles are able to withstand the maximum loading. In addition, the author designed a Platform Gap Filler for the C651 trains. The noise levels of the four locations (Ang Mo Kio, Bishan, Clementi and Jurong East) were measured and further investigation of the data collected would be made. Furthermore, temperature measurements of the C151 trains were recorded and they are approximately within the desired train temperature condition except for the journey from Bishan to City Hall Stations. In conclusion, the 22 weeks of Industrial Attachment has allowed the author to better appreciate the job scope of an engineer in the Rolling Stock Division of Land Transport Authority (LTA)
Performance of A-stage process treating combined municipal-industrial wastewater
No full textA biosorption column and a settling tank were operated for 6 months with combined municipal and industrial wastewaters (1 m3/hr) to study the effect of dissolved oxygen (DO) levels and Fe3þ dosage on removal efficiency of dissolved and suspended organics prior to biological treatment. High DO (>0.4 mg/L) were found to be detrimental for soluble chemical oxygen demand (COD) removals and iron dosing (up to 20 ppm) did not improve the overall performance. The system performed significantly better at high loading rate (>20 kg COD.m3.d1) where suspended solids and COD removals were greater than 80% and 60%, respectively. This is a significant improvement compared to conventional primary sedimentation tank and the process is a promising alternative for the pretreatment of industrial wastewater
Unraveling stroke gait deviations with movement analytics, more than meets the eye: a case control study
No full textBackground: This study aimed to identify and quantify the kinematic and kinetic gait deviations in post-stroke hemiplegic patients with matched healthy controls using Statistical Parametric Mapping (SPM). Methods: Fifteen chronic stroke patients [4 females, 11 males; age 53.7 (standard deviation 12.2) years; body mass 65.4 (10.4) kg; standing height 168.5 (9.6) cm] and 15 matched healthy controls [4 females, 11 males; age 52.9 (11.7) years; body weight 66.5 (10.7) years; standing height 168.3 (8.8) cm] were recruited. In a 10-m walking task, joint angles, ground reaction forces (GRF), and joint moments were collected, analyzed, and compared using SPM for an entire gait cycle. Results: Generally, when comparing the stroke patients’ affected (hemiplegic) and less-affected (contralateral) limbs with the control group, SPM identified significant differences in the late stance phase and early swing phase in the joint angles and moments in bilateral limbs (all p < 0.005). In addition, the vertical and anteroposterior components of GRF were significantly different in various periods of the stance phase (all p < 0.005), while the mediolateral component showed no differences between the two groups. Conclusion: SPM was able to detect abnormal gait patterns in both the affected and less-affected limbs of stroke patients with significant differences when compared with matched controls. The findings draw attention to significant quantifiable gait deviations in the less-affected post-stroke limb with the potential impact to inform gait retraining strategies for clinicians and physiotherapists.Published versionThe author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This study was funded by the Rehabilitation Research Grant (RRG3/19002) 2019
Author Correction: Comprehensive analysis of chromothripsis in 2,658 human cancers using whole-genome sequencing
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Risk Factors and Consequences of Cortical Thickness in an Asian Population
No full textCortical thickness has been suggested to be one of the most important markers of cortical atrophy. In this study, we examined potential risk factors of cortical thickness and its association with cognition in an elderly Asian population from Singapore. This is a cross-sectional study among 572 Chinese and Malay patients from the ongoing Epidemiology of Dementia in Singapore (EDIS) Study, who underwent comprehensive examinations including neuropsychological testing and brain magnetic resonance imaging (MRI). Cortical thickness (in micrometers) was measured using a model-based automated procedure. Cognitive function was expressed as composite and domain-specific Z-scores. Cognitive impairment was categorized into cognitive impairment no dementia (CIND)-mild, CIND-moderate, and dementia in accordance with accepted criteria. Linear regression models were used to examine the association between various risk factors and cortical thickness. With respect to cognition as outcome, both linear (for Z-scores) and logistic (for CIND/dementia) regression models were constructed. Initial adjustments were made for age, sex, and education, and subsequently for other cardiovascular risk factors and MRI markers. Out of 572 included patients, 171 (29.9%) were diagnosed with CIND-mild, 197 (34.4%) with CIND-moderate, and 28 (4.9%) with dementia. Risk factors related to a smaller cortical thickness were increased age, male sex, Malay ethnicity, higher blood glucose, and body mass index levels and presence of lacunar infarcts on MRI. Smaller cortical thickness was associated with CIND moderate/dementia [odds ratio (OR) per standard deviation (SD) decrease: 1.70; 95% confidence interval (CI): 1.19–2.44, P = 0.004] and with composite Z-score reflecting global cognitive functioning [mean difference per SD decrease: -0.094; 95% CI: -0.159; -0.030, P = 0.004]. In particular, smaller cortical thicknesses in the occipital and temporal lobes were related to cognitive impairment. Finally, in terms of specific cognitive domains, the most significant associations were found for executive function, visuoconstruction, and visual memory. Smaller cortical thickness is significantly associated with cognitive impairment, suggesting a contribution of diffuse cortical atrophy beyond the medial temporal lobe to cognitive function. These findings suggest that cortical thinning is a biomarker of neurodegenerative changes in the brain not only in dementia, but also in its preclinical stages.ImPhys/Imaging PhysicsApplied Science
Proteomic analysis of Sarcoptes scabiei reveals that proteins differentially expressed between eggs and female adult stages are involved predominantly in genetic information processing, metabolism and/or host-parasite interactions
No full textPresently, there is a dearth of proteomic data for parasitic mites and their relationship with the host animals. Here, using a high throughput LC-MS/MS-based approach, we undertook the first comprehensive, large-scale proteomic investigation of egg and adult female stages of the scabies mite, Sarcoptes scabiei–one of the most important parasitic mites of humans and other animals worldwide. In total, 1,761 S. scabiei proteins were identified and quantified with high confidence. Bioinformatic analyses revealed differentially expressed proteins to be involved predominantly in biological pathways or processes including genetic information processing, energy (oxidative phosphorylation), nucleotide, amino acid, carbohydrate and/or lipid metabolism, and some adaptive processes. Selected, constitutively and highly expressed proteins, such as peptidases, scabies mite inactivated protease paralogues (SMIPPs) and muscle proteins (myosin and troponin), are proposed to be involved in key biological processes within S. scabiei, host-parasite interactions and/or the pathogenesis of scabies. These proteomic data will enable future molecular, biochemical and physiological investigations of early developmental stages of S. scabiei and the discovery of novel interventions, targeting the egg stage, given its non-susceptibility to acaricides currently approved for the treatment of scabies in humans. Author summary Scabies is a neglected tropical disease caused by the parasitic mite Sarcoptes scabiei. The treatment and control of scabies are challenging, as there is no vaccine and the two mostly used broad-spectrum acaricides (i.e. ivermectin and permethrin) do not kill the key developmental stage (egg) of the mite that enables the re-establishment of infection. The availability of a well-assembled genome for S. scabiei now provides a foundation to explore the molecular biology, biochemistry and physiology of this mite. Here, we characterised the first somatic proteome of key developmental stages of S. scabiei using high throughput LC-MS/MS. Bioinformatic analyses of proteomic data indicate that proteins expressed differentially between egg and female adult stages are mainly involved in biological pathways or processes, such as genetic information processing, energy (oxidative phosphorylation), nucleotide, amino acid, carbohydrate and/or lipid metabolism in the mite. These proteomic data should underpin further investigations of early developmental stages of S. scabiei with a focus on identifying novel intervention targets for scabies
Novel method for detecting bitline contact misalignment using quantitative analysis of high-aspect ratio SEM images
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