MyMedR

Displaying publications 1 - 20 of 32 in total

Abstract:

Sort:

Comprehensive analysis of peripheral T-cell and natural killer/T-cell lymphoma in Asian patients: A multinational, multicenter, prospective registry study in Asia

Yoon SE, Song Y, Kim SJ, Yoon DH, Chen TY, Koh Y, et al.

Lancet Reg Health West Pac, 2021 May;10:100126.
PMID: 34327343 DOI: 10.1016/j.lanwpc.2021.100126

Background: Peripheral T-cell lymphomas (PTCLs) are uncommon and their frequency is regionally heterogeneous. Several studies have been conducted to evaluate the clinical features and treatment outcomes of this disease entity, but the majority of these were conducted in limited areas, making it difficult to comprehensively analyze their relative frequency and clinical features. Furthermore, no consensus treatment for PTCLs has been established. Therefore, we conducted an Asia-specific study to understand the relative frequency of PTCLs and assess treatments and their outcomes in Asian patients.
Methods: We performed a multinational, multicenter, prospective registry of adult patients with PTCLs that was named as the International Cooperative non-Hodgkin T-cell lymphoma prospective registry study where thirty-two institutes from six Asian countries and territories (Korea, China, Taiwan, Singapore, Malaysia, and Indonesia) participated.
Findings: A total of 486 patients were registered between April 2016 and February 2019, and more than a half of patients (57%) had stage III or IV. Extranodal natural killer (NK)/T- cell lymphoma was the most common subtype (n = 139,28.6%), followed by angioimmunoblastic T-cell lymphoma (AITL, n = 120,24.7%), PTCL-not otherwise specified (PTCL-NOS, n = 101,20.8%), ALK-positive anaplastic large cell lymphoma (ALCL, n = 34,6.9%), and ALK-negative ALCL (n = 30,6.2%). The median progression-free survival (PFS) and overall survival (OS) were 21.1 months (95% CI,10.6-31.6) and 83.6 months (95% CI, 56.7-110.5), respectively. Upfront use of combined treatment with chemotherapy and radiotherapy showed better PFS than chemotherapy alone in localized ENKTL whereas consolidation with upfront autologous stem cell transplantation (SCT) provided longer PFS in advance stage ENKTL. In patients with PTCLs other than ENKTL, anthracycline-containing chemotherapies were widely used, but the outcome of those regimens was not satisfactory, and upfront autologous SCT was not significantly associated with survival benefit, either. The treatment outcome of salvage chemotherapy was disappointing, and none of the salvage strategies showed superiority to one another.
Interpretation: This multinational, multicenter study identified the relative frequency of each subtype of PTCLs across Asian countries, and the survival outcomes according to the therapeutic strategies currently used.
Funding: Samsung Biomedical Research Institute.
Assessment of anti-inflammatory effect of 5β-hydroxypalisadin B isolated from red seaweed Laurencia snackeyi in zebrafish embryo in vivo model

Wijesinghe WA, Kim EA, Kang MC, Lee WW, Lee HS, Vairappan CS, et al.

Environ Toxicol Pharmacol, 2014 Jan;37(1):110-7.
PMID: 24317194 DOI: 10.1016/j.etap.2013.11.006

5β-Hydroxypalisadin B, a halogenated secondary metabolite isolated from red seaweed Laurencia snackeyi was evaluated for its anti-inflammatory activity in lipopolysaccharide (LPS)-induced zebrafish embryo. Preliminary studies suggested the effective concentrations of the compound as 0.25, 0.5, 1 μg/mL for further in vivo experiments. 5β-Hydroxypalisadin B, exhibited profound protective effect in the zebrafish embryo as confirmed by survival rate, heart beat rate, and yolk sac edema size. The compound acts as an effective agent against reactive oxygen species (ROS) formation induced by LPS and tail cut. Moreover, 5β-hydroxypalisadin B effectively inhibited the LPS-induced nitric oxide (NO) production in zebrafish embryo. All the tested protective effects of 5β-hydroxypalisadin B were comparable to the well-known anti-inflammatory agent dexamethasone. According to the results obtained, 5β-hydroxypalisadin B isolated from red seaweed L. snackeyi could be considered as an effective anti-inflammatory agent which might be further developed as a functional ingredient.
Fulltext Optimization of Micro and Nano Palm Oil Fuel Ash to Determine the Carbonation Resistance of the Concrete in Accelerated Condition

Tang WL, Lee HS, Vimonsatit V, Htut T, Singh JK, Wan Hassan WNF, et al.

Materials (Basel), 2019 Jan 03;12(1).
PMID: 30609786 DOI: 10.3390/ma12010130

The carbonation rate of reinforced concrete is influenced by three parameters, namely temperature, relative humidity, and concentration of carbon dioxide (CO₂) in the surroundings. As knowledge of the service lifespan of reinforced concrete is crucial in terms of corrosion, the carbonation process is important to study, and high-performance durable reinforced concretes can be produced to prolong the effects of corrosion. To examine carbonation resistance, accelerated carbonation testing was conducted in accordance with the standards of BS 1881-210:2013. In this study, 10⁻30% of micro palm oil fuel ash (mPOFA) and 0.5⁻1.5% of nano-POFA (nPOFA) were incorporated into concrete mixtures to determine the optimum amount for achieving the highest carbonation resistance after 28 days water curing and accelerated CO₂ conditions up to 70 days of exposure. The effect of carbonation on concrete specimens with the inclusion of mPOFA and nPOFA was investigated. The carbonation depth was identified by phenolphthalein solution. The highest carbonation resistance of concrete was found after the inclusion of 10% mPOFA and 0.5% nPOFA, while the lowest carbonation resistance was found after the inclusion of 30% mPOFA and 1.5% nPOFA.
Clinical evaluation and serum concentration of zuclopenthixol acetate in psychotic Asian patients: a single-dose preliminary study

Tan CH, Low BL, Ng LL, Khoo YM, Lee HS

Ther Drug Monit, 1993 Apr;15(2):108-12.
PMID: 8099240

Nineteen acutely disturbed psychotic Asian patients were treated with a single intramuscular injection of 50 mg of zuclopenthixol acetate in Viscoleo. Patients were assessed clinically before and after treatment using the Brief Psychiatric Rating Scale (BPRS). Serum zuclopenthixol and the inactive geometric isomer trans(E)-clopenthixol were determined by high-performance liquid chromatography after intramuscular injection. All patients improved, with the BPRS being significantly reduced (p < 0.001) at 72 h after injection. Adverse effects were generally few. The mean +/- SEM serum zuclopenthixol concentrations at 24, 48, and 72 h were 19.9 +/- 2.8, 31.5 +/- 4.5, and 17.8 +/- 2.9 micrograms/L, respectively. trans(E)-Clopenthixol concentrations ranged from negligible to 39.5 micrograms/L. This study confirms that a single intramuscular injection of 50 mg is adequate for managing severely disturbed psychotic patients for the first 3 days. The serum zuclopenthixol concentrations attained in the Asian patients were higher than those reported in Caucasian psychiatric patients. In some patients, a considerable amount of zuclopenthixol had been transformed to trans(E)-clopenthixol.
Fulltext Percutaneous dilational tracheostomy--a 3 year experience in a general hospital in Malaysia

Tan CC, Lee HS, Balan S

Med J Malaysia, 2004 Dec;59(5):591-7.
PMID: 15889560

All percutaneous tracheostomies performed in the general intensive care unit (ICU), Hospital Sultanah Aminah, Johor Bahru, Malaysia, from July 1999 to June 2002 were studied. The tracheostomies were performed as an elective bedside technique in the ICU. A total of 352 percutaneous tracheostomies were performed. Eighty-eight percent of the tracheostomies were completed within 15 minutes. The most common complication was bleeding which occurred in 52 patients (14.7%). The rest of the complications encountered were:- transient hypoxia twelve (3.4%), inability/ difficulty to insert tracheostomy tube eight (2.3%), false passage four (1.1%), transient hypotension two (0.6%), pneumothorax two (0.6%), peristomal infection two (0.6%), subcutaneous emphysema one (0.3%), cuff rupture one (0.3%), oesophageal cannulation one (0.3%), and granuloma formation one (0.3%). Conversion to conventional tracheostomies were performed on 7 patients (2%). There was one unfortunate death related to percutaneous tracheostomy. In conclusion, percutaneous dilational tracheostomy can be used safely to manage the airway of critically ill patients.
Fulltext High-density genotyping of immune-related loci identifies new SLE risk variants in individuals with Asian ancestry

Sun C, Molineros JE, Looger LL, Zhou XJ, Kim K, Okada Y, et al.

Nat Genet, 2016 Mar;48(3):323-30.
PMID: 26808113 DOI: 10.1038/ng.3496

Systemic lupus erythematosus (SLE) has a strong but incompletely understood genetic architecture. We conducted an association study with replication in 4,478 SLE cases and 12,656 controls from six East Asian cohorts to identify new SLE susceptibility loci and better localize known loci. We identified ten new loci and confirmed 20 known loci with genome-wide significance. Among the new loci, the most significant locus was GTF2IRD1-GTF2I at 7q11.23 (rs73366469, Pmeta = 3.75 × 10(-117), odds ratio (OR) = 2.38), followed by DEF6, IL12B, TCF7, TERT, CD226, PCNXL3, RASGRP1, SYNGR1 and SIGLEC6. We identified the most likely functional variants at each locus by analyzing epigenetic marks and gene expression data. Ten candidate variants are known to alter gene expression in cis or in trans. Enrichment analysis highlights the importance of these loci in B cell and T cell biology. The new loci, together with previously known loci, increase the explained heritability of SLE to 24%. The new loci share functional and ontological characteristics with previously reported loci and are possible drug targets for SLE therapeutics.
Higher dietary energy density is associated with stunting but not overweight and obesity in a sample of urban Malaysian children

Shariff ZM, Lin KG, Sariman S, Siew CY, Yusof BN, Mun CY, et al.

Ecol Food Nutr, 2016 Jul-Aug;55(4):378-89.
PMID: 27231732 DOI: 10.1080/03670244.2016.1181065

Although diets with high energy density are associated with increased risk of overweight and obesity, it is not known whether such diets are associated with undernutrition. This study assessed the relationship between dietary energy density (ED) and nutritional status of 745 urban 1- to 10-year-old children. Dietary intakes were obtained using food recall and record for two days. Dietary energy density was based on food and caloric beverages. Higher dietary ED was associated with lower intakes of carbohydrate, sugar, vitamins C and D, and calcium but higher fat, fiber, iron, and folate intakes. While intakes of fruits and milk/dairy products decreased, meat, fish, and legume intakes increased with higher dietary ED. Stunting, but not other growth problems, was associated with higher dietary ED. Future studies should confirm the cause-and-effect relationship between higher dietary ED and stunting.
Prevalence of elevated body mass index condition and its associated demographic variables among adults in urban areas in Johor, Malaysia

Rozita Z, Lim MT, Lee HS

Med J Malaysia, 2019 04;74(2):145-150.
PMID: 31079126

INTRODUCTION: The prevalence of overweight and obesity is increasing at an alarming rate. It is a major factor for many other metabolic disorders. This study aimed to determine the prevalence of increase body mass index (BMI) and obesity and their associated demographic characteristics among adults in an urban area.
METHODS: A retrospective study was conducted where data was extracted from the Health Status Screening Form (BSSK) at health clinics in Johor Bahru. Using the World Health Organization (WHO), criteria for obesity, BMI≥30.0 kg/m2 was specified as obese and combination of both BMI ranges for overweight (25.0-30.0kg/m2) and obesity (≥30.0kg/m2) as elevated BMI.
RESULTS: The overall prevalence of elevated BMI and obesity was 54.6% and 20.1% respectively. Men had a higher prevalence of elevated BMI (57.4%) with odds of 1.28 higher (95%CI: 1.04-1.58). High prevalence of elevated BMI and obesity were seen among the Indians (elevated BMI - 60.2%, obesity - 19.4%) followed by Malays (elevated BMI -57.8%, obesity - 23.1%) and Chinese showed the lowest (elevated BMI - 39.0%, obesity - 8.8%). The odds of elevated BMI and obesity were lower among younger adults as compared to older adults (≥30 years old).
CONCLUSION: Using WHO criteria, about one in two adults had elevated BMI while one in five were obese. Elevated BMI and obesity disparities were evident in age and ethnicity, but sex differences were encountered in elevated BMI group.
Fulltext An outbreak of dermatitis among stevodores

Phoon WH, Lee HS, Ho SF, Ngui SJ

Med J Malaysia, 1985 Sep;40(3):220-4.
PMID: 2948100

Cement is a common cause of dermatitis. Workers affected are usually those in cement factories and at building construction sites. Cement dermatitis among port-workers is not so commonly reported. This paper describes an outbreak of dermatitis among stevodores at a port handling cement. The cement was imported in bags, and because of breakage, there was much spillage. It was also hot and dusty inside the hatch of the ship, and some of the stevodores worked bare-bodied. Cases of dermatitis began to appear in January 1983 and reached a peak in April 1983, gradually subsiding over the next few months to August 1983. This coincided with the increased tonnage of cement handled at the port. A total of 33 stevodores were reported as having dermatitis over this period. Of the 15 cases examined, 13 had eczema, and in 19 the hands and wrists were affected. However, most of the cases had multiple site involvement, including the arms, legs and abdomen.
Samples of cement showed the presence of water-soluble chromium, varying from 9.9 to 17.8pg/g. As the stevodores were reluctant to go for skin patch-testing, only four were tested, but two did not return for the reading of the results. The other two were found to have a positive reaction to dichromates. The outbreak of dermatitis was probably due to several factors which are discussed.
Fulltext Amino acid signatures of HLA Class-I and II molecules are strongly associated with SLE susceptibility and autoantibody production in Eastern Asians

Molineros JE, Looger LL, Kim K, Okada Y, Terao C, Sun C, et al.

PLoS Genet, 2019 04;15(4):e1008092.
PMID: 31022184 DOI: 10.1371/journal.pgen.1008092

Human leukocyte antigen (HLA) is a key genetic factor conferring risk of systemic lupus erythematosus (SLE), but precise independent localization of HLA effects is extremely challenging. As a result, the contribution of specific HLA alleles and amino-acid residues to the overall risk of SLE and to risk of specific autoantibodies are far from completely understood. Here, we dissected (a) overall SLE association signals across HLA, (b) HLA-peptide interaction, and (c) residue-autoantibody association. Classical alleles, SNPs, and amino-acid residues of eight HLA genes were imputed across 4,915 SLE cases and 13,513 controls from Eastern Asia. We performed association followed by conditional analysis across HLA, assessing both overall SLE risk and risk of autoantibody production. DR15 alleles HLA-DRB1*15:01 (P = 1.4x10-27, odds ratio (OR) = 1.57) and HLA-DQB1*06:02 (P = 7.4x10-23, OR = 1.55) formed the most significant haplotype (OR = 2.33). Conditioned protein-residue signals were stronger than allele signals and mapped predominantly to HLA-DRB1 residue 13 (P = 2.2x10-75) and its proxy position 11 (P = 1.1x10-67), followed by HLA-DRB1-37 (P = 4.5x10-24). After conditioning on HLA-DRB1, novel associations at HLA-A-70 (P = 1.4x10-8), HLA-DPB1-35 (P = 9.0x10-16), HLA-DQB1-37 (P = 2.7x10-14), and HLA-B-9 (P = 6.5x10-15) emerged. Together, these seven residues increased the proportion of explained heritability due to HLA to 2.6%. Risk residues for both overall disease and hallmark autoantibodies (i.e., nRNP: DRB1-11, P = 2.0x10-14; DRB1-13, P = 2.9x10-13; DRB1-30, P = 3.9x10-14) localized to the peptide-binding groove of HLA-DRB1. Enrichment for specific amino-acid characteristics in the peptide-binding groove correlated with overall SLE risk and with autoantibody presence. Risk residues were in primarily negatively charged side-chains, in contrast with rheumatoid arthritis. We identified novel SLE signals in HLA Class I loci (HLA-A, HLA-B), and localized primary Class II signals to five residues in HLA-DRB1, HLA-DPB1, and HLA-DQB1. These findings provide insights about the mechanisms by which the risk residues interact with each other to produce autoantibodies and are involved in SLE pathophysiology.
Fulltext Confirmation of five novel susceptibility loci for systemic lupus erythematosus (SLE) and integrated network analysis of 82 SLE susceptibility loci

Molineros JE, Yang W, Zhou XJ, Sun C, Okada Y, Zhang H, et al.

Hum Mol Genet, 2017 03 15;26(6):1205-1216.
PMID: 28108556 DOI: 10.1093/hmg/ddx026

We recently identified ten novel SLE susceptibility loci in Asians and uncovered several additional suggestive loci requiring further validation. This study aimed to replicate five of these suggestive loci in a Han Chinese cohort from Hong Kong, followed by meta-analysis (11,656 cases and 23,968 controls) on previously reported Asian and European populations, and to perform bioinformatic analyses on all 82 reported SLE loci to identify shared regulatory signatures. We performed a battery of analyses for these five loci, as well as joint analyses on all 82 SLE loci. All five loci passed genome-wide significance: MYNN (rs10936599, Pmeta = 1.92 × 10-13, OR = 1.14), ATG16L2 (rs11235604, Pmeta = 8.87 × 10 -12, OR = 0.78), CCL22 (rs223881, Pmeta = 5.87 × 10-16, OR = 0.87), ANKS1A (rs2762340, Pmeta = 4.93 × 10-15, OR = 0.87) and RNASEH2C (rs1308020, Pmeta = 2.96 × 10-19, OR = 0.84) and co-located with annotated gene regulatory elements. The novel loci share genetic signatures with other reported SLE loci, including effects on gene expression, transcription factor binding, and epigenetic characteristics. Most (56%) of the correlated (r2 > 0.8) SNPs from the 82 SLE loci were implicated in differential expression (9.81 × 10-198
Fulltext The relationship between household income and dietary intakes of 1-10 year old urban Malaysian

Mohd Shariff Z, Lin KG, Sariman S, Lee HS, Siew CY, Mohd Yusof BN, et al.

Nutr Res Pract, 2015 Jun;9(3):278-87.
PMID: 26060540 DOI: 10.4162/nrp.2015.9.3.278

Diet plays an important role in growth and development of children. However, dietary intakes of children living in either rural or urban areas can be influenced by household income. This cross-sectional study examined energy, nutrient and food group intakes of 749 urban children (1-10 years old) by household income status.
Fulltext Neuraxial block and postoperative epidural analgesia: effects on outcomes in the POISE-2 trial†

Leslie K, McIlroy D, Kasza J, Forbes A, Kurz A, Khan J, et al.

Br J Anaesth, 2016 Jan;116(1):100-12.
PMID: 26209855 DOI: 10.1093/bja/aev255

BACKGROUND: We assessed associations between intraoperative neuraxial block and postoperative epidural analgesia, and a composite primary outcome of death or non-fatal myocardial infarction, at 30 days post-randomization in POISE-2 Trial subjects.
METHODS: 10 010 high-risk noncardiac surgical patients were randomized aspirin or placebo and clonidine or placebo. Neuraxial block was defined as intraoperative spinal anaesthesia, or thoracic or lumbar epidural anaesthesia. Postoperative epidural analgesia was defined as postoperative epidural local anaesthetic and/or opioid administration. We used logistic regression with weighting using estimated propensity scores.
RESULTS: Neuraxial block was not associated with the primary outcome [7.5% vs 6.5%; odds ratio (OR), 0.89; 95% CI (confidence interval), 0.73-1.08; P=0.24], death (1.0% vs 1.4%; OR, 0.84; 95% CI, 0.53-1.35; P=0.48), myocardial infarction (6.9% vs 5.5%; OR, 0.91; 95% CI, 0.74-1.12; P=0.36) or stroke (0.3% vs 0.4%; OR, 1.05; 95% CI, 0.44-2.49; P=0.91). Neuraxial block was associated with less clinically important hypotension (39% vs 46%; OR, 0.90; 95% CI, 0.81-1.00; P=0.04). Postoperative epidural analgesia was not associated with the primary outcome (11.8% vs 6.2%; OR, 1.48; 95% CI, 0.89-2.48; P=0.13), death (1.3% vs 0.8%; OR, 0.84; 95% CI, 0.35-1.99; P=0.68], myocardial infarction (11.0% vs 5.7%; OR, 1.53; 95% CI, 0.90-2.61; P=0.11], stroke (0.4% vs 0.4%; OR, 0.65; 95% CI, 0.18-2.32; P=0.50] or clinically important hypotension (63% vs 36%; OR, 1.40; 95% CI, 0.95-2.09; P=0.09).
CONCLUSIONS: Neuraxial block and postoperative epidural analgesia were not associated with adverse cardiovascular outcomes among POISE-2 subjects.
Cutaneous T-cell lymphoma in Asian patients: a multinational, multicenter, prospective registry study in Asia

Lee YP, Yoon SE, Song Y, Kim SJ, Yoon DH, Chen TY, et al.

Int J Hematol, 2021 Sep;114(3):355-362.
PMID: 34302593 DOI: 10.1007/s12185-021-03179-7

Cutaneous T-cell lymphomas (CTCLs) are a group of T-cell lymphomas with low incidence. Due to their indolent characteristics, treatment strategies have not yet been established for advanced CTCLs. In this study, relative incidence of CTCLs in Asia was estimated and the therapeutic outcomes presented based on various treatments currently used in clinics for advanced CTCLs. As part of a prospective registry study of peripheral T-cell lymphoma (PTCL) conducted across Asia, including Korea, China, Taiwan, Singapore, Malaysia, and Indonesia, subgroup analysis was performed for patients with CTCLs. Among 486 patients with PTCL, 37 with CTCL (7.6%) were identified between April 2016 and February 2019. Primary cutaneous ALK-negative anaplastic large cell lymphoma (ALCL, 35.1%) was the most common subtype. With a median follow-up period of 32.1 months, median progression-free survival (PFS) was 53.5 months (95% CI 0.0-122.5), and overall survival was not reached. 14 patients (48.2%) underwent subsequent treatment after the first relapse, but the response rate was 20% with a PFS of 2.2 months (95% CI 0.3-4.0). Six patients received autologous stem cell transplantation (auto-SCT). However, auto-SCT did not result in better outcomes. Additional studies are needed on standard care treatment of advanced or refractory and relapsed CTCLs.
Variability of plasma phenobarbitone concentration in Asian children in Singapore

Lee HS

Ther Drug Monit, 1984;6(2):182-8.
PMID: 6740737

In a study with 113 Asian children in which phenobarbitone was used as the sole antiepileptic drug in 75 children, including Chinese, Malays, and Indians, the mean phenobarbitone dosage required to produce a plasma level of 15 micrograms/ml was 5.2 mg/kg/day. While the mean plasma level/dose ratio varied, the differences between the three ethnic groups were not statistically significant. Also of little difference were the ratios between the male and female groups. For those patients with poor seizure control, however, the mean plasma level/dose ratio was significantly lower than in those whose seizures were controlled. Using additional anticonvulsant drugs concurrently with phenobarbitone in 40 children raised the mean plasma level/dose ratios significantly in each ethnic group. Further, the greater age level in those given additional antiepileptic drugs might have contributed slightly to a higher mean plasma level/dose ratio.
Pharmacokinetics of propofol infusion in Asian patients undergoing coronary artery bypass grafting

Lee HS, Khoo YM, Chua BC, Ng AS, Tan SS, Chew SL

Ther Drug Monit, 1995 Aug;17(4):336-41.
PMID: 7482686

The pharmacokinetics of propofol was studied in 11 Asian patients with fentanyl-isoflurane anaesthesia during cardiopulmonary bypass (CPB) and undergoing elective coronary artery bypass grafting (CABG). Instead of the usual increments of morphine and a benzodiazepine, propofol (4 mg/kg/h) was initiated at the start of CPB and ceased at CPB separation. Whole blood propofol concentrations were determined during and postinfusion using high-performance liquid chromatography with fluorescence detection. Data from four patients seemed to fit a two-compartment model, whereas those from seven patients were significantly (F test, p < 0.05) better fitted to a three-compartment model. The pharmacokinetic parameters were as follows: The mean (SD) of the initial distribution phase t1/2 pi, intermediate distribution phase t1/2 alpha, and elimination phase t1/2 beta were 2.22 (1.04) min, 42.9 (16.4) min, and 370 (138) min, respectively. The mean clearance of 1.31 (0.50) L/min was lower than those reported from other studies, whereas the mean blood concentration of 2.2 (1.0) mg/L at the 1-h infusion period was higher. The mean calculated apparent Css was 3.9 (1.5) mg/L. The low clearance is likely to be due to hemodynamic changes during CPB and CABG, thereby affecting drug distribution and blood flow to the liver.
Fulltext An effective and novel pore sealing agent to enhance the corrosion resistance performance of Al coating in artificial ocean water

Lee HS, Singh JK, Ismail MA

Sci Rep, 2017 02 03;7:41935.
PMID: 28157233 DOI: 10.1038/srep41935

A new technique was accepted to fill the porosity of Al coating applied by arc thermal spray process to enhance corrosion resistance performance in artificial ocean water. The porosity is the inherent property of arc thermal spray coating process. In this study, applied coating was treated with different concentrations of ammonium phosphate mono basic (NH4H2PO4: AP) solution thereafter dried at room temperature and kept in humidity chamber for 7d to deposit uniform film. The corrosion resistance of Al coating and treated samples have been evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic techniques with exposure periods in artificial ocean water. Electrochemical techniques, X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and field emission-scanning electron microscopy (FE-SEM) indicated that phosphate ion would have been retarding corrosion of Al coating effectively. The formation of AHP (Ammonium Aluminum Hydrogen Phosphate Hydrate: NH4)3Al5H6(PO4)8.18H2O) on Al coating surface after treatment with AP is nano sized, crystalline and uniformly deposited but after exposure them in artificial ocean water, they form AHPH (Aluminum hydroxide phosphate hydrate Al3(PO4)2(OH)3(H2O)5) that is very protective, adherent, uniform and plate like morphology of corrosion products. The AHPH is sparingly soluble and adherent to surface and imparted improved corrosion resistance.
Fulltext Protection of Reinforced Concrete Structures of Waste Water Treatment Reservoirs with Stainless Steel Coating Using Arc Thermal Spraying Technique in Acidified Water

Lee HS, Park JH, Singh JK, Ismail MA

Materials (Basel), 2016 Sep 03;9(9).
PMID: 28773875 DOI: 10.3390/ma9090753

Waste water treatment reservoirs are contaminated with many hazardous chemicals and acids. Reservoirs typically comprise concrete and reinforcement steel bars, and the main elements responsible for their deterioration are hazardous chemicals, acids, and ozone. Currently, a variety of techniques are being used to protect reservoirs from exposure to these elements. The most widely used techniques are stainless steel plating and polymeric coating. In this study, a technique known as arc thermal spraying was used. It is a more convenient and economical method for protecting both concrete and reinforcement steel bar from deterioration in waste water treatment reservoirs. In this study, 316L stainless steel coating was applied to a concrete surface, and different electrochemical experiments were performed to evaluate the performance of coatings in different acidic pH solutions. The coating generated from the arc thermal spraying process significantly protected the concrete surface from corrosion in acidic pH solutions, owing to the formation of a double layer capacitance-a mixture of Cr3+ enriched with Cr₂O₃ and Cr-hydroxide in inner and Fe3+ oxide on the outer layer of the coating. The formation of this passive film is defective owing to the non-homogeneous 316L stainless steel coating surface. In the pH 5 solution, the growth of a passive film is adequate due to the presence of un-dissociated water molecules in the aqueous sulfuric acid solution. The coated surface is sealed with alkyl epoxide, which acts as a barrier against the penetration of acidic solutions. This coating exhibits higher impedance values among the three studied acidic pH solutions.
Study on the Shielding Effectiveness of an Arc Thermal Metal Spraying Method against an Electromagnetic Pulse

Lee HS, Choe HB, Baek IY, Singh JK, Ismail MA

Materials (Basel), 2017 Oct 04;10(10).
PMID: 28976931 DOI: 10.3390/ma10101155

An electromagnetic pulse (EMP) explodes in real-time and causes critical damage within a short period to not only electric devices, but also to national infrastructures. In terms of EMP shielding rooms, metal plate has been used due to its excellent shielding effectiveness (SE). However, it has difficulties in manufacturing, as the fabrication of welded parts of metal plates and the cost of construction are non-economical. The objective of this study is to examine the applicability of the arc thermal metal spraying (ATMS) method as a new EMP shielding method to replace metal plate. The experimental parameters, metal types (Cu, Zn-Al), and coating thickness (100-700 μm) used for the ATMS method were considered. As an experiment, a SE test against an EMP in the range of 103 to 1010 Hz was conducted. Results showed that the ATMS coating with Zn-Al had similar shielding performance in comparison with metal plate. In conclusion, the ATMS method is judged to have a high possibility of actual application as a new EMP shielding material.
The heterogeneous effects of urbanisation and institutional quality on greenhouse gas emissions in Belt and Road Initiative countries

Lee HS, Arestis P, Chong SC, Yap S, Sia BK

Environ Sci Pollut Res Int, 2022 Jan;29(1):1087-1105.
PMID: 34341929 DOI: 10.1007/s11356-021-15699-0

The rise of urbanisation in Belt and Road Initiative (BRI) countries that contribute to the disruption of the ecosystem, which would affect global sustainability, is a pressing concern. This study provides new evidence of the impact of urbanisation and institutional quality on greenhouse gas (GHG) emissions in the selected 48 BRI countries from the years 1984 to 2017. The models of this study are inferred by using panel regression model and panel quantile regression model to meet the objectives of our study as it contemplates unobserved country heterogeneity. From the panel regression model, the findings indicate that although urbanisation in BRI supports the 'life effect' hypothesis that could dampen the environment quality, this effect could be reduced through better institutional quality. Using the quantile regression method, this study concludes that one-size-fits-all strategies to reduce GHG emissions in countries with different GHG emissions levels are improbable to achieve success for all. Hence, GHG emissions control procedures should be adjusted differently across high-emission, middle-emission and low-emission countries. Based on these results, this study provides novel intuitions for policymakers to wisely plan the urbanisation blueprints to eradicate unplanned urbanisation and improve institutional quality in meeting pollution mitigation goals.

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links