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Optimization of nonimaging focusing heliostat in dynamic correction of astigmatism for a wide range of incident angles

Chong KK

Opt Lett, 2010 May 15;35(10):1614-6.
PMID: 20479826 DOI: 10.1364/OL.35.001614

To overcome astigmatism has always been a great challenge in designing a heliostat capable of focusing the sunlight on a small receiver throughout the year. In this Letter, a nonimaging focusing heliostat with a dynamic adjustment of facet mirrors in a group manner has been analyzed for optimizing the astigmatic correction in a wide range of incident angles. This what is to the author's knowledge a new heliostat is not only designed to serve the purpose of concentrating sunlight to several hundreds of suns, but also to significantly reduce the variation of the solar flux distribution with the incident angle.
Fulltext A systematic method of interconnection optimization for dense-array concentrator photovoltaic system

Siaw FL, Chong KK

ScientificWorldJournal, 2013;2013:275169.
PMID: 24453823 DOI: 10.1155/2013/275169

This paper presents a new systematic approach to analyze all possible array configurations in order to determine the most optimal dense-array configuration for concentrator photovoltaic (CPV) systems. The proposed method is fast, simple, reasonably accurate, and very useful as a preliminary study before constructing a dense-array CPV panel. Using measured flux distribution data, each CPV cells' voltage and current values at three critical points which are at short-circuit, open-circuit, and maximum power point are determined. From there, an algorithm groups the cells into basic modules. The next step is I-V curve prediction, to find the maximum output power of each array configuration. As a case study, twenty different I-V predictions are made for a prototype of nonimaging planar concentrator, and the array configuration that yields the highest output power is determined. The result is then verified by assembling and testing of an actual dense-array on the prototype. It was found that the I-V curve closely resembles simulated I-V prediction, and measured maximum output power varies by only 1.34%.
Elucidating the structural, catalytic, and antibacterial traits of Ficus carica and Azadirachta indica leaf extract-mediated synthesis of the Ag/CuO/rGO nanocomposite

Fayyaz Z, Farrukh MA, Ul-Hamid A, Chong KK

Microsc Res Tech, 2024 May;87(5):957-976.
PMID: 38174385 DOI: 10.1002/jemt.24487

The present exploration demonstrates the efficient, sustainable, cost-effective, and environment-friendly green approach for the synthesis of silver (Ag)-doped copper oxide (CuO) embedded with reduced graphene oxide (rGO) nanocomposite using the green one-pot method and the green deposition method. Leaf extracts of Ficus carica and Azadirachta indica were used for both methods as reducing and capping agents. The effect of methodology and plant extract was analyzed through different characterization techniques such as UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM). The lowest band gap of 3.0 eV was observed for the Ag/CuO/rGO prepared by the green one-pot method using F. carica. The reduction of graphene oxide (GO) and the formation of metal oxide was confirmed through functional group detection using FT-IR. Calculation of thermodynamic parameters showed that all reactions involved were nonspontaneous and endothermic which shows the stability of nanocomposites. XRD studies revealed the crystallinity, phase purity and small average crystallite size of 32.67 nm. SEM images disclosed that the morphology of the nanocomposites was spherical with agglomeration and rough texture. The particle size of the nanocomposites calculated through HRTEM was found in agreement with the XRD results. The numerous properties of the synthesized nanocomposites enhanced their potential against the degradation of methylene blue, rhodamine B, and ciprofloxacin. The highest percentage degradation of Ag/CuO/rGO was found to be 97%, synthesized using the green one-pot method with F. carica against ciprofloxacin, which might be due to the lowest band gap, delayed electron-hole pair recombination, and large surface area available. The nanocomposites were also tested against the Gram-positive and Gram-negative bacteria. RESEARCH HIGHLIGHTS: Facile synthesis of Ag/CuO/rGO nanocomposite using a green one-pot method and the green deposition method. The lowest band gap of 3.0 eV was observed for nanocomposite prepared by a green one-pot method using Ficus carica. Least average crystallite size of 32.67 nm was found for nanocomposite prepared by a green one-pot method using F. carica. Highest antibacterial and catalytic activity (97%) was obtained against ciprofloxacin with nanocomposite prepared through green one-pot method using F. carica. A mechanism of green synthesis is proposed.
Challenges and opportunities for biochar to promote circular economy and carbon neutrality

Kurniawan TA, Othman MHD, Liang X, Goh HH, Gikas P, Chong KK, et al.

J Environ Manage, 2023 Apr 15;332:117429.
PMID: 36773474 DOI: 10.1016/j.jenvman.2023.117429

Biochar, derived from unused biomass, is widely considered for its potential to deal with climate change problems. Global interest in biochar is attributed to its ability to sequester carbon in soil and to remediate aquatic environment from water pollution. As soil conditioner and/or adsorbent, biochar offers opportunity through a circular economy (CE) paradigm. While energy transition continues, progress toward low-emissions materials accelerates their advance towards net-zero emissions. However, none of existing works addresses CE-based biochar management to achieve carbon neutrality. To reflect its novelty, this work provides a critical overview of challenges and opportunities for biochar to promote CE and carbon neutrality. This article also offers seminal perspectives about strengthening biomass management through CE and resource recovery paradigms, while exploring how the unused biomass can promote net zero emissions in its applications. By consolidating scattered knowledge in the body of literature into one place, this work uncovers new research directions to close the loops by implementing the circularity of biomass resources in various fields. It is conclusive from a literature survey of 113 articles (2003-2023) that biomass conversion into biochar can promote net zero emissions and CE in the framework of the UN Sustainable Development Goals (SDGs). Depending on their physico-chemical properties, biochar can become a suitable feedstock for CE. Biochar application as soil enrichment offsets 12% of CO2 emissions by land use annually. Adding biochar to soil can improve its health and agricultural productivity, while minimizing about 1/8 of CO2 emissions. Biochar can also sequester CO2 in the long-term and prevent the release of carbon back into the atmosphere after its decomposition. This practice could sequester 2.5 gigatons (Gt) of CO2 annually. With the global biochar market reaching USD 368.85 million by 2028, this work facilitates biochar with its versatile characteristics to promote carbon neutrality and CE applications.
Fulltext Integration of an on-axis general sun-tracking formula in the algorithm of an open-loop sun-tracking system

Chong KK, Wong CW, Siaw FL, Yew TK, Ng SS, Liang MS, et al.

Sensors (Basel), 2009;9(10):7849-65.
PMID: 22408483 DOI: 10.3390/s91007849

A novel on-axis general sun-tracking formula has been integrated in the algorithm of an open-loop sun-tracking system in order to track the sun accurately and cost effectively. Sun-tracking errors due to installation defects of the 25 m(2) prototype solar concentrator have been analyzed from recorded solar images with the use of a CCD camera. With the recorded data, misaligned angles from ideal azimuth-elevation axes have been determined and corrected by a straightforward changing of the parameters' values in the general formula of the tracking algorithm to improve the tracking accuracy to 2.99 mrad, which falls below the encoder resolution limit of 4.13 mrad.
Fulltext Chorea in Sporadic Creutzfeldt-Jakob Disease

Tan AH, Toh TH, Low SC, Fong SL, Chong KK, Lee KW, et al.

J Mov Disord, 2018 Sep;11(3):149-151.
PMID: 30086616 DOI: 10.14802/jmd.18017
Probiotics for Constipation in Parkinson Disease: A Randomized Placebo-Controlled Study

Tan AH, Lim SY, Chong KK, A Manap MAA, Hor JW, Lim JL, et al.

Neurology, 2021 02 02;96(5):e772-e782.
PMID: 33046607 DOI: 10.1212/WNL.0000000000010998

OBJECTIVE: To determine whether probiotics are effective for constipation, a common and often difficult-to-treat problem, in Parkinson disease (PD).
METHODS: In this double-blind, randomized, placebo-controlled, single-center trial, 280 patients with PD were screened, and 72 eligible patients were block-randomized (1:1) to receive either multistrain probiotics capsules (n = 34) or identical-appearing placebo (n = 38), for 4 weeks. The primary endpoint was the change in the average number of spontaneous bowel movements (SBM) per week during the last 2 weeks of intervention compared with the 2-week preintervention phase, recorded by daily stool diary. Secondary outcome measures included changes in stool consistency, constipation severity score, and quality of life related to constipation. Satisfaction with intervention received was assessed. Change in levels of fecal calprotectin, a marker of intestinal inflammation, was an exploratory outcome.
RESULTS: SBM increased by 1.0 ± 1.2 per week after treatment with probiotics and decreased by 0.3 ± 1.0 per week in the placebo group (mean difference 1.3, 95% confidence interval 0.8-1.8, p < 0.001). Significant improvements were also seen for secondary outcomes after correction for multiple comparisons, including stool consistency (p = 0.009) and quality of life related to constipation (p = 0.001). In the treatment group, 65.6% reported satisfaction with the intervention vs only 21.6% in the placebo group (p < 0.001). One patient (2.9%) in the treatment group withdrew due to a nonserious adverse event. Fecal calprotectin did not change significantly during the study.
CONCLUSIONS: Multistrain probiotics treatment was effective for constipation in PD. Further studies are needed to investigate the long-term efficacy and safety of probiotics in PD, as well as their mechanisms of action.
CLINICALTRIALSGOV IDENTIFIER: NCT03377322.
CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that, for people with PD, multistrain probiotics significantly increased the average number of SBM per week.
Fulltext Fecal Calprotectin in Parkinson's Disease and Multiple System Atrophy

Hor JW, Lim SY, Khor ES, Chong KK, Song SL, Ibrahim NM, et al.

J Mov Disord, 2021 Dec 24.
PMID: 34937162 DOI: 10.14802/jmd.21085

Objective: Converging evidence suggests that intestinal inflammation is involved in the pathogenesis of neurodegenerative diseases. Previous studies on fecal calprotectin in Parkinson's disease (PD) were limited by small sample sizes, and literature regarding intestinal inflammation in multiple system atrophy (MSA) is very scarce. We investigated the levels of fecal calprotectin, a marker of intestinal inflammation, in PD and MSA.
Methods: We recruited 169 subjects (71 PD, 38 MSA, and 60 age-similar nonneurological controls). Clinico-demographic data were collected. PD and MSA were subtyped and the severity assessed using the MDS-UPDRS and UMSARS, respectively. Fecal calprotectin and blood immune markers were analyzed.
Results: Compared to controls (median: 35.7 [IQR: 114.2] μg/g), fecal calprotectin was significantly elevated in PD (median: 95.6 [IQR: 162.1] μg/g, p = 0.003) and even higher in MSA (median: 129.5 [IQR: 373.8] μg/g, p = 0.002). A significant interaction effect with age was observed; between-group differences were significant only in older subjects (i.e., ≥ 61 years) and became more apparent with increasing age. A total of 28.9% of MSA and 18.3% of PD patients had highly abnormal fecal calprotectin levels (≥ 250 μg/g); however, this difference was only significant for MSA compared to controls. Fecal calprotectin correlated moderately with selected blood immune markers in PD, but not with clinical features of PD or MSA.
Conclusions: Elevated fecal calprotectin suggests a role for intestinal inflammation in PD and MSA. A more complete understanding of gut immune alterations could open up new avenues of research and treatment for these debilitating diseases.
Treatment intensification and therapeutic inertia of antihypertensive therapy among patients with type 2 diabetes and hypertension with uncontrolled blood pressure

Wan KS, Moy FM, Mohd Yusoff MF, Mustapha F, Ismail M, Mat Rifin H, et al.

Sci Rep, 2024 Jun 01;14(1):12625.
PMID: 38824234 DOI: 10.1038/s41598-024-63617-4

Treatment intensification is essential to ensure guideline targets are attained in diabetes patients. The failure to intensify treatment when the targets are not achieved is therapeutic inertia. This study aimed to determine the proportions and factors associated with treatment intensification and therapeutic inertia of antihypertensive therapy in type 2 diabetes patients with uncontrolled hypertension in Malaysia. A retrospective cohort analysis was conducted utilising registry data. Diabetes hypertensive patients with uncontrolled baseline systolic or diastolic blood pressure were included. Treatment intensification was the increase in the number of antihypertensive agents from the index treatment. Therapeutic inertia was the absence of treatment intensification when the second blood pressure reading was still uncontrolled. About 6956 patients were followed up over 2.5 ± 1.1 person-years. Treatment intensification was observed in 29.8% of patients, while 38.6% had therapeutic inertia. Chinese, Indian, and 'others' ethnic groups, retinopathy, more antihypertensive agents, and higher systolic blood pressure were associated with therapeutic inertia. Underweight, overweight patients and those with dyslipidaemia had lower risks for therapeutic inertia. The results indicate suboptimal quality of care in public health clinics in Malaysia. Further studies are needed to determine the underlying causes to formulate precise interventions to tackle the problem in Malaysia.