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Fulltext Structural and photoluminescence studies on catalytic growth of silicon/zinc oxide heterostructure nanowires

Chong SK, Dee CF, Abdul Rahman S

Nanoscale Res Lett, 2013;8(1):174.
PMID: 23590803 DOI: 10.1186/1556-276X-8-174

Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO.
Fulltext Hierarchical Si/ZnO trunk-branch nanostructure for photocurrent enhancement

Dee CF, Chong SK, Rahman SA, Omar FS, Huang NM, Majlis BY, et al.

Nanoscale Res Lett, 2014;9(1):469.
PMID: 25246872 DOI: 10.1186/1556-276X-9-469

Hierarchical Si/ZnO trunk-branch nanostructures (NSs) have been synthesized by hot wire assisted chemical vapor deposition method for trunk Si nanowires (NWs) on indium tin oxide (ITO) substrate and followed by the vapor transport condensation (VTC) method for zinc oxide (ZnO) nanorods (NRs) which was laterally grown from each Si nanowires (NWs). A spin coating method has been used for zinc oxide (ZnO) seeding. This method is better compared with other group where they used sputtering method for the same process. The sputtering method only results in the growth of ZnO NRs on top of the Si trunk. Our method shows improvement by having the growth evenly distributed on the lateral sides and caps of the Si trunks, resulting in pine-leave-like NSs. Field emission scanning electron microscope image shows the hierarchical nanostructures resembling the shape of the leaves of pine trees. Single crystalline structure for the ZnO branch grown laterally from the crystalline Si trunk has been identified by using a lattice-resolved transmission electron microscope. A preliminary photoelectrochemical (PEC) cell testing has been setup to characterize the photocurrent of sole array of ZnO NR growth by both hydrothermal-grown (HTG) method and VTC method on ITO substrates. VTC-grown ZnO NRs showed greater photocurrent effect due to its better structural properties. The measured photocurrent was also compared with the array of hierarchical Si/ZnO trunk-branch NSs. The cell with the array of Si/ZnO trunk-branch NSs revealed four-fold magnitude enhancement in photocurrent density compared with the sole array of ZnO NRs obtain from VTC processes.
A hybrid of ant colony optimization and minimization of metabolic adjustment to improve the production of succinic acid in Escherichia coli

Chong SK, Mohamad MS, Mohamed Salleh AH, Choon YW, Chong CK, Deris S

Comput Biol Med, 2014 Jun;49:74-82.
PMID: 24763079 DOI: 10.1016/j.compbiomed.2014.03.011

This paper presents a study on gene knockout strategies to identify candidate genes to be knocked out for improving the production of succinic acid in Escherichia coli. Succinic acid is widely used as a precursor for many chemicals, for example production of antibiotics, therapeutic proteins and food. However, the chemical syntheses of succinic acid using the traditional methods usually result in the production that is far below their theoretical maximums. In silico gene knockout strategies are commonly implemented to delete the gene in E. coli to overcome this problem. In this paper, a hybrid of Ant Colony Optimization (ACO) and Minimization of Metabolic Adjustment (MoMA) is proposed to identify gene knockout strategies to improve the production of succinic acid in E. coli. As a result, the hybrid algorithm generated a list of knockout genes, succinic acid production rate and growth rate for E. coli after gene knockout. The results of the hybrid algorithm were compared with the previous methods, OptKnock and MOMAKnock. It was found that the hybrid algorithm performed better than OptKnock and MOMAKnock in terms of the production rate. The information from the results produced from the hybrid algorithm can be used in wet laboratory experiments to increase the production of succinic acid in E. coli.
Fulltext Interpersonal psychotherapy for traumatic grief following a loss due to COVID-19: a case report

Abdul Samad FD, Pereira XV, Chong SK, Abdul Latif MHB

Front Psychiatry, 2023;14:1218715.
PMID: 37840803 DOI: 10.3389/fpsyt.2023.1218715

Interpersonal psychotherapy (IPT) is a highly regarded evidence-based psychotherapy that aims to alleviate the suffering of clients and improve their interpersonal functioning. Research has demonstrated the effectiveness of IPT in depressive, bipolar and eating disorders. IPT also focuses on grief and loss as a problem area to help clients address and process their grief symptoms, leading them to reach a phase of finding meaning. However, traumatic grief which is characterized by someone who has both symptoms of trauma and grief can further complicate treatment. As for Posttraumatic Stress Disorder (PTSD), IPT can be a choice of treatment by addressing perceived isolation and emotional dysregulation through mobilizing adequate social support. This case study highlights the efficacy of IPT in treating complicated grief with traumatic experiences caused by the loss of a loved one during the COVID-19 pandemic, without undergoing exposure-based therapy. The treatment course consisted of 12 sessions scheduled twice weekly, and the client received antidepressant medication augmented with antipsychotic medication. After undergoing IPT, the client experienced an improvement in symptoms, gradual recovery of functional disability, and more meaningful interpersonal relationships. The case study presented provides evidence to suggest that IPT is a promising treatment approach for individuals struggling with trauma related to grief.
Fulltext Structure deformation of indium oxide from nanoparticles into nanostructured polycrystalline films by in situ thermal radiation treatment

Chong SK, Azizan SN, Chan KW, Nguyen HQ, Chiu WS, Aspanut Z, et al.

Nanoscale Res Lett, 2013;8(1):428.
PMID: 24134646 DOI: 10.1186/1556-276X-8-428

A microstructure deformation of indium oxide (In2O3) nanoparticles by an in situ thermal radiation treatment in nitrous oxide plasma was investigated. The In2O3 nanoparticles were completely transformed into nanostructured In2O3 films upon 10 min of treatment time. The treated In2O3 nanoparticle sample showed improvement in crystallinity while maintaining a large surface area of nanostructure morphology. The direct transition optical absorption at higher photon energy and the electrical conductivity of the In2O3 nanoparticles were significantly enhanced by the treatment.
Fulltext Tropical countries may be willing to pay more to protect their forests

Vincent JR, Carson RT, DeShazo JR, Schwabe KA, Ahmad I, Chong SK, et al.

Proc Natl Acad Sci U S A, 2014 Jul 15;111(28):10113-8.
PMID: 24982171 DOI: 10.1073/pnas.1312246111

Inadequate funding from developed countries has hampered international efforts to conserve biodiversity in tropical forests. We present two complementary research approaches that reveal a significant increase in public demand for conservation within tropical developing countries as those countries reach upper-middle-income (UMI) status. We highlight UMI tropical countries because they contain nearly four-fifths of tropical primary forests, which are rich in biodiversity and stored carbon. The first approach is a set of statistical analyses of various cross-country conservation indicators, which suggests that protective government policies have lagged behind the increase in public demand in these countries. The second approach is a case study from Malaysia, which reveals in a more integrated fashion the linkages from rising household income to increased household willingness to pay for conservation, nongovernmental organization activity, and delayed government action. Our findings suggest that domestic funding in UMI tropical countries can play a larger role in (i) closing the funding gap for tropical forest conservation, and (ii) paying for supplementary conservation actions linked to international payments for reduced greenhouse gas emissions from deforestation and forest degradation in tropical countries.
A Review of Gene Knockout Strategies for Microbial Cells

Tang PW, Chua PS, Chong SK, Mohamad MS, Choon YW, Deris S, et al.

Recent Pat Biotechnol, 2015;9(3):176-97.
PMID: 27185502

BACKGROUND: Predicting the effects of genetic modification is difficult due to the complexity of metabolic net- works. Various gene knockout strategies have been utilised to deactivate specific genes in order to determine the effects of these genes on the function of microbes. Deactivation of genes can lead to deletion of certain proteins and functions. Through these strategies, the associated function of a deleted gene can be identified from the metabolic networks.
METHODS: The main aim of this paper is to review the available techniques in gene knockout strategies for microbial cells. The review is done in terms of their methodology, recent applications in microbial cells. In addition, the advantages and disadvantages of the techniques are compared and discuss and the related patents are also listed as well.
RESULTS: Traditionally, gene knockout is done through wet lab (in vivo) techniques, which were conducted through laboratory experiments. However, these techniques are costly and time consuming. Hence, various dry lab (in silico) techniques, where are conducted using computational approaches, have been developed to surmount these problem.
CONCLUSION: The development of numerous techniques for gene knockout in microbial cells has brought many advancements in the study of gene functions. Based on the literatures, we found that the gene knockout strategies currently used are sensibly implemented with regard to their benefits.