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Effect of autoclaving and sintering on the formation of β-wollastonite

Ismail H, Shamsudin R, Abdul Hamid MA

Mater Sci Eng C Mater Biol Appl, 2016 Jan 1;58:1077-81.
PMID: 26478406 DOI: 10.1016/j.msec.2015.09.030

β-wollastonite (β-CaSiO3) was synthesized from rice husk ash and calcium carbonate, and a study of the effects of the autoclaving and sintering steps is presented here. Autoclaving and sintering at 8h and 2h yielded the β-wollastonite phase in full, with improved crystallinity. Nucleation between rice husk ash and calcium oxide occurred around 135 °C, pressure 0.24 MPa, and growth proved to be more crystalline after the ripening period. For shorter processing times, and for both unsintered and unautoclaved samples, cristobalite and unstable tricalcium silicate phases were present. Crystallite size was increased by longer sintering times but reduced by longer autoclaving times. The β-wollastonite obtained had a random branch-like structure. In conclusion, the introduction of the autoclaving step successfully obtained β-wollastonite from a reaction between rice husk ash and calcium oxide.
Fulltext Data mining algorithm in the identification of accounting fraud by smart city information technology

Zheng X, Abdul Hamid MA, Hou Y

Heliyon, 2024 May 15;10(9):e30048.
PMID: 38726191 DOI: 10.1016/j.heliyon.2024.e30048

The identification of accounting fraud is an important measure to safeguard the interests of stakeholders and ensure the long-term development of the company. The current traditional methods for identifying accounting fraud rely on manual review and judgment, lacking objectivity and accuracy. In order to improve the accuracy of accounting fraud identification, improve identification efficiency and objectivity, this article combines smart city information technology to conduct in-depth research on data mining algorithms for accounting fraud identification. This article first provides a brief overview of smart cities and information technology, then introduces the basic theory of accounting fraud identification, and finally implements accounting fraud identification through k-means clustering mining algorithm. The data is divided into k clusters, and abnormal clusters are identified by checking the characteristics and attributes of each cluster. Compared with traditional rule-based and pattern based methods, this approach can more flexibly adapt to different types and forms of fraud, and can discover unknown patterns of fraud. In the experiment, this article used electronic data collection, analysis, and retrieval systems on the websites of the Shanghai Stock Exchange and Shenzhen Stock Exchange to collect 641 annual reports and financial characteristics from 62 listed companies that engaged in financial statement fraud and 84 companies that were not reported to have financial statement fraud from 2012 to 2021 as test samples. The results were tested and analyzed from several aspects, including the number of misjudgments, misjudgment rate, and ROC curve. The final test results show that compared to traditional accounting fraud identification methods, the comprehensive misjudgment rate of data mining algorithms based on smart cities has decreased by 3 %. The conclusion indicates that data mining algorithms used in smart city information technology to identify accounting fraud can help improve the accuracy of accounting fraud, improve audit objectivity and effectiveness.
Fulltext Radiolytic formation of Fe3O4 nanoparticles: influence of radiation dose on structure and magnetic properties

Abedini A, Daud AR, Abdul Hamid MA, Kamil Othman N

PLoS One, 2014;9(3):e90055.
PMID: 24608715 DOI: 10.1371/journal.pone.0090055

Colloidal Fe3O4 nanoparticles were synthesized using a gamma-radiolysis method in an aqueous solution containing iron chloride in presence of polyvinyl alcohol and isopropanol as colloidal stabilizer and hydroxyl radical scavenger, respectively. Gamma irradiation was carried out in a 60Co gamma source chamber at different absorbed doses. Increasing the radiation dose above a certain critical dose (100 kGy) leads to particle agglomeration enhancement, and this can influence the structure and crystallinity, and consequently the magnetic properties of the resultant particles. The optimal condition for formation of Fe3O4 nanoparticles with a uniform and narrow size distribution occurred at a dose of 100 kGy, as confirmed by X-ray diffractometry and transmission electron microscopy. A vibrating sample magnetometry study showed that, when radiation dose increased, the saturation and remanence magnetization decreased, whereas the coercivity and the remanence ratio increased. This magnetic behavior results from variations in crystallinity, surface effects, and particle size effects, which are all dependent on the radiation dose. In addition, Fourier transform infrared spectroscopy was performed to investigate the nature of the bonds formed between the polymer chains and the metal surface at different radiation doses.
Bioactivity and Cell Compatibility of β-Wollastonite Derived from Rice Husk Ash and Limestone

Shamsudin R, Abdul Azam F', Abdul Hamid MA, Ismail H

Materials (Basel), 2017 Oct 17;10(10).
PMID: 29039743 DOI: 10.3390/ma10101188

The aim of this study was to prepare β-wollastonite using a green synthesis method (autoclaving technique) without organic solvents and to study its bioactivity. To prepare β-wollastonite, the precursor ratio of CaO:SiO₂ was set at 55:45. This mixture was autoclaved for 8 h and later sintered at 950 °C for 2 h. The chemical composition of the precursors was studied using X-ray fluorescence (XRF), in which rice husk ash consists of 89.5 wt % of SiO₂ in a cristobalite phase and calcined limestone contains 97.2 wt % of CaO. The X-ray diffraction (XRD) patterns after sintering showed that only β-wollastonite was detected as the single phase. To study its bioactivity and degradation properties, β-wollastonite samples were immersed in simulated body fluid (SBF) for various periods of time. Throughout the soaking period, the molar ratio of Ca/P obtained was in the range of 1.19 to 2.24, and the phase detected was amorphous calcium phosphate, which was confirmed by scanning electron microscope with energy dispersive X-ray analysis (SEM/EDX) and XRD. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the peaks of the calcium and phosphate ions increased when an amorphous calcium phosphate layer was formed on the surface of the β-wollastonite sample. A cell viability and proliferation assay test was performed on the rice husk ash, calcined limestone, and β-wollastonite samples by scanning electron microscope. For heavy metal element evaluation, a metal panel that included As, Cd, Pb, and Hg was selected, and both precursor and β-wollastonite fulfilled the requirement of an American Society for Testing and Materials (ASTM F1538-03) standard specification. Apart from that, a degradation test showed that the loss of mass increased incrementally as a function of soaking period. These results showed that the β-wollastonite materials produced from rice husk ash and limestone possessed good bioactivity, offering potential for biomedical applications.
Fulltext A review on radiation-induced nucleation and growth of colloidal metallic nanoparticles

Abedini A, Daud AR, Abdul Hamid MA, Kamil Othman N, Saion E

Nanoscale Res Lett, 2013;8(1):474.
PMID: 24225302 DOI: 10.1186/1556-276X-8-474

This review presents an introduction to the synthesis of metallic nanoparticles by radiation-induced method, especially gamma irradiation. This method offers some benefits over the conventional methods because it provides fully reduced and highly pure nanoparticles free from by-products or chemical reducing agents, and is capable of controlling the particle size and structure. The nucleation and growth mechanism of metallic nanoparticles are also discussed. The competition between nucleation and growth process in the formation of nanoparticles can determine the size of nanoparticles which is influenced by certain parameters such as the choice of solvents and stabilizer, the precursor to stabilizer ratio, pH during synthesis, and absorbed dose.
Fulltext Highly Sensitive Magnesium-Doped ZnO Nanorod pH Sensors Based on Electrolyte-Insulator-Semiconductor (EIS) Sensors

Al-Khalqi EM, Abdul Hamid MA, Al-Hardan NH, Keng LK

Sensors (Basel), 2021 Mar 17;21(6).
PMID: 33802968 DOI: 10.3390/s21062110

For highly sensitive pH sensing, an electrolyte insulator semiconductor (EIS) device, based on ZnO nanorod-sensing membrane layers doped with magnesium, was proposed. ZnO nanorod samples prepared via a hydrothermal process with different Mg molar ratios (0-5%) were characterized to explore the impact of magnesium content on the structural and optical characteristics and sensing performance by X-ray diffraction analysis (XRD), atomic force microscopy (AFM), and photoluminescence (PL). The results indicated that the ZnO nanorods doped with 3% Mg had a high hydrogen ion sensitivity (83.77 mV/pH), linearity (96.06%), hysteresis (3 mV), and drift (0.218 mV/h) due to the improved crystalline quality and the surface hydroxyl group role of ZnO. In addition, the detection characteristics varied with the doping concentration and were suitable for developing biomedical detection applications with different detection elements.
Fulltext Amperometric Non-Enzymatic Hydrogen Peroxide Sensor Based on Aligned Zinc Oxide Nanorods

Al-Hardan NH, Abdul Hamid MA, Shamsudin R, Othman NK, Kar Keng L

Sensors (Basel), 2016 Jun 29;16(7).
PMID: 27367693 DOI: 10.3390/s16071004

Zinc oxide (ZnO) nanorods (NRs) have been synthesized via the hydrothermal process. The NRs were grown over a conductive glass substrate. A non-enzymatic electrochemical sensor for hydrogen peroxide (H₂O₂), based on the prepared ZnO NRs, was examined through the use of current-voltage measurements. The measured currents, as a function of H₂O₂ concentrations ranging from 10 μM to 700 μM, revealed two distinct behaviours and good performance, with a lower detection limit (LOD) of 42 μM for the low range of H₂O₂ concentrations (first region), and a LOD of 143.5 μM for the higher range of H₂O₂ concentrations (second region). The prepared ZnO NRs show excellent electrocatalytic activity. This enables a measurable and stable output current. The results were correlated with the oxidation process of the H₂O₂ and revealed a good performance for the ZnO NR non-enzymatic H₂O₂ sensor.
Fulltext Temperature-Driven Structural and Morphological Evolution of Zinc Oxide Nano-Coalesced Microstructures and Its Defect-Related Photoluminescence Properties

Lim K, Abdul Hamid MA, Shamsudin R, Al-Hardan NH, Mansor I, Chiu W

Materials (Basel), 2016 Apr 20;9(4).
PMID: 28773425 DOI: 10.3390/ma9040300

In this paper, we address the synthesis of nano-coalesced microstructured zinc oxide thin films via a simple thermal evaporation process. The role of synthesis temperature on the structural, morphological, and optical properties of the prepared zinc oxide samples was deeply investigated. The obtained photoluminescence and X-ray photoelectron spectroscopy outcomes will be used to discuss the surface structure defects of the prepared samples. The results indicated that the prepared samples are polycrystalline in nature, and the sample prepared at 700 °C revealed a tremendously c-axis oriented zinc oxide. The temperature-driven morphological evolution of the zinc oxide nano-coalesced microstructures was perceived, resulting in transformation of quasi-mountain chain-like to pyramidal textured zinc oxide with increasing the synthesis temperature. The results also impart that the sample prepared at 500 °C shows a higher percentage of the zinc interstitial and oxygen vacancies. Furthermore, the intensity of the photoluminescence emission in the ultraviolet region was enhanced as the heating temperature increased from 500 °C to 700 °C. Lastly, the growth mechanism of the zinc oxide nano-coalesced microstructures is discussed according to the reaction conditions.
A simple and sensitive fluorescence based biosensor for the determination of uric acid using H2O2-sensitive quantum dots/dual enzymes

Azmi NE, Ramli NI, Abdullah J, Abdul Hamid MA, Sidek H, Abd Rahman S, et al.

Biosens Bioelectron, 2015 May 15;67:129-33.
PMID: 25113659 DOI: 10.1016/j.bios.2014.07.056

A novel optical detection system consisting of combination of uricase/HRP-CdS quantum dots (QDs) for the determination of uric acid in urine sample is described. The QDs was used as an indicator to reveal fluorescence property of the system resulting from enzymatic reaction of uricase and HRP (horseradish peroxidase), which is involved in oxidizing uric acid to allaintoin and hydrogen peroxide. The hydrogen peroxide produced was able to quench the QDs fluorescence, which was proportional to uric acid concentration. The system demonstrated sufficient activity of uricase and HRP at a ratio of 5U:5U and pH 7.0. The linearity of the system toward uric acid was in the concentration range of 125-1000 µM with detection limit of 125 µM.
Fulltext High Sensitivity pH Sensor Based on Porous Silicon (PSi) Extended Gate Field-Effect Transistor

Al-Hardan NH, Abdul Hamid MA, Ahmed NM, Jalar A, Shamsudin R, Othman NK, et al.

Sensors (Basel), 2016 Jun 07;16(6).
PMID: 27338381 DOI: 10.3390/s16060839

In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions.
Fulltext Coding practice in national and regional kidney biopsy registries

Dendooven A, Peetermans H, Helbert M, Nguyen TQ, Marcussen N, Nagata M, et al.

BMC Nephrol, 2021 05 24;22(1):193.
PMID: 34030637 DOI: 10.1186/s12882-021-02365-3

BACKGROUND: Kidney biopsy registries all over the world benefit research, teaching and health policy. Comparison, aggregation and exchange of data is however greatly dependent on how registration and coding of kidney biopsy diagnoses are performed. This paper gives an overview over kidney biopsy registries, explores how these registries code kidney disease and identifies needs for improvement of coding practice.
METHODS: A literature search was undertaken to identify biopsy registries for medical kidney diseases. These data were supplemented with information from personal contacts and from registry websites. A questionnaire was sent to all identified registries, investigating age of registries, scope, method of coding, possible mapping to international terminologies as well as self-reported problems and suggestions for improvement.
RESULTS: Sixteen regional or national kidney biopsy registries were identified, of which 11 were older than 10 years. Most registries were located either in Europe (10/16) or in Asia (4/16). Registries most often use a proprietary coding system (12/16). Only a few of these coding systems were mapped to SNOMED CT (1), older SNOMED versions (2) or ERA-EDTA PRD (3). Lack of maintenance and updates of the coding system was the most commonly reported problem.
CONCLUSIONS: There were large gaps in the global coverage of kidney biopsy registries. Limited use of international coding systems among existing registries hampers interoperability and exchange of data. The study underlines that the use of a common and uniform coding system is necessary to fully realize the potential of kidney biopsy registries.