Khoo Kok Siong

Structure study of two-neutron halo nuclei, 22C using three-body model

Nucleus 22C is one of the exotic neutron-rich nuclei placed near neutron drip line has a Borromean system (core + n + n). The weakly bound system causes nucleus 22C has large radial extended. The structure of two-neutron halo 22C was investigated in the three-body model (20C+ n +n). Jacobi coordinates was used in this model and used to describe configuration-T and Y. Hamiltonian of three-body system was used to study neutron halo features such as binding energy of neutron valence, root mean square matter radii, and core deformation. In this study, the core deformation was used to determine the binding energy of neutron valence and root mean square matter radii. All the calculations were run in the MATLAB. The results showed that the 22C binding energies of neutron valence were in between −1.737 ~ −1.792 MeV, while the root mean squares matter radii were in between 6.451 ~ 7.011 fm, and the core of 22C has deformation values. Based on the results, 22C is considered as a halo nucleus due to the root mean sq...

Synthesis and characterization of exfoliated graphene oxide

Graphene oxide has many applications such as in electronic devices, as storage energy device, biosensor, biomedical application, water purification, coating technology, as a composite and paper like materials. Hummer’s method is one of the most common methods used in synthesizing graphene oxide. Graphene is different in size and structure because of oxidized layered of graphene oxide hence, the expanded interlayer structure of graphene oxide can be easily exfoliated by ultrasonication. We report on the preparation of exfoliated graphene oxide by using sonication method. Ultraviolet-visible spectrometer (UV-Vis) and Fourier-Transform Infrared Spectra Analyzer (FTIR) were used to characterize the exfoliated graphite oxide. Exfoliation of graphite oxide is conducted using water bath sonication. In order to confirm the chemical conformation and structure of the produced graphene oxide, FTIR and UV-Vis spectroscopy were utilized. Both peak of C=O and C-C bond are detected using UV-Vis and the results were conf...

Solubility of 238U radionuclide from various types of soil in synthetic gastrointestinal fluids using “US in vitro” digestion method

238U radionuclide is a naturally occuring radioactive material that can be found in soil. In this study, the solubility of 238U radionuclide obtained from various types of soil in synthetic gastrointestinal fluids was analysed by “US P in vitro” digestion method. The synthetic gastrointestinal fluids were added to the samples with well-ordered, mixed throughly and incubated according to the human physiology digestive system. The concentration of 238U radionuclide in the solutions extracted from the soil was measured using Induced Coupling Plasma Mass Spectrometer (ICP-MS). The concentration of 238U radionuclide from the soil samples in synthetic gastrointestinal fluids showed different values due to different homogenity of soil types and chemical reaction of 238U radionuclide. In general, the solubility of 238U radionuclide in gastric fluid was higher (0.050 – 0.209 ppm) than gastrointestinal fluids (0.024 – 0.050 ppm). It could be concluded that the US P in vitro digestion method is practicle for estimating the solubility of 238U radionuclide from soil materials and could be useful for monitoring and risk assessment purposes applying to environmental, health and contaminated soil samples.

Study of two-neutron halo structure nucleus 19B and 22C via core deformation parameter at s-and p-states

Nucleus 19B and 22C are the neutron-rich nuclei which has a Borromean system (core + n + n). These two nuclei were placed near to neutron drip line which mean it not very stable and tended to release two valence nucleon (neutron). In this case these two nuclei had two-neutron halo that are weakly bound between the core and the two valence nucleon. According to the experimental data, these two nuclei had low three-body binding energy which are −1.14 MeV (19B) and −1.360 MeV (22C). In this paper, we used cluster microscopic model (three-body model+shell model) to investigate the structure of two-neutron halo 19B and 22C. We used s- and p-state (wavefunction) approach to study the core deformation parameter and the binding energy of the three-body. The results showed the binding energy of valance nucleon of 19B were −1.248, −1.570 and −1.670 MeV, meanwhile for 22C were −1.239, −1.661 and −1.777 MeV. These two nuclei exhibit prolate shapes due to the values of core deformation parameter were 0.400 and 0.5357 for 19B and for 22C were 0.3600 and 0.5261. In conclusion, 19B and 22C still experienced halo phenomena for both s- and p-states.Nucleus 19B and 22C are the neutron-rich nuclei which has a Borromean system (core + n + n). These two nuclei were placed near to neutron drip line which mean it not very stable and tended to release two valence nucleon (neutron). In this case these two nuclei had two-neutron halo that are weakly bound between the core and the two valence nucleon. According to the experimental data, these two nuclei had low three-body binding energy which are −1.14 MeV (19B) and −1.360 MeV (22C). In this paper, we used cluster microscopic model (three-body model+shell model) to investigate the structure of two-neutron halo 19B and 22C. We used s- and p-state (wavefunction) approach to study the core deformation parameter and the binding energy of the three-body. The results showed the binding energy of valance nucleon of 19B were −1.248, −1.570 and −1.670 MeV, meanwhile for 22C were −1.239, −1.661 and −1.777 MeV. These two nuclei exhibit prolate shapes due to the values of core deformation parameter were 0.400 and 0.5357 ...

Biokinetic modelling development and analysis of arsenic dissolution into the gastrointestinal tract using SAAM II

A mathematical model comprising 8 compartments were designed to describe the kinetic dissolution of arsenic (As) from water leach purification (WLP) waste samples ingested into the gastrointestinal system. A totally reengineered software system named Simulation, Analysis and Modelling II (SAAM II) was employed to aid in the experimental design and data analysis. As a powerful tool that creates, simulate and analyze data accurately and rapidly, SAAM II computationally creates a system of ordinary differential equations according to the specified compartmental model structure and simulates the solutions based upon the parameter and model inputs provided. The experimental design of in vitro DIN approach was applied to create an artificial gastric and gastrointestinal fluids. These synthetic fluids assay were produced to determine the concentrations of As ingested into the gastrointestinal tract. The model outputs were created based upon the experimental inputs and the recommended fractional transfer rates pa...

Internal dose assessment of 238U contaminated soils based on in-vitro gastrointestinal protocol

Human exposure to natural radioactive uranium has been a great interest as more industrial rapidly growing contributes to radiation risks. The aim of this case study was to determine the internal dose in humans incorporated with ingestion of 238U contaminated soils. A gastrointestinal analogue test was employed to simulate the human digestive tract. In-vitro approach via German DIN 19738 model was developed in order to estimate the internal exposure of 238U due to ingestion of different types of soils. Synthetic gastrointestinal fluids assay via in-vitro method were produced to determine the concentration of 238U in various soils using ICP-MS. Based on the results, concentration of 238U in BRIS, laterite, peat and alluvium soils were in ranged between (0.0061 ± 0.0057 - 0.0488 ± 0.0148) ppm and (0.0005 ± 0.0004 - 0.0046 ± 0.0007) ppm in gastric and gastrointestinal phase respectively. Types of soil compositions and pH medium were some of the factors that influence mobilization and solubility of 238U conta...

Solubility assessment of 232Th from various types of soil in Malaysia using USP and DIN in Vitro digestion method

The overall results of the study showed that the concentrations of 232Th radionuclide using DIN digestion method during gastric phase are 0.0015 mg/kg – 0.0554 mg/kg and 0.0015 mg/kg – 0.0139 mg/kg during intestinal phase, respectively. As for USP digestion method during gastric phase are between 0.0877 mg/kg – 0.4964 mg/kg and 0.0207 mg/kg – 0.2291 mg/kg. The results from the measurements in various types of soils indicates some elevation of 232Th concentration in some types of soil compared to UNSCEAR reference values, in which may be a result from the impact of previous mining activity in the surrounding area and considered to be safe. In general, the results of 232Th concentrations from in vitro extraction technique is considered to be safe. By natural processes, thorium ingestion is getting transferred to living beings through different pathways and need to be monitored in order to assess possible hazards. Environmental studies are generally carried out to trace the pathway of radionuclides/radiotoxi...

The study of equivalent dose of uranium in long bean (V. U. Sesquipedalis) and the effect on human

In the case of accidental release of Uranium-238 (238U) radionuclides in a nuclear facility or in the environment, internal contamination by either acute or chronic exposure has the potential to induce both radiological and chemical toxic effects. A study was conducted to estimate the 238U radionuclide concentration in the long beans using Induced Coupled Mass Plasma-Spectrometry (ICP-MS). 238U radionuclide is a naturally occurring radioactive material that can be found in soil and can be transferred to the long bean (Vigna unguiculata subsp. Sesquapedalis) directly or indirectly via water or air. Kidney and liver are the major sites of deposition of 238U radionuclide. The obtained dose exposed in the liver and kidney is used to assess the safety level for public intake of 238U radionuclide from the consumption of long beans. The concentration of 238U radionuclide measured in long bean samples was 0.0226 ± 0.0009 mg/kg. Total activity of 238U radionuclide was 0.0044 ± 0.0002 Bq/day with the daily intake o...

Methanol as a Suitable Solvent for Polyaniline Emeraldine Base (PANI‐EB)

Conducting polyaniline is unique among conducting polymers on account of its excellent optical and electronic properties. The processing of conducting polymers has attracted considerable attention owing to their possible application in molecule‐based electronic devices, such as molecular rectifiers, field‐ effect transistors, molecular transducers and sensors. Methods that were applied in this study are addition method (powder), liquid homogeneous method and filtration method. The effects of bonding between methanol and Polyaniline emeraldine base (PANI‐EB) has been investigated. UV‐visible spectrum shows two sharp absorption peaks at 350nm (π‐ π*) and ∼720nm (polaron bands). FTIR spectra proved there is a distinct increase in wave number when PANI‐EB dissolved in methanol which caused by the H‐bonding interaction between PANI‐EB chains and methanol. Thus this make the PANI‐EB molecules change in size that supported by a DLS result. As a conclusion, it indicates that there is interaction between methanol molecules and polyaniline chains.

Synthesis CdS Nanocrystals in Various pH Values

Cadmium Sulfide nanocrystals were prepared by colloidal method. Thioglycolic Acid (TGA) as capping agent and NaOH as pH modifier have been used during synthesis. The CdS nanocrystals have been investigated at different pH. The characterizations of this CdS NCs were studied by using Uv‐Vis Absorption Spectrometer, Photoluminescence Spectrometer, and Transmission Electron Microscopic. Experiment shows a slight difference of optical properties resulting from acidic to alkaline conditions. The excitation wavelength for the samples is at 422 nm.