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Displaying publications 21 - 28 of 28 in total

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Photonic crystal fibre as a potential medium for radiotherapy dosimetry

Begum M, Rahman AKMM, Abdul-Rashid HA, Yusoff Z, Mat Nawi SN, Khandaker MU, et al.

Appl Radiat Isot, 2021 Aug;174:109771.
PMID: 34048992 DOI: 10.1016/j.apradiso.2021.109771

Present study concerns the key thermoluminescence (TL) properties of photonic crystal fibres (PCFs), seeking development of alternatively structured TL materials that are able to offer a advantages over existing passive dosimeters. In terms of their internal structure and light guiding properties the PCFs, collapsed and structured, differ significantly from that of conventional optical fibres. To investigate the dosimetric parameters of the PCFs use was made of a linear accelerator producing a 6 MV photon beam, delivering doses ranging from 0.5 Gy to 8 Gy. The parameters studied included TL response, linearity index, glow curves, relative sensitivity and TL signal fading, the results being compared against those obtained using TLD-100 chips. At 4 Gy photon dose the Ge-doped collapsed PCFs were found to provide a response 27 × that of structured PCF, also giving a TL yield similar to that of standard TLD-100 chips. Over post-irradiation periods of 15 and 30 days collapsed PCF TL signal fading were 8% and 17% respectively, with corresponding values of 37% and 64% for the structured PCF. Trapping parameters including the order of kinetics (b), activation energy (E) and frequency factor (s-1) were assessed with Chen's peak shape method. Lifetime of trapping centre was found to be (2.36 E+03) s and (9.03 E +01) s regarding the collapsed and structured PCF respectively with 6 Gy of photon beam. For the Ge-doped collapsed PCF, the high TL yield, sensitivity and low fading provide the basis of a highly promising system of TLD for radiotherapy applications.
Fulltext Effects of Tungsten Disulphide Coating on Tapered Microfiber for Relative Humidity Sensing Applications

Ali N, Azzuhri SR, Johari MAM, Rashid H, Khudus MIMA, Razak MZA, et al.

Sensors (Basel), 2021 Oct 27;21(21).
PMID: 34770442 DOI: 10.3390/s21217132

Tungsten disulphide (WS2) is a two-dimensional transition-metal dichalcogenide material that can be used to improve the sensitivity of a variety of sensing applications. This study investigated the effect of WS2 coating on tapered region microfiber (MF) for relative humidity (RH) sensing applications. The flame brushing technique was used to taper the standard single-mode fiber (SMF) into three different waist diameter sizes of MF 2, 5, and 10 µm, respectively. The MFs were then coated with WS2 via a facile deposition method called the drop-casting technique. Since the MF had a strong evanescent field that allowed fast near-field interaction between the guided light and the environment, depositing WS2 onto the tapered region produced high humidity sensor sensitivity. The experiments were repeated three times to measure the average transmitted power, presenting repeatability and sensing stability. Each MF sample size was tested with varying humidity levels. Furthermore, the coated and non-coated MF performances were compared in the RH range of 45-90% RH at room temperature. It was found that the WS2 coating on 2 µm MF had a high sensitivity of 0.0861 dB/% RH with linearity over 99%. Thus, MF coated with WS2 encourages enhancement in the evanescent field effect in optical fiber humidity sensor applications.
Latest developments in silica-based thermoluminescence spectrometry and dosimetry

Bradley DA, Jafari SM, Siti Shafiqah AS, Tamcheck N, Shutt A, Siti Rozaila Z, et al.

Appl Radiat Isot, 2016 Nov;117:128-134.
PMID: 26778762 DOI: 10.1016/j.apradiso.2015.12.034

Using irradiated doped-silica preforms from which fibres for thermoluminescence dosimetry applications can be fabricated we have carried out a range of luminescence studies, the TL yield of the fibre systems offering many advantages over conventional passive dosimetry types. In this paper we investigate such media, showing emission spectra for irradiated preforms and the TL response of glass beads following irradiation to an 241Am-Be neutron source located in a tank of water, the glass fibres and beads offering the advantage of being able to be placed directly into liquid. The outcomes from these and other lines of research are intended to inform development of doped silica radiation dosimeters of versatile utility, extending from environmental evaluations through to clinical and industrial applications.
Evaluation of potential bacterial protease inhibitor properties of selected hydroxyquinoline derivatives: an in silico docking and molecular dynamics simulation approach

Riaz F, Hossain MS, Roney M, Ali Y, Qureshi S, Muhammad R, et al.

J Biomol Struct Dyn, 2023 Nov;41(19):9756-9769.
PMID: 36399018 DOI: 10.1080/07391102.2022.2146200

Antimicrobial drug resistance (AMR) is a severe global threat to public health. The increasing emergence of drug-resistant bacteria requires the discovery of novel antibacterial agents. Quinoline derivatives have previously been reported to exhibit antimalarial, antiviral, antitumor, antiulcer, antioxidant and, most interestingly, antibacterial properties. In this study, we evaluated the binding affinity of three newly designed hydroxyquinolines derived from sulfanilamide (1), 4-amino benzoic acid (2) and sulfanilic acid (3) towards five bacterial protein targets (PDB ID: 1JIJ, 3VOB, 1ZI0, 6F86, 4CJN). The three derivatives were designed considering the amino acid residues identified at the active site of each protein involved in the binding of each co-crystallized ligand and drug-likeness properties. The ligands displayed binding energy values with the target proteins ranging from -2.17 to -8.45 kcal/mol. Compounds (1) and (3) showed the best binding scores towards 1ZI0/3VOB and 1JIJ/4CJN, respectively, which may serve as new antibiotic scaffolds. Our in silico results suggest that sulfanilamide (1) or sulfanilic acid (3) hydroxyquinoline derivatives have the potential to be developed as bacterial inhibitors, particularly MRSA inhibitors. But before that, it must go through the proper preclinical and clinical trials for further scientific validation. Further experimental studies are warranted to explore the antibacterial potential of these compounds through preclinical and clinical studies.Communicated by Ramaswamy H. Sarma.
Synthesis, characterization and thermoluminescence properties of LiCaPO4 phosphor for ionizing radiation dosimetry

Rahat MR, Mimi HA, Islam SA, Kamruzzaman M, Ferdous J, Begum M, et al.

Appl Radiat Isot, 2023 Dec;202:111047.
PMID: 37782983 DOI: 10.1016/j.apradiso.2023.111047

Many minerals and compounds show thermoluminescence (TL) properties but only a few of them can meet the requirements of an ideal dosimeter. Several phosphate materials have been studied for low-dose dosimetryin recent times. Among the various phosphates, ABPO4-type material shows interesting TL properties. In this study, an ABPO4-type (A = Lithium, B=Calcium) phosphor is synthesized using a modified solid-state diffusion method. Temperature is maintained below 800 °C in every step of phosphor preparation to obtain the pure phase of Lithium calcium phosphate (LiCaPO4). The purpose of this work is to synthesize LiCaPO4 using a simple method, examine its structural and luminescence properties in order to gain a deeper understanding of its TL characteristics. The general TL properties, such as TL glow curve, dose linearity, sensitivity, and fading, are investigated. Additionally, this study aims to determine various kinetic parameters through Glow Curve Deconvolution (GCD) method using the Origin Lab software together with the Chen model. XRD analysis confirmed the phase purity of the phosphor with a rhombohedral structure. Lattice parameters, unit cell volume, grain size, dislocated density, and microstrain were also calculated from XRD data. Raman analysis and Fourier Transform Infrared analysis were used to collect information about molecular bonds, vibrations, identity, and structure of the phosphor. To investigate TL properties and associated kinetic parameters, the phosphor was irradiated with 6.0 MV (photon energy) and 6.0 MeV (electron energy) from a linear accelerator for doses ranging from 0.5 Gy to 6.0 Gy. For both photon and electron energy, TL glow curves have two identical peaks near 200 °C and 240 °C.The TL glow curves for 0.5 Gy-6 Gy are deconvoluted, then fitted with the appropriate model and then calculated the kinetic parameters. Kinetic parameters such as geometric factor (μg), order of kinetics, activation energy (E), and frequency factor (s) are obtained from Chen's peak shape method. The dose against the TL intensity curve shows that the response is almost linear in the investigated dose range. For photon and electron energy, the phosphor is found to be the most sensitive at 2.0 Gy and 4.0 Gy, respectively. The phosphor shows a low fading and after 28 days of exposure, it shows a signal loss of better than 3%. The studied TL properties suggest the suitability of LiCaPO4 in radiation dosimetry and associated fields.
Fulltext An extendable optical fibre probe survey meter for naturally occurring radioactive material (NORM) and other weak emitters

Zubair HT, Bradley DA, Khairina MD, Oresegun A, Basaif A, Othman J, et al.

Sci Rep, 2023 Jul 24;13(1):11918.
PMID: 37488183 DOI: 10.1038/s41598-023-39180-9

We have developed a radioluminescence-based survey meter for use in industries in which there is involvement in naturally occurring radioactive material (NORM), also in support of those needing to detect other weak emitters of radiation. The functionality of the system confronts particular shortcomings of the handheld survey meters that are currently being made use of. The device couples a LYSO:Ce scintillator with a photodetector via a polymer optical fibre waveguide, allowing for "intrinsically safe" inspection within pipework, separators, valves and other such component pieces. The small-diameter optical fibre probe is electrically passive, immune to electromagnetic interference, and chemically inert. The readout circuit is entirely incorporated within a handheld casing housing a silicon photomultiplier (SiPM) detection circuit and a microprocessor circuit connected to an LCD display. A 15 m long flexible PMMA optical fibre waveguide is butt coupled to an ABS plastic probe that retains the LYSO:Ce scintillator. Initial tests have included the use of lab-based mixed gamma-ray sources, measurements being made in concert with a reference conventional GM survey-meter. Characterization, via NORM sources at a decontamination facility, has shown useful sensitivity, covering the dose-rate range 0.10- to 28 µSv h-1 (R-squared 0.966), extending to 80 µSv/h as demonstrated in use of a Cs-137 source. The system is shown to provide an effective tool for detection of radioactivity within hard to access locations, in particular for sources emitting at low radiation levels, down to values that approach background.
The thermoluminescence glow curve and the deconvoluted glow peak characteristics of erbium doped silica fiber exposed to 70-130 kVp x-rays

Alawiah A, Bauk S, Marashdeh MW, Nazura MZ, Abdul-Rashid HA, Yusoff Z, et al.

Appl Radiat Isot, 2015 Oct;104:197-202.
PMID: 26188687 DOI: 10.1016/j.apradiso.2015.07.011

In regard to thermoluminescence (TL) applied to dosimetry, in recent times a number of researchers have explored the role of optical fibers for radiation detection and measurement. Many of the studies have focused on the specific dopant concentration, the type of dopant and the fiber core diameter, all key dependencies in producing significant increase in the sensitivity of such fibers. At doses of less than 1 Gy none of these investigations have addressed the relationship between dose response and TL glow peak behavior of erbium (Er)-doped silica cylindrical fibers (CF). For x-rays obtained at accelerating potentials from 70 to 130 kVp, delivering doses of between 0.1 and 0.7 Gy, present study explores the issue of dose response, special attention being paid to determination of the kinetic parameters and dosimetric peak properties of Er-doped CF. The effect of dose response on the kinetic parameters of the glow peak has been compared against other fiber types, revealing previously misunderstood connections between kinetic parameters and radiation dose. Within the investigated dose range there was an absence of supralinearity of response of the Er-doped silica CF, instead sub-linear response being observed. Detailed examination of glow peak response and kinetic parameters has thus been shown to shed new light of the rarely acknowledged issue of the limitation of TL kinetic model and sub-linear dose response of Er-doped silica CF.
Fulltext Clinical characteristics, outcomes, and management of COVID-19 in kidney transplant recipients across Asia: an ASTREGO report

Kee T, Jeong JC, Ur-Rashid H, Begum NAS, Arakama MH, Danguilan R, et al.

Korean J Transplant, 2021 Dec 31;35(4):218-229.
PMID: 35769859 DOI: 10.4285/kjt.21.0024

BACKGROUND: Asia is the global epicenter of the coronavirus disease 2019 (COVID-19) pandemic; however, COVID-19-related mortality in Asia remains lower than in other parts of the world. It is uncertain whether the mortality of COVID-19-infected kidney transplant recipients (KTXs) from Asia follows the lower mortality trends of the younger Asian population.
METHODS: Specific transplant centers from countries in the Asian Society of Transplantation were invited to participate in a study to examine the epidemiology, clinical features, natural history, and outcomes of COVID-19 infections in KTXs. Data were analyzed and compared with those of large cohort studies from other countries.
RESULTS: The study population was 87 KTXs from nine hospitals in seven Asian countries. Within the study population, 9% were aged 60 years and older, and 79% had at least one comorbidity. The majority of patients (69%) presented with mild-to-moderate COVID-19 severity. Disease progression was more frequently encountered among those with moderate or severe infection (23%) and non-survivors (55%). The mortality rate was 23% (n=20) and differed according to the level of care 12% (n=1/8), 15% (n=10/67), and 100% (n=9/9) of patients managed as outpatients, in the general ward, and in the intensive care unit, respectively. Disease severity at the time of presentation was an independent predictor of mortality. Compared with the mortality rates in other studies worldwide, mortality rates in the current study were comparable.
CONCLUSIONS: Mortality in Asian KTXs who were infected with COVID-19 remains high and could be related to comorbidity burden and the constraints of the general healthcare system when the COVID-19 caseload is high.