Displaying publications 1 - 20 of 65 in total

Abstract:
Sort:
  1. Endotoxin, ergosterol, muramic acid and fungal DNA in dust from schools in Johor Bahru, Malaysia--Associations with rhinitis and sick building syndrome (SBS) in junior high school students
    Norbäck D, Hashim JH, Markowicz P, Cai GH, Hashim Z, Ali F, et al.
    Sci Total Environ, 2016 Mar 1;545-546:95-103.
    PMID: 26745297 DOI: 10.1016/j.scitotenv.2015.12.072
    This paper studied associations between ocular symptoms, rhinitis, throat and dermal symptoms, headache and fatigue in students by ethnicity and in relation to exposure to chemical microbial markers and fungal DNA in vacuumed dust in schools in Malaysia. A total of 462 students from 8 randomly selected secondary schools in Johor Bahru, Malaysia, participated (96% response rate). Dust was vacuumed from 32 classrooms and analysed for levels of five types of endotoxin as 3-hydroxy fatty acids (C10, C12, C14, C16 and C18 3-OH), muramic acid, ergosterol and five sequences of fungal DNA. Multiple logistic regression was applied. Totally 11.9% reported weekly ocular symptoms, 18.8% rhinitis, 15.6% throat and 11.1% dermal symptoms, 20.6% headache and 22.1% tiredness. Totally 21.1% reported pollen or furry pet allergy (atopy) and 22.0% parental asthma or allergy. Chinese students had less headache than Malay and Indian had less rhinitis and less tiredness than Malay. Parental asthma/allergy was a risk factor for ocular (odds ratio=3.79) and rhinitis symptoms (OR=3.48). Atopy was a risk factor for throat symptoms (OR=2.66), headache (OR=2.13) and tiredness (OR=2.02). There were positive associations between amount of fine dust in the dust samples and ocular symptoms (p<0.001) and rhinitis (p=0.006). There were positive associations between C14 3-OH and rhinitis (p<0.001) and between C18 3-OH and dermal symptoms (p=0.007). There were negative (protective) associations between levels of total endotoxin (LPS) (p=0.004) and levels of ergosterol (p=0.03) and rhinitis and between C12 3-OH and throat symptoms (p=0.004). In conclusion, the amount of fine dust in the classroom was associated with rhinitis and other SBS symptoms and improved cleaning of the schools is important. Endotoxin in the school dust seems to be mainly protective for rhinitis and throat symptoms but different types of endotoxin could have different effects. The ethnic differences in symptoms among the students deserve further attention.
  2. Association between indoor microbiome exposure and sick building syndrome (SBS) in junior high schools of Johor Bahru, Malaysia
    Fu X, Norbäck D, Yuan Q, Li Y, Zhu X, Hashim JH, et al.
    Sci Total Environ, 2021 Jan 20;753:141904.
    PMID: 32890872 DOI: 10.1016/j.scitotenv.2020.141904
    Sick building syndrome (SBS) is a collection of nonspecific syndromes linked with the built environment. The occurrence of SBS is associated with humidity, ventilation, moulds and microbial compounds exposure. However, no study has reported the association between indoor microbiome and SBS. In this study, 308 students were surveyed for SBS symptoms from 21 classrooms of 7 junior high schools from Johor Bahru, Malaysia, and vacuum dust from floor, desks and chairs was collected. High throughput amplicon sequencing (16S rRNA gene and ITS region) and quantitative PCR were conducted to characterize the absolute concentration of bacteria and fungi taxa. In total, 326 bacterial and 255 fungal genera were detected in dust with large compositional variation among classrooms. Also, half of these samples showed low compositional similarity to microbiome data deposited in the public database. The number of observed OTUs in Gammaproteobacteria was positively associated with SBS (p = 0.004). Eight microbial genera were associated with SBS (p 
  3. Volatile organic compounds (VOC), formaldehyde and nitrogen dioxide (NO2) in schools in Johor Bahru, Malaysia: Associations with rhinitis, ocular, throat and dermal symptoms, headache and fatigue
    Norbäck D, Hashim JH, Hashim Z, Ali F
    Sci Total Environ, 2017 Aug 15;592:153-160.
    PMID: 28319702 DOI: 10.1016/j.scitotenv.2017.02.215
    This paper studied associations between volatile organic compounds (VOC), formaldehyde, nitrogen dioxide (NO2) and carbon dioxide (CO2) in schools in Malaysia and rhinitis, ocular, nasal and dermal symptoms, headache and fatigue among students. Pupils from eight randomly selected junior high schools in Johor Bahru, Malaysia (N=462), participated (96%). VOC, formaldehyde and NO2 were measured by diffusion sampling (one week) and VOC also by pumped air sampling during class. Associations were calculated by multi-level logistic regression adjusting for personal factors, the home environment and microbial compounds in the school dust. The prevalence of weekly rhinitis, ocular, throat and dermal symptoms were 18.8%, 11.6%, 15.6%, and 11.1%, respectively. Totally 20.6% had weekly headache and 22.1% fatigue. Indoor CO2 were low (range 380-690 ppm). Indoor median NO2 and formaldehyde concentrations over one week were 23μg/m3 and 2.0μg/m3, respectively. Median indoor concentration of toluene, ethylbenzene, xylene, and limonene over one week were 12.3, 1.6, 78.4 and 3.4μg/m3, respectively. For benzaldehyde, the mean indoor concentration was 2.0μg/m3 (median<1μg/m3). Median indoor levels during class of benzene and cyclohexane were 4.6 and 3.7μg/m3, respectively. NO2 was associated with ocular symptoms (p<0.001) and fatigue (p=0.01). Formaldehyde was associated with ocular (p=0.004), throat symptoms (p=0.006) and fatigue (p=0.001). Xylene was associated with fatigue (p<0.001) and benzaldehyde was associated with headache (p=0.03). In conclusion, xylene, benzaldehyde, formaldehyde and NO2 in schools can be risk factors for ocular and throat symptoms and fatigue among students in Malaysia. The indoor and outdoor levels of benzene were often higher than the EU standard of 5μg/m3.
  4. Fulltext Expanding Opportunities for Science, Technology, Engineering and Mathematics Subjects Teaching and Learning: Connecting through Comics
    Adnan M, Abdullah JM, Ibharim LFM, Hoe TW, Janan D, Abdullah N, et al.
    Malays J Med Sci, 2019 Jul;26(4):127-133.
    PMID: 31496902 MyJurnal DOI: 10.21315/mjms2019.26.4.15
    This study presents the results of a year-long project focused on analysis and reflection on working with comics by Year One students in Hulu Langat districts. This study presents the use of science, technology, engineering and mathematics (STEM) comics to help children understand certain physical phenomena and try to make students interested in mathematics and science subject. Thirteen excellent teachers of science and mathematics from the Hulu Langat district were involved in the analysis of syllabus Year One science and mathematics subjects and the preparation of scripts while the STEM comic illustrator was created by two lecturers from the Faculty of Art, Computing and Creative Industry from Universiti Pendidikan Sultan Idris, Perak Malaysia. The study is based on observations of changing perception of phenomena by children as a result of the use of comics. As a result, a STEM comic that contains ten series for Year One science and mathematics subjects has been successfully developed. This comic is expected to attract and enhance the achievement of Year One students in science and mathematics. Implication of this study, STEM comics can be used by teachers as science and mathematics teaching aids. Comics are proven to be a modern pedagogical strategy, which is starting to gain its popularity in teaching about mathematics and science. Comics can be very helpful tools in making science and mathematics concepts interesting, fun learning and comprehensible for a Year One children.
  5. Fulltext Nutritional Compositions and Antiproliferative Activities of Different Solvent Fractions from Ethanol Extract of Cyphomandra betacea (Tamarillo) Fruit
    Mutalib MA, Rahmat A, Ali F, Othman F, Ramasamy R
    Malays J Med Sci, 2017 Oct;24(5):19-32.
    PMID: 29386969 MyJurnal DOI: 10.21315/mjms2017.24.5.3
    BACKGROUND: This study aims to examine various solvent extracts of Cyphomandra betacea (tamarillo) also known as the tree tomato, for their bioactive constituents and antioxidant activity. The study also aims to examine its effect on cancer cell death using two types of cancer cell lines (liver and breast cancer cell).

    METHODS: The first part of the study evaluates the nutritional composition of tamarillo. Then, phytochemical profiling using GC-MS analysis in ethanolic tamarillo extract was conducted. Different fractions of n-butanol, ethyl acetate and aqueous fractions were obtained from the ethanolic extract of tamarillo. Then, the fractions were subjected to the quantification of total phenol (TPC) and flavonoid contents (TFC), free radical scavenging activity (SA) and also antioxidant activity (AOX) assayed by beta-carotene bleaching (BCB) assay. Finally, the capability of the ethanolic extract of tamarillo and different fractions were evaluated for their anticancer properties.

    RESULTS: Findings from this study revealed that the nutritional composition (ash, protein, carbohydrate and total dietary fiber), and mineral levels (calcium, magnesium, potassium and iron) of tamarillo were moderate. The crude ethanol extract of tamarillo contained the highest phenolic and total flavonoid content. FT-IR analysis revealed the presence of alkanes, carboxylic acid, phenol, alkanes, carboxylic acids, aromatics and nitro compounds. Twelve bioactive constituents in tamarillo have been identified through GC-MS analysis. Cytotoxic activity suggests the potential of ethanolic extracts of tamarillo having a chemopreventive effect on breast and liver cancer cells.

    CONCLUSION: This study reveals that tamarillo has substantial antioxidant activity as well as anticancer properties.

  6. Fulltext Delayed reverse sural flap for cover of heel defect in a patient with associated vascular injury. A case report
    Ali F, Harunarashid H, Yugasmavanan K
    Indian J Surg, 2013 Jun;75(Suppl 1):148-9.
    PMID: 24426545 DOI: 10.1007/s12262-012-0565-x
    The delay reverse sural neurofasciocutaneous flap is used to reconstruct soft tissue defects in the lower third of the leg to improve outcome in patients with associated comorbidities such as diabetes mellitus, hypertension, hypercholesterolaemia, smokers and ischaemic heart disease. The author reports the use of a delayed reverse sural flap as soft tissue cover for a calcaneal defect in a patient with associated comorbidities who has an ipsilateral Gred 3C (Gustilo) tibial fracture after vascular reconstruction.
  7. Fulltext Impaired of a non-DNA dependent methylation status decides the fat decision of bone marrow-derived C3H10T1/2 stem cell
    Ali F, Ranneh Y, Ismail A, Vaes B
    Springerplus, 2013;2:590.
    PMID: 24294542 DOI: 10.1186/2193-1801-2-590
    A decrease in the lineage commitment of multipotent Mesenchymal stem cells (MSC) to the bone forming osteoblast lineage and an increase in the commitment to the fat forming adipocyte lineage is more common in bone marrow of elderly persons. A link between methylation status and MSC differentiation remains unclear. Therefore, we hypothesize that hypomethylation may decide the fate decisions of MSC. In the current study, murine bone marrow derived-C3H10T1/2 stem cell was used to examine the role of methylation mechanism on the differentiation potential of stem cells into osteoblasts or adipocytes. C3H10T1/2 cells were treated with Periodate oxidized adenosine (Adox), an inhibitor of S-adenosylhomocysteine-dependent hydrolase (SAHH), which in turn block the non-DNA methylation pathway. The effect of hypomethylation on C3H10T1/2 stem cell differentiation was determined by measuring the alkaline phosphates activity and the degree of mineralization as well as Oil-red O staining and lipid content. The ratio of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) was determined as a metabolic indicator of cellular methylation potential. It was clearly observed that hypomethylation significantly (P 
  8. Fulltext The inhibitory activity of cocoa phenolic extract against pro-inflammatory mediators secretion induced by lipopolysaccharide in RAW 264.7 cells
    Ranneh Y, Ali F, Al-Qubaisi M, Esa NM, Ismail A
    Springerplus, 2016;5:547.
    PMID: 27190746 DOI: 10.1186/s40064-016-2138-0
    Cocoa is a rich source of polyphenols that has been traditionally used as the treatment of several types of inflammation related disease. The response to inflammation comprises the consecutive release of mediators and the enlistment of circulating leukocytes, such as macrophages. Currently, Cocoa-derived polyphenolics have shown anti-inflammatory effects in vivo, but the therapeutic benefits in vitro remain unclear. Therefore, in this study, the effect of cocoa polyphenolic extract (CPE) on RAW 264.7 macrophage cells sensitized by lipopolysaccharide as in vitro inflammatory model was investigated. The anti-inflammatory activity of CPE was assessed by measuring its ability to inhibit the pro-inflammatory enzyme 5-lipoxygenase (5-LOX) and the pro-inflammatory mediators prostaglandin E2 (PGE2), reactive oxygen species (ROS), nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α). The results show that CPE significantly inhibits 5-LOX activity (p 
  9. Fulltext Ultra-Wideband (UWB) Antenna Sensor Based Microwave Breast Imaging: A Review
    Mahmud MZ, Islam MT, Misran N, Almutairi AF, Cho M
    Sensors (Basel), 2018 Sep 05;18(9).
    PMID: 30189633 DOI: 10.3390/s18092951
    Globally, breast cancer is reported as a primary cause of death in women. More than 1.8 million new breast cancer cases are diagnosed every year. Because of the current limitations on clinical imaging, researchers are motivated to investigate complementary tools and alternatives to available techniques for detecting breast cancer in earlier stages. This article presents a review of concepts and electromagnetic techniques for microwave breast imaging. More specifically, this work reviews ultra-wideband (UWB) antenna sensors and their current applications in medical imaging, leading to breast imaging. We review the use of UWB sensor based microwave energy in various imaging applications for breast tumor related diseases, tumor detection, and breast tumor detection. In microwave imaging, the back-scattered signals radiating by sensors from a human body are analyzed for changes in the electrical properties of tissues. Tumorous cells exhibit higher dielectric constants because of their high water content. The goal of this article is to provide microwave researchers with in-depth information on electromagnetic techniques for microwave imaging sensors and describe recent developments in these techniques.
  10. Fulltext A Polarization Independent Quasi-TEM Metamaterial Absorber for X and Ku Band Sensing Applications
    Hoque A, Tariqul Islam M, Almutairi AF, Alam T, Jit Singh M, Amin N
    Sensors (Basel), 2018 Nov 30;18(12).
    PMID: 30513675 DOI: 10.3390/s18124209
    In this paper, a dual-band metamaterial absorber (MMA) ring with a mirror reflexed C-shape is introduced for X and Ku band sensing applications. The proposed metamaterial consists of two square ring resonators and a mirror reflexed C-shape, which reveals two distinctive absorption bands in the electromagnetic wave spectrum. The mechanism of the two-band absorber particularly demonstrates two resonance frequencies and absorption was analyzed using a quasi-TEM field distribution. The absorption can be tunable by changing the size of the metallic ring in the frequency spectrum. Design and analysis of the proposed meta-absorber was performed using the finite-integration technique (FIT)-based CST microwave studio simulation software. Two specific absorption peaks value of 99.6% and 99.14% are achieved at 13.78 GHz and 15.3 GHz, respectively. The absorption results have been measured and compared with computational results. The proposed dual-band absorber has potential applications in sensing techniques for satellite communication and radar systems.
  11. Fulltext An Octagonal Ring-shaped Parasitic Resonator Based Compact Ultrawideband Antenna for Microwave Imaging Applications
    Hossain A, Islam MT, Almutairi AF, Singh MSJ, Mat K, Samsuzzaman M
    Sensors (Basel), 2020 Mar 01;20(5).
    PMID: 32121477 DOI: 10.3390/s20051354
    An Ultrawideband (UWB) octagonal ring-shaped parasitic resonator-based patch antenna for microwave imaging applications is presented in this study, which is constructed with a diamond-shaped radiating patch, three octagonal, rectangular slotted ring-shaped parasitic resonator elements, and partial slotting ground plane. The main goals of uses of parasitic ring-shaped elements are improving antenna performance. In the prototype, various kinds of slots on the ground plane were investigated, and especially rectangular slots and irregular zigzag slots are applied to enhance bandwidth, gain, efficiency, and radiation directivity. The optimized size of the antenna is 29 × 24 × 1.5 mm3 by using the FR-4 substrate. The overall results illustrate that the antenna has a bandwidth of 8.7 GHz (2.80 ̶ 11.50 GHz) for the reflection coefficient S11 < -10 dB with directional radiation pattern. The maximum gain of the proposed prototype is more than 5.7 dBi, and the average efficiency over the radiating bandwidth is 75%. Different design modifications are performed to attain the most favorable outcome of the proposed antenna. However, the prototype of the proposed antenna is designed and simulated in the 3D simulator CST Microwave Studio 2018 and then effectively fabricated and measured. The investigation throughout the study of the numerical as well as experimental data explicit that the proposed antenna is appropriate for the Ultrawideband-based microwave-imaging fields.
  12. Fulltext Low-Profile Slotted Metamaterial Antenna Based on Bi Slot Microstrip Patch for 5G Application
    Hoque A, Islam MT, Almutairi AF
    Sensors (Basel), 2020 Jun 11;20(11).
    PMID: 32545228 DOI: 10.3390/s20113323
    A low-profile high-directivity, and double-negative (DNG) metamaterial-loaded antenna with a slotted patch is proposed for the 5G application. The radiated slotted arm as a V shape has been extended to provide a low-profile feature with a two-isometric view square patch structure, which accelerates the electromagnetic (EM) resonance. Besides, the tapered patch with two vertically split parabolic horns and the unit cell metamaterial expedite achieve more directive radiation. Two adjacent splits with meta units enhance the surface current to modify the actual electric current, which is induced by a substrate-isolated EM field. As a result, the slotted antenna shows a 7.14 dBi realized gain with 80% radiation efficiency, which is quite significant. The operation bandwidth is 4.27-4.40 GHz, and characteristic impedance approximately remains the same (50 Ω) to give a VSWR (voltage Standing wave ratio) of less than 2, which is ideal for the expected application field. The overall size of the antenna is 60 × 40 × 1.52 mm. Hence, it has potential for future 5G applications, like Internet of Things (IoT), healthcare systems, smart homes, etc.
  13. Tea from the drinking to the synthesis of metal complexes and fabrication of PVA based polymer composites with controlled optical band gap
    Brza MA, Aziz SB, Anuar H, Ali F, Dannoun EMA, Mohammed SJ, et al.
    Sci Rep, 2020 Oct 22;10(1):18108.
    PMID: 33093604 DOI: 10.1038/s41598-020-75138-x
    In the present study black tea extract (BTE) solution which is familiar for drinking was used to prepare cerium metal-complexes (Ce(III)-complex). The prepared Ce(III)-complex was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV-Vis spectroscopy. The results indicate that BTE solution is a novel green coordination chemistry approach for the synthesis of metal complexes. The outcomes signify that coordination occurs between cerium cations and polyphenols. The synthesis of metal-complexes with superior absorption performance in the visible region is a challenge for optoelectronic device applications. The suspended Ce(III)-complex in distilled water was mixed with poly (vinyl alcohol) (PVA) polymer to fabricate PVA/ Ce(III)-complex composites with controlled optical properties. The PVA/Ce(III)-complexes composite films were characterized by FTIR, XRD, and UV-Vis spectroscopy. The XRD findings confirms the amorphous structure for the synthesized Ce(III)-complexes. The addition of Ce(III)-complex into the PVA host polymer led to the growth of polymer composites with controllable small optical band gaps. It is shown by the FTIR spectra of the composite films that the functional groups of the host PVA have a vigorous interaction with the Ce(III)-complex. The XRD deconvolution on PVA composites reveals the amorphous phase enlargement with increasing Ce(III)-complex concentration. It is indicated in the atomic force microscopy (AFM) that the surface roughness in the doped PVA films increases with the increase of the Ce(III)-complex. There is a decrease in absorption edge from 5.7 to 1.7 eV. It becomes possible to recognize the type of electron transition by studying both the Tauc's model and optical dielectric loss (ɛi) parameter.
  14. Fulltext Realization of frequency hopping characteristics of an epsilon negative metamaterial with high effective medium ratio for multiband microwave applications
    Islam MT, Moniruzzaman M, Alam T, Samsuzzaman M, Razouqi QA, Almutairi AF
    Sci Rep, 2021 Aug 19;11(1):16898.
    PMID: 34413377 DOI: 10.1038/s41598-021-96228-4
    In this paper, a meander-lines-based epsilon negative (ENG) metamaterial (MTM) with a high effective medium ratio (EMR) and near-zero refractive index (NZI) is designed and investigated for multiband microwave applications. The metamaterial unit cell is a modification of the conventional square split-ring resonator in which the meander line concept is utilized. The meander line helps to increase the electrical length of the rings and provides strong multiple resonances within a small dimension. The unit cell of proposed MTM is initiated on a low-cost FR4 substrate of 1.5 mm thick and electrical dimension of 0.06λ × 0.06λ, where wavelength, λ is calculated at the lowest resonance frequency (2.48 GHz). The MTM provides four major resonances of transmission coefficient (S21) at 2.48, 4.28, 9.36, and 13.7 GHz covering S, C, X, and Ku bands. It shows negative permittivity, near-zero permeability, and near-zero refractive index in the vicinity of these resonances. The equivalent circuit is designed and modeled in Advanced Design System (ADS) software. The simulated S21 of the MTM unit cell is compared with the measured one and both show close similarity. The array performance of the MTM is also evaluated by using 2 × 2, 4 × 4, and 8 × 8 arrays that show close resemblance with the unit cell. The MTM offers a high effective medium ratio (EMR) of 15.1, indicating the design's compactness. The frequency hopping characteristics of the proposed MTM is investigated by open and short-circuited the three outer rings split gaps by using three switches. Eight different combinations of the switching states provide eight different sets of multiband resonances within 2-18 GHz; those give the flexibility of using the proposed MTM operating in various frequency bands. For its small dimension, NZI, high EMR, and frequency hopping characteristics through switching, this metamaterial can be utilized for multiband microwave applications, especially to enhance the gain of multiband antennas.
  15. Fulltext SNG and DNG meta-absorber with fractional absorption band for sensing application
    Hoque A, Islam MT, Almutairi AF, Chowdhury MEH, Samsuzzaman M
    Sci Rep, 2020 Aug 04;10(1):13086.
    PMID: 32753600 DOI: 10.1038/s41598-020-69792-4
    This paper reports on a tunable transmission frequency characteristics-based metamaterial absorber of an X band sensing application with a fractional bandwidth. Tunable resonator metamaterial absorbers fabricated with dielectric surface have been the subject of growing attention of late. Absorbers possess electromagnetic properties and range modification capacity, and they have yet to be studied in detail. The proposed microstructure resonator inspired absorber with triple fractional band absorption consists of two balanced symmetrical vertical patches at the outer periphery and a tiny drop hole at two edges. Experimental verification depicted two absorption bands with single negative (SNG) characteristics for two resonances, but double negative (DNG) for single resonance frequency. The mechanism of sensing and absorption was analyzed using the transmission line principle with useful parameter analysis. Cotton, a hygroscopic fiber with moisture content, was chosen to characterize the proposed absorber for the X band application. The electrical properties of the cotton changed depending on the moisture absorption level. The simulation and the measured absorption approximately justified the result; the simulated absorption was above 90% (at 10.62, 11.64, and 12.8 GHz), although the steady level was 80%. The moisture content of the cotton (at different levels from 0 to 32.13%) was simulated, and the transmission resonance frequency changed its point in two significant ranges. However, comparing the two adopted measurement method and algorithm applied to the S parameter showed a closer variation between the two resonances (11.64 and 12.8 GHz) which signified that a much more accurate measurement of the cotton dielectric constant was possible up to a moisture content of 16.1%. However, certain unwanted changes were noted at 8.4-8.9 GHz and 10.6-12.4 GHz. The proposed triple-band absorber has potential applications in the X band sensing of moisture in capsules or tablet bottles.
  16. Fulltext An octa-band planar monopole antenna for portable communication devices
    Azim R, Alam T, Mia MS, Almutairi AF, Islam MT
    Sci Rep, 2021 Jul 27;11(1):15298.
    PMID: 34315996 DOI: 10.1038/s41598-021-94753-w
    Due to the rapid development of wireless communication systems, good numbers of services and devices use different frequency bands and protocols. To concurrently cover all these services, the antenna in communication devices should operate over multiple frequency bands. The use of wide and multi-band antennas not only reduces the number of antennas necessary to cover multiple frequency bands but also lessens the system complexity, size, and costs. To operate over eight frequency bands to cover sixteen well-established narrow service bands, a planar monopole antenna is proposed for portable communication devices. The proposed antenna is comprised of an inverted F-shaped monopole patch with a rotated L-shaped strip and an F-shaped ground strip with a rotated L-shaped branch. The studied antenna can excite at multiple resonant modes which helps it to achieve eight measured operating bands of 789-921 MHz, 1367-1651 MHz, 1995-2360 MHz, 2968-3374 MHz, 3546-3707, 4091-4405 MHz, 4519-5062 MHz and 5355-6000 MHz. The achieved measured operating bands can cover sixteen popular narrow service bands for 4G/3G/2G, MWT, WiFi, WiMAX, WLAN, and sub-6 GHz 5G wireless communication system. The studied antenna achieved good gain, efficiency and exhibits stable radiation characteristics. Moreover, the antenna does not use any lumped element and left ample space for other circuitries which makes it easier to use in portable devices such as tablets, laptops, etc. with low manufacturing cost.
  17. Fulltext Metamaterial array based meander line planar antenna for cube satellite communication
    Alam T, Almutairi AF, Samsuzzaman M, Cho M, Islam MT
    Sci Rep, 2021 Jul 08;11(1):14087.
    PMID: 34238984 DOI: 10.1038/s41598-021-93537-6
    This research article presents a design and performance analysis of a metamaterial inspired ultra-high frequency (UHF) compact planar patch antenna for the CubeSat communication system that could be smoothly integrated with commercially available 2U Cube Satellite structure and onboard subsystem. The proposed antenna consists of two layers, one is two different width meander line antenna patch with partial ground plane and another layer is 3 × 2 near-zero-indexed metamaterial (NZIM) metamaterial array structure with ground plane. The NZIM array layer has been utilized to minimize the coupling effect with Cube Satellite structure and improve the frequency stability with enhanced antenna gain and efficiency. The fabricated antenna can operate within the lower UHF frequency band of 443.5-455 MHz. with an average peak gain of 2.5 dB. The designed antenna impedance stability characteristic has been explored after integration with the 2U Cube Satellite body layout. Besides, the antenna communication performance has been verified using 2U Cube Satellite free space path loss investigation. Small antenna volume with trade-off between the antenna size and performance are the key advantages of the proposed design, as the antenna occupies only 80 × 40 × 3.35 mm3 space of the 2U Cube Satellite body structure and the geometrical parameters can be designed to provide the best performance between 449 and 468.5 MHz.
  18. Fulltext Polarization insensitivity characterization of dual-band perfect metamaterial absorber for K band sensing applications
    Hakim ML, Alam T, Almutairi AF, Mansor MF, Islam MT
    Sci Rep, 2021 Sep 08;11(1):17829.
    PMID: 34497289 DOI: 10.1038/s41598-021-97395-0
    Polarization insensitive metamaterial absorbers (MA) are currently very attractive due to their unique absorption properties at different polarization angles. As a result, this type of absorber is widely used in sensing, imaging, energy harvesting, etc. This paper presents the design and characterization of a dual-band polarization-insensitive metamaterial absorber (MA) for K-band applications. The metamaterial absorber consists of two modified split ring resonators with an inner cross conductor to achieve a 90% absorption bandwidth of 400 MHz (21.4-21.8 GHz) and 760 MHz (23.84-24.24 GHz) at transverse electromagnetic (TEM), transverse electric (TE), and transverse magnetic (TM) mode. Polarization insensitivity of different incident angles for TE and TM mode is also investigated, which reveals a similar absorption behavior up to 90°. The metamaterial structure generates single negative (SNG) property at a lower frequency of 21.6 GHz and double negative property (DNG) at an upper frequency of 24.04 GHz. The permittivity and pressure sensor application are investigated for the proposed absorber, which shows its useability in these applications. Finally, a comparison with recent works is also performed to demonstrate the feasibility of the proposed structure for K band application, like sensor, filter, invasive clock, etc.
  19. Fulltext Experimental tissue mimicking human head phantom for estimation of stroke using IC-CF-DMAS algorithm in microwave based imaging system
    Islam MS, Islam MT, Almutairi AF
    Sci Rep, 2021 11 10;11(1):22015.
    PMID: 34759284 DOI: 10.1038/s41598-021-01486-x
    This paper presents the preparation and measurement of tissue-mimicking head phantom and its validation with the iteratively corrected coherence factor delay-multiply-and-sum (IC-CF-DMAS) algorithm for brain stroke detection. The phantom elements are fabricated by using different chemical mixtures that imitate the electrical properties of real head tissues (CSF, dura, gray matter, white matter, and blood/stroke) over the frequency band of 1-4 GHz. The electrical properties are measured using the open-ended dielectric coaxial probe connected to a vector network analyzer. Individual phantom elements are placed step by step in a three-dimensional skull. The IC-CF-DMAS image reconstruction algorithm is later applied to the phantom to evaluate the effectiveness of detecting stroke. The phantom elements are preserved and measured multiple times in a week to validate the overall performance over time. The electrical properties of the developed phantom emulate the similar properties of real head tissue. Moreover, the system can also effectively detect the stroke from the developed phantom. The experimental results demonstrate that the developed tissue-mimicking head phantom is time-stable, and it shows a good agreement with the theoretical results in detecting and reconstructing the stroke images that could be used in investigating as a supplement to the real head tissue.
  20. Fulltext Vegetation-edaphic correlation and importance value index in himalayan 'ecotone' temperate conifer forest using the multivariate technique
    Ali F, Zeb M, Amin M, Rajpar MN, Hidayat S, Khan WR
    Saudi J Biol Sci, 2024 May;31(5):103983.
    PMID: 38590389 DOI: 10.1016/j.sjbs.2024.103983
    Himalayan 'Ecotone' temperate conifer forest is the cradle of life for human survival and wildlife existence. In spite of the importance of these areas, they have not been studied in depth. This study aimed to quantify the floristic structure, important value index (IVI), topographic and edaphic variables between 2019 and 2020 utilizing circular quadrant method (10 m x 10 m). The upper-storey layer consisted of 17 tree species belongs to 12 families and 9 orders. Middle-storey shrubs comprised of 23 species representing 14 families and 12 orders. A total of 43 species of herbs, grasses, and ferns were identified from the ground-storey layer, representing 25 families and 21 orders. Upper-storey vegetation structure was dominated by Pinus roxburghii (22.45 %) and middle-storey by Dodonaea viscosa (7.69 %). However, the ground layer vegetation was diverse in species composition (43 species) and distribution. The floral vegetation structure was encompassing of three floral communities which were diverse in IVI, such as, in Piro-Aial (Group 2), Pinus roxburghii (54.46 x 15.94) had the highest IVI value, followed by Pinus wallichiana (45.21 x 14.85) in Piwa-Quin (Group 3) and Ailanthus altissima (22.84 x 19.25) in Aial-Qugal (Group 1). However, the IVI values for Aesculus indica, Celtis australis, and Quercus incana in Aial-Qugal (Group 1) were not determined due to low detection rate. Nevertheless, eleven of these species showed 0 IVI values in Piro-Aial (Group 2) and Piwa-Quin (Group 3). CCA ordination biplot illustrated the significant differences among floral communities and its distribution, which impacted by temperature, rainfall, soil pH, altitude, and topographic features. Ward's agglomerative clustering finding reflected 'Ecotone' temperate conifer forest is rich and diverse floristic structure.
Related Terms
    Try searching for something
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links