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Fulltext Modified double dumbbell-shaped split-ring resonator-based negative permittivity metamaterial for satellite communications with high effective medium ratio

Hossain MB, Faruque MRI, Islam SS, Islam MT

Sci Rep, 2021 Sep 29;11(1):19331.
PMID: 34588523 DOI: 10.1038/s41598-021-98703-4

Metamaterial with negative permittivity demonstrate excellent performance in cutting-edge technology. Thus, this study modified the double dumbbell-shaped split-ring resonator (MDD-SRR) based negative permittivity for satellite communications. The proposed MDD-SRR unit cell comprises a square-shaped split-ring resonator and two dumbbell-shaped rings. Some parts of the outer square ring were extended to enlarge the electrical length which altered the inductance of the metamaterial unit cell. The dimension of the proposed unit cell is 9 × 9 × 1.524 mm3, fabricated on a Rogers RT6002 (lossy) substrate material. Based on the results, five resonances for the transmission coefficient were achieved at frequencies of 2.896 GHz, 8.11 GHz, 9.76 GHz, 12.48 GHz and 13.49 GHz, including the S, X and Ku band satellite communication frequency bands through numerical simulation in a high-frequency electromagnetic simulator Computer Simulation Technology (CST) microwave studio. Negative permittivity at frequencies ranging from 2.896-3.76 GHz, 8.11-8.592 GHz, 9.76-10.784 GHz, 12.496-12.768 GHz, 13.504-14.4 GHz, were observed and extracted using the Robust and Nicolson-Ross-Weir (NRW) methods. Meanwhile, an effective medium ratio (EMR) measured at 11.51 to 2.896 GHz specified the goodness of the metamaterial unit cell for satellite communication with higher bandwidth and gain. The simulated, circuit model and measured results that were compared for validation purposes indicated that the simulation results, the equivalent circuit model results and measured results occupied each other. Moreover, the numerical simulation of the double dumbbell-shaped metamaterial unit cell was performed using a High-Frequency Structure Simulator (HFSS) to confirm the results. To evaluate the parametric study, the proposed unit cell was subjected to change different substrate types, change of split gap of rings, change of direction of electromagnetic field propagation, and structural optimization. In conclusion, the S, X and Ku-bands in the proposed metamaterial are competent for satellite communications as they are also investigated using an array of a unit cell.
Fulltext An Ultra-Thin, Triple-Band, Incident Angle-Insensitive Perfect Metamaterial Absorber

Jahan MI, Faruque MRI, Hossain MB, Abdullah S

Materials (Basel), 2023 Feb 15;16(4).
PMID: 36837252 DOI: 10.3390/ma16041623

We created an ultra-thin, triple-band incident angle-insensitive perfect metamaterial absorber (MMA) with a metallic patch and a continuous metal ground isolated by a central dielectric substrate. The top metallic patch, placed across the edges of the 0.58 mm thickness Rogers RO4003C (lossy) substrate, forms the bulk of the projected absorber's ultra-thin layer. Nonetheless, absorption is exceedingly strong, covering C-band, X-band and K-band and reaching levels of 97.8%, 99.9%, and 99.9%, respectively, under normal and even oblique (0° to 45°) incident conditions. In chosen ranges of frequency of 6.24, 10.608, and 18.624 GHz for both TM and TE mode, the displayed Q-factors were 62.4, 17.68, and 26.61, respectively. We correspondingly calculated the RAB (relative absorption bandwidth) to evaluate absorption performance. An equivalent circuit proved its performance capabilities, indicating that it would produce a high-quality MMA from ADS software. Furthermore, the absorber's performance has been verified in free space on a sample being tested using a different array of unit cells. Moreover, the proposed structures with HFSS simulators to display the MMA's absolute absorption at each absorption peak are somewhat inconsistent with the results of the CST simulator. Because of its superior performance, the ultra-thin absorber is suited for a wide range of applications, including satellite applications such as radar systems, stealth technology, imaging, and electromagnetic interference reduction.
Reply to comment to Meta-analysis and systematic review of laparoscopic versus open mesh repair for elective incisional hernia. Jensen K, Jorgensen LN

Awaiz A, Rahman F, Hossain MB, Yunus RM, Khan S, Memon B, et al.

Hernia, 2015 Dec;19(6):1027-9.
PMID: 26496998 DOI: 10.1007/s10029-015-1432-z
Meta-Analysis of Early Endoscopic Retrograde Cholangiopancreatography (ERCP) ± Endoscopic Sphincterotomy (ES) Versus Conservative Management for Gallstone Pancreatitis (GSP)

Burstow MJ, Yunus RM, Hossain MB, Khan S, Memon B, Memon MA

Surg Laparosc Endosc Percutan Tech, 2015 Jun;25(3):185-203.
PMID: 25799261 DOI: 10.1097/SLE.0000000000000142

The utility of early endoscopic retrograde cholangiopancreatography (ERCP) ± endoscopic sphincterotomy (ES) in the treatment of gallstone pancreatitis (GSP) is still contentious.
Speckle Noise Diffusion in Knee Articular Cartilage Ultrasound Images

Shoaib MA, Hossain MB, Hum YC, Chuah JH, Mohd Salim MI, Lai KW

Curr Med Imaging, 2020;16(6):739-751.
PMID: 32723246 DOI: 10.2174/1573405615666190903143330

BACKGROUND: Ultrasound (US) imaging can be a convenient and reliable substitute for magnetic resonance imaging in the investigation or screening of articular cartilage injury. However, US images suffer from two main impediments, i.e., low contrast ratio and presence of speckle noise.
AIMS: A variation of anisotropic diffusion is proposed that can reduce speckle noise without compromising the image quality of the edges and other important details.
METHODS: For this technique, four gradient thresholds were adopted instead of one. A new diffusivity function that preserves the edge of the resultant image is also proposed. To automatically terminate the iterative procedures, the Mean Absolute Error as its stopping criterion was implemented.
RESULTS: Numerical results obtained by simulations unanimously indicate that the proposed method outperforms conventional speckle reduction techniques. Nevertheless, this preliminary study has been conducted based on a small number of asymptomatic subjects.
CONCLUSION: Future work must investigate the feasibility of this method in a large cohort and its clinical validity through testing subjects with a symptomatic cartilage injury.
Fulltext Green shared vision: A bridge between responsible leadership and green behavior under individual green values

Younas N, Hossain MB, Syed A, Ejaz S, Ejaz F, Jagirani TS, et al.

Heliyon, 2023 Nov;9(11):e21511.
PMID: 38027782 DOI: 10.1016/j.heliyon.2023.e21511

The pressure on businesses to be environmentally conscious and focus on sustainable development is accruing due to environmental challenges. Companies are adopting ecological practices and policies to improve their environmentally friendly performance. To achieve this, organizations must substantiate and change the behavior of workers to align their behavior with the organization's ecological objectives. The study endeavors to integrate research on the responsible style of leaders and green behaviors of employees (in-role and extra-role green behaviors) through the mediation of green shared vision and analyze the moderation mechanism of individual green values. For collecting the data, a questionnaire-based survey was conducted among MBA executive program students with at least a year of experience in manufacturing. Out of the 450 questionnaires distributed, only 307 useful responses were obtained. The collected data has been analyzed using SPSS and AMOS. Ethical standards were followed, and participants were assured that their responses would be confidential. The study found that responsible leadership positively impacts green behaviors among employees. This means that when leaders within an organization demonstrate responsible and environmentally conscious behavior, it tends to encourage employees to engage in green behaviors. The study also discovered that a "green shared vision" partially mediates the relationship between responsible leadership and in-role green behavior. In contrast, green shared vision does not mediate the relation between responsible leadership and extra role green behavior. Moreover, this study also finds that the relationship between green shared vision and in-role and extra-role green behavior is strengthened when individual green values moderate it. The study highlights the importance of responsible leadership and the role of green shared values and individual green values in promoting environmentally friendly behavior in the workplace.
Fulltext Data set on trace metals in surface sediment and water from a sub-tropical estuarine system, Bay of Bengal, Bangladesh

Hossain MB, Habib SB, Hossain MS, Jolly YN, Kamal AHM, Idris MH, et al.

Data Brief, 2020 Aug;31:105911.
PMID: 32637507 DOI: 10.1016/j.dib.2020.105911

Meghna River Estuary, the largest estuarine system (GBM, Ganges-Brahmaputra-Meghna) in Bangladesh, is a major spawning ground of national fish, Hilsha shad. In this study, we collected 24 surface sediment and 24 water samples from the entire lower estuary (4 sites, 3 sampling points from each site, 2 replicas from each sampling point) to detect trace/heavy metals. Sediment samples were collected from the top surface soil (0-5 cm) using Ekman grab sampler and water samples from 5 cm below the surface layer using plastic water bottles. After collection, sediment and water samples were preserved as necessary using HNO3 (for water). Immediately after reaching the laboratory, sediment samples were dried in an oven at 70°C until the constant weight gained. The metals were then analyzed using energy-dispersive X-ray fluorescence method (EDXRF) and calculated the metal concentrations. In total, 12 metals were detected and the average value (mg/Kg) of all metals for sediment samples followed the descending order of Fe > Ca > K >Ti >Sr >Zr >Rb> Cu > Zn >Pb >As > Ni, and for water the order (µg/mL) of Fe >Ti > Ca > Co >Mn > Ni > Zn >Sr > Cu > As > Se . Besides, several physicochemical parameters i.e. water pH, soil pH, temperature, salinity, dissolved oxygen, hardness, and alkalinity of the 12 sampling points were also measured in-situ using handheld instruments.
Fulltext Levels and health risk assessment of heavy metals in dried fish consumed in Bangladesh

Rakib MRJ, Jolly YN, Enyoh CE, Khandaker MU, Hossain MB, Akther S, et al.

Sci Rep, 2021 07 19;11(1):14642.
PMID: 34282166 DOI: 10.1038/s41598-021-93989-w

As a cheap source of high-quality protein, healthy fats and essential nutrients, dried fish is a common item in the daily diet of the Bangladesh populace. In this study, ten types of widely consumed dried fish (H. neherius, T. lepturu, P.chinensis, P. affinis, A. mola, P. microdon, I. megaloptera, C. dussumieri, L. calcarifer, and G. chapra) were analyzed for Cr, Mn, Fe, Co, Cu, Zn, Se, Rb, Hg, Pb, Ni and As by using an Energy Dispersive X-ray Fluorescence (EDXRF) technique. The concentration of the studied metals was found in the order Fe > Zn > Hg > Cu > Se > Cr > Mn > Co > Rb > Pb, while As and Ni were below the limit of detection. All fish species showed moderate to high pollution, where the species H. Neherius and P. Chinensis are the most and least polluted ones, respectively. The probable source of contamination is the leaching from the drying pans into the fish samples, atmospheric deposition, anthropogenic contamination, etc. of the water body where these fish were harvested. The calculated hazard index for the general population was below the maximum limiting value (i.e.,
Fulltext Bioaccumulation of heavy metals in some commercially important fishes from a tropical river estuary suggests higher potential health risk in children than adults

Ahmed ASS, Sultana S, Habib A, Ullah H, Musa N, Hossain MB, et al.

PLoS One, 2019;14(10):e0219336.
PMID: 31622361 DOI: 10.1371/journal.pone.0219336

The Karnaphuli River estuary, located in southeast coast of Bangladesh, is largely exposed to heavy metal contamination as it receives a huge amount of untreated industrial effluents from the Chottagram City. This study aimed to assess the concentrations of five heavy metals (As, Pb, Cd, Cr and Cu) and their bioaccumulation status in six commercially important fishes, and also to evaluate the potential human health risk for local consumers. The hierarchy of the measured concentration level (mg/kg) of the metals was as follows: Pb (13.88) > Cu (12.10) > As (4.89) > Cr (3.36) > Cd (0.39). The Fulton's condition factor denoted that fishes were in better 'condition' and most of the species were in positive allometric growth. The bioaccumulation factors (BAFs) of the contaminants observed in the species were in the following orders: Cu (1971.42) > As (1042.93) > Pb (913.66) > Cr (864.99) > Cd (252.03), and among the specimens, demersal fish, Apocryptes bato appeared to be the most bioaccumulative organism. Estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI) and carcinogenic risk (CR) assessed for potential human health risk implications suggest that the values were within the acceptable threshold for both adults and children. However, calculated CR values indicated that both age groups were not far from the risk, and HI values demonstrated that children were nearly 6 times more susceptible to non-carcinogenic and carcinogenic health effects than adults.
Fulltext Older adults with non-communicable chronic conditions and their health care access amid COVID-19 pandemic in Bangladesh: Findings from a cross-sectional study

Mistry SK, Ali ARMM, Yadav UN, Ghimire S, Hossain MB, Das Shuvo S, et al.

PLoS One, 2021;16(7):e0255534.
PMID: 34324556 DOI: 10.1371/journal.pone.0255534

BACKGROUND: Burgeoning burden of non-communicable disease among older adults is one of the emerging public health problems. In the COVID-19 pandemic, health services in low- and middle-income countries, including Bangladesh, have been disrupted. This may have posed challenges for older adults with non-communicable chronic conditions in accessing essential health care services in the current pandemic. The present study aimed at exploring the challenges experienced by older Bangladeshi adults with non-communicable chronic conditions in receiving regular health care services during the COVID-19 pandemic.
MATERIALS AND METHODS: The study followed a cross-sectional design and was conducted among 1032 Bangladeshi older adults aged 60 years and above during October 2020 through telephone interviews. Self-reported information on nine non-communicable chronic conditions (osteoarthritis, hypertension, heart disease, stroke, hypercholesterolemia, diabetes, chronic respiratory diseases, chronic kidney disease, cancer) was collected. Participants were asked if they faced any difficulties in accessing medicine and receiving routine medical care for their medical conditions during the COVID-19 pandemic. The association between non-communicable chronic conditions and accessing medication and health care was analysed using binary logic regression model.
RESULTS: Most of the participants aged 60-69 years (77.8%), male (65.5%), married (81.4%), had no formal schooling (58.3%) and resided in rural areas (73.9%). Although more than half of the participants (58.9%) reported having a single condition, nearly one-quarter (22.9%) had multimorbidity. About a quarter of the participants reported difficulties accessing medicine (23%) and receiving routine medical care (27%) during the pandemic, and this was significantly higher among those suffering from multimorbidity. In the adjusted analyses, participants with at least one condition (AOR: 1.95, 95% CI: 1.33-2.85) and with multimorbidity (AOR: 4.75, 95% CI: 3.17-7.10) had a higher likelihood of experiencing difficulties accessing medicine. Similarly, participants with at least one condition (AOR: 3.08, 95% CI: 2.11-4.89) and with multimorbidity (AOR: 6.34, 95% CI: 4.03-9.05) were significantly more likely to face difficulties receiving routine medical care during the COVID-19 pandemic.
CONCLUSIONS: Our study found that a sizeable proportion of the older adults had difficulties in accessing medicine and receiving routine medical care during the pandemic. The study findings highlight the need to develop an appropriate health care delivery pathway and strategies to maintain essential health services during any emergencies and beyond. We also argue the need to prioritise the health of older adults with non-communicable chronic conditions in the centre of any emergency response plan and policies of Bangladesh.