Metamaterial Inspired Multi-Band Antenna for MM-Wave 5G Wireless Communication

Due to the constant demand for speed and capacity in wireless communication, mm-wave bands are getting special interest. Most of the high-speed 5G bands are in the mm-wave region. As the mm-wave signal is prone to absorption and faces a significant free space path loss, an antenna with narrow beam, high gain, and high efficiency is required. The antenna also needs to be working in multiple frequencies, as there is a multitude of mm-wave frequencies allocated by the regulator for 5G communication. In this study, we designed an antenna capable of working in high 5G bands consisting of 25GHz,28GHz, and 38GHz. The idea of the metasurface is used to make the antenna resonant for multiple frequencies of mm-wave operation. The structure is tapered and curved in multiple places to funnel the flow of surface current, thereby generating a very sharp beam. In the numerical analysis using CST microwave studio, the efficiency is found to be around 90% and the average gain is approximately 4dB, combining all three bands

Sub-clinical mastitis prevalent in dairy cows in Chittagong district of Bangladesh: detection by different screening tests

Aim: Mastitis is recognized as one of the most costly health disorder affecting dairy cows. An epidemiological study was carried out at some selected farms in Chittagong district of Bangladesh to determine the prevalence and risk factors of sub-clinical mastitis (SCM) in dairy cows. Materials and Methods: For conducting the study, some dairy farms of Chittagong were selected from urban and periurban areas by stratified random sampling. A total of 444 quarter samples of 111 (56 from commercial dairy farms and 55 from backyards) lactating dairy cows were considered. Sub-clinical mastitis (SCM) was determined using three different indirect screening tests: California Mastitis Test (CMT), White Slide Test (WST) and Surf Field Mastitis Test (SFMT). Sensitivity and specificity were also determined to measure the accuracy of those tests. Results: The prevalence of SCM by CMT, WST and SFMT were 32.43% (n=144), 33.56% (n=149) and 31.53% (n=140), respectively. Distribution of SCM in relation to different variables at quarter level and animal level was also recorded. The prevalence of SCM was significantly (P<0.05) higher in aged, high yielding cows in addition with history of periparturient diseases, without dry cow therapy both at quarter and animal level. A significantly (p<0.01) higher prevalence (48.98%) of SCM was observed in higher parity number (>4) than others at quarter level. No significant difference (P>0.05) was found in relation to breed. Using CMT as a gold standard, sensitivity and specificity of WST and SFMT were also calculated at 95% confidence interval. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value and disease prevalence by WST and SFMT were comparable. Conclusion: This study recommends that regular screening of sub-clinical mastitis will reduce the prevalence of sub-clinical mastitis. The most effective way to control sub-clinical mastitis is to take preventive measures such as regular cleaning of the floor, keeping the udder clean, milkman's cleanliness, dry cow therapy specially in high yielding dairy cows

Subsurface Characteristics of Metal-Halide Perovskites Polished by Argon Ion Beam

Focused ion beam (FIB) techniques have been frequently used to section metal-halide perovskites for microstructural investigations. However, the ion beams directly irradiated to the sample surface may alter the properties far different from pristine, potentially leading to modified deterioration mechanisms under aging stressors. Here, we combine complementary approaches to measure the subsurface characteristics of polished perovskite and identify the chemical species responsible for the measured properties. Analysis of the experimental results in conjunction with Monte Carlo simulations indicates that atomic displacements and local heating occur in the subsurface of methylammonium lead iodide (MAPbI3) by glazing Ar+ beam irradiation (15 nm by 4 kV at 3 degree). The lead-rich, iodine-deficient surface promotes rapid phase segregation under thermal aging conditions. On the other hand, despite the subsurface modification, our experiments confirm the rest of the MAPbI3 bulk retains the material integrity. Our observation supports that polished perovskites could serve in studying the properties of bulk or buried junctions far away from the altered subsurface with care.Comment: six figure

Requirement of ESWL after ureterorenoscopy and lithotripsy in the management of upper ureteric stone: comparison between Holmium Yag laser and pneumatic lithotripsy in a referral hospital, Bangladesh

Various methods have been employed for the removal of ureteric calculi all over the world. Both Ureteroscopic Pneumatic and Laser lithotripsy are popular procedures for this purpose. However proximal migration of stone fragments are not uncommon in these procedures while treating upper ureteric stones. Extra corporeal shock wave lithotripsy (ESWL) may require to fragment those proximally migrated stones after the ureteroscopic Pneumatic or Laser lithotripsy. To compare the requirement of ESWL in the management of ureteric stone between Holmium Yag Laser and Pneumatic Lithotripsy. This study included 100 patients with upper ureteric stones who underwent ureteroscopic lithotripsy at the Department of Urology, CMH, Dhaka, between October 2010 and September 2012. Laser lithotripsy was used in 50 patients (Group A), and pneumatic lithotripsy was used in the remaining 50 patients (Group B). In each case, the same ureteroscope, video monitor, baskets, or irrigation devices were used. A kidney ureter and bladder radiograph and ultrasonograph were performed on patients one month and three months after lithotripsy. Patients with migrated fragments or insufficient clearance underwent a supplementary procedure such as ESWL. Mean age was 41.9}10.9 years and 41.3}12.3 years in Group A and Group B respectively. Males were predominant in both groups. Mean stone size was 1.36 } 0.36 cm in Group A and 1.37} 0.36 cm in Group B. Complete stone clearance was 94.0% in Group A and 76.0% in Group B. EWSL requirement rate was significantly higher in Group B (24.0%) than Group A (6.0%). Peri procedural complications like hemorrhage was significantly higher in Group B and mucosal disruption/perforation was almost same in both the groups. EWSL requirement rate was comparatively higher in pneumatic lithotripsy than laser lithotripsy. BSMMU J 2022; 15(2): 111-11