Search

This paper presents a highly isolated pattern diversity multiband MIMO antenna using two ring-shaped radiating elements with a rectangular stub placed inside it. The proposed multiband MIMO antenna is resonating at three frequencies centred at 2.45 GHz, 3.5 GHz, and 5.4 GHz. A high-quality factor U-shaped bandstop filter is designed and placed between the two antenna elements to achieve simultaneous high isolation and pattern diversity. The isolation between the antenna elements at 2.45 GHz, 3.5 GHz, and 5.4 GHz is −25 dB, −20 dB and −35 dB, respectively. The diversity gain is 10 dB, while the ECC is less than 0.05. The antenna is fabricated on a low-cost substrate, FR4, and its dimensions are 31 mm × 31 mm × 0.8 mm. Measured results verify the multiband behaviour of the proposed MIMO antenna. The proposed MIMO antenna is useful for WLAN, WiMAX and 5 G sub-6 GHz-based applications. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a potential option to achieve carbon neutrality. Although copper (Cu) shows the highest activity for the CO2 reduction reaction (CO2RR) to hydrocarbons among metals, high reaction overpotentials and significant H2 production limit its use. We investigate single‐atom alloys (SAAs) of ten metals (Ag, Au, Fe, Ir, Ni, Pd, Pt, Rh, Ru, Al) on Cu(111), which is the most‐favored facet on Cu for methane production, using density functional theory. We examined the dopants' ability to lower the free energy of the elementary reaction, *CO to *CHO, which is the potential‐determining step (PDS). Out of the SAAs studied, only Al‐doped Cu demonstrated a lowering of the PDS free energy. Additionally, weaker adsorption energies of *CO and *H on Al−Cu(111) suggest a preference for C1 hydrocarbons and inhibition of H2 evolution. Finally, activation barrier calculations for the PDS on Al−Cu(111) involving an explicitly hydrated proton indicated better intrinsic activity for C1 hydrocarbons compared to pure Cu(111). We also confirmed the stability of Al−Cu SAA compared to small Al clusters. Through a comprehensive study of both thermodynamics and kinetics, our study presents Al−Cu SAA as a promising catalyst for CO2 electroreduction to C1 hydrocarbons. [ABSTRACT FROM AUTHOR]

Water dissociation is an important reaction involved in many industrial processes. In this computational study, the dissociation of water is used as a model reaction for probing the activity of interfacial sites of globally optimized ZrO2 supported Pt and Rh clusters under the framework of density functional theory. Our findings demonstrate that the perimeter sites of these small clusters can activate water, but the dissociation behavior varies considerably between sites. It is shown that the studied clusters break scaling relationships for water dissociation, suggesting that these catalysts may achieve activities beyond the maximum imposed by such relations. Furthermore, we observed large differences in the thermodynamics of the water dissociation reaction between global minimum and near-global minimum isomers of the clusters. Overall, our results highlight the uniqueness of interfacial sites in catalytic reactions and the need for developing new concepts and tools to deal with the associated complexity. [ABSTRACT FROM AUTHOR]

Background and Aims: In pediatric patients undergoing infraumbilical procedures, caudal block is an efficient, dependable, and secure approach for analgesia during and after surgery. The primary purpose was to see how long effective analgesia lasted, with additional goals included calculating the overall amount of rescue analgesic used over the course of a 24-hour period, hemodynamic alterations, postoperative sedation, and side effects. Methods: This observational, randomized, twofold study included 80 children from ASA classes I and II who were undergoing various infraumbilical surgeries under general anesthesia and one of two groups was chosen at random: Group A (n = 40) received 0.2 percent levobupivacaine 0.75 ml/kg + dexmedetomidine 0.75 µg/kg making the volume 1 ml with normal saline, and Group B (n = 40) received 0.2 percent levobupivacaine 0.75 ml/kg + dexamethasone 0.1 mg/kg making the volume 1 ml with normal saline for caudal anesthesia. Results: Analgesia lasted substantially longer in Group A (613.88 ± 39.28 minutes) than in Group B (462.55 ± 25.35 minutes). (Note that the significance level is less than 0.05). In comparison with Group B, Group A received fewer total analgesic doses in 24 hours (P < 0.05). In the first several hours after surgery, Group A had a considerably greater mean sedation score than Group B. Both groups' hemodynamic parameters were comparable. Conclusion: For pediatric caudal analgesia with considerable postoperative analgesia and arousable sedation, dexmedetomidine, rather than dexamethasone, can be a superior adjuvant for levobupivacaine, with unremarkable side effects. [ABSTRACT FROM AUTHOR]

This paper examines the effect of the geometrical shapes of a defected ground-plane structure (DGS) slot on performance of the Hi-Lo microstrip low-pass filter (LPF). A three-pole LPF based on an arrowhead DGS slot has 67% less length as compared to a conventional three-pole LPF. It has insertion loss of 0.5 dB and 15-dB rejection in the stopband up to three times the cutoff frequency. Index Terms--Defected ground-plane structure (DGS) slot, low-pass filter (LPF), microstrip filter, slot in ground plane.

Background and Aims: Subarachnoid block is the most preferred anesthetic technique for infraumbilical surgeries as it provides better postoperative analgesia, effective muscle relaxation, and cost‑effectiveness. Levobupivacaine is preferable over bupivacaine due to its lower cardiotoxicity, prolonged sensory block, and shorter duration of motor block. Opioids as an adjuvant to intrathecal local anesthetics enhance the quality of both analgesia and anesthesia during intraoperative as well as postoperative period. The present study aimed to compare levobupivacaine with and without fentanyl in spinal anesthesia. Methods: In this prospective, randomized, double‑blinded study, a total of 80 patients belonging to the American Society of Anesthesiologists Physical Status I and II were enrolled for infraumbilical surgeries. Patients were randomly allocated into two groups. Group Levobupivacaine (L) (n = 40) received isobaric levobupivacaine 0.5% 2.5 ml with 0.5 ml normal saline and Group Levobupivacaine + fentanyl (LF) (n = 40) received isobaric levobupivacaine 0.5% 2.5 ml with fentanyl 25 µg (0.5 ml). Time of onset and duration of both sensory and motor block, Visual Analog Scale score, duration of analgesia, hemodynamic changes, and any adverse events were noted in both the groups. Results: The onset of both sensory and motor block was significantly faster in Group LF (P < 0.05). The duration of sensory block was significantly longer in Group LF (P < 0.05). The duration of motor block was found to be comparable between two groups with stable hemodynamics and no perioperative sedation (P > 0.05). The duration of analgesia was significantly longer in Group LF (336.5 ± 31.3 min) compared to Group L (223.65 ± 32.17 min) P < 0.001. Conclusion: Intrathecal fentanyl (25 µg) can be effectively used as an adjuvant to isobaric 0.5% levobupivacaine as it provides better block characteristics with minimal adverse effects in patients undergoing infraumbilical surgeries. [ABSTRACT FROM AUTHOR]