ABSTRACT
This study reports for the first time, to the best of our knowledge, a real-time detection of ultralow-concentration chemical gases using fiber-optic technology, combining a miniaturized Fabry-Perot interferometer (FPI) with metal-organic frameworks (MOFs). The sensor consists of a short and thick-walled silica capillary segment spliced to a lead-in single-mode fiber (SMF), housing a tiny single crystal of HKUST-1 MOF, imparting chemoselectivity features. Ethanol and benzene gases were tested, resulting in a shift in the FPI interference signal. The sensor demonstrated high sensitivity, detecting ethanol gas concentrations (EGCs) with a sensitivity of 0.428 nm/ppm between 24.9 and 40.11 ppm and benzene gas concentrations (BGCs) with a sensitivity of 0.15 nm/ppm between 99 and 124 ppm. The selectivity study involved a combination of three ultralow concentrations of ethanol, benzene, and toluene gases, revealing an enhancement factor of 436% for benzene and 140% for toluene, attributed to the improved miscibility of these conjugated ring molecules with the alkane chains of the ethanol-modified HKUST-1. Experimental tests confirmed the sensor's viability, demonstrating significantly improved response time and spectral characteristics through crystal polishing, indicating its potential for quantifying and detecting chemical gases at ultralow concentrations. This technology may prevent energy resource losses, and the sensor's small size and robust construction make it applicable in confined and hazardous locations.
ABSTRACT
BACKGROUND: External ureteral catheter (EUC) and double-J stent are both commonly used to drain upper urinary tract in percutaneous nephrolithotomy (PCNL). We compared the outcomes of using EUC versus double-J stent in performing PCNL in patients with renal stones in our settings in order to identify a better technique for the management of renal stones in terms of postoperative stent-related symptoms. METHODS: This randomized controlled trial was conducted at the Department of Urology, PAEC General Hospital, Islamabad, from January 2020 to December 2020. A total of 80 patients of either gender between ages 18 and 70 years planned for PCNL were enrolled and randomized into group I (double-J stent) and group II (EUC). Outcomes of the procedure were compared in both groups. RESULTS: There were 62.5% of patients in group I who demonstrated stent-related symptoms compared to 22.5% in group II (p=0.001). No statistically significant difference was noted in other outcome variables like urinary leak (10% vs. 20%, p=0.210), post-procedure fever (25% vs. 22.5%, p=0.793), mean analgesia requirement (60.8 mg vs. 58.5 mg, p=0.685), and mean length of hospital stay (3.9 days vs. 4.2 days, p=0.330). CONCLUSION: Stent-related symptoms were demonstrated by a significantly lesser number of patients who underwent PCNL with EUC when compared with patients who underwent PCNL with double-J stent. For other outcome variables (urinary leak, post-procedure fever, mean analgesia requirement, and mean length of hospital stay ), no significant difference was noted among both the groups.