Quantum of selectivity testing: detection of isomers and close homologs using an AZO based e-nose without a prior training

Tracing the chemical composition of the surrounding environment appeals to the design of highly sensitive and selective gas sensors. Primarily driven by IoT, miniaturized multisensor systems, like e-noses, are considered to address both selectivity and sensitivity issues. Although e-noses might enable discrimination between close homologs and isomers, they are required to be "trained", i.e. to project analyte-related signals into artificial space, prior to their in-field applications. In this study, using the programmed co-precipitation method, we synthesized aluminum-doped zinc oxide (AZO) and employed it as a sensing material in an e-nose to examine the sensing performance towards close C1-C5 alcohol homologs and isomers, e.g. 1-propanol and 2-propanol, 1-butanol and isobutanol in the frame of the multisensor paradigm. For the first time, we demonstrated selective recognition of the alcohol vapors without prior training of the e-nose. This was realized by matching projections of the known analytes' "fingerprints", used to build a chemical space, with the projections of analyte-related signals acquired using the e-nose in artificial space under machine learning algorithms. Moreover, the AZO based e-nose demonstrates a remarkable, up to 0.87, chemoresistive response to alcohol vapors, 0.9 ppm, in the mixture with air at 300 degrees C with a detection limit down to sub-ppb level. This opens a new avenue for the development of self-learning gas analytical systems, which might recognize new analytes whose profiles are not yet stored in their library.Peer reviewe

The "Birmingham stitch"--avoiding slippage in laparoscopic gastric banding.

BACKGROUND Slippage rates of 1.4-24 % are frequently quoted after adjustable gastric banding. This complication can be extremely serious and has contributed to many units offering more invasive interventions in the surgical management of morbid obesity. We present results of the first 1,140 Laparoscopic Bands performed in our unit. METHODS Between April 2003 and June 2007, 1140 consecutive patients, mean weight 121.5 kg (range 73-268 kg), mean body mass index (BMI) 44.3 kg/m(2) (range 35-88) underwent laparoscopic adjustable gastric banding (LAGB). An identical surgical technique of one gastropexy suture in addition to the two routine gastro-gastro tunnel sutures was used in all cases. Fluoroscopy-guided adjustments were performed at 3 and 6 months and fluoroscopic evaluations were performed later if clinically indicated. RESULTS There was no mortality and only one major septic complication of gastric perforation 1 week postoperatively which was managed conservatively. The mean stay was 1.02 days (range 0-30 days). Excess percent BMI loss in these patients at 3, 6, 12, 18, 24, 30, and 36 months were 25.4%, 34.7%, 38.3%, 41.1%, 43.7%, 44.4%, and 58.9%, respectively. Slippage with urgent readmission occurred in one patient (0.08%) at 5 months. Two partial slippages were noticed at 12 and 18 months, respectively. One patient had the band removed and the other was treated by band deflation and repositioning 6 months later. CONCLUSION These results demonstrate that in our unit, laparoscopic gastric band insertion is successful in producing weight loss and at the same time has a very low slippage and pouch dilatation rate. This difference is most probably secondary to operative technique