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Background and Aims: An audit was conducted between July 2017 and November 2017 to assess the adequacy of American Society of Anesthesiologists (ASA) fasting guidelines on 246 patients by means of gastric ultrasonography (USG). The relevance of this audit is that many of our patients have one or more risk factors for aspiration such as diabetes mellitus, chronic kidney disease (CKD), gastro-oesophageal reflux disease (GERD), and obesity. Methods: This audit was a prospective observational study which included all patients posted for surgery within the audit period. Patients were fasted according to ASA fasting guidelines. Their gastric content was assessed preoperatively using USG. The residual gastric volume was calculated using a validated formula. Statistical correlation between gastric volumes and the risk factors were analysed. Results: Of 246 patients, 69 (28.04%) had high residual gastric volume. We found no correlation between hours of fasting and residual gastric volume (P = 0.47). We found a linear correlation between rising body mass index and residual gastric volume (P < 0.0001). Patients with GERD had 2.3 times higher risk. The CKD patient subgroup had 24 patients (30%) with high residual gastric volume. No incidents of aspiration were noted. Conclusion: In our audit, we found that risk factor association has a greater effect on residual gastric volume than hours of fasting. While the current fasting guidelines are adequate for healthy individuals, they are not conclusive in patients with risk factors. Ultrasound assessment of preoperative gastric volume is an effective screening tool in patients with risk factors.

The physical dimensions of nanoscale objects are an important indicator of their functionality. However, measuring feature size from a SEM image is difficult not only because of fundamental considerations, such as the nature of beam interactions and the information transfer properties of the microscope, but because the magnification of the SEM image from which a measurement will be made is completely uncalibrated and additionally is subject to local distortions and variations. Nano-gauges fabricated by electron beam lithography - one or two dimensional structures on the size scale of the objects of interest - provide a local length standards within the image field from which the relative size of features can be accurately determined. In order to provide an absolute measurement of size the dimensions of the nano-gauge structure must themselves be calibrated against some primary standard. Because there are no convenient standards of appropriate scale available we propose that this can be done using a moire fringe technique to bridge the gap between the nanoscale and common length standards such as ruled diffraction gratings.

With the semiconductor industry moving into the 65nm technology node, the metrology of the critical dimension (CD) becomes an important part for the industry. Metrology relies not only on the precision, but also on the accuracy of the tools like the high performance CD-SEMs. A major area of concern affecting the accuracy of the high performance CD-SEMs is the magnification calibration. The purpose of the research is to address this area of concern by fabrication of magnification calibration artifact by using direct write electron beam lithography. A calibration artifact has been fabricated in negative resist Hydrogen Silsesquioxane (HSQ) onto a silicon substrate, thereby decreasing the contamination on the substrate. The design of the artifact has been corrected for the proximity effects, giving a 2-D dense grid structure with 100nm pitch. Pitch determination using optical metrology tools and the inbuilt laser interferometer in the electron beam lithography tool is being evaluated for making the artifact traceable to some national standards. Once the traceability is achieved, mass production at low cost using Nanoimprint technology is feasible.

It is important to be able to quantify the imaging performance of CD-SEMs for such purposes as verifying the specification, rechecking after a routine maintenance, or for tool matching. To perform tests such as these it is necessary to have both appropriate software for image analysis and suitable test samples. A package of 2-D Fourier transform and analysis software, designed as a plug-in for the shareware IMAGE-Java program, has been developed and is freely available on line. The requirement for a reproducible and well characterized sample has been met by using direct-write electron beam lithography to fabricate suitable Fresnel zone plate structures.