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The present study examines the impact of nitrogen sources (yeast extract, ammonium sulfate peptone, ammonium nitrate, urea, and sodium nitrate), salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, 0.3 g/L CaCl2), trace elements solution (0.1 g/L CuSO4, 0.1 g/L FeSO4, 0.02 g/L MnCl2, 0.02 g/L ZnSO4), operational parameters (temperature, aeration, agitation, initial pH and xylose concentration) and co- substrate supplementation (glucose, fructose, maltose, sucrose, and glycerol) on xylitol biosynthesis by Candida tropicalis ATCC 13803 using synthetic xylose. The significant medium components were identified using the Plackett Burman design followed by central composite designs to obtain the optimal concentration for the critical medium components in shaker flasks. Subsequently, the effect of operational parameters was examined using the One Factor At a Time method, followed by the impact of five co-substrates on xylitol biosynthesis in a 1 L bioreactor. The optimal media components and process parameters are as follows: peptone: 12.68 g/L, yeast extract: 6.62 g/L, salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, and 0.3 g/L CaCl2): 1.23 X (0.62 g/L, 0.62 g/L, and 0.37 g/L respectively), temperature: 30 °C, pH: 6, agitation: 400 rpm, aeration: 1 vvm, and xylose: 50 g/L. Optimization studies resulted in xylitol yield and productivity of 0.71 ± 0.004 g/g and 1.48 ± 0.018 g/L/h, respectively. Glycerol supplementation (2 g/L) further improved xylitol yield (0.83 ± 0.009 g/g) and productivity (1.87 ± 0.020 g/L/h) by 1.66 and 3.12 folds, respectively, higher than the unoptimized conditions thus exhibiting the potential of C. tropicalis ATCC 13803 being used for commercial xylitol production.

This paper proposes an algorithm to plan collision-free trajectories for emergency scenarios using path-velocity decomposition (PVD). PVD decouples longitudinal and lateral planning, enabling the use of a linear model predictive control based path planner, which can operate at the bounds of admissible controls, and has low computational cost. However, infeasibility may occur in this method due to insufficient lateral acceleration capability during evasive manoeuvres. The problem is further complicated by the presence of multiple obstacles, which may require multiple evasive manoeuvres. Our approach overcomes this issue by connecting individually feasible evasive manoeuvres using heuristics in order to plan a velocity profile that guarantees collision avoidance throughout the prediction horizon. For this purpose, a simple method to approximate the acceleration profile to maximize deviation for a given obstacle distance is used, which considers actuator as well as friction constraints. These profiles are then used in motion primitives to perform collision checks in the velocity planning stage, thus ensuring feasibility in the path planning stage. Simulation results for critical last-second emergency scenarios consisting of multiple static obstacles show that a collision-free trajectory on friction limits can be planned using our approach.

Aptamer-based protein sensing can be implemented using a variety of optical and non-optical detection methods. In this report, we present protein-induced fluorescence enhancement (PIFE) based detection of DNA aptamer binding to thrombin. We demonstrate that PIFE reports on direct binding of thrombin to the aptamer strand carrying the fluorophore and hence is unaffected by salt based stabilization of the aptamer conformations as observed in fluorescence resonance energy transfer (FRET) assays. PIFE based thrombin detection displayed excellent linearity in the range of 0.25 pM-25 nM with a detection limit of 8.9 pM. In an alternate scheme, PIFE was demonstrated by placing the fluorophore on a connector strand thus bypassing the requirement to label the aptamer directly. This strategy allowed us to examine thrombin binding by variously modified thrombin aptamers and can serve as a platform for aptamer screening. We finally show that PIFE based thrombin aptamer assay displays high specificity even in the presence of `natural' background such as blood plasma. We hence propose PIFE based aptamer sensing of protein ligands as a facile yet sensitive and general strategy for biosensing. (C) 2018 Elsevier B.V. All rights reserved.

Polymer induced turbulent drag reduction has significant industrial importance and finds application in industries, oil and gas, fire-fighting, marine, irrigation, biomedical etc. Most of the reported literature is focused on the skin drag reduction in pipe flow employing drag reducing additives (DRAs) like polymers, surfactants, fibres and suspensions. In this work, the effect of polymeric addition on the total drag reduction (skin and form) is studied for turbulent flow of water through various fittings like 45 degree elbow, 90 degree miter, sudden expansion and sudden contraction. Different polymers like PAM, PEO, HPMC have been employed as DRAs at various concentrations and pressure drops. The results indicate a complex and interesting behavior. When compared to the results reported for pipe flow, even in this case polymers are found to give total drag reduction (TDR) though less relative to skin drag alone. The extent of TDR is found to depend on the nature of fitting, polymer and its concentration and the pressure drop used. From the results, it is also clear that there is a strong need to further investigate the problem using sophisticated analytical tools on rheometry and polymer degradation.

Emergency scenarios may require trajectory planning at actuator and friction limits within tight obstacle constraints. This paper presents an approach to handle such scenarios using Linear Time Varying Model Predictive Control, in the presence of both static and dynamic obstacles. With the proposed approach, the controller transitions between a kinematic vehicle model, which is stable at low velocities, and a dynamic vehicle model, which is more accurate at high velocities, based on a threshold velocity. This ensures the functionality of the controller in emergency braking scenarios and enables manoeuvre initialization with a full braking trajectory. An adjustable safety distance concept is introduced that considers the criticality of the scenario and tightens or loosens the obstacle avoidance and friction constraints accordingly. Simulation results show that the controller is capable of handling various critical situations, including those when the vehicle comes to a stop at the end of a high speed evasive manoeuvre. Furthermore, it is more effective at keeping a safety distance from obstacles in such manoeuvres than by using fixed safety distance concept.

Smartphone-based fluorescence detection is a promising avenue for biosensing that can aid on-site analysis. However, quantitative detection with fluorescence in the field has been limited due to challenges with robust excitation and calibration requirements. Here, we show that ratiometric analysis with Förster resonance energy transfer (FRET) between dye pairs on DNA aptamers can enable rapid and sensitive kanamycin detection. Since our detection scheme relies on ligand binding-induced changes in the aptamer tertiary structure, it is limited only by the kinetics of ligand binding to the aptamer. Our FRET-based kanamycin binding aptamer (KBA) sensor displays two linear ranges of 0.05-5 nM (detection limit of 0.18 nM) and 50-900 nM of kanamycin. The aptamer displays high specificity even in the presence of the 'natural' background from milk. By immobilizing the aptamer in the flow cell, our KBA sensor design is also suitable for repeated kanamycin detection. Finally, we show that the ratiometric FRET-based analysis can be implemented on a cheap custom-built smartphone setup. This smartphone-based FRET aptamer scheme detects kanamycin in a linear range of 50-500 nM with a limit of detection (LOD) of 28 nM. © 2019 The Royal Society of Chemistry.