Surface-enhanced Raman spectroscopy (SERS) harnesses the confinement of light into metallic nanoscale hotspots to achieve highly sensitive label-free molecular detection that can be applied for a broad range of sensing applications. However, challenges related to irreversible analyte binding, substrate reproducibility, fouling, and degradation hinder its widespread adoption. Here we show how in-situ electrochemical regeneration can rapidly and precisely reform the nanogap hotspots to enable the continuous reuse of gold nanoparticle monolayers for SERS. Applying an oxidising potential of +1.5 V (vs Ag/AgCl) for 10 s strips a broad range of adsorbates from the nanogaps and forms a metastable oxide layer of few-monolayer thickness. Subsequent application of a reducing potential of -0.80 V for 5 s in the presence of a nanogap-stabilising molecular scaffold, cucurbit[5]uril, reproducibly regenerates the optimal plasmonic properties with SERS enhancement factors ≈106. The regeneration of the nanogap hotspots allows these SERS substrates to be reused over multiple cycles, demonstrating ≈5% relative standard deviation over at least 30 cycles of analyte detection and regeneration. Such continuous and reliable SERS-based flow analysis accesses diverse applications from environmental monitoring to medical diagnostics. 

In situ electrochemical regeneration of nanogap hotspots for continuously reusable ultrathin SERS sensors

Effects of Blade Number on the Centrifugal Pump Performance: A Review

The evaluation of the effect of gas content on the characteristics of a Centrifugal Pump

Liquivac pumps, with their unique shaped twin start helical rotor, have found utility in various sectors but the major drawback limiting in their global exploitation is their low performance. This paper investigates the study of performance of the Liquivac pump produced by Tomlinson Hall Ltd. Experimental data was used to validate a numerical model developed in Ansys Fluent 20.2 for the Liquivac pump. Four different geometric models of the rotor were tested numerically to find the optimum design using blade number and pitch length as the criteria to achieve improved efficiency. The choice of turbulence model is an important factor in the most accurate prediction with computational fluid dynamics (CFD) simulation. Four different turbulence models were validated with experimental measurements. The realizable K-ε model gave the most accurate performance predictions with a relative deviation of 3.8%. So, the realizable K-ε model was employed for further parametric optimization of the rotor. The results indicate a reasonable improvement in the head and efficiency of the Liquivac pump with a new rotor geometry of four equidistant blades in the front, back and four flights with 30 mm pitch. This is attributed to the most favourable balance between the different losses and most guided and uniform flow inside the rotor channels. 

/pdf/effect-of-geometric-configuration-of-the-impeller-on-the-1m4zz4lo.pdf

Effect of Geometric Configuration of the Impeller on the Performance of Liquivac Pump: Single Phase Flow (Water)

https://robots.iopscience.iop.org/article/10.1088/1757-899X/779/1/012050/pdf

Investigation of the flow part of a high-speed vane pump of a hydraulic unit using numerical hydrodynamic modeling

Crude oil transport is an essential task in oil and gas industries, where centrifugal pumps are extensively used. The design of a centrifugal pump involves a number of independent parameters which affect the pump performance. Altering some of the parameters within a realistic range improves pump performance and saves a significant amount of energy. The present research investigated the pump characteristics by modifying the number of blades and the exit blade-angles. Reynolds-Averaged Navier-Stokes equations with standard k - e two-equation turbulence closure were used for steady and incompressible flow of crude oil through the pump. The experimental set-up was installed and the pump performance calculated numerically  was compared with the experiments.   The investigations showed that the number of blades and the exit blade-angles have a significant influence on the head, shaft power, and efficiency. The vortical flow structures, recirculation and reverse flow characteristics around the impeller were investigated to explain the flow dynamics of impeller and casing. A larger number of blades on the rotor showed dominant streamlined flow without any wake phenomena. The combined effect of the number of blades and exit blade angle has led to an increase in head and efficiency through the parametric optimization.

/pdf/performance-optimization-of-centrifugal-pump-for-crude-oil-1ok53f3bjm.pdf

Performance Optimization of Centrifugal Pump for Crude Oil Delivery

A fast, simple, inexpensive, selective, rugged and reproducible HPLC method based on the use of a new generation Sunniest RP-Aqua C28 column is described for the analysis of adenine in plasma. Three methods for the extraction of adenine from human plasma i.e. by acetone, acetonitrile and solid phase cartridges are reported. The separation was performed via isocratic elution of adenine using water–acetonitrile (90:10, v/v) as mobile phase at a flow rate of 1.0 mL min−1 and with detection at 260 nm. The values of retention factor in standard and plasma samples were 2.53 and 2.60, respectively. The method was validated and found to be linear at a concentration range of 5–1000 μg mL−1. The limits of detection and quantification were lower than 0.3 and 0.91 μg mL−1, respectively. The intra- and inter-day precisions (% RSD) were less than 9%. The accuracy values were between 99.8 and 107.4%. The extraction recoveries ranged from 95–80%.

Fast HPLC analysis of adenine in human plasma using a new generation C28 column and different extraction methods

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Performance Optimization of Centrifugal Pump for Crude Oil Delivery

Fast HPLC analysis of adenine in human plasma using a new generation C28 column and different extraction methods