Pseudo Reference Research Articles

Generation of non-Gaussian stationary random excitations with specified cross-power spectral densities using zero memory non-linear transformation for fatigue test purposes

Zero-memory non-linear (ZMNL) methods have long been a type of very useful tools in creating super-Gaussian random excitations for fatigue test. The major drawback of this method is that the magnitude distortion can be seen in both auto-power spectral density (ASD) and cross power-spectral density (CSD) of the excitation if the dynamic range of the target power spectral density (PSD) is large. To study the problem, we introduced Fourier series of a Gaussian signal into a cubic system, which is a common mathematical model shared by most of the ZMNL functions. We found that the cubic system produces a component leading to the distortion of both ASD and CSD. Meanwhile, if the shape of the reference ASD is flat in a frequency band, the distortion will not happen in the band. Based on this findings, a novel method is proposed in this article. It employs a pseudo reference PSD with flat ASDs to generate non-Gaussian signals in order to avoid the PSD distortions. Designed FIR filters are then applied to rescale the ASDs of the generated signals. After, iterative processes are introduced to recover the kurtoses of these filtered signals. The method is applied on a two-input and two-output numerical model, the feasibility and the availability of the method is verified. Finally, two control schemes based on the proposed pseudo reference PSD method are provided for a shaker table test. Test results show that both control schemes can eliminate the mismatch between the target PSD and the measured PSD of a shaker table.

Reliability and Performance Improvement of PUC Converter Using a New Single-Carrier Sensor-Less PWM Method With Pseudo Reference Functions

A new single-carrier sensor-less pulsewidth modulation (PWM) method using suggested pseudo reference functions is proposed for packed U-cell (PUC) converter to improve performance and reliability of the PUC converter. It is composed of one PWM carrier signal and two suggested pseudo reference functions. By employing the proposed modulation method, the PUC dc capacitor voltage ripple is substantially decreased, and faster sensor-less capacitor voltage balancing is obtained. Moreover, the power losses are evenly distributed among all power switches. Consequently, notable reduction of the PUC dc capacitor voltage ripple and even distribution of the power loss among switches enhance the PUC converter's reliability and lifetime. In addition, odd multiples of the switching harmonic clusters are eliminated from the output voltage; thus, the values of output passive filter components are halved. Hence, applying the proposed single-carrier sensor-less PWM method remarkably improves the performance, power density, reliability, and lifetime of the PUC converter and notably simplifies implementation of the switching pattern. Provided experimental results and comparisons as well as reliability analysis verify the viability and effectiveness of the proposed PWM method.

Enabling Mg‐Based Ionic Liquid Electrolytes for Hybrid Dual‐Ion Capacitors

AbstractWe report on the reversible (de)intercalation of TFSI− anions from a Mg‐based ionic liquid electrolyte, Mg(TFSI)2 in Pyr14TFSI, in graphite activated carbon hybrid dual‐ion capacitor (DIC) cells. The role of different pseudo reference electrodes (PREs) including Ag‐wire and Li metal is discussed regarding the comparability of different battery cells. We show that an Ag‐wire PRE is not suitable for the designated purpose, while the use of a Li metal PRE results in high reproducibility. Mg‐based DIC cells are compared with cells based on pure Pyr14TFSI and LiTFSI‐Pyr14TFSI electrolytes, and with graphite Li metal dual‐ion cells employing LiTFSI‐Pyr14TFSI. At 5.2 V vs. Li|Li+, Mg‐containing DIC cells reveal an improved performance compared to Li‐based cells, i. e., higher capacity (87 vs. 85 mAh g−1) and higher Coulombic efficiency (98 vs. 96 %). These results may pave the way to further studies and performance improvements of Mg‐based batteries and to hybrid DIC chemistries with other cations, especially multi‐valent ones.

Silver Recovery from Silver Fluoride Solution Using Electrowinning

As solar technology becomes more popular, more modules with limited lifetimes will be manufactured. By 2050 there are expected to be 78 million tons of waste modules, which are rarely recycled today. Each module contains approximately 6 grams of silver, which is the most precious metal found in silicon modules. Hydrofluoric acid is proposed as the leaching agent to remove silver and other metals from the surface of the silicon, while electrowinning is used to recover the silver from the leachate and plate it onto a cathode. The electrowinning setup uses a three-electrode configuration with a pseudo reference electrode to control the half-cell potential. A silver pseudo-reference electrode was found to be sufficient for achieving a high mass recovery rate. Variable voltage trials were conducted and 0.7 V with reference to silver achieved a high mass recovery rate of 96.4% with a high purity of silver. Current efficiency is below 7% for all the voltages tested, which suggests parasitic reactions in the reaction vessel such as O2(g) + 4H+ + 4e− ⇌ 2H2O. The trials at 0.7 V vs silver in a nitrogen purge environment eliminated corrosion at the vapor-liquid interface on the cathode but did not improve the current efficiency. It is possible that the nitrogen purge environment still contains residual oxygen.

A hybrid correcting method considering heterozygous variations by a comprehensive probabilistic model

BackgroundThe emergence of the third generation sequencing technology, featuring longer read lengths, has demonstrated great advancement compared to the next generation sequencing technology and greatly promoted the biological research. However, the third generation sequencing data has a high level of the sequencing error rates, which inevitably affects the downstream analysis. Although the issue of sequencing error has been improving these years, large amounts of data were produced at high sequencing errors, and huge waste will be caused if they are discarded. Thus, the error correction for the third generation sequencing data is especially important. The existing error correction methods have poor performances at heterozygous sites, which are ubiquitous in diploid and polyploidy organisms. Therefore, it is a lack of error correction algorithms for the heterozygous loci, especially at low coverages.ResultsIn this article, we propose a error correction method, named QIHC. QIHC is a hybrid correction method, which needs both the next generation and third generation sequencing data. QIHC greatly enhances the sensitivity of identifying the heterozygous sites from sequencing errors, which leads to a high accuracy on error correction. To achieve this, QIHC established a set of probabilistic models based on Bayesian classifier, to estimate the heterozygosity of a site and makes a judgment by calculating the posterior probabilities. The proposed method is consisted of three modules, which respectively generates a pseudo reference sequence, obtains the read alignments, estimates the heterozygosity the sites and corrects the read harboring them. The last module is the core module of QIHC, which is designed to fit for the calculations of multiple cases at a heterozygous site. The other two modules enable the reads mapping to the pseudo reference sequence which somehow overcomes the inefficiency of multiple mappings that adopt by the existing error correction methods.ConclusionsTo verify the performance of our method, we selected Canu and Jabba to compare with QIHC in several aspects. As a hybrid correction method, we first conducted a groups of experiments under different coverages of the next-generation sequencing data. QIHC is far ahead of Jabba on accuracy. Meanwhile, we varied the coverages of the third generation sequencing data and compared performances again among Canu, Jabba and QIHC. QIHC outperforms the other two methods on accuracy of both correcting the sequencing errors and identifying the heterozygous sites, especially at low coverage. We carried out a comparison analysis between Canu and QIHC on the different error rates of the third generation sequencing data. QIHC still performs better. Therefore, QIHC is superior to the existing error correction methods when heterozygous sites exist.

Assessing site signal preservation in reference chronologies for dendro-provenancing.

Regional differences in tree growth can be used to approximate the geographical provenance of ring-width series (‘dendro-provenancing’). This method relies on cross-dated ring-width series (reference chronologies) that are thought to represent the radial growth signal of trees in a given region. Reference chronologies are often established from ring-width series of living tree populations. Frequently, they are too short to allow for investigating the provenance of historical wood. Thus, references are extended by ring-width series from buildings and art-historical objects that exhibit best matching growth patterns with the living tree references. Yet, series from other provenances may erroneously be included. Thereby the local or regional growth signal of the references is progressively contaminated, but this has received little attention to date. I investigate this contamination risk using a simulation approach that allows for generating pseudo site chronologies that preserve the relevant statistical properties of the real site chronologies. While the exact provenance of historical wood is unknown, for simulated ring-width series the provenance is unambiguous. Hence, pseudo reference chronologies may be established while monitoring the signal mixture. Specifically, 15 site chronologies of Norway spruce (Picea abies (L.) H. Karst.) from northeastern Switzerland were used to generate 15 pseudo site growth signals that span 1000 years. The simulation demonstrates that quasi uncontaminated references can be established in ideal circumstances for the study area. However, the thresholds for the similarity in between-series correlation must be very high. Even then, contaminated pseudo references occurred in rare cases during the simulation. Yet, elevation-specific pseudo references were established with lower thresholds. Simulation currently offers the only approach for assessing the contamination risk of reference chronologies, and it allows for elucidating the conditions under which acceptable levels of contamination can be guaranteed. Therefore, the present approach paves the way towards a practical simulation tool for dendro-provenancing.

TSPR: Deep network-based blind image quality assessment using two-side pseudo reference images

We present a deep network-based blind image quality assessment (BIQA) using two-side pseudo reference (TSPR) images. Different from a traditional reference with the perfect quality, two opposite images are introduced as pseudo references, which are generated via a restoration model and a degradation model, respectively. The bilateral distance (error) maps between the TSPR images and the pristine distorted images are first extracted, and then the regression neural network is utilized to simulate how the human brain processes information, i.e., dialectical thinking, in which both positive information and negative information are taken into consideration for predicting the quality of images. To avoid the complexity and differentiation of each optimization objective in the end-to-end strategy, the step-by-step strategy is adopted to make the model clearer and more explainable. Finally, four common distortions on the LIVE-2D, TID2013, and CSIQ datasets are evaluated using the proposed model, and the experiment results demonstrate the effectiveness and robustness of the algorithm, which delivers superior performance over the state-of-the-art NR methods.

A graphenic and potentiometric sensor for monitoring the growth of bacterial biofilms

Biofilm development on surfaces represents one of the most challenging issues in the medical field. The irreversibility of the biofilm developmental process, and the peculiar characteristics of biofilms (including the low permeability to antibacterial compounds), make biofilm associated infections difficult to treat and prone to relapse. Thanks to the short response time, low-cost, easy fabrication and potential for miniaturization, electrochemical sensors are expected to play an important role in monitoring biofilm formation. Here, we describe the use of a potentiometric sensor based on functionalized reduced graphene oxide for monitoring the formation and growth of biofilms from three bacterial species (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) in liquid and semisolid culture media. The Open Circuit Potential (OCP) between an Ag/AgCl pseudo reference electrode and a working electrode, both screen-printed on a flexible polyethylene terephthalate film, was measured during the growth of bacteria. The OCP decreased over time as bacteria grew on the sensor surface exhibiting a negative correlation.

Implication of Pseudo Reference Genes in Normalization of Data from Reverse Transcription-Quantitative PCR.

Pseudogenes are duplicated or retrotransposed DNA sequences of native functional genes. Amplification of pseudogenes along with gene of interest often produces false positive results, which is an innate problem in Reverse Transcription-quantitative PCR (RT-qPCR). Selecting a reference gene without any interference from pseudogene amplification is therefore a challenge to overcome. Among the common reference genes used for normalization (ACTB, GAPDH, HPRT1, TUBB, RNA18SN1 and B2M), B2M was found to have no pseudogenes in silico, which has also been confirmed by PCR and RT-qPCR. We also assessed the effect of pseudogenes on the determination of the stability of reference genes through data mining. The phylogenetic analysis of pseudogenes and functional genes revealed high sequence similarity among mammals. In addition, we demonstrated the deduction of pseudogene amplification signal using ValidPrime Assay (VPA) under conditions where genomic DNA contamination could not be avoided. Hence, we recommend the use of pseudo-free reference gene with consistent expression in the samples of interest or use VPA normalization method, where genomic DNA or pseudogene amplification is inevitable.

Electrochemical detection of fentanyl with screen-printed carbon electrodes using square-wave adsorptive stripping voltammetry for forensic applications

Square-wave adsorptive stripping voltammetry (SWAdSV) is proposed as a fast, simple, and sensitive approach toward the detection, identification, and semi-quantitation of fentanyl in seized drug samples using screen-printed carbon electrodes. Electrochemical oxidation of fentanyl resulted in the formation of two anodic peaks, one at 0.75 V (peak I) and the second at 0.88 V (peak II) versus a Ag/AgCl pseudo reference electrode. Voltammetric measurements were conducted under optimized experimental conditions using fentanyl standards ranging from 0.076 μg/mL to 6.9 μg/mL, which resulted in a limit of detection of 0.037 μg/mL. Reproducibility was assessed as the average percent relative standard deviation of the slopes of calibration curves and was 2.6% for oxidation peak I and 7.4% for oxidation peak II in cell. Detection capabilities were assessed in a 5-mL cell and in a 100 microliter drop. Interference studies were conducted with cocaine, methamphetamine, quinine, caffeine, and acetaminophen. The mechanism for the electrochemical oxidation of fentanyl to norfentanyl is also described. Accuracy and suitability of the method for seized drug analysis was assessed using 11 simulated samples. Suitability of the method for future analysis of fentanyl in oral fluid was assessed.

Electrochemical monitoring of the oxidative degradation of glyphosate with UV/H2O2

A voltammetric method optimized for the sensitive and reliable study of the UV/H2O2 oxidation of glyphosate (N- (phosphonomethyl) glycine) (GPS). The cell consisted of three electrodes in a compartment, silver wire coated with silver chloride as a pseudo reference electrode, platinum electrode as working electrode and stainless steel as auxiliary electrode. GPS cyclic voltammetric analysis suggests the formation of a GPS-Pt complex on the electrode surface, with an enhanced signal in perchloric acid between 1.3 to -1.3V; sensitive to protonation of the amino group, no response observed at pH values greater than 5.00. The oxidative degradation of GPS with UV/H2O2 is evident at pH 3.0, it exhibits first order pseudo kinetics with a half-life of 40 ± 4min. Two degradative routes are estimated depending on the concentration of H2O2: at low concentrations (H2O2/GPS 1: 100 ratio), the formation of sarcosine and then glycine is favored; at H2O2/GPS 1:20 and 1:10 ratios predominate the formation of glycine.

Test–retest variability and reference region-based quantification of 18F-BCPP-EF for imaging mitochondrial complex I in the human brain

Mitochondrial complex I (MC-I) is an essential regulator of brain bioenergetics and can be quantified in the brain using PET radioligand 18F-BCPP-EF. Here we evaluate the test–retest reproducibility of 18F-BCPP-EF in humans, and assess the use of a non-invasive quantification method (standardised uptake value ratio – SUVR). Thirty healthy volunteers had a 90-min dynamic 18F-BCPP-EF scan with arterial blood sampling, five of which received a second scan to be included in the test–retest analysis. Time-activity curves (TAC) were analysed using multilinear analysis 1 (MA1) and the two-tissue compartment model (2TC) to estimate volumes of distribution (VT). Regional SUVR-1 values were calculated from the 70 to 90-min TAC data using the centrum semiovale as a pseudo reference region, and compared to kinetic analysis-derived outcome measures. The mean absolute test–retest variability of VT ranged from 12% to 18% across regions. Both DVR-1and SUVR-1 had improved test–retest variability in the range 2%–7%. SUVR-1 was highly correlated with DVR-1 (r2 = 0.97, n = 30). In conclusion, 18F-BCPP-EF has suitable test–retest reproducibility and can be used to quantify MC-I in clinical studies.

Moving Toward Multicenter Therapeutic Trials in Amyotrophic Lateral Sclerosis: Feasibility of Data Pooling Using Different Translocator Protein PET Radioligands.

Neuroinflammation has been implicated in amyotrophic lateral sclerosis (ALS) and can be visualized using translocator protein (TSPO) radioligands. To become a reliable pharmacodynamic biomarker for ALS multicenter trials, TSPO radioligands have some challenges to overcome. We aimed to investigate whether multicenter data pooling of different TSPO tracers (11C-PBR28 and 18F-DPA714) is feasible, after validation of an established 11C-PBR28 PET pseudo reference analysis technique for 18F-DPA714. Methods: Seven ALS patients from Belgium (58.9 ± 6.7 y old, 5 men and 2 women), 8 healthy volunteers from Belgium (52.1 ± 15.2 y old, 3 men and 5 women), 7 ALS patients from the United States (53.4 ± 9.8 y old, 5 men and 2 women), and 7 healthy volunteers from the United States (54.6 ± 9.6 y old, 4 men and 3 women) from a previously published study underwent dynamic 18F-DPA714 (Leuven, Belgium) or 11C-PBR28 (Boston, Massachusetts) PET/MRI. For 18F-DPA714, maps of total volume of distribution (VT) were compared with SUV ratio (SUVR) images from 40 to 60 min after injection (SUVR40-60) calculated using the pseudo reference regions cerebellum, occipital cortex, and whole brain (WB) without ventricles. For 11C-PBR28, SUVR images from 60 to 90 min after injection using the WB without ventricles were calculated. Results: In line with previous studies, increased 18F-DPA714 uptake (17.0% ± 5.6%) in primary motor cortices was observed in ALS subjects, as measured by both VT and SUVR40-60 approaches. The highest sensitivity was found for SUVR calculated using the WB without ventricles (average cluster, 21.6% ± 0.1%). 18F-DPA714 VT ratio was highly correlated with the SUVR40-60 (r > 0.8, P < 0.001). A similar pattern of increased uptake (average cluster, 20.5% ± 0.5%) in the primary motor cortices was observed in ALS subjects for 11C-PBR28 SUVR calculated using the WB without ventricles. Analysis of the 18F-DPA714 and 11C-PBR28 data together resulted in a more extensive pattern of significantly increased glial activation bilaterally in the primary motor cortices. Conclusion: The same pseudo reference region analysis technique for 11C-PBR28 PET can be extended toward 18F-DPA714 PET. Therefore, in ALS, standardized analysis across these 2 tracers enables pooling of TSPO PET data across multiple centers and increases the power of TSPO as a biomarker for future therapeutic trials.

Screen-Printed Carbon Electrodes Modified with Graphene Oxide for the Design of a Reagent-Free NAD+-Dependent Biosensor Array.

A facile approach for the construction of reagent-free electrochemical dehydrogenase-based biosensors is presented. Enzymes and cofactors (NAD+ and Fe(CN)63-) were immobilized by modification of screen-printed carbon electrodes with graphene oxide (GO) and an additional layer of cellulose acetate. The sensor system was exemplarily optimized for an l-lactate electrode in terms of GO concentration, working potential, and pH value. The biosensor exhibited best characteristics at pH 7.5 in 100 mM potassium phosphate buffer at an applied potential of +0.250 V versus an internal pseudo Ag reference electrode. Thereby, sensor performance was characterized by a linear working range from 0.25 to 4 mM and a sensitivity of 0.14 μA mM-1. The detection principle was additionally evaluated with three other dehydrogenases (d-lactate dehydrogenase, alcohol dehydrogenase, and formate dehydrogenase, respectively). The developed reagentless biosensor array enabled simultaneous and cross-talk free determination of l-lactate, d-lactate, ethanol, and formate.

A Glucose Microfluidic Sensor Tested in Artificial Microgravity

A microfluidic device for the detection of glucose in artificial microgravity was tested, in order to study the behavior of an electrochemical system in these conditions. The electrochemical device was designed by computational simulation, and was constructed in PMMA by the computer numerical control machine. The device consisted of a V-shaped microfluidical channel with an inlet and an output. CuPt was electrodeposited on glassy carbon, and used as electrode sensor for glucose, Ag/GC was used as reference electrode, and Pt/GC as counterelectrode. The device was tested in earth conditions and microgravity conditions (10-7 G). Microgravity was simulated in a three-axis random position machine constructed in the INICTEL-UNI (Lima, Peru). Voltammetry studies (-100 mV to 400 mV vs. Ag pseudo reference) was performed with a remote controlled potentiostat, placed in the machine, the test were carried out in glucose solution 5 mM in PBS 7.4, and with blood. A current asociated to the glucose was observed in glucose and blood, meanwhile in the blank (PBS 7.4) this current was absent. This result opens possibility of testing glucose in microgravity conditions.

Electroreduction of indium tin oxide in a CaF2–NaF–CaO molten salt at the solid oxide membrane anode system

The electroreduction of indium tin oxide (ITO) using a solid oxide membrane anode was investigated in a molten salt of CaF2–NaF–CaO at 1150 °C under an inert atmosphere. In the CaF2–NaF blank salt, the first reduction peak did not change from −0.25 V (vs. W pseudo reference electrode (R. E.)) for the addition of up to 2 wt% CaO, but the second reduction peak was observed at −0.55 V (vs. W pseudo R. E.) in 1 wt% CaO, and −0.4 V (vs. W pseudo R. E.) in 2 wt% CaO. Cyclic voltammetry analysis was carried out using ITO as the cathode, and a reduction peak was observed at +0.31 V (vs. W pseudo R. E.). This is a positive value about 0.24 V greater than the theoretical value, probably arising because of the increase in the oxygen ion activity of CaO. The optimum ITO particle size was determined to be 600–1000 μm considering the maximum reduction efficiency dependent on the sedimentation rate, specific melt droplet growth, and reduced InSn film formation. The formation of an InSn alloy with almost the same mass ratio as the initial ITO was confirmed by combining the results of X-ray diffraction and energy dispersive X-ray spectroscopy analysis.

Longitudinal PET Monitoring of Amyloidosis and Microglial Activation in a Second-Generation Amyloid-β Mouse Model.

Nonphysiologic overexpression of amyloid-β (Aβ) precursor protein in common transgenic Aβ mouse models of Alzheimer disease likely hampers their translational potential. The novel AppNL-G-F mouse incorporates a mutated knock-in, potentially presenting an improved model of Alzheimer disease for Aβ-targeting treatment trials. We aimed to establish serial small-animal PET of amyloidosis and neuroinflammation in AppNL-G-F mice as a tool for therapy monitoring. Methods:AppNL-G-F mice (20 homozygous and 21 heterogeneous) and 12 age-matched wild-type mice were investigated longitudinally from 2.5 to 10 mo of age with 18F-florbetaben Aβ PET and 18F-GE-180 18-kDa translocator protein (TSPO) PET. Voxelwise analysis of SUV ratio images was performed using statistical parametric mapping. All mice underwent a Morris water maze test of spatial learning after their final scan. Quantification of fibrillar Aβ and activated microglia by immunohistochemistry and biochemistry served for validation of the PET results. Results: The periaqueductal gray emerged as a suitable pseudo reference tissue for both tracers. Homozygous AppNL-G-F mice had a rising SUV ratio in cortex and hippocampus for Aβ (+9.1%, +3.8%) and TSPO (+19.8%, +14.2%) PET from 2.5 to 10 mo of age (all P < 0.05), whereas heterozygous AppNL-G-F mice did not show significant changes with age. Significant voxelwise clusters of Aβ deposition and microglial activation in homozygous mice appeared at 5 mo of age. Immunohistochemical and biochemical findings correlated strongly with the PET data. Water maze escape latency was significantly elevated in homozygous AppNL-G-F mice compared with wild-type at 10 mo of age and was associated with high TSPO binding. Conclusion: Longitudinal PET in AppNL-G-F knock-in mice enables monitoring of amyloidogenesis and neuroinflammation in homozygous mice but is insensitive to minor changes in heterozygous animals. The combination of PET with behavioral tasks in AppNL-G-F treatment trials is poised to provide important insights in preclinical drug development.

Biochemical Oxygen Demand Microelectrode for Quantifying Concentration Gradients in Anaerobic Biofilms

Biochemical oxygen demand (BOD) is one of the widely used parameter to determinate the level of organic pollution in water. The standard method, BOD5 assay, is commonly used to measure BOD concentration but it takes a long time and cannot be integrated for online measurements. Additionally, BOD5 cannot be used to measure BOD in microscale systems, especially in anaerobic biofilms where the oxygen is absent. Because of the limitation of available tools for quantifying BOD concentration within anaerobic biofilms, a new, simple and miniaturized tool is needed for measuring local BOD concentrations in biofilms. The goal of this work is to develop a BOD microelectrode for quantifying concentration gradients in anaerobic biofilms. The developed BOD microelectrode uses an anaerobic mixed-culture-anodic biofilm as a transducer, which is grown on a carbon fiber tip diameter. The carbon fiber microelectrode acts as the working electrode, which is polarized using a potentiostat. A 100 µm platinum wire counter electrode and a Ag/AgCl-wire pseudo reference electrode are used to complete the electrochemical cell. The BOD microelectrode components are enclosed in a glass outer case. The BOD microelectrodes were calibrated using a standard BOD solution. The performance of the BOD microelectrode was assessed including response time and the linear BOD concentration range. Finally, concentration profiles in an anaerobic biofilm were measured to demonstrate its use.

Common-path interferometry with tilt carrier for surface measurement of complex optics.

We propose a novel common-path non-null interference system for the surface measurement of complex optics. Because of the common-path structure, systematic errors are mostly eliminated and the complexity of system calibration is reduced for the proposed setup. However, optical design of common-path non-null interference systems is of great difficulty because many off-axis beams are used to compensate for the local gradient of the measured piece. Different from the classical common-path interferometers, which pay more attention to the beam quality of the on-axis field of view (FOV), the proposed system requires better quality for both on-axis and off-axis outgoing beams. In the proposed setup, the lens groups with wide FOVs afford wave aberrations better than 0.1λ for the on-axis and off-axis FOVs. Simultaneously, the off-axis beams are prevented from generating pseudo reference beams by optimizing the parameters of the lenses and the aperture. In addition, multiple tilted test beams are generated by a point-source generator based on a fiber array, which is more versatile than a lens-array-type point-source generator. Further, a universal measurement system with high accuracy and time savings is formed, as evidenced by the measurement results of a parabolic mirror and different types of cylindrical mirrors.

Lab-on-a-screen-printed electrochemical cell for drop-volume voltammetric screening of flunitrazepam in untreated, undiluted alcoholic and soft drinks

Flunitrazepam, also known as “Rohypnol” or “Rophy” among other trade and street names, is an extremely potent benzodiazepine that is prescribed to treat severe insomnia. Due to these attributes, flunitrazepam, when is surreptitiously administered to an alcoholic or soft drink, is associated with “drug-facilitated sexual assault”. We report here for the first time, a low cost lab-on-a-screen-printed electrochemical cell (SPC) based on iron-sparked graphite working electrode modified with glucose oxidase (GOx) and glucose hydrogel droplets (GluHD) for the detection of flunitrazepam. Iron-spark modification increases the response of the sensor by ca. 3-fold compared with that of the plain electrode, while an in situ deoxygenation process, based on GOx-glucose enzyme reaction, depletes dissolved oxygen. As a result, the method enables interference free voltammetric measurements of the electro reduction of the nitro group of flunitrazepam at ca. −0.71 to −0.78 V vs. Ag printed pseudo reference electrode depending on the sample's matrix, and the detection of the drug at the sub-millimolar level. GOx/GluHD-FeSPC was directly applied to the drop-volume (∼60 μL) detection of flunitrazepam to a wide range of untreated and undiluted spiked samples (Pepsi cola®, Vodka, Whisky, Tequila, Gin, and Rum) of different acidity (pH 2.3–8.4), and alcohol content up to 40% v/v. Data demonstrate the excellent performance of the sensor for point-of-need screening of flunitrazepam and suggest that GOx/GluHD-FeSPC holds promise as an effective analytical tool to prevent phenomena of covert drug administration.