Minimal Detectable Values Research Articles

Characteristics and Dosimetric Properties of Tissue-Equivalent Thermoluminescent Glass Detector Based on Al-Li-Zn, Borate Oxide Dope Dy3+

Functionality and dosimetric properties of a tissue-equivalent thermoluminescent glass detector doped with Dy3+. This work investigated an Aluminium-Lithium-Zinc borate oxide matrix using the melting-quench method. X-ray diffraction confirms the glass sample is amorphous. Dysprosium ions doping raises the glass’s tissue equivalent effective atomic number (Zeff.), improving its ability to absorb radiation and its sensitivity, with reproducibility almost at the tolerable limit. The glass detector also reduces the fading rate and signal loss over time. The minimum detectable dose values were 53.04 mGy and 45.1 mGy for the un-doped and 1.5 mol Dy3+ doped Al-Li-Zn borate glasses, respectively. A bright peak was seen in photoluminescence spectra at 348 nm (yellow), 529 nm (green), and 625 nm (orange hue). These correspond to the Dy3+ transitions at 4H15/2 → 6P7/2, 4F9/2 → 6H15/2, 4F9/2 → 6H15/2, and 4F9/2 → 6H13/2 , respectively. There was a noticeable drop in Tg from 257°C in the undoped sample to 101°C in the doped sample, Tm from 862°C to 815°C, and Tc from 756°C to 444°C in the doped sample. These results may indicate a lower temperature at which the material transitions from a solid to a liquid state and a lower crystallisation threshold. The frequency component and energy of activation of the 1.5 mol Dy3+ doped Aluminium-Lithium-Zinc borate are 2.1×10 27 s-1 and 1.03 eV, respectively. The 1.5 Dy3+ doped Aluminium-Lithium-Zinc borate glasses exhibit promising dosimetric properties of the tissue-equivalent thermoluminescent glass detector, indicating its potential for accurate and consistent radiation dosimetry in various applications.

Instrumented Static and Reactive Balance in Collegiate Athletes: Normative Values and Minimal Detectable Change.

Wearable sensors are increasingly popular in concussion research because of their objective quantification of subtle balance deficits. However, normative data and minimal detectable change (MDC) values are necessary to serve as references for diagnostic use and tracking longitudinal recovery. To identify normative and MDC values for instrumented static- and reactive-balance tests, an instrumented static mediolateral (ML) root mean square (RMS) sway standing balance assessment and the instrumented, modified push and release (I-mP&R), respectively. Cross-sectional study. Clinical setting. Normative static ML RMS sway and I-mP&R data were collected on 377 (n = 184 female) healthy National Collegiate Athletic Association Division I athletes at the beginning of their competitive seasons. Test-retest data were collected in 36 healthy control athletes based on standard recovery timelines after concussion. Descriptive statistics, intraclass correlation coefficients (ICCs), and MDC values were calculated for primary outcomes of ML RMS sway in a static double-limb stance on firm ground and a foam block, and time to stability and latency from the I-mP&R in single- and dual-task conditions. Normative outcomes across static ML RMS sway and I-mP&R were sensitive to sex and type of footwear. Mediolateral RMS sway demonstrated moderate reliability in the firm condition (ICC = 0.73; MDC = 2.7 cm/s2) but poor reliability in the foam condition (ICC = 0.43; MDC = 11.1 cm/s2). Single- and dual-task times to stability from the I-mP&R exhibited good reliability (ICC = 0.84 and 0.80, respectively; MDC = 0.25 and 0.29 seconds, respectively). Latency from the I-mP&R had poor to moderate reliability (ICC = 0.38 and 0.55; MDC = 107 and 105 milliseconds). Sex-matched references should be used for instrumented static- and reactive-balance assessments. Footwear may explain variability in static ML RMS sway and time to stability of the I-mP&R. Moderate-to-good reliability suggests time to stability from the I-mP&R and ML RMS static sway on firm ground can be used for longitudinal assessments.

Characterization of a CZT-based spectrometer for underwater operation via simulations and experiments

The harsh environmental conditions in the marine environment pose variousconstraints on developing efficient instruments to carry out long-term, in situradioactivity measurements. In addition, the strong attenuation of γ-raysin the water medium, makes remote sensing of such radiation a challenging task.In the present work, we report on the efforts to find the optimal characteristicsand deployment scenarios of a new prototype γ-ray instrument based on asmall-size CZT crystal enclosed in seal-tight housing to be deployed for operationin large depths. Lab experiments and detailed Monte Carlo simulations were combinedto validate the actual crystal dimensions, determine its efficiency and energyresolution, as well as establish the minimum detectable activity values of theinstrument in different configurations and scenarios.

Evaluation of TL and OSL signals of MgB4O7:Tm,Li prepared by the solution combustion method

Magnesium tetraborate (MgB4O7) doped with rare-earth elements is recognized for its suitability in thermoluminescence (TL) dosimetry due to its low effective atomic number (Zeff = 8.4) and the potential applications in neutron dosimetry. The study investigates the luminescent (TL and OSL) properties of MgB4O7 doped with thulium (Tm3+) and lithium (Li+). Samples were synthesized using the solution combustion method and TL and OSL responses were evaluated using a spectrometer and an automated OSL/TL reader. The emission lines of Tm3+ are consistent with previous literature, with Li+ enhancing TL and OSL responses. TL emission spectra unveil distinct bands corresponding to [Tm3+]* transitions. The electron paramagnetic resonance (EPR) spectroscopy analysis carried out in unirradiated, irradiated and annealed samples.The results show that the signals corresponding to BO32− and O2− are seen upon irradiation and disappear after annealing at 200 °C, indicating the participation of these centers in the TL process. The results show that the TL response of MgB4O7:Tm,Li is much more sensitive to gamma radiation than MgB4O7:Tm, with a minimum detectable value of 0.084 mGy and a linear response with dose for the range studied, from 0 to 500 mGy, with R2 of 0.998.

Effects of high-profile crossover feet on gait biomechanics in 2 individuals with Syme amputation.

Prosthetic treatment options for people with ankle disarticulation (i.e., Syme amputation) are limited. Prosthetic feet designed for people with Syme amputation are often low profile to accommodate build-height restrictions, resulting in decreased energy return during gait. High-profile crossover feet that attach to the posterior proximal aspect of the prosthetic socket can bypass these restrictions and may promote a more physiologic gait pattern. To compare level-ground gait biomechanics and patient-reported outcomes between crossover and traditional energy-storing feet in people with Syme amputation. Within-participant pilot study. Both participants were fit with energy-storing and crossover feet and were randomized to the order they used the feet. Participants used each foot for 2 weeks before assessment. Step length symmetry, prosthetic ankle range of motion, prosthetic-side energy return, and peak sound-side loading were determined from motion capture data obtained in a laboratory. Mobility and balance confidence were measured using standardized patient-reported outcome measures. Foot preference was assessed with an ad hoc survey. Two participants with Syme amputations completed the study. Prosthetic ankle peak dorsiflexion and push-off power increased with the crossover foot compared with the energy-storing foot for both participants. Both participants reported an overall preference of the crossover foot. Changes in patient-reported outcomes did not exceed published minimum detectable change values. Crossover feet increased prosthetic ankle range of motion and energy return compared with traditional energy-storing feet in this pilot investigation of 2 participants. Crossover feet seem to promote physiologic gait and may be a promising alternative to traditional low-profile feet for people with Syme amputation.

A time-resolved fluorescence immunoassay for rapid and precise automatic quality control of human papillomavirus type 68 VLPs in human papillomavirus vaccine

The effectiveness and necessity of human papillomavirus (HPV) vaccination to prevent HPV infection and cervical cancer are increasingly recognized by people. The 15-valent HPV vaccine, which protects against almost high-risk types of HPV viruses identified by WHO, has attracted much attention. However, as the valence of vaccines increases, quality control in the HPV vaccine production process is facing more challenges. The precise quality control of the HPV type 68 virus-like particles (VLPs), one of the unique components of the 15-valent HPV vaccine that distinguishes it from existing vaccines, is the new requirement for vaccine manufacturers. Here we developed a novel time-resolved fluorescence immunoassay (TRFIA) for rapid and precise automatic quality control of HPV68 VLPs in HPV vaccine. Two murine monoclonal antibodies specifically targeting the HPV68 L1 protein were used to establish a classical sandwich assay. Except for pretreating the vaccine sample, the whole analysis process was performed by a fully automated machine, which saves detection time and gets rid of manual error. Multiple experiments established that the current novel TRFIA can efficiently and reliably analyses HPV68 VLPs. Present novel TRFIA has exhibited merits with speed, robustness, high sensitivity with a minimum detection value of 0.08 ng/mL, considerable accuracy, a wide detection range (up to 1000 ng/mL) and excellent specificity. It is also expected to provide a new detection method for quality control for each HPV type VLPs. To summarize, the novel TRFIA is of great interest for application in HPV vaccine quality control.

Iron Determination in Natural Waters Using a Synthesised 3-Hydroxy-4-Pyridione Ligand in a Newly Developed Microfluidic Paper-Based Device

This work describes the development of an iron sensor based on a microfluidic paper-based technique, to attain iron quantification in natural waters. A new water-soluble naphthalene-3-hydroxy-4-pyridione ligand was used as a colour reagent, as it formed an orange complex with iron. As a newly described ligand, several chemical and physical parameters, namely, the sample and reagent volumes and reagent concentrations, were studied related to the formation of the coloured complex. The microfluidic paper-based analytical device (μPAD) assembly, namely, the use of different types of filter paper and different numbers of layers, was developed to obtain the best performance. Under the optimal conditions, a linear correlation was obtained in the range of 0.25–2.00 mg/L of iron, with a minimum detectable value of 0.07 mg/L. The proposed μPAD method was validated by an analysis of the certified samples and by a comparison of the tested water samples with the inductively coupled plasma (ICP) results (RE < 10%). Then, the μPAD device was successfully applied to the determination of iron in tap water, well water, river water, and seawater, with no need for any prior sample pre-treatment; recovery studies were also performed (average = 100.3% with RSD = 4.2%).

Detection of the Altitude and On-the-Ground Objects Using 77-GHz FMCW Radar Onboard Small Drones

Small drones are being utilized by researchers for applications such as object tracking, imaging and remote sensing as they have become more available, inexpensive and mobile with the advancements in sensor and UAV technologies. They can be equipped with sensors such as cameras and radars. Radars can be used onboard for navigation aid by detecting range and velocity, as well as for radar imaging applications. Although they are used in the latter commonly, radars can be used in navigation aid as well since they are barely affected by weather conditions or smoke. FMCW radars are suitable for drones since they can be lightweight and can detect range and velocity. Therefore, an FMCW radar-equipped drone system is designed and implemented for UAV positioning applications. A postprocessing algorithm is developed for detecting the altitude above ground level as well as the amount of reflection coming from the material on the ground surface, and a range compensation method is proposed to improve the performance of the algorithm. The results of a field experiment showed that the radar system and the postprocessing algorithm can be used for drone-based airborne positioning applications. Altitude values obtained with the radar postprocessing are in agreement with the altitude of the drone. Reflections coming from the metal objects are distinguished from those coming from the ground. With the range compensation method, minimum detectable altitude value is improved and the magnitude of ground reflections obtained from different altitudes became similar. The proposed system and algorithm can be utilized in navigation and in landing aid applications.

Investigation of Head Shake Sensory Organization Test (HS-SOT) in three planes: Test-retest reliability and age-related differences

BackgroundIn recent years, it has been determined that SOT sensitivity is insufficient in patients who develop vestibular compensation and therefore the Head Shake Sensory Organization Test (HS-SOT) has been developed. Research QuestionHow differs the balance performance of healthy adults that is tested with HS-SOT according to age and test planes? What is the test-retest reliability level of the HS-SOT in three planes? MethodsOur prospective study, which has a methodological research design, included 80 participants divided into three groups by age range (Group 1: 20–39 years (n = 30); Group 2: 40–49 years (n = 30) and Group 3: 50–64 years (n = 20)). SOT and HSSOT ( yaw, pitch, roll) were performed to all participants. To investigate the testretest reliability of the HS-SOT, a total of 27 participants were re-evaluated one week later. The HS-SOT performance of the participants was compared between age groups and test planes. Intra-class correlation coefficient and minimum detectable change values (MDC) was calculated to test-retest reliability of HS-SOT. ResultsHS-SOT scores (HS-2 and HS-5) did not differ significantly between age groups. The balance performance of individuals for the pitch plane was lower than other planes. Only the HS-5 score showed a significant difference between the sessions. HS-5 scores were higher in the re-test; for the first group in the pitch plane and for the third group in the yaw plane. The test-retest reliability level of these conditions was "moderate-good" for both groups. The corresponding MDC value was highest (14.01) for the HS-5 (yaw) score of the elderly group. SignificanceThe findings from this study demonstrated that the test plane influences the HS-SOT, a learning/practice effect may occur because of repeated HS-SOT evaluation, and this effect is more explicit in the elderly. This study provides a perspective for the evaluation and follow-up processes of patients with balance problems.

Gamma Radioactivity Detection Limits and Associated Radionuclide Intakes Study in Artificial Human Urine Using Sodium-iodide and High-purity Germanium Detectors.

The performance of several gamma detectors was investigated for emergency urine bioassay screening of two radionuclides of concern: 131 I and 137 Cs. Unspiked artificial urine samples were measured for 10 min each on four different gamma detectors: 80% relative efficiency high-purity Ge detector in standard shielding, 102% low-background high-purity Ge detector equipped with top muon shield, 78% high-purity Ge well detector in standard shielding, and 4″ × 4″ NaI well detector in standard shielding. The measured gamma spectra were analyzed in two ways: (1) for the 364-keV peak region of 131 I and 662-keV peak region of 137 Cs and (2) for the total counts in the full energy spectrum (50-2,048 keV). The results were analyzed using the principles of signal detection theory according to the Currie's formalism extended by a complete uncertainty propagation. This enabled calculation of the detection capability in terms of detection limit (Bq L -1 ) of urine, the latter referred to as minimum detectable activity. The NaI well detector had the lowest minimum detectable activities for total spectra, whereas the high-purity Ge well detector had the lowest peak minimum detectable activity values. Minimum detectable inhalation and ingestion intakes from urine bioassay were calculated from the minimum detectable activity values for urine collection 1 d, 1 wk, and 1 mo past the initial intake. The calculated intakes were compared with annual limits on intake. The results are interpreted with respect to a large-scale radiological emergency response.

The Need for Consistency with Physical Laws and Logic in Choosing Between Competing Molecular Mechanisms in Biological Processes: A Case Study in Modeling ATP Synthesis.

Traditionally, proposed molecular mechanisms of fundamental biological processes have been tested against experiment. However, owing to a plethora of reasons-difficulty in designing, carrying out, and interpreting key experiments, use of different experimental models and systems, conduct of studies under widely varying experimental conditions, fineness in distinctions between competing mechanisms, complexity of the scientific issues, and the resistance of some scientists to discoveries that are contrary to popularly held beliefs-this has not solved the problem despite decades of work in the field/s. The author would like to prescribe an alternative way: that of testing competing models/mechanisms for their adherence to scientific laws and principles, and checking for errors in logic. Such tests are fairly commonly carried out in the mathematics, physics, and engineering literature. Further, reported experimental measurements should not be smaller than minimum detectable values for the measurement technique employed and should truly reflect function of the actual system without inapplicable extrapolation. Progress in the biological fields would be greatly accelerated, and considerable scientific acrimony avoided by adopting this approach. Some examples from the fundamental field of ATP synthesis in oxidative phosphorylation (OXPHOS) have been reviewed that also serve to illustrate the approach. The approach has never let the author down in his 35-yr-long experience on biological mechanisms. This change in thinking should lead to a considerable saving of both time and resources, help channel research efforts toward solution of the right problems, and hopefully provide new vistas to a younger generation of open-minded biological scientists.

Cost-Effective and Portable Instrumentation to Enable Accurate pH Measurements for Global Industry 4.0 and Vertical Farming Applications

Global Vertical Farming (VF) applications with characteristic Industry 4.0 connectivity will become more and more relevant as the challenges of food supply continue to increase worldwide. In this work, a cost-effective and portable instrument that enables accurate pH measurements for VF applications is presented. We demonstrate that by performing a well-designed calibration of the sensor, a near Nernstian response, 57.56 [mV/pH], ensues. The system is compared to a ten-fold more expensive laboratory gold standard, and is shown to be accurate in determining the pH of substances in the 2–14 range. The instrument yields precise pH results with an average absolute deviation of 0.06 pH units and a standard deviation of 0.03 pH units. The performance of the instrument is ADC-limited, with a minimum detectable value of 0.028 pH units, and a typical absolute accuracy of ±0.062 pH units. By meticulously designing bias and amplification circuitry of the signal conditioning stage, and by optimizing the signal acquisition section of the instrument, a (minimum) four-fold improvement in performance is expected.

INTEGRATION OF KALMAN FILTERING OF NEAR-CONTINUOUS SURFACE CHANGE TIME SERIES INTO THE EXTRACTION OF 4D OBJECTS-BY-CHANGE

Abstract. Automatic extraction of surface activity from near-continuous 3D time series is essential for geographic monitoring of natural scenes. Recent change analysis methods leverage the temporal domain to improve the detection in time and the spatial delineation of surface changes, which occur with highly variable spatial and temporal properties. 4D objects-by-change (4D-OBCs) are specifically designed to extract individual surface activities which may occur in the same area, both consecutively or simultaneously. In this paper, we investigate how the extraction of 4D-OBCs can improve by considering uncertainties associated to change magnitudes using Kalman filtering of surface change time series. Based on the change rate contained in the Kalman state vector, the method automatically detects timespans of accumulation and erosion processes. This renders change detection independent from a globally fixed minimum detectable change value. Considering uncertainties associated to change allows detecting and classifying more occurrences of relevant surface activity, depending on the change rate and magnitude. We compare the Kalman-based seed detection to a regression-based method using a three-month tri-hourly terrestrial laser scanning time series (763 epochs) acquired of mass movements at a high-mountain slope in Austria. The Kalman-based method successfully identifies all relevant changes at the example location for the extraction of 4D-OBCs, without requiring the definition of a global minimum change magnitude. In the future, we will further investigate which kind of change detection method is best suited for which types of surface activity.

Luminescence characterization of Ce and Gd doped MgB4O7 phosphors

This paper presents the results of the structural and luminescence characterization of Ce3+ and Gd3+ doped MgB4O7 powders produced by the solid-state synthesis technique. The phase composition of the samples was confirmed by X-ray Diffraction (XRD) method. Morphological characterization using a Scanning Electron Microscope (SEM) revealed a regular surface morphology with spherical/cylindrical grains. The luminescent properties were examined by measuring the RL emission spectra, Optically Stimulated Luminescence (OSL) decay signal, and Thermoluminescence (TL) glow curve. The correlation between luminescence intensity and concentration quenching of the prepared phosphor was investigated. The results show a maximum luminescence efficiency when the synthesis of MgB4O7:Ce,Gd was carried out using contents of 0.1 wt% Ce3+ and 3 wt% Gd3+. The data shows that at the heating rate of 5 °C/s, MgB4O7:Ce0.1%,Gd3% exhibits five TL peaks: two rapidly decaying peaks at about 80 °C and 110 °C, a shoulder peak at 180 °C, a high sensitivity peak at 235 °C TL and another shoulder peak at 320 °C (temperatures are approximate). The step annealing patterns suggest that the origin of the OSL signal is associated with the TL traps located between 180 and 235 °C. The kinetic parameters using various heating rate (VHR) technique, Tm-Tstop assisted extended initial rise method (IRM) and computerized glow curve deconvolution (CGCD) method were obtained and compared. The phosphor showed the dose linearity up to 10 Gy beta dose with a slight supralinearity for higher doses and the minimum detectable dose value of 743.1 ± 11 μGy. Fading and reusability studies of MgB4O7:Ce0.1%,Gd3% further confirmed the phosphor suitability for radiation dosimetry.

Contactless Measurement of Integrity of Silicone Coating on Self-Expandable Esophageal Nitinol Stents.

A stent is a mesh tube inserted into a natural passage in the body to prevent disease induction. Self-expandable esophageal nitinol stents such as SX-ELLA Stent Esophageal HV (HV Stent Plus) can be indicated for palliation of malignant esophageal strictures, for the treatment of benign esophageal strictures that are refractory to standard therapy and for the treatment of esophago-respiratory fistulas. A silicone-stent coating is used for tumor in-growth prevention and esophago-respiratory fistula occlusion. The thickness of the stent and the overall integrity of the silicone coating of all wires indicate the overall mechanical properties of the esophageal stent and the resistance to external adverse events such as corrosion and mechanical and chemical resistance. The polymer multicomponent epoxy resin - a mixture of Epon and Durcupan - was used as a method for robust sample stabilization. A cutting system using a thin water beam with a powder (Blue Line) was chosen as the best variant to obtain 6 samples for both-sided measurement (10 measuring sides). The optical microscopic reflective light method was used to examine wire crossing points in the sections. Fifty values were measured on either sample side for the internal, external and mesh thickness of the silicone stent layer. The wire crossing points were selected so that the silicone layer structure could be clearly seen, and the wires approached each other most closely. Only approximately 4 to 8 crossing points in each section could be measured when applying this approach. The resolution of the microscope and calibration (based on the camera used) was 0.677 μm/pixel. Additional data could be obtained on 8 planes. Two boundary samples were destroyed by the cutting process. Whole coating of the stent was around all mesh wires, especially in areas with higher mechanical stress (wire crossing). The minimum detectable and admissible value determined for all 3 measuring areas (internal, external, mesh) on the wire crossings was 6.77 μm, i.e., 10 pixels, based on the microscope resolution and manufacturer's methodology. The results were characterized by p < 0.001 for all 3 parameters. We tested opposite samples in each section to verify the section quality and data consistency. For the 4 areas, the data were significantly different, but the thickness differences were only on the order of units percent, so the measurements were not appreciably affected. We assume that the material cutting loss, making up 1-2 mm, contributed to the differences in the sections. We examined the overall integrity of the silicone coating of the esophageal stent. The method of HV stent anchoring in a polymeric bath followed by cutting with a waterjet and sample measurement under an optical microscope proved to be very simple and reliable. Sufficient thicknesses of the silicone layer on the wire cross sections were verified. The coated silicone layer thickness appeared to be significantly different along the stent from the proximal part to the distant part, presumably due to the manufacturing technology.

Distribution of 210Po in spice plants cultivated by conventional farming

Purpose To study the distribution of 210Po concentrations in various parts of spice plants cultivated by conventional farming in Nilgiris, South India and estimate effective radiation dose received. Materials and methods Parts of plant such as leaf, fruit, seed, flower bud and rhizome of selected spice plants cultivated at various locations in the study area have been collected for estimation of 210Po concentration. Organic materials in known mass of processed samples have been removed by chemical method. 210Po concentration in the digested sample has been electrostatically deposited on pre-polished silver disks at constant temperature. ZnS(Ag) detector-based alpha counting system with minimal detectable value 3.2 mBq has been used for estimation of 210Po activity concentration. Results Leaves of Curcuma longa have registered a high concentration of 45.6 ± 4.5 Bq kg−1 of 210Po and rhizome of Allium sativum has registered a low value of 4.7 ± 0.8 Bq kg−1. Leaves of spice plants have registered higher concentration of 210Po than their fruits, seeds, flower buds or rhizomes. Soil to plant transfer factor of 210Po has been found to vary from 0.13 for rhizome of A. sativum to 2.23 corresponding to leaf of C. longa. Concentration of 210Po estimated in leaves and mean leaf areas of spice plants has been found to have a correlation coefficient of 0.83, which indicates that absorption of 210Po deposited on surface area of leaves is the main source of this isotope in plant parts. Conclusions Consumption of various parts of spice plant does not pose significant radiological risk as effective dose received by the general public as 210Po has been found to vary from 6.34 to 46.05 µSv y−1, less than the value recommended by ICRP.

Evaluation of IUPAC limit of detection and ISO minimum detectable value - electrochemical determination of lead

The way of calculating the limit of detection recommended by IUPAC is compared to the minimum detectable value used by ISO as one of the most important performance characteristics of a measurement process. In this work, theoretical analysis of both characteristics is given together with directions for their practical use. Calculations are exemplified using electrochemical trace analysis of lead in surface water.

A chemiluminescence immunoassay for precise automatic quality control of glycoprotein in human rabies vaccine

Currently, quality control of glycoprotein in the human rabies vaccine is based on enzyme-linked immunosorbent assay (ELISA). However, ELISA does not match the needs of a modernised quality control system. For a long time, human rabies virus vaccine manufacturers have been devoted to seeking a detection platform that is sensitive, accurate, automatic, and feasible for practical applications. Therefore, our team invested major efforts into establishing a fully automated micromagnetic particle (MMP)-based chemiluminescence immunoassay (CLIA) platform. For vaccine quality control, MMP-coupled rabies virus glycoprotein monoclonal antibodies (S037) were used to capture the rabies virus. Another rabies virus glycoprotein antibody (S053) labelled with acridinium ester was added as a signal tracer. After pretreating the vaccine sample, the entire analysis was performed using a fully automated machine, which had a limited detection time (only 30 min) and eliminated manual error. Multiple experiments have identified the optimal conditions allowing valid and reliable assessment of vaccine potency. The CLIA platform has exhibited merits in terms of speed, robustness, high sensitivity (with a minimum detection value of 0.45 mIU/mL), considerable accuracy, and a wide linear range of detection (9.4–1200 mIU/mL). Furthermore, the results showed that the CLIA platform is consistent with the National Institutes of Health test and time-resolved fluorescent immunoassay (TRFIA) in quantitative analysis, and had a better analytic performance than TRFIA. Therefore, the CLIA platform presented here may be important for application in modern vaccine quality control.

All-optical enhancement of minimum detectable perturbation in intensity-based fiber sensors.

We present a novel optical signal processing scheme for enhancing the minimum detectable environmental perturbation of intensity-based fiber sensors. The light intensity is first stabilized by inducing a sinusoidal intensity modulation and extracting the first-order sideband generated by self-phase modulation (SPM) in a nonlinear medium. The light with stabilized intensity is then sent through a sensor and the sensor induced power variation is magnified by first inducing a sinusoidal intensity modulation, then undergoing SPM, and finally extracting a higher-order sideband. The advantage of the proposed stabilization-magnification (SM) sensing scheme is experimentally demonstrated by applying a damped vibration on an intensity-based fiber sensor and comparing the minimum detectable strain value of the proposed scheme with that of a conventional sensing scheme. Experimental results demonstrate minimum detectable strain improvement by a factor of 3.93. This new SM sensing scheme allows for the detection of perturbations originally too weak to be detected by a given intensity-based fiber sensor, which will be beneficial for a variety of applications such as high frequency ultra-sound detection.

Improved Detection Sensitivity of an Antigen Test for SARS-CoV-2 Nucleocapsid Proteins with Thio-NAD Cycling.

Antigen tests for infectious diseases are inexpensive and easy-to-use, but the limit of detection (LOD) is generally higher than that of PCR tests, which are considered the gold standard. In the present study, we combined a sandwich enzyme-linked immunosorbent assay (ELISA) with thionicotinamide-adenine dinucleotide (thio-NAD) cycling to improve the LOD of antigen tests for coronavirus disease 2019 (COVID-19). For recombinant nucleocapsid proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the LOD of our ELISA with thio-NAD cycling was 2.95 × 10-17 moles/assay. When UV-irradiated inactive SARS-CoV-2 was used, the minimum detectable virions corresponding to 2.6 × 104 RNA copies/assay were obtained using our ELISA with thio-NAD cycling. The assay volume for each test was 100 µL. The minimum detectable value was smaller than that of the latest antigen test using a fluorescent immunoassay for SARS-CoV-2, indicating the validity of our detection system for COVID-19 diagnosis.