Ultra-compact directional curvature sensor using an asymmetric fiber-optic microbubble Fabry-Perot interferometer.

A fiber surface plasmon resonance (SPR) curvature sensor has the advantage of being insensitive to axial strain and temperature, but there are still difficulties in multichannel cascade and curvature direction identification. In this article, a multichannel directional recognition SPR curvature sensor based on D-type double-clad multimode fiber was proposed. The asymmetric structure of D-type multimode fiber can well realize directional curvature sensing. When the light in the multimode core leaks to the silica clad, due to the existence of plastic clad, it can still continue to transmit. When the refractive index of UV curable adhesive coated in different sensing areas is different, wavelength-division multiplexing multichannel sensing can be realized. When the sensing probe is bent to be convex, the maximum intensity sensitivity is 0.0057 a.u./m−1, the resonance wavelength is redshift, and the wavelength sensitivity is 0.6114 nm/m−1. When the sensor probe is bent to be concave, the maximum intensity sensitivity is 0.0043 a.u./m−1, the wavelength is blueshift, and its highest sensitivity is 0.5831 nm/m−1. In addition, this article also realizes a three-channel directional recognition SPR curvature sensor based on a D-type double-clad multimode fiber, which provides a new scheme for multichannel directional curvature measurement.

In this study, the effects of the different initial random imperfections on the reliability of steel frames are studied. Different types of random imperfections are considered, including imperfections in the mechanical properties of the material, imperfections in external forces and imperfections in the geometry of the structural system. Two forms of geometric imperfections, namely geometric imperfections in the coordinates of the joints and geometric imperfections of the members due to the presence of initial curvature in the theoretical direction of different structural members, which is less studied in previous investigations are taken into account. Static nonlinear pushover analysis is performed, and the reliability of the desired system is calculated using the first-order reliability and Monte Carlo simulation methods. In addition, applying the direct differentiation sensitivity analysis the importance of each of these random variables are evaluated in terms of the impact they have on the behavior of the structural system. The results show that some of the mentioned geometric imperfections are of special importance in the reliability of steel frames, which indicates how even small variations in those parameters affect the probability of failure of the structural systems.KeywordsSteel framesRandom imperfectionsUncertaintyReliabilitySensitivity analysis

Multicore optical fiber can be used to implement multidimensional optical fiber sensors including curvature sensors. In this paper, a selective core inscription technique is used in order to inscribe a single long period grating in each of the outer cores of the optical fiber. A set of three different long period gratings is inscribed for implementing the curvature sensor. The ability of the sensor for measuring the magnitude and the direction of curvature is demonstrated. The optical fiber sensor is characterized experimentally for curvature magnitudes from 0 m−1 to 1.77 m−1 and curvature directions from 0° to 360°. The maximum curvature sensitivity of the developed sensor is −4.85 nm/m−1.

Computerized simulation of meshing and contact of enveloping gear tooth surfaces

A quantum magnetometer is an instrument that utilizes the quantum effect for high-precision magnetic field measurement. In this paper, a prototype quantum magnetometer is analyzed by innovative use of differential optical path, frequency tracking, and vector magnetometry. And based on analyzing its original departure, its sensitivity and broadband data situation is derived after testing, showing that the current system magnetic sampling rate is 15 Hz and the measured broadband is about 5 Hz. The results show that the Alternating Current (AC) vector magnetometry function, Direct Current (DC) vector magnetometry function and sensitivity calculation function are normal.

The screening and early diagnosis of diseases are crucial for a patient’s treatment to be successful and to improve their survival rate, especially for cancer. The development of non-invasive analytical methods able to detect the biomarkers of pathologies is a critical point to define a successful treatment and a good outcome. This study extensively reviews the electrochemical methods used for the development of biosensors in a liquid biopsy, owing to their ability to provide a rapid response, precise detection, and low detection limits. We also discuss new developments in electrochemical biosensors, which can improve the specificity and sensitivity of standard analytical procedures. Electrochemical biosensors demonstrate remarkable sensitivity in detecting minute quantities of analytes, encompassing proteins, nucleic acids, and circulating tumor cells, even within challenging matrices such as urine, serum, blood, and various other body fluids. Among the various detection techniques used for the detection of cancer biomarkers, even in the picogram range, voltammetric sensors are deeply discussed in this review because of their advantages and technical characteristics. This widespread utilization stems from their ability to facilitate the quantitative detection of ions and molecules with exceptional precision. A comparison of each electrochemical technique is discussed to assist with the selection of appropriate analytical methods.

Nanoparticles in biological fluids almost invariably become coated with proteins that may confer nanomedical and nanotoxicological effects. Understanding these effects requires quantitative measurements using simple systems. Adsorption of HSA to copolymer nanoparticles of varying hydrophobicity and curvature was studied using ITC, yielding stoichiometry, affinity, and enthalpy changes upon binding. The hydrophobicity was controlled via the co-monomer ratio, N-iso-propylacrylamide/N-tert-butylacrylamide. The most hydrophobic particles become fully covered with a single layer of protein, except at high curvature.

Non-invasive monitoring of biomarkers in biological fluids through the use of wearable sensors gained significant interest in the past several decades [1]. Research efforts have been focused on the development of chemical and biochemical sensors for a range of metabolites, including glucose, lactate, ethanol, trace metals and various ions, targeting several bodily fluids such as tears, saliva, and sweat [2]. Work presented here will discuss the development of a sensor system, capable of real-time monitoring of lactate levels in sweat. Such a device is desired in order to correlate increasing levels of lactate to fatigue levels of a person performing physically demanding activities [3]. Most existing systems employ traditional batteries as power sources for sensors. The system described here utilizes a light weight biofuel cell as the power source giving a complete bio-friendly sensor system. The system is comprised of three main elements: a biosensor, a biofuel cell, and electronics interface. The biosensor detects lactate levels in sweat via enzymatic reaction of Lactate Dehydrogenase (LDH). Sensor patch features a three electrode design assembled onto generic athletic tape and covered with medical gauze, providing both flexibility and sweat collection capability. LDH is immobilized at the working electrode via conductive carbon-based ink. The electrode surface is then further modified by vapor-deposited tetramethyl orthosilicate (TMOS) coating in order to provide greater stability to the sensor against temperature and pH fluctuations. Sensor calibration time period was relatively quick (5 minutes) and response was immediate with addition of lactate. Test results for the sensor patch showed an open circuit potential of ~0.06V vs. Ag/AgCl and an equilibrated current of approximately 30µA when held at 0.3V vs. Ag/AgCl. The patch also demonstrated a sensitivity of 0.2µA/mM lactate when tested in a range of 5-100mM lactate. A glucose-based biofuel cell provides the power to operate the biosensor. The anode, driving glucose oxidation, is comprised of immobilized Glucose Dehydrogenase (GDH) on a high surface area carbon felt (CF) electrode. Prior to enzyme immobilization, CF electrode surface was modified with electrochemically deposited polymethylene green (PMG) as well as chemically tethered Nicotinamide Adenine Dinucleotide (NAD). An oxygen-reducing cathode was employed as counter electrode. The biofuel cell generated an open circuit potential of 0.7V vs. Ag/AgCl, a total current of 81.0mA, and total power of 16.7mW. The patch sensor is coupled to the biofuel cell via external electrical components: an energy harvester and a micropotentiostat. The energy harvester component is connected to the biofuel cell. Its primary function is to continuously provide stable output voltage to the micropotentiostat. Thus it is constantly drawing power from the biofuel cell and up-converting the voltage from 0.7 to 3V. The patch sensor is connected to the micropotentiostat. A constant potential of 0.3V vs. Ag/AgCl is needed to operate the sensor, which is supplied by the micropotentiostat. Additionally, it is used to provide a read-out of an electrical signal, i.e. current, generated during sensor operation. System performance was demonstrated, employing artificial sweat. Results showed linear sensor response with increasing lactate content of the artificial sweat solution. [1] A. J. Bandodkar and J. Wang, "Non-Invasive Wearable Electrochemical sensors: A Review," Trends in Biotechnology, vol. 32, no. 7, pp. 363-371, 2014. [2] J. Kim, W. R. de Araujo, I. A. Samek, A. J. Bandodkar, W. Jia, B. Brunetti, T. R. Paixao and J. Wang, "Wearable temporary tattoo sensor for real-time trace metal monitoring in human sweat," Electrochemistry Communications, vol. 51, pp. 41-45, 2015. [3] S. Jadoon, S. Karim, M. R. Akram, A. K. Khan, M. A. Zia, A. R. Siddqi and G. Murtaza, "recent Developments in Sweat Analysis and Its Applications," International Journal of Analytical Chemistry, pp. 1-7, 2015. Figure 1

On first consideration it may not be immediately apparent that biological detection methods could be applied to oilfield fluid analysis; however there are strong analogies between the two. Like produced fluids, biological fluids such as blood are also complex multiphase liquids with solid components. Decades of research in healthcare has provided technologies which provide fast and accurate detection to ppm concentrations or below of a wealth of species present in bodily fluids. Many such techniques have been made simple and portable for home care formats. This paper will describe a range of detection techniques inspired by the life sciences being applied to the analysis of chemical additives in oilfield fluids, with particular focus on thermodynamic hydrate inhibitors and polymeric treatment chemicals.Colourimetric detection reagents have been developed for the analysis of methanol and monoethylene glycol (MEG) in produced fluids and the method has been qualified with real fluids using inexpensive equipment that is simple to operate. Also, novel chemical tags have been tested for use with polymeric treatment chemicals, with highly selective detection being provided by complementary detection reagents. The results show precise and robust detection of methanol and MEG (down to 1 part per million (ppm)) in produced fluids and comparison with gas chromatography (GC) is discussed. Results of a chemical tagging study are also presented and discussed in terms of tagging strategies, simplicity of detection method (using inexpensive handheld equipment) and the detection sensitivity (down to parts per billion (ppb)) of the tags in the presence of oilfield fluids.These methodologies demonstrate the promise of applying life science inspired technologies to the accurate, on-site measurement of chemicals which are difficult to detect using other, less simple methods. These technologies offer significant benefits to the production chemist due to the knowledge gleaned and the reduction in time to result.

Nucleic acids, including DNA and RNA, have received prodigious attention as potential biomarkers for precise and early diagnosis of cancers. However, due to their small quantity and instability in body fluids, precise and sensitive detection is highly important. Taking advantage of the ease-to-functionality and plasmonic effect of nanomaterials, fluorescence resonance energy transfer (FRET) and metal-enhanced fluorescence (MEF)-based biosensors have been developed for accurate and sensitive quantitation of cancer-related nucleic acids. This review summarizes the recent strategies and advances in recently developed nanomaterial-based FRET and MEF for biosensors for the detection of nucleic acids in cancer diagnosis. Challenges and opportunities in this field are also discussed. We anticipate that the FRET and MEF-based biosensors discussed in this review will provide valuable information for the sensitive detection of nucleic acids and early diagnosis of cancers.

Anabolic-androgenic steroids (AASs), a group of compounds frequently misused by athletes and, unfortunately, also by the general population, have lately attracted global attention; thus, significant demands for more precise, facile, and rapid AAS detection have arisen. The standard methods ordinarily used for AAS determination include liquid and gas chromatography coupled with mass spectrometry. However, good knowledge of steroid metabolism, pretreatment of samples (such as derivatization), and well-trained operators of the instruments are required, making this procedure expensive, complicated, and not routinely applicable. In the drive to meet current AAS detection demands, the scientific focus has shifted to developing novel, tailor-made approaches leading to time- and cost-effective, routine, and field-portable methods for AAS determination in various matrices, such as biological fluids, food supplements, meat, water, or other environmental components. Therefore, herein, we present a comprehensive review article covering recent advances in AAS determination, with a strong emphasis on the increasingly important role of chemically designed artificial sensors, biosensors, and antibody- and fluorescence-based methods.

Diagnosing Alzheimer’s disease (AD) remains a significant challenge due to its multifactorial nature and the limitations of traditional diagnostic methods, such as clinical assessments and neuroimaging, which often lack the specificity and sensitivity required for early detection. The urgent need for innovative diagnostic tools is further underscored by the potential of early intervention to improve treatment outcomes and slow disease progression. Recent advancements in biosensing technologies offer promising solutions for precise and non-invasive AD detection. Electrochemical and optical biosensors, in particular, provide high sensitivity, specificity, and real-time detection capabilities, making them valuable for identifying key biomarkers, including amyloid-β (Aβ) peptides and tau proteins. Additionally, integrating these biosensors with nanomaterials enhances their performance, stability, and detection limits, enabling improved diagnostic accuracy. Beyond nanomaterial-based sensors, emerging innovations in microfluidics, surface plasmon resonance (SPR), and artificial intelligence-assisted biosensing further contribute to the development of next-generation AD diagnostics. This review provides a comprehensive analysis of the latest advancements in biosensing technologies for AD, highlighting their mechanisms, advantages, and future perspectives in detecting biomarkers from biological fluids.

The output optical power and wavelength characteristics of semiconductor lasers exhibit high sensitivity to fluctuations in ambient temperature and drive current. To achieve precise, stable, and reliable detection results, this paper designs an integrated control system based on an STM32 microcontroller. The system consists of two core modules: a temperature control module and a constant current source control module. The temperature control module utilizes the ADN8835 chip to drive a thermoelectric cooler (TEC), achieving precise temperature regulation within $\pm 0.02^{\circ} \mathrm{C}$ by integrating temperature sensor feedback with an incremental PID algorithm. The constant current source control module dynamically adjusts the laser drive current via a voltage-controlled constant current source (VCCS). The drive circuit demonstrates exceptional stability, with current stability precision better than $0.006 \%$ and output power stab-ility precision reaching $0.5 \%$, meeting the stringent requirements for precise semiconductor laser regulation.

Among the atmospheric properties that adversely affect laser propagation is air turbulence. One common optical parameter of air turbulence is the refractive index structure constant that quantifies the fluctuations in the refractive index caused by temperature fluctuations and hence air density fluctuations. There is a reason to believe, from theory and from sparse data that, when propagation occurs under widespread cloudy conditions, the refractive index structure constant is significantly reduced. Therefore the intensity of a propagating laser beam will not be degraded nearly as much as would be expected under clear or lightly scattered cloud conditions. New experimental data will be presented that support this hypothesis. The refractive index structure constant was measured for various cloud-cover conditions during daytime with additional factors present, such as changing crosswinds and precipitation. It was possible to observe the apparent pattern of the decrease of the refractive index structure constant by two orders of magnitude during the periods of increasing cloud-cover evaluated by the measurement of solar irradiance. The statistical correlation coefficient between the log of solar irradiance and the log of the refractive index structure constant was found to be around 0.9 (the closer it is to the maximum of 1.0, the stronger the correlation). The measurements were conducted with a commercial scintillometer/anemometer (1 m above ground, 500-m optical path length) in Northern Alabama in late spring and summer. The effect is believed to be due to the reduction of solar radiation, which caused the temperature gradient that initiated convection in the air. The results of this work can find their application in designing free space laser communication systems and military laser systems. Distribution A. Approved for public release; distribution unlimited. 1 Sep 04

Earth-based gravitational waves interferometric detectors are shot-noise limited in the high-frequency region of their sensitivity band. While enhancing the laser input power is the natural solution to improve on the shot noise limit, higher power also increases the optical aberration budget due to the laser absorption in the highly reflective coatings of mirrors, resulting in a drop of the sensitivity of the detector. Advanced Virgo exploits Hartmann Wavefront Sensors (HWSs) to locally measure the absorption-induced optical aberrations by monitoring the optical path length change in the core optics. Despite the very high sensitivity of Hartmann sensors, temperature fluctuations can cause a spurious curvature term to appear in the reconstructed wavefront due to the thermal expansion of the Hartmann plate, that could affect the accuracy of the aberration monitoring. We present the implementation and validation of a control loop to stabilize the Advanced Virgo HWS temperature at the order of ΔT⩽0.01 K, keeping the spurious curvature within the detector’s requirements on wavefront sensing accuracy.