This paper describes a micro total analysis system for molecular analysis of Salmonella, a major food-borne pathogen. We developed a centrifugal microfluidic device, which integrated the three main ...steps of pathogen detection, DNA extraction, isothermal recombinase polymerase amplification (RPA), and detection, onto a single disc. A single laser diode was utilized for wireless control of valve actuation, cell lysis, and noncontact heating in the isothermal amplification step, thereby yielding a compact and miniaturized system. To achieve high detection sensitivity, rare cells in large volumes of phosphate-buffered saline (PBS) and milk samples were enriched before loading onto the disc by using antibody-coated magnetic beads. The entire procedure, from DNA extraction through to detection, was completed within 30 min in a fully automated fashion. The final detection was carried out using lateral flow strips by direct visual observation; detection limit was 10 cfu/mL and 102 cfu/mL in PBS and milk, respectively. Our device allows rapid molecular diagnostic analysis and does not require specially trained personnel or expensive equipment. Thus, we expect that it would have an array of potential applications, including in the detection of food-borne pathogens, environmental monitoring, and molecular diagnostics in resource-limited settings.
Perhaps the most successful application of plasmonics to date has been in sensing, where the interaction of a nanoscale localized field with analytes leads to high-sensitivity detection in real time ...and in a label-free fashion. However, all previous designs have been based on passively excited surface plasmons, in which sensitivity is intrinsically limited by the low quality factors induced by metal losses. It has recently been proposed theoretically that surface plasmon sensors with active excitation (gain-enhanced) can achieve much higher sensitivities due to the amplification of the surface plasmons. Here, we experimentally demonstrate an active plasmon sensor that is free of metal losses and operating deep below the diffraction limit for visible light. Loss compensation leads to an intense and sharp lasing emission that is ultrasensitive to adsorbed molecules. We validated the efficacy of our sensor to detect explosives in air under normal conditions and have achieved a sub-part-per-billion detection limit, the lowest reported to date for plasmonic sensors with 2,4-dinitrotoluene and ammonium nitrate. The selectivity between 2,4-dinitrotoluene, ammonium nitrate and nitrobenzene is on a par with other state-of-the-art explosives detectors. Our results show that monitoring the change of the lasing intensity is a superior method than monitoring the wavelength shift, as is widely used in passive surface plasmon sensors. We therefore envisage that nanoscopic sensors that make use of plasmonic lasing could become an important tool in security screening and biomolecular diagnostics.
In the past decade, responsive polymers exhibiting reversible or irreversible changes in physical properties and/or chemical structures in response to external stimuli have been extensively ...investigated. Among them, tertiary amine methacrylate-based block copolymers represent a unique category considering their responsiveness to multiple external stimuli (e.g., pH, temperature and salts), which are essentially relevant to the biological milieu. These intriguing properties allow for their applications in a variety of fields ranging from drug or gene delivery, imaging, diagnostics, antibacterial coatings, catalysis, and bio-separations. This review article highlights tertiary amine methacrylate-based block copolymers, focusing on recent advances in the synthesis of tertiary amine methacrylate-based block copolymers with varying chemical structures and chain topologies, their supramolecular self-assembly in aqueous media as well as in the bulk state, and the emerging functional applications.
Continuous online monitoring of rotating machines is necessary to assess real-time health conditions so as to enable early detection of operation problems and thus reduce the possibility of downtime. ...Rolling element bearings are crucial parts of many machines and there has been an increasing demand to find effective and reliable health monitoring technique and advanced signal processing to detect and diagnose the size and location of incipient defects. Condition monitoring of rolling element bearings, comprises four main stages which are, statistical analysis, fault diagnostics, defect size calculation, and prognostics. In this paper the effect of defect size, operating speed, and loading conditions on statistical parameters of acoustic emission (AE) signals, using design of experiment method (DOE), have been investigated to select the most sensitive parameters for diagnosing incipient faults and defect growth on rolling element bearings. A modified and effective signal processing algorithm is designed to diagnose localized defects on rolling element bearings components under different operating speeds, loadings, and defect sizes. The algorithm is based on optimizing the ratio of Kurtosis and Shannon entropy to obtain the optimal band pass filter utilizing wavelet packet transform (WPT) and envelope detection. Results show the superiority of the developed algorithm and its effectiveness in extracting bearing characteristic frequencies from the raw acoustic emission signals masked by background noise under different operating conditions. To experimentally measure the defect size on rolling element bearings using acoustic emission technique, the proposed method along with spectrum of squared Hilbert transform are performed under different rotating speeds, loading conditions, and defect sizes to measure the time difference between the double AE impulses. Measurement results show the power of the proposed method for experimentally measuring size of different fault shapes using acoustic emission signals.
Despite the growth of research in universities on point‐of‐care (POC) diagnostics for global health, most devices never leave the laboratory. The processes that move diagnostic technology from the ...laboratory to the field—the processes intended to evaluate operation and performance under realistic conditions—are more complicated than they might seem. Two case studies illustrate this process: the development of a paper‐based device to measure liver function, and the development of a device to identify sickle cell disease based on aqueous multiphase systems (AMPS) and differences in the densities of normal and sickled cells. Details of developing these devices provide strategies for forming partnerships, prototyping devices, designing studies, and evaluating POC diagnostics. Technical and procedural lessons drawn from these experiences may be useful to those designing diagnostic tests for developing countries, and more generally, technologies for use in resource‐limited environments.
Fielding questions: This Review shares lessons from two case studies in the development of point‐of‐care tests: a colorimetric, paper‐based liver function test using serum transaminases (left), and a test for sickle cell disease using aqueous multiphase systems and differences in the density of red blood cells characteristic of sickle cell disease (right).
A smartphone-based colorimetric reader (SBCR) was developed using a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4 or iPhone 5s), integrated with a custom-made dark hood and base holder ...assembly. The smartphone equipped with a back camera (5 megapixels resolution) was used for colorimetric imaging via the hood and base-holder assembly. A 96- or 24-well microtiter plate (MTP) was positioned on the gadget's screensaver that provides white light-based bottom illumination only in the specific regions corresponding to the bottom of MTP's wells. The pixel intensity of the captured images was determined by an image processing algorithm. The developed SBCR was evaluated and compared with a commercial MTP reader (MTPR) for three model assays: our recently developed human C-reactive protein sandwich enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase direct ELISA, and bicinchoninic acid protein estimation assay. SBCR had the same precision, dynamic range, detection limit and sensitivity as MTPR for all three assays. With advanced microfabrication and data processing, SBCR will become more compact, lighter, inexpensive and enriched with more features. Therefore, SBCR with a remarkable computing power could be an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC diagnostics, immunoassays and diversified bioanalytical applications.
We present a fast and efficient strategy for the preparation of photonic hydrogels for compression and organic solvent sensing by the self-assembly of monodisperse carbon-encapsulated Fe3O4 ...nanoparticles (NPs). The hydrogel film was composed of acrylamide (AM) and cross-linker N,N′-methylenebis(acrylamide) (BIS), and the formed 1D NPs chain structure can be fixed within the hydrogels under a magnetic field by in situ photopolymerization. The resulting photonic hydrogels display vivid structural color which can be tuned by pressing and organic solvent treatment. The 0.2 kPa compression applied to the photonic hydrogels can be detected by the 37 nm blue shift of a reflection peak. Importantly, the photonic hydrogels can recover to their original state (<1 s) after being compressed on a pattern. Moreover, the sensitivity of mechanochromic photonic hydrogels can be adjusted by manipulating the concentration of monomers, and a large reflection peak shift (4.3 kPa, 200 nm) was observed. The detection range of the compression sensor can thus increase from 0–4.3 to 0–130.6 kPa. The photonic hydrogels are nearly monochromatic, with high sensitivity and stability and fast reversibility, and are potentially useful in displays, diagnostics, compression and solvent sensing.
Highlights • We discuss the frontiers of POC diagnostic technologies using a drop of blood obtained from a finger prick. • A great challenge is still required to develop simple, inexpensive, rapid, ...and easy-to-use technologies for blood molecular diagnostics. • Proteins, nucleic acids, and other molecules, as well as downstream molecular analyses based on cancer cells isolated from the blood are surveyed for molecular diagnostics in a drop of blood. • Various technologies, including emerging biotechnologies, nanotechnologies, and microfluidics, hold the potential for rapid, accurate, and nonexpensive disease diagnostics.
•Fault detection and isolation of a dual spool gas turbine engine is investigated by using dynamic neural networks.•Banks of dynamic neural nets and time-delay neural nets are developed for solving ...the fault detection problem.•Results show certain engine variables have better detection capabilities as compared to others.•Fault detection performance was shown to be improved by monitoring several engine variables simultaneously.•Fault isolation uses multilayer perceptions as pattern classifier of residual signals that are generated from the fault detection phase.
The main goal of this paper is to design and develop a fault detection and isolation (FDI) scheme for aircraft gas turbine engines by using neural networks. Towards this end, first for the fault detection task two types of dynamic neural networks are used and compared to learn the engine dynamics. Specially, the dynamic neural model (DNM) and the time delay neural network (TDNN) are utilized. For both architectures a bank of neural networks is trained separately to capture the dynamic relationships among the engine measurable variables. The results show that certain engine parameters have better detection capabilities as compared to the others. Finally, the fault isolation task is accomplished by using a multilayer perception (MLP) network functioning as a pattern classifier applied to the residual signals that are generated by the two dynamic neural networks used for the purpose of the fault detection task. The simulation results do indeed substantiate and verify that our proposed FDI scheme represents a promising tool for aircraft engine diagnostics and health monitoring.
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