This review will examine the integration of two fields that are currently at the forefront of science, i.e. biosensors and microfluidics. As a lab-on-a-chip (LOC) technology, microfluidics has been enriched by the integration of various detection tools for analyte detection and quantitation. The application of such microfluidic platforms is greatly increased in the area of biosensors geared towards point-of-care diagnostics. Together, the merger of microfluidics and biosensors has generated miniaturized devices for sample processing and sensitive detection with quantitation. We believe that microfluidic biosensors (biosensors-on-chip) are essential for developing robust and cost effective point-of-care diagnostics. This review is relevant to a variety of disciplines, such as medical science, clinical diagnostics, LOC technologies including MEMs/NEMs, and analytical science. Specifically, this review will appeal to scientists working in the two overlapping fields of biosensors and microfluidics, and will also help new scientists to find their directions in developing point-of-care devices.
Fabrication of inexpensive and flexible electronic and electrochemical sensors is in high demand for a wide range of biochemical and biomedical applications. We explore hand fabrication of CNT modified AgNPs electrodes using wax-on-plastic platforms and their application in electrochemical immunosensing. Wax patterns were printed on polyethylene terephthalate-based substrates to laydown templates for the electrodes. Hand painting was employed to fabricate a silver conductive layer using AgNPs ink applied in the hydrophilic regions of the substrate surrounded by wax. CNT was drop cast on top of the working electrodes to improve their electrochemical signal. The device layers were characterized by scanning electron microscopy. The electrochemical performance of the hand fabricated AgNPs and CNT/AgNPs electrodes was tested using cyclic voltammetry, differential pulse voltammetry, and amperometry. The electrochemical response of CNT/AgNPs electrodes was relatively faster, higher, and more selective than unmodified AgNPs sensing electrodes. Finally, the hand-painted CNT/AgNPs electrodes were applied to detect carcinoembryonic antigen (CEA) by measuring the end-product of immunoassay performed on magnetic particles. The detection limit for CEA was found to be 0.46 ng/mL.
This study aimed to understand the synergistic effect of dolomite powder (DM) and metakaolin (MK) on the strengths and hydration products of Portland cement (PC), then facilitating DM application in PC. Results showed that the combination of DM and MK improved the flexural and compressive
strengths of mortars at 20 °C and 60 °C markedly. This was mainly due to that the combined effect of DM and MK improved the pore structure. At 20 °C, the incorporation of MK in the PC-DM pastes stimulated the generation of calcium carboaluminate including hemicarbonate (Hc) and
monocarbonate (Mc). An increase in the MK to DM ratio resulted in the increment of Hc at the early age. At the later age, further dissolution of DM promoted the transformation of Hc to Mc. At 60 °C, hydrotalcite (Ht) was found in the pastes with low MK dosages (≤5 wt%), and Ht was mainly
distributed in the DM particle surface. However, the additions of high MK dosages (≥10 wt%) restricted the formation of Ht. The lack of portlandite might be the major reason for the limitation of Ht formation. In addition, iron containing calcium carboaluminate could be identified in the
PC-DM-MK system cured at 60 °C, especially with high MK dosages.
The Collatz problem is related to the fixed point problem, and is widely used in mathematics. It has attracted a wide range of math enthusiasts, but is still difficult to solve. So, this article aimed to study the extension of the Collatz problem, more widely, in k-adic. We define a new sequence called Z transformation sequence. Under a suitable assumptions, we can prove that the limit set of the Z transformation sequence must be M = {1, 2}.
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