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Nanosensors in Diagnostics
Published in Sourav Bhattacharjee, Principles of Nanomedicine, 2019
AuNPs can also facilitate in amplifying the signal and, thus, enhance the sensitivity of the diagnostic platform when used in sandwich setups with gold surfaces, due to strong plasmonic field coupling between the AuNPs and gold surfaces [50–53]. In one such study [54], the maximal enhancement of the SPR signal was observed in 40 nm AuNPs conjugated with secondary antibodies or DNA strands and positioned at a distance of 5 nm from the gold surface, separated by a dithiothreitol spacer. The signal amplification was significant, and such techniques are certainly worth exploring in the future. AuNPs are also known to both enhance and quench the emission from fluorophores [55, 56]. Usually, AuNPs >80 nm cause enhancement, while the <80 nm ones cause quenching due to Förster/fluorescence resonance energy transfer (FRET) and/or NP surface energy transfer [57, 58]. The quenching effect can be felt even up to a distance of 40 nm [59], depending on the size of the AuNPs, whereas it is hardly 10 nm for popular organic quencher molecules. Hence, AuNPs have emerged as popular tools in FRET-based sensors, particularly useful in the detection of biomacromolecules like proteins. Additionally, AuNPs are excellent enhancers of the surface-enhanced Raman scattering (SERS) signal [60, 61] and are being used in SERS-based single-cell/molecule assays [62–65].
Applications of Nanosensor System in the Detection of Heavy Metals
Published in Pradipta Ranjan Rauta, Yugal Kishore Mohanta, Debasis Nayak, Nanotechnology in Biology and Medicine, 2019
Arun Kumar Pradhan, Soudamini Acharya
To construct nanostructures, normally DNA is the best biomolecule that joins with QDs. Tertiary structures of folded single-stranded DNA with the capacity to attach to a target molecule are called aptamers. Aptamers can be used as the molecular identification factor in a biosensor. For example, the thrombin-binding aptamer (TBA) is a 15-base oligonucleotide that combines with thrombin and is able to recognize Pb2+ ions. This recognition is based on the configuration of a G-quartet arrangement that TBA folds into with a Pb2+ ion at the core (W. Liu et al. 2011). Through a chemical selection method, aptamers can work together with a wide range of targets and can be chosen for new targets (Stoltenburg, Reinemann, and Strehlitz 2007). The relationship of an aptamer and its target usually causes a conformational alteration. This conformational alteration can be optically sensed with the utilization of fluorescent QDs and quenchers. A quencher absorbs energy from a donor molecule, such as a QD. This energy transfer event is known as fluorescence resonant energy transfer (FRET), or nanometal surface energy transfer (NSET) when metallic nanoparticles are used (Jennings et al. 2006).
Preliminary Concepts and Basic Equations
Published in Gautam Biswas, Amaresh Dalal, Vijay K. Dhir, Fundamentals of Convective Heat Transfer, 2019
Gautam Biswas, Amaresh Dalal, Vijay K. Dhir
At any distance from leading edge, qx″=−kf∂T∂y|y=0, because at the surface, energy transfer is through conduction. The expression is exact because at the surface, there is no fluid motion. So, we can write () h(Tw−T∞)=−kf∂T∂y|y=0
Urban Heat Implications from Parking, Roads, and Cars: a Case Study of Metro Phoenix
Published in Sustainable and Resilient Infrastructure, 2022
Christopher G. Hoehne, Mikhail V. Chester, David J. Sailor, David A. King
Following extensive previous research on modeling fundamental heat transfer, a 1D model is developed that predicts temperatures and sensible heat flux of a delineated material according to its thermophysical properties and surrounding environmental conditions. Only sensible heat transfer is considered as it is the dominant term affecting warming in arid climates such as Phoenix. The 1D transient heat conduction model ignores lateral heat transfer since the horizontal dimensions of paving are two orders of magnitude larger than the depth. The model balances surface energy transfer from convection, incoming solar radiation, and outgoing infrared radiation as well subsurface energy transfer via conduction (Figure 1). Simulated materials are idealized as a series of stacked nodes starting at the surface at continuing downward to a defined depth. Heat transfer is first balanced between the nodes at an initial condition, then solved by stepping forward in time using an explicit finite difference scheme. While many similar 1D models have been implemented and validated in literature, this methodology most closely replicates the implementation and some assumptions of Gui et al. (2007) because it was also implemented and validated for conditions in Phoenix, Arizona.