The polymerase chain reaction (PCR) is increasingly used as the standard method for detection and characterization of microorganisms and genetic markers in a variety of sample types. However, the method is prone to inhibiting substances, which may be present in the analysed sample and which may affect the sensitivity of the assay or even lead to false-negative results. The PCR inhibitors represent a diverse group of substances with different properties and mechanisms of action. Some of them are predominantly found in specific types of samples thus necessitating matrix-specific protocols for preparation of nucleic acids before PCR. A variety of protocols have been developed to remove the PCR inhibitors. This review focuses on the general properties of PCR inhibitors and their occurrence in specific matrices. Strategies for their removal from the sample and for quality control by assessing their influence on the individual PCR test are presented and discussed.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2012.05384.x

PCR inhibitors - occurrence, properties and removal.

Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

/pdf/heat-and-mass-transfer-1yaijfx8vp.pdf

Heat and Mass Transfer

Surfactants are an essential part of the droplet-based microfluidic technology. They are involved in the stabilization of droplet interfaces, in the biocompatibility of the system and in the process of molecular exchange between droplets. The recent progress in the applications of droplet-based microfluidics has been made possible by the development of new molecules and their characterizations. In this review, the role of the surfactant in droplet-based microfluidics is discussed with an emphasis on the new molecules developed specifically to overcome the limitations of ‘standard’ surfactants. Emulsion properties and interfacial rheology of surfactant-laden layers strongly determine the overall capabilities of the technology. Dynamic properties of droplets, interfaces and emulsions are therefore very important to be characterized, understood and controlled. In this respect, microfluidic systems themselves appear to be very powerful tools for the study of surfactant dynamics at the time- and length-scale relevant to the corresponding microfluidic applications. More generally, microfluidic systems are becoming a new type of experimental platform for the study of the dynamics of interfaces in complex systems.

/pdf/surfactants-in-droplet-based-microfluidics-46ibxp049e.pdf

Surfactants in droplet-based microfluidics.

Limiting dilution PCR has become an increasingly useful technique for the detection and quantification of rare species in a population, but the limit of detection and accuracy of quantification are largely determined by the number of reactions that can be analyzed. Increased throughput may be achieved by reducing the reaction volume and increasing processivity. We have designed a high-throughput microfluidic chip that encapsulates PCR reagents in millions of picoliter droplets in a continuous oil flow. The oil stream conducts the droplets through alternating denaturation and annealing zones, resulting in rapid (55-s cycles) and efficient PCR amplification. Inclusion of fluorescent probes in the PCR reaction mix permits the amplification process to be monitored within individual droplets at specific locations within the microfluidic chip. We show that amplification of a 245-bp adenovirus product can be detected and quantified in 35 min at starting template concentrations as low as 1 template molecule/167 droplets (0.003 pg/microL). The frequencies of positive reactions over a range of template concentrations agree closely with the frequencies predicted by Poisson statistics, demonstrating both the accuracy and sensitivity of this platform for limiting dilution and digital PCR applications.

/pdf/high-throughput-quantitative-polymerase-chain-reaction-in-4fu7p1zpw4.pdf

High-throughput quantitative polymerase chain reaction in picoliter droplets.

Micropumps, microvalves, and micromixers within PCR microfluidic chips: Advances and trends.

The use of two-phase flow in lab-on-chip devices, where chemical and biological reagents are enclosed within plugs separated from each other by an immiscible fluid, offers significant advantages for the development of devices with high throughput of individual heterogeneous samples. Lab-on-chip devices designed to perform the polymerase chain reaction (PCR) are a prime example of such developments. The internal circulation within the plugs used to transport the reagents affects the efficiency of the chemical reaction within the plug, due to the degree of mixing induced on the reagents by the flow regime. It has been hypothesised in the literature that all plug flows produce internal circulation. This work demonstrates experimentally that this is false. The particle image velocimetry (PIV) technique offers a powerful non-intrusive tool to study such flow fields. This paper presents micro-PIV experiments carried out to study the internal circulation of aqueous plugs in two phase flow within 762 μm internal diameter FEP Teflon tubing with FC-40 as the segmenting fluid. Experiments have been performed and the results are presented for plugs ranging in length from 1 to 13 mm with a bulk mean flow velocity ranging from 0.3 to 50 mm/s. The results demonstrate for the first time that circulation within the plugs is not always present and requires fluidic design considerations to ensure their generation.

PIV measurements of flow within plugs in a microchannel

https://ulir.ul.ie/bitstream/handle/10344/2398/Grimes,%20Ronan.pdf;sequence=2

Active cooling of a mobile phone handset

Modeling Electronic Cooling Axial Fan Flows

Tower systems are forecast to become the dominant CSP technology in the future due to the potential to achieve high working fluid temperatures, thereby enhancing thermodynamic efficiency in the power block and facilitating dispatchable electricity through thermal energy storage. The receiver links the solar collector field and power conversion cycle in a tower plant, and is therefore a critical component that requires careful consideration. Tubular receivers represent the most prominent in commercial scale applications, with many research efforts devoted to the characterisation and modelling of such concepts. This article compiles literature engaged in steady-state thermal and mechanical modelling of tubular solar receivers. The discussion outlines contrasting approaches adopted by various authors, while also detailing some important findings from their investigations. Recent studies concerned with evaluating receiver thermal performance indicates a trend towards semi-empirical techniques, offering greater flexibility and accuracy than simplified analytical methods, without imposing a considerable computational expense that is inherent with more detailed numerical models. Such advantages allow for the screening of a large number of geometries, configurations, heat transfer media, tube materials, and operational scenarios at the receiver design stage. Mechanical reliability investigations generally consider thermal and pressure induced stresses, estimating potential damage of the component across its desired lifetime using design code guidelines or tube material data. The selection of thermal stress theory and damage evaluation method is critical to the overall mechanical life prediction, with different approaches presented.

Ronan Grimes

Papers

PIV measurements of flow within plugs in a microchannel

Active cooling of a mobile phone handset

Modeling Electronic Cooling Axial Fan Flows

A review of steady-state thermal and mechanical modelling on tubular solar receivers

Low profile fan and heat sink thermal management solution for portable applications