Microfluidics device for single cell gene expression analysis in Saccharomyces cerevisiae

We have measured single-cell gene expression over time using a microfluidics-based flow cell which physically traps individual yeast using microm-sized structures (yeast jails). Our goal was to determine variability of gene expression within a cell over time, as well as variability between individual cells. In our flow cell system, yeast jails are fabricated out of PDMS and gene expression is visualized using fluorescently-tagged proteins of interest. Previously, single-cell yeast work has been done using micromanipulation on agar, or FACS. In the present device agar is eliminated, resulting in a superior optical system. The flow of media through the flow cell washes daughter cells away, eliminating the need for micromanipulation. Unlike FACS, the described device can track individual yeast over a time course of many hours. The flow cells are compatible with the needs of quantitative fluorescence microscopy, and allow simultaneous measurements to be done on a large number of individual yeast. We used these flow cells to determine the expression of HSP104-GFPand RAS2-YFP, genes known to affect yeast life span. The results demonstrate inter-cell variation in expression of both genes that could not have been detected without this single-cell analysis.     

Critical oxide thickness for efficient single-walled carbon nanotube growth on silicon using thin SiO2 diffusion barriers

The ability to integrate carbon nanotubes, especially single-walled carbon nanotubes, seamlessly onto silicon would expand their range of applications considerably. Though direct integration using chemical vapor deposition is the simplest method, the growth of single-walled carbon nanotubes on bare silicon and on ultrathin oxides is greatly inhibited due to the formation of a noncatalytic silicide. Using X-ray photoelectron spectroscopy, we show that silicide formation occurs on ultrathin oxides due to thermally activated metal diffusion through the oxide. Silicides affect the growth of single-walled nanotubes more than multi-walled nanotubes due to the increased kinetics at the higher single-walled nanotube growth temperature. We demonstrate that nickel and iron catalysts, when deposited on clean silicon or ultrathin silicon dioxide layers, begin to form silicides at relatively low temperatures, and that by 900 degrees C, all of the catalyst has been incorporated into the silicide, rendering it inactive for subsequent single-walled nanotube growth. We further show that a 4-nm silicon dioxide layer is the minimum diffusion barrier thickness that allows for efficient single-walled nanotube growth.     

The Biochemical Assessment of Mitochondrial Respiratory Chain Disorders

Mitochondrial respiratory chain (MRC) disorders are a complex group of diseases whose diagnosis requires a multidisciplinary approach in which the biochemical investigations play an important role. Initial investigations include metabolite analysis in both blood and urine and the measurement of lactate, pyruvate and amino acid levels, as well as urine organic acids. Recently, hormone-like cytokines, such as fibroblast growth factor-21 (FGF-21), have also been used as a means of assessing evidence of MRC dysfunction, although work is still required to confirm their diagnostic utility and reliability. The assessment of evidence of oxidative stress may also be an important parameter to consider in the diagnosis of MRC function in view of its association with mitochondrial dysfunction. At present, due to the lack of reliable biomarkers available for assessing evidence of MRC dysfunction, the spectrophotometric determination of MRC enzyme activities in skeletal muscle or tissue from the disease-presenting organ is considered the ‘Gold Standard’ biochemical method to provide evidence of MRC dysfunction. The purpose of this review is to outline a number of biochemical methods that may provide diagnostic evidence of MRC dysfunction in patients.     

Imaging-sonar observations of salmonid interactions with a vertical axis instream turbine

Anthropogenic activities and their influences on aquatic systems is an important topic, especially considering the growing interest in using the earth's resources in a sustainable way. One of those anthropogenic activities is the introduction of renewable technologies into the aquatic environment such as instream turbines. Environmental studies around those technologies are often still ongoing due to their novelty. During the spring of 2018, juvenile individuals of two salmonid species, Atlantic salmon and brown trout were released upstream a vertical axis instream turbine in the river Dal (Dalälven) in eastern Sweden. The aim of this study was to investigate the swimming behavior of the salmonids around a small-scale prototype vertical axis instream turbine. The swimming pattern and the possible response of avoiding the vertical axis instream turbine were documented with a multi beam sonar. A control area, next to the turbine, was used as reference. No consistent results were shown for trout as they were passing the control area with a statistically high variation, and specimens were rarely observed in proximity of the turbine, neither if the turbine was operating nor at stand still. Salmon clearly avoided the operating turbine, but did not avoid the turbine when it was at stand still, and was often observed swimming straight through the turbine area. These findings indicate that operating this type of instream turbine in a river affects the swimming behavior of Atlantic salmon but is unlikely to affect its migration paths. For brown trout, the statistical results are inconclusive, although data indicate a response of avoiding the turbine. The species are in little risk to suffer physical harm as no fish entered the rotating turbine, despite very turbid water conditions.     

Non‐food industrial products from crops: The example of biomolecular development in France

A brief review of the oils, fuels, additives, and other industrial products being derived from non‐food crops in France, and the potential market for them.     

Phase Transitions and Oxidation Behavior During Oxyacetylene Torch Testing of TaC–HfC Solid Solutions

Tantalum carbide (TaC) and hafnium carbide (HfC) have some of the highest melting temperatures among the transition metal carbides, borides, and nitrides, making them promising materials for high-speed flight and high-temperature structural applications. Solid solutions of TaC and HfC are of particular interest due to their enhanced oxidation resistance compared to pure TaC or HfC. This study looks at the effect of Hf content on the oxidation resistance of TaC–HfC sintered specimens. Five compositions are fabricated into bulk samples using spark plasma sintering (2173 K, 50 MPa, 10 min hold). Oxidation behavior of a subset of the compositions (100 vol% TaC, 80 vol% TaC + 20 vol% HfC, and 50 vol% TaC + 50 vol% HfC) is analyzed using an oxyacetylene torch for 60 s. The TaC–HfC samples exhibit a reduction in the oxide scale thickness and the mass ablation rate with increasing HfC content. The improved oxidation resistance can be attributed to the formation of a Hf₆Ta₂O₁₇ phase. This phase enhances oxidation resistance by reducing oxygen diffusion and serving as a protective layer for the unoxidized material. The superior oxidation resistance of TaC–HfC samples makes these materials strong contenders for the development of high-speed flight coatings.