The construction of colorimetry by committee

This paper explores the confrontation of physical and contextual factors involved in the emergence of the subject of color measurement, which stabilized in essentially its present form during the interwar period. The contentions surrounding the specialty had both a national and a disciplinary dimension. German dominance was curtailed by American and British contributions after World War I. Particularly in America, communities of physicists and psychologists had different commitments to divergent views of nature and human perception. They therefore had to negotiate a compromise between their desire for a quantitative system of description and the perceived complexity and human-centeredness of color judgement. These debates were played out not in the laboratory but rather in institutionalized encounters on standards committees. Groups such as this constitute a relatively unexplored historiographic and social site of investigation. The heterogeneity of such committees, and their products, highlight the problems of identifying and following such ephemeral historical 'actors'

Daylight Spectrum Index: A New Metric to Assess the Affinity of Light Sources with Daylighting

The current scenario of colorimetry shows a wide variety of different metrics which do not converge in the assessment of the color rendering of light sources. The limitations of the Color Rendering Index have promoted the emergence of new metrics, such as the Color Quality Scale. As in the case of the previous metric, these new concepts are based on the analysis of the deviation of different color samples in a color space, contrasting the results with those obtained with a light source reference, which can vary depending on the color temperature. Within this context, the Daylight Spectrum Index is proposed. This new concept aims to determine the affinity with daylighting of electric light sources, comparing the resulting spectral power distributions of the lamps studied and that observed under natural light. The affinity of an electric light source with daylighting allows for lower energy consumption due to the better performance of human vision. The new metric proposed is evaluated following the results obtained from 80 surveys, demonstrating the usefulness of this new concept in the quantification of color rendering of LED lamps and the affinity of electric light sources with daylighting.Government of Spain BIA2017-86997-

Effects of different slipping methods on the mortality of sardine, Sardina pilchardus, after purse-seine capture off the Portuguese Southern coast (Algarve)

The effects of two different slipping methods on the survival, physical and physiological response of sardines, Sardina pilchardus, captured in a purse-seine fishery were investigated in southern Portugal. Sardines were collected and transferred into holding tanks onboard a commercial fishing vessel after being captured, crowded and deliberately released using two slipping procedures: standard and modified. The standard slipping procedure aggregated fish at high densities and made them "roll over" the floatline, while the modified procedure aggregated the fish at moderate densities and enabled them to escape through an opening created by adding weights to the floatline. Both slipping methods were compared with minimally harmed non-slipped sardines (sardines collected from the loose pocket of the purse seine). Survival rates were monitored in captivity over 28 days using three replicates for each treatment. The estimated survival of sardines was 43.6% for the non-slipped fish, 44.7% for the modified slipping and 11.7% for the standard slipping treatments. Scale loss indicated the level of physical impact experienced, with dead fish from the non-slipped and modified slipping technique showing significantly lower scale loss than those fish from the standard slipping treatment within the same period. Of the physiological indicators of stress measured, cortisol, glucose, lactate and osmolality attained peak values during slipping and up to the first hours after introduction to captivity. This work indicates that although delayed mortality after release may be substantial, appropriately modified slipping techniques significantly enhance survival of slipped sardines.FCT [SFRH/BPD/116307/2016]; European Commission's Horizon 2020 Research and Innovation Programme [634495

Glyphosate in waters and soils from genetically modified canola cultivation in Parkes, NSW, Australia

Investigations were conducted of farmland from the Parkes region of New South Wales, Australia, cultivated with genetically modified canola, involving the determination of glyphosate (N-(phosphonomethyl)glycine) concentrations in water and soils, and its sorption. The soils are classified as loam under the USDA system (clay 13.8-15.8%, silt 39-43%, sand 41.2-47.2%). Firstly, a low-cost fluorometric method was developed for the analysis of glyphosate in waters and soils, calibrated against analytical standards and spectrophotometric and enzyme-linked immunosorbent assay (ELISA) methods. Soil and water samples were then collected using the NEPM sampling protocol into glass containers, chilled and analysed within two weeks. The samples were collected in multiple episodes, taking account of glyphosate and pesticide crop applications. The soil and water physical and chemical properties were characterised, and glyphosate levels were determined. Field concentrations of glyphosate ranged between 0.01 - 0.067 mg/L in water and 0.10 - 0.575 mg/kg in soil. The aqueous levels lie below Australian and international drinking water guidelines, but reach a Canadian freshwater guideline. Glyphosate levels varied with time of application and rainfall events. Glyphosate sorption isotherms were also constructed by batch tests on several soils, and were fitted with Freundlich and Langmuir isotherms. Desorption tests indicated 25% to 58% of soil glyphosate is extractable by 0.1M KH2PO4

A quantitative real-time RT-PCR assay for mature C. albicans biofilms

<p>Abstract</p> <p>Background</p> <p>Fungal biofilms are more resistant to anti-fungal drugs than organisms in planktonic form. Traditionally, susceptibility of biofilms to anti-fungal agents has been measured using the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxyanilide (XTT) assay, which measures the ability of metabolically active cells to convert tetrazolium dyes into colored formazan derivatives. However, this assay has limitations when applied to high <it>C. albicans </it>cell densities because substrate concentration and solubility are limiting factors in the reaction. Because mature biofilms are composed of high cell density populations we sought to develop a quantitative real-time RT-PCR assay (qRT-PCR) that could accurately assess mature biofilm changes in response to a wide variety of anti-fungal agents, including host immune cells.</p> <p>Results</p> <p>The XTT and qRT-PCR assays were in good agreement when biofilm changes were measured in planktonic cultures or in early biofilms which contain lower cell densities. However, the real-time qRT-PCR assay could also accurately quantify small-medium size changes in mature biofilms caused by mechanical biomass reduction, antifungal drugs or immune effector cells, that were not accurately quantifiable with the XTT assay.</p> <p>Conclusions</p> <p>We conclude that the qRT-PCR assay is more accurate than the XTT assay when measuring small-medium size effects of anti-fungal agents against mature biofilms. This assay is also more appropriate when mature biofilm susceptibility to anti-fungal agents is tested on complex biological surfaces, such as organotypic cultures.</p

The development and optimization of techniques for monitoring water quality on-board spacecraft using colorimetric solid-phase extraction (C-SPE)

Manned missions to the moon, Mars, and deep space are currently a top priority for NASA. However, the lack of technology capable of maintaining and monitoring a life support system for long-term spaceflight presents many significant challenges. Moreover, recent issues with potable water quality on-board the International Space Station (ISS) have underscored the need to develop techniques for monitoring water quality in flight. This dissertation focuses on the development and microgravity validation of colorimetric-solid phase extraction (C-SPE) technology for the in-flight monitoring of spacecraft water quality. C-SPE measures the change in the diffuse reflectance of indicator disks following exposure to a water sample. A typical C-SPE analysis can be performed in ∼2 min and requires only small, easy-to-use, lightweight hardware.;Specifically, this dissertation describes the development of C-SPE methods for determining formaldehyde and total silver. Formaldehyde is a contaminant that has recently been detected in the drinking water supplies on-board NASA spacecraft, while silver is currently used as a biocide to prevent microbial contamination of the ISS potable water supply. The formaldehyde method, which represents the first application of C-SPE to the detection of an organic analyte, can quantify formaldehyde concentrations from 0.08 to 20 ppm in ∼3 min using only ∼1 mL of sample. The total silver method builds on a C-SPE technique for detecting silver(I) that was previously developed in our laboratory. The new method determines the total concentration of silver (i.e., dissolved and colloidal) in the range of 0.1-1 ppm, which spans the ISS potable water target level of 0.3-0.5 ppm. This method also requires only ∼1 mL of water and can be completed in less than 3 min.;Included in the dissertation are the results of recent microgravity evaluations of C-SPE techniques on-board NASA\u27s C-9 microgravity simulator. These experiments established effective methods for accurately collecting water samples of a target volume in microgravity, which had previously proven very problematic. Importantly, the flight results validated the performance of our C-SPE analyses for silver(I) and iodine (I2) under reduced gravity conditions, paving the way for a six-month technology demonstration project, scheduled on ISS for mid-2009

From Sophisticated Analysis to Colorimetric Determination: Smartphone Spectrometers and Colorimetry

Smartphone-based spectrometer and colorimetry have been gaining relevance due to the widespread advances of devices with increasing computational power, their relatively low cost and portable designs with user-friendly interfaces, and their compatibility with data acquisition and processing for “lab-on-a-chip” systems. They find applications in interdisciplinary fields, including but not limited to medical science, water monitoring, agriculture, and chemical and biological sensing. However, spectrometer and colorimetry designs are challenging tasks in real-life scenarios as several distinctive issues influence the quantitative evaluation process, such as ambient light conditions and device independence. Several approaches have been proposed to overcome the aforementioned challenges and to enhance the performance of smartphone-based colorimetric analysis. This chapter aims at providing researchers with a state-of-the-art overview of smartphone-based spectrometer and colorimetry, which includes hardware designs with 3D printers and sensors and software designs with image processing algorithms and smartphone applications. In addition, assay preparation to mimic the real-life testing environments and performance metrics for quantitative evaluation of proposed designs are presented with the list of new and future trends in this field

Colorimetric detection of both total genomic and loci-specific DNA methylation from limited DNA inputs

Background: Aberrant DNA methylation marks are potential disease biomarkers, and detecting both total genomic and gene-specific DNA methylation can aid in clinical decisions. While a plethora of methods exist in research, simpler, more convenient alternatives are needed to enhance both routine diagnostics and research. Results: Herein, we describe colorimetric assays using methyl-binding domain (MBD) proteins for rapid and convenient evaluation of total genomic and gene-specific methylation from 50\ua0ng or less DNA input in under 2\ua0h. As little as 5\ua0% methylation differences can be detected and are enhanced by a novel MBD protocol for improved specificity. Our assays could differentiate naïve from de-methylating drug-treated cells and detect the presence of a methylated prostate cancer biomarker in the urine. Finally, the assay was evolved onto disposable screen-printed electrodes for convenient detection of gene-specific methylation in urine. Conclusions: Rapid MBD-based colorimetric and electrochemical approaches to detect DNA methylation from limited samples were successfully demonstrated and applied to clinical samples. We envision that the ease, low sample requirements and speed of these assays could have both clinical and research-wide applications

Development of a high-throughput screening method for transketolase and protein engineering for biotechnology applications

Abstract Transketolase (TK) is an interesting enzyme for the biotechnology industry because it can catalyse the formation of specific carbon-carbon bonds with high stereospecificity and selectivity. These characteristics make TK interesting for the formation of high-value chemicals and pharmaceutical intermediates such as those used to synthesise antibiotics and others according to the substrates on the bioconversion. However, its application within large-scale processes is currently limited by low activity on new reactions, and poor stability at the high temperatures often used during industrial processes. One route to overcome these limitations is to use site-directed mutagenesis or directed evolution to improve the enzyme function and stability. The success of directed evolution relies upon designing a suitable screening method that can directly identify the best mutants from large numbers of variants, with the desired set of attributes. This thesis aims to develop an improved screening platform by adaptation of a previous screening method based upon colorimetric reactions. To assess and quantify TK activity towards the conversion of lithium hydroxypyruvate (Li-HPA) and propionaldehyde (PA) to (3S)-1,3-dihydroxypentan-2-one (HK), over a wide range of substrate concentrations. Moreover, several experiments were performed to establish the best conditions to grow E. coli for TK production, protein extraction methods and quantification of TK. In addition, PCR conditions were established for the development of mutagenic libraries using the MEGAWHOP. Finally, five different truncated TK variants were generated, all of them showed activity using Li-HPA, glycolaldehyde (GA) and PA as substrates. Results obtained in this project set up the basis to generate TK variants with better stability and activity, screen large numbers of variants using the high-throughput platform developed and finally it was shown that truncated versions of TK could keep its activity