A modular microarray imaging system for highly specific COVID-19 antibody testing.

To detect the presence of antibodies in blood against SARS-CoV-2 in a highly sensitive and specific manner, here we describe a robust, inexpensive ($200), 3D-printable portable imaging platform (TinyArray imager) that can be deployed immediately in areas with minimal infrastructure to read coronavirus antigen microarrays (CoVAMs) that contain a panel of antigens from SARS-CoV-2, SARS-1, MERS, and other respiratory viruses. Application includes basic laboratories and makeshift field clinics where a few drops of blood from a finger prick could be rapidly tested in parallel for the presence of antibodies to SARS-CoV-2 with a test turnaround time of only 2-4 h. To evaluate our imaging device, we probed and imaged coronavirus microarrays with COVID-19-positive and negative sera and achieved a performance on par with a commercial microarray reader 100× more expensive than our imaging device. This work will enable large scale serosurveillance, which can play an important role in the months and years to come to implement efficient containment and mitigation measures, as well as help develop therapeutics and vaccines to treat and prevent the spread of COVID-19.

A Modular Microarray Imaging System for Highly Specific COVID-19 Antibody Testing.

To detect the presence of antibodies in blood against SARS-CoV-2 in a highly sensitive and specific manner, here we describe a robust, inexpensive ($200), 3D-printable portable imaging platform (TinyArray imager) that can be deployed immediately in areas with minimal infrastructure to read coronavirus antigen microarrays (CoVAMs) that contain a panel of antigens from SARS-CoV-2, SARS-1, MERS, and other respiratory viruses. Application includes basic laboratories and makeshift field clinics where a few drops of blood from a finger prick could be rapidly tested in parallel for the presence of antibodies to SARS-CoV-2 with a test turnaround time of only 2-4 h. To evaluate our imaging device, we probed and imaged coronavirus microarrays with COVID-19-positive and negative sera and achieved a performance on par with a commercial microarray reader 100x more expensive than our imaging device. This work will enable large scale serosurveillance, which can play an important role in the months and years to come to implement efficient containment and mitigation measures, as well as help develop therapeutics and vaccines to treat and prevent the spread of COVID-19.

From 'circumstances' to 'environment': Herbert Spencer and the origins of the idea of organism-environment interaction.

The word 'environment' has a history. Before the mid-nineteenth century, the idea of a singular, abstract entity--the organism--interacting with another singular, abstract entity--the environment--was virtually unknown. In this paper I trace how the idea of a plurality of external conditions or circumstances was replaced by the idea of a singular environment. The central figure behind this shift, at least in Anglo-American intellectual life, was the philosopher Herbert Spencer. I examine Spencer's work from 1840 to 1855, demonstrating that he was exposed to a variety of discussions of the 'force of circumstances' in this period, and was decisively influenced by the ideas of Auguste Comte in the years preceding the publication of Principles of psychology (1855). It is this latter work that popularized the word 'environment' and the corresponding idea of organism--environment interaction--an idea with important metaphysical and methodological implications. Spencer introduced into the English-speaking world one of our most enduring dichotomies: organism and environment.

"A great complication of circumstances"--Darwin and the economy of nature.

In 1749, Linnaeus presided over the dissertation "Oeconomia Naturae," which argued that each creature plays an important and particular role in nature's economy. This phrase should be familiar to readers of Darwin, for he claims in the Origin that "all organic beings are striving, it may be said, to seize on each place in the economy of nature." Many scholars have discussed the influence of political economy on Darwin's ideas. In this paper, I take a different tack, showing that Darwin's idea of an economy of nature stemmed from the views of earlier naturalists like Linnaeus and Lyell. I argue, in the first section of the paper, that Linnaeus' idea of oeconomia naturae is derived from the idea of the animal economy, and that his idea of politia naturae is an extension of the idea of a politia civitatis. In the second part, I explore the use of the concept of stations in the work of De Candolle and Lyell - the precursor to Darwin's concept of places. I show in the third part of the paper that the idea of places in an economy of nature is employed by Darwin at many key points in his thinking: his discussion of the Galapagos birds, his reading of Malthus, etc. Finally, in the last section, I demonstrate that the idea of a place in nature's economy is essential to Darwin's account of divergence. To tell his famous story of divergence and adaptation, Darwin needed the economy of nature.

A comparative study of the mechanical properties of Mytilid byssal threads.

Mytilid bivalves employ a set of threads (the byssus) to attach themselves to both hard and soft substrates. In this study, we measured the mechanical properties of byssal threads from two semi-infaunal mytilids (Geukensia demissa Dillwyn and Modiolus modiolus Linnaeus) and two epifaunal mytilids (Mytilus californianus Conrad and Mytilus edulis Linnaeus). We compared material properties with and without the assumption that changes of length and area during tensile testing are insignificant, demonstrating that previous researchers have overestimated extensibility values by 30% and may also have underestimated strength values. We detected significant differences in thread properties among tested mytilid species, contrary to previous findings. Threads from semi-infaunal species were significantly thinner than those from epifaunal species, perhaps to allow the production of a greater number of threads, which form a dense network within the substrate. Geukensia demissa threads were weaker than those of the other species, and had a significantly lower stiffness at failure. Modiolus modiolus threads were significantly stiffer than M. edulis threads but also significantly less extensible, suggesting a trade-off between stiffness and extensibility. The only thread property that did not show significant differences across species was toughness - even when byssal threads differ in strength or stiffness, they seem to absorb similar amounts of energy per unit volume prior to failure. This study reveals notable differences between the byssal thread properties of different mytilid bivalves and provides a reliable and thorough methodology for future comparative studies.

Biomechanics of byssal threads outside the Mytilidae: Atrina rigida and Ctenoides mitis.

The byssus is the set of proteinaceous threads widely used by bivalves to attach themselves to the substrate. Previous researchers have focused on a single byssate family, the Mytilidae. However, the properties of byssal threads from species outside this family are of interest - first, because evolutionary patterns are only detectable if species from a range of taxa are examined, and second, because recent biomimetic research efforts would benefit from a wider range of ;mussel glue' exemplars. In the present study, we measured the mechanical properties of the byssal threads of two species outside the Mytilidae, the pen shell Atrina rigida Lightfoot and the flame ;scallop' Ctenoides mitis Lamarck. The mechanical properties of their byssal threads were significantly different from those of mytilids. For instance, the byssal threads of both species were significantly weaker than mytilid threads. Atrina rigida threads were significantly less extensible than mytilid threads, while C. mitis threads exhibited the highest extensibility ever recorded for the distal region of byssal threads. However, there were also interesting similarities in material properties across taxonomic groups. For instance, the threads of A. rigida and Modiolus modiolus Linnaeus both exhibited a prominent double-yield behavior, high stiffness combined with low extensibility, and similar correlations between stiffness and other thread properties. These similarities suggest that the thread properties of some semi-infaunal species may have evolved convergently. Further research on these patterns, along with biochemical analysis of threads which exhibit unusual properties like double-yield behavior, promises to contribute to both evolutionary biology and materials engineering.