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We demonstrate laser frequency stabilization with at least 6 GHz of offset tunability using an in-phase/quadrature (IQ) modulator to generate electronic sidebands (ESB) on a titanium sapphire laser at 714 nm and we apply this technique to perform isotope shift spectroscopy of 226 Ra and 225 Ra. By locking the laser to a single resonance of a high finesse optical cavity and adjusting the lock offset, we determine the frequency difference between the magneto-optical trap (MOT) transitions in the two isotopes to be 2630.0 ± 0.3 MHz, a factor of 29 more precise than the previously available data. Using the known value of the hyperfine splitting of the 3 P 1 level, we calculate the isotope shift for the 1 S 0 to 3 P 1 transition to be 2267.0 ± 2.2 MHz, a factor of 8 more precise than the best available value. Our technique could be applied to countless other atomic systems to provide unprecedented precision in isotope shift spectroscopy and other relative frequency comparisons.

During the 1960s and 1970s population geneticists pushed beyond models of single genes to grapple with the effect on evolution of multiple genes associated by linkage. The resulting models of multiple interacting loci suggested that blocks of genes, maybe even entire chromosomes or the genome itself, should be treated as a unit. In this context, Richard Lewontin wrote his famous 1974 book The Genetic Basis of Evolutionary Change, which concludes with an argument for considering the entire genome as the unit of selection as a result of linkage. Why did Lewontin and others devote so much intellectual energy to the "complications of linkage" in the 1960s and 1970s? We argue that this attention to linkage should be understood in the context of research on chromosomal inversions and co-adapted gene complexes that occupied mid-century evolutionary genetics. For Lewontin, the complications of linkage were an extension of this chromosomal focus expressed in the new language of models for linkage disequilibrium., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Despite August Krogh's famous admonition that a 'convenient' organism exists for every biological problem, we argue that appeals to 'convenience' are not sufficient to capture reasoning about organism choice. Instead, we offer a detailed analysis based on empirical data and philosophical arguments for a working set of twenty criteria that interact with each other in the highly contextualized judgements that biologists make about organism choice. We propose to think of these decisions as a form of 'differential analysis' where researchers weigh multiple criteria for organismal choice against each other, and often utilize multidimensional refinement processes to finalize their choices. The specific details of any one case make it difficult to draw generalizations or to abstract away from specific research situations. However, this analysis of criteria for organismal choice and how these are related in practice allows us to reflect more generally on what makes a particular organism useful or 'good.', (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Many biologists appeal to the so-called Krogh principle when justifying their choice of experimental organisms. The principle states that "for a large number of problems there will be some animal of choice, or a few such animals, on which it can be most conveniently studied". Despite its popularity, the principle is often critiqued for implying unwarranted generalizations from optimal models. We argue that the Krogh principle should be interpreted in relation to the historical and scientific contexts in which it has been developed and used. We interpret the Krogh Principle as a heuristic, i.e., as a recommendation to approach biological problems through organisms where a specific trait or physiological mechanism is expected to be most distinctively displayed or most experimentally accessible. We designate these organisms "Krogh organisms". We clarify the differences between uses of model organisms and non-standard Krogh organisms. Among these is the use of Krogh organisms as "negative models" in biomedical research, where organisms are chosen for their dissimilarity to human physiology. Importantly, the representational scope of Krogh organisms and the generalizability of their characteristics are not fixed or assumed but explored through experimental studies. Research on Krogh organisms is steeped in the comparative method characteristic of zoology and comparative physiology, in which studies of biological variation produce insights into general physiological constraints. Accordingly, we conclude that the Krogh principle exemplifies the advantages of studying biological variation as a strategy to produce generalizable insights.

A method for alignment of a vector magnetometer to a rigidly attached prism is presented. This enables optical comparison of the magnetometer axes to physical surfaces in the apparatus, and thus an absolute determination of the magnetic field direction in space. This is in contrast with more common techniques, which focus on precise determination of the relative angles between magnetometer axes, and so are more suited to measuring differences in the direction of magnetic fields. Here we demonstrate precision better than 500 μrad on a fluxgate magnetometer, which also gives the coil orthogonality errors to a similar precision. The relative sensitivity of the three axes is also determined, with a precision of about 5 × 10 -4 .

In the early twentieth century, Tatsuo Aida in Japan, Øjvind Winge in Denmark, Richard Goldschmidt in Germany, and Calvin Bridges in the United States all developed different experimental systems to study the genetics of sex reversal. These locally specific experimental systems grounded these experimenters' understanding of sex reversal as well as their interpretation of claims regarding experimental results and theories. The comparison of four researchers and their experimental systems reveals how those different systems mediated their understanding of genetic phenomena, and influenced their interpretations of sex reversal.

In the 1960s, "developmental biology" became the dominant term to describe some of the research that had previously been included under the rubrics of embryology, growth, morphology, and physiology. As scientific societies formed under this new label, a new discipline took shape. Historians, however, have a number of different perspectives on what changes led to this new field of developmental biology and how the field itself was constituted during this period. Using the General Embryological Information Service, a global index of post-World War II development-related research, we have documented and visualized significant changes in the kinds of research that occurred as this new field formed. In particular, our analysis supports the claim that the transition toward developmental biology was marked by a growth in new topics and forms of research. Although many historians privilege the role of molecular biology and/or the molecularization of biology in general during this formative period, we have found that the influence of molecular biology is not sufficient to account for the wide range of new research that constituted developmental biology at the time. Overall, our work creates a robust characterization of the changes that occurred with regard to research on growth and development in the decades following World War II and provides a context for future work on the specific drivers of those changes., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The radioactive radium-225 ((225)Ra) atom is a favorable case to search for a permanent electric dipole moment. Because of its strong nuclear octupole deformation and large atomic mass, (225)Ra is particularly sensitive to interactions in the nuclear medium that violate both time-reversal symmetry and parity. We have developed a cold-atom technique to study the spin precession of (225)Ra atoms held in an optical dipole trap, and demonstrated the principle of this method by completing the first measurement of its atomic electric dipole moment, reaching an upper limit of |d((225)Ra)|<5.0×10(-22)  e cm (95% confidence).

Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse array of mechanisms for streaming motions. This paper focuses on the re-emergence of contraction among the molecular mechanisms proposed for protoplasmic streaming during the twentieth century. The revival of contraction is a result of a broader transition from colloidal chemistry to a macromolecular approach to the chemistry of proteins, the recognition of the phenomena of shuttle streaming and the pulse of protoplasm, and the influential analogy between protoplasmic streaming and muscle contraction., (© 2014 Institute of Botany, Chinese Academy of Sciences.)

In 1990, the National Institutes of Health (NIH) gave some organisms special status as designated model organisms. This article documents publication trends for these NIH-designated model organisms over the past 40 years. We find that being designated a model organism by the NIH does not guarantee an increasing publication trend. An analysis of model and nonmodel organisms included in GENETICS since 1960 does reveal a sharp decline in the number of publications using nonmodel organisms yet no decline in the overall species diversity. We suggest that organisms with successful publication records tend to share critical characteristics, such as being well developed as standardized, experimental systems and being used by well-organized communities with good networks of exchange and methods of communication., (Copyright © 2014 by the Genetics Society of America.)

We report the first experimental determination of the hyperfine quenching rate of the 6s(2) (1)S(0)(F = 1/2) - 6s6p (3)P(0)(F = 1/2) transition in (171)Yb with nuclear spin I = 1/2. This rate determines the natural linewidth and the Rabi frequency of the clock transition of a Yb optical frequency standard. Our technique involves spectrally resolved fluorescence decay measurements of the lowest lying (3)P(0,1) levels of neutral Yb atoms embedded in a solid Ne matrix. The solid Ne provides a simple way to trap a large number of atoms as well as an efficient mechanism for populating (3)P(0). The decay rates in solid Ne are modified by medium effects including the index-of-refraction dependence. We find the (3)P(0) hyperfine quenching rate to be (4.42 ± 0.35) × 10(-2) s(-1) for free (171)Yb, which agrees with recent ab initio calculations.

Richard Goldschmidt was one of the most controversial biologists of the mid-twentieth century. Rather than fade from view, Goldschmidt's work and reputation has persisted in the biological community long after he has. Goldschmidt's longevity is due in large part to how he was represented by Stephen J. Gould. When viewed from the perspective of the biographer, Gould's revival of Goldschmidt as an evolutionary heretic in the 1970s and 1980s represents a selective reinvention of Goldschmidt that provides a contrast to other kinds of biographical commemorations by scientists.

One of the most interesting challenges facing paleobiologists is explaining the Cambrian explosion, the dramatic appearance of most metazoan animal phyla in the Early Cambrian, and the subsequent stability of these body plans over the ensuing 530 million years. We propose that because phenotypic variation decreases through geologic time, because microRNAs (miRNAs) increase genic precision, by turning an imprecise number of mRNA transcripts into a more precise number of protein molecules, and because miRNAs are continuously being added to metazoan genomes through geologic time, miRNAs might be instrumental in the canalization of development. Further, miRNAs ultimately allow for natural selection to elaborate morphological complexity, because by reducing gene expression variability, miRNAs increase heritability, allowing selection to change characters more effectively. Hence, miRNAs might play an important role in shaping metazoan macroevolution, and might be part of the solution to the Cambrian conundrum.

The vast network of Drosphila geneticists spawned by Thomas Hunt Morgan's fly room in the early 20th century has justifiably received a significant amount of scholarly attention. However, most accounts of the history of Drosophila genetics focus heavily on the "boss and the boys," rather than the many other laboratory groups which also included large numbers of women. Using demographic information extracted from the Drosophila Information Service directories from 1934 to 1970, we offer a profile of the gendered division of labor within Drosophila genetics in the United States during the middle decades of the 20th century. Our analysis of the gendered division of labor supports a reconsideration of laboratory practices as different forms of work.

Through a case study of the controversies surrounding the molecular clock, this paper examines the role of visual representation in the dynamics of scientific controversies. Representations of the molecular clock themselves became objects of controversy and so were not a means for closure. Instead visual representations of the molecular clock became tools for the further articulation of an ongoing controversy.

In this article, we consider the tension between unification and pluralism in biological theory. We begin with a consideration of historical efforts to establish a unified understanding of evolution in the neo-Darwinian synthesis. The fragmentation of the evolutionary synthesis by molecular evolution suggests the limitations of the general unificationist ideal for biology but not necessarily for integrating explanations. In the second half of this article, we defend a specific variety of pluralism that allows for the integration required for explanations of complex phenomena without unification on a large scale.

Richard Goldschmidt is remembered today as one of the most controversial biologists of the twentieth century. Although his work on sex determination and physiological genetics earned him accolades from his peers, his rejection of the classical gene and his unpopular theories about evolution significantly damaged his scientific reputation. This article reviews Goldschmidt's life and work, with an emphasis on his controversial views.

During the early 20th century the diverse practices of genetics were unified by the concept of the gene. This classical gene was simultaneously a unit of structure, function, mutation, and recombination. Starting in the 1940s, however, the classical gene began to fragment. Today when we speak of a gene for some malady, a regulatory gene, a structural gene, or a gene frequency, it is entirely possible that we are deploying different gene concepts even though we are using the same term. The problem of the gene addresses the fragmentation of the classical gene concept by asking to what extent a comprehensive and unifying gene concept is possible or desirable. Fully comprehensive gene concepts seem untenable today, but, within different disciplinary domains, unifying, but non-comprehensive, gene concepts can be epistemically worthwhile. The problem of the gene persists, however, not because of its epistemic value, but because of its political value. Using both the arguments for newly proposed gene concepts and the historical dispute over the classical gene, I argue that the desirability of gene concepts rests in part on the political ramifications of their deployment and contestation.

Using an analogy between moths and men, in 1916, Richard Goldschmidt proposed that homosexuality was a case of genetic intersexuality. As he strove to create a unified theory of sex determination that would encompass animals ranging from moths to men, Goldschmidt's doubts grew concerning the association of homosexuality with intersexuality until, in 1931, he dropped homosexuality from his theory of intersexuality. Despite Goldschmidt's explicit rejection of his theory of homosexuality, Theo Lang, a researcher in the Genealogical-Demographic Department of the Institute for Psychiatric Research in Munich, revived it, maintained Goldschmidt's association with it, and argued on its behalf in publications from 1936 to 1960. Lang's appropriation of Goldschmidt's theory did not depend on his resolution of the difficulties Goldschmidt had found with his own theory. Lang and Goldschmidt, I argue, had fundamentally different scientific and social commitments that allowed one to reject this theory of homosexuality and the other to accept it.