San Francisco State University

About: San Francisco State University is a education organization based out in San Francisco, California, United States. It is known for research contribution in the topics: Population & Planet. The organization has 5669 authors who have published 11433 publications receiving 408075 citations. The organization is also known as: San Francisco State & San Francisco State Normal School.

Curved singular beams for three-dimensional particle manipulation

Abstract: For decades, singular beams carrying angular momentum have been a topic of considerable interest. Their intriguing applications are ubiquitous in a variety of fields, ranging from optical manipulation to photon entanglement, and from microscopy and coronagraphy to free-space communications, detection of rotating black holes, and even relativistic electrons and strong-field physics. In most applications, however, singular beams travel naturally along a straight line, expanding during linear propagation or breaking up in nonlinear media. Here, we design and demonstrate diffraction-resisting singular beams that travel along arbitrary trajectories in space. These curved beams not only maintain an invariant dark "hole" in the center but also preserve their angular momentum, exhibiting combined features of optical vortex, Bessel, and Airy beams. Furthermore, we observe three-dimensional spiraling of microparticles driven by such fine-shaped dynamical beams. Our findings may open up new avenues for shaped light in various applications.

Polygenic adaptation: From sweeps to subtle frequency shifts

Abstract: Evolutionary theory has produced two conflicting paradigms for the adaptation of a polygenic trait. While population genetics views adaptation as a sequence of selective sweeps at single loci underlying the trait, quantitative genetics posits a collective response, where phenotypic adaptation results from subtle allele frequency shifts at many loci. Yet, a synthesis of these views is largely missing and the population genetic factors that favor each scenario are not well understood. Here, we study the architecture of adaptation of a binary polygenic trait (such as resistance) with negative epistasis among the loci of its basis. The genetic structure of this trait allows for a full range of potential architectures of adaptation, ranging from sweeps to small frequency shifts. By combining computer simulations and a newly devised analytical framework based on Yule branching processes, we gain a detailed understanding of the adaptation dynamics for this trait. Our key analytical result is an expression for the joint distribution of mutant alleles at the end of the adaptive phase. This distribution characterizes the polygenic pattern of adaptation at the underlying genotype when phenotypic adaptation has been accomplished. We find that a single compound parameter, the population-scaled background mutation rate Θbg, explains the main differences among these patterns. For a focal locus, Θbg measures the mutation rate at all redundant loci in its genetic background that offer alternative ways for adaptation. For adaptation starting from mutation-selection-drift balance, we observe different patterns in three parameter regions. Adaptation proceeds by sweeps for small Θbg ≲ 0.1, while small polygenic allele frequency shifts require large Θbg ≳ 100. In the large intermediate regime, we observe a heterogeneous pattern of partial sweeps at several interacting loci.

Feminist Ethnography: Critique, Conflict, and Ambivalent Observance

Abstract: A mentor once remarked that I seem committed in my scholarship to telling well-intentioned, admirable, left-leaning people that they do not have things quite right. While the characterization initially took me aback—was I really so contentious?—I both recognize the truth in it and have come to understand that commitment as a peculiarly feminist one. Feminist activists and scholars are routinely in conflict with one another, even as we share aims, convictions, and commitments. Our conflicts help to generate, direct, and amend our concerted movements toward intellectual insight and social change. As Judith Taylor notes in her study of feminists’ accounts of conflict in memoir, even pained recollections of conflict suggest a hope for something else, an insistent sense that things could and should be otherwise (Taylor 2008, 2009). Taylor asserts, “feminists see the creation of a new ethics of social relations among women as a central movement goal” (2009, 127). We try both not to avoid conflict and to do conflict well. The sexuality education debate was remarkably contentious in the late 1990s when I began work on Risky Lessons: Sex Education and Social Inequality (2008), an ethnographic study of sexuality education debates and classroom practice in North Carolina. During my eighteen months of fieldwork, advocates of comprehensive sexuality education shared resources and