Two Tunnels to Inflation

We investigate the formation via tunneling of inflating (false-vacuum) bubbles in a true-vacuum background, and the reverse process. Using effective potentials from the junction condition formalism, all true- and false-vacuum bubble solutions with positive interior and exterior cosmological constant, and arbitrary mass are catalogued. We find that tunneling through the same effective potential appears to describe two distinct processes: one in which the initial and final states are separated by a wormhole (the Farhi-Guth-Guven mechanism), and one in which they are either in the same hubble volume or separated by a cosmological horizon. In the zero-mass limit, the first process corresponds to the creation of an inhomogenous universe from nothing, while the second mechanism is equivalent to the nucleation of true- or false-vacuum Coleman-De Luccia bubbles. We compute the probabilities of both mechanisms in the WKB approximation using semi-classical Hamiltonian methods, and find that -- assuming both process are allowed -- neither mechanism dominates in all regimes.Comment: 16 PRD-style pages, 13 figures. PRD, in press. Revised to match published versio

The acquisition of phototrophy : adaptive strategies of hosting endosymbionts and organelles

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Photosynthesis Research 107 (2011): 117-132, doi:10.1007/s11120-010-9546-8.Many non-photosynthetic species of protists and metazoans are capable of hosting viable algal endosymbionts or their organelles through adaptations of phagocytic pathways. A form of mixotrophy, acquired phototrophy (AcPh) encompasses a sweet of endosymbiotic and organelle retention interactions, that range from facultative to obligate. AcPh is a common phenomenon in aquatic ecosystems, with endosymbiotic associations generally more prevalent in nutrient poor environments, and organelle retention typically associated with more productive ones. All AcPhs benefit from enhanced growth due to access to photosynthetic products, however the degree of metabolic integration and dependency in the host varies widely. AcPhs are mixotrophic, using both heterotrophic and phototrophic carbon sources. AcPh is found in at least four of the major eukaryotic supergroups, and is the driving force in the evolution of secondary and tertiary plastid acquisitions. Mutualistic resource partitioning characterizes most algal endosymbiotic interactions, while organelle retention is a form of predation, characterized by nutrient flow (i.e. growth) in one direction. AcPh involves adaptations to recognize specific prey or endosymbionts and to house organelles or endosymbionts within the endomembrane system but free from digestion. In many cases, hosts depend upon AcPh for the production of essential nutrients, many of which remain obscure. The practice of AcPh has led to multiple independent secondary and tertiary plastid acquisition events among several eukaryote lineages, giving rise to the diverse array of algae found in modern aquatic ecosystems. This review highlights those AcPhs that are model research organisms for both metazoans and protists. Much of the basic biology of AcPhs remains enigmatic, particularly 1) which essential nutrients or factors make certain forms of AcPh obligatory, 2) how hosts regulate and manipulate endosymbionts or sequestered organelles, and 3) what genomic imprint, if any, AcPh leaves on non-photosynthetic host species.Supported by NSF grant OCE-085126

Regional Cultural Enterprises and Cultural Markets in Early Republican China: The Motion Picture as Case Study

The transition of the motion picture from foreign amusement to local enterprise was primarily the result of transnational commercial activity linking investors, entrepreneurs, and entertainment professionals. Amid the ongoing urbanization of China’s early Republican period, the enterprises emerging from this activity became increasingly profitable and, as a result, film production and exhibition became regularized phenomena, rooted in identifiable genres and standardized approaches to engaging audiences within the immersive space of the theater. By the early 1920s, those closest to the nascent industry were eager to legitimize its power by portraying the medium as a tool for political and social reform. However, commercial strategies and aesthetics remained relatively undisturbed despite this progressive rhetoric. In geographic terms, motion picture–related enterprises and culture remained strongly regional: affected and constrained by the non-Chinese national industries operating in politically divided China, by competing forms of local popular culture, and by existing geographies of exchange and infrastructure. The early Republican “experimental” period in Chinese cinema was, from an enterprise-centered perspective, one of numerous coexisting subnational cultural centers and zones. Keywords: modern Chinese history, Republican era (1911–1949), business history, cultural geography, Sino-foreign enterprise, media change, cinema, motion pictures (production and exhibition), film theaters, popular cultur

Quality Uncertainty and Grain Merchandising Risk: Vomitoxin in Spring Wheat

Marketing, Risk and Uncertainty,

Mesodinium rubrum exhibits genus-level but not species-level cryptophyte prey selection

The marine ciliate Mesodinium rubrum is known to form large non-toxic red water blooms in estuarine and coastal upwelling regions worldwide. This ciliate relies predominantly upon photosynthesis by using plastids and other organelles it acquires from cryptophyte prey. Although M. rubrum is capable of ingesting different species of cryptophytes, mainly Teleaulax amphioxeia plastids have been detected from wild M. rubrum populations. These observations suggest that either M. rubrum is a selective feeder, or T. amphioxeia are taken up because of higher availability. To test these hypotheses, we determined whether the ciliate showed different grazing rates, growth responses, or plastid retention dynamics when offered Storeatula major, T. amphioxeia, T. acuta, or a mix. When M. rubrum was offered the cryptophyte S. major as prey, no evidence was found for ingestion. In contrast, M. rubrum grazed both Teleaulax spp. equally, was able to easily switch plastid type between them, and the ratio of each in the ciliate reflected the abundance of free-living prey in the culture. M. rubrum grew equally well when acclimated to each plastid type or when having mixed plastids. However, when offered single prey, T. amphioxeia could sustain higher M. rubrum growth rates (mu) over longer periods. Compared to other M. rubrum strains, this culture had higher grazing rates, greater ingestion requirements for reaching mu(max), and appeared to rely more on plastid sequestration than de novo division of cryptophyte organelles. Our results suggest that while M. rubrum may prefer Teleaulax-like cryptophytes, they do not select among the species used here.Peer reviewe