Dancing with the Stars: Formation of the Fomalhaut triple system and its effect on the debris disks

Fomalhaut is a triple system, with all components widely separated (~1E5 au). Such widely separated binaries are thought to form during cluster dissolution, but that process is unlikely to form such a triple system. We explore an alternative scenario, where A and C form as a tighter binary from a single molecular cloud core (with semimajor axis ~1E4 au), and B is captured during cluster dispersal. We use N-body simulations augmented with the Galactic tidal forces to show that such a system naturally evolves into a Fomalhaut-like system in about half of cases, on a timescale compatible with the age of Fomalhaut. From initial non-interacting orbits, Galactic tides drive cycles in B's eccentricity that lead to a close encounter with C. After several close encounters, typically lasting tens of millions of years, one of the stars is ejected. The Fomalhaut-like case with both components at large separations is almost invariably a precursor to the ejection of one component, most commonly Fomalhaut C. By including circumstellar debris in a subset of the simulations, we also show that such an evolution usually does not disrupt the coherently eccentric debris disk around Fomalhaut A, and in some cases can even produce such a disk. We also find that the final eccentricity of the disk around A and the disk around C are correlated, which may indicate that the dynamics of the three stars stirred C's disk, explaining its unusual brightness.Comment: Accepted to MNRA

Corruption, Development and the Curse of Natural Resources

In 1995, Jeffrey Sachs and Andrew Warner found a negative relationship between natural resources and economic growth, and claimed that natural resources are a curse. Their work has been widely cited, with many economists now accepting the curse of natural resources as a welldocumented explanation of poor economic growth in some economies (e.g., Papyrakis and Gerlagh, 2004; Kronenberg, 2004). In this paper, we provide an alternative econometric framework for evaluating this claim, although we begin with a discussion of possible explanations for the curse and a critical assessment of the extant theory underlying the curse. Our approach is to identify natural resources that have the greatest rents and potential for exploitation through rent-seeking agents. The transmission mechanism that we specify works through the effect that rent seeking has on corruption and how that, in turn, impacts wellbeing. Our measure of wellbeing is the Human Development Index, although we find similar results for per capita GDP. While we find that resource abundance does not directly impact economic development, we do find that petroleum resources are associated with rent-seeking behavior that negatively affects wellbeing. Our regression results are robust to various model specifications and sensitivity analyses.natural resource curse, petroleum resources, unbalanced panels and GMM estimation

Applications of Effective Population Size in Conservation Biology Through an Experimental Study and Quantitative Review

Effective population size (Ne) is a key parameter in conservation biology, as it influences the degree of genetic drift and adaptive potential of a population. Although Ne is widely reported in individual studies, it is not well integrated into monitoring programs, and there is still much to learn about how it is impacted by human-induced stressors. My thesis attempted to bridge these gaps through (1) an experiment assessing how Ne changes within populations exposed to size- selective harvest, and (2) a quantitative review summarizing Ne estimates across and within taxa in wild populations. I showed experimentally that in populations of brook trout (Salvelinus fontinalis) exposed to size-selective harvest, change in Ne is buffered through density-dependent genetic compensation. Therefore, in the short-term, Ne can be resilient to harvest even with substantial decreases in population size. My review also showed that Ne varies between taxonomic groups in wild populations, and that a high human footprint is associated with lower Ne, especially in amphibians and mammals. There were two broad conclusions from this work. Firstly, many wild populations fall below key conservation thresholds (Ne of 50 or 500), and I discuss the caveats of using conservation thresholds based on broad generalizations across taxa that vary in life history traits and adaptations. Secondly, I emphasize the importance of integrating genetic and demographic factors in monitoring and risk assessments. Overall, these conclusions can help guide the integration of Ne into research, monitoring, and policy

The iFat1 transgene permits conditional endogenous n-3 PUFA enrichment both in vitro and in vivo

Fat-1 transgenic mice, which endogenously convert n-6 PUFA to n-3 PUFA, are a useful tool in health research; however with this model timing of n-3 PUFA enrichment cannot be directly controlled. To add such capability, the novel Cre-recombinase inducible fat-1 (iFat1) transgenic mouse has been developed. The aim of this study was to characterize the utility of the iFat1 transgene as a model of Cre-inducible endogenous n-3 PUFA enrichment. Functionality of the iFat1 transgene was screened both in vitro and in vivo. In the presence of Cre, the iFat1 transgene resulted in a balancing (p < 0.01) of the n-6/n-3 PUFA ratio within phospholipids in the human embryonic kidney 293T cell line. For in vivo analysis, iFat1 transgenic mice were crossed with the R26-Cre-ERT2 (Tam-Cre) mouse line, a tamoxifen inducible Cre-expression model. Tam-Cre/iFat1 double hybrids were transiently treated with tamoxifen at 6–7 weeks, then terminated 3 weeks later. Tamoxifen treated mice had increased (p < 0.05) tissue n-3 PUFA and ≥two-fold reduction (p < 0.05) in the n-6/n-3 PUFA ratio of liver, kidney and muscle phospholipids relative to vehicle treated controls. Collectively these findings suggest that the iFat1 transgenic mouse may be a promising tool to help elucidate the temporal effects through which n-3 PUFA impacts health related outcomes

Confronting the elephant in the room: Cleaning and wrangling data for collections and scholarly services

Librar

Food defense : protecting the food supply from intentional harm (2009)

New 11/09/2M

Single cell analysis shows decreasing FoxP3 and TGFβ1 coexpressing CD4+CD25+ regulatory T cells during autoimmune diabetes

Natural CD4+CD25+ regulatory T (CD4+CD25+ T reg) cells play a key role in the immunoregulation of autoimmunity. However, little is known about the interactions between CD4+CD25+ T reg cells and autoreactive T cells. This is due, in part, to the difficulty of using cell surface markers to identify CD4+CD25+ T reg cells accurately. Using a novel real-time PCR assay, mRNA copy number of FoxP3, TGFβ1, and interleukin (IL)-10 was measured in single cells to characterize and quantify CD4+CD25+ T reg cells in the nonobese diabetic (NOD) mouse, a murine model for type 1 diabetes (T1D). The suppressor function of CD4+CD25+CD62Lhi T cells, mediated by TGFβ, declined in an age-dependent manner. This loss of function coincided with a temporal decrease in the percentage of FoxP3 and TGFβ1 coexpressing T cells within pancreatic lymph node and islet infiltrating CD4+CD25+CD62Lhi T cells, and was detected in female NOD mice but not in NOD male mice, or NOR or C57BL/6 female mice. These results demonstrate that the majority of FoxP3-positive CD4+CD25+ T reg cells in NOD mice express TGFβ1 but not IL-10, and that a defect in the maintenance and/or expansion of this pool of immunoregulatory effectors is associated with the progression of T1D

Translation and Community in the work of Elizabeth Cary

Explores the role of female community within Elizabeth Cary\u27s translations and her play, The Tragedy of Mariam

Objects and categories: feature statistics and object processing in the ventral stream.

Recognizing an object involves more than just visual analyses; its meaning must also be decoded. Extensive research has shown that processing the visual properties of objects relies on a hierarchically organized stream in ventral occipitotemporal cortex, with increasingly more complex visual features being coded from posterior to anterior sites culminating in the perirhinal cortex (PRC) in the anteromedial temporal lobe (aMTL). The neurobiological principles of the conceptual analysis of objects remain more controversial. Much research has focused on two neural regions-the fusiform gyrus and aMTL, both of which show semantic category differences, but of different types. fMRI studies show category differentiation in the fusiform gyrus, based on clusters of semantically similar objects, whereas category-specific deficits, specifically for living things, are associated with damage to the aMTL. These category-specific deficits for living things have been attributed to problems in differentiating between highly similar objects, a process that involves the PRC. To determine whether the PRC and the fusiform gyri contribute to different aspects of an object's meaning, with differentiation between confusable objects in the PRC and categorization based on object similarity in the fusiform, we carried out an fMRI study of object processing based on a feature-based model that characterizes the degree of semantic similarity and difference between objects and object categories. Participants saw 388 objects for which feature statistic information was available and named the objects at the basic level while undergoing fMRI scanning. After controlling for the effects of visual information, we found that feature statistics that capture similarity between objects formed category clusters in fusiform gyri, such that objects with many shared features (typical of living things) were associated with activity in the lateral fusiform gyri whereas objects with fewer shared features (typical of nonliving things) were associated with activity in the medial fusiform gyri. Significantly, a feature statistic reflecting differentiation between highly similar objects, enabling object-specific representations, was associated with bilateral PRC activity. These results confirm that the statistical characteristics of conceptual object features are coded in the ventral stream, supporting a conceptual feature-based hierarchy, and integrating disparate findings of category responses in fusiform gyri and category deficits in aMTL into a unifying neurocognitive framework.This work was supported by a grant from the Medical Research Council (G0500842) to L. K. T., a British Academy (Grant Number LRG-45583) grant to L. K. T. and K. I. T., a Newton Trust grant to L. K. T. and K. I. T., the European Research Council (ERC) under the European Community ʼs Seventh Framework Programme (FP7/2007 – 2013)/ERC (Grant Agreement Number 249640) to L. K. T., and a Swiss National Science Foundation Ambizione Fellowship (Grant Number PZ00P1_126493) to K. I. T.This is the accepted version of the original publication available at: http://dx.doi.org/10.1162/jocn_a_00419 in Journal of Cognitive Neuroscience http://www.mitpressjournals.org/loi/joc

The market efficiency in the stock markets

We study the temporal evolution of the market efficiency in the stock markets using the complexity, entropy density, standard deviation, autocorrelation function, and probability distribution of the log return for Standard and Poor's 500 (S&P 500), Nikkei stock average index, and Korean composition stock price index (KOSPI). Based on the microscopic spin model, we also find that these statistical quantities in stock markets depend on the market efficiency.Comment: 8 pages, 5 figure