Using Bayesian Networks to Forecast Barrier Island Geomorphology and Impacts to Piping Plover Habitat Due to Sea-Level Rise

The ability to evaluate the impact of sea-level rise (SLR) on coastal landforms and habitats is important for informing management and policy decisions. A particular area of concern exists along the east coast of the United States, where the evolution of barrier islands over the remainder of the 21st century and beyond will require management and policy decisions in order to effectively balance human development demands and the protection of habitat quality. We developed methods to evaluate the evolution of barrier islands and associated habitat changes for piping plovers (Charadrius melodus), a threatened species that relies on beach and barrier island habitats, under different SLR scenarios. Our modeling approach provides probabilistic forecasts of barrier island morphology and habitat suitability under different rates of relative SLR. To implement this approach, we use Bayesian networks to predict the most likely (1) shoreline change rate, (2) barrier island morphology, and (3) plover habitat suitability. We show applications for several national parks and wildlife refuges in the northeastern United Sates. Our results show that distinct geomorphic conditions are associated with different long-term shoreline change rates and that shoreline change rates depend on SLR rates. This modeling framework also allows us to evaluate scenarios related to coastal management plans and/or future scenarios where shoreline-change rates may differ from those observed historically. Initial results show that modest SLR rates may increase the area of suitable piping plover nesting habitat in 50‒100 years and also indicate the level of effectiveness of certain management strategies in promoting habitat availability

Are Online Job Postings Informative to Investors?

Human capital is a key factor in value creation in the modern corporation. Yet the disclosure of investment in human capital is scant. We propose that a company’s online job postings are disclosures made outside of the investor-relations channel that contain forward-looking information that could be informative to investors about future growth. We find that changes in the number of job postings are positively associated with changes in future performance and that this relation is stronger when postings likely represent growth rather than replacement. Consistent with job postings providing new information to the market, investors react positively to changes in the number of job postings. The market reaction to postings is stronger when firms are likely to be hiring for growth rather than replacement and for firms with low labor intensity (and therefore high marginal productivity of labor). This paper was accepted by Brian Bushee, accounting

Profitability in Heterogeneity: A Comparative Study

This study relates Hambrick and Mason’s (1984) Proposition 21 of the Upper Echelons Theory (UET) to the texts of I and II Timothy. Proposition 21 of the UET states, “In turbulent environments, team heterogeneity will be positively associated with profitability” (p. 203). This study affirms the validity of this proposition within the heterogeneous leadership context of Paul and Timothy as seen in the turbulent environment described in I and II Timothy. After defining three key terms (heterogeneity, turbulent environment, profitability) of the UET, this study provides the definitions and rationale for translating these terms into a ministry context. This study supports a heterogeneous leadership relationship of Paul and Timothy by providing a brief sketch of Paul and Timothy’s personal background (birthplace, family, education, conversion experience, age) and past leadership experiences. This study supports that Paul and Timothy were functioning within a turbulent environment by providing a basic explanation of the nature of the heresies within I and II Timothy including a brief discussion of the identity of the heretics. The injunctions set forth for the Ephesian church and its conduct afterwards provide supporting evidence of the profitability aspect of Proposition 21. A summary of the study, benefits from this study, and suggestions for future research conclude this study

Energy invariance in capillary systems

We demonstrate the continuous translational invariance of the energy of a capillary surface in contact with reconfigurable solid boundaries. We present a theoretical approach to find the energy-invariant equilibria of spherical capillary surfaces in contact with solid boundaries of arbitrary shape and examine the implications of dynamic frictional forces upon of a reconfiguration of the boundaries. Experimentally, we realise our ideas by manipulating the position of a droplet in a wedge geometry using lubricant-impregnated solid surfaces, which eliminate the contact-angle hysteresis and provide a test bed for quantifying dissipative losses out of equilibrium. Our experiments show that dissipative energy losses for an otherwise energy-invariant reconfiguration are relatively small, provided that the actuation timescale is longer than the typical relaxation timescale of the capillary surface. We discuss the wider applicability of our ideas as a pathway for liquid manipulation at no potential energy cost in low-pinning, low-friction situations

"Clumpiness" Mixing in Complex Networks

Three measures of clumpiness of complex networks are introduced. The measures quantify how most central nodes of a network are clumped together. The assortativity coefficient defined in a previous study measures a similar characteristic, but accounts only for the clumpiness of the central nodes that are directly connected to each other. The clumpiness coefficient defined in the present paper also takes into account the cases where central nodes are separated by a few links. The definition is based on the node degrees and the distances between pairs of nodes. The clumpiness coefficient together with the assortativity coefficient can define four classes of network. Numerical calculations demonstrate that the classification scheme successfully categorizes 30 real-world networks into the four classes: clumped assortative, clumped disassortative, loose assortative and loose disassortative networks. The clumpiness coefficient also differentiates the Erdos-Renyi model from the Barabasi-Albert model, which the assortativity coefficient could not differentiate. In addition, the bounds of the clumpiness coefficient as well as the relationships between the three measures of clumpiness are discussed.Comment: 47 pages, 11 figure

The Carotenogenesis Pathway via the Isoprenoid-β-carotene Interference Approach in a New Strain of Dunaliella salina Isolated from Baja California Mexico

D. salina is one of the recognized natural sources to produce β-carotene, and an useful model for studying the role of inhibitors and enhancers of carotenogenesis. However there is little information in D. salina regarding whether the isoprenoid substrate can be influenced by stress factors (carotenogenic) or selective inhibitors which in turn may further contribute to elucidate the early steps of carotenogenesis and biosynthesis of β-carotene. In this study, Dunaliella salina (BC02) isolated from La Salina BC Mexico, was subjected to the method of isoprenoids-β-carotene interference in order to promote the interruption or accumulation of the programmed biosynthesis of carotenoids. When Carotenogenic and non-carotenogenic cells of D. salina BC02 were grown under photoautotrophic growth conditions in the presence of 200 µM fosmidomycin, carotenogenesis and the synthesis of β-carotene were interrupted after two days in cultured D. salina cells. This result is an indirect consequence of the inhibition of the synthesis of isoprenoids and activity of the recombinant DXR enzyme thereby preventing the conversion of 1-deoxy-D-xylulose 5-phosphate (DXP) to 2-C-methyl-D-erythritol (MEP) and consequently interrupts the early steps of carotenogenesis in D. salina. The effect at the level of proteins and RNA was not evident. Mevinolin treated D. salina cells exhibited carotenogenesis and β-carotene levels very similar to those of control cell cultures indicating that mevinolin not pursued any indirect action in the biosynthesis of isoprenoids and had no effect at the level of the HMG-CoA reductase, the key enzyme of the Ac/MVA pathway

"Clumpiness" Mixing in Complex Networks

Three measures of clumpiness of complex networks are introduced. The measures quantify how most central nodes of a network are clumped together. The assortativity coefficient defined in a previous study measures a similar characteristic, but accounts only for the clumpiness of the central nodes that are directly connected to each other. The clumpiness coefficient defined in the present paper also takes into account the cases where central nodes are separated by a few links. The definition is based on the node degrees and the distances between pairs of nodes. The clumpiness coefficient together with the assortativity coefficient can define four classes of network. Numerical calculations demonstrate that the classification scheme successfully categorizes 30 real-world networks into the four classes: clumped assortative, clumped disassortative, loose assortative and loose disassortative networks. The clumpiness coefficient also differentiates the Erdos-Renyi model from the Barabasi-Albert model, which the assortativity coefficient could not differentiate. In addition, the bounds of the clumpiness coefficient as well as the relationships between the three measures of clumpiness are discussed.Comment: 47 pages, 11 figure

MenT nucleotidyltransferase toxins extend tRNA acceptor stems and can be inhibited by asymmetrical antitoxin binding

Mycobacterium tuberculosis, the bacterium responsible for human tuberculosis, has a genome encoding a remarkably high number of toxin-antitoxin systems of largely unknown function. We have recently shown that the M. tuberculosis genome encodes four of a widespread, MenAT family of nucleotidyltransferase toxin-antitoxin systems. In this study we characterize MenAT1, using tRNA sequencing to demonstrate MenT1 tRNA modification activity. MenT1 activity is blocked by MenA1, a short protein antitoxin unrelated to the MenA3 kinase. X-ray crystallographic analysis shows blockage of the conserved MenT fold by asymmetric binding of MenA1 across two MenT1 protomers, forming a heterotrimeric toxin-antitoxin complex. Finally, we also demonstrate tRNA modification by toxin MenT4, indicating conserved activity across the MenT family. Our study highlights variation in tRNA target preferences by MenT toxins, selective use of nucleotide substrates, and diverse modes of MenA antitoxin activity