Forest industry byproducts improve soil quality and increase pepper growth in three soils infested with Phythophthora blight

Phytophthora blight is a serious threat to the Midwest vegetable industry, because the oomycete pathogen responsible for this disease, Phytophthora capsici, has a wide host range, can spread quickly in fields, and produces resilient oospores that can survive in soil for years. Phytophthora capsici has become resistant to commonly used fungicides and resistant crop varieties are rare. Amending soil with complex organic substrates has potential to improve soil quality and suppress soil-borne pathogens including P. capsici. Indiana has a significant forest industry with many residual products that could be used as locally available amendments to meet this goal. However, the mechanisms mediating how amendments induce disease suppressive activity in soil are not well understood, which currently limits their practical application as a disease control strategy. The objective of the experiments described in this thesis were to: (i) determine whether commercially available forest industry byproducts with different compositions and expected rates of decomposition, could suppress Phytophthora blight in pepper, and (ii) determine whether changes in soil physiochemical and biological properties were correlated with the suppressive activity of these amendments. In the first study, four forest industry byproducts were evaluated at a rate of 1% total carbon (w/w) soil. Changes in soil moisture, microbial activity and specific microbial taxa that have previously been associated with disease suppressive activity were monitored during a one month incubation period prior to pepper transplant, and changes in soil chemical properties were quantified at the end of the trial. In the second study, five forest industry byproducts were evaluated, each at one of two rates (1% or 3% total carbon (w/w) soil), and in either a high or low organic matter soil. The soils were amended with P. capsici inoculum to ensure sufficient disease pressure, and a variety of soil physiochemical and biological factors were quantified. The amendments tested in these trials included two biochar products and a locally-available compost derived from woody materials, and kraft pine lignin and sawdust generated as direct byproducts of the forest industry. Both experiments were conducted in the greenhouse using field soil collected from sites with recent outbreaks of Phytophthora blight. Results of these studies indicate that many of the amendments altered soil physiochemical properties including soil moisture, pH, nitrogen, magnesium, potassium, and calcium availability, microbial biomass, and microbial activity, particularly in the low organic matter soil. Several amendments also improved pepper root growth, indicating that they have potential to suppress Phytophthora blight. The suppressive activity of the amendments was not consistently correlated with specific soil physiochemical and biological factors, indicating that different mechanisms may be responsible for the suppressive activity induced by the different types of amendments. Results of these studies indicate that forest industry byproducts have potential to improve soil quality and reduce Phytophthora blight, but field trials and cost-benefit analyses will need to be conducted before these products can be recommended to growers. Additional studies that document differences in the biochemical quality of the amendments and quantify changes in microbial community structure using molecular tools are recommended to better understand how these amendments induce disease suppressive activity

On hypergraph Lagrangians

It is conjectured by Frankl and F\"uredi that the $r$-uniform hypergraph with $m$ edges formed by taking the first $m$ sets in the colex ordering of ${\mathbb N}^{(r)}$ has the largest Lagrangian of all $r$-uniform hypergraphs with $m$ edges in \cite{FF}. Motzkin and Straus' theorem confirms this conjecture when $r=2$. For $r=3$, it is shown by Talbot in \cite{T} that this conjecture is true when $m$ is in certain ranges. In this paper, we explore the connection between the clique number and Lagrangians for $r$-uniform hypergraphs. As an implication of this connection, we prove that the $r$-uniform hypergraph with $m$ edges formed by taking the first $m$ sets in the colex ordering of ${\mathbb N}^{(r)}$ has the largest Lagrangian of all $r$-uniform graphs with $t$ vertices and $m$ edges satisfying ${t-1\choose r}\leq m \leq {t-1\choose r}+ {t-2\choose r-1}-[(2r-6)\times2^{r-1}+2^{r-3}+(r-4)(2r-7)-1]({t-2\choose r-2}-1)$ for $r\geq 4.$Comment: 10 pages. arXiv admin note: substantial text overlap with arXiv:1312.7529, arXiv:1211.7057, arXiv:1211.6508, arXiv:1311.140

Stochastic Growth with the Social-Status Concern: The Existence of a Unique Stable Distribution

This paper extends Kurz¡¯s (1968) growth model to a stochastic growth framework with the social-status concern and production shocks. Using the stochastic monotonicity of stochastic dynamic system and methods using in Zhang (2007), the existence and stability of invariant distribution has been investigated. Different from the existence of multiple steady states under certainty, it is shown that there exists a unique stable invariant distribution under uncertainty.Stochastic growth, the Spirit of capitalism, Stochastic dominance, Multiple equilibria

Evolutionary Game for Mining Pool Selection in Blockchain Networks

In blockchain networks adopting the proof-of-work schemes, the monetary incentive is introduced by the Nakamoto consensus protocol to guide the behaviors of the full nodes (i.e., block miners) in the process of maintaining the consensus about the blockchain state. The block miners have to devote their computation power measured in hash rate in a crypto-puzzle solving competition to win the reward of publishing (a.k.a., mining) new blocks. Due to the exponentially increasing difficulty of the crypto-puzzle, individual block miners tends to join mining pools, i.e., the coalitions of miners, in order to reduce the income variance and earn stable profits. In this paper, we study the dynamics of mining pool selection in a blockchain network, where mining pools may choose arbitrary block mining strategies. We identify the hash rate and the block propagation delay as two major factors determining the outcomes of mining competition, and then model the strategy evolution of the individual miners as an evolutionary game. We provide the theoretical analysis of the evolutionary stability for the pool selection dynamics in a case study of two mining pools. The numerical simulations provide the evidence to support our theoretical discoveries as well as demonstrating the stability in the evolution of miners' strategies in a general case.Comment: Submitted to IEEE Wireless Communication Letter

A self-assembling peptide RADA16-I integrated with spider fibroin uncrystalline motifs

Mechanical strength of nanofiber scaffolds formed by the self-assembling peptide RADA16-I or its derivatives is not very good and limits their application. To address this problem, we inserted spidroin uncrystalline motifs, which confer incomparable elasticity and hydrophobicity to spider silk GGAGGS or GPGGY, into the C-terminus of RADA16-I to newly design two peptides: R3 (n-RADARADARADARADA-GGAGGS-c) and R4 (n-RADARADARADARADA-GPGGY-c), and then observed the effect of these motifs on biophysical properties of the peptide. Atomic force microscopy, transmitting electron microscopy, and circular dichroism spectroscopy confirm that R3 and R4 display ß-sheet structure and self-assemble into long nanofibers. Compared with R3, the ß-sheet structure and nanofibers formed by R4 are more stable; they change to random coil and unordered aggregation at higher temperature. Rheology measurements indicate that novel peptides form hydrogel when induced by DMEM, and the storage modulus of R3 and R4 hydrogel is 0.5 times and 3 times higher than that of RADA16-I, respectively. Furthermore, R4 hydrogel remarkably promotes growth of liver cell L02 and liver cancer cell SMCC7721 compared with 2D culture, determined by MTT assay. Novel peptides still have potential as hydrophobic drug carriers; they can stabilize pyrene microcrystals in aqueous solution and deliver this into a lipophilic environment, identified by fluorescence emission spectra. Altogether, the spider fibroin motif GPGGY most effectively enhances mechanical strength and hydrophobicity of the peptide. This study provides a new method in the design of nanobiomaterials and helps us to understand the role of the amino acid sequence in nanofiber formation