Genetic crosstalk and its effects on virulence and mating in Ustilago maydis.

Ustilago maydis is a model organism for study of fungal mating and host infection. Two compatible haploid mating types must mate to form a dikaryon in order for the fungus to infect its host, corn (Zea mays). There are a variety of genetic mechanisms that regulate mating and infection in the fungus, many of which coregulate both processes. The aim of this study was to investigate how alteration of certain regulatory proteins in U. maydis affects these basic processes as well as how alteration of genes involved in signaling pathways can affect the expression of one another. Primarily, the focus was on exploring the role of the ptn1 gene. This gene was disrupted and therefore found to be involved in tumorigenesis and teliospore development during infection. Additional disruption of the ust1 and unh1 genes, which play opposite roles in tumorigenesis, was attempted on these ptn1 deletion strains of U. maydis using a high fidelity CRISPR-Cas9 system to examine the influence of these genes on the ptn1 pathway. Further experiments were intended to generate ptn1 deletion mutant strains of U. maydis in which the pdc1 gene, encoding a major protein involved in cellular regulation, was simultaneously overexpressed. Phenotypes of pdc1 overexpression mutants of U. maydis were examined for both effects on U. maydis cells in culture and during plant infection. Ptn1 deletion strains were found to be more susceptible to cell wall stress, displayed lesser aerial hyphae formation during mating, and showed reduced infection symptoms including reduced tumor size and reduced number of tumors. Overexpression of pdc1 led to no changes in mating or virulence in wild type strains but may exert an added effect on ptn1 deletion strains and their corresponding phenotypes

The muddled middle of management

In management, there are rather simple principles that impact the work on an individual basis as well as simple principles on a large scale that define a company’s organizational basis. Yet much available management material focuses on the activities at the scale of middle managers, though it is not entirely clear it creates the desired effect or pushes organizations in the right direction. Process changes aimed at the muddled middle incur costs to implement and often offer no clear indication that a benefit equivalent to the cost was realized. Such initiatives and corresponding data can bog down organizations

Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses

Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources

Magnetic coupling in neutral and charged Cr-2, Mn-2, and CrMn dimers

Theoreticalab initio studies of neutral, cationic and anionic Cr2, Mn2, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr2 and Cr−2 have antiferromagnetically coupled atomic spins, Cr+2 has a ferromagneticground state closely followed by an antiferromagnetic state. On the other hand, all Mn2 dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available calculations and experiments and the difficulties associated with theoretical description and the experimental interpretations are discussed

Generative Dynamics of Supreme Court Citations : Analysis with a New Statistical Network Model

The significance and influence of U.S. Supreme Court majority opinions derive in large part from opinions' roles as precedents for future opinions. A growing body of literature seeks to understand what drives the use of opinions as precedents through the study of Supreme Court case citation patterns. We raise two limitations of existing work on Supreme Court citations. First, dyadic citations are typically aggregated to the case level before they are analyzed. Second, citations are treated as if they arise independently. We present a methodology for studying citations between Supreme Court opinions at the dyadic level, as a network, that overcomes these limitations. This methodology - the citation exponential random graph model, for which we provide user-friendly software - enables researchers to account for the effects of case characteristics and complex forms of network dependence in citation formation. We then analyze a network that includes all Supreme Court cases decided between 1950 and 2015. We find evidence for dependence processes, including reciprocity, transitivity, and popularity. The dependence effects are as substantively and statistically significant as the effects of exogenous covariates, indicating that models of Supreme Court citations should incorporate both the effects of case characteristics and the structure of past citations.Peer reviewe

Generative Dynamics of Supreme Court Citations : Analysis with a New Statistical Network Model

The significance and influence of U.S. Supreme Court majority opinions derive in large part from opinions' roles as precedents for future opinions. A growing body of literature seeks to understand what drives the use of opinions as precedents through the study of Supreme Court case citation patterns. We raise two limitations of existing work on Supreme Court citations. First, dyadic citations are typically aggregated to the case level before they are analyzed. Second, citations are treated as if they arise independently. We present a methodology for studying citations between Supreme Court opinions at the dyadic level, as a network, that overcomes these limitations. This methodology - the citation exponential random graph model, for which we provide user-friendly software - enables researchers to account for the effects of case characteristics and complex forms of network dependence in citation formation. We then analyze a network that includes all Supreme Court cases decided between 1950 and 2015. We find evidence for dependence processes, including reciprocity, transitivity, and popularity. The dependence effects are as substantively and statistically significant as the effects of exogenous covariates, indicating that models of Supreme Court citations should incorporate both the effects of case characteristics and the structure of past citations.Peer reviewe

Management and outcomes of traumatic hemothorax in children

Background: Adult guidelines for the management of traumatic hemothorax are well established; however, there have been no similar studies conducted in the pediatric population. The purpose of our study was to assess the management and outcomes of children with traumatic hemothorax. Materials and Methods: Following Institutional Review Board approval, we conducted a retrospective cross-sectional study of all trauma patients diagnosed with a hemothorax at a Level-1 pediatric trauma center from 2007 to 2012. Results: Forty-six children with hemothorax were identified, 23 from blunt mechanism and 23 from penetrating mechanism. The majority of children injured by penetrating mechanisms were treated with tube thoracostomy while the majority of blunt injury patients were observed (91.3% vs. 30.4% tube thoracostomy, penetrating vs. blunt, P = 0.00002). Among patients suffering from blunt mechanism, children who were managed with chest tubes had a greater volume of hemothorax than those who were observed. All children who were observed underwent serial chest radiographs demonstrating no progression and required no delayed procedures. Children with a hemothorax identified only by computed tomography, after negative plain radiograph, did not require intervention. No child developed a delayed empyema or fibrothorax. Conclusion: The data suggest that a small-volume hemothorax resulting from blunt mechanism may be safely observed without mandatory tube thoracostomy and with overall low complication rates