Toward the total synthesis of spirastrellolide A. Part 3: Intelligence gathering and preparation of a ring-expanded analogue

Different methods for the formation of the C.25–C.26 bond of spirastrellolide A (1) are evaluated that might qualify for the end game of the projected total synthesis, with emphasis on metathetic ways to forge the macrocyclic frame

Effects of No-tillage Fallow as Compared to Conventional Tillage in a Wheat-fallow System

The benefits of reducing tillage by use of herbicides for weed control emphasizes why research was started to study a fallow system where all tillage was replaced by herbicides. Wheat planting was then the only soil disturbing operation. Objectives of the research were to compare the effects of no-tillage (chemical), stubble-mulch and plow (bare fallow) systems of fallow on: 1. Grain yield. 2. Grain protein. 3. Residue retention. 4. Soil nitrate-nitrogen accumulation. 5. Soil water accumulations during fallow. Data presented are in the form of a progress report. These experiments will continue

Toward the Total Synthesis of Spirastrellolide A. Part 2: Conquest of the Northern Hemisphere

North and South: The unique biological activity of the natural product spirastrellolide A renders it an attractive lead for anticancer agents. The southern hemisphere (C1–C25) and the northern hemisphere (including the chlorinated [5,6,6]-bis-spiroacetal entity and the lateral C42–C47 chain) are prepared by concise and efficient routes. Consequently, the entire carbon framework of this potent phosphatase inhibitor, which contains 21 chiral centers, is prepared in an optically active form, and an important step toward structure determination by total synthesis is achieved

Toward the Total Synthesis of Spirastrellolide A. Part 1: Strategic Considerations and Preparation of the Southern Domain

North and South: The unique biological activity of the natural product spirastrellolide A renders it an attractive lead for anticancer agents. The southern hemisphere (C1–C25) and the northern hemisphere (including the chlorinated [5,6,6]-bis-spiroacetal entity and the lateral C42–C47 chain) are prepared by concise and efficient routes. Consequently, the entire carbon framework of this potent phosphatase inhibitor, which contains 21 chiral centers, is prepared in an optically active form, and an important step toward structure determination by total synthesis is achieved

Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years

Fertilizer Urea

This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Reproducibility of 3-dimensional ultrasound readings of volume of carotid atherosclerotic plaque

<p>Abstract</p> <p>Background</p> <p>Non-invasive 3-dimensional (3D) ultrasound (US) has emerged as the predominant approach for evaluating the progression of carotid atherosclerosis and its response to treatment. The aim of this study was to investigate the quality of a central reading procedure concerning plaque volume (PV), measured by 3D US in a multinational US trial.</p> <p>Methods</p> <p>Two data sets of 45 and 60 3D US patient images of plaques (mean PV, 71.8 and 39.8 μl, respectively) were used. PV was assessed by means of manual planimetry. The intraclass correlation coefficient (ICC) was applied to determine reader variabilities. The repeatability coefficient (RC) and the coefficient of variation (CV) were used to investigate the effect of number of slices (S) in manual planimetry and plaque size on measurement variability.</p> <p>Results</p> <p>Intra-reader variability was small as reflected by ICCs of 0.985, 0.967 and 0.969 for 3 appointed readers. The ICC value generated between the 3 readers was 0.964, indicating that inter-reader variability was small, too. Subgroup analyses showed that both intra- and inter-reader variabilities were lower for larger than for smaller plaques. Mean CVs were similar for the 5S- and 10S-methods with a RC of 4.7 μl. The RC between both methods as well as the CVs were comparatively lower for larger plaques.</p> <p>Conclusion</p> <p>By implementing standardised central 3D US reading protocols and strict quality control procedures highly reliable ultrasonic re-readings of plaque images can be achieved in large multicentre trials.</p

The role of asymmetric interactions on the effect of habitat destruction in mutualistic networks

Plant-pollinator mutualistic networks are asymmetric in their interactions: specialist plants are pollinated by generalist animals, while generalist plants are pollinated by a broad involving specialists and generalists. It has been suggested that this asymmetric ---or disassortative--- assemblage could play an important role in determining the equal susceptibility of specialist and generalist plants under habitat destruction. At the core of the argument lies the observation that specialist plants, otherwise candidates to extinction, could cope with the disruption thanks to their interaction with generalist pollinators. We present a theoretical framework that supports this thesis. We analyze a dynamical model of a system of mutualistic plants and pollinators, subject to the destruction of their habitat. We analyze and compare two families of interaction topologies, ranging from highly assortative to highly disassortative ones, as well as real pollination networks. We found that several features observed in natural systems are predicted by the mathematical model. First, there is a tendency to increase the asymmetry of the network as a result of the extinctions. Second, an entropy measure of the differential susceptibility to extinction of specialist and generalist species show that they tend to balance when the network is disassortative. Finally, the disappearance of links in the network, as a result of extinctions, shows that specialist plants preserve more connections than the corresponding plants in an assortative system, enabling them to resist the disruption.Comment: 14 pages, 7 figure

Total Synthesis of Spirastrellolide F Methyl Ester—Part 2: Macrocyclization and Completion of the Synthesis

Marvel of the sea: A concise and highly convergent total synthesis of the methyl ester of the marine macrolide spirastrellolide F (see picture), which has exquisite antimitotic properties, is reported. In this approach, the northern and the southern hemispheres of this intricate target are stitched together in only two consecutive steps (Suzuki coupling, Yamaguchi lactonization) without any interim protecting-group manipulations

Information is Power? Transparency and fetishism in International Relations

International actors, state and non-state, have embraced transparency as a solution to all manner of political problems. Theoretical analyses of these processes present transparency in a fetishtic manner, in which the social relations that generate transparency are misrecognized as the product of information itself. This paper will outline the theoretical problems that arise when transparency promotion is fetishized in International Relations theory. Examining the fetishism of transparency, we will note problematic conception of politics, the public sphere, and rationality they articulate. Confusing the relationship between data, information and knowledge, fetishized treatments of transparency muddy the historical dynamics responsible for the emergence of transparency as a political practice. This alters our understanding of the relationship between global governance institutions, their constituents, and the nature of knowledge production itself. Realizing the normative promise of transparency requires a reorientation of theoretical practice towards sociologically and historically sensitive approaches to the politics of knowledge