Engineered surfaces to control secondary electron emission for multipactor suppression

A significant problem for space-based systems is multipactor - an avalanche of electrons caused by repeated secondary electron emission (SEE). The consequences of multipactor range from altering the operation of radio frequency (RF) devices to permanent device damage. Existing efforts to suppress multipactor rely heavily on limiting power levels below a multipactor threshold [1]. This research applies surface micromachining techniques to create porous surfaces to control the secondary electron yield (SEY) of a material for multipactor suppression. Surface characteristics of interest include pore aspect ratio and density. A discussion is provided on the advantage of using electroplating (vice etching) to create porous surfaces for studying the relationships between SEY and pore aspect ratio & density (i.e. porosity). Preventing multipactor through SEY reduction will allow power level restrictions to be eased, leading to more powerful and capable space-based systems

First Occurrence of Chain Pickerel (Esox niger) in Ontario: Possible Range Expansion from New York Waters of Eastern Lake Ontario

In this paper, we document the first Chain Pickerel (Esox niger) collected in Ontario and the first on the northwestern side of the St. Lawrence River in Canada. The fish was caught by a local commercial fisherman in April 2008. Since 2008, five additional specimens have been caught and are also documented here: three in 2009 and two more through spring 2010. All individuals were mature adults in robust condition. The appearance of Chain Pickerel in the Ontario waters of eastern Lake Ontario and the upper St. Lawrence River may signal an expansion in the range of this species from New York state waters

Negro Segregation in Nebraska Schools — 1860 to 1870

During the October 1952 Term of the Supreme Court of the United States, the Court heard oral argument in five cases involving attacks under the Fourteenth Amendment upon the practice of segregating Negroes in public schools in various states. On June 8, 1953, the Supreme Court restored the cases to the docket and assigned them for reargument on October 12, 1953, which date was later extended to December 7, 1953, at the request of the Attorney General of the United States. The Court requested counsel to discuss particularly five questions.\u27 The first two were: 1. What evidence is there that the Congress which submitted and the State legislatures and conventions which ratified the Fourteenth Amendment contemplated or did not contemplate, understood or did not understand, that it would abolish segregation in public schools? 2. If neither the Congress in submitting nor the States in ratifying the Fourteenth Amendment understood that compliance with it would require immediate abolition of segregation in public schools, was it nevertheless the understanding of the framers of the Amendment a. that future Congresses might, in the exercise of their power under section 5 of the Amendment, abolish such segregation, or b. that it would be within the judicial power, in light of future conditions, to construe the amendment as abolishing such segregation of its own force? In order to accomplish the large research task necessary to answer these questions, counsel for the Negro petitioners secured assistance from persons in each of the thirty-six states which ratified the Fourteenth Amendment. It was requested that the research cover such facts as: whether or not public schools existed in the state at the time the Amendment was ratified; what treatment was accorded Negroes under the statutes and constitutions at that time; what legislative history there was concerning the actual ratification of the Amendment by the state; and the situation with respect to Negroes immediately after the state ratified the Amendment. The writers undertook to answer these questions for the State of Nebraska and the following is the result of their research. I. Introduction II. Ratification of the Fourteenth Amendment III. Constitution of Nebraska IV. School Laws V. Conclusio

Negro Segregation in Nebraska Schools — 1860 to 1870

During the October 1952 Term of the Supreme Court of the United States, the Court heard oral argument in five cases involving attacks under the Fourteenth Amendment upon the practice of segregating Negroes in public schools in various states. On June 8, 1953, the Supreme Court restored the cases to the docket and assigned them for reargument on October 12, 1953, which date was later extended to December 7, 1953, at the request of the Attorney General of the United States. The Court requested counsel to discuss particularly five questions.\u27 The first two were: 1. What evidence is there that the Congress which submitted and the State legislatures and conventions which ratified the Fourteenth Amendment contemplated or did not contemplate, understood or did not understand, that it would abolish segregation in public schools? 2. If neither the Congress in submitting nor the States in ratifying the Fourteenth Amendment understood that compliance with it would require immediate abolition of segregation in public schools, was it nevertheless the understanding of the framers of the Amendment a. that future Congresses might, in the exercise of their power under section 5 of the Amendment, abolish such segregation, or b. that it would be within the judicial power, in light of future conditions, to construe the amendment as abolishing such segregation of its own force? In order to accomplish the large research task necessary to answer these questions, counsel for the Negro petitioners secured assistance from persons in each of the thirty-six states which ratified the Fourteenth Amendment. It was requested that the research cover such facts as: whether or not public schools existed in the state at the time the Amendment was ratified; what treatment was accorded Negroes under the statutes and constitutions at that time; what legislative history there was concerning the actual ratification of the Amendment by the state; and the situation with respect to Negroes immediately after the state ratified the Amendment. The writers undertook to answer these questions for the State of Nebraska and the following is the result of their research. I. Introduction II. Ratification of the Fourteenth Amendment III. Constitution of Nebraska IV. School Laws V. Conclusio

Tidal stirring and the origin of dwarf spheroidals in the Local Group

N-Body/SPH simulations are used to study the evolution of dwarf irregular galaxies (dIrrs) entering the dark matter halo of the Milky Way or M31 on plunging orbits. We propose a new dynamical mechanism driving the evolution of gas rich, rotationally supported dIrrs, mostly found at the outskirts of the Local Group (LG), into gas free, pressure supported dwarf spheroidals (dSphs) or dwarf ellipticals (dEs), observed to cluster around the two giant spirals. The initial model galaxies are exponential disks embedded in massive dark matter halos and reproduce nearby dIrrs. Repeated tidal shocks at the pericenter of their orbit partially strip their halo and disk and trigger dynamical instabilities that dramatically reshape their stellar component. After only 2-3 orbits low surface brightness (LSB) dIrrs are transformed into dSphs, while high surface brightness (HSB) dIrrs evolve into dEs. This evolutionary mechanism naturally leads to the morphology-density relation observed for LG dwarfs. Dwarfs surrounded by very dense dark matter halos, like the archetypical dIrr GR8, are turned into Draco or Ursa Minor, the faintest and most dark matter dominated among LG dSphs. If disks include a gaseous component, this is both tidally stripped and consumed in periodic bursts of star formation. The resulting star formation histories are in good qualitative agreement with those derived using HST color-magnitude diagrams for local dSphs.Comment: 5 pages, 5 figures, to appear on ApJL. Simulation images and movies can be found at the Local Group web page at http://pcblu.uni.mi.astro.it/~lucio/LG/LG.htm

Rings Reconcile Genotypic and Phenotypic Evolution within the Proteobacteria.

Although prokaryotes are usually classified using molecular phylogenies instead of phenotypes after the advent of gene sequencing, neither of these methods is satisfactory because the phenotypes cannot explain the molecular trees and the trees do not fit the phenotypes. This scientific crisis still exists and the profound disconnection between these two pillars of evolutionary biology--genotypes and phenotypes--grows larger. We use rings and a genomic form of goods thinking to resolve this conundrum (McInerney JO, Cummins C, Haggerty L. 2011. Goods thinking vs. tree thinking. Mobile Genet Elements. 1:304-308; Nelson-Sathi S, et al. 2015. Origins of major archaeal clades correspond to gene acquisitions from bacteria. Nature 517:77-80). The Proteobacteria is the most speciose prokaryotic phylum known. It is an ideal phylogenetic model for reconstructing Earth's evolutionary history. It contains diverse free living, pathogenic, photosynthetic, sulfur metabolizing, and symbiotic species. Due to its large number of species (Whitman WB, Coleman DC, Wiebe WJ. 1998. Prokaryotes: the unseen majority. Proc Nat Acad Sci U S A. 95:6578-6583) it was initially expected to provide strong phylogenetic support for a proteobacterial tree of life. But despite its many species, sequence-based tree analyses are unable to resolve its topology. Here we develop new rooted ring analyses and study proteobacterial evolution. Using protein family data and new genome-based outgroup rooting procedures, we reconstruct the complex evolutionary history of the proteobacterial rings (combinations of tree-like divergences and endosymbiotic-like convergences). We identify and map the origins of major gene flows within the rooted proteobacterial rings (P < 3.6 × 10(-6)) and find that the evolution of the "Alpha-," "Beta-," and "Gammaproteobacteria" is represented by a unique set of rings. Using new techniques presented here we also root these rings using outgroups. We also map the independent flows of genes involved in DNA-, RNA-, ATP-, and membrane- related processes within the Proteobacteria and thereby demonstrate that these large gene flows are consistent with endosymbioses (P < 3.6 × 10(-9)). Our analyses illustrate what it means to find that a gene is present, or absent, within a gene flow, and thereby clarify the origin of the apparent conflicts between genotypes and phenotypes. Here we identify the gene flows that introduced photosynthesis into the Alpha-, Beta-, and Gammaproteobacteria from the common ancestor of the Actinobacteria and the Firmicutes. Our results also explain why rooted rings, unlike trees, are consistent with the observed genotypic and phenotypic relationships observed among the various proteobacterial classes. We find that ring phylogenies can explain the genotypes and the phenotypes of biological processes within large and complex groups like the Proteobacteria

Surface Feature Engineering through Nanosphere Lithography

How surface geometries can be selectively manipulated through nanosphere lithography (NSL) is discussed. Self-assembled monolayers and multilayers of nanospheres have been studied for decades and have been applied to lithography for almost as long. When compared to the most modern, state-of-the-art techniques, NSL offers comparable feature resolution with many advantages over competing technologies