Astronomy using basic Mark 2 very long baseline interferometry

Two experiments were performed in April and September 1976 to determine precise positions of radio sources using conventional Mark 2 VLBI techniques. Four stations in the continental United States observed at a wavelength of 18 cm. The recording bandwidth was 2 MHz. The preliminary results using analyses of fringe rate and delay are discussed and the source positions compared with the results of other measurements

Comparison of VLBI, TV and traveling clock techniques for time transfer

A three part experiment was conducted to develop and compare time transfer techniques. The experiment consisted of (1) a very long baseline interferometer (VLBI), (2) a high precision portable clock time transfer system between the two sites, and (3) a television time transfer. A comparison of the VLBI and traveling clock shows each technique can perform satisfactorily at the five nsec level. There was a systematic offset of 59 nsec between the two methods, which we attributed to a difference in epochs between VLBI formatter and station clock. The VLBI method had an internal random error of one nsec at the three sigma level for a two day period. Thus, the Mark II system performed well, and VLBI shows promise of being an accurate method of time transfer. The TV system, which had technical problems during the experiment, transferred time with a random error of about 50 nsec

The USNO/NRL Green Bank interferometer program

Application of the connected-element radio interferometer of the National Radio Astronomy Observation in Green Bank, West Virginia to the determination of improved source coordinates, astronomical constants, and variations in Earth rotation parameters is discussed. It is concluded that because of the brevity and discontinuity of the data so far no reliable conclusions regarding the accuracy of the data can be drawn

Are Child's Class C Patients With Acute Variceal Bleeding Worth Treating?

In the ten year period January 1980 to December 1989, 102 patients with Child’s Class C liver disease (Pugh's Modification) were admitted with acute variceal bleeding to one surgical unit with a policy of early sclerotherapy. There were 56 males and 46 females; the average age was 55 years (range 28–77). Fifty-three suffered from alcoholic cirrhosis. Four died before definitive treatment could be carried out, three from liver failure and one from uncontrolled bleeding. Of the remaining 98 patients, eight had urgent oesophageal transection with three deaths from hepatorenal failure; 90 had sclerotherapy with 19 hospital deaths, nine from recurrent bleeding, eight from liver failure often coupled with renal failure and two from respiratory complications. Of the 76 who survived to leave hospital, 52 received chronic injection sclerotherapy, 10 had elective oesophageal transection and 14 did not have further elective intervention for various reasons. Surviving patients have been followed up at a special Liver Clinic with minimum follow up of one year. Although no patient has yet survived ten years, the one, five and eight year survivals of 50%, 21% and 13% suggest that salvage of thdse patients is worthwhile

The evolution of genome size in ants

<p>Abstract</p> <p>Background</p> <p>Despite the economic and ecological importance of ants, genomic tools for this family (Formicidae) remain woefully scarce. Knowledge of genome size, for example, is a useful and necessary prerequisite for the development of many genomic resources, yet it has been reported for only one ant species (<it>Solenopsis invicta</it>), and the two published estimates for this species differ by 146.7 Mb (0.15 pg).</p> <p>Results</p> <p>Here, we report the genome size for 40 species of ants distributed across 10 of the 20 currently recognized subfamilies, thus making Formicidae the 4^thmost surveyed insect family and elevating the Hymenoptera to the 5^thmost surveyed insect order. Our analysis spans much of the ant phylogeny, from the less derived Amblyoponinae and Ponerinae to the more derived Myrmicinae, Formicinae and Dolichoderinae. We include a number of interesting and important taxa, including the invasive Argentine ant (<it>Linepithema humile</it>), Neotropical army ants (genera <it>Eciton </it>and <it>Labidus</it>), trapjaw ants (<it>Odontomachus</it>), fungus-growing ants (<it>Apterostigma</it>, <it>Atta </it>and <it>Sericomyrmex</it>), harvester ants (<it>Messor</it>, <it>Pheidole </it>and <it>Pogonomyrmex</it>), carpenter ants (<it>Camponotus</it>), a fire ant (<it>Solenopsis</it>), and a bulldog ant (<it>Myrmecia</it>). Our results show that ants possess small genomes relative to most other insects, yet genome size varies three-fold across this insect family. Moreover, our data suggest that two whole-genome duplications may have occurred in the ancestors of the modern <it>Ectatomma </it>and <it>Apterostigma</it>. Although some previous studies of other taxa have revealed a relationship between genome size and body size, our phylogenetically-controlled analysis of this correlation did not reveal a significant relationship.</p> <p>Conclusion</p> <p>This is the first analysis of genome size in ants (Formicidae) and the first across multiple species of social insects. We show that genome size is a variable trait that can evolve gradually over long time spans, as well as rapidly, through processes that may include occasional whole-genome duplication. The small genome sizes of ants, combined with their ecological, evolutionary and agricultural importance, suggest that some of these species may be good candidates for future whole-genome sequencing projects.</p

Análisis de introgresión en Apis mellifera iberiensis y Apis mellifera mellifera usando polimorfismos de nucleótidos simples (SNPs)

Diferentes estudios han agrupado las subespecies de A. mellifera en cuatro linajes evolutivos basados sobre marcadores morfométricos, ecológicos, microsatélites y mtDNA: Africano (A), Medio Oriente (O), Este y Centro de Europa (C), Norte y Oeste de Europa (M). El linaje M está representado por las subespecies A. m. iberiensis y A. m. mellifera, cuya distribución es la Península Ibérica para la primera y desde los Pirineos hacia el Norte de Europa para la segunda. Durante las últimas décadas, la introducción masiva de subespecies del linaje C por apicultores ha ocasionado un fuerte flujo génico y más aún al casi completo remplazamiento de A. m. mellifera, como ha sido reportado para Alemania. Por tanto, el análisis de niveles de introgresión en programas de crianza y conservación es de vital importancia para evitar la perdida de diversidad genética y sustitución de especies nativas. Este estudio busca identificar los niveles de introgresión de subespecies del linaje C en las subespecies pertenecientes al linaje M a través de un análisis amplio del genoma usando SNPs. Para 711 individuos correspondiente a A. m. iberiensis y 88 individuos A. m. mellifera fueron genotipados 1536 SNPs. Las subespecies de linaje C A. m. ligustica y A. m. carnica fueron usados como poblaciones de referencia. Los niveles de introgresión fueron evaluados usando un método de agrupamiento Bayesiano implementado en el software STRUCTURE. Nuestros resultados indicaron que la introgresión en A. m .iberiensis no es significante, a diferencia en A. m. mellifera que presentó de 8% a 30% de introgresión. Considerando que muchas de las muestras de A. m. mellifera son provenientes de poblaciones integradas en programas de conservación en el Norte de Europa, este resultado evidencia el profundo contraste entre las dos subespecies del linaje M con respecto a su estado de conservación

Genomic and karyotypic variation in Drosophila parasitoids (Hymenoptera, Cynipoidea, Figitidae)

Abstract Drosophila melanogaster Meigen, 1830 has served as a model insect for over a century. Sequencing of the 11 additional Drosophila Fallen, 1823 species marks substantial progress in comparative genomics of this genus. By comparison, practically nothing is known about the genome size or genome sequences of parasitic wasps of Drosophila. Here, we present the first comparative analysis of genome size and karyotype structures of Drosophila parasitoids of the Leptopilina Förster, 1869 and Ganaspis Förster, 1869 species. The gametic genome size of Ganaspis xanthopoda (Ashmead, 1896) is larger than those of the three Leptopilina species studied. The genome sizes of all parasitic wasps studied here are also larger than those known for all Drosophila species. Surprisingly, genome sizes of these Drosophila parasitoids exceed the average value known for all previously studied Hymenoptera. The haploid chromosome number of both Leptopilina heterotoma (Thomson, 1862) and Leptopilina victoriae Nordlander, 1980 is ten. A chromosomal fusion appears to have produced a distinct karyotype for Leptopilina boulardi (Barbotin, Carton et Keiner-Pillault, 1979)(n = 9), whose genome size is smaller than that of wasps of the Leptopilina heterotoma clade. Like Leptopilina boulardi, the haploid chromosome number for Ganaspis xanthopoda is also nine. Our studies reveal a positive, but non linear, correlation between the genome size and total chromosome length in Drosophila parasitoids. These Drosophila parasitoids differ widely in their host range, and utilize different infection strategies to overcome host defense. Their comparative genomics, in relation to their exceptionally well-characterized hosts, will prove to be valuable for understanding the molecular basis of the host-parasite arms race and how such mechanisms shape the genetic structures of insectcommunities

Reduced SNP panels for genetic identification and introgression analysis in the dark honey bee (Apis mellifera mellifera)

Beekeeping activities, especially queen trading, have shaped the distribution of honey bee (Apis mellifera) subspecies in Europe, and have resulted in extensive introductions of two eastern European C-lineage subspecies (A. m. ligustica and A. m. carnica) into the native range of the M-lineage A. m. mellifera subspecies in Western Europe. As a consequence, replacement and gene flow between native and commercial populations have occurred at varying levels across western European populations. Genetic identification and introgression analysis using molecular markers is an important tool for management and conservation of honey bee subspecies. Previous studies have monitored introgression by using microsatellite, PCR-RFLP markers and most recently, high density assays using single nucleotide polymorphism (SNP) markers. While the latter are almost prohibitively expensive, the information gained to date can be exploited to create a reduced panel containing the most ancestry-informative markers (AIMs) for those purposes with very little loss of information. The objective of this study was to design reduced panels of AIMs to verify the origin of A. m. mellifera individuals and to provide accurate estimates of the level of C-lineage introgression into their genome. The discriminant power of the SNPs using a variety of metrics and approaches including the Weir & Cockerham's FST, an FST-based outlier test, Delta, informativeness (In), and PCA was evaluated. This study shows that reduced AIMs panels assign individuals to the correct origin and calculates the admixture level with a high degree of accuracy. These panels provide an essential tool in Europe for genetic stock identification and estimation of admixture levels which can assist management strategies and monitor honey bee conservation programs

Temporal pattern of africanization in a feral honeybee population from Texas inferred from mitochondrial DNA

The invasion of Africanized honeybees (Apis mellifera L.) in the Americas provides a window of opportunity to study the dynamics of secondary contact of subspecies of bees that evolved in allopatry in ecologically distinctive habitats of the Old World. We report here the results of an 11-year mitochondrial DNA survey of a feral honeybee population from southern United States (Texas). The mitochondrial haplotype (mitotype) frequencies changed radically during the 11-year study period. Prior to immigration of Africanized honeybees, the resident population was essentially of eastern and western European maternal ancestry. Three years after detection of the first Africanized swarm there was a mitotype turnover in the population from predominantly eastern European to predominantly A. m. scutellata (ancestor of Africanized honeybees). This remarkable change in the mitotype composition coincided with arrival of the parasitic mite Varroa destructor, which was likely responsible for severe losses experienced by colonies of European ancestry. From 1997 onward the population stabilized with most colonies of A. m. scutellata maternal origin.PRODEP II - Medida 5/Acção 5.

Spatial patterns of single nucleotide polymorphisms (SNPs) support a scenario of secondary contact in Iberian honey bees (Apis mellifera iberiensis)

Dissecting diversity patterns of organisms endemic to Iberia has been truly challenging for a variety of plant and animal taxa, and the Iberian honey bee (A. m. iberiensis) is no exception. Here we used a genome-wide data set of 309 neutrally-tested SNPs, scattered across the 16 honey bee chromosomes, which were genotyped in 711 honey bee individuals. These SNPs were analyzed along with an intergenic locus of the mtDNA. The two markers revealed the existence of a strong and concordant structure supporting a process of secondary contact.We owe special thanks to beekeepers from Spain and Portugal for their valuable help in obtaining samples. Antonio Pajuelo provided the contacts of Spanish beekeepers. DNA extraction and SNP genotyping were performed by Colette Abbey. Special thanks to Margarida Neto, Andreia Brandão and Irene Muñoz for collaborating in the sampling. JC-G and DH are supported by Fundação para a Ciência e Tecnologia (FCT) through the scholarships SFRH/BD/68682/2010 and SFRH/BD/84195/2012, respectively. This research was funded by FCT and COMPETE/QREN/EU through the project PTDC/BIA-BEC/099640/2008 and BiodivERsA-FACCE2014-91.info:eu-repo/semantics/publishedVersio