Dielectric map of the Martian northern hemisphere and the nature of plain filling materials

[1] A number of observations suggest that an extended ocean once covered a significant part of the Martian northern hemisphere. By probing the physical properties of the subsurface to unprecedented depth, the MARSIS/Mars Express provides new geophysical evidences for the former existence of a Late Hesperian ocean. The Vastitas Borealis formation, located inside a putative shoreline of the ancient ocean, has a low dielectric constant compared with that of typical volcanic materials. We show that the measured value is only consistent with low-density sedimentary deposits, massive deposits of ground-ice, or a combination of the two. In contrast, radar observations indicate a distribution of shallow ground ice in equilibrium with the atmosphere in the south polar region. We conclude that the northern plains are filled with remnants of a late Hesperian ocean, fed by water and sediments from the outflow channels about 3 Gy ago.

A high-resolution comparative radiation hybrid map of equine chromosome 4q12-q22

In this study, we present a comprehensive 5000-rad radiation hybrid map of a 40-cM region on equine chromosome 4 (ECA4) that contains quantitative trait loci for equine osteochondrosis. We mapped 29 gene-associated sequence tagged site markers using primers designed from equine expressed sequence tags or BAC clones in the ECA4q12-q22 region. Three blocks of conserved synteny, showing two chromosomal breakpoints, were identified in the segment of ECA4q12-q22. Markers from other segments of HSA7q mapped to ECA13p and ECA4p, and a region of HSA7p was homologous to ECA13p. Therefore, we have improved the resolution of the human-equine comparative map, which allows the identification of candidate genes underlying traits of interest.

A human-horse comparative map based on equine BAC end sequences

In an effort to increase the density of sequence-based markers for the horse genome we generated 9473 BAC end sequences (BESs) from the CHORI-241 BAC library with an average read length of 677 bp. BLASTN searches with the BESs revealed 4036 meaningful hits (E map. The 4036 BLASTN hits allowed the anchoring of 3079 BAC clones to the human genome, on average one corresponding equine BAC clone per megabase of human DNA. We used the BLASTN anchored BESs for an in silico prediction of the gene content and chromosome assignment of comparatively mapped equine BAC clones. As a first verification of our in silico mapping strategy we placed 19 equine BESs with matches to HSA6 onto the RH map. All markers were assigned to the predicted localizations on ECA10, ECA20, and ECA31, respectively.

Single linkage group per chromosome genetic linkage map for the horse, based on two three-generation, full-sibling, crossbred horse reference families

A genetic linkage map of the horse consisting of 742 markers, which comprises a single linkage group for each of the autosomes and the X chromosome, is presented. The map has been generated from two three-generation full-sibling reference families, sired by the same stallion, in which there are 61 individuals in the F2 generation. Each linkage group has been assigned to a chromosome and oriented with reference to markers mapped by fluorescence in situ hybridization. The average interval between markers is 3.7 cM and the linkage groups collectively span 2772 cM. The 742 markers comprise 734 microsatellite and 8 gene-based markers. The utility of the microsatellite markers for comparative mapping has been significantly enhanced by comparing their flanking sequences with the human genome sequence; this enabled conserved segments between human and horse to be identified. The new map provides a valuable resource for genetically mapping traits of interest in the horse.

A second generation radiation hybrid map to aid the assembly of the bovine genome sequence

BACKGROUND: Several approaches can be used to determine the order of loci on chromosomes and hence develop maps of the genome. However, all mapping approaches are prone to errors either arising from technical deficiencies or lack of statistical support to distinguish between alternative orders of loci. The accuracy of the genome maps could be improved, in principle, if information from different sources was combined to produce integrated maps. The publicly available bovine genomic sequence assembly with 6x coverage (Btau_2.0) is based on whole genome shotgun sequence data and limited mapping data however, it is recognised that this assembly is a draft that contains errors. Correcting the sequence assembly requires extensive additional mapping information to improve the reliability of the ordering of sequence scaffolds on chromosomes. The radiation hybrid (RH) map described here has been contributed to the international sequencing project to aid this process. RESULTS: An RH map for the 30 bovine chromosomes is presented. The map was built using the Roslin 3000-rad RH panel (BovGen RH map) and contains 3966 markers including 2473 new loci in addition to 262 amplified fragment-length polymorphisms (AFLP) and 1231 markers previously published with the first generation RH map. Sequences of the mapped loci were aligned with published bovine genome maps to identify inconsistencies. In addition to differences in the order of loci, several cases were observed where the chromosomal assignment of loci differed between maps. All the chromosome maps were aligned with the current 6x bovine assembly (Btau_2.0) and 2898 loci were unambiguously located in the bovine sequence. The order of loci on the RH map for BTA 5, 7, 16, 22, 25 and 29 differed substantially from the assembled bovine sequence. From the 2898 loci unambiguously identified in the bovine sequence assembly, 131 mapped to different chromosomes in the BovGen RH map. CONCLUSION: Alignment of the BovGen RH map with other published RH and genetic maps showed higher consistency in marker order and chromosome assignment than with the current 6x sequence assembly. This suggests that the bovine sequence assembly could be significantly improved by incorporating additional independent mapping information.

Distribution Map

Understanding large software systems is a challenging task, and to support it many approaches have been developed. Often, the result of these approaches categorize existing entities into new groups or associates them with mutually exclusive properties. In this paper we present the Distribution Map as a generic technique to visualize and analyze this type of result. Our technique is based on the notion of focus, which shows whether a property is well-encapsulated or cross-cutting, and the notion of spread, which shows whether the property is present in several parts of the system. We present a basic visualization and complement it with measurements that quantify focus and spread. To validate our technique we show evidence of applying it on the result sets of different analysis approaches. As a conclusion we propose that the Distribution Map technique should belong to any reverse engineering toolkit.

On the postnatal development of the striate cortex (V1) in the tree shrew (Tupaia belangeri)

Histological serial sections, three-dimensional reconstructions and morphometry served to study the postnatal development of V1 in tree shrews. The main objectives were to evaluate the expansion of V1, the implications of its growth on the occipital cortex and, vice versa, the effects of the expanding neocortex on the topography of V1. The future V1 was identified on postnatal day 1 by its granular layer IV, covering the superior surface of the occipital cortices including the poles. A subdivision of layer IV, distinctive for the binocular part, was evident in the central region. V1 expanded continuously with age into all directions succeeded by the maturation of layering. The monocular part was recognized from day 15 onward, after the binocular part had reached its medial border. In reference to the retinotopic map of V1, regions emerged in a coherent temporo-spatial sequence delineating the retinal topography in a central to peripheral gradient beginning with the visual streak representation. The growth of V1 was greatest until tree shrews open their eyes, culminated during adolescence, and completed after a subsequent decrease in the young adult. Simultaneous expansion of the neocortex induced a shifting of V1. Translation and elongation of V1 entailed that the occipital cortex covered the superior colliculi along with a downward rotation of the poles. The enlargement of the occipital part of the hemispheres was in addition associated with the formation of a small occipital horn in the lateral ventricles, indicating an incipient 'true' occipital lobe harbouring mainly cortices involved in visual functions.

A radiation hybrid map of sheep chromosome 23 based on ovine BAC-end sequences

More than 375,000 BAC-end sequences (BES) of the CHORI-243 ovine BAC library have been deposited in public databases. blastn searches with these BES against HSA18 revealed 1806 unique and significant hits. We used blastn-anchored BES for an in silico prediction of gene content and chromosome assignment of comparatively mapped ovine BAC clones. Ovine BES were selected at approximately 1.3-Mb intervals of HSA18 and incorporated into a human-sheep comparative map. An ovine 5000-rad whole-genome radiation hybrid panel (USUoRH5000) was typed with 70 markers, all of which mapped to OAR23. The resulting OAR23 RH map included 43 markers derived from BES with high and unique BLAST hits to the sequence of the orthologous HSA18, nine EST-derived markers, 16 microsatellite markers taken from the ovine linkage map and two bovine microsatellite markers. Six new microsatellite markers derived from the 43 mapped BES and the two bovine microsatellite markers were linkage-mapped using the International Mapping Flock (IMF). Thirteen additional microsatellite markers were derived from other ovine BES with high and unique BLAST hits to the sequence of the orthologous HSA18 and also positioned on the ovine linkage map but not incorporated into the OAR23 RH map. This resulted in 24 markers in common and in the same order between the RH and linkage maps. Eight of the BES-derived markers were mapped using fluorescent in situ hybridization (FISH), to thereby align the RH and cytogenetic maps. Comparison of the ovine chromosome 23 RH map with the HSA18 map identified and localized three major breakpoints between HSA18 and OAR23. The positions of these breakpoints were equivalent to those previously shown for syntenic BTA24 and HSA18. This study presents evidence for the usefulness of ovine BES when constructing a high-resolution comprehensive map for a single sheep chromosome. The comparative analysis confirms and refines knowledge about chromosomal conservation and rearrangements between sheep, cattle and human. The constructed RH map demonstrates the resolution and utility of the newly constructed ovine RH panel.

An Isopach Map and Discussion of the Marine Jurassic of Western United Sates and Canada

Recent demands for petroleum to carry on the war effort have resulted in widespread prospecting in the northern Great Plains. Nearly all oil wells now drilled are of a depth to penetrate the marine Jurassic formations. It is known that these strata differ in thickness from place to place, but information of distribution, thickness, and lithology has not yet been compiled.

A Discussion of the Geology and an Isopach Map of the Pennsylvanian System in Wyoming and Adjacent Areas

Pennsylvanian strata in Wyoming and adjacent areas have been the subject of much work and discussion. Most of the work has been due to the economic importance of the system as an oil producer in this region. Oil production from strata of Pennsylvanian age is rather recent history; and therefore, much of the available information is local­ized and incomplete.