Rock Magnetic and Remanence Properties of Both Synthetic Martian Basaltic Intrusions and Dropstones Along the East Antarctic Margin, to Aid in the Understanding of the Carriers of Crustal Magnetic Anomalies

This thesis examines potential carriers of magnetic anomalies found in remote areas where direct sampling is impossible. The areas examined are the southern hemisphere of Mars and the East Antarctic Margin. We examine the rock magnetic and remanence properties of synthetic Mars basalts and Antarctic dropstones, to predict the type and intensity of anomaly they would produce. The anomalies measured within the Martian crust are entirely remanent magnetization and are remarkably orders of magnitude stronger than the strongest terrestrial anomaly. Two basalt compositions denoted M-type and T-type, deemed relevant to the crust of Mars, were synthesized to examine contrasts in rock magnetic and remanence properties following identical thermal histories and oxygen fugacity conditions. We examine the magnetic mineral assemblages produced and assess if they are efficient remanence carriers. The composition denoted T-type is rich in Al and poor in Fe, reflecting constraints provided by thermal emission spectroscopy that the Martian crust is somewhat terrestrial in character. The M-type composition is poor in Al and rich in Fe, reflecting the composition of basaltic liquid in equilibrium with Martian meteorite phase assemblages. The two compositions are identical with respect to MgO, SÌO2 , and TÌO2 . Batches of each composition were cooled from above 1200 °C to 1070 °C at 4 °C/h and annealed at 1070°C for 100 h, then quenched. Samples were then held at 650°C for periods ranging from 21 to 158 days under quartz-fayalite-magnetite (QFM)/02 buffer conditions, then quenched. The experimental conditions are germane to shallow igneous intrusions, which might be a significant volumetric fraction of the Martian crust and potential carriers of crustal magnetic anomalies, and provide an important contrast to a previous set of fast-cooled (3-230 °C/h) basalts our group performed on the same two compositions. M-type samples contain Fe-Ti-Al-Mg oxide grains 40-50 pm in diameter with skeletal and equant euhedral morphologies. T-type samples contain equant euhedral Fe- Ti-Al-Mg oxides with grain diameters ranging from 15-30 pm as well as elongated anhedral ilmenite grains. For M-type samples both the starting material and the samples annealed at 650 °C have narrow multidomain hysteresis loops. T-type starting materials and samples annealed at 650 °C have pseudo single domain (PSD) hysteresis loops, but the annealed samples plot lower and to the right within the PSD field on a Day plot, indicating coarser magnetic grains. Alternating field demagnetization of anhysteretic remanent magnetization (ARM) shows median destructive fields \u3c 10 mT. M-type samples exhibited higher magnetic susceptibility and intensity of remanence than T-type samples. Both M-type and T-type samples carry an intense natural remanent magnetization (NRM). The NRM is inferred to be a thermoremanent magnetization (TRM) acquired during quenching and air-cooling after the 650 °C anneal. NRM values range from 0.03 to 170 mAm2/kg for M-type samples and 0.005 to 47 mAm2/kg for Ttype samples, values comparable to those observed in rapidly cooled synthetic basalts of the same chemical composition. However, the slow- cooled samples have a much “softer” coercivity spectrum. The multi-domain magnetic mineral assemblage suggests that while intrusions generated by slow-cooled basaltic melts are capable of carrying intense TRMs they may be less stable over geologic time. The second portion of this study presents a catalog of the magnetic and petrographic properties of dropstones collected by United States Antarctic Program cruise NBP01-01. These dropstones provide direct samples of the subglacial geology and provide a range of susceptibility values, intensity of natural remanent magnetization, and description of the carriers of magnetization, which can help in the interpretation of magnetic anomaly surveys. Samples were collect in three main regions along the East Antarctic Margin, including the George V Coast, Prydz Bay, and MacRobertson Land. The samples are examined and classified optically through thin section analysis, and characterized magnetically through magnetic susceptibility, natural remanent magnetization, magnetic hysteresis, scanning electron microscopy and thermomagnetic measurements. The potential for each sample to generate a dominant induced or remnant magnetization was calculated using the Koenigsberger ratio, Q; where Q = Total Remnant Magnetization / Total Induced Magnetization. The majority of magnetic minerals are found in low abundances (\u3c1%) in granitic and metamorphic rocks and displayed Q values less than 1, suggesting they would produce induced dominated anomalies. The exception to this are two mafic igneous rocks, vesicular basalt and dolerite, that possess single domain magnetic minerals and recorded remanences several orders of magnitude higher than other east Antarctic rock types

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Comparative genomics reveals mobile pathogenicity chromosomes in Fusarium

International audienceFusarium species are among the most important phytopathogenic and toxigenic fungi. To understand the molecular underpinnings of pathogenicity in the genus Fusarium, we compared the genomes of three phenotypically diverse species: Fusarium graminearum, Fusarium verticillioides and Fusarium oxysporum f. sp. lycopersici. Our analysis revealed lineage-specific (LS) genomic regions in F. oxysporum that include four entire chromosomes and account for more than one-quarter of the genome. LS regions are rich in transposons and genes with distinct evolutionary profiles but related to pathogenicity, indicative of horizontal acquisition. Experimentally, we demonstrate the transfer of two LS chromosomes between strains of F. oxysporum, converting a non-pathogenic strain into a pathogen. Transfer of LS chromosomes between otherwise genetically isolated strains explains the polyphyletic origin of host specificity and the emergence of new pathogenic lineages in F. oxysporum. These findings put the evolution of fungal pathogenicity into a new perspective

Standardized Metadata for Human Pathogen/Vector Genomic Sequences

<div><p>High throughput sequencing has accelerated the determination of genome sequences for thousands of human infectious disease pathogens and dozens of their vectors. The scale and scope of these data are enabling genotype-phenotype association studies to identify genetic determinants of pathogen virulence and drug/insecticide resistance, and phylogenetic studies to track the origin and spread of disease outbreaks. To maximize the utility of genomic sequences for these purposes, it is essential that metadata about the pathogen/vector isolate characteristics be collected and made available in organized, clear, and consistent formats. Here we report the development of the GSCID/BRC Project and Sample Application Standard, developed by representatives of the Genome Sequencing Centers for Infectious Diseases (GSCIDs), the Bioinformatics Resource Centers (BRCs) for Infectious Diseases, and the U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), informed by interactions with numerous collaborating scientists. It includes mapping to terms from other data standards initiatives, including the Genomic Standards Consortium’s minimal information (MIxS) and NCBI’s BioSample/BioProjects checklists and the Ontology for Biomedical Investigations (OBI). The standard includes data fields about characteristics of the organism or environmental source of the specimen, spatial-temporal information about the specimen isolation event, phenotypic characteristics of the pathogen/vector isolated, and project leadership and support. By modeling metadata fields into an ontology-based semantic framework and reusing existing ontologies and minimum information checklists, the application standard can be extended to support additional project-specific data fields and integrated with other data represented with comparable standards. The use of this metadata standard by all ongoing and future GSCID sequencing projects will provide a consistent representation of these data in the BRC resources and other repositories that leverage these data, allowing investigators to identify relevant genomic sequences and perform comparative genomics analyses that are both statistically meaningful and biologically relevant.</p></div

Core Project Attributes.

<p>*Mandatory NCBI BioProject attributes.</p

Core Sample Attributes.

<p>*Mandatory NCBI BioSample attributes in the “Pathogen: clinical or host-associated” version 1.0 package.</p

Semantic Network of the Core Sample Data Fields.

<p>A semantic representation of the entities relevant to describe infectious disease samples based on the OBI and other OBO Foundry ontologies is shown. Distinctions are made between material entities (blue outlines), information entities and qualities (black outlines), and processes (red outlines). Entities are connected by standard semantic relations, in <i>italic</i>. The subset of entities selected as Core Sample fields are noted with ovals containing the respective Field ID. For example, the OBI:organism <i>has_quality</i> “Specimen Source Gender” (CS5), which is equivalent to the PATO:biological sex, and <i>has_quality</i> PATO:age, and <i>has_quality</i> “Specimen Source Health Status” (CS8), which is equivalent to PATO:organismal status. PATO:age <i>is_quality_measured_as</i> OBI:age since birth measurement datum, which <i>has_measurement_value</i> “Specimen Source Age – Value” (CS6) and <i>has_measurement_unit_label</i> “Specimen Source Age – Unit” (CS7).</p

Semantic Network of the Core Project Data Fields.

<p>A semantic representation of the entities relevant to describe infectious disease projects based on the OBI and other OBO Foundry ontologies is shown. Distinctions are made between material entities (blue outlines), information entities and qualities (black outlines), and processes (red outlines). Entities are connected by standard semantic relations, in <i>italic</i>. The subset of entities selected as Core Project fields are noted with ovals containing the respective Field ID. For example, both the “Project Title” (CP1) and “Project ID” (CP2) <i>denote</i> an OBI:Investigation; the “Project Description” (CP3) <i>is_about</i> the same OBI:Investigation.</p