Brittle Fracture of Dental Amalgam

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67331/2/10.1177_00220345650440053801.pd

In-dept sequence analysis of the tomato chromosome 12 centromeric region: indentification of a large CAA block and characterization of pericentromere retrotranposons

We sequenced a continuous 326-kb DNA stretch of a microscopically defined centromeric region of tomato chromosome 12. A total of 84% of the sequence (270 kb) was composed of a nested complex of repeat sequences including 27 retrotransposons, two transposable elements, three MITEs, two terminal repeat retrotransposons in miniature (TRIMs), ten unclassified repeats and three chloroplast DNA insertions. The retrotransposons were grouped into three families of Ty3-Gypsy type long terminal repeat (LTR) retrotransposons (PCRT1¿PCRT3) and one LINE-like retrotransposon (PCRT4). High-resolution fluorescence in situ hybridization analyses on pachytene complements revealed that PCRT1a occurs on the pericentromere heterochromatin blocks. PCRT1 was the prevalent retrotransposon family occupying more than 60% of the 326-kb sequence with 19 members grouped into eight subfamilies (PCRT1a¿PCRT1h) based on LTR sequence. The PCRT1a subfamily is a rapidly amplified element occupying tens of megabases. The other PCRT1 subfamilies (PCRT1b¿PCRT1h) were highly degenerated and interrupted by insertions of other elements. The PCRT1 family shows identity with a previously identified tomato-specific repeat TGR2 and a CENP-B like sequence. A second previously described genomic repeat, TGR3, was identified as a part of the LTR sequence of an Athila-like PCRT2 element of which four copies were found in the 326-kb stretch. A large block of trinucleotide microsatellite (CAA)n occupies the centromere and large portions of the flanking pericentromere heterochromatin blocks of chromosome 12 and most of the other chromosomes. Five putative genes in the remaining 14% of the centromere region were identified, of which one is similar to a transcription regulator (ToCPL1) and a candidate jointless-2 gene. The sequence data from this study have been submitted to GenBank under accession no. AY85039

Toward closing rice telomere gaps: mapping and sequence characterization of rice subtelomere regions.

Despite the collective efforts of the international community to sequence the complete rice genome, telomeric regions of most chromosome arms remain uncharacterized. In this report we present sequence data from subtelomere regions obtained by analyzing telomeric clones from two 8.8 × genome equivalent 10-kb libraries derived from partial restriction digestion with HaeIII or Sau3AI (OSJNPb HaeIII and OSJNPc Sau3AI). Seven telomere clones were identified and contain 25¿100 copies of the telomere repeat (CCCTAAA)n on one end and unique sequences on the opposite end. Polymorphic sequence-tagged site markers from five clones and one additional PCR product were genetically mapped on the ends of chromosome arms 2S, 5L, 10S, 10L, 7L, and 7S. We found distinct chromosome-specific telomere-associated tandem repeats (TATR) on chromosome 7 (TATR7) and on the short arm of chromosome 10 (TATR10s) that showed no significant homology to any International Rice Genome Sequencing Project (IRGSP) genomic sequence. The TATR7, a degenerate tandem repeat which is interrupted by transposable elements, appeared on both ends of chromosome 7. The TATR10s was found to contain an inverted array of three tandem repeats displaying an interesting secondary folding pattern that resembles a telomere loop (t-loop) and which may be involved in a protective function against chromosomal end degradatio

Study of the influence of imperfections on the dynamic stability of tanks

The influence of geometrical imperfections on the dynamic stability of liquid-filled shells under horizontal ground excitation is studied. Some basic concepts in the large deformation and large deformation thin shell theory are recalled. The work done by inertial and internal forces are given in the Gaussian surface coordinate system. A general imperfection pattern in the circumferential direction is introduced. The emphasis is particularly dedicated to the analysis of the geometrical stiffness term. Different patterns are studied to explain the occurrence of additional instability regions. 6 refs., 1 fig., 3 tabs

The Earth: Plasma Sources, Losses, and Transport Processes

This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere

High-Quality Genome Assemblies Reveal Evolutionary Dynamics of Repetitive DNA and Structural Rearrangements in the Drosophila virilis Subgroup

High-quality genome assemblies across a range of nontraditional model organisms can accelerate the discovery of novel aspects of genome evolution. The Drosophila virilis group has several attributes that distinguish it from more highly studied species in the Drosophila genus, such as an unusual abundance of repetitive elements and extensive karyotype evolution, in addition to being an attractive model for speciation genetics. Here, we used long-read sequencing to assemble five genomes of three virilis group species and characterized sequence and structural divergence and repetitive DNA evolution. We find that our contiguous genome assemblies allow characterization of chromosomal arrangements with ease and can facilitate analysis of inversion breakpoints. We also leverage a small panel of resequenced strains to explore the genomic pattern of divergence and polymorphism in this species and show that known demographic histories largely predicts the extent of genome-wide segregating polymorphism. We further find that a neo-X chromosome in Drosophila americana displays X-like levels of nucleotide diversity. We also found that unusual repetitive elements were responsible for much of the divergence in genome composition among species. Helitron-derived tandem repeats tripled in abundance on the Y chromosome in D. americana compared to Drosophila novamexicana, accounting for most of the difference in repeat content between these sister species. Repeats with characteristics of both transposable elements and satellite DNAs expanded by 3-fold, mostly in euchromatin, in both D. americana and D. novamexicana compared to D. virilis. Our results represent a major advance in our understanding of genome biology in this emerging model clade. © 2024 Oxford University Press. All rights reserved.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]