Shear Wave Splitting Analysis to Estimate Fracture Orientation and Frequency Dependent Anisotropy

Shear wave splitting is a well-known method for indication of orientation, radius, and length of fractures in subsurface layers. In this paper, a three component near offset VSP data acquired from a fractured sandstone reservoir in southern part of Iran was used to analyse shear wave splitting and frequency-dependent anisotropy assessment. Polarization angle obtained by performing rotation on radial and transverse components of VSP data was used to determine the direction of polarization of fast shear wave which corresponds to direction of fractures. It was shown that correct implementation of shear wave splitting analysis can be used for determination of fracture direction. During frequency- dependent anisotropy analysis, it was found that the time delays in shear- waves decrease as the frequency increases. It was clearly demonstrated throughout this study that anisotropy may have an inverse relationship with frequency. The analysis presented in this paper complements the studied conducted by other researchers in this field of research

Does Selection against Transcriptional Interference Shape Retroelement-Free Regions in Mammalian Genomes?

BACKGROUND: Eukaryotic genomes are scattered with retroelements that proliferate through retrotransposition. Although retroelements make up around 40 percent of the human genome, large regions are found to be completely devoid of retroelements. This has been hypothesised to be a result of genomic regions being intolerant to insertions of retroelements. The inadvertent transcriptional activity of retroelements may affect neighbouring genes, which in turn could be detrimental to an organism. We speculate that such retroelement transcription, or transcriptional interference, is a contributing factor in generating and maintaining retroelement-free regions in the human genome. METHODOLOGY/PRINCIPAL FINDINGS: Based on the known transcriptional properties of retroelements, we expect long interspersed elements (LINEs) to be able to display a high degree of transcriptional interference. In contrast, we expect short interspersed elements (SINEs) to display very low levels of transcriptional interference. We find that genomic regions devoid of long interspersed elements (LINEs) are enriched for protein-coding genes, but that this is not the case for regions devoid of short interspersed elements (SINEs). This is expected if genes are subject to selection against transcriptional interference. We do not find microRNAs to be associated with genomic regions devoid of either SINEs or LINEs. We further observe an increased relative activity of genes overlapping LINE-free regions during early embryogenesis, where activity of LINEs has been identified previously. CONCLUSIONS/SIGNIFICANCE: Our observations are consistent with the notion that selection against transcriptional interference has contributed to the maintenance and/or generation of retroelement-free regions in the human genome

Green catalytic valorization of hardwood biomass into valuable chemicals with the use of solid catalysts

Results of the study on green valorization of hardwood biomass into valuable chemicals with the use of solid catalysts were described. The heterogeneous catalytic processes of hemicelluloses and cellulose hydrolysis, wood oxidative fractionation and lignin depolymerization in supercritical spirits are suggested to employ for the green biorefinery of hardwood to xylose, pure cellulose, glucose, alcohols and liquid hydrocarbons

Multiple Roles of Alu-Related Noncoding RNAs

Repetitive Alu and Alu-related elements are present in primates, tree shrews (Scandentia), and rodents and have expanded to 1.3 million copies in the human genome by nonautonomous retrotransposition. Pol III transcription from these elements occurs at low levels under normal conditions but increases transiently after stress, indicating a function of Alu RNAs in cellular stress response. Alu RNAs assemble with cellular proteins into ribonucleoprotein complexes and can be processed into the smaller scAlu RNAs. Alu and Alu-related RNAs play a role in regulating transcription and translation. They provide a source for the biogenesis of miRNAs and, embedded into mRNAs, can be targeted by miRNAs. When present as inverted repeats in mRNAs, they become substrates of the editing enzymes, and their modification causes the nuclear retention of these mRNAs. Certain Alu elements evolved into unique transcription units with specific expression profiles producing RNAs with highly specific cellular functions

A review of a quarter century of International Workshops on seismic anisotropy in the crust (01WSA-121WSA)

In 25 years, the presence of azimuthally varying seismic anisotropy throughout the Earth’s crust has progressed from general denial to universal acceptance, so that many international geophysical meetings now have sessions on seismic anisotropy. Over this period, the proceedings of the biennial series of International Workshops in Seismic Anisotropy (IWSAs) have captured many of the notable advances in the theory, calculation, observation and interpretation of particularly shear-wave splitting (seismic birefringence) in the Earth’s crust. Shear-wave splitting is the almost-infallible indicator of seismic anisotropy along the ray path. This paper reviews 13 IWSA meetings (0IWSA–12IWSA) as a catalogue of 25 years of progress in seismic anisotropy. The evidence now suggests that shear-wave splitting monitors the low-level pre-fracturing deformation of the stress-aligned fluid-saturated microcracks pervading almost all in situ rocks in the crust. Shear-wave splitting indicates that microcracks are so closely spaced they are critical systems with all the universality, calculability, predictability, “butterfly wing’s” sensitivity, and deterministic chaos that that implies. This leads to a New Geophysics, where low-level deformation can be monitored with shear-wave splitting, future behaviour calculated–predicted with the anisotropic poro-elastic model of rock evolution, and in some circumstances even potentially controlled by feedback. We anticipate the New Geophysics will greatly invigorate IWSA