The energy release in earthquakes, and subduction zone seismicity and stress in slabs

Energy release in earthquakes is discussed. Dynamic energy from source time function, a simplified procedure for modeling deep focus events, static energy estimates, near source energy studies, and energy and magnitude are addressed. Subduction zone seismicity and stress in slabs are also discussed

The equation of state of Mg_(0.6)Fe_(0.4)O to 200 GPa

New Hugoniot data on polycrystalline (avg.porosity 6.9%) samples of the magnesiowustite Mg_(0.6)Fe_(0.4)O are presented, covering the pressure range up to 200 GPa. When our data are fit by a single 3rd order Eulerian Hugoniot with K_0 constrained to its ultrasonic value of 161.5 GPa, the required isentropic pressure derivative K_0′ is 4.37 +/− 0.37. This value is significantly lower than the ultrasonic one of 6.18; existing isothermal compression data, however, are in agreement with our value rather than the ultrasonic one. Our data are adequately explained without phase transitions. There is some marginal evidence for a possible phase transition around 120 GPa. If such a transition indeed occurs it is probably of small volume change compared to the transition observed in FeO; we place an extreme upper bound of 3% on the density change such a transformation could involve and still be consistent with the data. Contrary to earlier hypotheses, we believe that a phase transition in magnesiowustite is not a likely explanation of the seismic effects in the D″ region of the lower mantle. The wustite transition may be a more complex phenomenon than initially supposed — perhaps an effect of nonstoichiometry localized to the iron-rich end of the solid solution series

The energy release in earthquakes

Energy calculations are generally made through an empirical application of the familiar Gutenberg-Richter energy-magnitude relationships. The precise physical significance of these relationships is somewhat uncertain. We make use here of the recent improvements in knowledge about the earthquake source to place energy measurements on a sounder physical basis. For a simple trapezoidal far-field displacement source-time function with a ratio x of rise time to total duration T_0, the seismic energy E is proportional to [1/ x(1 - x)^2] M_0^2/T_0^3, where M_0 is seismic moment. As long as x is greater than 0.1 or so, the effect of rise time is not important. The dynamic energies thus calculated for shallow events are in reasonable agreement with the estimate E ≅ (5 × 10^(−5))M_0 based on elastostatic considerations. Deep events, despite their possibly different seismological character, yield dynamic energies which are compatible with a static prediction similar to that for shallow events. Studies of strong-motion velocity traces obtained near the sources of the 1971 San Fernando, 1966 Parkfield, and 1979 Imperial Valley earthquakes suggest that, even in the distance range of 1 to 5 km, most of the radiated energy is below 1 to 2 Hz in frequency. Far-field energy determinations using long-period WWSSN instruments are probably not in gross error despite their band-limited nature. The strong-motion record for the intermediate depth Bucharest earthquake of 1977 also suggests little teleseismic energy outside the pass-band of a long-period WWSSN instrument

Limited aperture light source streak photography

In shock wave equation‐of‐state experiments employing inclined mirror techniques, limited aperture light sources such as the xenon flash lamp are generally more convenient to use than extended light sources employing explosives, but can create alignment problems when mirror inclination angles are large. These problems can be solved by employing a wedge‐shaped inclined mirror in place of a flat one

Hugoniot equation of state of periclase to 200 GPa

New shock wave data on {100} oriented single crystal periclase covering the pressure range from 160 to 200 GPa suggest that MgO is described by a single Hugoniot up to 200 GPa, with no displacive phase transitions of volume change greater than 1-1.5 per cent. For a third order finite strain fit, with K_0 constrained to its ultrasonically determined value of 162.7 GPa, the implied K_0′ of 4.27 ± 0.24 is in agreement with ultrasonically determined value of 4.17 ± 0.14. The new data indicate a somewhat steeper Hugoniot than that suggested by previously published shock wave results under 120 GPa. A previously published result at 258 GPa shows more compression in the light of the present data than would be expected for MgO in the B1 structure, and may signal the onset of a phase transition, although we cannot confidently make this interpretation. If MgO forms an ideal solid solution with FeO, our data does not support the occurrence of a significant transition in magnesiowustite at lower mantle pressures

`Third' Quantization of Vacuum Einstein Gravity and Free Yang-Mills Theories

Based on the algebraico-categorical (:sheaf-theoretic and sheaf cohomological) conceptual and technical machinery of Abstract Differential Geometry, a new, genuinely background spacetime manifold independent, field quantization scenario for vacuum Einstein gravity and free Yang-Mills theories is introduced. The scheme is coined `third quantization' and, although it formally appears to follow a canonical route, it is fully covariant, because it is an expressly functorial `procedure'. Various current and future Quantum Gravity research issues are discussed under the light of 3rd-quantization. A postscript gives a brief account of this author's personal encounters with Rafael Sorkin and his work.Comment: 43 pages; latest version contributed to a fest-volume celebrating Rafael Sorkin's 60th birthday (Erratum: in earlier versions I had wrongly written that the Editor for this volume is Daniele Oriti, with CUP as publisher. I apologize for the mistake.

Evi1 Counteracts Anti-Leukemic and Stem Cell Inhibitory Effects of All-Trans Retinoic Acid on Flt3-ITD/Npm1c-Driven Acute Myeloid Leukemia Cells.

All-trans retinoic acid (atRA) has a dramatic impact on the survival of patients with acute promyelocytic leukemia, but its therapeutic value in other types of acute myeloid leukemia (AML) has so far remained unclear. Given that AML is a stem cell-driven disease, recent studies have addressed the effects of atRA on leukemic stem cells (LSCs). atRA promoted stemness of MLL-AF9-driven AML in an Evi1-dependent manner but had the opposite effect in Flt3-ITD/Nup98-Hoxd13-driven AML. Overexpression of the stem cell-associated transcription factor EVI1 predicts a poor prognosis in AML, and is observed in different genetic subtypes, including cytogenetically normal AML. Here, we therefore investigated the effects of Evi1 in a mouse model for cytogenetically normal AML, which rests on the combined activity of Flt3-ITD and Npm1c mutations. Experimental expression of Evi1 on this background strongly promoted disease aggressiveness. atRA inhibited leukemia cell viability and stem cell-related properties, and these effects were counteracted by overexpression of Evi1. These data further underscore the complexity of the responsiveness of AML LSCs to atRA and point out the need for additional investigations which may lay a foundation for a precision medicine-based use of retinoids in AML

Cardiovascular magnetic resonance:Diagnostic utility and specific considerations in the pediatric population

Cardiovascular magnetic resonance is a non-invasive imaging modality which is emerging as important tool for the investigation and management of pediatric cardiovascular disease. In this review we describe the key technical and practical differences between scanning children and adults, and highlight some important considerations that must be taken into account for this patient population. Using case examples commonly seen in clinical practice, we discuss the important clinical applications of cardiovascular magnetic resonance, and briefly highlight key future developments in this field

meCLICK-Seq, a Substrate-Hijacking and RNA Degradation Strategy for the Study of RNA Methylation.

The fates of RNA species in a cell are controlled by ribonucleases, which degrade them by exploiting the universal structural 2'-OH group. This phenomenon plays a key role in numerous transformative technologies, for example, RNA interference and CRISPR/Cas13-based RNA editing systems. These approaches, however, are genetic or oligomer-based and so have inherent limitations. This has led to interest in the development of small molecules capable of degrading nucleic acids in a targeted manner. Here we describe click-degraders, small molecules that can be covalently attached to RNA species through click-chemistry and can degrade them, that are akin to ribonucleases. By using these molecules, we have developed the meCLICK-Seq (methylation CLICK-degradation Sequencing) a method to identify RNA modification substrates with high resolution at intronic and intergenic regions. The method hijacks RNA methyltransferase activity to introduce an alkyne, instead of a methyl, moiety on RNA. Subsequent copper(I)-catalyzed azide-alkyne cycloaddition reaction with the click-degrader leads to RNA cleavage and degradation exploiting a mechanism used by endogenous ribonucleases. Focusing on N6-methyladenosine (m6A), meCLICK-Seq identifies methylated transcripts, determines RNA methylase specificity, and reliably maps modification sites in intronic and intergenic regions. Importantly, we show that METTL16 deposits m6A to intronic polyadenylation (IPA) sites, which suggests a potential role for METTL16 in IPA and, in turn, splicing. Unlike other methods, the readout of meCLICK-Seq is depletion, not enrichment, of modified RNA species, which allows a comprehensive and dynamic study of RNA modifications throughout the transcriptome, including regions of low abundance. The click-degraders are highly modular and so may be exploited to study any RNA modification and design new technologies that rely on RNA degradation.UKRI (BBSRC DTP scholarships to S.M. and H.K.C) and the Jardine Foundation and Cambridge Trust (PhD scholarship to M.E.H.)