Statistical Relationship Between the Decrease of Major Seismicity and Drought in Southern California Since 1900

The seismicity in Southern California significantly decreased over the last decades. The decrease went in parallel with the reduction of meteoric groundwater recharge, which is a well-known factor capable of affecting seismicity. In this work the existence of a systematic statistical relationship was investigated by comparing the time density of Mw ≥ 5.7 earthquakes since 1900 with the time series of the Palmer Drought Severity Index (PDSI), an indicator of soil moisture roughly correlated with groundwater recharge. Given the non-stationarity of the two signals, the formal comparison was performed using both binomial logistic regression and cointegration testing. The analysis showed a significant statistical relationship, with peaks of seismicity 8 years behind those of PDSI. This finding suggests the hypothesis that groundwater recharge might affect earthquakes at a multi-year time scale. Proving this theory requires accurate measures and hydrogeological modeling, which is behind the scope of this work. Nonetheless, according to previous studies, the observed time lag might be explained by the slow propagation of pore pressure from the surface to the seismogenic volume. The ongoing trend towards an arid climate, made more evident by the recent severe droughts, might have contributed to the earthquake reduction of the last decades. The connection is particularly evident in the Salton Trough, with possible implications for the interpretation of its paleoseismicity.

Green's Function Solutions of 1- and 2-D Dual-Phase-Lag Laser Heating Problems in Nano/Microstructures

Lasers and laser heating have a wide variety of applications such as spectroscopy, laser welding, laser cutting, and even biological applications like tumor irradiation and surgery. Theoretical modeling of laser heating has proven to be quite difficult, and classical heating equations have shown to be inaccurate due to the large temperature gradients created by the laser heating. Furthermore, the commonly-used Fourier's Law assumed the speed for a thermal wave to propagate as infinite; this is unrealistic in any medium and especially in domains with slow propagation speeds such as biological media and in fast nano/microscale heating applications. This study helps fill some of the gaps in accurate model of laser heating by presenting unique 1-D and 2-D models of the analytically solved Dual-Phase-Lag (DPL) heating equations which can much more accurately describe the temperature of such interactions in both the temporal and spatial domains.

Nuclear de-excitation lines as a probe of low-energy cosmic rays

Low-energy cosmic rays (LECRs) contribute substantially to the energy balance of the interstellar medium. They play also significant role in the heating and chemistry of gas, and, consequently, on the star formation process. Because of the slow propagation coupled with enhanced energy losses of subrelativistic particles, LECRs are concentrated around their acceleration sites. LECRs effectively interact with the ambient gas through nuclear reactions. Although these processes are energetically less effective compared to heating and ionization, they are extremely important from the point of view of nuclear de-excitation lines, which carry unique information about LECRs. We present results on production of de-excitation lines combining the numerical treatment of nuclear reactions using the code TALYS, with the propagation and energy losses of LECRs.

Accelerating Heat-Initiated Radical Reactions of Organic Halides with Tin Hydride Using Flow Microreactor Technologies

We herein report that flow microreactors can promote an efficiency of radical chain reactions. The chain reactions with a fast propagation step can be accelerated by virtue of an efficient heat-transfer character of the microreactors, whereas the yield of those reactions with a slow propagation step was increased by flow microreactors. Moreover, the yield was further increased by a sequential addition of the initiators, which was allowed by a flow-sequential-addition system.

A Theoretical Model of the Stress Intensity Factor Threshold of DHC for Fuel Cladding Tube

Delayed hydride cracking (DHC) is the result of a mechanism of crack initiation and slow propagation. In DHC, hydrogen diffusion in the metal is required. Gradients of concentration, temperature, and stress are all important factors in controlling diffusivity. The classic theory of DHC still has potential to be modified. In this study, a calculation formula for DHC SIF threshold is established with consideration of the temperature history, the temperature field and the stress field induced by the temperature gradient and the external mechanical loading. Moreover, the temperature gradient on crack surfaces has been considered in the model.