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Frictional sliding without geometrical reflection symmetry

The dynamics of frictional interfaces play an important role in many physical systems spanning a broad range of scales. It is well-known that frictional interfaces separating two dissimilar materials couple interfacial slip and normal stress variations, a coupling that has major implications on their stability, failure mechanism and rupture directionality. In contrast, interfaces separating identical materials are traditionally assumed not to feature such a coupling due to symmetry considerations. We show, combining theory and experiments, that interfaces which separate bodies made of macroscopically identical materials, but lack geometrical reflection symmetry, generically feature such a coupling. We discuss two applications of this novel feature. First, we show that it accounts for a distinct, and previously unexplained, experimentally observed weakening effect in frictional cracks. Second, we demonstrate that it can destabilize frictional sliding which is otherwise stable. The emerging framework is expected to find applications in a broad range of systems.Comment: 14 pages, 5 figures + Supplementary Material. Minor change in the title, extended analysis in the second par

Detailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake

Foreshocks can provide valuable information about possible nucleation process of a mainshock. However, their physical mechanisms are still under debate. In this study, we present a comprehensive analysis of the earthquake sequence preceding the 2010 Mw7.2 El Mayor‐Cucapah mainshock, including waveform detection of missing smaller events, relative relocation, and source parameter analysis. Based on a template matching method, we find a tenfold increase in the number of earthquakes than reported in the Southern California Seismic Network catalog. The entire sequence exhibits nearly continuous episodes of foreshocks that can be loosely separated into two active clusters. Relocated foreshocks show several seismicity streaks at depth, with a consistently active cluster at depths between 14 and 16 km where the mainshock was nucleated. Stress drop measurements from a spectral ratio approach based on empirical Green’s functions show a range between 3.8 and 41.7 MPa with a median of 13.0 MPa and no clear temporal variations. The relocation results, together with the source patches estimated from earthquake corner frequencies, revealed a migration front toward the mainshock hypocenter within last 8 hr and a chain of active burst immediately 6 min prior to the mainshock. Our results support combined effects of aseismic slip and cascading failure on the evolution of foreshocks.Plain Language SummaryThe 2010 Mw7.2 El Mayor‐Cucapah (EMC) earthquake was preceded by a prominent sequence of foreshocks starting ~21 days before the mainshock. Several methods based on the similarities of waveforms are applied to obtain spatiotemporal evolution of foreshocks. Ten times more events are found from a template matching method when compared to the SCSN catalog. The refined relative locations reveal two main active clusters in time, as well as two spatial patches with a shallower one to the north of the mainshock epicenter. The depth distribution indicates several linear lines of seismicity, with a consistently active cluster at depths of 14–16 km where mainshock started. An active cluster of foreshocks occurred in the last 6 min. They likely altered the stress state near the hypocenter and ultimately triggered the mainshock. Our analysis indicates that both aseismic slip and cascade triggering processes occurred and contributed to the eventual triggering of the EMC mainshock.Key PointsA waveform matching technique leads to tenfold increase in the number of foreshocks when compared with the SCSN catalogWe resolve the corner frequency of 20 foreshocks using the detected events as empirical Green’s functionsThe relocated catalog and estimated source patches reveal effects of both aseismic slip and cascading stress transferPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155988/1/jgrb54188.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155988/2/jgrb54188_am.pd

Working conditions of agricultural workers from the municipality of Monteria, Colombia

En el Departamento de Córdoba 8.000 empleos agrícolas son asumidos por personas que trabajan en la economía informal, la mayoría de ellas sin ningún tipo de seguridad social, derivando su sustento en explotaciones agrícolas. El objetivo de la investigación fue analizar las condiciones laborales de los trabajadores agrícolas de la zona rural de Montería, Córdoba (Colombia). Es una investigación de naturaleza cuantitativa no experimental de corte transversal, cuya muestra estuvo conformada por 100 trabajadores agrícolas seleccionados por un muestreo aleatorio simple por vivienda. Los datos se obtuvieron mediante la aplicación de una encuesta que se estructuró en tres secciones referidas a las condiciones socio demográficas, laborales y a las capacidades y oportunidades de la población; la técnica de interpretación hizo alusión a la triangulación múltiple. Los resultados del estudio demuestran que el 92% de los trabajadores tienen condiciones laborales precarias, tales como: mala remuneración, inestabilidad laboral, carecen de afiliación a pensión y riesgos profesionales, no les proporcionan elementos de protección personal y en sus lugares de trabajo no cuentan con agua potable para el consumo a pesar de la responsabilidad ética, legal y social que tienen los empleadores de proteger a los trabajadores en sus lugares de trabajo. La investigación evidencia que las condiciones laborales de estos trabajadores no brindan las oportunidades mínimas para la protección de su integridad ni para el desarrollo de sus capacidades, haciéndose necesario reorientar la política pública de tal forma que ofrezca las opciones necesarias para mejorar sus condiciones de trabajo y su desarrollo humano

Actividad antiinflamatoria de Gnaphalium Stramineum HBK (sanalotodo)

La presente investigación fue realizada con el propósito de evaluar la actividad antiinflamatoria de extractos y fracciones cromatográficas de las flores de la especie Gnaphalium stramineum HBK (Sanalotodo) y aislar él o los principales activos responsables de dicha actividad. Los ensayos in vivo de actividad antiinflamatoria y el estudio fitoquímico realizado, han permitido aislar compuestos derivados del ácido cafeoilquínico y glicósidos flavonoidales como los principales principios adictivos responsables de dicha actividad farmacológica

Bis(2,3,5,6-tetra-2-pyridylpyrazine-κ3 N 2,N 1,N 6)iron(II) bis­(dicyanamidate) 4.5-hydrate

In the title compound, [Fe(C24H16N6)2][N(CN)2]2·4.5H2O, the central iron(II) ion is hexa­coordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridylpyrazine (tppz) ligands. Two dicyanamide anions [dca or N(CN)2 −] act as counter-ions, and 4.5 water mol­ecules act as solvation agents. The structure contains isolated cationic iron(II)–tppz complexes and the final neutrality is obtained with the two dicyanamide anions. One of the dicyanamide anions and a water mol­ecule are disordered with an occupancy ratio of 0.614 (8):0.386 (8). O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds involving dca, water and tppz mol­ecules are observed

Cost effectiveness of commercial portable ex vivo lung perfusion at a low-volume US lung transplant center

Background: Portable ex vivo lung perfusion during lung transplantation is a resource-intensive technology. In light of its increasing use, we evaluated the cost-effectiveness of ex vivo lung perfusion at a low-volume lung transplant center in the USA. Methods: Patients listed for lung transplantation (2015–2021) in the United Network for Organ Sharing database were included. Quality-of-life was approximated by Karnofsky Performance Status scores 1-year post-transplant. Total transplantation encounter and 1-year follow-up costs accrued by our academic center for patients listed from 2018 to 2021 were obtained. Cost-effectiveness was calculated by evaluating the number of patients attaining various Karnofsky scores relative to cost. Results: Of the 13 930 adult patients who underwent lung transplant in the United Network for Organ Sharing database, 13 477 (96.7%) used static cold storage and 453 (3.3%) used ex vivo lung perfusion, compared to 30/58 (51.7%) and 28/58 (48.3%), respectively, at our center. Compared to static cold storage, median total costs at 1 year were higher for ex vivo lung perfusion (918 000 dollars vs. 516 000 dollars; p = 0.007) along with the cost of living 1 year with a Karnofsky functional status of 100 after transplant (1 290 000 dollars vs. 841 000 dollars). In simulated scenarios, each Karnofsky-adjusted life year gained by ex vivo lung perfusion was 1.00–1.72 times more expensive. Conclusions: Portable ex vivo lung perfusion is not currently cost-effective at a low-volume transplant centers in the USA, being 1.53 times more expensive per Karnofsky-adjusted life year. Improving donor lung and/or recipient biology during ex vivo lung perfusion may improve its utility for routine transplantation.</p

Normalized medical information visualization

A new mark-up programming language is introduced in order to facilitate and improve the visualization of ISO/EN 13606 dual model-based normalized medical information. This is the first time that visualization of normalized medical information is addressed and the programming language is intended to be used by medical non-IT professionals.S