Bounds for the time to failure of hierarchical systems of fracture

For years limited Monte Carlo simulations have led to the suspicion that the time to failure of hierarchically organized load-transfer models of fracture is non-zero for sets of infinite size. This fact could have a profound significance in engineering practice and also in geophysics. Here, we develop an exact algebraic iterative method to compute the successive time intervals for individual breaking in systems of height $n$ in terms of the information calculated in the previous height $n-1$. As a byproduct of this method, rigorous lower and higher bounds for the time to failure of very large systems are easily obtained. The asymptotic behavior of the resulting lower bound leads to the evidence that the above mentioned suspicion is actually true.Comment: Final version. To appear in Phys. Rev. E, Feb 199

Time dependence of breakdown in a global fiber-bundle model with continuous damage

A time-dependent global fiber-bundle model of fracture with continuous damage is formulated in terms of a set of coupled non-linear differential equations. A first integral of this set is analytically obtained. The time evolution of the system is studied by applying a discrete probabilistic method. Several results are discussed emphasizing their differences with the standard time-dependent model. The results obtained show that with this simple model a variety of experimental observations can be qualitatively reproduced.Comment: APS style, two columns, 4 figures. To appear in Phys. Rev.

Complicaciones de la colocación de malla sintética vaginal para la incontinencia urinaria de esfuerzo

ResumenAntecedentesLas mallas para la incontinencia urinaria (IU) se han utilizado a pesar de la falta de evidencia de nivel i en la literatura para evaluar su seguridad y eficacia a largo plazo. Las complicaciones relacionadas con la malla provocaron una advertencia emitida por la FDA en 2008 y dejaron de ser consideradas eventos raros. Las complicaciones más comunes son la retención aguda de orina, sangrado, recurrencia o persistencia de la IU, erosión de uretra e infección de la malla.ObjetivoConocer cuáles son las complicaciones derivadas del tratamiento quirúrgico de la IU femenina con la colocación de mallas suburetrales.Material y métodoSe analizaron los pacientes con diagnóstico de IU operadas con cirugía antiincontinencia y colocación de malla vaginal del año 2007 al 2014. Se analizó las complicaciones derivadas de la colocación de malla y la recuperación de continencia.ResultadosA 58 pacientes se les colocó sling (cabestrillo) con malla sintética; edad promedio de 56 años. El 51% de las pacientes tenían IU de esfuerzo y el 49% IU mixta. Las complicaciones tempranas fueron: 4 pacientes con retención aguda de orina. Las complicaciones tardías: dolor uretral o vaginal (12.2%), dispareunia (20%) y extrusión de malla (10%) manejado con retiro de la misma, 2 de ellas requiriendo 2 procedimientos quirúrgicos. El 12% presentaron urgencia de novo, el 90.2% evolucionaron sin incontinencia, el 9.7% con IU postoperatoria y 2 pacientes sin mejoría.DiscusiónNuestra serie, aunque pequeña, muestra una baja tasa de complicaciones a largo plazo relacionadas con la malla en comparación con la mayoría de las series que muestran una tasa de reoperación de hasta>70% y con múltiples casos de retiro de malla, por lo que en nuestra experiencia los slings suburetrales continúan siendo una opción adecuada en el manejo de la IU.ConclusionesLos slings suburetrales son una opción segura y efectiva en el manejo de la IU.AbstractBackgroundSurgical mesh has been used for treating urinary incontinence (UI) despite the lack of level i evidence in the literature evaluating its long-term safety and efficacy. Mesh-related complications were responsible for a warning issued by the FDA in 2008 and they stopped being considered rare events. The most common complications are acute urinary retention, bleeding, recurrence or persistence of UI, erosion of the urethra, and mesh infection.AimsTo determine the complications derived from surgical UI treatment with the placement of suburethral mesh in women.Material and methodPatients diagnosed with UI that underwent anti-incontinence surgery with the placement of vaginal mesh within the time frame of 2007 and 2014 were analyzed. Mesh placement complications and the recovery of continence were evaluated.ResultsA synthetic mesh sling was placed in 58 patients with a mean age of 56 years. A total of 51% of the patients had stress urinary incontinence and 49% had mixed urinary incontinence. Early complications were: 4 patients with acute urine retention. Late complications were: urethral or vaginal pain (12.2%), dyspareunia (20%), and mesh extrusion (10%) that was managed through mesh removal; 2 of those patients required surgical procedures. Twelve percent of the patients presented with de novo urgency, 90.2% progressed with no incontinence, 9.7% presented with postoperative UI, and 2 patients had no improvement.DiscussionAlthough small, our case series showed a low long-term complication rate with the use of surgical mesh, compared with the majority of case series that demonstrate a re-operation rate>70%, as well as numerous cases of mesh removal. Thus, it is our experience that suburethral slings continue to be an adequate UI management option.ConclusionsSuburethral slings are a safe and effective option in UI management

Real Space Renormalization Group Methods and Quantum Groups

We apply real-space RG methods to study two quantum group invariant Hamiltonians, that of the XXZ model and the Ising model in a transverse field defined in an open chain with appropiate boundary terms. The quantum group symmetry is preserved under the RG transformation except for the appearence of a quantum group anomalous term which vanishes in the classical case. We obtain correctly the line of critical XXZ models. In the ITF model the RG-flow coincides with the tensor product decomposition of cyclic irreps. of $SU_q(2)$ with $q^4=1$.Comment: 7 pages, LATEX, no figure

Influence of large-scale interplanetary structures on the propagation of solar energetic particles: The Multispacecraft event on 2021 October 9

An intense solar energetic particle (SEP) event was observed on 2021 October 9 by multiple spacecraft distributed near the ecliptic plane at heliocentric radial distances R ≲ 1 au and within a narrow range of heliolongitudes. A stream interaction region (SIR), sequentially observed by Parker Solar Probe (PSP) at R = 0.76 au and 48° east from Earth (ϕ = E48°), STEREO-A (at R = 0.96 au, ϕ = E39°), Solar Orbiter (SolO; at R = 0.68 au, ϕ = E15°), BepiColombo (at R = 0.33 au, ϕ = W02°), and near-Earth spacecraft, regulated the observed intensity-time profiles and the anisotropic character of the SEP event. PSP, STEREO-A, and SolO detected strong anisotropies at the onset of the SEP event, which resulted from the fact that PSP and STEREO-A were in the declining-speed region of the solar wind stream responsible for the SIR and from the passage of a steady magnetic field structure by SolO during the onset of the event. By contrast, the intensity-time profiles observed near Earth displayed a delayed onset at proton energies ≳13 MeV and an accumulation of ≲5 MeV protons between the SIR and the shock driven by the parent coronal mass ejection (CME). Even though BepiColombo, STEREO-A, and SolO were nominally connected to the same region of the Sun, the intensity-time profiles at BepiColombo resemble those observed near Earth, with the bulk of low-energy ions also confined between the SIR and the CME-driven shock. This event exemplifies the impact that intervening large-scale interplanetary structures, such as corotating SIRs, have in shaping the properties of SEP events

Diagnóstico del posgrado en México. Región Centro Occidente

El estudio tiene como propósito analizar la estructura institucional de la oferta del Posgrado en la Región Centro Occidente, con la finalidad de identificar fortalezas y debilidades y con ello proponer políticas públicas para el impulso de la calidad de los estudios de posgrado en México. Con base en la información nacional se elaboraron seis diagnósticos regionales y un diagnóstico nacional del posgrado. En este volumen se presentan los resultados de la Región Centro Occidente que incluye los estados Jalisco, Colima, Guanajuato, Nayarit, Michoacán y Aguascalientes. Se analizan las características de las Instituciones de Educación Superior que impactan en los posgrados que imparten, tales como origen de financiamiento, grado de desarrollo de su normativa, así como las formas de evaluación, entre otras. Se revisan las características académicas, administrativas y financieras de los programas de posgrado como niveles, orientación, modalidades, formación de competencias. Se da cuenta de las características de los actores del posgrado: estudiantes, coordinadores, egresados. Se presentan las relaciones de los posgrados con el entorno y se ofrece una sistematización y análisis cualitativo respecto a lo que los coordinadores identifican como problemas y perspectivas a futuro y estrategias de fortalecimiento del posgrado.Consejo Mexicano de Estudios de PosgradoConsejo Nacional de Ciencia y Tecnologí

Dominant Negative Mutants of Bacillus thuringiensis Cry1Ab Toxin Function as Anti-Toxins: Demonstration of the Role of Oligomerization in Toxicity

BACKGROUND:Bacillus thuringiensis Cry toxins, that are used worldwide in insect control, kill insects by a mechanism that depends on their ability to form oligomeric pores that insert into the insect-midgut cells. These toxins are being used worldwide in transgenic plants or spray to control insect pests in agriculture. However, a major concern has been the possible effects of these insecticidal proteins on non-target organisms mainly in ecosystems adjacent to agricultural fields. METHODOLOGY/PRINCIPAL FINDINGS:We isolated and characterized 11 non-toxic mutants of Cry1Ab toxin affected in different steps of the mechanism of action namely binding to receptors, oligomerization and pore-formation. These mutant toxins were analyzed for their capacity to block wild type toxin activity, presenting a dominant negative phenotype. The dominant negative phenotype was analyzed at two levels, in vivo by toxicity bioassays against susceptible Manduca sexta larvae and in vitro by pore formation activity in black lipid bilayers. We demonstrate that some mutations located in helix alpha-4 completely block the wild type toxin activity at sub-stoichiometric level confirming a dominant negative phenotype, thereby functioning as potent antitoxins. CONCLUSIONS/SIGNIFICANCE:This is the first reported case of a Cry toxin dominant inhibitor. These data demonstrate that oligomerization is a fundamental step in Cry toxin action and represent a potential mechanism to protect special ecosystems from the possible effect of Cry toxins on non-target organisms

Influence of Large-scale Interplanetary Structures on the Propagation of Solar Energetic Particles: The Multispacecraft Event on 2021 October 9

An intense solar energetic particle (SEP) event was observed on 2021 October 9 by multiple spacecraft distributed near the ecliptic plane at heliocentric radial distances R ≲ 1 au and within a narrow range of heliolongitudes. A stream interaction region (SIR), sequentially observed by Parker Solar Probe (PSP) at R = 0.76 au and 48° east from Earth (ϕ = E48°), STEREO-A (at R = 0.96 au, ϕ = E39°), Solar Orbiter (SolO; at R = 0.68 au, ϕ = E15°), BepiColombo (at R = 0.33 au, ϕ = W02°), and near-Earth spacecraft, regulated the observed intensity-time profiles and the anisotropic character of the SEP event. PSP, STEREO-A, and SolO detected strong anisotropies at the onset of the SEP event, which resulted from the fact that PSP and STEREO-A were in the declining-speed region of the solar wind stream responsible for the SIR and from the passage of a steady magnetic field structure by SolO during the onset of the event. By contrast, the intensity-time profiles observed near Earth displayed a delayed onset at proton energies ≳13 MeV and an accumulation of ≲5 MeV protons between the SIR and the shock driven by the parent coronal mass ejection (CME). Even though BepiColombo, STEREO-A, and SolO were nominally connected to the same region of the Sun, the intensity-time profiles at BepiColombo resemble those observed near Earth, with the bulk of low-energy ions also confined between the SIR and the CME-driven shock. This event exemplifies the impact that intervening large-scale interplanetary structures, such as corotating SIRs, have in shaping the properties of SEP events

The Pierre Auger Observatory III: Other Astrophysical Observations

Astrophysical observations of ultra-high-energy cosmic rays with the Pierre Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference, Beijing, China, August 201