A prototypical model for tensional wrinkling in thin sheets

The buckling and wrinkling of thin films has recently seen a surge of interest among physicists, biologists, mathematicians and engineers. This has been triggered by the growing interest in developing technologies at ever decreasing scales and the resulting necessity to control the mechanics of tiny structures, as well as by the realization that morphogenetic processes, such as the tissue-shaping instabilities occurring in animal epithelia or plant leaves, often emerge from mechanical instabilities of cell sheets. While the most basic buckling instability of uniaxially compressed plates was understood by Euler more than 200 years ago, recent experiments on nanometrically thin (ultrathin) films have shown significant deviations from predictions of standard buckling theory. Motivated by this puzzle, we introduce here a theoretical model that allows for a systematic analysis of wrinkling in sheets far from their instability threshold. We focus on the simplest extension of Euler buckling that exhibits wrinkles of finite length - a sheet under axisymmetric tensile loads. This geometry, whose first study is attributed to Lam´e, allows us to construct\ud a phase diagram that demonstrates the dramatic variation of wrinkling patterns from near-threshold to far-from-threshold conditions. Theoretical arguments and comparison to experiments show that for thin sheets the far-from-threshold regime is expected to emerge under extremely small compressive loads, emphasizing the relevance of our analysis for nanomechanics applications

Subacute Presentation of Central Cord Syndrome Resulting from Vertebral Osteomyelitis and Discitis: A Case Report

Introduction: Central cord syndrome (CCS) is a clinical syndrome of motor weakness and sensory changes. While CCS is most often associated with traumatic events. There have been few documented cases being caused by abscesses resulting from osteomyelitis.Case Report: A 56-year-old male presented to a regional trauma center complaining of excruciating neck and bilateral upper extremity pain. Computed tomography of the cervical and thoracic regions revealed severe discitis and osteomyelitis of the fourth and fifth cervical (C4-C5) with near-complete destruction of the C4 vertebral body, as well as anterolisthesis of C4 on C5 causing compression of the central canal. Empiric intravenous (IV) antibiotic therapy with ampicillin/sulbactam and vancomycin was initiated, and drainage of the abscess was scheduled. After the patient refused surgery, he was planned to be transferred to a skilled nursing facility to receive a six-week course of IV vancomycin therapy. A month later, patient returned to emergency department with the same complaint due to non-compliance with antibiotic therapy.Discussion: Delayed diagnosis and treatment of osteomyelitis can result in devastating neurological sequelae, and literature supports immediate surgical debridement. Although past evidence has suggested surgical intervention in similar patients with presence of abscesses, this case may suggest that antibiotic treatment may be an alternative approach to the management of CCS due to an infectious etiology. However, the patient had been non-compliant with medication, so it is unknown whether there was definite resolution of the condition.Conclusion: In patients presenting with non-traumatic central cord syndrome, it is vital to identify risk factors for infection in a thoroughly obtained patient history, as well as to maintain a low threshold for diagnostic imaging

Magneto-elastic oscillations of neutron stars: exploring different magnetic field configurations

We study magneto-elastic oscillations of highly magnetized neutron stars (magnetars) which have been proposed as an explanation for the quasi-periodic oscillations (QPOs) appearing in the decaying tail of the giant flares of soft gamma-ray repeaters (SGRs). We extend previous studies by investigating various magnetic field configurations, computing the Alfv\'en spectrum in each case and performing magneto-elastic simulations for a selected number of models. By identifying the observed frequencies of 28 Hz (SGR 1900+14) and 30 Hz (SGR 1806-20) with the fundamental Alfv\'en QPOs, we estimate the required surface magnetic field strength. For the magnetic field configurations investigated (dipole-like poloidal, mixed toroidal-poloidal with a dipole-like poloidal component and a toroidal field confined to the region of field lines closing inside the star, and for poloidal fields with an additional quadrupole-like component) the estimated dipole spin-down magnetic fields are between 8x10^14 G and 4x10^15 G, in broad agreement with spin-down estimates for the SGR sources producing giant flares. A number of these models exhibit a rich Alfv\'en continuum revealing new turning points which can produce QPOs. This allows one to explain most of the observed QPO frequencies as associated with magneto-elastic QPOs. In particular, we construct a possible configuration with two turning points in the spectrum which can explain all observed QPOs of SGR 1900+14. Finally, we find that magnetic field configurations which are entirely confined in the crust (if the core is assumed to be a type I superconductor) are not favoured, due to difficulties in explaining the lowest observed QPO frequencies (f<30 Hz).Comment: 21 pages, 16 figures, 6 tables, matched to version accepted by MNRAS with extended comparison/discussion to previous wor

The optimal P3M algorithm for computing electrostatic energies in periodic systems

We optimize Hockney and Eastwood's Particle-Particle Particle-Mesh (P3M) algorithm to achieve maximal accuracy in the electrostatic energies (instead of forces) in 3D periodic charged systems. To this end we construct an optimal influence function that minimizes the RMS errors in the energies. As a by-product we derive a new real-space cut-off correction term, give a transparent derivation of the systematic errors in terms of Madelung energies, and provide an accurate analytical estimate for the RMS error of the energies. This error estimate is a useful indicator of the accuracy of the computed energies, and allows an easy and precise determination of the optimal values of the various parameters in the algorithm (Ewald splitting parameter, mesh size and charge assignment order).Comment: 31 pages, 3 figure

Evaluación del comportamiento clínico inmediato de lesiones cervicales no cariosas restauradas con resina compuesta Bulk-fill utilizando un adhesivo hidrofóbico

Tesis (Cirujano Dentista)Las resinas compuestas (RC) son un material sintético que está compuesto por una matriz orgánica y un relleno inorgánico, que se unen gracias a un agente de conexión llamado silano.(1) En 1962, el Dr. Ray L. Bowen, perteneciente a la unidad de Investigación de la American Dental Association del Nacional Bureau of Standard, desarrolló el monómero de bisfenol A glicidil metacrilato (Bis-GMA), una resina dimetacrilato y un agente de conexión de silano orgánico que produce la unión entre el relleno y la matriz de resina. Desde entonces, las resinas compuestas han sido el material de elección para restauraciones estéticas directas en el sector anterior y posterior como selladores de fosas y fisuras, entre otros usos (2) Dentro de la innovación en odontología, la adhesión es una de las más importantes, debido a que su aparición conlleva a una odontología mínimamente invasiva, donde antiguamente la retención de los materiales en los dientes estaba dada básicamente por la cavidad, macroretención, lo que conlleva a desgastar mayor cantidad de tejido. Entendemos por adhesión “fenómeno mediante el cual dos superficies se mantienen unidas por fuerzas interfaciales, sean estas físicas, químicas o por la interacción de ambas” y en odontología significa “unir a un sustrato sólido (diente) el biomaterial a aplicar, manifestándose la adhesión como tal en la interfaz diente – restauración”. Para lograr la adhesión se utilizan sistemas adhesivos.(3) Los sistemas adhesivos están constituidos, en su mayoría, por un ácido, primer y adhesivo. Estos actúan en el sustrato dentario conformado por esmalte y dentina, los cuales se diferencian en el porcentaje de contenido orgánico, inorgánico y agua. El esmalte está compuesto por un 96% de hidroxiapatita, 1% contenido inorgánico y 3% de agua, a su vez la dentina está compuesta por un 70% de hidroxiapatita, 18% contenido inorgánico y 12% de agua.(4) Estas diferencias 7 hacen que el proceso de adhesión sea diferente entre un tejido y el otro. En 1955, Michael Buonocore, fue el primero en describir el efecto que tenía la aplicación de una solución ácida sobre el esmalte, la cual se lavaba y se secaba y con el fin de obtener un patrón de grabado ácido en la superficie adamantina.(5) Con el pasar de los años, este procedimiento de adhesión del esmalte se consolidó por su efectividad y confiabilidad. Desde el 2003 se comienza la búsqueda de la adhesión a la dentina, la cual se ve obstaculizada al no poseer características homogéneas que beneficien su adhesividad. Una de ella, es la presencia de una capa superficial que se forma después de la remoción de caries con instrumentos rotatorios llamada “barro dentinario” o “Smear layer” que está formada de detritus y dentina desorganizada. En 1980, Takao Fusayama sugiere realizar acondicionamiento ácido en dentina y de esta forma remover el barro dentinario, permitiendo el ingreso del adhesivo a los túbulos dentinarios, que luego de polimerizar quedando trabado mecánicamente.(6) Esta traba mecánica se le conoce como “capa híbrida”, cual fue descrita por Nakabayashi (1982) como “el resultado de la impregnación de los monómero en la superficie de los sustratos de dentina pre-tratados y su polimerización”.(7) Otra dificultad que presenta es el contenido de humedad de la dentina, la cual proviene de los procesos odontoblásticos que se aloja en los túbulos dentinarios, que es la continuación directa del tejido pulpar, y transporta fluidos tisulares manteniendo siempre la presencia de humedad.(8) El objetivo de este estudio es determinar el comportamiento clínico del Bis-GMA en el sellado de la capa de adhesivo en lesiones cervicales. Se ha observado que un gran porcentaje de las restauraciones clase V fracasan por el desalojo/retención de la resina compuesta (9). Lo anterior puede ser causado por la retención de monómeros y solventes residuales propios de la capa adhesiva, sumando la humectabilidad de la dentina, los componentes anteriores son considerados contaminantes de la capa híbrida que llevarían a la disminución de 8 la fuerza tensil y aumento de la microfiltración de la capa adhesiva. Por otra parte, se ha observado un auge del uso de resinas Bulk-Fill debido a su menor tiempo operatorio y tasa de contracción de la resina durante la polimerización. Actualmente, no existen estudios de comportamiento de uso resinas Bulk-Fill en lesiones cervicales. Realizaremos un estudio in-vivo de la impermeabilización de la capa adhesiva mediante el uso de resinas hidrófugas (Bis-GMA) sobre la capa adhesiva en cavidades clases V restauradas con resina Bulk-Fill, con el fin de evaluar el comportamiento clínico inmediato del uso del Bis-GMA en lesiones cervicales mediante los criterios clínicos World Dental Federation (FDI) esperando obtener una mejor retención y disminución de la sensibilidad postoperatoria

Electronic bill presentment and payment--is it just a click away?

This article addresses the following questions about electronic presentment and payment (EBPP) in the business-to-consumer marketplace: Why aren't electronically presented bills always paid electronically? And, if EBPP does aid in the migration to fully electronic end-to-end payment, what are the barriers to its adoption.Payment systems ; Electronic funds transfers

Towards NNLO accuracy for epsilon '/epsilon

The quantity $\varepsilon'/\varepsilon$ measures direct CP violation in Kaon decays. Recent SM predictions show a $2.9\sigma$ tension with data, with the theoretical uncertainty dominating. As rapid progress on the lattice is bringing nonperturbative long-distance effects under control, a more precise knowledge of short-distance contributions is needed. We describe the first NNLO results for $\varepsilon'/\varepsilon$ and discuss future prospects, as well as issues of scheme dependence and the separation of perturbative and nonperturbative effects. Finally we also comment on the solution of the renormalisation-group evolution in one of the talks at this conference and present the correct solution.Comment: 8 pages, Proceedings of the Kaon 2016 Conferenc

Generation of a human iPS cell line from a patient with retinitis pigmentosa due to EYS mutation

Retinitis pigmentosa (RP) is an inherited retinal degenerative disease. Mutations in EYS have been associated with autosomal recessive RP. The human iPS cell line, CABi002-A, derived from peripheral blood mononuclear cells from a patient carrying a heterozygous double mutation in EYS gene was generated by non-integrative reprogramming technology, using hOCT3/4, hSOX2, hc-MYC and hKLF4 reprogramming factors. Pluripotency and differentiation capacity were assessed by immunocytochemistry and RT-PCR. This iPSC line can be further differentiated towards the affected cells to understand the pathophysiology of the disease and test new therapeutic strategies.Cellex FoundationFundación Progreso y Salu

Prospección de mercado de hortalizas bajo producción integrada en cuatro ciudades de la Octava Región de Chile

Published by Asociación de Economistas Agrarios de Chilewillingness to purchase, vegetables, integrated production, Agribusiness, Consumer/Household Economics, Marketing,