General formalism for the stability of thin-shell wormholes in 2+1 dimensions

In this article we theoretically construct circular thin-shell wormholes in a 2+1 dimensional spacetime. The construction is symmetric with respect to the throat. We present a general formalism for the study of the mechanical stability under perturbations preserving the circular symmetry of the configurations, adopting a linearized equation of state for the exotic matter at the throat. We apply the formalism to several examples.Comment: 14 pages, 7 figures; v2: improved version, new references adde

What every professional working in palliative care should know about cancer pain management

El cuidado paliativo y el manejo del dolor están profundamente unidos en la práctica diaria. La actualización de los conocimientos fundamentales acerca del estado actual de los conceptos y técnicas para el manejo de los pacientes con Cáncer es de una enorme importancia para todos los profesionales que manejan este tipo de pacientes, tanto como fuente de información como de soluciones a sus problemas. El dolor agudo y crónico ocurre con gran frecuencia en los pacientes con cáncer, por lo cual la evaluación y el tratamiento inadecuados puede interferir con el tratamiento antitumoral y deteriorar su calidad de vida. Mientras que el control del dolor es importante independiente del estado de la enfermedad, se convierte en una prioridad en pacientes con estados avanzados de la enfermedad y que no son candidatos para terapias potencialmente curativas bajo el espectro de un cuidado paliativo integral

Optimization of refinery preheat trains: predictive maintenance and operations improvement

Deciding which heat exchanger to clean, when to clean and how to clean in refinery pre-heat trains is a challenging activity that typically relies on operator’s experience. In this paper, an algorithm that allow identifying the most economic cleaning schedule for a given refinery configuration and operating conditions is presented. The method relies on an advanced framework that incorporates rigorous heat exchanger models capable of predicting the fouling behaviour of the refinery as a function of configuration of the individual units and the network, process conditions and time. An industrial case study is presented to illustrate the benefits of the approach, showing that significant improvements over current practice can be obtained

Dilaton thin-shell wormholes supported by a generalized Chaplygin gas

In this article, we construct spherical thin-shell wormholes with charge in dilaton gravity. The exotic matter required for the construction is provided by a generalized Chaplygin gas. We study the stability under perturbations preserving the symmetry. We find that the increase of the coupling between the dilaton and the electromagnetic fields reduces the range of the parameters for which stable configurations are possible.Comment: 14 pages, 6 figures. v3: typos correcte

A Theoretical Construction of Thin Shell Wormhole from Tidal Charged Black hole

Recently, Dadhich et al [ Phys.Lett.B 487, 1 (2000)] have discovered a black hole solution localized on a three brane in five dimensional gravity in the Randall-Sundrum scenario. In this article, we develop a new class of thin shell wormhole by surgically grafting above two black hole spacetimes. Various aspects of this thin wormhole are also analyzed.Comment: 14 pages, 6 figures, Accepted in Gen.Rel.Gra

ENSO dynamics during the Last Glacial Maximum

We present a numerical eigenmode analysis of an intermediate El Nin˜o–Southern Oscillation (ENSO) model which is driven by present-day observed background conditions as well as by simulated background conditions for the Last Glacial Maximum (LGM) about 21,000 years ago. The background conditions are obtained from two LGM simulations which were performed with the National Center for Atmospheric Research climate system model (CSM1.4) and an Earth system model of intermediate complexity (ECBilt-CLIO). Our analysis clearly shows that the leading present-day unstable recharge-discharge mode changes its stability as well as its frequency during LGM conditions. Simulated LGM background conditions were favorable to support large-amplitude self-sustained interannual ENSO variations in the tropical Pacific. Our analysis indicates that off-equatorial climate conditions as well as a shoaling of the thermocline play a crucial role in amplifying the LGM ENSO mode

Crude Oil Fouling Deposition, Suppression, Removal, and Consolidation—and How to Tell the Difference

This research was partially performed under the UNIHEAT project for which EDB and SM wish to acknowledge the Skolkovo Foundation and BP for financial support. The support of Hexxcell Ltd, through provision of Hexxcell Studio, is also acknowledged

Impact of crude oil fouling composition on the thermohydraulic performance of refinery heat exchangers

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Crude oil fouling studies generally focus on the thermal impact of organic deposits. The hydraulic limit given by pressure drop is, however, frequent cause of shutdowns and cleaning. Inorganic matter is often found in deposit analysis, but ignored in most studies. A case study is presented based on published plant data from the Esfahan Refinery (Iran). A detailed thermo-hydraulic model of heat exchangers undergoing fouling, together with the available data and reasonable assumptions, is applied to study the exchanger most affected by fouling. Novel modifications are made to: i) capture the effect of inorganics on the deposit conductivity; and ii) use pressure drop measurements, instead of temperature, to fit key fouling parameters. Good agreement is obtained between model and plant data. This demonstrates the need and benefit of considering fouling layer composition and both temperature and pressure drop data in the fitting of model parameters and interpretation of plant data. The potential of using such a model for early detection of operative problems is highlighted.This research was partially performed under the UNIHEAT project. EDB and SM wish to acknowledge the Skolkovo Foundation and BP for financial support. The support of Hexxcell Ltd, through provision of Hexxcell Studio™, is also acknowledged.am201

Ultrasonic Cutting Device for Bone Surgery Based on a Cymbal Transducer

AbstractIn this study, we introduce a new prototype ultrasonic cutting device for bone surgery based on a class V flextensional cymbal transducer, configured for use in power ultrasonics applications, which removes many of the geometrical restrictions on the cutting tip of Langevin-based transducers. The benefit of incorporating a cymbal transducer is that since the cutting blade itself does not have to be tuned, blade design can focus more closely on delivering the best interaction with bone to provide a highly accurate cut. Small variations to the geometry of the blade do not affect the final resonance frequency. Also the ultrasonic device can be miniaturised to allow the design of devices for delicate orthopaedic procedures involving minimal-access surgery. The results show how the cymbal transducer, driven by a single piezoceramic disc, can excite sufficiently high vibration displacement amplitudes at lower driving voltages. This is achieved by adapting the configuration of the cymbal to remove the problem of epoxy layer debonding, and by optimising the cymbal end-cap and geometry through finite element modelling supported with experimental vibration characterisation. Preliminary characterisations of the resulting prototype ultrasonic bone cutting device, which operates at around 25kHz, illustrate the success of this novel device design