Cavitation Induction by Projectile Impacting on a Water Jet

The present paper focuses on the simulation of the high-velocity impact of a projectile impacting on a water-jet, causing the onset, development and collapse of cavitation. The simulation of the fluid motion is carried out using an explicit, compressible, density-based solver developed by the authors using the OpenFOAM library. It employs a barotropic two-phase flow model that simulates the phase-change due to cavitation and considers the co-existence of non-condensable and immiscible air. The projectile is considered to be rigid while its motion through the computational domain is modelled through a direct-forcing Immersed Boundary Method. Model validation is performed against the experiments of Field et al. [Field, J., Camus, J. J., Tinguely, M., Obreschkow, D., Farhat, M., 2012. Cavitation in impacted drops and jets and the effect on erosion damage thresholds. Wear 290–291, 154–160. doi:10.1016/j.wear.2012.03.006. URL http://www.sciencedirect.com/science/article/pii/S0043164812000968 ], who visualised cavity formation and shock propagation in liquid impacts at high velocities. Simulations unveil the shock structures and capture the high-speed jetting forming at the impact location, in addition to the subsequent cavitation induction and vapour formation due to refraction waves. Moreover, model predictions provide quantitative information and a better insight on the flow physics that has not been identified from the reported experimental data, such as shock-wave propagation, vapour formation quantity and induced pressures. Furthermore, evidence of the Richtmyer-Meshkov instability developing on the liquid-air interface are predicted when sufficient dense grid resolution is utilised

Stroboscopic back-action evasion in a dense alkali-metal vapor

We explore experimentally quantum non-demolition (QND) measurements of atomic spin in a hot potassium vapor in the presence of spin-exchange relaxation. We demonstrate a new technique for back-action evasion by stroboscopic modulation of the probe light. With this technique we study spin noise as a function of polarization for atoms with spin greater than 1/2 and obtain good agreement with a simple theoretical model. We point that in a system with fast spin-exchange, where the spin relaxation rate is changing with time, it is possible to improve the long-term sensitivity of atomic magnetometry by using QND measurements

Limits on new long range nuclear spin-dependent forces set with a K-3He co-magnetometer

A magnetometer using spin-polarized K and $^3$He atoms occupying the same volume is used to search for anomalous nuclear spin-dependent forces generated by a separate $^3$He spin source. We measure changes in the $^3$He spin precession frequency with a resolution of 18 pHz and constrain anomalous spin forces between neutrons to be less than $2 \times 10^{-8}$ of their magnetic or less than $2\times 10^{-3}$ of their gravitational interactions on a length scale of 50 cm. We present new limits on neutron coupling to light pseudoscalar and vector particles, including torsion, and constraints on recently proposed models involving unparticles and spontaneous breaking of Lorentz symmetry.Comment: 4 pages, 4 figures, latest version as appeared in PR

High Bandwidth Atomic Magnetometery with Continuous Quantum Non-demolition Measurements

We describe an experimental study of spin-projection noise in a high sensitivity alkali-metal magnetometer. We demonstrate a four-fold improvement in the measurement bandwidth of the magnetometer using continuous quantum non-demolition (QND) measurements. Operating in the scalar mode with a measurement volume of 2 cm^3 we achieve magnetic field sensitivity of 22 fT/Hz^(1/2) and a bandwidth of 1.9 kHz with a spin polarization of only 1%. Our experimental arrangement is naturally back-action evading and can be used to realize sub-fT sensitivity with a highly polarized spin-squeezed atomic vapor.Comment: 4 page

A Low-Noise High-Density Alkali Metal Scalar Magnetometer

We present an experimental and theoretical study of a scalar atomic magnetometer using an oscillating field-driven Zeeman resonance in a high-density optically-pumped potassium vapor. We describe an experimental implementation of an atomic gradiometer with a noise level below 10 fT/Hz^{1/2}, fractional field sensitivity below 10^{-9}/Hz^{1/2}, and an active measurement volume of about 1.5 cm^3. We show that the fundamental field sensitivity of a scalar magnetometer is determined by the rate of alkali-metal spin-exchange collisions even though the resonance linewidth can be made much smaller than the spin-exchange rate by pumping most atoms into a stretched spin state.Comment: 10 pages, 7 figures. Version 2 is longer, with more complete description of theoretical analysis and comparison between analytical and experimental result

Cavitation Induction by Projectile Impacting on a Water Jet

Following the work of Field et al. [4], who experimentally visualised cavity formation and shock propagation in impacted liquids at high velocities, the present study focuses on the simulation of the high velocity impact of a solid projectile on a water jet. The undeformable solid projectile is modelled through a direct forcing Immersed Boundary Method. The simulation is carried out using an explicit density based compressible solver, developed by Kyriazis et al. [6], which employs a two-phase flow model and includes phase change. This study gives a better insight on the phenomena following the impact of solids on liquids, including shock propagation and vapour formation, and demonstrates the capabilities of the presented Immersed Boundary Method to handle compressible cavitating flows

The Family \u3cem\u3eRhabdoviridae\u3c/em\u3e: Mono- and Bipartite Negative-Sense RNA Viruses with Diverse Genome Organization and Common Evolutionary Origins

The family Rhabdoviridae consists of mostly enveloped, bullet-shaped or bacilliform viruses with a negative-sense, single-stranded RNA genome that infect vertebrates, invertebrates or plants. This ecological diversity is reflected by the diversity and complexity of their genomes. Five canonical structural protein genes are conserved in all rhabdoviruses, but may be overprinted, overlapped or interspersed with several novel and diverse accessory genes. This review gives an overview of the characteristics and diversity of rhabdoviruses, their taxonomic classification, replication mechanism, properties of classical rhabdoviruses such as rabies virus and rhabdoviruses with complex genomes, rhabdoviruses infecting aquatic species, and plant rhabdoviruses with both mono- and bipartite genomes

Development of a discrete event simulation model for evaluating strategies of red blood cell provision following mass casualty events

Timely and adequate provision of blood following mass casualty events (MCEs) is critical to reducing mortality rates amongst casualties transported to hospital following an event. Developing planning strategies to ensure the blood transfusion demands of casualties are met is challenging. Discrete event simulation (DES) offers a novel solution to this problem which is financially efficient, less disruptive to services and allows for rich experimentation compared to the current industry standards of live exercises, round-table discussion or tabletop planning. There are currently no published models of this type for investigating blood provision in MCEs. The objective of this study was to develop a working model which could be used to target the in-hospital 'levers' and 'supply levels' of the transfusion system and improve outcomes during the response to future events. This was achieved through the robust design of a DES model using exclusive access to qualitative and quantitative data as well as a panel of experts from the field of transfusion and MCE management. The completed model was extensively and formally evaluated with secondary data from the 7th of July 2005 London bombings, the largest UK based civilian MCE in over 50 years. A subsequent sensitivity analysis revealed the five factors displaying the greatest influence on casualty outcomes. Experimental themes based on these findings have generated new solutions for managing future events which have since been presented to MCE stakeholders and policy makers

A Demand and Capacity Model For Home-Based Intermediate Care: Optimizing The ‘Step Down’ Pathway

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordIntermediate care supports timely discharge from hospital for patients with complex healthcare needs. The purpose of 'step-down' care is to enable patients to leave hospital as soon as medically fit, avoiding costly discharge delays and consequent risks to patient health and wellbeing. Determining optimal intermediate care capacity requires balancing costs to both acute hospital and community care providers. Too much community capacity results in underutilized resources and poor economic efficiency, while too little risks excessive hospital discharge delays. Application of discrete-time simulation shows that total costs across the acute-community interface can be minimized by identifying optimal community capacity in terms of the maximum number of patients for which home visits can be provided by the service. To our knowledge, this is the first simulation study to model the patient pathway from hospital discharge through to community visits. Simulation modeling has supported short-term resource planning in a major English healthcare system.Health Data Research U