Analysis techniques for evaluating the fuel savings associated with wind assistance

Before steam and diesel engines, all cargo merchant ships were propelled by wind power. The arrival of cheap, high-density energy sources such as coal and oil and the economic benefits of the service speed and reliability that this enabled removed wind as a form of propulsion for much of the 20th century. However, higher prices for these energy commodities and environmental regulation, has led some to speculate that wind could return once again as a source of at least some share of a modern merchant ship’s propulsion energy requirement. A number of proposals for the technology that could enable this exist (e.g. soft-sails, wingsails and flettners), all share in common difficulties in their fair assessment, both relative to each other and relative to a conventionally powered ship. A moderately sized rig can supply anywhere between 0-100% of a merchant ship’s propulsion requirements, but this varies as a function of wind speed and direction, which in turn could vary several times a day over the course of multiple-day voyage. The weather, its variability and the specifics of a ship’s route are therefore all key components that render simpler ‘generic’ energy savings assessments meaningless. Furthermore, whilst conventional ships might sail a shortest distance route that avoids extreme weather, a wind-assisted ship might undertake more extreme variation in route and speed over the course of the voyage to maximize benefit obtained from the wind, and this in turn therefore needs to be taken into account in a fair comparison. This paper describes an analysis process that can be applied to any ship design and wind-assistance technology, to fairly evaluate the performance over a range of conditions, and then simulate the performance on a specific voyage using historical records of metocean parameters. The process is applied to an example design to illustrate the method

Optimal parametrizations of adiabatic paths

The parametrization of adiabatic paths is optimal when tunneling is minimized. Hamiltonian evolutions do not have unique optimizers. However, dephasing Lindblad evolutions do. The optimizers are simply characterized by an Euler-Lagrange equation and have a constant tunneling rate along the path irrespective of the gap. Application to quantum search algorithms recovers the Grover result for appropriate scaling of the dephasing. Dephasing rates that beat Grover imply hidden resources in Lindblad operators.Comment: 4 pages, 2 figures; To prevent from misunderstanding, we clarified the discussion of an apparent speedup in the Grover algorithm; figures improved + minor change

High-quality ion beams by irradiating a nano-structured target with a petawatt laser pulse

We present a novel laser based ion acceleration scheme, where a petawatt circularly polarized laser pulse is shot on an ultra-thin (nano-scale) double-layer target. Our scheme allows the production of high-quality light ion beams with both energy and angular dispersion controllable by the target properties. We show that extraction of all electrons from the target by radiation pressure can lead to a very effective two step acceleration process for light ions if the target is designed correctly. Relativistic protons should be obtainable with pulse powers of a few petawatt. Careful analytical modeling yields estimates for characteristic beam parameters and requirements on the laser pulse quality, in excellent agreement with one and two-dimensional Particle-in Cell simulations.Comment: 18 pages, 7 figures, accepted in New. J. Phy

Chapter 08: Vulnerability of seagrasses in the Great Barrier Reef to climate change

Seagrasses are flowering plants and, along with mangroves, have greater affinities to terrestrial plants than other marine macrophytes such as algae. Approximately 55 species of seagrass occur in five different plant families and represent at least three independent evolutionary lineages. Thus, seagrasses are not a taxonomically unified group but a ‘biological’ or ‘ecological’ group85,149. The evolutionary adaptations required for survival in the marine environment have led to convergence in morphology. Seagrasses evolved under differing ambient CO2 and temperature conditions so may have different tolerances to changing environmental conditions. A wide range of tolerances across marine environments exist amongst the extant diversity of seagrasses, reflecting their substantial adaptive capacity as a group.This is Chapter 8 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13

Quantum response of dephasing open systems

We develop a theory of adiabatic response for open systems governed by Lindblad evolutions. The theory determines the dependence of the response coefficients on the dephasing rates and allows for residual dissipation even when the ground state is protected by a spectral gap. We give quantum response a geometric interpretation in terms of Hilbert space projections: For a two level system and, more generally, for systems with suitable functional form of the dephasing, the dissipative and non-dissipative parts of the response are linked to a metric and to a symplectic form. The metric is the Fubini-Study metric and the symplectic form is the adiabatic curvature. When the metric and symplectic structures are compatible the non-dissipative part of the inverse matrix of response coefficients turns out to be immune to dephasing. We give three examples of physical systems whose quantum states induce compatible metric and symplectic structures on control space: The qubit, coherent states and a model of the integer quantum Hall effect.Comment: Article rewritten, two appendices added. 16 pages, 2 figure

Does quantitative heterogeneity of human fetal hemoglobin (Hb F) reveal friends or foes of KLF1 in globin gene switching?

The chemical heterogeneity of fetal hemoglobin (Hb F) due to variable ratios of the Gγ and Aγ globin subunits reflects genetic complexity because of common dimorphisms such as Hb F Sardegna (or Aγ75(E19) Ile>Thr; also known as AγT) in Caucasians, and common variants such the Gγ globin variant, Hb F Malta I (or Gγ117(G19) His>Arg) that is in tight linkage disequilibrium with the β globin variant Hb Valletta (or β87(F3) Thr>Pro) and is found in 1.8% of neonates from Malta.peer-reviewe

Validation of four-dimensional flow cardiovascular magnetic resonance for aortic stenosis assessment

The management of patients with aortic stenosis (AS) crucially depends on accurate diagnosis. The main aim of this study were to validate the four-dimensional flow (4D flow) cardiovascular magnetic resonance (CMR) methods for AS assessment. Eighteen patients with clinically severe AS were recruited. All patients had pre-valve intervention 6MWT, echocardiography and CMR with 4D flow. Of these, ten patients had a surgical valve replacement, and eight patients had successful transcatheter aortic valve implantation (TAVI). TAVI patients had invasive pressure gradient assessments. A repeat assessment was performed at 3–4 months to assess the remodelling response. The peak pressure gradient by 4D flow was comparable to an invasive pressure gradient (54 ± 26 mmHG vs 50 ± 34 mmHg, P = 0.67). However, Doppler yielded significantly higher pressure gradient compared to invasive assessment (61 ± 32 mmHG vs 50 ± 34 mmHg, P = 0.0002). 6MWT was associated with 4D flow CMR derived pressure gradient (r = −0.45, P = 0.01) and EOA (r = 0.54, P < 0.01) but only with Doppler EOA (r = 0.45, P = 0.01). Left ventricular mass regression was better associated with 4D flow derived pressure gradient change (r = 0.64, P = 0.04). 4D flow CMR offers an alternative method for non-invasive assessment of AS. In addition, 4D flow derived valve metrics have a superior association to prognostically relevant 6MWT and LV mass regression than echocardiography

Tracking azimuthons in nonlocal nonlinear media

We study the formation of azimuthons, i.e., rotating spatial solitons, in media with nonlocal focusing nonlinearity. We show that whole families of these solutions can be found by considering internal modes of classical non-rotating stationary solutions, namely vortex solitons. This offers an exhaustive method to identify azimuthons in a given nonlocal medium. We demonstrate formation of azimuthons of different vorticities and explain their properties by considering the strongly nonlocal limit of accessible solitons.Comment: 11 pages, 7 figure

Anomalous Self-Generated Electrostatic Fields in Nanosecond Laser-Plasma Interaction

Electrostatic (E) fields associated with the interaction of a well-controlled, high-power, nanosecond laser pulse with an underdense plasma are diagnosed by proton radiography. Using a current 3D wave propagation code equipped with nonlinear and nonlocal hydrodynamics, we can model the measured E-fields that are driven by the laser ponderomotive force in the region where the laser undergoes filamentation. However, strong fields of up to 110 MV/m measured in the first millimeter of propagation cannot be reproduced in the simulations. This could point to the presence of unexpected strong thermal electron pressure gradients possibly linked to ion acoustic turbulence, thus emphasizing the need for the development of full kinetic collisional simulations in order to properly model laser-plasma interaction in these strongly nonlinear conditions.Comment: 12 pages, 4 figures, submitted to Physics of Plasma