Bounding the graviton mass with binary pulsar observations

By comparing the observed orbital decay of the binary pulsars PSRB1913+16 and PSRB1534+12 to that predicted by general relativity due to gravitational-wave emission, we are able to bound the mass of the graviton to be less than $7.6\times10^{-20} \text{eV}/c^2$ at 90% confidence. This is the first such bound to be derived from dynamic gravitational fields. It is approximately two orders of magnitude weaker than the static-field bound from solar system observations, and will improve with further observations.Comment: 9 pages, 1 figure. Presented at Fourth Edoardo Amaldi Conference on Gravitational Waves, Perth, 200

A Review of the External Validity of Clinical Trials with Beta-Blockers in Heart Failure

This is an open-access article distributed under the terms of the Creative Commons CC-BY-NC 3.0 License.Background: Beta-blockers (BBs) are the mainstay prognostic medication for all stages of chronic heart failure (CHF). There are many classes of BBs, each of which has varying levels of evidence to support its efficacy in CHF. However, most CHF patients have one or more comorbid conditions such as diabetes, renal impairment, and/or atrial fibrillation. Patient enrollment to randomized controlled trials (RCTs) often excludes those with certain comorbidities, particularly if the symptoms are severe. Consequently, the extent to which evidence drawn from RCTs is generalizable to CHF patients has not been well described. Clinical guidelines also underrepresent this point by providing generic advice for all patients. The aim of this review is to examine the evidence to support the use of BBs in CHF patients with common comorbid conditions. Methods: We searched MEDLINE, PubMed, and the reference lists of reviews for RCTs, post hoc analyses, systematic reviews, and meta-analyses that report on use of BBs in CHF along with patient demographics and comorbidities. Results: In total, 38 studies from 28 RCTs were identified, which provided data on six BBs against placebo or head to head with another BB agent in ischemic and nonischemic cardiomyopathies. Several studies explored BBs in older patients. Female patients and non-Caucasian race were underrepresented in trials. End points were cardiovascular hospitalization and mortality. Comorbid diabetes, renal impairment, or atrial fibrillation was detailed; however, no reference to disease spectrum or management goals as a focus could be seen in any of the studies. In this sense, enrollment may have limited more severe grades of these comorbidities. Conclusions: RCTs provide authoritative information for a spectrum of CHF presentations that support guidelines. RCTs may provide inadequate information for more heterogeneous CHF patient cohorts. Greater Phase IV research may be needed to fill this gap and inform guidelines for a more global patient population

Use of shear sensitive coloured guest component to track powder mixing in adhesive binary mixtures

The mixing performance in binary powder blends with components exhibiting guest and host type interactions was assessed by tracking the colour change of the mixture. The operation parameters like mixing time and speed were studied in compositions containing lactose monohydrate as host and iron oxide nanoparticle as coloured guest components. The mixing characteristics were analysed through visual imaging and colorimetric estimations. Furthermore, surface analytical techniques like scanning electron microscope (SEM) for surface area coverage (SAC) determination and Finite Dilution Inverse Gas chromatography (FD-IGC) for surface energy heterogeneity characterisation were employed. The mixing sensitivity of the coloured tracer and the consequent colour transitions under different conditions helped in validating the mixing performance and operation conditions. The FD-IGC results showed a lowering of the energetic heterogeneity for better quality mixtures. Thus, a shear sensitive coloured nano-tracer can be utilised for a simple, quick and cost-effective estimation of the mixture quality and for the validation of mixing process

A numerical analysis of the influence of material properties on dry powder coating performance

Dry powder coating is a preferable surface modification technique over the traditional aqueous coating technique due to reduced energy waste and less environmental impact. Despite the benefits of dry powder coating, excessive amount of coating powder energy input is often applied to ensure sufficient coating is achieved. In this study, the Discrete Element Method (DEM) is utilised to assess the influence of material properties on dry coating efficiency in a blade-driven system. Granular Bond number is used to predict coating performance based on multiple simulations with varied material properties. This provides insight on the optimal range of material properties (size ratio, density ratio and surface energy) to achieve uniformly distributed coatings, thus providing precise control of the quantity of coating material required and minimising energy consumption

The plastic number and its generalized polynomial

The polynomial $X^{3}-X-1$ has a unique positive root known as plastic number, which is denoted by $\rho$ and is approximately equal to $1.32471795$. In this note we study the zeroes of the generalized polynomial $X^{k}-\sum_{j=0}^{k-2}X^{j}$ for $k\geq 3$ and prove that its unique positive root $\lambda_{k}$ tends to the golden ratio $\phi=\frac{1+\sqrt{5}}{2}$ as $k \to \infty$. We also derive bounds on $\lambda_{k}$ in terms of Fibonacci numbers.Comment: Publisher's pdf versio

Bounding the mass of the graviton using gravitional-wave observations of inspiralling compact binaries

If gravitation is propagated by a massive field, then the velocity of gravitational waves (gravitons) will depend upon their frequency and the effective Newtonian potential will have a Yukawa form. In the case of inspiralling compact binaries, gravitational waves emitted at low frequency early in the inspiral will travel slightly slower than those emitted at high frequency later, modifying the phase evolution of the observed inspiral gravitational waveform, similar to that caused by post-Newtonian corrections to quadrupole phasing. Matched filtering of the waveforms can bound such frequency-dependent variations in propagation speed, and thereby bound the graviton mass. The bound depends on the mass of the source and on noise characteristics of the detector, but is independent of the distance to the source, except for weak cosmological redshift effects. For observations of stellar-mass compact inspiral using ground-based interferometers of the LIGO/VIRGO type, the bound on the graviton Compton wavelength is of the order of $6 \times 10^{12}$ km, about double that from solar-system tests of Yukawa modifications of Newtonian gravity. For observations of super-massive black hole binary inspiral at cosmological distances using the proposed laser interferometer space antenna (LISA), the bound can be as large as $6 \times 10^{16}$ km. This is three orders of magnitude weaker than model-dependent bounds from galactic cluster dynamics.Comment: 8 pages, RevTeX, submitted to Phys. Rev.

Formation and Structure of a Current Sheet in Pulsed-Power Driven Magnetic Reconnection Experiments

We describe magnetic reconnection experiments using a new, pulsed-power driven experimental platform in which the inflows are super-sonic but sub-Alfv\'enic.The intrinsically magnetised plasma flows are long lasting, producing a well-defined reconnection layer that persists over many hydrodynamic time scales.The layer is diagnosed using a suite of high resolution laser based diagnostics which provide measurements of the electron density, reconnecting magnetic field, inflow and outflow velocities and the electron and ion temperatures.Using these measurements we observe a balance between the power flow into and out of the layer, and we find that the heating rates for the electrons and ions are significantly in excess of the classical predictions. The formation of plasmoids is observed in laser interferometry and optical self-emission, and the magnetic O-point structure of these plasmoids is confirmed using magnetic probes.Comment: 14 pages, 12 figures. Accepted for publication in Physics of Plasma

Radial Squeezed States and Rydberg Wave Packets

We outline an analytical framework for the treatment of radial Rydberg wave packets produced by short laser pulses in the absence of external electric and magnetic fields. Wave packets of this type are localized in the radial coordinates and have p-state angular distributions. We argue that they can be described by a particular analytical class of squeezed states, called radial squeezed states. For hydrogenic Rydberg atoms, we discuss the time evolution of the corresponding hydrogenic radial squeezed states. They are found to undergo decoherence and collapse, followed by fractional and full revivals. We also present their uncertainty product and uncertainty ratio as functions of time. Our results show that hydrogenic radial squeezed states provide a suitable analytical description of hydrogenic Rydberg atoms excited by short-pulsed laser fields.Comment: published in Physical Review

An Experimental Platform for Pulsed-Power Driven Magnetic Reconnection

We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on exploding wire arrays driven in parallel [Suttle, L. G. et al. PRL, 116, 225001]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The layer exists for long enough to allow evolution of complex processes such as plasmoid formation and movement to be diagnosed by a suite of high spatial and temporal resolution laser-based diagnostics. We can access a wide range of magnetic reconnection regimes by changing the wire material or moving the electrodes inside the wire arrays. We present results with aluminium and carbon wires, in which the parameters of the inflows and the layer which forms are significantly different. By moving the electrodes inside the wire arrays, we change how strongly the inflows are driven. This enables us to study both symmetric reconnection in a range of different regimes, and asymmetric reconnection.Comment: 14 pages, 9 figures. Version revised to include referee's comments. Submitted to Physics of Plasma

Why do dogs (Canis familiaris) select the empty container in an observational learning task?

Many argue that dogs show unique susceptibility to human communicative signals that make them suitable for being engaged in complex co-operation with humans. It has also been revealed that socially provided information is particularly effective in influencing the behaviour of dogs even when the human’s action demonstration conveys inefficient or mistaken solution of task. It is unclear, however, how the communicative nature of the demonstration context and the presence of the human demonstrator affect the dogs’ object-choice behaviour in observational learning situations. In order to unfold the effects of these factors, 76 adult pet dogs could observe a communicative or a non-communicative demonstration in which the human retrieved a tennis ball from under an opaque container while manipulating another distant and obviously empty (transparent) one. Subjects were then allowed to choose either in the presence of the demonstrator or after she left the room. Results showed a significant main effect of the demonstration context (presence or absence of the human’s communicative signals), and we also found some evidence for the response-modifying effect of the presence of the human demonstrator during the dogs’ choice. That is, dogs predominantly chose the baited container, but if the demonstration context was communicative and the human was present during the dogs’ choice, subjects’ tendency to select the baited container has been reduced. In agreement with the studies showing sensitivity to human’s communicative signals in dogs, these findings point to a special form of social influence in observational learning situations when it comes to learning about causally opaque and less efficient (compared to what comes natural to the dog) action demonstrations