Measurement of pressure and assessment of cavitation for a 22.5-kHz intra-arterial angioplasty device

This study was performed to understand better the mechanisms of action of an (22.5 kHz) ultrasonic wire catheter device used to remove atheromatous plaque in diseased blood vessels (ultrasonic angioplasty). During a clinical procedure, the wire acts as an acoustic waveguide to transfer acoustic energy from a generator outside the body to the ball tip of the wire, which is inserted in the blood vessel. The acoustic field radiated by the vibrating ball tip (1.5- to 3.0-mm diameter), was mapped in a relatively large (600 L) water tank and compared to the field from a well-characterized simple source. A dipolelike radiation pattern due to the translating ball tip was observed. At low power settings, standing wave effects in a smaller cylindrical volume (200-mm diameter, 350-mm height), which was used to simulate anthropometric dimensions, increase relative to the larger tank measurements. The standing wave ratio is dependent upon the pc characteristics of the medium and the dimensions of the volume, rather than on the absorption at this frequency. At high power-settings of the device, cavitation at the tip of the wire was measured using a 20-MHz passive cavitation detection scheme

Lay-led and peer support interventions for adolescents with asthma.

BACKGROUND: Adolescents with asthma are at high risk of poor adherence with treatment. This may be compounded by activities that worsen asthma, in particular smoking. Additional support above and beyond routine care has the potential to encourage good self-management. We wanted to find out whether sessions led by their peers or by lay leaders help to reduce these risks and improve asthma outcomes among adolescents. OBJECTIVES: To assess the safety and efficacy of lay-led and peer support interventions for adolescents with asthma. SEARCH METHODS: We identified trials from the Cochrane Airways Trials Register, which contains reports of randomised trials obtained from multiple electronic and handsearched sources, and we searched trial registries and reference lists of primary studies. We conducted the most recent searches on 25 November 2016. SELECTION CRITERIA: Eligible studies randomised adolescents with asthma to an intervention led by lay people or peers or to a control. We included parallel randomised controlled trials with individual or cluster designs. We included studies reported as full text, those published as abstract only and unpublished data. DATA COLLECTION AND ANALYSIS: Two review authors screened the searches, extracted numerical data and study characteristics and assessed each included study for risk of bias. Primary outcomes were asthma-related quality of life and exacerbations requiring at least a course of oral steroids. We graded the analyses and presented evidence in a 'Summary of findings' table.We analysed dichotomous data as odds ratios, and continuous data as mean differences (MD) or standardised mean differences, all with a random-effects model. We assessed clinical, methodological and statistical heterogeneity when performing meta-analyses, and we described skewed data narratively. MAIN RESULTS: Five studies including a total of 1146 participants met the inclusion criteria for this review. As ever with systematic reviews of complex interventions, studies varied by design (cluster and individually randomised), duration (2.5 to 9 months), setting (school, day camp, primary care) and intervention content. Most risk of bias concerns were related to blinding and incomplete reporting, which limited the meta-analyses that could be performed. Studies generally controlled well for selection and attrition biases.All participants were between 11 and 17 years of age. Asthma diagnosis and severity varied, as did smoking prevalence. Three studies used the Triple A programme; one of these studies tested the addition of a smoke-free pledge; another delivered peer support group sessions and mp3 messaging to encourage adherence; and the third compared a peer-led asthma day camp with an equivalent camp led by healthcare practitioners.We had low confidence in all findings owing to risk of bias, inconsistency and imprecision. Results from an analysis of asthma-related quality of life based on the prespecified random-effects model were imprecise and showed no differences (MD 0.40, 95% confidence interval (CI) -0.02 to 0.81); a sensitivity analysis based on a fixed-effect model and a responder analysis suggested small benefit may be derived for this outcome. Most other results were summarised narratively and did not show an important benefit of the intervention; studies provided no analysable data on asthma exacerbations or unscheduled visits (data were skewed), and one study measuring adherence reported a drop in both groups. Effects on asthma control favoured the intervention but findings were not statistically significant. Results from two studies with high levels of baseline smoking showed some promise for self-efficacy to stop smoking, but overall nicotine dependence and smoking-related knowledge were not significantly better in the intervention group. Investigators did not report adverse events. AUTHORS' CONCLUSIONS: Although weak evidence suggests that lay-led and peer support interventions could lead to a small improvement in asthma-related quality of life for adolescents, benefits for asthma control, exacerbations and medication adherence remain unproven. Current evidence is insufficient to reveal whether routine use of lay-led or peer support programmes is beneficial for adolescents receiving asthma care.Ongoing and future research may help to identify target populations for lay-led and peer support interventions, along with attributes that constitute a successful programme

Growth of primordial black holes in a universe containing a massless scalar field

The evolution of primordial black holes in a flat Friedmann universe with a massless scalar field is investigated in fully general relativistic numerical relativity. A primordial black hole is expected to form with a scale comparable to the cosmological apparent horizon, in which case it may go through an initial phase with significant accretion. However, if it is very close to the cosmological apparent horizon size, the accretion is suppressed due to general relativistic effects. In any case, it soon gets smaller than the cosmological horizon and thereafter it can be approximated as an isolated vacuum solution with decaying mass accretion. In this situation the dynamical and inhomogeneous scalar field is typically equivalent to a perfect fluid with a stiff equation of state $p=\rho$. The black hole mass never increases by more than a factor of two, despite recent claims that primordial black holes might grow substantially through accreting quintessence. It is found that the gravitational memory scenario, proposed for primordial black holes in Brans-Dicke and scalar-tensor theories of gravity, is highly unphysical.Comment: 24 pages, accepted for publication in Physical Review

Accretion with back reaction

We calculate analytically a back reaction of the stationary spherical accretion flow near the event horizon and near the inner Cauchy horizon of the charged black hole. It is shown that corresponding back-reaction corrections to the black hole metric depend only on the fluid accretion rate and diverge in the case of an extremely charged black hole. In result, the test fluid approximation for stationary accretion is violated for extreme black holes. This behavior of the accreting black hole is in accordance with the third law of black hole thermodynamics, forbidding the practical attainability of the extreme state.Comment: 5 pages, 2 figures; new figure and references adde

Semi-Static Hedging Based on a Generalized Reflection Principle on a Multi Dimensional Brownian Motion

On a multi-assets Black-Scholes economy, we introduce a class of barrier options. In this model we apply a generalized reflection principle in a context of the finite reflection group acting on a Euclidean space to give a valuation formula and the semi-static hedge.Comment: Asia-Pacific Financial Markets, online firs

Doppler cooling of gallium atoms: 2. Simulation in complex multilevel systems

This paper derives a general procedure for the numerical solution of the Lindblad equations that govern the coherences arising from multicoloured light interacting with a multilevel system. A systematic approach to finding the conservative and dissipative terms is derived and applied to the laser cooling of gallium. An improved numerical method is developed to solve the time-dependent master equation and results are presented for transient cooling processes. The method is significantly more robust, efficient and accurate than the standard method and can be applied to a broad range of atomic and molecular systems. Radiation pressure forces and the formation of dynamic dark-states are studied in the gallium isotope 66Ga.Comment: 15 pages, 8 figure

A complete classification of spherically symmetric perfect fluid similarity solutions

We classify all spherically symmetric perfect fluid solutions of Einstein's equations with equation of state p/mu=a which are self-similar in the sense that all dimensionless variables depend only upon z=r/t. For a given value of a, such solutions are described by two parameters and they can be classified in terms of their behaviour at large and small distances from the origin; this usually corresponds to large and small values of z but (due to a coordinate anomaly) it may also correspond to finite z. We base our analysis on the demonstration that all similarity solutions must be asymptotic to solutions which depend on either powers of z or powers of lnz. We show that there are only three similarity solutions which have an exact power-law dependence on z: the flat Friedmann solution, a static solution and a Kantowski-Sachs solution (although the latter is probably only physical for a1/5, there are also two families of solutions which are asymptotically (but not exactly) Minkowski: the first is asymptotically Minkowski as z tends to infinity and is described by one parameter; the second is asymptotically Minkowski at a finite value of z and is described by two parameters. A complete analysis of the dust solutions is given, since these can be written down explicitly and elucidate the link between the z>0 and z<0 solutions. Solutions with pressure are then discussed in detail; these share many of the characteristics of the dust solutions but they also exhibit new features.Comment: 63 pages. To appear in Physical Review

A Causal Entropy Bound

The identification of a causal-connection scale motivates us to propose a new covariant bound on entropy within a generic space-like region. This "causal entropy bound", scaling as the square root of EV, and thus lying around the geometric mean of Bekenstein's S/ER and holographic S/A bounds, is checked in various "critical" situations. In the case of limited gravity, Bekenstein's bound is the strongest while naive holography is the weakest. In the case of strong gravity, our bound and Bousso's holographic bound are stronger than Bekenstein's, while naive holography is too tight, and hence typically wrong.Comment: 12 pages, no figures, a reference added and minor typos correcte

Cosmological Constraints on a Dynamical Electron Mass

Motivated by recent astrophysical observations of quasar absorption systems, we formulate a simple theory where the electron to proton mass ratio $\mu =m_{e}/m_{p}$ is allowed to vary in space-time. In such a minimal theory only the electron mass varies, with $\alpha$ and $m_{p}$ kept constant. We find that changes in $\mu$ will be driven by the electronic energy density after the electron mass threshold is crossed. Particle production in this scenario is negligible. The cosmological constraints imposed by recent astronomical observations are very weak, due to the low mass density in electrons. Unlike in similar theories for spacetime variation of the fine structure constant, the observational constraints on variations in $\mu$ imposed by the weak equivalence principle are much more stringent constraints than those from quasar spectra. Any time-variation in the electron-proton mass ratio must be less than one part in $10^{9}$since redshifts $z\approx 1.$This is more than one thousand times smaller than current spectroscopic sensitivities can achieve. Astronomically observable variations in the electron-proton must therefore arise directly from effects induced by varying fine structure 'constant' or by processes associated with internal proton structure. We also place a new upper bound of $2\times 10^{-8}$ on any large-scale spatial variation of $\mu$ that is compatible with the isotropy of the microwave background radiation.Comment: New bounds from weak equivalence principle experiments added, conclusions modifie