Short-lived Radio Bursts from the Crab Pulsar

Our high-time-resolution observations reveal that individual main pulses from the Crab pulsar contain one or more short-lived microbursts. Both the energy and duration of bursts measured above 1 GHz can vary dramatically in less than a millisecond. These fluctuations are too rapid to be caused by propagation through turbulence in the Crab Nebula or the interstellar medium; they must be intrinsic to the radio emission process in the pulsar. The mean duration of a burst varies with frequency as $\nu^{-2}$, significantly different from the broadening caused by interstellar scattering. We compare the properties of the bursts to some simple models of microstructure in the radio emission region.Comment: 34 pages, 10 figures; accepted for publication in Ap

Educators\u27 knowledge and attitude regarding NJ\u27s Core Curriculum Content Standards

This study examined the knowledge of teachers regarding NJ\u27s Core Curriculum Content Standards and their attitudes towards those standards. A survey was distributed and collected from 35 participants. Items on the survey were factored into three categories. These categories described how well-informed educators were regarding NJ\u27s CCCS, their feelings towards the standards and how well-prepared they as educators felt they were. Results reveal that educators have some knowledge regarding NJ\u27s CCCS, however, that knowledge-base must be broadened. Results also showed that the majority of educators have either a positive attitude or an indifferent attitude towards implementing NJ\u27s CCCS and that showed that only half of the participants had a copy of NJ\u27s CCCS. Practical applications of research implications are discussed and suggestions for future research are provided

Analogy Between Surface Shock Waves in a Liquid and Shocks in Compressible Gases: Experimental Study of Hydraulic-Jump Interactions

It has been known for some time that an analogy exists between the flow of a liquid with a free surface and the flow of a compressible gas. A less accurate analogy has been shown to obtain between hydraulic jumps and compression shocks. The interaction of shocks can occur in two forms; the regular or two-shock configuration and the Mach or three-shock configuration. The latter configuration is not yet completely understood, either in the case of hydraulic jumps in a free-surface liquid or in the case of shocks in a compressible gas. This experimental study was primarily concerned with the Mach interactions of hydraulic jumps. The conclusions of this study are: (a) there is a definite disagreement between experiment and existing theory; (b) a depth discontinuity, or wave, rather than a velocity discontinuity separates the region behind the Mach wave from the region behind the reflected wave; (c) there is evidence that, for interactions of weak hydraulic jumps, there is a deviation from constant depth between waves; (d) the Mach wave is convex for the interaction of the stronger hydraulic jumps, but is concave for the interaction of weak hydraulic jumps; (e) measurements should not be made so as to allow for curvature of the Mach without considering the curvature of the incident and reflected waves in the neighborhood of the triple point

On the Stability of a Planetary System Embedded in the Beta Pictoris Debris Disk

It has recently been stated that the warp structure observed around the star Beta Pictoris may be due to four planets embedded in its debris disk (Wahhaj et al., 2003). It, therefore, becomes important to investigate for what range of parameters, and for how long such a multibody system will be dynamically stable. We present the results of the numerical integration of the suggested planetary system for different values of the mass and radii of the planets, and their relative positions and velocities. We also present a statistical analysis of the results in an effort to understand the relation between the different regions of the parameter-space of the system and the duration of the orbital stability of the embedded planets.Comment: 4 pages, 2 figures, 1 table, to appear in the proceedings of "The Search for Other Worlds." The 14th Annual October Astrophysics Conference in Maryland. Eds. D. Deming and S. Holt (PASP Style

Do consumers gamble to convexify?

The combination of credit constraints and indivisible consumption goods may induce some risk-averse individuals to gamble to have a chance of crossing a purchasing threshold. This idea has been demonstrated theoretically, but not explored empirically. We test this idea by focusing on a key implication: income effects for individuals who choose to gamble are likely to be larger than for the general population. Using UK data on gambling wins, other windfalls and durable goods purchases, we show that winners display higher income effects than non-winners but only amongst those likely to be credit-constrained. This is consistent with credit-constrained, risk-averse agents gambling to convexify their budget set.This work was supported in part by the ESRC-funded Centre for Microeconomic Analysis of Public Policy at the Institute for Fiscal Studies (grant number RES-544-28-5001.)This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.jebo.2016.07.02

Responsibility, resilience and symbolic power

The reciprocal nature of the relationship between the concepts of responsibilisation and resilience appears, in policy and political circles at least, almost natural. Whilst both concepts have been subjected to sustained academic critique for their presentation as largely individual or familial qualities, and their negation of social and structural pressures, there has been more limited attention paid to the potential of the concepts if they were put to work in a different way. This article attempts to sketch out ways in which the fundamentally relational aspects of the concepts of responsibility and resilience can be brought to the fore. In doing so, it builds on Rose and Lentzos’s argument that we should perhaps ‘argue not against responsibility and resilience but on the territory of responsibilities and resiliencies’ and sets out the case for engaging with, rather than withdrawing from or resisting discussions of the meanings and uses of these concepts, in tandem. Extending the work of Bourdieu and Wacquant, it argues for the need to turn the lens on the structures and mechanisms of power which promote and maintain inequality and divisive complex social relations, which undermine the possibility of collective ‘resilience’. The article advocates our collective ‘responsibility’ as engaging in processes that challenge and redefine these practices and structures to enable resistance and progressive action

The analogy between surface waves in a liquid and shocks in compressible gases: experimental study of wave forms

The subject matter covered in this report concerns the characteristics of the surface waves produced in the ripple tank by the wave generators and the effect on the wave form of adding detergents to the working fluid. The results will be presented under the following headings: 1. Experimental procedure. 2. The wave generators. 3. Variables affecting wave strength. 4. Effect of adding detergents to working fluid. 5. Summary and conclusions

Insights into sulfur cycling at subduction zones from in-situ isotopic analysis of sulfides in high-pressure serpentinites and ‘hybrid’ samples from Alpine Corsica

Devolatilisation of serpentinites at depth in subduction zones contributes significant quantities of sulfur and other redox sensitive elements to the sub-arc mantle. However, the fate of sulfur in subducted serpentinites is poorly constrained. Textures of sulfur-bearing phases in subducted serpentinites are rarely studied, yet provide important information on the changes to sulfur distribution throughout the subduction cycle and as a result of fluid infiltration. d34S values of sulfides provide constraints on sulfur sources, the redox state of sulfur in the host mineral, and on processes that have occurred subsequent to sulfide crystallisation, including interaction with oxidised or reduced fluids. Therefore, it is possible to use d34S values in subducted serpentinites to constrain the redox state of sulfur in sulfides and subduction zone fluids. Furthermore, the proximity of serpentinites to ocean crust and metasediments may influence enrichment or depletion of34S during subduction relative to serpentinites distal to such lithologies. This study investigates the redox state, the likelihood of sulfur addition to the sub-arc mantle from serpentinite dehydration, and the distribution of sulfur within subducted serpentinites and ‘hybrid’ mafic/ultramafic rocks from Alpine Corsica. The techniques utilised include petrographic analysis, in-situ sulfur isotopic analysis and trace element analysis of sulfides hosted in these rocks. All sulfides investigated have high d34S values of 1.9–15.5‰ which suggests that mantle-derived sulfur (d34S ~0.1‰), was not the sole source of sulfur. The highest d34S values are recorded in pyrites of a hybrid mafic/ultramafic sample. High d34S values are preserved in sulfides attributed to prograde metamorphism, and is most consistent with the retention of sulfur derived from hydrothermal sulfate reduction on the seafloor. However, a shift towards higher d34S values in sulfides associated with the advanced stages of exhumation suggests that late stage exhumation enables enhanced access to slab-derived fluids bearing oxidised sulfur (SO42-or SO2). Such fluids may have been derived from the devolatilisation of serpentinite at greater depth, or from other lithologies

Structural lubricity: Role of dimension and symmetry

When two chemically passivated solids are brought into contact, interfacial interactions between the solids compete with intrabulk elastic forces. The relative importance of these interactions, which are length-scale dependent, will be estimated using scaling arguments. If elastic interactions dominate on all length scales, solids will move as essentially rigid objects. This would imply superlow kinetic friction in UHV, provided wear was absent. The results of the scaling study depend on the symmetry of the surfaces and the dimensionalities of interface and solids. Some examples are discussed explicitly such as contacts between disordered three-dimensional solids and linear bearings realized from multiwall carbon nanotubes.Comment: 7 pages, 1 figur