Nuclear Equation of State from Observations of Short Gamma-Ray Burst Remnants

The favoured progenitor model for short $\gamma$-ray bursts (SGRBs) is the merger of two neutron stars that triggers an explosion with a burst of collimated $\gamma$-rays. Following the initial prompt emission, some SGRBs exhibit a plateau phase in their $X$-ray light curves that indicates additional energy injection from a central engine, believed to be a rapidly rotating, highly magnetised neutron star. The collapse of this `protomagnetar' to a black hole is likely to be responsible for a steep decay in $X$-ray flux observed at the end of the plateau. In this letter, we show that these observations can be used to effectively constrain the equation of state of dense matter. In particular, we show that the known distribution of masses in binary neutron star systems, together with fits to the $X$-ray light curves, provide constraints that exclude the softest and stiffest plausible equations of state. We further illustrate how a future gravitational wave observation with Advanced LIGO/Virgo can place tight constraints on the equation of state, by adding into the picture a measurement of the chirp mass of the SGRB progenitor.Comment: accepted for publication in Phys. Rev.

IUE observations of Fe 2 galaxies

Repeated observations of the Seyfert 1 galaxies I Zw 1 and II Zw 136, which have very strong Fe II emission lines in the optical region, were made at low resolution with the IUE Satellite. The ultraviolet spectra are very similar: both are variable and show broad emission features of Fe II (especially the UV multiplets 1, 33, 60, 62, and 63) as well as the emission lines usually strong in Seyferts and quasars. The data strongly support the hypothesis that the optical Fe II emission lines are primarily due to collisional excitation and that resonance fluorescence makes only a minor contribution to the excitation of these lines

Gravitational waves from rapidly rotating neutron stars

Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed as an interesting source of gravitational waves. In this chapter we present estimates of the gravitational wave emission for various scenarios, given the (electromagnetically) observed characteristics of these systems. First of all we focus on the r-mode instability and show that a 'minimal' neutron star model (which does not incorporate exotica in the core, dynamically important magnetic fields or superfluid degrees of freedom), is not consistent with observations. We then present estimates of both thermally induced and magnetically sustained mountains in the crust. In general magnetic mountains are likely to be detectable only if the buried magnetic field of the star is of the order of $B\approx 10^{12}$ G. In the thermal mountain case we find that gravitational wave emission from persistent systems may be detected by ground based interferometers. Finally we re-asses the idea that gravitational wave emission may be balancing the accretion torque in these systems, and show that in most cases the disc/magnetosphere interaction can account for the observed spin periods.Comment: To appear in 'Gravitational Waves Astrophysics: 3rd Session of the Sant Cugat Forum on Astrophysics, 2014', Editor: Carlos F. Sopuert

Observations of turbulence beneath sea ice in southern McMurdo Sound, Antarctica

The first turbulence profiler observations beneath land fast sea ice which is directly adjacent to an Antarctic ice shelf are described. The stratification in the 325 m deep water column consisted of a layer of supercooled water in the upper 40 m lying above a quasi-linearly stratified water column with a sharp step in density at mid-depth. Turbulent energy dissipation rates were on average 3×10<sup>−8</sup> m<sup>2</sup> s<sup>−3</sup> with peak bin-averaged values reaching 4×10<sup>−7</sup> m<sup>2</sup> s<sup>−3</sup>. The local dissipation rate per unit area was estimated to be 10 m Wm<sup>−2</sup> on average with a peak of 50 m Wm<sup>−2</sup>. These values are consistent with a moderate baroclinic response to the tides. The small-scale turbulent energetics lie on the boundary between isotropy and buoyancy-affected. This will likely influence the formation and aggregation of frazil ice crystals within the supercooled layer. The data suggest that the large crystals observed in McMurdo Sound will transition from initial growth at scales smaller than the Kolmogorov lengthscale to sizes substantially (1–2 orders of magnitude) greater than the Kolmogorov scale. An estimate of the experiment-averaged vertical diffusivity of mass <i>K</i>ρ</sub> yields a coefficient of around 2×10<sup>−4</sup> m<sup>2</sup>s<sup>−1</sup> although this increased by a factor of 2 near the surface. Combining this estimate of <i>K</i>ρ</sub> with available observations of average and maximum currents suggests the layer of supercooled water can persist for a distance of ~250 km from the front of the McMurdo Ice Shelf

Housing system, milk production, and zero-grazing effects on lameness and leg injury in dairy cows

The aim of this study was to assess the effect of grazing (G) vs. zero-grazing (ZG), level of milk production,and quality and type of housing system [free stalls (FS)and straw yards (SY)] on the prevalence of lamenessand leg injuries in dairy cows. Observations were madeon 37 commercial dairy farms across Great Britain. Asingle visit of 5 d duration was made to each farm.During this visit, lameness scores and the incidence ofswellings, rubs, and injuries to hocks and knees wererecorded on all the peak- or mid-lactation cows. Aspectsof the quality of housing and management that werelikely to affect foot and leg health were recorded. Therewere more lame cows on ZG farms (39 ± 0.02%) thanon grazing (G) farms (15 ± 0.01%), and lameness scoreswere higher on FS farms compared with SY farms (0.25± 0.01 vs. 0.05 ± 0.01). Cows on SY farms had fewerhock and knee injuries compared with FS farms. The frequency of knee swellings was higher on ZG farms(0.31 ± 0.02) than on G farms (0.15 ± 0.01). Aspects of the free-stall design affected foot and leg health. The number of hock swellings increased with increasing stall gradient (0.16 ± 0.01 with no slope vs. 0.39 ± 0.02at a 0 to 1.5% slope). There was an interaction between the length of the free-stall lunging space and the hip width of the cow, indicating that the incidence of lameness is generally highest on farms with small free stalls and heavy cows. High levels of milk production did not affect lameness or leg injury. The results indicate that housing cows throughout the year potentially has adetrimental effect on foot and leg health. However, good free-stall design may reduce lameness and leg lesion

Patient centred diagnosis: sharing diagnostic decisions with patients in clinical practice.

Patient centred diagnosis is best practised through shared decision making; an iterative dialogue between doctor and patient, whichrespects a patient’s needs, values, preferences, and circumstances. Shared decision making for diagnostic situations differs fundamentally from that for treatment decisions. This has important implications when considering its practical application. The nature of dialogue should be tailored to the specific diagnostic decision; scenarios with higher stakes or uncertainty usually require more detailed conversation

Elasticity of Semiflexible Biopolymer Networks

We develop a model for gels and entangled solutions of semiflexible biopolymers such as F-actin. Such networks play a crucial structural role in the cytoskeleton of cells. We show that the rheologic properties of these networks can result from nonclassical rubber elasticity. This model can explain a number of elastic properties of such networks {\em in vitro}, including the concentration dependence of the storage modulus and yield strain.Comment: Uses RevTeX, full postscript with figures available at http://www.umich.edu/~fcm/preprints/agel/agel.htm

The Role of Feeding Behavior in Sustaining Copepod Populations in the Tropical Ocean

A fundamental question regarding marine copepods is how the many species coexist and persist in the oligotrophic environment (i.e. Hutchinson’s paradox). This question is addressed with a stochastic, object-oriented Lagrangian model that explicitly simulates the distinct foraging behaviors of three prominent tropical species: Clausocalanus furcatus, Paracalanus aculeatus and Oithona plumifera. The model also individually tracks all prey cells. Each particle’s motion combines sinking, turbulent diffusion and active swimming when applicable. The model successfully simulates observed size partitioned carbon uptake rates. Based on the model results, the wide-ranging translational ambit employed by C. furcatus is best suited for the acquisition of passive prey while the relatively stationary behavior of O. plumifera promotes the capture of larger, quickly sinking cells. The model results further suggest that the slow velocities and feeding current employed by P. aculeatus are best suited for acquiring the smallest cells though it also has a slight advantage over C. furcatus in acquiring the largest prey. A resource threshold, at a prey concentration of 530 cells mL–1,is consistently exhibited by all three modeled species. Overall, these results imply that the size-partition preferences due to their different foraging behavior contribute to the coexistence of these three species. (c) The Author 2005

Face-based perception of emotions in dairy goats

Faces of conspecifics convey information about identity, but also gaze, and attentional or emotional state. As a cognitive process, face-based emotion recognition can be subject to judgment bias. In this study we investigated whether dairy goats (n = 32) would show different responses to 2-D images of faces of familiar conspecifics displaying positive or negative emotional states. We also examined the possible use of images of faces as stimuli in cognitive bias studies. The faces of four subjects were photographed in a positive and a negative situation. Three types of images of ambiguous facial expressions were then created using morphing software (75% positive, 50% positive, and 25% positive). In a test-pen, each goat was exposed for 3 seconds to each type of image, obtained from the same goat. All goats were shown non-morphed faces first, before being shown the three types of morphed faces, balanced for order. Finally, the first non-morphed face was shown again. Spontaneous behavioural reactions including ear postures (forward, backward and asymmetrical) and interactions with the screen (time spent looking or touching) were recorded during the 3 seconds. Results were analysed using REML with repeated measurements. Goats spent more time with their ears forward when the negative was shown compared to the positive(F4,121.3 = 2.51, P = 0.018), indicating greater interest in negative faces. Identity of the photographed goat influenced the time spent with the ears forward (F2,57.4 = 7.01, P = 0.002). We conclude that goats react differently to images of faces displaying different emotional states and that they seem to perceive the emotional valence expressed in these images. Response to morphed faces was not necessarily intermediate to response to negative and positive faces, and not on a continuum. Further study is thus needed to clarify the potential use of faces in cognitive bias studies