Shocks and Tides Quantified in the "Sausage" Cluster, CIZA J2242.8+5301, using N-body/hydro-dynamical Simulations

The colliding cluster, CIZA J2242.8+5301, displays a spectacular, almost 2 Mpc long shock front with a radio based Mach number M ~ 5, that is puzzlingly large compared with the X-ray estimate of M ~ 2.5. The extent to which the X-ray temperature jump is diluted by cooler unshocked gas projected through the cluster currently lacks quantification. Thus, here we apply our self-consistent N-body/hydro-dynamical code (based on FLASH) to model this binary cluster encounter. We can account for the location of the shock front and also the elongated X-ray emission by tidal stretching of the gas and dark matter between the two cluster centers. The required total mass is $8.9 \times 10^{14}$ Msun with a 1.3:1 mass ratio favoring the southern cluster component. The relative velocity we derive is $\simeq 2500$ km/s initially between the two main cluster components, with an impact parameter of 120 kpc. This solution implies that the shock temperature jump derived from the low angular resolution X-ray satellite SUZAKU is underestimated by a factor of two, due to cool gas in projection, bringing the observed X-ray and radio estimates into agreement. We propose that the complex southern relics in CIZA J2242.8+5301, have been broken up as the southerly moving "back" shocked gas impacts the gas still falling in along the collision axis. Finally, we use our model to generate Compton-y maps to estimate the reduction in radio flux caused by the thermal Sunyaev-Zel'dovich (SZ) effect. At 30 GHz, this amounts to $\Delta S_n = -0.072$ mJy/arcmin$^2$ and $\Delta S_s = -0.075$ mJy/arcmin$^2$ at the locations of the northern and southern shock fronts respectively. Our model estimate agrees with previous empirical estimates that have inferred the measured radio spectra can be significantly affected by the SZ effect, with implications for charged particle acceleration models of the radio relics.Comment: 8 pages, 7 figures and 1 table, submitted to the Astrophysical Journal for publication on March

Multi-Phenomena Modeling of the New Bullet Cluster, ZwCl008.8+52, using N-body/hydrodynamical Simulations

We use hydrodynamical/N-body simulations to interpret the newly discovered Bullet-cluster-like merging cluster, ZwCl 0008.8+5215 (ZwCl 0008 hereafter), where a dramatic collision is apparent from multi-wavelength observations. We have been able to find a self-consistent solution for the radio, X-ray, and lensing phenomena by projecting an off-axis, binary cluster encounter viewed just after first core passage. A pair radio relics traces well the leading and trailing shock fronts that our simulation predict, providing constraints on the collision parameters. We can also account for the observed distinctive comet-like X-ray morphology and the positions of the X-ray peaks relative to the two lensing mass centroids and the two shock front locations. Relative to the Bullet cluster, the total mass is about 70% lower, ($1.2\pm0.1) \times 10^{15}$ Msun, with a correspondingly lower infall velocity, $1800\pm300$ km/s, and an impact parameter of $400\pm100$ kpc. As a result, the gas component of the infalling cluster is not trailing significantly behind the associated dark matter as in the case of the Bullet cluster. The degree of agreement we find between all the observables provides strong evidence that dark matter is effectively collisionless on large scales calling into question other claims and theories that advocate modified gravity.Comment: 9 pages, 3 figures, and 1 table, submitted to the Astrophysical Journal for publicationon on December 18. Coments are welcom

A Hydrodynamical Solution for the "Twin-Tailed" Colliding Galaxy Cluster "El Gordo"

The distinctive cometary X-ray morphology of the recently discovered massive galaxy cluster "El Gordo" (ACT-CT J0102-4915; z=0.87) indicates that an unusually high-speed collision is ongoing between two massive galaxy clusters. A bright X-ray "bullet" leads a "twin-tailed" wake, with the SZ centroid at the end of the Northern tail. We show how the physical properties of this system can be determined using our FLASH-based, N-body/hydrodynamic model, constrained by detailed X-ray, Sunyaev-Zel'dovich (SZ), and Hubble lensing and dynamical data. The X-ray morphology and the location of the two Dark Matter components and the SZ peak are accurately described by a simple binary collision viewed about 480 million years after the first core passage. We derive an impact parameter of ~300 kpc, and a relative initial infall velocity of ~2250 km/sec when separated by the sum of the two virial radii assuming an initial total mass of 2.15x10^(15) Msun and a mass ratio of 1.9. Our model demonstrates that tidally stretched gas accounts for the Northern X-ray tail along the collision axis between the mass peaks, and that the Southern tail lies off axis, comprising compressed and shock heated gas generated as the massive component plunges through the main cluster. The challenge for LCDM will be to find out if this physically extreme event can be plausibly accommodated when combined with the similarly massive, high infall velocity case of the "Bullet cluster" and other such cases being uncovered in the new SZ based surveys.Comment: 9 pages, 5 Figures and 1 Table, accepted for publication in the Astrophysical Journa

Rational physical agent reasoning beyond logic

The paper addresses the problem of defining a theoretical physical agent framework that satisfies practical requirements of programmability by non-programmer engineers and at the same time permitting fast realtime operation of agents on digital computer networks. The objective of the new framework is to enable the satisfaction of performance requirements on autonomous vehicles and robots in space exploration, deep underwater exploration, defense reconnaissance, automated manufacturing and household automation

Motor deficits are produced by removing some cortical transplants grafted into injured sensorimotor cortex of neonatal rats.

Fetal frontal cortex was transplanted into cavities formed in the right motor cortex of neonatal rats. As adults, the animals were trained to press two levers in rapid succession with their left forelimb to receive food rewards. Once they had reached an optimal level of performance, the effect of removing their transplants was assessed. Surgical removal of transplants significantly impaired the performance of 2 of 4 subjects. Placing a cross-strain skin graft to induce the immunological rejection of the transplants produced a behavioral deficit in 1 of 2 subjects with complete transplant removal. Skin grafts produced no behavioral effects in four subjects that had surviving transplants. Since the motor deficits produced by transplant removal resembled those observed following the removal of normal motor cortex, we propose that these three transplants functioned within the host brain. Histology showed that the procedures used to remove cortical grafts did not injure any host brains. Therefore, host brain damage is unlikely to account for the behavioral deterioration that followed transplant removals

An Algorithmic Study of Manufacturing Paperclips and Other Folded Structures

We study algorithmic aspects of bending wires and sheet metal into a specified structure. Problems of this type are closely related to the question of deciding whether a simple non-self-intersecting wire structure (a carpenter's ruler) can be straightened, a problem that was open for several years and has only recently been solved in the affirmative. If we impose some of the constraints that are imposed by the manufacturing process, we obtain quite different results. In particular, we study the variant of the carpenter's ruler problem in which there is a restriction that only one joint can be modified at a time. For a linkage that does not self-intersect or self-touch, the recent results of Connelly et al. and Streinu imply that it can always be straightened, modifying one joint at a time. However, we show that for a linkage with even a single vertex degeneracy, it becomes NP-hard to decide if it can be straightened while altering only one joint at a time. If we add the restriction that each joint can be altered at most once, we show that the problem is NP-complete even without vertex degeneracies. In the special case, arising in wire forming manufacturing, that each joint can be altered at most once, and must be done sequentially from one or both ends of the linkage, we give an efficient algorithm to determine if a linkage can be straightened.Comment: 28 pages, 14 figures, Latex, to appear in Computational Geometry - Theory and Application

Functional compounds of einkorn and emmer genotypes

Three einkorn and two emmer genotypes were analysed for concentration of microelements (Fe, Zn and Se) and lipid soluble antioxidants (α-tocopherol, α-tocotrienol and β-carotene). A diversity was observed in micronutrient content, but most of the genotypes have significantly higher trace element and antioxidant contents than the control wheat variety. The emmer genotypes contain lower Fe and β-carotene concentration than einkorn genotypes. The einkorn genotypes have significant higher antioxidant content than the wheat control. On average einkorn has more than three times more β-carotene than the wheat variety. Our results are useful for species/variety choice in functional food production not only for organic but also for conventional farmers, who have/want to operate under low input conditions, especially in Central Europe