Chandra Observation of the Merging Cluster A168: A Late Stage in the Evolution of a Cold Front

We present Chandra observations of the cool cluster A168, for which previous X-ray imaging and optical studies indicated a merger of two subclusters nearly in the plane of the sky. We derive a temperature map for A168, which shows that the merger has proceeded beyond the core passage and is near subcluster turnaround. It also reveals an unusual feature -- the gas core of one of the subclusters forms a tongue-like structure extending ahead (in the direction of motion) of the subcluster center. The coolest cluster gas is found in a crescent-shaped region at the tip of this tongue, and forms a cold front in pressure equilibrium with the external gas. In contrast with this feature's forward location, previously observed merger cold fronts (e.g., A3667, 1E0657--56) lagged behind their host subclusters, as expected in the presense of ram pressure. We propose that A168 illustrates a much later stage in the evolution of a cold front, when its host subcluster approaches the apocenter of the merger orbit where the ram pressure on its gas drops sharply. As a result, a large chunk of the subcluster gas ``slingshots'' past the dark matter center, becomes unbound from the subcluster and expands adiabatically, as seen in some recent hydrodynamic simulations.Comment: 4 pages, 3 figures, to be published in ApJ Letter

Electrical Safety on the Farm

Over the years, electrically powered farm equipment has become an indispensable element of modern farming. With the widespread use of electricity on the farm, more emphasis needs to be placed on using electricity and electrical equipment safely. Nationaly, approximately 30 to 40 people a year are electrocuted on farms. This factsheet covers electric shock, Basics of electrical systems, common precautions, safety hazards and first aid

Lightning Protection for farms

Lightning, one of natures most powerful forces, can cause a great deal of damage, particularly in a farm environment. A lightning strike can start fires in buildings, damage electrical equipment, and electrocute humans and livestock. Losses from lightning can be very costly. Replacing buildings, equipment or livestock disrupts farm operations and incurs considerable expense, and of course a human life can not be replaced. This factsheet covers characteristics of lightning, principles of lightning protection, lightning hazards and protection systems as well as personal safety

Krylov-aware stochastic trace estimation

We introduce an algorithm for estimating the trace of a matrix function $f(\mathbf{A})$ using implicit products with a symmetric matrix $\mathbf{A}$. Existing methods for implicit trace estimation of a matrix function tend to treat matrix-vector products with $f(\mathbf{A})$ as a black-box to be computed by a Krylov subspace method. Like other recent algorithms for implicit trace estimation, our approach is based on a combination of deflation and stochastic trace estimation. However, we take a closer look at how products with $f(\mathbf{A})$ are integrated into these approaches which enables several efficiencies not present in previously studied methods. In particular, we describe a Krylov subspace method for computing a low-rank approximation of a matrix function by a computationally efficient projection onto Krylov subspace.Comment: Figure 5.1 differs somewhat from the published version due to a clerical error made when uploading the images to the journa

Safer Farm Environments for Children

The family farm has always been a place where work, play and life's other activities intertwine at a single location. Generations passed on there beliefs values and work ethics to succeeding generations through shared activities on the farm. Today however, the pastoral farming lifestyle is becoming a high-tech industry. Although the farm has always had its share of hazards, modern agriculture has become one of the nations most perilous industries. Because farm children live and play on the work site, they are exposed to potentially dangerous situations every day. This factsheet discusses the stages of child development, basic tenets of child safety, protection from hazards and safety education of children

Animal Handling Safety

Animals are handled daily on nearly half of New York farms. In the Northeast, animal handling accidents rank second in reported farm accidents. Every year at least one New York farmer dies as a direct result of a confrontation with a farm animal. This factsheet covers animal characteristics, hazards and precautions, and safe facilities