Memetic Multilevel Hypergraph Partitioning

Hypergraph partitioning has a wide range of important applications such as VLSI design or scientific computing. With focus on solution quality, we develop the first multilevel memetic algorithm to tackle the problem. Key components of our contribution are new effective multilevel recombination and mutation operations that provide a large amount of diversity. We perform a wide range of experiments on a benchmark set containing instances from application areas such VLSI, SAT solving, social networks, and scientific computing. Compared to the state-of-the-art hypergraph partitioning tools hMetis, PaToH, and KaHyPar, our new algorithm computes the best result on almost all instances

RITUAL, TIME, AND ENTERNITY

It is argued here that the construction of time and eternity are among ritual's entailments. In dividing continuous duration into distinct periods ritual distinguishes two temporal conditions: (1) that prevailing in mundane periods and (2) that prevailing during the intervals between them. Differences in the frequency, length, and relationship among the rituals constituting different liturgical orders are considered, as are differences between mundane periods and ritual's intervals with respect to social relations, cognitive modes, meaningfulness, and typical interactive frequencies. Periods, it is observed, relate to intervals as everchanging to never-changing, and close relationships of never changing to eternity, eternity to sanctity, and sanctity to truth are proposed. In the argument that ritual's “times out of time” really are outside mundane time, similarities to the operations of digital computers and Herbert Simon's discussion of interaction frequencies in the organization of matter are noted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72989/1/j.1467-9744.1992.tb00996.x.pd

Increased vulnerability to atrial fibrillation is associated with increased susceptibility to alternans in old sheep

BackgroundAtrial fibrillation (AF) is common in the elderly but rare in the young, however the changes that occur with age that promote AF are not fully understood. Action potential (AP) alternans may be involved in the initiation of AF. Using a translationally relevant model, we investigated if age-associated atrial vulnerability to AF was associated with susceptibility to AP alternans.Methods and ResultsAF was induced in conscious young and old sheep using 50 Hz burst pacing. Old sheep were more vulnerable to AF. Monophasic and cellular APs were recorded from the right atrium in vivo and from myocytes isolated from the left and right atrial appendages. AP alternans occurred at lower stimulation frequencies in old sheep than young in vivo (old 3.0 ± 0.1 Hz; young 3.3 ± 0.1 Hz, p&lt;0.05), and in isolated myocytes (old 1.6 ± 0.1 Hz; young 2.0 ± 0.1 Hz, p&lt;0.05). Simultaneous recordings of [Ca2+]i and membrane potential in myocytes showed that alternans of APs and [Ca2+]i often occurred together. However, at low stimulation rates [Ca2+]i alternans could occur without AP alternans, while at high stimulation rates AP alternans could still be seen despite disabling Ca2+ cycling using thapsigargin. Conclusions We have shown for the first time in a large mammalian model that ageing is associated with increased duration of AF and susceptibility to AP alternans. We suggest that instabilities in Ca2+ handling initiate alternans at low stimulation rates but that AP restitution alone can sustain alternans at higher rates.<br/