No abstract

Mobile agents operating in networked environments face threats from other agents as well as from the hosts (i.e., network sites) they visit. A black hole is a harmful host that destroys incoming agents without leaving any trace. To determine the location of such a harmful host is a dangerous but crucial task, called black hole search. The most important parameter for a solution strategy is the number of agents it requires (the size); the other parameter of interest is the total number of moves performed by the agents (the cost). It is known that at least two agents are needed; furthermore, with full topological knowledge, (n log n) moves are required in arbitrary networks. The natural question is whether, in specific networks, it is possible to obtain (topology-dependent but) more cost efficient solutions. It is known that this is not the case for rings. In this article, we show that this negative result does not generalizes. In fact, we present a general strategy that allows two agents to locate the black hole with O(n) moves in common interconnection networks: hypercubes, cube-connected cycles, star graphs, wrapped butterflies, chordal rings, as well as in multidimensional meshes and tori of restricted diameter. These results hold even if the networks are anonymous.

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This pa per re-as sesses the tectono-ther mal evo lu tion of the fron tal Infratatricum part of the In ner West ern Carpathians orogen based on new geo log i cal-pet ro log i cal and zir con fis sion track (ZFT) data and pub lished 40 Ar-39 Ar and K-Ar data. The study area is in the Považský Inovec Mts. in West ern Slovakia, where the Infratatric Inovec Nappe com prises a micaschist-gneiss base ment and Up per Car bon if er ous-Lower Cre ta ceous cover with the Ju ras sic-Lower Cre ta ceous Humienec Suc ces sion; this lat ter is re con structed from olistoliths in the Horné Belice Suc ces sion Up per Cre ta ceous flysch. The Infratatric Inovec Nappe pos te rior part is thrust over its fron tal Humienec tec tonic Slice with infolded Up per Cre ta ceous sed i ments. This nappe ex hib its very low-tem per a ture tectono-ther mal over print ing, and this is doc u mented by elec tron probe microanalysis of meta mor phic phases and P-T es ti mates. The late Early Cre ta ceous age of this D1 stage event at approx i mately 115-95 Ma is re corded by 114 ±2 and 106 ±4 Ma phengitic white mica 40 Ar-39 Ar ages from a Lower Cre ta ceous cherty slate, and by 101 ±3 Ma 40 Ar-39 Ar age and 102 ±4 Ma ZFT age from Perm ian meta-sand stone. The Inovec Nappe was thus de rived from an Albian-Early Cenomanian accretionary wedge. The hemipelagic Up per Turonian to Lower Santonian red marls and up ward syn-orogenic Up per Santonian to Maastrichtian flysch were de pos ited on the fron tal at ten u ated part of the Inovec Nappe-type base ment in the in ferred Pieninic-Váhic (~South-Penninic) zone. This flysch con tains olistolithic to clastogeneous meta mor phosed ma te rial, in clud ing the Lower Cre ta ceous slates, sup plied from the pos te rior part of the Inovec Nappe. The 40 Ar-39 Ar age of 86 ±2 Ma from this nappes' Perm ian meta-sand stone is con sis tent with D2 thrust ing at ap prox i mately 95-85 Ma and Horné Belice fore land flysch ba sin sup ply in the D3 stage at ~85-65 Ma. The Inovec Nappe fron tal Humienec tec tonic Slice with infolded Up per Cre ta ceous sed i ments sug gests for ma tion of a Paleocene-Eocene accretionary wedge at ap prox i mately 65-40 Ma in the D4 stage. This event is con strained by 40 Ar-39 Ar age of 48 ±2 Ma from the Tatricum hang ing wall blastomylonites and whole-rock K-Ar age of 46 ±3 Ma from a Perm ian ba salt olistolith in the footwall Infratatricum Horné Belice flysch. The Infratatricum fi nally be came part of an Eocene accretionary wedge north of the Hrádok-Zlatníky thrust-fault, and re heat ing and ex hu ma tion cool ing is doc u mented by 57-37 Ma ZFT ages. Al though the Infratatricum ex hib its Late Cre ta ceous and Eocene tectono-ther mal im prints, it is a rem nant of the Early Cre ta ceous structure at the In ner West ern Carpathian front. This im poses the Infratatricum as a dis tal con ti nen tal mar gin of the Penninicum.

This study reports the Neotethyan Meliata Basin ophiolite fragments in the Late Jurassic-Early Cretaceous accretionary wedge mélange in the southern part of the Inner Western Carpathians (IWC). Here we present new lithostratigraphical, petrographical, geochemical, and geochronological data obtained from the mélange blocks used to reconstruct the Meliaticum paleotectonic zones in a tentative evolutionary model of this accretionary wedge. The Dobšiná mélange block continental margin carbonatic and siliciclastic sediments have calc-alkaline basalt intercalations. The basalt Concordia age dated to 245.5 ± 3.3 Ma by U-Pb SIMS on zircon most likely indicates the pre-oceanic advanced early Middle Triassic continental rifting stage. The evolving marginal oceanic crust is composed of Middle to Upper Triassic cherty shales to radiolarites. The detrital zircon U-Pb SIMS Concordia ages of 247 ± 4 Ma and 243 ± 4 Ma from a cherty shale, and the xenocryst zircon population Concordia age of 266 ± 3 Ma from a 0.5 m thick "normal" mid-ocean ridge (N-MOR) basalt layer in this cherty shale reveal the connection of the oceanic basin to the adjacent rifting continental margin. The chertified reddish limestone transition to radiolarite indicates syn-rift basin deepening. Upwards, regular alternating N-MOR basalts and radiolarites are often disturbed by peperite breccia horizons. The Nd isotope values of these basalts (εNd 240 = 7-8) are consistent with their chondrite normalized rare earth element (REE) patterns and indicate a depleted mantle source. The Triassic ophiolitic suite also comprises rare ocean island (OI) basalts (εNd 240 = 5) and serpentinized subduction unrelated peridotites. The Middle to Late Jurassic shortening and southward intra-oceanic and continental margin subduction at approximately 170-150 Ma enhanced the formation of the trench-like Jurassic flysch succession which preceded the closure of the Meliata Basin. The flysch sediments form a mélange matrix of olistolithic unsubducted, obducted, and MP-HP/LT metamorphosed exhumed blocks of the Triassic to Lower Jurassic successions. Blocks of peridotites, rodingites, blueschists, greenschists, rare amphibolites, deep-water shaly sediments and shallow-to deep-water carbonates are typical members of the mélange. The Meliatic accretionary wedge mélange nappe outliers were incorporated in the IWC orogenic wedge in the late Early Cretaceous according to metamorphic rutile U-Pb SIMS ages of 100 ± 10 Ma determined from a Jaklovce metabasalt.