945 research outputs found
First record of Mermithidae (Nematoda) parasitic in Plecoptera
The first record of Nematoda Mermithidae in adults and larvae of two Protonemura species (Plecoptera Nemouridae) and of Isoperla rivulorum (Pictet) (Plecoptera Perlodidae) from North Italy and Bavaria (Germany) is presented. The malformed genitalia of several parasitically castrated adults are described and illustrated. Primi reperti di Mermithidae (Nematoda) endoparassiti di Plecoptera. Viene segnalata per la prima volta la presenza di Mermithidae (Nematoda) nell’addome di adulti e di ninfe di due specie di Protonemura (Plecoptera Nemouridae) e di Isoperla rivulorum (Pictet) (Plecoptera Perlodidae), raccolte rispettivamente nell’Italia settentrionale ed in Baviera (Germania). I genitali malformati di alcuni adulti, deformità causate da castrazione parassitaria, sono descritti e illustrati
Unconventional magnetism in the 4d based () honeycomb system AgLiRuO
We have investigated the thermodynamic and local magnetic properties of the
Mott insulating system AgLiRuO containing Ru
(4) for novel magnetism. The material crystallizes in a monoclinic
structure with RuO octahedra forming an edge-shared
two-dimensional honeycomb lattice with limited stacking order along the
-direction. The large negative Curie-Weiss temperature ( = -57
K) suggests antiferromagnetic interactions among Ru ions though magnetic
susceptibility and heat capacity show no indication of magnetic long-range
order down to 1.8 K and 0.4 K, respectively. Li nuclear magnetic
resonance (NMR) shift follows the bulk susceptibility between 120-300 K and
levels off below 120 K. Together with a power-law behavior in the temperature
dependent spin-lattice relaxation rate between 0.2 and 2 K, it suggest dynamic
spin correlations with gapless excitations. Electronic structure calculations
suggest an description of the Ru-moments and the possible importance of
further neighbour interactions as also bi-quadratic and ring-exchange terms in
determining the magnetic properties. Analysis of our SR data indicates
spin freezing below 5 K but the spins remain on the borderline between static
and dynamic magnetism even at 20 mK.Comment: 10 pages, 11 figures. accepted in Phys. Rev.
Long quantum channels for high-quality entanglement transfer
High-quality quantum-state and entanglement transfer can be achieved in an
unmodulated spin bus operating in the ballistic regime, which occurs when the
endpoint qubits A and B are coupled to the chain by an exchange interaction
comparable with the intrachain exchange. Indeed, the transition amplitude
characterizing the transfer quality exhibits a maximum for a finite optimal
value , where is the channel length. We show that
scales as for large and that it ensures a
high-quality entanglement transfer even in the limit of arbitrarily long
channels, almost independently of the channel initialization. For instance, the
average quantum-state transmission fidelity exceeds 90% for any chain length.
We emphasize that, taking the reverse point of view, should be
experimentally constrained, high-quality transfer can still be obtained by
adjusting the channel length to its optimal value.Comment: 12 pages, 9 figure
The Impatient May Use Limited Optimism to Minimize Regret
Discounted-sum games provide a formal model for the study of reinforcement
learning, where the agent is enticed to get rewards early since later rewards
are discounted. When the agent interacts with the environment, she may regret
her actions, realizing that a previous choice was suboptimal given the behavior
of the environment. The main contribution of this paper is a PSPACE algorithm
for computing the minimum possible regret of a given game. To this end, several
results of independent interest are shown. (1) We identify a class of
regret-minimizing and admissible strategies that first assume that the
environment is collaborating, then assume it is adversarial---the precise
timing of the switch is key here. (2) Disregarding the computational cost of
numerical analysis, we provide an NP algorithm that checks that the regret
entailed by a given time-switching strategy exceeds a given value. (3) We show
that determining whether a strategy minimizes regret is decidable in PSPACE
A Molecular Phylogeny for the Leaf-Roller Moths (Lepidoptera: Tortricidae) and Its Implications for Classification and Life History Evolution
Tortricidae, one of the largest families of microlepidopterans, comprise about 10,000 described species worldwide, including important pests, biological control agents and experimental models. Understanding of tortricid phylogeny, the basis for a predictive classification, is currently provisional. We present the first detailed molecular estimate of relationships across the tribes and subfamilies of Tortricidae, assess its concordance with previous morphological evidence, and re-examine postulated evolutionary trends in host plant use and biogeography.We sequenced up to five nuclear genes (6,633 bp) in each of 52 tortricids spanning all three subfamilies and 19 of the 22 tribes, plus up to 14 additional genes, for a total of 14,826 bp, in 29 of those taxa plus all 14 outgroup taxa. Maximum likelihood analyses yield trees that, within Tortricidae, differ little among data sets and character treatments and are nearly always strongly supported at all levels of divergence. Support for several nodes was greatly increased by the additional 14 genes sequenced in just 29 of 52 tortricids, with no evidence of phylogenetic artifacts from deliberately incomplete gene sampling. There is strong support for the monophyly of Tortricinae and of Olethreutinae, and for grouping of these to the exclusion of Chlidanotinae. Relationships among tribes are robustly resolved in Tortricinae and mostly so in Olethreutinae. Feeding habit (internal versus external) is strongly conserved on the phylogeny. Within Tortricinae, a clade characterized by eggs being deposited in large clusters, in contrast to singly or in small batches, has markedly elevated incidence of polyphagous species. The five earliest-branching tortricid lineages are all species-poor tribes with mainly southern/tropical distributions, consistent with a hypothesized Gondwanan origin for the family.We present the first robustly supported phylogeny for Tortricidae, and a revised classification in which all of the sampled tribes are now monophyletic
Fault Locking, Block Rotation and Crustal Deformation in the Pacific Northwest
We interpret Global Positioning System (GPS) measurements in the northwestern United States and adjacent parts of western Canada to describe relative motions of crustal blocks, locking on faults and permanent deformation associated with convergence between the Juan de Fuca and North American plates. To estimate angular velocities of the oceanic Juan de Fuca and Explorer plates and several continental crustal blocks, we invert the GPS velocities together with seafloor spreading rates, earthquake slip vector azimuths and fault slip azimuths and rates. We also determine the degree to which faults are either creeping aseismically or, alternatively, locked on the block-bounding faults. The Cascadia subduction thrust is locked mainly offshore, except in central Oregon, where locking extends inland. Most of Oregon and southwest Washington rotate clockwise relative to North America at rates of 0.4-1.0 ° Myr-1. No shear or extension along the Cascades volcanic arc has occurred at the mm/yr level during the past decade, suggesting that the shear deformation extending northward from the Walker Lane and eastern California shear zone south of Oregon is largely accommodated by block rotation in Oregon. The general agreement of vertical axis rotation rates derived from GPS velocities with those estimated from palaeomagnetic declination anomalies suggests that the rotations have been relatively steady for 10-15 Ma. Additional permanent dextral shear is indicated within the Oregon Coast Range near the coast. Block rotations in the Pacific Northwest do not result in net westward flux of crustal material¿the crust is simply spinning and not escaping. On Vancouver Island, where the convergence obliquity is less than in Oregon and Washington, the contractional strain at the coast is more aligned with Juan de Fuca¿North America motion. GPS velocities are fit significantly better when Vancouver Island and the southern Coast Mountains move relative to North America in a block-like fashion. The relative motions of the Oregon, western Washington and Vancouver Island crustal blocks indicate that the rate of permanent shortening, the type that causes upper plate earthquakes, across the Puget Sound region is 4.4 ± 0.3 mm yr-1. This shortening is likely distributed over several faults but GPS data alone cannot determine the partitioning of slip on them. The transition from predominantly shear deformation within the continent south of the Mendocino Triple Junction to predominantly block rotations north of it is similar to changes in tectonic style at other transitions from shear to subduction. This similarity suggests that crustal block rotations are enhanced in the vicinity of subduction zones possibly due to lower resisting stress
Spectroscopic signatures of spin-charge separation in the quasi-one-dimensional organic conductor TTF-TCNQ
The electronic structure of the quasi-one-dimensional organic conductor
TTF-TCNQ is studied by angle-resolved photoelectron spectroscopy (ARPES). The
experimental spectra reveal significant discrepancies to band theory. We
demonstrate that the measured dispersions can be consistently mapped onto the
one-dimensional Hubbard model at finite doping. This interpretation is further
supported by a remarkable transfer of spectral weight as function of
temperature. The ARPES data thus show spectroscopic signatures of spin-charge
separation on an energy scale of the conduction band width.Comment: 4 pages, 4 figures; to appear in PR
Confinement of Interchain Hopping by Umklapp Scattering in Two-Coupled Chains
The effect of umklapp scattering on interchain hopping has been investigated
for two-coupled chains of interacting electrons with half-filled band. By
analyzing in terms of renormalization group method, we have found that
interchain hopping is renormalized to zero and is confined when a gap induced
by umklapp scattering becomes larger than a critical value. From a phase
diagram calculated on a plane of the interchain hopping and the gap, we discuss
a role of the correlation gap which has been studied in metallic state at
temperatures above spin density wave state in organic conductors.Comment: 5 pages, 3 figure
Non-fermi-liquid single particle lineshape of the quasi-one-dimensional non-CDW metal Li_{0.9}Mo_{6}O_{17} : comparison to the Luttinger liquid
We report the detailed non-Fermi liquid (NFL) lineshape of the dispersing
excitation which defines the Fermi surface (FS) for quasi-one-dimensional
Li_{0.9}Mo_{6}O_{17}. The properties of Li_{0.9}Mo_{6}O_{17} strongly suggest
that the NFL behavior has a purely electronic origin. Relative to the
theoretical Luttinger liquid lineshape, we identify significant similarities,
but also important differences.Comment: 5 pages, 3 eps figure
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