17,010 research outputs found
Generic changes in United States Issini (Hemiptera, Fulgoroidea, Issidae)
Three new genera of the family Issidae are described for species formerly included in the genus Hysteropterum sensu lato: Balduza Gnezdilov and O’Brien, gen. n. (type species: Hysteropterum unum Ball 1910), Stilbometopius Gnezdilov and O’Brien, gen. n. (type species: Issus auroreus Uhler 1876), Abolloptera Gnezdilov and O’Brien, gen. n. (type species: Hysteropterum bistriatum Caldwell 1945),. The genus Tylanira Ball 1936 is redescribed. The male genitalia of Tylanira bifurca Ball 1936 is described and illustrated. Tylana ustulata Uhler 1876 is transfered to Tylanira. Hysteropterum bufo Van Duzee 1923 is transfered to Balduza gen. n. and the male genitalia of the species is described and illustrated. The subgenus Paralixes Caldwell 1945 of the genus Ulixes Stål 1861 is raised to genus – Paralixes Caldwell 1945, stat. n. A key to the issid genera of the United States is given. New data on the distribution of 7 species are given
Lithospheric failure on Venus
We develop a predictive model which has the ability to explain a postulated style of episodic plate tectonics on Venus, through the periodic occurrence of lithospheric subduction events. Present-day incipient subduction zones are associated with the existence of arcuate trenches on the Venusian lithosphere. These trenches resemble terrestrial subduction zones, and occur at the rim of coronae, uplift features thought to be due to deep-mantle convective plumes. The model we adopt represents the lithosphere as the thermal boundary layer which lies above a convective plume. We assume a temperature-dependent nonlinear viscoelastic rheology, and we assume a stress-based criterion for plastic yield. In developing this latter criterion, we are led to a re-interpretation of the strength envelope which is commonly used in analysing lithospheric stress, and we propose that the plastic yield strength has meaning (and is finite) below the lithosphere, using behaviour in the Earth as our 'laboratory' justification for this view. An inferred yield stress on the Earth is ca. 300 bar (30 MPa). Our model then shows that a thickening lithosphere becomes progressively more fluid as the stresses induced by the buoyant convective plume become large. Failure occurs when the effective lithosphere viscosity becomes equal to that of the underlying mantle. We show that reasonable expected values of yield stress in the range 100-200 bar (10-20 MPa) for Venusian mantle rocks are consistent within the framework of the model with radii of coronal trenches in the range 100-1200 km, and with the approximate time (200-800 Myr) which they may take to develop
Density-matrix simulation of small surface codes under current and projected experimental noise
We present a full density-matrix simulation of the quantum memory and
computing performance of the distance-3 logical qubit Surface-17, following a
recently proposed quantum circuit and using experimental error parameters for
transmon qubits in a planar circuit QED architecture. We use this simulation to
optimize components of the QEC scheme (e.g., trading off stabilizer measurement
infidelity for reduced cycle time) and to investigate the benefits of feedback
harnessing the fundamental asymmetry of relaxation-dominated error in the
constituent transmons. A lower-order approximate calculation extends these
predictions to the distance- Surface-49. These results clearly indicate
error rates below the fault-tolerance threshold of surface code, and the
potential for Surface-17 to perform beyond the break-even point of quantum
memory. At state-of-the-art qubit relaxation times and readout speeds,
Surface-49 could surpass the break-even point of computation.Comment: 10 pages + 8 pages appendix, 12 figure
Sphaleron of a 4 dimensional SO(4) Higgs model
We construct the finite energy path between topologically distinct vacua of a
4 dimensional SO(4) Higgs model which is known to support an instanton, and
show that there is a sphaleron with Chern-Simons number N_CS=1/2 at the top of
the energy barrier. This is carried out using the original geometric loop
construction of Manton.Comment: 9 pages, 2 figures, LaTex format, minor text corrections. To be
published in Phys. Lett.
Uncovering anorexia nervosa in a biofeedback clinic for bowel dysfunction
Biofeedback is a conservative treatment based on behavioural techniques, which can be used in the management of bowel dysfunction. This article reports the results of a retrospective review of the clinical notes of 87 female patients attending a biofeedback service at St Mark's Hospital, Harrow. The initial review was conducted to examine the incidence of polycystic ovary syndrome (PCOS) in patients attending this service. Seven percent were found to have PCOS, which is within the normal range. However, a significant proportion of patients (11.5%) had a current history of anorexia nervosa, a higher rate than in the general population, which prompted further investigation. In this article, Sonya Chelvanayagam, Julie Duncan, Brigitte Collins and Lorraine O'Brien report on the results of this review and discuss the significance of its findings. © Copyright Terms & conditions
Testing isomorphism of graded algebras
We present a new algorithm to decide isomorphism between finite graded
algebras. For a broad class of nilpotent Lie algebras, we demonstrate that it
runs in time polynomial in the order of the input algebras. We introduce
heuristics that often dramatically improve the performance of the algorithm and
report on an implementation in Magma
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