A database of genus 2 curves over the rational numbers

We describe the construction of a database of genus 2 curves of small discriminant that includes geometric and arithmetic invariants of each curve, its Jacobian, and the associated L-function. This data has been incorporated into the L-Functions and Modular Forms Database (LMFDB).Comment: 15 pages, 7 tables; bibliography formatting and typos fixe

Electrical conductivity of the Pampean Shallow Subduction Region of Argentina near 33 S: evidence for a slab window

We present a three-dimensional (3-D) interpretation of 117 long period (20–4096 s) magnetotelluric (MT) sites between 31°S and 35°S in western Argentina. They cover the most horizontal part of the Pampean shallow angle subduction of the Nazca Plate and extend south into the more steeply dipping region. Sixty-two 3-D inversions using various smoothing parameters and data misfit goals were done with a nonlinear conjugate gradient (NLCG) algorithm. A dominant feature of the mantle structure east of the horizontal slab is a conductive plume rising from near the top of the mantle transition zone at 410 km to the probable base of the lithosphere at 100 km depth. The subducted slab is known to descend to 190 km just west of the plume, but the Wadati-Benioff zone cannot be traced deeper. If the slab is extrapolated downdip it slices through the plume at 250 km depth. Removal of portions of the plume or blocking vertical current flow at 250 km depth significantly changes the predicted responses. This argues that the plume is not an artifact and that it is continuous. The simplest explanation is that there is a “wedge”-shaped slab window that has torn laterally and opens down to the east with its apex at the plume location. Stress within the slab and seismic tomography support this shape. Its northern edge likely explains why there is no deep seismicity south of 29°S.Fil: Burd, Aurora I.. University of Washington; Estados UnidosFil: Booker, John R.. University of Washington; Estados UnidosFil: Mackie, Randall. Land General Geophysics; ItaliaFil: Pomposiello, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; ArgentinaFil: Favetto, Alicia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotopica; Argentin

Very long period magnetotellurics at Tucson Observatory: implications for mantle conductivity

In a companion paper (Egbert et al., this issue) we describe the estimation of very long period (0.16 < T < 91 days) magnetotelluric (MT) impedances from 11 years of data collected at the Tucson geomagnetic observatory. Here we discuss the implications of these data for mantle conductivity. Using minimum norm (flattest and smoothest) inversions, we find simple one-dimensional models of electrical conductivity in the depth range 0-1500 km. We use forward modeling, a linearized resolution analysis, and constrained one-dimensional inver­tions to delineate the range of models which are consistent with the estimated impedances. Although the MT data have limited resolution, large-scale vertical averages of mantle conductivity are well constrained. We reach the following conclusions concerning mantle conductivity beneath Tucson: (1) The upper 200 km has a conductance of order 10⁴ Siemens (S). This anomalously high conductance may be concentrated in an aesthenospheric high conductivity layer, but the geometry of the conductive zone is not constrained. (2) Typical conductivities in the transition zone (400-700 km) are = 0.1-0.3 S m⁻¹. A step increase to reach this value at or near the 400 km olivine-spinet phase transition is consistent with, but not required by, the data. An upper mantle which is relative throughout (O.0S S m⁻¹ or less) is not allowed by the data. (3) Resolvable large-scale averages of conductivity increase from = 0.2 S m-⁻¹ to = 1.0 S m-⁻¹ between 600 and 900 km depth. A range of models, including those with step increases, and step decreases, at the 670 km seismic discontinuity are consistent with the data. (4) Between 900-1500 km, conductivity increases slowly. Average conductivities in this region are of the order of 1 S m⁻¹, to within a factor of 2 or 3. While limited zones of highly resistive mantle are consistent with the data, a lower mantle which is resistive throughout is not. Models in which conductivity is always above 5 S m⁻¹ below 1000 km can also be ruled out. In conjunction with improved laboratory estimates of electrical conductivities of mantle minerals at high temperatures and pressures, these constraints can provide important clues to the composition and physical state of the mantle

Imaging crustal structure in southwestern Washington with smalll magnetometer arrays

We use data from a series of small (three to five stations) overlapping magnetovariational (MV) arrays to image variations of vertically integrated electrical conductivity in the crust of southwestern Washington. Two principal structures are revealed: a large north-south trending anomaly (the southern Washington Cascades Conductor (SWCC), which has been detected by several previous induction experiments), and a smaller anomaly which branches off the SWCC just north of Mount St. Helens and trends westward beneath the Chehallis Basin. A weaker east-west trending anomaly is evident farther to the north beneath southern Puget Sound. The MV results concerning the SWCC are reasonably consistent with the model of Stanley et al. (1987), who interpret he anomaly as a suture zone of mid-late Eocene age, but the array data allows us to map the horizontal extent and complex three-dimensional character of the SWCC in greater detail. We suggest that the SWCC represents a section of the early Cenozoic subduction zone which is analogous to the present-day Olympic Peninsula. In the region west of the Cascades, the array data show that crustal conductivity is distinctly three dimensional, consisting of highly resistive blocks (crystalline rocks) separated (in the upper 5-10 km at least) by interconnected narrow regions of higher conductivity (sedimentary units). This pattern of conductivity variations is consistent with the inferred origin of the region as a seamount complex, which was subsequently broken into discrete blocks which have been thrust together during and after accretion to the North American continent. The distribution of anomalous electric currents and our model for crustal conductance are in striking agreement with a variety of other geophysical constraints, including gravity, magnetics, present crustal seismicity, and the pattern of recent volcanic vents. The St. Helens seismic zone (SHZ), which coincides with the western edge of the broad southern portion of the SWCC, is abruptly terminatedi n the north by the smaller east-west trending conductive zone. North of the SHZ near Mount Rainier, seismicity is concentrated in a narrow band coincident with the very narrow northern portion of the SWCC. In addition, volcanic vents are concentrated around the edges of the SWCC but are rare in the interior of the zone of high conductivity. The magnetometer array data thus suggest that present patterns of crustal deformation and volcanism are in part controlled by the complex tectonic history (and resulting crustal structure) of the region

Very long period magnetotellurics at Tucson Observatory: estimation of impedances

Eleven years (1932-1942) of electric potential and magnetic measurement at the Tucson observatory represent a unique very long period magnetotelluric (MT) data set. We report here on a careful reanalysis of this data using modern processing techniques. We have developed and used novel methods for separating out the quasi-periodic daily variation fields and for cleaning up outliers and filling in missing data in the time domain. MT impedance tensors, estimated using the cleaned and filled data and using robust frequency domain methods, are well determined and smoothly varying for periods between 4 hours and 10 days. At longer periods the electric field data are swamped by large-amplitude incoherent noise, particularly after the third year of the experiment. Although we find no evidence for contamination of any field components by oceanic motional induction at tidal periods, the MT impedance estimates do show evidence of small systematic biases due to finite spatial scale geomagnetic sources at harmonics of the daily variation period. These periods are thus removed from the time series and not used in further analysis. We show that the resulting impedance tensor is well modeled by a real, frequency-independent distortion of a scalar impedance, which is consistent with non-inductive distortion of the electric fields by local surface geology. To estimate the undetermined static shift of the MT impedance, we compare the long-period MT results to equivalent MT impedances determined from 46 years of geomagnetic data. Combining the geomagnetic and undistorted MT impedances results in scalar impedance estimates for periods 0 .17 < T < 91 days of unprecedented precision. However, for periods less than one day, the phase and amplitude of this impedance, while individually consistent, are not mutually consistent with any one dimensional conductivity distribution. The inconsistency probably results from a combination of subtle multidimensional effects and systematic biases

The Clinchfield and Unicoi County: Documenting the Oral History and Traditions of a Railroad Community

The panel will focus on the oral history and traditions of the Clinchfield from those that were there, as passengers, employees, landowners, and various other stakeholders of the railroad and Unicoi County

Engaging with community researchers for exposure science: lessons learned from a pesticide biomonitoring study

A major challenge in biomonitoring studies with members of the general public is ensuring their continued involvement throughout the necessary length of the research. The paper presents evidence on the use of community researchers, recruited from local study areas, as a mechanism for ensuring effective recruitment and retention of farmer and resident participants for a pesticides biomonitoring study. The evidence presented suggests that community researchers' abilities to build and sustain trusting relationships with participants enhanced the rigour of the study as a result of their on-the-ground responsiveness and flexibility resulting in data collection beyond targets expected

Cellular and synaptic phenotypes lead to disrupted information processing in Fmr1-KO mouse layer 4 barrel cortex

Sensory hypersensitivity is a common and debilitating feature of neurodevelopmental disorders such as Fragile X Syndrome (FXS). How developmental changes in neuronal function culminate in network dysfunction that underlies sensory hypersensitivities is unknown. By systematically studying cellular and synaptic properties of layer 4 neurons combined with cellular and network simulations, we explored how the array of phenotypes in Fmr1-knockout (KO) mice produce circuit pathology during development. We show that many of the cellular and synaptic pathologies in Fmr1-KO mice are antagonistic, mitigating circuit dysfunction, and hence may be compensatory to the primary pathology. Overall, the layer 4 network in the Fmr1-KO exhibits significant alterations in spike output in response to thalamocortical input and distorted sensory encoding. This developmental loss of layer 4 sensory encoding precision would contribute to subsequent developmental alterations in layer 4-to-layer 2/3 connectivity and plasticity observed in Fmr1-KO mice, and circuit dysfunction underlying sensory hypersensitivity.</p