83,513 research outputs found
Additions to the Checklist of the Illinois Spiders
Five families and 140 species of spiders not included in former Illinois checklists are recorded. Two of these families, Antrodiaetidae and Scytodidae, and 40 of the species have been cited in earlier revisionary or other literature. The families Oonopidae, Symphytognathidae (slat.) and Ctenidae, and the remaining 100 species of spiders are recorded from Illinois for the first time. Locality data are given as counties only, and months of capture of mature specimens are presented. The total known spider fauna of Illinois now stands at 500 species in 27 families
Chameleon Vector Bosons
We show that for a force mediated by a vector particle coupled to a conserved
U(1) charge, the apparent range and strength can depend on the size and density
of the source, and the proximity to other sources. This "chameleon" effect is
due to screening from a light charged scalar. Such screening can weaken
astrophysical constraints on new gauge bosons. As an example we consider the
constraints on chameleonic gauged B-L. We show that although Casimir
measurements greatly constrain any B-L force much stronger than gravity with
range longer than 0.1 microns, there remains an experimental window for a long
range chameleonic B-L force. Such a force could be much stronger than gravity,
and long or infinite range in vacuum, but have an effective range near the
surface of the earth which is less than a micron.Comment: 10 page
Applying a social justice framework to ensure good practice in monitoring student learning engagement
A current Australian Learning and Teaching Council (ALTC) funded action research project aims to provide a set of practical resources founded on a social justice framework, to guide good practice for monitoring student learning engagement (MSLE) in higher education. The project involves ten Australasian institutions, eight of which are engaged in various MSLE type projects. A draft framework, consisting of six social justice principles which emerged from the literature has been examined with reference to the eight institutional approaches for MSLE in conjunction with the personnel working on these initiatives during the first action research cycle. The cycle will examine the strategic and operational implications of the framework in each of the participating institutions. Cycle 2 will also build capacity to embed the principles within the institutional MSLE program and will identify and collect examples and resources that exemplify the principles in practice. The final cycle will seek to pilot the framework to guide new MSLE initiatives. In its entirety, the project will deliver significant resources to the sector in the form of a social justice framework for MSLE, guidelines and sector exemplars for MSLE. As well as increasing the awareness amongst staff around the criticality of transition to university (thereby preventing attrition) and the significance of the learning and teaching agenda in enhancing student engagement, the project will build leadership capacity within the participating institutions and provide a knowledge base and institutional capacity for the Australasian HE sector to deploy the deliverables that will safeguard student learning engagement At this early stage of the project the workshop session provides an opportunity to discuss and examine the draft set of social justice principles and to discuss their potential value for the participantsâ institutional contexts. Specifically, the workshop will explore critical questions associated with the principles
The Quantum Modular Group in (2+1)-Dimensional Gravity
The role of the modular group in the holonomy representation of
(2+1)-dimensional quantum gravity is studied. This representation can be viewed
as a "Heisenberg picture", and for simple topologies, the transformation to the
ADM "Schr{\"o}dinger picture" may be found. For spacetimes with the spatial
topology of a torus, this transformation and an explicit operator
representation of the mapping class group are constructed. It is shown that the
quantum modular group splits the holonomy representation Hilbert space into
physically equivalent orthogonal ``fundamental regions'' that are interchanged
by modular transformations.Comment: 23 pages, LaTeX, no figures; minor changes and clarifications in
response to referee (basic argument and conclusions unaffected
On Measurement of Helicity Parameters in Top Quark Decay
To enable an evaluation of future measurements of the helicity parameters for
" t --> W b " decay in regard to " T_FS violation", this paper considers the
effects of an additional pure-imaginary coupling, (i g/2 Lambda) or (i g),
associated with a specific, single additional Lorentz structure, i = S, P, S +
P, ... Sizable " T_FS violation" signatures can occur for low-effective mass
scales (< 320 GeV), but in most cases can be more simply excluded by 10%
precision measurement of the probabilities P(W_L) and P(b_L). Signatures for
excluding the presence of " T_FS violation" associated with the two dynamical
phase-type ambiguities are investigated.Comment: 15 pages, 1 table, 7 figures, no macro
Stratigraphy and reserves of pumiceous sand deposits in Perry's 'Asparagus Block' at Horotiu
The stratigraphic relationships between the deposits of the Hinuera Formation and the Taupo Pumice Alluvium are described over a 16 ha plot of land known as the 'Asparagus Block' at Horotiu. The Hinuera Formation is exposed at the surface at the southern end of this block, and is overlain by a wedge of Taupo Pumice Alluvium which increases in thickness from 0 to 8 m northwards across the block. Lithofacies in the Hinuera Formation are dominated by trough cross-bedded gravelly sands (lithofacies AI), with common cross-laminated sands (lithofacies B) and massive to horizontally laminated silts (lithofacies D). The pumice content of these deposits is mainly 70%. Lithofacies in the Taupo Pumice Alluvium are dominated by horizontally to inclined (tabular cross-) bedded slightly gravelly sands and sands (lithofacies G 1/2), with common occurrences of horizontally bedded to massive sandy silts (lithofacies D). The pumice content of these Taupo deposits is high, typically >80%. Cross-sections are presented showing an interpreted subsurface distribution of these lithofacies from south to north through the 'Asparagus Block'. The estimated reserve of extractable pumice sand from the block is of the order of about 400,000 to 450,000 mÂł
How effective is harassment on infalling late-type dwarfs?
A new harassment model is presented that models the complex, and dynamical
tidal field of a Virgo like galaxy cluster. The model is applied to small,
late-type dwarf disc galaxies (of substantially lower mass than in previous
harassment simulations) as they infall into the cluster from the outskirts.
These dwarf galaxies are only mildly affected by high speed tidal encounters
with little or no observable consequences; typical stellar losses are ,
producing very low surface brightness streams ( mag arcsec),
and a factor of two drop in dynamical mass-to-light ratio. Final stellar discs
remain disc-like, and dominated by rotation although often with tidally induced
spiral structure. By means of Monte-Carlo simulations, the statistically likely
influences of harassment on infalling dwarf galaxies are determined. The
effects of harassment are found to be highly dependent on the orbit of the
galaxy within the cluster, such that newly accreted dwarf galaxies typically
suffer only mild harassment. Strong tidal encounters, that can morphologically
transform discs into spheroidals, are rare occurring in of dwarf
galaxy infalls for typical orbits of sub-structure within CDM cluster
mass halos. For orbits with small apocentric distances (250 kpc), harassment
is significantly stronger resulting in complete disruption or heavy mass loss
( dark matter and stellar), however, such orbits are expected
to be highly improbable for newly infalling galaxies due to the deep potential
well of the cluster.Comment: 15 pages, 11 figures, 4 table
Recommended from our members
Towards an understanding of nanometric dielectrics
Dielectric studies are described aimed at providing an understanding of the charge storage and transport of an epoxy resin containing TiO2 nanoparticles. Comparative results for conventionally filled composites are given, and the results discussed in terms of the underlying physics. It is shown that nanometric fillers mitigate the interfacial polarization characteristic of conventional materials with a reduction in the internal field accumulations
A Relative Position Code for Saccades in Dorsal Premotor Cortex
Spatial computations underlying the coordination of the hand and eye present formidable geometric challenges. One way for the nervous system to simplify these computations is to directly encode the relative position of the hand and the center of gaze. Neurons in the dorsal premotor cortex (PMd), which is critical for the guidance of arm-reaching movements, encode the relative position of the hand, gaze, and goal of reaching movements. This suggests that PMd can coordinate reaching movements with eye movements. Here, we examine saccade-related signals in PMd to determine whether they also point to a role for PMd in coordinating visualâmotor behavior. We first compared the activity of a population of PMd neurons with a population of parietal reach region (PRR) neurons. During center-out reaching and saccade tasks, PMd neurons responded more strongly before saccades than PRR neurons, and PMd contained a larger proportion of exclusively saccade-tuned cells than PRR. During a saccade relative position-coding task, PMd neurons encoded saccade targets in a relative position code that depended on the relative position of gaze, the hand, and the goal of a saccadic eye movement. This relative position code for saccades is similar to the way that PMd neurons encode reach targets. We propose that eye movement and eye position signals in PMd do not drive eye movements, but rather provide spatial information that links the control of eye and arm movements to support coordinated visualâmotor behavior
Quantum geometry from 2+1 AdS quantum gravity on the torus
Wilson observables for 2+1 quantum gravity with negative cosmological
constant, when the spatial manifold is a torus, exhibit several novel features:
signed area phases relate the observables assigned to homotopic loops, and
their commutators describe loop intersections, with properties that are not yet
fully understood. We describe progress in our study of this bracket, which can
be interpreted as a q-deformed Goldman bracket, and provide a geometrical
interpretation in terms of a quantum version of Pick's formula for the area of
a polygon with integer vertices.Comment: 19 pages, 11 figures, revised with more explanations, improved
figures and extra figures. To appear GER
- âŠ