2,372 research outputs found
Historic Designation and Residential Property Values
The State of California enacted the Mills Act in 1972. This act allows local municipalities the option of setting up a historic designation program. The main feature of the program is to allow the owners of historic buildings a reduction in their property taxes in return for an agreement to not alter the exterior façade of the designated building. This paper uses hedonic regression analysis to estimate the impact of the historic designation on the value of single-family residences in the City of San Diego. The results suggest that the designation creates a 16 percent increase in housing value. This is higher than the capitalization of the property tax savings would suggest, implying market value in the historic designation itself. The Mills Act represents an innovative approach to historic structure management and may provide guidance to governments elsewhere in the U.S. as well as internationally when designing historic preservation programs.historic designation; housing values; hedonic model
Unparticle Self-Interactions and Their Collider Implications
In unparticle physics, operators of the conformal sector have
self-interactions, and these are unsuppressed for strong coupling. The 3-point
interactions are completely determined by conformal symmetry, up to a constant.
We do not know of any theoretical upper bounds on this constant. Imposing
current experimental constraints, we find that these interactions mediate
spectacular collider signals, such as , , , , , and
, with cross sections of picobarns or larger at the Large Hadron Collider.
Self-interactions may therefore provide the leading discovery prospects for
unparticle physics.Comment: 12 pages, 5 figures; v2: published versio
Rethinking Spatiotemporal Feature Learning: Speed-Accuracy Trade-offs in Video Classification
Despite the steady progress in video analysis led by the adoption of
convolutional neural networks (CNNs), the relative improvement has been less
drastic as that in 2D static image classification. Three main challenges exist
including spatial (image) feature representation, temporal information
representation, and model/computation complexity. It was recently shown by
Carreira and Zisserman that 3D CNNs, inflated from 2D networks and pretrained
on ImageNet, could be a promising way for spatial and temporal representation
learning. However, as for model/computation complexity, 3D CNNs are much more
expensive than 2D CNNs and prone to overfit. We seek a balance between speed
and accuracy by building an effective and efficient video classification system
through systematic exploration of critical network design choices. In
particular, we show that it is possible to replace many of the 3D convolutions
by low-cost 2D convolutions. Rather surprisingly, best result (in both speed
and accuracy) is achieved when replacing the 3D convolutions at the bottom of
the network, suggesting that temporal representation learning on high-level
semantic features is more useful. Our conclusion generalizes to datasets with
very different properties. When combined with several other cost-effective
designs including separable spatial/temporal convolution and feature gating,
our system results in an effective video classification system that that
produces very competitive results on several action classification benchmarks
(Kinetics, Something-something, UCF101 and HMDB), as well as two action
detection (localization) benchmarks (JHMDB and UCF101-24).Comment: ECCV 2018 camera read
Hidden Charged Dark Matter
Can dark matter be stabilized by charge conservation, just as the electron is
in the standard model? We examine the possibility that dark matter is hidden,
that is, neutral under all standard model gauge interactions, but charged under
an exact U(1) gauge symmetry of the hidden sector. Such candidates are
predicted in WIMPless models, supersymmetric models in which hidden dark matter
has the desired thermal relic density for a wide range of masses. Hidden
charged dark matter has many novel properties not shared by neutral dark
matter: (1) bound state formation and Sommerfeld-enhanced annihilation after
chemical freeze out may reduce its relic density, (2) similar effects greatly
enhance dark matter annihilation in protohalos at redshifts of z ~ 30, (3)
Compton scattering off hidden photons delays kinetic decoupling, suppressing
small scale structure, and (4) Rutherford scattering makes such dark matter
self-interacting and collisional, potentially impacting properties of the
Bullet Cluster and the observed morphology of galactic halos. We analyze all of
these effects in a WIMPless model in which the hidden sector is a simplified
version of the minimal supersymmetric standard model and the dark matter is a
hidden sector stau. We find that charged hidden dark matter is viable and
consistent with the correct relic density for reasonable model parameters and
dark matter masses in the range 1 GeV < m_X < 10 TeV. At the same time, in the
preferred range of parameters, this model predicts cores in the dark matter
halos of small galaxies and other halo properties that may be within the reach
of future observations. These models therefore provide a viable and
well-motivated framework for collisional dark matter with Sommerfeld
enhancement, with novel implications for astrophysics and dark matter searches.Comment: 29 pages; v2: references added; v3: published versio
Oxidative protein folding in eukaryotes: mechanisms and consequences
The endoplasmic reticulum (ER) provides an environment that is highly optimized for oxidative protein folding. Rather than relying on small molecule oxidants like glutathione, it is now clear that disulfide formation is driven by a protein relay involving Ero1, a novel conserved FAD-dependent enzyme, and protein disulfide isomerase (PDI); Ero1 is oxidized by molecular oxygen and in turn acts as a specific oxidant of PDI, which then directly oxidizes disulfide bonds in folding proteins. While providing a robust driving force for disulfide formation, the use of molecular oxygen as the terminal electron acceptor can lead to oxidative stress through the production of reactive oxygen species and oxidized glutathione. How Ero1p distinguishes between the many different PDI-related proteins and how the cell minimizes the effects of oxidative damage from Ero1 remain important open questions
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