2,766 research outputs found
Mixed tenure orthodoxy: practitioner reflections on policy effects
This article examines mixed tenure as a policy orthodoxy. It first sets out how mixed tenure may be considered to constitute an orthodoxy within planning, being generally accepted as a theory and practice even in the absence of supporting evidence. Five elements of this orthodoxy are identified, relating to (1) housing and the environment, (2) social change, (3) economic impacts, (4) sustainable communities, (5) and sociospatial integration. Interviews with practitioners involved with three social housing estates that have experienced mixed-tenure policy interventions are reported to consider why the implementation and effects of mixed tenure might not correspond with the orthodox understanding. It is argued that policy ambiguity and weaknesses in policy theory and specification, alongside practical constraints, lie behind incomplete and counterproductive policy implementation, but a belief in pursuing the policy orthodoxy persists nevertheless
Sound propagation over uneven ground and irregular topography
Theoretical, computational, and experimental techniques for predicting the effects of irregular topography on long range sound propagation in the atmosphere was developed. Irregular topography here is understood to imply a ground surface that is not idealized as being perfectly flat or that is not idealized as having a constant specific acoustic impedance. The interest focuses on circumstances where the propagation is similar to what might be expected for noise from low altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence
Bootstrapping Monte Carlo Tree Search with an Imperfect Heuristic
We consider the problem of using a heuristic policy to improve the value
approximation by the Upper Confidence Bound applied in Trees (UCT) algorithm in
non-adversarial settings such as planning with large-state space Markov
Decision Processes. Current improvements to UCT focus on either changing the
action selection formula at the internal nodes or the rollout policy at the
leaf nodes of the search tree. In this work, we propose to add an auxiliary arm
to each of the internal nodes, and always use the heuristic policy to roll out
simulations at the auxiliary arms. The method aims to get fast convergence to
optimal values at states where the heuristic policy is optimal, while retaining
similar approximation as the original UCT in other states. We show that
bootstrapping with the proposed method in the new algorithm, UCT-Aux, performs
better compared to the original UCT algorithm and its variants in two benchmark
experiment settings. We also examine conditions under which UCT-Aux works well.Comment: 16 pages, accepted for presentation at ECML'1
Sound propagation over uneven ground and irregular topography
The development of theoretical, computational, and experimental techniques for predicting the effects of irregular topography on long range sound propagation in the atmosphere is discussed. Irregular topography here is understood to imply a ground surface that (1) is not idealizable as being perfectly flat or (2) that is not idealizable as having a constant specific acoustic impedance. The study focuses on circumstances where the propagation is similar to what might be expected for noise from low-altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence
On Neutrinos and Fermionic Mass Patterns
Recent data on neutrino mass differences are consistent with a hierarchical
neutrino mass structure strikingly similar to what is observed for the other
fermionic masses.Comment: 8pages, 2figure
Measuring the Small-Scale Power Spectrum of Cosmic Density Fluctuations Through 21 cm Tomography Prior to the Epoch of Structure Formation
The thermal evolution of the cosmic gas decoupled from that of the cosmic
microwave background (CMB) at a redshift z~200. Afterwards and before the first
stars had formed, the cosmic neutral hydrogen absorbed the CMB flux at its
resonant 21cm spin-flip transition. We calculate the evolution of the spin
temperature for this transition and the resulting anisotropies that are
imprinted on the CMB sky due to linear density fluctuations during this epoch.
These anisotropies at an observed wavelength of 10.56[(1+z)/50] meters, contain
an amount of information that is orders of magnitude larger than any other
cosmological probe. Their detection, although challenging, could tightly
constrain any possible running of the spectral index from inflation (as
suggested by WMAP), small deviations from Gaussianity, or any significant
contribution from neutrinos or warm dark matter to the cosmic mass budget.Comment: 4 pages, 3 figures, accepted for publication in Physical Review
Letter
A General Analysis of Corrections to the Standard See-saw Formula in Grand Unified Models
In realistic grand unified models there are typically extra vectorlike matter
multiplets at the GUT scale that are needed to explain the family hierarchy.
These contain neutrinos that, when integrated out, can modify the usual
neutrino see-saw formula. A general analysis is given. It is noted that such
modifications can explain why the neutrinos do not exhibit a strong family
hierarchy like the other types of fermions.Comment: 30 page
Clinical pharmacology as a foundation for translational science.
The evolution of enabling technologies and their associated perspectives into molecular mechanisms underlying disease has extended beyond the abilities of scientific and clinical structures to advance their translation into new algorithms that improve the health of patients and populations.1 Research programs have yielded a vast array of novel molecules related to pathophysiological mechanisms that represent diagnostic and therapeutic targets which have the potential for personalized healthcare management. Yet, despite extraordinary scientific advances, routine successful translation of discovery into new therapeutic tools remains a distant vision. Beyond constraints in bridging discovery science with clinical translation due to obstacles in facilities, resources and in skilled specialized investigators, 95% of therapies brought into product development by the pharmaceutical and biotechnology sector eventually fail, reflecting negative balance between efficacy and adverse effects
Next nearest neighbour Ising models on random graphs
This paper develops results for the next nearest neighbour Ising model on
random graphs. Besides being an essential ingredient in classic models for
frustrated systems, second neighbour interactions interactions arise naturally
in several applications such as the colour diversity problem and graphical
games. We demonstrate ensembles of random graphs, including regular
connectivity graphs, that have a periodic variation of free energy, with either
the ratio of nearest to next nearest couplings, or the mean number of nearest
neighbours. When the coupling ratio is integer paramagnetic phases can be found
at zero temperature. This is shown to be related to the locked or unlocked
nature of the interactions. For anti-ferromagnetic couplings, spin glass phases
are demonstrated at low temperature. The interaction structure is formulated as
a factor graph, the solution on a tree is developed. The replica symmetric and
energetic one-step replica symmetry breaking solution is developed using the
cavity method. We calculate within these frameworks the phase diagram and
demonstrate the existence of dynamical transitions at zero temperature for
cases of anti-ferromagnetic coupling on regular and inhomogeneous random
graphs.Comment: 55 pages, 15 figures, version 2 with minor revisions, to be published
J. Stat. Mec
Cooperation and Contagion in Web-Based, Networked Public Goods Experiments
A longstanding idea in the literature on human cooperation is that
cooperation should be reinforced when conditional cooperators are more likely
to interact. In the context of social networks, this idea implies that
cooperation should fare better in highly clustered networks such as cliques
than in networks with low clustering such as random networks. To test this
hypothesis, we conducted a series of web-based experiments, in which 24
individuals played a local public goods game arranged on one of five network
topologies that varied between disconnected cliques and a random regular graph.
In contrast with previous theoretical work, we found that network topology had
no significant effect on average contributions. This result implies either that
individuals are not conditional cooperators, or else that cooperation does not
benefit from positive reinforcement between connected neighbors. We then tested
both of these possibilities in two subsequent series of experiments in which
artificial seed players were introduced, making either full or zero
contributions. First, we found that although players did generally behave like
conditional cooperators, they were as likely to decrease their contributions in
response to low contributing neighbors as they were to increase their
contributions in response to high contributing neighbors. Second, we found that
positive effects of cooperation were contagious only to direct neighbors in the
network. In total we report on 113 human subjects experiments, highlighting the
speed, flexibility, and cost-effectiveness of web-based experiments over those
conducted in physical labs
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