7,113 research outputs found
Public participation and New Urbanism: a conflicting agenda?
The challenges to public participation in planning are numerous. Inclusive and equitable processes are recognised as an ideal in much planning theory and practice, yet this ideal is increasingly difficult to realise in today’s societies that comprise diverse and multiple publics. Within the wider sustainability debate, ‘New Urbanism’ has emerged as a pragmatic alternative to convention allow-density development. Concomitant with a range of prescribed physical outcomes, the New Urbanism movement advocates a process of ‘citizen-based participatory planning and design’. Charrettes, with urban design workshops, are the favoured tools for achieving this goal. However, it is argued that the adherence to a single type of participatory tool can be inconsistent with accepted ideals of participation processes and has several implications. Of particular concern is the role of the charrette planner or facilitator, a figure who has the potential to manipulate the public because of his/her inevitable allegiance to the New Urban agenda. In addition, the examination of a charrette process in a small New Zealand town raises several broader questions about the ability of the approach to address issues of inclusiveness and the recognition of difference, two fundamental elements of good participatory processes
Role of chondroitin sulfate proteoglycans (CSPGs) in synaptic plasticity and neurotransmission in mammalian spinal cord.
Chronic unilateral hemisection (HX) of the adult rat spinal cord diminishes conduction through intact fibers in the ventrolateral funiculus (VLF) contralateral to HX. Intraspinal injections of Chondroitinase-ABC, known to digest chondroitin sulfate proteoglycans (CSPGs) in the vicinity of injury, prevented this decline of axonal conduction. This was associated with improved locomotor function. We further injected three purified CSPGs into the lateral column of the uninjured cord at T10: NG2 and neurocan, which increase in the vicinity of a spinal injury, and aggrecan, which decreases. Intraspinal injection of NG2 acutely depressed axonal conduction through the injection region in a dose dependent manner. Similar injections of saline, aggrecan, or neurocan had no significant effect. These results identify a novel acute action of CSPGs on axonal conduction in spinal cord, and suggest that antagonism of proteoglycans reverses or prevents the decline of axonal conduction, in addition to stimulating axonal growth
Anisotropic random resistor networks: a model for piezoresistive response of thick-film resistors
A number of evidences suggests that thick-film resistors are close to a
metal-insulator transition and that tunneling processes between metallic grains
are the main source of resistance. We consider as a minimal model for
description of transport properties in thick-film resistors a percolative
resistor network, with conducting elements governed by tunneling. For both
oriented and randomly oriented networks, we show that the piezoresistive
response to an applied strain is model dependent when the system is far away
from the percolation thresold, while in the critical region it acquires
universal properties. In particular close to the metal-insulator transition,
the piezoresistive anisotropy show a power law behavior. Within this region,
there exists a simple and universal relation between the conductance and the
piezoresistive anisotropy, which could be experimentally tested by common
cantilever bar measurements of thick-film resistors.Comment: 7 pages, 2 eps figure
DeWitt-Schwinger Renormalization and Vacuum Polarization in d Dimensions
Calculation of the vacuum polarization, , has seen a recent resurgence, notably
for black hole spacetimes. To date, most calculations of this type have been
done only in four dimensions. Extending these calculations to dimensions
includes -dimensional renormalization. Typically, the renormalizing terms
are found from Christensen's covariant point splitting method for the
DeWitt-Schwinger expansion. However, some manipulation is required to put the
correct terms into a form that is compatible with problems of the vacuum
polarization type. Here, after a review of the current state of affairs for
calculations and a thorough introduction to
the method of calculating and for certain spacetimes is discussed, with application to four and
five dimensions.Comment: 21 pages, 2 tables, 3 figures. References added, rewritten to clarify
some points, corrections performed, our claim in the first version that there
is an error in Anderson's calculations is incorrec
Stress-Energy Tensor for the Massless Spin 1/2 Field in Static Black Hole Spacetimes
The stress-energy tensor for the massless spin 1/2 field is numerically
computed outside and on the event horizons of both charged and uncharged static
non-rotating black holes, corresponding to the Schwarzschild,
Reissner-Nordstrom and extreme Reissner-Nordstr\"om solutions of Einstein's
equations. The field is assumed to be in a thermal state at the black hole
temperature. Comparison is made between the numerical results and previous
analytic approximations for the stress-energy tensor in these spacetimes. For
the Schwarzschild (charge zero) solution, it is shown that the stress-energy
differs even in sign from the analytic approximation. For the
Reissner-Nordstrom and extreme Reissner-Nordstrom solutions, divergences
predicted by the analytic approximations are shown not to exist.Comment: 5 pages, 4 figures, additional discussio
Vacuum polarization for lukewarm black holes
We compute the renormalized expectation value of the square of a quantum scalar field on a Reissner-Nordström–de Sitter black hole in which the temperatures of the event and cosmological horizons are equal (“lukewarm” black hole). Our numerical calculations for a thermal state at the same temperature as the two horizons indicate that this renormalized expectation value is regular on both the event and cosmological horizons. We are able to show analytically, using an approximation for the field modes near the horizons, that this is indeed the case
Kinetic and adsorption behaviour of aqueous cadmium using a 30 nm hydroxyapatite based powder synthesized via a combined ultrasound and microwave based technique
The removal of heavy metals such as cadmium from contaminated waterways and soils is a very important aspect of environmental remediation. This study investigated the kinetic and adsorption performance of a nanometre scale hydroxyapatite (HAP) synthesised from a combined ultrasound and microwave based technique for the removal of cadmium from an aqueous salt solution. Parameters such as contact time, initial pH, initial cadmium concentration and temperature were investigated. The Freundlich isotherm resulted in a more precise modelling of the communicated experimental data. Maximum monolayer adsorption capacity of absorber was found to be 123.45 mg/g at 298 K. Kinetic studies established cadmium adsorption tended to follow a pseudo-second order model and intra-particle diffusion played a significant role in determining the rate. Adsorption was endothermic, spontaneous and resulted in structural changes to the HAP matrix. The structural changes were investigated using both X-ray diffraction and field emission scanning electron microscopy
Dynamic Bayesian Combination of Multiple Imperfect Classifiers
Classifier combination methods need to make best use of the outputs of
multiple, imperfect classifiers to enable higher accuracy classifications. In
many situations, such as when human decisions need to be combined, the base
decisions can vary enormously in reliability. A Bayesian approach to such
uncertain combination allows us to infer the differences in performance between
individuals and to incorporate any available prior knowledge about their
abilities when training data is sparse. In this paper we explore Bayesian
classifier combination, using the computationally efficient framework of
variational Bayesian inference. We apply the approach to real data from a large
citizen science project, Galaxy Zoo Supernovae, and show that our method far
outperforms other established approaches to imperfect decision combination. We
go on to analyse the putative community structure of the decision makers, based
on their inferred decision making strategies, and show that natural groupings
are formed. Finally we present a dynamic Bayesian classifier combination
approach and investigate the changes in base classifier performance over time.Comment: 35 pages, 12 figure
Spin and charge excitations in incommensurate spin density waves
Collective excitations both for spin- and charge-channels are investigated in
incommensurate spin density wave (or stripe) states on two-dimensional Hubbard
model. By random phase approximation, the dynamical susceptibility
\chi(q,\omega) is calculated for full range of (q,\omega) with including all
higher harmonics components. An intricate landscape of the spectra in
\chi(q,\omega) is obtained. We discuss the anisotropy of the dispersion cones
for spin wave excitations, and for the phason excitation related to the motion
of the stripe line. Inelastic neutron experiments on Cr and its alloys and
stripe states of underdoped cuprates are proposed
Fluctuation-induced first-order phase transition in Dzyaloshinskii-Moriya helimagnets
Two centuries of research on phase transitions have repeatedly highlighted
the importance of critical fluctuations that abound in the vicinity of a
critical point. They are at the origin of scaling laws obeyed by thermodynamic
observables close to second-order phase transitions resulting in the concept of
universality classes, that is of paramount importance for the study of
organizational principles of matter. Strikingly, in case such soft fluctuations
are too abundant they may alter the nature of the phase transition profoundly;
the system might evade the critical state altogether by undergoing a
discontinuous first-order transition into the ordered phase.
Fluctuation-induced first-order transitions have been discussed broadly and are
germane for superconductors, liquid crystals, or phase transitions in the early
universe, but clear experimental confirmations remain scarce. Our results from
neutron scattering and thermodynamics on the model Dzyaloshinskii-Moriya (DM)
helimagnet (HM) MnSi show that such a fluctuation-induced first-order
transition is realized between its paramagnetic and HM state with remarkable
agreement between experiment and a theory put forward by Brazovskii. While our
study clarifies the nature of the HM phase transition in MnSi that has puzzled
scientists for several decades, more importantly, our conclusions entirely
based on symmetry arguments are also relevant for other DM-HMs with only weak
cubic magnetic anisotropies. This is in particular noteworthy in light of a
wide range of recent discoveries that show that DM helimagnetism is at the
heart of problems such as topological magnetic order, multiferroics, and
spintronics.Comment: 19 pages, 9 figures, 2 table
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