1,483 research outputs found
Portable LED fluorescence instrumentation for the rapid assessment of potable water quality
Characterising the organic and microbial matrix of water are key issues in ensuring a safe potable water supply.
Current techniques only confirm water quality retrospectively via laboratory analysis of discrete samples. Whilst
such analysis is required for regulatory purposes, it would be highly beneficial to monitor water quality in-situ in
real time, enabling rapid water quality assessment and facilitating proactive management of water supply
systems.
A novel LED-based instrument, detecting fluorescence peaks C and T (surrogates for organic and microbial matter,
respectively), was constructed and performance assessed. Results from over 200 samples taken from source
waters through to customer tap from three UK water companies are presented. Excellent correlation was
observed between the new device and a research grade spectrophotometer (r
2 = 0.98 and 0.77 for peak C and
peak T respectively), demonstrating the potential of providing a low cost, portable alternative fluorimeter. The
peak C/TOC correlation was very good (r
2 = 0.75) at low TOC levels found in drinking water. However, correlations
between peak T and regulatory measures of microbial matter (2 day/3 day heterotrophic plate counts
(HPC), E. coli, and total coliforms) were poor, due to the specific nature of these regulatory measures and the general
measure of peak T. A more promising correlation was obtained between peak T and total bacteria using flow
cytometry. Assessment of the fluorescence of four individual bacteria isolated from drinking water was also considered
and excellent correlations found with peak T (Sphingobium sp. (r
2 = 0.83); Methylobacterium sp. (r
2 =
1.0); Rhodococcus sp. (r
2 = 0.86); Xenophilus sp. (r
2 = 0.96)). It is notable that each of the bacteria studied exhibited
different levels of fluorescence as a function of their number. The scope for LED based instrumentation for insitu,
real time assessment of the organic and microbial matrix of potable water is clearly demonstrated
Tricritical scaling at the N_t=6 chiral phase transition for 2 flavour lattice QCD with staggered quarks
We have simulated lattice QCD directly in the chiral limit of zero quark mass
by adding an additional, irrelevant 4-fermion interaction to the standard
action. Using lattices having temporal extent of six and spatial extents of
twelve and eighteen, we find that the theory with 2 massless staggered quark
flavors has a second order finite temperature phase transition. The critical
exponents , and are measured and favour tricritical
behaviour over that expected by universality arguments. The pion screening mass
is consistent with zero below the transition, but is degenerate with the
nonzero mass above the transition, indicating the restoration of
chiral symmetry.Comment: 12 pages, 3 postscript figures Letter has been rewritten to reflect a
reinterpretation of our results as indicating tricritical critical indices
rather than those predicted by standard universality arguments. Some
additional analysis which supports this interpretation is included. The
comparison of our methods with those of others has been expande
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Finishing of precision generated metal optical components
Diamond turning and precision generation of aspheric metal surfaces has promoted a change in lapping techniques due to the extremely close figure tolerances and surface finishes that have been achieved. Special tooling, diamond abrasive, silicon oil and special techniques used to polish the unusual aspheric figures are described. The studies include small flat diamond turned samples of copper, electroplated copper, electroplated silver, electroplated nickel and silver as well as large aspheres such as an f/0.75, 35 cm dia copper ellipse. Results from cleaning studies on flat samples using ultrasonics and vapor degreasers are also summarized. Interferograms of wavefront distortion and analysis of focal volume are included as well as 10.6 m reflectivity and a summary of laser damage experiments. (TFD
Universal features of the order-parameter fluctuations : reversible and irreversible aggregation
We discuss the universal scaling laws of order parameter fluctuations in any
system in which the second-order critical behaviour can be identified. These
scaling laws can be derived rigorously for equilibrium systems when combined
with the finite-size scaling analysis. The relation between order parameter,
criticality and scaling law of fluctuations has been established and the
connexion between the scaling function and the critical exponents has been
found. We give examples in out-of-equilibrium aggregation models such as the
Smoluchowski kinetic equations, or of at-equilibrium Ising and percolation
models.Comment: 19 pages, 10 figure
Cloud microphysical effects of turbulent mixing and entrainment
Turbulent mixing and entrainment at the boundary of a cloud is studied by
means of direct numerical simulations that couple the Eulerian description of
the turbulent velocity and water vapor fields with a Lagrangian ensemble of
cloud water droplets that can grow and shrink by condensation and evaporation,
respectively. The focus is on detailed analysis of the relaxation process of
the droplet ensemble during the entrainment of subsaturated air, in particular
the dependence on turbulence time scales, droplet number density, initial
droplet radius and particle inertia. We find that the droplet evolution during
the entrainment process is captured best by a phase relaxation time that is
based on the droplet number density with respect to the entire simulation
domain and the initial droplet radius. Even under conditions favoring
homogeneous mixing, the probability density function of supersaturation at
droplet locations exhibits initially strong negative skewness, consistent with
droplets near the cloud boundary being suddenly mixed into clear air, but
rapidly approaches a narrower, symmetric shape. The droplet size distribution,
which is initialized as perfectly monodisperse, broadens and also becomes
somewhat negatively skewed. Particle inertia and gravitational settling lead to
a more rapid initial evaporation, but ultimately only to slight depletion of
both tails of the droplet size distribution. The Reynolds number dependence of
the mixing process remained weak over the parameter range studied, most
probably due to the fact that the inhomogeneous mixing regime could not be
fully accessed when phase relaxation times based on global number density are
considered.Comment: 17 pages, 10 Postscript figures (figures 3,4,6,7,8 and 10 are in
reduced quality), to appear in Theoretical Computational Fluid Dynamic
Weak convergence of finite element approximations of linear stochastic evolution equations with additive noise II. Fully discrete schemes
We present an abstract framework for analyzing the weak error of fully
discrete approximation schemes for linear evolution equations driven by
additive Gaussian noise. First, an abstract representation formula is derived
for sufficiently smooth test functions. The formula is then applied to the wave
equation, where the spatial approximation is done via the standard continuous
finite element method and the time discretization via an I-stable rational
approximation to the exponential function. It is found that the rate of weak
convergence is twice that of strong convergence. Furthermore, in contrast to
the parabolic case, higher order schemes in time, such as the Crank-Nicolson
scheme, are worthwhile to use if the solution is not very regular. Finally we
apply the theory to parabolic equations and detail a weak error estimate for
the linearized Cahn-Hilliard-Cook equation as well as comment on the stochastic
heat equation
On the nature of the finite-temperature transition in QCD
We discuss the nature of the finite-temperature transition in QCD with N_f
massless flavors. Universality arguments show that a continuous (second-order)
transition must be related to a 3-D universality class characterized by a
complex N_f X N_f matrix order parameter and by the symmetry-breaking pattern
[SU(N_f)_L X SU(N_f)_R]/Z(N_f)_V -> SU(N_f)_V/Z(N_f)_V, or [U(N_f)_L X
U(N_f)_R]/U(1)_V -> U(N_f)_V/U(1)_V if the U(1)_A symmetry is effectively
restored at T_c. The existence of any of these universality classes requires
the presence of a stable fixed point in the corresponding 3-D Phi^4 theory with
the expected symmetry-breaking pattern. Otherwise, the transition is of first
order. In order to search for stable fixed points in these Phi^4 theories, we
exploit a 3-D perturbative approach in which physical quantities are expanded
in powers of appropriate renormalized quartic couplings. We compute the
corresponding Callan-Symanzik beta-functions to six loops. We also determine
the large-order behavior to further constrain the analysis. No stable fixed
point is found, except for N_f=2, corresponding to the symmetry-breaking
pattern [SU(2)_L X SU(2)_R]/Z(2)_V -> SU(2)_V/Z(2)_V equivalent to O(4) ->
O(3). Our results confirm and put on a firmer ground earlier analyses performed
close to four dimensions, based on first-order calculations in the framework of
the epsilon=4-d expansion. These results indicate that the finite-temperature
phase transition in QCD is of first order for N_f>2. A continuous transition is
allowed only for N_f=2. But, since the theory with symmetry-breaking pattern
[U(2)_L X U(2)_R]/U(1)_V -> U(2)_V/U(1)_V does not have stable fixed points,
the transition can be continuous only if the effective breaking of the U(1)_A
symmetry is sufficiently large.Comment: 30 pages, 3 figs, minor correction
Integrating Maternal Depression Screening Into an Early Intervention Program: An Implementation Evaluation
Background: In all 50 states, early intervention (EI) services to improve long-term child cognitive and academic outcomes are provided to infants and toddlers with suspected or diagnosed developmental delays. When mothers of EI-enrolled children experience depressive symptoms, uptake of EI services can be compromised. Aims: The purpose of the article is to present a depressive symptom screening intervention for mothers consisting of toolkit development for EI staff and families, symptom screening for mothers and follow-up protocol. To formally evaluate the implementation of the intervention, our research team followed the consolidated framework for implementation research (CFIR). Methods: Participants were 12 EI service coordinators across two offices. Focus groups and individual interviews were used to develop the toolkit and education module. Through the five CFIR domains, we evaluated the implemented intervention in order to allow other teams to learn from our experiences. Results: Our team successfully partnered with SCs to develop the intended deliverables. Still, the SCs found it challenging to conduct the screenings and reported mixed success. Conclusions: Preparation of EI SCs to integrate mental health screenings into their existing skillsets requires a high level of support from the research team, resulting in a rich understanding of the barriers-and potential rewards-for staff and families
Striking divergences in Earth Observation products may limit their use for REDD+
Countries are required to generate baselines of carbon emissions, or Forest Reference Emission Levels, for implementing REDD+ under the United Nations Framework Convention on Climate Change and to access results-based payments. Developing these baselines requires accurate maps of carbon stocks and historical deforestation. Global remote sensing products provide low-cost solutions for this information, but there has been little validation of these products at national scales. This study compares the ability of currently available products obtained from remote sensing data to deliver estimates of deforestation and associated carbon emissions in Guinea-Bissau, a West African country encompassing the climate and vegetation gradients that are typical of sub-Saharan Africa. We show that disagreements in estimates of deforestation are striking, and this variation leads to high uncertainty in derived emissions. For Guinea-Bissau, we suggest that higher temporal resolution of remote sensing products is required to reduce this uncertainty by overcoming current limitations in differentiating deforestation from seasonality. In contrast, existing datasets of carbon stocks show better agreement, and contribute much less to the variation in estimated emissions. We conclude that using global datasets based on Earth Observation data is a cost-effective solution to make REDD+ operational, but deforestation maps in particular should be derived carefully and their uncertainty assessed
The 3-D O(4) universality class and the phase transition in two-flavor QCD
We determine the critical equation of state of the three-dimensional O(4)
universality class. We first consider the small-field expansion of the
effective potential (Helmholtz free energy). Then, we apply a systematic
approximation scheme based on polynomial parametric representations that are
valid in the whole critical regime, satisfy the correct analytic properties
(Griffiths' analyticity), take into account the Goldstone singularities at the
coexistence curve, and match the small-field expansion of the effective
potential. From the approximate representations of the equation of state, we
obtain estimates of several universal amplitude ratios.
The three-dimensional O(4) universality class is expected to describe the
finite-temperature chiral transition of quantum chromodynamics with two light
flavors. Within this picture, the O(4) critical equation of state relates the
reduced temperature, the quark masses, and the condensates around T_c in the
limit of vanishing quark masses.Comment: 19 pages, 5 fig
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