526 research outputs found
Hydraulic and Hydrologic Model Calibration and Validation for an Earthquake-prone Three-Waters Network
This paper summarises the three-waters network (water, wastewater, storm water) model calibration and validation work undertaken in Christchurch after the devastating 2010–2011 earthquakes. The paper outlines some unusual and unique challenges during model calibration due to continual earthquakes in the region and the post-earthquake rebuild work. In case of water supply network model, the validation peak summer date was chosen carefully so that earthquake-related damage and associated rebuild works would have minimal impact on the captured data. The wastewater network was damaged significantly due to the earthquakes. Wastewater flow data were influenced by earthquake damage and post-earthquake major construction activities. Christchurch’s storm water network faced a number of changes – changes in topography, ground levels, river channels and liquefaction – due to the earthquakes. Ongoing model maintenance and updating was a big challenge during model calibration, and an effective collaboration among various teams – GIS, construction contractors, network operations and survey – was important for data collection, data interpretation, model calibration and validation work
Farmers’ Perception and Adoption of Agroforestry Practices in Faridpur District of Bangladesh
This study mainly focused on exploring perception of farmers' towards agroforestry practices and identifying the demographic factors influencing agroforestry adoption in Faridpur district. Field survey was conducted during November-December, 2016 using semi-structured questionnaire. Multi-stage random sampling was used to select upazillas, unions and villages. Snowball purposive sampling was applied to select 84 respondents in total for the questionnaire survey. Chi-square was used to test variables at 5% level of significance. Homestead agroforestry was found to be the most common agroforestry practice (39.28%), followed by fruit-based agroforestry (21.42%), woodlot plantation (13.09%) and so on. Agroforestry was perceived to increase farm productivity by 82.14% of the respondents, 73.8% opined that agroforestry increase household income, while 30.95% perceived it as a means to food security. On the contrary, 34.52% opined that agroforestry practices decrease cash crops production, 17.85% of the respondents stated agroforestry as a difficult practice. Chi-square test showed no significant association between the adoption of agroforestry practices and respondent's age (P > 0.05) or income range (P > 0.05) of the respondents. On the other hand, there is a positive significant association between the adoption of agroforestry practices and educational level (p< 0.05) as well as the farm size (p< 0.05) of the respondents. The study suggests raising awareness regarding the benefits of agroforestry practices as well as providing technical assistance
Connecting protein and mRNA burst distributions for stochastic models of gene expression
The intrinsic stochasticity of gene expression can lead to large variability
in protein levels for genetically identical cells. Such variability in protein
levels can arise from infrequent synthesis of mRNAs which in turn give rise to
bursts of protein expression. Protein expression occurring in bursts has indeed
been observed experimentally and recent studies have also found evidence for
transcriptional bursting, i.e. production of mRNAs in bursts. Given that there
are distinct experimental techniques for quantifying the noise at different
stages of gene expression, it is of interest to derive analytical results
connecting experimental observations at different levels. In this work, we
consider stochastic models of gene expression for which mRNA and protein
production occurs in independent bursts. For such models, we derive analytical
expressions connecting protein and mRNA burst distributions which show how the
functional form of the mRNA burst distribution can be inferred from the protein
burst distribution. Additionally, if gene expression is repressed such that
observed protein bursts arise only from single mRNAs, we show how observations
of protein burst distributions (repressed and unrepressed) can be used to
completely determine the mRNA burst distribution. Assuming independent
contributions from individual bursts, we derive analytical expressions
connecting means and variances for burst and steady-state protein
distributions. Finally, we validate our general analytical results by
considering a specific reaction scheme involving regulation of protein bursts
by small RNAs. For a range of parameters, we derive analytical expressions for
regulated protein distributions that are validated using stochastic
simulations. The analytical results obtained in this work can thus serve as
useful inputs for a broad range of studies focusing on stochasticity in gene
expression
The Loudest Event Statistic: General Formulation, Properties and Applications
The use of the loudest observed event to generate statistical statements
about rate and strength has become standard in searches for gravitational waves
from compact binaries and pulsars. The Bayesian formulation of the method is
generalized in this paper to allow for uncertainties both in the background
estimate and in the properties of the population being constrained. The method
is also extended to allow rate interval construction. Finally, it is shown how
to combine the results from multiple experiments and a comparison is drawn
between the upper limit obtained in a single search and the upper limit
obtained by combining the results of two experiments each of half the original
duration. To illustrate this, we look at an example case, motivated by the
search for gravitational waves from binary inspiral.Comment: 11 pages, 8 figure
Detecting transient gravitational waves in non-Gaussian noise with partially redundant analysis methods
There is a broad class of astrophysical sources that produce detectable,
transient, gravitational waves. Some searches for transient gravitational waves
are tailored to known features of these sources. Other searches make few
assumptions about the sources. Typically events are observable with multiple
search techniques. This work describes how to combine the results of searches
that are not independent, treating each search as a classifier for a given
event. This will be shown to improve the overall sensitivity to
gravitational-wave events while directly addressing the problem of consistent
interpretation of multiple trials.Comment: 11 pages, 5 figure
Voids as a Precision Probe of Dark Energy
A signature of the dark energy equation of state may be observed in the shape
of voids. We estimate the constraints on cosmological parameters that would be
determined from the ellipticity distribution of voids from future spectroscopic
surveys already planned for the study of large scale structure.
The constraints stem from the sensitivity of the distribution of ellipticity
to the cosmological parameters through the variance of fluctuations of the
density field smoothed at some length scale. This length scale can be chosen to
be of the order of the comoving radii of voids at very early times when the
fluctuations are Gaussian distributed. We use Fisher estimates to show that the
constraints from void ellipticities are promising. Combining these constraints
with other traditional methods results in the improvement of the Dark Energy
Task Force Figure of Merit on the dark energy parameters by an order of hundred
for future experiments. The estimates of these future constraints depend on a
number of systematic issues which require further study using simulations. We
outline these issues and study the impact of certain observational and
theoretical systematics on the forecasted constraints on dark energy
parameters.Comment: Submitted to PRD, 22 pages 9 figure
Improving the LSST dithering pattern and cadence for dark energy studies
The Large Synoptic Survey Telescope (LSST) will explore the entire southern
sky over 10 years starting in 2022 with unprecedented depth and time sampling
in six filters, . Artificial power on the scale of the 3.5 deg LSST
field-of-view will contaminate measurements of baryonic acoustic oscillations
(BAO), which fall at the same angular scale at redshift . Using the
HEALPix framework, we demonstrate the impact of an "un-dithered" survey, in
which of each LSST field-of-view is overlapped by neighboring
observations, generating a honeycomb pattern of strongly varying survey depth
and significant artificial power on BAO angular scales. We find that adopting
large dithers (i.e., telescope pointing offsets) of amplitude close to the LSST
field-of-view radius reduces artificial structure in the galaxy distribution by
a factor of 10. We propose an observing strategy utilizing large dithers
within the main survey and minimal dithers for the LSST Deep Drilling Fields.
We show that applying various magnitude cutoffs can further increase survey
uniformity. We find that a magnitude cut of removes significant
spurious power from the angular power spectrum with a minimal reduction in the
total number of observed galaxies over the ten-year LSST run. We also determine
the effectiveness of the observing strategy for Type Ia SNe and predict that
the main survey will contribute 100,000 Type Ia SNe. We propose a
concentrated survey where LSST observes one-third of its main survey area each
year, increasing the number of main survey Type Ia SNe by a factor of
1.5, while still enabling the successful pursuit of other science
drivers.Comment: 9 pages, 6 figures, published in SPIE proceedings; corrected typo in
equation
Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian background
We describe a general approach to detection of transient gravitational-wave
signals in the presence of non-Gaussian background noise. We prove that under
quite general conditions, the ratio of the likelihood of observed data to
contain a signal to the likelihood of it being a noise fluctuation provides
optimal ranking for the candidate events found in an experiment. The
likelihood-ratio ranking allows us to combine different kinds of data into a
single analysis. We apply the general framework to the problem of unifying the
results of independent experiments and the problem of accounting for
non-Gaussian artifacts in the searches for gravitational waves from compact
binary coalescence in LIGO data. We show analytically and confirm through
simulations that in both cases the likelihood ratio statistic results in an
improved analysis.Comment: 10 pages, 6 figure
Presto-Color: A Photometric Survey Cadence for Explosive Physics and Fast Transients
We identify minimal observing cadence requirements that enable photometric astronomical surveys to detect and recognize fast and explosive transients and fast transient features. Observations in two different filters within a short time window (e.g., g-and-i, or r-and-z, within 1.5 hr) are desirable for this purpose. Such an observing strategy delivers both the color and light curve evolution of transients on the same night. This allows the identification and initial characterization of fast transient—or fast features of longer timescale transients—such as rapidly declining supernovae, kilonovae, and the signatures of SN ejecta interacting with binary companion stars or circumstellar material. Some of these extragalactic transients are intrinsically rare and generally all hard to find, thus upcoming surveys like the Large Synoptic Survey Telescope (LSST) could dramatically improve our understanding of their origin and properties. We colloquially refer to such a strategy implementation for the LSST as the Presto-Color strategy (rapid-color). This cadence's minimal requirements allow for overall optimization of a survey for other science goals
Presto-Color: A Photometric Survey Cadence for Explosive Physics and Fast Transients
We identify minimal observing cadence requirements that enable photometric astronomical surveys to detect and recognize fast and explosive transients and fast transient features. Observations in two different filters within a short time window (e.g., g-and-i, or r-and-z, within 1.5 hr) are desirable for this purpose. Such an observing strategy delivers both the color and light curve evolution of transients on the same night. This allows the identification and initial characterization of fast transient—or fast features of longer timescale transients—such as rapidly declining supernovae, kilonovae, and the signatures of SN ejecta interacting with binary companion stars or circumstellar material. Some of these extragalactic transients are intrinsically rare and generally all hard to find, thus upcoming surveys like the Large Synoptic Survey Telescope (LSST) could dramatically improve our understanding of their origin and properties. We colloquially refer to such a strategy implementation for the LSST as the Presto-Color strategy (rapid-color). This cadence's minimal requirements allow for overall optimization of a survey for other science goals
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