2,254 research outputs found
Analysis of Nitrogen Loading Reductions for Wastewater Treatment Facilities and Non-Point Sources in the Great Bay Estuary Watershed
In 2009, the New Hampshire Department of Environmental Services (DES) published a proposal for numeric nutrient criteria for the Great Bay Estuary. The report found that total nitrogen concentrations in most of the estuary needed to be less than 0.3 mg N/L to prevent loss of eelgrass habitat and less than 0.45 mg N/L to prevent occurrences of low dissolved oxygen. Based on these criteria and an analysis of a compilation of data from at least seven different sources, DES concluded that 11 of the 18 subestuaries in the Great Bay Estuary were impaired for nitrogen. Under the Clean Water Act, if a water body is determined to be impaired, a study must be completed to determine the existing loads of the pollutant and the load reductions that would be needed to meet the water quality standard. Therefore, DES developed models to determine existing nitrogen loads and nitrogen loading thresholds for the subestuaries to comply with the numeric nutrient criteria. DES also evaluated the effects of different permitting scenarios for wastewater treatment facilities on nitrogen loads and the costs for wastewater treatment facility upgrades. This modeling exercise showed that: Nitrogen loads to the Great Bay, Little Bay, and the Upper Piscataqua River need to be reduced by 30 to 45 percent to attain the numeric nutrient criteria. Both wastewater treatment facilities and non-point sources will need to reduce nitrogen loads to attain the numeric nutrient criteria. The percent reduction targets for nitrogen loads only change minimally between wet and dry years. Wastewater treatment facility upgrades to remove nitrogen will be costly; however, the average cost per pound of nitrogen removed from the estuary due to wastewater facility upgrades is lower than for non-point source controls. The permitting options for some wastewater treatment facilities will be limited by requirements to not increase pollutant loads to impaired waterbodies. The numeric nutrient criteria and models used by DES are sufficiently accurate for calculating nitrogen loading thresholds for the Great Bay watershed. Additional monitoring and modeling is needed to better characterize conditions and nitrogen loading thresholds for the Lower Piscataqua River. This nitrogen loading analysis for Great Bay may provide a framework for setting nitrogen permit limits for wastewater treatment facilities and developing watershed implementation plans to reduce nitrogen loads
Quantum Fluctuations in Josephson Junction Comparators
We have developed a method for calculation of quantum fluctuation effects, in
particular of the uncertainty zone developing at the potential curvature sign
inversion, for a damped harmonic oscillator with arbitrary time dependence of
frequency and for arbitrary temperature, within the Caldeira-Leggett model. The
method has been applied to the calculation of the gray zone width Delta Ix of
Josephson-junction balanced comparators driven by a specially designed
low-impedance RSFQ circuit. The calculated temperature dependence of Delta Ix
in the range 1.5 to 4.2K is in a virtually perfect agreement with experimental
data for Nb-trilayer comparators with critical current densities of 1.0 and 5.5
kA/cm^2, without any fitting parameters.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
Control-Flow Integrity for Real-Time Embedded Systems
Attacks on real-time embedded systems can endanger lives and critical infrastructure. Despite this, techniques for securing embedded systems software have not been widely studied. Many existing security techniques for general-purpose computers rely on assumptions that do not hold in the embedded case. This paper focuses on one such technique, control-flow integrity (CFI), that has been vetted as an effective countermeasure against control-flow hijacking attacks on general-purpose computing systems. Without the process isolation and fine-grained memory protections provided by a general-purpose computer with a rich operating system, CFI cannot provide any security guarantees. This work proposes RECFISH, a system for providing CFI guarantees on ARM Cortex-R devices running minimal real-time operating systems. We provide techniques for protecting runtime structures, isolating processes, and instrumenting compiled ARM binaries with CFI protection. We empirically evaluate RECFISH and its performance implications for real-time systems. Our results suggest RECFISH can be directly applied to binaries without compromising real-time performance; in a test of over six million realistic task systems running FreeRTOS, 85% were still schedulable after adding RECFISH
Spatial modes in waveguided parametric down-conversion
The propagation of several spatial modes has a significant impact on the
structure of the emission from parametric down-conversion in a nonlinear
waveguide. This manifests itself not only in the spatial correlations of the
photon pairs but also, due to new phase-matching conditions, in the output
spectrum, radically altering the degree of entanglement within each pair. Here
we investigate both theoretically and experimentally the results of
higher-order spatial-mode propagation in nonlinear waveguides. We derive
conditions for the creation of pairs in these modes and present observations of
higher-order mode propagation in both the spatial and spectral domains.
Furthermore, we observe correlations between the different degrees of freedom
and finally we discuss strategies for mitigating any detrimental effects and
optimizing pair production in the fundamental mode.Comment: 8 pages, 10 figure
Higher-order mutual coherence of optical and matter waves
We use an operational approach to discuss ways to measure the higher-order
cross-correlations between optical and matter-wave fields. We pay particular
attention to the fact that atomic fields actually consist of composite
particles that can easily be separated into their basic constituents by a
detection process such as photoionization. In the case of bosonic fields, that
we specifically consider here, this leads to the appearance in the detection
signal of exchange contributions due to both the composite bosonic field and
its individual fermionic constituents. We also show how time-gated counting
schemes allow to isolate specific contributions to the signal, in particular
involving different orderings of the Schr\"odinger and Maxwell fields.Comment: 11 pages, 2 figure
On the Incorporation of Psychologically-Driven 'Music' Preference Models for Music Recommendation
There are hundreds of millions of songs available to the public, necessitating the use
of music recommendation systems to discover new music. Currently, such systems
account for only the quantitative musical elements of songs, failing to consider
aspects of human perception of music and alienating the listener’s individual
preferences from recommendations. Our research investigated the relationships
between perceptual elements of music, represented by the MUSIC model, with
computational musical features generated through The Echo Nest, to determine how a
psychological representation of music preference can be incorporated into
recommendation systems to embody an individual’s music preferences. Our resultant
model facilitates computation of MUSIC factors using The Echo Nest features, and
can potentially be integrated into recommendation systems for improved
performance
Do Health Beliefs and Behaviors Differ According to Severity of Obesity? A Qualitative Study of Australian Adults
Public responses to obesity have focused on providing standardized messages and supports to all obese individuals, but there is limited understanding of the impact of these messages on obese adults. This descriptive qualitative study using in-depth interviews and a thematic method of analysis, compares the health beliefs and behaviors of 141 Australian adults with mild to moderate (BMI 30−39.9) and severe (BMI ≥ 40) obesity. Mildly obese individuals felt little need to change their health behaviors or to lose weight for health reasons. Most believed they could “lose weight” if they needed to, distanced themselves from the word obesity, and stigmatized those “fatter” than themselves. Severely obese individuals felt an urgent need to change their health behaviors, but felt powerless to do so. They blamed themselves for their weight, used stereotypical language to describe their health behaviors, and described being “at war” with their bodies. Further research, particularly about the role of stigma and stereotyping, is needed to fully understand the impact of obesity messaging on the health beliefs, behaviors, and wellbeing of obese and severely obese adults
FishNet: an online database of zebrafish anatomy
Background: Over the last two decades, zebrafish have been established as a genetically versatile model system for investigating many different aspects of vertebrate developmental biology. With the credentials of zebrafish as a developmental model now well recognized, the emerging new opportunity is the wider application of zebrafish biology to aspects of human disease modelling. This rapidly increasing use of zebrafish as a model for human disease has necessarily generated interest in the anatomy of later developmental phases such as the larval, juvenile, and adult stages, during which many of the key aspects of organ morphogenesis and maturation take place. Anatomical resources and references that encompass these stages are non-existent in zebrafish and there is therefore an urgent need to understand how different organ systems and anatomical structures develop throughout the life of the fish. Results: To overcome this deficit we have utilized the technique of optical projection tomography to produce three-dimensional (3D) models of larval fish. In order to view and display these models we have created FishNet http://www.fishnet.org.au, an interactive reference of zebrafish anatomy spanning the range of zebrafish development from 24 h until adulthood. Conclusion: FishNet contains more than 36 000 images of larval zebrafish, with more than 1 500 of these being annotated. The 3D models can be manipulated on screen or virtually sectioned. This resource represents the first complete embryo to adult atlas for any species in 3D
Public health campaigns and obesity - a critique
<p>Abstract</p> <p>Background</p> <p>Controlling obesity has become one of the highest priorities for public health practitioners in developed countries. In the absence of safe, effective and widely accessible high-risk approaches (e.g. drugs and surgery) attention has focussed on community-based approaches and social marketing campaigns as the most appropriate form of intervention. However there is limited evidence in support of substantial effectiveness of such interventions.</p> <p>Discussion</p> <p>To date there is little evidence that community-based interventions and social marketing campaigns specifically targeting obesity provide substantial or lasting benefit. Concerns have been raised about potential negative effects created by a focus of these interventions on body shape and size, and of the associated media targeting of obesity.</p> <p>Summary</p> <p>A more appropriate strategy would be to enact high-level policy and legislative changes to alter the obesogenic environments in which we live by providing incentives for healthy eating and increased levels of physical activity. Research is also needed to improve treatments available for individuals already obese.</p
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