Impact of Organic Matter Composition from Urban Streams and Storm Water on Oxygen Consumption in the Jordan River

Coarse particulate organic matter (CPOM) is an essential part of the food chain in aquatic ecosystems because it represents a readily available carbon and energy source. The process by which it decomposes in rivers has been well studied and documented. However, the rate and extent of biodegradability of various CPOM components (i.e., twigs, leaves, grass, etc.) in storm drains is not well understood. The Jordan River TMDL study identified storm water generated CPOM as a likely cause of low dissolved oxygen levels in the lower Jordan River, but recent investigations have suggested that dissolved organic matter generated from this CPOM in storm drains and culverts entering into the Jordan River, rather than the CPOM itself, is the main driver of oxygen impairment. The degradability of CPOM components transported and stored in the storm drain system was studied to understand its relative impact on dissolved oxygen and nutrient status in the Jordan River. Results indicate the generation of highly degradable organic material is a function of the starting CPOM, and oxygen consumption is associated with the dissolved portion of organic material leached from CPOM in water. Leaves and grass produced the highest levels of all parameters studied. Between 93% to 95% of total oxygen demand is generated within the first 1 to 3 hours of the 24 hour test. Chemical oxygen demand and dissolved organic carbon proved to be the best indicator of biochemical oxygen demand. By using the results of the leaching study an estimate of water quality indicator levels in the Jordan River was made, and was compared to levels in samples collected from the Jordan River. The estimate proved accurate for dissolved organic carbon but not for total or volatile suspended solids. Results of this study were used to discuss possible solutions to reduce oxygen demand in the Jordan River

A (Bounded) Bestiary of Feynman Integral Calabi-Yau Geometries

We define the rigidity of a Feynman integral to be the smallest dimension over which it is non-polylogarithmic. We argue that massless Feynman integrals in four dimensions have a rigidity bounded by 2(L-1) at L loops, and we show that this bound may be saturated for integrals that we call marginal: those with (L+1)D/2 propagators in (even) D dimensions. We show that marginal Feynman integrals in D dimensions generically involve Calabi-Yau geometries, and we give examples of finite four-dimensional Feynman integrals in massless $\phi^4$ theory that saturate our predicted bound in rigidity at all loop orders.Comment: 5+2 pages, 11 figures, infinite zoo of Calabi-Yau manifolds. v2 reflects minor changes made for publication. This version is authoritativ

Toward a Sunny Future? Global Integration in the Solar PV Industry

Policymakers seem to face a trade-off when designing national trade and investment policies related to clean energy sectors. They have pledged to address climate change and accelerate the large-scale deployment of renewable energy technologies, which would benefit from increased global integration, but they are also tempted to nurture and protect domestic clean technology markets to create green jobs at home and ensure domestic political support for more ambitious climate policies. This paper analyzes the global integration of the solar photovoltaic (PV) sector and looks in detail at the industry’s recent growth patterns, industry cost structure, trade and investment patterns, government support policies and employment generation potential. In order to further stimulate both further growth of the solar industry and local job creation without constructing new trade and investment barriers, we recommend the following: (1) Governments must provide sufficient and predictable long-term support to solar energy deployment. Such long-term frameworks bring investments forward and encourage cost cutting and innovation, so that government support can decrease over time. A price on carbon emissions would provide an additional long-term market signal and likely accelerate this process. (2) Policymakers should focus not on solely the manufacturing jobs in the solar industry, but on the total number of jobs that could possibly be created including those in research, project development, installation, operations and maintenance. (3) Global integration and broader solar PV technology deployment through lower costs can be encouraged by keeping global solar PV markets open. Protectionist policies risk slowing the development of global solar markets and provoking retaliatory actions in other sectors. Lowering existing trade barriers—by abolishing tariffs, reducing non-tariff barriers and harmonizing industry standards—would create a positive policy environment for further global integration.Solar PV, climate change, renewable energy, government support, green protectionism, green jobs, global integration

Homogeneity of the Inverse Relationship Between Motor Unit Recruitment Threshold and Firing Rate Across the Lifespan

It is well understood that there is an inverse relationship between the recruitment thresholds and firing rates for a group of motor units. In other words, at any given force level, earlier-recruited, low-threshold motor units have higher firing rates than later-recruited ones. The majority of previous investigations that have examined this relationship have done so in healthy, young adults. While some evidence suggests that aging may result in decreased maximal firing rates, it is unclear if the control scheme which governs the recruitment and firing behavior of motor units is consistent across the lifespan. Therefore, the purpose of this study was to examine the motor unit recruitment threshold versus mean firing rate relationship in children and younger and older adults. Eight boys (mean ± SD age = 12 ± 2 years; body mass = 49.9 ± 13.2 kg) and five younger (age = 26 ± 3 years; body mass = 68.6 ± 5.5 kg) and six older (age = 72 ± 4 years; body mass = 79.5 ± 9.6 kg) men participated in this investigation. Subjects performed isometric, constant-force contractions at 50% of their maximal voluntary contraction (MVC) force while bipolar surface electromyographic (EMG) signals were detected from the vastus lateralis muscle. A surface EMG signal decomposition algorithm was used to determine the recruitment thresholds and firing rates of motor units that demonstrated accuracy levels ≥ 93%. For each subject, the relationship between the recruitment thresholds and the mean firing rates was examined using linear regression. Two separate one-way analyses of variance (ANOVA) were used to examine age-related differences in the linear slope coefficients (pulses per second [pps]/% MVC) and y-intercepts (pps) from the recruitment threshold vs. firing rate calculations. The mean ± SD slope coefficients for the boys and younger and older men were -0.33 ± 0.12, -0.49 ± 0.32, and -0.60 ± 0.38 pps/%MVC, respectively. The mean ± SD for the y-intercepts for the boys and younger and older men were 21.17 ± 4.16, 26.80 ± 4.68, and 27.60 ± 6.77 pps, respectively. The ANOVAs did not reveal any significant age-related differences in the linear slope coefficients (F = 1.700, p = 0.214) or y-intercepts (F = 3.150, p = 0.070). Although larger studies with additional subjects may be required to verify these findings, the results of the present investigation suggested that the inverse relationship between motor unit recruitment thresholds and firing rates is fixed across the lifespan

The Elliptic Double-Box Integral: Massless Amplitudes Beyond Polylogarithms

We derive an analytic representation of the ten-particle, two-loop double-box integral as an elliptic integral over weight-three polylogarithms. To obtain this form, we first derive a four-fold, rational (Feynman-)parametric representation for the integral, expressed directly in terms of dual-conformally invariant cross-ratios; from this, the desired form is easily obtained. The essential features of this integral are illustrated by means of a simplified toy model, and we attach the relevant expressions for both integrals in ancillary files. We propose a normalization for such integrals that renders all of their polylogarithmic degenerations pure, and we discuss the need for a new 'symbology' of iterated elliptic/polylogarithmic integrals in order to bring them to a more canonical form.Comment: 4+2 pages, 2 figures. Explicit results are included as ancillary files. v2: minor changes made for clarification; references adde

Prospectus, March 11, 1998

https://spark.parkland.edu/prospectus_1998/1008/thumbnail.jp