The distribution of stable isotopes and heavy metals in Dreissena polymorpha (zebra mussel): Chemical tracers for environmental contamination in Lake St. Clair (Ontario, Michigan).

The zebra mussel (Dreissena polymorpha) was employed to biomonitor heavy metal (Fe, Zn, and Mn) pollution and to evaluate the distribution of carbon and oxygen stable isotopes in the Lake St. Clair and Detroit River mouth aquatic system. The shells were deposited close to isotopic equilibrium with the ambient water, with the delta13C being depleted by 0.7‰ with respect to the equilibrium value in Lake St. Clair. Shells taken from the Detroit River mouth displayed the most enriched delta 13C values. The average concentrations of the heavy metals Fe, Zn, and Mn in the mussel shells were 149 +/- 102, 9 +/- 8, and 14 +/- 7 ppm (n = 15), respectively. (Abstract shortened by UMI.)Dept. of Earth Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1999 .T43. Source: Masters Abstracts International, Volume: 39-02, page: 0459. Advisers: Ihsam Al-Aasm; Bryan Fryer. Thesis (M.Sc.)--University of Windsor (Canada), 1999

Achieving a lasting impact in rural water services: a case study from south-west Uganda

The achievement of lasting beneficial impacts through rural water supply services has been elusive. In too many cases significant effort and investment has been devoted to providing a service, but after a few years (or even a few months) the system breaks down and no longer provides a useful service to the community. Much thought has gone into the question of what is required to bring about sustainable services, but there remain missing dimensions in much of the existing literature and practice. This paper describes a small research project, focused on one long-term rural water and sanitation programme in south-west Uganda, which specifically addresses the question of sustainability. The paper outlines the research aims and methodology, and presents part of the conceptual thinking derived from literature and key-informant interviews. Field work is on-going at the time of writing, but will be completed in time for oral presentation at the conference

COVID-19 an atypical presentation

Coronavirus disease 2019 (COVID-19) pneumonia usually presents as an unilateral or bilateral lower zone opacities. We wish to highlight a case of COVID 19 presenting as upper lobe consolidation with pre-existing co morbidities and unknown primary source of infection

Financial Modeling in a Fast Mean-Reverting Stochastic Volatility Environment

We present a derivative pricing and estimation methodology for a class of stochastic volatility models that exploits the observed 'bursty' or persistent nature of stock price volatility. Empirical analysis of high-frequency S&P 500 index data confirms that volatility reverts slowly to its mean in comparison to the tick-by- tick fluctuations of the index value, but it is fast mean- reverting when looked at over the time scale of a derivative contract (many months). This motivates an asymptotic analysis of the partial differential equation satisfied by derivative prices, utilizing the distinction between these time scales. The analysis yields pricing and implied volatility formulas, and the latter provides a simple procedure to 'fit the skew' from European index option prices. The theory identifies the important group parameters that are needed for the derivative pricing and hedging problem for European-style securities, namely the average volatility and the slope and intercept of the implied volatility line, plotted as a function of the log- moneyness-to-maturity-ratio. The results considerably simplify the estimation procedure. The remaining parameters, including the growth rate of the underlying, the correlation between asset price and volatility shocks, the rate of mean-reversion of the volatility and the market price of volatility risk are not needed for the asymptotic pricing formulas for European derivatives, and we derive the formula for a knock-out barrier option as an example. The extension to American and path-dependent contingent claims is the subject of future work.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42745/1/10690_2004_Article_200681.pd

Implications of phosphor coating on the thermal characteristics of phosphor-converted white LEDs

The phosphor layer in phosphor-converted white Light Emitting Diodes (pcLEDs) affects their optical and thermal performances. This paper reports the effects of phosphor thickness and particle concentration on the optical efficiency and temperature rise on conformal phosphor-coated LED package. It is observed that a thicker phosphor layer and a higher phosphor particle concentration will increase the amount of backscattering and back reflection of light from the phosphor layer. These light extraction losses not only reduce the optical efficiency of the light output but also cause heat accumulation in the phosphor layer, leading to higher LED junction temperature. At 2700 K correlated colour temperature (CCT), the temperature rise is observed to increase by as much as 2.6 times as compared to its blue emitting LED package. However, the self-heating effect can be reduced through its die-bonding configuration. Structure function-based thermal evaluation shows heat accumulation in the phosphor layer and that flip-chip bonding can dissipate the heat generated in the GaN LED and phosphor layer effectively. Evidence in this study demonstrates that optical efficiency and thermal resistance of pcLEDs are dependent on the CCT ratings

Effect of ethnic diversity on the saccadic reaction time among healthy Indian and Dutch adults

Eye movement perimetry (EMP) expresses the decline in visual field (VF) responsiveness based on the deviation in saccadic reaction times (SRTs) from their expected age-similar responses (normative database). Since ethnic dissimilarities tend to affect saccade parameters, we evaluated the effect of such a factor on SRT and its interaction with age, stimulus eccentricity, and intensity. 149 healthy adults, spread into five age groups, drawn from Indian and Dutch ethnicities underwent a customized EMP protocol integrated with a saccade task from which the SRTs to ‘seen’ visual stimuli were computed. The EMP test had a total of 54 coordinates (five stimulus eccentricities) tested using Goldmann size III visual stimuli presented at four stimulus intensity (SI) levels against a constant background. Considering SRT as a dependent variable, a Generalized Linear Mixed Model analysis was conducted that revealed a statistically significant (p &lt; 0.001) influence of ethnicity and interaction between the tested factors (ethnicity × age × stimulus eccentricity × intensity). However, during the post hoc analysis, out of the 100 possible pair-wise comparisons, only 6% (minor proportion) of the estimates showed statistical significance. Hence, the ethnic-specific differences need not be accounted for while implementing EMP in a diverse set of populations instead a collective database might serve the purpose.</p

Effect of ethnic diversity on the saccadic reaction time among healthy Indian and Dutch adults

Eye movement perimetry (EMP) expresses the decline in visual field (VF) responsiveness based on the deviation in saccadic reaction times (SRTs) from their expected age-similar responses (normative database). Since ethnic dissimilarities tend to affect saccade parameters, we evaluated the effect of such a factor on SRT and its interaction with age, stimulus eccentricity, and intensity. 149 healthy adults, spread into five age groups, drawn from Indian and Dutch ethnicities underwent a customized EMP protocol integrated with a saccade task from which the SRTs to ‘seen’ visual stimuli were computed. The EMP test had a total of 54 coordinates (five stimulus eccentricities) tested using Goldmann size III visual stimuli presented at four stimulus intensity (SI) levels against a constant background. Considering SRT as a dependent variable, a Generalized Linear Mixed Model analysis was conducted that revealed a statistically significant (p &lt; 0.001) influence of ethnicity and interaction between the tested factors (ethnicity × age × stimulus eccentricity × intensity). However, during the post hoc analysis, out of the 100 possible pair-wise comparisons, only 6% (minor proportion) of the estimates showed statistical significance. Hence, the ethnic-specific differences need not be accounted for while implementing EMP in a diverse set of populations instead a collective database might serve the purpose.</p

Overview of the Habitat Demonstration Unit Power System Integration and Operation at Desert RATS 2010

A habitat demonstration unit (HDU) was constructed at NASA Johnson Space Center (JSC) and designed by a multicenter NASA team led out of NASA Kennedy Space Center (KSC). The HDU was subsequently utilized at the 2010 Desert Research and Technology Studies (RATS) program held at the Black Point Lava Flow in Arizona. This report describes the power system design, installation and operation for the HDU. The requirements for the power system were to provide 120 VAC, 28 VDC, and 120 VDC power to the various loads within the HDU. It also needed to be capable of providing power control and real-time operational data on the load's power consumption. The power system had to be capable of operating off of a 3 phase 480 VAC generator as well as 2 solar photovoltaic (PV) power systems. The system operated well during the 2 week Desert RATS campaign and met all of the main goals of the system. The power system is being further developed to meet the future needs of the HDU and options for this further development are discussed