FW2_5D: A MATLAB 2.5-D electrical resistivity modeling code

We present a 2.5-D forward modeling algorithm for electrical resistivity data. The algorithm incorporates a boundary condition and source singularity correction that greatly reduces the need to pad the model space. In addition, the algorithm includes an optimization method for estimating the appropriate Fourier coefficients to achieve an accurate 2.5-D approximation. The optimization scheme uses a gradient-based search to find the optimal coefficients. We compare results from our algorithm to two analytical solutions. We are able to achieve errors on the order 1% when compared to these models. We have implemented the algorithm as an open source MATLAB-based forward modeling package. The MATLAB code is useful for exploring subsurface current flow. It has been coded so that it can be easily ported to work with inversion routines. The code is computationally efficient and suitable for solving 2-D problems with a large number of model parameters.     

Pedagogical approaches for technology-integrated science teaching

The two separate projects described have examined how teachers exploit computer-based technologies in supporting learning of science at secondary level. This paper examines how pedagogical approaches associated with these technological tools are adapted to both the cognitive and structuring resources available in the classroom setting. Four teachers participated in the first study, undertaken as part of the InterActive Education project in Bristol; all of them used multimedia simulations in their lessons. The second study presented was part of the wider SET-IT project in Cambridge; 11 teachers in eight schools were observed using multimedia simulations, data logging tools and interactive whiteboards. Teachers were interviewed in all cases to elicit their pedagogical thinking about their classroom use of ICT.     

Workplace innovation: bridging knowledge and practice

The article draws on a decade of work in the UK by the UK Work Organisation Network (UKWON), and recommends a systematic approach. Taking cases in the National Health Service, the focus is on employee involvement, partnership and the development of social capital. High and low road approaches are compared, in an evaluation of the Improving Working Lives programme.

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Between the lines: documenting the multiple dimensions of computer-supported collaborations

This paper discusses the development of a documentation technique for collaborative interactions. We describe the original version of the technique as used for a single learner collaborating with a software based learning partner; the second generation of the technique, which required adaptation for application to the analysis of group use of multimedia; and finally the current variation, which is being used to record young children using digital toys and associated software. Particular attention is paid to the way in which the original approach has been adapted in order to accommodate learning contexts that involve technology beyond the desktop computer. We explore some of the challenges these different learning situations pose for those involved in the evaluation of collaborative learning and suggest that tried and tested techniques can be adapted and re-used, provided that the foci of interactivity are clearly specified and the appropriate data sources identified.     

Micromachined,silicon filament light source for spectrophotometric microsystems

A miniature broadband light source is a critical element in a spectrophotometric microsystem. The design, fabrication, and characterization of a highly stable, miniature broadband light source that comprises filaments of single-crystal silicon are presented. Electrical current versus voltage and radiant emittance spectra under constant voltage bias are measured and related to filament dimensions. A maximum stable operating temperature for these filaments is estimated to be 1200 K. Resistance drift is demonstrated to be less than 0.5% over a 10-h period of continuous operation with visible incandescence. Emittance spectra of a multifilament array, measured at three different electrical biases, are presented and shown to compare well with theoretical blackbody radiation spectra. A continuous, total radiated power of 10.7 mW was achieved with a 1 mm x 1 mm filament array with peak emittance at lambda=2.7 micrometers.     

Pre to post‐dialysis plasma sodium change better predicts clinical outcomes than dialysate to plasma sodium gradient in quotidian hemodialysis

Sodium balance across a hemodialysis treatment influences interdialytic weight gain (IDWG), pre‐dialysis blood pressure, and the occurrence of intradialytic hypotension, which associate with patient morbidity and mortality. In thrice weekly conventional hemodialysis patients, the dialysate sodium minus pre‐dialysis plasma sodium concentration (δDPNa+) and the post‐dialysis minus pre‐dialysis plasma sodium (δPNa+) are surrogates of sodium balance, and are associated with both cardiovascular and all‐cause mortality. However, whether δDPNa+ or δPNa+ better predicts clinical outcomes in quotidian dialysis is unknown. We performed a retrospective analysis of clinical and demographic data from the Southwestern Ontario Regional Home Hemodialysis program, of all patients since 1985. In frequent nocturnal hemodialysis, δPNa+ was superior to δDPNa+ in predicting IDWG (R² = 0.223 vs. 0.020, P = 0.002 vs. 0.76), intradialytic change in systolic (R² = 0.100 vs. 0.002, P = 0.02 vs. 0.16) and diastolic (R² = 0.066 vs. 0.019, P = 0.02 vs. 0.06) blood pressure, and ultrafiltration rate (R² = 0.296 vs. 0.036, P = 0.001 vs. 0.52). In short hours daily hemodialysis, δDPNa+ was better than δPNa+ in predicting intradialytic change in diastolic blood pressure (R² = 0.101 vs. 0.003, P = 0.02 vs. 0.13). However, δPNa+ was better than δDPNa+ in predicting IDWG (R² = 0.105 vs. 0.019, P = 0.04 vs. 0.68) and pre‐dialysis systolic blood pressure (R² = 0.103 vs. 0.007, P = 0.02 vs. 0.82). We also found that the intradialytic blood pressure fall was greater in frequent nocturnal hemodialysis patients than in short hours daily patients, when exposed to a dialysate to plasma sodium gradient. These results provide a basis for design of prospective trials in quotidian dialysis modalities, to determine the effect of sodium balance on cardiovascular outcome.     

The culpability of drivers killed in New Zealand road crashes and their use of alcohol and other drugs

Over a period of five years, blood samples were taken from 1046 drivers killed as a result of a motor vehicle crash on New Zealand roads. These were analysed for the presence of alcohol and a range of both illicit drugs and psychoactive medicinal drugs. Driver culpability was determined for all crashes. The control group of drug- and alcohol-free drivers comprised 52.2% of the study population. Drivers positive for psychoactive drugs were more likely to be culpable (odds ratio (OR) 3.5, confidence interval (CI) 95% 2.4–5.2) than the control group. Driver culpability exhibited the expected positive association with alcohol use (OR 13.7, 95% CI 4.3–44) and with combined alcohol and cannabis use (OR 6.9, 95% CI 3.0–16). There was only a weak positive association between cannabis use (with no other drug) and culpability (OR 1.3, CI 95% 0.8–2.3). Furthermore, the OR for drivers with blood tetrahydrocannabinol (THC) concentrations greater than 5 ng/mL was lower (OR 1.0, CI 95% 0.4–2.4) than drivers with blood THC concentrations less than 2 ng/mL (OR 3.1, CI 95% 0.9–10). This is inconsistent with results reported by other studies where a significant increase in crash risk was found with blood THC levels greater than 5 ng/mL. In this study, there were very few drivers who had used a single drug, other than cannabis or alcohol. Therefore, from this study, it is not possible to comment on any relationship between opioid, stimulant or sedative drug use and an increased risk of being killed in a crash for the drivers using these drugs. The results from a multivariate analysis indicate that driver gender, age group and licence status, (P = 0.022, P = 0.016, P = 0.026, respectively), the type of vehicle being driven (P = 0.013), the number of vehicles in the crash (P < 0.001), the blood alcohol concentration of the driver (P < 0.001) and the use of any drug other than alcohol and cannabis (P = 0.044), are all independently associated with culpability.     

Hypolimnetic withdrawal in two north american lakes with anoxic phosphorus release from the sediment

Hypolimnetic withdrawal has been used to decrease eutrophication in two Connecticut lakes. This restoration technique is based on the forced discharge of nutrient-rich bottom waters in lakes with anoxic hypolimnia, while surface outflows are dammed. Internal phosphorus load amounted to 600 mg m⁻² summer⁻¹ before withdrawal. Most of this load probably originated from the sediment since the experimentally determined sediment phosphorus release rates of 2–12 mg m⁻² day⁻¹ can account for the internal load. The smaller lake responded to hypolimnetic withdrawal with decreasing epilimnetic and hypolimnetic phosphorus concentrations, decreased anoxia and internal loads. The larger lake also showed a tendency towards improvement which is, however, not statistically significant.     

Modeling wildfire potential in residential parcels: A case study of the north-central Colorado Front Range

This study evaluated if present-day wildfire potential (i.e. potential fireline intensity and percentage crown fire) differs for residential parcels developed at different time periods in the north–central Colorado Front Range. To answer this question, a model of wildfire potential was built based on 2001 fuels and vegetation and compared the output to actual fire severity of the 2002 Hayman and 2004 Picnic Rock fires (measured by satellite imagery). Except for low-load fuel types such as grass, the modeled wildfire potential corresponded well to observed fire severity. Wildfire potential was then evaluated within 7 classes: developed (1880–1944, 1945–1959, 1960–1974, 1975–1989, 1990–2005) and undeveloped (either zoned or not zoned for development). The results suggest that there is one class characterized by relatively low wildfire potential (developed 1880–1944) and three classes characterized by relatively high wildfire potential (developed 1960–1974 and the two undeveloped parcel classes). These results hold both for 99th percentile (extreme) and 50th percentile (average) fuel conditions. The results suggest that under current zoning regulations, future structures are likely to be built on parcels that, on average, have somewhat higher potential fireline intensity and higher percentage of crown fire compared to currently developed parcels. However, the location of future development may be influenced by forest changes, such as the visual degradation and perceived fire hazard of trees killed by the continuing mountain pine beetle outbreak. Overall, this study introduces an improved method for quantifying wildfire potential in the rapidly developing wildland–urban interface that could be applied to other areas.