Use of an artificial neural network to predict air temperature, surface temperature, dew point and wind speed for the prediction of frost

Frost forms on bridges in Iowa about thirty times per year and presents a potentially hazardous condition for motorists. Accurate frost forecasts allow roadway maintenance personnel to make timely applications of preventative or suppressant material and minimize environmental impact from fugitive chemicals. However, accurate predictions present a challenge to forecasters due to high spatial variability of key meteorological factors leading to frost. A series of models were developed through the use of an artificial neural network to forecast the parameters (air temperature and dew point, bridge surface temperature, and winds) needed to drive an algorithm for frost deposition on bridges. The neural network was trained on model output and observations for four observation sites from three cold seasons (1995-1998). The frost model was then tested on data from the 2001-2002 and 2002-2003 cold seasons in Ames, IA. The frost forecast was developed to be issued at 18 UTC (12 PM) daily for twenty minute intervals beginning at 00 UTC (6 PM) and ending at 15 UTC (9 AM) local time. Results show that the artificial neural network forecast method produces more accurate forecasts in the short term than model output statistics derived from the 6 AM local time run of one of the National Weather Service models. Over the forecast period, the artificial neural network displayed a bias for under forecasting dew point, air temperature and surface temperature. Despite these biases, it is shown that the use of an artificial neural network as a tool for forecasting meteorological parameters is possible given the appropriate data

Conceptual and Scaling Evaluation of Vehicle Traffic Thermal Effects on Snow/Ice-Covered Roads*

The potential thermal effects of traffic on road surface thermal energy balance under frost/snow cover conditions have been largely ignored in meteorological evaluations of road ice deposit conditions. Preliminary exploration of these effects, particularly for heavy traffic scenarios with calm wind conditions and an ambient temperature of 0°C, is provided in this study using a conceptual model. Observational data were used to constrain the model, and parameterizations were employed to estimate the various heat transfer processes involved. The results indicate that, for heavy traffic situations, as well as for stopped traffic at intersections, the traffic thermal flux contribution at the surface is noticeable in a wide range of possible frost/snow-covered road conditions. The sensitivity to variation in traffic density, speed, and the emissivity of vehicle radiative surfaces, among others, is evaluated. Simple quantification of these traffic thermal effects, which might be considered in operational meteorological model forecasting of icy road conditions, is offered

Identification and characterization of the dif Site from Bacillus subtilis

Bacteria with circular chromosomes have evolved systems that ensure multimeric chromosomes, formed by homologous recombination between sister chromosomes during DNA replication, are resolved to monomers prior to cell division. The chromosome dimer resolution process in Escherichia coli is mediated by two tyrosine family site-specific recombinases, XerC and XerD, and requires septal localization of the division protein FtsK. The Xer recombinases act near the terminus of chromosome replication at a site known as dif (Ecdif). In Bacillus subtilis the RipX and CodV site-specific recombinases have been implicated in an analogous reaction. We present here genetic and biochemical evidence that a 28-bp sequence of DNA (Bsdif), lying 6° counterclockwise from the B. subtilis terminus of replication (172°), is the site at which RipX and CodV catalyze site-specific recombination reactions required for normal chromosome partitioning. Bsdif in vivo recombination did not require the B. subtilis FtsK homologues, SpoIIIE and YtpT. We also show that the presence or absence of the B. subtilis SPβ-bacteriophage, and in particular its yopP gene product, appears to strongly modulate the extent of the partitioning defects seen in codV strains and, to a lesser extent, those seen in ripX and dif strains

Microbial effects on the development of forensically important blow fly species

Colonisation times and development rates of specific blow fly species are used to estimate the minimum Post Mortem Interval (mPMI). The presence or absence of bacteria on a corpse can potentially affect the development and survival of blow fly larvae. Therefore an understanding of microbial-insect interactions is important for improving the interpretation of mPMI estimations. In this study, the effect of two bacteria (Escherichia coli and Staphylococcus aureus) on the growth rate and survival of three forensically important blow fly species (Lucilia sericata, Calliphora vicina and Calliphora vomitoria) was investigated. Sterile larvae were raised in a controlled environment (16:8 h day: night light cycle, 23:21 °C day: night temperature cycle and a constant 35% relative humidity) on four artificial diets prepared with 100 μl of 105 CFU bacterial solutions as follows: (1) E. coli, (2) S. aureus, (3) a 50:50 E. coli:S. aureus mix and (4) a sterile bacteria-free control diet. Daily measurements (length, width and weight) were taken from first instar larvae through to the emergence of adult flies. Survival rates were also determined at pupation and adult emergence. Results indicate that bacteria were not essential for the development of any of the blow fly species. However, larval growth rates were affected by bacterial diet, with effects differing between blow fly species. Peak larval weights also varied according to species-diet combination; C. vomitoria had the largest weight on E. coli and mixed diets, C. vicina had the largest weight on S. aureus diets, and treatment had no significant effect on the peak larval weight of L. sericata. These results indicate the potential for the bacteria that larvae are exposed to during development on a corpse to alter both developmental rates and larval weight in some blow fly species.Daphne Jackson Trus