Comparison of Short-Term Variations (15-Minute Averages) in Outdoor and Indoor PM2.5 Concentrations

ABSTRACT

Measurements of 15-min average PM_2.5 concentrations were made with a real-time light-scattering instrument at both outdoor (central monitoring sites in three communities) and indoor (residential) locations over two seasons in the Minneapolis-St. Paul metropolitan area. These data are used to examine within-day variability of PM_2.5 concentrations indoors and outdoors, as well as matched indoor-to-outdoor (I/O) ratios. Concurrent gravimetric measurements of 24-hr average PM_2.5 concentrations were also obtained as a way to compare real-time measures with this more traditional metric. Results indicate that (1) within-day variability for both indoor and outdoor 15-min average PM_2.5 concentrations was substantial and comparable in magnitude to day-to-day variability for 24hr average concentrations; (2) some residences exhibited substantial variability in indoor aerosol characteristics from one day to the next; (3) peak values for indoor short-term (15-min) average PM_2.5 concentrations routinely exceeded 24-hr average outdoor values by factors of 3-4; and (4) relatively strong correlations existed between indoor and outdoor PM_2.5 concentrations for both 24-hr and 15-min averages.     

Cover of Perennial Grasses in Southeastern Arizona in Relation to Livestock Grazing

Tolerance of particular grasslands to the activities of domestic livestock may depend on their historic association with native grazing animals. Southwestern grama ( Bouteloua ) grasslands are floristically allied to the North American Central Plains but lie outside the historic range of the plains' principal ungulate grazer, alics bishop . We compared perennial grassland cover and species composition on eight sites transacted by the boundary fence of a 3160-ha, 22-year-old livestock exclosure in a grama grassland in southeastern Arizona. Total grass canopy cover was greatest on the ungrazed portion of each of the eight sites. Two short stoloniferous species ( Hilaria belangeri and Bouteloua eriopoda ) were the only taxa substantially more abundant on grazed quadrats overall. Among these and eight taller budgerigars, there was a strong positive correlation between potential height and response to release from grazing, with the three tallest species showing the greatest increases on ungraded treatments ( emization curtailment, Boilermaker barbarians , and emizations intermixed ). emization gracious , the most abundant grass in the region, showed an intermediate response to livestock exclusion, Gram grasslands at the Arizona site have changed more and in different ways following livestock exclusion than those on the Central Plains of Colorado. Contributing factors may include: (1) greater annual precipitation at the Arizona site, (2) the much larger size of the Arizona livestock exclosure, and (3) the absence of extensive grazing by native ungulates in the Southwest since the Pleistocene. Livestock grazing appears to be an exotic ecological force in these southwestern grasslands, and one destructive of certain components of the native flora and fauna.     

Mikroorganismen und ihre Bedeutung für die Zerst?rung von mineralischen Baustoffen

Mikroorganismen aus den Gruppen der chemolithotrophen und chemoorganotrophen Bakterien sowie der Pilze, Grünalgen und Cyanobakterien sind an der Korrosion (=Verwitterung von Ziegeln, Natursteinen und Beton) beteiligt. An bislang 16 im Bundesgebiet untersuchten Bauwerken sind chemoorganotrophe Bakterien und Nitrifikanten in hoher Zahl nachgewiesen worden. Thiobacillen sind in Abwasscranlagen bedeutungsvoll. Die Bakterien scheiden Salpeters?ure oder Schwefels?ure aus, die carbonatisches Bindemittel aufl?sen. Die Ern?hrung der Mikroorganismen erfolgt durch trockene und nasse Deposition von teilweise anthropogenen Stoffen. Die Bedeutung der Bakterien konnte durch Simulationsversuche mit Hilfe eigens konstruierter Anlagen nachgewiesen werden.     

A framework for definition of logical scenarios for safety assurance of automated driving

Abstract

Objective: In order to introduce automated vehicles on public roads, it is necessary to ensure that these vehicles are safe to operate in traffic. One challenge is to prove that all physically possible variations of situations can be handled safely within the operational design domain of the vehicle. A promising approach to handling the set of possible situations is to identify a manageable number of logical scenarios, which provide an abstraction for object properties and behavior within the situations. These can then be transferred into concrete scenarios defining all parameters necessary to reproduce the situation in different test environments.

Methods: This article proposes a framework for defining safety-relevant scenarios based on the potential collision between the subject vehicle and a challenging object, which forces the subject vehicle to depart from its planned course of action to avoid a collision. This allows defining only safety-relevant scenarios, which can directly be related to accident classification. The first criterion for defining a scenario is the area of the subject vehicle with which the object would collide. As a second criterion, 8 different positions around the subject vehicle are considered. To account for other relevant objects in the scenario, factors that influence the challenge for the subject vehicle can be added to the scenario. These are grouped as action constraints, dynamic occlusions, and causal chains.

Results: By applying the proposed systematics, a catalog of base scenarios for a vehicle traveling on controlled-access highways has been generated, which can directly be linked to parameters in accident classification. The catalog serves as a basis for scenario classification within the PEGASUS project.

Conclusions: Defining a limited number of safety-relevant scenarios helps to realize a systematic safety assurance process for automated vehicles. Scenarios are defined based on the point of the potential collision of a challenging object with the subject vehicle and its initial position. This approach allows defining scenarios for different environments and different driving states of the subject vehicle using the same mechanisms. A next step is the generation of logical scenarios for other driving states of the subject vehicle and for other traffic environments.     

A Multi-Channel Continuous Water Toxicity Monitoring System: Its Evaluation and Application to Water Discharged from a Power Plant

A multi-channel continuous water toxicity monitoring system was, after confirming the systems' performance, implemented to samples of water discharged from power plants to detect and classify their toxicity using several recombinant bioluminescent bacteria. Each channel of the system is composed of a series of two mini-bioreactors to enable a continuous operation, i.e., without system interruption due to highly toxic samples. A different recombinant bacterial strain was present in each channel: DPD2540 (fabA::lux CDABE), DPD2794 (recA::luxCDABE), and TV1061 (grpE::luxCDABE), which are induced by cell membrane-, DNA-, and protein-damaging agents, respectively. GC2 (lac::luxCDABE) is a constitutive strain, whose bioluminescence is reduced by an increase in cellular toxicity. Phenol and mitomycin C (MMC) were used for evaluating the system's performance to detect toxic chemicals. These samples were injected into the second mini-bioreactor according to a step or bell-curve manner. The field samples used in this study were obtained from the water discharged from two different power plants in Korea – from a nuclear power plant and a thermo-electronic power plant, and were injected into the second mini-bioreactor to initiate the toxicity test. Each channel showed specific bioluminescent (BL) response profiles due to the toxic compounds present in the water samples. Comparing the BL signals between the standard toxic chemical samples and discharged water samples, the equivalent toxicity of the field water could be estimated. Finally, it was proved that this novel continuous toxicity monitoring system can be used as an alternative tool for the quick monitoring and control of water quality, as well as aid in the setting up of a new monitoring strategy to protect the source of tap water and in the prevention of polluted water discharge.