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Scanning electron microscopy and X-ray dispersive energy microanalysis were used to investigate the formation of carbonate crystals by Deleya halophila. The formation of calcium carbonate crystals (polymorphous aragonite) by D. halophila is a sequential process that commences with a nucleus formed by the aggregation of a few calcified bacterial cells and(More)
Surface ozone (O 3) was analyzed to investigate the role of the bay breeze on air quality at two locations in Edgewood, Maryland (lat: 39.4°, lon: −76.3°) for the month of July 2011. Measurements were taken as part of the first year of NASA's " Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air(More)
A total of 21 raw, washed and ground Spanish kaolins were studied. Kaolinite, mica, quartz, feldspars and occasionally anatase and analcime were present. Calcined samples in which the kaolinite had been transformed into metakaolinite (650 8C, 3 h), as shown by X-ray diffraction and observed using SEM were also studied. These samples featured particles with(More)
Commercial talcs are pulverized mineral products with a variable chemical and mineralogic composition, widely used in industry. Although generally white, they have color variations. The aim of this study was to establish relationships between color parameters and the chemical and mineralogic composition of commercial talc samples, in order to investigate(More)
Total-column nitrogen dioxide (NO 2) data collected by a ground-based sun-tracking spectrometer system (Pandora) and an photolytic-converter-based in-situ instrument were analyzed to study the relationship between total-column and surface NO 2 measurements. The measurements span more than a year and cover all seasons. Surface mixing ratios are estimated via(More)
This article describes the experimental calibration of a three-dimensional numerical model of an Alfa Pendular train vehicle based on modal parameters. The dynamic tests of the carbody and bogie of the vehicle allowed the determination of the frequencies and modal configurations of 13 vibration modes, by applying the data-driven stochastic subspace(More)
Keywords: Finite element model updating Railway bridge Bowstring-arch Experimental modal parameters Genetic algorithm Experimental validation a b s t r a c t This article describes the calibration of the numerical model of a bowstring-arch railway bridge based on modal parameters. An ambient vibration test allowed the identification of the natural(More)
UNLABELLED This study investigates the sources of fine particulate matter (aerodynamic diameter ≤2.5 μm; PM(2.5)) composition for the Baltimore, Maryland, metropolitan area, covering a 6-year period (2008-2013). Data obtained from the U.S. Environmental Protection Agency (EPA) Air Quality System (AQS) were used for the identification of eight chemical(More)
UNLABELLED Canadian wildfire smoke impacted air quality across the northern Mid-Atlantic (MA) of the United States during June 9-12, 2015. A multiday exceedance of the new 2015 70-ppb National Ambient Air Quality Standard (NAAQS) for ozone (O3) followed, resulting in Maryland being incompliant with the Environmental Protection Agency's (EPA) revised 2015 O3(More)