University of Maryland, Baltimore County

About: University of Maryland, Baltimore County is a education organization based out in Baltimore, Maryland, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.

A study of oxygen transfer in shake flasks using a non-invasive oxygen sensor.

Abstract: We describe a study of oxygen transfer in shake flasks using a non-invasive optical sensor. This study investigates the effect of different plugs, presence of baffles, and the type of media on the dissolved oxygen profiles during Escherichia coli fermentation. We measured the volumetric mass transfer coefficient (k(L)a) under various conditions and also the resistances of the various plugs. Finally, we compared shake flask k(L)a with that from a stirred tank fermentor. By matching k(L)a's we were able to obtain similar growth and recombinant protein product formation kinetics in both a fermentor and a shake flask. These results provide a quantitative comparison of fermentations in a shake flask vs. a bench-scale fermentor and should be valuable in guiding scale-up efforts.

A Chandra Survey of Quasar Jets: First Results

Abstract: We present results from Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat-spectrum radio-emitting quasars with jetlike extended structure. Twelve of 20 quasar jets are detected in 5 ks ACIS-S exposures. The quasars without X-ray jets are not significantly different from those in the sample with detected jets except that the extended radio emission is generally fainter. New radio maps are combined with the X-ray images in order to elucidate the relation between radio and X-ray emission in spatially resolved structures. We find a variety of morphologies, including long straight jets and bends up to 90°. All X-ray jets are one-sided although the radio images used for source selection often show lobes opposite the X-ray jets. The FR II X-ray jets can all be interpreted as inverse Compton scattering of cosmic microwave background photons by electrons in large-scale relativistic jets although deeper observations are required to test this interpretation in detail. Applying this interpretation to the jets as a population, we find that the jets would be aligned to within 30° of the line of sight generally, assuming that the bulk Lorentz factor of the jets is 10.

A global climatology of tropospheric and stratospheric ozone derived from Aura OMI and MLS measurements

Abstract: A global climatology of tropospheric and stratospheric column ozone is derived by combining six years of Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone measurements for the period October 2004 through December 2010. The OMI/MLS tropospheric ozone climatology exhibits large temporal and spatial variability which includes ozone accumulation zones in the tropical south Atlantic year-round and in the subtropical Mediterranean! Asia region in summer months. High levels of tropospheric ozone in the northern hemisphere also persist in mid-latitudes over the eastern North American and Asian continents extending eastward over the Pacific Ocean. For stratospheric ozone climatology from MLS, largest ozone abundance lies in the northern hemisphere in the latitude range 70degN-80degN in February-April and in the southern hemisphere around 40degS-50degS during months August-October. The largest stratospheric ozone abundances in the northern hemisphere lie over North America and eastern Asia extending eastward across the Pacific Ocean and in the southern hemisphere south of Australia extending eastward across the dateline. With the advent of many newly developing 3D chemistry and transport models it is advantageous to have such a dataset for evaluating the performance of the models in relation to dynamical and photochemical processes controlling the ozone distributions in the troposphere and stratosphere.

Land Use and Climate Variability Amplify Carbon, Nutrient, and Contaminant Pulses: A Review with Management Implications

Abstract: Nonpoint source pollution from agriculture and urbanization is increasing globally at the same time climate extremes have increased in frequency and intensity. We review >200 studies of hydrologic and gaseous fluxes and show how the interaction between land use and climate variability alters magnitude and frequency of carbon, nutrient, and greenhouse gas pulses in watersheds. Agricultural and urban watersheds respond similarly to climate variability due to headwater alteration and loss of ecosystem services to buffer runoff and temperature changes. Organic carbon concentrations/exports increase and organic carbon quality changes with runoff. Nitrogen and phosphorus exports increase during floods (sometimes by an order of magnitude) and decrease during droughts. Relationships between annual runoff and nitrogen and phosphorus exports differ across land use. CH4 and N2O pulses in riparian zones/floodplains predominantly increase with: flooding, warming, low oxygen, nutrient enrichment, and organic carbon. CH4, N2O, and CO2 pulses in streams/rivers increase due to similar factors but effects of floods are less known compared to base flow/droughts. Emerging questions include: (1) What factors influence lag times of contaminant pulses in response to extreme events? (2) What drives resistance/resilience to hydrologic and gaseous pulses? We conclude with eight recommendations for managing watershed pulses in response to interactive effects of land use and climate change.