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 & Aerosol. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.

Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by type-II parametric down-conversion.

Abstract: We report a new two-photon polarization correlation experiment for realizing the Einstein-Podolsky-Rosen-Bohm (EPRB) state and for testing Bell-type inequalities. We use the pair of orthogonally polarized light quanta generated in type-II parametric down-conversion. In a 1 nm bandwidth, we observe from the output of a 0.5 mm \ensuremath{\beta}-${\mathrm{BaB}}_{2}$${\mathrm{O}}_{4}$ crystal the EPRB correlations in coincidence counts, and measure an associated Bell inequality violation of 22 standard deviations.

Global assimilation of satellite surface soil moisture retrievals into the NASA Catchment land surface model

Abstract: [1] Global retrievals of surface soil moisture from the Scanning Multichannel Microwave Radiometer for the period 1979–87 are assimilated into the NASA Catchment land surface model as it is driven with surface meteorological data derived from observations. Validation against ground-based measurements in Eurasia and North America from the Global Soil Moisture Data Bank demonstrates a long assumed (but rarely proven) property of soil moisture fields derived from data assimilation – that the assimilation product is superior to either satellite data or model data alone. An analysis of the innovations reveals that the filter is only partially operating within its underlying assumptions and offers clues how spatially distributed model error parameters could further enhance filter performance.

Structure of the HIV-1 RNA packaging signal

Abstract: The 5' leader of the HIV-1 genome contains conserved elements that direct selective packaging of the unspliced, dimeric viral RNA into assembling particles. By using a (2)H-edited nuclear magnetic resonance (NMR) approach, we determined the structure of a 155-nucleotide region of the leader that is independently capable of directing packaging (core encapsidation signal; Ψ(CES)). The RNA adopts an unexpected tandem three-way junction structure, in which residues of the major splice donor and translation initiation sites are sequestered by long-range base pairing and guanosines essential for both packaging and high-affinity binding to the cognate Gag protein are exposed in helical junctions. The structure reveals how translation is attenuated, Gag binding promoted, and unspliced dimeric genomes selected, by the RNA conformer that directs packaging.

Regulation of reactive oxygen species, DNA damage, and c-Myc function by peroxiredoxin 1.

Abstract: Overexpression of c-Myc results in transformation and multiple other phenotypes, and is accompanied by the deregulation of a large number of target genes. We previously demonstrated that peroxiredoxin 1 (Prdx1), a scavenger of reactive oxygen species (ROS), interacts with a region of the c-Myc transcriptional regulatory domain that is essential for transformation. This results either in the suppression or enhancement of some c-Myc functions and in the altered expression of select target genes. Most notably, c-Myc-mediated transformation is inhibited, implying a tumor suppressor role for Prdx1. Consistent with this, prdx1-/- mice develop age-dependent hemolytic anemias and/or malignancies. We now show that erythrocytes and embryonic fibroblasts from these animals contain higher levels of ROS, and that the latter cells show evidence of c-Myc activation, including the ability to be transformed by a ras oncogene alone. In contrast, other primary cells from prdx1-/- mice do not have elevated ROS, but nonetheless show increased oxidative DNA damage. This apparent paradox can be explained by the fact that ROS localize primarily to the cytoplasm of prdx1+/+ cells, whereas in prdx1-/- cells, much higher levels of nuclear ROS are seen. We suggest that increased DNA damage and tumor susceptibility in prdx1-/- animals results from this shift in intracellular ROS. prdx1-/- mice should be useful in studying the role of oxidative DNA damage in the causation of cancer and its prevention by antioxidants. They should also help in studying the relationship between oncogenes such as c-Myc and DNA damage.

Modified angström exponent for the characterization of submicrometer aerosols.

Abstract: The classical Angstrom exponent is an operationally robust optical parameter that contains size information on all optically active aerosols in the field of view of a sunphotometer. Assuming that the optical effects of a typical (radius) size distribution can be approximated by separate submicrometer and supermicrometer components, we show that one can exploit the spectral curvature information in the measured optical depth to permit a direct estimation of a fine-mode (submicrometer) Angstrom exponent (αf) as well as the optical fraction of fine-mode particles (η). Simple expressions that enable the estimation of these parameters are presented and tested by use of simulations and measurements.