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.

Extended versus Ensemble Kalman Filtering for Land Data Assimilation

Abstract: The performance of the extended Kalman filter (EKF) and the ensemble Kalman filter (EnKF) are assessed for soil moisture estimation. In a twin experiment for the southeastern United States synthetic observations of near-surface soil moisture are assimilated once every 3 days, neglecting horizontal error correlations and treating catchments independently. Both filters provide satisfactory estimates of soil moisture. The average actual estimation error in volumetric moisture content of the soil profile is 2.2% for the EKF and 2.2% (or 2.1%; or 2.0%) for the EnKF with 4 (or 10; or 500) ensemble members. Expected error covariances of both filters generally differ from actual estimation errors. Nevertheless, nonlinearities in soil processes are treated adequately by both filters. In the application presented herein the EKF and the EnKF with four ensemble members are equally accurate at comparable computational cost. Because of its flexibility and its performance in this study, the EnKF is a promising ...

GPCP Pentad Precipitation analyses: An experimental dataset based on gauge observations and satellite estimates

Abstract: As part of the Global Precipitation Climatology Project (GPCP), analyses of pentad precipitation have been constructed on a 2.58 latitude‐longitude grid over the globe for a 23-yr period from 1979 to 2001 by adjusting the pentad Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) against the monthly GPCP-merged analyses. This adjustment is essential because the precipitation magnitude in the pentad CMAP is not consistent with that in the monthly CMAP or monthly GPCP datasets primarily due to the differences in the input data sources and merging algorithms, causing problems in applications where joint use of the pentad and monthly datasets is necessary. First, pentad CMAP-merged analyses are created by merging several kinds of individual data sources including gauge-based analyses of pentad precipitation, and estimates inferred from satellite observations. The pentad CMAP dataset is then adjusted by the monthly GPCP-merged analyses so that the adjusted pentad analyses match the monthly GPCP in magnitude while the high-frequency components in the pentad CMAP are retained. The adjusted analyses, called the GPCP-merged analyses of pentad precipitation, are compared to several gauge-based datasets. The results show that the pentad GPCP analyses reproduced spatial distribution patterns of total precipitation and temporal variations of submonthly scales with relatively high quality especially over land. Simple applications of the 23-yr dataset demonstrate that it is useful in monitoring and diagnosing intraseasonal variability. The Pentad GPCP has been accepted by the GPCP as one of its official products and is being updated on a quasi-real-time basis.

Myeloid-Derived Suppressor Cells: Critical Cells Driving Immune Suppression in the Tumor Microenvironment.

Abstract: Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that suppress innate and adaptive immunity. MDSCs are present in many disease settings; however, in cancer, they are a major obstacle for both natural antitumor immunity and immunotherapy. Tumor and host cells in the tumor microenvironment (TME) produce a myriad of pro-inflammatory mediators that activate MDSCs and drive their accumulation and suppressive activity. MDSCs utilize a variety of mechanisms to suppress T cell activation, induce other immune-suppressive cell populations, regulate inflammation in the TME, and promote the switching of the immune system to one that tolerates and enhances tumor growth. Because MDSCs are present in most cancer patients and are potent immune-suppressive cells, MDSCs have been the focus of intense research in recent years. This review describes the history and identification of MDSCs, the role of inflammation and intracellular signaling events governing MDSC accumulation and suppressive activity, immune-suppressive mechanisms utilized by MDSCs, and recent therapeutics that target MDSCs to enhance antitumor immunity.

Uninstructed human responding: sensitivity to ratio and interval contingencies.

Abstract: College students' presses on a telegraph key were occasionally reinforced by light onsets in the presence of which button presses (consummatory responses) produced points later exchangeable for money. One student's key presses were reinforced according to a variable-ratio schedule; key presses of another student in a separate room were reinforced according to a variable-interval schedule yoked to the interreinforcement intervals produced by the first student. Instructions described the operation of the reinforcement button, but did not mention the telegraph key; instead, key pressing was established by shaping. Performances were comparable to those of infrahuman organisms: variable-ratio key-pressing rates were higher than yoked variable-interval rates. With some yoked pairs, schedule effects occurred so rapidly that rate reversals produced by schedule reversals were demonstrable within one session. But sensitivity to these contingencies was not reliably obtained with other pairs for whom an experimenter demonstrated key pressing or for whom the reinforcer included automatic point deliveries instead of points produced by button presses. A second experiment with uninstructed responding demonstrated sensitivity to fixed-interval contingencies. These findings clarify prior failures to demonstrate human sensitivity to schedule contingencies: human responding is maximally sensitive to these contingencies when instructions are minimized and the reinforcer requires a consummatory response.

Non‐spherical aerosol retrieval method employing light scattering by spheroids

Abstract: Received 4 December 2001; revised 5 February 2002; accepted 8 February 2002; published 24 May 2002. [1] Numerous studies indicate the need to account for particle non-sphericity in modeling the optical properties of dustlike aerosols. The methods for simulating the scattering of light by various non-spherical shapes have rapidly evolved over the last two decades. However, the majority of aerosol remote-sensing retrievals still rely on the Mie theory because retrievals accounting for particle non-sphericity are not as well defined methodologically and are demanding computationally. We propose a method for the retrieval of the optical properties of non-spherical aerosol based on the model of a shape mixture of randomly oriented polydisperse spheroids. This method is applied to angular and spectral radiation measurements from the Aerosol Robotic Network (AERONET) in locations influenced by desert dust. Comparisons with Mie-based retrievals show a significant improvement in dust-particle phase functions, size distributions, and refractive indices. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0933 Exploration Geophysics: Remote sensing; 0994 Exploration Geophysics: Instruments and techniques