University of Oklahoma

About: University of Oklahoma is a education organization based out in Norman, Oklahoma, United States. It is known for research contribution in the topics: Population & Radar. The organization has 25269 authors who have published 52609 publications receiving 1821706 citations. The organization is also known as: OU & Oklahoma University.

Multi-Rate Layered Decoder Architecture for Block LDPC Codes of the IEEE 802.11n Wireless Standard

Abstract: We present a new multi-rate architecture for decoding block LDPC codes in IEEE 802.11n standard. The proposed architecture utilizes the value-reuse property of offset min-sum, block-serial scheduling of computations and turbo decoding message passing algorithm. Techniques of data-forwarding and out-of-order processing are used to deal with the irregularity of the codes. The decoder has the following advantages when compared to recent state-of-the-art architectures: 55% savings in memory, reduction of routers by 50% and increase of throughput by 2times.

The Clinical Validity of Normal Compression Ultrasonography in Outpatients Suspected of Having Deep Venous Thrombosis

Abstract: Background: Ultrasonography using vein compression accurately detects proximal deep venous thrombosis in symptomatic outpatients. Repeated testing is required for patients with normal results at pr...

Confined subsurface microbial communities in Cretaceous rock

Abstract: Deep subsurface microbial communities1 are believed to be supported by organic matter that was either deposited with the formation sediments or which migrated from the surface along groundwater flowpaths. Investigation has therefore focused on the existence of microorganisms in recently deposited or highly permeable sediments2,3. Fewer reports have focused on consolidated rocks4–7. These findings have often been limited by inadequate tracer methodology or non-sterile sampling techniques. Here we present evidence for the presence of spatially discrete microbial communities in Cretaceous rocks and advance a mechanism for the long-term survival of these subterranean communities. Samples were collected using aseptic methods and sensitive tracers8. Our results indicate that the main energy source for these communities is organic material trapped within shales. Microbial activity in shales appears to be greatly reduced, presumably because of their restrictive pore size9. However, organic material or its fermentation products could diffuse into adjacent, more permeable sandstones, where microbial activity was much more abundant. This process resulted in the presence of microbial communities at sandstone–shale interfaces. These microorganisms presumably ferment organic matter and carry out sulphate reduction and acetogenesis.

Observational Constraints on Dark Energy and Cosmic Curvature

Abstract: Current observational bounds on dark energy depend on our assumptions about the curvature of the universe. We present a simple and efficient method for incorporating constraints from cosmic microwave background (CMB) anisotropy data and use it to derive constraints on cosmic curvature and dark energy density as a free function of cosmic time using current CMB, Type Ia supernova (SN Ia), and baryon acoustic oscillation data. We show that there are two CMB shift parameters, $R\ensuremath{\equiv}\sqrt{{\ensuremath{\Omega}}_{m}{H}_{0}^{2}}r({z}_{\mathrm{CMB}})$ (the scaled distance to recombination) and ${l}_{a}\ensuremath{\equiv}\ensuremath{\pi}r({z}_{\mathrm{CMB}})/{r}_{s}({z}_{\mathrm{CMB}})$ (the angular scale of the sound horizon at recombination), with measured values that are nearly uncorrelated with each other. Allowing nonzero cosmic curvature, the three-year WMAP (Wilkinson Microwave Anisotropy Probe) data give $R=1.71\ifmmode\pm\else\textpm\fi{}0.03$, ${l}_{a}=302.5\ifmmode\pm\else\textpm\fi{}1.2$, and ${\ensuremath{\Omega}}_{b}{h}^{2}=0.02173\ifmmode\pm\else\textpm\fi{}0.00082$, independent of the dark energy model. The corresponding bounds for a flat universe are $R=1.70\ifmmode\pm\else\textpm\fi{}0.03$, ${l}_{a}=302.2\ifmmode\pm\else\textpm\fi{}1.2$, and ${\ensuremath{\Omega}}_{b}{h}^{2}=0.022\ifmmode\pm\else\textpm\fi{}0.00082$. We give the covariance matrix of $(R,{l}_{a},{\ensuremath{\Omega}}_{b}{h}^{2})$ from the three-year WMAP data. We find that $(R,{l}_{a},{\ensuremath{\Omega}}_{b}{h}^{2})$ provide an efficient and intuitive summary of CMB data as far as dark energy constraints are concerned. Assuming the Hubble Space Telescope (HST) prior of ${H}_{0}=72\ifmmode\pm\else\textpm\fi{}8\text{ }\text{ }(\mathrm{km}/\mathrm{s})\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$, using 182 SNe Ia (from the HST/GOODS program, the first year Supernova Legacy Survey, and nearby SN Ia surveys), $(R,{l}_{a},{\ensuremath{\Omega}}_{b}{h}^{2})$ from WMAP three-year data, and SDSS (Sloan Digital Sky Survey) measurement of the baryon acoustic oscillation scale, we find that dark energy density is consistent with a constant in cosmic time, with marginal deviations from a cosmological constant that may reflect current systematic uncertainties or true evolution in dark energy. A flat universe is allowed by current data: ${\ensuremath{\Omega}}_{k}=\ensuremath{-}{0.006}_{\ensuremath{-}0.012\ensuremath{-}0.025}^{+0.013+0.025}$ for assuming that the dark energy equation of state ${w}_{X}(z)$ is constant, and ${\ensuremath{\Omega}}_{k}=\ensuremath{-}{0.002}_{\ensuremath{-}0.018\ensuremath{-}0.032}^{+0.018+0.041}$ for ${w}_{X}(z)={w}_{0}+{w}_{a}(1\ensuremath{-}a)$ (68% and 95% confidence levels). The bounds on cosmic curvature are less stringent if dark energy density is allowed to be a free function of cosmic time, and are also dependent on the assumption about the early time property of dark energy. We demonstrate this by studying two examples. Significant improvement in dark energy and cosmic curvature constraints is expected as a result of future dark energy and CMB experiments.