2,026 research outputs found
Factors Affecting the Radioimmunological Determination of Carcinoembryonic Antigen in Human Plasma
Peer Reviewe
High resolution, low temperature photoabsorption cross-section of C2H2 with application to Saturn's atmosphere
New laboratory observations of the VUV absorption cross-section of C2H2, obtained under physical conditions approximating stratospheres of the giant planets, were combined with IUE observations of the albedo of Saturn, for which improved data reduction techniques have been used, to produce new models for that atmosphere. When the effects of C2H2 absorption are accounted for, additional absorption by other molecules is required. The best-fitting model also includes absorption by PH3, H2O, C2H6 and CH4. A small residual disagreement near 1600 A suggests that an additional trace species may be required to complete the model
Hepatitis C virus genotypes in liver transplant recipients: Impact on posttransplant recurrence, infections, response to interferon-α therapy and outcome
Background. End-stage liver disease due to hepatitis C virus (HCV) is the most common indication for liver transplantation in U.S. veterans. We investigated the influence of HCV genotypes on the incidence and timing of recurrent HCV hepatitis, survival, infectious morbidity, and response to interferon-α therapy in this unique patient population. Methods. HCV genotype was determined by direct sequencing of the NS5 region of HCV with type-specific primers. Results. Genotype 1a (66%, 32/47) was the predominant genotype. Type 1b was found in 25% (12/47) of patients and type 2b was found in 9% (4/47). His topathologically recurrent HCV hepatitis developed in 53% (25/47) of the patients after transplantation. This group included 45% (14/31) of the patients with type 1a, 67% (8/12) of the patients with type 1b, and 25% (1/4) of the patients with type 2b (P>0.5). The time to recurrence and the severity of HCV recurrence as defined by aminotransferase levels or Knodell scores were not different among the three genotypes. There was a trend toward a higher incidence of major infections in patients with type 1b (75%) versus type 1a (48%) and type 2b (50%) (P=0.11). The response to interferon-α therapy did not differ significantly among the genotypes. Mortality at 5 years was 16% (5/31) in patients with genotype 1a, 42% (5/12) in patients with genotype 1b, and 50% (2/4) in patients with genotype 2b (P=0.06). Conclusions. The incidence, time to recurrence, and response to interferon-α therapy did not differ be tween the various genotypes in our liver transplant recipients. However, there was a trend toward higher infectious morbidity and overall mortality in patients with genotype 1b after transplantation
Characterizing and reducing equifinality by constraining a distributed catchment model with regional signatures, local observations, and process understanding
Distributed catchment models are widely used tools for predicting
hydrologic behavior. While distributed models require many parameters to
describe a system, they are expected to simulate behavior that is more
consistent with observed processes. However, obtaining a single set of
acceptable parameters can be problematic, as parameter equifinality often
results in several behavioral sets that fit observations (typically
streamflow). In this study, we investigate the extent to which equifinality
impacts a typical distributed modeling application. We outline a
hierarchical approach to reduce the number of behavioral sets based on
regional, observation-driven, and expert-knowledge-based constraints. For our
application, we explore how each of these constraint classes reduced the
number of behavioral parameter sets and altered distributions of
spatiotemporal simulations, simulating a well-studied headwater catchment,
Stringer Creek, Montana, using the distributed hydrology–soil–vegetation model
(DHSVM). As a demonstrative exercise, we investigated model performance
across 10 000 parameter sets. Constraints on regional signatures, the
hydrograph, and two internal measurements of snow water equivalent time
series reduced the number of behavioral parameter sets but still
left a small number with similar goodness of fit. This subset was ultimately
further reduced by incorporating pattern expectations of groundwater table
depth across the catchment. Our results suggest that utilizing a hierarchical
approach based on regional datasets, observations, and expert knowledge to
identify behavioral parameter sets can reduce equifinality and bolster more
careful application and simulation of spatiotemporal processes via
distributed modeling at the catchment scale
Photocapacitance study of type-II GaSb/GaAs quantum ring solar cells
In this study, the density of states associated with the localization of holes in GaSb/GaAs quantum rings are determined by the energy selective charging of the quantum ring distribution. The authors show, using conventional photocapacitance measurements, that the excess charge accumulated within the type-II nanostructures increases with increasing excitation energies for photon energies above 0.9 eV. Optical excitation between the localized hole states and the conduction band is therefore not limited to the Γ(k = 0) point, with pseudo-monochromatic light charging all states lying within the photon energy selected. The energy distribution of the quantum ring states could consequently be accurately related from the excitation dependence of the integrated photocapacitance. The resulting band of localized hole states is shown to be well described by a narrow distribution centered 407 meV above the GaAs valence band maximum
- …