3,488 research outputs found
Regionalization of Hydrologic Response in the Great Lakes Basin: Considerations of Temporal Scales of Analysis
Methods for predicting streamflow in areas with limited or nonexistent measures of hydrologic response commonly rely on regionalization techniques, where knowledge pertaining to gauged watersheds is transferred to ungauged watersheds. Hydrologic response indices have frequently been employed in contemporary regionalization research related to predictions in ungauged basins. In this study, we developed regionalization models using multiple linear regression and regression tree analysis to derive relationships between hydrologic response and watershed physical characteristics for 163 watersheds in the Great Lakes basin. These models provide an empirical means for simulating runoff in ungauged basins at a monthly time step without implementation of a rainfall-runoff model. For the dependent variable in these regression models, we used monthly runoff ratio as the indicator of hydrologic response and defined it at two temporal scales: (1) treating all monthly runoff ratios as individual observations and (2) using the mean of these monthly runoff ratios for each watershed as a representative observation. Application of the models to 62 validation watersheds throughout the Great Lakes basin indicated that model simulations were far more sensitive to the temporal characterization of hydrologic response than to the type of regression technique employed, and that models conditioned on individual monthly runoff ratios (rather than long term mean values) performed better. This finding is important in light of the increased usage of hydrologic response indices in recent regionalization studies. Models using individual observations for the dependent variable generally simulated monthly runoff with reasonable skill in the validation watersheds (median Nash-Sutcliffe efficiency = 0.53, median R2 = 0.66, median absolute value of deviation of runoff volume = 13%). These results suggest the viability of empirical 3 approaches to simulate runoff in ungauged basins. This finding is significant given the many regions of the world with sparse gaging networks and limited resources for gathering the field data required to calibrate rainfall-runoff models
Certified data-driven physics-informed greedy auto-encoder simulator
A parametric adaptive greedy Latent Space Dynamics Identification (gLaSDI)
framework is developed for accurate, efficient, and certified data-driven
physics-informed greedy auto-encoder simulators of high-dimensional nonlinear
dynamical systems. In the proposed framework, an auto-encoder and dynamics
identification models are trained interactively to discover intrinsic and
simple latent-space dynamics. To effectively explore the parameter space for
optimal model performance, an adaptive greedy sampling algorithm integrated
with a physics-informed error indicator is introduced to search for optimal
training samples on the fly, outperforming the conventional predefined uniform
sampling. Further, an efficient k-nearest neighbor convex interpolation scheme
is employed to exploit local latent-space dynamics for improved predictability.
Numerical results demonstrate that the proposed method achieves 121 to 2,658x
speed-up with 1 to 5% relative errors for radial advection and 2D Burgers
dynamical problems.Comment: arXiv admin note: substantial text overlap with arXiv:2204.1200
Chromosome-wide identification of novel imprinted genes using microarrays and uniparental disomies
Genomic imprinting refers to a specialized form of epigenetic gene regulation whereby the expression of a given allele is dictated by parental origin. Defining the extent and distribution of imprinting across genomes will be crucial for understanding the roles played by imprinting in normal mammalian growth and development. Using mice carrying uniparental disomies or duplications, microarray screening and stringent bioinformatics, we have developed the first large-scale tissue-specific screen for imprinted gene detection. We quantify the stringency of our methodology and relate it to previous non-tissue-specific large-scale studies. We report the identification in mouse of four brain-specific novel paternally expressed transcripts and an additional three genes that show maternal expression in the placenta. The regions of conserved linkage in the human genome are associated with the Prader–Willi Syndrome (PWS) and Beckwith–Wiedemann Syndrome (BWS) where imprinting is known to be a contributing factor. We conclude that large-scale systematic analyses of this genre are necessary for the full impact of genomic imprinting on mammalian gene expression and phenotype to be elucidated
Gaugino-pair production in polarized and unpolarized hadron collisions
We present an exploratory study of gaugino-pair production in polarized and
unpolarized hadron collisions, focusing on the correlation of beam polarization
and gaugino/Higgsino mixing in the general Minimal Supersymmetric Standard
Model. Helicity-dependent cross sections induced by neutral and charged
electroweak currents and squark exchanges are computed analytically in terms of
generalized charges, defined similarly for chargino-pair, neutralino-chargino
associated, and neutralino-pair production. Our results confirm and extend
those obtained previously for negligible Yukawa couplings and nonmixing
squarks. Assuming that the lightest chargino mass is known, we show numerically
that measurements of the longitudinal single-spin asymmetry at the existing
polarized pp collider RHIC and at possible polarization upgrades of the
Tevatron or the LHC would allow for a determination of the gaugino/Higgsino
fractions of charginos and neutralinos. The theoretical uncertainty coming from
factorization scale and squark mass variations and the expected experimental
error on the lightest chargino mass is generally smaller than the one induced
by the polarized parton densities, so that more information on the latter would
considerably improve on the analysis.Comment: 18 pages, 11 figure
(1R,1′R,3S,3′S)-5,5′,10,10′-Tetramethoxy-1,1′,3,3′-tetramethyl-3,3′,4,4′-tetrahydro-1H,1′H-8,8′-bi[benzo[g]isochromene]
In the title compound, C34H38O6, the methyl groups on each pyran ring exhibit 1,3-cis stereochemistry, established during synthesis by pseudo-axial delivery of hydride during a lactol reduction step. In the crystal structure, the molecule lies on a twofold rotation axis and the torsion angle about the central diaryl bond is 41.3 (1)°. The molecules pack in a herringbone arrangement
Effectiveness of Ledipasvir/Sofosbuvir with/without Ribavarin in Liver Transplant Recipients with Hepatitis C.
Background and Aims: Recurrent infection of hepatitis C virus (HCV) in liver transplant (LT) recipients is universal and associated with significant morbidity and mortality. Methods: We retrospectively evaluated the safety and efficacy of ledipasvir/sofosbuvir with and without ribavirin in LT recipients with recurrent genotype 1 hepatitis C. Results: Eighty-five LT recipients were treated for recurrent HCV with ledipasvir/sofosbuvirwith and without ribavirin for 12 or 24 weeks. The mean (± standard deviation [SD]) time from LT to treatment initiation was 68 (±71) months. The mean (± SD) age of the cohort was 63 (±8.6) years old. Most recipients were male (70%). Baseline alanine transaminase, total bilirubin, and HCV ribonucleic acid (RNA) values (± SD) were 76.8 (±126) mg/dL, 0.8 (±1.3) U/L, and 8,010,421.9 (±12,420,985) IU/mL, respectively. Five of 43 recipients who were treated with ribavirin required drug cessation due to side effects, with 4 of those being anemia complications. No recipient discontinued the ledipasvir/sofosbuvir. Eighty-one percent of recipients had undetectable viral levels at 4 weeks after starting therapy, and all recipients had complete viral suppression at the end of therapy. The sustained viral response at 12 weeks after completion of therapy was 94%. Conclusion : Ledipasvir and sofosbuvir with and without ribavirin therapy is an effective and well-tolerated interferon-free treatment for recurrent HCV infection after LT. Anemia is not uncommon in LT recipients receiving ribavirin
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Enhancement of SMN protein levels in a mouse model of spinal muscular atrophy using novel drug-like compounds
Spinal muscular atrophy (SMA) is a neurodegenerative disease that causes progressive muscle weakness, which primarily targets proximal muscles. About 95% of SMA cases are caused by the loss of both copies of the SMN1 gene. SMN2 is a nearly identical copy of SMN1, which expresses much less functional SMN protein. SMN2 is unable to fully compensate for the loss of SMN1 in motor neurons but does provide an excellent target for therapeutic intervention. Increased expression of functional full-length SMN protein from the endogenous SMN2 gene should lessen disease severity. We have developed and implemented a new high-throughput screening assay to identify small molecules that increase the expression of full-length SMN from a SMN2 reporter gene. Here, we characterize two novel compounds that increased SMN protein levels in both reporter cells and SMA fibroblasts and show that one increases lifespan, motor function, and SMN protein levels in a severe mouse model of SMA
The Uniqueness Theorem for Entanglement Measures
We explore and develop the mathematics of the theory of entanglement
measures. After a careful review and analysis of definitions, of preliminary
results, and of connections between conditions on entanglement measures, we
prove a sharpened version of a uniqueness theorem which gives necessary and
sufficient conditions for an entanglement measure to coincide with the reduced
von Neumann entropy on pure states. We also prove several versions of a theorem
on extreme entanglement measures in the case of mixed states. We analyse
properties of the asymptotic regularization of entanglement measures proving,
for example, convexity for the entanglement cost and for the regularized
relative entropy of entanglement.Comment: 22 pages, LaTeX, version accepted by J. Math. Phy
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