664 research outputs found
Nucleation in scale-free networks
We have studied nucleation dynamics of the Ising model in scale-free networks
with degree distribution by using forward flux sampling
method, focusing on how the network topology would influence the nucleation
rate and pathway. For homogeneous nucleation, the new phase clusters grow from
those nodes with smaller degree, while the cluster sizes follow a power-law
distribution. Interestingly, we find that the nucleation rate decays
exponentially with the network size , and accordingly the critical nucleus
size increases linearly with , implying that homogeneous nucleation is not
relevant in the thermodynamic limit. These observations are robust to the
change of and also present in random networks. In addition, we have
also studied the dynamics of heterogeneous nucleation, wherein impurities
are initially added, either to randomly selected nodes or to targeted ones with
largest degrees. We find that targeted impurities can enhance the nucleation
rate much more sharply than random ones. Moreover, scales as and for targeted and
random impurities, respectively. A simple mean field analysis is also present
to qualitatively illustrate above simulation results.Comment: 7 pages, 5 figure
The iterative solution of fully implicit discretizations of three-dimensional transport models
We investigate the use of approximate factorization and diagonalizing techniques for solving iteratively fully implicit numerical models of three-dimensional transport-chemistry problems. In particular, we investigate various possibilities that can take advantage of the parallelization and vectorization facilities offered by parallel vector computers
Potential of ileal bile acid transporter inhibition as a therapeutic target in Alagille syndrome and progressive familial intrahepatic cholestasis
Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC) are rare, inherited cholestatic liver disorders that manifest in infants and children and are associated with impaired bile flow (ie cholestasis), pruritus and potentially fatal liver disease. There are no effective or approved pharmacologic treatments for these diseases (standard medical treatments are supportive only), and new, noninvasive options would be valuable. Typically, bile acids undergo biliary secretion and intestinal reabsorption (ie enterohepatic circulation). However, in these diseases, disrupted secretion of bile acids leads to their accumulation in the liver, which is thought to underlie pruritus and liver-damaging inflammation. One approach to reducing pathologic bile acid accumulation in the body is surgical biliary diversion, which interrupts the enterohepatic circulation (eg by diverting bile acids to an external stoma). These procedures can normalize serum bile acids, reduce pruritus and liver injury and improve quality of life. A novel, nonsurgical approach to interrupting the enterohepatic circulation is inhibition of the ileal bile acid transporter (IBAT), a key molecule in the enterohepatic circulation that reabsorbs bile acids from the intestine. IBAT inhibition has been shown to reduce serum bile acids and pruritus in trials of paediatric cholestatic liver diseases. This review explores the rationale of inhibition of the IBAT as a therapeutic target, describes IBAT inhibitors in development and summarizes the current data on interrupting the enterohepatic circulation as treatment for cholestatic liver diseases including ALGS and PFIC
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