7,231 research outputs found
Treating hepatic steatosis and fibrosis by modulating mitochondrial pyruvate metabolism
A hepatic comorbidity of metabolic syndrome, known as nonalcoholic fatty liver disease (NAFLD), is increasing in prevalence in conjunction with the pandemics of obesity and diabetes. The spectrum of NAFLD ranges from simple hepatic fat accumulation to a more severe disease termed nonalcoholic steatohepatitis (NASH), involving inflammation, hepatocyte death, and fibrosis. Importantly, NASH is linked to a much higher risk of cirrhosis, liver failure, and hepatocellular carcinoma, as well as an increased risk for nonhepatic malignancies and cardiovascular disease. Interest in the understanding of the disease processes and search for treatments for the spectrum of NAFLD-NASH has increased exponentially, but there are no approved pharmacologic therapies. In this review, we discuss the existing literature supporting insulin-sensitizing thiazolidinedione compounds as potential drug candidates for the treatment of NASH. In addition, we put these results into new context by summarizing recent studies suggesting these compounds alter mitochondrial metabolism by binding and inhibiting the mitochondrial pyruvate carrier. Keywords: Nonalcoholic Steatohepatitis, Mitochondria, Pyruvate, Thiazolidinedion
A Polynomial-time Bicriteria Approximation Scheme for Planar Bisection
Given an undirected graph with edge costs and node weights, the minimum
bisection problem asks for a partition of the nodes into two parts of equal
weight such that the sum of edge costs between the parts is minimized. We give
a polynomial time bicriteria approximation scheme for bisection on planar
graphs.
Specifically, let be the total weight of all nodes in a planar graph .
For any constant , our algorithm outputs a bipartition of the
nodes such that each part weighs at most and the total cost
of edges crossing the partition is at most times the total
cost of the optimal bisection. The previously best known approximation for
planar minimum bisection, even with unit node weights, was . Our
algorithm actually solves a more general problem where the input may include a
target weight for the smaller side of the bipartition.Comment: To appear in STOC 201
Enabling Interactive Analytics of Secure Data using Cloud Kotta
Research, especially in the social sciences and humanities, is increasingly
reliant on the application of data science methods to analyze large amounts of
(often private) data. Secure data enclaves provide a solution for managing and
analyzing private data. However, such enclaves do not readily support discovery
science---a form of exploratory or interactive analysis by which researchers
execute a range of (sometimes large) analyses in an iterative and collaborative
manner. The batch computing model offered by many data enclaves is well suited
to executing large compute tasks; however it is far from ideal for day-to-day
discovery science. As researchers must submit jobs to queues and wait for
results, the high latencies inherent in queue-based, batch computing systems
hinder interactive analysis. In this paper we describe how we have augmented
the Cloud Kotta secure data enclave to support collaborative and interactive
analysis of sensitive data. Our model uses Jupyter notebooks as a flexible
analysis environment and Python language constructs to support the execution of
arbitrary functions on private data within this secure framework.Comment: To appear in Proceedings of Workshop on Scientific Cloud Computing,
Washington, DC USA, June 2017 (ScienceCloud 2017), 7 page
Decoherence suppression by uncollapsing
We show that the qubit decoherence due to zero-temperature energy relaxation
can be almost completely suppressed by using the quantum uncollapsing
procedure. To protect a qubit state, a partial quantum measurement moves it
towards the ground state, where it is kept during the storage period, while the
second partial measurement restores the initial state. This procedure
preferentially selects the cases without energy decay events. Stronger
decoherence suppression requires smaller selection probability; a desired point
in this trade-off can be chosen by varying the measurement strength. The
experiment can be realized in a straightforward way using the superconducting
phase qubit.Comment: 4 page
Heitler-London model for acceptor-acceptor interactions in doped semiconductors
The interactions between acceptors in semiconductors are often treated in
qualitatively the same manner as those between donors. Acceptor wave functions
are taken to be approximately hydrogenic and the standard hydrogen molecule
Heitler-London model is used to describe acceptor-acceptor interactions. But
due to valence band degeneracy and spin-orbit coupling, acceptor states can be
far more complex than those of hydrogen atoms, which brings into question the
validity of this approximation. To address this issue, we develop an
acceptor-acceptor Heitler-London model using single-acceptor wave functions of
the form proposed by Baldereschi and Lipari, which more accurately capture the
physics of the acceptor states. We calculate the resulting acceptor-pair energy
levels and find, in contrast to the two-level singlet-triplet splitting of the
hydrogen molecule, a rich ten-level energy spectrum. Our results, computed as a
function of inter-acceptor distance and spin-orbit coupling strength, suggest
that acceptor-acceptor interactions can be qualitatively different from
donor-donor interactions, and should therefore be relevant to the control of
two-qubit interactions in acceptor-based qubit implementations, as well as the
magnetic properties of a variety of p-doped semiconductor systems. Further
insight is drawn by fitting numerical results to closed-form energy-level
expressions obtained via an acceptor-acceptor Hubbard model.Comment: 19 pages, 10 figures, text revised, figure quality improved,
additional references adde
Ribozymes: the characteristics and properties of catalytic RNAs
Ribozymes, or catalytic RNAs, were discovered a little more than 15 years ago. They are found in the organelles of plants and lower eukaryotes, in amphibians, in prokaryotes, in bacteriophages, and in viroids and satellite viruses that infect plants. An example is also known of a ribozyme in hepatitis delta virus, a serious human pathogen. Additional ribozymes are bound to be found in the future, and it is tempting to regard the RNA component(s) of various ribonucleoprotein complexes as the catalytic engine, while the proteins serve as mere scaffolding - an unheard-of notion 15 years ago! In nature, ribozymes are involved in the processing of RNA precursors. However, all the characterized ribozymes have been converted, with some clever engineering, into RNA enzymes that can cleave or modify targeted RNAs (or even DNAs) without becoming altered themselves. While their success in vitro is unquestioned, ribozymes are increasingly used in vivo as valuable tools for studying and regulating gene expression. This review is intended as a brief introduction to the characteristics of the different identified ribozymes and their propertie
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