129 research outputs found
Linear sampling method for identifying cavities in a heat conductor
We consider an inverse problem of identifying the unknown cavities in a heat
conductor. Using the Neumann-to-Dirichlet map as an input data, we develop a
linear sampling type method for the heat equation. A new feature is that there
is a freedom to choose the time variable, which suggests that we have more data
than the linear sampling methods for the inverse boundary value problem
associated with EIT and inverse scattering problem with near field data
Computing Volume Bounds of Inclusions by EIT Measurements
The size estimates approach for Electrical Impedance Tomography (EIT) allows
for estimating the size (area or volume) of an unknown inclusion in an
electrical conductor by means of one pair of boundary measurements of voltage
and current. In this paper we show by numerical simulations how to obtain such
bounds for practical application of the method. The computations are carried
out both in a 2D and a 3D setting.Comment: 20 pages with figure
Inverse Modeling for MEG/EEG data
We provide an overview of the state-of-the-art for mathematical methods that
are used to reconstruct brain activity from neurophysiological data. After a
brief introduction on the mathematics of the forward problem, we discuss
standard and recently proposed regularization methods, as well as Monte Carlo
techniques for Bayesian inference. We classify the inverse methods based on the
underlying source model, and discuss advantages and disadvantages. Finally we
describe an application to the pre-surgical evaluation of epileptic patients.Comment: 15 pages, 1 figur
Regularized Linear Inversion with Randomized Singular Value Decomposition
In this work, we develop efficient solvers for linear inverse problems based
on randomized singular value decomposition (RSVD). This is achieved by
combining RSVD with classical regularization methods, e.g., truncated singular
value decomposition, Tikhonov regularization, and general Tikhonov
regularization with a smoothness penalty. One distinct feature of the proposed
approach is that it explicitly preserves the structure of the regularized
solution in the sense that it always lies in the range of a certain adjoint
operator. We provide error estimates between the approximation and the exact
solution under canonical source condition, and interpret the approach in the
lens of convex duality. Extensive numerical experiments are provided to
illustrate the efficiency and accuracy of the approach.Comment: 20 pages, 4 figure
Antitumor effect of oncolytic virus and paclitaxel encapsulated in extracellular vesicles for lung cancer treatment
Standard of care for cancer is commonly a combination of surgery with radiotherapy or chemoradiotherapy. However, in some advanced cancer patients this approach might still remaininefficient and may cause many side effects, including severe complications and even death. Oncolytic viruses exhibit different anti-cancer mechanisms compared with conventional therapies, allowing the possibility for improved effect in cancer therapy. Chemotherapeutics combined with oncolytic viruses exhibit stronger cytotoxic responses and oncolysis. Here, we have investigated the systemic delivery of the oncolytic adenovirus and paclitaxel encapsulated in extracellular vesicles (EV) formulation that, in vitro, significantly increased the transduction ratio and the infectious titer when compared with the virus and paclitaxel alone. We demonstrated that the obtained EV formulation reduced the in vivo tumor growth in animal xenograft model of human lung cancer. Indeed, we found that combined treatment of oncolytic adenovirus and paclitaxel encapsulated in EV has enhanced anticancer effects both in vitro and in vivo in lung cancer models. Transcriptomic comparison carried out on the explanted xenografts from the different treatment groups revealed that only 5.3% of the differentially expressed genes were overlapping indicating that a de novo genetic program is triggered by the presence of the encapsulated paclitaxel: this novel genetic program might be responsible of the observed enhanced antitumor effect. Our work provides a promising approach combining anticancer drugs and viral therapies by intravenous EV delivery as a strategy for the lung cancer treatment.Peer reviewe
RF thermal and new cold part design studies on TTF-III input coupler for Project-X
RF power coupler is one of the key components in superconducting (SC) linac.
It provides RF power to the SC cavity and interconnects different temperature
layers (1.8K, 4.2K, 70K and 300K). TTF-III coupler is one of the most promising
candidates for the High Energy (HE) linac of Project X, but it cannot meet the
average power requirements because of the relatively high temperature rise on
the warm inner conductor, some design modifications will be required. In this
paper, we describe our simulation studies on the copper coating thickness on
the warm inner conductor with RRR value of 10 and 100. Our purpose is to
rebalance the dynamic and static loads, and finally lower the temperature rise
along the warm inner conductor. In addition, to get stronger coupling, better
power handling and less multipacting probability, one new cold part design was
proposed using 60mm coaxial line; the corresponding multipacting simulation
studies have also been investigated.Comment: 5 pages, 12 figures. Submitted to Chinese Physics C (Formerly High
Energy Physics and Nuclear Physics
Hierarchical Bayesian level set inversion
The level set approach has proven widely successful in the study of inverse problems for inter- faces, since its systematic development in the 1990s. Re- cently it has been employed in the context of Bayesian inversion, allowing for the quantification of uncertainty within the reconstruction of interfaces. However the Bayesian approach is very sensitive to the length and amplitude scales in the prior probabilistic model. This paper demonstrates how the scale-sensitivity can be cir- cumvented by means of a hierarchical approach, using a single scalar parameter. Together with careful con- sideration of the development of algorithms which en- code probability measure equivalences as the hierar- chical parameter is varied, this leads to well-defined Gibbs based MCMC methods found by alternating Metropolis-Hastings updates of the level set function and the hierarchical parameter. These methods demon- strably outperform non-hierarchical Bayesian level set methods
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