A Lattice Boltzmann Method for the Advection-Diffusion Equation with Neumann Boundary Conditions

In this paper, we study a lattice Boltzmann method for the advection-diffusion equation with Neumann boundary conditions on general boundaries. A novel mass conservative scheme is introduced for implementing such boundary con- ditions, and is analyzed both theoretically and numerically. Second order convergence is predicted by the theoretical analysis, and numerical investigations show that the convergence is at or close to the predicted rate. The nu- merical investigations include time-dependent problems and a steady-state diffusion problem for computation of effective diffusion coefficients

The impact of interfaces in laminated packaging on transport of carboxylic acids

The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry. (C) 2016 Elsevier B.V. All rights reserved

Eps8 controls Src- and FAK-dependent phenotypes in squamous carcinoma cells

Eps8 is an actin regulatory scaffold protein whose expression is increased in squamous cell carcinoma (SCC) cells. It forms a complex with both focal adhesion kinase (FAK, also known as PTK2) and Src in SCC cells derived from skin carcinomas induced by administration of the chemical DMBA followed by TPA (the DMBA/TPA model). Here, we describe two new roles for Eps8. Firstly, it controls the spatial distribution of active Src in a FAK-dependent manner. Specifically, Eps8 participates in, and regulates, a biochemical complex with Src and drives trafficking of Src to autophagic structures that SCC cells use to cope with high levels of active Src when FAK is absent. Secondly, when FAK is expressed in SCC cells, thereby meaning active Src becomes tethered at focal adhesion complexes, Eps8 is also recruited to focal adhesions and is required for FAK-dependent polarization and invasion. Therefore, Eps8 is a crucial mediator of Src- and FAK-regulated processes; it participates in specific biochemical complexes and promotes actin re-arrangements that determine the spatial localization of Src, and modulates the functions of Src and FAK during invasive migration

Edge detection in microscopy images using curvelets

BACKGROUND: Despite significant progress in imaging technologies, the efficient detection of edges and elongated features in images of intracellular and multicellular structures acquired using light or electron microscopy is a challenging and time consuming task in many laboratories. RESULTS: We present a novel method, based on the discrete curvelet transform, to extract a directional field from the image that indicates the location and direction of the edges. This directional field is then processed using the non-maximal suppression and thresholding steps of the Canny algorithm to trace along the edges and mark them. Optionally, the edges may then be extended along the directions given by the curvelets to provide a more connected edge map. We compare our scheme to the Canny edge detector and an edge detector based on Gabor filters, and show that our scheme performs better in detecting larger, elongated structures possibly composed of several step or ridge edges. CONCLUSION: The proposed curvelet based edge detection is a novel and competitive approach for imaging problems. We expect that the methodology and the accompanying software will facilitate and improve edge detection in images available using light or electron microscopy

Contribution of CXCL12 secretion to invasion of breast cancer cells

INTRODUCTION: Neu (HER2/ErbB2) is overexpressed in 25% to 30% of human breast cancer, correlating with a poor prognosis. Researchers in previous studies who used the mouse mammary tumor virus Neu-transgenic mouse model (MMTV-Neu) demonstrated that the Neu-YB line had increased production of CXCL12 and increased metastasis, whereas the Neu-YD line had decreased metastasis. In this study, we examined the role of increased production of CXCL12 in tumor cell invasion and malignancy. METHODS: We studied invasion in the tumor microenvironment using multiphoton intravital imaging, in vivo invasion and intravasation assays. CXCL12 signaling was altered by using the CXCR4 inhibitor AMD3100 or by increasing CXCL12 expression. The role of macrophage signaling in vivo was determined using a colony-stimulating factor 1 receptor (CSF-1R) blocking antibody. RESULTS: The Neu-YD strain was reduced in invasion, intravasation and metastasis compared to the Neu-YB and Neu deletion mutant (activated receptor) strains. Remarkably, in the Neu-YB strain, in vivo invasion to epidermal growth factor was dependent on both CXCL12-CXCR4 and CSF1-CSF-1R signaling. Neu-YB tumors had increased macrophage and microvessel density. Overexpression of CXCL12 in rat mammary adenocarcinoma cells increased in vivo invasion as well as microvessel and macrophage density. CONCLUSIONS: Expression of CXCL12 by tumor cells results in increased macrophage and microvessel density and in vivo invasiveness

Long-term follow-up of adult women with urinary tract infection in childhood

Acute pyelonephritis is common in young children and can lead to permanent renal damage. Renal damage increases the risk of complications such as hypertension and decreased renal function later in life. For women with renal damage there is also an increased risk of pregnancy complications. During the years 1982 to 1984 a long-term follow-up study was performed in women who had had urinary tract infections (UTI) in childhood. The material consisted of 111 women, born between 1950 and 1968, 54 with known renal damage detected by urography and 57 with proneness to UTI but without renal damage. During the years 2001 to 2004, 86 of these patients were reinvestigated. The aim of the new study was to evaluate 1) if the patients with renal damage had an increased prevalence of hypertension; 2) if renal function, as measured by the glomerular filtration rate (GFR), had deteriorated since the last study; 3) if the pattern of UTI had changed with increasing age; 4) if patients with renal damage had higher prevalence of gestational hypertension, preeclampsia or other complications during their pregnancies. Each patient was interviewed according to a structured questionnaire concerning UTI and was investigated with DMSA scan, EDTA clearance, office blood pressure, and 24-hour ambulatory blood pressure monitoring. Hospital and antenatal clinic records were also studied. The results showed that women with bilateral or severe unilateral renal damage had higher blood pressure than those without damage. Women with bilateral damage had significantly lower GFR than those with unilateral or no damage. Decrease of GFR since the previous study was seen only in the group with bilateral damage. The proneness to febrile UTI decreased with age. Women with renal damage had significantly higher blood pressure during pregnancy but no increased frequency of other pregnancy complications. Women with bilateral or severe unilateral renal damage associated with UTI in childhood have an increased risk of high blood pressure and decreased renal function in adult age. Follow-up of blood pressure and renal function should be considered in these women. Extra monitoring of blood pressure during pregnancy is also recommended

On boundary value problems for intracellular subdiffusion and signaling pathways, and for geometric flows

The main part of this thesis concerns mathematical models for diffusion of proteins inside cells, including reactions between the proteins. Initially, such models are applied to describe signaling pathways in yeast cells, and the properties of the model are studied, especially in relation to models that do not include diffusion. The results show that it is sometimes necessary to include diffusion in the model to capture important aspects of the biological system. The thesis also contains work on the numerical methods used to compute solutions to the reaction-diffusion equations inside domains. Specifically, the Immersed Interface Method, which allows efficient numerical solution inside arbitrary domains using uniform rectangular grids, is applied on Boolean grids, which give the same accuracy as uniform grids while using fewer grid points. The third part of the thesis also concerns models for protein diffusion inside cells, but now describing the phenomenon subdiffusion (or anomalous diffusion), which has been observed inside cells and manifests itself as a qualitatively different, and slower, diffusion behaviour of proteins. The cause of this phenomenon is the crowdedness of the interior of the cell, where other proteins and larger structures interfere with the motion of the proteins. In the thesis, a new mathematical model for anomalous diffusion in the form of a parabolic pseudo-differential equation is proposed, and a proof of existence of solutions for boundary value problems representing anomalous diffusion inside a cell is given. Experiments using Fluorescence Correlation Spectroscopy which support the model have also been performed. Finally, the thesis contains a convergence result for a computational scheme for approximation of mean curvature flows inside a domain, that is the description of the motion of surfaces which move at each point with a velocity depending on the mean curvature at that point. The scheme allows a quite general dependence on the curvature and concerns the case when the moving surface is inside a domain and intersects the domain boundary at a right angle

Analytical Solutions for the Pencil-Beam Equation with Energy Loss and Straggling

In this article, we derive equations approximating the Boltzmann equation for charged particle transport under the continuous slowing down assumption. The objective is to obtain analytical expressions that approximate the solution to the Boltzmann equation. The analytical expressions found are based on the Fermi-Eyges solution, but include correction factors to account for energy loss and spread. Numerical tests are also performed to investigate the validity of the approximations