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Dynamics of false vacuum bubbles: beyond the thin shell approximation
Hansen, Jakob,Hwang, Dong-il,Yeom, Dong-han IOP Publishing Ltd 2009 Journal of high energy physics Vol.2009 No.11
We numerically study the dynamics of false vacuum bubbles which are inside an almost flat background; we assumed spherical symmetry and the size of the bubble is smaller than the size of the background horizon. According to the thin shell approximation and the null energy condition, if the bubble is outside of a Schwarzschild black hole, unless we assume Farhi-Guth-Guven tunneling, expanding and inflating solutions are impossible. In this paper, we extend our method to beyond the thin shell approximation: we include the dynamics of fields and assume that the transition layer between a true vacuum and a false vacuum has non-zero thickness. If a shell has sufficiently low energy, as expected from the thin shell approximation, it collapses (Type 1). However, if the shell has sufficiently large energy, it tends to expand. Here, via the field dynamics, field values of inside of the shell slowly roll down to the true vacuum and hence the shell does not inflate (Type 2). If we add sufficient exotic matters to regularize the curvature near the shell, inflation may be possible without assuming Farhi-Guth-Guven tunneling. In this case, a wormhole is dynamically generated around the shell (Type 3). By tuning our simulation parameters, we could find transitions between Type 1 and Type 2, as well as between Type 2 and Type 3. Between Type 2 and Type 3, we could find another class of solutions (Type 4). Finally, we discuss the generation of a bubble universe and the violation of unitarity. We conclude that the existence of a certain combination of exotic matter fields violates unitarity.
Hansen, H.G.,Pristovsek, N.,Kildegaard, H.F.,Lee, G.M. Pergamon Press ; Elsevier Science Ltd 2017 Biotechnology advances Vol.35 No.1
<P>Chinese hamster ovary (CHO) cells are the preferred cell factory for the production of therapeutic glycoproteins. Although efforts primarily within bioprocess optimization have led to increased product titers of recombinant proteins (r-proteins) expressed in CHO cells, post-transcriptional bottlenecks in the biosynthetic pathway of r-proteins remain to be solved. To this end, the ectopic expression of transgenes (effector genes) offers great engineering potential. However, studies on effector genes have in some cases led to inconsistent results. Whereas this can in part be attributed to product specificity, other experimental and cellular factors are likely important contributors to these conflicting results. Here, these factors are reviewed and discussed with the objective of guiding future studies on effector genes. (C) 2016 Elsevier Inc. All rights reserved.</P>
Hansen, Henning Gram,Kildegaard, Helene Faustrup,Lee, Gyun Min,Kol, Stefan WILEY‐VCH Verlag 2016 Biotechnology journal Vol.11 No.12
<P><B>Abstract</B></P><P>Accurate titer determination of recombinant proteins is crucial for evaluating protein production cell lines and processes. Even though enzyme‐linked immunosorbent assay (ELISA) is the most widely used assay for determining protein titer, little is known about the accuracy of commercially available ELISA kits. We observed that estimations of recombinant human ø1‐antitrypsin (<I>r</I>ø1AT) titer by Coomassie‐stained SDS‐PAGE gels did not correspond to previously obtained titers obtained by a commercially available ELISA kit. This prompted us to develop two independent quantification assays based on biolayer interferometry and reversed‐phase high‐performance liquid chromatography. We compared the rø1AT titer obtained by these assays with three different off‐the‐shelf ELISA kits and found that the ELISA kits led to inconsistent results. The data presented here show that recombinant protein titers determined by ELISA kits cannot be trusted <I>per se</I>. Consequently, any ELISA kit to be used for determining recombinant protein titer must be validated by a different, preferably orthogonal method.</P>