Non-Perturbative Formulation of Time-Dependent String Solutions

We formulate here a new world-sheet renormalization-group technique for the bosonic string, which is non-perturbative in the Regge slope alpha' and based on a functional method for controlling the quantum fluctuations, whose magnitudes are scaled by the value of alpha'. Using this technique we exhibit, in addition to the well-known linear-dilaton cosmology, a new, non-perturbative time-dependent background solution. Using the reparametrization invariance of the string S-matrix, we demonstrate that this solution is conformally invariant to alpha', and we give a heuristic inductive argument that conformal invariance can be maintained to all orders in alpha'. This new time-dependent string solution may be applicable to primordial cosmology or to the exit from linear-dilaton cosmology at large times

On the consistency of a non-Hermitian Yukawa interaction

We study different properties of an anti-Hermitian Yukawa interaction, motivated by a scenario of radiative anomalous generation of masses for the right-handed sterile neutrinos. The model, involving either a pseudo-scalar or a scalar, is consistent both at the classical and quantum levels, and particular attention is given to its properties under improper Lorentz transformations. The path integral is consistently defined with a Euclidean signature, and we discuss the energetics of the model, which show that no dynamical mass generation can occur, unless extra interactions are considered.Comment: 7 pages, comments adde

The Presence of GC-C in Extracellular Vesicles Secreted by Colorectal Cancer Cells

Background: Guanylyl Cyclase C (GC-C) is a membrane-bound protein found on intestinal epithelial cells involved in the activation of CFTR. This protein has previously been involved in the development of colorectal cancer. Extracellular vesicles (EVs) are bilayered vesicles of varying size (30 to 1,000 + nm in diameter) that believed to be secreted by all cells in the human body. In the past decade, EVs have garnered attention due to their impact in the field of oncology, where they have been shown to potentially serve as biomarkers for various cancers. In this study, we looked at the EVs secreted by GC-C+ and GC-C- cell lines. We expected GC-C to be present on the EVs secreted by GC-C+ cell lines and that this finding may intake a role for GC-C at tissues distal to the intestinal epithelial cells. Methods: GC-C+ cells lines (T84 and CT26-hGCC) and GC-C- cell lines (SW480 and CT26-WT) were cultured and their media was harvested, then ultracentrifuged to extract the EVs from the media. These EVs were then checked for the presence and absence of various markers (GC-C, Calnexin, TSG101) via Western Blot. Exosome size was assessed via NTA to further provide evidence for the identity of these EVs. Results: Western blot confirmed the presence of TSG101 in both EV types samples, as well as the presence of GC-C in EVs derived from GC-C+ cell lines, but not from GC-C- cell lines. Calnexin was found to be absent in EV samples, excluding the possibility of lysate contamination. NTA analysis confirmed the correct size for the exosomes in sample. Discussion: This study assessed the contents of EVs secreted by colorectal cancer cell lines. Our findings indicate the presence of GC-C on exosomes and microvesicles. Further studies will need to be conducted in order to assess the function of these GC-C+ EVs in the setting of colorectal cancer

Mass Hierarchies in Lorentz-Violation-induced Dynamical Mass Models

We discuss the issue of fermion mass hierarchies between lepton and quark families in toy models of dynamical generation of fermion masses through minimal Lorentz Invariance Violation. Realistic hierarchies in chiral theories necessitate an extended gauge structure, which includes both vector and axial-vector interactions.Comment: 4 page

Dark Energy as an off-shell Tachyon Background in four-dimensional Strings

We consider a time-dependent bosonic string in graviton, dilaton and tachyon backgrounds, for which it was already shown that conformal invariance is respected to all orders in alpha' and in any space-time dimension. Assuming that the tachyon is off-shell, we show in this note that the specific time-homogeneity of the corresponding space time effective action leads to a power-law expanding Universe, that can be accelerating or decelerating, depending on the range of parameter space considered. We interpret this result as dark energy. We arrive at this result without requiring the knowledge of the structure of the string effective action, which is not known to all orders in alpha'. Moreover, in our approach, the background configurations are consistent in a four-dimensional space time, without any need for extra dimensions.Comment: 10 pages, typos correcte