Discovery potential of the LHC for extended gauge symmetries

Many models of physics beyond the Standard Model are based on extended gauge symmetries and predict the existence of new heavy particles, often at the TeV scale. Such particles include heavy Wand Z bosons, doubly charged higgses, heavy majorana neutrinos, leptoquarks and heavy fermions. The discovery potential of the LHC, which will start in 2008, for various particles predicted in extended gauge theories will be described in this paper

Lateral diffusion of receptor-ligand bonds in membrane adhesion zones: Effect of thermal membrane roughness

The adhesion of cells is mediated by membrane receptors that bind to complementary ligands in apposing cell membranes. It is generally assumed that the lateral diffusion of mobile receptor-ligand bonds in membrane-membrane adhesion zones is slower than the diffusion of unbound receptors and ligands. We find that this slowing down is not only caused by the larger size of the bound receptor-ligand complexes, but also by thermal fluctuations of the membrane shape. We model two adhering membranes as elastic sheets pinned together by receptor-ligand bonds and study the diffusion of the bonds using Monte Carlo simulations. In our model, the fluctuations reduce the bond diffusion constant in planar membranes by a factor close to 2 in the biologically relevant regime of small bond concentrations.Comment: 6 pages, 5 figures; to appear in Europhysics Letter

The Language of Love: Dating with Aphasia

“Stroke and aphasia can negatively affect a person’s ability to maintain healthy social relationships, both within the family and also with friends and the wider network” (Fotiadou et al., 2014). However, very few studies explicitly target skills needed for successful dating among clients with aphasia. Survey data was collected from adults with chronic aphasia to determine perceived barriers, confidence, fear, and success associated with dating, and previous experience in speech therapy. This session will include a literature review related to aspects of communication needed for successful dating, aphasia-related deficits, and the potential impact on the dating process. Participant responses will be analyzed and presented. Additionally, goals, target selection, and other considerations for intervention will be discussed.https://griffinshare.fontbonne.edu/slp-posters-2023/1028/thumbnail.jp

Coexistence of dilute and densely packed domains of ligand-receptor bonds in membrane adhesion

We analyze the stability of micro-domains of ligand-receptor bonds that mediate the adhesion of biological model membranes. After evaluating the effects of membrane fluctuations on the binding affinity of a single bond, we characterize the organization of bonds within the domains by theoretical means. In a large range of parameters, we find the commonly suggested dense packing to be separated by a free energy barrier from a regime in which bonds are sparsely distributed. If bonds are mobile, a coexistence of the two regimes should emerge, which agrees with recent experimental observations.Comment: 6 pages, 6 figures, accepted by EP

I Dreamt This Was My Home: Construction of Forest and Rural Settler Identity in Mission, British Columbia

As places for rich sensorial and symbolic experiences, forestry recreation sites provide contact not only with biosphere ecology, but with tropes and values expressed through managed ‘nature space’. Articulating these tropes and values reveals that ‘nature’ itself has been socially constructed and conceptually intersects with power, including rights of access and production of capital. By bringing multimodal research-creation practices into contact with my own production of place-based knowledge in the forests of my hometown in Mission, British Columbia, I assemble a situated account of spatial narratives and ideological work taking place in managed, recreational forests of the Fraser Valley. In so doing, I also demonstrate ways of provoking reflexive interplay between sensory impressions, poetic meanings, dominant narratives, and knowledge. After forming analyses through documentary research, situated encounters, creative process, and critical theory, I present the two overarching arguments of this project: 1) ideological work around jurisdiction and enclosure takes place in rural communities through managed nature reserves and ossified narratives in ‘natural zones’ and 2) multimodal creative research can be used to notice ways that sensory and poetic meanings of a site are entangled with knowledge and power structures and to illuminate occupations and construction of space, place, and imagination

Search for Second Generation Leptoquarks with ATLAS at the LHC

The Large Hadron Collider will collide protons with protons at a center-of-mass energy of up to 14 TeV. New physics phenomena and new particles are predicted to be detectable with the ATLAS detector at the Large Hadron Collider. One of these predicted new particles beyond the Standard Model are leptoquarks. This thesis deals with the search for scalar second generation leptoquarks produced in pairs. Second generation leptoquarks decay into a muon-type lepton and a quark. In this thesis the decay of both second generation leptoquarks into a muon and a quark is considered. Since pair production is studied the final state consists of two high-energetic muons and two high-energetic jets. This thesis studies second generation leptoquarks with masses of mLQ = 300 GeV, mLQ = 400 GeV, mLQ = 600 GeV and mLQ = 800 GeV. The best cut variables for the discrimination between the signal and the main Standard Model backgrounds ttbar and Z/gamma* found in this analysis are the pT of the muons, ST (the scalar sum of the transverse momenta of the two selected muons and the transverse energies of the two selected jets), the mass of the selected dimuon system and the reconstructed leptoquark mass. The latter three cut variables have been optimized for a discovery with a 5 significance including the systematic uncertainties and trigger efficiencies. Second generation leptoquarks have been excluded up to the mass of 300 GeV with a 95% confidence level at present experiments. The expected integrated luminosities needed for a 5 discovery of the tested second generation leptoquark masses with the ATLAS detector have been calculated. This thesis shows that for a disocvery with 5 significance of a second generation leptoquark with mLQ = 300 GeV and mLQ = 400 GeV an expected integrated luminosity of 1.51 pb−1 and 7.42 pb−1 is needed respectively; this corresponds to a very early phase, i.e. the first few months, of the Large Hadron Collider run. For the discovery with a 5 significance of second generation leptoquarks with masses of mLQ = 600 GeV and mLQ = 800 GeV an expected integrated luminosity of 103.3 pb−1 and 663 pb−1 is needed respectively; this corresponds to several months and about half a year to a year of the Large Hadron Collider run respectively

Line Tension and Stability of Domains in Cell-Adhesion Zones Mediated by Long and Short Receptor-Ligand Complexes

Submicron scale domains of membrane-anchored receptors play an important role in cell signaling. Central questions concern the stability of these microdomains, and the mechanisms leading to the domain formation. In immune-cell adhesion zones, microdomains of short receptor-ligand complexes form next to domains of significantly longer receptor-ligand complexes. The length mismatch between the receptor-ligand complexes leads to membrane deformations and has been suggested as a possible cause of the domain formation. The domain formation is a nucleation and growth process that depends on the line tension and free energy of the domains. Using a combination of analytical calculations and Monte Carlo simulations, we derive here general expressions for the line tension between domains of long and short receptor-ligand complexes and for the adhesion free energy of the domains. We argue that the length mismatch of receptor-ligand complexes alone is sufficient to drive the domain formation, and obtain submicron-scale minimum sizes for stable domains that are consistent with the domain sizes observed during immune-cell adhesion

Binding cooperativity of membrane adhesion receptors

The adhesion of cells is mediated by receptors and ligands anchored in apposing membranes. A central question is how to characterize the binding affinity of these membrane-anchored molecules. For soluble molecules, the binding affinity is typically quantified by the binding equilibrium constant K3D in the linear relation [RL] = K3D [R][L] between the volume concentration [RL] of bound complexes and the volume concentrations [R] and [L] of unbound molecules. For membrane-anchored molecules, it is often assumed by analogy that the area concentration of bound complexes [RL] is proportional to the product [R][L] of the area concentrations for the unbound receptor and ligand molecules. We show here (i) that this analogy is only valid for two planar membranes immobilized on rigid surfaces, and (ii) that the thermal roughness of flexible membranes leads to cooperative binding of receptors and ligands. In the case of flexible membranes, the area concentration [RL] of receptor-ligand bonds is proportional to the square of [R][L] for typical lengths and concentrations of receptors and ligands in cell adhesion zones. The cooperative binding helps to understand why different experimental methods for measuring the binding affinity of membrane-anchored molecules have led to values differing by several orders of magnitude.Comment: 9 pages, 4 figures; to appear in Soft Matte

Segregation of receptor-ligand complexes in cell adhesion zones: Phase diagrams and role of thermal membrane roughness

The adhesion zone of immune cells, the 'immunological synapse', exhibits characteristic domains of receptor-ligand complexes. The domain formation is likely caused by a length difference of the receptor-ligand complexes, and has been investigated in experiments in which T cells adhere to supported membranes with anchored ligands. For supported membranes with two types of anchored ligands, MHCp and ICAM1, that bind to the receptors TCR and LFA1 in the cell membrane, the coexistence of domains of TCR-MHCp and LFA1-ICAM1 complexes in the cell adhesion zone has been observed for a wide range of ligand concentrations and affinities. For supported membranes with long and short ligands that bind to the same cell receptor CD2, in contrast, domain coexistence has been observed for a rather narrow ratio of ligand concentrations. In this article, we determine detailed phase diagrams for cells adhering to supported membranes with a statistical-physical model of cell adhesion. We find a characteristic difference between the adhesion scenarios in which two types of ligands in a supported membrane bind (i) to the same cell receptor or (ii) to two different cell receptors, which helps to explain the experimental observations. Our phase diagrams fully include thermal shape fluctuations of the cell membranes on nanometer scales, which lead to a critical point for the domain formation and to a cooperative binding of the receptors and ligands.Comment: 23 pages, 6 figure