Spatial Organization of the Cytoskeleton enhances Cargo Delivery to Specific Target Areas on the Plasma Membrane of Spherical Cells

Intracellular transport is vital for the proper functioning and survival of a cell. Cargo (proteins, vesicles, organelles, etc.) is transferred from its place of creation to its target locations via molecular motor assisted transport along cytoskeletal filaments. The transport efficiency is strongly affected by the spatial organization of the cytoskeleton, which constitutes an inhomogeneous, complex network. In cells with a centrosome microtubules grow radially from the central microtubule organizing center towards the cell periphery whereas actin filaments form a dense meshwork, the actin cortex, underneath the cell membrane with a broad range of orientations. The emerging ballistic motion along filaments is frequently interrupted due to constricting intersection nodes or cycles of detachment and reattachment processes in the crowded cytoplasm. In order to investigate the efficiency of search strategies established by the cell's specific spatial organization of the cytoskeleton we formulate a random velocity model with intermittent arrest states. With extensive computer simulations we analyze the dependence of the mean first passage times for narrow escape problems on the structural characteristics of the cytoskeleton, the motor properties and the fraction of time spent in each state. We find that an inhomogeneous architecture with a small width of the actin cortex constitutes an efficient intracellular search strategy.Comment: 14 pages, 9 figure

Modeling IoT-aware Business Processes - A State of the Art Report

This research report presents an analysis of the state of the art of modeling Internet of Things (IoT)-aware business processes. IOT links the physical world to the digital world. Traditionally, we would find information about events and processes in the physical world in the digital world entered by humans and humans using this information to control the physical world. In the IoT paradigm, the physical world is equipped with sensors and actuators to create a direct link with the digital world. Business processes are used to coordinate a complex environment including multiple actors for a common goal, typically in the context of administrative work. In the past few years, we have seen research efforts on the possibilities to model IoT- aware business processes, extending process coordination to real world entities directly. This set of research efforts is relatively small when compared to the overall research effort into the IoT and much of the work is still in the early research stage. To create a basis for a bridge between IoT and BPM, the goal of this report is to collect and analyze the state of the art of existing frameworks for modeling IoT-aware business processes.Comment: 42 page

Trade-offs between personal immunity and reproduction in the burying beetle, N. vespilloides

We know that parental investment and immune investment are costly processes, but it is unclear which trait will be prioritised when both may be required. Here we address this question using the burying beetle Nicrophorus vespilloides, carrion breeders that exhibit biparental care of young. Our results show that immunosuppression occurs during provision of parental care. We measured Phenoloxidase (PO) on Day 1-8 of the breeding bout and results show a clear decrease in PO immediately from presentation of the breeding resource onwards. Having established baseline immune investment during breeding we then manipulated immune investment at different times by applying a wounding challenge. Beetles were wounded prior to and during the parental care period and reproductive investment quantified. Different effects on reproductive output occur depending on the timing of wounding. Challenging the immune system with wounding prior to breeding does not affect reproductive output and subsequent Lifetime Reproductive Success (LRS). LRS is also unaffected by applying an immune elicitor prior to breeding, though different arms of the immune system are up/downregulated, perhaps indicating a trade-off between cellular and humoral immunity. In contrast, wounding during breeding reduces reproductive output and to the greatest extent if the challenge is applied early in the breeding bout. Despite being immunosuppressed, breeding beetles can still respond to wounding by increasing PO, albeit not to pre-breeding levels. This upregulation of PO during breeding may affect parental investment, resulting in a reduction in reproductive output. The potential role of juvenile hormone in controlling this trade-off is discussed

Modeling the Continuous Pressing Process for Wood-Based Composites

The quantitative and economical importance of continuous pressing has increased steadily over the last two decades. An analytical model will be helpful in better understanding and improving this process and in developing new manufacturing techniques. Reported here is a simulation model that accounts for heat and mass transfer as well as rheological and adhesion mechanisms that occur in three dimensions as mat material passes through a continuous press. The model enables one to predict the evolution of important variables including temperature, moisture content, air and water vapor pressure, density profile, and adhesive bond strength. The scientific principles upon which the model depends are summarized along with the boundary conditions and modeling strategy employed. Model predictions are presented and discussed for a typical medium density fiberboard (MDF) production plant

Epitaxial strain adaption in chemically disordered FeRh thin films

Strain and strain adaption mechanisms in modern functional materials are of crucial importance for their performance. Understanding these mechanisms will advance innovative approaches for material properties engineering. Here we study the strain adaption mechanism in a thin film model system as function of epitaxial strain. Chemically disordered FeRh thin films are deposited on W-V buffer layers, which allow for large variation of the preset lattice constants, e.g. epitaxial boundary condition. It is shown by means of high resolution X-ray reciprocal space maps and transmission electron microscopy that the system reacts with a tilting mechanism of the structural units in order to adapt to the lattice constants of the buffer layer. This response explained by density functional theory calculations, which evidence an energetic minimum for structures with a distortion of c/a =0.87. The experimentally observed tilting mechanism is induced by this energy gain and allows the system to remain in the most favorable structure. In general, it is shown that the use of epitaxial model heterostructures consisting of alloy buffer layers of fully miscible elements and the functional material of interest allows to study strain adaption behaviors in great detail. This approach makes even small secondary effects observable, such as the directional tilting of the structural domains identified in the present case study

Domain Growth in Ising Systems with Quenched Disorder

We present results from extensive Monte Carlo (MC) simulations of domain growth in ferromagnets and binary mixtures with quenched disorder. These are modeled by the "random-bond Ising model" and the "dilute Ising model" with either nonconserved (Glauber) spin-flip kinetics or conserved (Kawasaki) spin-exchange kinetics. In all cases, our MC results are consistent with power-law growth with an exponent $\theta (T,\epsilon)$ which depends on the quench temperature $T$ and the disorder amplitude $\epsilon$. Such exponents arise naturally when the coarsening domains are trapped by energy barriers which grow logarithmically with the domain size. Our MC results show excellent agreement with the predicted dependence of $\theta (T,\epsilon)$.Comment: 11 pages, 15 figure

Many-body Green's function theory for electron-phonon interactions: the Kadanoff-Baym approach to spectral properties of the Holstein dimer

We present a Kadanoff-Baym formalism to study time-dependent phenomena for systems of interacting electrons and phonons in the framework of many-body perturbation theory. The formalism takes correctly into account effects of the initial preparation of an equilibrium state, and allows for an explicit time-dependence of both the electronic and phononic degrees of freedom. The method is applied to investigate the charge neutral and non-neutral excitation spectra of a homogeneous, two-site, two-electron Holstein model. This is an extension of a previous study of the ground state properties in the Hartree (H), partially self-consistent Born (Gd) and fully self-consistent Born (GD) approximations published in Ref. [arXiv:1403.2968]. We show that choosing a homogeneous ground state solution leads to unstable dynamics for a sufficiently strong interaction, and that allowing a symmetry-broken state prevents this. The instability is caused by the bifurcation of the ground state and understood physically to be connected with the bipolaronic crossover of the exact system. This mean-field instability persists in the partially self-consistent Born approximation but is not found for the fully self-consistent Born approximation. By understanding the stability properties, we are able to study the linear response regime by calculating the density-density response function by time-propagation. This functions amounts to a solution of the Bethe-Salpeter equation with a sophisticated kernel. The results indicate that none of the approximations is able to describe the response function during or beyond the bipolaronic crossover for the parameters investigated. Overall, we provide an extensive discussion on when the approximations are valid, and how they fail to describe the studied exact properties of the chosen model system.Comment: 12 figure