SB24-09/10: ASUM Transportation Fee

SB24-09/10: ASUM Transportation Fee. This resolution passed during the March 17, 2010 meeting of the Associated Students of the University of Montana (ASUM)

Coral Microcosms: Challenges and Opportunities for Global Change Biology

Well‐maintained coral‐microcosm systems provide a good opportunity for performing global‐change simulations under controlled conditions and allow long‐term experiments while avoiding problems with natural fluctuations. However, despite rapid technical progress over the last few years in maintaining corals, microcosm experiments remain demanding and challenging. Therefore, this paper focuses on problems and opportunities associated with maintaining corals for global‐change experiments, and the pitfalls associated with simulating natural and anthropogenic disturbances. We start in Section 1 with a brief assessment of the global situation of coral reefs and discuss problems and challenges associated with microcosm experiments. Section 2 covers the technical setup of coral‐aquarium systems in respect to the necessary hardware and safety precautions. Section 3 provides information on coral‐species selection, coral‐propagation techniques, and the choice of associated fauna and flora. Problems with maintaining controlled conditions are deliberated in Section 4, including water chemistry as well as pest and disease control. The paper closes with conclusions for global‐change studies in coral‐microcosm systems (Section 5). As this review provides important insights into the rapidly developing field of coral‐microcosm experiments, it might be of particular interest for graduate and post‐graduate students in marine sciences, for global‐change researchers, as well as for administrators and technicians interested in maintaining corals under fully‐controlled conditions

Stochastic Yield Catastrophes and Robustness in Self-Assembly

A guiding principle in self-assembly is that, for high production yield, nucleation of structures must be significantly slower than their growth. However, details of the mechanism that impedes nucleation are broadly considered irrelevant. Here, we analyze self-assembly into finite-sized target structures employing mathematical modeling. We investigate two key scenarios to delay nucleation: (i) by introducing a slow activation step for the assembling constituents and, (ii) by decreasing the dimerization rate. These scenarios have widely different characteristics. While the dimerization scenario exhibits robust behavior, the activation scenario is highly sensitive to demographic fluctuations. These demographic fluctuations ultimately disfavor growth compared to nucleation and can suppress yield completely. The occurrence of this stochastic yield catastrophe does not depend on model details but is generic as soon as number fluctuations between constituents are taken into account. On a broader perspective, our results reveal that stochasticity is an important limiting factor for self-assembly and that the specific implementation of the nucleation process plays a significant role in determining the yield

SB14-09/10: Amending ASUM Transportation Board Bylaws

SB14-09/10: Amending ASUM Transportation Board Bylaws. This resolution passed unanimously during the October 28, 2009 meeting of the Associated Students of the University of Montana (ASUM)

Subdiffusive Activity Spreading in the Diffusive Epidemic Process

The diffusive epidemic process is a paradigmatic example of an absorbing state phase transition in which healthy and infected individuals spread with different diffusion constants. Using stochastic activity spreading simulations in combination with finite-size scaling analyses we reveal two qualitatively different processes that characterize the critical dynamics: subdiffusive propagation of infection clusters and diffusive fluctuations in the healthy population. This suggests the presence of a strong coupling regime and sheds new light on a long-standing debate about the theoretical classification of the system

Potential for interactive design simulations in discrete element modelling

This study investigates the potential for combining lower fidelity models with high performance solution strategies such as efficient graphical processing unit (GPU) based discrete element modelling (DEM) to not only do simulations faster but differently. Specifically this study investigates interactive simulation and design for which the simulation environment BlazeDEM-GPU was developed that allows researchers and engineers to interact with simulations. The initial results prove to be promising and warranting extensive research to be conducted in future which may allow for the development of alternative paradigms. In addition to the design cycle, the role that this interactive simulation and design will play in education is invaluable as an in-house corporate training tool for young engineers to actively train and develop understanding for specific industrial processes. This would also allow engineers to conduct just-in-time (JIT) simulation based assessment of processes before commencing on actual site visits, allowing for shorter and more focussed site excursions

Validation of the gpu based blaze-dem framework for hopper discharge

Understanding the dynamical behavior of particulate materials is extremely important to many industrial processes, with typical applications that range from hopper flows in agriculture to tumbling mills in the mining industry. The discrete element method (DEM) has become the defacto standard to simulate particulate materials. The DEM is a compu- tationally intensive numerical approach that is limited to a moderate amount (thousands) of particles when considering fully coupled densely packed systems modeled by realistic par- ticle shape and history dependent constitutive relationships. A large number (millions) of particles can be simulated when the coupling between particles is relaxed to still accurately simulated lesser dense systems. Massively large scale simulations (tens of millions) are possi- ble when particle shapes are simplified, however this may lead to oversimplification when an accurate representation of the particle shape is essential to capture the macroscopic transport of particulates. Polyhedra represent the geometry of most convex particulate materials well and when combined with appropriate contact models predicts realistic mechanical behavior to that of the actual system. Detecting collisions between polyhedra is computationally ex- pensive often limiting simulations to only hundreds of thousands of particles. However, the computational architecture e.g. CPU and GPU plays a significant role on the performance that can be realized. The parallel nature of the GPU allows for a large number of simple independent processes to be executed in parallel. This results in a significant speed up over conventional implementations utilizing the Central Processing Unit (CPU) architecture, when algorithms are well aligned and optimized for the threading model of the GPU. We recently introduced the BLAZE-DEM framework for the GPU architecture that can model millions of pherical and polyhedral particles in a realistic time frame using a single GPU. In this paper we validate BLAZE-DEM for hopper discharge simulations. We firstly compare the flow-rates and patterns of polyhedra and spheres obtained with experiment to that of DEM. We then compare flow-rates between spheres and polyhedra to gauge the effect of particle shape. Finally we perform a large scale DEM simulation using 16 million articles to illustrate the capability of BLAZE-DEM to predict bulk flow in realistic hoppers

In-situ studies of the competitive adsorption of lubricant additives

It is known that different types of surface-affine additives (i.e. antiwear/anti-corrosion/ anti-friction) can have very different adsorption behaviour on surfaces (e.g. [1–3]). The interactions can be synergistic or antagonistic in character and influences the near-surface chemistry of the sliding surfaces and therefore also the tribological performance of the system. For wear protection additives, it is for instance known that phosphor and sulfur containing layers are formed under tribological conditions (e.g. [4,5]). In this presentation we will give an overview on an ongoing study of the adsorption of selected additives using novel in-situ approaches. The found correlations are also compared to tribological experiments in order to answer the question whether synergistic effects in adsorption also lead to synergistic effects in wear reduction

In Situ Studies on the Competitive Adsorption of Lubricant Additives

A key factor for improvement and innovation in lubricant development is a fundamental understanding of adsorption processes and competing adsorption mechanisms [1]. Many different base oils and additives, as well as various surfaces build a complex interaction space, which has been difficult to map with in-situ methods so far. Here we present a study on the adsorption of corrosion inhibitors, anti-wear additives and friction modifiers from a synthetic and a mineral base oil on metal (Fe2O3) surfaces. In order to obtain quantitative and spatial data during the adsorption process we set up a combined quartz crystal microbalance (QCM-D) and confocal scanning laser microscope (CLSM) [2]. In addition to QCM-D and CLSM, also a UHV-tribometer was used to study the performance of gas phase deposited additives films without environmental interferences. In combination with macroscopic performance tests using a “ball-on-three-plates-tribometer” and corrosion tests, the adsorption, the morphology and the mechanical properties of the additives were correlated with their performance. The multidisciplinary results provide exciting new insights into lubrication fundamentals and reveal so far undescribed phenomes and mechanisms of action. [1] J. Guegan et al. ,Friction Modifier Additives, Synergies and Antagonisms, Tribology Letters 67 (2019) [2] J. Honselmann et al., submitted, 201

Two-Species Active Transport along Cylindrical Biofilaments is Limited by Emergent Topological Hindrance

Active motion of molecules along filamentous structures is a crucial feature of cell biology and is often modeled with the paradigmatic asymmetric simple exclusion process. Motivated by recent experimental studies that have addressed the stepping behavior of kinesins on microtubules, we investigate a lattice gas model for simultaneous transport of two species of active particles on a cylinder. The species are distinguished by their different gaits: While the first species moves straight ahead, the second follows a helical path. We show that the collective properties of such systems critically differ from those of one-species transport in a way that cannot be accounted for by standard models. This is most evident in a jamming transition far below full occupation, as well as in nonequilibrium pattern formation. The altered behavior arises because-unlike the case in single-species transport-any given position may be targeted by two particles from different directions at the same time. However, a particle can leave a given position only in one direction. This simple change in connectivity significantly amplifies the impact of steric interactions and thus becomes a key determinant of mixed species transport. We computationally characterize this type of hindrance and develop a comprehensive theory for collective two-species transport along a cylinder. Our observations show high robustness against model extensions that account for additional biomolecular features and demonstrate that even small fractions of a second species can significantly alter transport. This suggests that our analysis is also relevant in a biological context