Quasar Feedback: More Bang for Your Buck

We propose a two-stage model for the effects of feedback from a bright quasar on the cold gas in a galaxy. It is difficult for feedback from near the accretion disk to directly impact dense molecular clouds at ~kpc. But if such feedback can drive a weak wind or outflow in the hot, diffuse ISM (a relatively 'easy' task), then in the wake of such an outflow passing over a cold cloud, a combination of instabilities will drive the cloud material to effectively expand in the direction perpendicular to the outflow. Such expansion dramatically increases the effective cross section of the cloud material and makes it more susceptible to ionization and momentum coupling from absorption of the incident quasar radiation field. Even a moderate effect of this nature can dramatically alter the ability of clouds at large radii to be fully ionized and driven into a secondary outflow by radiation pressure. Since the amount of momentum and volume which can be ionized by observed quasar radiation field is more than sufficient to affect the entire cold gas supply once it has been altered in this manner (and the 'initial' feedback need only initiate a moderate wind in the low-density hot gas), this reduces by an order of magnitude the required energy budget for feedback to affect a host galaxy. Instead of ~5% of the radiated energy (~100% momentum) needed if the initial feedback must directly heat or blow out the galactic gas, if only ~0.5% of the luminosity (~10% momentum) can couple to drive the initial hot outflow, this mechanism could be efficient. This amounts to hot gas outflow rates from near the accretion disk of only 5-10% of the BH accretion rate.Comment: 9 pages, 2 figures, accepted to MNRAS (revised to match published version, methodology expanded

More Bang for Your Buck: Improved use of GPU Nodes for GROMACS 2018

We identify hardware that is optimal to produce molecular dynamics trajectories on Linux compute clusters with the GROMACS 2018 simulation package. Therefore, we benchmark the GROMACS performance on a diverse set of compute nodes and relate it to the costs of the nodes, which may include their lifetime costs for energy and cooling. In agreement with our earlier investigation using GROMACS 4.6 on hardware of 2014, the performance to price ratio of consumer GPU nodes is considerably higher than that of CPU nodes. However, with GROMACS 2018, the optimal CPU to GPU processing power balance has shifted even more towards the GPU. Hence, nodes optimized for GROMACS 2018 and later versions enable a significantly higher performance to price ratio than nodes optimized for older GROMACS versions. Moreover, the shift towards GPU processing allows to cheaply upgrade old nodes with recent GPUs, yielding essentially the same performance as comparable brand-new hardware.Comment: 41 pages, 13 figures, 4 tables. This updated version includes the following improvements: - most notably, added benchmarks for two coarse grain MARTINI systems VES and BIG, resulting in a new Figure 13 - fixed typos - made text clearer in some places - added two more benchmarks for MEM and RIB systems (E3-1240v6 + RTX 2080 / 2080Ti

More Bang For Your Buck: Quorum-Sensing Capabilities Improve the Efficacy of Suicidal Altruism

Within the context of evolution, an altruistic act that benefits the receiving individual at the expense of the acting individual is a puzzling phenomenon. An extreme form of altruism can be found in colicinogenic E. coli. These suicidal altruists explode, releasing colicins that kill unrelated individuals, which are not colicin resistant. By committing suicide, the altruist makes it more likely that its kin will have less competition. The benefits of this strategy rely on the number of competitors and kin nearby. If the organism explodes at an inopportune time, the suicidal act may not harm any competitors. Communication could enable organisms to act altruistically when environmental conditions suggest that that strategy would be most beneficial. Quorum sensing is a form of communication in which bacteria produce a protein and gauge the amount of that protein around them. Quorum sensing is one means by which bacteria sense the biotic factors around them and determine when to produce products, such as antibiotics, that influence competition. Suicidal altruists could use quorum sensing to determine when exploding is most beneficial, but it is challenging to study the selective forces at work in microbes. To address these challenges, we use digital evolution (a form of experimental evolution that uses self-replicating computer programs as organisms) to investigate the effects of enabling altruistic organisms to communicate via quorum sensing. We found that quorum-sensing altruists killed a greater number of competitors per explosion, winning competitions against non-communicative altruists. These findings indicate that quorum sensing could increase the beneficial effect of altruism and the suite of conditions under which it will evolve.Comment: 8 pages, 8 figures, ALIFE '14 conferenc

More bang for your buck: tax compliance in the United States and Italy

This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this record.I investigate the relationship between perception of public institutions and tax com- pliance using a large tax compliance laboratory experiment conducted in Italy and the United States. In the rst test, I conduct a simple tax compliance game to uncover that given the exact same decisions, contributions to the public good do not di er between Italy and the United States. Secondly, I ask participants to pay taxes to their national government, pension fund, and re department. In these rounds, behaviors diverge with Italian participants complying signi cantly less than Americans. Theoretically, I provide evidence demonstrating that how individuals perceive their institutions is a crucial component of the tax compliance decision. Methodologically, I provide a unique experiment, which can help us to better explain cross-country variation in tax compliance, by asking subjects to make country-specific tax decisions.Funds for this research were provided by the European Research Council (Grant Agreement No. 295675 )

More bang for your buck: Boosting performance with capped power consumption

Achieving faster performance without increasing power and energy consumption for computing systems is an outstanding challenge. This paper develops a novel resource allocation scheme for memory-bound applications running on High-Performance Computing (HPC) clusters, aiming to improve application performance without breaching peak power constraints and total energy consumption. Our scheme estimates how the number of processor cores and CPU frequency setting affects the application performance. It then uses the estimate to provide additional compute nodes to memory-bound applications if it is profitable to do so. We implement and apply our algorithm to 12 representative benchmarks from the NAS parallel benchmark and HPC Challenge (HPCC) benchmark suites and evaluate it on a representative HPC cluster. Experimental results show that our approach can effectively mitigate memory contention to improve application performance, and it achieves this without significantly increasing the peak power and overall energy consumption. Our approach obtains on average 12.69% performance improvement over the default resource allocation strategy, but uses 7.06% less total power, which translates into 17.77% energy savings

More Bang for your Buck: Bolstering Learning Via Refutation Text with Refutation-based Elaborated Feedback

The current study examines the effects of refutation text and refutation-based elaborated feedback on conceptual understanding, self-efficacy, interest, beliefs, attitudes, and knowledge, within the context of learning about climate change. The study also tests whether elaborated feedback moderates the refutation text effect through an interaction. One hundred and fifty nine undergraduate students were recruited to participate in this study, which was administered via computer. They completed measures of their self-efficacy and interest in learning about climate change, as well as climate change beliefs, attitudes, and knowledge. Approximately half of the participants read a refutation text and half read a comparison expository text. Participants then completed a series of multiple choice questions either with or without elaborated refutation-based feedback, creating four mutually exclusive groups based on type of text by type of feedback design. Participants then answered five open-ended questions as a measure of deep conceptual understanding before completing the self-efficacy, interest, beliefs, attitudes, and knowledge measures again. There were no significant interaction effects of text and feedback by time on the variables of interest. However, there was a significant increase in overall interest, beliefs, and knowledge from pretest to posttest. Limitations and future research directions are discussed

The Grizzly, August 30, 2001

Construction on Campus: Residents Return to Numerous Campus Improvement Projects • What is a Watson? • Lending a Helping Hand: Class of 2005 Volunteers at Philadelphia\u27s Cobb Creek Park • UC Students Complete Summer Research • Class of 2005 Receives Dell Laptops • Tumultuous Tuition? • Opinions: Potty Improvement?; Pet for a New Age; Mind the Dust: A Student Perspective of Construction on Campus • More Bang for Your Buck: A Comparative Report on the Prices of Condoms in Collegeville • What is There to do in Collegeville? • Francoise Gilot Exhibit in Berman Museum of Art • Art Fair Coming to Berman Museum of Art • Looking Back: The Life of an Ursinus Student in 1870 • What\u27s in a Name? • Drug-Testing for College Athletes • New Fitness Area Not Quite Ready for Students • Ursinus College Football Head Coach Peter Gallagher • Dog Days of Summer May Lead to Heat-Related Illnesseshttps://digitalcommons.ursinus.edu/grizzlynews/1491/thumbnail.jp