The effect of secondary hardening on the notch toughness of molybdenum alloyed steel

The effect of secondary hardness on the notch toughness of a medium carbon steel alloyed with molybdenum was investigated. As a result of the transition from liquid to solid fuels in many of the rocket and missile systems currently employed by the armed services, materials requirements for the missile bodies have undergone a drastic revision

Economic Analysis of Simulation Selection Problems

Ranking and selection procedures are standard methods for selecting the best of a finite number of simulated design alternatives based on a desired level of statistical evidence for correct selection. But the link between statistical significance and financial significance is indirect, and there has been little or no research into it. This paper presents a new approach to the simulation selection problem, one that maximizes the expected net present value of decisions made when using stochastic simulation. We provide a framework for answering these managerial questions: When does a proposed system design, whose performance is unknown, merit the time and money needed to develop a simulation to infer its performance? For how long should the simulation analysis continue before a design is approved or rejected? We frame the simulation selection problem as a “stoppable” version of a Bayesian bandit problem that treats the ability to simulate as a real option prior to project implementation. For a single proposed system, we solve a free boundary problem for a heat equation that approximates the solution to a dynamic program that finds optimal simulation project stopping times and that answers the managerial questions. For multiple proposed systems, we extend previous Bayesian selection procedures to account for discounting and simulation-tool development costs

Lessons Learned from Educational Research of a National Science Foundation Research Experiences for Undergraduates

Participation in an archaeological field school is the entry point to a professional career in the discipline. Despite the importance of field schools, few scholars have investigated achieved student-learning outcomes or lasting impacts on students from participation in archaeological field research. We report on the educational design, learning objectives, and results of three years of formative and summative assessments for an interdisciplinary, archaeology and ecology research program for undergraduate students. Our learning objectives include promoting scientific literacy and communication, critical thinking and STEM skills, and capacities in archaeological and ecological interdisciplinarity. Using developed rubrics that account for both critical thinking and STEM understanding, self-administered competency surveys, and program-developed items, we found significant gains in nearly all learning objectives. Students demonstrated growth in program specific content, perceived abilities in their scientific and discipline specific skills, critical thinking skills, and scientific communication skills. These educational outcomes and assessment tools have implications for how we design and evaluate field learning in archaeology and may be applied to field school instruction

New Data and Tools for Integrating Discrete and Continuous Population Modeling Strategies

Realistic population models have interactions between individuals. Such interactions cause populations to behave as systems with nonlinear dynamics. Much population data analysis is done using linear models assuming no interactions between individuals. Such analyses miss strong influences on population behavior and can lead to serious errors—especially for infectious diseases. To promote more effective population system analyses, we present a flexible and intuitive modeling framework for infection transmission systems. This framework will help population scientists gain insight into population dynamics, develop theory about population processes, better analyze and interpret population data, design more powerful and informative studies, and better inform policy decisions. Our framework uses a hierarchy of infection transmission system models. Four levels are presented here: deterministic compartmental models using ordinary differential equations (DE); stochastic compartmental (SC) models that relax assumptions about population size and include stochastic effects; individual event history models (IEH) that relax the SC compartmental structure assumptions by allowing each individual to be unique. IEH models also track each individual's history, and thus, allow the simulation of field studies. Finally, dynamic network (DNW) models relax the assumption of the previous models that contacts between individuals are instantaneous events that do not affect subsequent contacts. Eventually it should be possible to transit between these model forms at the click of a mouse. An example is presented dealing with Cryptosporidium . It illustrates how transiting model forms helps assess water contamination effects, evaluate control options, and design studies of infection transmission systems using nucleotide sequences of infectious agents.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75616/1/j.1749-6632.2001.tb02756.x.pd

Using non-homogeneous point process statistics to find multi-species event clusters in an implanted semiconductor

The Poisson distribution of event-to-ith-nearest-event radial distances is well known for homogeneous processes that do not depend on location or time. Here we investigate the case of a non-homogeneous point process where the event probability (and hence the neighbour configuration) depends on location within the event space. The particular non-homogeneous scenario of interest to us is ion implantation into a semiconductor for the purposes of studying interactions between the implanted impurities. We calculate the probability of a simple cluster based on nearest neighbour distances, and specialise to a particular two-species cluster of interest for qubit gates. We show that if the two species are implanted at different depths there is a maximum in the cluster probability and an optimum density profile

Simulations to Evaluate HIV Vaccine Trial Designs

Many HIV vaccine trials have been proposed to evaluate susceptibility of individuals. However, vac cines may also affect an epidemic's course at the population level by altering the infectiousness of vaccinated individuals who become infected. A vac cine trial design that does not estimate both suscep tibility and infectiousness might reject a proposed vaccine that is capable of halting the HIV epidemic. We describe a vaccine trial design called the Retro spective Partner Trial (RPT), which can quantify vaccine effects on both susceptibility and infectious ness. We describe HIVSIM, a simulation environ ment that generates simulated populations and al lows for empirical evaluation of the statistical power of the RPT. HIVSIM explicitly models a number of factors which influence transmission and preva lence, and which have proven difficult to model us ing standard models. These factors include the infec tion stage of infected individuals, partnership selec tion, the duration of partnerships and concurrence, and transmission of HIV. The simulation analysis indicates that the RPT design has substantially greater statistical power for identifying vaccines which, in spite of exhibiting poor protection against infection, are nonetheless capable of halting the HIV epidemic by substantially reducing the infectious ness of vaccinated individuals who become infected.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68501/2/10.1177_003754979807100403.pd

The war from both sides : how Dutch and German visitors experience an exhibit of Second World War stories

At the 75th anniversary of the end of the Second World War, questions arise if contemporary audiences still find historical accounts relevant. Fundamental to understanding the relevance of stories from the war is assessing their emotional impact on leisure participants from various social groups. We used the social identity theory framework to assess differences in emotional reactions of Dutch and German visitors to stories of the Second World War presented at a Dutch museum exhibit. Emotional reactions were measured using physiological signals of heart rate and heart rate variability as well as self-report. Emotions experienced were mixed and often, but not always, different between Dutch and German participants. Patterns in the physiological and self-report data differed. Many of the significant differences were generally consistent with a collective guilt account of German social identity, but the findings as a whole were more complex than could be predicted by existing social identity accounts. Specifically, participants did not simply categorize themselves with either national or human identities of characters based on what their respective stories emphasized. We conclude that stories of the Second World War are still relevant, but touch on audiences’ nationalities in a complex way, beyond simple historical categories

Integrase-deficient lentiviral vectors mediate efficient gene transfer to human vascular smooth muscle cells with minimal genotoxic risk

We have previously shown that injury-induced neointima formation was rescued by adenoviral-Nogo-B gene delivery. Integrase-competent lentiviral vectors (ICLV) are efficient at gene delivery to vascular cells but present a risk of insertional mutagenesis. Conversely, integrase-deficient lentiviral vectors (IDLV) offer additional benefits through reduced mutagenesis risk, but this has not been evaluated in the context of vascular gene transfer. Here, we have investigated the performance and genetic safety of both counterparts in primary human vascular smooth muscle cells (VSMC) and compared gene transfer efficiency and assessed the genotoxic potential of ICLVs and IDLVs based on their integration frequency and insertional profile in the human genome. Expression of enhanced green fluorescent protein (eGFP) mediated by IDLVs (IDLV-eGFP) demonstrated efficient transgene expression in VSMCs. IDLV gene transfer of Nogo-B mediated efficient overexpression of Nogo-B in VSMCs, leading to phenotypic effects on VSMC migration and proliferation, similar to its ICLV version and unlike its eGFP control and uninfected VSMCs. Large-scale integration site analyses in VSMCs indicated that IDLV-mediated gene transfer gave rise to a very low frequency of genomic integration compared to ICLVs, revealing a close-to-random genomic distribution in VSMCs. This study demonstrates for the first time the potential of IDLVs for safe and efficient vascular gene transfer

Gas loading of graphene-quartz surface acoustic wave devices

Copyright © 2013 AIP PublishingGraphene was transferred to the propagation path of quartz surface acoustic wave devices and the attenuation due to gas loading of air and argon measured at 70 MHz and 210 MHz and compared to devices with no graphene. Under argon loading, there was no significant difference between the graphene and non-graphene device and the values of measured attenuation agree well with those calculated theoretically. Under air loading, at 210 MHz, there was a significant difference between the non-graphene and graphene devices, with the average value of attenuation obtained with the graphene devices being approximately twice that obtained from the bare quartz devices.Royal Societ