Results of the 2010 Mathematical Contest in Modeling

Modeling ForumA total of 2,254 teams of undergraduates from hundreds of institutions and departments in 14 countries, spent a weekend in February working on applied mathematicsproblems inthe 26thMathematicalContest inModeling(MCM)!R . The 2010MCMbegan at 8:00 P.M. EST on Thursday, February 18, and ended at 8:00 P.M. EST on Monday, February 22. During that time, teams of up to three undergraduates researched, modeled, and submitted a solution to one of two open-ended modeling problems. Students registered, obtained contest materials, downloaded the problem and data, and entered completion data through COMAP’s MCM Website. After a weekend of hard work, solution papers were sent to COMAP on Monday. Two of the top papers appear in this issue of The UMAP Journal, together with commentaries

The numbing effect of experience

Master of ScienceDepartment of Psychological SciencesJin LeeJob experience is a pervasive metric used in human resource functioning; however, its predictive validity might not be as intuitive as it seems especially regarding safety outcomes. While research suggests a positive relationship between experience and performance (McDaniel, Schmidt, & Hunter, 1988; Sturman, 2003), there are instances when experience may have a null or negative relationship with performance (Woltz et al., 2000). Specifically, this occurs when the perceived similarity between prior experience and a new task is actually discrepant. Also, rigidities in problem-solving can form from job experience, leading to impaired performance (Dokko, Wilk, & Rothbard, 2009; Bilalić, McLeod, & Gobet, 2008). The relationship between job experience and safety outcomes is more intricate. Self-appraisals of safety performance can be discrepant, which is problematic when tasks include safety behaviors that individuals assume they can adequately enact. The means of informing self-efficacy can also be inequitable, such that positive safety behavior feedback (e.g., no injury or accident) can go ungiven or unnoticed, while performance feedback is often a focus of organizations (Gun, 1993). This might contribute to the false perception of similarity in discrete job tasks and safety behaviors (i.e., task performance vs. safety performance). Individuals can be exposed to work experiences which do not provide adequate opportunities to discern work system components, inherent hazards, and risks. This study aims to observe the effect prior experience has on performance of a task, the execution of safety behaviors, and participants’ appraisals of their self-efficacy regarding both the task and their safety behaviors

Understanding the alternative work arrangement

Doctor of PhilosophyDepartment of Psychological SciencesJin LeeThe alternative work arrangement, or work that deviates from employment under a single employer with consistent hours and location, has become a common form of employment due to its flexibility in hiring (Landsbergis et al., 2014; Kuhn, 2016), and has been rapidly growing (BLS, 2018; Statista, 2021). Prior research shows that there are reduced financial (Gash, 2008; Reichenberg & Berglund, 2019), health (Rousseau & Libuser, 1999), and well-being outcomes (Åkerblad, 2017) for those that predominantly engage in this type of work, with a potential for positive outcomes like freedom and flexibility (Friedman, 2014; Kuhn, 2016). The current research explores the utility of using proposed work features, Job Characteristics Theory, and Self-Determination Theory as a combined framework to meaningfully compare the alternative work arrangement to their traditional counterparts and other alternative work. Results replicate prominent differences across arrangements, such as alternative workers experiencing lower job security but higher autonomy than traditional workers. Alternative workers were also able to be parsed into four unique profiles based on the features within the combined framework. These results show that while there are broader differences between the alternative and traditional work arrangements, it is necessary to acknowledge their uniqueness. Specifically, certain work features such as flexibility, characteristics of the job, and motivational factors can contribute to understanding this uniqueness within the alternative work arrangement

In regard to Minniti et al.: "Current status and recent advances in resection cavity irradiation of brain metastases — roundup to cover all angles"

We read with great interest the recent review, entitled “Current status and recent advances in resection cavity irradiation of brain metastases”. It is a comprehensive summary of currently available techniques for treatment of post-resection cavity in patients with this diagnosis. We would like to complement this manuscript by including intraoperative techniques as other viable approaches in the management of these patients

Analysis of High Temperature Degradation of Multi-layer Insulation (MLI) Systems for Liquid Hydrogen Storage Tanks

The interest in hydrogen-based green energy is increasing worldwide, and the same is true for hydrogenpowered vehicles. Among the possible solutions to store hydrogen in such vehicles, cryogenic tanks equipped with multi-layer insulation (MLI) are the most promising to increase the amount of energy stored per unit volume. However, MLI is affected by severe deterioration when exposed to an external source of heat such as a fire following a car accident, leaving the tank unprotected and leading to failure in a relatively short time. In this work, a one-dimensional model to evaluate MLI thermal degradation when a liquid hydrogen tank is exposed to fire is presented. The relevance of taking MLI degradation into account when simulating the pressure increase due to external fire exposure is here demonstrated through the analysis of several case studies. The results show that MLI systems performance depletes within a few minutes of exposure to hydrocarbon poolfire

INTRAGO: intraoperative radiotherapy in glioblastoma multiforme – a Phase I/II dose escalation study

Background: Glioblastoma multiforme (GBM) is the most frequent primary malignant brain tumor in adults. Despite multimodal therapies, almost all GBM recur within a narrow margin around the initial resected lesion. Thus, novel therapeutic intensification strategies must target both, the population of dispersed tumor cells around the cavity and the postoperative microenvironment. Intraoperative radiotherapy (IORT) is a pragmatic and effective approach to sterilize the margins from persistent tumor cells, abrogate post-injury proliferative stimuli and to bridge the therapeutic gap between surgery and radiochemotherapy. Therefore, we have set up INTRAGO, a phase I/II dose-escalation study to evaluate the safety and tolerability of IORT added to standard therapy in newly diagnosed GBM. In contrast to previous approaches, the study involves the application of isotropic low-energy (kV) x-rays delivered by spherical applicators, providing optimal irradiation properties to the resection cavity. Methods/Design: INTRAGO includes patients aged 50 years or older with a Karnofsky performance status of at least 50% and a histologically confirmed (frozen sections) supratentorial GBM. Safety and tolerability (i.e., the maximum tolerated dose, MTD) will be assessed using a classical 3 + 3 dose-escalation design. Dose-limiting toxicities (DLT) are wound healing deficits or infections requiring surgical intervention, IORT-related cerebral bleeding or ischemia, symptomatic brain necrosis requiring surgical intervention and early termination of external beam radiotherapy (before the envisaged dose of 60 Gy) due to radiotoxicity. Secondary end points are progression-free and overall survival. Trial registration: The study is registered with clinicaltrials.gov, number: NCT02104882 (Registration Date: 03/26/2014)

Loss of HIF-1α in endothelial cells disrupts a hypoxia-driven VEGF autocrine loop necessary for tumorigenesis

AbstractWe deleted the hypoxia-responsive transcription factor HIF-1α in endothelial cells (EC) to determine its role during neovascularization. We found that loss of HIF-1α inhibits a number of important parameters of EC behavior during angiogenesis: these include proliferation, chemotaxis, extracellular matrix penetration, and wound healing. Most strikingly, loss of HIF-1α in EC results in a profound inhibition of blood vessel growth in solid tumors. These phenomena are all linked to a decreased level of VEGF expression and loss of autocrine response of VEGFR-2 in HIF-1α null EC. We thus show that a HIF-1α-driven, VEGF-mediated autocrine loop in EC is an essential component of solid tumor angiogenesis