Essays in Health Economics: A Focus on the Built Environment

The dissertation investigates how individual behaviors and health outcomes interplay with surrounding built environments, in three essays. We conceptually focus on travel behaviors and accessibility. In the first essay, we hypothesize that urban sprawl increases requisite travel time which limits leisure time available as inputs to health production. We utilize the American Time Use Survey to quantify decreases in health-related activity participation due to commuting time. We identify significant evidence of trade-offs between commuting time and exercise, food preparation, and sleep behaviors, which exceed labor time trade-offs on a per-minute basis. Longer commutes are additionally associated with an increased likelihood of non-grocery food purchases and substitution into less strenuous exercise activities. We also utilize daily metropolitan traffic accidents as instruments which exogenously lengthen a particular day’s commute. The second essay tests whether the likelihood of food insecurity and “paradoxical” joint insecurity-obesity occurrences vary over the degree of urban sprawl. We utilize data from the Behavioral Risk Factor Surveillance System’s Social Context Module merged with urban sprawl measures developed by Smart Growth America. We find significantly negative associations between urban sprawl and the likelihood of food insecurity, and that insecurity is more likely in areas of less developed street connectivity. We find that joint outcomes are more likely in less sprawled areas and that likelihood is greater in areas of greater street connectivity, which fails to support theories proposing that healthy food inaccessibility is a determinant of joint outcomes. The third essay evaluates research claims that walking and cycling to school increases students’ physical activity levels in a predominantly urban sample. We utilize the third wave of the Survey of Adults and Youth–a geocoded dataset–to identify determinants of walking or cycling to school, and in turn to explore to what extent active travel impacts adolescents\u27 weekly exercise levels. Consistent with the literature, we find that the distance between home and school is the largest influence on the travel mode decision. We also find no evidence that active travel increases the number of students’ weekly exercise sessions. These results suggest that previous findings may not extend to all environments or populations

Convergence to multi-resource fairness under end-to-end window control

International audienceThe paper relates to multi-resource sharing between flows with heterogeneous requirements as arises in networks with wireless links or software routers implementing network function virtualization. Bottleneck max fairness (BMF) is a sharing objective in this context with good performance. The paper shows that BMF results when local fairness is imposed at each resource while flow rates are controlled by an end-to-end window. We analytically prove convergence to BMF under a fluid model when flows share a network limited to 2 resources while numerical results confirm BMF convergence for larger networks. Simulation results illustrate the impact of packetized transmission

The drinking water contaminant dibromoacetonitrile delays G1-S transition and suppresses Chk1 activation at broken replication forks

Abstract Chlorination of drinking water protects humans from water-born pathogens, but it also produces low concentrations of dibromoacetonitrile (DBAN), a common disinfectant by-product found in many water supply systems. DBAN is not mutagenic but causes DNA breaks and elevates sister chromatid exchange in mammalian cells. The WHO issued guidelines for DBAN after it was linked with cancer of the liver and stomach in rodents. How this haloacetonitrile promotes malignant cell transformation is unknown. Using fission yeast as a model, we report here that DBAN delays G1-S transition. DBAN does not hinder ongoing DNA replication, but specifically blocks the serine 345 phosphorylation of the DNA damage checkpoint kinase Chk1 by Rad3 (ATR) at broken replication forks. DBAN is particularly damaging for cells with defects in the lagging-strand DNA polymerase delta. This sensitivity can be explained by the dependency of pol delta mutants on Chk1 activation for survival. We conclude that DBAN targets a process or protein that acts at the start of S phase and is required for Chk1 phosphorylation. Taken together, DBAN may precipitate cancer by perturbing S phase and by blocking the Chk1-dependent response to replication fork damage

Some problems associated with sum and integral inequalities

In 2 , the following extension of the higher order Rellich inequality / AV(x) 2>7(n,a,i) / /(x) 2- (1) JRn lxl JRn lxl was proven by W. Allegretto for all / G C£ (Rn {0}). The constant 7 is calculated explicitly by the author for all n > 2, a > 0 and j 6 N, giving the value of the constant in the previously unknown case n *(n>a,4) / l/(x) 2 (2) JRn lxl JRn lxl found by W.D. Evans and R.T. Lewis in 15 for n = 2,3,4. The magnetic Laplacian is of the form Aa = (V zA)2 where in spherical coordinates H*(*i)ei ifn = 2, with e L (0,27r) and (0) = (2r). The potential A is of Aharonov- Bohm type and the constant $ is dependant upon the distance of the magnetic flux to the integers Z. By finding the discrete spectrum of the Friedrichs extension of A a in L2(Sn_1), the author is able to extend the Rellich type inequality (2) to all n > 2 and a > 0. Consequently, the higher order Rellich type inequality / Ai/(x) a>n(n,a,*,j)/ l/(x) 2 (4) JRn Ix x j can be constructed. The inequality (4) is shown to be non-trivial for all n 2. Furthermore, a CLR type bound for the number of negative eigenvalues of the operator AA can be found in L2(R8), a space in which there is no CLR bound for the operator A4

Compensation effects in GaN:Mg probed by Raman spectroscopy and photoluminescence measurements

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Appl. Phys. 113, 103504 (2013) and may be found at https://doi.org/10.1063/1.4794094.Compensation effects in metal organic chemical vapour deposition grown GaN doped with magnesium are investigated with Raman spectroscopy and photoluminescence measurements. Examining the strain sensitive E2(high) mode, an increasing compressive strain is revealed for samples with Mg-concentrations lower than 7 × 1018 cm−3. For higher Mg-concentrations, this strain is monotonically reduced. This relaxation is accompanied by a sudden decrease in crystal quality. Luminescence measurements reveal a well defined near band edge luminescence with free, donor bound, and acceptor bound excitons as well as a characteristic donor acceptor pair (DAP) luminescence. Following recent results, three acceptor bound excitons and donor acceptor pairs are identified. Along with the change of the strain, a strong modification in the luminescence of the dominating acceptor bound exciton and DAP luminescence is observed. The results from Raman spectroscopy and luminescence measurements are interpreted as fingerprints of compensation effects in GaN:Mg leading to the conclusion that compensation due to defect incorporation triggered by Mg-doping already affects the crystal properties at doping levels of around 7 × 1018 cm−3. Thereby, the generation of nitrogen vacancies is introduced as the driving force for the change of the strain state and the near band edge luminescence.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

A Multiagent CyberBattleSim for RL Cyber Operation Agents

Hardening cyber physical assets is both crucial and labor-intensive. Recently, Machine Learning (ML) in general and Reinforcement Learning RL) more specifically has shown great promise to automate tasks that otherwise would require significant human insight/intelligence. The development of autonomous RL agents requires a suitable training environment that allows us to quickly evaluate various alternatives, in particular how to arrange training scenarios that pit attackers and defenders against each other. CyberBattleSim is a training environment that supports the training of red agents, i.e., attackers. We added the capability to train blue agents, i.e., defenders. The paper describes our changes and reports on the results we obtained when training blue agents, either in isolation or jointly with red agents. Our results show that training a blue agent does lead to stronger defenses against attacks. In particular, training a blue agent jointly with a red agent increases the blue agent's capability to thwart sophisticated red agents.Comment: To appear in Proceedings of the 2022 International Conference on Computational Science and Computational Intelligenc

The \u3ci\u3ePseudomonas syringae \u3c/i\u3etype III effector HopG1 targets mitochondria, alters plant development, and suppresses plant innate immunity

The bacterial plant pathogen Pseudomonas syringae uses a type III protein secretion system to inject type III effectors into plant cells. Primary targets of these effectors appear to be effector-triggered immunity (ETI) and pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI). The type III effector HopG1 is a suppressor of ETI that is broadly conserved in bacterial plant pathogens. Here we show that HopG1 from P. syringae pv. tomato DC3000 also suppresses PTI. Interestingly, HopG1 localizes to plant mitochondria, suggesting that its suppression of innate immunity may be linked to a perturbation of mitochondrial function. While HopG1 possesses no obvious mitochondrial signal peptide, its N-terminal two-thirds was sufficient for mitochondrial localization. A HopG1-GFP fusion lacking HopG1’s N-terminal 13 amino acids was not localized to the mitochondria reflecting the importance of the N-terminus for targeting. Constitutive expression of HopG1 in Arabidopsis thaliana, Nicotiana tabacum (tobacco) and Lycopersicon esculentum (tomato) dramatically alters plant development resulting in dwarfism, increased branching and infertility. Constitutive expression of HopG1 in planta leads to reduced respiration rates and an increased basal level of reactive oxygen species. These findings suggest that HopG1’s target is mitochondrial and that effector/target interaction promotes disease by disrupting mitochondrial functions

Surface and Bulk Relaxation of Vapour-Deposited Polystyrene Glasses

We have studied the liquid-like response of the surface of vapour-deposited glassy films of polystyrene to the introduction of gold nanoparticles on the surface. The build-up of polymer material was measured as a function of time and temperature for both as-deposited films, as well as films that have been rejuvenated to become normal glasses cooled from the equilibrium liquid. The temporal evolution of the surface profile is well described by the characteristic power law of capillary-driven surface flows. In all cases, the surface evolution of the as-deposited films and the rejuvenated films are enhanced compared to bulk and are not easily distinguishable from each other. The temperature dependence of the measured relaxation times determined from the surface evolution is found to be quantitatively comparable to similar studies for high molecular weight spincast polystyrene. Comparisons to numerical solutions of the glassy thin film equation provide quantitative estimates of the surface mobility. For temperatures sufficiently close to the glass-transition temperature, particle embedding is also measured and used as a probe of bulk dynamics, and in particular bulk viscosity