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    Does reactance against cigarette warning labels matter? Warning label responses and downstream smoking cessation amongst adult smokers in Australia, Canada, Mexico and the United States
    (Public Library of Science, 2016-07-13) Cho, Yoo Jin; Thrasher, James F.; Swayampakala, Kamala; Yong, Hua-Hie; McKeever, Robert; Hammond, David; Anshari, Dien; Cummings, K. Michael; Borland, Ron
    Objective Some researchers have raised concerns that pictorial health warning labels (HWLs) on cigarette packages may lead to message rejection and reduced effectiveness of HWL messages. This study aimed to determine how state reactance (i.e., negative affect due to perceived manipulation) in response to both pictorial and text-only HWLs is associated with other types of HWL responses and with subsequent cessation attempts. Methods Survey data were collected every 4 months between September 2013 and 2014 from online panels of adult smokers in Australia, Canada, Mexico, and the US were analyzed. Participants with at least one wave of follow-up were included in the analysis (n = 4,072 smokers; 7,459 observations). Surveys assessed psychological and behavioral responses to HWLs (i.e., attention to HWLs, cognitive elaboration of risks due to HWLs, avoiding HWLs, and forgoing cigarettes because of HWLs) and cessation attempts. Participants then viewed specific HWLs from their countries and were queried about affective state reactance. Logistic and linear Generalized Estimating Equation (GEE) models regressed each of the psychological and behavioral HWL responses on reactance, while controlling for socio-demographic and smoking-related variables. Logistic GEE models also regressed having attempted to quit by the subsequent survey on reactance, each of the psychological and behavioral HWL responses (analyzed separately), adjustment variables. Data from all countries were initially pooled, with interactions between country and reactance assessed; when interactions were statistically significant, country-stratified models were estimated. Results Interactions between country and reactance were found in all models that regressed psychological and behavioral HWL responses on study variables. In the US, stronger reactance was associated with more frequent reading of HWLs and thinking about health risks. Smokers from all four countries with stronger reactance reported greater likelihood of avoiding warnings and forgoing cigarettes due to warnings, although the association appeared stronger in the US. Both stronger HWLs responses and reactance were positively associated with subsequent cessation attempts, with no significant interaction between country and reactance. Conclusions Reactance towards HWLs does not appear to interfere with quitting, which is consistent with its being an indicator of concern, not a systematic effort to avoid HWL message engagement.
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    Impact of soil salinity on the structure of the bacterial endophytic community identified from the roots of caliph medic (Medicago truncatula)
    (Public Library of Science, 2016-07-08) Yaish, Mahmoud W.; Al-Lawati, Abbas; Jana, Gerry Aplang; Patankar, Himanshu Vishwas; Glick, Bernard R.
    In addition to being a forage crop, Caliph medic (Medicago truncatula) is also a model legume plant and is used for research focusing on the molecular characterization of the interaction between rhizobia and plants. However, the endophytic microbiome in this plant is poorly defined. Endophytic bacteria play a role in supplying plants with the basic requirements necessary for growth and development. Moreover, these bacteria also play a role in the mechanism of salinity stress adaptation in plants. As a prelude to the isolation and utilization of these bacteria in Caliph medic farming, 41 bacterial OTUs were identified in this project from within the interior of the roots of this plant by pyrosequencing of the small ribosomal subunit gene (16S rDNA) using a cultivation-independent approach. In addition, the differential abundance of these bacteria was studied following exposure of the plants to salinity stress. About 29,064 high-quality reads were obtained from the sequencing of six libraries prepared from control and salinity-treated tissues. Statistical analysis revealed that the abundance of ~70% of the OTUs was significantly (p ≤ 0.05) altered in roots that were exposed to salinity stress. Sequence analysis showed a similarity between some of the identified species and other, known, growth-promoting bacteria, marine and salt-stressed soil-borne bacteria, and nitrogen-fixing bacterial isolates. Determination of the amendments to the bacterial community due to salinity stress in Caliph medic provides a crucial step toward developing an understanding of the association of these endophytes, under salt stress conditions, in this model plant. To provide direct evidence regarding their growth promoting activity, a group of endophytic bacteria were isolated from inside of plant roots using a cultivation-dependent approach. Several of these isolates were able to produce ACC-deaminase, ammonia and IAA; and to solubilize Zn+2 and PO4-3. This data is consistent with the predicted occurrence (based on cultivation-independent techniques) of these bacteria and provides some insight into the importance of the endophytic bacteria in Caliph medic when grown under normal and saline conditions.
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    Occupational physicians' reasoning about recommending early return to work with work modifications
    (Public Library of Science, 2016-07-01) Horppu, Ritva; Martimo, Kari-Pekka; Viikari-Juntura, Eira; Lallukka, Tea; MacEachen, Ellen
    Previous research indicates that work modifications can effectively enhance return to work (RTW) at an early stage of work disability. We aimed to examine how occupational physicians (OPs) reason about recommending early return to work (RTW) with work modifications. Pre-defined propositions regarding the use of work modifications in promoting early RTW were discussed in four focus groups with altogether 11 Finnish OPs. Discussions were audio recorded, and the transcribed data were analyzed using qualitative content analysis. Five different rationales for supporting early RTW were identified: to manage medical conditions, to enhance employee well-being, to help workplace stakeholders, to reduce costs to society, and to enhance OP’s own professional fulfillment. However, OPs identified situations and conditions in which early RTW may not be suitable. In addition, there were differences between the OPs in the interpretation of the rationales, suggesting variation in clinical practice. In conclusion, encouraging early RTW with work modifications was perceived by OPs as a meaningful task and, to a large extent, beneficial for employees and several stakeholders. However, this practice was not accepted without consideration to the RTW situation and context. If early RTW and work modifications are to be promoted, OPs should be offered education that addresses their views regarding this practice.
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    A Hamiltonian Systems Approach to Neural Network Optimization
    (University of Waterloo, 2026-05-21) George, Joshua Joseph
    We propose and analyze structure-preserving methods for first-order optimization of Lipschitz smooth objectives by interpreting the dynamics as a dissipative Hamiltonian system, in which the model parameters evolve jointly with an auxiliary momentum variable. This formulation induces a natural energy dissipation mechanism that motivates the design of optimization algorithms that inherit a discrete energy decay property. We develop discrete gradient (DG) methods that pre- serve an exact discrete time energy decay property, ensuring monotone dissipation independent of stepsize. Building on this framework, we introduce variants which empirically reduce oscillations, improve runtime, and improve robustness to ill-conditioned problems. To address the computational cost of the implicit DG methods, we propose semi-implicit discrete gradient (SIDG) schemes obtained by linearizing the DG updates and incorporating curvature through L-BFGS Hessian approximations, which are used to efficiently solve the result- ing linear systems. These schemes retain key structure-preserving properties while significantly reducing computational cost, yielding a practical balance between stability and efficiency. We es- tablish monotone energy decay, boundedness of iterates, and sublinear convergence to first-order stationary points. Numerical experiments on ill-conditioned least-squares problems, regularized logistic regres- sion, physics-informed neural networks, and CIFAR-10 image classification demonstrate good performance despite ill-conditioning and competitive performance as compared to widely used optimizers such as ADAM, Stochastic gradient descent, and L-BFGS.
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    Computing and Bounding the Scattering Number of Graphs
    (University of Waterloo, 2026-05-21) Arsénio Nunes Vitorino, Dinis
    In this thesis we study the scattering number of graphs, a parameter introduced by Jung in 1978, from two different perspectives. First, we investigate it under a computational lens, proving that the scattering number of bipartite and planar graphs cannot be computed in polynomial time unless P=NP, but that the scattering number of graphs with bounded tree-width can be computed in polynomial time. Secondly, we focus on upper bounding the scattering number of graphs in special graph classes. In particular, we obtain bounds on the scattering number of planar graphs with given vertex-connectivity and minimum degree. These are generalizations of lower bounds on the matching number of such graphs obtained by Baybars and Nishizeki in 1979 and our proof strategy is strongly inspired by theirs. We further generalize these results by bounding the scattering number of maximally K5-minor-free graphs with minimum degree at least four, but this result relies on a substantially different and somewhat more involved proof. All bounds we derive are tight up to constant additive terms.