Bridge trisections in rational surfaces

We study smooth isotopy classes of complex curves in complex surfaces from the perspective of the theory of bridge trisections, with a special focus on curves in $\mathbb{CP}^2$ and $\mathbb{CP}^1\times\mathbb{CP}^1$. We are especially interested in bridge trisections and trisections that are as simple as possible, which we call "efficient". We show that any curve in $\mathbb{CP}^2$ or $\mathbb{CP}^1\times\mathbb{CP}^1$ admits an efficient bridge trisection. Because bridge trisections and trisections are nicely related via branched covering operations, we are able to give many examples of complex surfaces that admit efficient trisections. Among these are hypersurfaces in $\mathbb{CP}^3$, the elliptic surfaces $E(n)$, the Horikawa surfaces $H(n)$, and complete intersections of hypersurfaces in $\mathbb{CP}^N$. As a corollary, we observe that, in many cases, manifolds that are homeomorphic but not diffeomorphic have the same trisection genus, which is consistent with the conjecture that trisection genus is additive under connected sum. We give many trisection diagrams to illustrate our examples.Comment: 46 pages, 28 color figure

2006 Warm Fire: effects on habitat and prey species of the northern goshawk, The

2015 Spring.Includes bibliographical references.Reductions in the frequency of fire in Southwestern ponderosa pine and mixed-conifer forests since initiation of forest management early in 20th century changed the composition and structure of the forest habitats of the northern goshawks (Accipiter gentilis), a food-limited species of conservation concern, and the birds and mammals it feeds on. A conservation strategy for the species in the goshawk's food web in these forest types recommends restoring the mix of predator and prey habitats that historically characterized these forests--characteristics that were sustained by frequent low-severity surface fire. Thus, the effects of fire severities (high- and low-severity) and lack of fire on today's habitats may influence the abundances of bird and mammal goshawk prey. . The 2006 Warm Fire burned 235 km² of ponderosa pine and mixed-conifer forest on the North Kaibab Ranger District in northern Arizona in late June and early July 2006. Forest habitat metrics such as live tree and snag densities, cone production, canopy and ground cover estimates were collected from 2007-2010 on 60 0.5km transects to compare the effects of high- and low-severity fire and no fire on a suite of 13 important prey species of the goshawk. I describe habitat changes resulting from the different fire severities in ponderosa pine and mixed conifer forests. I estimated abundances for 13 bird and mammal prey species in forests burned by different fire severities and tested predictive models designed to gain an understanding which habitat characteristics, affected by fire, best predicted individual bird and mammal abundances. Red squirrels and golden-mantled ground squirrels showed the most sensitivity to fire, while chipmunks were evenly distributed across fire severities. Hairy woodpeckers and northern flickers, in contrast, benefitted from high-severity fire, due to increased snags, cavity nesting opportunities, and foraging. American robins and Steller's jays were also evenly distributed across fire severities. High-severity fire had a significant impact on forest ecosystems. Changes in forest structure were found to be detrimental to some species while creating short- and possibly intermediate-term benefits for others. Lowering the risk of high-severity fire by restoring composition and structure should also protect the habitats of goshawk and the prey species most sensitive to fire. The effects of low-severity fire were mixed, suggesting that it may be possible to return fire to ecosystem without a significant impact to many birds and mammals in the short term. Frequent low-severity fire could also help to maintain sub-canopy and understory grass / shrub openings by removing excess growth and ground debris

An Algebraic Characterization of Total Input Strictly Local Functions

This paper provides an algebraic characteriza- tion of the total input strictly local functions. Simultaneous, noniterative rules of the form A→B/C D, common in phonology, are defin- able as functions in this class whenever CAD represents a finite set of strings. The algebraic characterization highlights a fundamental con- nection between input strictly local functions and the simple class of definite string languages, as well as connections to string functions stud- ied in the computer science literature, the def- inite functions and local functions. No effec- tive decision procedure for the input strictly local maps was previously available, but one arises directly from this characterization. This work also shows that, unlike the full class, a restricted subclass is closed under composition. Additionally, some products are defined which may yield new factorization methods

Improved real-time imaging spectrometer

An improved AOTF-based imaging spectrometer that offers several advantages over prior art AOTF imaging spectrometers is presented. The ability to electronically set the bandpass wavelength provides observational flexibility. Various improvements in optical architecture provide simplified magnification variability, improved image resolution and light throughput efficiency and reduced sensitivity to ambient light. Two embodiments of the invention are: (1) operation in the visible/near-infrared domain of wavelength range 0.48 to 0.76 microns; and (2) infrared configuration which operates in the wavelength range of 1.2 to 2.5 microns

Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayers

In a number of recent experiments, it has been shown that femtosecond laser pulses can control magnetization on picosecond timescales, which is at least an order of magnitude faster compared to conventional magnetization dynamics. Among these demonstrations, one material system (GdFeCo ferromagnetic films) is particularly interesting, as deterministic toggle-switching of the magnetic order has been achieved without the need of any symmetry breaking magnetic field. This phenomenon is often referred to as all optical switching (AOS). However, so far, GdFeCo remains the only material system where such deterministic switching has been observed. When extended to ferromagnetic systems, which are of greater interest in many technological applications, only a partial effect can be achieved, which in turn requires repeated laser pulses for full switching. However, such repeated pulsing is not only energy hungry, it also negates the speed advantage of AOS. Motivated by this problem, we have developed a general method for single-shot, picosecond timescale, complete all optical switching of ferromagnetic materials. We demonstrate that in exchange-coupled layers of Co/Pt and GdFeCo, single shot, switching of the ferromagnetic Co/Pt layer is achieved within 7 picoseconds after irradiation by a femtosecond laser pulse. We believe that this approach will greatly expand the range of materials and applications for ultrafast magnetic switching.Comment: 11 pages, 3 figures, supplementary material

Symplectic 4-manifolds admit Weinstein trisections

We prove that every symplectic 4-manifold admits a trisection that is compatible with the symplectic structure in the sense that the symplectic form induces a Weinstein structure on each of the three sectors of the trisection. Along the way, we show that a (potentially singular) symplectic braided surface in $\mathbb{CP}^2$ can be symplectically isotoped into bridge position.Comment: 28 pages, 9 figures. [v2] A necessary technical hypothesis was omitted from the statement of Lemma 5.5(1) in the first version, and the proof of Theorem 5.9 has been modified to account for this hypothesi

Post-Secondary Academic Self-Limitation of Rural High School Students in Northeast Georgia

The purpose of this phenomenological study was to describe the phenomenon of academic post-secondary self-limitation of rural high school students in northeast Georgia. The theory guiding this study was based upon self-determination theory, as described by Deci and Ryan (2008). Most high school students must make a decision as to whether or not they continue their education into the post-secondary years. This transcendental phenomenological study examined post-secondary academic self-limitation of high school students in rural, northeast Georgia. This type of phenomenology suggests that the whole of human experience is descriptive and leads to absolute knowledge (Moustakas, 1994). This approach was appropriate because the researcher sought to describe how the identified phenomenon manifested itself in the lives of the subjects. The participants were purposefully selected to ensure that all research participants experience the phenomenon (see Appendix A). Therefore, the participants were students who had chosen not to pursue post-secondary education even though they may have had the academic and financial ability to do so. The participants were surveyed, individually interviewed, and interviewed in a focus group setting in an attempt to determine the essence of the phenomenon. The data were analyzed using methods such as phenomenological reduction, systemic coding, horizonalization, and thick descriptions, all considered appropriate for this qualitative study. The results supported major elements of self-determination theory, and suggested a strong link between the effects of parental values and support, and a student\u27s values and motivational growth. The results of this study may be used to develop programs that will assist in decreasing the incidence of academic self-limitation among this population

Nucleus-specific linker histones Hho1 and Mlh1 form distinct protein interactions during growth, starvation and development in Tetrahymena thermophila

Chromatin organization influences most aspects of gene expression regulation. The linker histone H1, along with the core histones, is a key component of eukaryotic chromatin. Despite its critical roles in chromatin structure and function and gene regulation, studies regarding the H1 protein-protein interaction networks, particularly outside of Opisthokonts, are limited. The nuclear dimorphic ciliate protozoan Tetrahymena thermophila encodes two distinct nucleus-specific linker histones, macronuclear Hho1 and micronuclear Mlh1. We used a comparative proteomics approach to identify the Hho1 and Mlh1 protein-protein interaction networks in Tetrahymena during growth, starvation, and sexual development. Affinity purification followed by mass spectrometry analysis of the Hho1 and Mlh1 proteins revealed a non-overlapping set of co-purifying proteins suggesting that Tetrahymena nucleus-specific linker histones are subject to distinct regulatory pathways. Furthermore, we found that linker histones interact with distinct proteins under the different stages of the Tetrahymena life cycle. Hho1 and Mlh1 co-purified with several Tetrahymena-specific as well as conserved interacting partners involved in chromatin structure and function and other important cellular pathways. Our results suggest that nucleus-specific linker histones might be subject to nucleus-specific regulatory pathways and are dynamically regulated under different stages of the Tetrahymena life cycle.York University Librarie

Improving interventions for physical activity and depression

Background: There is increasing evidence supporting the potential use of physical activity as an intervention for depression. However, effective behavioural interventions which focus on encouraging physical activity in people with depression are needed. Aim: This thesis reports on the development and pilot evaluation of a web-based intervention based on behavioural activation (BA) and physical activity promotion for people with depression (eMotion). There is also a specific focus on intervention fidelity. Method: A systematic review was conducted to identify how fidelity is assessed in behavioural interventions promoting physical activity in adults. Findings from the systematic review and the Centre for eHealth and Disease Management (CeHReS) Roadmap informed the development of eMotion. A novel “design fidelity” methodology was devised, which involved using an independent coder to systematically verify the presence or absence of intended and non-intended behaviour change techniques (BCTs). A pilot RCT of eMotion was conducted to provide evidence on the feasibility and acceptability of eMotion, and exploratory data on outcomes. A mixed methods process evaluation of the understanding, feasibility and enactment of the main BCTs used in eMotion, and participant’s perceptions of eMotion was conducted. Results: The systematic review presents a critical appraisal of the wide range of methods and measures used to assess intervention fidelity. The eMotion intervention consisted of weekly modules designed to re-engage people in routine, pleasurable, necessary or physical activities. Design fidelity of the intervention was excellent with discrepancies between intervention materials and the intended design for 12 out of 221 (AC1 =0.91) and 14 out of 221 (AC1 = 0.88) BCTs relating to BA and physical activity respectively. In the pilot trial, 62 people (≥10 on the PHQ-8) were randomised, and the two-month attrition rate was 19% (95% CI: 11 to 30%). Study completers in the eMotion group (n=25) had a significantly larger reduction in depressive symptoms than the waiting list control group (n=25) (Adj Mean Diff -3.6, 95% CI: -6.1 to -1.1). Participants using eMotion also reported significantly higher levels of understanding, ability and enactment of most BCTs compared with controls. Interviews with participants revealed a number of possible mechanisms by which eMotion may have changed behaviour (e.g. increased awareness of the link between mood and activity) and reduced depression (e.g. through distraction). Conclusion: This thesis has reported on the development and pilot evaluation of a behavioural intervention promoting physical activity for depression while focussing on fidelity. Further insight into a number of methodological and clinical implications for the conduct of future RCTs in this area has also been provided.Economic and Social Research Counci

Taking a One-Week Break from Social Media Improves Well-Being, Depression, and Anxiety:A Randomized Controlled Trial

The present study aimed to understand the effects of a 1-week break from social media (SM) (Facebook, Instagram, Twitter, and TikTok) on well-being, depression, and anxiety compared with using SM as usual. We also aimed to understand whether time spent on different SM platforms mediates the relationship between SM cessation and well-being, depression, and anxiety. We randomly allocated 154 participants (mean age of 29.6 years) to either stop using SM (Facebook, Twitter, Instagram, and TikTok) for 1 week or continue to use SM as usual. At a 1-week follow-up, significant between-group differences in well-being (mean difference [MD] 4.9, 95% confidence interval [CI] 3.0-6.8), depression (MD -2.2, 95% CI -3.3 to -1.1), and anxiety (MD -1.7, 95% CI -2.8 to -0.6) in favor of the intervention group were observed, after controlling for baseline scores, age, and gender. The intervention effect on well-being was partially mediated by a reduction in total weekly self-reported minutes on SM. The intervention effect on depression and anxiety was partially mediated by a reduction in total weekly self-reported minutes on Twitter and TikTok, and TikTok alone, respectively. The present study shows that asking people to stop using SM for 1 week leads to significant improvements in well-being, depression, and anxiety. Future research should extend this to clinical populations and examine effects over the longer term.</p