Hestenes' Tetrad and Spin Connections

Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation of the Dirac Lagrangian in which the bispinor field is mapped to a set of Yang-Mills gauge potentials and a complex scalar field. This result was previously proved for a Minkowski space-time using Fierz identities. As an application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary linear connection acting on Hestenes' tetrad and scalar fields. We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered form invariance of the Dirac equation as a criterion for defining a general spin connection

Measuring a Kaluza-Klein radius smaller than the Planck length

Hestenes has shown that a bispinor field on a Minkowski space-time is equivalent to an orthonormal tetrad of one-forms together with a complex scalar field. More recently, the Dirac and Einstein equations were unified in a tetrad formulation of a Kaluza-Klein model which gives precisely the usual Dirac-Einstein Lagrangian. In this model, Dirac's bispinor equation is obtained in the limit for which the radius of higher compact dimensions of the Kaluza-Klein manifold becomes vanishingly small compared with the Planck length. For a small but finite radius, the Kaluza-Klein model predicts velocity splitting of single fermion wave packets. That is, the model predicts a single fermion wave packet will split into two wave packets with slightly different group velocities. Observation of such wave packet splits would determine the size of the Kaluza-Klein radius. If wave packet splits were not observed in experiments with currently achievable accuracies, the Kaluza-Klein radius would be at least twenty five orders of magnitude smaller than the Planck length

General reference frames and their associated space manifolds

We propose a formal definition of a general reference frame in a general spacetime, as an equivalence class of charts. This formal definition corresponds with the notion of a reference frame as being a (fictitious) deformable body, but we assume, moreover, that the time coordinate is fixed. This is necessary for quantum mechanics, because the Hamiltonian operator depends on the choice of the time coordinate. Our definition allows us to associate rigorously with each reference frame F, a unique "space" (a three-dimensional differentiable manifold), which is the set of the world lines bound to F. This also is very useful for quantum mechanics. We briefly discuss the application of these concepts to G\"odel's universe.Comment: 14 pages in standard 12pt format. v2: Discussion Section 4 reinforced, now includes an application to G\"odel's universe

Einflüsse der Umwelt auf Synthesefasern

To get more information on the long term behaviour of technical textiles and on related degradation processes, the degradation of different synthetic fibres (polyester, PYC-coated polyester, polypropylene, polyethylene, polyamide 6 and 6.6, m-aramide) were investigated under the combined influence of pollution gases and light. Laboratory weathering experiments were performed in a specially designed climatic chamber, using different atmospheres such as normal air, zero air and zero air with pollution gases (NO2, SO2, O3, NO2/O3) added. Outdoor exposure tests are in progress at eight sites in Switzerland each having its specific meteorological conditions and typical environmental load. The exposure sites were chosen at locations of the Swiss National Air Pollution Monitoring Network (NABEL), where concentrations of air pollutants and climatic data are registered continuously. Results of tensile tests on laboratory and outdoor exposed samples are given. Comparison is made between laboratory ageing and outdoor exposure

Competing risks of cancer mortality and cardiovascular events in individuals with multimorbidity

Background: Cancer patients with cardiovascular and other comorbidities are at concurrent risk of multiple adverse outcomes. However, most treatment decisions are guided by evidence from single-outcome models, which may be misleading for multimorbid patients. Objective: We assessed the interacting effects of cancer, cardiovascular, and other morbidity burdens on the competing outcomes of cancer mortality, serious cardiovascular events, and other-cause mortality. Design: We analyzed a cohort of 6,500 adults with initial cancer diagnosis between 2001 and 2008, SEER 5-year survival ≥26%, and a range of cardiovascular risk factors. We estimated the cumulative incidence of cancer mortality, a serious cardiovascular event (myocardial infarction, coronary revascularization, or cardiovascular mortality), and other-cause mortality over 5 years, and identified factors associated with the competing risks of each outcome using cause-specific Cox proportional hazard models. Results: Following cancer diagnosis, there were 996 (15.3%) cancer deaths, 328 (5.1%) serious cardiovascular events, and 542 (8.3%) deaths from other causes. In all, 4,634 (71.3%) cohort members had none of these outcomes. Although cancer prognosis had the greatest effect, cardiovascular and other morbidity also independently increased the hazard of each outcome. The effect of cancer prognosis on outcome was greatest in year 1, and the effect of other morbidity was greater in individuals with better cancer prognoses. Conclusion: In multimorbid oncology populations, comorbidities interact to affect the competing risk of different outcomes. Quantifying these risks may provide persons with cancer plus cardiovascular and other comorbidities more accurate information for shared decision-making than risks calculated from single-outcome models. Journal of Comorbidity 2014:4(1):29–3

Office-Based Educational Handout for Influenza Vaccination: A Randomized Controlled Trial

This is the author accepted manuscript. The final version is available from American Academy of Pediatrics via the DOI in this recordData sharing statement: De-identified individual participant data will not be made available.OBJECTIVES: To assess the impact of a parent educational intervention about influenza disease on child vaccine receipt. METHODS: A convenience sample of parents of children ≥6 months old with a visit at 2 New York City pediatric clinics between August 2016 and March 2017 were randomly assigned (1:1:1) to receive either usual care, an educational handout about influenza disease that was based on local data, or an educational handout about influenza disease that was based on national data. Parents received the handout in the waiting room before their visit. Primary outcomes were child influenza vaccine receipt on the day of the clinic visit and by the end of the season. A multivariable logistic regression was used to assess associations between intervention and vaccination, with adjustment for variables that were significantly different between arms. RESULTS: Parents who received an intervention (versus usual care) had greater odds of child influenza vaccine receipt by the end of the season (74.9% vs 65.4%; adjusted odds ratio 1.68; 95% confidence interval: 1.06-2.67) but not on the day of the clinic visit. Parents who received the national data handout (versus usual care) had greater odds of child influenza vaccine receipt on the day of the clinic visit (59.0% vs 52.6%; adjusted odds ratio 1.79; 95% confidence interval: 1.04-3.08) but not by the end of the season. CONCLUSIONS: Providing an educational intervention in the waiting room before a pediatric provider visit may help increase child influenza vaccine receipt.European CommissionNIH - Ruth L. Kirschstein National Research Service Awar

The Distorting Prism of Social Media: How Self-Selection and Exposure to Incivility Fuel Online Comment Toxicity

This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this recordThough prior studies have analyzed the textual characteristics of online comments about politics, less is known about how selection into commenting behavior and exposure to other people’s comments changes the tone and content of political discourse. This article makes three contributions. First, we show that frequent commenters on Facebook are more likely to be interested in politics, to have more polarized opinions, and to use toxic language in comments in an elicitation task. Second, we find that people who comment on articles in the real world use more toxic language on average than the public as a whole; levels of toxicity in comments scraped from media outlet Facebook pages greatly exceed what is observed in comments we elicit on the same articles from a nationally representative sample. Finally, we demonstrate experimentally that exposure to toxic language in comments increases the toxicity of subsequent comments.Dartmouth CollegeEuropean Union Horizon 202

A new measure of the ‘democratic peace’: what country feeling thermometer data can teach us about the drivers of American and Western European foreign policy

This is the final version. Available on open access from Taylor & Francis via the DOI in this recordReplication data is available on the first authors' Harvard dataverse page.While the existence of a ‘Democratic Peace’ (DP) is widely accepted, the various DP theories that seek to explain why democracies rarely fight one another are highly contested. A ‘commercial/capitalist peace’ counterargument maintains that the relationship between democratic politics and peace is spurious: the actual driver is greater trade among democracies. Meanwhile, Realists counter that it is alliances among democratic states, not their democratic nature, that causes peace among them. This research note utilizes novel country feeling thermometer data to explore the debate’s micro-foundations: the underlying drivers of international amity and enmity among democratic citizens in the US, UK, France, and Germany. Utilizing Freedom House and other quantitative measures of freedom, trade, military strength, and racial and cultural difference, it pits the micro-foundations of the DP against its rivals to explain attitude formation among a group of Western democratic publics. Given the resurgence of authoritarianism around the world today, a better understanding of the role of regime type in shaping public opinion – and subsequently war and peace – is urgently needed