6,865 research outputs found
Casimir self-energy of a \delta-\delta' sphere
We extend previous work on the vacuum energy of a massless scalar field in
the presence of singular potentials. We consider a single sphere denoted by the
so-called "delta-delta prime" interaction. Contrary to the Dirac delta
potential, we find a nontrivial one-parameter family of potentials such that
the regularization procedure gives an unambiguous result for the Casimir
self-energy. The procedure employed is based on the zeta function
regularization and the cancellation of the heat kernel coefficient a_2. The
results obtained are in agreement with particular cases, such as the Dirac
delta or Robin and Dirichlet boundary conditions
Colloids in light fields: particle dynamics in random and periodic energy landscapes
The dynamics of colloidal particles in potential energy landscapes have
mainly been investigated theoretically. In contrast, here we discuss the
experimental realization of potential energy landscapes with the help of light
fields and the observation of the particle dynamics by video microscopy. The
experimentally observed dynamics in periodic and random potentials are compared
to simulation and theoretical results in terms of, e.g. the mean-squared
displacement, the time-dependent diffusion coefficient or the non-Gaussian
parameter. The dynamics are initially diffusive followed by intermediate
subdiffusive behaviour which again becomes diffusive at long times. How
pronounced and extended the different regimes are, depends on the specific
conditions, in particular the shape of the potential as well as its roughness
or amplitude but also the particle concentration. Here we focus on dilute
systems, but the dynamics of interacting systems in external potentials, and
thus the interplay between particle-particle and particle-potential
interactions, is also mentioned briefly. Furthermore, the observed dynamics of
dilute systems resemble the dynamics of concentrated systems close to their
glass transition, with which it is compared. The effect of certain potential
energy landscapes on the dynamics of individual particles appears similar to
the effect of interparticle interactions in the absence of an external
potential
Trends in Cause of Death among Puerto Rican and United States Multiple Myeloma Patients
Background/Objective: Multiple myeloma (MM) is an incurable, yet treatable, cancer of plasma cells. Due to recent improvements in treatment, people diagnosed with MM have been living longer, and other co-morbid conditions may be of increasing importance. This study examines temporal trends in specific causes of death among MM patients in Puerto Rico (PR) and United States (US).
Methods: We analyzed primary cause of death among all incident MM cancer cases recorded in the Puerto Rico Central Cancer Registry (PRCCR) (n=3,018) and the US Surveillance, Epidemiology, and End Results Program (SEER) (n=67,733) between 1987-2013, overall and by follow-up time, age, and sex. We calculated the cumulative incidence of death due to seven selected causes and analyzed age-adjusted mortality trends by MM and other causes using joinpoint regression.
Results: MM accounted for 71.7% and 71.3% of all reported deaths in PR and US, respectively, among people diagnosed with MM. In PR, the proportion of patients that died from MM decreased with increasing follow-up time since diagnosis (72.3% of deaths with ≤2 years vs 65.6% with \u3e5 years of follow-up) and the proportion of patients who died from circulatory (4.6% vs 9.0%) and respiratory system (3.7% vs 5.0%) diseases increased slightly. A similar trend of decreasing MM deaths with follow-up time was observed in the US (73.2% of deaths with ≤2 years vs 66.5% with \u3e5 years of follow-up). Joinpoint regression showed a decreasing trend in MM mortality in the US (APC1987-2007=-2.8%, and APC2007-2013=-18.4%) and a similar, though somewhat weaker, trend in PR (APC1987-2013=-2.73).
Conclusion: In both PR and the US, people diagnosed with MM are still more likely to die from MM than from another cause. However, a decrease in MM mortality is evident, particularly in more recent years, but this decrease is lower in Puerto Rico
Out-of-pocket health expenditures in Colombia: a systematic review
Objectives
To review the evidence of out-of-pocket (OOPE) and catastrophic expenditures (CHE) in health in Colombia.
Methods
Systematic review of the literature (SLR). Searches were performed in PubMed, Scopus, Scielo and Google Scholar. We used the MESH terms: out-of-pocket, catastrophic health expenditure, health and Colombia. We included cost description or cost analysis studies. Cost-effectiveness analysis of health technologies and qualitative studies were excluded. Data about period of analysis, type of study, costing perspective, OOPE, and CHE were extracted. Studies were classified as macroeconomic, microeconomic, and diseases analysis. All costs were indexed to 2018 and reported in Colombian pesos (COP)
Data intimacies: building infrastructures for intensified embodied encounters with air pollution
The air is, in many urban contexts, polluted. Governments and institutions monitor particles and gas concentrations to better understand how they perform in the light of air quality guidance and legislation, and to make predictions in terms of future environmental health targets. The visibility of these data is considered crucial for citizens to manage their own health, and a proliferation of new informational forms and apps have been created to achieve this. And yet, beyond everyday decisions (when to use a mask or when to do sports outdoors), it is not clear whether current methods of engaging citizens produce behavioural change or stronger citizen engagement with air pollution. Drawing on the design, construction and ethnography of an urban infrastructure to measure, make visible and remediate particulate matter (PM2.5) through a water vapour cloud that we installed at the Seoul Biennale of Architecture and Urbanism 2017, we examined the effects and affects of producing a public space that allows for physical interaction with data. In Yellow Dust, data from PM2.5 were translated into mist, the density of which was responsive to the number of particles suspended in the air. Data were made sense/ible by the changing conditions of the air surrounding the infrastructure, which can be experienced in embodied, collective and relational ways: what we call ‘molecular intimacies’. By reflecting on how the infrastructure facilitated new modes of sensing data, we consider how ‘data intimacies’ can re-specify action by producing different forms of engagement with air pollution
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