Infrarenal aortic dimensions in siblings of patients with infrarenal abdominal aortic aneurysm or aortoiliac occlusive disease

OBJECTIVE: To compare the dimensions of the infrarenal aorta and the prevalence of undiagnosed infrarenal abdominal aortic aneurysms in the siblings of patients operated on for either infrarenal abdominal aortic aneurysm or aortoiliac occlusive disease. DESIGN: Prospective screening study. SETTING: University hospital, Finland. SUBJECTS: 220 siblings of patients operated for either abdominal aortic aneurysm or aortoiliac occlusive disease. INTERVENTIONS: Abdominal aortic ultrasound. MAIN OUTCOME MEASURES: Anteroposterior and transversal diameters of infrarenal and suprarenal aorta. RESULTS: There was a group of 5 siblings (4 men and 1 woman, aged 59 years or more) among the aneurysm patients who had a disposition to infrarenal aneurysm formation defined as a dilatation of 30 mm or more. This contrasted with none among the siblings of the patients with aortoiliac occlusive disease (p = 0.07, 95% confidence interval 0.49 to 165.3). The two factors affecting the diameter of the infrarenal aorta were age and sex. The aortic dimensions tended to be bigger in the siblings of the aneurysm patients but the differences were not significant. The ratio of infrarenal to suprarenal diameter was bigger in the siblings of the aneurysm patients also after excluding the cases with detected dilatations (p = 0.05) and in the multivariate analysis the only factor explaining this difference was the type of the disease of the proband. CONCLUSIONS: The screening of male siblings (over 55 years old) of patients with infrarenal abdominal aortic aneurysms might be justified.     

An Introduction to Variational Methods for Graphical Models

This paper presents a tutorial introduction to the use of variational methods for inference and learning in graphical models (Bayesian networks and Markov random fields). We present a number of examples of graphical models, including the QMR-DT database, the sigmoid belief network, the Boltzmann machine, and several variants of hidden Markov models, in which it is infeasible to run exact inference algorithms. We then introduce variational methods, which exploit laws of large numbers to transform the original graphical model into a simplified graphical model in which inference is efficient. Inference in the simpified model provides bounds on probabilities of interest in the original model. We describe a general framework for generating variational transformations based on convex duality. Finally we return to the examples and demonstrate how variational algorithms can be formulated in each case.     

Thermal detection of ESR on spin-polarized hydrogen: Study of surface recombination

We introduce a new method for the detection of electron-spin resonance in spin-polarized atomic hydrogen gas (H). Instead of observing the microwave power absorbed in the ESR transition, we monitor the recombination heat deposited by ESR-induced spin-up atoms (H) onto a liquid-helium coated carbon bolometer. The signal from this sensor reproduces well the ESR absorption lineshape registered by our 128 GHz homodyne spectrometer. Using the recombination detection we have achieved a density detection limit of n=3·10¹⁰ atoms/cm³ for 0.2 nW microwave power incident on the resonant cavity at the temperature T=150 mK. We have studied the decay rate of recombination heat absorbed by the bolometer after an ESR excitation pulse and the dependence of this rate on T, n and nuclear polarization of the H sample. The bolometer signal is found to be related mainly to second-order H + H recombination to ortho-H₂ on the surfaces of the sample cell. From the signals we have determined the rate constant K _bc ^c =3.2(5)·10^–5T cm²/s·K^–1/2 in the interval from T=250 to 425 mK in a field of 4.5 T.     

Tree-based reparameterization framework for analysis of sum-product and related algorithms

We present a tree-based reparameterization (TRP) framework that provides a new conceptual view of a large class of algorithms for computing approximate marginals in graphs with cycles. This class includes the belief propagation (BP) or sum-product algorithm as well as variations and extensions of BP. Algorithms in this class can be formulated as a sequence of reparameterization updates, each of which entails refactorizing a portion of the distribution corresponding to an acyclic subgraph (i.e., a tree, or more generally, a hypertree). The ultimate goal is to obtain an alternative but equivalent factorization using functions that represent (exact or approximate) marginal distributions on cliques of the graph. Our framework highlights an important property of the sum-product algorithm and the larger class of reparameterization algorithms: the original distribution on the graph with cycles is not changed. The perspective of tree-based updates gives rise to a simple and intuitive characterization of the fixed points in terms of tree consistency. We develop interpretations of these results in terms of information geometry. The invariance of the distribution, in conjunction with the fixed-point characterization, enables us to derive an exact expression for the difference between the true marginals on an arbitrary graph with cycles, and the approximations provided by belief propagation. More broadly, our analysis applies to any algorithm that minimizes the Bethe free energy. We also develop bounds on the approximation error, which illuminate the conditions that govern their accuracy. Finally, we show how the reparameterization perspective extends naturally to generalizations of BP (e.g., Kikuchi (1951) approximations and variants) via the notion of hypertree reparameterization.     

Technical control of nanoparticle emissions from desktop 3D printing

Material extrusion (ME) desktop 3D printing is known to strongly emit nanoparticles (NP), and the need for risk management has been recognized widely. Four different engineering control measures were studied in real-life office conditions by means of online NP measurements and indoor aerosol modeling. The studied engineering control measures were general ventilation, local exhaust ventilation (LEV), retrofitted enclosure, and retrofitted enclosure with LEV. Efficiency between different control measures was compared based on particle number and surface area (SA) concentrations from which SA concentration was found to be more reliable. The study found out that for regular or long-time use of ME desktop 3D printers, the general ventilation is not sufficient control measure for NP emissions. Also, the LEV with canopy hood attached above the 3D printer did not control the emission remarkably and successful position of the hood in relation to the nozzle was found challenging. Retrofitted enclosure attached to the LEV reduced the NP emissions 96% based on SA concentration. Retrofitted enclosure is nearly as efficient as enclosure attached to the LEV (reduction of 89% based on SA concentration) but may be considered more practical solution than enclosure with LEV.     

Residential dampness problems and symptoms and signs of bronchial obstruction in young Norwegian children

To assess the role of dampness problems and house dust mite exposure in the development of bronchial obstruction in early life, a cohort of 3,754 children born in Oslo during 1992 and 1993 was followed for 2 yr. Bronchial obstruction was defined as two or more episodes with symptoms and signs of obstruction or one lasting 1 mo or more. A matched case-control study was carried out in 251 cases of bronchial obstruction (response rate: 98%) and their 251 paired controls. Information on home dampness problem(s), house dust mite exposure, and potential confounders was collected during home visits and by questionnaires. Dampness problems were confirmed in the homes of 27% of the cases and 14% of the controls, while a concentration of Dermatophagoides pteronyssinus allergens > 2 microg/g dust was found in the beds of 11 (4.5%) cases and three (1.2%) controls. In conditional logistic regression analysis controlling for potential confounders, confirmed dampness problems increased the risk of bronchial obstruction (adjusted odds ratio: 3.8; 95% confidence interval: 2.0-7.2). Exposure to D. pteronyssinus allergens > 2 microg/g dust increased the risk of bronchial obstruction (adjusted odds ratio: 2.8; 95% confidence interval: 0.7-11.7). Residential dampness problems in Oslo dwellings seem to increase symptoms and signs of bronchial obstruction in young children, apparently without increasing their exposure to house dust mites.     

The Office Environment Model: A Conceptual Analysis of the Sick Building Syndrome*

Abstract This paper examines the phenomenon sick building syndrome and related concepts, and proposes a theoretical model, the Office Environment Model, to explain the relationship between office environment and health. The sick building syndrome should be thought of as a figurative concept of everyday language, rather than as a single disease entity. This is because the phenomenon consists of several types of relations between different environmental determinants and health. Based on Popper's framework of three worlds, the model divides the office environment ontologically into physical and social, and the health outcomes into physiological and psychological. The outcome is further categorized into two dimensions: anatomic site (eyes, respiratory tract, skin, and central nervous system), and hypothesized underlying mechanism (mechanical irritation and inflammation, immunological reaction, toxicity, infection, and environmental psychological stress). The model stipulates the following types of causal relations. The physical environment causes physical and psychological effects via physiological and/or psychological processes. The social environment causes physical and psychological effects via psychological processes. The physical and social environment may have synergistic effects, and constitutional factors such as gender and atopy are additional determinants of the outcomes, as well as possible modifiers of the relations between environment and health. To understand the health effects of the office environment, it is necessary to focus separately on different determinant-outcome relations, bearing in mind that the different determinants affect human health concurrently and sometimes the effects may be synergistic.     

Emission Rates Due to Indoor Activities: Indoor Aerosol Model Development,Evaluation, and Applications

This study presents an indoor aerosol model based on size-resolved and multi-compartment approach. The current indoor aerosol model is also developed with a semi-empirical technique to estimate the emission rates due to indoor sources of aerosol particles. We present in this study a methodology to predict and estimate the best-fit input parameters for the current indoor aerosol model. The performance of the current indoor aerosol model in its single-compartment form was evaluated against previously measured indoor-outdoor aerosol data sets from an office room with mechanical ventilation and a family house with natural ventilation. The indoor aerosol model simulations show that the current methodology used to predict the best-fit input parameters to the indoor aerosol model is efficient. As expected, the penetration factor, aerosol particle deposition, and ventilation rate are the most important parameters in the indoor-outdoor relationship of aerosol particles transport. The emission rate analysis showed that fine aerosol particles production was as high as 26 particle/cm ³ s during wood burning in a fireplace. The emission rate was about eight times this value during grilling in a fireplace and sauna heating. Indoor activities take place in another room may significantly increase the aerosol particle concentrations in other rooms in the building. Therefore, it is recommended to use extra air cleaners in houses to reduce the number concentrations of emitted aerosol particles. The quantitative and qualitative results obtained by the current indoor aerosol model in this study are building and condition specific. Applying the current model to a broad range of conditions and previously measured indoor-outdoor aerosol data sets provides better understanding of aerosol particle characteristics indoors, especially regarding the aerosol particles produced during different indoor activities.