Dynamic line integral convolution for visualizing electromagnetic phenomena

Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2001.Includes bibliographical references (leaves 62-63).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Vector field visualization is a useful tool in science and engineering, giving us a powerful way of understanding the structure and evolution of the field. A fairly recent technique called Line Integral Convolution (LIC) has improved the level of detail that can be visualized by convolving a random input texture along the streamlines in the vector field. This thesis extends the technique to time-varying vector fields, where the motion of the field lines is specified explicitly via another vector field. The sequence of images generated is temporally coherent, clearly showing the evolution of the fields over time, while at the same time each individual image retains the characteristics of the LIC technique. This thesis describes the new technique, entitled Dynamic Line Integral Convolution, and explores its application to experiments in electromagnetism.by Andreas Sundquist.S.B.M.Eng.and S.B

Bacterial flora-typing with targeted, chip-based Pyrosequencing

<p>Abstract</p> <p>Background</p> <p>The metagenomic analysis of microbial communities holds the potential to improve our understanding of the role of microbes in clinical conditions. Recent, dramatic improvements in DNA sequencing throughput and cost will enable such analyses on individuals. However, such advances in throughput generally come at the cost of shorter read-lengths, limiting the discriminatory power of each read. In particular, classifying the microbial content of samples by sequencing the < 1,600 bp 16S rRNA gene will be affected by such limitations.</p> <p>Results</p> <p>We describe a method for identifying the phylogenetic content of bacterial samples using high-throughput Pyrosequencing targeted at the 16S rRNA gene. Our analysis is adapted to the shorter read-lengths of such technology and uses a database of 16S rDNA to determine the most specific phylogenetic classification for reads, resulting in a weighted phylogenetic tree characterizing the content of the sample. We present results for six samples obtained from the human vagina during pregnancy that corroborates previous studies using conventional techniques.</p> <p>Next, we analyze the power of our method to classify reads at each level of the phylogeny using simulation experiments. We assess the impacts of read-length and database completeness on our method, and predict how we do as technology improves and more bacteria are sequenced. Finally, we study the utility of targeting specific 16S variable regions and show that such an approach considerably improves results for certain types of microbial samples. Using simulation, our method can be used to determine the most informative variable region.</p> <p>Conclusion</p> <p>This study provides positive validation of the effectiveness of targeting 16S metagenomes using short-read sequencing technology. Our methodology allows us to infer the most specific assignment of the sequence reads within the phylogeny, and to identify the most discriminative variable region to target. The analysis of high-throughput Pyrosequencing on human flora samples will accelerate the study of the relationship between the microbial world and ourselves.</p

Neighbourhood socioeconomic status and cardiovascular risk factors: a multilevel analysis of nine cities in the Czech Republic and Germany

Background: Previous studies have shown that deprived neighbourhoods have higher cardiovascular mortality and morbidity rates. Inequalities in the distribution of behaviour related risk factors are one possible explanation for this trend. In our study, we examined the association between cardiovascular risk factors and neighbourhood characteristics. To assess the consistency of associations the design is cross-national with data from nine industrial towns from the Czech Republic and Germany. Methods: We combined datasets from two population based studies, one in Germany ('Heinz Nixdorf Recall (HNR) Study'), and one in the Czech Republic ('Health, Alcohol and Psychosocial Factors in Eastern Europe (HAPIEE) Study'). Participation rates were 56% in the HNR and 55% in the HAPIEE study. The subsample for this particular analysis consists of 11,554 men and women from nine German and Czech towns. Census based information on social characteristics of 326 neighbourhoods were collected from local administrative authorities. We used unemployment rate and overcrowding as area-level markers of socioeconomic status (SES). The cardiovascular risk factors obesity, hypertension, smoking and physical inactivity were used as response variables. Regression models were complemented by individual-level social status (education) and relevant covariates. Results: Smoking, obesity and low physical activity were more common in deprived neighbourhoods in Germany, even when personal characteristics including individual education were controlled for. For hypertension associations were weak. In the Czech Republic associations were observed for smoking and physical inactivity, but not for obesity and hypertension when individual-level covariates were adjusted for. The strongest association was found for smoking in both countries: in the fully adjusted model the odds ratio for 'high unemployment rate' was 1.30 [95% CI 1.02-1.66] in the Czech Republic and 1.60 [95% CI 1.29-1.98] in Germany. Conclusion: In this comparative study, the effects of neighbourhood deprivation varied by country and risk factor; the strongest and most consistent effects were found for smoking. Results indicate that area level SES is associated with health related lifestyles, which might be a possible pathway linking social status and cardiovascular disease. Individual-level education had a considerable influence on the association between neighbourhood characteristics and risk factors

Evaluation of the forces in the Älvsborg Suspension Bridge using the vibration method and analysis

Föreliggande rapport behandlar mätning och analys av krafter i Älvsborgsbron i Göteborgsom underlag för klassningsberäkning. Den metod som används för bestämning av krafternaär den s.k. vibrationsmetoden där konstruktionselement sätts i svängning och dessas egenfrekvenserbestäms med hjälp av accelerometrar. Med kända egenfrekvenser för t.ex. kablaroch hängare kan krafterna i dessa analyseras fram. Eftersom flera av de aktuella elementenhar egenskaper som inte är enkla att beskriva med hjälp av faktorer som geometriska mått,massa, styvhet och inspänningsförhållanden, har möda lagts ner på att använda så noggrannametoder som möjligt för att kunna bestämma krafter och kraftfördelning. Metoderna beskrivsi rapporten och resultat och noggrannhet diskuteras och bedöms.De resultat som presenteras beträffande krafter bedöms ha en så god noggrannhet som det f.n.går att analysera fram med idag kända någorlunda enkla metoder.QC 2011111

Gamla Årstabron, Utvärdering av verkningssätt hos betongvalv genom mätning och FEM-modellering – Etapp 1

QC 2011111

Full Scale Tests and Structural Evaluation of Soil-Steel Flexible Culverts for High-Speed Railways

In this paper, results from full-scale tests on a corrugated soil-steel flexible culvert for railway traffic are presented. The bridge was instrumented with strain gauges, accelerometers and displacement gauges, measuring the response from passing trains. The aim of the measurement campaign was to gain knowledge of the dynamic behaviour due to train induced vibrations, both of the bridge structure and the overlying railway embankment. From the measured data, the load distribution and soil-stiffness can be estimated. The results also serve as input for calibration of numerical models that are used for predicting the behaviour due to high-speed trains.QC 2012061

Risk of incident and fatal melanoma in individuals with a family history of incident or fatal melanoma or any cancer.

Background: A family history of melanoma is associated with an increased risk of melanoma and probably of other, discordant cancers. Limited data are available on familial mortality in melanoma. If fatal forms of melanoma were associated with fatal forms of melanoma or of some other cancers, only studies on familial mortality rather than on familial incidence might be able to detect them. Furthermore, estimates on familial aggregation based on mortality are free from bias of overdiagnosis. Objectives: The aim of this study was the estimation of familial aggregation of concordant melanoma and of melanoma and any other cancers both based on incidence and mortality. Methods: We used the nation-wide Swedish Family-Cancer Database to calculate standardized incidence ratios (SIR) for incident melanoma for relatives of any cancer patients and standardized mortality ratios (SMR) for death in melanoma for relatives of individuals who died from any other cancer. Similar risks were determined for any common cancer when relatives were affected by melanoma. Results: For concordant melanoma, familial incidence equalled familial mortality, SIR=SMR. Familial clustering (SIRs increased) of melanoma and esophageal, colorectal, breast, prostate, kidney, nervous system and connective tissue cancers and myeloma and leukaemia was observed. The SMRs for pancreatic and nervous system cancers were increased in relatives whose parents had died from melanoma. Conclusions: These data should encourage search for fatal subtypes of familial cancer, which may eventually have clinical implications

Familial Mortality and Familial Incidence in Cancer.

PURPOSE An overwhelming majority of data on familial risk in cancer is based on incident cancer, whereas familiality in cancer mortality is largely unknown. If fatal form of cancer was a highly familial subtype, then familial risk for mortality may exceed that of incidence, which would be particularly relevant for clinical decision making and counseling. PATIENTS AND METHODS The individuals in the nationwide Swedish Family-Cancer Database were classified according to family history of fatal and nonfatal cancer. Familial risks of incident and fatal concordant cancer were calculated for offspring based on their parental family history using a Cox model with hazard ratio (HR); offspring without family history were the reference. Results Most HRs for offspring incident cancers were somewhat higher for fatal compared with nonfatal parental family history. For breast (HR, 1.87 fatal v 1.66 nonfatal; P < .001) and prostate (HR, 2.30 fatal v 1.84 nonfatal; P < .001) cancers, 51.0% of patients with familial breast cancer and 56.6% of patients with prostate cancer had fatal family history. HRs for death in offspring according to a fatal compared with nonfatal family history were significantly increased for colorectal (HR, 1.76 v 1.47, respectively; P = .02), breast (HR, 1.97 v 1.51, respectively; P = .002), and prostate (HR, 2.03 v 1.59, respectively; P = .002) cancers. TNM classification did not seem to differ between the family histories. We showed also that an overwhelming proportion of offspring were diagnosed after the parental death. CONCLUSION Familial breast, prostate, and colorectal cancers might have a yet unidentified genetic component associated with poorer survival. It may be useful to record survival data in family history records