Exploratory topic modeling with distributional semantics

As we continue to collect and store textual data in a multitude of domains, we are regularly confronted with material whose largely unknown thematic structure we want to uncover. With unsupervised, exploratory analysis, no prior knowledge about the content is required and highly open-ended tasks can be supported. In the past few years, probabilistic topic modeling has emerged as a popular approach to this problem. Nevertheless, the representation of the latent topics as aggregations of semi-coherent terms limits their interpretability and level of detail. This paper presents an alternative approach to topic modeling that maps topics as a network for exploration, based on distributional semantics using learned word vectors. From the granular level of terms and their semantic similarity relations global topic structures emerge as clustered regions and gradients of concepts. Moreover, the paper discusses the visual interactive representation of the topic map, which plays an important role in supporting its exploration.Comment: Conference: The Fourteenth International Symposium on Intelligent Data Analysis (IDA 2015

Do changes in health reveal the possibility of undiagnosed pancreatic cancer? Development of a risk-prediction model based on healthcare claims data.

Background and objectiveEarly detection methods for pancreatic cancer are lacking. We aimed to develop a prediction model for pancreatic cancer based on changes in health captured by healthcare claims data.MethodsWe conducted a case-control study on 29,646 Medicare-enrolled patients aged 68 years and above with pancreatic ductal adenocarcinoma (PDAC) reported to the Surveillance Epidemiology an End Results (SEER) tumor registries program in 2004-2011 and 88,938 age and sex-matched controls. We developed a prediction model using multivariable logistic regression on Medicare claims for 16 risk factors and pre-diagnostic symptoms of PDAC present within 15 months prior to PDAC diagnosis. Claims within 3 months of PDAC diagnosis were excluded in sensitivity analyses. We evaluated the discriminatory power of the model with the area under the receiver operating curve (AUC) and performed cross-validation by bootstrapping.ResultsThe prediction model on all cases and controls reached AUC of 0.68. Excluding the final 3 months of claims lowered the AUC to 0.58. Among new-onset diabetes patients, the prediction model reached AUC of 0.73, which decreased to 0.63 when claims from the final 3 months were excluded. Performance measures of the prediction models was confirmed by internal validation using the bootstrap method.ConclusionModels based on healthcare claims for clinical risk factors, symptoms and signs of pancreatic cancer are limited in classifying those who go on to diagnosis of pancreatic cancer and those who do not, especially when excluding claims that immediately precede the diagnosis of PDAC

On the Significance of the Die Design for Electromagnetic Sheet Metal Forming

Electromagnetic Forming is a high speed forming process using a pulsed magnetic field to form metals with high electrical conductivity, such as copper or aluminium alloys. During the process, typical pressure peaks up to 200 MPa and velocities in the range of 300 m/s can be achieved. As significant process parameters the pressure maximum as well as the local and temporal varying pressure distribution have been identified. As of a certain drawing depth and distance between workpiece and tool coil, the pressure does not act any longer on the workpiece, but the deformation process is still driven by the inertia forces. It has been found out that the velocity distribution within the sheet metal during the forming stages as well as at the time of impact with a die significantly influences the forming result. Additionally, a special undesired effect is the rebound behaviour of flat workpiece areas being in contact with the die. To investigate the influence capability of the die concerning this effect, the parameters stiffness and damping properties have been varied by means of simulation using a mechanical substitute model

Aspects of Die Design for the Electromagnetic Sheet Metal Forming Process

Within the electromagnetic sheet metal forming process, workpiece velocities of more than 300m/s can occur, causing typical effects when forming into a die, which will be described and discussed in the present paper. These effects make numerous demands regarding the die design. In order to analyze these requirements, experimental as well as numerical investigations have been carried out. Thereby, special focus is put on the possibilities to accomplish these requirements, which are discussed in the following

Seasonality of the pelagic ichthyofauna in the Lazarev Sea

The Southern Ocean is characterised by an extreme seasonality which is best observed by the huge variation in sea ice extent. It expands from a minimum extent of 4 million square kilometres in February to a maximum of 19 million square kilometres in September and influences the physics and chemistry of the surface layers and the corresponding life histories of organisms. Reduced light condition and sea ice cover have a pronounced impact on primary production and predation risk in the pelagic zone. Here we present comparison of the distribution of fish in the Lazarev Sea correlated to biotic an abiotic features. Samples were collected in the framework of three LAKRIS (Lazarev Krill Study) campaigns onboard RV Polarstern during summer, fall and winter. The main focus was on factors affecting krill distribution. As such a wide variety of biotic and abiotic measures were made. Fish and fish larvae were collected from trawls from the upper 200m during both seasons. Both during summer and winter larval composition was dominated by pre-metamorphic Electrona antarctica and Notolepis coatsi. Post-metamorphic E. antarctica showed a pronounced seasonal difference in occurrence

Novel Layers for Dies Used in Electromagnetic Sheet Metal Forming Processes

Due to the high forming velocities during electromagnetic sheet metal forming processes, a high impact force acts between workpiece and die. Here, the die surface sustains high damages shown by high wear and galling of the workpiece on the die surface. To enhance the die lifetime, a novel coating concept based on the PVD (physical vapour deposition) process was developed. In doing so, the hardness and the toughness of the designed layers were varied and adjusted to the demands of AlMg-sheet forming process

DNA transport by a micromachined Brownian ratchet device

We have micromachined a silicon-chip device that transports DNA with a Brownian ratchet that rectifies the Brownian motion of microscopic particles. Transport properties for a DNA 50mer agree with theoretical predictions, and the DNA diffusion constant agrees with previous experiments. This type of micromachine could provide a generic pump or separation component for DNA or other charged species as part of a microscale lab-on-a-chip. A device with reduced feature size could produce a size-based separation of DNA molecules, with applications including the detection of single nucleotide polymorphisms.Comment: Latex: 8 pages, 4 figure

Principles for the post-GWAS functional characterisation of risk loci

Several challenges lie ahead in assigning functionality to susceptibility SNPs. For example, most effect sizes are small relative to effects seen in monogenic diseases, with per allele odds ratios usually ranging from 1.15 to 1.3. It is unclear whether current molecular biology methods have enough resolution to differentiate such small effects. Our objective here is therefore to provide a set of recommendations to optimize the allocation of effort and resources in order maximize the chances of elucidating the functional contribution of specific loci to the disease phenotype. It has been estimated that 88% of currently identified disease-associated SNP are intronic or intergenic. Thus, in this paper we will focus our attention on the analysis of non-coding variants and outline a hierarchical approach for post-GWAS functional studies