Danish Data Set Research Articles

Robust and validated models to predict high risk of non-sentinel node metastases in breast cancer patients with micrometastases or isolated tumor cells in the sentinel node

Background. Benefit from axillary lymph node dissection in sentinel node positive breast cancer patients is under debate. Based on data from 1820 Danish breast cancer patients operated in 2002–2008, we have developed two models to predict high risk of non-sentinel node metastases when micrometastases or isolated tumor cells are found in sentinel node. The aim of this study was to validate these models in an independent Danish dataset. Material and methods. We included 720 breast cancer patients with micrometastases and 180 with isolated tumor cells in sentinel node operated in 2009–2010 from the Danish Breast Cancer Cooperative Group database. Accuracy of the models was tested in this cohort by calculating area under the receiver operating characteristic curve (AUC) as well as sensitivity and specificity. Results. AUC for the model for patients with micrometastases was comparable to AUC in the original cohort: 0.63 and 0.64, respectively. The sensitivity and specificity for predicting risk of non-sentinel node metastases over 30% was 0.36 and 0.81, respectively, in the validation cohort. AUC for the model for patients with isolated tumor cells decreased from 0.73 in the original cohort to 0.60 in the validation cohort. When dividing patients with isolated tumor cells into high and low risk of non-sentinel node metastases according to number of risk factors present, 37% in the high-risk group had non-sentinel node metastases. Specificity and sensitivity was 0.48 and 0.88, respectively, in the validation cohort when using this cut-point. Conclusion. In this independent dataset, the model for patients with micrometastases was robust with accuracy similar to the original cohort, while the model for patients with isolated tumor cells was less accurate. The models may be used to identify patients where axillary lymph node dissection should still be considered.

A bias-reduced estimator for the mean of a heavy-tailed distribution with an infinite second moment

We use bias-reduced estimators of high quantiles of heavy-tailed distributions, to introduce a new estimator for the mean in the case of infinite second moment. The asymptotic normality of the proposed estimator is established and checked in a simulation study, by four of the most popular goodness-of-fit tests. The accuracy of the resulting confidence intervals is evaluated as well. We also investigate the finite sample behavior and compare our estimator with some versions of Peng's estimator of the mean (namely those based on Hill, t-Hill and Huisman et al. extreme value index estimators). Moreover, we discuss the robustness of the tail index estimators used in this paper. Finally, our estimation procedure is applied to the well-known Danish fire insurance claims data set, to provide confidence bounds for the means of weekly and monthly maximum losses over a period of 10 years.

The use of wildcards in forensic DNA database searches

Forensic genetic databases contain millions of DNA profiles worldwide. An allelic drop-out at a heterozygous locus (two different alleles) erroneously results in an observed homozygous profile. To guard against this, wildcards are induced for homozygous profiles. The wildcard represents any allele including the observed allele.In this paper, theoretical expressions for the number of matching loci are derived, results shown from a Danish dataset with more than 50,000 DNA profiles and simulations used to link homozygosity with the drop-out probability, which best mimics wildcard matching.

Infectious risk factors for individual postweaning multisystemic wasting syndrome (PMWS) development in pigs from affected farms in Spain and Denmark

Two prospective longitudinal studies in 13 postweaning multisystemic wasting syndrome (PMWS)-affected farms from Spain (n=3) and Denmark (n=10) were performed. Blood samples from pigs were longitudinally collected from 1st week until the occurrence of the PMWS outbreak. Wasted and healthy age-matched pigs were euthanized, necropsied and histopathologically characterised. PMWS diagnosis was confirmed by means of lymphoid lesions and detection of porcine circovirus type 2 (PCV2) in these tissues by in situ hybridization or immunohistochemistry. Serological analyses were performed in longitudinally collected serum samples to detect antibodies against, PCV2, porcine reproductive and respiratory syndrome virus (PRRSV), porcine parvovirus (PPV), swine influenza virus (SIV) and Lawsonia intracellularis (law), Mycoplasma hyopneumoniae, Aujeszky’s disease virus (ADV) and Salmonella spp. A Cox proportional hazards model was used to investigate the simultaneous effects of seroconversion and maternal immunity against the studied pathogens. Results showed that high levels of maternal immunity against PCV2 had a protecting effect in farms from both countries. Moreover, for the Danish dataset, seroconversion against law had an overall protecting effect, but for animals with very low levels of maternal antibody levels against this pathogen, the effect appeared neutral or aggravating. Otherwise, for the Spanish dataset, maternal immunity against PPV and PRRSV gave protective and aggravating effects, respectively. In conclusion, the present study reflects the complex interaction among different pathogens and their effects in order to trigger PMWS in PCV2 infected pigs.

Gene expression profiles in stages II and III colon cancers: application of a 128-gene signature

A 128-gene signature has been proposed to predict outcome in patients with stages II and III colorectal cancers. In the present study, we aimed to reproduce and validate the 128-gene signature in external and independent material. Gene expression data from the original material were retrieved from the Gene Expression Omnibus (GEO) (n = 111) in addition to a Danish data set (n = 37). All patients had stages II and III colon cancers. A Prediction Analysis of Microarray classifier, based on the 128-gene signature and the original training set of stage I (n = 65) and stage IV (n = 76) colon cancers, was reproduced. The stages II and III colon cancers were subsequently classified as either stage I-like (good prognosis) or stage IV-like (poor prognosis) and assessed by the 36months cumulative incidence of relapse. In the GEO data set, results were reproducible in stage III, as patients predicted to be stage I-like had a significant lower risk of relapse than patients predicted as stage IV-like (P = 0.04, Gray test). Results were not reproducible in stage II patients (P > 0.05, Gray test). In the Danish data set, two of four stage III patients with relapse were correctly predicted as stage IV-like, and the remaining patients were predicted as stage I-like and unclassifiable, respectively. Stage II patients could not be stratified. The 128-gene signature showed reproducibility in stage III colon cancer, but could not predict recurrence in stage II. Individual patient predictions in an independent Danish material were unsatisfactory. Additional validation in larger cohorts is warranted.

Analysis of matches and partial-matches in a Danish STR data set

AbstractOver the recent years, the national databases of STR profiles have grown in size due to the success of forensic DNA analysis in solving crimes. The accumulation of DNA profiles implies that the probability of a random match or near match of two randomly selected DNA profiles in the database increases.We analysed 53,295 STR profiles from individuals investigated in relation to crime case investigations at the Department of Forensic Medicine, Faculty of Health Sciences, University of Copenhagen, Denmark. Incomplete STR profiles (437 circa 0.8% of the total), 48 redundant STR profiles from monozygotic twins (0.09%), 6 redundant STR profiles of unknown cause and 1283 STR profiles from repeated testing of individuals were removed leaving 51,517 complete 10 locus STR profiles for analysis. The number corresponds to approximately 1% of the Danish population. We compared all STR profiles to each other, i.e. 1.3×109 comparisons.With these large number of comparisons, it is likely to observe DNA profiles that coincide on many loci, which has concerned some commentators and raised questions about “overstating” the power of DNA evidence. We used the method of Weir [11,12] and Curran et al. [3] to compare the observed and expected number of matches and near matches in the data set. We extended the methods by computing the covariance matrix of the summary statistic and used it for the estimation of the identical-by-descent parameter, θ. The analysis demonstrated a number of close relatives in the Danish data set and substructure. The main contribution to the substructure comes from close relatives. An overall θ-value of 1% compensated for the observed substructure, when close familial relationships were accounted for.

Evaluating the relationship between chemical exposure and cryptorchidism

One method for the evaluation of complex environmental and health datasets is the discrete mathematical method Hasse diagram technique based on partial orders. The introduced software program package is named PyHasse. In this paper we evaluate a possible human association between maternal exposure to organochlorine compounds used as pesticides and cryptorchidism among male children in Finland and Denmark. We identified differences in comparable and incomparable objects and quantified these differences by the software tool Similarity Analysis in the program PyHasse. Furthermore we interpreted the corresponding Hasse diagrams concerning chosen “striking objects”. We found the position of the chemicals AHCH (alpha-Hexachlorohexane), CHCE (cis-Heptachloroepoxide), DIEL (Dieldrin), and MIRE (Mirex) has some influence on the differentiation of the Hasse diagrams and hence of each two datasets analyzed. The largest disparities can be observed when we compare the Finnish and Danish datasets concerning cryptorchidism. The disparities are demonstrated in the corresponding Hasse diagrams.

Political Attention and Public Policy: A Study of How Agenda Setting Matters

Political science research on agenda setting has been focused on how and why political agendas change over time. This article addresses the different but equally important question about how agenda setting actually matters to the policy outputs of national policy making. Do changes in the political agenda foreshadow changes in public policies? And does the effect of changes in the political agenda depend upon the policy preferences expressed by the mass public? Integrating research on policy agendas with well-established ideas about re-election-oriented representation, this article offers a new approach to the study of such agenda effects. Furthermore, it demonstrates the empirical validity of this approach using a Danish dataset of public opinion, public policy and the national political agenda spanning a quarter of a century and covering several different issues.

Timing of Increased Autistic Disorder Cumulative Incidence

Autistic disorder (AD) is a severe neurodevelopmental disorder typically identified in early childhood. Both genetic and environmental factors are implicated in its etiology. The number of individuals identified as having autism has increased dramatically in recent years, but whether some proportion of this increase is real is unknown. If real, susceptible populations may have exposure to controllable exogenous stressors. Using literature AD data from long-term (approximately 10-year) studies, we determined cumulative incidence of AD for each cohort within each study. These data for each study were examined for a changepoint year in which the AD cumulative incidence first increased. We used data sets from Denmark, California, Japan, and a worldwide composite of studies. In the Danish, California, and worldwide data sets, we found that an increase in AD cumulative incidence began about 1988-1989. The Japanese study (1988-1996) had AD cumulative incidence increasing continuously, and no changepoint year could be calculated. Although the debate about the nature of increasing autism continues, the potential for this increase to be real and involve exogenous environmental stressors exists. The timing of an increase in autism incidence may help in screening for potential candidate environmental stressors.

Reduction of Asymmetric Information Through Corporate Governance Mechanisms – The Importance of Ownership Dispersion and Exposure toward the International Capital Market

ABSTRACTManuscript Type: EmpiricalResearch Question/Issue: The purpose of this study is to examine how differences in “ownership dispersion” and “exposure to the international capital market” affect the particular use of the corporate governance mechanisms “transparency” and “board independence” in listed companies.Research Findings/Insights: Our findings are based on a Danish dataset that includes 100 listed companies. We find that transparency is a more important corporate governance mechanism for companies with exposure to the international capital market, while differences in ownership dispersion do not affect the use of the transparency mechanism. In contrast, we find that board independence in the context of a two‐tier board member system is an important corporate governance mechanism for companies with widely dispersed ownership and not for companies with exposure to the international capital market.Theoretical/Academic Implications: The relationships identified in our study contribute to improved understanding of the contextual relationship between good corporate governance and the companies' choice of corporate governance mechanisms within a given corporate governance system. This is important in order to interpret inconsistencies in prior research findings and provide insight for the design of future studies into the seemingly endogenous nature of many corporate governance relationships.Practitioner/Policy Implications: The requirement to adhere to the “comply or explain rules” for corporate governance has become commonplace for listed companies. The study provides insight into valid reasons for differences in compliance. Regulators and other capital market participants should acknowledge that companies may differ in their use of corporate governance mechanisms for various reasons, including differences in ownership dispersion and exposure to the international capital market.

Within- and Cross-Firm Mobility and Earnings Growth

While it is well established that both promotions within firms and mobility across firms lead to significant earnings progression, little is known about the interaction between these types of mobility. Exploiting a large Danish panel data set and controlling for unobserved individual heterogeneity, we show that cross-firm moves at the non-executive level provide sizeable short-run gains (similar to the effect of a promotion), consistent with the existing literature. These gains, however, appear modest when compared with the persistent impact on earnings growth of promotions (either within or across firms) and subsequent mobility at a higher hierarchy level.

Marriage and the city: Search frictions and sorting of singles

This paper develops and tests a model where cities play an important role as marriage markets. The idea is simple. Cities are dense areas where singles can meet more potential partners than in rural areas. To enjoy those benefits, they are willing to pay a premium in terms of higher housing prices. Once married, the benefits from meeting more potential partners vanish and married couples move out of the city. Attractive singles benefit most from a dense market and are therefore more likely to move to the city. Those predictions are tested and confirmed with a unique Danish data set.

Reduction of Asymmetric Information Through Corporate Governance Mechanisms - The Importance of Ownership Dispersion and International Orientation

Manuscript Type: Empirical Research Question/Issue: Is the reduction of asymmetric information through Corporate Governance mechanisms more important for some listed companies than for others? The purpose of this study is to examine how differences in and affect the particular use of the Corporate Governance mechanisms and in listed companies. Research Findings/Insights: Our findings are based on a Danish dataset which includes 100 listed companies. We find that transparency is a more important Corporate Governance mechanism for companies with an international orientation, while differences in ownership dispersion do not affect the use of this mechanism. In contrast, we find that board independence is a more important Corporate Governance mechanism for companies with dispersed ownership while international orientation has less importance. Theoretical/Academic Implications: The study contributes to an improved understanding of the circumstantial relationship between good Corporate Governance and good corporate performance. This is important in order to interpret differences in prior research findings and provide insight for the design of future studies of the seemingly endogenous nature of many Corporate Governance relationships. Practitioner/Policy Implications: The requirement to adhere to the comply or explain rules for Corporate Governance has become commonplace for listed companies. The study provides insight into valid reasons for differences in compliance. Regulators and other capital market participants should acknowledge that companies may differ in their use of Corporate Governance mechanisms for various reasons, including differences in ownership dispersion and international orientation.

Does an Increase in Unemployment Income Lead to Longer Unemployment Spells? Evidence using Danish Unemployment Assistance Data

Danish unemployment assistance depends on age; it increases by 70% when unemployed individuals turn 25. This feature is used to identify the impact of income on the unemployment-to-employment hazard rate. A mixed proportional hazard framework based on a 10% representative Danish registry data set is used. The results indicate that the income effect for females is negative and significant, corresponding to an income elasticity of -0.4. The effect for males is positive but insignifcant.

Crustal structure of the Innuitian region of Arctic Canada and Greenland from gravity modelling: implications for the Palaeogene Eurekan orogen

SUMMARY New gravity observations collected over Ellesmere Island and Axel Heiberg Island have been integrated with existing Canadian and Danish data sets to produce a comprehensive regional compilation over the Innuitian Region of the Canadian and Greenland High Arctic. This compilation has provided quantitative assessment of the geometry of the plate boundary between northern Greenland and Ellesmere Island and crustal structures across the Cretaceous‐Palaeogene Eurekan Orogen. A large amplitude linear gravity low—Nares Strait Gravity Low (NSGL) (<‐160 mGal)— extends obliquely across Nares Strait from northern Greenland to Ellesmere Island. This feature closely correlates with the distribution of the Palaeozoic Franklinian Margin sequences and is cross-cut by the Cenozoic Eurekan Frontal Thrust (EFT), which represents the mappable western limit of the undeformed Greenland Plate associated with the Eurekan Orogen. Newly identified linear gravity features occur north of the NSGL: the Hazen Plateau Gravity High (HPGH), corresponding with the low-lying topography of the Hazen Trough and the Grantland Gravity Low (GGL), over the elevated topography of the Grantland Uplift. Gravity models for profiles crossing the NSGL, the HPGH and the GGL indicate that the long-wavelength component of the gravity anomalies is produced by systematic variations in Moho depth. Although significant Eurekan-age thrusting and thickening of low-density Palaeozoic strata is observed on Ellesmere Island, locally contributing to the mass-deficit generating the NSGL, equivalent strata on Greenland are undeformed. The NSGL is interpreted to be primarily the signature of the remnant (Early Palaeozoic) margin with the downwards flexure of the crust beneath a northwards thickening sedimentary wedge rather than purely the result of crustal thickening from the Eurekan Orogeny. Digital bathymetry and sediment thickness data were used to determine a residual ‘crustal’ gravity field, which in turn was used to calculate depth-to-Moho and crustal thicknesses. These have been interpreted in terms of crustal affinity and crustal thinning and thickening processes associated with the Late Cretaceous‐Palaeogene plate tectonics of the area. Significant crustal thinning is observed beneath the Lancaster Basin, between Baffin Island and Devon Island, corresponding with 40 km of separation. This is interpreted to be a failed rift-arm of the Eocene spreading system in Baffin Bay. A Fourier-domain transfer function analysis (Q) determined an intermediate average crustal strength (flexural rigidity of 10 22 N m) over the Innuitian region. Comparisons with theoretical models, based on a simple thin elastic plate model, suggest that the crust is relatively thin (30 km) and in near-isostatic equilibrium—that is, not flexurally supporting the existing sedimentary or topographic load. A clearly defined anisotropy is identified, correlating with the direction of Eocene plate convergence, suggesting that the Eurekan collisional forces have not yet dissipated and are at least partially supporting large-scale orogenic structures.

Predicting the distribution of the invasive alienHeracleum mantegazzianumat two different spatial scales

ABSTRACTModelling the distribution of invasive alien species is widely used for predicting future dispersal, response to climate change, and effects of management, but little information is available on the scale dependence of spatial models. This study is focused onHeracleum mantegazzianum, a problematic invasive plant in central and north‐western Europe. The main objective was to model the current distribution of this species at national (43,000 km2) and regional scale (4900 km2) using autologistic regression with a Danish data set. Presence–absence data were used in a grid system with 5 × 5 km2or 2 × 2 km2as basic units. To avoid misleading presence–absence models and unreliable probability values due to unbalanced data, the prevalence was used as cut‐off value, and a favourability function was applied to the model predictions. The national model showed a widespread distribution ofH. mantegazzianumwith highest habitat suitability in the eastern and northern parts of the country where human population density is high, winters more severe and/or loamy soils more common. At a regional scale the distribution ofH. mantegazzianumis associated with alluvial sand cover, high human population density, spring precipitation, and presence of the species in neighbour grid units. The observed widespread national distribution is likely the result of anthropogenic spread of this ornamental plant, while the locally clumped distribution suggests thatH. mantegazzianumnaturally spreads mainly over short distances. The current distribution in Denmark resembles an intermediate invasion stage where long‐distance dispersal is less important, while spread from suitable neighbour habitats is significant. The study demonstrates that the favourability function leads to improved mapping standards for invasive species.

Pedotransfer functions estimating soil hydraulic properties using different soil parameters

AbstractEstimates of soil hydraulic properties using pedotransfer functions (PTF) are useful in many studies such as hydrochemical modelling and soil mapping. The objective of this study was to calibrate and test parametric PTFs that predict soil water retention and unsaturated hydraulic conductivity parameters. The PTFs are based on neural networks and the Bootstrap method using different sets of predictors and predict the van Genuchten/Mualem parameters. A Danish soil data set (152 horizons) dominated by sandy and sandy loamy soils was used in the development of PTFs to predict the Mualem hydraulic conductivity parameters. A larger data set (1618 horizons) with a broader textural range was used in the development of PTFs to predict the van Genuchten parameters. The PTFs using either three or seven textural classes combined with soil organic mater and bulk density gave the most reliable predictions of the hydraulic properties of the studied soils. We found that introducing measured water content as a predictor generally gave lower errors for water retention predictions and higher errors for conductivity predictions. The best of the developed PTFs for predicting hydraulic conductivity was tested against PTFs from the literature using a subdata set of the data used in the calibration. The test showed that the developed PTFs gave better predictions (lower errors) than the PTFs from the literature. This is not surprising since the developed PTFs are based mainly on hydraulic conductivity data near saturation and sandier soils than the PTFs from the literature. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Why do families actually pool their income? Evidence from Denmark

This paper analyzes income-pooling by using a unique Danish data set that includes questions on income pooling among 1,696 couples. The analyses show that most Danish households use some kind of income pooling and that the proportion of income pooled varies considerably according to individual characteristics (age, education, occupation, past partners, upbringing) and household characteristics (household income, duration of marriage, location of residence and the existence of public goods, including children). However, when all variables are evaluated in a common model, the duration of marriage and the existence of children predominantly affect the likelihood of income pooling.

Point and parameter pedotransfer functions for water retention predictions for Danish soils

Estimates of soil water retention characteristics using pedotransfer functions (PTFs) are useful in many studies, such as hydrological modelling and soil mapping. The objective of this study was to calibrate and validate point and parametric PTF models based on neural networks and the Bootstrap method using different sets of predictors. The point PTF models estimated retention points at −1, −10, −100, and −1500 kPa pressure and the parametric PTF models estimated the van Genuchten retention parameters. A Danish soil data set (3226 horizons) dominated by sandy and sandy loamy soils was used in the analysis. The data were split up into a calibration data set ( N=1618 horizons) and a testing data set ( N=1608). The data were evaluated with the root mean square residuals (RMSR) and the Akaike Information Criterion (AIC), both obtained from measured and predicted water contents at the four retention points. The results for the point PTF models show similar predictions using detailed soil textural classification (seven textural classes) compared to a simplified textural classification (sand, silt, and clay). In general, we found that adding bulk density (BD) and soil organic matter (SOM) as predictors increased the prediction capability. The RMSR values varied between 0.037 and 0.051 cm 3 cm −3 and the lowest RMSR values were found for the models that used the most detailed data. The AIC followed the change in RMSR closely. The RMSR values for the parametric PTF models were generally 0.011 cm 3 cm −3 higher than the point PTF models using the same predictors. This was mainly due to an imperfect fit of the van Genuchten retention model to the retention data at 1500 kPa. Adding measured soil water content at −10 kPa in the parametric PTF models reduced the RMSR by 0.006 cm 3 cm −3. Adding additional soil water contents measured at −1 kPa, −100 kPa, and −1500 kPa improved the predictions only to a minor degree. The uncertainty in the prediction of water content using both the point and parametric PTF increased with increasing clay content. Another finding was that the absolute uncertainty in point PTF predictions of water content at −10 kPa was generally higher than the uncertainty found at −1, −100, and −1500 kPa.

Rent control and unemployment duration

In this paper we analyse how rent control affects the duration of individual unemployment. In a theoretical search model we distinguish between two effects of rent control. On one hand, rent control reduces housing mobility and hence mobility in the labour market. On the other hand, to maintain rent control benefits, unemployed individuals are more likely to accept job offers in the local labour market. Based on a rich Danish data set, we find that the probability of finding a local job increases with the rent control intensity of the housing unit, whereas the probability of finding a job outside the local labour market decreases with the rent control intensity.