A note on the choice of the number of slices in sliced inverse regression

Sliced inverse regression (SIR) is a clever technique for reducing the dimension of the predictor in regression problems, thus avoiding the curse of dimensionality. There exist many contributions on various aspects of the performance of SIR. Up to now, few attention has been paid to the problem of choosing the number of slices within the SIR procedure appropriately. The aim of this paper is to show that especially the estimation of the reduced dimension can be strongly in?uenced by the chosen number of slices. --dimension reduction,estimation of dimension

Is there a Superior Distance Function for Matching in Small Samples?

The study contributes to the development of ’standards’ for the application of matching algorithms in empirical evaluation studies. The focus is on the first step of the matching procedure, the choice of an appropriate distance function. Supplementary o most former studies, the simulation is strongly based on empirical evaluation ituations. This reality orientation induces the focus on small samples. Furthermore, ariables with different scale levels must be considered explicitly in the matching rocess. The choice of the analysed distance functions is determined by the results of former theoretical studies and recommendations in the empirical literature. Thus, in the simulation, two balancing scores (the propensity score and the index score) and the Mahalanobis distance are considered. Additionally, aggregated statistical distance functions not yet used for empirical evaluation are included. The matching outcomes are compared using non-parametrical scale-specific tests for identical distributions of the characteristics in the treatment and the control groups. The simulation results show that, in small samples, aggregated statistical distance functions are the better choice for summarising similarities in differently scaled variables compared to the commonly used measures.distance functions, matching, microeconometric evaluation, propensity score, simulation

Population-based studies on the epidemiology of migraine and Parkinson's disease

With epidemiologic analyses the effect of certain exposures on diseases can be studied in large population samples. Pharmacoepidemiology is a speciality which focuses on beneficial or harmful drug effects on the development of diseases. In my thesis I carried out different epidemiological studies in order to increase the knowledge on the natural history of migraine and Parkinson's disease. Another focus was to evaluate the effect of certain drug therapies on teh risk of developing migraine or Parkinson's disease (PD) or complications of the diseases. I used data from the General Practice Research Database (GPRD), which contains electronic records from primary-care of several million people in the United Kingdom (UK). Additionally, information on patient demographics (e.g. age, gender, body mass index, smoking status) is available for a large portion of the patiens as well as data on hospital and specialist diagnoses. The GPRD has been the source for many important studies in epidemiology as well as in drug safety. In my first project I identified 51'688 individuals of the FPRD with a firyst-time migraine diagnosis between 1994 and 2001 and an equal amount of control subjects without such a diagnosis. The incidence rates (IR) of first-time diagnoses of migraine by the general practitioners (GPs) were 2.5 times higher in women than in men and highest in puberty. The comorbid disorders of the migraineurs were also quantified in migraineurs and controls. By means of a case-control study design which included matching on several important confounders such as gender, age, general practice and index date, the odds ratios (ORs) for the comorbidities in migraineurs compared to non-migraineurs were investigated. This resulted in an increased OR for the migraineurs for most chronic diseases. Determination of the health resource utilisation (HRU) revealed that migraineurs with triptan prescriptions needed more health care, defined as visits to their GP or neurological specialists as well as prescriptions for headeche related drugs. In a second part of the migraine project I followed a cohort of migraineurs and their matched controls until they developed a stroke, a transient ischaemic attack (TIA), they died of until they were diagnosed with asthma for the first time. Again IRs were calculated and a nested case-control analysis performed. A previous history of migraine was associated with an approximately twofold increased risk for stroke or TIA, however, residual confounding by migraine recency or severity could not totally be ruled out. Furthermore it is challenging to determine the stroke risk in association with prior triptan use because in the GPRD the actual timing of the drug intake is not recorded. The mortality of migraineurs was slightly decreased and no increased asthma risk was seen in migraineurs with or without triptan use. In my second project I investigated the impact of prior drug use on the risk of being diagnosed with PD. During the study period from 1994 to 2005 3'637 individuals with idiopathic PD were identified from the GPRD. The majority of the cases with a first-time PD diagnosis were men older than 60 years of age. In two separate case-control studies, in which I used the same matching criteria as in the migraine project, I found a decreased risk of PD in patients with current use of calcium channel blockers. This finding is in accordance with a recent hypothesis regarding the involvement of calcium channels in the PD pathophysiology. After the assumption of an increased risk for PD associated with the use of statins, the results of the other case control study gave reassurance that in a large population sample from the GPRD the risk for a PD diagnosis was not increased for current or past use of statins. To conclude, the GPRD data is very useful for the description of the natural history of diseases as well as for the investigation of particular drug safety questions. The potentials of the database could be further increased if genetic information was also available in future. Certainly, special diligence has to be exercised regarding the issue of data protection

A Survey of Psychologists’ Attitudes Towards and Utilization of Exposure Therapy for PTSD

Although research supports the efficacy of exposure therapy for PTSD, some evidence suggests that exposure is under-utilized in general clinical practice. The purpose of this study was to assess licensed psychologists’ use of imaginal exposure for PTSD and to investigate perceived barriers to its implementation. A total of 852 psychologists from 3 states were randomly selected and surveyed. An additional 50 members of a trauma special interest group of a national behavior therapy organization were also surveyed. The main survey results indicate that a large majority of licensed doctoral level psychologists do not report use of exposure therapy to treat patients with PTSD. Although approximately half of the main study sample reported that they were at least somewhat familiar with exposure for PTSD, only a small minority used it to treat PTSD in their clinical practice. Even among psychologists with strong interest and training in behavioral treatment for PTSD, exposure therapy is not completely accepted or widely used. Clinicians also appear to perceive a significant number of barriers to implementing exposure

Steuerung Alt Entfernen / Re-boot Science

Wissen, Wissenssammlungen und Wissensordnungen haben sich im Laufe der Jahre verändert, ebenso wie die Wissensproduktion, die Schaffung neuen Wissens, die Wissenschaft selbst. Der Baum des Wissens, arbor porphyriana oder auch arbor scientiae war seit der Antike eine gültige Metapher und das Klassifikationsschema für die Struktur des Wissens, die epistemologische Ordnung. So lehnte auch Denis Diderot die Ordnung seiner berühmten Enzyklopädie an die Baumstruktur des Wissens von Francis Bacon an. (...

Decentralization effects in ecological fiscal transfers - the case of Portugal

Portugal has a unitary system in which the central government transfers funds to lower government levels for their public functions. In 2007, Portugal introduced Ecological Fiscal Transfers (EFT), where municipalities receive transfers for hosting Protected Areas (PA). We study whether introducing EFT in Portugal incentivized municipalities to designate PA and has led to a decentralization of conservation decisions. We employ a Bayesian structural time series approach to estimate the effect of introducing EFT in comparison to a simulated counterfactual time series. Quantitative results show a significant increase in the ratio of municipal and national PA designations following Portugal’s EFT introduction. The analysis furthermore places emphasis on the importance of relevant municipal conservation competencies and the role of local decision makers’ motivations for PA designations. Results have important implications for conservation policy-making in terms of allocating budgets and competencies in multi-level governments

Neoliberal Economic, Social, and Spatial Restructuring: Valparaíso and Its Agricultural Hinterland

The analysis of the neoliberal restructuring of Chilean port cities and their hinterland suggests there was a functional coupling of neoliberalisation, precarisation, reterritorialisation, extraction, and logistics. To address this process properly, we expanded the boundaries of our analytical scale to include not only the port city, but also its hinterland, and be able to examine the flow of commodities and labour. The analysis demonstrated that the effects of neoliberal restructuring of Valparaíso and its hinterland has had interconnected ambivalent effects. Although social and economic restructuring of agricultural hinterland and port terminals in Chile increased land and port productivity and economic competitiveness, this pattern of capitalist modernisation benefitted neither the increasing masses of temporary precarious workers in the countryside nor port cities such as Valparaíso, marked by territorial inequality, socioecological damage, urban poverty, and a growing sense of closure of the littoral and reduced access to the ocean. These negative externalities and frictions have triggered local political controversies, commercial and economic disputes, labour strikes, and urban and socio-territorial conflicts

Specificity of the Social Interaction Self-Statement Test in Social Phobia

The specificity of the Social Interaction Self-Statement Test (SISST) was evaluated in sample of 277 patients seeking treatment for anxiety. Both the positive and negative scales significantly discriminated between patients diagnosed with social phobia and other anxiety disorder patients. Patients with social phobia scored significantly higher on the negative scale and significantly lower on the positive scale as compared with other treatment-seeking anxiety disorder patients. Negative SISST scores were significantly correlated with the Beck Anxiety Inventory (BAI) and Beck Depression Inventory (BDI). The positive scale was significantly correlated with the BDI. Despite this relationship, differences in BAI and BDI scores did not account for SISST findings. The present study provides further support for the use of the SISST with clinical populations