Publications by authors named "Christian Weiss"

The marginal accuracy of fit between prosthetic restorations and abutment teeth represents an essential aspect with regard to long-term clinical success. Since the final gap is also influenced by the luting techniques and materials applied, this study analyzed the accuracy of the fit of single-tooth zirconia copings before and after cementation using different luting materials. Forty plaster dies with a corresponding zirconia coping were manufactured based on a single tooth chamfer preparation.

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The novel circumstance-driven bivariate integer-valued autoregressive (CuBINAR) model for non-stationary count time series is proposed. The non-stationarity of the bivariate count process is defined by a joint categorical sequence, which expresses the current state of the process. Additional cross-dependence can be generated via cross-dependent innovations.

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Discrete-Valued Time Series.

Entropy (Basel)

November 2023

Time series are sequentially observed data in which important information about the phenomenon under consideration is contained not only in the individual observations themselves, but also in the way these observations follow one another [...

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Article Synopsis
  • Interventional left atrial appendage occlusion (LAAO) is a treatment option that replaces long-term oral anticoagulation for patients with nonvalvular atrial fibrillation, particularly those with a high risk of bleeding.
  • A study examined the impact of spontaneous echo contrast (SEC) on the risk of device-related thrombus (DRT) and thromboembolic events (TEs) in two groups of patients: those with SEC and those without it.
  • The results showed that while procedural success was high in both SEC groups, DRT was only noted in the SEC- group and TEs were rare in both, suggesting that SEC presence might not significantly affect post-LAAO outcomes.
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In a time series context, the study of the partial autocorrelation function (PACF) is helpful for model identification. Especially in the case of autoregressive (AR) models, it is widely used for order selection. During the last decades, the use of AR-type count processes, i.

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Ordinal patterns can be used to construct non-parametric hypothesis tests that aim to discover (possibly non-linear) serial dependence in a real-valued time series. We derive the asymptotic distribution of the vector of sample frequencies of ordinal patterns and that of various corresponding tests statistics such that the targeted tests for serial dependence are easily implemented based on asymptotic approximations. Simulations are used to check the finite-sample performance of these tests as well as their power properties with respect to various alternative scenarios.

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Common count distributions, such as the Poisson (binomial) distribution for unbounded (bounded) counts considered here, can be characterized by appropriate Stein identities. These identities, in turn, might be utilized to define a corresponding goodness-of-fit (GoF) test, the test statistic of which involves the computation of weighted means for a user-selected weight function f. Here, the choice of f should be done with respect to the relevant alternative scenario, as it will have great impact on the GoF-test's performance.

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The family of cumulative paired ϕ-entropies offers a wide variety of ordinal dispersion measures, covering many well-known dispersion measures as a special case. After a comprehensive analysis of this family of entropies, we consider the corresponding sample versions and derive their asymptotic distributions for stationary ordinal time series data. Based on an investigation of their asymptotic bias, we propose a family of signed serial dependence measures, which can be understood as weighted types of Cohen's κ, with the weights being related to the actual choice of ϕ.

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Time Series Modelling.

Entropy (Basel)

September 2021

Time series consist of data observed sequentially in time, and they are assumed to stem from an underlying stochastic process [...

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Aim: Percutaneous left atrial appendage (LAA) closure has been established as alternative stroke prophylaxis in patients with non-valvular atrial fibrillation (AF) and high bleeding risk. However, little is known regarding the outcome after LAA closure depending on the HAS-BLED score.

Methods: A sub-analysis of the prospective, multicenter, Left-Atrium-Appendage Occluder Register-GErmany (LAARGE) registry was performed assessing three different groups with respect to the HAS-BLED score (0-2 [group 1] vs.

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In real applications, time series often exhibit missing observations such that standard analytical tools cannot be applied. While there are approaches of how to handle missing data in quantitative time series, the case of categorical time series seems not to have been treated so far. Both for the case of ordinal and nominal time series, solutions are developed that allow to analyze their marginal and serial properties in the presence of missing observations.

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Coherent forecasting techniques for count processes generate forecasts that consist of count values themselves. In practice, forecasting always relies on a fitted model and so the obtained forecast values are affected by estimation uncertainty. Thus, they may differ from the true forecast values as they would have been obtained from the true data generating process.

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For the modeling of categorical time series, both nominal or ordinal time series, an extension of the basic discrete autoregressive moving-average (ARMA) models is proposed. It uses an observation-driven regime-switching mechanism, leading to the family of RS-DARMA models. After having discussed the stochastic properties of RS-DARMA models in general, we focus on the particular case of the first-order RS-DAR model.

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Left atrial appendage closure (LAAC) is an alternative to oral anticoagulation therapy in patients with non-valvular atrial fibrillation for the prevention of embolic stroke and systemic embolism. Although elderly patients (>75 years) have both higher ischemic and bleeding risk as compared with younger patients, they benefit from optimal anticoagulation. The subanalysis aimed to assess the indications, the safety, efficacy, and 1-year outcomes of interventional LAAC in elderly patients (≥ 75 years) compared with younger (< 75 years) patients in clinical practice.

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Aims: Several left atrial appendage (LAA) closure systems are available. Due to differences in device design, the results of specific occluders derived from trials cannot simply be generalised to all devices. The present analysis sought to assess two contemporary LAA closure devices in clinical practice.

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Purpose: Anal squamous cell carcinomas (ASCC) are increasing in frequency across the developed world. The 3-year disease-free survival (DFS) in patients with locally-advanced disease is approximately 60% after primary radiochemotherapy (RCT). There is a strong rationale for combining immunotherapy with RCT in patients with ASCC due to its association with human papilloma virus (HPV) infection.

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Objectives: Chronic kidney disease (CKD) is associated with an increased complication rate after cardiac interventions. Although CKD has a high prevalence among atrial fibrillation patients, the impact of CKD on periprocedural complications and the outcome after an interventional left atrial appendage closure (LAAC) is unclear. The present study, therefore, aimed to investigate whether CKD influences the procedure's effectiveness and safety.

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Article Synopsis
  • - The study investigates the effectiveness of left atrial appendage closure (LAAC) in patients with atrial fibrillation and varying levels of left ventricular ejection fraction (LVEF), revealing that LVEF reduction does not significantly affect procedural success or safety during the procedure.
  • - A total of 619 patients from 37 centers were analyzed, showing that lower LVEF correlates with increased cardiovascular comorbidity but similar rates of procedural complications across all LVEF categories.
  • - Despite a trend towards reduced stroke-free survival associated with lower LVEF, the findings suggest that the LAAC procedure remains effective and safe, regardless of LVEF levels, emphasizing its utility in high-risk patient populations.
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Background: The aim of this study was to evaluate the efficacy and safety of chemoradiotherapy (RCT) combined with regional deep hyperthermia (RHT) of high-risk bladder cancer after transurethral resection of bladder tumor (TUR-BT).

Materials And Methods: Between 1982 and 2016, 369 patients with pTa, pTis, pT1, and pT2 cN0-1 cM0 bladder cancer were treated with a multimodal treatment after TUR-BT. All patients received radiotherapy (RT) of the bladder and regional lymph nodes.

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Background: Preclinical studies demonstrate synergism between cancer immunotherapy and local radiation, enhancing anti-tumor effects and promoting immune responses. BI1361849 (CV9202) is an active cancer immunotherapeutic comprising protamine-formulated, sequence-optimized mRNA encoding six non-small cell lung cancer (NSCLC)-associated antigens (NY-ESO-1, MAGE-C1, MAGE-C2, survivin, 5T4, and MUC-1), intended to induce targeted immune responses.

Methods: We describe a phase Ib clinical trial evaluating treatment with BI1361849 combined with local radiation in 26 stage IV NSCLC patients with partial response (PR)/stable disease (SD) after standard first-line therapy.

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Background: In heart failure (HF) patients with implantable cardioverter defibrillators (ICD) or cardiac resynchronisation therapy defibrillators (CRT-D), remote monitoring has been shown to result in at least non-inferior outcomes relative to in-clinic visits. We aimed to provide further evidence for this effect, and to assess whether adding telephone follow-ups to remote follow-ups influenced outcomes.

Methods: InContact was a prospective, randomised, multicentre study.

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Aims: The aim of this study was to investigate the effect of contact-to-balloon time on mortality in ST-segment elevation myocardial infarction (STEMI) patients with and without haemodynamic instability.

Methods And Results: Using data from the prospective, multicentre Feedback Intervention and Treatment Times in ST-Elevation Myocardial Infarction (FITT-STEMI) trial, we assessed the prognostic relevance of first medical contact-to-balloon time in n = 12 675 STEMI patients who used emergency medical service transportation and were treated with primary percutaneous coronary intervention (PCI). Patients were stratified by cardiogenic shock (CS) and out-of-hospital cardiac arrest (OHCA).

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Purpose: To evaluate the performance of a model-based optimisation process for volumetric modulated arc therapy applied to prostate cancer in a multicentric cooperative group. The RapidPlan (RP) knowledge-based engine was tested for the planning of Volumetric modulated arc therapy with RapidArc on prostate cancer patients. The study was conducted in the frame of the German RapidPlan Consortium (GRC).

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We propose a compressed sampling and dictionary learning framework for fiber-optic sensing using wavelength-tunable lasers. A redundant dictionary is generated from a model for the reflected sensor signal. Imperfect prior knowledge is considered in terms of uncertain local and global parameters.

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