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Peter molenaar

Peter C M Molenaar
Equivalences of two classes of dynamic models for weakly stationary multivariate time series are discussed: dynamic factor models and autoregressive models. It is shown that exploratory dynamic factor models can be rotated, yielding an infinite set of equivalent solutions for any observed series. It also is shown that dynamic factor models with lagged factor loadings are not equivalent to the currently popular state-space models, and that restriction of attention to the latter type of models may yield invalid results...
February 16, 2017: Multivariate Behavioral Research
Lu Ou, Sy-Miin Chow, Linying Ji, Peter C M Molenaar
The autoregressive latent trajectory (ALT) model synthesizes the autoregressive model and the latent growth curve model. The ALT model is flexible enough to produce a variety of discrepant model-implied change trajectories. While some researchers consider this a virtue, others have cautioned that this may confound interpretations of the model's parameters. In this article, we show that some-but not all-of these interpretational difficulties may be clarified mathematically and tested explicitly via likelihood ratio tests (LRTs) imposed on the initial conditions of the model...
December 16, 2016: Multivariate Behavioral Research
Inga Koneczny, Jo A A Stevens, Anna De Rosa, Saif Huda, Maartje G Huijbers, Abhishek Saxena, Michelangelo Maestri, Konstantinos Lazaridis, Paraskevi Zisimopoulou, Socrates Tzartos, Jan Verschuuren, Silvère M van der Maarel, Philip van Damme, Marc H De Baets, Peter C Molenaar, Angela Vincent, Roberta Ricciardi, Pilar Martinez-Martinez, Mario Losen
Autoimmunity mediated by IgG4 subclass autoantibodies is an expanding field of research. Due to their structural characteristics a key feature of IgG4 antibodies is the ability to exchange Fab-arms with other, unrelated, IgG4 molecules, making the IgG4 molecule potentially monovalent for the specific antigen. However, whether those disease-associated antigen-specific IgG4 are mono- or divalent for their antigens is unknown. Myasthenia gravis (MG) with antibodies to muscle specific kinase (MuSK-MG) is a well-recognized disease in which the predominant pathogenic IgG4 antibody binds to extracellular epitopes on MuSK at the neuromuscular junction; this inhibits a pathway that clusters the acetylcholine (neurotransmitter) receptors and leads to failure of neuromuscular transmission...
February 2017: Journal of Autoimmunity
Alejandro M Gomez, Jo A A Stevens, Marina Mané-Damas, Peter Molenaar, Hans Duimel, Fons Verheyen, Judith Cossins, David Beeson, Marc H De Baets, Mario Losen, Pilar Martinez-Martinez
Myasthenia gravis (MG) is an autoimmune disease mediated by autoantibodies that target proteins at the neuromuscular junction, primarily the acetylcholine receptor (AChR) and the muscle-specific kinase. Because downstream of kinase 7 (Dok-7) is essential for the full activation of muscle-specific kinase and consequently for dense clustering of AChRs, we hypothesized that reduced levels of Dok-7 increase the susceptibility to passive transfer MG. To test this hypothesis, Dok-7 expression was reduced by transfecting shRNA-coding plasmids into the tibialis anterior muscle of adult rats by in vivo electroporation...
October 2016: American Journal of Pathology
Melissa C Kilby, Peter C M Molenaar, Semyon M Slobounov, Karl M Newell
The experiment was setup to investigate the control of human quiet standing through the manipulation of augmented visual information feedback of selective properties of the motion of two primary variables in postural control: center of pressure (COP) and center of mass (COM). Five properties of feedback information were contrasted to a no feedback dual-task (watching a movie) control condition to determine the impact of visual real-time feedback on the coordination of the joint motions in postural control in both static and dynamic one-leg standing postures...
September 19, 2016: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Arja Gerritsen, Thijs de Rooij, Marcel G Dijkgraaf, Olivier R Busch, Jacques J Bergman, Dirk T Ubbink, Peter van Duijvendijk, G Willemien Erkelens, Mariël Klos, Philip M Kruyt, Dirk Jan Bac, Camiel Rosman, Adriaan C Tan, I Quintus Molenaar, Jan F Monkelbaan, Elisabeth M Mathus-Vliegent, Marc G Besselink
OBJECTIVES: Electromagnetic (EM)-guided bedside placement of nasoenteral feeding tubes by nurses may improve efficiency and reduce patient discomfort and costs compared with endoscopic placement by gastroenterologists. However, evidence supporting this task shift from gastroenterologists to nurses is limited. We aimed to compare the effectiveness of EM-guided and endoscopic nasoenteral feeding tube placement. METHODS: We performed a multicenter randomized controlled non-inferiority trial in 154 adult patients who required nasoenteral feeding and were admitted to gastrointestinal surgical wards in five Dutch hospitals...
August 2016: American Journal of Gastroenterology
John R Nesselroade, Peter C M Molenaar
Primarily from a measurement standpoint, we question some basic beliefs and procedures characterizing the scientific study of human behavior. The relations between observed and unobserved variables are key to an empirical approach to building explanatory theories and we are especially concerned about how the former are used as proxies for the latter. We believe that behavioral science can profitably reconsider the prevailing version of this arrangement because of its vulnerability to limiting idiosyncratic aspects of observed/unobserved variable relations...
March 2016: Multivariate Behavioral Research
John R Nesselroade, Peter C M Molenaar
Three commentaries on the Nesselroade and Molenaar target article in this issue are responded to in the interest of elaborating and defending the points of view expressed in our article. The commentaries feature philosophy of science, general structural modeling, and broad behavioral research perspectives. Responding to the commentaries afforded us the opportunity to clarify further matters that we deem critical to the fundamental matter of measurement in behavioral science, especially as it emphasizes (properly, we believe) the individual as the primary unit of analysis...
March 2016: Multivariate Behavioral Research
Adriene M Beltz, Aidan G C Wright, Briana N Sprague, Peter C M Molenaar
The nomothetic approach (i.e., the study of interindividual variation) dominates analyses of clinical data, even though its assumption of homogeneity across people and time is often violated. The idiographic approach (i.e., the study of intraindividual variation) is best suited for analyses of heterogeneous clinical data, but its person-specific methods and results have been criticized as unwieldy. Group iterative multiple model estimation (GIMME) combines the assets of the nomothetic and idiographic approaches by creating person-specific maps that contain a group-level structure...
August 2016: Assessment
Jos J Mellema, Job N Doornberg, Rik J Molenaars, David Ring, Peter Kloen
OBJECTIVES: The purpose of this study was to assess the interobserver reliability and diagnostic accuracy for 2-dimensional (2D) and 3-dimensional (3D) computed tomography (CT)-based evaluation of tibial plateau fracture characteristics. We hypothesized that recognition of specific tibial plateau fracture characteristics is equally reliable and accurate in 2DCT and 2D- and 3DCT. METHODS: Eighty-one orthopedic trauma surgeons and residents were randomized to either 2DCT or 2D- and 3DCT evaluation of 15 complex tibial plateau fractures using web-based platforms to recognize 4 tibial plateau fracture characteristics: (1) a posteromedial component, (2) a lateral component, (3) a tibial tubercle component, and (4) a tibial spine (central) component...
May 2016: Journal of Orthopaedic Trauma
Adriene M Beltz, Peter C M Molenaar
Structural vector autoregressive models (VARs) hold great potential for psychological science, particularly for time series data analysis. They capture the magnitude, direction of influence, and temporal (lagged and contemporaneous) nature of relations among variables. Unified structural equation modeling (uSEM) is an optimal structural VAR instantiation, according to large-scale simulation studies, and it is implemented within an SEM framework. However, little is known about the uniqueness of uSEM results...
March 2016: Multivariate Behavioral Research
Iris M Markusse, Gülsah Akdemir, Linda Dirven, Yvonne P M Goekoop-Ruiterman, Johannes H L M van Groenendael, K Huub Han, T H Esmeralda Molenaar, Saskia Le Cessie, Willem F Lems, Peter A H M van der Lubbe, Pit J S M Kerstens, André J Peeters, H Karel Ronday, Peter B J de Sonnaville, Irene Speyer, Theo Stijnen, Saskia Ten Wolde, Tom W J Huizinga, Cornelia F Allaart
BACKGROUND: Treat-to-target therapy is effective for patients with rheumatoid arthritis (RA), but long-term results of continued targeted treatment are lacking. OBJECTIVE: To evaluate long-term outcomes in patients with early RA after 10 years of targeted treatment in 4 treatment strategies. DESIGN: Randomized trial. (Nederlands Trial Register: NTR262 and NTR265). SETTING: The Netherlands. PATIENTS: 508 patients with early active RA...
April 19, 2016: Annals of Internal Medicine
Yao Zheng, Peter C M Molenaar, Rosalind Arden, Kathryn Asbury, David M Almeida
Most behavioural genetic studies focus on genetic and environmental influences on inter-individual phenotypic differences at the population level. The growing collection of intensive longitudinal data in social and behavioural science offers a unique opportunity to examine genetic and environmental influences on intra-individual phenotypic variability at the individual level. The current study introduces a novel idiographic approach and one novel method to investigate genetic and environmental influences on intra-individual variability by a simple empirical demonstration...
September 2016: Behavior Genetics
Siwei Liu, Peter Molenaar
This article introduces phase resampling, an existing but rarely used surrogate data method for making statistical inferences of Granger causality in frequency domain time series analysis. Granger causality testing is essential for establishing causal relations among variables in multivariate dynamic processes. However, testing for Granger causality in the frequency domain is challenging due to the nonlinear relation between frequency domain measures (e.g., partial directed coherence, generalized partial directed coherence) and time domain data...
2016: Multivariate Behavioral Research
Peter Molenaar
No abstract text is available yet for this article.
2016: Multivariate Behavioral Research
Lotte Heimans, Gülşah Akdemir, Kirsten V C Wevers-de Boer, Yvonne P Goekoop-Ruiterman, Esmeralda T Molenaar, Johannes H L M van Groenendael, Andreas J Peeters, Gerda M Steup-Beekman, Leroy R Lard, Peter B J de Sonnaville, Bernard A M Grillet, Tom W J Huizinga, Cornelia F Allaart
BACKGROUND: Early suppression of disease activity in (rheumatoid) arthritis (RA) patients may result in drug-free remission and prevent damage. We assessed 2-year clinical and radiological outcomes of two disease activity score (DAS)-remission-steered treatment strategies in early arthritis patients. METHODS: Patients (n = 610) with early RA or undifferentiated arthritis (UA) were treated with methotrexate (MTX) and tapered high dose of prednisone. Patients in early remission (44/53 joints DAS <1...
January 21, 2016: Arthritis Research & Therapy
Jos J Mellema, Job N Doornberg, Rik J Molenaars, David Ring, Peter Kloen
INTRODUCTION: Tibial plateau fracture classification systems have limited interobserver reliability and new systems emerge. The purpose of this study was to compare the reliability of the Luo classification and the Schatzker classification for two-dimensional computed tomography (2DCT) and to study the effect of adding three-dimensional computed tomography (3DCT). MATERIALS AND METHODS: Eighty-one observers, orthopedic surgeons and residents, were randomized to either 2DCT or 2D- and 3DCT evaluation of a spectrum of 15 complex tibial plateau fractures using web-based platforms in order to classify according to the Schatzker and according to Luo's Three Column classification...
April 2016: Injury
Boris M Hogema, Michel Molier, Margret Sjerps, Mirjam de Waal, Peter van Swieten, Thijs van de Laar, Marijke Molenaar-de Backer, Hans L Zaaijer
BACKGROUND: The incidence of hepatitis E virus (HEV) infection in the Netherlands is high. Blood donors are not routinely screened for HEV infection, but since January 2013, donations used for the production of solvent/detergent (S/D)-treated plasma have been screened for HEV RNA. STUDY DESIGN AND METHODS: Donations were screened for HEV RNA in pools of 96 and 192 donations. In addition, all donations made between 60 days before and after each HEV RNA-positive donation were tested individually for HEV RNA and anti-HEV immunoglobulin G...
March 2016: Transfusion
Peter C M Molenaar, Adriene M Beltz, Kathleen M Gates, Stephen J Wilson
Most connectivity mapping techniques for neuroimaging data assume stationarity (i.e., network parameters are constant across time), but this assumption does not always hold true. The authors provide a description of a new approach for simultaneously detecting time-varying (or dynamic) contemporaneous and lagged relations in brain connectivity maps. Specifically, they use a novel raw data likelihood estimation technique (involving a second-order extended Kalman filter/smoother embedded in a nonlinear optimizer) to determine the variances of the random walks associated with state space model parameters and their autoregressive components...
January 15, 2016: NeuroImage
Linda J Valentijn, Jan Koster, Danny A Zwijnenburg, Nancy E Hasselt, Peter van Sluis, Richard Volckmann, Max M van Noesel, Rani E George, Godelieve A M Tytgat, Jan J Molenaar, Rogier Versteeg
Whole-genome sequencing detected structural rearrangements of TERT in 17 of 75 high-stage neuroblastomas, with five cases resulting from chromothripsis. Rearrangements were associated with increased TERT expression and targeted regions immediately up- and downstream of TERT, positioning a super-enhancer close to the breakpoints in seven cases. TERT rearrangements (23%), ATRX deletions (11%) and MYCN amplifications (37%) identify three almost non-overlapping groups of high-stage neuroblastoma, each associated with very poor prognosis...
December 2015: Nature Genetics
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