Jan Bulla

Jan Bulla
University of Bergen | UiB · Department of Mathematics

Professor

About

113
Publications
31,884
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1,313
Citations
Introduction
Additional affiliations
August 2014 - present
University of Bergen
Position
  • Professor (Full)

Publications

Publications (113)
Article
Full-text available
Background Tinnitus is a heterogeneous condition which may be associated with moderate to severe disability, but the reasons why only a subset of individuals is burdened by the condition are not fully clear. Ecological momentary assessment (EMA) allows a better understanding of tinnitus by capturing the fluctuations of tinnitus symptoms, such as di...
Preprint
Full-text available
A very common way to estimate the parameters of a hidden Markov model (HMM) is the relatively straightforward computation of maximum likelihood (ML) estimates. For this task, most users rely on user-friendly implementation of the estimation routines via an interpreted programming language such as the statistical software environment R (R Core Team,...
Article
Full-text available
A very common way to estimate the parameters of a hidden Markov model (HMM) is the relatively straightforward computation of maximum likelihood (ML) estimates. For this task, most users rely on user‐friendly implementation of the estimation routines via an interpreted programming language such as the statistical software environment R. Such an appr...
Article
Full-text available
In this paper, we report robust evidence that the process of corporate defaults is time‐dependent and can be modelled by extending an autoregressive count time series model class via the introduction of regime‐switching. That is, some of the parameters of the model depend on the regime of an unobserved Markov chain, capturing the model changes duri...
Preprint
Full-text available
Background Tinnitus is a heterogeneous condition associated with moderate to severe disability, but the reasons why only a subset of individuals is burdened by the condition are not fully clear. Ecological momentary assessment (EMA) allows a better understanding of tinnitus by allowing individualized models and by capturing the fluctuations of tinn...
Article
Full-text available
Background: The heterogeneity of tinnitus is thought to underlie the lack of objective diagnostic measures. Methods: Longitudinal data from 20,349 participants of the Swedish Longitudinal Occupational Survey of Health (SLOSH) cohort from 2008 to 2018 was used to understand the dynamics of transition between occasional and constant tinnitus. The...
Article
Full-text available
Two methods for clustering data and choosing a mixture model are proposed. First, we derive a new classification algorithm based on the classification likelihood. Then, the likelihood conditional on these clusters is written as the product of likelihoods of each cluster, and AIC- respectively BIC-type approximations are applied. The resulting crite...
Article
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Hidden Markov and semi-Markov models (H(S)MMs) constitute useful tools for modeling observations subject to certain dependency structures. The hidden states render these models very flexible and allow them to capture many different types of latent patterns and dynamics present in the data. This has led to the increased popularity of these models, w...
Article
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Twin and adoption studies point towards a genetic contribution to tinnitus; however, how the genetic risk applies to different forms of tinnitus is poorly understood. Here, we perform a familial aggregation study and determine the relative recurrence risk for tinnitus in siblings (λs). Four different Swedish studies (N = 186,598) were used to estim...
Article
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Tinnitus, the perception of sound in the absence of a corresponding sound, and the distress caused by it, is rarely a static phenomenon. It rather fluctuates over time depending on endogenous and exogenous factors. The COVID-19 pandemic is a potential environmental stressor that might influence the individually perceived tinnitus distress. Since no...
Article
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The vestibular system is responsible for sensing every angular and linear head acceleration, mainly during periods of motor activity. Previous animal and human experiments have shown biological rhythm disruptions in small rodents exposed to a hypergravity environment, but also in patients with bilateral vestibular loss compared to a control populat...
Article
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Many individuals with tinnitus report experiencing hyperacusis (enhanced sensitivity to sounds). However, estimates of the association between hyperacusis and tinnitus is lacking. Here, we investigate this relationship in a Swedish study. A total of 3645 participants (1984 with tinnitus and 1661 without tinnitus) were enrolled via LifeGene, a study...
Article
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Gait is one of the most basic movements, and walking activity accomplished in dual task conditions realistically represents daily life mobility. Much is known about diurnal variations of gait components such as muscle power, postural control, and attention. However, paradoxically only little is known about gait itself. The aim of this study was to...
Article
Full-text available
The heterogeneity of tinnitus is likely accounting for the lack of effective treatment approaches. Headaches have been related to tinnitus, yet little is known on how headaches impact tinnitus. We use cross-sectional data from the Swedish Tinnitus Outreach Project to i) evaluate the association between headaches and tinnitus (n = 1,984 cases and 1,...
Article
Two monovalent vaccines against pasteurellosis were developed and tested for efficacy using a previously established bath challenge model. High levels of specific antibodies were detected following vaccination. While the vaccine efficacy trial indicated that some level of protection was obtained, high mortality was still observed. qPCR analysis of...
Article
Full-text available
There is increasing evidence of associations between the presence of temporomandibular joint (TMJ) disorders and tinnitus. It has been recently proposed that tinnitus patients with TMJ complaints could constitute a subtype, meaning a subgroup of tinnitus patients responsive to specific treatments. Tinnitus patients with TMJ complaints are often you...
Article
Full-text available
Introduction: Chronic tinnitus is a condition estimated to affect 10-15% of the population. No treatment has shown efficacy in randomized clinical trials to reliably and effectively suppress the phantom perceptions, and little is known why patients react differently to the same treatments. Tinnitus heterogeneity may play a central role in treatment...
Article
Full-text available
Abstract Ototoxicity is one of the major side-effects of platinum-based chemotherapy, in particular cisplatin (cis-diammine dichloroplatinum II). To our knowledge, no systematic review has previously provided a quantitative summary estimate of the impact of genetics upon the risk of developing hearing loss. We searched Embase, Medline, ASSIA, Pubme...
Article
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This research presents an application of a mixed hidden Markov model to data from a multichannel retailer. The objective of this research is to develop a dynamic model of channel choice and purchasing behavior that accounts for consumer heterogeneity, changes in behavior over time, and the influence of marketing activities on managerially relevant...
Article
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Retailers are experiencing a systematic shift in the buying habits of their customers as more customers buy across different channels. Marketing managers face the daunting task of embracing online and offline channels to engage consumers, influence choice, and create habits to sustain a competitive advantage. We develop a dynamic segmentation model...
Article
This study aimed to test the validity and reliability of the latest version of the Anipill® device including a calibration assessment step and an in-vivo testing in rodents. After performing a calibration procedure, 10 rats were intraperitoneally implanted with a pair of sensors, one Anipill® (8.2 mm diameter, 17.2 mm length) and one Jonah® (8.7 mm...
Preprint
Full-text available
This article extends the autoregressive count time series model class by allowing for a model with regimes, that is, some of the parameters in the model depend on the state of an unobserved Markov chain. We develop a quasi-maximum likelihood estimator by adapting the extended Hamilton-Grey algorithm for the Poisson log-linear autoregressive model,...
Article
Full-text available
Background: DNA methylation patterns store epigenetic information in the vast majority of eukaryotic species. The relatively high costs and technical challenges associated with the detection of DNA methylation however have created a bias in the number of methylation studies towards model organisms. Consequently, it remains challenging to infer kin...
Article
Full-text available
The aim of the study was to test the effect of total sleep deprivation on performance and time-of-day pattern of Subjective Visual Vertical (SVV) and postural control. Nineteen healthy young participants (4 females and 15 males 21.9 {plus minus} 1.2 years) were engaged in two counterbalanced experimental sessions with or without total sleep depriva...
Article
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The assessment of pollution exposure is based on the analysis of a multivariate time series that include the concentrations of several pollutants as well as the measurements of multiple atmospheric variables. It typically requires methods of dimensionality reduction that are capable of identifying potentially dangerous combinations of pollutants an...
Preprint
Full-text available
Background DNA methylation patterns store epigenetic information in the vast majority of eukaryotic species. The relatively high costs and technical challenges associated with the detection of DNA methylation however have created a bias in the number of methylation studies towards model organisms. Consequently, it remains challenging to infer kingd...
Article
Full-text available
Rainfall is a continuous-time phenomenon typically characterized by precipitation states such as rain, showers, and dry whose dependence varies over a variety of space-time scales. Here attention is focused on the effective identification of rain and shower precipitation states over a region where these states have been determined by a hidden semi-...
Article
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Preterm infants frequently develop atypical sensory profiles, the tactile modality being particularly affected. However, there is a lack of recent investigation of neonatal tactile perception in a passive context, especially in preterms who are particularly exposed to this tactile stimuli. Our aims were to provide evidence of orienting responses (b...
Article
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Animals use distal and proximal visual cues to accurately navigate in their environment, with the possibility of the occurrence of associative mechanisms such as cue competition as previously reported in honey-bees, rats, birds and humans. In this pilot study, we investigated one of the most common forms of cue competition, namely the overshadowing...
Data
Representation of visual cues used in the study. (A) Distal visual cues consisted of four white posters (20 × 20 cm) displaying different black geometrical shapes. They were suspended on the black curtains of the room walls at a distance of 123 cm from maze (from the top of the cues to the center of the maze). (B) Proximal visual cues consisted of...
Article
Full-text available
Background: Sedation for colonoscopy using intravenous propofol has become standard in many Western countries. Objective: Gender-specific differences have been shown for general anaesthesia in dentistry, but no such data existed for gastrointestinal endoscopy. Design: A prospective observational study. Setting: An academic teaching hospital...
Article
Full-text available
Purpose: Genetic contributions to tinnitus have been difficult to determine due to the heterogeneity of the condition and its broad etiology. Here, we evaluated the genetic and nongenetic influences on self-reported tinnitus from the Swedish Twin Registry (STR). Methods: Cross-sectional data from the STR was obtained. Casewise concordance rates...
Article
Background Interference of ongoing neuronal activity and brain stimulation motivated this study to prove the concept of a combined treatment approach integrating repetitive transcranial magnetic stimulation (rTMS) and relaxation techniques in patients with chronic tinnitus. Methods Forty-two patients received rTMS consisting of ten sessions of hig...
Article
Full-text available
Objective: The need for validated measures enabling clinicians to classify tinnitus patients according to the severity of tinnitus and screen the progress of therapies in our country led us to translate into Polish and to validate two tinnitus questionnaires, namely the Tinnitus Handicap Inventory (THI) and the Tinnitus Functional Index (TFI). Desi...
Article
Full-text available
Interference of ongoing neuronal activity and brain stimulation motivated this study to combine repetitive transcranial magnetic stimulation (rTMS) and relaxation techniques in tinnitus patients. Forty-two patients were enrolled in this one-arm proof-of-concept study to receive ten sessions of rTMS applied to the left dorsolateral prefrontal cortex...
Article
Full-text available
Reports about luxury categories and premium brands growing during recession are multiple. This marketplace behavior, however, is counterintuitive to what traditional economics would predict. The authors propose and test a theory to explain why demand for premium brands may grow despite a contraction in the economy. They define cross-category indulg...
Poster
Full-text available
This poster was presented during the French Annual Bioinformatics Days (2016). We showed that our method to predict DNA methylation (5-methyl-cytosine) by means of CpG o/e ratios coincides with the literature.