Otto-von-Guericke University Magdeburg

• We provide theoretical insights on inferred sparse Full-Order Models for discrete time dynamical systems with a focus on accuracy and stability. • For one-dimensional linear advection, we formulate and validate an explicit ”sampling CFL” condition, connecting the stability of the sFOM to the spatial and temporal resolution of the training data. • We present numerical results on the sFOM inference for two nonlinear test cases (2D Burgers’ equation and incompressible cavity flow) and draw connections to our theoretical findings. In this work, we investigate the data-driven inference of a discrete-time dynamical system via a sparse Full-Order Model (sFOM). We first formulate the involved Least Squares (LS) problem and discuss the need for regularization, indicating a connection between the typically employed l 2 regularization and the stability of the inferred discrete-time sFOM. We then provide theoretical insights considering the consistency and stability properties of the inferred numerical schemes that form the sFOM and exemplify them via illustrative, 1D test cases of linear diffusion and linear advection. For linear advection, we analytically derive a “sampling CFL” condition, which dictates a bound for the ratio of spatial and temporal discretization steps in the training data that ensures stability of the inferred sFOM. Finally, we investigate the sFOM inference for two nonlinear problems, namely a 2D Burgers’ test case and the incompressible flow in an oscillating lid-driven cavity, and draw connections between the theoretical findings and the properties of the inferred, nonlinear sFOMs. Novelty statement: sparse FOM inference for dynamical systems in discrete time. Theoretical insights on the analytical solution of the sparse FOM least-squares problem. Established connection between the stability of sparse FOM and the l 2 regularization of the least-squares problem.

This study investigates the relationship between phase retardation and strain rates in combined extensional–shear flows using the Jeffery–Hamel flow formalism, which yields an analytical velocity solution. Flow birefringence was measured in a 1.0 wt% cellulose nanocrystal (CNC) suspension using a high-speed polarization camera. The velocity field was validated via particle image velocimetry (PIV), which showed good agreement with the analytical solution. In regions dominated by either shear or extensional components, the birefringence behavior was consistent with prior theoretical and experimental findings. In the combined extensional–shear regions of the Jeffery–Hamel flow, the birefringence magnitude followed the root-sum-square (RSS) of the shear- and extension-induced contributions. This observation aligns with the principal stress formulation derived from Mohr’s circle, in which the principal stress is expressed as the RSS of extensional and shear stresses. This finding provides a basis for extending stress–birefringence analysis to flows with coexisting deformation modes. • Flow birefringence in combined extensional–shear fields was investigated using the Jeffery–Hamel flow formalism with an analytical velocity solution. • Phase retardation in cellulose nanocrystal (CNC) suspensions was measured using high-speed polarization imaging, and the velocity field was validated independently by particle image velocimetry (PIV). • In the shear- and extension-dominant regions, the measured birefringence behavior was consistent with prior theoretical and experimental results. • In the combined region, Δ n was successfully described by a root-sum-square of birefringence contributions from shear and extensional deformation. • This study presents the first experimentally validated, interpretable framework for birefringence in combined extensional–shear flows, extending stress-optic applications.

Multitasking research has shown that individuals differ in whether they prefer a more serial or a more parallel mode of task processing at the level of whole tasks. Such preferences can be identified using the task switching with preview (TSWP) paradigm. This paradigm allows, but does not require, individuals to preview the stimulus of the next task switch in a predictable task switching procedure [AAABBB...]. Although several studies have shown that some participants consistently use the preview information, it is still unclear when exactly this information is used and, thus, how parallel processing takes place. The present study is an important step in clarifying this issue. In two experiments, I investigated when exactly individuals who prefer parallel processing during task switching use a preview to prepare for the next task switch. In Experiment 1, the onset and thus the length of the preview was varied within participants. This allowed to disentangle whether parallel processing of the preview depends on the length of the preview (i.e., its likelihood increases with longer preview presentation), or occurs contingent on a single trial (i.e., is a rapid process). Strikingly, parallel processing occurred regardless of preview duration, suggesting that a short preview may be sufficient. In Experiment 2, participants received the preview in discrete steps, i.e., with the same length throughout the sequence. There was a clear peak in the use of the preview immediately before a task switch. This suggests that although individuals who prefer parallel processing are able to process information in parallel throughout a task sequence, they clearly prefer to do so just before the task switch.

Schizophrenia encompasses positive, negative, and cognitive symptoms, and accumulating evidence suggests that the orexin system may modulate circuits relevant to these domains. Here, we investigated whether orexin-related interventions influence schizophrenia-like behaviors induced by the NMDA receptor antagonist dizocilpine in female and male mice. Two distinct approaches were used: nasal orexin A administration and chemogenetic activation of orexin neurons via DREADDs. Behavioral assessments included prepulse inhibition (PPI), locomotion and exploratory activity in the open field, social behavior, and working memory in the Y-maze. Overall, dizocilpine robustly induced schizophrenia-like phenotypes across these paradigms. Nasal orexin A exacerbated the dizocilpine-induced PPI deficit but attenuated the associated increase in startle reactivity, did not modify dizocilpine-induced hyperactivity, and partially rescued working memory impairments. Chemogenetic activation reproduced the PPI pattern observed with nasal orexin A, increased locomotion in both control- and dizocilpine-treated mice, induced anxiolytic-like effects in the open field, restored exploratory rearing, facilitated social recognition, and fully rescued working memory deficits. In some cases, the effects of these orexin-related interventions were differently pronounced in the two sexes. These findings indicate that activating the orexin system may worsen behavioral endophenotypes related to positive symptoms while alleviating those associated with negative and cognitive symptoms. However, substantial variability across assays, potentially related to the dosing of dizocilpine, orexin A, and CNO, as well as protocol-dependent constraints in some behavioral paradigms, limits definitive interpretation. Nevertheless, the present data reveal novel and domain-specific effects of orexin signaling in schizophrenia-relevant behavioral circuits and highlight the importance of exploring interventions with intermediate efficacy, including newly emerging orexin receptor agonists, to more precisely delineate orexin-dependent mechanisms and their therapeutic potential for negative and cognitive symptom domains.

IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder in which IgG4+ B cells and T cells interact to drive chronic organ inflammation. Patients with multiorgan involvement may become refractory to standard therapy, resulting in progressive organ damage and risk of organ failure. Here, we report a patient with treatment-refractory multiorgan IgG4-RD treated with CD19-directed chimeric antigen receptor (CAR) T cells and describe the clinical and immunologic effects over more than 12 months of follow-up. A 60-year-old man with IgG4-RD involving the pancreas, hepatobiliary tract, and lungs, who was refractory to long-term immunosuppression, received autologous CD19-directed CAR T cells. Disease course was monitored longitudinally and multimodal immune profiling was performed on peripheral blood. CAR T cell therapy was well tolerated, with only grade 1 cytokine release syndrome, no neurotoxicity, and transient cytopenias without infections. Treatment induced B-cell aplasia lasting 6 months, while serum IgG4 levels normalized by month 8 and remained within the reference range thereafter. FAPI (fibroblast activation protein inhibitor) PET/CT demonstrated regression of fibroinflammatory activity, accompanied by improved lung function and quality of life. Immunosuppressive therapy was completely discontinued without disease flares for more than 12 months. B cell reconstitution consisted predominantly of naïve and transitional subsets. This was paralleled by a decline in T follicular helper cells and CD4+ cytotoxic T cells and attenuation of fibro-inflammatory and B cell-mediated signaling networks on interactome analyses. In this treatment-refractory case of multiorgan IgG4-RD, CD19-directed CAR T cell therapy induced durable, treatment-free remission with normalization of serum IgG4 and improvement across multiple clinical endpoints. Multimodal immune profiling indicates that CAR T cells can reset the B cell compartment and dampen pathogenic T cell and stromal interactions, supporting prospective evaluation of CAR T cell therapy in IgG4-RD.

Mean-field theories of grain growth have been established for more than 70 years. They rely on the concepts of average grain size and self-similar size and edge distributions. In contrast, mesoscopic computer simulations enable the observation of a large number of grains over long annealing time spans. Thus, they allow the detailed surveillance of the behavior of individual grains. Hence, while the average grain size is an important construct for mean-field theories, using computer simulations we show that individual grains with the same number of edges from one polycrystalline structure evolve by distinct paths. As a result, the self-similar grain size and number of edges distributions form in a complex manner.