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"Frank, Anna"
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Digital technologies in designing mathematics education tasks : potential and pitfalls
This book is about the role and potential of using digital technology in designing teaching and learning tasks in the mathematics classroom and explores mathematics task design when digital technology is part of the teaching and learning environment.
Book
Efficient construction of Markov state models for stochastic gene regulatory networks by domain decomposition
Background
The dynamics of many gene regulatory networks (GRNs) is characterized by the occurrence of metastable phenotypes and stochastic phenotype switches. The chemical master equation (CME) is the most accurate description to model such stochastic dynamics, whereby the long-time dynamics of the system is encoded in the spectral properties of the CME operator. Markov State Models (MSMs) provide a general framework for analyzing and visualizing stochastic multistability and state transitions based on these spectral properties. Until now, however, this approach is either limited to low-dimensional systems or requires the use of high-performance computing facilities, thus limiting its usability.
Results
We present a domain decomposition approach (DDA) that approximates the CME by a stochastic rate matrix on a discretized state space and projects the multistable dynamics to a lower dimensional MSM. To approximate the CME, we decompose the state space via a Voronoi tessellation and estimate transition probabilities by using adaptive sampling strategies. We apply the robust Perron cluster analysis (PCCA+) to construct the final MSM. Measures for uncertainty quantification are incorporated. As a proof of concept, we run the algorithm on a single PC and apply it to two GRN models, one for the genetic toggle switch and one describing macrophage polarization. By comparing the results with reference solutions, we demonstrate that our approach correctly identifies the number and location of metastable phenotypes with adequate accuracy and uncertainty bounds. We show that accuracy mainly depends on the total number of Voronoi cells, whereas uncertainty is determined by the number of sampling points.
Conclusions
A DDA enables the efficient computation of MSMs with quantified uncertainty. Since the algorithm is trivially parallelizable, it can be applied to larger systems, which will inevitably lead to new insights into cell-regulatory dynamics.
Journal Article
Transmission of Bacterial Endophytes
Plants are hosts to complex communities of endophytic bacteria that colonize the interior of both below- and aboveground tissues. Bacteria living inside plant tissues as endophytes can be horizontally acquired from the environment with each new generation, or vertically transmitted from generation to generation via seed. A better understanding of bacterial endophyte transmission routes and modes will benefit studies of plant–endophyte interactions in both agricultural and natural ecosystems. In this review, we provide an overview of the transmission routes that bacteria can take to colonize plants, including vertically via seeds and pollen, and horizontally via soil, atmosphere, and insects. We discuss both well-documented and understudied transmission routes, and identify gaps in our knowledge on how bacteria reach the inside of plants. Where little knowledge is available on endophytes, we draw from studies on bacterial plant pathogens to discuss potential transmission routes. Colonization of roots from soil is the best studied transmission route, and probably the most important, although more studies of transmission to aerial parts and stomatal colonization are needed, as are studies that conclusively confirm vertical transfer. While vertical transfer of bacterial endophytes likely occurs, obligate and strictly vertically transferred symbioses with bacteria are probably unusual in plants. Instead, plants appear to benefit from the ability to respond to a changing environment by acquiring its endophytic microbiome anew with each generation, and over the lifetime of individuals.
Journal Article
Handbook of critical policy studies
Critical policy studies, as illustrated in this handbook, challenges the conventional approaches of public policy inquiry. But it offers important innovations as well, in particular its focus on discursive politics, policy argumentation and deliberation and interpretive modes of analysis. This volume offers a compilation of critical work that assesses past developments and appraises emerging issues.
Book
The persuasive effects of emotional green packaging claims
Purpose
The purpose of this paper is to investigate the effects of rational green packaging claims vs emotional green packaging claims on consumers’ purchase propensity for organic coffee.
Design/methodology/approach
Three within-subjects experiment were carried out (N=87, N=245, N=60). The experimental design encompasses packaging with rational green claims, emotional green claims, as well as a neutral (control) claim. Measured variables are introduced to assess participants’ environmental commitment and information processing ability. A manipulated between-subjects variable is introduced to test how distraction interacts with preference for the claims.
Findings
Overall, consumers prefer products with green claims over those with neutral (control) claims, and products with emotional green claims to those with rational green claims. The studies also reveal that this effect is moderated by participants’ environmental commitment, information processing ability and by distraction. The findings were statistically significant (p<0.05).
Research limitations/implications
As a lab experiment, the study provides limited generalizability and external validity.
Practical implications
For most organic FMCG products, it is advisable to employ emotional packaging claims.
Social implications
The presented findings provide marketers with tools to influence consumer behavior toward sustainable choices.
Originality/value
The paper validates previous contributions on the effects of product claim types, and extends them by introducing comprehensive empirical data on all the Elaboration Likelihood Model’s criteria for rational decision-making; motivation, opportunity and ability.
Journal Article
Isolation and propagation of primary human cholangiocyte organoids for the generation of bioengineered biliary tissue
Pediatric liver transplantation is often required as a consequence of biliary disorders because of the lack of alternative treatments for repairing or replacing damaged bile ducts. To address the lack of availability of pediatric livers suitable for transplantation, we developed a protocol for generating bioengineered biliary tissue suitable for biliary reconstruction. Our platform allows the derivation of cholangiocyte organoids (COs) expressing key biliary markers and retaining functions of primary extra- or intrahepatic duct cholangiocytes within 2 weeks of isolation. COs are subsequently seeded on polyglycolic acid (PGA) scaffolds or densified collagen constructs for 4 weeks to generate bioengineered tissue retaining biliary characteristics. Expertise in organoid culture and tissue engineering is desirable for optimal results. COs correspond to mature functional cholangiocytes, differentiating our method from alternative organoid systems currently available that propagate adult stem cells. Consequently, COs provide a unique platform for studies in biliary physiology and pathophysiology, and the resulting bioengineered tissue has broad applications for regenerative medicine and cholangiopathies.Bioengineered biliary tissue suitable for biliary reconstruction is obtained from cholangiocyte organoids derived from human primary extra- or intrahepatic duct cholangiocytes.
Journal Article
Intermittent hypoxia treatments cause cellular priming in human microglia
Obstructive sleep apnoea syndrome (OSAS) is a sleep‐disordered breathing characterized by nocturnal collapses of the upper airway resulting in cycles of blood oxygen partial pressure oscillations, which lead to tissue and cell damage due to intermittent hypoxia (IH) episodes. Since OSAS‐derived IH may lead to cognitive impairment through not fully cleared mechanisms, herein we developed a new in vitro model mimicking IH conditions to shed light on its molecular effects on microglial cells, with particular attention to the inflammatory response. The in vitro model was set‐up and validated by measuring the hypoxic state, HIF‐1α levels, oxidative stress by ROS production and mitochondrial activity by MTS assay. Then, the mRNA and protein levels of certain inflammatory markers (NF‐κB and interleukin 6 (IL‐6)) after different IH treatment protocols were investigated. The IH treatments followed by a normoxic period were not able to produce a high inflammatory state in human microglial cells. Nevertheless, microglia appeared to be in a state characterized by increased expression of NF‐κB and markers related to a primed phenotype. The microglia exposed to IH cycles and stimulated with exogenous IL‐1β resulted in an exaggerated inflammatory response with increased NF‐κB and IL‐6 expression, suggesting a role for primed microglia in OSAS‐driven neuroinflammation.
Journal Article
Structure of Current Sheets Formed in 2D Magnetic Configurations with X-Type Null Lines in the Presence of the Hall Currents and Inverse Currents
We present experimental results on the formation and evolution of current sheets in two-dimensional magnetic configurations with an X-type null line. Typical features of both the initial magnetic field and the current sheet are their symmetry properties. The experiments were carried out using the CS-3D setup. The formation of a current sheet occurs just after the magneto-sonic wave converges at the null line; then, both the electric current and plasma become compressed in a planar 2D sheet, which accumulates an excess of magnetic energy. The excitation of the Hall currents, which build up the out-of-plane magnetic fields inside the 2D current sheet, brings about the modification of the sheet structure. As a result, the magnetic fields and plasma currents become 3D. The dynamic plasma processes give rise to additional current sheet deformations, which are caused by the excitation of inverse currents at the side edges of the sheet. As a consequence, the out-of-plane magnetic fields are reversed, and strong Ampère’s forces of the opposite directions come into play. These forces slow down the previously accelerated high-speed plasma flows so that the flows become limited in time and space.
Journal Article
Dragging, instrumented abduction and evidence, in processes of conjecture generation in a dynamic geometry environment
In a dynamic geometry environment (DGE) conjectures can be generated by manipulating figures with different dragging strategies. One strategy (maintaining dragging) that has been the focus of various studies, consists of inducing a specific geometric property and trying to maintain it. In this paper I focus on abduction and evidence within such processes of the generation of conjectures. I discuss the particular nature of the abductive process associated with the use of maintaining dragging (instrumented abduction). In respect of other forms of abduction reported in the literature, I highlight their key role in bridging phenomenological evidence and theoretical evidence. Results from analysis of a case study suggest that using maintaining dragging leads students to the generation of conjectures with solid phenomenological evidence. On the other hand, the process withholds a potential fragility with respect to proof of the conjectures generated, due to the scarce theoretical evidence stemming from it.
Journal Article