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Glioblastomas are incurable primary brain tumors harboring a heterogeneous landscape of genetic and metabolic alterations. Longitudinal imaging by MRI and [18F]FET-PET measurements enable us to visualize the features of evolving tumors in a dynamic manner. Yet, close-meshed longitudinal imaging time points for characterizing temporal and spatial metabolic alterations during tumor evolution in patients is not feasible because patients usually present with already established tumors. The replication-competent avian sarcoma-leukosis virus (RCAS)/tumor virus receptor-A (tva) system is a powerful preclinical glioma model offering a high grade of spatial and temporal control of somatic gene delivery in vivo. Consequently, here, we aimed at using MRI and [18F]FET-PET to identify typical neuroimaging characteristics of the platelet-derived growth factor B (PDGFB)-driven glioma model using the RCAS-tva system. Our study showed that this preclinical glioma model displays MRI and [18F]FET-PET features that highly resemble the corresponding established human disease, emphasizing the high translational relevance of this experimental model. Furthermore, our investigations unravel exponential growth dynamics and a model-specific tumor microenvironment, as assessed by histology and immunochemistry. Taken together, our study provides further insights into this preclinical model and advocates for the imaging-stratified design of preclinical therapeutic interventions. [ABSTRACT FROM AUTHOR]

Repetitive mild traumatic brain injury (rmTBI) is a prominent public health concern, with linkage to debilitating chronic sequelae. Developing reliable and well-characterized preclinical models of rmTBI is imperative in the investigation of the underlying pathophysiological mechanisms, as models can have varying parameters, affecting the overall pathology of the resulting injury. The lateral fluid percussion injury (FPI) model is a reliable and frequently used method of TBI replication in rodent subjects, though it is currently relatively underutilized in rmTBI research. In this study, we have performed a novel description of a variation of the lateral repetitive mild FPI (rmFPI) model, showing the graded acute behavioral impairment and histopathology occurring in response to one, two or fourmild FPI (1.25 atm) or sham surgeries, implemented 24h apart. Beam walking performance revealed significant motor impairment in injured animals, with dysfunction increasing with additional injury. Based upon behavioral responses and histological observations, we further investigated the subacute pathophysiological outcomes of the dual FPI (dFPI). Immunoreactivity assessments showed that dFPI led to regionally- specific reductions in the post-synaptic protein neurogranin and increased subcortical white matter staining of the presynaptic protein synaptophysin at 2 weeks following dFPI. Immunohistochemical assessments of the microglial marker Iba-1 showed a striking increase in in several brain regions, and assessment of the astrocytic marker GFAP showed significantly increased immunoreactivity in the subcortical white matter and thalamus. With this study, we have provided a novel account of the subacute post injury outcomes occurring in response to a rmFPI utilizing these injury and frequency parameters, and thereby also demonstrating the reliability of the lateral FPI model in rmTBI replication. [ABSTRACT FROM AUTHOR]

Repetitive mild traumatic brain injury (rmTBI) is a prominent public health concern, with linkage to debilitating chronic sequelae. Developing reliable and well-characterized preclinical models of rmTBI is imperative in the investigation of the underlying pathophysiological mechanisms, as models can have varying parameters, affecting the overall pathology of the resulting injury. The lateral fluid percussion injury (FPI) model is a reliable and frequently used method of TBI replication in rodent subjects, though it is currently relatively underutilized in rmTBI research. In this study, we have performed a novel description of a variation of the lateral repetitive mild FPI (rmFPI) model, showing the graded acute behavioral impairment and histopathology occurring in response to one, two or four mild FPI (1.25 atm) or sham surgeries, implemented 24h apart. Beam walking performance revealed significant motor impairment in injured animals, with dysfunction increasing with additional injury. Based upon behavioral responses and histological observations, we further investigated the subacute pathophysiological outcomes of the dual FPI (dFPI). Immunoreactivity assessments showed that dFPI led to regionally-specific reductions in the post-synaptic protein neurogranin and increased subcortical white matter staining of the presynaptic protein synaptophysin at 2 weeks following dFPI. Immunohistochemical assessments of the microglial marker Iba-1 showed a striking increase in in several brain regions, and assessment of the astrocytic marker GFAP showed significantly increased immunoreactivity in the subcortical white matter and thalamus. With this study, we have provided a novel account of the subacute post injury outcomes occurring in response to a rmFPI utilizing these injury and frequency parameters, and thereby also demonstrating the reliability of the lateral FPI model in rmTBI replication.

Three-dimensional cell cultures may better mimic avascular tumors. Yet, they still lack characterization and standardization. Therefore, this study aimed to (a) generate multicellular aggregates (MCAs) of four breast cell lines: MCF7, MDA-MB-231, and SKBR3 (tumoral) and MCF12A (non-tumoral) using ultra-low attachment (ULA) plates, (b) detail the methodology used for their formation and analysis, providing technical tips, and (c) characterize the MCAs using morphometry, qualitative cytology (at light and electron microscopy), and quantitative immunocytochemistry (ICC) analysis. Each cell line generated uniform MCAs with structural differences among cell lines: MCF7 and MDA-MB-231 MCAs showed an ellipsoid/discoid shape and compact structure, while MCF12A and SKBR3 MCAs were loose, more flattened, and presented bigger areas. MCF7 MCAs revealed glandular breast differentiation features. ICC showed a random distribution of the proliferating and apoptotic cells throughout the MCAs, not fitting in the traditional spheroid model. ICC for cytokeratin, vimentin, and E-cadherin showed different results according to the cell lines. Estrogen (ER) and progesterone (PR) receptors were positive only in MCF7 and human epidermal growth factor receptor 2 (HER-2) in SKBR3. The presented characterization of the MCAs in non-exposed conditions provided a good baseline to evaluate the cytotoxic effects of potential anticancer compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] Uveitis is a group of inflammatory ocular pathologies. Endotoxin-Induced Uveitis (EIU) model represent a well-known model induced by administration of Lipopolysaccharide (LPS). The aim is to characterize two models of EIU through two routes of administration with novel noninvasive imaging techniques. 29 rats underwent Intraocular Pressure (IOP) measurements, Optical Coherence Tomography (OCT), proteomic analysis, and Positron Emission Tomography and Computed Tomography (PET/CT). Groups included healthy controls (C), BSS administered controls (Ci), systemically induced EIU with LPS (LPSs), and intravitreally induced EIU with LPS (LPSi) for IOP, OCT, and proteomic studies. For 18F-FDG PET/CT study, animals were divided into FDG-C, FDG-LPSs and FDG-LPSi groups and scanned using a preclinical PET/CT system. LPSi animals exhibited higher IOP post-induction compared to C and LPSs groups. LPSi showed increased cellular infiltrate, fibrotic membranes, and iris inflammation. Proinflammatory proteins were more expressed in EIU models, especially LPSi. PET/CT indicated higher eye uptake in induced models compared to FDG-C. FDG-LPSi showed higher eye uptake than FDG-LPSs but systemic uptake was higher in FDG-LPSs due to generalized inflammation. OCT is valuable for anterior segment assessment in experimental models. 18F-FDG PET/CT shows promise as a noninvasive biomarker for ocular inflammatory diseases. Intravitreal induction leads to higher ocular inflammation. These findings offer insights for future inflammatory disease research and drug studies. [ABSTRACT FROM AUTHOR]

Aluminium-alloys are widely used in aeronautical engineering due to the advantages of high strength and easy processing. Low temperature inevitably occurs in aero-structures of aluminium-alloys, and cryogenic crack propagation of aeronautic aluminium-alloys is received a great deal of attention and research. The advances in cryogenic crack propagation of aeronautic aluminium-alloys is summarized, and the experiment investigations on cryogenic crack growth of aeronautic aluminium-alloys are described, and the failure mechanisms on cryogenic fracture are concluded. The characterization models and life evaluation methodologies on cryogenic crack growth of aeronautic aluminium-alloys are summarized and further research problems are argued for engineering design and application of aeronautic aluminium-alloys.

Glioblastomas are incurable primary brain tumors harboring a heterogeneous landscape of genetic and metabolic alterations. Longitudinal imaging by MRI and [18F]FET-PET measurements enable us to visualize the features of evolving tumors in a dynamic manner. Yet, close-meshed longitudinal imaging time points for characterizing temporal and spatial metabolic alterations during tumor evolution in patients is not feasible because patients usually present with already established tumors. The replication-competent avian sarcoma-leukosis virus (RCAS)/tumor virus receptor-A (tva) system is a powerful preclinical glioma model offering a high grade of spatial and temporal control of somatic gene delivery in vivo. Consequently, here, we aimed at using MRI and [18F]FET-PET to identify typical neuroimaging characteristics of the platelet-derived growth factor B (PDGFB)-driven glioma model using the RCAS-tva system. Our study showed that this preclinical glioma model displays MRI and [18F]FET-PET features that highly resemble the corresponding established human disease, emphasizing the high translational relevance of this experimental model. Furthermore, our investigations unravel exponential growth dynamics and a model-specific tumor microenvironment, as assessed by histology and immunochemistry. Taken together, our study provides further insights into this preclinical model and advocates for the imaging-stratified design of preclinical therapeutic interventions.

There is a pressing requirement to design a simple battery thermal model that balances simulation accuracy regarding battery thermal characteristics and engineering application feasibility. The paper carries out the experimental study and model characterization of thermoelectric coupling characteristics of ternary lithium batteries with different shapes under ambient temperature conditions. The paper designs a characterization method of the battery thermoelectric coupling model. It conducts experiments to analyze the battery's charging and discharging characteristics and extracts essential modeling parameters. It reveals the differences in the modeling parameters of ternary lithium batteries with different shapes and constructs the thermoelectric coupling models of the square and 21700 cylindrical ternary lithium battery respectively. At the same time, the paper applies the model to carry out the simulation and experimental verification of the battery thermal behavior. The experimental data monitored by the infrared thermal imager and temperature sensors are compared with the simulation results. The errors are less than 5 %. It can provide a reference for related researches and engineering applications of battery thermal behavior and thermal management. • Designing a model characterization method for batteries with different shapes. • Revealing differences in modeling parameters of batteries with different shapes. • Constructing a simpler battery thermal model with low calculation volume. • Balancing the accuracy of simulation with the feasibility of applications. [ABSTRACT FROM AUTHOR]

Three-dimensional cell cultures may better mimic avascular tumors. Yet, they still lack characterization and standardization. Therefore, this study aimed to (a) generate multicellular aggregates (MCAs) of four breast cell lines: MCF7, MDA-MB-231, and SKBR3 (tumoral) and MCF12A (non-tumoral) using ultra-low attachment (ULA) plates, (b) detail the methodology used for their formation and analysis, providing technical tips, and (c) characterize the MCAs using morphometry, qualitative cytology (at light and electron microscopy), and quantitative immunocytochemistry (ICC) analysis. Each cell line generated uniform MCAs with structural differences among cell lines: MCF7 and MDA-MB-231 MCAs showed an ellipsoid/discoid shape and compact structure, while MCF12A and SKBR3 MCAs were loose, more flattened, and presented bigger areas. MCF7 MCAs revealed glandular breast differentiation features. ICC showed a random distribution of the proliferating and apoptotic cells throughout the MCAs, not fitting in the traditional spheroid model. ICC for cytokeratin, vimentin, and E-cadherin showed different results according to the cell lines. Estrogen (ER) and progesterone (PR) receptors were positive only in MCF7 and human epidermal growth factor receptor 2 (HER-2) in SKBR3. The presented characterization of the MCAs in non-exposed conditions provided a good baseline to evaluate the cytotoxic effects of potential anticancer compounds.

Rationale: Huntington disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive and neuropsychiatric symptoms. HD is usually diagnosed by the appearance of motor deficits, resulting in skilled hand use disruption, gait abnormality, muscle wasting and choreatic movements. The BACHD transgenic rat model for HD represents a well-established transgenic rodent model of HD, offering the prospect of an in-depth characterization of the motor phenotype.Objective: The present study aims to characterize different aspects of motor function in BACHD rats, combining classical paradigms with novel high-throughput behavioral phenotyping.Methods: Wild-type (WT) and transgenic animals were tested longitudinally from 2 to 12 months of age. To measure fine motor control, rats were challenged with the pasta handling test and the pellet reaching test. To evaluate gross motor function, animals were assessed by using the holding bar and the grip strength tests. Spontaneous locomotor activity and circadian rhythmicity were assessed in an automated home-cage environment, namely the PhenoTyper. We then integrated existing classical methodologies to test motor function with automated home-cage assessment of motor performance.Results: BACHD rats showed strong impairment in muscle endurance at 2 months of age. Altered circadian rhythmicity and locomotor activity were observed in transgenic animals. On the other hand, reaching behavior, forepaw dexterity and muscle strength were unaffected.Conclusions: The BACHD rat model exhibits certain features of HD patients, like muscle weakness and changes in circadian behavior. We have observed modest but clear-cut deficits in distinct motor phenotypes, thus confirming the validity of this transgenic rat model for treatment and drug discovery purposes.

Rationale: Huntington disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive and neuropsychiatric symptoms. HD is usually diagnosed by the appearance of motor deficits, resulting in skilled hand use disruption, gait abnormality, muscle wasting and choreatic movements. The BACHD transgenic rat model for HD represents a well-established transgenic rodent model of HD, offering the prospect of an in-depth characterization of the motor phenotype. Objective: The present study aims to characterize different aspects of motor function in BACHD rats, combining classical paradigms with novel high-throughput behavioral phenotyping. Methods: Wild-type (WT) and transgenic animals were tested longitudinally from 2 to 12 months of age. To measure fine motor control, rats were challenged with the pasta handling test and the pellet reaching test. To evaluate gross motor function, animals were assessed by using the holding bar and the grip strength tests. Spontaneous locomotor activity and circadian rhythmicity were assessed in an automated home-cage environment, namely the PhenoTyper. We then integrated existing classical methodologies to test motor function with automated home-cage assessment of motor performance. Results: BACHD rats showed strong impairment in muscle endurance at 2 months of age. Altered circadian rhythmicity and locomotor activity were observed in transgenic animals. On the other hand, reaching behavior, forepaw dexterity and muscle strength were unaffected. Conclusions: The BACHD rat model exhibits certain features of HD patients, like muscle weakness and changes in circadian behavior. We have observed modest but clear-cut deficits in distinct motor phenotypes, thus confirming the validity of this transgenic rat model for treatment and drug discovery purposes. [ABSTRACT FROM AUTHOR]

Anxiety as a common feature of several neurodegenerative/polyglutamine diseases is an important aspect for the face validity of an animal model for Spinocerebellar Ataxia type 17 (SCA17). Risk assessment and anxiety-like traits were characterised in 3–6–9 months old rats of a transgenic model for SCA17 using the standard behavioural test elevated plus maze. In addition, c-Fos immunostainings in the basolateral amygdala evaluated neuronal activation in correlation to the behavioural responses. The most prominent behavioural effect was a higher level of risk assessment in the transgenic rats. In addition, an increase in anxiety-related behaviour in these rats was found. Although the EPM caused no overall effect on c-Fos expression, a negative correlation with the anxiety-like behavioural response was observed. Our results suggest that the SCA17 rat model displays an anxious phenotype already at 3 months of age resembling the generalized anxiety in early symptomatic SCA17 patients, thus confirming the validity of this rat model. [ABSTRACT FROM AUTHOR]

The distributions obtained by left-truncating atka mixed Poisson distribution, denotedkT-MP, and those obtained by mixing previously left-truncated Poisson distributions, denoted M-kTP, are characterized by means of their probability generating function. The main consequence is that everykT-MP distribution is a M-kTP distribution, but not the other way around. [ABSTRACT FROM PUBLISHER]

Cortical information processing originates from the exchange of action potentials between many cell types. To capture the essence of these interactions, it is of critical importance to build mathematical models that reflect the characteristic features of spike generation in individual neurons. We propose a framework to automatically extract such features from current-clamp experiments, in particular the passive properties of a neuron (i.e., membrane time constant, reversal potential, and capacitance), the spike-triggered adaptation currents, as well as the dynamics of the action potential threshold. The stochastic model that results from our maximum likelihood approach accurately predicts the spike times, the subthreshold voltage, the firing patterns, and the type of frequency-current curve. Extracting the model parameters for three cortical cell types revealed that cell types show highly significant differences in the time course of the spike-triggered currents and moving threshold, that is, in their adaptation and refractory properties but not in their passive properties. In particular, GABAergic fast-spiking neurons mediate weak adaptation through spike-triggered currents only, whereas regular spiking excitatory neurons mediate adaptation with both moving threshold and spike-triggered currents. GABAergic nonfast-spiking neurons combine the two distinct adaptation mechanisms with reduced strength. Differences between cell types are large enough to enable automatic classification of neurons into three different classes. Parameter extraction is performed for individual neurons so that we find not only the mean parameter values for each neuron type but also the spread of parameters within a group of neurons, which will be useful for future large-scale computer simulations. [ABSTRACT FROM AUTHOR]

We present a physics-based finite-element model of operation of an AlGaN/GaN HEMT with device geometry inputs taken from transmission electron microscope cross sections and calibrated by comparison with measured electrical data comprising standard field-effect transistor metrics and less well-known model parameters. A variety of electrical outputs from the model are compared to experiment, and the level of agreement is reported. [ABSTRACT FROM AUTHOR]

Abstract: Previous model classification efforts have led to a broad group of models from site-scale (non-spatial) gap models to continental-scale biogeographical models due to a lack of definition of landscape models. Such classifications become inefficient to compare approaches and techniques that are specifically associated with forest landscape modeling. This paper provides definitions of key terminologies commonly used in forest landscape modeling to classify forest landscape models. It presents a set of qualitative criteria for model classification. These criteria represent model definitions and key model implementation decisions, including the temporal resolution, number of spatial processes simulated, and approaches to simulate site-level succession. Four approaches of simulating site level succession are summarized: (1) no site-level succession (spatial processes as surrogates), (2) successional pathway, (3) vital attribute, and (4) model coupling. Computational load for the first three approaches is calculated using the Big O Notation, a standard method. Classification criteria are organized in a hierarchical order that creates a dichotomous tree with each end node representing a group of models with similar traits. The classified models fall into various groups ranging from theoretical and empirical to strategic and tactical. The paper summarizes the applications of forest landscape models into three categories: (1) spatiotemporal patterns of model objects, (2) sensitivities of model object to input parameters, and (3) scenario analyses. Finally, the paper discusses two dilemmas related to the use of forest landscape models: result validation and circular reasoning. [Copyright &y& Elsevier]

When using a model to predict the behavior of a physical system of interest, engineers must be confident that, under the conditions of interest, the model is an adequate representation of the system. The process of building this confidence is called model validation. It requires that engineers have knowledge about the system and conditions of interest, properties of the model and their own tolerance for uncertainty in the predictions. To reduce time and costs, engineers often reuse preexisting models that other engineers have developed. However, if the user lacks critical parts of this knowledge, model validation can be as time consuming and costly as developing a similar model from scratch. In this article, we describe a general process for performing model validation for reused behavioral models that overcomes this problem by relying on the formalization and exchange of knowledge. We identify the critical elements of this knowledge, discuss how to represent it and demonstrate the overall process on a simple engineering example. [ABSTRACT FROM AUTHOR]

The paper presents new characterizations of the integer-valued moving average model. For four model variants, we give moments and probability generating functions. Yule–Walker and conditional least-squares estimators are obtained and studied by Monte Carlo simulation. A new generalized method of moment estimator based on probability generating functions is presented and shown to be consistent and asymptotically normal. The small sample performance is in some instances better than those of alternative estimators. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Computational modeling for additive manufacturing has proven to be a powerful tool to understand physical mechanisms, predict fabrication quality, and guide design and optimization. Varieties of models have been developed with different assumptions and purposes, and these models are sometimes difficult to choose from, especially for end-users, due to the lack of quantitative comparison and standardization. Thus, this study is focused on quantifying model uncertainty due to the modeling assumptions, and evaluating differences based on whether or not selected physical factors are incorporated. Multiple models with different assumptions, including a high-fidelity thermal-fluid flow model resolving individual powder particles, a low-fidelity heat transfer model simplifying the powder bed as a continuum material, and a semi-analytical thermal model using a point heat source model, were run with a variety of manufacturing process parameters. Experiments were performed on the National Institute of Standards and Technology (NIST) Additive Manufacturing Metrology Testbed (AMMT) to validate the models. A data analytics-based methodology was utilized to characterize the models to estimate the error distribution. The cross comparison of the simulation results reveals the remarkable influence of fluid flow, while the significance of the powder layer varies across different models. This study aims to provide guidance on model selection and corresponding accuracy, and more importantly facilitate the development of AM models.