bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear and nonlinear vibrations of variable cross‐section beams using shear deformation theory
Authors: Sohani Fatemeh , Eipakchi Hamidreza 
Published: January 2021

AbstractIn the present paper, the governing equations of a vibratory beam with moderately large deflection and arbitrary cross‐section are derived by using the first‐order shear deformation theory. The beam is homogenous, isotropic and it is subjected to the axial loads. The kinematic of the problem is according to the von‐Kármán strain‐displacement relations and the Hooke law is used as the constitutive equations. The partial differential governing equations describing the axial and transverse vibrations of homogeneous beams contain four coupled nonlinear equations with variable coefficients which are derived employing Hamilton's principle. The Galerkin method in conjunction with the perturbation technique is applied to obtain the linear natural frequencies. A parametric study is performed and the effects of different thickness functions such as linear, polynomial and trigonometric on the results are investigated. The non‐linear frequencies which contain the corrections on the linear frequencies are calculated. The corrected parts of the non‐linear frequencies are functions of the axial as well as the transverse amplitudes of the vibrations. The influences of the axial load and aspect ratio on the linear and non‐linear frequencies are studied too. To confirm the reliability of the vibration analysis carried out in the present paper, the analytical results are checked with the corresponding numerical results obtained from the finite element analysis. The numerical and analytical results are in a good agreement.
MRI Mapping of the Blood Oxygenation Sensitive Parameter T2* in the Kidney: Basic Concept
Authors: Li Lu-Ping , Hack Bradley , Seeliger Erdmann , Prasad Pottumarthi V. 
Published: January 2021

AbstractThe role of hypoxia in renal disease and injury has long been suggested but much work still remains, especially as it relates to human translation. Invasive pO2 probes are feasible in animal models but not for human use. In addition, they only provide localized measurements. Histological methods can identify hypoxic tissue and provide a spatial distribution, but are invasive and allow only one-time point. Blood oxygenation level dependent (BOLD) MRI is a noninvasive method that can monitor relative oxygen availability across the kidney. It is based on the inherent differences in magnetic properties of oxygenated vs. deoxygenated hemoglobin. Presence of deoxyhemoglobin enhances the spin–spin relaxation rate measured using a gradient echo sequence, known as R2* (= 1/T2*). While the key interest of BOLD MRI is in the application to humans, use in preclinical models is necessary primarily to validate the measurement against invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRI acquisitions in preclinical settings involves several challenges both in terms of logistics and data acquisition. This section will introduce the concept of BOLD MRI and provide some illustrative applications. The following sections will discuss the technical issues associated with data acquisition and analysis.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
Hyperpolarized Carbon (13C) MRI of the Kidneys: Basic Concept
Authors: von Morze Cornelius , Reed Galen D. , Wang Zhen J. , Ohliger Michael A. , Laustsen Christoffer 
Published: January 2021

AbstractExisting clinical markers for renal disease are limited. Hyperpolarized (HP) 13C MRI is based on the technology of dissolution dynamic nuclear polarization (DNP) and provides new avenues for imaging kidney structure, function, and most notably, renal metabolism, addressing some of these prior limitations. Changes in kidney structure and function associated with kidney disease can be evaluated using [13C]urea, a metabolically inert tracer. Metabolic changes can be assessed using [1-13C]pyruvate and a range of other rapidly metabolized small molecules, which mainly probe central carbon metabolism. Results from numerous preclinical studies using a variety of these probes demonstrated that this approach holds great potential for monitoring renal disease, although more work is needed to bridge intelligently into clinical studies. Here we introduce the general concept of HP 13C MRI and review the most relevant probes and applications to renal disease, including kidney cancer, diabetic nephropathy and ischemic kidney injury.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
MR Elastography of the Abdomen: Basic Concepts
Authors: Serai Suraj D. , Yin Meng 
Published: January 2021

AbstractMagnetic resonance elastography (MRE) is an emerging imaging modality that maps the elastic properties of tissue such as the shear modulus. It allows for noninvasive assessment of stiffness, which is a surrogate for fibrosis. MRE has been shown to accurately distinguish absent or low stage fibrosis from high stage fibrosis, primarily in the liver. Like other elasticity imaging modalities, it follows the general steps of elastography: (1) apply a known cyclic mechanical vibration to the tissue; (2) measure the internal tissue displacements caused by the mechanical wave using magnetic resonance phase encoding method; and (3) infer the mechanical properties from the measured mechanical response (displacement), by generating a simplified displacement map. The generated map is called an elastogram.While the key interest of MRE has traditionally been in its application to liver, where in humans it is FDA approved and commercially available for clinical use to noninvasively assess degree of fibrosis, this is an area of active research and there are novel upcoming applications in brain, kidney, pancreas, spleen, heart, lungs, and so on. A detailed review of all the efforts is beyond the scope of this chapter, but a few specific examples are provided. Recent application of MRE for noninvasive evaluation of renal fibrosis has great potential for noninvasive assessment in patients with chronic kidney diseases. Development and applications of MRE in preclinical models is necessary primarily to validate the measurement against “gold-standard” invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRE acquisitions in preclinical settings involves challenges in terms of available hardware, logistics, and data acquisition. This chapter will introduce the concepts of MRE and provide some illustrative applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by another separate chapter describing the experimental protocol and data analysis.
Monitoring Renal Hemodynamics and Oxygenation by Invasive Probes: Experimental Protocol
Authors: Cantow Kathleen , Ladwig-Wiegard Mechthild , Flemming Bert , Pohlmann Andreas , Niendorf Thoralf , Seeliger Erdmann 
Published: January 2021

AbstractRenal tissue hypoperfusion and hypoxia are early key elements in the pathophysiology of acute kidney injury of various origins, and may also promote progression from acute injury to chronic kidney disease. Here we describe methods to study control of renal hemodynamics and tissue oxygenation by means of invasive probes in anesthetized rats. Step-by-step protocols are provided for two setups, one for experiments in laboratories for integrative physiology and the other for experiments within small-animal magnetic resonance scanners.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by a separate chapter describing the basic concepts of quantitatively assessing renal perfusion and oxygenation with invasive probes.
Essential Practical Steps for MRI of the Kidney in Experimental Research
Authors: Pohlmann Andreas , Periquito João S. , Niendorf Thoralf 
Published: January 2021

AbstractMagnetic resonance imaging (MRI) is an emerging method to obtain valuable functional and structural information about the kidney noninvasively. Before performing specialized MR measurements for probing tissue structure and function, some essential practical steps are needed, which are common for most applications. Here we describe in a step-by-step manner how to (1) achieve the double-oblique slice orientation coronal-to-the-kidney, (2) adapt the scan protocol for avoiding aortic flow artifacts and covering both kidneys, (3) perform localized shimming on the kidney, and (4) check perfusion in the large renal blood vessels using time-of-flight (TOF) angiography. The procedures are tailored to preclinical MRI but conceptionally are also applicable to human MRI.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter explains the initial and essential MRI steps that precede specific functional and structural MR imaging techniques (T1- and T2*-mapping, DWI, ASL, etc.), which are described in separate chapters.
Experimental Protocol for MRI Mapping of the Blood Oxygenation-Sensitive Parameters T2* and T2 in the Kidney
Authors: Pohlmann Andreas , Zhao Kaixuan , Fain Sean B. , Prasad Pottumarthi V. , Niendorf Thoralf 
Published: January 2021

AbstractRenal hypoxia is generally accepted as a key pathophysiologic event in acute kidney injury of various origins, and has also been suggested to play a role in the development of chronic kidney disease. Here we describe a step-by-step experimental protocol for indirect monitoring of renal blood oxygenation in rodents via the deoxyhemoglobin sensitive MR parameters T2* and T2—a contrast mechanism known as the blood oxygenation level dependent (BOLD) effect. Since an absolute quantification of renal oxygenation from T2*/T2 remains challenging, the effects of controlled and standardized variations in the fraction of inspired oxygen are used for bench marking. This MRI method may be useful for investigating renal blood oxygenation of small rodents in vivo under various experimental (patho)physiological conditions.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.
Renal MRI Diffusion: Experimental Protocol
Authors: Periquito João S. , Meier Martin , Niendorf Thoralf , Pohlmann Andreas , Jerome Neil Peter 
Published: January 2021

AbstractRenal diffusion-weighted imaging (DWI) can be used to obtain information on the microstructure of kidney tissue, and has the potential to provide MR-biomarkers for functional renal imaging. Here we describe in a step-by-step experimental protocol the MRI method for measuring renal diffusion coefficients in rodents using ADC or IVIM models. Both methods provide quantification of renal diffusion coefficients; however, IVIM, a more complex model, allows for the calculation of the pseudodiffusion and fraction introduced by tissue vascular and tubular components. DWI provides information of renal microstructure contributing to the understanding of the physiology and the underlying processes that precede the beginning of pathologies.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.
Renal pH Mapping Using Chemical Exchange Saturation Transfer (CEST) MRI: Experimental Protocol
Authors: Pavuluri Kowsalya Devi , Consolino Lorena , Longo Dario Livio , Irrera Pietro , Sun Phillip Zhe , McMahon Michael T. 
Published: January 2021

AbstractChemical exchange saturation transfer (CEST) is recognized as one of the premier methods for measuring pH with this environmental variable expected to be an excellent biomarker for kidney diseases. Here we describe step-by-step CEST MRI experimental protocols for producing pH and perfusion maps for monitoring kidney pH homeostasis in rodents after administering iopamidol as contrast agent. Several CEST techniques, acquisition protocols and ratiometric approaches are described. The impact of length of acquisition time on the quality of the maps is detailed. These methods may be useful for investigating progression in kidney disease in vivo for rodent models.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol is complemented by two separate chapters describing the basic concepts and data analysis.
Sodium (23Na) MRI of the Kidney: Experimental Protocol
Authors: Grist James T. , Hansen Esben Søvsø , Zöllner Frank G. , Laustsen Christoffer 
Published: January 2021

AbstractSodium handling is a key physiological hallmark of renal function. Alterations are generally considered a pathophysiologic event associated with kidney injury, with disturbances in the corticomedullary sodium gradient being indicative of a number of conditions. This experimental protocol review describes the individual steps needed to perform 23Na MRI; allowing accurate monitoring of the renal sodium distribution in a step-by-step experimental protocol for rodents.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.
Preparation and Monitoring of Small Animals in Renal MRI
Authors: Kaucsar Tamas , Hosszu Adam , Seeliger Erdmann , Reimann Henning M. , Fekete Andrea 
Published: January 2021

AbstractRenal diseases remain devastating illnesses with unacceptably high rates of mortality and morbidity worldwide. Animal models are essential tools to better understand the pathomechanism of kidney-related illnesses and to develop new, successful therapeutic strategies. Magnetic resonance imaging (MRI) has been actively explored in the last decades for assessing renal function, perfusion, tissue oxygenation as well as the degree of fibrosis and inflammation. This chapter aims to provide an overview of the preparation and monitoring of small animals before, during, and after surgical interventions or MR imaging. Standardization of experimental settings such as body temperature or hydration of animals and minimizing pain and distress are essential for diminishing nonexperimental variables as well as for conducting ethical research.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.
Fluorine (19F) MRI to Measure Renal Oxygen Tension and Blood Volume: Experimental Protocol
Authors: Hu Lingzhi , Pan Hua , Wickline Samuel A. 
Published: January 2021

AbstractFluorinated compounds feature favorable toxicity profile and can be used as a contrast agent for magnetic resonance imaging and spectroscopy. Fluorine nucleus from fluorinated compounds exhibit well-known advantages of being a high signal nucleus with a natural abundance of its stable isotope, a convenient gyromagnetic ratio close to that of protons, and a unique spectral signature with no detectable background at clinical field strengths. Perfluorocarbon core nanoparticles (PFC NP) are a class of clinically approved emulsion agents recently applied in vivo for ligand-targeted molecular imaging. The objective of this chapter is to outline a multinuclear 1H/19F MRI protocol for functional kidney imaging in rodents for mapping of renal blood volume and oxygenation (pO2) in renal disease models.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by a separate chapter describing the basic concept of functional imaging using fluorine (19F) MR methods.
Quantitative Analysis of Renal Perfusion by Arterial Spin Labeling
Authors: Chuang Kai-Hsiang , Kober Frank , Ku Min-Chi 
Published: January 2021

AbstractThe signal intensity differences measured by an arterial-spin-labelling (ASL) magnetic resonance imaging (MRI) experiment are proportional to the local perfusion, which can be quantified with kinetic modeling. Here we present a step-by-step tutorial for the data post-processing needed to calculate an ASL perfusion map. The process of developing an analysis software is described with the essential program code, which involves nonlinear fitting a tracer kinetic model to the ASL data. Key parameters for the quantification are the arterial transit time (ATT), which is the time the labeled blood takes to flow from the labeling area to the tissue, and the tissue T1. As ATT varies with vasculature, physiology, anesthesia and pathology, it is recommended to measure it using multiple delay times. The tutorial explains how to analyze ASL data with multiple delay times and a T1 map for quantification.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This analysis protocol chapter is complemented by two separate chapters describing the basic concept and experimental procedure.
Analysis Protocol for the Quantification of Renal pH Using Chemical Exchange Saturation Transfer (CEST) MRI
Authors: Kim Hahnsung , Wu Yin , Villano Daisy , Longo Dario Livio , McMahon Michael T. , Sun Phillip Zhe 
Published: January 2021

AbstractThe kidney plays a major role in maintaining body pH homeostasis. Renal pH, in particular, changes immediately following injuries such as intoxication and ischemia, making pH an early biomarker for kidney injury before the symptom onset and complementary to well-established laboratory tests. Because of this, it is imperative to develop minimally invasive renal pH imaging exams and test pH as a new diagnostic biomarker in animal models of kidney injury before clinical translation. Briefly, iodinated contrast agents approved by the US Food and Drug Administration (FDA) for computed tomography (CT) have demonstrated promise as novel chemical exchange saturation transfer (CEST) MRI agents for pH-sensitive imaging. The generalized ratiometric iopamidol CEST MRI analysis enables concentration-independent pH measurement, which simplifies in vivo renal pH mapping. This chapter describes quantitative CEST MRI analysis for preclinical renal pH mapping, and their application in rodents, including normal conditions and acute kidney injury.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This analysis protocol chapter is complemented by two separate chapters describing the basic concepts and experimental procedure.
Ultrasound and Photoacoustic Imaging of the Kidney: Basic Concepts and Protocols
Authors: Meyer Sandra , Fuchs Dieter , Meier Martin 
Published: January 2021

AbstractNoninvasive, robust, and reproducible methods to image kidneys are provided by different imaging modalities. A combination of modalities (multimodality) can give better insight into structure and function and to understand the physiology of the kidney. Magnetic resonance imaging can be complemented by a multimodal imaging approach to obtain additional information or include interventional procedures. In the clinic, renal ultrasound has been essential for the diagnosis and management of kidney disease and for the guidance of invasive procedures for a long time. Adapting ultrasound to preclinical requirements and for translational research, the combination with photoacoustic imaging expands the capabilities to obtain anatomical, functional, and molecular information from animal models. This chapter describes the basic concepts of how to image kidneys using different and most appropriate modalities.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
Ethik und Moral
Authors: Werner Micha H. 
Published: January 2021

ZusammenfassungEthische Grundfragen:Ethik ist die wichtigste aller Wissenschaften. Freilich, Wissenschaftler/innen neigen stets dazu, ihre eigene Disziplin für die allerwichtigste zu halten. Für die Ethik spricht jedoch zumindest ihre Fragestellung: Was könnte wichtiger sein als zu wissen, woran wir unser Handeln in letzter Hinsicht orientieren sollen? Welche Einsicht ist bedeutsamer als die Einsicht, worin ein gutes und gelingendes Leben besteht und wie wir ein solches Leben führen können? Was tut mehr Not als die Erkenntnis dessen, was wir unbedingt tun und unterlassen müssen, wie wir uns also überhaupt verhalten dürfen? Kaum jemand wird bestreiten, dass dies Fragen von größter Bedeutung sind.
Ethik im Kontext normativer Subsysteme
Authors: Werner Micha H. 
Published: January 2021

ZusammenfassungNormativität sozialer Institutionen: Der Pluralismus normativ-ethischer Theorien ist nicht der einzig mögliche Grund für Unzufriedenheit mit der Moralphilosophie. Man mag auch befürchten, dass die Antworten auf moralische Gegenwartsfragen, die sich aus moralphilosophischen Theorien ableiten lassen, letztlich trivial oder unterkomplex sind. Die Befürchtung liegt nahe, wenn man (wie bislang in diesem Lehrbuch) nur Ansätze der allgemeinen Ethik und nicht auch der bereichsspezifischen Ethik in den Blick nimmt.