Combination of Time‐Dependent Self‐Diffusion Measurements (Dynamic Imaging) with Magnetic Resonance Imaging

The new NMR method, demonstrated in the present work, allows within local small volumes the determination of integral structural parameters like the surface‐to‐pore volume ratio or the tortuosity of a fluid‐filled porous medium. A combination of conventional imaging (MRI) with measurements of observation‐time dependent self‐diffusion (dynamic imaging) was used.     

Application of Magnetic Resonance Imaging (MRI) to Determine the Influence of Fluid Dynamics on Desulfurization in Bench Scale Reactors

The influence of fluid dynamics on the hydrodesulfurization (HDS) reactions of a diesel oil in bench‐scale reactors was evaluated. The porosities and liquid saturations of catalyst beds were quantified by using the MRI technique. The gas‐liquid systems used in the experiments were nitrogen diesel and hydrogen diesel. An apparatus was especially constructed, allowing in situ measurements of gas and liquid distributions in packed beds at elevated pressure and temperature up to 20 bar and 200 °C, respectively. The reactor itself had a length of 500 mm and an internal diameter of 19 mm. The packed beds used in this MRI study consisted of: (1) 2 mm diameter nonporous spherical glass beads and (2) 1.3 mm diameter porous Al₂O₃ trilobes having the same size as the original trilobe catalyst used in HDS bench‐scale experiments. The superficial gas and liquid velocities were set within the range of trickle flow, e.g., u_0G = 20–500 mm/s and u_0L = 0.1–6 mm/s. In parallel with the MRI experiments, the hydrodesulfurization of a gas oil was investigated in a bench‐scale plant. Its reactor had the same dimensions of the trickle‐bed column used in the MRI experiments and was filled with original trilobe catalyst. These catalytic experiments were carried out at a wide range of operating conditions (p = 30–80 bar, T = 300–380 °C, LHSV = 1–4 h^–1). The results of both fluid dynamic and catalytic reaction experiments were then combined for developing a simulation model to predict the HDS performance by accounting for fluid dynamic nonidealities.     

Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Different NMR techniques were combined to obtain the structure and velocity information for a systematic investigation of fixed beds with low aspect ratio (tube diameter to particle diamter, d_t/d_p) in the range 1.4 to 32. The structure of the void space was determined for a variety of packed beds of glass beads or regular and irregular porous pellets by magnetic resonance imaging (MRI). Based on the images the radial distribution of the voids within the bed was obtained. Ordering effects were found even for non‐spherical and polydisperse particles, and a maximum of the fluid density near the tube wall was confirmed for all pellet geometries and sizes. By combining MRI with velocity encoding, velocity profiles and distributions of flow velocity components of a single fluid phase through packed beds have been acquired. The radial velocity distribution follows an oscillatory pattern which largely reflects the ordering of the particles, which can be accessed from the density distribution of the interparticle fluid. Maximum velocities of up to four times the average value were found to occur near the tube wall. This wall effect was observed for all but the smallest particles, where the aspect ratio was d_t/d_p = 32. Moreover, a visualisation of flow pattern in the presence of packed particles was achieved by using a tagging technique, and the stationary flow field could be identified for an experimental time of several hours.     

Collagen-Specific Molecular Magnetic Resonance Imaging of Prostate Cancer

Constant interactions between tumor cells and the extracellular matrix (ECM) influence the progression of prostate cancer (PCa). One of the key components of the ECM are collagen fibers, since they are responsible for the tissue stiffness, growth, adhesion, proliferation, migration, invasion/metastasis, cell signaling, and immune recruitment of tumor cells. To explore this molecular marker in the content of PCa, we investigated two different tumor volumes (500 mm³ and 1000 mm³) of a xenograft mouse model of PCa with molecular magnetic resonance imaging (MRI) using a collagen-specific probe. For in vivo MRI evaluation, T1-weighted sequences before and after probe administration were analyzed. No significant signal difference between the two tumor volumes could be found. However, we detected a significant difference between the signal intensity of the peripheral tumor area and the central area of the tumor, at both 500 mm³ (p < 0.01, n = 16) and at 1000 mm³ (p < 0.01, n = 16). The results of our histologic analyses confirmed the in vivo studies: There was no significant difference in the amount of collagen between the two tumor volumes (p > 0.05), but within the tumor, higher collagen expression was observed in the peripheral area compared with the central area of the tumor. Laser ablation with inductively coupled plasma mass spectrometry further confirmed these results. The 1000 mm³ tumors contained 2.8 ± 1.0% collagen and the 500 mm³ tumors contained 3.2 ± 1.2% (n = 16). There was a strong correlation between the in vivo MRI data and the ex vivo histological data (y = −0.068x + 1.1; R² = 0.74) (n = 16). The results of elemental analysis by inductively coupled plasma mass spectrometry supported the MRI data (y = 3.82x + 0.56; R² = 0.79; n = 7). MRI with the collagen-specific probe in PCa enables differentiation between different tumor areas. This may help to differentiate tumor from healthy tissue, potentially identifying tumor areas with a specific tumor biology.     

Heating of Foods Studied by Magnetic Resonance Imaging

MRI is the only technique that has the potential to map the temperature distribution of water in food non‐invasively in three dimensions (Nott and Hall, 1999), as well as to acquire data sensitive to the physical changes induced by heating, including delineating between frozen and thawed regions. Its practical use is illustrated here by the following set of applications: microwave heating of plastic trays containing a model gel, as well as chilled and frozen lasagne; thawing of a frozen whole chicken either at ambient temperature or by microwave heating; and by cooking of an egg in hot water. The strengths and limitations of MRI temperature mapping of real foods is discussed.     

Obesity-Related Neuroinflammation: Magnetic Resonance and Microscopy Imaging of the Brain

Obesity is a major risk factor of Alzheimer’s disease and related dementias. The principal feature of dementia is a loss of neurons and brain atrophy. The mechanistic links between obesity and the neurodegenerative processes of dementias are not fully understood, but recent research suggests that obesity-related systemic inflammation and subsequent neuroinflammation may be involved. Adipose tissues release multiple proinflammatory molecules (fatty acids and cytokines) that impact blood and vessel cells, inducing low-grade systemic inflammation that can transition to tissues, including the brain. Inflammation in the brain—neuroinflammation—is one of key elements of the pathobiology of neurodegenerative disorders; it is characterized by the activation of microglia, the resident immune cells in the brain, and by the structural and functional changes of other cells forming the brain parenchyma, including neurons. Such cellular changes have been shown in animal models with direct methods, such as confocal microscopy. In humans, cellular changes are less tangible, as only indirect methods such as magnetic resonance (MR) imaging are usually used. In these studies, obesity and low-grade systemic inflammation have been associated with lower volumes of the cerebral gray matter, cortex, and hippocampus, as well as altered tissue MR properties (suggesting microstructural variations in cellular and molecular composition). How these structural variations in the human brain observed using MR imaging relate to the cellular variations in the animal brain seen with microscopy is not well understood. This review describes the current understanding of neuroinflammation in the context of obesity-induced systemic inflammation, and it highlights need for the bridge between animal microscopy and human MR imaging studies.     

Errors in the Calculation of 27Al Nuclear Magnetic Resonance Chemical Shifts

Computational chemistry is an important tool for signal assignment of ²⁷Al nuclear magnetic resonance spectra in order to elucidate the species of aluminum(III) in aqueous solutions. The accuracy of the popular theoretical models for computing the ²⁷Al chemical shifts was evaluated by comparing the calculated and experimental chemical shifts in more than one hundred aluminum(III) complexes. In order to differentiate the error due to the chemical shielding tensor calculation from that due to the inadequacy of the molecular geometry prediction, single-crystal X-ray diffraction determined structures were used to build the isolated molecule models for calculating the chemical shifts. The results were compared with those obtained using the calculated geometries at the B3LYP/6-31G(d) level. The isotropic chemical shielding constants computed at different levels have strong linear correlations even though the absolute values differ in tens of ppm. The root-mean-square difference between the experimental chemical shifts and the calculated values is approximately 5 ppm for the calculations based on the X-ray structures, but more than 10 ppm for the calculations based on the computed geometries. The result indicates that the popular theoretical models are adequate in calculating the chemical shifts while an accurate molecular geometry is more critical.     

Modeling of Droplet Separation Kinetics in Granular Bed Filters Based on MRI Measurements

In droplet separation by granular bed filters, the transient loading regime plays an important role because, for gases with low droplet concentrations, steady state will be reached only after a long time. A mathematical model describing this transient loading regime as well as steady state was developed. It is based on differential balances for the dispersed droplets and for the separated liquid. The time‐dependent and spatially resolved liquid loading is calculated and compared with data obtained by magnetic resonance imaging (MRI), a noninvasive measuring technique. The good agreement between simulated and measured loading curves proves the general applicability of the model.     

化工热力学中从生活中来到生产中去的实例

生动的实例是改变化工热力学枯燥、抽象局面的良药。本文列举了多个“从生活中来到生产中去”与热力学原理密切相关的实例，以期激发学生的兴趣，使他们体会到化工热力学的魅力。     

化学反应工程课程体系与实践教学模式的探讨

我们以化学反应工程教学为对象,针对化学反应工程在化工类人才培养中的核心地位,对课程体系的构架、教学内容、教学方法,以及该课程的实践教学环节进行了探讨。为适应培养具有工程意识和创新能力的化工人才的需求,本文提出了化学反应工程课程体系与实践教学的模式。     

化工专业反应精馏案例教学实践研究

当前世界范围内,新一轮科技革命与产业变革正在加速进行,我国经济发展面临着产业转型升级和新旧动能转换的艰巨任务。高等工程教育必须深化改革,面向未来产业需求和技术发展趋势建设新工科,培养多样化、创新型卓越工程人才。高等分离工程与化工生产联系非常紧密,但是传统授课过程中注重理论知识的讲解,缺乏对学生解决实际工程问题的能力和设计能力的培养。本文以醋酸甲酯水解的反应精馏工程案例建设和实施过程为例,介绍如何通过案例教学强化学生实践能力的培养,并对案例教学应用于高等分离工程课程教学的情况进行了分析研究。     

Enhanced Tumor Imaging Using Glucosamine-Conjugated Polyacrylic Acid-Coated Ultrasmall Gadolinium Oxide Nanoparticles in Magnetic Resonance Imaging

Owing to a higher demand for glucosamine (GlcN) in metabolic processes in tumor cells than in normal cells (i.e., GlcN effects), tumor imaging in magnetic resonance imaging (MRI) can be highly improved using GlcN-conjugated MRI contrast agents. Here, GlcN was conjugated with polyacrylic acid (PAA)-coated ultrasmall gadolinium oxide nanoparticles (UGONs) (d_avg = 1.76 nm). Higher positive (brighter or T₁) contrast enhancements at various organs including tumor site were observed in human brain glioma (U87MG) tumor-bearing mice after the intravenous injection of GlcN-PAA-UGONs into their tail veins, compared with those obtained with PAA-UGONs as control, which were rapidly excreted through the bladder. Importantly, the contrast enhancements of the GlcN-PAA-UGONs with respect to those of the PAA-UGONs were the highest in the tumor site owing to GlcN effects. These results demonstrated that GlcN-PAA-UGONs can serve as excellent T₁ MRI contrast agents in tumor imaging via GlcN effects.     

Biological Properties of Iron Oxide Nanoparticles for Cellular and Molecular Magnetic Resonance Imaging

Superparamagnetic iron-oxide particles (SPIO) are used in different ways as contrast agents for magnetic resonance imaging (MRI): Particles with high nonspecific uptake are required for unspecific labeling of phagocytic cells whereas those that target specific molecules need to have very low unspecific cellular uptake. We compared iron-oxide particles with different core materials (magnetite, maghemite), different coatings (none, dextran, carboxydextran, polystyrene) and different hydrodynamic diameters (20–850 nm) for internalization kinetics, release of internalized particles, toxicity, localization of particles and ability to generate contrast in MRI. Particle uptake was investigated with U118 glioma cells und human umbilical vein endothelial cells (HUVEC), which exhibit different phagocytic properties. In both cell types, the contrast agents Resovist, B102, non-coated Fe₃O₄ particles and microspheres were better internalized than dextran-coated Nanomag particles. SPIO uptake into the cells increased with particle/iron concentrations. Maximum intracellular accumulation of iron particles was observed between 24 h to 36 h of exposure. Most particles were retained in the cells for at least two weeks, were deeply internalized, and only few remained adsorbed at the cell surface. Internalized particles clustered in the cytosol of the cells. Furthermore, all particles showed a low toxicity. By MRI, monolayers consisting of 5000 Resovist-labeled cells could easily be visualized. Thus, for unspecific cell labeling, Resovist and microspheres show the highest potential, whereas Nanomag particles are promising contrast agents for target-specific labeling.     

工科院校化学化工专业开设化工环境保护概论课程的教学实践与探索

化工污染是化工行业发展过程中亟待解决的重大问题。为适应学科发展需要,我校将化工环境保护概论课程纳入化学工程与工艺专业本科教学体系,希望学生能够具备环境学基础知识和环境保护基本素质。课题组在教学中经探索和尝试,形成了以传授学生污染防治技术与培养学生环保意识为目的,以突出化工特色与强调工程实践能力培养为导向,以优化教学内容和过程为核心,以案例教学和实践教学为主要教学手段的教学模式,收到了显著的教学效果。     

Newtonian and Non‐Newtonian Low Re Number Flow Through Bead Packings

The results of measurements of velocity distributions of Newtonian and non‐Newtonian fluids flowing through porous media are described in this contribution. The porous matrix was modeled by glass beads of different diameters forming a random bead packing confined by a circular tube. These packings were passed through by aqueous solutions of glucose and xanthane gum. Nuclear magnetic resonance (NMR) methods were applied to investigate the flow field in the packing. Spatially resolved and integral displacement distribution measurements were reported.     

固体核磁共振技术及其在氟聚合物研究中的应用

固体核磁共振作为一种重要的现代分析研究手段，在许多研究领域都有广泛的用途。通过对常用的固体核磁共振技术的介绍结合其在聚四氟乙烯、聚偏氟乙烯、四氟乙烯-六氟丙烯共聚物分析研究中的应用，说明固体核磁共振技术是研究常见氟聚合物结构和分子运动的重要方法。     

Magnetic Resonance Imaging in Animal Models of Alzheimer’s Disease Amyloidosis

Amyloid-beta (Aβ) plays an important role in the pathogenesis of Alzheimer’s disease. Aberrant Aβ accumulation induces neuroinflammation, cerebrovascular alterations, and synaptic deficits, leading to cognitive impairment. Animal models recapitulating the Aβ pathology, such as transgenic, knock-in mouse and rat models, have facilitated the understanding of disease mechanisms and the development of therapeutics targeting Aβ. There is a rapid advance in high-field MRI in small animals. Versatile high-field magnetic resonance imaging (MRI) sequences, such as diffusion tensor imaging, arterial spin labeling, resting-state functional MRI, anatomical MRI, and MR spectroscopy, as well as contrast agents, have been developed for preclinical imaging in animal models. These tools have enabled high-resolution in vivo structural, functional, and molecular readouts with a whole-brain field of view. MRI has been used to visualize non-invasively the Aβ deposits, synaptic deficits, regional brain atrophy, impairment in white matter integrity, functional connectivity, and cerebrovascular and glymphatic system in animal models of Alzheimer’s disease amyloidosis. Many of the readouts are translational toward clinical MRI applications in patients with Alzheimer’s disease. In this review, we summarize the recent advances in MRI for visualizing the pathophysiology in amyloidosis animal models. We discuss the outstanding challenges in brain imaging using MRI in small animals and propose future outlook in visualizing Aβ-related alterations in the brains of animal models.     

Highly Resolved Determination of Structure and Particle Deposition in Fibrous Filters by MRI

A new method for the quantitative three‐dimensional structure determination of a coarse filter medium as well as the particle deposition inside this medium is described. The filter structure was imaged at a voxel resolution of 59 μm which is close to the mean fiber diameter, therefore allowing individual fibers and their position to be determined. The data processing method for determining the filter structure as well as the quantification of the mass deposited in the filter are explained in detail. For particle deposition investigations the spatial resolution used was 235 μm. Hereby, a linear correlation between deposited mass and signal intensity was observed.     

Structure Characterization of Filled Polymers by Means of MRI

The structure of foams and filled polymers can be analyzed by means of Magnetic Resonance Imaging (MRI). It is also possible to observe the deformation behavior of the structure of foams and filled polymers in situ. A displacement experiment was performed in a magnet and observed by MRI. The NMR images are analyzed by image processing. Average distances between particles are estimated by the use of the autocorrelation function and the spectrum of the autocorrelation function. The spectrum shows the spatial frequency of the distances. The displacement field was calculated by the cross‐correlation function. Thus, information concerning the particle distances and micromechanical deformation can be obtained by NMR imaging methods by combining autocorrelation and cross‐correlation. Such data are important for the evaluation of the mechanical strength of filled polymers.