The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
V. V. Dil'man - One of the best experts on this subject based on the ideXlab platform.
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Wave concept in the theory of hydrodynamical dispersion a Maxwellian type approach
Chemical Engineering Research and Design, 1996Co-Authors: Klaas R. Westerterp, Alexander E. Kronberg, Arno H. Benneker, V. V. Dil'manAbstract:A new approach to the modelling of chemical reactors and contactors is discussed. This approach argues that the dispersion should, under most circumstances, be based on Maxwell's, rather than Fick's Diffusion Law. As a pair of first-order partial differential equations of the hyperbolic type and requiring only inlet conditions, the wave model is more realistic physically, has a much wider range of validity and in many practical cases is simpler mathematically. Only mass transfer problems are considered, but the results apply equally well to the hydrodynamic dispersion of heat. It is explained why the standard dispersion model fails in many practical applications and why the new wave model gives much better results.
Hyundong Shin - One of the best experts on this subject based on the ideXlab platform.
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Connectivity in Molecular Communication With Random Time Constraints
IEEE Access, 2019Co-Authors: Dung Phuong Trinh, Youngmin Jeong, Hyundong ShinAbstract:The spatial randomness of nanomachines and propagation time of molecules play an essential role for determining the quality of molecular communication between nanomachines. In this study, we introduce a connectivity model in which the connection between a transmit nanomachine (TN), which is randomly distributed in space, and a receive nanomachine (RN) is achieved when a molecule emitted from the TN arrives at the RN within a time constraint. In particular, this time constraint is modeled as a random lifetime to explain the dissipation phenomenon of molecules in a medium or the random arrival time of interfering molecules. Then, we characterize the local connectivity of the RN in terms of the in-degree by averaging over the spatial randomness of nanomachines and the random first passage time of molecules, which is governed by an anomalous Diffusion Law.
Thorsten Wohland - One of the best experts on this subject based on the ideXlab platform.
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to hop or not to hop exceptions in the fcs Diffusion Law
Biophysical Journal, 2020Co-Authors: Anjali Gupta, Inn Yee Phang, Thorsten WohlandAbstract:Abstract Diffusion obstacles in membranes have not been directly visualized because of fast membrane dynamics and the occurrence of subresolution molecular complexes. To understand the obstacle characteristics, mobility-based methods are often used as an indirect way of assessing the membrane structure. Molecular movement in biological plasma membranes is often characterized by anomalous Diffusion, but the exact underlying mechanisms are still elusive. Imaging total internal reflection fluorescence correlation spectroscopy (ITIR-FCS) is a well-established mobility-based method that provides spatially resolved Diffusion coefficient maps and is combined with FCS Diffusion Law analysis to examine subresolution membrane organization. In recent years, although FCS Diffusion Law analysis has been instrumental in providing new insights into the membrane structure below the optical diffraction limit, there are certain exceptions and anomalies that require further clarification. To this end, we correlate the membrane structural features imaged by atomic force microscopy (AFM) with the dynamics measured using ITIR-FCS. We perform ITIR-FCS measurements on supported lipid bilayers (SLBs) of various lipid compositions to characterize the anomalous Diffusion of lipid molecules in distinct obstacle configurations, along with the high-resolution imaging of the membrane structures with AFM. Furthermore, we validate our experimental results by performing simulations on image grids with experimentally determined obstacle configurations. This study demonstrates that FCS Diffusion Law analysis is a powerful tool to determine membrane heterogeneities implied from dynamics measurements. Our results corroborate the commonly accepted interpretations of imaging FCS Diffusion Law analysis, and we show that exceptions happen when domains reach the percolation threshold in a biphasic membrane and a network of domains behaves rather like a meshwork, resulting in hop Diffusion.
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the imaging fcs Diffusion Law in the presence of multiple diffusive modes
Methods, 2017Co-Authors: Sapthaswaran Veerapathiran, Thorsten WohlandAbstract:Abstract The cellular plasma membrane is the barrier over which cells exchange materials and communicate with their surroundings, and thus plays the central role in cellular sensing and metabolism. Therefore, the investigation of plasma membrane organization and dynamics is required for understanding of cellular functions. The plasma membrane is a heterogeneous matrix. The presence of structures such as lipid and protein domains and the cytoskeleton meshwork poses a hindrance to the free Diffusion of membrane associated biomolecules. However, these domains and the cytoskeleton meshwork barriers are below the optical diffraction limit with potentially short lifetimes and are not easily detected even in super-resolution microscopy. Therefore, dynamic measurements are often used to indirectly prove the existence of domains and barriers by analyzing the mode of Diffusion of probe molecules. One of these tools is the Fluorescence Correlation Spectroscopy (FCS) Diffusion Law. The FCS Diffusion Law is a plot of Diffusion time (τd) versus observation area. For at least three different diffusive modes – free, domain confined, and meshwork hindered hop Diffusion – the expected plots have been characterized, typically by its y-intercept (τ0) when fit with a linear model, and have been verified in many cases. However, a description of τ0 has only been given for pure diffusive modes. But in many experimental cases it is not evident that a protein will undergo only one kind of Diffusion, and thus the interpretation of the τ0 value is problematic. Here, we therefore address the question about the absolute value of τ0 in the case of complex diffusive modes, i.e. when either one molecule is domain confined and cytoskeleton hindered or when two molecules exhibit different diffusive behavior at the same position in a sample. In addition, we investigate how τ0 changes when the diffusive mode of a probe alters upon disruption of domains or the cytoskeleton by drug treatments. By a combination of experimental studies and simulations, we show that τ0 is not influenced equally by the different diffusive modes as typically found in cellular environments, and that it is the relative change of τ0 rather than its absolute value that provides information on the mode of Diffusion.
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Spatiotemporal mapping of Diffusion dynamics and organization in plasma membranes.
Methods and Applications in Fluorescence, 2016Co-Authors: Xue Wen Ng, Jagadish Sankaran, Thorsten WohlandAbstract:: Imaging fluorescence correlation spectroscopy (FCS) and the related FCS Diffusion Law have been applied in recent years to investigate the Diffusion modes of lipids and proteins in membranes. These efforts have provided new insights into the membrane structure below the optical diffraction limit, new information on the existence of lipid domains, and on the influence of the cytoskeleton on membrane dynamics. However, there has been no systematic study to evaluate how domain size, domain density, and the probe partition coefficient affect the resulting imaging FCS Diffusion Law parameters. Here, we characterize the effects of these factors on the FCS Diffusion Law through simulations and experiments on lipid bilayers and live cells. By segmenting images into smaller 7 × 7 pixel areas, we can evaluate the FCS Diffusion Law on areas smaller than 2 µm and thus provide detailed maps of information on the membrane structure and heterogeneity at this length scale. We support and extend this analysis by deriving a mathematical expression to calculate the mean squared displacement (MSDACF) from the autocorrelation function of imaging FCS, and demonstrate that the MSDACF plots depend on the existence of nanoscopic domains. Based on the results, we derive limits for the detection of domains depending on their size, density, and relative viscosity in comparison to the surroundings. Finally, we apply these measurements to bilayers and live cells using imaging total internal reflection FCS and single plane illumination microscopy FCS.
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characterization of lipid and cell membrane organization by the fluorescence correlation spectroscopy Diffusion Law
Chimia, 2015Co-Authors: Xue Wen Ng, Thorsten WohlandAbstract:: The plasma membrane organization of live cells defines a plethora of cellular processes important for cell functionality. Many membrane structures that define this organization exist at a spatial resolution below the optical diffraction limit and are highly dynamic. Therefore, a method with millisecond time resolution and nanometer spatial resolution is required for the investigation of plasma membrane organization. However, spatial and temporal resolutions of the currently available biophysical techniques are often mutually exclusive. In a novel realization, Lenne and coworkers developed a spot-variation modality of fluorescence correlation spectroscopy (FCS), also known as FCS Diffusion Law, to harvest nanoscopic information from microscopic measurements. The FCS Diffusion Law, so far, has been instrumental to decode the physico-chemical origin of membrane organization and its relationship with biological processes. Overall, the structural information of plasma membrane obtained by FCS Diffusion Law provides a better understanding of its coupling to the underlying cellular processes.
Klaas R. Westerterp - One of the best experts on this subject based on the ideXlab platform.
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Wave concept in the theory of hydrodynamical dispersion a Maxwellian type approach
Chemical Engineering Research and Design, 1996Co-Authors: Klaas R. Westerterp, Alexander E. Kronberg, Arno H. Benneker, V. V. Dil'manAbstract:A new approach to the modelling of chemical reactors and contactors is discussed. This approach argues that the dispersion should, under most circumstances, be based on Maxwell's, rather than Fick's Diffusion Law. As a pair of first-order partial differential equations of the hyperbolic type and requiring only inlet conditions, the wave model is more realistic physically, has a much wider range of validity and in many practical cases is simpler mathematically. Only mass transfer problems are considered, but the results apply equally well to the hydrodynamic dispersion of heat. It is explained why the standard dispersion model fails in many practical applications and why the new wave model gives much better results.
Li Wang - One of the best experts on this subject based on the ideXlab platform.
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moisture transformation and transport during the drying process for radix paeoniae alba slices
Applied Thermal Engineering, 2017Co-Authors: Ran Li, Chenwei Zhang, Jianbiao Shen, Li WangAbstract:Abstract The moisture-binding type and change in moisture content of Radix Paeoniae Alba (RPA) slices were determined during their drying process. Water in RPA slices exists in two types: bound water (BW) and free water (FW). During the drying process, FW diffuses from inside the sample to outside it; simultaneously, it is mutually transformed with BW. The drying rate (R) exhibits a nonlinear relationship with the moisture content (M) of RPA slices, and the slope of R (dR/dM) changes non-monotonically with M. When the Diffusion Law of FW as well as the mutual transformation between FW and BW are considered, the drying process of the slices can be divided into three stages: FW drying, mix-drying, and BW-drying periods. Mutual transformation between FW and BW is simplified as a reversible conversion process, and a drying model is established for RPA slices based on Fick’s second Law.
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Investigation on moisture Diffusion in COB packaging [chip on board]
Fifth International Conference onElectronic Packaging Technology Proceedings 2003. ICEPT2003., 2003Co-Authors: Weidong Huang, Li Wang, Xuhong Wang, Mei Sheng, Liqiang Xu, F. StubhanAbstract:The moisture Diffusion in globtop material, globtop coated with SiNx film, globtop coated with silicone and globtop coated with SiNx plus silicone were measured by humidity sensors wire-bonded on FR4 boards in three different temperature/humidity environments. The experimental results were simulated by the finite element method and Fick Diffusion Law. The moisture Diffusion coefficients were calculated to quantitatively compare various coatings' moisture-resistance. Our experimental and simulation results show that a double-layered coating with SiNx plus silicone has excellent moisture-resistance because it can not only smooth the steps on the PCB but also keep the good moisture-resistance of inorganic films.