Proposed Cell Model Research Articles

Low-energy green light alleviates senescence-like phenotypes in a cell model of photoaging.

Ultraviolet B (UVB) affects diverse pathways in skin cells, resulting in skin photoaging. Skin fibroblasts internalize and degrade elastin and collagen, playing prominent roles in photoaging. Green light is used in many fields of dermatology, but few studies have examined its role in photoaging. The present work aimed to assess low-energy green light for its effects in a previously proposed cell model of photoaging and to explore the possible anti-photoaging mechanism. The stress-induced premature senescence (SIPS) model was constructed via repeated treatment of MDFs with UVB. Senescence-like phenotypes were compared among normal, low-energy green light pretreatment and UVB groups, for example, cell morphological properties, senescence-associated β-galactosidase (SA-β-gal) amounts, extracellular matrix (ECM) biosynthesis and degradation, and autophagy. In comparison with the UVB group, the green light pretreatment group showed significantly decreased number of senescent mast cells and markedly declined signal intensity and amounts of SA-β-gal-positive cells. Furthermore, green light pretreatment directly affected ECM by increasing type I and type III collagen production and decreasing MMP-1 amounts. Moreover, changes in autophagy levels induced by green light pretreatment provided a potential mechanism underlying its anti-aging property. Low-energy green light pretreatment improves senescence-like phenotypes in vitro, indicating a possible application for anti-aging in clinic after future research has uncovered the potential mechanism.

Reprint of “A proposed cell model for multiple-occurrence regional landslide events: Implications for landslide susceptibility mapping”

Multiple-occurrence regional landslide events (MORLEs) consist of hundreds to thousands of shallow landslides occurring more or less simultaneously within defined areas, ranging from tens to thousands of square kilometres. While MORLEs can be triggered by rainstorms and earthquakes, this paper is confined to those landslide events triggered by rainstorms. Globally, MORLEs occur in a range of geological settings in areas of moderate to steep slopes subject to intense rainstorms. Individual landslides in rainstorm-triggered events are dominantly small, shallow debris and earth flows, and debris and earth slides involving regolith or weathered bedrock.The model used to characterise these events assumes that energy distribution within the event area is represented on the land surface by a cell structure; with maximum energy expenditure within an identifiable core and rapid dissipation concentrically away from the centre. The version of the model presented here has been developed for rainfall-triggered landslide events. It proposes that rainfall intensity can be used to determine different critical landslide response zones within the cell (referred to as core, middle, and periphery zones). These zones are most readily distinguished by two conditions: the proportion of the slope that fails and the particular type of the slope stability factor that assumes dominance in determining specific sites of landslide occurrence. The latter condition means that the power of any slope stability factor to distinguish between stable and unstable sites varies throughout the affected area in accordance with the landslide response zones within the cell; certain factors critical for determining the location of landslide sites in one part of the event area have little influence in other parts of the event area. The implication is that landslide susceptibility maps (and subsequently derived mitigation measures) based on conventional slope stability factors may have only limited validity for many events.The overall ability to predict the impact of these events and consequently the development of effective mitigation measures is limited by the ability to predict the travel path, storm centre, and intensity range within the cell structure of extreme weather systems.

A proposed cell model for multiple-occurrence regional landslide events: Implications for landslide susceptibility mapping

Multiple-occurrence regional landslide events (MORLEs) consist of hundreds to thousands of shallow landslides occurring more or less simultaneously within defined areas, ranging from tens to thousands of square kilometres. While MORLEs can be triggered by rainstorms and earthquakes, this paper is confined to those landslide events triggered by rainstorms. Globally, MORLEs occur in a range of geological settings in areas of moderate to steep slopes subject to intense rainstorms. Individual landslides in rainstorm-triggered events are dominantly small, shallow debris and earth flows, and debris and earth slides involving regolith or weathered bedrock.The model used to characterise these events assumes that energy distribution within the event area is represented on the land surface by a cell structure; with maximum energy expenditure within an identifiable core and rapid dissipation concentrically away from the centre. The version of the model presented here has been developed for rainfall-triggered landslide events. It proposes that rainfall intensity can be used to determine different critical landslide response zones within the cell (referred to as core, middle, and periphery zones). These zones are most readily distinguished by two conditions: the proportion of the slope that fails and the particular type of the slope stability factor that assumes dominance in determining specific sites of landslide occurrence. The latter condition means that the power of any slope stability factor to distinguish between stable and unstable sites varies throughout the affected area in accordance with the landslide response zones within the cell; certain factors critical for determining the location of landslide sites in one part of the event area have little influence in other parts of the event area. The implication is that landslide susceptibility maps (and subsequently derived mitigation measures) based on conventional slope stability factors may have only limited validity for many events.The overall ability to predict the impact of these events and consequently the development of effective mitigation measures is limited by the ability to predict the travel path, storm centre, and intensity range within the cell structure of extreme weather systems.

Discretized Cell Modeling for Optimal Facility Layout Plans of Unequal and Irregular Facilities

AbstractFacility layout design is an essential planning task to resolve potential spatial conflicts and overlapping during practical operations. A discretized cell optimization model is developed to optimize site space usages. Site areas and facilities are represented by small unit cells to effectively model irregularities, and the availability of unit cells for use in a facility setup is modeled by binary-type variables. With size and shape requirements through linear constraints, the site layout design can be formulated as a binary mixed integer-linear programming (BMILP) problem to allocate different facilities onto different site available areas in optimal shapes and locations. Total material transportation costs across facilities are optimized subject to various design constraints ensuring safety, homogenous facility setups, physical size, and orientation requirements. The proposed cell model is verified by comparing optimization results with results obtained by conventional point notation methods. A...

A Compact Model for Single-Poly Multitime Programmable Memory Cells

A compact model for the single-poly multitime programmable (MTP) memory cells is presented in this paper for the first time. It is based on the charge balance approach, while the traditional old model is on the fixed capacitive coupling approach. The proposed cell model has been implemented by Verilog-A and integrated into commercial SPICE simulator. The model supports both dc and transient analyses, and the simulated results are consistent very well with those from device simulation and measurement, whereas the results by the traditional old model deviate substantially. Furthermore, the comprehensive optimization of the MTP cells is made feasible thanks to the new model, such as device size, high voltage ramp rate, and reliability prediction. As a result, this compact cell model will be very useful for the designers to evaluate and optimize a single-poly MTP cell.

Simulation of barchan dynamics with inter-dune sand streams

A group of barchans, crescent sand dunes, exhibit a characteristic flying-geese pattern in deserts on Earth and Mars. This pattern implies that an indirect interaction between barchans, mediated by an inter-dune sand stream, which is released from one barchan's horns and caught by another barchan, plays an important role in the dynamics of barchan fields. We used numerical simulations of a recently proposed cell model to investigate the effects of inter-dune sand streams on barchan fields. We found that a sand stream from a point source moves a downstream barchan laterally until the head of the barchan is finally situated behind the stream. This final configuration was shown to be stable by a linear stability analysis. These results indicate that flying-geese patterns are formed by the lateral motion of barchans mediated by inter-dune sand streams. By using simulations we also found a barchan mono-corridor generation effect, which is another effect of sand streams from point sources.

Modelling and simulation of substrate elasticity sensing in stem cells

Recently, we have developed a multiscale soft matter cell model aiming at improving the understanding of mechanotransduction mechanism of stem cells, which is responsible for information exchange between cells and their extracellular environment. In this paper, we report the preliminary results of our research on multiscale modelling and simulation of soft contact and adhesion of stem cells. The proposed multiscale soft matter cell model may be used to model soft contact and adhesion between cells and their extracellular substrates. To the authors' best knowledge, this may be the first time that a soft matter model has been developed for cell contact and adhesion. Moreover, we have developed and implemented a Lagrange-type meshfree Galerkin formulation and related computational algorithms for the proposed cell model. Comparison study with experimental data has been conducted to validate the parameters of the cell model. By using the soft matter cell model, we have simulated the soft adhesive contact process between cells and extracellular substrates. The simulation shows that the cell can sense substrate elasticity by responding it in different manners from cell spreading to cell contact configuration and molecular conformation changes.

From c-Photina® Mouse Embryonic Stem Cells to High-Throughput Screening of Differentiated Neural Cells via an Intermediate Step Enriched in Neural Precursor Cells

The use of engineered mouse embryonic stem (mES) cells in high-throughput screening (HTS) can offer new opportunities for studying complex targets in their native environment, increasing the probability of discovering more meaningful hits. The authors have generated and developed a mouse embryonic stem cell line called c-Photina mES stably expressing a Ca(2+)-activated photoprotein as a reporter gene. This reporter cell line retains the ability to differentiate into any cell lineage and can be used for miniaturized screening processes in 384-well microplates. The c-Photina mES cell line is particularly well suited for the study of the pharmacological modulation of target genes that induce Ca(2+) mobilization. The authors differentiated this mES reporter cell line into neuronal cells and screened the LOPAC(1280) library monitoring the agonistic or antagonistic activities of compounds. They also demonstrate the possibility to generate and freeze bulk preparations of cells at an intermediate stage of differentiation and enriched in neural precursor cells, which retain the ability to form fully functional neural networks once thawed. The proposed cell model is of high value for HTS purposes because it offers a more physiological environment to the targets of interest and the possibility of using frozen batches of neural precursor cells.

Multiscale modeling and simulation of soft adhesion and contact of stem cells

Recently, we have developed a multiscale soft matter model for stem cells or primitive cells in general, aiming at improving the understanding of mechanotransduction mechanism of cells that is responsible for information exchange between cells and their extracellular environment. In this paper, we report the preliminary results of our research on multiscale modeling and simulation of soft contact and adhesion of cells. The proposed multiscale soft matter cell model may be used to model soft contact and adhesion between cells and their extracellular substrates. This model is a generalization of the Fluid Mosaic Model ( Singer and Nicolson, 1972), or an extension of Helfrich’s liquid crystal membrane model ( Helfrich, 1973). To the best of the authors’ knowledge, this may be the first time that a soft matter model is developed for cell contact and adhesion. Moreover we have developed and implemented a Lagrange type meshfree Galerkin formulation and the computational algorithm for the proposed cell model. Comparison study with experimental data has been conducted to validate the parameters of the model. By using the soft matter cell model, we have simulated the soft adhesive contact process between cells and their extracellular substrates. The simulation shows that the cell can sense substrate elasticity by responding in different manners from cell spreading motion to cell contact configurations.

A probabilistic cell model in background corrected image sequences for single cell analysis

BackgroundMethods of manual cell localization and outlining are so onerous that automated tracking methods would seem mandatory for handling huge image sequences, nevertheless manual tracking is, astonishingly, still widely practiced in areas such as cell biology which are outside the influence of most image processing research. The goal of our research is to address this gap by developing automated methods of cell tracking, localization, and segmentation. Since even an optimal frame-to-frame association method cannot compensate and recover from poor detection, it is clear that the quality of cell tracking depends on the quality of cell detection within each frame.MethodsCell detection performs poorly where the background is not uniform and includes temporal illumination variations, spatial non-uniformities, and stationary objects such as well boundaries (which confine the cells under study). To improve cell detection, the signal to noise ratio of the input image can be increased via accurate background estimation. In this paper we investigate background estimation, for the purpose of cell detection. We propose a cell model and a method for background estimation, driven by the proposed cell model, such that well structure can be identified, and explicitly rejected, when estimating the background.ResultsThe resulting background-removed images have fewer artifacts and allow cells to be localized and detected more reliably. The experimental results generated by applying the proposed method to different Hematopoietic Stem Cell (HSC) image sequences are quite promising.ConclusionThe understanding of cell behavior relies on precise information about the temporal dynamics and spatial distribution of cells. Such information may play a key role in disease research and regenerative medicine, so automated methods for observation and measurement of cells from microscopic images are in high demand. The proposed method in this paper is capable of localizing single cells in microwells and can be adapted for the other cell types that may not have circular shape. This method can be potentially used for single cell analysis to study the temporal dynamics of cells.

Explicit numerical study of softening in porous ductile solids

Axisymmetric unit cell model calculations are widely used to study void growth to coalescence in a material containing a periodic array of ellipsoidal voids. The objective of the present paper is to compare the predictions of a proposed cell model quasi-static explicit calculations with the results from numerical implicit cell model analyses. The unit cell is presumed to be remotely loaded in an axisymmetric fashion with predominant axial stress and overall stress triaxiality kept constant during the whole process of deformation. Computations with different void shapes, overall stress triaxiality and material parameters are performed. A global view of the obtained results indicates that there is reasonably good agreement between both approaches. As an example, the proposed numerical technique is used to study the plastic collapse of an axisymmetric unit cell with a primary spherical void embedded in a porous matrix material. Consistent with experimental and theoretical results available in literature, the obtained results substantiate the sensitivity of coalescence to the presence of the secondary voids. It is found in particular that failure mechanisms depend on both initial void volume fractions and stress triaxiality essentially.

A New Model with Feedback Structure for Thermal Process and its Application to Decoupling Control

In thermal processes, thermal distribution on the conduction surface is observed in both steady state and transient state. Uniform temperature control is required in many industrial application fields for quality improvement. For thermal plant with strong interference, decoupling controller using black-box model based on input-output relations has been applied. In this paper, a novel cell model with feedback structure which describes the thermal interaction explicitly is derived, and its application to a new decoupling control is proposed. First, uniform cell model is considered based on physical energy, and is applied to experimental plant. The thermal distribution is simulated by the FEM method. Secondly, design of decoupling controller using the proposed cell model is shown, and the effectiveness is evaluated.

Influence of interphase layer on the overall elasto-plastic behaviors of HA/PEEK biocomposite

A three-dimensional finite element unit cell model has been designed and constructed for studying mechanical properties of hydroxyapatite (HA) reinforced polyetheretherketone (PEEK) biocomposite. The model consists of an elastic-brittle HA spherical particle, an elasto-plastic matrix and an interphase layer between the particle and the matrix. The interphase layers with four different kinds of material behaviors have been taken into consideration to examine their effects on the overall properties of the composite. The damage evolution in the matrix and the interphase layer, and the interface failure, were also taken into account. Some other factors, such as mesh sensitivity, loading velocity and mass scale scheme, were also discussed in this investigation. A general-purpose finite element software package, ABAQUS, incorporated with a user-defined material subroutine, was used to perform the analysis. The predicted results were compared with the experimental data obtained from existing literatures. The results predicted by using the cell model with consideration of the matrix degradation and the effects of the damage and failure on the interphase layer are in good agreement with the experimental ones. Hence, the suitability of our proposed cell model incorporated with an appropriate type of the interphase layer for modeling the mechanical properties of the particulate biocomposite could be verified.

Rat neuronal cells in primary culture as a model for nociceptin/orphanin FQ metabolism

Cortical cells in primary culture contain active proteolytic enzymes capable of cleaving nociceptin/orphanin FQ (N/OFQ) and dynorphins to shorter, bioactive fragments. Cells were divided into subpopulations (neurons, astrocytes and oligodendrocytes), and the metabolic pathways in particular populations of the cells were investigated. Processing of N/OFQ and dynorphins in the cytosolic fractions differed significantly. The proposed cell model can be used for the more detailed studies on the central nervous system proteomics.

Novel approach to super Yang-Mills theory on lattice. Exact fermionic symmetry and ``Ichimatsu'' pattern

We present a lattice theory with an exact fermionic symmetry, which mixes the link and the fermionic variables. The staggered fermionic variables may be reconstructed into a Majorana fermion in the continuum limit. The gauge action has a novel structure. Though it is the ordinary plaquette action, two different couplings are assigned in the ``Ichimatsu pattern'' or the checkered pattern. In the naive continuum limit, the fermionic symmetry survives as a continuum (or an $O(a^0)$) symmetry. The transformation of the fermion is proportional to the field strength multiplied by the difference of the two gauge couplings in this limit. This work is an extension of our recently proposed cell model toward the realization of supersymmetric Yang-Mills theory on lattice.

Expression and localization of the Na-K-2Cl cotransporter in the rat cochlea

We identified the localization of the basolateral bumetanide-sensitive Na-K-2Cl cotransporter (BSC2) in the cochlea using an in situ hybridization method. In the rat cochlea, the BSC2 mRNA was mainly expressed in the strial marginal cells. Although the fibrocytes localized at the spiral prominence showed a weak expression of BSC2 mRNA, no expression was observed in the organ of Corti or spiral ganglion cells. The present findings are well consistent with a proposed cell model of ion transport in the marginal cell.

A three-layer over-the-cell multi-channel router for a new cell model

This paper proposes a new cell model for over-the-cell routing, and presents a heuristic three-layer over-the-cell multi-channel routing method for the new cell model. In the proposed cell model, terminals can be placed arbitrarily on the second metal (M2) layer of a cell so that each cell does not require the extra routing region on the first metal (M1) layer of a cell to align terminals. Unlike conventional cell models, some parts of the M2 layer may also be utilized for intra-cell routing in order to reduce the chip area. Therefore the size of a cell with the proposed cell model can be smaller than that with conventional cell models. The proposed three-layer over-the-cell routing method consists of three phases. In order to utilize the proposed cell model effectively, in phase 1, we simultaneously handle all channels to determine the most effective routing patterns from the set of possible routing patterns to minimize the chip area. In phase 2, for the routing patterns of nets selected in phase 1, over-the-cell routing nets are selected by a new greedy algorithm considering obstacles in over-the-cell regions. Finally, in phase 3, the conventional three-layer channel routing algorithm is applied for remaining nets. From the experimental results with MCNC benchmarks, the proposed cell model and routing algorithm produce the smaller height of layouts as compared to those produced by conventional cell models and algorithms, and the effectiveness of the proposed cell model and routing method was shown.

Deformative properties of flexible plastic foams in compression

A calculation of the compression diagrams of flexible plastic foams during their long-time testing under a load is given on the basis of the proposed cell model, on the assumption that permanent set is related to buckling of the strands. The character of change of the nominal compressive strength and corresponding deformation as a function of the magnitude of permanent set is established. A marked change of the second section of the compression diagram (plateau), even to its degeneration, in the presence of considerable permanent set was found. A comparison of the experimental and calculated data showed their satisfactory correspondence.

Computer Models for Simulating Alcohol Displacement in Porous Media

Abstract This investigation attempts to describe and simulate the alcohol displacement process by means of a cell model, as employed in chemical engineering practice. The proposed model is more simple than previously proposed models, and utilizes parameters chosen on a theoretical basis. The model successfully reproduced the formation of the stabilized bank and the breakthrough of alcohol, the latter depending on one of the model parameters, which may be correlated with the length of the porous medium. Moreover, the effects of the phase behavior of the liquid system involved, as observed in experimental studies, were reproduced. Several variations of the basic model were devised and tested on a digital computer. These included the cases in which: the actual value of fractional flow was used in cell-to-cell computations; the number of cells was varied within the same run; and incomplete rather than complete phase equilibrium was assumed within each cell. The proposed cell model clarifies the basic mechanism of the process. Detailed concentration profiles obtained for each cell, for instance, showed the mechanism of bank formation in relation to the phase behavior characteristics. The results obtained indicated a varying degree of phase equilibrium concommitant with changes in the velocities of the phases in an actual alcohol displacement. This condition was approximated by changing the number of cells during the simulation. Interesting information was obtained on the influence of path length on the efficiency of alcohol displacement, which has been the subject of some controversy. Certain limitations preclude the use of the proposed model as a substitute for experimental studies. The results obtained were, nevertheless, of value in interpreting the experimental results. Introduction During recent years considerable effort has been directed toward an understanding of alcohol displacement, the process whereby oil and water are recovered from a porous medium by the continuous injection of a solvent. The complex nature of the physical process involved has so far defied a complete mathematical treatment. Other methods of approach, amounting to an overall material balance, have been proposed, yielding useful information on certain aspects of the process. Taber et al, in particular, defined the displacement mechanism in terms of the phase behavior of the alcohol-oil-brine system involved. Wachmann reported a mathematical treatment of alcohol displacement subject to certain simplifying assumptions. Donohue proposed the use of a "cell model" for simulating alcohol displacement. The nature of the assumptions involved limited the utility of the model. The present work attempts to examine the variables involved in the simulation of alcohol displacement and discusses several possible versions of the basic cell model. Under certain conditions the model results are similar to the experimental results. In particular, the spontaneous formation of the stabilized bank and the effects of the system phase behavior were successfully reproduced. PREVIOUS WORK ON CELL MODELS Cell models and the theoretical plate concept are often used in solving chemical engineering problems in which an explicit mathematical solution may be difficult or impossible to obtain. Examples of such applications occur in distillation, gas-liquid chromatography, reactor technology, absorption, etc. In petroleum engineering, such a model was used by Attra to describe non-equilibrium gas drive, and by Higgins and Leighton to calculate sweep efficiency in water flooding. Aris and Amundsen pointed out the equivalence between the diffusion model and perfectly mixed cells connected in series. SPEJ P. 89ˆ