Matrix Configuration Research Articles

3D collagen type I matrix inhibits the antimigratory effect of doxorubicin

BackgroundThe cell microenvironment, especially extracellular matrix proteins, plays an important role in tumor cell response to chemotherapeutic drugs. The present study was designed to investigate whether this microenvironment can influence the antimigratory effect of an anthracycline drug, doxorubicin, when tumor cells are grown in a matrix of type I collagen, a three-dimensional (3D) context which simulates a natural microenvironment.MethodsTo this purpose, we studied the migratory parameters, the integrin expression, and the activation state of focal adhesion kinase (FAK) and GTPase RhoA involved in the formation of focal adhesions and cell movement. These parameters were evaluated at non toxic concentrations which did not affect HT1080 cell proliferation.ResultsWe show that while doxorubicin decreased cell migration properties by 70% in conventional two-dimensional (2D) culture, this effect was completely abolished in a 3D one. Regarding the impact of doxorubicin on the focal adhesion complexes, unlike in 2D systems, the data indicated that the drug neither affected β1 integrin expression nor the state of phosphorylation of FAK and RhoA.ConclusionThis study suggests the lack of antiinvasive effect of doxorubicin in a 3D environment which is generally considered to better mimic the phenotypic behaviour of cells in vivo. Consistent with the previously shown resistance to the cytotoxic effect in a 3D context, our results highlight the importance of the matrix configuration on the tumor cell response to antiinvasive drugs.

Mathematical Modeling of Polymer Biodegradation and Erosion

The biodegradable polymers are widely used in therapeutic surgery and pharmaceutics, in which the degradation process has drawn significant attention in recent years. In this paper, we propose a mathematical model to predict the polymer degradation in tissue engineering applications. A stochastic model is introduced to characterize the hydrolysis reaction in an elemental basis and the mass transport is also performed to investigate the diffusive transport of polymer erosion. Two representative polymeric films in different configurations are studied. It is found that for biodegradable systems, mass transport plays an important role in controlling the erosion pathway, in which the matrix configuration could be one of the key factors that determine the characteristics of erosion and drug release rates. The proposed model makes a useful benefit to the design optimization of the matrix architectures for biodegradable devices.

Linear-control-based synchronization of coexisting attractor networks with time delays

This paper introduces the concept of linear-control-based synchronization of coexisting attractor networks with time delays. Within the new framework, closed loop control for each dynamic node is realized through linear state feedback around its own arena in a decentralized way, where the feedback matrix is determined through consideration of the coordination of the node dynamics, the inner connected matrix and the outer connected matrix. Unlike previously existing results, the feedback gain matrix here is decoupled from the inner matrix; this not only guarantees the flexible choice of the gain matrix, but also leaves much space for inner matrix configuration. Synchronization of coexisting attractor networks with time delays is made possible in virtue of local interaction, which works in a distributed way between individual neighbours, and the linear feedback control for each node. Provided that the network is connected and balanced, synchronization will come true naturally, where theoretical proof is given via a Lyapunov function. For completeness, several illustrative examples are presented to further elucidate the novelty and efficacy of the proposed scheme.

Fault-Tolerant Structure and Modulation Strategies With Fault Detection Method for Matrix Converters

This paper proposes a fault-tolerant matrix converter with reconfigurable structure and modified switch control schemes, along with a fault diagnosis technique for open-circuited switch failures. The proposed fault recognition method can detect and locate a failed bidirectional switch with voltage error signals dedicated to each switch, based on a direct comparison of the input and the output voltages. Following the fault detection, the designed converter architecture isolates the faulty parts and bypasses the remaining load phase, resulting in a 3 × 2 matrix configuration with six bidirectional switches. Based on the reconfigured hardware topology, novel fault-tolerant modulation strategies are developed to produce three-phase balanced sinusoidal output voltages/currents with only six bidirectional switches, but at a reduced output voltage magnitude as compared with the normal matrix converter. Thus, the developed switching function matrices for the reconfigurable converter structure, containing an appropriate positive- and negative-sequence set of matrices with input voltage vector, can preserve continuous operation even after switch failures and improve reliability of the drives.

Absorber intercooling in CO2 absorption by piperazine‐promoted potassium carbonate

AbstractIntercooling was evaluated as a process option in CO2 absorption by piperazine (PZ) promoted potassium carbonate. The system performance with 4.5 m K+/4.5 m PZ was simulated by a model in Aspen Plus® RateSep™. The absorber was evaluated for use with a double matrix stripper by optimizing the position of the semilean feed and intercooling stages to maximize CO2 removal. Additionally, a simple absorber system was modeled to observe the effect of intercooling on systems with variable CO2 lean loading. Intercooling increases CO2 removal by as much as 10% with the double matrix configuration. With a simple absorber, the effectiveness of intercooling depends on solvent rate. Near a critical liquid/gas ratio (L/G) there is a large improvement with intercooling. This is related to the position of the temperature bulge. An approximation is proposed to estimate the critical L/G where intercooling may maximize removal. © 2009 American Institute of Chemical Engineers AIChE J, 2010

Cerebellar Damage Loosens the Strategic Use of the Spatial Structure of the Search Space

The influence of a hemicerebellar lesion on the exploration of environments with different spatial distributions of multiple rewards was analyzed. Hemicerebellectomized (HCbed) and intact rats were submitted to a search task in which they had to explore nine food trays in an open field, avoiding repeated visits. Trays were spatially arranged in four configurations: cross, 3 x 3 matrix, circle, and three clusters of three trays each. Lesioned and intact rats' performances improved in all configurations used. However, the explorative activity of the HCbed animals differed from that of intact rats. Lesioned animals spent more time, made more errors, displayed lower search efficiency, exhibited shorter final spans, and traveled longer distances. They tended to perseverate and to neglect some trays. The cerebellar damage differentially influenced performances as a specific effect of the susceptibility of the configurations to being explored in a principled way. In the cross configuration that had strong spatial constraints, both groups made their lowest number of errors. In the circle configuration, the altered explorative strategies of lesioned animals made extremely demanding the acquisition of the task of searching multiple rewards, in spite of the attempt of favoring their altered procedures through an appropriate spatial arrangement. Since the procedural impairment elicited by cerebellar damage affected the central exploration, the matrix configuration was the most difficult configuration to be explored by the HCbed rats. The poor performances in the cluster configuration indicated that chunking was a strategy of relative strength in rats in general and in HCbed rats in particular.

Influence of the Number and Location of Recording Contacts on the Selectivity of a Nerve Cuff Electrode

A 56-contact matrix nerve cuff electrode (seven rings with eight contacts each) was used to obtain recordings from the rat sciatic nerve, which were then discriminated as originating from one of three fascicles (tibial, peroneal, and sural branches). The influence of the number and location of the recording contacts on the classification accuracy was studied. The performance of a classifier was shown to be superior when data was available from all 56 contacts, compared to when only the eight contacts of the middle ring were used (as in previously proposed multicontact tripolar cuff designs). By examining the performance variations as contacts were included one at a time (in order of decreasing positive impact on performance), it was further shown that the matrix configuration could outperform the single-ring configuration with only a small number of contacts. We can therefore conclude that the performance improvement is not due to the sheer number of contacts, but rather to the possibility of selecting the most informative locations around the nerve. The results could have important implications for the design and use of multicontact nerve cuff electrodes.

Plasma wave field effect transistor as a resonant detector for 1 terahertz imaging applications

The possibility of using plasma wave field effect transistor in a time domain terahertz (THz) spectroscopy setup is presented. We demonstrate that High Electron Mobility Transistors (HEMTs) is an efficient device for detection of pulsed terahertz electric fields generated with a femtosecond laser oscillator. The response was observed in the frequency range of about 1 THz, far above the cutoff frequency of the transistors at room temperature. We show that the physical mechanism of the detection is related to the plasma waves excited in the transistor channel and that significant improvement of the active device can be achieved by increasing the drain current. The two-dimensional terahertz imaging applications clearly demonstrate that plasma wave nanometer HEMT should be employed as efficient future detectors in a matrix configuration.

High deposition rates of uniform films in tetramethylsilane-based plasmas generated by elementary microwave sources in matrix configuration

Plasma scaling up can be achieved by distributing elementary microwave plasma sources on planar rectangular networks. These so-called matrix plasmas can generate uniform sheets of plasma over a wide argon pressure range, from 7.5 to 750 Pa, with densities between 10 12 and 10 13 cm − 3 . In order to estimate the capabilities of matrix plasmas for PACVD processing in terms of deposition rate and uniformity, SiOCH and SiNCH films were deposited using TMS (tetramethylsilane), as the organic gas precursor of silicon, mixed with oxygen or nitrogen flows. Plasmas of O 2 / TMS and N 2 / TMS gas mixtures can be sustained between 5 and 25 Pa. Variations in the deposition rate as a function of microwave power and nitrogen partial pressure are reported. Thickness uniformity of SiOCH and SiNCH films was measured across a silicon wafer. The obtained deposition rates exceed 1.3 μm/min and the films present a uniformity better than 5% on 75 mm diameter silicon wafers. Composition of the films has also been analyzed by XPS as a function of process parameters: microwave input power, composition of gas mixture, and N 2 partial pressure. In particular, these analyses have shown a very low yield of nitrogen incorporation when using N 2 gas as nitrogen precursor and high Si and Si–Si bonding contents in the films, probably due to a strong fragmentation of the TMS precursor in the high density plasma.

Characterization of hydrogen microwave plasmas produced by elementary sources in matrix configuration

In a previous study, a planar plasma reactor comprising 4 × 3 elementary microwave plasma sources distributed according to a square lattice matrix configuration was first characterized with argon. In this work, the objective is to characterize these so-called matrix plasmas with hydrogen in view of surface processing applications. In the absence of a static magnetic field, hydrogen plasmas can be sustained uniformly in the medium pressure range from 10 to 70 Pa. Using a cylindrical Langmuir probe, plasma density and electron temperature have been investigated at a distance of 20 mm from the source plane as functions of pressure and microwave power. The results show that the electron temperature Te is of the order of 1.2 eV and that plasma densities up to a few 1011 cm−3 can be reached. Under the same experimental conditions, optical emission spectroscopy measurements have been performed in order to determine the gas temperature and the degree of dissociation of hydrogen. The gas temperature, calculated from the α–Fulcher Q branch emission band (2–2) , varies from 600 to 850 K ± 50 K. The degree of dissociation has also been determined by using a spectroscopic method based on emission line intensities of Hα, Hβ and H2 (2–2) (N = 1) species. The maximum degree of dissociation of 50% has been obtained for the operating conditions corresponding to the highest plasma density.

Characterization of matrix and isolated organic solar cells

P3HT:PCBM bulk heterojunction solar cells were fabricated in two different configurations and were compared. A solar cell in matrix configuration showed lower R s, R sh, and V oc than an isolated cell due to the increased number of parasitic paths through neighboring devices. Solar cells in the matrix configuration were simulated using discrete cell parameters and the J sc obtained was corroborated with experimental value. The PEDOT:PSS layer enhances the effect of lateral charge transport and results in cross-talk-like behavior between arrays of solar cells with a common anode. These lead to significant errors, as high as 72.1%, in the calculated power conversion efficiencies.

Inherited complex I deficiency is associated with faster protein diffusion in the matrix of moving mitochondria

Mitochondria continuously change shape, position, and matrix configuration for optimal metabolite exchange. It is well established that changes in mitochondrial metabolism influence mitochondrial shape and matrix configuration. We demonstrated previously that inhibition of mitochondrial complex I (CI or NADH:ubiquinone oxidoreductase) by rotenone accelerated matrix protein diffusion and decreased the fraction and velocity of moving mitochondria. In the present study, we investigated the relationship between inherited CI deficiency, mitochondrial shape, mobility, and matrix protein diffusion. To this end, we analyzed fibroblasts of two children that represented opposite extremes in a cohort of 16 patients, with respect to their residual CI activity and mitochondrial shape. Fluorescence correlation spectroscopy (FCS) revealed no relationship between residual CI activity, mitochondrial shape, the fraction of moving mitochondria, their velocity, and the rate of matrix-targeted enhanced yellow fluorescent protein (mitoEYFP) diffusion. However, mitochondrial velocity and matrix protein diffusion in moving mitochondria were two to three times higher in patient cells than in control cells. Nocodazole inhibited mitochondrial movement without altering matrix EYFP diffusion, suggesting that both activities are mutually independent. Unexpectedly, electron microscopy analysis revealed no differences in mitochondrial ultrastructure between control and patient cells. It is discussed that the matrix of a moving mitochondrion in the CI-deficient state becomes less dense, allowing faster metabolite diffusion, and that fibroblasts of CI-deficient patients become more glycolytic, allowing a higher mitochondrial velocity.

Study on the yield behavior of Al 2O 3–SiO 2(sf)/Al–Si metal matrix composites

As the yield behavior of Al 2O 3–SiO 2(sf)/Al–Si MMCS is concerned, effects of heat treatment and parameters of short fiber, including volume fraction, size, distribution mode, were investigated. Dislocation configurations adjacent to interface between matrix and fiber were observed by TEM. Macro-yield stress ( σ 0.2) and micro-yield stress ( σ MYS) vary with parameters of short fiber, and effects of these parameters on σ 0.2 appear to be opposite to those on σ MYS. This phenomenon was interpreted by thermal residual stress in matrix and dislocation configuration. Suitable quenching followed aging treatment is an effective method to enhance the σ MYS and the σ 0.2 simultaneously. For the specimen with heat treatment of 550 °C/1 h WQ + 170 °C/6 h (T6) AC, σ 0.2 and σ MYS reach 200 and 58 MPa, respectively, and they are almost as twice as those as-cast.

Characterization of high density matrix microwave argon plasmas by laser absorption and electric probe diagnostics

Microwave plasma sources distributed on a planar matrix configuration can produce uniform bi-dimensional plasmas free from magnetic field in the 100 Pa pressure range. In argon, such uniform sheets of plasma have been obtained with ion densities in the range of 1012 to 1013 cm−3 with microwave power ranging from 0.4 to 2 kW. The electrical characterization of the plasma has been investigated using a cylindrical Langmuir probe. A first feature concerns the plasma potential that exhibits quite high values due to the large increase in the electron temperature towards the source plane where the microwave electric field is applied. Secondly, the decrease in the electron temperature observed when increasing the microwave power can be justified by the apparition of multi-step ionization mechanisms via metastable and higher excited states of Ar atom. The concentration and temperature of Ar(3P2) metastables have been measured by laser diode absorption spectroscopy. The results indicate that the presence of Ar(3P2) metastables is significant at 2 cm from the source plane with concentration and temperature values varying from 1010 to 1011 cm−3 and from 500 K to 1300 K, respectively, as functions of argon pressure and microwave power. An analytical model using a few simplifying assumptions provides a plasma picture in good agreement with the experimental results.

Studies of diffusion coefficients in disordered porous matrices confined in a slit-pore

We present a series of molecular dynamics simulations to study the structure of porous matrices confined in a slit-pore. The matrices were prepared by two different methods. In the first method we used direct simulations of a fluid at a fixed density and the matrix was taken from the last configuration of its particles. In the second method we simulated a binary mixture where one of the components served as a template material and the final porous matrix configuration was obtained by removing template particles from the mixture. In both methods the matrices were confined by two parallel walls (slit-pore) modeled by continuous solid surfaces. The results show that the matrix structure and porosity were affected by the method of preparation of the porous matrices. Moreover, we found smaller void cavities in these matrices than in matrices prepared without walls. Finally, diffusion of a fluid inside the matrices was investigated and it was found that the diffusion coefficient did not decrease with the fluid density, and presented a maximum at certain values of the fluid density.

Formation of bone-like apatite on poly(L-lactide) to improve osteoblast-like compatibility in vitro and in vivo

The biomimetic apatite coating process was adopted to modify poly(L-lactide) (PLLA) surfaces with osteoblasts-like cell compatibility. The apatite coating was formed on the pre-hydrolyzed PLLA film and scaffold surfaces by incubating in simulated body fluid (SBF). Scanning electron microscopy and energy dispersive X-ray analyzer were utilized to characterize the composition and the structure of the apatite coating. The cytocompatibility of the modified PLLA films was investigated by testing osteoblast-like attachment, proliferation, alkaline phosphatase (ALP) activity, and cell cycle. Subsequently, the modified PLLA scaffolds were co-cultured with the osteoblasts-like in vitro and subcutaneously implanted into nude mice. The experimental results showed that the formed apatite had a nano-sized particle and matrix configuration. The surface modification of PLLA with apatite coating significantly promoted osteoblast-like compatibility. After a four-week culture in vivo, no significant inflammatory signs were observed in the implanted regions and osteoblast-like congeries with bone-like structure began to form in the scaffolds. The positive results of this study suggest a good way to produce desirable PLLA biomaterials for bone tissue engineering.

Extracellular matrix configuration modulates TGF-β effects in primary hepatocytes

In vitro models to study TGF-β effects on the liver include cell lines, primary fetal cells and primary hepatocytes, the last resembling closer most of the phenotipic features of an intact liver. We compared the behaviour of primary mosue hepatocytes cultured on collagen type I as a dry monolyer or as gel sandwich and their response to TGF-β. Hepatocytes cultured on dry matrix displayed a typical cuboidal shape for the initial 24h, but started to spread and dedifferentiate constantly thereafter. Bile canaliculi was absent in this culture condition. Cells cultured in collagen sandwich started to form bile canaliculi from day 1 which persisted even after 5 days. Bile canaliculi function was evaluated by CMFDA secretion. Cell morphology was consistently better preserved as compared to dry matrix, as judged by nuclear/cytoplasmic ratio, cytoplasm granulosity and cell refringence. Upon TGF-β stimulation, cells in dry matrix displayed slight enhanced dedifferentiation. Very weak apoptosis induction was observed. Contrary to the dry collagen system, TGF-β treated cells showed strong morphologycal changes in time, progressing through a clear dedifferentiation resembling epithelial to mesenchymal transition. This changes were acompanied with expression of profibrogenic markers like CTGF. After 72h of stimulation, strong apoptosis was observed. This was confirmed by PARP degradation and Caspase–3 activation. Antiapoptotic proteins Bcl–2 and Bcl-xL were downregulated by TGF-β treatment. Interestingly, the p38 inhibitor SB203580 strongly atenuated apoptosis induction, but had no effect on dedifferentiation and CTGF expression, while ALK5 inhibitor SB431542 inhibited every feature induced by TGF-β. Our findings indicate that hepatocytes cultured on gel matrix preserve their features better and for a longer time than on a dry matrix, which allows a more sensitive response to TGF-β.

Exhaustive approach to the coupling matrix synthesis problem and application to the design of high degree asymmetric filters

In this paper a new approach to the synthesis of coupling matrices for microwave filters is presented. The new approach represents an advance on existing direct and optimization methods for coupling matrix synthesis in that it will exhaustively discover all possible coupling matrix solutions for a network if more than one exists. This enables a selection to be made of the set of coupling values, resonator frequency offsets, parasitic coupling tolerance etc that will be suited to the technology it is intended to realize the microwave filter with. To demonstrate the use of the method, the case of the recently - introduced 'extended box ' coupling matrix configuration is taken. The extended box is a new class of filter configuration adapted to the synthesis of asymmetric filtering characteristics of any degree. For this configuration the number of solutions to the coupling matrix synthesis problem appears to be high and offers therefore some flexibility that can be used during the design phase. We illustrate this by carrying out the synthesis process of two asymmetric filters of 8 th and 10 th degree. In the first example a ranking criterion is defined in anticipation of a dual mode realization and allows the selection of a best coupling matrix out of 16 possible ones. For the 10 th degree filter a new technique of approximate synthesis is presented yielding some simplifications of the practical realization of the filter as well as of its computer aided tuning phase.

Primary culture of rat hepatocytes in 96-well plates: Effects of extracellular matrix configuration on cytochrome P450 enzyme activity and inducibility, and its application in in vitro cytotoxicity screening

Basal level enzyme activities and enzyme inducibility were compared for rat hepatocytes that were cultured in 96-well plates with three different extracellular matrix configurations: single layer (SL) collagen type I, SL Matrigel, and collagen/Matrigel (C/M) sandwich. Overall, C/M sandwich and SL Matrigel plates were both superior to SL collagen type I plates in maintaining enzyme activities and inducibility and C/M sandwich plates had higher induced activity for CYP3A enzymes than SL Matrigel plates did. Cytotoxicity of nine reference compounds to rat hepatocytes (C/M sandwich configuration), rat hepatoma H4IIE and mouse fibroblast Balb/c 3T3 (3T3) cells was evaluated in 96-well plates using neutral red uptake (for 3T3) and tetrazolium salt MTS assays (for H4IIE and rat hepatocytes). For compounds chlorpromazine, quinidine, trichlorfon, thiopental, and antipyrine, the absolute differences in cytotoxicity Log IC 50 values obtained from different cell types were relatively small and without an obvious trend. The Δ Log IC 50 values between cultured hepatocytes and the cell lines were much larger for acetaminophen and cyclophosphamide (1.35 ⩽ ∣Δ Log IC 50∣ ⩽ 3.40), and for clofibrate and thioacetamide (not cytotoxic in hepatocytes at their highest dose levels). These large differences were likely the result of metabolism of these compounds in rat hepatocytes. The relationship between in vitro cytotoxicity Log IC 50 values and in vivo mouse or rat oral acute Log LD 50 values showed that compared to the cell lines, cultured rat hepatocytes improved correlation for acetaminophen and cyclophosphamide. The potential benefit of conducting in vitro cytotoxicity screening using a combination of permanent cell lines and cultured hepatocytes would allow us to obtain mechanistic insight on bioactivation, as well as improve the predictability of metabolism-mediated toxicity.

High density distributed microwave plasma sources in a matrix configuration: concept, design and performance

Plasma scaling up can be achieved by distributing elementary microwave plasma sources over two or tri-dimensional networks. This concept is applied to a planar reactor comprising 4 × 3 microwave plasma sources distributed according to a square lattice matrix configuration. In each elementary plasma source, the plasma is produced at the end of a coaxial applicator implemented perpendicularly to the planar source. An argon plasma can be sustained in the medium pressure range from 7.5 to 750 Pa. The sheet of plasma thus obtained becomes uniform at a distance from the source plane of 15 mm, i.e. less than half the 40 mm lattice mesh. Using a cylindrical Langmuir probe, plasma density and electron temperature have been investigated as functions of pressure and microwave power. Results show that the plasma can reach densities between 1012 and 1013 cm−3 with a uniformity better than ±3.5%.