Network-like Pattern Research Articles

Commuting Pattern Recognition of Industrial Parks Using Mobile Phone Signaling Data: A Case Study of Nanjing, China

As a novel industrial space to cope with global competition, industrial parks have gradually become important growth poles to promote regional development and provide a large number of employment opportunities. This study utilizes mobile phone signaling data to identify the commuting origins and destinations (OD) of different industrial parks in Nanjing while comparing the distribution of the working population, residential population, and commuting patterns across varying types and levels of industrial parks. The level of coordination of the employment–residential system in each park is quantified by calculating the resident commuting index (HSCi), employee commuting index (WSCi), and their coupling coordination degree. Additionally, geographic detectors are employed to identify the influencing factors and interaction effects that impact the employment–residential balance in industrial parks. Results show that industrial parks located in the central urban area attract more residential and working populations. The commuting volume of national and municipal as well as high-tech industrial parks is higher than other types of industrial parks. Most industrial parks experience more inward than outward commuting, and there is an uneven distribution of commuting flows, resulting in a network-like pattern of “central dense, peripheral sparse”. Various industrial parks exhibit a highly coupled job–housing system, and those with high HSCi tend to have high WSCi as well. The coupling coordination of industrial parks ranged from 0.16 to 0.93, with 13 being primary coordination or above and 3 being disordered. Industrial parks are classified into three types: employment-oriented, residential-oriented, and employment–residential balanced, with the residential-oriented type being predominant. The density of public transportation stops, park area, and land use mix are the primary factors affecting the employment–residential balance. Industrial parks with larger scale, better land allocation, and higher service facility levels are more likely to achieve coordination in the employment–residential system. Our work utilizes mobile signaling data to characterize the commuting patterns of industrial parks, providing insights for industrial park planning and promoting the integration of industry and city.

Evaluation of Fracturing Effect of Tight Reservoirs Based on Deep Learning.

The utilization of hydraulic fracturing technology is indispensable for unlocking the potential of tight oil and gas reservoirs. Understanding and accurately evaluating the impact of fracturing is pivotal in maximizing oil and gas production and optimizing wellbore performance. Currently, evaluation methods based on acoustic logging, such as orthogonal dipole anisotropy and radial tomography imaging, are widely used. However, when the fractures generated by hydraulic fracturing form a network-like pattern, orthogonal dipole anisotropy fails to accurately assess the fracturing effects. Radial tomography imaging can address this issue, but it is challenged by high manpower and time costs. This study aims to develop a more efficient and accurate method for evaluating fracturing effects in tight reservoirs using deep learning techniques. Specifically, the method utilizes dipole array acoustic logging curves recorded before and after fracturing. Manual labeling was conducted by integrating logging data interpretation results. An improved WGAN-GP was employed to generate adversarial samples for data augmentation, and fracturing effect evaluation was implemented using SE-ResNet, ResNet, and DenseNet. The experimental results demonstrated that ResNet with residual connections is more suitable for the dataset in this study, achieving higher accuracy in fracturing effect evaluation. The inclusion of the SE module further enhanced model accuracy by adaptively adjusting the weights of feature map channels, with the highest accuracy reaching 99.75%.

Transcriptome Analysis Reveals the Variations in Enzyme Production of Saccharopolyspora rosea A22 under Different Temperatures.

Saccharopolyspora is a key microorganism in the fermentation of traditional fermented foods, capable of producing saccharifying and liquefying enzymes at elevated temperatures. However, the specific mechanisms and regulatory pathways governing Saccharopolyspora's response to ambient temperatures are not yet fully understood. In this study, the morphological differences in Saccharopolyspora rosea screened from traditional handmade wheat Qu at different temperatures were initially explored. At 37 °C, the mycelium exhibited abundant growth and radiated in a network-like pattern. As the temperature increased, the mycelium aggregated into clusters. At 50 °C, it formed highly aggregated ellipsoidal structures, with the mycelium distributed on the spherical surface. Subsequently, we assessed the biomass, saccharifying enzyme activity and liquefying enzyme activity of Saccharopolyspora rosea cultured at 37 °C, 42 °C and 50 °C. Furthermore, transcriptome analysis demonstrated that Saccharopolyspora rosea employs mechanisms related to the carbon metabolism, the TCA cycle, glycine, serine and threonine metabolisms, and microbial metabolism in diverse environments to coordinate its responses to changes in environmental temperature, as verified by the expression of typical genes. This study enhances our understanding of the differences in high-temperature enzyme production by Saccharopolyspora, and offers valuable guidance for the traditional fermented food industry to drive innovation.

Brecciation and fracturing by water ingress into the Genbudo basaltic andesitic lava flow, Iwate volcano, northeastern Japan

The Genbudo lava, the late Pleistocene basaltic-andesitic lava flow in the southwestern part of Iwate Volcano, Japan, is a 70 m thick columnar jointed flow that can be divided into three parts from bottom to top: the colonnade, the entablature, and the partly-brecciated uppermost part. Two main types of fractures developed in the entablature: pseudopillow fractures that formed in a branching network-like pattern throughout the entablature, and sheet fractures with curved surfaces that are nearly parallel to each other. At the uppermost part of the flow, finger-like structures of lava extend upward from the coherent lava, and cogenetic autoclastic rocks form between the fingers. This occurrence suggests that hyaloclastites were generated during emplacement in the uppermost part of the flow, apparently when water from a dammed river valley covered the flow. The texture of the lava near the pseudopillow fractures in the entablature is commonly hypocrystalline, while the texture in other parts is holocrystalline. There are two types of pyroxene microlites, large prismatic (average size ~ 30 µm) and dendritic (< 10 µm in length) crystals in the lava near the pseudopillow fractures. These suggest that the cooling rate of the lava was greatest in the vicinity of the pseudopillow fractures. Networks of palagonite-filled micro-fractures (less than 10 µm in width) are found in this part of the flow, and many bubbles are observed along the fractures. This is clear evidence that the rapid cooling of the lava was caused by water infiltration through the pseudopillow fractures. From the measurement of Fe-rich droplet sizes that formed due to liquid immiscibility within the lava, we estimate the cooling rate within the colonnade as about 49 °C/h and within the entablature as 642 °C/h, consistent with much more rapid cooling by water infiltration from above.

Aβ Amyloid Fibers Drastically Alter the Topography and Mechanical Properties of Lipid Membranes.

Alzheimer's disease (AD) is related to the fibrillation of the Aβ peptides at neuronal membranes, a process that depends on the lipid composition and may impart different physical states to the membrane. In the present work, we study the properties of the Aβ peptide when mixed with a zwitterionic lipid (DMPC), using the Langmuir monolayer technique as an approach to control membrane physical conditions. First, we build on previous characterizations of pure Aβ monolayers and observe that, in addition to high shear, these films present a pronounced compressional hysteresis. When Aβ is assembled with DMPC in a binary film, the resulting membranes become heterogeneous, with a peptide-enriched phase distributed in a network-like pattern, and they exhibit a lateral transition that depends on the Aβ content. At lower peptide proportions, the films segregate into two well-defined phases: one consisting of lipids and another enriched with peptides. The reflectivity of these phases differs from that obtained for pure Aβ films. Thus, the formed fibers effectively cover most of the interface area and remain stable at higher pressures (from 20 to 30 mN m-1 depending on Aβ content) compared to pure peptide films (17 mN m-1). Furthermore, such structures induce a compressional hysteresis in the film, similar to that of pure peptide films (which is nonexistent in the pure lipid monolayer), even at low peptide proportions. We claim that the mechanical properties at the interface are governed by the size of the fibril-like structures. Based on the low molar fractions and surface packing at which these phenomena were observed, we postulate that as a consequence of peptide intermolecular interactions, Aβ may have drastic effects on the molecular arrangement and mechanical properties of a lipid membrane.

Investigation of the Microstructure and Properties of CoCrFeNiMo High-Entropy Alloy Coating Prepared through High-Speed Laser Cladding

High-speed laser cladding was introduced to prepare a CoCrFeNiMo high-entropy alloy (HEA) coating. The microstructure, composition distribution, micromechanical properties, and corrosion resistance of the CoCrFeNiMo coating were characterized. As a result, the coating exhibited a dual FCC- and BCC-phase structure, and the grain size of the coating prepared through high-speed laser cladding was only 2~5 μm. The upper and lower parts of the coating were composed of equiaxed cellular crystals and slender columnar crystals, respectively. The interdendritic structure was a Mo-rich phase that was distributed in a network-like pattern. The nanoindentation tests revealed that the interdendritic BCC phase had high hardness and an elastic modulus as well as excellent resistance to deformation, while the intradendritic FCC phase possessed superior crack propagation resistance. In addition, the two phases could generate cooperative elastic deformation during the elastic deformation stage. The electrochemical performance of the coating was tested in 3.5 wt% NaCl solution, and the corrosion potential Ecorr and corrosion current density Icorr of the coating were −0.362 V and 3.69 × 10−6 A/cm2, respectively. The high-speed laser cladding CoCrFeNiMo HEA coating had excellent corrosion resistance thanks to the presence of the easily passivating element Mo and grain refinement.

Viscoelastic phase separation in biological cells

Biological phase separation forming membraneless organelles in cytoplasm and nucleus has attracted considerable attention. Liquid-like condensates are often created as spherical droplets. However, various condensates with network-like morphologies, including protein granules, localisation bodies, and centrosome assemblies, have recently been discovered in cells. Therefore, what controls the morphology of biological phase separation is a critical issue but remains elusive. Here, based on the knowledge of viscoelastic phase separation in soft matter physics, we propose that the difference in the molecular dynamics between the two phases controls the condensate morphology. Small and large mobility differences between the two phases should lead to droplet-like and network-like morphologies of the minority phase, respectively. We show that asymmetric partitioning of high-molecular-weight unstructured polymers (e.g., messenger RNA) between the two phases increases the dynamic asymmetry between the phases to form a network-like pattern of the slower phase, which may further be stabilised through inter-polymer binding.

Localised Grey Matter Atrophy in Multiple Sclerosis and Clinically Isolated Syndrome-A Coordinate-Based Meta-Analysis, Meta-Analysis of Networks, and Meta-Regression of Voxel-Based Morphometry Studies.

Background: Atrophy of grey matter (GM) is observed in the earliest stages of multiple sclerosis (MS) and is associated with cognitive decline and physical disability. Localised GM atrophy in MS can be explored and better understood using magnetic resonance imaging and voxel-based morphometry (VBM). However, results are difficult to interpret due to methodological differences between studies. Methods: Coordinate-based analysis is a way to find the reliably observable results across multiple independent VBM studies. This work uses coordinate-based meta-analysis, meta-analysis of networks, and meta-regression to summarise the evidence from voxel-based morphometry of regional GM hanges in patients with MS and clinically isolated syndrome (CIS), and whether these measured changes are relatable to clinical features. Results: Thirty-four published articles reporting forty-four independent experiments using VBM for the assessment of GM atrophy between MS or CIS patients and healthy controls were identified. Analysis identified eight clusters of consistent cross-study reporting of localised GM atrophy involving both cortical and subcortical regions. Meta-network analysis identified a network-like pattern indicating that GM loss occurs with some symmetry between hemispheres. Meta-regression analysis indicates a relationship between disease duration or age and the magnitude of reported statistical effect in some deep GM structures. Conclusions: These results suggest consistency in MRI-detectible regional GM loss across multiple MS studies, and the estimated effect sizes and symmetries can help design prospective studies to test specific hypotheses.

Flow-induced Reorganization of Laminin-integrin Networks Within the Endothelial Basement Membrane Uncovered by Proteomics

The vessel wall is continuously exposed to hemodynamic forces generated by blood flow. Endothelial mechanosensors perceive and translate mechanical signals via cellular signaling pathways into biological processes that control endothelial development, phenotype and function. To assess the hemodynamic effects on the endothelium on a system-wide level, we applied a quantitative mass spectrometry approach combined with cell surface chemical footprinting. SILAC-labeled endothelial cells were subjected to flow-induced shear stress for 0, 24 or 48 h, followed by chemical labeling of surface proteins using a non-membrane permeable biotin label, and analysis of the whole proteome and the cell surface proteome by LC-MS/MS analysis. These studies revealed that of the >5000 quantified proteins 104 were altered, which were highly enriched for extracellular matrix proteins and proteins involved in cell-matrix adhesion. Cell surface proteomics indicated that LAMA4 was proteolytically processed upon flow-exposure, which corresponded to the decreased LAMA4 mass observed on immunoblot. Immunofluorescence microscopy studies highlighted that the endothelial basement membrane was drastically remodeled upon flow exposure. We observed a network-like pattern of LAMA4 and LAMA5, which corresponded to the localization of laminin-adhesion molecules ITGA6 and ITGB4. Furthermore, the adaptation to flow-exposure did not affect the inflammatory response to tumor necrosis factor α, indicating that inflammation and flow trigger fundamentally distinct endothelial signaling pathways with limited reciprocity and synergy. Taken together, this study uncovers the blood flow-induced remodeling of the basement membrane and stresses the importance of the subendothelial basement membrane in vascular homeostasis.

Effects of Solution Treatment on the Microstructure, Tensile Properties, and Impact Toughness of an Al–5.0Mg–3.0Zn–1.0Cu Cast Alloy

This study investigates the effect of solution treatment (at 470 °C for 0–48 h) on the microstructural evolution, tensile properties, and impact properties of an Al–5.0Mg–3.0Zn–1.0Cu (wt%) alloy prepared by permanent gravity casting. The results show that the as-cast microstructure consists of α-Al dendrites and a network-like pattern of T-Mg32(AlZnCu)49 phases. Most of the T-phases were dissolved within 24 h at 470 °C; and a further prolonging of solution time resulted in a rapid growth of α-Al grains. No transformation from the T-phase to the S-Al2CuMg phase was discovered in this alloy. Both the tensile properties and impact toughness increased quickly, reached a maximum peak value, and decreased gradually as the solution treatment proceeded. The impact toughness is more closely related to the elongation, and the relationship between impact toughness and elongation appears to obey an equation: $${\text{IT}} = 8.43{\text{EL}} - 3.46$$ . After optimal solution treatment at 470 °C for 24 h, this alloy exhibits excellent mechanical properties with the ultimate tensile strength, yield strength, elongation and impact toughness being 431.6 MPa, 270.1 MPa, 19.4% and 154.7 kJ/m2, which are comparable to that of a wrought Al–6.0Mg–0.7Mn alloy (5E06, a 5xxx aluminum alloy). Due to its excellent comprehensive combination of mechanical properties, this cast alloy has high potential for use in components which require medium strength, high ductility and high toughness.

Relationship of microcirculation pattern and histopathologic factors in choroidal melanoma

Background Biological behavior of choroidal melanoma is closely related with angiogenesis.The microcirculation pattern in which tumor cells may be involved is different from neovascularization. Objective This study was to observe the microcirculation pattern of the choroidal melanoma tissue and analyze its relationship with the clinical pathology factor and the degree of cellular proliferation. Methods Forty-eight specimen of choroidal melanoma tissue were collected at Beijing Tongren Eye Centre from November 1997 through March 2006.Periodate acid Schiff staining was used to determine the microcirculation pattern of choroidal melanoma.The morphology of the tumor cells and the distribution of microcirculation pattern in the tumor were observed under a fluorescence microscopy with 544 nm wavelength,and the Ki-67 expression in the tumor was detected by immunochemistry.The relationships between the choroidal melanoma clinical pathology factor with Ki-67 expression and microcirculation pattern were evaluated by multiple stepwise regression model. Results A total of 9 kinds of microcirculation patterns were found by periodate acid Schiff staining.The occurring rate of loop- or network-like vascular pattern showed a significant elevation in the tumor tissue with epithelial cells in comparison with the tumor with spindle-like cells (66.7％ vs.30.6％ ) ( P=0.027 ).The expression rates of Ki-67 were 18.961 ± 10.995 and 19.481 ± 12.167 in the tumor tissue with loop- or network-like microvascular pattern,and those in the tumor tissue without loop- or network-like microvascular pattern were 10.261 ±5.669 and 12.021 ± 6.802,presenting significant differences between them ( P =0.000,P =0.010).Loop-like microvascular pattern was determined as the risk factor of the proliferation and metastasis of choroidal melanoma by multiple stepwise regression analysis (P=0.002). Conclusions Among the nine microcirculation patterns in choroidal melanoma,networks pattern is the most fashion,and Ki-67 expression is more strong in the tumor with epitheliod cells,suggesting that this microcirculation pattern is associated to the malignant degree and extent of proliferation in choroidal melanoma. Key words: Choroidal melanoma; Microcirculation pattern; Cell proliferation

Morphological and Molecular Characterization of Globodera Populations from Oregon and Idaho

An unusual population of cyst nematode was found in soils collected from a Powell Butte, OR field with a cropping history including potato, wheat, other crops, and significant weed presence. These nematodes could not be placed with certainty into any known species and exhibited some unique morphological features in some specimens. Compared with Globodera pallida, the cyst body length was slightly longer and the second-stage juvenile stylet length was slightly shorter. In some individuals, the J2 stylet knob height was greater and the tail annules were more prominent than in G. pallida, and the tail abruptly narrowed, with a slight constriction near the posterior third of the hyaline terminus. Compared with G. rostochiensis, the hyaline tail terminus had a larger number of refractive bodies, and cysts of this population had a smaller Granek's ratio and fewer cuticular ridges between the anus and vulva. In some individuals, the tail termini of second-stage juveniles were more bluntly pointed, and the stylet knobs were more anteriorly directed with greater height. Unlike G. tabacum, the cyst wall often lacked a network-like pattern and, in some individuals, the juvenile tail terminus distinctly narrowed after a constriction. Molecularly, the population was distinct from G. pallida, G. rostochiensis, and G. tabacum. Multiplex polymerase chain reaction of the internal transcribed spacer (ITS) rDNA region gave results similar to G. tabacum; however, ITS restriction fragment length polymorphism patterns were observed to have individual bands in common with G. rostochiensis and G. pallida. Phylogenetic analysis based on ITS1 and -2 rDNA sequences showed greatest similarity to populations from Argentina and Chile; together, they form a moderately supported clade, distinct from G. rostochiensis, G. tabacum, G. "mexicana," European type G. pallida, and several G. pallida populations from South America.

Hereditary cutaneous mucinosis in shar pei dogs is associated with increased hyaluronan synthase‐2 mRNA transcription by cultured dermal fibroblasts

Shar pei dogs are known for the distinctive feature of thick, wrinkled skin as a consequence of high dermal mucin content. Excessive dermal deposition of mucinous substance leading to severe skin folding, and/or to the more severe vesicular form characterized by dermal vesicles or bullae, is highly prevalent in this breed and is known as idiopathic mucinosis. Hyaluronic acid (HA) is the main component that accumulates in the dermis, and high levels of HA have also been detected in the serum of shar pei dogs. In this study, the cellular and molecular mechanisms underlying cutaneous mucinosis of shar pei dogs were investigated. Thirteen shar pei dogs and four control dogs of other breeds were included. In primary dermal fibroblast cultures, transcription of the family of hyaluronan synthases (HAS) involved in HA synthesis, and of hyaluronidases (HYAL) involved in HA degradation, were studied by reverse transcriptase polymerase chain reaction. The location of HA in cell cultures was studied by immunofluorescence and confocal laser microscopy. Dermal fibroblasts transcribed HAS2, HAS3, HYAL1 and HYAL2, but no amplification for HAS1 was found. A higher transcription of HAS2 was demonstrated in shar pei dogs compared with control dogs. By confocal microscopy, HA was detected as a more diffuse and intense network-like pattern of green fluorescence in the fibroblast cells of shar pei dogs in comparison with control dogs. Together, these results provide additional evidence that hereditary cutaneous mucinosis in shar pei dogs may be a consequence of over-transcription or increased activity of HAS2.

Characterization of MYR1, a dosage suppressor of YPT6 and RIC1 deficient mutants

Membrane traffic is tightly regulated and the Rab protein family of small GTPases plays a central role in this regulation. One member of this family is the Saccharomyces cerevisae protein Ypt6. To search for new genes interacting with Ypt6-related pathways, we performed a genetic screen for high copy suppressors of ypt6Delta temperature sensitivity at 35 degrees C. Among the suppressors, MYR1 was also able to suppress the temperature sensitive mutant lacking Ric1, a subunit of the Ypt6 guanine exchanging factor complex Ric1/Rgp1. Myr1 is characterized by a coiled coil region and a GYF domain, a protein module binding proline-rich sequences. Myr1 is able to bind membranes but is also associated with larger structures insoluble in Triton X-100. By immunofluorescence, Myr1 shows a network-like pattern as well as small foci. Overexpression of Myr1 influences nuclear envelope morphology and high levels are lethal. This lethality is rescued when the N-terminal region, containing the GYF domain, is deleted. The transcription profile of a myr1Delta strain shows effects on genes involved in nuclear migration, Ras signalling and transcription. Taken together, these results suggest that Myr1 is a novel factor linked to the secretory pathway and important cellular regulatory mechanisms.

Membrane potential governs lateral segregation of plasma membrane proteins and lipids in yeast

The plasma membrane potential is mainly considered as the driving force for ion and nutrient translocation. Using the yeast Saccharomyces cerevisiae as a model organism, we have discovered a novel role of the membrane potential in the organization of the plasma membrane. Within the yeast plasma membrane, two non-overlapping sub-compartments can be visualized. The first one, represented by a network-like structure, is occupied by the proton ATPase, Pma1, and the second one, forming 300-nm patches, houses a number of proton symporters (Can1, Fur4, Tat2 and HUP1) and Sur7, a component of the recently described eisosomes. Evidence is presented that sterols, the main lipid constituent of the plasma membrane, also accumulate within the patchy compartment. It is documented that this compartmentation is highly dependent on the energization of the membrane. Plasma membrane depolarization causes reversible dispersion of the H(+)-symporters, not however of the Sur7 protein. Mitochondrial mutants, affected in plasma membrane energization, show a significantly lower degree of membrane protein segregation. In accordance with these observations, depolarized membranes also considerably change their physical properties (detergent sensitivity).

Spatial Pattern Formation in a Cholesteric Liquid Crystal Under a Rapid Temperature Change

We have investigated the characteristic behavior of a cholesteric liquid crystal, cholesteryl oleyl carbonate, under a thermally nonequilibrium condition. It has been found that a rapid temperature increase causes the instability of the uniform planar texture, and a network-like spatial pattern is induced. We have studied this phenomenon by performing two experiments: the spectroscopic measurement of optical transmission and the dynamic light scattering measurement which proves the structural variation of the helical structure and the dynamical fluctuation of the director under the thermally equilibrium condition, respectively. We discuss the mechanism of the spatial pattern formation process by combining the results of these measurements.

Viscoelastic phase separation in polymer blends

In this paper, the dynamics and morphology of viscoelastic phase separation in polymer blends is investigated based on the two-fluid model in two dimensions. At critical composition, we have carefully checked the role of shear modulus, without taking account of bulk modulus. The results show that the higher shear modulus component tends to form a dispersed phase in the intermediate stage of phase separation, if the difference between the shear moduli of the components is large enough. This is opposite to the role of bulk modulus, that the higher bulk modulus component forms a networklike pattern without taking account of the shear modulus even if it is the minority phase. The morphological formation is determined by the competition of opposite effects of shear modulus and bulk modulus. For polymer blends at critical composition, the bulk modulus difference leads to a networklike pattern formed by the higher modulus component in the intermediate stage of phase separation. But if the difference between the shear moduli of the components is large enough, a co-continuous structure is observed, resulting from the competition between shear and bulk moduli. For off-critical composition, difference in bulk modulus also leads to a networklike pattern of the component with higher bulk modulus in the intermediate stage of phase separation, but phase inversion is observed rapidly. A small difference between the shear moduli of the components can support the networklike pattern to continue for longer time. But the networklike pattern does not occur for large difference between shear moduli.

Photopolymerization-induced phase separation in binary blends of photocurable/linear polymers

Phase separation behavior and morphology of polymer blends induced by photopolymerization have been investigated in a binary blend of photocurable polymer (2,2-bis(4-(acryloxy diethoxy)phenyl)propane; BPE4) and linear polymer (polysulfone; PSU) using electron microscopy techniques. A ternary phase diagram of mono-BPE4/poly-BPE4/PSU exhibits a lower critical solution temperature (LCST) behavior. In situ polymerization of BPE4 over a wide range of PSU compositions (5–70 wt%) results in network-like bicontinuous phase separated structures at high temperatures, while semi-interpenetrating polymer network (IPN) structures are cured at low temperatures. Even at 10 wt% PSU, the PSU-rich phase is a continuous network-like phase. BPE4-rich domains in the network-like structures are controlled from the nano-scale (30 nm) to the microscale (1 μm) by varying the composition, curing temperature and irradiation intensity. By means of time-evolution study of the phase structure, it is found that BPE4-rich domains appeared in a PSU-rich matrix after the induction time. These domains quickly grow in size up to the sub-micron level, but further growth appears to be slow. The PSU-rich matrix develops into the network-like pattern by the increase in the number and growth of the BPE4-rich domains.

Ordered networks of rat hippocampal neurons attached to silicon oxide surfaces

The control of neuronal cell position and outgrowth is of fundamental interest in the development of applications ranging from cellular biosensors to tissue engineering. We have produced rectangular networks of functional rat hippocampal neurons on silicon oxide surfaces. Attachment and network formation of neurons was guided by a geometrical grid pattern of the adhesion peptide PA22-2 which matches in sequence a part of the A-chain of laminin. PA22-2 was applied by contact printing onto the functionalised silicon oxide surface and was immobilised by hetero-bifunctional cross-linking with sulfo-GMBS. Geometric pattern matching was achieved by microcontact printing using a polydimethylsiloxane (PDMS) stamp. In this way the produced grid pattern ranged from 3 to 20 μm in line width and from 50 to 100 μm in line distances. As shown by atomic force microscopy (AFM), line widths and line distances of the peptide pattern differ less than 0.5 μm from the used PDMS stamp. The height of the layer of immobilised PA22-2 was approximately 3.5 nm implying the layer to be monomolecular. Immobilised PA22-2 was capable of binding anti-PA22-2 antibodies indicating that the function of the peptide was not compromised by immobilisation. Rat hippocampal neurons, cultured at low density in serum-free medium, were applied to the growth matrix of PA22-2-coated substrates and, within 1–3 h of culture, formed a network-like pattern that more or less matched the printed grid. Reliability and reproducibility of neuronal network formation depended on the geometry, line width and node diameter of the grid pattern. The immobilised neurons showed resting membrane potentials comparable with controls and, already after 1 day of culture, were capable of eliciting action potentials. The suitability of the immobilised neurons for the study of man-made neural networks and for multi-site recordings from a functional neuronal network is discussed.

Network domain structure in phase-separating polymer solutions

Results from molecular dynamics simulations of phase separation in a quenched polymer solution are presented for both two- and three-dimensional systems. Simulations clearly demonstrate the existence of a networklike pattern formation at an early to intermediate time regime for sufficiently dense polymer solutions. This network structure, however, relaxes at late times as the minimization of the interface energy wins over the elastic stress of the network. A crossover of domain growth exponent from a smaller value at intermediate times to the Lifshitz–Slyozov value of 1/3 at late times is seen in three-dimensional (3D) simulations of network breakup. Our results for the late-time growth exponent and dynamical scaling of the structure factors strongly indicate that the late-time growth kinetics of quenched polymer solutions belong to the same universality class of small molecular mixtures.