140 research outputs found

    Topological Evolution of Dynamical Networks: Global Criticality from Local Dynamics

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    We evolve network topology of an asymmetrically connected threshold network by a simple local rewiring rule: quiet nodes grow links, active nodes lose links. This leads to convergence of the average connectivity of the network towards the critical value Kc=2K_c =2 in the limit of large system size NN. How this principle could generate self-organization in natural complex systems is discussed for two examples: neural networks and regulatory networks in the genome.Comment: 4 pages RevTeX, 4 figures PostScript, revised versio

    3D Printed Silicone Meniscus Implants: Influence of the 3D Printing Process on Properties of Silicone Implants

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    Osteoarthritis of the knee with meniscal pathologies is a severe meniscal pathology suffered by the aging population worldwide. However, conventional meniscal substitutes are not 3D-printable and lack the customizability of 3D printed implants and are not mechanically robust enough for human implantation. Similarly, 3D printed hydrogel scaffolds suffer from drawbacks of being mechanically weak and as a result patients are unable to execute immediate post-surgical weight-bearing ambulation and rehabilitation. To solve this problem, we have developed a 3D silicone meniscus implant which is (1) cytocompatible, (2) resistant to cyclic loading and mechanically similar to native meniscus, and (3) directly 3D printable. The main focus of this study is to determine whether the purity, composition, structure, dimensions and mechanical properties of silicone implants are affected by the use of a custom-made in-house 3D-printer. We have used the phosphate buffer saline (PBS) absorption test, Fourier transform infrared (FTIR) spectroscopy, surface profilometry, thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) to effectively assess and compare material properties between molded and 3D printed silicone samples

    Fully Differential Investigation of Two-Center Interference in Dissociative Capture in p + H₂ Collisions

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    We have measured and calculated fully differential cross sections for vibrational dissociation following capture in 75-keV p + H2 collisions. For a molecular orientation perpendicular to the projectile beam axis and parallel to the transverse momentum transfer we observe a pronounced interference structure. The positions of the interference extrema suggest that the interference term is afflicted with a phase shift which depends on the projectile scattering angle. However, no significant dependence on the kinetic-energy release was observed. Considerable discrepancies between our calculations and experimental data were found

    Target Dependence of Postcollision Interaction Effects on Fully Differential Ionization Cross Sections

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    We have measured and calculated fully differential cross sections (FDCS) for ionization of helium by 75-keV proton impact. Ejected electrons with a speed close to and above the projectile speed were investigated. This range of kinematics represents a largely unexplored regime. A high sensitivity of the FDCS to the details of the description of the few-body dynamics, reported earlier for ionization of H2, was confirmed. A peak structure was found in an electron angular range between the regions where the so-called binary and recoil peaks are usually observed. The need for nonperturbative calculations using a two-center basis set is demonstrated

    The evolutionary young miR-1290 favors mitotic exit and differentiation of human neural progenitors through altering the cell cycle proteins.

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    Regulation of cellular proliferation and differentiation during brain development results from processes requiring several regulatory networks to function in synchrony. MicroRNAs are part of this regulatory system. Although many microRNAs are evolutionarily conserved, recent evolution of such regulatory molecules can enable the acquisition of new means of attaining specialized functions. Here we identify and report the novel expression and functions of a human and higher primate-specific microRNA, miR-1290, in neurons. Using human fetal-derived neural progenitors, SH-SY5Y neuroblastoma cell line and H9-ESC-derived neural progenitors (H9-NPC), we found miR-1290 to be upregulated during neuronal differentiation, using microarray, northern blotting and qRT-PCR. We then conducted knockdown and overexpression experiments to look at the functional consequences of perturbed miR-1290 levels. Knockdown of miR-1290 inhibited differentiation and induced proliferation in differentiated neurons; correspondingly, miR-1290 overexpression in progenitors led to a slowing down of the cell cycle and differentiation to neuronal phenotypes. Consequently, we identified that crucial cell cycle proteins were aberrantly changed in expression level. Therefore, we conclude that miR-1290 is required for maintaining neurons in a differentiated state

    3D Printed Silicone Meniscus Implants: Influence of the 3D Printing Process on Properties of Silicone Implants

    Get PDF
    Osteoarthritis of the knee with meniscal pathologies is a severe meniscal pathology suffered by the aging population worldwide. However, conventional meniscal substitutes are not 3D-printable and lack the customizability of 3D printed implants and are not mechanically robust enough for human implantation. Similarly, 3D printed hydrogel scaffolds suffer from drawbacks of being mechanically weak and as a result patients are unable to execute immediate post-surgical weight-bearing ambulation and rehabilitation. To solve this problem, we have developed a 3D silicone meniscus implant which is (1) cytocompatible, (2) resistant to cyclic loading and mechanically similar to native meniscus, and (3) directly 3D printable. The main focus of this study is to determine whether the purity, composition, structure, dimensions and mechanical properties of silicone implants are affected by the use of a custom-made in-house 3D-printer. We have used the phosphate buffer saline (PBS) absorption test, Fourier transform infrared (FTIR) spectroscopy, surface profilometry, thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) to effectively assess and compare material properties between molded and 3D printed silicone samples
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