Ceramic identity contributes to mechanical properties and osteoblast behavior on macroporous composite scaffolds.

Implants formed of metals, bioceramics, or polymers may provide an alternative to autografts for treating large bone defects. However, limitations to each material motivate the examination of composites to capitalize on the beneficial aspects of individual components and to address the need for conferring bioactive behavior to the polymer matrix. We hypothesized that the inclusion of different bioceramics in a ceramic-polymer composite would alter the physical properties of the implant and the cellular osteogenic response. To test this, composite scaffolds formed from poly(lactide-co-glycolide) (PLG) and either hydroxyapatite (HA), β-tricalcium phosphate (TCP), or bioactive glass (Bioglass 45S®, BG) were fabricated, and the physical properties of each scaffold were examined. We quantified cell proliferation by DNA content, osteogenic response of human osteoblasts (NHOsts) to composite scaffolds by alkaline phosphatase (ALP) activity, and changes in gene expression by qPCR. Compared to BG-PLG scaffolds, HA-PLG and TCP-PLG composite scaffolds possessed greater compressive moduli. NHOsts on BG-PLG substrates exhibited higher ALP activity than those on control, HA-, or TCP-PLG scaffolds after 21 days, and cells on composites exhibited a 3-fold increase in ALP activity between 7 and 21 days versus a minimal increase on control scaffolds. Compared to cells on PLG controls, RUNX2 expression in NHOsts on composite scaffolds was lower at both 7 and 21 days, while expression of genes encoding for bone matrix proteins (COL1A1 and SPARC) was higher on BG-PLG scaffolds at both time points. These data demonstrate the importance of selecting a ceramic when fabricating composites applied for bone healing

Photometry and dynamics of the minor mergers AM\,1228-260 and AM\,2058-381

We investigate interaction effects on the dynamics and morphology of the galaxy pairs AM\,2058-381 and AM\,1228-260. This work is based on $r'$ images and long-slit spectra obtained with the Gemini Multi-Object Spectrograph at the Gemini South Telescope. The luminosity ratio between the main (AM\,2058A) and secondary (AM\,2058B) components of the first pair is a factor of $\sim$ 5, while for the other pair, the main (AM\,1228A) component is 20 times more luminous than the secondary (AM\,1228B). The four galaxies have pseudo-bulges, with a S\'ersic index $n<2$. Their observed radial velocities profiles (RVPs) present several irregularities. The receding side of the RVP of AM\,2058A is displaced with respect to the velocity field model, while there is a strong evidence that AM\,2058B is a tumbling body, rotating along its major axis. The RVPs for AM\,1228A indicate a misalignment between the kinematic and photometric major axes. The RVP for AM\,1228B is quite perturbed, very likely due to the interaction with AM\,1228A. NFW halo parameters for AM\,2058A are similar to those of the Milky Way and M\,31. The halo mass of AM\,1228A is roughly 10\% that of AM\,2058A. The mass-to-light (M/L) of AM\,2058 agrees with the mean value derived for late-type spirals, while the low M/L for AM\,1228A may be due to the intense star formation ongoing in this galaxy.Comment: 20 pages, 10 figures, accepted for publication in MNRA

Synchronization of the Frenet-Serret linear system with a chaotic nonlinear system by feedback of states

A synchronization procedure of the generalized type in the sense of Rulkov et al [Phys. Rev. E 51, 980 (1995)] is used to impose a nonlinear Malasoma chaotic motion on the Frenet-Serret system of vectors in the differential geometry of space curves. This could have applications to the mesoscopic motion of biological filamentsComment: 12 pages, 7 figures, accepted at Int. J. Theor. Phy