Resolution of dark matter problem in f(T) gravity

In this paper, we attempt to resolve the dark matter problem in f(T) gravity. Specifically, from our model we successfully obtain the flat rotation curves of galaxies containing dark matter. Further, we obtain the density profile of dark matter in galaxies. Comparison of our analytical results shows that our torsion-based toy model for dark matter is in good agreement with empirical data-based models. It shows that we can address the dark matter as an effect of torsion of the space.Comment: 14 pages, 3 figure

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

Biomedical applications of natural-based polymers combined with bioactive glass nanoparticles

In recent years, the combination of natural polymers with nanoparticles has permitted the development of sophisticated and efficient bioinspired constructs. In this regard, the incorporation of bioactive glass nanoparticles (BGNPs) confers a bioactive nature to these constructs, which can then induce the formation of a bone-like apatite layer upon immersion in a physiological environment. Moreover, the incorporation of bioactive glass nanoparticles has been found to be beneficial; the constructs proved to be biocompatible, promote cell adhesion and spreading, and regulate osteogenic commitment. This review provides a summary and discussion of the composition, design, and applications of bioinspired nanocomposite constructs based on BGNPs. Examples of nanocomposite systems will be highlighted with relevance to biomedical applications. It is expected that understanding the principles and the stateof-the-art of natural nanocomposites may lead to breakthroughs in many research areas, including tissue engineering and orthopaedic devices. The challenges regarding the future translation of these nanostructured composites into clinical use are also summarized.A´lvaro J. Leite acknowledges the Portuguese Foundation for Science and Technology (FCT) for his doctoral grant (SFRH/BD/73174/2010).info:eu-repo/semantics/publishedVersio

Native Nucleus Pulposus Tissue Matrix Promotes Notochordal Differentiation of Human Induced Pluripotent Stem Cells with Potential for Treating Intervertebral Disc Degeneration

Native porcine nucleus pulposus (NP) tissue harbors a number of notochordal cells (NCs). Whether the native NP matrix supports the homeostasis of notochordal cells is poorly understood. We hypothesized the NP matrix alone may contain sufficient regulatory factors and can serve as stimuli to generate notochordal cells (NCs) from human pluripotent stem cells. NCs are a promising cell sources for cell-based therapy to treat some types of intervertebral disc (IVD) degeneration. One major limitation of this emerging technique is the lack of available NCs as a potential therapeutic cell source. Human pluripotent stem cells derived from reprogramming or somatic cell nuclear transfer technique may yield stable and unlimited source for therapeutic use. We devised a new method to use porcine NP matrix to direct notochordal differentiation of human induced pluripotent stem cells (hiPSCs). The results showed that hiPSCs successfully differentiated into NC-like cells under the influence of devitalized porcine NP matrix. The NC-like cells expressed typical notochordal marker genes including brachyury (T), cytokeratin-8 (CK-8) and cytokeratin-18 (CK-18), and they displayed the ability to generate NP-like tissue in vitro, which was rich in aggrecan and collagen type II. These findings demonstrated the proof of concept for using native NP matrix to direct notochordal differentiation of hiPSCs. It provides a foundation for further understanding the biology of NCs, and eventually towards regenerative therapies for disc degeneration

Preparation and Bioactive Characteristics of Porous Borate Glass Substrates

Whereas silicate-based bioactive glasses and glass-ceramics have been widely investigates for bone repair or as scaffolds for cell-based bone tissue engineering, recent data have demonstrated that silica-free borate glasses also exhibit bioactive behavior. The objectives of this study were to fabricate porous, three-dimensional substrates by in vitro cell culture with human mesenchymal stem cells (hMSCs) and hMSC-derived osteoblasts (hMSC-Obs).Borate glass particles with sizes 212-355 µm were loosely compacted and then sintered at 600⁰C to form porous disc-shaped substrates (porosity ≈40%).Partial or nearly complete conversion of the glass substrates to a calcium phosphate(Ca-P) material was achieved by soaking the substrates for 1 day or 7 days in a 0.25 molar K2HPO4 solution at 37⁰C and at pH of 9.0. Bone marrow derived hMSC-Obs markedly synthesized alkaline phosphatase, an early osteogenic marker. These data indicate strong bioactive characteristics for the borate glass constructs and the potential use of the constructs for bone tissue engineering

Bioactive Borate Glass Scaffold for Bone Tissue Engineering

Borate glass particles and microspheres with size distributions in the range of approximately 100-400 μm, were loosely compacted and sintered for 10 min at 600 °C to form a porous, three-dimensional construct (porosity 25-40%). Conversion of the borate glass to hydroxyapatite was investigated by soaking the constructs in a solution of K2HPO4 (0.25 M) at 37 °C and with a pH value of 9.0, and measuring the weight loss of the constructs as a function of time. Almost full conversion of the borate glass to hydroxyapatite was achieved in less than 6 days. X-ray diffraction revealed an initially amorphous product that subsequently crystallized to hydroxyapatite. The biocompatibility of the porous constructs was investigated by in vitro cell culture with human mesenchymal stem cells derived from bone marrow (bMSC) and human mesenchymal stem cell derived osteoblasts (MSC-Ob). The cells adhered to the scaffolds and the MSC-Obs produced alkaline phosphatase which is an indication of osteogenic differentiation. The data suggest strong bioactive characteristics for the borate glass constructs and the potential use of the constructs as scaffolds for tissue engineering of bone

Preparation and Bioacttve Characteristics of Porous Borate Glass Substrates

Whereas silicate-based bioactive glasses and glass-ceramics have been widely investigated for bone repair or as scaffolds for cell-based bone tissue engineering, recent data have demonstrated that silica-free borate glasses also exhibit bioactive behavior. the objectives of this study were to fabricate porous, three-dimensional substrates of a borate glass and to investigate the biocompatibility of the borate glass substrates by in vitro cell culture with human mesenchymal stem cells (hMSCs) and hMSC-derived osteoblasts (hMSC-Obs). Borate glass particles with sizes 212-355 μm were loosely compacted and then sintered at 600°C to form porous discshaped substrates (porosity ∽ 40%). Partial or nearly complete conversion of the glass substrates to a calcium phosphate (Ca-P) material was achieved by soaking the substrates for 1 day or 7 days in a 0.25 molar K2HPO4 solution at 37°C and at pH of 9.0. Bone marrow derived hMSCs and hMSC-Obs seeded in the samples both adhered to the porous constructs whereas hMSC-Obs markedly synthesized alkaline phosphatase, an early osteogenic marker. These data indicate strong bioactive characteristics for the borate glass constructs and the potential use of the constructs for bone tissue engineering