Allowed slepton intergenerational mixing in light of light element abundances

We studied allowed region on the intergenerational mixing parameters of sleptons from a viewpoint of big-bang nucleosynthesis in a slepton-neutralino coannihilation scenario. In this scenario, $^7$Li and $^6$Li problems can be solved by considering exotic reactions caused by bound-state effects with a long-lived slepton. Light element abundances are calculated as functions of the relic density and lifetime of the slepton which considerably depend on the intergenerational mixing parameters. Compared with observational light element abundances, we obtain allowed regions on the intergenerational mixing. Ratio of selectron component to stau component, $c_e$, is allowed in $2\times 10^{-11} \lesssim c_e \lesssim 2\times 10^{-9}$ with solving both the $^7$Li and $^6$Li problems. Similarly, the ratio for smuon, $c_{\mu}$, is allowed in $10^{-7} \lesssim c_{\mu} \lesssim 5\times 10^{-5}$ for mass difference between slepton and neutralino, which is smaller than muon mass, and $$ for the mass difference in range between muon mass and 125 MeV. We also discuss collider signatures of the slepton decays. We find characteristic double peaks in momentum distribution of event number of the slepton decays with allowed mixing parameters. Discoveries of the double peaks at future collider experiments should confirm our scenario.Comment: 10 pages, 6 figure

Stau relic density at the Big-Bang nucleosynthesis era consistent with the abundance of the light element nuclei in the coannihilation scenario

We calculate the relic density of stau at the beginning of the Big-Bang Nucleosynthesis (BBN) era in the coannihilation scenario of minimal supersymmetric standard model (MSSM). In this scenario, stau can be long-lived and form bound states with nuclei. We put constraints on the parameter space of MSSM by connecting the calculation of the relic density of stau to the observation of the light elements abundance, which strongly depends on the relic density of stau. Consistency between the theoretical prediction and the observational result, both of the dark matter abundance and the light elements abundance, requires the mass difference between the lighter stau and the lightest neutralino to be around 100MeV, the stau mass to be 300 -- 400 GeV, and the mixing angle of the left and right-handed staus to be $\sin\theta_{\tau} = (0.65 \textrm{--} 1)$.Comment: 9 pages, 5 figures, figure 5 correcte

Possible solution to the 7^7Li problem by the long lived stau

Modification of standard big-bang nucleosynthesis is considered in the minimal supersymmetric standard model to resolve the excessive theoretical prediction of the abundance of primordial lithium 7. We focus on the stau as a next-lightest superparticle, which is long lived due to its small mass difference with the lightest superparticle. It provides a number of additional decay processes of $\mathrm{^{7}Li}$ and $\mathrm{^{7}Be}$. A particularly important process is the internal conversion in the stau-nucleus bound state, which destroys the $\mathrm{^{7}Li}$ and $\mathrm{^{7}Be}$ effectively. We show that the modification can lead to a prediction consistent with the observed abundance of $\mathrm{^{7}Li}$.Comment: 6 pages, 5 figure

Big-bang nucleosynthesis and the relic abundance of dark matter in a stau-neutralino coannihilation scenario

A scenario of the Big-Bang Nucleosynthesis is analyzed within the Minimal Supersymmetric Standard Model which is consistent with a stau-neutralino coannihilation scenario to explain the relic abundance of dark matter. We find that we can account for the possible descrepancy of the abundance of $\mathrm{^{7}Li}$ between the observation and the prediction of the Big-Bang Nucleosynthesis by taking the mass of the neutralino as $300 \mathrm{GeV}$ and the mass difference between the stau and the neutralino as $(100 -- 120) MeV$. We can therefore simultaneously explain the abundance of the dark matter and that of $\mathrm{^{7}Li}$ by these values of parameters. The lifetime of staus in this scenario is predicted to be $O(100 -- 1000) sec$.Comment: 9 pages, 2 figure

Scaffold-free tissue engineering for injured joint surface restoration

Abstract Articular cartilage does not heal spontaneously due to its limited healing capacity, and thus effective treatments for cartilage injuries has remained challenging. Since the first report by Brittberg et al. in 1994, autologous chondrocyte implantation (ACI) has been introduced into the clinic. Recently, as an alternative for chondrocyte-based therapy, mesenchymal stem cell (MSC)-based therapy has received considerable research attention because of the relative ease in handling for tissue harvest, and subsequent cell expansion and differentiation. In this review, we discuss the latest developments regarding stem cell-based therapies for cartilage repair, with special focus on recent scaffold-free approaches

Cartilage Repair in the Inflamed Joint: Considerations for Biological Augmentation Toward Tissue Regeneration

Cartilage repair/regeneration procedures (e.g., microfracture, autologous chondrocyte implantation [ACI]) typically result in a satisfactory outcome in selected patients. However, the vast majority of patients with chronic symptoms and, in general, a more diseased joint, do not benefit from these surgical techniques. The aims of this work were to (1) review factors negatively influencing the joint environment; (2) review current adjuvant therapies that can be used to improve results of cartilage repair/regeneration procedures in patients with more diseased joints, (3) outline future lines of research and promising experimental approaches. Chronicity of symptoms and advancing patient age appear to be the most relevant factors negatively affecting clinical outcome of cartilage repair/regeneration. Preliminary experience with hyaluronic acid, platelet-rich plasma, and mesenchymal stem cell has been positive but there is no strong evidence supporting the use of these products and this requires further assessment with high-quality, prospective clinical trials. The use of a Tissue Therapy strategy, based on more mature engineered tissues, holds promise to tackle limitations of standard ACI procedures. Current research has highlighted the need for more targeted therapies, and (1) induction of tolerance with granulocyte colony-stimulating factor (G-CSF) or by preventing IL-6 downregulation; (2) combined IL-4 and IL-10 local release; and (3) selective activation of the prostaglandin E2 (PGE2) signaling appear to be the most promising innovative strategies. For older patients and for those with chronic symptoms, adjuvant therapies are needed in combination with microfracture and ACI