Regulation of mesenchymal stem cell adhesion and orientation in 3D collagen scaffold by electrical stimulus

Cell adhesion and orientation are important for both natural and engineered tissues to fully achieve physiologic functions. Based on diverse cellular responses induced by electrical stimulus on 2D substrate, we applied non-invasive electrical stimulus to regulate cell adhesion and orientation of bone marrow-derived mesenchymal stem cells (MSCs) and fibroblasts in a reconstituted 3D collagen-based scaffold. While fibroblasts were induced to reorient perpendicularly in response to direct current electrical stimulus, rat MSCs showed only slight changes in cell reorientation. Multiphoton microscopy revealed that rat MSCs exhibited much stronger 3D adhesion, which appears to resist cell reorientation. Only in response to a large electrical stimulus (e.g., 10 V/cm), collagen fibers around rat MSCs became disconnected and loosely reorganized. In contrast, the collagen fibers surrounding the fibroblasts were entangled in a random network and became preferentially aligned in the direction of the electrical stimulus. When incubated with integrin antibodies, both fibroblasts and rat MSCs failed to respond to electrical stimulus, providing evidence that integrin-dependent molecular mechanisms are involved in 3D cell adhesion and orientation. Elucidation of physical regulation of 3D cell adhesion and orientation may offer a novel approach in controlling cell growth and differentiation and could be useful for stem cell-based therapeutic application and engineering tissue constructs.     

Weighted estimates of solutions to second order parabolic equations

We evaluate the rate of decay for solutions to second order parabolic equations, which vanish on the boundary, while the right-hand side is allowed to be unbounded. Our approach is based on a special growth lemma, and it works for both divergence and non-divergence equations, in domains satisfying a general “exterior measure condition” (A). The result for elliptic case is published in Cho and Safonov (2007) [2].     

Classification of α-Ricci flat graphs with girth at least five

Lin, Lu and Yau classified Ricci flat graphs with girth at least 5 in Lin et al., 2014 [7] and Cushing et al., 2018 [4,5]. In Lin et al., 2014, they defined $\alpha$-Ricci curvature for the definition of Ricci curvature. We will classify $\alpha$-Ricci flat graphs with girth at least 5 for all $\alpha \in (0,1)$.     

Finite group action and Gromov-Witten invariants in symplectic four-manifolds

Let a finite group act semi-freely on a closed symplectic four-manifold with a 2-dimensional fixed point set. Then we show that the relative Gromov-Witten invariants are the same as the invariants on the quotient set-up with respect to the fixed point set.     

Operator-valued Feynman integral via conditional Feynman integrals on a function space

Let C ₀ ^r [0; t] denote the analogue of the r-dimensional Wiener space, define X _t : C ^r [0; t] → ?^2r by X _t (x) = (x(0); x(t)). In this paper, we introduce a simple formula for the conditional expectations with the conditioning function X _t . Using this formula, we evaluate the conditional analytic Feynman integral for the functional $$ \Gamma _t \left( x \right) = exp \left\{ {\int_0^t {\theta \left( {s,x\left( s \right)} \right)d\eta \left( s \right)} } \right\}\varphi \left( {x\left( t \right)} \right) x \in C^r \left[ {0,t} \right] $$ , where η is a complex Borel measure on [0, t], and θ(s, ·) and φ are the Fourier-Stieltjes transforms of the complex Borel measures on ? ^r . We then introduce an integral transform as an analytic operator-valued Feynman integral over C ^r [0, t], and evaluate the integral transform for the function Γ _t via the conditional analytic Feynman integral as a kernel.     

Approximating zeros of monotone operators by proximal point algorithms

In this paper, we introduce two kinds of iterative algorithms for the problem of finding zeros of maximal monotone operators. Weak and strong convergence theorems are established in a real Hilbert space. As applications, we consider a problem of finding a minimizer of a convex function.     

On the stability of the generalized Cauchy–Jensen set-valued functional equations

In this paper, we prove the Hyers–Ulam–Rassias stability of the generalized Cauchy–Jensen set-valued functional equation defined by

$$\begin{aligned} \alpha f\left( \frac{x+y}{\alpha } + z\right) = f(x) \oplus f(y)\oplus \alpha f(z) \end{aligned}$$

for all \(x,y,z \in X\) and \(\alpha \ge 2\) on a Banach space by using the fixed point alternative theorem.

     

Measurement of isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions induced by bremsstrahlung

We measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions were (4.95 ± 0.51) × 10^?4, (5.72 ± 0.72) × 10^?4, (6.03 ± 0.50) × 10^?4, and (9.27 ± 0.83) × 10^?4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.     

P4S10/dimethicone tandem: efficient reagent for thionation of various aromatic amides and esters

Organosulfur compounds are valuable because of their rich and varied chemistry especially in biological field. We report a new and efficient way for thionation of various aromatic amides and esters using P₄S₁₀/dimethicone tandem. The ease of handling and higher yield makes this protocol economical.