Mass‐producible Nano‐featured Polystyrene Surfaces for Regulating the Differentiation of Human Adipose‐derived Stem Cells

In this study, we report an efficient and cost‐effective method of fabricating polystyrene (PS) nano‐featured substrates containing nanopore (NPo) and nanopillar (NPi) arrays based on hot embossing using nickel nano‐stamps. We investigate the behavior of adipose‐derived stem cells (ASCs), including adhesion, morphology, proliferation and differentiation, on the replicated PS surfaces. Compared to a flat substrate, NPo‐ and NPi‐featured substrates do not alter the morphology of stem cells. However, both NPo‐ and NPi‐featured substrates induce different integrin expression and lower formation of focal adhesion complexes. In addition, ASCs on the NPo‐featured substrate exhibit greater adipogenic differentiation, while the NPi‐featured substrate induces higher osteogenic differentiation.

     

Which subnormal Toeplitz operators are either normal or analytic?

We study subnormal Toeplitz operators on the vector-valued Hardy space of the unit circle, along with an appropriate reformulation of P.R. Halmos?s Problem 5: Which subnormal block Toeplitz operators are either normal or analytic? We extend and prove Abrahamse?s theorem to the case of matrix-valued symbols; that is, we show that every subnormal block Toeplitz operator with bounded type symbol (i.e., a quotient of two bounded analytic functions), whose analytic and co-analytic parts have the “left coprime factorization”, is normal or analytic. We also prove that the left coprime factorization condition is essential. Finally, we examine a well-known conjecture, of whether every subnormal Toeplitz operator with finite rank self-commutator is normal or analytic.     

Iterative methods for solving nonlinear equations with finitely many roots in an interval

In this paper we consider a nonlinear equation f(x)=0$f\left(x\right)=0$ having finitely many roots in a bounded interval. Based on the so-called numerical integration method [B.I. Yun, A non-iterative method for solving non-linear equations, Appl. Math. Comput. 198 (2008) 691–699] without any initial guess, we propose iterative methods to obtain all the roots of the nonlinear equation. In the result, an algorithm to find all of the simple roots and multiple ones as well as the extrema of f(x)$f\left(x\right)$ is developed. Moreover, criteria for distinguishing zeros and extrema are included in the algorithm. Availability of the proposed method is demonstrated by some numerical examples.     

Interspecific competition underlying mutualistic networks

Multiple classes of interactions may exist affecting one another in a given system. For the mutualistic networks of plants and pollinating animals, it has been known that the degree distribution is broad but often deviates from power-law form more significantly for plants than animals. To illuminate the origin of such asymmetry, we study a model network in which links are assigned under generalized preferential-selection rules between two groups of nodes and find the sensitive dependence of the resulting connectivity pattern on the model parameters. The nonlinearity of preferential selection can come from interspecific interactions among animals and among plants. The model-based analysis of real-world mutualistic networks suggests that a new animal determines its partners not only by their abundance but also under the competition with existing animal species, which leads to the stretched-exponential degree distributions of plants.     

Size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots

We investigate size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots (QDs) grown using molecular beam epitaxy and atomic layer epitaxy. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy with increasing ZnTe buffer thicknesses. This shift of the PL peak can be attributed to size variation of the CdTe QDs. In particular, carrier dynamics in CdTe QDs grown on various ZnTe buffer layer thicknesses is studied using time-resolved PL measurements. As a result, the decay time of CdTe QDs is shown to increase with increasing ZnTe buffer layer thicknesses due to the reduction of the exciton oscillator strength in the larger QDs.     

New limits on interactions between weakly interacting massive particles and nucleons obtained with CsI(Tl) crystal detectors

New limits are presented on the cross section for weakly interacting massive particle (WIMP) nucleon scattering in the KIMS CsI(T?) detector array at the Yangyang Underground Laboratory. The exposure used for these results is 24?524.3 kg·days. Nuclei recoiling from WIMP interactions are identified by a pulse shape discrimination method. A low energy background due to alpha emitters on the crystal surfaces is identified and taken into account in the analysis. The detected numbers of nuclear recoils are consistent with zero and 90% confidence level upper limits on the WIMP interaction rates are set for electron equivalent energies from 3 to 11 keV. The 90% upper limit of the nuclear recoil event rate for 3.6-5.8 keV corresponding to 2-4 keV in NaI(T?) is 0.0098 counts/kg/keV/day, which is below the annual modulation amplitude reported by DAMA. This is incompatible with interpretations that enhance the modulation amplitude such as inelastic dark matter models. We establish the most stringent cross section limits on spin-dependent WIMP-proton elastic scattering for the WIMP masses greater than 20 GeV/c2.     

Single-pulse coherent diffraction imaging using soft x-ray laser

We report a coherent diffraction imaging (CDI) using a single 8 ps soft x-ray laser pulse at a wavelength of 13.9 nm. The soft x-ray pulse was generated by a laboratory-scale intense pumping laser providing coherent x-ray pulses up to the level of 10(11) photons/pulse. A spatial resolution below 194 nm was achieved with a single pulse, and it was shown that a resolution below 55 nm is feasible with improved detector capability. The single-pulse CDI might provide a way to investigate dynamics of nanoscale molecules or particles.