Donghua University

About: Donghua University is a education organization based out in Shanghai, China. It is known for research contribution in the topics: Fiber & Nanofiber. The organization has 21155 authors who have published 21841 publications receiving 393091 citations. The organization is also known as: Dōnghuá Dàxué & China Textile University.

Critical mass for infinite-time aggregation in a chemotaxis model with indirect signal production

Abstract: We study the Neumann initial-boundary problem for the chemotaxis system    ut = ∆u−∇ · (u∇v), x ∈ Ω, t > 0, 0 = ∆v − μ(t) + w, x ∈ Ω, t > 0, τwt + δw = u, x ∈ Ω, t > 0, (⋆) in the unit disk Ω := B1(0) ⊂ R, where δ ≥ 0 and τ > 0 are given parameters and μ(t) := − ∫ Ω w(x, t)dx, t > 0. It is shown that this problem exhibits a novel type of critical mass phenomenon with regard to the formation of singularities, which drastically differs from the well-known threshold property of the classical Keller-Segel system, as obtained upon formally taking τ → 0, in that it refers to blow-up in infinite time rather than in finite time: Specifically, it is first proved that for any sufficiently regular nonnegative initial data u0 and w0, (⋆) possesses a unique global classical solution. In particular, this shows that in sharp contrast to classical Keller-Segel-type systems reflecting immediate signal secretion by the cells themselves, the indirect mechanism of signal production in (⋆) entirely rules out any occurrence of blow-up in finite time. However, within the framework of radially symmetric solutions it is next proved that • whenever δ > 0 and ∫ Ω u0 8πδ, one can find initial data such that ∫ Ω u0 = m, and such that for the corresponding solution we have ‖u(·, t)‖L∞(Ω) → ∞ as t → ∞.

Self-cleaning cotton fabrics via combination of photocatalytic TiO2 and superhydrophobic SiO2

Abstract: Fluorine-free superhydrophobic cotton fabrics with photocatalytic self-cleaning property were prepared by the combination of photoactive TiO2 and superhydrophobic SiO2. Organically modified silica (ormosil) aerogel with a high surface area and high porosity was first prepared. TiO2 nanocrystals were then synthesized and simultaneously deposited onto preformed porous ormosil aerogel at low temperature (below 100 °C) to obtain TiO2–SiO2 composite particles. XRD measurements prove that the formed TiO2 is of anatase phase. SEM and TEM images disclose the highly porous structure of the TiO2–SiO2 composite particles and further confirm the existence of highly crystalline TiO2 within the SiO2 matrix. IR spectra indicate the presence of abundant methyl groups on the TiO2–SiO2 composite particle surface. BET measurements show a high surface area of 379.0 m2/g for the TiO2–SiO2 composite particles, which is advantageous to enhance the photocatalysis. The cotton fabrics coated with TiO2–SiO2 composite particles exhibit superhydrophobicity with a water contact angle of 160.5°. However, the superhydrophobic cotton fabrics can be easily wetted by oil dirt and become superhydrophilic. Herein, the TiO2–SiO2 composite particle coated cotton fabric, which was contaminated with oleic acid, can recover its superhydrophobicity after UV irradiation for 4 h.

How Copper Nanowires Grow and How To Control Their Properties.

Abstract: Scalable, solution-phase nanostructure synthesis has the promise to produce a wide variety of nanomaterials with novel properties at a cost that is low enough for these materials to be used to solve problems. For example, solution-synthesized metal nanowires are now being used to make low cost, flexible transparent electrodes in touch screens, organic light-emitting diodes (OLEDs), and solar cells. There has been a tremendous increase in the number of solution-phase syntheses that enable control over the assembly of atoms into nanowires in the last 15 years, but proposed mechanisms for nanowire formation are usually qualitative, and for many syntheses there is little consensus as to how nanowires form. It is often not clear what species is adding to a nanowire growing in solution or what mechanistic step limits its rate of growth. A deeper understanding of nanowire growth is important for efficiently directing the development of nanowire synthesis toward producing a wide variety of nanostructure morpholog...

Fractal calculus and its application to explanation of biomechanism of polar bear hairs

Abstract: The polar bear hairs have special hierarchical structure with fractal dimensions of golden ratio, which endows the creature with remarkable cool prevention. Fractal calculus is adopted in this pape...