Voltage-controlled reverse filament growth boosts resistive switching memory

Nonvolatile memory devices based on filamentary resistance switching （KS） are among the frontrunners to fuel future devices and sensors of the internet of things （IoT） era. The capability of many two distinctive resistive states in response to an external electrical stimulus has been demonstrated. Through years of selection, cells based on the drift of metal ions, namely conductive-bridge memory devices, have shown a wide range of applications with nanosecond switching speeds, nanometer scalability, high-density, and low power-consumption. However, for low （sub-10-~A） current operation, a critical challenge is still represented by programming variability and by the stability of the conductive filament over time. Here, by introducing the concept of reverse filament growth （RFG）, we managed to control the structural reconfiguration of the conductive filament inside a memory cell with significant enhancements of each of the aforementioned properties. A first-in-class Cu-based switching device is demonstrated, with a dedicated stack that enabled us to systematically trigger RFG, thus tuning the device＇s properties. Along with nanosecond switching speeds, we achieved an endurance of up to 106 cycles with a 102 read window, with outstanding disturb immunity and optimal stability of the filament over time. Furthermore, by tuning the filament＇s shape, an excellent control of multi-level bit operations was achieved. Thus, this device offers high flexibility in memory applications.

Early stages of non-classic crystal growth

Investigation of early stages of crystal growth revealed that crystal growth in some systems may not follow the classic route.In the early stages of inorganic crystal growth,precursor molecules and/or nanocrystallites may aggregate into large and disordered particles with the assistance of some polymers or biomolecules.Surface crystallization of these aggregates would then take place to form shells with high crystallinity and density,followed by an extension of the crystallization from surface to core.This so-called reversed crystal growth mechanism has been found in crystallization of several inorganic compounds including zeolites,perovskites,metals and metal oxides,and will be identified in more material systems.The establishment of this new crystal growth route gave us more freedom to control the morphology of crystals and to understand the formation mechanism of many natural minerals.This article gives a brief review of the recent research in this field by featuring some typical examples of the reversed crystal growth.

Aberrant expression of growth factor Wnt-5A in six urinary malignant cell lines

Objective To investigate the expression of growth factor Wnt 5A in urinary tumor cell lines. Methods By semi quantitative RT PCR (reverse transcriptase polymerase chain reaction), the expression of Wnt 5A in six urinary malignant cell lines, one primary cultured renal fibroblast and one case of normal human renal tissue was detected using Gel Doc 1000 computer controlled molecular analysis system. Results The expression of Wnt 5A in urinary tumor cell lines was much higher than that in primary cultured renal fibroblasts (PRF) and normal human renal tissue (NRT). The levels of Wnt 5A mRNA were different between six malignant cell lines. Conclusion The overexpression of growth factor Wnt 5A has a potential effect on the oncogenesis of urinary malignancies.

Mesoporogen-free synthesis of hierarchical sodalite as a solid base catalyst from sub-molten salt-activated aluminosilicate

A rapid and environmentally friendly approach to synthesize hierarchical sodalite from natural aluminosilicate mineral without the involvement of any mesoporogen or post-synthesis treatment was developed.This strategy involves three important steps:the first is the depolymerization of an aluminosilicate mineral into highly reactive silicon and aluminum species with ideal meso-scale structures through activation of a sub-molten salt.The second step is the hydrolysis and condensation of the activated aluminosilicate mineral into zeolitic precursors that also have a meso-scale structure.The third is the rapid zeolitization of the zeolitic precursors through the reversed crystal growth route at room temperature and ambient pressure to form hierarchical sodalite.The physicochemical properties of the as-synthesized sodalite were systematically characterized,and the formation mechanism of the hierarchical pore structure was discussed.When used as a solid base catalyst for Knoevenagel condensation,the as-synthesized sodalite and its potassium ion-exchanged product with hierarchical micro-meso-macroporous structure both exhibited high catalytic activity and product selectivity.

Regularity for Quasi-linear Degenerate Elliptic Equations with VMO Coefficients

In this paper we establish an interior regularity of weak solution for quasi-linear degenerate elliptic equations under the subcritical growth if its coefficient matrix A（x, u） satisfies a VMO condition in the variable x uniformly with respect to all u, and the lower order item B（x, u, △↓u） satisfies the subcritical growth （1.2）. In particular, when F（x） ∈ L^q（Ω） and f（x） ∈ L^γ（Ω） with q,γ 〉 for any 1 〈 p 〈 ＋∞, we obtain interior HSlder continuity of any weak solution of （1.1） u with an index κ = min{1 - n/q, 1 - n/γ}.