No abstract

Formononetin, a phytoestrogen extracted from various herbal plants, has been investigated as an anticancer agent against diverse types of cancer. The aim of the present study was to investigate the induction of apoptotic cell death by formononetin in the FaDu pharyngeal squamous cell carcinoma cell line. Formononetin significantly increased FaDu cell death, with an estimated IC 50 value of 50 µM; however, it did not affect the viability of normal L929 mouse fibroblasts used as normal control at 5-25 µM. Typical characteristics of apoptosis, such as morphological alterations, chromatin condensation, DNA fragmentation and the size of the apoptotic cell population, were increased in FaDu cells treated with formononetin for 24 h. Furthermore, formononetin-induced FaDu cell death involved the death receptor-mediated extrinsic and the mitochondria-dependent intrinsic apoptotic pathways by activating the caspase cascade. The chemotherapeutic effects of formononetin were mediated by the suppression of mitogen-activated protein kinases, including extracellular signal-regulated kinase 1/2 and p38, and nuclear factor-κB phosphorylation in FaDu cells. Finally, the oral administration of formononetin decelerated tumor growth through the expression of cleaved caspase-3 in a FaDu cell xenograft animal model. Taken together, these findings indicate that formononetin holds promise as a chemotherapeutic agent and may be of value in the treatment of human head and neck squamous cell carcinoma.

Single‐crystalline inorganic semiconductor nanomembranes (NMs) have attracted great attention over the last decade, which poses great advantages to complex device integration. Applications in heterogeneous electronics and flexible electronics have been demonstrated with various semiconductor nanomembranes. Single‐crystalline aluminum nitride (AlN), as an ultrawide‐bandgap semiconductor with great potential in applications such as high‐power electronics has not been demonstrated in its NM forms. This very first report demonstrates the creation, transfer‐printing, and characteristics of the high‐quality single‐crystalline AlN NMs. This work successfully transfers the AlN NMs onto various foreign substrates. The crystalline quality of the NMs has been characterized by a broad range of techniques before and after the transfer‐printing and no degradation in crystal quality has been observed. Interestingly, a partial relaxation of the tensile stress has been observed when comparing the original as‐grown AlN epi and the transferred AlN NMs. In addition, the transferred AlN NMs exhibits the presence of piezoelectricity at the nanoscale, as confirmed by piezoelectric force microscopy. This work also comments on the advantages and the challenges of the approach. Potentially, the novel approach opens a viable path for the development of the AlN‐based heterogeneous integration and future novel electronics and optoelectronics.

To efficiently develop an extremely intensive storage memory, the resistive random‐access memory (RRAM), which operates by producing and rupturing conductive filaments, is essential. However, due to the stochastic nature of filament production, this filamentary type resistive switching has an inherent limitation, which entails the unpredictability of the driving voltage and resistance states. Several strategies such as doping, research into multilayer stacks, and interface engineering, are suggested to tackle this challenge. This work fabricates a CMOS‐compatible TiN/HfOx/TiN‐NCs (nanocrystals)/HfOx/TiN RRAM to implement analog resistive switching and advance the development of the synaptic device. Specifically, atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are utilized to observe the formation of TiN nanocrystals, which play a crucial role in the enhancement of resistive switching. By comparing HfOx–based RRAM devices with and without NCs, the DC I–V curves, retention, endurance, and switching speed are properly examined. Interestingly, it is found that the TiN/HfOx/TiN‐NCs/HfOx/TiN device is more appropriately utilized as an artificial synapse in neuromorphic systems mainly due to its stable and reliable resistive switching properties. Finally, this work demonstrates well‐controlled resistive switching 3D vertical RRAM with TiN‐NCs, which is particularly suitable for high‐density memory.

Epitaxial regrowth of GaN pn junctions is a key technology for realization of a variety of high-performance GaN power electronic devices. However, the regrowth process can introduce impurities and defects that degrade a device’s performance. Here, we show that scanning Kelvin probe force microscopy and scanning capacitance microscopy can be used in a cross-sectional geometry to probe dopant distributions and an electronic structure in epitaxially grown GaN pn junctions. These measurements enable profiling of potential and dopant distributions across GaN pn junctions produced by uninterrupted epitaxial growth and by regrowth on an etched surface. Clear differences are observed in comparisons to the electronic structure of these two types of junctions that can be correlated with results of complementary characterization of dopant distributions reported for similarly grown structures. These measurements also suggest the presence of defects in etch-and-regrow pn junction structures that extend nearly 1 μm below the regrown interface.