Giant Magnetoimpedance Effect of Multilayered Thin Film Meanders Formed on Flexible Substrates.

The giant magnetoimpedance effect of multilayered thin films under stress has great application prospects in magnetic sensing, but related studies are rarely reported. Therefore, the giant magnetoimpedance effects in multilayered thin film meanders under different stresses were thoroughly investigated. Firstly, multilayered FeNi/Cu/FeNi thin film meanders with the same thickness were manufactured on polyimide (PI) and polyester (PET) substrates by DC magnetron sputtering and MEMS technology. The characterization of meanders was analyzed by SEM, AFM, XRD, and VSM. The results show that multilayered thin film meanders on flexible substrates also have the advantages of good density, high crystallinity, and excellent soft magnetic properties. Then, we observed the giant magnetoimpedance effect under tensile and compressive stresses. The results show that the application of longitudinal compressive stress increases the transverse anisotropy and enhances the GMI effect of multilayered thin film meanders, while the application of longitudinal tensile stress yields the opposite result. The results provide novel solutions for the fabrication of more stable and flexible giant magnetoimpedance sensors, as well as for the development of stress sensors.

Stretching-Tunable High-Frequency Magnetic Properties of Wrinkled CoFeB Films Grown on PDMS.

We demonstrated a convenient method via applying uniaxial tensile strains to continuously tune the high-frequency properties of flexible magnetic films. CoFeB films were magnetron sputtered onto prestretched polydimethylsiloxane (PDMS) membranes. They exhibit a self-assembled periodic wrinkling surface structure because of the large mismatch of Young's moduli between the elastomeric PDMS substrates and the metal layers. The wrinkling morphology and the residual tensile stress caused by the Poisson effect can be continuously tuned by a uniaxial stretching strain less than the growth prestrain, which consequently results in changes in high-frequency performance. The initial permeability and the ferromagnetic resonance frequency of flexible CoFeB thin films can be monotonously tuned in wide ranges of about hundreds and 1 GHz, respectively. A good repeatability over thousands of stretching-relaxing cycles has been demonstrated without any obvious reduced high-frequency properties. This flexible CoFeB films with excellent stretching-tunable high-frequency performances are promising for application in flexible and tunable microwave devices.

Effective plasmon coupling in conical cavities for sensitive surface enhanced Raman scattering with quantitative analysis ability.

Conical silver nanocavity arrays are fabricated by directly depositing Ag on porous alumina templates with V-shaped nanopores. By controlling the thickness of deposited Ag, complete and cracked cavity arrays are constructed respectively. The cracked cavity arrays with the cavity wall consisting of Ag nanoparticles are demonstrated to exhibit higher surface enhanced Raman scattering (SERS) activity than the complete one. Numerical simulation reveals that an effective coupling of the cavity modes with the surface plasmons of Ag nanoparticles (NPs) generates a significantly enhanced local electric field on the cavity wall responsible for the high SERS activity. The optimized cavity array presents an enhancement factor (EF) of ∼7.4 × 106 and an excellent uniformity with a relative standard deviation (RSD) as small as ∼5% for rhodamine 6G (R6G) molecules. Moreover, a good linear correlation between the logarithmic Raman intensity and the molecular concentration endows the array with quantitative analysis ability. These cavity arrays therefore are of great potential for qualitative and quantitative chemical and biomedical analysis with high sensitivity and reproducibility.

Latent Infection of Valsa mali in the Seeds, Seedlings and Twigs of Crabapple and Apple Trees is a Potential Inoculum Source of Valsa Canker.

A real-time quantitative PCR assay using a species-specific primer pair was developed to rapidly and accurately quantify Valsa mali, the causative pathogen of apple Valsa canker (AVC), in crabapple seeds, crabapple seedlings, apple twigs and apple seeds. Surveys were conducted in different regions, and crabapple or apple seeds were collected for V. mali detection by qPCR assay. Our results showed that 12.87% to 49.01% of crabapple seeds collected from different regions were positive for V. mali. The exopleura and endopleura were the two major areas of V. mali infection in crabapple seeds. The presence of V. mali infection in crabapple seeds was also confirmed by a high-throughput sequencing approach. With the growth of crabapple seedlings, the concentration of V. mali gDNA in crabapple seedlings gradually increased until eight or more leaf blades emerged. One-year-old twigs from an apple scion nursery were infected with V. mali, and only apple seeds from infected apple trees showing evident Valsa canker symptoms carried V. mali. In conclusion, this study reports that crabapple seeds and apple seeds carried V. mali as latent inoculum sources. V. mali infected not only apple tissues but also crabapple seedlings, which are the rootstocks of apple trees. This study indicated that the inoculum sources for AVC vary. Application of a novel qPCR assay can potentially improve the accuracy of early diagnosis, and is helpful to reveal the epidemic regularity of AVC.