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Current-induced domain wall oscillations in a nanowire imaged by time-resolved photoemission electron microscopy
摘要： We study reversible domain wall motion in half-ring Ni80Fe20 nanowires on a nanosecond (ns) timescale in a truly current-induced pump-probe experiment using an energy filtered, aberration-corrected photoemission electron microscope. The x-ray magnetic circular dichroism signal is probed at different time delays before, during and after the current pulse in a stroboscopic mode with circularly polarized synchrotron radiation in the energy range of the Fe L3-edge (707 eV). We observe lateral domain wall oscillations with a frequency of ～ 0.4 GHz. Comparing the results to a proposed string model, we find that the domain wall oscillations can be described as string-like asymmetric oscillations.
关键词： Synchrotron radiation,Photoemission electron microscopy,X-ray magnetic circular dichroism,Pump-probe mode
更新于2025-09-23 15:23:52
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AFM-assisted investigation of conformal coatings in electronics
摘要： Purpose – This paper aims to presents a new method of investigation of local properties of conformal coatings utilized in microelectronics. Design/methodology/approach – It is based on atomic force microscopy (AFM) technique supplemented with the ability of local electrical measurements, which apart from topography acquisition allows recording of local impedance spectra, impedance imaging and dc current mapping. Potentialities of the proposed AFM-assisted approach have been demonstrated on commercially available epoxy-coated electronic printed boards in as-received state and after six-year service. Findings – The technique proved to be capable of identi?cation, spatial localization and characterization of conformal coating defects. Practical implications – The proposed approach can be utilized for assessment of protective ?lm state in such demanding ?elds as electronics or electrotechnics where the classical techniques of anticorrosion coatings investigation cannot be employed due to small element dimensions and relatively low coating thickness. Originality/value – The approach adopted by the author is novel in the ?eld of organic coatings investigation.
关键词： Degradation,Corrosion,Electronics,Microscopy,Coatings and linings
更新于2025-09-23 15:23:52
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Surfactant templated oriented 1-D nanoscale platinum and palladium systems on a modified silicon surface
摘要： A templating method has been improved to form oriented one-dimensional metal nanostructures on a silicon surface. To achieve this, the silicon surface is modified with 3-aminopropyl trimethoxysilane. The cationic surfactant cetyltrimethylammonium bromide is used as a micellar template. The average width of the obtained Pt strips is 35 nm, the average width of the obtained Pd strips is 60 nm.
关键词： Platinum group,Atomic force microscopy,Surface modification,Nanostructured materials,Micelle templates
更新于2025-09-23 15:23:52
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Intracortical neural stimulation with untethered, ultrasmall carbon fiber electrodes mediated by the photoelectric effect
摘要： Objective: Neural stimulation with tethered, electrically activated probes is damaging to neural tissue and lacks good spatial selectivity and stable chronic performance. The photoelectric effect, which converts incident light into electric potential and heat, provides an opportunity for a tetherless stimulation method. We propose a novel stimulation paradigm that relies on the photoelectric effect to stimulate neurons around a free-floating, ultrasmall (7-8μm diameter) carbon fiber probe. Methods: A 2-photon microscope induced photo-stimulation with a laser. Chronoamperometry and chronopotentiometry were used to characterize the electrochemical properties of photo-stimulation, while the fluorescence of Rhodamine-B was used to quantify temperature changes. Results: Photo-stimulation caused a local cathodic potential pulse with minimal leakage current. Stimulation induced voltage deflections of 0.05 - 0.4V in vitro, varying linearly with the power of the laser source (5 – 40 mW). Temperature increases in the immediate vicinity of the electrode were limited to 2.5°C, suggesting that this stimulation modality can be used without inducing heat damage. Successful stimulation was supported in vivo by increased calcium fluorescence in local neurons at stimulation onset in a transgenic GCaMP-3 mouse model. Furthermore, cells activated by photo-stimulation were closer to the electrode than in electrical stimulation under similar conditions, indicating increased spatial precision. Conclusion: Our results support the hypothesis that the proposed photoelectric method is effective for neural stimulation. Significance: Photoelectric stimulation is precise and avoids the need for a potentially destructive tether, making it a promising alternative to electrical stimulation.
关键词： GCaMP,electrochemistry,neuromodulation,photovoltaic effect,2-photon microscopy,temperature-dependent,fluorescence
更新于2025-09-23 15:23:52
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The stability and degradation of PECVD fluoropolymer nanofilms
摘要： Fluoropolymer films are frequently used in microfabrication and for producing hydrophobic and low-k dielectric layers in various applications. As the reliability of functional coatings is becoming a more pressing issue in industry, it is necessary to determine the physical stability and degradation properties of this important class of films. To this end, a study has been undertaken to ascertain the aging characteristics of fluoropolymer films under various environmental conditions that such a film may experience during its use. In particular, fluorocarbon films formed by plasma-enhanced chemical vapour deposition (PECVD) using octafluorocyclobutane, or c-C4F8, as a precursor gas have been exposed to abrasive wear, elevated temperatures, ultraviolet radiation, as well as oxygen plasma and SF6 plasma, the latter being commonly used in conjunction with these films in ion etching processes. The results show that sub-micron thick fluoropolymer films exhibit a significant amount of elastic recovery during nanoscratch tests, minimising the impact of wear. The films exhibit stability when exposed to 365 nm UV light in air, but not 254 nm light in air, which generated significant decreases in thickness. Exposure to temperatures up to 175 °C did not generate loss of material, whereas temperatures higher than 175 °C did. Etching rates upon exposure to oxygen and SF6 plasmas were also measured.
关键词： Octafluorocyclobutane,Plasma deposition,Atomic force microscopy,Wear,Ellipsometry
更新于2025-09-23 15:23:52
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Reflectance confocal microscopy margin mapping and monitoring of an amelanotic melanoma <i>in situ</i> of the ear
摘要： In situ amelanotic melanoma represents a diagnostic challenge for clinicians. Poor demarcation of these lesions often results in repeated therapeutic intervention until appropriate clearance has been achieved. Reflectance confocal microscopy (RCM) is a noninvasive bedside imaging modality which allows real-time visualisation, to a near-histological level, of the epidermis and reticular dermis. We present a case of an amelanotic melanoma in situ in which reflectance confocal microscopy margin mapping allowed for demarcation of the melanocytic proliferation and targeted therapeutic intervention with topical imiquimod. Reflectance confocal microscopy was further utilised for noninvasive assessment of therapeutic response.
关键词： margin mapping,reflectance confocal microscopy,amelanotic melanoma
更新于2025-09-23 15:23:52
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A single-stranded coordination copolymer affords heterostructure observation and photoluminescence intensification
摘要： Few artificial systems can be exfoliated into, and observed as, single wires with lengths of more than several micrometers, and no previous example features a copolymer structure; this is in contrast with biopolymers such as single-strand DNAs. Here, we create a set of one-dimensional coordination copolymers featuring bis(dipyrrinato)zinc complex motifs in the main chain. A series of random copolymers is synthesized from two types of bridging dipyrrin proligand and zinc acetate, with various molar ratios between the proligands. Sonication of the bulk solid copolymer in organic solvent exfoliates single strands with lengths of 1.4 to 3.0 mm. Atomic force microscopy at ambient conditions visualizes the copolymer structure as height distributions. The copolymer structure improves its photoluminescence (up to 32%) relative to that of the corresponding homopolymers (3 and 10%). Numerical simulation based on a restricted random walk model reproduces the photoluminescence intensification, suggesting at the same time the existence of fast intrawire exciton hopping.
关键词： exciton hopping,atomic force microscopy,photoluminescence,coordination copolymer,heterostructure
更新于2025-09-23 15:23:52
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Fluorescence microscopy as a tool for determining self-incompatibility in apricot cultivars
摘要： Fluorescence microscopy is a relatively rapid and reliable method to determine self-incompatibility in fruit-tree species. It is based on observation of pollen-tube growth in the pistils. Pollen tubes stained with fluorochromes show fluorescence when exposed to ultraviolet light. Testing of the self-compatibility trait was carried out in 123 apricot cultivars using fluorescence microscopy. In self-compatible cultivars, in the majority of pistils (60-100%), the pollen tubes reached the ovary. In contrast, in self-incompatible cultivars, pollen tubes growth ceased in the style, with plugs forming at their tips. In these cultivars, pollen tubes rarely (0-30%) reached the base of the style. Although apricot cultivars of the European eco-geographical group are traditionally considered self-compatible, we identified many self-incompatible cultivars, especially among those originating from new North American and West European breeding programs. About half (62) of the studied cultivars were self-incompatible. Given that self-incompatibility occurs frequently among new apricot cultivars, special care should be taken when considering cultivar composition in new orchard plantings.
关键词： fluorescence microscopy,self-incompatibility,pollen tube growth,Prunus armeniaca,Rosaceae
更新于2025-09-23 15:23:52
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Fullerene-to-MWCNT Structural Evolution Synthesized by Arc Discharge Plasma
摘要： The growth of multi-walled carbon nanotubes (MWCNTs) has been extensively studied using electron microscopy. The ex situ structural behavior was examined to investigate the growth of the MWCNTs under different environments and pressures using electron microscopy. The arc discharge plasma technique was applied to synthesize the MWCNTs by evaporating carbon through the arc plasma between two cylindrical graphite rods, with a background pressure of 10?2 to 102 mbar, inside a vacuum chamber under different ambient environments. The results showed that long MWCNT structures were successfully grown. We suggest that the mechanism involves: (i) fullerene formation; (ii) the elongation of fullerenes; and (iii) the growth of MWCNTs. Agglomeration with other structures then forms MWCNT bundles. We note that the pressure and environment in the vacuum chamber can affect the structure of the MWCNTs.
关键词： arc discharge,electron microscopy,carbon nanotube,nanostructured
更新于2025-09-23 15:23:52
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Controlling the Dynamics and Optical Binding of Nanoparticle Homodimers with Transverse Phase Gradients
摘要： While transverse phase gradients enable studies of driven nonequilibrium phenomena in optical trapping, the behavior of electrodynamically interacting particles in a transverse phase gradient has not been explored in detail. In this Letter we study electrodynamically interacting pairs of identical nanoparticles (homodimers) in transverse phase gradients. We establish that the net driving force on homodimers is modulated by a separation-dependent interference effect for small phase gradients. By contrast, large phase gradients break the symmetry of the interaction between particles and profoundly change the electrodynamic interparticle energy landscape. Our findings are particularly important for understanding multiparticle dynamics during the self-assembly and rearrangement of optical matter.
关键词： nonequilibrium,optical trapping,optical microscopy
更新于2025-09-23 15:23:52