Nanotip electron gun for the scanning electron microscope

Experimental nanotips have shown significant improvement in the resolution performance of a cold field emission scanning electron microscope (SEM). Nanotip electron sources are very sharp electron emitter tips used as a replacement for the conventional tungsten field emission (FE) electron sources. Nanotips offer higher brightness and smaller electron source size. An electron microscope equipped with a nanotip electron gun can provide images with higher spatial resolution and with better signal-to-noise ratio. This could present a considerable advantage over the current SEM electron gun technology if the tips are sufficiently long-lasting and stable for practical use. In this study, an older field-emission critical dimension (CD) SEM was used as an experimental test platform. Substitution of tungsten nanotips for the regular cathodes required modification of the electron gun circuitry and preparation of nanotips that properly fit the electron gun assembly. In addition, this work contains the results of the modeling and theoretical calculation of the electron gun performance for regular and nanotips, the preparation of the SEM including the design and assembly of a measuring system for essential instrument parameters, design and modification of the electron gun control electronics, development of a procedure for tip exchange, and tests of regular emitter, sharp emitter and nanotips. Nanotip fabrication and characterization procedures were also developed. Using a "sharp" tip as an intermediate to the nanotip clearly demonstrated an improvement in the performance of the test SEM. This and the results of the theoretical assessment gave support for the installation of the nanotips as the next step and pointed to potentially even better performance. Images taken with experimental nanotips showed a minimum two-fold improvement in resolution performance than the specification of the test SEM. The stability of the nanotip electron gun was excellent; the tip stayed useful for high-resolution imaging for several hours during many days of tests. The tip lifetime was found to be several months in light use. This paper summarizes the current state of the work and points to future possibilities that will open when electron guns can be designed to take full advantage of the nanotip electron emitters.     

CW-diode laser crystallization of sputtered amorphous silicon on glass, SiNx, and SiO2 intermediate layers

CW-diode laser crystallization of amorphous silicon (a-Si) deposited by sputtering or by electron beam evaporation onto different substrates (glass without or with SiN_x or SiO₂ intermediate layers) is investigated. The resulting grain sizes and orientations are characterized by electron backscatter diffraction, optical microscopy, and x-ray diffraction. We demonstrate that 200 nm thick sputtered a-Si layers can be crystallized on all of the used substrates to result in grains from 1 up to 100 μm in size, depending on the laser irradiation parameters (intensity, exposure time). Electron beam evaporated a-Si films can be crystallized only on sputtered SiN_x intermediate layers to result in grains of 100 μm in size. Similar crystallographic film properties follow from laser treatment if the product of laser peak intensity and square root of exposure time is kept constant, independent of the scan velocity used. A high fraction of preferred (100)-oriented silicon grains can only be observed for samples with crystallites less than 10 μm in size.     

A note on the Jaccardized Czekanowski similarity index

It is shown that the “Jaccardized Czekanowski index” is actually a reinterpretation of the Ru?i?ka index. Thereby, it is proved that its one-complement is a true distance function, which makes it particularly suitable for use in similarity studies even with multidimensional statistical techniques.     

The effect of the martensitic packet size on the machinability of modified AISI P20 prehardened mold steel

The effect of martensitic packet size on the machinability of prehardened mold steel at a hardness of ~40 HRC (typical hardness for prehardened mold steels) was studied in terms of cutting force and tool life. The machinability tests were performed in end milling using coated, cemented carbide tools at three different cutting speeds. The results showed that an increase in the martensite packet size led to higher cutting force and shorter tool life. The increase in cutting force was related to the increase of work hardening. The work material with a coarser martensite packet size showed a higher amount of work hardening that can explain the higher cutting force. The longer tool life in the workpieces with finer structure was correlated to smaller amplitude of the variation in cutting force.     

A cross‐cultural comparison of colour emotion for two‐colour combinations

Psychophysical experiments were conducted in the UK, Taiwan, France, Germany, Spain, Sweden, Argentina, and Iran to assess colour emotion for two‐colour combinations using semantic scales warm/cool, heavy/light, active/passive, and like/dislike. A total of 223 observers participated, each presented with 190 colour pairs as the stimuli, shown individually on a cathode ray tube display. The results show consistent responses across cultures only for warm/cool, heavy/light, and active/passive. The like/dislike scale, however, showed some differences between the observer groups, in particular between the Argentinian responses and those obtained from the other observers. Factor analysis reveals that the Argentinian observers preferred passive colour pairs to active ones more than the other observers. In addition to the cultural difference in like/dislike, the experimental results show some effects of gender, professional background (design vs. nondesign), and age. Female observers were found to prefer colour pairs with high‐lightness or low‐chroma values more than their male counterparts. Observers with a design background liked low‐chroma colour pairs or those containing colours of similar hue more than nondesign observers. Older observers liked colour pairs with high‐lightness or high‐chroma values more than young observers did. Based on the findings, a two‐level theory of colour emotion is proposed, in which warm/cool, heavy/light, and active/passive are identified as the reactive‐level responses and like/dislike the reflective‐level response. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2012     

Diagnostic Tools for Wireless Sensor Networks: A Comparative Survey

The availability of tools to diagnose Wireless Sensor Network (WSN) failures is a key success factor for this type of networks as already demonstrated by several long-running deployments. By nature, WSNs are resource-constrained, fragile, complex to analyse, and failure-prone. Naturally, with the growing number of installations, it is becoming fundamental to efficiently diagnose failures as soon as possible, in order to deal with the underlying causes. In accordance with this, from 2005 onwards, the offer of diagnostic tools has been increasing, as the other base technologies (e.g. networking, operating system, localisation, synchronisation) become reasonably stable. The purpose of this survey is to provide an overview of existing post-deployment WSN diagnostic tools, by briefly presenting their functionality, architecture and constraints, in order to enable a basic understating of each tool. The survey also includes a multi-dimensional comparative analysis of the various tools, based on a proposed classification scheme and evaluation criteria, as well as an identification of the main open research issues. Although the number of diagnostic tools is high and considerable work has been done in this area, we conclude that there are still several challenges concerning post-deployment WSN diagnostic tools, regarding scope, flexibility, generality, mobility and security. Moreover, there is a need for mature, native diagnostic-oriented functionality in WSN platforms and operating systems.     

Clotrimazole-loaded Eudragit® RS100 nanocapsules: Preparation,characterization and in vitro evaluation of antifungal activity against Candida species

Clotrimazole is a common choice for the treatment of vulvovaginal infections, but its low solubility and some side effects pose a challenge to its application. This work evaluated the feasibility to formulate clotrimazole-loaded cationic nanocapsules using Eudragit® RS100 and medium chain triglycerides as polymer and oily core, respectively, by the method of interfacial deposition of a preformed polymer. The physicochemical characteristics of nanocapsule formulations were evaluated at 0 day and 60 days after preparation. Particle size, zeta potential, polydispersity index, pH and drug content were stable during this period. In addition, nanocapsules were able to protect clotrimazole from photodegradation under UV radiation. By the dialysis bag diffusion technique, the nanosized formulations showed prolonged release of clotrimazole by anomalous transport and first order kinetics. A microbiological study was carried out by the microdilution method and showed that nanocapsules (mean size: 144 nm; zeta potential: + 12 mV) maintained the antifungal activity of clotrimazole against Candida albicans and Candida glabrata strains susceptible and resistant to fluconazole.