Separator of primary and signal electrons for very low energy SEM

High resolution can be obtained in the scanning electron microscope (SEM) for a very low landing energy of electrons, even for that below 50 eV, when a cathode lens is used with the specimen as a cathode held at a high negative potential but the detection of signal electrons is totally different compared with classical SEM. Primary electrons with an energy of the order of tens of keV are decelerated in the field of the cathode lens to a very low landing energy and signal electrons originating in the specimen are accelerated and collimated by the same field to a narrow beam with an electron energy nearly the same as that of the primary beam. To detect these signal electrons we must deflect them from the optical axis without deteriorating the properties of the primary beam. The design of a novel type of separator of the primary and signal electrons consisting of two stages, each of them formed by the electric and magnetic crossed fields, is presented, together with calculated trajectories for both primary and signal electrons.Presented at the Seminar on Secondary Electrons in Electron Spectroscopy, Microscopy, and Microanalysis, Chlum (The Czech Republic), 21–24 September 1993.For computations of fields and trajectories, the software package of the Delft Particle Optics Foundation developed by Dr. B. Lencová and Dr. G. Wisselink [10] was used. The design was consulted with Dr. M. Lenc.     

The Formulae of Kontsevich and Verlinde¶from the Perspective of the Drinfeld Double

A two dimensional gauge theory is canonically associated to every Drinfeld double. For particular doubles, the theory turns out to be e.g. the ordinary Yang–Mills theory, the G/G gauged WZNW model or the Poisson σ-model that underlies the Kontsevich quantization formula. We calculate the arbitrary genus partition function of the latter. The result is the q-deformation of the ordinary Yang–Mills partition function in the sense that the series over the weights is replaced by the same series over the q-weights. For q equal to a root of unity the series acquires the affine Weyl symmetry and its truncation to the alcove coincides with the Verlinde formula. Received: 10 December 1999 / Accepted: 8 October 2000     

Über Abkömmlinge der Nitrohemipinsäure

Ohne Zusammenfassung     

ToF-SIMS characterisation of diterpenoic acids after chromatographic separation

Microcolumn liquid chromatography (μHPLC) coupled on-line with time of flight secondary ion mass spectrometry (ToF-SIMS) was applied for mixture of diterpenoic acids (abietic, gibberellic and kaurenoic) analysis. Chromatographic effluent, with analytes separated, was carried out directly onto different, ToF-SIMS compatible surface substrates, for further ToF-SIMS analysis. Silica gel Si₆₀, aluminium backplate modified Si₆₀, monolithic silica gel and Raman spectroscopy chromatographic thin layers were used as the deposition substrates in this experiment. By ToF-SIMS surface imaging the deposition trace picture has been obtained. Effluent deposition surface area was scanned for diterpenoic acid fragment mass values based on mass spectrometric library. Measured ToF-SIMS dataset of fragment abundance and intensities were used for preliminary fragmentation schemes construction. The lowest substrate background activity has been established for monolithic silica gel thin layer and aluminium backplate modified Si₆₀ thin layer. In the case of Raman spectroscopy pre-treated thin layer or conventional chromatographic thin layer Si₆₀, the both, high background signal intensity and impossibility to construct negative ions surface image, were observed. Diterpenoic acids studied serve the similar mass spectrum but ToF-SIMS coupled with liquid chromatographic separation brings new impact to the positive identification of analytes studied.     

Why is polonium simple cubic and so highly anisotropic?

Using the state-of-the-art ab initio electronic structure calculations, we explain why alpha-Po prefers the simple cubic structure (it is due to the relativistic mass-velocity and Darwin terms), elucidate its extreme elastic anisotropy (this is an intrinsic property of the simple cubic crystal structure), and predict a transformation to a mixture of two trigonal structures at pressures of 1-3 GPa.     

The Length-scale Effect in the Buckling of Thin Periodic Plates Resting on a Periodic Winkler Foundation

In this paper a new modelling method, called the tolerance averaging method, is presented and applied to analyse a buckling of thin periodic plates resting on a periodically heterogeneous Winkler foundation. The derived length-scale model makes it possible to take into account the effect of periodicity cell size (the length-scale effect) on the overall plate behaviour, on the contrary to the known homogenised models of periodic plates neglecting this effect. In order to evaluate obtained results the buckling problems of those plates are analysed using not only the proposed model but also a certain effective stiffnesses model. A comparison between obtained results leads to a conclusion that the length-scale effect could not be neglected in buckling of periodic plates resting on a Winkler foundation.     

Misfit‐Layered Bi1.85Sr2Co1.85O7.7−δ for the Hydrogen Evolution Reaction: Beyond van der Waals Heterostructures

Recent research on stable 2D nanomaterials has led to the discovery of new materials for energy‐conversion and energy‐storage applications. A class of layered heterostructures known as misfit‐layered chalcogenides consists of well‐defined atomic layers and has previously been applied as thermoelectric materials for use as high‐temperature thermoelectric batteries. The performance of such misfit‐layered chalcogenides in electrochemical applications, specifically the hydrogen evolution reaction, is currently unexplored. Herein, a misfit‐layered chalcogenide consisting of CoO₂ layers interleaved with an SrO–BiO–BiO–SrO rock‐salt block and having the formula Bi_1.85Sr₂Co_1.85O_7.7?δ is synthesized and examined for its structural and electrochemical properties. The hydrogen‐evolution performance of misfit‐layered Bi_1.85Sr₂Co_1.85O_7.7?δ, which has an overpotential of 589 mV and a Tafel slope of 51 mV per decade, demonstrates the promising potential of misfit‐layered chalcogenides as electrocatalysts instead of classical carbon.     

Iridium‐ and Osmium‐decorated Reduced Graphenes as Promising Catalysts for Hydrogen Evolution

Renewable energy sources are highly sought after as a result of numerous worldwide problems concerning the environment and the shortage of energy. Currently, the focus in the field is on the development of catalysts that are able to provide water splitting catalysis and energy storage for the hydrogen evolution reaction (HER). While platinum is an excellent material for HER catalysis, it is costly and rare. In this work, we investigated the electrocatalytic abilities of various graphene–metal hybrids to replace platinum for the HER. The graphene materials were doped with 4f metals, namely, iridium, osmium, platinum and rhenium, as well as 3d metals, namely, cobalt, iron and manganese. We discovered that a few hybrids, in particular iridium‐ and osmium‐doped graphenes, have the potential to become competent electrocatalysts owing to their low costs and—more importantly—to their promising electrochemical performances towards the HER. One of the more noteworthy observations of this work is the superiority of these two hybrids over MoS₂, a well‐known electrocatalyst for the HER.