Microfabricated ion traps

Ion traps offer the opportunity to study fundamental quantum systems with a high level of accuracy highly decoupled from the environment. Individual atomic ions can be controlled and manipulated with electric fields, cooled to the ground state of motion with laser cooling and coherently manipulated using optical and microwave radiation. Microfabricated ion traps hold the advantage of allowing for smaller trap dimensions and better scalability towards large ion trap arrays also making them a vital ingredient for next generation quantum technologies. Here we provide an introduction into the principles and operation of microfabricated ion traps. We show an overview of material and electrical considerations which are vital for the design of such trap structures. We provide guidance on how to choose the appropriate fabrication design, consider different methods for the fabrication of microfabricated ion traps and discuss previously realised structures. We also discuss the phenomenon of anomalous heating of ions within ion traps, which becomes an important factor in the miniaturisation of ion traps.     

Modeling and Simulation of Rate-Dependent Magneto-Active Polymers

In the present work, the magneto-viscoelastic behavior of MAPs is studied by a thermodynamically consistent constitutive model. A finite deformation based framework of nonlinear magneto-viscoelastic coupling is introduced with a multiplicative decomposition of the deformation gradient. The viscosity is captured by evolution equations of the internal variables introduced. We propose energy functions for pure magnetic and magneto-mechanical coupling such that saturation behavior of the magnetostriction and magnetization is captured. After having established the general framework, the model is studied for homogeneous deformations for the purpose of a least-square-based parameter identification from experimental data. The model predictions of non-linear magneto-mechanical responses with strong rate and field dependency are presented. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Revealing direction of coupling between neuronal oscillators from time series: phase dynamics modeling versus partial directed coherence

The problem of determining directional coupling between neuronal oscillators from their time series is addressed. We compare performance of the two well-established approaches: partial directed coherence and phase dynamics modeling. They represent linear and nonlinear time series analysis techniques, respectively. In numerical experiments, we found each of them to be applicable and superior under appropriate conditions: The latter technique is superior if the observed behavior is "closer" to limit-cycle dynamics, the former is better in cases that are closer to linear stochastic processes.     

Recrystallization of Cu-poor CuInS2 assisted by metallic Cu or Ag

We monitor the recrystallization of Cu-poor CuInS₂ thin films assisted by pure Cu or pure Ag by means of real-time synchrotron-based polychromatic X-ray diffraction. In both cases a new microstructure is formed accompanied by an increase in grain size. In the case of Cu, the onset temperature of the thin-film recrystallization is higher than 370 °C. In the case of Ag, the thin-film recrystallization comes to an end at 270 °C. The Ag-assisted recrystallization occurs in the presence of the body-centered cubic β-Ag₂S phase. We find that domain growth and diffusion of silver into the film occur simultaneously.     

MALDI analysis of proteins after extraction from dissolvable ethylene glycol diacrylate cross‐linked polyacrylamide gels

Although the extraction of intact proteins from polyacrylamide gels followed by mass spectrometric molecular mass determination has been shown to be efficient, there is room for alternative approaches. Our study evaluates ethylene glycol diacrylate, a cleavable cross‐linking agent used for a new type of dissolvable gels. It attains an ester linkage that can be hydrolyzed in alkali conditions. The separation performance of the new gel system was tested by 1D and 2D SDS‐PAGE using the outer chloroplast envelope of Pisum sativum as well as a soluble protein fraction of human lymphocytes, respectively. Gel spot staining (CBB), dissolving, and extracting were conducted using a custom‐developed workflow. It includes protein extraction with an ammonia–SDS buffer followed by methanol treatment to remove acrylamide filaments. Necessary purification for MALDI‐TOF analysis was implemented using methanol–chloroform precipitation and perfusion HPLC. Both cleaning procedures were applied to several standard proteins of different molecular weight as well as ‘real’ biological samples (8–75 kDa). The protein amounts, which had to be loaded on the gel to detect a peak in MALDI‐TOF MS, were in the range of 0.1 to 5 μg, and the required amount increased with increasing mass.     

Electrochemically induced oxygen spillover and diffusion on Pt(111): PEEM imaging and kinetic modelling

Electrochemically induced oxygen spillover and diffusion in the Pt(O(2))|YSZ system is investigated in a combined experimental and theoretical study. The spreading of spillover oxygen is imaged by photoelectron emission microscopy (PEEM) on dense and epitaxial Pt(111) thin film electrodes prepared by pulsed laser deposition (PLD). Two different models are used to obtain surface diffusion coefficients from the experimental data, (i) an analytical solution of Fick's 2nd law of diffusion, and (ii) a numerical reaction-diffusion model that includes recombinative desorption of O(2) into the gas phase. The resulting diffusion coefficient has an activation energy of 50 kJ mol(-1) and a preexponential factor of 0.129 cm(2) s(-1) with an estimated uncertainty of ±20% for the activation energy and ±50% for the absolute value. The Fickian model slightly overpredicts diffusion coefficients due to the neglect of oxygen desorption. Experimental and theoretical results and limitations are discussed and compared to previous work.     

A fast and inexpensive procedure for the isolation of synthetic cannabinoids from ‘Spice’ products using a flash chromatography system

In the age of the Internet, the variety of drugs offered online is constantly increasing, and new drugs emerge every month. One group of drugs showing such an enormous increase is that of synthetic cannabinoids. Since their first identification in ‘herbal mixtures’, new structural modifications continue to appear on the market. In order to keep up with this process, toxicological screening methods need to be up to date. This can become extremely difficult if no reference material is available. In this article, a fast and effective way to extract and purify synthetic cannabinoids from ‘herbal mixtures’ is presented. This method opens a new opportunity for a timely reaction by obtaining reference material straight out of the ‘herbal mixtures’ ordered via the Internet. Isolation was carried out on a flash chromatography system with gradient elution on a C18 column using methanol and 0.55 % formic acid as mobile phases. The obtained purity of all compounds exceeded 99 %. In addition to the isolation of single compounds, the method proved to be suitable for the separation of various synthetic cannabinoids in one mixture, including the diastereomers cis- and trans-CP-47,497-C8. This approach for obtaining pure standards of new drugs proved to be effective, inexpensive and much quicker than waiting for the substances to be commercially available as reference material.