Nanofabricated atom optics: Atom chips

Abstract

Small tight trapping and guiding potentials can be created for neutral atoms moving microns above surfaces patterned with nanofabricated charged and current-carrying structures. Surfaces holding such structures form atom chips which, for coherent matter wave optics, may form the basis for a variety of novel applications and research tools, similar to integrated circuits in electronics. In this paper we describe the basic principles of atom chip experiments.     

Changing Frames of Mobility through Radical Policy Interventions? The Stockholm Congestion Tax

The introduction of a congestion tax was a significant moment in the management of mobility in Stockholm. This paper critically examines this apparent consensus on confronting car based mobility, by analysing how mobility was framed at key stages in policy making, from the 1970s through to the trial in 2006 and subsequent implementation. Changing transport objectives are compared, and winners and losers are traced in relation to motility and environmental quality. The paper argues that a car-based automobility frame survives, even in the implementation of a radical policy of congestion taxation.     

6‐Pyridinium benzo[a]phenazine‐5‐oxide derivatives as visible photosensitisers for polymerisation

Several 6‐pyridinium benzo[a]phenazine‐5‐oxide derivatives have been synthesised and characterised by proton nuclear magnetic resonance spectroscopy and mass spectrometry. The spectroscopic and electrochemical properties of these dyes were examined. The dyes were used as reducible sensitisers for selected electron donors (phenylthioacetic acid, phenoxyacetic acid, N‐phenylglycine, and ethyl 4‐N,N‐dimethylaminobenzoate) and as oxidisable sensitisers for electron acceptors (onium and N‐alkoxypyridinium salts). These photoredox pairs were found to be effective visible‐wavelength photoinitiators for the free radical polymerisation of trimethylolpropane triacrylate under visible light. The cationic photopolymerisation of cyclohexene oxide by the studied dyes and the onium salt photoredox pairs was ineffective. The obtained results are discussed on the basis of both free energy change for electron transfer to or from the benzo[a]phenazine dyes and the photochemical properties of the dyes, particularly their photobleaching. The proposed mechanism of dye fading is supported by density functional theory calculations and spectroscopic characterisation of the radical cation of the dye.     

Mechanical Properties of a Lithium Disilicate Strengthened Lithium Aluminosilicate Glass‐Ceramic

A glass composition in the Li₂O–Al₂O₃–SiO₂ (LAS)‐ternary phase diagram is presented, which enables the crystallization of Li₂Si₂O₅ as well as LiAlSi₂O₆ upon a well‐defined heat treatment. Li₂Si₂O₅ is the minor crystalline phase in the glass‐ceramic and generates through the bulk strengthening of the LAS glass‐ceramic. A flexural strength as higher as 400 MPa is measured in the proposed glass‐ceramic formulation, thus outperforming conventional LAS‐glass‐ceramics. A combination of the presence of those two crystalline phases of very different mechanical properties and coefficient of thermal expansion as well as the microstructure are believed to contribute largely to the enhancement of the measured properties.     

Nanocrystal shape and the mechanism of exciton spin relaxation

The rate of exciton spin relaxation (flips) between the bright exciton states (F = +/-1) of CdSe nanocrystals is reported as a function of shape, for dots and nanorods. The spin relaxation is measured using an ultrafast transient grating method with a crossed linearly polarization sequence. It is found that the spin relaxation rate depends on the radius, not length, of the nanocrystals. That observation is explained by deriving an expression for the electronic coupling matrix element that mixes the bright exciton states.     

In situ observations of microscale damage evolution in unidirectional natural fibre composites

Synchrotron X-ray tomographic microscopy (XTM) has been used to observe in situ damage evolution in unidirectional flax fibre yarn/polypropylene composites loaded in uniaxial tension at stress levels between 20% and 95% of the ultimate failure stress. XTM allows for 3D visualization of the internal damage state at each stress level. The overall aim of the study is to gain a better understanding of the damage mechanisms in natural fibre composites. This is necessary if they are to be optimized to fulfil their promising potential. Three dominating damage mechanisms have been identified: (i) interface splitting cracks typically seen at the interfaces of bundles of unseparated fibres, (ii) matrix shear cracks, and (iii) fibre failures typically seen at fibre defects. Based on the findings in the present study, well separated fibres with a low number of defects are recommended for composite reinforcements.     

Experimental and theoretical studies on NIR luminescence of titanate-germanate glasses doped with Pr3+ and Tm3+ ions

Near-infrared (NIR) luminescence of Pr³⁺ and Tm³⁺ ions in titanate-germanate glasses has been studied for laser and fiber amplifier applications. The effect of the molar ratio GeO₂:TiO₂ (from 5:1 to 1:5) on spectroscopic properties of glass systems was studied by absorption, luminescence measurements, and theoretical calculations using the Judd–Ofelt theory. It was found that independent of the TiO₂ concentration, intense NIR emissions at 1.5 and 1.8 μm were observed for glasses doped with Pr³⁺ and Tm³⁺ ions, respectively. Moreover, several spectroscopic and NIR laser parameters for Pr³⁺ and Tm³⁺ ions, such as emission bandwidth, stimulated emission cross-section, quantum efficiency, gain bandwidth, and figure of merit, were determined. The results were discussed in detail and compared to the different laser glasses. Systematic investigations indicate that Pr³⁺-doped system with GeO₂:TiO₂ = 2:1 and Tm³⁺-doped glass with GeO₂:TiO₂ = 1:2 present profit laser parameters and could be successfully applied to NIR lasers and broadband optical amplifiers.     

Fortification of low-nitrite canned pork with willow herb (Epilobium angustifolium L.)

Nitrite is a multifunctional additive used for meat products. However, cancerogenic N-nitrosoamines (NAs) can be formed from nitrite. For this reason, nitrite should be reduced or eliminated. This study aimed to (1) determine the phenolic content, composition, and in vitro antioxidant and antimicrobial activity of water lyophilized extracts of willow herb (WH); and (2) assess the effect of the extracts on lipid oxidation, colour, microbiological and chemical safety of canned pork with lower nitrite content during storage. For the preparation of extract, redistilled water at a temp. of 90°C (1:10) was used. The extracts were filtered and freeze-dried for 72 h (−80°C, 0.04 mbar). Five different variants of product were tested in the study: control (with 100 mg kg⁻¹ NaNO₂) and herbal samples (with 50, 100, 150, and 1000 mg kg⁻¹ WH). The samples were assessed for their colour, antioxidant capacity, lipid oxidation, pH, sensory characteristics, and the presence of N-nitrosamines and pathogenic bacteria. Oenothein B was found as the predominating compound in the analysed extract (HPLC) followed by querceti-3-O-rhamnoside and oenothein A, myricetin 3-O-glucoside. The addition of WH extract contributed to maintaining the typical, cured colour of canned meat as well as reducing the NaNO₂ content. Furthermore, fortification with 150 mg kg⁻¹ of Epilobium angustifolium L. extract allowed stabilising the antioxidant properties of canned meat during storage to a greater extent compared to 1000 mg kg⁻¹ of extract.     

Pathomechanisms in the Kidneys in Selected Protozoan Parasitic Infections

Leishmaniasis, malaria, toxoplasmosis, and acanthamoebiasis are protozoan parasitic infections. They remain important contributors to the development of kidney disease, which is associated with increased patients’ morbidity and mortality. Kidney injury mechanisms are not fully understood in protozoan parasitic diseases, bringing major difficulties to specific therapeutic interventions. The aim of this review is to present the biochemical and molecular mechanisms in kidneys infected with Leishmania spp., Plasmodium spp., Toxoplasma gondii, and Acanthamoeba spp. We present available mechanisms of an immune response, oxidative stress, apoptosis process, hypoxia, biomarkers of renal injury in the serum or urine, and the histopathological changes of kidneys infected with the selected parasites. Pathomechanisms of Leishmania spp. and Plasmodium spp. infections have been deeply investigated, while Toxoplasma gondii and Acanthamoeba spp. infections in the kidneys are not well known yet. Deeper knowledge of kidney involvement in leishmaniasis and malaria by presenting their mechanisms provides insight into how to create novel and effective treatments. Additionally, the presented work shows gaps in the pathophysiology of renal toxoplasmosis and acanthamoebiasis, which need further research.