Correction of Optical Aberrations in Elliptic Neutron Guides

Modern, nonlinear ballistic neutron guides are an attractive concept in neutron beam delivery and instrumentation, because they offer increased performance over straight or linearly tapered guides. However, like other ballistic geometries they have the potential to create significantly non-trivial instrumental resolution functions. We address the source of the most prominent optical aberration, namely coma, and we show that for extended sources the off-axis rays have a different focal length from on-axis rays, leading to multiple reflections in the guide system. We illustrate how the interplay between coma, sources of finite size, and mirrors with non-perfect reflectivity can therefore conspire to produce uneven distributions in the neutron beam divergence, the source of complicated resolution functions. To solve these problems, we propose a hybrid elliptic-parabolic guide geometry. Using this new kind of neutron guide shape, it is possible to condition the neutron beam and remove almost all of the aberrations, whilst providing the same performance in beam current as a standard elliptic neutron guide. We highlight the positive implications for a number of neutron scattering instrument types that this new shape can bring.Comment: Presented at NOP2010 Conference in Alpe d'Huez, France, in March 201

Synthesis of Di(s-triazinyl) Sulphides and Disulphides. The-Promoting Effect of Oxidants on the Cleavage of the Thioether Bond

Synthesis of a number of di(s-triazinyl) sulphides and disu1phides is described. The behaviour of these compounds on oxidative attack has been examined. It has been found that instead of the expected sulphoxide and/or sulphone formation upon oxidation, a simple scission of the thioether linkage takes place, yielding a hydroxytriazine and the corresponding disulphide

Synthesis of Di(s-triazinyl) Sulphides and Disulphides. The-Promoting Effect of Oxidants on the Cleavage of the Thioether Bond

Synthesis of a number of di(s-triazinyl) sulphides and disu1phides is described. The behaviour of these compounds on oxidative attack has been examined. It has been found that instead of the expected sulphoxide and/or sulphone formation upon oxidation, a simple scission of the thioether linkage takes place, yielding a hydroxytriazine and the corresponding disulphide

Characterization of polymerized ionic liquids-based hydrogels

Polymerized Ionic Liquids (PILs) are hydrogels synthesized from ionic liquids. They combine the positive characteristics of ionic liquids and polymers which is why they have a wide range of applications, e.g. in the pharmaceutical sector. They are characterized by properties such as high mechanical strength, biocompatibility, and favorable swelling behavior. In this study, the extremely high mechanical strength of novel polymerized ionic liquids (PILs)-based hydrogels was confirmed by mechanical tests. The swelling behavior was studied of hydrogels based on 1-Vinyl-3-alkylimidazolium bromide with different crosslinkers in various solvents – aqueous and organic

Study of Cyclization Mechanism of N-Substituted-2-amino- benzophenones into 1,4-Benzodiazepines; B-Participation of an Vinylogous Amide Nitrogen

2-(N-B-Bromoalkyl)-amino-5-substiJtuted ben:oophenones 28, 32, 33 .and 38 have been i:nduced by treatment in ethanolic solution of hexamethyleintetramine or rammonia ·to ring c1osure into 1,4-beinzcidiazepiines 39-46. Deuterium B-labe1ed compound 28 gave on cyclization two 1,4-benzodfazepiines (39 and 40) in the rntio 45/55, reveal1ng B-par!ticipation of :nitrogen atom. The neighbouri:ng grnup participa·tion was further investigated by deternniniing the ratio and configuration of the 2- and 3-substituted chiral 1,4-benzodi. azepines 1resulting on ring closure: 32 gave (S)-41 and (S)-42 (ratio 82/18), 33 gave (S)-43 and {S)-44 ~rntio 92/8), 38 gave 45 and 46 (ratio 58/42). High regioselectiviity was also 1observed for recyclization of aziridines 36 in (S)-41 and (R)-42 (rntio 63/37), and 37 in (S)-43 and (R)-44 (ratio 76/24), respectively. Arn opposite stereochemical course of formaition of 42 and 44 f.rom 32 and 33, as :Dram 36 and 37 is observed. Absolute configurntfon of (-)- and ( + )-42 and 44 was determined by comparison of their CD spectra with those of (S)-50, and mecha1nistic scheme is offered accountLng for all exper-imental results

A human organotypic knock-down skin model to study molecules involved in epidermal keratinocyte differentiation. An alternative to knock-out animal experiments in dermatological research

Formation of the epidermal barrier is a complex process involving the tight regulation of the expression of structural proteins, enzymes and cytokines, implementing different signaling pathways depending on the differentiation stage of KC. Alterations of skin barrier formation occur as consequence of many skin diseases but can also be the primary event leading to skin diseases. Organotypic skin models have greatly contributed to delineate molecular mechanisms underlying the epidermal differentiation process. In this thesis we have adapted a human organotypic skin model to knock-down individual genes and study their impact on the differentiation of epidermal KC in vitro. Using this model we have provided new insights in the formation of the skin barrier of human skin.This work was partially supported by the European Union COST initiative on skin barrier in atopic dermatitis, by the Deutsche Forschungsgemeinschaft (SCHR 305 / 5-1) and by the Centre de Recherches et d´Investigations Èpidermiques et Sensorielles de CHANEL (CE.R.I.E.S). Financial support for printing of this thesis was provided by CellSystems.UBL - phd migration 201

Wolter Optics for Neutron Focusing

Focusing optics based on Wolter optical geometries developed for x-ray grazing incidence beams can be designed for neutron beams. Wolter optics are formed by grazing incidence reflections from two concentric conic sections (for example, a paraboloid and a hyperboloid). This has transformed observational X-ray astronomy by increasing the sensitivity by many orders of magnitude for research in astrophysics and cosmology. To increase the collection area, many reflecting mirrors of different diameters are nested with a common focal plane. These mirrors are fabricated using nickel-electroformed replication techniques. We apply these ideas to neutron focusing using nickel mirrors. We show an initial test of a conical mirror using a beam of cold neutrons. key words: electroformed nickel replication, focusing optics, grazing angle incidence, mirror reflection, neutron focusing, Wolter optic

Grazing-Incidence Neutron Optics based on Wolter Geometries

The feasibility of grazing-incidence neutron imaging optics based on the Wolter geometries have been successfully demonstrated. Biological microscopy, neutron radiography, medical imaging, neutron crystallography and boron neutron capture therapy would benefit from high resolution focusing neutron optics. Two bounce optics can also be used to focus neutrons in SANS experiments. Here, the use of the optics would result in lower values of obtainable scattering angles. The high efficiency of the optics permits a decrease in the minimum scattering vector without lowering the neutron intensity on sample. In this application, a significant advantage of the reflective optics over refractive optics is that the focus is independent of wavelength, so that the technique can be applied to polychromatic beams at pulsed neutron sources

Investigating the post-stimulus undershoot of the BOLD signal – A simultaneous fMRI and fNIRS study

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Impaired hemodynamics and neural activation? A fMRI study of major cerebral artery stenosis

Functional MRI motor mapping was performed in two women with unilateral high-grade stenosis of the middle cerebral artery (MCA) to determine the influence of impaired hemodynamics on the blood oxygenation level dependent (BOLD) response. In both patients no structural lesions were present in primary motor pathways. A redistribution of the motor network to the healthy hemisphere was the main indicator of chronic hemodynamic compromise