Ultrafast NEXAFS spectroscopy in the lab using laser based sources and advanced X ray optics

Laboratory based laser driven short pulse X ray sources like laser produced plasmas LPP and high harmonic generation HHG exhibit a great potential for spectroscopy in the soft X ray range. These sources are complementary to large scale facilities like synchrotrons or free electron lasers. For applications of LPP or HHG sources for time resolved X ray absorption spectroscopy in the water window or beyond a high photon flux is crucial. The available photon flux strongly depends on energy, pulse duration and repetition rate of the pump laser. Depending on the experimental needs in time resolved experiments pulse durations of the X ray pulse ranging from nanoseconds to sub femtoseconds are required. In our contribution we will present a highly brilliant LPP source emitting soft X rays in the photon energy range between 50 and 1500 eV based on CPA and thin disk laser technology as well as the high average power thin disk laser based OPCPA system for high photon flux HHG. In addition we present a new generation of reflection zone plates on spherical substrates, that promises a remarkable high resolution over a wide spectral range making it an ideal and highly efficient diffractive optic for time resolved NEXAFS experiments in the la

Genealogies of Slavery

This chapter addresses the concept of slavery, exploring its character and significance as a dark page in history, but also as a specifically criminological and zemiological problem, in the context of international law and human rights. By tracing the ambiguities of slavery in international law and international development, the harms associated with slavery are considered. Harms include both those statutorily proscribed, and those that are not, but that can still be regarded as socially destructive. Traditionally, antislavery has been considered within the parameters of abolition and criminalization. In this context recently, anti-trafficking has emerged as a key issue in contemporary anti-slavery work. While valuable, anti-trafficking is shown to have significant limitations. It advances criminalization and stigmatization of the most vulnerable and further perpetuates harm. At the same time, it identifies structural conditions like poverty, vulnerability, and “unfreedom” of movement only to put them aside. Linked to exploitation, violence and zemia, the chapter brings to the fore some crucial questions concerning the prospects of systemic theory in the investigation of slavery, that highlight the root causes of slavery, primarily poverty and inequality. Therefore, the chapter counterposes an alternative approach in which the orienting target is not abolition of slavery but advancing structural changes against social harm

Prox1 Regulates the Notch1-Mediated Inhibition of Neurogenesis

During development of the spinal cord, Prox1 controls the balance between proliferation and differentiation of neural progenitor cells via suppression of Notch1 gene expression

Investigations on fire gilding

Fire gilding is a historic technique for the application of golden layers on a number of different base materials utilizing a gold amalgam. This technique leaves a significant amount of Hg in the golden layer, giving archeometrists a reliable indicator to identify fire gildings. Recent findings on presumably fire gilded objects have shown in several cases significantly lower Hg content than previously studied objects. This prompted a synchrotron based X ray fluorescence investigation into the Hg distribution along the material gilding interface, as well as a series of measurements regarding the Hg content development in fire gilded samples during artificial aging. This work presents findings on laboratory prepared fire gildings, indicating an Hg enrichment at the interface of fire gilded silver samples. Notably, such an enrichment is missing in fire gilded copper samples. Further, it is confirmed that fire gilded layers typically do not undercut an Hg bulk content of 5 . In this light, it seems improbable that ancient samples that contain lt;5 Hg are fire gilded. The results presented in this study might lead to a non destructive method to identify the Hg enrichment at the interface. This might be obtained by a combination of different non destructive measurements and might also work unambiguously in samples in which the gold top layer is altere

Preparation of Reinforced Anisometric Patchy Supraparticles for Self Propulsion

The preparation of fumed silica based anisometric supraparticles with well defined catalytically active patches suitable for self propulsion is presented here. These sub millimeter sized particles can self propel as they contain Pt covered magnetite Fe3O4 nanoparticles, where the Pt can decompose catalytically a fuel like H2O2 and thereby propel the supraparticles. By their magnetic properties, the catalytically active nanoparticles can be concentrated in patches on the supraparticle surface. The goal is to obtain robust supraparticles with well defined patchiness and long time stability during self propulsion through evaporation induced self assembly EISA on a superhydrophobic surface. The latter is a major issue as oxygen evolution can lead to the disintegration of the supraparticles. Therefore, enhanced mechanical stability is sought using a number of different additives, where the best results are obtained by incorporating polystyrene microspheres followed by heat treatment or reinforcement with microfibrillated cellulose MFC and sodium trisilicate Na2SiO3 . The detailed internal structure of the different types of particles is investigated by confocal micro X ray fluorescence spectroscopy CMXRF , which allows for precisely locating the catalytic Fe3O4 Pt nanoparticles within the supraparticles with a resolution in the m range. The insights on the supraparticle structure, together with their long time stability, allow fabricating optimized patchy supraparticles for potential applications in propulsion enhanced catalysi

Quantitative Analysis and 2D 3D Elemental Imaging of Cocoa Beans Using X ray Fluorescence Techniques

As an important raw material for the confectionery industry, the cocoa bean Theobroma cacao L. has to meet certain legal requirements in terms of food safety and maximum contaminant levels in order to enter the cocoa market. Understanding the enrichment and distribution of essential minerals but also toxic metals is of utmost importance for improving the nutritional quality of this economically important raw food material. We present three X ray fluorescence XRF techniques for elemental bio imaging of intact cocoa beans and one additional XRF technique for quantitative analysis of cocoa pellets. The interrelation of all the methods presented gives a detailed picture of the content and 3D resolved distribution of elements in complete cocoa beans for the first tim