X-ray Ptychographic Imaging and Spectroscopic Studies of Plasma-Treated Plastic Films

Polyethylene terephthalate (PET) is a thermoplastic polyester with numerous applications in industry. However, it requires surface modification on an industrial scale for printing and coating processes and plasma treatment is one of the most commonly used techniques to increase the hydrophilicity of the PET films. Systematic improvement of the surface modification by adaption of the plasma process can be aided by a comprehensive understanding of the surface morphology and chemistry. However, imaging large surface areas (tens of microns) with a resolution that allows understanding the surface quality and modification is challenging. As a proof-of-principle, plasma-treated PET films were used to demonstrate the capabilities of X-ray ptychography, currently under development at the soft X-ray free-electron laser FLASH at DESY, for imaging macroscopic samples. In combination with scanning electron microscopy (SEM), this new technique was used to study the effects of different plasma treatment processes on PET plastic films. The studies on the surface morphology were complemented by investigations of the surface chemistry using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). While both imaging techniques consistently showed an increase in roughness and change in morphology of the PET films after plasma treatment, X-ray ptychography can provide additional information on the three-dimensional morphology of the surface. At the same time, the chemical analysis shows an increase in the oxygen content and polarity of the surface without significant damage to the polymer, which is important for printing and coating processes

Whole-genome, transcriptome, and methylome analyses provide insights into the evolution of platycoside biosynthesis in Platycodon grandiflorus, a medicinal plant

Triterpenoid saponins (TSs) are common plant defense phytochemicals with potential pharmaceutical properties. Platycodon grandiflorus (Campanulaceae) has been traditionally used to treat bronchitis and asthma in East Asia. The oleanane-type TSs, platycosides, are a major component of the P. grandiflorus root extract. Recent studies show that platycosides exhibit anti-inflammatory, antiobesity, anticancer, antiviral, and antiallergy properties. However, the evolutionary history of platycoside biosynthesis genes remains unknown. In this study, we sequenced the genome of P. grandiflorus and investigated the genes involved in platycoside biosynthesis. The draft genome of P. grandiflorus is 680.1Mb long and contains 40,017 protein-coding genes. Genomic analysis revealed that the CYP716 family genes play a major role in platycoside oxidation. The CYP716 gene family of P. grandiflorus was much larger than that of other Asterid species. Orthologous gene annotation also revealed the expansion of beta -amyrin synthases (bASs) in P. grandiflorus, which was confirmed by tissue-specific gene expression. In these expanded gene families, we identified key genes showing preferential expression in roots and association with platycoside biosynthesis. In addition, whole-genome bisulfite sequencing showed that CYP716 and bAS genes are hypomethylated in P. grandiflorus, suggesting that epigenetic modification of these two gene families affects platycoside biosynthesis. Thus whole-genome, transcriptome, and methylome data of P. grandiflorus provide novel insights into the regulation of platycoside biosynthesis by CYP716 and bAS gene families

Element-Selective Investigation of Femtosecond Spin Dynamics in Nix_{x}Pd1−x_{1-x} Magnetic Alloys using Extreme Ultraviolet Radiation

Since Beaurepaire et al. discovered optically induced ultrafast magnetization dynamics in Ni thin films in 1996, a variety of experimental and theoretical studies have been made to understand the underlying physical mechanism of the magnetization dynamics. Among the suggested mechanisms, spin-ip electron-phonon scattering described by the microscopic three-temperature model (M3TM)[3] and superdiffusive spin transport[4],[5] are currently considered to be major physical mechanisms contributing substantially to the ultrafast spin dynamics. It is believed that more than one mechanism is responsible for the dynamics. The analysis of magnetization dynamics in Ni$_{x}$Pd$_{1-x}$ alloys with varying composition presented in this thesis provides deeper insight into the relation between the spin dynamics and spin-orbit coupling (SOC) in these materials. Our measurements were mostly done in the transversal magneto-optic Kerr effect (T-MOKE) geometry. To measure ultrafast magnetization dynamics with element selectivity, femtosecond pulses in the extreme ultraviolet (XUV) regime have been produced by laser-based high-order harmonic generation (HHG) in a noble gas. The XUV light from neon gas with an energy range from 20 to 72 eV covering the M$_{2,3}$-edges of ferromagnetic materials (52.7 eV for Fe, 58.9 eV for Co, and 68, 66.2 eV for Ni) can be expanded to form a spectrum, by a optical grating introduced on the sample surface. The magnetic contrast and the optically-induced dynamic response can be obtained using XUV light with energy corresponding to the absorption edges of the involved elements. In the Ni$_{x}$Pd$_{1-x}$ alloys, the intrinsically paramagnetic Pd is expected to be magnetically coupled to ferromagnetic Ni via complex exchange paths. One can study spin dynamics in the paramagnetic material (Pd) with induced magnetic moment as a consequence of the exchange coupling with ferromagnetic material (Ni). In addition, element selective measurements allow investigation of questions related to a possible superdiffusive spin transport between the Ni and Pd subsystems. The influence of the increased SOC on the spin dynamics in the Ni$_{x}$Pd$_{1-x}$ alloys can be also investigated by varying the mixing ratio of Ni and Pd in the alloy system. From static T-MOKE, we experimentally confirmed that increasing the Pd content in the alloy gives rise to a pronounced magnetic asymmetry of a bipolar shape at the Pd N$_{3}$-absorption edge (50.9 eV). Varying the mixing ratio in the Ni$_{x}$Pd$_{1-x}$ alloy changes the magnetic properties such as the magnetic moment $\mu$, the Curie temperature T$_{C}$, and the spin-flip scattering probability a$_{sf}$ of the alloy. We show that these parameters are closely related to the magnetization dynamics. Especially, the spin-flip scattering probability a$_{sf}$ scales with the atomic number Z as a$_{sf} \varpropto Z^{4}$ due to SOC. The magnetization dynamics in the Ni$_{x}$Pd$_{1-x}$ alloys can be tuned by the alloy stoichiometry due to a considerable difference in atomic numbers of Ni (Z$_{Ni}$=28) and Pd (Z$_{Pd}$=46). Our results can then be explained by considering the spin-flip scattering probability a$_{sf}$ within the framework of M3TM, and point to the crucial role of the Pd-mediated SOC in optically-induced spin dynamics in the Ni$_{x}$Pd$_{1-x}$ alloys

Single-shot ptychography at a soft X-ray free-electron laser

Ptychograhy is a scanning coherent diffraction imaging technique capable of providing images of extended samples withdiffraction-limited resolution. However, ptychography experiments are time-consuming due to their scanning nature which alsoprevents their use for imaging of dynamical processes. Recently, setups based on two con-focal lenses were proposed toperform single-shot ptychography in the visible regime by measuring the diffraction pattern produced by multiple overlappingbeams in one shot. However, this approach cannot be extended straightforwardly to X-ray wavelengths due to the application ofrefractive optics. In this work, we demonstrate a novel and nascent single-shot ptychography setup utilizing the combination ofX-ray focusing optics with a two-dimensional beam-splitting diffraction grating. It allows single-shot imaging of extended samplesat X-ray wavelengths. As a proof of concept, we performed single-shot ptychography in the XUV range at the free-electronlaser FLASH and obtained a high-resolution reconstruction of the sample

X-ray Ptychographic Imaging and Spectroscopic Studies of Plasma-Treated Plastic Films

Polyethylene terephthalate (PET) is a thermoplastic polyester with numerous applications in industry. However, it requires surface modification on an industrial scale for printing and coating processes and plasma treatment is one of the most commonly used techniques to increase the hydrophilicity of the PET films. Systematic improvement of the surface modification by adaption of the plasma process can be aided by a comprehensive understanding of the surface morphology and chemistry. However, imaging large surface areas (tens of microns) with a resolution that allows understanding the surface quality and modification is challenging. As a proof-of-principle, plasma-treated PET films were used to demonstrate the capabilities of X-ray ptychography, currently under development at the soft X-ray free-electron laser FLASH at DESY, for imaging macroscopic samples. In combination with scanning electron microscopy (SEM), this new technique was used to study the effects of different plasma treatment processes on PET plastic films. The studies on the surface morphology were complemented by investigations of the surface chemistry using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). While both imaging techniques consistently showed an increase in roughness and change in morphology of the PET films after plasma treatment, X-ray ptychography can provide additional information on the three-dimensional morphology of the surface. At the same time, the chemical analysis shows an increase in the oxygen content and polarity of the surface without significant damage to the polymer, which is important for printing and coating processes

The PERCIVAL detector: first user experiments

The PERCIVAL detector is a CMOS imager designed for the soft X-ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free-electron laser, holographic imaging at a storage ring and preliminary tests on X-ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X-ray science