Melanie Mucke

Bio: Melanie Mucke is an academic researcher from Uppsala University. The author has contributed to research in topics: Photoionization & Ionization. The author has an hindex of 18, co-authored 56 publications receiving 1286 citations. Previous affiliations of Melanie Mucke include Stockholm University & Max Planck Society.

A hitherto unrecognized source of low-energy electrons in water

Abstract: Most of the low-energy electrons emitted from a material when it is subjected to ionization radiation are believed to be directly ionized secondary electrons. Coincidence measurements of the electrons ejected from water clusters suggests many are produced by a quantitatively new mechanism, known as intermolecular Coulombic decay. Low-energy electrons are the most abundant product of ionizing radiation in condensed matter. The origin of these electrons is most commonly understood to be secondary electrons1 ionized from core or valence levels by incident radiation and slowed by multiple inelastic scattering events. Here, we investigate the production of low-energy electrons in amorphous medium-sized water clusters, which simulate water molecules in an aqueous environment. We identify a hitherto unrecognized extra source of low-energy electrons produced by a non-local autoionization process called intermolecular coulombic decay2 (ICD). The unequivocal signature of this process is observed in coincidence measurements of low-energy electrons and photoelectrons generated from inner-valence states with vacuum-ultraviolet light. As ICD is expected to take place universally in weakly bound aggregates containing light atoms between carbon and neon in the periodic table2,3, these results could have implications for our understanding of ionization damage in living tissues.

Ultrafast X-ray Auger probing of photoexcited molecular dynamics

Abstract: Molecules can efficiently and selectively convert light energy into other degrees of freedom Disentangling the underlying ultrafast motion of electrons and nuclei of the photoexcited molecule pres

Probing ultrafast ππ*/nπ* internal conversion in organic chromophores via K-edge resonant absorption

Abstract: Many photoinduced processes including photosynthesis and human vision happen in organic molecules and involve coupled femtosecond dynamics of nuclei and electrons Organic molecules with heteroatoms often possess an important excited-state relaxation channel from an optically allowed ππ* to a dark nπ* state The ππ*/nπ* internal conversion is difficult to investigate, as most spectroscopic methods are not exclusively sensitive to changes in the excited-state electronic structure Here, we report achieving the required sensitivity by exploiting the element and site specificity of near-edge soft X-ray absorption spectroscopy As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrum at the heteroatom K-edge exhibits an additional resonance We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ*/nπ* internal conversion takes place within (60 ± 30) fs High-level-coupled cluster calculations confirm the method’s impressive electronic structure sensitivity for excited-state investigations Many photo-induced processes such as photosynthesis occur in organic molecules, but their femtosecond excited-state dynamics are difficult to track Here, the authors exploit the element and site selectivity of soft X-ray absorption to sensitively follow the ultrafast ππ*/nπ* electronic relaxation of hetero-organic molecules

Probing ultrafast \pi\pi*/n\pi* internal conversion in organic chromophores via K-edge resonant absorption

Abstract: Organic chromophores with heteroatoms possess an important excited state relaxation channel from an optically allowed {\pi}{\pi}* to a dark n{\pi}*state. We exploit the element and site specificity of soft x-ray absorption spectroscopy to selectively follow the electronic change during the {\pi}{\pi}*/n{\pi}* internal conversion. As a hole forms in the n orbital during {\pi}{\pi}*/n{\pi}* internal conversion, the near edge x-ray absorption fine structure (NEXAFS) spectrum at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept with the nucleobase thymine, a prototypical heteroatomic chromophore. With the help of time resolved NEXAFS spectroscopy at the oxygen K-edge, we unambiguously show that {\pi}{\pi}*/n{\pi}* internal conversion takes place within (60 \pm 30) fs. High-level coupled cluster calculations on the isolated molecules used in the experiment confirm the superb electronic structure sensitivity of this new method for excited state investigations.

Dynamics of hollow atom formation in intense x-ray pulses probed by partial covariance mapping

Abstract: When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called ‘‘partial covariance mapping’’ to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Machine learning with Python

Abstract: This presentation is a case study taken from the travel and holiday industry. Paxport/Multicom, based in UK and Sweden, have recently adopted a recommendation system for holiday accommodation bookings. Machine learning techniques such as Collaborative Filtering have been applied using Python (3.5.1), with Jupyter (4.0.6) as the main framework. Data scale and sparsity present significant challenges in the case study, and so the effectiveness of various techniques are described as well as the performance of Python-based libraries such as Python Data Analysis Library (Pandas), and Scikit-learn (built on NumPy, SciPy and matplotlib). The presentation is suitable for all levels of programmers.

X-Rays and Extreme Ultraviolet Radiation: Principles and Applications

Abstract: This self-contained, comprehensive book describes the fundamental properties of soft x-rays and extreme ultraviolet (EUV) radiation and discusses their applications in a wide variety of fields, including EUV lithography for semiconductor chip manufacture and soft x-ray biomicroscopy. The author begins by presenting the relevant basic principles such as radiation and scattering, wave propagation, diffraction, and coherence. He then goes on to examine a broad range of phenomena and applications. The topics covered include EUV lithography, biomicroscopy, spectromicroscopy, EUV astronomy, synchrotron radiation, and soft x-ray lasers. He also provides a great deal of useful reference material such as electron binding energies, characteristic emission lines and photo-absorption cross-sections. The book will be of great interest to graduate students and researchers in engineering, physics, chemistry, and the life sciences. It will also appeal to practicing engineers involved in semiconductor fabrication and materials science.